EP1760303B1 - Method for performing a leakage test of a fuel tank purge system - Google Patents

Method for performing a leakage test of a fuel tank purge system Download PDF

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Publication number
EP1760303B1
EP1760303B1 EP06014440A EP06014440A EP1760303B1 EP 1760303 B1 EP1760303 B1 EP 1760303B1 EP 06014440 A EP06014440 A EP 06014440A EP 06014440 A EP06014440 A EP 06014440A EP 1760303 B1 EP1760303 B1 EP 1760303B1
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EP
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Prior art keywords
valve
negative pressure
tank
adsorption filter
tev
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EP06014440A
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German (de)
French (fr)
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EP1760303A1 (en
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Armin Köhler
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Audi AG
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Audi AG
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M25/00—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture
    • F02M25/08—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture adding fuel vapours drawn from engine fuel reservoir
    • F02M25/0809—Judging failure of purge control system

Definitions

  • the invention relates to a method for checking the gas-tightness of a motor vehicle tank ventilation system according to the preamble of claim 1.
  • a tank ventilation system consists of a fuel tank, an adsorption filter and a vent line connecting the fuel tank with the adsorption filter. Further, the adsorption filter is connected to the atmosphere via a fresh air line in which a controllable shut-off valve is arranged as an adsorption filter shut-off valve (AAV). In addition, the adsorption filter is connected to the intake manifold of an internal combustion engine by a regeneration line in which a controllable regeneration valve is arranged as a tank ventilation valve (TEV).
  • TSV tank ventilation valve
  • the fuel vapors outgassing from the fuel are sucked out by the vacuum present in the intake manifold.
  • the cached in the adsorption fuel vapors are disposed of and thus regenerated the adsorption.
  • the tank system is vented through the adsorption filter, where outgassing fuel vapors are cached therein.
  • Such a generic method is known from DE 40 03 751 A1 known.
  • the adsorption filter shut-off valve (AAV) is closed and the tank vent valve (TEV) is opened, the system evacuated and checked after closing the TEV's by means of a pressure sensor, if the vacuum reduction gradient in the tank ventilation system corresponds to a predetermined Grenzunterdruckgradienten.
  • AAV adsorption filter shut-off valve
  • TEV tank vent valve
  • This method has the disadvantage that the negative pressure generated via the intake manifold vacuum in the tank ventilation system is not constant, but depends on variable parameters. This procedure is not accurate enough to detect minor leaks.
  • the object of the invention is to develop a generic method for checking the gas-tightness of a motor vehicle tank ventilation system so that it is possible to reliably assess the gas-tightness of a tank ventilation system with a simple construction of the tank ventilation system and a simple process control.
  • the elaborate corrections explained above are required, which take into account the outgassing of the fuel.
  • Such complex corrections are dispensable in the present inventive method, since the addition of the vacuum build-up time t 1 and the negative pressure degradation time t 2 results in a compensation of the outgassing of the fuel.
  • This sum as the diagnostic sum time t D is a measure of the tightness of the tank ventilation system and is compared with a corresponding diagnostic time threshold t DS . When falling below the corresponding diagnosis time threshold t DS a leak is detected and generates an error signal for further processing.
  • the tank venting valve (TEV) is preferably designed as a control valve according to claim 2, which is controllable with respect to its flow passage and which is slowly opened during the vacuum build-up time t 1 up to a predetermined opening cross-section.
  • Such a slow opening time of the tank venting valve (TEV) up to a predetermined opening cross section (duty cycle) may preferably be on the order of about 10 seconds.
  • Monitoring with the method according to the invention is feasible in a temperature range of -7 ° C to 40 ° C, which may be required by law.
  • the outgassing of the fuel is also taken into account in the process according to the invention, but without these having to be determined separately with the system closed and used for corrective purposes.
  • the outgassing of the fuel is automatically compensated in such a way, that a small outgassing caused a short negative pressure build-up time P 1 and associated with long negative pressure reduction time t 2 and that a strong outgassing results in a long negative pressure buildup time t 1 and an associated short negative pressure reduction time t 2 , as a measure of the tightness of the tank, the diagnostic sum time t D is decisive in comparison to a diagnostic time threshold t DS .
  • AAV adsorption filter shut-off valve
  • the required for the diagnosis at least one pressure sensor according to claim 4 preferably in the vent line between the fuel tank and arranged the adsorption filter. Depending on the circumstances, however, a different arrangement in the printing system can be made.
  • An assigned pressure switch can be used for each of the two required pressure threshold values.
  • a continuously operating pressure sensor is also possible with which switching signals for the respective associated valves are generated at the two pressure threshold values, in each case via a downstream evaluation unit.
  • a pressure switch is proposed with a hysteresis corresponding to the vacuum-Avembauschwelle P S2 and the vacuum-Abauschwelle P S1 .
  • a known activated carbon filter is used as adsorption.
  • an air filter is arranged in a conventional manner at the free end of the fresh air line according to claim 7.
  • this variable can be determined as a variable in each case as a function of detected boundary conditions, but the automatic compensation with respect to the outgassing of the fuel as described above still occurs.
  • a tank ventilation system 1 consisting of a fuel tank 2 with filler neck 3 and an adsorption filter 4 as activated carbon filter.
  • the adsorption filter 4 is connected to the fuel tank 2 through a vent line 5, to which a pressure switch 6 with a hysteresis for two pressure thresholds is arranged.
  • the adsorption filter 4 is connected via a fresh air line 7 and an end air filter 8 to the atmosphere, wherein in the fresh air line 7, a controllable shut-off valve as Adsorptionsfilter shut-off valve (AAV) is arranged in the manner of a switchable two-point solenoid valve.
  • AAV Adsorptionsfilter shut-off valve
  • the adsorption filter 4 is connected to the intake manifold of an internal combustion engine 9 through a regeneration line 10 in which a controllable regeneration valve is arranged as a tank vent valve (TEV).
  • the tank vent valve (TEV) is designed as a controllable control valve with a variable opening cross section.
  • the pressure switch 6 and the controllable valves (AAV) and (TEV) are connected to a (not shown) control / evaluation unit, wherein in the diagram Fig. 2 controlled process steps are performed controlled:
  • the pressure in the tank ventilation system 1 is set to ambient pressure level P 0 by controlled closing of the tank ventilation valve (TEV) with the adsorption filter shut-off valve (AAV) open.
  • TEV tank ventilation valve
  • AAV adsorption filter shut-off valve
  • the adsorption filter shut-off valve (AAV) is closed and the tank vent valve (TEV) is opened.
  • the opening of the tank ventilation valve (TEV) is gradual and slow up to a given opening cross-section according to a duty cycle in percent, as indicated by the dashed line in the lower part of the diagram Fig. 2 in connection with the opening diagram for TEV. Due to the slow opening of the tank ventilation valve (TEV) with the adsorption filter shut-off valve (AAV) closed, a negative pressure builds up in the tank ventilation system 1 because of the negative pressure in the intake manifold of the internal combustion engine 9.
  • the vacuum build-up takes place until a predetermined negative pressure build-up wave P S2 is detected by the pressure switch 6.
  • the time from the beginning of the opening of the tank venting valve (TEV) until reaching the vacuum build-up shaft P S2 is measured as the associated vacuum build-up time t 1 and stored for further use.
  • the tank venting valve (TEV) Upon reaching the vacuum boosting shaft P S1 , the tank venting valve (TEV) is quickly closed. Also the Adsorptionsfilter shut-off valve (AAV) remains closed, so that the system of the fuel tank 2, the adsorption filter 4, the fresh air line 7, the Regenerierieitung 10 and the vent line 5 is closed.
  • AAV Adsorptionsfilter shut-off valve
  • the negative pressure build-up time t 1 and the negative pressure reduction time t 2 are summed to form a diagnostic sum time t D and compared with a diagnosis time threshold t DS . If there is a long diagnostic total time t D and if the diagnostic time threshold t DS is exceeded, the tank ventilation system 1 is identified as being leak-tight. With a short diagnostic sum time t D and below the corresponding diagnostic time threshold t DS , however, the tank ventilation system is detected as leaking, with an error signal is generated for further use.

