Method and computing unit for adjusting a modeled reaction kinetics of a catalytic converter

Abstract

The invention relates to a method for adjusting the reaction kinetics of a reaction taking place in a catalytic converter using model-based filling level regulation. A target value of a filling level of exhaust gas components stored in the catalytic converter is predefined; the filling level of the catalytic converter is calculated using exhaust gas sensors upstream of the catalytic converter and a catalytic converter model; the composition of the air-fuel mixture is adjusted depending on the filling level such that the calculated filling level approaches the predefined target value; the difference in the signals of the exhaust gas sensors upstream and downstream of the catalytic converter is acquired; the adjustment of the composition of the air-fuel mixture depending on the filling level is deactivated; the difference in the signals of the exhaust gas sensors upstream and downstream of the catalytic converter upon deactivation of the adjustment is reacquired, and the reaction kinetics of the reaction taking place in the catalytic converter is corrected in accordance with the difference between the difference in the signals of the exhaust gas sensors upstream and downstream of the catalytic converter upon activation and deactivation of the adjustment.

Description

Technical Field

[0001] The present invention relates to a method for adjusting the modeled reaction kinetics of a catalyst, and a computing unit and a computer program for implementing the method. Background Technology

[0002] In the internal combustion engines of motor vehicles, such as diesel engines, gasoline engines, or rotary piston engines, the incomplete combustion of the air-fuel mixture produces a large number of combustion products in addition to nitrogen (N2), carbon dioxide (CO2), and water (H2O). These combustion products include at least hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). X This is subject to legal restrictions. The applicable exhaust emission limits for motor vehicles, based on current technology, can only be met using catalytic converters. Through the use of, for example, a three-way catalytic converter, the aforementioned harmful substances can be converted into relatively harmless exhaust components, such as carbon dioxide, nitrogen, and water.

[0003] For three-way catalytic converters, high efficiency is required for the simultaneous emission of HC, CO, and NO. X The conversion rate is achieved only within a narrow λ range around the stoichiometric operating point (λ=1), the so-called "catalytic converter window." To operate the catalyst within this window, λ adjustment is typically used, based on signals from λ detectors before and after the catalyst. The λ detector is used to measure the oxygen content of the exhaust gas before the catalyst to adjust the λ value. Based on this measurement, the adjustment corrects the amount of fuel supplied to the internal combustion engine. For more precise adjustment, another λ detector is used to analyze the exhaust gas after the catalyst. This signal is used for guided adjustment that overlaps with the λ adjustment before the catalyst. As the λ detector after the catalyst, abrupt-λ detectors are typically used, which have a very steep characteristic curve at λ=1 and therefore can display λ=1 very accurately.

[0004] In addition to the generally slow steering adjustment that only corrects for small deviations from λ=1, current motor control systems typically have a function that, based on large deviations from λ=1, is responsible for reaching the catalyst window more quickly again in the form of λ pre-control.

[0005] A drawback of many current regulation schemes is that they only identify cases leaving the catalyst window after the voltage of a jump-λ detector following the catalyst.

[0006] An alternative to the regulation of a three-way catalyst on the basis of the signal of a lambda probe behind the catalyst is the regulation of the average oxygen filling level of the catalyst. Since this average filling level cannot be measured, it can only be modeled by means of a path model. Such a regulation makes it possible to recognize a breakthrough that is imminent and to react to it before the breakthrough actually occurs. A corresponding model-based regulation of the filling level of the catalyst on the basis of the kinetics of the most important reactions taking place in the three-way catalyst and the oxygen storage capacity is explained in DE 10 2016 222 418 A1. The stored model parameter sets can also flow into such a model-based catalyst regulation. The storage capacity of the catalyst can also be adapted to the current operating point. Such a method is known, for example, from DE 10 2018 216 980 A1 and DE 10 2018 251 720 A1. SUMMARY

[0007] According to the application, a method for adjusting the modeled reaction kinetics of at least one reaction taking place in a catalyst with a model-based filling level regulation and a computing unit and a computer program for implementing the method are proposed. Advantageous design options are the subject of the explanations below.

[0008] Model-based regulation of the filling level of a three-way catalyst, like that explained in the already mentioned DE 10 2016 222 418 A1, represents the environment of the application. For a better understanding, its most important functions, namely the path model, the filling level pre-control, the filling level regulator and the adaptation, are therefore briefly described again here.

