Fuel vapor filter purging in supercharged internal combustion engines in suction mode

Abstract

A method for operating an internal combustion engine 1 is provided, which comprises at least one combustion engine 2, a fresh gas line 6 for supplying fresh gas to the combustion engine 2, and a fuel tank system. A fresh gas compressor 7 and a differential pressure valve 19 are integrated in the fresh gas line 6. The fuel tank system comprises a fuel tank 22, a fuel vapor filter 24 which is fluidically connected to the environment, a tank ventilation line 28 which leads from the fuel tank 22 to the fuel vapor filter 24, a first purge gas line 26 and a second purge gas line 27 which each lead from the fuel vapor filter 24 to the fresh gas line 6.

Description

Technical Field

[0001] The invention relates to a method for operating an internal combustion engine having a fuel tank system which can be ventilated. The internal combustion engine can in particular be part of a motor vehicle. Background Art

[0002] A fuel tank system for a combustion engine of a motor vehicle may have a tank ventilation line which allows the pressure in the fuel tank of the fuel tank system to be released into the environment, which is caused by the evaporation of the fuel, for example at relatively high ambient temperatures. In the process, fuel vapors should not be allowed to enter the environment as far as possible, also for reasons of emission regulations. This is prevented by integrating a fuel vapor filter in the tank ventilation line, which absorbs the fuel vapors. Such fuel vapor filters are usually designed in the form of activated carbon filters.

[0003] In order to regenerate such a fuel vapor filter, the corresponding fuel tank system is usually additionally equipped with a purge gas line, which is connected to the fuel vapor filter on the one hand and to the fresh gas line of the internal combustion engine on the other hand. During the operation of the internal combustion engine, ambient air can sometimes be sucked in through the connection of the fuel vapor filter to the environment with the help of a negative pressure, which is present in the region of the opening of the purge gas line into the fresh gas line compared to the ambient pressure. The ambient air flows through the fuel vapor filter in the opposite direction to the flow direction of the fuel vapor from the fuel tank into the fuel vapor filter and thus purges the fuel vapor filter. In this way, the fuel vapor from the fuel vapor filter is supplied to the combustion chamber of the combustion engine of the internal combustion engine via the fresh gas line.

[0004] Patent document DE 10 2017 216 728 B3 discloses an internal combustion engine supercharged by means of an exhaust gas turbocharger, which has a fuel tank system, wherein the associated purge gas line is divided into two sub-lines downstream of the tank ventilation valve, wherein the first sub-line leads to the fresh gas line downstream of the fresh gas compressor of the exhaust gas turbocharger, and the second sub-line leads to a venturi nozzle, which is integrated in the bypass relative to the fresh gas compressor. Check valves are also integrated in each of the two sub-lines, which open when the pressure on the tank ventilation valve side is too high.

[0005] Patent document DE 10 2016 224 973 A1 also discloses an internal combustion engine supercharged by means of an exhaust gas turbocharger, which has a fuel tank system, wherein the associated purge gas line is divided into two sub-lines downstream of the fuel tank ventilation valve, wherein the first sub-line opens into the fresh gas line downstream of the fresh gas compressor, and the second sub-line opens into the fresh gas line upstream of the fresh gas compressor. The inlet of the second sub-line is arranged downstream of a differential pressure valve, by means of which a relatively low fresh gas pressure can be set downstream of the differential pressure valve. The internal combustion engine also includes an exhaust gas recirculation line, which branches off from the exhaust gas line of the internal combustion engine downstream of the exhaust gas turbine and opens into a section of the fresh gas line between the differential pressure valve and the inlet of the second sub-line of the purge gas line. If a fuel vapor filter of the fuel tank system is to be purged during the suction operation of the internal combustion engine, the purge gas guided via the purge gas line is introduced via the first subline and thus into the section of the fresh gas line downstream of the fresh gas compressor, since in this case there is a sufficient pressure drop across the first subline. During the compression operation of the internal combustion engine, the purge gas is introduced via the second subline, wherein in this case a sufficient pressure drop across the second subline is provided by closing the differential pressure valve sufficiently far enough. Summary of the invention

[0006] The object of the present invention is to achieve an advantageous purging of a fuel vapor filter of a fuel tank system of a supercharged internal combustion engine.