Description

Die Erfindung betrifft ein Verfahren zur Überprüfung der Gasdichtheit einer Kraftfahrzeug-Tankentlüftungsanlage nach dem Oberbegriff des Anspruchs 1.The invention relates to a method for checking the gas-tightness of a motor vehicle tank ventilation system according to the preamble of claim 1.

Eine Tankentlüftungsanlage besteht aus einem Kraftstofftank, einem Adsorptionsfilter und einer den Kraftstofftank mit dem Adsorptionsfilter verbindenden Entlüftungsleitung. Weiter ist der Adsorptionsfilter mit der Atmosphäre über eine Frischluftleitung verbunden, in der ein steuerbares Absperrventil als Adsorptionsfilter-Absperrventil (AAV) angeordnet ist. Zudem ist der Adsorptionsfilter mit dem Saugrohr einer Brennkraftmaschine durch eine Regenerierleitung verbunden in der ein steuerbares Regenerationsventil als Tankentlüftungsventil (TEV) angeordnet ist.A tank ventilation system consists of a fuel tank, an adsorption filter and a vent line connecting the fuel tank with the adsorption filter. Further, the adsorption filter is connected to the atmosphere via a fresh air line in which a controllable shut-off valve is arranged as an adsorption filter shut-off valve (AAV). In addition, the adsorption filter is connected to the intake manifold of an internal combustion engine by a regeneration line in which a controllable regeneration valve is arranged as a tank ventilation valve (TEV).

Im Betrieb der Brennkraftmaschine werden bei geöffnetem Absperrventil (AAV) und geöffnetem Tankentlüftungsventil (TEV) die aus dem Kraftstoff ausgasenden Kraftstoffdämpfe durch den im Saugrohr anliegenden Unterdruck abgesaugt. Zudem werden auch die im Adsorptionsfilter zwischengespeicherten Kraftstoffdämpfe entsorgt und somit der Adsorptionsfilter regeneriert. Bei abgestelltem Fahrzeug wird das Tanksystem über den Adsorptionsfilter belüftet, wobei ausgasende Kraftstoffdämpfe darin zwischengespeichert werden.During operation of the internal combustion engine, when the shut-off valve (AAV) is open and the tank-venting valve (TEV) is open, the fuel vapors outgassing from the fuel are sucked out by the vacuum present in the intake manifold. In addition, the cached in the adsorption fuel vapors are disposed of and thus regenerated the adsorption. When the vehicle is parked, the tank system is vented through the adsorption filter, where outgassing fuel vapors are cached therein.

