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Automotive Tips --- Continuously Variable Transmission


									Automotive Tips --- Continuously Variable Transmission

Continuously Variable Transmission
Continuously Variable Transmission (CVT - continuously variable transmission)
It does not have the traditional gear transmission structure, but rather the two can
change the diameter of the drive wheel, put on the middle to bring drive transmission.
Basic principle is to drive around in a cone with both ends of the pulley, the pulley by
the diameter size of the hydraulic stepless change in size. Started, the active pulley
diameter into the largest diameter, while the passive pulley into a minimum, to
achieve a higher transmission ratio. As the speed increases and changes in the various
sensor signals, the computer control system to determine control of the control of two
wheeled hydraulic, eventually changing the pulley diameter of the continuous changes,
which in the whole process to continuously variable transmission. The greatest feature
of CVT is stepless control of output speed ratio, in the sense of moving to fill the gap,
so there is no shift feel. Shift crew can not feel the impact, dynamic interface
consistency. This CVT is moving to increase the comfort, speed will be faster than the
automatic transmission.

Continuously Variable Transmission Systems - Development Overview

Continuously Variable Transmission
CVT technology, already had 100 years of history. Germany's
Mercedes-Benz is in the car with the originator of CVT technology, will be back in
1886 V-rubber belt CVT installed in the company's gasoline engine car. In
1958, the Dutch company DAF, Dr. H. VanDoorne called Variomatic the successful
development of the double V-type rubber belt-type CVT, and equipment
manufactured in the DAF Daffodil car on more than one million of its sales. However,
due to the presence of a rubber belt CVT defects: power limited (limited to 135Nm
less torque), clutch job instability, hydraulic pump, transmission belt and clamping
bodies larger energy loss, which was not generally accepted automotive industry.

However, to improve performance and CVT transmission with a transmission power
limit of the research has been ongoing, will be integrated into the CVT torque
converter systems, the main, driven wheel clamping force to achieve electronic
control, the use of energy-saving pump in the CVT, belt with metal with a rubber band
instead of the traditional. New technological advances have overcome previous
technical defects CVT system, resulting in greater transmission torque capacity and
good performance of the available second-generation CVT.

90 20th century, automobile sector research and development of CVT technology
increasing attention, especially in the micro-car, CVT is considered the key
technology. The rapid development of global science and technology, making the new
electronic technology and control technology has been used to the CVT in the.
First half of 1997, Japan's Nissan developed the car used in the 2.0L CVT.
On this basis, in 1998, Nissan has developed a medium-sized sedan designed to
include a manual shift mode of the CVT. New CVT using a newly developed
high-strength, wide belt and a high-hydraulic control system. By using these advanced
techniques to obtain greater torque capacity CVT Nissan research and development of
electronic control technology, the transmission ratio of the whole file to change the
implementation of electronic control, the car has been under downhill speed control
can engine brake, and In order to smooth the wet roads increase the ratio to prevent
slipping. Nissan plans to its CVT to expand the application range from 1.0L to 3.0L

Mitsubishi has selected the smooth CVT transmission without energy loss in direct
injection engine power to drive the car. V-belt / drive wheel mechanism ensures that
all engine power rate pass smoothly without interruption. Eradication of the
traditional CVT automatic transmission shift through the gears teeth to fight the
phenomenon of time to gain a more satisfactory response and control. Mitsubishi
ready to use direct injection engines (1.5L or smaller) and CVT combination.

Japan's Fuji Heavy Industries CVT also has 15 years of development
experience. May 1997, Fuji Heavy Industries to its mini-vehicle equipped with Vistro
all computer-controlled E-CVT (with six-speed manual shift mode of the CVT). The
driver can not operate the clutch on a six-speed transmission. Subaru Pleo micro car
in the lock-type torque converter with a kind of electronic control type CVT, through
the small torque converter can lock the slide to keep the minimum planetary gear is
used to switch the forward gears / back file. Gear ratio range from 1:10-5.5:1.

First half of 1999, U.S. companies Ford and ZF of Germany for the Ford car and light
truck production CVT. Batavia, Ohio, in the new joint venture and in 2001 production
from the Ford design, with electronic management of CFT23 type CVT. ZF-designed
CVT is a torque converter type transmission, the engine used for the installation of
horizontal steel front wheel drive vehicle production. ZF company can install the front
wheel drive longitudinal engine rear wheel drive cars and car production CVT series.
ZF company said: Compared with the fourth gear automatic transmission, CVT
system can accelerate the performance of the 10% increase in fuel economy by 10%
-15%. Compared with the lock-type torque converter, CVT systems under the premise
of not leaking more efficient. Ford and the company is designing a light truck that
matches all the traction drive CVT, including rear-wheel drive and all-wheel drive
truck. Traction drive using special synovial fluid of movable along the slider instead
of belt and pulley. Sliding part of the relative position of the transmission ratio of the
decision by a very thin layer of fluid between parts oil to pass power.

