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					                                                                  LuK Clutch Course
                                                                  An introduction to clutch technology
                                                                  for passenger cars




LuK-Aftermarket Service oHG
                               999 6000 96 1475/1.0/09.2004/ABC




Paul-Ehrlich-Straße 21
D-63225 Langen, Germany
Phone: +49 (0) 61 03-753-0
Fax:   +49 (0) 61 03-753-295

info@LuK-AS.de
www.LuK-AS.com
                                                                  passenger cars
Introduction                                          Contents
Knowledge is power …                                  A history of clutch technology                                              4–8

... as the saying goes, and these words acquire       Chart 1: Functional Schematic with components                                 9
new meaning in an age of changing technolo-
gies and increasing standards of convenience          Chart 2: Clutch disc- detail parts, torsion damper and cushion deflection    12
and engineering. It is no longer a matter of
gaining mastery over others, but of mastering         Chart 3: Clutch disc – designs, torsion damper graphs                        14
technologies and the problems they pose.
                                                      Chart 4: Clutch pressure plate assembly – designs and graphs                 16
This assumes appropriate training and a
constant flow of information about changes            Chart 5: Clutch pressure plate assembly – designs and installation principles 18
and about experience gathered. As a maker of
clutches for almost every automotive manufac-         Chart 13: SAC clutch cover assembly – designs types and characteristics      20
turer in the world, LuK knows that its products
can only display their qualities to the full when     Chart 11: Dual-mass flywheel (DMF) – design and function                     22
they are properly installed and professionally
maintained.                                           Chart 12: DFC – Damped Flywheel Clutch (Compact DMF) – Layout and function 24

This brochure is intended to give all readers an      Index                                                                        26
overview of the basic principles and designs of
modern clutch technology. An important aim is
to make clear that clutches have become
precision parts which need careful handling
and must be installed and removed exactly as
per the assembly instructions.

Supplementary training documents, such as
the NOK brochure are likewise available for
purchase. AS/LuK has also developed an inter-
active teaching programme.


The European Training Concept

This deals with the basic principles of clutch
technology, correct diagnosis of damage and
essential service tips. This training programme,
which works with the aid of video, can be
purchased as a self-tutoring unit (for private
study) or as a trainer guide (for trainers).

AS can provide you with more information if
you need it – please call +49 6103 753251.

LuK hopes that you enjoy working with this
booklet and wishes you every success both
learning and subsequently working “on the spot”.




AS Autoteile-Service GmbH & Co.
LuK Aftermarket-Service Ltd




                                       Thomas Petri
Siegfried Kronmüller              Customer Service/
Managing Director              Engineering Manager

                                                                                                                                         3
    A history of clutch technology
    In the course of over 100 years of automotive
    history, nearly all components have undergone
    enormous technological developments. Relia-
    bility, production costs and service-friend-
    liness as well as, more recently, environmental
    safety, have been and continue to be the crite-
    ria demanding new and better solutions from
    automotive engineers. The basic designs are
    usually known early on, but only the availability
    of new materials and processing procedures
    makes their realisation feasible.

    It was not until the end of the first decade of
    this century that the internal combustion
    engine surpassed the competing steam and
    electricity-based automotive drive concepts
    on a large scale. In 1902, a petrol-engined
    vehicle for the first time broke the overall
    speed record; up to then, electric and steam-
    powered vehicles had set the standards, and                                                                                                                                            Cross section of a cone clutch showing the typical
    proponents of the three drive concepts con-                                                                                                                                            components: clutch cone and correspondingly turned-out
                                                                                                                                                                                           flywheel.
    tinued to compete for the absolute speed
                                                                                                                                                                                           Schwungrad            crankshaft flange
    record throughout the first decade.                                                                                                                                                    Kurbelwellenflansch   flywheel
                                                                                                                                                                                           Kupplungsfußhebel     release sleeve
                                                                                                                                                                                           Ausrückmuffe          clutch pedal
                                                         Transmission belt clutch from the Benz patented motor car of 1886.                                                                Ausrückhebel          release lever
    Steam and electric drives have a decisive                                                                                                                                              Kupplungswelle        clutch shaft
    advantage over “motorised vehicles with liquid                                                                                                                                         Kupplungsgehäuse      clutch housing
                                                                                                                                                                                           Kupplungsfeder        clutch spring
    fuels”, as they used to be called. Thanks to the     under rainy conditions, on one hand and the                    from Daimler, which had a cone/bevel friction                      Kupplungskegel        clutch cone
                                                                                                                                                                                           Kupplungsbelag        clutch lining
    almost ideal torque band, they required neither      necessity of variable-speed transmissions for                  clutch. Here a freely moving frictional cone
    clutches nor transmissions, and thus were            the gradually increasing engine outputs on the                 located on the engine shaft and firmly
    easier to operate, had fewer malfunctions and        other hand, induced engineers to seek better                   connected to the clutch shaft via the clutch                       clutch part came to rest much more slowly
    were easier to service. As an internal combus-       alternatives to transmission clutches.                         housing engages in the conically machined out                      than was required after the release for gear
    tion engine only delivers its output at engine                                                                      flywheel. A spring presses the cone into the fly-                  changing (transmissions were not yet synchro-
    speed, there must be a division between              The results were a wide variety of clutch types                wheel recess so that pressure on the foot                          nised). To remedy this problem, around 1910 an
    engine and transmission. The speed-depend-           – including the forerunners of our present-day                                                                                    additional clutch brake or transmission brake
    ent drive principle of the petrol engine necessi-    clutches – all based on the principle of the fric-                                                                                was installed which had to be actuated via a
    tates a mechanical aid for starting, as suffi-       tion clutch. Here the disc is located on the end                                                                                  second foot pedal – usually in conjunction with
    cient output (torque) is only available after        of the crankshaft and is joined by a second,                                                                                      the clutch pedal and located together with the
    certain engine speeds have been attained.            stationary disc. When the two make contact,                                                                                       latter on a common pedal shaft.
    Besides the function of a starting clutch, how-      friction is produced and the secondary disc is
    ever, that of a dividing clutch is equally import-   set in motion. As the clamping load is                                                                                            The habit of many drivers of allowing the clutch
    ant, for it allows load-free gear changing while     increased, the driving disc carries along the                                                                                     to slip instead of changing gears when regulat-
    driving. Because of the complexity of the            driven disc with increasing speed until power                                                                                     ing the vehicle speed, heated the flywheel
    related problems, many smaller vehicles in the       transmission is reached, and both discs have                                                                                      more than it did the friction cone, which was
    early years of automotive design did not have a      the same rotational speed. In the period up to                                                                                    thermally insulated by the leather lining. After a       View of a chassis with a cone clutch. During disengagement, the clutch brake ensured quick speed reduction of the large
    starting clutch; the motor car had to be pushed      full engagement, the main driving energy is                                                                                       spell of rugged driving, the cone could engage           mass with a cone clutch.
    into motion.                                         converted into heat as the discs slide across                  Design of the cone/bevel friction clutch dominant through-         more deeply in the flywheel as it had been
                                                         one another. This arrangement meets the two                    out the 1920s.                                                     expanded by the heat – leaving it jammed tight                                                                         Motor                               engine
                                                                                                                                                                                                                                                                                                                  Kupplung                            clutch
    The operating principles of the first clutches       chief demands – on the one hand gradual and                    Motorschwungrad mit Hohlkegel   engine flywheel with hollow cone   when it cooled down.                                                                                                   Kupplungsfußhebel                   clutch pedal
                                                                                                                        vom Motor                       from engine                                                                                                                                               Wechselgetriebe                     variable-speed transmission
    originated in the mechanised factories of early      gentle engagement, so that, when driving off,                  Anpreßfeder                     coil spring                                                                                                                                               Kreuzgelenk                         universal joint
    modern industry. By analogy with the trans-          the engine is not cut off and does not jerk with               zum Getriebe                    to transmission                    By the end of the First World War, metallic                                                                            Gelenkwelle                         propshaft
                                                                                                                        Mitnehmerkegel mit Lederbelag   driver cone with leather lining                                                                                                                           Linkes Hinterrad                    rear left wheel
    mission belts used there, flat leather belts were    the drive train, and on the other hand loss-free                                                                                  friction linings were becoming increasingly                                                                            Gelenkwellenrohr                    propshaft tube
                                                                                                                                                                                                                                                                                                                  Tellerrad                           differential ring gear
    now introduced into motor cars. When ten-            power transmission with the clutch engaged.                                                                                       popular. Previously, one had experimented                                                                              Feder                               spring
                                                                                                                                                                                                                                                                                                                  Linke Hinterachswelle               left rear axle shaft
    sioned by a roller, the belt transmitted the drive                                                                  pedal will pull the cone back against the spring                   with other solutions: For example, the “Neue                                                                           Hinterachsbrücke                    rear-axle housing
    output of the engine’s belt pulley to the drive      The clutch is actuated via the foot pedal, which               pressure via the freely movable clutch release                     Automobil-Gesellschaft (NAG)” constructed a                                                                            Schubkugel zur Aufnahme des         torque ball for absorbing
                                                                                                                                                                                                                                                                                                                  Hinterachsschubes und Übertragung   rear-axle thrust and
    gears, and when loosened, it slipped through –       pulls back the cone carrier via a release lever                sleeve, thereby interrupting the power trans-                      clutch containing a camel-hair lined cone,                                                                             auf den Fahrgestellrahmen           transferring it to chassis frame
                                                                                                                                                                                                                                                                                                                  Hinterachsgehäuse                   differential housing
    i. e. disengaged. As this procedure caused the       against the spring force and thus disengages                   mission. Camel hair belts originally functioned                    stamped from sheet metal and equipped with                                                                             Antriebskegelrad                    differential bevel pinion
                                                                                                                                                                                                                                                                                                                  Rechte Hinterachswelle              right rear axle shaft
    leather belts to wear out fast, a new tactic was     the clutch.                                                    as friction linings on the cone surface, but                       fan-like blades for cooling, which engaged in                                                                          Ausgleichgetriebe                   differential
    adopted of installing an idler pulley of the same                                                                   were soon replaced by leather belts. The latter                    a two-part, leather-lined ring screwed into the                                                                        Fahrgestellrahmen                   chassis frame
                                                                                                                                                                                                                                                                                                                  Rechtes Hinterrad                   rear right wheel
    size beside the drive belt pulley. By moving a       The basic form of this design principle was                    were soaked in castor oil as a protective                          flywheel. The two-part construction allowed
    lever, the transmission belt could be guided         already used in 1889, in the steel wheel cars                  measure against moisture, grease and oil.                          the ring to be easily removed, simplifying
    from the idler pulley on to the drive pulley.                                                                                                                                          maintenance and reducing the frequency of                                                                              was able to persevere until the First World War
    The motor car patented by Benz in 1886, which                                                                       The advantages – self-adjusting, no strain on                      jamming.                                                 Cone clutch with spring-compressed leather lining.
                                                                                                                                                                                                                                                                                                                  thanks to an ingenious design.
    Bertha Benz used to make the first long-dis-                                                                        the drive or transmission shaft – were, how-
    tance journey in the history of motor vehicles –                                                                    ever, out-weighed by the disadvantages: on the                     The Daimler engine corporation developed an                                                                            In the spring band clutch, a sturdy, spiral-
    from Mannheim to Pforzheim – already oper-                                                                          one hand, the friction lining wore out fast and                    open friction clutch with a bare aluminium               clutches with cylindrical friction surfaces did               shaped spring band, which received the drum-
    ated according to this clutch concept.                                                                              replacement was complicated; hence one                             cone. For a soft release, oil had to be dripped          not win acceptance because of their poor                      shaped end of the transmission shaft, was
                                                                                                                        switched to designs with spring-loaded pins or                     onto the frictional surfaces at regular intervals.       operational characteristics. Only the spring                  fitted in a recess of the flywheel. One end of the
    The disadvantages of a belt drive, such as low                                                                      leaf springs under the leather lining. Secondly,                                                                            band clutch, a derivative of the cylindrical                  coil spring was connected to the flywheel,
                                                         The basic principle of the friction clutch:
    efficiency, high susceptibility to wear and inad-    The driven disc is pressed onto the driving disc until the     the flywheel and clutch cone were very large,                      Cone clutches continued to dominate through-             clutch that had been installed in Mercedes                    while the other was fastened to the cover of
    equate running characteristics especially            frictional connection is made.                                 so that, owing to its high moment of inertia, the                  out the 1920s thanks to their simplicity. Metallic       cars by Daimler since the turn of the century,                the spring housing. The actuation of the clutch

