DE102019122917A1 - Regeneration of a NOx storage catalytic converter of an exhaust gas aftertreatment device - Google Patents

Abstract

An internal combustion engine arrangement (1), which has an internal combustion engine (2), a charger (9) with a compressor (11) and a turbine (12), an exhaust gas aftertreatment device (5) with a NOx storage catalytic converter (13) and a low-pressure Exhaust gas recirculation flow channel (33) comprising an inlet downstream of the exhaust gas aftertreatment device (5). There is a flow channel (46) which branches off from the low-pressure exhaust gas recirculation flow channel (33) and which has a first valve (47), a fan (48) arranged downstream of the first valve (47), a heater (48) arranged downstream of the fan (48). 49) and an outlet (50) which is arranged upstream of the exhaust gas aftertreatment device (5) and which leads into an exhaust gas flow channel (18) downstream of the turbine (12) of the supercharger (9).

Description

The present invention relates to an internal combustion engine arrangement, a method for regenerating a NOx storage catalytic converter of an internal combustion engine arrangement. The invention also relates to a motor vehicle and a computer program product.

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 the increasingly strict legal requirements for emissions from motor vehicles, there are far-reaching challenges for exhaust gas aftertreatment. In particular, the emissions that arise in connection with a cold start of a diesel engine represent a challenge in connection with compliance with future emissions standards. To store the emissions after a cold start or at low load, for example when driving within a city with low exhaust gas temperatures (e.g. below 200 degrees Celsius) , nitrogen oxides generated, a NOx storage catalytic converter is usually used, which is arranged upstream of a catalytic converter for selective catalytic reduction (SCR - Selective Catalytic Reduction).

The NOx storage catalytic converter stores nitrogen oxides before the SCR catalytic converter has reached its operating temperature. In this case, however, it is necessary that the NOx storage catalytic converter 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 NOx storage catalytic converters are used, for example, which then have to be 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 NOx storage catalytic converter as well as the high thermal inertia of the NOx storage catalytic converter - which means that it takes an increased time to heat up - are disadvantageous. A first disadvantage is the high level of heat required Installation space, a second disadvantage is the thermal inertia already mentioned. In the documents US20080083215A1 and US9790830 describes methods for regenerating a NOx storage catalytic converter, wherein the temperature of the exhaust gas is increased.

In order to ensure a stable efficiency of the NOx storage catalytic converter, it is necessary that the NOx storage catalytic converter can also be regenerated during a low engine load, for example a torque below 40 Nm. However, regeneration briefly requires operation with a rich fuel-air mixture, which, however, is not possible with a low engine load. Diesel combustion under low engine load characterizes combustion with a very lean fuel-air mixture. In this situation, even brief combustion with a rich fuel-air mixture requires a strong throttling of the fresh air supply, which results in noticeable fluctuations in torque.

Against the background described, it is the object of the present invention to provide an internal combustion engine arrangement and an improved method for exhaust gas aftertreatment which, in particular, improve exhaust gas aftertreatment in connection with a cold start or with a low engine load.

This object is achieved by an internal combustion engine arrangement according to claim 1, a method for regenerating a NOx storage catalytic converter of an internal combustion engine arrangement according to claim 7, a motor vehicle according to claim 11 and a computer program product according to claim 12. The dependent claims contain further advantageous embodiments of the present invention.

The internal combustion engine arrangement according to the invention comprises an internal combustion engine, a charger with a compressor and a turbine, for example a turbocharger, an exhaust gas aftertreatment device with a NOx storage catalytic converter and a low-pressure exhaust gas recirculation flow channel with an inlet downstream of the exhaust gas aftertreatment device. Furthermore, the internal combustion engine arrangement comprises a flow channel branching off from the low-pressure exhaust gas recirculation flow channel. The branching flow channel comprises a first valve, a fan arranged downstream of the first valve, a heater arranged downstream of the fan and an outlet arranged upstream of the exhaust gas aftertreatment device. The outlet opens or leads into the exhaust gas flow channel downstream of the turbine of the supercharger. A further flow channel, which comprises an inlet and an outlet, is preferably arranged upstream of the fan. The outlet is fluidically connected to the branching flow channel and the inlet is fluidically connected to a fresh air supply flow channel or branches off from it.

