Design Of Hmcvt Hydraulic System For Heavy Intelligent Tractor

Hydraulic mechanical continuously variable transmission is mainly used in heavy tractors.It concentrates the advantages of hydraulic and mechanical transmission technology.It increases transmission efficiency,increases transmission power,and has stronger impact resistance.Moreover,the design of multiple segments can achieve speed regulation in a large speed ratio range.This paper designs and develops a hydraulic system suitable for HMCVT test prototype of four planetary gear mechanism.According to the transmission scheme of HMCVT in heavy tractor,the design schematic diagram of the shift and lubrication hydraulic system is determined.In the paper,AMEsim hydraulic platform is used for modeling and simulation to verify the rationality and correctness of the design of the hydraulic system,and the influence of key parameters on the working quality of the hydraulic system is also studied.The hydraulic system is designed as an integrated valve body by Solidworks.The flow field data in the hydraulic integrated valve block are simulated to provide theoretical basis for flow channel optimization.The fluid structure coupling analysis of the hydraulic integrated valve block is carried out by FLUENT and Mechanical.The strength and deformation of the valve block are checked and the material of the valve block is optimized.The test bench of the hydraulic system is built,and the basic function of the hydraulic system is verified by the test structure.Besides,the influence of key factors on the working quality of the shift hydraulic system is studied through the test.Through the above design and research,the key parameters of the hydraulic system are determined,and the hydraulic pumps and valves which meet the design requirements are selected according to the schematic diagram.AMEsim simulation results show that the hydraulic system can reasonably match the oil-filling pressure and flow rate of the shift clutch to achieve the change of segment,and analyze the choosing range of throttle hole diameter,spring stiffness and valve core quality.At the same time,the simulation results optimize the diameter of the lubrication hole,so that the oil of the lubrication system can be reasonably distributed,and ensure the reliable service life of the gearbox.The analysis of flow field data inside the valve block shows that the swirl at the right corner of the pipeline increases the energy loss of the hydraulic system,and the right corner should be minimized in design.The fluid structure coupling analysis results of the hydraulic integrated valve block show that the designed valve block meets the requirements of strength and deformation,and nodular cast iron is the most suitable material for manufacturing the integrated valve block among several common materials,and the most suitable material is nodular cast iron.Finally,nodular cast iron is selected as the processing material of the valve block designed in this paper.The bench test results of the hydraulic system show that the accumulator has great influence on the pressure fluctuation,while the working pressure and flow rate have little influence on the working quality of the valve body.