Method for functionally testing a solenoid valve in a brake system

Abstract

The invention relates to a method for functionally testing an electropneumatic solenoid valve (3) in an electropneumatic brake system (1) of a vehicle (20), wherein the solenoid valve (3) has: an input connection (4), an output connection (7) to which a brake path (28) is connected, a control volume (18) for controlling a connection between the input connection (4) and the output connection (7), an inlet valve (10) which closes and opens an inlet path (16) from the input connection to the control volume, said method having the following steps: applying an input pressure to the input connection (4), electrically actuating the inlet valve (10) in a test signal phase (TP) which has at least a first time at which compressed air flows through the open inlet valve (10) into the control volume (18) and second times at which compressed air is discharged from the control volume (18), measuring a pressure value (p) in the brake system (1) during the test signal phase (TP), evaluating the measured pressure value (p) and assessing the functionality of the solenoid valve (3).

Description

[0001] Hanover, September 3, 2024

[0002] IP, Rabe, Bremer / MM

[0003] 305303-DE-NP

[0004] Method for functional testing of a solenoid valve in a brake system

[0005] The invention relates to a method for functional testing of a solenoid valve in a braking system, in particular an electropneumatic braking system, a control device for carrying out the method and an electropneumatic braking system.

[0006] Vehicles, especially commercial vehicles, have complex braking systems with a multitude of different brake components, including electropneumatic valves. Impaired brake components can lead to critical driving situations, particularly during braking. ABS control valves are specifically installed upstream of the brake cylinders to maintain, reduce, and increase brake pressure during the ABS control phases. A malfunction of the solenoid valve, for example, in the inlet or outlet area of ​​an ABS control valve, can impair braking performance and lead to braking maneuvers that reduce the vehicle's braking power or cause unwanted lateral forces due to differing braking torques on the sides of the vehicle.

[0007] US 8,532,897B2 and US 9,283,937B2 disclose methods in which brake components are monitored by comparing a steering angle specification with the actual steering angle and by means of pressure sensors on the brake actuators of the wheels.

[0008] EP 3 753 794 A1 discloses a method for monitoring the braking performance of a vehicle by monitoring and comparing the braking performance of individual wheels. US 2012 / 0010779A1 describes a method in which predetermined parameters must be achieved in a brake test.

[0009] Various sensors are provided to detect relevant operating and driving parameters. Wheel speed sensors can determine and compare the wheel speeds of individual wheels. This enables, in particular, the operation of anti-lock braking systems (ABS). Pressure sensors allow for the adjustment of brake pressures and the detection of brakes with impaired performance; however, pressure sensors are generally not mounted directly on the vehicle's brakes, meaning that malfunctioning solenoid valves, especially ABS control valves, cannot be detected by pressure measurement.

[0010] ABS control valves are generally connected between a brake modulator or other electromagnetic valve and the wheel brakes, enabling the ABS control phases of pressure holding, pressure reduction, and pressure increase to limit wheel slip during braking. In their unenergized state, ABS control valves are generally open between their inlet and outlet ports to the wheel brakes, for example, with a control volume that is vented in the unenergized state and, when vented, blocks the connection between the inlet and outlet ports. Energizing the inlet valve allows the control volume to be drawn to the inlet port, thus venting it and blocking the connection. A subsequent release valve can then be used to reduce the trapped pressure.

[0011] Degradation in solenoid valves is particularly problematic, as it can impair the opening and closing of valve seats and also affect the airflow within the valves. However, such performance-impairing degradation is often not visible externally, meaning that the valves can only be checked through regular inspections involving valve removal.

[0012] The invention is based on the objective of creating a method for functional testing of a solenoid valve in a compressed air system, as well as a control device for carrying out the method, which enables the solenoid valve to be checked for impairments with minimal effort.

[0013] This problem is solved by a method according to independent claim 1. The dependent claims describe preferred embodiments. Furthermore, a control device for carrying out the method is provided, as well as a braking system comprising the control device and a solenoid valve. Thus, an inlet valve of the solenoid valve is energized differently during a test signal phase, specifically between a first energization state in which the control volume is disconnected from the inlet port and the control volume is vented, and a second energization state in which the inlet port is connected to the control volume. In a first step, the inlet port is pressurized with an inlet pressure, which can in particular be a supply pressure and is, for example, passed through by an axis modulator.In a second step, the inlet valve is electrically actuated during the test signal phase, specifically alternately with periods in the first energized state and periods in the second energized state, so that compressed air flows into the control volume through the open inlet valve at times and is vented from the control volume at other times. During the test signal phase, a pressure value in the brake system is measured and evaluated, and the functionality of the solenoid valve is assessed based on this value.

