DE102018120556A1 - Method for operating an internal combustion engine and internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine (10) with at least one combustion chamber (12). The internal combustion engine (10) is connected via its inlet (16) to an air supply system (20) and via its outlet (18) to an exhaust system (40) of the internal combustion engine (10). At least one exhaust gas aftertreatment component (46, 48, 54, 64) for converting pollutants in the exhaust gas of the internal combustion engine (10) is arranged in the exhaust system (40). The load state (P) of the internal combustion engine (10) and the route-related emissions (EG / D), in particular the route-related NOx emissions, are determined. If the route-related emissions approach a defined threshold value (EG / D) and if it can be foreseen that these route-related emissions (EG / D) cannot be met if the engine parameters remain unchanged, the exhaust gas recirculation rate (EGR) will be determined in high-load operation of the internal combustion engine (10) raised to reduce the raw emissions of the internal combustion engine (10). The invention further relates to an internal combustion engine (10) with an air supply system (20) and an exhaust system (40) for carrying out such a method.

Description

The invention relates to a method for operating an internal combustion engine with an air supply system and an exhaust system, and to 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 takes place 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.

In the case of a highly dynamic driving style, long-lasting high-load operation can lead to a predeterminable route-related emission value being exceeded. In the case of diesel engines, nitrogen oxide emissions are particularly affected. In particular, the exhaust gas temperature and / or the temperature of the catalytic converters can reach a temperature at which the exhaust system is warmed up and under long-term high-load operation, at which selective catalytic reduction of nitrogen oxides is only possible to a limited extent.

From the DE 10 2014 217 591 A1 A method for controlling an exhaust gas recirculation valve is known, the actual exhaust gas recirculation quantity being compared with a target exhaust gas recirculation quantity for the exhaust gas recirculation quantity in dynamic engine operation. The opening pressure of an exhaust gas recirculation valve to avoid a drop in torque is adjusted such that the amount of exhaust gas recirculation is increased to the extent that the boost pressure built up to avoid a drop in torque is built up.

From the DE 10 2016 210 243 A1 A method for adapting the air supply to the combustion chambers of an internal combustion engine is known, in which a bypass is opened in the event of a sudden gas release (tip-out) in order to increase the fresh air supply to the combustion chambers of the internal combustion engine and to reduce the exhaust gas recirculation quantity in order to ensure that the engine runs smoothly or avoid misfires.

From the DE 10 2016 211 311 A1 a method for adjusting the exhaust gas recirculation rate in an internal combustion engine is known. An estimated amount of recirculated exhaust gas is compared with a measured actual amount and a model for calculating the exhaust gas recirculation rate is adjusted accordingly based on the determined offset.

A disadvantage of the known methods, however, is that none of these methods deals with emission reduction in high-load operation, since such operating conditions have not been checked in the previous emission tests. As part of the conversion and recording of real driving emissions (RDE), the focus has shifted to those load points that were not checked in the previous emissions test.

The object of the invention is to reduce the emissions of an internal combustion engine, in particular in high-load operation, and thus to relieve the environment.

• - Erfassen eines Lastzustandes und eines streckenbezogenen Emissionswertes des Verbrennungsmotors, wobei
• - bei einer Annäherung des streckenbezogenen Emissionswertes an einen definierten Schwellenwert und einem Erkennen eines Hochlastbetriebs des Verbrennungsmotors die Abgasrückführungsrate des Verbrennungsmotors angehoben wird.

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 is connected via its inlet to an air supply system and via its outlet to an exhaust system of the internal combustion engine. At least one exhaust gas aftertreatment component for converting pollutants in the exhaust gas of the internal combustion engine is arranged in the exhaust system. The process includes the following steps:

• - Detection of a load state and a route-related emission value of the internal combustion engine, wherein
• - When the route-related emission value approaches a defined threshold value and a detection of high-load operation of the internal combustion engine, the exhaust gas recirculation rate of the internal combustion engine is increased.

In this context, high-load operation is to be understood as operation of the internal combustion engine in which a complete conversion of the harmful exhaust gas components by the exhaust gas aftertreatment devices is not possible due to the space velocity and / or the exhaust gas volume and / or the exhaust gas temperature. By increasing the exhaust gas recirculation rate by one percent, the raw emissions, especially the NOx emissions, of the internal combustion engine can be reduced by 3-5 percent. At the same time, the performance of the internal combustion engine drops only insignificantly, so that the driver feels this increase in the exhaust gas recirculation rate only slightly or not at all in the driving behavior of the motor vehicle.

