METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE WITH AN HC SENSOR INTEGRATED INTO A PURGE GAS LINE

Description

[0001] The invention relates to a method for operating an internal combustion engine with a fuel tank system, which, on the one hand, comprises a fuel vapor filter to enable venting of a fuel tank of the fuel tank system as needed, and, on the other hand, has a purge gas line leading from the fuel vapor filter to a fresh gas line of the internal combustion engine to enable purging of the fuel vapor filter or the fuel tank system itself as needed. The invention further relates to an internal combustion engine suitable for carrying out such a method, as well as to a motor vehicle having such an internal combustion engine.

[0002] A fuel tank system for a motor vehicle's internal combustion engine typically includes a vent line that allows the fuel tank of the fuel tank system to be vented, i.e., to release rising pressure in the fuel tank to the environment, resulting, for example, from fuel evaporating at relatively high ambient temperatures. In this case, emissions regulations also require that no fuel vapors be released into the environment. This is prevented by integrating a fuel vapor filter, typically in the form of an activated carbon filter, into the vent line. This filter absorbs the fuel vapors when the fuel tank is vented.

[0003] Such a fuel tank system is additionally equipped with a purge gas line, particularly for regenerating the fuel vapor filter, which is connected on the one hand to the fuel vapor filter and on the other hand to the fresh gas line of the internal combustion engine. During operation of the internal combustion engine, ambient air can be temporarily drawn in via an ambient opening of the fuel vapor filter by means of a negative pressure that prevails in the area where the purge gas line enters the fresh gas line compared to the ambient pressure. This ambient air then flows through the fuel vapor filter in the opposite direction to the flow direction in which the fuel vapors coming from the fuel tank flowed through the fuel vapor filter, thereby purging the fuel vapor filter. The fuel vapors from the fuel vapor filter are thus fed to the combustion chambers of the internal combustion engine of the internal combustion engine via the purge gas line and the fresh gas line.

[0004] If the mass flow of the fuel introduced via the purge gas line into the fresh gas system and from there into the combustion chambers is not known with sufficient precision, such regeneration or purging of the fuel vapor filter can result in the internal combustion engine temporarily operating with a combustion air / fuel ratio that deviates from a corresponding target value. This can at least worsen the raw pollutant emissions of the internal combustion engine. Such a deterioration in the raw pollutant emissions can be determined using an exhaust gas sensor, for example a lambda sensor, which makes it possible, based on the measured values ​​of this exhaust gas sensor, to adjust the fuel quantities introduced into the combustion chambers or the fresh gas system via fuel injectors in order to set a combustion air / fuel ratio that corresponds as closely as possible to a corresponding target value, even during purging of the fuel vapor filter.

[0005] The disadvantage of this procedure is that the adjustment of the fuel quantities introduced into the combustion chambers only takes place when the exhaust gas sensor has already determined relatively poor pollutant raw emissions from the combustion engine.

[0006] To avoid this disadvantage, it may be possible to determine the fuel mass flow introduced into the fresh gas system via the purge gas line when the fuel vapor filter is purged, in order to proactively adjust the fuel quantities introduced into the combustion chambers or the fresh gas system via the fuel injectors. This requires the most precise possible knowledge of the purge gas mass flow conducted via the purge gas line and the concentration of the fuel, i.e., the hydrocarbons, in this purge gas mass flow.

[0007] The concentration of hydrocarbons in a purge gas mass flow can be determined directly using a suitable (HC) sensor. However, such an HC sensor can exhibit significant measurement deviations. Furthermore, it is advisable to be able to detect a defect in such an HC sensor as quickly as possible after the defect occurs in order to avoid prolonged operation of the combustion engine with a combustion air ratio that deviates significantly from the target value.

[0008] DE 10 2010 048 313 A1 relates to a method for operating a tank ventilation system, in which a purge gas mass flow flowing in a purge gas line is determined as a function of the purge gas density and the pump characteristics of a purge gas delivery device. It may also be provided to determine a hydrocarbon concentration of the purge gas using an HC sensor.

[0009] DE 10 2017 209 127 A1 discloses a method for calculating a mass flow of a fuel / air mixture transferred from a tank ventilation system into an intake manifold of an internal combustion engine. A fuel / air ratio of the mass flow is taken into account when calculating the mass flow.

