Research On Safety Margin Of Transmission Reliability Of Metal Belt Continuously Variable Transmission Under Lubrication

CVT is a non-unidirectional motion system with self-coupling effect.The metal belt is affected by the comprehensive influence of variable and extreme working conditions,macro and micro parameters during the energy transfer process,which can easily lead to the reduction of the belt carrying capacity and the failure of the dynamic system.In order to solve the above problems,this paper takes the lubricating oil film between the metal belt and the pulley as the research object,and uses a combination of theory and experiment to identify the mapping relationship between the lubrication state and the working condition parameters,and clarify the law of the oil film stiffness between the friction pairs.Determine the dynamic balance threshold of oil film traction between the metal belt and the pulley,reveal the failure mechanism of the dynamic system under the coupling of macro and micro working conditions,construct the boundary of the critical instability safety zone of the system,and quantify the safety margin.The main research content of this paper includes the following four aspects:(1)The composition structure and working principle of the metal belt continuously variable transmission are described.Based on the actual operating conditions of the transmission,a numerical model of the oil film characteristics between the metal sheet and the pulley is established by using the linear contact elastohydrodynamic lubrication theory,using multiple grids method and FORTRAN programming for iterative calculation of eigenvectors such as oil film pressure,film thickness,and oil film temperature rise.(2)Using numerical simulation results to study the change law of the oil film pressure,film thickness and temperature between the metal sheet and the pulley,using MATLAB simulation to analyze the influence of the friction pair roughness amplitude(microscopic variables)on the oil film pressure and thickness.On this basis,the variation law of friction pair oil film stiffness with roughness amplitude is studied.By completing the experiment of measuring the axial pressure and torque ratio of the metal belt,the influence of the transmission input and output torque ratio(macro variable)on the oil film pressure and thickness is systematically analyzed,then the variation law of friction pair oil film stiffness with transmission torque ratio is quantitatively studied.(3)The failure function is established for the failure of CVT sliding friction transmission,and whether the shear stress of the oil film reaches its limit value is determined as the basis for judging transmission failure.Based on the convex theory,the convex model of the CVT sliding friction transmission interval is established,the torque ratio-roughness amplitude interference model is used to evaluate the reliability index of the model.Based on the MGDA gradient strategy,the numerical relationship between the safety threshold of the oil film stiffness of the CVT pulley-metal sheet friction pair and the torque ratio and the roughness amplitude is calculated and analyzed,afterwards,the Pareto optimal solution of the safety threshold of oil film stiffness is calculated.(4)Combined with the application of new carbon nanomaterials in vehicle oil wear detection,a continuously variable transmission oil condition monitoring system is designed.Using the selective effect of the fluorescent carbon quantum dots on the iron and nickel elements in the RDC150 type transmission metal belt material,the fluorescence intensity quenching rate of the carbon quantum dots is calculated,and it is determined that the main fault location of the continuously variable transmission is the steel ring.The combination of oil spectrum analysis technology and immune principle further verified the validity and rationality of the experimental conclusions.