CN117780527A - Method for adjusting the oxygen filling level of a catalyst in the exhaust gas of an internal combustion engine - Google Patents
Method for adjusting the oxygen filling level of a catalyst in the exhaust gas of an internal combustion engine Download PDFInfo
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- CN117780527A CN117780527A CN202311261860.6A CN202311261860A CN117780527A CN 117780527 A CN117780527 A CN 117780527A CN 202311261860 A CN202311261860 A CN 202311261860A CN 117780527 A CN117780527 A CN 117780527A
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- 239000003054 catalyst Substances 0.000 title claims abstract description 101
- 239000007789 gas Substances 0.000 title claims abstract description 81
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 69
- 239000001301 oxygen Substances 0.000 title claims abstract description 69
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 69
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 60
- 238000000034 method Methods 0.000 title claims abstract description 46
- 238000004140 cleaning Methods 0.000 claims abstract description 10
- 230000008569 process Effects 0.000 claims abstract description 8
- 239000000446 fuel Substances 0.000 claims description 24
- 230000003197 catalytic effect Effects 0.000 claims description 21
- 238000006243 chemical reaction Methods 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 8
- 230000009849 deactivation Effects 0.000 claims description 7
- 230000015556 catabolic process Effects 0.000 claims description 6
- 238000004590 computer program Methods 0.000 claims description 6
- 238000011144 upstream manufacturing Methods 0.000 claims description 6
- 230000032683 aging Effects 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 3
- 230000010354 integration Effects 0.000 claims description 2
- 230000001419 dependent effect Effects 0.000 claims 2
- 101100497221 Bacillus thuringiensis subsp. alesti cry1Ae gene Proteins 0.000 claims 1
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 11
- 229930195733 hydrocarbon Natural products 0.000 description 7
- 150000002430 hydrocarbons Chemical class 0.000 description 7
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000001569 carbon dioxide Substances 0.000 description 6
- 230000008901 benefit Effects 0.000 description 5
- 239000007924 injection Substances 0.000 description 4
- 238000002347 injection Methods 0.000 description 4
- 230000001052 transient effect Effects 0.000 description 4
- 238000004422 calculation algorithm Methods 0.000 description 3
- 238000012937 correction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 241000282326 Felis catus Species 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000001143 conditioned effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000002045 lasting effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/0295—Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1439—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the position of the sensor
- F02D41/1441—Plural sensors
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
- F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
- F02D2041/1413—Controller structures or design
- F02D2041/1431—Controller structures or design the system including an input-output delay
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0814—Oxygen storage amount
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0816—Oxygen storage capacity
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2250/00—Engine control related to specific problems or objectives
- F02D2250/14—Timing of measurement, e.g. synchronisation of measurements to the engine cycle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1473—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method
- F02D41/1475—Regulating the air fuel ratio at a value other than stoichiometry
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
The invention relates to a method for adjusting the oxygen filling level of a catalyst in the exhaust gas of an internal combustion engine, in which method the actual oxygen filling level of the catalyst is modeled using a catalyst model, wherein the state of the internal combustion engine is detected, in which state a brief combustion of lean gas occurs, in particular for a few milliseconds, the actual oxygen filling level of the catalyst is ascertained during a predefinable first time interval, wherein the ascertained actual oxygen filling level is stored at the end of the first time interval and a second time interval is started when the actual oxygen filling level exceeds a predefinable (oxygen filling level) threshold value, wherein a second signal downstream of the catalyst is ascertained continuously as the second time interval begins, wherein at least one gradient is ascertained from the signal of the second sensor in the second time interval, wherein a cleaning process of the catalyst is started when the at least one gradient exceeds the predefinable gradient threshold value.
Description
Technical Field
The invention relates to a method for adjusting the oxygen filling level of a catalytic converter in the exhaust gas of an internal combustion engine, to a computer program, to a machine-readable storage medium and to an electronic control unit.
