METHOD FOR MONITORING REGENERATION OF A PARTICULATE FILTER IN THE EXHAUST GAS SYSTEM OF AN INTERNAL COMBUSTION ENGINE

Abstract

Regeneration monitoring of a particulate filter in an exhaust gas system of an internal combustion engine of a motor vehicle. Different soot loading stages for the particulate filter are defined. A soot loading of the particulate filter is determined by use of a soot loading model. A soot loading of the particulate filter via a differential pressure measurement across the particulate filter is determined. A regeneration of the particulate filter is initiated when a certain soot loading stage of the particulate filter is reached. A soot discharge from the particulate filter is compared, expected via the soot loading model, to a soot discharge from the particulate filter that is determined via a differential pressure measurement. An error message is outputted 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.

Claims

1. A method for monitoring regeneration of a particulate filter in an exhaust gas system of an internal combustion engine, the internal combustion engine comprising at least one combustion chamber at which a spark plug for igniting a combustible fuel-air mixture is arranged, the internal combustion engine further comprising a fuel injection valve for feeding a fuel into an intake tract of the internal combustion engine and/or into the combustion chamber of the internal combustion engine, the method comprising: 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 soot loading to one of a 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; comparing the soot loading stage determined via the soot loading model to the soot loading stage of the particulate filter determined via the differential pressure measurement; and outputting an error message when the regeneration stage of the particulate filter, determined by the soot loading model, does not correlate with the regeneration stage that is determined via the differential pressure measurement.

2. The method according to claim 1, wherein when the 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, and checking whether the soot loading stage determined using the soot loading model correlates with the decrease in the soot loading stage determined via the differential pressure measurement.

3. The method according to claim 1, wherein an error is recognized when an increase in the soot loading stages of the particulate filter measured, determined by the differential pressure measurement, does not correlate with an increase in the soot loading stages determined via the soot loading model.

4. The method according to claim 1, wherein a differential pressure range of the differential pressure measured across the particulate filter is associated with each soot loading stage in the soot loading model.

5. The method according to claim 1, wherein the soot loading model includes at least three soot loading stages for the particulate filter, 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 stage a controlled regeneration of the particulate filter taking place.

6. The method according to claim 5, wherein the soot loading model includes 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.

7. The method according to claim 6, wherein the soot loading model includes a further soot loading stage in which replacement of the particulate filter is required.

8. The method according to claim 1, wherein during regeneration, information is output to the driver beginning at a certain soot loading stage.

9. The method according to claim 1, wherein upon reaching a certain soot loading stage, engine-internal measures for initiating a regeneration and/or for assisting the regeneration of the particulate filter are initiated.

10. A control unit to perform the method according to claim 1, the control unit comprising: a memory; a processor; and a computer program code that is stored in the memory unit, wherein the method is carried out when the computer program code is executed by the processing unit.

11. An internal combustion engine comprising: at least one combustion chamber; a fuel injection valve to feed a fuel into an intake tract of the internal combustion engine and/or into the combustion chamber of the internal combustion engine, a spark plug for igniting a combustible fuel-air mixture being arranged at the combustion chamber; and an outlet being connected to an exhaust gas system in which a particulate filter is arranged, and being connected to the control unit according to claim 10.

12. The internal combustion engine according to claim 11, wherein a three-way catalytic converter as a first exhaust aftertreatment component is situated in the exhaust gas system in a flow direction of an exhaust gas stream of the internal combustion engine through the exhaust gas system, and the particulate filter is arranged downstream from the three-way catalytic converter.

13. The internal combustion engine according to claim 12, wherein a further three-way catalytic converter is arranged downstream from the particulate filter.

14. The internal combustion engine according to claim 11, wherein the particulate filter has a catalytically active coating.

15. The internal combustion engine according to claim 11, wherein the internal combustion engine is designed as a spark ignition internal combustion engine that is charged using an exhaust gas turbocharger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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:

[0027] FIG. 1 shows an example of an internal combustion engine with an exhaust gas system and a control unit for carrying out a method according to the invention for monitoring a particulate filter in the exhaust gas system of the internal combustion engine,

[0028] FIG. 2 shows an example of an internal combustion engine for carrying out a method according to the invention for monitoring a particulate filter in the exhaust gas system of the internal combustion engine,

[0029] FIG. 3 shows a flow chart for carrying out a method according to the invention for monitoring a particulate filter in the exhaust gas system of an internal combustion engine,

[0030] FIG. 4 shows a loading stage model for a particulate filter,

[0031] FIG. 5 shows a regeneration diagram for regenerating a particulate filter during proper regeneration of the particulate filter, and

[0032] FIG. 6 shows a regeneration diagram for regenerating the particulate filter during an excessively frequent regeneration of the particulate filter due to increased particulate emissions from the internal combustion engine.

DETAILED DESCRIPTION

[0033] FIG. 1 shows a schematic illustration of an internal combustion engine 10. The internal combustion engine 10 is designed as a direct injection gasoline engine. The internal combustion engine 10 has multiple combustion chambers 12. A fuel injector with a fuel injection valve 14 for injecting a fuel 58 into the particular combustion chamber 12, and a spark plug 16 for igniting a fuel-air mixture in the particular combustion chamber 12, are situated at each of the combustion chambers 12. The combustion chamber 12 is delimited by a piston 18 that is displaceable in the axial direction. The oscillating movement of the piston is transferred into a rotary movement of a crankshaft 28 of the internal combustion engine by a connecting rod 27. The internal combustion engine 10 via its inlet 20 is connected to an air supply system, and via its outlet 22 is connected to an exhaust gas system 30. Situated at the combustion chambers 12 are intake valves 24 and exhaust valves 26, via which a fluidic connection from the air supply system to the combustion chambers 12 or from the combustion chambers 12 to the exhaust gas system 30 may be opened or closed. Alternatively or additionally, the internal combustion engine 10 may have one or more fuel injection valves 14 that are situated in an intake tract of the internal combustion engine 10.

