Braking system for a commercial vehicle, commercial vehicle and method for operating the braking system

Abstract

Braking system (2) for a commercial vehicle (1), the braking system (2) comprising: an electronic brake control unit (28), a pneumatic parking brake circuit (24) with at least one spring-loaded cylinder (16, 17, 29, 30), a parking brake valve (26) designed to control a parking brake pressure in the parking brake circuit (24), and at least one 3 / 3-way valve (11) arranged in a pneumatic line of the parking brake circuit (24) between the parking brake valve (26) and at least one of the spring-loaded cylinders (16, 17, 29, 30), where the 3 / 3-way valve (11) can be controlled by the electronic brake control unit (28), and the 3 / 3-way valve (11) is designed to vent the pneumatic line between the 3 / 3-way valve (11) and at least one of the spring-loaded cylinders (16, 17, 29, 30) to a predetermined pressure in order to cause the at least one of the spring-loaded cylinders (16, 17, 29, 30) to engage a brake (18, 19, 20, 21) associated with the spring-loaded cylinder (16, 17, 29, 30).

Description

[0001] The invention relates to a braking system for a commercial vehicle, a commercial vehicle and a method for operating the braking system, in particular for electronic braking systems.

[0002] To enable a vehicle to be decelerated in the event of a braking system component failure, various service brake redundancy concepts exist. Redundancy is primarily implemented at the control level using mechatronic components.

[0003] In today's ECE R13 compliant systems, the backup circuits are designed with two pneumatic circuits and must still provide an auxiliary braking effect in the range of 2 - 2.6 m / s in the event of a failure of one pneumatic circuit. 2Such failures can be caused, for example, by a defect in a pneumatic circuit supply line, such as to a pressure vessel or an electro-pneumatic module, a defective pressure vessel, a defective compressed air line between the electro-pneumatic module and a brake cylinder, or a defective diaphragm in the brake cylinder. For safety reasons, a multi-circuit protection valve is typically provided so that a certain safety pressure, with which the legally required auxiliary braking effect can be achieved, remains in intact circuits even though the pressure in the defective circuit is lost.

[0004] However, in driverless, highly automated vehicles with an SAE automation level 4 or higher, the highest possible deceleration of, for example, 4 m / s should be achieved even in the event of a supply circuit failure. 2However, this is not always possible with just one intact pneumatic circuit. One option would therefore be to provide another pneumatic circuit as an additional fallback. However, this would entail additional effort and high additional costs, including for the installation and piping of the braking system.

[0005] Document DE 10 2019 103 901 A1 discloses a braking system with a pneumatic parking brake circuit with a spring-loaded cylinder for a commercial vehicle. A parking brake valve controls the parking brake pressure in the parking brake circuit, and two 2 / 2-way valves, each controlled by a 3 / 2-way valve, vent a pneumatic line to a predetermined pressure. The line is connected to both of the 3 / 2-way valves on the one hand and to the spring-loaded cylinder on the other hand, in order to engage an associated brake via the spring-loaded cylinder.

[0006] The publication CN 105 905 087 A also provides for two 2 / 2-way valves between a relay valve as a parking brake valve and the spring-loaded cylinders.

[0007] In DE 10 2013 107 503 A1, a valve unit with either a 3 / 2-way valve or two 2 / 2-way valves is provided between a valve unit with a parking brake control unit in order to be able to carry out a stretch braking of a trailer.

[0008] The invention is based on the object of providing a braking system, a commercial vehicle, and a method for operating the braking system that eliminates the above-mentioned disadvantages. The invention provides a braking system, a commercial vehicle, and a method that cost-effectively ensures safe operation when braking, even in a driverless, highly automated vehicle with correspondingly high deceleration, even in the event of a pneumatic circuit failure.

[0009] The object is achieved by a braking system according to claim 1, a commercial vehicle according to claim 15, and a method according to claim 16. Advantageous further developments are contained in the dependent claims.