[0007] The solution to the technical problem is achieved by a method according to the invention for operating an internal combustion engine, namely a method for operating an internal combustion engine having

[0008] - Combustion engines;

[0009] a fresh gas line for supplying fresh gas to the combustion engine, wherein a fresh gas compressor and a differential pressure valve are integrated in the fresh gas line; and

[0010] - A fuel tank system, the fuel tank system comprising:

[0011] - fuel tank;

[0012] a fuel vapor filter which is connected in fluid-conducting communication with the environment;

[0013] - a fuel tank ventilation line leading from the fuel tank to the fuel vapor filter;

[0014] a first purge gas line which leads from the fuel vapor filter to a first section of the fresh gas line, the first section being situated downstream of the differential pressure valve and upstream of the fresh gas compressor; and

[0015] a second purge gas line which leads from the fuel vapor filter to a second section of the fresh gas line, the second section being situated downstream of the fresh gas compressor,

[0016] It is characterized in that, at least temporarily during an intake operation of the internal combustion engine with a fuel vapor filter purge, the differential pressure valve is at least partially closed and purge gas is thereby introduced via the first purge gas line into the first section of the fresh gas line.

[0017] Advantageous embodiments of the method according to the invention are described in the further claims and / or result from the following description of the invention.

[0018] According to the invention, a method for operating an internal combustion engine is provided, the internal combustion engine comprising at least one combustion engine, in particular a gasoline engine or another combustion engine, which is at least temporarily ignited from an external source, a fresh gas line for supplying fresh gas to the combustion engine, and a fuel tank system. At least one fresh gas compressor, which can be in particular part of an exhaust gas turbocharger, and a differential pressure valve, in particular designed as a valve, are integrated in the fresh gas line. The fuel tank system has at least one fuel tank, a fuel vapor filter connected to the ambient fluid, a fuel tank ventilation line leading from the fuel tank to the fuel vapor filter, a first purge gas line leading from the fuel vapor filter to the fresh gas line of the internal combustion engine, and a second purge gas line leading from the fuel vapor filter to the fresh gas line. In this case, the first purge gas line opens into a first section of the fresh gas line located downstream of the differential pressure valve and upstream of the fresh gas compressor, while the second purge gas line opens into a second section of the fresh gas line located downstream of the fresh gas compressor, preferably into a (second) section also located downstream of a throttle device, for example in the form of a valve (throttle valve), which is integrated in the fresh gas line. Here, the first purge gas line and the second purge gas line can preferably be constructed as a whole in a partial section, in particular in a first section coming out of the fuel vapor filter. In addition, a fuel tank ventilation valve can be provided for regulating the mass flow of the purge gas introduced into the fresh gas line from at least one purge gas line. Such a fuel tank ventilation valve can be arranged in particular in a preferably integral section of the two purge gas lines. According to the invention, it is provided that, at least temporarily, during the suction operation of the internal combustion engine with the purge of the fuel vapor filter (i.e., the fuel vapor filter is purged at the same time and the purge gas is thus guided through at least one purge gas line), the differential pressure valve is at least partially closed, and the purge gas is thus introduced into the fresh gas line through the first purge gas line. In particular, it can be provided that the closing position of the differential pressure valve is changed or adjusted in order to specifically set a defined purge gas mass flow to be conducted through the first purge gas line.

[0019] The "intake operation" of an internal combustion engine with fresh gas compression on which the present invention is based is to be understood as an operating state in which the means for regulating the intensity of the fresh gas compression are in an inactive initial position or minimum position, i.e. not in an active control operation. In particular, it can be provided that in the section of the fresh gas line between the fresh gas compressor and the combustion engine there is a (medium) pressure of the fresh gas which is less than or equal to the ambient pressure.

