DE102017102874A1 - Exhaust after-treatment system of an internal combustion engine and method for loading and / or regeneration of particulate filters - Google Patents

Abstract

The invention relates to an exhaust aftertreatment system for an internal combustion engine. The exhaust aftertreatment system is designed to be single-flow in a first region downstream of an outlet of the internal combustion engine and is divided downstream into two exhaust gas flows in a second region, wherein a particle filter is arranged in each of the exhaust gas flows. In this way, the flow cross-section of the exhaust system can be increased and thus an increase in the exhaust back pressure by the loading of one or more particulate filter at least moderated werden.Es is provided that depending on the engine power and / or the exhaust gas flow rate of the internal combustion engine, a sequential or parallel loading of the two Particle filter takes place in the different exhaust gas flows. For regeneration of the particulate filter, it is provided that these are preferably regenerated sequentially in order to preserve the possibility of active component protection by passing hot, oxygen-rich exhaust gas over the substantially unloaded particulate filter in critical phases.

Description

The invention relates to an exhaust aftertreatment system for an internal combustion engine and to a method for loading and / or regeneration of particulate filters in such an exhaust aftertreatment system of an internal combustion engine.

The continuous tightening of the exhaust emission legislation places high demands on the vehicle manufacturers, which are solved by appropriate measures for the reduction of the engine raw emissions and by a corresponding exhaust aftertreatment. With the introduction of the legislative level EU6, a limit value for gasoline engines is prescribed for a number of particles, which in many cases necessitates the use of an Otto particle filter. Such soot particles are created especially after a cold start of the internal combustion engine due to incomplete combustion in combination with a superstoichiometric combustion air ratio and cold cylinder walls during the cold start. The cold start phase is thus decisive for compliance with the legally prescribed particle limit values. When driving, such an Otto particle filter is further loaded with soot. So that the exhaust gas backpressure does not increase too much, this Otto particle filter must be regenerated continuously or periodically. The increase in the exhaust back pressure can lead to an increase in consumption of the internal combustion engine, loss of power and impairment of smoothness to misfires. In order to carry out a thermal oxidation of the soot retained in the Otto particle filter with oxygen, a sufficiently high temperature level in conjunction with simultaneously existing oxygen in the exhaust system of the gasoline engine is necessary. Since modern gasoline engines are normally operated without oxygen surplus with a stoichiometric combustion air ratio (λ = 1), additional measures are required. These come as measures, for example, a temperature increase by a Zündwinkelverstellung, a temporary lean adjustment of the gasoline engine, the injection of secondary air into the exhaust system or a combination of these measures in question. An ignition angle adjustment in the direction of late in combination with a lean adjustment of the gasoline engine is preferably used so far, since this method requires no additional components and can deliver a sufficient amount of oxygen in most operating points of the gasoline engine.

From the DE 102 41 898 A1 is the division of an exhaust gas stream into two or more partial streams known to introduce a targeted the exhaust gas stream active substance in only a partial flow, while the other partial flow is not acted upon by the active substance. As a result, for example, targeted portions of an exhaust aftertreatment device can be regenerated.

From the DE 10 2008 063 809 A1 is an exhaust aftertreatment device for a diesel engine with a particulate filter and a bypass line to the particulate filter, in which two fluidically parallel portions of a particulate filter can be regenerated independently by a targeted flap control, by the respective other area can be coupled out of the exhaust gas flow. The aim of this invention is to ensure a temperature necessary for the regeneration of the particulate filter and to minimize the waste heat losses between the outlet of the internal combustion engine and the particulate filter.

Even if the solutions known from the prior art allow a targeted regeneration of partial areas of the particulate filter and by dividing the particulate filter into two subregions satisfy comparatively low exhaust gas flows to reach the necessary temperature for regeneration, the flow cross-section remains constant in the exhaust duct, so that a Loading the particulate filter with soot particles leads to a rapid increase in exhaust back pressure. In addition, the concepts known from the prior art deal with the exhaust aftertreatment of self-igniting internal combustion engines according to the diesel principle, which in principle less responsive to an increase in exhaust backpressure as spark-ignition internal combustion engines according to the Otto principle.

The invention is based on the object to keep the increase of the exhaust backpressure by the loading of the particulate filter in a spark-ignition internal combustion engine without additional regeneration intervals of the particulate filter as low as possible and thus the disadvantages mentioned in an increase in exhaust backpressure, namely an additional consumption, a loss of power or a To avoid loss of smoothness of the internal combustion engine.

