| 摘要 |
A yoke housing (4) that receives an armature (7) has a plurality of permanent magnets (primary magnetic poles) (5, 6) secured to an inner peripheral surface of the yoke housing (4). Furthermore, the yoke housing (4) includes a plurality of groove-like reduced thickness portions (4f, 4g) for increasing a magnetic resistance. Each reduced thickness portion (4f, 4g) extends along a center line of a corresponding one of the permanent magnets (5 or 6). <IMAGE> |
