| 摘要 |
PROBLEM TO BE SOLVED: To ensure a magnetic path of a rotor magnet sufficiently while restraining the increase in weight as much as possible, without increasing the overall thickness of a frame. SOLUTION: A plurality of rotor magnets 2 are disposed at the inner peripheral part of a frame 3 made of iron plate. A ring member 7 made of magnetic substance is disposed at the outer peripheral part of an annular wall 5. The rotor magnet 2, the frame 3, and the ring member 7 are integrally formed out of resin 8. The magnetic path of the rotor magnet 2 is ensured by the annular wall 5 and the ring member 7. Retaining part 6 for retaining the ring member 7 is provided at the end part of the annular wall.
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