DE10153901B4 - Method and device for desulfurization of a diesel engine downstream NOx storage catalyst - Google Patents

Abstract

Process for the desulfurization of a NOX storage catalytic converter (34) connected downstream of a diesel engine (10), the NOX storage catalytic converter (34) being heated at least approximately to a desulfurization temperature during a heating phase (TH) and alternating with it in a subsequent wobble phase (TW) a rich exhaust gas lambda with λ <1 and a lean exhaust gas lambda with λ> 1 at a specifiable mean exhaust gas lambda, characterized in that regulation of the exhaust gas lambda during the heating phase (TH) of the NOX storage catalytic converter (34) by influencing an exhaust gas recirculation rate of one of the Exhaust gas recirculation device (26) assigned to the diesel engine takes place as a manipulated variable of the control.

Description

The invention relates to a process for the desulfurization of a diesel engine downstream NO _x storage catalytic converter with the features mentioned in the preamble of the independent claim 1 and a device for carrying out the method according to the preamble of claim 18.

In the course of constantly stricter legal exhaust emission limits for internal combustion engines of motor vehicles, the development of increasingly effective methods for exhaust aftertreatment is necessary. In the case of self-igniting internal combustion engines (diesel engines), the focus of developments is on the reduction of particulate and nitrogen oxide emissions. Particulate emissions can already be effectively reduced today by the use of regenerable particle filters. Furthermore, it is known that a raw emission of nitrogen oxides NO _X , whose catalytic conversion causes problems, in particular in lean-running internal combustion engines, by exhaust gas recirculation measures. In this case, a part of an exhaust gas flow of the internal combustion engine is removed and supplied to the combustion chamber, whereby a combustion temperature is lowered and thus the formation of nitrogen oxides is reduced. However, as exhaust gas recirculation causes an increase in particulate emissions, their application is limited.

In order to reduce the NO _x emissions, the use of NO _x storage catalytic converters is therefore known, in particular in spark-ignited internal combustion engines (gasoline engines). According to the current state of the art, NO _x storage catalysts comprise a barium salt-based NO _x storage component and a 3-way catalytic component for converting unburned hydrocarbons HC, carbon monoxide CO and NO _x . The catalyst component usually consists of platinum, rhodium and / or palladium. In a lean operating mode of the internal combustion engine, in which due to the oxygen excess in the exhaust gas, no complete 3-way catalytic conversion of nitrogen oxides is possible, there is an absorption of NO _x in the form of nitrate by the storage component. In exhausted storage capacity of the NO _x -storage device in periodically performed regeneration phases denitrification of the NO _x -storage device is performed, wherein the NO _X storage catalytic converter for a short time, typically for about 5 seconds, with a rich exhaust gas atmosphere in a preferred temperature range of 200 to 350 ° C is applied (NO _X regeneration). Under these conditions, NO _{x is desorbed} from the reservoir and a reduction in the catalyst component to nitrogen.

A contained in today's gasoline sulfur content is a problem for NO _X storage catalytic converters because the mainly with NO _X also intercalates as SO ₂ in the exhaust gas present sulfur competitive in the NO _X storage component in the form of sulfate. The storage locations occupied by the sulfur are then no longer available for the NO _x absorption, so that there is a decrease in the NO _x storage capacity and the NO _x conversion rate. The sulfur incorporation is not reversible under the conditions of NO _x regeneration. Rather, the desorption of sulfur requires much higher catalyst temperatures, usually above 600 ° C, and significantly longer periods of rich exhaust gas, for example, over 240 s. For this reason is known wherein a detected as based on a decreasing NO _X -Konvertierungsrate sulfur poisoning desulfurization carried out under the conditions mentioned. For this purpose, heating of the NO _x storage catalytic converter is initially effected in a heating phase by means of suitable engine measures to a temperature which corresponds at least approximately to a catalyst-specific minimum desulphurisation temperature. Subsequently, the actual desulfurization takes place by charging the NO _x storage catalytic converter with a stoichiometric or rich exhaust gas atmosphere.

