| 摘要 |
PROBLEM TO BE SOLVED: To provide a pre-load variable method for bearing which is freely adjustable for the pre-load by increasing or decreasing a supply current to a motor, in response to the size of the pre-load without providing a hydraulic means. SOLUTION: This method comprises two bearings, respectively bearing a main shaft 1 at both the end portions of a main shaft 1, an outer frame constituted with a frame 7 and a bracket 8, a main shaft 1 supported freely rotatably by this outer frame through the bearings 5, 6, a rotor 2 mounted on the main shaft 1, and stator 3 fixed to a frame 7 via a slight gap facing opposite the rotor 2. In this case, a stator 3 and a rotor 2 have tapered surfaces respectively, and a gap 4 is created between these tapered surfaces, or a deviationδis provided between the center attaching positions of the stator 3 and the rotor 2 in the axial direction, a motor current is adjusted and the magnetic thrust between the stator 3, and the rotor 2 is varied in response to the rotation of the rotor 2.
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