| ABSTRACT:The main pump and main valve of the positive flow control system are controlled by the same pilot to improve system responsiveness, with the difference response of the main pump and the main valve to the same pilot, mismatch of the main pump and the main valve are aroused, meanwhile hydraulic impact, vibration and the overflow problem are generated to decrease the efficiency and operational performance of excavator. Being as the platform, excavator with positive flow control system was researched on the adjusting mechanism of the pump displacement, the dynamic response of the main valve-pump system and its coordination match characteristic. Taking response characteristics of main pump and the matching response characteristics of main pump and main valve as research objects, the optimization of response to the subsystem was studied.Introduction of typical hydraulic system application examples in the hydraulic excavator, describe of the significance of feature matching research in excavator hydraulic system, and sketch out the application of excavator hydraulic system simulation technology.The basic structure and working principle of the shuttle valve group, the main pump, multi-channel valve and hydraulic positive flow system of the hydraulic excavator were analyzed. With detailed analysis, the mathematical model of main pump displacement regulating mechanism and variable pump six multi-way valve system was established.The hydraulic simulation models of each function parts were set up based on AMESim. The working characteristics of the shuttle valve group and the coordinate matching control characteristics of the main pump and the main valve were analyzed. The results show that the real-time and accurate adjustment of main pump displacement was unable to be realized with the selected maximum pilot signal at work. Pressure impacts at the valve port and the overflow problems in the hydraulic system were mainly caused by the unmatched response of pilot signal of the main pump to the main valve in collaborative working process of pilot-main pump-main valve system. In order to solve these problems, solutions for each problem were put forward, which were analyzed through simulation. The analysis results show that after optimization, the pressure impacts and pressure fluctuation at the valve port were effectively reduced. Meanwhile, the real-time and accurate adjustment control of the main pump displacement was realized.Experiments were conducted on SWE240Z hydraulic excavator, through the analysis of experimental data, the simulation model was verified. |
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