To ensure a smooth start of the car
This is the primary function of the clutch. Before the car starts, naturally start the engine. And when the car starts, the car is gradually accelerating from a completely static state. If the driveline (which is in contact with the entire car) is rigidly connected to the engine, the gear will suddenly roll forward, but it will not start. This is because the car from the static to the forward, there is a great inertia, the engine caused a lot of resistance torque. Under the action of the moment of inertia resistance, the engine in the instantaneous speed dropped sharply to the lowest stable speed (usually 300-500RPM) the following, the engine is stalled and can not work, of course, the car can not start.
So we need the help of the clutch. After the engine starts, before the car starts, the driver first depresses the clutch pedal, separates the clutch, disengages the engine and the driveline, hangs the gearshift, and then loosens the clutch pedal to gradually engage the clutch. In the process of joining, the engine resistance torque gradually increased, it should also gradually step on the accelerator pedal, that is, gradually increase the fuel supply to the engine, so that the engine speed is always maintained at the lowest stable speed, At the same time, due to the tightening of the clutch is gradually increased, the engine transmission to the drive wheel torque will gradually increase to the traction enough to overcome the starting resistance, the car from the static movement and gradually accelerated.