Patent ID: 8106560
Filing Date: 2012-01-31
Classification: G11B,H02K

Abstract:
1. A brushless motor mounted on a disk drive comprising: a motor shaft; a head being movable in a radial direction of a disk; a rotor arranged to mount a disk, the rotor rotatably supported by the motor shaft; a motor-driving annular magnet arranged to drive a motor, the magnet fixedly attached around the periphery of the rotor and arranged to rotate with the rotor as a unit; a stator core facing the motor-driving annular magnet with a small gap and comprising a plurality of teeth, each of which having a polyphase motor-drive coil wound thereupon, and each of which extending radially from an annular portion of the stator core, the number of the teeth being an integral multiple of the number of coil-drive phases; and a motor base supporting the motor shaft, the motor base arranged to mount the stator core and, having one or more coil relief holes being formed thereon, wherein each coil relief hole allows the motor-drive coil wound around the teeth to enter, the number of the coil relief holes being less than the number of the teeth by the number of coil-drive phase multiplied by N, where N is a natural number, wherein the number of turns of the motor-drive coil wound around teeth corresponding to the portion of the motor base where the coil relief holes are not formed is set to less than the number of turns of the motor-drive coil wound around teeth corresponding to the portion of the motor base where the coil relief holes are formed, and wherein the coil relief holes are not provided for the portion of the motor base corresponding to one line or to the vicinity adjacent to the one line, the one line: a) intersecting with the motor shaft at a right angle on the motor base, b) passing through the center of the motor shaft, and c) lying generally in the direction of the head movement.