[0010] According to one aspect of the invention, a braking system for a commercial vehicle comprises an electronic brake control unit, a pneumatic parking brake circuit with at least one spring-loaded cylinder and a parking brake valve configured to control a parking brake pressure in the parking brake circuit, and at least one 3 / 3-way valve arranged in a pneumatic line of the parking brake circuit between the parking brake valve or an intermediate parking brake relay valve and at least one of the spring-loaded cylinders. The 3 / 3-way valve is controllable by the electronic brake control unit and is configured to vent the pneumatic line between the 3 / 3-way valve and the at least one of the spring-loaded cylinders to a predetermined pressure in order to cause the at least one of the spring-loaded cylinders to engage a brake associated with the spring-loaded cylinder.

[0011] This braking system enables the use of an existing parking brake circuit to support a service brake of the commercial vehicle in the event of a pneumatic brake circuit failure, controlled by the electronic brake control unit, so that the provision of an additional pneumatic backup circuit is not necessary.

[0012] In an advantageous embodiment of the braking system, the 3 / 3-way valve is designed as a pressure control valve, wherein the predetermined pressure can not only be reduced to a fixed pressure, for example an ambient pressure, but can also be regulated and maintained at another suitable pressure under appropriate boundary conditions.

[0013] In a further advantageous embodiment of the braking system, the 3 / 3-way valve is designed to be controllable by the electronic brake control unit so that it functions as an ABS valve.

[0014] Such a 3 / 3-way valve enables the function of the braking system, which is enabled by an ABS system integrated in the braking system during normal operation, to be maintained even in an emergency situation, such as the failure of a service brake circuit.

[0015] In an advantageous embodiment of the braking system, it has at least one service brake circuit, each with at least one service brake cylinder, wherein one of the at least one service brake cylinder is designed to engage the brake assigned to the spring brake.

[0016] This makes it possible, in the event of a service brake circuit failure, to actuate the brake, which is equipped with a spring-loaded cylinder for a parking brake, via the parking brake circuit without the need for additional pneumatic installation work.

[0017] In a further advantageous embodiment of the braking system, the service brake cylinder and the spring-loaded cylinder are designed integrally as a combined brake cylinder.

[0018] The combination brake cylinder allows the assigned brake to be engaged both via control through the service brake circuit and via control through the parking brake circuit, thus saving installation space and costs.

[0019] In an advantageous embodiment of the braking system, the parking brake circuit has two spring-loaded cylinders and a single 3 / 3-way valve, the braking system has at least two service brake circuits, one of the service brake circuits has two service brake cylinders, the two service brake cylinders are designed to engage the brakes assigned to the two spring-loaded cylinders, the 3 / 3-way valve is arranged in the pneumatic line between the parking brake valve and the two spring-loaded cylinders and the 3 / 3-way valve is designed to cause the two spring-loaded cylinders to engage the brakes assigned to the two spring-loaded cylinders.

[0020] This makes it possible, in the event of a service brake circuit failing, which, for example, acts on a rear axle equipped with spring-loaded cylinders for a parking brake, to replace this failure of the braking effect of the service brake on the rear axle with the parking brake circuit without the need for additional pneumatic installation work.

[0021] Through another advantageous embodiment of the braking system, the parking brake circuit has two spring-loaded cylinders and two 3 / 3-way valves, the two 3 / 3-way valves are arranged in the pneumatic line between the parking brake valve and one of the spring-loaded cylinders each, the braking system has at least two service brake circuits, one of the service brake circuits has two service brake cylinders, the two service brake cylinders are designed to allow the brakes assigned to the two spring-loaded cylinders to engage and the two 3 / 3-way valves are designed to cause the two spring-loaded cylinders each to allow the brake assigned to the spring-loaded cylinders to engage individually and independently of one another.

[0022] This design makes it possible to control the brakes of a brake circuit differently even in an emergency, so that, especially when ABS control is provided, safe operation without locking of the wheels is still possible.

