Research On The Matching Characteristics Between Pilot Valve And Multi-way Valve Of The Skid Steer Loader

In recent years, with the rapid development of China’s economy and improvement ofinfrastructure, small construction machinery market warmed up rapidly. Skid steer loaderhas gained rapid development and wide application as one typical kind of smallconstruction machinery. As one of the key subsystems of skid steer loader, the performanceof working system directly affects the efficiency of the machine. Skid steer loader workinghydraulic system mostly uses the pilot control and the main control valve is the multi-wayvalve. If the parameter selection is unreasonable and the output pressure characteristics ofpilot valve and the flow control characteristics of multi-way valve cannot match well，itwill cause that the actuator cannot follow the control signals given by the operator toperforms motion. This will affect the stability and micro-mobility of the working device,reduce the work efficiency and safety problems will arise. At present，there is nosystematic theoretical basis when the OEMs solve this problem. They only rely on simplecalculations and frequent replacement of the spring to improve the matching characteristicswhich increased the design cost. So the theoretical study on matching characteristics is ofgreat significance and practical value at this stage.This paper is based on the school-enterprise cooperation project "matchingcharacteristics optimization between pilot valve and multi-way valve of skid steer loader ".With solving practical problems existing in a prototype as the starting point, deeply studythe matching characteristics of pilot valve and multi-way valve. Put forward the matchingprinciple of pilot valve and multi-valve，form a match theory that can be universallyapplied to the pilot control system and provide ideas and basis for OEMs in solving similarproblems. The main research contents of this paper are as follows: (1) Described the internal structure and working principle of the pilot valve andmulti-valve in detail. Respectively expounded the output pressure characteristic of pilotvalve and the flow control characteristic of multi-way valve and established the appropriatemathematical model. Draw the matching characteristics curve，found the factors that affectthe matching characteristics by simultaneous equations. Analyzed each of the factors byusing the matching characteristic curve，and put forward the matching principle andoptimization methods between pilot valve and multi-valve.(2) Used AMESim software to establish a simulation model of a certain type of skidsteer loader working hydraulic system，analyzed its current matching characteristicssituation by simulation and defined the optimized direction. Put forward specificoptimization program based on matching principle and optimization methods combiningsimulation means. The correctness of theoretical analysis and optimization program isverified by comparative analysis of matching characteristics simulation curve before andafter optimization in three typical working conditions.(3) Designed pilot valve and multi-valve matching characteristics experimental testprogram，test the control performance of pilot system before and after optimization intypical working conditions. The experimental results verified the correctness of thetheoretical analysis and optimization programs. Meanwhile the correctness of thesimulation model is verified by comparing test curve and simulation curve, so thetheoretical analysis, simulation model and experimental study can verify and guide eachother.