EP3559432A1

EP3559432A1 - Fuel tank system and method for testing the leak-tightness of a fuel tank system of this kind

Info

Publication number: EP3559432A1
Application number: EP17822581.9A
Authority: EP
Inventors: Silke Weddig; Jens Wodausch; Florian Imbt; Matthias BÄTJE
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2016-12-20
Filing date: 2017-12-11
Publication date: 2019-10-30
Anticipated expiration: 2037-12-11
Also published as: EP3559432B1; DE102016225512A1; WO2018114408A1

Abstract

A fuel tank system having - a fuel tank (10), - a fuel vapour filter (14), which is fluidically connected to an opening into the environment (62), - a breather line (12) leading from the fuel tank (10) to the fuel vapour filter (14), - a scavenging air line (16) leading from the fuel vapour filter (14) to a fresh gas line (18) of the internal combustion engine, - a compressor (64) integrated into the scavenging air line (16) and - a shut-off valve (60) integrated into the scavenging air line (16), which valve is arranged between an opening (50) of the scavenging air line (16) into the fresh gas line (18) and the compressor (64), is characterised in that a specified gas permeability is implemented for the compressor (64) in the event that it is not operating. A fuel tank system of this kind makes an advantageous testing of the leak-tightness of the fuel tank system possible, in that a specified pneumatic pressure is generated in at least one section of the scavenging air line (16) centrally encompassing the compressor (64), which section is specifically closed against the inflow and outflow of a gas, and then a distinction is made between an adequate and inadequate leak-tightness of this section on the basis of a change in this pressure.

Description

description

Fuel tank system and method for testing the tightness of such

Fuel tank system

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 supplied via an environmental orifice of the vacuum prevailing in the region of the mouth of the scavenging air line in the fresh gas line

Be sucked fuel vapor filters, which flows through the fuel vapor filter in the opposite direction to that flow direction in which the fuel vapors flow from the fuel tank in the fuel vapor filter, and thereby flushes. The fuel vapors from the fuel vapor filter are so through the fresh gas line to the combustion chambers of

Internal combustion engine supplied to 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. 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 between an ambient orifice and the fuel vapor filter in a

Ambient air line integrated compressor, the purge air line is emptied of fuel vapors still present in it, to prevent these fuel vapors from entering the environment via the fresh gas line. 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, the fuel vapor filter filters out the fuel vapor.

A lack of tightness of a fuel tank system would become an uncontrolled

Escape of fuel vapors into the environment leads to what needs to be avoided.

From DE 10 201 1 084 403 A1 discloses a tank ventilation 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

Tank bleed valve and the change in pressure in the pipe between the

Tank bleeder valve and the check valve is based on the function of

Tank vent line, the check valve and the tank vent valve closed. 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.

DE 10 2012 218 933 A1 discloses a method for determining the loading of an activated carbon filter in a tank ventilation system, wherein the tank ventilation system comprises 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 pipe 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, becomes on the load condition of the activated carbon filter

closed. 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. DE 38 04 183 A1 describes a shaft seal for centrifugal pumps for the promotion of, for example, hot water, which uses an internal circulation flow to an atmosphere-side mechanical seal, adapted to a changing operating conditions, continuous removal of resulting in a sealing chamber heat energy and dirt or wear particles also without ensuring an external cooling device.

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

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 invention

Fuel tank system 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 includes 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 port, a vent line leading from the fuel tank to the fuel vapor filter, a purge air line leading from the fuel vapor filter to a fresh gas line of the internal combustion engine integrated in the scavenging air, preferably driven by an electric motor

Compressor (i.e., a device for conveying gases) and a shut-off valve integrated in the scavenging air line, which is connected between an opening of the scavenging air line in the

Fresh gas train and the compressor is arranged. Such a fuel tank system is characterized in that for the compressor in its non-operation, a defined (ie deliberately provided and preferably also known in terms of (pressure-dependent) height) 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. Here, a "central" arrangement of the compressor in the section of the scavenging air line means that a partial section of this section is provided on both sides of the compressor. "Defined" against an influx or outflow of a gas "closed" is the section to be tested, if as far as possible is prevented or in a (compared to an opening state) reduced dimensions and in known (possibly pressure-dependent) height is possible A distinction between a sufficient and an insufficient tightness can by comparison with a defined limit or limit range

