DE102018117124B4 - Internal combustion engine and method for exhaust gas aftertreatment of such an internal combustion engine - Google Patents

Abstract

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 to an air supply system (30) via its inlet (20) and being connected to an exhaust system (50) by its outlet (22). at least one outlet valve (18) is 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, wherein in an exhaust gas duct (52) of the exhaust system (50 ) A turbine (54) of an exhaust gas turbocharger (46) is arranged downstream of the outlet (22), 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 valve (76) with which the exhaust gas duct (52) downstream of the exhaust gas aftertreatment component (64, 66, 68, 70) is blocked rden, comprising the following steps: - determining an actual temperature (Tactual) of the at least one exhaust gas aftertreatment component (64, 66, 68, 70), - comparing the determined actual temperature (Tactual) of the exhaust gas aftertreatment component (64, 66, 68, 70) with a target temperature (Tsetpoint), - closing the exhaust gas flap (76) to increase the exhaust gas back pressure in the exhaust gas duct (52) and changing the opening times of the at least one exhaust valve (18) in order to extract the exhaust gas from the exhaust system (50) by means of a to suck internal exhaust gas recirculation back into the combustion chamber (12) when the actual temperature (Tactual) of the exhaust gas aftertreatment component (64, 66, 68 70) is below the target temperature (Tsetpoint), with the opening times of the outlet valve (18) through an additional opening process of the exhaust valve (18) can be extended, wherein- an engine operating point of the internal combustion engine (10) is determined, and depending on the engine operating point a target exhaust gas back pressure in the exhaust gas duct (52) s is determined downstream of the outlet (22) and upstream of the turbine (54), and wherein- the speed of the internal combustion engine (10) is increased as a function of the dynamic pressure in the exhaust system (50).

Description

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

The current exhaust gas legislation and one that will become increasingly strict in the future place high demands on engine raw emissions and the exhaust gas aftertreatment of combustion engines. The demands for a further reduction 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. 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 separating soot particles and optionally further catalytic converters. Ammonia is preferably used as the reducing agent. Because handling pure ammonia is complicated, vehicles usually use a synthetic, aqueous urea solution, which is mixed with the hot exhaust gas flow in a mixing device upstream of the SCR catalytic converter. This mixing heats up the aqueous urea solution, with the aqueous urea solution releasing ammonia in the exhaust gas duct. A commercially available, aqueous urea solution is generally made up of 32.5% urea and 67.5% water. However, before the light-off temperature of the SCR catalytic converter is reached, 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 should be minimized and/or the exhaust gas aftertreatment components should be heated up quickly.

It is known from the prior art to reduce the raw NOx emissions in a diesel engine by internal and external exhaust gas recirculation, late injection starts for fuel injection into the combustion chambers of the internal combustion engine and a corresponding shift in the center of combustion. Furthermore, it is known that such a retarded shift in the center of combustion 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 gas 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 start-up.

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

From the DE 10 2011 014 239 A1 an internal combustion engine with an intake tract and an exhaust system is known, with a throttle valve being arranged in the intake tract of the internal combustion engine, via which the fresh air quantity 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, to to increase the amount of exhaust gas recirculated via the internal exhaust gas recirculation and thus to raise the exhaust gas temperature.

the DE 10 2016 118 309 A1 discloses an internal combustion engine supercharged by means of an exhaust gas turbocharger with an intake tract and an exhaust system, with a throttle flap being arranged in the intake tract and an exhaust flap in the exhaust gas duct in the exhaust system downstream of an oxidation catalytic converter and a particle filter with a coating for the selective catalytic reduction of nitrogen oxides, in order to Low-pressure exhaust gas recirculation to control the amount of exhaust gas recirculated.

From the DE 10 2006 014 996 A1 a method for operating a gasoline engine with direct gasoline injection is known, in which the mixture is ignited at least at individual operating points in a controlled self-ignition. The gasoline engine has a valve train with variable opening times and exhaust gas recirculation. A mixture is produced via exhaust gas recirculation and fuel injection, which self-ignites at the end of the compression phase.

the DE 10 2004 036 802 A1 discloses a method for keeping warm a catalyst in the exhaust system of an internal combustion engine. The method has the following steps: determining a catalytic activity of the catalyst; checking whether the catalytic activity is within a predetermined range; and triggering a throttling of the Air supply when the catalytic activity is within the predetermined range. The method is characterized in that, in addition to throttling the air supply, the exhaust gas recirculation rate of the internal combustion engine is increased or the combustion center of the internal combustion engine is shifted, at least in a sub-area of the predetermined area.

