Shifting method for hydrodynamic-mechanical transmission

Abstract

In a hydrodynamic-mechanical transmission for motor vehicles, consisting of a torque converter followed by a planetary gear with hydraulically actuable shift mechanism associated with the several transmission elements to select the various speeds, the planetary gear including a first sun gear connectable by way of a first clutch to the turbine rotor of the torque converter, a second sun gear connectable by way of a second clutch to the turbine rotor, a planetary mount connectable by way of a third clutch, bypassing the torque converter, directly to the engine drive shaft, on which mount first and second planet gears in engagement with each other and with the sun gears are mounted, and an internal gear constituting the drive output and in engagement with second planet gears meshing with the second sun gear, the possibility exists of reaching the third, direct speed either by purely hydrodynamic means including the torque converter by engaging the first and second clutches, by purely mechanical means bypassing the torque converter by engaging all three clutches, or in branched power trains by engaging the first or the second clutch and the third clutch. To achieve smooth transitions to and from third speed, when shifting up automatically from second to third speed, first the hydrodynamic train with first and second clutches engaged is to be selectable, and then the mechanical train by additionally engaging the third clutch. Then, shortly before shifting to fourth speed, the branched power train is to be selectable briefly by disengaging the first or the second clutch.