DE102017118455A1 - Exhaust after-treatment system for an internal combustion engine and method for exhaust aftertreatment of an internal combustion engine - Google Patents

Abstract

The invention relates to an internal combustion engine (10) with a low-pressure exhaust gas recirculation (60). In this case, an exhaust gas recirculation cooler (64) is arranged in a main channel (66) of the low-pressure exhaust gas recirculation (60). In order to be able to bypass this exhaust gas recirculation cooler (64) in certain operating situations and to reduce the recirculated exhaust gas in these operating situations to such an extent that water vapor contained in the exhaust gas condenses out, a bypass (68) is provided which allows exhaust gas recirculation without additional cooling of the exhaust gas. In this case, a control valve (62), with which an exhaust gas stream of the internal combustion engine (10) between the bypass (68) and the Main channel (66) is controllable. Furthermore, when the exhaust flap (48) is closed, a deflection of the exhaust gas flow through the main passage (66) and a return into the exhaust passage (48) through the bypass (68), so that the residual heat of the exhaust gas can be used to the coolant of the internal combustion engine ( 10) to heat and not let escape unused through the exhaust passage (48).

Description

The invention relates to an exhaust aftertreatment system for an internal combustion engine and a method for exhaust aftertreatment 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 to engine developers. In gasoline engines, exhaust gas purification takes place in a known manner via a three-way catalytic converter, as well as the three-way catalytic converter. Catalyst upstream and downstream further catalysts. For diesel engines exhaust gas aftertreatment systems are currently used, which have an oxidation catalyst or NOx storage catalyst, a catalyst for the selective catalytic reduction of nitrogen oxides (SCR catalyst) and a particulate filter for the separation of soot particles and optionally other catalysts. The reducing agent used is preferably ammonia. Because the handling of pure ammonia is complicated, in vehicles usually a synthetic, aqueous urea solution is used, which is mixed in a SCR catalyst upstream mixing device with the hot exhaust gas stream. By this mixing, the aqueous urea solution is heated, wherein the aqueous urea solution releases ammonia in the exhaust gas passage. A commercial aqueous urea solution generally consists of 32.5% urea and 67.5% water. In addition to the emissions of the limited exhaust gas components is still the demand for a further reduction in consumption of internal combustion engines and an increase in the thermal efficiency.

BACKGROUND OF THE INVENTION Internal combustion engines with low-pressure exhaust gas recirculation are known, in which the exhaust gas of the internal combustion engine downstream of an exhaust aftertreatment component, in particular a particulate filter, is discharged from the exhaust gas duct and fed to the air supply system upstream of a compressor. In this case, an exhaust gas recirculation cooler is usually provided in low-pressure exhaust gas recirculation, with which the exhaust gas temperature of the recirculated exhaust gas is reduced. However, a disadvantage of such a solution is that with cold exhaust gas, in particular in conjunction with cold cooling medium in the exhaust gas recirculation cooler, the water vapor present in the recirculated exhaust gas may condense out and lead to damage to the compressor.

From the DE 10 2008 020 408 A1 an internal combustion engine with a low-pressure exhaust gas recirculation is known in which the exhaust gas can be fed back to the exhaust passage after flowing through the exhaust gas recirculation cooler to lower the exhaust gas temperature. The in the DE 10 2008 020 408 A1 However, the proposed solution does not make it possible to reduce or raise the temperature in the exhaust gas recirculation less.

From the EP 2 956 657 B1 For example, an internal combustion engine with a mechanically driven compressor and a bypass duct is known, with which the mechanical compressor can be bypassed, wherein a control valve is provided with which an inlet or an outlet of the mechanically driven compressor can be selectively opened or closed.

The object of the invention is to allow a low-pressure exhaust gas recirculation as early as possible after a cold start and to use the residual heat of the exhaust gas to avoid condense of liquid in the low-pressure exhaust gas recirculation.

