To provide a hydrodynamic bearing device which can achieve a stable thrust floating-up characteristic even when the temperature in a working environment changes.
The clearance A at a thrust dynamic pressure generating groove surface, the clearance B at the oil sump portion on the outer circumferential surface of a flange 3, the clearance C between the surface of the flange 3 on the side of a sleeve 1 and the sleeve 1, the clearance G at radial dynamic pressure generating groove portions, the clearance D at the oil sump portion between the G portion and the C portion, and the clearance H at the oil sump portion neighboring with the G portion on the open side of the bearing satisfies the following relations, GH, AB, AD, CB, CD, BH, DH, and the viscosity of the base oil of lubricating oil or grease at 40C is 4 cSt or higher, The stable thrust floating-up characteristic can be achieved by fixing one of the outer periphery of the sleeve 1 and the outer periphery of a shaft 2 to a base 6, and by fixing the other of them to a rotatable hub rotor 7.
SAITO HIROAKI
KUSAKA KEIGO
ITO DAISUKE
Hiroki Naito
Daisuke Nagano