Background
When the air-fuel mixture in the gasoline engine is not completely combusted, the fuel other than nitrogen (N 2 ) Carbon dioxide (CO) 2 ) And water (H) 2 O) also emits a large amount of combustion products, among which Hydrocarbons (HC), carbon monoxide (CO) and Nitrogen Oxides (NO) x ) Is legally restricted. The effective exhaust gas limit values of motor vehicles can only be complied with by catalytic exhaust gas aftertreatment according to the current state of the art. The harmful substance component may be converted by using a three-way catalyst. The simultaneous high conversion of HC, CO and NOx is achieved in the three-way catalyst only in a narrow lambda range around the stoichiometric operating point (lambda=1), the so-called conversion window.
A problem that arises in very short lean phases, for example, when shifting gears or closing cylinders, is that the exhaust gas sensor downstream of the catalyst, directly after the lean phase, has not yet reacted to the lean phase because of the gas operating time from the combustion chamber of the engine to this sensor, and therefore indicates a still rich exhaust gas if this has already been done before the lean phase.
DE 10 2016 222 418 A1 discloses a method for regulating the charge of an exhaust gas component store of a catalytic converter (26) in the exhaust gas of an internal combustion engine (10), in which method the actual filling level (θ) of the exhaust gas component store is determined using a first catalytic converter model (100). The method is distinguished in that a lambda setpoint value (lambda) is formed, wherein a predetermined setpoint filling level (theta) is converted into a base lambda setpoint value by a second controlled object model (104) which is opposite to the first catalytic converter model (100), wherein a deviation of the actual filling level (theta) from the predetermined setpoint filling level (theta) is determined and processed by a filling level adjustment (124) into lambda setpoint correction values, a sum of the base lambda setpoint value and the lambda setpoint correction values is formed, and this sum is used to form correction values, with which the fuel metering of at least one combustion chamber (20) of the internal combustion engine (10) is influenced.
Disclosure of Invention
The object of the invention is therefore to make it possible to improve the catalyst cleaning after a short lean phase.
The invention relates to a method for adjusting the oxygen filling level of a catalyst in the exhaust gas of an internal combustion engine according to the independent claim. The invention further relates to a computer program which is designed to carry out one of the methods.
In a first aspect, a method for adjusting the oxygen filling level of a catalyst in the exhaust gas of an internal combustion engine is disclosed, in which method the actual oxygen filling level of the catalyst is modeled using a catalyst model, wherein a state of the internal combustion engine is detected in which a transient lean combustion, in particular of a few milliseconds, occurs, such that an actual oxygen filling level of the catalyst is determined during a predefinable first time interval, wherein the determined actual oxygen filling level is stored at the end of the first time interval when the actual oxygen filling level exceeds a predefinable oxygen filling level threshold value and a second time interval is started, wherein a second signal downstream of the catalyst is continuously determined as the second time interval begins, wherein an oxygen breakdown associated with the oxygen charge determined in the first time interval can be deduced by means of the second signal, wherein at least one gradient is determined from the signal of the second sensor in the second time interval, wherein the fuel mixture is pre-enriched at the end of the first time interval is set to an actual oxygen filling level, and the fuel mixture is pre-conditioned (at the end of the first time interval is set to an actual oxygen filling level).
The method has the particular advantage that the actual oxygen filling level of the catalyst during the first time interval is detected on the basis of the model and stored at the end of the first time interval, and the reaction of the lean gas charge into the catalyst in the second time interval is monitored immediately downstream of the catalyst by means of an exhaust gas sensor. According to the monitoring, a possible oxygen breakdown due to oxygen charging during the first time interval can be reacted quickly and in a satisfactory manner and can be cleaned, for example, by means of a catalytic converter, that is to say by means of a combustion enrichment, auxiliary measures being carried out.
The method also has the advantage that unnecessary catalyst cleaning after a short lean phase can be avoided by such monitoring. Thereby generating less CO, HC and NH3 emissions and less fuel consumption than at the minimum of normal clean-up. On the other hand, the method has the advantage over a direct interruption of the catalyst cleaning after a short lean phase that the catalyst can be returned from the stored oxygen filling level into its catalyst window in a controlled manner, which is faster and more accurate than can be achieved with only pilot regulation when the catalyst actually has to be cleaned.
The catalyst cleaning after a short lean phase can thus be performed more specifically and the robustness of the catalyst cleaning is increased.
