Patent ID: 7950854

Claim:
A hydrodynamic bearing type rotary device, comprising: a shaft; a sleeve having a bearing hole in which the shaft is relative-rotatably inserted with a clearance; a hub attached to one of the sleeve and the shaft, said one of the sleeve and the shaft being a rotating member; a radial bearing portion having a radial hydrodynamic groove formed in at least one of an external peripheral surface of the shaft and an internal peripheral surface of the sleeve; a thrust bearing portion having a thrust hydrodynamic groove formed with at least one of a surface of the sleeve opposite the hub and a surface of the hub opposite the sleeve, or with at least one of a surface of the sleeve opposite the shaft and a surface of the shaft opposite the sleeve; a communicating hole allowing fluid communication between a groove end of the radial hydrodynamic groove on a side opposite the thrust hydrodynamic groove and a groove end of the thrust hydrodynamic groove on a side opposite the radial hydrodynamic groove, a cross section of the communicating hole being a substantially rectangular shape or a D-cut shape; and lubricant for filling the radial bearing portion, the thrust bearing portion, and the communicating hole; wherein the groove pattern of at least one of the radial hydrodynamic groove and the thrust hydrodynamic groove creates a conveying force for conveying the lubricant from the thrust bearing portion to the radial bearing portion or from the radial bearing portion to the thrust bearing portion, and is formed in such a manner that the magnitude of the conveying force created in the radial hydrodynamic groove and the magnitude of the conveying force created in the thrust hydrodynamic groove differ; and wherein the relationships Pr>Pp 1 and Pt>Pp 1 are satisfied, where Pr is a capillary pressure function at the clearance of the radial bearing portion, Pt is a capillary pressure function at the clearance of the thrust bearing portion, and Pp 1 is a capillary pressure function at the communicating hole, and Pr, Pt, and Pp 1 are defined as follows: Pr =(π× Do ×γ×cos θ+π× Di ×γ×cos θ)/(π×( Do 2 −Di 2 )/4) Pr: capillary pressure function at the clearance of the radial bearing portion [Pa] γ: surface tension of lubricant [N/m] θ: contact angle of lubricant [radians] Do: outside diameter of cylinder [m] Di=Do− 2 ×r r: lubricant film thickness on cylinder [m] Pt= 2 π×Dt ×γ×cos θ/(π× Dt×S ) Pt: capillary pressure function at the clearance of the thrust bearing portion [Pa] Dt: outside diameter of thrust bearing portion [m] S: lubricant film thickness in thrust bearing portion Pp 1=(2×( u+t )×γ×cos θ)/( u×t ) =2×γ×cos θ×( u+t )/( u×t ) Pp 1 : capillary pressure function at the communicating hole [Pa] u: width of cross section [m] t: opposite end dimension of cross section [m].