DE102021113252A1 - Process for controlling an internal combustion engine with an exhaust aftertreatment system - Google Patents

Abstract

The invention relates to a method for controlling an internal combustion engine (10) with at least one combustion chamber (12), wherein an outlet (18) of the internal combustion engine (10) is connected to an exhaust system (20), in which, in the direction of flow of an exhaust gas stream of the internal combustion engine (10 ) a turbine (26) of an exhaust gas turbocharger (24) and downstream of the turbine (26) an electrically heatable three-way catalytic converter (30) close to the engine is arranged, with an exhaust gas duct (22) of the exhaust system (20) downstream of the turbine ( 26) and upstream of the electrically heatable three-way catalytic converter (30) there is an inlet point (28) for secondary air. It is provided that the internal combustion engine (10) is operated from a start with a sub-stoichiometric or stoichiometric combustion air ratio and the electrically heatable Catalyst (30) is electrically heated at the same time. Once a light-off temperature of the electrically heatable catalytic converter (30) has been reached, the internal combustion engine (10) is operated with a sub-stoichiometric combustion air ratio and, at the same time, secondary air downstream of the turbine (26) and upstream of the electrically heatable catalytic converter (30) at the inlet point (28). blown in.

Description

The invention relates to a method for controlling an internal combustion engine with an exhaust aftertreatment system and an internal combustion engine with an exhaust aftertreatment system for carrying out such a method.

The continuous tightening of the exhaust gas legislation places high demands on the vehicle manufacturers, which are solved by appropriate measures to reduce engine raw emissions and appropriate exhaust gas aftertreatment. The emission standards of the EU determine how many pollutants may be emitted by vehicles. Various sub-categories (Euro6 b, c, d-Temp) have been introduced within the current emission class EU6, the main differences between which lie in the test procedure used to measure the pollutant emissions of a motor vehicle. Since the introduction of Euro 6c, emissions have been determined using the so-called WLTP (Worldwide harmonized Light vehicles Test Procedure). In addition, with the Euro 6d-Temp standard, so-called real driving emissions (RDE) are carried out, in which emissions are measured during a real drive on the road. The subcategories Euro 6d-Temp and Euro 6d differ in the factor by which the RDE result may exceed the specified limit value. Here, a distinction is made between an urban, an interurban and a freeway portion.

With the introduction of a future Euro 7 emissions legislation, there are plans to further drastically reduce the limit values for nitrogen oxides. These strict limit values should also have to be complied with in an urban part of an RDE driving cycle, with a minimum driving distance of the urban part being specified for determining the specific NOx emissions.

The cold start portion of the nitrogen oxide emissions is of particular importance for compliance with the future nitrogen oxide limit values. The cold start emissions and the subsequent warm-up of the combustion engine with the associated warming up of the catalytic converters up to the light-off of the catalytic converters account for the major part of the total emissions in the city part of the test cycle.

Catalysts coated with precious metal are installed in the exhaust system of the internal combustion engine in order to be able to effectively convert the raw emissions that cannot be completely avoided into the engine. So that these catalytic converters can convert the pollutants, a minimum temperature level of the exhaust gas and the catalytic converter must be exceeded in the exhaust system. In order to bring these catalytic converters to an operating temperature as quickly as possible after a cold start of the combustion engine, engine heating measures such as retarding the ignition angle or sub-stoichiometric operation of the combustion engine with the simultaneous introduction of secondary air are used. In order to heat the catalytic converter quickly and in a targeted manner, it is possible to heat the catalytic converter using an electrical heating element.

Internal engine heating measures have the disadvantage that the raw emissions from the internal combustion engine deteriorate. In addition, such internal engine heating measures are not possible in the complete engine map of a combustion engine. For example, the effectiveness of retarding the ignition angle decreases with increased load due to a dynamic descent. In addition, the heat is generated significantly upstream of the catalytic converter, so that heat losses occur in the combustion chambers of the internal combustion engine and in the exhaust system upstream of the catalytic converter to be heated.

