Electro-pneumatic parking brake unit with self-holding in case of fault

Description

[0001] The invention relates to an electropneumatic valve arrangement for actuating a parking brake function of an electropneumatic braking system of a commercial vehicle, comprising a bistable pilot control unit with an electromagnetic solenoid valve having a first electromagnet and a second electromagnet, wherein the pilot control unit controls a pilot pressure depending on an electronic parking brake signal, and a main valve unit that receives the pilot pressure and controls a parking brake pressure at at least one spring brake connection depending on the pilot pressure. The invention further relates to a method for controlling a parking brake function of a commercial vehicle with an electropneumatic braking system and to a commercial vehicle with an electronically controlled pneumatic braking system.

[0002] Electropneumatic valve assemblies for actuating a parking brake function are used in both Europe and the USA. A parking brake function of an electropneumatic braking system typically uses so-called spring-applied brake cylinders, which are closed by spring force and open when vented. Therefore, these spring-applied brake cylinders should be vented and thus open while driving, and vented and thus closed when the vehicle is parked.

[0003] A solution for venting such spring-applied brake cylinders is disclosed in DE 10 2017 005 757 A1. The solution disclosed therein according to the preamble of claim 1 utilizes a pilot control unit and a main valve unit, wherein the pilot control unit comprises an electromagnetic solenoid valve in the form of a bistable valve. In the solution disclosed therein, the main valve unit is formed by a relay valve. Depending on the switching position of the electromagnetic bistable valve, a control pressure is applied to the main valve unit, which then correspondingly controls a volume pressure for the spring-applied brake cylinders. A bistable valve is a solenoid valve that has two stable switching positions, in particular a stable venting position and a stable venting position. For this purpose, one or two coils and one or two permanent magnets can be provided.If two coils are provided, energizing a first coil moves the solenoid valve's armature, which preferably carries a permanent magnet, into a first position, so that the solenoid valve assumes the venting position. Energizing a second coil moves the solenoid valve's armature into a second position, so that the solenoid valve assumes the venting position. Both end positions are detent positions in which the solenoid valve is magnetically locked. If no other force acts on the armature, or if it can be mechanically and / or magnetically locked in these positions, the respective switching position is stable, as it can be maintained without further energizing.

[0004] In the US, however, so-called push-pull valves are used in the driver's cab, allowing the driver to manually vent or depressurize the spring brake cylinders. When the push-pull valve is pushed in, a pneumatic connection is established, venting and thus releasing the spring brake cylinders of the towing vehicle. Conversely, when the driver pulls the push-pull valve out, the spring brake cylinders are depressurized and engage. A solution that already allows for pneumatic switching of the push-pull valves is disclosed in DE 10 2018 108 202 A1.

[0005] Since the complexity of the pneumatic piping from the corresponding valves that implement the parking brake function, the spring-applied brake cylinders (usually located on the rear axle), and the driver's cab is relatively high, there is a need to simplify this process. Furthermore, there is a need to improve the safety of such push-pull valves.

[0006] Another solution that generates pneumatic bistability or self-holding, thus enabling stable engagement of the parking brake even without further energizing an electromagnetic valve, is disclosed in WO 2019 / 030242 A1. The solution disclosed therein uses a pneumatically switchable 3 / 2-way valve as the main valve unit and two electrically switchable 3 / 2-way valves as the pilot unit. One of the electrically switchable 3 / 2-way valves feeds back the pressure controlled by the main valve unit and actuates a pneumatic control port of the main valve unit. This achieves pneumatic self-holding in the event that the main valve unit is controlling a pneumatic pressure.If a fault occurs, or if the reservoir supplying the main valve unit with pressure is depleted, no pressure will be released by the main valve unit. As a result, the main valve unit switches to a monostable position in which the corresponding spring brake connection is vented. Even if the compressed air reservoir is refilled, for example by a service technician or because the vehicle has power again, the parking brake will not automatically release, as the main valve unit is in the venting position and no pneumatic pressure is being returned.

[0007] This solution, specifically designed for the US market, is not readily applicable in Europe, depending on the vehicle's design. Furthermore, there is a need to implement additional functionalities, including an improved valve arrangement, and to explore ways to create synergies between individual products.

[0008] In a first aspect of the invention, the problem is solved in an electropneumatic valve arrangement of the type mentioned above by providing the solenoid valve with a safety control port for receiving a safety control pressure, wherein the solenoid valve supplies the pilot unit with supply pressure or connects it to a vent depending on the safety control pressure, wherein the safety control pressure is a pressure controlled by the solenoid valve or a pressure derived therefrom. In this way, it can be ensured that the solenoid valve does not necessarily remain in a detent position caused by the at least one permanent magnet when the pressure controlled by the solenoid valve changes.

[0009] In solutions that use a conventional bistable solenoid valve as part of electropneumatic valve arrangements to actuate the parking brake function, there is a risk that the solenoid valve will remain in a venting position even after a vehicle fault due to the magnetic force exerted by the at least one permanent magnet. If the vehicle is switched off after a fault and the compressed air supply is consequently depleted, the spring brake cylinders are applied, even without the solenoid valve being moved to the venting position. Therefore, it can remain in the venting position due to its two magnetic detent positions: the venting position and the venting position.If the vehicle is then reconnected to the power supply and consequently the compressed air reservoir is replenished, or replenished by other means, the spring brake cylinders may be vented and thus released, which can lead to the vehicle rolling away unintentionally. To prevent this, it is known to move the solenoid valve to a venting position after the spring brake cylinders have been vented, whereby the pressure controlled by the solenoid valve is held back by another, further valve, such as a 2 / 2-way valve.