The features listed in the dependent claims enable advantageous improvements and further developments of the method for exhaust gas aftertreatment specified in the independent claim.

In a preferred embodiment of the method, it is provided that an exhaust gas temperature and / or a component temperature of an exhaust gas aftertreatment component is additionally recorded, the exhaust gas recirculation rate being increased as a function of a component temperature of the exhaust gas aftertreatment component. The exhaust gas recirculation rate is increased with increasing exhaust gas temperature or increasing component temperature of the exhaust gas aftertreatment component, in particular the catalysts. As a result, the raw emissions can be reduced accordingly, so that the limit values for the route-related exhaust emissions are not reached.

In a preferred embodiment of the method, it is provided that the exhaust gas recirculation quantity is increased in a load range in which the internal combustion engine has at least 60% of its nominal output, preferably at least 70% of its nominal output, particularly preferably at least 80% of its nominal output and / or at least 60% of it Nominal speed, preferably at least 70% of its nominal speed, particularly preferably at least 80% of its nominal speed. A high-load operation of the internal combustion engine is typically present when at least one of the above criteria is reached or exceeded. While below these threshold values a sufficient conversion of the pollutants by the exhaust gas aftertreatment components can take place, above these threshold values additional measures are necessary to avoid an increase in the tailpipe emissions of the motor vehicle. By increasing the exhaust gas recirculation rate, the raw emissions can be reduced as described, so that the route-related emission limits are also not reached in these high-load phases.

In a further improvement of the method, it is provided that after the increase in the exhaust gas recirculation quantity, a further comparison of the route-related emission values with the current emission values takes place and, if the route-related emission values are expected to be exceeded, the power and / or the torque of the internal combustion engine is limited. In the event that, despite an increase in the exhaust gas recirculation rate, there is a risk that the route-related emission values will not be achieved, additional measures can be initiated to reduce the raw emissions of the internal combustion engine and / or to improve the effectiveness of the exhaust gas aftertreatment components. This goal can be achieved by limiting the power and / or the torque of the internal combustion engine. However, this measure should only be initiated as a secondary measure, since it means a noticeable intervention for the driver and thus reduces driving comfort.

In a preferred embodiment of the invention it is provided that the internal combustion engine is designed as a self-igniting internal combustion engine according to the diesel principle and the route-related emission value is the nitrogen oxide tailpipe emissions of the internal combustion engine. By increasing the exhaust gas recirculation rate, the raw NOx emissions in particular can be significantly reduced. Overall, the temperature in the combustion chambers drops due to the increase in the exhaust gas recirculation rate, which means that this measure can also have a positive impact on further emissions.

It is advantageously provided that the route-related nitrogen oxide emissions are recorded by at least one NOx sensor in the exhaust system. The nitrogen oxide emissions in the exhaust gas of the internal combustion engine can be determined in a simple manner by means of a NOx sensor. This makes it possible to recognize whether there is a risk that the route-related emission values will not be reached and that an increase in the exhaust gas recirculation rate and, if necessary, secondary measures may be initiated.

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 gas aftertreatment component for converting pollutants in the exhaust gas of the internal combustion engine is provided in the exhaust system. The internal combustion engine has a control unit which is set up for this purpose perform the inventive method 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, particularly in the high-load phase, by increasing the amount of exhaust gas recirculation, so that the exhaust gas contains fewer emissions. These can then be converted more effectively by the exhaust aftertreatment components, so that tailpipe emissions are significantly reduced. In this way, the strict emission limits can be observed even at operating points of the internal combustion engine that were not relevant for testing.

In a preferred embodiment of the internal combustion engine, it is provided that an air mass meter and a pressure sensor are arranged in the air supply system. The quantity of fresh air supplied to the combustion chambers of the internal combustion engine can be determined by an air mass meter. The measuring accuracy can be further improved by an additional pressure sensor in the air supply system, whereby the regulation of the combustion air ratio and thus the engine combustion can be optimized. As a result, the raw emissions of the internal combustion engine can be reduced, so that less harmful exhaust gas components have to be converted by the exhaust gas aftertreatment components.

In a preferred embodiment of the internal combustion engine, a first catalytic converter, in particular an oxidation catalytic converter or a NOx storage catalytic converter, is arranged in the exhaust system and a particle filter is arranged downstream of the first catalytic converter. The particle filter has a coating for the selective catalytic reduction of nitrogen oxides, or an SCR catalytic converter is connected downstream of the particle filter. Such an exhaust system enables highly efficient exhaust gas aftertreatment of a diesel engine. Nitrogen oxides can be reduced at three points on the exhaust system, namely on the NOx storage catalytic converter, on an SCR coating of the particle filter and on an SCR catalytic converter downstream of the particle filter. This enables efficient exhaust gas aftertreatment with regard to NOx emissions in every load range of the internal combustion engine.

