Knowledge, air bearing know? - bearing knowledge

Bearing, believes everyone not unfamiliar, we often use the rolling bearing should be the most familiar, it is the important parts of modern machinery and equipment. What is air bearing? What is the air bearing? Air bearing ( 气体轴承) : using gas as lubricant 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. Air bearing refers to the use of the bearing pressure air film formed between the sliding surface of deputy to the bearing load bearing, 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. Air bearing classification according to the pressure of air film formation mechanism of air bearing is divided into two main categories: 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. Because the air dynamic pressure bearing does not require an external source, therefore, also known as 'the bearing'. Aerostatic bearing pressure air is compressed air by external membrane through the choke import formed between the sliding surface of vice. Aerostatic bearing need to clean the external gas source. Figure 1 air dynamic pressure bearing principle figure 2 working principle of the aerostatic bearing characteristics of air bearing (1) very 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. (2) the applicable speed range of gas bearing friction is low, low temperature, 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. (3) 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 ℃. (4) low carrying capacity of dynamic pressure bearing capacity 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. (5) high precision 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. 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. In air bearing, ball bearing by air instead. One of the most familiar application of air bearing is perhaps the hovercraft. Giant fan blowing air at the bottom of the hovercraft, through elastic rubber 'skirt' prevent air escaping. Below the hovercraft produced by high pressure to support body weight, so that it floats on a cushion of air. 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.