• 1.) Es muss unter allen Betriebsbedingungen eine hinreichende Durchmischung des unterstöchiometrischen Abgasstrom des Verbrennungsmotors mit der zugeführten Sekundärluft sichergestellt werden.
• 2.) Für die Nachoxidation der unverbrannten Kraftstoffkomponenten des unterstöchiometrischen Abgases des Verbrennungsmotors müssen innerhalb der Abgasanlage stromaufwärts des Katalysators zwingend Temperaturen sichergestellt werden, welche zu einer Entzündung der unverbrannten Abgaskomponenten und einer Oxidation mit der Sekundärluft führen. Die dazu benötigte Temperatur muss allein durch den Abgasstrom sichergestellt werden.
• 3.) Aufgrund dieser Temperaturbedingungen ist eine sichere Nachverbrennung der unverbrannten Abgaskomponenten nur im Bereich der Auslassventile möglich. Die Sekundärluft muss daher teils unter erheblichem konstruktiven Mehraufwand für den Verbrennungsmotor in die Auslasskanäle des Verbrennungsmotors zugeführt werden
• 4.) Die Sekundärluftzufuhr muss für eine sichere Nachverbrennung stromaufwärts der Turbine des Abgasturboladers erfolgen. Allerdings ist das Druckniveau stromaufwärts der Turbine deutlich höher als unmittelbar stromaufwärts des Katalysators. Somit müssen die Sekundärluftverdichter für ein höheres Druckniveau ausgelegt werden.
• 5.) Aufgrund des hohen Druckniveaus stromaufwärts der Turbine ist das Heizen mit Sekundärluft nur in einem kleinen Betriebsbereich des Verbrennungsmotors möglich. Bei höheren Lastpunkten des Verbrennungsmotors mit entsprechend höheren Abgasgegendrücken muss das Sekundärluftheizen unterbrochen werden.
• 6.) Die Stichkanäle zur Zufuhr der Sekundärluft stellen ein Dämpfungsvolumen dar und dämpfen somit die Druckstöße, welche durch das Öffnen der Auslassventile auftreten. Dies führt zu einer Absenkung der für die Aufladung zur Verfügung stehenden Energie und führt insbesondere bei Motoren mit größerem Zündabstand, wie beispielsweise Dreizylindermotoren zu Einbußen in der Dynamik durch einen verzögerten Ladedruckaufbau.

A secondary air injection in combination with a sub-stoichiometric combustion air ratio in the combustion chambers of the combustion engine leads to the following challenges:

• 1.) Sufficient mixing of the sub-stoichiometric exhaust gas flow of the combustion engine with the supplied secondary air must be ensured under all operating conditions.
• 2.) For post-oxidation of the unburned fuel components of the substoichiometric exhaust gas of the combustion engine, it is imperative to ensure temperatures within the exhaust system upstream of the catalytic converter, which lead to ignition of the unburned exhaust gas components and oxidation with the secondary air. The temperature required for this must be ensured solely by the exhaust gas flow.
• 3.) Due to these temperature conditions, safe post-combustion of the unburned exhaust gas components is only possible in the area of the exhaust valves. The secondary air must therefore be fed into the exhaust ducts of the internal combustion engine, some of which involves considerable additional design effort for the internal combustion engine
• 4.) The secondary air supply must be upstream of the turbine of the exhaust gas turbocharger to ensure safe post-combustion. However, the pressure level upstream of the turbine is significantly higher than immediately upstream of the catalyst. The secondary air compressors must therefore be designed for a higher pressure level.
• 5.) Due to the high pressure level upstream of the turbine, heating with secondary air is only possible in a small operating range of the combustion engine. At higher load points of the internal combustion engine with correspondingly higher exhaust gas back pressures, the secondary air heating must be interrupted.
• 6.) The branch ducts for supplying the secondary air represent a damping volume and thus dampen the pressure surges that occur when the outlet valves open. This leads to a reduction in the energy available for charging and, in particular in engines with a larger ignition interval, such as three-cylinder engines, leads to losses in dynamics due to a delayed build-up of charge pressure.

An electrically heatable catalytic converter has the disadvantage that the electrical output of the electrically heatable catalytic converter is limited by the energy available to an on-board network of the motor vehicle and is dependent on the capacity and the state of charge of the battery. In the case of electrically heatable catalysts known from the prior art, the maximum heat output is approximately 5 KW. In the case of dynamic cold departures, i.e. high performance requirements with a cold exhaust system, higher heating outputs that contribute to a faster light-off of the catalytic converter are desirable in order to be able to completely convert the pollutants. If the electrical power of the electrically heatable catalytic converter has to be provided by a generator of the internal combustion engine, this results in additional emission disadvantages for the associated shift in the operating point of the internal combustion engine, which cannot be compensated for by the advantage of the heat output introduced into the catalytic converter.