From the DE 10 2016 014 767 A1 a method for operating an internal combustion engine with the following method steps is known: adjusting an exhaust flap in the exhaust system of the internal combustion engine from an open position to an at least partially closed position; Adjusting an exhaust gas recirculation valve arranged in an exhaust gas recirculation line of the internal combustion engine, the exhaust gas flap and the exhaust gas recirculation valve being continuously adjusted into respective positions between the respective closed position and the respective open position.

Furthermore, fully variable electrohydraulic valve drives are known from the prior art, which allow almost any variation of the valve lift of an internal combustion engine, which is only limited upwards by the maximum lift curve resulting from the cam contour.

From "Increasing the exhaust gas temperature in the diesel engine through variable valve train"; MTZ 74 (2013), pp. 308-315, it is known to carry out a second lift of an exhaust valve during the intake phase.

A disadvantage of the known methods for exhaust gas aftertreatment, however, is that they can lead to increased particle emissions, increased fuel consumption and the associated increased CO ₂ emissions, problems with packaging in narrow engine compartments and a lack of effectiveness, especially 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, particularly 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, the internal combustion engine being connected to an air supply system via its inlet and to an exhaust system via its outlet. At least one outlet 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 gas duct of the exhaust system downstream of the outlet. At least one exhaust gas aftertreatment component, preferably at least one catalytic converter with one oxidation stage, a particle filter and a catalytic converter for the selective catalytic reduction of nitrogen oxides (SCR catalytic converter) is arranged in the flow direction of an exhaust gas from 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 can be blocked at least to the greatest possible extent downstream of the at least one exhaust gas aftertreatment component. 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 aftertreatment component with a target temperature,
• - Closing the exhaust flap to increase the exhaust back pressure in the exhaust duct and changing the opening times of the at least one exhaust valve in order to draw the exhaust gas from the exhaust system into the at least one combustion chamber by means of 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 ensure efficient conversion of pollutants, to reduce the raw emissions of the internal combustion engine. Closing the exhaust flap increases the exhaust back pressure, meaning that the piston in the combustion engine has to do more work to push the exhaust gas out of the combustion chamber and into the exhaust duct. As a result of the increase in the exhaust back pressure and the additional work, the exhaust gas temperature in the exhaust duct rises. The raw NOx emissions can be reduced by simultaneously increasing the amount of exhaust gas via internal exhaust gas recirculation, i.e. sucking back exhaust gas during the downward movement of the piston in the intake phase.

According to the invention, the opening times of the outlet valves are extended by an additional opening process. Through an additional opening process of the exhaust valves, in particular through an overlapping of the opening times of exhaust valves and intake valves in an intake stroke of the combustion engine engine, the internal exhaust gas recirculation can be improved by sucking back exhaust gas from the exhaust system.

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

According to the invention, it is also provided that the speed of the internal combustion engine is increased as a function of the dynamic pressure in the exhaust system. 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.

Advantageous improvements and further developments of the exhaust gas aftertreatment method specified in the independent claim are possible as a result of the features listed in the dependent claims.

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 gas valve, the pressure in the intake duct of the air supply system downstream of the throttle valve can be reduced by closing the throttle valve. Due to the increased throttling losses, the work to be performed also increases, 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 variable turbine geometry, the variable geometry of the turbine being adjusted to increase 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 guide vanes of the turbine can be adjusted, are known from the prior art in order to improve the response behavior of the exhaust gas turbocharger and/or to increase performance. In a cold start phase, it can make sense to deliberately reverse this effect and use the adjustment device for the variable turbine geometry in order to reduce efficiency and response. 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 point efficient storage or conversion of nitrogen oxides is possible is.

In a preferred embodiment of the method, it is provided that the exhaust gas duct has a turbine bypass, which branches off from the exhaust gas duct at a junction upstream of the turbine and re-enters the exhaust gas duct at a junction downstream of the turbine, with a bypass flap in the turbine bypass being opened when the Actual temperature of the exhaust aftertreatment component is below the target temperature. A turbine bypass can avoid an increased cylinder filling with fresh air, since the speed of the turbine of the exhaust gas turbocharger and thus the output of the compressor in the intake port can be reduced by the bypass. As a result, the efficiency of the internal combustion engine, in particular the maximum temperature in the combustion chambers, can be lowered, as a result of which the untreated nitrogen oxide emissions can be reduced. At the same time, the reduction in efficiency means that more energy is removed from the combustion chamber via the exhaust gas, which accelerates the heating of the exhaust gas aftertreatment components.

