Method for operating a drive device for a motor vehicle and corresponding drive device

Abstract

The invention relates to a method for operating a drive device (1) for a motor vehicle, which drive device has a drive unit (2) which generates exhaust gas and has a plurality of combustion chambers, and has a lambda probe (5) for measuring an actual combustion air ratio in the exhaust gas, wherein the drive unit (2) is operated with a fuel-air mixture the composition of which is set to a desired combustion air ratio and wherein a total concentration of an exhaust gas component of the exhaust gas is determined for the actual combustion air ratio. According to the invention, the total concentration is corrected using combustion-chamber-specific values for the actual combustion air ratio. The invention also relates to a drive device (1) for a motor vehicle.

Description

[0001] AUDI AG P22860 _____________________________________________________________ Method for operating a drive device for a motor vehicle and corresponding drive device _____________________________________________________________ DESCRIPTION: The invention relates to a method for operating a drive device for a motor vehicle, which drive device has a drive unit that generates exhaust gas and has a plurality of combustion chambers and a lambda probe for measuring an actual combustion air ratio in the exhaust gas, wherein the drive unit is operated with a fuel-air mixture whose composition is adjusted to a target combustion air ratio based on the measured actual combustion air ratio, and wherein a total concentration of an exhaust gas component of the exhaust gas is determined for the actual combustion air ratio. The invention further relates to a drive device for a motor vehicle.For example, US Pat. No. 10,865,721 B1 is known from the prior art. This describes a method comprising the following steps: diagnosing a torque imbalance in a multi-cylinder engine while the engine is operating at a lean air-fuel ratio in response to determining that an amount of ammonia stored in a selective catalytic reduction system is greater than a threshold amount and a temperature of the engine is greater than a threshold temperature; and, in response to the torque imbalance, adjusting fuel delivery based on a deviation in the air-fuel ratio of each cylinder determined while adjusting the lean air-fuel ratio.The object of the invention is to propose a method for operating a drive device for a motor vehicle which has advantages over known methods, in particular ensures precise determination of the total concentration of the exhaust gas component. This is achieved according to the invention with a method for operating a drive device for a motor vehicle with the features of claim 1. It is provided that the total concentration is corrected using combustion chamber-specific values ​​for the actual combustion air ratio. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims. It is pointed out that the exemplary embodiments explained in the description are not restrictive; rather, any variations of the features disclosed in the description, the claims and the figures can be implemented.The drive device serves to drive the motor vehicle, i.e. to provide a drive torque directed towards driving the motor vehicle. To provide the drive torque, the drive device has the drive unit. During operation of the drive device, fuel and fresh gas are supplied to the drive unit at least temporarily, wherein the fresh gas at least temporarily contains fresh air. In addition, the fresh gas can comprise exhaust gas, provided that exhaust gas recirculation is implemented, in which the exhaust gas generated by the drive unit is at least partially recirculated to the drive unit, namely as a component of the fresh gas. The fuel and the fresh gas supplied to the drive unit form a fuel-fresh gas mixture with a specific composition, which is reacted in the drive unit.The reaction takes place in the multiple combustion chambers of the drive unit, in particular with a time delay. The combustion chambers are located in multiple cylinders of the drive unit, each of the combustion chambers being delimited by a cylinder wall of the respective cylinder, a cylinder roof of the respective cylinder, and a piston displaceably arranged in the respective cylinder. In this case, the drive unit is an internal combustion engine, more precisely a reciprocating piston engine. During operation of the drive unit, the chemical reaction between fuel and fresh gas produces exhaust gas, which is discharged towards the outside environment of the drive device or motor vehicle. The exhaust gas produced in each of the multiple combustion chambers is combined before being released into the outside environment, preferably by means of at least one exhaust manifold.Since the exhaust gas generated by the drive unit contains pollutants, the exhaust gas is preferably first fed to an exhaust gas aftertreatment device before being released into the outside environment. In the exhaust gas aftertreatment device, the pollutants are at least partially converted into less hazardous products. Only after passing through the exhaust gas aftertreatment device is the exhaust gas discharged into the outside environment. The exhaust gas aftertreatment device is present, for example, as a vehicle catalytic converter, in particular as a three-way catalytic converter, oxidation catalytic converter, NOx storage catalytic converter, or SCR catalytic converter. However, it can also be designed as a particulate filter, in particular as a gasoline particulate filter or as a diesel particulate filter, preferably with an integrated vehicle catalytic converter, for example with a catalytic coating.The conversion rate and thus the conversion efficiency of the exhaust gas aftertreatment system, with which the pollutants are converted into less hazardous products, depend in particular on the composition of the exhaust