EP3555448B1 - Method for testing the sealing tightness of a fuel tank system of an internal combustion engine - Google Patents

Method for testing the sealing tightness of a fuel tank system of an internal combustion engine Download PDF

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Publication number
EP3555448B1
EP3555448B1 EP17811952.5A EP17811952A EP3555448B1 EP 3555448 B1 EP3555448 B1 EP 3555448B1 EP 17811952 A EP17811952 A EP 17811952A EP 3555448 B1 EP3555448 B1 EP 3555448B1
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EP
European Patent Office
Prior art keywords
compressor
air line
internal combustion
combustion engine
scavenging
Prior art date
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Application number
EP17811952.5A
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German (de)
French (fr)
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EP3555448A1 (en
Inventor
Silke Weddig
Jens Wodausch
Jörg Giere
Florian Imbt
Matthias BÄTJE
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Volkswagen AG
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Volkswagen AG
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Publication of EP3555448A1 publication Critical patent/EP3555448A1/en
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Classifications

    • 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
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/003—Adding fuel vapours, e.g. drawn from engine fuel reservoir
    • F02D41/0032—Controlling the purging of the canister as a function of the engine operating conditions
    • F02D41/0035—Controlling the purging of the canister as a function of the engine operating conditions to achieve a special effect, e.g. to warm up the catalyst
    • F02D41/0037—Controlling the purging of the canister as a function of the engine operating conditions to achieve a special effect, e.g. to warm up the catalyst for diagnosing 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
    • 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
    • F02M25/0818—Judging failure of purge control system having means for pressurising the evaporative emission space
    • 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
    • F02M25/089—Layout of the fuel vapour installation
    • 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
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust

Definitions

  • the invention relates to a method for testing the tightness of a fuel tank system of an internal combustion engine
  • Fuel tank systems for internal combustion engines of motor vehicles regularly have a vent line which makes it possible to relieve an increasing pressure in the fuel tank of the tank system as a result of, for example, fuel evaporating at high ambient temperatures. Due to emission regulations, as far as possible no fuel vapors may enter the environment. This is prevented by a fuel vapor filter, regularly in the form of an activated carbon filter, which absorbs the fuel vapors, is integrated into the ventilation line.
  • such tank systems are additionally provided with a purge air line which is connected on the one hand to the fuel vapor filter and on the other hand to the fresh gas line of the internal combustion engine.
  • a purge air line which is connected on the one hand to the fuel vapor filter and on the other hand to the fresh gas line of the internal combustion engine.
  • ambient air can temporarily be sucked in via an ambient opening of the fuel vapor filter by means of the negative pressure prevailing in the area of the opening of the scavenging air line in the fresh gas line, which air flows through the fuel vapor filter in the opposite direction to the flow direction in which the fuel vapors flow from the fuel tank into the fuel vapor filter and rinse it.
  • the fuel vapors from the fuel vapor filter are thus fed to the combustion chambers of the internal combustion engine of the internal combustion engine via the fresh gas line.
  • Such a tank system of an internal combustion engine of a motor vehicle is from DE 10 2004 030 909 A1 known.
  • the scavenging air line is emptied of any fuel vapors still present therein in order to prevent these fuel vapors from entering the fresh gas line the environment.
  • the compressor conveys the gases contained in the ventilation line and the gases flowing in via the fresh gas line via the Fuel vapor filter and the ambient air line into the environment, the fuel vapor filter filtering out the fuel vapors.
  • a lack of tightness of a ventilation system of a tank system would lead to an uncontrolled escape of fuel vapors into the environment, which is to be avoided.
  • a tank ventilation system for an internal combustion engine with a fuel tank, an activated carbon filter, a tank ventilation valve and at least one check valve is known.
  • a pressure sensor is arranged between the tank ventilation valve and the check valve.
  • a negative pressure is set between the tank ventilation valve and the check valve, which is lower than the ambient pressure.
  • the set pressure is changed by activating the tank ventilation valve.
  • the change in the pressure in the line between the tank ventilation valve and the check valve is measured by means of the pressure sensor and assigned to the activation of the tank ventilation valve.
  • the function of the tank ventilation line, the check valve and the tank ventilation valve is deduced from the correlation of the opening state of the tank ventilation valve and the change in the pressure in the line between the tank ventilation valve and the check valve.
  • the DE 10 2012 218 933 A1 discloses a method for determining the loading of an activated carbon filter in a tank ventilation system, the tank ventilation system having at least one first valve between a fuel tank and the activated carbon filter and at least one second valve between the activated carbon filter and an intake pipe of an internal combustion engine. For this purpose, when the first valve is closed and when the second valve is closed, a volume of gas is applied to the activated carbon filter. Based on measured values that represent the pressure in the activated carbon filter, conclusions are drawn as to the loading status of the activated carbon filter.
  • the activated carbon filter can be charged with the gas volume by means of a compressor which is part of a known module for diagnosing tank leaks, which is arranged on the side of a ventilation opening of the activated carbon filter and is in fluid-conducting connection with the environment via a fresh air filter.
  • the US 2014/299111 A1 , the DE 10 2014 216 451 A1 , the DE 10 2014 217 195 A1 and the DE 198 29 423 A1 each disclose a method for testing the tightness of a tank ventilation system in which a defined overpressure is generated in at least one section of the tank ventilation system closed off by means of valves by means of a flushing gas delivery device and the pressure profile is then monitored over time.
  • the WO 2017/195436 A1 describes according to the as DE 11 2017 001 972 T5 published translation a method for testing the tightness of a tank ventilation system, in which a flushing gas delivery device is operated at a defined speed and depending on the pressure that is provided by the operation of the flushing air pump, a possible leakage is concluded.
  • the invention is based on the object of specifying an advantageous possibility for checking the tightness of a fuel tank system of an internal combustion engine.
  • a method for testing the tightness (at least of a section) of a fuel tank system of an internal combustion engine, in particular an internal combustion engine of a motor vehicle comprises at least one fuel tank, a fuel vapor filter (preferably a sorption filter, in particular an activated carbon filter), which is in fluid-conducting connection with an ambient mouth, a vent line leading from the fuel tank to the fuel vapor filter, and one leading from the fuel vapor filter to a fresh gas line of the internal combustion engine Purge air line, a preferably electric motor-driven compressor integrated into the purge air line (ie a device for conveying gases) and a shut-off valve integrated into the purge air line, which is arranged between an opening of the purge air line in the fresh gas line and the compressor.
  • a fuel vapor filter preferably a sorption filter, in particular an activated carbon filter
  • a test for sufficient tightness by means of the compressor in at least one section of the scavenging air line (and possibly in (a) further section (s) of the fuel tank system connected in a fluid-conducting manner to this section in the defined operating state)
  • Section of the purge air line a defined pressure level is generated by the compressor and one or more operating parameters of the compressor, in particular the strength of the electrical current with which a drive motor of the compressor is applied to achieve the pressure level, and / or the resulting drive speed of the compressor, are compared with the associated setpoint (ranges) that have been determined, for example, by tests on the same or a comparable fuel tank system in a (known) state of sufficient tightness of the section to be tested.
  • the associated setpoint ranges
  • An additional or even primary function of the compressor can be to ensure that the fuel vapor filter is flushed when there is no or too little pressure gradient between the ambient pressure and the pressure in the fresh gas line in the area of the mouth of the scavenging air line, so this is preferably a suitably efficient design of the compressor is provided.
  • an inflow or outflow of gases into or out of the section of the purge air line to be tested (with the exception of possible leaks) is only possible by means of or via the compressor .
  • the shut-off valve should be closed as completely as possible.
  • a defined opening of the shut-off valve can also define the defined operating state of the fuel tank system provided for carrying out the method, which can also be changed in a defined manner.
  • a compressor in the form of a reciprocating compressor ie one based on the displacement principle
  • working compressor in which gas is encapsulated, compressed and ejected again cyclically for delivery
  • a compressor in the form of a flow compressor fan
  • the compressor to generate an overpressure or a negative pressure (in each case compared to the ambient pressure) in a section of the scavenging air line to be tested, whereby the generation of overpressure can have procedural advantages. Furthermore, there is basically the possibility of carrying out a simultaneous test in the two sections of the purge air line adjoining the compressor on different sides by generating a negative pressure in one section and an overpressure in the other section by means of the compressor.
  • shut-off valve is integrated in an ambient air line between the fuel vapor filter and the ambient mouth.
  • This shut-off valve can preferably be closed are held when a test is (also) carried out on the section of the purge air line between the compressor and the fuel vapor filter. Since, despite this closed shut-off valve, there is a fluid-conducting connection via the fuel vapor filter between this section of the purge air line on the one hand and the vent line and thus also the fuel tank on the other hand, in this case not only the section of the purge air line between the compressor and the fuel vapor filter but also in particular the ventilation line and the fuel tank must also be checked for adequate leaks.
  • a scavenging air line is branched, with a first opening into the fresh gas line upstream of a fresh gas compressor integrated into the fresh gas line and used for charging an internal combustion engine of the internal combustion engine, and a second opening the purge air line is arranged in the fresh gas line downstream of the fresh gas compressor.
  • the compressor can be integrated into the scavenging air line between the branch on the one hand and the first opening or the second opening on the other hand. It is then also preferably provided that a shut-off valve is also integrated into the branch of the scavenging air line in which the compressor is not integrated.
  • the or each of the shut-off valves of a fuel tank system, in which the method according to the invention can be used can be designed to be active (controllable) or passive (i.e. independently actuating, for example in the form of a non-return valve).
  • the use of a method according to the invention in an internal combustion engine can also be provided in an advantageous manner, in which the fuel vapor filter has an (additional) tank leak diagnosis module, for example a tank leak diagnosis module, as is shown in FIG DE 10 2012 218 933 A1 is described, is assigned.
  • an (additional) tank leak diagnosis module for example a tank leak diagnosis module, as is shown in FIG DE 10 2012 218 933 A1 is described, is assigned.
  • a compressor can be integrated into the fuel tank system, the additional or even primary function of which is to flush the fuel vapor filter when there is insufficient negative pressure in the fresh gas line, whereby the integration of this compressor can prevent that section of the purge air line that is open which is located on the distal side of the compressor with respect to the fuel vapor filter or the tank leak diagnosis module, can also be checked by the tank leak diagnosis module.
  • this section of the scavenging air line can then be checked in a manner according to the invention.
  • a tank leak diagnosis module which in particular can also include an (additional) compressor, to carry out a test for sufficient tightness of the entire fuel tank system, provided that a compressor that is provided according to the invention and integrated into the purge air line would be dispensed with or at least not in form a reciprocating compressor but in the form of a flow compressor (fan) (because it is then sufficiently gas-permeable even at standstill).
  • a compressor that is provided according to the invention and integrated into the purge air line would be dispensed with or at least not in form a reciprocating compressor but in the form of a flow compressor (fan) (because it is then sufficiently gas-permeable even at standstill).
  • this can have disadvantages.
  • this may require a pressure-tight design of the fuel vapor filter and / or the integration of a further shut-off valve or other design measures that prevent an undesired pressure increase in the fuel tank when the fuel vapor filter is flushed using the tank leak diagnosis module.
  • the method according to the invention can be used in particular in a fuel tank system of an internal combustion engine which comprises an internal combustion engine operated according to the Otto principle, because the fuel used to operate such internal combustion engines is relatively volatile (especially compared to diesel fuel), which means that it is not only the special need for tank ventilation but also a test of the tightness of the fuel tank system is justified.
  • the term “fuel vapor filter” does not mean that it has to filter the volatile fuel in gaseous form. Rather, the fuel can already be (partially) condensed out again during the filtering.
  • the Fig. 1 Fig. 10 shows a fuel tank system of an internal combustion engine. This comprises a fuel tank 10, which is connected via a vent line 12 to a fuel vapor filter 14, which can be designed in particular in the form of an activated carbon filter or at least one comprising such a filter.
  • the fuel vapor filter 14 is also connected to a fresh gas line 18 of the internal combustion engine via a scavenging air line 16, the scavenging air line 16 running from a branch 20 in two branches 22, 24, of which a first branch 22 enters the fresh gas line 18 upstream (with respect to the direction of flow from Fresh gas in the fresh gas line 18 starting from a fresh gas inlet (not shown) to an internal combustion engine 26 of the internal combustion engine) of a fresh gas compressor 28 integrated in the fresh gas line 18 and the second, optionally present branch 24 downstream of the fresh gas compressor 28 and in particular also downstream of a likewise downstream of the fresh gas compressor 28
  • the throttle valve 54 integrated into the fresh gas line 18 opens.
  • the fresh gas compressor 28 is part of an exhaust gas turbocharger which further comprises an exhaust gas turbine 30 which is integrated into an exhaust gas line 32 of the internal combustion engine.
  • mixtures of fresh gas which consists entirely or essentially of ambient air, and, for example, injected directly into the combustion chambers 34, are in a known manner in a defined order in combustion chambers 34 of internal combustion engine 26, some of which are delimited by cylinders 34 of internal combustion engine 26
  • Fuel is burned, the pressure increases thus generated in the combustion chambers 34 being used to move pistons 38, which are guided in a longitudinally axially movable manner in the cylinders 36.
  • the side of the fuel vapor filter 14 of the fuel tank system facing away from the vent line 12 and the purge air line 16 is in gas-conducting connection via an ambient air line 42 with a (first) shut-off valve 44 integrated therein, including the ambient air line 42 a surrounding mouth 62 forms.
  • the first shut-off valve 44 can be controlled by means of a control device 48 (e.g. the engine control of the internal combustion engine), i. this can be actively opened or closed.
  • a tank leak diagnosis module 46 which is known in principle, can also be integrated into the ambient air line 42, in which case the first shut-off valve 44 can also be an integral part of the tank leak diagnosis module 46.
  • the fuel tank 10 is partially filled with liquid fuel, some of this fuel being vaporized, so that fuel is also present in the fuel tank 10 in a gaseous state.
  • Such evaporation of fuel in the fuel tank 10 is intensified by a relatively high temperature of the fuel, which is the case in particular at comparatively high ambient temperatures.
  • the fuel vapor filter 14 preventing such pressure equalization from leading to an escape of fuel vapors into the environment.
  • Such a venting of the fuel tank leads to increasing saturation of the fuel vapor filter 14, which in turn requires it to be regenerated at regular intervals.
  • the fuel vapor filter 14 is flushed in that ambient air is sucked in via the ambient air line 42 and the first, then opened shut-off valve 44 integrated therein.
  • This ambient air flows through the fuel vapor filter 14 in the opposite flow direction compared to the flow when venting the fuel tank 10, whereby fuel molecules absorbed in the fuel vapor filter 10 are carried along by the ambient air and entered into the fresh gas line 18 via the scavenging air line 16, whereby this fuel is subjected to combustion the combustion chambers 34 of the internal combustion engine 26 is supplied.
  • Such a flushing of the fuel vapor filter 14 is only provided temporarily and always during the operation of the internal combustion engine 26, because only then can the fuel introduced into the fresh gas line 18 by flushing the fuel vapor filter 14 also be safely fed to combustion in the combustion chambers 34.
  • this second orifice 52 (as close as possible) downstream of a throttle valve 54, a pressure drop brought about by the throttle valve 54 can be used; however, this pressure drop is often not sufficient to actually create a sufficient pressure gradient across the To realize purge air line 16.
  • a check valve 56 is therefore integrated, by means of which this branch 24 of the scavenging air line 16 is automatically kept closed if there is an overpressure in the area of the second opening 52 compared to the section of the on the other side of the check valve second branch 24 of the scavenging air line 16 is present.
  • a (second) shut-off valve 58 which can be actively controlled by means of the control device 48, is integrated into the second branch 24 of the scavenging air line 16 upstream (with respect to the direction of flow when flushing the fuel vapor filter 14).
  • the shut-off valve 58 is designed to be sufficiently overpressure-resistant (i.e. it must keep sufficiently tightly closed with the at least temporarily occurring overpressures on the side of the charge air path of the fresh gas line 18).
  • the first branch of the purge air line 22 opens into a section of the fresh gas line 18 located upstream of the fresh gas compressor 28, a (third) shut-off valve 60 being integrated into the section of this branch 22 of the purge air line 16 between the fresh gas compressor 28 and this (first) opening 50, which is arranged as close as possible to the first mouth 50 or preferably integrated into it.
  • the pressure of the fresh gas (when the fresh gas compressor 28 is in operation) is lower than in the charge air line, so that with respect to this first opening 50 of the scavenging air line, a sufficient pressure gradient is relatively often in comparison (and starting) of the ambient pressure present at the ambient mouth 62.
  • this is not always the case, for example when a motor vehicle comprising the internal combustion engine is operated with the internal combustion engine not being operated (for example due to an automatic start / stop function).
  • the fuel tank system of the internal combustion engine also includes a compressor 64, also known as a "flushing pump", which can be designed in the form of a piston compressor and, for example, a vane compressor.
  • a compressor 64 By operating this compressor 64, ambient air can be actively sucked in via the ambient opening 62, which then flows through the fuel vapor filter 14 to flush it and is conveyed via the compressor 64 to the first opening 50 of the flushing air line 16.
  • the second shut-off valve 58 which is integrated into the second branch 52 of the scavenging air line 16 and then kept closed, but at least that is itself Automatically closing check valves 56 also prevent fresh gas from being sucked in via the second opening 52 from the charge air path of the fresh gas line 18.
  • a scavenging air line 16 which does not include the first branch 22 would be sufficient for scavenging the fuel vapor filter 14.
  • the first branch 22 of the Purge air line 16 may be necessary since purging via only the second branch 24 is often not possible.
  • the use of the compressor 64 may be useful or necessary for sufficient flushing of the fuel vapor filter 14.
  • a pressure change is brought about by sucking in ambient air via the opened first shut-off valve 44 integrated in the ambient air line and pouring it into the fuel vapor filter 14 the corresponding section of the purge air line 16 is conveyed or gas present in this section of the purge air line 16 is partially evacuated by means of the compressor 64 and conveyed in the direction of the fuel vapor filter 14.
  • this section of the purge air line 16 In addition to the pressure in this section of the purge air line 16, the course of which can be determined by means of a pressure sensor 66, the (drive) speed of a drive motor (not shown) of the compressor 64 and the strength of the electrical current applied to this drive motor is determined. By evaluating and in particular by comparing these parameters, a distinction can be made between an adequate and an insufficient tightness of this section of the scavenging air line 16, as can be seen, for example, from FIG Fig. 2 can be seen.
  • Fig. 2 are in two diagrams the (simultaneous) courses on the one hand (upper diagram) of the current I (course lines 68, 70) and on the other hand (lower diagram) of the pressure p (course lines 72, 74) and the drive speed n (course lines 76, 78; percentage in Compared to a maximum speed determined by design or control technology for the compressor), with the course for each of these parameters on the one hand the course with (known) best possible tightness of this section of the purge air line 16 (thick line width) and on the other hand the course with a known leak according to a reference leak with a Size of 0.5 mm (thin line width) are compared.
  • setpoints or setpoint ranges for these operating parameters of the compressor 64 are determined on the basis of the curves of the current intensity I and the drive speed n, which were determined for the section of the purge air line that is known to be the best possible leak-proof, then this can be done regularly by generating the same or a comparable operating state (defined by the mean pressure p) generated for the determination of the setpoint values or setpoint ranges are compared, whether the then determined values or value curves of these operating parameters have defined deviations from the setpoints or setpoint ranges, from which then a sufficient (no or below a limit value) deviations or not sufficient (relatively large deviations) tightness can be closed.
  • the Fig. 3 shows an embodiment of an internal combustion engine in which the fuel tank system compared to that of the internal combustion engine according to FIG Fig. 1 is slightly modified. Specifically, it is provided that in the fuel tank system according to Fig. 1 Second shut-off valve 58 integrated in the second branch 24 of the scavenging air line 16 is to be arranged upstream of the junction 20 (with regard to the flow through the scavenging air line 16 when the fuel vapor filter 14 is flushed). With regard to the Fig. 1 and 2 described Checking the section of the scavenging air line 16 arranged between the compressor 64 and the third shut-off valve 60 associated with the first opening 50, this changed arrangement of the second shut-off valve has no effects.
  • these sections of the purge air line 16 are evacuated, the evacuated gas being expelled via the first opening 50 of the purge air line 16 into the fresh gas line 18.
  • this should then be dimensioned in such a way that the non-return valve 56 is still reliably kept closed.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Supplying Secondary Fuel Or The Like To Fuel, Air Or Fuel-Air Mixtures (AREA)
  • Examining Or Testing Airtightness (AREA)

