DE102021205976A1 - Procedure for checking the functionality of a controllable shut-off valve in a tank ventilation system - Google Patents

Abstract

A method for checking the functionality of a controllable shut-off valve (1400) in a tank ventilation system (1000), which has: - a tank area (1200) which has a fuel tank (1210), - a storage area (1100) which has a fuel vapor storage device (1110) - a degassing line (1300) which connects the fuel vapor accumulator 1110 and the fuel tank (1210), - the controllable shut-off valve 1400 which is arranged in the degassing line (1300) and which, in a closed state, equalizes the pressure between the tank area (1200) and the storage area (1100), and which in an open state allows a pressure equalization between the tank area (1200) and the storage area (1100), - a pressure changing device (1800) for changing the pressure in the storage area (1100), - a pressure detection device ( 1500) for detecting the pressure in the storage area (1100), the method following p steps comprises: - activating the pressure detection device (1500) and detecting the output values, - controlling the shut-off valve (1400) in the direction of the closed state, - operating the pressure changing device (1800) in terms of changing the pressure in the storage area (1100), - evaluating the detected output values of the pressure detection device (1500) as to whether a first change in pressure in the storage chamber (1100) caused by the operation of the pressure changing device (1800) meets a first plausibility criterion, - detecting a fault in the shut-off valve (1400) if the evaluation shows that the first plausibility criterion is not met.

Description

The invention relates to a method for checking the functionality of a controllable shut-off valve in a tank ventilation system and a computer program product and a control device for carrying out this method.

According to legal regulations, it is important to ensure that the fuel vapors produced in a fuel tank do not escape into the environment in an uncontrolled manner. Vehicles with internal combustion engines are therefore usually equipped with a tank ventilation system. The core element of the tank ventilation system is a fuel vapor reservoir, to which the fuel vapors produced in the fuel tank are fed. The vapors are adsorbed by an adsorbent (usually activated carbon) contained in the fuel vapor accumulator and thereby stored. In order to avoid saturation of the adsorbent, the fuel vapor accumulator must be regenerated from time to time. For this purpose, the fuel vapor accumulator is flushed with fresh air, whereby the stored fuel vapors are supplied to the engine combustion in a controlled manner.

In vehicles powered purely by an internal combustion engine, the fuel vapors from the fuel tank are continuously fed to the fuel vapor storage device. This is possible because the internal combustion engine, as the only power source, is in operation very frequently and therefore regeneration of the fuel vapor accumulator is not a problem. With hybrid drive concepts, i.e. vehicles with an electric motor and an internal combustion engine as the drive sources, longer and longer distances are covered without any activation of the internal combustion engine, which means that the possibilities for regenerating the fuel vapor accumulator are becoming increasingly rare. For this reason, pressure tank solutions are now being used, which are separated from the fuel vapor reservoir by a controllable shut-off valve. The hydrocarbon vapors escaping therein are held back under pressure in these pressure tanks until the vapors can escape in the direction of the fuel vapor accumulator by controlled opening of the shut-off valve.

Legal regulations require the functionality of the tank ventilation system or its components to be checked. The functionality of the shut-off valve is very relevant because it must be ensured that the fuel tank is depressurized before the tank cap is opened in order to prevent hydrocarbons from escaping uncontrolled into the environment.

It is the object of the present invention to provide a method, a computer program product and a control device by means of which the functionality of a shut-off valve of a tank ventilation system can be checked.

This object is solved by the subject matter of the independent claims. Advantageous configurations of the invention are described in the dependent claims.

• - Aktivieren der Druckerfassungsvorrichtung (1500) und Erfassen der Ausgangswerte,
• - Steuern des Absperrventils (1400) im Sinne des geschlossenen Zustands,
• - Betreiben der Druckänderungseinrichtung (1800) im Sinne einer Änderung des Drucks im Speicherbereich (1100),
• - Auswerten der erfassten Ausgangswerte der Druckerfassungsvorrichtung (1500) dahingehend, ob eine durch den Betrieb der Druckänderungseinrichtung (1800) verursachte erste Druckänderung im Speicherraum (1100) ein erstes Plausibilitätskriterium erfüllt,
• - Erkennen eines Fehlers des Absperrventils (1400), falls die Auswertung ergibt, dass das erste Plausibilitätskriterium nicht erfüllt ist.

A method according to claim 1 relates to checking the functionality of a controllable shut-off valve in a tank ventilation system. The tank ventilation system includes a tank area, which has a fuel tank, a storage area, which has a fuel vapor storage, a degassing line, which connects the fuel vapor storage and the fuel tank, the controllable shut-off valve, which is arranged in the degassing line and which, in a closed state, ensures pressure equalization between the Tank area and the storage area prevents and which allows pressure equalization between the tank area and the storage area in an open state. The tank ventilation system also includes a pressure changing device for changing the pressure in the storage area and a pressure detection device for detecting the pressure in the storage area and for outputting output values which represent the detected pressure. The procedure has the following steps:

• - activation of the pressure detection device (1500) and detection of the output values,
• - Control of the shut-off valve (1400) in terms of the closed state,
• - Operating the pressure changing device (1800) in terms of changing the pressure in the storage area (1100),
• - evaluating the detected output values of the pressure detection device (1500) to determine whether a first change in pressure in the storage chamber (1100) caused by the operation of the pressure changing device (1800) meets a first plausibility criterion,
• - Detecting a fault in the shut-off valve (1400) if the evaluation shows that the first plausibility criterion is not met.

