PURPOSE: To eliminate a drilling process and ensure the easy processing of an armature by providing a recess at the center of the armature and supporting the armature in such a way as to be capable of free turn via a projection engaged with the aforesaid recess.

CONSTITUTION: A recess 28a is formed at the center of the intermediate part 28 of an armature 28 and engaged with the projection 29 of an elastic winding frame 27 forming an electromagnet together with a coil 30, via a resin material and the like, thereby supporting the armature 28 in such a way as to capable of free turn. Consequently, it is unnecessary to drill a small hole in the armature 28 for the pivotal support thereof for free turn and it becomes easy to process the armature 28.