DE102023202164A1 - Method for operating a drive device for a motor vehicle and corresponding drive device - Google Patents

Abstract

The invention relates to a method for operating a drive device (1) for a motor vehicle, which has a drive unit (2) that generates exhaust gas and has 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 set 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. It is provided that the total concentration is corrected using combustion chamber-specific values for the actual combustion air ratio. The invention further relates to a drive device (1) for a motor vehicle.

Description

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, 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, 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. The invention further relates to a drive device for a motor vehicle.

The state of the art includes, for example, the publication US10,865,721 B1 This describes a method comprising the steps of: 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.

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.

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 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 is used to drive the motor vehicle, i.e. to provide a drive torque aimed at 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 fed to the drive unit at least temporarily, the fresh gas containing fresh air at least temporarily. In addition, the fresh gas can contain exhaust gas if exhaust gas recirculation is implemented, in which the exhaust gas generated by the drive unit is at least partially fed back into the drive unit, namely as a component of the fresh gas. The fuel and the fresh gas fed 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 several combustion chambers of the drive unit, in particular with a time delay. The combustion chambers are located in several cylinders of the drive unit, with 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 that is arranged so that it can be moved 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, exhaust gas is produced due to the chemical reaction between fuel and fresh gas, which is discharged in the direction of an external environment of the drive device or the motor vehicle. The exhaust gas produced in the multiple combustion chambers is combined before being released into the external 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 external environment. In the exhaust gas aftertreatment device, the pollutants are at least partially converted into less dangerous products. The exhaust gas is only discharged into the external environment after passing through the exhaust gas aftertreatment device.

The exhaust gas aftertreatment device is, for example, a vehicle catalyst, in particular a three-way catalyst, oxidation catalyst, NO _x storage catalyst or SCR catalyst. However, it can also be designed as a particle filter, in particular as an Otto particle filter or as a diesel particle filter, preferably with an integrated vehicle catalyst, for example with a catalytic coating. A conversion rate and thus the conversion performance of the The effectiveness of the exhaust gas aftertreatment device, with which the pollutants are converted into less dangerous products, depends in particular on the composition of the exhaust gas fed to the exhaust gas aftertreatment device and/or on the oxygen loading of the exhaust gas aftertreatment device, which in turn is related to the composition of the exhaust gas.

It is therefore important to determine the composition of the exhaust gas produced by the drive unit with high accuracy, in particular in order to draw conclusions about the conversion performance of the exhaust gas aftertreatment device and/or to determine the composition of the exhaust gas released into the outside environment. For this purpose, a calculation 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 calculation model calculates the concentration of at least one pollutant in the exhaust gas downstream of the exhaust gas aftertreatment device from the total concentration.

If this concentration exceeds a threshold value, an error signal is generated or the drive unit is stopped, for example, by interrupting the fuel supply to the drive unit. The concentration of the exhaust gas component is therefore used, 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 outside environment. In this description, the concentration or concentrations 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 emitted from the drive unit, in particular before it passes through the exhaust gas aftertreatment device. However, the total concentration is present in the exhaust gas that has already been combined, i.e. downstream of a point at which the exhaust gas from the several combustion chambers is combined. The exhaust gas component is particularly preferably 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 therefore 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 an appropriate 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, particularly 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 a single 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 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 carry out a 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 is determined for the actual combustion air ratio. 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 during 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 fuel-air mixture is burned completely uniformly in the combustion chambers. However, this is not the case at least at times and the values for the actual combustion air ratio for each combustion chamber differ from one another. This means that for at least one of the combustion chambers, the actual combustion air ratio in it differs 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 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 there is a value for the actual combustion air ratio that is smaller, while for another of the combustion chambers there is a larger combustion chamber-specific value. For this reason, it is intended 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 the uneven 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 uneven running is thus determined and the combustion chamber-specific values are deduced from this using the measured actual combustion air ratio.

The uneven running results, for example, from a torque component of the drive torque provided during an expansion of the respective combustion chamber. Preferably, a speed of a crankshaft or a drive shaft of the drive unit is measured and the uneven running and thus the combustion chamber-specific values for the actual combustion air ratio are deduced from fluctuations in the speed or from a gradient of the speed over time. The fact that the combustion chamber-specific values are on average equal to the measured actual combustion air ratio and thus also the target combustion air ratio can be exploited here.