• - während des Betriebs der Druckänderungseinrichtung ein erster Druckgradient im Speicherbereich zumindest einen vorgegebenen ersten Gradientengrenzwert bzw. Gradientenschwellenwert erreicht oder der erste Druckgradient im Speicherbereich sich innerhalb eines vorgegebenen ersten Druckgradientenwertebereichs befindet, oder
• - durch den Betrieb der Druckänderungseinrichtung der Druck im Speicherbereich einen vorgegebenen ersten Druckgrenzwert bzw. Druckschwellenwert zumindest erreicht oder der Druck im Speicherbereich sich innerhalb eines vorgegebenen ersten Druckwertebereichs befindet oder der Druck im Speicherbereich 1100 sich um mindestens einen vorgegebenen ersten Minimalbetrag ändert., oder
• - während des Betriebs der Druckänderungseinrichtung ein erster Druckverlauf im Speicherbereich einem vorgegebenen ersten Referenzverlauf folgt oder der erste Druckverlauf innerhalb eines vorgegebenen ersten Toleranzbereichs um den ersten Referenzverlauf bleibt

It is checked whether the shut-off valve can be properly closed. In the best case, i.e. if the shut-off valve can be moved properly into the closed state, the storage area and the tank area are pneumatically separated. This reduces the effective pneumatic volume on which the pressure-changing device acts the volume of the storage area. In the bad case, i.e. if the shut-off valve is jammed when open and the tank area and storage area are pneumatically connected, the effective pneumatic volume is made up of the volume of the tank area and the volume of the storage area and is therefore considerably larger than the pneumatically effective volume in the good case. In the good case, it is therefore to be expected that the first pressure change in the storage area caused by the activation of the pressure-changing device is significantly more pronounced than in the bad case. These different characteristics of the pressure changes in good and bad cases in turn allow a plausibility check of the pressure curve and therefore an extended conclusion about the functionality of the shut-off valve. If it is detected that the first change in pressure does not meet a first plausibility criterion, then a fault in the shut-off valve is detected. In this bad case, it would be determined that the shut-off valve can no longer be switched to the closed state, or that it is jammed in the open state. In one embodiment of the method according to claim 2, the evaluation shows that the first plausibility criterion is met if

• - during the operation of the pressure changing device, a first pressure gradient in the storage area reaches at least a predetermined first gradient limit value or gradient threshold value or the first pressure gradient in the storage area is within a predetermined first pressure gradient value range, or
• - due to the operation of the pressure changing device, the pressure in the storage area at least reaches a predetermined first pressure limit value or pressure threshold value, or the pressure in the storage area is within a predetermined first pressure value range, or the pressure in storage area 1100 changes by at least a predetermined first minimum amount., or
• - During the operation of the pressure-changing device, a first pressure curve in the storage area follows a predetermined first reference curve or the first pressure curve remains within a predetermined first tolerance range around the first reference curve

• - Steuern des Absperrventils im Sinne des geöffneten Zustands,
• - Auswerten der erfassten Ausgangswerte der Druckerfassungsvorrichtung dahingehend, ob eine durch das Steuern des Absperrventils im Sinne des geöffneten Zustands verursachte zweite Druckänderung im Speicherraum ein zweites Plausibilitätskriterium erfüllt
• - Erkennen eines Fehlers des Absperrventils, falls die Auswertung ergibt, dass das zweite Plausibilitätskriterium nicht erfüllt.

In one embodiment of the method according to claim 3, the following steps are carried out if the first plausibility criterion is met:

• - control of the shut-off valve in terms of the open state,
• - Evaluation of the detected output values of the pressure detection device to determine whether a second change in pressure in the storage chamber caused by the control of the shut-off valve in the direction of the open state satisfies a second plausibility criterion
• - Recognition of a fault in the shut-off valve if the evaluation shows that the second plausibility criterion is not met.

By controlling the shut-off valve to be open, the storage area and the tank area should be connected pneumatically. In the good case, ie if the controllable shut-off valve can be moved properly into the open position, pressure equalization takes place between the tank area and the storage area. The pneumatic volume suddenly expands by the volume of the tank area. In the worst case, i.e. if the controllable shut-off valve cannot be moved to the open position and remains in the closed state (jammed), pressure equalization between the tank area and storage area is still not possible. The pneumatic volume is then still limited to the volume of the storage area. Controlling the shut-off valve in the sense of the open state would therefore lead to a marked change in the pressure in the accumulator area in the best case. This effect allows a plausibility check of the pressure profile and therefore a conclusion as to the functionality of the shut-off valve. If it is detected that the second change in pressure does not meet the second plausibility criterion, then a fault in the shut-off valve is detected. In this bad case, it would be determined that the shut-off valve can no longer be moved into the open state, or that it is jammed in the closed state.
An advantage of the invention is that the pressure in the storage area is monitored and not the pressure in the tank area to assess the functionality of the shut-off valve. Since the tank area has a significantly larger volume than the storage area, pressure changes in the storage area are much easier to recognize. Furthermore, pressure conditions in the storage area are less exposed to disturbances than in the tank area, where the movement of the fuel contained therein ("sloshing") or spontaneous outgassing can lead to larger pressure fluctuations. This means that checking the shut-off valve is much more robust and precise.

