Patent ID: 7241050

Claim:
A hydrodynamic bearing device comprising: a shaft; a sleeve including a bearing hole with an open end that opens and a close end that is closed, the shaft being inserted into the bearing hole for freely rotating with a predetermined gap in between; and a cover for covering an end face on the open end of the sleeve, a dynamic pressure generating groove formed on at least one of an outer peripheral surface of the shaft and an inner peripheral surface of the sleeve where the shaft and the sleeve face each other, said dynamic pressure generating groove supporting the shaft with respect to the sleeve in a relatively rotatable fashion in a radial direction in a non-contacting manner, a communicating path formed in the sleeve, for communicating a space region on the close end face of the sleeve and a space region between the cover and the end face on the open end of the sleeve, and an operating fluid being filled into a space in the sleeve including a space between the cover and the sleeve, whereby when the shaft is relatively rotated with respect to the sleeve, the operating fluid is circulated through a space between the shaft and the sleeve, said space region on the close end side leading to the space between the shaft and the sleeve, said communicating path leading to the space region on the close end side, and the space between the cover and the sleeve leading to the communicating path, wherein an introducing minimum clearance for causing capillary phenomenon is formed to extend to the open end of the bearing hole from a location in a proximity of the opening of the communicating path between the cover and the end face on the open end of the sleeve, so that the operating fluid from the communicating path flows into the bearing hole due to the capillary phenomenon, a vent hole leading to an outside air is formed at a location not formed with the introducing minimum clearance of the cover, and a fluid storage space for storing the operating fluid is formed by being depressed so as to become a space larger than the clearance of the introducing minimum clearance at an inside surface of the cover facing the end face on the open end of the sleeve or at the end face on the open end of the sleeve, thereby to communicate the introducing minimum clearance and the vent hole in the circumferential direction.