Study On Form Grinding And Transmission Tribological Performance For Cycloid Gear

As important transmission parts,cycloid gears are widely used in various reducers and industrial robots due to their advantages of high transmission accuracy and long service life.Their machining accuracy,lubrication and contact performances in the transmission process have important impacts on the operation of the reducers and industrial robots.Most of the current researches on cycloid gear,however,have focused on the grinding method,profile modification and transmission performance without considering the lubrication effect.And there are only few researches on the surface quality of cycloid gear,such as the temperature field,grinding surface roughness and residual stress,as well as the lubrication and tribological performances under the grease lubrication.Therefore,supported by the National Key R&D Program(No.2017YFB13000700)named after "RV Reducer performance evolution and active control",this thesis studies the grinding surface temperature,optimization of the grinding parameters,the lubrication and contact performance of the finite line contact considering the thermal effect during the transmission contact process,as well as the grinding quality of cycloid gear.The main research contents are as follows:Firstly,based on the moving heat source theory,the temperature field distribution of the cycloid gear forming grinding is studied.To this end,ANSYS APDL parametric programming is used.And then the influences of cycloid size parameters and grinding parameters on the grinding temperature are analyzed.The numerical results show that the grinding temperature of the cycloid gear increases first and then decreases along the profile direction.Moreover,the use of grinding fluid can effectively reduce the maximum grinding temperature.In addition,the maximum grinding temperature of the cycloid gear can be effectively reduced by properly reducing the number of cycloid gear teeth,wheel speed and grinding depth,or increasing the distribution circle radius and feed speed.Furthermore,the prediction model of the grinding temperature in the profile direction of the cycloid gear is established,and the grinding condition parameters of cycloid gear with the fixed sizes are optimized.To this end,the radial basis function neural network(RBF)is used to predict the temperature in the profile direction,and genetic algorithm is used to optimize the grinding condition parameters.Based on the function relationship established by RBF,the grinding parameters are set as independent variables and the maximum grinding temperature is set as the optimization objective.The grinding parameters with the lowest grinding temperature are obtained through the multi-level optimization of genetic algorithm.Then,the thermal elasto-hydrodynamic lubrication model of the finite length line contact for the cycloid pin gear pair is established under the grease lubrication.Based on the model,the lubrication and contact performances of the cycloid pinwheel pair are studied.To this end,the fast Fourier transform(FFT)is used to accelerate the solutions of the deformation and von Mises stress of the cycloid gear.The results show that in the contact region,the pressure and temperature of the film increase greatly on both sides of the tooth width.And the maximum elastic von Mises at the subsurface of the cycloidal gear in the symmetrical plane of the tooth width decreases with increasing short amplitude coefficient and cycloid gear number,and decreasing surface roughness,grease rheology index and cycloid gear output torque.Besides,the rougher the surface of cycloid pinwheel pair,the more obvious the fluctuations of the grease film pressure,film thickness and temperature in the center section of tooth width direction.Finally,the cycloid gear forming grinding experiment is carried out,and the influences of grinding parameters on the surface roughness and residual stress of cycloid gear are studied.The numerical results show that the profile of the grinding surface is better and the grinding surface is smoother with the relatively small feed speed and grinding depth and relatively large grinding wheel,while the residual stress increases with decreasing feed speed,grinding depth and wheel speed.The experimental results indirectly verify some of the simulation conclusions.