DE102017111454A1 - Otto engine with particle filter and method for operating a gasoline engine - Google Patents

Abstract

The invention relates to a gasoline engine, with an intake tract (4), an exhaust tract (6), a particle filter (8), which is arranged in the exhaust tract (6), and a bypass line (10) for supplying oxygen to the particulate filter (8), wherein the bypass line (10) at a first end (12) with the intake tract (4) and a second end (14) is connected to the exhaust gas tract (6).

Description

The invention relates to a gasoline engine with a particulate filter and a method for operating such a gasoline engine.

In modern gasoline engines, in particular those with direct injection, particulate filters or Otto particle filters (OPF) are used to filter particles from the exhaust gas and thus reduce particulate emissions.

The increasing particulate filtration load of the particulate filter leads to a rising exhaust back pressure, which leads to an increase in fuel consumption and a reduction in engine performance. In order to reduce the loading of the particulate filter, a regular regeneration or discharge of the particulate filter is required.

The discharge or regeneration takes place by oxidation of the soot embedded in the particle filter with oxygen. In other words, the soot collected in the particulate filter is burned as part of the discharge. In order to enable regeneration or discharge of the particulate filter, therefore, oxygen must be contained in the exhaust gas.

However, especially in high load, high speed operating conditions, such as high speed highway driving, gasoline engines are usually operated under oxygen deficiency, so that the exhaust gas contains substantially no oxygen that can be used to regenerate the particulate filter. In this operating state, a regeneration or discharge of the particulate filter is therefore not possible.

Especially in the area of high load and high speed, the particulate loading of the particulate filter is particularly high, so that the consumption-increasing and power-reducing exhaust gas back pressure increases. In addition to an increase in fuel consumption, insufficient regeneration of the particulate filter can therefore lead to a reduction in the maximum available engine power, which is felt by the driver in the form of a sinking maximum speed.

Against this background, the invention is based on the technical problem to provide a gasoline engine with particulate filter and a method for operating such a gasoline engine, which do not have the disadvantages described above or at least to a lesser extent, and allow reliable regeneration or discharge of the particulate filter, in particular also in the operation of the gasoline engine under oxygen deficiency.

The technical problem described above is achieved by a gasoline engine according to claim 1, a method for operating such a gasoline engine according to claim 9 and a method according to claim 10. Advantageous embodiments of the invention will become apparent from the dependent claims and the description below.

According to a first aspect, the invention relates to a gasoline engine with an intake tract, an exhaust tract, a particulate filter disposed in the exhaust tract, and a bypass conduit for supplying oxygen to the particulate filter, the bypass conduit having at a first end the intake tract and a second end is connected to the exhaust tract.

By means of the bypass line, it is possible to decouple the regeneration or discharge of the particulate filter from the operating state of the engine. If, for example, the engine is operated under oxygen deficiency (enrichment), so that essentially no oxygen is present in an exhaust gas flow of the exhaust gas tract, fresh air or oxygen can be added to the particulate filter via the bypass line.

The oxygen supply of the particulate filter is therefore carried out separately and independently of a rich (λ <1) or lean (λ> 1) engine operation or an engine operation with a stoichiometric combustion air ratio (λ = 1). The specifically supplied in this way oxygen can be used to oxidize the soot stored in the particulate filter. In order for a gasoline engine is specified in which at any time, especially in operation under oxygen deficiency, a reliable regeneration or discharge of the particulate filter is guaranteed. Thus, in the operation of the gasoline engine under oxygen deficiency essentially no performance losses or fuel consumption increases due to an increase in the exhaust gas back pressure due to an excessive charge of the particulate filter to record.

According to a development of the gasoline engine, it is provided that the second end of the bypass line is arranged upstream of the particulate filter in a flow direction of the exhaust gas tract. In this way it can be ensured that the entire oxygen supplied via the bypass line to the exhaust tract passes through the particle filter and can be used to oxidize the soot stored in the particle filter.

According to a further embodiment of the gasoline engine is provided that the second end of the bypass line is connected to the particulate filter. The particulate filter, for example, a connection for coupling the bypass line have to direct fresh air or oxygen from the intake directly into the particulate filter. Such a connection for connecting or coupling the bypass line can therefore be an integral part of the particulate filter. In this way, a retrofitting of a particulate filter together with a bypass line can be made possible in a simple manner.

