Efficiency Model of Hydraulic Pump-Motor for Tractor Hydro-Mechanical CVT Under All Operating Conditions
Hydro-mechanical continuously variable transmission(CVT)is one of the mainstream technologies for the future development of tractor transmission systems,and the efficiency characteristics of the hydraulic pump-motor are crucial for the dynamic performance of CVT.To solve the existing problems in predicting the efficiency of hydraulic pump-motors,including in defect of the analysis on the power loss between friction parts and taking much calculation time with the finite element efficiency model,a semi-empirical efficiency model was proposed based on loss mechanism for all operating conditions to evaluate exactly the efficiency of hydraul-ic pump-motor.Considering the nonlinear changing regularity of system parameter,some functions of the model were designed to predict the power loss,to fit the compound system parameters based on experimental data,fi-nally to obtain a complete efficiency model for the hydraulic pump-motor.Experimental data shows that the av-erage relative error of the model is 6.36％.The volumetric loss in high-pressure differential regions and the mechanical loss in low-pressure differential regions are the main influence on the pump-motor efficiency.Caus-ing the difficulty in improving efficiency of hydraulic pump-motor under margin working conditions,the main reasons are the flow leakage,compressible volumetric loss and Coulomb friction loss.It is the beneficial for im-proving pump-motor efficiency and enhancing the overall transmission efficiency of CVT to operate the pump-motor in medium to high displacement regions and avoid low-pressure and high-speed conditions.
hydro-mechanicalcontinuously variable transmission(CVT)hydraulic pump-motorefficiency model
万方数据
维普
