Method for operating a motor vehicle comprising a power take-off unit

1. A method of operating a motor vehicle with a motor, a driving transmission having at least one shifting element, a power take-off and a power take-off clutch by which the power take-off is coupleable to the driving transmission, the method comprising at least the following steps:

detecting a request to couple the power take-off;

checking whether respective boundary conditions for coupling the power take-off are fulfilled;

when the respective boundary conditions are fulfilled, building-up a system pressure sufficient for actuating the power take-off clutch;

checking whether a system pressure sufficient for actuating the power take-off clutch has been built up;

when sufficient system pressure has been built up, producing a confirmation signal that actuation of the power take-off clutch is permitted; and

modifying a driving transmission control unit in reaction to the confirmation signal, in order to actuate the at least one shifting element of the driving transmission with a higher actuation pressure than with an unmodified driving transmission control unit.

2. The method according to claim 1 , further comprising, with the modification of the driving transmission control unit, in addition deactivating a learning function for an actuation pressure when actuating the at least one shifting element of the driving transmission.

3. The method according to claim 1 , further comprising, in reaction to the confirmation signal, modifying a motor control unit with at least one of the following functions:

specification of at least one rotation speed limit for the motor; and

specification of a limit for the power drawn from the motor.

4. The method according to claim 1 , further comprising, along with the modification of the transmission control unit, in addition activating a different shifting program for the driving transmission.

5. The method according to claim 1 , further comprising the following steps:

checking whether the power take-off has been coupled, within a predetermined time interval, after producing the confirmation signal; and

reducing the system pressure for actuating the power take-off clutch and cancelling the confirmation signal, when the power take-off has not been coupled within the predetermined time interval.

6. The method according to claim 1 , further comprising the following steps:

after the power take-off has been coupled, checking whether the relevant boundary conditions for coupling the power take-off are still fulfilled; and

while the power take-off is currently coupled, cancelling the confirmation signal when the relevant boundary conditions are no longer fulfilled.

7. The method according to claim 6 , further comprising, even after the confirmation signal has been cancelled, maintaining the system pressure for actuating the power take-off clutch at least until the power take-off has been decoupled.

8. The method according to claim 1 , further comprising, for the modification of the driving transmission control unit in reaction to the confirmation signal, determining a value for increasing the actuation pressure compared with an unmodified actuation pressure as a function of the following factors:

a rotation speed applied at the drive input of the driving transmission; and

a torque applied at the drive input of the driving transmission.

9. The method according to claim 1 , further comprising calculating an actual torque at a drive input of the driving transmission as a function of at least one of the following parameters:

a torque provided at a crankshaft of the motor;

a consumer loss;

a motor braking force when driving downhill; and

a calculated torque applied on the power take-off.

10. The method according to claim 9 , further comprising calculating a torque at the power take-off in each case once as a function of a characteristic of the power take-off and once as a function of a converter slip, and when the torque calculated as the function of the converter slip is smaller than the torque calculated as the function of the characteristic of the power take-off, using that torque for control purposes.

11. A control unit designed to carry out the method according to claim 1 .

12. A computer program designed to enable a control unit to carry out the method according to claim 1 , when the computer program is run on the control unit.