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

Abstract

Method for operating a drive unit (1) for a motor vehicle, which has a drive unit (2) generating exhaust gas and having several combustion chambers, and a lambda probe (5) for measuring an actual air-fuel ratio in the exhaust gas, wherein the drive unit (2) is operated with a fuel-air mixture, the composition of which is adjusted to a constant target air-fuel ratio based on the measured actual air-fuel ratio, and wherein a total concentration of an exhaust gas component of the exhaust gas is determined for the actual air-fuel ratio, wherein the total concentration determined for the actual air-fuel ratio is corrected using combustion chamber-specific values ​​for the actual air-fuel ratio, characterized in that the combustion chamber-specific values ​​for the actual air-fuel ratio are determined based on running roughness of the drive unit (2).

Description

[0001] The invention relates to a method for operating a drive device for a motor vehicle, which has a drive unit that generates exhaust gas and has a plurality of combustion chambers, as well as a lambda probe for measuring an actual combustion air ratio in the exhaust gas. 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 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.

[0002] 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.

[0003] It is an object of the invention to propose a method for operating a drive device for a motor vehicle, which has advantages over known methods, in particular ensures an accurate determination of the total concentration of the exhaust gas component.

[0004] This is achieved according to the invention with a method for operating a drive device for a motor vehicle having 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.

[0005] Advantageous embodiments with useful further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments explained in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are feasible.

[0006] 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 into 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.

[0007] The reaction takes place in the drive unit's multiple combustion chambers, particularly with a time delay. The combustion chambers are located in several cylinders of the drive unit, with each of the combustion chambers defined by a cylinder wall of the respective cylinder, a cylinder roof of the respective cylinder, and a piston displaceably arranged within the respective cylinder. In this case, the drive unit is an internal combustion engine, more precisely, a reciprocating piston engine.

[0008] During operation of the drive unit, exhaust gas is produced due to the chemical reaction between fuel and fresh 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.

[0009] The exhaust gas aftertreatment device is available, for example, as a vehicle catalyst, in particular as a three-way catalyst, oxidation catalyst, NO x Storage catalyst or as an SCR catalyst. 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 catalyst, for example with a catalytic coating. The conversion rate and thus the conversion performance 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 supplied to the exhaust gas aftertreatment system and / or on the oxygen loading of the exhaust gas aftertreatment system, which in turn is related to the composition of the exhaust gas.

[0010] In this respect, it is important to determine the composition of the exhaust gas generated by the drive unit with high accuracy, in particular to draw conclusions about the conversion efficiency of the exhaust gas aftertreatment device and / or to determine the composition of the exhaust gas released into the ambient environment. For this purpose, a computational model of the exhaust gas aftertreatment device is preferably used, to which the total concentration of the exhaust gas component present upstream of the exhaust gas aftertreatment device is fed. The computational model calculates the concentration of at least one pollutant in the exhaust gas downstream of the exhaust gas aftertreatment device from the total concentration.

[0011] If this concentration exceeds a threshold value, an error signal is generated, for example, or the drive unit is stopped, particularly by interrupting the fuel supply to the drive unit. Thus, the concentration of the exhaust component 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 the pollutant from escaping into the external environment. For the purposes of this description, the concentration(s) is / are specified as a molar mass ratio or as parts per million (ppm).

[0012] 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 the manner described.

[0013] In principle, the total concentration of the exhaust gas component could of course be measured using a corresponding sensor. However, this is often impractical, 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 the concentration of the exhaust gas component in the combined exhaust gas from all combustion chambers.

[0014] The actual combustion air ratio is measured using the lambda probe. This serves to measure the combustion air 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 combustion air ratio is then determined. The measured actual combustion air ratio preferably serves not only to determine the total concentration of the exhaust gas component, but also to perform 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 controlled to the target combustion air ratio, namely by adjusting the composition of the fuel-air mixture.

