DYNAMIC PRESSURE BEARING DEVICE AND MOTOR HAVING THE DEVICE, AND DISC DEVICE USING THE MOTOR

摘要

PROBLEM TO BE SOLVED: To provide a dynamic pressure device to suppress the occurrence of NRRO by reducing the vibration width of a ripple at an interface between lubrication fluid and air, improve rotation precision of a motor, and not to entrain air in lubrication fluid. SOLUTION: One of radial dynamic pressure generating grooves Gr2 is formed such that an interface between lubrication fluid L and the atmosphere is positioned on one side and one of thrust dynamic pressure generating grooves Gs1 is positioned on the other side. The radial dynamic pressure generating groove Gr2 forms a herringbone-form groove unbalanced in an axial direction in which the lubrication fluid L is caused to flow in the direction of the thrust dynamic pressure generating groove Gs1 . The thrust dynamic pressure generating groove Gs1 formed adjacently to the radial dynamic pressure generating groove Gr2 forms a spiral-form groove through which the lubrication fluid L is caused to flow radially internally. The number of the grooves of the unbalanced part of the herringbone-form groove is greater than that of grooves of a balance part.