[0010] In this configuration, if the brake system is de-energized or a control module fails, the other valve returns to a monostable open position. The solenoid valve is still in the venting position at this point, allowing the spring brake cylinders to be vented. Refilling the compressed air reservoir does not automatically vent the spring brake cylinders in this case. However, even in such situations, a fault can occur before the solenoid valve returns to the venting position, potentially leading to the aforementioned problem of venting the spring brake cylinders when the reservoir pressure is restored.

[0011] According to the invention, the switching position of the solenoid valve is therefore made dependent not only on the electromagnetically set switching position, but also on the control pressure of the safety control pressure, i.e., the pressure controlled by the solenoid valve. This provides an additional level of safety. Preferably, it is provided that as soon as the safety control pressure falls below a first predetermined threshold, the solenoid valve is moved into a venting position independently of electromagnetic switching signals. This can be achieved pneumatically, mechanically, or by other means. Preferably, this occurs independently of any energizing process.

[0012] The safety control pressure is a pressure controlled by the solenoid valve or a pressure derived from it. For example, a return line or return bore can be provided directly at a connection of the solenoid valve, supplying the pressure controlled by the solenoid valve as the safety control pressure at the safety control connection. Alternatively, a return line can branch off directly before the main valve unit or even downstream of it, for example, before or at the spring brake connection. The parking brake pressure is a pressure derived from the solenoid valve.

[0013] In a first preferred embodiment, the solenoid valve has a first solenoid valve port receiving the supply pressure, a second solenoid valve port controlling the pilot pressure, and a third solenoid valve port connected to a vent. Preferably, in a venting position or first switching position of the solenoid valve, the first solenoid valve port is connected to the second solenoid valve port, and in a venting position or second switching position of the solenoid valve, the third solenoid valve port is connected to the second solenoid valve port. By energizing at least one coil, the solenoid valve can be selectively switched to either the venting position or the venting position, with the solenoid valve being magnetically held in the respective switching position by means of the at least one permanent magnet.Preferably, it is further provided that if the safety control pressure falls below a first threshold value, the solenoid valve is switched to the venting position regardless of any previous switching position. This ensures that the solenoid valve remains in the venting position even when de-energized and in the event of a fault, and that restoring a supply pressure does not immediately release spring-applied brake cylinders. The solenoid valve can generally comprise a coil and a permanent magnet, which is then preferably arranged in the armature of the solenoid valve. By appropriately energizing one coil, the armature, together with the permanent magnet, can be moved in one direction or the other, magnetically locking the armature in place when it comes into contact with a corresponding valve seat, so that the solenoid valve has two magnetic detent positions.In some variations, two coils and one permanent magnet, two coils and two permanent magnets, or one coil and two permanent magnets can be used. If two permanent magnets are used, they are preferably attached to a valve housing and each acts on the armature, thus magnetically holding the armature in its end positions and locking it in place. More than two coils and permanent magnets can also be used.

[0014] Furthermore, it is preferred that, in the event that the safety control pressure exceeds the first threshold, the solenoid valve is held in its previous switching position and can preferably be switched to either the venting or purging position by energizing the at least one coil. It is therefore preferably provided that, if the safety control pressure exceeds the first threshold, the solenoid valve can be held in the venting or purging position, depending on which of these positions the solenoid valve would be electromagnetically switched to. However, it can also be provided that the solenoid valve is switched to the purging switching position.

[0015] Preferably, if the safety control pressure exceeds a second threshold, which is preferably higher than the first threshold, the solenoid valve is switched to the venting position. Preferably, in this case, the solenoid valve can be switched to the venting position by energizing the at least one coil. If the safety control pressure exceeds the second threshold, this can not only maintain the switching position but also actively switch the solenoid valve to the venting position. For this to occur, the force exerted by the safety control pressure preferably exceeds a magnetic holding force or detent torque exerted by at least one permanent magnet. Nevertheless, it is preferably provided that the solenoid valve can be switched to the venting position by energizing the at least one coil.When the coil is energized, an additional force is exerted on the armature, which in turn can exceed the force exerted by the safety control pressure, thus moving the armature to the other switching position. By energizing at least one coil, the control pressure above the second threshold can therefore be overridden to force the venting position.

[0016] The first threshold is preferably in the range of 200 kPa to 400 kPa, more preferably 250 kPa to 350 kPa. These values ​​should be below the usual value of the storage pressure. The second threshold is preferably in the range of 500 kPa to 900 kPa, more preferably 600 kPa to 800 kPa.

[0017] It is further preferred that the solenoid valve has a preferred position. That is, the solenoid valve is preferably biased into one of the first and second switching positions, preferably the venting position. Preferably, the pilot control unit is connected to the vent in the preferred position. It can be provided that the release of the safety control pressure above the first threshold value cancels the preferred position. As soon as the safety control pressure exceeds the first threshold value, the solenoid valve preferably no longer has a preferred position. However, if the safety control pressure falls below the first threshold value, the solenoid valve has the preferred position and switches to the preferred position when de-energized, namely preferably to the venting position. The preferred position can be implemented, for example, by a spring biasing the solenoid valve into the preferred position.This ensures that the solenoid valve is mechanically biased into its preferred position and is moved into this preferred position if the safety control pressure falls below the set point. In this case, the safety control pressure counteracts the spring force.

[0018] In a further preferred embodiment, an emergency release connection is provided, with an emergency release path for applying an emergency release pressure that releases the parking brake pressure at the at least one spring brake connection. The emergency release connection serves, in particular, to manually or via an additional pressure source apply the emergency release pressure in order to release the parking brake pressure at the at least one spring brake connection. This allows the spring brake cylinder(s) to be vented and released via the emergency release pressure. This can be necessary and helpful if the commercial vehicle is in a power-less or defective state and the compressed air supply to the spring brake connection cannot provide sufficient pressure or volume.In this way, for example, a service technician can control the emergency release pressure, for example via a supply that is available in a service vehicle, and thus release the spring brake cylinder(s).