[0010] DE 10 2015 114 071 A1 describes an internal combustion engine with a valve control module, a purge fraction module, and a diagnostic module. The valve control module opens a purge valve in an evaporative emissions system to allow a flow of purge vapor to an intake system of the internal combustion engine. The purge fraction module determines a first and second fraction of purge vapor delivered to the engine relative to a total amount of air and purge vapor delivered to the internal combustion engine based on a first and second input. The first input comes from a hydrocarbon sensor arranged in the evaporative emissions system of the internal combustion engine. The second input comes from an oxygen sensor arranged in an exhaust system of the internal combustion engine.The diagnostic module selectively diagnoses a fault in at least one of the evaporative emission system and the hydrocarbon sensor based on the first and second purge portions when the purge valve is open.

[0011] DE 11 2011 103 454 B4 discloses a method for operating an internal combustion engine having at least one cylinder, an exhaust system having a measuring device, and a tank ventilation system with a purge air line which is designed for pneumatic communication between the tank ventilation system and the at least one cylinder and which has at least one sensor for determining a hydrocarbon content of a gas stream, comprising the method steps: Determining a hydrocarbon content of a gas flow flowing from the tank ventilation system to the at least one cylinder depending on a measurement signal from the sensor, controlling a fuel metering into the at least one cylinder depending on the determined hydrocarbon content, detecting an exhaust gas characteristic of an exhaust gas flow flowing in the exhaust system by means of the measuring device, comparing the exhaust gas characteristic with a predetermined target value and, if the difference between the measured exhaust gas parameter and the specified target value exceeds a specified limit value, checkwhether the sensor is malfunctioning, comprising: determining the hydrocarbon content of the gas stream in a predetermined operating range of the internal combustion engine, comparing the hydrocarbon content thus determined with a specific hydrocarbon setpoint predetermined for the operating range and determining whether the sensor is malfunctioning depending on a deviation between the determined hydrocarbon content and the predetermined specific hydrocarbon setpoint.

[0012] US 2011 / 0313642 A1 discloses a method by which the influence of a crankcase ventilation or of blow-by gases flowing into the combustion chambers of an internal combustion engine on the combustion is to be compensated.

[0013] The invention was based on the object of correcting measurement deviations of an HC sensor integrated in a purge gas line of a fuel tank system of an internal combustion engine and / or of determining a defect of such an HC sensor.

[0014] This object is achieved by a method according to patent claim 1. An internal combustion engine suitable for carrying out such a method is the subject of patent claim 5. Advantageous embodiments of the method according to the invention and preferred embodiments of the internal combustion engine according to the invention are the subject of the further patent claims and / or emerge from the following description of the invention.

[0015] According to the invention, a method for operating an internal combustion engine is provided, wherein the internal combustion engine comprises at least the following components: a preferably spark-ignited and quantity-controlled internal combustion engine (e.g. a gasoline engine) which has at least one combustion chamber and preferably a plurality of combustion chambers, a fresh gas line for supplying fresh gas to the internal combustion engine, an exhaust line for discharging exhaust gas from the internal combustion engine with an exhaust gas sensor integrated therein, for example in the form of a so-called lambda probe, and a fuel tank system.

[0016] The fuel tank system comprises at least a fuel tank, a fuel vapor filter which is in fluid communication with an ambient opening, a vent line leading from the fuel tank to the fuel vapor filter and a purge gas line leading from the fuel vapor filter to the fresh gas line, into which an HC sensor on the one hand and a tank vent valve on the other hand, by means of which the mass flow of the purge gas guided via the purge gas line can be adjusted by throttling to a greater or lesser extent or not at all, and / or a purge gas conveying device by means of which the purge gas can be actively conveyed through the purge gas line as required, are integrated.

[0017] According to the invention, during operation of the internal combustion engine, with purge gas conducted via the purge gas line, the hydrocarbon content of the purge gas is determined by means of the HC sensor and the mass flow of the purge gas, and from these values, a fuel mass flow introduced into the fresh gas line is determined. Furthermore, the amount of fuel introduced into the combustion chamber and / or the fresh gas line by means of at least one fuel injector is adjusted in order to compensate for the additional amount of fuel introduced via the purge gas, taking into account a defined total amount of fuel to be supplied to the combustion chamber per working cycle.

