Patent ID: 7529063
Filing Date: 2009-05-05
Classification: G11B

Abstract:
1. A spindle motor for a disk drive comprising: a base; a sleeve fixed on the base and having a space portion therein; a shaft rotatably installed in the space portion of the sleeve and having a shape such that a diameter of the shaft decreases from a middle portion of the shaft in a lengthwise direction to both ends thereof, wherein a bearing gap generated between an outer circumferential surface of the shaft and an inner circumferential surface of the sleeve is filled with air, and a first plurality of grooves formed in an outer circumferential surface of a first portion of the shaft, the first portion defined between one end of the shaft and the middle portion, and a second plurality of grooves formed in the outer circumferential surface of a second portion of the shaft, the second portion defined between the other end of the shaft and the middle portion, wherein each groove of the first plurality of grooves extends in a different direction than each of groove of the second plurality of grooves, and each groove of the first plurality of grooves intersects a groove of the second plurality of grooves at the middle portion.