Arrangement for supplying compressed air to a pneumatic brake system and method for applying a parking brake by limiting the flow rate

Abstract

The invention relates to a compressed air supply arrangement (100) for supplying compressed air to an electronically controllable pneumatic braking system (200) of a commercial vehicle (300), an electronically controllable pneumatic braking system (200) having such a compressed air supply arrangement (100), and a corresponding commercial vehicle. Furthermore, the invention relates to a method for engaging a parking brake (1) in the event of a fault in an electronically controllable pneumatic braking system (200) of a commercial vehicle. The compressed air supply arrangement (100) comprises a compressor (101), an air treatment unit (105), at least one compressed air supply (101, 102, 103) for providing a supply pressure (pV, pV1, pV2, pV3) and a delivery rate limiting device (120, 121) with a switchable valve unit (130-137, 151) for limiting the compressed air flow conveyed from the compressor (104) to the at least one compressed air supply (101, 102, 103).In the event of a fault in the braking system (200), the switchable valve unit (130-137, 151) is switched by a switching signal (SigS) received from an electronic brake control unit (242) of the braking system (200).

Description

The invention relates to a compressed air supply arrangement for supplying a electronically controllable pneumatic brake system of a commercial vehicle with compressed air, an electronically controllable pneumatic brake system having such a compressed air supply arrangement, and a method for engaging a parking brake in the event of a fault in an electronically controllable pneumatic brake system of a commercial vehicle, and a corresponding commercial vehicle.Modern commercial vehicles frequently have an electronically controllable pneumatic brake system. As a rule, spring-loaded brakes are part of the brake system as parking brakes, which are also referred to as parking brakes. The parking brakes act by spring force and can be released or fixed by venting spring brake cylinders with a fixing pressure. For regulating a service brake pressure, valves are electronically controlled within a service brake system. The valves can be provided in so-called axle modulators or outside the same. The axle modulators can be automated or partially automated and / or can be electronically controlled by an autonomous unit. The parking brakes are also controlled electronically. For example, by actuating a solenoid valve, the venting or venting of the spring-loaded brake cylinders can be regulated. The spring-loaded brake cylinders can be combined with service brake cylinders, so that the spring-loaded brake and the service brake act on the same brake pistons. In order to avoid a mechanical overload of the brake pistons by adding brake forces from the service brakes and the spring-loaded brakes, suitable structural measures can be taken. If the service brakes are actuated while the parking brakes are active, the spring-loaded brake cylinders are simultaneously ventilated in order to avoid the addition of the braking forces. Such a function is also referred to as an "anti-compound function".In some markets, venting of the spring brake cylinders is provided for safety reasons, provided that the supply pressure in the service brake system falls. Service brake and parking brake can also be assigned to different brake circuits. When different brake circuits are assigned, it is partially ensured by a so-called "bleed-back function" that a reservoir pressure drop in the brake circuit for the service brake also vents the brake circuit for the spring-loaded brake. In some countries, the service brake and the parking brake do not have to have separate brake circuits. The brake circuit for the parking brake is then at the same time the brake circuit for the service brake, so that in the event of a drop in the reservoir pressure in the brake circuit, the spring-loaded brake cylinders are already vented.The parking brake must be insertable by a driver of the vehicle. In some markets, this is done by an electronic parking brake request to the parking brake device. In the event of a fault, the driver is held by intentionally induced lowering of the supply pressure in the brake circuit for the service brake to vent the spring-loaded brake cylinders and thus to activate the parking brake. For this purpose, the driver brakes the vehicle with the service brake, shuts down the motor, so that the delivery of compressed air is interrupted, and subsequently actuates the service brake several times. As a result, the brake circuit for the service brake is gradually evacuated. As a result, the spring-loaded brake cylinders are also vented. For the described sequence, attention and timely intervention of the driver are required.In electropneumatic brake systems for modern vehicles, safety concepts are of high relevance. In particular in the case of vehicles having automated or partially automated driving functions, braking functions must remain available at least to a limited extent even in the event of a fault in the brake system, such as a malfunction on the software side, a hardware fault (e.g. as a result of failure or damage) or in the event of a power failure of a control unit. Only in this way can the safety of the vehicle, its occupants and further road users be guaranteed. For this purpose, it is known to provide redundancy levels which can still provide an at least limited braking function even in the event of failure of a primary system. It is known, for example, to use the parking brake as an auxiliary brake or auxiliary brake for cases in which a fault has occurred in the service brake system.In addition to the service brakes, a redundancy level is also desired for the parking brake, since vehicles can be safely parked only with the parking brake engaged in most cases. In order to expand the functionality and, in particular independently of the occurrence of a fault in one of the various levels, be it the operating level or a redundancy level of the brake system, to be able to ventilate the corresponding spring-loaded cylinders of the parking brake and thus to be able to release it, it is desirable that the spring-loaded brake cylinders can be actuated via two independent paths. This is intended to increase the range of functions, the operational readiness of the vehicle and above all the safety. By providing a redundancy level, safe parking of the vehicle can thus be ensured even in the event of one or more faults in the brake system.DE 10 2021 122 497 A1 discloses a method for operating an electropneumatic brake system for a vehicle, wherein the brake system comprises a service brake system and a parking brake system. The parking brake system comprises at least one spring brake cylinder. The method is characterized by the steps of: providing a control signal for holding a spring-accumulator venting pressure venting the at least one spring-accumulator brake cylinder by a control unit, interrupting the provision of the control signal in the event of a fault and / or a power failure and / or a diagnostic event of the control unit, thereby automatically ending the holding of the spring-accumulator venting pressure for venting the at least one spring-accumulator brake cylinder, thereby triggering a spring-accumulator failure braking of the vehicle by the parking brake system, wherein the venting of the spring-accumulator venting pressure takes place by a service-brake venting function of the service brake system. The service brake venting function enables at least one venting path, which is opened in particular continuously or temporarily interrupted, in the service brake system for venting the at least one spring brake cylinder. The service brake venting function is implemented in particular by a valve in the service brake system, preferably an outlet valve and / or a further outlet valve.DE 10 2020 132 875 A1 discloses a method for emergency application of a parking brake of a vehicle, wherein a service brake control unit causes, under defined conditions, a lowering of the supply pressure in at least one brake circuit for the service brake under program-controlled control. It is provided that the service brake control unit deactivates a compressed air delivery into the brake circuits in order to avoid the possibility of an increase in pressure in the brake circuit for the service brake. EP 3 145 769 A1 describes that in the case of electropneumatic brake control devices for controlling a parking brake of a vehicle, failure of the electrical energy supply represents a problem because electromagnetic valve devices can then no longer be actuated and, in addition, the electrical parking brake signal transmitter also fails. Automatic venting of the spring brake cylinders of the spring brake brake when an electrical power supply fails during a running trip (emergency braking) is ruled out as problematic because of the risk of an accident. With reference to EP 1 968 830 B1, it is established that a compressor delivers by continued delivery when the electrical power supply is intact, when the supply pressure in the compressed air supplies is lowered as a result of actuation of the service brake, which can prevent a pressure threshold value of the supply pressure of the service brake from being undershot, said pressure threshold value being required for applying the parking brake. However, this problem is considered to be not serious insofar as, in the event of a failure of the electrical energy supply, the drive machine of the vehicle and thus a further delivery through the compressor usually fails. By repeated actuation of the service brake, the compressed air supplies of the service brake are emptied, whereby the spring brake is applied. Since the service brake was previously repeatedly actuated, it is assumed that the vehicle is then already in a braked state or at a standstill. Indeed, some vehicles or vehicle configurations do not ensure that the compressor is shut down in all fault cases. The compressor then continues to deliver compressed air (follow-up delivery), although a drop in the supply pressure is desired due to an error that has occurred, in order for the parking brake to be engaged in order to brake or park the vehicle securely.In the prior art, a so-called "pumping down" is used in driver-guided vehicles, in which the driver actuates the service brake multiple times. As a result, the air consumption is greatly increased, with the aim of lowering the pressure level so greatly that the spring-loaded brake cylinders of the vehicle are subsequently clamped. Further partially redundant systems are known from DE 10 2022 101 142 A1, DE 10 2021 122 498 A1 and DE 10 2021 122 499 A1.Even if redundant possibilities for engaging a parking brake have already been created by known systems, there is a need for further improvements. One problem is the follow-up of the running compressor. The follow-up delivery of the running compressor can prevent or at least delay the engagement of the parking brake by maintaining or increasing the supply pressure. It happens that when the compressor is delivering, the reservoir pressure is not lowered or not lowered fast enough, for example by so-called pumping down, i.e. the multiple actuation of the service brake, so that the parking brake does not apply reliably. The achievable compressed air consumption of the service brake is therefore not sufficient to be able to engage the parking brake quickly and reliably. Another problem exists in vehicles of higher automation levels (SAE level 4 or 5), where there is not always a driver who could take measures manually to engage the parking brake or to reduce the reservoir pressure required for this purpose.At this point, the invention starts, the object of which is to specify an improved electronically controllable pneumatic brake system in which the engagement of the parking brake is made possible reliably and preferably quickly, in particular even when the compressor of the compressed air supply is running. In particular, the parking brake should also be able to be reliably engaged in the event of a fault in the brake system, i.e. in the event of redundancy, preferably also in the case of vehicles of higher degrees of automation (e.g. SAE level 4 or 5).This object is achieved in particular by a compressed air supply arrangement for supplying compressed air to an electronically controllable pneumatic brake system of a commercial vehicle, comprising: a compressor for generating compressed air; an air processing unit for processing compressed air conveyed by the compressor; at least one compressed air supply for providing a supply pressure for applying compressed air to at least one spring brake cylinder of a parking brake of the brake system, wherein the compressed air supply is connected via at least one compressed air conveying line to a compressed air outlet of the compressor; and at least one delivery quantity limiting device, which comprises a switchable valve unit, for limiting the compressed air flow conveyed from the compressor through the at least one compressed air conveying line to the at least one compressed air supply, wherein the switchable valve unit is designed to be switched in the event of a fault in the brake system by a switching signal received from an electronic brake control unit of the brake system.The invention therefore proposes limiting the compressed air flow (re-conveyed) conveyed from the compressor to the at least one compressed air supply, as a result of which (at least when a sufficiently large compressed air consumption) the supply pressure available for pressurizing a spring-loaded brake cylinder is also limited. In preferred embodiments, the delivery-volume limiting device reaches the limitation of the compressed-air flow delivered to the compressed-air supply when the compressor is running, that is to say preferably not by switching off (i.e. shutting down) the compressor, in particular not by switching off the drive of the compressor. In this respect, the valve unit for limiting the compressed air flow is preferably switched when the compressor is running. In the running state of the compressor, in particular the drive of the compressor runs, wherein the compressor is preferably connected (coupled) to the drive (via a clutch). The drive of the compressor is typically a drive of the vehicle, for example a vehicle engine.The spring-loaded brake cylinders are designed in particular in such a way that, when a specific