Bearing mechanism, motor, and blower fan

A bearing mechanism comprising:

• a first component portion including a first tubular portion centered on a central axis extending in a vertical direction;
• a second component portion including a second tubular portion centered on the central axis, and arranged to be rotatable relative to the first component portion, an inner circumferential surface of the second tubular portion being arranged radially opposite an outer circumferential surface of the first tubular portion;
• and
• a lubricating oil;
• wherein
• one of the first and second component portions includes a shaft centered on the central axis, while the other of the first and second component portions includes a sleeve in which the shaft is inserted;
• the lubricating oil is arranged to continuously exist between a portion including the sleeve and a portion including the shaft;
• a radial dynamic pressure bearing portion is defined between the shaft and the sleeve, or a thrust dynamic pressure bearing portion is defined in a thrust gap between an upper surface of the sleeve and a member opposed to the upper surface of the sleeve;
• the outer circumferential surface of the first tubular portion and the inner circumferential surface of the second tubular portion are arranged to together define a seal gap therebetween, the seal gap including a seal portion in which a surface of the lubricating oil is located;
• a member including the first tubular portion is either a resin-molded article or a metal die-cast article;
• the first tubular portion includes, in an area where the outer circumferential surface of the first tubular portion and the lubricating oil are in contact with each other, a maximum outside diameter portion at which the first tubular portion is arranged to have a greatest outside diameter, an annular shoulder portion including a surface facing toward the surface of the lubricating oil and at which the first tubular portion is arranged to have an outside diameter smaller than that of the maximum outside diameter portion, and an inclined portion at which the outside diameter of the first tubular portion is arranged to gradually decrease from the annular shoulder portion toward the surface of the lubricating oil;
• and
• the outer circumferential surface of the first tubular portion includes a line joining the maximum outside diameter portion and the annular shoulder portion to each other.