[0014] The first and second times are preferably dimensioned such that an impairment of the inlet path and / or the outlet path leads to a different filling state of the control volume.

[0015] This alone achieves several advantages:

[0016] According to the invention, by intermittently energizing and de-energizing the inlet valve or its solenoid, a test is enabled in which the airflow behavior through the inlet path into the control volume and / or the flow behavior from the control volume to the vent can be evaluated. Preferably, the energization is such that any impairment of the flow cross-section leads to a different filling or venting of the control volume. Thus, the flow behavior can be directly evaluated without, for example, removing and examining the valve. An in-situ evaluation is possible, which can reveal even minor impairments.

[0017] Another advantage is that the functional test can be performed while the vehicle is stationary. The test can be carried out, for example, before driving begins, or even autonomously or automatically after the vehicle is switched on and / or before driving starts. This makes it possible to conduct a test where brake application does not interfere. In particular, the functional test can also be performed autonomously, for example, when the vehicle is switched on, allowing for regular checks. The test can generally be performed in such a way that the driver notices nothing, as long as no error message is displayed.

[0018] Another advantage is that the solenoid valve can be safely checked without additional equipment, using elements already present in the brake system, i.e. the solenoid valve, a pressure sensor and the control unit for activating the solenoid valve, and without endangering the vehicle or the journey.

[0019] Pressure measurement can be performed in the brake path from the solenoid valve to the brake cylinder if a pressure sensor is already installed there. This allows direct determination of whether the solenoid valve is open or closed during the test phases. However, according to an advantageous embodiment, pressure measurement is also possible using a pressure sensor upstream of the solenoid valve under test, particularly at the upstream pressure reservoir and / or axle modulator, which are generally provided, especially in the pressure reservoirs of service brake circuits. In this case, the pressure drop over time can be measured, and even a slight pressure drop can be attributed to a high airflow to the brake path, particularly to a brake cylinder that was previously empty.Thus, the pressure measurement can determine the time of opening of the outlet port and also determine that the brake path with the brake cylinder was not filled until then.

[0020] For the test, it is advantageous to select a control method that does not correspond to a conventional control method for switching the inlet valve, but rather, with the first and second phases (i.e., the inlet valve being intermittently open and intermittently closed), is closer to a limiting behavior where the respective switching behavior is not yet achieved. Preferably, during the first phases, compressed air flows through the open inlet valve into the control volume, and during the second phases, compressed air is released from the control volume. Thus, at least one test signal phase is provided in which at least the inlet valve or its solenoid is intermittently energized and intermittently de-energized. In particular, the inlet valve is alternately energized and de-energized during the test signal phase.

[0021] According to a preferred embodiment, the first energizing state of the inlet valve is the energized state in which the inlet path is open and the control volume is vented, so that the connection between the inlet port and the outlet port is closed. Correspondingly, the second energizing state is, in particular, the non-energized ground state in which the inlet path is closed and thus the control volume is preferably not vented, in particular vented, so that the inlet port is connected to the outlet port.

[0022] The solenoid valve can be installed, in particular, as an ABS control valve upstream of the wheel brakes and enable the ABS control phases of pressure maintenance, pressure reduction, and pressure increase. The solenoid valve has, for example, a diaphragm, preferably bistable, which is controlled by the control volume and presses against a valve seat.

[0023] According to an advantageous embodiment, a functional test of the inlet path of the inlet valve, in particular from the inlet port to the control volume, is provided, in which, in particular, performance-impairing degradation in the inlet path can be detected. During the test signal phase, the inlet valve is alternately energized and de-energized in such a way that

[0024] - with a proper inlet path, the inlet valve opens for a sufficient length of time overall, or in the sum of the energized phases, so that the control volume is adequately filled with compressed air, so that the connection between the inlet port and the outlet port is closed by the control volume,

[0025] - if the inlet path is not functioning properly, e.g., narrowed or impaired by degradation, the control volume as a whole or in the sum of the energized phases is not sufficiently filled with compressed air, so that the connection between the inlet port and the outlet port is not interrupted.

[0026] This ensures a reliable functional test of the inlet path with minimal effort and a clear result.

[0027] According to a further advantageous embodiment, a functional test of the outlet path is provided, which in particular runs from the control volume to a vent, thus enabling the detection of performance-impairing degradation in the inlet path. During the test signal phase, the inlet valve is alternately energized and de-energized in such a way that

[0028] - if a proper outlet path allows sufficient compressed air to flow out of the control volume, thus preventing the control volume from being sufficiently filled with air and thus ensuring that the connection between the inlet port and the outlet port is not interrupted, and

[0029] - if the outlet path is not properly aligned, the compressed air does not flow sufficiently out of the control volume and the control volume is filled with compressed air to such an extent that the connection between the inlet port and the outlet port is interrupted.