[0009] The path model consists, for example, of an input emission model, a catalyst model and an output lambda model.

[0010] The signal in the lambda probe before the catalyst is converted into one or more input variables for the following catalyst model by means of the input emission model. It is advantageous here to convert the signal of the lambda probe into the concentration of one or more exhaust gas components. It is advantageous, for example, to convert lambda into the concentrations of oxygen, carbon dioxide, hydrogen and hydrocarbons before the catalyst.

[0011] The catalyst model models at least one filling level of the catalyst using parameters calculated by the input emission model and, if necessary, additional input parameters such as exhaust gas temperature or catalyst temperature, exhaust gas mass flow and the current maximum oxygen storage capacity of the catalyst. In order to be able to depict the filling and emptying processes more realistically, the catalyst is preferably divided into a plurality of (axial) zones, and the concentrations of the individual exhaust gas components are obtained by means of the reaction kinetics for each of these zones. These concentrations can be converted into a filling level of the individual zones, preferably into an oxygen filling level normalized to the current maximum oxygen storage capacity, respectively. The current maximum oxygen storage capacity here depicts the oxygen storage capacity which the catalyst has at the current operating conditions when the oxygen is completely emptied from the catalyst. The filling levels of the individual or all zones can be combined into a total filling level by means of suitable weighting, which reflects the state of the catalyst. For example, in the simplest case, the filling levels of all zones can be weighted identically and the average filling level is thus obtained. However, with suitable weighting it is also possible to take into account that the filling level in the small region at the outlet of the catalyst is decisive for the current exhaust gas composition after the catalyst, while the filling level and its development in the space present are decisive for the development of the filling level in this small region at the outlet of the catalyst. For the sake of simplicity, the average oxygen filling level will be assumed in the following.

[0012] The reaction kinetics mentioned depict the temporal course of reactions taking place in the catalyst, such as the storage of oxygen in the catalyst and / or the outtake of stored oxygen in the catalyst. Other reactions, such as the oxidation of rich gas components, the reduction of nitrogen oxides, etc., can also be obtained and taken into account with corresponding reaction kinetics. Each reaction kinetics is characterized, inter alia, by a time constant which depicts the time required for a predetermined amount of material to react in a predetermined concentration of the respective reaction partner. The reaction kinetics typically depends on the temperature, so that the respective reaction kinetics to be taken into account can be stored in the memory of the controller, for example, as a characteristic curve in the form of a time constant depending on the temperature.

[0013] In order to adapt the path model, the concentrations of the individual exhaust gas components at the outlet of the catalyst calculated by means of the catalyst model are converted into signals which can be compared with the signals of the exhaust gas sensor after the catalyst. Lambda after the catalyst is preferably modeled. This modeling of the lambda value after the catalyst represents an output lambda model.

[0014] The filling level pre-control can be designed as an inversion of the path model. This has the advantage that the regulator has to intervene only if the actual filling level of the catalytic converter, which is modeled by means of the path model, deviates from the target filling level trajectory calculated by means of the pre-control. The path model converts the input lambda before the catalytic converter into the (average) oxygen filling level of the catalytic converter, while the pre-control converts the average target oxygen filling level into the corresponding target lambda before the catalytic converter.

[0015] The (average) oxygen filling level, which is modeled by means of the path model, can be calibrated to a target value which minimizes the likelihood of breakthroughs of lean or rich exhaust gas and thus causes minimal emissions. The target value is preferably pre-filtered. The pre-filtered target value for the oxygen filling level as an instruction variable is provided to the pre-control mechanism on the one hand and to the regulator on the other hand. The output signals of the pre-control mechanism and the regulator are summed. The summed signal represents the target lambda before the catalytic converter.

[0016] Since the input variables of the path model, in particular the signal of the lambda probe before the catalytic converter, are subject to uncertainties, the path model can be adapted. The pre-control mechanism and, if necessary, the regulator parameters can likewise be adapted. For example, the signal of the lambda probe after the catalytic converter is used as a basis for the adaptation. In this way, the path model is adjusted when breakthroughs of rich or lean gas occur through the catalytic converter, so that these breakthroughs are less frequent over time.

