Method and Control Unit for Operating a Hybrid Vehicle

A method for operating a hybrid vehicle that includes an electric machine (3) as a first prime mover, an internal combustion engine (2) as a second prime mover, a separating clutch (4) connected between the internal combustion engine (2) and the electric machine (3), and a transmission (5) connected between the electric machine (3) and a driven end (6), the transmission (5) including a plurality of shift elements (7), the hybrid vehicle optionally including a hydrodynamic starting component (8) connected between the electric machine (3) and the transmission (5) and including a torque converter (9) and a shift element configured as a torque converter lockup clutch (10), the separating clutch (4) disengaged during purely electric driving of the hybrid vehicle, the separating clutch (4) engaged during hybrid travel or driving under internal combustion engine power, the method comprising:

• to start the internal combustion engine (2) during purely electric driving of the hybrid vehicle, at least partially engaging the separating clutch (4) in order to crank the internal combustion engine (2) via the electric machine (3);
• determining one of the shift elements (7, 10) arranged between the electric machine (3) and the driven end (6) to be utilized for decoupling of slip of the internal combustion engine start and a decoupling differential speed for the one of the shift elements (7, 10) depending on whether
• a starting process of the hybrid vehicle is carried out,
• the transmission (5) is transferred from a torque-transmitting state into a non-torque-transmitting state or, vice versa, from a non-torque-transmitting state into a torque-transmitting state,
• a gear ratio change is carried out in the transmission (5), and
• the hybrid vehicle includes the hydrodynamic starting component (8);
• and
• bringing the one of the shift elements (7, 10) arranged between the electric machine (3) and the driven end (6) is brought into slippage for decoupling of slip of the driven end (6).

A control unit (13) for operating a hybrid vehicle that includes an electric machine (3) as a first prime mover, an internal combustion engine (2) as a second prime mover, a separating clutch (4) connected between the internal combustion engine (2) and the electric machine (3), and a transmission (5) connected between the electric machine (3) and a driven end (6), the transmission (5) including a plurality of shift elements (7), the hybrid vehicle optionally including a hydrodynamic starting component (8) connected between the electric machine (3) and the transmission (5) and including a torque converter (9) and a shift element configured as a torque converter lockup clutch (10), wherein the control unit (13) is configured to:

• determine one of the shift elements (7, 10) arranged between the electric machine (3) and the driven end (6) to be utilized for decoupling of slip of the internal combustion engine start and a decoupling differential speed depending on
• whether a starting process of the hybrid vehicle is carried out,
• whether the transmission (5) is transferred from a torque-transmitting state into a non-torque-transmitting state or, vice versa, from a non-torque-transmitting state into a torque-transmitting state,
• whether a gear ratio change is carried out in the torque-transmitting transmission (5), and
• whether the hybrid vehicle includes the hydrodynamic starting component (8).