From the DE 10 2009 020 809 B4 a cold start control system for an internal combustion engine is known. The cold start system includes an electrically heated catalytic converter and a secondary air system. The catalytic converter is electrically heated below a first predetermined temperature by the electrical heating element. Above this first predetermined temperature and below a second predetermined temperature, secondary air is conveyed into the exhaust system by the secondary air system. The internal combustion engine is operated with a sub-stoichiometric combustion air ratio, as a result of which carbon monoxide (CO) and unburned hydrocarbons (HC) are fed to the catalytic converter, which are reacted exothermally with the secondary air on the catalytic converter.

the DE 10 2017 113 366 A1 describes an exhaust aftertreatment system for a spark-ignited internal combustion engine based on the Otto principle. The internal combustion engine is connected to an exhaust system on the outlet side, with an electrically heatable three-way catalytic converter in the exhaust system in the direction of flow of an exhaust gas through the exhaust system, downstream of the electrically heatable three-way catalytic converter and a four-way catalytic converter downstream of the four-way -Catalyst another three-way catalyst are arranged. Before the internal combustion engine is started, the electrically heatable three-way catalytic converter and preferably also the four-way catalytic converter are heated in order to enable efficient exhaust aftertreatment of the raw emissions from the internal combustion engine as soon as the internal combustion engine is started. The exhaust aftertreatment system is also set up to enable efficient conversion of the pollutants even during regeneration of the four-way catalytic converter and thus to ensure particularly low emissions in all operating states of the motor vehicle.

Furthermore, from the DE 10 2017 107 378 A1 a method for heating an electrically heatable catalytic converter in an exhaust gas duct of a motor vehicle with an internal combustion engine is known. In order to heat up the catalytic converter before the internal combustion engine is started, it is provided that the catalytic converter is already electrically heated up before the internal combustion engine is started and the oxygen storage capacity of the electrically heatable catalytic converter is filled. Efficient exhaust gas aftertreatment is thus possible as soon as the combustion engine is started. After an electrical preheating phase after starting the engine, the catalytic converter is heated up further by combined electrical and chemical heating through the exothermic conversion of unburned fuel components on a catalytically active surface of the electrically heatable catalytic converter.

The invention is now based on the object of further improving the heating of a three-way catalytic converter in the exhaust system of an internal combustion engine.

• - Ermitteln einer Temperatur des elektrisch beheizbaren Drei-Wege-Katalysators
• - Starten des Verbrennungsmotors, wobei der Verbrennungsmotor mit einem stöchiometrischen oder unterstöchiometrischen Verbrennungsluftverhältnis betrieben wird und ein Zündwinkel der Verbrennung in dem mindestens einen Brennraum in Richtung „spät“ verstellt wird, wenn die Temperatur des elektrisch beheizbaren Katalysators unterhalb einer ersten Schwellentemperatur liegt,
• - elektrisches Beheizen des elektrisch beheizbaren Drei-Wege-Katalysators spätestens ab dem Start des Verbrennungsmotors, wenn die Temperatur des elektrisch beheizbaren Drei-Wege-Katalysators unterhalb einer zweiten Schwellentemperatur liegt, und
• - Umschalten auf ein unterstöchiometrisches Verbrennungsluftverhältnis in dem mindestens einen Brennraum des Verbrennungsmotors und gleichzeitiges Einblasen von Sekundärluft an der Einleitstelle stromabwärts der Turbine des Abgasturboladers und stromaufwärts des elektrisch beheizbaren Drei-Wege-Katalysators, wenn der elektrisch beheizbare Drei-Wege-Katalysator zumindest an seiner einlassseitigen Stirnfläche eine Temperatur oberhalb einer dritten Schwellentemperatur erreicht hat.

This object is achieved by a method for controlling an internal combustion engine with at least one combustion chamber, with the internal combustion engine being connected at its outlet to an exhaust system in which, in the direction of flow of an exhaust gas stream of the internal combustion engine, there is a turbine of an exhaust gas turbocharger and, downstream of the turbine, a close-coupled, electrically heatable Three-way catalyst is arranged. In this case, an inlet point for secondary air is formed on an exhaust gas duct of the exhaust system downstream of the turbine and upstream of the electrically heatable three-way catalytic converter. The procedure includes the following steps:

