EP0819213A1 - Device for detecting a leak in a fuel-supply system - Google Patents

Device for detecting a leak in a fuel-supply system

Info

Publication number
EP0819213A1
EP0819213A1 EP96902879A EP96902879A EP0819213A1 EP 0819213 A1 EP0819213 A1 EP 0819213A1 EP 96902879 A EP96902879 A EP 96902879A EP 96902879 A EP96902879 A EP 96902879A EP 0819213 A1 EP0819213 A1 EP 0819213A1
Authority
EP
European Patent Office
Prior art keywords
fuel
pressure
leak
fuel pump
gradient
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP96902879A
Other languages
German (de)
French (fr)
Other versions
EP0819213B1 (en
Inventor
Dieter-Andreas Dambach
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP0819213A1 publication Critical patent/EP0819213A1/en
Application granted granted Critical
Publication of EP0819213B1 publication Critical patent/EP0819213B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • 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
    • F02M65/00—Testing fuel-injection apparatus, e.g. testing injection timing ; Cleaning of fuel-injection apparatus
    • F02M65/006—Measuring or detecting fuel leakage of fuel injection apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B77/00—Component parts, details or accessories, not otherwise provided for
    • F02B77/08—Safety, indicating or supervising devices
    • F02B77/088—Safety, indicating or supervising devices relating to tightness
    • 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
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/02—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively
    • F02M63/0205—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively for cutting-out pumps or injectors in case of abnormal operation of the engine or the injection apparatus, e.g. over-speed, break-down of fuel pumps or injectors ; for cutting-out pumps for stopping the engine
    • 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
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/02—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively
    • F02M63/0225—Fuel-injection apparatus having a common rail feeding several injectors ; Means for varying pressure in common rails; Pumps feeding common rails
    • 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
    • F02M65/00—Testing fuel-injection apparatus, e.g. testing injection timing ; Cleaning of fuel-injection apparatus
    • 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
    • F02M69/00—Low-pressure fuel-injection apparatus ; Apparatus with both continuous and intermittent injection; Apparatus injecting different types of fuel
    • F02M69/46—Details, component parts or accessories not provided for in, or of interest apart from, the apparatus covered by groups F02M69/02 - F02M69/44
    • F02M69/462—Arrangement of fuel conduits, e.g. with valves for maintaining pressure in the pipes after the engine being shut-down
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • F02D2041/224—Diagnosis of the fuel system
    • F02D2041/225—Leakage detection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2231/00—Fail safe
    • F23N2231/18—Detecting fluid leaks

