油液含气量对液压机械换段性能的影响

Fluid Air Content Affecting the Power Shift Performance of the Hydro-mechanical Variable Transmission

研究油液含气量对液压机械无级传动换段过程中动态性能的影响规律。开展油液体积模量的理论分析,进行油液不同含气量时体积模量的试验研究,将理论曲线与试验曲线进行比较,结果表明,油液正割体积模量理论值和试验值基本一致,其数学模型可用于液压机械闭式液压回路换段过程仿真分析。采用将液压机械闭式液压回路等效为双作用液压缸系统的方法,建立液压机械无级传动闭式液压回路换段过程数学模型,并在Matlab/Simulink中进行仿真分析。结果表明,油液含气量越大,体积模量越小,换段时定排量液压元件转速波动越大,换段品质降低;控制变排量液压元件排量变化和延长负载反向时间,可以有效减小换段中液压回路压力和定排量液压元件转速波动。

The influence rules about fluid air content affecting dynamic behavior of the hydro-mechanical variable transmission during power shift is researched. The theoretical analysis about oil bulk modulus is carried out, and the experimental research of oil bulk modulus with different air content is done. The theoretical curves of the fluid secant bulk modulus are in accord with the experimental results, which shows its mathematical model can be used in power shift simulation analysis of the hydro-mechanical variable transmission closed hydraulic circuit. The power shift mathematical model of the closed hydraulic circuit in hydro- mechanical variable transmission is built with the method that the closed hydraulic circuit is equivalent to a loop consisting of two double-acting hydraulic cylinders, and it is simulated in Matlab/Simulink. The results show that the more air in fluid, the lower bulk modulus and the greater speed fluctuation of the fixed displacement hydraulic component during the power shift, so the power shift quality is worse; control of the hydraulic component＇s displacement and extension of load torque reverse time can effectively reduce the fixed displacement component speed and pressure fluctuation of the closed hydraulic circuit.