According to a further embodiment of the gasoline engine can be provided that two or more bypass lines are provided to direct oxygen or fresh air from the intake to the exhaust tract. Thus, a reliable oxygen supply of the particulate filter can be ensured.

A refinement of the gasoline engine is characterized in that a control valve is arranged in the bypass line, in particular in order to release, block and / or meter an oxygen supply to the particle filter. By means of the control valve, the oxygen supply to the particulate filter can be adjusted specifically.

For example, the gasoline engine may be configured to control the control valve as a function of an exhaust gas backpressure detected in the exhaust gas tract. If a maximum value for the exhaust counterpressure predetermined for an operating point of the engine is exceeded, the valve for supplying oxygen to the particulate filter is opened completely or partially in order to regenerate the particulate filter.

If the gasoline engine is operated, for example, with an excess of oxygen (lean; λ> 1) or with a stoichiometric combustion air ratio (λ = 1) and if enough oxygen is available for regeneration of the particulate filter in the exhaust gas, the valve can open the bypass line between the intake tract and the exhaust gas tract lock. If the engine is operated under oxygen deficiency (rich; λ <1), for example at high speed highway exit described above, the control valve may open or release the bypass line to supply fresh air or oxygen from the intake tract to the exhaust tract to allow and cause a regeneration or discharge of the particulate filter by oxidation. Once the regeneration of the particulate filter is completed, the bypass line can be locked again.

Depending on the engine concept and design of the intake and the exhaust tract there are a variety of ways to divert the bypass line from the intake and feed the exhaust tract. In the following, some variants of the integration of the bypass line are described in order to connect the intake tract with the exhaust gas tract to the oxygen supply of the particulate filter decoupled from the operating state of the engine.

According to a development of the gasoline engine, it is provided that the first end of the bypass line, viewed in a flow direction of the intake tract, is arranged after a compressor and / or after a charge air cooler and / or after a throttle flap.

For reliable supply of the particulate filter with oxygen via the bypass line, it is necessary that in the area of the bypass line there is a pressure gradient from the intake tract to the exhaust tract. For this purpose, it can be provided that a separate device for conveying oxygen or fresh air from the intake to the exhaust gas is provided, such as a pump or the like. Such a system can be easily retrofitted to a supercharged gasoline engine or a naturally aspirated engine. A branch of the bypass line could be arranged upstream of a compressor, ie upstream of a compressor, in a turbocharged engine viewed in a direction of flow of the intake tract. Such an arrangement has the advantage that an optionally provided in the bypass line control valve is exposed to lower temperature loads, since the branched off before the compressor air is not heated by the compression process.

According to a further embodiment of the gasoline engine is provided that the first end of the bypass line is arranged in a flow direction of the intake after a compressor, that is arranged downstream of a compressor. A diversion of fresh air or oxygen after the compressor has the advantage that a pressure gradient across the bypass line from the intake to the exhaust tract can be generated in a simple manner, so no additional means for conveying oxygen or fresh air from the intake to the exhaust system required are.

According to one embodiment of the invention, it is provided that the first end of the bypass line is arranged viewed in a flow direction of the intake before or after an electric compressor. Alternatively or in addition to an exhaust gas turbocharger, an electric compressor may be provided which, viewed for example in a flow direction of the intake tract, can be arranged downstream, ie downstream of an exhaust gas turbocharger. The electric compressor can therefore be used for conveying fresh air or oxygen through the bypass line.

According to a further embodiment of the gasoline engine is provided that the first end of the bypass line in a flow direction of the Intake tract considered after a charge air cooler is arranged. Depending on the operating point, the air temperature can be up to 200 ° C immediately after a compressor, so that a possibly provided in the bypass line control valve in the case of a branch immediately after a compressor endure high temperatures and must be actively cooled. A branch after the intercooler has the advantage that a possibly provided in the bypass line control valve is exposed to low temperature loads.

According to an alternative embodiment of the gasoline engine is provided that a diversion of the bypass line in the intake takes place after a compressor, in particular after a compressor and in front of a charge air cooler. This arrangement has the advantage that the air supplied to the particle filter is already heated by the compression process and thus a regeneration of the particle filter is favored.

According to a development of the gasoline engine, it is provided that the first end of the bypass line, viewed in a flow direction of the intake tract, is arranged in front of a throttle valve. For example, the first end of the bypass line may be arranged in the direction of flow of the intake tract downstream of a charge air cooler and in front of the throttle valve.

