Method for the brake control of a vehicle combination

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 (ΔpPI) and a duration (ΔtPI) 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 (pBC) 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 (pBC_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 (ΔpPD) 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 (ΔtPD) of the pressure drop (ΔpPD) and the mean pressure gradient ((dpPD/dtPD)m) of the pressure drop (ΔpPD);
• and
• determining, on the basis of at least one of the duration of the pressure drop (ΔtPD) and the mean pressure gradient ((dpPD/dtPD)m) of the pressure drop (ΔpPD), the volume of the at least one trailer brake control line (28, 29, 32) of the at least one trailer vehicle (6, 8).