[0030] This allows the inlet path and outlet path to be checked independently of each other, and especially successively, with minimal effort.

[0031] According to a preferred embodiment, a verification phase is provided after the test signal phase. In this phase, with the inlet valve closed and the inlet pressure still applied at the inlet port, the pressure value is measured over time and evaluated to determine whether filling of the brake path and brake cylinder is detected. Filling can be determined, in particular, as a pressure drop, e.g., a small but significant pressure drop, in the pressure supply to the solenoid valve. If impaired performance was observed during the inlet path test, i.e., the control volume was not filled and thus the connection to the brake path was open, the brake path should already be filled, so no pressure drop is expected. This allows for falsification or verification of the measurement from the test signal phase.Accordingly, the functional test of the outlet path can be falsified; if impaired performance of the outlet path was detected during the test signal phase, the control volume should be filled and the brake path should not be filled, so that a filling process should then be detected during the verification phase, in particular again by a small but significant pressure drop in the supply line.

[0032] Thus, with minimal effort and minimal additional time expenditure, a supplementary check, in particular to falsify the measurement of the test signal phase, is possible.

[0033] The inlet port of the solenoid valve can be subjected to a constant inlet pressure, preferably the maximum supply pressure, to obtain a strong pressure signal that allows even small changes to be detected. Performing the functional test while the system is stationary ensures that this does not impair performance.

[0034] The test signal phase can be carried out in particular simultaneously or shortly after the pressurization at the input port, so that the open solenoid valve does not allow compressed air to pass through to the brake path before the test signal phase.

[0035] According to an advantageous design, several first times, i.e., at least two first times, and / or several second times, i.e., at least two second times, are provided alternately and / or sequentially during the test signal phase. Alternating the control with several first times (energization times) and several second times (non-energization times) results in more consistent behavior and avoids switching back and forth.

[0036] The invention will be explained below with reference to one embodiment shown in the accompanying drawings. The drawings show:

[0037] Fig. 1 shows an electropneumatic brake circuit with an electropneumatic solenoid valve; Fig. 2 shows a representation of Fig. 1 with indication of the pressure ranges in the solenoid valve;

[0038] Fig. 3 Measurement and signal diagrams of a method for functional testing of an inlet path in the solenoid valve of Figure 1, 2;

[0039] Fig. 4 Measurement and signal diagrams of a method for functional testing of an outlet path in the solenoid valve of Figures 1 and 2; and

[0040] Fig. 5 shows a flowchart of a process according to one embodiment.

[0041] Fig. 6 shows a flowchart of a process according to a further embodiment;

[0042] Fig. 7 Measurement and signal diagrams of a method for functional testing of an outlet path according to an alternative design to Fig. 4.

[0043] An electropneumatic brake system 1 has several brake circuits 2, one of which, with its relevant elements, is shown schematically here. An electropneumatic 3 / 2-way solenoid valve 3 is connected via its supply port 4 to a compressed air reservoir 6 through an axle modulator 5. The axle modulator 5 can be designed as a conventional 3 / 2-way valve. Furthermore, the solenoid valve 3 is connected via its output port 7 to a brake cylinder 8 or a brake chamber of a wheel brake. An outlet 9 serves as a vent for the solenoid valve 3 in the usual manner. The solenoid valve 3 also has an inlet valve 10 with electrical contacts 11a, 11b, which are controlled by a control unit 12 with a first control signal S1.A pressure sensor 14 is provided on a supply line from the compressed air reservoir 6 to the solenoid valve 3, in particular between the axis modulator 5 and the compressed air reservoir 6, which outputs a pressure measurement signal S2 to the control unit 12. The control unit 12 can also switch the axis modulator 5 by means of a second control signal S2.

[0044] The control unit 12 can be the control unit of the axle modulator 5 or the EBS ECU of the entire brake system 1. The solenoid valve 3 serves in particular as an ABS control valve, which is conventionally designed to allow the pressure pO controlled by the axle modulator 5 to pass through to the brake cylinder 8 or to maintain, lower, and increase it during the ABS control phases. For this purpose, the solenoid valve 3 has an additional outlet valve 17 besides the inlet valve 10. The inlet port 4 is connected via an inlet path 16 to a control volume 18, which acts on a diaphragm 19 that opens and closes a connection between the inlet port 4 and the outlet port 7. Figures 1 and 2 show the open normal state of the solenoid valve 3, in which the inlet path 16 is closed and thus the connection between the inlet port 4 and the outlet port 7 is open. In Figure 1, the solenoid valve 3 is shown in the open state.For clarity, the control volume 18 and the passage between the input port 4 and the output port 7 are hatched differently.

