Electro-pneumatic ABS braking system for commercial vehicles

Abstract

To obtain an electro-pneumatic ABS brake system for commercial vehicles that enables reliable brake control with relatively little effort. [Solution] In an electro-pneumatic ABS brake system 1 for a commercial vehicle 2, a second pressure sensor 54 is provided separately from the first pressure sensor 52 and is configured to output a second pressure signal S2 to an electronic control unit 60. The electronic control unit 60 is configured to receive both pressure signals S1 and S2 and to control at least one of the ABS valves 14, 17, 23, 27, 42 and / or axle valve units 10, 20 depending on the pressure signals S1 and S2.

Description

Technical Field

[0001] The present invention relates to an electro-pneumatic ABS brake system for commercial vehicles and such commercial vehicles.

Background Art

[0002] An ABS brake system for commercial vehicles generally includes a foot brake valve, which is operated by a driver via, for example, a brake pedal, and has at least two analog pneumatic output channels, namely, a first pneumatic output channel for the front axle service brake circuit and a second pneumatic output channel for the rear axle service brake circuit. The analog brake pressure controlled by the foot brake valve is subsequently supplied to the wheel service brakes via the ABS valve of the wheel brake circuit, optionally via a relay valve for amplification of the air volume. Preferably, an axle valve unit can be provided in each of the front axle service brake circuit and the rear axle service brake circuit, and the axle valve unit enables switching from the brake pressure applied by the driver for autonomous braking to the supply air connection via the ABS valve of the wheel brake circuit. Different from the EBS brake system, an axle modulator for setting an analog brake pressure even during braking by the driver based on an electrical sensing of the driver's braking intention is not provided during a normal braking process.

[0003] A pressure sensor is often provided to measure the controlled brake pressure. At this time, the pressure sensor can be used to detect the controlled brake pressure and for the electronic control unit to be used for the electronic control unit to perform pressure control. Furthermore, a brake system for measuring the brake pressure in a trailer service brake circuit is known.

[0004] Patent Document 1 describes a monostable and fault-tolerant parking brake valve device for an electronically controllable pneumatic brake system of a commercial vehicle in which the parking brake is controlled via a shuttle valve, wherein a pressure sensor is provided at each connection of the shuttle valve prior to the electro-pneumatic parking brake valve, and the pressure sensors output their measurement signals to different ECUs.

[0005] Patent Document 2 describes an electro-pneumatic control module for an electronically controllable pneumatic braking system of a vehicle consisting of a towing vehicle and a trailer vehicle, which is provided with a trailer control valve unit having one or more electro-pneumatic valves and parking brake units, wherein the parking brake unit comprises a spring accumulator connection for a spring accumulator for the towing vehicle and a parking brake valve unit. Here, the electro-pneumatic control module is equipped with redundant pressure sensors, which are located in a first redundant pressure line or redundant pressure connection and are configured to detect pneumatic redundant pressure in the redundant pressure connection or first redundant pressure line and to provide a corresponding redundant pressure signal as a brake representative pressure, which represents the driver's intent and is compared with a service brake signal received from a central module or another control unit.

[0006] Therefore, it is known that pressure sensors are used in such parking brake systems. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] German Patent Application Publication No. 102019133011 [Patent Document 2] German Patent Application Publication No. 102017005979 Specification [Overview of the project] [Problems that the invention aims to solve]

[0008] The fundamental problem of this invention is to provide an electro-pneumatic ABS brake system for commercial vehicles that enables reliable brake control with relatively little effort. [Means for solving the problem]

[0009] The problem is solved by the electro-pneumatic ABS brake system according to claim 1. Furthermore, a commercial vehicle having the brake system, a combination of a commercial vehicle and a trailer vehicle, and a method for operating the electro-pneumatic ABS brake system are also envisioned.

[0010] Therefore, a brake system is obtained having an electro-pneumatic axle valve unit and an ABS valve controlled by a single electronic control unit or ECU. Such an electro-pneumatic brake system is also called an ABS brake system. In this invention, a first pressure sensor and a second pressure sensor are provided at different locations in the brake system, and these pressure sensors output their pressure signals to an electronic control unit, i.e., an ECU. The ECU receives both pressure signals and can perform different processes based on the pressure signals.

