Study On Characteristics Analysis And Simulation Of The Hydro-mechanical Continuously Variable Transmission Of High-power Tractor

Hydro-mechanical Continuously Variable Transmission(HMCVT)can achieve the function of stepless variable speed,which combines the hydrostatic power and mechanical power based on the power split fundamental principle.With the characteristics of stepless variable speed and high transmission efficiency,HMCVT will improve and enhance the power and fuel economy of tractors,and it will have a good application prospect in large and medium-sized tractors.With the rapid development of modernized agriculture in our country,the demand of highpower tractor will be more and more heavily in the agricultural machinery market,so the research and development of HMCVT for highpower tractor is of great importance and necessity.The research and design of HMCVT scheme is carried out according to the 200 horsepower tractor of Wuzheng Group.The transmission characteristics of the system are analyzed based on the simulation model of the tractor drivetrain which is established throngh professional system simulation software.The main research contents of the study are as follows:(1)Based on the theory of HMCVT,the speed characteristics of two typical HMCVT are analyzed by Matlab software as well as the speed and power characteristics of two basic transmission schemes,which indicate that the scheme of multi-range HMCVT with dual planetary gears is suitable for the high power tractor.(2)Based on the analysis of the technical parameters of 200 horsepower tractor and the velocity distribution of its driveline,the output coupled HMCVT scheme with five range and its transmission mechanism are designed.Then the transmission parameters are calculated.The speed,power and efficiency characteristics of HMCVT are analyzed based on the expression of its transmission characteristics.The analysis result shows that the transmission schem can realize the infinitely variable speed of the tractor in the range of 0 ~ 50 km/h,and it has high transmission efficiency in the full speed range.(3)According to the structure of HMCVT,the simulation model of the HMCVT is established through AMESim software.And the transmission characteristics of the HMCVT are analyzed.The result shows that HMCVT scheme can satisfy the requirement of the tractor speed.And simulation analysis result is in conformity with that of the theoretical analysis,which proves the correctness of the simulation model as well as the simulation method.Based on the system simulation model,the simulation analysis of the influence between the change rate of the hydraulic displacement and the tractor speed performance is carried out.