• - Determining a temperature of the electrically heatable three-way catalytic converter
• - Starting the internal combustion engine, wherein the internal combustion engine is operated with a stoichiometric or sub-stoichiometric combustion air ratio and an ignition angle of the combustion in the at least one combustion chamber is adjusted in the “retarded” direction if the temperature of the electrically heatable catalytic converter is below a first threshold temperature,
• - Electrical heating of the electrically heatable three-way catalytic converter at the latest from the start of the internal combustion engine if the temperature of the electrically heatable three-way catalytic converter is below a second threshold temperature, and
• - Switching to a sub-stoichiometric combustion air ratio in the at least one combustion chamber of the internal combustion engine and simultaneous injection of secondary air at the inlet point downstream of the turbine of the exhaust gas turbocharger and upstream of the electrically heatable three-way catalytic converter if the electrically heatable three-way catalytic converter is at least on its inlet side Face has reached a temperature above a third threshold temperature.

In this context, an electrically heatable three-way catalytic converter is a catalytic converter with a three-way function, which can be heated by means of an electric heating element integrated into the catalytic converter. The three-way catalytic converter can in particular also have an additional function for filtering soot particles and can be designed as a so-called four-way catalytic converter. The electrical heating element can be formed as a separate heating element or formed by an electrically conductive substrate of the catalytic converter. In this context, an arrangement close to the engine means an arrangement of the electrically heatable three-way catalytic converter with an exhaust gas path length of less than 80 cm from an outlet from the combustion chambers of the internal combustion engine.

A method according to the invention makes it possible to heat the largest possible catalytic converter volume to its operating temperature as quickly as possible after a cold start of the internal combustion engine and at the same time to minimize the emissions in this cold start phase. Here, engine heating measures are advantageously combined with an additional exothermic reaction of oxidizable exhaust gas components with the secondary air and an electrical heating process.

The ignition angle retard is an effective method for increasing the exhaust gas temperature and increasing the exhaust gas mass flow with the same effective torque. Due to the associated deterioration in combustion efficiency, the exhaust gas temperature can be significantly increased. The heating measures of the engine ignition angle retardation can also be increased by further late injections (homogeneous split operation).

Otto engine rich operation with sub-stoichiometric air ratios significantly smaller than Lambda(engine) = 1.0 is sometimes possible up to the running limit of λ ~ 0.6. In the sub-stoichiometric range, the concentration of unburned emission components, in particular HC, CO and hydrogen, increases significantly. The unburned components can be post-combusted in the exhaust system with the addition of oxygen in the form of an exothermic after-reaction (e.g. by means of secondary air supply). The nitrogen oxide emission decreases very sharply in the sub-stoichiometric range.

A fundamental advantage of the sub-stoichiometric engine operation during the KAT heating phase is the significantly lower NOx raw emissions of the combustion engine, accompanied by a sharp increase in the oxidizable exhaust gas components CO and HC as well as H. According to the invention, these must be oxidized on a three-way catalytic converter located downstream in the exhaust system will. If necessary, the oxidation can be supported by the electrical heating element of the electrically heatable three-way catalytic converter.

Immediately after starting the internal combustion engine, the electrically heatable three-way catalytic converter is first heated up conventionally by the electric heating element and the ignition angle is retarded. As soon as at least a portion of the electrically heatable three-way catalytic converter has reached its light-off temperature, engine operation is switched to a sub-stoichiometric combustion air ratio, with secondary air being injected at the same time. This switching point is preferably reached within 5 seconds from the start of the internal combustion engine.

Advantageous when blowing in the secondary air downstream of the turbine of the exhaust gas turbocharger is that in contrast to the secondary air systems known from the prior art with an injection point upstream of the turbine, a significantly lower pressure level prevails. At a lower pressure level, with conventional secondary air compressors, larger amounts of secondary air can be introduced into the exhaust gas, and the possible operating range of the secondary air injection in the engine map can be significantly increased. The exothermic conversion of the oxidizable exhaust gas components in combination with the secondary air introduced on the front surface of the electrically heated three-way catalytic converter, which has previously been heated to light-off temperature, results in a significantly accelerated heating of the entire catalytic converter volume of the electrically heated three-way catalytic converter.

The features listed in the dependent claims allow advantageous improvements and non-trivial further developments of the method for controlling an internal combustion engine with exhaust gas aftertreatment system mentioned in the independent patent claim.

