Patent ID: 8007176
Filing Date: 2011-08-30
Classification: F16C,G11B,H02K

Abstract:
1. A dynamic pressure bearing in which a shaft having a protruding tubular section for inserting into a toric thrust plate and a sleeve is fitted to an outer periphery of said shaft having said toric thrust plate fitted and fixed thereto so as to be rotatable relatively to the shaft, a clearance section for generating a thrust dynamic pressure by an axial inner face of said thrust plate and an opposite axial outer face of the protruding tubular section, a clearance section for generating a radial dynamic pressure by an inner peripheral face of the protruding tubular section of said sleeve and an opposite outer peripheral face of the shaft, and a magnetic fluid is retained and sealed in the clearance sections, wherein an annular cover made of a nonmagnetic material is formed on the sleeve outwardly from said thrust plate in an axial direction via a clearance section, a radially inward end of said annular cover serves as an opening, at least two clearance sections of the clearance section between said thrust plate and said annular cover and a clearance section between a position radially outward from said thrust plate and an opposite position radially inward from the sleeve are used as a reservoir for reserving the magnetic fluid, an end portion of the magnetic fluid is kept in the clearance section between said thrust plate and said annular cover, which forms said reservoir, and a magnetomotive force member positioned radially outward the end portion of the magnetic fluid and producing concentrated flux lines on magnetic fluid located radially outward from the end portion.