Trailer braking system

Abstract

A trailer brake system comprises a park brake control 2 (e.g. valve) and a spring brake modulator valve arrangement (SBMV) 60 adapted to control pressure to spring brakes 33-38 on the trailer. The mod

Description

The invention relates to a braking system, in particular for a towed vehicle such as a three axle semi-trailer or full trailer. Motor vehicle technology is increasingly making use of digitization and one of the main strands of development is in the area of autonomous or highly automated vehicles, in which functions currently carried out by the driver will be replaceable by automated systems on the vehicle. This automation generally requires integration of additional functions sensors and electrical and electronic subsystems. As vehicles are more fully automated, the general acceptance of or at least toleration of road accidents with drop significantly as errors by machines or electronic are less accepted than the generic problem of driver error. An additional issue for operators is that the trailer will become more expensive as a capital good, even if total operational costs are reduced, and so there will be pressure on the owner to increase the availability of the trailer for use. Therefore, compared to known trailer vehicles, the level of safety should be increased and the availability, performance of critical functions ensured and error rates reduced. Problems with trailer safety systems can be generally divided into pneumatic problems or errors and electrical problems or errors. The probability of an electrical failure is significantly higher than a pneumatic failure. Examples of pneumatic problems include; decoupling or rupture of the supply, which will lead to the triggering of the emergency brake; rupture of the control line, which will lead to the triggering of the emergency brake via the truck trailer control module; rupture of the main reservoir on the trailer leading to decompression of the supply line, which if the leak is large enough will lead to the emergency brake being triggered and finally failure of a valve or similar, which will result in one of the typically two brake channels being unable to sustain the intended brake pressure, which in turn leads to asymmetric brake forces and potential vehicle instability. Examples of modes of electrical failure include a failure of the power supply e.g. due to a disconnected cable or an ECU failure. In either case, the electronic braking system operation would be inoperative with the loss of ABS and RSP functions and brake response times increased. In an automated driving use case any single fault described above would force the vehicle combination to an uncontrolled and immediate stop (potentially causing an accident), a severe speed reduction and / or stop on the highway or a loss of legally required braking functionality (ABS, RSP) and a potentially dangerous condition of the vehicle when emergency brake actuations or braking in non-optimal conditions is required. GB2557424 discloses a known braking system in which a commercial vehicle electronic braking and communication system for a trailer has a connector to connect the system to a prime mover. The connector comprises an electronic control module with a first ISO7638 compliant databus connection, which carries braking related data signals and to which a brake pressure control device is attached. The connector also comprises a second databus ISO12098 compliant connection, which carries data relating to non-braking functions, such as lighting, camera, object detection (radar, lidar, ultrasonic). The trailer braking and communication system may act as a combined brake, brake and chassis control, lighting and autonomous driving controller. EPl538054 discloses a brake system with a service brake unit with a first brake circuit, and a parking brake unit with a second circuit, for wheels on an axle. A control device prevents locking of at least one wheel due to a pressure drop in the second circuit, while the vehicle is in motion. The device acts on a shuttle valve with an input, which is connected to an output of the first brake circuit on one side of the vehicle only, and to all outputs of the second circuit. The speed of the wheels is measured by a speed sensor on at least one wheel, or by two sensors on two wheels of the same axle. A further known trailer braking system is disclosed in GB2505948. GB2583533 discloses a trailer brake system with two pneumatic supply circuits, which system comprises a service brake system, and spring brake system, in which the pressure to the spring brakes is controlled by a second ECU and a spring brake modulator valve arrangement. The spring brake modulator valve arrangement comprises a back up valve, and so the valve arrangement is capable of increasing and reducing the pressure in the spring brake system regardless of the pneumatic control pressure of the spring brake modulator, providing brake function redundancy for most of the possible brake system malfunctions. The approach in GB2583533 is comprehensive but may be too expensive for certain markets The present invention aims to provide a brake control arrangement which remains available with a range of electric malfunctions in the brake system. According to the invention there is provided a trailer braking system in accordance with the characteristics of Claim 1. Preferred aspects of the invention can be found in the sub-claims. The invention advantageously makes use of the spring brake portion that is already installed in standard vehicles, or additionally installed spring brake portions, to provide redundancy in the brake system. The brake force is controlled by modulation of the air pressure in spring brake portion of the brake system using a valve arrangement. The invention advantageously makes use of the spring brake portion that is already installed in standard vehicles to provide redundant, side by side control in the brake system. The spring brake modulator valve arrangement is thereby controllable to provide brake and stability management using the spring brake modulator valve arrangement. In contrast to known solutions in the present invention the simplified spring brake control valve arrangement does not include a back up valve. The valve arrangement can therefore control the pressure in the spring brake system between zero (0) and the pneumatic control pressure of the spring brake modulator. Although the functionality of the system is reduced compared to the prior art, the redundancy and availability of the brake system is still ensured for the most likely electric malfunctions. Exemplary embodiments of the invention, in which like parts are described with like numbers, will now be described in greater detail in which: Fig. 1 shows a first embodiment of a trailer brake system with redundancy; Fig. 2 shows a second embodiment of a trailer brake system; Fig. 3 shows a single channel spring brake modulator Fig. 4 shows a two channel spring brake modulator; Fig. 5 shows a two channel spring brake modulator with pressure sensors; Fig. 6 shows a two channel spring brake modulator with pressure sensors, and relay valves; Fig. 7 shows a two channel spring brake modulator with pressure sensors, relay valves, and integrated ECU. Figure 1 shows a block diagram of a redundant trailer brake system comprising a first pneumatic connection 1 for service braking (red line) connected to a park and release valve 2, which controls air flow in use into a reservoir 3, another and a further output to a relay emergency valve 4. The park and release valve 2 provide the park brake control. The trailer brake system further comprises a second pneumatic connection 8 for control (yellow line), which is connected to the relay emergency valve 4, the output of which is connected to the trailer brake module 6 via a 3 / 2 cut off solenoid valve 5, which is used to shut down pneumatic functionality of the trailer brake module by