In a preferred embodiment of the invention, it is provided that the sub-stoichiometric combustion air ratio is chosen to be λ _E <0.95, preferably λ _E <0.9. By lowering the combustion air ratio to less than 0.95, the raw emissions of nitrogen oxides from the combustion engine can be reduced. This effect is particularly pronounced when the combustion air ratio is reduced to λ _E < 0.9.

In an advantageous embodiment of the method, it is provided that the electrically heatable three-way catalytic converter is already electrically heated before the internal combustion engine is started. In this case, the engine can be started and operated sub-stoichiometrically in the heating phase of the electrically heated three-way catalytic converter, provided that the oxidizable pollutant components are reacted in conjunction with the secondary air directly on the heated disk of the electrically heated three-way catalytic converter. For this purpose, the heating disc of the electrically heated three-way catalytic converter is additionally provided with a catalytically active three-way coating. The preheating phase can also be supported by controlling the secondary air pump. As a result, the amount of heat introduced into the heated disk can be transferred further via convection to the part of the catalytic converter located downstream of the heated disk, and the preheated volume is thus increased at the time the internal combustion engine is started. This alternative can also be carried out without a coated heating pane.

In an advantageous further development of the method, it is provided that the internal combustion engine is operated with a stoichiometric combustion air ratio when an amount of energy defined in a program code has been introduced into the electrically heatable catalytic converter.

In an advantageous further development of the method, it is provided that the internal combustion engine is operated with a stoichiometric combustion air ratio if at least 50% of the catalyst volume, preferably at least 80% of the catalyst volume, particularly preferably at least 90% of the catalyst volume of the electrically heatable catalyst is its light-off temperature has reached. If at least 50% of the catalyst volume is heated to the light-off temperature, the pollutants contained in the exhaust gas flow of the combustion engine can be effectively converted. The exothermic conversion of these pollutants means that the remaining catalyst volume also heats up to the light-off temperature.

In a preferred embodiment, it is provided that the third threshold temperature is a light-off temperature of the electrically heatable catalytic converter or is above a light-off temperature of the electrically heatable catalytic converter. This ensures that the unburned exhaust gas components can chemically react with the secondary air on the surface of the electrically heatable three-way catalytic converter, releasing heat.

In another preferred embodiment of the invention, it is provided that the first threshold temperature and/or the second threshold temperature is below a light-off temperature of the electrically heatable three-way catalytic converter. If the temperature of the electrically heatable catalytic converter is below the light-off temperature, the limited exhaust gas components contained in the exhaust gas flow of the internal combustion engine cannot be effectively converted. Therefore, below the light-off temperature, it is necessary to warm up the catalyst. By selecting a suitable threshold temperature, this can now take place through the motorized fat adjustment, the electrical heating element or a combination of these two measures.

Another aspect of the invention relates to an engine control unit with a memory unit and a computing unit and a machine-readable program code stored in the memory unit, the engine control unit being set up to carry out such a method when the maschi readable program code is executed by the processing unit of the engine control unit.

A further partial aspect of the invention relates to an internal combustion engine with at least one combustion chamber, the internal combustion engine being connected at its outlet to an exhaust system in which, in the direction of flow of an exhaust gas stream of the internal combustion engine, there is a turbine of an exhaust gas turbocharger and, downstream of the turbine, an electrically heatable three-way catalytic converter close to the engine is arranged. In this case, an inlet point for secondary air is formed on an exhaust gas duct of the exhaust system downstream of the turbine and upstream of the electrically heatable three-way catalytic converter. The internal combustion engine includes a secondary air system for conveying secondary air to this point of introduction and such an engine control unit. Such an internal combustion engine makes it possible to significantly reduce cold start emissions, in particular nitrogen oxide emissions. This means that even stricter emissions legislation can be met.

In an advantageous embodiment of the invention, it is provided that the secondary air system comprises a secondary air compressor and a secondary air line which connects the secondary air compressor to the inlet point, with a secondary air flow through the secondary air line being controllable by a secondary air valve. This enables a particularly precise regulation of the secondary air quantity, so that the secondary air can be adapted to the sub-stoichiometric combustion air ratio in the combustion chambers of the internal combustion engine and a stoichiometric exhaust gas is established downstream of the point of introduction.

