Patent ID: 7183684

Claim:
A permanent magnet rotary motor comprising: a stator including a stator core having N slots and N magnetic pole sections (N: a natural number of 2 or more) and exciting windings wound on said N magnetic pole sections, each of said N slots and said N magnetic pole sections being arranged to be spaced at equal intervals in a peripheral direction thereof; and a rotor having a rotor core and P permanent magnets (P: a natural number of 2 or more), said rotor rotating with respect to said stator, said P permanent magnets being provided on a surface of said rotor core or a rotor shaft to be spaced at equal intervals in a peripheral direction of said rotor core or said rotor shaft, said P permanent magnets having magnetic pole surfaces opposing to said magnetic pole sections in a radial direction of said rotor core or said rotor shaft; each of magnetic pole surfaces of said N magnetic pole sections being so formed as to be located on a virtual cylindrical surface centering on a center of said stator core; and each of said magnetic pole surfaces of said permanent magnets comprising an arc surface and a pair of inclined surfaces located on both sides of the arc surface in the peripheral direction of said rotor core, the arc surface being located at a central portion of the magnetic pole surface and being formed so that a gap between the arc surface and the magnetic pole surface of the magnetic pole section is constant, the pair of inclined surfaces being inclined in such a manner that a gap between the inclined surface and the magnetic pole surface of the magnetic pole section spreads toward the peripheral direction as leaving from the arc surface; wherein a pair of end surfaces of each of said permanent magnets, located on both sides of each of said permanent magnets in the peripheral direction of said rotor core or said rotor shaft and opposing to each other in the peripheral direction, are so formed as to be substantially parallel to a virtual plane, said virtual plane extending in the radial direction while passing through said center of said stator core and a center of the arc surface; and a length of the arc surface in the peripheral direction of said rotor core or said rotor shaft and inclinations of the inclined surfaces are so determined that a pole arc ratio Ψ 1 of the arc surface of each of said permanent magnets and a pole arc ratio Ψ 2 of the magnetic pole surface of said each of said permanent magnets satisfy a relation of P/2N≦Ψ 2 −Ψ 1 ≦1.38×P/2N.