DE102018117124A1 - Internal combustion engine and method for exhaust gas aftertreatment of such an internal combustion engine - Google Patents

Abstract

The invention relates to an internal combustion engine (10) and a method for exhaust gas aftertreatment of such an internal combustion engine (10). The internal combustion engine has at least one combustion chamber (12) and is connected to an exhaust system (50) on the outlet side. A turbine (54) of an exhaust gas turbocharger is arranged in the exhaust gas system (50), at least one exhaust gas aftertreatment component (64, 66, 68, 70) downstream of the turbine and at least one exhaust gas aftertreatment component downstream of at least one exhaust gas aftertreatment component, with which the exhaust duct (52) blocks It is provided that an actual temperature (T) of the exhaust gas aftertreatment component (64, 66, 68, 70) is determined and compared with a target temperature (T) for the exhaust gas aftertreatment component (64, 66, 68, 70) , If the actual temperature (T) is below the target temperature (T), the exhaust flap (76) is closed to increase the exhaust gas back pressure. At the same time, the opening times of the exhaust valves (18) of the internal combustion engine (10) are adjusted such that the exhaust gas from the exhaust system (50) is sucked back into the combustion chamber (12) of the internal combustion engine (10) by means of internal exhaust gas recirculation in order to reduce the nitrogen oxide emissions to minimize.

Description

The invention relates to an internal combustion engine with an air supply system and an exhaust system and a method for exhaust gas aftertreatment of such an internal combustion engine according to the preamble of the independent claims.

The current exhaust gas legislation, which will become increasingly stringent in the future, places high demands on raw engine emissions and exhaust gas aftertreatment of internal combustion engines. The demands for a further decrease in consumption and the further tightening of the exhaust gas standards with regard to the permissible nitrogen oxide emissions represent a challenge for the engine developers. In gasoline engines, exhaust gas cleaning is carried out in a known manner using a three-way catalytic converter and the three-way Catalyst upstream and downstream further catalysts. Exhaust gas aftertreatment systems are currently used in diesel engines, which have an oxidation catalytic converter, a catalytic converter for the selective catalytic reduction of nitrogen oxides (SCR catalytic converter) and a particle filter for the separation of soot particles and, if appropriate, further catalytic converters. Ammonia is preferably used as the reducing agent. Because the use of pure ammonia is complex, a synthetic, aqueous urea solution is usually used in vehicles, which is mixed with the hot exhaust gas stream in a mixing device upstream of the SCR catalytic converter. This mixing heats the aqueous urea solution, the aqueous urea solution releasing ammonia in the exhaust gas duct. A commercially available, aqueous urea solution generally consists of 32.5% urea and 67.5% water. Before the light-off temperature of the SCR catalytic converter is reached, however, the NOx emissions cannot be converted into harmless exhaust gas components by this catalytic converter. Therefore, especially in the cold start phase, the raw NOx emissions of the internal combustion engine must be minimized and / or the exhaust gas aftertreatment components heated up quickly.

It is known from the prior art to reduce the raw NOx emissions in a diesel engine by means of internal and external exhaust gas recirculation, late starts of injection for fuel injection into the combustion chambers of the internal combustion engine and a corresponding shift in the center of gravity of the combustion. Furthermore, it is known that such a shift in the center of gravity of the combustion towards late leads to a decrease in the thermal efficiency of the internal combustion engine and an increase in the exhaust gas temperature. In addition, it is known to heat the exhaust aftertreatment components to their operating temperature by means of electrical heating elements or a fuel-operated exhaust gas burner in order to minimize emissions after starting.

From the DE 10 2009 057 394 A1 An exhaust gas aftertreatment system for an internal combustion engine is known which is charged by means of an exhaust gas turbocharger, an oxidation catalytic converter and a particle filter being arranged in the exhaust gas system downstream of the turbine of the exhaust gas turbocharger, and an exhaust gas flap being provided in the exhaust gas duct downstream of these exhaust gas aftertreatment components. Exhaust gas recirculation to control the amount of exhaust gas returned.

From the DE 10 2011 014 239 A1 An internal combustion engine with an intake tract and an exhaust system is known, wherein a throttle valve is arranged in the intake tract of the internal combustion engine, by means of which the amount of fresh air supplied to the combustion chambers of the internal combustion engine can be varied, the position of the throttle valve being used, in particular in a warm-up phase of the internal combustion engine increase the amount of exhaust gas recirculated via the internal exhaust gas recirculation and thus raise the exhaust gas temperature.