(For example, for the gradient of the pressure change), by which a sufficient tightness is defined, carried out, which is signaled by exceeding or falling below the defined limit or threshold range, 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 who is in the evaluation regarding a sufficient or not

sufficient tightness can be included. 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 in the context of carrying out a method according to the invention, it should preferably be provided that a

Changing the pressure in at least the section to be tested of the scavenging air line is possible only 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 mouth into the fresh gas train and the compressor, a fuel tank system according to the invention may preferably at least also have a between the fuel vapor filter and the

Surrounding mouth arranged (integrated into an ambient air line) shut-off valve include. This makes it possible to essentially separate the entire fuel tank system by means of the shut-off valves with respect to an influx or outflow of gas from or into the environment, so that a test substantially the entire fuel tank system to 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 a purging of the fuel vapor filter when no or too low a pressure gradient between the ambient pressure and the pressure in the fresh gas line in the region of the mouth of the

Rinsing air line is given, so that preferably a correspondingly powerful

Design of 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 contemplated that the compressor is a reciprocating compressor (i.e., a positive displacement compressor which cyclically encapsulates, compresses, and expels gas for delivery in a volume) because such a compressor

Piston compressor can have advantages in terms of the realization of a preferably provided flushing functionality of the fuel tank system for the fuel vapor filter.

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. As a "compressor bypass" is an integrated into the compressor or externally arranged from this

Surrounding line understood, via which a gas (with open shut-off valve) under To bypass a pressure chamber by a gas is compressed in the operation of the compressor, can flow.

Basically, there is the possibility of a compressor bypass even with a

Flow compressor trained compressor use 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 can be provided that the compressor a

Vane compressor is whose wings are pressed during operation (possibly only) 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 in non-operating spaced from the inner wall of the housing is 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 a connection to the environment, for example, over the mouth of the scavenging air line in the fresh gas line or over standing with the fuel vapor filter in the gas-conducting connection

Ambient (in order to increase the pressure) ambient air is sucked into the fuel tank system or (for pressure reduction), a gas contained in the fuel tank system is discharged to the environment. In a second step, 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, then due to the defined gas permeability, which is realized according to the invention for the compressor, a pressure equalization between the lying on both sides of the compressor Subsections of the section to be tested (or the tank system in total) can adjust. 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 encompasses the compressor can furthermore also be effected by means of a tank leak diagnosis module, for example by means of a tank leak diagnosis module, as described in DE 10 2012 218 933 A1, preferably between the

Fuel vapor filter and the environmental orifice is arranged and further preferably may include a compressor and / or a shut-off valve. In this way, an as

Bulk product available on the market and thus relatively inexpensive

Tank leak diagnostic module are used to test at least a portion, preferably substantially the entire fuel tank system in terms of sufficient tightness.

In a preferred embodiment of a tank system according to the invention

be provided that the scavenging air line is branched, wherein a first mouth in the Frischgasstrang upstream of a fresh gas compressor integrated in the Frischgasstrang and a second mouth of the scavenging air line in the Frischgasstrang downstream of the Fresh gas compressor is arranged. In this case, the compressor between the junction on the one hand and the first mouth or the second mouth on the other hand in the

Be integrated flushing air duct. 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 may be particularly advantageous in terms of purging of the fuel vapor filter, which on a pressure gradient in the scavenging air line between the fuel vapor filter and one of the orifices in the

Fresh gas train (and thus possibly also without an operation of the built-in the purge air compressor) is performed, affect.

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 with an inventive

Fuel tank system, wherein the internal combustion engine preferably comprises a running according to the Otto principle internal combustion engine, because for the operation of such

Combustion engines used fuels are relatively volatile (especially compared to diesel fuel), which not only the special need for

Tank venting 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 mean that it has to filter the volatile fuel in gaseous form. Rather, the fuel can already (partially) be condensed out again during the filtering. 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. Correspondingly thus concretized

Components are thus to be understood that they are present at least once and may be present more than once.