4                                                                                                                                                                                                                                                                                                                                                                                        5
    A history of clutch technology
                                                               At about the same time that the Daimler                        As the spring pressure eased off, the plates                                                                                       was relatively complicated. The clutch housing                clutch became progressively heavier. In addi-
                                                               corporation were developing their spring band                  disengaged again, in part supported by the                                                                                         was flanged onto the flywheel, and the clutch                 tion to this, the bearings for the release levers
                                                               clutch, Professor Hele-Shaw from England                       spring-loaded strips bent out from the plane of                                                                                    cover screwed into the housing. This cover                    were constantly under strain, making them
                                                               was already experimenting with a multi-plate                   the plate. By varying the number of plate pairs,                                                                                   held lug levers which were pressed inwards by                 susceptible to wear, and the spring housings,
                                                               clutch that can be regarded as the forerunner                  a basic clutch type could be adjusted to each                                                                                      springs and which transmitted pressure from                   especially when gear changing at high engine
                                                               of today’s conventional single-disc dry                        engine output.                                                                                                                     an intermediate disc via the friction plate and               speeds, quickly wore through.
                                                               clutch. Multi-plate clutches, named “Weston                                                                                                                                                       hence the power transmission from the fly-
                                                                                                                              Multi-plate clutches operated either immersed                                                                                      wheel. The friction disc was connected to the                 To overcome these systematic drawbacks, the
                                                                                                                              in oil/petroleum or dry, in which case, however,                                                                                   connecting or transmission shaft by a driver.                 diaphragm spring clutch was developed, cre-
                                                                                                                              special, riveted friction linings were used.                                                                                       The clutch was engaged and disengaged by a                    ated in the research laboratories of General
                                                                                                                                                                                                                                                                 slip-ring disc that moved a cone back and forth.              Motors in 1936 and entering volume production
                                                                                                                                                                                                                                                                                                                               in the US in the late 1930s. In Europe, it became
                                                                                                                                                                                                                                                                                                                               especially familiar from the American GMC
                                                                                                                                                                                                                                                                                                                               military trucks used after the Second World
                                                                                                                                                                                                                                                                                                                               War, and starting in the mid-1950s it was used
                                                                                                                                                                                                                                                                                                                               on an individual basis by European manufac-
                                                                                                                                                                                                                                                                                                                               turers. The Porsche 356, the Goggomobil, the
                                                                                                                                                                                                                                                                                                                               BMW 700 and DKW Munga were the first
                                                                                                                                                                                                                                                                                                                               German-made vehicles to be so equipped. The
                                                                                                                                                                                                                                                                                                                               clutch entered volume production in 1965
                                                                                                                                                                                                                                                                                                                               with the Opel Rekord.
                                                                                                                                                                                                  De Dion & Bouton were the first to recognise that single-                                                                    As the diaphragm spring is rotationally sym-
                                                                                                                                                                                                  plate clutches would be the way of the future.
                                                                                                                                                                                                                                                                                                                               metric and therefore speed-insensitive, its
    NAG clutch with two-part hollow cone ring, which greatly
    simplified maintenance.
                                                               Professor Hele-Shaw from England was the first to experi-                                                                          who towards the end of that decade granted
                                                               ment with multi-plate clutches.                                Oil-immersed multi-plate clutch.
                                                                                                                                                                                                  licences to European manufacturers. Within a
                                                                                                                              Schwungrad             flywheel                                     few years, the single-plate had superseded
                                                                                                                              Kurbelwellenflansch    crankshaft flange
                                                               clutches” after the first large-scale producer,                Kupplungsfußhebel      clutch housing                               cone and multi-plate clutches.
                                                               had a decisive advantage over the cone fric-                   Kupplungsgehäuse       clutch hub                                   While De Dion & Bouton still lubricated the
                                                                                                                              Kupplungsnabe          clutch pedal
                                                               tion clutch: much greater friction surface area                Kupplungsscheiben      clutch plates                                friction surfaces of their multi-plate clutches
                                                                                                                              Kupplungsfeder         clutch spring
                                                               with a lower space requirement and constant                    Druckscheibe           pressure plate                               with graphite, clutch technology greatly
                                                                                                                              Gelenkauge             propshaft flange
                                                               engagement.                                                    Kupplungswelle         clutch shaft                                 advanced with the advent of Ferodo-asbestos
                                                                                                                              Ausrückmuffe           release sleeve                               linings, which were used from about 1920 to
                                                               In the case of the multi-plate clutch, the fly-                                                                                    the present day, when they were replaced by                    This form of coil spring clutch, with the clutch springs
                                                                                                                                                                                                                                                                 arranged parallel to the central axis, predominated through
                                                               wheel is connected to a drum-shaped housing                                                                                        asbestos-free linings. The advantages of the                   the 1960s.
                                                               that has grooves on the inside corresponding                                                                                       single-plate dry clutch were clear: the low
                                                                                                                                                                                                                                                                 Schwungrad             flywheel
                                                               to the shape of the outer edge of the plate,                                                                                                                                                      Kupplungsbelag         clutch lining
                                                               allowing it to turn with the crankshaft or                                                                                                                                                        Kupplungsscheibe
                                                                                                                                                                                                                                                                 Kurbelwelle
                                                                                                                                                                                                                                                                                        clutch plate
                                                                                                                                                                                                                                                                                        crankshaft
                                                               flywheel and at the same time to move longitu-                                                                                                                                                    Druckscheibe           pressure plate
                                                                                                                                                                                                                                                                 6 Kupplungsfedern      6 clutch springs
                                                               dinally. An identical number of discs with                                                                                                                                                        Ausrückmuffe           release sleeve
                                                                                                                                                                                                                                                                 Kupplungswelle         clutch shaft
                                                               matching inner recesses are centred on a hub                                                                                                                                                      Kupplungsdeckel        clutch cover
                                                               connected to the clutch shaft. The discs can                                                                                                                                                      3 Abzughebel           operating levers x3
    Cone clutch of the Daimler Engine Corporation, with
    aluminium cone.                                            move longitudinally along the clutch shaft on
                                                               the hub. During installation, inner and outer                                                                                                                                                     The sides of the cone accordingly actuated the
    pedal tensioned the spring band, which then                clutch plates are alternately combined to form                                                                                                                                                    spring-pressured lug levers, which stressed or
    coiled itself (self-reinforcing) more and more             a plate packet, so that a driving and a driven                                                                                                                                                    released, i. e. engaged/disengaged, the inter-                In Britain and the US, the Borg & Beck model with springs
                                                                                                                                                                                                                                                                                                                               located under the clutch cover was the most popular …
    firmly around the drum, driving the trans-                 disc always follow one another.                                                                                                                                                                   mediate disc. As the cone rotated about the
                                                                                                                                                                                                                                                                                                                               Kupplungsgehäuse                  Bellhousing
    mission shaft – and engaging the clutch. The                                                                                                                                                                                                                 slip-ring disc at rest, lubrication was required              Kupplungskorb (Kupplungsdeckel)   clutch cover
    compression of the springs required only                                                                                                                                                                                                                     at regular intervals.                                         Kupplungsdruckfeder
                                                                                                                                                                                                                                                                                                                               Ausrücklager
                                                                                                                                                                                                                                                                                                                                                                 clutch compression spring
                                                                                                                                                                                                                                                                                                                                                                 release bearing
    slight force and effected a gentle engagement                                                                                                                                                                                                                                                                              (dauergeschmiert)                 (permanently lubricated)
                                                                                                                                                                                                                                                                                                                               Kupplungsgabel                    release lever
    of the clutch.                                                                                                                                                                                                                                               The coil spring clutch, in which the clamping                 Ausrückhebel                      clutch fork
                                                                                                                                                                                                                                                                                                                               Einstellmutter                    adjusting nut
                                                                                                                                                                                                                                                                 load is produced by coil springs, was able to                 Druckplatte (Anpreßplatte)        pressure plate
                                                                                                                              Multi-plate dry clutch with riveted lining.                                                                                        gain acceptance. At first, experiments were                   Mitnehmerscheibe
                                                                                                                                                                                                                                                                                                                               (gefedert und stoßgedämpft)
                                                                                                                                                                                                                                                                                                                                                                 driven plate
                                                                                                                                                                                                                                                                                                                                                                 (spring-loaded and damped)
                                                                                                                              Führungsbolzen                   guide pin                                                                                         made with centrally arranged springs, but only                Schwungrad                        flywheel
                                                                                                                              Mitnehmscheibe zur               drive disc for clutch shaft        Initial design of the coil spring clutch with clutch springs
                                                                                                                              Kupplungswelle                                                                                                                     the version with several smaller coil or clutch
                                                                                                                              Druckteller mit Ausrückmuffe     thrust plate with release sleeve   perpendicular to the central axis.
                                                                                                                              Kupplungsfeder                   clutch spring
                                                                                                                                                                                                                                                                 springs distributed along the outer edge of the
                                                                                                                                                                                                  Schwungrad                      flywheel
                                                                                                                              Innere Kupplungsscheiben         inner clutch plates
                                                                                                                                                                                                  Kupplungsgehäuse                clutch housing                 clutch housing entered large-scale production.                hour of triumph occurred in the 1960s, when
                                                                                                                              Äußere Kupplungsscheiben mit     outer clutch plates with clutch
                                                                                                                              Kupplungsbelag                   lining                             Kupplungsdeckel                 clutch cover                   The levers compress the coil springs via a                    high-speed engines with overhead camshafts
                                                               Plate pair from a multi-plate clutch: left, the inner clutch                                                                       Feder                           spring
                                                                                                                              Kupplungswelle                   clutch shaft
                                                               plate, right the outer plate.                                  Ausrückmuffe                     release sleeve                     Nasenhebel                      lug lever                      release bearing that moves freely on the clutch               (Glas, BMW, Alfa Romeo) largely superseded
                                                                                                                                                                                                  Kegel                           cone
                                                                                                                                                                                                  a: ausgerückt / b: eingerückt   a: disengaged / b: engaged     shaft, releasing the pressure plate and thus                  the push-rod designs. By the end of the 1960s,
                                                                                                                                                                                                  Schleifringscheibe              slip ring disc
                                                               The plate pairs formed in this fashion, originally             The greatest drawback of the multi-plate                            Federgelenk                     spring joint                   disengaging. The clamping load could be                       nearly all manufacturers had shifted to dia-
                                                               with a bronze disc always turning against a                    clutch was certainly the drag effect, especially                    Verbindungswelle                connection shaft               varied by using different spring packages but                 phragm spring clutches. Here LuK played a
                                                                                                                                                                                                  Lederbelag                      leather lining
                                                               steel one, were pressed together by a pressure                 in the oil bath, causing only partial disengage-                    Mitnehmer                       drive disc                     had the crucial disadvantage that, as the                     pivotal role in making the diaphragm spring
                                                                                                                                                                                                  Reibscheibe                     friction disc
                                                               plate under the force of a clutch spring. In this              ment, and thus making gear changing difficult.                      Zwischenscheibe                 intermediate disc              engine speed increased, the coil springs                      clutch ready for mass production. The replace-
                                                               way, all clutch plates were constantly                                                                                                                                                            located outside on the pressure plate were                    ment of the complete lever – coil spring system
                                                               engaged.                                                       By 1904, De Dion & Bouton had introduced the                        mass of the clutch plate allowed it to come to                 pressed further outwards against the spring                   by a diaphragm spring that assumed both
                                                                                                                              single-plate clutch principle, which because of                     rest more quickly when released, making shift-                 housings by centrifugal force. The friction                   functions brought many advantages: Simple
                                                               This gradual increase of frictional effect                     the initially inadequate materials only came                        ing much easier – farewell to transmission                     arising between the spring and the housing                    mechanical construction, constant clamp
    The Daimler spring band clutch, which, owing to its
    ingeniously simple design, was produced up to the First    enabled the multi-plate clutch to engage very                  into widespread use in the US during the 1920s                      brakes.                                                        then caused the clamp load characteristics to                 loads, less space required for relatively high
    World War.                                                 gently.                                                        – largely on demand from the supply industry,                       The initial design of the single-plate dry clutch              change. As the engine speed increased, the                    clamp loads (very important with transversely

