Method of monitoring regeneration of particulate filter in exhaust system of internal combustion engine

Abstract

The invention relates to a method of monitoring regeneration of a particulate filter in an exhaust system of an internal combustion engine having a combustion chamber at which a spark plug is located and comprising a fuel injection valve, the method comprising the steps of: defining different soot loading stages for the particulate filter; determining a soot load of the particulate filter by using the soot load model; determining a soot loading of the particulate filter via a differential pressure measurement on the particulate filter; initiating regeneration of the particulate filter when a certain soot loading stage of the particulate filter determined via the differential pressure measurement is reached; soot emissions from the particulate filter expected via the soot load model are compared to soot emissions from the particulate filter determined via the differential pressure measurement, and an error message is output when a regeneration stage of the particulate filter determined by the soot load model is not correlated to a regeneration stage determined via the differential pressure measurement.

Description

Technical Field

[0001] The invention relates to a method for monitoring the regeneration of a particle filter in an exhaust system of a spark-ignition internal combustion engine for excessively frequent regeneration operations, a control unit for controlling the regeneration of the particle filter, and an internal combustion engine having an exhaust system and a control unit for carrying out such a method. Background Art

[0002] Increasingly stringent exhaust emission regulations place high demands on automakers, which must be met through appropriate measures to reduce uncontrolled engine emissions and suitable exhaust aftertreatment. EU6 legislation stipulates particle count limit values ​​for gasoline engines, which in many cases necessitates the use of gasoline particulate filters. Such soot particles are particularly generated after a cold start of an internal combustion engine due to incomplete combustion, combined with a superstoichiometric combustion air ratio, cold cylinder walls, and uneven mixture distribution in the combustion chamber of the internal combustion engine. In contrast to the loading of diesel particulate filters, the soot loading of gasoline particulate filters is largely dependent on the combustion chamber temperature and decreases with increasing combustion chamber temperature. Therefore, the cold start phase plays a crucial role in complying with the prescribed particle limits for both particle mass and particle count. At cold outside temperatures, particularly below 0°C, particulate emissions in gasoline engines are particularly high due to low mixture homogenization, fuel evaporation, and starting enrichment. Furthermore, cold starts with a substoichiometrically rich combustion air ratio result in higher emissions of carbon monoxide (CO) and unburned hydrocarbons (HC), as conversion to carbon dioxide and water vapor is not yet possible due to the cold catalytic converter. During driving, in motor vehicles equipped with a gasoline particulate filter, the filter subsequently becomes further loaded with soot. Such filters must be continuously or periodically regenerated to prevent excessive exhaust backpressure. Increased exhaust backpressure can lead to increased fuel consumption, power loss, impaired running smoothness, and even misfires in the internal combustion engine. Thermal oxidation of soot retained in the gasoline particulate filter with oxygen requires a sufficiently high temperature level and the simultaneous presence of oxygen in the gasoline engine's exhaust system. Since current gasoline engines typically operate at a stoichiometric combustion air ratio (λ=1) without excess oxygen, additional measures are necessary. Examples of such measures include increasing the temperature by adjusting the ignition angle, temporarily adjusting the gasoline engine to lean burn conditions, injecting secondary air into the exhaust system, or a combination of these measures. Until now, adjusting the ignition angle in the retarded direction in conjunction with adjusting the gasoline engine towards lean combustion has been preferred, as this approach requires no additional components and is able to deliver a sufficient amount of oxygen at most operating points of the gasoline engine. Furthermore, with the introduction of new, stricter exhaust emission standards, it may become necessary to continuously monitor the correct function of the exhaust aftertreatment components within the scope of on-board monitoring using appropriate sensors in the exhaust system.

[0003] DE 10 2013 217 622 A1 discloses a motor vehicle comprising an internal combustion engine, an exhaust system having a particulate filter for retaining soot particles from the exhaust flow of the internal combustion engine, a sensor, and a controller. The sensor measures the instantaneous differential pressure across the particulate filter. The controller executes a process for selectively enabling or disabling the performance of an efficiency diagnostic for the particulate filter based on a learned differential pressure offset value. The controller also compares the differential pressure with a calibrated threshold value and executes a control action when the differential pressure is within a permissible range of the threshold value.