Description

Die Erfindung betrifft ein Verfahren zur Prüfung der Dichtheit eines Kraftstofftanksystems einer BrennkraftmaschineThe invention relates to a method for testing the tightness of a fuel tank system of an internal combustion engine

Kraftstofftanksysteme für Brennkraftmaschinen von Kraftfahrzeugen weisen regelmäßig eine Entlüftungsleitung auf, die es ermöglicht, einen ansteigenden Druck in dem Kraftstofftank des Tanksystems infolge von beispielsweise bei hohen Umgebungstemperaturen verdampfendem Kraftstoff an die Umgebung zu entlasten. Dabei dürfen aufgrund von Emissionsvorschriften möglichst keine Kraftstoffdämpfe in die Umgebung gelangen. Dies wird verhindert, indem in die Entlüftungsleitung ein Kraftstoffdampffilter, regelmäßig in Form eines Aktivkohlefilters, integriert ist, der die Kraftstoffdämpfe absorbiert.Fuel tank systems for internal combustion engines of motor vehicles regularly have a vent line which makes it possible to relieve an increasing pressure in the fuel tank of the tank system as a result of, for example, fuel evaporating at high ambient temperatures. Due to emission regulations, as far as possible no fuel vapors may enter the environment. This is prevented by a fuel vapor filter, regularly in the form of an activated carbon filter, which absorbs the fuel vapors, is integrated into the ventilation line.

Zur Regeneration der Kraftstoffdampffilter sind solche Tanksysteme zusätzlich mit einer Spülluftleitung versehen, die einerseits mit dem Kraftstoffdampffilter und andererseits mit dem Frischgasstrang der Brennkraftmaschine verbunden ist. Im Betrieb der Brennkraftmaschine kann zeitweise mittels des im Bereich der Mündung der Spülluftleitung in dem Frischgasstrang herrschenden Unterdrucks Umgebungsluft über eine Umgebungsmündung des Kraftstoffdampffilters angesaugt werden, die den Kraftstoffdampffilter in Gegenrichtung zu derjenigen Strömungsrichtung, in der die Kraftstoffdämpfe aus dem Kraftstofftank in den Kraftstoffdampffilter strömen, durchströmen und diesen dadurch spülen. Die Kraftstoffdämpfe aus dem Kraftstoffdampffilter werden so über den Frischgasstrang den Brennräumen des Verbrennungsmotors der Brennkraftmaschine zugeführt.To regenerate the fuel vapor filter, such tank systems are additionally provided with a purge air line which is connected on the one hand to the fuel vapor filter and on the other hand to the fresh gas line of the internal combustion engine. During operation of the internal combustion engine, ambient air can temporarily be sucked in via an ambient opening of the fuel vapor filter by means of the negative pressure prevailing in the area of the opening of the scavenging air line in the fresh gas line, which air flows through the fuel vapor filter in the opposite direction to the flow direction in which the fuel vapors flow from the fuel tank into the fuel vapor filter and rinse it. The fuel vapors from the fuel vapor filter are thus fed to the combustion chambers of the internal combustion engine of the internal combustion engine via the fresh gas line.

Ein solches Tanksystem einer Brennkraftmaschine eines Kraftfahrzeugs ist aus der DE 10 2004 030 909 A1 bekannt. Bei diesem ist ergänzend vorgesehen, dass nach einem Abschalten der Brennkraftmaschine während einer definierten Nachlaufzeit mittels eines zwischen einer Umgebungsmündung und dem Kraftstoffdampffilter in eine Umgebungsluftleitung integrierten Verdichters die Spülluftleitung von darin noch vorhanden Kraftstoffdämpfen entleert wird, um zu vermeiden, dass diese Kraftstoffdämpfe über den Frischgasstrang in die Umgebung gelangen können. Der Verdichter fördert dabei die in der Entlüftungsleitung enthaltenen sowie über den Frischgasstrang nachströmende Gase über den Kraftstoffdampffilter und die Umgebungsluftleitung in die Umgebung, wobei der Kraftstoffdampffilter die Kraftstoffdämpfe herausfiltert.Such a tank system of an internal combustion engine of a motor vehicle is from DE 10 2004 030 909 A1 known. In this case, it is additionally provided that after the internal combustion engine has been switched off during a defined follow-up time by means of a compressor integrated in an ambient air line between an ambient outlet and the fuel vapor filter, the scavenging air line is emptied of any fuel vapors still present therein in order to prevent these fuel vapors from entering the fresh gas line the environment. The compressor conveys the gases contained in the ventilation line and the gases flowing in via the fresh gas line via the Fuel vapor filter and the ambient air line into the environment, the fuel vapor filter filtering out the fuel vapors.