[0019] In one variant, the solenoid valve supplies the pilot control unit with reservoir pressure or connects it to the vent, depending on the emergency release pressure. For example, the emergency release path can lead into a vent path of the solenoid valve. It is conceivable, and preferred, for the emergency release path to lead into the vent path via a check valve or a double check valve, in order to control a pilot pressure via the solenoid valve's vent path. When the vehicle is de-energized or depressurized, the solenoid valve should be in the vent position, connecting the pilot control unit to the vent. This means that in this switching position, the emergency release pressure can be applied via the vent path to provide the pilot control unit with the corresponding pilot pressure. This, in turn, can control the parking brake pressure.

[0020] It is further preferred that the emergency release pressure is controlled via the emergency release path at the safety control port of the solenoid valve or at another control port of the solenoid valve. This allows the solenoid valve to be returned to its initial switching position, in which it is preferably in a venting position, in order to control a pilot pressure at the main valve unit. For this purpose, the emergency release pressure can be controlled at the same safety control port of the solenoid valve where the safety control pressure is also controlled, or at a separate, dedicated control port. Both can trigger the preferred position and / or switch the solenoid valve to the venting position.

[0021] In a further preferred embodiment, it is provided that if the emergency release pressure exceeds one or the second threshold value, the solenoid valve is switched to the venting position. According to this embodiment, not only is the preferred position released, but the venting position is assumed, contrary to the preferred position. Preferably, however, it is also provided here that the at least one coil can be overridden by a corresponding current, and thus the solenoid valve can be switched to the venting position despite the emergency release pressure being above the second threshold value.

[0022] It is further preferred that the electropneumatic valve assembly is integrated into a module, which preferably has one or more reservoir connections, a spring brake connection, a vent, and optionally an emergency release connection. Such a module can, in particular, be designed as a parking brake module or a handbrake module. Preferably, such a module has its own electronic control unit, which can receive one or more signals from a higher-level control unit, for example, via a vehicle bus, another bus, or direct wiring. The module's electronic control unit can then output one or more switching signals to the electromagnetically switchable valve(s) to effect a switching action.However, it is also possible for the individual electromagnetic valves of the electropneumatic valve arrangement to be switched via a direct signal from a higher-level control unit. A higher-level control unit can be, in particular, a central control unit, a vehicle control unit, or the like.

[0023] In a second aspect, the aforementioned problem is solved by a method for controlling a parking brake function of a commercial vehicle with an electropneumatic braking system and preferably an electropneumatic valve arrangement according to one of the preferred embodiments of an electropneumatic valve arrangement described above according to the first aspect of the invention, comprising the steps of: electromagnetically switching an electromagnetic solenoid valve with at least one first permanent magnet from a venting position to a venting position to control a parking brake pressure at at least one spring brake cylinder connection to vent at least one spring brake cylinder, locking in a pilot pressure controlled by the solenoid valve and / or holding the solenoid valve in the venting position.and when the supply pressure to the solenoid valve drops below a first threshold value: pneumatically or mechanically switching of the solenoid valve to the venting position.

[0024] It should be understood that the method according to the second aspect and the electropneumatic valve arrangement according to the first aspect of the invention have identical and similar sub-aspects, as set forth in particular in the dependent claims. In this respect, full reference is made to the above description of the first aspect of the invention.

[0025] The electromagnetic switching of the solenoid valve from a venting position to a ventilation position is preferably achieved by energizing at least one coil. By energizing at least one coil and optionally a further coil, the solenoid valve can be selectively switched to either the ventilation or venting position.

[0026] Preferably, the method provides that the solenoid valve has a preferred position which can be overridden by applying a safety control pressure at a safety control port of the solenoid valve. That is, if no or insufficient safety control pressure is applied at the safety control port, the solenoid valve is in the preferred position; if the safety control pressure exceeds the first threshold value, this preferred position is overridden or compensated for, so that the solenoid valve then has no preferred position.

[0027] Preferably, the method further comprises the step of: controlling a safety control pressure at a safety control port of the solenoid valve to hold the solenoid valve in the venting position or to switch the solenoid valve into the venting position, wherein the safety control pressure is a pressure controlled by or derived from the solenoid valve. For this purpose, the safety control pressure preferably exceeds the first threshold value.

[0028] The method can include the step of applying an emergency release pressure to release the parking brake pressure at the at least one spring brake connection. The emergency release pressure can be applied to a venting path of the solenoid valve. Additionally or alternatively, the emergency release pressure can also be applied to the safety control port of the solenoid valve or another control port of the solenoid valve. If the safety control pressure or emergency release pressure applied at the safety control port exceeds one or the second threshold value, the solenoid valve is preferably switched to the venting position, regardless of its previous switching position. However, even in this case, it can be provided that the solenoid valve can be switched to the venting position by energizing the at least one coil.

[0029] In a third aspect, the invention solves the aforementioned problem by means of a commercial vehicle with an electronically controlled pneumatic braking system, which has an electropneumatic valve arrangement according to one of the preferred embodiments of an electropneumatic valve arrangement described above, as described in the first aspect of the invention. Preferably, the commercial vehicle is configured to at least partially carry out the method according to the second aspect of the invention.

[0030] It should be understood that the electropneumatic valve arrangement according to the first aspect of the invention, the method according to the second aspect of the invention, and the commercial vehicle according to the third aspect of the invention have identical and similar sub-aspects, which are set out in particular in the dependent claims. In this respect, full reference is made to the above description. The electropneumatic valve arrangement according to the first aspect of the invention can be implemented in the commercial vehicle according to the third aspect of the invention, in particular in the form of a parking brake module.

