How a vehicle clutch works
There are many different types and designs of vehicle clutches, yet they all work to achieve the same thing. That is to help convert the turning motion produced in the cars engine into the turning motion at the wheels. Most designs are based around one or two friction plates pressed tightly together or against the flywheel. The clutch can be engaged and disengaged using the clutch pedal, this will always be found to the left of the brake pedal.
Disengaged: When a clutch is disengaged (Clutch pedal pressed down) the clutch release mechanism pushes or pulls on the clutch fork. This causes the fork to rotate on the pivot ball and slide the release bearing (attached to end of fork) along the transmission input shaft and into the diaphragm of the pressure plate. This causes the pressure plate casting to release its grip on the friction plate and allow it to move freely against the flywheel. Now the engine crankshaft can remain spinning without spinning the friction plate and transmission input shaft. This allows the car to idle without stalling and change gears.
Engaged: When the clutch pedal is raised of the floor the reverse happens and you are engaging the clutch. The pressure plate tightens its grip on the friction plate pushing it up against the flywheel. Now the friction plate spins with the flywheel and the movement is transmitted from the engine crankshaft to the transmission input shaft. This creates movement at the wheels.
PARTS OF A CLUTCH
There are two types of pressure plates, they are a diaphragm type and spring type. The diaphragm type basically consists of a cover, steel diaphragm, fulcrum rings, support rings, straps and a pressure plate casting. The spring type is made up of a cover, thrust springs, release fingers and a pressure plate casting. As its name suggests the pressure plate puts pressure on the clutch disc forcing it to grab the flywheel.
The clutch disc consists of a metal plate covered in a frictional material similar to that found on brake pads. There is a splined hub in the centre of the disc that moulds to the teeth of the transmissions input shaft. The clutch disc sits in between the pressure plate and flywheel.
RELEASE BEARING ( THROW OUT BEARING )
The release bearing is located between the clutch fork and the pressure plate diaphragm or fingers. The bearing only operates when the clutch is disengaged. When the clutch is disengaged the bearing slides down a hollow shaft at the front of the transmission housing and into the diaphragm of the pressure plate releasing its grip on the clutch disc.
The flywheel is bolted to the crankshaft of the engine. It has many functions in the vehicle including dampening engine vibrations, acting as a balancer for the engine and providing a smooth friction surface that the clutch can contact. However its main functions is helping transfer torque from the engine to the transmission.