电动车两档变速箱非接触超越离合器的优化设计

Optimal Design of Non-contact Overrunning Clutch for Two-speed Electric Vehicle Transmissions

与固定速比减速器相比,两档变速器可以有效提升电动汽车动力性和经济性。针对燃油车辆开发的液力式自动变速技术和双离合自动变速技术可实现档位平顺切换,然而需要两套摩擦离合器和执行器等一系列较复杂的结构,而且中高速巡航时始终存在多片离合器的拖曳损失。电控机械式变速器结构精简效率高,但却存在换档动力中断问题,影响驾乘品质和坡道行驶安全性。因此提出一种超越状态时楔紧元件与旋转元件非接触的棘轮式可控超越离合器,可实现双向锁紧、单向超越和双向超越3种工作状态。通过该机构和一个助力摩擦离合器的协同控制,解决了机械式变速器换档动力中断问题,同时避免了运行过程中不必要的摩擦能耗和噪声。以电动轻卡的两档变速箱为例,设计出所提出的棘轮式非接触可控超越离合器的具体结构;动力学仿真验证了该类型自动变速器无动力中断换档的特性。进一步优化超越离合器空转角至3.18°,有效地降低了换档冲击;最后强度分析表明所设计的可控超越离合器的寿命满足使用要求。

Compared with the fixed speed ratio reducer,the two-speed transmission can effectively improve the power performance and economy of electric vehicles.The hydraulic automatic transmission technology and dual clutch automatic transmission technology developed for fuel vehicles can realize smooth shift,but it requires a series of complex structures such as two sets of friction clutches and actuators,and there is always the drag loss of multiple clutches when cruising at medium and high speed.Electronic mechanical transmission has a simplified structure and high efficiency,but it has the problem of shifting power interruption,which affects the driving quality and the safety of the ramps.Therefore,a ratchet type controllable overrunning clutch is proposed,which has no contact between the wedge element and the rotating element in the overrunning state,and can realize three working states of bidirectional locking,one-way overrunning and bidirectional overrunning.Through the cooperative control of the mechanism and a power-assisted friction clutch,the problem of shifting power interruption of mechanical transmission is solved,and unnecessary friction energy consumption and noise during operation are avoided.Taking the two-speed transmission of an electric light truck as an example,the structure of the proposed ratchet non-contact controllable overrunning clutch is designed.The performance of shifting without power interruption of this type of automatic transmission is verified through the dynamic simulation.The idling angle of the overrunning clutch is further optimized to 3.18°,which effectively reduces the shift impact.Finally,the strength analysis shows that the life of the designed controllable overrunning clutch meets the requirements of use.