[0004] DE 10 20 20 10 3 894 A1 describes a method for monitoring the regeneration of a particle filter in the exhaust system of a gasoline engine. The method comprises the following steps:

[0005] a) determining in which regeneration stage of a defined number of regeneration stages the particle filter is regenerated or regenerated last;

[0006] b) detecting a measure for at least one first test criterion characterizing a change in the loading of the particulate filter,

[0007] c) Checking whether a first test criterion is met, and changing to a higher regeneration level if the first test criterion is not met, and changing to a lower regeneration level or maintaining the current regeneration level if the first test criterion is met.

[0008] DE 10 2011 077 097 A1 discloses a method for diagnosing a particulate filter in an exhaust gas duct of an internal combustion engine. A particle sensor is used to predict a particulate filter load, determined as the soot loading of the particulate filter, based on differential pressure measurements and / or a soot loading model. Based on the diagnostic result, a regeneration operation of the particulate filter is initiated. The method provides for verifying the diagnostic result regarding the function of the particulate filter as a function of the particulate filter load and the exhaust gas volume flow or the gradient of the exhaust gas volume flow in the exhaust gas duct. Based on this verification, the particulate filter is classified as functional or defective, or the diagnostic result for the particulate filter is classified as unusable. Summary of the Invention

[0009] The object underlying the present invention is to monitor the regeneration of a particle filter in an exhaust system of an internal combustion engine and, in particular, to avoid frequent regeneration cycles which are associated with an increase in uncontrolled emissions of the internal combustion engine and / or an increase in tailpipe emissions of the internal combustion engine.

[0010] This object is achieved by a method for monitoring the regeneration of a particle filter in an exhaust system of an internal combustion engine. The internal combustion engine has at least one combustion chamber, preferably a plurality of combustion chambers, wherein a fuel injector for injecting fuel into the combustion chamber and / or a fuel injection valve for injecting fuel into an intake tract of the internal combustion engine is located at each combustion chamber, and a spark plug for igniting a combustible fuel-air mixture is located at the combustion chamber. The method comprises the following steps:

[0011] - defining different soot loading levels for the particulate filter,

[0012] - determining the soot loading of the particulate filter by using a soot loading model and assigning the determined soot loading to one of the defined soot loading classes,

[0013] - determining the soot loading of the particulate filter via a pressure difference measurement across the particulate filter and assigning the determined soot loading to one of the defined soot loading classes,

[0014] - initiating regeneration of the particle filter when a certain soot loading level of the particle filter is reached, determined via differential pressure measurement,

[0015] - comparing the level determined via the soot loading model with the soot loading level determined via the pressure difference, wherein

[0016] If the regeneration level of the particle filter determined by the soot loading model does not correlate with the regeneration level determined via the differential pressure measurement, an error message is output.

[0017] The method according to the invention makes it possible to monitor the regeneration of the particulate filter and, in particular, to monitor excessively frequent regeneration of the particulate filter and / or excessively high, uncontrolled particulate emissions of the internal combustion engine leading to frequent regeneration operations of the particulate filter, which lead to an increase in tailpipe emissions due to engine-internal measures that initiate or accompany the regeneration.

[0018] By using the features stated in the technical solution of the invention, advantageous improvements and enhancements of the method stated in the invention for monitoring a particulate filter in an exhaust system of an internal combustion engine are possible.

[0019] In a preferred embodiment of the present invention, when regeneration is initiated and performed due to exceeding a pressure differential threshold, a check is performed to determine, for a soot loading level associated with the threshold, whether the soot loading level determined using a soot loading model correlates with a decrease in the load level determined via the pressure differential measurement. The maximum achievable regeneration level of the soot loading model is preferably the same for the entire regeneration operation. If there is a sufficient correlation between the soot loading level determined via the pressure differential measurement and the soot loading level determined by the soot loading model, it can be assumed that the regeneration of the particulate filter triggered by the pressure differential sensor is justified. If this is not the case, it can be assumed that the internal combustion engine is emitting more soot than expected, or more soot than it should be emitting during normal operation. Thus, the particulate filter can be monitored for excessively frequent regenerations.

