Design And Simulation Of The Valve For Tractor's Electro-hydraulic Hitch System

Fast development of agricultural modernization speeds the process of tractor intellectualization.The plowing operation as the major operation form of tractor,the improvement of electric hydraulic suspension system for which is an important research direction for current agricultural researchers.Mechatronics Technology applied in the suspension system improves technologies used in tractors and enhances their working performance.Hydraulic valve integration technology reducing the using area and energy consumption is the key technology to realize agricultural modernization and therefore the main part of this paper.The structural principle of electric hydraulic suspension system of tractor was analyzed in the paper,the advantages and disadvantages of different integration methods of valve were compared,according to which the plug-in valve was used to alternate the traditional tube type.The threaded cartridge valve instead of traditional electromagnetic proportional directional valve and relief valve lowers the constructional cost and using space of hydraulic cycle.Four DHF08-228L solenoid valves and one YF06-00 relief valve were calculated to consist the hydraulic control part of electric hydraulic suspension system.The hydraulic schematic was improved and then the 3D structural drawing and assembly drawing were completed.In order to verify the rationality and reliability of the design of the valve,structural statics and hydrodynamics analysis was conducted by ANSYS Workbench and FLUENT.The results showed that,when applying 20MPa oil pressure to the oil inlet,the maximum pressure of oil wall was 36.9MPa,which was much lower than the allowable stress-187MPa of 45#structural steel.Maximum deformation was 0.2mm which met the requirement of valve's reliability.The valves with three oil types and three different diameters of process hole were analyzed in FLUENT.The results show that turbulent energy is the main cause of pressure lost and enlarging the diameter of process hole and reduce the right angle bend can lower the turbulent energy significantly,which provides a reference for the design of valve.Since pressure adjustment of electric hydraulic suspension system depends on the relief valve,the relief valve was simulated in AMESIM to get its flow pressure curve and dynamic response curve.The simulation of closed loop control and force position control of suspension system was conducted in AMESIM and Simulink,which shows that using plug-in valve can lead to the fast response of plowing depth adjustment.Finally,a test platform was built to verify the rationality of the design of the valve and the realization of closed loop control and force position control for hydraulic cylinder,which shows the fast response of plug-in valve.