DE102015215365A1 - A method for the regeneration of exhaust aftertreatment components of an internal combustion engine and exhaust aftertreatment device for an internal combustion engine - Google Patents

Abstract

The invention relates to a method for the exhaust aftertreatment of an exhaust aftertreatment device of an internal combustion engine (10) having a first NOx storage catalyst (12), a downstream in the flow direction of an exhaust gas of the internal combustion engine (10) downstream of the first NOx storage catalyst (12) arranged particulate filter (16) and a downstream of the first NOx storage catalyst (12) arranged second NOx storage catalyst (18) comprising the steps of - operating the internal combustion engine (10) with a lean of stoichiometric or stoichiometric combustion air ratio, wherein NOx emissions in the first NOx storage catalyst (12) and be stored in the second NOx storage catalyst (18) in the form of nitrates and soot particles are stored in the particulate filter (16); - when a need for regeneration of at least the second NOx storage catalyst (18) or the particulate filter (16) is detected; Heating the exhaust gas in an exhaust passage (20) of the internal combustion engine (10) until a regeneration temperature necessary for regeneration of the NOx storage catalysts (12, 18) and of the particulate filter (16) is reached; - Regenerating the first NOx storage catalyst (12), the second NOx storage catalyst (18) and the particulate filter (16) by alternately operating the internal combustion engine (10) with a substoichiometric combustion air ratio and a stoichiometric combustion air ratio. The invention further comprises an apparatus for carrying out such a method.

Description

The invention relates to a method for exhaust aftertreatment of an internal combustion engine and an exhaust aftertreatment device for an internal combustion engine for carrying out such a method.

The current and increasingly stringent future exhaust gas legislation places high demands on engine raw emissions and the exhaust aftertreatment of internal combustion engines. Furthermore, the vehicle and engine manufacturers are required to reduce the consumption of internal combustion engines and the associated CO ₂ emissions. Among other things, this leads to the development of consumption-optimized combustion processes for internal combustion engines. One way to reduce the consumption of a gasoline engine is a lean burn process, ie a combustion process in which the internal combustion engine is operated as far as possible with a superstoichiometric combustion air ratio. Since in a lean burn process, the NOx emissions can not be sufficiently implemented with a conventional three-way catalyst from the exhaust, additional catalysts such as NOx storage catalytic converters are required. The NOx emissions are stored as nitrates in the NOx storage catalytic converter. These NOx storage catalysts must be regenerated periodically by means of a motorized rich phase. In fuels, different levels of sulfur may be present. These lead during operation of the internal combustion engine to a reduction in the storage capacity of the NOx storage catalytic converters. This effect is reversible and can be reversed by taking appropriate measures. One possibility for the regeneration of a NOx storage catalyst is the desulfurization by a phase of a combustion engine with a rich, substoichiometric combustion air ratio. The ammonia occurring in this phase can be stored in a catalyst for the selective reduction of nitrogen oxides (SCR catalyst) and used in the further operation for exhaust aftertreatment. Furthermore, with the introduction of the exhaust emission standard EU6 for petrol engines, a limit value for the particulate emission is prescribed, so that it may also be necessary for gasoline engines to use a particulate filter. During operation, the particle filter may be loaded with soot particles, with an exhaust gas back pressure in the exhaust gas channel increasing with the load. This load causes the particulate filter must be periodically regenerated, so that the exhaust back pressure does not rise in impermissible areas and reduces the efficiency of the internal combustion engine.

From the DE 10 2006 017 300 A1 a method for the regeneration and desulfurization of a NOx storage catalyst and a particulate filter is known in which a high frequency alternating change of substoichiometric and superstoichiometric combustion air ratio of the engine is provided so that the NOx storage catalyst and the particulate filter are quasi regenerated simultaneously.

However, a disadvantage of such a method is that the oxygen reservoirs in the exhaust duct are filled or emptied with each change between substoichiometric combustion air ratio and superstoichiometric combustion air ratio, so that the effectiveness of such a process is relatively low when using three-way catalysts.