[0020] In another preferred embodiment of the present invention, an error is detected when an increase in the soot loading level of the particulate filter measured via the differential pressure measurement does not correlate with an increase in the soot loading level determined via the soot loading model. When the internal combustion engine is operating normally, the increase in the differential pressure determined via the differential pressure measurement and the soot loading level of the particulate filter should correlate with an increase in the soot loading level of the particulate filter determined via the soot loading model. If this is not the case, particularly if the increase in the soot loading level determined via the differential pressure measurement occurs much faster than the soot loading level determined via the soot loading model, it is assumed that the internal combustion engine is emitting more soot particles than would be expected during normal operation, and therefore more frequent regeneration of the particulate filter is necessary. Such errors can be detected in an operationally reliable manner by the method in order to prevent further damage to the particulate filter and / or avoid an unacceptable increase in emissions.

[0021] In an advantageous embodiment of the method, provision is made for assigning a pressure differential range of the pressure differential measured at the particle filter to each soot loading level in the soot loading model. This makes it possible to assign the soot loading levels of the soot loading model to the soot loading of the particle filter measured via the pressure differential particularly simple.

[0022] In another preferred embodiment of the method, a soot loading profile is provided that includes at least three soot loading stages, wherein no regeneration of the particulate filter is required in the first stage, a simple regeneration of the particulate filter occurs in the second stage, and a controlled regeneration of the particulate filter occurs in the third soot loading stage. Using such a hierarchical profile, excessively frequent regeneration of the particulate filter can be avoided, since forced regeneration of the particulate filter using internal engine measures only occurs when the particulate filter load has reached a certain soot loading stage.

[0023] In an advantageous development of the method, the soot load model includes a further soot load level at which regeneration during driving operation is no longer permitted and the driver is prompted to have the particle filter checked at a workshop. If the particle filter reaches a critical soot load level at which there is a risk of uncontrolled soot burnout and / or heat input into the particle filter during regeneration, which would lead to permanent thermal damage to the particle filter, the driver is prompted to take the motor vehicle to a workshop and perform an external regeneration of the particle filter in order to avoid permanent damage to the particle filter.

[0024] In another enhancement of the method, the soot loading model includes additional soot loading levels at which particulate filter replacement is necessary. If the particulate filter load exceeds the load described in the preceding section and / or if initiation of a regeneration operation no longer results in a reduction in the differential pressure, the particulate filter must be replaced. This situation can be identified using the described method, prompting the driver to visit a repair shop to replace the particulate filter in order to avoid increased tailpipe emissions, in particular increased particulate emissions, and / or damage to the internal combustion engine, in particular due to excessive exhaust gas backpressure.

[0025] According to another advantageous embodiment of the method, provision is made for information to be output to the driver during regeneration, starting at a certain soot loading level of the particulate filter. In this process, regeneration occurs at lower regeneration levels that are not noticeable to the driver. Regeneration at higher regeneration levels, which typically last longer and are noticeable to the driver due to the activation of internal engine measures, is indicated by a warning message, allowing the driver to associate the internal engine measures with regeneration of the particulate filter. This prevents, in particular, the driver from inadvertently shutting down the internal combustion engine during a regeneration operation and thus performing an incomplete regeneration of the particulate filter.

[0026] In a preferred embodiment of the method, engine-internal measures for initiating regeneration and / or assisting regeneration of the particulate filter are initiated upon reaching a certain soot loading level. When the vehicle is routinely driven at high partial or full load, such as when traveling on a highway, normal operation of the internal combustion engine may be sufficient to provide operating conditions for the particulate filter, under which regeneration of the particulate filter occurs by oxidizing soot particles retained in the particulate filter. However, if the particulate filter reaches a higher load level and operating conditions, particularly the regeneration temperature of the particulate filter, are not reached during driving, regeneration can be initiated by increasing the exhaust gas temperature via engine-internal measures. In this way, regeneration of the particulate filter can be initiated while preventing the soot loading of the particulate filter from exceeding a critical level.

[0027] Another sub-aspect of the present invention relates to a control unit for executing the method described in the preceding section, the control unit comprising a memory unit and a processing unit, as well as computer program code stored in the memory unit, and the method being executed when the computer program code is executed by the processing unit. Such a control unit allows an internal combustion engine and an exhaust gas aftertreatment system of the internal combustion engine to be controlled in such a manner that the method according to the present invention for monitoring and regenerating a particulate filter in an exhaust gas system of an internal combustion engine can be executed.