A further improvement of the method provides that a fresh air mass flow is determined in the air supply system and the bypass flap is adjusted as a function of the determined fresh air mass flow. In order to improve the control of the output and the efficiency of the exhaust gas turbocharger, it is planned to measure the air mass flow in the intake duct and to take this into account when controlling the bypass valve.

Alternatively, it is advantageously provided that the opening times of the exhaust valves are adjusted in the “retarded” direction in such a way that the exhaust gas is sucked back from the exhaust system into the combustion chamber. Alternatively, internal exhaust gas recirculation can be achieved by shifting and/or lengthening the opening times of the exhaust valves.

According to the invention, an internal combustion engine with at least one combustion chamber is proposed whose inlet is connected to an air supply system and whose outlet is connected to an exhaust system, at least one outlet 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 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 system. The exhaust system also has an exhaust flap, with which the exhaust gas duct can be blocked downstream of the exhaust gas aftertreatment component. Provision is made for the internal combustion engine to be 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 untreated emissions of the internal combustion engine by carrying out a method according to the invention. The raw emissions are reduced, especially in a starting phase, particularly preferably during a cold start, of the internal combustion engine by closing the exhaust gas valve and the internal exhaust gas recirculation and the exhaust gas temperature is increased in order to bring the components of the exhaust gas aftertreatment more quickly to the operating temperature required for the conversion of pollutants.

In a preferred embodiment of the internal combustion engine, it is provided that the internal combustion engine has an adjusting mechanism for adjusting the opening times of the exhaust valves. Such an adjusting 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 open while the piston of the internal combustion engine increases the volume of the combustion chamber in an intake stroke.

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

In a preferred embodiment of the internal combustion engine, 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, is 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 aftertreatment components of a diesel engine is a NOx storage catalytic converter or an oxidation catalytic converter, a particulate filter and an SCR catalytic converter. The particulate filter and the SCR catalytic converter can be combined in one component if the particulate filter is provided with an SCR coating .

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

In another preferred embodiment of the invention, a branch is provided in the exhaust system downstream of the turbine, at which branch an exhaust gas recirculation line of a low-pressure exhaust gas recirculation system 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. The untreated emissions of an internal combustion engine can be reduced in a known manner by low-pressure exhaust gas recirculation. In order to achieve an effective increase in the exhaust back pressure in the starting phase of the 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, in this phase, the exhaust gas recirculation valve in the low-pressure exhaust gas recirculation is closed to allow back pressure to build up in the exhaust system.

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

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 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 associated drawings. Show it:

• 1 a first embodiment of an internal combustion engine with an air supply system and an exhaust system;
• 2 a further exemplary embodiment of an internal combustion engine with an air supply system and an exhaust system, a turbine bypass being provided for a turbine of the exhaust gas turbocharger;
• 3 a simplified flow chart for carrying out a method according to the invention for the exhaust gas aftertreatment of an internal combustion engine;
• 4 a further flowchart for carrying out a method according to the invention for the exhaust gas aftertreatment of an internal combustion engine;
• 5 a further flow chart for carrying out a method according to the invention for the 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. Internal combustion engine 10 has multiple combustion chambers 12 . A fuel injector 14 for injecting a fuel into the respective combustion chamber 12 is arranged on each of the combustion chambers 12 . The internal combustion engine 10 is connected to an air supply system 30 at its inlet 20 and to an exhaust system 50 at its outlet 22 . The internal combustion engine 10 also includes a high-pressure exhaust gas recirculation system 24 with a high-pressure exhaust gas recirculation valve 26, via which an exhaust gas from the internal combustion engine 10 can be recirculated from the outlet 22 to the inlet 20. Inlet valves 16 and outlet valves 18 are arranged on the combustion chambers 12, with which a fluidic 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, an adjustment mechanism 28 is provided on the internal combustion engine 10, via which the opening times of the exhaust valves 18 can be changed. In addition, there can be a further adjustment mechanism, not shown, for adjusting the opening times of the intake valve. The adjusting mechanism 28, in particular an adjusting shaft, can be controlled via an adjusting element 94, so that the opening times of the exhaust valve 18 can be adjusted to at least two operating states of the internal combustion engine 10. The opening times can be adjusted, for example, via a switchable additional cam, electronic valve control, a hydraulic or electric camshaft adjuster or a similar adjusting mechanism, which enables an additional opening process of the exhaust valves 18 or a corresponding adjustment of the opening times of the exhaust valves 18 in such a way that internal exhaust gas recirculation can be carried out, in which the exhaust gas from the exhaust system 50 is sucked back into the combustion chambers 12. In particular, an overlapping of the opening times of the intake valves 16 and the exhaust valves 18 is provided during an intake stroke of the internal combustion engine 10 in order to fill the combustion chambers 12 with an increased amount of exhaust gas and a reduced amount of fresh air.

