Patent Application
20240410308
This nonprovisional application claims priority under 35 U.S.C. § 119 (a) to German Patent Application No. 10 2023 115 282.3, which was filed in Germany on Jun. 12, 2023, and which is herein incorporated by reference.
The invention relates to a method for monitoring regeneration of a particulate filter in the exhaust gas system of a spark ignition internal combustion engine for excessively frequent regeneration operations, a control unit for controlling the regeneration of the particulate filter, and an internal combustion engine with an exhaust gas system and a control unit for carrying out such a method according to the preamble of the respective independent claims.
The increasing stringency of exhaust emission regulations has placed high demands on automotive manufacturers, which are addressed by suitable measures to reduce uncontrolled engine emissions and appropriate exhaust aftertreatment. The EU6 legislation prescribes a particle count limit for gasoline engines, which in many cases requires use of a gasoline engine particulate filter. Such soot particles arise in particular after a cold start of the internal combustion engine due to incomplete combustion, in combination with an overstoichiometric combustion air ratio after the cold start, cold cylinder walls, and the heterogeneous mixture distribution in the combustion chambers of the internal combustion engine. In contrast to the loading of a diesel particulate filter, the soot loading of a gasoline engine particulate filter takes place essentially as a function of the combustion chamber temperature, and decreases with increasing combustion chamber temperature. Thus, the cold start phase plays a crucial role in compliance with the regulatory particulate limits, with regard to the particle mass as well as the particle count. At cold outside temperatures, in particular at ambient temperatures below 0° C., particulate emissions are particularly high in a gasoline engine due to the low degree of mixture homogenization and evaporation of the fuel, as well as the starting enrichment. In addition, a cold start with an understoichiometric, rich combustion air ratio results in higher emissions of carbon monoxide (CO) and unburned hydrocarbons (HC), since conversion to carbon dioxide and water vapor is not yet possible due to the cold catalytic converter. During driving operation, for motor vehicles with a gasoline engine particulate filter, this gasoline engine particulate filter then becomes further loaded with soot. This gasoline engine particulate filter must be continuously or periodically regenerated to prevent excessive exhaust back pressure. The increase in exhaust back pressure may result in increased fuel consumption by the internal combustion engine, power loss, and impaired running smoothness, even misfiring. Carrying out thermal oxidation of the soot, retained in the gasoline engine particulate filter, with oxygen requires a sufficiently high temperature level together with the simultaneous presence of oxygen in the exhaust gas system of the gasoline engine. Since current gasoline engines are normally operated with 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 conditions, blowing secondary air into the exhaust gas system, or a combination of these measures. Thus far, adjustment of the ignition angle in the retarded direction in combination with an adjustment of the gasoline engine to lean has been preferred, since this method does not require additional components, and is able to deliver a sufficient quantity of oxygen in most operating points of the gasoline engine. Furthermore, with the introduction of new, more stringent exhaust emission standards, there may be a requirement for continuous monitoring of the proper functioning of the exhaust aftertreatment component within the scope of on-board monitoring, using appropriate sensors in the exhaust gas system.
A motor vehicle is known from DE 10 2013 217 622 A1, which corresponds to US 2014/0069081, and which includes an internal combustion engine, an exhaust gas system having a particulate filter that retains soot particles from the exhaust gas stream of the internal combustion engine, a sensor, and a controller. The sensor measures an instantaneous differential pressure across the particulate filter. The controller carries out a process to selectively activate or deactivate performance of an efficiency diagnosis of the particulate filter as a function of a learned differential pressure offset value. The controller may also compare the differential pressure to a calibrated threshold and carry out a control action when the differential pressure is in an allowable range of the threshold.
