CN107762591B

CN107762591B - Device and method for regenerating a particle filter

Info

Publication number: CN107762591B
Application number: CN201710713284.2A
Authority: CN
Inventors: D.诺瓦克
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2016-08-18
Filing date: 2017-08-18
Publication date: 2021-03-26
Anticipated expiration: 2037-08-18
Also published as: DE102016115322A1; CN107762591A

Abstract

The invention relates to a device for regenerating a particle filter in an exhaust gas duct of an internal combustion engine having a turbocharger, wherein a turbine of the turbocharger is arranged in the exhaust gas duct of the internal combustion engine and drives a compressor for a fresh air supply of the internal combustion engine, wherein an electrical additional compressor is provided which, in addition to the compressor of the turbocharger, compresses the fresh air of the internal combustion engine. It is provided that the additional compressor is connected to an exhaust gas channel of the internal combustion engine via a secondary air line, wherein the secondary air line opens into the exhaust gas channel upstream of the particle filter, in order to achieve an air supply of the particle filter for oxidizing soot stored therein and thus for regenerating the particle filter. The invention further relates to a method for regenerating a particle filter in an exhaust gas duct of an internal combustion engine.

Description

Device and method for regenerating a particle filter

Technical Field

The present invention relates to an apparatus and a method for regenerating a particulate filter in an exhaust passage of an internal combustion engine.

Background

Current and future increasingly stringent exhaust gas regulations place high demands on the untreated emissions of motors and the exhaust gas aftertreatment of internal combustion engines. In addition, vehicle and engine manufacturers strive to reduce the consumption of internal combustion engines and the CO associated therewith₂And (5) discharging. With the introduction of the next exhaust gas legislation level EU6, the particulate limit for gasoline engines was also specified for the first time. This can result in the need to use a particle filter also in motor vehicles with gasoline engines. Over the service life of the internal combustion engine, the particle filter is loaded with dust and soot particles. Dust particles represent the inorganic and non-regenerable load of the soot particle filter. In the case of correspondingly high temperatures and an excess of oxygen, soot particles stored in the particle filter, which are generated during operation of the gasoline engine, can oxidize in the exhaust gas duct and thereby regenerate the particle filter.

Methods for regenerating a particle filter in the exhaust gas duct of a gasoline engine are known from the prior art, in which the gasoline engine is operated with lean operation and thus an excess of oxygen occurs in the exhaust gas duct. Furthermore, regeneration methods of particulate filters are known in which secondary air is brought into the exhaust gas channel of an internal combustion engine by means of a secondary air pump in order to provide a sufficient amount of oxygen for regenerating the particulate filter.

However, the disadvantage of the known solutions is that they are associated with high control engineering effort in order to simultaneously achieve the required temperatures and oxygen excess in the exhaust gas duct for the regeneration. Furthermore, the additional secondary air pump increases the costs for the exhaust gas aftertreatment device.

The power demand of modern gasoline engines in terms of driving power is constantly increasing. In order to provide high torques even at low rotational speeds and low exhaust gas volumes of the internal combustion engine, it is recommended to use an electrically driven compressor (electric booster). The electrically driven compressor assists the exhaust gas turbocharger with regard to the build-up of boost pressure. Due to the fact that the electronic booster has no additional exhaust gas turbine, no additional exhaust gas back pressure is caused by the electronic booster.

DE 10023022 a1 discloses an internal combustion engine with an exhaust gas turbocharger, wherein an additional compressor is connected in parallel or in series with the exhaust gas turbocharger, wherein the additional compressor can be driven independently of the drive cycle of the internal combustion engine, wherein the compressor compresses air in addition to the exhaust gas turbocharger in order to overcome a so-called turbo orifice (turbo). In addition, a secondary air line is provided, by means of which air can be supplied to the exhaust gas duct of the internal combustion engine by means of an additional compressor, in order to bring the catalytic converter in the exhaust gas duct to the operating temperature more quickly during a cold start phase of the internal combustion engine.

DE 10231107 a1 discloses an internal combustion engine with an exhaust gas turbocharger, in which the compressor of the exhaust gas turbocharger can be driven by an electric motor in addition to the exhaust gas turbine. In this case, the electric motor can be used to set the rotational speed of the compressor independently of the rotational speed or power of the internal combustion engine and independently of the exhaust gas flow. The compressor is connected to the exhaust gas channel of the internal combustion engine via a secondary air line in order to be able to assist the heating of the catalyst.