In a further embodiment, a predefinable first time interval is executed which starts at a predefinable first time point and ends at a predefinable second time point, wherein the predefinable first time point is selected as a function of the started cylinder shut-down or the started shift, and the predefinable second time point corresponds to the end of the cylinder shut-down or the end of the shift.
A particular advantage of this is that the short-lived lean combustion can thus be limited in time in a robust manner.
In a special embodiment, a predefinable second time interval is performed, which starts at a predefinable second time point and ends at a predefinable third time point, wherein the predefinable third time point is selected as a function of the gas operating time or as a function of the current exhaust gas mass flow and/or as a function of the aging factor of the catalyst, wherein the gas operating time corresponds to the time that the exhaust gas takes to pass from the combustion chamber of the engine through the catalyst to the second exhaust gas sensor.
A particular advantage of this is that the period of time for possible oxygen breakdown can be limited to be a reaction to a short preceding lean phase and thus the robustness of the process can be improved.
Furthermore, the first catalytic converter model may in particular be a reaction dynamics model or an integration model, wherein the actual oxygen filling level is determined by means of the catalytic converter model as a function of the first air-fuel ratio upstream of the catalytic converter and/or of aging factors of the catalytic converter and/or of the catalytic converter temperature.
In a particular embodiment, the second exhaust gas sensor may be a second lambda sensor, wherein the second lambda sensor determines an air-fuel ratio or a voltage signal downstream of the catalytic converter.
In a further embodiment, the second exhaust gas sensor may be configured as a NOx concentration sensor, wherein the NOx concentration sensor determines a NOx concentration, an air-fuel ratio or a voltage signal downstream of the catalyst.
In one advantageous embodiment, a state is detected in which a brief lean combustion of the internal combustion engine occurs during a gear change or during an active cylinder closure, wherein the brief lean combustion preferably lasts between 10 and 1000 milliseconds.
In other aspects, the invention relates to a device, in particular a controller, and a computer program, which are set up, in particular programmed, for carrying out one of the methods. In yet another aspect, the present invention relates to a machine-readable storage medium having a computer program stored thereon.
Drawings
Embodiments of the invention are illustrated in the accompanying drawings and explained in more detail in the following description. The same reference numbers in different drawings refer here to identical or at least functionally similar elements, respectively.
Fig. 1 shows in schematic form an internal combustion engine with an exhaust system as the technical field of the invention;
FIG. 2 shows in schematic form functional block diagrams of controlled object models, respectively; and is also provided with
Fig. 3 shows in schematic form a functional block diagram of an exemplary embodiment of the method according to the invention.
Detailed Description
The invention is described below using a three-way catalyst as an example and with respect to oxygen as the exhaust gas component to be stored. The invention can also be applied in the sense of other catalyst types and exhaust gas components such as nitrogen oxides and hydrocarbons. The following takes for simplicity the exhaust system with a three-way catalyst as starting point. The invention can also be used in the sense of an exhaust system with a plurality of catalytic converters. The front and rear zones described below may in this case extend over a plurality of catalytic converters or be located in different catalytic converters.
Fig. 1 shows an internal combustion engine 10 of a vehicle with an air input system 12, an exhaust system 14, and a controller 16 in detail. Located in the air supply system 12 is an air mass measuring device 18 and a throttle valve, which is arranged downstream of the air mass measuring device 18, of a throttle valve unit 19. The air flowing into the internal combustion engine 10 through the air input system 12 is mixed in the combustion chamber 20 of the internal combustion engine 10 with gasoline directly injected into the combustion chamber 20 via the injection valve 22. The resulting combustion chamber charge is ignited and combusted by an ignition device 24, such as a spark plug. The rotational angle sensor 25 detects the rotational angle of the shaft of the internal combustion engine 10 and allows the controller 16 to trigger ignition in a predetermined angular position of the shaft. Exhaust gas resulting from combustion is directed through exhaust system 14.
The exhaust system 14 has a catalyst 26. The catalyst 26 is, for example, a three-way catalyst, which is known to convert three exhaust gas components, namely nitrogen oxides, hydrocarbons and carbon monoxide, in three reaction paths and has the function of storing oxygen. The three-way catalyst 26 has a first zone 26.1 and a second zone 26.2 in the example shown. The two zones are flown through by exhaust gas 28. The front first zone 26.1 extends in the flow direction past the front region of the three-way catalyst 26. The second rear zone 26.2 extends downstream of the first zone 26.1 through a region behind the three-way catalyst 26. Of course, further regions can be provided before the front region 26.1 and after the rear region 26.2 and between the two regions, for which the respective filling level can likewise be modeled if necessary.
