Patent ID: 11938913
Assignee: ZF CV SYSTEMS GLOBAL GMBH
Field: Transport (Mechanical engineering)
Classification: CPC B | IPC B

Claim 13:
14. A method for controlling a pressure-medium-operated secondary brake system (50; 50′, 68; 100) in a power brake system (1.1, 1.2, 1.3, 1.4) of a vehicle (2), the power brake system including a pressure medium source (14), a pressure-medium-operated primary brake system (30), which can be used as a service brake and steering brake system, the primary brake system (30) including at least one foot brake valve (36a, 36b) and at least two wheel brake cylinders (40a, 40b) arranged on opposite sides on a drive axle (8) and configured to be actuated independently of one another, a pressure-medium-operated secondary brake system (50; 50′; 68; 100) operable independently of the primary brake system (30) and configured to be used at least as an auxiliary brake system, the secondary brake system (50; 50′; 68; 100) including a brake control valve (56; 70; 102) and at least one brake cylinder (62a, 62b; 62a′, 62b′; 82a, 82b), acting on wheel brakes of a vehicle axle (4, 8), wherein the secondary brake system (50; 50′; 68; 100) is electronically controllable and includes the brake control valve (56; 70; 102) configured as a solenoid valve for setting a braking force of by feeding or removing pressure medium to or from the at least one brake cylinder (62a, 62b; 62a′, 62b′; 82a, 82b); a pressure sensor (64; 90) connected to a working line (60; 60′; 74, 80) leading to the at least one brake cylinder (62a, 62b; 62a′, 62b′; 82a, 82b); and an electronic brake control unit (46) for evaluating a pressure signal of the pressure sensor (64; 90) and for controlling the brake control valve (56; 70; 102) in accordance with a braking value signal (SBW);
the method comprising the step of:
controlling the brake control valve (56; 70; 102) based on characteristic curves (A, B, C; D, E, F) which are valid for different operating modes of the secondary brake system (50; 50′, 68; 100) and stored in a non-volatile data memory (78) assigned to the brake control unit (46);
wherein the characteristic curves include a first characteristic curve, a second characteristic curve, and a third characteristic curve,
wherein the second characteristic curve (B) for an auxiliary braking function and the third characteristic curve (C) for an additional braking function are generated from the first characteristic curve (A) for an emergency braking function of the secondary brake system (50; 50′) via a transfer function with variable reduction of a working pressure (pB) over the braking value signal (SBW),
wherein the variable reduction of the working pressure (pB) is greater at low values of the braking value signal than at high values of the braking value signal.