pressure level is undershot, they overcome and tension the pneumatic pressure force on account of a spring force. When pressurized air is applied, the parking brake is thus releasable. The parking brake is preferably electronically controllable.The compressed air feed line can comprise a plurality of (partial) sections, in particular a first compressed air feed line (partial) section between the compressor and an air processing unit and a second compressed air feed line (partial) section between the air processing unit and the at least one compressed air supply (compressed air supply store, preferably compressed air tank). The compressed air feed line can comprise branches (and mergings), in particular a bypass line.The at least one compressed air supply is in particular (each) designed as a compressed air storage tank (compressed air tank) and supplies at least one brake circuit of the brake system, in particular at least one service brake circuit and one parking brake circuit, with compressed air. In addition, an auxiliary compressed air circuit of the commercial vehicle can be provided, for example for the provision of compressed air for the air suspension of the commercial vehicle or of the driver's cab and for the transmission control.The delivery quantity limiting device is arranged in particular upstream of the at least one compressed air supply, preferably upstream of a branch point at which the compressed air delivery line for supplying compressed air to a service brake (of a service brake circuit) and for supplying compressed air to the parking brake (of a parking brake circuit) divides (branches).The parking brake, in particular a parking brake valve unit of the parking brake, is preferably supplied at least by a first compressed air supply or a second compressed air supply, or a third compressed air supply, but preferably by both the first and the second compressed air supply. For this purpose, the parking brake can have a push-pull valve which connects both the first and the second compressed air supply in a pressure-conducting manner to the spring-loaded brake cylinders. Alternatively, it is also conceivable for the parking brake unit to be supplied with supply pressure directly from the air processing unit. In particular in electronically controllable pneumatic brake systems as used in North America, Canada or partially also in other regions of the world, it is customary for spring-loaded brake cylinders of a parking brake to be supplied by two compressed-air supplies, such as in particular the first and second compressed-air supplies, which are provided for a front-axle brake circuit and a rear-axle brake circuit.The air treatment unit can have functions of compressed air treatment, such as compressed air cleaning, in particular oil separation, or compressed air drying. On the other hand, the compressed air processing unit can take over the (pneumatic) control of the compressor, preferably via a compressor control line. The air processing unit can furthermore have a multi-circuit protection valve known per se or be connected to the latter, which valve is designed for distributing the compressed air flowing into the air processing unit to a plurality of compressed air supplies (compressed air storage stores), which are assigned in particular to different brake circuits of the brake system.Limiting the compressed air flow conveyed by the compressor through the at least one compressed air conveying line can comprise, in addition to reducing the flow rate (lower flow rate not equal to zero), in particular by (local) reducing the flow cross section, also the (complete) blocking and / or venting of the compressed air conveying line (flow rate equal to zero). The compressed air feed line can be lockable (closable) by controlling the switchable valve unit and / or connectable to an (atmospheric) pressure sink. The blocking of the compressed air feed line can be understood as a reduction of the flow cross section to zero. The compressed air flow conveyed through the compressed air conveying line can be limited by venting, for example by connecting the compressed air conveying line to a pressure sink (atmospheric environment) at a point between the compressed air outlet of the compressor and a compressed air supply, insofar as the compressor does indeed feed compressed air into the compressed air conveying line, but this compressed air escapes towards the pressure sink on account of the venting and is not conveyed to the compressed air supply. Venting (directly into the environment) is also understood to mean if, for example, a line and / or a silencer and / or a leaf valve are provided. In this respect, a blocking (blocking) or venting of the compressed air conveying line (of a line section of the compressed air conveying line) can be understood as a limitation of the flow through the (entire) compressed air conveying line (up to the compressed air supply) to zero.The switchable valve unit of the delivery quantity limiting device preferably comprises at least one (electrically) switchable (controllable) valve (solenoid valve) and can be designed as an (electrically) switchable valve (solenoid valve). The switchable valve unit preferably comprises at least one 2 / 2-way valve (2 / 2-way solenoid valve) or a 3 / 2-way valve (3 / 2-way solenoid valve). In one embodiment, the switchable valve unit is a switchable shut-off valve (2 / 2-way valve). A switchable valve unit designed as an electromagnetic valve (solenoid valve) is preferably not supplied with current in a first switching position (for conveying compressed air) and is supplied with current in a second switching position (for limiting the conveying amount).The switchable valve unit receives the switching signal, in particular from a (secondary) electronic brake control unit of the brake system. The valve unit is switched as a function of the received switching signal in order to limit the compressed air flow conveyed (conveyed) into the compressed air supply. A limited supply of compressed air promotes the drop in the supply pressure (supply pressure level) due to the air consumption of the braking system, preferably of the secondary braking system. In particular, the maintenance or (re)increases in the reservoir pressure is prevented by supplying compressed air through the compressor, so that the spring-loaded brake cylinders are reliably clamped. In particular, the supply pressure level is lowered by the switched delivery quantity limiting device and the (simultaneous) air consumption of the brake system to such an extent that the at least one spring brake cylinder is tensioned and the vehicle is thus braked. The air consumption can be caused by the actuation of the service brake. It can be provided that the service brake control unit brings about the lowering of the supply pressure in at least one of the brake circuits for the service brake by an actuation of the service brake. This means that the reservoir pressure in the brake circuit is lowered by the in particular multiple actuation of the service brake (so-called pumping down), i.e. preferably by multiple venting and venting of brake cylinders of the service brake. The compressed air supply arrangement ensures in particular that the compressed air consumption flow through at least one service brake (service brake circuit) exceeds the compressed air flow conveyed by the compressor by an appropriate value in order to achieve a (rapid) reduction in the supply pressure.A switching of the valve unit of the delivery quantity limiting device is provided in particular for a fault case of the brake system, in which a primary electronic brake control unit does not function or not function correctly and also a secondary electronic brake control unit does not function or not function correctly, or another relevant system does not function or no longer function correctly, so that as a result the corresponding switching signal is provided for the switchable valve unit of the delivery quantity limiting device in order to brake the vehicle securely. In general, a fault case of the brake system can be understood to mean a function that is not intended, such as a malfunction on the software side, a hardware fault (e.g. due to failure or damage) or a power failure of a brake control unit.The invention has the advantage that the engagement of the parking brake is reliably made possible on account of the restriction of the compressed air delivery rate by the switchable delivery rate restriction device-in the case of a sufficiently large (simultaneous) compressed air consumption of the brake system, in particular by actuating the service brake of the brake system-in particular even when the compressor of the compressed air supply is running. The parking brake can also be reliably engaged in the event of a fault in the brake system, in particular even in the case of vehicles of higher degrees of automation.In one embodiment of the compressed air supply arrangement, the switchable valve unit, in a switching position for limiting the delivery rate, prevents compressed air from being conveyed by the compressor into the at least one compressed air supply at least partially. In particular, a first switching position of the valve unit serves for conveying compressed air and a second switching position serves for limiting the conveying amount.In one embodiment of the compressed air supply arrangement, the supply pressure provided by the compressed air supply in a second switching position of the switchable valve unit is reduced in comparison with the supply pressure provided by the compressor in a first switching position of the switchable valve unit by conveying compressed air into the compressed air supply by means of the compressor. This reduced supply pressure can be ensured in the second switching position of the switchable valve unit preferably by a (simultaneous) consumption of compressed air from the at least one compressed air supply, in particular by venting a service brake actuator (service brake cylinder) before and / or while the switchable valve unit is switched into the second switching position. Preferably, the conveyed compressed air flow (delivery quantity) (in the second switching position) is equal to or less than the consumed compressed air flow (consumption quantity). Preferably, a second supply pressure value, which is provided in the compressed air supply (compressed air storage store) in the (second) switching position of the switchable valve unit (for limiting the delivery rate), is reduced in comparison with a first supply pressure value, which is provided in the compressed air supply in a (first) switching position of the switchable valve unit (for delivering compressed air by means of the compressor).In one embodiment of the compressed air supply arrangement, the air processing unit is arranged upstream of the at least one compressed air supply and the at least one switchable valve unit of the delivery quantity limiting device is arranged upstream of a compressed air inlet of the air processing unit or integrated into the air processing unit. Integration of the delivery quantity limiting unit into the air processing unit can be understood to mean the arrangement within a common housing.In one embodiment of the compressed air supply arrangement, the air processing unit is arranged upstream of the at least one compressed air supply, wherein the compressed air supply arrangement comprises a first compressed air supply of a first service brake circuit of the brake system for supplying at least one first service brake actuator on a first axle of the commercial vehicle with compressed air and a second compressed air supply of a second service brake circuit of the brake system for supplying at least one second service brake actuator on a second axle of the commercial vehicle with compressed air, wherein the air processing unit is arranged upstream of the first compressed air supply and the second compressed air supply and,wherein the switchable valve unit of a first delivery quantity limiting device is arranged downstream of a compressed air outlet of the air processing unit and upstream of a compressed air inlet of the first compressed air supply, and / orwherein the switchable valve unit of a second delivery quantity limiting device is arranged downstream of a compressed air outlet of the air processing unit and upstream of a compressed air inlet of the second compressed air supply.In this way, a limitation of the delivery quantity (conveyed compressed air flow) in at least one of the two compressed air supplies can be achieved, in particular separately from one another. By limiting the compressed air delivery rate, the supply pressure in the respective compressed air supply can also be limited depending on the compressed air consumption by the brake system, in particular by the service brake. A first service brake circuit can be assigned to the first compressed air supply and a second compressed air supply can be assigned to a second service brake circuit for (independent) compressed air supply. The first and / or the second compressed air supply can be connected (fluidically) to a third compressed air supply, optionally via at least one interposed valve, so that a limitation (reduction) of the delivery quantity into the first and / or second compressed air supply (and of the supply pressure therein) (also) leads to a limitation (reduction) of the delivery quantity into the third compressed air supply (and of the supply pressure therein). The third compressed air supply is preferably assigned to a parking brake circuit in order to supply it with compressed air.In one embodiment of the compressed air supply arrangement, the switchable valve unit of the delivery quantity limiting device is designed to shut off the compressed air delivery line on the basis of the switching signal received from an electronic brake control unit of the brake system and / or to connect at least one line section of the compressed air delivery line to a flow reduction section of the delivery quantity limiting device. The switchable valve unit (the switchable valve) is in particular configured to connect a first line section of the compressed air conveying line to an inlet end of the flow reduction section and a second line section of the compressed air conveying line to an outlet end of the flow reduction section. A (fluidic) connection can be understood to mean that a compressed air stream can flow from the compressor to the compressed air supply, in particular through at least one (pneumatic) line. The switchable valve unit