Fluid dynamic bearing, spindle motor, disk drive, and manufacturing method of fluid dynamic bearing

A fluid dynamic bearing supporting a rotating member in a rotatable manner relative to a stationary member, the fluid dynamic bearing comprising:

• a first member including a substantially cylindrical sleeve;
• a second member including a shaft arranged inside the sleeve, the shaft being rotatable relative to the sleeve;
• a radial dynamic bearing and a thrust dynamic bearing supporting one of the first and second members in a rotatable manner relative to the other of the first and second members;
• and
• lubricating fluid retained in the radial dynamic bearing and the thrust dynamic bearing;
• wherein
• the first and second members respectively have thrust bearing surfaces defining the thrust dynamic bearing, the thrust bearing surfaces being opposed to each other with a thrust gap interposed therebetween;
• one of the thrust bearing surfaces has a plurality of dynamic pressure generating grooves provided thereon, the dynamic pressure generating grooves generating a dynamic pressure of the lubricating fluid in the thrust gap during relative rotation of one of the first and second members to the other;
• and
• a flat region is arranged at and along an outer peripheral edge of the one of the thrust bearing surfaces, a distance between the thrust bearing surfaces being larger in the flat region than in a remaining region of the one of the thrust bearing surfaces.

A manufacturing method of a dynamic bearing member having a thrust bearing surface, the method comprising the steps of:

• forming a plurality of dynamic pressure generating grooves on the thrust bearing surface;
• holding an extraneous portion surrounding an outer peripheral edge of the thrust bearing surface;
• and
• cutting the thrust bearing surface from the extraneous portion by pressing the outer peripheral edge of the thrust bearing surface in a direction that is substantially perpendicular to the thrust bearing surface.