[0020] According to the invention, the differential pressure valve integrated upstream of the opening of the first purge gas line into the fresh gas line should therefore be used (also) to achieve a pressure drop in the first purge gas line during suction operation, so that purge gas can be conducted through the first purge gas line if necessary.

[0021] Preferably, provision can be made that, at least temporarily during suction operation with fuel vapor filter purging, purge gas is introduced into the fresh gas line via the second purge gas line, which is advantageously possible due to the suction effect of the combustion engine and in particular the suction effect of the throttle device in the section immediately downstream of the second purge gas line, and the pressure drop resulting therefrom in the second purge gas line, during suction operation of the internal combustion engine. It can be particularly preferably provided that the purge gas is conducted via the second purge gas line simultaneously with the purge gas conducted via the first purge gas line, thereby enabling a relatively large (total) purge gas mass flow to be achieved during suction operation. In this case, additionally conducting purge gas via the first purge gas line can be particularly advantageous, since the purge gas mass flow conducted solely via the (second) purge gas line, which opens into the fresh gas line downstream of the fresh gas compressor, can be relatively greatly restricted due to the suction operation. In this case, these limitations may result from a pressure ratio on the (second) purge gas line (ratio of fresh gas pressure in the region of the inlet of the purge gas line to ambient pressure), which, upon reaching a critical value between 0.52 and 0.53, no longer permits an increase in the purge gas guided through the (second) purge gas line, wherein this critical pressure ratio occurs relatively early at relatively high ambient temperatures and relatively low ambient pressures (in particular due to operation of the internal combustion engine at a relatively high geographical altitude) and therefore permits only relatively low purge gas mass flows through the (second) purge gas line. A further advantage that can result from guiding the purge gas through the first purge gas line is that, due to the relatively long guidance of the fresh gas (comprising at least air and purge gas) in the fresh gas line until it reaches the combustion engine, the purge gas is better mixed with the air.

[0022] Since the at least partial closing of the differential pressure valve for introducing purge gas into the fresh gas line via the first purge gas line during the suction operation of the internal combustion engine with fuel vapor filter purging is accompanied by a pressure loss in the fresh gas guided via the fresh gas line, which pressure loss can have a negative effect on the operating performance of the internal combustion engine, it can be preferably provided that the purge gas is guided in a targeted manner via the first purge gas line only when a sufficiently large purge gas mass flow cannot be guided via the second purge gas line. It can therefore be provided within the scope of the method according to the invention that during the suction operation with fuel vapor filter purging, the differential pressure valve is closed in order to guide the purge gas via the first purge gas line only when the target total purge gas mass flow to be introduced into the fresh gas line is above a limit value, wherein the limit value defines the maximum purge gas mass flow that can be guided via the second purge gas line in the current operating state of the internal combustion engine. In this case, the current operating state is influenced both by internal operating parameters, in particular the load and speed of the combustion engine operation, and by external operating parameters, in particular the temperature and pressure of the ambient air. Against this background, it can be provided within the scope of the method according to the invention that during the suction operation with fuel vapor filter purging, if the target total purge gas mass flow is below the limit value, the differential pressure valve is temporarily opened as much as possible. This can achieve that the fresh gas flow is throttled as little as possible by the differential pressure valve, if such throttling is not desired and is not necessary. Therefore, this can be the case in particular when the differential pressure valve is only provided to achieve a pressure drop on the first purge gas line when necessary, so as to enable the purge gas to be guided through the first purge gas line. However, if necessary, at least partial closing of the differential pressure valve and the resulting generation of a relatively low local pressure of the fresh gas can also be suitable for other purposes. In this case, such closing of the differential pressure valve should preferably not occur (in order to guide the purge gas through the first purge gas line in a targeted manner) to an extent that exceeds that required for other purposes.

