Patent ID: 7652405

Claim:
A permanent magnet embedment rotating electric machine, comprising: an annular stator; a plurality of teeth arranged on an inner circumference of the stator, a slot is defined between each adjacent pair of the teeth; a plurality of coils, each coil being arranged in one of the slots; a rotor located inside of the stator, the rotor defining a rotational axis, a virtual circumferential surface about the rotational axis, and an outer circumference, wherein the outer circumference has a plurality of circumferential portions, the circumferential portions being included in the virtual circumferential surface, and each of the circumferential portion defining an angular width A and a radius R relative to the rotational axis; a plurality of permanent magnets embedded inside the rotor, the permanent magnets defining a number of poles p, each of the permanent magnets having a magnetic pole center, wherein each of the circumferential portions corresponds to the magnetic pole center, and wherein the circumferential portions, which correspond to the permanent magnets, respectively, are spaced from each other; and a plurality of convex portions located inside of the virtual circumferential surface, each convex portion connecting an adjacent pair of the circumferential portions with each other, each convex portion being an arcuate curve bulging radially outward, wherein each convex portion defines a minimum radius, which is a minimum value of a distance between the rotational axis and the convex portion, wherein the difference between the radius R and the minimum radius is a depth Dh, where Dhr=Dh×25.5/R, and wherein the range of the angular width A and the range of the depth Dh are set by the following expression, (5.6 ×Dhr+ 11.3)°×6 /p≦A< 35°×6 /p and A<[ 360 /p− 2×arccos(1 −Dhr /25.5)]° (1).