The object of the invention is to refine such a regeneration method, to further improve the quality of the exhaust gas purification and to minimize the additional consumption in the regeneration of the exhaust gas aftertreatment device.

• – Betreiben des Verbrennungsmotors mit einem stöchiometrischen oder überstöchiometrischen Verbrennungsluftverhältnis, wobei NOx-Emissionen in dem ersten NOx-Speicherkatalysator und in dem zweiten NOx-Speicherkatalysator in Form von Nitraten eingelagert werden und Rußpartikel in dem Partikelfilter eingelagert werden;
• – wenn eine Notwendigkeit zur Regeneration zumindest des zweiten NOx-Speicherkatalysators oder des Partikelfilters detektiert wird, Aufheizen des Abgases in einem Abgaskanal des Verbrennungsmotors, bis eine zur Regeneration der NOx-Speicherkatalysatoren und des Partikelfilters notwendige Regenerationstemperatur erreicht ist;
• – Regenerieren des ersten NOx-Speicherkatalysators, des zweiten NOx-Speicherkatalysators und des Partikelfilters durch alternierendes Betreiben des Verbrennungsmotors mit einem unterstöchiometrischen Verbrennungsluftverhältnis und einem überstöchiometrischen Verbrennungsluftverhältnis.

The object is achieved by a method according to the invention for the regeneration of an exhaust aftertreatment device of an internal combustion engine having a first NOx storage catalytic converter, a particle filter arranged downstream of the first NOx storage catalytic converter in the flow direction of an exhaust gas, and a second NOx storage catalytic converter arranged downstream of the first NOx storage catalytic converter which comprises the following steps:

• Operating the internal combustion engine with a stoichiometric or superstoichiometric combustion air ratio, wherein NOx emissions are stored in the first NOx storage catalyst and in the second NOx storage catalyst in the form of nitrates and soot particles are stored in the particulate filter;
• - If a need for the regeneration of at least the second NOx storage catalyst or the particulate filter is detected, heating the exhaust gas in an exhaust passage of the internal combustion engine until a regeneration temperature necessary for the regeneration of the NOx storage catalytic converter and the particulate filter is reached;
• - Regenerating the first NOx storage catalyst, the second NOx storage catalyst and the particulate filter by alternately operating the internal combustion engine with a substoichiometric combustion air ratio and a stoichiometric combustion air ratio.

By a first and a second NOx storage catalyst and a particulate filter improved exhaust gas purification can be achieved, wherein a common regeneration of the NOx storage catalytic converter and the particulate filter is energetically cheaper than a separate, individual regeneration of the components, since only one heating phase is required for the common regeneration, in which the exhaust gas is heated in the exhaust duct to a regeneration temperature. As a result, a total of fewer heating phases are required for the regeneration of the exhaust aftertreatment components and the total consumption is reduced compared to a single, separate regeneration of the exhaust aftertreatment components. According to the invention, in this method, moreover, the heat which arises during the regeneration of the first NOx storage catalytic converter can be used for heating and for achieving a regeneration temperature of the particulate filter. The regeneration of the NOx storage catalysts is primarily a desulfurization (desulfurization) of the NOx storage catalysts, ie the removal of stored sulfur oxides. Since the duration and the temperature for the desulfurization of the NOx storage catalysts approximately corresponds to the duration and the temperature for the regeneration of the particulate filter, these two regenerations can advantageously be combined with one another.