Upstream of the three-way catalyst 26, an exhaust gas sensor 32 that receives the front of the exhaust gas 28 is arranged immediately before the three-way catalyst 26. Downstream of the three-way catalyst 26, an exhaust gas sensor 34 is arranged directly behind the three-way catalyst 26, which likewise receives the rear of the exhaust gas 28. The first exhaust gas sensor 32 is preferably a broadband lambda probe that allows measurement of the first air-fuel ratio lambda over a wide range of air-coefficients 1 。
The first exhaust gas sensor 32 is disposed downstream of the internal combustion engine 10 and upstream of the three-way catalyst 26.
The second exhaust gas sensor 34 is therefore preferably a so-called step lambda sensor downstream of the three-way catalyst 26, with which the air coefficient lambda=1 can be measured particularly accurately, since the signal of this exhaust gas sensor 34 changes stepwise there. See Boshi, handbook of automotive engineering, 23 rd edition, page 524.
The second exhaust gas sensor 34 obtains a second air-fuel ratio lambda 2 。
In an alternative embodiment, the second exhaust gas sensor 34 may also be configured as a NOx sensor, which determines the NOx concentration NOx downstream of the catalyst 26 2 Air-fuel ratio lambda 2 Or a voltage signal lambda U2 。
In the illustrated embodiment, a temperature sensor 36 that is subject to exhaust gas 28 may be disposed at three-way catalyst 26 in thermal contact with exhaust gas 28, the temperature sensor detecting a temperature T of three-way catalyst 26 cat 。
The controller 16 processes the signals of the air mass measuring device 18, of the steering angle sensor 25, of the first exhaust gas sensor 32, of the second exhaust gas sensor 34 and of the optional temperature sensor 36, and generates therefrom drive signals for setting the angular position of the throttle valve, for triggering ignition by the ignition device 24 and for injecting fuel by the injection valve 22. The controller 16 alternatively or additionally also processes signals of other or further sensors for actuating the indicated actuators or also of further or further actuators, for example signals of a driver intention sensor 40, which detects the accelerator pedal position. The coasting operation (schiebetrieb) with the fuel input stopped is triggered, for example, by releasing the accelerator pedal. This and the functions which will be described further below are implemented by an engine control program 16.1 which is run in the controller 16 during operation of the internal combustion engine 10. In addition, adjustments to fuel injection or mixture preparation and control of cylinder deactivation are stored on controller 16. The activated cylinder is deactivated for storage at the controller 16 using the status bit. In addition, the control unit 16 also stores when a shift of the vehicle is to be performed
A brief lean phase of combustion also occurs during cylinder deactivation and also during gear shifting, so that oxygen is introduced into the exhaust system. A relatively very short lean phase lasting several milliseconds, in particular 10ms to several hundred milliseconds, is involved. During this brief lean phase, oxygen is introduced into the catalyst 26.
In the present application, the oxygen filling level of the catalyst 26 is modeled using the controlled object model 100, the catalyst model 102 (reaction kinetics model).
Alternatively, an integral model may be used.
Fig. 2 shows a functional block diagram of the controlled object model 100. The controlled object model 100 is constituted by a catalyst model 102. The catalyst model 102 has an input emissions model 108 and a fill level and output emissions model 110. The catalyst model 102 also has an average oxygen filling level for calculating the catalyst 26Is provided) 112. The models are in each case algorithms which are implemented in the controller 16 and combine the input variables which also act on the real object modeled by the calculation model into output variables in such a way that the calculated output variables correspond as accurately as possible to the output variables of the real object.
The input emission model 108 is designed to convert the signal λin, meas of the first exhaust gas sensor 32 arranged upstream of the three-way catalyst 26 as an input variable into the input variable w required for the subsequent filling level model 110 in,mod . Conversion of lambda to ternary by means of the input emission model 108O before the catalyst 26 2 、CO、H 2 And the concentration of HC, for example, is advantageous.