A further partial aspect of the invention relates to a motor vehicle with a hybrid drive arrangement comprising at least one electric drive motor and an internal combustion engine according to the invention. Hybrid drives with an electric drive motor and a combustion engine tend to have a colder exhaust gas system due to the electric driving mode, since the exhaust gas is colder in phases with electric support or with purely electric operation than with the same performance requirement, which is only met by the combustion engine. It is therefore often necessary to warm up the catalytic converter and blow secondary air into the exhaust system when driving, especially in hybrid vehicles. In order to keep the dynamics of the secondary air compressor low and to regulate the exhaust gas to a stoichiometric exhaust gas with a sub-stoichiometric combustion air ratio in the combustion chambers, it is advantageous if the secondary air injection takes place downstream of the turbine of the exhaust gas turbocharger and upstream of the electrically heatable three-way catalytic converter. In this way, a dynamic load requirement when the catalytic converter is cold can be largely or completely dealt with by the electric drive motor of the hybrid drive, so that the electrically heatable catalytic converter is heated simultaneously by the electric heating element and by the exothermic reaction of the unburned exhaust gas components with the secondary air.

Unless stated otherwise in the individual case, the various embodiments of the invention mentioned in this application can advantageously be combined with one another.

• 1 einen Verbrennungsmotor mit einem Abgasnachbehandlungssystem zur Durchführung eines erfindungsgemäßen Verfahrens zur Steuerung des Verbrennungsmotors;
• 2 ein Kraftfahrzeug mit einem Hybrid-Antrieb aus einem Verbrennungsmotor und einem elektrischen Antriebsmotor; und
• 3 ein Ablaufdiagramm zur Durchführung eines erfindungsgemäßen Verfahrens zur Steuerung eines Verbrennungsmotors mit Abgasnachbehandlungssystem.

The invention is explained below in exemplary embodiments with reference to the associated drawings. Show it:

• 1 an internal combustion engine with an exhaust gas aftertreatment system for carrying out a method according to the invention for controlling the internal combustion engine;
• 2 a motor vehicle with a hybrid drive consisting of an internal combustion engine and an electric drive motor; and
• 3 a flowchart for carrying out a method according to the invention for controlling an internal combustion engine with an exhaust gas aftertreatment system.

1 shows a spark-ignited internal combustion engine 10 based on the Otto principle. The internal combustion engine has at least one combustion chamber 12, preferably as in 1 shown several combustion chambers 12 on. A fuel injector 14 for injecting fuel into the respective combustion chamber 12 and a spark plug 16 for igniting an ignitable fuel-air mixture in the respective combustion chamber 12 are arranged on each of the combustion chambers 12 . The internal combustion engine 10 is connected to an exhaust system 20 by its outlet 18 . Outlet valves are arranged on the combustion chambers 12 and can be used to open or close a fluidic connection from the combustion chambers 12 to the exhaust system 20 .

The exhaust system 20 includes an exhaust gas duct 22 in which a turbine 26 of an exhaust gas turbocharger 24 and downstream of the turbine 26 an electrically heatable three-way catalytic converter 30 are arranged in the flow direction of an exhaust gas stream of the internal combustion engine 10 . The electrically heatable catalytic converter 30 comprises an electric heating element 32, a supporting disc 34 and a ceramic or metallic catalytic converter body 36 with a precious metal coating. Downstream of the turbine 26 of the exhaust gas turbocharger 24 and upstream of the electrically heatable three-way catalytic converter 28 is on the exhaust gas duct 22 an introduction point 28 is formed for introducing secondary air. The secondary air can flow through a secondary air system 40, which has a secondary air compressor 42, in particular a secondary air blower 48, and a secondary air valve 44. The secondary air compressor 42 is connected to the inlet point 28 via a secondary air line 46 , the secondary air valve being arranged in the secondary air line 46 between the secondary air compressor 42 and the inlet point 28 .

A further three-way catalytic converter 60 can be arranged downstream of the electrical three-way catalytic converter 30 . Furthermore, a particle filter 62 can be arranged in the exhaust system downstream of the electrically heatable three-way catalytic converter. Alternatively, the electrically heatable three-way catalytic converter 30 can also additionally have a particle filter function and be designed as a so-called four-way catalytic converter 64 .

A first lambda probe 66, in particular a broadband probe, is arranged downstream of the turbine 26 and upstream of the electrically heatable three-way catalytic converter 30. A second exhaust gas probe 68 , in particular a second lambda probe 70 , is arranged downstream of the electrically heatable three-way catalytic converter 30 and upstream of a second three-way catalytic converter 60 . The second lambda probe 70 is preferably designed as a jump probe, but can also be designed as a broadband probe. Alternatively, the second exhaust gas probe 68 can also be designed as a NOx-NH3 combination sensor 72 . Furthermore, one or more temperature sensors 38 can be arranged in the exhaust system 20 .