[0023] Other purposes for which the at least partial closing of the differential pressure valve may be used may be, in particular, the realization of exhaust gas recirculation. A corresponding internal combustion engine that can be used within the scope of the method according to the invention may include an exhaust gas recirculation line for this purpose, which leads from the exhaust gas line of the internal combustion engine to a first section of the fresh gas line located downstream of the differential pressure valve and upstream of the fresh gas compressor, the exhaust gas line being used to discharge the exhaust gas from the combustion engine and to introduce at least a portion of the exhaust gas into the environment. In this case, the exhaust gas recirculation line may branch off from the exhaust gas line, in particular downstream of the exhaust gas turbine, in order to realize a so-called low-pressure exhaust gas recirculation. Furthermore, preferably, an exhaust gas recirculation valve may be integrated in the exhaust gas recirculation line, which is designed and arranged to regulate the exhaust gas mass flow guided through the exhaust gas recirculation line. The method according to the invention for operating such an internal combustion engine can provide that, at least temporarily during suction operation with fuel vapor filter purging, exhaust gas is conducted through an exhaust gas recirculation line (in order to achieve exhaust gas recirculation), wherein the exhaust gas mass flow conducted through the exhaust gas recirculation line in this process is regulated, in particular controlled, by means of an exhaust gas recirculation valve. It can be particularly preferably provided that the influence of the closed position of the differential pressure valve, which is regulated as a function of the purge gas mass flow to be introduced into the fresh gas line via the first purge gas line, and the influence of the closed position on the exhaust gas mass flow is compensated by means of the exhaust gas recirculation valve. In this case, the closed position of the differential pressure valve should therefore be selected solely as a function of the purge gas mass flow to be conducted through the first purge gas line and the pressure drop required for this in the first purge gas line, while the unavoidable (but also desired) influence of the at least partially closed differential pressure valve or the relatively small local pressure generated thereby on the exhaust gas mass flow conducted through the exhaust gas recirculation line is taken into account in the regulation of the exhaust gas mass flow by corresponding control of the exhaust gas recirculation valve.

[0024] The internal combustion engine used within the scope of the method according to the invention can in particular be part of a motor vehicle. In this case, the combustion engine of the internal combustion engine can in particular be provided to directly or indirectly provide drive power for the motor vehicle. The motor vehicle can in particular be a wheel-based motor vehicle (preferably a car or a truck or a similar mobile working machine) rather than a motor vehicle traveling on tracks.

[0025] According to the invention, the name "fuel vapor filter" does not restrict it to necessarily filter or absorb volatile fuels in gaseous form. Instead, the fuel may also have been (partially) condensed out again during the filtering process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following is based on Figure 1 The present invention is explained in detail by the embodiments shown in the accompanying drawings.

[0027] Figure 1A schematic diagram of an internal combustion engine according to the invention is shown. DETAILED DESCRIPTION

[0028] Figure 1 An internal combustion engine 1 that can be used within the scope of the method according to the invention is shown in a simplified form. The internal combustion engine has a combustion engine 2 in which a plurality of combustion chambers 3 are formed. During operation of the internal combustion engine 1, a mixture quantity is combusted in a known manner in a defined sequence in a plurality of combustion chambers 3, which are partially delimited by cylinders 4 of the combustion engine 2 and pistons 5 guided movably in the cylinders, wherein the pressure increase thus generated in the combustion chambers 3 is used to move the pistons 5. The movement of the pistons 5 is converted into a rotational movement of a crankshaft (not shown) with the interposition of a connecting rod (not shown), wherein the pistons 5 are simultaneously moved back and forth in a circular motion by means of the crankshaft's guidance of the pistons 5 via the connecting rods.

