Patent ID: 7776802

Claim:
A hydrodynamic bearing device comprising: a shaft structure with a diameter of 1-4 mm and having a shaft first end; a sleeve including a sleeve first end, and the sleeve being positioned so that a radial gap of 1-5 μm is formed between the sleeve and shaft structure; a hub connected to the shaft first end, such that the gap extends between the hub and the sleeve first end; and a lubricant disposed in the gap between the shaft structure and the sleeve, wherein the lubricant contains a diester with a total carbon number of 20-28, the diester being selected from the group consisting of, (1) a diester obtained from dipropylene glycol and n-nonanoic acid, and (2) a diester obtained from (a) a combined glycol obtained via condensation of a least one molecule of ethylene glycol and at least one molecule of propylene glycol, and (b) a saturated monovalent fatty acid selected from the group consisting of n-heptanoic acid, n-octanoic acid and n-nonanoic acid, and the diester having a viscosity of 2-5 mPa·sec at 80° C., a low-temperature solidification point of ≦−20° C. and a volume resistivity of ≦1×10 11 Ω·cm at 20° C., wherein at least one of the shaft structure and the sleeve has a dynamic pressure-generating mechanism.