gas fed to the exhaust gas aftertreatment system and / or on the oxygen load of the exhaust gas aftertreatment system, which in turn is related to the composition of the exhaust gas. It is therefore important to determine the composition of the exhaust gas generated by the drive unit with high accuracy, in particular in order to draw conclusions about the conversion efficiency of the exhaust gas aftertreatment system and / or to determine the composition of the exhaust gas released into the outside environment. For this purpose, a computational model of the exhaust gas aftertreatment system is preferably used, to which the total concentration of the exhaust gas component present upstream of the exhaust gas aftertreatment system is fed.The calculation model uses the total concentration to calculate the concentration of at least one pollutant in the exhaust gas downstream of the exhaust gas aftertreatment device. If this concentration exceeds a threshold value, for example, an error signal is generated or the drive unit is stopped, in particular by interrupting the fuel supply to the drive unit. The concentration of the exhaust gas component thus serves, at least indirectly, to control the drive unit. It is also important to determine the concentration with high accuracy in order to reliably detect and, if necessary, prevent any escape of the pollutant into the outside environment. For the purposes of this description, the concentration(s) is / are specified as a molar mass ratio or as parts per million (ppm).The total concentration of the exhaust gas component to be determined is considered downstream of the drive unit or - if the exhaust gas aftertreatment device is present - in terms of flow between the drive unit and the exhaust gas aftertreatment device, in particular with respect to a main flow direction of the exhaust gas. The total concentration of the exhaust gas component corresponds to its concentration in the raw emissions of the drive unit, i.e. in the exhaust gas immediately after it is expelled from the drive unit, in particular before passing through the exhaust gas aftertreatment device. However, the total concentration is present in the already combined exhaust gas, i.e. downstream of a point at which the exhaust gas from the multiple combustion chambers is combined. Particularly preferably, the exhaust gas component is one of several exhaust gas components for which the respective total concentration is determined.In particular, the total concentrations of several exhaust gas components are determined, namely in each case in the manner described. In principle, the total concentration of the exhaust gas component could of course be measured using a corresponding sensor. However, this is often not practical, particularly if the total concentrations of several exhaust gas components are to be determined and a separate sensor cannot be provided for each exhaust gas component. For this reason, the total concentration of the exhaust gas component should be determined based on the actual combustion air ratio, in particular based on the combustion air ratio upstream of the exhaust gas aftertreatment device. It should be noted here that the total concentration of the exhaust gas component of the exhaust gas is determined jointly for all combustion chambers of the drive unit.The total concentration therefore describes the concentration of the exhaust gas component not for an individual combustion chamber, but for all combustion chambers together. The total concentration is therefore the concentration of the exhaust gas component in the combined exhaust gas from all combustion chambers. The actual air-to-fuel ratio is measured using the lambda probe. This serves to measure the air-to-fuel ratio present in the exhaust gas, preferably upstream of the exhaust gas aftertreatment device, in particular by measuring the residual oxygen content of the exhaust gas, from which the actual air-to-fuel ratio is then determined. The measured actual air-to-fuel ratio preferably serves not only to determine the total concentration of the exhaust gas component, but also to carry out lambda control, by means of which the composition of the fuel-air mixture with which the drive unit is operated is adjusted.For this purpose, the actual combustion air ratio is set to the target combustion air ratio, preferably regulated to the target combustion air ratio, namely by adjusting the composition of the fuel-air mixture. First, the total concentration of the exhaust gas component of the exhaust gas for the actual combustion air ratio is determined. This is done, for example, by reading the total concentration for the current actual combustion air ratio from a memory. The total concentration of the exhaust gas component for different values ​​of the actual combustion air ratio is stored in the memory. The memory is, for example, part of a control unit of the drive device or the drive unit. The total concentration for the different values ​​of the actual combustion air ratio is preferably stored in the memory in a fixed or unchangeable manner.However, the applicant has determined through investigations that the total concentration can be determined with good accuracy in this way if the drive unit is operating completely uniformly, i.e. if the combustion of the fuel-air mixture in the combustion chambers is completely uniform. However, this is not the case, at least temporarily, and the values ​​for the actual combustion air ratio for each combustion chamber deviate from one another. This means that for at least one of the combustion chambers, the actual combustion air ratio in that combustion chamber deviates from the actual combustion air ratio in the other combustion chambers. Since the actual combustion air ratio is set to the target combustion air ratio, even with the combustion chamber-specific deviation from the actual combustion air ratio, the actual combustion air ratio in the exhaust