DE102016205265A1 - Method and device for operating an SCR exhaust aftertreatment device - Google Patents

Abstract

The invention relates to a method and a device for operating an exhaust aftertreatment device (1) in the exhaust system of a motor vehicle having an internal combustion engine (2), the operation of the internal combustion engine (2) being carried out as a function of the requirements of the operation of the exhaust aftertreatment device (1). According to the invention, the exhaust aftertreatment device is an SCR exhaust aftertreatment device (1), and the motor vehicle is an autonomous driving vehicle whose driving profile is determined by an algorithm, the driving profile being dependent on the needs of the operation of the SCR exhaust aftertreatment device (1). is determined.

Description

The invention relates to a method and a device for operating an exhaust aftertreatment device in the exhaust system of a motor vehicle with an internal combustion engine, wherein the operation of the internal combustion engine is carried out depending on the needs of the operation of the exhaust aftertreatment device, according to the preambles of the independent claims.

Internal combustion engines often generate significant amounts of nitrogen oxides (NOx, ie NO and NO ₂ ) during operation. Especially in diesel and petrol engines used in motor vehicles, the amounts of nitrogen oxide in the exhaust gas are generally above the permissible limits, so that an exhaust aftertreatment to reduce the NOx emissions is necessary. In many engines, the reduction of nitrogen oxides by the non-oxidized constituents contained in the exhaust gas, namely by carbon monoxide (CO) and unburned hydrocarbons (HC), using a three-way catalyst. However, this process is not available in particular in the case of diesel and Otto lean-burn engines, since the reduction of NOx is not or hardly occurs due to the high proportion of oxygen in the exhaust gas. In lean-burn engines, therefore, according to a widespread method, an NOx storage catalytic converter (Lean NOx Trap, LNT) is used, which receives and stores the nitrogen oxides contained in the exhaust gas of the internal combustion engine. From time to time, there is a regeneration of the NOx storage catalytic converter, for which a fuel excess is generated in the exhaust gas conducted through the NOx storage catalytic converter.

An alternative or additionally usable method for nitrogen oxide reduction is SCR exhaust aftertreatment, i. H. with Selective Catalytic Reaction (SCR), which also meets very strict standards for vehicle emission limits. SCR exhaust aftertreatment devices are z. B. SCR catalysts and SCR-coated diesel particulate filter, called SDPF.

For selective catalytic reduction, ammonia (NH ₃ ) is admixed to the exhaust gas, in the case of motor vehicle internal combustion engines in the form of an aqueous urea solution called AdBlue. The urea dosing must correspond to the current nitrogen oxide emission of the internal combustion engine and therefore depends on the current operating conditions of the engine. If the dosage is too low, too little nitrogen oxide is reduced to comply with the pollutant limits. If the dosage is too high, excess ammonia enters the exhaust gas, which is called NH ₃ slip. This must be prevented because ammonia is harmful to health, even in very small concentrations leads to an odor nuisance and may affect downstream exhaust aftertreatment devices. At higher temperatures, ammonia can also oxidize and form NOx, reducing net NOx conversion efficiency.

From the US 2014/0150409 A1 and the US 2011/0202253 A1 It is known to optimize the NOx conversion efficiency of an SCR exhaust aftertreatment device in a driver-controlled motor vehicle on the basis of engine parameters, and from the US 8 392 091 B2 It is known to carry out such an optimization on the basis of position and / or traffic data. Furthermore, it is from the US 8 800 274 B2 Known to change motor parameters when NH ₃ slip occurs.

In an SCR exhaust aftertreatment device, self-diagnostics (OBD) must also be performed at predetermined intervals, inter alia to monitor their heat aging, which will reduce NOx conversion efficiency as a function of the temperatures to which the SCR exhaust after-treatment device is exposed is getting smaller over time. Some US emissions agencies also require a minimum number of monitoring operations over a period of operation.

The US 2014/0331752 A1 teaches that SCR exhaust aftertreatment devices can only be monitored to a limited extent while the vehicle is traveling on the road, because order, timing and control of diagnostic procedures are often not ideal, and suggests making diagnostics while the vehicle is stationary and the engine is in an appropriate state Operating point is running.

