| 摘要 |
PURPOSE:To obtain a spindle motor having good vibration characteristics by making the configuration of the rotor yolk symmetrical to the boundary formed by a fiducial line passing through the center in the direction parallel to the rotational shaft of the magnetic core, and at the same time, being orthogonal to the rotational shaft. CONSTITUTION:A hub 8 is fixed to the rotational shaft 7 of a spindle motor 30. The rotor yolk 31 of a magnetic member is fixed to the yolk supporting unit 8A extruded downwardly to the hub 8. Then, the thickness in the direction parallel to a rotational shaft 7 is made greater than the thickness in the direction parallel to the rotational shaft 7 of a rotor magnet 12, so that a closed magnetic circuit having an excellent efficiency is formed. Also, the centers of the thickness of the rotor magnet 12 and rotor yolk 31 are respectively positioned on the straight line C orthogonal to the rotational shaft 7. As a result, the configurations of the rotor magnet 12 and rotor yolk 31 on the (a) side and (b) side of the end parts become symmetrical to a fiducial line C. Therefore, the magnetic flux returning in the direction of the rotor yolk 31 becomes almost equal in the vertical direction, and allows the resonance frequency of the spindle motor 30 to be stabilized, thus enabling the vibration characteristics to be improved. |