The DE 10 2016 118 309 A1 discloses an internal combustion engine charged by means of an exhaust gas turbocharger with an intake tract and an exhaust gas system, a throttle valve being arranged in the intake tract and an exhaust gas flap in the exhaust gas duct in the exhaust gas system downstream of an oxidation catalytic converter and a particle filter with a coating for the selective catalytic reduction of nitrogen oxides Control low-pressure exhaust gas recirculation of exhaust gas.

A disadvantage of the known methods for exhaust gas aftertreatment, however, is that they can lead to increased particle emissions, increased fuel consumption and, consequently, increased CO ₂ emissions, problems with packaging in narrow engine compartments and inefficiency, particularly in the cold start phase of the internal combustion engine ,

The object of the invention is to minimize the raw emissions of an internal combustion engine, in particular in the cold start phase of the internal combustion engine, and to accelerate the heating of the exhaust gas aftertreatment components to their respective light-off temperature.

• - Ermitteln einer Ist-Temperatur einer Abgasnachbehandlungskomponente
• - Vergleichen der ermittelten Ist-Temperatur der Abgasnachbehandlungskomponente mit einer Soll-Temperatur,
• - Schließen der Abgasklappe zur Erhöhung des Abgasgegendrucks im Abgaskanal und Veränderung der Öffnungszeiten des mindestens einen Auslassventils, um das Abgas aus der Abgasanlage mittels einer internen Abgasrückführung in den mindestens einen Brennraum zu saugen, wenn die Ist-Temperatur der Abgasnachbehandlungskomponente unterhalb der Soll-Temperatur liegt.

According to the invention, this object is achieved by a method for exhaust gas aftertreatment of an internal combustion engine with at least one combustion chamber solved, the internal combustion engine is connected via its inlet to an air supply system and by means of its outlet to an exhaust system. At least one exhaust valve is arranged on the at least one combustion chamber, with which a fluidic connection from the combustion chamber to the exhaust system can be closed or opened. A turbine of an exhaust gas turbocharger is arranged in an exhaust duct of the exhaust system downstream of the outlet. At least one exhaust gas aftertreatment component, preferably at least one catalytic converter with an oxidation stage, a particle filter and a catalytic converter for the selective catalytic reduction of nitrogen oxides (SCR catalytic converter) are arranged in the flow direction of an exhaust gas of the internal combustion engine through the exhaust gas duct downstream of the turbine. Furthermore, an exhaust gas flap is provided, with which the exhaust gas duct downstream of the at least one exhaust gas aftertreatment component can be at least largely blocked. The method according to the invention comprises the following steps:

• - Determining an actual temperature of an exhaust gas aftertreatment component
• Comparing the determined actual temperature of the exhaust gas aftertreatment component with a target temperature,
• - Closing the exhaust flap to increase the exhaust gas back pressure in the exhaust duct and changing the opening times of the at least one exhaust valve in order to suck the exhaust gas from the exhaust system into the at least one combustion chamber by means of an internal exhaust gas recirculation if the actual temperature of the exhaust gas aftertreatment component is below the target temperature ,

The method according to the invention makes it possible, particularly in a cold start phase of the internal combustion engine, when the exhaust gas aftertreatment components have not yet reached their operating temperature and cannot yet guarantee an efficient conversion of pollutants, in the raw emissions of the internal combustion engine. Closing the exhaust flap increases the exhaust gas back pressure so that the piston of the internal combustion engine has to do more work to push the exhaust gas out of the combustion chamber into the exhaust gas duct. As a result of the increase in exhaust gas back pressure and the additional work, the exhaust gas temperature in the exhaust gas duct rises. By simultaneously increasing the amount of exhaust gas via the internal exhaust gas recirculation, i.e. sucking back exhaust gas during the downward movement of the piston in the intake phase, the raw NOx emissions can be reduced.

Advantageous improvements and further developments of the method for exhaust gas aftertreatment specified in the independent claim are possible due to the features listed in the dependent claims.

In a preferred embodiment of the method, it is provided that an engine operating point of the internal combustion engine is determined and, depending on the engine operating point, a target exhaust back pressure is determined in the exhaust duct downstream of the outlet and upstream of the turbine. Since an internal exhaust gas recirculation does not make sense at all operating points of the internal combustion engine, the operating point can also be determined with regard to speed and effective torque and depending on this operating point it can be decided whether internal exhaust gas recirculation makes sense by opening the exhaust valve additionally.

An advantageous improvement of the method provides that a throttle valve is arranged in the air supply system, the throttle valve being closed in order to raise the exhaust gas temperature. In addition to increasing the exhaust gas back pressure by closing the exhaust flap, closing the throttle valve can reduce the pressure in the intake duct of the air supply system downstream of the throttle valve. The increased throttle losses also increase the work to be done, which also increases the exhaust gas temperature.

