Study On Dynamic Pressure Effect Of Hydrostatic Thrust Bearing Under Extreme Working Conditions

Hydrostatic thrust bearing has been gradually recognized and widely used in the production practice and has become the key component of numerical control equipment because of its high running accuracy,stable process and a series of advantages.However,the demands of highway overload processing equipment on the stability and bearing performance of hydrostatic thrust bearing are becoming more and more high.In the processing,oil film becomes more thinner because of the combined effect of temperature and pressure on the hydrostatic thrust bearing which leads to big deformations of the rotary table and base and friction failure.So the study and improvement on the friction failure is imperative.In this paper,hydrostatic thrust bearing of high speed heavy duty vertical lathe is the research object and prediction model of oil film is found out by the theoretical analysis,numerical simulation and experiment and the reason of friction failure is analyzed.Finally,the shape of oil film clearance is effectively improved and friction failure is prevented by the adjustment of oil pad structure,hydrodynamic effect generated by the connection of the oil cushion and base and the adjustment on deformation of bearing friction pair by the dynamic pressure.The bearing capacity,flat flow and static pressure loss of the hydrostatic thrust bearing under the condition of high speed and heavy loads are theoretically calculated.Then three-dimensional modeling software is used for constructing models and fabrication of film,oil pads,rotary table and base,the mesh grid of film model divided by ANSYS ICEM CFD software is saved as a CFX file and the boundary conditions of film are set.By the iterative computations in ANSYS CFX,the oil film temperature field and pressure field under the condition of 35t-160 r/min are computed and the oil filmtemperature field and pressure field are imported into ANSYS workbench to analyze the overall deformation of rotary table and base,predict the shape of oil film and the friction failure behaviors.Finally,the size and structure of the oil pad and the connection form with base are adjusted to make it be the tilting type oil pad and generate the hydrodynamic effect based on the tilting type oil pad to compensate the static pressure loss,obtain constant oil film thickness and ensure the stable operation of hydrostatic thrust bearing.The experimental verification which takes the 5 meter vertical lathe as research objects is conducted in Qiqihar Heavy CNC equipment Limited by Share Ltd.Each kind of oil pad structure between inner oil film and lateral oil film is measured with a displacement sensor Z to the deformation in the condition of35t-160r/min,data is collected and analyzed and oil film thickness is calculated.The experimental results are compares with the numerical results which verify the validity of experimental results and numerical analysis.Finally,a more reasonable structure of oil mat is found out by theoretical calculation,simulation and experiments.