| 摘要 |
PROBLEM TO BE SOLVED: To provide a brush device which is used in a DC motor, whose drive speed can be changed, and which can suppress a short circuit caused by a non-selected high potential side brush to avoid defective commutation. SOLUTION: This brush device 4 has a low potential side brush 5, a low speed high potential side brush 6, and a high speed high potential side brush 7. The low potential side brush 5 is connected to a low potential side power supply. One of the low speed high potential side brush 6 and the high speed high potential side brush 7 is selected and connected to a high potential side power supply. A permanent magnet 16 is provided in the high speed high potential side brush 7 and an electromagnet 13 is fixed to a brush holder 12. Ends 14a and 14b of a core 14 constituting the electromagnet 13 are arranged on the side surface of the high speed high potential side brush 7 at positions offset from the pole ends of the permanent magnet 16 in the radial direction of a commutator 3. The high speed high potential side brush 7 is brought into/out of contact with the commutator 3 by the attracting/repulsing force between the electromagnet 13 and the permanent magnet 16.
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