Patent ID: 8110957

Claim:
A permanent magnet motor comprising: a stator having a stator core and a coil wound on the stator core; and a rotor having a plurality of permanent magnets arranged in a ring shape, the stator core having a ring-shaped yoke part and teeth parts extending radially from the yoke part, wherein the transverse cross section of the permanent magnet has an inside periphery consisting of a first arc having the center of curvature O 1 and the radius of curvature R 1 , and an outside periphery consisting of a second arc having the center of curvature O 2 and the radius of curvature R 2 , a third arc having the center of curvature O 3 and the radius of curvature R 3 and joined to one end of the second arc, and a fourth arc having the center of curvature O 4 and the radius of curvature R 4 and joined to the other end of the second arc; when the middle point of the second arc is A, one end thereof is C, and the other end is C′, the center of curvature O 2 is disposed on a line segment AO 1 where the line segment AO 1 is a line segment connecting the center of curvature O 1 to the middle point A, the center of curvature O 3 is disposed on a line segment CO 2 where the line segment CO 2 is a line segment connecting the center of curvature O 2 to the one end C of the second arc, and the center of curvature O 4 is disposed on a line segment C′O 2 where the line segment C′O 2 is a line segment connecting the center of curvature O 2 to the other end C′ of the second arc; and the radii of curvature R 2 , R 3 and R 4 and the length of the line segment AO 1 satisfy Formula 1: AO1>R2>R3=R4. (Formula 1).