Dynamic pressure bearing apparatus and fan

A dynamic pressure bearing apparatus comprising:

• a bearing portion;
• 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 inner circumferential surface of the bearing portion and the outer circumferential surface of the shaft on an upper side of the radial dynamic pressure bearing 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, and fixed to an upper portion of the bearing portion;
• wherein
• a minute vertical gap extending in an axial direction is defined between the outer circumferential surface of the shaft and an inner circumferential surface of the annular member;
• 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.