Patent ID: 6892869

Claim:
A multi-plate friction clutch comprising: a clutch outer; a clutch inner surrounded by the clutch outer; a plurality of first friction plates which are axially slidably spline-coupled to the clutch outer; a plurality of second friction plates which are superposed alternately with the first friction plates and axially slidably spline-coupled to the clutch inner; a pressure-receiving plate fixed to the clutch outer to be opposed to one side of a group of the first and second friction plates; and a clutch piston which is fitted to the clutch outer and which is capable of being hydraulically operated to press the group of the first and second friction plates toward the pressure-receiving plate, the clutch piston having a pressing surface adapted to press the group of the first and second friction plates and an annular retaining groove formed in the pressing surface, and a buffering Belleville spring being accommodated in the retaining groove and capable of resiliently abutting against the group of the first and second friction plates, wherein the retaining groove has an annular projection formed at its axial opening edge for inhibiting the disengagement of the Belleville spring from the retaining groove.