According to the invention, the object is achieved by an internal combustion engine with an air supply system and an exhaust system, and with a low-pressure exhaust gas recirculation, which connects the exhaust system downstream of a turbine of an exhaust gas turbocharger with the air supply system upstream of a compressor of the exhaust gas turbocharger. In this case, an exhaust flap is provided in the exhaust system, with which an exhaust passage of the exhaust system can be at least partially blocked. The low pressure exhaust gas recirculation includes a main passage and a bypass, wherein the main passage of the low pressure exhaust gas recirculation downstream of the turbine and upstream of the exhaust valve branches off from the exhaust passage at a branch point and opens into a low pressure exhaust gas recirculation passage. In the main channel an exhaust gas recirculation cooler is arranged. Parallel to the main channel, a bypass is formed, which bridges the exhaust gas recirculation cooler, wherein at a junction or a branch of the main channel and the bypass, a control valve is arranged, with which an exhaust gas flow between the bypass and the main channel controllable, in particular between the main channel and the bypass switchable or divisible is. An internal combustion engine according to the invention has the advantage that it can be switched between a shutdown of the low-pressure exhaust gas recirculation, an uncooled exhaust gas recirculation and a cooled exhaust gas recirculation with only one control valve. Thus, the low-pressure exhaust gas recirculation in a simple and cost-effective manner to the respective operating temperature of the internal combustion engine be adapted and condensation of liquid in the low-pressure exhaust gas recirculation can be reliably avoided.

The features listed in the dependent claims advantageous improvements and developments of the internal combustion engine specified in the independent claim are possible.

In a preferred embodiment of the invention, it is provided that the control valve is designed as a 3/3-way valve. By a 3/3-way valve, a particularly simple switching between the individual operating states of the internal combustion engine is possible. Alternatively, two simple valves can be used, which are connected in series so that there is a 3/3-way function.

It is particularly preferred if a first port of the control valve to the main channel, a second port to the bypass and a third port to the low pressure exhaust gas recirculation line are connected. If the main duct of the low-pressure exhaust gas recirculation with a first connection opening, the bypass with a second connection opening and the low-pressure exhaust gas recirculation line connected to a third connection opening of the control valve, a simple control and distribution of the exhaust gas flow is possible, so that the exhaust gas flow in dependence on the exhaust gas temperature and / or Cooling water temperature of the engine can be returned accordingly or the exhaust duct is supplied.

In a further preferred embodiment of the invention it is provided that the bypass downstream of the exhaust valve is connected to the exhaust passage of the internal combustion engine. This can be accelerated over the exhaust flap, a heating of the engine to its operating temperature by the exhaust stream of the engine is passed through the located in the main channel of the low-pressure exhaust gas recirculation exhaust gas recirculation cooler and thus can be used in addition to the heating of the cooling water. Thus, the waste heat of the exhaust gas can be used for heating the internal combustion engine.

In an alternative embodiment of the invention is advantageously provided that the bypass upstream and downstream of the exhaust gas recirculation cooler is connected to the main channel of the low-pressure exhaust gas recirculation. As a result, a particularly simple and cost-effective design of an internal combustion engine according to the invention is possible. In this case, only one connection opening is required on the exhaust duct for the low-pressure exhaust gas recirculation, so that a particularly simple installation of the exhaust system is possible.

According to a preferred embodiment of the invention it is provided that in each case a filter is arranged in the main channel and in the bypass. Through a filter, the penetration of soot particles in the low-pressure exhaust gas recirculation can be avoided or reduced. Thereby, the wear on the control valve as well as on the components of the air supply system of the internal combustion engine downstream of the junction of the low pressure exhaust gas recirculation line can be reduced. Furthermore, malfunctions can be prevented by soot particles, which would deposit without filter on the control valve.

In an advantageous improvement of the invention it is provided that the main channel branches off downstream of a particulate filter with a coating for the selective, catalytic coating of nitrogen oxides from the exhaust passage of the internal combustion engine. By branching off the low-pressure exhaust gas recirculation downstream of the particle filter, a majority of the particles can already be removed by the particle filter from the exhaust gas flow of the internal combustion engine and retained in the particle filter. Particularly preferred is a particulate filter with a coating for the selective, catalytic reduction of nitrogen oxides, since this also causes a significant reduction in nitrogen oxide emissions.

