PURPOSE: To aim at reducing the burden to a driver and a follower by disposing a planetary transmission mechanism between a rotary shaft and a rotary member so that the planetary transmission mechanism is controlled by an adjusting means and a torque limiter, thereby to enable the rotational speed ratio between the rotary shaft and the rotary member to be changed.

CONSTITUTION: If the crankshaft of an internal combustion engine is used as a rotary shaft 10, an adjusting means 40 is suitably set so that a second housing 43 is completely locked when the rotational speed of the second housing 43 reaches a predetermined rotational speed, and accordingly, the motion initiating point of a torque limiter 50 is set such that a carrier 24 is changed over so as to be freely rotatable relative to the second housing 43 and an outer ring 22. Then, it is possible to limit the rotation of the rotary member 30 so that the rotational speed of the rotary member 30 is not increased so much even though the rotational speed of the crankshaft is increased. Accordingly, it is possible to transmit a necessary but minimum power to the accessory with no excessive load being applied, and it is also possible to reduce the burden of the internal combustion engine on the drive side.