DE102018104275A1 - Exhaust gas aftertreatment system and method for exhaust aftertreatment of an internal combustion engine - Google Patents

Abstract

The invention relates to an exhaust aftertreatment system (20) for the exhaust aftertreatment of an exhaust gas of an internal combustion engine (10), in particular a self-igniting internal combustion engine. The exhaust aftertreatment system (20) has an exhaust passage (22) in which an oxidation catalyst (24), a particulate filter (26) and a catalyst (28) for the selective, catalytic reduction of nitrogen oxides are arranged. Furthermore, the exhaust aftertreatment system (20) comprises a preferably switchable bypass (30) which opens into the exhaust gas duct (22) upstream of the oxidation catalytic converter (24). In this case, a metering element (32) for metering in fuel is provided on the bypass (30). Furthermore, an electrically heatable catalyst (34) is provided in the bypass (30).
It is envisaged that to increase the exhaust gas temperature (T _EG ) in the exhaust duct (22) fuel is metered through the metering module (32) in the bypass (30) which is exothermically reacted on a catalytically active surface of the electrically heatable catalyst (34) ,

Description

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

The current and increasingly stringent future exhaust gas legislation places high demands on the engine raw emissions and the exhaust aftertreatment of internal combustion engines. The demands for a further reduction in consumption and the further tightening of emission standards with regard to permissible nitrogen oxide emissions pose a challenge for the engine developers. In gasoline engines, the exhaust gas purification takes place in a known manner via a three-way catalyst, and optionally the three-way catalyst -Catalyst upstream and downstream further catalysts. For diesel engines exhaust gas aftertreatment systems are currently used, which have an oxidation catalyst, a catalyst for the selective catalytic reduction of nitrogen oxides (SCR catalyst) and a particle filter for the separation of soot particles and optionally other catalysts. In this case, the particle filter can be provided with a coating for selective, catalytic reduction in order to combine both functionalities in one component. In order to bring the catalysts to an operating temperature after a cold start of the internal combustion engine, it is desirable to arrange the catalytic converters as closely as possible to the engine. However, this is not always possible because the space is limited. Therefore, SCR catalytic converters and soot particle filters are often arranged in a motorized underbody layer of a motor vehicle.

Furthermore, so-called NOx storage catalytic converters are used for exhaust gas purification to absorb the nitrogen oxides formed during the combustion of the fuel-air mixture in the combustion chambers of the internal combustion engine. However, these NOx storage catalysts must be regenerated periodically by a stoichiometric operation, resulting in increased fuel consumption. Another disadvantage of NOx storage catalysts is that at high exhaust gas temperatures no nitrogen oxides can be stored in the NOx storage catalyst. In addition, NOx storage catalysts are susceptible to aging, so that the storage capacity decreases significantly with the lifetime of the NOx storage catalyst. To compensate for the tendency to age large catalyst volumes and correspondingly high amounts of noble metals are necessary, which brings with it corresponding disadvantages in terms of space requirements and costs.

Catalysts for the selective catalytic reduction of nitrogen oxides, which are referred to below as SCR catalysts, have the disadvantage that a noticeable conversion of nitrogen oxides only begins at a temperature of about 170 ° C. The ammonia used to reduce the nitrogen oxides, which is usually obtained from an aqueous urea solution, oxidized at temperatures above 450 ° C, so above this temperature also only a small conversion of harmful nitrogen oxides by means of the SCR catalyst is possible. In addition, there is the risk in engines with a low-pressure exhaust gas recirculation that the reducing agent enters the exhaust gas recirculation, where it attaches at low temperatures on the walls of the exhaust passage. In this case, the urea crystallizes out of the aqueous urea solution, which can lead to deposits on the walls of the exhaust gas channel of the low-pressure exhaust gas recirculation, which can limit the function of the exhaust gas recirculation. Furthermore, there is the risk that ammonia obtained from the aqueous urea solution, which is not converted to the SCR catalyst, passes through the low-pressure exhaust gas recirculation system into the combustion chambers of the internal combustion engine and is oxidized during combustion, as a result of which the NOx emissions increase.

