The present invention relates to a modular clutch construction, particularly to a modular clutch construction wherein the peripheral wall of a clutch cover is marginally fitted at one end onto the cylindrical surface of a flywheel.
A conventional clutch comprises mainly a clutch cover assembly retaining a pressure plate fixed to a flywheel, and a clutch disc assembly located between the flywheel and the pressure plate of the clutch cover assembly.
The clutch cover end extends radially outward in a flange, and the clutch cover assembly thus is mounted to the flywheel by fixing the flange to an end-face thereof. Therein, the outside diameter of the flywheel must be larger than that of the clutch disc assembly by the radial width of the flange.
Japanese Utility Model Provisional Number No. 1762 of 1975 discloses a clutch cover attachment structure for minimization of flywheel dimensions, wherein the peripheral wall of the clutch cover is circumferentially assembled onto the cylindrical surface of the flywheel. The outer diameter of the flywheel is on the order of that of the clutch cover, since the flange of a conventional clutch cover is eliminated.
In the foregoing, bolts fix the clutch cover peripheral wall to the flywheel cylindrical surface. Due to the curvature of the flywheel cylindrical surface, the area of contact in seating the fixing bolts is limited. Consequently, retaining friction between the surfaces is insufficient, such that the bolts tend to loosen and portions in seating contact tend to wear. Moreover, shearing forces on the clutch cover act directly upon the bolts, occasionally breaking them off. A solution to this problem is to increase the number of bolts; however, a larger number of bolts adds complexity to the assembly stage.
Furthermore, the clutch cover tends to expand radially outward under centrifugal force generated by rotation of the flywheel. As a result, there is a load on the bolts fastening the clutch cover to the flywheel, which tends to loosen them.