| 摘要 |
PROBLEM TO BE SOLVED: To provide a brush 4 which can suppress increase in the contact resistance that accompanies abrasion of the brush 4 and which can prevent deterioration in the output of a motor 1. SOLUTION: The brush 4, when it is not in use, consists of a low-copper percentage portion 8, a medium copper percentage portion 10 and a high-copper percentage portion 9, which are provided so that the content of copper is increased in three steps toward the portion where a lead wire 5 is buried, from a portion where the brush is in slidable contact with a commutator 3. As a result, when the slide contact surface 6 is retreated and the low-copper percentage portion 8 is set extinct and the medium-copper percentage portion 10 comes into contact with the commutator 3, since the content of copper (Cu ratio), in the vicinity of the surface in slidable contact with the commutator 3, becomes higher than that immediately after the start of use, the contact resistance between the brush 4 and the commutator 3 will not fluctuate significantly, even if an energizing force exerted by a brush spring is lowered that accompanies the slide contact surface 6 retreat. As a result, increase in the contact resistance, accompanying the abrasion of the brush 4 can be suppressed and deterioration in the motor 1 output, can be prevented. COPYRIGHT: (C)2008,JPO&INPIT
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