Method for operating a drive unit for a hybrid vehicle

Method for operating a drive unit for a hybrid vehicle, whereas the drive unit comprises a drive assembly (3) with an internal combustion engine (1) and an electric motor (2) and a transmission (5) featuring several sub-transmissions (6, 7) shifting between the drive assembly (3) and an output (4), whereas, through a planetary transmission (10), the electric motor (2) is coupled to an input shaft (8) of a first sub-transmission (6) and an input shaft (9) of a second sub-transmission (7) shifted in parallel to the first sub-transmission (6), whereas, through a frictional-locking separating clutch (11), the internal combustion engine (1) is able to be coupled to the input shaft (8) of the first sub-transmission (6) and, if the separating clutch (11) is locked, is coupled to the same element (15) of the planetary transmission (10) together with the input shaft (8) of the first sub-transmission (6), and whereas a positive-locking or frictional-locking bypass shift element (12) works together with the planetary transmission (10) in such a manner that, with a locked bypass shift element (12), a torque-proof connection between the electric motor (2), the input shaft (8) of the first sub-transmission (6) and the input shaft (9) of the second sub-transmission (7) and thus a mandatory equality of rotational speed between the same, exist, while, with an open bypass shift element (12), this torque-proof connection between the electric motor (2) and the two input shafts (8, 9) of the two sub-transmissions (6, 7), and thus the mandatory equality of rotational speed, do not exist, characterized in that, for the execution of a power shift, shortly prior to the engagement of a positive-locking shift element to be locked for the power shift, the frictional-locking separating clutch (11) is brought into slip for the decoupling of the inertial mass of the internal combustion engine (1).