DE102019202349A1 - Method for regenerating a lean NOx trap of an exhaust aftertreatment device - Google Patents

Abstract

A method for regenerating a lean NOx trap (13) of an exhaust gas aftertreatment device (5) of an internal combustion engine arrangement (1) comprising an internal combustion engine (2) and an electrically driven charger (9, 41) is described. The method comprises the following steps: detection (51) that the internal combustion engine (2) has been switched off; Determining (52) the loading of the lean NOx trap (13); Determining (53) the current operating temperature of the exhaust gas aftertreatment device (5); if the specific loading of the lean NOx trap (13) exceeds a specified threshold value (54) and the specific current operating temperature exceeds a specified threshold value (55), regenerating (56) the lean NOx trap (13) after switching off the Internal combustion engine (2), with fresh air being fed to the lean NOx trap (13) by means of the electrically driven charger (9, 41) and heated in the process, and the fresh air upstream of the lean NOx trap (13) with evaporated fuel rich air-fuel mixture is mixed.

Description

The present invention relates to a method for regenerating a lean NOx trap of an exhaust gas aftertreatment device. The invention also relates to a control device for regenerating a lean NOx trap or a NOx storage catalytic converter, an exhaust gas aftertreatment device, an engine arrangement and a motor vehicle.

With exhaust gas aftertreatment devices, combustion gases are cleaned mechanically, catalytically or chemically after they have left the combustion chamber or the combustion chamber of an internal combustion engine driving the motor vehicle, in order to be able to comply with statutory pollutant limits.

In connection with increasingly stringent legal requirements for emissions from motor vehicles, there are far-reaching challenges for exhaust gas aftertreatment. In particular, the emissions arising in connection with a cold start of a diesel engine pose a challenge in connection with compliance with future emissions standards. To store the nitrogen oxides generated after a cold start, a lean NOx trap is usually used, which is arranged upstream of a catalytic converter for selective catalytic reduction (SCR - Selective Catalytic Reduction). The lean NOx trap is used to store nitrogen oxides before the SCR catalytic converter has reached its operating temperature. In this case, however, it is necessary that the lean NOx trap has the required storage capacity in the event of a cold start, that is to say that it is not fully charged. To ensure this, sufficiently large lean NOx traps are used, for example, which then have to be flushed or regenerated at a load of 50% to 60% in order to ensure the storage capacity required for the next cold start. The large volume required and the space required for the lean NOx trap, as well as the high thermal inertia of the lean NOx trap - which means that it requires an increased time to heat up - are disadvantageous. A first disadvantage is the high installation space required, a second disadvantage is the thermal inertia mentioned above.

In the document JP 3997868 B2 describes a method for regenerating the intake system after the engine has been stopped by means of an electrically driven turbocharger rotor. In the document US 7213396 describes a method for preventing hydrocarbon emissions after an internal combustion engine has been switched off, wherein an electric turbocharger is used. In the document JP 2004308595 A describes a configuration with two supercharger pumps, whereby the exhaust gas scavenging from the engine is improved. In the document US 8468801 a system for warming up a catalyst is described, also in the document US 2011/0146274 A1 .

Against the background described, the object of the present invention is to provide an improved method for exhaust gas aftertreatment which, in particular, improves exhaust gas aftertreatment in connection with a cold start.

This object is achieved by a method for regenerating a lean NOx trap of an exhaust gas aftertreatment device according to claim 1, a control device for the regeneration of a lean NOx trap according to claim 7, an exhaust gas aftertreatment device according to claim 8, an engine arrangement according to claim 11, a motor vehicle according to claim 7 Claim 12 and a computer program product according to Claim 13 solved. The dependent claims contain further advantageous developments of the present invention.

