Patent ID: 8327992

Claim:
A friction plate having a friction surface formed by attaching a unitary, annular friction material to a substantially annular core plate, wherein: said friction surface is provided with a plurality of first oil grooves and a plurality of second oil grooves, each first oil groove having an opening portion opened to an inner peripheral edge of said friction plate and an end portion terminating at a point between the inner peripheral edge and an outer peripheral edge, each second oil groove having an opening portion opened to the outer peripheral edge of said friction plate and an end portion terminating at a point between the inner peripheral edge and the outer peripheral edge, said first oil grooves and said second oil grooves are alternately arranged in a circumferential direction equidistantly, a circumferential width of each first oil groove is the same from the inner peripheral edge to the corresponding end portion, the circumferential width of each first oil groove is greater than a circumferential width of each second oil groove, and from the end portion to the opening portion of each second oil groove, the circumferential width of each second oil groove does not decrease; wherein each of the second oil grooves has a tapered configuration with gradually increasing circumferential width in plan view.