The internal combustion engine arrangement according to the invention has the advantage that, regardless of the operating state of the internal combustion engine, i.e. also during a cold start or when the internal combustion engine is operated under low load, the NOx storage catalytic converter can be regenerated via the branching flow channel and possibly the further flow channel. Regeneration of the NOx storage catalytic converter is possible even when the combustion engine is switched off. In addition, the operation of the internal combustion engine is not influenced by a regeneration of the NOx storage catalytic converter.

The further flow channel advantageously comprises a second valve and / or an air mass sensor. In this way, if necessary, fresh air can be introduced into the branching flow channel in a targeted manner.

In a further variant, a third valve is arranged downstream of the turbine and upstream of the outlet of the branching flow channel. By closing this valve, the NOx storage catalytic converter can be regenerated even when the internal combustion engine is switched off.

A device for supplying and vaporizing fuel and / or a temperature sensor and / or a lambda probe is advantageously arranged upstream of the NOx storage catalytic converter and downstream of the outlet of the branching flow channel. In this way, a rich fuel-air mixture can be generated for regeneration directly upstream of the NOx storage catalytic converter. Furthermore, the temperature of the exhaust gas and / or the combustion air ratio can be measured and the regeneration can be controlled, in particular regulated, as a function thereof.

The internal combustion engine assembly may also include a high pressure exhaust gas recirculation flow passage. This can be used to operate the internal combustion engine with high-pressure exhaust gas recirculation during regeneration of the NOx storage catalytic converter.

The method according to the invention for regenerating the NOx storage catalytic converter of a previously described internal combustion engine arrangement according to the invention comprises the following steps: A request for regenerating the NOx storage catalytic converter is detected. The combustion air ratio (fuel-air ratio) upstream of the NOx storage catalytic converter is recorded. If the recorded combustion air ratio falls below a specified limit value, the first valve of the branching flow channel is opened, the fan is switched on, exhaust gas is introduced from the low-pressure exhaust gas recirculation flow channel through the branching flow channel into the exhaust gas flow channel upstream of the NOx storage catalytic converter and fuel is introduced upstream of the NOx- Storage catalyst injected into the exhaust gas flow channel.

The temperature of the exhaust gas is preferably detected, for example measured, upstream, in particular immediately upstream, of the NOx storage catalytic converter. If the detected temperature falls below a specified threshold value, the exhaust gas returned via the branching flow channel is heated by means of a heater arranged downstream of the fan. This means that regeneration is possible even with a cold start or a low engine load.

In a further variant, the exhaust gas flow rate is detected, for example measured, upstream, preferably immediately upstream, of the NOx storage catalytic converter. If the detected exhaust gas flow rate falls below a specified threshold value, the second valve is opened and fresh air is introduced via the further flow channel into the exhaust gas returned via the branching flow channel. In this way, the fuel-air mixture required for regeneration can be generated.

If the internal combustion engine is not operated, the third valve can be closed and the NOx storage catalytic converter can be regenerated by supplying an exhaust-air mixture via the branching flow channel and the further flow channel and injecting fuel upstream of the NOx storage catalytic converter. Regeneration is therefore also possible when the internal combustion engine is switched off.

The motor vehicle according to the invention comprises an internal combustion engine arrangement according to the invention. Additionally or alternatively, it is designed to be operated in accordance with a previously described method according to the invention. The motor vehicle according to the invention has the advantages already mentioned. In particular, it enables the NOx storage catalytic converter to be regenerated even after the internal combustion engine has been switched off and thus ensures 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.

The computer program product according to the invention comprises instructions that, when executed of the program by a computer cause the latter to carry out an already 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 invention is explained in more detail below on the basis of exemplary embodiments with reference to the accompanying figures. Although the invention is illustrated and described in more detail by the preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.

The figures are not necessarily true to detail and to scale and can be enlarged or reduced in order to provide a better overview. The functional details disclosed here are therefore not to be understood as restrictive, but merely as an illustrative basis which offers the person skilled in the art in this field of technology guidance in order to use the present invention in a wide variety of ways.

• 1 zeigt schematisch eine erfindungsgemäße Verbrennungsmotoranordnung.
• 2 zeigt schematisch ein erfindungsgemäßes Verfahren in Form eines Flussdiagramms.
• 3 zeigt schematisch ein erfindungsgemäßes Kraftfahrzeug.