The method according to the invention for regenerating a lean NOx trap of an exhaust gas aftertreatment device of an internal combustion engine arrangement relates to an internal combustion engine arrangement which comprises an internal combustion engine and an electrically driven charger. The method according to the invention comprises the following steps: A shutdown of the internal combustion engine is detected. The loading of the lean NOx trap is determined. The load is determined, for example, with the help of models in the engine control system, the load is thus calculated and the value is immediately available when the engine is switched off. The current operating temperature of the exhaust gas aftertreatment device is determined, for example on a specified component of the exhaust gas aftertreatment device. If the specific loading of the lean NOx trap exceeds a specified threshold value and the specific current operating temperature exceeds a specified threshold value, the lean NOx trap is regenerated after the internal combustion engine has been switched off. In this case, fresh air is fed to the lean NOx trap by means of the electrically driven charger, in particular to the inlet of the lean NOx trap. The fresh air is heated and the fresh air upstream of the lean NOx trap, preferably immediately upstream of the lean NOx trap, i.e. preferably at the inlet of the lean NOx trap, is mixed with evaporated fuel to form a rich air-fuel mixture.

The described method according to the invention has the advantage that the lean NOx trap can also be regenerated when the internal combustion engine is not in operation, that is to say in particular after the internal combustion engine has been switched off. Another advantage is that the storage capacity of the lean NOx trap can be fully used. The lean NOx trap can for example be dimensioned in such a way that its storage capacity is optimized in relation to the required storage capacity during a cold start. In this way, the lean NOx trap can be kept as small as possible and its thermal inertia can be reduced at the same time.

It also prevents the oil from being diluted by fuel, as can happen with a post-injection in the cylinder. Furthermore, when the method according to the invention is used, the lean NOx trap is always prepared for a subsequent cold start after the internal combustion engine has been switched off. In addition, no additional air supply or corresponding air supply systems are required, in particular in order to feed in preheated air upstream of the lean NOx trap.

In an advantageous variant, the fresh air is passed through an exhaust gas recirculation flow channel to the inlet of the lean NOx trap. The exhaust gas recirculation flow channel has a flow direction that is defined for the exhaust gas recirculation. The fresh air is preferably passed through the exhaust gas recirculation flow duct to the inlet of the lean NOx trap in a direction opposite to this flow direction. The use of the exhaust gas recirculation flow channel for feeding fresh air upstream of the lean NOx trap in connection with the regeneration of this has the advantage that no additional flow channels need to be provided for regenerating the lean NOx trap. This saves installation space and reduces the complexity and susceptibility of the arrangement to errors. In an advantageous variant, the exhaust gas recirculation flow channel is designed as a high pressure exhaust gas recirculation flow channel.

In a particularly advantageous variant, the fresh air is heated by means of the exhaust gas aftertreatment device and / or the internal combustion engine. This has the advantage that no additional devices for heating the fresh air are required and the residual heat present in the exhaust gas aftertreatment device is optimally used. The fresh air can be heated, for example, by the heat given off by the internal combustion engine, for example radiated heat. For this purpose, the fresh air can, for example, be conducted through an exhaust gas recirculation flow ducts integrated in the cylinder head and / or in the engine block in the vicinity of the cylinder head and / or the engine block. In this case, the internal combustion engine comprises a cylinder head and an engine block.

The computer program product according to the invention comprises commands which, when the program is executed by a computer, leave the computer to execute a previously described method according to the invention. The computer program product according to the invention has the advantages already mentioned in connection with the method according to the invention.

The control device according to the invention for the regeneration of a lean NOx trap is characterized in that the control device has a device for detecting a shutdown of the internal combustion engine, a device for determining the loading of the lean NOx trap and a device for determining the current operating temperature of the Comprises exhaust gas aftertreatment device and is designed to carry out a previously described method according to the invention. The control device according to the invention has the features and advantages already mentioned in connection with the method according to the invention.

The device for determining the current operating temperature of the exhaust gas aftertreatment device can comprise a temperature sensor. For example, the device for determining the current operating temperature of the exhaust gas aftertreatment device can be arranged on a fixed component of the exhaust gas aftertreatment device, in particular on a component arranged upstream or downstream of the lean NOx trap. By determining or recording the current operating temperature of the exhaust gas aftertreatment device and taking this into account in connection with the initiation of a regeneration process for the lean NOx trap, it is ensured that the temperature of the fresh air supplied during the regeneration of the lean NOx trap is maintained during the Regeneration is present.