gas overall corresponds to the target combustion air ratio.However, in one of the combustion chambers, a value for the actual combustion air ratio is present which is smaller, while for another of the combustion chambers, a larger, combustion-chamber-specific value is present. For this reason, it is provided to correct the previously determined total concentration for the exhaust gas component, namely by using the combustion-chamber-specific values ​​for the actual combustion air ratio. This can further improve the accuracy of the total concentration. A further development of the invention provides that the combustion-chamber-specific values ​​for the actual combustion air ratio are determined based on rough running of the drive unit or by leaning out the fuel-air mixture until a misfire threshold is reached. During operation of the drive unit, the rough running is thus determined, and from this, the combustion-chamber-specific values ​​are deduced using the measured actual combustion air ratio.The rough running results, for example, from a torque component of the drive torque provided during expansion of the respective combustion chamber. Preferably, a speed of a crankshaft or a drive shaft of the drive unit is measured, and fluctuations in the speed or a gradient of the speed over time are used to determine the rough running and thus the combustion chamber-specific values ​​for the actual combustion air ratio. This can utilize the fact that the combustion chamber-specific values ​​are on average equal to the measured actual combustion air ratio and thus also to the target combustion air ratio. Alternatively, the fuel-air mixture in each of the combustion chambers can be individually leaned out until the misfire threshold is reached, i.e., until at least one misfire occurs in the respective combustion chamber.Based on the extent of leaning achieved until the misfire threshold is reached, the combustion chamber-specific value for the actual combustion air ratio before leaning can be determined. Overall, the combustion chamber-specific values ​​for the actual combustion air ratio can be determined with good accuracy in the manner described. A further development of the invention provides that the total concentration is determined by reading a concentration value stored for the actual combustion air ratio or by reading a concentration value stored for a fixed combustion air ratio independently of the actual combustion air ratio and subsequently correcting it based on the actual combustion air ratio. This has already been pointed out in principle.For example, the total concentration is stored in the form of the concentration value for different actual combustion air ratios or different values ​​of the actual combustion air ratio. Based on the measured actual combustion air ratio, the total concentration of the exhaust gas component is read out. Since the drive unit is usually operated with a constant target combustion air ratio, for example a target combustion air ratio of λ = 1, the concentration value can be stored in a relatively small data memory. In principle, however, the described procedure is also applicable for different actual combustion air ratios; in this case, however, a larger memory is required. The total concentration corresponds to the read-out concentration value.In order to be able to determine the total concentration precisely even with a small data memory, it is alternatively provided that the concentration value is only stored for a fixed combustion air ratio, in particular only for a single combustion air ratio. The concentration value is available, for example, as the output variable of a mathematical relationship, a table or a characteristic map in which it is stored. As an input variable for the mathematical relationship, the table or the characteristic map, in particular at least one operating variable of the drive device or the drive unit is used. One such operating variable is, for example, the operating point of the drive unit, which is characterized in particular by the torque currently provided by the drive unit and / or a current speed of the drive unit. Particularly preferably, several input variables are used.The input variable(s), or their number, is selected in particular such that the stored concentration value, and thus also the read-out concentration value, corresponds with high accuracy to the actual concentration value present in the exhaust gas for the fixed combustion air ratio. Therefore, if the actual combustion air ratio measured in the exhaust gas is equal to the fixed combustion air ratio for which the concentration value is stored, the stored concentration value corresponds with high accuracy to the actual concentration value present in the exhaust gas, in particular with a deviation of no more than 1%, no more than 0.5%, or no more than 0.1%.Particularly preferably, at least the operating point, i.e. at least the torque currently provided by the drive unit and / or the current speed of the drive unit, is used as the input variable, so that the read-out concentration value is available as a function of this. Since the concentration value is only stored for the fixed combustion air ratio, for example for a combustion air ratio of λ = 1, and an actual combustion air ratio that deviates from the fixed combustion air ratio can also occur during operation of the drive device, it is necessary to correct the read-out concentration value depending on the measured actual combustion air ratio. In this case, the read-out concentration value is adjusted in such a way that the read-out concentration value is adjusted in the direction of the concentration value actually present in the exhaust gas.Ideally, the concentration value thus corrected corresponds to the concentration value actually present in the exhaust gas with a high degree of accuracy, i.e. again with an error of at most 1%, at most 0.5%, or at most 0.1%. Preferably, the