Aus Gründen des Umweltschutzes werden zunehmend Messverfahren gefordert, mit deren Hilfe Undichtheiten in Tankentlüftungsanlagen von Kraftfahrzeugen erkannt und angezeigt werden.For reasons of environmental protection measurement methods are increasingly required, with the help of leaks in tank ventilation systems of motor vehicles are detected and displayed.

Ein solches gattungsgemäßes Verfahren ist aus der DE 40 03 751 A1 bekannt. Hierbei wird das Adsorptionsfilter-Absperrventil (AAV) geschlossen und das Tankentlüftungsventil (TEV) geöffnet, das System evakuiert und nach Schließen des TEV's mittels eines Drucksensors überprüft, ob der Unterdruckabbaugradient in der Tankentlüftungsanlage einem vorgegebenen Grenzunterdruckgradienten entspricht. Dieses Verfahren hat den Nachteil, dass der über den Saugrohrunterdruck in der Tankentlüftungsanlage erzeugte Unterdruck nicht konstant ist, sondern von veränderlichen Parametern abhängt. Für das Erkennen kleinerer Undichtheiten ist dieses Verfahren nicht genau genug. Insbesondere kann ein kleines Leck durch eine so einfache Druckprüfung nicht ohne weiteres erkannt werden, da der Kraftstoff aufgrund seines Dampfdruckverhaltens Temperatur- und Außendruckabhängig einen Eigendruck aufbaut und weitere Einflüsse wie der Füllstand, die Kraftstoffqualität oder mechanische Bewegungen des Kraftstofftanks den Einfluss eines kleinen Lecks überdecken können.Such a generic method is known from DE 40 03 751 A1 known. Here, the adsorption filter shut-off valve (AAV) is closed and the tank vent valve (TEV) is opened, the system evacuated and checked after closing the TEV's by means of a pressure sensor, if the vacuum reduction gradient in the tank ventilation system corresponds to a predetermined Grenzunterdruckgradienten. This method has the disadvantage that the negative pressure generated via the intake manifold vacuum in the tank ventilation system is not constant, but depends on variable parameters. This procedure is not accurate enough to detect minor leaks. In particular, a small leak by such a simple pressure test can not be readily recognized, since the fuel due to its vapor pressure behavior temperature and external pressure dependent builds a self-pressure and other influences such as the level, the fuel quality or mechanical movements of the fuel tank can cover the influence of a small leak ,

Es sind daher bereits Weiterbildungen des vorstehenden Verfahrens bekannt, um insbesondere auch kleinere Undichtheiten erkennen zu können, wobei insbesondere eine Korrektur für das Ausgasen des Kraftstoffs durchgeführt wird. Beispielsweise wird in der DE 42 27 698 C2 auf einen vorgegebenen Unterdruck bei einem stabilen Luft-Kraftstoffgemisch geregelt und von dort ausgehend für eine Dichtheitsdiagnose der Druckverlauf in der abgesperrten Tankentlüftungsanlage erfasst und ausgewertet. Bei einem anderen bekannten Verfahren nach DE 197 13 085 A1 werden Einflussparameter erfasst und aufwendige Korrekturrechnungen aufgrund eines physikalischen Models für den gemessenen Druckverlauf ausgeführt. In einem anderen bekannten Verfahren nach DE 44 27 688 C2 wird das dynamische Verhalten des Druckverlaufs anhand mehrerer aufeinander folgender Druckwerte erfasst und ein daraus gebildeter Mittelwert ausgewertet. Auch in DE 101 43 329 A1 werden Korrekturgrößen durch Auswertung von Druckänderungen in mehreren Messzyklen ermittelt.There are therefore already known developments of the above method, in particular to be able to detect even minor leaks, in particular, a correction for the outgassing of the fuel is performed. For example, in the DE 42 27 698 C2 regulated to a predetermined negative pressure at a stable air-fuel mixture and detected and evaluated from there, starting for a leak diagnosis of the pressure profile in the shut-off tank ventilation system. In another known method according to DE 197 13 085 A1 Influence parameters are recorded and complex correction calculations based on a physical model for the measured pressure curve are executed. In another known method according to DE 44 27 688 C2 is the dynamic behavior of the pressure curve based recorded several successive pressure values and evaluated a mean value formed therefrom. Also in DE 101 43 329 A1 Correction values are determined by evaluating pressure changes in several measuring cycles.

Aufgabe der Erfindung ist es, ein gattungsgemäßes Verfahren zur Überprüfung der Gasdichtheit einer Kraftfahrzeug-Tankentlüftungsanlage so weiterzubilden, dass sich mit einem einfachen Aufbau der Tankentlüftungsanlage und einer einfachen Verfahrensführung zuverlässig die Gasdichtheit einer Tankentlüftungsanlage beurteilen lässt.The object of the invention is to develop a generic method for checking the gas-tightness of a motor vehicle tank ventilation system so that it is possible to reliably assess the gas-tightness of a tank ventilation system with a simple construction of the tank ventilation system and a simple process control.

