DE102016225512A1 - Fuel tank system and method of testing the tightness of such a fuel tank system - Google Patents

Abstract

A fuel tank system having a fuel tank (10), a fuel vapor filter (14) in fluid communication with an environmental port (62), a vent line (12) leading from the fuel tank (10) to the fuel vapor filter (14), one of the fuel vapor filter (14) leading to a fresh gas line (18) of the internal combustion engine scavenging air line (16), - one in the scavenging air line (16) integrated compressor (64) and one in the scavenging air line (16) integrated shut-off valve (60) between a mouth (50) of the scavenging air line (16) in the fresh gas line (18) and the compressor (64) is arranged, characterized in that for the compressor (64) in its non-operation, a defined gas permeability is realized. Such a fuel tank system allows an advantageous test of the tightness of the fuel tank system by a defined pneumatic pressure is generated in at least one of the compressor (64) centrally comprehensive portion of the scavenging air line (16), which is closed against a gas flow and flows closed, and then, by means of a change in this pressure, a distinction is made between a sufficient and an insufficient tightness of this section.

Description

The invention relates to a fuel tank system for an internal combustion engine and a method for testing the tightness of such a fuel tank system.

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 due to, for example, at high ambient temperatures evaporating fuel to the environment. Due to emission regulations, no fuel vapors should enter the environment as far as possible. This is prevented by integrating into the vent line a fuel vapor filter, usually in the form of an activated carbon filter, which absorbs the fuel vapors.

For regeneration of the fuel vapor filter, such tank systems are additionally provided with a scavenging air line, which is connected on the one hand to the fuel vapor filter and on the other hand to the fresh gas train of the internal combustion engine. During operation of the internal combustion engine, ambient air can be temporarily drawn in via an ambient orifice of the fuel vapor filter by means of the negative pressure prevailing in the region of the mouth of the scavenging air line, which flows through the fuel vapor filter in the opposite direction to that direction of flow in which the fuel vapors flow from the fuel tank into the fuel vapor filter and this flushes it. The fuel vapors from the fuel vapor filter are thus supplied via the fresh gas train to the combustion chambers of the internal combustion engine of the internal combustion engine.

Such a tank system of an internal combustion engine of a motor vehicle is known from DE 10 2004 030 909 A1 known. In this, it is additionally provided that after a shutdown of the internal combustion engine during a defined follow-up time by means of a compressor integrated between an environmental orifice and the fuel vapor filter in an ambient air line the purge air is emptied of fuel vapors still present therein to avoid that these fuel vapors on the Frischgasstrang in the environment can get. The compressor thereby promotes the gases contained in the scavenging air line and also via the fresh gas line via the fuel vapor filter and the ambient air line into the environment, wherein the fuel vapor filter filters out the fuel vapors.

A lack of tightness of a fuel tank system would lead to an uncontrolled escape of fuel vapors into the environment, which should be avoided.

From the DE 10 2011 084 403 A1 a tank venting system for an internal combustion engine with a fuel tank, an activated carbon filter, a tank vent valve and at least one check valve is known. Between the tank vent valve and the check valve, a pressure sensor is arranged. To diagnose the tank venting system, a vacuum is set between the tank vent valve and the check valve that is less than the ambient pressure. The set pressure is changed by activating the tank venting valve. The change in the pressure in the line between the tank venting valve and the check valve is measured by means of the pressure sensor and associated with the activation of the tank venting valve. From the correlation of the opening state of the tank venting valve and the change in the pressure in the line between the tank vent valve and the check valve is closed to the function of the tank vent line, the check valve and the tank vent valve. In particular, it can also be concluded that the tightness of the tank ventilation system in the section between the tank vent valve and the check valve. However, it is not possible to check the tightness of the remaining sections of the tank ventilation system.

The DE 10 2012 218 933 A1 discloses a method for determining the loading of an activated carbon filter in a tank venting system, the tank venting system having at least a first valve between a fuel tank and the activated carbon filter and at least a second valve between the activated carbon filter and an intake manifold of an internal combustion engine. For this purpose, when the first valve is closed and the second valve is closed, the activated carbon filter is charged with a gas volume. On the basis of measured values, which represent the pressure in the activated carbon filter, the load condition of the activated carbon filter is concluded. The loading of the activated carbon filter with the gas volume can be effected by means of a compressor which is part of a known module for the diagnosis of tank leakage, which is arranged on the side of a ventilation opening of the activated carbon filter and is in fluid communication with the environment via a fresh air filter.