correction is carried out in such a way that a correction value is determined from the actual combustion air ratio, which is used to correct the read-out concentration value. The total concentration corresponds to the corrected concentration value. The determination of the correction value is preferably carried out analogously to the procedure explained below for determining the correction value for correcting the combustion chamber concentrations. The described procedure enables reliable control of the drive unit depending on the total concentration of the exhaust gas component or the (corrected) concentration value.In particular, based on the determined total concentration and, above all, with the aid of the corrected total concentration, the aforementioned calculation model of the exhaust gas aftertreatment device can be operated with high accuracy, so that the concentration of at least one pollutant downstream of the exhaust gas aftertreatment device is also known with high accuracy. The drive device or drive unit is operated as a function of the pollutant concentration, i.e., at least indirectly as a function of the concentration of the exhaust gas component present downstream of the drive unit and / or upstream of the exhaust gas aftertreatment device or the corrected concentration value.This ensures that the total concentration of at least one pollutant always falls below a certain threshold value, thus ensuring adequate aftertreatment of the exhaust gas by the exhaust gas aftertreatment device. A further development of the invention provides that the corrected total concentration is determined from combustion chamber concentrations determined for the combustion chambers, which are calculated from the uncorrected total concentration and corrected using the cylinder-specific values. First, the respective combustion chamber concentrations are determined for each of the combustion chambers, namely from the uncorrected total concentration. The combustion chamber concentrations are then corrected using the cylinder-specific values. The corrected total concentration is then calculated from the corrected combustion chamber concentrations.This procedure enables a high degree of accuracy in the corrected total concentration. A further development of the invention provides for the calculation of the combustion chamber concentrations from the uncorrected total concentration based on a number of combustion chambers. It is assumed that, particularly during stationary operation of the drive unit, the combustion chamber concentrations for the combustion chambers are identical. They correspond to the uncorrected total concentration divided by the number of combustion chambers in the drive unit. This also serves to achieve a high degree of accuracy.A further development of the invention provides that the correction of the combustion chamber concentrations for an exhaust gas component present as an oxygen input component is carried out by multiplying by a correction value calculated from the actual combustion air ratio and / or for an exhaust gas component present as an oxygen discharge component by dividing by the correction value. The correction value is determined in such a way that it is also greater than one for a combustion air ratio greater than one and also less than one for a combustion air ratio less than one. The correction of the combustion chamber concentrations is based on the assumption that for lean exhaust gas, i.e. for a combustion air ratio greater than one, the concentration of an exhaust gas component to be reduced changes proportionally to a specific coefficient over the actual combustion air ratio.Conversely, it is assumed that the concentration of an exhaust gas component to be oxidized changes inversely proportional to the same coefficient across the actual combustion air ratio. Accordingly, in the rich range, i.e., for a combustion air ratio of less than one, the concentration of an exhaust gas component to be reduced changes inversely proportional to the determined coefficient across the actual combustion air ratio, and the concentration of a component to be oxidized changes proportionally to the same coefficient. If the concentrations of several exhaust gas components are determined, the respective combustion chamber concentration for each of the several exhaust gas components is corrected using the measured actual combustion air ratio, namely by multiplying by the correction value or by dividing by the correction value determined from the measured actual combustion air ratio.This means that the same correction value is used to correct the combustion chamber concentrations of the multiple exhaust gas components. For each determination of the combustion chamber concentrations of the multiple exhaust gas components, the correction value is preferably calculated only once from the measured actual combustion air ratio and subsequently used to correct all combustion chamber concentrations to be determined for this measured actual combustion air ratio. This makes it possible to determine the combustion chamber concentrations and total concentrations of the multiple exhaust gas components with little computational effort yet with high accuracy. For the total concentration of each exhaust gas component, either the relationship ^ applies. ^ ^ 1 ^^ if the exhaust gas component is present as an oxygen input component or the relationship ^ ^^ 1 if the exhaust gas component is present as an oxygen exhaust component. Here, n denotes the number of combustion chambers, i an index, x i the correction value for the combustion chamber with the index i, ζ0 the uncorrected total concentration and ζ1 the corrected total concentration. Assuming that half of the combustion chambers are operated substoichiometrically and the other half overstoichiometrically, these relationships can be 1 ^ 1 1 ^^ 1 2 ^ ^^ + 1where x is determined from the deviation of the combustion