In an advantageous embodiment variant it is provided that the turbine of the exhaust gas turbocharger is designed as a turbine with a variable turbine geometry, the variable geometry of the turbine being adjusted in order to raise the temperature in such a way that the efficiency of the exhaust gas turbocharger is reduced. Exhaust gas turbochargers with variable turbine geometry, in which the turbine guide vanes are adjustable, are known from the prior art in order to improve the response behavior of the exhaust gas turbocharger and / or to increase the output. In a cold start phase, it can make sense to consciously reverse this effect and use the adjustment device for the variable turbine geometry in order to reduce the efficiency and the response behavior. As a result, an increased filling of the combustion chambers with a correspondingly high thermal efficiency can be avoided, so that the components of the exhaust gas aftertreatment, in particular a NOx storage catalytic converter and / or an SCR catalytic converter, are heated to their operating temperature, from which an efficient storage or conversion of nitrogen oxides is possible is.

In a further preferred embodiment of the invention it is provided that the speed of the internal combustion engine is dependent on the Exhaust gas temperature, the temperature of the exhaust gas aftertreatment components and / or the dynamic pressure in the exhaust system is raised. By increasing the speed, the friction and gas exchange losses can be increased in order to increase the heating of the exhaust gas in a cold start phase of the internal combustion engine. In addition, the smooth running of the internal combustion engine can be improved so that the combustion noise can be reduced.

In a preferred embodiment of the method, it is provided that the exhaust gas duct has a turbine bypass, which branches off the exhaust gas duct at a branch upstream of the turbine and re-opens into the exhaust gas duct at an opening downstream of the turbine, a bypass flap in the turbine bypass being opened when the The actual temperature of the exhaust gas aftertreatment component is below the target temperature. A turbine bypass can avoid increased cylinder filling with fresh air, since the bypass can reduce the speed of the turbine of the exhaust gas turbocharger and thus the performance of the compressor in the intake duct. As a result, the efficiency of the internal combustion engine, in particular the maximum temperature in the combustion chambers, can be reduced, as a result of which the raw nitrogen oxide emissions can be reduced. At the same time, by reducing the efficiency, more energy is discharged from the combustion chamber via the exhaust gas, which accelerates the heating of the exhaust gas aftertreatment components.

In a further improvement of the method it is provided that a fresh air mass flow is determined in the air supply system and the bypass flap is adjusted depending on the fresh air mass flow determined. In order to improve the control of the performance and the efficiency of the exhaust gas turbocharger, provision is made to measure the air mass flow in the intake duct and to take this into account when controlling the bypass flap.

In an advantageous embodiment of the method it is provided that the opening times of the exhaust valves are extended by an additional opening process. The internal exhaust gas recirculation can be improved by sucking back exhaust gas from the exhaust system by an additional opening process of the exhaust valves, in particular by an overlap of the opening times of exhaust valves and intake valves in an intake stroke of the internal combustion engine.

Alternatively, it is advantageously provided that the opening times of the exhaust valves are adjusted in the "late" direction in such a way that the exhaust gas is sucked back out of the exhaust system into the combustion chamber. Alternatively, the internal exhaust gas recirculation can be achieved by shifting and or extending the opening times of the exhaust valves in the "late" direction.

According to the invention, an internal combustion engine with at least one combustion chamber is proposed, the inlet of which is connected to an air supply system and the outlet of which is connected to an exhaust system, at least one exhaust valve being arranged on each combustion chamber, with which a fluidic connection from the combustion chamber to the exhaust system can be closed or opened. A turbine of an exhaust gas turbocharger is arranged in an exhaust gas duct of the exhaust gas system downstream of the outlet, at least one exhaust gas aftertreatment component being arranged downstream of the turbine in the flow direction of an exhaust gas of the internal combustion engine through the exhaust gas system. The exhaust system also has an exhaust flap with which the exhaust duct downstream of the exhaust gas aftertreatment component can be blocked. It is provided that the internal combustion engine is connected to an engine control unit, which is set up to carry out a method according to the invention when a machine-readable program code is executed by the control unit. Such an internal combustion engine makes it possible to reduce the raw emissions of the internal combustion engine by carrying out a method according to the invention. The raw emissions are reduced in particular in a starting phase, particularly preferably during a cold start, of the internal combustion engine by closing the exhaust gas flap and the internal exhaust gas recirculation, and the exhaust gas temperature is raised in order to bring the components of the exhaust gas aftertreatment to their operating temperature required for converting pollutants more quickly.

In a preferred embodiment of the internal combustion engine, it is provided that the internal combustion engine has an adjustment mechanism for adapting the opening times of the exhaust valves. Such an adjustment mechanism can in particular have a hydraulic or electric camshaft adjuster, a fully variable valve train, a switchable additional cam or similar mechanisms which are suitable for enabling the exhaust valves to be opened while the piston of the internal combustion engine increases the volume of the combustion chamber in one intake stroke.

