1. Technical Field
The present invention relates to a spindle motor.
2. Description of the Related Art
A spindle motor that is used as a disk driving apparatus driving a recording disk such as a hard disk or the like has been widely used because of the increased necessity of a portable auxiliary memory and subsequently, has improved day-by-day. The spindle motor uses a lubricant fluid such as oil or the like as a fluid dynamic bearing, in order to support a shaft and a sleeve to be relatively rotatable. However, an interface of oil is axially formed so that it is very weak against external impact and the viscosity of oil lowers at high temperature, causing the oil to run down due to gravity.
More specifically, FIG. 1 is a cross-sectional view schematically showing a spindle motor according to the prior art. As shown in the figure, a spindle motor 100 includes a shaft 110, a hub 120, a sleeve 130, a magnet 140, and an armature 150. When power is applied to the armature 150 configured of a core and coils, the shaft 110 and the hub 120 are rotatably driven by electromagnetic force generated between the armature 150 and the magnet 140.
As the interface of oil, used as the fluid dynamic bearing, is formed between the hub 120 and the sleeve 130 opposite to each other in the circumferential direction of the shaft, the interface of oil is very weak against impact in the axial direction of the shaft and the leakage of oil may generate when external impact are applied, while the interface of oil being momentarily collapsed. When viscosity of oil lowers at a high temperature, the viscosity of oil lowers to run down due to gravity.