[0011] This already achieves several advantages:

[0012] The brake system according to the present invention can be formed with minimal effort and is equipped with only two pressure sensors, i.e., only one additional pressure sensor compared to known service brake systems. Therefore, in particular, the formation of a digital foot brake module is unnecessary, and the first pressure sensor can directly measure the brake pressure controlled by the foot brake valve, and thus it is possible to identify the driver's intention to brake or the driver's operation of the brake pedal.

[0013] Therefore, it is possible to compare the pressure values ​​indicated by the pressure signals from both sensors, and this comparison allows for the measurement of equivalent values, particularly under certain conditions, and enables multiple processes using two sensors that can be mutually validated.

[0014] Another advantage is that the system can be retrofitted, for example, by connecting a second pressure sensor or one of the two pressure sensors as an external pressure sensor later, and appropriately programming the electronic control unit. Therefore, modifications require only a small amount of additional effort. Updates can also be performed with minimal effort.

[0015] Furthermore, by incorporating additional pressure sensors, the existing brake system concept can be easily extended, thereby improving functional reliability (safety).

[0016] According to one preferred embodiment, a comparison of pressure values ​​indicated by pressure signals is performed, and this comparison enables a plurality of processes, particularly, - In particular, to enable validation, for example, to recognize sensor errors, failures or malfunctions, the functionality of both pressure sensors can be evaluated by, for example, evaluating the difference in pressure values ​​or the temporal behavior of pressure values, and / or - For example, calibrating the pressure signals of both pressure sensors to identify and set a common minimum and / or maximum value, and / or - Identifying the different braking behaviors of the service brake and the service brake at the axle, which may result from different braking behaviors due to, for example, axle load or friction coefficient conditions, and / or - Controlling the axle valve unit and / or ABS valve. This is possible.

[0017] In this case, it is possible to identify and compare the zero value of the pressure signal, especially for calibration and / or error identification, during the unbraked phase.

[0018] During driver-operated and / or autonomous braking, i.e., during braking, it is possible to perform another step. In this step, it is possible to specify braking behavior based on absolute, relative, and / or temporal variations, particularly using differences in pressure values.

[0019] Unlike the EBS brake system, both axle valve units are configured to control analog braking by the driver during normal operation, whereas the EBS system, in normal operation, is intended to sense the driver's intention via sensors and provide pneumatic control of the wheel brakes based on the supply pressure via proportional valves.

[0020] The first and second axles are, in particular, the front and rear axles of a commercial vehicle. In this case, a commercial vehicle having multiple axles, for example, three axles equipped with six ABS valves, is also feasible.

[0021] In one preferred embodiment, the brake system includes a trailer service brake circuit, which is connected to a front axle service brake circuit and / or a rear axle service brake circuit, particularly behind each axle valve unit. In this case, the trailer service brake circuit includes a trailer ABS valve controlled by an electronic control unit to adjust or regulate trailer brake pressure, a trailer control valve, i.e., a TCV (trailer control valve), which also generally accepts supply pressure, a first coupling head for outputting analog control pressure, particularly brake pressure from the driver, to the trailer, and another coupling head for outputting supply pressure to the trailer. In addition, an electrical interface and / or an electronic interface can be provided. Thus, the trailer ABS valve is controlled by an ECU to adjust the trailer brake pressure, and the trailer brake pressure is subsequently output as pneumatic control pressure to the connected trailer brake system via the trailer control valve and coupling head. A second pressure sensor is preferably located in the trailer service brake circuit to measure the trailer brake pressure and output it to the electronic control unit. This allows the electronic control unit to perform pressure adjustment or closed-loop control of the trailer service brake circuit by measuring the brake pressure to be controlled and controlling the trailer ABS valve. The trailer brake pressure can be adjusted very precisely by closed-loop control or pressure adjustment, and in particular, its dynamic behavior can be adjusted more effectively, thereby improving reliability (safety).

