Control method for calibrating an actuation of a converter lock-up clutch of a hydrodynamic torque converter

Control method for calibrating an actuation of a converter lock-up clutch (22) of a hydrodynamic torque converter (14) with a pump wheel (18) and a turbine wheel (20), which is connected to a power-split transmission (16), wherein the transmission (16) comprises at least two clutches (32, 34, 36) each associated with a respective power-split shaft assembly (26, 28, 30), which clutches can be actuated separately to close and open in order to apply a clutch torque (MK) to the turbine wheel (20) so that a rotation speed difference (Δn) between the pump wheel (18) and the turbine wheel (20) changes, the said method comprising the steps:

• opening (S1) the converter lock-up clutch (22) and the at least two clutches (32, 34, 36) each associated with a respective power-split shaft assembly (26, 28, 30) of the transmission (16), wherein the at least two clutches are configured to apply a clutch torque (MK) to the turbine wheel (20);
• rotating (S2) the pump wheel (18) at a specified rotation speed (n);
• and
• applying (S3) a clutch torque (MK) to the turbine wheel (20) as a function of an actual rotation speed difference (ΔnIST) in order to reach a specified set-point rotation speed difference (ΔnSOLL), wherein at least two clutches (32, 34), each associated with a respective power-split shaft assembly (26, 28) of the transmission (16), are actuated to close.