[0023] In another advantageous embodiment of the braking system, the parking brake circuit has four spring-loaded cylinders and four 3 / 3-way valves, the four 3 / 3-way valves are arranged in the pneumatic line between the parking brake valve and one of the spring-loaded cylinders each, the braking system has at least two service brake circuits, two of the service brake circuits each have two service brake cylinders, the two service brake cylinders are designed to engage the brakes assigned to the four spring-loaded cylinders and the four 3 / 3-way valves are designed to cause the four spring-loaded cylinders to each engage the brake assigned to the respective spring-loaded cylinder individually and independently of one another.

[0024] This design improves safety because, in the event of a service brake circuit failure, several brakes can still be controlled individually and independently of one another via the 3 / 3-way valve.

[0025] In a further advantageous embodiment of the braking system, it comprises a trailer control valve configured to control pneumatic brakes of a trailer of the commercial vehicle, and a further 3 / 3-way valve arranged in a pneumatic line between a parking brake actuation element and the trailer control valve. The further 3 / 3-way valve can be controlled by the electronic brake control unit and is configured to vent the pneumatic line between the 3 / 3-way valve and the trailer control valve to a predetermined pressure.

[0026] This configuration also makes it possible to brake the trailer's brakes in the event of a brake circuit failure, without requiring additional pneumatic installation work.

[0027] In an advantageous embodiment of the braking system, the further 3 / 3-way valve is designed as a further pressure control valve, wherein the predetermined pressure can not only be reduced to a fixed pressure, for example an ambient pressure, but can also be regulated to a suitable pressure under appropriate boundary conditions.

[0028] In a further advantageous embodiment of the brake system, the further pressure control valve is designed to be controllable by the electronic brake control unit in such a way that it functions as an ABS valve.

[0029] Such an additional pressure control valve enables the function of the braking system, which is enabled by an ABS system integrated in the braking system during normal operation, to be maintained even in an emergency situation, such as the failure of a service brake circuit of the trailer.

[0030] In a further advantageous embodiment of the braking system, the braking system has an air treatment unit and / or an electric parking brake and / or a further control unit and control elements of the electronic brake control unit for the 3 / 3-way valve are integrated into a control unit of the air treatment unit and / or the electric parking brake and / or in the further control unit.

[0031] This configuration enables even more cost-effective provision of security functions.

[0032] According to a further aspect of the invention, a commercial vehicle has such a braking system.

[0033] According to yet another aspect of the invention, a method for operating the brake system is provided, comprising the steps of: releasing the brake assigned to the spring-loaded cylinder by actuating the parking brake valve and increasing the pressure in the parking brake circuit, detecting a failure of a function of a service brake circuit by the electronic brake control unit, and actuating the at least one 3 / 3-way valve to vent the pneumatic line between the at least one 3 / 3-way valve and the spring-loaded cylinder to a predetermined pressure in order to engage the brake assigned to the spring-loaded cylinder.

[0034] This method makes it possible to use an existing parking brake circuit to support a service brake of the commercial vehicle in the event of a service brake circuit failure, controlled by the electronic brake control unit.

[0035] In an advantageous embodiment of the method, it includes the steps of: detecting a locking of a wheel of the commercial vehicle and setting the predetermined pressure in the pneumatic line between the 3 / 3-way valve and the spring-loaded cylinder so that locking of the wheel is no longer detected.

[0036] These steps ensure that the function enabled by the ABS system during normal operation of the braking system can be maintained even in an emergency situation, such as the failure of a service brake circuit.

[0037] In a further advantageous embodiment of the method, it includes the additional step of controlling the at least one 3 / 3-way valve and venting the pneumatic line between the at least one 3 / 3-way valve and the trailer control valve to a predetermined pressure in order to engage the brake of the trailer assigned to a trailer spring-loaded cylinder.

[0038] This procedure also makes it possible to cause the trailer to brake in the event of a failure of its service brake circuit, without the need for increased pneumatic installation work.