[0015] First, the total concentration of the exhaust gas component 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 system or 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.

[0016] However, the applicant has determined through investigations that, while 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, this is not the case, at least temporarily, and the values ​​for the actual combustion air ratio in 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 differs from the actual combustion air ratio in the other combustion chambers.

[0017] Since the actual combustion air ratio is set to the target combustion air ratio, even if the combustion chamber-specific deviation from the actual combustion air ratio occurs overall in the exhaust gas, the actual combustion air ratio corresponding to the target combustion air ratio is obtained. However, in one of the combustion chambers, the actual combustion air ratio is lower, while for another of the combustion chambers, a larger combustion-chamber-specific value is present. For this reason, it is planned 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.

[0018] A further development of the invention provides that the combustion chamber-specific values ​​for the actual air-fuel ratio are determined based on the rough running of the drive unit or by leaning the fuel-air mixture until a misfire threshold is reached. Thus, the rough running is determined during operation of the drive unit, and the combustion chamber-specific values ​​are derived from this using the measured actual air-fuel ratio.

[0019] The rough running results, for example, from a torque component of the drive torque provided during expansion of the respective combustion chamber. Preferably, a rotational speed of a crankshaft or a drive shaft of the drive unit is measured, and the rough running and thus the combustion-chamber-specific values ​​for the actual combustion air ratio are deduced from fluctuations in the rotational speed or a gradient of the rotational speed over time. This can exploit 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.

[0020] Alternatively, the fuel-air mixture can be leaned individually in each combustion chamber until the misfire threshold is reached, i.e., until at least one misfire occurs in the respective combustion chamber. Based on the degree of leaning achieved until the misfire threshold is reached, the combustion chamber-specific value for the actual air-fuel ratio before leaning can be determined. Overall, the combustion chamber-specific values ​​for the actual air-fuel ratio can be determined with good accuracy using the method described.

[0021] 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 present for this value is read out.Since the drive unit is typically 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, although in this case, a larger memory is required. The total concentration corresponds to the read concentration value.

[0022] In order to be able to accurately determine the total concentration even with a small data storage capacity, it is alternatively provided that the concentration value is stored only 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. In particular, at least one operating variable of the drive device or drive unit is used as the input variable for the mathematical relationship, the table, or the characteristic map.

[0023] 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, multiple 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 readout concentration value, corresponds with high accuracy to the concentration value actually present in the exhaust gas for the fixed combustion air ratio.

[0024] Thus, if the actual combustion air ratio actually 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 to the actual concentration value present in the exhaust gas with high accuracy, in particular with a deviation of at most 1%, at most 0.5%, or at most 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.

[0025] 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 occur during operation of the drive system, it is necessary to correct the read concentration value depending on the measured actual combustion air ratio. In this process, the read concentration value is adjusted in such a way that the read concentration value is aligned with the concentration value actually present in the exhaust gas.

[0026] Ideally, the thus corrected concentration value corresponds to the actual concentration value present in the exhaust gas with a high degree of accuracy, i.e., again, with an error of no more than 1%, no more than 0.5%, or no more than 0.1%. Preferably, the correction is performed by determining a correction value from the actual combustion air ratio, which is used to correct the read concentration value. The total concentration corresponds to the corrected concentration value. The correction value is preferably determined analogously to the procedure explained below for determining the correction value for correcting the combustion chamber concentrations.

[0027] 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 system can be operated with high accuracy, so that the concentration of at least one pollutant downstream of the exhaust gas aftertreatment system is also known with high accuracy.

[0028] The drive device or drive unit operates depending on the concentration of the pollutant, i.e., at least indirectly depending on 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, thus ensuring adequate aftertreatment of the exhaust gas by the exhaust gas aftertreatment device.

[0029] 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. Subsequently, the combustion chamber concentrations are 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 for the corrected total concentration.