can be designed as a (precisely one) valve, for example as a 2 / 2-way valve (2 / 2-way solenoid valve) or as a 3 / 2-way valve (3 / 2-way solenoid valve), wherein the flow reduction section can be part of the valve. The flow-reduction section is in particular designed to reduce the compressed air flow conveyed from the compressed air outlet of the compressor to the at least one compressed air supply (compressed air storage store), preferably by a (sectionally) reduced line cross section (nominal cross section, preferably nominal diameter). The flow reduction section can be designed as a (continuous) line section (flow reduction line section) or as a through opening (flow reduction opening) with a flow cross section (line cross section) reduced in comparison to the compressed air feed line. A flow reduction section (cross-sectional constriction) generally leads to a pressure loss of the flow and thus to a lowering of the pressure across the flow reduction section, whereby the supplied reservoir pressure is reduced.In one embodiment of this compressed air supply arrangement, the flow reduction section is designed as a throttle section. A flow reduction section designed as a throttle section (nozzle) has, in particular, a flow cross section which continuously decreases upstream of a minimum opening diameter in the flow direction and continuously increases downstream of the minimum opening diameter. A throttle section (a throttle) leads to a pressure loss and thus to a lowering of the pressure difference across the throttle section. As a result, the conveyed compressed air flow (the delivery quantity) is limited, namely reduced to a smaller compressed air flow. The supply pressure which is established in a compressed air supply and is provided for supplying compressed air can also be limited as a result, namely reduced to a lower maximum supply pressure (in comparison to the compressed air supply without a throttle section) depending on the volume flow balance of the conveyed and consumed compressed air flow. In one embodiment, the throttle section is part of the movable valve body, preferably as a throttle-shaped passage opening.In another embodiment, the throttle section is a (immovable) line section (channel section) of the valve (valve housing), which is connected in particular to an outlet of the valve (3 / 2-way valve).In a further embodiment, the flow reduction section (throttle section) is arranged as a line section of a bypass line (parallel line) of the compressed air feed line branching off from the compressed air feed line, wherein the switchable valve of the delivery quantity limiting device blocks a line section of the compressed air feed line on the basis of a control signal from an electronic brake control unit of the brake system and conducts the compressed air flow fed by the compressor through the flow reduction section (throttle section) of the bypass line to a compressed air inlet of the air processing unit and / or the at least one compressed air supply.In one embodiment of the compressed air supply arrangement, the switchable valve unit (switchable ABS valve unit) of the delivery quantity limiting device is designed to shut off and / or vent the compressed air delivery line on the basis of the switching signal received from an electronic brake control unit of the brake system. In particular, the switchable valve unit can be configured to connect the compressed air outlet of the compressor to the at least one compressed air supply in a first switching position and to interrupt the compressed air feed line or to connect it to a venting outlet of the valve unit in a second switching position.In one embodiment of the compressed air supply arrangement, the switchable valve unit of the at least one delivery quantity limiting device is designed as a switchable ABS valve unit. In this case, a first valve connection of the switchable ABS valve unit is connected to a compressed air outlet of the compressor, a second valve connection of the switchable ABS valve unit is connected to a compressed air inlet of the air processing unit or to the at least one compressed air supply, and a third valve connection of the switchable ABS valve unit is connected to a vent. The ABS valve unit is thereby used for flow restriction. ABS valve units (ABS valves) are well known in the art. They have a relatively large nominal cross section. Therefore, ABS valves can be used advantageously to vent a specific compressed air path quickly and with a short reaction time. In this respect, known ABS valves are particularly suitable for venting the compressed air feed line and / or the compressed air supply (compressed air storage tank). Such venting limits the reservoir pressure, namely typically lowered to atmospheric pressure. Known ABS valves are also suitable for outputting a brake pressure over a time determined by the received switching signals.In one embodiment of this compressed air supply arrangement, the switchable ABS valve unit has a pneumatically switchable inlet valve, a pneumatically switchable outlet valve, an electromagnetic inlet valve and an electromagnetic outlet valve. On the one hand, the compressed air flow conveyed by the compressor can be interrupted via the 2 / 2-way inlet valve part of the ABS valve unit, comprising the pneumatically switchable inlet valve and the electromagnetic (electromagnetically switchable) inlet valve. On the other hand, the compressed air supply (compressed air storage tank, preferably compressed air tank) can be selectively vented, in particular as a function of the switching signal received from a (secondary) electronic brake control unit of the brake system, via the 2 / 2-way outlet valve part of the ABS valve unit, comprising the pneumatically switchable outlet valve and the electromagnetic (electromagnetically switchable) outlet valve. The venting can be switched independently of the shutoff of the compressed air supply. As a result, no actuation of the service brake is required, in particular by "pumping down" (cyclic venting and venting). This has the advantage that a continuous resulting holding brake pressure can be applied to the service brake via the service brake during the emergency application of the parking brake, in particular before the compressed air supply is vented.In one embodiment, a first delivery quantity limiting device, which is arranged upstream of a compressed air inlet of the first compressed air supply, has a first ABS valve (a first ABS valve unit) and a second delivery quantity limiting device, which is arranged upstream of a compressed air inlet of the second compressed air supply, has a second ABS valve (a second ABS valve unit). In particular, a controllable solenoid valve of the first ABS valve and a controllable solenoid valve of the second ABS valve can be controlled by a (secondary) electronic brake control unit of the brake system.In one embodiment of the compressed air supply arrangement, the air processing unit is connected to a control unit of the compressor via a compressor control line for providing a compressor control pressure, and the switchable valve unit of the delivery quantity limiting device is arranged in the compressor control line. The switchable valve unit may include multiple (e.g., two) switchable valves connected in series. In particular, the compressor control line is connected to a control unit of the compressor, which controls the operation of the compressor, in particular its rotational speed and / or its connection to a drive (of the vehicle) via a clutch. The compressor control pressure may correspond to the supply pressure in at least one of the pressure reserves. The operating state of the compressor can be controlled via the compressor control line, preferably via a (pneumatic) control unit of the air processing unit, in such a way that the compressor is switched from a delivery operating state (load running or full load running) into an operating state with reduced delivery capacity (partial load running or idling) or, preferably by opening the drive clutch, into a non-delivery operating state (standstill). In the non-delivery operating state, the compressor is preferably separated (decoupled) from the drive, so that it does not (no longer) run (rotate). This prevents the further delivery of compressed air by the compressor into the compressed air supply. In one embodiment of this compressed air supply arrangement, the switchable valve unit is designed to connect a control pressure inlet of the compressor to a control pressure outlet of the air processing unit in a first switching position and to vent the compressor control line in a second switching position. In this embodiment, the compressor delivers compressed air when the compressor control line is vented (i.e., when the compressor control line is pressurized with a non-zero compressor control pressure) and does not deliver compressed air when the compressor control line is vented.In an alternative embodiment of this compressed air supply arrangement, the switchable valve unit is designed to connect a control pressure inlet of the compressor to a control pressure outlet of the air processing unit in a first switching position and to connect the control pressure inlet of the compressor to an auxiliary supply pressure of the brake system in a second switching position. In this embodiment, the compressor delivers compressed air when the compressor control line is depressurized and does not deliver compressed air when the compressor control line is vented. In particular, in the second switching position, the control pressure inlet of the compressor is connected via a redundant compressor control line section to an auxiliary supply pressure of the brake system. In one embodiment, the auxiliary supply pressure is provided by a compressed air supply of an auxiliary compressed air circuit of the brake system, which can be referred to as an auxiliary supply pressure source in this respect. In the compressor control line portion, a pressure retaining device for retaining the auxiliary reserve pressure as the compressor control pressure may optionally be provided. The pressure retaining device can be designed as a check valve or (actively) switchable holding valve (solenoid valve). In addition to a (first and second) compressed air supply for supplying the service brake circuits and optionally a (third) compressed air supply for supplying the parking brake circuit, a separate (fourth) compressed air supply for supplying the auxiliary compressed air circuit can be provided. The switchable valve unit is preferably designed as a solenoid valve, which is non-energized in the first switching position and energized in the second switching position.In one embodiment of the compressed air supply arrangement, the delivery quantity limiting device comprises a pressure sensor for detecting a compressor control pressure in the compressor control line. The pressure sensor is designed to transmit a compressor control pressure signal representing the detected compressor control pressure to an electronic brake control unit of the brake system. The pressure sensor is arranged in particular in the compressor control line, preferably in the compressor control line section connected to the control pressure inlet of the compressor. The (secondary) electronic brake control unit is configured, in particular, to output a switching signal to the switchable valve unit in the compressor control line on the basis of the received compressor control pressure signal, in particular when a compressor control pressure detected by the pressure sensor falls below a predetermined pressure level (predetermined pressure value). A drop in the compressor control pressure indicates in particular a drop in the reservoir pressure, which is caused in particular by a (desired, in particular intentionally brought about) air consumption of the service brake. In this way, the further delivery of compressed air by the compressor into the compressed air supply can be prevented as soon as the supply pressure has started to decrease. A (re)untilizing of the supply pressure is thereby prevented.The object mentioned is also achieved in particular by an electronically controllable pneumatic brake system for a commercial vehicle, comprisinga compressed air supply arrangement according to the invention, in particular according to one of the embodiments described above,a parking brake having at least one spring-loaded brake cylinder, which can be acted upon with compressed air by a provided supply pressure of the at least one compressed-air supply for releasing the parking brake, andat least one electronic brake control unit which is configured to output a switching signal to the switchable valve unit of the at least one delivery quantity limiting unit in the event of a fault in the brake system.The electronically controllable pneumatic brake system, which is described herein, can also have at least one second service brake circuit in addition to the at least one first service brake circuit. For example, the first service brake circuit is a rear axle brake circuit, while a second service brake circuit is a front axle brake circuit. In addition, further brake circuits, such as a trailer brake circuit, for example, or further brake circuits for further axles can be provided. It is also conceivable that brake circuits are not divided according to axles, but rather comprise other subgroups of the brake system, such as the left and right sides of the vehicle. In this respect, in addition to the first primary service brake pressure modulator, a second primary service brake pressure modulator is typically provided in the electronically controllable pneumatic brake system, which second primary service brake pressure modulator actuates one or the second axle. Preferably, the primary electronic brake control unit is connected to the second primary service brake pressure modulator and provides second primary switching signals at the latter for switching at least one electromagnetic valve of the second primary service brake pressure modulator.In addition, a primary plane and at least one secondary plane are provided, wherein structurally one or more valves or one or more modulators can be assigned to both the primary and the secondary plane. The primary plane is driven by the primary brake electronic control unit, while the secondary plane is driven by the secondary brake electronic control unit. The electronically controllable pneumatic brake system is preferably operated in the secondary level when one or more errors occur in the