• - nach dem Steuern des Absperrventils im Sinne des geöffneten Zustands eine Druckgradientenänderung im Speicherbereich (1100) einen vorgegebenen Minimalwert zumindest erreicht oder ein zweiter Druckgradient im Speicherbereich (1100) sich innerhalb eines vorgegebenen zweiten Druckgradientenwertebereichs befindet, oder
• - nach dem Steuern des Absperrventils im Sinne des geöffneten Zustands sich der Druck im Speicherbereich (1100) mindestes um einen vorgegebenen zweiten Minimalbetrag ändert oder der Druck im Speicherbereich (1100) sich innerhalb eines vorgegebenen zweiten Druckwertebereichs befindet, oder
• - nach dem Steuern des Absperrventils im Sinne des geöffneten Zustands ein zweiter Druckverlauf im Speicherbereich (1100) einem vorgegebenen zweiten Referenzverlauf folgt oder der zweite Druckverlauf innerhalb eines vorgegebenen zweiten Toleranzbereichs um den zweiten Referenzverlauf bleibt

According to one embodiment of the method according to claim 4, the evaluation shows that the second plausibility criterion is met if

• - After controlling the shut-off valve in the direction of the open state, a pressure gradient change in the storage area (1100) at least reaches a predetermined minimum value or a second pressure gradient in the storage area (1100) is within a predetermined one second pressure gradient value range is located, or
• - after the shut-off valve has been controlled in the sense of the open state, the pressure in the storage area (1100) changes by at least a predetermined second minimum amount or the pressure in the storage area (1100) is within a predetermined second pressure value range, or
• - After controlling the shut-off valve in the sense of the open state, a second pressure curve in the storage area (1100) follows a predetermined second reference curve or the second pressure curve remains within a predetermined second tolerance range around the second reference curve

• - eine Belüftungsleitung, über welche der Kraftstoffdämpfespeicher mit der Umgebung verbunden ist,
• - ein steuerbares Belüftungsventil, welches in der Belüftungsleitung angeordnet ist, um den Gasstrom durch die Belüftungsleitung zu steuern,
• - eine Entlüftungsleitung, über welche der Kraftstoffdämpfespeicher mit einer Unterdruckquelle verbunden ist,
• - ein steuerbares Entlüftungsventil, welches in der Entlüftungsleitung angeordnet ist, um den Gasstrom durch die Entlüftungsleitung zu steuern,

wobei zur Änderung des Drucks im Speicherbereich das Belüftungsventil geschlossen und das Entlüftungsventil geöffnet wird, um einen Unterdruck im Speicherbereich zu erzeugen.In one embodiment of the method according to claim 5, the pressure-changing device also has:

• - a ventilation line, via which the fuel vapor accumulator is connected to the environment,
• - a controllable ventilation valve, which is arranged in the ventilation line in order to control the gas flow through the ventilation line,
• - a vent line, via which the fuel vapor accumulator is connected to a vacuum source,
• - a controllable vent valve, which is arranged in the vent line to control the gas flow through the vent line,

wherein the aeration valve is closed and the vent valve is opened to change the pressure in the storage area in order to generate a negative pressure in the storage area.

By opening the vent valve, the storage area is pneumatically connected to the vacuum source. The vacuum source is, for example, an air intake pipe of an internal combustion engine, a Venturi nozzle, a suction jet nozzle, or a vacuum pump. A negative pressure prevails in the air intake pipe of the internal combustion engine downstream of a throttle element arranged therein in many operating states of the internal combustion engine. By connecting the storage space with the air intake pipe at this position, gas flow towards the internal combustion engine and evacuation of the storage space occurs. According to this exemplary embodiment, the activation of the pressure-changing device leads to a negative pressure in the storage area.

• - eine Belüftungsleitung, über welche der Kraftstoffdämpfespeicher mit der Umgebung verbunden ist,
• - ein steuerbares Belüftungsventil, welches in der Belüftungsleitung angeordnet ist, um den Gasstrom durch die Belüftungsleitung zu steuern,
• - eine Entlüftungsleitung, über welche der Kraftstoffdämpfespeicher mit einer Unterdruckquelle verbunden ist,
• - ein steuerbares Entlüftungsventil, welches in der Entlüftungsleitung angeordnet ist, um den Gasstrom durch die Entlüftungsleitung zu steuern,

wobei zur Änderung des Drucks im Speicherbereich das Belüftungsventil und das Entlüftungsventil geöffnet werden, um einen Unterdruck im Speicherbereich zu erzeugen.In one embodiment of the method according to claim 6, the pressure changing device has:

• - a ventilation line, via which the fuel vapor accumulator is connected to the environment,
• - a controllable ventilation valve, which is arranged in the ventilation line in order to control the gas flow through the ventilation line,
• - a vent line, via which the fuel vapor accumulator is connected to a vacuum source,
• - a controllable vent valve, which is arranged in the vent line to control the gas flow through the vent line,

wherein the aeration valve and the vent valve are opened to change the pressure in the storage area in order to generate a negative pressure in the storage area.