According to an alternative development of the gasoline engine, it is provided that the first end of the bypass line, viewed in a flow direction of the intake tract, is arranged after a throttle flap.

According to a further embodiment of the invention, the second end of the bypass line is arranged downstream of a turbine and / or downstream of a catalytic converter in a flow direction of the exhaust tract. In order to avoid post-reactions in the exhaust tract, it can be done that the second end immediately before the particulate filter, i. especially after a turbine and / or a catalyst, opens into the exhaust system. Thus, post-reactions can be avoided by the supplied via the bypass line oxygen, which can lead to damage to the catalyst.

According to an alternative embodiment of the gasoline engine, it is provided that the second end of the bypass line, viewed in a flow direction of the exhaust gas tract, is arranged in front of a catalytic converter and / or in front of a turbine. In this way, the most homogeneous possible mixing of the fresh air supplied via the bypass line or of the oxygen with the exhaust gas can take place, so that homogeneous oxidation can take place in the particle filter.

Catalyst and particulate filter can be combined as a unit in one component. In the exhaust tract both a particulate filter and other systems for exhaust aftertreatment may be provided, such as NOx storage catalysts or selective catalytic reduction (SCR) systems.

A catalytic converter and / or the particulate filter may be arranged upstream in the direction of flow of the exhaust tract and thus in front of a turbine. Alternatively, a catalytic converter and / or the particulate filter may be arranged downstream in the direction of flow of the exhaust tract and thus downstream of a turbine.

The particulate filter may be arranged upstream of a catalytic converter in a flow direction of the exhaust tract. Alternatively, the particulate filter may be arranged downstream of a catalytic converter when viewed in a flow direction of the exhaust tract.

The gasoline engine may be a conventional naturally aspirated or supercharged engine.

The gasoline engine may have a secondary air supply, which serves to reduce emissions in the cold start of the gasoline engine.

The bypass line may be designed to supply secondary air to the exhaust tract as a Y-line. Accordingly, the bypass line may have a branch associated with the intake manifold, which is branched into two separate strands of wire. The at least two separate strands of wire open at two separate, spaced locations in the exhaust tract.

It can be provided that a third end of the bypass line opens to the secondary air supply in an outlet channel, wherein in particular a control valve for releasing, locking and / or dosing of the secondary air is provided.

It can be provided that a separate end or a separate branch for secondary air supply is provided for each cylinder. Thus, the bypass line may have on a side associated with the exhaust tract a first end, which opens into the exhaust tract for the regeneration of the particulate filter. In addition, a plurality of further ends may be provided, each opening into an outlet channel of a cylinder. For example, a bypass line on a side assigned to the exhaust tract may have a number of ends corresponding to the number of cylinders for secondary air supply plus an end for regeneration of the particulate filter. For a four-cylinder engine has such a bypass line for example, one end for supplying oxygen to the particle filter and four other ends for secondary air supply. The five ends can be fanned out of a single branch from the intake tract.

The secondary air supply can be controlled via a control valve. A plurality of valves may be provided to separately regulate the secondary air for individual cylinders.

In the bypass line, a first control valve for controlling the oxygen or fresh air supply to the particulate filter and at least a second control valve for regulating secondary air can be provided, so that at least two strands of the bypass line can be controlled separately.

• – Betreiben des Ottomotors unter Sauerstoffmangel (fett; λ < 1) oder mit stöchiometrischem Verbrennungsluftverhältnis (λ = 1);
• – Zuführen von Sauerstoff zu dem Partikelfilter über die Bypass-Leitung.

According to a further aspect, the invention relates to a method for operating a gasoline engine according to the invention, wherein at least the following method steps are carried out:

• - operating the gasoline engine under oxygen deficiency (fat, λ <1) or with stoichiometric combustion air ratio (λ = 1);
• - Supplying oxygen to the particulate filter via the bypass line.

• – Betreiben des Ottomotors unter Sauerstoffmangel oder mit stöchiometrischem Verbrennungsluftverhältnis;
• – Zuführen von Sauerstoff zu dem Partikelfilter über die Bypass-Leitung und/oder Zuführen von Sekundärluft zu dem Abgastrakt, wobei die Sekundärluftzufuhr insbesondere nach einem Kaltstart des Ottomotors erfolgt.