[0029] The mixture quantity provided for the combustion in the combustion chamber 3 comprises, on the one hand, fresh gas, which is composed entirely or predominantly of ambient air sucked in from the environment and is supplied to the combustion engine 2 via a fresh gas line 6. In this case, the fresh gas is guided via a fresh gas compressor 7 of an exhaust gas turbocharger, which is integrated in the fresh gas line 6, by means of which the fresh gas can be compressed in the compression mode of the internal combustion engine 1. The mixture quantity also comprises fuel, which can be introduced directly into the combustion chamber 3 by means of a fuel injector 8 and ignited by means of an ignition device 9 and thus burns. The exhaust gas generated when the fresh gas-fuel mixture quantity is burned in the combustion chamber 3 is discharged via an exhaust gas line 10 and in the process flows through an exhaust gas turbine 11 of the exhaust gas turbocharger and subsequently through a plurality of exhaust gas aftertreatment devices, for example first through a first three-way catalytic converter 12, then through a particle filter 13 and finally through a second three-way catalytic converter 14.

[0030] At least temporarily during operation of the combustion engine 2, a portion of the exhaust gas conducted through the exhaust gas line 10 can be introduced into the fresh gas line 6 via an exhaust gas recirculation line 15. An exhaust gas cooler 40, a temperature sensor 16, an exhaust gas recirculation valve 17 and a differential pressure sensor 18 are integrated in the exhaust gas recirculation line 15, which branches off from the exhaust gas line 10 downstream of the exhaust gas turbine 11 and in particular from a section arranged between the particle filter 13 and the second three-way catalytic converter 14 and opens into the fresh gas line 6 upstream of the fresh gas compressor 7, in particular into a section of the fresh gas line 6 arranged upstream of the fresh gas compressor 7 and downstream of the differential pressure valve 19.

[0031] An air filter 20 and an air quality sensor 21 arranged downstream of the air filter 20 are also integrated in the fresh gas line 6 upstream of the differential pressure valve 19 .

[0032] The fuel to be introduced into the combustion chamber 3 by means of the fuel injector 8 comes from a fuel tank 22 of a fuel tank system of the internal combustion engine 1. A fuel tank leak diagnostic module 23 is connected to the fuel tank 2, in addition to which the fuel tank system also includes a fuel vapor filter 24, which can be designed in particular in the form of an activated carbon filter or includes an activated carbon filter and is connected to the fuel tank 22 via a fuel tank ventilation line 25. The fuel vapor filter 24 is also connected to the fresh gas line 6 of the internal combustion engine 1 via two purge gas lines 26, 27, wherein the two purge gas lines 26, 27 are integrally formed in a first section leading away from the fuel vapor filter 24. An actively controllable tank ventilation valve 28 and a combined pressure and temperature sensor 29 between the fuel vapor filter 24 and the tank ventilation valve 28 are integrated in the integral section of the two purge gas lines 26, 27, while a nonreturn valve 30 is respectively integrated in the separate sections of the two purge gas lines 26, 27, which automatically closes in the event of a negative pressure on the side of the tank ventilation valve 28. The first of the purge gas lines 26, 27, the purge gas line 26, opens into the fresh gas line 6 upstream of the fresh gas compressor 7, specifically into the (first) section 6a of the fresh gas line 6 between the differential pressure valve 19 and the fresh gas compressor 7, but downstream of the opening into the exhaust gas recirculation line 15.

[0033] The first purge gas line 26 opens (indirectly) into the fresh gas line 6 via a Venturi nozzle 32, wherein the outlet of the Venturi nozzle 32 opens into the fresh gas line 6, and the main inlet of the Venturi nozzle 32 is connected to a drive line 33, which branches off from the fresh gas line 6 downstream of the fresh gas compressor 7. The first purge gas line 26 opens into a secondary inlet of the Venturi nozzle 32, which is arranged in the region of the reduced cross section of the Venturi nozzle 32. By means of the fresh gas flow from the drive line 33 flowing through the Venturi nozzle 32, purge gas can be sucked in through the first purge gas line 26 and the secondary inlet of the Venturi nozzle 32.