[0017] The method according to the application is used for adjusting a modelled reaction kinetics of at least one reaction taking place in a catalytic converter with model-based filling level regulation, the method comprising the following steps: predefining a target value for at least one filling level of at least one exhaust gas component which can be stored in the catalytic converter; calculating at least one filling level of the catalytic converter using a signal of an exhaust gas sensor upstream of the catalytic converter and a catalytic converter model having at least one storage capacity and at least one reaction kinetics of a reaction taking place in the catalytic converter; adjusting the composition of the air-fuel mixture as a function of the filling level such that the calculated filling level approximates the predefined target value; acquiring a difference between the detected signal of the exhaust gas sensor upstream of the catalytic converter and the detected signal of the exhaust gas sensor downstream of the catalytic converter; and deactivating the filling level-dependent adjustment of the composition of the air-fuel mixture; reacquiring the difference between the signals of the exhaust gas sensors upstream and downstream of the catalytic converter when the filling level-dependent adjustment of the composition of the air-fuel mixture is deactivated, and correcting the reaction kinetics of the at least one reaction taking place in the catalytic converter as a function of the difference between the detected signals of the exhaust gas sensors upstream and downstream of the catalytic converter when the filling level-dependent adjustment of the composition of the air-fuel mixture is activated and deactivated. The method thus enables the modelled reaction kinetics of the at least one reaction to be matched to the kinetics actually present, so that model and reality approach one another, which has a positive effect on the control and / or regulation.

[0018] For the catalytic converter model described at the outset, the kinetics of the most important reactions taking place in the catalytic converter are required. These are, for example, the adsorption of gaseous oxygen on the catalytic converter material or the oxidation of gaseous carbon monoxide with the stored oxygen. However, a plurality of or other reactions can also be taken into account. The kinetics of each of the considered reactions are acquired in the application range as a function of the catalytic converter temperature, for example the average catalytic converter temperature, and stored in the motor controller, for example in the form of temperature-dependent characteristic curves. The reaction kinetics are preferably acquired for different ageing stages of the catalytic converter, for example for a new catalytic converter and for an aged catalytic converter, and stored in the controller in the form of model parameter sets, respectively. Interpolation between the different model parameter sets can then be carried out as a function of the age of the catalytic converter.

[0019] Due to component dispersion and different aging states, deviations of the modeled reaction kinetics from the actual reaction kinetics can occur in the field over the service life of the vehicle. The result of these deviations is that the model-based regulation does not optimally set the filling level of the catalytic converter when the reaction kinetics are not only entered into the path model but also into the pre-control mechanism of the catalytic converter filling level, which is designed as an inversion of the path model. This leads to an increase in emissions. The adaptation to the path model explained at the outset, although permanently compensating for the signs of these deviations, does not compensate for their causes. If the adaptation demand becomes too high, there is a risk that the adaptation demand cannot be compensated sufficiently quickly or that an error is recorded in the error memory of the controller without authorization. For example, the controller can assume that the lambda probe before the catalytic converter is defective when the adaptation demand becomes too high. The method according to the application has the advantage that it eliminates the causes of the deviations and thus avoids the described problems by adjusting the modeled reaction kinetics.

[0020] The point is utilized in the adaptation of the reaction kinetics that deviations of the modeled reaction kinetics from the actual reaction kinetics can only be perceived when the regulation intervention for the regulation of the filling level of the catalytic converter is active, since only this regulation uses the modeled reaction kinetics. In the presence of deviations of the reaction kinetics, the correct emission-optimized filling level of the catalytic converter is not set by this regulation, but a too low or too high filling level. This leads to too rich or too lean exhaust gas lambda after the catalytic converter. The adaptation explained at the outset compensates for this by means of the jump-lambda probe after the catalytic converter, which leads to a stoichiometric exhaust gas lambda = 1 after the catalytic converter, but also to a correspondingly more lean or more rich exhaust gas lambda before the catalytic converter. The in this sense false or erroneous modeling of the reaction kinetics when the regulation intervention for the filling level regulation is active thus leads to a higher deviation between the lambda values before and after the catalytic converter.

[0021] When the regulation intervention is not active, the modeled reaction kinetics do not play a role and the mentioned higher deviation between the lambda values before and after the catalytic converter does not occur. The lambda difference that can remain is only caused by the lambda probe offset or a so-called fuel correction error that can arise due to a leak in the exhaust system. However, the inaccuracy of the modeled reaction kinetics does not contribute to this remaining lambda difference.

[0022] The method according to the application therefore provides that the difference between the lambda values measured before the catalytic converter and after the catalytic converter when the regulating intervention for adjusting the filling level of the catalytic converter is activated is compared with the difference between the lambda values measured before the catalytic converter and after the catalytic converter when the regulating intervention for adjusting is deactivated.