According to a last aspect, the invention relates to methods for operating a gasoline engine according to the invention, wherein the gasoline engine has a secondary air supply and wherein at least the following method steps are carried out:

• - Operating the gasoline engine under oxygen deficiency or with stoichiometric combustion air ratio;
• - Supplying oxygen to the particulate filter via the bypass line and / or supplying secondary air to the exhaust tract, wherein the secondary air supply takes place in particular after a cold start of the gasoline engine.

The invention will be described in detail with reference to an exemplary embodiments illustrative drawing. Each show schematically:

1 a gasoline engine according to the invention;

2 another gasoline engine according to the invention;

3 another gasoline engine according to the invention;

4 another gasoline engine according to the invention.

In 1 is schematically the operation of a gasoline engine 2 shown. The gasoline engine 2 has an intake tract 4 , an exhaust tract 6 , a particle filter 8th who is in the exhaust tract 6 is arranged, and a bypass line 10 for supplying oxygen from the intake tract 4 to the particle filter 8th , The bypass line 10 is at a first end 12 with the intake tract 4 and at a second end 14 with the exhaust tract 6 connected.

The second end 14 the bypass line 10 is in a flow direction 16 the exhaust tract 6 considered upstream of the particulate filter 8th arranged. This will ensure that the whole of the intake tract 4 branched oxygen or from the intake tract 4 Fresh air diverted the particle filter 8th completely happened and for the regeneration or discharge of the particulate filter 8th can be used.

According to alternative embodiments of the invention it can be provided that the second end of the bypass line is connected directly to the particle filter or coupled to the particle filter. Such a particle filter with an immediately coupled bypass line can be retrofitted to an existing gasoline engine in a simple manner.

In the bypass line 10 is a control valve 18 arranged. The control valve 18 serves to provide an oxygen or fresh air supply from the intake system 4 to the exhaust tract 6 to release, lock and / or dose.

Will in the present embodiment, the gasoline engine 2 operated with low oxygen (enrichment), stands in the exhaust tract 6 discharged exhaust gas no or not enough oxygen for the regeneration or discharge of the particulate filter 8th to disposal. In this case, opens the control valve 18 the bypass line 10 between the intake tract 4 and the exhaust tract 6 to oxygen or fresh air from the intake tract 4 to the exhaust tract 6 respectively. In this way, a regeneration or discharge of the Otto particle filter 8th allows in oxygen-poor engine operation, in which in the particulate filter 8th embedded soot through the oxygen supply via the bypass line 10 is oxidized.

The first end 12 the bypass line 10 is in a flow direction 20 the intake tract 4 considered after a compressor 22 arranged. The compressor 22 forms together with the turbine 24 an exhaust gas turbocharger.

Through the compressor 22 is between the intake tract 4 and the exhaust tract 6 over the bypass lines 10 away a pressure gradient between the first end 12 the bypass line 10 and the second end 14 the bypass line 10 generated. There are therefore no additional means for conveying fresh air or oxygen from the intake tract 4 to the exhaust tract 6 required. The bypass line 10 Therefore, it can be integrated into an existing gasoline engine with turbocharger in a simple manner.

According to further embodiments of the invention can be provided that a bypass line is integrated into a conventional naturally aspirated engine without exhaust gas turbocharger or electric compressor.

The second end 14 the bypass line 10 is present between a catalyst 26 and the particulate filter 8th arranged.

According to further embodiments of the invention can be provided that the catalyst and the particulate filter are integrated in one component. Alternatively or additionally, it can be provided that further systems for exhaust aftertreatment, in particular NOx storage catalysts or systems for selective catalytic reduction, are integrated into the exhaust gas tract for exhaust gas aftertreatment.

The compressor 22 is a diverter valve 28 assigned. Next are in the intake system 4 a throttle 30 and a charge air cooler 32 arranged, a suction pipe 34 upstream. The intake tract 4 flows into a cylinder block 36 , of which in turn the exhaust tract 6 going on.

2 shows a further embodiment of a gasoline engine 2 , wherein like reference numerals are assigned to the same components. In order to avoid repetition, the following will be based solely on differences from the embodiment described above 1 received.

The in 2 schematically illustrated gasoline engine 2 differs solely by the above-described embodiment, that in the intake 4 in addition to the exhaust gas turbocharger, the turbine 24 and compressors 22 is formed, in the flow direction 20 the intake tract 4 considers an electric compressor 38 with a bypass 40 is downstream. The electric compressor 40 can for conveying oxygen or fresh air from the intake tract 4 to the exhaust tract 6 serve.

3 and 4 show further embodiments of a gasoline engine 2 , to avoid repetition, only the differences from the above-described embodiments will be discussed.