Definitions

  • the invention relates to a device for detecting a leak in a Kraf material supply system in an internal combustion engine according to the preamble of the main claim.
  • the fuel In motor vehicles with an internal combustion engine, the fuel is conveyed from the fuel tank with the aid of an electric fuel pump and supplied to the injection valves via fuel lines. Excess fuel usually gets back into the fuel tank via a return line. To ensure that a sufficient amount of fuel is always available, the fuel is delivered by the electric fuel pump with an overpressure.
  • the electric fuel pump is regulated in a suitable manner, for example by measuring the fuel pressure and using it for evaluation.
  • the return line is dispensed with
  • the device according to the invention with the features of the main claim has the advantage that the entire fuel supply system can be monitored for leaks.
  • the simplicity of the device according to the invention is particularly advantageous, which can be used in most conventional fuel supply systems without the use of complex additional components.
  • This advantage is achieved by measuring the fuel pressure with the aid of a pressure sensor and by checking after switching off the electric fuel pump whether the overpressure in the fuel supply system changes in a specifiable manner. If this is not the case, it can be immediately recognized that there is a leak or a leak in the fuel supply system.
  • the leak detection can be carried out as a so-called “on-board diagnosis” and takes place, for example, in the control unit of the motor vehicle. It is also advantageous that the leak detection can be used both in fuel systems with a return line and in those without a return line.
  • the leak detection can advantageously also take place under special operating conditions of the internal combustion engine, for example if the control unit detects an engine overrun phase in which no fuel is supplied to the injection valves during the overrun fuel cutoff. During the overrun fuel cut-off, the electric fuel pump is then switched off and the leak diagnosis is then carried out.
  • a leak diagnosis during the overrun mode has the advantages that it can be carried out more often, that it can be repeated while driving and that no control unit overrun is required to carry out the diagnosis.
  • the figure shows the components of a fuel supply system of an internal combustion engine that are necessary for understanding the invention.
  • the fuel tank is designated by 10, in the fuel tank there is the fuel pump 11, usually an electric fuel pump and a check valve 12, which is integrated into the fuel pump 11, for example.
  • the flow 13 leads from the fuel pump 11 to the fuel distributor 14, via which the fuel is supplied to the injection valves 15.
  • the control of the fuel pressure takes place with the help of the pressure regulator 16, which is connected to the fuel tank 10 in a fuel supply system with a fuel return line or return 17 via the return 17 and optionally a pressure control valve 18 and optionally via a connection 28 to the intake manifold Internal combustion engine.
  • the fuel tank 10 is connected to the intake manifold 21 of the internal combustion engine via a line 19 in which there is a ventilation valve 20. Between the fuel tank 10 and the vent valve 20 there is also an adsorption filter 22 in which the fuel vapors are collected.
  • the control device 23 to which the required quantities are supplied or which emits the required control signals, is used to control or regulate the internal combustion engine.
  • the necessary calculations are carried out in the control unit.
  • the leak detection according to the invention is also carried out in the control unit.
  • a pressure sensor 24 is shown in the figure, which measures the pressure p of the fuel in the distributor 14.
  • a differential pressure sensor 25 which is connected to the return line 17 via a line 26 and measures the differential pressure ⁇ p.
  • the connections between the control unit 23 and the fuel pump 11 and the connection between the control unit and the venting valve 20, which depend on the prevailing conditions, are indicated in the figure as connections via which controls take place is closed or open. Furthermore, there may be a connection between the control unit 23 and the pressure regulator 16.
  • the leak diagnosis can run under the following boundary conditions:
  • control unit If the control unit detects an engine overrun phase, an overrun cut-off can take place during which no more fuel is supplied to the injection valves. The fuel pump can then be switched off during the fuel cut-off.
  • the check valve 12 in the fuel circuit which is integrated, for example, in the fuel pump 11, maintains the system pressure p for some time after the fuel pump has been switched off.
  • the pressure sensor 24, which measures the fuel pressure p is located on the pressure side of the check valve 12 in the fuel supply system. Even after the fuel pump 11 has been switched off, this pressure is measured and evaluated in the control unit.
  • the control device or that contained in the control device can be obtained from the pressure curve obtained Microprocessor determine the pressure gradient.
  • This pressure gradient which serves as a measure of the pressure change, can be determined according to one of the known gradient determination methods, for example the pressure gradient can be determined from two pressure values which were determined at a predeterminable time interval from one another.
  • control unit is alerted to the presence of a leak or one
  • Leaks are closed and a display 2 "can take place, for example, or warning signals can be emitted.
  • a sensor with an analog output variable can be used as the pressure sensor 24; it is also possible to use a contact switch in which the pressure gradient gradp is determined over the time between the switching off of the fuel pump and the switching time of the switch when the system pressure falls below a predetermined value .
  • the pressure sensor 24 is preferably arranged at the location shown in the figure, but it can also be located elsewhere. In the case of return-free fuel supply systems, the entire fuel system can be monitored if the pressure sensor 24 is installed at the point indicated in the figure.
  • Fuel supply systems with a fuel return 17 can also be completely monitored, that is to say also in the return area, provided that they are in addition to the check valve
  • a pressure holding valve 18 is also attached to the fuel pump 11 at the outlet opening of the return line in the fuel tank. It is then possible to monitor not only the forward flow area but also the return area up to the exit into the fuel tank.
  • a pressure sensor in this case a differential pressure sensor 25 is used, which measures the differential pressure ⁇ p between the fuel supply and the return, for example at the fuel pressure regulator.
  • the combination of the detection of combustion misfires on a specific injection valve and a leak detected in the fuel system at the same time can be used to infer a leaky injection valve and thereby prevent or prevent possible engine damage the leaky valve can be located correctly right away.
  • the control unit can detect the leak each time the fuel pump is switched off. It is also possible for this detection to take place only under predefinable conditions, for example only after the fuel pump has been switched on for a long time. Since the method for leak detection takes place in the control unit of the internal combustion engine, such a detection is an "on-board diagnosis".
  • the detection of an existing leak in the fuel supply system or directly in an injection valve can be stored in a memory of the control unit 23 and is then available as information the next time the workshop is visited.
  • the control unit must continue to run for a sufficient period of time, ie the control unit must still be supplied with voltage after the BKM has been switched off so that the required functions still work can expire. If the diagnosis is to take place in overrun, it is necessary that the fuel pump can be controlled directly by the control unit, ie independently of the ignition lock.

Abstract

Described is a device for detecting a leak in a fuel-supply system, the device measuring the fuel-pressure gradient after the fuel pump has been switched off and indicating the presence of a leak if the over pressure in part of the fuel-supply system drops more rapidly than expected.