According to an advantageous development of the method, it is provided that the duration of the regeneration is controlled by a model-based calculation. While the regeneration of the NOx storage catalysts is considered to be complete with respect to the nitrates bound therein when a stoichiometric rich combustion air ratio is detected in the exhaust duct downstream of the second NOx storage catalyst, this is insufficient to detect sufficient desulfurization. During the regeneration of the NOx storage catalytic converter and the particulate filter, the combustion air ratio λ _{E of} the internal combustion engine alternately between a substoichiometric combustion air ratio λ _E <1 for desulfurization of the NOx storage catalytic converters and a superstoichiometric combustion air ratio λ _E > 1 is changed to regenerate the particulate filter. The sulfur in the NOx storage catalytic converters is removed by the substoichiometric, rich combustion air ratio. After complete regeneration of the NOx storage catalytic converters, further operation of the internal combustion engine with a substoichiometric, rich combustion air ratio leads to a rich overrunning of the second NOx storage catalytic converter, so that a substoichiometric combustion air ratio is established in the exhaust duct downstream of the second NOx storage catalytic converter. This decrease in the oxygen concentration downstream of the second NOx storage catalytic converter can be easily detected, for example, by a lambda probe. According to the model-based calculation of the NOx storage catalyst is then run over a certain time in fat until a largely complete desulfation of NOx storage catalysts is assumed.

According to a further advantageous embodiment, it is provided that the heating of the exhaust gas takes place in a regeneration phase by an ignition angle adjustment of the internal combustion engine in the direction of "late" or supported. As a result, no additional heating elements or further measures to increase the exhaust gas temperature such as a secondary air injection are necessary.

According to a further improvement of the method, it is provided that the superstoichiometric combustion air ratio λ _E > 1 in a range between 1.05 and 1.2 and the substoichiometric combustion air ratio λ _E <1 in a range between 0.85 and 0.95, preferably between 0.9 and 0.93, is chosen. A superstoichiometric combustion air ratio λ _E > 1 is necessary for the regeneration of the particle filter, that is to say for the oxidation of the soot particles retained in the particle filter. In this case, a combustion air ratio of λ _E between 1.05 and 1.2 is advantageous, since in this area, on the one hand, a sufficient amount of oxygen for the oxidation of the soot is available, on the other hand, the oxygen concentration is low enough, however, to uncontrolled burning and thus associated permanent damage or destruction of the particulate filter. A substoichiometric combustion air ratio λ _E <1 is necessary to reduce the nitrates and sulfates in the NOx storage catalyst. In this combustion air ratio, on the one hand the emergence of larger amounts of soot can be prevented, which would lead to a heavy loading of a particulate filter or corresponding tailpipe emissions. Therefore, a combustion air ratio λ _E of 0.9 to 0.93 in the substoichiometric rich phase of the internal combustion engine is particularly advantageous. On the other hand, in this combustion air ratio, ammonia, which can be stored in an SCR coating of the particulate filter and thus used in a subsequent lean operation, ie a phase in which the internal combustion engine is operated with a superstoichiometric combustion air ratio, is used to reduce NOx emissions.

According to a further development of the method, it is provided that the substoichiometric combustion air ratio and the superstoichiometric combustion air ratio be changed at intervals of 50-200s, preferably 80-120s. As a result, the NOx storage catalysts can be desulphurized alternately and the soot particle filter regenerated.

According to a further advantageous embodiment of the method, it is provided that the Regeneration in a range of 600 ° C to 650 ° C is selected. In this temperature range, both a sufficient temperature level for the desulfurization of the NOx storage catalytic converter and the particle filter is achieved. However, the temperature is not so high that a permanent thermal damage to the NOx storage catalysts or the particulate filter would be feared.

According to another aspect of the invention, an exhaust gas aftertreatment device for an internal combustion engine with an exhaust gas duct is also proposed, wherein a first, close-coupled NOx storage catalytic converter and a second NOx storage catalytic converter remote from the engine and a particle filter are arranged in the exhaust gas duct, the particle filter and the second catalytic converter NOx storage catalytic converter are arranged downstream of the first NOx storage catalytic converter, characterized in that in the exhaust duct downstream of the second NOx storage catalytic converter, a lambda sensor for detecting a regeneration state of the second NOx storage catalytic converter is arranged. With such an exhaust aftertreatment device, a method according to the invention can be carried out. By means of a lambda probe arranged downstream of the NOx storage catalytic converter, an on-board diagnosis of the NOx storage catalytic converters can take place. Thus, a simple control or regulation of the regeneration process is possible.