The present invention will be explained in more detail with reference to an exemplary embodiment shown in the drawings. In the drawings shows, in a schematic representation:

1 shows an internal combustion engine with a fuel tank system according to the invention;

Fig. 2: a vane compressor for a fuel tank system according to the invention in

Business; and

Fig. 3: the vane compressor of FIG. 2 in non-operation.

Fig. 1 shows an internal combustion engine with a fuel tank system. This comprises a fuel tank 10, which is connected via 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. The fuel vapor filter 14 is further connected via a scavenging air line 16 to a fresh gas line 18 of the internal combustion engine, wherein the scavenging air line 16, starting from a branch 20 in two branches 22, 24, of which a first branch 22 in the fresh gas line 18 upstream (with respect

Flow direction of 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) integrated into the fresh gas line 18 fresh gas compressor 28 and the second branch 24 downstream of the fresh gas compressor 28 and in particular downstream of a likewise downstream of the fresh gas compressor 28 in the fresh gas line 18 integrated throttle valve 54 opens. The fresh gas compressor 28 is part of an exhaust gas turbocharger, which further comprises an exhaust gas turbine 30, which is integrated in an exhaust line 32 of the internal combustion engine.

During operation of the internal combustion engine are in a known manner in a defined sequence in combustion chambers 34 of the engine 26, partially of cylinders 34 of the

Combustion engine 26 are limited, mixtures of fresh gas, the complete or im Substantially consists of ambient air, and burned, for example, directly into the combustion chambers 34 injected fuel, the pressure increases thus generated in the

Combustion chambers 34 are used to move in the cylinders 36 longitudinal axial movable guided piston 38. These movements of the piston 38 (not shown) with the interposition of connecting rods in a rotational movement of a crankshaft translated (not shown), wherein the leadership of the piston 38 via the connecting rods by means of the crankshaft simultaneously to a cyclic reciprocating movement of the piston 38 leads. The resulting during combustion of the fresh gas-fuel mixtures in the combustion chambers 34 exhaust gas is discharged through the exhaust line 32 and flows through the exhaust gas turbine 30, resulting in a

rotating drive a turbine runner (not shown) leads. 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, whereby the fresh gas compressor 28 provides for a compression of fresh gas via the fresh gas line 18 to the internal combustion engine 26 supplied fresh gas.

The fuel vapor filter 14 of the fuel tank system stands with 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, to which the ambient air line 42 forms an environmental mouth 62. The first shut-off valve 44 is controllable by means of a control device 48 (for example the engine control of the internal combustion engine), i. this can be actively opened or closed. Optionally, a basically known tank leak diagnostic module 46 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, wherein a portion of this fuel is vaporized, so that in the fuel tank 10 and fuel in the gaseous state is present. Such vaporization of fuel in the fuel tank 10 is enhanced by a relatively high temperature of the fuel, which is particularly the case at comparatively high ambient temperatures. In order to avoid an excessively high overpressure in the fuel tank 10 caused by this evaporation, 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 via the ambient air line 42 is avoided, whereby the fuel vapor filter 14 is avoided. that such pressure equalization leads to the 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 conditioned to regenerate this at regular intervals. For this purpose, a purging of the fuel vapor filter 14 is provided by

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 compared to the flow in the venting of

Fuel tanks 10 opposite flow direction, whereby in the

Fuel vapor filter 10 absorbed fuel molecules are taken through the ambient air and introduced via the scavenging air line 16 in the fresh gas line 18, so that this fuel combustion in the combustion chambers 34 of the engine 26 is supplied. Such purging of the fuel vapor filter 14 is provided only temporarily and always during operation of the internal combustion engine 26, because only then introduced by the purging of the fuel vapor filter 14 in the fresh gas line 18 fuel can be safely supplied to combustion in the combustion chambers 34. An introduction in the

Fresh gas train 18 in a non-operation of the internal combustion engine 26, however, could lead to the gaseous fuel could escape via leaks in the fresh gas line 18 and in particular via a suction port of the fresh gas line 18 into the environment.

