The working principle and characteristics of air bearing

The working principle and characteristics of air bearing 2020 - 12 - 01 bearing, as we all know, as the main components of the rotating body, its use effect for itself. Bearing types are many, according to the different way of rotation can be divided into rolling bearing and sliding bearing, but I don't know if you know air bearing, air bearing also belong to a kind of sliding bearing type, today to share with you the related knowledge about air bearing. What is the air bearing? Air bearing can also be called floating bearing, refers to the air ( May also be other gases) As a lubricant of sliding bearing. The most commonly used gas lubricant for air, according to the needs and available nitrogen, argon, hydrogen, helium and carbon dioxide. In the gas compressor and expander and circulator, often with working medium as a lubricant. What is the structure of the air bearing? Air bearing structure: the bearing inner ring and outer ring, outer ring on the air hole of imports and exports, on the inner ring nozzle. The working principle of air bearing air bearing refers to the use of bearing pressure air film formed between the sliding surface of vice will load bearing, bearing up at work entirely by gas membrane separation between sliding surface of vice. Air bearing belongs to the sliding bearing, sliding bearing of the fluid for fluid lubrication at work, its lubricating medium of air. According to the pressure of air film forming mechanism of air bearing is mainly divided into two categories: the air dynamic pressure bearing and aerostatic bearing. Air dynamic pressure bearing the pressure of the air film is through the mutual movement of the sliding pair bring air into sliding pair of convergence between surface area and formed, gas film roughly wedge-shaped ( See figure 1) 。 Because the air dynamic pressure bearing does not require an external source, therefore, also known as' role since the bearing. Figure 1 air dynamic pressure bearing principle figure 2 aerostatic bearing principle of work of the aerostatic bearing pressure air is compressed air by external membrane through the choke import (formed between sliding surface of vice See figure 2) 。 Aerostatic bearing need to clean the external gas source. In air bearing, ball bearing by air instead. One of the most familiar application of air bearing is perhaps the hovercraft, See figure 3) 。 Giant fan blowing air at the bottom of the hovercraft, through elastic rubber 'skirt' to prevent air escaping. Below the hovercraft produced by high pressure to support body weight, so that it floats on a cushion of air. Huge air cushion not only have the effect of support body weight, but also as a soft spring make smooth hull were floating on the surface rough surface or land. Figure 3 hovercraft can apply the same principles to shaft bearing. The high pressure air into the gap between the shaft and fixed bearing. The gap is very small, About 1% of the mm) , making the gap of the air pressure stays the same. And it is significantly reduced in a narrow gap 'elastic cushion, so that the shaft fixed very accurately, which can only produce low dynamic eccentricity. Because of low friction shaft can rotate freely, and the air pressure to ensure than with a fixed axis bearing surface in contact. Characteristics of air bearing using 01 low friction due to gas was much lower than the liquid viscosity, viscosity of air at room temperature is only one over five thousand of the number 10 machine oil, and the bearing friction is proportional to the viscosity, so the gas bearing friction is lower than liquid lubricated bearing. 02 for wide speed range of gas bearing friction is low, low temperature rise, the speed of up to 50000 RPM, the temperature rise not to exceed 20 ~ 30 ℃, speed is even up to 1. 3 million RPM. Aerostatic bearing can also used for low speed, even zero speed. 03 wide applicable temperature gas can in great temperature range gas, its viscosity is influenced by temperature is small ( Viscosity at higher temperatures also increases slightly, such as temperature from 20 ℃ to 100 ℃, and the air viscosity increased by 23%) And, therefore, the application of the gas bearing temperature range can be up to - 265 ℃ to 1650 ℃. 04 bearing capacity of the bearing capacity of the low dynamic pressure bearing is proportional to the viscosity, the bearing capacity of gas dynamic pressure bearing only same size liquid dynamic pressure bearing a few parts per thousand. Due to the compressibility of the gas, gas dynamic pressure bearing capacity limit value, average unit load can only be added to the projection area 0. 36 million mpa. 05 high machining accuracy requirements in order to improve the bearing capacity of the gas bearing gas film stiffness, usually adopt bearing clearance (smaller than liquid lubricated bearing Less than zero. 015 mm) , we need to improve the parts precision accordingly. Air bearing faults in the process of manufacturing high geometric accuracy clean and dry of pressurized air supply. In from empty to remove oil and grease, oil, environment, use the condition of air shaft will stay cleaner. Air bearing does not have the opposite effect to the environment, therefore, is a clean environment ( Such as: disk drives manufacturing) Ideal application products. In fact, a specially designed westerly air spindle also can be used under the condition of high vacuum, such as: in the application of semiconductor silicon wafer manufacturing. The application of air bearing air bearing air elastic potential energy is used to a new type of bearing supporting role. The only use of lubricant is the air; Thus must demand for pollution-free artifacts, or work environment, air bearing technology is ideal. Since the 50 s, the application of gas bearing more and more widely, and has been widely and in-depth research. The gas bearing can be used in textile machinery, cable machinery, instrument machine tools, gyroscope, high-speed centrifuge, the drill, low temperature operation of chiller, hydrogen and high temperature operation of gas expander cycle and etc. （ Source: bearing industry magazine)