Internal combustion engine 10 is operatively connected to an engine control unit 50 which is connected via signal lines to fuel injectors 14 and exhaust gas probes 66 , 68 , 70 , 72 arranged in exhaust system 20 and to secondary air system 40 . Control unit 50 includes a memory unit 52, in which machine-readable program code 56 for carrying out a method described below is stored, and a processing unit 54, which executes such a method when machine-readable program code 56 is executed by processing unit 54.

In 2 a motor vehicle 100 with a hybrid drive 102 with a drive assembly 110 with at least one electric drive motor 104 and an internal combustion engine 10 is shown. The drive arrangement also includes a generator 106 that can be coupled to the internal combustion engine 10 and a battery 108 in which electrical current can be stored. The generator 106 and the electric drive motor 104 are preferably combined in one assembly. Particularly preferably, the electric drive motor 104 itself can have a generator function. Since the exhaust system can cool down quickly, particularly in partially electric and fully electric operation of a hybrid vehicle 100, the proposed method for heating a catalytic converter 30 by means of a substoichiometric combustion air ratio in the combustion chambers 12 of the internal combustion engine 10 and simultaneous blowing in of secondary air through the secondary air system 40 is special in such a hybrid vehicle 100 useful to reduce the exhaust emissions during operation of the internal combustion engine 10.

In 3 a flowchart for carrying out a method according to the invention for controlling an internal combustion engine with an exhaust gas aftertreatment system is shown. In a method step <100>, a temperature of the electrically heatable three-way catalytic converter 30 is determined. This can be done directly, in particular by a temperature sensor 38 on the electrically heatable three-way catalytic converter 30, or indirectly, in particular from an ambient temperature and the operating conditions of the internal combustion engine 10.

In a method step <110>, the internal combustion engine 10 is started. In a method step <120>, the temperature of the electrically heatable three-way catalytic converter 30 is compared with a first threshold temperature T _S1 and the internal combustion engine 10 is operated with a stoichiometric or sub-stoichiometric combustion air ratio while at the same time adjusting the ignition angle of the combustion in the combustion chambers 12 in the "retarded" direction "Operated when the determined temperature of the electrically heatable three-way catalytic converter 30 is below the first threshold temperature T _S1 .

In a method step <130>, the temperature of the electrically heatable three-way catalytic converter 30 is compared to a second threshold temperature T _S2 . If the temperature is below this second threshold temperature T _S2 , then in a method step <140> the electrically heatable three-way catalytic converter 30 is electrically heated when the internal combustion engine 10 is started. In a method step <150>, the temperature of the electrically heatable three-way catalytic converter 30 is compared with a third threshold temperature T _S3 and in a method step <160> switched to a sub-stoichiometric combustion air ratio in the combustion chambers 12 of the internal combustion engine 10 and at the same time at the inlet point 28 downstream of the turbine 26 of the exhaust gas turbocharger 24 and upstream of the electrically heatable three-way catalytic converter 30 secondary air into the exhaust gas blown position when the electrically heatable three-way catalytic converter 30 has reached a temperature at least on its inlet-side end face, which is above the third threshold temperature T _S3 .

In a method step <170>, the heating of the electrically heatable three-way catalytic converter 30 by means of secondary air injection and sub-stoichiometric operation of the internal combustion engine 10 is terminated when a defined amount of energy, which is defined in a program code 56 stored in the memory unit 52, in the electrically heatable Three-way catalyst 30 was entered.

Method steps <120> and <130> as well as <140> can also be carried out in reverse order or in parallel with one another.

reference list

10

combustion engine

12

combustion chamber

14

fuel injector

16

spark plug

18

outlet

20

exhaust system

22

exhaust duct

24

exhaust gas turbocharger

26

turbine

28

discharge point

30

electrically heated three-way catalytic converter

32

electric heating element

34

support washer

36

catalyst body

38

temperature sensor

40

secondary air system

42

secondary air compressor

44

secondary air valve

46

secondary air line

48

secondary air blower

50

engine control unit

52

storage unit

54

unit of account

56

program code

60

second three-way catalytic converter

62

particle filter

64

Four-way catalytic converter

66

first lambda probe

68

second exhaust gas probe

70

second lambda probe

72

NH3-NOx combination sensor

100

motor vehicle

102

hybrid drive

104

electric drive motor

106

generator

108

battery

110

drive assembly

QUOTES INCLUDED IN DESCRIPTION

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

Patent Literature Cited

• DE 102009020809 B4 [0009]
• DE 102017113366 A1 [0010]
• DE 102017107378 A1 [0011]

