BEARING MECHANISM, HARD DISK DRIVE MECHANISM AND POLYGON MIRROR DRIVE MECHANISM USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a bearing mechanism capable of raising dynamic pressure generated in a thrust gearing clearance or/and a radial bearing clearance to increase a load capacity without lowering bearing rigidity, and to provide a hard disk drive mechanism and a polygon mirror drive mechanism using this bearing mechanism. SOLUTION: Any one of an upper end surface 23a of a lower thrust plate 23 and a lower end surface 31d of a sleeve 31 respectively forming a lower thrust bearing space GS2 is provided with a lower thrust dynamic pressure generating groove 23b. A ratio of the depth D of the lower thrust dynamic pressure generating groove 23b in the axial direction to a dimension S2 of the lower thrust bearing clearance part GS2 is set within a range 1.0-2.5 to relatively increase the depth D of the lower thrust dynamic pressure generating groove 23b to increase the flow capacity of a hydraulic fluid, and the dimension S2 of the lower thrust bearing clearance part GS2 is relatively reduced to raise the lower thrust dynamic pressure to secure a sufficient thrust load capacity without lowering the rigidity of the bearing mechanism 1.