多模式机液复合传动装置设计方案分析

液压传动柔性特征适用于起步工况，机液传动高效无级调速特征适用于作业工况，机械传动高效变速特征适用于转场工况。分析集液压传动、机液传动和机械传动为一体的多模式机液复合传动装置的设计思路在汽车工程上具有理论研究意义和实际应用价值。研究了机液复合传动的功率流传递机理，分析了换挡机构处于功率分流机构、复合传动机构、功率汇流机构和后置换挡机构一处或多处时，分段式机液传动装置各自的性能特征。研究结果表明：功率分流传动方式多适用于中小功率车辆，且马达转矩与传动装置输出转矩比值保持不变；功率汇流传动方式多适用于大功率车辆，使小功率液压件传递大功率成为可能，并能够在输出端起到减速增矩的效果；功率分流和功率汇流互换的传动方式可通过控制行星齿轮双接口及后置换挡机构，保证机液复合传动在不同速度分段中的高效运行；当换挡机构在行星齿轮之间时，可在2个不同区段改变行星齿轮机构的特性参数，使得在整个工作区范围内保持合理的功率配额；当采用多段式行星齿轮功率汇流传动方式时，后置换挡机构扩大了传动装置转速和转矩的覆盖范围。根据上述5类机液传动设计思路，提出对应的多模式机液复合传动装置设计方案。以一款用于扫地车的机液复合传动装置为研究对象，进行运动学和动力学分析，确定相关参数，绘制调速曲线和效率特性曲线，并对其挡位切换优化问题做了简要介绍。该方案充分利用液压传动的无级调速性能和机械传动的高效变速性能，较好地满足了车辆起步、作业和转场工况的要求。

Design Schemes Analysis of Multi-mode Hydro-mechanical Composite Transmission Devices

The flexible characteristic of a hydrostatic transmission is suitable for starting conditions; the effectively stepless speed regulation characteristic of a hydro-mechanical transmission is suitable for working conditions; the effective speed change characteristic of a mechanical transmission is suitable for transition conditions. The research on the design schemes of integrated multi-mode hydro-mechanical composite transmission device with hydrostatic, hydro-mechanical, and mechanical transmission properties have important theoretical research significance and practical application value. The power flow transference mechanism of a hydro-mechanical composite transmission was studied and the respective performance characteristics of multi-range hydro-mechanical transmission devices were analyzed when the shift mechanism was in one or more positions of power split, composite transmission, power confluence, or rear shift mechanisms. Research shows that the power split transmission mode is more suitable for medium and low power vehicles, and the motor torque to transmission device output torque ratio remains unchanged. The power confluence transmission mode is more suitable for high power vehicles, which makes it possible for low power hydraulic parts to transmit high power, and can reduce the speed and increase the output torque. The transmission exchange mode between the power split and power confluence can ensure the high efficiency operation of a hydro-mechanical composite transmission in different speed ranges by controlling planetary gear double interfaces and the rear shift mechanism. When the shift mechanism is between planetary gears, planetary gear mechanism characteristic parameters can be changed in two ranges, and a reasonable power quota can be kept throughout the entire working range. When the multi-range planetary gear power confluence transmission mode is adopted, the transmission device speed and torque coverage can be expanded. According to the five hydro-mechanical transmission design ideas discussed above; corresponding design schemes of multi-mode hydro-mechanical composite transmission devices are proposed. A hydro-mechanical composite transmission device used for a street sweeper was selected as the research object, kinematic and dynamic analyses are conducted, related parameters are determined, speed regulation and efficiency characteristic curves are drawn, and the transmission device shift switching optimization is also briefly introduced. The result shows that the scheme can satisfy the demands of starting condition, working condition, and transferring condition by making full use of stepless speed regulation performance for hydrostatic transmission and effective speed change performance for mechanical transmission.