Image Number 5 for United States Patent #8113715.
In this type of fluid dynamic bearing device, a dynamic pressure generating part having high molding accuracy is formed at low cost. A rotating member 2 includes a shaft part 9, and a holding member 10 as a thrust member provided in one end of the shaft part 9. In a partial annular region of a lower end surface 10a1 of a disk part 10a making up the holding member 10, a region where a plurality of dynamic pressure grooves 10a2 and a plurality of sectioning parts 10a3 formed between the plurality of dynamic pressure grooves 10a2 to section the respective dynamic pressure grooves 10a2 are arrayed spirally is formed. The above-described dynamic-pressure-groove 10a2 arrayed region is opposed to an upper end surface 8a of a housing part 8, and forms a thrust bearing clearance of a thrust bearing part T between the dynamic-pressure-groove 10a2 and the upper end surface 8a during the rotation of the shaft part 9. The above-described dynamic-pressure-groove 10a2 arrayed region is molded in the lower end surface 10a1 of the holding member 10 by press working.