Positive and negative rotation gas dynamic pressure bearing, spindle motor having dynamic pressure bearing, and rotator device having spindle motor as driving source

摘要

A positive and negative rotation gas dynamic pressure bearing comprises a stationary bearing member, a movable bearing member mounted for rotation relative to the stationary bearing member, dynamic pressure generating grooves having first and second ends and formed in one of confronting surfaces of the stationary bearing member and the movable bearing member, a self-switch valve connected to the movable bearing member for rotation therewith, and conducting holes having first and second ends and formed in the movable bearing member. During rotation of the movable bearing member in a first direction of rotation, a high dynamic pressure is generated at central portions of the dynamic pressure generating grooves, and a valve body of the self-switch valve moves toward a lower space of a valve case of the self-switch valve to close the second ends of the conducting holes. During rotation of the movable member in a second direction of rotation opposite the first direction of rotation, a high dynamic pressure is generated at the first and second ends of the dynamic pressure generating grooves so that the valve body moves toward an upper space of the valve case to close a through-bore of the valve case and to open the second ends of the conducting holes to allow air taken in by air taking holes of the self-switch valve to be supplied to the central portions of the dynamic pressure generating grooves through the conducting holes.