Electropneumatic parking brake system with parking brake redundancy unit

Abstract

The invention relates to a parking brake device (1) for venting and bleeding spring brake cylinders (254c, 254d, 254e, 254f), comprising a parking brake valve unit (2), and a parking brake redundancy unit (10), which is designed to connect a parking compressed air path (12) to a vent (14) independently of the parking brake valve unit (2) for venting at least one spring brake cylinder (254c, 254d, 254e, 254f), wherein the parking brake redundancy unit (10) has a first vent path (18) which comprises a main connection (16) for receiving a pressure (pFS, pV) of the parking compressed air path (12), a first redundancy valve unit (20), a second redundancy valve unit (22), and a redundancy vent (14), wherein the first Redundancy valve unit (20) is controllable by a first control unit (26), and wherein the second redundancy valve unit (22) is controllable by a second control unit (28),and wherein the parking brake redundancy unit (10) is configured to connect the main connection (16) to the redundancy vent (14) in order to vent the main connection (16). Furthermore, the invention relates to a brake system (200), a vehicle (300), and a method.

Description

The invention relates to an electropneumatic parking brake device for venting and venting one or more spring-loaded brake cylinders of an at least partially electronically controllable pneumatic brake system for a vehicle, comprising an electropneumatic parking brake valve unit having a supply connection for receiving supply pressure from a compressed air supply, and a parking brake control unit, wherein the parking brake valve unit is designed to control a parking pressure at at least one spring-loaded connection as a function of a parking brake signal. The invention further relates to an electronically controllable pneumatic brake system and a vehicle comprising such a brake system.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".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 other 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.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 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.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 in order to vent them. This is intended to increase the range of functions and the operational readiness of the vehicle. 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, wherein 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.Further partially redundant systems are known from DE 10 2022 101 142 A1, DE 10 2021 122 498 A1, DE 10 2021 122 499 A1, DE 10 2020 132 875 A1 and EP 3 145 769 B1.Even if known systems already partially provide a redundant possibility for engaging or releasing a parking brake, there is a need for further improvements. In particular, in the aforementioned known possibilities, assembly and production costs can be high, since the connection to the service brake system may require long line paths. In addition, the achievable system dynamics can be limited.It is therefore desirable to improve the engagement of a parking brake. In particular, venting of at least one spring brake cylinder is to be made possible in a reliable manner and with little effort.At this point, the invention starts, the object of which is to specify an improved electropneumatic parking brake device which makes it possible to vent a spring-loaded brake cylinder easily and / or reliably even in the event of redundancy.In a first aspect, the invention achieves this object with an electropneumatic parking brake device according to Claim 1. Proceeding from an electropneumatic parking brake device of the type mentioned at the beginning, an electropneumatic parking brake redundancy unit is furthermore provided, which is designed to connect a parking pressure air path to a vent independently of the electropneumatic parking brake valve unit for venting at least one spring brake cylinder, wherein the parking brake redundancy unit has a first vent path which comprises a main connection for receiving a pressure of the parking pressure air path, a first electropneumatic redundancy valve unit, a second electropneumatic redundancy valve unit, and a redundancy vent into the environment. The first electropneumatic redundancy valve unit can be controlled by a first control unit, and the second electropneumatic redundancy valve unit can be controlled by a second control unit, which is independent of the first control unit. The parking brake redundancy unit is designed to connect the main connection to the redundancy vent via the first venting path of the parking brake redundancy unit in order to vent the main connection directly into the environment. In addition to the electropneumatic parking brake valve unit, the parking brake redundancy unit is therefore also provided for venting a spring-loaded brake cylinder of the brake system and thus engaging the parking brake. For this purpose, the parking brake valve unit can connect a parking pressure air path to a vent, wherein this connection can take place independently of the electropneumatic parking brake valve unit. Thus, a spring brake cylinder can be vented even if the electropneumatic parking brake valve unit has a fault, is not supplied with voltage or is otherwise limited in its function. The parking compressed air path is a compressed air path which is associated with the parking brake of the vehicle. This may be a compressed air path which is directly connected to one or more spring brake cylinders. For example, the parking pressure air path can be a compressed air path between the spring accumulator connection of the parking brake valve unit and the spring accumulator of the spring accumulator brake cylinder. However, it can be provided, for example and preferably, that the parking pressure air path is a supply path which connects a compressed air supply of the brake system to the parking brake.The parking brake redundancy unit comprises at least one venting path. The first venting path connects a main connection of the parking brake redundancy unit to a redundancy venting into the environment. The redundancy venting opens directly into the environment. Therefore, no further functional units of a brake system are provided between the redundancy vent and the environment. However, it can be provided that the redundancy venting comprises one or more passive elements, such as a silencer and / or a line. In particular, no switchable components or modulators are arranged between the redundancy venting and the environment. The direct connection of the redundancy venting to the environment excludes further sources of error. In addition, high system dynamics can be achieved. Furthermore, line lengths can be reduced, as a result of which the assembly and production outlay of the parking brake device can be reduced. Preferably, the first vent path is parallel to a primary vent path of the parking brake valve unit. The primary vent path connects the spring accumulator port of the parking brake valve unit to a primary vent of the parking brake valve unit. The first venting path of the parking brake redundancy unit and the primary venting path of the parking brake valve unit are preferably connected to one another at the spring accumulator connection. However, it can also be provided that the first venting path and the primary venting path open into a connecting line to the spring brake cylinder. In other variations, the first venting path and the primary venting path are completely separated.The first electropneumatic redundancy valve unit can be controlled by a first control unit and the second electropneumatic redundancy valve unit can be controlled by a second control unit. The control units can be control units of the parking brake device, but do not have to be so. Preferably, the first control unit and / or the second control unit is a service brake control unit of a brake system. The second control unit is independent of the first control unit. As a result, it is possible to further increase the reliability of the parking brake device, since in the event of failure of one of the control units, the respective other control unit can continue to be functional.In a first preferred development, the first control unit and / or the second control unit is independent of the parking brake control unit. This makes it possible to ensure that at least one of the control units is independent of the parking brake control unit. In the event that only the parking brake control unit has a fault, at least the first control unit or the second control unit is still operable. Preferably, both the first control unit and the second control unit are independent of the parking brake control unit. However, in variants it can also be provided that the first control unit or the second control unit is formed by the parking brake control unit, or that the parking brake control unit comprises the first control unit or the second control unit.The first electropneumatic redundancy valve unit preferably has a bistable valve unit having a first position and a second position, wherein the first position is a venting position in which the bistable valve unit allows a pneumatic connection of the main connection to the redundancy venting, and wherein the bistable valve unit interrupts the first venting path in the second switching position. In the second switching position, the bistable valve unit interrupts the first venting path and thus prevents an air flow through the first venting path. The bistable valve unit can thus prevent, for example, an undesired venting of a spring-loaded brake cylinder. In the first position, the bistable valve unit preferably releases the first venting path or enables at least one flow through the bistable valve unit through the venting path. The bistable valve unit is stable in the first position and in the second position and remains in the previously assumed position in particular also in the de-energized state. The bistable valve unit thus enables, for example, the switching between an autonomous operating mode and a manual operating mode. For example, the bistable valve unit can only be in the first position in an autonomous operating mode of a brake system. In this case, venting of the parking brake path by means of the redundancy valve unit is then possible, for example, only in the autonomous operating case for which redundancy is particularly important. The bistable valve unit may comprise one or more valves which provide the bistable functionality. In a preferred embodiment, the bistable valve unit is or comprises a bistable valve, preferably an electrically switchable bistable valve, particularly preferably an electrically switchable solenoid-operated bistable valve. In other variants, the bistable function of the bistable valve unit can, however, also be achieved by suitable interconnection of a plurality of valves which do not necessarily have to be designed as bistable valves.Preferably, the first electropneumatic redundancy valve unit has a first monostable holding valve which is connected in series along the first venting path with the bistable valve unit, in particular a bistable valve of the bistable valve unit. The first monostable hold valve has only one stable state. In the de-energized state, the monostable holding valve switches into this stable state. Preferably, the monostable holding valve enables the first venting path in the non-energized state or in the stable state. In the de-energized state, the monostable holding valve then allows a flow through the same or is open. Preferably, the first holding valve can be switched into a closed state by the first control unit. For example and preferably, the first holding valve can be a solenoid valve which can be switched into a closed position by energizing an electromagnet. The first control unit can then switch the first holding valve depending on the operating case in order to release or not open the first venting path. In the event of a fault in the first control unit, the first holding valve automatically switches into the open state and thus allows the parking brake to be engaged or the parking brake path to be vented even in the event of a fault (provided that any further valves along the first venting path also allow the same to flow through).In a preferred variant, the second electropneumatic redundancy valve unit comprises a second monostable holding valve which is connected in series along the first venting path with the bistable valve unit, in particular a bistable valve of the bistable valve unit. The second monostable holding valve can preferably be designed analogously to the first monostable holding valve. Preferably, the first monostable holding valve of the first electropneumatic redundancy valve unit and the second monostable holding valve of the second electropneumatic redundancy valve unit are each prestressed into an open state and / or open in the non-energized state. In this case, the holding valves release the first venting path when they are de-energized. The parking brake redundancy unit then advantageously remains controllable even in the event of a partial fault. If, for example, the first control unit has a fault and therefore the first monostable holding valve of the first electropneumatic redundancy valve unit is not supplied with electrical voltage, then the first holding valve switches into the open state and releases the section of the first venting path running through the first holding valve. The second control unit, which is still functional in this scenario, can then open up or not open up the first venting path by appropriate actuation of the second monostable holding valve in order to connect the main connection to the redundancy venting and thus to conduct the pressure of the fixed compressed air path received at the main connection into the environment.In a preferred development of a variant of the electropneumatic parking brake device, the second monostable holding valve is arranged along the first venting path between the bistable valve unit, in particular a bistable valve of the bistable valve unit, and the first monostable holding valve.Preferably, the parking brake redundancy unit comprises at least one pressure sensor. The pressure sensor is configured to sense a pressure in the first venting path. The pressure sensor is preferably connectable to the first control unit and / or the second control unit in order to provide signals corresponding to the detected pressure of the venting path for the first control unit and / or the second control unit. The pressure sensor allows a state diagnosis for the parking brake redundancy unit. For example, a first control unit connected to the pressure sensor may determine, using the pressure sensor, whether or not a pressure is present at the main port of the parking brake redundancy unit. If the main connection is connected to a spring brake cylinder, for example, it can be determined, using the pressure sensor, whether or not the parking brake is engaged. The pressure sensor is preferably designed to determine the pressure at the main connection or to provide pressure signals which correspond to the pressure at the main connection. However, the pressure sensor can also be provided, for example, for determining a pressure upstream or downstream of the bistable valve unit, in particular a bistable valve of the bistable valve unit, downstream or upstream of the first monostable holding valve or downstream or upstream of the second monostable holding valve. The flow direction is viewed from the main connection in the direction of the redundancy venting, so that the main connection is arranged upstream of the redundancy venting.In a further preferred embodiment, the parking brake redundancy unit comprises a second redundancy vent and a second vent path which can be vented via the second redundancy vent, wherein the bistable valve unit can be controlled via the second vent path. It should be understood that even only a first valve of the bistable valve unit can be controlled via the second venting path, and that at least one second valve of the bistable valve unit can act on the second venting path for controlling this first valve of the bistable valve unit, in particular can open, block and / or vent via the second redundant ventingIn a preferred development of the embodiment with first and second venting paths, the bistable valve unit comprises a first electronically switchable monostable holding valve which is arranged in the second venting path, and a pneumatically switchable third holding valve, in particular relay valve, which is arranged in the first venting path and comprises a pneumatic control connection which is connected to the second venting path. The second electropneumatic redundancy valve unit comprises a second electronically switchable monostable holding valve which is arranged in the first venting path. Preferably, the third holding valve is open when a control pressure is provided at the pneumatic control port, which preferably exceeds a pressure limit value.Preferably, the parking brake redundancy unit further comprises a return path, wherein the return path connects an outlet port of the third holding valve to the pneumatic control port of the third holding valve. The holding valve may then be self-holding as soon as it has been initially switched to an open state. Preferably, a throttle and / or a check valve is provided in the return path. The throttle can throttle a compressed air volume flow through the return path. The check valve preferably prevents a compressed air flow from the pneumatic control connection to the outlet connection of the third holding valve. The throttle can, for example, prevent a high working pressure in the first venting path from preventing venting of the pneumatic control connection. The throttle then optionally ensures that the pneumatic control connection can be vented to interrupt the first venting path, in particular in that the second venting path connected to the second control connection is at least partially vented.The parking brake device preferably further comprises a flow limiter which limits a maximum volume flow through the parking brake redundancy unit. The flow limiter can be designed, for example, as a constriction in the first venting path. By limiting the maximum volume flow, the speed at which a parking pressure air path connected to the main connection can be emptied via the parking brake redundancy unit can be reduced or the time requirement for emptying can be increased. If, for example, the parking pressure air path is connected to the spring brake cylinder, the flow limiter can bring about a gentle engagement of the parking brake, since the parking brake cylinder is not abruptly ventilated. This is particularly advantageous if the parking brake is to be used in the case of redundancy for braking a moving vehicle. The flow limiter can be a passive element, in particular a throttle, or a switchable component, for example an electronically controllable throttle valve.In a second aspect, the invention achieves the object mentioned at the beginning with an electronically controllable pneumatic brake system for a vehicle, comprising at least one first front axle brake actuator and one second front axle brake actuator for a front axle of the vehicle and at least one first rear axle brake actuator and one second rear axle brake actuator for a rear axle of the vehicle. The brake system further comprises a primary system having a primary control unit at least for actuating the first front axle brake actuator and the second front axle brake actuator and / or for actuating the first rear axle brake actuator and the second rear axle brake actuator, and an electropneumatic parking brake device according to one of the above-described preferred embodiments according to the first aspect of the invention. The at least one spring accumulator connection of the electropneumatic parking brake valve unit is preferably connected to at least one first spring accumulator brake cylinder. The primary system is preferably a service brake system of the vehicle. The primary control unit is typically independent of the parking brake control unit. The electropneumatic parking brake valve unit of the parking brake device is designed to ventilate a parking brake cylinder connected to the spring accumulator connection (releasing the parking brake). Furthermore, the parking brake valve unit is preferably designed to vent the parking brake cylinder which is fired at the spring accumulator connection. This is preferably done by corresponding signals from the parking brake control unit. The parking brake valve unit thus typically serves as a primary device for engaging and releasing the parking brake of the vehicle. The parking brake redundancy unit preferably forms a redundancy for the parking brake valve unit and allows the parking brake to be engaged even if the parking brake valve unit, in particular the parking brake control unit, has a fault. However, it should be understood that the main connection of the parking brake redundancy unit does not have to be connected to the spring brake cylinder for this purpose.In a first preferred embodiment of the brake system, however, the first spring brake cylinder is connected to the main connection of the parking brake redundancy unit. The parking brake redundancy unit is preferably switchable in order to connect the spring brake cylinder to the redundancy vent via the first venting path in order to vent the spring brake cylinder. In this case, the parking pressure air path is therefore a compressed air path connected to at least one spring brake cylinder.In an alternative embodiment of the electronically controllable pneumatic brake system, the main connection is connected to a first compressed air supply of the brake system. The parking brake redundancy unit is switchable to connect the compressed air supply via the first venting path to the redundancy venting in order to vent the first compressed air supply. In this variant, the locking compressed air path is thus a compressed air path connected to a first compressed air supply. The parking brake redundancy unit can connect the compressed air supply to the redundancy vent and thus bring about a pressure drop in a supply compressed air path of the brake system. This can then cause the parking brake to be engaged. For example, in brake systems for the North American market, a push-pull valve may typically be provided, which automatically applies the parking brake as soon as a supply pressure or supply pressure falls below a predefined pressure level.Preferably, the primary control unit is or comprises the first control unit. The primary control unit can then control the first electropneumatic redundancy valve unit. Since the primary control unit and the parking brake control unit are typically units independent of one another, the primary control unit can thus form a redundancy level for the parking brake control unit. It is particularly advantageous in this respect that an already present control unit can be used as a redundancy level. However, it can also be provided that the first control unit is a separate control unit.In a preferred development of the embodiments described above, the electronically controllable pneumatic brake system furthermore has a secondary system with a secondary control unit, wherein the secondary system is designed to actuate the first front axle brake actuator and the second front axle brake actuator and / or to actuate the first rear axle brake actuator and the second rear axle brake actuator. The secondary system is preferably designed to actuate the first front axle brake actuator and the second front axle brake actuator and / or to actuate the first rear axle brake actuator and the second rear axle brake actuator if a fault is ascertained in the primary system. The secondary system then preferably forms a redundancy level for the primary system, which is provided in particular in vehicles with a high degree of automation. The secondary system can therefore also be, in particular, a redundancy operating brake system.Preferably, the secondary control unit is or comprises the second control unit. In this preferred variant, too, an already present control unit can then be used as redundancy for the parking brake control unit.In a preferred variant, the electronically controllable pneumatic brake system has a first voltage source and a second voltage source, wherein the first voltage source is provided for supplying the first control unit with electrical voltage and wherein the second voltage source is provided for supplying the second control unit with electrical voltage. The provision of mutually independent voltage sources can further increase the reliability of the brake system, since a failure of an individual voltage source does not cause a total failure of the parking brake system. The parking brake control unit can be connected to the first voltage source or to the second voltage source for supplying electrical voltage.According to a third aspect of the invention, the object mentioned at the beginning is achieved by a utility vehicle having a front axle, at least one first rear axle and an electronically controllable pneumatic brake system according to one of the above-described preferred embodiments of an electronically controllable pneumatic brake system according to the second aspect of the invention.In a fourth aspect, the invention achieves the object mentioned at the outset by means of a method for operating an electronically controllable brake system for a vehicle. The brake system comprises at least one spring brake cylinder and an electropneumatic parking brake device according to one of the above-described embodiments of the first aspect of the invention, in which the first electropneumatic redundancy valve unit comprises a bistable valve unit. The spring accumulator connection of the electropneumatic parking brake valve unit is connected to the at least one spring accumulator brake cylinder for ventilating the spring accumulator brake cylinder with a parking pressure, and the main connection of the electropneumatic parking brake redundancy unit is connected to a parking pressure air path of the brake system. The method comprises the steps of: ascertaining whether an at least partially autonomous operating mode or a manual operating mode of the brake system is present; switching the bistable valve unit into the venting position if an at least partially autonomous operating mode of the brake system is present; switching the bistable valve unit into the second switching position if the manual operating mode of the brake system is present; and venting the at least one spring brake cylinder by the electropneumatic parking brake valve unit. The bistable valve unit, which is or comprises preferably a bistable valve, is therefore preferably switched, depending on the operating mode present, into the venting position, in which the bistable valve unit allows a pneumatic connection of the main connection to the redundancy venting, or into the second switching position, in which the bistable valve unit interrupts the first venting path. A selection between the manual operating mode and the at least partially autonomous operating mode may be made, for example, manually, by a human user, or automatically by an autonomous driving unit or other control unit of the vehicle. Venting of the spring-loaded brake cylinder is possible only in the at least partially autonomous operating mode, since the bistable valve unit only opens up the venting path in this case. In the manual operating mode, a human driver is preferably present, so that a redundancy ventilation function may not be necessary. In the manual operating mode, the bistable valve unit can therefore interrupt the first venting path.In a first preferred embodiment, the method comprises the steps of: determining whether a fault of the electropneumatic parking brake valve unit is present, determining whether a parking brake request is present, and at least temporarily interrupting the first venting path by a first holding valve and / or the bistable valve unit if no fault of the electropneumatic parking brake valve unit is determined and no parking brake request is determined; or opening the first holding valve and / or the bistable valve unit if a fault of the electropneumatic parking brake valve unit is determined and a parking brake request is determined in order to at least partially open the first venting path. If the electropneumatic parking brake valve unit has no fault or there is no fault in the electropneumatic parking brake valve unit, it can be assumed in a multiplicity of cases that the electropneumatic parking brake valve unit can vent the spring-loaded brake cylinder in order to engage the parking brake. Venting of the parking pressure air path through the parking brake redundancy unit is therefore generally not necessary as long as the electropneumatic parking brake valve unit has no fault. In the event that the electropneumatic parking brake valve unit has a fault, the first holding valve and / or the bistable valve unit can be opened and at least partially open the venting path. However, the at least partial release preferably takes place only when a parking brake request is provided, for example by a unit for autonomous driving or by a human driver. Even if the first venting valve and / or the bistable valve unit partially opens up the first venting path, it can nevertheless be provided that a second venting valve interrupts the first venting path.In a preferred development, the method comprises the step of: at least second interruption of the first venting path by a second holding valve if no fault of the parking brake control unit is determined and no parking brake request is determined, wherein the at least temporary interruption by the second holding valve preferably takes place when the first holding valve releases the first venting path, no fault of the parking brake control unit is determined and no parking brake request is determined. If there is no parking brake request, the first venting path can thus be interrupted alternately by the first holding valve (and / or the bistable valve unit) and the second holding valve, which can have a positive effect on the service life of the holding valves.Preferably, the first holding valve and / or the bistable valve unit is actuated by a first control unit for at least second interruptions of the first venting path and the second holding valve is actuated by a second control unit for at least second interruptions of the first venting path. The first control unit and the second control unit are preferably connected, in particular connected via a CAN bus, and are designed to determine whether the respective other control unit enables or interrupts the first venting path.It is to be understood that the electronically controllable pneumatic brake system according to the second aspect of the invention, the commercial vehicle according to the third aspect of the invention and the method for operating a brake system according to the fourth aspect of the invention have the same and similar sub-aspects as are laid down in particular in the dependent claims relating to the first aspect of the invention and to the second aspect of the invention.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. For the sake of simplicity, the same reference numerals are used below for identical or similar parts or parts with identical or similar function.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 utility vehicle having an electronically controllable pneumatic brake system; FIG. 2 shows a schematic illustration of a first exemplary embodiment of a parking brake device; FIG. 3 shows a schematic illustration of a second exemplary embodiment of a parking brake device; FIG. 4 shows a schematic illustration of a third exemplary embodiment of a parking brake device; FIG. 5 shows a schematic illustration of a fourth exemplary embodiment of a parking brake device; and FIG. 6 shows a schematic illustration of a fifth exemplary embodiment of a parking brake device.FIG. 1 shows an electronically controllable pneumatic brake system 200 having an electropneumatic parking brake device 1. the electronically controllable pneumatic brake system 200 is used in the present case in a vehicle 300 designed as a commercial vehicle 302, which is shown here in a highly schematic manner, in particular having a front axle VA, a first rear axle HA 1 and a second rear axle HA 2.The electronically controllable pneumatic brake system 200 here has first, second, third, fourth, fifth and sixth service brake actuators 208 a- 208 ffor in each case one wheel of the vehicle 300. To provide brake pressures to the first through sixth service brake actuators 208 a- 208 f, a rear axle brake circuit 202 and a front axle brake circuit 204 are provided. The service brake actuators 208 a, 208 bare associated with the front axle VA and are therefore also referred to as front axle brake actuators 208 a, 208 b. Analogously, the service brake actuators 208 c- 208 fassociated with the rear axles HA 1, HA 2 are also referred to as rear axle brake actuators 208 c- 208 f. The rear axle brake circuit 202 is supplied by a first compressed air supply 206 and the front axle brake circuit 204 is supplied by a second compressed air supply 210. The utility vehicle 300 is designed here as a towing vehicle and comprises a trailer brake circuit 207 having a trailer module 209, which is provided for supplying a trailer (not illustrated) connected to the utility vehicle 300 with compressed air.The electronically controllable pneumatic brake system 200 has an operating level and a first redundancy level. In the operating level, the electronically controllable pneumatic brake system 200 comprises a primary system 212 with an electronic primary 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 brake request signals SA from an autonomous driving unit 218 via a vehicle BUS 216. Moreover, the primary electronic control unit 214 is connected to and supplied with electrical energy from a first voltage source 222 via a first supply line 220. The primary electronic control unit 214 converts the brake request signals SA and, based thereon, outputs operational brake signals SB to a first operational axle modulator 224. The first operating axle modulator 224 is here a front axle modulator 228 provided for the front axle VA. Alternatively or additionally, brake request signals SA can also be provided by an electronic foot brake pedal 264 at the primary control unit 214.The first operating axle modulator 224 is connected to the second compressed air supply 210 and receives supply pressure pV therefrom. The first operating axle modulator 224 controls, based on the received operating brake signals SB, a first service brake pressure pB 1 at a first service brake pressure connection 232.1 and a second service brake connection 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 operating axle modulator 224 is designed as a dual-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 operating axle modulator 224 can be designed as a single-channel axle modulator which controls the first service brake pressure pB1 in the proper axis.A first wheel speed sensor 234 is also provided on the front axle VA, which first wheel speed signals SD are provided to the primary control unit 214. The primary control unit 214 is configured to process the first wheel speed signals SD and provide ABS switching signals to ABS valves 238 of the front axle VA, so as to achieve slip control or ABS modulation of the first service brake pressure pB 1 and to avoid locking of front wheels of the vehicle 300.For braking the first and second rear axles HA 1, HA 2, the electronically controllable pneumatic brake system 200 comprises, in the operating plane, a second operating axle modulator 236, which is provided for the first and second rear axles HA 1, HA 2 and can thus also be referred to as a rear axle modulator 237. In the exemplary embodiment shown in FIG. 1, the rear axle modulator 237 is installed with the electronic primary control unit 214 to form a module, which is referred to here as a central module 240. However, it should be understood that the rear axle modulator 237 and the primary control unit 214 may also be separate or structurally separate. The primary control unit 214 and the rear axle modulator 237 can then be connected to one another, for example, via a signal line or a BUS line. Internally, the primary electronic control unit 214 controls the rear axle modulator 237 in accordance with the brake request signals SA that the primary control unit 214 has received from the autonomous driving unit 218.A supply connection 230 of the second operating axle modulator 236 is connected to the first compressed air supply 206 and receives supply pressure pV therefrom. In accordance with its activation by the primary control unit 214, the rear axle modulator 237 controls at least one second service brake pressure pB 2, but in the exemplary embodiment shown here it also controls a third service brake pressure pB 3. The second service brake pressure pB2 is provided for the right vehicle side and the third service brake pressure pB3 is provided for the left vehicle side in the exemplary embodiment shown in FIG. 1. The rear-axle modulator 237 is therefore designed here as a dual-channel axle modulator. The second service brake pressure pB2 is determined for a fourth and a sixth service brake actuator 208d, 208f, while the third service brake pressure pB3 is provided for a third and a fifth service brake actuator 208c, 208e. In other variants, however, the first operating axis modulator 236 can also be designed as a single-channel modulator or as a multi-channel modulator having more than two outputs.In the redundancy level, the electronically controllable pneumatic brake system 200 comprises a secondary control unit 242 of a secondary system 241, 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 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 control unit 214 or the like.The secondary electronic control unit 242 is also connected to the autonomous driving unit 218 via the vehicle BUS 216 and also receives brake request signals SA therefrom. In contrast to the primary control unit 214, the secondary control unit 242 is connected to a second voltage source 246 via a second supply line 244 and is supplied with electrical energy therefrom. 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. The primary electronic control unit 214 and the secondary electronic control unit 242 are thus electrically independent of one another.In order to be able to exchange signals, the primary control unit 214 and the secondary control unit 242 are connected to one another via a redundancy BUS 248. In this way, the secondary control unit 242 can determine the availability of the primary control unit 214 and only take over the control of the electronically controllable pneumatic brake system 200 if the primary control unit 214 is not available or is no longer correctly available. However, in variants, communication of primary control unit 214 and secondary control unit 242 can also take place, for example, via vehicle BUS 216.In the redundancy level, a redundancy axle modulator 250 is provided, which is connected to the secondary control unit 242 and receives redundancy brake signals SR from the latter. In the exemplary embodiment according to FIG. 1, the secondary control unit 242 is integrated into the redundancy axis modulator 250. In other variants, however, the secondary control unit 242 and the redundancy axle modulator 250 can also be physically separate units from one another.The redundancy axis modulator 250 is connected to the second compressed air supply 210, which is independent of the first compressed air supply 206, so that the second compressed air supply 210 can also provide supply pressure pV if the first compressed air supply 206 has failed. In other embodiments, however, the redundancy axis modulator 250 can also be connected to the second compressed air supply 210 or to the first compressed air supply 206 and the second compressed air supply 210.The redundancy axle modulator 250 controls a redundancy brake pressure pBR 1 at a redundancy brake pressure connection 252 as a function of the redundancy brake signals SR. The redundancy brake pressure pBR1gesteuerte at the redundancy brake pressure port 252 is provided to the front axle modulator 228. The redundancy axle modulator 250 is shown in FIG. 1 as a single-channel axle modulator with only one redundancy brake pressure connection 252, but can also be designed as a multi-channel axle modulator, which can realize, for example, lateral modulation of redundancy brake pressures.The secondary control unit 242 can actuate the redundancy axle modulator 250 in such a way that, in the event of a fault in the primary control unit 214, a brake pressure, namely the redundancy brake pressure pBR 1, is nevertheless provided at the front axle brake actuators 208 a, 208 b. Unlike the illustration in FIG. 1, the redundancy level can also be provided for braking the first and second rear axles HA 1, HA 2. This can be realized by means of the redundancy axis modulator 250 or by means of a second redundancy axis modulator. The secondary control unit 242 can then preferably also be provided for controlling such a second redundancy axis modulator.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 tension the brakes of the vehicle 300 when they are depressurized or depressurized. The spring-loaded brake cylinders 254 c- 254 fare thus advantageously usable as a parking brake, which does not have to be provided with compressed air 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 pressure pFS. This parking pressure pFS entgegen the spring accumulator and releases the brakes of the vehicle 300.To provide the parking brake function, the brake system 200 comprises the parking brake device 1. this comprises an electropneumatic parking brake valve unit 2, which is supplied with supply pressure pV via a supply connection 4. In the exemplary embodiment shown, the supply connection 4 is connected to the first compressed air supply 206. Here, the parking brake valve unit 2 is additionally also supplied with supply pressure pV from the second compressed air supply 210. In other variants, the electropneumatic parking brake valve unit 2 can alternatively or additionally be connected to a third compressed air supply, which is preferably independent of the first compressed air supply 206 and of the second compressed air supply 210. It should be understood that the electropneumatic parking brake valve unit 2 can be supplied only by the first compressed air supply 206, only by the second compressed air supply 210, only by the third compressed air supply 206, by at least two compressed air supplies or by the first compressed air supply 206, by the second compressed air supply 210 and by the third compressed air supply.The electropneumatic parking brake valve unit 2 includes a parking brake control unit 6 connected to the autonomous driving unit 218 via the vehicle bus 216. For engaging the parking brake, the autonomous driving unit 218 provides a parking brake signal SFS to the parking brake control unit 6 via the vehicle bus 216, which parking brake signal thereupon provides the parking pressure pSW at 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 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 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 second parking brake signals at the parking brake control unit 6 or when parking brake signals SFS are no longer provided by the parking brake control unit 6.In order to provide redundancy for the electropneumatic parking brake valve unit 2, the electropneumatic parking brake device 1 furthermore comprises an electropneumatic parking brake redundancy unit 10. This can be done directly or indirectly. Thus, as shown in the exemplary embodiment according to FIG. 1, the parking brake redundancy unit 10 can connect a parking pressure air path 12 which is directly connected to the spring-loaded brake cylinders 254 c- 254 fto a redundancy vent 14. In alternative variants, however, the fixed compressed air path 12 can also be connected to the first compressed air supply 206 and / or the second compressed air supply 210. Furthermore, the parking compressed air path 12 can alternatively or additionally also be connected to a third compressed air supply, which is not shown in FIG. 1. The parking brake redundancy unit 10 then connects this parking pressure air path 12, which is connected to the first compressed air supply 206, the second compressed air supply 210 or a third compressed air supply, to the redundancy vent 14, in order to thus effect venting of the spring-loaded brake cylinders 254 c- 254 f. The parking brake redundancy unit 10 can thus be used for venting only one compressed air supply 206, 210 or for venting a plurality of compressed air supplies 206, 210.The parking brake redundancy unit 10 comprises a main port 16 provided for connection to the parking compressed air path 12. In FIG. 1, the spring-loaded brake cylinders 254 c- 254 fare directly connected to the main connection 16 and the spring-loaded connections 8 a, 8 b. In the exemplary embodiment shown in FIG. 1, the parking brake redundancy unit 10 thus receives the parking pressure pFSat the main connection 16 if the parking brake of the vehicle 300 is released or the spring-loaded brake cylinders 254 c- 254 fare aerated. The parking brake redundancy unit 10 is designed to connect the main connection 16 to the redundancy vent 14 via a first venting path 18 (cf. FIG. 2 ). In the exemplary embodiment according to FIG. 1, the fixing pressure pFScan be directly vented into the environment via the first venting path 18. Even if venting via the electropneumatic parking brake valve unit 2 should therefore no longer be possible on account of a fault, the parking brake cylinders 254 c- 254 fcan be connected via the first venting path 18 to the redundancy vent 14 or the environment and can thus be vented.FIG. 1 also schematically shows a first electropneumatic redundancy valve unit 22 and a second electropneumatic redundancy valve unit 24. The first redundancy valve unit 22 can be controlled by a first control unit 26, which in the exemplary embodiment shown is the primary control unit 214. For this purpose, the first redundancy valve unit 22 is connected to the primary control unit 214 via a first redundancy signal line 256. The second redundancy valve unit 24 can be controlled in an analogous manner by a second control unit 28, which is formed here by the secondary control unit 242. The connection of secondary control unit 242 and second redundancy valve unit 24 takes place via a second redundancy signal line 258. The primary control unit 214 and the secondary control unit 242 are independent of one another and are supplied by separate voltage sources 222, 246, so that a redundancy level with high reliability can be created in a particularly simple manner by using the primary control unit 214 as the first control unit 26 and the secondary control unit 242 as the second control unit 28.In the exemplary embodiment shown in FIG. 1, both the first control unit 26 and the second control unit 28 are independent of the parking brake control unit 6. however, in other embodiments, the parking brake control unit 6 can also form or comprise the first control unit 26 or the second control unit 28, for example.FIG. 2 now schematically shows a first exemplary embodiment of the electropneumatic parking brake device 1, wherein, for simplification, the first rear axle HA 1 with the associated parking brake cylinders 254 c, 254 dis also shown. The electropneumatic parking brake valve unit 2 is shown schematically, wherein the spring accumulator connections 8 a, 8 bare represented here in simplified form as a common spring accumulator connection 8. The main connection 16 is likewise shown only in a greatly simplified manner and opens into the parking-pressure air path 12, which is here a connecting line between the spring-accumulator connection 8 of the parking brake valve unit 2 and the spring-accumulator brake cylinders 254 c, 254 d.The first venting path 18 of the parking brake redundancy unit 10 connects the main connection 16 indirectly to the redundancy vent 14. The first redundancy valve unit 22 comprises a bistable valve unit 30, which is designed here as a bistable valve 31, and a first monostable holding valve 32. The bistable valve 31, the second monostable holding valve 34 and the first monostable holding valve 32 are connected in series along the first venting path 18, wherein the second holding valve 34 is arranged between the bistable valve 31 and the first holding valve 32. The second monostable holding valve 34 is thus arranged along the first venting path 18 downstream of the bistable valve 1 and upstream of the first monostable holding valve 32.In FIG. 2, the first control unit 26 and the second control unit 28 are not illustrated. However, it should be understood that the bistable valve 1 and the first monostable holding valve 32 of the first redundancy valve unit 22 can be controlled by the first control unit 26. The second monostable holding valve 34, on the other hand, can be controlled by the second control unit 28.Here, the first monostable holding valve 32 and the second monostable holding valve 34 are each designed as electrically switchable solenoid valves. The first holding valve 32 is a 2 / 2-way valve that is biased into an open state in which the holding valve 32 opens the first venting path 18. In the exemplary embodiment shown, the first holding valve 32 can be energized by the first control unit 26 in order to switch the first holding valve 32 into a closed state in which it interrupts the first venting path 18. Spring accumulator pressure pFS empfangen at main connection 16 from parking pressure air path 12 cannot then be vented to the environment via parking brake redundancy unit 10. As long as the first control unit 26 is functional, it can thus prevent venting of the spring-loaded brake cylinders 254 c, 254 d.The second holding valve 34 is designed as a 3 / 2-way valve. In the state shown in FIG. 2, in which the second holding valve 34 is prestressed, the second holding valve 34 opens up the first venting path 18. For this purpose, it connects a first path connection 34.1 to a second path connection 34.2. In the second position, not shown in FIG. 2, on the other hand, the second path connection 34.2 is connected to a vent 34.3 and the first vent path 18 is interrupted. The vent 34.3 of the second holding valve 34 is shown here as a separate vent, but can also be the redundancy vent 14. The second control unit 28 can switch the second monostable holding valve 34 from the open position illustrated in FIG. 2 into the closed position, not shown, in which it energizes the second holding valve 34 or its electromagnet. The second control unit 28 can thus prevent venting of the sensed pressure air path 12 by switching the second monostable holding valve 34 to the closed state. In the closed state, the second path connection 34.2 is connected to the vent 34.3 and the locking compressed air path 12 is interrupted.The bistable valve unit 30, which is formed here by the bistable valve 30, has a first position 36, which is also referred to in the present case as a venting position 38, and a second position 40. The first control unit 26 is designed to switch the bistable valve unit 30 between these two positions 36, 40. In the venting position 38, the bistable valve 31 opens up the first venting path 18 and thus permits a pneumatic connection of the main connection 16 to the redundancy vent 14, if the holding valves 32, 34 are also open. The bistable valve unit 30 is stable both in the first position 36 and in the second position 40. If the bistable valve 31 is not controlled by the first control unit 26, it remains in the position 36, 40 last assumed, so that the bistable valve 31 remains in the venting position 38, for example, even if the second control unit 26 has a fault and can no longer provide switching signals for the bistable valve 31 or the bistable valve unit 30.In the exemplary embodiment shown, the bistable valve unit 30 can be used to switch between a manual operating mode and an autonomous operating mode of the brake system 200. In the manual operating mode, a human driver performs at least some of the control tasks of the vehicle 300. In the event that one of the control units 6, 26, 28, 218 of the brake system 200 fails or has a fault, the human driver can take over the task of this control unit 6, 26, 28, 218. A redundancy level for the parking brake control unit 6 of the parking brake valve unit 2 may then not be necessary. In such cases, the bistable valve 31 can be switched into the second switching position 40. The first venting path 18 is then permanently interrupted by the bistable valve 31 and venting of the parking pressure air path 12 via the parking brake redundancy unit 10 is not possible.During (partially) autonomous operation of the vehicle 300, the parking brake of the brake system 200 should generally also be able to be securely engaged if the parking brake control unit 6 of the parking brake valve unit 2 has a fault and venting of the spring-loaded brake cylinders 254 c, 254 dvia the parking brake valve unit 2 is not possible. In this case, the bistable valve 31 of the first redundancy valve unit 22 can be switched into the venting position 38. This takes place, for example, when the vehicle 300 is put into operation or when the trip begins. In the venting position 38, the bistable valve 31 opens up the first venting path 18 and thus basically permits direct venting of the parking pressure air path 12 via the parking brake redundancy unit 10.In particular, different fault scenarios are conceivable during autonomous operation of the vehicle 300. If only the parking brake control unit 6 has a failure, the parking air path 12 may be exhausted via the parking brake redundancy unit 10. For this purpose, the first control unit 26 must open the first holding valve 32 and the second control unit 28 must open the second holding valve 34 while the bistable valve 31 is in the venting position 38. The main connection 16 is then connected in a fluid-conducting manner to the redundancy vent 14 and the locking compressed air path 12 can be directly vented into the environment. A functional control unit 26, 28 can prevent venting of the parking pressure air path 12 by supplying a corresponding current to the first holding valve 32 or the second holding valve 34.In the first embodiment shown in FIG. 2, each of the control units 26, 28 may prevent venting of the fixed pressure air path 12 because the first holding valve 32 and the second holding valve 34 are connected in series. For example, even if the first controller 26 fails and switches the first monostable holding valve 32 to the open position shown in FIG. 2, the second controller 28 may energize the second monostable holding valve 34 and thus interrupt the first bleed path 18.In the case that both the first control unit 26 and the second control unit 28 have a fault, the parking brake redundancy unit 10 in the first exemplary embodiment according to FIG. 2 is also designed to provide an emergency braking function. The first monostable holding valve 32 and the second monostable holding valve 34 are each biased into an open state and therefore open the first venting path 18 as soon as they are not energized by the first control unit 26 and the second control unit 28, respectively. If the bistable valve 31 is also in the venting position 38, then in the event of a fault in the first control unit 26 and the second control unit 28, the main connection 16 is automatically connected in a fluid-conducting manner to the redundancy vent 14 and the parking-pressure air path 12 is directly vented. In the first exemplary embodiment, the parking pressure pFS is thus vented to the environment and the spring-loaded brake cylinders 254 c, 254 db brake the first rear axle HA 1. In order to prevent locking of the wheels of the first rear axle HA 1, a flow limiter, not shown, may be provided in the first venting path 18. This can prevent sudden emptying of the spring-loaded brake cylinders 254 c, 254 d, which can lead to locking of the wheels of the first rear axle HA 1.FIG. 3 illustrates a second exemplary embodiment of the parking brake device 1, the illustration being substantially analogous to the first exemplary embodiment. In FIG. 3, in addition to the parking brake valve unit 2 and the parking brake redundancy unit 10, the first control unit 26 and the second control unit 28 are also shown. The first control unit 26 is supplied with electrical voltage by the likewise shown first voltage source 222. The first voltage source 222 is also connected to the parking brake valve unit 2. The second control unit 28, on the other hand, is supplied with electrical voltage by the second voltage source 246. The separate voltage supply of the first control unit 26 and the second control unit 28 prevents a failure of one of the voltage sources 222, 246 from resulting in a total failure of the parking brake redundancy unit 10.In the second exemplary embodiment (FIG. 3 ), the first redundancy valve unit 22 and the second redundancy valve unit 24 are substantially identical to the first exemplary embodiment (FIG. 2 ). Here, however, the parking brake redundancy unit 10 further comprises a first pressure sensor 42 and a second pressure sensor 44. Both pressure sensors 42, 44 are configured to detect a pressure of the first venting path 18. Here, the pressure sensors 42, 44 are connected to the second control unit 28 and provide signals corresponding to the respectively detected pressure to the second control unit 28. In other variants of the parking brake device 1, the first pressure sensor 42 and / or the second pressure sensor 44 can, however, also be connected to the first control unit 26.In the second exemplary embodiment according to FIG. 3, the first pressure sensor 42 is provided for detecting a pressure present at the main connection 16. The second control unit 28 is designed to determine, using the signals from the first pressure sensor 42, which pressure is present at the main connection 16. In the embodiment shown, the second control unit 28 can thus ascertain, for example, whether the parking pressure pFSis present on the parking pressure air path 12 or whether the spring-loaded brake cylinders 254 c, 254 dare ventilated or deaerated. For this purpose, the first pressure sensor 42 for detecting the pressure is arranged upstream of the bistable valve 31 of the bistable valve unit 30. The second pressure sensor 44 is designed to determine the pressure downstream of the bistable valve 31. The second control unit 28, which is not provided here for controlling the bistable valve unit 30, can thus determine, using the signals of the first pressure sensor 42 and the second pressure sensor 44, whether the bistable valve unit 30 is in the first switching position 36 or in the second switching position 40.FIG. 4 illustrates a third exemplary embodiment. The parking brake redundancy unit 10 is designed analogously to the first exemplary embodiment. In this variant of the brake system 200, however, the parking-pressure air path 12 is not a direct connection between the parking brake valve unit 2 and spring-loaded brake cylinders 254 c- 254 f,but rather a supply path. The main connection 16 is connected via a select high valve 260 to the first compressed air supply 206 and the second compressed air supply 210. However, it should be understood that the select-high valve 258 can also be omitted and / or that the main connection 16 can also be connected only to the first compressed air supply 206, only to the second compressed air supply 210, only to a third compressed air supply and / or to at least two compressed air supplies from the first compressed air supply 206, the second compressed air supply 210 and a third compressed air supply.For venting at least one spring-loaded brake cylinder 254 c- 254 fof the brake system 200 of the vehicle 300, the parking brake redundancy unit 10 connects the main connection 16 to the redundancy vent 14. As a result, the pressure level of the reservoir pressure pV falls. As soon as the pressure level of the reservoir pressure pV falls below a predefined pressure limit value, a push-pull valve 262 shown in FIG. 1 automatically vents the spring-loaded brake cylinders 254 c- 254 f. In the third exemplary embodiment according to FIG. 4, the parking brake redundancy unit 10 therefore connects the parking-brake-air path 12 connected to the first compressed-air supply 206 and the second compressed-air supply 210 to the vent 14, in order to indirectly vent at least one spring-loaded brake cylinder 254 c- 254 f. Alternatively or additionally, a corresponding function within the parking brake valve unit 2 can automatically vent the spring-loaded brake cylinders 254 c- 254 fif the pressure level of the supply pressure pV falls below the predefined limit value.A fourth exemplary embodiment of a parking brake device 1 is illustrated in FIG. 5, wherein, analogously to the first and second exemplary embodiments, a parking-air path 12 and the first rear axle HA 1 with the spring-loaded brake cylinders 254 c, 254 dare additionally shown. Analogous to the second embodiment illustrated in FIG. 3, the first control unit 26, the second control unit 28, the first voltage source 222 and the second voltage source 246 are furthermore shown in FIG. 5.In the fourth exemplary embodiment, the first redundancy valve unit 22 comprises only the bistable valve unit 30, which here again comprises only the bistable valve 31. The first monostable holding valve 32 is omitted in this variant. The second redundancy valve unit 24 again comprises only the second monostable holding valve 34. For detecting a pressure downstream of the bistable valve 31, the second pressure sensor 44 is again provided, which is connected here to the second control unit 28. By providing only one monostable holding valve 34, the parking brake redundancy unit 10 according to the fourth exemplary embodiment can be produced cost-effectively. In order to be able to vent the parking pressure air path 12 using the parking brake redundancy unit 10 even in the event of a fault in the first control unit 26 or the first voltage source 222, the bistable valve 31 is preferably switched to the venting position 38 when the brake system 200 is put into operation. The bistable valve 1 maintains the venting position 38 even if it is de-energized due to a fault in the first control unit 26 or a failure of the first voltage source 222. In the fault-free driving mode, the second control unit 28 maintains the second monostable holding valve 34 in the closed state and thus prevents an unintentional venting of the parking pressure air path 12. The still functional first control unit 26 can then optionally switch the bistable valve 31 into the second switching position 36 in order to prevent venting of the parking pressure air path 12.FIG. 6 illustrates a fifth exemplary embodiment of a parking brake device 1 of a brake system 200, the illustration being substantially analogous to FIG. 5. For simplicity, the voltage sources 222, 246 have been omitted from FIG. 6.The parking brake redundancy unit 10 according to the fifth embodiment provides substantially similar functionality to the parking brake redundancy unit 10 of the fourth embodiment illustrated in FIG. 5. However, the bistable valve unit 30 does not comprise a bistable valve 31 here, wherein a bistable valve 31 could in principle be provided. The bistable function of the bistable valve unit 30 is provided in the fifth exemplary embodiment via a plurality of valves 32, 50, 52. The bistable valve unit 30 is illustrated in FIG. 6 by a dashed line around its valves 32, 50, 52.The parking brake redundancy unit 10 is also designed to connect the parking pressure air path 12 to a redundancy vent 14. For this purpose, a first venting path 18 is again provided, via which the main connection 16 can be connected to the first redundancy venting 14. This first venting path 18 serves as a primary venting path for venting the fixed pressure air path 12. The main connection 16 can be connected to a second redundancy vent 48 via the second vent path 46. A spring brake cylinder 254 c- 254 fcan thus basically also be vented via the second venting path 46. However, in the fifth exemplary embodiment of the parking brake redundancy unit 10, the second venting path 46 is used primarily for controlling the bistable function of the bistable valve unit 30. However, in other embodiments (cf. analogously to FIG. 4 ), the second venting path 46 can alternatively or additionally also be used to vent a parking pressure air path 12 connected to at least one compressed air supply 206, 210 directly into the environment and thus indirectly vent a spring-loaded brake cylinder 254 c- 254 f.The first redundancy valve unit 22 of the fifth exemplary embodiment of a parking brake device 1 illustrated in FIG. 6 comprises the bistable valve unit 30, which has a first monostable holding valve 32, a third holding valve 50 and a fourth electrically electronically switchable holding valve 52. By contrast, the second redundancy valve unit 24 comprises, analogously to the fourth exemplary embodiment (FIG. 5 ), again only the second electronically switchable holding valve 34.The fourth holding valve 52 and the first holding valve 32 are each designed as a 2 / 2-way valve which is prestressed into a closed state. The second holding valve 34 is likewise designed as a 2 / 2-way valve, but is prestressed here into an open state. The fourth holding valve 52 is designed as a solenoid valve and can be actuated by the first control unit 26. The first control unit 26 also controls the first holding valve 32, and the second control unit 28 can supply current to the second holding valve 32 and thus block the first venting path 18. In the event of a fault in the second control unit 28, the second holding valve 34 releases the first venting path 18, since the second holding valve 34 is de-energized in this case.In the exemplary embodiment according to FIG. 6, the bistable valve unit 30 is designed, analogously to the exemplary embodiment according to FIG. 5, to open or close the first venting path 18 running from the main connection 16 to the first redundancy venting 14. For this purpose, the bistable valve unit 30 comprises, analogously to the bistable valve 31, a venting position 38 and a second switching position 40. In the venting position 38, the third holding valve 50 releases the venting path 18 and connects the main connection 16 to the second holding valve 34 in a fluid-conducting manner. In the second switching position 40, the third holding valve 50 interrupts the first venting path 18.The third holding valve 50 is here a pneumatically switchable valve 54, namely a relay valve 56. the relay valve 56 has an input connection 56.1, an outlet connection 56.2 and a pneumatic control connection 56.3. By applying a pneumatic control pressure to the pneumatic control port 56.3, the relay valve 56 can be switched into an open state in which the inlet port 56.1 is connected in a fluid-conducting manner to the outlet port 56.2. The relay valve 56 can thus be switched by providing a pneumatic control pressure at the control connection 56.3 in such a way that it opens up the first venting path 18. In this case, the bistable valve unit 30 is then in the venting position 38. If the second holding valve 34 is also open, the parking pressure air path 12 connected to the main connection 16 can thus be connected to the first redundancy vent 14 and vented via the relay valve 56 and the second holding valve 34.The pneumatic control port 56.3 is connected to the second vent path 46. The relay valve 56 and thus the bistable valve unit 30 can thus be controlled via the second venting path 46. In the exemplary embodiment shown, the second venting path 46 is used substantially for actuating the relay valve 56 or for providing the bistable function of the bistable valve unit 30 and can therefore also be referred to as a control path. The pneumatic control pressure of the relay valve 56 can be provided initially via the second venting path 46. The parking pressure pFSapplied in the parking pressure air path 12 is also provided at the first holding valve 32 via the main connection 16. The first control unit 26 may energize the first holding valve 32 and thus switch to an open state while maintaining the fourth holding valve 52 closed to prevent venting of the fixed pressure air path 12. The parking pressure pFSthus reaches a first path section 58 of the second venting path 46, which connects the first holding valve 32 to the fourth holding valve 52. The pneumatic control connection 56.3 of the relay valve 56 is connected to this first path section 58 and the relay valve 56 switches into the open state when the detection pressure pFSis present. The bistable valve unit 30 is then in the venting position 38.In the venting position 38 of the bistable valve unit 30, the fixing pressure pFSwhich is likewise present at the inlet connection 56.1 via the main connection 16 thus reaches the outlet connection 56.2 through the relay valve 56. The second control unit 28 energizes the second holding valve 34 and holds it in the closed state. The detent pressure pFSis therefore included in a second path portion 60 connecting the relay valve 56 to the second holding valve 34.The second path section 60 of the first venting path 18 is connected to the first path section 58 of the second venting path 46 via a return path 62. Through the return path 62, the outlet port 56.2 of the relay valve 56 is connected to the control port 56.3 of the relay valve 56, and the relay valve 56 can maintain itself in the open state. Even if the first control unit 26 closes the first holding valve 32 or automatically switches the first holding valve 32 into the closed state on account of a fault in the first control unit 26, the relay valve 56 remains in the open switching position since a parking pressure pSW continues to be present at the pneumatic control connection 56.3 via the second path section 60, the return path 62 and the first path section 58.The relay valve 56 or the bistable valve unit 30 is thus stable in the venting position 38. By briefly opening the first holding valve 32, in particular at the start of operation of the vehicle 300, the relay valve 56 can be brought into a self-holding state in which the relay valve 56 also remains when the first holding valve 32 is closed again. Even if the first control unit 26 has a fault, venting of the first fixed pressure air path 12 via the first venting path 18 is still possible. The second control unit 28, which is still functional, can supply current to the second holding valve 34 and hold it in the closed state or interrupt the first venting path 18. If the parking brake of the vehicle 300 is to be engaged, the second control unit 28 no longer supplies the second holding valve 34 with electric voltage and thus switches the second holding valve 34 to the open state. The spring accumulator pressure pFScan then be vented to the environment via the first venting path 18 and the first redundancy venting 14.If only the second control unit 28 has a fault, the first control unit 26 can actuate the bistable valve unit 30 in order to open or shut off the first venting path 18. The release takes place analogously to the above description by venting the pneumatic control connection 56.3 via the first holding valve 32. In order to block the first compressed air path 18, the first control unit 26 opens the fourth holding valve 52 and thus connects the first path section 58 of the second venting path 46 to the second redundancy vent 48. The bistable valve unit 30 is then in the second switching position 40.In the fifth exemplary embodiment shown, the return path 62 comprises a throttle 64. In addition or in addition to the throttle 64, however, a check valve could also be provided, for example. The throttle 64 limits the possible volume flow through the return path 62. The throttle 64 here allows only a small part of the compressed air flow along the first venting path 18, that is to say a compressed air flow from the main connection 16, via the relay valve 56 and the second holding valve 34 to the first redundancy venting 14, to pass through the return path 62.If both the first control unit 26 and the second control unit 28 have a fault, the second holding valve 34 likewise switches into the open state, with the result that an emergency braking function can also be realized by the parking brake redundancy unit 10 of the fifth exemplary embodiment.In cases of emergency, however, the main connection 16 can optionally also be connected to the second redundancy vent 48 via the second venting path 46 or through the first holding valve 32 and the fourth holding valve 52 and thus be vented. This can be advantageous, for example, if the second holding valve 34 has a mechanical fault and can no longer be switched into the open position.Reference Sign (Part of Description)1 Parking brake device 2 parking brake valve unit 4 supply connection 6 parking brake control unit 8, 8 a, 8 bspring accumulator connections 10 parking brake redundancy unit 12 parking pressure air path 14 redundancy venting 16 main connection 18 first venting path 22 first redundancy valve unit 24 second redundancy valve unit 26 first control unit 28 second control unit 30 bistable valve unit 31 bistable valve 32 first monostable holding valve 34 second monostable holding valve 34.1 first path connection 34.2 second path connection 34.3 venting of the second holding valve 36 first switching position 38 venting position 40 second switching position 42 first pressure sensor 44 second pressure sensor 46 second venting path 48 second redundancy venting 50 third holding valve 52 fourth holding valve 54 pneumatically switchable valve 56 relay valve 56.1 input connection of the relay valve 56.2 output connection of the relay valve 56.3 pneumatic control connection 58 first path section 60 second path section 62 return path 64 throttle 200 electronically controllable Pneumatic brake system 202 rear axle brake circuit 204 front axle brake circuit 206 first compressed air supply 207 trailer brake circuit 208 a- 208 fservice brake actuators 208 a, 208 bfront axle brake actuators 208 c, 208 d, rear axle brake actuators 208 e, 208 f 209 trailer module 210 second compressed air supply 212 primary system 214 primary control unit 216 vehicle BUS 218 unit for autonomous driving 220 first supply line 222 first voltage source 224 first operating axle modulator 228 front axle modulator 230 supply connection 232.1 first service brake pressure connection 232.2 second service brake pressure connection 234 wheel rotational speed sensor 236 second operating axle modulator 237 rear axle modulator 238 ABS valves 240 central module 241 secondary system 242 secondary control unit 244 second supply line 246 second voltage source 248 redundancy BUS 250 redundancy axle modulator 252 redundancy brake pressure connection 254 c- 254 fspring brake cylinder 256 first redundancy signal line 258 second redundancy signal line 260 select high valve 262 push-pull valve 264 foot brake pedal 300 vehicle 302 commercial vehicle HA 1 First rear axle HA2 Second rear axle pB1 First service brake pressure pB2 Second service brake pressure pB3 Third service brake pressure pBR1 Redundancy brake pressure pFS Parking pressure SA Brake request signals SB Operating brake signals SD Wheel speed signals SFS Parking brake signal VA Front axleReferences 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

[0006] DE 10 2022 101 142 A1

[0007] DE 10 2021 122 498 A1

[0007] DE 10 2021 122 499 A1

[0007] DE 10 2020 132 875 A1

[0007] EP 3 145 769 B1

[0007]

Claims

Electropneumatic parking brake device (1) for ventilating and venting one or more spring-loaded brake cylinders (254c, 254d, 254e, 254f) of an at least partially electronically controllable pneumatic brake system (200) for a vehicle (300), comprising an electropneumatic parking brake valve unit (2) having a supply connection (4) for receiving supply pressure (pV) from a compressed air supply (210), and a parking brake control unit (6), wherein the parking brake valve unit (2) is designed to actuate a parking pressure (pFS) at at least one spring-loaded connection (8a, 8b) as a function of a parking brake signal (SP), an electropneumatic parking brake redundancy unit (10) which is designed to actuate at least one spring-loaded brake cylinder (254c) independently of the electropneumatic parking brake valve unit (2) for venting at least one spring-loaded brake cylinder (254c, 254d, 254e, 254f) to connect a parking pressure air path (12) to a vent (14), wherein the parking brake redundancy unit (10) has a first vent path (18), which comprises a main connection (16) for receiving a pressure (pEV, pV) of the parking pressure air path (12), a first electropneumatic redundancy valve unit (22), a second electropneumatic redundancy valve unit (24), and a redundancy vent (14) into the environment, wherein the first electropneumatic redundancy valve unit (22) can be controlled by a first control unit (26), and wherein the second electropneumatic redundancy valve unit (24) can be controlled by a second control unit (28), which is independent of the first control unit (26), and wherein the parking brake redundancy unit (10) is designed to control the environment, connecting the main connection (16) to the redundancy vent (14) via the first venting path (18) of the parking brake redundancy unit (10) in order to vent the main connection (16) directly into the environment.Electropneumatic parking brake device (1) according to Claim 1, wherein the first control unit (26) and / or the second control unit (28) is independent of the parking brake control unit (6).The electropneumatic parking brake device (1) according to claim 1, wherein the parking brake control unit (6) comprises the first control unit (26) or the second control unit (28).Electropneumatic parking brake device (1) according to one of Claims 1 to 3, wherein the first electropneumatic redundancy valve unit (22) has a bistable valve unit (30) having a first position (36) and a second position (40), wherein the first position (36) is a venting position (38) in which the bistable valve unit (30) allows the main connection (16) to be connected pneumatically to the redundancy vent (14), and wherein the bistable valve unit (30) interrupts the first venting path (18) in the second switching position (40).The electropneumatic parking brake device (1) according to claim 4, wherein the first electropneumatic redundancy valve unit (22) has a first monostable holding valve (32) which is connected in series with the bistable valve unit (30) along the first venting path (18).The electropneumatic parking brake device (1) according to claim 4 or 5, wherein the second electropneumatic redundancy valve unit (24) has a second monostable holding valve (34) which is connected in series with the bistable valve unit (30) along the first venting path (18).The electro-pneumatic parking brake device (1) according to claims 5 and 6, wherein the second monostable holding valve (34) is arranged along the first venting path (18) between the bistable valve unit (30) and the first monostable holding valve (32).Electropneumatic parking brake device (1) according to one of Claims 4 to 7, furthermore having a second redundancy vent (48) and a second vent path (46) which can be vented via the second redundancy vent (48), it being possible for the bistable valve unit (30) to be actuated via the second vent path (46).The electropneumatic parking brake device (1) according to claim 8, wherein the bistable valve unit (30) has a first electronically switchable monostable holding valve (32) which is arranged in the second venting path (46), and a pneumatically switchable third holding valve (50, 54), in particular relay valve (56), which is arranged in the first venting path (18) and comprises a pneumatic control connection (56.3) which is connected to the second venting path (18), wherein the second electropneumatic redundancy valve unit (24) has a second electronically switchable monostable holding valve (34) which is arranged in the first venting path (18).Electropneumatic parking brake device (1) according to Claim 9, further having a return path (62), wherein the return path (62) connects an outlet connection (56.2) of the third holding valve (50, 54) to the pneumatic control connection (56.3) of the third holding valve (50, 54), wherein a throttle (64) and / or a nonreturn valve is preferably provided in the return path (62).Electropneumatic parking brake device (1) according to one of Claims 1 to 10, wherein the parking brake redundancy unit (10) has at least one pressure sensor (42, 44) for detecting a pressure (pFS) in the first venting path (18).Electropneumatic parking brake device (1) according to one of Claims 1 to 11, furthermore having a flow limiter which limits a maximum volume flow through the parking brake redundancy unit (10).Electronically controllable pneumatic brake system (200) for a vehicle (300), comprising at least a first front axle brake actuator (208a, 208b) and a second front axle brake actuator (208a, 208b) and at least a first rear axle brake actuator (208c, 208d, 208e, 208f) and a second rear axle brake actuator (208c, 208d, 208e, 208f); a primary system (212) having a primary control unit (214) at least for actuating the first front axle brake actuator (208s, 208b) and the second front axle brake actuator (208a, 208b) and / or for actuating the first rear axle brake actuator (208c, 208d, 208e, 208f) and the second rear axle brake actuator (208c, 208d, 208e, 208f); and an electropneumatic parking brake device (1) according to one of Claims 1 to 12, at least one first spring-loaded brake cylinder (254c, 254d, 254e, 254f) being connected to the at least one spring-loaded connection (8) of the electropneumatic parking brake valve unit (2).Electronically controllable pneumatic brake system (200) according to Claim 13, wherein at least the first spring-loaded brake cylinder (254c, 254d, 254e, 254f) is connected to the main connection (16) of the parking brake redundancy unit (10), wherein the parking brake redundancy unit (10) is switchable in order to connect the spring-loaded brake cylinder (254c, 254d, 254e, 254f) via the first venting path (18) to the redundancy venting (14) in order to vent the spring-loaded brake cylinder (254c, 254d, 254e, 254f).Electronically controllable pneumatic brake system (200) according to claim 13, wherein the main connection (16) is connected to a first compressed air supply (206, 210) of the brake system (200), and wherein the parking brake redundancy unit (10) is switchable to connect at least the first compressed air supply (206, 210) via the first venting path (18) to the redundancy venting (14) in order to vent the first compressed air supply (206, 210).Electronically controllable pneumatic brake system (200) according to any of claims 13 to 15, wherein the primary control unit (214) is or comprises the first control unit (26).Electronically controllable pneumatic brake system (200) according to one of Claims 13 to 16, further comprising a secondary system (241) having a secondary control unit (242), wherein the secondary system (241) is designed to actuate the first front-axle brake actuator (208a, 208b) and the second front-axle brake actuator (208a, 208b) and / or to actuate the first rear-axle brake actuator (208c, 208d, 208e, 208f) and the second rear-axle brake actuator (208c, 208d, 208e, 208f) if a fault is determined in the primary system (212).Electronically controllable pneumatic brake system (200) according to claim 17, wherein the secondary control unit (242) is or comprises the second control unit (28).Electronically controllable pneumatic brake system (200) according to one of Claims 13 to 18, having a first voltage source (222) and a second voltage source (246), wherein the first voltage source (222) is provided for supplying the first control unit (26) with electrical voltage and wherein the second voltage source (246) is provided for supplying the second control unit (28) with electrical voltage.Vehicle (300), in particular commercial vehicle (302), having at least one front axle (VA), at least one first rear axle (HA1) and an electronically controllable pneumatic brake system (1) according to one of the preceding claims 13 to 19.Method for operating an electronically controllable pneumatic brake system (200) for a vehicle (300), which comprises at least one spring-loaded brake cylinder (254c, 254d, 254e, 254f) and an electropneumatic parking brake device (1) according to Claim 4, wherein the spring-loaded connection (8a, 8b) of the electropneumatic parking brake valve unit (2) is connected (254c, 254d, 254e, 254f) to the at least one spring-loaded brake cylinder at a parking pressure (pFS), and wherein the main connection (16) of the electropneumatic parking brake redundancy unit (10) is connected to a parking-pressure air path (12) of the brake system (200), the method comprising the steps of: - determining whether an at least partially autonomous operating mode or a manual operating mode of the brake system (200) is present; - switching the bistable valve unit (30) into the venting position (38) if an at least partially autonomous operating mode of the brake system (200) is present; - switching the bistable valve unit (30) into the second switching position if the manual operating mode of the brake system (200) is present; and - venting the at least one spring brake cylinder (254c, 254d, 254e, 254f) by the electropneumatic parking brake valve unit (2).Method according to claim 21, wherein the method further comprises: - determining whether a fault of the electropneumatic parking brake valve unit (2) is present, - determining whether a parking brake request is present, and - at least temporarily interrupting the first venting path (18) by a first holding valve (32) if no fault of the electropneumatic parking brake valve unit (2) is determined and no parking brake request is determined; or - opening the first holding valve (32) if a fault of the electropneumatic parking brake valve unit (2) is determined and a parking brake request is determined in order to at least partially open the first venting path (18).Method according to Claim 22, further comprising - at least second-time interrupting the first venting path (18) by a second holding valve (34) if no fault of the parking brake control unit (6) is determined and no parking brake request is determined, wherein the at least temporary interrupting by the second holding valve (34) preferably takes place when the first holding valve (32) releases the first venting path (18), no fault of the parking brake control unit (6) is determined and no parking brake request is determined.Method according to Claim 23, wherein the first holding valve (32) is actuated by a first control unit (26) for at least second interruptions of the first venting path (18), wherein the second holding valve (34) is actuated by a second control unit (28) for at least second interruptions of the first venting path (18); and wherein the first control unit (26) and the second control unit (28) are connected, in particular connected via a CAN bus, and are designed to determine whether the respective other control unit (26, 28) opens or interrupts the first venting path (18).

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