cutting of control line pressure to the trailer brake module. The system is further provided with first and second communication bus connections 50, 51 towards the towing vehicle connected to main ECU 7 and ECU 17, respectively. It will be appreciated that the first electrical connection 9 and the first communication bus 50 may be combined in a single electrical connector such as the ISO7638 and the second electrical connection 10 and the second communication bus 51 may be combined in a single electrical connector such as the ISO12098. The main ECU 7 provides power management of the first and second electrical connection 9, 10 and provides two local trailer power circuits 13, 14 where circuit-2 14 provides power to the primary brake control module 6. The main ECU 7 additionally provides first and second local communication circuits 15, 16 and is the gateway between the local buses and first and second communication buses. The ECU 7 is operatively connected to the cut off valve 5 to provide the necessary control signals. The trailer brake module 6 receives a first pneumatic inputs from the reservoir, which input is connected to a respective relay valve 18,19 and a respective 22 solenoid load valve 20,21. The said pneumatic connection is provided with a respective pressure transducer 22, which is electrically connected to the main ECU 17. A further transducer is provided on the control line input, which transducer is connected to the main ECU 17. On each of the two brake channels a respective further two 2 / 2 solenoid backup valve 24,25 load valves 20, 21 and exhaust valve 26,27 are provided. The solenoid valves 20, 21, 24, 25, 26, 27 pilot the two relay valves 18,19, the outputs of which are supplied to ports 21 22 to provide the pressure to the trailer brakes. A respective transducer 28,29 is provided in the pneumatic pathway from the relay valve to the brake channels, with the transducer electrical signals being connected to the ECU 17. Each of the back-up, load and exhaust valves is controlled from the ECU 17 by way of respective electrical connections. In the illustrated embodiment the trailer is provided with three axles having a respective brake 33-38 on each wheel end. Axles 2 and 3 (the two rear axles) are each provided with a spring brake, which is pneumatically connected via the spring brake modulator valve 50 to the output of the anti compounding valve 30, so that the spring brakes can be independently controlled. A wheel speed sensor is associated with each wheel end, the output of which for axle 3 is passed to the main ECU 7, axles 1 and 2 are passed to the primary trailer brake module ECU 17. The reservoir is in fluid connection with the spring brake modulator valve arrangement 60 shown here schematically. Control of the flow of air to the spring brakes can be made either by the trailer brake module or by the spring brake control module, which is configured to receive electrical signals from the main ECU 7. In the event of a failure, the ECU 7 can close off control line input to the trailer brake module 6 by means of the cut off valve 5 so as to prevent the pneumatic output. For instance in case of an electronic fault in the trailer brake module this is important as the output pressure to the service brake cannot be reduced, so that e.g. ABS control would not be possible. As the ECU 7 integrates or processes all necessary brake system relevant sensor input (e.g. acceleration, wheel speeds) it can perform brake and stability management using the spring brake modulator valve 60, which provides a redundancy mode in the system. With this mode all of the faults outlined above brake functionality can be maintained as the vehicle still has full graduable brake and stability functionality. The brakes do not have to be applied via emergency function in case of a single pneumatic failure. Instead the safety of the vehicle is ensured. The emergency functionality can be provided in case of two severe failures, as a second level of redundancy. Figure 2 shows a further alternative embodiment, in which all three axles are provided with spring brakes and the spring brake modulator valve is connected to each of the six spring brakes. The trailer brake system further comprises a second pneumatic connection 8 for control (yellow line), which is connected to the primary trailer brake module 6. The spring brake modulator valve (SBMV) comprises one or more relay valves and therefore has a supply input pneumatically connected to a second reservoir with the control pressure being provided under the control of the park and release valve 2. The relay emergency function and the anti-compounding valve in this embodiment is integrated as a valve arrangement (REV+AC) 30 into the main trailer brake module. A wheel speed sensor is associated with each wheel end, the output of which is passed to the ECU 17 as well as the ECU 7. Figure 3 shows a single channel spring brake modulator valve in which the PCV valve arrangement can control the output pressure (21, 22) between zero and the input pressure (4). In this embodiment of the spring brake modulator valve, electronically wheel speed controlled braking as well as single Channel ABS and RSP is possible in redundancy mode. Figure 4 show a two channel variant of the spring brake modulator valve in which the two PCV valve arrangements, each receiving the control pressure 4, can control the output pressure (21, 22) independently between zero(O) and the input pressure (4). Each PCV valve arrangement is connected to the exhaust. In this embodiment electronically wheel speed controlled braking as well as 2-Channel ABS and RSP is possible in redundancy mode Figure 5 shows a two channel spring brake modulator valve with pressure sensors. It would be possible to implement a similar arrangement in a single channel arrangement. In this embodiment pressure sensors 63,64 are provided in the output channels 21, 22. This enables the measurement of the output pressure and to provide a feedback or target value for a pressure control loop. In this embodiment electronically and load dependent controlled braking as well as 2-Channel ABS and RSP is possible in redundancy mode. Figure 6 shows a two channel spring brake modulator with pressure sensors and relay valves 65,66, which receive an input pressure (11) from a brake air reservoir and a control pressure (4) from the output of the anti compounding valve (AC 30 or REV+AC 30). This could also be implemented in a single channel embodiment. In normal operation, the input port 4 is connected to the control portion of the relay valve that then in turn uses input from port 11 and the exhaust port to regulate output pressure for ports 21 and 22 respectively, which are connected to the brakes. The advantage of using the relay valves is that control of the spring brakes and the large masses of air associated with that can be performed much faster than without relay valves. With this embodiment electronically and load dependent controlled braking as well as accurate 2-Channel ABS and RSP is possible in redundancy mode. Figure 7 shows a two channel spring brake modulator valve with pressure sensors, relay valves and integrated control. The provision of the integrated control simplifies the wiring harness as fewer electrical connections are required. The integrated ECU 68 provides a simpler interface to the main ECU and integrates the pressure control logic. It can also provide wheel-speed sensor input thereby simplifying the vehicle wiring further. With this embodiment electronically and load dependent controlled braking as well as even more accurate 2-Channel ABS and RSP is possible in redundancy mode. Trailer in the context of the invention is a trailer of category 03 or 04, that is trailers over 3.5 tonnes. At this time, the standards in force are ISO 1185:2003 ISO 7638-1 / 2:2018, ISO 11992:2021, 18012098:2020 and SAE 560:2020. The invention has particular application in highly autonomous trailers.

