Clutch (Hydraulic Operation): Description and operation

Hydraulic Operation

When the clutch pedal (9) is depressed, the piston (8) is pushed into the master cylinder (7). The piston pressurizes the fluid in the master cylinder forcing the pressurized fluid along the hydraulic tube (10). The pressure is felt at the piston (11) of the slave cylinder (12) which moves under the hydraulic force applied.

When the clutch pedal (9) is released, force from the compressed fingers of the diaphragm (6), pushes against the release fork (14) through the release bearing. The release fork rotates which in turn rotates the release lever (13).

The release lever pushes the piston (11) back into the slave cylinder (12). This returns hydraulic fluid back up the hydraulic tube (10) and into the master cylinder (7).

Mechanism Operation

When the clutch pedal (9) is depressed, the hydraulic pressure extends the piston (11) rod in the slave cylinder (12). The extension of the piston rod pushes the release lever (13) which transfers its rotary movement to the release fork (14) to which it is connected.

The release fork (14) pivots towards the engine and converts its rotary movement into linear movement of the release bearing (15). The release bearing pushes on the fingers of the diaphragm (6) which pivots about its fulcrum on the pressure plate housing (5). As the diaphragm is deflected, its pressure is removed from the pressure plate (16). The three leaf springs (4) pull the pressure plate away from the drive plate (17).

The removal of force from the pressure plate (16) on the drive plate (17) reduces the friction between the drive plate and the flywheel (3). The drive plate slips against the flywheel and cannot transfer the drive from the flywheel to the gearbox primary shaft (2).

When the clutch pedal is released, hydraulic pressure is removed from the piston (11) in the slave cylinder (12). The removal of the pressure allows the release bearing (15) to be pushed back along the gearbox primary shaft (2) by the fingers of the diaphragm (6). The linear movement of the release bearing is transferred to rotary movement of the release fork (14) and the release lever (13) which pushes the piston (11) into the slave cylinder (12).

The diaphragm (6) pivots on its fulcrum on the pressure plate housing (5). This applies pressure to the pressure plate (16) and overcomes the opposing force applied by the leaf springs (4). The pressure plate moves towards the flywheel (3) and applies force to the drive plate (17).

The force applied to the drive plate (17) by the pressure plate (16) increases the friction between the drive plate and the flywheel (3). As the clutch pedal (9) is released the friction increases and rotary movement of the flywheel is transferred to the drive plate, which in turn rotates the primary shaft (2) of the gearbox.

When the pedal is released fully, the pressure applied to the pressure plate (16) by the diaphragm (6) forces the drive plate (17) onto the flywheel with no slippage.