Dynamic pressure bearing device

摘要

A dynamic pressure bearing device includes a sleeve and a shaft member which is rotatably fitted into the sleeve. The sleeve is made of an aluminum alloy containing a carbon fiber and has a radial bearing surface formed in an inner peripheral surface and a thrust bearing surface formed in a lower end surface. The shaft member includes a base portion having a thrust receiving surface formed on an upper surface, and a shaft portion extending upright from the base portion and having a radial receiving surface formed on an outer peripheral surface. A first dynamic pressure generating groove is formed in at least one of the radial bearing surface and the radial receiving surface, and a second dynamic pressure generating groove is formed in at least one of the thrust bearing surface and the thrust receiving surface. The shaft member including the shaft portion and the base portion is molded from a synthetic resin as a unitary body. The thrust bearing surface is tapered so that a thrust bearing gap formed between the thrust bearing surface and the thrust receiving surface increases gradually, radially and outwardly.