1. Ensure a smooth start car.
Before starting the car is stationary, if the engine and gearbox are rigidly connected, once in gear, the car will suddenly due to a sudden power plug pediment, not only will cause mechanical damage, but the driving force is not enough to overcome the car pediment enormous inertia force generated, a sharp decline in the rotational speed of the engine stall. If you use the clutch at the start temporarily separated from the engine and gearbox, and the clutch engagement gradually, due to the existence of the phenomenon of slippery ground between the active part of the clutch and the driven part, you can make outgoing clutch torque increases from zero, the car's driving force is gradually increased, so that the car started smoothly.
2. Easy to shift.
Cars with the process, often for different transmission gear to adapt to changing driving conditions. If you do not clutch the engine and gearbox temporary separation, then the power transmission gear meshing gearbox load does not drop because of its engaging tooth surface pressure between the large and difficult to separate. Another gear due to unequal treatment of both peripheral speed and difficult to engage. Even if forced into engagement with the teeth side will have a huge impact, easily damaged parts. The use of the engine and gearbox clutch shift after temporary separation, then the original pair of gears meshing load dropped because the pressure between the mating surfaces is greatly reduced, it is easy to separate. And another pair of gears to be engaged, the rotation of the drive gear and a small moment of inertia of the engine separately using the appropriate action can shift the gear to be engaged with the peripheral speed equal to or nearly equal, to avoid or reduce the impact between the gears.
3. Prevent transmission system overload.