[0034] The second purge gas line 27 opens into the second section 6 b of the fresh gas line 6 downstream of the fresh gas compressor 7 and the charge air cooler 34 as well as the throttle valve 35 .

[0035] The fuel vapor filter 24 is connected with its side facing away from the tank ventilation line 25 (due to its filtering action against fuel vapors) via an ambient air line 31 in an air-conducting manner to the environment.

[0036] The fuel tank 22 is filled with fuel, wherein a portion of the originally liquid fuel usually evaporates, so that a gaseous aggregate of fuel is still present in the fuel tank 22. Such evaporation of the fuel in the fuel tank 22 occurs in particular at relatively high ambient temperatures and, for example, due to a motor vehicle with an internal combustion engine 1 driving uphill at relatively low ambient pressures, since the evaporation temperatures of the various fuel components decrease according to the associated vapor pressure curves due to the drop in ambient pressure. In order to avoid an inadmissibly high overpressure in the fuel tank 22 due to such evaporation, a pressure equalization with the ambient pressure can be carried out via the fuel tank ventilation line 25, the fuel vapor filter 24 and the ambient air line 31, wherein the fuel vapor filter 24 prevents such pressure equalization from causing fuel vapor to leak into the environment.

[0037] The ventilation of the fuel tank 22 leads to an increasing saturation of the fuel vapor filter 24, which in turn requires occasional regeneration of the fuel vapor filter. For this purpose, the fuel vapor filter 24 is purged by drawing in ambient air through an ambient air line 31. The ambient air flows through the fuel vapor filter 24, so that the fuel molecules absorbed in the fuel vapor filter 24 are carried along by the ambient air and introduced into the fresh gas line 6 via at least one of the purge gas lines 26, 27. The mass flow of the purge gas can be specifically adjusted by means of a fuel tank ventilation valve 28. By introducing the purge gas and the fuel molecules contained therein, they are supplied to the combustion chamber 3 of the combustion engine 2 for heat utilization or combustion.

[0038] In order to draw in only ambient air via ambient air line 31 and not additionally fuel vapor via tank vent line 25 during the purging of fuel vapor filter 24 , tank vent line 25 can be blocked by means of a tank shutoff valve 36 .

[0039] The purging of the fuel vapor filter 24 is only temporarily provided, but always during the operation of the combustion engine 2, because only in this case can the fuel introduced into the fresh gas line 6 by purging the fuel vapor filter 24 also be safely or surely supplied to the combustion chamber 3 for combustion. In addition, in this case, a sufficient pressure drop over at least one of the purge gas lines 26, 27 can be ensured.

[0040] According to the invention, when the fuel vapor filter 24 is purged during the suction operation of the internal combustion engine 1, purge gas is introduced into the fresh gas line 6 both via the first purge gas line 26 and via the second purge gas line 27. In this case, a sufficient pressure drop is present in the second purge gas line 27, essentially due to the suction effect of the internal combustion engine 2 during such a suction operation. The sufficient purge gas pressure drop in the first purge gas line 26 is ensured by at least partially closing the differential pressure valve 19, thereby generating a pressure drop in the differential pressure valve 19, i.e., a negative pressure in comparison with the ambient pressure on the downstream side of the differential pressure valve 19. In this case, the Venturi nozzle 32 does not contribute or contributes only slightly to the generation of a sufficient pressure drop in the first purge gas line 19, since a significant overpressure is required on the downstream side of the fresh gas compressor 7 in comparison with the upstream side of the fresh gas compressor 7 for its suction effect in order to guide the fresh gas through the drive line 33. However, such a pressure increase does not occur during the suction operation of the internal combustion engine.

