Method for operating a drivetrain

A method of operating a motor vehicle drivetrain, the drivetrain comprising at least a hybrid drive with an internal combustion engine and an electric motor, a clutch being interposed between the combustion engine and the electric motor, a transmission being arranged between the hybrid drive and a drive output, with which a main hydraulic pump and an auxiliary hydraulic pump are associated, and a transmission-internal or a transmission-external starting element, the method comprising the steps of:

• when the combustion engine is at rest, the clutch, interposed between the combustion engine and the electric motor, and the starting element are disengaged, and a brake pedal actuated, initiating starting of the electric motor by:
• operating the auxiliary hydraulic pump, at a first power level, to supply the transmission with a pressure required for retaining a gear;
• recognizing a desire to start;
• changing the auxiliary hydraulic pump from the first power level to a second power level to supply another pressure to the transmission required for producing either a starting power or a starting torque;
• increasing the speed of the electric motor, only after a lapse of a defined time interval after changing the auxiliary hydraulic pump from the first to the second power level, to produce either the desired starting power or the desired starting torque.

A method for operating a motor vehicle drivetrain, the drivetrain comprising at least a hybrid drive with an internal combustion engine and an electric motor, a clutch being interposed between the combustion engine and the electric motor, a transmission being arranged between the hybrid drive and a drive output, with which a main hydraulic pump and an auxiliary hydraulic pump are associated, and a transmission-internal or a transmission-external starting element, the method comprising the steps of:

• when the combustion engine is at rest, the clutch, interposed between the combustion engine and the electric motor, and the starting element are disengaged, and a brake pedal actuated, initiating starting of the electric motor by:
• initially retaining the auxiliary hydraulic pump in a switched off state;
• recognizing a desire to start;
• changing the auxiliary hydraulic pump to a power level to supply the transmission with a pressure required for engagement of a defined gear and producing a starting torque;
• increasing a speed of the electric motor, only after a lapse of a defined time interval after the auxiliary hydraulic pump has been changed to the power level to supply the transmission with the pressure required for the engagement of the defined gear, to produce a desired starting power or a desired starting torque.