Gemäß Anspruch 1 wird ein Verfahren mit folgenden Verfahrensschritten vorgeschlagen:

  • während des Betriebs der Brennkraftmaschine (9) wird durch gesteuertes Schließen des Tankentlüftungsventils (TEV) bei geöffnetem Adsorptionsfilter-Absperrventil (AAV) der Druck in der Tankentlüftungsanlage (1) auf Umgebungsdruckniveau (P0) eingestellt,
  • in einem stabilen Betriebspunkt der Brennkraftmaschine wird das Adsorptionsfilter-Absperrventil (AAV) geschlossen und das Tankentlüftungsventil (TEV) geöffnet, wodurch sich ein Unterdruck aufbaut,
  • der Unterdruck-Aufbau wird bis zu einer vorgegebenen, durch den wenigstens einen Drucksensor (6) erfassten Unterdruck-Aufbauschwelle (PS2) ermittelt, die zugeordnete Unterdruck-Aufbauzeit (t1) wird gemessen,
  • beim Erreichen der Unterdruck-Aufbauschwelle (PS2) wird das Tankentlüftungsventil (TEV) geschlossen, wodurch sich der Unterdruck wieder abbaut,
  • der Unterdruckabbau wird bis zu einer vorgegebenen, durch den wenigstens einen Drucksensor (6) erfassten Unterdruck-Abbauschwelle (PS1) ermittelt und die zugeordnete Unterdruck-Abbauzeit (t2) wird gemessen,
  • die Unterdruck-Aufbauzeit (t1) und die Unterdruck-Abbauzeit (t2) werden zu einer Diagnose-Summenzeit (tD) summiert und mit einer Diagnose-Zeitschwelle (tDS) verglichen, wobei beim Unterschreiten der Diagnose-Zeitschwelle (tDS) ein Fehlersignal erzeugt wird.
According to claim 1, a method with the following method steps is proposed:
  • during operation of the internal combustion engine (9) the pressure in the tank ventilation system (1) is set to ambient pressure level (P 0 ) by controlled closing of the tank ventilation valve (TEV) with the adsorption filter shut-off valve (AAV) open,
  • in a stable operating point of the internal combustion engine, the adsorption filter shut-off valve (AAV) is closed and the tank venting valve (TEV) is opened, whereby a negative pressure builds up,
  • the negative pressure build-up is determined up to a predetermined negative pressure build-up shaft (P S2 ) detected by the at least one pressure sensor (6), the associated negative pressure build-up time (t 1 ) is measured,
  • upon reaching the negative pressure build-up shaft (P S2 ), the tank-venting valve (TEV) is closed, whereby the negative pressure degrades again,
  • the negative pressure reduction is determined up to a predetermined, by the at least one pressure sensor (6) detected vacuum decompression wave (P S1 ) and the associated negative pressure degradation time (t 2 ) is measured,
  • the negative pressure build-up time (t 1 ) and the negative pressure reduction time (t 2 ) are summed to a diagnostic sum time (t D ) and compared with a diagnostic time threshold (t DS ), which falls below the diagnostic time threshold (t DS ) an error signal is generated.

Um sicherzustellen, dass es bei tatsächlich dichter Tankentlüftungsanlage zu keiner unzutreffenden Fehlererkennung kommt, sind bei den Unterdrucksystemen nach dem Stand der Technik die eingangs erläuterten aufwendigen Korrekturen erforderlich, die das Ausgasen des Kraftstoffs berücksichtigen. Solche aufwendigen Korrekturen sind beim vorliegenden erfindungsgemäßen Verfahren entbehrlich, da sich durch die Addition der Unterdruck-Aufbauzeit t1 und der Unterdruck-Abbauzeit t2 eine Kompensation der Ausgasung des Kraftstoffs ergibt. Diese Summe als Diagnose-Summenzeit tD ist ein Maß für die Dichtheit der Tankentlüftungsanlage und wird mit einer korrespondierenden Diagnose-Zeitschwelle tDS verglichen. Beim Unterschreiten der korrespondierenden Diagnose Zeitschwelle tDS wird eine Undichtheit erkannt und ein Fehlersignal für eine Weiterverarbeitung erzeugt.To ensure that there is no incorrect fault detection in actually dense tank ventilation system, in the negative pressure systems of the prior art, the elaborate corrections explained above are required, which take into account the outgassing of the fuel. Such complex corrections are dispensable in the present inventive method, since the addition of the vacuum build-up time t 1 and the negative pressure degradation time t 2 results in a compensation of the outgassing of the fuel. This sum as the diagnostic sum time t D is a measure of the tightness of the tank ventilation system and is compared with a corresponding diagnostic time threshold t DS . When falling below the corresponding diagnosis time threshold t DS a leak is detected and generates an error signal for further processing.

Dazu wird bevorzugt nach Anspruch 2 das Tankentlüftungsventil (TEV) als Regelventil ausgebildet, das bezüglich seines Strömungsdurchgangs steuerbar ist und das während der Unterdruckaufbauzeit t1 langsam bis zu einem vorgegebenen Öffnungsquerschnitt aufgesteuert wird.For this purpose, the tank venting valve (TEV) is preferably designed as a control valve according to claim 2, which is controllable with respect to its flow passage and which is slowly opened during the vacuum build-up time t 1 up to a predetermined opening cross-section.