[0028] Another sub-aspect of the present invention relates to an internal combustion engine comprising at least one combustion chamber, a fuel injector for injecting fuel into the combustion chamber, and a spark plug located in the combustion chamber for igniting the combustible fuel-air mixture. The internal combustion engine is connected at its outlet to an exhaust system in which a particulate filter is located. The internal combustion engine is also connected to the control unit described in the preceding section. In such an internal combustion engine, emissions can be reduced during regeneration of the particulate filter because unnecessary regeneration measures that would otherwise increase emissions can be omitted.

[0029] In one advantageous embodiment of the internal combustion engine, a three-way catalytic converter is provided as the first exhaust gas aftertreatment component, located in the exhaust gas system in the direction of flow of the exhaust gas flow of the internal combustion engine through the exhaust gas system, and the particulate filter is located downstream of the three-way catalytic converter. This allows for particularly advantageous exhaust gas aftertreatment, as the three-way catalytic converter quickly reaches operating temperature after a cold start due to its location near the engine, thus enabling efficient conversion of limited pollutants in the exhaust gas flow of the internal combustion engine immediately after a cold start of the internal combustion engine. Furthermore, this arrangement allows the particulate filter to be located near the engine as well, thereby simplifying its heating for initiating regeneration. In this context, a location near the engine is understood to mean a location of the inlet of the exhaust gas aftertreatment component with an exhaust gas extension of less than 80 cm, preferably less than 60 cm, from the outlet of the internal combustion engine.

[0030] It is particularly advantageous to have an additional three-way catalytic converter located downstream of the particulate filter. This allows the catalytic converter volume for the three-way catalytic converter to be distributed across two units. Consequently, the first three-way catalytic converter, located near the engine, can be designed with a smaller volume and thus reach its light-off temperature more quickly. Furthermore, secondary emissions generated during soot oxidation during regeneration of the particulate filter can be converted by the second three-way catalytic converter, resulting in little or no increase in tailpipe emissions.

[0031] Alternatively, the particulate filter and the additional three-way catalytic converter can be designed so that they are combined in a single component as a so-called four-way catalytic converter. To this end, the particulate filter has a catalytically active coating, which is preferably applied to the filter structure of the particulate filter as a washcoat, and which can oxidize a limited number of pollutants, such as unburned hydrocarbons and carbon monoxide, and can reduce nitrogen oxides.

[0032] In one advantageous embodiment, the internal combustion engine is designed as a spark-ignition internal combustion engine according to the Otto principle, which is supercharged using an exhaust gas turbocharger. Supercharging the internal combustion engine can improve the filling of the combustion chamber of the internal combustion engine. This measure, particularly in combination with fuel injectors capable of delivering injection pressures in the range of up to 350 bar, can lead to a reduction in uncontrolled particulate emissions and, therefore, a reduction in the frequency with which the particulate filter must be regenerated.

[0033] Unless stated otherwise in individual cases, the various embodiments of the invention mentioned in this patent application can be advantageously combined with one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention is explained below in exemplary embodiments with reference to the associated drawings, which show the following:

[0035] Figure 1 A preferred exemplary embodiment of an internal combustion engine with an exhaust system and a control unit for carrying out the method according to the invention for monitoring a particle filter in an exhaust system of an internal combustion engine is shown.

[0036] Figure 2 shows a further preferred exemplary embodiment of an internal combustion engine for carrying out the method according to the invention for monitoring a particle filter in an exhaust system of an internal combustion engine,

[0037] Figure 3 shows a flow chart for carrying out the method according to the invention for monitoring a particle filter in an exhaust system of an internal combustion engine,

[0038] Figure 4 shows a load level model for a particulate filter,

[0039] Figure 5 shows a regeneration map for regenerating a particulate filter during normal regeneration of the particulate filter, and

[0040] Figure 6 A regeneration map is shown for regenerating a particulate filter during overly frequent regeneration of the particulate filter due to increased particulate emissions from an internal combustion engine. DETAILED DESCRIPTION