According to the invention, a method for exhaust aftertreatment of an internal combustion engine according to the invention is proposed, wherein in a first operating state of the internal combustion engine no exhaust gas recirculation via the low pressure exhaust gas recirculation takes place in a second operating state uncooled exhaust gas recirculation via the bypass and in a third operating state of the internal combustion engine, a cooled exhaust gas recirculation over the Main channel and the exhaust gas recirculation cooler of the low-pressure exhaust gas recirculation takes place. By means of a method according to the invention, depending on the temperature of the exhaust gas, of the cooling water and / or of the engine oil of the internal combustion engine, an exhaust gas recirculation via the low-pressure exhaust gas recirculation can be controlled in such a way that a condensation out of liquid is avoided. Due to the possibility of an uncooled exhaust gas recirculation, the low-pressure exhaust gas recirculation can be activated earlier in time after a cold start of an internal combustion engine, whereby the emissions of the internal combustion engine can be reduced.

In an advantageous improvement of the method is provided that in the first operating state, the exhaust valve is at least partially closed, wherein an exhaust gas flow through the Main channel of the low-pressure exhaust gas recirculation is passed and the control valve is set such that the exhaust gas flow is passed through the bypass back into the exhaust passage of the internal combustion engine. Thereby, the residual heat of the exhaust gas can be used to heat the cooling water of the engine via the exhaust gas recirculation cooler and thus contribute to a cold start of the engine to the fact that the engine reaches its operating temperature faster. As a result, the low-pressure exhaust gas recirculation can be activated faster and the emissions of the internal combustion engine can be reduced.

In a preferred embodiment of the method is provided that under a first threshold temperature of the exhaust gas or the cooling water of the engine exhaust gas recirculation via the low-pressure exhaust gas recirculation, above the first threshold temperature and below a second threshold temperature of the exhaust gas or the cooling water of the engine uncooled exhaust gas recirculation via the bypass takes place and above the second threshold temperature, a cooled exhaust gas recirculation via the main channel of the low-pressure exhaust gas recirculation takes place. Below the first threshold temperature, in particular below a cooling water temperature of 50 ° C. and an exhaust gas temperature of less than 120 ° C., there is the risk that the steam contained in the exhaust gas condenses out in the low-pressure exhaust gas recirculation and enters the air supply system of the internal combustion engine as a water plug. This can lead to damage to the compressor of the exhaust gas turbocharger and to parts of the internal combustion engine. Therefore, exhaust gas recirculation via the low-pressure exhaust gas recirculation is prevented below this first threshold temperature. Above the first threshold temperature and below a second threshold temperature, additional cooling of the exhaust gas flow recirculated via the low-pressure exhaust gas recirculation may cause the water vapor to condense out. Therefore, in a temperature range above the first threshold temperature and below a second threshold temperature of about 80 ° cooling water temperature and 180 ° C exhaust gas temperature, the exhaust bypasses the bypass on the exhaust gas recirculation cooler to additional cooling of the exhaust gas and the associated risk of condense of water droplets avoid. Above the second threshold temperature, the exhaust gas stream is advantageously returned to the air supply system via the main channel of the low-pressure exhaust gas recirculation and the exhaust gas recirculation cooler in order to lower the combustion temperature in the combustion chambers of the internal combustion engine and thus to reduce the raw nitrogen oxide emissions.

