DC MOTOR, BRUSH DEVICE OF DC MOTOR AND WIPER DEVICE FOR VEHICLE

摘要

PROBLEM TO BE SOLVED: To improve motor output during low rotation driving and restrain generation of electromagnetic wave noise and vibration, in a DC motor having a brush for low speed driving and a brush for high speed driving. SOLUTION: The width L1 of a brush 6 for high speed driving in the rotation direction in made less than the width L2 of a brush 5 for low speed driving in the rotating direction. When low rotation driving is performed by supplying a driving power source to a commutator 12 (rotor 10) via the brush 5 for low speed driving, a time when the brush 6 for high speed driving short-circuits adjacent commutator segments 12a is reduced. Although an induced voltage (back electromotive force) is generated in a coil arranged between the short- circuited commutator segments 12a, the induced voltage (counter electromotive force) is restrained t be small because the time for short-circuiting is reduced.