The DE 38 04 183 A1 describes a shaft seal for centrifugal pumps for promoting, for example, hot water, which uses an internal circulation flow at an atmospheric side mechanical seal to ensure adapted to changing operating conditions, continuous removal of heat generated in a sealing chamber heat energy and dirt or wear particles even without an external cooling device ,

The WO 2012/025423 A1 discloses a diaphragm pump with a by means of a membrane separated from a hydraulic chamber delivery chamber, wherein the fillable with a working fluid hydraulic space can be acted upon with a pulsating working fluid pressure and wherein the hydraulic chamber is connected via a leak-relief valve with a working fluid reservoir.

The invention has for its object to provide an advantageous in terms of tightness to be tested fuel tank system for an internal combustion engine.

This object is achieved by means of a fuel tank system according to the patent claim 1. A method for testing the tightness of such a fuel tank system is the subject of claim 13. Advantageous embodiments of the fuel tank system according to the invention and advantageous embodiments of the method according to the invention are objects of the other claims and / or will become apparent from the following description of the invention.

According to the invention, a fuel tank system for an internal combustion engine, in particular for an internal combustion engine of a motor vehicle, is provided. This comprises at least one fuel tank, a fuel vapor filter (preferably a sorption filter, in particular an activated carbon filter) in fluid communication with an environmental orifice, a vent line leading from the fuel tank to the fuel vapor filter, a scavenge air line leading from the fuel vapor filter to a fresh gas line of the internal combustion engine integrated in the scavenging air, preferably electric motor driven compressor (ie, a device for conveying gases) and an integrated in the scavenging air shut-off valve which is disposed between an opening of the scavenging air line in the fresh gas line and the compressor. Such a fuel tank system is characterized in that for the compressor in its non-operation a defined (i.e., deliberately provided and preferably also with respect to the (pressure-dependent) height known) gas permeability is realized.

A method according to the invention for testing the tightness (of at least one section) of such a fuel tank system provides that in at least one section of the scavenging air line which is centrally closed to the compressor and which is closed in a defined manner against a gas flow, a defined pneumatic pressure (for example by means of an active pressure increase or pressure reduction) is generated and is then distinguished on the basis of a determination of a change in this pressure between a sufficient and an insufficient tightness of at least this section. In this case, a "central" arrangement of the compressor in the section of the scavenging air line means that a subsection of this section is provided on each side of the compressor. "Defined" against an influx or outflow of a gas "closed" is the section to be tested when an inflow / outflow is prevented as far as possible or in a (compared to an open state) reduced dimensions and in known (possibly pressure-dependent) height is possible. A distinction between a sufficient and an insufficient tightness can be made by a comparison with a defined limit or limit range (for example for the gradient of the pressure change), by which a sufficient tightness is defined, by exceeding or falling below the defined limit or Limit value is signaled an insufficient tightness.

Due to the defined gas permeability for the compressor, pressure generation and / or pressure determination (in each case) may be sufficient in one of the sections of the section comprising the compressor centrally, because a defined pressure equalization between the two sections can take place via the compressor which may be included in the evaluation for sufficient or insufficient tightness. In order to realize a sufficiently rapid pressure equalization over the compressor, it can preferably be provided that the defined gas permeability is at least 10 liters per minute.

In order to be able to determine relatively small leaks within the scope of carrying out a method according to the invention, it should preferably be provided that a change in the pressure in at least the section of the scavenging air line to be tested is possible exclusively via possibly existing leakage openings. Thus, it should preferably be provided that the shut-off valves delimiting the section to be tested are as completely closed as possible when carrying out a method according to the invention.

In addition to the shut-off valve arranged in the scavenging air line between the opening in the fresh gas line and the compressor, a fuel tank system according to the invention may preferably also comprise at least one shut-off valve (integrated into an ambient air line) between the fuel vapor filter and the surrounding mouth. This allows substantially the entire fuel tank system, if necessary, by means of the shut-off valves with respect to a supply or effluent of gas from or into the Separate environment so that a test substantially the entire fuel tank system for sufficient or insufficient tightness in the context of a method according to the invention is possible. About the fuel vapor filter can be given a fluid-conducting connection between the scavenging air on the one hand and the vent line and thus also the fuel tank on the other hand.

An additional or even primary function of the compressor may be to ensure purging of the fuel vapor filter when there is no or too little pressure gradient between the ambient pressure and the pressure in the fresh gas line in the region of the mouth of the scavenging air line, so that preferably a correspondingly high-performance design the compressor is provided.