DE 10 2020 103 894 A1, which is incorporated herein by reference, describes a method for monitoring the regeneration of a particulate filter situated in an exhaust gas system of a gasoline engine. The method comprises the following steps: determining in which regeneration stage, of a defined number of regeneration stages, the particulate filter is being regenerated or was last regenerated; detecting a measure for at least one first test criterion that is characteristic of a change in the loading of the particulate filter; and/or checking whether the first test criterion is met, and changing to a higher regeneration stage if the first test criterion is not met, and changing to a lower regeneration stage or maintaining the present regeneration stage if the first test criterion is met.
A method for diagnosing a particulate filter in the exhaust duct of a combustion engine is known from DE 10 2011 077 097 A1, wherein a particulate filter loading, determined as soot loading of the particulate filter, is predicted based on differential pressure measurements and/or a soot loading model, using a particle sensor. Based on the diagnostic result, a regeneration operation of the particulate filter is initiated. It is provided that a validation of the diagnostic result for the particulate filter with regard to its functionality is carried out as a function of the particulate filter loading and an exhaust gas volume flow in the exhaust duct or a gradient of the exhaust gas volume flow, and based on this validation, the particulate filter is classified as functioning or defective, or the diagnostic result for the particulate filter is classified as unusable.
It is therefore an object of the invention to monitor regeneration of a particulate filter in the exhaust gas system of an internal combustion engine, and in particular to avoid frequent regeneration cycles, which are associated with worsening of the uncontrolled emissions of the internal combustion engine and/or worsening of the tailpipe emissions of the internal combustion engine.
The object is achieved, in an example, by a method for monitoring regeneration of a particulate filter in the exhaust gas 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 a fuel into the combustion chamber and/or a fuel injection valve for injecting a fuel into the intake tract of the internal combustion engine is situated at each combustion chamber, and a spark plug for igniting a combustible fuel-air mixture is situated at the combustion chamber. The method comprises the following steps: defining different soot loading stages for the particulate filter; determining a soot loading of the particulate filter by use of a soot loading model and assigning the determined soot loading to one of the defined soot loading stages; determining a soot loading of the particulate filter via a differential pressure measurement across the particulate filter and assigning the determined soot loading to one of the defined soot loading stages; initiating a regeneration of the particulate filter when a certain soot loading stage of the particulate filter, determined via the differential pressure measurement, is reached; and/or comparing the stage determined via the soot loading model to the soot loading stage determined via the differential pressure, wherein an error message is output when a regeneration stage of the particulate filter, determined by the soot loading model, does not correlate with a regeneration stage that is determined via the differential pressure measurement.
The method according to the invention makes it possible to monitor the regeneration of a particulate filter, and in particular to monitor that an excessively frequent regeneration of the particulate filter and/or excessively high uncontrolled particulate emissions of the internal combustion engine result(s) in frequent regeneration operations of the particulate filter, which due to the engine-internal measures that initiate or accompany the regeneration lead to an increase in the tailpipe emissions.
In an example, it is provided that when a regeneration is initiated and carried out due to an exceedance of a threshold value for the differential pressure, with the soot loading stage that is associated with the threshold value, it is checked whether the soot loading stage determined using the soot loading model correlates with the decrease in the loading stage determined via the differential pressure measurement. The maximum achieved regeneration stage of the soot loading model is preferably over the complete regeneration operation. If there is a sufficient correlation between the soot loading stage determined via the differential pressure measurement and the soot loading stage determined by the soot loading model, it may be assumed that the regeneration of the particulate filter, triggered by the differential pressure sensor, is plausible. If this is not the case, it may be assumed that the internal combustion engine is emitting more soot than expected, or more than it should emit when properly functioning. The particulate filter may thus be monitored for excessively frequent regenerations.