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 Ausführungsbeispiel eines erfindungsgemäßen Verbrennungsmotors, wobei in einer Niederdruck-Abgasrückführung eine Abgasrückführung mit einem Abgasrückführungskühler und eine parallele Abgasrückführung ohne einen Kühler vorgesehen sind, welche über ein Steuerventil schaltbar sind;
• 2 einen ersten Betriebszustand der Verbrennungsmotors, wobei eine Abgasrückführung in den Ansaugtrakt unterbunden ist, und ein Abgasstrom des Verbrennungsmotors durch den Hauptkanal und den Bypass zurück in den Abgaskanal geleitet wird;
• 3 einen dritten Betriebszustand des Verbrennungsmotors, bei dem das Abgas über den Hauptkanal und den Abgasrückführungskühler in den Ansaugtrakt des Verbrennungsmotors zurückgeführt wird;
• 4 eine Betriebssituation des Verbrennungsmotors, bei dem ein Abgasstrom über den Hauptkanal zurückgeführt und dann geteilt wird, sodass ein erster Teilstrom über die Niederdruck-Abgasrückführung in den Ansaugtrakt zurückgeführt wird und ein zweiter Teilstrom über den Bypass zurück in den Abgaskanal geleitet wird;
• 5 einen zweiten Betriebszustand des Verbrennungsmotors, wobei ein Abgasstrom über den Bypass an dem Abgasrückführungskühler vorbei in den Ansaugtrakt zurückgeführt wird;
• 6 ein alternatives Ausführungsbeispiel eines erfindungsgemäßen Verbrennungsmotors, wobei der Bypass stromaufwärts und stromabwärts des Abgasrückführungskühlers mit dem Hauptkanal der Niederdruck-Abgasrückführung verbunden ist; und
• 7 ein weiteres alternatives Ausführungsbeispiel eines erfindungsgemäßen Verbrennungsmotors, wobei der Bypass stromaufwärts und stromabwärts des Abgasrückführungskühlers mit dem Hauptkanal der Niederdruck-Abgasrückführung verbunden ist und das Steuerventil stromabwärts des Abgasrückführungskühlers angeordnet ist.

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

• 1 an embodiment of an internal combustion engine according to the invention, wherein in a low-pressure exhaust gas recirculation exhaust gas recirculation with an exhaust gas recirculation cooler and a parallel exhaust gas recirculation are provided without a cooler, which are switchable via a control valve;
• 2 a first operating state of the internal combustion engine, wherein an exhaust gas recirculation is inhibited in the intake tract, and an exhaust gas stream of the internal combustion engine through the main channel and the bypass is fed back into the exhaust duct;
• 3 a third operating state of the internal combustion engine, in which the exhaust gas is returned via the main passage and the exhaust gas recirculation cooler in the intake manifold of the internal combustion engine;
• 4 an operating situation of the internal combustion engine, in which an exhaust gas flow is returned via the main channel and then shared, so that a first partial flow is returned via the low-pressure exhaust gas recirculation in the intake and a second partial flow is passed through the bypass back into the exhaust duct;
• 5 a second operating state of the internal combustion engine, wherein an exhaust gas stream is returned to the intake tract via the bypass past the exhaust gas recirculation cooler;
• 6 an alternative embodiment of an internal combustion engine according to the invention, wherein the bypass upstream and downstream of the exhaust gas recirculation cooler is connected to the main channel of the low-pressure exhaust gas recirculation; and
• 7 A further alternative embodiment of an internal combustion engine according to the invention, wherein the bypass upstream and downstream of the exhaust gas recirculation cooler is connected to the main channel of the low-pressure exhaust gas recirculation and the control valve is arranged downstream of the exhaust gas recirculation cooler.

1 shows an internal combustion engine 10 for a motor vehicle, which serves as a self-igniting internal combustion engine 10 is designed according to the diesel principle. The internal combustion engine 10 is with his outlet 16 with an exhaust system 40 connected. The outlet 16 includes an exhaust manifold, which the exhaust gases of the different combustion chambers 12 of the internal combustion engine 10 an exhaust duct 44 the exhaust system 30 supplies. The internal combustion engine 10 is with an inlet 14 with an air supply system 20 connected. The air supply system 20 points in the direction of flow of fresh air through the air supply system 20 an air filter 22 and downstream of this air filter 22 a compressor 24 an exhaust gas turbocharger 36 on, with which the sucked air is compressed and the combustion chambers 12 of the internal combustion engine 10 is supplied. The air supply system 20 also has a fresh gas line 26 on which the air filter 22 with the inlet 14 of the internal combustion engine 10 combines. Downstream of the air filter 22 is an air mass meter 30 at the fresh gas line 26 intended. At the internal combustion engine 10 is a coolant circuit 18 provided with which the engine block and other radiator, in particular a charge air cooler 28 , be supplied with coolant. Downstream of the intercooler 28 and upstream of the inlet 14 is a control flap 32 for controlling the air quantity of the internal combustion engine 10 intended. Further, on the internal combustion engine is a high-pressure exhaust gas recirculation valve 34 provided with which exhaust gas can be returned within the engine.