According to an advantageous development of the device, it is provided that the storage capacity of the first NOx storage catalytic converter is smaller than the storage capacity of the second NOx storage catalytic converter. Thus, the first NOx storage catalyst can be made small and compact, wherein the first NOx storage catalyst is provided with increased thermal stability and can be integrated, for example, in a three-way catalyst with NOx storage function. The second NOx storage catalyst provides a larger storage volume, whereby the frequency of a necessary regeneration of the NOx storage catalytic converters can be reduced or adapted to the regeneration cycles of the particulate filter.

According to an advantageous development of the device, provision is made for the first NOx storage catalytic converter to be close to the engine and the second NOx storage catalytic converter and the particle filter to be arranged in a position remote from the engine, in particular in an underfloor position of a motor vehicle. Here, an arrangement near the engine is understood to mean a mean exhaust gas flow path of at most 50 cm, in particular of at most 30 cm, according to a cylinder outlet of the internal combustion engine. Due to this proximity to the internal combustion engine, a particularly rapid starting of the first NOx storage catalytic converter or of a three-way catalytic converter with NOx storage function is achieved after a cold start, so that it also functions as a starting catalyst. By contrast, the arrangement of the second NOx storage catalytic converter remote from the engine prevents these components from coming into contact with very hot exhaust gases and resulting in spontaneous desorption of NOx and thermal damage to the second NOx storage catalytic converter. In addition, there is a relatively large amount of space available in the underbody area. Under a remote engine arrangement, a mean exhaust flow path of at least 80 cm, in particular of at least 100 cm, understood after cylinder outlet.

According to an advantageous embodiment, it is provided that the particle filter is arranged between the first NOx storage catalytic converter and the second NOx storage catalytic converter and has a coating for the selective catalytic reduction of nitrogen oxides (SCR coating). By means of an SCR coating, for example, in a substoichiometric, rich operation of the internal combustion engine carried out for desulphurising the NOx storage catalytic converter, ammonia can be stored on the SCR coating and in a subsequent lean operation, ie operation of the internal combustion engine with a superstoichiometric combustion air ratio, the reduction of the Support nitrogen oxides (NOx).

Preferably, the device is designed and set up to carry out the method according to the invention. For this purpose, a control device can be provided, for example, in which a computer-readable algorithm for executing the method and possibly necessary maps are stored. The control device can in particular have an input channel for receiving a signal of the lambda probe and / or a differential pressure sensor arranged upstream and downstream of the particle filter in the exhaust gas channel in order to determine the initiation as well as the end of the regeneration.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 A first embodiment of an exhaust aftertreatment device according to the invention,

2 A second embodiment of an exhaust gas aftertreatment device according to the invention of an internal combustion engine,

3 a further embodiment of an exhaust aftertreatment device according to the invention of an internal combustion engine,

4 a further embodiment of an exhaust aftertreatment device according to the invention of an internal combustion engine,

5 a further embodiment of an exhaust aftertreatment device according to the invention of an internal combustion engine,

6 a further embodiment of an exhaust aftertreatment device according to the invention of an internal combustion engine, and

7 a regeneration scheme for the time course of the combustion air ratio during the regeneration of the components of the exhaust aftertreatment device.

1 shows an internal combustion engine 10 with a device for exhaust aftertreatment of the internal combustion engine 10 , In the internal combustion engine 10 in particular, it is a gasoline engine, which is operated predominantly stoichiometrically or superstoichiometrically, ie with excess air λ _E > 1.

