Patent ID: 9080614
Filing Date: 2015-07-14
Classification: F16D

Abstract:
1. A driving force transmission system, comprising: an annular wet clutch plate having lubrication grooves formed of multiple grooves in at least one of both axial end faces, the at least one of the both end faces having the lubrication grooves and a frictional engagement surface, wherein the frictional engagement surface is covered with a diamond-like carbon film and has a plurality of small grooves 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; and a mean value of surface roughness of the frictional engagement surface having the small grooves is a value equal to or higher than 3.0 μm but equal to or less than 4.0 μm when the surface roughness is measured with use of Rz (JIS B 0601:1982) at three positions that are offset from each other by 120° in the circumferential direction around a central axis of the annular clutch plate; a second clutch plate that is arranged so as to be opposed to the end face, and that is formed in an annular shape around a second center; a first rotary member arranged so that the clutch plate is immovable in a circumferential direction but movable in an axial direction; a second rotary member arranged so that the second clutch plate is immovable in a circumferential direction but movable in the axial direction; and lubricating oil retained between the clutch plate and the second clutch plate, wherein the first rotary member and the second rotary member are placed in state where torque is allowed to be transmitted, when the clutch plate and the second clutch plate are engaged with each other, and placed in a state where torque is not allowed to be transmitted, when the clutch plate and the second clutch plate are disengaged from each other, and wherein the small grooves have a depth of no more than about 4 μm, and a change in the torque being transmitted when the clutch plate and the second clutch plate are engaged with each other at a temperature of minus 40° C. with respect to a torque being transmitted when the clutch plate and the second clutch plate are engaged with each other at a temperature of 50° C. is 30% or less.