CROSS-REFERENCE TO RELATED APPLICATION

The present application is related and has right of priority to German Patent Application No. 102020214422.2 filed in the German Patent Office on Nov. 17, 2020, which is incorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

The invention relates generally to a method for operating a transmission of a motor vehicle. Moreover, the invention relates generally to a control unit for operating a transmission of a motor vehicle.

BACKGROUND

A motor vehicle includes a prime mover and a transmission connected between the prime mover and a driven end. During an implementation of a gear shift in the transmission, i.e., during an implementation of a gear change, a changeover takes place from an actual gear of the implementing gear shift into a target gear of the gear shift to be implemented. A gear shift is triggered on the control side when a motor vehicle-side rotational speed, in particular a rotational speed of the prime mover or a rotational speed of the driven end, reaches a trigger speed. The rotational speed of the driven end is in a defined ratio with the rotational speed of the prime mover depending on the ratio of the actual gear.

DE 10 2006 016 710 A1 describes a method for operating a transmission of a motor vehicle, namely for triggering a gear shift in the transmission, in which a maximum permissible prime mover speed, on the one hand, and, on the other hand, a gear change-maximum prime mover speed, which is lower than the maximum permissible prime mover speed, are predefined. If the prime mover speed should exceed the maximum permissible prime mover speed, the prime mover speed must be governed. In order to prevent this, the gear change-maximum prime mover speed is lower than the maximum permissible prime mover speed. It is known from DE 10 2006 016 710 A1 that the trigger speed, at which the gear shift to be implemented is triggered on the control side, is to be determined depending on the gear change-maximum prime mover speed, depending on a gradient of the prime mover speed, and depending on a response time of the gear shift to be implemented. The response time of a gear shift to be implemented is the period of time that passes after a control-side triggering of the gear shift until a speed transition begins to transition the prime mover speed from the synchronous speed of the actual gear of the gear shift to be implemented to the synchronous speed of the target gear of the gear shift to be implemented.

In order to ensure the sportiest gear shifts possible, a gear shift is to be triggered as late as possible and, in fact, at a highest possible, permissible limit speed for the gear shift to be implemented, which means that the gear change-maximum prime mover speed is to be as close as possible to the maximum permissible prime mover speed.

The gradient of the motor vehicle-side rotational speed, as a function of which the trigger speed for triggering a gear shift is determined, is not exactly known. In known methods, this can result in a trigger speed for triggering a gear shift to be implemented being erroneously determined and, for the case in which the limit speed for the gear shift to be implemented, which is also referred to as the gear change-maximum prime mover speed, is close to the maximum permissible prime mover speed, the prime mover speed exceeds the maximum permissible prime mover speed during the implementation of the gear shift, and so the prime mover speed must then be governed. This is disadvantageous.

There is a need to more precisely ascertain the trigger speed for a gear shift to be implemented in a transmission of a motor vehicle, and so, on the one hand, acceleration losses can be avoided during the implementation of the gear shift and, on the other hand, an intervention of a governor that governs a prime mover speed is avoided during the implementation of the gear shift.

SUMMARY OF THE INVENTION

Example aspects of the invention provide a method for operating a transmission of a motor vehicle. According to example aspects of the invention, the trigger speed, as a function of which the gear shift to be implemented in the transmission is triggered on the control side, is adapted depending on a driver-input torque. The trigger speed can be advantageously adapted for the gear shift to be implemented depending on the driver-input torque. Shift points that are too low, with acceleration losses, as well as an intervention of a governor that governs the prime mover speed can be avoided.

According to one advantageous example refinement of the invention, the trigger speed for the gear shift to be implemented depends, furthermore, on an actual prime mover torque that is actually provided, preferably depending on a difference or a ratio between the driver-input torque and the actual prime mover torque that is actually provided. For the case in which the trigger speed is adapted for the gear shift to be implemented also depending on the actual prime mover torque that is actually provided, and, in fact, preferably depending on the difference or the ratio between the driver-input torque and the actual prime mover torque that is actually provided, the trigger speed can be even more advantageously adapted and, in fact, while avoiding acceleration losses and avoiding an intervention of a governor.

According to one advantageous example refinement of the invention, depending on the driver-input torque and preferably depending on the difference or the ratio between the driver-input torque and the actual prime mover torque that is actually provided, an offset value is preferably determined in a characteristic map-dependent manner, via which the trigger speed for the gear shift to be implemented is adapted. The determination of an offset value, as a function of which the trigger speed is adapted, is particularly preferred.

Preferably, for the case in which the driver-input torque is lower than a limit value, an offset value is predefined that is identical for all differences or ratios between the driver-input torque and the actual prime mover torque that is actually provided. Preferably, for the case in which the driver-input torque is greater than a limit value, an offset value is predefined that is that much greater, the greater the difference or the ratio is between the driver-input torque and the actual prime mover torque that is actually provided. This permits a particularly advantageous adaptation of the trigger speed for the gear shift to be implemented while avoiding acceleration losses and avoiding an intervention of a governor.