[0030] 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. This assumes that, particularly during stationary operation of the drive unit, the combustion chamber concentrations for the combustion chambers are identical. They therefore correspond to the uncorrected total concentration divided by the number of combustion chambers in the drive unit. This also serves to achieve high accuracy.

[0031] A further development of the invention provides that the combustion chamber concentrations are corrected for an exhaust gas component present as an oxygen input component by multiplying the value by a correction value calculated from the actual combustion air ratio and / or for an exhaust gas component present as an oxygen output component by dividing the value by the correction value. The correction value is determined such 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.

[0032] The correction of combustion chamber concentrations is based on the assumption that for lean exhaust gases, 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 across 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. Similarly, in the rich range, i.e., for a combustion air ratio less than one, the concentration of an exhaust gas component to be reduced changes inversely proportional to the specific coefficient across the actual combustion air ratio, and the concentration of a component to be oxidized changes proportionally to the same coefficient.

[0033] If the concentrations of several exhaust gas components are determined, the respective combustion chamber concentration is corrected for each of the several exhaust gas components 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 for correction for the combustion chamber concentrations of the several exhaust gas components. For each determination of the combustion chamber concentrations of the several exhaust gas components, the correction value is preferably calculated only once from the measured actual combustion air ratio and subsequently used for correction for 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 and yet high accuracy.

[0034] For the total concentration of each exhaust gas component, either the relationship ζ1=∑i=1n1nζ0xi if the exhaust gas component is present as an oxygen input component or the relationship ζ1=∑i=1n1nζ0xi 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.

[0035] Assuming that half of the combustion chambers are operated substoichiometrically and the other half overstoichiometrically, these relationships can be ζ1=12ζ0x+12ζ0x=12ζ0(x+1x)=12ζ0x2+1x where x is determined from the deviation of the individual combustion chamber values ​​of the actual combustion air ratio from the target combustion air ratio. This assumes that when the drive unit is operated at an actual combustion air ratio corresponding to the target combustion air ratio, the individual combustion chamber 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 superstoichiometrically.

[0036] 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 expressed as a polynomial, in particular as 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.

[0037] A further development of the invention provides that the correction value is determined based on the relationship x2+(0.42λk−0.42k)x−1=0 or based on the relationship x2+0.42−0.42λkx−λ=0 where x is the correction value, λ is the actual combustion air ratio and k is a coefficient.

[0038] The actual combustion air ratio can basically be calculated using the relationship λ=2CO2+2CCO2+CH2O+CCO+CNO+2CNO22CCO+CH2+9CC3H6+10CC3H8+2CCO2+CH20 be calculated, where C x describes the concentration of the respective exhaust gas component, particularly as a molar mass ratio or as parts per million (ppm). Where x 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 represents all oxygen input components, and the denominator represents all oxygen output components.

[0039] 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 (expressed as a molar mass ratio). The relationship can therefore be λ=2CO2+CCO+CNO+2CNO2+0.422CCO+CH2+9CC3H6+10CC3H8+0.42 be simplified. Alternatively, the sum of the mole 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.

[0040] Summarizing the concentrations of the oxygen input components and the concentrations of the oxygen output components, this relationship can be described as λ=CO,in+0.42CO,out+0.42 where C O,ein for the sum of the concentrations of the oxygen input components and C O,aus stands for the sum of the concentrations of the oxygen release components. The relationships CO,ein=2CO2+CCO+CNO+2CNO2 and CO,aus=2CCO+CH2+9CC3H6+10CC3H8 to be taken into account.

[0041] Since, for the actual combustion air ratio around or equal to one, the sum of the molar fractions or the concentrations of the oxygen input components agree to within a few percent with the sum of the molar fractions or the 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 λ=0.420.42−CO,in+CO,out Using the correction value mentioned above, the relationship λ=0.420.42−kx+k / x be set up, whereby k=CO,a and x is the correction factor. The relationship can be converted into the quadratic equation x2+(0.42λk−0.42k)x−1=0 This in turn can be solved using the pq formula, where for any quadratic equation x2+px+q=0 the solution x1 / 2=−P2±(P2)2−q results.

