Hydraulic clutch operation with master and slave cylinders

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.

In the case of a hydraulic clutch operating system, pressing the clutch pedal primes a volume of fluid in the master cylinder. The pressure and the displaced volume of fluid are transferred to the slave cylinder via a connecting line. Using a piston, this generates the stroke which is required to disengage the clutch.

Master and slave cylinders for clutch operation are, like master cylinders and wheel cylinders in the brake system, equipped with sealing boots. However, the components of a hydraulic clutch operating system have completely different wear characteristics compared to brake assemblies. This is due to their different tasks and the different stresses they are subjected to.

Accordingly, the seals of clutch master and slave cylinders are subjected to the full pressure throughout the entire stroke required for operation and are thus susceptible to greater wear. In contrast, the seals of master brake cylinders and wheel cylinders are subjected to a continuously rising pressure and only have to travel over a minimal stroke distance.

In order to minimise the wear of clutch master and slave cylinders, special production processes are used to manufacture these assemblies. In addition, pistons and cylinders are measured before assembly and assigned to tolerance groups. This ensures that the specified clearance between the piston and cylinder is maintained and the stringent requirements of these assemblies are fulfilled.