Patent ID: 7854552
Filing Date: 2010-12-21
Classification: F16C

Abstract:
1. A hydrodynamic bearing device, comprising: a sleeve that has an insertion hole that is open at one end; a shaft configured to be disposed in the insertion hole of the sleeve so as to be capable of rotation relative to the sleeve, and have a main portion and a large-diameter portion provided to the main portion and having a larger diameter than the main portion; a lubricating fluid that fills a clearance formed between the sleeve and the shaft; a bearing portion configured to support the sleeve and the shaft in the rotational direction and the axial direction with the lubricating fluid interposed in between; and a flange cover that is provided to the sleeve and disposed opposing to one axial side of the large-diameter portion of the shaft, wherein the shaft has at least one first communicating hole that communicates between the one axial side of the large-diameter portion that faces the flange cover and the other axial side of the large-diameter portion that does not face the flange cover, the sleeve has at least one second communicating hole which communicates between two end faces of the sleeve, the equivalent diameter Df, length Lf, and number Nf of the first communicating hole and the equivalent diameter Ds, length Ls, and number Ns of the second communicating hole satisfy the following relational formula (1): and the equivalent diameters Df and Ds of the first and second communicating holes are four times of the quotients obtained by dividing the cross sectional areas Af and As of the first and second communicating holes by the peripheral lengths Sf and Ss, respectively, as expressed by the following relational formula (2): where the constants n and m in the relational formula (1) are numbers greater than or equal to 1, and the combination of the constants (n, m) satisfies at least one of (4, 1), 4.75, 1.75), and (5, 2).