Method for the brake control of a vehicle combination

1. A method for controlling brakes of a vehicle combination ( 2 ) composed of a tractor vehicle ( 4 ) with an electronically controlled hydraulic or pneumatic braking system ( 5 ) and a trailer vehicle ( 6 , 8 ) with a pneumatically controlled pneumatic braking system ( 7 , 9 ), the method comprising the following steps:

introducing, during a brake operation, via an electronically controlled trailer control valve ( 13 ) of the tractor vehicle ( 4 ), a brake control pressure (psc) of the trailer vehicle ( 6 , 8 ) into at least one tractor brake control line ( 19 ) extending to a tractor vehicle-side “brake” coupling head ( 26 );

introducing, at the beginning of the braking operation, a pressure pulse ( 34 ) exceeding a target brake control pressure (p BC_soll ) to be applied into the tractor brake control line ( 19 );

ascertaining determining, by an electronic control unit (ECU), an available internal volume of at least one trailer brake control line ( 28 , 29 , 32 ) coupled to the “brake” coupling head ( 26 ) and in fluid communication with the tractor brake control line ( 19 ), wherein the available internal volume depends on a quantity of trailer vehicles coupled to the brake coupling head ( 26 ) via the at least one trailer brake control line ( 28 , 29 , 32 ); and

determining at least one of an absolute value (Δp PI ) and a duration (Δt PI ) of the pressure pulse ( 34 ) communicated to the at least one trailer brake control line ( 28 , 29 , 32 ) depending on the volume of the at least one trailer brake control line ( 28 , 29 , 32 ) wherein the volume of the at least one trailer-side brake control line ( 28 , 29 , 32 ) is determined via the following steps:

detecting, via sensors, during a pressure drop (Δp PD ) due to a disengagement of the wheel brakes ( 35 , 36 , 37 , 38 ; 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ) of the vehicle combination ( 2 ), the air pressure prevailing in the tractor brake control line ( 19 ) and the at least one trailer brake control line ( 28 , 29 , 32 ) connected to the tractor vehicle-side “brake” coupling head ( 26 );

determining, based on a time profile of the air pressure, at least one of the duration (Δt PD ) of the pressure drop (Δp PD ) and the mean pressure gradient ((dp PD /dt PD ) m ) of the pressure drop (Δp PD ); and

determining, on the basis of at least one of the duration of the pressure drop (Δt PD ) and the mean pressure gradient ((dp PD /dt PD ) m ) of the pressure drop (Δp PD ), the volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of the at least one trailer vehicle ( 6 , 8 ).

2. The method as claimed in claim 1 , wherein the

ascertained determining available volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of the trailer vehicle ( 6 , 8 ) is ascertaining determining after every start-up of the tractor vehicle ( 4 ) and, thereafter, stored in a non-volatile data memory of then electronic control unit (ECU).

3. The method as claimed in claim 1 , comprising the further step of inferring, in response to a long duration (Δt PD ) of the pressure drop (Δp PD ) exceeding a predetermined time period, a total volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of more than one trailer vehicle ( 6 , 8 ).

4. The method as claimed in claim 1 , wherein, in the event that the mean pressure gradient (|(dp PD /dt PD ) m |) of the pressure drop (Δp PD ) falls below a predetermined limit pressure gradient, a total volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of more than one trailer vehicle ( 6 , 8 ) is inferred.

5. The method as claimed in claim 1 , wherein, when a current value of the available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) has not been ascertained determined, a value of the available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) is utilized that was ascertaining determining, and stored, in a preceding driving operation of the vehicle combination ( 2 ).

6. The method as claimed in claim 1 , wherein, when a current value of the available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) has not been ascertained determined, a predefined standard value of the available internal volume of the at least one brake control line ( 28 , 29 , 32 ) is utilized.

7. The method as claimed in claim 1 , wherein the absolute value (Δp PI ) of the pressure pulse, as compared to the target brake control pressure (p BC_soll ) is greater with increasing volume of the at least one trailer brake control line ( 28 , 29 , 32 ).

8. The method as claimed in claim 1 , wherein the absolute value (Δp PI ) of the pressure pulse, as compared to the target brake control pressure (p BC_soll ) to be applied, is limited by a previously established maximum permissible pressure (p BC_max ) in the at least one trailer brake control line ( 28 , 29 , 32 ) in such a way that the previously established maximum pressure (p BC_max ) in the at least one trailer brake control line ( 28 , 29 , 32 ) is not exceeded during the pressure pulse (p BC_soll +Δp PI ≤p BC_max ).

9. The method as claimed in claim 1 , wherein the duration (Δt PI ) of the pressure pulse is greater with increasing volume of the at least one trailer brake control line ( 28 , 29 , 32 ).