In driver-controlled internal combustion engine and SCR exhaust aftertreatment devices, driver commands in the form of accelerator pedal position and possibly gear selection normally override the operating needs of the SCR exhaust aftertreatment device to optimize NOx conversion efficiency, minimize NH ₃ slip, and perform self-diagnostics at predetermined intervals. This limits the ability to keep the SCR exhaust aftertreatment device in optimal working ranges for the stated objectives. In addition, a more aggressive driving style is accompanied by sudden changes in temperature and volumetric flow of the exhaust gas flowing into and through the exhaust aftertreatment device, which makes prescribed diagnoses difficult or unreliable or even impossible.

From the US Pat. No. 7,621,120 B2 a method for driving a NOx storage catalyst and a particulate filter for the purpose of regeneration in hybrid vehicles is known. In a vehicle with hybrid drive, an internal combustion engine and an electric motor are provided, the output torques of which can be conducted to the drive wheels of the vehicle. The electric motor is able to be operated as a generator and thus can also apply braking torques to the vehicle wheels. In the known method, an operating state of the internal combustion engine is adapted for producing a suitable operating state of the NOx storage catalytic converter, for example for the purpose of regeneration. If the torque output in this adjusted operating state of the internal combustion engine does not match the driving intention currently set by the driver of the hybrid vehicle, the electric motor is operated as a motor in order to possibly provide additional torque to the drive wheels of the vehicle. If necessary, the electric motor can also be operated as a generator, so that in the operating state of the internal combustion engine desired for the regeneration, torque also emitted can be converted into electrical energy for charging accumulators of the hybrid vehicle. This is the case, in particular, when the current driving intention of the driver of the hybrid vehicle retrieves a drive torque of the drive wheels which is lower than that provided by the internal combustion engine.

The DE 101 58 480 C1 discloses a method and apparatus having the features of the preambles of the independent claims wherein operating parameters of the internal combustion engine are adjusted in response to probabilities of characteristics for its future operation to achieve optimal efficiency of the exhaust aftertreatment device while optimizing fuel economy.

It is conceivable that in the DE 101 58 480 C1 disclosed methods instead of performing in a driver-controlled vehicle in a vehicle capable of autonomous driving, as for example in the DE 39 12 353 A1 is described and whose driving profile is determined by an algorithm. In this case, nothing else would have to be done than simply replacing the probabilities of parameters with parameters resulting from the set driving profile.

The invention is based on the object to be able to meet even better operating needs of exhaust aftertreatment devices in motor vehicles.

This object is achieved according to the invention by a method and an apparatus having the features of the independent claims.

Advantageous developments of the invention are specified in the dependent claims.

According to the invention, the exhaust aftertreatment device is an SCR exhaust aftertreatment device, i. H. an exhaust aftertreatment device with selective catalytic reduction, and the motor vehicle is an autonomous driving capable vehicle whose driving profile is determined not by the driver but by an algorithm, the driving profile being determined depending on the needs of the operation of the SCR exhaust aftertreatment device.

In the invention, something other than what would happen in a vehicle capable of autonomous driving, in which the in the DE 101 58 480 C1 disclosed method is performed. It is not adapted to the needs of the exhaust aftertreatment device, the operation of the internal combustion engine taking into account a driving profile, but the driving profile itself is adjusted so that the needs are met. This makes it possible to better meet the special needs of SCR exhaust aftertreatment devices, which have higher demands on certain operating conditions than z. B. nitrogen oxide storage catalysts.

According to the invention, the motor vehicle is a vehicle capable of autonomous driving. This is generally understood to mean a motor vehicle that autonomously steers regularly on public roads in order to move people and / or goods from one place to another without anyone having to operate any pedals, a gear lever or a steering wheel. For the purposes of the present invention, the vehicle capable of autonomous driving should also be a partially autonomous motor vehicle, in which the driver still has certain monitoring functions and possibly even steers himself or at least can carry out corrective steering interventions, since the present invention also applies to motor vehicles If it is sufficient that the accelerator pedal and brake pedal as well as the clutch pedal and gear selector remain unchecked on a given route.

In such a motor vehicle, it is possible to carry out the autonomous driving operation depending on the needs of the operation of the exhaust gas aftertreatment device, because in contrast to driver-controlled motor vehicles much more leeway exists, the operating parameters of the Combustion engine in favor of the needs of the SCR exhaust aftertreatment device to choose.

In particular, the internal combustion engine may be operated during autonomous driving both in response to any computationally generated driving commands to reach the driving destination along a driveway to be traveled, as occurs in autonomous automobiles, and depending on the needs of the SCR exhaust aftertreatment device. The computationally generated travel commands may include speed, torque and engaged gear of a transmission of the internal combustion engine.