German company ZF mid-1999 to provide steel for the Rover216 cars driven
VT1-type CVT. This includes helical gear or CVT transmission, the right hydraulic
system, wet clutch. ECU in the system allows integration of mechanical, hydraulic
and electronic systems further combinations, which make better use of the unique
advantages of various systems.

Germany's Bosch electronic CVT control system is based on sensors and
actuators based on the electronic control unit / hydraulic module. Bosch has
independent components, actuators, sensors and ECU Shift to form a separate module,
just to increase transmission manufacturers an integrated control unit.

Continuously variable transmission system - working principle

Continuously Variable Transmission
CVT system includes active wheel, driven wheel, metal belts and hydraulic pumps
and other basic components. Metal band made up of two bundles of metal rings and
hundreds of metal composition. Driving wheel units and idler wheel units by the
movable plate and fixed plate composition, and the tank can be wheeled around the
side of the slide in the shaft, the other side is fixed. Movable plate and fixed plate are
conical structures, they form a V-groove to cone and V-belt metal meshing. The
engine output shaft power output of the first initiative passed to the CVT wheel, and
then passed through the V-belt to the driven wheel, and finally by the reducer,
differential transmission to the wheels to drive the car. Work through the driving
wheel and driven wheels of the movable plate for axial movement to change the
driving wheel, driven wheel cone and V-belt meshing working radius, thus changing
the transmission ratio. Axial movement of movable disk capacity is needed by the
driver through the control system regulating wheel, driven wheel cylinder hydraulic
pressure to achieve. As the driving wheel and idler wheel work continuously
adjustable radius can be achieved in order to achieve a continuously variable

In the metal belt CVT hydraulic system, driven role is to control the metal cylinder
with the tension, to ensure that power from the engine efficient and reliable delivery.
Active Cylinder Control Bevel wheel position along the axial movement of the active
metal with a wheel moving along the V-groove, the length of the metal with the same,
the driven wheel on the metal strip along the V-groove in the opposite direction of
change . Metal band in the driving wheel units and idler wheel units on the radius of
gyration change, achieve continuous speed ratio change.

Car to start, the smaller the radius of the capstan work, get a larger transmission ratio
transmission, drive axle in order to ensure that sufficient torque to ensure the car has a
higher acceleration. As the speed increases, the work of driving wheel radius
decreases, the working radius of the driven wheel corresponding increase, CVT
transmission ratio declined, making cars to travel at higher speed.

Continuously Variable Transmission Systems - Features
Continuously Variable Transmission
1 economy
CVT can achieve very wide range of continuously variable transmission, power train
and engine to gain the best match working conditions, improve vehicle fuel economy.
Germany's Volkswagen car on their own GolfVR6 installing a 4-AT and
CVT for ECE ECE urban cycle and suburban circulation tests to demonstrate that
CVT can effectively save fuel (see Table 1)
Table 1 to install 4-AT and CVT's public companies GolfVR6 the fuel
consumption compared
Test fuel 4-ATCVT
ECE urban cycle, L/100km14.413.2
ECE rural / remote loop, L/100km10.89.8
90km / h constant speed, L/100km8.37.0
120km / h, L/100km10.39.2

2 dynamic
Back-up power determines the vehicle's climbing ability and vehicle
acceleration. Greater reserve power vehicles, the driving force of the better car.
Because of the continuously variable transmission CVT features access to back-up
power most of the transmission ratio, the CVT is better than the dynamic performance
of mechanical transmission (MT) and automatic transmission (AT). Table 2 is
mounted on 4-AT and CVT's Chrysler Voyager car power comparison, the
installation CVT has a better car dynamic performance.
Table 2 install 4-AT and CVT in grams to Eisner dynamic contrast Voyager cars
Item 4-ATCVT
Acceleration time (s)

3 emissions
CVT speed ratio, wide range of work, enabling the engine to optimum working
conditions, thus improving the combustion process, reduces exhaust emissions. ZF
CVT production company will own loading test, exhaust emissions than to install
4-AT car has dropped by about 10%.

4 Cost
CVT system is simple, the number of components than the AT (about 500) less (about
300), when car manufacturers began mass production, CVT cost will be smaller than
AT. As a result of the system saves fuel, as well as large-scale production systems,
materials innovation, CVT components (such as the transmission belt or drive chain
wheel, driven wheels and the hydraulic pump) in production costs, will be reduced by
20% -30% .