Eine mangelnde Dichtheit eines Entlüftungssystems eines Tanksystems würde zu einem unkontrollierten Entweichen von Kraftstoffdämpfen in die Umgebung führen, was zu vermeiden ist.A lack of tightness of a ventilation system of a tank system would lead to an uncontrolled escape of fuel vapors into the environment, which is to be avoided.

Aus der DE 10 2011 084 403 A1 ist ein Tankentlüftungssystem für eine Brennkraftmaschine mit einem Kraftstofftank, einem, Aktivkohlefilter, einem Tankentlüftungsventil und mindestens einem Rückschlagventil bekannt. Zwischen dem Tankentlüftungsventil und dem Rückschlagventil ist ein Drucksensor angeordnet. Zur Diagnose des Tankentlüftungssystems wird zwischen dem Tankentlüftungsventil und dem Rückschlagventil ein Unterdruck eingestellt, der geringer ist als der Umgebungsdruck. Der eingestellte Druck wird durch Ansteuern des Tankentlüftungsventils geändert. Die Änderung des Drucks in der Leitung zwischen dem Tankentlüftungsventil und dem Rückschlagventil wird mittels des Drucksensors gemessen und der Ansteuerung des Tankentlüftungsventils zugeordnet. Aus der Korrelation des Öffnungszustands des Tankentlüftungsventils und der Änderung des Drucks in der Leitung zwischen dem Tankentlüftungsventil und dem Rückschlagventil wird auf die Funktion der Tankentlüftungsleitung, des Rückschlagventils und des Tankentlüftungsventils geschlossen. Insbesondere kann dabei auch auf die Dichtheit des Tankentlüftungssystems in dem Abschnitt zwischen dem Tankentlüftungsventil und dem Rückschlagventil geschlossen werden. Eine Überprüfung der Dichtheit der übrigen Abschnitte des Tankentlüftungssystems ist damit jedoch nicht möglich.From the DE 10 2011 084 403 A1 a tank ventilation system for an internal combustion engine with a fuel tank, an activated carbon filter, a tank ventilation valve and at least one check valve is known. A pressure sensor is arranged between the tank ventilation valve and the check valve. To diagnose the tank ventilation system, a negative pressure is set between the tank ventilation valve and the check valve, which is lower than the ambient pressure. The set pressure is changed by activating the tank ventilation valve. The change in the pressure in the line between the tank ventilation valve and the check valve is measured by means of the pressure sensor and assigned to the activation of the tank ventilation valve. The function of the tank ventilation line, the check valve and the tank ventilation valve is deduced from the correlation of the opening state of the tank ventilation valve and the change in the pressure in the line between the tank ventilation valve and the check valve. In particular, it is also possible to infer the tightness of the tank ventilation system in the section between the tank ventilation valve and the check valve. A check of the tightness of the remaining sections of the tank ventilation system is not possible with this.

Die DE 10 2012 218 933 A1 offenbart ein Verfahren zur Bestimmung der Beladung eines Aktivkohlfilters in einem Tankentlüftungssystem, wobei das Tankentlüftungssystem wenigstens ein erstes Ventil zwischen einem Kraftstofftank und dem Aktivkohlefilter und wenigstens ein zweites Ventil zwischen dem Aktivkohlefilter und einem Ansaugrohr einer Brennkraftmaschine aufweist. Dazu wird bei geschlossenem ersten Ventil und bei geschlossenem zweiten Ventil der Aktivkohlefilter mit einem Gasvolumen beaufschlagt. Anhand von Messwerten, die den Druck im Aktivkohlefilter repräsentieren, wird auf den Beladungszustand des Aktivkohlefilters geschlossen. Die Beaufschlagung des Aktivkohlefilters mit dem Gasvolumen kann mittels eines Verdichters erfolgen, der Teil eines als bekannt beschriebenen Moduls zur Diagnose von Tankleckagen ist, das auf der Seite einer Belüftungsöffnung des Aktivkohlefilters angeordnet und über einen Frischluftfilter mit der Umgebung in fluidleitender Verbindung steht.The DE 10 2012 218 933 A1 discloses a method for determining the loading of an activated carbon filter in a tank ventilation system, the tank ventilation system having at least one first valve between a fuel tank and the activated carbon filter and at least one second valve between the activated carbon filter and an intake pipe of an internal combustion engine. For this purpose, when the first valve is closed and when the second valve is closed, a volume of gas is applied to the activated carbon filter. Based on measured values that represent the pressure in the activated carbon filter, conclusions are drawn as to the loading status of the activated carbon filter. The activated carbon filter can be charged with the gas volume by means of a compressor which is part of a known module for diagnosing tank leaks, which is arranged on the side of a ventilation opening of the activated carbon filter and is in fluid-conducting connection with the environment via a fresh air filter.

Die US 2014/299111 A1 , die DE 10 2014 216 451 A1 , die DE 10 2014 217 195 A1 und die DE 198 29 423 A1 offenbaren jeweils ein Verfahren zur Prüfung der Dichtheit eines Tankentlüftungssystems, bei dem mittels einer Spülgasfördervorrichtung ein definierter Überdruck in zumindest einem mittels Ventilen abgeschlossenen Abschnitt des Tankentlüftungssystems erzeugt und anschließend der Verlauf des Drucks über der Zeit kontrolliert wird.The US 2014/299111 A1 , the DE 10 2014 216 451 A1 , the DE 10 2014 217 195 A1 and the DE 198 29 423 A1 each disclose a method for testing the tightness of a tank ventilation system in which a defined overpressure is generated in at least one section of the tank ventilation system closed off by means of valves by means of a flushing gas delivery device and the pressure profile is then monitored over time.

Die WO 2017/195436 A1 beschreibt gemäß der als DE 11 2017 001 972 T5 veröffentlichten Übersetzung ein Verfahren zur Prüfung der Dichtheit eines Tankentlüftungssystems, bei dem eine Spülgasfördervorrichtung mit einer definierten Drehzahl betrieben und in Abhängigkeit von dem Druck, der durch den Betrieb der Spülluftpumpe bereitgestellt wird, auf eine mögliche Leckage geschlossen wird.The WO 2017/195436 A1 describes according to the as DE 11 2017 001 972 T5 published translation a method for testing the tightness of a tank ventilation system, in which a flushing gas delivery device is operated at a defined speed and depending on the pressure that is provided by the operation of the flushing air pump, a possible leakage is concluded.

Der Erfindung liegt die Aufgabe zugrunde, eine vorteilhafte Möglichkeit zur Überprüfung der Dichtheit eines Kraftstofftanksystems einer Brennkraftmaschine anzugeben.The invention is based on the object of specifying an advantageous possibility for checking the tightness of a fuel tank system of an internal combustion engine.

Diese Aufgabe wird mittels eines Verfahrens gemäß dem Patentanspruch 1 gelöst. Vorteilhafte Ausführungsformen des erfindungsgemäßen Verfahrens sind Gegenstände der weiteren Patentansprüche und/oder ergeben sich aus der nachfolgenden Beschreibung der Erfindung.This object is achieved by means of a method according to patent claim 1. Advantageous embodiments of the method according to the invention are the subject matter of the further patent claims and / or result from the following description of the invention.

Erfindungsgemäß ist ein Verfahren zur Prüfung der Dichtheit (zumindest eines Abschnitts) eines Kraftstofftanksystems einer Brennkraftmaschine, insbesondere einer Brennkraftmaschine eines Kraftfahrzeugs, vorgesehen. Das hierfür verwendete Kraftstofftanksystem umfasst zumindest einen Kraftstofftank, einen Kraftstoffdampffilter (vorzugsweise ein Sorptionsfilter, insbesondere ein Aktivkohlefilter), der in fluidleitender Verbindung mit einer Umgebungsmündung steht, eine von dem Kraftstofftank zu dem Kraftstoffdampffilter führende Entlüftungsleitung, eine von dem Kraftstoffdampffilter zu einem Frischgasstrang der Brennkraftmaschine führende Spülluftleitung, einen in die Spülluftleitung integrierten, vorzugsweise elektromotorisch angetriebenen Verdichter (d.h. eine Vorrichtung zur Förderung von Gasen) und ein in die Spülluftleitung integriertes Absperrventil, das zwischen einer Mündung der Spülluftleitung in den Frischgasstrang und dem Verdichter angeordnet ist. Zur Prüfung der Dichtheit eines solchen Kraftstofftanksystems ist vorgesehen, dass durch einen Vergleich mindestens eines bei einem definierten Betriebszustand des Kraftstofftanksystems ermittelten Werts oder Wertverlaufs eines Parameters, der einem Betriebsparameter des Verdichters entspricht, mit einem dazugehörigen, diesen Betriebszustand repräsentierenden Sollwert oder Sollwertbereich, der einer ausreichenden Dichtheit entspricht, zwischen ausreichender und nicht ausreichender Dichtheit unterschieden wird.According to the invention, a method for testing the tightness (at least of a section) of a fuel tank system of an internal combustion engine, in particular an internal combustion engine of a motor vehicle, is provided. The fuel tank system used for this comprises at least one fuel tank, a fuel vapor filter (preferably a sorption filter, in particular an activated carbon filter), which is in fluid-conducting connection with an ambient mouth, a vent line leading from the fuel tank to the fuel vapor filter, and one leading from the fuel vapor filter to a fresh gas line of the internal combustion engine Purge air line, a preferably electric motor-driven compressor integrated into the purge air line (ie a device for conveying gases) and a shut-off valve integrated into the purge air line, which is arranged between an opening of the purge air line in the fresh gas line and the compressor. To test the tightness of such a fuel tank system, it is provided that by comparing at least one value or value curve of a parameter determined in a defined operating state of the fuel tank system, which corresponds to an operating parameter of the compressor, with an associated setpoint or setpoint range representing this operating state, the corresponds to sufficient tightness, a distinction is made between sufficient and insufficient tightness.

Erfindungsgemäß kann insbesondere vorgesehen sein, mittels des Verdichters in zumindest einem Abschnitt der Spülluftleitung (und gegebenenfalls in (einem) mit diesem Abschnitt in dem definierten Betriebszustand fluidleitend verbunden weiteren Abschnitt(en) des Kraftstofftanksystems) eine Prüfung auf ausreichende Dichtheit durchzuführen, indem in dem entsprechenden Abschnitt der Spülluftleitung durch den Verdichter ein definiertes Druckniveau erzeugt wird und ein oder mehrere Betriebsparameter des Verdichters, insbesondere die Stärke des elektrischen Stroms, mit der ein Antriebsmotor des Verdichters zur Realisierung des Druckniveaus beaufschlagt wird, und/oder die sich dabei einstellende Antriebsdrehzahl des Verdichters, mit dazugehörigen Sollwert(bereich)en verglichen werden, die beispielsweise durch Versuche an demselben oder einem vergleichbaren Kraftstofftanksystem in einem (bekannten) Zustand ausreichender Dichtheit des zu prüfenden Abschnitts ermittelt worden sind. Bei bestimmten Abweichungen der aktuell ermittelten Betriebsparameter im Vergleich zu den dazugehörigen Sollwert(bereich)en kann dann auf eine nicht ausreichende Dichtheit geschlossen werden.According to the invention, it can be provided in particular to carry out a test for sufficient tightness by means of the compressor in at least one section of the scavenging air line (and possibly in (a) further section (s) of the fuel tank system connected in a fluid-conducting manner to this section in the defined operating state) Section of the purge air line, a defined pressure level is generated by the compressor and one or more operating parameters of the compressor, in particular the strength of the electrical current with which a drive motor of the compressor is applied to achieve the pressure level, and / or the resulting drive speed of the compressor, are compared with the associated setpoint (ranges) that have been determined, for example, by tests on the same or a comparable fuel tank system in a (known) state of sufficient tightness of the section to be tested. In the event of certain deviations in the currently determined operating parameters compared to the associated setpoint (ranges), it can then be concluded that there is insufficient tightness.

