Method for controlling a braking system of a motor vehicle

1. A method for controlling a brake system ( 1 ) of a motor vehicle, which includes an electric generator ( 4 ) and a number of hydraulic, electronically controllable friction brakes ( 2 ) allocated respectively to one axle of the motor vehicle, and the brake torque is composed of a brake torque of the generator ( 4 ) and a brake torque of the friction brakes ( 2 ), the method comprising:

initially, activating only the generator ( 4 ) according to specification of a situation responsively determined total nominal brake torque;

connecting the friction brakes ( 2 ) in a delayed manner only when the total nominal brake torque exceeds a maximum available brake torque of the generator ( 4 ) by a predetermined first maximum brake torque difference; and

maintaining the friction brakes at a constant brake torque before a minimum brake torque difference is attained between the total nominal brake torque and the maximum available brake torque of the generator.

2. A method for controlling a brake system ( 1 ) of a motor vehicle, which includes an electric generator ( 4 ) and a number of hydraulic, electronically controllable friction brakes ( 2 ) allocated respectively to one axle of the motor vehicle, and the brake torque is composed of a brake torque of the generator ( 4 ) and a brake torque of the friction brakes ( 2 ), the method comprising:

initially, activating only the generator ( 4 ) according to specification of a situation responsively determined total nominal brake torque;

connecting the friction brakes ( 2 ) in a delayed manner only when the total nominal brake torque exceeds a maximum available brake torque of the generator ( 4 ) by a predetermined first maximum brake torque difference, wherein

only friction brakes ( 2 ), of the brake system ( 1 ) are initially connected, that are not allocated to an axle of the motor vehicle that is connected to the generator ( 4 ); and

maintaining the friction brakes at a constant brake torque before a minimum brake torque difference is attained between the total nominal brake torque and the maximum available brake torque of the generator.

3. A method according to claim 2 , wherein based on the total nominal brake torque and the maximum available brake torque of the generator ( 4 ), a nominal brake torque is determined for friction brakes ( 2 ) that are allocated to an axle connected to the generator ( 4 ), and these friction brakes ( 2 ) are connected in a delayed manner only when the total nominal brake torque exceeds the nominal brake torque determined for the friction brakes ( 2 ) that are allocated to an axle connected to the generator by a predetermined second maximum brake torque difference.

4. A method according to claim 3 , wherein a maximum brake torque difference ranging between zero Nm and approximately 300 Nm is predetermined.

5. A method according to claim 3 , wherein a theoretical nominal brake torque is determined, based on the total nominal brake torque and the maximum available brake torque of the generator ( 4 ), for those friction brakes ( 2 ), which are not allocated to an axle of the motor vehicle connected to the generator ( 4 ), and an allocated minimum brake torque is predetermined in each case as a nominal brake torque to these friction brakes ( 2 ) until the theoretical nominal brake torque determined for this axle has dropped to a predetermined limit value.

6. A method according to claim 5 , further comprising determining a theoretical nominal brake torque based on the total nominal brake torque and the maximum available brake torque of the generator ( 4 ), for those friction brakes ( 2 ), which are allocated to an axle of the motor vehicle connected to the generator ( 4 ), and an allocated minimum brake torque is predetermined in each case as a nominal brake torque to these friction brakes ( 2 ) until the theoretical nominal brake torque determined for this axle has dropped to a predetermined limit value.

7. A method according to claim 2 , wherein a theoretical nominal brake torque is determined for each friction brake ( 2 ) by way of the total nominal brake torque and the maximum available brake torque and the maximum available brake torque of the generator ( 4 ), and the difference between the theoretical nominal brake torque that is actually output to the respective friction brake and the theoretical nominal brake torque being determined for it, which difference occurs on those friction brakes ( 2 ) being allocated to an axle of the motor vehicle connected to the generator ( 4 ), is output in a predetermined share as an additional nominal brake torque to those friction brakes ( 2 ), which are not allocated to the axle of the motor vehicle connected to the generator ( 4 ).

8. A method according to claim 7 , wherein the output in a predetermined share is approximately 25%.

9. A brake system ( 1 ) of a motor vehicle which includes an electric generator ( 4 ) and a number of hydraulic, electronically controllable friction brakes ( 2 ) being allocated to axles of the motor vehicle, with the brake system ( 1 ) controllable by of a control unit ( 12 ), wherein the brake system ( 1 ) is controlled using a method comprising: initially, activating only the generator ( 4 ) according to specification of a situation responsively determined total nominal brake torque;

connecting the friction brakes ( 2 ) in a delayed manner only when the total nominal brake torque exceeds a maximum available brake torque of the generator ( 4 ) by a predetermined first maximum brake torque difference; and

maintaining the friction brakes at a constant brake torque before a minimum brake torque difference is attained between the total nominal brake torque and the maximum available brake torque of the generator.

10. A brake system according to claim 9 , wherein only friction brakes ( 2 ), of the brake system ( 1 ) are initially connected, that are not allocated to an axle of the motor vehicle that is connected to the generator ( 4 ).