Fluid dynamic pressure bearing device, spindle motor and disk drive apparatus

A fluid dynamic bearing mechanism comprising:

• a stationary shaft arranged to extend in a vertical direction along a central axis;
• a sleeve portion arranged to rotate with respect to the shaft;
• a tubular thrust portion fixed to the shaft on a lower side of the sleeve portion, and including an upper end surface arranged opposite to a lower end surface of the sleeve portion;
• a cover portion attached to the sleeve portion and arranged opposite to an outside surface of the thrust portion;
• and
• a lubricating oil;
• wherein
• the shaft and the sleeve portion are arranged together to define a radial gap therebetween, the lower end surface of the sleeve portion and the upper end surface of the thrust portion are arranged together to define a thrust gap therebetween, and the lubricating oil is arranged in the radial gap, the thrust gap, and a gap between the thrust portion and the cover portion;
• the radial gap includes a radial bearing portion arranged to generate a radial dynamic pressure acting on the lubricating oil through a dynamic pressure groove;
• the thrust gap includes a thrust bearing portion arranged to generate a thrust dynamic pressure acting on the lubricating oil through a dynamic pressure groove;
• the cover portion and the outside surface of the thrust portion are arranged together to define a tapered gap therebetween, the tapered gap gradually increasing in width in a downward direction, and including an interface of the lubricating oil located therein;
• the thrust portion is fixed to the shaft;
• an inside surface of the thrust portion includes:
• an inside surface contact portion arranged in direct contact with an outside surface of the shaft;
• and
• an inside surface lower non-contact portion spaced away from the outside surface of the shaft, and arranged to extend downward from a lower end of the inside surface contact portion;
• the outside surface of the thrust portion includes an outside surface inclined portion defined by a substantially conical surface arranged to become gradually closer to the central axis with decreasing height, and arranged in contact with the interface of the lubricating oil;
• and
• the lower end of the inside surface contact portion is arranged at a level higher than that of a lower end of the outside surface inclined portion.