[0022] In addition to this, or as an alternative, it is possible to perform towed vehicle detection or trailer detection at the coupling head, which identifies whether the trailer is connected to its trailer brake system based on a pressure signal. Therefore, the presence of a connected trailer brake system can be estimated based on the dynamic behavior of the measured pressure value, and thus, for example, it is possible to estimate that a trailer is connected based on the slow temporal behavior of changes in the pressure value.

[0023] The second pressure sensor can be arranged, for example, between the trailer ABS valve and the trailer control valve, whereby the pressure is measured directly after the regulating unit, so that in particular a dynamic or rapid control of the trailer brake pressure is achieved. Furthermore, the second pressure sensor can be arranged between the trailer control valve and the coupling head, where the control is somewhat delayed in time in some cases, but here the brake pressure measured behind the trailer control valve directly depends on whether the connected trailer brake system consumes compressed air, so that the trailer detection function is improved.

[0024] According to another embodiment, the second pressure sensor is directly connected to the pneumatic output channel of the foot brake module to which the first pressure sensor is not connected. Such an arrangement can be provided particularly in a brake system without a trailer service brake circuit, but it is also possible to be provided in a brake system having a trailer service brake circuit. Therefore, since the pressure is measured in both output channels, these values can be directly compared with each other, particularly for validity verification or fault detection and / or calibration. However, it is also possible to identify the braking behavior of both axle service brake circuits. Therefore, different compressed air consumptions at the axles can be detected during a strong braking operation.

[0025] Preferably, the pressure sensors can be formed identically or uniformly, so that the number of components is limited, the cost is kept low, and directly comparable pressure signals are output. The pressure sensor can be integrated, for example, into the foot brake module and / or can be installed later as an external sensor. This enables particularly high flexibility and modifiability. Furthermore, it is also possible to provide more than two, particularly three, pressure sensors, for example by retrofitting one or two pressure sensors due to, for example, a combined arrangement at both pneumatic output channels and further in the trailer service brake circuit.

[0026] Therefore, both commercial vehicles with such braking systems and combinations of vehicles with attached trailers can be obtained.

[0027] The present invention will be described in detail below with reference to several embodiments, based on the attached drawings. [Brief explanation of the drawing]

[0028] [Figure 1] This is an electro-pneumatic wiring diagram of a brake system according to one embodiment of the present invention, which has a pressure sensor located in the trailer's service brake circuit. [Figure 2] This figure shows another embodiment of a brake system having a pressure sensor connected in front of the coupling head in a trailer brake circuit. [Figure 3] This figure shows one embodiment of a brake system that does not have a trailer service brake circuit. [Modes for carrying out the invention]

[0029] Figure 1 shows an electro-pneumatic ABS service brake system 1. This ABS service brake system is formed in a commercial vehicle 2, such as a truck, as suggested herein, and comprises a brake pedal 3 with a foot brake valve 4, and two pneumatic output channels 5-1 and 5-2 of the foot brake valve 4. Since the front axle service brake circuit 6 and the rear axle service brake circuit 8 are connected to the pneumatic output channels 5-1 and 5-2, these front axle service brake circuit 6 and the rear axle service brake circuit 8 are supplied with analog compressed air brake signals in parallel from the foot brake valve 4. A front axle valve unit 10 is provided in the front axle service brake circuit 6 and is directly connected to the first pneumatic output channel 5-1. On the other hand, a left front wheel service brake circuit 11, which has a left front wheel ABS valve 14 and a left front wheel service brake 15 for the left front wheel 16, is connected to the front axle service brake circuit 6. Correspondingly, a right front wheel service brake circuit 12, which has a right front wheel ABS valve 17 and a right front wheel service brake 18 for braking the right front wheel 19, is connected to the front axle service brake circuit 6. Correspondingly, the rear axle is formed by a rear axle valve unit 20 connected to the second pneumatic output channel 5-2 of the foot brake valve 4, and rear wheel service brake circuits 22, 29 connected to the rear axle valve unit 20. In the rear wheel service brake circuits, the rear wheel service brakes are connected via ABS valves 23, 27. Specifically, the left rear wheel service brake 22 is connected to the left rear wheel service brake 25 of the left rear wheel 26 via the left rear wheel ABS valve 23, and correspondingly, the right rear wheel service brake circuit 29 is connected to the right rear wheel service brake 28 of the right rear wheel 30 via the right rear wheel ABS valve 27. Any additional parking brake system is not shown here.

