Design And Dynamic Characteristics Research On The Hydro-mechanical Continuously Variable Transmission Of Tractor

Tractors often work in the complex environment.In order to adapt to the various conditions of load and speed requirements,the transmission of tractor needs to set more working gears,so that the transmission have complex structure,difficult operation and the economy can not be guaranteed.Hydro-mechanical CVT is a new type transmission device with the parallel form of hydraulic speed regulation and mechanical speed,combined with the characteristics of hydraulic stepless speed and mechanical transmission efficiency,full speed can be adjusted continuously,it has good maneuverability and fuel economy,especially suitable for high-power tractor in complex operation.The planet row is the core of the hydro-mechanical CVT,whose internal gears are the main transmission part.The gears are working under the constant speed and load,and the tooth surface is damaged by the impact of the load.Related research at home and abroad to carry out relatively less,so it has a great significance for research on dynamic characteristics of hydro-mechanical CVT.Therefore,this paper was supported by Jiangsu science and technology support plan(BE2014134)and Jiangsu Union Innovation Fund(BY2014128-04),designed a transmission scheme of hydro-mechanical CVT for high-power tractor,and did the dynamic simulation analysis of the planet row.The main research contents are as follows:1.According to the running speed of tractor and the work environment requirements determine the working period of transmission,and designed the transmission scheme of hydro-mechanical CVT.And transmission ratio and gear ratio was calculated based on transmission scheme.The hydraulic oil circuit is designed,and the hydraulic components are selected according to the transmission output power.The speed and torque characteristics of the designed scheme are analyzed,and the theoretical model of the rotational speed and torque is established.2.Based on hydro-mechanical CVT scheme,hydraulic machinery stepless gearbox and tractor AMESim machine simulation models are established.Use Creo2.0 3D modeling soft ware to establish the planetary model of virtual prototype.Based on the Hertz elastic contact theory analysis and simulation parameters of gear contact force calculation,established planetary dynamics simulation model of Adams.3.The pump control hydraulic motor system and the clutch test bench are built.The speed regulation characteristics of the pump controlled hydraulic motor and the characteristics of the clutch oil filling are analyzed.Results show that the variable pump forward-biased or reverse-biased,there is a linear relationship between the transmission ratio of pump controlled hydraulic motor system and excitation voltage.By controlling the change of the excitation voltage,the drive ratio of the pump controlled hydraulic motor system can be controlled.The variation trend of the pump control hydraulic motor bench test and the simulation results are consistent.The oil filling process of the clutch is oil filling,boosting and pressure maintaining.The change of the oil pressure of the clutch is fast,and there is pressure buffer in the unloading process.Clutch test bench test oil pressure variation and simulation results are basically the same4.Based on the classical formula of gear meshing force,the theoretical value of the planetary gear meshing force is calculated,and the dynamic analysis is carried out with Adams.The simulation results are basically consistent with the theoretical values.Based on planet row simulation,change regulation in different displacement ratio,engine speed and load of planet row were researched.The results show that the different displacement ratio and load has great influence on the force of planetary gear meshing,influence of different speed are positively correlated;the gear meshing force of micro engine.5.Study on the process of speed control and change process of planet row meshing impact law.The results show that the speed of adjustable speed rate and different load speed has obvious impact on the lower planet row,the impact strength increases with the increase of speed and load rate.In the process of the main oil pressure control valve and the flow changes very little of the planetary gear meshing impact.The change of segment time has great influence on the meshing impact of planet gear teeth,with the increase of overlap time,the meshing impact is also increased.6.Study on the tractor under typical working conditions of planetary gear meshing impact law.The results show that under the plough condition,the meshing impact of planet row increases with the deep tillage increased.The row of planets also has a great impact on the acceleration of the replacement of the plough.Under the condition of seeding,the planetary row has a great impact on the speed of the engine and the speed change.In conclusion,the paper designed transmission system scheme of hydro-mechanical CVT which was used in tractors.The dynamic characteristics of hydro-mechanical CVT was studied.Provides a theoretical basis for the optimization design of planet row transmission and reduce noise and vibration.