In this way, a driving profile of the autonomously driving motor vehicle with respect to one or more driving profile parameters such. B. driving speed and gear ratio of a transmission are adapted such that at least one of the needs of the SCR exhaust aftertreatment device corresponding operating parameters of the SCR exhaust aftertreatment device is within a setpoint window.

The invention therefore consciously uses a degree of freedom for influencing operating parameters of the SCR exhaust gas aftertreatment device which is present in an autonomously driving vehicle. According to the invention it has been recognized that this degree of freedom is the independence of a given driver's request. With this knowledge, it is possible to influence the driving profile of the autonomously driving vehicle without this being perceived as unpleasant or undesirable by the occupants of the autonomously driving vehicle. As a result, the operating parameters of the SCR exhaust gas aftertreatment device can be influenced in a simple and effective manner, so that optimal or phase-specific other conditions for their operation prevail over a longer period of time.

In one embodiment of the invention, the operating needs of the exhaust aftertreatment device include optimizing its NOx conversion efficiency and minimizing NH ₃ slip and NH ₃ oxidation.

In another embodiment of the invention, the operational needs of the exhaust aftertreatment device include self-diagnostics at predetermined intervals. In response to a request to diagnose the heat aging of the exhaust aftertreatment device, the autonomous driving operation and the operation of the internal combustion engine may be performed such that the temperature and the space velocity of the exhaust gas flowing into and through the exhaust after-treatment device move within predetermined limits during self-diagnosis.

The abovementioned embodiments have in common that the operating requirements of the exhaust gas aftertreatment device include that one or more operating parameters of the exhaust gas aftertreatment device at least temporarily lie in one or more predefined windows, and that the autonomous driving operation and the operation of the internal combustion engine are performed such that the operating parameters of the exhaust gas aftertreatment device are at least temporarily held in the window or windows.

The following is a description of embodiments with reference to the drawings. Show:

1 a possible arrangement of an SCR catalyst in the exhaust line of a turbocharged internal combustion engine;

2 the temperature dependence of the NH ₃ slip of an SCR catalyst; and

3 Temperature dependencies of the NOx conversion efficiency of an SCR catalyst for different space velocities and rates of aging.

1 shows a possible arrangement of an SCR catalyst 1 in the exhaust system of an internal combustion engine 2 , which may be in particular a diesel or gasoline engine with an exhaust gas turbocharger whose turbine 3 before the SCR catalyst 1 located in the exhaust gas flow path. Upstream and / or downstream of the SCR catalyst 1 For example, further exhaust aftertreatment devices may be arranged, and the SCR catalyst 1 can also be integrated into a diesel particulate filter (SDPF). The SCR catalyst 1 may be located at a relatively random location along the exhaust line. The closer he is to the combustion engine 2 is located and the fewer additional exhaust aftertreatment devices are arranged therebetween, the more direct the temperature of the SCR catalyst 1 by changes in the operating conditions of the internal combustion engine 1 affected.

In the following description of operating methods provided for such SCR exhaust aftertreatment devices installed in an automotive vehicle capable of autonomous driving, the term SCR system is used interchangeably instead of the terms SCR catalyst, SDPF or other SCR exhaust aftertreatment device. Insofar as the term SCR catalyst is used in particular, the corresponding statements may also apply to other SCR systems.

In a first embodiment, virtual driver inputs, namely drive commands of the autonomous driving enabled vehicle, which substitute corresponding human driver inputs, are used to optimize the operating conditions of an SCR system using the virtual driver inputs to improve NOx conversion efficiency In addition, NH ₃ slip and oxidation are minimized.

For SCR systems, the challenge is to optimize NO x conversion efficiency with minimal NH ₃ slip. An SCR system stores ammonia injected by an upstream ammonia injector (active SCR). And if a NOx storage catalyst is used upstream of the SCR system, regeneration of the NOx storage catalyst can produce a larger amount of ammonia, which is then stored in the SCR system (passive SCR).

Ideally, the NH ₃ stored in the SCR system converts all nitrogen oxides in the exhaust into N ₂ , which oxides of nitrogen originate from the engine or may be temporarily stored and desorbed or generated in an upstream exhaust after-treatment device.