[0031] Embodiments of the invention are now described below with reference to the drawings. These are not necessarily intended to represent the embodiments to scale; rather, the drawings are presented in a schematic and / or slightly distorted form where this is helpful for clarification. With regard to additions to the teachings directly apparent from the drawings, reference is made to the relevant prior art. It should be noted that numerous modifications and changes concerning the form and detail of an embodiment can be made without altering the subject matter of the claims. For the sake of simplicity, the same reference numerals are used below for identical or similar parts or parts with identical or similar functions. Further advantages, features, and details of the invention will become apparent from the following description of the preferred embodiments and from the drawings; these show in: Figure 1 shows a first embodiment of an electropneumatic valve arrangement; Figure 2 shows a second embodiment of an electropneumatic valve arrangement; Figure 3 shows a third embodiment of an electropneumatic valve arrangement; and Figure 4 shows a commercial vehicle.

[0032] An electropneumatic valve arrangement 1 is shown in the embodiment in the Fig. 1 bis 3 designed as a parking brake module 2, although this is not strictly necessary, and the electropneumatic valve arrangement 1 can also be integrated with other units and / or the individual valves described below can also be separate and / or distributed in a brake system 102 (see Fig. 4 ) be arranged.

[0033] The parking brake module 2 has a supply port 4 to which a first compressed air reservoir 6 and a second compressed air reservoir 7 are connected via a reservoir changeover valve 5, each providing a supply pressure pV, so that the supply pressure pV is present at the supply port 4. It is not strictly necessary for two compressed air reservoirs 6, 7 to be connected to the supply port 4; rather, it may also be sufficient if only one compressed air reservoir is connected there, or if the supply port 4 is supplied via another module.

[0034] The electropneumatic valve assembly 1 comprises a bistable pilot unit 8 and a main valve unit 10. The bistable pilot unit 8 includes an electromagnetic solenoid valve 12. The solenoid valve 12 has a first solenoid valve port 12.1, a second solenoid valve port 12.3, and a third solenoid valve port 12.2. The first solenoid valve port 12.1 is connected to the supply port 4 and receives supply pressure pV. The second solenoid valve port 12.2 is connected to the main valve unit 10, in which Fig. 1 The illustrated embodiment uses a holding valve 14. The third solenoid valve port 12.3 is connected to a vent 3. The solenoid valve 12 has a first, in Fig. 1 Switching position not shown, in which the first solenoid valve port 12.1 is connected to the second solenoid valve port 12.2. In the Fig. 1 In the second switching position shown, the third solenoid valve port 12.3 is connected to the second solenoid valve port 12.2. Therefore, the first switching position can also be referred to as the venting position and the second as the venting position. In the venting position, a pilot pressure pSV is controlled via the solenoid valve 12. The solenoid valve 12 is switched depending on a parking brake signal SFB, which is received by the parking brake module 2, for example, via a vehicle bus 16, or can also be provided directly at the solenoid valve 12.

[0035] The solenoid valve 12 has a first permanent magnet 13.1 and a second permanent magnet 13.2. In the illustrated embodiment, the solenoid valve 12 also has a first coil 13.3 and a second coil 13.4. Depending on the parking brake signal SFB, either the first coil 13.3 or the second coil 13.3 is energized. When the first coil 13.3 is energized, an armature of the solenoid valve 12 is attracted in a generally known manner, thus switching the solenoid valve 12 into the venting position. The armature is then held in the venting position by the first permanent magnet 13.1, which is therefore a magnetic detent position. The first permanent magnet 13.1 and the first coil 13.3 are associated with the venting position. If, on the other hand, the second coil 13.4 is energized, the armature is pulled into the opposite detent position, and the solenoid valve 12 is switched into the venting position.In this detent position, the armature is held by the second permanent magnet 13.2. However, it is also possible that only one coil 13.3, 13.4 is provided, which would then need to be reversed to switch the solenoid valve 12 between the venting and aeration positions. It is also conceivable that only one permanent magnet 13.1, 13.2 is provided, which would then preferably be arranged on the armature of the solenoid valve 12.

[0036] In the Fig. 1 In the illustrated embodiment, the parking brake module 2 is equipped with its own electronic control unit (ECU), although this is not mandatory. It receives the parking brake signal (SFB) and subsequently triggers at least one first switching signal (S1) at the solenoid valve 12 to selectively switch it between the first and second switching positions. If the parking brake module 2 does not have its own electronic control unit (ECU), the first switching signal (S1) can also be provided directly by an external control unit. The solenoid valve 12 can be switched to either the first or second switching position by a pulse. In the illustrated embodiment, the solenoid valve 12 has a preferred position in addition to that of conventional solenoid valves; specifically, the solenoid valve 12 is in the second position. Fig. 1 The switch position shown is pre-tensioned. For this purpose, a spring 18 is provided which moves the solenoid valve 12 into the second position. Fig. 1 The shown switch position (venting position) brings.

[0037] The pilot pressure pSV controlled by the solenoid valve 12 is supplied to the main valve unit 10 via the holding valve 14. The main valve unit 10 comprises a relay valve 20, which has a relay valve reservoir port 20.1, a relay valve working port 20.2, a relay valve vent port 20.3, and a relay valve control port 20.4. The relay valve reservoir port 20.1 is connected to reservoir port 4 and receives reservoir pressure pV. The relay valve working port 20.2 is connected to a spring accumulator port 21 of the parking brake module 2, at which the main valve unit 10 controls a parking brake pressure pBP. The relay valve vent port 20.3 is connected to vent 3, and the relay valve control port 20.4 is connected to the pilot unit 8 and receives the pilot pressure pSV. One or more spring brake cylinders 108a, 108b (see below) can be connected to the spring brake connection 21. Fig. 4 ) are connected, which are vented and tightened by means of a spring force.