[0039] The invention is explained below using exemplary embodiments with reference to the accompanying drawings.

[0040] In particular, it shows: Fig. 1 shows in principle a commercial vehicle with a braking system according to a first embodiment; Fig. 2 the braking system of the commercial vehicle, according to a second embodiment; Fig. 3 the braking system of the commercial vehicle, according to a third embodiment; and Fig. 4 the braking system of the commercial vehicle, according to a fourth embodiment.

[0041] Fig. 1 shows in principle a commercial vehicle 1 with a braking system 2 according to a first embodiment of the invention.

[0042] The braking system 2 comprises a compressor 3, an air treatment unit 4, and several pressure vessels 5, 5', 5". Furthermore, the braking system 2 comprises a foot brake module 6 and pressure control modules 7, 8. Furthermore, the braking system 2 comprises so-called 3 / 3 valves 9, 10, 11 and service brake cylinders 12, 13, 14, 15 as well as spring-loaded cylinders 16, 17, each of which is assigned a brake 18, 19, 20, 21. The spring-loaded cylinders 16, 17 are each constructed integrally with the service brake cylinders 14, 15 as so-called combination brake cylinders. Alternatively, separate components can also be provided.

[0043] The compressor 3 provides compressed air at a suitable pressure, which is processed in the air processing device 4, i.e., filtered and dehumidified. The compressed air is then conveyed to the pressure vessels 5, 5', 5", each forming a compressed air reservoir there. The pressure vessel 5 is contained in a first pneumatic service brake circuit 22, and the pressure vessel 5' is contained in a second pneumatic service brake circuit 23. The pressure vessel 5" forms the compressed air reservoir for both a pneumatic parking brake circuit 24 and a pneumatic trailer brake circuit 25. In alternative embodiments, the first pneumatic service brake circuit 22 and the second pneumatic service brake circuit 23 are not provided, but rather at least one service brake circuit or more than two service brake circuits, which can also be designed redundantly. Furthermore, in an alternative embodiment, the trailer brake circuit 25 is not provided.

[0044] The pneumatic parking brake circuit 24 includes a parking brake actuating element in the form of a parking brake valve 26 and a parking brake relay valve 27. For the parking brake to function, the parking brake relay valve 27, actuated by the parking brake valve 26, controls the parking brake pressure such that a pneumatic line between the parking brake relay valve 27 and the spring-loaded cylinders 16, 17 is depressurized or contains only a small amount of parking brake pressure. The spring-loaded cylinders 16, 17 function such that, when actuated without pressure, they exert a force on the respective associated brakes 20, 21 to brake the commercial vehicle 1.If there is a parking brake pressure in the pneumatic line between the parking brake relay valve 27 and the spring-loaded cylinders 16, 17 that is sufficiently increased above a threshold value and is controlled by the parking brake relay valve 27 via the parking brake actuating element 26, the spring-loaded cylinders 16, 17 release the respective associated brakes 20, 21. In alternative embodiments, the parking brake relay valve 27 is not provided, but the parking brake is controlled directly via the parking brake valve 26.

[0045] A pressure of the compressed air in the first service brake circuit 22 is provided by the compressor 3 via the compressed air preparation unit 4 and the pressure vessel 5, according to a position of the foot brake module 6, passed on to the service brake cylinders 14, 15 of the brakes 20, 21 on a rear axle of the commercial vehicle 1 in order to activate the brakes 20, 21 respectively assigned to the spring-loaded cylinders 16, 17 when the pressure increases and to engage the brakes 20, 21 according to the pressure or to release them when the pressure decreases or to reduce a braking force.In the second service brake circuit 23, the pressure of the compressed air provided in an analogous manner is passed on from the pressure vessel 5' according to the position of the foot brake module 6 to the service brake cylinders 12, 13 of the brakes 18, 19 on a front axle of the commercial vehicle 1 in order to activate the brakes 18, 19 when the pressure increases according to the pressure and to engage the brakes 20, 21 or to release them when the pressure decreases or to reduce the braking force. In alternative embodiments, in the service brake circuits 22, 23 either only a single brake 18, 19, 20, 21 with a single service brake cylinder 12, 13, 14, 15 is provided or more than two brakes 18, 19, 20, 21 and thus more than two service brake cylinders 12, 13, 14, 15 can be provided.