[0042] In this case, the solution can therefore be x=−12(0.42λk−0.42k)+(12(0.42λk−0.42k))2+1 be expressed, since the negative solution does not make physical sense.

[0043] Alternatively, the already known relationship λ+C0,in+0.42C0,out+0.42 the relationship λ=C0,einx+0.42C0,aus / x+0.42 This results in the following by transforming λ=C0,einx2+0.42xC0,aus+0.42x and subsequently this can be done by further rearranging as λC0,out+0.42λx=C0,inx2+0.42x Since for a combustion air ratio of one k=C0,in=C0,out applies, the relationship can be considered x2+0.42−0.42λkx−λ=0 This, in turn, can be solved using the pq formula. The described relationships allow the correction value and, consequently, the corrected concentration value to be determined with high accuracy.

[0044] 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 just like the total concentration of the at least one exhaust gas component and is read out for the actual combustion air ratio measured by means of the lambda probe or - alternatively - independently of the actual combustion air ratio for the fixed combustion air ratio. Of course, it can be provided that the oxygen input component corresponds to the at least one exhaust gas component.

[0045] The coefficient based on the relationship k=C0,ein=2C02+CCO+CNO+2CNO2 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 specified concentrations, or alternatively the coefficient, are stored for the actual combustion air ratio or the fixed combustion air ratio and are read out, particularly depending on the same variable(s) as the concentration value, for example, the operating point.

[0046] A further development of the invention provides that one of the following components is used as the oxygen-introducing component: oxygen, carbon dioxide, water, and nitrogen oxide. The oxygen-introducing 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. 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-introducing components.

[0047] Particularly preferably, several of the aforementioned components, in particular all of the aforementioned components, are used as oxygen input components, so that oxygen, carbon monoxide, carbon dioxide, water, nitrogen monoxide, and nitrogen dioxide form the oxygen input components. The use of the aforementioned components allows the total concentration of at least one exhaust gas component to be determined with high accuracy and as simply as possible. The concentrations of carbon dioxide and water can be combined in a simplified manner, as explained.

[0048] A further development of the invention provides that one of the following components is used as the oxygen removal component: carbon dioxide, 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 introduced into the exhaust gas aftertreatment device.

[0049] As already explained, carbon oxide is understood to mean 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. Preferably, however, several or even all of the named components are 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. Again, this procedure results in a high degree of accuracy of the total concentration of the exhaust gas component.

[0050] A further development of the invention provides for the use of a broadband lambda sensor as the lambda sensor. The broadband lambda sensor enables the detection of the residual oxygen content or the corresponding lambda value over a wider measuring range. The lambda sensor or broadband lambda sensor is used to implement lambda control and, accordingly, to adjust the composition of the fuel-fresh gas mixture supplied to the drive unit.

[0051] Particularly preferably, a further lambda sensor is provided in addition to the lambda sensor, namely downstream of the exhaust aftertreatment device. The further 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 of 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.

[0052] A further development of the invention provides that the corrected total concentration is used as an input variable for a computational model of an exhaust gas aftertreatment device, which provides at least a concentration of at least one pollutant downstream of the exhaust gas aftertreatment device as an output variable. If the concentration of the at least one pollutant exceeds a threshold value, an error signal is generated. Reference has already been made to the computational model of the exhaust gas aftertreatment device. 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.

[0053] The corrected total concentration is fed to the calculation model as an input variable. The calculation model provides the concentration of the at least one pollutant as an output variable. Such calculation models are generally assumed to be known. If the concentration of the at least one pollutant exceeds the threshold value, the error signal is generated. The error signal comprises, for example, a visual display in an interior of the motor vehicle, preferably on a dashboard of the motor vehicle. Additionally or alternatively, provision can be made to throttle the power of the drive unit, i.e., to limit a maximum power, or to deactivate the drive unit completely.

