| 主权项 |
1. An annular magnet for a rotor, comprising:
a hollow magnet body having an outer circumferential surface that defines a cylindrical shape and an inner circumferential surface that defines an inlet hole, which is adapted for receiving a back iron, and which has a cross-section substantially shaped in an equiangular polygon, said magnet body further having a plurality of magnetic sectors that surround a central axis of said inlet hole; wherein said magnetic sectors correspond respectively to the sides of the equiangular polygon, each of said magnetic sectors having a magnetic polarity opposite to that of an adjacent one of said magnetic sectors, a thickness of said magnet body at a junction between two adjacent ones of said magnetic sectors being smaller than a thickness of said magnet body at a center portion of each of said magnetic sectors. |