Eine solche langsame Aufsteuerzeit des Tankentlüftungsventils (TEV) bis zu einem vorgegebenen Öffnungsquerschnitt (Tastverhältnis) kann bevorzugt in einer Größenordnung von ca. 10 Sekunden liegen. Wird eine lange Diagnose-Summenzeit aus der Unterdruck-Aufbauzeit t1 und der Unterdruckabbauzeit t2 erfasst, beispielsweise ca. 50 Sekunden wird die Tankentlüftungsanlage als dicht oder bei einer kurzen Diagnose-Summenzeit tD von beispielsweise 10 Sekunden als undicht erkannt. Die Überwachung mit dem erfindungsgemäßen Verfahren ist in einem Temperaturbereich von -7°C bis 40°C, der gesetzlich vorgeschrieben sein kann, durchführbar.Such a slow opening time of the tank venting valve (TEV) up to a predetermined opening cross section (duty cycle) may preferably be on the order of about 10 seconds. Will be a long diagnostic cumulative time detected from the negative pressure build-up time t 1 and the negative pressure reduction time t 2 , for example, about 50 seconds, the tank ventilation system is detected as tight or at a short diagnostic sum time t D, for example, 10 seconds as leaking. Monitoring with the method according to the invention is feasible in a temperature range of -7 ° C to 40 ° C, which may be required by law.

Die Ausgasung des Kraftstoffs wird auch beim efindungsgemäßen Verfahren berücksichtigt aber ohne dass diese separat bei geschlossenem System bestimmt und zu Korrekturzwecken verwendet werden muss. Durch die Betrachtung des Systemverhaltens beim Aufsteuern des Tankentlüftungsventils (TEV) zur Erzeugung des notwendigen Prüfunterdrucks als Unterdruck-Aufbauschwelle PS2 und das Systemverhalten nach Schließen des Tankentlüftungsventils (TEV) wird die Ausgasung des Kraftstoffs automatisch kompensiert dergestalt,
dass eine kleine Ausgasung eine kurze Unterdruckaufbauzeit P1 und zugeordnet lange Unterdruckabbauzeit t2 bedingt und
dass eine starke Ausgasung eine lange Unterdruckaufbauzeit t1 und eine zugeordnet kurze Unterdruck-Abbauzeit t2 ergibt,
wobei als Maß für die Dichtheit des Tanks die Diagnose-Summenzeit tD im Vergleich zu einer Diagnose-Zeitschwelle tDS maßgeblich ist.The outgassing of the fuel is also taken into account in the process according to the invention, but without these having to be determined separately with the system closed and used for corrective purposes. By considering the system behavior when controlling the tank ventilation valve (TEV) to generate the necessary test vacuum as negative pressure build-up shaft P S2 and the system behavior after closing the tank ventilation valve (TEV), the outgassing of the fuel is automatically compensated in such a way,
that a small outgassing caused a short negative pressure build-up time P 1 and associated with long negative pressure reduction time t 2 and
that a strong outgassing results in a long negative pressure buildup time t 1 and an associated short negative pressure reduction time t 2 ,
as a measure of the tightness of the tank, the diagnostic sum time t D is decisive in comparison to a diagnostic time threshold t DS .

Das Adsorptionsfilter-Absperrventil (AAV) wird bei einer Umsteuerung schnell geschlossen und kann daher nach Anspruch 3 als einfaches schaltbares Magnetventil (2-Punkt-Ventil) ausgebildet sein.The adsorption filter shut-off valve (AAV) is quickly closed during a reversal and can therefore be designed according to claim 3 as a simple switchable solenoid valve (2-point valve).

Der für die Diagnose erforderliche wenigstens eine Drucksensor wird nach Anspruch 4 bevorzugt in der Entlüftungsleitung zwischen dem Kraftstofftank und dem Adsorptionsfilter angeordnet. Je nach den Gegebenheiten kann jedoch auch eine andere Anordnung im Drucksystem vorgenommen werden.The required for the diagnosis at least one pressure sensor according to claim 4 preferably in the vent line between the fuel tank and arranged the adsorption filter. Depending on the circumstances, however, a different arrangement in the printing system can be made.

Für die beiden erforderlichen Druckschwellwerte kann jeweils ein zugeordneter Druckschalter verwendet werden. Alternativ ist auch ein kontinuierlich arbeitender Drucksensor möglich mit dem an den beiden Druckschwellwerten jeweils über eine nachgeordnete Auswerteeinheit Schaltsignale für die jeweils zugeordneten Ventile erzeugt werden. In einer konstruktiv einfachen und kostengünstigen Ausführung nach Anspruch 5 wird ein Druckschalter mit einer Hysterese entsprechend der Unterdruck-Aufbauschwelle PS2 und der Unterdruck-Abbauschwelle PS1 vorgeschlagen.An assigned pressure switch can be used for each of the two required pressure threshold values. Alternatively, a continuously operating pressure sensor is also possible with which switching signals for the respective associated valves are generated at the two pressure threshold values, in each case via a downstream evaluation unit. In a structurally simple and inexpensive embodiment according to claim 5, a pressure switch is proposed with a hysteresis corresponding to the vacuum-Aufbauschwelle P S2 and the vacuum-Abauschwelle P S1 .

Nach Anspruch 6 wird als Adsorptionsfilter ein an sich bekannter Aktivkohlefilter verwendet. Weiter ist in an sich bekannter Weise am freien Ende der Frischluftleitung nach Anspruch 7 ein Luftfilter angeordnet.According to claim 6, a known activated carbon filter is used as adsorption. Next, an air filter is arranged in a conventional manner at the free end of the fresh air line according to claim 7.