[0034] 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.

[0035] 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.

[0036] FIG. 2 illustrates an example of an internal combustion engine 10. The internal combustion engine 10 is designed as a direct injection gasoline engine. The internal combustion engine 10 has multiple combustion chambers 12. A fuel injector with a fuel injection valve 14 for injecting a fuel 58 into the particular combustion chamber 12, and a spark plug 16 for igniting a fuel-air mixture in the particular chamber 12, are situated at each of the combustion chambers 12. The combustion chamber 12 is delimited by a piston 18 that is displaceable in the axial direction. The oscillating movement of the piston is transferred into a rotary movement of a crankshaft 28 of the internal combustion engine by a connecting rod 27. The internal combustion engine 10 via its inlet 20 is connected to an air supply system, and via its outlet 22 is connected to an exhaust gas system 30. Situated at the combustion chambers 12 are intake valves 24 and exhaust valves 26, via which a fluidic connection from the air supply system to the combustion chambers 12 or from the combustion chambers 12 to the exhaust gas system 30 may be opened or closed. Alternatively or additionally, the internal combustion engine 10 may have one or more fuel injection valves 14 that are situated in an intake tract of the internal combustion engine 10.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] FIG. 3 illustrates a flow chart for carrying out a method according to the invention for monitoring a particulate filter in the exhaust gas system of an internal combustion engine.

[0041] Different soot loading stages for the particulate filter 40 are defined in a method step <100>. Thus, as illustrated in FIG. 4, for example, seven different loading stages may be defined.

[0042] 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>.

[0043] 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>.

[0044] 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.

[0045] 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>.

[0046] 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.

[0047] FIG. 4 illustrates a table for a loading stage model for a particulate filter 40. In a loading stage 0 the particulate filter 40 has no soot loading, so that measures for regenerating the particulate filter 40 are not necessary. In a loading stage 1 the particulate filter 40 has slight soot loading, for example a soot loading of 0.1 g/L to 0.5 g/L particulate filter volume. Regeneration of the particulate filter 40 is possible in the first loading stage, but no active measures for starting a regeneration of the particulate filter 40 are initiated. In a loading stage 2 the particulate filter has a loading that is above the loading of the first loading stage 1, for example 1 g/L to 2 g/L particulate filter volume. Regeneration is possible in the second loading stage 2, but in this loading stage generally no engine-internal heating measures are undertaken to initiate a regeneration of the particulate filter 40. Loading stage 3 represents a loading state of the particulate filter 40 in which regeneration of the particulate filter 40 is desirable in order to avoid a further increase in the exhaust back pressure and associated adverse consequences such as an increase in the fuel consumption or misfires of the internal combustion engine 10. In loading stage 4, regeneration of the particulate filter 40 is absolutely necessary in order to maintain the effectiveness of the exhaust aftertreatment and avoid worsening of emissions from the internal combustion engine 10. In loading stage 5, regeneration of the particulate filter 40 during a driving operation of the motor vehicle is no longer possible, or at least is not possible without the risk of permanent damage to the particulate filter 40, in particular thermal damage due to excessive heat input during the oxidation of the soot retained in the particulate filter 40. If the regeneration of the particulate filter 40 is disturbed or the internal combustion engine emits more particulate than expected, when a sixth loading stage is reached the driver is prompted to visit a repair shop and have 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, replaced.

[0048] FIG. 5 illustrates a regeneration model for the particulate filter 40. Regeneration of the particulate filter 40 is monitored in order to recognize errors in the regeneration of the particulate filter 40 and avoid excessively frequent initiation of a regeneration operation. As soon as a certain soot loading stage RBS_dd of the particulate filter 40e is reached via measurement of the differential pressure DD across the particulate filter 40, a modeled soot mass within a modeled soot loading stage m of the soot loading model is initialized. The modeled soot mass may either increase or decrease, depending on the physical input. When a regeneration of the particulate filter 40 is initiated, it is to be assumed that the modeled soot loading stage RBS_m likewise decreases, and correlates with the decrease of the soot loading stage RBS_dd determined via the differential pressure. When an appropriate portion of the modeled soot mass is removed, theoretically the actual soot mass has also been reduced to a comparable quantity, resulting in a lower modeled regeneration level. In the time period in which a certain regeneration of the particulate filter 40 is triggered and successfully carried out via the differential pressure sensor 48, the soot loading model should have likewise recognized a certain regeneration stage or soot loading stage, and thus a certain loading of the particulate filter 40. Such a pattern is assumed when there is a sufficient correlation between the decreases of the soot loading stage RBS_dd determined via the differential pressure measurement and the soot loading stage RBS_m determined by the soot loading model.

[0049] 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 FIG. 6. The monitoring may be focused on soot loading stages in which an adverse environmental impact results from engine-related measures. Via defined conditions it is ruled out that non-functional regeneration is indicated. Separate monitoring is available for this purpose. The maximum regeneration stage reached or a minimum soot loading stage RBS_m of the soot loading model over the entire monitoring period is determined. A comparison of the request for the soot loading stage RBS_dd reached via the differential pressure measurement and the minimum soot loading stage RBS_m of the soot loading model reached during the regeneration takes place only when the request by the differential pressure sensor 48 for regeneration of the particulate filter 40 has successfully taken place.

[0050] 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.