Clutch plate, clutch unit and driving force transmission system

摘要

An annular wet clutch plate (1) has lubrication grooves (2) formed of multiple grooves in at least one of both axial end faces (11), the at least one of the both end faces having the lubrication grooves and a frictional engagement surface (13). The frictional engagement surface has a plurality of small grooves (15) having a width and a depth that are smaller than those of the lubrication grooves. At least one of the small grooves is extended in a direction that crosses a circumferential direction of the annular clutch plate. A mean value of surface roughness of the frictional engagement surface having the small grooves is from 3.0 µm to 4.0 µm when the surface roughness is measured with the use of Rz at three positions that are offset from each other by 120° in the circumferential direction around a central axis of the annular clutch plate.