| 摘要 |
PROBLEM TO BE SOLVED: To devise a thrust load working on a rotor to constantly work in one direction without increasing the thrust load large whichever of forwarding and backwarding directions rotation of an electric motor is in. SOLUTION: Rotation of a rotor 15 of an electric motor 5 is transmitted to a sun gear S1 through a rotor hub 19 and a shaft 20, decelerated by a first planetary gear 6b, decelerated further by a second planetary gear 6a from the sun gear S2, and output from an output shaft 10. The both sun gears S1, S2 are made of helical gears of helix angles in the opposite directions, and thrust loads work in a direction to push each other or in a direction to separate from each other in accordance with the rotating direction of the rotor. In the case of pushing each other, the thrust load of the sun gear S1 works on the shaft 20 through a step part 20a and works on the side of a car body against the thrust load of the sun gear S2. In the case of separating from each other, the thrust load of the sun gear S1 mainly works on the side of the car body.
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