The exhaust aftertreatment device comprises an exhaust passage 20 , wherein in the flow direction of the exhaust gas of the internal combustion engine 10 through the exhaust duct 20 a three-way catalyst 26 with an integrated first NOx storage catalytic converter 12 , downstream of the three-way catalyst 26 with integrated first NOx storage catalytic converter 12 a particle filter 16 and downstream of the particulate filter 16 a second NOx storage catalyst 18 are arranged. Downstream of the second NOx storage catalyst 18 is in the exhaust duct 20 a lambda probe 22 arranged to measure the oxygen content in the exhaust gas. The three-way catalyst 26 with integrated first NOx storage catalytic converter 12 is preferably installed close to the engine, while the particle filter 16 and the second NOx storage catalyst 18 remote from the engine, preferably in Unterbodenlage a motor vehicle, are installed.

The three-way catalyst 26 with integrated NOx storage catalytic converter 21 has a catalytic coating capable of both oxidizing hydrocarbons HC and carbon monoxide CO to carbon dioxide CO ₂ and water, as well as reducing nitrogen oxides NOx to nitrogen N ₂ . For this purpose, the coating has in particular a platinum group element, in particular Pt or Pd, as well as another element, such as rhodium Rh. However, complete conversion of all three exhaust gas components is only possible with a stoichiometric exhaust gas (λ = 1). The particle filter 16 is able to filter out soot particles from the exhaust gas and retain them. The second NOx storage catalytic converter 18 has in its coating a NOx storage component, in particular an alkali or alkaline earth metal carbonate, for example barium carbonate BaCO ₃ , which stores NOx in the form of nitrate, for example barium nitrate Ba (NO ₃ ) ₂ under lean conditions. In rich operating phases, the nitrate releases the nitrogen oxides again. To reduce this, the NOx storage catalytic converter contains 18 also a catalytic metal, such as Pt or Rh, which catalyzes this reduction.

In 2 is an alternative embodiment of an exhaust aftertreatment device of an internal combustion engine 10 shown. For the most part the same structure is compared below only to the differences 1 received. In this example, the particulate filter indicates 16 a coating for the selective catalytic reduction of nitrogen oxides (SCR coating) 24 on. The SCR effective coating 24 For example, it can store ammonia occurring during substoichiometric combustion and use it in a subsequent lean phase in order to support the reduction of nitrogen oxides (NOx).

In 3 an alternative embodiment of an exhaust aftertreatment aftertreatment device according to the invention is shown. For the most part the same construction will be discussed below only on the differences. Compared to the embodiment according to 1 Here is an additional three-way catalyst 30 between an outlet of the internal combustion engine 10 and the three-way catalyst 26 with integrated first NOx storage catalytic converter 12 arranged.

In 4 is a further embodiment of an exhaust aftertreatment device according to the invention shown. For the most part the same construction will be explained below only for the differences from the embodiment 3 received. The particle filter 16 additionally has an SCR coating 24 on, with a reduction of nitrogen oxides is possible.

In 5 is a further embodiment of an exhaust aftertreatment device according to the invention shown. For the most part the same structure as in 1 Here is the three-way catalyst 26 with integrated NOx storage catalytic converter 12 through a three-way catalyst 30 and a separate first NOx storage catalyst 12 replaced. As a result, the individual components are less complex, so that in case of a defect However, it must be replaced with an additional component in the exhaust duct 20 be integrated, which increases on the one hand the space requirement and on the other hand the assembly effort.

In 6 is a further embodiment of an exhaust aftertreatment device according to the invention shown. For the most part the same structure as in 5 the particle filter additionally has an SCR-effective coating 24 on.

In 7 is a diagram with a time profile of the combustion air ratio of the internal combustion engine 10 in the regeneration of the components 12 . 16 . 18 in the exhaust duct 20 shown. In operation of the internal combustion engine 10 emissions, generated by the device for exhaust aftertreatment from the exhaust gas of the internal combustion engine 10 have to be converted. The inventive method for the regeneration of the exhaust aftertreatment device serving for this purpose can be subdivided into three phases.