Air supply system 30 includes an intake line 38, in which, in the flow direction of fresh air through intake line 38, is an air filter 32, downstream of the air filter is an air mass meter 34, in particular a hot-film air mass meter, downstream of the air mass meter is a compressor 36 of an exhaust gas turbocharger 46, and downstream of compressor 36 is a throttle valve 38 and a charge air cooler 42 are arranged further downstream. The air mass meter 34 can also be arranged in a filter housing of the air filter 32, so that the air filter 32 and the air mass meter 34 form an assembly. A junction 44 is provided downstream of the air filter 32 and upstream of the compressor 36 , at which an exhaust gas recirculation line 86 of a low-pressure exhaust gas recirculation system 80 opens into the intake passage 38 .

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

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

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

In 2 another exemplary embodiment of an internal combustion engine 10 is shown. With essentially the same structure as 1 embodied, a turbine bypass 56 is additionally provided in this exemplary embodiment, which branches off from the exhaust gas duct 52 at a junction 60 upstream of the turbine 54 and re-enters the exhaust gas duct 52 immediately downstream of the turbine 54 at a junction 62 . A bypass valve 58 , in particular a bypass valve, is arranged in the turbine bypass 56 in order to control the flow of exhaust gas through the turbine 54 and/or through the turbine bypass 56 .

In 3 a flowchart for carrying out a method according to the invention for the exhaust gas aftertreatment of an internal combustion engine 10 is shown. In a first method step <100>, the actual temperature of an exhaust gas aftertreatment component, in particular a catalytic converter 64, 66, 74 or a particle filter 68, is determined. In a second method step <110>, the actual temperature of the exhaust gas aftertreatment component 64, 66, 68, 70, 74 is compared to 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 . If the temperature of the exhaust gas aftertreatment components 64, 66, 68, 70, 74 is below the target temperature, so that efficient exhaust gas aftertreatment by this exhaust gas component is not yet possible, then in a method step <120> the exhaust gas flap 76 in the exhaust gas duct 52 is closed in order to increase exhaust back pressure. At the same time, in a method step <130>, internal exhaust gas recirculation into the combustion chambers 12 of the internal combustion engine 10 is activated by adjusting the opening times of the exhaust valves 18 and, in particular, by carrying out an additional opening process of the exhaust valves 18 by means of a second lift of the exhaust valves 18. The exhaust gas temperature is increased by the increased exhaust 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, so that the exhaust gas aftertreatment components reach their light-off temperature or activation temperature more quickly. Furthermore, through the internal exhaust gas recirculation, the recirculated exhaust gas quantity increased, whereby the raw NOx emissions during the combustion of the fuel in the combustion chambers 12 of the internal combustion engine 10 are reduced. In addition, the throttle flap 40 in the intake passage 38 can be closed, which increases the throttle losses, which also leads to an increase in the exhaust gas temperature.

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

In 5 a flowchart of a modified method for exhaust gas aftertreatment of an internal combustion engine 10 is shown, in which a turbine bypass 56 for the turbine 54 of the exhaust gas turbocharger 46 is provided. In a first method step <300>, the actual temperature of an exhaust gas aftertreatment component, in particular a catalytic converter 64, 66, 74 or a particle filter 68, is determined. In a second method step <310>, the actual temperature of the exhaust gas aftertreatment component 64, 66, 68, 70, 74 is compared to 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. In a method step <315>, the target exhaust gas back pressure in the exhaust system 50 is calculated at the pressure sensor 78 downstream of the outlet 22 and upstream of the turbine 54 . In a method step <320>, the exhaust gas valve 76 is set to a target value in order to adapt the exhaust gas back pressure accordingly. In a method step <321>, a fresh air mass flow in the intake duct 38 of the air supply system 30 is determined via the air mass meter 34 . In a method step <322>, the bypass valve 58 in the turbine bypass 56 of the turbine 54 is adjusted accordingly in order to route the exhaust gas flow accordingly via the turbine bypass 56, the turbine 54 or proportionally via both. In a method step <325>, the engine operating point of the internal combustion engine 10 is determined with regard to the speed and the effective torque. Depending on this engine operating point, the internal exhaust gas recirculation is then optionally activated in a method step <330> in order to increase the amount of exhaust gas recirculated into the combustion chambers 12 .

