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

Claim 12:
13. 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);
the method further comprising at least one of the steps of:
performing, wherein the secondary brake system (50; 50′) includes actively acting brake cylinders (62a, 62b; 62a′, 62b′), an emergency braking function by activating the secondary brake system to assist or to replace an operation of the service brake system (30), by increasing a working pressure (pB) linearly according to a first characteristic curve (A), starting from a minimum brake pressure (pB_min) close to 0 Pa at a value of the braking value signal of SBW=0%, and, as the value of the braking value signal increases, increasing the working pressure (pB) up to a maximum brake pressure (pB_max) at a value of the braking value signal of SBW=100%;
performing, wherein the secondary brake system (50; 50′) includes actively acting brake cylinders (62a, 62b; 62a′, 62b′), an auxiliary braking function, by activating the secondary brake system to replace a braking effect of the service brake system on the vehicle, by increasing a working pressure (pB) according to a second characteristic curve (B), starting from a minimum brake pressure (pB_min) at a value of the braking value signal of SBW=0%, as the value of the braking value signal increases, increasing the working pressure (pB) up to a maximum brake pressure set for a normal operation (pB_max-N), which is below a maximum brake pressure (pB_max), at a braking value signal of SBW=100%;
performing, wherein the secondary brake system (50; 50′) includes actively acting brake cylinders (62a, 62b; 62a′, 62b′), an additional braking function, by activating the secondary brake system to assist the service brake system (30) in braking by activating the secondary brake system when braking value signals require a high braking pressure, by increasing a working pressure (pB) progressively according to a third characteristic curve (C), starting from a minimum brake pressure (pB_min) at a value of the braking value signal of SBW=0%, as the value of the braking value signal increases, from a defined starting value of the braking value signal (SBW_Start), increasing the working pressure (pB) up to a working pressure (pB), at a braking value signal SBW=100%, which is between the minimum brake pressure (pB_min) and a maximum brake pressure set for normal operation (pB_max-N);
performing, wherein the secondary brake system (68; 100) includes passively acting brake cylinders (82a, 82b), an emergency braking function, by activating the secondary brake system to assist or to replace the service brake system (30) in braking by reducing a working pressure (pFSB) largely linearly according to a seventh characteristic curve (D), starting from a maximum working pressure (pFSB_max) at a value of the braking value signal of SBW=0%, and as the values of the braking value signal increase, increasing the working pressure (pB) to a minimum working pressure (pFSB_min) close to 0 Pa at a value of the braking value signal of SBW=100%;
performing, wherein the secondary brake system (68; 100) includes passively acting brake cylinders (82a, 82b), an auxiliary braking function, by activating the secondary brake system to replace the service brake system (30) with respect to a braking effect on the vehicle by reducing a working pressure (pFSB) according to an eighth characteristic curve (E), starting from a maximum working pressure (pFSB_max) at a value of the braking value signal of SBW=0%, and as the values of the braking value signal increase, reducing the working pressure (pFSB) to a minimum working pressure in normal operation (pFSB_min-N) at a value of the braking value signal of SBW=100% which is above the minimum working pressure (pFSB_min); or
performing, wherein the secondary brake system (68; 100) includes passively acting brake cylinders (82a, 82b), an additional braking function, by activating the secondary brake system to assist the service brake system (30) in braking in situation with higher values of the braking value signal by reducing a working pressure (pB) according to a ninth characteristic curve (F), starting from the maximum working pressure (pFSB_max) at a value of the braking value signal of SBW=0%, from a defined starting value of the braking value signal (SBW_Start), and as the Values of the Braking value signal increase, reducing the working pressure to a working pressure (pFSB), at a braking value signal SBW=100%, which is between the maximum working pressure (pFSB_max) and the minimum working pressure in normal operation (pFSB_min-N).