One possibility for realizing a defined gas permeability of the compressor in non-operation is to form this as a flow compressor (blower), since such basically causes no relevant seal between the two connected by these sections of the scavenging air due to the structural design.

Alternatively, it may be provided that the compressor is a reciprocating compressor (ie, a compressor operating on the displacement principle in which gas is cyclically encapsulated in a volume, compressed and ejected again), because such a reciprocating compressor has advantages with regard to the realization of a preferably provided Flushing functionality of the fuel tank system for the fuel vapor filter may have.

Such a reciprocating compressor is typically designed so that it has no relevant gas permeability in its non-operation. In order to realize such a defined gas permeability provided according to the invention also for a compressor designed as a piston compressor, it is possible, for example, to provide a compressor bypass, which is preferably closed by means of a shut-off valve as required. A "compressor bypass" is understood to be an integrated in the compressor or externally arranged therefrom environmental line through which a gas (with open shut-off valve), bypassing a pressure chamber on by a gas is compressed during operation of the compressor can flow.

In principle, it is possible to use a compressor bypass even with a compressor designed as a flow compressor in order to realize an (additional) defined gas permeability for the compressor.

Alternatively or in addition to the realization of a defined gas permeability for a reciprocating compressor by means of a compressor bypass can be provided that this constructively designed and / or integrated into the fuel tank system (or arranged in this) is that this in non-operating a defined gas permeability over the pressure chamber having. For example, it may be provided that the compressor is a vane compressor, the wings of which are pressed during operation (possibly exclusively) centrifugally loaded against an inner wall of a housing of the vane compressor, wherein the configuration and / or arrangement of the vane compressor is provided such that at least one of the wings spaced apart from the inner wall of the housing in non-operation to effect the defined gas permeability of the vane compressor. In this case, the spaced apart from the inner wall arrangement of the at least one wing in the non-operation of the vane compressor can be realized exclusively gravity loaded. Alternatively, it is also possible to apply one, several or all of the wings by means of one or more spring elements in the direction of an arrangement spaced from the inner wall, wherein this load is overcompensated by the one or more spring elements during operation of the vane compressor due to centrifugal force, so that these are then pressed against the inner wall of the housing to ensure a sufficiently dense separation of individual pressure chambers of the pressure chamber of the vane compressor.

A determination of the pneumatic pressure in the fuel tank system (s) to be tested for sufficient tightness can preferably be carried out by means of one or more pressure sensors, which can be arranged, for example, in the fuel tank and / or in the ventilation line and / or in the scavenging air line. In the case of an arrangement of a plurality of pressure sensors in the scavenging air line, it can preferably be provided that in each case at least one pressure sensor is arranged in the two subsections of the section comprising the compressor centrally.

The generation of the defined pneumatic pressure in at least the section of the scavenging air line which surrounds the compressor can on the one hand be effected by an operation of the compressor itself. For this purpose, it may be provided, for example, that in a first step by means of the compressor an increase in pressure or a pressure reduction in a section of the scavenging air line connected to the pressure side or suction side of the compressor (and optionally in other sections of the fuel tank system gas-connected to this section at this time) is generated by connecting via a port the environment, for example, via the mouth of the scavenging air line in the fresh gas line or via the standing with the fuel vapor filter in the gas-conducting environment mouth, (to increase the pressure) ambient air is sucked into the fuel tank system or (for pressure reduction) containing in the fuel tank system gas is discharged to the environment , In a second step, then by closing a correspondingly arranged shut-off valve, a gas-conducting connection of the fuel tank system or the portion to be tested thereof with the previously used connection to the environment (partially or completely) are interrupted, in which case due to the defined gas permeability for the compressor is realized according to the invention, can set a pressure equalization between lying on the two sides of the compressor sections of the section to be tested (or the tank system as a whole). Subsequently, it can be distinguished by a change in the pressure in the section to be tested between a sufficient and an insufficient tightness.

The generation of a defined pneumatic pressure in at least the section of the scavenging air line which centrally surrounds the compressor can also be carried out by means of a tank leak diagnosis module, for example by means of a tank leak diagnosis module, as described in US Pat DE 10 2012 218 933 A1 described, which is preferably arranged between the fuel vapor filter and the surrounding mouth and further preferably may comprise a compressor and / or a shut-off valve. In this way, a tank leak diagnostic module which is available on the market as a mass product and thus relatively inexpensive can be used to check at least one section, preferably substantially the entire fuel tank system, with regard to sufficient tightness.

