FLUID DYNAMIC BEARING DEVICE, SPINDLE MOTOR AND DISK DRIVE APPARATUS

摘要

A fluid dynamic bearing device includes a sleeve having a bearing hole into which a shaft is inserted, the sleeve rotatably supporting the shaft to make relative rotation about a center axis and a bearing housing made of a cold-rolled steel plate or a galvanized steel plate, the sleeve being received within the bearing housing. The bearing housing is filled with lubricating oil mainly composed of ester. A radial dynamic pressure bearing portion is provided between an outer circumferential surface of the shaft and an inner circumferential surface of the sleeve, the radial dynamic pressure bearing portion having radial dynamic pressure grooves for holding the lubricating oil as working fluid and for inducing a fluid dynamic pressure in the lubricating oil during the relative rotation. At least a surface region of the bearing housing remaining in contact with the lubricating oil is coated with a layer mainly composed of nickel.