In a normal operation of the internal combustion engine 10 , which as a loading phase of the NOx storage catalyst 12 . 18 and as loading phase of the particulate filter 16 can be designated, the internal combustion engine 10 in a lean operation, with more than stoichiometric or a stoichiometric combustion air ratio operated. In lean operation, the resulting NOx emissions can not be controlled by any of the three-way catalysts 26 . 30 be reduced so that the NOx emissions on the first NOx storage catalyst 12 and the second NOx storage catalyst 18 stored in the form of nitrates. Downstream of the second NOx storage catalyst 18 Thus, no or only a very low NOx concentration is measured in the exhaust gas. The NOx storage catalyst 18 has limited storage capacity so it needs to be periodically regenerated. If this is the case, a regeneration of the exhaust aftertreatment device follows.

In a first phase, the exhaust system by increasing the exhaust gas temperature of the engine 10 heated. Effective regeneration of the particulate filter requires a minimum temperature of approx. 600 ° C. The desulphurisation of the NOx storage catalytic converters 12 . 18 and a three-way catalyst 26 with integrated first NOx storage catalytic converter 12 requires a similar temperature level. This temperature level is set to "late" by known methods such as ignition timing of the internal combustion engine.

In the second phase, the first NOx storage catalyst 12 and the second NOx storage catalyst 18 or a three-way catalyst 26 with integrated first NOx storage catalytic converter 12 and the second NOx storage catalyst 18 Desorbed at the elevated temperature level and a substoichiometric, rich combustion air ratio and chemically converted the stored sulfur and / or the stored sulfur compounds. For this purpose, a combustion air ratio of 0.85-0.95, preferably about 0.92 is set following the heating phase described above. This combustion air ratio is maintained until the oxygen storage capacity (OSC) of all components in the exhaust gas channel has been eliminated and the second NOx storage catalytic converter 18 in the underfloor position of the motor vehicle fat, so substoichiometric, is run over. This is for example by a signal of the lambda probe 22 in the exhaust duct 20 downstream of the second NOx storage catalyst 18 to recognize. Alternatively, this state can also be determined via a calculation model.

In the third phase, the particle filter 18 by a lean adjustment of the internal combustion engine 10 regenerated. The regeneration of the particle filter 16 requires in addition to the elevated temperature level, a residual oxygen content in the exhaust gas in order to oxidize the carbon of the soot particles. For this purpose, immediately after the sub-stoichiometric combustion air ratio present in the second phase, a lean engine phase with a lean of stoichiometric combustion air ratio is introduced. Due to a low excess of oxygen, for example in the range λ _E = 1.05, a too high conversion rate of the carbon black is avoided, which leads to uncontrolled Rußabbrand, an associated increase in temperature and thermal damage or destruction of the particulate filter 16 could lead.

The second and the third phase of the regeneration process are operated alternately until the first NOx storage catalytic converter or the three-way catalytic converter with integrated NOx storage catalytic converter and the second NOx catalytic converter are considered desulphurised. Furthermore, the particle filter may 16 have no or only a very small soot load, which for example via a differential pressure measurement before and after the particle filter 16 in the exhaust duct 20 can be determined. When the temperature drops, for example in a weak load point of the internal combustion engine, it may be necessary for an additional heating phase to be integrated between the second and the third phase or between the third phase and the second phase, in particular when the temperature at the particle filter 16 or the second NOx storage catalyst 18 in Unterbodenlage below the necessary for regeneration minimum temperature decreases. By combining the desulfurization of the first NOx storage catalyst 12 or the three-way catalyst 26 with integrated NOx storage catalytic converter 12 , the second NOx storage catalyst 18 and the particulate filter 16 The consumption-intensive heating phases are reduced and thus achieved a total lower consumption in the regeneration of the exhaust aftertreatment device.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

first NOx storage catalyst

16

particulate Filter

18

second NOx storage catalyst

20

exhaust duct

22

Lambda probe

24

SCR coating

26

Three-way catalytic converter with NOx storage function

30

Three-way catalytic converter

λ _E

 Combustion air ratio

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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 assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006017300 A1 [0003]