An error can be recognized when an increase in the soot loading stages of the particulate filter measured determined via the differential pressure measurement does not correlate with an increase in the soot loading stages determined via the soot loading model. When the internal combustion engine is operating properly, the increase in the differential pressure and the soot loading stages of the particulate filter determined via the differential pressure measurement should correlate with an increase in the soot loading stages of the particulate filter determined via the soot loading model. If this is not the case, in particular if an increase in the soot loading stages determined via the differential pressure measurement takes place much more quickly than the soot loading stages determined via the soot loading model, it is to be assumed that the internal combustion engine is emitting more soot particles than would be expected during proper operation, and therefore more frequent regenerations of the particulate filter are necessary. Such an error may be recognized by the method in an operationally reliable manner in order to prevent further damage to the particulate filter and/or to avoid an unallowable increase in the emissions.
A differential pressure range of the differential pressure measured across the particulate filter is assigned to each of the soot loading stages in the soot loading model. A particularly simple assignment of the soot loading stages of the soot loading model to the soot loading of the particulate filter measured via the differential pressure is thus possible.
The soot loading model can include at least three soot loading stages, in a first stage no regeneration of the particulate filter being necessary, in a second stage a simple regeneration of the particulate filter taking place, and in a third soot loading stage a controlled regeneration of the particulate filter taking place. Excessively frequent regenerations of the particulate filter may be avoided by use of such a phased model, since a mandatory regeneration of the particulate filter using engine-internal measures takes place only when the loading of the particulate filter has reached a certain soot loading stage.
The soot loading model can include a further soot loading stage in which regeneration during driving operation is no longer allowable, and the driver is prompted to have the particulate filter checked in a repair shop. If the particulate filter reaches such a critical soot loading stage, in which during regeneration there is a risk of uncontrolled soot burn-off and/or heat input into the particulate filter, which would result in permanent thermal damage to the particulate filter, the driver is prompted to take the motor vehicle to a repair shop and have an external regeneration of the particulate filter performed in order to avoid permanent damage to the particulate filter.
The soot loading model can include a further soot loading stage in which replacement of the particulate filter is required. If the loading of the particulate filter exceeds the loading described in the preceding sections, and/or if the initiation of a regeneration operation no longer results in a decrease in the differential pressure, the particulate filter must be replaced. Such a condition may be recognized by the described method, so that the driver is prompted to visit a repair shop to have the particulate filter replaced in order to avoid increased tailpipe emissions, in particular increased particulate emissions and/or damage to the internal combustion engine, in particular due to excessively high exhaust back pressure.
During regeneration, information may be output to the driver beginning at a certain soot loading stage of the particulate filter. In the process, regenerations take place in a lower regeneration stage, unnoticeable to the driver. A regeneration in a higher regeneration stage, which generally lasts longer and is noticeable to the driver due to the initiation of engine-internal measures, is indicated by a warning message, so that the driver may associate the engine-internal measures with the regeneration of the particulate filter. In particular, the situation may thus be prevented that the driver inadvertently switches off the internal combustion engine during a regeneration operation, and an incomplete regeneration of the particulate filter is thus carried out.
Upon reaching a certain soot loading stage, engine-internal measures for initiating a regeneration and/or for assisting the regeneration of the particulate filter can be initiated. When the vehicle is routinely driven under high partial load or full load, for example when driving on expressways, the normal operation of the internal combustion engine may be sufficient to provide operating conditions for the particulate filter in which regeneration of the particulate filter takes place by oxidation of the soot particles retained in the particulate filter. However, if the particulate filter reaches a higher loading stage, and the operating conditions, in particular the regeneration temperature of the particulate filter, are not reached during driving operation, regeneration may be initiated by increasing the exhaust gas temperature via engine-internal measures. In this way, regeneration of the particulate filter may be initiated, and soot loading of the particulate filter may be prevented from exceeding a critical level.
A control unit is also provided for carrying out the method described herein, the control unit including a memory unit and a processing unit as well as a computer program code that is stored in the memory unit, and the method being carried out when the computer program code is executed by the processing unit. Such a control unit allows an internal combustion engine and an exhaust aftertreatment system of the internal combustion engine to be controlled in such a way that a method according to the invention for monitoring and regenerating a particulate filter in the exhaust gas system of an internal combustion engine may be carried out.