[0054] 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. Preferably, the calculation model is 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.

[0055] The invention further relates to a drive device for a motor vehicle, in particular for carrying out the method according to the embodiments 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, as well as 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.

[0056] The advantages of such a drive direction configuration or such a procedure have already been pointed out. Both the drive device and the method for its operation can be further developed according to the explanations in this description, so reference is made to these in this regard.

[0057] The features and feature combinations described in the description, in particular the features and feature combinations 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 considered to be encompassed by the invention that are not explicitly shown or explained in the description and / or the figures, but which follow from or can be derived from the explained embodiments.

[0058] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. In the drawings: Fig. 1 a schematic representation of a drive device for a motor vehicle, and Fig. 2 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.

[0059] The Fig. Figure 1 shows a schematic representation of a drive system 1 comprising an exhaust-generating drive unit 2 and an exhaust aftertreatment device 3, here in the form of a vehicle catalytic converter. Fuel and fresh gas are supplied to the drive unit 2, forming a fuel-fresh gas mixture and chemically reacting with each other to produce exhaust gas. The exhaust gas is supplied to the exhaust aftertreatment device 3 and flows through it in the direction of arrow 4.

[0060] 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 location. 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.

[0061] The Fig.Figure 2 shows several diagrams in which curves 11 to 22 are plotted purely as examples over time. Curve 11 shows the actual combustion air ratio measured by 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 occurs at λ = 1.The curves 14, 16, 18, 20 and 22, however, show a corrected total concentration, which is determined from the total concentration using the correction factor.

[0062] Using the correction value calculated from the measured actual air / fuel ratio, corrected total concentrations of the aforementioned exhaust gas components can be determined in a simple and extremely accurate manner from previously determined (uncorrected) total concentrations. This is done by correcting the determined total concentrations using the correction value. The exhaust gas components hydrocarbons, 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.

[0063] For example, the total concentrations are used as input variables for a computer model of the exhaust gas aftertreatment device 3, which uses them to calculate 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. LIST OF REFERENCE SYMBOLS: 1 drive device 2 drive unit 3 Exhaust aftertreatment system 4 Arrow 5 1. Lambda sensor 6 2. Lambda sensor 7 lambda controllers 8 trim controls 9 Entrance 10 Calculation module 11 History 12 History 13 History 14 History 15 History 16 History 17 History 18 History 19 History 20 History 21 History 22 History QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 10865721 B1

[0002]

Claims

[1] Method for operating a drive device (1) for a motor vehicle, which has a drive unit (2) generating exhaust gas and having a plurality of combustion chambers and 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 adjusted to a desired 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 by that the total concentration is corrected using combustion chamber-specific values ​​for the actual combustion air ratio. [2] Method according to claim 1, characterized bythat the combustion chamber-specific values ​​for the actual combustion air ratio are determined on the basis of uneven running of the drive unit (2) or by leaning out the fuel-air mixture until a misfire threshold is reached. [3] Method according to one of the preceding claims, characterized by that the total concentration is determined by reading out a concentration value stored for the actual combustion air ratio or by reading out a concentration value stored for a fixed combustion air ratio independently of the actual combustion air ratio and then correcting it based on the actual combustion air ratio. [4] Method according to one of the preceding claims, characterized bythat 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 by 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 by 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 by dividing by the correction value. [7] Method according to one of the preceding claims, characterized bythat the correction value is calculated using the relationship x2+(0.42λk−0.42k)x−1=0 or based on the relationship x2+0.42−0.42λkx−λ=0 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 by 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 bythat the corrected total concentration is used as an input variable for a calculation model of an exhaust gas aftertreatment device (3), which delivers as an output variable at least one 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) generating exhaust gas and having 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, the composition of which 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 by 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.

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