[0038] To release the spring brake cylinders 108a, 108b, the spring brake connection 21 must be vented so that the parking brake pressure pBP is released. For this purpose, the solenoid valve 12 is opened by the Fig. 1 shown venting position in the Fig. 1 The valve is moved to the ventilation position not shown, so that the pilot pressure pSV is controlled. The holding valve 14 is in the open switching position. The holding valve 14 has a first holding valve port 14.1 and a second holding valve port 14.2, wherein the first holding valve port 14.1 is connected to the solenoid valve 12, more precisely to the second solenoid valve port 12.2, and receives the pilot pressure pSV. The second holding valve port 14.2 is connected to the main valve unit 10, more precisely to the relay valve control port 20.4. The holding valve 14 is electromagnetically and monostable and can be controlled by the stable first in Fig. 1 The switching position shown, which is an open position, can be changed to a second closed, unstable switching position by providing a second switching signal S2, which energizes an electromagnet in the holding valve 14. Thus, if the solenoid valve 12 is first switched so that the pilot pressure pSV is controlled and the holding valve 14 is open, the pilot pressure pSV is passed on and controlled at the relay valve control port 20.4, which then amplifies this pressure by volume and controls the parking brake pressure pBP at the spring accumulator port 21. Now the holding valve 14 can be moved to the closed second switching position, so that the pilot pressure pSV is trapped between the second holding valve port 14.2 and the relay valve control port 20.4. The solenoid valve 12 can now be moved back to the first position. Fig. 1 The venting position shown is brought into place. The spring brake cylinders 108a and 108b remain vented and thus released. Although only one variant with pilot unit 8 and main valve unit 10 is described here, it should be understood that the main valve unit 10 is not strictly necessary and the pilot pressure pSV could also be directly controlled as the parking brake pressure pBP. In this case, the second holding valve connection 14.2 would be connected to the spring brake connection 21 without the intermediate main valve unit 10.

[0039] However, as an alternative control mechanism, the holding valve 14 can also remain open in its stable switching position. To now engage the solenoid valve 12 in the first position... Fig. 1 To maintain the ventilation position not shown, the solenoid valve 12 has a safety control port 12.4. The safety control port 12.4 is connected via a safety line 22 to a first control line 24, which connects the second solenoid valve port 12.2 and the first holding valve port 14.1. The safety line 22 thus returns the pressure controlled by the solenoid valve 12 to the safety control port 12.4. When the pilot pressure pSV is controlled by the solenoid valve 12, it is supplied to the safety control port 12.4 via the safety line 22, so that it is present at the solenoid valve 12 as the safety control pressure pSS. The safety control port 12.4 is arranged such that the safety control pressure pSS acts on the solenoid valve 12 in such a way that it opens into the first position shown. Fig. 1 The switching position not shown, i.e., the ventilation position, is subjected to a load. In particular, internal control surfaces are selected such that the safety control pressure pSS exerts a force approximately equal to that of spring 18, so that applying the safety control pressure pSS can release or neutralize the preferred position of the solenoid valve 12. In this state, the solenoid valve 12 can also be switched to the inlet or outlet position by appropriately energizing the first and second coils 13.3, 13.4, since spring 18 and the safety control pressure pSS essentially cancel each other out. In the respective switching positions, the magnetic force of either the first or second permanent magnet 13.1, 13.2 then acts, so that the switching positions are detent positions, and the armature can only be moved out of the respective detent positions by overcoming the magnetic forces with a certain minimum force.

[0040] However, if the safety control pressure pSS falls below a first threshold value, which can be in the range of approximately 200 kPa to 400 kPa, the force exerted by the safety control pressure pSS is less than that of the spring force exerted by spring 18, so that the solenoid valve 12 again has a preferred position and moves into the second position. Fig. 1 The indicated venting position falls back. Therefore, if, in the event of a fault in the commercial vehicle 100, the reservoir pressure pV drops because both the first and second compressed air reservoirs 6, 7 are emptied, have a leak, or are actively pumped down by the driver, the pilot pressure pSV also drops when the solenoid valve 12 in the Fig. 1 The ventilation position is not shown. However, if the pilot pressure pSV drops, the safety control pressure pSS also drops simultaneously, so that from a certain point, namely preferably when the first threshold value is undershot, the preferred position of the solenoid valve 12 engages again and the spring 18 moves the solenoid valve 12 into the position shown. Fig. 1 The unit is in the venting position shown, so that as a result the relay valve control port 20.4 is vented and no parking brake pressure pBP is controlled. The spring brake cylinders 108a and 108b are completely vented.

[0041] Should the first and / or second compressed air reservoir 6, 7 now need to be refilled in this state, for example because the commercial vehicle 100 has regained power or the first and second compressed air reservoirs 6, 7 are refilled by a service technician, the solenoid valve 12 will still be in the second position. Fig. 1 In the vented position shown, the spring accumulator connection 21 is not automatically and unintentionally vented. Only by providing the parking brake signal SFB or the first switching signal S1 and energizing the first coil 13.3 can the solenoid valve 12 return to the position shown. Fig. 1 The ventilation position (not shown) must be moved to allow ventilation so that the spring brake cylinders 108a and 108b can be released again. Unintentional release of the spring brake cylinders 108a and 108b is effectively prevented.

[0042] The parking brake module 2, in the embodiment shown here ( Fig. 1 Furthermore, a first pressure sensor 26 and a second pressure sensor 28 are provided. The first pressure sensor 26 is connected to the reservoir port 4 via a first pressure measuring line 27 and thus measures the reservoir pressure pV and provides a corresponding first pressure signal SD1 to the electronic control unit (ECU). The second pressure sensor 28 is connected to the spring brake port 21 via a second pressure measuring line 29 and thus determines the parking brake pressure pBP and provides a corresponding second pressure signal SD2 to the electronic control unit (ECU). The first and second pressure signals SD1 and SD2 can be used to verify and validate the control of the pressures and the switching position of the individual valves.

