Clutch is installed between the engine and the transmission, is directly associated with the engine in the vehicle powertrain Assembly. Normally clutch and flywheel of the engine crankshaft are installed together, was cut off and power transmission between engine and powertrain components. Car in the whole process from start to driving, drivers can be manipulated as needed the clutch, the engine and transmission to temporarily separate, or gradual engagement, to cut off or passes the engine to the transmission output power.
It is between the engine and the transmission to gradual engagement, so as to ensure a smooth start; temporarily cut off contact between the engine and transmission, in order to shift gears and reduce the impact of shifting; when the vehicle can play a separate role in emergency braking to prevent transmission, transmission system overload, which play a role in the protection. Clutches are similar to switches, junction or breaking up power transmission function, therefore, any form of cars had clutch, but in a different form.