Due to the development of increasingly efficient internal combustion engines and combustion processes, the exhaust gas temperatures are decreasing. In order to achieve high conversion rates of exhaust aftertreatment even at low engine loads and low ambient temperatures, the catalysts must be heated to their respective light-off temperature after a cold start of the internal combustion engine and kept above this light-off temperature during operation. For heating the catalysts internal engine heating methods are known in which the injection timing is shifted late. However, this can lead to increased emissions of unburned hydrocarbons, oil dilution and, associated therewith, increased wear of the internal combustion engine. In addition, engine-internal heating measures lead to a deteriorated thermal efficiency and thus to an additional consumption of the internal combustion engine. Moreover, it is known to thermally isolate at least a portion of the exhaust passage to minimize heat loss and improve the heating of the catalysts in this manner.

Furthermore, heating measures are known in which the catalysts are heated by a flue gas arranged on the exhaust gas duct. However, this is associated with additional components and thus a significant increase in the cost of the exhaust aftertreatment system.

From the DE 10 2008 032 601 A1 For example, an exhaust aftertreatment system with such an exhaust gas burner is known. A disadvantage of such a solution, however, is that an additional exhaust gas burner is needed, with which the entire exhaust gas flow of the engine must be heated, whereby high burner performance is necessary.

The invention is based on the object to enable a simple and rapid heating of the components of the exhaust aftertreatment and thus efficient conversion of the pollutants and in particular to minimize the emissions after a cold start of the internal combustion engine.

According to the invention this object is achieved by an exhaust aftertreatment system for an internal combustion engine, which is connectable to an outlet of the internal combustion engine, wherein the exhaust aftertreatment system comprises an exhaust passage in which in the flow direction of an exhaust gas of the internal combustion engine through the exhaust passage an oxidation catalyst and downstream of the oxidation catalyst, a particulate filter with a Coating for the selective catalytic reduction of nitrogen oxides or a particulate filter and an SCR catalyst are arranged. In this case, a bypass is provided on the exhaust passage, which branches off downstream of the outlet of the internal combustion engine from the exhaust duct and opens upstream of the oxidation catalyst back into the exhaust duct. At the bypass, a metering element for metering fuel is arranged in the bypass, which is followed by an electrically heatable catalyst in the bypass. In this case, the oxidation catalytic converter and the particle filter with the coating for the selective, catalytic reduction of nitrogen oxides are preferably arranged in a position close to the engine in the exhaust gas duct. In this case, a position close to the engine is understood to mean a position in the exhaust system with a mean exhaust gas flow path of at most 80 cm, in particular of at most 50 cm, after the outlet of the internal combustion engine. The oxidation catalyst may additionally have a coating for the temporary storage of nitrogen oxides and be designed as a NOx storage catalyst. By means of a metering element for metering in fuel and a downstream, electrically heatable catalyst, the exhaust gas in the bypass can be heated substantially independently of the operating situation of the internal combustion engine. In this case, the fuel is metered into the bypass only when the electrically heatable catalyst has a sufficient temperature for the exothermic reaction of unburned fuel. The thus heated exhaust gas is then introduced upstream of the first catalytically active components in the exhaust passage to heat the exhaust aftertreatment components in the exhaust passage substantially independent of the operating situation of the internal combustion engine. As a result, emissions can be minimized. Since the exhaust gas flow through the bypass is substantially lower compared to the main exhaust gas flow and the bypass can be made with a smaller diameter than the exhaust gas channel, the electrically heatable catalyst can be designed correspondingly small volume. In this case, compared to a heating element in the exhaust duct significantly less electrical power needed for heating. In addition, the electrically heatable catalyst can be made comparatively small and inexpensive. In addition, there is the advantage over engine-internal heating measures that the risk of oil dilution is virtually eliminated by a late fuel injection. Furthermore, a regeneration of the particulate filter can be carried out without internal engine heating measures.

