between the flywheel and the pressure plate. There are two types of pressure plates - the coil spring type and the diaphragm type.
Coil spring pressure plate uses small coil springs similar to valve springs (fig. 4-6). The face of the pressure plate is a large, flat ring that contacts the clutch disc during clutch engagement. The backside of the pressure plate has pockets for the coil springs and brackets for hinging the release levers. During clutch action, the pressure plate moves back and forth inside the clutch cover. The release levers are hinged inside the pressure plate to pry on and move the pressure plate face away from the clutch disc and flywheel. Small clip-type springs fit around the release levers to keep them rattling when fully released. The pressure plate cover fits over the springs, the release levers, and the pressure plate face. Its main purpose is to hold the assembly together. Holes around the outer edge of the cover are for bolting the pressure plate to the flywheel.
Diaphragm pressure plate (fig. 4-7) uses a single diaphragm spring instead of coil springs. This type of pressure plate functions similar to that of the coil spring type. The diaphragm spring is a large, round disc of spring steel. The spring is bent or dished and has pie-shaped segments running from the outer edge to the center. The diaphragm spring is mounted in the pressure plate with the outer edge touching the back of the pressure plate face. The outer rim of the diaphragm is secured to the pressure plate and is pivoted on rings (pivot rings) approximately 1 inch from the outer edge.
Figure 4-6. - Coil spring pressure plate.
Figure 4-7. - Diaphragm pressure plate operation.Continue Reading