| 摘要 |
PURPOSE:To realize low torque at the start of rotation without any friction even after long-period use by forming two thrust bearings which are considerably different in gap and load capacity characteristic on both surfaces of a collar, and providing a pivot spherical bearing small in contact area at stop to the side of a bearing less in rigidity. CONSTITUTION:The collar 3 is provided to a thrust bearing, a pivot bearing 4 is provided in a V groove 5 at the upper end center part of a fixed shaft 1, and a herringbone bearing 7 is provided to the top surface 8 of the collar 3. A herringbone has such a groove shape that lubricating fluid is forced in both a centrifugal and a center direction. Oil film pressure is generated on bearing surfaces 7 and 11 by rotation and the herringbone 7 carries forcibly the lubricating fluid 201, so that large pressure is generated by pumping effect and wedge effect even if there is a sufficient gap delta2. A step bearing 11, on the other hand, varies in relative gap in a peripheral direction, so a plus load is obtained. Consequently, both upper and lower bearing surfaces 7 and 11 of the collar 3 keep an uncontacted state in a low-torque rotation state at the start of rotation. |