This embodiment is an alternative to the embodiment according to claim 5, wherein the ventilation valve is not closed but opened. This achieves a scavenging effect in the fuel vapor accumulator, which regenerates it. Although only a lower negative pressure can be generated in comparison to the embodiment according to claim 6, the functional check of the shut-off valve can be carried out at the same time as the fuel vapor accumulator is being flushed, which is necessary from time to time anyway. In order to generate as strong a negative pressure as possible, the vent valve can be opened to the maximum and the process can preferably be carried out when the negative pressure generated by the negative pressure source is particularly high.

• - eine Belüftungsleitung, über welche der Kraftstoffdämpfespeicher mit der Umgebung verbunden ist,
• - ein steuerbares Belüftungsventil, welches in der Belüftungsleitung angeordnet ist, um den Gasstrom durch die Belüftungsleitung zu steuern,
• - eine steuerbare Pumpe, welche in der Belüftungsleitung stromabwärts des Belüftungsventils angeordnet ist, um zur Erzeugung eines Überdrucks im Speicherbereich Umgebungsluft aus der Atmosphäre in den Kraftstoffdämpfespeicher zu pumpen,
• - eine Entlüftungsleitung, über welche der Kraftstoffdämpfespeicher mit einer Unterdruckquelle verbunden ist,
• - ein steuerbares Entlüftungsventil, welches in der Entlüftungsleitung angeordnet ist, um den Gasstrom durch die Entlüftungsleitung zu steuern,

wobei zu Änderung des Drucks im Speicherbereich das Belüftungsventil geöffnet, das Entlüftungsventil geschlossen und die Pumpe betrieben wird, um im Speicherbereich einen Überdruck zu erzeugen.In one embodiment of the method according to claim 7, the pressure changing device has:

• - a ventilation line, via which the fuel vapor accumulator is connected to the environment,
• - a controllable ventilation valve, which is arranged in the ventilation line in order to control the gas flow through the ventilation line,
• - a controllable pump, which is arranged in the ventilation line downstream of the ventilation valve in order to pump ambient air from the atmosphere into the fuel vapor storage to generate an overpressure in the storage area,
• - a vent line, via which the fuel vapor accumulator is connected to a vacuum source,
• - a controllable vent valve, which is arranged in the vent line to control the gas flow through the vent line,

wherein to change the pressure in the storage area, the ventilation valve is opened, the vent valve is closed and the pump is operated in order to generate an overpressure in the storage area.

This embodiment represents an alternative to the embodiment according to claims 5 and 6. The pumping of ambient air into the storage area leads to overpressure there.

A computer program product according to claim 8 can be loaded into the memory of a computer. It has software code sections which, when executed on a computer, lead to the implementation of the method.

A control device for controlling a tank ventilation system according to claim 9 has a computer and a memory on which the computer program product according to claim 8 is loaded.

Such a control device is also designed with all the necessary interfaces in order to be connected to a tank ventilation system. When the control device is operated, the computer program product loaded thereon runs and the method is carried out.

With regard to the advantages of the computer program product and the control device, reference is made to the statements relating to claims 1 to 8, which apply in an analogous manner.

• 1 Eine schematische Darstellung einer Tankentlüftungsanlage für ein Kraftfahrzeug:
• 2 Ein Ablaufdiagramm eines Ausführungsbeispiels eines Verfahrens zur Überprüfung der Tankentlüftungsanlage

The invention is explained in more detail below using an exemplary embodiment with reference to the accompanying figures. In the figures are:

• 1 A schematic representation of a tank ventilation system for a motor vehicle:
• 2 A flowchart of an embodiment of a method for checking the tank ventilation system

In 1 a tank ventilation system 1000 for a motor vehicle (not shown) with an internal combustion engine 2000 is shown schematically. The tank ventilation system 1000 has a storage area 1100 and a tank area 1200 .

In the exemplary embodiment, the tank area 1200 has a fuel tank 1210 for storing fuel 1211 , a level sensor 1213 and a delivery pump 1214 for delivering fuel in the direction of the internal combustion engine 2000 .

In the exemplary embodiment, storage area 1100 has a fuel vapor storage device 1110 . The fuel vapor accumulator 1110 is designed as an activated charcoal canister and is used for the temporary storage of hydrocarbons which outgas from the fuel tank 1210 .

