PURPOSE: To transmit torque in either direction only from the driving shaft side by mounting a roller interposingly between a plane part formed at the driving shaft and a driven shaft fitted at the periphery of the plane part, connecting a weight and holding the roller with an elastically deformable cylinder body.

CONSTITUTION: In a clutch 15, a hollow driving shaft 21 with a flat part 25 is fixed at a motor shaft 14, and a hollow driven shaft 22 is rotatably fitted at the flat part of the driving shaft 21. A roller 26 is interposingly mounted between a fitting cylinder part 22a and the plane part 25, disposed at the window 28 of a cylinder body 27 fitted between the driving shaft 21 and the fitting cylinder part 22a of the driven shaft and held by a presser spring 29 in the elastically deformable state. The cylinder body 27 is connected to a weight body 31 as well as elastically connected to the driving shaft 21. When the driving shaft starts its rotation, the weight body remains motionless by its inertia, and the roller 26 is engaged to be locked so as to transmit torque. The rotational torque on the driven shaft 22 side runs idle in a minute clearance between the driving shaft 21 and the driven shaft 2, and thereby the transmission of torque does not take place.