The exhaust gas aftertreatment device according to the invention comprises a lean NOx trap and an electrically driven charger, for example an electrically driven compressor or turbocharger. The electrically driven charger is preferably a charger that is already present for charging the internal combustion engine. The exhaust gas aftertreatment device according to the invention comprises a previously described control device according to the invention. Additionally or alternatively, the exhaust gas aftertreatment device according to the invention is designed to to carry out a method according to the invention as described above. The exhaust gas aftertreatment device according to the invention has the features and advantages already mentioned.

The lean NOx trap preferably includes an inlet. A device for evaporating and / or injecting fuel into a flow channel leading to the inlet of the lean NOx trap is advantageously arranged upstream of the lean NOx trap. The device for injecting fuel can in particular be designed to inject fuel in vaporized form and to mix it with fresh air supplied.

In a further advantageous variant, the electrically driven charger is designed as an electrical turbocharger or an electrically driven compressor. The described use of the electrically driven charger has the advantage that, after the internal combustion engine has been switched off, fresh air for regenerating the lean NOx trap can be routed through exhaust gas recirculation channels that are already present.

The engine arrangement according to the invention comprises an internal combustion engine and an exhaust gas aftertreatment device according to the invention described above. The motor vehicle according to the invention comprises an engine arrangement according to the invention. The engine arrangement according to the invention and the motor vehicle according to the invention have the advantages already mentioned. In particular, they enable the lean NOx trap to be regenerated even after the internal combustion engine has been switched off and thus ensure optimal conditions for a subsequent cold start of the internal combustion engine with regard to a reduction in nitrogen oxide emissions in connection with a cold start. The motor vehicle according to the invention can be a motorcycle, a passenger car, a truck, a bus or a minibus.

• 1 zeigt schematisch eine erfindungsgemäße Motoranordnung.
• 2 zeigt schematisch eine weitere Variante einer erfindungsgemäßen Motoranordnung.
• 3 zeigt schematisch ein erfindungsgemäßes Verfahren in Form eines Flussdiagramms.
• 4 zeigt schematisch eine erfindungsgemäße Steuervorrichtung.
• 5 zeigt schematisch ein erfindungsgemäßes Kraftfahrzeug.

The figures show:

• 1 shows schematically a motor arrangement according to the invention.
• 2 shows schematically a further variant of a motor arrangement according to the invention.
• 3 shows schematically a method according to the invention in the form of a flow chart.
• 4th shows schematically a control device according to the invention.
• 5 shows schematically a motor vehicle according to the invention.

The ones in the 1 engine arrangement shown schematically 1 includes an internal combustion engine 2 , an exhaust aftertreatment device 5 and a high pressure exhaust gas recirculation device 6th . Optionally, the motor assembly includes 1 also a low-pressure exhaust gas recirculation device 7th . The motor assembly also includes 1 one by means of an electric motor 8th driven turbocharger 9 . The electric motor 8th can also be designed as a generator at the same time. The turbocharger 9 includes a compressor 11 and a turbine 12 .

The exhaust aftertreatment device 5 includes a lean NOx trap 13 and one downstream of the lean NOx trap 13 arranged particle filter with optional SCR coating 14th . In addition, one is the lean NOx trap 13 bridging bypass flow channel 15th with a valve 65 arranged. The lean NOx trap 13 includes an inlet 16 and an outlet 17th . Immediately upstream of the inlet 16 the lean NOx trap 13 is a device 19th for vaporizing or injecting fuel into the lean NOx trap 13 leading flow channel 18th arranged. The bypass flow channel 15th is arranged so that it is upstream of the inlet 16 the lean NOx trap 13 from the flow channel 18th branches off and downstream of the outlet 17th the lean NOx trap 13 and upstream of the particulate filter with SCR coating 14th to the flow channel 18th returns.

The internal combustion engine 2 includes a number of cylinders 3 , in the variant shown four cylinders, one flywheel 4th , an intake manifold 20th and an exhaust manifold 21st . Furthermore is in the internal combustion engine 2 an oil cooler 22nd and a high pressure fuel pump 23 arranged.