6                                                                                                                                                                                                                                                                                                                                                                                             7
    A history of clutch technology                                                                                                                                                                  Functional Schematic with components Chart 1
                                                                                                                                                                                                      LuK Clutch Course                                                                                                          Chart 1




    With the multi-plate clutch developed by Chevrolet, also known as the Chevrolet or Inboard clutch, the coil springs were replaced by a diaphragm spring.


    Vorderes Führungslager der Kupplungswelle                          spigot bearing
    Haltefeder mit Schraube                                            retaining spring with screw
    Teller- oder Membranfeder mit den fingerförmigen Ausrücklamellen   diaphragm spring with pre-formed fingers
    Ausrücker                                                          release ring
    Haltefeder                                                         retaining spring
    Kugelbolzen zur Lagerung der Kupplungsgebel                        ball pin for clutch fork
    Schwungrad                                                         flywheel
    Mitnehmerscheibe                                                   drive disc
    Druckplatte                                                        pressure plate
    Innerer Führungsring                                               inner fulcrum ring
    Äußerer Führungsring                                               outer fulcrum ring
    Kupplungskorb                                                      clutch cover
    Kupplungsgabel                                                     release fork
    Rückzugsfeder der Kupplungsgabel                                   return spring of release fork



    installed engines) and speed-insensitivity.
    Thanks to these features, the diaphragm spring                     Easy operation was also promoted by various
    clutch is today nearly the only type used, it                      attempts to automate the clutch process: in
    is also finding increasing applications in utility                 1918 Wolseley had the first idea of an electro-
    vehicles – long a domain of coil spring                            magnetic clutch. In the early 1930s the French
    clutches.                                                          firm Cotal built a pre-selector gearbox with an
                                                                       electromagnetic clutch, which was used in                                                                                    Internal combustion engines provide useful         Diaphragm spring clutches, as displayed in         Besides the main function of connecting or
    Parallel to this development, the clutch plate                     luxury cars. Best known were the centrifugal                                                                                 output only over a certain speed range. To be      chart 1, are also being increasingly used in       separating the crankshaft (14) and the trans-
    was optimised. The continually changing                            clutch, which regulated its clamping load by                                                                                 able to use this range for various driving con-    utility vehicles. They have the following advan-   mission input shaft (17), a modern clutch has
    speed and fluctuating torque of an internal                        the centrifugal force, and automatic clutches                                                                                ditions, vehicles must have a gearbox or trans-    tages over the coil spring clutches previously     several further tasks.
    combustion engine produce vibrations that are                      such as Saxomat (Fichtel & Sachs), LuKomat                                                                                   mission. Today, the transmission is generally      used:
    transmitted from the crankshaft, clutch and                        (LuK), Manumatik (Borg & Beck) and Ferlec                                                                                    connected to the engine via a “single-plate dry                                                       It must:
    transmission shaft to the transmission. Noise                      (Ferodo).                                                                                                                    clutch”. Only in special cases are dual-disc dry   • less space                                       • enable gentle and jerk-free starting
    and severe tooth profile wear are the result.                                                                                                                                                   clutches found, such as sports cars and heavy      • insensitivity to engine speeds                   • ensure fast gear changing of the transmission
    Lower flywheel mass and light construction in                      None of these was able to prevail; the com-                                                                                  lorries. Unlike “dry” clutches (i.e. clutches      • lower release loads                              • keep engine torsional vibrations as far away
    modern vehicles amplify these effects, so that                     petition from manual and automatic trans-                                                                                    operating in air as the medium), wet clutches      • longer life                                        from the transmission and thereby decreas-
    clutch plates were provided with torsion                           missions with torque converters was too great.              … while on the European continent the version                    operate immersed in oil or oil mist. They are                                                           ing noise and wear
    dampers and spring-loaded facings.                                                                                             with springs externally located above the clutch cover           generally used as multi-plate clutches in auto-    The diagram on the right, shows a typical          • serve as an overload protection for the entire
                                                                                                                                   prevailed.                                                       matic transmissions, building machinery,           clutch installation and highlights its basic use     drive train (e. g. in case of faulty gearchang-
    While clutch operation for a long time required                                                                                Schwungrad                  flywheel                             special vehicles and predominantly in motor-       as a connection/separation element between           ing)
                                                                                                                                   Druckplatte                 pressure plate
    strong legs, as pedal loads had to be trans-                                                                                   Einstellmutter              adjusting nut                        cycles.                                            the engine and transmission.                       • be durable and easily replaceable
                                                                                                                                   Ausrückhebel                release lever
    mitted via the linkage and shafts, comfort was                     Reprinted with permission from “MARKT”                      Ausrückring                 thrust plate
    improved in the 1930s with the use of control                      magazine for classic cars and motorcycles.                  Kupplungswelle              clutch shaft
                                                                                                                                   Ausrücker mit Graphitring   release bearing with graphite ring
    cables, and in the 1950s with the use of                                                                                       Mitnehmerscheibe            driven plate
                                                                                                                                   Kupplungsdruckfeder         clutch compression spring
    hydraulic actuation.                                                                                                           Kupplungsdeckel             clutch cover




8                                                                                                                                                                                                                                                                                                                                                             9
     Functional Schematic with components                                                                                                                                                                                                                              Chart 1
     The main components of a complete clutch            Engine and transmission are now discon-             The transmittable torque of a single-plate
     unit are:                                           nected                                              clutch is calculated as follows:

     The clutch cover assembly (1) with individual       The facing segment cushion spring (22) can be
     parts consisting of the clutch cover pressing       seen on the cutaway diagram. By applying the             Md = rm x n x µ x Fa
     (2) clutch pressure plate (3) as the frictional     load uniformly across the facing it ensures a
     counterpart on the clutch side for the clutch       smooth and gentle clutch engagement
     plate, the diaphragm spring (4) for generating                                                          where:
     the clamp load, the tangential leaf spring (5) as   Although not a requirement for the basic oper-      rm = mean radius of facings
     a spring-loaded connection between the cover        ational function of a clutch, the importance of     n = number of facings
     pressing and pressure plate for providing           the torsion damper (9) cannot be understated.       m = coefficient of friction of facings
     pressure plate lift, the fulcrum ring (6) and the   Through a combination of coil springs and           Fa = clamp load
     diaphragm rivet (7) for positioning and provid-     friction washers tailored to suit specific          Md = transmittable torque
     ing a mounting for the diaphragm spring.            vehicle applications it can dampen out uneven
                                                         crankshaft rotation, reducing noise levels, and     An example:
     The clutch driven plate (8) with individual parts   avoiding premature wear on transmission             Inner diameter of facing:                134 mm
     consisting of the hub (12), torsion damper (9)      assemblies. (illustrations 2 and 3 deal with        Outside diameter of facing:              190 mm
     with friction device (10) and stop pin (23), the    torsion dampers in detail).                         Clamp load F:                             3500 N
     segment cushion spring (22) and the facings
     riveted to them (11). The flywheel (13) with the    The spigot (pilot) bearing (15) serves as a guide           di +da 134mm+190mm
     spigot (pilot) bearing (15).                        and bearing for the transmission input shaft            dm =      =
                                                         (17).                                                          2          2
     The release mechanism with release bearing                                                                = 162mm mean facing diameter
     guide tube (gearbox quill) (18), release bearing    The guide sleeve (gearbox quill) (18) guides the
     (19) and release fork (20).                         release bearing (19) centrally to the clutch.
                                                                                                                      dm 162mm
                                                                                                                 rm =      =        = 81mm
                                                         The shaft seals at the engine (16) and trans-                 2       2
     How the clutch works.                               mission (21) are designed to keep the clutch
                                                         bell-housing free of oil. Even the slightest
                                                                                                               = 81 x 10 –3m mean facing radius
     The two diagrams on the left show how a             amount of grease or oil on the clutch facings
     single-plate dry clutch with diaphragm spring       can considerably impair the friction coef-
     operates.                                           ficient.                                            Coefficient of friction µ

     With the clutch engaged (left), the drive from                                                          0.27 – 0.32 (for organic facings)
     the crankshaft (14) is transmitted via the fly-                                                         0.36 – 0.40 (for inorganic facings)
     wheel (13) to the clutch cover assembly. The
     clutch driven plate, (8) which is positively                                                            Md (81 x 10 –3 m) x 2 x O,27 x 3.500N.
     engaged to the flywheel and clutch pressure                                                             Md: = 153 Nm
     plate through the action of the diaphragm
     spring (4) transmits the drive via the hub                                                              The transmittable torque of a clutch must
     assembly (12) to the transmission input                                                                 always be greater than the maximum engine
     shaft.(17).                                                                                             torque.

     Thus the engine – transmission connection is
     made.

     To disconnect the drive between engine and
     transmission requires the clutch pedal to be
     depressed, and via the release mechanism
     (cable or hydraulic) the release fork (20) and
     the release bearing (19) connected to it moves
     towards the clutch cover assembly (2), the
     release bearing acts against the fingers of the
     diaphragm spring and depresses the dia-                                                                                                                    Coil spring clutch
     phragm spring fingers. As further pressure is
     applied, diaphragm spring load is relieved, and                                                                                                            For the purpose of showing a complete picture,        Whereas in the case of a diaphragm spring
     with the aid of the leaf springs (5) the clutch                                                                                                            we have included the design of a coil spring          clutch the clamping element and lever form a
     pressure plate moves away from the driven                                                                                                                  clutch. The clutch housing (1) contains metal         single part, the coil spring clutch requires a
     plate. the clutch driven plate is now able to                                                                                                              housings (2) for retaining the coil springs (3).      release lever as well as clamp load springs.
     rotate freely.                                                                                                                                             These springs press the pressure plate (4)            The pressure plate is moved through the entire
                                                                                                                                                                towards the flywheel (5) and thereby clamp the        lifting stroke against the increasing spring
                                                                                                                                                                clutch plate (6). The torque can thus be trans-       pressure. This is responsible for the com-
                                                                                                                                                                mitted via the flywheel (5), the clutch housing       paratively higher actuating force in a coil
                                                                                                                                                                (1) and pressure plate (4) to the clutch plate (6),   spring clutch for the same clamp load. Further
                                                                                                                                                                located on the transmission input shaft (8).          disadvantages are the relatively low speed-
                                                                                                                                                                                                                      resistance as well as the greater space
                                                                                                                                                                                                                      requirement for coil spring clutches.




10                                                                                                                                                                                                                                                                               11
     Clutch plate – Designs, torsion damper and                                                                                                                cushion deflection                                                                                                                  Chart 2
                                                                                                                                                                The middle torsion damper is designed simi-        The facing cushion springs (segments)                Multi-plate cushion spring is the most com-
                                                                                                                                                                larly to the upper one, but is additionally pro-                                                        mon version. The carrier plate of the facings is
       LuK Clutch Course                                                                                                         Chart 2                        vided with two friction washers (8). They are
                                                                                                                                                                made of either organic material or plastic.
                                                                                                                                                                                                                   The lower part of the illustration shows the four
                                                                                                                                                                                                                   most common types of facing springs. The
                                                                                                                                                                                                                                                                        slotted and corrugated at the outer edge,
                                                                                                                                                                                                                                                                        where the facing lies. It functions in essentially
                                                                                                                                                                Organic friction washers offer higher frictional   facing springs lie between the clutch facings.       the same way as the single segment cushion
                                                                                                                                                                coefficients, while plastic friction washers       They ensure gentle clutch engagement and             spring and is primarily used where there is no
                                                                                                                                                                provide less friction, but excellent wear resis-   hence smooth take up of drive. The pressure          room for riveting the single segments to the
                                                                                                                                                                tance.                                             plate of the clutch must at first press the clutch   carrier plate. With more heavily stressed
                                                                                                                                                                                                                   plate against the flywheel, acting against the       clutch plates, the comparatively thin carrier
                                                                                                                                                                The lower torsion damper has a 3-stage friction    spring load of the facing springs. As this load      plate in the area of the torsion damper must be
                                                                                                                                                                assembly dependent on the torsion angle, a         builds up slowly and draws out the engage-           reinforced by a second counterplate.
                                                                                                                                                                two-stage main damper and a separate two-          ment process, the transmission speed can be
                                                                                                                                                                stage idle damper. The separate idle damper,       adjusted to the engine speed with a delay            Intermediate cushion plate spring is generally
                                                                                                                                                                consisting of an idle damper flange (24) and       by the flexing of the plates. Besides smooth         used for heavy commercial vehicles. The seg-
                                                                                                                                                                idle damper retainer plate (25) with idle damp-    take off, good wear resistance, a better wear        ment-like, corrugated panels are riveted on
                                                                                                                                                                ing springs of the 1st stage (10) and 2nd stage    pattern and, a more uniform heat distribution        one side of the carrier plate that is extended to
                                                                                                                                                                (11), is primarily used in cars with diesel        are further advantages of the facing springs.        the outer edge. They therefore act only along
                                                                                                                                                                engines. It acts at lower engine torque’s and      We basically distinguish between four types of       one direction. A disadvantage is the large
                                                                                                                                                                dampens during idling. The three friction          facing cushion spring systems (from left to          flywheel effect of the disc.
                                                                                                                                                                washers (8) of the 3-stage friction assembly       right):
                                                                                                                                                                begin to act at different torsion angles. The 2-
                                                                                                                                                                stage main damper (12) and (13) operates simi-     Single segment cushion spring, in which the
                                                                                                                                                                larly to the above-described systems.              facings on both sides are riveted to thin, bowed
                                                                                                                                                                                                                   segments that in turn are riveted to the drive
                                                                                                                                                                                                                   disc. The advantages are the small flywheel
                                                                                                                                                                                                                   effect of the disc and the easier operation of
                                                                                                                                                                                                                   the cushioning

                                                                                                                                                                                                                   With a dual segment cushion spring, the
                                                                                                                                                                                                                   facings are riveted to two segments lying on
                                                                                                                                                                                                                   top of one another and acting in opposite direc-
                                                                                                                                                                                                                   tions. As with single segment cushion spring,
                                                                                                                                                                                                                   the segments are riveted at the drive disc. The
                                                                                                                                                                                                                   advantage of better cushioning and better utili-
                                                                                                                                                                                                                   sation of the available cushion space is offset
     The clutch plate is the central connecting          Torsion damper                                     spring compression is dampened by a friction                                                           by the disadvantages of a greater flywheel
     element of the clutch. It forms a friction system                                                      assembly (7, 8, 9, 20). The transfer torque of                                                         effect and a higher price.
     between the engine flywheel and the clutch          Torsion dampers have the task of damping           the damper must always be greater than the
     pressure plate. With the clutch engaged, it is      vibrations between the engine and trans-           engine torque, to prevent the hub flange (19)
     pressed between the flywheel and clutch             mission.                                           from striking against the stop pin (6).
     pressure plate and actuated by friction. It
     transmits the drive torque to the transmission      Unlike electrical motors and turbines, internal    In modern vehicle construction, two- and
     input shaft through the hub splines.                combustion engines do not deliver a constant       multiple-stage characteristic curves are often
                                                         torque. The constantly changing angular            required. The stages are produced by springs
     In modern vehicles, only clutch plates with         speeds of the crankshaft produce vibrations        with various spring rates and variously sized
     torsion dampers and spring-loaded facings are       that are transmitted via the clutch and trans-     windows. The friction assemblies also differ
     used. Organic friction facings are used almost      mission input shaft to the transmission, where     largely due to different friction and spring
     without exception in car construction. Metal-       unpleasant rattling noises are the result.         washers. The characteristic curves are usually
     ceramic sintered facings are used primarily         Torsion dampers are designed to minimise           not symmetrical, but display in the direction of
     for special vehicles and tractors.                  these vibrations between engine and trans-         drive a steeper line with a higher stop torque
                                                         mission.                                           than in the ‘coast’or ‘overrun’ direction (for
     The diagram on the left shows a typical car                                                            further details, see “Designs and Torsion
     clutch plate with a two-stage torsion damper,       The constant reduction in flywheel mass and        Damping Diagrams” in the commentary to
     integrated idle damper and a variable friction      the lighter construction of modern vehicles        chart 3).
     control assembly.                                   increase these undesirable effects. Accord-
                                                         ingly, every vehicle today must be subjected to    The upper torsion damper has a simple friction
     Its components are: The clutch facings (1),         special tuning, which has led to a wide variety    device with a friction washer producing con-
     which are riveted to the spring segments (3)        of dampers and designs. Illustration 2 therefore   stant friction and a two-stage characteristic
     with the facing rivets (2). These spring seg-       shows only a few typical designs.                  curve. The hub flange (19) runs between the
     ments are fastened to the retainer plate (17)       On the right of the illustration, three types of   drive disc (17) and retainer plate (18), and is
     with rivets. The retainer plate (17) is aligned     torsion damper are displayed.                      supported by the main damper springs of the
     to rotate on the hub by means of the pivot                                                             1st stage (12) and 2nd stage (13). The hub
     bush (22).                                          They operate according to the following basic      flange (19) can be turned up to 16 degrees
                                                         principle:                                         against the drive disc (17) and retainer plate
     The torsion damper is composed of the idle          The hub (15), supported on bushes between the      (18) before striking the stop pin (6). In this
     damper (with springs 10 and 11), the main           drive disc (17) and the retainer plate (18), is    way the coil springs lying in the windows of
     damper (with springs 12 and 13) and the friction    spring-loaded via the hub flange (19) and the      the clutch and retainer plates, which have
     control assembly (friction washer 8, and fric-      damper springs (10-13) against the drive disc      different spring rates, are tensioned. Vibration
     tion control plate 20, spring washer 7, and         and the retainer plate, so that under load         is converted to friction through the spring
     support washer 9).                                  large or small angular motion is achieved. The     washer (7).

