Method for determination of at least a drag torque effective on the input side of an automatic motor vehicle transmission

A method of determining at least one drag torque (MGetr, MKup 1) acting on an input side of an automatic motor vehicle transmission (3) of a motor vehicle such that, prior the determination, a separator clutch (2) located between the motor vehicle transmission (3) and a drive engine (1) is disengaged (S4), the method comprising the steps of:

• shifting the motor vehicle transmission (3) into neutral (S2) once the motor vehicle is stopped;
• initiating deactivation of the drive engine and disengaging the separator clutch after the drive engine (1) is deactivated;
• calculating, via a processor of a transmission control unit, the at least one drag torque (MGetr, MKup 1);
• determining (S5), via the processor of the transmission control unit, a first gradient ({dot over (n)}Getr, I) of a transmission input rotational speed (nGetr), before an engine rotational speed (nMot) of the drive engine (1) falls below the transmission input rotational speed;
• determining (S7), via the processor of the transmission control unit, a second gradient ({dot over (n)}Getr, II) of the transmission input rotational speed (nGetr), after the engine rotational speed (nMot) falls below the transmission input rotational speed (nGetr);
• initiating the method with a routine of a computer program stored in a memory of a control unit of the motor vehicle only once the motor vehicle completely stops;
• ensuring that deactivation of the drive engine is initialed;
• monitoring the engine rotational speed and the transmission input rotational speed after disengagement of the separator clutch;
• calculating at least one of a drag torque of the separator clutch and a drag torque of a drive input side part of the motor vehicle transmission shifted to neutral during deactivation of the drive engine;
• calculating, with the control unit, at least one of the drag torque of the separator clutch and the drag torque of the drive input side part of the motor vehicle transmission shifted to neutral, during deactivation of the drive engine, based on a mass moment of inertia of the drive input side part of the motor vehicle transmission shifted to neutral, which is stored in the control unit;
• and
• recording, in a memory of the control unit, the drag torque of the separator clutch as a function of a current road inclination.