Für eine zusätzliche Verfeinerung des Verfahrens kann anstelle einer festen vorgegebenen Diagnosezeitschwelle diese als veränderliche Größe jeweils in Abhängigkeit von erfassten Randbedingungen festgelegt werden, wobei jedoch nach wie vor die vorstehend beschriebene automatische Kompensation bezüglich der Ausgase des Kraftstoffs erfolgt.For an additional refinement of the method, instead of a fixed predefined diagnosis time threshold, this variable can be determined as a variable in each case as a function of detected boundary conditions, but the automatic compensation with respect to the outgassing of the fuel as described above still occurs.

Anhand einer Zeichnung wird die Erfindung näher erläutert.Reference to a drawing, the invention is explained in detail.

Es zeigen:

Fig. 1
eine schematische Darstellung einer Tankentlüftungsanlage und
Fig. 2
ein Ablaufschema des erfindungsgemäßen Verfahrens.
Show it:
Fig. 1
a schematic representation of a tank ventilation system and
Fig. 2
a flow chart of the method according to the invention.

In Fig. 1 ist schematisch eine Tankentlüftungsanlage 1 dargestellt, bestehend aus einem Kraftstofftank 2 mit Einfüllstutzen 3 und einem Adsorptionsfilter 4 als Aktivkohlefilter.In Fig. 1 schematically a tank ventilation system 1 is shown, consisting of a fuel tank 2 with filler neck 3 and an adsorption filter 4 as activated carbon filter.

Der Adsorptionsfilter 4 ist mit dem Kraftstofftank 2 durch eine Entlüftungsleitung 5 verbunden, an der ein Druckschalter 6 mit einer Hysterese für zwei Druckschwellen angeordnet ist.The adsorption filter 4 is connected to the fuel tank 2 through a vent line 5, to which a pressure switch 6 with a hysteresis for two pressure thresholds is arranged.

Weiter ist der Adsorptionsfilter 4 über eine Frischluftleitung 7 und einen endseitigen Luftfilter 8 mit der Atmosphäre verbunden, wobei in der Frischluftleitung 7 ein steuerbares Absperrventil als Adsorptionsfilter-Absperrventil (AAV) in der Art eines schaltbaren Zweipunkt-Magnetventils angeordnet ist.Next, the adsorption filter 4 is connected via a fresh air line 7 and an end air filter 8 to the atmosphere, wherein in the fresh air line 7, a controllable shut-off valve as Adsorptionsfilter shut-off valve (AAV) is arranged in the manner of a switchable two-point solenoid valve.

Zudem ist der Adsorptionsfilter 4 mit dem Saugrohr einer Brennkraftmaschine 9 durch eine Regenerierleitung 10 verbunden, in der ein steuerbares Regenerationsventil als Tankentlüftungsventil (TEV) angeordnet ist, Das Tankentlüftungsventil (TEV) ist als steuerbares Regelventil mit veränderbarem öffnungsquerschnitt ausgebildet. Der Druckschalter 6 sowie die steuerbaren Ventile (AAV) und (TEV) sind an eine (nicht dargestellte) Steuer-/Auswerteeinheit angeschlossen, wobei die im Diagramm nach Fig. 2 dargestellten Verfahrensschritte gesteuert durchgeführt werden:In addition, the adsorption filter 4 is connected to the intake manifold of an internal combustion engine 9 through a regeneration line 10 in which a controllable regeneration valve is arranged as a tank vent valve (TEV). The tank vent valve (TEV) is designed as a controllable control valve with a variable opening cross section. The pressure switch 6 and the controllable valves (AAV) and (TEV) are connected to a (not shown) control / evaluation unit, wherein in the diagram Fig. 2 controlled process steps are performed controlled:

Während des Betriebs der Brennkraftmaschine 9 wird durch gesteuertes Schließen des Tankentlüftungsventils (TEV) bei geöffnetem Adsorptionsfilter-Absperrventil (AAV) der Druck in der Tankentlüftungsanlage 1 auf Umgebungsdruckniveau P0 eingestellt.During operation of the internal combustion engine 9, the pressure in the tank ventilation system 1 is set to ambient pressure level P 0 by controlled closing of the tank ventilation valve (TEV) with the adsorption filter shut-off valve (AAV) open.

In einem stabilen Betriebspunkt der Brennkraftmaschine, beispielsweise im Leerlauf wird das Adsorptionsfilter-Absperrventil (AAV) geschlossen und das Tankentlüftungsventil (TEV) geöffnet. Die Öffnung des Tankentlüftungsventils (TEV) erfolgt allmählich und langsam bis zu einem vorgegebenen Öffnungsquerschnitt entsprechend einem Tastverhältnis in Prozent, wie dies durch die strichlierte Linie im unteren Bereich des Diagramms nach Fig. 2 in Verbindung mit dem Öffnungsdiagramm für TEV dargestellt ist. Durch das langsame Öffnen des Tankentlüftungsventils (TEV) bei geschlossenem Adsorptionsfilter-Absperrventil (AAV) baut sich in der Tankentlüftungsanlage 1 wegen des Unterdrucks im Saugrohr der Brennkraftmaschine 9 ein Unterdruck auf. Der Unterdruckaufbau erfolgt solange bis durch den Druckschalter 6 eine vorgegebene Unterdruck-Aufbauschwelle PS2 erfasst wird. Die Zeit vom Öffnungsbeginn des Tankentlüftungsventils (TEV) bis zum Erreichen der Unterdruck-Aufbauschwelle PS2 wird als zugeordnete Unterdruck-Aufbauzeit t1 gemessen und für die weitere Verwendung gespeichert.In a stable operating point of the internal combustion engine, for example, at idle, the adsorption filter shut-off valve (AAV) is closed and the tank vent valve (TEV) is opened. The opening of the tank ventilation valve (TEV) is gradual and slow up to a given opening cross-section according to a duty cycle in percent, as indicated by the dashed line in the lower part of the diagram Fig. 2 in connection with the opening diagram for TEV. Due to the slow opening of the tank ventilation valve (TEV) with the adsorption filter shut-off valve (AAV) closed, a negative pressure builds up in the tank ventilation system 1 because of the negative pressure in the intake manifold of the internal combustion engine 9. The vacuum build-up takes place until a predetermined negative pressure build-up wave P S2 is detected by the pressure switch 6. The time from the beginning of the opening of the tank venting valve (TEV) until reaching the vacuum build-up shaft P S2 is measured as the associated vacuum build-up time t 1 and stored for further use.

