Abstract: A multi-plate clutch system includes: a pressure plate which is biased by a clutch spring in a direction in which driving friction plates and driven friction plates are brought into pressure contact with each other; and at least one of assist device configured to increase a pressure contact force when torque is changed for acceleration and the slipper device configured to decrease the pressure contact force when the torque is changed for deceleration. A ring member whose inner peripheral surface is put in sliding contact with an outer peripheral surface of one cam plate out of paired cam plates, which are included in at least one of the assist device and the slipper device, is fixed to a clutch inner, and oil discharging passages for guiding oil to a sliding contact portion between the one cam plate and the ring member are provided in outer peripheral edge portions of concave cams formed in the one cam plate.

Abstract: A one-way clutch of the invention includes an inner race supported for rotation on a power transmission shaft, an outer race concentrically surrounding the inner race, and torque transmitting members interposed between the inner race and the outer race and capable of transmitting torque in one direction of the inner race to the outer race. The outer race is integrally provided with an extending portion that extends inwardly in a radius direction thereof. The extending portion is capable of being engaged with the power transmission shaft.