12                                                                                                                                                                                                                                                                                                                           13
     Clutch plate – Designs, torsion damper graphs                                                                                                                                                                                                                         Chart 3
                                                                                                                                                                  Two-stage torsion damper, separate                   Two-stage torsion damper, integrated
                                                                                                                                                                  idle damper.                                         idle damper, variable friction control.
       LuK Clutch Course                                                                                                            Chart 3                       The principles previously described also apply       In the version illustrated on the right, the idle
                                                                                                                                                                  to the design of two-stage torsion dampers           damper springs (10, 11) are located not in the
                                                                                                                                                                  with separate idle dampers, as shown in the          clutch plate, but in the spring windows.
                                                                                                                                                                  centre of the illustration. Added is the separate
                                                                                                                                                                  idle damper (10, 11). It was previously used         Whereas the friction was constant in the
                                                                                                                                                                  primarily for diesel vehicles. Thanks to the         preceding versions, here it is made variable by
                                                                                                                                                                  lighter construction and the resulting high level    the two separate friction washers (8), with two
                                                                                                                                                                  of vibration elimination, this design is also        corresponding spring washers (7). One oper-
                                                                                                                                                                  increasingly being used for petrol engines.          ates in the first main damper stage and the
                                                                                                                                                                                                                       other in the 2nd main damper stage. They take
                                                                                                                                                                  The torsion damper diagram is clearly different      effect only after the corresponding torsion
                                                                                                                                                                  from the preceding one. The torsional charac-        angle is achieved (5 degrees and 8.5 degrees,
                                                                                                                                                                  teristic curve stays flat around the zero posi-      respectively, on the ‘drive’ side and 1 degree
                                                                                                                                                                  tion, to prevent the transmission gears from         and 7 degrees, respectively, on the ‘coast’
                                                                                                                                                                  “rattling” especially with diesel engines at idle    side).
                                                                                                                                                                  speeds. The 1st main stage (12) is applied at
                                                                                                                                                                  barely 10 degrees torsional angle and very low       The torsional characteristic curve and friction
                                                                                                                                                                  torque.                                              damping cannot be predetermined for a
                                                                                                                                                                                                                       vehicle type. Extensive tuning, together with
                                                                                                                                                                  With this type of clutch plate, the idle damper      vibration computations for the vehicle are
                                                                                                                                                                  (10, 11), which produce the flat characteristic      indispensable for optimising the torsional
                                                                                                                                                                  curve at zero, is separately inserted in the         characteristic curves and friction damping.
                                                                                                                                                                  retainer plate and the idle damper cover plate
                                                                                                                                                                  (20) riveted to it. The idle damper flange (18) is
                                                                                                                                                                  connected to the hub. The idle damper stage
                                                                                                                                                                  must therefore always be turned to the maxi-
                                                                                                                                                                  mum, until the mechanism of the main damper
                                                                                                                                                                  stages (12, 13) described above is applied.

                                                                                                                                                                  This clutch plate has a friction washer (8)
                                                                                                                                                                  between the hub flange (17) and the cover
                                                                                                                                                                  plate (16). The frictional force is produced by
     Tasks:                                             Designs:                                             As the springs alone cannot absorb vibrations,       two spring washers located between the hub
                                                                                                             an additional friction assembly is required for      and retainer plate and between the hub flange
     As the friction ‘mate’ between the flywheel and    The designs are selected according to vehicle        damping. It is composed of the friction washers      (17) and the retainer plate (15).
     the pressure plate, the clutch plate has the       type and requirements. The mode of operation         (8) lying to the right and left of the hub flange,
     primary task of transmitting the engine torque     can be displayed by “torsion damping graphs”,        the support washer (9) and the spring washer
     to the transmission input shaft.                   as shown in chart 3, below the clutch discs.         (7). The spring washer presses via a support
                                                        The torsion angle of the torsion damper is           washer (9) on to the right hand friction washer
     The main components are:                           plotted as a function of the given torque. The       and also, via the fixed connection between the
                                                        dashed/dotted line represents the theoretical        cover plate (16) and the retainer plate (15), on
     • drive disc (15)                                  torsional characteristic curve, while the            to the left hand friction washer lying between
     • clutch facings riveted in pairs (1)              shaded band shows the torsional character-           the retainer plate (15) and hub flange (17).
     • splined hub                                      istic curve when friction is taken into account
                                                        (hysteresis).                                        When the engine provides the torque, the
     As already shown in chart 2, it also has several                                                        two springs (12) are first compressed at the
     other tasks, which we briefly mention here                                                              lower spring rate, i.e. damping stage 1 up to a
     again:                                             Two-stage torsion damper                             torsion angle of 4 degrees. In this position, in
                                                                                                             the example shown, they receive a torque of
     It must allow smooth take up and fast gear-        The left hand illustration shows a two-stage         20 Nm.
     changing, keep engine vibrations away from         torsion damper. The four tangential windows
     the transmission and thus prevent trans-           contain coil springs (12, 13) with two different     From this point on, the two springs (13) of
     mission noise generated by gear rattle.            spring rates for the two stages. The springs         damping stage 2 are also engaged. They cause
                                                        lying opposite each other are identical.             the torsional characteristic curve to climb
     The fulfilment of these tasks – an absolute                                                             more steeply up to the stop, at a torsion angle
     “must” for the modern vehicles of today –          The hub flange (17) lying between the drive          of 8 degrees and 140 Nm.
     requires a few additional components:              disc (15) and retainer plate (16) can be turned
                                                        against spring pressure. The drive disc (15) and     The torsion dampers are designed so that the
     • segments (3)                                     retainer plate (16) are firmly connected to the      maximum torque is well above the engine
     • torsion damper (7–13)                            stop pin (6).                                        torque.

                                                        Torque introduced via the drive disc (15) and        If the vehicle is decelerating, the 1st damping
                                                        retainer plate (16) is transmitted via the torsion   stage (12) acts up to an angle of 7 degrees and
                                                        springs to the hub flange (17) and thus to the       a torque of 40 Nm. From this point on, the 2nd
                                                        input shaft.                                         damper stage (13) acts up to a torsion angle of
                                                                                                             8 degrees, corresponding to a torque of 65 Nm.



14                                                                                                                                                                                                                                                                                   15
     Clutch cover assembly – Designs and graphs                                                                                                                                                                                                                                                              Chart 4
                                                                                                                                                                     Diaphragm spring clutch with a triangular leaf         Clutch characteristic curves and load dia-           The dashed line shows the lifting of the press-
                                                                                                                                                                     spring design.                                         grams.                                               ure plate above the release bearing travel. In
       LuK Clutch Course                                                                                                             Chart 4                         First, observe the version presented on the            The lower part of illustration 4 shows some
                                                                                                                                                                                                                                                                                 this case the lever ratio in the clutch is clear: 8
                                                                                                                                                                                                                                                                                 mm release travel corresponds to 2 mm lift, i.e.
                                                                                                                                                                     right in illustration 4. It essentially differs from   examples of clutch characteristic curves and         to a ratio of 4:1 (not considering the elasticity of
                                                                                                                                                                     the standard design by having a different type         load diagrams. They do not directly refer to the     the clutch). This also applies to the ratio
                                                                                                                                                                     of connection between the clutch cover (1) and         designs pictured above them, but apply gen-          between clamp load and release load.
                                                                                                                                                                     the pressure plate (2). As the design does             erally.
                                                                                                                                                                     not allow lugs to be attached to the pressure                                                               In the centre and right-hand diagrams, the
                                                                                                                                                                     plate (2), because of a pot or recessed fly-           The load is specified along the y-axis on the        measurements are contrasted for clutches
                                                                                                                                                                     wheel, a triangular leaf spring arrangement            left, while the abscissa represents the release      with and without considering the spring com-
                                                                                                                                                                     was chosen.                                            travel – in the diagram on the left shows the        pression of the clutch plate cushion springs.
                                                                                                                                                                                                                            release bearing travel as well – and the y-axis      The commentary to illustration 2 already noted
                                                                                                                                                                     The leaf springs are riveted at both ends to           on the right gives the lift of the pressure plate.   the advantages of cushion springs, such as
                                                                                                                                                                     the clutch cover (1), with the pressure plate                                                               gentle clutch engagement and more favour-
                                                                                                                                                                     fastened to the centre of each leaf spring.            The continuous curve in the diagram on the left      able wear characteristics. Without the cushion
                                                                                                                                                                                                                            represents the development of clamp load.            springs, the effective clamp load (solid line)
                                                                                                                                                                     Instead of the cover rib as a support and              With a newly installed clutch plate. (operating      falls off linearly and relatively sharply during
                                                                                                                                                                     fulcrum ring for the diaphragm spring (3), an          point: new pressure plate assy).As the facing        disengagement. Conversely, it increases just
                                                                                                                                                                     additional steel fulcrum ring (4) is used here.        begins to wear the clamp load increases to it’s      as steeply and suddenly during clutch engage-
                                                                                                                                                                                                                            optimum level.                                       ment.