[0030] In the embodiments shown in Figures 1 and 2, a trailer service brake circuit 40 is further provided, which is connected to the front axle service brake circuit 6, for example, behind the front axle valve unit 10. Basically, the trailer service brake circuit 40 can also be connected to the rear axle service brake circuit 8, and moreover, a valve device is usually provided to allow pneumatic pressure to be supplied to the trailer service brake circuit 40 from both the front axle service brake circuit 6 and the rear axle service brake circuit 8. On the other hand, the trailer service brake circuit 40 is provided with a trailer ABS valve 42, to which a pneumatic coupling head 48 provided for control pressure is connected via a trailer control valve, i.e., a TCV (trailer control valve) 44, in order to connect a trailer 50 having the trailer brake system 51 shown herein. Therefore, the trailer 50 is typically equipped with trailer wheels 55, which are braked via the trailer wheel service brakes 56 of the trailer brake system 51. Although only one trailer axle is shown here for simplification, it is possible to have multiple trailer axles. Thus, the pneumatic trailer control pressure p-TCV is controlled in the trailer service brake circuit 40 via an electrically operated trailer ABS valve 42 and is typically output to the trailer 50 via the trailer control valve TCV 44 and coupling head 48. In addition, a separate coupling head is generally provided for supply pressure.

[0031] A first pressure sensor 52 is connected to the front axle service brake circuit 6, and this first pressure sensor measures the air pressure p1 and outputs a first pressure signal S1. In the embodiment shown in Figure 1, a second pressure sensor 54 is provided between the trailer ABS valve 42 and the trailer control valve 44, and this second pressure sensor measures the air pressure p-TCV and outputs a second pressure signal S2.

[0032] The electronic control unit ECU 60 receives both pressure signals S1 and S2, and generally also receives wheel rotation speed signals for wheels 16, 19, 26, and 30. The ECU 60 also controls the axle valve units 10 and 20, and advantageously, the ABS valves 14, 17, 23, and 27 for ABS control. The axle valve units 10 and 20 receive analog pneumatic control pressure provided in both output channels 5-1 and 5-2 via the foot brake valve 4, and guide this control pressure to the wheel service brake circuits 11, 12 or 22, and 29. Furthermore, by guiding the axle valve units 10 and 20 to a supply pressure p0 subsequently adjusted by the ECU 60 via the ABS valves 14, 17, 23, and 27 instead of the pneumatic control pressure provided via output channels 5-1 and 5-2, the brake system 1, which has an autonomous braking function, can also be performed by the ECU 60, for example, autonomous braking for autonomous stability intervention. This enables autonomous braking functionality, similar to that known from ABS brake systems, even without an EBS system where pneumatic output channels 5-1 and 5-2 are used solely for redundant backup levels (fallback levels, degraded operating levels).

[0033] Therefore, in the embodiment shown in Figure 1, the first pressure sensor 52 is directly connected to the first pneumatic output channel 5-1 and thus directly measures the brake pressure p1 adjusted by the driver via the brake pedal 3, converts the brake pressure into a first pressure signal S1 and outputs it to the ECU 60, so that the ECU can directly detect the driver's brake request even without a digital output channel of the foot brake valve 4. In this case, the first pressure sensor 52 can be connected to the front axle service brake circuit 6 as an external pressure sensor, or it can be integrated into the foot brake valve 4. The ECU 60 can directly utilize the digital value of the brake operation by the first brake signal S1. The second pressure sensor 54 measures the trailer brake pressure p-TCV behind the trailer ABS valve 42, so that the trailer brake pressure is adjusted by the ECU 60 depending on the control of the ABS valve 42. Therefore, the ECU 60 can directly control or close-loop control the trailer ABS valve 42 and directly measure the resulting trailer brake pressure p-TCV.