In a further improvement of the internal combustion engine, it is provided that at least one exhaust gas sensor for detecting the current emissions of the internal combustion engine, in particular at least one NOx sensor, is arranged in the exhaust system. The nitrogen oxide emissions in the exhaust gas of the internal combustion engine can be determined in a simple manner by means of a NOx sensor. This makes it possible to recognize whether there is a risk that the route-related emission values will not be reached and that an increase in the exhaust gas recirculation rate and, if necessary, secondary measures may be initiated. Furthermore, further exhaust gas sensors, in particular a temperature sensor or a lambda probe, can be present in order to control the exhaust gas aftertreatment and to increase the efficiency of the exhaust gas aftertreatment.

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

• 1 ein erstes Ausführungsbeispiel eines Verbrennungsmotors mit einem Luftversorgungssystem und einer Abgasanlage;
• 2 ein weiteres Ausführungsbeispiel eines Verbrennungsmotors mit einem Luftversorgungssystem und einer Abgasanlage;
• 3 ein vereinfachtes Ablaufdiagramm zur Durchführung eines erfindungsgemäßen Verfahrens zur Abgasnachbehandlung eines Verbrennungsmotors;
• 4 ein Diagramm zur Anpassung der Abgasrückführungsmenge in Abhängigkeit der streckenbezogen Emissionen;
• 5 ein Diagramm zur Anpassung des Drehmoments und/oder der Leistung, wenn die Anpassung der Abgasrückführungsmenge allein nicht zum Erreichen der streckenbezogenen Emissionen ausreicht.

The invention is explained below in exemplary embodiments with reference to the accompanying drawings. The same components or components with the same function are identified in the different figures with the same reference numerals. 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;
• 3 a simplified flow chart for performing an inventive method for exhaust gas aftertreatment of an internal combustion engine;
• 4 a diagram for adjusting the exhaust gas recirculation quantity depending on the route-related emissions;
• 5 a diagram for adjusting the torque and / or the power if the adjustment of the exhaust gas recirculation quantity alone is not sufficient to achieve the route-related emissions.

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 16 with an air supply system 20 and with its outlet 18 with an exhaust system 40 connected. The internal combustion engine 10 also includes high pressure exhaust gas recirculation 32 with an exhaust gas recirculation line 34 and a high pressure exhaust gas recirculation valve 36 , via which an exhaust gas of the internal combustion engine 10 from the outlet 18 to the entrance 16 can be traced back. To the combustion chambers 12 Inlet valves and outlet valves are arranged, with which a fluid connection from the air supply system 20 to the combustion chambers 12 or from the combustion chambers 12 to the exhaust system 40 can be opened or closed.

The air supply system 20 includes an intake pipe 28 , in which in the direction of flow of fresh air through the intake pipe 28 an air filter 22 , an air mass meter downstream of the air filter 24 , in particular a hot film air mass meter, and downstream of the air mass meter 24 a compressor 26 of an exhaust gas turbocharger 38 are arranged. The air mass meter 24 also in a filter housing of the air filter 22 be arranged so that the air filter 22 and the air mass meter 24 form an assembly.

The exhaust system 40 includes an exhaust duct 42 , in which in the flow direction of an exhaust gas of the internal combustion engine 10 through the exhaust duct 22 a turbine 44 of the exhaust gas turbocharger 38 arranged which is the compressor 26 in the air supply system 20 drives over a shaft. The exhaust gas turbocharger 38 is preferably designed as an exhaust gas turbocharger with variable turbine geometry. For this are a turbine wheel of the turbine 44 adjustable guide vanes upstream, through which the flow of the exhaust gas onto the blades of the turbine 44 can be varied. Downstream of the turbine 44 are several exhaust aftertreatment components 46 . 48 . 54 . 56 intended. It is immediately downstream of the turbine 44 a NOx storage catalytic converter as the first component of exhaust gas aftertreatment 48 arranged, which is an oxidation catalyst 46 includes. Downstream of the NOx storage catalytic converter 48 is a particle filter 54 with a coating 56 arranged for the selective catalytic reduction of nitrogen oxides. Downstream of the NOx storage catalytic converter 48 and upstream of the particulate filter 54 is a dosing element 50 with a dosing valve 52 arranged with which a reducing agent, in particular aqueous urea solution, into the exhaust duct 42 of the internal combustion engine 10 can be dosed. Also in the exhaust system 40 an exhaust gas sensor 68 , in particular a NOx sensor, with which the exhaust gas emissions can be monitored while the engine is running.