The exhaust system 40 has an exhaust duct 44 in which in the flow direction of an exhaust gas of the internal combustion engine 10 through the exhaust system 40 a turbine 42 the exhaust gas turbocharger 36 and downstream of the turbine 42 at least one first exhaust aftertreatment component 46 for exhaust aftertreatment of the internal combustion engine 10 , preferably a particle filter 54 , particularly preferably an oxidation catalyst 58 with a downstream particle filter 54 with a coating for the selective, catalytic reduction of nitrogen oxides are arranged. In the illustrated embodiment of the internal combustion engine 10 are downstream of the turbine 42 the exhaust gas turbocharger 36 first a NOx storage catalytic converter 50, downstream of the NOx storage catalytic converter 50, a metering system 52 for a reducing agent and downstream of the metering system 52 a particle filter 54 arranged with a coating for the selective, catalytic reduction of nitrogen oxides. Downstream of the particulate filter 54 with the SCR coating branches off the exhaust duct 44 at a branching point 78 a main channel 66 a low-pressure exhaust gas recirculation 60 from. The main channel 66 connects the exhaust duct 44 with a low pressure exhaust gas recirculation line 70 , In the main channel 66 is an exhaust gas recirculation cooler 64 arranged, with which the temperature of the recirculated exhaust gas can be reduced. This is the exhaust gas recirculation cooler 64 to the coolant circuit 18 of the internal combustion engine 10 connected and flows through the coolant. The low pressure exhaust gas recirculation line 70 opens downstream of the air filter 22 and upstream of the compressor 24 in the fresh gas channel 26 , Downstream of the pub 78 is in the exhaust duct 44 an exhaust flap 48 arranged. The exhaust duct 44 is downstream of the branching point 78 through the exhaust flap 48 at least partially closed. Downstream of the exhaust flap 48 are in the exhaust duct 44 another SCR catalyst 56 and an oxidation catalyst 58 arranged.

Downstream of the exhaust flap 48 and upstream of the further SCR catalyst 56 branches at another branching point 80 a bypass 68 from the exhaust duct 44 from and runs substantially parallel to the main channel 66 the low-pressure exhaust gas recirculation 60 , At a merge 82 of the main channel 66 and the bypass 68 is a control valve 62 arranged. The control valve 62 is preferably designed as a 3/3-way valve. Here are a first connection opening 84 of the control valve 62 with the main channel 66 , a second connection opening 86 of the control valve 62 with the bypass 68 and a third connection opening 88 with the low pressure exhaust gas recirculation line 70 the low-pressure exhaust gas recirculation 60 connected. The low pressure exhaust gas recirculation line 70 flows at a junction 76 downstream of the air mass meter 30 and upstream of the compressor 24 in the fresh gas line 26 of the air supply system 20 , At the main channel 66 and the bypass 68 is each a filter 72 . 74 arranged, which the penetration of soot particles in the low-pressure exhaust gas recirculation 70 prevents or at least reduces.

At the internal combustion engine 10 is also a controller 90 provided with a machine-readable program code, which via signal lines 92 with the exhaust flap 48 and the control valve 62 connected is. About the control unit 90 is the position of the exhaust flap 48 and the control valve 62 adjustable, so that the exhaust gas flow through the low-pressure exhaust gas recirculation 60 can be controlled.

In 2 is a first operating state of the internal combustion engine 10 illustrated in which the low pressure exhaust gas recirculation passage 70 through the control valve 62 is closed. In this first operating state, in particular with a cold internal combustion engine, cold cooling water, cold exhaust gas and / or cold engine oil, the exhaust flap 48 in the exhaust duct 44 employed, so that the exhaust duct 44 is essentially closed. This will be the Exhaust gas flow of the internal combustion engine 10 upstream of the exhaust flap 48 through the main channel 66 passed and through the control valve 62 then in the bypass 68 deflected, so that the deflected exhaust gas flow downstream of the exhaust flap 48 and upstream of the further SCR catalyst 56 again the exhaust duct 44 is supplied. In this case, the exhaust gas flow through the exhaust gas recirculation cooler 64 passed, wherein the residual heat of the exhaust gas flow to the coolant of the exhaust gas recirculation cooler 64 and thus on the coolant circuit 18 is transmitted. Thus, the residual heat of the exhaust gas, in particular after a cold start of the internal combustion engine 10 used to the internal combustion engine 10 as soon as possible after a cold start to bring to its operating temperature. By closing the low pressure exhaust gas recirculation line 70 eliminates the risk of water vapor in the low pressure exhaust gas recirculation line 70 or in the fresh gas line 26 condenses out and the water droplets lead to damage to the components.