[0023] If the regulating scheme otherwise corresponds functionally to the model-based adapted regulating scheme explained at the outset, the difference between the lambda difference when the regulating intervention is activated and when the regulating intervention is deactivated should only be attributed to a deviation of the modeled reaction kinetics from the actual reaction kinetics. From the difference between the two lambda differences, an adaptation requirement for the modeled reaction kinetics is derived. The adaptation requirement can be learned, for example, from the characteristic curve saved in the controller as a function of the difference between the two lambda differences. The modeled reaction kinetics is thus adjusted such that the difference between the lambda differences when the regulating intervention is activated and when the regulating intervention is deactivated disappears. The modeled reaction kinetics then corresponds to the actual reaction kinetics. If, for example, the difference between the lambda differences when the regulating intervention is activated and when the regulating intervention is deactivated is positive, that is, the lambda difference when the regulating intervention is activated is greater than the lambda difference when the regulating intervention is deactivated, this indicates that (more) lean is required when the regulating intervention is activated for setting the stoichiometric exhaust-gas lambda after the catalytic converter. As a result, a more rich exhaust-gas lambda after the catalytic converter actually occurs than was intended. This indicates that the reaction kinetics for the storage of oxygen in the catalytic converter actually proceeds more quickly than corresponds to the kinetics saved in the controller. The kinetics saved in the controller for the storage of oxygen is therefore to be increased in order to adapt it to the actual kinetics. After such an adjustment of the kinetics, the lambda difference when the regulating intervention is activated coincides with the lambda difference when the regulating intervention is deactivated. If this is not the case after the first correction, the method can be implemented repeatedly.

[0024] Since the comparison is typically carried out at a specific (or currently prevailing) catalytic converter temperature, it is in particular provided that the reaction kinetics is not only adapted for this one temperature, but also scaled accordingly for other temperature support points saved in the controller.

[0025] Since a short-term (lasting a few seconds) deactivation of the regulation intervention for adjusting the catalytic converter can lead to an increase in emissions, the comparison of the lambda difference is preferably only carried out when an unexpectedly high difference between lambda before the catalytic converter and lambda after the catalytic converter is observed while the regulation intervention is active and a deviation of the modeled reaction kinetics from the actual reaction kinetics is suspected. In this case, the short-term deactivation of the regulation intervention does not lead to an increase in emissions, but rather to a decrease in emissions. The comparison is not necessary at short time intervals, since a compensation for long-term effects is involved here.

[0026] The comparison is preferably only carried out when the current operating conditions allow a reliable result of the comparison, that is to say, in particular, when there is a stable catalytic converter temperature and steady-state operating conditions of the internal combustion engine, such as rotational speed, load and exhaust gas mass flow, so that a measurement of the lambda difference with and without the regulation intervention can be carried out under the same boundary conditions.

[0027] By the adaptation of the reaction kinetics according to the application, the accuracy and robustness of the model-based regulation of the filling level of the catalytic converter is improved in situ over the service life of the vehicle. Emissions can thereby be further reduced.

[0028] It is advantageous here if the difference between the signals of the exhaust gas sensors upstream and downstream of the catalytic converter deviates from an offset value by more than a predefined difference threshold, the filling level-dependent regulation of the composition of the air-fuel mixture is deactivated. The offset value can here be zero, that is to say, a deviation between the lambda values upstream and downstream of the catalytic converter is not to be expected, or can also deviate from zero, in particular if specific operating modes require this. The deactivation can thereby only have to be carried out when a relevant demand is identified, that is to say, when the adaptation of the reaction kinetics leads to a reduction in the emission of harmful substances overall, which can generally have a negative effect on the quality of the exhaust gases emitted.

[0029] The at least one filling level advantageously depicts the currently stored amount of at least one exhaust gas component of the internal combustion engine in the catalytic converter, the exhaust gas component being selected in particular from the group consisting of oxygen, nitrogen oxides, carbon monoxide and hydrocarbons. This is a decisive exhaust gas component for the control of the catalytic converter, which influences the emission behavior overall.

[0030] In particular, the catalytic converter can be part of an exhaust gas aftertreatment device of a motor vehicle. This is an application case in which a particularly large improvement potential can be expected and in addition high legal requirements are placed on the corresponding exhaust gas aftertreatment.