It is particularly preferred if the adjusting mechanism has an adjusting shaft with a control cam, the control cam being adjustable. The exhaust valves of several combustion chambers can be changed at the same time by means of an adjusting shaft, so that internal exhaust gas recirculation takes place in all combustion chambers.

In a preferred embodiment of the internal combustion engine it is provided that at least one catalytic converter with an oxidation stage, in particular an oxidation catalytic converter or NOx storage catalytic converter, a particle filter and an SCR catalytic converter are arranged in the exhaust system of the internal combustion engine downstream of the turbine of the exhaust gas turbocharger. For effective exhaust gas aftertreatment of an internal combustion engine, in particular a diesel engine, it is advantageous if an oxidation stage, a reduction stage and an exhaust gas aftertreatment component for removing solids from the exhaust gas of the internal combustion engine are present. A preferred combination of exhaust gas aftertreatment components of a diesel engine are a NOx storage catalytic converter or an oxidation catalytic converter, a particle filter and an SCR catalytic converter. The particle filter and the SCR catalytic converter can be combined in one component if the particle filter is provided with an SCR coating ,

It is particularly preferred if the catalytic converter with the oxidation stage is designed as a NOx storage catalytic converter, in particular as a low-temperature NOx storage catalytic converter. Since SCR catalysts only enable efficient conversion of nitrogen oxides above a temperature of around 200 ° C, it is advantageous if the nitrogen oxides can be stored in a NOx storage catalyst at lower temperatures, i.e. at temperatures below 200 ° C, at least until the SCR catalytic converter has reached its operating temperature. Therefore, a low-temperature NOx storage catalyst can effectively contribute to reducing the emissions of the internal combustion engine, particularly in the cold start phase of the internal combustion engine.

In a further preferred embodiment of the invention, it is provided that a branch is provided in the exhaust system downstream of the turbine, at which an exhaust gas recirculation line of a low-pressure exhaust gas recirculation branches off from the exhaust gas duct. The exhaust gas recirculation line connects the exhaust gas duct to an intake duct of the air supply system upstream of a compressor of the exhaust gas turbocharger, an exhaust gas recirculation valve being provided in the exhaust gas recirculation line. Low-pressure exhaust gas recirculation can reduce the raw emissions of an internal combustion engine in a known manner. In order to achieve an effective increase in the exhaust gas back pressure in the starting phase of the internal combustion engine, it must be ensured that the exhaust gas does not flow back via the low-pressure exhaust gas recirculation in this operating phase. Therefore, the exhaust gas recirculation valve in the low-pressure exhaust gas recirculation is closed in this phase in order to allow the build-up of dynamic pressure in the exhaust system.

In an advantageous further development of the internal combustion engine it is provided that a turbine bypass is provided in the exhaust system, which branches off the exhaust duct at a branch upstream of the turbine and re-opens into the exhaust duct at a junction downstream of the turbine, a switchable bypass valve in the turbine bypass, in particular a switchable bypass flap is arranged. The output of the exhaust gas turbocharger can be controlled by a turbine bypass. A switchable valve, in particular a flap, is provided in the turbine bypass in order to control the exhaust gas flow through the turbine or the turbine bypass.

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

• 1 ein erstes Ausführungsbeispiel eines Verbrennungsmotors mit einem Luftversorgungssystem und einer Abgasanlage;
• 2 ein weiteres Ausführungsbeispiel eines Verbrennungsmotor mit einem Luftversorgungssystem und einer Abgasanlage, wobei ein Turbinenbypass für eine Turbine des Abgasturboladers vorgesehen ist;
• 3 ein vereinfachtes Ablaufdiagramm zur Durchführung eines erfindungsgemäßen Verfahrens zur Abgasnachbehandlung eines Verbrennungsmotors;
• 4 ein weiteres Ablaufdiagramm zur Durchführung eines erfindungsgemäßen Verfahrens zur Abgasnachbehandlung eines Verbrennungsmotors;
• 5 ein weiteres Ablaufdiagramm zur Durchführung eines erfindungsgemäßen Verfahrens zur Abgasnachbehandlung eines Verbrennungsmotors.

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

• 1 a first embodiment of an internal combustion engine with an air supply system and an exhaust system;
• 2 a further embodiment of an internal combustion engine with an air supply system and an exhaust system, wherein a turbine bypass is provided for a turbine of the exhaust gas turbocharger;
• 3 a simplified flowchart for performing an inventive method for exhaust gas aftertreatment of an internal combustion engine;
• 4 a further flow chart for carrying out a method according to the invention for exhaust gas aftertreatment of an internal combustion engine;
• 5 a further flow chart for carrying out a method according to the invention for exhaust gas aftertreatment of an internal combustion engine.

