| 摘要 |
PURPOSE:To restrain the generation of sparks upon starting a motor, by a method wherein a ratio of the size of length of a carbon brush in the circumferential direction of a commutator to the size of length in the outer periphery of the commutator is determined so as to have a value within a predetermined range. CONSTITUTION:A carbon brush 2 is formed so that the size of length L in the circumferential direction of a commutator 4 becomes 8-14% of the size of length in the outer periphery of the commutator 4. The phase difference thetaof the carbon brush 2 between the initial condition of using and the later condition of using is reduced, therefore, the generation of sparks upon starting a motor may be restrained.
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