汽车起重机动力加压落幅系统研究

Dynamic pressure falling system of truck crane

【目的】汽车起重机重力落幅系统存在落幅速度不均匀和操控性差等问题,而动力落幅系统存在起重臂易抖动等问题.针对上述系统存在的两个问题,结合重力落幅系统和动力落幅系统的优点,提出一种动力加压落幅方案,即向变幅油缸有杆腔加压,增加了起重臂大角度的落幅速度;同时改变变幅平衡阀的控制方式,由控制手柄直接控制,避免有杆腔油压对变幅平衡阀的影响.【方法】通过理论研究和MATLAB仿真研究,定性分析了平衡阀的流量饱和特性.【结果】平衡阀阀芯节流槽通流面积越大,达到饱和的流量越大,而压差越小.将研究结果应用于汽车起重机的动力加压落幅系统,通过变更平衡阀的阀芯结构,以限制起重臂小角度的落幅速度.【结论】通过试验测试,动力加压落幅系统的落幅均匀性提高,最大流量差减少约61%,全程落幅时间缩短约38%.

【Objective】The gravity pressure falling system of truck crane exists the problems of uneven falling speed and poor handling and being unstable of dynamic falling system sometimes.To improve the uniformity of dynamic falling range,the dynamic pressure falling system was proposed based on the upper two falling systems.The pressure oil was supplied into the rod port of amplitude cylinder to increase the falling speed at large luffing angle.Meanwhile the control method was changed to avoid the impact of pressure in rod cavity on amplitude counterbalance valve.【Method】The flow saturation characteristic of counterbalance valve was researched theoretically and simulated by MATLAB.【Result】The results showed that the saturation flow increased with the increase of flow area in throttling grooves,but the differential pressure decreased.The result was applied to the dynamic pressure falling system to change the valve core structure of counterbalance valve and limit the falling speed at small luffing angle.【Conclusion】The new system can improve the uniformity of dynamic pressure falling range.The maximum flow difference reduced by 61% and the whole falling time reduced by 38%.