According to the invention the object is achieved by an exhaust aftertreatment system for an internal combustion engine, wherein an exhaust passage downstream of an outlet of the internal combustion engine having a first portion in which the exhaust passage is designed einflutig and in which a three-way catalyst is arranged, wherein the exhaust passage downstream of the three -Wege catalyst has a second section, at which the single-flow exhaust passage divides at a branch into a first exhaust gas flow and a second exhaust gas flow, and wherein in the first exhaust gas flow, a first particulate filter and in the second exhaust gas flow, a second particulate filter is arranged. Preferably, the three-way Catalyst while close to the engine and the two particulate filter arranged in a bottom layer of a motor vehicle. In this context, an arrangement close to the engine is understood as meaning an arrangement of the three-way catalyst at a distance of not more than 60 cm, preferably not more than 30 cm, from the outlet of the internal combustion engine. The particulate filters preferably have a three-way catalytically active coating, but in a simple version of the present invention, they can also be made uncoated.

Due to the double-flow design, the back pressure in the exhaust aftertreatment system can be kept low even at high volume flows, whereby the intervals between two necessary regenerations of the particulate filter can be kept comparatively long. This increases the ride comfort of a motor vehicle with such an internal combustion engine and reduces the additional consumption of the engine, since the increase in the exhaust backpressure is comparatively slow and easy to control.

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

In a preferred embodiment of the invention it is provided that in the exhaust passage downstream of the three-way catalyst at least one actuator, preferably at least one exhaust valve, is arranged, with an exhaust gas stream of the engine at least substantially through the first exhaust gas flow, through the second exhaust gas flow or through both exhaust gas flows can be passed. By one or more control elements in the exhaust passage of the exhaust aftertreatment system, the particulate filter can optionally be loaded in parallel or sequentially and / or regenerated. In addition, a loaded particulate filter for reasons of component protection, to avoid uncontrolled Rußabbrand in a coasting phase of the internal combustion engine, be coupled out of the exhaust stream of the internal combustion engine.

According to a preferred embodiment of the invention it is provided that the adjusting element, in particular an exhaust gas flap, is arranged at the branch. Thus, it is possible with only one control element to selectively guide the exhaust gas flow of the internal combustion engine through both exhaust gas flows or only one of the two exhaust gas flows. In this case, the back pressure in the exhaust system can be minimized by the exhaust gas flow is switched upon reaching a critical load state of a particulate filter in one of the exhaust gas passages of the exhaust passage to the unloaded particulate filter in the other exhaust gas flow.

Alternatively, it is advantageously provided that a first exhaust gas flap is arranged in the first exhaust gas flow and a second exhaust gas flap is arranged in the second exhaust gas flow, with which the respective exhaust gas flows can be blocked or released. By means of two separate exhaust flaps, the two exhaust gas floods can be selectively opened and / or closed individually so that the exhaust gas flow of the internal combustion engine is conducted either through one of the exhaust gas flows or through both exhaust gas flows. In addition, in a coasting operation of the internal combustion engine opens up the possibility of increasing the braking performance of the engine brake by both exhaust valves are closed and the back pressure upstream of the exhaust valves is increased. This possibility exists in particular when the exhaust flaps are arranged upstream of the particulate filter in the two exhaust gas flows, since in this case both particulate filters are substantially decoupled from the exhaust gas flow.

It is particularly preferred if the exhaust valves are arranged in the two floods in the flow direction downstream of the particulate filter. By arranging the exhaust flaps in the two floods downstream of the particulate filter, the thermal load of the exhaust valves can be kept low. As a result, comparatively simple and cost-effective materials for the exhaust gas flaps can be used and expensive, high-temperature resistant special alloys can be dispensed with.

In a further preferred embodiment of the invention, it is provided that at least one introduction point for introducing secondary air into the exhaust gas passage is provided downstream of the three-way catalytic converter. By introducing secondary air in conjunction with a catalytic coating of the particulate filter targeted heating of the particulate filter by a combination of secondary air and substoichiometric combustion air ratio of the engine is possible. The unburned or partially combusted fuel constituents of the combustion mixture are exothermically reacted on the catalytically active surface of the particulate filter, so that the particulate filter heats up faster and reliably reaches its temperature necessary for regeneration.

