A vehicular multi-mode continuously variable transmission (CVT) with a speed ratio range of 0.7-1.5 is presented,which can ensure by mode switch and power split that its branch power split ratio is less than 65％,with a transmission ratio range of 0.5-1.0.The bond graph model for vehicle equipped with multi-mode CVT is established and the state equation of the system is derived.Then vehicle model is created with MATLAB/Simulink and a simulation on multi-mode CVT is conducted with UDDS driving cycle and optimal fuel economy control strategy adopted.The results show that throughout the UDDS driving cycle,multi-mode CVT works in PX mode at low speed with high torque,and works in XP mode at high speed,effectively reducing the power flowing through metal belt CVT,enhancing the efficiency and load-bearing capacity of powertrain,and effectively avoiding the system vibration,caused by the mode switch between XP mode and PX mode through transition mode.%提出一种调速范围为0.7～1.5的车用多模式无级变速器,通过模式切换和功率分流,能保证无级变速支路功率分流比小于65％,而无级变速器传动比在0.5～1.0范围内.建立装备多模式无级变速器的整车键合图模型,并推导出该系统的状态方程.以MATLAB/Simulink为平台建立整车仿真模型,选取UDDS循环工况,采用最佳燃油经济性控制策略,对多模式无级变速器进行仿真.结果表明:在UDDS循环工况下,多模式无级变速器,在低速大转矩时,工作于PX型模式,高速时,工作于XP型模式,能有效减少流过金属带无级变速器支路的功率流,提高车辆传动系统效率和承载能力;且通过过渡模式,有效避免XP模式与PX模式切换引起的系统振动.
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