[0031] Preferably, the method comprises the following steps in addition before deactivating the filling level-dependent regulation of the composition of the air-fuel mixture: comparing the expected oxygen discharge from the catalytic converter from the start of the emptying of the catalytic converter until reaching a target value of the filling level of the catalytic converter with the reacted oxygen discharge from the start of the emptying until a downstream exhaust gas sensor of the catalytic converter, and if the deviation between the two comparison variables exceeds a predefined threshold value, correcting the storage capacity of the catalytic converter model. Thereby, influences on the exhaust gas composition downstream of the catalytic converter that are not caused by the modeled reaction kinetics can already be compensated for before the adjustment of the reaction kinetics, so that the remaining influences are caused only by the reaction kinetics. Thereby, the matching of the model to the actual catalytic converter is significantly simplified and made more precise.

[0032] The computing unit according to the application, such as a controller of a motor vehicle, is in particular programmed technically for carrying out the method according to the application.

[0033] It is also advantageous to carry out the method according to the application in the form of a computer program or computer program product with program code for carrying out all the method steps, since this leads to particularly low costs, in particular if the controller used for the execution is also used for other tasks and is therefore already present. Suitable data carriers for providing the computer program are in particular magnetic memories, optical memories and electrical memories, such as for example hard disks, flash memories, EEPROMs, DVDs, etc. The program can also be downloaded via a computer network (Internet, Intranet, etc.).

[0034] Further advantages and design solutions of the application result from the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0035] The application is illustrated schematically in the drawings by means of an embodiment and described below with reference to the drawings. In which:

[0036] Figure 1 An apparatus is shown in a greatly simplified illustration, which is set up for carrying out an advantageous embodiment of the method according to the application;

[0037] Figure 2 An advantageous design solution of the method according to the application is shown in the form of a simplified flow chart. DETAILED DESCRIPTION

[0038] In Figure 1 A device 100 is shown schematically as a block diagram in which the method according to the application can be applied, which can be part of a vehicle. The device 100 is preferably set up for carrying out the method according to the application in the form of Figure 2The method 200 and the device 100 have an internal combustion engine 120, such as a gasoline engine, a catalytic converter 130, and a computing unit 140. Furthermore, the device 100 can comprise a fuel preparation device 110, such as in the form of a fuel injection pump or pumps, a turbocharger or turbochargers, or the like, or be composed of a combination thereof.

[0039] Furthermore, such a device has exhaust gas sensors 145, 147, in particular lambda probes, which are arranged in the exhaust system of the device 100 upstream and downstream of the catalytic converter 130.

[0040] The computing unit 140 controls the operation of the internal combustion engine 120, in particular by controlling the ignition timing, the valve opening times, and the composition, quantity, and / or pressure of the air-fuel mixture provided by the fuel preparation device 110.

[0041] The exhaust gas produced when the internal combustion engine 120 is operating is fed to the catalytic converter 130. Upstream of the catalytic converter 130, the air coefficient lambda of the exhaust gas is measured by means of a first lambda probe 145 and this first lambda value is transmitted to the computing unit 140. By means of the catalytic converter 130, such as a three-way catalytic converter, the reactions of the exhaust gas components with one another are accelerated or only made possible, so that harmful components, such as carbon monoxide, nitrogen oxides, and incompletely combusted hydrocarbons, are converted into relatively harmless products, such as water vapor, nitrogen, and carbon dioxide. Downstream of the catalytic converter 130, a second lambda value is acquired by means of a second lambda probe 147 and transmitted to the computing unit 140.

[0042] The first and second lambda values can temporarily or permanently differ from one another, since the composition of the exhaust gas upstream and downstream of the catalytic converter 130 differs from one another as a result of the reactions in the catalytic converter 130. Furthermore, the exhaust gas requires a certain time to flow through the catalytic converter 130 (so-called dead time). This dead time depends, in particular, on the current volume flow of the exhaust gas, that is to say on the current operating state of the internal combustion engine 120. For example, at full load operation of the internal combustion engine 120, a higher quantity of exhaust gas is produced per time unit than at idling operation. The respective dead time thus varies depending on the operating state of the internal combustion engine 120, since the volume of the catalytic converter 130 is constant.

