Research On Electro-Hydraulic Shifting System Of Loader Transmission Based On Mechanical And Hydraulic Buffer Valve

As a kind of high working efficiency engineering machinery,loader can operate under bad environment and complicated working conditions,so it is widely used in urban construction,mining,railways,highways,hydropower,national defense and airport construction.As an important transmission module of the loader,the performance of the gearbox will directly affect the working efficiency of the loader.The loader needs to constantly switch gear in the operation process,if the shifting process is not stable and the shock is very large,it will not only reduce the working efficiency,but also cause a great sense of driving fatigue and great danger to drivers.Therefore,it is necessary to study the gearbox electro-hydraulic shifting system of loader to improve the smoothness of shifting process and reduce the shifting shock,and this is the purpose of this paper.In the first chapter,the paper summarizes the current status of the research on the gearbox electro-hydraulic shifting system of the loader at home and abroad and the current research status of the mechanical and hydraulic buffer valve.Contrasting the existing strategy of reducing the shock of gearbox shifting,the research way of electro-hydraulic shifting system of loader gearbox based on mechanical and hydraulic buffer valve is put forward,and the research contents of this subject are clarified,which indicates the direction for follow-up work.In the second chapter,ZL50 loader is taken as the research object,composition and working principle of the transmission system are described in this paper,the evaluation index of loader shifting smoothness are put forward.The dynamic analysis of the transmission process is carried out.Combining the mathematical model of evaluation index with dynamic analysis,the controllable factors affecting the shifting smoothness are found,which provides a theoretical basis for the following control and research objectives.In the third chapter,the ideal boosting curve of shifting process is firstly presented.A mechanical and hydraulic buffer valve is introduced for shifting hydraulic system,and the structure and working principle of the valve are analyzed.The buffering mechanism of the buffer valve is theoretically studied,and its cushioning effect is verified theoretically.In the fourth chapter,the paper studied the electro-hydraulic shifting system with a mechanical and hydraulic buffer valve.Firstly,a new shift control strategy is proposed for the shifting hydraulic system,and set up a simulation model of the electro-hydraulic shifting system using the AMESim software.The influence of the change of different parameters of the system on the boosting curve of the shift clutch is analyzed.The feasibility of the electro-hydraulic shifting system to reduce the shifting shock is verified from the simulation point of view,and the simulation basis for the experiments below is provided.In the fifth chapter,the paper carries out an experimental study on the shifting process of the loader.The experimental platform is built with the ZL50 loader,taking the simulation model as the reference,the boosting curve of the shifting clutch and the impact acceleration during gear shifting process are tested under different working conditions.The optimal solution is obtained by constantly adjusting the throttle aperture of the public oil road and the shift time parameters.In the sixth chapter,the main work of this research topic is summarized,and making a prospect for the problems and the follow-up research work.