Research On The Combined Hydro-mechanical Transmission System Of Tractor

Hydro-Mechanical Transmission(HMT)is a hybrid transmission system which divides the input power into the hydraulic and mechanical transmission and then realizes the converged output.The HMT with a hydraulic pump as power divider can cut off the transmission path of power and realize the function of clutch.The combined hydro-mechanical transmission(CHMT)is made up of two sets of this kind of HMT.CHMT takes advantage of the clutch function of HMT to form a mechanical hydraulic mixing system with properties of the dual clutch transmission(DCT).In CHMT,the shift process of DCT which causes significant wear of clutch is replaced by the regulating of the pressure,flow and flow rate of of the hydraulic components.In this paper,the CHMT system is used to replace the power shift part of a tractor transmission,and the transmission characteristics and the shift process of the system are studied.The main contents of the work are as follows:(1)The internal shunt HMT is designed according to the shunt principle of the pump as the power divider.The functions of parts and components in the system and their actual process are analized detailedly.By calculating the input and output of the hydraulic pump and motor in HMT,the speed,torque transfer relationship and power transfer efficiency of the input and output of the HMT are obtained.And The working process of HMT system is analyzed.(2)CHMT structure is designed based on HMT.The speed ratio,torque ratio,transmission efficiency and hydraulic power ratio of each HMT system are calculated respectively.The pressure,flow rate of the pump and motor and the gear ratio in CHMT system are determined according to the parameters of the replacement power shift module and engine.(3)The shift strategy of CHMT system is put forward,and the changes of the output parameters of the system during the shift process are calculated and analyzed.And the adjustment of the output of the engine in the shift process system is also analyzed.(4)Based on the Simulink simulation platform,the whole vehicle modeling and simulation on whether to adjust the engine in the shift process is carried out,and the simulation results are analyzed.(5)The experimental device and the overall arrangement of the experimental platform are designed.the assembly drawing of the experimental device is drawn.