Dynamic pressure bearing apparatus and fan

摘要

A dynamic pressure bearing apparatus includes a bearing portion; a shaft; a substantially annular bushing; a radial dynamic pressure bearing portion; and a seal gap. A minute horizontal gap extending radially is defined between an upper surface of the bearing portion and a lower surface of the bushing. The seal gap is arranged to be in communication with an exterior space through the horizontal gap.

主权项

1. A dynamic pressure bearing apparatus comprising:
a bearing portion, the bearing portion comprising:
a sleeve made of a metallic sintered body, the sleeve having an inner circumferential surface, an outer circumferential surface and an upper surface; anda bearing housing comprising an annular upper portion and a circumferential body, the annular upper portion inwardly extended from the circumferential body, a lower surface of the annular upper portion covering the upper surface of the sleeve, and an inner surface of the circumferential body covering the outer circumferential surface of the sleeve, a shaft inserted in the bearing portion, and arranged to rotate about a central axis relative to the bearing portion, an outer circumferential surface of the shaft including an attachment surface to which an impeller is to be attached directly or through one or more members; a radial dynamic pressure bearing portion defined by an inner circumferential surface of the bearing portion, the outer circumferential surface of the shaft, and a portion of a lubricating oil which exists in a radial gap defined between the inner circumferential surface of the bearing portion and the outer circumferential surface of the shaft, and arranged to generate a fluid dynamic pressure in the portion of the lubricating oil; a seal gap defined by the outer circumferential surface of the shaft and an inner surface of the annular upper portion, the seal gap including a seal portion having a surface of the lubricating oil defined therein; and an annular member arranged in an annular shape, the annular member fixed to an upper surface of the annular upper portion such that the annular member is radially opposed to an outer circumferential surface of the shaft, a vertical gap extending in an axial direction, the vertical gap defined between the outer circumferential surface of the shaft and an inner circumferential surface of the annular member, the seal gap opposed to the vertical gap in the axial direction; a minimum radial width of the vertical gap is arranged to be smaller than a maximum radial width of an opening of the seal gap; and the seal gap is arranged to be in communication with an exterior space through the vertical gap.