| 摘要 |
An electromagnetic clutch includes an armature 42 having a rotor contact surface 46a segmented in the radial direction by an annular groove 44 to form a plurality of rings, the groove being formed concentrically with the armature 42 for obstructing magnetic flux; and a rotor 43 having a contact surface, wherein the armature 42 is attracted toward the contact surface of the rotor 43 by magnetic force caused by an electromagnetic coil to couple the armature with the rotor for transmitting power. The armature 42 is formed by the steps of: preparing an armature material 42 with a groove 44 formed thereon, the groove having a width of w1; and narrowing the groove width from w1 to w2 by applying pressure on a pressed portion 47 in a peripheral edge region of the groove 44 to cause plastic flow in a horizontal direction along the material 42. |