[0045] The control unit 12 outputs a first control signal S1, which energizes the inlet valve 10 or its solenoid, thus opening the inlet path 16 between the inlet port 4 and the control volume 18. When the axis modulator 5 is then open and compressed air is present at the inlet port 4, the control volume 18 is vented and presses the diaphragm 19 against a stop in the housing of the solenoid valve 3, thus closing the connection between the inlet port 4 and the outlet port 7.

[0046] With the inlet valve 10 not actuated, the outlet path 26 from the control volume 18 to the outlet 9, i.e., the vent, is open, so that the control volume 18 is vented in its normal state. Furthermore, the control unit 12 outputs a third control signal S4, shown here with dotted lines for clarity, to the outlet valve 17, through which the outlet port 7 is vented again to reduce brake pressure in the brake path 28 and the brake cylinder 18.

[0047] Degradation can also affect the inlet path 16 and the outlet path 26, as this can significantly impair the sealing and switching behavior of the solenoid valve 3, potentially leading to leakage or behavior that is not intended in the braking process.

[0048] A method is provided for the functional testing of the solenoid valve 3, which is explained below using an embodiment and is in particular multi-stage.

[0049] The functional test procedure is performed with the commercial vehicle 20 stationary, i.e., at a speed of v=0, e.g., when the commercial vehicle 20 is switched on and / or off. The aim is to evaluate the inflow behavior of compressed air via the supply connection 4 and the inlet path 16, as well as the outflow behavior of compressed air from the outlet path 26, by appropriately controlling the inlet valve 10. Electrical controls via the control signal S1 are selected, where even minor impairments of the flow behavior lead to different filling or venting behavior of the control volume 18.

[0050] Advantageously, a first control routine is provided, which checks for constriction due to degradation in the inlet path 16 and is illustrated in the signal diagram of Fig. 3, as well as a second control routine, which checks for constriction due to degradation in the outlet path 26 and is illustrated in the signal diagram of Fig. 4. Diagrams a) to d) in Fig. 3 and Fig. 4 are each plotted against time t, with a test signal phase TP and a verification phase NP shown on the abscissa or horizontal axis. In diagram a) in Fig. 3 and 4, the supply pressure p measured by the pressure sensor 14 is shown, and in diagram b) the brake cylinder pressure in brake path 28 and in brake cylinder 8 is shown, which cannot be measured directly in this embodiment. Diagram c) shows the control signal S3 for the axis modulator 5, which thus applies the input pressure pO to the input port 4.Diagram d) shows the first control signal S1, which actuates the inlet valve 10. When S1 = 1, the inlet valve 10 is energized, opening the inlet path 16 and closing the outlet path 26. Diagrams a and b of Figures 3 and 4 show the pressure profiles as solid lines for proper configuration and as dashed lines for impaired configuration.

[0051] The following section describes, with reference to Fig. 3, the functional test of a performance-impairing degradation in the inlet path 16. For this purpose, in the flow diagram of Fig. 5, after the start in step StO, the solenoid valve 3 is pressurized at its inlet port 4 according to step St1. For this, the axis modulator 5 is preferably controlled by the control unit 12 with the second control signal S3=1 such that it allows compressed air at pressure pO from the compressed air reservoir 6 to pass through to the inlet port 4, preferably without further pressure regulation. Figure 3 shows, accordingly in diagram c, that at a first time t1, the axis modulator 5 is energized by the control signal S3 of the control unit 12 and thus opens, so that the reservoir pressure pO is present at the inlet port 4. Since the inlet valve 10 is not yet energized, it is open between its inlet port 4 and the outlet port 7. the entrance path 16, i.e.h. the pneumatic connection to the control volume 18 is closed and the control volume 18 is vented via the outlet path 26.

[0052] Simultaneously with or immediately following step St1, the test signal phase TP is initiated in step St2. During this phase, the inlet valve 10 is intermittently or temporarily activated by the first control signal S1 as a test signal until time t3. The first control signal S1 is generated as a test signal, primarily from short current pulses or voltages. The test signal St1 energizes the inlet valve 10 multiple times, e.g., 100 times, alternating between first periods dt1 for, e.g., 1.5 ms (i.e., S1 = 1) and second periods dt2 for 8.5 ms (i.e., S1 = 0). Other first periods (on-times) and second periods (off-times) can also be specified. While the inlet valve 10 is energized, compressed air at pressure pO flows into the control volume 18 via the inlet path 16, and while the inlet valve 10 is not energized, air flows out of the control volume 18 via the outlet path 26.This ensures that the control volume 18 is filled sufficiently quickly for non-degrading inlet paths 16, since the initial inlet times are sufficiently long relative to the subsequent outlet times, or just long enough, to increase the overall pressure in the control volume 18, causing it to press against the diaphragm 19 and close. By energizing the inlet valve 10 with the first control signal S1 as a test signal simultaneously with or shortly after pressurizing the inlet port 4, the control volume 18 is filled sufficiently quickly, and the diaphragm 19 is closed, provided the inlet path 16 is functioning correctly. This prevents any or no relevant pressure from building up in the brake cylinder 8. The diaphragm 19 can, in particular, be designed as a bistable diaphragm 19a.