primary level, which partially or completely prevent a regular modulation of a service brake pressure in the primary level.The parking brake has, in particular, a parking brake valve unit for providing a parking brake pressure, with which the at least one spring-loaded brake cylinder (for releasing the parking brake) is acted upon.Furthermore, a first voltage source is preferably provided for the electrical supply of the primary electronic brake control unit. Preferably, a second voltage source is also provided for supplying the secondary electronic brake control unit. The first and second voltage sources are preferably independent of each other, so that the failure of the first voltage source does not result in the failure of the second voltage source, and vice versa.In one embodiment of the electronically controllable pneumatic brake system, the electronic brake control unit is a secondary electronic brake control unit which is configured to receive maneuver-related brake data via a vehicle bus from an autonomous driving vehicle control unit or a redundant autonomous driving vehicle control unit. The secondary electronic brake control unit is configured to at least partially control at least one service brake circuit of the brake system in the event of a fault in a primary electronic brake control unit of the brake system.In one embodiment of the electronically controllable pneumatic brake system, the electronically controllable parking brake comprises a parking brake valve unit supplied with supply pressure for providing a parking brake pressure, with which the at least one spring-loaded brake cylinder can be loaded, wherein the supply pressurea first compressed air supply of a first service brake circuit of the electronically controllable pneumatic brake system for supplying at least one first service brake actuator at a first axle of the commercial vehicle with compressed air,a second compressed air supply of a second service brake circuit of the electronically controllable pneumatic brake system for supplying at least one second service brake actuator at a second axle of the commercial vehicle with compressed air,a third compressed air supply of a parking brake circuit for supplying the parking brake valve unit with compressed air and / ordirectly provided by an air processing unit for processing the compressed air conveyed by a compressor.The object mentioned is also achieved in particular by a method for engaging a parking brake of an electronically controllable pneumatic brake system of a utility vehicle, in particular according to one of the embodiments described above, comprising the following steps:detecting a fault in the electronically controllable pneumatic brake system, preferably by an electronic brake control unit of the electronically controllable pneumatic brake system, wherein the detected fault prevents the engagement of the electronically controllable parking brake by a switching process of a parking brake valve unit of the parking brake such that at least one spring brake cylinder of the parking brake is vented;outputting a switching signal to a switchable valve unit of at least one delivery quantity limiting device of a compressed air supply arrangement for supplying the electronically controllable pneumatic brake system, in particular according to one of the embodiments described above, by an electronic brake control unit of the electronically controllable pneumatic brake system, wherein the switching signal has the effect that the compressed air flow delivered by the compressor to at least one compressed air supply of the electronically controllable pneumatic brake system is limited; andlowering a supply pressure for the application of at least one spring brake cylinder of an electronically controllable parking brake of the electronically controllable pneumatic brake system by using compressed air in at least one service brake circuit or parking brake circuit of the electronically controllable pneumatic brake system.The method according to the invention has the same or similar embodiments and advantages as the previously described compressed air supply arrangement according to the invention and the electronically controllable pneumatic brake system according to the invention. In particular, the engagement of the parking brake is reliably made possible on account of the limitation of the delivery quantity by the switchable delivery quantity limiting device (and the limitation of the supply pressure which can be achieved thereby-with simultaneous compressed air consumption of the brake system), in particular even when the compressor of the compressed air supply is running. The parking brake is reliably engaged even in the event of a fault in the brake system, in particular also in the case of vehicles of relatively high levels of automation. The method can implement and carry out all or some of the previously described functional or method-related features of the embodiments of the compressed air supply arrangement and of the electronically controllable pneumatic brake system and (optional) variants thereof as embodiments of the method, in particular as corresponding method steps. In particular, the method can have the same or similar sub-aspects as the compressed air supply arrangement and the electronically controllable pneumatic brake system, in particular the sub-aspects specified in the dependent claims. In this respect, for preferred developments of the method, reference is also made in its entirety to the above description.The detected fault in the electronically controllable pneumatic brake system may be understood as a fault affecting (i.e. affecting) the electronically controllable pneumatic brake system, such as a software-side malfunction, a hardware fault (e.g. due to failure or damage) or a power failure of the primary or the secondary voltage source. The fault is preferably detected by a (primary or secondary) electronic brake control unit of the electronically controllable pneumatic brake system or a (higher-order) vehicle control unit for autonomous driving. The electronic brake control unit of the electronically controllable pneumatic brake system for outputting a switching signal to a switchable valve unit is preferably a secondary electronic operating control unit of the brake system or a (secondary) electronic control unit of the parking brake.Detecting a fault in the electronically controllable pneumatic brake system, which prevents the engagement of the electronically controllable parking brake by a switching process of a parking brake valve unit of the parking brake, also includes, in particular, the non-switchability of the switchable valve unit of a delivery quantity limiting device on account of a failure of the power supply of the electronic brake control unit, e.g. on account of a short circuit, as a result of which no switching signal is output.In one embodiment of the method, the reservoir pressure is lowered by at least partially venting at least one or more service brake actuators of at least one service brake circuit of the electronically controllable pneumatic brake system. This method step can be carried out before and / or during the method steps of the method according to the invention. The lowering of the reservoir pressure can be brought about by manual or automatic actuation (venting) of at least one service brake actuator (service brake cylinder) of a service brake (so-called "pumping down"), in particular by electrical and / or electronic control commands (venting signals). In particular, an electrical bleed signal may be output by a secondary brake electronic control unit to a service brake actuator. The object mentioned is also achieved in particular by a commercial vehicle comprising a compressed air supply arrangement according to the invention for supplying an electronically controllable pneumatic brake system, in particular according to one of the embodiments described above, and / or an electronically controllable pneumatic brake system according to the invention, in particular according to one of the embodiments described above. An electronic brake control unit of the brake system is designed, in particular, to execute the method according to the invention, in particular according to one of the embodiments described above. The utility vehicle has in particular at least one front axle and at least one rear axle.Embodiments of the invention will now be described below with reference to the drawings. These are not necessarily intended to represent the embodiments to scale, but rather the drawings are embodied in schematic and / or slightly distorted form, if this is useful for explanation. With regard to additions to the teachings that can be directly recognized from the drawings, reference is made to the relevant prior art. It should be understood that various modifications and changes may be made to the form and detail of an embodiment without departing from the general spirit of the invention. The features of the invention disclosed in the description, in the drawings and in the claims can be essential for the development of the invention both individually and in any combination. Moreover, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiments shown and described below, or limited to an object that would be limited compared to the object claimed in the claims. In the case of specified rated ranges, values lying within the stated limits should also be disclosed as limit values and can be used and claimed as desired.Further advantages, features and details of the invention are apparent from the following description of the preferred embodiments and from the drawings, in which: FIG. 1 shows a schematic illustration of a more detailed layout of an embodiment of an electronically controllable pneumatic brake system installed in a commercial vehicle according to the invention; FIG. 2 shows a schematic illustration of an embodiment of an electronically controllable pneumatic brake system according to the invention; FIG. 3 shows a schematic illustration of a compressed air supply arrangement according to the invention with various possible positions of the delivery quantity limiting device; FIG. 4 shows a schematic illustration of a further embodiment of a delivery quantity limiting device as a shut-off valve with the aid of switching symbols; FIG. 5 shows a schematic illustration of a further embodiment of a delivery quantity limiting device having a throttle section with the aid of switching symbols; FIG. 6 shows a schematic illustration of a further embodiment of a delivery quantity limiting device having a throttle section with the aid of switching symbols; FIG. 7 shows a schematic illustration of a further embodiment of a delivery quantity limiting device as an ABS valve unit with the aid of circuit symbols; FIG. 8 shows a schematic illustration of an embodiment of the compressed air supply arrangement according to the invention with a delivery quantity limiting device designed as an ABS valve unit with the aid of switching symbols; FIG. 9 shows a schematic illustration of an embodiment of the compressed air supply arrangement according to the invention with two delivery quantity limiting devices designed as an ABS valve unit with the aid of switching symbols; FIG. 10 shows a schematic illustration of a first embodiment of the compressed air supply arrangement according to the invention with a delivery quantity limiting device in a compressor control line with the aid of switching symbols; FIG. 11 shows a schematic illustration of a second embodiment of the compressed air supply arrangement according to the invention with a delivery quantity limiting device in a compressor control line with the aid of switching symbols.The same reference numerals are used below for structurally identical or similar elements or elements having an identical or similar function.The electronically controllable pneumatic brake system 200 illustrated in FIG. 1 is installed in a utility vehicle 300 (see illustration of the front axle VA, the rear axles HA 1, HS 1 and the schematic illustration of the wheels in plan view as rounded rectangles). The electronically controllable pneumatic brake system 200 is also applicable to vehicles having only one rear axle or two front axles or three or more rear axles.The electronically controllable pneumatic brake system 200 has an operating level and at least one first redundancy level (levels not shown). In the operating level, the electronically controllable pneumatic brake system 200 comprises a primary system with a primary electronic control unit 214 which controls the electronically controllable pneumatic brake system 200 in the operating level. The primary electronic control unit 214 is connected to and receives maneuver-related maneuver-related brake data, such as brake request signals, from an autonomous driving vehicle control unit 218 via an electronic connection, here a vehicle bus 216. Moreover, the primary electronic brake control unit 214 is connected to a first voltage source 222 and is supplied with electrical voltage by the latter. The primary electronic brake control unit 214 converts the brake request signals and, based thereon, controls first primary switching signals, for example in the form of operational brake signals SigB, to a first primary service brake pressure modulator 224. The first primary service brake pressure modulator 224 is provided here for a rear axle HA and can thus also be referred to as a primary rear-axle service brake pressure modulator or a primary rear-axle modulator.The first primary service brake pressure modulator 224 is connected to a first compressed air supply 101 and receives supply pressure pV1and pV(see further below) therefrom. The first primary service brake pressure modulator 224 controls, based on the received operating brake signals SigB, a first service brake pressure pB 1 at at least one first service brake pressure port 232.1 and preferably at least one second service brake port 232.2. At the first and second service brake pressure connections 232.1, 232.2, the first service brake pressure pB1 is preferably controlled in accordance with the wheel, and the first primary service brake pressure modulator 224 is designed as a two-channel modulator. In other embodiments, however, the first service brake pressure connection 232.1 and the second service brake pressure connection 232.2 can also be combined and the first primary service brake pressure modulator 224 can thus be designed as a single-channel axle modulator which controls the first service brake pressure pB1 in