Furthermore, for example DE 198 35 808 A and DE 198 49 082 A for lean-burn internal combustion engines known to perform the fat injection of the NO _X storage catalyst during desulfurization in a so-called wobble operation, in which the internal combustion engine is operated in a fast lean-fat change by a mean lambda value of λ ≤ 1. Owing to the short lean phases occurring in this case, oxygen storage in the NO _x storage catalytic converter occurs, as a result of which the evolution of hydrogen sulphide H ₂ S can be counteracted effectively in favor of the formation of sulfur dioxide SO ₂ .

In practice, the use of NO _x storage catalytic converters for diesel engines has not yet been realized. This is due in particular to the fact that diesel engines are not readily operable due to their heterogeneous mixture formation in the rich operating conditions necessary for the desulfurization of the NO _x storage catalytic converter. In particular, in a substoichiometric mixture composition no reliable ignition can be guaranteed and it must be expected with unfavorable torque fluctuations.

DE 198 47 875 A describes carrying out the desulfurization of a NO _x storage catalytic converter of a diesel engine, wherein after a heating phase, the actual desulfurization is performed. The required enrichment of the air-fuel mixture to a lambda value ≤ 1 takes place by partial throttling of the engine, increasing the EGR rate, lowering the boost pressure, increasing the pilot injection quantity, increasing the post-injection quantity and / or lowering the main injection quantity. DE 198 47 875 A contains no information as to whether or how a lambda control takes place during the desulfurization.

The invention is therefore an object of the invention to provide a method for desulfurization of a NO _x storage catalytic converter in diesel engines available, in which an emission of hydrogen sulfide H ₂ S, carbon dioxide COS and carbon disulfide CS _{2 is} suppressed as much as possible and at the same time a reliable ignition and ensures high torque neutrality. In particular, the method should ensure a fast and accurate lambda control. In addition, a device is to be provided with which the method can be carried out.

This object is achieved by methods having the features mentioned in the independent claim 1 as well as by a device according to claim 18.

According to the inventive method, the regulation of the exhaust lambda during a pre-heating phase of the NO _x storage phase preceding the wobble phase is effected by influencing an exhaust gas recirculation rate (manipulated variable), all other combustion-relevant operating parameters, such as intake manifold throttle position, boost pressure, rail pressure of a fuel injection system, in particular of a high-pressure injection system, activation start and activation duration of pre-, main- and post-injection, map-dependent pilot-controlled. Advantage of the lambda control over the exhaust gas recirculation rate over control over fuel quantity is here a lower sensitivity to control deviations.

According to a preferred embodiment of the method, a regulation of the exhaust gas lambda takes place during the alternating exhaust gas charging of the NO _x storage catalytic converter by influencing an injected fuel quantity of at least one injection of a working cycle of at least one cylinder of the diesel engine. Thus, the injected amount of fuel is used as the actual manipulated variable for controlling the air-fuel ratio during the wobble phase. In contrast to the lambda control, which is usually air-side in gasoline engines, the fuel-side control offers the advantage of being able to set the desired air conditions very quickly, in the engine's operating stroke speed, and with high precision. It has proven particularly advantageous to influence the injected fuel quantity over a control period of the at least one injection taking place in the working cycle. Typically, diesel engines are operated in standard mode with two fuel injections, a pilot injection and a main injection. Here, the activation duration of the main injection for lambda control can preferably be varied. Particularly advantageously, a lambda reduction (enrichment) required for the desulfurization of the NO _x storage catalytic converter is realized by an additional post-injection made after top dead center. In this case, it is particularly advantageous to influence the amount of fuel over the activation period of the post-injection.