Claims (10)

Method for controlling an internal combustion engine (10) with at least one combustion chamber (12), an outlet (18) of the internal combustion engine (10) being connected to an exhaust system (20) in which a turbine ( 26) of an exhaust gas turbocharger (24) and downstream of the turbine (26) an electrically heatable three-way catalytic converter (30) close to the engine is arranged, with an exhaust gas duct (22) of the exhaust system (20) downstream of the turbine (26) and upstream of the electrically heatable three-way catalytic converter (30), an inlet point (28) for secondary air is formed, comprising the following steps: - Determining a temperature of the electrically heatable three-way catalytic converter (30), - Starting the internal combustion engine (10), the internal combustion engine being operated with a stoichiometric or sub-stoichiometric combustion air ratio and an ignition angle of the combustion in the at least one combustion chamber (12) being adjusted in the “retarded” direction when the temperature of the electrically heatable three-way Catalyst (30) is below a first threshold temperature, - Electrical heating of the electrically heatable three-way catalytic converter (30) at the latest from the start of the internal combustion engine (10) if the temperature of the electrically heatable three-way catalytic converter is below a second threshold temperature, and - Switching to a sub-stoichiometric combustion air ratio in the at least one combustion chamber (12) and simultaneous injection of secondary air downstream of the turbine (26) of the exhaust gas turbocharger (24) and upstream of the electrically heatable three-way catalytic converter (30) when the electrically heatable three-way Way catalyst has reached a temperature above a third threshold temperature at least on its inlet-side face. procedure after claim 1 , characterized in that the sub-stoichiometric combustion air ratio is selected with λ _E <0.95. procedure after claim 1 or 2 , characterized in that the electrically heatable three-way catalytic converter (30) is electrically heated even before the internal combustion engine (10) is started. Procedure according to one of Claims 1 until 3 , characterized in that the internal combustion engine (10) is operated with a stoichiometric combustion air ratio when a program code (56) defined amount of energy in the heatable three-way catalytic converter (30) was introduced. Procedure according to one of Claims 1 until 4 , characterized in that the third threshold temperature (T _S3 ) is a light-off temperature (T _LO ) of the electrically heatable three-way catalyst (30) or above a light-off temperature (T _LO ) of the electrically heatable three -way catalytic converter (30) is located. Procedure according to one of Claims 1 until 5 , characterized in that the first threshold temperature (T _S1 ) and / or the second threshold temperature (T _S2 ) below a light-off temperature (T _LO ) of the electrically heatable catalyst (30). Engine control unit (50) with a memory unit (52) and a computing unit (54) as well as a machine-readable program code (56) stored in the memory unit (52), wherein the engine control unit (50) is set up to implement a method according to one of the Claims 1 until 5 to be carried out when the machine-readable program code (56) is executed by the computing unit (54) of the engine control unit (50). Internal combustion engine (10) with at least one combustion chamber (12), wherein the internal combustion engine (10) is connected with its outlet (18) to an exhaust system (20), in which in the flow direction of an exhaust gas stream of the internal combustion engine (10) a turbine (26) of a Exhaust gas turbocharger (24) and downstream of the turbine (26) an electrically heatable three-way catalytic converter (30) is arranged close to the engine, wherein on an exhaust gas duct (22) of the exhaust system (20) downstream of the turbine (26) and upstream of the electrically heatable Three-way catalytic converter (30) formed an introduction point (28) for secondary air and a secondary air system (40) for conveying secondary air to the introduction point (28) and with a control unit claim 7 . Internal combustion engine (10) after claim 8 , characterized in that the secondary air system (40) comprises a secondary air compressor (42) and a secondary air line (46) which connects the secondary air compressor (42) to the inlet point (28), the secondary air flow through the secondary air line (46) through a secondary air valve ( 44) is adjustable. Motor vehicle (100) with a hybrid drive (102), comprising an internal combustion engine (10). claim 8 or 9 and an electric drive motor (104), wherein the electrically heatable catalytic converter (30) is heated by the electric heating element (32) when the motor vehicle (100) is driven by the electric drive motor (104).

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