The features listed in the dependent claims advantageous improvements and developments of the exhaust gas aftertreatment system specified in the independent claim are possible.

In a preferred embodiment of the invention it is provided that the electrically heatable catalyst in the bypass downstream of an oxidation catalyst. An additional oxidation catalyst reduces the space velocity in the bypass, increasing the efficiency of the catalysts. In addition, more fuel can be exothermically reacted in the bypass and thus the heating power can be increased without increasing the catalyst volume of the electrically heated catalyst and thus its thermal inertia.

In an advantageous embodiment of the invention, it is provided that a turbine of an exhaust gas turbocharger is arranged in the exhaust gas passage, wherein the bypass is a wastegate channel of the exhaust gas turbocharger. An arrangement of dosing element and electrically heatable catalyst in a wastegate channel of an exhaust gas turbocharger, a particularly compact and space-optimized embodiment of the exhaust aftertreatment system can be represented, since such a waste gate channel in an exhaust gas turbocharger is usually present anyway and only the Design of the waste gate channel must be changed.

Alternatively, the bypass may also branch off of the exhaust passage downstream of the outlet and upstream of the turbine and back into the exhaust passage downstream of the turbine and upstream of the oxidation catalyst. By introducing the exhaust gas into the bypass upstream of the turbine, relatively warm and energy-containing exhaust gas can be introduced into the bypass, whereby the required heating power is reduced relative to a discharge point downstream of the turbine in order to enable ignition of the fuel introduced via the metering element.

Alternatively, an embodiment is provided in which a turbine of an exhaust gas turbocharger is arranged in the exhaust passage, wherein the bypass branches off downstream of the turbine from the exhaust duct and opens upstream of the oxidation catalyst again into the exhaust duct. By removing the exhaust gas flow downstream of the turbine, the maximum exhaust gas energy can be used to drive the turbine of the exhaust gas turbocharger and thus the response of the exhaust gas turbocharger over the above embodiments can be improved. In addition, any partial flow through the bypass can be passed through a control flap in the exhaust duct, so that a division between guided through the exhaust duct and guided through the bypass exhaust gas flow is particularly easy. In addition, a further exhaust flap can be arranged in the bypass in order to further improve the division of the exhaust gas flow and / or to further reduce the space velocity in the bypass.

In a further improvement of the invention it is provided that a mixing element is arranged at an opening of the bypass in the exhaust passage. By means of a mixing element, improved mixing of the hot exhaust gas stream from the bypass with the exhaust gas stream from the exhaust gas channel before entry into the oxidation catalytic converter is possible.

In an advantageous embodiment of the invention it is provided that an exhaust gas recirculation passage of the internal combustion engine is fed from the bypass. As a result, exhaust gas recirculation can be integrated in a simple manner into the exhaust gas aftertreatment system according to the invention.

It is particularly preferred if the exhaust gas recirculation passage branches off from the bypass downstream of a branch of the bypass from the exhaust gas duct and upstream of the metering module. In this way, a high-pressure exhaust gas recirculation can be integrated without further design effort, whereby a compact embodiment of the exhaust aftertreatment system is possible.

Alternatively, it is advantageously provided that the exhaust gas recirculation passage branches off from the bypass downstream of the electrically heatable catalyst, in particular downstream of the oxidation catalyst in the bypass, and upstream of an opening of the bypass into the exhaust gas passage. By removing the recirculated exhaust gas stream downstream of the electrically heatable catalyst, the recirculated exhaust gas can be specifically conditioned. Depending on the mixture composition and heating capacity, the temperature in the exhaust gas recirculation can be raised and mixed with highly reactive exhaust components. Returned to the combustion chamber, this exhaust gas can positively influence the combustion or the raw emissions of the internal combustion engine. With a removal of the exhaust gas downstream of the oxidation catalyst, the temperature of the recirculated exhaust gas can be increased again.