the proper axis.For braking at least one further axle, the electronically controllable pneumatic brake system 200 comprises, in the operating plane, a second primary service brake pressure modulator 236, which is provided for a front axle VA, for example, and can thus also be referred to as a front axle modulator. The second primary service brake pressure modulator 236 receives supply pressure pV2or pV (see further below) from a second compressed air supply 102 and controls a second brake pressure pB2on at least one third service brake pressure connection 236.1 and preferably one fourth service brake pressure connection 236.2 in the proper axis, side-pass or wheel direction. The second primary service brake pressure modulator 236 can also be designed as a single-channel or dual-channel axle modulator and is preferably designed as a dual-channel axle modulator.In the redundancy level, the electronically controllable pneumatic brake system 200 comprises a secondary electronic brake control unit 242 of a secondary or redundancy system, which is provided to control the electronically controllable pneumatic brake system 200 in the event that the operating level has one or more errors. The secondary electronic brake control unit 242 can thus control the electronically controllable pneumatic brake system 200 for example in the event of a power failure in the first voltage source 222, an electronic fault in the primary electronic brake control unit 214 or the like.The secondary electronic brake control unit 242 is also connected to the autonomous driving vehicle control unit 218 via the vehicle bus 216 and also receives maneuver-related brake data, such as brake request signals or redundant brake request signals, therefrom. In contrast to the primary electronic brake control unit 214, the secondary electronic brake control unit 242 is connected to a second voltage source 246 and is supplied with electrical voltage by the latter. The first and second voltage sources 222, 246 are independent of each other such that a failure in the first voltage source 222 does not result in a loss of the second voltage source 246, and vice versa. That is, the primary brake electronic control unit 214 and the secondary brake electronic control unit 242 are electrically independent from each other.In order to be able to exchange signals, the primary electronic brake control unit 214 and the secondary electronic brake control unit 242 are connected to one another via a redundancy bus 248. In this way, the secondary electronic brake control unit 242 can determine the availability of the primary electronic brake control unit 214 and only take over the control of the electronically controllable pneumatic brake system 200 if the primary electronic brake control unit 214 is not available or is not correctly available. However, in variants, communication between primary electronic brake control unit 214 and secondary electronic brake control unit 242 can also be effected, for example, via vehicle BUS 216.In the redundancy level, a first secondary service brake pressure modulator 250 is provided, which is connected to the secondary electronic brake control unit 242 and receives first secondary switching signals, for example in the form of redundancy brake signals, from the latter. Here, the secondary brake electronic control unit 242 is integrated with the first secondary service brake pressure modulator 250. In other variations, however, the secondary brake electronic control unit 242 and the first secondary service brake pressure modulator 250 may also be physically separate units. The first secondary service brake pressure modulator 250 is connected to the first compressed air supply 101, which is independent of the second compressed air supply 102, so that the first compressed air supply 101 can also provide supply pressure pV if the second compressed air supply 102 has failed. In other embodiments, the first secondary service brake pressure modulator 250 can, however, also be connected to the first compressed air supply 101 or both to the first compressed air supply 101 and the second compressed air supply 102, or even be supplied from a third compressed air supply 103 (see, for example, FIG. 3 ).The first secondary service brake pressure modulator 250 controls a first redundancy brake pressure pBR 1 at a first secondary working connection 250.1 as a function of a redundancy brake signal. The first axle, preferably the rear axle, can be redundantly braked via the first redundant brake pressure pBR 1 and can thus be braked in the secondary plane. This can be done on the axle axis or on the wheel axis.In the exemplary embodiment shown here, a second secondary service brake pressure modulator 252 is furthermore provided, which is provided in particular to replace the second primary service brake pressure modulator 236. The second secondary service brake pressure modulator 252, like the first secondary service brake pressure modulator 250, receives redundancy brake signals and controls a second redundancy brake pressure pBR2 at a second redundancy brake pressure connection 252.1 as a function of these signals.The brake actuators assigned to the wheels of the rear axles HA 1, HA 2 are designed here as double-acting brake actuators, which are also referred to as tri-stop cylinders. In addition to the service brake actuators 208 c- 208 f, these also each comprise a spring-loaded brake cylinder 254 c- 254 f. The spring-loaded brake cylinders 254 c- 254 fare designed to apply the brakes of the utility vehicle 300 when they are depressurized or depressurized. The spring-loaded brake cylinders 254 c- 254 fare thus advantageously usable as a parking brake, since no compressed air has to be provided to the latter for braking the rear axles HA 1, HA 2. To release the rear wheels, the spring-loaded brake cylinders 254 c- 254 fmust be ventilated with a parking brake pressure pFS. This parking brake pressure pWD acts against the spring accumulator and releases the brakes of the vehicle 300.To provide the parking brake function, the brake system 200 comprises a parking brake 1. this comprises an electropneumatic parking brake valve unit 2 which is supplied via a first supply connection 4 with supply pressure pV1from the first compressed air supply 101, via a second supply connection 5 with supply pressure pV2from the second compressed air supply 102 and optionally (not illustrated) via a further supply connection with supply pressure pV3from the third compressed air supply 103 (see, for example, FIG. 3 ). Depending on the design of the compressed air supplies 101, 102, 103 and their pneumatic connection to one another, the supply pressures pV 1, pV 2 and pV 3 can be compensated for from a fluidic standpoint and in this respect collectively referred to as the supply pressure pV. However, the parking brake valve unit 2 could also be supplied with supply pressure pV (or precisely pV1, pV2or pV3) only from one of the two compressed air supplies 101, 102 or from a third compressed air supply 103 or directly from an air processing unit 105.The electropneumatic parking brake valve unit 2 includes a parking brake control unit 6 connected to the autonomous driving vehicle control unit 218 via the vehicle bus 216. For engaging the parking brake 1, the vehicle control unit for autonomous driving 218 provides a parking brake signal to the parking brake control unit 6 via the vehicle bus 216, which parking brake signal then provides the parking brake pressure pFSat a first spring accumulator port 8 aand a second spring accumulator port 8 b. In FIG. 1, the first spring-accumulator connection 8 ais connected to the spring-accumulator brake cylinders 254 d, 254 fand the second spring-accumulator connection 8 bis connected to the spring-accumulator brake cylinders 254 c, 254 e. By providing the parking brake pressure pFS, the electropneumatic parking brake valve unit 2 vents the spring-loaded brake cylinders 254 c- 254 fand thus releases the parking brake. To engage the parking brake of the commercial vehicle 300, the electropneumatic parking brake valve unit 2 can vent the spring accumulator connections 8 a, 8 bor the spring accumulator brake cylinders 254 c- 254 fconnected thereto. This can take place in response to the receipt of corresponding parking brake signals at the parking brake control unit 6 or when parking brake signals are no longer provided by the parking brake control unit 6.The invention relates in particular to the case that a fault occurs in the brake system 200, which prevents the parking brake 1 from being engaged or which makes it necessary for the parking brake 1 to be redundantly engaged in order to stop or hold the vehicle 300 reliably, for example, instead of a service brake 9 that is not functioning or not functioning correctly. The service brake 9 includes, in particular, the service brake actuators 208 c- 208 f.The first compressed air supply 101 is provided here for a first brake circuit BK 1, which corresponds to a rear axle brake circuit. The second compressed air supply 102 is provided for a second brake circuit BK 2, which corresponds to a front axle brake circuit. The electronically controllable pneumatic brake system 200 has a total of six service brake actuators, namely first and second service brake actuators 208 a, 208 bat the front axle VA, and third, fourth, fifth, sixth service brake actuators 208 c- 208 fat the first and second rear axles HA 1, HA 2. The service brake actuators 208 c- 208 fat the rear axles HA 1, HA 2 are combined with the spring-loaded brake cylinders 254 c- 254 finto so-called tri-stop cylinders.The primary electronic brake control unit 214 is combined with the first primary service brake pressure modulator 224 to form a module and is shown as a structural unit. The module can also be referred to as a (primary) central module and has the function of both the primary electronic brake control unit 214 and a primary rear axle modulator which here controls the first service brake pressure pB1 laterally at the first service brake pressure connection 232.1 and the second service brake pressure connection 232.2. This means that both the first and the second rear axles HA 1, HA 2 are braked in the same direction, but a separate pressure is output on the left and right for the vehicle 300. The primary electronic brake control unit 214 or the central module is connected via an electrical line to the second primary service brake pressure modulator 236, which is designed here as a primary front axle modulator. In the exemplary embodiment shown here, the second primary service brake pressure modulator 236 does not have its own intelligence, but rather the electromagnetic valves provided there in a known manner are switched directly by the primary electronic brake control unit 214 by means of the service brake signals SigB. As a function of the service brake signals SigB, a second service brake pressure pB 1 is controlled in a manner appropriate to the axis at the front axle VA, since the second primary service brake pressure modulator 236 is designed here as a single-channel modulator. In order to achieve wheel-appropriate braking, the electronically controllable pneumatic brake system 200 in the exemplary embodiment shown here has first and second ABS valves 238 a, 238 b, which are actuated in a known manner by the primary electronic brake control unit 214. To this end, the primary brake electronic control unit 214 also receives wheel speed signals from first and second wheel speed sensors 239 a, 239 bat the front axle VA. Wheel speed sensors 239c, 239d, 239e, 239f are also provided on the first and second rear axles HA1, HA2. All wheel speed sensors 239a-239f are directly wired to and provide wheel speed signals to the primary electronic brake control unit 214. The primary brake electronic control unit 214 is connected to the autonomous driving vehicle control unit 218 via the vehicle bus 216.The primary electronic brake control unit 214 and also the first primary service brake pressure modulator 224, i.e. overall the central module, are supplied with electrical energy by the first voltage source 222. In the normal operating case, the primary electronic brake control unit 214 receives maneuver-related brake data from the vehicle control unit for autonomous driving 218, such as in particular brake request signals, trajectory data and the like, and uses this to determine the service brake pressure pB 1, pB 2 to be provided in each case for individual axles or wheels. At the first and second rear axles HA 1, HA 2, the central module can correspondingly directly control the first service brake pressure pB 1; at the front axle VA, the central module provides the brake signals SigB to the second primary service brake pressure modulator 236, in order to switch valves there accordingly and control the second service brake pressure pB 2. If wheel slip now occurs, the central module can react directly at the rear axles HA 1, HA 2 and switch the first and second ABS valves 238 a, 238 bat the front axle VA.As a first redundancy level in the secondary system, the secondary brake electronic control unit 242 is provided. The secondary electronic brake control unit 242 is here combined with both the first secondary service brake pressure modulator 250 and the second secondary service brake pressure modulator 252 to form a module which can be referred to as a secondary or redundant central module. While the (primary) central module comprising the primary electronic brake control unit 214 and the first primary service brake pressure modulator 224 is supplied with supply pressure pV only from the first compressed air supply 101, since the central module only actuates the rear axle brake circuit, the redundant central module comprising the secondary electronic brake control unit 242, the first secondary service brake pressure modulator 250 and the second secondary service brake pressure modulator 252 is also connected to the second compressed air supply 102, since it also actuates the front axle VA.The redundant central module is also connected to an autonomous driving vehicle controller 218 via the vehicle bus 216, and also receives maneuver-related brake data, trajectory data, or the like from the autonomous driving vehicle controller 218. In the event that the central module is not functioning or not functioning correctly, the redundant central module can take over the control of the brake system 200.In the electronically controllable pneumatic brake system 200 shown here, a second redundancy level or human redundancy level is additionally provided, in