chamber-specific values ​​of the actual combustion air ratio from the target combustion air ratio. The basis for this is that when the drive unit is operated at an actual combustion air ratio corresponding to the target combustion air ratio, the combustion chamber-specific values ​​correspond on average to the target combustion air ratio. This means in particular that with a target combustion air ratio of one, one half of the combustion chambers are operated substoichiometrically while the other half are operated overstoichiometrically. A further development of the invention provides that the correction value is calculated from the measured actual combustion air ratio using a polynomial relationship.A mathematical relationship exists between the correction value and the measured actual combustion air ratio, and the correction value is calculated from the measured actual combustion air ratio using this mathematical relationship. The mathematical relationship is a polynomial, in particular a polynomial with an order of at least two. This achieves a high degree of accuracy for the correction value and, accordingly, the corrected combustion chamber concentrations. A further development of the invention provides that the correction value is calculated using the relationship ^. ^ 2 − 0,42 ^ ^^ − or using the relationship ^ ^ 2 +0.42 − 0.42 ^^^^ ^^ − ^^ = 0, where x is the correction value, λ is the actual combustion air ratio, and k is a coefficient. The actual combustion air ratio can basically be calculated using the relationship ^^2 ^^ ^^2 + 2 ^^ ^^ ^^2 + ^^ ^^2 ^^ + ^^ ^^ ^^ + ^^ ^^ ^^ + 2 ^^ ^^2 can be calculated, where Cx describes the concentration of the respective exhaust gas component, particularly as a molar mass ratio or as parts per million (ppm). In the index x, O2 stands for molecular oxygen, CO2 for carbon dioxide, H2O for water, CO for carbon monoxide, NO for nitrogen monoxide, NO2 for nitrogen dioxide, H2 for molecular hydrogen, C3H6 for propene, and C3H8 for propane. The numerator contains all oxygen input components, and the denominator contains all oxygen output components. For an actual combustion air ratio around one or equal to one, the sum of the molar fractions of carbon dioxide and water, or the sum of their concentrations, is 0.42 (given as a molar mass ratio). The relationship can therefore be written as ^^ = 2 ^^ ^^2 + ^^ ^^ ^^ + ^^ ^^ ^^ + 2 ^^ ^^ ^^2 + 0.42 2 ^^ ^^ ^^ + ^^ ^^2 + 9 ^^ ^^3 ^^6 + 10 ^^ ^^3 ^^8 + 0.42. Alternatively, the sum of the molar fractions of carbon dioxide and water can be expressed as ppm. Then the value in the respective relationship changes from 0.42 to 420,000. Summarizing the concentrations of the oxygen input components and the concentrations of the oxygen output components, this relationship can thus be expressed as ^ ^ = ^^ ^^, ^^ ^^ ^^ + 0.42^^ ^^, ^^ ^^ ^^ + 0.42, where CO,in represents the sum of the concentrations of the oxygen input components and CO,out represents the sum of the concentrations of the oxygen output components. The relationships here are therefore ^^^^, ^^ ^^ ^^= 2 ^^ ^^2 + ^^ ^^ ^^ + ^^ ^^ ^^ + 2 ^^ ^^ ^^2 and ^^^^, ^^ ^^ ^^= 2 ^^ ^^ ^^ + ^^ ^^2 + 9 ^^ ^^3 ^^6 + 10 ^^ ^^3 ^^8to be taken into account. Since, for the actual combustion air ratio around or equal to one, the sum of the molar fractions or concentrations of the oxygen input components agree to within a few percent with the sum of the molar fractions or concentrations of the oxygen output components, the concentrations of the oxygen input components can be transferred from the numerator to the denominator, so that the relationship 0 ,42 ^^ = 0.42 − ^^ ^^, ^^ ^^ ^^ + ^^ ^^, ^^ ^^ ^^. Using the mentioned correction value, the relationship 0 ,42 ^^ = 0.42 − ^^ ^^ + ^^ / ^^, where ^^ = ^^^^, ^^ ^^ ^^ and x is the correction factor. The relationship can be converted into the quadratic equation ^ ^ 2 − 0,42 ^ ^^ − This in turn can be solved using the pq formula, where for any quadratic equation ^^ 2 + ^^ ^^ + ^^ = 0 the solution 2 In this case, the solution can be given as 2 be expressed, since the negative solution is not physically meaningful. Alternatively, from the already known relationship ^^ =^^ ^^, ^^ ^^ ^^ + 0.42 ^^ ^^, ^^ ^^ ^^ + 0.42the relationship ^^ =^^ ^^, ^^ ^^ ^^ ^^ + 0.42^^ ^^, ^^ ^^ ^^ / ^^ + 0.42 can be derived. From this, by transforming ^ ^ = ^^ ^^, ^^ ^^ ^^ ^^2 + 0.42 ^^ ^^ ^^, ^^ ^^ ^^ + 0.42 ^^and subsequently this can be written by further rearranging as ^^ ^^^^, ^^ ^^ ^^+ 0.42 ^^ ^^ = ^^^^, ^^ ^^ ^^^^ 2 + 0.42 ^^. Since for a combustion air ratio of one ^^ = ^^^^, ^^ ^^ ^^= ^^^^, ^^ ^^ ^^ holds, the relationship can be defined as ^ ^ 2 0.42−0.42 ^^ ^^ − ^^ This, in turn, can be solved using the pq formula. The described relationships enable the correction value and consequently the corrected concentration value to be determined with high accuracy. A further development of the invention provides that the coefficient is determined from a concentration of at least one oxygen input component for the actual combustion air ratio or for the fixed combustion air ratio. The coefficient is therefore not constant, but changes, in particular, depending on the operating variable of the drive device or the drive unit, preferably depending on the operating point.The concentration of the at least one oxygen input component is thus stored, as is the total concentration of the at least one exhaust gas component, and is read out for the actual combustion air ratio measured by the lambda probe or—alternatively—for the fixed combustion air ratio independently of the actual combustion air ratio. Of course, it can be provided that the oxygen input component corresponds to the at least one exhaust gas component. The coefficient is preferably calculated based on the relationship ^^ = ^^^^, ^^ ^^ ^^= 2 ^^. ^^2 + ^^ ^^ ^^ + ^^ ^^ ^^ + 2 ^^ ^^ ^^2determined and thus as a function of the concentrations of the exhaust gas components molecular