[0018] Furthermore, the invention provides that, based on an exhaust gas composition determined by the exhaust gas sensor, the (averaged) combustion air ratio of fuel-fresh gas mixture quantities supplied to the combustion chamber is monitored for a deviation from a target value (which may, in particular, correspond to a stoichiometric combustion air ratio), which may occur despite the adjustment of the fuel introduced by the fuel injector. If such a deviation is detected, the measured value of the HC sensor or the fuel mass flow determined therefrom is corrected, or the HC sensor is determined or assessed as defective.It is provided that a correction of the measured value of the HC sensor or the fuel mass flow determined therefrom is carried out if the deviation is below a threshold value or corresponds to this threshold value, and the HC sensor is determined to be defective if the deviation is above a (different) or the (same) threshold value.

[0019] An internal combustion engine according to the invention comprises on the one hand at least a preferably spark-ignited and quantity-controlled internal combustion engine with at least one combustion chamber and preferably with a plurality of combustion chambers, a fresh gas line for supplying fresh gas to the internal combustion engine, an exhaust line for discharging exhaust gas from the internal combustion engine, wherein an exhaust gas sensor is integrated into the exhaust line, and a fuel tank system comprising at least one fuel tank, a fuel vapor filter which is in fluid communication with an ambient opening, a vent line leading from the fuel tank to the fuel vapor filter, a purge gas line leading from the fuel vapor filter to the fresh gas line, into which an HC sensor on the one hand and a tank vent valve and / or a purge gas conveying device on the other hand are integrated.

[0020] Furthermore, an internal combustion engine according to the invention has a control device which is designed for the automated implementation of a method according to the invention.

[0021] According to the invention, the term "fuel vapor filter" does not necessarily imply that the volatile fuel must be filtered in gaseous form. Rather, the fuel may already have (partially) condensed during the filtering process.

[0022] Determining the mass flow of the purge gas within the scope of a method according to the invention can, on the one hand, be achieved (exclusively) by one or more measurements. An internal combustion engine according to the invention can then comprise one or more corresponding sensors. Furthermore, such a determination can also be carried out by modeling, i.e., by a computational determination based on (possibly measured) operating parameters of individual or multiple components of the internal combustion engine, for example, based on the opening position of the tank venting valve and / or the drive power of the purge gas delivery device.

[0023] The invention is based on the finding that an exhaust gas sensor integrated into the exhaust system can advantageously be used to determine measurement deviations of the HC sensor and / or to check the functionality of the HC sensor. It is particularly advantageous that such an exhaust gas sensor, typically at least in the form of a lambda sensor, is usually provided in an internal combustion engine anyway, so that essentially no additional structural components of the internal combustion engine are required to carry out a method according to the invention.

[0024] In principle, it is possible that the exhaust gas sensor also provides inaccurate measured values, or that deviations in the combustion air ratio from the target value, which were determined based on an exhaust gas composition determined by the exhaust gas sensor, can be attributed to other "error sources" in the operation of the internal combustion engine. To prevent this from having a negative impact on the functional test according to the invention, i.e., on the possible correction of the measured value of the HC sensor or the fuel mass flow determined therefrom, or on the possible determination of the HC sensor as defective, it can preferably be provided that a calibration of the measured value of the exhaust gas sensor is carried out during operation of the internal combustion engine with deactivated purging of the fuel tank system, i.e., when no purge gas is conducted via the purge gas line.Consequently, if no purge gas is fed via the purge gas line due to deactivated purge of the fuel tank system, the measured value of the exhaust gas sensor can be calibrated and, if necessary, adjusted in such a way that, with fuel introduced into the combustion chamber(s) exclusively via the fuel injector(s) and which can be determined with sufficient accuracy - and with oxygen also supplied to the combustion chamber and which can be determined with sufficient accuracy - the resulting combustion air ratio corresponds to a defined, associated exhaust gas composition. Due to such a calibration of the measured value of the exhaust gas sensor, it can then be assumed with sufficient certainty that with purge gas fed via the purge gas line, i.e.When flushing the fuel tank system, a deviation of the combustion air ratio from the corresponding target value determined based on the measured value of the exhaust gas sensor results in a measurement error of the HC sensor and thus in a consequent, incorrect adjustment of fuel introduced into the combustion chamber and / or into the fresh gas line by means of the fuel injector.