Storage area 1100 and tank area 1200 are coupled to one another via a degassing line 1300 . A controllable shut-off valve 1400 is arranged in the degassing line 1300, which in a closed state prevents a pressure equalization between the tank area 1200 and the storage area 1100, and which in an open state allows a pressure equalization between the tank area 1200 and the storage area 1100. The shut-off valve 1400 can be designed as a pulse width modulated, electric valve.

The tank ventilation system 1000 also includes a ventilation line 1600, via which the fuel vapor accumulator 1110 is connected to the atmosphere or the environment, and a controllable ventilation valve 1610, which is arranged in the ventilation line 1600 in order to control the gas flow through the ventilation line 1600. A controllable pump 1620 is also arranged in the ventilation line 1600 downstream of the ventilation valve 1610, which pumps ambient air from the atmosphere into the fuel vapor storage device 1110 to generate an overpressure in the storage area 1100 when the ventilation valve 1610 is open.

The fuel vapor accumulator 1110 is also connected to a vacuum source 2100 via a vent line 1700 . In the exemplary embodiment, an air intake pipe 2100 of internal combustion engine 2000 serves as the vacuum source. When the internal combustion engine 2000 is in operation, there is negative pressure at this position. Alternatively, a venturi or suction jet nozzle can also be used as a vacuum source. A controllable vent valve 1710 is arranged in the vent line 1700 and can be used to control the gas flow through the vent line 1700 .

The tank area is delimited by the fuel tank 1210, the shut-off valve 1400 and the section of the degassing line 1300 lying in between.

The storage area is defined by the fuel vapor storage 1110, the shut-off valve 1400, the section of the degassing line 1300 lying between the fuel vapor storage 1110 and the shut-off valve 1400, the ventilation valve 1610, the section of the ventilation line 1600 lying between the fuel vapor storage 1110 and the ventilation valve 1610, the ventilation valve 1710 and the section between the fuel vapor storage 1110 and vent valve 1710 lying portion of the vent line 1700 limited.

The ventilation line 1600, the controllable ventilation valve 1610, the pump 1620, the ventilation line 1700 and the controllable ventilation valve 1710 together form a pressure-changing device 1800, by means of which the pressure in the storage area 1100 can be changed. To generate an overpressure in the storage area 1100 (relative to the pressure in the tank area 1200), the shut-off valve 1400 is closed, the vent valve 1710 is closed, the vent valve 1610 is opened and the pump 1620 is operated. Alternatively, to create a negative pressure in the storage area 1100 (relative to the pressure in the tank area 1200), the shut-off valve 1400 is closed, the ventilation valve 1610 is closed and the vent valve 1710 is opened, whereby the storage area 1100 is connected to the air intake pipe.

The tank ventilation system also includes a pressure detection device 1500 which has a storage pressure sensor 1510 for detecting the gas pressure in the storage area 1100 . Pressure determination device 1500 can optionally also have a tank pressure sensor 1520 for detecting the gas pressure in tank region 1200 (as in the exemplary embodiment in 1 ). In the embodiment of 1 the accumulator pressure sensor 1510 is arranged in the vent line upstream of the vent valve 1710 and the tank pressure sensor 1520 is arranged in the fuel tank 1200 .

A control device 3000 is provided, which is connected to the tank ventilation system 1000 . The control device is designed to detect, store, evaluate, interpret, quantify, qualitatively and quantitatively evaluate and compare output values from accumulator pressure sensor 1510 and output values from tank pressure sensor 1520 .

The fuel contained in the fuel tank 1210 tends to outgas hydrocarbons. In the closed state, the shut-off valve 1400 prevents the gaseous hydrocarbons from escaping from the tank area 1200, as a result of which the pressure there continues to rise. From time to time decongestion of the tank area 1200 is necessary. By switching shut-off valve 1400 to the open state, the gaseous hydrocarbons flow off in a controlled manner due to the pressure drop into fuel vapor accumulator 1110 and are temporarily stored there. However, the fuel vapor accumulator 1110 has a limited capacity and needs to be regenerated from time to time. For this purpose, the shut-off valve 1400 is closed and the ventilation valve 1610 is opened. By controlling the vent valve 1710, the fuel vapor accumulator 1110 is connected to the air intake pipe 1700, which results in a scavenging effect due to the prevailing pressure drop, whereby the stored hydrocarbons are sucked into the air intake pipe 1700 and then fed to the internal combustion engine 2000, where they participate in combustion. The scavenging process can be assisted by operating the pump 1620, which enables the fuel vapor reservoir 1110 to be scavenged even when the vacuum around the air intake pipe is very low.

• Das Verfahren startet mit Schritt 100, beispielsweise beim Start des Verbrennungsmotors durch einen Fahrzeugführer.

It is a legal requirement to verify the operation of the 1400 isolation valve. An exemplary embodiment of a method for checking the isolation valve 1400 is described with reference to the flow chart of FIG 2 explained in more detail:

• The method starts with step 100, for example when a vehicle driver starts the internal combustion engine.

In step 200, the pressure detection device 1500 is activated or operated and its output values are detected. This means that current output values from storage pressure sensor 1510, which represent the pressure in the storage area, and optionally current output values from tank pressure sensor 1520, which represent the pressure in the fuel tank, are recorded and stored at predetermined time intervals or continuously, e.g. by control device 3000. These current output values are then recorded and stored during all subsequent method steps.