[0034] Furthermore, in the non-braking stage, when the brake pedal 3 is not operated and no autonomous braking is input via the front axle valve unit 10, the ECU 60 can compare the zero values ​​of brake pressure p1 and p-TCV via pressure signals S1 and S2, enabling redundancy or checking capability. In this stage, pressures p1 and p-TCV basically correspond (match), but in some cases there is a corresponding pressure drop in the pipeline. Therefore, comparison or calibration can be performed here, for example, to calibrate the trailer pressure p-TCV to brake pressure p1, and to detect a defect in one of the pressure sensors 52 and 54.

[0035] In the embodiment shown in Figure 2, in an otherwise unchanged configuration, the second pressure sensor 54 is also located in the trailer service brake circuit 40, but is positioned between the trailer control valve 44 and the coupling head 48. Therefore, it is possible to measure the trailer pressure p-TCV output via the coupling head 48. Since the pressure is not measured directly behind the trailer ABS valve 42, control by the ECU 60 via the trailer ABS valve 42 is sometimes somewhat more indirect; however, for this reason, the second pressure sensor 54 in Figure 2 enables better trailer detection: when the brake system of the trailer 50 is connected to the coupling head 48, the dynamic behavior of the brake pressure value at the coupling head 48 changes. Therefore, the pressure value output or provided, particularly via the trailer control valve 44, is not transmitted very dynamically in the connected trailer 5. As a result, changes in the pressure value at the outlet of the coupling head 48 or the trailer control valve 44 generally appear more slowly, or more gradually, i.e., with a time delay. Therefore, when compressed air is consumed in the trailer 50, the pressure value in the second pressure sensor 54 also temporarily decreases, which can be appropriately detected and associated with the presence of the trailer 50. Such trailer detection is also possible in the embodiment shown in Figure 1.

[0036] The embodiment in Figure 3 shows an electro-pneumatic brake system 1 for a commercial vehicle 2 that does not have a trailer service brake circuit 40. The other configurations remain unchanged from Figures 1 and 2, except that here, a second pressure sensor 54 is connected to a second pneumatic output channel 5-2, i.e., the rear axle service brake circuit 8, and measures the brake pressure p2 provided therein, outputting a second pressure signal S2 to the ECU 60. Therefore, a redundancy check is possible here, allowing for direct comparison of both pressure signals S1 and S2. In the absence of brake operation, or generally during braking, the brake pressure should first be measured at the same brake pressure p1, p2 or at the ratio pneumatically represented in the characteristic curve of the foot brake valve; if the pressure consumption differs between the front axle service brake circuit 6 and the rear axle service brake circuit 8, correspondingly, dynamically different or slightly deviated values ​​may occur, for example, the brake pressure p1 or p2 in the brake circuit 6 or 8 with higher pressure consumption may decrease slightly. Such connection of the second pressure sensor 54 to the second pneumatic output channel 5-2 is also possible in the embodiments shown in Figures 1 and 2. [Explanation of Symbols]

[0037] 1. Electro-pneumatic ABS braking system 2. Commercial vehicles 3. Brake pedal 4 Foot brake valve 5-1 First pneumatic output channel of foot brake valve 4 5-2 Second pneumatic output channel of foot brake valve 4 6. Front axle service brake circuit 8. Rear axle service brake circuit 10 Front Axle Valve Unit 11. Left front wheel service brake line 12 Right front wheel service brake line 14. Left front wheel ABS valve 15. Left front brake 16 Left front wheel 17 Right front wheel ABS valve 18 Right rear brake 19 Right front wheel 20 Rear Axle Valve Unit 22 Left rear wheel service brake circuit 23. Left rear wheel ABS valve 25. Left rear brake 26 Left rear wheel 27 Right rear wheel ABS valve 28 Right rear brake 29 Right rear wheel service brake circuit 30 Right rear wheel 40 Trailer service brake circuit in commercial vehicle 2 42 Trailer ABS Valve 44 Trailer control valve (TCV) 48 Pneumatic coupling head 50 Trailer 51 Trailer brake system in trailer 50 connected to trailer service brake circuit 40 of commercial vehicle 2 52 First pressure sensor 54 Second pressure sensor 55 Trailer Wheels 56 Trailer wheel service brake 60 Electronic Control Unit (ECU) p0 supply pressure p1 Driver brake pressure in the first pneumatic output channel 5-1 p2 Driver brake pressure in the second pneumatic output channel 5-2 p-TCV Trailer Brake Pressure S1 First pressure signal S2 Second pressure signal