The term “and / or” as used herein, when used in a series of two or more items, means that any of the listed items can be used alone, or any combination of two or more of the listed items can be used. For example, if a composition is described that it contains components A, B and / or C, the composition A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

• 1 shows schematically an internal combustion engine arrangement according to the invention.
• 2 shows schematically a method according to the invention in the form of a flowchart.
• 3rd shows schematically a motor vehicle according to the invention.

The one in the 1 internal combustion engine arrangement shown schematically 1 includes an internal combustion engine 2 , an exhaust aftertreatment device 5 , a high pressure exhaust gas recirculation device 6th and a low pressure exhaust gas recirculation device 7th . The motor assembly also includes 1 a turbocharger 9 . The turbocharger 9 includes a compressor 11 and a turbine 12th .

The exhaust aftertreatment device 5 includes a NOx storage catalytic converter 13th and one downstream of the NOx storage catalytic converter 13th arranged particle filter with optional SCR coating 14th . The NOx storage catalytic converter 13th includes an inlet 16 and an outlet 17th . Immediately upstream of the inlet 16 of the NOx storage catalytic converter 13th is a device 19th for vaporizing or injecting fuel into the NOx storage catalytic converter 13th leading flow channel 18th arranged.

Downstream of the exhaust aftertreatment device 5 and downstream of the low pressure exhaust gas recirculation device 7th is an exhaust valve 65 arranged.

The internal combustion engine 2 includes a number of cylinders 3rd , in the variant shown four cylinders, one flywheel 4th , an intake manifold 20th and an exhaust manifold 21 . 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 3rd 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. In the variant shown, the air filter comprises 24 a first air mass sensor 39 . 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 20th and to the cylinders 3rd directed.

In the variant shown, a high-pressure exhaust gas recirculation flow channel is optional 29 present, which from the exhaust manifold 21 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 21 to the turbine 12th 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 is passed through the exhaust valve 65 to 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 EGR 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.

From the low pressure EGR flow passage 33 a branching flow channel branches off 46 from. The direction of flow of the exhaust gas through the branching flow channel 46 is indicated by arrows with the reference number 45 marked. The branching flow channel 46 includes a first valve 47 , a fan disposed downstream thereof 48 , one downstream of the fan 48 arranged heater 49 and one upstream of the exhaust aftertreatment device 5 arranged outlet 50 , which in the exhaust flow channel 18th downstream of the turbine 12th of the loader 9 flows out. Upstream of the fan 48 is another flow channel 51 with an inlet 52 and an outlet 53 is arranged, the outlet 53 fluidically with the branching flow channel 46 is connected and the inlet 52 from the fresh air supply flow channel 25th branches off. The other flow channel 51 includes a second valve 54 and a second air mass sensor 55 .

Optionally includes the exhaust flow channel 18th one downstream of the turbine 12th and upstream of the outlet 50 of the branching flow channel 46 arranged third valve 56 .

The internal combustion engine arrangement shown 1 can be operated, for example, as follows: During normal operation of the internal combustion engine 2 are the first valve 47 and the second valve 54 closed and the third valve opened. The blower 48 and the stoker 49 are not in operation. The internal combustion engine 2 can be operated with low pressure exhaust gas recirculation and / or high pressure exhaust gas recirculation.

When a request to regenerate the NOx storage catalytic converter 13th is detected and the torque or the load of the internal combustion engine falls below a specified limit value, the low-pressure exhaust gas recirculation valve 36 closed and the internal combustion engine 2 optionally operated with high pressure exhaust gas recirculation. The internal combustion engine 2 can continue to operate with lean combustion, which avoids noticeable torque fluctuations. Based on the immediately upstream of the NOx storage catalytic converter 13th detected combustion air ratio is by means of the fuel injector 19th a certain amount of fuel in the exhaust flow passage 18th immediately upstream of the NOx storage catalytic converter 13th injected to produce a rich fuel-air mixture. At the same time, the first valve 47 opened and the fan activated in order to achieve a high exhaust gas return flow, whereby the amount of fuel to be injected can be minimized. The recirculation of hot exhaust gas can reduce the exothermic reactions within the exhaust gas aftertreatment device 5 to increase the efficiency of the regeneration of the NOx storage catalytic converter 13th can be used advantageously. The exhaust gas recirculation can be achieved by suitably setting the opening of the exhaust valve 65 to be controlled.