Description

Einrichtung zur Erkennung eines Lecks in einem Kraftstoff-Device for detecting a leak in a fuel
VersorgungssystemSupply system
Stand der TechnikState of the art
Die Erfindung geht aus von einer Einrichtung zur Erkennung eines Lecks in einem Kraf stoffversorgungssystem bei einer Brennkraf maschine nach der Gattung des Hauptanspruchs.The invention relates to a device for detecting a leak in a Kraf material supply system in an internal combustion engine according to the preamble of the main claim.
Bei Kraftfahrzeugen mit einer Brennkraftmaschine wird der Kraftstoff mit Hilfe einer Elektrokraftstoffpumpe aus dem Kraf stoffbehälter gefördert und über Kraftstoffleitungen den Einspritzventilen zugeführt. Überschüssiger Kraftstoff gelangt üblicherweise über eine Rücklaufleitung in den Kraf stoffbehälter zurück. Damit stets eine ausreichende Menge an Kraftstoff zur Verfügung steht, wird der Kraftstoff von der Elektrokraftstoffpumpe mit einem Überdruck geför- dert, dabei erfolgt die Regelung der Elektrokraftstoffpumpe in geeigneter Weise, indem beispielsweise der Kraftstoff- druck gemessen und zur Auswertung verwendet wird.In motor vehicles with an internal combustion engine, the fuel is conveyed from the fuel tank with the aid of an electric fuel pump and supplied to the injection valves via fuel lines. Excess fuel usually gets back into the fuel tank via a return line. To ensure that a sufficient amount of fuel is always available, the fuel is delivered by the electric fuel pump with an overpressure. The electric fuel pump is regulated in a suitable manner, for example by measuring the fuel pressure and using it for evaluation.
Bei einigen Kraftstoffversorgungssystemen wird auf die Rück- laufleitung verzichtet, es erfolgt eine bedarfsorientierteIn some fuel supply systems, the return line is dispensed with;
Regelung der Kraftstoffördermenge. Bei beiden Kraftstoffver¬ sorgungssystemen ist es erforderlich, ein Leck bzw. eine Un- dichtheit im Kraftstoffkreislauf sicher und zuverlässig zu erkennen, da andernfalls austretender Kraftstoff oder aus¬ tretende Kraftstoffdämpfe zum einen zu unzulässigen Emissionswerten führen könnten und da zum anderen bei un¬ dichten Einspritzventilen unter Umständen Motorschäden auf- treten könnten, wenn infolge der undichten Einspritzventile ungewollt Kraftstoff in einen Motorzylinder gelangen könnte.Regulation of the fuel flow. In both fuel supply systems, it is necessary to reliably and reliably seal a leak or a leak in the fuel circuit Recognize that otherwise escaping fuel or escaping fuel vapors could lead to impermissible emission values on the one hand and, on the other hand, engine damage could occur in the case of leaky injectors if fuel could accidentally get into an engine cylinder as a result of the leaky injectors.
Ausgehend von dieser Problemstellung sind bereits Verfahren bzw. Vorrichtungen bekannt, mit deren Hilfe undichte Ein- spritzventile erkannt werden können oder mit deren Hilfe im Zusammenhang mit einem Tankentlüftungssystem eine Leckerken¬ nung durchgeführt wird. Solche Verfahren bzw. Vorrichtungen sind beispielsweise in der DE-OS 42 43 178 oder der DE-OS 40 40 896 beschrieben. Dabei wird in der DE-OS 42 43 178 ein Verfahren angegeben, bei dem undichte Einspritzventile erkannt werden, indem jeweils beim Start der Brennkraf maschine auch Zylinder gezündet werden, in die noch kein Kraftstoff eingespritzt wurde. Führen solche Zündungen zu einem erkennbaren Anstieg der Drehzahl, muß das zugehörige Einspritzventil undicht sein, so daß Kraftstoff in den betreffenden Zylinder gelangen konnte.Starting from this problem, methods and devices are already known, with the aid of which leaky injection valves can be detected or with the aid of which leak detection is carried out in connection with a tank ventilation system. Such methods and devices are described for example in DE-OS 42 43 178 or DE-OS 40 40 896. In DE-OS 42 43 178, a method is specified in which leaky injection valves are detected by firing cylinders at the start of the internal combustion engine, into which no fuel has yet been injected. If such ignitions lead to a noticeable increase in engine speed, the associated injection valve must be leaky so that fuel could get into the cylinder in question.
Bei dem aus der DE-OS 40 40 896 bekannten Verfahren bzw. der Vorrichtung zum Überprüfen der Dichtheit eines Tankentlüf- tungssystems wird geprüft, ob nach dem Öffnen des Tankent¬ lüf ungsven ils sich der im Tank aufbauende Unterdruck in der vorhergesagten Weise ändert. Dazu wird die gesamte An¬ lage auf Funktionsfähigkeit überwacht und es erfolgt eine Beurteilung der Anlage als nicht funktionsfähig, wenn der Unterdruckaufbaugradient unter einem vorgebbaren Schwellwert liegt.In the method known from DE-OS 40 40 896 or the device for checking the tightness of a tank ventilation system, it is checked whether the vacuum build-up in the tank changes in the predicted manner after the tank ventilation valve has been opened. For this purpose, the entire system is monitored for functionality and the system is assessed as inoperable if the negative pressure build-up gradient is below a predefinable threshold value.