When operating the internal combustion engine 2 becomes the cylinders 3 via the fuel pump 23 Fuel supplied. Furthermore, it is through an air filter 24 Charge air by means of the compressor 11 sucked in. The one from the air filter 24 to the compressor 11 leading flow channel is with the reference number 25th marked. The one by the compressor 11 Compressed charge air or the exhaust gas mixed with the charge air in the case of exhaust gas recirculation is passed through a flow channel 26th to a thrush 27 and further through an intercooler 28 to the intake manifold 21st and to the cylinders 3 directed.

In the variant shown is a high pressure exhaust gas recirculation flow channel 29 present, which from the exhaust manifold 21st branches off and immediately upstream of the intake manifold 20th flows into this. The flow channel 29 also includes a high pressure exhaust gas recirculation valve 30th .

That the internal combustion engine 2 Exiting exhaust is through the exhaust manifold 21st to the turbine 12 directed, causing the compressor 11 is driven. The exhaust gas is then passed through the flow channel 18th routed to the exhaust aftertreatment components already mentioned. After passing the exhaust aftertreatment device 5 the cleaned exhaust gas becomes the outlet 31 directed. The direction of flow of the exhaust gas is indicated by the reference number 32 marked.

Upstream of the outlet 31 is a low pressure exhaust gas recirculation flow passage 33 arranged. This low pressure exhaust gas recirculation flow passage 33 includes a dirt filter 34 and a cooler 35 , as well as a valve 36 . In the variant shown, the exhaust gas recirculation cooler 35 from a bypass flow channel 37 with a low pressure exhaust gas recirculation bypass valve 38 bridged. The low pressure exhaust gas recirculation duct 33 is also via an exhaust gas recirculation combination valve 43 with the flow channel 25th connected. During the application of the method according to the invention, the exhaust gas recirculation combination valve is 43 closed and the high pressure exhaust gas recirculation valve 33 open.

The following is the operation of the engine assembly shown 1 described according to the method of the invention. First, the internal combustion engine is switched off 2 detected. The loading of the lean NOx trap 13 is known from the continuous, model-based determination. Furthermore, the current operating temperature of the exhaust gas aftertreatment device, in particular the lean NOx trap 13 certainly. A sensor that is already present can preferably be used. Typically, the gas temperature becomes downstream of the lean NOx trap 13 or upstream of an SCR catalytic converter, for example the particulate filter with SCR coating 14th , measured to ensure the function of the SCR catalytic converter. This variable can, if necessary together with the operating time, be used to determine the component temperature of the lean NOx trap 13 to determine, in particular to model. The temperature inside the lean NOx trap 13 is for example determined continuously by a model that this temperature based on the mass flows, the temperature upstream and downstream of the lean NOx trap 13 as well as the chemical composition of the exhaust gas. Chemical reactions that release heat and increase the temperature inside are also taken into account

If the loading of the lean NOx trap 13 exceeds a specified threshold and the determined current operating temperature exceeds a specified threshold, becomes the lean NOx trap 13 after switching off the combustion engine 2 regenerated. This is done by means of the electric motor 8th the turbocharger 9 operated and sucked in fresh air.

The direction of flow of the fresh air drawn in is indicated by arrows with the reference number 40 marked. In the high pressure exhaust gas recirculation flow channel 29 runs the direction of flow 40 in the opposite direction to the flow direction of the exhaust gas in the case of exhaust gas recirculation.

The one about the compressor 11 fresh air drawn in then passes through the high pressure exhaust gas recirculation flow channel 26th and is then with an open high-pressure exhaust gas recirculation valve 30th via the high pressure exhaust gas recirculation flow channel 29 on the internal combustion engine 2 passed by. The air that is sucked in is thereby carried by the flow channel 26th and the high pressure exhaust gas recirculation flow channel 29 heated, especially by the cylinders 3 , so the cylinder head and / or the cylinder block, heat dissipated heat. The heated air reaches through the flow channel 18th the inlet 16 the lean NOx trap 13 . Upstream of the inlet 16 the lean NOx trap 13 is about the device for vaporizing and injecting fuel 19th Fuel is supplied to the intake air and mixed with it. A rich air-fuel mixture is generated with which the lean NOx trap 13 is regenerated. In doing so, the high pressure EGR flow passage becomes 29 The sucked-in air flows through it in a flow direction opposite to that used in the context of high-pressure exhaust gas recirculation. This means that there are no additional flow channels for regenerating the lean NOx trap 13 after the combustion engine has been switched off 2 required. By means of the electric motor 8th powered turbocharger 9 can the air even after switching off the combustion engine 2 sucked in and to the lean NOx trap 13 be directed.