If the upstream of the NOx storage catalytic converter 13th the detected exhaust gas temperature is below a threshold temperature set for carrying out a regeneration, the heater can 49 be put into operation. If the recirculated exhaust gas mass flow is below a threshold value established for carrying out a regeneration, the second valve can 54 be opened and via the further flow channel 51 Fresh air can be supplied. The mass flow of the fresh air can be measured by means of the first air mass sensor 39 and the second air mass sensor 55 be monitored.

In the case of regeneration with the combustion engine switched off 2 can the third valve 56 be closed, the first valve 47 and the second valve 54 can be opened, blower 48 and heater 49 can be put into operation to generate the mass flow required for regeneration. In order to generate a rich fuel-air mixture, fuel is injected using the fuel injector.

The 2 shows schematically a variant of a method according to the invention in the form of a flow chart. In step 71 a request to regenerate the NOx storage catalytic converter is detected. In step 72 the combustion air ratio (fuel-air ratio) is recorded upstream of the NOx storage catalytic converter. In step 73 the temperature of the exhaust gas upstream of the NOx storage catalytic converter is detected, for example measured. In step 74 the exhaust gas flow rate upstream of the NOx storage catalytic converter is detected, for example measured.

In step 75 it is checked whether the recorded combustion air ratio falls below a specified limit value. If this is the case, step 77 the first valve of the branching flow channel is opened, the fan is switched on, exhaust gas from the low-pressure exhaust gas recirculation flow channel is introduced through the branching flow channel into the exhaust gas flow channel upstream of the NOx storage catalytic converter and fuel is injected into the exhaust gas flow channel upstream of the NOx storage catalytic converter. If the recorded combustion air ratio does not fall below the specified limit value, step 76 the NOx storage catalytic converter without the in step 77 measures mentioned regenerated.

In step 78 it is checked whether the recorded temperature falls below a specified threshold value. If the recorded temperature falls below the specified threshold value, step 79 the exhaust gas returned via the branching flow channel is heated by means of a heater arranged downstream of the fan. If the recorded temperature does not fall below the defined threshold value, the method jumps to step 71 back.

In step 80 it is checked whether the recorded exhaust gas flow rate falls below a specified threshold value. If this is the case, step 81 the second valve is opened and fresh air is introduced via the further flow channel into the exhaust gas returned via the branching flow channel. Otherwise the process jumps to step 71 back.

The steps 72 to 74 and the steps 75 , 78 and 80 can also be carried out in a different order. The steps 73 , 74 and 78 to 81 are optional.

The 3rd shows schematically a motor vehicle according to the invention 10 . The motor vehicle according to the invention 10 comprises an internal combustion engine assembly according to the invention 1 , for example one based on the 1 internal combustion engine assembly described 1 . The internal combustion engine arrangement 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 2 explained method according to the invention.

List of reference symbols

1

Internal combustion engine assembly

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

9

turbocharger

10

Motor vehicle

11

compressor

12th

turbine

13th

NOx storage catalytic converter

14th

Particle filter with SCR coating

16

inlet

17th

Outlet

18th

Flow channel

19th

Fuel injector

20th

Intake manifold

21

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

39

first air mass sensor

40

Direction of flow of the fresh air drawn in

43

Exhaust gas recirculation combination valve

44

Direction of flow of recirculated exhaust gas

45

Direction of flow through the branching flow channel

46

branching flow channel

47

first valve

48

fan

49

Stoker

50

Outlet

51

another flow channel

52

inlet

53

Outlet

54

second valve

55

second air mass sensor

56

third valve

65

Exhaust valve

71

Detecting a request to regenerate the NOx storage catalytic converter

72

Detection of the combustion air ratio upstream of the NOx storage catalytic converter

73

Detecting the temperature of the exhaust gas upstream of the NOx storage catalytic converter

74

Detecting the exhaust gas flow rate upstream of the NOx storage catalytic converter

75

Does the recorded combustion air ratio fall below a specified limit value?

76

Regeneration of the NOx storage catalytic converter

77

Opening the first valve, switching on the fan, introducing exhaust gas through the branching flow channel into the exhaust gas flow channel upstream of the NOx storage catalytic converter and injecting fuel upstream of the NOx storage catalytic converter

78

Does the recorded temperature fall below a specified threshold value?