• 1. Der Betrieb des SCR-Systems einschließlich des NOx-Umwandlungswirkungsgrades hängt von seinen Betriebsbedingungen Temperatur und Raumgeschwindigkeit, welche einen auf das Katalysatorvolumen normierten Volumenstrom bzw. eine reziproke Verweilzeit des Abgases im SCR-Systems darstellt, und auch von der Ammoniakbeladung des SCR-Systems ab.
• 2. Bei höheren Temperaturen oxidiert Ammoniak und kann NOx bilden, was den NOx-Umwandlungswirkungsgrad vermindert.
• 3. Bei höheren Temperaturen und/oder und Raumgeschwindigkeiten desorbiert gespeichertes Ammoniak aus dem SCR-System, was zu unerwünschtem NH₃-Schlupf führt.
• 4. Ein SCR-System ist nur oberhalb einer Anspringtemperatur funktionsfähig; darunter ist der NOx-Umwandlungswirkungsgrad vernachlässigbar.

The functionality of the SCR system is subject to the following restrictions:

• 1. The operation of the SCR system, including NOx conversion efficiency, depends on its operating conditions of temperature and space velocity, which represents a volumetric flow normalized to catalyst volume, or a reciprocal dwell time of the exhaust gas in the SCR system, and also the ammonia load of the SCR system from.
• 2. At higher temperatures, ammonia oxidizes and may form NOx, which reduces NOx conversion efficiency.
• 3. Ammonia stored at higher temperatures and / or space velocities desorbs from the SCR system, resulting in undesirable NH ₃ slip.
• 4. An SCR system is only functional above a light-off temperature; below that, the NOx conversion efficiency is negligible.

An autonomous driving mode makes it possible to influence the operating conditions of the internal combustion engine and consequently the operating conditions temperature and space velocity of the SCR system.

If a motor vehicle capable of autonomous driving is autonomous driving in its operating mode, the driving profile is no longer determined by the driver, but by an algorithm. This algorithm includes here to optimize the operation of the SCR system.

• 1. Der genaue Sollwert der Fahrzeuggeschwindigkeit, der die vom Motor zu liefernde Leistung und auch die in das Abgas abgegebene Wärme beeinflusst.
• 2. Die Gangwahl, die die Kombination von Motordrehzahl und Motorlast für ein gegebenes Fahrzeuggeschwindigkeits- und Straßenprofil beeinflusst. Diese Kombination kann im Hinblick auf eine benötigte Leistung an den Rädern optimiert werden, indem zwischen einer Kombination niedrigere Motordrehzahl und höhere Motorlast und einer Kombination höhere Motordrehzahl und niedrigere Motorlast gewählt wird. Dabei hat eine Erniedrigung oder Erhöhung des Drehmoments des Verbrennungsmotors direkten Einfluss auf die Temperatur im SCR-System, und der Abgasvolumenstrom kann durch Ändern der Abgasrückführungseinstellungen und der Zylinderfüllung mit der Motorlast beeinflusst werden. Außerdem hat eine Änderung der Motordrehzahl direkten Einfluss auf den Abgasvolumenstrom.
• 3. Die Stärke von Beschleunigungen und Verzögerungen.

During the "autonomous drivers" operating mode, the speed and load of the internal combustion engine can be controlled by the following variables:

• 1. The exact setpoint of the vehicle speed, which affects the power to be supplied by the engine and also the heat released into the exhaust.
• 2. Gear selection, which affects the combination of engine speed and engine load for a given vehicle speed and road profile. This combination can be optimized for required power at the wheels by choosing between a combination of lower engine speed and higher engine load and a combination of higher engine speed and lower engine load. Herein, decreasing or increasing the torque of the internal combustion engine directly affects the temperature in the SCR system, and the exhaust gas volumetric flow can be influenced by changing the exhaust gas recirculation settings and the cylinder charge with the engine load. In addition, a change in the engine speed has a direct influence on the exhaust gas volume flow.
• 3. The strength of accelerations and decelerations.

• 1) das SCR-System im optimalen Betriebsfenster für NOx-Umwandlung zu halten;
• 2) NH₃-Oxidation zu minimieren (z. B. Begrenzen von Lastspitzen des Verbrennungsmotors z. B. bei Beschleunigungen) oder z. B. Steuern von Beschleunigungen derart, dass sie sanft und gleichmäßig stattfinden;
• 3) NH₃-Schlupf zu begrenzen; und
• 4) das Aufwärmen des Katalysators auf seine Anspringtemperatur zu unterstützen.

This freedom can be used to optimize the operation of the SCR system, namely

• 1) keep the SCR system in the optimal NOx conversion operating window;
• 2) to minimize NH ₃ oxidation (eg limiting load peaks of the internal combustion engine, eg during accelerations) or z. B. controlling accelerations such that they take place smoothly and evenly;
• 3) to limit NH ₃ slip; and
• 4) to assist in warming the catalyst to its light-off temperature.