In step 300, the shut-off valve 1400 is controlled in the closed state. In the closed state, a pressure equalization and a gas flow between the storage area 1100 and the tank area 1200 is prevented. In step 400, the pressure changing device 1800 is operated to change the pressure in the storage area 1100 and remains activated throughout the process. To generate an overpressure, the vent valve 1710 is closed, the vent valve 1610 is opened and the pump 1620 is operated. In order to generate a negative pressure, the ventilation valve 1610 is closed or opened and the vent valve 1710 is opened, as a result of which the storage area 1100 is connected to the air intake pipe 2000 as a source of negative pressure.

In step 500, the detected output values of the pressure detection device 1500 are evaluated to determine whether a first change in pressure in the storage space 1100 caused by the operation of the pressure changing device 1800 satisfies a first plausibility criterion. In this step, it is checked whether the first change in pressure in storage area 1100 is plausible, assuming that shut-off valve 1400 is actually closed. This is because if the shut-off valve 1400 is actually in the closed state, the first pressure change will be significantly greater than if the shut-off valve remains in the open state (sticks). The term "first change in pressure" not only stands for the change in value of the pressure at a certain point in time, but is representative of all quantitative and qualitative criteria, values, sets of values, numbers, sets of numbers, key figures and values with which a change in the pressure in the Storage area 1100 can be characterized or quantified or evaluated, e.g. the pressure gradient, the pressure curve (sequence of several pressure values at different points in time), the pressure change in terms of value at a specific point in time, the actual pressure value at a specific point in time relative to a predetermined fixed comparison value, etc. As The output values of the accumulator pressure sensor 1510 serve as the basis for determining the "first pressure change".

For example, the first plausibility criterion is considered to be met if, during the operation of pressure changing device 1800, a first pressure gradient in storage area 1100 determined on the basis of the output values of accumulator pressure sensor 1510 at least reaches a predetermined first gradient limit value, or the first pressure gradient in storage area (1100) is within a predetermined first Pressure gradient value range remains. The predetermined first gradient limit value or gradient threshold value is defined in such a way that if the first pressure gradient does not reach it, it can be assumed that the shut-off valve 1400 is jammed open. Correspondingly, the predefined first pressure gradient value range has data such that if the first pressure gradient is not within this first pressure gradient value range, it can be assumed that the shut-off valve 1400 is jammed open.

The first plausibility criterion is also considered to be met, for example, if the operation of pressure changing device 1800 causes the pressure in storage area 1100 to at least reach a predefined first pressure limit value or pressure threshold value, or the pressure in storage area 1100 remains within a predefined first pressure value range, or the pressure in storage area 1100 changes changes by at least a predetermined first minimum amount. The predetermined first pressure limit value is defined in such a way that if the pressure in the storage area 1100 does not reach it, it can be assumed that the shut-off valve 1400 is jammed open. Correspondingly, the predefined first pressure value range has data such that if the pressure in storage area 1100 is not within this first pressure value range, it can be assumed that shut-off valve 1400 is jammed open. Correspondingly, the data on the first minimum amount are such that if the pressure in storage area 1100 does not change by at least this first minimum amount, it can be assumed that shutoff valve 1400 is jammed open.

The first plausibility criterion is also considered to be met, for example, if during the operation of pressure changing device 1800 a first pressure profile in storage area 1100 follows a predefined first reference profile or the first pressure profile remains within a predefined first tolerance range around the first reference profile. In this case, the predefined first reference curve is defined in such a way that if the first pressure curve leaves the first reference curve, it can be assumed that the shut-off valve 1400 is jammed open. Correspondingly, the predefined first tolerance range is defined in such a way that if the first pressure curve lies outside of this first tolerance range, it can be assumed that shut-off valve 1400 is jammed open.

If it is determined in step 500 that the first plausibility criterion is not met, then in step 510 a fault in shut-off valve 1400 is detected and the method is ended in step 800. Because if the shut-off valve 1400 were functional, it would actually have to have assumed its closed state in step 300, as a result of which the pressure in the storage area 1100 would have had to change to such an extent that the first plausibility criterion would have been met. However, if the first plausibility criterion is not met, it can be assumed that the pressure in the storage chamber 1100 has not changed sufficiently, which is interpreted in such a way that the shut-off valve 1400 is stuck in the open state, i.e. it can no longer be brought into the closed state.

If it is determined in step 500 that the first plausibility criterion is met, then the method continues with step 600, with shut-off valve 1400 being controlled in the sense of the open state. This step can be made dependent on whether the pressure in the tank area 1200 differs from the pressure in the storage area 1100 by a predetermined minimum, the control of the shut-off valve 1400 in the sense of open a state only occurs if the test result is positive. In the open state, pressure equalization and gas flow between the storage area 1100 and the tank area 1200 is now possible. As mentioned at step 400, the pressure sensing device 1500 continues to operate in terms of a pressure change in the storage area.