[0043] Furthermore, the electropneumatic valve arrangement 1, according to the embodiment shown here, has a release control port 30. Such a release control port 30 is also referred to as an anti-compound port, through which a release control pressure pL can be applied. The release control port 30 is connected to a release control path 32. The release control pressure pL applied via the release control port 30 causes the release of the parking brake pressure pBP at the at least one spring brake port 21. The release control path 32 comprises a release line 33 extending from the release control port 30. The release control pressure pL is typically the pressure of another axle, for example, the front or rear axle, and in particular the service brake pressure.In the event that the spring brake cylinders 108a, 108b connected to the spring brake port 21 are also used for auxiliary or emergency braking, this is intended to prevent excessive actuation of the spring brake cylinders 108a, 108b, which could lead to the vehicle 100 locking up. Therefore, if the service brakes on the rear axle are activated, the spring brake cylinders 108a, 108b should not be engaged simultaneously if possible. It is therefore advantageous to supply the service brake pressure of the rear axle as the release control pressure pL to the release control port 30 in order to release the spring brake cylinders 108a, 108b inversely to the engagement of the service brakes.

[0044] In the Fig. 1 In the illustrated embodiment, the release control line 33 is connected to a changeover valve 34. The release control pressure pL can be supplied to the relay valve control port 20.4 via the release control path 32. The changeover valve 34 has a first changeover valve port 34.1, a second changeover valve port 34.2, and a third changeover valve port 34.3. The changeover valve 34 is designed such that it forwards the higher of the pressures applied to the first and second changeover valve ports 34.1 and 34.2 to the third changeover valve port 34.3. The first changeover valve port 34.1 is connected here to the second holding valve port 14.2 via a second control line 36, but can also be connected directly to the second holding valve port 14.2 or to the solenoid valve 12. In any case, the first changeover valve port 34.1 is connected to the pilot unit 8 and receives the pilot pressure pSV. The second changeover valve port 34.2 is connected to the release control port 30 and receives the release control pressure pL. The third changeover valve port 34.3 is connected to the relay valve control port 20.4, so that the higher of the pilot pressure pSV or the release control pressure pL is controlled at the relay valve control port 20.4 to control the parking brake pressure pBP.

[0045] The in Fig. 2 The second embodiment shown is basically based on the first embodiment ( Fig. 1 ), so that identical and similar elements are provided with the same reference numerals. In this respect, full reference is made to the above description of the first embodiment ( Fig. 1 ) referred to. The differences from the first embodiment are highlighted in particular below.

[0046] The essential difference in the second embodiment ( Fig. 2 The feature is that an emergency release port 38 is provided, through which an emergency release pressure pSN can be supplied. In this embodiment, the emergency release port 38 is connected to the solenoid valve 12 via an emergency release path 39, more precisely, to the safety control port 12.4, and can provide the emergency release pressure pSN at the safety control port 12.4. For this purpose, an emergency release changeover valve 42 is connected between the safety line 22 and the safety control port 12.4, which is connected to the emergency release port 38 via an emergency release line 40. The emergency release changeover valve 42 is designed in the same way as the first changeover valve 34, such that either the higher of the safety control pressure pSS or the emergency release pressure pSN is controlled at the safety control port 12.4. In this way, the solenoid valve 12 can be switched from the first to the safety control port 12.4. Fig. 2 shown switch position in the second in Fig. 2 The emergency release pressure pSN is moved to the venting position (not shown), particularly when the emergency release pressure pSN exceeds a second threshold, preferably in the range of 400 kPa to 800 kPa, which exceeds the force applied by the spring 18 and, optionally, a detent force for the solenoid valve's armature that holds it in the venting position, allowing the solenoid valve 12 to switch. In this way, the supply pressure pV can then be provided to the pilot control unit 8 to control the pilot pressure pSV and consequently vent the spring accumulator port 21. The emergency release pressure pSN is used, in particular, to switch the solenoid valve 12 in the event that the switching signal S1 cannot be provided. For example, the emergency release pressure pSN can be a manually controlled pressure supplied via an externally connected reservoir, such as tire pressure.However, the pressure from another compressed air reservoir (not shown here), another module, another axis, or the like can also be used. The emergency release pressure pSN serves in particular to vent the spring brake connection 21 in the event that the solenoid valve 12 can no longer be switched electronically to the venting position. For example, the solenoid valve 12 could be reset in this way by the service brake pressure of another axis.

[0047] One variant of this is in Fig. 3 shown. Fig. 3 is in turn based on the Fig. 1 and 2 , and identical and similar elements are provided with the same reference numerals, so that the above description of the first and second embodiments applies in full ( Fig. 1 , Fig. 2 ) will be referenced. The differences between the first and second embodiments will be highlighted below.

[0048] In contrast to the first embodiment ( Fig. 1 ) the electropneumatic valve arrangement 1 according to the third embodiment ( Fig. 3 ) again the emergency release connection 38. This differs from the second embodiment ( Fig. 2 However, the emergency release port 38 is not connected to the safety control port 12.4 of the solenoid valve 12, but rather leads to a vent path 44 of the pilot unit 8, more precisely of the solenoid valve 12. In this sense, the emergency release port 38 is again connected to the solenoid valve 12, but to the third solenoid valve port 12.3. The emergency release pressure pSN can therefore be controlled via the emergency release port 38 at the third solenoid valve port 12.4 via the vent path 44, so that when the solenoid valve 12 is in the venting position, this in turn triggers the control of the pilot pressure pSV. The holding valve 14 is de-energized in this case in the open position. Fig. 3 in the switching position shown, so that the pilot pressure pSV can be controlled by means of the emergency release pressure pSN at the main valve unit 10, so that the main valve unit 10 can subsequently control the parking brake pressure pBP. The third embodiment ( Fig. 3 ) is therefore not based like the second embodiment ( Fig. 2 ) on a manual or pneumatic additional switching of the solenoid valve 12 into the venting position, but uses the venting path 44 of the solenoid valve 12 to control the emergency release pressure via this, and in this way to cause the spring brake cylinders 108a, 108b to be released.