Using the parameters w calculated by the input emission model 108 in,mod And optionally additional input variables, for example exhaust gas or catalyst temperature T cat Mass flow of exhaust gasAnd the current maximum oxygen storage capacity of three-way catalyst 26, the filling level θ of three-way catalyst 26 in filling level and output emission model 110 mod Modeling.
In order to be able to more actually describe the charging and discharging process, three-way catalyst 26 is preferably divided by an algorithm into a plurality of successive zones or partial volumes 26.1, 26.2 in the flow direction of exhaust gas 28, and the concentration of the various exhaust gas components is determined from the reaction power of each of these zones 26.1, 26.2. These concentrations can in turn be converted into the filling levels of the individual regions 26.1, 26.2, respectively, preferably into the oxygen filling level normalized to the current maximum oxygen storage capacity.
The filling level of the individual or all zones 26.1, 26.2 can be summarized by means of suitable weighting to a total filling level, which reflects the state of the three-way catalyst 26. In the simplest case, the filling levels of all the regions 26.1, 26.2 can be weighted identically, for example, and thus an average filling level is determined. However, it is also conceivable with suitable weighting for the filling level in the small region 26.2 at the output of the three-way catalytic converter 26 to be decisive for the instantaneous exhaust gas composition downstream of the three-way catalytic converter 26, and for the filling level in this small region 26.2 at the output of the three-way catalytic converter 26 to be decisive for the development of the filling level in the region 26.1 lying upstream thereof. For simplicity, an average oxygen filling level is assumed hereinafter.
The controlled object model 100 is thus used on the one hand for at least one average oxygen filling level for the catalyst 26Modeling, the average oxygen fill level is adjusted to a nominal fill level at which the catalyst 26 is safely within the catalyst window.
Fig. 3 shows an exemplary flow of the method according to the invention for adjusting the charge of a catalyst in an exhaust system.
In a first step 200, the start-up condition of the method is monitored in the controller 16. The method is turned on when the controller 16 confirms the state of combustion, at which time transient lean combustion is performed. The short lean combustion is in the time range between 10 milliseconds and several hundred milliseconds. In this case, the short-term lean combustion results in less oxygen charge being introduced into the exhaust system and thus into the catalyst 26. The invention has the task of improving the catalytic converter cleaning after a short lean phase and of making it possible to better determine the strength of the catalytic converter cleaning to be set in this case.
At the present time, when, for example, a cylinder shutdown of the internal combustion engine 10 is requested or activated, there is a brief lean combustion process of the internal combustion engine 10. The onset of cylinder deactivation is preferably indicated by a status bit stored in the controller 16. The status bits may occupy states 0 and 1 herein. In state 0, cylinder deactivation is inactive, and in state 1 cylinder deactivation is active, and thus a brief lean combustion process is performed. If the state bit is switched to state 0 again, the cylinder deactivation is ended and there is no longer a brief lean combustion.
The controller 16 now continuously monitors the status bit and when cylinder shut-down is performed, i.e. the status bit switches to state 1, the method is turned on and continues in step 210.
In an alternative embodiment, a brief lean combustion is detected as a function of the shift. Here, status bits in the controller 16 are likewise used for recognition. In state 0 for the state gear, the gear is engaged, and in state 1, no gear is currently engaged, so a shift is performed, and there is a brief lean combustion during the shift.
If it is determined that the status bit has been switched from state 0 to state 1 by the controller 16, then the method is authorized to be started and continued in step 210.
In step 210, at time t 1 Start first time interval deltat 12 And continuously determining the actual oxygen filling level of the catalyst 26For this purpose, the catalyst model 102 with the algorithm 112 illustrated in fig. 2 is used in order to +_ for the actual oxygen filling level>Modeling.
First time point t 1 Corresponding here to the point in time of the opening from step 200.
The controller 16 now continuously monitors the state of the status bit. If the state of the state bit is changed from state 1 back to state 0, the transient lean combustion is ended. This time point is taken as time point t in the controller 16 2 Store and additionally store the determined actual oxygen filling level
The actual oxygen filling level is then fed by the controller 16And a predefinable oxygen filling level threshold S 1 A comparison is made.