10. A method for controlling brakes of a vehicle combination ( 2 ) including a tractor vehicle ( 4 ) with an electronically controlled hydraulic or pneumatic braking system ( 5 ) and a trailer vehicle ( 6 , 8 ) with a pneumatically controlled pneumatic braking system ( 7 , 9 ), the method comprising the following steps:

determining, by an electronic control unit (ECU), an available internal volume of at least one trailer brake control line ( 28 , 29 , 32 ) coupled to a tractor vehicle-side “brake” coupling head ( 26 ) of a tractor vehicle ( 4 ), the trailer brake control line in fluid communication with at least one tractor brake control line ( 19 ) that extends to the “brake” coupling head, wherein the available internal volume depends on a quantity of trailer vehicles coupled to the “brake” coupling head ( 26 ) via the at least one trailer brake control line ( 28 , 29 , 32 ); and

after determining the volume of the at least one trailer brake control line, determining, depending on the determined volume of the at least one trailer brake control line ( 28 , 29 , 32 ), at least one of an absolute value (Δp PI ) and a duration (Δt PI ) of a pressure pulse ( 34 ) to be applied and communicated to the at least one trailer brake control line ( 28 , 29 , 32 );

wherein the tractor vehicle ( 4 ) includes an electronically controlled trailer control valve ( 13 ) wherein, during a braking operation, a brake control pressure (p BC ) of the trailer vehicle ( 6 , 8 ) is introduced via the electronically controlled trailer control valve ( 13 ) of the tractor vehicle ( 4 ) into the at least one tractor brake control line ( 19 ) that extends to the coupling head ( 26 ); and introducing, at the beginning of the braking operation, the pressure pulse ( 34 ), wherein the pressure pulse exceeds a target brake control pressure (p BC_soll ) to be applied into the tractor brake control line ( 19 );

wherein the available internal volume of the at least one trailer-side brake control line ( 28 , 29 , 32 ) is determined via the following steps:

detecting, via sensors, during a pressure drop (Δp PD ) due to a disengagement of the wheel brakes ( 35 , 36 , 37 , 38 ; 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ) of the vehicle combination ( 2 ), the air pressure prevailing in the tractor brake control line ( 19 ) and the at least one trailer brake control line ( 28 , 29 , 32 ) connected to the tractor vehicle-side “brake” coupling head ( 26 );

determining, based on a time profile of the air pressure, at least one of the duration (Δt PD ) of the pressure drop (Δp PD ) and the mean pressure gradient ((dp PD /dt PD ) m ) of the pressure drop (Δp PD ); and

determining, on the basis of at least one of the duration of the pressure drop (Δt PD ) and the mean pressure gradient ((dp PD /dt PD ) m ) of the pressure drop (Δp PD ), the volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of the at least one trailer vehicle ( 6 , 8 ).

11. The method as claimed in claim 10 , wherein the available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of the trailer vehicle ( 6 , 8 ) is determined after every start-up of the tractor vehicle ( 4 ) and, thereafter, stored in a non-volatile data memory of the electronic control unit (ECU).

12. The method as claimed in claim 10 , comprising the further step of determining, in response to a long duration (Δt PD ) of the pressure drop (Δp PD ) exceeding a predetermined time period, a total available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of more than one trailer vehicle ( 6 , 8 ).

13. The method as claimed in claim 10 , wherein, in the event that the mean pressure gradient (|(dp PD /dt PD ) m |) of the pressure drop (Δp PD ) falls below a predetermined limit pressure gradient, a total available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) of more than one trailer vehicle ( 6 , 8 ) is determined.

14. The method as claimed in claim 10 , wherein, when a current value of the available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) has not been determined, a value of the available internal volume of the at least one trailer brake control line ( 28 , 29 , 32 ) is utilized that was determined, and stored, in a preceding driving operation of the vehicle combination ( 2 ) for determining the absolute value or duration of the pressure pulse.

15. The method as claimed in claim 10 , wherein, when a current value of the volume of the at least one trailer brake control line ( 28 , 29 , 32 ) has not been determined, a predefined standard value of the available internal volume of the at least one brake control line ( 28 , 29 , 32 ) is utilized to determine the absolute value or duration of the pressure pulse.

16. The method as claimed in claim 10 , wherein the absolute value (Δp PI ) of the pressure pulse, as compared to the target brake control pressure (p BC_soll ) is greater with increasing volume of the at least one trailer brake control line ( 28 , 29 , 32 ).

17. The method as claimed in claim 10 , wherein the absolute value (Δp PI ) of the pressure pulse, as compared to the target brake control pressure (p BC_soll ) to be applied, is limited by a previously established maximum permissible pressure (p BC_max ) in the at least one trailer brake control line ( 28 , 29 , 32 ) in such a way that the previously established maximum pressure (p BC_max ) in the at least one trailer brake control line ( 28 , 29 , 32 ) is not exceeded during the pressure pulse (p BC_soll +Δp PI ≤p BC_max ).

18. The method as claimed in claim 10 , wherein the duration (Δt PI ) of the pressure pulse is greater with increasing volume of the at least one trailer brake control line ( 28 , 29 , 32 ).