| 摘要 |
PROBLEM TO BE SOLVED: To avoid the deterioration of a rotation characteristics of a disc drive motor which has ball bearings whose inner rings and outer rings are made of steel and whose rolling elements are made of a ceramic even if the motor is turned at a high revolution and, further, avoid the deterioration of the rotation characteristics and the support stability of the ball bearings when a disc fixing annular member is attached to the disc drive motor. SOLUTION: A disc drive motor has a column-shaped fixed shaft 1, a pair of ball bearings 3a and 3b which are coupled with the fixed shaft 1, whose inner rings 7a and 7b and outer rings 8a and 8b are made of steel and whose rolling elements 9a and 9b are made of a ceramic, a cylindrical rotary unit 2 which is rotatably supported by the pair of ball bearings 3a and 3b and on the outer circumferential surface of which a disc is loaded, a stator 4 fixed to the fixed shaft 1 between the pair of ball bearings 3a and 3b, and a rotor magnet which is fixed to the inner circumference of the rotary unit 2 so as to face the stator 4, and preliminary pressure is added to the pair of ball bearings 3a and 3b. The thermal expansion coefficient of the material of the fixed shaft 1 is smaller than the coefficient of the material of the rotary unit.
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