Patent ID: 8472132
Filing Date: 2013-06-25
Classification: F16C,G11B,H02K

Abstract:
1. A fluid dynamic bearing apparatus comprising: a shaft arranged to extend in an upward/downward direction to define a central axis; a substantially cup-shaped lower thrust washer including an annular portion extending radially outward from an outer circumferential surface of the shaft, and a tubular portion extending upward from an outer edge portion of the annular portion; and a rotating member including a cylindrical portion radially opposed to the shaft and arranged to rotate with respect to the shaft; wherein a first gap is defined between the outer circumferential surface of the shaft and an inner circumferential surface of the cylindrical portion; a second gap is defined between a lower surface of the cylindrical portion and an upper surface of the annular portion axially opposed thereto; and a third gap is defined between an outer circumferential surface of the cylindrical portion and an inner circumferential surface of the tubular portion radially opposed thereto; wherein the first gap, the second gap, and the third gap are in communication with one another and arranged to be filled with a lubricating oil; the rotating member includes a through hole filled with the lubricating oil, and an upper opening portion of the through hole is in communication with the first gap and a lower opening portion of the through hole is in communication with the second gap; the third gap includes a tapered seal portion where a radial width of the third gap gradually decreases in a downward direction, and the lubricating oil includes a liquid interface located within the tapered seal portion; the second gap includes a fourth gap and a fifth gap, the fifth gap being located radially outward of the fourth gap; at least one of the lower surface of the cylindrical portion and the upper surface of the annular portion which combine to define the fourth gap includes a plurality of thrust dynamic pressure generating grooves arranged to induce a fluid dynamic pressure on the lubricating oil held in the fourth gap during rotation of the rotating member; the fourth gap has a smaller axial dimension than that of the fifth gap; and the lower opening portion of the through hole is located at the fifth gap, and at least one of the lower surface of the cylindrical portion and the upper surface of the annular portion which combine to define the fifth gap includes a plurality of dynamic pressure generating grooves arranged to induce a radially inward fluid dynamic pressure on the lubricating oil held in the fifth gap during the rotation of the rotating member.