Beide bekannten Systeme zur Erkennung von Undichtheiten in einem Teilbereich des Kraftstoffversorgungssystems einer Brennkraftmaschine sind entweder ziemlich aufwendig oder ge- währleisten nicht, daß eine Leckerkennung im gesamten Kraft¬ stoffVersorgungssystem möglich ist.Both known systems for the detection of leaks in a partial area of the fuel supply system of an internal combustion engine are either rather complex or do not ensure that leak detection is possible in the entire fuel supply system.
Vorteile der ErfindungAdvantages of the invention
Die erfindungsgemäße Einrichtung mit den Merkmalen des Hauptanspruchs hat demgegenüber den Vorteil, daß das gesamte Kraftstoffversorgungssystem auf Dichtheit überwacht werden kann. Besonders vorteilhaft ist die Einfachheit der erfin- dungsgemäßen Einrichtung, die bei den meisten herkömmlichen Kraftstoffversorgungssystemen ohne Einsatz aufwendiger zu¬ sätzlicher Bauelemente eingesetzt werden kann.The device according to the invention with the features of the main claim has the advantage that the entire fuel supply system can be monitored for leaks. The simplicity of the device according to the invention is particularly advantageous, which can be used in most conventional fuel supply systems without the use of complex additional components.
Erzielt wird dieser Vorteil, indem mit Hilfe eines Drucksen- sors der Kraftstoffdruck gemessen wird und indem nach Ab¬ schalten der Elektrokraftstoffpumpe überprüft wird, ob sich der Überdruck im Kraftstoffversorgungssystem in einer vor¬ gebbaren Weise ändert. Ist dies nicht der Fall, kann sofort erkannt werden, daß ein Leck bzw. eine Undichtheit im Kraft- Stoffversorgungssystem vorhanden ist.This advantage is achieved by measuring the fuel pressure with the aid of a pressure sensor and by checking after switching off the electric fuel pump whether the overpressure in the fuel supply system changes in a specifiable manner. If this is not the case, it can be immediately recognized that there is a leak or a leak in the fuel supply system.
Weitere Vorteile der Erfindung werden durch die in den Unteransprüchen aufgeführten Maßnahmen erzielt. Dabei ist besonders vorteilhaft, daß die Leckerkennung als sogenannte "on-board-Diagnose" durchführbar ist und beispielsweise im Steuergerät des Kraftfahrzeuges abläuft. Weiterhin ist vor¬ teilhaft, daß die Leckerkennung sowohl bei KraftstoffSyste¬ men mit Rücklauf als auch bei solchen ohne Rücklaufleitung eingesetzt werden kann.Further advantages of the invention are achieved by the measures listed in the subclaims. It is particularly advantageous that the leak detection can be carried out as a so-called "on-board diagnosis" and takes place, for example, in the control unit of the motor vehicle. It is also advantageous that the leak detection can be used both in fuel systems with a return line and in those without a return line.
In Verbindung mit anderen Auswertungen und Fehlererkennun¬ gen, die im Steuergerät ablaufen, kann genau erkannt werden, welches Einspritzventil undicht ist. Dies ist beispielsweise möglich, indem die Leckerkennung mit einem Verfahren zur Verbrennungsaussetzererkennung kombiniert wird. Die Leckerkennung kann vorteilhafterweise auch bei speziel¬ len Betriebsbedingungen der Brennkraftmaschine erfolgen, beispielsweise wenn das Steuergerät eine Motorschubphase er¬ kennt, in der dem Motor während der Schubabschaltung den Einspritzventilen kein Kraftstoff mehr zugeführt wird. Während der Schubabschaltung wird dann die Elektrokraft- stoffpumpe abgeschaltet und danach die Leckdiagnose durchge¬ führt.In conjunction with other evaluations and error detections that take place in the control unit, it can be precisely recognized which injector is leaking. This is possible, for example, by combining the leak detection with a misfire detection method. The leakage detection can advantageously also take place under special operating conditions of the internal combustion engine, for example if the control unit detects an engine overrun phase in which no fuel is supplied to the injection valves during the overrun fuel cutoff. During the overrun fuel cut-off, the electric fuel pump is then switched off and the leak diagnosis is then carried out.
Eine Leckdiagnose während des Schubbetriebeε hat die Vortei¬ le, daß sie öfters durchgeführt werden kann, daß sie während einer Fahrt wiederholbar ist und daß zur Durchführung der Diagnose kein Steuergerätenachlauf erforderlich ist.A leak diagnosis during the overrun mode has the advantages that it can be carried out more often, that it can be repeated while driving and that no control unit overrun is required to carry out the diagnosis.
Zeichnungdrawing
Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und wird in der nachfolgenden Beschreibung näher erläutert. Dabei zeigt die einzige Figur schematisch die wesentlichen Bestandteile eines Kraftstoff ersorgungs¬ systems, in dem die erfindungsgemäße Leckerkennung ablaufen kann.An embodiment of the invention is shown in the drawing and is explained in more detail in the following description. The single figure shows schematically the essential components of a fuel supply system in which the leak detection according to the invention can take place.
