Patent ID: 8113329

Claim:
A friction clutch for transmitting torque from a crankshaft of an engine to a transmission, the clutch comprising: a drive side rotating body which has a first plate and an axis of rotation, and which is configured to rotate in response to rotation of the crankshaft; a driven side rotating body arranged coaxially with the drive side rotating body and having a second plate opposite to the first plate in a predetermined direction along the axis of rotation, the driven side rotating body receiving torque from the drive side rotating body causing it to rotate when the clutch is engaged; a pressure plate supported on the drive side rotating body so as to be movable in an axial direction with respect to the drive side rotating body and so as to rotate together with the drive side rotating body, wherein a slide arm is formed in the pressure plate; an elastic member urging the pressure plate in the predetermined direction to press the first plate and the second plate into frictional contact with each other when the clutch is engaged; a power-assist mechanism configured to receive torque of the pressure plate and convert the received torque into a force for moving the pressure plate in a direction for separating the first plate and the second plate from each other when the clutch is disengaged; and a sub clutch configured to transmit torque from the pressure plate to the power-assist mechanism, the sub clutch comprising: a friction plate configured to rotate together with the pressure plate, the friction plate having a first friction surface formed on one side and a second friction surface formed on the other side, wherein the friction plate is slidably engaged with the slide arm of the pressure plate; a pressing member adapted to come into contact with the first friction surface to press the friction plate from the first side toward the second side when the clutch is to be disengaged; and a torque transmission member disposed opposite to the second friction surface of the friction plate and being placed in frictional contact with the friction plate by the pressing member to receive torque of the pressure plate when the clutch is disengaged, the torque transmission member transmitting the received torque to the power-assist mechanism; an operating shaft arranged to move the pressing member toward the friction plate; and a device which operates the operating shaft to move the pressing member toward the friction plate.