Patent ID: 6936944
Filing Date: 2005-08-30
Classification: G11B

Abstract:
1. A spindle motor for hard disk drives, comprising: a base formed as a lower portion of the spindle motor; a hub, rotatably fitted on the base, for fixedly mounting a platter; a stator constructed for a coil to be wound around a plurality of poles, the poles being radially formed along an outer circumference of a core of the stator, the core being formed with an open press-fit portion; an aerodynamic bearing assembly comprising a main bearing body establishing aerodynamic pressure in cooperation with the hub and an auxiliary bearing body firmly supported in the open press-fit portion of the stator; and a permanent magnet, fitted on an inner circumferential surface of the hub, for generating a magnetic field in cooperation with the coil, wherein a midpoint of the vertical width of the poles wound around by the coil of the stator is placed within a magnetic field in a manner so as not to be flush with a midpoint of the vertical width of the permanent magnet fitted on the inner circumferential surface of the hub, forming a mechanical offset between the poles and the permanent magnet, thereby when power is not supplied, magnetic forces in both radial and thrust directions, which are generated between the poles and the permanent magnet between which the mechanical offset is formed, cause a mechanical preload to be established between the hub and the aerodynamic bearing assembly so that an air gap is maintained between the hub and the aerodynamic bearing assembly.