Provided is also an internal combustion engine that can include at least one combustion chamber, with a fuel injector for injecting fuel into the combustion chamber and a spark plug for igniting a combustible fuel-air mixture being situated at the combustion chamber. At its outlet the internal combustion engine is connected to an exhaust gas system in which a particulate filter is situated. The internal combustion engine is also connected to a control unit, described in the preceding section. In such an internal combustion engine, the emissions may be reduced during the regeneration of the particulate filter, since unnecessary regeneration measures that result in increased emissions may be dispensed with.
A three-way catalytic converter as a first exhaust aftertreatment component can be situated in the exhaust gas system in the flow direction of an exhaust gas stream of the internal combustion engine through the exhaust gas system, and a particulate filter is situated downstream from the three-way catalytic converter. Particularly advantageous exhaust aftertreatment is possible in this way, since after a cold start, the three-way catalytic converter quickly reaches operating temperature due to the position near the engine, and efficient conversion of the limited pollutants in the exhaust gas stream of the internal combustion engine is thus made possible immediately after a cold start of the internal combustion engine. In addition, this arrangement allows the particulate filter to likewise be situated near the engine, thus simplifying heating up of the particulate filter for initiating a regeneration. In this context, a position near the engine is understood to mean a position of an inlet of the exhaust aftertreatment component with an exhaust gas run length of less than 80 cm, preferably less than 60 cm, beginning at an outlet of the internal combustion engine.
A further three-way catalytic converter can be situated downstream from the particulate filter. The catalytic converter volume for the three-way catalytic converters may thus be distributed over two units, as a result of which the first three-way catalytic converter near the engine may be designed with a smaller volume, and thus reaches its light-off temperature more quickly. In addition, the secondary emissions that arise during the oxidation of the soot during the regeneration of the particulate filter may be converted by the second three-way catalytic converter, so that the regeneration results in little or no increase in the tailpipe emissions.
The particulate filter and the further three-way catalytic converter may be designed so that they are combined in a single component as a so-called four-way catalytic converter. For this purpose, the particulate filter has a catalytically active coating, which preferably is applied as a washcoat to the filter structure of the particulate filter, and which may oxidize the limited pollutants such as unburned hydrocarbons and carbon monoxide, and may reduce nitrogen oxides.
The internal combustion engine can be designed as a spark ignition internal combustion engine according to the Otto principle, which is charged using an exhaust gas turbocharger. The filling in the combustion chambers of the internal combustion engine may be improved by charging the internal combustion engine. This measure, in particular in combination with a fuel injector that can deliver an injection pressure in the range of up to 350 bar, may result in a reduction in the uncontrolled particulate emissions, and thus in the frequency with which a particulate filter must be regenerated.
The various examples of the invention mentioned in the present patent application may advantageously be combined with one another.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinaitons, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
The exhaust gas system 30 includes an exhaust duct 32 in which a three-way catalytic converter 38 near the engine as a first exhaust aftertreatment component, a particulate filter 40 downstream from the three-way catalytic converter near the engine, and a second three-way catalytic converter 42 farther downstream are situated in the flow direction of an exhaust gas stream of the internal combustion engine 10, the second three-way catalytic converter 42 preferably being situated in an underbody position of a motor vehicle. In addition, a turbine 36 of an exhaust gas turbocharger 34 may be situated 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 stream is situated in the exhaust gas system, downstream from the outlet 22 of the internal combustion engine 10 and upstream from the first three-way catalytic converter 38. A second lambda sensor 46, in particular a jump sensor, is situated downstream from the first three-way catalytic converter 38 and upstream from the second three-way catalytic converter 42, in particular downstream from the first three-way catalytic converter 38 and upstream from the particulate filter 40. Furthermore, situated in the exhaust gas system 30 is a first temperature sensor 50, downstream from the first three-way catalytic converter 38 and upstream from the particulate filter 40, and a second temperature sensor 52, downstream from the particulate filter 40 and upstream from the second three-way catalytic converter 42. A differential pressure sensor 48 that determines a pressure difference between an inlet to the particulate filter 40 and an outlet from the particulate filter 40 is situated at the particulate filter 40. The pressure difference across the particulate filter 40 is correlated with the particulate loading of the particulate filter 40; when a defined threshold value for the differential pressure is reached, regeneration of the particulate filter 40 is initiated in order to avoid further loading and associated potential damage to the particulate filter 40.