oxygen, carbon monoxide, nitrogen monoxide and nitrogen dioxide. The described procedure enables a particularly precise determination of the coefficient and consequently the corrected combustion chamber concentrations. The stated concentrations or alternatively the coefficient are stored for the actual combustion air ratio or the fixed combustion air ratio and are read out, in particular depending on the same variable or variables as the concentration value, for example the operating point. A further development of the invention provides that one of the following components is used as the oxygen input component: oxygen, carbon dioxide, water and nitrogen oxide.The oxygen input component is understood to be a component that contains oxygen and can release oxygen in the exhaust gas aftertreatment device. The oxygen is preferably present in molecular form. The carbon oxide is in particular carbon monoxide or carbon dioxide. The nitrogen oxide, on the other hand, is understood to be nitrogen monoxide or nitrogen dioxide. Preferably, both carbon monoxide and carbon dioxide and / or both nitrogen monoxide and nitrogen dioxide are used as oxygen input components. Particularly preferably, several of the aforementioned components, in particular all of the aforementioned components, are used as oxygen input components, so that in total oxygen, carbon monoxide, carbon dioxide, water, nitrogen monoxide and nitrogen dioxide form the oxygen input components.The use of the components mentioned enables the total concentration of at least one exhaust gas component to be determined with high accuracy and in the simplest possible manner. The concentrations of carbon dioxide and water can be summarized in a simplified manner as explained. A further development of the invention provides that one of the following components is used as the oxygen removal component: carbon oxide, hydrogen, hydrocarbon and water. The oxygen removal component is a component that can remove oxygen from the exhaust gas aftertreatment device, for example, oxidize it as it passes through the exhaust gas aftertreatment device and / or remove the oxygen it itself has introduced into the exhaust gas aftertreatment device from it again. As already explained, carbon oxide is to be understood as carbon monoxide or carbon dioxide.The hydrocarbon corresponds, for example, to a specific hydrocarbon or to different hydrocarbons. For example, propene (C3H6) or propane (C3H8) can be used as the hydrocarbon. For example, only one of the named components is used as the oxygen removal component. However, several or even all of the named components are preferably used, i.e., a total of carbon oxide, carbon dioxide, hydrogen, one or more hydrocarbons, and water. Propene and propane are particularly used as hydrocarbons. This procedure again results in a high degree of accuracy for the total concentration of the exhaust gas component. A further development of the invention provides for a broadband lambda sensor to be used as the lambda sensor. The broadband lambda sensor enables the residual oxygen content or the corresponding lambda value to be detected over a wider measuring range.The lambda sensor or the broadband lambda sensor is used to carry out lambda control and accordingly to adjust the composition of the fuel-fresh gas mixture supplied to the drive unit. Particularly preferably, in addition to the lambda sensor, there is another lambda sensor, namely downstream of the exhaust gas aftertreatment device. The additional lambda sensor can be a step-change lambda sensor. The step-change lambda sensor has a narrower measuring range than the broadband lambda sensor; in particular, it is used (only) to detect a lambda value of one. However, the measuring accuracy of the step-change lambda sensor is higher than that of the broadband lambda sensor. Deviations and errors in the broadband lambda sensor are at least partially compensated for by means of a trim control or by using the step-change lambda sensor.This allows the composition of the fuel-fresh gas mixture to be adjusted with high precision. A further development of the invention provides that the corrected total concentration is used as an input variable for a computer model of an exhaust gas aftertreatment device, which delivers at least a concentration of at least one pollutant downstream of the exhaust gas aftertreatment device as an output variable, wherein an error signal is generated if the concentration of the at least one pollutant exceeds a threshold value. The computer model of the exhaust gas aftertreatment device has already been mentioned. This serves to determine the concentration of the at least one pollutant downstream of the exhaust gas aftertreatment device, i.e. in the exhaust gas that is subsequently discharged into the outside environment. The corrected total concentration is fed to the computer model as an input variable.The calculation model provides the concentration of at least one pollutant as an output variable. Such calculation models are generally assumed to be known. If the concentration of at least one pollutant exceeds the threshold value, the error signal is generated. The error signal comprises, for example, a visual display in the interior of the motor vehicle, preferably on a vehicle instrument panel. Additionally or alternatively, it may be provided to throttle the power of the drive unit, i.e., to limit maximum power, or to deactivate the drive unit completely.For example, it is provided to accumulate the concentration of at least one pollutant over a distance traveled by the motor vehicle or over time, and to implement at least one or more of the aforementioned measures if the threshold value is exceeded by the accumulated concentration within a specific distance or within a specific time interval. This effectively prevents the pollutant from being released into the outside environment in excessive quantities. The calculation model is