[0043] The computing unit 140 is advantageously set up to implement a method according to a preferred embodiment of the application in Figure 2The method 200 is explained in more detail in the following. For this purpose, the catalytic converter 130 is operated in a normal operating step 210 with model-based filling level regulation, in order to control the internal combustion engine 120 for producing exhaust gases having a composition which is suitable for regulating the filling level of the catalytic converter 130 with respect to at least one exhaust gas component, in particular oxygen, in accordance with a filling level specification. Here, in particular, the measurement data of the first lambda sensor 145 described above are used in order to calculate the filling level on the basis of a filling level model. Figure 1 The filling level is calculated on the basis of a filling level model, in particular with the measurement data of the first lambda sensor 145 described above.

[0044] In a step 220, first and second lambda values are measured by means of the lambda probes 145, 147 upstream and downstream of the catalytic converter 130. This can be done not only in the context of the normal operation according to step 210, but also for adaptation purposes and / or diagnostic purposes, for example in order to adjust the catalytic converter model for the normal operation 210 or in order to determine whether the catalytic converter 130 is functioning in accordance with the specification.

[0045] In a step 230, the two acquired lambda values of the sensors 145, 147 are compared with one another and the difference between the two values is compared with an expected or acceptable offset value. If the difference between the first and second lambda values is within the range of the acceptable offset value, the method 200 can return to the normal operating step 210 and, if necessary, adjust the catalytic converter model on the basis of the measurement values.

[0046] However, if the difference between the lambda values exceeds the difference threshold value which can be predefined, the method 200 continues with a step 240 in which the filling level regulation is switched off. The lambda values upstream and downstream of the catalytic converter 130 are then determined again in a step 250 which follows immediately thereon and the difference between the first and second lambda values is acquired. The difference between the difference when the filling level regulation is active and when it is switched off is used in a step 260 to calculate an adjustment of the reaction kinetics for at least one reaction which takes place in the catalytic converter 130, for example the storage of oxygen or the reaction of oxygen out. Since these measurements can only be carried out at the temperature which currently prevails, it is expedient to specify that the reaction kinetics are also adapted for other temperatures in consideration of the respective scaling parameters. For this purpose, all saved support points of the respective temperature-dependent characteristic curve can be adjusted on the basis of the calculated adjustment of the reaction kinetics for the current temperature. It can be considered here, for example, that the respective time constant changes more strongly with increasing temperature, so that the temperature-dependent adjustment can include a compression or a lengthening and a shift of the combination of the respective characteristic curves.

[0047] If, in contrast, the storage of oxygen, for example in the catalytic converter 130, takes place faster than the degree corresponding to the stored kinetics in the control unit 140, the lean exhaust gas is actually reduced better and an exhaust gas lambda actually richer than expected downstream of the catalytic converter 130, since the model-based regulation 210 of the catalytic converter 130 starts from the stored kinetics. This deviation of the exhaust gas lambda actually measured after the catalytic converter 130 from the expected (typically stoichiometric) exhaust gas lambda is a measure for the deviation of the actual kinetics from the stored kinetics. The conversion of the lambda difference into a correction factor for the kinetics can take place, for example, by means of a correction characteristic. In the present example, the time constant for the storage of oxygen is reduced due to the rich lambda deviation of the exhaust gas lambda in the stored kinetics. Similarly, an actually faster removal of oxygen would lead to a better oxidation of the rich exhaust gas and to a leaner exhaust gas lambda. Likewise, if the respective slower reaction speed is indicated due to the difference of the lambda values upstream and downstream of the catalytic converter, the adaptation of the kinetics can of course include a respective increase of the time constant.

[0048] Since other effects independent of the reaction kinetics can also lead to a deviation of the actual lambda value after the catalytic converter from the expected lambda value (such as a tolerance of the lambda sensor before the catalytic converter), an adaptation of the reaction kinetics is not advantageous in such cases. In order to distinguish between the different causes, the difference of the lambda values when the regulation intervention for the model-based regulation 210 of the catalytic converter 130 is active in step 220 and when the regulation intervention for the model-based regulation of the catalytic converter is not active in step 250 is detected. Only the difference between the two differences can be caused by the catalytic converter model not reflecting the real reaction kinetics.

[0049] After the adaptation of the stored reaction kinetics in step 260, the method returns to the normal operation step 210 and reactivates the filling level regulation of the catalytic converter 130.