1 shows the schematic representation of an internal combustion engine 10 , The internal combustion engine 10 is designed as a direct-injection diesel engine. The internal combustion engine 10 has several combustion chambers 12 on. At the combustion chambers 12 is a fuel injector 14 for injecting a fuel into the respective combustion chamber 12 arranged. The internal combustion engine 10 is with his entrance 20 with an air supply system 30 and with its outlet 22 with an exhaust system 50 connected. The internal combustion engine 10 also includes a high pressure exhaust gas recirculation 24 with a high pressure exhaust gas recirculation valve 26 , via which an exhaust gas of the internal combustion engine 10 from the outlet 22 to the entrance 20 can be traced back. At the combustion chambers 12 are intake valves 16 and exhaust valves 18 arranged with which a fluid connection from the air supply system 30 to the combustion chambers 12 or from the combustion chambers 12 to the exhaust system 50 can be opened or closed. Furthermore, is on the internal combustion engine 10 an adjustment mechanism 28 provided over which the opening times of the exhaust valves 18 are changeable. In addition, another adjustment mechanism, not shown, for adjusting the opening times of the inlet valve can be present. The adjustment mechanism 28 , in particular an adjusting shaft, is via an adjusting element 94 controllable so that the opening times of the exhaust valve 18 at at least two operating states of the internal combustion engine 10 can be customized. The opening times can be adjusted, for example, via a switchable additional cam, an electronic valve control, a hydraulic or electric camshaft adjuster or a similar adjustment mechanism, which involves an additional opening process for the exhaust valves 18 or a corresponding adjustment of the opening times of the exhaust valves 18 enables such that an internal exhaust gas recirculation can be carried out, in which the exhaust gas from the exhaust system 50 into the combustion chambers 12 is sucked back. In particular, during an intake stroke of the internal combustion engine 10 an overlap of the opening times of the intake valves 16 and the exhaust valves 18 provided to the combustion chambers 12 to fill with an increased amount of exhaust gas and a reduced amount of fresh air.

The air supply system 30 includes an intake pipe 38 , in which in the flow direction of fresh air through the intake pipe 38 an air filter 32 , an air mass meter downstream of the air filter 34 , in particular a hot film air mass meter, a compressor downstream of the air mass meter 36 of an exhaust gas turbocharger 46 , downstream of the compressor 36 a throttle valve 38 and further downstream an intercooler 42 are arranged. The air mass meter 34 also in a filter housing of the air filter 32 be arranged so that the air filter 32 and the air mass meter 34 forms an assembly. Downstream of the air filter 32 and upstream of the compressor 36 is a confluence 44 provided on which an exhaust gas recirculation line 86 a low pressure exhaust gas recirculation 80 into the intake duct 38 empties.

The exhaust system 50 includes an exhaust duct 52 , in which in the flow direction of an exhaust gas of the internal combustion engine 10 through the exhaust duct 52 a turbine 54 of the exhaust gas turbocharger 46 arranged which is the compressor 36 in the air supply system 30 drives over a shaft. The exhaust gas turbocharger 46 is preferably designed as an exhaust gas turbocharger with variable turbine geometry. For this are a turbine wheel of the turbine 54 adjustable guide blades connected upstream, through which the flow of exhaust gas onto the blades of the turbine 54 can be varied. Downstream of the turbine 54 are several exhaust aftertreatment components 64 . 66 . 68 . 70 . 74 intended. It is immediately downstream of the turbine 54 A NOx storage catalytic converter 66, which is an oxidation catalytic converter, is arranged as the first component of the exhaust gas aftertreatment 64 includes. Downstream of the NOx storage catalytic converter 64 is a particle filter 68 with a coating 70 arranged for the selective catalytic reduction of nitrogen oxides. Downstream of the particle filter 68 is an SCR catalyst 74 arranged. Further downstream is in the exhaust duct 52 an exhaust flap 76 provided with which the cross section of the exhaust duct 52 can be at least partially blocked to the exhaust back pressure in the exhaust duct 52 to increase. Downstream of the particle filter 68 and upstream of the SCR catalyst 74 is on the exhaust duct 52 a branch 72 provided on which an exhaust gas recirculation line 86 a low pressure exhaust gas recirculation 80 from the exhaust duct 52 branches. The low pressure exhaust gas recirculation 80 includes in addition to the exhaust gas recirculation line 86 a low pressure exhaust gas recirculation cooler 82 and an exhaust gas recirculation valve via which the exhaust gas recirculation through the exhaust gas recirculation line 86 is controllable. On the exhaust gas recirculation line 86 the low pressure exhaust gas recirculation 80 is a temperature sensor 88 provided, via which an exhaust gas temperature in the low-pressure exhaust gas recirculation can be determined to the low-pressure exhaust gas recirculation 80 to activate as soon as the exhaust gas temperature in the low-pressure exhaust gas recirculation 80 has exceeded a defined threshold. This can prevent water vapor or the reducing agent contained in the exhaust gas from condensing out for the selective catalytic reduction of nitrogen oxides, in particular liquid urea solution, and leading to damage or deposits in the low-pressure exhaust gas recirculation system or in the air supply system.