Continuously Variable Transmission Systems - Development
Continuously Variable Transmission
The future development of CVT technology can be analyzed from the following four

CVT components
Push belt and chain drive transmission in torque capacity and specificity to further
strengthen. As the rapid increase in the number of products, with products to further
automate the process, the cost will be significantly reduced.
CVT dedicated hydraulic pump will be promoting. Used to automatically jump
together and emergency braking small electronic drive pumps, and for the normal
operation of the engine-driven pump to work together to further improve the overall
transmission efficiency.
Pulley system optimal design will not only reduce the quality and reduce costs, and
ensure that in the main, driven wheel and drive with the maximum transmission
torque between. Different components, microprocessors, and test equipment for
electronic control differences, leading to very high research and manufacturing costs,
the electro-hydraulic control through modular design and mass production of the
decrease of the function to be flexible and low cost organic combination.
CVT because more and more into the market, manufacturers have begun research and
development work CVT dedicated transmission fluid, which will further optimize the
operating characteristics CVT.

CVT transmission
A number of different arrangements possible, not only because of differences and
requirements of automotive drive (FWD, RWD, AWD), but also due to the increase
continuing transmission ratio coverage requirements.
Will bring electronic transmission ratio, speed, pressure and torque of a faster, more
precise control, to ensure better regulation of the engine and transmission, providing a
different travel modes, such as sports, comfort, and cruise control, allowing users to
access a full range of "driving pleasure."

Integrated control of engine and CVT
More accurate, faster CVT control, together with the engine control integrated into the
powertrain management system, making further reduce fuel consumption and
emissions. Integrated engine management unit with the first prototype of a CVT
transmission has been driving cycle test.

Hybrid CVT transmission
CVT will bear with flywheel energy storage hybrid powertrain design an important
role. CVT transmission with a hybrid vehicle may reduce fuel consumption 30%,
emissions may be reduced by 50%.

Continuously Variable Transmission Systems - Applications
Continuously Variable Transmission
In 1987, the Japanese Subaru vehicles equipped with CVT transmission to market
success. Ford and Fiat in Europe will VDT-CVT equipped in displacement to 1.1L to
1.6L the cars on. As technology advances, the energy crisis lead to a worldwide
energy conservation and environmental protection awareness, at the conclusion of the
first generation of CVT based on the experience, developed a better performance,
higher capacity Zhuanju CVT. Currently, the world's major car
manufacturers to improve the competitiveness of their products are strong R
& D work carried out CVT. Now NISSAN, TOYOTA, FORD, GM, AUDI
and other famous brands, there are cars equipped with CVT transmission sales, the
world's annual output of CVT car has nearly 500,000. It is noteworthy that,
equipped with CVT auto market, from the initial Japanese, European, have infiltrated
the North American market, the development of CVT cars are the main trends of
today's cars.

Our country has a huge automobile market, auto industry is one of China's
national industry. However, the Chinese automotive industry required automatic
transmission (AT) all the dependence on imports, which makes domestic cars
equipped with AT, the costs increase greatly, and equipment development and
production of their own CVT transmission, the cost increase, which indicated that the
market outlook CVT optimistic.

China is currently considering the development of Automatic Transmission problems.
Since the "Ninth Five-Year" period cars belt type stepless
automatic transmission research and development of the country have been included
in major scientific and technological research programs, to track the
world's technology and vehicle development for the Chinese situation.

Continuously Variable Transmission - using items

Continuously Variable Transmission
For the proper use of the CVT should note the following:
1, driving, do not pull the lever "N" file.
2, back from the forward variable, changing from the back forward file, to be
completely stopped cars, slam the brake pedal while operating the gear shift, or has
the potential to damage the gearbox.
3, when going downhill, you should use "S" low profile or
manual mode, use the engine braking effect, avoid prolonged braking to brake shoe
produces heat recession, making the braking performance deteriorated.
4, due to the structure and working principle of CVT, all the controls are carried out
by internal hydraulic completed. It should be in accordance with the time limit
specified by the manufacturer check the CVT of oil, fuel, and regular replacement of
oil meet the manufacturers requirements.
5, in order to maximize the improvement of its fuel economy, driving is best to use the
automatic mode CVT gearbox. This keeps the whole engine and transmission to keep
the best match of the state, maximizing the use of engine torque and power output,
speed up the economy to improve fuel economy.
6, due to the structure of CVT, if its related components or circuit after maintenance
or power failure must be a special kind of internal set-up process can play a normal
state to CVT. So, relative to the maintenance of CVT gearbox repair units should go
to a professional repair.

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