In a preferred embodiment of a tank system according to the invention it can be provided that the scavenging air line is branched, wherein a first opening in the fresh gas line upstream of a fresh gas compressor integrated in the fresh gas line and a second mouth of the scavenging air line is arranged in the fresh gas line downstream of the fresh gas compressor. In this case, the compressor between the branch on the one hand and the first mouth or the second mouth on the other hand be integrated into the scavenging air line. Further preferably, it can then be provided that a shut-off valve is integrated into the branch of the scavenging air line into which the compressor is not integrated. Such an embodiment of the fuel tank system can be particularly advantageous in terms of purging of the fuel vapor filter, which is carried out on a pressure gradient in the scavenging air line between the fuel vapor filter and one of the mouths in the fresh gas line (and thus possibly without an operation of the integrated compressor in the scavenge air line) impact.

The, several or each of the shut-off valves of a fuel tank system according to the invention may be actively (controllably) or passively (i.e., self-actuating, for example in the form of a check valve).

The possibility of testing a section and in particular also essentially the entire fuel tank system with regard to sufficient tightness makes it possible to connect the individual gas-carrying components of the fuel tank system, for example between the compressor and / or the shut-off valve integrated between it and the mouth into the fresh gas line on the one hand and the two components connect the line section of the scavenging air line releasably, for example by means of corresponding quick couplings form, although such releasable connections represent a typical cause of leaks, but then can be advantageously detected according to the invention. The detachable design of these compounds can be advantageous in terms of assembly and maintenance of the fuel tank system.

The invention further relates to an internal combustion engine having a fuel tank system according to the invention, wherein the internal combustion engine preferably comprises an internal combustion engine operated according to the Otto principle, because the used for the operation of such internal combustion engines fuels (especially in comparison to diesel fuel) are relatively volatile, which not only the special need for a tank ventilation but also a test of the tightness of the fuel tank system is justified.

According to the invention, the term "fuel vapor filter" does not require that it must filter the volatile fuel in gaseous form. Rather, the fuel in the filtering again (partially) be condensed out.

The indefinite articles ("a", "an", "an" and "an"), in particular in the patent claims and in the description generally describing the claims, are to be understood as such and not as numerical words. Corresponding to this concretized components are thus to be understood that they are present at least once and may be present more than once.

• 1: eine Brennkraftmaschine mit einem erfindungsgemäßen Kraftstofftanksystem;
• 2: einen Flügelzellenverdichter für ein erfindungsgemäßes Kraftstofftanksystem im Betrieb; und
• 3: den Flügelzellenverdichter gemäß 2 im Nichtbetrieb.

The present invention will be described below with reference to an illustrated in the drawings Embodiment explained in more detail. In the drawings shows, in a schematic representation:

• 1 an internal combustion engine with a fuel tank system according to the invention;
• 2 a vane compressor for a fuel tank system according to the invention in operation; and
• 3 : the vane compressor according to 2 in non-operation.

The 1 shows an internal combustion engine with a fuel tank system. This includes a fuel tank 10 that has a vent line 12 with a fuel vapor filter 14 , which may be formed in particular in the form of an activated carbon filter or at least one such, is connected. The fuel vapor filter 14 is still via a scavenging air line 16 with a fresh gas train 18 the internal combustion engine connected, wherein the scavenging air line 16 starting from a branch 20 in two branches 22 . 24 runs, of which a first branch 22 in the fresh gas train 18 upstream (with respect to the flow direction of fresh gas in the fresh gas line 18 from a fresh gas inlet (not shown) to an internal combustion engine 26 the internal combustion engine) one in the fresh gas train 18 integrated fresh gas compressor 28 and the second branch 24 downstream of the fresh gas compressor 28 and in particular also downstream of a likewise downstream of the fresh gas compressor 28 in the fresh gas train 18 integrated throttle 54 empties. The fresh gas compressor 28 is part of an exhaust gas turbocharger, which continues to be an exhaust gas turbine 30 that covers an exhaust line 32 the internal combustion engine is integrated.

