Dynamics Research And Phase Optimization Of CVT Reverse Double-planet Gear Train

Continuously variable transmission(CVT),as a kind of automobile transmission,is widely used because it can bring better comfort to the driver.The double-planet gear train is used to control the switching between the forward gear and the reverse gear in the CVT,and its performance directly affects the stability of the vehicle equipped with the CVT in the reverse gear.Therefore,this paper takes the double-planet gear train of the metal belt CVT as the research object,and studies its dynamic response through the dynamic model.According to the mechanism of “phase suppression of vibration”,based on the traditional planet phasing theory,a model of composite mesh phase is proposed,which weakens the impact of mesh stiffness.The main research contents are as follows:(1)Dynamic model of double-planet gear train.Based on the working mode of double-planet gear train when the CVT is in reverse gear,the translational-torsional coupled dynamic model of double-planet gear train is established by the lumped parameter method,and its dynamic differential equation s are deduced.In order to improve the convergence of dynamic differential equation s,the dimensionless processing is carried out,and the solution method and idea are introduced.(2)Time-varying mesh stiffness of a helical gear pair.Based on the improved potential energy method,the helical gear pair is analyzed using the slicing method and the idea of summation,and the time-varying mesh stiffness of the helical gear is obtained through the relationship between the length of contact line and the contact ratio.In addition,the dynamic simulation of the helical gear pair is carried out by the finite element method,and the same mesh stiffness as the theoretical calculation is obtained based on the pure torsional dynamic model of the gear pair.(3)Composite mesh phase based on weakening mesh stiffness impact.The mesh phase difference calculation model considering the modification coefficient is established,and the mesh phase difference between each gear pair of double-planet gear train is solved.In order to weaken the impact of the mesh stiffness in gear pairs,a composite mesh phase model is proposed based on the planet phasing theory.By reasonably controlling the parameters,the model can make the mesh stiffness of each gear pair present the phenomenon of reaching the maximum or minimum value at the same time.(4)Vibration characteristic analysis and phase optimizatio n of double-planet gear train.The dynamic equations of double-planet gear train are solved,and its dynamic response is obtained.On this basis,with the angle of mesh phase,the parameters of double-planet gear train are optimized,and the phase optimal model based on the composite mesh phase theory is obtained.Compared with the traditional optimization model,this model has greater advantages in the mechanism of “phase suppression of vibration”.In this paper,when the dynamics of double-planet gear train is studied,the proposed phase optimization method not only makes the sun gear in the state of optimal phase,but also weakens the impact of mesh stiffness between gear pairs.It has made a certain contribution to the vibration and noise reduction of double-planet gear train.