Patent ID: 8337086
Filing Date: 2012-12-25
Classification: F16C,G11B

Abstract:
1. A bearing apparatus comprising: a shaft arranged along a central axis and extending in a vertical direction; a thrust cup including an annular portion extending radially outward from an outer circumferential surface of the shaft, and a cylindrical portion projecting upward from an outer edge portion of the annular portion; a substantially annular thrust washer extending radially outward from the outer circumferential surface of the shaft; a rotating member arranged above the thrust cup and rotatably supported around the shaft; and a lubricating oil; wherein the rotating member includes a through hole extending in an axial direction, an axially lowermost portion of the through hole including a circumferentially chamfered portion; the lubricating oil is arranged to fill a space including the through hole, a first gap defined between the outer circumferential surface of the shaft and a portion of the rotating member which is arranged radially opposite to the outer circumferential surface of the shaft, a second gap defined between a lower surface of the rotating member and an upper surface of the annular portion, and a third gap defined between a lower surface of the thrust washer and an upper surface of the rotating member; at least one of the outer circumferential surface of the shaft and the portion of the rotating member which is arranged radially opposite to the outer circumferential surface of the shaft includes a plurality of dynamic pressure grooves arranged thereon to generate a dynamic pressure in a portion of the lubricating oil which is present in the first gap during rotation of the rotating member, and to cause the portion of the lubricating oil which is present in the first gap to flow upward in the first gap; an outer circumferential surface of the rotating member and an inner circumferential surface of the cylindrical portion together define a lower capillary seal portion in communication with the space and including a radial dimension gradually decreasing in a downward direction, the lower capillary seal portion including a lower surface of the lubricating oil located therewithin; the second gap includes a first region in communication with the lower capillary seal portion, and a second region positioned radially inward of the first region and including an axial dimension smaller than that of the first region; the through hole includes an upper end portion in communication with the first gap, and a lower end portion open at a location radially outwardly away from a boundary between the first region and the second region; an outer circumferential surface of the thrust washer and an inner circumferential surface of the rotating member together define an upper capillary seal portion in communication with the space and including a radial dimension gradually decreasing in the downward direction, the upper capillary seal portion including an upper surface of the lubricating oil located therewithin; a pumping groove is arranged on at least one of the upper surface and the inner circumferential surface of the rotating member and the outer circumferential surface and the lower surface of the thrust washer to pump a portion of the lubricating oil in a vicinity of the upper surface of the lubricating oil toward an inside of the bearing apparatus; a first edge is arranged at a boundary between the axially lowermost portion of the through hole and an axially lower surface of the rotating member, and a second edge is arranged at a boundary between a sloping portion and one of an axially lowermost surface of the rotating member and an axially uppermost surface of the annular member; and the first edge is arranged to face the first region and the second edge is arranged to face the second region, and the first edge is arranged radially outward from the second edge.