Reactions that can take place in the SCR system are:

Conversion:

• 4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O
• 2NO ₂ + 4NH ₃ + O ₂ → 3N ₂ + 6H ₂ O
• NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O

Oxidation:

• 4NH ₃ + 3O ₂ → 2N ₂ + 6H ₂ O This reaction becomes relevant at higher temperatures.

Ammonia slip:

• NH ₃ + * → NH ₃ * (adsorption, temperature insensitive)
• NH ₃ * → NH ₃ * (desorption, temperature sensitive) The desorption reaction becomes relevant at higher temperatures. Desorption can lead to NH ₃ slip at higher temperatures, especially at high mass flow.

2 shows measured values of the NH ₃ slippage of an SCR catalyst for different catalyst temperatures, which correspond essentially to the inlet temperature of the exhaust gas in a pure SCR catalytic converter. At higher temperatures, NH ₃ slip increases significantly due to desorption. At lower temperatures, however, there is hardly any NH ₃ slippage, so that this can be avoided by the influences described above.

In a second embodiment, the virtual driver inputs are used in the autonomous vehicle to optimize the diagnosis of an SCR system.

The second embodiment eliminates the difficulty of monitoring SCR catalysts in exhaust aftertreatment devices in accordance with regulatory requirements. The monitoring methods must meet so-called IUPR requirements, which specify a minimum level of monitoring events during actual vehicle use by the user. These requirements are difficult to meet with the known monitoring methods.

The difficulty is that the performance and performance of an SCR catalyst is highly dependent on its operating conditions, mainly temperature and space velocity. Thus, for different monitoring methods, the ability to differentiate between different aging states of the SCR catalyst is not uniform across all operating conditions, or there is only a narrow window of operating conditions in which to maximize reliability between a fresh, healthy SCR catalyst aged, no longer sufficiently functional SCR catalyst can be distinguished.

To ensure the robustness of the monitoring, conditions are set under which monitoring is carried out. This limits the detection of inadequate performance or performance of the SCR catalyst to a window of operating conditions under which this detection and a good distinction between different performance or performance is robust.

In practice, the operating conditions of the SCR catalyst depend heavily on the driving profile and engaged gear, which ultimately determine the engine speed and torque, as explained in connection with the first embodiment.

When the autonomous vehicle is in autonomous driving mode, the engine speed and torque of the engine may be controlled such that the operating conditions of the SCR catalyst are within an operating window that provides optimal detection of insufficient performance or performance of the SCR -Catalyst allowed. In particular, the operating window is optimized here for optimum distinction between different aging states, but the monitoring method described in this context can also be used to optimize other diagnoses of an SCR catalytic converter or other SCR system of an internal combustion engine in a motor vehicle capable of autonomous driving.

Similar to the first embodiment, the control of the engine speed and load of the internal combustion engine takes place according to an algorithm, the z. B. on the vehicle speed profile acts (accelerations, delays, exact steady state speed) and gear selection. The driving profile is no longer determined by the driver but, as in the first embodiment, by an algorithm that is expanded in this second embodiment to optimize SCR diagnostics.

In a known method of monitoring an SCR catalyst, NOx conversion efficiency during the warm-up phase is evaluated. With increasing aging, the light-off temperature of an SCR catalyst shifts towards higher temperatures, which means a later start of NOx conversion. This phenomenon can be evaluated in the phase after a cold start.

Another known method of monitoring an SCR catalyst is to evaluate NOx conversion efficiency after the SCR catalyst has started. 3 Figure 4 illustrates that in a typical SCR catalyst, the discernment for aging at higher space velocities (SV) is better. High space velocities could in the operating mode autonomous driving z. B. be favored by delaying the upshift into a higher gear.

During the autonomous driver mode, the engine speed and engine load may be controlled by the same quantities 1 to 3 as indicated above in the first embodiment.

This freedom is used in the second embodiment to control the operating conditions of the SCR catalyst so that diagnostics is possible in a window of optimal operating conditions.

3 shows how the NOx conversion efficiency changes with the operating conditions. There are curves for high and low space velocity and high and low grades depending on the temperature shown.

How to get out 3 recognizes, exists in a wide temperature window A good discrimination between a fresh and an aged SCR catalyst, especially at higher space velocities or volume flows. In temperature window A, the NOx conversion efficiency of a fresh SCR catalyst is generally high, which normally results in greater absolute differences with an aged SCR catalyst, which facilitates the distinction between aging conditions.

