Clutch, General
The primary role of the clutch system is to disengage the transmission when shifting, transfer torque and to allow comfortable starting.
Disengagement of the clutch driven plate when shifting is a very important part of this functionality. When the driver presses the clutch pedal, the throwout bearing moves a given distance towards the diaphragm spring and disengages the clutch driven plate. The clutch is raised and held in position by the springs riveted to the pressure plate.
Complete disengagement takes place during the last quarter of clutch pedal travel.
The clutch driven plate is trapped between the flywheel and pressure plate to transfer the torque. The torque is transferred via the clutch to the input shaft.
The torque is transferred across the crankshaft via the flywheel to the clutch driven plate. Half of the torque is transferred via the clutch screw to the clutch housing through lifting springs, over to the pressure plate and to the clutch driven plate. The clutch driven plate then transfers the torque via its hub and splines to the input shaft.
During down-shifting the rotation speed of the clutch driven plate increases. It decreases during up-shifting. The engine speed (RPM) is then synchronized with the vehicle speed when the clutch is released. If there is no disengagement during shifting, there would be abnormal synchronization wear in the transmission.
Pre-tensioned lifting springs connect the clutch housing and the pressure plate.
The clutch is defined by the 3 characteristic curves:
- pressure plate pressure against the clutch driven plate
- diaphragm spring pressure against the throwout bearing
- the lift of the pressure plate.
The pressure of the pressure plate increases as the clutch driven plate wears. This increase in pressure increases the pressure at the diaphragm spring and with it pedal effort as the clutch driven plate wears. The diaphragm spring moves backwards as the clutch driven plate wears. The clutches are guaranteed to tolerate wear of 1.5 mm to the facing. This means that the clutch cover has a wear capacity of 8-9 mm to compensate for rearward movement of the throwout bearing.