Beschreibung des AusführungsbeispielsDescription of the embodiment
In der Figur sind die für das Verständnis der Erfindung er¬ forderlichen Bestandteile eines Kraftstoffversorgungssyste- mes einer Brennkraftmaschine dargestellt. Dabei ist der Kraftstoffbehälter mit 10 bezeichnet, im Kraftstoffbehälter befindet sich die Kraftstoffpumpe 11, üblicherweise eine Elektrokraftstoffpumpe sowie ein Rückschlagventil 12, das beispielsweise in die Kraftstoffpumpe 11 integriert ist. Von der Kraftstoffpumpe 11 führt der Vorlauf 13 zum Kraft¬ stoffverteiler 14, über den der Kraftstoff den Einspritzven¬ tilen 15 zugeführt wird. Die Regelung des Kraftstoffdruckes erfolgt mit Hilfe des Druckreglers 16, der bei einem Kraft¬ stoffversorgungssystem mit einer Kraftstoffrückführleitung bzw. Rücklauf 17 über den Rücklauf 17 sowie gegebenenfalls ein Druckhalteventil 18 mit dem Kraftstoffbehälter 10 in Verbindung steht und gegebenenfalls über eine Verbindung 28 mit dem Saugrohr der Brennkraftmaschine.The figure shows the components of a fuel supply system of an internal combustion engine that are necessary for understanding the invention. The fuel tank is designated by 10, in the fuel tank there is the fuel pump 11, usually an electric fuel pump and a check valve 12, which is integrated into the fuel pump 11, for example. The flow 13 leads from the fuel pump 11 to the fuel distributor 14, via which the fuel is supplied to the injection valves 15. The control of the fuel pressure takes place with the help of the pressure regulator 16, which is connected to the fuel tank 10 in a fuel supply system with a fuel return line or return 17 via the return 17 and optionally a pressure control valve 18 and optionally via a connection 28 to the intake manifold Internal combustion engine.
Zur Entlüftung ist der Kraftstoffbehälter 10 über eine Lei¬ tung 19, in der sich ein Entlüftungsventil 20 befindet mit dem Saugrohr 21 der Brennkraftmaschine verbunden. Zwischen dem Kraftstoffbehälter 10 und dem Entlüftungsventil 20 ist noch ein Adsorbtionsfilter 22 vorhanden, in dem die Kraft¬ stoffdämpfe aufgefangen werden.For ventilation, the fuel tank 10 is connected to the intake manifold 21 of the internal combustion engine via a line 19 in which there is a ventilation valve 20. Between the fuel tank 10 and the vent valve 20 there is also an adsorption filter 22 in which the fuel vapors are collected.
Zur Steuerung bzw. Regelung der Brennkraftmaschine dient das Steuergerät 23, dem die erforderlichen Größen zugeführt wer- den bzw. das die erforderlichen Ansteuersignale abgibt. Im Steuergerät laufen die erforderlichen Berechnungen ab. Die erfindungsgemäße Leckerkennung wird ebenfalls im Steuergerät vorgenommen.The control device 23, to which the required quantities are supplied or which emits the required control signals, is used to control or regulate the internal combustion engine. The necessary calculations are carried out in the control unit. The leak detection according to the invention is also carried out in the control unit.
Die Messung der zur Steuerung bzw. Regelung benötigten Größe erfolgt mit Hilfe geeigneter Sensoren. In der Figur ist zum einen ein Drucksensor 24 dargestellt, der den Druck p des Kraftstoffs im Verteiler 14 mißt. Alternativ zum Drucksensor 24 kann ein Differenzdrucksensor 25 vorhanden sein, der über eine Leitung 26 mit dem Rücklauf 17 in Verbindung steht und den Differenzdruck δp mißt. Als Verbindungen, über die An- steuerungen erfolgen, sind in der Figur angegeben die Ver¬ bindung zwischen dem Steuergerät 23 und der Kraftstoffpumpe 11 sowie die Verbindung zwischen dem Steuergerät und dem Entlüftungsventil 20, das je nach herrschenden Bedingungen geschlossen oder geöffnet ist. Weiterhin kann eine Verbin¬ dung zwischen dem Steuergerät 23 und dem Druckregler 16 vor¬ handen sein.The size required for control or regulation is measured with the aid of suitable sensors. A pressure sensor 24 is shown in the figure, which measures the pressure p of the fuel in the distributor 14. As an alternative to the pressure sensor 24, there can be a differential pressure sensor 25 which is connected to the return line 17 via a line 26 and measures the differential pressure δp. The connections between the control unit 23 and the fuel pump 11 and the connection between the control unit and the venting valve 20, which depend on the prevailing conditions, are indicated in the figure as connections via which controls take place is closed or open. Furthermore, there may be a connection between the control unit 23 and the pressure regulator 16.
Mit der in der Figur dargestellten Einrichtung kann dieWith the device shown in the figure, the
Kraftstoffversorgungssystemleckdiagnose ablaufen. Die Leck¬ diagnose kann unter folgenden Randbedingungen ablaufen:Fuel supply system leak diagnosis run. The leak diagnosis can run under the following boundary conditions:
1) Sobald das Steuergerät eine Motorschubphase erkennt, in der dem Motor während der "Schubabschaltung" der Einspritz¬ ventile 15 kein Kraftstoff mehr zugeführt wird. Dann wird die Kraftstoffpumpe 11 abgeschaltet und die Prüfung durchge¬ führt.1) As soon as the control unit detects an engine overrun phase in which no more fuel is supplied to the engine during the "overrun fuel cut-off" of the injection valves 15. Then the fuel pump 11 is switched off and the test is carried out.
