| 摘要 |
PROBLEM TO BE SOLVED: To suppress an occurrence of sparking at a front end of a brush. SOLUTION: In a rotary electric motor, when the width in circumferential direction of each segment 3 composing of a commutator 1 is set as a, the width of an under cut 4 is set as b, the width of high resistance brush member 2B is set as c and the width of a low resistance brush member 2A is set as d, the following relations 1-4 are established. c+d>a+2.b...1, d>c...2, b<c...3, d<a+b...4 Accordingly, a double layer brush 2 can be made contact across three segments 3 at the maximum continued in the circumferential direction, when naming the three segments 3 as the first segment, the second segment and the third segment in the order from the front side in the rotating direction, before making contact the front end of the brush member 2A with the third segment, the front end of the brush member 2B can be brought into contact with the second segment and also the rear end of the brush member 2B can be brought into contact with the first segment.
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