According to an advantageous embodiment of the invention, provision is made for the point of introduction to be located in the single-flow section of the exhaust gas duct upstream of the branching. At a position of the secondary air introduction point downstream of the three-way catalyst and upstream of the Branching is only a point of introduction to heat both exhaust gas flows necessary. As a result, fewer components are needed and the secondary air system can be made cheaper.

According to an alternative embodiment of the invention it is provided that in each of the exhaust gas flows downstream of the branching and upstream of the respective particulate filter, a point of introduction for introducing secondary air into the exhaust gas channel is provided. By means of two separate introduction points for introducing secondary air into the two exhaust gas flows, the run length between the secondary air introduction and the catalytically coated particle filter can be reduced. The two flue gases can be supplied with secondary air independently of each other.

It is particularly preferred if the discharge points are supplied in the different exhaust gas flows via a common secondary air source. If both discharge points are supplied by a common secondary air source, in particular by a common secondary air pump, it is possible to dispense with a second secondary air pump. This lowers the cost of the secondary air system.

According to the invention, a method for loading and / or regeneration of at least two particulate filters in an exhaust aftertreatment system of an internal combustion engine is proposed in which downstream of an outlet of the internal combustion engine, the exhaust duct is designed to be single-flow and the exhaust gas of the internal combustion engine is passed through a three-way catalyst, wherein the exhaust duct downstream of the three-way catalytic converter divides at a branch into a first exhaust gas flow and a second exhaust gas flow, wherein in each of the two exhaust gas flows in each case a particle filter is arranged, and wherein in a normal operation of the internal combustion engine at least one of the particulate filter with those during combustion in the internal combustion engine resulting soot particles is loaded. By the method according to the invention, it is possible to keep the increase of the exhaust back pressure during the loading of the particulate filter low and thus to reduce negative effects such as increased fuel consumption, power losses or losses in the smoothness of the internal combustion engine.

In an improvement of the method is provided that the exhaust gas flow through the particulate filter is controlled by at least one actuator in the exhaust aftertreatment system downstream of the three-way catalyst. By one or more control elements in the exhaust passage of the exhaust aftertreatment system, the particulate filter can optionally be loaded in parallel or sequentially and / or regenerated. In addition, a loaded particulate filter for reasons of component protection, to avoid uncontrolled Rußabbrand in a coasting phase of the internal combustion engine, be coupled out of the exhaust stream of the internal combustion engine. In addition, additional degrees of freedom result in the regeneration strategy of the particle filter.

It is preferred if, in a first operating state of the internal combustion engine, in particular in a (lower) part-load operation of the internal combustion engine, one of the exhaust gas flows is opened and the respective other exhaust gas flow is closed or closed. In a partial load operation, in particular after a cold start of the internal combustion engine, a moderate, low exhaust gas volume flow can be sufficiently cleaned by one of the two particle filters, without causing an impermissible increase in the exhaust backpressure. This has the advantage that the further particulate filter can be retained in the other exhaust gas substantially unladen and thus either in a subsequent operating state to lower the exhaust back pressure or for component protection of the loaded particulate filter in a critical for the loaded particulate filter operating situation of the engine can be used ,

According to a further improvement of the method, it is provided that in a second operating state of the internal combustion engine, in particular in a regeneration of the particulate filter, the exhaust gas flow is opened with the more heavily laden particulate filter, and the other exhaust gas flow is closed or closed with the less heavily loaded particulate filter , In a partial load operation, it is advantageous to guide the exhaust gas flow only through the exhaust gas flow with the loaded particulate filter in order to have the lowest possible waste heat losses and thus to heat the loaded particulate filter as quickly as possible to its temperature necessary for regeneration.

It is particularly preferred if the exhaust gas flow is opened with the less heavily loaded particulate filter, when the internal combustion engine is operated in a third operating state with a higher load than in the second operating state, and the power of the engine or the exhaust back pressure in the exhaust gas flow with the more heavily loaded Particle filter exceeds a threshold. If the exhaust gas volume and / or the exhaust gas backpressure exceeds a critical threshold due to an increase in the power demand on the internal combustion engine, the second exhaust gas flow is additionally opened in order to lower the exhaust back pressure and increase the flow cross section downstream of the branching.