2) Falls das Steuergerät einen sogenannten "Nachlauf" be¬ sitzt, d. h. nach dem Abstellen des Motors noch für eine gewisse "Haltezeit" eingeschaltet bleibt, kann die Diagnose während dieser Haltezeit durchgeführt werden, nachdem die Kraftstoffpumpe 11 abgeschaltet wird.2) If the control device has a so-called "overrun", i. H. remains on for a certain "hold time" after the engine has been switched off, the diagnosis can be carried out during this hold time after the fuel pump 11 is switched off.
3) Wenn das Steuergerät eine Motorschubphase erkennt, kann eine Schubabschaltung erfolgen, während der den Einspritz¬ ventilen kein Kraftstoff mehr zugeführt wird. Während der Schubabschaltung kann dann die Kraftstoffpumpe abgeschaltet werden.3) If the control unit detects an engine overrun phase, an overrun cut-off can take place during which no more fuel is supplied to the injection valves. The fuel pump can then be switched off during the fuel cut-off.
Das Rückschlagventil 12 im Kraftstoffkreislauf, das bei¬ spielsweise in der Kraftstoffpumpe 11 integriert ist, hält nach dem Abschalten der Kraftstoffpumpe den Systemdruck p noch einige Zeit aufrecht. Im KraftstoffVersorgungssystem liegt auf der Druckseite des Rückschlagventils 12 der Druck¬ sensor 24, der den Kraftstoffdruck p mißt. Auch nach dem Ab¬ stellen des Kraftstoffpumpe 11 wird dieser Druck gemessen und im Steuergerät ausgewertet. Aus dem erhaltenen Druckver- lauf kann das Steuergerät bzw. der im Steuergerät enthaltene Mikroprozessor den Druckgradienten ermitteln. Dieser Druck¬ gradient, der als Maß für die Druckänderung dient, kann nach einer der bekannten Gradientenermittlungsmethoden bestimmt werden, beispielsweise kann der Druckgradient aus zwei Druckwerten ermittelt werden, die in einem vorgebbaren Zeit- abstand voneinander ermittelt wurden.The check valve 12 in the fuel circuit, which is integrated, for example, in the fuel pump 11, maintains the system pressure p for some time after the fuel pump has been switched off. The pressure sensor 24, which measures the fuel pressure p, is located on the pressure side of the check valve 12 in the fuel supply system. Even after the fuel pump 11 has been switched off, this pressure is measured and evaluated in the control unit. The control device or that contained in the control device can be obtained from the pressure curve obtained Microprocessor determine the pressure gradient. This pressure gradient, which serves as a measure of the pressure change, can be determined according to one of the known gradient determination methods, for example the pressure gradient can be determined from two pressure values which were determined at a predeterminable time interval from one another.
Ist der ermittelte Druckgradient steiler als eine in ge¬ eigneter Weise festzulegende Schwelle SW, wird im Steuergerät auf das Vorliegen einer Undichtheit bzw. einesIf the determined pressure gradient is steeper than a threshold SW to be determined in a suitable manner, the control unit is alerted to the presence of a leak or one
Lecks geschlossen und es kann beispielsweise eine Anzeige 2" erfolgen bzw. es können Warnsignale abgegeben werden.Leaks are closed and a display 2 "can take place, for example, or warning signals can be emitted.
Als Drucksensor 24 kann ein Sensor mit analoger Ausgangs- große verwendet werden, es ist auch möglich, einen Kontakt¬ schalter einzusetzen, bei dem der Druckgradient gradp über die Zeit zwischen dem Ausschalten der Kraftstoffpumpe und dem Schaltzeitpunkt des Schalters bei Unterschreitung eines vorzugebenden Systemsdrucks bestimmt wird.A sensor with an analog output variable can be used as the pressure sensor 24; it is also possible to use a contact switch in which the pressure gradient gradp is determined over the time between the switching off of the fuel pump and the switching time of the switch when the system pressure falls below a predetermined value .
Der Drucksensor 24 wird vorzugsweise an der in der Figur dargestellten Stelle angeordnet, er kann sich aber auch an anderer Stelle befinden. Bei rücklauffreien KraftstoffVer¬ sorgungssystemen kann dabei das gesamte Kraftstoffsystem überwacht werden, wenn der Drucksensor 24 an der in der Figur angegebenen Stelle eingebaut wird.The pressure sensor 24 is preferably arranged at the location shown in the figure, but it can also be located elsewhere. In the case of return-free fuel supply systems, the entire fuel system can be monitored if the pressure sensor 24 is installed at the point indicated in the figure.
Kraftstoffversorgungssysteme mit Kraftstoffrücklauf 17 kön¬ nen ebenfalls vollständig überwacht werden, also auch im Rücklaufbereich, sofern zusätzlich zu dem RückschlagventilFuel supply systems with a fuel return 17 can also be completely monitored, that is to say also in the return area, provided that they are in addition to the check valve
