Clutch (Td4 Engines): Description and operation (page 2 of 2)

Td4 Engines: When the clutch pedal is released, force from the compressed fingers of the diaphragm spring pushes against the release bearing. The release bearing in turn pushes the piston back into the slave cylinder which returns hydraulic fluid back up the clutch pipe to the master cylinder.

Mechanical Operation When the clutch pedal is depressed, the hydraulic pressure extends the piston in the slave cylinder.

K1.8 Engines: The extension of the piston rod pushes the release lever which transfers its rotary movement to the release fork to which it is connected. The release fork pivots towards the engine and converts its rotary movement into linear movement of the release bearing.

Td4 Engines: The extension of the piston is transferred into linear movement of the release bearing.

All Models: The release bearing pushes on the fingers of the diaphragm spring which pivots about its fulcrum on the clutch cover. As the diaphragm spring is deflected, its force is removed from the pressure plate. The three drive straps pull the pressure plate away from the clutch driven plate.

The removal of force from the pressure plate on the clutch driven plate reduces the friction between the clutch driven plate and the flywheel. The clutch driven plate slips against the flywheel and cannot transfer the drive from the flywheel to the gearbox primary shaft. When the clutch pedal is released, hydraulic pressure is removed from the piston in the slave cylinder. Removal of the pressure allows the release bearing to be pushed back along the gearbox primary shaft by the fingers of the diaphragm spring.

K1.8 Engines: The linear movement of the release bearing is transferred to rotary movement of the release fork and the release lever which pushes the piston into the slave cylinder.

Td4 Engines: The linear movement of the release bearing pushes the piston into the slave cylinder.

All Models: The diaphragm spring pivots on its fulcrum on the clutch cover. This applies force to the pressure plate and overcomes the opposing force applied by the drive straps. The pressure plate moves towards the flywheel and applies force to the clutch driven plate.

The force applied to the clutch driven plate by the pressure plate increases the friction between the clutch driven plate and the flywheel. As the clutch pedal is released the friction increases and rotary movement of the flywheel is transferred to the clutch driven plate, which in turn rotates the primary shaft of the gearbox.

When the pedal is released fully, the force applied to the pressure plate by the diaphragm spring forces the clutch driven plate onto the flywheel with no slippage.