According to a further, advantageous improvement of the method it is provided that in a fourth operating state, in particular in a coasting phase of the internal combustion engine at high particulate filter temperatures of the more heavily laden particulate filter, the exhaust gas flow is closed with the more heavily laden particulate filter and the exhaust gas stream is passed via the respective other exhaust gas flow with the substantially unloaded particulate filter. If the internal combustion engine is operated suddenly in a coasting operation after a high-load or full-load operation, in which both exhaust gas flows were opened, oxygen is conveyed into the strongly heated exhaust gas channel by the unburned internal combustion engine. This can lead to an uncontrolled burnup of the soot and thus damage to the particulate filter in the case of a loaded particulate filter. To avoid this, the exhaust gas flow is passed through the empty particulate filter in the second exhaust gas flow, and the first exhaust gas flow is blocked with the loaded particulate filter in order to protect the particulate filter in the first exhaust gas flow from thermal damage due to uncontrolled Rußabbrand.

In an alternative embodiment of the method, it is provided that after an operating phase in which the exhaust gas flow of the internal combustion engine is passed in parallel through both exhaust gas flows and both particle filters are loaded, a regeneration of the particulate filter takes place in succession, and the other particulate filter by a position of the control element or the adjusting elements is coupled out of the exhaust gas stream of the internal combustion engine. Sequential regeneration of the particulate filters ensures that at least one of the particulate filters is decoupled cold and out of the exhaust gas flow, so that it can be switched on at short notice as a component protection measure or to increase the flow cross section.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

• 1 ein erstes Ausführungsbeispiel einer erfindungsgemäßen Abgasnachbehandlungsanlage;
• 2 ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Abgasnachbehandlungsanlage mit einer zentralen Abgasklappe;
• 3 ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Abgasnachbehandlungsanlage, wobei an den einflutigen Abschnitt des Abgaskanals eine Einleitstelle für Sekundärluft vorgesehen ist;
• 4 ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Abgasnachbehandlungsanlage, wobei an den beiden Abgasfluten jeweils eine Einleitstelle für Sekundärluft vorgesehen ist;
• 5 ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Abgasnachbehandlungsanlage, wobei an beiden Abgasfluten jeweils eine Einleitstelle für Sekundärluft vorgesehen ist, welche aus einer gemeinsamen Sekundärluftquelle gespeist werden;
• 6 ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Abgasnachbehandlungsanlage, wobei an den beiden Abgasfluten jeweils eine Einleitstelle für Sekundärluft vorgesehen ist, jedoch nur eine Abgasflut eine Abgasklappe aufweist;
• 7 ein weiteres Ausführungsbeispiel einer erfindungsgemäßen Abgasnachbehandlungsanlage, wobei an den einflutigen Abschnitt des Abgaskanals eine Einleitstelle für Sekundärluft vorgesehen ist, jedoch nur eine Abgasflut eine Abgasklappe aufweist;
• 8 eine Beladung eines Partikelfilters in einem ersten Betriebszustand des Verbrennungsmotors;
• 9 eine parallele Beladung beider Partikelfilter in einem weiteren Betriebszustand des Verbrennungsmotors;
• 10 ein Steuerdiagramm zur Stellung der Abgasklappen in Abhängigkeit des Abgasgegendrucks und des Abgasvolumenstroms;
• 11 eine Regeneration des ersten Partikelfilters in einem zweiten Betriebszustand des Verbrennungsmotors;
• 12 eine Regeneration des ersten Partikelfilters in einem dritten Betriebszustand des Verbrennungsmotors; und
• 13 eine Unterbrechung der Regeneration des ersten Partikelfilters in einem vierten Betriebszustand des Verbrennungsmotors zum Bauteilschutz des beladenen Partikelfilters.

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

• 1 a first embodiment of an exhaust aftertreatment system according to the invention;
• 2 a further embodiment of an exhaust aftertreatment system according to the invention with a central exhaust flap;
• 3 a further embodiment of an exhaust aftertreatment system according to the invention, wherein at the einflutigen portion of the exhaust passage, a discharge point for secondary air is provided;
• 4 a further embodiment of an exhaust aftertreatment system according to the invention, wherein in each case a discharge point for secondary air is provided at the two exhaust gas flows;
• 5 a further embodiment of an exhaust aftertreatment system according to the invention, wherein in each case a discharge point for secondary air is provided at both exhaust gas flows, which are fed from a common secondary air source;
• 6 a further embodiment of an exhaust aftertreatment system according to the invention, wherein in each case a discharge point for secondary air is provided at the two exhaust gas flows, but only one exhaust gas flow has an exhaust gas flap;
• 7 a further embodiment of an exhaust aftertreatment system according to the invention, wherein at the einflutigen portion of the exhaust passage, a discharge point for secondary air is provided, but only an exhaust gas flow has an exhaust valve;
• 8th a loading of a particulate filter in a first operating state of the internal combustion engine;
• 9 a parallel loading of the two particulate filters in a further operating state of the internal combustion engine;
• 10 a control diagram for the position of the exhaust valves as a function of the exhaust back pressure and the exhaust gas flow rate;
• 11 a regeneration of the first particulate filter in a second operating state of the internal combustion engine;
• 12 a regeneration of the first particulate filter in a third operating state of the internal combustion engine; and
• 13 an interruption of the regeneration of the first particulate filter in a fourth operating state of the internal combustion engine for component protection of the loaded particulate filter.

