FLUID DYNAMIC BEARING DEVICE AND MOTOR WITH SAME

摘要

A fluid dynamic bearing device including: a bearing sleeve fixed to an inner periphery of a housing; a shaft member removably inserted along an inner periphery of the bearing sleeve; an annular member having an inner peripheral surface for defining a radial gap together with an outer peripheral surface of the shaft member; and radial bearing portions and a thrust bearing portion for supporting the shaft member. At least the radial bearing gap at each of the radial bearing portions, and a bottom gap having the thrust bearing portion received therein are filled with lubricating oil. A void section is formed in an interior space of the housing. Assuming that d1 represents a gap width of the radial bearing gap and d2 represents a gap width of the radial gap, a relationship of 30d1≦d2≦250d1 is satisfied.

主权项

1. A fluid dynamic bearing device, comprising:
a housing formed into a bottomed cylindrical shape so as to have one open axial end and another closed axial end; a bearing sleeve fixed to an inner periphery of the housing; a shaft member removably inserted along an inner periphery of the bearing sleeve; an annular member having an inner peripheral surface for defining a radial gap together with an outer peripheral surface of the shaft member, the annular member being fixed to an inner periphery of the one open axial end of the housing in a state of engaging with the bearing sleeve in an axial direction; a radial bearing portion for supporting the shaft member in a radial direction by an oil film of lubricating oil, which is formed in a radial bearing gap defined between an inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member; a thrust bearing portion for supporting the shaft member in a thrust direction; and a bottom gap having the thrust bearing portion received therein, and being filled with the lubricating oil, wherein the housing has a void section formed in an interior space thereof, and wherein assuming that d1 represents a gap width of the radial bearing gap and d2 represents a gap width of the radial gap, a relationship of 30d1≦d2≦250d1 is satisfied.