Research On Static And Dynamic Characteristics Of Static Pressure Thrust Air Bearing With Double Row Holes

Static pressure thrust air bearing is the core component of ultra-precision machine tool spindle,guide rail and air floating turntable.Due to the low bearing capacity and weak rigidity of hydrostatic thrust air bearing,self-excited vibration of air hammer and disturbance are easy to occur,which leads to the reduction of the precision of air bearing.This seriously restricts the machining accuracy of ultra-precision machine tools and the measurement accuracy of air floating turntable.Therefore,in order to improve the bearing capacity and stiffness of the thrust air bearing,to avoid bearing disturbance and self-excited vibration of the air hammer.This article mainly adopts the method of combining theoretical calculation,ANSYS-Fluent static and dynamic simulation calculation and experimental testing to research the static and dynamic characteristics of the open and closed static pressure thrust air bearing.Main research contents and achievements are as follows:(1)The correctness of the ANSYS-Fluent static simulation calculation method is verified by the theoretical calculation method,simple orifice throttling theory and others' simulation and experimental results.Using ANSYS-Fluent static simulation method,the mechanical properties of single and double row hole open static pressure thrust air bearing are compared,and then the structural form is improved.The open and closed hydrostatic thrust air bearing with double-row holes and disc-shaped pressure equalizing grooves is proposed.The results show that the bearing capacity and stiffness of the open bearing with the disc-shaped equalizing groove are greater than those without the disc-shaped equalizing groove.The bearing capacity and rigidity of double-row hole open bearing are greater than those of single-row hole bearing.The simple orifice throttling theory can quickly and accurately verify the correctness of simulation calculation.(2)The structural parameters of double-row holes open static pressure thrust air bearing were studied and optimized by ANSYS-Fluent static and dynamic simulation.The results show that increasing the diameter of the equalizing groove can increase the stiffness and bearing capacity of the bearing.When the diameter of the orifice and the diameter of the equalizing groove are maximized at the same time,the bearing capacity of the bearing is the largest,and the maximum value is 2418.8N.When the diameter of the pressure equalizing groove takes the maximum value,the stiffness of the bearing is the largest when the height of the gas film and the diameter of the orifice are the minimum,the maximum value is 159.9 N/?m.(3)The ANSYS-Fluent dynamic simulation calculation method of bidirectional passive motion dynamic grid is proposed,and the static and dynamic performance of the loaded closed static pressure thrust air bearing is studied by this method,and the performance of the open bearing is compared with that of the closed bearing.The results show that the dynamic calculation results are consistent with the simple orifice throttling theory.When the total height of the gas film is the same,the bearing capacity and stiffness of the closed bearing are greater than those of the open bearing.When the load is 50 kg,the bearing capacity is larger than that when the load is 30 kg.When the one-way pressure fluctuates by 10%,the maximum variation of eccentricity of 17.31 nm has a great influence on the bearing support accuracy,while when the one-way pressure fluctuates by 0.1%-1% or the upper and lower pressures fluctuate by less than 10%,the maximum variation of eccentricity of 1.89 nm has little influence on the bearing support accuracy.The studied bearing can resist the disturbance of 9.8N force when the load is 30 kg.Under the inlet pressure of 0.5MPa,the condition of no vibration is the height of bilateral gas film h0?0.032 mm,and under the height of 0.032 mm gas film,the condition of no vibration is the inlet pressure P1?0.7MPa.(4)A closed double-row holes static pressure thrust air bearing test bench with pressure equalizing groove was built for experimental testing.The comparison between experimental results and ANSYS-Fluent dynamic simulation shows that the error between experimental results and simulation results is within 10%.The stiffness of the bearing under 16.2kg load is greater than that under 10.8kg.The error between the air supply pressure measured experimentally when the bearing reaches the first order vibration and the air supply pressure calculated by simulation when the bearing reaches the first order vibration is about 4%.In this paper,the static and dynamic characteristics of static pressure thrust air bearing are comprehensively studied by using different calculation methods and the proposed new method.The influence rules of structural parameters and working conditions of the bearing on its bearing capacity,rigidity and stability are obtained,and the calculation of resistance to pressure fluctuation and load disturbance capability and simulation prediction of self-excited vibration of air hammer are successfully carried out for closed static pressure thrust air bearing with load,which provides the parameter and method basis for the design and precision improvement of open and closed static pressure thrust air bearing.