For rinsing the fuel vapor filter 14, a sufficient pressure gradient from the ambient pressure in the vicinity of the ambient mouth 62 to the (respective) pressure in the fresh gas line 18 in the region of the orifices 50, 52 is required, which is not always given 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 region of the (second) orifice 52 of the second branch 24 of the scavenging air line 16 is often not even a pressure gradient but a pressure increase, because this second orifice 52 in the area between the fresh gas compressor 28 and the internal combustion engine 26 extending

Charge air path of the fresh gas train 18 is located in the fresh gas due to

Compression by the fresh gas compressor 28 is often present with significant overpressure. By arranging this second orifice 52 (as close as possible) downstream of a throttle valve 54, it is possible to utilize a pressure reduction effected by the throttle valve 54; However, this pressure reduction is often not sufficient to actually realize a sufficient pressure drop across the scavenging air line 16. In this second branch 24 of

Spülluftleitung 16 is therefore a check valve 56 is integrated, by which this branch 24 of 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 56th located portion of the second branch 24 of the scavenging air line 16 is present. In addition to this, upstream of the purging air line 16 (with respect to the direction of flow when purging the fuel vapor filter 14), an actively activatable (second) shut-off valve 58 by the control device 48 is integrated into the second branch 24 of the purging air line 16. 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 sufficiently overpressure-resistant (ie, this must remain sufficiently tightly closed at the at least temporary overpressures on the side of the charge air section of the fresh gas train 18).

In contrast, the first branch of the scavenging air line 22 opens into an upstream of the

Fresh gas compressor 28 located portion of the fresh gas line 18, wherein in the portion of this branch 22 of the scavenging air line 16 between the fresh gas compressor 28 and this (first) orifice 50, a (third) shut-off valve 60 is integrated, which is arranged as close to the first orifice 50, or preferably in this is integrated. In the section of the fresh gas line 18 in the region of the first orifice 50, the pressure of the fresh gas (during operation of the fresh gas compressor 28) is lower than in the charge air path, so that with respect to this first orifice 50 of the scavenging air line 16, a sufficient pressure gradient relatively often compared to (and starting from) the ambient pressure applied to the ambient mouth 62 may be present. 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. In order to allow a purging of the fuel vapor filter 14 at any time, so that a complete saturation of the same can be reliably prevented, the fuel tank system of the internal combustion engine therefore also comprises a compressor 64, also referred to as a "flushing pump", which is designed in the form of a piston compressor and, for example, as a vane compressor 2 and 3. By operation of this compressor 64, ambient air can actively flow over the

Mouth 62 are sucked, which then flows through the fuel vapor filter 14 to the scavenging and which is conveyed via the compressor 64 to the first mouth 50 of the scavenging air line 16. The integrated in the second branch 52 of the scavenging air line 16, then kept closed second shut-off valve 58, but at least the self-closing check valve 56 prevents suction of fresh gas via the second orifice 52 from the charge air path of the fresh gas line 18th

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 a portion of the fuel tank system, in particular for substantially the entire fuel tank system and optionally using the compressor 64 also used as a "scavenge".

For this purpose, it may be provided, for example, that in the context of a method according to the invention by means of the compressor 64, fresh gas is sucked out of the fresh gas line 18 via the first orifice 50 of the scavenging air line 16 and into the flow of the latter

Fresh gas downstream of the compressor 64 lying portion of the scavenging air line 16, including the second branch 24 thereof up to the second shut-off valve 58, is conveyed. About the scavenging air line 16, the fresh gas passes into the fuel vapor filter 14, from this into the vent line 42 (and optionally in an integrated therein

Tank leak diagnosis module 46) up to the closed first shut-off valve 44. Furthermore, the fresh gas passes from the fuel vapor filter 14 into the vent line 12 and in the connected to the vent line 12 fuel tank 10, the, with