[0041] Figure 1 A schematic diagram of an internal combustion engine 10 is shown. Internal combustion engine 10 is designed as a direct-injection gasoline engine. Internal combustion engine 10 has multiple combustion chambers 12. Located in each combustion chamber 12 is a fuel injector having a fuel injection valve 14 for injecting fuel 58 into a particular combustion chamber 12, and a spark plug 16 for igniting the fuel-air mixture in that particular combustion chamber 12. Combustion chamber 12 is bounded by an axially displaceable piston 18. The piston's oscillating motion is converted into rotational motion of the engine's crankshaft 28 via a connecting rod 27. Internal combustion engine 10 is connected to an air supply system (not shown) via its inlet 20 and to an exhaust system 30 via its outlet 22. Located in each combustion chamber 12 are an intake valve 24 and an exhaust valve 26, which can open or close the fluid connection from the air supply system to the combustion chamber 12, or from the combustion chamber 12 to the exhaust system 30. Alternatively or additionally, internal combustion engine 10 may have one or more fuel injection valves 14 located in an intake passage of internal combustion engine 10 .

[0042] The exhaust system 30 includes an exhaust gas conduit 32. Located in the exhaust gas conduit 32 are a three-way catalytic converter 38 located near the engine as a first exhaust gas aftertreatment component, a particulate filter 40 located downstream of the three-way catalytic converter, and a further downstream second three-way catalytic converter 42 located in the direction of flow of the exhaust gas from the internal combustion engine 10. The second three-way catalytic converter 42 is preferably located under the vehicle. Furthermore, the turbine 36 of the exhaust gas turbocharger 34 may be located in the exhaust gas system 30. A first lambda sensor 44, specifically a broadband sensor, for detecting the oxygen concentration in the exhaust gas flow is located in the exhaust gas system downstream of the outlet 22 of the internal combustion engine 10 and upstream of the first three-way catalytic converter 38. A second lambda sensor 46, specifically a skip sensor, is located downstream of the first three-way catalytic converter 38 and upstream of the second three-way catalytic converter 42, specifically downstream of the first three-way catalytic converter 38 and upstream of the particulate filter 40. Furthermore, located in the exhaust system 30 is a first temperature sensor 50 downstream of the first three-way catalytic converter 38 and upstream of the particulate filter 40, as well as a second temperature sensor 52 downstream of the particulate filter 40 and upstream of the second three-way catalytic converter 42. A differential pressure sensor 48, which determines the pressure difference between the inlet of the particulate filter 40 and the outlet from the particulate filter 40, is located at the particulate filter 40. The pressure difference across the particulate filter 40 is correlated with the particulate load of the particulate filter 40; when a defined threshold of the pressure difference is reached, regeneration of the particulate filter 40 is initiated in order to avoid further loading of the particulate filter 40 and associated potential damage.

[0043] The internal combustion engine 10 is connected to a control unit 60 comprising a memory unit 62 and a processing unit 64. Computer program code 66 is stored in the memory unit 62 and performs the method according to the invention when the computer program code is executed by the processing unit of the control unit.

[0044] Figure 2 The figure shows another preferred exemplary embodiment of an internal combustion engine 10. Internal combustion engine 10 is designed as a direct-injection gasoline engine. Internal combustion engine 10 has multiple combustion chambers 12. Located in each combustion chamber 12 is a fuel injector having a fuel injection valve 14 for injecting fuel 58 into a particular combustion chamber 12, and a spark plug 16 for igniting the fuel-air mixture in that particular chamber 12. Combustion chamber 12 is bounded by an axially displaceable piston 18. The piston's oscillating motion is converted into rotational motion of the engine's crankshaft 28 via a connecting rod 27. Internal combustion engine 10 is connected to an air supply system (not shown) via its inlet 20 and to an exhaust system 30 via its outlet 22. Located in each combustion chamber 12 are an intake valve 24 and an exhaust valve 26, which can open or close the fluid connection from the air supply system to the combustion chamber 12, or from the combustion chamber 12 to the exhaust system 30. Alternatively or additionally, internal combustion engine 10 may have one or more fuel injection valves 14 located in an intake passage of internal combustion engine 10 .

