Hydrodynamic gas bearing structure and optical deflection scanner comprising the same

Abstract

A hydrodynamic gas bearing structure can prevent the occurrence of whirl not only in high-speed rotation but also in low-speed rotation, and is capable of suppressing dispersion of a floating rotational frequency. The hydrodynamic gas bearing structure includes a shaft body (1) and a bearing body (2). A groove (11) is formed on the outer peripheral surface of the shaft body (1). The groove (11) consists of at least two concave parts, of which the depths substantially differ from each other, which are formed serially in the circumferential direction, and which each have a circumferentially asymmetrical shape in a cross section perpendicular to the axis. A circumferential distance a is defined between the intersection point (15) of the outer circular peripheral line (Q) of the shaft body and a line (C) connecting the deepest point (14) of the groove (11) with the center (O) of the shaft body (1), and one edge (16) of the groove (11) positioned downstream with respect to an air current (P) generated during rotation in relation to the intersection point (15). This circumferential distance a is larger than the circumferential distance b between the intersection point (15) and the other edge (17) of the groove (11) positioned upstream with respect to the air current (P) in relation to the intersection point (15). The hydrodynamic gas bearing structure is employed for a rotation driving part of an optical deflection scanner.

Dependencies are inferred from the claim text.