During operation of the internal combustion engine are in a known manner in a defined order in combustion chambers 34 of the internal combustion engine 26 partly from cylinders 34 of the internal combustion engine 26 are limited, mixtures of fresh gas, which consists entirely or substantially of ambient air, and for example directly into the combustion chambers 34 injected fuel burned, the pressure increases thus generated in the combustion chambers 34 used in the cylinders 36 longitudinal axial movably guided pistons 38 to move. These movements of the pistons 38 are translated with the interposition of connecting rods (not shown) in a rotational movement of a crankshaft (not shown), wherein the leadership of the piston 38 via the connecting rods by means of the crankshaft at the same time to a cyclic back-and-forth movement of the piston 38 leads. That when burning the fresh gas-fuel mixtures in the combustion chambers 34 resulting exhaust gas is via the exhaust system 32 dissipated and flows through the exhaust gas turbine 30 resulting in a rotating drive of a turbine runner (not shown). This rotation of the turbine runner is by means of a shaft 40 on a compressor wheel (not shown) of the fresh gas compressor 28 transferred, causing the fresh gas compressor 28 for a compression of the over the fresh gas train 18 the internal combustion engine 26 supplied fresh gas provides.

The fuel vapor filter 14 the fuel tank system stands with his respect to the vent line 12 and the scavenging air line 16 opposite side (based on its filtering effect for fuel vapors) via an ambient air line 42 with an integrated (first) shut-off valve 44 with the environment in gas-conducting connection, including the ambient air line 42 an environment muzzle 62 formed. The first shut-off valve 44 is by means of a control device 48 (eg the engine control of the internal combustion engine) controllable, ie this can be actively opened or closed. Optionally, in the ambient air line 42 also a basically known tank leak diagnosis module 46 be integrated, in which case the first shut-off valve 44 also an integral part of the tank leak diagnostic module 46 can be.

The fuel tank 10 is partially filled with liquid fuel, with a portion of this fuel is vaporized, so that in the fuel tank 10 Also fuel is present in gaseous state. Such vaporization of fuel in the fuel tank 10 is amplified by a relatively high temperature of the fuel, which is the case in particular at relatively high ambient temperatures. To a caused by this evaporation, unacceptably high pressure in the fuel tank 10 to avoid is the possibility of at least partial pressure equalization with the ambient pressure via the vent line 12 and the fuel vapor filter 14 as well as over the ambient air line 42 provided by the fuel vapor filter 14 it is avoided that such a pressure equalization leads to an escape of fuel vapors into the environment.

Such a venting of the fuel tank 10 leads to an increasing saturation of the fuel vapor filter 14 which, in turn, conditionally regenerate it on a regular basis. For this purpose, a purging of the fuel vapor filter 14 provided by ambient air through the ambient air duct 42 and the integrated first, then opened shut-off valve 44 is sucked. This ambient air flows through the fuel vapor filter 14 in comparison to the flow through the ventilation of the fuel tank 10 opposite flow direction, whereby in the fuel vapor filter 10 absorbed fuel molecules carried by the ambient air and the scavenging air line 16 in the fresh gas train 18 be introduced so that this fuel combustion in the combustion chambers 34 of the internal combustion engine 26 is supplied. Such a purging of the fuel vapor filter 14 is only temporary and always during operation of the internal combustion engine 26 provided, because only by the purging of the fuel vapor filter 14 in the fresh gas train 18 introduced fuel also safe combustion in the combustion chambers 34 can be supplied. An introduction into the fresh gas train 18 in a non-operation of the internal combustion engine 26 On the other hand, it could cause the gaseous fuel to leak through the fresh gas line 18 and in particular via a suction port of the fresh gas line 18 could escape into the environment.

For flushing the fuel vapor filter 14 is a sufficient pressure drop from the ambient pressure in the vicinity of the surrounding mouth 62 up to the (respective) pressure in the fresh gas line 18 in the area of estuaries 50 . 52 required due to strongly fluctuating pressures in the fresh gas line 18 not always given. 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) mouth 52 of the second branch 24 the scavenging air line 16 Often there is not even a pressure gradient but a pressure increase, because this second orifice 52 in the area of between the fresh gas compressor 28 and the internal combustion engine 26 extending charge air route of the fresh gas train 18 located in which the fresh gas as a result of compression by the fresh gas compressor 28 often present with significant overpressure. By an arrangement of this second mouth 52 (as close as possible) downstream of a throttle 54 Although one through the throttle 54 exploited pressure reduction can be exploited; However, this pressure reduction is often not sufficient to actually a sufficient pressure drop across the scavenge air line 16 to realize. In this second branch 24 the scavenging air line 16 is therefore a check valve 56 integrated, through which this branch 24 the scavenging air line 16 is kept automatically closed when in the region of the second orifice 52, an overpressure compared to that on the other side of the check valve 56 located section of the second branch 24 the scavenging air line 16 is present. In addition to this is upstream (with respect to the flow direction when purging the fuel vapor filter 14 ) actively by means of the control device 48 controllable (second) shut-off valve 58 in the second branch 24 the scavenging air line 16 integrated. Basically, there is the possibility due to the arrangement of this shut-off valve 58 on the check valve 56 to dispense, provided the shut-off valve 58 is designed sufficiently overpressure (ie this must be at the at least temporarily occurring overpressures on the side of the charge air path of the fresh gas line 18 keep sufficiently tightly closed).

