Method for the operation of a hybrid drive train in a motor vehicle

A method for operating a hybrid drive train for a motor vehicle, wherein the hybrid drive train comprises an internal combustion engine and an electric motor as drive units, and wherein a parallel variable speed transmission is disposed in the hybrid drive train, comprising:

• a first transmission input shaft, a second transmission input shaft and a transmission output shaft, wherein the first transmission input shaft can be coupled to the transmission output shaft through at least one first gear, and the second transmission input shaft can be coupled to the transmission output shaft through at least two second gears, wherein the internal combustion engine can be brought into operative engagement with the first transmission input shaft through a first clutch and can be brought into operative engagement with the second transmission input shaft through a second clutch, and wherein the electric motor is in driving engagement with the second transmission input shaft,
• wherein a first gear is shifted and torque is transferred from the internal combustion engine through the first clutch to the first transmission input shaft,
• wherein a first second gear is shifted with the second clutch open and torque is transferred by the electrical motor through the first transmission input shaft and through the first second gear to the transmission output shaft,
• wherein clutch slippage is created at the first clutch by reducing the torque transferred by the first clutch, while the torque provided by the electric motor is increased,
• wherein subsequently the torque provided by the electric motor is substantially reduced to zero and a second gear is shifted, while the slippage at the first clutch is reduced by increasing the torque transferred by the first clutch, and
• wherein torque is subsequently transferred from the electrical motor through the first transmission input shaft and through the second second gear to the transmission output shaft.