中文摘要：

为消除多段液压机械无级变速器（HMCVT）循环换段现象,以东方红400马力轮式拖拉机所装备的多段HMCVT为例,分析了多段HMCVT的传动特性,研究了循环换段的产生原因,提出了消除循环换段的机理。基于有限状态机原理,以实际排量比、理论排量比、多段HMCVT输出转速为控制参数,仿真证明了所提机理的有效性。研究结果表明,多段HMCVT在换段前后效率差异的影响因素中的泵-马达容积效率是产生循环换段的主要原因;通过控制多段HMCVT理论排量比增大的同时保持实际排量比不变,有效地避免了多段HMCVT换段过程中的循环换段。为HMCVT控制系统的开发提供了理论基础。

英文摘要：

To avoid the circularly shift range on multi-range hydro-mechanical continuously variable transmission（HMCVT）,taking the multi-range hydro-mechanical CVT of the wheel tractor of YTO-400 as example,the transmission characteristic of multi-range hydro-mechanical CVT is analyzed.The causes of the circularly shift range are researched,and eliminating mechanism is presented.The effectiveness of principle of averting the circularly shift range is simulated by using the theory of Finite State Machine,which employs the actual and theoretical displacement ratio,output speeds of multi-range hydro-mechanical CVT as the control parameter.The research results indicate that,the volumetric efficiency of the pump-motor system is the important reason for the factor of efficiency difference of the circularly shift range.By controlling the increase of the theory displacement ratio of the multi-range hydro-mechanical CVT,the actual displacement ratio is maintained at the same time,which effectively avoids the cycle change of the multi-range hydro-mechanical CVT.A theoretical foundation for the development of multi-range hydro-mechanical CVT control system is provided.