Eine zusätzliche oder sogar primäre Funktion des Verdichters kann darin liegen, ein Spülen des Kraftstoffdampffilters zu gewährleisten, wenn kein oder ein zu geringes Druckgefälle von dem Umgebungsdruck zu dem Druck im Frischgasstrang im Bereich der Mündung der Spülluftleitung gegeben ist, so das vorzugsweise eine entsprechend leistungsfähige Auslegung des Verdichters vorgesehen ist.An additional or even primary function of the compressor can be to ensure that the fuel vapor filter is flushed when there is no or too little pressure gradient between the ambient pressure and the pressure in the fresh gas line in the area of the mouth of the scavenging air line, so this is preferably a suitably efficient design of the compressor is provided.

Um bei dem erfindungsgemäßen Verfahren auch relativ kleine Undichtheiten ermitteln zu können, sollte vorzugsweise vorgesehen sein, dass ein Zuströmen oder Abströmen von Gasen in den oder aus dem zu prüfenden Abschnitt der Spülluftleitung (mit Ausnahme möglicher Leckagen) ausschließlich mittels des beziehungsweise über den Verdichter möglich ist. Somit sollte beispielsweise bei einer Prüfung zumindest des zwischen dem Verdichter einerseits und dem zwischen diesem und der Mündung in den Frischgasstrang liegenden Absperrventil andererseits liegenden Abschnitts der Spülluftleitung das Absperrventil möglichst vollständig geschlossen sein. Zwingend erforderlich ist dies jedoch nicht, weil beispielsweise auch eine definierte Öffnung des Absperrventils den definierten, für die Durchführung des Verfahrens vorgesehen Betriebszustand des Kraftstofftanksystems, der auch definiert veränderlich sein kann, definieren kann. Aus demselben Grund kann vorzugsweise auch vorgesehen sein, einen Verdichter in Form eines Kolbenverdichters (d.h. eines nach dem Verdrängerprinzip arbeitenden Verdichters, bei dem zyklisch Gas zur Förderung in einem Volumen gekapselt, verdichtet und wieder ausgestoßen wird) zu verwenden, wodurch ein möglichst exakter Zusammenhang zwischen der Antriebsdrehzahl des Kolbenverdichters und der in den oder aus dem zu prüfenden Abschnitt geförderten Gasmenge erhalten werden kann. Alternativ besteht aber auch die Möglichkeit, einen Verdichter in Form eines Strömungsverdichters (Gebläse) zu verwenden.In order to be able to determine relatively small leaks in the method according to the invention, it should preferably be provided that an inflow or outflow of gases into or out of the section of the purge air line to be tested (with the exception of possible leaks) is only possible by means of or via the compressor . Thus, for example, when testing at least that section of the scavenging air line located between the compressor on the one hand and the shut-off valve located between it and the opening in the fresh gas line, on the other hand, the shut-off valve should be closed as completely as possible. However, this is not absolutely necessary because, for example, a defined opening of the shut-off valve can also define the defined operating state of the fuel tank system provided for carrying out the method, which can also be changed in a defined manner. For the same reason, a compressor in the form of a reciprocating compressor (ie one based on the displacement principle) can preferably also be provided working compressor, in which gas is encapsulated, compressed and ejected again cyclically for delivery), whereby the most exact possible relationship between the drive speed of the piston compressor and the amount of gas delivered into or out of the section to be tested can be obtained. Alternatively, there is also the possibility of using a compressor in the form of a flow compressor (fan).

Um ein möglichst deutliches Unterscheidungsergebnis erlangen zu können, kann vorzugsweise vorgesehen sein, dass mehrere Parameter mit einem dazugehörigen Sollwert oder Sollwertbereich verglichen werden. Demnach kann vorgesehen sein, dass sowohl der Druck in dem zu prüfenden Abschnitt der Spülluftleitung, die Stromstärke, mit der der Antriebsmotor des Verdichters beaufschlagt wird, und die sich dadurch ergebende Antriebsdrehzahl des Verdichters genutzt werden, wobei der Druck zur Definition des Betriebszustands herangezogen wird und die beiden anderen Parameter beziehungsweise zu diesen Parametern ermittelte Werte mit jeweils einem Sollwert oder Sollwertbereich verglichen werden.In order to be able to obtain the clearest possible differentiation result, it can preferably be provided that several parameters are compared with an associated setpoint or setpoint range. Accordingly, it can be provided that both the pressure in the section of the purge air line to be tested, the current strength with which the drive motor of the compressor is applied, and the resulting drive speed of the compressor are used, the pressure being used to define the operating state and the two other parameters or values determined for these parameters are compared with a nominal value or nominal value range in each case.

Grundsätzlich besteht die Möglichkeit, mittels des Verdichters in einem zu prüfenden Abschnitt der Spülluftleitung einen Überdruck oder einen Unterdruck (jeweils im Vergleich zu dem Umgebungsdruck) zu erzeugen, wobei eine Erzeugung von Überdruck verfahrenstechnische Vorteile aufweisen kann. Weiterhin besteht grundsätzlich die Möglichkeit, eine gleichzeitige Prüfung in den beiden, an verschiedenen Seiten an den Verdichter angrenzenden Abschnitten der Spülluftleitung durchzuführen, indem mittels des Verdichters in dem einen Abschnitt ein Unterdruck und in dem anderen Abschnitt ein Überdruck erzeugt wird.Basically, there is the possibility of using the compressor to generate an overpressure or a negative pressure (in each case compared to the ambient pressure) in a section of the scavenging air line to be tested, whereby the generation of overpressure can have procedural advantages. Furthermore, there is basically the possibility of carrying out a simultaneous test in the two sections of the purge air line adjoining the compressor on different sides by generating a negative pressure in one section and an overpressure in the other section by means of the compressor.

Weiterhin besteht auch die Möglichkeit, in den beiden, an verschiedenen Seiten an den Verdichter angrenzenden Abschnitten der Spülluftleitung (nacheinander) eine Prüfung auf ausreichende Dichtheit durchzuführen, indem der Verdichter zunächst gemäß einer ersten Förderrichtung betrieben wird, wodurch in einem zuerst zu prüfenden Abschnitt ein Überdruck oder Unterdruck erzeugt wird, und anschließend den Verdichter gemäß einer zweiten Förderrichtung zu betreiben, um in dem dann zu prüfenden Abschnitt einen Überdruck oder Unterdruck zu erzeugen.Furthermore, there is also the possibility of performing a test for sufficient tightness in the two sections of the purge air line adjoining the compressor on different sides (one after the other) by initially operating the compressor in a first conveying direction, which creates an overpressure in a section to be tested first or negative pressure is generated, and then to operate the compressor according to a second conveying direction in order to generate an overpressure or negative pressure in the section then to be tested.

In einer bevorzugten Ausführungsform eines erfindungsgemäßen Verfahrens kann vorgesehen sein, dieses bei einer Brennkraftmaschine anzuwenden, bei der zwischen dem Kraftstoffdampffilter und der Umgebungsmündung ein Absperrventil in eine Umgebungsluftleitung integriert ist. Dieses Absperrventil kann vorzugsweise geschlossen gehalten werden, wenn eine Prüfung (auch) des zwischen dem Verdichter und dem Kraftstoffdampffilter liegenden Abschnitts der Spülluftleitung durchgeführt wird. Da dabei trotz dieses geschlossenen Absperrventils über den Kraftstoffdampffilter eine fluidleitende Verbindung zwischen diesem Abschnitt der Spülluftleitung einerseits und der Entlüftungsleitung und damit auch dem Kraftstofftank andererseits gegeben ist, kann in diesem Fall nicht nur der zwischen dem Verdichter und dem Kraftstoffdampffilter liegende Abschnitt der Spülluftleitung sondern gleichzeitig insbesondere auch die Entlüftungsleitung und der Kraftstofftank auf ausreichende Dichtheit überprüft werden.In a preferred embodiment of a method according to the invention, it can be provided that this is used in an internal combustion engine in which a shut-off valve is integrated in an ambient air line between the fuel vapor filter and the ambient mouth. This shut-off valve can preferably be closed are held when a test is (also) carried out on the section of the purge air line between the compressor and the fuel vapor filter. Since, despite this closed shut-off valve, there is a fluid-conducting connection via the fuel vapor filter between this section of the purge air line on the one hand and the vent line and thus also the fuel tank on the other hand, in this case not only the section of the purge air line between the compressor and the fuel vapor filter but also in particular the ventilation line and the fuel tank must also be checked for adequate leaks.

In einer weiterhin bevorzugten Ausführungsform eines erfindungsgemäßen Verfahrens kann eine Verwendung bei einer Brennkraftmaschine vorgesehen sein, bei der die Spülluftleitung verzweigt ist, wobei eine erste Mündung in den Frischgasstrang stromauf eines in den Frischgasstrang integrierten, zur Aufladung eines Verbrennungsmotors der Brennkraftmaschine dienenden Frischgasverdichters und eine zweite Mündung der Spülluftleitung in den Frischgasstrang stromab des Frischgasverdichters angeordnet ist. Dabei kann der Verdichter zwischen der Verzweigung einerseits und der ersten Mündung oder der zweiten Mündung andererseits in die Spülluftleitung integriert sein. Weiterhin bevorzugt ist dann noch vorgesehen, dass auch in den Zweig der Spülluftleitung, in den der Verdichter nicht integriert ist, ein Absperrventil integriert ist.In a further preferred embodiment of a method according to the invention, use in an internal combustion engine can be provided in which the scavenging air line is branched, with a first opening into the fresh gas line upstream of a fresh gas compressor integrated into the fresh gas line and used for charging an internal combustion engine of the internal combustion engine, and a second opening the purge air line is arranged in the fresh gas line downstream of the fresh gas compressor. The compressor can be integrated into the scavenging air line between the branch on the one hand and the first opening or the second opening on the other hand. It is then also preferably provided that a shut-off valve is also integrated into the branch of the scavenging air line in which the compressor is not integrated.

Das oder jedes der Absperrventile eines Kraftstofftanksystems, bei dem das erfindungsgemäße Verfahren zur Anwendung kommen kann, kann aktiv (ansteuerbar) oder passiv (d.h. selbständig betätigend, beispielsweise in Form eines Rückschlagventils) ausgebildet sein.The or each of the shut-off valves of a fuel tank system, in which the method according to the invention can be used, can be designed to be active (controllable) or passive (i.e. independently actuating, for example in the form of a non-return valve).