Reference List

10

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 mechanism

30

air supply system

32

air filter

34

mass airflow meter

36

compressor

38

intake duct

40

throttle

42

intercooler

44

confluence

46

exhaust gas turbocharger

50

exhaust system

52

exhaust duct

54

turbine

56

turbine bypass

58

bypass valve

60

branch

62

confluence

64

oxidation catalyst

66

NOx storage catalyst

68

particle filter

70

SCR coating

72

branch

74

SCR catalytic converter

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 element

Claims (12)

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 to an air supply system (30) via its inlet (20) and being connected to an exhaust system (50) by its outlet (22). at least one outlet valve (18) is 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, wherein in an exhaust gas duct (52) of the exhaust system (50 ) A turbine (54) of an exhaust gas turbocharger (46) is arranged downstream of the outlet (22), 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 valve (76) with which the exhaust gas duct (52) downstream of the exhaust gas aftertreatment component (64, 66, 68, 70) is blocked rden, comprising the following steps: - determining an actual temperature (T _ist ) of the at least one exhaust gas aftertreatment component (64, 66, 68, 70), - comparing the determined actual temperature (T _ist ) of the exhaust gas aftertreatment component (64, 66, 68, 70) with a set temperature (T _soll), - closing the exhaust valve (76) to increase the exhaust back pressure in the exhaust passage (52) and changing the opening times of the at least one exhaust valve (18) to the exhaust gas from the exhaust system (50 ) to suck back into the combustion chamber (12) by means of an internal exhaust gas recirculation, when the actual temperature (T _ist) of the exhaust gas aftertreatment component (64, 66, 68, 70) below the set temperature (T _soll) is located, wherein - the opening times of the Exhaust valve (18) are extended by an additional opening process of the exhaust valve (18), wherein - an engine operating point of the internal combustion engine (10) is determined, and depending on the engine operating point, a target exhaust gas back pressure in the Ab gas channel (52) downstream of the outlet (22) and upstream of the turbine (54) is determined, and wherein - the speed of the internal combustion engine (10) depending on the dynamic pressure in the exhaust system (50) is increased. Process for exhaust aftertreatment claim 1 , 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 aftertreatment claim 1 or 2 , 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 in such a way that the efficiency of the exhaust gas turbocharger (46) is reduced. Process for exhaust gas aftertreatment according to one of Claims 1 until 3 , characterized in that the exhaust gas duct (52) has a turbine bypass (56) which branches off at a junction (60) upstream of the turbine (54) from the exhaust gas duct (52) and downstream of the turbine (54) at a junction (62) again opens into the exhaust passage (52), wherein a bypass valve (58) opens in the turbine bypass (56) when the actual temperature (T _ist) of the exhaust-gas treatment component (64, 66, 68, 70) below the setpoint temperature (T _should ) lies. Process for exhaust aftertreatment claim 4 , wherein a fresh air mass flow in the air supply system (30) is determined and the bypass valve (58) is adjusted depending on the determined fresh air mass flow. Internal combustion engine (10) with at least one combustion chamber (12), wherein the internal combustion engine (10) is connected to an air supply system (30) via its inlet (20) and is connected to an exhaust system (50) by its outlet (22), wherein at at least one outlet valve (18) is arranged in 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 gas 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 at least one exhaust gas aftertreatment component (64, 66, 68, 70) is arranged 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), and with an exhaust gas flap (76) with which the exhaust gas duct (52) can be blocked downstream of the exhaust gas aftertreatment component (64, 66, 68, 70), characterized in that the internal combustion engine (10) is connected to an engine control unit (90) which is set up to a method according to one of Claims 1 until 5 to be carried out when a machine-readable program code is executed by the control unit. Internal combustion engine (10) after claim 6 , 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 7 , characterized in that the adjusting mechanism (28) has an adjusting shaft with a control cam. Internal combustion engine (10) according to one of Claims 6 until 8th , 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 9 , characterized in that the catalytic converter (64, 66) is designed with an oxidation stage as a NOx storage catalytic converter (66). Internal combustion engine (10) according to one of Claims 6 until 10 , characterized in that downstream of the turbine (54) of the exhaust gas turbocharger (46) there is a branch (72) at which an exhaust gas recirculation line (86) of a low-pressure exhaust gas recirculation system (80) branches off from the exhaust gas duct (52) and the exhaust gas duct (52 ) connects to 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 Claims 6 until 11 , characterized in that in the exhaust system (50) a turbine bypass (56) is provided, which branches off at a branch (60) upstream of the turbine (54) from the exhaust gas duct (52) 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).

Images