The first branch of the scavenging air line 22 on the other hand flows into an upstream of the fresh gas compressor 28 located section of the fresh gas train 18 , being in the section of this branch 22 the scavenging air line 16 between the fresh gas compressor 28 and this (first) estuary 50 a (third) shut-off valve 60 integrated as close to the first mouth 50 arranged or preferably integrated in this. In the section of the fresh gas line 18 in the area of the first estuary 50 is the pressure of the fresh gas (during operation of the fresh gas compressor 28 ) lower than in the charge air path, so that in terms of this first orifice 50 the scavenging air line 16 relatively often a sufficient pressure gradient compared to (and starting from) the at the surrounding mouth 62 may be present ambient pressure. However, this is not always the case, for example in an operation of the internal combustion engine in an operating state which is characterized by a relatively low supply of fresh gas. To rinse the fuel vapor filter at any time 14 to allow so that a complete saturation of the same can be reliably prevented, therefore, the fuel tank system of the internal combustion engine also includes a compressor also referred to as "rinse pump" 64 , which is formed in the form of a piston compressor and, for example, as a vane compressor according to the 2 and 3 can be trained. By operation of this compressor 64 can active ambient air over the environment mouth 62 be sucked, then the fuel vapor filter 14 flows through to the rinsing and the through the compressor 64 until the first estuary 50 the scavenging air line 16 is encouraged. That in the second branch 52 the scavenging air line 16 integrated, then kept closed second shut-off valve 58 but at least the self-closing check valve 56 prevents suction of fresh gas through the second orifice 52 from the charge air path of the fresh gas train 18 ,

To avoid the influence of escaping fuel vapors on the environment, it is useful and sometimes required by law to regularly check the fuel tank system for a sufficient tightness. This is intended according to the invention for at least one section of the fuel tank system, in particular for substantially the entire fuel tank system and, if appropriate, using the compressor, which is also used as a "flushing pump" 64 respectively.

For this purpose, for example, be provided that in the context of a method according to the invention by means of the compressor 64 Fresh gas over the first estuary 50 the scavenging air line 16 from the fresh gas line 18 sucked in and with respect to this flow of fresh gas downstream of the compressor 64 lying section of the flushing air 16 including the second branch 24 from this to the second shut-off valve 58 , is promoted. About the scavenging air line 16 the fresh gas enters the fuel vapor filter 14 , of this in the vent line 42 (and in optionally a tank leak diagnostic module integrated therein 46 ) up to the closed first shut-off valve 44. Furthermore, the fresh gas passes from the fuel vapor filter 14 in the vent line 12 and in the vent line 12 connected fuel tank 10 which, with the exception of the connection to the vent line 12 , should be designed gas-tight. In this way, in those sections of the fuel tank system in which the fresh gas by means of the compressor 64 is promoted, an increase in pressure generated. Afterwards, this will also be in the first branch 22 the scavenging air line 16 in the area of the first estuary 50 integrated (third) shut-off valve 60 closed and operation of the compressor 64 completed. Due to a defined gas permeability for the compressor 64 , for example by means of a compressor bypass 68 with a built-in (fourth), then opened shut-off valve 70 can be realized, results in a pressure equalization in the on the different sides of the compressor 64 arranged sections of the scavenging air line 16 (and the other gas-connected components of the fuel tank system). Subsequently, by means of one or more pressure sensors 66 the time course of the pressure in the fuel tank system over a defined test period with shut-off valves kept closed 44 . 58 and 60 and when a change in the measured pressure within the test period, a comparison of a derived gradient of the pressure change with a defined limit or threshold range for this gradient are made to distinguish between a sufficient and an insufficient tightness. In this case, a sufficient tightness does not have to correspond to a substantially complete tightness. Rather, insufficient tightness can also only be assumed if a determined leak is greater than a leak that would occur under the same or comparable state conditions of the fuel tank system due to a reference leakage opening with a size of, for example, 0.5 mm.