[0025] Depending on how the purge gas mass flow is determined, this conclusion may also require that the measured value of a sensor used to determine the purge gas mass flow be calibrated during engine operation with the fuel tank system purge deactivated. This may be the case, for example, if a pressure sensor integrated into the purge gas line is used to determine the purge gas mass flow. This measured value can then be verified during engine operation with the purge deactivated, for example, by comparing it with the ambient pressure, and calibrated if necessary.

[0026] If, on the other hand, the mass flow of the purge gas is determined during active purging of the fuel tank system, for example, by integrating at least two sensors into the fresh gas line, by means of which the mass flow of the fresh gas in the fresh gas line can be determined upstream and downstream of the outlet of the purge gas line, their potential influence on a deviation of the measured value of the exhaust gas sensor during active purging can be excluded by taking their measured values ​​into account when calibrating the measured value of the exhaust gas sensor when purging is deactivated.

[0027] The purge gas conducted through the purge gas line during purge of the fuel tank system can, in particular, be a mixture of gaseous fuel or gaseous hydrocarbons and ambient air, as is the case when the fuel vapor filter is regenerated by backflushing using ambient air. However, the purge gas can also consist (essentially) exclusively of gaseous fuel or gaseous hydrocarbons, for example, when fuel vapors present in the fuel tank are "vented" directly into the fresh gas line rather than into the environment.

[0028] An internal combustion engine according to the invention can, in particular, be part of a motor vehicle. The internal combustion engine of the internal combustion engine can, in particular, be provided for directly or indirectly providing the drive power for the motor vehicle. The invention therefore further relates to a motor vehicle, in particular a wheel-based and non-rail-bound motor vehicle (preferably a car or a truck), with an internal combustion engine according to the invention.

[0029] The invention will be explained in more detail below with reference to an embodiment shown in the drawings. Fig. 1 shows a schematic representation of an internal combustion engine according to the invention.

[0030] The Fig. 1shows an internal combustion engine according to the invention for a motor vehicle with a fuel tank system. This comprises a fuel tank 1, which is connected via a vent line 2 to a fuel vapor filter 3, which may in particular be designed in the form of an activated carbon filter or at least comprise such a filter. The fuel vapor filter 3 is further connected via a purge gas line 4 to a fresh gas line 5 of the internal combustion engine, wherein the purge gas line 4 opens into the fresh gas line 5 upstream (with respect to the flow direction of fresh gas in the fresh gas line 5 in the direction of an internal combustion engine 6 of the internal combustion engine) of a fresh gas compressor 7 integrated into the fresh gas line 5. The fresh gas compressor 7 is part of an exhaust gas turbocharger, which further comprises an exhaust gas turbine 8 integrated into an exhaust line 9 of the internal combustion engine.In the charge air section of the fresh gas line 5 located between the fresh gas compressor 7 and the combustion engine 6, a throttle valve 10 is also provided, which divides the charge air section into an upstream section, often referred to as a pressure pipe, and a downstream section, often referred to as an intake pipe.

[0031] During operation of the internal combustion engine, mixtures are combusted in a known manner in a defined sequence in combustion chambers 11 of the internal combustion engine 6, which are partially bounded by cylinders 12 of the internal combustion engine 6. These mixtures consist of fresh gas, which consists entirely or primarily of ambient air and has been drawn in from the environment via an air filter 13, and entirely or primarily of fuel injected, for example, directly into the combustion chambers 11 by means of fuel injectors 14. The pressure increases in the combustion chambers 11 generated by the combustion processes are used to move pistons 15 guided in the cylinders 12.These movements of the pistons 15 are converted into a rotary movement of a crankshaft (not shown) with the interposition of connecting rods (not shown), whereby the guidance of the pistons 15 via the connecting rods by means of the crankshaft simultaneously leads to a cyclical back and forth movement of the pistons 15. The exhaust gas produced during the combustion of the fresh gas-fuel mixture in the combustion chambers 11 is discharged via the exhaust line 9 and flows through the exhaust turbine 8, which leads to a rotating drive of a turbine impeller (not shown). This rotation of the turbine impeller is transmitted by means of a shaft 16 to a compressor impeller (not shown) of the fresh gas compressor 7, whereby the fresh gas compressor 7 ensures compression of the fresh gas to be supplied to the combustion engine 6 via the fresh gas line 5.

