To control in the finite speed range of an output member regardless of the rotational fluctuation of an input member.

The control device is equipped with an output member which is rotatably combined with an input member 13 having a cam surface 13a, a ring 17 which is built in the output member, and forms an oil chamber 19 in an eccentric shape in a space interspaced from the cam surface 13a, a plurality of vane chambers 20 which are bored out of the oil chamber forming surface of the ring 17 in the radial direction, and adjusting springs 23 each of which energizes each vane 22 disposed in each vane chamber 20 to the cam surface 13a against centrifugal force, and restrains the floating of hydraulic fluid O sealed in the oil chamber 19 as far as the output member remains within a specified revolving speed. By this constitution, the output member can thereby be so controlled as to be less than a specified revolution speed regardless of an increase in revolution speed by the input member.