Weiterhin kann auch in vorteilhafter Weise die Anwendung eines erfindungsgemäßen Verfahrens bei einer Brennkraftmaschine vorgesehen sein, bei der dem Kraftstoffdampffilter ein (zusätzliches) Tankleckdiagnosemodul, beispielsweise ein Tankleckdiagnosemodul, wie es in der DE 10 2012 218 933 A1 beschrieben ist, zugeordnet ist. Dann kann insbesondere vorgesehen sein, den Abschnitt der Spülluftleitung zwischen dem Verdichter einerseits und dem Kraftstoffdampffilter beziehungsweise dem Tankleckdiagnosemodul andererseits und/oder die Entlüftungsleitung und den Kraftstofftank mittels des Tankleckdiagnosemoduls hinsichtlich einer ausreichenden Dichtheit zu überprüfen, während (gleichzeitig oder zeitlich versetzt) zumindest der Abschnitt zwischen dem Verdichter einerseits und der Mündung der Spülluftleitung in den Frischgasstrang oder dem dazwischen angeordnete Absperrventil andererseits auf erfindungsgemäße Weise hinsichtlich einer ausreichenden Dichtheit überprüft wird. Auf diese Weise kann ein als Massenprodukt auf dem Markt erhältliches und somit relativ kostengünstiges Tankleckdiagnosemodul eingesetzt werden, um einen oder mehrere Abschnitte des Kraftstofftanksystems hinsichtlich einer ausreichenden Dichtheit zu überprüfen. Gleichzeitig kann in das Kraftstofftanksystem ein Verdichter integriert sein, dessen zusätzliche oder sogar primäre Funktion ein Realisieren eines Spülens des Kraftstoffdampffilters bei einem unzureichenden Unterdruck in dem Frischgasstrang ist, wobei infolge der Integration dieses Verdichters verhindert sein kann, dass auch derjenige Abschnitt der Spülluftleitung, der auf der bezüglich des Kraftstoffdampffilters beziehungsweise des Tankleckdiagnosemoduls distalen Seite des Verdichters gelegen ist, ebenfalls durch das Tankleckdiagnosemodul überprüft werden kann. Dieser Abschnitt der Spülluftleitung kann dann jedoch auf erfindungsgemäße Weise geprüft werden.Furthermore, the use of a method according to the invention in an internal combustion engine can also be provided in an advantageous manner, in which the fuel vapor filter has an (additional) tank leak diagnosis module, for example a tank leak diagnosis module, as is shown in FIG DE 10 2012 218 933 A1 is described, is assigned. It can then be provided in particular to check the section of the scavenging air line between the compressor on the one hand and the fuel vapor filter or the tank leak diagnosis module on the other hand and / or the vent line and the fuel tank by means of the tank leak diagnosis module with regard to sufficient tightness, while (at the same time or offset in time) at least the section between the compressor on the one hand and the opening of the purge air line in the fresh gas line or the shut-off valve arranged between them on the other hand is checked in a manner according to the invention with regard to sufficient tightness. In this way, a mass product available on the market and thus relative Inexpensive tank leak diagnosis module can be used to check one or more sections of the fuel tank system for sufficient tightness. At the same time, a compressor can be integrated into the fuel tank system, the additional or even primary function of which is to flush the fuel vapor filter when there is insufficient negative pressure in the fresh gas line, whereby the integration of this compressor can prevent that section of the purge air line that is open which is located on the distal side of the compressor with respect to the fuel vapor filter or the tank leak diagnosis module, can also be checked by the tank leak diagnosis module. However, this section of the scavenging air line can then be checked in a manner according to the invention.

Grundsätzlich besteht die Möglichkeit, mittels eines solchen Tankleckdiagnosemoduls, das insbesondere auch einen (zusätzlichen) Verdichter umfassen kann, eine Prüfung auf ausreichende Dichtheit des gesamten Kraftstofftanksystems durchzuführen, sofern auf einen erfindungsgemäß vorgesehenen, in die Spülluftleitung integrierten Verdichter verzichtet würde oder dieser zumindest nicht in Form eines Kolbenverdichters sondern in Form eines Strömungsverdichters (Gebläse) ausgebildet ist (weil er dann auch im Stillstand ausreichend gasdurchlässig ist). Dies kann jedoch mit Nachteilen verbunden sein. Insbesondere kann dies eine druckfeste Auslegung des Kraftstoffdampffilters und/oder die Integration eines weiteren Absperrventils oder anderer konstruktiver Maßnahmen, die beim Spülen des Kraftstoffdampffilters mittels des Tankleckdiagnosemoduls eine gegebenenfalls ungewollte Druckerhöhung in dem Kraftstofftank verhindern, erforderlich machen.In principle, there is the possibility of using such a tank leak diagnosis module, which in particular can also include an (additional) compressor, to carry out a test for sufficient tightness of the entire fuel tank system, provided that a compressor that is provided according to the invention and integrated into the purge air line would be dispensed with or at least not in form a reciprocating compressor but in the form of a flow compressor (fan) (because it is then sufficiently gas-permeable even at standstill). However, this can have disadvantages. In particular, this may require a pressure-tight design of the fuel vapor filter and / or the integration of a further shut-off valve or other design measures that prevent an undesired pressure increase in the fuel tank when the fuel vapor filter is flushed using the tank leak diagnosis module.

Das erfindungsgemäße Verfahren kann insbesondere bei einem Kraftstofftanksystem einer Brennkraftmaschine zur Anwendung kommen, die einen nach dem Otto-Prinzip betriebenen Verbrennungsmotor umfasst, weil die für den Betrieb solcher Verbrennungsmotoren genutzten Kraftstoff relativ (insbesondere im Vergleich zu Diesel-Kraftstoff) leicht flüchtig sind, wodurch nicht nur die besondere Notwendigkeit einer Tankentlüftung sondern auch einer Prüfung der Dichtheit des Kraftstofftanksystems begründet ist.The method according to the invention can be used in particular in a fuel tank system of an internal combustion engine which comprises an internal combustion engine operated according to the Otto principle, because the fuel used to operate such internal combustion engines is relatively volatile (especially compared to diesel fuel), which means that it is not only the special need for tank ventilation but also a test of the tightness of the fuel tank system is justified.

Die Bezeichnung "Kraftstoffdampffilter" bedingt erfindungsgemäß nicht, dass dieser den flüchtigen Kraftstoff in gasförmiger Form filtern muss. Vielmehr kann der Kraftstoff bei der Filterung auch schon wieder (teilweise) auskondensiert sein.According to the invention, the term “fuel vapor filter” does not mean that it has to filter the volatile fuel in gaseous form. Rather, the fuel can already be (partially) condensed out again during the filtering.

Die unbestimmten Artikel ("ein", "eine", "einer" und "eines"), insbesondere in den Patentansprüchen und in der die Patentansprüche allgemein erläuternden Beschreibung, sind als solche und nicht als Zahlwörter zu verstehen. Entsprechend damit konkretisierte Komponenten sind somit so zu verstehen, dass diese mindestens einmal vorhanden sind und mehrfach vorhanden sein können.The indefinite articles ("a", "an", "an" and "an"), in particular in the claims and in the description which generally explains the claims, are as such and not as numerals. Components specified in this way are therefore to be understood in such a way that they are present at least once and can be present several times.

Die vorliegende Erfindung wird nachfolgend anhand von in den Zeichnungen dargestellten Ausführungsbeispielen näher erläutert. In den Zeichnungen zeigt:

Fig. 1:
ein zur Durchführung eines erfindungsgemäßen Verfahrens geeignetes Kraftstofftanksystem einer Brennkraftmaschine;
Fig. 2:
in zwei Diagrammen die Verläufe des Drucks in einem auf ausreichende Dichtheit zu prüfenden Abschnitt der Spülluftleitung einer Brennkraftmaschine gemäß der Fig. 1 sowie der Stromstärke und der Antriebsdrehzahl des für die Druckerzeugung genutzten Verdichters bei einer definierten Undichtheit im Vergleich zu den entsprechenden Verläufen bei einer bestmöglichen Dichtheit desselben Abschnitts der Spülluftleitung; und
Fig. 3:
eine zu dem Kraftstofftanksystem gemäß der Fig. 1 leicht abgewandelte Ausgestaltungsform eines ebenfalls zur Durchführung eines erfindungsgemäßen Verfahrens geeigneten Kraftstofftanksystems einer Brennkraftmaschine.
The present invention is explained in more detail below with reference to the exemplary embodiments shown in the drawings. In the drawings shows:
Fig. 1:
a fuel tank system of an internal combustion engine suitable for carrying out a method according to the invention;
Fig. 2:
In two diagrams, the pressure curves in a section of the scavenging air line of an internal combustion engine to be checked for sufficient tightness according to FIG Fig. 1 as well as the current intensity and the drive speed of the compressor used for pressure generation in the case of a defined leak in comparison to the corresponding curves in the case of the best possible tightness of the same section of the purge air line; and
Fig. 3:
one to the fuel tank system according to FIG Fig. 1 slightly modified embodiment of a fuel tank system of an internal combustion engine which is also suitable for carrying out a method according to the invention.

Die Fig. 1 zeigt ein Kraftstofftanksystem einer Brennkraftmaschine. Dieses umfasst einen Kraftstofftank 10, der über eine Entlüftungsleitung 12 mit einem Kraftstoffdampffilter 14, der insbesondere in Form eines Aktivkohlefilters oder zumindest einen solchen umfassend ausgebildet sein kann, verbunden ist. Der Kraftstoffdampffilter 14 ist weiterhin über eine Spülluftleitung 16 mit einem Frischgasstrang 18 der Brennkraftmaschine verbunden, wobei die Spülluftleitung 16 ausgehend von einer Verzweigung 20 in zwei Zweigen 22, 24 verläuft, von denen ein erster Zweig 22 in den Frischgasstrang 18 stromauf (bezüglich der Strömungsrichtung von Frischgas in dem Frischgasstrang 18 ausgehend von einem Frischgaseinlass (nicht dargestellt) zu einem Verbrennungsmotor 26 der Brennkraftmaschine) eines in den Frischgasstrang 18 integrierten Frischgasverdichters 28 und der zweite, optional vorhandene Zweig 24 stromab des Frischgasverdichters 28 und insbesondere auch stromab einer ebenfalls stromab des Frischgasverdichters 28 in den Frischgasstrang 18 integrierten Drosselklappe 54 mündet. Der Frischgasverdichter 28 ist Teil eines Abgasturboladers, der weiterhin eine Abgasturbine 30 umfasst, die in einen Abgasstrang 32 der Brennkraftmaschine integriert ist.The Fig. 1 Fig. 10 shows a fuel tank system of an internal combustion engine. This comprises a fuel tank 10, which is connected via a vent line 12 to a fuel vapor filter 14, which can be designed in particular in the form of an activated carbon filter or at least one comprising such a filter. The fuel vapor filter 14 is also connected to a fresh gas line 18 of the internal combustion engine via a scavenging air line 16, the scavenging air line 16 running from a branch 20 in two branches 22, 24, of which a first branch 22 enters the fresh gas line 18 upstream (with respect to the direction of flow from Fresh gas in the fresh gas line 18 starting from a fresh gas inlet (not shown) to an internal combustion engine 26 of the internal combustion engine) of a fresh gas compressor 28 integrated in the fresh gas line 18 and the second, optionally present branch 24 downstream of the fresh gas compressor 28 and in particular also downstream of a likewise downstream of the fresh gas compressor 28 The throttle valve 54 integrated into the fresh gas line 18 opens. The fresh gas compressor 28 is part of an exhaust gas turbocharger which further comprises an exhaust gas turbine 30 which is integrated into an exhaust gas line 32 of the internal combustion engine.

Im Betrieb der Brennkraftmaschine wird in bekannter Weise in definierter Reihenfolge in Brennräumen 34 des Verbrennungsmotors 26, die teilweise von Zylindern 34 des Verbrennungsmotors 26 begrenzt sind, Gemische aus Frischgas, das vollständig oder im Wesentlichen aus Umgebungsluft besteht, und beispielsweise direkt in die Brennräume 34 eingespritztem Kraftstoff verbrannt, wobei die so erzeugten Druckerhöhungen in den Brennräumen 34 dazu genutzt werden, in den Zylindern 36 längsaxial beweglich geführte Kolben 38 zu bewegen. Diese Bewegungen der Kolben 38 werden unter Zwischenschaltung von Pleueln (nicht dargestellt) in eine Drehbewegung einer Kurbelwelle (nicht dargestellt) übersetzt, wobei die Führung der Kolben 38 über die Pleuel mittels der Kurbelwelle gleichzeitig zu einer zyklischen Hin-und-her-Bewegung der Kolben 38 führt. Das bei der Verbrennung der Frischgas-Kraftstoff-Gemische in den Brennräumen 34 entstandene Abgas wird über den Abgasstrang 32 abgeführt und durchströmt dabei die Abgasturbine 30, was zu einem drehenden Antrieb eines Turbinenlaufrads (nicht dargestellt) führt. Diese Drehung des Turbinenlaufrads wird mittels einer Welle 40 auf ein Verdichterlaufrad (nicht dargestellt) des Frischgasverdichters 28 übertragen, wodurch der Frischgasverdichter 28 für eine Verdichtung des über den Frischgasstrang 18 dem Verbrennungsmotor 26 zugeführten Frischgases sorgt.During operation of the internal combustion engine, mixtures of fresh gas, which consists entirely or essentially of ambient air, and, for example, injected directly into the combustion chambers 34, are in a known manner in a defined order in combustion chambers 34 of internal combustion engine 26, some of which are delimited by cylinders 34 of internal combustion engine 26 Fuel is burned, the pressure increases thus generated in the combustion chambers 34 being used to move pistons 38, which are guided in a longitudinally axially movable manner in the cylinders 36. These movements of the pistons 38 are translated into a rotary movement of a crankshaft (not shown) with the interposition of connecting rods (not shown), the guiding of the pistons 38 over the connecting rods by means of the crankshaft simultaneously to a cyclic back and forth movement of the pistons 38 leads. The exhaust gas resulting from the combustion of the fresh gas / fuel mixtures in the combustion chambers 34 is discharged via the exhaust gas line 32 and flows through the exhaust gas turbine 30, which leads to a rotating drive of a turbine impeller (not shown). This rotation of the turbine impeller is transmitted by means of a shaft 40 to a compressor impeller (not shown) of the fresh gas compressor 28, as a result of which the fresh gas compressor 28 compresses the fresh gas supplied to the internal combustion engine 26 via the fresh gas line 18.

