Patent ID: 8714329

Claim:
An electromagnetic clutch comprising: a rotating member; an electromagnetic coil that is arranged on a rotational axis of the rotating member and generates electro-magnetic force; an output mechanism that has an armature to which return force in a direction away from the electromagnetic coil is applied by a return spring; a cam mechanism that is juxtaposed along the rotational axis to the output mechanism, and that has a cam member that is unable to rotate relative to the rotating member, and a cam follower that is able to roll between the cam member and the armature so as to permit limited relative rotation between the armature and the cam member; and a relative rotation restricting device that is arranged on an axis of the cam mechanism, and that is configured to restrict relative rotation between the armature and the cam member when the electromagnetic coil is in a de-energized state, the restriction on relative rotation between the armature and the cam member imposed by the relative rotation restricting device restricting the relative rotation to be less than the limited relative rotation permitted by the rolling of the cam follower between the cam member and the armature.