| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to punch a stator piece and a rotor piece simultaneously by a press working operation by a method wherein recesses which are pressed by using a press are formed concentrically in a part of the rotor piece which is pressed and worked. SOLUTION: In a state immediately after a stator is punched, yoke parts 2a for a step motor are formed in the radiant direction at the outside of a rotor piece 2. Recesses which are pressed and crushed by a ring-shaped punch are formed in concentric positions of the rotor piece 2. Every recess is formed so as to have a width W of 1mm and a crushed depth F of about 0.01 to 0.05mm, and the outside diameter D1 of the rotor piece 2 can be made a little larger than an outside diameter D1 immediately after a punching operation. Consequently, an air gap A composed of the difference between the outside diameter D1 and the inside diameter D2 of a stator piece 3 can be made smaller than that is a press working operation, and it is possible to form the air gap A in, e.g. 10μm which is required by the step motor.
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