| 摘要 |
PURPOSE:To reduce unstableness of positioning by installing the parts each having a large magnetic resistance at the proper places in the circumferential direction so that the magnetic flux of a permanent magnet hardly passes through yokes in the circumferential direction. CONSTITUTION:Grooves 18 are cut at equal intervals in the axial direction on the inside and the outside stator yokes 13 and 14 of a stator part 11, and the magnetic resistance in the circumferential direction is made exceedingly large. Although the magnetic flux of a permanent magnet 12 in the stator part 11 passes from the outside stator yoke 14 to an outside rotor yoke 17 and from an inside rotor yoke 16 to the inside stator yoke 13, the shifting interference of the magnetic flux is reduced markedly, even if the interval between yokes varies partly, by increasing the magnetic resistance in the circumferential direction, so unstableness of positioning due to deviation of the magnetic flux can be reduced. |