In the exhaust system 50 is downstream of the outlet 22 of the internal combustion engine 10 and upstream of the turbine 54 of the exhaust gas turbocharger 46 a pressure sensor 78 provided, via which a pressure in the exhaust system 50 can be determined. Furthermore, is in the exhaust duct 52 , preferably on one of the exhaust gas aftertreatment components 64 . 66 . 68 . 70 . 74 , especially on the particle filter 66 or on the SCR catalytic converter 74 a temperature sensor 92 provided with which an exhaust gas temperature T _EG in the exhaust system 50 can be monitored to a effective and efficient exhaust gas aftertreatment of the exhaust gas of the internal combustion engine 10 to enable.

The internal combustion engine 10 is with an engine control unit 90 connected, which via signal lines, not shown, to the pressure and temperature sensors 78 . 88 . 92 as well as with the control devices 24 . 94 of the internal combustion engine 10 , the air supply system 34 . 40 and the exhaust system 76 . 84 connected is.

In 2 is another embodiment of an internal combustion engine 10 shown. With essentially the same structure as for 1 executed, in this embodiment, a turbine bypass is also 56 provided which is at a junction 60 upstream of the turbine 54 from the exhaust duct 52 branches off and immediately downstream of the turbine 54 at a confluence 62 back into the exhaust duct 52 opens. In the turbine bypass 56 is a bypass valve 58 , in particular a bypass valve, arranged to the exhaust gas flow through the turbine 54 and / or through the turbine bypass 56 to control.

In 3 is a flowchart for performing a method for exhaust aftertreatment of an internal combustion engine according to the invention 10 shown. In a first step <100> becomes the actual temperature of an exhaust gas aftertreatment component, in particular a catalytic converter 64 . 66 . 74 or a particle filter 68 determined. In a second step <110> becomes the actual temperature of the exhaust aftertreatment component 64 . 66 . 68 . 70 . 74 with a target temperature of the exhaust gas aftertreatment component, in particular a light-off temperature or an activation temperature of a catalytic converter 64 . 66 . 74 , compared. Is the temperature of the exhaust aftertreatment component 64 . 66 . 68 . 70 . 74 below the target temperature, so that an efficient exhaust gas aftertreatment by this exhaust gas component is not yet possible in one process step <120> the exhaust flap 76 in the exhaust duct 52 closed to increase the exhaust gas back pressure. In parallel, in one process step <130> an internal exhaust gas recirculation into the combustion chambers 12 of the internal combustion engine 10 activated by the opening times of the exhaust valves 18 be adjusted and in particular an additional opening process of the exhaust valves 18 by a second stroke of the exhaust valves 18 is carried out. Due to the increased push-out work of the internal combustion engine 10 against the increased exhaust back pressure in the exhaust system due to the closing of the exhaust flap 76 the exhaust gas temperature is raised so that the exhaust aftertreatment components reach their light-off temperature or activation temperature more quickly. Furthermore, the recirculated exhaust gas quantity is increased by the internal exhaust gas recirculation, as a result of which the raw NOx emissions during the combustion of the fuel in the combustion chambers 12 of the internal combustion engine 10 be lowered. In addition, the throttle valve 40 in the intake duct 38 be closed, whereby the throttle losses increase, which also leads to an increase in the exhaust gas temperature.

In 4 is a further flow chart of a method according to the invention for exhaust gas aftertreatment of an internal combustion engine 10 shown. In a first step <200> becomes the actual temperature of an exhaust gas aftertreatment component, in particular a catalytic converter 64 . 66 . 74 or a particle filter 68 determined. In a second step <210> becomes the actual temperature of the exhaust aftertreatment component 64 . 66 . 68 . 70 . 74 with a target temperature of the exhaust gas aftertreatment component, in particular a light-off temperature or an activation temperature of a catalytic converter 64 . 66 . 74 compared. In one step <215> becomes the target exhaust back pressure in the exhaust system 50 on the pressure sensor 78 downstream of the outlet 22 and upstream of the turbine 54 calculated. In one step <220> becomes the exhaust flap 76 set to a setpoint to adjust the exhaust back pressure accordingly. In one step <225> becomes the engine operating point of the internal combustion engine 10 determined with regard to the speed and the effective torque. Depending on this engine operating point, it is then optionally carried out in one process step <230> the internal exhaust gas recirculation activates the in the combustion chambers 12 increase the amount of exhaust gas returned.

