To improve the accuracy of the rotation of a disc for high density recording by preventing the deviation of non-repeatable run-out (NRRO) of a spindle motor arising from the deformation of circularity caused by the mounting error of ball bearing which supports a hub, on which a disc is placed, in such a way as to make it rotatable freely or by press fit or adhesion of a bearing ring.
A hub 5 is supported with two pairs of bearings against a shaft 3. The bearings include at least one ball bearing 4, which has outside circumferential surface 6a on an outer ring 6 and inside circumferential surface 7a on an inner ring 7. At least one of these surfaces is clearance fit to opposing surfaces 3a, 5a. This structure minimizes the NRRO arising form the mounting method of the ball bearings and thereby improves the NRRO of the total spindle motor.
MURAKI HIROMITSU
TANAKA KATSUHIKO
FURUMURA KYOSABURO
