Dynamic-pressure gas bearing structure and optical deflection scanning apparatus

摘要

A dynamic-pressure gas bearing structure includes a columnar shaft made of a silicon-nitride-based ceramic sintered body, a hollow cylindrical sleeve opposed to the shaft as keeping a clearance in a radial direction, the sleeve being made of a silicon-nitride-based ceramic sintered body, and at least three flat face portions located on a peripheral surface of the shaft and at equal intervals to the circumference along the peripheral surface. The flat face portion includes a plurality of unit planes continuously formed at predetermined angles to a direction of the circumference on the peripheral surface of the shaft. The unit planes are formed so as to extend substantially in parallel with an axial direction of the shaft.