农机化研究

果树修枝机作业过程中会产生强烈的液压冲击，为了探究其原因，利用AMESim软件中的HCD液压元件设计模块，建立了由齿轮泵、三位四通电磁换向阀和柱塞马达组成的液压系统模型。通过分析马达进油口、换向阀进油口和换向阀回油口的压力和流量可知，液压冲击来源于负载冲击和液流惯性两个方面。为了进一步验证这一结论，进行了田间试验，通过分析短暂抱死、长时间抱死和正常工作工况下的压力变化，以及设备启停和换向时的压力超调量，得到压力变化率分别为4.37、7.82、4.43 MPa/s,液流惯性引起的最大超调量为3 268%。由此表明：负载冲击具有随机性和突变性的特点，是引起液压系统冲击振动的最主要因素；液流惯性具有振荡起伏剧烈、作用时间短、平息速度快的特点，仅在设备换向启停时发生。研究结果有助于进一步优化果树修枝机的液压设计和工作性能，为后续液压冲击抑制提供了参考和依据。

The fruit tree pruning machine would generate strong hydraulic impact during pruning work. In order to explore the reason, the HCD hydraulic component design module in AMESim software was used to establish a hydraulic system model consisting of gear pump, three-way four-way electromagnetic directional valve, and plunger motor. By analyzing the pressure and flow rate at the motor inlet, directional valve inlet, and directional valve return ports, the following conclusions could be drawn: the hydraulic shock was caused by load shock and fluid flow inertia. In order to verify the conclusion, field experiments were conducted. By analyzing the pressure changes undershort-term lock up, long-term lock up, and normal operation, as well as the pressure overshoot during equipment start stop and reversing, the pressure change rates were 4.37, 7.82, and 4.43 MPa/s, respectively. The maximum overshoot caused by liquid flow inertia was 3268%. These results confirmed that load impact was random and mutational, which was the primary factor inducing impact vibrations in hydraulic systems. The inertia of liquid flow had the characteristics of severe oscillation, short action time, and fast calming, occurring solely during the directional switching and start-stop phases. The research findings contributed to the further optimization of the hydraulic design and operational performance of fruit tree pruning machines, and provided a reference and basis for subsequent hydraulic shock suppression.