POWER TRANSMISSION DEVICE

The present invention provides a power transmission apparatus that is able to prevent sudden, untimely power transmission caused by accidental operation of a pressing assist cam when a vehicle including a centrifugal clutch means starts to move. [0002] In the course of movement of a weight member 10 of a centrifugal clutch means 9 from a radially inner position to a radially outer position and a resulting increase in torque transmitted from an input gear 1 to an output shaft 3, a power transmission apparatus includes a first torque region α1 where the apparatus restricts operation of a pressing assist cam and a second torque region α2 where the apparatus allows operation of the pressing assist cam.