Furthermore, DE 19840629 a1 discloses an internal combustion engine for a motor vehicle having an exhaust gas turbocharger and a secondary air blower. In this case, a secondary air pump is provided in order to blow fresh air into the exhaust gas duct of the internal combustion engine upstream of the catalyst and thus to assist the heating of the catalyst. In addition, a secondary air pump may be used to assist the compressor of the turbocharger and to utilize the compressed air to supply the internal combustion engine.

Disclosure of Invention

The present invention is based on the object of providing a device and a method with which a simple and reliable regeneration of a particle filter can be achieved in the majority of operating states of an internal combustion engine with turbocharging.

This object is achieved by a device for exhaust gas aftertreatment of an internal combustion engine having an exhaust gas turbocharger, having a turbine arranged in an exhaust gas channel of the internal combustion engine, which turbine drives a compressor arranged in a fresh air line of the internal combustion engine on its side, and having an electrically driven additional compressor, which compresses fresh air in the fresh air line to the internal combustion engine substantially independently of the load and the rotational speed of the internal combustion engine, and having a secondary air line, which connects the additional compressor to the exhaust gas channel of the internal combustion engine, wherein the secondary air line opens into the exhaust gas channel of the internal combustion engine upstream of the particle filter. In this way, regeneration of the particle filter, that is to say oxidation of the soot particles remaining in the particle filter, can be carried out without having to leave the stoichiometric operation of the internal combustion engine. In addition, the amount of oxygen required for regenerating the particle filter can thereby be taken into the exhaust gas duct essentially independently of the speed and load of the internal combustion engine.

By means of the features specified in the invention, advantageous improvements and improvements of a device for the exhaust gas aftertreatment of an internal combustion engine are achieved.

In a preferred embodiment of the invention, it is provided that a catalytic converter is arranged in the exhaust gas duct upstream of the particulate filter in the flow direction of the exhaust gas of the internal combustion engine through the exhaust gas duct, wherein the secondary air line opens into the exhaust gas duct downstream of the catalytic converter and upstream of the particulate filter. The oxygen supplied to the exhaust gas channel via the secondary air line can thus be used directly for the regeneration of the particle filter, and dead times are dispensed with, during which the oxygen storage capacity of the catalyst is first activated upstream of the catalyst in the event of oxygen being introduced.

In a further preferred embodiment of the invention, it is provided that a shut-off element for closing the secondary air line or for throttling the flow through the secondary air line is arranged in the secondary air line downstream of the additional compressor and upstream of the opening of the secondary air line into the exhaust gas duct. As a result, undesirable backflow of exhaust gas in the opposite direction to the flow direction provided for the secondary air can be avoided, in particular in the case of switching off the additional compressor.

In this case, it is particularly preferred for the shut-off element to be embodied as a throttle valve. The throttle valve is a simple and cost-effective component in order to regulate the air flow from the additional compressor to the exhaust gas channel via the secondary air line.

In a preferred embodiment of the invention, the fresh air line is divided downstream of the compressor into a first channel and a second channel, wherein a throttle valve for controlling the air supply to the internal combustion engine is arranged in the first channel and an additional compressor is arranged in the second channel. In the area of the additional compressor, the parallel guidance of the fresh air via the first and second channels achieves that the fresh air can flow via the additional compressor into the combustion chamber of the internal combustion engine and thus does not create additional flow resistance in the fresh air guidance due to the additional compressor.

According to a preferred development of the invention, it is provided that the first and second channels are connected to one another downstream of the throttle valve and downstream of the additional compressor by a third channel, wherein a further shut-off element, in particular a further throttle valve, is arranged in the third channel for closing the third channel or for throttling the flow through the third channel. Through the third channel, a simple connection of the fresh air compressed by the additional compressor to the fresh air line is achieved. In this way, fresh air which is passed through the compressor in parallel and is compressed by the additional compressor can be fed in the direction of the inlet of the internal combustion engine.

According to the invention, a method for regenerating a particle filter in an exhaust gas channel of an internal combustion engine is proposed, wherein fresh air for an air supply of the internal combustion engine is provided by a compressor, which is driven by a turbine of an exhaust gas turbocharger of the internal combustion engine, wherein an additional compressor is provided, which is electrically driven and which effects a compression of the fresh air substantially independently of the rotational speed or the load of the internal combustion engine, and wherein the fresh air compressed by the additional compressor is blown into the exhaust gas channel upstream of the particle filter by means of a secondary air line connecting the additional compressor to the exhaust gas channel. By means of the method according to the invention, a regeneration of the particle filter is achieved, in which the internal combustion engine is operated continuously with a stoichiometric air/fuel ratio. Thus, HC, CO and NOx emissions cannot also result during regeneration, since they are converted by the catalyst.