                                                                                                                                                                     Diaphragm spring clutch with a keyhole cover           The clutch plate thickness decreases by about        In the diagram on the right, however, we see
                                                                                                                                                                     design.                                                1.5 to 2 mm during its lifetime. The clamp load is   that the available release load, along which the
                                                                                                                                                                                                                            calculated so that the clutch begins to slip         clamp load diminishes, is about twice as great.
                                                                                                                                                                     The latest design is the diaphragm spring              shortly before the rivets of the clutch facing run   On the other hand, with the clutch engaged, the
                                                                                                                                                                     clutch with keyhole tabs shown in the centre of        against the pressure plate or the flywheel and       clamp load slowly increases along a curve, as
                                                                                                                                                                     illustration 4. The keyhole tabs are formed so         thereby avoiding additional damage.                  the cushion spring must first be compressed.
                                                                                                                                                                     as to pull the rivets (5) outwards. As a result,                                                            Thanks to the relatively gentle climb of the
                                                                                                                                                                     the diaphragm spring (3) is constantly held in         The dashed/dotted line shows the develop-            clamp load curve (solid line), the pronounced
                                                                                                                                                                     position despite wear which will occur at the          ment of the release load, i.e. the load required     load peak at the required release load is
                                                                                                                                                                     diaphragm spring seats. The advantage; uni-            to actuate the new clutch and (compare the           reduced. As long as the pressure plate (2) still
                                                                                                                                                                     form lift throughout the entire life of the clutch.    dotted line) that load after facing wear. The        makes contact with the clutch plate, the clamp
                                                                                                                                                                                                                            release load initially increases until the operat-   load and cushion spring correspond to one
                                                                                                                                                                                                                            ing point is reached, and then slowly drops          another.
     Tasks                                                The diaphragm spring                                Designs                                                                                                       again. The curve for the release load with
                                                                                                                                                                                                                            facing wear has been moved to the left for
     The clutch cover assembly forms a frictional         A central component of all these designs is the     Diaphragm spring clutch, standard design.                                                                     better representation of the ratio of clamp load
     system together with the flywheel and the            diaphragm spring. It is made flatter and lighter                                                                                                                  to release load. The larger the clamp load at
     clutch plate. It is secured to the flywheel via      than the coil springs. Especially important is      The left-hand diagram in illustration 4 shows                                                                 the operating point the greater the release
     the bolts of the cover pressing and acts to          the characteristic curve of the diaphragm           the standard version of a diaphragm spring                                                                    load.
     transmit the engine torque via the clutch plate      spring, which clearly differs from the linear       clutch. The clutch cover (1) encloses the dia-
     to the transmission input shaft. One of the most     curve of a coil spring.                             phragm spring (3) and pressure plate (2). The
     important components of modern vehicle                                                                   pressure plate (2) is connected to the clutch
     clutches is the diaphragm spring (3). It has         Precise design of the diaphragm inside and          cover via tangential leaf springs (7). They are
     almost completely replaced the previously            outside diameters, thickness, opening angle         riveted to the pressure plate (2) at three lugs.
     conventional coil springs in car clutches.           and material hardness allow a characteristic        The tangential leaf springs (7) perform three
                                                          curve to be produced as represented by the          basic functions:
     Other important components: The clutch cover         continuous curve in the left-hand diagram in
     (1) serves as a carrier for the diaphragm spring     chart 4.                                            • lifting the pressure plate during disengage-
     (3), which is supported by fulcrum rivets (5)                                                              ment
     and/or fulcrum rings (4) on the cover. The dia-      While the clamp load with a coil spring clutch      • transmitting the engine torque from the cover
     phragm spring (3) presses the pressure plate         linearly decreases with decreasing facing             to the pressure plate
     (2) against the clutch facing. Tangential leaf       thickness due to wear, here it initially            • aligning the pressure plate
     springs (7) or triangular leaf springs (8) form a    increases and then drops again. The design is
     connection between the cover (1) and the             selected so that the clutch begins to slip before   The diaphragm spring is clamped between the
     pressure plate (2).                                  the wear limit of the facing is reached. The        pressure plate (2) and the clutch cover (1) so
                                                          necessity of a clutch change is thus signalled      as to produce the load required to clamp the
     The balance hole (9) is made to compensate for       in due time, so that further damage, e.g. by an     clutch plate between the flywheel and press-
     the imbalance of the pressure plate (2). Dowel       ingress of the facing rivets, is avoided. More-     ure plate (1). In doing so, it is supported by a rib
     holes (10) assist in aligning the cover (1) to the   over, because of the diaphragm spring char-         in the clutch cover (1) and by a fulcrum ring (4).
     flywheel.                                            acteristic curve the requisite pedal force is       The outside diameter of the diaphragm sits on
                                                          less than with coil spring clutches.                the pressure plate (2). If the clutch is actuated,
                                                                                                              the release bearing presses on the ends of the
                                                                                                              diaphragm spring fingers (3) – the pressure
                                                                                                              plate (2) is lifted and the clutch plate is dis-
                                                                                                              engaged




16                                                                                                                                                                                                                                                                                                                                      17
     Clutch cover assembly – Designs and installation                                                                                                           principles                                                                                                                         Chart 5
                                                                                                                                                                 Diaphragm spring clutch LuK TS                       The seats of the pressure plate (2) protrude        Spring loaded diaphragm spring clutch
                                                                                                                                                                                                                      through the openings in the clutch housing (1).
       LuK Clutch Course                                                                                                          Chart 5                        The diaphragm spring clutch LuK TS is a
                                                                                                                                                                 pressed steel clutch. It is recognised by the
                                                                                                                                                                                                                      The outer diaphragm spring is supported by
                                                                                                                                                                                                                      these seats, and is mounted at the housing by
                                                                                                                                                                                                                                                                          The diaphragm spring clutch with second steel
                                                                                                                                                                                                                                                                          pressing is a special version. Here the fulcrum
                                                                                                                                                                 integration of clutch and flywheel. The poly-        the fulcrum rivets (5) and fulcrum rings (4). The   rings have been completely replaced by a rib in
                                                                                                                                                                 gonal hub (15) of the clutch is bolted together      release bearing is mounted so as to slide on the    the clutch cover (1) and by a sprung second
                                                                                                                                                                 with the V-belt pulley to the crankshaft, which      outside diameter of the polygonal hub. The          steel pressing (16) formed as a further fulcrum.
                                                                                                                                                                 has the corresponding matching taper.                torque is transmitted via the clutch plate (14)     In this way, any wear can be compensated for
                                                                                                                                                                                                                      to the transmission input shaft, formed as a        and automatic re-adjustment is achieved.
                                                                                                                                                                 The drive line is through the clutch cover (1) to    hollow shaft and positioned on the crankshaft       Otherwise this design does not differ from
                                                                                                                                                                 the flywheel fastened to it. The pressure plate      end – between the clutch and the engine. In         those shown in illustration 4.
                                                                                                                                                                 (2) is seated between the clutch cover (1) and       this way, the transmission could be integrated
                                                                                                                                                                 clutch plate (14). It is connected via tangential    into the lower half of the engine.
                                                                                                                                                                 leaf springs (7) to the clutch pressure plate (2).




     Diaphragm spring clutches are used almost         Pulled diaphragm spring clutch                       This construction constrains the design of the
     exclusively in automotive construction today.                                                          clutch in the following way: the outer edge of
     The coil spring clutches used so frequently in    The left clutch in chart 5 was specially             the diaphragm spring (3) is supported by the
     the past have practically disappeared, owing      designed for the VW Golf and Jetta. With             clutch cover (1) and the inner edge by the
     to a number of disadvantages, but especially      respect to the support position of the dia-          pressure plate.
     because of their considerably larger instal-      phragm springs, one speaks of a pulled clutch;
     lation space requirement and greater weight.      of course, because of the reversed installation      A reversal of the diaphragm springs, as with
                                                       compared with the usual design, actuation is         standard clutches, does not occur during dis-
     The most important advantages of the dia-         only through pressing. Usually the drive pro-        engagement. The diaphragm spring (3) is
     phragm spring clutch compared to the coil         ceeds from the crankshaft to the flywheel and        simply lifted via the thrust plate (11), which is
     spring version are:                               then to the clutch and transmission. Here, how-      inserted in the diaphragm spring points. The
                                                       ever, the clutch is initially bolted to the crank-   thrust plate is actuated via a push rod sup-
     • insensitivity to high engine speeds             shaft. The flywheel is attached after the clutch     ported by bearings in the hollow transmission
     • despite the small space, clamp loads are        plate is fixed and then connected to the clutch.     input shaft and extending to the rear of the
       achieved at low release loads                                                                        transmission end, where the release bearing
     • the diaphragm spring fingers also function as                                                        and release arm are located.
       release levers
     • fewer wearing parts

     The diaphragm spring also makes a big differ-
     ence for the driver, as the lower release load
     means that only low pedal efforts need be
     applied.

