Abstract: A spindle motor has a rotor, a stator and an air dynamic pressure bearing for supporting the rotor for rotation about a rotational axis relative to the stator. The air dynamic pressure bearing comprises a first dynamic pressure bearing portion and a second dynamic pressure bearing portion. The first dynamic pressure bearing portion comprises a convex side bearing member having a conical convex portion, a concave side bearing member having a conical concave portion receiving the conical convex portion, and dynamic pressure generating grooves formed on one of a surface of the conical convex portion and a surface of the conical concave portion.

Abstract: A hydrodynamic bearing assembly includes a support shaft provided on a stationary member, a rotating member rotatably supported on the support shaft through a hydrodynamic radial bearing and a hydrodynamic thrust bearing, a magnet provided at a stationary side, and a magnetic member provided on the rotating member opposite the magnet. The magnetic member is attracted by the magnetic force from the magnet so that a force acting on the thrust hydrodynamic bearing is cancelled or reduced.

Abstract: A polygon mirror rotor includes a ceramic ring of a generally hollow cylindrical shape having a cylindrical inner surface serving as a sliding surface of a radial hydrodynamic bearing and a pair of end surfaces each serving as a sliding surface of a thrust hydrodynamic bearing. A plastic ring is fixedly fitted over the ceramic ring, and a polygon mirror made of aluminum is fixedly fitted over the plastic ring by shrinkage fit. The plastic ring has a thermal expansion coefficient greater than that of the ceramic ring as well as greater than that of the aluminum polygon mirror, thereby providing a polygon mirror rotor which does not adversely affect the jitter characteristic of a motor incorporating the rotor.

Abstract: A polygon mirror is made up of a rotor including a ceramic ring, a yoke and a mirror surface formation member. The yoke and the mirror surface formation member are secured to an outer periphery of the ceramic ring. A radial dynamic pressure bearing is defined by an inner periphery of the ceramic ring and an outer periphery of the fixing shaft. A thrust dynamic pressure bearing is defined by both end surfaces of the ceramic ring and surfaces of a thrust plate fixedly secured to the stator and confronting both end surfaces of the ceramic ring. The ceramic ring, the yoke and the mirror surface formation member are integrated by the material making up the mirror surface formation member during the molding of the member to form the rotor.