[0046] The braking system 2 further includes an electronic brake control unit 28. The brake control unit 28 is connected to the foot brake module 6, the pressure control modules 7, 8, and the 3 / 3-way valve 11 and, among other things, controls the corresponding pressures in the brake circuits.

[0047] The valve functioning as an ABS valve is a 3 / 3-way valve 11 designed as a pressure control valve. In alternative embodiments, the 3 / 3-way valve 11 does not function as an ABS valve or is not designed as a pressure control valve, but rather as a pure on / off valve.

[0048] The 3 / 3-way valve 11 is arranged in the pneumatic line of the parking brake circuit 24 between the parking brake relay valve 27 and the spring brake cylinders 16, 17 and can be controlled by the electronic brake control unit 28. In the alternative embodiment without the parking brake relay valve 26, the 3 / 3-way valve 11 is arranged between the parking brake valve 26 and the spring brake cylinders 16, 17. The 3 / 3-way valve 11 can vent the pneumatic line between the 3 / 3-way valve 11 and the spring brake cylinders 16, 17 to a predetermined pressure in order to cause the spring brake cylinders 16, 17 to engage a brake 20, 21 assigned to the spring brake cylinders 16, 17 and exert a braking effect.In the case of a 3 / 3-way valve 11 that is not designed as a pressure control valve, the predetermined pressure can be ambient pressure or, particularly when the 3 / 3-way valve functions as the ABS valve, for example, a pressure that prevents a wheel of the commercial vehicle from locking but still achieves a sufficient braking effect. Such a pressure is typically applied in a pulsating manner. For this purpose, sensors for detecting a wheel speed and an evaluation unit for determining whether the wheel is locking are provided in the commercial vehicle 1. A signal regarding locking or non-locking is then converted accordingly by the electronic brake control unit 28.

[0049] Fig. 2 shows the braking system 2 according to a second embodiment. The braking system 2 according to the second embodiment differs from the braking system 2 according to the first embodiment in that, instead of a single 3 / 3-way valve 11 arranged in the pneumatic line between the parking brake relay valve 27 and the spring-loaded cylinders 16, 17, two 3 / 3-way valves 11, 11' are provided, each arranged between the parking brake relay valve 27 and one of the spring-loaded cylinders 16, 17. The 3 / 3-way valve 11' is also connected to the electronic brake control unit 28. By providing the two 3 / 3-way valves, the two brakes 20, 21 can be controlled individually and independently of one another.

[0050] Fig. 3 shows the braking system 2 according to a third embodiment. The braking system 2 according to the third embodiment differs from the braking system 2 according to the second embodiment in that spring-loaded cylinders 29, 30 are also provided on the front axle, namely on the brakes 18, 19. These spring-loaded cylinders 29, 30 are shown integrally with the service brake cylinders 12, 13 as combined brake cylinders, but can alternatively also be separate components. In this embodiment, the two 3 / 3-way valves 11", 11''' are arranged in the pneumatic line between the spring-loaded cylinders 29, 30 and the parking brake relay valve 27, so that a total of four 3 / 3-way valves 11, 11', 11'', 11''' are arranged between the parking brake relay valve 27 and the respective spring-loaded cylinder 16, 17, 29, 30.The 3 / 3-way valves 11'', 11''' are also connected to the brake control unit 28 and have the same function as the 3 / 3-way valves 11, 11' described in connection with the second embodiment.