[0050] It goes without saying that some of the explained steps can also be combined or, if necessary, can be carried out in other, for example reversed, order. It can be necessary for a specific diagnostic function, for example, to deactivate the filling level regulation of the catalytic converter. If such a function is carried out, the difference of the lambda values when the regulation intervention for the filling level regulation is not active can of course also be acquired first before the difference when the regulation intervention is active is acquired. Furthermore, the acquisition of the measured values and the judgment of whether the threshold values are exceeded by the measured values or by the quantities derived therefrom can be combined into a single step, for example. Figure 2 It goes without saying that some of the explained steps can also be combined or, if necessary, can be carried out in other, for example reversed, order. It can be necessary for a specific diagnostic function, for example, to deactivate the filling level regulation of the catalytic converter. If such a function is carried out, the difference of the lambda values when the regulation intervention for the filling level regulation is not active can of course also be acquired first before the difference when the regulation intervention is active is acquired. Furthermore, the acquisition of the measured values and the judgment of whether the threshold values are exceeded by the measured values or by the quantities derived therefrom can be combined into a single step, for example.

Claims

1. A method (200) for adjusting the modeled reaction kinetics of at least one reaction carried out in a catalyst (130) using model-based fill level adjustment (210), the method comprising: A target value is given in advance for at least one fill level of at least one exhaust gas component that can be stored in the catalyst; The at least one fill level of the catalyst is calculated using the signal from the exhaust sensor (145) upstream of the catalyst (130) and a catalyst model having at least one storage capacity and at least one reaction kinetics in the catalyst (130). The composition of the air-fuel mixture is adjusted according to the fill level so that the calculated fill level is close to the pre-given target value; Obtain (220) the difference between the signal detected by the exhaust sensor (145) upstream of the catalyst (130) and the signal detected by the exhaust sensor (147) downstream of the catalyst (130); and (240) Deactivate (250) the fill level-dependent adjustment of the air-fuel mixture composition; re-acquire (250) the difference between the signals of the upstream and downstream exhaust sensors (145, 147) of the catalyst (130) when the fill level-dependent adjustment of the air-fuel mixture composition is deactivated, and correct (260) the reaction kinetics of the at least one reaction in the catalyst (130) according to the difference between the detected signals of the upstream and downstream exhaust sensors of the catalyst when the fill level-dependent adjustment of the air-fuel mixture composition is activated and deactivated.

2. The method (200) according to claim 1, wherein if the difference between the signals of the upstream and downstream exhaust sensors (145, 147) of the catalyst (130) and the offset value differ (230) from a predetermined difference threshold, then the adjustment of the air-fuel mixture composition dependent on the fill level is deactivated (240).

3. The method (200) according to claim 1 or 2, wherein the at least one fill level describes the amount of at least one exhaust gas component of the internal combustion engine (120) currently stored in the catalyst (130).

4. The method (200) according to claim 1 or 2, wherein the exhaust gas components are selected from the group consisting of oxygen, nitrogen oxides, carbon monoxide and hydrocarbons.

5. The method (200) according to claim 1 or 2, wherein the catalyst (130) is part of an exhaust aftertreatment device for a motor vehicle.

6. The method (200) according to claim 1 or 2, further comprising the following steps before discontinuing (240) the adjustment of the composition of the air-fuel mixture depending on the fill level: The anticipated oxygen emission from the catalyst from the start of purging until the target fill level is reached is compared with the oxygen emission from the start of purging until the reaction at the downstream exhaust sensor (147) of the catalyst (130). If the deviation of the comparison exceeds a pre-given threshold, the storage capacity of the catalyst model is corrected.

7. The method (200) according to claim 1 or 2, wherein the correction (260) for the reaction kinetics includes correction of the time constants of the at least one reaction carried out in the catalyst (130) for at least two different temperatures.

8. The method (200) according to claim 1 or 2, wherein the correction (260) for the reaction kinetics is performed such that there is no difference between the signals of the exhaust sensors (145, 147) upstream and downstream of the catalyst (130) when the adjustment of the composition of the air-fuel mixture depending on the fill level is subsequently activated or deactivated.

9. A calculation unit (140) configured to implement all method steps of the method (200) according to any one of claims 1 to 8.

10. A computer program product which, when executed on a computing unit (140), causes the computing unit (140) to perform all the method steps of the method (200) according to any one of claims 1 to 8.

11. A machine-readable storage medium having a computer program stored thereon, which, when executed on a computing unit (140), causes the computing unit (140) to perform all the method steps of the method (200) according to any one of claims 1 to 8.

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