In 5 is a second operating state of the internal combustion engine 10 shown in which the internal combustion engine 10 , the coolant circuit 18 and / or the engine oil has a higher temperature than in the 2 sketched first operating state. This is the exhaust flap 48 essentially completely open, so that the exhaust gas flow through the exhaust duct 44 in the direction of the other SCR catalyst 56 flows. A partial flow of the exhaust gas passes through the bypass 68 into the low pressure exhaust gas recirculation line 70 but without the exhaust gas recirculation cooler 64 to happen. Thus, the risk of condensation of water droplets is reduced. As a result, even with less hot exhaust gas, less warm coolant or engine oil, the low-pressure exhaust gas recirculation 60 be activated and exhaust gas of the intake air in the fresh gas line 26 be mixed. As a result, in a known manner, the formation of nitrogen oxides in the combustion of the fuel in the combustion chambers 12 of the internal combustion engine 10 be reduced, so the exhaust system 40 less nitrogen oxide raw emissions are supplied.

In 3 is a third operating state of the internal combustion engine 10 shown in which the internal combustion engine 10 has reached its operating temperature and a partial flow of the exhaust gas over the main channel 66 returned to the low-pressure exhaust gas recirculation and through the main channel 66 arranged exhaust gas recirculation cooler 64 is cooled. This is the exhaust flap 48 employed, so that the exhaust back pressure in the exhaust passage 44 is increased. Further, the control valve 62 placed such that a connection from the main line 66 to the low pressure exhaust gas recirculation line 70 is open. This allows the combustion temperature in the combustion chambers 12 of the internal combustion engine 10 be reduced, which has a positive effect on the nitrogen oxide raw emissions of the internal combustion engine 10 effect.

In 4 is another operating state of the internal combustion engine 10 shown. Here is the exhaust flap 48 essentially closed, so that a large part of the exhaust gas flow of the internal combustion engine 10 in the main channel 66 the low-pressure exhaust gas recirculation 60 is initiated. This exhaust gas flow is through the control valve 62 divided into a first partial flow and a second partial flow. The first partial flow is via the low pressure exhaust gas recirculation line to the air supply system 20 supplied, so that the combustion temperature and associated with the raw emissions of the internal combustion engine 10 can be lowered. The second partial flow is via the bypass 68 back into the exhaust duct 44 directed. As a result, a maximum heat recovery of the waste heat of the exhaust gas via the exhaust gas recirculation cooler 64 and a simultaneous, cooled low-pressure exhaust gas recirculation possible.

If the exhaust gas temperature drops T _EC and / or the coolant temperature T _CF below a first threshold temperature T _S1 or is the coolant temperature T _CF or the exhaust gas temperature T _EF after a cold start of the internal combustion engine 10 below this first threshold temperature T _S1 , There is a risk that the water vapor contained in the exhaust gas in the low-pressure exhaust gas recirculation 60 condenses out and at an exhaust gas recirculation the compressor 24 the exhaust gas turbocharger 36 damaged. In order to avoid this, exhaust gas recirculation via the low-pressure exhaust gas recirculation is avoided in a first operating state. If the exhaust gas temperature drops T _EC in operation below a second threshold temperature T _S2 or are the exhaust gas temperature T _EC and / or the coolant temperature T _CF after a cold start of the internal combustion engine 10 below this second threshold temperature T _S1 , There is a risk that the water vapor contained in the exhaust gas in the low-pressure exhaust gas recirculation 60 condensed out, if the exhaust gas flow additionally through the exhaust gas recirculation cooler 64 is cooled. This is especially with cold coolant and correspondingly strong cooling effect of the exhaust gas recirculation cooler 64 critical. In this second operating state, the recirculated exhaust gas flow through the bypass 68 and thus past the exhaust gas recirculation cooler 64 passed, so that the exhaust gas temperature of the low-pressure exhaust gas recirculation 60 recirculated exhaust gas remains substantially constant. Such an operating state is in 5 shown. This is the exhaust flap 48 essentially fully open, to allow exhaust gas to enter the main channel 66 the low-pressure exhaust gas recirculation 60 to avoid. By the flow resistance of the other SCR catalyst 56 and the oxidation catalyst 58 is a partial flow of the exhaust gas in the bypass 68 passed from there uncooled via the low pressure exhaust gas recirculation line in the air supply system 20 upstream of the compressor 24 ,