With the exception of the activation duration of the relevant injection used for the lambda control, all the other combustion-relevant remaining parameters are kept at least approximately constant during the wobble operation, wherein a characteristic-diagram-dependent control is provided. The parameters include in particular an exhaust gas recirculation rate, a Saugrohrdrosselklappenstellung, a boost pressure, a rail pressure of a fuel injection system, in particular a high-pressure injection system, Ansteuerbeginne of pre-, main and post injection and the Ansteuerdauern the respective not influenced for lambda control injections. In this case, preferably the operating parameters set during the previous heating phase by regulation or pilot control are adopted.

The average exhaust lambda in the wobble mode is in particular 0.97 to 1.03, preferably 0.99 to 1.01 and particularly advantageously exactly 1.00.

According to a particularly advantageous embodiment of the method, during the alternating exhaust gas charging of the NO _x storage catalytic converter, a motor torque output by the diesel engine to a transmission is kept constant with respect to a motor torque delivered before the wobble operation. This is preferably done by adjusting the exhaust gas recirculation rate as a function of a deviation of the fuel quantity injected before the wobble operation from an average fuel quantity injected during the wobble operation.

The present object is further achieved by an apparatus characterized by means adapted to control the exhaust lambda during the heating phase of the NO _X - Storage catalytic converter by influencing an exhaust gas recirculation rate of the diesel engine associated exhaust gas recirculation perform. Preferably, the means are further configured to perform a regulation of the exhaust gas lambda during the alternating exhaust gas charging of the NO _x storage catalyst (wobble phase) by influencing an injected fuel quantity of at least one injection of a working cycle of at least one cylinder of the diesel engine.

The means preferably comprise an algorithm for carrying out the regulation of the exhaust gas lambda during the heating phase and / or during the alternating exhaust gas charging of the NO _x storage catalytic converter in digital form. The algorithm can be integrated in a control unit, in particular in a conventional engine control unit.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The invention will be explained in more detail in an embodiment with reference to the accompanying drawings. Show it:

1 schematically a diesel engine with downstream exhaust system;

2 time profiles of vehicle speed, exhaust lambda and activation periods of pre, main and post-injection during a desulphurisation of a NO _x storage catalytic converter according to FIG 1 ;

3 chronological courses of activation start of pilot, main and post-injection during desulphurisation;

4 Temporal characteristics of throttle position, exhaust gas recirculation rate, boost pressure and rail pressure during desulfurization and

5 chronological courses of temperatures at different locations of the diesel engine and the exhaust system during desulfurization.

An in 1 illustrated diesel engine 10 includes, for example, four cylinders 12 , in which a direct fuel injection by means of a likewise indicated high-pressure injection system 14 he follows. An air supply to the cylinders 12 of the diesel engine 10 via an air intake pipe 16 in which a throttle 18 is arranged to control a sucked air mass via a throttle valve actuator, not shown here. It may also also not shown exhaust gas turbocharger for compression of the cylinders 12 be provided supplied air mass.

The diesel engine 12 is also with an exhaust gas recirculation device 20 fitted. This includes an exhaust gas recirculation line 22 , via which a partial exhaust gas flow of a diesel engine 10 downstream exhaust duct 24 taken and the sucked air mass and thus combustion chambers of the cylinder 12 is supplied. An exhaust gas recirculation (EGR) rate is by means of one in the exhaust gas recirculation line 22 arranged EGR valves 26 variably adjustable by means of an EGR actuator, not shown. The measure of the exhaust gas recirculation causes a lowering of the combustion temperature in the cylinders 12 , Due to a pronounced temperature sensitivity of the nitrogen oxide formation of the combustion process, the exhaust gas recirculation leads to a reduction of the NO _x raw emission of the diesel engine 10 reached. However, due to an increased tendency for particle formation with increasing EGR rates, exhaust gas recirculation is limited.

All combustion-relevant parameters are controlled by an engine control unit 28 partly controlled or regulated as a function of stored speed and engine load dependent maps. In particular, the EGR rate is controlled by driving the EGR valve 26 that the diesel engine 10 supplied air mass by controlling the position of the throttle 18 and a boost pressure of the turbocharger not shown by the engine control unit 28 predetermined and controlled. Furthermore, there is the engine control unit 28 all injection parameters of the high-pressure injection system 14 in front. These are in particular a rail pressure with which the fuel is injected into the combustion chamber, the number of injections during a working cycle of a cylinder 12 as well as the drive starts and drive durations of the various injections.

