Clutch cover assemblies for push- or pull-type operation are the main focus of attention - thoroughly tried and tested components that are well developed and have the advantages of a very high degree of efficiency, low release forces, low weight and simple structure.

Clutch cover

The clutch cover is screwed to the engine flywheel. It transfers the engine torque to the clutch disc on the transmission input shaft.

The clutch cover is composed of the clutch housing (1) and the diaphragm spring (2) which presses the axially displaceable pressure plate (3) against the clutch disc and flywheel when the clutch is engaged.

Technically, the diaphragm spring is a disc spring with integrated control levers (the diaphragm spring tongues). It is mounted in such a way in the housing that it can be tilted by means of two wire rings or one wire ring (4) around a flanged edge (5). Diaphragm spring, wire ring(s) and housing are connected to spacer bolts (6) by rivets.

The pressure plate is secured and adjusted concentrically on the housing by leaf springs (7). Half of the engine torque is transferred by the pressure plate and leaf springs, the other half is transmitted directly from the flywheel to the clutch disc.

Two forces act on the clutch cover: the clamp load which causes the pressure plate to press against the clutch disc, and the release force which lifts the pressure plate away from the clutch disc by means of the diaphragm spring tongues.

engaged

released

Push-type Operation

Clutch covers are either known as ‘push’ or ‘pull’ clutch covers depending on whether the acting release force is a compressive force or a tractive force. Push-type clutch covers are easier to assemble and dismantle. When the clutch is pressed down, the releaser presses the diaphragm spring tongues towards the flywheel which causes the outer diameter of the diaphragm spring to move in the opposite direction. The tangential leaf springs ensure that the pressure plate follow after the diaphragm spring. The release travel is large enough for the clutch disc to rotate freely when released. This is necessary for the transmission to be shifted correctly.

 

 

Pull-type Operation

engaged

released

The pull-type clutch cover has the advantages that the release force is smaller because the leverage ratio (a:b) of the diaphragm spring is larger and the deformation losses of the housing are lower. Pull-type clutches are standard in heavy commercial vehicles. The releaser pulls the diaphragm spring towards the transmission. The contact area of the pressure plate also moves towards the transmission because the diaphragm spring is mounted in the housing by its outer diameter. In other words, the push and pull operation has the same effect on the pressure plate. Releaser and tongues must be connected to one another to be able to transfer the release force to the clutch. This can occur when the clutch is installed if the control lever mounted in the clutch housing is able to slide into its end position at the release when engine and transmission are pushed together. If the structure does not permit this, then a snap connection is used; this is snapped into place from the outside after the engine and transmission have been screwed together.

 

Fields of application for Sachs clutch covers

Torque ranges for clutch covers on passenger vehicle
Torque ranges for clutch covers on heavy goods vehicle