[0053] However, if the inlet path 16 is degraded, the airflow through the inlet path 16 is obstructed, so that the airflow into the control volume 18 is not sufficiently filled with air during the initial phases or on-phases of the test signal S1. As a result, the diaphragm 19 remains open, and the full supply pressure pO flows from the inlet port 4 through the open diaphragm 19 to the outlet port 7. Consequently, a brake pressure pB is built up in the brake cylinder 8 (brake chamber) up to the supply pressure pO, as shown by the dashed line in diagram b) of Fig. 3. If a pressure sensor is provided in the area of ​​the brake path 28, this brake pressure pB of diagram b) can be measured directly; in the embodiment shown, the pressure sensor 14 measures the pressure p in the area of ​​the pressure reservoir 6 or another point in the supply line.The opening of the solenoid valve 3 can also be detected in the sensed pressure p: When the solenoid valve 3 is open, compressed air flows suddenly or rapidly through the open solenoid valve 3 and the subsequent brake line 28 to the brake cylinder 8 and fills it, so that a small but significant pressure drop delta-p can also be detected in the measured pressure p.

[0054] From time t2 to t3, the verification phase NP follows, in which the first control signal S1, or test signal, is set, i.e., S1 = 0. The verification phase can be performed, in particular, to falsify or verify a detected fault. Once S1 is permanently set to 0, the inlet valve 10 remains de-energized and closed, so that the brake path 28 is pressurized with the supply pressure pO through the open solenoid valve 3. If the inlet path 16 is impaired or degraded, and the brake path 28 was therefore already below the supply pressure pO according to the dashed line in diagram b), no signal change is to be expected in diagrams a) and b). In a proper inlet path 16, however, the diaphragm 19 is reset and opens the connection between the inlet port 4 and the outlet port 7, so that according to the fixed line in diagram a), a pressure drop delta-p is to be expected from time t2.

[0055] Thus, the false-positive rate can be significantly reduced without further effort through the verification phase NP, and a fault can still be assigned to a specific side of the vehicle by successively opening the solenoid valves 3 on the left and right sides of the brake circuit 2. To detect performance-impairing degradation in the outlet path 26, the input port 4 of the solenoid valve 3 is again pressurized with input pressure pO, according to the signal diagram in Figure 4. This means that the axle modulator 5 is controlled accordingly by the control unit 12 with a second control signal S3=1, so that it applies the supply pressure pO as input pressure to the input port 4. Subsequently, the solenoid valves are opened sequentially, e.g., 150 times. B. also between 50 and 200 times, the inlet valve 10 in the solenoid valve 3 is alternately energized in first times dt1 for e.g. 3 ms and not energized in second times dt2 for e.g. 7 ms.While the inlet valve 10 is energized, air flows via the inlet path 16 into the control volume 18 of the solenoid valve 3; while the inlet valve 10 is not energized, air flows via the outlet path 26 out of the control volume 18. The first times dt1 and second times dt2 in this functional test of the outlet path 26 – unlike in the functional test of the inlet path 16 described above – are dimensioned such that, with proper airflow, i.e., without performance-impairing degradation in the outlet path 26, sufficient venting occurs, so that the solenoid valve 3 is open between the inlet port 4 and the outlet port 7, and, according to the solid lines in diagram b, a pressure increase of the brake pressure pB in the brake cylinder 8 occurs during the test signal phase TP.According to diagram a), a pressure drop delta-p is detected by the pressure sensor 14 from t1 onwards because a significant volume of air flows out via the open solenoid valve 3.

[0056] Following the test signal phase TP, a verification phase NP is provided from time t2 onwards. In this phase, with the axis modulator 5 still open (i.e., S3 = 1) and thus with the input port 4 pressurized, the energization of the inlet valve 10 is terminated (i.e., S1 = 0). The verification phase can be performed at any time or, in particular, to falsify or verify a performance-impaired condition in the test signal phase TP, i.e., if no or an insufficient pressure drop Δp was detected in diagram a. Therefore, from t2 onwards, the inlet valve 10 is no longer energized and is closed, i.e., the control volume 18 is vented, allowing the diaphragm 19 to open and the brake cylinder 8 to be pressurized with pressure p through the open solenoid valve 3.If the brake cylinder 8 was not filled with compressed air up to that point, a pressure drop delta-p is to be expected according to the dashed curve in diagram a, which in turn can be clearly detected. Thus, the false-positive rate can be significantly reduced by this subsequent pressurization.