[0045] The exhaust system 30 includes an exhaust gas duct 32, in which a three-way catalytic converter 38, located near the engine, as a first exhaust gas aftertreatment component, and a particulate filter 40 having a catalytically active coating 54, located downstream of the three-way catalytic converter 38, are located in the flow direction of the exhaust gas flow from the internal combustion engine 10. The particulate filter 40 can be designed, in particular, as a so-called four-way catalytic converter 56; such a four-way catalytic converter combines the functions of the three-way catalytic converter 42 and the particulate filter 40 in a single component. The filter substrate of the particulate filter 40 is coated with a washcoat layer that performs the function of a three-way catalytic converter. Furthermore, the turbine 36 of the exhaust gas turbocharger 34 can be located in the exhaust gas system 30. A first lambda sensor 44, in particular a broadband sensor, for detecting the oxygen concentration in the exhaust gas flow is located in the exhaust gas system downstream of the outlet 22 of the internal combustion engine 10 and upstream of the first three-way catalytic converter 38. A second lambda sensor 46, in particular a skip sensor, is located downstream of the first three-way catalytic converter 38 and upstream of the particulate filter 40.

[0046] Furthermore, a first temperature sensor 50 is located in the exhaust system 30, downstream of the first three-way catalytic converter 38 and upstream of the particulate filter 40. A differential pressure sensor 48, which determines the pressure difference between the inlet to the particulate filter 40 and the outlet from the particulate filter 40, is located at the particulate filter 40. The pressure difference across the particulate filter 40 is correlated with the particulate load of the particulate filter 40; when a defined threshold for the pressure difference is reached, regeneration of the particulate filter 40 is initiated in order to avoid further loading of the particulate filter 40 and associated potential damage.

[0047] The internal combustion engine 10 is connected to a control unit 60 comprising a memory unit 62 and a processing unit 64. Computer program code 66 is stored in the memory unit 62 and when executed by the processing unit of the control unit 60 performs the method according to the invention.

[0048] Figure 3 The flowchart for carrying out the method according to the invention for monitoring a particle filter in an exhaust system of an internal combustion engine is shown.

[0049] In the method steps <100> Different soot loading levels for the particulate filter 40 are defined in FIG. Figure 4 As shown in , for example, seven different load levels can be defined.

[0050] In the method steps <110> In step 5, the current soot load of the particulate filter 40 is determined by the soot load model implemented in the control unit 60. In the same step, the soot load determined by the soot load model is assigned to the soot loads in step 5. <100> One of the soot loading levels defined in .

[0051] In the method steps <120> In the method step, the soot load of the particulate filter 40 is determined via a pressure difference measurement across the particulate filter 40, which can be combined with the method step <110> occur in parallel or in method steps <110> In the same step, the soot load determined via the pressure difference measurement is assigned to the soot load in step <100> One of the soot loading levels defined in .

[0052] In the method steps <130> In the embodiment of the present invention, regeneration of the particulate filter 40 is initiated when a certain soot loading level of the particulate filter 40 is reached, which is determined via a pressure difference measurement.

[0053] In the method steps <140> In FIG. 1 , the soot loading level determined via the soot loading model is compared with the soot loading level of the particulate filter 40 determined via the pressure differential measurement.

[0054] When the regeneration level of the particulate filter 40 determined by the soot loading model does not correlate with the regeneration level determined via the pressure difference measurement, in method step <150> Output error message.

[0055] Figure 4 A table illustrating a load level model for the particulate filter 40 is shown. In load level 0, the particulate filter 40 has no soot loading, making measures for regenerating the particulate filter 40 unnecessary. In load level 1, the particulate filter 40 has a slight soot loading, for example, a soot loading of 0.1 g / L to 0.5 g / L of particulate filter volume. Regeneration of the particulate filter 40 is possible in the first load level, but no effective measures are initiated to initiate regeneration of the particulate filter 40. In load level 2, the particulate filter has a higher load than in the first load level 1, for example, 1 g / L to 2 g / L of particulate filter volume. Regeneration is possible in the second load level 2, but internal engine heating measures are generally not taken to initiate regeneration of the particulate filter 40 in this load level. Load level 3 represents a load state of the particulate filter 40 in which regeneration of the particulate filter 40 is desirable to avoid a further increase in exhaust gas backpressure and associated adverse consequences, such as increased fuel consumption or misfire of the internal combustion engine 10. In load level 4, regeneration of the particulate filter 40 is absolutely necessary in order to maintain the effectiveness of the exhaust gas aftertreatment and to avoid a deterioration in the emissions from the internal combustion engine 10. In load level 5, regeneration of the particulate filter 40 is no longer possible during driving operation of the motor vehicle, or at least not without the risk of causing permanent damage to the particulate filter 40, in particular thermal damage due to excessive heat input during oxidation of the soot retained in the particulate filter 40. If regeneration of the particulate filter 40 is interrupted or the internal combustion engine emits more particulates than expected, the driver is prompted to visit a repair shop and replace the particulate filter 40 and / or components of the internal combustion engine 10, in particular the fuel injectors 14 and / or the spark plugs 16, when the sixth load level is reached.

