Patent ID: 8487495

Claim:
A rotor comprising: a cylindrically shaped hub secured to an output shaft; an annularly shaped rotor core disposed radially outward of the hub and connected to the hub with a plurality of ribs therebetween so as to be formed integrally with the hub, the rotor core including openings substantially equally spaced apart from one another in a circumferential direction of the rotor; holes formed between the hub and the rotor core so as to be provided among the ribs, each of the holes including an arc-shaped surface and a recessed portion, the arc-shaped surface centering on a center of the hub and corresponding to an inner circumferential surface of the rotor core, the recessed portion bulging more outward than the arc-shaped surface in a radial direction of the rotor; and permanent magnets retained in the openings, wherein salient poles are each formed between the openings in the circumferential direction of the rotor and provided on an outer circumference of the rotor core, and wherein, when viewed from a front along a line of axis of the rotor, a radially outermost part of the recessed portion is provided in a region enclosed by a first virtual line and a second virtual line, the first virtual line connecting the center of the hub and a circumferential middle position on an outer circumference of a magnetic pole of the rotor core having the permanent magnets provided therein, a the second virtual line connecting the center of the hub and a circumferential middle position on an outer circumference of the salient pole adjacent to the magnetic pole at a leading side in a rotational direction of the rotor.