     Depending on the design and type of clutch
     actuation, we distinguish between:

     • pulled diaphragm spring clutch
     • spring loaded diaphragm spring clutch




18                                                                                                                                                                                                                                                                                                                           19
     SAC clutch cover assembly – design types and                                                                                                              characteristics                                                                                                                          Chart 13
                                                                                                                                                    8

                                                                                                                                                    7
                                                                                                                                                                                                                                        sensor diaphragm spring
                                                                                                                                                    1

                                                                                                                                                                                                                                        pivot point of the
                                                                                                                                                    2                                                                                   main diaphragm spring


                                                                                                                                                                                                                                        adjustment wedge
                                                                                                                                                    6



                                                                                                                                                                                                                                        main diaphragm spring

                                                                                                                                                    11
                                                                                                                                                    10




                                                                                                                                                                             load sensor




                                                                                                                                                                                                                         release load
                                                                                                                                                    4


                                                                                                                                                    3

                                                                                                                                                    5


                                                                                                                                                                                           new      worn                                             worn
                                                                                                                                                    9
                                                                                                                                                                                                                                           new
                                                                              1) cover pressing         5) sensor diaphragm spring    9) pressure plate
                                                                              2) adjustment wedge       6) stop rivet                10) stop plate
                                                                              3) coil spring            7) strap rivet               11) driven plate
                                                                              4) main diphragm spring   8) drive strap

                                                                                                                                                                Figure 1: principle of the self adjusting clutch (SAC)


     As has already been mentioned on page 18, the      The most important advantages of this                This in turn results in a whole range of           Principle of the self adjusting clutch                             Design of a wear-sdjusting clutch with
     diaphragm spring clutch is almost exclusive to     type of design in relation to previous               secondary advantages:                              (SAC):                                                             a load sensor.
     modern vehicle construction.                       formats are:
                                                                                                             • No further need for servo systems (on utility    The LuK wear adjustment feature works on                           The load sensor with the thickness adjustment     An additional advantage is the higher wear
     Further technological development on this          • Low disengagement forces, which remain               vehicles)                                        the following principle: the load sensor deter-                    wedge can be realized in a simple and elegant     capacity, which no longer depends on the
     component has been pushed ahead vigorously           constant throughout the entire service life,       • Simpler release systems                          mines the increased release load due to wear                       manner. Figure 2 shows such a design. In com-     length of the diaphragm spring curve (as
     in the past few years (e.g. diaphragm spring       • Resulting in high levels of driving comfort        • Shorter pedal travel                             and correctly compensates for the reduction in                     parison to the conventional clutch, the only      in conventional clutches), but rather on the
     key hole cover; for description, see pages 17        throughout the entire service life,                • Uniform pedal forces across the entire range     facing thickness.                                                  additional parts required by this design are a    ramp height, which can easily be increased to
     and 18), and has now evolved into the current      • Increased wear reserves, and therefore               of engines                                       Figure 1 shows a schematic representation of                       sensor diaphragm spring (red) and a ramp ring     4 mm for small and up to 10 mm for very large
     new development, the SAC clutch.                     longer service life thanks to automatic wear       • New possibilities for reducing clutch dia-       the SAC. As opposed to the conventional                            (yellow).                                         clutches. This represents a decisive step
                                                          adjustment,                                          meters (torque transfer)                         clutch, the (main) diaphragm spring is sup-                        The sensor diaphragm spring is suspended in       towards the development of clutches with high
     The abbreviation SAC stands for Self-Adjusting     • The over-travel of the release bearing is          • Shorter release bearing travel throughout        ported by a sensor diaphragm spring instead                        the cover. Its inside fingers position the main   durability.
     Clutch.                                              limited by the diaphragm spring stop.                the service life                                 of being riveted to the cover.                                     diaphragm spring. Because of centrifugal
                                                                                                                                                                In contrast to the strongly regressive main dia-                   forces, the wedges that provide the actual
     Higher performance engines of the type gain-                                                                                                               phragm spring, the sensor diaphragm spring                         adjustment are positioned circularly instead of
     ing ground nowadays also need clutches with                                                                                                                provides a sufficiently wide range of almost                       radially. A plastic ring with twelve ramps
     higher-transmission moments, this means that                                                                                                               constant load.                                                     moves on opposing ramps in the cover.
     pedal force has also increased. It may have                                                                                                                The constant load range of the sensor dia-                         The plastic ring (adjustment or ramp ring) is
     been possible to keep this increase within cer-                                                                                                            phragm spring is designed to be slightly higher                    circularly preloaded with three small coil
     tain limits by means of various measures (such                                                                                                             than the targeted release load. The pivot point                    springs which force the ring to fill the gap
     as improved release systems), but, despite this,                                                                                                           of the main diaphragm spring remains station-                      between the diaphragm spring and the cover
     the demands are steadily growing for clutches                                                                                                              ary as long as the release load is smaller than                    when the sensor spring moves.
     with reduced actuation force.                                                                                                                              the load of the sensor spring.                                     Figure 3 shows the release load curves for a
                                                                                                                                                                When facing wear increases the release load                        conventional clutch in new and worn facing
                                                                                                                                                                increases, the opposing load of the sensor                         condition. In contrast, compare the lower
                                                                                                                                                                spring is overcome and the pivot point moves                       release load of the SAC, which has a characte-
                                                                                                                                                                towards the flywheel to a position where the                       ristic curve that remains virtually unchanged
                                                                                                                                                                release load again falls below the sensor load.                    over its service life.
                                                                                                                                                                Graphically, this means that the intersection
                                                                                                                                                                point between the two curves has returned to
                                                                                                                                                                its original location. When the sensor spring
                                                                                                                                                                deflects, a gap develops between pivot point
                                                                                                                                                                and cover, which can be compensated for by
                                                                                                                                                                introducing a wedge-shaped component.


                                                        Figure 2: self adjusting clutch (SAC)
20                                                                                                                                                                                                                                                                                                                                   21
     Dual-mass flywheel (DMF) – Design and function                                                                                                                                                                                                                                             Chart 11
                                                                                                                                                                 Function:                                           interfere with driving comfort, as the engine is     The advantages of the LuK dual-mass
                                                                                                                                                                                                                     not operated in this speed range.                    flywheel at a glance:
       LuK Clutch Course                                                                                                       Chart 11                          Physical study of drive trains has revealed that
                                                                                                                                                                 the resonance speed range can be shifted by         An added positive effect is provided by the          • first-class driving comfort
                                                                                                                                                                 changing the allocation of angular moments.         reduced angular momentum on the engine               • absorption of vibrations
                                                                                                                                                                 As the transmission angular momentum                side: Gear changing is improved thanks to the        • noise insulation
                                                                                                                                                                 increases, the resonance speed, which gener-        lower mass to be synchronised, and the syn-          • fuel saving due to lower engine speeds
                                                                                                                                                                 ates loud noise, drops below the idle speed and     chromesh units are subject to less wear.             • increased gearchanging comfort
                                                                                                                                                                 thus falls outside the engine’s rev range.          The effects on torsional vibrations can be seen      • less synchronisation wear
                                                                                                                                                                                                                     from the diagram With previous conventional          • overload protection for the drive train
                                                                                                                                                                 Using the dual-mass flywheel (DMF), LuK was         flywheels and torsion-damped clutch plates,
                                                                                                                                                                 able to develop a large-scale product that          the torsional vibrations in the idle speed range
                                                                                                                                                                 embodies this principle and thereby keeps           were transmitted to the transmission with the
                                                                                                                                                                 resonance amplitude extremely low.                  least possible filtering, causing the teeth of the
                                                                                                                                                                                                                     transmission gears to strike against one
                                                                                                                                                                 As shown in the “function” diagram, with the        another (transmission rattle).
                                                                                                                                                                 DMF the angular moment is decreased in front
                                                                                                                                                                 of the torsion damper and increased behind it.      The use of a dual-mass flywheel however,
                                                                                                                                                                 The angular moment of the engine is now             filters out the torsional vibrations of the engine
                                                                                                                                                                 assigned to the primary mass of the DMF, while      by the complex construction of the torsion
                                                                                                                                                                 that of the transmission is assigned to the         damper, preventing vibration from affecting the
                                                                                                                                                                 secondary mass including the clutch driven          transmission components – rattling does not
                                                                                                                                                                 plate and the clutch pressure plate. In this way,   occur, and driver comfort is fully ensured.
                                                                                                                                                                 the resonance speed is shifted from approx.
                                                                                                                                                                 1300 rpm to about 300 rpm and can no longer




     The increase in noise sources owing to inad-      Design:                                              The flange (7) in the form of a diaphragm spring
     equate natural damping is a noticeable fea-                                                            engages with its lugs between the curved com-
     ture of modern automotive construction. The       The division of the conventional flywheel into       pression springs (5). It lies frictionally engaged
     causes lie in the reduced weight of the           two parts results in a primary flywheel mass (1)     between the friction and support rings (10)
     vehicles and in the wind-tunnel optimised         with starter ring gear (21) on the engine side,      riveted on the secondary side. The diaphragm
     bodies, whose low wind noise now makes            and a secondary flywheel mass (2) with vent          spring load is designed so that the friction
     other noise sources perceptible. But also sleek   slots (22) for heat transfer, which increases the    torque is greater than the maximum engine
     body designs and extremely low-revving            angular momentum on the transmission side.           torque.
     engines, as well as 5-speed transmissions and
     thin oils, contribute to this phenomenon.         The two masses are connected to one another          An additional friction device (15, 16), bearing-
                                                       via a spring/damping system and supported by         floated on the hub (4), is carried by one of the
     The periodical combustion process of the          a radial ball bearing (11) to allow free rotation.   retaining plates.
     reciprocating engine induces torsional            Sealing is provided by the O-ring (12) and the
     vibrations in the drive train, which as trans-    seal (13).                                           As the spring/damping system is integrated in
     mission rattle and body noise interfere with                                                           the dual-mass flywheel, a rigid version of the
     driving comfort.                                  Two moulded sheet metal parts (1, 3) laser-          clutch plate (B) is used without a torsion
                                                       welded to the outer edge (25) form the ring-         damper.
                                                       shaped grease cavity (8), in which the curved
                                                       compression springs (5) with spring guides (6)       Usually a diaphragm spring clutch with a key-
                                                       are located. Sealing is provided by the dia-         hole cover positioned via dowel pins (20) is
                                                       phragm (9).                                          used as a clutch cover (A).