Der Kraftstoffdampffilter 14 des Kraftstofftanksystems steht mit seiner bezüglich der Entlüftungsleitung 12 und der Spülluftleitung 16 abgewandten Seite (bezogen auf dessen Filterwirkung für Kraftstoffdämpfe) über eine Umgebungsluftleitung 42 mit einem darin integrierten (ersten) Absperrventil 44 mit der Umgebung in gasleitender Verbindung, wozu die Umgebungsluftleitung 42 eine Umgebungsmündung 62 ausbildet. Das erste Absperrventil 44 ist mittels einer Steuervorrichtung 48 (z.B. der Motorsteuerung der Brennkraftmaschine) ansteuerbar, d.h. dieses kann aktiv geöffnet oder geschlossen werden. Optional kann in die Umgebungsluftleitung 42 auch ein grundsätzlich bekanntes Tankleckdiagnosemodul 46 integriert sein, wobei in diesem Fall das erste Absperrventil 44 auch integraler Bestandteil des Tankleckdiagnosemodul 46 sein kann.The side of the fuel vapor filter 14 of the fuel tank system facing away from the vent line 12 and the purge air line 16 (based on its filtering effect for fuel vapors) is in gas-conducting connection via an ambient air line 42 with a (first) shut-off valve 44 integrated therein, including the ambient air line 42 a surrounding mouth 62 forms. The first shut-off valve 44 can be controlled by means of a control device 48 (e.g. the engine control of the internal combustion engine), i. this can be actively opened or closed. Optionally, a tank leak diagnosis module 46, which is known in principle, can also be integrated into the ambient air line 42, in which case the first shut-off valve 44 can also be an integral part of the tank leak diagnosis module 46.

Der Kraftstofftank 10 ist teilweise mit flüssigem Kraftstoff gefüllt, wobei ein Teil dieses Kraftstoffs verdampft ist, so dass in dem Kraftstofftank 10 auch Kraftstoff in gasförmigem Aggregatzustand vorliegt. Ein solches Verdampfen von Kraftstoff in dem Kraftstofftank 10 wird durch eine relativ hohe Temperatur des Kraftstoffs verstärkt, was insbesondere bei vergleichsweise hohen Umgebungstemperaturen der Fall ist. Um einen durch dieses Verdampfen bedingten, unzulässig hohen Überdruck in dem Kraftstofftank 10 zu vermeiden, ist die Möglichkeit eines zumindest teilweisen Druckausgleichs mit dem Umgebungsdruck über die Entlüftungsleitung 12 und den Kraftstoffdampffilter 14 sowie über die Umgebungsluftleitung 42 bereitgestellt, wobei durch den Kraftstoffdampffilter 14 vermieden wird, dass ein solcher Druckausgleich zu einem Entweichen von Kraftstoffdämpfen in die Umgebung führt.The fuel tank 10 is partially filled with liquid fuel, some of this fuel being vaporized, so that fuel is also present in the fuel tank 10 in a gaseous state. Such evaporation of fuel in the fuel tank 10 is intensified by a relatively high temperature of the fuel, which is the case in particular at comparatively high ambient temperatures. In order to avoid an inadmissibly high overpressure in the fuel tank 10 caused by this evaporation, there is the possibility of at least partial pressure equalization with the ambient pressure via the ventilation line 12 and the fuel vapor filter 14 and provided via the ambient air line 42, the fuel vapor filter 14 preventing such pressure equalization from leading to an escape of fuel vapors into the environment.

Ein solches Entlüften des Kraftstofftanks führt zu einer zunehmenden Sättigung des Kraftstoffdampffilters 14, was wiederum bedingt, diesen in regelmäßigen Abständen zu regenerieren. Hierzu ist ein Spülen des Kraftstoffdampffilters 14 vorgesehen, indem Umgebungsluft über die Umgebungsluftleitung 42 und das darin integrierte erste, dann geöffnete Absperrventil 44 angesaugt wird. Diese Umgebungsluft durchströmt den Kraftstoffdampffilter 14 in im Vergleich zu der Durchströmung bei der Entlüftung des Kraftstofftanks 10 entgegengesetzter Durchströmungsrichtung, wodurch in dem Kraftstoffdampffilter 10 absorbierte Kraftstoffmoleküle durch die Umgebungsluft mitgenommen und über die Spülluftleitung 16 in den Frischgasstrang 18 eingetragen werden, wodurch dieser Kraftstoff einer Verbrennung in den Brennräumen 34 des Verbrennungsmotors 26 zugeführt wird. Ein solches Spülen des Kraftstoffdampffilters 14 ist lediglich zeitweise und stets während des Betriebs des Verbrennungsmotors 26 vorgesehen, weil nur dann der durch das Spülen des Kraftstoffdampffilters 14 in den Frischgasstrang 18 eingebrachte Kraftstoff auch sicher einer Verbrennung in den Brennräumen 34 zugeführt werden kann. Ein Einbringen in den Frischgasstrang 18 bei einem Nichtbetrieb des Verbrennungsmotors 26 könnte dagegen dazu führen, dass der gasförmige Kraftstoff über Undichtheiten im Frischgasstrang 18 und insbesondere über eine Ansaugöffnung des Frischgasstrangs 18 in die Umgebung entweichen könnte.Such a venting of the fuel tank leads to increasing saturation of the fuel vapor filter 14, which in turn requires it to be regenerated at regular intervals. For this purpose, the fuel vapor filter 14 is flushed in that ambient air is sucked in via the ambient air line 42 and the first, then opened shut-off valve 44 integrated therein. This ambient air flows through the fuel vapor filter 14 in the opposite flow direction compared to the flow when venting the fuel tank 10, whereby fuel molecules absorbed in the fuel vapor filter 10 are carried along by the ambient air and entered into the fresh gas line 18 via the scavenging air line 16, whereby this fuel is subjected to combustion the combustion chambers 34 of the internal combustion engine 26 is supplied. Such a flushing of the fuel vapor filter 14 is only provided temporarily and always during the operation of the internal combustion engine 26, because only then can the fuel introduced into the fresh gas line 18 by flushing the fuel vapor filter 14 also be safely fed to combustion in the combustion chambers 34. An introduction into the fresh gas line 18 when the internal combustion engine 26 is not in operation, however, could lead to the gaseous fuel being able to escape into the environment via leaks in the fresh gas line 18 and in particular via an intake opening of the fresh gas line 18.

Für ein Spülen des Kraftstoffdampffilters 14 ist ein ausreichendes Druckgefälle von dem Umgebungsdruck bis zu dem Druck im Frischgasstrang 18 im Bereich der Mündungen 50, 52 der Spülluftleitung 16 erforderlich, die aufgrund stark schwankender Drücke in dem Frischgasstrang 18 nicht immer gegeben ist. Hinsichtlich des Druckgefälles von dem Umgebungsdruck zu dem Druck im Frischgasstrang 18 im Bereich der (zweiten) Mündung 52 des zweiten Zweigs 24 der Spülluftleitung 16 liegt häufig nicht einmal ein Druckgefälle sondern ein Druckanstieg vor, weil diese zweite Mündung 52 im Bereich der sich zwischen dem Frischgasverdichter 28 und dem Verbrennungsmotor 26 erstreckenden Ladeluftstrecke des Frischgasstrangs 18 gelegen ist, in der das Frischgas infolge der Verdichtung durch den Frischgasverdichter 28 häufig mit erhöhtem Druck vorliegt. Durch eine Anordnung dieser zweiten Mündung 52 (möglichst nahe) stromab einer Drosselklappe 54 kann zwar eine durch die Drosselklappe 54 bewirkte Druckabsenkung ausgenutzt werden; diese Druckabsenkung ist jedoch häufig nicht ausreichend, um tatsächlich ein ausreichendes Druckgefälle über der Spülluftleitung 16 zu realisieren. In diesen zweiten Zweig 24 der Spülluftleitung 16 ist daher ein Rückschlagventil 56 integriert, durch das dieser Zweig 24 der Spülluftleitung 16 selbsttätig geschlossen gehalten wird, wenn im Bereich der zweiten Mündung 52 ein Überdruck im Vergleich zu dem auf der anderen Seite des Rückschlagventils gelegenen Abschnitt des zweiten Zweigs 24 der Spülluftleitung 16 vorliegt. Ergänzend dazu ist stromauf (bezüglich der Durchströmungsrichtung beim Spülen des Kraftstoffdampffilters 14) ein aktiv mittels der Steuervorrichtung 48 ansteuerbares (zweites) Absperrventil 58 in den zweiten Zweig 24 der Spülluftleitung 16 integriert. Grundsätzlich besteht die Möglichkeit, infolge der Anordnung dieses Absperrventils 58 auf das Rückschlagventil 56 zu verzichten, sofern das Absperrventil 58 ausreichend überdruckfest ausgelegt ist (d.h. dieses muss bei den zumindest temporär auftretenden Überdrücken auf der Seite der Ladeluftstrecke des Frischgasstrangs 18 ausreichend dicht geschlossen halten).For flushing the fuel vapor filter 14, a sufficient pressure gradient from the ambient pressure to the pressure in the fresh gas line 18 in the area of the mouths 50, 52 of the scavenging air line 16 is required, which is not always the case due to strongly fluctuating pressures in the fresh gas line 18. With regard to the pressure gradient from the ambient pressure to the pressure in the fresh gas line 18 in the area of the (second) opening 52 of the second branch 24 of the purge air line 16, there is often not even a pressure gradient but a pressure increase, because this second opening 52 is in the area between the fresh gas compressor 28 and the internal combustion engine 26 extending charge air path of the fresh gas line 18, in which the fresh gas is often present at increased pressure as a result of the compression by the fresh gas compressor 28. By arranging this second orifice 52 (as close as possible) downstream of a throttle valve 54, a pressure drop brought about by the throttle valve 54 can be used; however, this pressure drop is often not sufficient to actually create a sufficient pressure gradient across the To realize purge air line 16. In this second branch 24 of the scavenging air line 16, a check valve 56 is therefore integrated, by means of which this branch 24 of the scavenging air line 16 is automatically kept closed if there is an overpressure in the area of the second opening 52 compared to the section of the on the other side of the check valve second branch 24 of the scavenging air line 16 is present. In addition, a (second) shut-off valve 58, which can be actively controlled by means of the control device 48, is integrated into the second branch 24 of the scavenging air line 16 upstream (with respect to the direction of flow when flushing the fuel vapor filter 14). In principle, it is possible to dispense with the check valve 56 as a result of the arrangement of this shut-off valve 58, provided that the shut-off valve 58 is designed to be sufficiently overpressure-resistant (i.e. it must keep sufficiently tightly closed with the at least temporarily occurring overpressures on the side of the charge air path of the fresh gas line 18).

