| 摘要 |
PURPOSE:To obtain a low leakage magnetic circiut by performing an annular magnetic void with the first and the second yokes which are fixed at a magnet and the upper and the lower end faces of it, providing a through hole where a driving transmission member is pierced at the upper part of the magnetic void and providing the third yoke which is connected with the second yoke at the outer peripheral part. CONSTITUTION:Assuming that, as the direction of magnetization of a magnet 16, a face contacting with a bottom plate 15 is set as ana N-pole and the face contacting with the first top plate is set as an S-pole, the leakage flux of a magnetic circuit 29 is shown as a broken line at a right half cross section. Namely, so that the first top plate 17 which performs the S-pole is enclosed by the bottom plate 15, the second top plate 19 and a cylindrical yoke 21, the leakage flux is not leaked to the outside of the magnetic circuit 29. Thus, by enclosing the first yoke by the second and the third yokes which perform other magnetic pole, the leakage flux is generated between the first yoke and the second and the third yokes and is not leaked to the outside of the space that is enclosed by the second and the third yokes. |