The internal combustion engine 10 is connected to a control unit 60 that includes a memory unit 62 and a processing unit 64. A computer program code 66 is stored in the memory unit 62, and carries out a method according to the invention when the computer program code is executed by the processing unit of the control unit.
The exhaust gas system 30 includes an exhaust duct 32 in which a three-way catalytic converter 38 near the engine as a first exhaust aftertreatment component, and a particulate filter 40 with a catalytically active coating 54, downstream from the three-way catalytic converter 38 near the engine, are situated in the flow direction of an exhaust stream of the internal combustion engine 10. The particulate filter 40 may in particular be designed as a so-called four-way catalytic converter 56; such a four-way catalytic converter combines the functionality of a three-way catalytic converter 42 and a particulate filter 40 in a single component. The filter substrate of the particulate filter 40 is covered with a washcoat having the functionality of a three-way catalytic converter. In addition, a turbine 36 of an exhaust gas turbocharger 34 may be situated 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 stream is situated in the exhaust gas system, downstream from the outlet 22 of the internal combustion engine 10 and upstream from the first three-way catalytic converter 38. A second lambda sensor 46, in particular a jump sensor, is situated downstream from the first three-way catalytic converter 38 and upstream from the particulate filter 40.
Furthermore, a first temperature sensor 50 is situated in the exhaust gas system 30, downstream from the first three-way catalytic converter 38 and upstream from the particulate filter 40. A differential pressure sensor 48 that determines a pressure difference between an inlet to the particulate filter 40 and an outlet from the particulate filter 40 is situated at the particulate filter 40. The pressure difference across the particulate filter 40 is correlated with the particulate loading of the particulate filter 40; when a defined threshold value for the differential pressure is reached, regeneration of the particulate filter 40 is initiated in order to avoid further loading and associated potential damage to the particulate filter 40.
The internal combustion engine 10 is connected to a control unit 60 that includes a memory unit 62 and a processing unit 64. A computer program code 66 is stored in the memory unit 62, and carries out a method according to the invention when the computer program code is executed by the processing unit of the control unit 60.
Different soot loading stages for the particulate filter 40 are defined in a method step <100>. Thus, as illustrated in
A present soot loading of the particulate filter 40 is determined in a method step <110> by a soot loading model that is implemented in the control unit 60. In the same step, the soot loading determined by the soot loading model is assigned to one of the soot loading stages defined in step <100>.
A soot loading of the particulate filter 40 is determined via a differential pressure measurement across the particulate filter 40 in a method step <120>, which may take place in parallel with method step <110> or before or after method step <110>. In the same step, the soot loading determined via the differential pressure measurement is assigned to one of the soot loading stages defined in step <100>.
Regeneration of the particulate filter 40 is initiated in a method step <130> when a certain soot loading stage of the particulate filter 40, determined via the differential pressure measurement, is reached.
The soot loading stage determined via the soot loading model is compared to the soot loading stage of the particulate filter 40 determined via the differential pressure measurement in a method step <140>.
An error message is output in a method step <150> when the regeneration stage of the particulate filter 40, determined by the soot loading model, does not correlate with the regeneration stage that is determined via the differential pressure measurement.
If this is not the case, it may be assumed that the internal combustion engine 10 is emitting more soot than expected when the internal combustion engine 10 is properly functioning. Such a case is illustrated in
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2023 115 282.3 | Jun 2023 | DE | national |
