Research On Shift Quality Of Combined Transmission Of Medium And Large Horsepower Tractor Based On Fixed-axis AT

As a key component of the vehicle's transmission system,the gearbox can be traditionally divided into a continuous power transmission and a manual mechanical step-shifted transmission.Due to their large load and large number of gears,agricultural tractors,heavy-duty trucks usually adopt a combined gearbox system combining continuous power transmission with the manual mechanical step-shifted transmission,which has the advantages of simple shifting and fast shifting.Thus,the comprehensive performance of the vehicle such as fuel cost and power performance of the vehicle can be improved.In this paper,based on the fixed-axis AT medium-high horsepower tractor combined transmission,research and analysis of the shifting quality of the AT section of the power shift section are mainly studied,including following contents.(1)Focusing on the targeted vehicle model,study and formulate the overall scheme of the combined variable speed transmission system using the fixed axis AT;(2)Parameter design of multiple wet clutches,and model and simulate the friction force of the cylinder seal during clutch engagement,and the friction curve is obtained;(3)Based on the force analysis of the tractor,establish the dynamic model of the tractor,analyze the shifting process of the power shift section,determine the working state of each clutch,and construct the corresponding dynamic equation;(4)Based on the friction characteristics of the friction pair,the evaluation index of the tractor shift quality and its influencing factors are analyzed.According to the tractor dynamics equation,a joint simulation system based on AMESim and Simulink is built.Based on the simulation analysis,the hydraulic pressure control strategy of the actuator is provided.(5)Design a test and test verification plan,and perform system test,test result analysis and parameter optimization when conditions are satisfied.