Research On Contact Model Of Cycloidal Pinwheel Based On Fractal Theory

Cycloidal pinwheel transmission system is widely used in high-precision manufacturing industry for its advantages of large transmission ratio,high transmission efficiency,high rotation accuracy and long service life.At present,the research on the contact characteristics of cycloidal pinwheel drive is mostly based on Hertz contact model,ignoring the influence of the contact surface on the contact characteristics,and there is a large error in calculating the contact area.Therefore,the study of the micro morphology of the joint surface of cycloidal pinwheel is of great significance to accurately calculate the contact stress of cycloidal pinwheel and improve the machining accuracy and meshing quality of cycloidal gear and pin gear.From the microscopic point of view,this paper studies the influence of cycloidal pinwheel surface micro morphology on contact performance based on fractal theory.The main research contents are as follows:(1)Based on the fractal theory and WM function,the two-dimensional and three-dimensional rough surface topography are simulated,and the effects of the changes of fractal dimension D,roughness amplitude parameter G and micro convex frequency index n on the surface topography are studied.The results show that the increase of parameter D and the decrease of G and n will reduce the surface roughness and smooth the contact surface morphology.(2)On the basis of MB fractal model,by introducing friction coefficient and curved surface contact coefficient,the fractal contact model of cycloidal pinwheel considering the influence of friction is established and simulated to analyze the friction coefficient μ、Fractal dimension D,roughness amplitude parameter G,material characteristic parameter φ and roughness Ra and its influence on fractal contact model.The results show that the parametersμ and G decrease,and φ The increase is conducive to improve the contact performance.The values of parameters D and Ra are different,and there is an optimal value for the influence on the fractal model.Verify the accuracy of the cycloidal pinwheel fractal contact model.(3)The relevant parameters of cycloidal pinwheel are brought into the fractal contact model,and the contact stress based on fractal theory is calculated.Through parametric modeling and finite element simulation,the contact stress based on finite element method is obtained.The contact stress is calculated by Hertz contact theory.The results show that the contact stress of cycloidal pinwheel transmission system increases first and then decreases gradually with the increase of needle tooth number,and the calculation results of fractal model are large,which verifies the correctness of fractal theory calculation method.(4)Combining the fractal contact model of cycloid gear with the contact thermal conductivity formula,the contact thermal conductivity model of cycloid pin gear is established.The contact load P,fractal dimension D,roughness amplitude parameter G and material property parameters are analyzed φ Friction coefficient μ Influence of other parameters on contact thermal conductivity H.Then,the thermal structure of the cycloidal pinwheel model considering the reciprocal of contact thermal conductivity(contact thermal resistance)is simulated,and the influence of contact thermal resistance on the cycloidal pinwheel transmission system is analyzed.The results show that the contact thermal conductivity is related to the parameters P,D,φ Positively correlated with G,μ Considering the contact thermal resistance will increase the temperature and thermal deformation of the cycloidal pinwheel transmission system.