It is preferred, if in a bypass operation, in which the low-pressure exhaust gas recirculation 60 recirculated exhaust gas to the exhaust gas recirculation cooler 64 past the fresh gas line 26 is introduced at the intercooler 28 of the internal combustion engine 10 also a bypass is provided, with which this intercooler 28 can also be bridged. As a result, at a high exhaust gas recirculation rate, the heating of the internal combustion engine 10 be favored, and the recirculated energy is not through the intercooler 28 to the coolant circuit 18 dissipated.

In 6 is an alternative embodiment of an internal combustion engine according to the invention 10 shown. With essentially the same structure as 1 to 5 will be explained below, only the differences from the first embodiment. In this embodiment, the bypass branches 68 from the main channel 66 upstream of the exhaust gas recirculation cooler 64 at a junction 94 and flows downstream of the exhaust gas recirculation cooler 64 at the merger 82 back in the main channel 66 , The exhaust flap 48 may be downstream of the branching point as in the first embodiment 78 and upstream of the further SCR catalyst 56 Alternatively, an arrangement of the exhaust valve downstream of the other SCR catalyst 56 , in particular downstream of the oxidation catalyst 58 at any point of the exhaust duct 44 downstream of the branching point 78 possible. In this embodiment, there is no direct connection of the bypass 68 to the exhaust duct 44 available. The control valve 62 is at the junction 94 arranged so that an exhaust gas recirculation selectively blocked, the recirculated exhaust gas flow cooled via the exhaust gas recirculation cooler 64 or uncooled over the bypass 68 can be returned.

In 7 is another alternative embodiment of an internal combustion engine according to the invention 10 shown. With essentially the same structure as 6 executed, in this embodiment, the control valve 62 at the merger 82 from bypass 68 and main channel 66 the low pressure exhaust gas recirculation 60 arranged. Alternatively, also at the junction 94 and the merge 82 each simple switching valves, in particular exhaust valves, be arranged, with which the exhaust gas flow through the bypass 68 and / or through the main channel 66 the low-pressure exhaust gas recirculation is passed.

In summary, it can be stated that by an internal combustion engine according to the invention 10 the residual heat of the exhaust gas can be used and a condensation of in the low-pressure exhaust gas recirculation 40 recirculated exhaust gas contained water vapor is avoided. In this case, the low-pressure exhaust gas recirculation can be activated faster after a cold start when uncooled exhaust gas is returned, whereby the nitrogen oxide emissions of the internal combustion engine can be reduced.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

combustion chamber

14

inlet

16

outlet

18

Coolant circuit

20

Air supply system

22

air filter

24

compressor

26

Fresh gas line

28

Intercooler

30

Air flow sensor

32

control flap

34

High-pressure exhaust gas recirculation valve

36

turbocharger

40

exhaust system

42

turbine

44

exhaust duct

46

first exhaust aftertreatment component

48

exhaust flap

50

NOx storage catalytic converter

52

dosing

54

Particulate filter with SCR coating

56

SCR catalyst

58

oxidation catalyst

60

Low-pressure exhaust gas recirculation

62

control valve

64

Exhaust gas recirculation cooler

66

Main channel of the low-pressure exhaust gas recirculation

68

Bypass of low-pressure exhaust gas recirculation

70

Low-pressure exhaust gas recirculation line

72

filter

74

filter

76

junction

78

branching point

80

branching point

82

together

84

first connection opening

86

second connection opening

88

third connection opening

90

control unit

92

signal line

94

branch

T

temperature

T _CF

Coolant temperature of the internal combustion engine

T _CFL

Threshold for the coolant temperature

T _EC

exhaust gas 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 102008020408 A1 [0004]
• EP 2956657 B1 [0005]

