Power transmission device

A power transmission device comprising:

• a clutch housing rotatable with an input member, the input member rotatable by a drive force of an engine of a vehicle, a plurality of driving clutch plates attached to the clutch housing;
• a clutch member coupled to an output member that can rotate a wheel of the vehicle, a plurality of driven clutch plates alternating with the driving clutch plates of the clutch housing, the driven clutch plates attached to the clutch member;
• a pressure member movable between an actuation position and a non-actuation position, in the actuation position the drive force of the engine can be transmitted to the wheel with the driving clutch plates and the driven clutch plates brought into press contact with each other, in the non-actuation position, transmission of the drive force of the engine to the wheel can be blocked by releasing a press-contact force between the driving clutch plates and the driven clutch plates;
• a weight member disposed in a groove portion in the clutch housing, the groove portion extends in a radial direction, the weight member is movable by a centrifugal force, due to rotation of the clutch housing, from a radially inner position to a radially outer position of the groove portion;
• and
• an interlocking member moves the pressure member from the non-actuation position to the actuation position as the weight member is moved from the radially inner position to the radially outer position,
• the clutch member includes
• a first clutch member coupled to the output member,
• a second clutch member attached to the driven clutch plates, and
• a back torque transmission cam bringing the driving clutch plates and the driven clutch plates into press contact with each other by moving the second clutch member when the pressure member is located at the non-actuation position and a rotational force is input to the first clutch member via the output member, and
• a torque transmission portion formed on each of the first clutch member and the second clutch member to transmit a rotational force transmitted to the second clutch member to the first clutch member not via the back torque transmission cam.