1 shows an internal combustion engine 10 for a motor vehicle, preferably a combustion engine spark-ignited with spark plugs 10 according to the Otto principle, which with its outlet 14 with an exhaust aftertreatment system 12 connected is. The outlet 14 comprises an exhaust manifold, which the exhaust gases of the different combustion chambers of the internal combustion engine an exhaust passage 20 the exhaust aftertreatment system 12 supplies. The exhaust duct 20 is downstream of the outlet 14 executed in single-flow, wherein in the exhaust passage 20 close to the engine, a three-way catalyst 18 is arranged. The exhaust duct 20 shares downstream of the three-way catalyst 18 at a junction 36 in a first exhaust gas flow 22 and a second exhaust gas flow 24 , The area of the exhaust gas channel forms 20 from the outlet 14 to the junction 36 a first section 52 , and the area downstream of the branch 36 a second section 54 the exhaust duct 20 , In the first flood of the exhaust 22 is downstream of the junction 36 a first particle filter 26 and in the second exhaust gas flow 24 downstream of the junction 36 a second particle filter 28 arranged. In the first flood of the exhaust 22 is downstream of the first particulate filter 26 a first exhaust flap 32 is arranged, with which the first exhaust gas flow 22 can be locked. In the second exhaust gas flow 24 is downstream of the second particulate filter 28 a second exhaust flap 34 arranged, with which the second exhaust gas flow 24 can be locked. Alternatively, the exhaust valves 32 . 34 in the two exhaust fumes 22 . 24 also downstream of the junction 36 and upstream of the particulate filters 26 . 28 to be ordered. An arrangement downstream of the particulate filter 26 . 28 However, it has the advantage that the thermal load on the exhaust flaps 32 . 34 is reduced and, where appropriate, cheaper materials can be used, which have a lower temperature resistance.

In 2 is an alternative embodiment of an exhaust aftertreatment system according to the invention 12 shown. With essentially the same structure as 1 running, here is instead of the two exhaust flaps 32 . 34 a central actuator 30, preferably an exhaust flap 30 at the junction 36 arranged, with which the exhaust gas flow of the internal combustion engine 10 optionally in the first exhaust gas flow 22 , in the second exhaust gas flow 24 or in both exhaust fumes 22 . 24 can be initiated.

3 shows a further embodiment of an exhaust aftertreatment system according to the invention 12 , With essentially the same structure as 1 is executed in this embodiment, in addition, in the single-flow first section 52 the exhaust duct 20 downstream of the three-way catalyst 18 and upstream of the junction 36 a discharge point 46 provided for the introduction of secondary air. The secondary air is through a secondary air source 38 , preferably by a secondary air pump 40 , provided and at the discharge point 46 in the exhaust duct 20 initiated to heat up the particulate filter 26 . 28 to support a regeneration temperature and / or the oxidation of the in the particulate filters 26 . 28 retained soot particles necessary oxygen to provide.

In 4 is another embodiment of an exhaust aftertreatment system according to the invention 12 shown. With essentially the same structure as 3 are described in this embodiment instead of a discharge point 46 upstream of the junction 36 in every flood of exhaust 22 . 24 , downstream of the junction 36 and upstream of the respective particulate filter 26 . 28 a discharge point 48 . 50 for introducing secondary air into the respective exhaust gas flow 22 . 24 the exhaust duct 20 intended. In the process, the two discharge points become 48 . 50 via two secondary air pumps 42 . 44 independently supplied with secondary air.

In 5 is another embodiment of an exhaust aftertreatment system according to the invention 12 shown. With essentially the same structure as 4 executed, the two discharge points 48 . 50 in this embodiment, from a common secondary air source 38 , preferably a common secondary air pump 40 , fed.