According to the invention, a method is proposed for the exhaust aftertreatment of an internal combustion engine with an exhaust aftertreatment system according to the invention, wherein the electrically heated catalyst is heated to raise the exhaust gas temperature in the exhaust passage at least up to a first threshold temperature, in particular the light-off temperature of the electrically heatable catalyst, from which a exothermic conversion of fuel through the electrically heatable catalyst is possible. Subsequently, fuel is metered into the bypass upstream of the electrically heatable catalyst by the metering module, and this fuel exothermically reacted on a catalytically active surface of the electrically heated catalyst, wherein the heated exhaust gas is introduced at a junction upstream of the oxidation catalyst in the exhaust passage. As a result, the oxidation catalytic converter and the subsequent exhaust gas aftertreatment components can be heated to their operating temperature substantially independently of the operating state of the internal combustion engine, and thus the cold start emissions can be significantly reduced. It is preferred if the electric heating element of the electrically heatable catalyst is switched off when the electrically heatable catalyst has reached a second threshold temperature, which is above the first threshold temperature. As a result, thermal damage to the electrical heating element and / or the electrically heatable catalyst can be avoided.

In a further improvement of the method for exhaust aftertreatment, it is provided that the method comprises at least one further exhaust-gas-promoting measure. Among the other exhaust gas-promoting measures are in particular a reduction of the exhaust gas mass flow through the exhaust aftertreatment system, for example by throttling the intake air flow on the inlet side, an exhaust-side throttling of the exhaust gas flow, in particular by an exhaust flap or an adjustable guide geometry of the turbine of the exhaust gas turbocharger, a change in the valve opening times of the internal combustion engine and / or cylinder deactivation. Further For example, the exhaust gas temperature may be increased by increased recirculation of hot exhaust gases, by high pressure exhaust gas recirculation, and / or by in-engine exhaust gas recirculation through valve overlap of intake and exhaust valve opening times. As a result, the heating can be accelerated again and it is a total of a higher exhaust gas temperature level possible. Thus, tailpipe emissions can be further reduced.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

• 1 ein erstes Ausführungsbeispiel eines Verbrennungsmotors mit einem erfindungsgemäßen Abgasnachbehandlungssystem;
• 2 ein weiteres Ausführungsbeispiel eines Verbrennungsmotors mit einem erfindungsgemäßen Abgasnachbehandlungssystem;
• 3 ein drittes Ausführungsbeispiel eines Verbrennungsmotors mit einem erfindungsgemäßen Abgasnachbehandlungssystem; und
• 4 ein Ablaufdiagramm zur Durchführung eines erfindungsgemäßen Verfahrens zur Abgasnachbehandlung eines Verbrennungsmotors.

The invention will be explained below in embodiments with reference to the accompanying drawings. Identical components or components with the same function are identified in the figures with the same reference numerals. Show it:

• 1 a first embodiment of an internal combustion engine with an exhaust aftertreatment system according to the invention;
• 2 a further embodiment of an internal combustion engine with an exhaust aftertreatment system according to the invention;
• 3 A third embodiment of an internal combustion engine with an exhaust aftertreatment system according to the invention; and
• 4 a flowchart for carrying out a method according to the invention for the exhaust aftertreatment of an internal combustion engine.

1 shows an internal combustion engine 10 with an inlet 12 and an outlet 14 to which an exhaust aftertreatment system according to the invention 20 connected. The internal combustion engine 10 has a plurality of combustion chambers 18 on, in which a fuel-air mixture is burned. At the internal combustion engine 10 is a high pressure exhaust gas recirculation 16 provided, which the outlet 14 with the inlet 12 combines. In the high-pressure exhaust gas recirculation 16 is an exhaust gas recirculation valve 72 arranged, via which the amount of recirculated exhaust gas can be controlled. In the high-pressure exhaust gas recirculation 16 can be arranged, not shown, high-pressure exhaust gas recirculation cooler, which is preferably bypassed via a bypass, also not shown. The internal combustion engine is preferred as a self-igniting internal combustion engine 10 formed according to the diesel principle.

