Abstract: A circumferential flow type dynamic pressure bearing 1 is comprised of a shaft 2 having a multiple-arc-shaped pressure generating surface and a circular sleeve 3 fitted on the shaft 2. The shaft or the sleeve is formed with a plurality of proximity portions 4 each of which is close in distance to the surface opposed thereto whereby the support force of gas is generated. A plurality of grooves 5 formed at locations spaced from each other by an angle obtained by dividing the circumference by the number of proximity portions 4 or a divisor thereof. Use of such bearing ensures compatibility with high-humidity environmental conditions by provision of grooves, and at the same time it is capable of eliminating or reducing noise generated by vibration caused by radial deviations of the shaft due to provision of the grooves.

Abstract: A dynamic-pressure gas bearing wherein a rotational shaft is disposed to surround an outer circumference of a stationary shaft or to be surrounded by an inner circumference of a stationary shaft, and a dynamic pressure is generated between the stationary shaft and the rotational shaft through rotation of the rotational shaft, characterized in that a water relief portion is provided. In a dynamic-pressure gas-bearing having a water relief portion, even when the bearing is used in a high-humidity environment or even when water (water vapor) contained in a gas liquefies due to high pressure, a pressure change, or the like, the water relief portion prevents a water film from being formed to thereby prevent an increase in a shear force acting between the stationary shaft and the rotational shaft.