PURPOSE: To enable the smooth operation with a very simple structure at low cost by combining a centrifugal force function to be generated by circulating and rotating steel balls in a cavity by pressure so that it may acceleration-act on the outer peripheral surface of an eccentric track by making use of an inner peripheral truck surface.

CONSTITUTION: Brackets 13 are provided in a cavity 6 of a main body A, a plurality of steel balls 7 are provided in a space 6' formed of the brackets 13 and the cavity 6, the steel balls 7 are so held as to be slid along the inner peripheral surface 5 of the main body A, and therefore, a plurality of steel balls 7 are circulated and rotated on the inner peripheral surface 5 when a driving shaft 12 starts the rotation. Accordingly, pressure of centrifugal force of the steel balls 7 is automatically acts according to torque, and the main body A can be rotated at the required speed. Therefore, the smooth clutch operation can be performed from the idling to the high speed operation as the indispensable condition in starting of an automobile by one accelerator operation.