Research On Matching Method Between About Multi-way Valve And Pilot Valve For The Wheel Loader

The hydraulic multi-way valve and pilot valve are widely applied in the constructionmachinery. The pilot valve is used to control the valve spool movement, which can reduce thecontrol force of the handle. Increasing the stiffness of the spring can offset the effect of thefluid dynamic to the movement of valve spool. However，the loader operation comfort largelydepends on the matching characteristic of pilot valve and multi-way valve, the microperformance of working device and the free stroke of pilot valve.This paper takes pilot valve and multi-way valve on a type of loader as research objects.The internal structures of the pilot valve and the multi-way valve were deeply analyzed, therelation between the pilot valve displacement pressure curve, multi-way valve displacementpressure curve and the multi-way valve displacement flow curve was deeply studied. Inaddition, the relation between the pressures at the start position and the end position of thepilot valve and the opening of multi-way valve was determined, the relation between the pilotvalve displacement and the multi-way valve flow was finally confirmed, and the matchingprinciples and methods of pilot valve and multi-way valve were proposed. The main worksand research contents are listed as follows:1. Describing the working principles of pilot valve and multi-way valveThe internal structures of the pilot valve and multi-way valve were described, theirworking mechanism was analyzed, and the matching method of multi-way valve and pilotvalve was established.2. Establishing the mathematical model of multi-way valve and pilot valveAccording to the analysis of the internal structures of the pilot valve and multi-way valve,the static characteristic formula, the matching principle and method of the pilot valve and themulti-way valve were proposed, providing a basis for the simulation work in the future.3. Simulation of multi-way valve and pilot valveThe simulation models of pilot valve and multi-way valve were established in theAMESim simulation environment. According to the surveyed structural parameters, theparameters of the model components were set, and the opening processes of the multi-wayvalve and the pilot valve spools were simulated. Various factors affecting the opening of thepilot valve spool and multi-way valve spool were analyzed.4. Analysis of simulation resultsThe simulation study of multi-way valve and pilot valve was done jointly using theirAMESim model. And the curve output from AMESim was analyzed and the key parametersaffecting the reasonable matching of pilot valve and multi-way valve were found. The rigidityof the adjusting spring of pilot valve and the extension spring of multi-way valve wereoptimized to form the linear relation between the course from the starting point to the end point and the displacement of multi-way valve spool. It brings a good inching performanceand control ability for the pilot valve. The correctness of simulation models was verified bytesting, and the design was optimized by using simulation models.5. Testing the optimized multi-way valve and pilot valveThe optimized results were tested again on the machine to verify the stability of theoptimized working implement motion. The measured curve and simulation curve werecompared to find the differences, and the simulation model was changed again.The models of multi-way valve and pilot valve were established using AMESim, anddynamic simulation of the opening processes of the multi-way valve spool and the pilot valvespool were conducted. Various factors affecting the performance of the pilot valve andmulti-way valve were analyzed. On this base, the matching of multi-way valve and pilot valvewas optimized and critical parameters were determined. The optimized multi-way valve andpilot valve was tested again to verify the accuracy of the models. According to thecomparison, the testing curve and the simulation curve are closely identical, which shows thatthe models are accurate. The research results in this essay offer new methods for the matchingof multi-way valve and pilot valve, which is not only practically significant for the pilothydraulic system design of loaders, but also valuable and instructive for the study of pilothydraulic system design for all construction machinery industry.