One from the diesel engine 10 produced exhaust gas is used to reduce the emission of pollutants in a total with 30 designated exhaust system aftertreated. The exhaust system 30 includes one in the exhaust passage 24 arranged catalyst system 32 . 34 and a number of different sensors 36 . 38 . 40 . 42 , The catalyst system includes in an advantageous embodiment, a small volume, close to the engine arranged Oxidationsvorkatalysator 32 which mainly supports conversion of unburned hydrocarbons HC and carbon monoxide CO and nitrogen monoxide NO to nitrogen dioxide NO ₂ . A large-volume, downstream NO _X storage catalytic converter 34 absorbed in lean operating phases of the diesel engine 10 Nitrogen oxides NO _{x of} the exhaust gas and releases them in short intermediate fat regeneration phases again and reduces them to nitrogen.

A monitoring and control of the air-fuel mixture of the diesel engine 10 he follows by measuring the Abgaslambda with an oxygen-sensitive measuring device 36 , which is in particular a lambda probe, preferably a broadband lambda probe. Monitoring NO _x conversion activity of the storage catalyst 34 is advantageously carried out with this downstream NO _x sensor 38 measuring a concentration of nitrogen oxides in the exhaust gas. Optionally, upstream and / or downstream of the storage catalyst 34 temperature sensors 40 . 42 arranged, which detect an exhaust gas temperature and the determination of the catalyst temperature of the storage catalyst 34 allow. All from the sensors 36 . 38 . 40 . 42 provided signals are sent to the engine control unit 28 transmitted and processed. The engine control unit 28 controls the various operating parameters of the diesel engine in response to these signals 10 , For example, at one through the NO _x sensor 38 detected, decreasing conversion rate of the NO _x storage catalyst 34 the diesel engine 10 briefly tuned to a rich mixture to a regeneration of the storage catalyst 34 to effect. In particular, the engine control unit comprises 28 also an algorithm 44 to carry out a desulfurization of the NO _x storage catalytic converter 34 according to the present invention.

The process of the invention for the desulfurization of the NO _x storage catalytic converter 34 should be based on the 2 to 5 be explained. These figures show the time course of different operating parameters of the diesel engine 10 and various control, manipulated and controlled variables during the execution of a desulfurization according to an advantageous embodiment of the method according to the invention. The starting point of the method is the determination of a sulfurization of the NO _x storage catalytic converter 34 , In this case, the monitoring of the degree of sulfurization of the NO _x storage catalytic converter 34 with the help of the downstream NO _X sensor 38 take place, for example, despite a successful NO _x regeneration of the storage catalyst 34 detected a critical NO _X breakthrough in lean operation. Alternatively, the Verschwefelungsgrad also calculated by the engine control unit 28 depending on suitable operating parameters of the diesel engine 10 , such as engine speed, engine load and / or vehicle speed, are modeled.

If a need for desulfurization has been determined, it is first checked whether an operating point of the engine that is favorable for desulphurisation is used 10 is present. For example, to carry out the desulfurization, a vehicle speed (curve 50 . 2 to 5 ) between 50 and 160 km / h, in particular between 70 and 140 km / h. Desulfurization can be carried out particularly advantageously at a speed of between 90 and 100 km / h, since relatively high exhaust-gas temperatures are already present in this region and, at the same time, torque compensation is possible over a wide range.

If the above conditions are met, a heating phase TH is first introduced to the NO _x storage catalytic converter 34 at least approximately to the required minimum desulfurization temperature. This is dependent on the catalyst composition and in the present example is about 550 ° C. The heating of the catalyst 34 takes place by lowering the initially lean air-fuel mixture to a substantially stoichiometric ratio with λ = 1. Shown in the 2 to 5 is that with the broadband lambda probe 36 measured exhaust lambda (curve 52 ). Alternatively, a slightly lean lambda in the range of 1 to 1.3 can be set during the heating phase, with final switching at the end of the heating phase TH to λ = 1.

