两段式液压机械无级传动机构运动特性研究

两段式液压机械无级传动能够实现大传动比、宽传动范围的无级变速，并且可以降低液压元件的额定功率，提高全程的传动效率。该传动机构的运动特性关系着整车工作模式的设定及其性能的发挥。分析了液压机械无级传动机构分矩汇速型、分速汇速型和分速汇矩型三种类型的分汇流形式。利用杠杆法分析了外力构件位置对机械点分布、液压元件正反相位和功率流类型的影响，获得了两段式液压机械无级传动机构的可行分汇流形式。总结了各个段内液压元件转速与输出转速的关系，并基于无速差换段理论对段间输出转速的衔接规律进行了研究。通过液压元件正反相位的往返变化，实现了两段式液压机械无级传动输出转速的连续无级变化。搭建了采用分矩汇速+分矩汇速型液压机械无极变速器的ZL50型装载机的仿真平台，进行装载机在典型V循环工况下运动特性的模拟，分析了变速器的输出转矩和传动效率，结果验证了理论分析结果的正确性。研究揭示了液压机械无级传动机构的段内运动特性及段间的运动衔接规律，为液压机械无级传动机构的设计及工程应用提供了理论依据。

Research on kinematic characteristics of two-stage hydro-mechanical continuously variable transmission mechanism

The two-stage hydro-mechanical continuously variable transmission can realize continuously variable transmission with large transmission ratio and wide transmission range, reduce the rated power of hydraulic components and improve the whole transmission efficiency. The kinematic characteristics of the transmission mechanism are related to the setting of the working mode and the performance of the whole vehicle. This paper analyzed three types of split and confluence forms of hydro-mechanical continuously variable transmission mechanism: the split-torque confluence-speed type, the split-speed confluence-speed type and the split-speed confluence-torque type. Using the lever method, the influence of the position of external force components on the distribution of mechanical points, the positive and negative phases of hydraulic components and the power split type were studied, and the feasible form of split and confluence of the two-stage hydro-mechanical continuously variable transmission mechanism was obtained. The relationship between the rotation speed of hydraulic components and the output rotation speed in each segment was summarized, and the connection law of the output rotation speed between segments was studied based on the theory of no speed difference range-shift. Through the round-trip change of the positive and negative phases of the hydraulic components, the continuous variable variation of the output rotation speed of the two-stage hydro-mechanical continuous transmission was realized. A simulation platform of ZL50 loader was built, which adopted the hydro-mechanical continuously variable transmission of the split-torque confluence-speed and split-torque confluence-speed. The movement characteristics of the loader under typical V cycle working conditions were simulated, and the output torque and transmission efficiency of the transmission was analyzed. The result verified the correctness of the theoretical analysis result. The research reveals the motion characteristics of the hydro-mechanical continuously variable transmission mechanism and the motion connection law between the segments, which provides a theoretical basis for the design and engineering application of the hydro-mechanical continuously variable transmission mechanism.