Patent ID: 8257221

Claim:
A method of operating a hybrid drive system with a main driving machine ( 11 ) and a supplementary driving machine ( 12 ) for a motor vehicle, comprising: a first gear changing partial drive ( 15 ) with an input shaft ( 17 ) and an output shaft ( 23 ) and a first group of gear changing pairs of gearwheels each having a gearwheel connected in a rotationally fast way to its shaft and a switching gearwheel which can be switchably coupled to its shaft and whose input shaft ( 17 ) can be coupled to the main driving machine ( 11 ); a second gear changing partial drive ( 16 ) with an input shaft ( 18 ) and an output shaft ( 24 ) and a second group of gear changing pairs of gearwheels each having a gearwheel connected in a rotationally fast way to its shaft and a switching gearwheel which can be switchably coupled to its shaft and whose input shaft ( 18 ) is connectable in respect of drive to the supplementary driving machine ( 12 ); wherein the two input shafts ( 17 , 18 ) can be connected to one another in a rotationally fast way via a coupling unit ( 29 ), characterised in that, during operation by means of the main driving machine ( 11 ) only there is effected a gear change between two gears adjoining one another in the gear changing sequence by changing the torque flow from one gear changing partial drive to the other gear changing partial drive.