Der erste Zweig der Spülluftleitung 22 mündet dagegen in einen stromauf des Frischgasverdichters 28 gelegenen Abschnitt des Frischgasstrangs 18, wobei in den Abschnitt dieses Zweigs 22 der Spülluftleitung 16 zwischen dem Frischgasverdichter 28 und dieser (ersten) Mündung 50 ein (drittes) Absperrventil 60 integriert ist, das möglichst nah an der ersten Mündung 50 angeordnet oder vorzugsweise in diese integriert ist. In dem Abschnitt des Frischgasstrangs 18 im Bereich der ersten Mündung 50 ist der Druck des Frischgases (im Betrieb des Frischgasverdichters 28) niedriger als in der Ladeluftstrecke, so dass bezüglich dieser ersten Mündung 50 der Spülluftleitung relativ häufig ein ausreichendes Druckgefälle im Vergleich (und ausgehend) von dem an der Umgebungsmündung 62 anliegenden Umgebungsdruck vorliegen kann. Dies ist jedoch nicht immer der Fall, beispielsweise bei einem Betrieb eines die Brennkraftmaschine umfassenden Kraftfahrzeugs mit nicht betriebenem Verbrennungsmotor (beispielsweise aufgrund einer automatischen Start/Stopp-Funktion).The first branch of the purge air line 22, on the other hand, opens into a section of the fresh gas line 18 located upstream of the fresh gas compressor 28, a (third) shut-off valve 60 being integrated into the section of this branch 22 of the purge air line 16 between the fresh gas compressor 28 and this (first) opening 50, which is arranged as close as possible to the first mouth 50 or preferably integrated into it. In the section of the fresh gas line 18 in the area of the first opening 50, the pressure of the fresh gas (when the fresh gas compressor 28 is in operation) is lower than in the charge air line, so that with respect to this first opening 50 of the scavenging air line, a sufficient pressure gradient is relatively often in comparison (and starting) of the ambient pressure present at the ambient mouth 62. However, this is not always the case, for example when a motor vehicle comprising the internal combustion engine is operated with the internal combustion engine not being operated (for example due to an automatic start / stop function).

Um jederzeit ein Spülen des Kraftstoffdampffilters 14 zu ermöglichen, so dass sicher eine vollständige Sättigung desselben verhindert werden kann, umfasst das Kraftstofftanksystem der Brennkraftmaschine noch einen auch als "Spülpumpe" bezeichneten Verdichter 64, der in Form eines Kolbenverdichters und beispielsweise als Flügelzellenverdichter ausgebildet sein kann. Durch einen Betrieb dieses Verdichters 64 kann aktiv Umgebungsluft über die Umgebungsmündung 62 angesaugt werden, die dann den Kraftstoffdampffilter 14 zu dessen Spülung durchströmt und über den Verdichter 64 bis zu der ersten Mündung 50 der Spülluftleitung 16 gefördert wird. Das in den zweiten Zweig 52 der Spülluftleitung 16 integrierte, dann geschlossen gehaltene zweite Absperrventil 58, zumindest jedoch das sich dabei selbständig schließende Rückschlagventil 56 verhindern dabei ein Ansaugen auch von Frischgas über die zweite Mündung 52 aus der Ladeluftstrecke des Frischgasstrangs 18.In order to allow the fuel vapor filter 14 to be flushed at any time, so that complete saturation of the same can be prevented, the fuel tank system of the internal combustion engine also includes a compressor 64, also known as a "flushing pump", which can be designed in the form of a piston compressor and, for example, a vane compressor. By operating this compressor 64, ambient air can be actively sucked in via the ambient opening 62, which then flows through the fuel vapor filter 14 to flush it and is conveyed via the compressor 64 to the first opening 50 of the flushing air line 16. The second shut-off valve 58, which is integrated into the second branch 52 of the scavenging air line 16 and then kept closed, but at least that is itself Automatically closing check valves 56 also prevent fresh gas from being sucked in via the second opening 52 from the charge air path of the fresh gas line 18.

Bei einer nicht-aufgeladenen Brennkraftmaschine ohne Frischgasverdichter 28 wäre eine Spülluftleitung 16, die den ersten Zweig 22 nicht umfasst, ausreichend für eine Spülung des Kraftstoffdampffilters 14. Bei einem aufgeladenen Verbrennungsmotor gemäß dem vorliegenden Ausgestaltungsbeispiel, kann (ausschließlich oder ergänzend) der erste Zweig 22 der Spülluftleitung 16 notwendig sein, da eine Spülung über ausschließlich den zweiten Zweig 24 häufig nicht möglich ist. Infolge der aktuellen Tendenz, den Verbrennungsmotor 26 einer Brennkraftmaschine stark entdrosselt zu betreiben, kann der Einsatz des Verdichters 64 sinnvoll oder notwendig für ein ausreichendes Spülen des Kraftstoffdampffilters 14 sein.In the case of a non-supercharged internal combustion engine without a fresh gas compressor 28, a scavenging air line 16 which does not include the first branch 22 would be sufficient for scavenging the fuel vapor filter 14. In a supercharged internal combustion engine according to the present exemplary embodiment, the first branch 22 of the Purge air line 16 may be necessary since purging via only the second branch 24 is often not possible. As a result of the current tendency to operate the internal combustion engine 26 of an internal combustion engine in a strongly dethrottled manner, the use of the compressor 64 may be useful or necessary for sufficient flushing of the fuel vapor filter 14.

Da in die Umgebung entweichende Kraftstoffdämpfe potenziell umwelt-und gesundheitsschädlich sind, ist es sinnvoll und teilweise auch gesetzlich vorgeschrieben, das Kraftstofftanksystem regelmäßig hinsichtlich einer ausreichenden Dichtheit zu prüfen. Dies soll erfindungsgemäß für zumindest einen Abschnitt des Kraftstofftanksystems unter Verwendung des auch als "Spülpumpe" genutzten Verdichters 64 erfolgen.Since fuel vapors escaping into the environment are potentially harmful to the environment and health, it is sensible, and in some cases also prescribed by law, to regularly check the fuel tank system for adequate tightness. According to the invention, this should take place for at least one section of the fuel tank system using the compressor 64, which is also used as a “flushing pump”.

Hierzu ist vorgesehen, dass im Rahmen eines erfindungsgemäßen Verfahrens mittels des Verdichters 64 in zumindest einem Abschnitt der Spülluftleitung 16 (und gegebenenfalls in einem oder mehreren an diesen Abschnitt der Spülluftleitung 16 gasleitend angeschlossenen weiteren Abschnitten des Kraftstofftanksystems), beispielsweise in dem Abschnitt zwischen dem Verdichter 64 und dem in den ersten Zweig 50 der Spülluftleitung 16 integrierten dritten Absperrventil 60 (bei geschlossenem dritten Absperrventil 60) eine Druckveränderung bewirkt wird, indem gemäß dem Vorgehen beim Spülen des Kraftstoffdampffilters 14 über das in die Umgebungsluftleitung integrierte, geöffnete erste Absperrventil 44 Umgebungsluft angesaugt und in den entsprechenden Abschnitt der Spülluftleitung 16 gefördert oder in diesem Abschnitt der Spülluftleitung 16 vorhandenes Gas teilweise mittels des Verdichters 64 evakuiert und in Richtung des Kraftstoffdampffilters 14 gefördert wird. Dabei werden neben dem Druck in diesem Abschnitt der Spülluftleitung 16, dessen Verlauf mittels eines Drucksensors 66 ermittelt werden kann, auch die (Antriebs-)Drehzahl eines Antriebsmotors (nicht dargestellt) des Verdichters 64 sowie die Stärke des elektrischen Stroms, mit dem dieser Antriebsmotor beaufschlagt wird, ermittelt. Durch eine Auswertung und insbesondere durch einen Vergleich dieser Parameter kann zwischen einer ausreichenden und einer nicht ausreichenden Dichtheit dieses Abschnitts der Spülluftleitung 16 unterschieden werden, wie dies beispielsweise aus der Fig. 2 ersichtlich ist.For this purpose, it is provided that within the scope of a method according to the invention, by means of the compressor 64, in at least one section of the purge air line 16 (and possibly in one or more further sections of the fuel tank system connected to this section of the purge air line 16 in a gas-conducting manner), for example in the section between the compressor 64 and the third shut-off valve 60 integrated in the first branch 50 of the scavenging air line 16 (with the third shut-off valve 60 closed), a pressure change is brought about by sucking in ambient air via the opened first shut-off valve 44 integrated in the ambient air line and pouring it into the fuel vapor filter 14 the corresponding section of the purge air line 16 is conveyed or gas present in this section of the purge air line 16 is partially evacuated by means of the compressor 64 and conveyed in the direction of the fuel vapor filter 14. In addition to the pressure in this section of the purge air line 16, the course of which can be determined by means of a pressure sensor 66, the (drive) speed of a drive motor (not shown) of the compressor 64 and the strength of the electrical current applied to this drive motor is determined. By evaluating and in particular by comparing these parameters, a distinction can be made between an adequate and an insufficient tightness of this section of the scavenging air line 16, as can be seen, for example, from FIG Fig. 2 can be seen.

In der Fig. 2 sind in zwei Diagrammen die (zeitgleichen) Verläufe einerseits (oberes Diagramm) der Stromstärke I (Verlaufslinien 68, 70) und andererseits (unteres Diagramm) des Drucks p (Verlaufslinien 72, 74) und der Antriebsdrehzahl n (Verlaufslinien 76, 78; prozentual im Vergleich zu einer konstruktiv oder regelungstechnisch für den Verdichter festgelegten Maximaldrehzahl) dargestellt, wobei für jeden dieser Parameter einerseits der Verlauf bei (bekanntermaßen) bestmöglicher Dichtheit dieses Abschnitts der Spülluftleitung 16 (dicke Strichstärke) und andererseits der Verlauf bei einer bekannten Undichtheit gemäß einem Referenzleck mit einer Größe von 0,5 mm (dünne Strichstärke) gegenübergestellt sind. Dabei setzt die Unterscheidung zwischen ausreichend und nicht ausreichend dicht gemäß einem erfindungsgemäßen Verfahren einen definierten Betriebszustand des Kraftstofftanksystems beziehungsweise des zu prüfenden Abschnitts voraus, der für das Ausführungsbeispiel gemäß der Fig. 2 durch die Erzeugung eines in beiden Fällen annähernd gleichen (mittleren) Drucks p in dem zu prüfenden Abschnitt definiert ist. Zu erkennen ist, dass zur Erzeugung eines im Wesentlichen gleichgroßen mittleren Drucks p in dem zu prüfenden Abschnitt der Spülluftleitung 16, einerseits bei bekanntermaßen dichtem Abschnitt und andererseits bei bekannter Undichtheit dieses Abschnitts, unterschiedliche Betriebsparameter des Verdichters 64 erforderlich sind, wobei bei undichtem Abschnitt sowohl die Antriebsdrehzahl n als auch die Stromstärke I deutlich größer sind (zudem schwankt die Stromstärke I deutlich stärker). Werden somit anhand der Verläufe der Stromstärke I und der Antriebsdrehzahl n, die für den bekanntermaßen bestmöglich dichten Abschnitt der Spülluftleitung ermittelt wurden, Sollwerte oder Sollwertbereiche für diese Betriebsparameter des Verdichters 64 ermittelt, kann anschließend regelmäßig durch die Erzeugung desselben oder eines vergleichbaren Betriebszustands (definiert durch den für die Ermittlung der Sollwerte oder Sollwertbereiche erzeugten mittleren Druck p) verglichen werden, ob die dann ermittelten Werte oder Wertverläufe dieser Betriebsparameter definierte Abweichungen gegenüber den Sollwerten oder Sollwertbereichen aufweisen, woraus dann auf eine ausreichende (keine oder unterhalb eines Grenzwerts liegende Abweichungen) oder nicht ausreichende (relativ große Abweichungen) Dichtheit geschlossen werden kann.In the Fig. 2 are in two diagrams the (simultaneous) courses on the one hand (upper diagram) of the current I (course lines 68, 70) and on the other hand (lower diagram) of the pressure p (course lines 72, 74) and the drive speed n (course lines 76, 78; percentage in Compared to a maximum speed determined by design or control technology for the compressor), with the course for each of these parameters on the one hand the course with (known) best possible tightness of this section of the purge air line 16 (thick line width) and on the other hand the course with a known leak according to a reference leak with a Size of 0.5 mm (thin line width) are compared. The distinction between sufficiently and not sufficiently tight according to a method according to the invention presupposes a defined operating state of the fuel tank system or of the section to be tested, which for the exemplary embodiment according to FIG Fig. 2 is defined by the generation of an approximately equal (mean) pressure p in both cases in the section to be tested. It can be seen that in order to generate an essentially equally large mean pressure p in the section of the scavenging air line 16 to be tested, on the one hand if the section is known to be tight and on the other hand if this section is known to be leaky, different operating parameters of the compressor 64 are required, with both the The drive speed n and the current I are significantly greater (the current I also fluctuates significantly more). If setpoints or setpoint ranges for these operating parameters of the compressor 64 are determined on the basis of the curves of the current intensity I and the drive speed n, which were determined for the section of the purge air line that is known to be the best possible leak-proof, then this can be done regularly by generating the same or a comparable operating state (defined by the mean pressure p) generated for the determination of the setpoint values or setpoint ranges are compared, whether the then determined values or value curves of these operating parameters have defined deviations from the setpoints or setpoint ranges, from which then a sufficient (no or below a limit value) deviations or not sufficient (relatively large deviations) tightness can be closed.