According to the illustrated preferred embodiment, the required enrichment is carried out by a post injection of fuel after top dead center in at least one cylinder 12 , In the present example, the post-injection takes place with a control start at 33 ° KWnOT (curve 54 in 3 ). Start of control of pre-injection (curve 56 ) and main injection (curve 58 ) are compared to the lean operation of the diesel engine 10 slightly pre-adjusted, here at 35 or 10 ° KWvOT. The post-injected fuel only partially participates in the combustion. In order to compensate for the component participating in the combustion and the torque generated thereby, the activation duration of the main injection is reduced (curve 60 in 2 ). The activation duration according to the illustrated example during the heating phase TH is 180 μs for the pre-injection (curve 62 ), 320 μs for the main injection (curve 60 ) and 500 μs for the post-injection (curve 64 ). All values given here for the various parameters are dependent on a current operating point of the diesel engine 10 given, in particular of engine speed and load, and therefore may differ significantly in individual cases from the values exemplified here.

As well as the mentioned activation periods (curves 60 . 62 . 64 in 2 ) and activation starts (curves 54 . 56 . 58 in 3 ) of the various injections during the heating phase TH - with the exception of the exhaust gas recirculation rate - the other combustion-relevant parameters are piloted to largely constant map-dependent specifications. As in 4 can be seen, these are in particular the position of the throttle 18 , which is represented by the size of the duty cycle of the throttle valve actuator (curve 66 ), by the Duty cycle of the boost pressure plate of the exhaust gas turbocharger reproduced boost pressure (curve 68 ) as well as the rail pressure (curve 70 ), which in the representation of the 4 (lying at 820 bar) essentially of the course of the exhaust lambras 52 is covered.

In the heating phase TH according to the invention by the broadband lambda probe 36 measured exhaust lambda (curve 52 ) is adjusted by influencing the exhaust gas recirculation rate to the desired target value of λ = 1 here. The necessary control actions therefore lead during the heating phase TH to fluctuations in the duty cycle of the EGR controller (curve 72 ).

By the lambda reduction from the original lean lambda to λ = 1 in the heating phase TH, on the one hand an increase in the combustion temperature and thus the catalyst temperatures is achieved. This is especially true of the in 5 shown course of the exhaust gas temperature upstream of the oxidation catalyst 32 (Curve 74 ), which shows a sharp increase immediately after onset of post-injection. A further heating effect is achieved by the not participating in the combustion of the fuel supplied by the post-injection amount of fuel. The post-injected fuel leads to an increase of unburned hydrocarbons HC and carbon monoxide CO in the exhaust gas, which are mainly due to the oxidation catalyst 32 be implemented (afterburning). The exotherm of the catalytic afterburning leads to a heating of the oxidation catalyst 32 and the exhaust gas temperature downstream of the oxidation catalyst 32 (Curve 76 ). Due to an exhaust gas runtime between oxidation catalyst 32 and NO _X storage catalyst 34 is upstream of the NO _X storage catalyst 34 only with some time delay, an increase in the exhaust gas temperature and certain heat losses observed (curve 78 ). Like the course of the exhaust gas temperature behind the NO _X storage catalytic converter 34 (Curve 80 ) illustrates, finds a warming of the storage catalyst 34 again considerably delayed, which is mainly due to the thermal inertia of the relatively large catalyst mass. Furthermore, in 5 with the curves 82 and 84 the curves of the exhaust gas temperatures shown upstream or downstream of the exhaust gas turbocharger, which also reflect the heating of the exhaust gas.

