Patent ID: 7883270

Claim:
A hydrodynamic bearing type rotary device comprising: a shaft having a radial hydrodynamic bearing surface provided on an outer peripheral surface thereof; a flange provided integrally with the shaft at a lower portion of the shaft; a sleeve having a bearing hole, the sleeve being fitted to the shaft so as to be relatively rotatable, wherein a radial gap G 1 is interposed between the sleeve and the shaft, a gap S 1 is interposed between the sleeve and the flange, and the flange forms a thrust bearing surface of the gap S 1 with a lower end surface of the sleeve; radial hydrodynamic grooves disposed on at least one of the outer periphery of the shaft and an inner periphery of the sleeve; thrust hydrodynamic grooves disposed on at least one of the lower end surface of the sleeve and an upper surface of the flange; a hub integrally fixed to an outer periphery of the sleeve, wherein a radial gap having a maximum gap G 2 is provided between an outer peripheral surface of the flange and an inner surface of the hub which opposes the flange, and wherein a communication path which communicates with the flange is provided on the sleeve or the hub; a lubricant held at least in the gaps S 1 and G 1 , and the communication path, wherein at least the gap G 1 , the gap S 1 , and the communication path form a circulation path in which the lubricant circulates, wherein the gap G 1 has a parameter Pg 1 and the gap G 2 has a parameter Pg 2 , and each of the gaps G 1 and G 2 forms a lubricant reservoir having a tube shape, and wherein Pg 1 >Pg 2 , and the parameters Pg 1 and Pg 2 are calculated as follows: Fgo=π×Do ×γ×cos θ Fgi=π×Di ×γ×cos θ Di=Do− 2 ×rg Fg=Fgo+Fgi Ag =π×( Do^ 2 −Di^ 2)/4 Pg=Fg/Ag γ: Surface tension of lubricant [N/m] θ: Contact angle of oil [radian] Do: Outer diameter of tube [m] Di: Inner diameter of tube [m] rg: Oil film thickness of tube [m].