[0049] To enable the introduction of the emergency release pressure pSN into the venting path 44, which must also be connected to the vent 3, the following is used as in the second embodiment ( Fig. 2 In this case, too, the emergency release changeover valve 42 is used. This valve is arranged such that it allows, on the one hand, a connection between the pilot unit 8 and the vent 3, and on the other hand, the control of the emergency release pressure pSN to the pilot unit 8 via the vent path 44. For this purpose, the emergency release changeover valve has a first emergency release changeover valve port 42.1, which is connected to the emergency release port 38. It has a second emergency release changeover valve port 42.2, which is connected to the vent 3, and a third emergency release changeover valve port 42.3, which in turn is connected to the third solenoid valve port 12.3. The emergency release changeover valve 42 also has a preferred position and is thus preferably designed as a single check valve. To achieve the preferred position, a return line 46 is provided, which causes a valve element 48 to pneumatically open the first emergency release changeover valve connection 42.1 closes. In the basic state and when the pilot control unit 8 is vented via the vent path 44, the valve element 48 is pre-tensioned in this way and the second and third emergency release changeover valve ports 42.2, 42.3 are connected. Only when the emergency release pressure pSN is applied against the unpressurized vent path 44 is the valve element 48 released from the in . Fig. 3 The valve is raised to the position shown and releases the first emergency release changeover valve connection 42.1. Besides pneumatic implementation via the return line 46, this can also be achieved mechanically using a spring. Preferably, the second and third emergency release changeover valve connections 42.2, 42.3 are permanently and unobstructed connected to each other during venting operation and are pressureless.

[0050] Fig. 4 Finally, a vehicle 100, namely a commercial vehicle, is illustrated with a braking system 102, which here is designed as an electronically controlled pneumatic braking system. The vehicle 100 has a front axle VA and a rear axle HA. A central module 104, which is also designed as a rear axle modulator, brakes the rear axle HA, and a front axle modulator 106 is assigned to the front axle VA. The central module 104 and the front axle modulator 106 are connected to each other via an electronic line 107 and thus exchange signals, such as brake signals in particular. In addition to first and second spring-applied brake cylinders 108a, 108b, first and second service brake cylinders 109a, 109b are also provided on the rear axle HA, which together with the spring-applied brake cylinders 108a, 108b can be housed in so-called tristop cylinders.On the front axle VA, the front axle modulator 106 controls corresponding brake pressures at the front axle service brake cylinders 110a, 110b. The spring-applied brake cylinders 108a, 108b are controlled via a parking brake module 2, in which the electropneumatic valve arrangement 1 according to the invention is implemented. The parking brake module 2 has the spring-applied brake connection 21, which is as shown in . Fig. 4 shown with the spring-applied brake cylinders 108a, 108b. The vehicle bus 16 connects the parking brake module 2 to the central unit 104. Reference symbol list (part of the description)

[0051] 1 Electropneumatic valve assembly 2 Parking brake module 3 Vent 4 Reservoir connection 5 Reservoir changeover valve 6 First compressed air reservoir 7 Second compressed air reservoir 8 Pilot unit 10 Main valve unit 12 Electromagnetic solenoid valve 12.1 First solenoid valve connection 12.2 Second solenoid valve connection 12.3 Third solenoid valve connection 12.4 Safety control connection 13.1 First permanent magnet 13.2 Second permanent magnet 13.3 First coil 13.4 Second coil 14 Holding valve 14.1 First holding valve connection 14.2 Second holding valve connection 16 Vehicle bus 18 Spring 20 Relay valve 20.1 Relay valve reservoir connection 20.2 Relay valve working connection 20.3 Relay valve vent connection 20.4 Relay valve control connection 21 Spring accumulator connection 22 Safety line 24 First control line 26 First pressure sensor 27 First pressure measuring line 28 Second pressure sensor 29 Second pressure measuring line 30 Release control connection 32 Release control path 33 Release line 34 Changeover valve 34.1 First changeover valve connection 34.2 Second changeover valve connection 34.3 Third changeover valve connection 36 Second control line 38 Emergency release connection 39 Emergency release path 40 Emergency release line 42 Emergency release changeover valve 42.1 First emergency release changeover valve connection 42.2 Second emergency release changeover valve connection 42.3 Third emergency release changeover valve connection 44 Venting path 46 Return 48 Valve element 100 Commercial vehicle 102 Brake system 104 Central module 106 Front axle modulator 108a, 108b Spring-applied brake cylinder 109a, 109b Rear axle service brake cylinder 110a, 110b Front axle service brake cylinder ECU Electronic control unit pBP Parking brake pressure pLL Release control pressure pSN Emergency release pressure pSS Safety control pressure pSV Pilot pressure pV Reservoir pressure S1 First Switching signal S2 Second switching signal SFB Parking brake signal SD1 First pressure signal SD2 Second pressure signal VAV Front axle HAH Rear axle.