12 an der Kraftstoffpumpe 11 noch ein Druckhalteventil 18 an der Austrittsöffnung der Rücklaufleitung im Kraftstoffbehäl¬ ter angebracht wird. Es ist dann möglich, nicht nur den Vor¬ lauf-, sondern auch den Rücklaufbereich bis zum Austritt in den Kraftstoffbehälter zu überwachen. Als Drucksensor wird in diesem Fall ein Differenzdrucksensor 25 verwendet, der den Differenzdruck δp zwischen dem Kraftstoffvorlauf und dem Rücklauf mißt, beispielsweise am Kraftstoffdruckregier. Bei Undichtheiten im Vorlauf ist der Gradient des Differenz- drucks grad δp (mit δp= [pVθrlauf ~ PRücklauf - • > welcher wiederum im Steuergerät ermittelt wird, nach Abschalten der Kraftstoffpumpe zunächst kleiner als bei dichten Systemen, bei Undichtheiten im Rücklauf ist der Differenzdruckgradient grad δp nach Abschalten der Kraftstoffpumpe zunächst größer als bei dichten Systemen. Über die Auswertung des Differenz¬ druck-Gradienten δp und Vergleich mit zwei anzupassenden oberen und unteren Schwellwerten SW0 und SWU kann im Steuer¬ gerät die Leckerkennung erfolgen und eine entsprechende An¬ zeige erfolgen.12 a pressure holding valve 18 is also attached to the fuel pump 11 at the outlet opening of the return line in the fuel tank. It is then possible to monitor not only the forward flow area but also the return area up to the exit into the fuel tank. As a pressure sensor in this case a differential pressure sensor 25 is used, which measures the differential pressure δp between the fuel supply and the return, for example at the fuel pressure regulator. In the event of leaks in the supply line, the gradient of the differential pressure is δp (with δp = [p Vθ rlauf ~ PRreturn - •> which in turn is determined in the control unit, after switching off the fuel pump, is initially smaller than in the case of leaky systems, in the case of leaks in the return line it is After the fuel pump has been switched off, the differential pressure gradient δp is initially greater than in the case of dense systems. By evaluating the differential pressure gradient δp and comparing it with two upper and lower threshold values SW 0 and SW U to be adapted, the leakage detection can take place in the control unit and a corresponding On ¬ show.
Bei einem System mit einer Brennkraftmaschine, bei der im Steuergerät ohnehin eine Verbrennungsaussetzererkennung durchgeführt wird, kann aus der Kombination der Erkennung von Verbrennungsaussetzern an einem bestimmten Einspritzven- til und gleichzeitig erkanntem Leck im KraftstoffSystem auf ein undichtes Einspritzventil geschlossen werden und dadurch ein möglicher Motorschaden verhindert oder das undichte Ven¬ til gleich richtig lokalisiert werden.In a system with an internal combustion engine, in which combustion misfire detection is carried out in the control unit anyway, the combination of the detection of combustion misfires on a specific injection valve and a leak detected in the fuel system at the same time can be used to infer a leaky injection valve and thereby prevent or prevent possible engine damage the leaky valve can be located correctly right away.
Die Leckerkennung kann vom Steuergerät nach jedem Abschalten der Kraftstoffpumpe durchgeführt werden, es ist auch mög¬ lich, daß diese Erkennung nur unter vorgebbaren Bedingungen erfolgt, beispielsweise nur nach längerer Einschaltung der Kraftstoffpumpe. Da das Verfahren zur Leckerkennung im Steuergerät der Brennkraftmaschine abläuft, handelt es sich bei einer solchen Erkennung um eine "on-board-Diagnose" . Die Erkennung eines vorhandenen Lecks im KraftstoffVersorgungs¬ system oder direkt in einem Einspritzventil kann in einem Speicher des Steuergerätes 23 abgelegt werden und steht dann beim nächsten Werkstattbesuch als Information zur Verfügung. Falls die Leckerkennung nach Abschalten der Kraftstoffpumpe und damit auch nach Abschalten der Brennkraftmaschine er¬ folgt, ist ein Nachlauf des Steuergerätes von ausreichender Dauer erforderlich, d. h. das Steuergerät muß nach dem Ab¬ schalten der BKM noch mit Spannung versorgt werden, damit die erforderlichen Funktionen noch ablaufen können. Falls die Diagnose im Schub erfolgen soll, ist es erforderlich, daß die Kraf stoffpumpe vom Steuergerät direkt, also unab- hängig vom Zündschloß angesteuert werden kann. The control unit can detect the leak each time the fuel pump is switched off. It is also possible for this detection to take place only under predefinable conditions, for example only after the fuel pump has been switched on for a long time. Since the method for leak detection takes place in the control unit of the internal combustion engine, such a detection is an "on-board diagnosis". The detection of an existing leak in the fuel supply system or directly in an injection valve can be stored in a memory of the control unit 23 and is then available as information the next time the workshop is visited. If the leakage detection occurs after the fuel pump has been switched off and thus also after the internal combustion engine has been switched off, the control unit must continue to run for a sufficient period of time, ie the control unit must still be supplied with voltage after the BKM has been switched off so that the required functions still work can expire. If the diagnosis is to take place in overrun, it is necessary that the fuel pump can be controlled directly by the control unit, ie independently of the ignition lock.

