| 摘要 |
PROBLEM TO BE SOLVED: To enable mass eccentricity to be corrected excellently so as to be suitable for rotation speed by using magnetic balls in a disk clamper. SOLUTION: With an optical disk 4 loaded, three magnetic balls 13 are freely rollably stored in a disk clamper 12 that holds the optical disk 4 between it and a turntable 3; a permanent magnet 14 fixed nearly in the center of the disk clamper 12 attracts the magnetic balls by generating a magnetic force that is larger than the centrifugal force actuating at the time of low speed rotation and that is smaller at the time of high speed rotation. At the time of high speed rotation, the magnetic balls 13, while being attracted by the magnetic force of the permanent magnet 14, are dispersed by the centrifugal force in the circumferential direction in an engaged contact with the inner circumferential wall of the disk clamper 12. At the time of low speed rotation, the magnetic balls 13 are attracted toward the permanent magnet 14 by the magnetic force against the weaker centrifugal force and restrained nearly in the center part of the disk clamper 12. Thus, the optical disk 4 is rotated stably.
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