Electromagnetic clutch with improved frictional surfaces

摘要

An electromagnetic clutch is disclosed comprising a rotor and an armature plate with improved frictional surfaces. The armature plate is disposed to face the rotor with a predetermined axial gap. The rotor or the armature plate is provided with a contact surface which contains spiral concaves and projections with a predetermined pitch. This surface has a layer of metal plating with a hardness lower than that of the magnetic materials which make up the rotor and armature plate.