Claims

1. A brake system for a trailer vehicle having a plurality of axles, each of which axles has a wheel end on a respective side of the vehicle, the brake system comprising one or more pneumatic circuits for supplying air pressure to brake devices at the wheel ends, the air pressure to the wheel ends being controllable by means of a trailer brake module having a first brake ECU being part of a trailer brake module, characterised in thatthe system further comprises a park brake control and a spring brake modulator valve arrangement adapted to control pressure to spring brakes on the vehicle, which modulator valve arrangement receives a control pressure from the park brake control or through an anti compounding valve, wherein flow of air to the brakes is controllable either by the trailer brake module or control of the anti-compounding valve, to thereby control the pressure in the spring brake system between zero (0) and the pneumatic control pressure of the spring brake modulator.

2. A brake system according to Claim 1, wherein the spring brake modulator valve arrangement is configured to receive electrical signals from a second ECU independently operable from the first brake ECU.

3. A brake system according to Claim 1 or Claim 2, wherein the spring brake modulator valve further comprises an additional pressure control block to enable a separation of outputs to thereby provide two channel brake control.

4. A brake system according to any one of Claims 1 to 3, wherein at least one pressure sensor is provided in an output channel of the spring brake modulator valve to enable the measurement of the output pressure to thereby provide a feedback or target value for a pressure control loop.

5. A brake system according to any one of Claims 2 to 4, wherein the spring brake modulator comprises a relay valve, which relay valve receives an inputpressure from the pressure supply line and a control pressure from the pressure control block.

6. A brake system according to any one of Claims 2 to 5, wherein the system has an integrated ECU to directly control the solenoid valves.

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