Beim Erreichen der Unterdruckaufbauschwelle PS1 wird das Tankentlüftungsventil (TEV) schnell geschlossen. Auch das Adsorptionsfilter-Absperrventil (AAV) bleibt weiter geschlossen, so dass das System aus dem Kraftstofftank 2, dem Adsorptionsfilter 4, der Frischluftleitung 7, der Regenerierieitung 10 und der Entlüftungsleitung 5 geschlossen ist.Upon reaching the vacuum boosting shaft P S1 , the tank venting valve (TEV) is quickly closed. Also the Adsorptionsfilter shut-off valve (AAV) remains closed, so that the system of the fuel tank 2, the adsorption filter 4, the fresh air line 7, the Regenerierieitung 10 and the vent line 5 is closed.

In diesem geschlossenen System erfolgt nun ein Unterdruckabbau, der je nach Größe einer Leckage mehr oder weniger schnell erfolgt. Dieser Unterdruckabbau wird mit dem Druckschalter 6 bis zu einer Unterdruck-Abbauschwelle PS1 erfasst. Es wird die Zeit für den Unterdruckabbau als Unterdruckabbauzeit t2 gemessen.In this closed system now takes place a vacuum reduction, which takes place more or less quickly depending on the size of a leak. This vacuum reduction is detected with the pressure switch 6 up to a vacuum decompression wave P S1 . It is the time for the vacuum reduction measured as a vacuum reduction time t 2 .

In der Auswerteeinheit werden die Unterdruckaufbauzeit t1 und die Unterdruckabbauzeit t2 zu einer Diagnose-Summenzeit tD summiert und mit einer Diagnose-Zeitschwelle tDS verglichen. Beim Vorliegen einer langen Diagnose-Summenzeit tD und einem Überschreiten der Diagnose-Zeitschwelle tDS wird die Tankentlüftungsanlage 1 als dicht erkannt. Bei einer kurzen Diagnose-Summenzeit tD und einem Unterschreiten der korrespondierenden Diagnosezeitschwelle tDS wird dagegen die Tankentlüftungsanlage als undicht erkannt, wobei ein Fehlersignal zur weiteren Verwertung erzeugt wird.In the evaluation unit, the negative pressure build-up time t 1 and the negative pressure reduction time t 2 are summed to form a diagnostic sum time t D and compared with a diagnosis time threshold t DS . If there is a long diagnostic total time t D and if the diagnostic time threshold t DS is exceeded, the tank ventilation system 1 is identified as being leak-tight. With a short diagnostic sum time t D and below the corresponding diagnostic time threshold t DS , however, the tank ventilation system is detected as leaking, with an error signal is generated for further use.

Claims (8)

