Patent ID: 8138641

Claim:
A permanent-magnet rotary electric machine comprising: a stator including an approximately ring-shaped core back portion having an angular or rounded outer shape, and 4m main poles radially projecting from the core back portion where m is an integer equal to or larger than 2, each of the main poles having Ns inductor teeth at a tip thereof where Ns is an integer equal to or larger than 2; and a rotor opposed to the stator via an air gap to be freely rotatable and including two rotor units adjacent to each other in an axial direction, each of the rotor units including a pair of rotor magnetic poles and a permanent magnet which arranged between the rotor magnetic poles, the permanent magnet of one of the rotor units and the permanent magnet of the other rotor unit being magnetized in opposite directions along the axial direction; wherein each of the rotor magnetic poles has Nr magnetic teeth at a regular pitch on an outer periphery thereof where Nr is an integer equal to or larger than 2, the pair of rotor magnetic poles of each of the rotor units are arranged with the magnetic teeth of one of the rotor magnetic poles offset from those of the other rotor magnetic pole by half of the pitch in a circumferential direction and with the magnetic teeth of adjacent rotor magnetic poles aligned with each other in the axial direction; a tooth pitch of the inductor teeth of each of the main poles of the stator is different from the pitch of the magnetic teeth of the rotor to generate a fourth harmonic component of a permeance between the stator and the rotor substantially zero; and adjacent rotor magnetic poles of the rotor units have a same polarity as one another.