Alternatively, the fuel-air mixture can be leaned out individually in each of the combustion chambers 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 out achieved until the misfire threshold is reached, the combustion chamber-specific value for the actual combustion air ratio before leaning out 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 determination of the total concentration takes place 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. 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. The total concentration of the exhaust gas component present for this is read out based on the measured actual combustion air ratio. 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 procedure described can also be used for different actual combustion air ratios, although in this case a larger memory is required. The total concentration corresponds to the concentration value read out.

In order to be able to determine the total concentration precisely even with a small data storage, 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 value of a mathematical relationship, a table or a characteristic map in which it is stored. As an input value for the mathematical relationship, the table or the characteristic map is used in particular to take into account at least one operating variable of the drive device or the drive unit.

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. It is particularly preferred to use several input variables. The input variable or the input variables or their number is selected in particular such that the stored concentration value and thus also the read concentration value corresponds with a high degree of accuracy to the concentration value actually present in the exhaust gas for the fixed combustion air ratio.

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 concentration value actually 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 concentration value read out 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 occur during operation of the drive device, it is necessary to correct the read concentration value depending on the measured actual combustion air ratio. In this case, the read concentration value is adjusted in such a way that the read 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 concentration value read out. The total concentration corresponds to the corrected concentration value. The correction value is preferably determined in a similar way 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 of the concentration. In particular, the aforementioned calculation model of the exhaust gas aftertreatment device can be operated with high accuracy on the basis of the determined total concentration and, above all, with the help of the corrected total concentration, so that the concentration of the at least one pollutant downstream of the exhaust gas aftertreatment device is also known with high accuracy.

The drive device or the drive unit is operated 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 can ensure that the total concentration of the at least one pollutant always falls below a certain threshold value, so that sufficient aftertreatment of the exhaust gas by means of the exhaust gas aftertreatment device is ensured.

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. Firstly, 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 of the corrected total concentration.

A further development of the invention provides that the calculation of the combustion chamber concentrations from the uncorrected total concentration is carried out on the basis of a number of combustion chambers. It is assumed here that, in particular 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 level 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 of greater than one and also less than one for a combustion air ratio of 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 of greater than one, the concentration of an exhaust gas component to be reduced changes proportionally to a certain coefficient over the actual combustion air ratio. Conversely, it is assumed that the concentration of an exhaust gas component to be oxidized changes inversely proportionally to the same coefficient over 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 proportionally to the certain coefficient over 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 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 that is 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 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 several exhaust gas components with little computational effort and yet with high accuracy.

falls die Abgaskomponente als Sauerstoffeintragskomponente vorliegt oder die Beziehung $${\mathrm{\zeta }}_1={\displaystyle {\sum }_{\text{i}=1}^{\text{n}}\frac{1}{\text{n}}\raisebox{1ex}{${\zeta }_0$}\!\left/ \!\raisebox{-1ex}{$x_i$}\right.}$$

falls die Abgaskomponente als Sauerstoffaustragskomponente vorliegt. Hierbei bezeichnet n die Anzahl der Brennräume, i einen Index, x_i den Korrekturwert für den Brennraum mit dem Index i, ζ₀ die unkorrigierte Gesamtkonzentration und ζ₁ die korrigierte Gesamtkonzentration.For the total concentration of each exhaust gas component, either the relationship $${\mathrm{\zeta }}_1={\displaystyle {\sum }_{\text{i}=1}^{\text{n}}\frac{1}{\text{n}}{\mathrm{\zeta }}_0{x}_i}$$

if the exhaust gas component is present as an oxygen input component or the relationship $${\mathrm{\zeta }}_1={\displaystyle {\sum }_{\text{i}=1}^{\text{n}}\frac{1}{\text{n}}\raisebox{1ex}{${\zeta }_0$}\!\left/ \!\raisebox{-1ex}{$x_i$}\right.}$$

if the exhaust gas component is present as an oxygen discharge 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, ζ ₀ the uncorrected total concentration and ζ ₁ the corrected total concentration.