In the in the 2 The variant shown differs from that in the 1 A turbocharger without an electric drive is provided. Additionally is downstream of the compressor 11 of the turbocharger 9 another compressor 41 provided which by an electric motor 42 is operated. As part of the application of the method according to the invention by means of an in the 2 The configuration shown is for drawing in air after the internal combustion engine has been switched off 2 the electrically driven compressor 41 used. Otherwise, the functionality corresponds to that in connection with the 1 described functionality. The electrically powered compressor 41 can in an alternative embodiment also upstream of the turbocharger 9 or be arranged in another suitable position.

The 3 shows schematically a method according to the invention in the form of a flow chart. In a first step 51 the internal combustion engine is switched off 2 detected. Is the internal combustion engine 2 switched off, so in step 52 the loading of the lean NOx trap 13 certainly. In step 53 becomes the current operating temperature of the lean NOx trap 13 or another exhaust aftertreatment component. The steps 52 and 53 can also be carried out simultaneously or in reverse order.

In step 54 it is checked whether the specific loading of the lean NOx trap 13 exceeds a specified threshold. If this is the case, the procedure starts with step 55 continued. If this is not the case, the procedure jumps to step 51 back. In step 55 it is determined whether the determined current operating temperature of the lean NOx trap 13 exceeds a specified threshold. The steps 54 and 55 can also be carried out simultaneously or in reverse order.

If the determined current operating temperature does not exceed the defined threshold value, the method jumps to step 51 back. If the current operating temperature exceeds the defined threshold value, the lean NOx trap becomes 13 in step 56 regenerated or flushed, using the electrically powered charger 9 or 41 , for example as in connection with the 1 and 2 described fresh air to the lean NOx trap 13 directed, heated and upstream of the lean NOx trap 13 , preferably just before the inlet 16 the lean NOx trap 13 , is mixed with vaporized fuel to form a rich air-fuel mixture.

The 4th shows schematically a control device according to the invention 60 . The control device 60 includes a facility 61 to determine the loading of the lean NOx trap 13 , An institution 62 to determine the current operating temperature of the lean NOX trap 13 , for example a temperature sensor, a device 63 for detecting a shutdown of the internal combustion engine 2 and an evaluation device 64 . The facilities mentioned 61 , 62 and 63 are designed to send signals to the evaluation device 64 transferred to. The control device 60 is designed to carry out a method according to the invention, for example in connection with the 3 described procedure.

The 5 shows schematically a motor vehicle according to the invention 10 . The motor vehicle according to the invention 10 includes a motor assembly according to the invention 1 , for example one based on the 1 or 2 described motor arrangement 1 . In addition, the motor vehicle 10 or the engine layout 1 a control device according to the invention 60 include. The engine assembly according to the invention 1 is designed to carry out a method according to the invention, for example a method in connection with the in 3 explained method according to the invention.

List of reference symbols

1

Motor arrangement

2

Internal combustion engine

3

cylinder

4th

flywheel

5

Exhaust aftertreatment device

6th

High pressure exhaust gas recirculation device

7th

Low pressure exhaust gas recirculation device

8th

Electric motor

9

turbocharger

10

Motor vehicle

11

compressor

12

turbine

13

Lean NOx trap

14th

Particle filter with SCR coating

15th

Bypass flow channel

16

inlet

17th

Outlet

18th

Flow channel

19th

Fuel injector

20th

Intake manifold

21st

Exhaust manifold

22nd

oil cooler

23

High pressure fuel pump

24

Air filter

25th

Flow channel

26th

Flow channel

27

throttle

28

Intercooler

29

High pressure exhaust gas recirculation flow channel

30th

High pressure exhaust gas recirculation valve

31

Outlet

32

Direction of flow

33

Low pressure exhaust gas recirculation flow passage

34

Dirt filter

35

cooler

36

Valve

37

Bypass flow channel

38

Low pressure exhaust gas recirculation bypass valve

40

Direction of flow of the fresh air drawn in

41

compressor

42

Electric motor

43

Exhaust gas recirculation combination valve

51

Detecting a shutdown of the internal combustion engine

52

Determine the loading of the lean NOx trap

53

Determine the current operating temperature of the lean NOx trap

54

Has the specified threshold value for loading the lean NOx trap been exceeded?