In 5 FIG. 10 is a flowchart of a modified method for exhaust gas aftertreatment of an internal combustion engine 10 shown, in which a turbine bypass 56 for the turbine 54 of the exhaust gas turbocharger 46 is provided. In a first step <300> becomes the actual temperature of an exhaust gas aftertreatment component, in particular a catalytic converter 64 . 66 . 74 or a particle filter 68 determined. In a second step <310> becomes the actual temperature of the exhaust aftertreatment component 64 . 66 . 68 . 70 . 74 with a target temperature of the exhaust gas aftertreatment component, in particular a light-off temperature or an activation temperature of a catalytic converter 64 . 66 . 74 compared. In one step <315> becomes the target exhaust back pressure in the exhaust system 50 on the pressure sensor 78 downstream of the outlet 22 and upstream of the turbine 54 calculated. In one step <320> becomes the exhaust flap 76 set to a setpoint to adjust the exhaust back pressure accordingly. In one step <321> is about the air mass meter 34 a fresh air mass flow in the intake duct 38 of the air supply system 30 determined. In one step <322> becomes the bypass valve 58 in the turbine bypass 56 the turbine 54 posed accordingly to match the exhaust gas flow via the turbine bypass 56 , the turbine 54 or to run proportionately over both. In one step <325> becomes the engine operating point of the internal combustion engine 10 determined with regard to the speed and the effective torque. Depending on this engine operating point, it is then optionally carried out in one process step <330> the internal exhaust gas recirculation activates the in the combustion chambers 12 increase the amount of exhaust gas returned.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

combustion chamber

14

fuel injector

16

intake valve

18

outlet valve

20

inlet

22

outlet

24

High-pressure exhaust gas recirculation

26

High-pressure exhaust gas recirculation valve

28

adjustment

30

Air supply system

32

air filter

34

Air flow sensor

36

compressor

38

intake port

40

throttle

42

Intercooler

44

junction

46

turbocharger

50

exhaust system

52

exhaust duct

54

turbine

56

turbine bypass

58

bypass valve

60

branch

62

junction

64

oxidation catalyst

66

NOx storage catalytic converter

68

particulate Filter

70

SCR coating

72

branch

74

SCR catalyst

76

exhaust flap

78

pressure sensor

80

Low-pressure exhaust gas recirculation

82

Low pressure exhaust gas recirculation cooler

84

Exhaust gas recirculation valve

86

Exhaust gas recirculation line

88

temperature sensor

90

control unit

92

temperature sensor

94

adjustment

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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 102009057394 A1 [0004]
• DE 102011014239 A1 [0005]
• DE 102016118309 A1 [0006]

Claims (15)