[0057] In both control tests of Figs. 3 and 4, the fault can be assigned to a brake cylinder 8 or a vehicle side by successively applying pressure to the vehicle sides or the individual brake cylinders 8 of the brake path 2.

[0058] Figure 5 shows a flowchart of a method according to the invention, which is intended for functional testing of both the inlet path 16 and the outlet path 26 and can therefore be executed twice. After starting in step StO, in step St1, the supply pressure pO is applied to the inlet port 4, in particular by opening the axis modulator 5 with appropriate control S3 = 1. Simultaneously or subsequently, according to step St2, the test signal phase TP is initiated, with a temporary or alternating current S1(t) of the inlet valve 10, i.e., with the first times or on-times or current-energizing times and the second times dt2 or off-times or non-current-energizing times, so that different flow patterns of the compressed air occur in the solenoid valve 3 in a properly functioning and in a performance-impaired configuration.After step St3, a pressure value is measured by a pressure sensor, according to the embodiment shown in Fig. 1 by the pressure sensor 14 and the diagram of Fig. 3 a). Alternatively, according to the diagram of Fig. 3b), the pressure p in the brake path 28 can also be measured directly.

[0059] In step St4, the test signal phase TP is set, i.e., S1(t) is set to 0, thereby initiating the verification phase NP. In step ST5, the pressure p is again measured during the verification phase, in particular by the pressure sensor 14 according to the diagram in Fig. 3a). Subsequently, in this embodiment, an evaluation is performed in step St6, and a fault signal F is set to F=0 if a proper progression according to the solid lines in Fig. 3a) and b) is present, or to F=1 if the impaired or degraded state according to the dashed lines has been detected. The procedure can also be carried out solely through the test signal phase TP, without the verification phases in steps St4 and St5, so that after step St3, the evaluation of whether a fault exists is performed in step St6.

[0060] As shown in Figures 5 and 6, the procedure can be continued in different ways after step St6, i.e., after the evaluation of the inlet path 16, whereby steps St2 to St4 can in particular be repeated several times, i.e., the procedure is subsequently or after further steps reset to before step St1 or directly before step St2.

[0061] According to Fig. 5, the procedure for the subsequent functional test of the outlet path 26 is reset by subsequently actuating the outlet valve 17 with, for example, a short outlet pulse after step St6. This occurs in step St7 with S4=1 to vent the brake path 28 and the brake chamber 8, and then in step St8 by closing the outlet valve 17 again with S4=0. This is also shown accordingly in Fig. 7, which is a modification of Fig. 4. Thus, after step St8, the brake path 28 and the brake chamber 8 are vented, so that the test of the outlet path 26 can be carried out directly in steps St2 to St6 according to Fig. 4 or Fig. 7 without resetting S3, i.e., S3=1 can be retained. Subsequently, in step St2, during the test signal phase TP, the first times dt1 and second times dt2 are recorded as above in Fig. 7.4 is described such that venting occurs when the outlet path 26 is functioning correctly, and no venting occurs when the outlet path 26 is degraded. Therefore, in the functional test of the outlet path 26, there is advantageously a larger ratio of dt2 to dt1, i.e., the second times or off times dt2 are relatively longer than in the functional test of the inlet path 16.

[0062] The verification phase of steps St4 and St5 can also be carried out when checking outlet path 26, but it can also be omitted in principle.

[0063] As shown in Fig. 6, after testing the inlet path 16 in step St9, the axis modulator 5 can also be closed with S3=0 to vent the input port 4, so that the process is then reset to the state before step St1. This creates the same conditions for testing the outlet path 26 according to Fig. 4 as before testing the inlet path 16 in Fig. 3. However, this reset of the input port 4 by setting S3=0 is not strictly necessary.

[0064] Furthermore, according to a preferred embodiment, the test can be carried out successively for the individual brake cylinders 8 of the brake circuit 2, i.e., with axle-wise division of the brake circuit 2 on the left and right sides. For this purpose, the loop of Fig. 5 or 6 can generally be fully executed in each case; however, according to an advantageous embodiment, it is sufficient if the re-inspection phase NP in steps St4 and St5 is carried out successively for one side, e.g., left, and subsequently for the other side, e.g., right, of the brake circuit 2.