Exception of the connection to the vent line 12, to be made gas-tight. In this way, in those sections of the fuel tank system, in which the fresh gas is conveyed by means of the compressor 64, a pressure increase is generated. Subsequently, the (third) shut-off valve 60 integrated into the first branch 22 of the scavenging air line 16 in the region of the first orifice 50 is also closed and an operation of the compressor 64 is ended. As a result of a defined gas permeability for the compressor 64, for example by means of a

Compressor 68 can be realized with an integrated therein (fourth), then opened shut-off valve 70, there is a pressure equalization in the arranged on the different sides of the compressor 64 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 profile of the pressure in the

Fuel tank system can be determined over a defined test period with shut-off valves 44, 58 and 60 kept closed and 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 to be made between a sufficient and an insufficient tightness to distinguish. In this case, a sufficient tightness does not have an im

Essentially complete leakproofness. 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 the generation of a defined overpressure in the

Fuel tank system by means of the compressor 64, this overpressure can also be realized by means of a built-in tank leak diagnostic module 46 compressor 72, wherein this

Compressor 72, for example, via the open first check valve 44 suck in ambient air and can promote in the downstream of the tank leak diagnosis module 46 arranged portions of the fuel tank system.

As an alternative to generating 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 gas contained in the fuel tank system (partially) evacuated and then the previously open shut-off valve 44, 60 is closed, which in turn carried out an evaluation of a change in the (sub) pressure in the fuel tank system to distinguish between a sufficient and insufficient tightness can be.

As an alternative to generating 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 achieve a defined pneumatic pressure within the fuel tank

Fuel tank system by a defined temperature of the fuel tank system or at least the gas enclosed therein to effect and then by means of a change in this pressure, which results from a defined temperature change, to distinguish between a sufficient and an insufficient tightness.

Alternatively or in addition to the provision of the compressor bypass 68 may also be provided to achieve the defined gas permeability for the compressor 64 by a corresponding structural design of the compressor 64 itself. A possible

Design of such a defined gas-permeable compressor 64 is shown in FIGS. 2 and 3.

The compressor 64 according to FIGS. 2 and 3 is designed in the form of a vane-type compressor and comprises a housing 74 which forms a pressure chamber 76 of circular cross-section and a gas inlet 78 and a gas outlet 80. Eccentric within the

Pressure chamber 76, a rotor 82 is rotatably mounted. The rotor 82 comprises a main body 84, which forms a radially aligned with respect to a rotational axis of the rotor 82 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 selected such that the main body 84 of the rotor 82, the pressure chamber 76 bounding inner wall of the housing 74 in a section between the gas inlet 78 and the gas outlet 80 section permanently, ie in each Drehausrichtung the rotor 82, slightly contacted, resulting in a sickle shape of the pressure chamber 76 results. The pressure chamber 76 is separated by means of the wings 86 in a total of three pressure chambers whose sizes change cyclically between approximately zero and a maximum value. The direction of rotation of the rotor 82 is selected such that in each case the pressure chamber communicating with the gas inlet 78 increases, while in each case the pressure chamber connected to the gas outlet 80 decreases, whereby on the one hand cyclically sucked gas via the gas inlet 78 and compressed gas via the gas outlet 80 is ejected. By reversing the direction of rotation of the rotor 82 is the

Possibility to reverse the conveying direction of the compressor 64, wherein the gas inlet 78 acts as a gas outlet and the gas outlet 80 as a gas inlet.

The wings 86 are loaded in the operation of the compressor 64 by means of a spring element 88 to train, resulting from the rotation of the rotor 82, acting on the wings 86 centrifugal forces lead to radially outward shifts of the wings 86 within the receiving slot until the Wing 86 contact with the respective outer end of the inner wall of the housing 74, whereby the pressure chambers are substantially completely separated from each other. This displacement of the vanes 86 radially outwardly results in stressing the spring element 88 to tension, which is thereby pre-stressed. When the operation of the compressor 64 is adjusted, this biasing of the spring element 88 causes the vanes 86 to be displaced radially inward by means of the spring element 88 within the receiving slot, causing the outboard ends of the vanes 86 to be at a defined distance from one another Inner wall of the housing 74 are arranged. 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 via the gas inlet 78, the pressure chamber 76 and the gas outlet 80 the compressor 64th

