汽车采用的无级变速功率分流变速器的设计

Design of continuously variable power split Transmissionsystem for Automotive Applications

在汽车应用方面提出了无级变速功率分流变速箱的一种设想 ,该装置由两可变速带轮 (变速器 )和一行星齿轮系所谓太阳轮和内齿圈三转动构件组合而成。“功率分流”的布置特点是输入轴同时把功率传到太阳轮和主动带轮 ,并通过变速器传到行星齿轮传动的内齿圈。因为输入轴传递的输入功率一分为二 (传到太阳轮和主动带轮 ) ,变速器中仅通过输入轴总功率流的一小部分 ,行星齿轮传动的第三转动件 (转臂 )收集了由内齿圈和太阳轮传来的功率流 ,把总功率传到输出轴传到车辆。该特徵提高了发动机功率在汽车应用的许可范围 ,该特徵特别在低速 -高转矩情况下提供无级变速可变传动比的范围时还降低了与动力传动有关的功率损失。建立一个所谓“增益系数”,用它通过变速箱的可变速元件和速比间隔来确定总功率流的两个分量的大小。用一外齿轮箱可以在发动机和变速箱的最佳范围内扩展无级变速范围。提出了一个采用外啮合有级齿轮传动 (同步变速器 )实现有效传动比间隔的无级变速范围应用于汽车的设计程序 。

The continuously variable power split transmission (CVPST) concept is presented in the context of an automotive application. The system consists of varable pull ey set (variator) coupling two of the three rotating elements of a planetary gea r train, namely the sun and the ring gears. The arrangement is such that a ‘pow er split’ feature is attained in which the input shaft delivers power to the su n gear as well as as to the driving pulley, which in turn drives the ring gear of the planetary through the variator. Because the input shaft delivers the input power at two locations (at the sun ge ar and at the driving pulley), the variator carries only a fraction of the total power flowing through the input shaft. The third rotating element of the planet ary gear set (the planet carrier) collects the power flows from the ring and the sun gears, delivering the total power output to the vehicle. This feature allows an increased engine power envelope for potential automotive applications. This feature also reduces the power losses associated with power t ransmission, especially at the low speed high torque modes, while providing con tinuously variable transmission ratio capability. A term dubbed the ‘cross over coefficient's is established which can be used to prescribe both the fraction of total power flowing through the variable eleme nt and the velocity ratio span for the transmission. An extension of this can be obtained by means of an external gearbox, allowing a stepless span in the optim um range of both engine and transmission. Design procedures are presented for an automotive application in which a steples s extension (synchronized variator) of the useful transmission ratio span is ach ieved by means of an external step up gearbox. The two stage system allows ope ration in the optimum range of both engine and transmission.