Patent ID: 7514831
Filing Date: 2009-04-07
Classification: F16C,G11B,H02K

Abstract:
1. A motor having a fluid dynamic bearing, comprising: a rotary unit; a stationary member forming the fluid dynamic bearing with the rotary unit inserted therein for supporting the rotary unit in opposed relation thereto rotatably around a center axis through a minuscule gap therebetween; a rotor magnet mounted concentrically with the center axis on the rotary unit and having a plurality of magnetic poles arranged alternately along a peripheral direction thereof; a stator with coils wound on teeth (magnetic pole teeth) arranged radially of the center axis and mounted on the stationary member concentrically with the center axis; a power supply means for supplying a field drive voltage to the coils; a plurality of dynamic pressure generation grooves arranged equidistantly along the peripheral direction on at least one of opposed surfaces of the rotary unit and the stationary member making up the fluid dynamic bearing; and a lubricating fluid held in the minuscule gap, wherein a greatest common divisor of a number P of poles and a number S of teeth is not smaller than a number N of drive phases for energizing the coils on the one hand, and the number P of the poles, the number S of the teeth and a number C of the dynamic pressure generation grooves satisfy relations iP≠C, P/j≠C, mS≠C, and S/n≠C on the other hand, where i, j, m, n are independent and arbitrary natural numbers.