Air Dynamic Pressure Bearing

Application

Air dynamic pressure bearing is the use of gas lubricant the most commonly used gas lubricant for the air bearing, according to the need also available nitrogen, argon, hydrogen, helium or carbon dioxide, etc. In gas compressors, expanders and circulators, the working medium is often used as the lubricant. In the selection of air bearing materials, there are mainly tool steel, bronze, tungsten cobalt molybdenum alloy, powder metallurgy porous materials, ceramics and engineering plastics, etc. 

Advantages

(1) Extremely low friction: because the gas viscosity is much lower than the liquid, at room temperature, the air viscosity is only five thousand times of No. 10 mechanical oil, and the bearing friction is proportional to the viscosity, so the gas bearing friction is lower than the liquid lubrication bearing.

(2) Wide range of applicable speed: low friction of gas bearing, low temperature rise, when the speed is up to 50,000 RPM, the temperature rise does not exceed 20 ~ 30℃, and the speed is even up to 1.3 million RPM.Gas hydrostatic bearings can also be used for extremely low or even zero speed.

（3）Wide range of applicable temperature: gas can be in a large temperature range to maintain the gaseous state, its viscosity by temperature is very small (temperature rise viscosity also slightly increased, such as temperature from 20℃ to 100℃, air viscosity increased by 23%), therefore, the applicable temperature range of gas bearings can be up to -265℃ to 1650℃.

（4）Low bearing capacity. The bearing capacity of the dynamic pressure bearing is proportional to the viscosity; the bearing capacity of the gas dynamic pressure bearing is only a few thousandths of the liquid dynamic pressure bearing of the same size. Due to the small compressibility of gas, the gas dynamic pressure bearing is low of bearing capacity.

High machining accuracy requirements: In order to improve the bearing capacity and gas film stiffness of the gas bearing, the bearing clearance (less than 0.015mm) smaller than that of the liquid lubricated bearing is usually adopted, and the precision of the parts needs to be improved accordingly.

The gas enters the air chamber through the air supply hole, and then flows through the choke into the clearance between the bearing and the journal, and then flows out of the bearing from both ends, forming a static pressure air film supporting the load in the clearance. The surface of inner hole in the gas hydrostatic bearing generally does not open the air chamber; in order to increase the stiffness of atmospheric film, improve the stability.