zusammengefasst werden, wobei x aus der Abweichung der brennraumindividuellen Werte des Istverbrennungsluftverhältnisses von dem Sollverbrennungsluftverhältnis bestimmt wird. Dabei wird zugrunde gelegt, dass bei einem Betrieb des Antriebsaggregats bei einem dem Sollverbrennungsluftverhältnis entsprechenden Istverbrennungsluftverhältnis die brennraumindividuellen Werte im Mittel dem Sollverbrennungsluftverhältnis entsprechen. Das heißt insbesondere, dass bei einem Sollverbrennungsluftverhältnis von eins die eine Hälfte der Brennräume soweit unterstöchiometrisch betrieben wird wie die andere Hälfte der Brennräume überstöchiometrisch.Assuming that half of the combustion chambers are operated substoichiometrically and the other half overstoichiometrically, these relationships can be $${\mathrm{\zeta }}_1=\frac{1}{2}{\mathrm{\zeta }}_{0}x+\frac{1}{2}\raisebox{1ex}{${\mathrm{\zeta }}_0$}\!\left/ \!\raisebox{-1ex}{$x$}\right.=\frac{1}{2}{\mathrm{\zeta }}_0\left(x+\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$x$}\right.\right)=\frac{1}{2}{\mathrm{\zeta }}_0\frac{x^2+1}{x}$$

where 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 and the other half of the combustion chambers 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. There is a mathematical relationship 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 in the form of a polynomial, in particular as a polynomial with an order of at least two. This achieves a high degree of accuracy of the correction value and the corrected combustion chamber concentrations.

oder anhand der Beziehung $$x^2+\frac{\mathrm{0,42}-\mathrm{0,42}\lambda }{k}x-\lambda =0$$

berechnet wird, wobei x der Korrekturwert, λ das Istverbrennungsluftverhältnis und k ein Koeffizient ist.A further development of the invention provides that the correction value is determined using the relationship $$x^2+\left(\frac{0.42}{\lambda k}-\frac{0.42}{k}\right)x-1=0$$

or based on the relationship $$x^2+\frac{0.42-0.42\lambda }{k}x-\lambda =0$$

where x is the correction value, λ is the actual combustion air ratio and k is a coefficient.

berechnet werden, wobei C_x die Konzentration der jeweiligen Abgaskomponente beschreibt, insbesondere als Molmassenverhältnis oder als parts per million (ppm). In dem Index x steht O2 für molekularen Sauerstoff, CO2 für Kohlenstoffdioxid, H2O für Wasser, CO für Kohlenstoffmonoxid, NO für Stickstoffmonoxid, NO2 für Stickstoffdioxid, H2 für molekularen Wasserstoff, C3H6 für Propen und C3H8 für Propan. Im Zähler stehen hierbei alle Sauerstoffeintragskomponenten, im Nenner alle Sauerstoffaustragskomponenten.The actual combustion air ratio can basically be calculated using the relationship $$\lambda =\frac{2{\mathrm{<figure-callout\; id="2"\; label="C\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_O+2{\mathrm{<figure-callout\; id="2"\; label="C\; C\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{CO}+C_{H2O}+C_{CO}+C_{NO}+2{\mathrm{<figure-callout\; id="2"\; label="C\; N\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{NO}}{2C_{CO}+{\mathrm{<figure-callout\; id="2"\; label="C\; H"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_H+9C_{C3\mathrm{<figure-callout\; id="6"\; label="H"\; filenames="DE102023202164A1\_0027.png"\; state="\{\{state\}\}">H</figure-callout>}6}+10C_{C3\mathrm{<figure-callout\; id="8"\; label="H"\; filenames="DE102023202164A1\_0027.png"\; state="\{\{state\}\}">H</figure-callout>}8}+2{\mathrm{<figure-callout\; id="2"\; label="C\; C\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{CO}+{\mathrm{<figure-callout\; id="20"\; label="C\; H"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_H}$$

where C _x describes the concentration of the respective exhaust gas component, in particular 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, the denominator all oxygen output components.

vereinfacht werden. Alternativ kann die Summe der Molanteile von Kohlenstoffdioxid und Wasser als ppm angegeben werden. Dann ändert sich der Wert in der jeweiligen Beziehung von 0,42 auf 420.000.For an actual combustion air ratio of 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 expressed as $$\lambda =\frac{2{\mathrm{<figure-callout\; id="2"\; label="C\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_O+C_{CO}+C_{NO}+2{\mathrm{<figure-callout\; id="2"\; label="C\; N\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{NO}+0.42}{2C_{CO}+{\mathrm{<figure-callout\; id="2"\; label="C\; H"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_H+9C_{C3\mathrm{<figure-callout\; id="6"\; label="H"\; filenames="DE102023202164A1\_0027.png"\; state="\{\{state\}\}">H</figure-callout>}6}+10C_{C3\mathrm{<figure-callout\; id="8"\; label="H"\; filenames="DE102023202164A1\_0027.png"\; state="\{\{state\}\}">H</figure-callout>}8}+0.42}$$

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.

ausgedrückt werden, wobei C_O,ein für die Summe der Konzentrationen der Sauerstoffeintragskomponenten und C_O,aus für die Summe der Konzentrationen der Sauerstoffaustragskomponenten steht. Es sind hierbei also die Beziehungen $$C_{O,ein}=2C_{O2}+C_{CO}+C_{NO}+2C_{NO2}$$

und $$C_{O,aus}=2C_{CO}+C_{H2}+9C_{C3H6}+10C_{C3H8}$$

zu berücksichtigen.Summarizing the concentrations of the oxygen input components and the concentrations of the oxygen output components, this relationship can be described as $$\lambda =\frac{C_{O,ein}+0.42}{C_{O,aus}+0.42}$$

where C _O,in is the sum of the concentrations of the oxygen input components and C _O,out is the sum of the concentrations of the oxygen output components. The relationships $$C_{O,ein}=2{\mathrm{<figure-callout\; id="2"\; label="C\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_O+C_{CO}+C_{NO}+2{\mathrm{<figure-callout\; id="2"\; label="C\; N\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{NO}$$

and $$C_{O,aus}=2C_{CO}+{\mathrm{<figure-callout\; id="2"\; label="C\; H"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_H+9C_{C3\mathrm{<figure-callout\; id="6"\; label="H"\; filenames="DE102023202164A1\_0027.png"\; state="\{\{state\}\}">H</figure-callout>}6}+10C_{C3\mathrm{<figure-callout\; id="8"\; label="H"\; filenames="DE102023202164A1\_0027.png"\; state="\{\{state\}\}">H</figure-callout>}8}$$

to be taken into account.

ergibt. Unter Verwendung des erwähnten Korrekturwerts kann die Beziehung $$\lambda =\frac{\mathrm{0,42}}{\mathrm{0,42}-kx+k/x}$$

aufgestellt werden, wobei $$k=C_{O,ein}$$

entspricht und x der Korrekturfaktor ist. Die Beziehung kann in die quadratische Gleichung $$x^2+\left(\frac{\mathrm{0,42}}{\lambda k}-\frac{\mathrm{0,42}}{k}\right)x-1=0$$

umgestellt werden. Diese wiederum kann mit der p-q-Formel gelöst werden, wobei sich für eine beliebige quadratische Gleichung $$x^2+px+q=0$$

die Lösung $$x_{1/2}=-\frac{P}{2}\pm \sqrt{{\left(\frac{P}{2}\right)}^2-q}$$

ergibt.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 with the sum of the molar fractions or the concentrations of the oxygen output components to within a few percent, the concentrations of the oxygen input components can be transferred from the numerator to the denominator, so that the relationship $$\lambda =\frac{0.42}{0.42-C_{O,ein}+C_{O,aus}}$$

Using the correction value mentioned above, the relationship $$\lambda =\frac{0.42}{0.42-kx+k/x}$$

be set up, whereby $$k=C_{O,ein}$$

and x is the correction factor. The relationship can be converted into the quadratic equation $$x^2+\left(\frac{0.42}{\lambda k}-\frac{0.42}{k}\right)x-1=0$$

This in turn can be solved using the pq formula, whereby for any quadratic equation $$x^2+px+q=0$$

the solution $$x_{1/2}=-\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">P</figure-callout>}}{2}\pm \sqrt{{\left(\frac{P}{2}\right)}^2-q}$$

results.

ausgedrückt werden, da die negative Lösung physikalisch nicht sinnvoll ist.In the present case, the solution can therefore be $$x=-\frac{1}{2}\left(\frac{0.42}{\lambda k}-\frac{0.42}{k}\right)+\sqrt{{\left(\frac{1}{2}\left(\frac{0.42}{\lambda k}-\frac{0.42}{k}\right)\right)}^2+1}$$

because the negative solution does not make physical sense.

die Beziehung $$\lambda =\frac{C_{\mathrm{0,}ein}x+\mathrm{0,42}}{C_{\mathrm{0,}aus}/x+\mathrm{0,42}}$$

abgeleitet werden. Hieraus ergibt sich durch Umformen $$\lambda =\frac{C_{\mathrm{0,}ein}{x}^2+\mathrm{0,42}x}{C_{\mathrm{0,}aus}+\mathrm{0,42}x}$$

und nachfolgend kann dies durch weiteres Umstellen als $$\lambda C_{\mathrm{0,}aus}+\mathrm{0,42}\lambda x=C_{\mathrm{0,}ein}{x}^2+\mathrm{0,42}x$$

geschrieben werden. Da für ein Verbrennungsluftverhältnis von eins $$k=C_{\mathrm{0,}ein}=C_{\mathrm{0,}aus}$$

gilt, kann die Beziehung als $$x^2+\frac{\mathrm{0,42}-\mathrm{0,42}\lambda }{k}x-\lambda =0$$

geschrieben werden. Diese kann wiederum mittels der p-q Formel gelöst werden. Die beschriebenen Beziehungen ermöglicht das Bestimmen des Korrekturwerts und folglich des korrigierten Konzentrationswerts mit hoher Genauigkeit.Alternatively, the already known relationship $$\lambda +\frac{{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}ein}+0.42}{{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{0.aus}+0.42}$$

the relationship $$\lambda =\frac{{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}ein}x+0.42}{{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}aus}/x+0.42}$$

This results in the transformation $$\lambda =\frac{{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}ein}{x}^2+0.42\mathrm{<figure-callout\; id="0"\; label="x\; C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">x</figure-callout>}}{C_{}}$$

and subsequently this can be done by further rearranging as $$\mathrm{<figure-callout\; id="0"\; label="\lambda \; C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">\lambda </figure-callout>}{C}_{}{}_{\mathrm{0,}aus}+0.42\lambda x={\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}ein}{x}^2+0.42x$$

be written. Since for a combustion air ratio of one $$k={\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}ein}={\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}aus}$$

is valid, the relationship can be considered $$x^2+\frac{0.42-0.42\lambda }{k}x-\lambda =0$$

This can in turn be solved using the pq formula. The relationships described allow 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 not constant in this respect, but changes in particular depending on the operating size 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 in the same way as 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. It can of course be provided that the oxygen input component corresponds to the at least one exhaust gas component.

ermittelt und somit als Funktion aus den Konzentrationen der Abgaskomponenten molekularer Sauerstoff, Kohlenstoffmonoxid, Stickstoffmonoxid und Stickstoffdioxid. Die beschriebene Vorgehensweise ermöglicht eine besonders genaue Ermittlung des Koeffizienten und folglich der korrigierten Brennraumkonzentrationen. Die genannten Konzentrationen oder alternativ der Koeffizient sind für das Istverbrennungsluftverhältnis oder das feste Verbrennungsluftverhältnis hinterlegt und werden ausgelesen, insbesondere in Abhängigkeit von der gleichen Größe beziehungsweise den gleichen Größen wie der Konzentrationswert, beispielsweise dem Betriebspunkt.The coefficient based on the relationship $$k={\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{0,}ein}=2C_{02}+C_{CO}+C_{NO}+2{\mathrm{<figure-callout\; id="2"\; label="C\; N\; O"\; filenames="DE102023202164A1\_0027.png,DE102023202164A1\_0028.png"\; state="\{\{state\}\}">C</figure-callout>}}_{NO}$$

and thus as a function of the concentrations of the exhaust gas components molecular oxygen, carbon monoxide, nitrogen monoxide and nitrogen dioxide. The procedure described enables a particularly precise determination of the coefficient and consequently of the corrected combustion chamber concentrations. The concentrations mentioned 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 size or the same sizes 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 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 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 components mentioned, in particular all of the components mentioned, 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 the at least one exhaust gas component to be determined with high accuracy 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 which removes oxygen from the exhaust gas afterburning treatment device, for example, oxidise when passing through the exhaust gas aftertreatment device and/or remove the oxygen they themselves 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 different hydrocarbons. For example, propene (C ₃ H ₆ ) or propane (C ₃ H ₈ ) can be used as a hydrocarbon. For example, only one of the components mentioned is used as an oxygen removal component. Preferably, however, several or even all of the components mentioned are used, i.e. a total of carbon oxide, carbon dioxide, hydrogen, one or more hydrocarbons and water. Propene and propane are used in particular as hydrocarbons. Again, this procedure results in a high degree of accuracy of the total concentration of the exhaust gas component.

A further development of the invention provides that a broadband lambda probe is used as the lambda probe. The broadband lambda probe enables the residual oxygen content or the corresponding lambda value to be recorded over a wider measuring range. The lambda probe or the broadband lambda probe is used to carry out the 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 other lambda sensor can be a step lambda sensor. The step 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 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 using a trim control or using the step lambda sensor. This enables the composition of the fuel-fresh gas mixture to be set with high accuracy.

A further development of the invention provides that the corrected total concentration is used as an input variable for a calculation model of an exhaust gas aftertreatment device, which provides as an output variable at least a concentration of at least one pollutant downstream of the exhaust gas aftertreatment device, wherein an error signal is generated if a threshold value is exceeded by the concentration of the at least one pollutant. The calculation 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 which is subsequently discharged into the outside environment.

The corrected total concentration is fed to the calculation model as an input variable. The calculation model supplies the concentration of at least one pollutant as an output variable. Such calculation models are assumed to be known in principle. 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 an interior of the motor vehicle, preferably on an instrument panel of the motor vehicle. Additionally or alternatively, it can be provided to throttle the power of the drive unit, i.e. to limit a maximum power, or to deactivate the drive unit completely.

For example, it is intended to accumulate the concentration of at least one pollutant over a distance traveled by the motor vehicle or over time and to carry out at least one or more of the measures mentioned if the threshold value is exceeded by the accumulated concentration within a certain distance or within a certain 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 all pollutants.

The invention further relates to a drive device for a motor vehicle, in particular for carrying out the method according to the statements in the context of this description, wherein the drive device has a drive unit that generates exhaust gas and has several 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, 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. 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 operating it can be further developed in accordance with the statements in this description, so reference is made to these in this respect.

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 combination specified in each case, 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 being encompassed by the invention that are not explicitly shown or explained in the description and/or the figures, but which emerge from the embodiments explained or can be derived from them.

• 1 eine schematische Darstellung einer Antriebseinrichtung für ein Kraftfahrzeug, sowie
• 2 mehrere Diagramme, in welchen ein Istverbrennungsluftverhältnis, ein aus dem Istverbrennungsluftverhältnis ermittelter Korrekturwert sowie die Gesamtkonzentrationen mehrerer Abgaskomponenten in dem von einem Antriebsaggregat der Antriebseinrichtung erzeugten Abgas aufgetragen sind.

The invention is explained in more detail below with reference to the embodiments shown in the drawing, without limiting the invention. In the drawing:

• 1 a schematic representation of a drive device for a motor vehicle, as well as
• 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.

The 1 shows a schematic representation of a drive device 1, which has a drive unit 2 that generates exhaust gas and an exhaust gas aftertreatment device 3, here in the form of a vehicle catalyst. Fuel and fresh gas are fed to the drive unit 2, which form a fuel-fresh gas mixture and react chemically with one another to produce 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 using a first lambda probe 5 and downstream of the exhaust gas aftertreatment device 3, a second measured value is measured using 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 target value 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.

The 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 means of 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 occurs at λ = 1. The curves 14, 16, 18, 20 and 22, on the other hand, 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 exhaust gas components mentioned 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 present as oxygen discharge components are divided by the correction value. The determined total concentrations of the exhaust gas components present as oxygen input components The components oxygen and nitrogen monoxide are multiplied by the correction value. This allows the total concentration of the exhaust gas components described to be determined with a high degree of accuracy.

For example, the total concentrations are used as input variables for a calculation 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.

LIST OF REFERENCE SYMBOLS:

1

Drive system

2

Drive unit

3

Exhaust aftertreatment system

4

Arrow

5

1. Lambda sensor

6

2. Lambda sensor

7

Lambda controller

8

Trim control

9

Entrance

10

Calculation module

11

Course

12

Course

13

Course

14

Course

15

Course

16

Course

17

Course

18

Course

19

Course

20

Course

21

Course

22

Course

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• US 10865721 B1 [0002]

Claims (10)

Method for operating a drive device (1) for a motor vehicle, which has a drive unit (2) which generates exhaust gas and has 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 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. Procedure according to Claim 1 , characterized in that the combustion chamber-individual 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. Method according to one of the preceding claims, characterized in that the determination of the total concentration is carried out 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 subsequently correcting it based on the actual combustion air ratio. 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. 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 on the basis of a number of combustion chambers. 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 by dividing by the correction value. Method according to one of the preceding claims, characterized in that the correction value is determined based on the relationship $$x^2+\left(\frac{0.42}{\lambda k}-\frac{0.42}{k}\right)x-1=0$$

or based on the relationship $$x^2+\frac{0.42-0.42\lambda }{k}x-\lambda =0$$

where x is the correction value, λ is the combustion air ratio and k is a coefficient. 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. 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), 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 when a threshold value is exceeded by the concentration of the at least one pollutant. 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) which generates exhaust gas and has a plurality of combustion chambers, and 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 set 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.

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