Control Method and Control Unit for a Drivetrain

A method for operating a drive train of a motor vehicle, the drive train including a plurality of prime movers (1, 2), a transmission (3), and a driven end (4), the transmission (3) including a plurality of shift elements (9), the method comprising:

• wherein, in order to implement a gearchange from an actual gear into a target gear, a shift element (9), which is engaged in the actual gear and is disengaged in the target gear, is disengaged, and a shift element (9), which is disengaged in the actual gear and is engaged in the target gear, is engaged;
• in order to implement the gearchange, determining target torques for the first prime mover (1) and the second prime mover (2) at least depending on a driver-demanded output torque;
• when a form-locking shift element (9) is disengaged for the gearchange to be implemented, relieving or approximately relieving the form-locking shift element (9) to be disengaged of load, via an actuation of the first prime mover (1) and the second prime mover (2) depending on the calculated target torques, in such a way that the target torque is decreased at one of the prime movers and the target torque is increased at another one of the prime movers, in order to disengage the shift element (9) to be disengaged in a load-free or approximately load-free manner while providing the driver-demanded output torque at the driven end (4);
• wherein, the form-locking shift element (9) to be disengaged is already actuated with a defined actuating pressure or a defined actuating force in the direction of disengagement before a theoretical relief from load or a theoretical approximate relief from load depending on the target torques;
• monitoring whether and at which actual torques of the first prime mover (1) and the second prime mover (2) the form-locking shift element (9) to be disengaged begins to move;
• and
• determining the actual torques of the first prime mover (1) and the second prime mover (2) at which the form-locking shift element (9) to be disengaged begins to move as actual torques at which the form-locking shift element (9) to be disengaged has actually been relieved of load or has been approximately relieved of load.

A control unit for operating a drive train of a motor vehicle, the drive train including a plurality of prime movers (1, 2), a transmission (3), and a driven end (4), and the transmission (3) includes a plurality of shift elements (9), the control unit configured such that:

• in order to implement a gearchange from an actual gear into a target gear, the control unit actuates a shift element (9), which is engaged in the actual gear and is disengaged in the target gear, to disengage and actuates a shift element (9), which is disengaged in the actual gear and is engaged in the target gear, to engage;
• in order to implement the gearchange, the control unit determines target torques for the first prime mover (1) and the second prime mover (2) at least depending on a driver-demanded output torque;
• wherein, when a form-locking shift element (9) is disengaged for the gearchange to be implemented, the control unit relieves the load or approximately relieves the load of the form-locking shift element (9) to be disengaged, via an actuation of the first prime mover (1) and the second prime mover (2) depending on the calculated target torques, in such a way that the target torque is decreased at one of the prime movers and the target torque is increased at another one of the prime movers, in order to disengage the shift element (9) to be disengaged in a load-free or approximately load-free manner while providing the driver-demanded output torque at the driven end (4);
• the control unit actuates the form-locking shift element (9) to be disengaged with a defined actuating pressure or a defined actuating force in the direction of disengagement already before a theoretical relief from load or a theoretical approximate relief from load depending on the target torques;
• the control unit monitors whether and at which actual torques of the first prime mover (1) and the second prime mover (2) the form-locking shift element (9) to be disengaged begins to move;
• and
• the control unit determines the actual torques of the first prime mover (1) and the second prime mover (2), at which the form-locking shift element (9) to be disengaged begins to move, as actual torques at which the form-locking shift element (9) to be disengaged has actually been relieved of load or has been approximately relieved of load.