Patent ID: 7307364

Claim:
A motor comprising: a stator having cores and coils; a rotor having a permanent magnet arranged in a ring shape on the radial inner side of said stator, facing said cores and coils; and a fluid dynamic bearing which rotatably supports said rotor with respect to said stator, said fluid dynamic bearing having a shaft body fixed to said rotor, a shaft body support part, which has a closed end and is fixed to said stator, and in which a shaft body insertion hole is formed for rotatably accommodating said shaft body, and a fluid which is filled into a clearance formed between said shaft body and said shaft body insertion hole, wherein said shaft body has a thrust shaft part formed in a flange shape in an axial central part, and a radial shaft part and a support part which are formed cylindrically on the opposite axial sides of said thrust shaft part, wherein said shaft body support part has a small diameter cylinder part which forms a closed end side of said shaft body insertion hole, and into which said radial shaft part is inserted such that it rotates freely, a large diameter cylinder part which forms an open end side of said shaft body insertion hole, and into which said thrust shaft part is inserted such that it rotates freely, and a counter plate which covers the open end of said 10 shaft body insertion hole, and forms a capillary seal between itself and said support part, and a dynamic pressure generation unit comprising said fluid, and dynamic pressure generating grooves formed in at least one of the outer faces of said thrust shaft part and the outer faces of said radial shaft part, and the inner face of said shaft body insertion hole facing these outer faces, wherein a ratio of the outer diameter of said thrust shaft part to the outer diameter of said permanent magnet is approximately 1 to 2.