In step 700 the detected output values of the pressure detection device 1500 are evaluated to determine whether the second pressure change in the storage area 1100 caused by the control of the shut-off valve 1400 towards the open state satisfies a second plausibility criterion. In this step, it is checked whether the second change in pressure in storage area 1100 is plausible, assuming that shut-off valve 1400 is actually open. Because if the shut-off valve 1400 is now actually in the open state, a significant second pressure change can be seen compared to the case in which the shut-off valve remains in the closed state (sticks). The term "second pressure change" does not only stand for the change in value of the pressure at a certain point in time, but is representative of all quantitative and qualitative criteria, values, sets of values, numbers, sets of numbers, key figures and values with which a change in pressure can be measured can be characterized or quantified or evaluated in the storage area, e.g. the pressure gradient, the pressure profile (sequence of several pressure values at different points in time), the value-based pressure change at a specific point in time, the actual pressure value at a specific point in time relative to a specified fixed comparison value, etc. As The output values of the accumulator pressure sensor serve as the basis for determining the "second pressure change".

For example, the second plausibility criterion is considered to be met if, after the shut-off valve 1400 has been controlled in the sense of the open state, a pressure gradient change in the storage area (1100) at least reaches a predetermined minimum value or a second pressure gradient in the storage area (1100) is within a predetermined second pressure gradient value range . The predefined minimum value is defined in such a way that if the second pressure gradient change at least reaches it, it can be assumed that the shut-off valve 1400 is actually open. Correspondingly, the predefined second pressure gradient value range has data such that if the second pressure gradient is in this second pressure gradient value range, it can be assumed that the shut-off valve 1400 is properly open.

The second plausibility criterion is also considered to be met, for example, if after the shut-off valve has been controlled in the sense of the open state, the pressure in the storage area (1100) changes by at least a predetermined second pressure amount or the pressure in the storage area (1100) changes within a predetermined second pressure value range located. The predefined second pressure amount is defined in such a way that if the second pressure changes by at least this second pressure amount, it can be assumed that the shut-off valve 1400 is properly open. Correspondingly, the predefined second pressure value range has data such that if the pressure in the storage area 1100 is in this second pressure value range, it can be assumed that the shut-off valve 1400 is properly open.

The second plausibility criterion is also considered to be met, for example, if after the shut-off valve has been controlled in the sense of the open state, a second pressure profile in storage area 1100 follows a predefined second reference profile or the second pressure profile remains within a predefined second tolerance range around the second reference profile. In this case, the predefined second reference profile is defined in such a way that if the second pressure profile follows the second reference profile, it can be assumed that the shut-off valve 1400 is properly open. Correspondingly, the predefined second tolerance range is defined in such a way that if the second pressure curve lies within this second tolerance range, it can be assumed that the shut-off valve 1400 is properly open.

The data can be obtained, for example, from laboratory tests or from online tests in the vehicle.

If it is determined in step 700 that the second plausibility criterion is not met, then in step 710 a fault in shut-off valve 1400 is detected and the method is ended in step 800. Because if the shut-off valve 1400 were functional, it would have to have assumed its open state in step 600, as a result of which the pressure in the storage area 1100 would have had to change to such an extent that the second pressure change criterion would have been met. However, if the second pressure change criterion is not met, it can be assumed that the pressure in the storage chamber 1100 has changed to an insufficient extent, which is interpreted in such a way that the shut-off valve 1400 is stuck in the closed state, i.e. it can no longer be put into the open state leaves.

If it is determined in step 700 that the second plausibility criterion is met, the method continues with step 720, where shut-off valve 1400 is assessed as functional.

The method then terminates at step 800.

The method can be repeated regularly and/or in specific operating states of the internal combustion engine.

The method can be implemented as a computer program product which can be loaded onto a computer (microcomputer). The computer program product has software code sections which, when executed on the computer, carry out corresponding arithmetic operations, output control commands and read in and process data. The computer program product can be loaded in the memory of a control device 3000 (control unit), as shown in 1 is shown schematically. The control device 3000 has all the necessary equipment features that are required for storing and executing the computer program product, for transmitting and receiving data, and for controlling the tank ventilation system. In particular, control device 3000 has a digital memory, a processor and interfaces for coupling to components of tank ventilation system 1000 and internal combustion engine 2000 .

Claims (9)

