The Static Performance Analysis On Aerostatic Bearing Under Vacuum Condition

In recently years,with the increasing development of lithograph,measurement of laser interference and the detection of semiconductor machining,in more and more situation,the static platform and its support bearings needs working in high vacuity and merit rating.But,the performance of its capacity,stiffness,leakage and the consumption is different from aerostatic using in normal pressure.In current,the researches on the mechanism of it most based on corresponding slip model of viscous,a few consider the influence of molecular flow.And most of them ignored the transition flow's influence when reference to the properties of bearing's capacity,stiffness,gas consumption which are treat as static performance index.The different geometry parameters' research,which has the influence on bearing performance,sometimes always limited to the bearing be studied,they do not have universal significance.The striding flow field in the gas bearing's film is worth studying too.In view of the above problems,this paper takes the aerostatic thrust bearing in vacuum environment as the research object,the following several is my main study.(1)By crossing field equation of pipe,we got the influence of bearing's radius,the thickness of gas film and the pressure of gas,who have great effect on no-slot bearing.Based on the comparative analysis of the conductance in each part of the bearing leakage zone,the formulas for calculating the flow conductance and leakage of the seal area are obtained.It can be provided to reduce the leakage of bearing.(2)Combining the no slip model,second-order slip model of speed and DSMC algorithm we proved the correctness of the whole flow field stratification model.The article where the model original used was referred to also prove its usability.(3)Through the crossing flow flied stratification model,the bearing structure parameters,bearing entrance pressure variation ratio,gas film thickness`s influence on the static performance of the bearing was obtained,we optimized the bearing structure,reduced the leakage.Promoted the bearing`s capacity and stiffness by choosing the best gas film thickness and pressure ratio.(4)The structural strength analysis of the vacuum system of the bearing detection device is carried out.The resist compression structure of vacuum chamber is designed.Based on the calculation of the natural outgassing rate of the vacuum chamber,the pump speed for the vacuum chamber to reach the target vacuum are deduced.And,the performance of bearing is tested using this vacuum system.