In a further development of the method, it is provided that the shut-off device in the secondary air line is opened only when a sufficient temperature is achieved in the exhaust gas duct for the regeneration of the particle filter. This prevents the additional compressor from blowing secondary air into the exhaust gas duct in operating states in which this is unnecessary or even harmful.

According to an advantageous development of the method, the air quantity is adjusted in the case of regeneration of the particle filter by means of an additional compressor or a shut-off valve in the secondary air line in such a way that an exhaust-gas-air ratio λ of 1.05 to 1.3 occurs in the exhaust gas duct upstream of the particle filter_A. Sufficient oxygen is provided by the over-stoichiometric exhaust gas for oxidizing the soot particles retained in the particulate filter. The exhaust gas-air ratio lambda is in the range of 1.05 to 1.3_AThis is particularly advantageous, since the risk of uncontrolled soot burning on the particle filter and the associated thermal damage of the particle filter is very low.

According to a further advantageous development of the method, it is provided that, in the case of both fresh air which requires an additional fresh air supply for the internal combustion engine compressed by an additional compressor and secondary air which is required for regenerating the particle filter, the fresh air supply for the internal combustion engine has a priority before the secondary air for regenerating the particle filter is provided. By prioritizing the fresh air supply for the internal combustion engine before the secondary air supply, a higher torque of the internal combustion engine and, in connection therewith, a better response and/or a greater power can be achieved. However, since this operating state, in particular the maximum acceleration, only lasts for a short time, the regeneration of the particle filter can then be continued. Furthermore, such operation of the internal combustion engine increases the exhaust gas temperature, thereby maintaining obtaining a sufficient exhaust gas temperature for regenerating the particulate filter.

The different embodiments of the invention described in the present document can advantageously be combined with one another, as long as they are not individually specified in a specific case.

Drawings

The invention is explained in the following in embodiments according to the dependent figures. Wherein:

fig. 1 shows an embodiment of a device according to the invention for regenerating a particle filter in the exhaust gas duct of an internal combustion engine; and

fig. 2 shows a flow chart of a method according to the invention for regenerating a particle filter in an exhaust gas duct of an internal combustion engine.

Detailed Description

Fig. 1 shows an internal combustion engine 10, which is connected on the input side to a fresh air line 22 and on the output side to an exhaust gas duct 12. In the exhaust passage 12, the turbine 14 of the exhaust turbocharger 20 is arranged downstream of the output portion 56 of the internal combustion engine 10 in the flow direction of the exhaust gas of the internal combustion engine 10. A bypass with a wastegate 46 is provided at the turbine 14 in order to achieve a pressure drop in the exhaust gas duct 12 in a known manner. A catalyst 16, preferably a three-way catalyst, is arranged further downstream in the exhaust passage 12 in the flow direction. In the exhaust gas duct 12, a particle filter 18 is arranged further downstream, which filters out soot particles from the exhaust gas of the internal combustion engine 12 and can deposit the soot particles at the surface of the particle filter. In exhaust passage 12, a first lambda sensor 48 is disposed downstream of turbine 14 and upstream of catalyst 16,in order to adjust the internal combustion engine 10 to the stoichiometric air-fuel ratio lambda_E=1, and effective and efficient exhaust gas aftertreatment by the catalyst 16 is achieved.

In the fresh air line 22, a compressor 24 is arranged, which is driven by the turbine 14 of the exhaust gas turbocharger 20 and thus supplies the internal combustion engine 10 with pre-compressed air. Downstream of the compressor 24 in the flow direction of the fresh air, the fresh air line 22 is divided into a first channel 40 and a second channel 42, wherein a first throttle 38 for controlling the fresh air supplied to the internal combustion engine 10 is arranged in the first channel 40. In the second channel 42, an additional compressor 26 is arranged, which is electrically driven and thus effects the compression of fresh air substantially independently of the speed and load of the internal combustion engine 10. The additional compressor 26 is connected to the exhaust gas duct 12 via a secondary air line 28, wherein the secondary air line 28 opens into the exhaust gas duct 12 downstream of the catalytic converter 16 and upstream of the particle filter 18 at an opening 30. A shut-off element 32, preferably a throttle valve 34, is arranged in the secondary air line 22, with which throttle valve 34 the air supply to the exhaust gas duct 12 can be opened or closed. The first and

second passages

40, 42 are connected to one another downstream of the first throttle 38 and downstream of the additional compressor 26 via a third passage 44, wherein a further shut-off element 36, in particular a further throttle, is arranged in the third passage 44.

