As in all CVT transmissions, two pairs of taper disks are connected together non-positively and not positively. In this case, they are embraced by a chain whose crossbars are bevelled so that they fit exactly in the wedge-shaped gap between the two pairs of taper disks with the maximum surface contact. One of the two taper disks in each pair is mobile. Electrohydraulic control not only changes the transmission ratio but also matches the compressive force to the torque measured in the transmission. Sensors to determine the rotational speeds of the input and output shafts and possibly an additional torque sensor help here. The compressive force is thus never much greater than that required by the torque to be transmitted. This decisively improves efficiency.
This non-positively connected chain drive is combined with a simple or combined planetary gearset to make reversing possible. A wet clutch is also necessary. A further one enables starting up. Since with CVT transmissions the same speed is possible in the forward and reverse directions, the bevel gearsets are not altered hereby.
Control would probably be barely possible without a (CAN bus) connection to the engine control unit. It transmits data such as load and rotational speed. In the other case it may also reduce torque when starting up or with an overheated transmission. The two together even succeed in simulating the tendency to creep known from the stepped fully automatic transmission and thus for example facilitating controlled reversing or hill starts. Unfortunately, probably in order to ease the changeover for drivers, the spacing of the gear ratios is also simulated.
The possibilities of this kind of transmission are still far from having been exhausted. Controlled slip, for example. could be imagined for taking on some of the tasks of the dual-mass flywheel. Even the complete separation of the engine and the drive wheels, thus saving fuel in some operating modes, is possible here, in contrast to the fully automatic transmission with torque converter.
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