Claims (10)

Method for regeneration of an exhaust aftertreatment device of an internal combustion engine ( 10 ) with a first NOx storage catalyst ( 12 ), one in the flow direction of an exhaust gas of the internal combustion engine ( 10 ) downstream of the first NOx storage catalyst ( 12 ) arranged particulate filter ( 16 ) and a downstream of the first NOx storage catalyst ( 12 ) arranged second NOx storage catalyst ( 18 ), comprising the following steps: - operating the internal combustion engine ( 10 ) with a lean of stoichiometric or stoichiometric combustion air ratio, wherein NOx emissions in the first NOx storage catalyst ( 12 ) and in the second NOx storage catalyst ( 18 ) are stored in the form of nitrates and soot particles in the particulate filter ( 16 ) are stored; If there is a need to regenerate at least the second NOx storage catalyst ( 18 ) or the particulate filter ( 16 ) is detected; Heating the exhaust gas in an exhaust duct ( 20 ) of the internal combustion engine ( 10 ), to one for the regeneration of the NOx storage catalysts ( 12 . 18 ) and the particulate filter ( 16 ) necessary regeneration temperature is reached; Regeneration of the first NOx storage catalyst ( 12 ), the second NOx storage catalyst ( 18 ) and the particulate filter ( 16 ) by alternately operating the internal combustion engine ( 10 ) with a substoichiometric combustion air ratio and a superstoichiometric combustion air ratio. A method according to claim 1, characterized in that the regeneration desulfurization of the NOx storage catalysts ( 12 . 18 ). A method according to claim 1 or claim 2, characterized in that the heating of the exhaust gas in a regeneration phase by an ignition angle adjustment of the internal combustion engine ( 10 ) takes place in the direction of "late" or is supported. Method according to one of claims 1 to 3, characterized in that the superstoichiometric combustion air ratio in a range between 1.05 and 1.2 and the substoichiometric combustion air ratio in a range of 0.85 to 0.95, preferably from 0.9 to 0 , 93, is elected. Method according to one of claims 1 to 4, characterized in that the substoichiometric combustion air ratio and the superstoichiometric combustion air ratio in time intervals of 50 to 200s, preferably from 80 to 120s, are changed. Method according to one of claims 1 to 5, characterized in that the regeneration is carried out in a range of 600 ° C to 650 ° C. Exhaust after-treatment device for an internal combustion engine ( 10 ), with an exhaust duct ( 20 ), wherein in the exhaust duct ( 20 ) a first, close-coupled NOx storage catalyst ( 12 ) and a second, engine-remote NOx storage catalyst ( 18 ) as well as a particle filter ( 16 ) are arranged, wherein the particulate filter ( 16 ) and the second NOx storage catalyst ( 18 ) downstream of the first NOx storage catalyst ( 12 ) are arranged, characterized in that in the exhaust duct ( 20 ) downstream of the second NOx storage catalyst ( 18 ) a Lamdba probe ( 22 ) for detecting a regeneration state of the second NOx storage catalyst ( 18 ), wherein the apparatus is arranged for carrying out a method according to one of claims 1 to 6. Apparatus according to claim 7, characterized in that the storage capacity of the first NOx storage catalyst ( 12 ) smaller than the storage capacity of the second NOx storage catalyst ( 18 ). Device according to one of claims 7 or 8, characterized in that the first NOx storage catalyst ( 12 ) into a three-way catalyst ( 14 ) is integrated. Device according to one of claims 7 to 9, characterized in that the particulate filter ( 16 ) between the first NOx storage catalyst ( 12 ) and the second NOx storage catalyst ( 18 ) and a coating ( 24 ) for the selective catalytic reduction of nitrogen oxides (SCR coating).

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