  1. Method for testing the gas tightness of a fuel tank purging system (1), comprising
    - a fuel tank (2),
    - an adsorption filter (4),
    - a purging line (5) connecting the fuel tank (2) to the adsorption filter (4),
    - a fresh air line (7) connecting the adsorption filter (4) to the atmosphere, said fresh air line having arranged within it a controllable shut-off valve as adsorption filter shut-off valve (AAV),
    - a regeneration line (10) connecting the adsorption filter (4) to the air inlet pipe of an internal combustion engine (9), said regeneration line having arranged within it a controllable regeneration valve as tank purging valve (TEV),
    - at least one pressure sensor (6) in the tank purging system (1), and
    - a control/evaluation unit, wherein for testing the tank purging system (1), with the adsorption filter shut-off valve (AAV) closed, through controlled opening of the tank purging valve (TEV), in the tank purging system a negative pressure is generated whose variation is evaluated after controlled closing of the tank purging valve (TEV) for a tank leakage diagnosis,
    characterised by the following method steps:
    - during operation of the internal combustion engine (9), by controlled closing of the tank purging valve (TEV) with the adsorption filter shut-off valve (AAV) open, the pressure in the tank purging system (1) is set to the ambient pressure level (P0),
    - at one operating point of the internal combustion engine, the adsorption filter shut-off valve (AAV) is closed and the tank purging valve (TEV) is opened, so that a negative pressure is built up,
    - the build-up of negative pressure is detected as far as a predetermined negative pressure build-up threshold (PS2) by the at least one pressure sensor (6) and the associated negative pressure build-up time (t1) is measured,
    - on reaching the negative pressure build-up threshold (PS2), the tank purging valve (TEV) is closed, so that the negative pressure decreases again,
    - the negative pressure decrease is detected as far as a predetermined negative pressure decrease threshold (PS1) by the at least one pressure sensor (6) and the associated negative pressure decrease time (t2) is measured,
    - the negative pressure build-up time (t1) and the negative pressure decrease time (t2) are totalled to give a diagnosis total time (tD) and this is compared with a diagnosis time threshold (tDS), wherein if it undershoots the diagnosis time threshold (tDS), an error signal is generated.
  2. Method according to claim 1, characterised in that the tank purging valve (TEV) is a control valve which is controllable with regard to its flow pressure variation and which, during the negative pressure build-up time (t1), is slowly driven to a predetermined opening cross-section (%).
  3. Method according to claim 1 or 2, characterised in that the adsorption filter shut-off valve (AAV) is a switchable solenoid valve.
  4. Method according to one of the claims 1 to 3, characterised in that the at least one pressure sensor (6) is arranged in the purging line (5) between the fuel tank (2) and the adsorption filter (4).
  5. Method according to one of the claims 1 to 4, characterised in that the pressure sensor is a pressure switch (6) with hysteresis corresponding to the negative pressure build-up threshold (PS2) and the negative pressure decrease threshold (PS1.).
  6. Method according to one of the claims 1 to 5, characterised in that the adsorption filter (4) is an activated carbon filter.
  7. Method according to one of the claims 1 to 6, characterised in that an air filter (8) is arranged at the free end of the fresh air line (7).
  8. Method according to one of the claims 1 to 7, characterised in that the diagnosis time threshold (tDS) is set as a variable value depending, in each case, on detected limit conditions.
EP06014440A 2005-08-31 2006-07-12 Method for performing a leakage test of a fuel tank purge system Expired - Fee Related EP1760303B1 (en)

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Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005054880B3 (en) * 2005-11-17 2007-06-28 Siemens Ag Method for checking the tightness of a tank ventilation system without pressure sensor
DE102007016217A1 (en) * 2007-04-04 2008-10-09 Audi Ag Low pressure valve movability testing method for e.g. car, involves testing position of low pressure valve in response to increase in pressure inside of fuel system when low pressure valve resides in closed condition
WO2009059159A2 (en) * 2007-11-02 2009-05-07 King Kegan Y Pressure tank fault detector and method
DE102008011453B4 (en) * 2008-02-27 2021-08-26 Dr. Ing. H.C. F. Porsche Aktiengesellschaft Method and test stand for determining a buffer effect of an activated carbon filter in a motor vehicle tank ventilation system
EP2541224B1 (en) * 2011-06-27 2014-03-26 Elster GmbH Method for checking that safety valves are sealed
DE102014009213A1 (en) * 2014-06-25 2015-12-31 Mann+Hummel Gmbh Internal combustion engine with tank ventilation system
US20160084405A1 (en) * 2014-09-24 2016-03-24 George Paul Baker, Jr. Online full stroke testing overpressurization safety relief valve
DE102016121900A1 (en) * 2016-11-15 2018-05-17 Dr. Ing. H.C. F. Porsche Aktiengesellschaft Method for diagnosing a tank venting valve
US10337537B2 (en) 2017-08-30 2019-07-02 Caterpillar Inc. System and method for determining a health status of a tank

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4342431A1 (en) 1993-12-11 1995-06-14 Bosch Gmbh Robert Procedure for determining statements about the condition of a tank ventilation system
US5817925A (en) * 1997-03-26 1998-10-06 Siemens Electric Limited Evaporative emission leak detection system
DE19713085C2 (en) * 1997-03-27 2003-06-12 Siemens Ag Method for checking the functionality of a tank ventilation system for a motor vehicle
DE19830234C2 (en) 1998-07-07 2000-06-08 Daimler Chrysler Ag Method for testing a tank system in a motor vehicle for leaks
US6164123A (en) 1999-07-06 2000-12-26 Ford Global Technologies, Inc. Fuel system leak detection
US6382017B1 (en) * 1999-11-10 2002-05-07 Delphi Technologies, Inc. Evaporative emission leak detection method with vapor generation compensation
US6334355B1 (en) * 2000-01-19 2002-01-01 Delphi Technologies, Inc. Enhanced vacuum decay diagnostic and integration with purge function
US6840089B2 (en) * 2001-01-30 2005-01-11 Hickok Incorporated Fuel tank tester
DE10140954A1 (en) * 2001-08-27 2003-04-03 Bosch Gmbh Robert Method and device for the emission-monitoring operation of a storage container for storing a volatile medium, in particular a fuel storage tank of a motor vehicle
DE10143329A1 (en) 2001-09-05 2003-04-03 Bosch Gmbh Robert Detecting leaks in motor vehicle tank venting systems, involves determining correction value representing gas formation with venting, ventilating valves closed after detecting pressure change
US6807847B2 (en) * 2002-02-21 2004-10-26 Delphi Technologies, Inc. Leak detection method for an evaporative emission system including a flexible fuel tank
DE10217378B3 (en) * 2002-04-18 2004-01-29 Siemens Ag Leak detection method in a plastic container

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US20070044550A1 (en) 2007-03-01
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US7418856B2 (en) 2008-09-02

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