[0032] The fuel vapor filter 3 of the fuel tank system is connected to the environment via an ambient air line 17 with its side facing away from the vent line 2 and the purge gas line 4 (in relation to its filtering effect for fuel vapors), for which purpose the ambient air line 17 forms an ambient opening 18.

[0033] The fuel tank 1 is partially filled with fuel, whereby a portion of this fuel, which is actually liquid under normal ambient conditions, has generally evaporated, so that fuel in a gaseous state is also present in the fuel tank 1. Such evaporation of fuel in the fuel tank 1 is particularly favored by relatively high ambient temperatures and by a reduction in the ambient pressure, for example as a result of a motor vehicle incorporating the internal combustion engine driving uphill. In order to avoid an impermissibly high overpressure in the fuel tank 1 caused by such evaporation, the possibility of pressure equalization with the ambient pressure is provided via the vent line 2 and the fuel vapor filter 3 as well as via the ambient air line 17, whereby the fuel vapor filter 3 prevents such pressure equalization from leading to the escape of fuel vapors into the environment.

[0034] Such venting of the fuel tank 1 leads to increasing saturation of the fuel vapor filter 3, which in turn requires it to be regenerated at regular intervals. For this purpose, the fuel vapor filter 3 is purged by drawing in ambient air via the ambient opening 18 and the ambient air line 17. This ambient air flows through the fuel vapor filter 3 in the opposite direction to the flow of the vaporous fuel through the fuel vapor filter 3 during venting of the fuel tank 1, whereby fuel molecules absorbed in the fuel vapor filter 1 are entrained by the ambient air and introduced into the fresh gas line 5 via the purge gas line 4. This fuel is thus fed for combustion in the combustion chambers 11 of the internal combustion engine 6.

[0035] Such purging of the fuel vapor filter 3 is only provided temporarily and always during operation of the internal combustion engine 6, because only then can the fuel introduced into the fresh gas line 5 by purging the fuel vapor filter 3 be reliably supplied for combustion in the combustion chambers 11. Introducing it into the fresh gas line 5 when the internal combustion engine 6 is not in operation, however, could result in the gaseous fuel escaping into the environment via leaks in the fresh gas line 5 and, in particular, via an intake opening of the fresh gas line 5.

[0036] A tank vent valve 20 is integrated into the purge gas line 4, which is arranged as close as possible to the opening 19 of the purge gas line 4 into the fresh gas line 5 or is integrated into it.

[0037] Flushing the fuel vapor filter 3 requires a sufficient pressure gradient between, on the one hand, the ambient pressure and, on the other hand, the pressure in the fresh gas line 5 in the region of the opening 19 of the purge gas line 4. This pressure gradient may not always be present due to strongly fluctuating pressures in the fresh gas line 5 during operation of the internal combustion engine 6. To enable purging of the fuel vapor filter 3 at any time, so that complete saturation of the same can be reliably prevented, the fuel tank system of the internal combustion engine also includes a purge gas delivery device 21 integrated into the purge gas line 4. This device is commonly also referred to as a "purge air pump" and can be designed, for example, in the form of a piston compressor, in particular a vane-type compressor, or a radial fan.By operating this purge gas conveying device 21, ambient air can be actively sucked in via the ambient orifice 18, which then flows through the fuel vapor filter 9 to purge it and which can be conveyed via the purge gas conveying device 21 and the then at least partially opened tank vent valve 20 to the orifice 19 of the purge gas line 4.

[0038] At least the purge gas delivery device 21, the tank venting valve 20, the throttle valve 10, and the fuel injectors 14 can be controlled by a control device 22 (e.g., in the form of a central engine control unit of the internal combustion engine). At the same time, the control device 22 receives measurement signals from an HC sensor 23 integrated into the purge gas line 4 in a section between the purge gas delivery device 21 and the tank venting valve 20, an exhaust gas sensor 25 integrated into the exhaust system 9 downstream of the exhaust turbine 8, a mass flow sensor 24 integrated into the fresh gas system 5 upstream of the outlet 19 of the purge gas line 4, and a pressure sensor 26 integrated into the fresh gas system 5 downstream of the outlet 19.

