| In order to make the system meet the requirements of heavy duty,high frequency and high precision,good guiding performance is the necessary condition.At the same time,the servo hydraulic cylinder requires the friction between the piston rod and cylinder to maintain a small value.In addition,the piston rod is often affected by lateral load during the working process,so the hydrostatic bearing technology becomes the best choice for the high frequency cylinder.In view of the precise design of the hydrostatic bearing structure,the structure of the oil cavity,the fit gap between the piston rod and the cylinder have a direct impact on the effect of the hydrostatic bearing,this paper optimizes the hydrostatic bearing structure of the servo cylinder through theoretical analysis,simulation and test verification,and obtains the optimal design parameters of the hydrostatic bearing.The main research contents and conclusions are as follows:(1)According to the actual working conditions,determine the structural design scheme of the static pressure bearing.A hydrostatic bearing structure is designed for 90 tons load,21 MPa rated pressure and 50 Hz operating condition.The size of each structure of the hydrostatic bearing is determined by correlation analysis,and the flow rate and bearing capacity are checked.(2)Based on the finite element technique,the static pressure bearing performance of four different eccentric conditions is analyzed.The flow field pressure,leakage and bearing capacity of the static pressure bearing are analyzed under four different eccentric working conditions.The static and dynamic characteristics of cylinder and cylinder are analyzed and studied,and the constraint conditions of static pressure bearing structure optimization are determined.(3)According to the theoretical analysis results of hydrostatic bearing oil chamber and throttle,combined with FLUENT fluid simulation,MOGA genetic algorithm is used to optimize the structure of hydrostatic bearing.Six groups of initial vectors,such as unloading groove width,sealing bandwidth,oil film outer diameter,oil cavity length,diameter of slender hole and length of slender hole,were selected as optimization variables.MOGA algorithm was used to select the six groups of parameters within the selected range,and the optimization objective was to improve the oil film stiffness of hydrostatic support.The optimization results are as follows: when the first-order mode of the hydrostatic bearing oil cavity structure increases by 4.9%,the internal pressure of the oil cavity increases by 5%,and the oil film stiffness increases by 5.55%.(4)The hydrostatic bearing oil film characteristic test was carried out to verify the optimization effect of hydrostatic bearing structure.The test includes: no-load friction resistance characteristic test,starting pressure characteristic test and servo cylinder system performance test.The test results show that the antifriction effect of the hydrostatic support is significant.After the hydrostatic support is opened in the oil chamber,not only the fluctuation of the system pressure difference is small when the piston starts to produce displacement,but also the maximum pressure difference is significantly reduced compared with the condition without the hydrostatic support.The optimized hydrostatic bearing improves the oil film stiffness and the performance of high frequency and heavy duty servo hydraulic cylinder. |