If the actual oxygen filling level is determinedExceeding a predefinable oxygen filling level threshold S 1 The method continues in step 220.
If the actual oxygen filling level is determinedDoes not exceed a predefinable oxygen filling level threshold S 1 The method starts again from the head in step 200.
The second time interval Δt now starts in step 220 23 . This second time interval follows a second time point t 2 Beginning and at a third point in time t 3 And (5) ending the process.
With a second point in time t 2 At the beginning of the sequence, the signal of the second exhaust gas sensor 34 is now continuously determined and the current exhaust gas mass flow is additionally determinedAnd (5) integrating.
In a preferred embodiment, the signal of the second exhaust gas sensor 34 is the air-fuel ratio λ 2 。
The signal alternative of the second exhaust gas sensor 34 may be a voltage signal lambda U2 And/or NOx concentration NOx 2 。
Second time interval delta t 23 The design here is such that during this time interval, the second exhaust gas sensor 34 downstream of the catalyst 26 can react to oxygen introduced into the catalyst 26 when the catalyst 26 should not be able to store oxygen completely.
It is provided here that the determined duration, i.e. the third time t, is determined from the gas operating time 3 。
The gas operating time is here the time that the exhaust gas passes through the catalyst 26 in the combustion chamber of the internal combustion engine 10 until the second exhaust gas sensor 34. Typical gas operation times between the combustion chamber of the internal combustion engine 10 and the second exhaust gas sensor 34 downstream of the catalyst 26 are tens to hundreds of ms.
The gas run time depends critically on the characteristics of the catalyst 26 used, such as the length and volume of the catalyst 26, the materials used for the catalyst 26, the oxygen storage capacity of the catalyst 26, the aging of the catalyst 26, and the exhaust gas layout between the internal combustion engine 10, the catalyst 26, and the second exhaust gas sensor 24 downstream of the catalyst 26. The exhaust layout preferably refers to the spacing between these mentioned components.
In the application phase, the controller 16 therefore determines the gas operating times as a function of the different exhaust gas mass flows and stores them in the first characteristic field K 1 Is a kind of medium.
If at time t 2 Upper continuous integral exhaust mass flowExceeding the exhaust gas mass flow threshold->Then a third point in time t is determined 3 。
At the same time following the second time interval deltat 23 At least one gradient lambda is determined from the signal of the second exhaust gas sensor 34 Grad And compares it with a predefinable gradient threshold S Grad Comparison.
At least one gradient lambda Grad From the signals of the second exhaust gas sensor 34 at two different points in time. In particular, the second point in time t can be used 2 Upper and third time point t 3 Measured values of the above.
In a special embodiment, gradients can also be determined from the measured values of the signal of the second exhaust gas sensor 34 at different points in time and then summarized as an average value.
Thus, for example, for an air-fuel ratio λ as a signal of the second exhaust gas sensor 34 2 To illustrate the method. Here, the time interval Δt which can be predetermined is determined 23 Air-fuel ratio lambda at different time points 2 And from this at least one gradient lambda is determined Grad 。
If at least one gradient lambda Grad Exceeds a predefinable gradient threshold S Grad There is then an oxygen breakdown through the catalyst 26 due to the brief lean combustion process.
Here, the gradient threshold S is selected in this way Grad Such that the gradient threshold allows detection as a pair at a first time interval t 12 Oxygen breakdown by catalyst 26 for the reaction of the transient lean burn of the gas.
The gradient threshold S in the application phase for the respective second exhaust gas sensor 34 is preferably determined Grad Wherein the gradient threshold S is selected in such a way Grad So that the change in the oxygen or the oxygen content in the exhaust gas can be determined in a robust manner.
The method continues immediately in step 230.
If at least one gradient lambda Grad Does not exceed a predefinable gradient threshold S Grad The method may start or end from scratch in step 200.
In step 230, the time point t will now be 2 The actual oxygen filling level determined aboveIs set to an actual value for pre-control or regulation of fuel injection or mixture preparation. Actual oxygen filling level +.>Predefinable nominal oxygen filling level with the catalyst 26>The deviation of (2) is compensated for by the pre-control or regulation and results in a cleaning process of the catalyst 26, that is to say an oxygen-rich combustion of the internal combustion engine 10 is required. The method may then be started or ended from the beginning in step 200.
