Abstract: An electromagnetic clutch includes a clutch rotor and an annular electromagnet. The clutch rotor has a rotor which sectional side view is a U-shaped configuration and a pulley mounted at an outer peripheral surface of the rotor. The annular electromagnet is disposed in an annular cavity of the rotor. An armature plate facing to a front end surface of the rotor is supported elastically by a stopper plate through a plurality of leaf springs. The stopper plate is fixed to an outer end of a drive shaft. First engaging elements are formed at an outer peripheral surface of the rotor. Second engaging elements are formed at an inner peripheral surface of the pulley. The first and second engaging elements are complementary and prevent the relative rotational motion of the pulley and the rotor when engaged. A stopper provided on the outer peripheral surface of the rotor prevents the relative axial movement of the pulley and the rotor.

Abstract: A method for producing a magnetic rotatable member as a part of a pulley in an electromagnetic clutch is proposed. In order to reduce the producing time and the wasted material amount, the rotatable member is formed by press-drawing a magnetic circular plate to form an annular body consisted of an outer annular cylindrical portion, an inner annular cylindrical portion and an axial end annular plate portion connecting therebetween. Thereafter, the blank is subjected to ironing to form a radial annular rim on the outer surface of the outer annular cylindrical portion at the axial end, and also subjected to cutting-away and bending processes to cut away the outer edge of the inner annular cylindrical portion and to bend the resultant annular thin wall portion radially inwardly so that a radial flange is formed.