Patent ID: 7901139
Filing Date: 2011-03-08
Classification: F16C,H02K

Abstract:
1. A hydrodynamic bearing type rotary device, comprising: a sleeve having a bearing hole and an inner peripheral surface and being formed of a first material having a first elastic limit; a shaft having an outer peripheral surface and being formed of a second material having a second elastic limit, and which is inserted into the bearing hole of the sleeve so as to be relatively rotatable, a gap being formed between the shaft and the sleeve; a hub rotor which is attached to either of the sleeve or the shaft, and which rotates; a bearing surface having hydrodynamic grooves formed on at least one of the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve; and an ester oil held in the gap between the shaft and the sleeve, wherein a value of a function (Nd) represented by the following relational expression (1) is 1,000,000 or higher, such that surface pressure at the bearing surface when the shaft and the sleeve contact each other is within the first elastic limit of the first material of the sleeve and the second elastic limit of the second material of the shaft, and an absolute viscosity of the ester oil is in a range from 2 to 5 centipoises (0.002 to 0.005 [N·S/m^2]) at 70° C.: the floating rotation corresponding function, Ff, is defined as follows: the stiffness corresponding function, Fs, is defined as follows: