WO2014187516A1

WO2014187516A1 - Method for operating a drive device and corresponding drive device

Info

Publication number: WO2014187516A1
Application number: PCT/EP2014/000894
Authority: WO
Inventors: Günter ZITZLER; Guido Schäffner; Tim SPÄDER; Andrea PROSPERO
Original assignee: Mtu Friedrichshafen Gmbh
Priority date: 2013-05-22
Filing date: 2014-04-03
Publication date: 2014-11-27
Also published as: DE102013209487A1; DE102013209487B4

Abstract

The invention relates to a method for operating a drive device (1) with an internal combustion engine (2) and an exhaust gas purification device (9), through which exhaust gas of the internal combustion engine (2) is made to flow in order to clean the latter, wherein the exhaust gas purification device (9) has at least one catalytic converter element for catalytically converting nitrogen monoxide into nitrogen dioxide with a specific conversion rate (η), wherein a first nitrogen oxide concentration variable is determined by means of a first nitrogen oxide sensor (15) upstream of the catalytic converter element, and a second nitrogen oxide concentration variable is determined by means of a second nitrogen oxide sensor (16) downstream of the catalytic converter element, and wherein a nitrogen dioxide concentration is obtained from the difference between the first nitrogen oxide concentration variable and the second nitrogen oxide concentration variable. There is provision here that the first nitrogen oxide sensor (15) and the second nitrogen oxide sensor (16) are calibrated at an exhaust gas temperature (T) for which the conversion rate (η) is lower than a specific conversion rate. The invention further relates to a drive device (1).

Description

Method for operating a drive device

and corresponding drive device

The invention relates to a method for operating a drive device with an internal combustion engine and an exhaust gas purification device, the exhaust of the

Internal combustion engine is flowed through for its purification, wherein the

Exhaust gas purification device at least one catalyst element for catalytic

Conversion of nitric oxide into nitrogen dioxide with a specific

Conversion rate, and wherein by means of a first nitrogen oxide sensor

upstream of the catalyst element, a first nitrogen oxide concentration size and a second nitrogen oxide concentration size is determined by means of a second nitrogen oxide sensor downstream of the catalyst element. The invention further relates to a

Drive device.

The drive device serves, for example, for driving a motor vehicle or a watercraft. For this purpose, by the internal combustion engine, which is designed for example as a diesel engine, a torque

provided. The exhaust gas generated by the internal combustion engine is the

Exhaust gas purification device supplied and freed in this at least partially from pollutants. It is often advantageous if the exhaust gas purification device flowing through the exhaust gas has a certain proportion of nitrogen dioxide, for example, this for the regeneration of a particulate filter and / or for reduction

Using nitrogen monoxide in a catalyst.

Immediately downstream of the internal combustion engine, however, there is only a small amount of nitrogen gas or no nitrogen dioxide at all in the exhaust gas. In contrast, the proportion of nitrogen monoxide in the exhaust gas is comparatively high. For this reason, the at least one catalyst element is provided in the exhaust gas purification device. This is used to catalytically convert nitrogen monoxide to nitrogen dioxide at the particular conversion rate. Downstream of the catalyst element - with respect to a main flow direction of the exhaust gas - in the exhaust gas of the internal combustion engine so a higher proportion of nitrogen dioxide or a larger amount of this before than upstream of the catalyst element is the case.

The catalyst element has at least one catalytically active component

or a catalyst material, for example platinum or a platinum alloy. However, as the catalyst element has a longer service life, the catalytic effect of this catalyst material and hence of the catalyst element is reduced, in particular due to thermal aging or chemical poisoning, which is unavoidable by certain components of a lubricant and / or fuel used to operate the internal combustion engine.

Accordingly, the amount of nitrogen dioxide generated by the catalytic conversion is reduced.

It is therefore desirable to determine the nitrogen dioxide concentration in the exhaust gas, for example in order to determine the efficiency of the catalyst element or its conversion rate. For this purpose, the first nitrogen oxide sensor and the second nitrogen oxide sensor are provided, the former being arranged upstream and the latter downstream of the catalyst element. With the aid of the nitrogen oxide sensors, the nitrogen oxide concentration resulting from the

Nitrogen monoxide concentration and nitrogen dioxide concentration can be determined. This is due to the fact that nitrogen oxide sensors, as they are usually used in the drive device or the exhaust gas purification device, are basically designed to determine the nitrogen monoxide concentration, but have a pronounced cross sensitivity to nitrogen dioxide.

Both the first nitrogen oxide sensor and the second nitrogen oxide sensor thus react both to the nitrogen monoxide contained in the exhaust gas and also the nitrogen dioxide likewise obtained, and thus also supply the already mentioned

Nitrogen concentration of the exhaust gas at the respective position. Due to the cross-sensitivity and the finding that almost all of the nitrogen dioxide present in the exhaust gas by means of the catalyst element from the nitrogen monoxide can now be calculated from the difference between the first

Nitrogen concentration concentration and the second nitrogen oxide concentration size on the nitrogen dioxide concentration, in particular the nitrogen dioxide concentration

downstream of the catalyst element. For example, EP 2 232 255 B1 is known from the prior art. However, the nitrogen oxide sensors are subject to an aging process, which leads to a deviation of the

Nitrogen concentration sizes and therefore the erroneous determination of the

Nitrogen dioxide concentration can lead.

It is therefore an object of the invention to provide a method for operating a

Drive device to propose, which in particular a much higher

Accuracy in determining the nitrogen dioxide concentration allows.

This is achieved according to the invention by a method having the features of claim 1. It is provided that a calibration of the first nitrogen oxide sensor and the second nitrogen oxide sensor is carried out at an exhaust gas temperature for which the conversion rate is less than a certain conversion rate. The method according to the invention can be explained particularly simply in the case where the

Conversion rate is zero. In this case, the equivalent

Nitrogen dioxide concentration upstream of the catalyst element, ie at the

Position of the first nitrogen oxide sensor, that of the downstream of the catalyst element, that is, at the position of the second nitrogen oxide sensor. Accordingly, the first nitrogen oxide concentration size and the second nitrogen oxide concentration size must be the same. If this is not the case, a corresponding correction value, for example, for the second nitrogen oxide sensor is determined and subsequently for determining the second

Nitrogen concentration used.

Overall, therefore, the nitrogen dioxide concentration is determined from the difference between the first nitrogen oxide concentration size and the second nitrogen oxide concentration size. The first and the second nitrogen oxide sensor are designed such that they detect any nitrogen oxides, in particular both nitrogen monoxide and nitrogen dioxide, and the concentration in the form of the first or the second

Provide nitric oxide concentration size. Because, however, the amount of that of the

Nitrogen dioxide formed by the internal combustion engine is negligible, can directly from the difference between the two nitric oxide concentration on the Nitrogen dioxide concentration is converted, which has been converted from the catalyst element of the nitrogen monoxide and thus downstream of the

Catalyst element is present in the exhaust gas.

The first nitrogen oxide sensor and the second nitrogen oxide sensor are preferable

Nitrous oxide sensors, however, have a cross-sensitivity to nitrogen dioxide. The nitrogen oxide sensors therefore respond to both nitric oxide and nitrogen dioxide. For example, IR measuring methods, chemiluminescence measuring methods and / or electrochemical measuring methods can be used as measuring methods for the nitrogen oxide sensors. Based on the thus determined

Nitrogen dioxide concentration, for example, a rules of

Nitrogen dioxide concentration, in particular to a certain concentration which is greater than or equal to a minimum concentration or equivalent.

Calibration of the two nitrogen oxides sensors is now performed at the exhaust gas temperature for which the conversion rate is less than the determined one

Conversion rate is. Because the nitrogen oxide sensors as well as the catalyst element are subject to an aging process, it is necessary to calibrate

for example, at regular intervals. The exhaust gas temperature before and / or in the catalyst element should be selected such that the conversion rate, which is directly dependent on the exhaust gas temperature, is low, for example less than 10%, in particular less than 5%, less than 2.5%, less than 1 % or less than 0.5%; the determined conversion rate thus corresponds to one of the abovementioned values. In this case, only a small amount is produced during the overflow of the catalyst element by the nitrogen monoxide

Nitrogen dioxide. Of course, the particular conversion rate may be significantly less than the above-mentioned values, and preferably at most 0.25%, at most 0.1%, or at most 0.05%.

Accordingly, the calibration of the nitrogen oxide sensors can be carried out such that the first nitrogen oxide concentration variable is equated with the second nitrogen oxide concentration variable or vice versa. Thus, an aging of the sensors and / or a series dispersion of the sensors can be compensated. Preferably, the conversion rate must be less than the determined one during the entire calibration process

Conversion rate to avoid errors. Accordingly, the preferred Is selected exhaust gas temperature throughout the calibration process and preferably be less than a certain exhaust gas temperature, for which the said condition is met. Alternatively, the exhaust gas temperature may also be greater than the specific exhaust gas temperature, because the conversion rate also decreases for high exhaust gas temperatures. Particularly preferred is the exhaust gas temperature throughout

Calibration process constant or at least kept almost constant.

A development of the invention provides that a downstream of the

Catalyst element arranged catalyst of the exhaust gas purification device is designed as an SCR catalyst. For example, the exhaust gas purification device has the catalyst, which is provided downstream of the catalyst element. The catalyst serves to carry out a selective catalytic reduction of pollutants contained in the exhaust gas, in particular of nitrogen oxides, that is to say in particular of nitrogen monoxide and / or nitrogen dioxide. It is particularly advantageous if a reducing agent is introduced into the exhaust gas upstream of the catalyst,

for example in the form of ammonia or a urea-water solution from which ammonia is formed in the exhaust gas. This reducing agent, together with the exhaust gas, enters the catalyst and serves to carry out the reduction of the nitrogen oxides.

The occurring reactions can, for example, by the

reaction equations

4N0 ₂ + 4NH ₃ + 0 ₂ - »· 4N ₂ + 6H ₂ 0 (Equation 1)

6NO ₂ + 8NH ₃ 7N ₂ + 12H ₂ 0 (Equation 2)

N0 ₂ + NO + 2NH ₃ - "2N ₂ + 3H ₂ 0 (Equation 3) are described. Equation 3 describes a particularly efficient reaction path in which the nitrogen dioxide reacts directly with the nitrogen monoxide. In order to preferentially drain this reaction path, it is necessary that the exhaust gas contain the same amounts of nitrogen monoxide and nitrogen dioxide.

Accordingly, the molar ratio is chosen equal to one. Preferably, at least approximately each nitrogen monoxide molecule is thus provided with a nitrogen dioxide molecule for the reaction. In other words, the ratio between nitrogen monoxide and nitrogen dioxide is chosen such that in the catalyst Exhaust gas purification device at least the reaction path of the selective catalytic reaction of the exhaust gas according to equation 3, in which the nitrogen reacts with participation of a reductant introduced into the reducing agent with the nitrogen dioxide, is always running, but at least in the largest possible

Temperature range.

A further embodiment of the invention provides that the exhaust gas purification device is associated with a particulate filter. In this case, for example, the internal combustion engine is designed as a diesel internal combustion engine. The particle filter serves to filter out particles contained in the exhaust gas of the internal combustion engine, in particular soot particles or carbon particles, from the exhaust gas. Particularly preferred is the

Particulate filter as continuous regenerating particle filter (CRT: Continuously

Regeneration trap). The particulate filter is arranged, for example downstream of the catalyst element, so that it is traversed by the exhaust gas of the internal combustion engine only after the catalyst element. The nitrogen dioxide present in the exhaust gas at this point, which is essentially produced by the catalyst element from the nitrogen monoxide, now serves to regenerate the particle filter preferably continuously at a specific regeneration rate. The

Regeneration rate may be referred to as Rußabbrandrate in the case of the particulate filter. The regeneration is over wide areas of the map of the

Internal combustion engine provided or at least possible.

Preferably, the regeneration rate is selected such that a reliable filtering of the exhaust gas by means of the particulate filter in the entire power range of the internal combustion engine is always possible. In other words, the regeneration rate should be chosen so that the regeneration of the particulate filter is always sufficient to a

to realize reliable function of the particulate filter. The regeneration rate

Thus, for example, the Rußabbrandrate is selected such that even with permanent full load of the internal combustion engine, the particle filter is not added or blocked by the particles, in particular soot particles. In particular, when the particles are present as soot particles, they can be converted into carbon dioxide and nitrogen monoxide by means of the nitrogen dioxide contained in the exhaust gas. In order to achieve the specific regeneration rate or Rußabbrandrate, so it is necessary that a certain nitrogen dioxide concentration is present. For example, a minimum concentration for the nitrogen dioxide is dependent determined by the regeneration rate, so preferably such that the particulate filter is reliably regenerated even with permanent full load of the internal combustion engine.

In an advantageous embodiment of the invention it is provided that the second nitrogen oxide sensor is arranged upstream of the catalyst and / or the particulate filter. In that regard, the second nitrogen oxide sensor is fluidically between the catalyst element and the catalyst or the particulate filter.

Accordingly, the second nitrogen oxide sensor becomes the whole of the

Catalyst element formed amount of nitrogen dioxide acted upon. This would not be the case with a downstream arrangement, because in the catalyst or the particulate filter usually a part of the nitrogen dioxide is reacted, as already explained above. This means that no further measures to

Consideration of the catalyst or the particulate filter are necessary.

A particularly advantageous embodiment of the invention provides that in the

Calibrating a conversion target rate is taken into account based on the

Exhaust gas temperature is determined. According to the invention, the exhaust gas temperature should be selected such that the conversion rate is less than the specific conversion rate. However, at realistic exhaust gas temperatures, the conversion rate usually does not reach the ideal case for which it is zero. Rather, the conversion rate will always be greater than zero, so that the catalyst element converts at least small amounts of nitrogen monoxide into nitrogen dioxide. However, this affects the accuracy of the calibration. Accordingly, the exhaust gas temperature is determined and determined therefrom the conversion target rate, for example based on a mathematical relationship, a table and / or a map. In addition, the instantaneous age of the catalyst element can be taken into account. The

Conversion set rate gives at least approximately the theoretical in the

Overflow of the catalyst element resulting amount of nitrogen dioxide again. This is taken into account when calibrating the nitrogen oxide sensors.

A preferred embodiment of the invention provides that the second nitrogen oxide sensor is arranged downstream of the catalytic converter and / or of the particulate filter and the second nitrogen oxide concentration variable is determined from a measured value of the second nitrogen oxide sensor and a correction value taking into account the catalytic converter and / or the particulate filter. Of course, the second nitrogen oxide sensor is preferred immediately provided downstream of the catalyst element, at least so upstream of the catalyst and / or the particulate filter. However, this is not possible in every case.

Accordingly, the second nitrogen oxide sensor is in this case downstream of the

Catalyst and / or the particulate filter arranged and detects the measurements at this point.

This means, however, that the exhaust gas no longer has the nitrogen dioxide concentration present immediately downstream of the catalyst element, because nitrogen dioxide has already been reacted in the catalyst or particulate filter. For this reason, the correction value in the determination of the second

Nitrogen concentration size from the measured value are taken into account. Of the

Correction value describes, for example, the amount of nitrogen dioxide in the exhaust gas converted by the catalyst and / or the particulate filter. The correction value stands in particular as a function of the temperature of the exhaust gas.

In such an approach, it may be provided that the correction value is determined by means of a mathematical relationship, a table and / or a map. For example, the exhaust gas temperature is used as an input variable, as the output variable directly the correction value is obtained. The correction value describes the amount of nitrogen dioxide, which is reacted in the flow through the catalyst or the particulate filter. Accordingly, the correction value must be added to the actually measured second nitrogen oxide concentration variable.

A development of the invention provides that adjusting the conversion rate by changing at least one operating parameter of the internal combustion engine, in particular the injection parameter, the boost pressure of a supercharger, a

Exhaust gas recirculation rate and / or a control parameter of at least one inlet valve and / or at least one exhaust valve occurs. The nitrogen monoxide emission of the internal combustion engine or the exhaust gas temperature can be influenced by numerous operating parameters of the internal combustion engine. Under this

Operating parameters include, for example, the injection parameters, the boost pressure, the exhaust gas recirculation rate and / or the activation parameters of the intake valve or the exhaust valve. The injection parameter is, for example, an amount of the fuel supplied to the internal combustion engine per unit time and / or the period during which the

Feeding takes place. The latter is defined by the start of injection, the duration of injection and / or the end of injection. The charge pressure of the charger corresponds to the pressure

downstream of the supercharger or the pressure of the internal combustion engine supplied fresh charge, in particular fresh air. The loader is, for example, a turbocharger, in particular an exhaust gas turbocharger, or a compressor. The

Exhaust gas recirculation rate is the amount of exhaust gas which is recirculated to the internal combustion engine per unit time. The activation parameter of the intake valve

or the exhaust valve, for example, an opening time, a

Closing time and / or an opening period during which the respective valve is at least partially open. The activation parameter of the intake valve

or the outlet valve corresponds to the timing of the respective valve, ie the opening time, the opening duration and / or the closing time.

At least one of the mentioned operating parameters, but preferably several

Operating parameters are now preferred for achieving the desired

Nitrogen monoxide output or the desired exhaust gas temperature set, this being controlled and / or regulated, in particular in dependence on the exhaust gas temperature can be made before the catalyst element.

The invention further relates to a drive device, in particular for carrying out the method according to the preceding embodiments, with an internal combustion engine and an exhaust gas purification device, which is traversed by exhaust gas of the internal combustion engine for its purification, wherein the exhaust gas purification device at least one

Catalyst element for the catalytic conversion of nitrogen monoxide into

Nitrogen dioxide having a conversion rate, wherein by means of a first

Nitrous oxide sensor upstream of the catalyst element has a first

Nitrogen concentration size and by means of a second nitrogen oxide sensor downstream of the catalyst element, a second nitrogen oxide concentration size is determined, and wherein the drive means is adapted to a nitrogen dioxide concentration from the difference between the first nitrogen oxide concentration size and the second

Determine nitric oxide concentration size. The drive device is characterized in that a calibration of the first nitrogen oxide sensor and the second nitrogen oxide sensor is provided at an exhaust gas temperature, for which the conversion rate is less than a certain

Conversion rate is. On the advantages of such an embodiment of

Drive device or such a procedure has already been discussed. The drive device and the corresponding method can be developed further in accordance with the above statements, so that reference is made to this extent.

The invention will be described below with reference to the drawing

Embodiments explained in more detail, without any limitation of the invention. Showing:

Fig. 1 is a schematic representation of a drive device with a

Internal combustion engine and an exhaust gas purification device,

Fig. 2 is a schematic representation of the exhaust gas purification device, and

Fig. 3 is a diagram in which conversion rates of a catalyst element of

Exhaust gas purification device are plotted against the temperature of the exhaust gas of the internal combustion engine.

1 shows a schematic representation of a drive device 1, which has an internal combustion engine 2, of which only one cylinder 3 is shown with a piston 4 here. Via an inlet valve 5, the cylinder 3 fresh charge, so for example fresh air or a fresh air-fuel mixture, are supplied. In the embodiment shown here, an injection valve 6 is also provided, which serves to introduce fuel into the cylinder 3 and a combustion chamber of the cylinder 3. Finally, the cylinder 3 is assigned at least one exhaust valve 7, through which exhaust gas from the cylinder 3 or the combustion chamber,

For example, via an exhaust manifold 8, an exhaust purification device 9 is supplied.

The exhaust gas purification device 9 has, for example, a

Oxidation catalyst 10 and Diesel Oxidation Catalyst (DOC), a Particulate filter 11 and a catalyst 12 for selective catalytic reduction (SCR catalyst). The oxidation catalyst 10, the particulate filter 11 and the catalyst 12 are flowed through in the order mentioned by the exhaust gas of the internal combustion engine 2. Downstream of the catalytic converter 12, the exhaust gas is discharged into an external environment 13 of the drive device 1, in particular by a tail pipe 14. In the oxidation catalytic converter 10, a catalyst element not identified here is provided which, for example, in the form of a coating, in particular a noble metal coating, in the oxidation catalytic converter 10 is trained. As a precious metal, for example, platinum or a platinum alloy is used. This catalyst element serves to convert nitrogen monoxide contained in the exhaust into the nitrogen dioxide at a certain conversion rate. The nitrogen dioxide subsequently serves, that is, downstream of the oxidation catalyst 10, for realizing a continuous regeneration of the particulate filter 11 at a certain regeneration rate and / or performing a rapid reaction path in the catalyst 12 for decomposing the nitrogen monoxide contained in the exhaust gas.

In the particulate filter 11 are particles, in particular carbon particles, according to the reaction equation

2NO ₂ + C ^ C0 ₂ + 2NO decomposed to carbon dioxide and nitric oxide. Accordingly stands the

Particulate filter always available for receiving further by the exhaust gas supplied particles. In the catalyst 12, however, the reaction path according to the reaction equation

N0 ₂ + NO + 2NH ₃ -> 2N ₂ + 3H ₂ 0, wherein the ammonia (NH ₃ ) is preferably introduced into the exhaust gas upstream of the catalyst 12. This introduction takes place for example in the form of urea, which according to the reaction equation

(NH ₂ ) ₂ CO + H ₂ O - + 2NH ₃ + 2C0 ₂ together with the water contained in the exhaust gas to ammonia and

Carbon dioxide reacts.

FIG. 2 shows a further schematic representation of the drive device 1 with internal combustion engine 2 and exhaust gas purification device 9, the latter having at least the oxidation catalytic converter 10 as well as the particle filter 11 and / or the catalytic converter 12. Upstream of the oxidation catalyst 10, in which the catalyst element is present, a first nitrogen oxide sensor 15 is provided, by means of which a first

Nitrogen concentration size is determined. Either downstream of

Oxidation catalyst 10 or fluidically between this on the one hand and the particulate filter 11 and / or the catalyst 12 on the other hand or downstream of the particulate filter 11 and the catalyst 12, a second nitrogen oxide sensor 16 is arranged, wherein the determination of a second

Nitric Oxide concentration size is used.

In the case of the arrangement of the second nitrogen oxide sensor 16 upstream of the particulate filter 11 and the catalyst 12, an instantaneous nitrogen dioxide concentration can be directly determined from the difference between the first nitrogen oxide concentration quantity and the second nitrogen oxide concentration quantity, because usually the amount of nitrogen dioxide directly generated by the engine 2 is negligible. If, on the other hand, the second nitrogen oxide sensor 16 is provided downstream of the particle filter 11 and / or the catalytic converter 12, then the second nitrogen oxide concentration variable is determined from a measured value of the second nitrogen oxide sensor 16 and a correction value, this correction value being the particle filter 11 or the catalytic converter 12

considered. For example, the first nitrogen oxide concentration variable and the second nitrogen oxide concentration variable are preferably preferred by a control unit 17 of FIG

Drive device 1 is supplied, which serves to drive the internal combustion engine 2.

FIG. 3 shows a diagram in which a first profile 18 has a conversion rate η above the temperature T of the exhaust gas immediately upstream of the exhaust gas

Catalyst element at the beginning of its life shows. In contrast, the course 19 shows the conversion rate η over the temperature T for an already aged one

Catalyst element. The diagram clearly shows that with increasing aging of the catalyst element not only the conversion rate η decreases, but that also shifts that temperature T at which there is a maximum of the conversion rate.

In addition, it can be clearly seen that the conversion rate η drops significantly on both sides of its maximum, ie for decreasing temperatures T and increasing temperatures T. This knowledge can be used to calibrate the nitrogen oxide sensors 15 and 16. In particular, the exhaust gas temperature T is selected such that the conversion rate η is smaller than a certain conversion rate. This particular conversion rate may in principle be chosen arbitrarily, but is preferably at most 10%, at most 5%, at most 2.5%, at most 1% or at most 0.5%. The conversion rate describes the proportion of nitrogen monoxide, which is converted in the sweeping of the catalyst element. For example, to achieve a conversion rate η of less than 5%, the exhaust gas temperature T must be less than about 220 ° C (for curve 18) and less than 235 ° C (for curve 19), respectively.

Claims

claims

Method for operating a drive device (1) with a

Internal combustion engine (2) and an exhaust gas purification device (9) through which exhaust gas of the internal combustion engine (2) flows through, the exhaust gas purification device (9) comprising at least one catalyst element for the catalytic conversion of nitrogen monoxide into nitrogen dioxide at a specific conversion rate (η). wherein by means of a first nitrogen oxide sensor (15) upstream of the catalyst element, a first nitrogen oxide concentration size and by means of a second nitrogen oxide sensor (16) downstream of the

A nitrogen dioxide concentration is determined from the difference between the first nitrogen oxide concentration size and the second nitrogen oxide concentration size, characterized in that a calibration of the first

Nitrous oxide sensor (15) and the second nitrogen oxide sensor (16) at a

Exhaust gas temperature (T) is made, for which the conversion rate (η) is less than a certain conversion rate.

A method according to claim 1, characterized in that a downstream of the catalyst element arranged catalyst (12) is formed as an SCR catalyst.

Method according to one of the preceding claims, characterized in that the exhaust gas purification device (9) is associated with a particulate filter (11).

4. The method according to any one of the preceding claims, characterized in that the second nitrogen oxide sensor (16) upstream of the catalyst (12) and / or the particulate filter (11) is arranged.

5. The method according to any one of the preceding claims, characterized in that in the calibration, a conversion target rate is taken into account, which is determined based on the exhaust gas temperature (T).

6. The method according to any one of the preceding claims, characterized in that the second nitrogen oxide sensor (16) downstream of the catalyst (12) and / or the particulate filter (11) is arranged and the second nitrogen oxide concentration from a measured value of the second nitrogen oxide sensor (16) and a the catalyst (12) and / or the particulate filter (11) taking into account correction value is determined.

7. The method according to any one of the preceding claims, characterized in that the correction value is determined by means of a mathematical relationship, a table and / or a map.

8. The method according to any one of the preceding claims, characterized in that the setting of the conversion rate by changing at least one operating parameter of the internal combustion engine, in particular the

Injection parameters, the boost pressure of a supercharger, an exhaust gas recirculation rate and / or a control parameter of at least one intake valve and / or at least one exhaust valve takes place

9. The method according to any one of the preceding claims, characterized in that the operating parameter or a plurality of operating parameters is controlled and / or regulated set / are.

10. Drive device (1), in particular for carrying out the method according to one or more of the preceding claims, with an internal combustion engine (2) and an exhaust gas purification device (9), which is flowed through by exhaust gas of the internal combustion engine (2) for its purification, wherein the exhaust gas purification device (9) at least one catalyst element for the catalytic conversion of Nitrogen monoxide in nitrogen dioxide with a conversion rate (η), wherein by means of a first nitrogen oxide sensor (15) upstream of the catalyst element, a first nitrogen oxide concentration size and by means of a second nitrogen oxide sensor (16) downstream of the catalyst element a second

Nitrogen concentration size is determined, and wherein the drive device (1) is adapted to a nitrogen dioxide concentration from the difference between the first nitrogen oxide concentration size and the second

Determine nitrogen oxide concentration size, characterized in that a calibration of the first nitrogen oxide sensor (15) and the second nitrogen oxide sensor (16) at an exhaust gas temperature (T) is provided, for which the

Conversion rate (η) is less than a certain conversion rate.