Description and operation of mechanical clutch operating system by clutch cable

The task of the clutch operating system is to boost the pedal force applied by the driver and transfer it to the release bearing. Depending on the design of the vehicle manufacturer, the clutch is operated mechanically or hydraulically.

Mechanical clutch operation generally takes place via a clutch cable. These are available in two versions: with self-adjustment and manual adjustment.

When the clutch pedal is depressed, the foot force is transferred to the release bearing by the cable and release lever. The lever ratios on the clutch pedal and release lever are designed so that the foot force required to disengage the clutch is not too high and the pedal travel is not too long.

On a mechanical clutch operating system, there is a clearance of 1 mm to 3 mm between the release bearing and the tongues of the diaphragm spring and a clearance of approx. 10 mm to 30 mm at the clutch pedal. Due to wear on the lining on the clutch plate, the pressure plate moves towards the flywheel. The tongues of the diaphragm spring thus move outwards towards the release bearing. This reduces the clearance at the release bearing and clutch pedal. If the clearance is not adjusted, the release bearing turns continuously and the clutch no longer fully closes. This results in increased wear and clutch slip. Correct adjustment of the clutch clearance is thus an important requirement for a long clutch service life.

In the case of clutch cables with manual adjustment, the clearance is either adjusted at the release lever or at the clutch pedal by turning an adjusting nut. Clutch cables with automatic adjustment device automatically adjust the clearance. They automatically keep the clutch clearance between the release bearing and tongues of the diaphragm spring at "zero".