Claims

1. Electropneumatic valve assembly (1) for actuating a parking brake function of an electropneumatic brake system (102) of a commercial vehicle (100), comprising a pilot control unit (8) having an electromagnetic solenoid valve (12) which has at least one first permanent magnet (13.1), the pilot control unit (8) modulating a pilot control pressure (pSV) depending on an electronic parking brake signal (SFB); and a main valve unit (10) which receives the pilot control pressure (pSV) and, depending on the pilot control pressure (pSV), modulates a parking brake pressure (pBP) at at least one spring-loaded connection (21); characterized in that the solenoid valve (12) comprises a safety control connection (12.4) for receiving a safety control pressure (pSS), the solenoid valve (12), depending on the safety control pressure (pSS), supplying the pilot control unit (8) with supply pressure (pV) or connecting said unit to a vent (3), the safety control pressure (pSS) being a pressure modulated by the solenoid valve (12) or a pressure derived therefrom.

2. Electropneumatic valve assembly according to claim 1, wherein the solenoid valve (12) comprises a first solenoid valve connection (12.1) receiving the supply pressure (pV), a second solenoid valve connection (12.2) modulating the pilot control pressure (pSV), and a third solenoid valve connection (12.3) connected to a vent (3), wherein, in a ventilation position of the solenoid valve (12), the first solenoid valve connection (12.1) is connected to the second solenoid valve connection (12.2), and, in a venting position of the solenoid valve (12), the third solenoid valve connection (12.3) is connected to the second solenoid valve connection (12.2), wherein, by energizing at least one coil (13.3, 13.4), the solenoid valve (12) can be selectively switched to the ventilation position or the venting position, wherein the solenoid valve (12) can be magnetically held in the relevant switching position by means of the at least one permanent magnet (13.1), and wherein, in the event that the safety control pressure (pSS) falls below a first threshold value, the solenoid valve (12) is switched to the venting position regardless of a previous switching position.

3. Electropneumatic valve assembly according to claim 2, wherein, in the event that the safety control pressure (pSS) exceeds the first threshold value, the solenoid valve (12) is held in the previous switching position, and can preferably be selectively switched to the ventilation position or the venting position by energizing at least one coil (13.3, 13.4).

4. Electropneumatic valve assembly according to claim 2 or claim 3, wherein, in the event that the safety control pressure (pSS) exceeds a second threshold value which is higher than the first threshold value, the solenoid valve (12) is switched to the ventilation position and can preferably be switched to the venting position by energizing at least one coil (13.3, 13.4).

5. Electropneumatic valve assembly according to claim 2 or claim 3, wherein the first threshold value is in a range from 200 kPa to 400 kPa, preferably 250 kPa to 350 kPa.

6. Electropneumatic valve assembly according to claim 4, wherein the second threshold value is in a range from 500 kPa to 900 kPa, preferably 600 kPa to 800 kPa.

7. Electropneumatic valve assembly according to any of the preceding claims, wherein the solenoid valve (12) has a preferred position.

8. Electropneumatic valve assembly according to claim 7, wherein in the preferred position, the pilot control unit (8) is connected to the vent (3).

9. Electropneumatic valve assembly according to any of the preceding claims, comprising an emergency release connection (38) having an emergency release path (39) for introducing an emergency release pressure (pSN) which effects modulation of the parking brake pressure (pBP) at at least one spring-loaded connection (21).

10. Electropneumatic valve assembly according to claim 9, wherein, depending on the emergency release pressure (pSN), the solenoid valve (12) supplies the pilot control unit (8) with supply pressure (pV) or connects said unit to a vent (3).

11. Electropneumatic valve assembly according to claim 9 or claim 10, wherein the emergency release path (39) opens into a vent path (44) of the solenoid valve (12).

12. Electropneumatic valve assembly according to claim 9 or claim 10 and claim 2, wherein the emergency release pressure (pSN) is modulated via the emergency release path (39) at the safety control connection (12.4) of the solenoid valve (12) or at a further control connection of the solenoid valve (12).

13. Electropneumatic valve assembly according to claim 12, wherein, in the event that the emergency release pressure (pSN) exceeds a or the second threshold value, the solenoid valve (12) is switched to the ventilation position.

14. Method for controlling a parking brake function of a commercial vehicle (100) comprising an electropneumatic brake system (102) and preferably an electropneumatic valve assembly (1) according to any of the preceding claims, the method comprising the steps of: - electromagnetically switching an electromagnetic solenoid valve (12) having at least one first permanent magnet (13.1) from a venting position to a ventilation position in order to modulate a parking brake pressure (pB) at at least one spring-loaded connection (21) in order to ventilate at least one spring brake actuator (108a, 108b); - locking in a pilot control pressure (pSV) modulated by the solenoid valve (12) and / or holding the solenoid valve (12) in the ventilation position; and - pneumatically or mechanically switching the solenoid valve (12) to the venting position when a supply pressure (pV) supplied to the solenoid valve (12) falls below a first threshold value.

15. Method according to claim 14, wherein the solenoid valve (12) has a preferred position which can be revoked by modulating a safety control pressure (pSS) at a safety control connection (12.4) of the solenoid valve (12).

16. Method according to claim 14 or claim 15, comprising the step of: - modulating a safety control pressure (pSS) at a safety control connection (12.4) of the solenoid valve (12) in order to hold the solenoid valve (12) in the venting position or switch the solenoid valve (12) to the venting position, wherein the safety control pressure (pSS) is a pressure modulated by the solenoid valve (12) or a pressure derived therefrom.

17. Method according to any of claims 14 to 16, comprising the steps of: - modulating an emergency release pressure (pSN) in order to control the parking brake pressure (pB) at the at least one spring-loaded connection (21).

18. Method according to claim 17, wherein the emergency release pressure (pSN) is introduced into a vent path (44) of the solenoid valve (12).

19. Method according to claim 16 and claim 17, wherein the emergency release pressure (pSN) is modulated at the safety control connection (12.4) of the solenoid valve (12) or at a further control connection of the solenoid valve (12).

20. Commercial vehicle (100) comprising an electronically controllable pneumatic brake system (102) having an electropneumatic valve assembly (1) according to any of claims 1 to 13.