| 摘要 |
<p>PROBLEM TO BE SOLVED: To suppress a movement of a lubricant liquid to a top end to a comparatively small amount, in the case where pressure with which the lubricant moves to the top end is generated in a top side radial bearing part when a rotating sleeve body rotates. SOLUTION: An annular recessed portion 60 having an opening on the outer side in a radial direction is provided between upper and lower radial bearings part 56, 58 on an outer peripheral surface of a fixing shaft member 12a. In an upper part of the annular recessed portion 60 which is formed with a middle clearance enlarged portion 62 in radio direction in a space to the outer peripheral surface of a fixing shaft member 12a, a outer diameter reduces comparatively abruptly and in a lower part thereof, an outer diameter reduces comparatively slowly. On the upper and lower sides boundary part of the annular recessed portion 60, an inner opening 64b of a ventilating hole 64 in the fixing shaft member 12a is provided, and an outer opening 64a is provided near a boundary part between the lower radial bearing part 58 and an lower end clearance enlarged portion 28 in radial direction. Therefore, when a rotating sleeve body 18 rotates, an lower end side interface of lubricant 44 is pulled into the upper part or above of the lower end clearance enlarged portion 28 in radial direction to open the outer opening 64a to outside air.</p> |