preferably used to determine the concentrations of several pollutants, with the comparison being made with a respective threshold value for several of these pollutants or for all pollutants.The invention further relates to a drive device for a motor vehicle, in particular for carrying out the method according to the explanations in the context of this description, wherein the drive device has a drive unit that generates exhaust gas and has a plurality of combustion chambers and a lambda probe for measuring an actual combustion air ratio in the exhaust gas, wherein the drive device is provided and designed to operate the drive unit with a fuel-air mixture whose composition is adjusted to a target combustion air ratio based on the measured actual combustion air ratio, and wherein a total concentration of an exhaust gas component of the exhaust gas is determined for the actual combustion air ratio. The drive device is further provided and designed to correct the total concentration using combustion chamber-specific values ​​for the actual combustion air ratio.The advantages of such a design of the drive direction or such a procedure have already been pointed out. Both the drive device and the method for its operation can be further developed in accordance with the explanations in this description, so that reference is made to these in this regard. The features and combinations of features described in the description, in particular the features and combinations of features described in the following description of the figures and / or shown in the figures, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also to be regarded as encompassed by the invention which are not explicitly shown or explained in the description and / or the figures, but which arise from or can be derived from the explained embodiments.The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without this being a limitation of the invention. Figure 1 shows a schematic representation of a drive device for a motor vehicle, and Figure 2 shows several diagrams in which an actual combustion air ratio, a correction value determined from the actual combustion air ratio and the total concentrations of several exhaust gas components in the exhaust gas generated by a drive unit of the drive device are plotted. Figure 1 shows a schematic representation of a drive device 1 which has a drive unit 2 which generates exhaust gas and an exhaust gas aftertreatment device 3, here in the form of a vehicle catalytic converter. Fuel and fresh gas are supplied to the drive unit 2, which form a fuel-fresh gas mixture and react chemically with one another to generate exhaust gas.The exhaust gas is fed to the exhaust gas aftertreatment device 3 and flows through it in the direction of arrow 4. Upstream of the exhaust gas aftertreatment device 3, a first measured value is measured by a first lambda probe 5, and downstream of the exhaust gas aftertreatment device 3, a second measured value is measured by a second lambda probe 6. The two measured values ​​each describe a residual oxygen content of the exhaust gas or a combustion air ratio at the respective point. A lambda controller 7 is operated using the first measured value, and a trim controller 8 is operated using the second measured value. Output variables of the two controllers 7 and 8 are calculated with a setpoint supplied via an input 9, namely in a calculation module 10. The composition of the fuel-fresh gas mixture is determined from the result of the calculation.Furthermore, the composition of the exhaust gas downstream of the exhaust gas aftertreatment device 3 is determined using an exhaust gas aftertreatment model. This is done for at least one exhaust gas component, but preferably for several exhaust gas components. Figure 2 shows several diagrams in which curves 11 to 22 are plotted, purely as an example, over time. Curve 11 shows the actual combustion air ratio measured by the lambda sensor 5. Curve 12 shows a correction value x, which is calculated from the measured actual combustion air ratio. It can be seen that for a combustion air ratio of λ = 1, the correction value also has the value x = 1.Curves 13 to 22 show total concentrations of individual exhaust gas components, namely curves 13 and 14 for hydrocarbons, curves 15 and 16 for carbon monoxide, curves 17 and 18 for molecular hydrogen, curves 19 and 20 for molecular oxygen, and curves 21 and 22 for nitrogen monoxide. Curves 13, 15, 17, 19, and 21 each show a total concentration that exists at λ = 1. Curves 14, 16, 18, 20, and 22, however, show a corrected total concentration, which is determined from the total concentration using the correction factor.Using the correction value calculated from the measured actual combustion air ratio, corrected total concentrations of the aforementioned exhaust gas components can be determined in a simple and extremely precise manner from previously determined (uncorrected) total concentrations, namely by correcting the determined total concentrations using the correction value. The exhaust gas components hydrocarbon, carbon monoxide, and hydrogen, which are present as oxygen removal components, are divided by the correction value. The determined total concentrations of the exhaust gas components oxygen and nitrogen monoxide, which are present as oxygen input components, are multiplied by the correction value. This allows the total concentration of the aforementioned exhaust gas components to be determined with high accuracy.For example, the total concentrations are used as input variables for a computer model of the exhaust gas aftertreatment device 3, which calculates from them a concentration of at least one pollutant downstream of the exhaust gas aftertreatment device 3. Based on this concentration of the pollutant, for example, an error signal is generated, namely as soon as the concentration exceeds a threshold value. Otherwise, the error signal is not generated.