Once the NO _X storage catalyst 34 has a minimum desulfurization temperature, the actual sulfur discharge from the NO _X storage catalyst begins 34 by thermal dissociation of the incorporated sulfate in SO ₃ and subsequent reduction of the catalyst component. It is known that at a constant admission of the catalyst 34 with a rich exhaust atmosphere due to the virtual absence of oxygen in the exhaust gas and in an oxygen storage of the NO _x storage catalyst 34 the sulfur is largely discharged in the form of hydrogen sulfide H ₂ S, carbon dioxide sulfide COS and carbon disulfide CS ₂ . However, these compounds are odorous and / or toxic, which is why their formation should be largely suppressed. Therefore, once using the temperature sensors 40 . 42 a temperature is determined which is at a predefinable desulphurisation temperature of the NO _x storage catalytic converter 34 close, initiating a so-called wobble phase TW, while that of the NO _X storage catalyst 34 is acted upon in a quick change with a rich and lean exhaust lambda. The short lean phases become a partial replenishment of the oxygen storage of the NO _x storage catalyst 34 causes, which is reduced in the fat phases, the released SO ₃ only up to the oxidation state of SO ₂ and discharged. Preferably, according to the present invention, the "wobble" is performed by a mean exhaust lambda of λ = 1, which was already adjusted at least at the end of the previous heating phase TH. The lean specification of the wobble phase TW is advantageously set to a maximum of 1.10, preferably to 1.05, and the fat specification to a minimum of 0.90, preferably to 0.95.

According to the invention, the regulation of the exhaust gas lambda takes place during the wobble phase TW by influencing the fuel quantity, in particular that of the post-injection. This is preferably carried out by changing the activation duration of the post-injection ( 2 , Curve 64 ), which allows a particularly fast and precise control. For this purpose, the fastest possible lambda controller should be used.

The control parameters of the parameters activation periods of pre-injection and main injection, control start of pilot, main and post injection, throttle position, boost pressure and rail pressure are also pre-controlled during the wobble phase TW, the specifications of the heating phase TH are taken. Furthermore, the duty cycle of the EGR controller present at the end of the heating phase TH is "frozen" and initially also taken over (FIG. 4 , Curve 72 ).

In order to ensure the highest possible torque neutrality during the wobble phase TW, the fuel quantity injected in the wobble phase TW is adjusted to the fuel quantity injected in the heating phase TH. This is done during the alternating admission of the NO _x storage catalytic converter 34 a time average of the amount of fuel or the drive duration of that injection determined, which is used for lambda control, in the present case the post-injection. This mean value is then compared with the fuel quantity or the activation duration of the relevant injection during the heating phase TH. If a deviation between mean fuel quantity / activation duration is determined before and during the wobble operation, a correction of the exhaust gas recirculation rate is undertaken.

This change in the EGR rate takes place - depending on a sign of the deviation - in the direction of a greater or lower EGR rate and is preferably carried out by stepwise adjustment of the duty cycle of the EGR controller.

To determine the step size different strategies are conceivable. First, a fixed step size can be specified, which is applied as often as practically no mean value deviation is detected. According to another possibility, the step size is determined as a function of a height of the deviation of the mean value using a stored characteristic curve. Finally, it is conceivable to determine the step size as a function of the height of the mean value deviation and the output value of the initially frozen duty cycle of the EGR controller using a corresponding characteristic map.

Thus, while the lambda control over the control period of the post-injection (curve 64 ) is still active while maintaining the rich and lean Lambdavorgaben, automatically sets by the described EGR correction, a reduction in the deviation of the mean driving time of the post-injection from the pre-controlled operation before the wobble operation of the post-injection. As soon as there is a compensation of the activation periods, the duty cycle of the EGR controller or the EGR rate is frozen again.

It can also be advantageously provided by the NO _x storage catalytic converter 34 downstream temperature sensor 42 to monitor the exhaust gas temperature during desulfurization to detect temperature peaks caused by the exothermic combustion of HC. In this way becomes a critical, the NO _X storage catalyst 34 Detected damaging temperature, the desulfurization is initially interrupted until a sufficient cooling is detected, and then again (as described) initiated and completed.