The gasoline engine 2 according to 3 is characterized by the fact that the bypass line 10 as Y-line with a third end 42 or a secondary air supply 42 , is designed. In this way is via a secondary air supply 42 an emission improvement in the cold start of the gasoline engine 2 possible. The secondary air supply 42 is a control valve 44 assigned to block, meter or release the supply of secondary air. Thus, the two ends 42 . 12 the Y-line 10 be controlled separately and independently.

4 shows a further variant of a gasoline engine 2 also with a secondary air supply 42 Is provided. Behind the control valve 44 is the strand of the secondary air supply 42 into several, in this case three branches 46 fanned out into exhaust ducts 48 single cylinder 50 lead. In this way, the secondary air supply immediately after or behind an outlet valve of each cylinder 50 respectively.

LIST OF REFERENCE NUMBERS

2

gasoline engine

4

intake system

6

exhaust tract

8th

Particle filter / Otto particle filter

10

Bypass line

12

first end of the bypass line 10

14

second end of the bypass line 10

16

Flow direction in the exhaust tract 6

18

control valve

20

Flow direction in the intake tract 4

22

compressor

24

turbine

26

catalyst

28

Diverter valve

30

throttle

32

Intercooler

34

suction tube

36

cylinder block

38

electric compressor

40

Bypass of the electric compressor 38

42

third end / secondary air supply

44

Control valve of the secondary air supply 42

46

branches

48

exhaust ports

50

cylinder

Claims (10)

Otto engine, with an intake tract ( 4 ), an exhaust tract ( 6 ), a particulate filter ( 8th ) located in the exhaust tract ( 6 ), and a bypass line ( 10 ) for supplying oxygen to the particulate filter ( 8th ), whereby the bypass line ( 10 ) at a first end ( 12 ) with the intake tract ( 4 ) and a second end ( 14 ) with the exhaust tract ( 6 ) connected is. Otto engine according to claim 1, characterized in that the second end ( 14 ) of the bypass line ( 10 ) in a flow direction ( 16 ) of Exhaust tracts ( 6 ) considered upstream of the particulate filter ( 8th ) is arranged. Otto engine according to claim 1, characterized in that the second end ( 14 ) of the bypass line ( 10 ) to the particle filter ( 8th ) connected. Otto engine according to one of the preceding claims, characterized in that in the bypass line ( 10 ) a control valve ( 18 ), in particular, in order to supply oxygen to the particle filter ( 8th ) to release, lock and / or dose. Otto engine according to one of the preceding claims, characterized in that the first end ( 12 ) of the bypass line ( 10 ) in a flow direction ( 20 ) of the intake tract ( 4 ) considered after a compressor ( 22 ) and / or after a charge air cooler ( 32 ) and / or after a throttle valve ( 30 ) is arranged. Otto engine according to one of the preceding claims, characterized in that the second end ( 14 ) of the bypass line ( 10 ) in a flow direction ( 16 ) of the exhaust tract ( 6 ) considered after a turbine ( 24 ) and / or arranged after a catalyst. Otto engine according to one of the preceding claims, characterized in that a secondary air supply ( 42 ), in particular that the bypass line ( 10 ) is designed to supply secondary air as Y-line. A gasoline engine according to claim 7, characterized in that a third end ( 42 ) or a branch ( 46 ) of the bypass line ( 10 ) to the secondary air supply into the exhaust gas tract ( 6 ), in particular an outlet channel ( 48 ), in particular a control valve ( 44 ) is provided for releasing, locking and / or dosing of the secondary air supply. Method for operating a gasoline engine, wherein the gasoline engine ( 2 ) according to one of the preceding claims 1 to 8 and wherein at least the following method steps are carried out: - operating the gasoline engine ( 2 ) under oxygen deficiency or with stoichiometric combustion air ratio; Feeding oxygen to the particulate filter ( 8th ) via the bypass line ( 10 ). Method for operating a gasoline engine, wherein the gasoline engine is designed according to one of the preceding claims 7 or 8 and wherein at least the following method steps are carried out: - operating the gasoline engine ( 2 ) under oxygen deficiency or with stoichiometric combustion air ratio; Feeding oxygen to the particulate filter ( 8th ) via the bypass line ( 10 ) and / or supplying secondary air to the exhaust gas tract ( 6 ), wherein the secondary air supply takes place in particular after a cold start of the gasoline engine.

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