[0039] Exhaust gas produced during the combustion of the fuel-fresh gas mixture in the combustion chambers 11 of the internal combustion engine 6 flows around the exhaust gas sensor 25 integrated into the exhaust system 9, which then generates a measurement signal that, for example, indicates the proportion of residual oxygen in the exhaust gas. This measurement signal is transmitted to the control device 22.

[0040] When the fuel tank system is purged, the mass flow of fuel or hydrocarbons introduced from the purge gas line 4 into the fresh gas line 5 is determined. For this purpose, the mass flow of the purge gas flowing in the purge gas line 4 is determined by comparing the mass flows of the fresh gas flowing through the fresh gas line 5, which are determined by means of the mass flow sensor 24 arranged upstream of the opening 19 of the purge gas line 4 and by means of the pressure sensor 26 arranged downstream of the opening 19. The content or concentration of hydrocarbons in this purge gas is measured by means of the HC sensor 23.

[0041] To compensate for this additional mass of fuel, which enters the combustion chambers 11 as part of the purge gas and thus also of the fresh gas, the individual quantities of fuel introduced into the combustion chambers 11 by means of the fuel injectors 14 are adjusted accordingly in order to maintain a defined, in particular stoichiometric, combustion air ratio, taking into account the specific operating state of the internal combustion engine 6 and the fresh gas masses supplied to the combustion chambers 11. Whether this combustion air ratio has actually been maintained is monitored by the exhaust gas sensor 25.If the determined combustion air ratio, which was derived from an exhaust gas composition determined by the exhaust gas sensor 25, deviates from a corresponding target value, provided the deviation is below or corresponds to a threshold value, a corresponding correction of the measured value of the HC sensor 23 or the fuel mass flow determined from this measured value is carried out such that the determined combustion air ratio corresponds to the target value. If, however, this deviation is above the threshold value, the HC sensor 23 is determined to be defective. This can lead to a corresponding error message, which can be stored in the control device and, if necessary, also displayed on the instrument panel of a motor vehicle.

[0042] If, however, the fuel vapor filter 3 or the entire fuel tank system is not flushed, no purge gas is conducted via the purge gas line 4 and thus is not introduced into the fresh gas line 5. The fuel quantities required for the intended operation of the internal combustion engine 6 are then supplied to the combustion chambers 11 exclusively by means of the fuel injectors 14. These fuel quantities can be determined with sufficient accuracy, for example, from the pressure of the fuel supplied to the fuel injectors 14 and from the duration of the activation of the fuel injectors 14 by the control device 22 and thus the respective opening duration of the fuel injectors 14.

[0043] The fresh gas mass flow simultaneously supplied to the combustion chambers 11 can also be determined with sufficient accuracy by means of the mass flow sensor 14 and / or the pressure sensor 16, whereby these two sensors should then deliver identical or comparable values. Accordingly, during operation of the internal combustion engine with the purging of the fuel tank system deactivated, the combustion air ratio of the fuel-fresh gas mixture quantities supplied to the combustion chambers 11 can be set relatively precisely. Therefore, if during such operation of the internal combustion engine with the purging of the fuel tank system deactivated, deviations occur in the exhaust gas composition determined by the exhaust gas sensor 25 from one that should actually correspond to the set combustion air ratio, purging of the fuel tank system can be ruled out as the cause of this deviation because such purging is not performed.This makes it possible to adapt or calibrate the measured value of the exhaust gas sensor 25 accordingly by generating an adaptation value, so that this calibrated measured value corresponds to an exhaust gas composition that matches the set combustion air ratio. By calibrating the measured value of the exhaust gas sensor in this way, it can then be ensured that, during a subsequent purging of the fuel tank system, deviations in the combustion air ratio of the fuel / fresh gas mixture quantities supplied to the combustion chambers 11 from a corresponding target value, which were determined using the exhaust gas composition measured by the exhaust gas sensor 25, can be attributed to measurement errors of the HC sensor 23.This is because errors in the determination of the fuel quantities introduced via the fuel injectors 14, in the determination of the mass flows of the fresh gas conducted via the fresh gas line and in the determination of the mass flow of the purge gas conducted via the purge gas line 4 and introduced into the fresh gas line were adapted during calibration during operation of the internal combustion engine with the purge of the fuel tank system deactivated. List of reference symbols