can flow through. Fuel tank

vent line

Fuel vapor filter

flushing air

Fresh gas line

Branching of the scavenging air line

first branch of the scavenging air line

second branch of the scavenging air line

internal combustion engine

Fresh gas compressor

exhaust turbine

exhaust gas line

Combustion chamber of the internal combustion engine

Cylinder of the internal combustion engine

Piston of the internal combustion engine

wave

Ambient air duct

(first) shut-off valve

Tank leak diagnostic module

control device

first mouth of the scavenging air line

second mouth of the scavenging air line

throttle

check valve

(second) shut-off valve

(third) shut-off valve

around the mouth

compressor

pressure sensor

compressor bypass

(fourth) shut-off valve

Compressor of tank leak diagnostic module

Housing of the compressor

Pressure chamber of the compressor 78 Gas inlet of the compressor

80 Gas outlet of the compressor

82 Rotor of the compressor

84 main body of the rotor

86 wing of the rotor

88 spring element of the rotor

Claims

claims

1. Fuel tank system with

a fuel tank (10),

- A fuel vapor filter (14) in fluid communication with a

Environmental muzzle (62) is,

- One of the fuel tank (10) leading to the fuel vapor filter (14)

Vent line (12),

- One of the fuel vapor filter (14) to a fresh gas line (18) of

Internal combustion engine leading scavenging air line (16),

- One in the scavenging air line (16) integrated compressor (64) and

a shut-off valve (60) integrated into the scavenging air line (16) and arranged between an orifice (50) of the scavenging air line (16) in the fresh gas line (18) and the compressor (64),

characterized in that for the compressor (64) in its non-operation, a defined gas permeability is realized.

2. Fuel tank system according to claim 1, characterized in that the compressor (64) is a flow compressor.

3. Fuel tank system according to claim 1 or 2, characterized by a

Compressor bypass (68).

4. Fuel tank system according to claim 1 or 3, characterized in that the compressor (64) is a reciprocating compressor.

5. Fuel tank system according to claim 4, characterized in that the compressor (64) is a vane compressor, the wings (86) are urged in operation centrifugally loaded against an inner wall of a housing (74) of the vane compressor, wherein the configuration and / or the arrangement of Vane compressor is provided such that at least one of the wings (86) in the non-operation of the

Vane compressor is arranged spaced from the inner wall to realize a defined gas permeability of the compressor (64).

6. 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).

7. Fuel tank system according to one of the preceding claims, characterized by a Tankleckdiagnosemodul (46).

8. Fuel tank system according to claim 7, characterized in that the

Tank leak diagnostic module (46) comprises a compressor (72).

9. Fuel tank system according to claim 7 or 8, characterized in that the tank leak diagnosis module (46) between the fuel vapor filter (14) and the

Environmental orifice (68) is arranged.

10. Fuel tank system according to one of the preceding claims, characterized by a between the fuel vapor filter (14) and the surrounding mouth (68) arranged shut-off valve (44).

1 1. Fuel tank system according to one of the preceding claims, characterized

characterized in that the scavenging air line (16) is branched, wherein a first mouth (50) in the Frischgasstrang (18) upstream of a fresh gas in the line (18) integrated Frischgasverdichters (28) and a second mouth (52) of the scavenging air line (16) the fresh gas line (18) is arranged downstream of the fresh gas compressor (28).

12. Fuel tank system according to claim 1 1, 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.

13. A method for testing the tightness of a fuel tank system according to one of

The preceding claims, characterized in that in at least one of the compressor (64) centrally comprehensive portion of the scavenging air line (16), which is closed against discharge and inflow of a gas defined, a defined pneumatic pressure is generated and then by changing this pressure between a sufficient and an insufficient tightness of this section is distinguished.

14. The method according to claim 13, characterized in that the defined pneumatic pressure by means of the compressor (64) is generated.

15. The method according to claim 13 for checking the tightness of a fuel tank system according to claim 8 or according to one of the claim 8 dependent claims, characterized in that the defined pneumatic pressure by means of the compressor (72) of the tank leak diagnosis module (46) is generated.