Alternatively or in addition to generating a defined overpressure in the fuel tank system by means of the compressor 64 This overpressure can also by means of a in the tank leak diagnosis module 46 integrated compressor 72 be realized, this compressor 72 for example, via the opened first shut-off valve 44 Aspirate ambient air and into the downstream of the tank leak diagnostic module 46 arranged portions of the fuel tank system can promote.

Alternatively, to generate an overpressure in the fuel tank system by means of the compressor 64 and / or by means of the compressor 72 of the tank leak diagnosis module 46 It is also possible to generate a negative pressure by means of these components in the fuel tank system, in a first step via one of the open shut-off valves 44 . 66 In the fuel tank system containing gas (partially) evacuated and then the previously opened shut-off valve 44 . 60 is closed, where then again an evaluation of a change in the (sub) pressure in the fuel tank system to distinguish between a sufficient and an insufficient tightness can be performed.

Alternatively to generate an overpressure or a negative pressure in the fuel tank system by means of the compressor 64 and / or by means of the compressor 72 of the tank leak diagnosis module 46 It is also possible to effect a defined pneumatic pressure within the fuel tank system by a defined temperature of the fuel tank system or at least the gas enclosed therein and then by a change in this pressure, which results from a defined temperature change, between a sufficient and an insufficient tightness to distinguish.

Alternatively or in addition to providing the compressor bypass 68 may also be provided, the defined gas permeability for the compressor 64 by a corresponding structural design of the compressor 64 reach yourself. One possible embodiment of such a defined gas-permeable compressor 64 is in the 2 and 3 shown.

The compressor 64 according to the 2 and 3 is in the form of a vane compressor and includes a housing 74 which has a pressure chamber which is circular in cross-section 76 as well as a gas inlet 78 and a gas outlet 80 formed. Eccentric within the pressure chamber 76 is a rotor 82 rotatably mounted. The rotor 82 includes a main body 84 that is radial with respect to a rotational axis of the rotor 82 aligned receiving slot in which two wings 86 of the rotor 82 are mounted radially displaceable. The eccentric arrangement of the rotor 82 within the pressure chamber 76 is chosen such that the main body 84 of the rotor 82 the pressure room 76 limiting inner wall of the housing 74 in one between the gas inlet 78 and the gas outlet 80 permanently located, ie in each Drehausrichtung the rotor 82 , easily contacted, resulting in a sickle shape of the pressure chamber 76 results. The pressure room 76 is by means of the wings 86 separated into a total of three pressure chambers whose sizes are change cyclically between approximately zero and a maximum value. The direction of rotation of the rotor 82 is chosen such that each with the gas inlet 78 associated pressure chamber increases while each with the gas outlet 80 reduced pressure chamber, thereby cyclically on the one hand gas through the gas inlet 78 sucked and compressed gas is discharged via the gas outlet 80. By reversing the direction of rotation of the rotor 82 there is the possibility of the conveying direction of the compressor 64 reverse, being that the gas inlet 78 as gas outlet and the gas outlet 80 acts as a gas inlet.

The wings 86 are in operation of the compressor 64 by means of a spring element 88 loaded on train, resulting from the rotation of the rotor 82 resulting, on the wings 86 acting centrifugal forces to radially outward shifts of the wings 86 inside the receiving slot lead up to the wings 86 with the respective outer end of the inner wall of the housing 74 contact, whereby the pressure chambers are substantially completely separated from each other. This moving the wings 86 radially outwards leads to a load on the spring element 88 on train being biased by it. Will the operation of the compressor 64 set, this bias of the spring element performs 88 to that the wings 86 by means of the spring element 88 be displaced radially inward within the receiving slot, whereby the outer ends of the wings 86 at a defined distance from the inner wall of the housing 74 to be ordered. This spaced arrangement of the wings 86 with respect to the inner wall of the housing 74 leads to a defined gas permeability of the compressor 64 because gas is above the gas inlet 78 , the pressure room 76 as well as the gas outlet 80 the compressor 64 can flow through.