which a driver has to take action. For this purpose, a brake value generator 266 is provided, which, however, can also be omitted at higher degrees of automation. The brake encoder 266 is electrically connected to both the primary electronic brake control unit 214 and the secondary electronic brake control unit 242 and may provide brake encoder signals thereto so that these two electronic control units may also be capable of manually implementing braking requests manually input by a vehicle operator via the brake encoder 266. However, the brake value generator 266 is also connected to the second compressed air supply 102 and receives supply pressure pV from the second compressed air supply 102. By actuating a brake pedal of the brake signal transmitter 266, a pneumatic brake signal transmitter brake pressure pBis controlled out, which is then likewise provided to the first and second select-high valves 260, 262, such that said pneumatic brake signal transmitter brake pressure can be provided at the corresponding first and second redundancy connections 263, 264 as an alternative to the first and second redundancy brake pressures pBR 1, pBR 2, respectively. In the event that the electronically controllable pneumatic brake system 200 is thus not powered, but the first and second compressed air reservoirs 101, 102 are still sufficiently filled, purely pneumatic and manually controlled braking can be achieved via the brake value generator 266.The parking brake 1 has a parking brake valve unit 2 and a parking brake control unit 6, wherein the parking brake control unit 6 is connected to the autonomous driving vehicle control unit 218 via the vehicle bus 216, and can receive parking brake signals from the latter, for example. However, the primary electronic control unit 214 could also request parking brake signals of this type via the vehicle bus 216, in order, for example, to park the commercial vehicle 300 or to use the parking brake 1 as an additional brake or auxiliary brake. In addition, the parking brake 1 is connected to a push-pull valve 268, via which, in the embodiment shown here, a request for venting the spring-loaded brake cylinders 254 c- 254 fby a driver can also be made electrically. For this purpose, the push-pull valve 268 is also electrically connected to the parking brake control unit 6.In the embodiment shown, the parking brake 1 comprises a relay valve 8, which is shown separately here and receives the parking brake pressure pSW from the parking brake valve unit 2 or a parking brake control pressure derived therefrom. The relay valve 8 can then increase the volume of this pressure and correspondingly pass it on to the spring-loaded brake cylinders 254 c- 254 f. For this purpose, the relay valve 8 can additionally be connected to the first and second compressed air supply 101, 102 or to the third compressed air supply 103 (see, for example, FIG. 3 ). The first service brake pressure pB 1 is also provided to the relay valve 8, in order to be able to implement an anti-compound function in this way.If the first secondary working connection 250.1 and the second secondary working connection 252.1 are now vented by a suitable valve circuit, the compressed air consumption in the redundancy level is increased in such a way that the supply pressure level falls. Since this relates to the supply pressure pV1 of the first compressed air supply 101, the supply pressure pV2 of the second compressed air supply 102 and the supply pressure pV3 of the (optionally present) third compressed air supply 103, the level of the supply pressure pV decreases overall, such that, when a certain threshold is undershot, the spring force provided in the spring-loaded brake cylinders 254 c- 254 fexceeds the counterforce which is built up by the parking brake pressure pFS, and thus brake the spring-loaded brake cylinders 254 c- 254 fand brake the vehicle 300.In the exemplary embodiment shown here, a trailer control valve 280 is also provided, which has a red and a blue or yellow coupling head in a known manner and is likewise connected to the first and second compressed air supply 101, 102. The trailer control valve 280 is electrically controlled directly from the primary electronic brake control unit 214 and does not necessarily have its own intelligence. It can also be controlled purely pneumatically from the front axle brake circuit BK 2 and is likewise connected for this purpose to the second select high valve 262, namely an outlet of the second select high valve 262, in order in this way to receive the second redundancy brake pressure pBR 2 or brake value generator pressure pW, in order likewise to brake the trailer redundantly. To implement a parking brake function in the trailer, the trailer control valve 280 is also connected to the parking brake 1 and can receive parking brake pressure pFSfrom the latter, for example.The exemplary embodiment of an electronically controllable pneumatic brake system 200 shown in FIG. 2 is represented on the basis of functional blocks. In practice, these blocks may be optionally integrated and combined into different modules. In this respect, solid lines around the individual elements do not necessarily show a separate housing, even if this can be provided in the individual case.The electronically controllable pneumatic brake system 200 comprises a service brake 9 and a parking brake 1. the service brake 9 is controlled by the secondary electronic brake control unit 242, which is connected via a signal line 217 to the vehicle BUS 216. The parking brake 1 is controlled by the parking brake control unit 6, which is connected to the vehicle bus 216 via the signal line 215.The service brake 9 comprises two service brake circuits BK 1, BK 2. The parking brake 1 comprises a parking brake circuit BK 3. The first service brake circuit BK 1 with the service brake actuators 208 c- 208 fon the rear axles HA 1, HA 2 of the commercial vehicle 300 and the first primary service brake pressure modulator 224 is supplied with compressed air via the first compressed air supply 101. The second service brake circuit BK 2 with the service brake actuators 208 a, 208 bat the front axle VA of the commercial vehicle 300 and the second primary service brake pressure modulator 236 is supplied with compressed air via the second compressed air supply 102. The parking brake circuit BK 3 with the spring-loaded brake cylinders 254 c- f, likewise at the rear axles HA 1, HA 2 of the commercial vehicle 300 and the parking brake valve unit 2 is supplied with compressed air via the third compressed air supply 103.As components of the compressed air supply arrangement 100, the compressed air supplies 101, 102 and 103 are connected to one another via a known multi-circuit protection valve 111 and are fed with compressed air from the air processing unit 105 via the compressed air outlet 109. The running compressor 104 conveys a compressed air stream through a compressed air conveying line 106 to the air processing unit 105 for supplying the service brake circuit BK 1, BK 2 and the parking brake circuit BK 3. The compressed air supplies (compressed air tanks) 101, 102 and 103 each provide a supply pressure pV1, pV2 and pV3, respectively. According to the invention, the compressed air supply arrangement 100 has a delivery-volume limiting device 120, which is arranged here downstream of the compressed air outlet 107 of the compressor 104 and upstream of the air processing unit 105, but could also be arranged downstream of the air processing unit 105 upstream of a branch of the compressed air delivery line 106 to the respective compressed air reserves 101, 102, 103. The delivery quantity limiting device 100 comprises a switchable valve unit 130- 138 for limiting the delivery quantity (compressed air delivery quantity) of the compressor 104. By limiting the delivery quantity, with sufficient (simultaneous) compressed air consumption of the electronically controllable pneumatic brake system 200, preferably by actuating the service brake 9, it is also possible to achieve a limitation of the supply pressure pV 1, pV 2, pV 3 (collectively referred to as supply pressure pV). Depending on a switching signal SigS output by the secondary electronic brake control unit 242 (preferred) or the electronic parking brake control unit 6 via the electrical signal line 113 to the switchable valve unit 130- 138, the valve unit 130- 138 assumes a first switching position SS 1 for conveying compressed air or a second switching position SS 2 for limiting the conveying amount. By means of the second switching position SS 2 of the switchable valve unit 130- 138, it is also possible to achieve a limitation of the supply pressure pV, namely when a sufficiently large quantity of air (compressed air consumption) is taken (simultaneously) from the compressed air supplies 101, 102, 103 during the delivery of a compressed air stream into the compressed air supplies 101, 102, 103, e.g. by (multiple) actuation of the service brake 9. embodiments of the switchable valve unit 130- 138 and the switching positions SS 1, SS 2 are described in detail below.FIG. 3 shows a compressed air supply arrangement 100 for supplying an electronically controllable pneumatic brake system 200 of a commercial vehicle 300 with compressed air. The compressed air supply arrangement 100 has a compressor 101 for generating compressed air, an air processing unit 105 for processing compressed air conveyed by the compressor 104, and at least one first, second and third compressed air supply 101, 102, 103 for providing a supply pressure pV 1, pV 2 and pV 3, respectively. The compressed air supplies 101, 102, 103, which are designed as compressed air tanks, are typically connected to one another via a multi-circuit protection valve known per se, with the result that the common supply pressure level is referred to overall as the supply pressure pV. The compressed air supply 101, 102, 103 is connected via the compressed air feed line 106 to a compressed air outlet 107 of the compressor 104. The air treatment unit 105 is arranged upstream of the compressed air supplies 101, 102, 103, 112. According to the invention, at least one delivery quantity limiting device 120, 121 is provided, which comprises a switchable valve unit 130- 137, 151 (see FIGS. 3-11 ) and serves to limit the compressed air flow delivered from the compressor 104 through the compressed air delivery line 106 and its line sections 106 a, 106 b, 106 cto the compressed air supplies 101, 102, 103, 112. The switchable valve unit 130- 137, 151 is configured to be switched by a switching signal SigS received from the secondary electronic brake control unit 242 in the event of a fault in the electronically controllable pneumatic brake system 200.The compressed air supply arrangement 100 supplies the first service brake circuit BK 1 with service brake actuators 208 c- 208 fat the rear axle HA of the commercial vehicle 300 with compressed air via the first compressed air supply 101. In addition, the compressed air supply arrangement 100 supplies the second service brake circuit BK 2 with compressed air with the service brake actuators 208 a, 208 bat the front axle VA of the utility vehicle 300 via the second compressed air supply 102. In addition, the compressed air supply arrangement 100 supplies a third brake circuit BK 3, namely the parking brake circuit, with compressed air via the third compressed air supply 103. An auxiliary compressed air circuit HK, for example for the air suspension of the commercial vehicle, the air suspension of the driver's cab, the transmission control system or pneumatically actuatable vehicle doors (in the case of buses) and other pneumatic auxiliary functions of the commercial vehicle 300, is also supplied with compressed air via the fourth compressed air supply 112.The delivery quantity limiting device 120, 121 can be arranged at different positions of the compressed air supply arrangement 100, in particular at the four different positions illustrated in FIG. 3. The switchable valve unit 130- 137 of the delivery quantity limiting device 120, 121 can be arranged upstream of a compressed air inlet 108 of the compressed air processing unit 105 (left-hand position in FIG. 3 ) or integrated into the air processing unit 105 (second position from the left in FIG. 3 ). The air processing unit 105 is arranged upstream of the first compressed air supply 101, the second compressed air supply 102 and the third compressed air supply 103. A switchable valve unit 130- 137 (see FIGS. 4- 7 ) of a delivery quantity limiting device 120, 121 can be arranged downstream of a compressed air outlet 109 of the air processing unit 105 and upstream of a compressed air inlet 110 of the first compressed air supply 101. Additionally or alternatively, the switchable valve unit 130- 137 of a delivery quantity limiting device 120, 121 can be arranged downstream of the compressed air outlet 109 and upstream of the compressed air inlet 110 of the second compressed air supply 102 (see the two right positions in FIG. 3 ). In particular, each embodiment of the delivery quantity limiting device 120, 121 described in the following FIGS. 4-7 can be arranged at each of the positions shown in FIG. 3, also as shown in FIGS. 8 and 9.The delivery quantity limiting device 120, 121 also reduces (indirectly) the supply pressure pV, which is available for generating a parking brake pressure pVL for pressurizing a spring-loaded brake cylinder 254 c- fof the parking brake 1, by limiting the delivered compressed air flow. This limitation of the supply pressure pV is achieved in that the delivery rate limiting device 120, 121 prevents a compressed air stream delivered by the compressor 104 from entering one (or more) of the compressed air supplies 101, 102, 103 and prevents or slows down the drop in the supply pressure pV desired for engaging the parking brake 1 by a follow-up delivery of the compressor 104 (in the case of no or too low consumption of compressed air), in particular also in the case of a (still) running compressor 104.In FIG. 4, the switchable valve unit 130 of the delivery quantity limiting device 120, 121 is designed as a switchable shut-off valve, namely as a switchable electromagnetic 2 / 2-way valve (solenoid valve). The valve unit 130 can interrupt the compressed air flow delivered by the compressor 104 as a function of the switching signal SigS output by the secondary electronic brake control unit 242 and thereby limit the supply pressure pV. In a first switching position SS 1 for conveying compressed air, the valve unit 130 is not supplied with current and allows conveyed compressed air to pass through the line section 106 aof the compressed air conveying line 106 to the line section 106 b. The line section 106 bmay be connected to a compressed air inlet 108 of the compressed air processing unit 105 or directly to a compressed air inlet 110 of the compressed air supplies 101, 102, 103. In the second shift position SS 2, the supplied supply pressure pV is reduced in comparison with the supply pressure pV supplied in a first shift position SS 1. The switchable valve unit 130 is therefore designed to shut off the compressed air feed line 106 on the basis of the switching signal SigS received from the secondary electronic brake control unit 242.In the embodiment according to FIG. 5, the switchable valve unit 131 of the delivery quantity limiting device 120, 121 is designed as a switchable valve, namely as a switchable electromagnetic 2 / 2-way valve (solenoid valve), wherein the valve has a flow reduction section 140 which is designed as a throttle section 141 (in the form of a nozzle). The throttle section 141 is here part of the movable valve body of the valve unit 131, namely as a throttle-shaped passage opening. Unlike in the embodiment according to FIG. 4, the compressed air flow conveyed by the compressor 104 is not completely shut off, but rather is reduced by the throttle section 141 in order to limit, namely to reduce, the supply pressure pV. The supply pressure pV drops when the compressed air consumption exceeds the (reduced) conveyed compressed air quantity. The throttle section leads to a pressure loss and thus to a lowering of the pressure across the throttle section, whereby the supplied reservoir pressure pV is reduced. The throttle effect is determined decisively by the nominal diameter of the throttle section 141, wherein a smaller nominal diameter leads to a larger pressure loss and limits the supply pressure pV to a greater extent (i.e. to a lower pressure level). The switchable valve unit 131 is therefore configured to connect the compressed air delivery line 106, specifically the line sections 106 a, 106 b, to a flow reduction section 140 (throttle section 141) of the delivery quantity limiting device 120, 121 on the basis of the switching signal SigS received from the secondary electronic brake control unit 242. Here, in the second switching position SS 2, the pipe portion 106 aof the compressed air supply pipe 106 is connected to an inlet end of the flow reducing portion 140 (throttle portion 141), and the pipe portion 106 bof the compressed air supply pipe 106 is connected to an outlet end of the flow reducing portion 140.The embodiment according to FIG. 6 is a variant of the embodiment according to FIG. 5. the switchable valve unit 132 of the delivery quantity limiting device 120, 121 is designed as a switchable valve, namely as a switchable electromagnetic 3 / 2-way valve (solenoid valve), wherein the valve has a flow reduction section 140 which is designed as a throttle section 141 (in the form of a nozzle). The throttle section 141 is designed here as a line section of the valve in the valve housing, which line section can be connected to a valve outlet 144 of the 3 / 2-way valve in a second switching position SS 2. Incidentally, the valve unit 132 functions like the valve unit 131.In the embodiment according to FIG. 7, the switchable valve unit of the delivery quantity limiting device 120, 121 is designed as a switchable ABS valve unit 137, 138. A first valve connection 139 aof the switchable ABS valve unit 137, 138 can be connected via the line section 106 a-depending on the position of the delivery quantity limiting device 120, 121 in the compressed air supply arrangement 100-optionally to a compressed air outlet 107 of the compressor 104 or to a compressed air outlet 109 of the air processing unit 105. A second valve connection 139 bof the switchable ABS valve unit 137, 138 can be connected via the line section 106 b-depending on the position of the delivery quantity limiting device 120, 121 in the compressed air supply arrangement 100-to a compressed air inlet 108 of the air processing unit 105 or directly to a compressed air inlet 110 of a compressed air supply 101, 102, 103. A third valve connection 139 cof the switchable ABS valve unit 137, 138 is connected to a vent 3. The ABS valve unit 137, 138 known per se is used in this way on the one hand for flow restriction and thus for restriction of the compressed air supply pV. On the other hand, a compressed air supply 101, 102, 103 can be vented via the ABS valve unit 137, 138.The switchable ABS valve unit 137, 138 includes a pneumatically switchable inlet valve 134, a pneumatically switchable outlet valve 136, an electromagnetic inlet valve 133 and an electromagnetic outlet valve 135. On the one hand, the compressed air flow conveyed by the compressor can be interrupted in a second switching position SS 2 via the 2 / 2-way inlet valve part of the ABS valve unit, which comprises the pneumatically switchable inlet valve 133 and the electromagnetic inlet valve 134. On the other hand, the compressed air supply (compressed air storage, preferably compressed air tank) can be selectively vented, in particular as a function of the switching signal received from a (secondary) electronic brake control unit (242) of the brake system (200), via the 2 / 2-way outlet valve part of the ABS valve unit, which comprises the pneumatically switchable outlet valve 136 and the electromagnetic outlet valve 136. In the switching position of the pneumatically switchable outlet valve 136 shown in FIG. 7, the compressed air supplies 101, 102, 103 connectable via the second valve connection 139 bare not vented, but the current supply pressure pV is maintained.The intake and exhaust electromagnetic valves 133, 135 are switchable via switching signals SigS received from the secondary brake electronic control unit 242. The electromagnetic inlet valve 133 is connected via a first control line 142 to a pneumatic control connection of the pneumatically switchable inlet valve 134. The electromagnetic outlet valve 135 is connected via a second control line 143 to a pneumatic control connection of the pneumatically switchable outlet valve 136. Both electromagnetic valves 133, 135 are de-energized in the switching position shown in FIG. 7, in which the first control line 142 is connected to the vent 3 via the electromagnetic inlet valve 133. The pneumatic control connection of the pneumatically switchable outlet valve 136 can be supplied with the delivery pressure originating from the first valve connection 139 a, which the compressor 104 supplies via the line section 106 aof the compressed air delivery line 106. In the switching position shown in FIG. 7, no delivery pressure is present at the first valve connection 139 a. However, when a delivery pressure is provided by the compressor 104, the pneumatically switchable inlet valve 134 is automatically switched into the switching position not shown in FIG. 7 via a return line, so that it is then the open position. The conveyed compressed air flow can then flow first valve connection 139 ato second valve connection 139 band further into a connected compressed air supply 101, 102, 103. Since the second control line 143 is supplied with precisely this delivery pressure, the switching position is not changed by the return at the pneumatically switchable outlet valve 136, so that the vent 3 remains shut off. If, on the other hand, the electromagnetic outlet valve 135 is energized, no more pressure is triggered in the second control line 143, so that when the pneumatically switchable inlet valve 134 is open, the pneumatically switchable outlet valve 136 also automatically switches and thus connects the second valve outlet 139 bto the vent 3, whereby the compressed air supplies 101, 102, 103 are vented. This venting can be ended by de-energizing electromagnetic outlet valve 135 or by energizing electromagnetic inlet valve 133. In this way, the ABS valve unit 137, 138 is used to limit the delivery rate and thereby preferably also limit the supply pressure pV.In the embodiment according to FIG. 8, a delivery quantity limiting device 120, 121, which is designed as an ABS valve unit 137, 138, is arranged, for example, in the compressed air delivery line 106 upstream of the air processing unit 105.In the embodiment according to FIG. 9, a delivery quantity limiting device 120 designed as an ABS valve unit 137 is arranged downstream of the air processing unit 105 and upstream of the first compressed air supply 101 in the compressed air delivery line 106 between the line section 106 band 106 cto limit the delivery quantity into the compressed air supply 101, wherein the compressed air supply 101 can be vented at the supply pressure pV 1 by the ABS valve unit 137. Analogously, a delivery quantity limiting device 121, which is designed as an ABS valve unit 138, is arranged downstream of the air processing unit 105 and upstream of the second compressed air supply 102 in the compressed air delivery line 106 between the line section 106 band 106 cto limit the delivery quantity into the compressed air supply 102, wherein the compressed air supply 102 can be vented by the ABS valve unit 138 at the supply pressure pV2. The levels of the supply pressures pV1 and pV2 can thus be limited independently of one another.In the embodiment according to FIG. 10, the air conditioning unit 105 is connected to a control unit of the compressor 104 via a compressor control line 150 in order to provide a compressor control pressure pK. The switchable valve unit 151 of the discharge restriction device 120 is disposed in the compressor control line 150. The switchable valve unit 151 is configured to connect the control pressure inlet 154 of the compressor 104 to the control pressure outlet 153 of the air treatment unit 105 in the first switching position SS 1. In the second shift position SS 2, the compressor control line 150 is vented. In this embodiment, the compressor 104 delivers compressed air when the compressor control line 150 is vented and does not deliver compressed air when the compressor control line 150 is vented. The operating state of the compressor 104 can be controlled via the compressor control line 150 in such a way that the compressor 104 delivers less compressed air, or preferably no compressed air any longer, if a drop in the storage pressure pV is desired. Preferably, the compressor 104, like the clutch shift, is disconnected from the drive when the compressor control pressure pK drops below a certain pressure level.The pressure sensor 152 is for sensing the compressor control pressure pK in the compressor control line 150 and transmits a corresponding compressor control pressure signal SigK to an electronic brake control unit 242. The pressure sensor 152 is disposed in the compressor control line portion connected to the control pressure inlet 154 of the compressor 104. The secondary electronic brake control unit 242 outputs a switching signal SigS to the switchable valve unit 151 on the basis of the received compressor control pressure signal SigK when a compressor control pressure pK detected by the pressure sensor 152 falls below a predetermined pressure level.As a result, the drop in the supply pressure pV can be detected and a further delivery of the compressor 104 can be prevented.In the embodiment according to FIG. 11 that is alternative to FIG. 10, the switchable valve unit 151 is designed to connect the control pressure inlet 154 of the compressor 104 to the control pressure outlet 153 of the air processing unit 105 in the first switching position SS 1. In the second switching position SS 2, the control pressure inlet 154 of the compressor 104 is connected to the auxiliary supply pressure pSWin the fourth compressed air supply 112 in order to ventilate the compressor control line 150. In this embodiment, the compressor 104 delivers compressed air when the compressor control line 150 is depressurized and does not deliver compressed air when the compressor control line 150 is vented. In the second switching position SS 2, the control pressure inlet 154 is connected to the auxiliary supply pressure pSW via the redundant compressor control line section 155. The auxiliary supply pressure pHVis provided by the fourth compressed air supply 112 of the auxiliary compressed air circuit HKof the electronically controllable pneumatic brake system 200. In the compressor control line section 155, a pressure retaining device for retaining the auxiliary reserve pressure pHVas the compressor control pressure pK, for example by means of a check valve 156 or an active holding valve, can optionally be provided.The embodiments of the invention shown have the advantage that the engagement of the parking brake 1 is reliably made possible on account of the restriction of the compressed air delivery rate by the switchable delivery rate restriction device 120, 121, in particular even when the compressor 104 is running, above all also in the event of a fault in the electronically controllable pneumatic brake system 200 in the case of vehicles of relatively high degrees of automation.Reference Sign (Part of Description)1 Parking brake 2 Parking brake valve unit 3 Vent 4 First supply connection of the parking brake valve unit 5 Second supply connection of the parking brake valve unit 6 Parking brake control unit 8 aFirst spring accumulator connection 8 bSecond spring accumulator connection 8 Relay valve 9 Service brake HA 1First rear axle HA 2Second rear axle VA Front axle BK 1, BK 2 Brake circuit, namely service brake circuit BK 3 Brake circuit, namely parking brake circuit HK auxiliary compressed air circuit 100 compressed air supply arrangement 101 first compressed air supply 102 second compressed air supply 103 third compressed air supply 104 compressor 105 air processing unit 106 compressed air feed line 106 a- cof the compressed air feed line 107 compressed air outlet of compressor 108 compressed air inlet of air processing unit 109 compressed air outlet of air processing unit 110 compressed air inlet of compressed air supply 111 multi-circuit protection valve 112 fourth compressed air supply 113 signal line 120, 121 delivery quantity limiting device 130- 132 switchable valve unit 133 electromagnetic inlet valve 134 pneumatically switchable inlet valve 135 electromagnetic outlet valve 136 pneumatically switchable outlet valve 137, 138 switchable ABS valve unit 139 afirst valve port of ABS valve 139 bsecond valve port of ABS valve 139 cthird valve port of ABS valve 140 flow reduction portion 141 throttle portion 142 first control line 143 first control line 144 valve outlet 150 compressor control line 151 switchable valve unit 152 pressure sensor 153 control pressure outlet of air conditioning unit 154 control pressure inlet of compressor 155 redundant compressor control line portion 156 check valve 200 electronically controllable pneumatic brake system 208 c- 208 fservice brake actuators 214 (primary) electronic brake control unit 215 signal line 216 vehicle BUS 217 signal line 218 autonomous driving vehicle control unit 222 first voltage source 224 first primary service brake pressure modulator (primary rear axle modulator) 232.1 first service brake pressure port 232.2 second service brake pressure port 236 second primary service brake pressure modulator (primary rear axle modulator) Third service brake pressure connection 236.2 Fourth service brake pressure connection 238a First ABS valve 238b Second ABS valve 242 (secondary) Electronic brake control unit 246 Second voltage source 250 First secondary service brake pressure modulator 250.1 First secondary working connection 252 Second secondary service brake pressure modulator 252.1 Second secondary working connection 254c-254f Spring brake cylinder 260 First select high valve 262 Second select high valve 263 First redundancy connection 264 Further redundancy connection 266 Brake value transmitter 268 Push pull valve 280 Trailer control valve 300 Commercial vehicle pV Supply pressure pV1, pV2 Supply pressure pV3 Supply pressure pK Compressor control pressure pSW Auxiliary supply pressure pB1 First service brake pressure pB2 Second service brake pressure pSW Parking brake pressure pBR1 First redundancy brake pressure pBR2 Second redundancy brake pressure pW Brake value generator brake pressure SigB Operating brake signal SigS Switching signal SigK Compressor control pressure signal SS1 First switching position (for delivering compressed air) SS2 Second switching position (for limiting the delivery quantity)References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2021 122 497 A1