After desulphurization has ended, all combustion-relevant parameters or the corresponding actuators are restored to their initial state.

LIST OF REFERENCE NUMBERS

10

diesel engine

12

cylinder

14

High-pressure injection

16

air intake pipe

18

throttle

20

Exhaust gas recirculation device

22

Exhaust gas recirculation line

24

exhaust duct

26

Exhaust gas recirculation valve

28

Engine control unit

30

exhaust system

32

oxidation catalyst

34

NO _X storage catalyst

36

Broadband lambda probe

38

NO _x sensor

40

temperature sensor

42

temperature sensor

50

vehicle speed

52

lambda

54

Activation start post-injection

56

Start of control pilot injection

58

Start of control main injection

60

Activation time main injection

62

Control duration pilot injection

64

Activation time post-injection

66

Duty cycle throttle valve actuator

68

Duty cycle boost pressure plate

70

rail pressure

72

Duty cycle AGR controller

74

Exhaust gas temperature before oxidation catalyst

76

Exhaust gas temperature after oxidation catalyst

78

Exhaust gas temperature before NO _X storage catalytic converter

80

Exhaust gas temperature after NO _X storage catalytic converter

82

Exhaust gas temperature in front of turbocharger

84

Exhaust temperature after turbocharger

TH

heating phase

TW

Wobble phase

Claims (21)

