WET FRICTION MATERIAL

摘要

In order to obtain excellent drag torque reduction effects in a friction material across a wide range of relative rotation speed by further improving the discharge of a lubricant oil when unengaged while maintaining a wide lining area to an extent that does not affect torque transmission capacity, heat resistance, and peeling resistance, a segmented friction material (1A) acting as a wet friction material is provided with, in three locations on the circumference exclusively on the surface of a portion of segment pieces (3A) from among 30 segment pieces (3, 3A), sets of drag torque reducing grooves (5A) along a direction that is roughly orthogonal to a straight line connecting the center (O) of the circumference and the center point (5Aa) of the drag torque reducing grooves (5A), which span over sets of five segment pieces (3A). As a result, major drag torque reduction effects are obtained across a wide range of relative rotation speed (500 rpm to 5000 rpm) without narrowing the lining area, by improving ATF discharge and forming an oil film on the surface of the segment pieces (3A).