The internal combustion engine 10 is with an engine control unit 70 connected, which via signal lines, not shown, to the exhaust gas sensor 68 as well as with the dosing element 50 is connected to metering reducing agent. Furthermore, the control unit with the injectors 14 connected to the injection timing of the fuel as well as the amount of fuel in the combustion chambers 12 to control injected fuel.

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 pressure sensor is also in the air supply system 30 intended. It is also downstream of the compressor 26 of the exhaust gas turbocharger 38 and upstream of the inlet 16 of the internal combustion engine 10 A charge air cooler is provided, with which the compressed air before entering the combustion chambers 12 cooled and thus the filling of the combustion chambers is improved. In the exhaust system 40 is downstream of the outlet 18 and upstream of the turbine 44 of the exhaust gas turbocharger 38 another pressure sensor 66 intended. It is also downstream of the particulate filter 54 an SCR catalyst 64 arranged. To do this is downstream of the particulate filter 54 and upstream of the SCR catalyst 64 another dosing element 60 with a dosing valve 62 provided for metering a reducing agent. Also on the exhaust duct 42 several exhaust gas sensors 68 provided, in 2 a selection of possible positions for the exhaust gas sensors 68 is shown. As an alternative to a NOx storage catalytic converter 48, the first catalytic converter can also be used as an oxidation catalytic converter 46 be executed. The particle filter can also be used 54 instead of an SCR coating also with another catalytically active coating 58 , in particular with an oxidatively effective coating. Alternatively, the particle filter 54 with a downstream SCR catalytic converter 64 also be uncoated, in which case one of the metering elements 50 . 60 can be omitted.

In 3 is a flowchart for performing an inventive method for exhaust gas aftertreatment of an internal combustion engine 10 shown. In a first step I becomes the NOx concentration in the exhaust duct 42 by one in the control unit 70 stored exhaust gas model calculated or by the exhaust gas sensor 68 measured. In parallel, in one process step II the exhaust gas mass flow from the air mass flow at the air mass meter 24 and through the fuel injectors 14 injected fuel quantity determined. In one step III the current mass-related emissions are determined on the basis of these two parameters. In one step IV the current mass-related emissions become the cumulative emissions in the exhaust duct 42 certainly. Furthermore, in one process step VI the distance actually traveled and in one process step VII determines the minimum distance that can be specified, with the larger value being included in the calculation. In a process step V, the route-related emissions are calculated on the basis of the accumulated exhaust gas emissions and the distance traveled EC / D determined. Is optional in one process step VIII the exhaust gas temperature T _EG or the temperature T _CAT one Exhaust aftertreatment component determined. Using one in the control unit 70 stored map of the internal combustion engine 10 it is now determined whether the route-related emissions EC / D are below a defined limit. It is foreseeable that with the current engine parameters the route-related emissions EC / D cannot be achieved, so in one process step IX the EGR rate EGR elevated.

In 4 is a graph for adjusting the EGR rate EGR depending on the route-related emissions EC / D and the exhaust gas temperature T _EG shown. In normal operation of the internal combustion engine 10 the emission curve corresponds to the curve shown in the first curve. The exhaust gas recirculation rate that is returned during normal operation EGR defined as 100%. At high load operation and exhaust gas temperatures of more than 600 ° C, the exhaust gas recirculation rate EGR adjusted according to the curves shown to the raw emissions of the internal combustion engine 10 to reduce and thus continue to fall below the limit values for the route-related emissions.

In 5 is a graph for adjusting the torque and / or the power when the adjustment of the exhaust gas recirculation amount alone is not sufficient to achieve the route-related emissions. The performance P and / or the torque M of the internal combustion engine 10 limited accordingly. The intervention in the engine control system is correspondingly pronounced the more a limit temperature is exceeded at which compliance with the route-related emission values can be expected. In addition to throttling the power or the torque, other engine parameters, in particular the injection timing and the injection quantity, can also be adapted to the raw emissions of the internal combustion engine 10 to minimize.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

