Patent ID: 7732963

Claim:
A small-sized motor comprising: a motor casing having an inner circumferential surface; an adhesive; a field magnet attached to said inner circumferential surface of said motor casing via said adhesive, said field magnet having four or more magnetic poles, wherein the field magnet is formed of a single ring-shaped magnet member having a predetermined thickness with respect to a radial direction and a predetermined length with respect to a thrust direction, the magnet member having a thin portion having a reduced thickness with respect to the radial direction of said magnet member, said thin portion and said inner circumferential surface defining a clearance, said adhesive being inserted into said clearance, said thin portion being located at a portion between said magnetic poles formed through magnetization, the thin portion being formed by cutting the magnet member from a radially outward side of said magnet member to form removed portions, said magnetization being performed in the radial direction such that S poles and N poles are alternately formed in the circumferential direction, said magnet member having cut portions formed at opposite end portions of said magnet member with respect to the thrust direction, each of said cut portions being located between the magnetic poles, each of said removed portions having one or more of an arcuate cross section, a semicircular cross section, a flat cross section and a concave cross section, wherein each said thin portion has different widths at opposite ends thereof with respect to the thrust direction.