[0056] Figure 5The diagram illustrates a regeneration model for particulate filter 40. Regeneration of particulate filter 40 is monitored to identify errors in regeneration of particulate filter 40 and avoid overly frequent initiation of regeneration operations. Once a certain soot loading level RBS_dd of particulate filter 40e is reached by measuring the differential pressure DD across particulate filter 40e, a simulated soot mass within the simulated soot loading level m of the soot loading model is initialized. Depending on the physical input, the simulated soot mass may increase or decrease. When regeneration of particulate filter 40e is initiated, the simulated soot loading level RBS_m is assumed to also decrease, correlated with the decrease in soot loading level RBS_dd determined via the differential pressure. When an appropriate portion of the simulated soot mass is removed, the actual soot mass is theoretically reduced to a comparable amount, resulting in a lower simulated regeneration level. During a period of time during which a regeneration of particulate filter 40e is triggered and successfully executed via differential pressure sensor 48, the soot loading model should also identify a certain regeneration level or soot loading level of particulate filter 40e, and therefore a certain loading of particulate filter 40. Such a pattern is assumed when there is a sufficient correlation between the reduction in the soot loading level RBS_dd determined via the pressure difference measurement and the soot loading level RBS_m determined by the soot loading model.

[0057] If this is not the case, it can be assumed that the internal combustion engine 10 is emitting more soot than would be expected when the internal combustion engine 10 is operating normally. Figure 6 The monitoring can focus on soot loading levels that result from engine-related measures leading to adverse environmental impacts. Defined conditions can be used to exclude situations indicating non-functional regeneration. For this purpose, separate monitoring can be performed. The maximum regeneration level achieved during the entire monitoring period, or the minimum soot loading level RBS_m of the soot loading model, is determined. The comparison of the soot loading level RBS_dd achieved via differential pressure measurement with the minimum soot loading level RBS_m of the soot loading model achieved during regeneration occurs only when a request for regeneration of the particulate filter 40 has been successfully made by the differential pressure sensor 48.

[0058] Reference Signs List

[0059] 10 Internal combustion engine

[0060] 12 Combustion Chamber

[0061] 14 Fuel injection valve

[0062] 16 Spark plugs

[0063] 18 piston

[0064] 20 Entrance

[0065] 22 Exit

[0066] 24 Intake valve

[0067] 26 Wastegate Valve

[0068] 27 Connecting rod

[0069] 28 Crankshaft

[0070] 30 Exhaust system

[0071] 32 Exhaust duct

[0072] 34 Exhaust gas turbocharger

[0073] 36 Turbine

[0074] 38 First three-way catalytic converter

[0075] 40 particulate filter

[0076] 42 Second three-way catalytic converter

[0077] 44 First lambda sensor

[0078] 46 Second lambda sensor

[0079] 48 differential pressure sensor

[0080] 50 First temperature sensor

[0081] 52 Second temperature sensor

[0082] 54 Catalytically active coating

[0083] 56 Four-way catalytic converter

[0084] 58 fuel

[0085] 60 control unit

[0086] 62 memory cells

[0087] 64 processing units

[0088] 66 Computer program code.

