Patent ID: 8025138

Claim:
A multi-plate clutch system comprising: an outer clutch member which is operatively connected to an input member; a backing plate, fixed to an output member via a spline connection therebetween; a plurality of first clutch plates engaged with the outer clutch member so as not to rotate relative to the outer clutch member; a plurality of second clutch plates arranged alternately with the first clutch plates in an axial direction; a central spool which is formed separately from the backing plate, wherein the central spool has a first side oriented toward the backing plate and a second side oriented facing away from the backing plate and wherein the second clutch plates are engaged with the central spool so as not to rotate relative to the central spool; a pressure plate disposed proximate the second side of the central spool and that holds, in the axial direction, the first clutch plates and the second clutch plates in the interstice formed between the pressure plate and the backing plate; a clutch spring that biases the pressure plate to a side so as to pressure-contact the first clutch plates and the second clutch plates with each other; and a cam mechanism that is provided between the backing plate and the first side of the central spool, wherein the cam mechanism transmits the drive power of the input member from the central spool to the backing plate, and which pushes the pressure plate, with the central spool interposed in between, to a side so as to make the pressure plate move away from the backing plate against the biasing force of the clutch spring when reverse drive power is applied from the output member, wherein the cam mechanism includes a protruding cam and a recessed cam each having at least one convex surface, each of the protruding cam and the recessed cam has a first inclined face and a second inclined face, which are inclined in the same direction with respect to the circumferential direction, and the cams are respectively configured and arranged such that during clutch engagement, a convex surface of the protruding cam is brought into point contact with a convex surface of the recessed cam.