22                                                                                                                                                                                                                                                                                                                    23
     DFC – Damped Flywheel Clutch – (Compact-DMF)                                                                                                                                                                          Layout and function                                                                                                              Chart 12
                                                                                                                                        6                                                                                  Total technology
                                                                                                                                        9
                                                                                                                                        4                                                              3                   Clutch cover:
                                                                                                                                        12                                                             11

                                                                                                                                        21                                                             34
                                                                                                                                                                                                                           The pot-shaped primary mass (1) which forms
                                                                                                                                        1                                                              39
                                                                                                                                                                                                                           the damper housing for the arc springs, the
                                                                                                                                                                                                                           cover (3) that belongs to it, the secondary
                                                                                                                                        2                                                              12
                                                                                                                                                                                                                           mass (2), and the cover ring (7) are deep-drawn
                                                                                                                                        8                                                              38
                                                                                                                                                                                                                           from one single blank.
                                                                                                                                        13                                                             37
                                                                                                                                                                                                                           The secondary mass (2) and the pressure
                                                                                                                                        17                                                             30                  plate (25) are made of gray cast iron, which has
                                                                                                                                        18                                                             31                  extremely good thermal conductivity proper-
                                                                                                                                        19                                                             36                  ties. The carefully designed ventilation and air-
                                                                                                                                        15                                                             27                  cooling system provides excellent cooling
                                                                                                                                                                                                       32                  effect for the flywheel and the pressure plate.
                                                                                                                                                                                                       24                                                                            Bearings:                                          Installation and logistics:
                                                                                                                                        41                                                             33

                                                                                                                                                                                                       25
                                                                                                                                                                                                                           Damper springs:                                           A special design of bearing makes it possible      The DFC drastically reduces the effort and
                                                                                                                                        40
                                                                                                                                                                                                                                                                                     for it to be arranged inside the crankshaft bolt   expenditure needed for installation during
                                                                                                                                        14                                                             29
                                                                                                                                                                                                                           The arc spring damper, already in use in the              housing. The bearing (14) is subjected con-        vehicle manufacture, as well as in the work-
                                                                                                                                        43                                                             28
                                                                                                                                                                                                                           dual-mass flywheel, is integrated in the DFC              stantly to the rotational vibrations of the        shop.
                                                                                                                                        16                                                             26
                                                                                                                                                                                                                           unit. The spring damping system is required to            engine, with no further relative motion occur-
                                                                                                                                        5                                                              20                  fulfil two contradictory requirements.                    ring between the inner and outer ring. It must     The cover assembly can be removed from the
                                                                                                                                        35                                                             10                                                                            also withstand peak operating temperatures.        unit, in order to replace the driven plate if
                                                                                                                                        22                                                             42                  1. Under normal operating conditions, the                 These operating conditions impose an extra-        necessary (oil contamination etc.).
                                                                                                                                        7                                                              23                     irregular shape of the engine vibration curve          ordinarily high burden on the bearing.
                                                                                                                                                                                                                              means that there are only low working                                                                     A further advantage is the arrangement of the
                                                                                                                                                                                                                              angles in the damper. In this operating                The solution is an integrated bearing concept      components: All the parts are matched to one
                                                                                                                                                                                                                              range, low spring rates associated with low            with special seals, which guarantees lubri-        another, and are, as a rule, delivered and
      1) primary flywheelmass     4) arc coil spring          11) support plate               18) retainer plate                                     25) pressure plate with friction surface   36) segment rivet
         and damper housing       5,10) gland seal            12) balance weight              20) dowel                                              28) fulcrum ring                           37) driven plate segment      damping qualities are required to attain opti-         cation throughout the entire service life. A       replaced complete.
      2) secondary flywheelmass   6) arc spring guide race    14) deep grooved ball bearing   21) dowel pin                                          29) stretch bolt                           38) lining rivet
         with friction surface    7) cover ring and flange    15) socket head cap screw       22) grease cavity                                      30) leaf spring                            39) linings                   mum vibration damping.                                 thermal insulation cap also resists even the
      3) cover                    8,13,26) ventilation slot   16,19,27,35) diaphragm spring   23) laser welding                                      31,40,43) rivet                            42) inertia ring
         (primary flywheelmass)   9) starter ring gear        17) load friction plate         24,32) access opening for removal/installation tool    33) hub                                                                                                                         most extreme operating temperatures.               The number and variety of types can be
                                                                                                                                                                                                                                                                                                                                        reduced dramatically, which accordingly cuts
                                                                                                                                                                                                                                                                                                                                        down on logistics and overall expenditure
                                                                                                                                                                                                                                                                                                                                        (parts stocks, catalogue applications, etc.).
     Layout and function                                               There were two basic problems which                                          With regard to environmental protec-
                                                                       needed to be overcome in this context:                                       tion positive results are also becoming
                                                                                                                                                                                                                                           400
     The dual-mass flywheel provides a highly effi-                                                                                                 apparent.
     cient system for the damping of torsional                         1. The installation space in front transverse                                                                                                                                        Vibration curve in the
     vibrations in the drive train. It has proved its                     engine vehicles is very restricted.                                       • Thanks to the excellent noise reduction at                                                            normal drive condition
                                                                                                                                                                                                                                           300              with low damping
     worth in the prestige vehicle sector.                             2. The price structure on which this class of                                  low engine speeds, there are fewer gear
                                                                          vehicle is based makes cost-optimised                                       changes, as well as the average operating




                                                                                                                                                                                                                             Engine [Nm]
     The middle range sector and those referred to                        solutions essential.                                                        speeds of the engine dropping.
     as compact vehicles, with transverse engines                                                                                                                                                                                          200
     are steadily growing in demand. The demands                       The DFC is already effectively cutting out                                   • The degree of efficiency of the system as a
     for used engines and those with reduced pollu-                    engine vibrations when idling; in other words,                                 whole is boosted, and the fuel consumption                                                                                Large damping on
     tant emissions is also growing, but at the same                   there is no more gearbox rattle, and the                                       and emissions of pollutants usually associ-                                          100                                  load change
     time this is leading to increased irregularities in               unpleasant drumming of the bodywork at cer-                                    ated with this are reduced.
     engine performance, especially in the direct-                     tain engine speed ranges has become a thing
     injection Diesel engine sector. LuK has now                       of the past.                                                                 The DFC is an integrated assembly of dual-
     developed the DFC, to provide top-of-the-range                                                                                                 mass flywheel, cover assembly, and driven                                                0
     driving comfort for the middle range sector.                                                                                                   plate.                                                                                       0     10            20              30          40
                                                                                                                                                                                                                                                                                Torsion angle [°]
                                                                                                                                                                                                                                                     Calculated
                                                                                                                                                    It is supplied complete to the vehicle manufac-                                                  Measured
                                                                                                                                                    turer, including the crankshaft bolts, and can
                                                                                                                                                    then be fitted as a unit in one operation on the                       2. With the typical load changes (e. g. full
                                                                                                                                                    vehicle assembly line. The crankshaft bolts can                           acceleration), the engine vibration curve
                                                                                                                                                    be tightened through drillholes in the driven                             then changes, which to a considerable
                                                                                                                                                    plate and the cover assembly.                                             degree leads to the creation of noise. This
                                                                                                                                                                                                                              effect can only be offset by a torsion damper,
                                                                                                                                                    Other advantages in relation to                                           which has an extremely low spring rate and,
                                                                                                                                                    conventional systems:                                                     at the same time, a high damping quality.

                                                                                                                                                    • Lower weight                                                         The arc spring resolves this contradiction, at
                                                                                                                                                    • Less imbalance of the system as a whole                              high operating angles it provides a high damp-
                                                                                                                                                    • Reduced set up height tolerances for the                             ing effect at very low spring rates. At normal
                                                                                                                                                      diaphragm spring.                                                    operating angles it provides a low damping
                                                                                                                                                                                                                           effect at low spring rates, providing perfect
                                                                                                                                                                                                                           isolation against vibration.



24                                                                                                                                                                                                                                                                                                                                                                                      25
     Index of terms                                                                                                                                                                                         Index of terms
                                                                                           Table                                                                                  Page                                                                                                            Table                                                                                  Page


     Adjuster ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20                              L aser welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24
     Air gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24                      Leaf spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 20, 24
     Applied force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14 18                      Lift. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 11, 16, 17
     Arc spring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24, 25                    Lifting stroke. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
                                                                                                                                                                                                            Load sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21


     Balance hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16, 18
                                                                                                                                                                                                            Main damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14
                                                                                                                                                                                                            Metal housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

     Centrifugal clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     Clutch brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     Clutch facing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10 12, 14, 24                 Overload protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 23
     Clutch housing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 16, 17, 18, 19
     Clutch plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 5, 11, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 12, 18, 19, 20, 22
     Clutch pressure plate. . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10
     Cone clutch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5, 6                        P olygon hub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18,19
     Cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20, 22, 24, 25                Pressure plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     Cover plate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15               Pressure plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 4, 5, 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 16, 17, 18, 19, 20, 24, 25
     Crank shaft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10                       Primary flywheel mass. . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24, 25
     Cushion spring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 12, 13, 14


                                                                                                                                                                                                            R elease bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10
     Damped flywheel clutch . . . . . . . . . . . . . . . . . . . . . . 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24                                         Release fork. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10
     Diaphragm spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3, 4, 5, 11, 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 14, 15, 16, 17, 18, 20, 22, 24   Release lever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     Diaphragm spring clutch . . . . . . . . . . . . . . . . . . . . . . . 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 11, 16, 17, 18, 19                   Release system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     Diaphragm spring clutch bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7,11                                       Resonance frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     Dowel hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16                          Retainer plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 12, 13, 15
     Dual cushion spring . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13                             Return spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     Dual mass flywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     Dual segment cushion . . . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12,13

                                                                                                                                                                                                            S AC clutch plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
                                                                                                                                                                                                            Starter ring gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24
     F lywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 18               Secondary flywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24, 25
     Friction device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10                           Segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10
     Friction material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 15, 22               Sensor – diaphragm spring. . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     Friction plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 15                            Shaft seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10
     Friction washer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10 ,12, 15, 22               Single segment cushion . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13
                                                                                                                                                                                                            Spacer bolt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10
                                                                                                                                                                                                            Spigot bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,10
                                                                                                                                                                                                            Spring band clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     Gearbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 14                                                                                                          Spring segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14, 24
     Gearbox snout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,10                           Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
                                                                                                                                                                                                            Stop bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 13, 14
                                                                                                                                                                                                            Stop plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14, 22
                                                                                                                                                                                                            Stop ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10
     Hub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3, 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 14, 22, 24          Stop spring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18, 19
     Hub flange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15


                                                                                                                                                                                                            T angential strap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 16, 18, 19
     Idle damper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14, 15                     Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 11, 14, 16
     Idle damper flange . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15                     Torsion damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 14, 15
     Idle damper stop plate . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15                       Triangular straps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
                                                                                                                                                                                                            Twin plate clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9


     L aser welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24
     Leaf spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 20, 24
     Lift. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 11, 16, 17
     Lifting stroke. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     Load sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21




26                                                                                                                                                                                                                                                                                                                                                                                                                     27

				
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