Design And Research Of HMT Hydrostatic Transmission System For Corn Harvester

Faced with the contradiction between the country’s accelerated agricultural modernization process and the backward performance of China’s agricultural harvesting equipment,the research and development of corn harvesting machinery that has gradually emerged in recent years has become one of the important directions.The transmission speed change form is one of the research focuses.At present,the corn harvester applying HST(Hydro Static Transmission)hydrostatic drive technology has exposed shortcomings such as low transmission efficiency,easy oil leakage,and high driver labor intensity.The hydro-mechanical continuously variable transmission(HMT)hydrostatic transmission system,which combines hydraulic transmission and mechanical transmission,application to the corn harvester is the focus of research at home and abroad.The HMT transmission system is a dual power transmission structure that combines the power generated by the hydraulic system and the mechanical system with power output from the planetary gear train.This transmission structure not only relieves the driver’s labor intensity,but also improves transmission efficiency.The research focus of this subject is to improve the existing HST-type hydrostatic transmission system.Through a full study of HMT hydrostatic transmission systems at home and abroad,a new type of HMT-type hydrostatic transmission is designed for the domestic 4-row corn harvester.Established the related theoretical model of HMT transmission system dual-flow transmission,analyzed the relevant characteristics of the transmission structure,calculated the relevant transmission parameters,and simulated the system and the whole machine.The main research work is as follows:(1)The design uses a two-speed mechanical transmission to increase the speed range and determine the maximum design speed reaches 35km/h after analyzes the driving structure of the applied corn harvester.Then compare and analyze the characteristics of the branching structure of the output coupling type and the input coupling type,which indicate that the scheme of output coupling type HMT transmission gearbox with single-row planetary gear less clutch,include high and low step-variable gear train,differential and so on.(2)The characteristics of output speed,power split ratio,and system efficiency are analyzed by establishing the theoretical model of the speed,torque and power of the HMT transmission system,and the matching design of the relevant transmission ratio parameters is carried out.(3)Analyze the HST hydraulic system circuit,calculate the required power of the hydraulic system through the HMT system power model,work out design and selection of the overall HST,and analyze its related characteristics to calculate the relevant pressure parameters of the hydraulic system;The transmission structure and key components of the HMT transmission system are designed;Use ADAMS to establish the kinematics model of HMT transmission system in low gear and perform simulation analysis,the force at the gearbox support hole was added to the corresponding position of the ANSYS Workbench static model to perform the static simulation of the box structure and check its strength.(4)Use AMEsim to build a complete machine physical model.First of all,the driving conditions are simulated,including the simulation analysis of the static characteristics of the hydraulic system,the driving speed of the harvester,and the impact of braking conditions and displacement ratio changes on driving performance,get the corresponding curve;Then the simulation analysis is performed on the matching relationship between the rotation speed of each component in the HMT transmission model sub-convergence structure and the increasing speed forward,decelerating forward,stationary,reverse speed increasing,and decelerating reverse of the equipment driving conditions.Simulation results show that the HMT transmission system has a high and low speed range of-2.9～+8.8 m/s and-1.3～+3.8 m/s meets the requirements for continuously variable transmission design,and the larger the speed difference between the planetary carrier and the ring gear,the greater the output speed.