| 摘要 |
Reducing cogging of a small permanent magnet, while maintaining its magnetization characteristics favorable. Denoting the inner diameter of the permanent magnet by D, the pitch per one magnetic pole by P, and the phase number of an alternating current by M, and when D is 20 mm or less and the thickness of the permanent magnet t is set to fulfill the formula (4), then a good permanent magnet with low cogging is obtained. piD/(0.75PM-pi)<t<=piD/(0.5PM-pi) . . . (4). In the present embodiment, a permanent magnet for an outer rotor type is explained, but the formula (4) is applicable also to a permanent magnet for an inner rotor type. Moreover, in the present embodiment, it can be applied desirably to the small permanent magnet with an outer diameter of 20 mm or less. Further, in the present embodiment, the Sm-Co (samarium cobalt) based magnetic material was adopted as the magnetic material.
|