[0051] Fig. Figure 4 shows the braking system 2 according to a fourth embodiment. The braking system 2 according to the fourth embodiment differs from the braking system 2 according to the third embodiment in that an additional 3 / 3-way valve 11"" is provided in the trailer brake circuit 25 between a trailer control valve 33 and the parking brake valve 26. The additional 3 / 3-way valve 11"" is also connected to the brake control unit 28 and is controlled thereby.

[0052] The function of this additional 3 / 3-way valve 11'''' is analogous to that of the 3 / 3-way valves 11, 11', 11'', 11'''. In the event of a failure of the trailer brake circuit 25, the additional 3 / 3-way valve 11'''' is controlled by the brake control unit 28 such that the pressure in the trailer brake circuit 25 is reduced, thus venting the pneumatic line between the additional 3 / 3-way valve 11'''' and the trailer control valve 33 to a predetermined pressure, and thereby causing a trailer spring-loaded cylinder of the trailer to engage the brake assigned to it.

[0053] The valve functioning as an additional ABS valve is also an additional 3 / 3-way valve 11'''', which is designed as an additional pressure control valve. In alternative embodiments, the additional 3 / 3-way valve 11'''' does not function as an additional ABS valve or is not designed as an additional pressure control valve.

[0054] The brake control unit 28, and thus its control elements for the 3 / 3-way valve, is according to the Fig. 1 to 4 as a separate component. In alternative embodiments, the control elements for the 3 / 3-way valve can also be integrated into a control unit of the compressed air treatment device 4, into a control unit of an electric parking brake, or into another control unit.

[0055] During operation, the parking brake is released to drive the commercial vehicle 1. For this purpose, the parking brake relay valve 27 is controlled by the parking brake valve 26 so that the pressure in the parking brake circuit 25 is increased to such an extent that the spring-loaded cylinders 16, 17 and, if applicable, the spring-loaded cylinders 29, 30 and the trailer spring-loaded cylinder release the respective associated brakes 18, 19, 20, 21.

[0056] If the brake control unit 28 detects a functional failure of a service brake circuit 22, 23, and possibly of the trailer brake circuit 25, the 3 / 3-way valve(s) 11, 11', 11'', 11''' are activated upon a braking request from the foot brake module 6, so that the pneumatic line between the 3 / 3-way valve 11, 11', 11'', 11''' and the spring-loaded cylinders 16, 17, 29, 30 is vented to a predetermined pressure in order to engage the brakes 12, 13, 14, 15 assigned to the spring-loaded cylinders 16, 17, 29, 30. The predetermined pressure can be controlled according to the braking request.

[0057] If necessary, a locking of a wheel of the commercial vehicle 1 is detected and the predetermined pressure in the pneumatic line between the 3 / 3-way valve 11, 11', 11'', 11''' is adjusted so that just no more locking of the wheel is detected.

[0058] If provided, in the event of a failure of the trailer brake circuit 25, the 3 / 3-way valve 11"" between the parking brake valve 26 and the trailer control valve 33 is activated, and the pneumatic line between the 3 / 3-way valve 11 and the trailer control valve 33 is vented to a predetermined pressure to engage the trailer brake assigned to the trailer spring-loaded cylinder. This is achieved by controlling an output of the trailer control valve 33 to a predetermined pressure or depressurizing it.

[0059] All features presented in the description, the following claims and the drawings may be essential to the invention both individually and in any combination with one another. LIST OF REFERENCE SYMBOLS 1 commercial vehicle 2 braking system 3 Compressor 4 Compressed air treatment unit 5, 5', 5'' pressure vessel 6 Foot brake module 7 Pressure control module 8 Pressure control module 9 ABS valve 10 ABS valve 11, 11', 11'', 11''', 11'''' 3 / 3-way valve 12 service brake cylinders 13 service brake cylinders 14 service brake cylinders 15 service brake cylinders 16 spring-loaded cylinders 17 spring-loaded cylinders 18 Brake 19 Brake 20 Brake 21 Brake 22 first service brake circuit 23 second service brake circuit 24 Parking brake circuit 25 Trailer brake circuit 26 Parking brake valve 27 Parking brake relay valve 28 electronic brake control unit 29 spring-loaded cylinders 30 spring-loaded cylinders 31 Trailer control valve

