Patent ID: 6082900
Filing Date: 2000-07-04
Classification: F16C,G02B

Abstract:
A hydrodynamic gas bearing structure comprising a columnar shaft body (1) and a hollow cylindrical bearing body (2) being opposed to said shaft body (1) while keeping a clearance in the radial direction so that a substantially cylindrical clearance is formed by the outer peripheral surface of said shaft body (1) and the inner peripheral surface of said bearing body (2) when so arranging said shaft body (1) and said bearing body (2) that the central axes of the respective ones coincide with each other and said shaft body (1) has a groove (11) extending in the axial direction on the outer peripheral surface, whereinsaid groove (11) has a circumferentially asymmetrical shape so that the circumferential distance a between an intersection point (15) of a line (C) connecting the deepest point (14) of said groove (11) and the center (O) of said shaft body and the outer peripheral line (Q) of said shaft body (1) before said groove (11) is formed and one edge (16) of said groove (11) positioned downstream an air current (P) generated when either said shaft body (1) or said bearing body (2) rotates in relation to said intersection point (15) becomes larger than the circumferential distance b between said intersection point (15) and the other edge (17) of said groove (11) positioned upstream said air current (P) in relation to said intersection point (15) in a cross section perpendicular to the axis,further, said groove (11) consists of at least two concave parts, whose depths substantially differ from each other, being formed serially in the circumferential direction of said shaft body (1), andthe ratio (d.sub.2 /d.sub.1) of the mean depth d.sub.2 of a relatively shallow part of said groove (11) to the mean depth d.sub.1 of a relatively deep part of said groove (11) is less than 0.3.