Clutch Disc
Clutch Disc Components
| Item | Description |
|---|---|
| 1 | Friction lining |
| 2 | Rivet |
| 3 | Multi-spline hub |
| 4 | Torsion spring |
| 5 | Carrier plate |
Clutch Disc Function
The clutch disc makes sure clutch engagement is vibration free, compensates for tolerances between the surfaces of the pressure plate and the flywheel, and reduces vibrations in the transmission.
Wear and generation of heat
Wear can be compensated for via an automatic adjustment mechanism.
Overheating of the clutch disc surface causes it to glaze. The friction lining surface may display cracks and start to become brittle. It is not a rare occurrence for individual segments of the friction lining surface to become detached. The coefficient of friction, and therefore the amount of torque which can be transmitted for a given clamp load, is reduced as a result of glazing.
This damage is not undone by normal wear.
If the friction lining is connected to the carrier plate with adhesive, the latter can become soft if the components overheat, and as a result the friction lining can be displaced or detached over large areas. If this happens the clutch will no longer function as intended.
On wet clutches, the coolant can be chemically changed as a result of continuously high temperatures. If oil is used as the coolant, this can lead to increased oxidation or to the cracking of oil molecules. Cracking means that the structure of the oil molecule chain is changed in comparison to the original structure. Changes to the oil molecule chain can have a detrimental effect on the function of the clutch.
A hot spot can occur if there is a local build-up of heat between the friction lining and the pressure plate as a result of a localized concentration of heat, this is referred to as a hot spot. The thermal peaks created in the process occur as a result of uneven accumulation of material on the friction lining and pressure plate.
Clutch Disc Function
On the inside, the multi-splines on the clutch disc hub allow it to be moved axially in relation to the transmission input shaft while not permitting any relative rotation.
The splines allow the clutch disc to release from the flywheel after the pressure plate has been lifted off. If this axial freedom of movement is no longer given, for example, due to rust, or the clutch disc has too much runout, the clutch will no longer fully disengage. Torque is then still transmitted from the engine to the transmission. This places correspondingly higher loads on the synchronizer assembly. This can result in difficult and noisy gearshifts.
During engagement of the clutch, the clutch disc is clamped between the pressure plate and the flywheel. If no dual-mass flywheel is fitted, coil springs which are arranged tangentially in the intermediate layers and which permit limited radial twisting provide damping for noises from the transmission (rattling) and other vibrations.