Patent ID: 7569960

Claim:
A yoke assembly for a stator of a starter motor, comprising: a cylindrical yoke having an inner peripheral wall; a plurality of subassemblies including magnet springs and auxiliary poles, with each of the magnet springs and each of the auxiliary poles being assembled to each other in advance after which the subassemblies are fixedly secured to the inner peripheral wall of the yoke at circumferentially and equidistantly spaced positions thereof; and a plurality of stator elements, each composed of a main pole made of a permanent magnet, which are fixedly secured to the inner peripheral wall of the yoke and each of which is fixedly retained with adjacent magnet springs, wherein each of the magnet springs includes a back plate, fixedly secured to the inner peripheral wall of the cylindrical yoke, and side plates radially extending from the back plate toward the center of the cylindrical yoke, with the back plate and the side plates formed in a nearly U-shape in cross section and opening toward the center of the cylindrical yoke, wherein each of the auxiliary poles is supported with one of the side plates and held in contact with the main pole on a side increasing magnetic fluxes, and each of the subassemblies is unitized such that one of each auxiliary pole and each magnet spring has a concaved portion and the other has a convexed portion with the concaved portion and the convexed portion being held in mating engagement with each other.