The invention relates to a method for producing a diaphragm spring where only specific portions of the diaphragm spring are subjected to a shot-peening process. The shot-peening step is performed only to one side of an outer circumferential portion and an inner circumferential portion of the elastic portion (5a) of the diaphragm spring (5).
A generally disc-shaped flywheel which is an integral one-piece forged structure formed by forging of a carbon steel blank and consisting of an inner portion having a friction surface and an outer ring gear portion disposed radially outwardly of the inner portion. The flywheel is formed by forging the carbon steel blank to obtain an intermediate product consisting of the inner portion and the outer ring gear portion, hardening the friction surface of the inner portion of the intermediate product, and shot peening the hardened friction surface to form a multiplicity of recesses in the hardened friction surface.
A plate spring of a substantially circular-ring-shaped form having a substantially externally conical upper side (12) and a substantially internally conical underside (13) between which there are positioned an outer annular edge (14) and an inner annular edge (15), wherein, in the unloaded condition, the surface layer (17) of the underside (13) comprises a higher inherent compressive stress than the surface layer (16) of the upper side (12).