[0041] When the fuel vapor filter 24 is purged during compression operation of the internal combustion engine, however, the purge gas is conducted exclusively through the first purge gas line 26, since the nonreturn valve integrated in the second purge gas line 27 is closed due to the excess pressure (compared to the ambient pressure) which is present in the fresh gas line 6 in the region of the opening of the second purge gas line 27, which is generated by means of the fresh gas compressor 7. During such compression operation with fuel vapor filter purging, a sufficient pressure drop across the first purge gas line 26 is achieved on the one hand by the opening of the first purge gas line 26 or the outlet of the venturi nozzle 32 being located on the low-pressure side of the fresh gas compressor 7 and, in addition, by the action of the venturi nozzle 32. During such compression operation with fuel vapor filter purging, it is not necessary to at least partially close the differential pressure valve 19 in order to conduct the purge gas through the first purge gas line 26. In this case, however, at least partial closing of the differential pressure valve 19 can be provided in order to achieve a sufficient pressure drop across the exhaust gas recirculation line 15 in order to introduce sufficient exhaust gas into the fresh gas line 6 via the exhaust gas recirculation line 15. Control and in particular regulation of the exhaust gas mass flow conducted through the exhaust gas recirculation line 15 in the process can be achieved only by corresponding adjustment of the differential pressure valve 19 or by a combined position of the differential pressure valve 19 and the exhaust gas recirculation valve 17 or a position superimposed on their action.

[0042] If, however, exhaust gas recirculation is also provided during the intake operation of the internal combustion engine with fuel vapor filter purging, the adjustment of the exhaust gas mass flow conducted via the exhaust gas recirculation line 15 is carried out within the scope of the control and, in particular, regulation of the exhaust gas mass flow only with the aid of the exhaust gas recirculation valve 17, wherein the influence of the closed position of the differential pressure valve 19, which is adjusted in order to produce a sufficient pressure drop in the first purge gas line 26, is compensated with the aid of the exhaust gas recirculation valve.

[0043] exist Figure 1 In the figure, it is shown that the internal combustion engine 1 also includes a device for ventilating the cylinder crankcase 37 of the combustion engine 2, as is generally known. For this purpose, a case ventilation line 38 is provided, which branches off from the space for accommodating the crankshaft defined by the cylinder crankcase 37 of the combustion engine 2, and a separation device 39 is integrated in the case ventilation line, which is used to separate liquid and solid foreign matter from the ventilation gas guided through the case ventilation line 38. Downstream of the separation device 39, the case ventilation line 38 is divided into a first subline 38a, which opens into the fresh gas line 6 upstream of the fresh gas compressor 7, and a second subline 38b, the corresponding opening of which is arranged downstream of the fresh gas compressor 7 and specifically also downstream of the opening of the second purge gas line 27. Depending on the compression power generated by the fresh gas compressor 7 or depending on whether the internal combustion engine is in suction operation or compression operation, the ventilation gas can be introduced into the fresh gas line 6 either through the first subline 38a or through the second subline 38b of the case ventilation line 38.