The exhaust aftertreatment system 20 includes an exhaust passage 22 in which in the flow direction of an exhaust gas of the internal combustion engine 10 through the exhaust duct 22 a turbine 40 an exhaust gas turbocharger 42 and downstream of the turbine 40 a plurality of catalysts 24 . 26 . 56 is arranged. As the first exhaust aftertreatment component is in the exhaust passage 22 a close-coupled oxidation catalyst 24 arranged, which a close-coupled particle filter 26 with a coating 28 for the selective catalytic reduction of nitrogen oxides is prefixed. The particle filter 26 with the coating represents a first SCR catalyst for the selective catalytic reduction of nitrogen oxides. Downstream of the oxidation catalyst 24 and upstream of the particulate filter 26 is a first dosing module 52 for dosing a reducing agent, in particular liquid urea solution, in the exhaust gas duct 22 arranged. Downstream of the particulate filter 26 with the coating 28 For the selective catalytic reduction of nitrogen oxides further catalysts, in particular one or more further, in 2 and 3 exemplified, SCR catalysts 56 to reduce nitrogen oxide emissions in the exhaust duct 22 be arranged. Downstream of the oxidation catalyst 24 and upstream of the particulate filter 26 with the coating 28 for the selective catalytic reduction of nitrogen oxides, an exhaust gas mixer 54 be provided to an improved mixing of the metered reducing agent with the exhaust gas of the internal combustion engine 10 to enable. Alternatively, the particulate filter 26 Also be carried out as an uncoated particulate filter, which is an SCR catalyst 56 is downstream.

The turbocharger 42 has a waste gate channel 44 on which upstream of the turbine 40 from the exhaust duct 22 branches off and downstream of the turbine 40 and upstream of the oxidation catalyst 24 back in the exhaust duct 22 opens. It is at the junction 50 at which the bypass 30 from the exhaust duct 22 branches off, a control flap 62 provided, which via an actuator 64 is adjustable. This control flap 62 can bypass 30 lock, so that the entire exhaust gas flow of the internal combustion engine 10 through the exhaust duct 22 is directed. Furthermore, the control flap 62 the exhaust duct 22 at least partially block, so that at least a partial flow of the exhaust gas through the bypass 30 is directed. At the bypass 30 is a dosing element 32 for metering fuel into the bypass 30 intended. Downstream of the metering element 32 are in the bypass 30 an electrically heatable catalyst 34 and an oxidation catalyst 36 arranged to exotherm the fuel injected by the metering element in the bypass 30 on the catalytically active surfaces of the catalysts 34 . 36 exothermic conversion. Downstream of the oxidation catalyst 36 the bypass opens 30 back in the exhaust duct 22 , where the confluence 38 of the bypass downstream of the turbine 40 the exhaust gas turbocharger 42 and upstream of the oxidation catalyst 24 lies. At the junction 38 is a mixing element 46 provided to the exhaust flow from the bypass 30 with the exhaust gas flow in the exhaust duct 22 to mix and thus for improved heating and a more homogeneous exhaust gas composition of the exhaust gas in the exhaust passage 22 to care. The mixing element 46 can be carried out adjustable to selectively, in particular operating point-dependent, a particularly high degree of mixing or a low flow resistance in the exhaust duct 22 to realize. In the exhaust duct 22 are additional sensors 66 . 68 , in particular an exhaust gas temperature sensor 66 and a differential pressure sensor 68 provided, which not shown signal lines with a control unit 60 of the internal combustion engine 10 are connected. Particularly preferred is when both in the exhaust passage 22 as well as in the bypass 30 one exhaust gas temperature sensor each 66 . 66a and in each case a differential pressure sensor 68 . 68a are arranged to the ratio of the mass flow through the bypass 30 and the exhaust duct 22 and to determine the necessary heating power.

Alternatively, the internal combustion engine 10 cooperate as part of a hybrid system with an electric drive motor and in particular be connected via a common transmission with a drive train of a motor vehicle.