In 6 is another embodiment of an exhaust aftertreatment system according to the invention 12 shown. With substantially the same expansion as too 4 executed, is in the first exhaust gas flow 22 downstream of the first particulate filter 26 no exhaust flap 32 arranged, but only an exhaust flap 34 in the second exhaust gas flow 24 downstream of the second particulate filter 28 , Alternatively, the second exhaust gas flow can also be used 24 be performed without exhaust valves and only one exhaust flap 32 in the first flood of the exhaust 22 downstream of the first particulate filter 26 be provided.

In 7 is another embodiment of an exhaust aftertreatment system according to the invention 12 shown. With essentially the same structure as 3 executed, is in the first exhaust gas flow 22 downstream of the first particulate filter 26 no exhaust flap 32 arranged, but only an exhaust flap 34 in the second exhaust gas flow 24 downstream of the second particulate filter 28 , Alternatively, the second exhaust gas flow can also be used 24 be performed without exhaust valves and only one exhaust flap 32 in the first flood of the exhaust 22 downstream of the first particulate filter 26 be provided.

Especially with high performance variants of internal combustion engines 10 With high exhaust gas mass flows, a particulate filter in a single-flow exhaust aftertreatment system 12 can lead to an increase in the exhaust backpressure. This becomes critical especially if the design of the cross section of the exhaust duct 20 and the diameter of the particulate filter are limited. By a division of the exhaust gas channel 20 on two exhaust fumes 22 . 24 downstream of a close-coupled three-way catalyst 18 each with one in Unterbodenlage a motor vehicle built particle filter 26 . 28 in each of the exhaust fumes 22 . 24 the exhaust back pressure can be significantly reduced. This results from two separate particle filters 26 . 28 in the two exhaust fumes 22 . 24 additional degrees of freedom in the regeneration of the particle filter 26 . 28 as well as with regard to component protection measures in order to prevent uncontrolled soot combustion on one of the particle filters 26, 28 and thus thermal damage. For example, a fired overrun operation of a loaded particulate filter 26 . 28 by a separate regeneration of the two particle filters 26 . 28 in the two exhaust fumes 22 . 24 be avoided if a corresponding component protection is required.

In 8th is a load of the first particulate filter 26 in the first flood of the exhaust 22 at a partial load operation of the internal combustion engine 10 shown. In the partial load, comparatively small exhaust gas mass flows occur, so that the complete exhaust gas flow is guided through the first exhaust gas flow 22 and through the first particle filter 26 can be cleaned without causing a large increase in the exhaust back pressure. With increasing loading of the first particle filter 26 Upon reaching a threshold value for the loading and / or the exhaust back pressure the exhaust valves 32 . 34 be made such that now the first exhaust gas flow (with the loaded first particulate filter 26 ) is locked and the second exhaust gas flow 24 with the still empty second particle filter 28 is opened. Thereby, the second particulate filter 28 in the second exhaust gas flow 24 after the first particle filter 26 loaded in the first exhaust gas flow, creating a rarer initiate a regeneration of the particulate filter than in a single-flow exhaust aftertreatment system 12 is possible without the exhaust back pressure rises inadmissible.

In 9 is the loading of the particle filters 26 . 28 in a high load or full load operation of the internal combustion engine 10 shown. These are the two exhaust valves 32 . 34 in the two exhaust fumes 22 . 24 opened, so that the exhaust gas of the internal combustion engine 10 parallel through the first exhaust gas flow 22 and the second exhaust tide 24 flows. As a result, the flow cross section in the exhaust passage 20 downstream of the junction 36 increased, whereby the exhaust backpressure can be reduced or increases only moderately despite full load. Both particle filters are used 26 . 28 loaded in parallel. Alternatively, the exhaust gas flow of the internal combustion engine 10 also by a central control at the junction 36 on the two exhaust fumes 22 . 24 be split.