[0002] LIST OF REFERENCE SYMBOLS: 1 Drive system 2 Drive unit 3 Exhaust aftertreatment system 4 Arrow 5 1st lambda probe 6 2nd lambda probe 7 Lambda controller 8 Trim controller 9 Input 10 Calculation module 11 Curve 12 Curve 13 Curve 14 Curve 15 Curve 16 Curve 17 Curve 18 Curve 19 Curve 20 Curve 21 Curve 22 Curve

Claims

PATENT CLAIMS:

1. A method for operating a drive device (1) for a motor vehicle, which drive device has a drive unit (2) that generates exhaust gas and has a plurality of combustion chambers, as well as a lambda probe (5) for measuring an actual combustion air ratio in the exhaust gas, wherein the drive unit (2) is operated with a fuel-air mixture whose composition is adjusted to a target combustion air ratio based on the measured actual combustion air ratio, and wherein a total concentration of an exhaust gas component of the exhaust gas is determined for the actual combustion air ratio, characterized in that the total concentration is corrected using combustion chamber-specific values for the actual combustion air ratio. 2.Method according to claim 1, characterized in that the combustion chamber-specific values for the actual combustion air ratio are determined based on rough running of the drive unit (2) or by leaning the fuel-air mixture until a misfire threshold is reached.

3. Method according to one of the preceding claims, characterized in that the total concentration is determined by reading a concentration value stored for the actual combustion air ratio or by reading a concentration value stored for a fixed combustion air ratio independently of the actual combustion air ratio and subsequently correcting it based on the actual combustion air ratio. 4.Method according to one of the preceding claims, characterized in that the corrected total concentration is determined from combustion chamber concentrations determined for the combustion chambers, which are calculated from the uncorrected total concentration and corrected using the cylinder-individual values.

5. Method according to one of the preceding claims, characterized in that the calculation of the combustion chamber concentrations from the uncorrected total concentration is carried out based on a number of combustion chambers.

6. Method according to one of the preceding claims, characterized in that the correction of the combustion chamber concentrations for an exhaust gas component present as an oxygen input component is carried out by multiplying by a correction value determined from the actual combustion air ratio and / or for an exhaust gas component present as an oxygen discharge component is carried out by dividing by the correction value.

7. Method according to one of the preceding claims, characterized in that the correction value is determined based on the relationship ^ ^ 2 − 0,42 ^ ^^ − or using the relationship ^ ^ 2 + 0.42 − 0.42 ^^^^^ − ^^ = 0 ^is calculated, where x is the correction value, λ is the combustion air ratio, and k is a coefficient.

8. Method according to one of the preceding claims, characterized in that the coefficient is determined from a concentration of at least one oxygen input component for the actual combustion air ratio or for the fixed combustion air ratio.

9. Method according to one of the preceding claims, characterized in that the corrected total concentration is used as an input variable for a calculation model of an exhaust gas aftertreatment device (3). is used, which provides as an output variable at least a concentration of at least one pollutant downstream of the exhaust gas aftertreatment device (3), wherein an error signal is generated if a threshold value is exceeded by the concentration of the at least one pollutant.

10. Drive device (1) for a motor vehicle, in particular for carrying out the method according to one or more of the preceding claims, wherein the drive device (1) has a drive unit (2) that generates exhaust gas and has a plurality of combustion chambers, as well as a lambda probe (5) for measuring an actual combustion air ratio in the exhaust gas, wherein the drive device (1) is provided and designed to operate the drive unit (2) with a fuel-air mixture whose composition is adjusted to a target combustion air ratio based on the measured actual combustion air ratio,and wherein a total concentration of an exhaust gas component of the exhaust gas is determined for the actual combustion air ratio, characterized in that the drive device (1) is further provided and designed to correct the total concentration using combustion chamber-specific values for the actual combustion air ratio.,

Images