Patent ID: 7530284

Claim:
A multiplate clutch outer part which is formed by pressing a steel plate and which comprises: an end wall portion; and a cylindrical portion having its one end formed continuously with an outer peripheral end of the end wall portion, and opened at the other end, the cylindrical portion including: a plurality of spline grooves and spline projections which are formed in an inner peripheral face of the cylindrical portion, and which extend in an axial direction, the spline grooves and the spline projections being alternately arranged in a circumferential direction of the cylindrical portion; and outer projections and outer grooves which are formed in an outer peripheral face of the cylindrical portion, and which are arranged in positions corresponding respectively to those of the spline grooves and the spline projections, wherein a bottom face of each of the outer grooves is formed to be an inclined face which is farther from an axis of the cylindrical portion toward the open end of the cylindrical portion, and wherein arc faces formed at inner corners of each of the outer grooves has an increasing radius of curvature toward the open end of the cylindrical portion.