| 摘要 |
PROBLEM TO BE SOLVED: To prevent dimension variance and inconsistent treatment of a magnet cover by eliminating anneal treatment after press in the magnet cover, to improve the ease of assembly, and to reduce cogging torque. SOLUTION: The roughly cylindrical magnet cover 28 formed in stainless steel is attached to a rotor 3 of a brushless motor 1. The magnet cover 28 is formed by means of drawing within a drawing ratio of 0.5-1 and used in a magnetized state. The cogging torque is restrained to be a predetermined reference value or less in the drawing ratio of 0.5-1 regardless of with/without anneal treatment. The anneal treatment while is thereby eliminated, while restraining the cogging torque to be the reference value or less. It is preferable that relative plate thickness of the magnet cover 28 is 0.8% or less from a viewpoint of output decrease prevention, and the plate thickness of the magnet cover 28 is 0.35 mm or less from a viewpoint of cogging torque decrease. COPYRIGHT: (C)2008,JPO&INPIT
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