Power transmission apparatus

A power transmission apparatus comprising:

• a clutch housed in a clutch housing that rotates together with an input that rotates due to a driving force of an engine of a vehicle, the clutch housing having a plurality of driving clutch plates attached thereto, the clutch including a plurality of driven clutch plates attached thereto, the driven clutch plates being alternately arranged with the driving clutch plates, the clutch being connected to an output that is able to rotate a wheel of the vehicle;
• a pressure applicator movable between an operating position where the driving and driven clutch plates are pressed against each other so as to enable transmission of the driving force of the engine to the wheel and a non-operating position where a pressing force exerted on the driving and driven clutch plates is released so as to cut off transmission of the driving force of the engine to the wheel;
• and
• a centrifugal clutch including a mass movable from a radially inner position to a radially outer position with centrifugal force produced by rotation of the clutch housing, the centrifugal clutch being configured to, when the mass is located at the radially outer position, press the driving and driven clutch plates against each other so as to enable transmission of the driving force of the engine to the wheel and configured to, when the mass is located at the radially inner position, release the pressing force exerted on the driving and driven clutch plates so as to cut off transmission of the driving force of the engine to the wheel;
• wherein
• the centrifugal clutch includes:
• a holder to hold the mass such that the mass is movable between the radially inner position and the radially outer position;
• a press to press the driving and driven clutch plates against each other by moving in a stacking direction of the driving and driven clutch plates in response to movement of the mass from the radially inner position to the radially outer position;
• a first spherical body that is partially protruded from a first opening of a through hole defined in the mass and is in contact with a rolling contact surface of the press so as to be rollable thereto;
• and
• a second spherical body that is partially protruded from a second opening of the through hole defined in the mass and is in contact with a rolling contact surface of the holder so as to be rollable thereon;
• the through hole has a tapered shape from the first opening to the second opening;
• and
• disconnection of the first spherical body is prevented by an outer peripheral edge of one of the first opening and the second opening that has a smaller diameter.