Claims (10)

Internal combustion engine (10) with an air supply system (20) and an exhaust system (40), and with a low-pressure exhaust gas recirculation (60), the exhaust system (40) downstream of a turbine (42) of an exhaust gas turbocharger (36) with the air supply system (20) upstream of a compressor (24) of the exhaust gas turbocharger (36), and with an exhaust flap (48) with which an exhaust passage (44) of the exhaust system (40) can be at least partially blocked, wherein a main channel (66) of the low-pressure exhaust gas recirculation ( 60) downstream of the turbine (42) and upstream of the exhaust flap (48) branches off at a branch point (78) from the exhaust passage (44) and into a low-pressure exhaust gas recirculation line (70), and wherein in this main channel (66) an exhaust gas recirculation cooler (64) is arranged, characterized in that parallel to the main channel (66), a bypass (68) is formed, which bridges the exhaust gas recirculation cooler (64), wherein at a Zusammenfü is arranged (82) or a branch (94) of the main channel (66) and the bypass (68), a control valve (62) with which an exhaust gas flow between the bypass (68) and the main channel (66) is controllable. Internal combustion engine (10) after Claim 1 , characterized in that the control valve (62) is designed as a 3/3-way valve or a combination of two valves to a 3/3-way function. Internal combustion engine (10) after Claim 1 or 2 characterized in that a first port (84) of the control valve (62) is connected to the main channel (66), a second port (86) to the bypass (68) and a third port (88) to the low pressure exhaust gas recirculation line (70) , Internal combustion engine (10) according to one of Claims 1 to 3 , characterized in that the bypass (68) downstream of the exhaust valve (48) with the exhaust passage (44) of the internal combustion engine (10) are connected. Internal combustion engine (10) according to one of Claims 1 to 3 characterized in that the bypass (68) is connected upstream and downstream of the exhaust gas recirculation cooler (64) to the main passage (66) of the low pressure exhaust gas recirculation (60). Internal combustion engine (10) according to one of Claims 1 to 5 , characterized in that in the main channel (66) and in the bypass (68) each have a filter is arranged. Internal combustion engine (10) according to one of Claims 1 to 6 , characterized in that the main channel (66) of the low-pressure exhaust gas recirculation (60) branches off downstream of a particulate filter (54) with a coating for the selective, catalytic reduction of nitrogen oxides from the exhaust duct (44) of the internal combustion engine (10). Method for the exhaust aftertreatment of an internal combustion engine (10) according to one of Claims 1 to 7 characterized in that - in a first operating state, no exhaust gas recirculation takes place via the low-pressure exhaust gas recirculation, - uncooled exhaust gas recirculation takes place via the bypass (68) in a second operating state, and - in a third operating state, a cooled exhaust gas recirculation via the main passage (66) the low-pressure exhaust gas recirculation (60) takes place. Method according to Claim 8 , characterized in that in the first operating state, the exhaust valve (48) is at least partially closed, wherein an exhaust gas flow through the main channel (66) of the low-pressure exhaust gas recirculation is passed and the control valve (62) is set such that the exhaust gas flow through the bypass (68) is passed back into the exhaust passage (44) of the internal combustion engine (10). Method according to Claim 8 , characterized in that below a first threshold temperature (T _S1 ) of the exhaust gas or the cooling water of the internal combustion engine (10) no exhaust gas recirculation via the low-pressure exhaust gas recirculation, above the first threshold temperature (T _S1 ) and below a second threshold temperature (T _S2 ) of the Exhaust gas or the cooling water of the internal combustion engine (10) an uncooled exhaust gas recirculation via the bypass (68) and above the second threshold temperature (T _S2 ) is a cooled exhaust gas recirculation via the main channel (66) of the low-pressure exhaust gas recirculation (60).

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