| 摘要 |
PROBLEM TO BE SOLVED: To lower surface temperatures of a commutator and a brush automatically when a temperature around the commutator is higher than predetermined. SOLUTION: A rotor 72 has a commutator 78 brought in contact with the brush 74, and a rotor shaft 76. A fan until 12 which can rotate together with/ relatively to the rotor shaft 76 and send cooling air to the neighborhood of the commutator 78 by the solid rotation, and a bimetal 13 which can switch the rotation mode between the same rotation and the relative rotation, are provided. When the temperature around the commutator is higher that predetermined, the fan unit 12 is made to rotate together with the rotary shaft 76 by the bimetal 13.
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