Clutch role sum up the following points:

 1. To ensure a smooth start car 2. Easy to shift 3. To prevent the transmission system overload 4. To reduce torsional vibration impact

1. To ensure a smooth start of the car: before the start of the car at a standstill, if the engine and gearbox is rigidly connected, once the file on the hook, the car will suddenly suddenly pushed forward due to power, not only cause damage to mechanical parts, and drive The force is not enough to overcome the huge inertial force generated by the car forward, so that the engine speed dropped sharply and turn off. If the clutch is used at the beginning to temporarily separate the engine and the transmission and the clutch is gradually engaged, the clutch torque will gradually increase from zero due to the friction between the active portion and the driven portion of the clutch, The driving force of the car is also gradually increased, so that the car started smoothly.

2. Easy to shift: the car driving process, often with different gearbox stalls to adapt to changing driving conditions. If there is no clutch to temporarily disengage the engine from the gearbox, the force transmitting gear engaged in the gearbox will not be removed due to the load and the pressure between the meshing tooth faces will be large and difficult to separate. The other treats the meshing gears which are difficult to mesh due to the unequal circumferential speed of the two. Even forced into the mesh will have a great tooth-end impact, easy to damage the machine. After the clutch and the engine are temporarily separated from the transmission, the pair of originally engaged gears are removed due to the load and the pressure between the engagement surfaces is greatly reduced to be easily separated. The other pair of gears to be engaged, because the driving gear and the engine after the moment of inertia is very small, the use of appropriate gear shift action can make the gear circumferential speed equal to or close to equal, so as to avoid or reduce the impact between gears.

3. To prevent overloading the powertrain: the car emergency braking, the sudden sharp deceleration of the wheel, and the engine connected to the transmission due to the inertia of rotation, still maintain the original speed, which tend to produce in the transmission system is much larger than the engine torque The moment of inertia, so that the drive train parts easily damaged. Because the clutch is by friction to transfer torque, so when the drive train load exceeds the friction can transfer the torque, the clutch main and follower parts will automatically slip, which played a role in preventing the drive train overload .

4. To reduce torsional vibration impact: the working principle of the car engine determines the output torque is not stable. During the power stroke, the gas explosion in the combustion chamber produces a great amount of impact torque, whereas on other strokes it is by the inertial anti-drag engine. Although the inertia of the engine's own rotating system can reduce the torsional vibration, the remaining impact force will still adversely affect the subsequent gearbox and transmission shaft. The clutch damping spring (tangential distribution), can significantly reduce the torsional vibration caused by the engine to extend the life of gear.