[0044] 1Fuel tank 2Vent line 3Fuel vapor filter 4Purge gas line 5Fresh gas line 6Combustion engine 7Fresh gas compressor 8Exhaust turbine 9Exhaust line 10Throttle valve 11Combustion chamber 12Cylinder 13Air filter 14Fuel injector 15Piston 16Shaft 17Ambient air line 18Ambient outlet 19Purge gas line outlet 20Tank vent valve 21Purge gas delivery device 22Control device 23HC sensor 24Mass flow sensor 25Exhaust gas sensor 26Pressure sensor

Claims

1. Method for operating an internal combustion engine comprising - a combustion unit (6) having at least one combustion chamber (11), - a fresh gas system (5), - an exhaust gas system (9) having an exhaust gas sensor (25) integrated therein, and - a fuel tank system, wherein the fuel tank system has - a fuel tank (1), - a fuel vapor filter (3) which is connected to a surroundings opening (18) in a fluid-conducting manner, - a vent line (2) leading from the fuel tank (1) to the fuel vapor filter (3), and - a purge gas line (4) leading from the fuel vapor filter (3) to the fresh gas system (5), in which - a HC sensor (23) and - a tank vent valve (20) and / or a purge gas conveying device (21) are integrated, wherein during operation of the internal combustion engine, when purge gas is conducted via the purge gas line (4), - the hydrocarbon content of the purge gas is determined by means of the HC sensor (23), as well as the mass flow of the purge gas, and, from these values in combination, a fuel mass flow which is introduced into the fresh gas system is determined, and - an amount of fuel introduced into the combustion chamber (11) and / or into the fresh gas system (5) by means of at least one fuel injector is adjusted, wherein the air-fuel equivalence ratio of fuel-fresh gas mixture amounts which are supplied to the combustion chamber is monitored, with respect to a deviation from a target value, from an exhaust gas composition determined by means of the exhaust gas sensor (25), characterized in that when such a deviation is determined, a correction of the measured value of the HC sensor (23) or the fuel mass flow determined therefrom is carried out, or the HC sensor (23) is determined to be defective, wherein a correction of the measurement signal from the HC sensor (23) or of the fuel mass flow determined therefrom is carried out if the deviation is below a threshold value or corresponds to this threshold value, and the HC sensor (23) is determined to be defective if the deviation is above a or the threshold value.

2. Method according to claim 1, characterized in that, during operation of the internal combustion engine, when the purging of the fuel tank system is deactivated, a calibration of the measured value of the exhaust gas sensor (25) is carried out.

3. Method according to either of the preceding claims, characterized in that, during operation of the internal combustion engine, when the purging of the fuel tank system is deactivated, a calibration of the measured value of a sensor that is used to determine the mass flow of the purge gas is carried out.

4. Method according to any of the preceding claims, characterized in that the mass flow of the purge gas is measured or modeled.

5. Internal combustion engine comprising - a combustion unit (6) having at least one combustion chamber (11), - a fresh gas system (5), - an exhaust gas system (9) having an exhaust gas sensor (25) integrated therein, - a fuel tank system which has - a fuel tank (1), - a fuel vapor filter (3) which is connected to a surroundings opening (18) in a fluid-conducting manner, - a vent line (2) leading from the fuel tank (1) to the fuel vapor filter (3), - a purge gas line (4) leading from the fuel vapor filter (3) to the fresh gas system (5), in which - a HC sensor (23) and - a tank vent valve (20) and / or a purge gas conveying device (21) - are integrated, and comprising - a control device (22), characterized in that the control device (22) is designed to carry out a method according to any of the preceding claims in an automated manner.

6. Internal combustion engine according to claim 5, characterized by a sensor (24; 26) for determining the mass flow of the purge gas.

7. Motor vehicle comprising an internal combustion engine according to either of claims 5 or 6.