HYDRODYNAMIC BEARING DEVICE, SPINDLE MOTOR, AND INFORMATION DEVICE

摘要

The hydrodynamic bearing device has a sleeve composed of a sintered material and having a compression-absorbing space inside the sleeve, the sleeve having a bearing hole in the center thereof; a shaft rotatably inserted into the bearing hole; a bearing portion formed between the bearing hole and the shaft; a hydrodynamic groove formed on at least one of the internal peripheral surface of the bearing hole and the external peripheral surface of the shaft; a concavity having one or more steps and formed to one end of the sleeve in the axial direction; a convexity formed to the other end of the sleeve in the axial direction, the convexity having a shape similar to the concavity; and a lubricating fluid filled in the gap of the bearing portion. The hydrodynamic bearing device has a readily obtainable predetermined shape precision, the internal density of the sintered material is made uniform, and lubricating fluid therein does not leak from the surface.