In the exhaust gas duct 12, a further oxygen sensor, in particular a further lambda sensor 50, is arranged downstream of the inlet 30 and upstream of the particle filter 18 in order to determine the exhaust gas air ratio λ before entering the particle filter 18_A.

Lambda sensors

48,50 and additional compressor 26 are connected via a signal line 54 to a control unit 52 of internal combustion engine 10 and can be actuated electrically by control unit 52.

In normal operation <100>, the internal combustion engine 10 draws in fresh air via a fresh air line 22, the fresh air is compressed by a compressor 22 of the exhaust gas turbocharger 20 and is supplied to the internal combustion engine 10. In this case, the air quantity supplied to the internal combustion engine 10 is regulated by the first throttle 38. As long as there is no higher load demand, the shut-off

elements

32,36 are closed.

If, starting from the current operating state, a boost pressure request is made in method step <110> which exceeds the current power level of the compressor 22 of the exhaust gas turbocharger 20, the additional compressor 26 is activated and the shut-off element 36, which is preferably designed as a second throttle, is opened in method step <120 >. Thereby, additional compressed air may be provided by the additional compressor 26. The additional compressed air quantity can be adjusted by the power supplied to the additional compressor 26. In addition, the shut-off element 32, in particular the third throttle valve 34, in the secondary air line 28 is closed, so that exhaust gas cannot flow out of the exhaust gas channel 12 through the secondary air line 28 in the direction of the inlet 58 of the internal combustion engine 10.

If it is determined in method step <130> that the particulate filter 18 has reached a load state in which regeneration is required (this can be done by means of a pressure difference measurement across the particulate filter 18 or by means of a load model stored in the control unit 52), the exhaust gas temperature in the region of the particulate filter 18 is determined in method step <140 >. If the temperature is above the regeneration temperature of the particulate filter 18, regeneration of the particulate filter may be introduced. Otherwise, measures for heating the exhaust gas are introduced in method step <150>, for example, the ignition angle of the internal combustion engine is adjusted in the "late" direction until a regeneration temperature of a minimum of 550 ℃, preferably a minimum of 600 ℃, is reached. The exhaust gas temperature can be determined here by a temperature sensor at the exhaust gas duct 12 or by a calculation model.

If a load of the particulate filter 18 occurs in which regeneration is required and the exhaust gas temperature in the region of the particulate filter 18 is above the regeneration temperature, the shut-off element 32, in particular the third throttle valve 34, is preferably fully opened and the shut-off element 36, i.e. the second throttle valve, is closed in method step <160 >. With the aid of the second lambda sensor 50, the oxygen content in the exhaust gas can be determined and, in stoichiometric operation of the internal combustion engine 10, adjusted by the output of the additional compressor 26. Alternatively, the amount of air delivered via the secondary air line can also be controlled or regulated by the position of the shut-off element 32. As the load on the particulate filter 18 increases, the amount of oxygen that is maximally delivered to the particulate filter 18 via the secondary air line 28 must be limited in accordance with the exhaust gas temperature in order to avoid thermal damage to the particulate filter 18 due to uncontrolled soot combustion. If the particle filter 18 is completely regenerated, the internal combustion engine 10 is operated again in normal operation in method step <170>, and the shut-off

elements

32 and 36 are closed again.

This characteristic may be stored in a characteristic map in controller 52 and the desired amount of oxygen for regenerating particulate filter 18 may be adjusted by the power of electrically-supplemented compressor 26. Now, if there is additionally a boost pressure demand for the additional compressor 26 during the regeneration of the particulate filter 18, the second throttle or shut-off element 36 can be opened in order to assist the compressor 24 of the exhaust gas turbocharger 20 during the boost pressure build-up. In order to set the desired oxygen concentration in the exhaust gas channel 12 upstream of the particle filter 18, the air mass flow through the secondary air line 28 can be adapted by means of a third throttle valve 34. If the desired boost pressure is not available, the third throttle valve 34 is closed and regeneration of the particulate filter 18 is interrupted or stopped. Fig. 2 shows a flow chart of a method for regenerating a particle filter.

In the case of a suitable cooler, the secondary air line 28 also serves as an exhaust gas recirculation line in the case of a regulated opening of the second throttle 36 and of the third throttle 34.

List of reference numerals

10 internal combustion engine

12 exhaust gas channel

14 turbine

16 catalytic converter

18 particle filter

20 turbo charger

22 fresh air line

24 compressor

26 additional compressor

28 two-stage air pipeline

30 inlet part

32 shut-off element

34 (third) throttle valve

36 (second) throttle valve

38 (first) throttle valve

40 first channel

42 second channel

44 third channel

46 waste gate

48 first lambda sensor

50 second lambda sensor

52 controller

54 signal line

56 output part

58 input section.