Method for exhaust gas aftertreatment of an internal combustion engine (10) with at least one combustion chamber (12), the internal combustion engine (10) being connected via its inlet (20) to an air supply system (30), the internal combustion engine (10) having its outlet (22) An exhaust system (50) is connected, at least one outlet valve (18) being arranged on the combustion chamber (12), with which a fluidic connection from the combustion chamber (12) to the exhaust system (50) can be closed or opened, with an exhaust duct ( 52) of the exhaust system (50) downstream of the outlet (22), a turbine (54) of an exhaust gas turbocharger (46) is arranged, and wherein in the flow direction of an exhaust gas of the internal combustion engine (10) through the exhaust duct (52) downstream of the turbine (54) Exhaust gas turbocharger (46) at least one exhaust aftertreatment component (64, 66, 68, 70) are arranged, as well as with an exhaust flap (76) with which the exhaust duct (52) downstream of the exhaust aftertreatment comp onente (64, 66, 68, 70) can be blocked, comprising the following steps: - determining an actual temperature (T _ist ) of an exhaust gas after-treatment component (64, 66, 68, 70), - comparing the determined actual temperature (T _ist ) the exhaust gas aftertreatment component (64, 66, 68, 70) with a target temperature (T _soll ), - closing the exhaust flap (76) to increase the exhaust gas back pressure in the exhaust duct (52) and changing the opening times of the at least one exhaust valve (18), to suck the exhaust gas from the exhaust system (50) by means of an internal exhaust gas recirculation back into the combustion chamber (12) when the actual temperature (T _ist ) of the exhaust gas aftertreatment component (64, 66, 68 70) is below the target temperature (T _soll )lies. Process for exhaust gas aftertreatment after Claim 1 , characterized in that an engine operating point of the internal combustion engine (10) is determined and, depending on the engine operating point, a target exhaust back pressure in the exhaust duct (52) downstream of the outlet (22) and upstream of the turbine (54) is determined. Process for exhaust gas aftertreatment after Claim 1 or 2 , characterized in that a throttle valve (40) is arranged in the air supply system (30), the throttle valve (40) being closed in order to raise the exhaust gas temperature (T _EG ). Process for exhaust gas aftertreatment according to one of the Claims 1 to 3 , characterized in that the turbine (54) of the exhaust gas turbocharger (46) is designed as a turbine (54) with variable turbine geometry, the variable geometry of the turbine (54) being adjusted such that the efficiency of the exhaust gas turbocharger (46) is reduced. Process for exhaust gas aftertreatment according to one of the Claims 1 to 4 , The speed of the internal combustion engine (10) depending on the exhaust gas temperature, the temperature of the exhaust aftertreatment component (64, 66, 68, 70) and / or the dynamic pressure in the exhaust system (50) is increased. Process for exhaust gas aftertreatment according to one of the Claims 1 to 5 , characterized in that the exhaust duct (52) has a turbine bypass (56) which branches off the exhaust duct (52) at a branch (60) upstream of the turbine (54) and downstream of the turbine (54) at an opening (62) again opens into the exhaust gas duct (52), a bypass valve (58) in the turbine bypass (56) being opened when the actual temperature (T _ist ) of the exhaust gas aftertreatment component (64, 66, 68, 70) is below the target temperature (T _should ). Process for exhaust gas aftertreatment after Claim 6 A fresh air mass flow is determined in the air supply system (30) and the bypass valve (58) is adjusted as a function of the fresh air mass flow determined. Process for exhaust gas aftertreatment according to one of the Claims 1 to 7 , characterized in that the opening times of the exhaust valve (18) are extended by an additional opening process of the exhaust valve (18). Internal combustion engine (10) with at least one combustion chamber (12), the internal combustion engine (10) being connected via its inlet (20) to an air supply system (30), the internal combustion engine (10) having an outlet (22) having an exhaust system (50 ) is connected, at least one outlet valve (18) being arranged on the combustion chamber (12), with which a fluidic connection from the combustion chamber (12) to the exhaust system (50) can be closed or opened, in an exhaust duct (52) of the exhaust system (50) downstream of the outlet (22), a turbine (54) of an exhaust gas turbocharger (46) is arranged, and wherein in the flow direction of an exhaust gas of the internal combustion engine (10) through the exhaust gas duct (52) downstream of the turbine (54) of the exhaust gas turbocharger (46) at least one exhaust gas aftertreatment component (64, 66, 68, 70) is arranged, and with an exhaust gas flap (76) with which the exhaust gas duct (52) downstream of the exhaust gas aftertreatment component (64, 66, 68, 70) is blocked can, characterized in that the internal combustion engine (10) is connected to an engine control unit (90) which is set up to implement a method according to one of the Claims 1 to 8th perform when a machine-readable program code is executed by the control unit. Internal combustion engine (10) after Claim 9 , characterized in that the internal combustion engine (10) has an adjustment mechanism (28) with which the opening times of the exhaust valves (18) can be changed. Internal combustion engine (10) after Claim 10 , characterized in that the adjusting mechanism (28) has an adjusting shaft with a control cam. Internal combustion engine (10) according to one of the Claims 9 to 11 , characterized in that in the exhaust system (50) downstream of the turbine (54) of the exhaust gas turbocharger (46) at least one catalytic converter (64, 66) with an oxidation stage, a particle filter (68) and an SCR catalytic converter (70, 74) are arranged are. Internal combustion engine (10) after Claim 12 , characterized in that the catalyst (64, 66) is designed with an oxidation stage as a NOx storage catalyst (66). Internal combustion engine (10) according to one of the Claims 9 to 13 , characterized in that a branch (72) is provided downstream of the turbine (54) of the exhaust gas turbocharger (46), on which an exhaust gas recirculation line (86) of a low-pressure exhaust gas recirculation (80) branches off from the exhaust gas duct (52) and the exhaust gas duct (52 ) with an intake duct (38) of the air supply system (30) upstream of a compressor (36) of the exhaust gas turbocharger (46), an exhaust gas recirculation valve (84) being provided in the exhaust gas recirculation line (86). Internal combustion engine (10) according to one of the Claims 9 to 14 characterized in that a turbine bypass (56) is provided in the exhaust system (50), which branches off from the exhaust gas duct (52) at a branch (60) upstream of the turbine (54) and at a junction (62) downstream of the turbine ( 54) again opens into the exhaust gas duct (52), a switchable bypass valve (58) being arranged in the turbine bypass (56).

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