Alternatively, there is some such discrimination at lower space velocities in a narrower temperature window B.

A further advantageous application of the autonomous motor vehicle freedom to control the operating conditions of the SCR catalyst is to influence the steady state speed with respect to optimum operating conditions. For example, if 120 km / h is allowed in a stretch of road, it could be optimized to between 100 km / h and 120 km / h.

In addition, the gear selection could be optimized to affect the engine speed toward high exhaust flow rates, which improves the distinction between aging conditions.

The discrimination and any threshold models often suffer from aggressive driving profiles that result in sudden changes in the temperature and flow rate of the SCR catalyst, making the prediction of the phenomenon more difficult and making the evaluation of the monitoring less robust. Due to the freedom gained, accelerations and decelerations can be made more uniform to eliminate sudden changes in temperature and volumetric flow, e.g. During the warm-up phase of the SCR catalyst.

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

• US 2014/0150409 A1 [0005]
• US 2011/0202253 A1 [0005]
• US 8392091 B2 [0005]
• US 8800274 B2 [0005]
• US 2014/0331752 A1 [0007]
• US 7621120 B2 [0009]
• DE 10158480 C1 [0010, 0011, 0016]
• DE 3912353 A1 [0011]

Claims (10)

Method for operating an exhaust aftertreatment device ( 1 ) in the exhaust line of a motor vehicle with an internal combustion engine ( 2 ), wherein the operation of the internal combustion engine ( 2 ) depending on the needs of the operation of the exhaust aftertreatment device ( 1 ), characterized in that the exhaust aftertreatment device is an SCR exhaust aftertreatment device ( 1 ) and that the motor vehicle is an autonomous driving vehicle whose driving profile is determined by an algorithm, the driving profile being dependent on the needs of the operation of the SCR exhaust after-treatment device ( 1 ). Method according to Claim 1, characterized in that the internal combustion engine ( 2 ) during autonomous driving both as a function of computationally generated driving commands for reaching the destination and the needs of the SCR exhaust aftertreatment device ( 1 ) is operated. A method according to claim 1 or 2, characterized in that a driving profile of the autonomously driving motor vehicle with respect to one or more driving profile parameters is adjusted such that at least one of the needs of the SCR exhaust aftertreatment device ( 1 ) corresponding operating parameters of the SCR exhaust aftertreatment device ( 1 ) is within a setpoint window. Method according to one of the preceding claims, characterized in that the speed, torque and engaged gear of a transmission of the internal combustion engine ( 2 ) during autonomous driving to meet the needs of the SCR exhaust aftertreatment device ( 1 ) to get voted. Method according to one of the preceding claims, characterized in that the operating requirements of the SCR exhaust aftertreatment device ( 1 ) to optimize their NOx conversion efficiency. Method according to one of the preceding claims, characterized in that the operating requirements of the SCR exhaust aftertreatment device ( 1 ) to minimize NH ₃ slip and / or NH ₃ oxidation. Method according to one of the preceding claims, characterized in that the operating requirements of the SCR exhaust aftertreatment device ( 1 ) to perform a self-diagnosis at predetermined intervals. Method according to claim 7, characterized in that upon request, the heat aging of the SCR exhaust aftertreatment device ( 1 ), the autonomous driving and the operation of the internal combustion engine ( 2 ) can be performed such that the temperature and the space velocity of the SCR exhaust aftertreatment device (or 1 ) flowing exhaust gas during self-diagnosis within predetermined limits. Method according to one of the preceding claims, wherein the operating requirements of the SCR exhaust aftertreatment device ( 1 ) include that one or more operating parameters of the SCR exhaust aftertreatment device ( 1 ) lie at least temporarily in one or more predetermined windows, characterized in that the autonomous driving operation and the operation of the internal combustion engine ( 2 ) are performed such that the operating parameters of the SCR exhaust aftertreatment device ( 1 ) are held at least temporarily in the or the given windows. Device for operating an exhaust aftertreatment device ( 1 ) in the exhaust line of a motor vehicle with an internal combustion engine ( 2 ), wherein the operation of the internal combustion engine ( 2 ) depending on the needs of the operation of the exhaust aftertreatment device ( 1 ), characterized in that the exhaust aftertreatment device is an SCR exhaust aftertreatment device ( 1 ) that the motor vehicle is a vehicle capable of autonomous driving and that the device is arranged for carrying out the method according to one of the preceding claims.

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