Claims

[1] Braking system (2) for a commercial vehicle (1), the braking system (2) comprising: an electronic brake control unit (28), a pneumatic parking brake circuit (24) with at least one spring-loaded cylinder (16, 17, 29, 30), a parking brake valve (26) designed to control a parking brake pressure in the parking brake circuit (24), and at least one 3 / 3-way valve (11) arranged in a pneumatic line of the parking brake circuit (24) between the parking brake valve (26) and at least one of the spring-loaded cylinders (16, 17, 29, 30), where the 3 / 3-way valve (11) can be controlled by the electronic brake control unit (28), and the 3 / 3-way valve (11) is designed to vent the pneumatic line between the 3 / 3-way valve (11) and at least one of the spring-loaded cylinders (16, 17, 29, 30) to a predetermined pressure in order to cause the at least one of the spring-loaded cylinders (16, 17, 29, 30) to engage a brake (18, 19, 20, 21) associated with the spring-loaded cylinder (16, 17, 29, 30). [2] Brake system (2) according to claim 1, wherein the 3 / 3-way valve is designed as a pressure control valve. [3] Brake system (2) according to one of the preceding claims, wherein the 3 / 3-way valve (11) is designed to be controllable by the electronic brake control unit (28) so that it functions as an ABS valve. [4] Brake system (2) according to one of the preceding claims, wherein the brake system (2) has at least one service brake circuit (22, 23) each having at least one service brake cylinder (12, 13, 14, 15), wherein one of the at least one service brake cylinder (12, 13, 14, 15) is designed to engage the brake (18, 19, 20, 21) associated with the spring-loaded cylinder (16, 17, 29, 30). [5] Brake system (2) according to claim 4, wherein the service brake cylinder (12, 13, 14, 15) and the spring-loaded cylinder (16, 17, 29, 30) are integrally formed as a combination brake cylinder. [6] Brake system (2) according to claim 5 or 6, wherein the parking brake circuit (24) has two spring-loaded cylinders (16, 17, 29, 30) and a single 3 / 3-way valve (11), the brake system (2) has at least two service brake circuits (22, 23), one of the service brake circuits (22, 23) has two service brake cylinders (12, 13, 14, 15), and the two service brake cylinders (12, 13, 14, 15) are designed to engage the brakes assigned to the two spring-loaded cylinders (16, 17, 29, 30), the 3 / 3-way valve (11) is arranged in the pneumatic line between the parking brake valve (26) and the two spring-loaded cylinders (16, 17, 29, 30), and the 3 / 3-way valve (11) is designed to cause the two spring-loaded cylinders (16, 17, 29, 30) to engage the brakes (18, 19, 20, 21) associated with the two spring-loaded cylinders (16, 17, 29, 30). [7] Brake system (2) according to claim 4 or 5, wherein the parking brake circuit (24) has two spring-loaded cylinders (16, 17, 29, 30) and two 3 / 3-way valves (11, 11'), the two 3 / 3-way valves (11, 11') are arranged in the pneumatic line between the parking brake valve (26) and one of the spring-loaded cylinders (16, 17, 29, 30), the brake system (2) has at least two service brake circuits (22, 23), one of the service brake circuits (22, 23) has two service brake cylinders (12, 13, 14, 15), the two service brake cylinders (12, 13, 14, 15) are designed to engage the brakes (18, 19, 20, 21) associated with the two spring-loaded cylinders (16, 17, 29, 30), and the two 3 / 3-way valves (11, 11') are designed to cause the two spring-loaded cylinders (16, 17, 29, 30) to each cause the brake (18, 19, 20, 21) associated with the respective spring-loaded cylinder (16, 17, 29, 30) to engage individually and independently of one another. [8] Brake system (2) according to claim 4 or 5, wherein the parking brake circuit (24) has four spring-loaded cylinders (16, 17, 29, 30) and four 3 / 3-way valves (11, 11', 11'', 11'''), the four 3 / 3-way valves (11, 11', 11'', 11''') are arranged in the pneumatic line between the parking brake valve (26) and one of the spring-loaded cylinders (16, 17, 29, 30), the