| 摘要 |
PROBLEM TO BE SOLVED: To realize high density and high speediness of a hard disk device when it is assembled in a spindle motor, by setting roundness of at least either one raceway surface of an inner or outer ring to a specific value or less. SOLUTION: A ball 3 of a rolling body is arranged between an inner ring raceway track 1a formed in an external peripheral surface of an inner ring 1 and an outer ring raceway track 2a formed in an internal peripheral surface of an outer ring 2, the ball 3 is held with an equal space around a shaft by a retainer 4. The inner ring with roundness of the inner ring raceway track 1a of 0.05μm or less is assembled in a rolling bearing, a value of asynchronous rotational oscillation (NRRO) of the bearing is measured, as a result, a value of outer/inner ring component of the NRRO is both reduced regardless of a rotational speed. Further, in a hard disk device assembled with the rolling bearing to use a spindle motor serving as a rotational drive source of a magnetic disk, the magnetic disk can be very accurate rotated at a high speed, and high density of the magnetic disk, that is, large capacity and high speediness of the hard disk device can be realized.
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