Die Fig. 3 zeigt eine Ausgestaltungsform einer Brennkraftmaschine, bei der das Kraftstofftanksystem gegenüber demjenigen der Brennkraftmaschine gemäß der Fig. 1 leicht abgewandelt ist. Konkret ist vorgesehen, das bei dem Kraftstofftanksystem gemäß der Fig. 1 in den zweiten Zweig 24 der Spülluftleitung 16 integrierte zweite Absperrventil 58 stromauf (bezüglich der Durchströmung der Spülluftleitung 16 beim Spülen des Kraftstoffdampffilters 14) der Abzweigung 20 anzuordnen. Hinsichtlich der anhand der Fig. 1 und 2 beschriebenen Prüfung des zwischen dem Verdichter 64 und dem der ersten Mündung 50 zugeordneten dritten Absperrventils 60 angeordneten Abschnitts der Spülluftleitung 16 hat diese geänderte Anordnung des zweiten Absperrventils keine Auswirkungen. Ermöglicht wird dagegen jedoch eine Prüfung der Abschnitte der Spülluftleitung 16, die zum einen zwischen diesem zweiten Absperrventil 58 und dem Verdichter 64 und zum anderen zwischen der Abzweigung 20 und dem Rückschlagventil 56 in dem zweiten Zweig 24 der Spülluftleitung 16 angeordnet sind. Durch ein Schließen des zweiten Absperrventils 58 kann mittels des Verdichters 64 in diesen Abschnitten der Spülluftleitung 16 ein definiertes Druckniveau und damit ein definierter Betriebszustand eingestellt werden (wozu der Drucksensor 66 an einer Stelle in diesen Abschnitten angeordnet werden könnte), was ermöglicht, durch einen Vergleich der für das Einstellen dieses Betriebszustands erforderlichen Betriebsparameter des Verdichters 64 zwischen einer ausreichenden und einer nicht ausreichenden Dichtigkeit zu unterscheiden, wie dies anhand der Fig. 2 erläutert worden ist. Dabei kann vorgesehen sein, diese Abschnitte der Spülluftleitung 16 zu evakuieren, wobei das evakuierte Gas über die erste Mündung 50 der Spülluftleitung 16 in den Frischgasstrang 18 ausgestoßen wird. Es besteht aber auch die Möglichkeit einer Erzeugung eines definierten Überdrucks, wobei dieser dann so bemessen sein sollte, dass weiterhin ein sicheres Geschlossenhalten des Rückschlagventils 56 gewährleistet ist.The Fig. 3 shows an embodiment of an internal combustion engine in which the fuel tank system compared to that of the internal combustion engine according to FIG Fig. 1 is slightly modified. Specifically, it is provided that in the fuel tank system according to Fig. 1 Second shut-off valve 58 integrated in the second branch 24 of the scavenging air line 16 is to be arranged upstream of the junction 20 (with regard to the flow through the scavenging air line 16 when the fuel vapor filter 14 is flushed). With regard to the Fig. 1 and 2 described Checking the section of the scavenging air line 16 arranged between the compressor 64 and the third shut-off valve 60 associated with the first opening 50, this changed arrangement of the second shut-off valve has no effects. On the other hand, it enables the sections of the purge air line 16 to be checked which are arranged on the one hand between this second shut-off valve 58 and the compressor 64 and on the other hand between the branch 20 and the check valve 56 in the second branch 24 of the purge air line 16. By closing the second shut-off valve 58, a defined pressure level and thus a defined operating state can be set by means of the compressor 64 in these sections of the purge air line 16 (for which the pressure sensor 66 could be arranged at a point in these sections), which is made possible by a comparison the operating parameters of the compressor 64 required for setting this operating state to differentiate between an adequate and an insufficient tightness, as shown on the basis of FIG Fig. 2 has been explained. It can be provided that these sections of the purge air line 16 are evacuated, the evacuated gas being expelled via the first opening 50 of the purge air line 16 into the fresh gas line 18. However, there is also the possibility of generating a defined overpressure, in which case this should then be dimensioned in such a way that the non-return valve 56 is still reliably kept closed.

BezugszeichenlisteList of reference symbols

1010
KraftstofftankFuel tank
1212
EntlüftungsleitungVent line
1414th
KraftstoffdampffilterFuel vapor filter
1616
SpülluftleitungPurge air line
1818th
FrischgasstrangFresh gas line
2020th
Verzweigung der SpülluftleitungBranch of the purge air line
2222nd
erster Zweig der Spülluftleitungfirst branch of the purge air line
2424
zweiter Zweig der Spülluftleitungsecond branch of the purge air line
2626th
VerbrennungsmotorInternal combustion engine
2828
FrischgasverdichterFresh gas compressor
3030th
AbgasturbineExhaust gas turbine
3232
AbgasstrangExhaust system
3434
Brennraum des VerbrennungsmotorsCombustion chamber of the internal combustion engine
3636
Zylinder des VerbrennungsmotorsInternal combustion engine cylinder
3838
Kolben des VerbrennungsmotorsPistons of the internal combustion engine
4040
Wellewave
4242
UmgebungsluftleitungAmbient air duct
4444
(erstes) Absperrventil(first) shut-off valve
4646
TankleckdiagnosemodulTank leak diagnosis module
4848
SteuervorrichtungControl device
5050
erste Mündung der Spülluftleitungfirst opening of the purge air line
5252
zweite Mündung der Spülluftleitungsecond opening of the purge air line
5454
Drosselklappethrottle
5656
Rückschlagventilcheck valve
5858
(zweites) Absperrventil(second) shut-off valve
6060
(drittes) Absperrventil(third) shut-off valve
6262
UmgebungsmündungSurrounding mouth
6464
Verdichtercompressor
6666
DrucksensorPressure sensor
6868
Verlauf der Stromstärke I bei dichtem AbschnittCourse of the current I in a dense section
7070
Verlauf der Stromstärke I bei undichtem AbschnittCurrent intensity I curve for a leaky section
7272
Verlauf des Drucks p bei dichtem AbschnittPressure p curve for a dense section
7474
Verlauf des Drucks p bei undichtem AbschnittPressure p curve in the case of a leaky section
7676
Verlauf der Antriebsdrehzahl n bei dichtem AbschnittCourse of the drive speed n with a dense section
7878
Verlauf der Antriebsdrehzahl n bei undichtem AbschnittCourse of the drive speed n in the case of a leaky section

Claims (10)

  1. Method for testing the leak-tightness of a fuel tank system of an internal combustion engine, wherein the fuel tank system comprises
    - a fuel tank (10),
    - a fuel vapour filter (14) which is connected in fluid-conducting fashion to an opening to surroundings (62),
    - a ventilation line (12) which leads from the fuel tank (10) to the fuel vapour filter (14),
    - a scavenging-air line (16) which leads from the fuel vapour filter (14) to a fresh-gas tract (18) of the internal combustion engine,
    - a compressor (64) which is integrated into the scavenging-air line (16), and
    - a shut-off valve (60) which is integrated into the scavenging-air line (16) and which is arranged between an opening (50) of the scavenging-air line (16) into the fresh-gas tract (18) and the compressor (64),
    characterized in that a distinction between adequate and inadequate leak-tightness is made by way of a comparison of at least one value or value profile, ascertained in a defined operating state of the fuel tank system, of an operating parameter of the compressor (64) with an associated setpoint value or setpoint value range which represents said operating state and which corresponds to an adequate leak-tightness.
  2. Method according to Claim 1, characterized in that a positive pressure is generated in the section for testing by means of the compressor (64).
  3. Method according to Claim 1 or 2, characterized in that the intensity of the electrical current applied to a drive motor of the compressor (64), and/or the drive rotational speed of the compressor (64), is utilized as operating parameter.
  4. Method according to Claim 3, characterized in that the pressure in at least one section for testing of the scavenging-air line (16) is used for the definition of the operating state, and the current intensity and/or the drive rotational speed are compared with a (respective) setpoint value or setpoint value range.
  5. Method according to any of the preceding claims, characterized in that the compressor (64) is operated with a first conveying direction and subsequently with a second conveying direction in order to successively test two sections of the scavenging-air line (16) which are situated on different sides of the compressor (64).
  6. Method according to any of the preceding claims, characterized by the use of a piston-type compressor.
  7. Method according to any of the preceding claims, characterized by use in an internal combustion engine in which a shut-off valve (44) is integrated into a surroundings air line (42) between the fuel vapour filter (14) and the opening to surroundings (68) .
  8. Method according to any of the preceding claims, characterized by use in an internal combustion engine in which the scavenging-air line (16) is branched, wherein a first opening (50) into the fresh-gas tract (18) is arranged upstream of a fresh-gas compressor (28) which is integrated into the fresh-gas tract (18), and a second opening (52) of the scavenging-air line (16) into the fresh-gas tract (18) is arranged downstream of the fresh-gas compressor (28).
  9. Method according to Claim 8, characterized by use in an internal combustion engine in which the compressor (64) is integrated into the scavenging-air line (16) between the branching point (20), at one side, and the first opening (50) or the second opening (52), at the other side.
  10. Method according to any of the preceding claims, characterized by use in an internal combustion engine in which the fuel vapour filter (14) is assigned a tank leakage diagnostic module (46).
EP17811952.5A 2016-12-15 2017-12-11 Method for testing the sealing tightness of a fuel tank system of an internal combustion engine Active EP3555448B1 (en)

Applications Claiming Priority (2)

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DE102016225206.2A DE102016225206A1 (en) 2016-12-15 2016-12-15 Method for testing the tightness of a fuel tank system of an internal combustion engine
PCT/EP2017/082114 WO2018108761A1 (en) 2016-12-15 2017-12-11 Method for testing the sealing tightness of a fuel tank system of an internal combustion engine

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DE102018111116B4 (en) * 2018-05-09 2020-06-18 Eagle Actuator Components Gmbh & Co. Kg Arrangement for regenerating an activated carbon filter
DE102021202516A1 (en) 2021-03-15 2022-09-15 Volkswagen Aktiengesellschaft Method for functional testing of a fuel tank system of an internal combustion engine

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DE19639116B4 (en) * 1996-09-24 2009-01-15 Robert Bosch Gmbh Tank ventilation device for motor vehicles
DE19829423B4 (en) * 1998-07-01 2007-03-22 Mahle Filtersysteme Gmbh Device for venting the fuel tank of an internal combustion engine
DE10006186C1 (en) * 2000-02-11 2001-06-13 Bosch Gmbh Robert Seal testing method for automobile fuel tank system, has measurement repeated when leak is indicated for verification before leakage signal is supplied
DE10018441B4 (en) * 2000-04-13 2005-12-29 Robert Bosch Gmbh Method and device for environmentally sound leak testing of a container
DE102004030909A1 (en) 2004-06-25 2006-01-19 Mahle Filtersysteme Gmbh Tank ventilation system for combustion engine fuel tank, especially of motor vehicle, has controller for controller for driving pump for defined period following engine shut-off to provide overrun period
DE102011086955A1 (en) * 2011-08-18 2013-02-21 Robert Bosch Gmbh Air supply system of an internal combustion engine
DE102011084403A1 (en) 2011-10-13 2013-04-18 Robert Bosch Gmbh Tank ventilation system and method for its diagnosis
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DE102014216451A1 (en) * 2014-08-19 2016-02-25 Continental Automotive Gmbh The fuel tank system
DE102014217195A1 (en) * 2014-08-28 2016-03-03 Continental Automotive Gmbh Method for leak diagnosis in a fuel tank system
US9771884B2 (en) * 2014-10-31 2017-09-26 GM Global Technology Operations LLC System and method for controlling the amount of purge fluid delivered to cylinders of an engine based on an operating parameter of a purge pump
DE102015209651B4 (en) * 2015-05-27 2022-08-18 Robert Bosch Gmbh Tank ventilation system and method for diagnosing a tank ventilation system
JP2017203415A (en) * 2016-05-11 2017-11-16 愛三工業株式会社 Evaporated fuel treatment device

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