In a simplified form of the invention, the oxidation catalyst 36 in the bypass 30 also omitted.

In 2 is another embodiment of an exhaust aftertreatment system according to the invention 20 for an internal combustion engine 10 shown. With essentially the same structure as 1 executed, the bypass branches 30 in this embodiment, downstream of the turbine 40 the exhaust gas turbocharger 42 from the exhaust duct 22 from and flows upstream of the oxidation catalyst 24 back in the exhaust duct 22 , The turbocharger 42 is preferably as an exhaust gas turbocharger 42 with adjustable guide geometry (VTG loader). Further, downstream of the particulate filter 26 with the coating 28 for the selective catalytic reduction of nitrogen oxides on the exhaust gas channel 22 a second dosing module 74 provided, which a second SCR catalyst 56 is downstream.

In operation of the internal combustion engine 10 It may, in particular after a cold start or after a low load phase or a purely electric drive phase of a hybrid drive, come to operating conditions in which the catalysts 24 . 26 . 56 do not have the necessary for the conversion of pollutants in the exhaust gas temperature. Is the temperature in the exhaust channel 22 , in particular on the oxidation catalyst 24 , below a threshold temperature, becomes the electrically heatable catalyst 34 electrically heated in the bypass at least up to its light-off temperature and then by means of the metering element 32 Fuel in the bypass 30 injected, so that this fuel on the catalytically active surface of the electrically heated catalyst 34 is exothermic and the exhaust gas in the bypass 30 heated. This heated exhaust gas gets over the confluence 38 of the bypass 30 in the exhaust duct 22 and can thus the exhaust aftertreatment components in the exhaust passage 22 to heat up to their respective operating temperature or regeneration temperature. Thus, internal engine heating measures such as a late post-injection in a diesel engine, which increases the risk of dilution of the engine oil with the fuel and thus increased wear of the engine 10 be avoided, and it is possible the exhaust aftertreatment components 24 . 26 . 56 in the exhaust duct 22 essentially independent of the operating state of the internal combustion engine 10 to heat up to their operating temperature or regeneration temperature. Thus, the emissions can not only in the cold start phase, but also in a regeneration of the particulate filter 26 be reduced. In order to achieve a sufficient pressure gradient, so that the exhaust gas flow at least partially through the bypass 30 is directed, the control flap 62 the exhaust duct 22 at least partially obstruct. Furthermore, the control flap 62 be arranged so that they in at least one operating state of the internal combustion engine 10 the bypass 30 closes to the flow conditions in the exhaust duct 22 to optimize.

In 3 is another embodiment of an exhaust aftertreatment system according to the invention 20 shown. With essentially the same structure as 1 and 2 executed, in this embodiment, one or more exhaust gas recirculation channels 48 provided, which from the bypass 30 branch off and on the inlet side with the internal combustion engine 10 are connected. It is in the exhaust gas recirculation 16 an exhaust gas recirculation valve 72 provided, via which the amount of recirculated exhaust gas can be controlled or regulated. Here are at the bypass 30 four different, with I to IV designated branching points provided, to which an exhaust gas recirculation passage 48 from the bypass 30 can branch off. In addition, downstream of the oxidation catalyst 36 and upstream of the confluence 38 a bypass flow control valve 58 . 58a . 58b . 58c . 58d provided, with which the amount of recirculated exhaust gas can be influenced. When using appropriate bypass flow control valves 58a . 58b . 58c . 58d can the exhaust gas recirculation valve 72 in the high pressure exhaust gas recirculation 16 omitted. The branch point I essentially corresponds to a known one High-pressure exhaust gas recirculation 16 , The branch point II downstream of the metering element 32 and upstream of the electrically heatable catalyst 34 allows enrichment of the recirculated exhaust gas with fuel, whereby a substantially homogeneous fuel-air mixture can be produced, which is the fresh air before entering the combustion chamber 18 can be added. This can reduce the combustion process in the combustion chambers 18 of the internal combustion engine 10 influence positively. Such exhaust gas recirculation can be carried out not only during a heating phase, in particular after a cold start, but also in normal operation, the emissions of the internal combustion engine 10 influence positively.