Claims

1. An arrangement for the exhaust-gas aftertreatment of an internal combustion engine (10) having an exhaust-gas turbocharger (20), having a turbine (14) of the exhaust-gas turbocharger (20), which is arranged in an exhaust gas duct (12) of the internal combustion engine (10) and which drives a compressor (24) arranged in a fresh air line (22) of the internal combustion engine (10); an additional compressor (26) which can be driven electrically and which can compress fresh air in the fresh air line (22) to the internal combustion engine (10) independently of the exhaust gas turbocharger (20); and a secondary air line (28) connecting the additional compressor (26) to an exhaust gas duct (12) of the internal combustion engine (10), characterized in that the secondary air line (28) opens into the exhaust gas duct (12) of the internal combustion engine (10) upstream of a particle filter (18), wherein additional compressed air can be supplied to the internal combustion engine by means of the additional compressor (26).

2. The device for exhaust gas aftertreatment according to claim 1, characterised in that a catalyst (16) is arranged in the exhaust gas channel (12) upstream of the particulate filter (18) in the flow direction of the exhaust gas of the internal combustion engine (10) through the exhaust gas channel (12), wherein the secondary air line (28) opens into the exhaust gas channel (12) downstream of the catalyst (16) and upstream of the particulate filter (18).

3. The device for exhaust gas aftertreatment according to claim 1 or 2, characterized in that a shut-off element (32) for closing the secondary air line (28) or for throttling the flow through the secondary air line (28) is arranged in the secondary air line (28) downstream of the additional compressor (26) and upstream of an opening (30) of the secondary air line (28) into the exhaust gas channel (12).

4. An arrangement for exhaust gas aftertreatment according to claim 3, characterised in that the shut-off element (32) is a throttle valve (34).

5. The device for exhaust gas aftertreatment according to claim 1 or 2, characterised in that the fresh air line (22) is divided downstream of the compressor (24) into a first channel (40) and a second channel (42), wherein a throttle valve (38) for controlling the air supply of the internal combustion engine (10) is arranged in the first channel (40) and the additional compressor (26) is arranged in the second channel (42).

6. Arrangement for exhaust gas aftertreatment according to claim 5, characterized in that the first and second channel (40, 42) are connected to each other downstream of the throttle valve (38) and downstream of the additional compressor (26) by a third channel (44), wherein a further shut-off element (36) is arranged in the third channel (44) for closing the third channel (44) or for throttling the flow through the third channel (44).

7. A method for regenerating a particle filter (18) in an exhaust gas channel (12) of an internal combustion engine (10), wherein fresh air for the air supply of the internal combustion engine (10) is provided by a compressor (24), the compressor is driven by a turbine (14) of an exhaust-gas turbocharger (20) of the internal combustion engine (10), and an additional compressor (26) is provided, which is electrically driven and which effects the compression of fresh air substantially independently of the speed or load of the internal combustion engine (10), characterized in that fresh air compressed by the additional compressor (26) is blown into the exhaust gas channel (12) upstream of the particle filter (18) via a secondary air line (28) connecting the additional compressor (26) to the exhaust gas channel (12), wherein additional compressed air can be supplied to the internal combustion engine by means of the additional compressor (26).

8. Method according to claim 7, characterized in that a shut-off element (32) in the secondary air line (28) is opened when a sufficient temperature is achieved in the exhaust gas channel (12) for regenerating the particle filter (18).

9. Method according to claim 7 or 8, characterized in that in the case of regeneration of the particle filter (18) the air quantity is adjusted by the additional compressor (26) in such a way that the exhaust-air ratio λ is set upstream of the particle filter (18) in the exhaust gas duct (12)_AAdjusted to 1.05 to 1.3.

10. Method according to claim 8, characterized in that in the case of regeneration of the particle filter (18) the air quantity is adjusted by means of the shut-off element (32) in such a way that the exhaust-air ratio λ is set upstream of the particle filter (18) in the exhaust gas duct (12)_AAdjusted to 1.05 to 1.3.

11. Method according to claim 7 or 8, characterized in that the fresh air supply for an internal combustion engine (10) has a priority before providing secondary air for regenerating the particle filter (18) when fresh air for an additional fresh air supply for the internal combustion engine (10) compressed by the additional compressor (26) and secondary air for regenerating the particle filter (18) are simultaneously required.