combustion chamber

14

fuel injector

16

inlet

18

outlet

20

Air supply system

22

air filter

24

Air flow sensor

26

compressor

28

intake port

30

pressure sensor

32

High-pressure exhaust gas recirculation

34

Exhaust gas recirculation passage

36

Exhaust gas recirculation valve

38

turbocharger

40

exhaust system

42

exhaust duct

44

turbine

46

oxidation catalyst

48

NOx storage catalytic converter

50

dosing

52

metering valve

54

particulate Filter

56

SCR coating

58

catalytic coating

60

second dosing module

62

second metering valve

64

SCR catalyst

66

pressure sensor

68

Exhaust gas sensor / NOx sensor

70

control unit

EC / D

distance-related emission value

EGR

Exhaust gas recirculation rate

N _N

Rated speed

P

power

P _is

load state

P _N

rated capacity

T

temperature

T _EG

exhaust gas temperature

T _CAT

catalyst temperature

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 102014217591 A1 [0004]
• DE 102016210243 A1 [0005]
• DE 102016211311 A1 [0006]

Claims (10)

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 (20) via its inlet (16), the internal combustion engine (10) being connected to its outlet (18) is connected to an exhaust gas system (40), wherein at least one exhaust gas aftertreatment component (46, 48, 54, 64) for converting pollutants in the exhaust gas of the internal combustion engine (10) is arranged in the exhaust gas system (40), comprising the following steps: P _ist ) and a route-related emission value (EG / D) of the internal combustion engine (10), wherein - when the route-related emission value (EG / D) approaches a defined threshold value (EG / D _S ) and a detection of high-load operation of the internal combustion engine (10 ) the exhaust gas recirculation rate (EGR) of the internal combustion engine (10) is increased. Exhaust gas aftertreatment process after Claim 1 , characterized in that an exhaust gas temperature (T _EG ) and / or a component temperature (T _KAT ) of an exhaust gas aftertreatment component (46, 48, 54, 64) is additionally recorded, the increase in the exhaust gas recirculation rate (EGR) depending on the exhaust gas temperature (T _EG ) or the component temperature (T _KAT ) of the exhaust gas aftertreatment component (46, 48, 54, 64). Exhaust gas aftertreatment process after Claim 1 or 2 , characterized in that the increase in the exhaust gas recirculation quantity (EGR) takes place in a load range in which the internal combustion engine (10) reaches at least 60% of its nominal output (P _N ) and / or 60% of its nominal speed (N _N ). Process for exhaust gas aftertreatment according to one of the Claims 1 to 3 , characterized in that after the increase in the exhaust gas recirculation quantity (EGR), a further comparison of the route-related emission values (EG / D) with the current emission values takes place and, if the route-related emission values (EG / D) are expected to be exceeded, the power (P) and / or the torque (M) of the internal combustion engine (10) is limited. Process for exhaust gas aftertreatment according to one of the Claims 1 to 4 , characterized in that the internal combustion engine (10) is designed as a self-igniting internal combustion engine (10) according to the diesel principle and the route-related emission value (EG / D) is the nitrogen oxide emissions (NOx) of the internal combustion engine (10). Exhaust gas aftertreatment process after Claim 5 , characterized in that the route-related nitrogen oxide emissions (EG / D) are recorded by at least one NOx sensor (68) in the exhaust system (40). Internal combustion engine (10) with at least one combustion chamber (12), the internal combustion engine (10) being connected via its inlet (16) to an air supply system (20), the internal combustion engine (10) having an outlet (18) having an exhaust system (40 ) is connected, wherein at least one exhaust gas aftertreatment component (46, 48, 54, 64) for converting pollutants in the exhaust gas of the internal combustion engine (10) is arranged in the exhaust system (40), and with a control unit (70) which is set up to an inventive method according to one of the Claims 1 to 6 to be carried out when a machine-readable program code is executed by the control device (70). Internal combustion engine (10) after Claim 7 , characterized in that an air mass meter (24) and / or a pressure sensor (30) is arranged in the air supply system (20). Internal combustion engine (10) after Claim 7 or 8th , characterized in that in the exhaust system (40) a first catalytic converter (46, 48), in particular an oxidation catalytic converter (46) or a NOx storage catalytic converter (48), and a particle filter (54) downstream of the first catalytic converter (46, 48) are arranged, the particle filter (54) having a coating (56) for the selective, catalytic reduction of nitrogen oxides and / or the particle filter (54) being followed by an SCR catalytic converter (64). Internal combustion engine (10) according to one of the Claims 7 to 9 , characterized in that at least one sensor (68) for detecting the current emissions, in particular at least one NOx sensor (68), is arranged in the exhaust system (40).

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