79

Activate heater

80

Does the recorded exhaust gas flow rate fall below a specified threshold value?

81

Opening the second valve and introducing fresh air

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

• US 20080083215 A1 [0004]
• US 9790830 [0004]

Claims (12)

Internal combustion engine arrangement (1), which has an internal combustion engine (2), a charger (9) with a compressor (11) and a turbine (12), an exhaust gas aftertreatment device (5) with a NOx storage catalytic converter (13) and a low-pressure exhaust gas recirculation flow channel (33 ) with an inlet downstream of the exhaust gas aftertreatment device (5), characterized in that there is a flow channel (46) which branches off from the low-pressure exhaust gas recirculation flow channel (33) and which has a first valve (47), one downstream of the first valve (47) Fan (48), a heater (49) arranged downstream of the fan (48) and an outlet (50) arranged upstream of the exhaust gas aftertreatment device (5) which leads into an exhaust gas flow channel (18) downstream of the turbine (12) of the supercharger (9) , includes. Internal combustion engine assembly (1) according to Claim 1 , characterized in that a further flow channel (51) with an inlet (52) and an outlet (53) is arranged upstream of the fan (48), the outlet (53) being fluidically connected to the branching flow channel (46) and the Inlet (52) is fluidically connected to a fresh air supply flow channel (25). Internal combustion engine assembly (1) according to Claim 2 , characterized in that the further flow channel (51) comprises a second valve (54) and / or an air mass sensor (55). Internal combustion engine arrangement (1) according to one of the Claims 1 to 3rd , characterized in that a third valve (56) is arranged downstream of the turbine (12) and upstream of the outlet (50) of the branching flow channel (46). Internal combustion engine arrangement (1) according to one of the Claims 1 to 4th , characterized in that a device for supplying and evaporating fuel (19) and / or a temperature sensor and / or a lambda probe is arranged upstream of the NOx storage catalytic converter (13) and downstream of the outlet (50) of the branching flow channel (46). Internal combustion engine arrangement (1) according to one of the Claims 1 to 5 , characterized in that the internal combustion engine assembly (1) comprises a high pressure exhaust gas recirculation flow channel (29). Method for regenerating the NOx storage catalytic converter (13) of an internal combustion engine arrangement (1) according to one of the Claims 1 to 6th , characterized in that the method comprises the following steps: - Detecting a request to regenerate the NOx storage catalytic converter (71), - Detecting the combustion air ratio upstream of the NOx storage catalytic converter (72), - If the detected combustion air ratio falls below a specified limit value (75 ), Opening the first valve of the branching flow channel, switching on the fan, introducing exhaust gas from the low-pressure exhaust gas recirculation flow channel through the branching flow channel into the exhaust gas flow channel upstream of the NOx storage catalyst and injecting fuel upstream of the NOx storage catalyst into the exhaust gas flow channel (77). Procedure according to Claim 7 , characterized in that the temperature of the exhaust gas is recorded upstream of the NOx storage catalyst (73) and, if the recorded temperature falls below a specified threshold value (78), the exhaust gas returned via the branching flow channel is heated (79) by means of a heater arranged downstream of the fan ). Procedure according to Claim 7 or Claim 8 combined with Claim 3 , characterized in that the exhaust gas flow rate upstream of the NOx storage catalytic converter is recorded (74) and if the recorded exhaust gas flow rate falls below a specified threshold value (80), opening the second valve and introducing fresh air via the further flow channel into the exhaust gas returned via the branching flow channel (81). Method according to one of the Claims 7 to 9 combined with Claim 4 , characterized in that if the internal combustion engine (2) is not operated, the third valve (56) is closed and the NOx storage catalytic converter (13) by supplying an exhaust gas-air mixture via the branching flow channel (46) and the further flow channel (51) and injecting fuel upstream of the NOx storage catalytic converter (13) is regenerated. Motor vehicle (10) having an internal combustion engine arrangement (1) according to one of the Claims 1 to 6th comprises and / or is designed according to a method according to one of the Claims 7 to 10 to be operated. A computer program product comprising instructions that are used when the program is executed a computer cause this, a method according to one of the Claims 7 to 10 to execute.

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