Design And Analysis Of Transmission On Hydraulic Menchanical Continuously Variable Transmission Of High-power Tractors

Because of complex operation,the working condition of tractors' transmission is far inferior than ordinary vehicles.When it refers to high-power tractors,the situation looks harder.In order to realize more stable transmission under complex condition,high-power usually equips with many gears,however,regularly shifting between different gears brings much inconvenience.Hydraulic mechanical continuously variable transmission(HMCVT)has unique advantages in riding comfort,power performance,fuel economy and operation convenience,Compared to the traditional stepped transmission,it is particularly suitable for high-power tractor.HMCVT has been successfully applied in different brands of tractor abroad,in China,HMCVT still stay in the research stage,therefore mature product doesn,t appear in China's market.In order to promote the development of HMCVT applied on high-power tractors,this paper chosen KAT1804 type tractor as the research object,designed the hydraulic mechanical continuously variable transmission,and then carry on the experiment and simulation analysis,mainly research contents are shown below:1.In this paper,transmission characteristics of volume speed-modulating loop and planetary gear were analyzed.According to tractor's power and structure parameters,this paper effectively combined hydraulic speed control circuit and planetary gear mechanism,analyzed the influence of different quantity of planet rows,layout of power input and power output component in planter gear,and the number of hydro-mechanical section.Then,two different schemes were put forward:arithmetic type transmission and geometric type transmission.After compared and analyzed the transmission characteristics of these schemes,this paper finally adapt geometric transmission scheme.2.Optimal matching of gearbox transmission parameters was done by genetic algorithm.First of all,this paper defined the objective function,then decided the limit of parameters based on tractor's related parameters,experienced value range,and transmission relationship,and therefore used the algorithm to optimize parameters by real-valued coding,real-valued crossover operator,real-valued mutation operator,and different selection strategy.This paper obtained the corresponding transmission parameters of HMCVT,derived its output speed,torque characteristic,and hydraulic power split ratio,and chosen variable pump and constant displacement motor according to existing products.3.This transmission's structure was designed.This paper designed the structure and bearing of key components in the planter gear,and adopted load balancing mechanism using the principle of elastic moderating impact.After that,the strength of these pair of gears and shafts were checked,and wet clutch supplying oil by axial feed also was selected.Making use of Creo,this paper created 3D model of the transmission,where gears and clutches were established by parametric modeling,and then examined if there is assembly interference.4.This paper did experiment about hydraulic speed regulation system to identify the system.Changing the speed of engine,this paper acquired related experimental data when variable pump in both positive deflection and reverse deflection status.After filtering process with the help of Matlab,system model is obtained by Matlab system identification toolbox,this model's accuracy is high,and can be used for transmission's further research.5.With the help of simulation softrware-AMESim,hydraulic mechanical continuously variable transmission's simulation model was established,including engine experimental model,hydraulic speed regulation circle model,wet clutch model,dual-planetary gear model,and back transmission model.This paper simulated the transmission's working,and it showed that the transmission can realize stepless speed regulation with geometric transmission characteristic.Through these research contents above,this paper designed hydraulic mechanical continuously variable transmission with conveniently operation,high transmission efficiency,and effectively impact mitigating,it provides a reliable material base for further working condition experiment,driving comfort and control strategy research,and can significantly promote the development of HMCVT in domestic high-power tractors.