A removal of the exhaust gas flow for the exhaust gas recirculation at the branching point III has the advantage that the recirculated exhaust gas can be specifically conditioned. In addition, the recirculated exhaust gas may contain highly reactive molecules when the recirculated exhaust gas flow has a combustion air ratio λ <1. Returned to the combustion chamber 18 For example, these highly reactive molecules can be used for combustion or for raw emissions of the internal combustion engine 10 influence positively. An extraction at the branch point IV downstream of the oxidation catalyst 36 in the bypass allows the return of a particularly hot exhaust gas, which is chemically inactive, resulting in certain operating situations also benefits for the combustion or the raw emissions of the engine 10 can result. It is preferably at each of the branching points I - IV a shut-off valve is provided to selectively operate the exhaust gas recirculation 16 to enable.

In 4 is a flowchart for a method according to the invention for exhaust aftertreatment shown. In a first process step <100> at least one temperature T determined or calculated in the exhaust system. This temperature T is in a step < 110 > with a threshold temperature T _S1 compared, wherein at a temperature below the threshold temperature T _S1 an actuator 64 an actuator 62 at the junction 50 of the bypass 30 from the exhaust duct 22 in a method step <120> adjusted such that an exhaust gas stream of the internal combustion engine 10 at least partially through the bypass 30 the exhaust duct 22 is directed. In one step < 130 > becomes the electrically heatable catalyst 34 electrically heated by a heating element until the catalytically active surface of the electrically heatable catalyst 34 at least their light-off temperature T _LO has reached. In one step < 140 > gets through the dosing element 32 Fuel in the bypass 30 upstream of the electrically heatable catalyst 34 injected and at the catalytically active surface of the electrically heatable catalyst 34 implemented exothermically. Has the oxidation catalyst 36 In the bypass also reaches its light-off temperature, the fuel is also implemented on its catalytically active surface, so that the exhaust gas flow is further heated. In this process step < 150 > can the electric heating element of the electrically heated catalyst 34 remain active, so that in parallel an electrical and a chemical heating of the exhaust gas in the bypass take place. This hot exhaust gas flows over the junction 38 in the exhaust duct 22 , This will be in the exhaust duct 22 arranged exhaust aftertreatment components 24 . 26 . 56 heated. Has the oxidation catalyst 24 in the exhaust duct 22 reaches its operating temperature, the actuator becomes 62 through the actuator in one step < 160 > Adjusted again so that the exhaust gas of the internal combustion engine 10 through the exhaust duct 22 flows and the bypass 30 essentially from the exhaust gas flow of the internal combustion engine 10 is decoupled. Furthermore, the control strategy by appropriate sensors 66 . 66a . 68 . 68a in the bypass 30 and in the exhaust duct 22 an enthalpy consideration and / or a heat capacity analysis of the components of the exhaust aftertreatment system 20 be refined, creating a more precise feedforward control of the exhaust gas temperature T _EC on the catalysts 24 . 28 is possible.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

inlet

14

outlet

16

High-pressure exhaust gas recirculation

18

combustion chamber

20

aftertreatment system

22

exhaust duct

24

oxidation catalyst

26

particulate Filter

28

Coating for the selective, catalytic reduction of nitrogen oxides

30

bypass

32

metering

34

electrically heatable catalyst

36

oxidation catalyst

38

junction

40

turbine

42

turbocharger

44

Waste gate channel

46

mixing element

48

Exhaust gas recirculation passage

50

branch

52

dosing

54

exhaust mixer

56

SCR catalyst

58

Bypass flow control valve

58a

Bypass flow control valve

58b

Bypass flow control valve

58c

Bypass flow control valve

58d

Bypass flow control valve

60

control unit

62

control flap

64

actuator

66

Exhaust gas temperature sensor

66a

Exhaust gas temperature sensor

68

Differential Pressure Sensor

68a

Differential Pressure Sensor

70

throttle

72

High-pressure exhaust gas recirculation valve

74

second dosing module

T

temperature

T _EC

exhaust gas temperature

T _LO

Light-off temperature

T _S1

first threshold temperature

T _S2

second threshold temperature

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102008032601 A1 [0007]

