| 摘要 |
PROBLEM TO BE SOLVED: To provide a hard disk device employing a ceramic dynamic pressure bearing, in which abrasion is hardly generated on a thrust plane at a time of start or stop, and vibrations are reduced to implement stable rotation. SOLUTION: In the ceramic dynamic pressure bearing 3, at least one of the following conditions (1)-(6) is satisfied: (1) flatness of a thrust dynamic pressure gap forming face (hereafter, referred to as an A forming face) of a second member facing a thrust plate is 3 μm or less, or (2) flatness of a thrust dynamic pressure gap forming face (hereafter, referred to as a B forming face) of the thrust plate facing the second member is 3 μm or less; (3) the sum of the flatness of the A forming face and the flatness of a thrust dynamic pressure gap forming face of the thrust plate facing the thrust dynamic pressure gap forming face of the second member is 3 μm or less; (4) an inner peripheral portion of the A forming face projects from an outermost peripheral portion thereof by more than 0 μm and not more than 2.5 μm, or (5) an inner peripheral portion of the B forming face projects from an outermost peripheral portion thereof by more than 0 μm and not more than 2.5 μm; and (6) in the thrust dynamic pressure gap forming face of the second member and that of the thrust plate facing each other, the outer most peripheral face of one thrust dynamic pressure gap forming face is separated from that of the other thrust dynamic pressure gap forming face by more than 0 μm and not more than 2.5 μm. |