LIST OF REFERENCE NUMBERS

10

Fuel tank

12

vent line

14

Fuel vapor filter

16

flushing air

18

Fresh gas line

20

Branching of the scavenging air line

22

first branch of the scavenging air line

24

second branch of the scavenging air line

26

internal combustion engine

28

Fresh gas compressor

30

exhaust turbine

32

exhaust gas line

34

Combustion chamber of the internal combustion engine

36

Cylinder of the internal combustion engine

38

Piston of the internal combustion engine

40

wave

42

Ambient air duct

44

(first) shut-off valve

46

Tank leak diagnostic module

48

control device

50

first mouth of the scavenging air line

52

second mouth of the scavenging air line

54

throttle

56

check valve

58

(second) shut-off valve

60

(third) shut-off valve

62

around the mouth

64

compressor

66

pressure sensor

68

compressor bypass

70

(fourth) shut-off valve

72

Compressor of tank leak diagnostic module

74

Housing of the compressor

76

Pressure chamber of the compressor

78

Gas inlet of the compressor

80

Gas outlet of the compressor

82

Rotor of the compressor

84

Basic body of the rotor

86

Wing of the rotor

88

Spring element of the rotor

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102004030909 A1 [0004]
• DE 102011084403 A1 [0006]
• DE 102012218933 A1 [0007, 0025]
• DE 3804183 A1 [0008]
• WO 2012/025423 A1 [0009]

Claims (15)

A fuel tank system comprising - a fuel tank (10), - a fuel vapor filter (14) in fluid communication with an environmental port (62), - a vent conduit (12) leading from said fuel tank (10) to said fuel vapor filter (14) from the fuel vapor filter (14) to a fresh gas line (18) of the internal combustion engine leading scavenging air line (16), - one in the scavenging air line (16) integrated compressor (64) and - one in the scavenging air line (16) integrated shut-off valve (60) which between an orifice (50) of the scavenging air line (16) in the fresh gas line (18) and the compressor (64) is arranged, characterized in that for the compressor (64) in its non-operation, a defined gas permeability is realized. Fuel tank system according to Claim 1 , characterized in that the compressor (64) is a flow compressor. Fuel tank system according to Claim 1 or 2 characterized by a compressor bypass (68). Fuel tank system according to Claim 1 or 3 , characterized in that the compressor (64) is a reciprocating compressor. Fuel tank system according to Claim 4 , characterized in that the compressor (64) is a vane compressor, the wings (86) are pressed in operation centrifugally loaded against an inner wall of a housing (74) of the vane compressor, wherein the configuration and / or the arrangement of the vane compressor is provided such that at least one of the vanes (86), when the vane compressor is not in operation, is arranged at a distance from the inner wall in order to realize a defined gas permeability of the compressor (64). Fuel tank system according to one of the preceding claims, characterized by one or more in the fuel tank (10) and / or in the vent line (12) and / or in the scavenging air line (16) arranged pressure sensors (66). Fuel tank system according to one of the preceding claims, characterized by a tank leak diagnosis module (46). Fuel tank system according to Claim 7 , characterized in that the tank leak diagnostic module (46) comprises a compressor (72). Fuel tank system according to Claim 7 or 8th characterized in that the tank leak diagnostic module (46) is disposed between the fuel vapor filter (14) and the ambient orifice (68). Fuel tank system according to one of the preceding claims, characterized by a shut-off valve (44) arranged between the fuel vapor filter (14) and the surrounding mouth (68). Fuel tank system according to one of the preceding claims, characterized in that the scavenging air line (16) is branched, wherein a first orifice (50) in the Frischgasstrang (18) upstream of a fresh gas in the line (18) integrated fresh gas compressor (28) and a second orifice ( 52) of the scavenging air line (16) is arranged in the fresh gas line (18) downstream of the fresh gas compressor (28). Fuel tank system according to Claim 11 , characterized in that the compressor (64) between the branch (20) on the one hand and the first orifice (50) or the second orifice (52) on the other hand in the scavenging air line (16) is integrated. Method for checking the tightness of a fuel tank system according to one of the preceding claims, characterized in that in at least one section of the scavenging air line (16) which encloses the compressor (64) in a defined manner and is closed off against a gas flow, a defined pneumatic Pressure is generated and is then distinguished by a change in this pressure between a sufficient and an insufficient tightness of this section. Method according to Claim 13 , characterized in that the defined pneumatic pressure is generated by means of the compressor (64). Method according to Claim 13 for checking the tightness of a fuel tank system according to Claim 8 or according to one of Claim 8 dependent claims, characterized in that the defined pneumatic pressure by means of the compressor (72) of the Tankleckdiagnosemoduls (46) is generated.

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