Method for checking the functionality of a controllable shut-off valve (1400) in a tank ventilation system (1000), which has: - a tank area (1200) which has a fuel tank (1210), - a storage area (1100) which has a fuel vapor storage (1110), - a degassing line (1300) which connects the fuel vapor accumulator 1110 and the fuel tank (1210), - the controllable shut-off valve 1400, which is arranged in the degassing line (1300) and which, in a closed state, prevents pressure equalization between the tank area (1200) and the storage area (1100), and which, in an open state, prevents pressure equalization between the tank area (1200 ) and the memory area (1100) allowed, - a pressure changing device (1800), which is connected to the storage area in order to change the pressure in the storage area (1100), - a pressure detection device (1500) for detecting the pressure in the storage area (1100), the method having the following steps: - activation of the pressure detection device (1500) and detection of the output values, - Control of the shut-off valve (1400) in terms of the closed state, - Operating the pressure changing device (1800) in terms of changing the pressure in the storage area (1100), - evaluating the detected output values of the pressure detection device (1500) to determine whether a first change in pressure in the storage chamber (1100) caused by the operation of the pressure changing device (1800) meets a first plausibility criterion, - Detecting a fault in the shut-off valve (1400) if the evaluation shows that the first plausibility criterion is not met. procedure after claim 1 , wherein the evaluation shows that the first plausibility criterion is met if - during operation of the pressure changing device (1800), a first pressure gradient in the storage area (1100) reaches a predetermined first gradient limit value or the first pressure gradient in the storage area (1100) is within a predetermined first pressure gradient value range remains, or - due to the operation of the pressure changing device (1800), the pressure in the storage area (1100) reaches a predetermined first pressure limit value, or the pressure in the storage area (1100) is within a predetermined first pressure value range, or the pressure in the storage area (1100) is at least changes a predetermined first minimum amount, or - during operation of the pressure changing device (1800), a first pressure curve in the storage area (1100) follows a predetermined first reference curve or the first pressure curve within a predetermined first tolerance range around the first reference history remains, or Procedure according to one of Claims 1 until 2 , In the event that the first plausibility criterion is met, the following steps are carried out: - Controlling the shut-off valve (1400) in terms of the open state, - Evaluating the detected output values of the pressure detection device (1500) to determine whether a through the control of the shut-off valve (1400) in terms of the open state caused second pressure change in the storage chamber (1100) meets a second plausibility criterion - detection of a fault in the shut-off valve (1400) if the evaluation shows that the second plausibility criterion is not met. procedure after claim 3 , wherein the evaluation shows that the second plausibility criterion is met if - after controlling the shut-off valve in the sense of the open state, a pressure gradient change in the storage area (1100) at least reaches a predetermined minimum value or a second pressure gradient in the storage area (1100) is within a predetermined second pressure gradient value range, - after the shut-off valve has been controlled in the sense of the open state, the pressure in the storage area (1100) changes by at least a predetermined second pressure amount or the pressure in the storage area (1100) changes within a predetermined second pressure value range, or - after the shut-off valve has been controlled in the sense of the open state, a second pressure curve in the storage area (1100) follows a predetermined second reference curve or the second pressure curve remains within a predetermined second tolerance range around the second reference curve Procedure according to one of Claims 1 until 4 , wherein the pressure changing device (1800) has: - a ventilation line (1600) via which the fuel vapor accumulator (1110) is connected to the atmosphere, - a controllable ventilation valve (1610) which is arranged in the ventilation line (1600) in order to regulate the gas flow to be controlled through the ventilation line (1600), - a ventilation line (1700) via which the fuel vapor accumulator (1110) is connected to a vacuum source (2100), - a controllable ventilation valve (1710), which is arranged in the ventilation line (1700), to control the flow of gas through the vent line (1700), wherein to change the pressure in the storage area (1100) the vent valve (1610) is closed and the vent valve (1710) is opened to create a negative pressure in the storage area (1100). Procedure according to one of Claims 1 until 4 , wherein the pressure changing device (1800) has: - a ventilation line (1600) via which the fuel vapor accumulator (1110) is connected to the atmosphere, - a controllable ventilation valve (1610) which is arranged in the ventilation line (1600) in order to regulate the gas flow to be controlled through the ventilation line (1600), - a ventilation line (1700) via which the fuel vapor accumulator (1110) is connected to a vacuum source (2100), - a controllable ventilation valve (1710), which is arranged in the ventilation line (1700), to control the flow of gas through the vent line (1700), wherein to change the pressure in the storage area (1100), the vent valve (1610) and the vent valve (1710) are opened to create a negative pressure in the storage area (1100). Procedure according to one of Claims 1 until 4 , wherein the pressure changing device (1800) has: - a ventilation line (1600) via which the fuel vapor accumulator (1110) is connected to the atmosphere, - a controllable ventilation valve (1610) which is arranged in the ventilation line (1600) in order to regulate the gas flow through the ventilation line (1600), - a controllable pump (1620), which is arranged in the ventilation line (1600) downstream of the ventilation valve (1610) in order to generate an overpressure in the storage area (1100) ambient air from the atmosphere into the fuel vapor storage (1110) to pump, - a vent line (1700), via which the fuel vapor accumulator (1110) is connected to a vacuum source (2100), - a controllable vent valve (1710), which is arranged in the vent line (1700) to the gas flow to control through the vent line (1700), wherein to change the pressure in the storage area (1100) opens the vent valve (1610), the En ventilation valve (1710) is closed and the pump (1620) is operated in order to generate an overpressure in the storage area (1100). Computer program product which can be loaded into the memory of a computer and which has software code sections according to which the method according to one of Claims 1 until 7 is executed when the computer program product runs on the computer. Control device (3000) for controlling a tank ventilation system (1000), with a computer and a memory on which the computer program product claim 8 is loaded.

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