Patent ID: 7495863

Claim:
A hydrodynamic bearing device, comprising at least one of a shaft structure and a sleeve having a dynamic pressure-generating mechanism, and a dynamic pressure-generating liquid present in a gap between the shaft structure and the sleeve; wherein the main component of the dynamic pressure-generating liquid is at least one selected from the group consisting of ionic liquids having viscosity index of 150 or more; ionic liquids having surface tension of 35 mN/m or more at 20° C.; and ionic liquids having mean coefficient of volume expansion between 0° C. and 80° C. of 7.0×10 −4 K −1 or less; and each of the ionic liquids are at least one selected from the group consisting of imidazolium salts, pyridinium salts, ammonium salts and phosphonium salts as positive ions, and at least one selected from the group consisting of halides, nitrates, sulfur containing groups, fatty acids, cyano groups and perfluoro groups as negative ions.