Reliability Analysis Of Metal Belt CVT Slip Operation Based On EHL

The low transmission efficiency in the clamping force control strategy of CVT is widespread.The slip rate control strategy,which will be the development trend in the future,make the transmission efficiency become more efficient.However,the relative sliding of the friction pair between the belt and the pulley will increase the failure probability of the transmission.In order to improve the real-time reliability of CVT sliding friction transmission,such work has been finished as follow:(1)Based on the structural characteristics and the principle of sliding transmission of CVT,The position of larger slip rate is determined.According to structure and working parameters of CVT,the range of working parameters of secondary driven friction pairs is calculated.The mechanism of slippage in metal belt CVT transmission and the influence of slippage on transmission torque and transmission efficiency are analyzed.(2)A numerical calculation model between metal belt and pulley is established based on the theory of elastohydrodynamic lubrication.According to the range of load and relative velocity of elastohydrodynamic lubrication film,the change curves between minimum film thickness,maximum film pressure and CVT operating parameters are obtained under different working conditions.(3)By analyzing the failure modes of the lubricating oil film,the failure mode of the CVT driven wheel friction pair is determined to be the shearing failure.Then,Taking the maximum shear stress as the failure criterion,the Monte Carlo numerical simulation method is used to solve the CVT slip drive reliability under multi operating conditions,and the change rules between the CVT operating parameters and the failure probability are obtained.The MAP diagram of the work parameters and the reliability change is plotted.(4)Based on the MAP diagram,a reliability based sliding rate clamping force control strategy for bench test is completed.The experimental results show that the proposed sliding clamping force reliability control strategy is feasible.It can improve the CVT slip during the transmission of real-time reliability,and has important significance for the development of CVT.