Patent ID: 8995093
Filing Date: 2015-03-31
Classification: F16C,G11B

Abstract:
1. A pivot bearing unit for a hard disk actuator comprising: a shaft member having a flange portion at an axial end portion; a pair of bearings each including an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, a cage which holds individually the plurality of rolling elements, and a shield member which is mounted in an annular groove formed in an axial end portion of the outer ring and which has a ring portion extending towards the inner ring, and the pair of bearings are disposed parallel to each other on an outer circumference of the shaft member; and a shield cap which is mounted on the other axial end of the shaft member and of which an axial inner surface extends in a radial direction so as to face oppositely an axial end face of the outer ring of one of the pair of bearings, wherein the axial inner surface of the shield cap is formed into a stepped shape by a first cap surface which faces oppositely the ring portion of the shield member of the one bearing, a second cap surface which lies radially outwards and axially outwards of the first cap surface and which faces oppositely the axial end face of the outer ring, and a cap rising surface which connects the first and second cap surfaces; and the axial inner surface of the shield cap is formed so that an axial minimum gap defined between the first cap surface and the ring portion of the shield member of the one bearing is narrower than an axial minimum gap defined between the second cap surface and the axial end face of the outer ring and so that a minimum gap defined between the cap rising surface and a boundary position between the axial end face of the outer ring and the annular groove is narrower than the axial minimum gap between the second cap surface and the axial end face of the outer ring.