[0065] Reference symbol list (part of the description)

[0066] 1 electropneumatic braking system

[0067] 2 brake circuits

[0068] 3 electropneumatic 3 / 2 solenoid valve

[0069] 4 Input connection / Supply connection

[0070] 5-axis modulator

[0071] 6 compressed air reservoir

[0072] 7 Output port

[0073] 8 brake cylinders

[0074] 9 Outlet

[0075] 10 Inlet valve

[0076] 11a, 11b electrical contacts of the inlet valve 10

[0077] 12 Control unit

[0078] 14 Pressure sensor

[0079] 15 Supply line

[0080] 16 Entrance path

[0081] 17 Exhaust valve

[0082] 18 Control volumes

[0083] 19 Membran

[0084] 20 commercial vehicles

[0085] 26 Outlet path 28 Brake path pO Supply pressure p Measured pressure pB Pressure in brake cylinder 8

[0086] 51 First control signal for the inlet valve 10

[0087] 52 Pressure measurement signal

[0088] 53 Second control signal for the axis modulator 5

[0089] 54 third control signal to the exhaust valve 17

[0090] TP Test Signal Phase

[0091] NP verification phase t1, t2, t3 Time points dt1 First times in TP with S1 = 1, current-energizing times dt2 Second times in TP with S1 = 0, non-current-energizing times delta-p Pressure drop, time-dependent drop of the measured pressure p

Claims

Claims 1. Method for functional testing of an electropneumatic solenoid valve (3) in an electropneumatic brake system (1) of a vehicle (20), wherein the solenoid valve (3) comprises: an inlet port (4) which can be pressurized with an inlet pressure (pO), an outlet port (7) to which a brake path (28) with a brake cylinder (8) is connected, a control volume (18) for controlling a connection between the inlet port (4) and the outlet port (7), an electromagnetic inlet valve (10) which closes and opens an inlet path (16) from the inlet port (4) to the control volume (18) depending on an energization of the inlet valve (10), wherein the inlet valve (10) connects the inlet port (4) to the control volume (18) in a first energization state (S1 = 1) and in a second energization state (S1 = 0) the control volume (18) from the inlet port (4) separates and vents the control volume (18),the procedure comprises the following steps: (St1) Applying an inlet pressure (pO) to the inlet port (4), electrically actuating the inlet valve (10) in a test signal phase (TP) that has at least one first time (dt1) in the first energization state (S1 = 1) and at least one second time (dt2) in the second energization state (S1 = 0) such that in the at least one first time (dt1) compressed air flows through the open inlet valve (10) into the control volume (18) and in the at least one second time (dt2) compressed air is released from the control volume (18), (ST2) measuring a pressure value (p) in the brake system (1) during the test signal phase (TP), (St3) Evaluation of the measured pressure value (p) and assessment of the functionality of the solenoid valve (3) (F=0, F=1 ) (St6).

2. Method according to claim 1, characterized in that it is carried out when the vehicle (20) is stationary (v=0), in particular autonomously.

3. Method according to one of the preceding claims, characterized in that - the first energizing state (S1 = 1 ) of the inlet valve (10) is the energized state (S1 = 1 ) that opens the inlet path (16) and connects the inlet port (4) to the control volume (18), so that the connection between the inlet port (4) and the outlet port (7) is closed, - the second energized state (S1 = 0) of the inlet valve (10) is the non-energized ground state (S1 = 0) which closes the inlet path (16) and separates the inlet port (4) from the control volume (18), so that the connection between the inlet port (4) and the outlet port (7) is open.

4. Method according to one of the preceding claims, characterized in that the pressure value (p) is measured in a supply line (15) to the inlet port (4) of the solenoid valve (3), and - a drop in the measured pressure value (p) over time (delta-p) indicates a filling process of the brake path (28) with the brake cylinder (8), - if there is no decrease in the measured pressure value (p) over time, it is concluded that no filling process of the brake path (28) with the brake cylinder (8) has taken place.

5. Method according to claim 4, characterized in that the pressure value (p) is measured at - a compressed air reservoir (6) of the brake system (1) and / or - on an axle modulator (5) for regulating a brake pressure, wherein the axle modulator is provided between the pressure reservoir (6) and the input port (4).

6. Method according to one of the preceding claims, characterized in that it comprises a functional test of the inlet path (16), wherein in the test signal phase (TP) the inlet valve (10) is alternately energized and de-energized in such a manner that - with a proper inlet path (16) the inlet valve (10) opens for such a long time that the control volume (18) is sufficiently filled with compressed air so that the connection between the inlet port (4) and the outlet port (7) is closed by the control volume (18), - if the inlet path (16) is not in proper working order and / or impaired, the control volume (18) is not sufficiently filled with compressed air so that the connection between the inlet port (4) and the outlet port (7) is not interrupted.

