Research On Control Performance Of The Main Control Valve Of Medium-sized Hydraulic Excavator

The main control valve is an integrated valve assembled by more than two valve blocks and can control the operation of multiple actuators; the pilot hydraulic valve is the key actuator that controls the commutation of the valve spool. As core components of the hydraulic excavator, the performance of main control valve and pilot valve determines the control performance of the machine.The arm and bucket of the medium-sized hydraulic excavator was researched. The curve of comprehensive characteristics was obtained and the assessment method of the control performance of the main control valve was put forward and analyzed. And the optimization strategy was discussed. The main works were as follows:(1)The mathematical model of the displacement characteristics of the valve spool and the flow characteristics of the valve port was built. Thorough analyzing the relationship among the curve of the pressure characteristics of the pilot valve, the displacement characteristics of the valve spool and the flow characteristics of the valve port, the relevance between the displacement of the valve spool and the flow of the valve port was figured out—the curve of comprehensive characteristics of the pilot valve and main control valve, which was used as the assessment method.(2)Base simulation on AMESim and Fluent, the curve of comprehensive characteristics of existing bucket and arm was obtained and evaluated from the aspects of the percentage of linear control efficiency, linearity and sensitivity. The results show that the existing main control valves are disadvantageous in narrow range of speed adjustment, poor performance in fine adjustment of flow and poor flow resolution. Through adjusting the pilot pressure relief spring and the rigidity and preload of the reset spring, the range of speed adjustment was widen; by increasing the gradient of the flow area curve, the performance in micro-adjustment of flow was improved.(3)Relevant experiments on medium-sized hydraulic excavator were conducted including the test of pilot pressure and single operation test of arm and bucket. Through comparison between experimental results and simulation ones, the simulation analysis and the feasibility of the optimizing strategies were verified.