Claims

Ansprüche Expectations
1. Einrichtung zur Erkennung eines Lecks in einem Kraft- stoffVersorgungssystem bei einer Brennkraftmaschine, bei der der Kraftstoff von einer Kraftstoffpumpe unter Druck aus dem Kraftstoffbehälter gefördert wird und über entsprechende Leitungen zu den Einspritzventilen gelangt, mit einem Druck¬ sensor, der den Kraftstoffdruck fortlaufend mißt und einer Recheneinrichtung, in der ausgehend aus gemessenen Größen1. Device for detecting a leak in a fuel supply system in an internal combustion engine, in which the fuel is delivered under pressure from the fuel tank by a fuel pump and reaches the injection valves via corresponding lines, with a pressure sensor which continuously measures the fuel pressure and a computing device in which starting from measured variables
Ansteuergrößen gebildet werden, dadurch gekennzeichnet, daß die Recheneinrichtung den Verlauf des Kraf stoffdruckes nach Abschalten der Kraftstoffpumpe ermittelt und den Verlauf mit einem vorgebbaren Verlauf vergleicht und bei erkannten Ab- weichungen eine Fehleranzeige auslöst.Control variables are formed, characterized in that the computing device determines the course of the fuel pressure after the fuel pump is switched off and compares the course with a predeterminable course and triggers an error display if any deviations are detected.
2. Einrichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Recheneinrichtung das Steuergerät der Brennkraftmaschine ist, in dem die erforderlichen Berechnungen ablaufen.2. Device according to claim 1, characterized in that the computing device is the control unit of the internal combustion engine, in which the necessary calculations run.
3. Einrichtung nach Anspruch 1 oder 2, dadurch gekennzeich¬ net, daß zur Ermöglichung der Diagnose der Kraftstoffrück- führleitung ein Druckhalteventil am Austritt der Leitung in den Kraftstoffbehälter vorhanden ist.3. Device according to claim 1 or 2, characterized gekennzeich¬ net that a pressure maintaining valve is provided at the outlet of the line in the fuel tank to enable diagnosis of the fuel return line.
4. Einrichtung nach Anspruch 1, 2 oder 3, dadurch gekenn¬ zeichnet, daß aus dem nach Abstellen der Kraftstoffpumpe er¬ mittelten Druck der Gradient (gradp) des Druckes ermittelt wird und dieser Gradient mit einem vorgebbaren Schwellwert (SW) verglichen wird. 4. Device according to claim 1, 2 or 3, characterized gekenn¬ characterized in that the gradient (gradp) of the pressure is determined from the pressure determined after switching off the fuel pump and this gradient is compared with a predeterminable threshold value (SW).
5. Einrichtung nach einem der vorhergehenden Ansprüche, da¬ durch gekennzeichnet, daß anstelle des Drucksensors (24) ein Differenzdrucksensor (25) eingesetzt wird, der den Diffe- renzdruck zwischen Kraftstoffvorlauf und Kraftstoffrücklauf mißt und der Gradient des Differenzdruckes (gradδp) nach Ab¬ stellen der Kraf stoffpumpe ermittelt wird und dieser Gra¬ dient mit einem Schwellwert (SWU bzw. SW0) verglichen wird und eine Fehlererkennung erfolgt, wenn der Gradient des Differenzdrucks größer ist als der Schwellwert (SW0) bzw. kleiner ist als der Schwellwert (SWU) .5. Device according to one of the preceding claims, da¬ characterized in that instead of the pressure sensor (24), a differential pressure sensor (25) is used, which measures the differential pressure between the fuel flow and fuel return and the gradient of the differential pressure (gradδp) after Ab¬ the fuel pump is determined and this graph is compared with a threshold value (SW U or SW 0 ) and an error is detected if the gradient of the differential pressure is greater than the threshold value (SW 0 ) or less than the threshold value (SW U ).
6. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß in der Recheneinrichtung zusätz- lieh eine Aussetzererkennung abläuft, mit der erkannt wird, in welchen Zylindern keine Verbrennung stattgefunden hat und die Aussetzererkennung und die Leckerkennung miteinander kombiniert, zur eindeutigen Festlegung, welches der Ein¬ spritzventile undicht ist.6. Device according to one of the preceding claims, characterized in that a misfire detection runs in the computing device, with which it is recognized in which cylinders no combustion has taken place and the misfire detection and leak detection are combined with one another, for the unambiguous determination of which of the Injection valves are leaking.
7. Einrichtung nach einem der vorhergehenden Ansprüche, da¬ durch gekennzeichnet, daß vom Steuergerät eine Schuberken¬ nung durchgeführt wird und bei erkanntem Schubbetrieb die Kraftstoffpumpe abgeschaltet wird und eine Leckerkennung erfolgt. 7. Device according to one of the preceding claims, da¬ characterized in that a Schuberken¬ voltage is carried out by the control unit and when the overrun mode is detected, the fuel pump is switched off and a leak detection takes place.
EP96902879A 1995-04-07 1996-02-22 Device for detecting a leak in a fuel-supply system Expired - Lifetime EP0819213B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19513158 1995-04-07
DE19513158A DE19513158A1 (en) 1995-04-07 1995-04-07 Device for detecting a leak in a fuel supply system
PCT/DE1996/000273 WO1996031693A1 (en) 1995-04-07 1996-02-22 Device for detecting a leak in a fuel-supply system

Publications (2)

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EP0819213A1 true EP0819213A1 (en) 1998-01-21
EP0819213B1 EP0819213B1 (en) 2000-05-03

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EP (1) EP0819213B1 (en)
JP (1) JP3856827B2 (en)
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CN (1) CN1066242C (en)
DE (2) DE19513158A1 (en)
WO (1) WO1996031693A1 (en)

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EP0819213B1 (en) 2000-05-03
CN1066242C (en) 2001-05-23
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DE59605135D1 (en) 2000-06-08
KR19980703636A (en) 1998-12-05
CN1181125A (en) 1998-05-06
KR100413559B1 (en) 2004-03-31
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WO1996031693A1 (en) 1996-10-10
DE19513158A1 (en) 1996-10-10

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