Method for desulphurizing a diesel engine ( 10 ) downstream NO _x storage catalytic converter ( 34 ), wherein the NO _x storage catalyst ( 34 ) During a heating phase (TH) is at least approximately heated to a desulfurization temperature, and (in a subsequent wobble phase TW) is alternately supplied with a rich exhaust gas the lambda with λ <1, and a lean exhaust gas the lambda with λ> 1 at a predeterminable mean exhaust gas lambda, characterized characterized in that a regulation of the exhaust gas lambda during the heating phase (TH) of the NO _x storage catalytic converter ( 34 ) by influencing an exhaust gas recirculation rate of an exhaust gas recirculation device assigned to the diesel engine ( 26 ) as the manipulated variable of the control. A method according to claim 1, characterized in that during the heating phase (TH) of the NO _x storage catalytic converter ( 34 ), the operating parameters Saugrohrdrosselklappenstellung, boost pressure, rail pressure of a fuel injection system, control start of pre-, main and post-injection and control duration of pre-, main and post injection are map controlled depending on the map. A method according to claim 1 or 2, characterized in that during the heating phase (TH), the average exhaust lambda to λ ≥ 1, in particular to 1 to 1.3, is regulated. Method according to one of the preceding claims, characterized in that the regulation of the exhaust gas lambda during the alternating exhaust gas charging (TW) of the NO _x storage catalytic converter ( 34 ) by influencing an injected fuel quantity of at least one injection of a working cycle of at least one cylinder ( 12 ) of the diesel engine ( 10 ) as the manipulated variable of the control. A method according to claim 4, characterized in that during the alternating exhaust gas charging (TW) of the NO _x storage catalytic converter ( 34 ) the injected fuel quantity over a control period of the at least one injection of the working cycle of the cylinder ( 12 ) being affected. A method according to claim 5, characterized in that the injected fuel quantity over the control period before a top dead center of the at least one cylinder ( 12 ) starting main injection is influenced. A method according to claim 5, characterized in that the injected amount of fuel over the driving time of a subsequent to the production of the middle exhaust lambda in addition to the main and / or a pilot injection and after top dead center starting post-injection is influenced. Method according to one of claims 4 to 7, characterized in that during the alternating exhaust gas charging (TW) of the NO _x storage catalytic converter ( 34 ) the operating parameters exhaust gas recirculation rate, intake manifold throttle position, boost pressure, rail pressure of a fuel injection system ( 14 ), Control start of pre, main and post injection and control duration of not influenced for lambda control injection are controlled at least approximately constant. Method according to claim 8, characterized in that during the alternating exhaust gas charging (TW) of the NO _x storage catalytic converter (TW) 34 ) the operating parameters of the previous heating phase (TH) are at least initially adopted. Method according to one of claims 4 to 7, characterized in that during the alternating exhaust gas charging (TW) of the NO _x storage catalytic converter ( 34 ) an engine torque of the diesel engine ( 10 ) is maintained at least substantially constant by adjusting the exhaust gas recirculation rate relative to an engine torque delivered before the alternate exhaust gas application. A method according to claim 10, characterized in that a change in the engine torque during the alternating Abgasbeaufschlagung (TW) is determined by comparing an average amount of fuel during the alternating Abgasbeaufschlagung (TW) for lambda control influenced injection compared to the injected before the alternating Abgasbeaufschlagung amount of fuel of this injection. Method according to one of claims 4 to 11, characterized in that during the alternating exhaust gas charging (TW) of the NO _x storage catalytic converter ( 34 ) the average exhaust lambda is 0.97 to 1.03, in particular 0.99 to 1.01. Method according to one of claims 4 to 12, characterized in that during the alternating exhaust gas charging (TW) of the NO _x storage catalytic converter ( 34 ) is the rich exhaust lambda ≥ 0.90, in particular 0.95, and the lean exhaust lambda ≤ 1.10, in particular 1.05, is. Method according to one of the preceding claims, characterized in that the desulfurization at a speed of one of the diesel engine ( 10 ) driven vehicle between 50 and 160 km / h, in particular between 70 and 140 km / h, in particular between 90 and 100 km / h, is performed. Method according to one of the preceding claims, characterized in that a degree of sulfurization of the NO _x storage catalytic converter ( 34 ) using a NO _x storage catalytic converter ( 34 ) downstream NO _x sensor ( 38 ) or depending on operating parameters of the diesel engine ( 10 ) is calculated. Method according to one of the preceding claims, characterized in that the exhaust lambda via an oxygen-sensitive measuring device ( 36 ), in particular a lambda probe, in particular a broadband lambda probe is measured. Method according to one of the preceding claims, characterized in that the Catalyst temperature of the NO _x storage catalyst ( 34 ) based on an upstream and / or downstream of the NO _x storage catalytic converter ( 34 ) with a temperature sensor ( 40 . 42 ) measured exhaust gas temperature is determined and / or modeled by calculation. Device for the desulphurisation of a diesel engine ( 10 ) downstream NO _x storage catalytic converter ( 34 ), wherein the NO _x storage catalyst ( 34 ) is heated during a heating phase (TH) at least approximately to a desulfurization temperature and in a subsequent wobble phase (TW) alternately with a rich exhaust lambda with λ <1 and a lean Abgaslambda with λ> 1 is acted upon at a predetermined mean exhaust lambda by means that are arranged, a regulation of the exhaust lambda during the heating phase (TH) of the NO _x storage catalytic converter ( 34 ) by influencing an exhaust gas recirculation rate of an exhaust gas recirculation device assigned to the diesel engine ( 22 ) as the manipulated variable of the control. Apparatus according to claim 18, characterized in that the means are further arranged, a regulation of the exhaust gas lambda during the alternating exhaust admission (TW) of the NO _x storage catalytic converter ( 34 ) by influencing an injected fuel quantity of at least one injection of a working cycle of at least one cylinder ( 12 ) of the diesel engine ( 10 ) as the manipulated variable of the control. Device according to claim 18 or 19, characterized in that the means comprise an algorithm ( 44 ) in digital form for carrying out the regulation of the exhaust gas lambda during the heating phase (TH) of the NO _x storage catalytic converter ( 34 ) and / or during the alternate exhaust gas charging (TW) of the NO _x storage catalytic converter (TW) 34 ). Device according to claim 20, characterized in that the algorithm ( 44 ) in a control unit, in particular in an engine control unit ( 28 ) is integrated.

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