Claims

1. A method for monitoring the regeneration of a particle filter (40) in an exhaust system (30) of an internal combustion engine (10), the internal combustion engine (10) having at least one combustion chamber (12), a spark plug (16) for igniting a combustible fuel-air mixture being located at the at least one combustion chamber (12), and the internal combustion engine (10) comprising a fuel injection valve (14) for feeding fuel into an intake tract of the internal combustion engine (10) and / or into the combustion chamber (12) of the internal combustion engine (10), the method comprising the following steps: - defining different soot loading levels for the particulate filter (40), - determining the soot loading of the particle filter (40) by using a soot loading model and assigning the soot loading to one of the defined soot loading classes, - determining the soot loading of the particle filter (40) via a pressure difference measurement across the particle filter (40) and assigning the determined soot loading to one of the defined soot loading classes, - initiating regeneration of the particle filter (40) when a certain soot loading level of the particle filter (40) is reached, determined via the pressure difference measurement, - comparing the soot loading level determined via the soot loading model with the soot loading level of the particulate filter (40) determined via the pressure difference measurement, and - outputting an error message when the regeneration level of the particulate filter (40) determined by the soot loading model does not correlate with the regeneration level determined via the pressure difference measurement.

2. The method according to claim 1, wherein: When regeneration is initiated and performed due to exceeding a threshold value of the pressure difference, for the soot loading level associated with the threshold it is checked whether the soot loading level determined using the soot loading model correlates to the reduction in the soot loading level determined via the pressure difference measurement.

3. The method according to claim 1 or 2, wherein: An error is detected when an increase in the soot loading level of the particulate filter (40) measured by the differential pressure measurement does not correlate with an increase in the soot loading level determined via the soot loading model.

4. The method according to any one of claims 1 to 3, wherein: A pressure differential range of the pressure differential measured across the particulate filter (40) is associated with each soot loading level in the soot loading model.

5. The method according to any one of claims 1 to 4, wherein: The soot loading model includes at least three soot loading levels for the particulate filter (40), in a first level no regeneration of the particulate filter (40) is required, in a second level simple regeneration of the particulate filter (40) occurs, and in a third soot loading level controlled regeneration of the particulate filter (40) occurs.

6. The method according to claim 5, wherein: The soot loading model includes a further soot loading level in which regeneration during driving operation is no longer permitted and the driver is prompted to have the particulate filter (40) checked in a repair shop.

7. The method according to claim 6, wherein: The soot loading model includes additional soot loading levels at which replacement of the particulate filter (40) is required.

8. The method according to any one of claims 1 to 7, wherein: During regeneration, information is output to the driver starting from a certain soot load level.

9. The method according to any one of claims 1 to 8, wherein: When a certain soot loading level is reached, engine-internal measures are initiated for initiating regeneration and / or for assisting the regeneration of the particulate filter (40).

10. A control unit (60) for executing the method according to any one of claims 1 to 9, the control unit (60) comprising a memory unit (62) and a processing unit (64) and a computer program code (66) stored in the memory unit (62), and executing the method when the computer program code (66) is executed by the processing unit (64).

11. An internal combustion engine (10) having at least one combustion chamber (12), the internal combustion engine (10) comprising a fuel injection valve (14) for feeding fuel into an intake tract of the internal combustion engine (10) and / or into a combustion chamber (12) of the internal combustion engine (10), a spark plug (16) for igniting a combustible fuel-air mixture at the combustion chamber (12), the internal combustion engine (10) being connected at its outlet (22) to an exhaust system (30) and to a control unit (60) according to claim 10, a particulate filter (40) being located in the exhaust system (30).

12. The internal combustion engine (10) according to claim 11, wherein: A three-way catalytic converter (38) as a first exhaust gas aftertreatment component is located in the exhaust system (30) in the flow direction of the exhaust gas flow of the internal combustion engine (10) through the exhaust system (30), and a particulate filter (40) is located downstream of the three-way catalytic converter (38).

13. The internal combustion engine (10) according to claim 12, wherein: A further three-way catalytic converter (42) is located downstream of the particulate filter (40).

14. An internal combustion engine (10) according to any one of claims 11 to 13, wherein: The particle filter (40) has a catalytically active coating (54).

15. An internal combustion engine (10) according to any one of claims 11 to 14, wherein: The internal combustion engine (10) is designed as a spark ignition internal combustion engine (10) supercharged using an exhaust gas turbocharger (30).

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