拖拉机串联式液力机械复合传动系统设计与试验

针对现有拖拉机变速器存在机械结构复杂、挡位数较多、模式切换繁琐等问题,提出了一种串联式液力机械复合传动方案(Series hydraulic and mechanical hybrid transmission, HMD)及其配套拖拉机总体设计方法,包括功能需求、传动路线设计、组件特性分析、性能参数计算、仿真模型搭建、作业性能对比。针对无级调速模块有效性设计牵引性能与匹配性能试验,合理的发动机匹配使得液力传动最高效率达到0.894,重载与轻载区段能够实现无级变速,工况适应性良好。性能对比结果表明:HMD牵引特性场位于原拖拉机与HMCVT之间,各挡牵引功率峰值幅度变化平稳,深谷面积明显减小;犁耕工况下,牵引力覆盖范围平均提升15.3%,负载作业速度平均提升8.2%;旋耕工况下,动力输出功率平均提升1.7%。研究可为多模式无级变速拖拉机总体设计提供技术路线参考。

Design and Test of Tractor Serial Hydraulic and Mechanical Hybrid Transmission System

Most tractors in the world still use manual mechanical shifting transmissions. Such transmissions face problems for instance power interruption and cumbersome operation during gear shifts, which is extremely unfavorable for vehicles with load operations such as construction machinery, which not only increases the fatigue intensity of the driver, but also reduces productivity. To ensure the maximum flexibility of use at each speed and exploit the maximum engine power available under all working conditions. A series hydraulic and mechanical hybrid transmission system (HMD) and its supporting tractor overall design method were proposed, including functional requirements, transmission route design, component characteristics analysis, performance parameter calculation, simulation model building, and operation performance comparison. The system scheme was based on the series combination of hydraulic torque converter (TC) and dual clutch transmission (DCT). Based on the proposed design method, the Dongfanghong 1804 tractor was selected as the research object. According to the effectiveness of stepless speed regulation module, the traction performance and matching performance test were designed. Reasonable engine matching made the maximum efficiency of hydraulic transmission reach 0.894, and the stepless variable speed can be realized in heavy and light load sections, and the adaptability of working conditions was excellent. The comparison results showed that the traction characteristic field of HMD was located between the original tractor and HMCVT, and the peak amplitude of tractive force in each gear varied smoothly and the area of deep valley was significantly reduced. Under ploughing tillage, traction coverage was increased by an average of 15.3%, and the load operation speed was increased by an average of 8.2%. Under rotary tillage, the take-off power was increased by 1.7% on average. The research can provide a technical route reference for the overall design of multimodal infinitely variable speed tractors.