[0044] Reference numerals list

[0045] 1 Internal combustion engine

[0046] 2 Combustion Engine

[0047] 3 Combustion chamber of a combustion engine

[0048] 4 Cylinders of a combustion engine

[0049] 5 Piston of a combustion engine

[0050] 6 Fresh gas line

[0051] 6a First section of fresh gas line

[0052] 6b Second section of fresh gas line

[0053] 7 Fresh gas compressor

[0054] 8 Fuel Injectors

[0055] 9 Ignition device

[0056] 10 Exhaust gas line

[0057] 11 Exhaust gas turbine

[0058] 12 First three-way catalytic converter

[0059] 13 Particle filter

[0060] 14 Second three-way catalytic converter

[0061] 15 Exhaust gas recirculation line

[0062] 16 Temperature Sensor

[0063] 17 Exhaust gas recirculation valve

[0064] 18 Differential pressure sensor

[0065] 19 Differential pressure valve

[0066] 20 Air filter

[0067] 21 Air Quality Sensor

[0068] 22 Fuel Tank

[0069] 23 Fuel tank leak diagnostic module

[0070] 24 Fuel vapor filter

[0071] 25 Fuel tank ventilation line

[0072] 26 First purge gas line

[0073] 27 Second purge gas line

[0074] 28 Fuel tank ventilation valve

[0075] 29 Pressure and temperature sensors

[0076] 30 Check valve

[0077] 31 Ambient air line

[0078] 32 Venturi nozzle

[0079] 33 Drive pipeline

[0080] 34 Charge air cooler

[0081] 35 Throttle

[0082] 36 Fuel tank shut-off valve

[0083] 37 Crankcase of a combustion engine

[0084] 38 Box ventilation line

[0085] 38a First sub-circuit of the box ventilation line

[0086] 38b Second sub-circuit of the box ventilation line

[0087] 39 Separation device

[0088] 40 Exhaust gas cooler

Claims

1. A method for operating an internal combustion engine (1), the internal combustion engine having - a combustion engine (2); - a fresh gas line (6) for supplying fresh gas to the combustion engine (2), wherein A fresh gas compressor (7) and a differential pressure valve (19) are integrated in the fresh gas line (6); and - A fuel tank system, the fuel tank system comprising: - a fuel tank (22); a fuel vapor filter (24) which is connected in fluid-conducting communication with the surrounding environment; - a fuel tank ventilation line (25) leading from the fuel tank (22) to the fuel vapor filter (24); a first purge gas line (26) which leads from the fuel vapor filter (24) to a first section (6a) of the fresh gas line (6), the first section being located downstream of the differential pressure valve (19) and upstream of the fresh gas compressor (7); and a second purge gas line (27) which leads from the fuel vapor filter (24) to a second section (6b) of the fresh gas line (6), the second section being located downstream of the fresh gas compressor (7), It is characterized in that, at least temporarily during an intake operation of the internal combustion engine (1) with fuel vapor filter purging, the differential pressure valve (19) is at least partially closed and purge gas is thereby introduced via the first purge gas line (26) into the first section (6a) of the fresh gas line (6).

2. The method according to claim 1, characterized in that The closing position of the differential pressure valve (19) is varied in order to adjust the purge gas mass flow to be conducted through the first purge gas line (26).

3. The method according to claim 1 or 2, characterized in that: At least temporarily during suction operation with fuel vapor filter purging, purge gas is introduced into the fresh gas line (6) via the second purge gas line (27).

4. The method according to claim 3, characterized in that At least temporarily during suction operation with fuel vapor filter purging, purge gas is introduced into the fresh gas line (6) via the first purge gas line (26) and the second purge gas line (27).

5. The method according to claim 3 or 4, characterized in that: During suction operation with fuel vapor filter purging, the differential pressure valve (19) is at least partially closed in order to conduct purge gas via the first purge gas line only when a target total purge gas mass flow to be introduced into the fresh gas line (6) is above a limit value, the limit value defining the maximum purge gas mass flow that can be conducted via the second purge gas line (27) in the operating state of the internal combustion engine.

6. The method according to claim 5, characterized in that During suction operation with fuel vapor filter purging, the differential pressure valve (19) is opened as far as possible if the target total purge gas mass flow falls below the limit value.

7. The method according to any one of the preceding claims, characterized in that At least temporarily during suction operation with fuel vapor filter purging, exhaust gas is guided through an exhaust gas recirculation line (15), which leads from an exhaust gas line (10) of the internal combustion engine (1) to a first section (6a) of the fresh gas line (6) located downstream of the differential pressure valve (19) and upstream of the fresh gas compressor (7), wherein the exhaust gas mass flow guided through the exhaust gas recirculation line (15) is regulated by means of an exhaust gas recirculation valve (17) integrated in the exhaust gas recirculation line (15).

8. The method according to claim 7, characterized in that The influence of the closed position of the differential pressure valve (19) on the exhaust gas mass flow is compensated by means of the exhaust gas recirculation valve (17).

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