Claims (10)

Aftertreatment system (20) for an internal combustion engine (10) which is connectable to an outlet (14) of the internal combustion engine (10), wherein the exhaust aftertreatment system (20) has an exhaust gas duct (22) in which in the flow direction of an exhaust gas of the internal combustion engine (10) an oxidation catalytic converter (24) and downstream of the oxidation catalytic converter (24) a particle filter (26) with a coating (28) for the selective catalytic reduction of nitrogen oxides or a particle filter (26) and an SCR catalytic converter (56) are arranged, characterized a bypass (30) is provided on the exhaust gas duct (22) which branches off from the exhaust gas duct (22) downstream of the outlet (14) of the internal combustion engine (10) and returns into the exhaust gas duct (22) upstream of the oxidation catalytic converter (24), wherein at the bypass (30) a metering element (32) for metering fuel is arranged, which is followed by an electrically heatable catalyst (34). Exhaust after-treatment system (20) according to Claim 1 , characterized in that the electrically heatable catalyst (34) in the bypass (30) an oxidation catalyst (36) is connected downstream. Exhaust after-treatment system (20) according to Claim 1 or 2 , characterized in that in the exhaust passage (22) a turbine (40) of an exhaust gas turbocharger (42) is arranged, wherein the bypass (30) is a waste gate channel (44) of the exhaust gas turbocharger (42). Exhaust after-treatment system (20) according to one of Claims 1 or 2 in which a turbine (40) of an exhaust-gas turbocharger (42) is arranged in the exhaust-gas duct (22), the bypass (30) branching off from the exhaust-gas duct (22) downstream of the turbine (40) and back into the exhaust-gas duct upstream of the oxidation catalytic converter (24) (22) opens. Exhaust after-treatment system (20) according to one of Claims 1 to 4 , characterized in that at a junction (38) of the bypass (30) in the exhaust passage (22) a preferably adjustable mixing element (46) is arranged. Exhaust after-treatment system (20) according to one of Claims 1 to 5 , characterized in that from the bypass (30) at least one exhaust gas recirculation passage (48) is fed. Exhaust after-treatment system (20) according to Claim 6 characterized in that the exhaust gas recirculation passage (48) branches off the bypass (30) downstream of a branch (50) of the bypass (30) from the exhaust passage (22) and upstream of the metering element (32). Exhaust after-treatment system (20) according to Claim 6 or 7 , characterized in that the exhaust gas recirculation passage (48) branches off from the bypass (30) downstream of the electrically heatable catalyst (34) and upstream of a junction (38) of the bypass (30) into the exhaust passage (22). A method for exhaust aftertreatment of an internal combustion engine (10) with an exhaust aftertreatment system (20) according to one of Claims 1 to 8th , characterized in that for raising the exhaust gas temperature in the exhaust passage (22) of the electrically heatable catalyst (34) is heated at least up to a first threshold temperature (T _S1 ), from which an exothermic conversion of fuel through the electrically heatable catalyst (34) possible is metered and by the metering element (32) fuel in the bypass (30) upstream of the electrically heatable catalyst (34) which is exothermically reacted on this catalyst (34), wherein the heated exhaust gas at an orifice (38) upstream of the Oxidation catalyst (24) is introduced into the exhaust passage (22). Process for exhaust aftertreatment after Claim 9 , characterized in that the method at least one further exhaust gas temperature-promoting measure, in particular a reduction of the exhaust gas mass flow through the exhaust aftertreatment system (20) and / or a return of hot exhaust gas by a high-pressure exhaust gas recirculation (18).

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