55

Has the defined threshold value for the current operating temperature been exceeded?

56

Regeneration of the lean NOx trap

60

Control device

61

Device for determining the loading of the lean NOx trap

62

Means for determining the current operating temperature of the lean NOx trap

63

Device for detecting a shutdown of the internal combustion engine

64

Evaluation facility

65

Valve

J

Yes

N

No

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• JP 3997868 B2 [0004]
• US 7213396 [0004]
• JP 2004308595 A [0004]
• US 8468801 [0004]
• US 2011/0146274 A1 [0004]

Claims (13)

Method for regenerating a lean NOx trap (13) of an exhaust gas aftertreatment device (5) of an internal combustion engine arrangement (1) which comprises an internal combustion engine (2) and an electrically driven charger (9, 41), characterized in that the method comprises the following steps - Detecting (51) a shutdown of the internal combustion engine (2), - Determining (52) the loading of the lean NOx trap (13), - Determining (53) the current operating temperature of the exhaust gas aftertreatment device (5), - If the determined loading the lean NOx trap (13) exceeds a specified threshold value (54) and the specific current operating temperature exceeds a specified threshold value (55), regeneration (56) of the lean NOx trap (13) after switching off the internal combustion engine (2) , wherein by means of the electrically driven charger (9, 41) fresh air is passed to the lean NOx trap (13) and heated and the fresh air upstream of the lean NOx trap (13) with dil ampftem fuel is mixed to a rich air-fuel mixture. Procedure according to Claim 1 , characterized in that the fresh air is passed through an exhaust gas recirculation flow channel (26, 29) to the lean NOx trap (13). Procedure according to Claim 2 , characterized in that the exhaust gas recirculation flow channel (29) has a flow direction defined for the exhaust gas recirculation and the fresh air is conducted in the opposite direction (40) to this flow direction through the exhaust gas recirculation flow channel (29) to the lean NOx trap (13). Procedure according to Claim 2 or Claim 3 , characterized in that the exhaust gas recirculation flow channel is designed as a high pressure exhaust gas recirculation flow channel (29). Method according to one of the Claims 1 to 4th , characterized in that the fresh air is heated by means of the exhaust gas aftertreatment device (5) and / or the internal combustion engine (2). Procedure according to Claim 5 , characterized in that the fresh air is heated by the heat given off by the internal combustion engine (2). Control device (60) for the regeneration of a lean NOx trap (2), characterized in that the control device (60) has a device (63) for detecting a shutdown of the internal combustion engine (2), a device (61) for determining the loading the lean NOx trap (13) and a device (62) for determining the current operating temperature of the exhaust gas aftertreatment device (5) and is designed to implement a method according to one of the Claims 1 to 6th execute. Exhaust gas aftertreatment device (5) which comprises a lean NOx trap (5) and an electrically driven charger (9, 41), characterized in that the exhaust gas aftertreatment device (5) comprises a control device (60) according to Claim 7 comprises and / or is designed to provide a method according to one of the Claims 1 to 6th execute. Exhaust aftertreatment device (5) after Claim 8 , characterized in that the lean NOx trap (13) comprises an inlet (16) and, upstream of the lean NOx trap (16), a device (19) for vaporizing and / or injecting fuel into an inlet (16) ) the lean NOx trap (13) leading flow channel (18) is arranged. Exhaust aftertreatment device (5) according to one of the Claims 8 or 9 , characterized in that the electrically driven charger (9, 41) is designed as an electric turbocharger (9) or an electric supercharger or an electrically driven compressor (41). Motor arrangement (1), which comprises an internal combustion engine (2) and an exhaust gas aftertreatment device (5) according to one of the Claims 8 to 10 includes. Motor vehicle (10) having an engine arrangement (1) according to Claim 11 includes. Computer program product, comprising instructions which cause the program to be executed by a computer, a method according to one of the Claims 1 to 6th execute.

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