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					Dual Clutch Transmission
A.Jaya Krishna (08MEA008) 29/07/2009

Contents:
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Introduction Manual transmission Automatic transmission Dual clutch transmission Purpose Modules Dual clutch transmission shafts Multi plate clutches Control module Working Performance issue Advantages & disadvantages

Introduction:
Most of us know that there are 2 types of transmission:
 

Manual transmission Automatic transmission

Another type of transmission has been evolved that combines the features of both manual and automatic transmissions. It is dual clutch transmission(DCT).

Manual transmission:
The changing of gear ratio in this type includes:
  

Pressing the clutch pedal Moving the shift stick to attain desired gear ratio Removing the pressure on clutch pedal

By applying pressure on clutch pedal we disengage engine from gear box. This allows changing of gear ratio.

Automatic transmission:
   

These doesn’t have clutch pedal. These also do not have gear shifts. Uses torque converter in place of clutch. Uses planetary gear set to change gears.

Dual clutch transmission:
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It uses 2 clutches, each clutch is operated independently. Gears are parted into 2 sets. Each set is operated with one clutch. It has no clutch pedal. ECM system handles electric motor actuation of the dual clutch. Transmission control ensures that two gears are always engaged simultaneously.

Purpose:
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Manual and automatic transmissions disengages power flow while changing gear ratio. This results in loss of efficiency. Manual transmissions cause shift shocks.

Modules:
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Dual clutch transmission shafts. Multi-plate clutches. Control module.

Dual clutch transmission shafts:
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As the gears are parted into odd and even gears, each set is connected to a different shaft. The second shaft is nested inside the first shaft. Outer shaft feeds 2nd and 4th gears, while inner one feeds 1st, 3rd, 5th gears.

Multi-plate Clutches:
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 

These are used in place of torque converters. It is operated by hydraulic pressure. 2 types: wet and dry clutches.

Control module:
It is a micro controller fed with following sensors:
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Throttle position sensor Transmission sensor Clutch travel sensor Drive gear sensor

Control module gives signals to actuators to change the gears.

Schematic-Working:

Performance issue:
The comparison between manual and DCT is shown,

Both manual and DCT have same top speed but the acceleration is good for DCT.

Advantages & Disadvantages:
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Improves fuel economy.
Provides smooth acceleration. No torque interruption. Ideal for high performance cars. It costs more. It is also difficult to replace existing transmissions with DCT’s.

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References:
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Bernd Matthes, “Dual clutch transmissions-lessons learned and future potential”, dated 11th April 2005, SAE Technical papers. Automotive Mechanics by Crouse and Anglin.

Automobile Engineering by K.K.Jain. Automotive hand book by Bosch. www.automobileelektronike.com www.howstuffworks.com www.wikipedia.org

Thank you


				
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posted:10/30/2009
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