| 摘要 |
PROBLEM TO BE SOLVED: To maintain rigidity of a dynamic pressure fluid bearing at a nearly constant level independently of temperature, while excluding that bearing material is limited by coefficient of expansion, excessive working precision is required, bearing gap is narrowed at a high temperature region, and reliability is deteriorated. SOLUTION: A permanent magnet 21 magnetized in the shaft center direction, a magnetic path part member 22, and a columnar magnetostriction part member 23 are fitted in a penetrating hole of a fixed shaft body 12, and a closing thread 24 is screwed in the upper end portion to be fixed. The whole part of the outer peripheral surface of the magnetostriction part member 23 is rigidly bonded to the inner periphery of the fixed shaft body 12. At a normal temperature or lower, the magnetic flux of the permanent magnet 21 excellently passes the magnetic path part member 22. The magnetostriction part member 23 is intensively magnetized in the shaft center direction, stretched in the shaft center direction by magnetostriction, the external diameter is decreased, and the external diameter of a shaft part 12a is also decreased, so that the bearing gap is increased. At a high temperature region, the magnetic path part member 22 turns to paramagnetic material, and the magnetostriction part member 23 is scarcely magnetized, so that the external diameters of the magnetostriction part member 23 and the shaft part 12a increase and the bearing gap is reduced. |