Claims

1. An electro-pneumatic ABS brake system (1) for a commercial vehicle (2), wherein the brake system (1) is - A foot brake valve (4) that is operable via a brake pedal (3) and has a first pneumatic output channel (5-1) and a second pneumatic output channel (5-2), - A first axle service brake circuit (6) connected to the first pneumatic output channel (5-1) has a first axle valve unit (10) and at least one first ABS service brake circuit (11, 12, 40) which is connected to the first axle valve unit (10) and has at least one ABS valve (14, 17, 42) that controls at least one wheel service brake (16, 18, 56), - A second axle service brake circuit (8) connected to the second pneumatic output channel (5-2) has a second axle valve unit (20) and at least one second ABS brake circuit (22, 29) connected to the second axle valve unit (20) and having at least one ABS valve (23, 27) that controls at least one second wheel service brake (25, 28), - An electronic control unit (60) that controls the ABS valves (14, 17, 23, 27, 42), the first axle valve unit (10), and the second axle valve unit (20), - A first pressure sensor (52) is connected to one of the two pneumatic output channels (5-1, 5-2) and is configured to measure the pneumatic control pressure (p1) output from the foot brake valve (4) and to output a first pressure signal (S1) to the electronic control unit (60). In the brake system (1) provided, A brake system (1) characterized in that a second pressure sensor (54) is provided separately from the first pressure sensor (52) and is configured to output a second pressure signal (S2) to the electronic control unit (60), and the electronic control unit (60) is configured to receive both pressure signals (S1, S2) and to control at least one of the ABS valves (14, 17, 23, 27, 42) and / or the axle valve units (10, 20) depending on the pressure signals (S1, S2).

2. The brake system (1) according to claim 1, characterized in that when the driver brakes by operating the brake pedal, the analog brake pressure output to the pneumatic output channels (5-1, 5-2) via the foot brake valve (4) is guided to the ABS service brake circuits (11, 12, 22, 29, 40) via the axle valve units (10, 20), respectively.

3. The electronic control unit (60) compares the two pressure signals (S1, S2) with each other, and based on the comparison, - Evaluate the functionality of both pressure sensors (52, 54), and / or - Calibrate the pressure signals (S1, S2) of both pressure sensors (52, 54), and / or - Identify the different braking behaviors of the first wheel service brakes (15, 18) and the second wheel service brakes (25, 28), and / or - Controls the axle valve unit and / or the ABS valves (14, 17, 23, 27, 42) The brake system (1) according to claim 1 or 2, characterized in that it is the brake system (1) described above.

4. The brake system (1) according to claim 3, characterized in that the electronic control unit (60) receives zero values ​​of the pressure signals (S1, S2) and compares them with each other when braking is not being performed.

5. The electronic control unit (60) performs the following steps during autonomous braking and / or braking by the driver: - A step of measuring the absolute value, relative value and / or time variation of the pressure values ​​of the pressure signals (S1, S2), - A step of forming the difference between the measured pressure values ​​of the two pressure signals (S1, S2), - A step to identify the time variation of the ratio and / or difference of the pressure values ​​of the two pressure signals (S1, S2). A brake system (1) according to any one of claims 1 to 4, characterized by performing one or more of the above.

6. The brake system (1) according to any one of claims 1 to 5, characterized in that the electronic control unit (60) is further configured to perform brake slip control without specifically controlling the axle valve units (10, 20) by measuring the wheel rotation speed and controlling the ABS valves (14, 17, 23, 27, 42).

7. The first axle valve unit (10) and / or the second axle valve unit (20) are equipped with a supply pressure connection for receiving supply pressure (p0), - The electronic control unit (60) includes the following elements, particularly as an autonomous braking process and / or as stability control: - The first axle valve unit (10) guides the supply pressure to the first service brake circuit (11, 12, 40), - The second axle valve unit (20) guides the supply pressure to the second service brake circuit (22, 29), - ABS valves (14, 17, 23, 27, 42) adjust the brake pressure to the wheel service brakes (15, 18, 25, 28, 56). The brake system (1) according to any one of claims 1 to 6, characterized in that it is configured to autonomously operate the wheel service brakes (15, 18, 25, 28, 56) by controlling one or more of the above.

