Patent ID: 7250703

Claim:
A permanent magnet motor comprising: a stator; a rotor including a rotor core made by stacking a plurality of steel plates and having a plurality of magnetic insertion holes aligned peripherally and a plurality of permanent magnets of a plurality of magnetic poles serving as field magnets and inserted in the magnetic insertion holes respectively, wherein the rotor core includes a plurality of magnetic pole sections further including magnetic pole faces opposing the stator from a radial direction with a gap between the stator and the magnetic pole faces, each magnetic pole section having both peripheral ends and including first to third faces, the first face being formed substantially on a peripherally central part thereof and having a substantially peripherally uniform width of the gap, the first face being formed substantially into a circular arc shape, each of the second and third faces being formed on both peripheral ends thereof respectively and having a width of the gap which is rendered larger as each of the second and third faces comes close to a boundary between the magnetic poles; and the first face ranges from ±15 degrees to ±35 degrees in electrical angle about a center of the magnetic pole and has such a circular arc shape that the gap width is increased by about 10% relative to a minimum gap width and each of the second and third faces has such a shape that a maximum gap width at the boundary side of the magnetic pole is three times as large as the minimum gap width or above.