7. Method according to one of the preceding claims, characterized in that it comprises a functional test of an outlet path (26) from the control volume (18) to a vent (9), wherein in the test signal phase (TP) the inlet valve (10) is energized in the at least one first time (dt1 ) and is not energized in the at least one second time (dt2) such that - if a proper outlet path (26) is used, sufficient compressed air flows out of the control volume (18) and the control volume (18) is not sufficiently filled with compressed air so that the connection between the inlet port (4) and the outlet port (7) is not interrupted, and - if the outlet path (26) is not properly installed, the compressed air does not flow sufficiently out of the control volume (18) and the control volume (18) is filled with compressed air in such a way that the connection between the inlet port (4) and the outlet port (7) is interrupted.

8. Method according to one of the preceding claims, characterized in that a verification phase (NP) is provided after the test signal phase (TP), wherein in the verification phase (NP) with the inlet valve (10) closed and / or not energized and the inlet pressure (pO) still applied to the inlet port (4) the temporal behavior of the measured pressure value (p) is measured and it is evaluated whether a filling of the brake path (28) and brake cylinder (8) is detected in the verification phase (NP), for falsification or verification of the evaluation of the functionality in the test signal phase (T).

9. Method according to claim 6 and claim 8, characterized in that during the functional test of the inlet path (16) in the verification phase (NP) the pressure value (p) is measured and it is evaluated whether a filling process of the brake cylinder (8) has taken place in the verification phase (NP), wherein, upon detection of a filling process (delta-p) of the brake cylinder (8), a verification of a proper test result (F=0) or a falsification of an improper test result (F=1) is carried out, and upon detection of a failure of a filling process (delta-p=0) of the brake cylinder (8), a falsification of a proper test result (F=1) or a verification of an improper test result (F=1) is carried out.

10. Method according to claim 6 and claim 7, characterized in that during the functional test of an outlet path (26) in the verification phase (NP) the pressure value (p) is measured and it is evaluated whether a filling process of the brake cylinder (8) has taken place in the verification phase (NP), wherein if a filling process (delta-p) of the brake cylinder (8) is detected, a proper test result (F=0) is falsified or a non-proper test result (F=0) is verified, and if a failure to fill a brake cylinder (8) is detected, a proper test result (F=1) is verified or a non-proper test result (F=1) is falsified.

11. Method according to one of the preceding claims, characterized in that during the test signal phase (TP) and / or the verification phase (NP) the input port (4) is subjected to a constant input pressure (pO), in particular a maximum supply pressure (pO) (St1 ).

12. Method according to one of the preceding claims, characterized in that the test signal phase (TP) (ST2) is initiated simultaneously or directly after the input terminal (4) is subjected to the input pressure (pO) (St1).

13. Method according to one of the preceding claims, characterized in that in the test signal phase (TP) (ST2) several first times (dt1 ) and / or several second times (dt2) are provided alternately and / or in succession.

14. Control device (12) of a brake system (2), wherein the control device (12) is configured and designed to perform a method according to any of the preceding claims by the control device (12) performing one or more of the following performs the following steps: - Output of a first control signal (S1 ) to the inlet valve (10) of the solenoid valve (3) to switch between the first and the second energizing state (S1=1 , S1=0), - Outputting a second control signal (S3) to a valve device (5) to apply the inlet pressure (pO) to the inlet port (4), - Receiving a pressure measurement signal (S3) with the pressure value (p), - Assess whether a proper inlet path (16) and / or a proper outlet path (26) is present, - Detection and output of an error signal (F) upon detection of an improper inlet path (16) and / or improper outlet path (26).

15. Electropneumatic braking system (1) which features - a control device according to claim 14 - the solenoid valve (3), which features: = one input port (4), one output port (7), = a control volume (18) for controlling a connection between the input port (4) and the output port (7), = an electromagnetic inlet valve (10) that closes and opens an inlet path (16) from the inlet port (4) to the control volume (18) depending on an energization of the inlet valve (10), and - a brake path (18) connected to the output port (7) of the solenoid valve (3) with a brake cylinder (8).

16. Electropneumatic braking system (1 ) according to claim 15, characterized in that the solenoid valve (3) is an ABS valve (3) in which, in the unenergized basic state (S1 = 0), the connection between the input port (4) and the output port (7) is open, wherein the output port (7) can be disconnected from the input port (4) by actuating the inlet valve (10).

17. Electropneumatic braking system (1 ) according to claim 15 or 16, characterized in that the solenoid valve (3) has a diaphragm (19), in particular a bistable diaphragm (19a), which is adjustable by the control volume (18).

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