8. The brake system (1) according to any one of claims 1 to 7, characterized in that the first axle service brake circuit is a front axle service brake circuit (6), and the second axle service brake circuit is a rear axle service brake circuit (8).

9. The brake system (1) includes a trailer service brake circuit (40) connected to the first axle service brake circuit (6) and / or the second axle service brake circuit (8) at the rear of each axle valve unit (10, 20), and the trailer service brake circuit (40) includes, - A trailer ABS valve (42) controllable by the ECU (60) for adjusting the trailer brake pressure (p-TCV), which is connected to the first axle service brake circuit (6) and / or the second axle service brake circuit (8), - A connecting head (48) that connects the trailer control valve (44) and the trailer brake system (51) of the trailer (50) A system is in place, - The second pressure sensor (54) - Between the trailer ABS valve (42) and the trailer control valve (44), or - Between the trailer control valve (44) and the connecting head (48) A brake system (1) according to any one of claims 1 to 8, characterized in that it is provided.

10. The brake system (1) according to claim 9, characterized in that the electronic control unit (60) performs brake control by receiving the second pressure signal (S2) and by controlling the trailer ABS valve (42) as a closed-loop control circuit for controlling the trailer brake pressure (p-TCV).

11. The aforementioned electronic control unit (60) - Based on the second pressure signal (S2), and / or - Based on the time variation of the second pressure signal (S2), and / or - Based on a comparison of the two pressure signals (S1, S2), and / or - Based on a comparison of the time evolution of the two pressure signals (S1, S2), The brake system (1) according to claim 9 or 10, characterized in that the electronic control unit (60) is configured to perform trailer detection by detecting whether the trailer brake system (51) of the trailer (50) is connected to the coupling head (48).

12. The second pressure sensor (54) is connected to another pneumatic output channel (5-2) to which the first pressure sensor (52) is not connected, and the electronic control unit (60) controls the system based on a comparison of the two pressure signals (S1, S2) and / or a comparison of the time variations of the two pressure signals (S1, S2), - Identify redundancy and / or - Estimate a defect in one of the two pressure sensors (52, 54) or in the foot brake valve (4), and / or - Measure the different compressed air consumption of the first service brake circuit (6) and the second service brake circuit (8). A brake system (1) according to any one of claims 1 to 11, characterized by the features described herein.

13. One or both of the aforementioned pressure sensors (52, 54) belong to the following group: One or both of the foot brake valve (4), the trailer control valve (44), and the two valve units (10, 20) A brake system (1) according to any one of claims 1 to 12, characterized in that it is integrated into one or two of the components.

14. The brake system (1) according to any one of claims 1 to 12, characterized in that one or both of the two pressure sensors (52, 54) are connected to the ABS service brake circuit.

15. A commercial vehicle (2) having an electro-pneumatic ABS brake system (1) according to any one of claims 1 to 14.

16. A vehicle combination comprising a commercial vehicle (2) as described in claim 15 and a trailer (50) connected to the commercial vehicle (2).

17. A method for operating an electro-pneumatic ABS brake system (1) according to any one of claims 1 to 14, wherein both pressure sensors (52, 54) measure the current pressure value and output the pressure signals (S1, S2) to the electronic control unit (60), and the electronic control unit (60) performs the following process: - The electronic control unit (60) checks whether a defect exists in at least one of the two pressure sensors (52, 54), performing redundancy identification or comparative identification. - By receiving the second pressure signal (S2) and controlling the trailer ABS valve (42), pressure control is performed in the trailer service brake circuit (40), - Evaluation of different compressed air consumption in the ABS service brake circuit for evaluating the brake behavior of the commercial vehicle (2), - Trailer detection to determine whether the trailer brake system (51) of the trailer (50) is connected to the coupling head (48) A method characterized by performing one or more of the following.

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