Working fluid injection apparatus, method of injecting working fluid, and method of manufacturing fluid dynamic pressure bearing

A method of injecting working fluid comprising the steps of:

• providing a bearing unit having a housing and a shaft that is inserted in the housing to form between the shaft and the housing a gap into which the working fluid is to be injected;
• storing the working fluid in an upper chamber of two chambers divided into the upper chamber and a lower chamber by a partition having a tapered hole, in a state in which a tapered shaft is inserted in the tapered hole from above to close it, and housing the bearing unit in the lower chamber with the gap of the bearing unit arranged vertically under the tapered hole;
• exhausting air from each of the upper chamber and the lower chamber to place the upper and lower chambers in a decompressed state;
• moving the tapered shaft in the vertical direction to open the tapered hole and to drop the working fluid in the upper chamber so as to fill an open portion of the gap of the bearing unit;
• inserting the tapered shaft into the tapered hole to close it;
• and thereafter releasing the decompressed state in the lower chamber.

A method of manufacturing a fluid dynamic pressure bearing comprising the steps of:

• constructing a bearing unit by inserting a shaft in a housing with a gap formed between the shaft and the housing, and exposing one end of the shaft from an opening portion of the housing;
• storing a working fluid in an upper chamber of two chambers divided into the upper chamber and a lower chamber by a partition having a tapered hole, in a state in which a tapered shaft is inserted in the tapered hole from above to close it, and housing the bearing unit in the lower chamber with a ring-shaped open portion of the gap formed between the opening portion of the housing and the bearing unit shaft being located vertically under the tapered hole;
• exhausting air from each of the upper chamber and the lower chamber to place the upper and lower chambers in a decompressed state;
• moving the tapered shaft in the vertical direction to open the tapered hole, and dropping the working fluid in the lower chamber so as to fill the open portion of the gap of the bearing unit in the lower chamber;
• inserting the tapered shaft into the tapered hole to close it;
• and thereafter releasing the decompressed state in the lower chamber.