Patent ID: 7699527

Claim:
A fluid dynamic bearing device comprising: a housing having an opening at a first end thereof and a bottom portion at a second end thereof; a sealing portion sealing the opening of the housing; a bearing sleeve accommodated in the housing; a shaft member accommodated in the housing; a radial bearing portion having a radial bearing clearance between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve, the radial bearing portion radially supporting the shaft member in a non-contact fashion by means of a lubricant film when the shaft member rotates relative to the bearing sleeve; and a thrust bearing portion supporting the shaft member in a thrust direction, wherein a sealing space is provided between an inner peripheral surface of the sealing portion the outer peripheral surface of the shaft member, wherein the inner peripheral surface of the sealing portion includes a protrusion extending radially inwards, the protrusion constituting a first portion of the inner peripheral surface which protrudes from a second portion of the inner peripheral surface, and wherein the shaft member is provided with a small diameter portion, the protrusion and the small diameter portion being axially engaged with each other to prevent the shaft member from coming off.