[0007] DE 10 2020 132 875 A1

[0008] EP 3 145 769 A1

[0008] EP 1 968 830 B1

[0008] DE 10 2022 101 142 A1

[0009] DE 10 2021 122 498 A1

[0009] DE 10 2021 122 499 A1

[0009]

Claims

Compressed air supply arrangement (100) for supplying compressed air to an electronically controllable pneumatic brake system (200) of a commercial vehicle (300), comprising: - a compressor (101) for generating compressed air; - an air processing unit (105) for processing compressed air conveyed by the compressor (104); - at least one compressed air supply (101, 102, 103) for providing a supply pressure (pV, pV1, pV2, pV3) for applying compressed air to at least one spring-loaded brake cylinder (254c-254f) of a parking brake (1) of the brake system (200), wherein the compressed air supply (101, 102, 103) is connected to a compressed air outlet (107) of the compressor (104) via at least one compressed air conveying line (106); and - at least one delivery quantity limiting device (120, 121), which comprises a switchable valve unit (130-138, 151), for limiting the compressed air flow delivered from the compressor (104) through the at least one compressed air delivery line (106) to the at least one compressed air supply (101, 102, 103), wherein the switchable valve unit (130-138, 151) is designed to be switched in the event of a fault in the brake system (200) by a switching signal (SigS) received from an electronic brake control unit (242) of the brake system (200).Compressed air supply arrangement (100) according to Claim 1, wherein the switchable valve unit (130-138, 151), in a switching position (SS2) limiting the delivery rate, at least partially prevents compressed air from being conveyed by the compressor (104) into the at least one compressed air store (101, 102, 103).Compressed air supply arrangement (100) according to Claim 1 or 2, wherein the supply pressure (pV, pV1, pV2, pV3) provided by the compressed air supply (101, 102, 103) in a second switching position (SS2) of the switchable valve unit (130-138, 151) is reduced in comparison with the supply pressure (pV, pV1, pV2, pV3) provided by the compressed air supply (101, 102, 103) in a first switching position (SS1) of the switchable valve unit (130-138, 151) by conveying compressed air by means of the compressor.Compressed air supply arrangement (100) according to one of the preceding claims, wherein the air processing unit (105) is arranged upstream of the at least one compressed air supply (101, 102, 103) and the at least one switchable valve unit (130-138) of the delivery quantity limiting device (120, 121) is arranged upstream of a compressed air inlet (108) of the air processing unit (105) or is integrated into the air processing unit (105).Compressed air supply arrangement (100) according to one of the preceding claims, wherein the air processing unit (105) is arranged upstream of the at least one compressed air supply (101, 102, 103), - wherein the compressed air supply arrangement (100) comprises a first compressed air supply (101) of a first service brake circuit (BK1) of the brake system (200) for supplying at least one first service brake actuator (208c-208f) on a first axis of the commercial vehicle (300) with compressed air and a second compressed air supply (102) of a second service brake circuit (BK2) of the brake system (200) for supplying at least one second service brake actuator (208a, 208b) on a second axis of the commercial vehicle (300) with compressed air, - wherein the air processing unit (105) is arranged upstream of the first compressed air supply (101) and the second compressed air supply (102), and, wherein the switchable valve unit (130-138) of a first delivery quantity limiting device (120) is arranged downstream of a compressed air outlet (109) of the air processing unit (105) and upstream of a compressed air inlet (110) of the first compressed air supply (101), and / or wherein the switchable valve unit (130-138) of a second delivery quantity limiting device (121) is arranged downstream of a compressed air outlet (109) of the air processing unit (105) and upstream of a compressed air inlet (110) of the second compressed air supply (102).Compressed air supply arrangement (100) according to one of the preceding claims, wherein the switchable valve unit (130-132) of the delivery quantity limiting device (120, 121) is designed to shut off the compressed air delivery line (106) on the basis of the switching signal (SigS) received from an electronic brake control unit (242) of the brake system (200) and / or to connect at least one line section (106a, 106b) of the compressed air delivery line (106) to a flow reduction section (140) of the delivery quantity limiting device (120, 121).Compressed air supply arrangement (100) according to Claim 6, wherein the flow reduction section (140) is designed as a throttle section (141).Compressed air supply arrangement (100) according to one of the preceding claims 1 to 5, wherein the switchable valve unit (133-136) of the at least one delivery quantity limiting device (120, 121) is designed as a switchable ABS valve unit (137, 138), wherein a first valve connection (139a) of the switchable ABS valve unit (137, 138) is connected to a compressed air outlet (107) of the compressor (104), a second valve connection (139b) of the switchable ABS valve unit (137, 138) is connected to a compressed air inlet (108) of the air processing unit (105) or to the at least one compressed air supply (101, 102, 103), and a third valve connection (139c) of the switchable ABS valve unit (137, 138) is connected to a vent (3).The compressed air supply arrangement (100) according to claim 8, wherein the switchable ABS valve unit (137, 138) comprises a pneumatically switchable inlet valve (134), a pneumatically switchable outlet valve (136), an electromagnetic inlet valve (133) and an electromagnetic outlet valve (135).Compressed air supply arrangement (100) according to one of the preceding claims, wherein the air processing unit (105) is connected to a control unit of the compressor (104) for the purpose of providing a compressor control pressure (pK) via a compressor control line (150), and the switchable valve unit (151) of the delivery quantity limiting device (120) is arranged in the compressor control line (150).Compressed air supply arrangement (100) according to Claim 10, wherein the switchable valve unit (151) is designed - to connect a control pressure inlet (154) of the compressor (104) to a control pressure outlet (153) of the air processing unit (105) in a first switching position (SS1) and to vent the compressor control line (150) in a second switching position (SS2), or - to connect a control pressure inlet (154) of the compressor (104) to a control pressure outlet (153) of the air processing unit (105) in a first switching position (SS1) and to connect the control pressure inlet (154) of the compressor (104) to an auxiliary supply pressure (pSW) of the brake system (200) in a second switching position (SS2).Compressed air supply arrangement (100) according to either of Claims 10 and 11, wherein the delivery quantity limiting device (120) comprises a pressure sensor (152) for detecting a compressor control pressure (pK) in the compressor control line (150), wherein the pressure sensor (152) is designed to transmit a compressor control pressure signal (SigK) representing the detected compressor control pressure (pK) to an electronic brake control unit (242) of the brake system (200).Electronically controllable pneumatic brake system (200) for a commercial vehicle (300), comprising - a compressed air supply arrangement (100) according to one of Claims 1 to 12, - a parking brake (1) having at least one spring-loaded brake cylinder (254c-254f) which can be acted upon by compressed air by a supplied supply pressure (pV, pV1, pV2, pV3) of the at least one compressed air supply (101, 102, 103) for releasing the parking brake (1), and - at least one electronic brake control unit (242) which is configured to output a switching signal (SigS) to the switchable valve unit (130-138, 151) of the at least one delivery-quantity limiting unit (120, 121) in the event of a fault in the electronically controllable pneumatic brake system (200).Electronically controllable pneumatic brake system (200) according to claim 13, wherein the electronic brake control unit (242) is a secondary electronic brake control unit (242) which is configured to receive maneuver-related brake data via a vehicle bus (216) from an autonomous driving vehicle control unit (218) or a redundant autonomous driving vehicle control unit, wherein the secondary electronic brake control unit (242) is configured to at least partially control at least one service brake circuit (BK1, BK2) of the electronically controllable pneumatic brake system (200) in the event of a fault of a primary electronic brake control unit (214) of the electronically controllable pneumatic brake system (200).Electronically controllable pneumatic brake system (200) according to Claim 13 or 14, wherein the electronically controllable parking brake (1) comprises a parking brake valve unit (2) which is supplied with supply pressure (pV, pV1, pV2, pV3) and is intended to provide a parking brake pressure (pWD), with which the at least one spring-loaded brake cylinder (254c-254f) can be acted upon, wherein the supply pressure (pV, pV1, pV2, pV3) - by a first compressed-air supply (101) of a first service brake circuit (BK1) of the electronically controllable pneumatic brake system (200) for supplying at least one first service brake actuator (208c-208f) with compressed air or, a second compressed air supply (102) of a second service brake circuit (BK2) of the electronically controllable pneumatic brake system (200) for supplying at least one second service brake actuator (208a, 208b) on a second axle of the commercial vehicle (300) with compressed air or, a third compressed air supply (103) of a parking brake circuit (BK3) for supplying the parking brake valve unit (2) with compressed air or an air processing unit (105) for processing the compressed air conveyed by a compressor (104).Method for engaging a parking brake (1) of an electronically controllable pneumatic brake system (200) of a commercial vehicle (300), in particular according to one of Claims 13 to 15, comprising the following steps: detecting a fault in the electronically controllable pneumatic brake system (200), wherein the detected fault prevents the engagement of the electronically controllable parking brake (1) by a switching process of a parking brake valve unit (2) of the parking brake (1) in such a way that at least one spring-loaded brake cylinder (254c-254f) of the parking brake (1) is vented; outputting a switching signal (SigS) by an electronic brake control unit (242) of the brake system (200) to a switchable valve unit (130-138, 151) of at least one delivery quantity limiting device (120, 121) of a compressed air supply arrangement (100) for supplying the electronically controllable pneumatic brake system (200), in particular according to one of Claims 1 to 12, wherein the switching signal (SigS) has the effect that the compressed air flow delivered by the compressor (104) to at least one compressed air supply (101, 102, 103) of the electronically controllable pneumatic brake system (200) is limited; and lowering a supply pressure (pV, pV1, pV2, pV3) for acting on at least one spring-loaded brake cylinder (254c-254f) of an electronically controllable parking brake (1) of the electronically controllable pneumatic brake system (200) by using compressed air in at least one service brake circuit (BK1, BK2) or parking brake circuit (BK3) of the electronically controllable pneumatic brake system (200).Method according to Claim 16, wherein the supply pressure (pV, pV1, pV2, pV3) is lowered by at least partially venting at least one or more times at least one service brake actuator (208a-208f) of at least one service brake circuit (BK1, BK2) of the electronically controllable pneumatic brake system (200).Commercial vehicle (300) comprising a compressed air supply arrangement (100) for supplying an electronically controllable pneumatic brake system (200) according to one of Claims 1 to 12 and / or an electronically controllable pneumatic brake system (200) according to one of Claims 13 to 15, wherein an electronic brake control unit (242) of the brake system (200) is designed in particular to carry out the method according to 16 or 17.

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