brake system (2) has at least two service brake circuits (22, 23), two of the service brake circuits (22, 23) each have two service brake cylinders (12, 13, 14, 15), the two service brake cylinders (12, 13, 14, 15) are designed to engage the brakes (18, 19, 20, 21) associated with the four spring-loaded cylinders (16, 17, 29, 30), and the four 3 / 3-way valves (11, 11', 11'', 11''') are designed to cause the four spring-loaded cylinders to engage the brake (18, 19, 20, 21) assigned to the respective spring-loaded cylinder (16, 17, 29, 30) individually and independently of one another. [9] Braking system (2) according to one of the preceding claims, wherein the braking system (2) further comprises: a trailer control valve (31) designed to control pneumatic brakes of a trailer of the commercial vehicle (1), and a further 3 / 3-way valve (11'''') arranged in a pneumatic line between a parking brake actuating element (26) and the trailer control valve (31), wherein the further 3 / 3-way valve (11'''') can be controlled by the electronic brake control unit (28), and the further 3 / 3-way valve (11'''') is designed to vent the pneumatic line between the 3 / 3-way valve (11'''') and the trailer control valve (31) to a predetermined pressure. [10] Brake system (2) according to claim 9, wherein the further 3 / 3-way valve (11'''') is designed as a further pressure control valve. [11] Brake system (2) according to claim 10, wherein the further pressure control valve is designed to be controllable by the electronic brake control unit (8) so that it functions as an ABS valve. [12] Brake system (2) according to one of the preceding claims, wherein the brake system (2) comprises an air treatment unit (4), and control elements of the electronic brake control unit (28) for the 3 / 3-way valve (11, 11', 11'', 11''', 11'''') are integrated into a control unit of the air treatment unit (4). [13] Brake system (2) according to one of the preceding claims, wherein the brake system (2) comprises an electric parking brake, and control elements of the electronic brake control unit (28) for the 3 / 3-way valve (11, 11', 11'', 11''', 11'''') are integrated into a control unit of the electric parking brake. [14] Brake system (2) according to one of the preceding claims, wherein the brake system (2) has a further control unit, and control elements of the electronic brake control unit (28) for the 3 / 3-way valve are integrated into this further control unit. [15] Commercial vehicle (1) with a braking system (2) according to one of the preceding claims. [16] Method for operating a braking system (2) according to one of the preceding claims, comprising the steps: Releasing the brake (18, 19, 20, 21) associated with the spring-loaded cylinder (16, 17, 29, 30) by actuating the parking brake valve (26) and increasing the pressure in the parking brake circuit (24); Detecting a failure of a function of a service brake circuit (22, 23) by the electronic brake control unit (8); and Controlling the at least one 3 / 3-way valve (11) and venting the pneumatic line between the at least one 3 / 3-way valve (11) and the spring-loaded cylinder (16, 17, 29, 30) to a predetermined pressure in order to engage the brake (18, 19, 20, 21) associated with the spring-loaded cylinder (16, 17, 29, 30). [17] Method according to claim 16, comprising the steps: Detecting a locking of a wheel of the commercial vehicle (1); and Setting the predetermined pressure in the pneumatic line between the 3 / 3-way valve (11) and the spring-loaded cylinder (16, 17, 29, 30) so that wheel locking is no longer detected. [18] A method according to claim 15 or 16, comprising the additional step of: Actuating the at least one 3 / 3-way valve (11'''') and venting the pneumatic line between the at least one 3 / 3-way valve (11'''') and the trailer control valve (31) to a predetermined pressure in order to engage the brake of the trailer of the commercial vehicle (1) assigned to a trailer spring-loaded cylinder.

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