Claims (10)
1. Method for adjusting the oxygen filling level of a catalyst (26) in the exhaust gas of an internal combustion engine (10), in which method the actual oxygen filling level of the catalyst (26) is set by a catalyst model (102)Modeling, which is characterized in that,
a state of the internal combustion engine (10) is detected, in which a brief lean combustion, in particular of a few milliseconds, occurs,
in a first time interval (Deltat 12 ) During which the actual oxygen filling level of the catalyst (26) is determined
Wherein, when the actual oxygen filling levelDuring a first time interval (Deltat 12 ) When a predefinable (oxygen filling level) threshold value (c) is exceeded, a first time interval (Δt 12 ) Storing the determined actual oxygen filling level +.>And starts a second time interval (Δt 23 )，
Wherein, with the second time interval (Δt 23 ) Continuously determining a second signal downstream of the catalytic converter (26), wherein a second signal can be used to infer a value that is equal to the value obtained at the first time interval (Δt 12 ) Oxygen breakdown associated with oxygen loading determined in (c),
wherein the second time interval (Δt 23 ) The signal of the second sensor of the series (x) is used to determine at least one gradient (lambda) Grad )，
Wherein when at least one gradient (lambda Grad ) Exceeds a predefinable gradient threshold (S Grad ) At this time, a cleaning process of the catalyst (26) is started, wherein the catalyst is to be cleaned at a first time interval (Δt 12 ) Actual oxygen filling level stored at endIs set as an actual value for pre-controlling or adjusting the fuel mixture, wherein enrichment of the fuel mixture is performed.
2. The method of claim 1, wherein performing energy-dependent pre-processingAt a fixed first point in time (t 1 ) A second time point (t 2 ) Ending a predefinable first time interval (delta t 12 ) Wherein a predefinable first point in time (t) is selected as a function of a started cylinder shut-down or a started gear shift 1 ) And a second time point (t 2 ) Corresponding to the end of cylinder deactivation or the end of a shift.
3. Method according to claim 2, characterized in that the energy-dependent predetermined second point in time (t 2 ) A third time point (t 3 ) Ending the second time interval (Δt 23 ) Wherein, according to the gas operation time or according to the current exhaust gas mass flowAnd/or the aging factor of the catalyst (26) selects a predefinable third point in time (t) 3 ) Wherein the gas operation time corresponds to the time that the exhaust gas passes from the internal combustion engine of the engine through the catalyst (26) to the second exhaust gas sensor.
4. The method according to claim 1, characterized in that the first catalyst model (102) is a reaction kinetics model or an integration model, wherein, according to a first air-fuel ratio (λ) upstream of the catalyst (26) in,meas ) And/or the ageing factor of the catalyst (26) and/or the catalyst temperature (T Cat ) Determining an actual oxygen filling level of the catalyst (26)
5. The method of claim 1, wherein the second exhaust gas sensor is a second lambda sensor (34), wherein the second lambda sensor (34) determines an air-fuel ratio (lambda) downstream of the catalyst (26) 2 ) Or a voltage signal (lambda) U2 )。
6. The method according to claim 1, characterized in that the second exhaust gas sensor (34) is a NOx concentration sensor, wherein the NOx concentration sensor determines the NOx concentration (NOx) downstream of the catalyst (26) 2 ) And/or air-fuel ratio (lambda) 2 ) And/or a voltage signal (lambda) U2 )。
7. Method according to claim 1, characterized in that the state of the internal combustion engine (10) in which the brief lean combustion takes place corresponds to the duration of the gear change or the activated cylinder closure, wherein the brief lean combustion preferably takes place for between 10 and 1000 milliseconds.
8. Computer program set up to perform each step of the method according to any one of claims 1 to 7.
9. A machine-readable storage medium having stored thereon a computer program according to claim 8.
10. An electronic controller configured to perform each step of the method according to any one of claims 1 to 7.
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| DE102022210290.8 | 2022-09-28 | ||
| DE102022210290.8A DE102022210290A1 (en) | 2022-09-28 | 2022-09-28 | Method for controlling the oxygen level of a catalytic converter in the exhaust gas of an internal combustion engine |
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