In 10 is a control diagram for the position of the exhaust valves during the loading of the particulate filter 26 . 28 as a function of the exhaust backpressure and the exhaust gas volume flow of the internal combustion engine 10 shown. The exhaust gas volume flow V is on the abscissa and the exhaust back pressure p _G plotted on the ordinate. At low exhaust volumes is only the first exhaust gas flow 22 or the second exhaust gas flow 24 open and the other exhaust gas flow 22 , 24 through the corresponding exhaust flap 32 . 34 locked. The course of the exhaust backpressure with opened first exhaust gas flow 22 and closed second exhaust gas flow 24 is in the curve p ₁ shown. It can be seen in the curve section p ₁ * that the exhaust gas back pressure in the high load range with only one open exhaust gas flow 22 . 24 the maximum allowable exhaust back pressure p _max would exceed. Exceeds the exhaust back pressure p _G a threshold value p _s , then in addition the second exhaust valve 32 . 34 opened and the exhaust gas flow is distributed to both exhaust gas flows 22 . 24 the exhaust duct 20 , The exhaust back pressure at both open exhaust gas flows is in the curve p _{1 + 2} shown. This ensures that even when the nominal power is reached P _N in full load operation of the internal combustion engine 10 the exhaust back pressure p _G below the maximum allowable backpressure p _max remains. In principle, over the entire characteristic map of the internal combustion engine 10 during the loading phase of the particulate filter 26 . 28 with two open exhaust flaps 32 34 are driven. Then both particle filters 26 . 28 almost equal to the soot particles of the internal combustion engine 10 loaded. Alternatively, in particular during a cold start of the internal combustion engine 10 , one of the two exhaust flaps 32 . 34 be closed and the entire exhaust stream of the engine 10 over only one of the exhaust fumes 22 . 24 be guided. This will only one of the particulate filters 26 . 28 loaded with the soot particles emitted during the cold start. The other particle filter 26 . 28 in the closed exhaust 22 . 24 remains essentially unladen. This results in the advantage that in a partial load regeneration phase, the entire exhaust gas mass flow over the loaded particulate filter 22 . 24 is guided and thus by the high heat flow a very fast and effective regeneration of the particulate filter 26 . 28 is possible. In addition, there is the possibility of an effective component protection measure of the loaded particulate filter 26, by in critical phases of engine operation, the exhaust gas of the internal combustion engine 10 over the unloaded particle filter 28 is directed.

In the 11 to 13 is a load-dependent flap circuit of the exhaust valves 32 . 34 during the regeneration of the particulate filter 26 . 28 shown. It is in a first Flap position of the exhaust flaps 32 . 34 the first exhaust gas flow 22 opened and the second exhaust gas flow 24 closed. In a second flap position of the exhaust valves 32 . 34 are both exhaust flaps 32 . 34 and thus both exhaust gas flows 22 . 24 open. In a third flap position of the exhaust valves 32 . 34 is the first exhaust gas flow 22 closed and the second exhaust gas flow 24 open. Was just a particle filter 26 . 28 laden, for example, the first particle filter 26 in the first flood of the exhaust 22 so this one, as in 11 shown in a partial load operation of the internal combustion engine 10 be regenerated in the first flap position. Will during the regeneration in a higher load point of the internal combustion engine 10 changed, which is to exceed the maximum allowable exhaust back pressure p _max would lead, as in 12 shown in the second flap position of the exhaust valves 32, 34 switched. Is a component protection of the first particle filter 26 necessary, for example, at high temperatures in the exhaust duct 20 and a coasting phase of the internal combustion engine 10 at the same time high particle loading of the first particulate filter 26 , so will, as in 13 shown, in the third flap position of the exhaust valves 32 . 34 switched and the exhaust gas flow through the unloaded second particulate filter 28 in the second exhaust gas flow 24 directed.

Have been in the loading phase, the particulate filter 26 . 28 loaded, these can either successively in the first and third flap position of the exhaust flaps 32 . 34 or simultaneously in the second flap position of the exhaust valves 32 . 34 be regenerated. Part protection of the particle filters 26 . 28 is only possible in the first and in the third flap position, since in the second flap position both particle filters 26 . 28 are heated. For this reason, a sequential regeneration of the particulate filter 26 . 28 compared to a parallel regeneration of both particle filters 26 . 28 prefers. When changing to a higher engine load of the internal combustion engine 10 but also has to be in a sequential regeneration of the two particulate filter 26 . 28 in the second flap position of the exhaust valves 32, 34 are switched to the exhaust back pressure p _G not above the maximum permissible exhaust back pressure p _max to rise. In this case, additional measures for component protection, such as a prohibition of overrun operation, may be taken to prevent uncontrolled soot burn-off on one of the particulate filters 26 . 28 due to high temperatures and high oxygen concentrations in the exhaust gas channel 20 to avoid.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

aftertreatment system

14

outlet

16

exhaust manifold

18

Three-way catalytic converter

20

exhaust duct

22

first exhaust gas flow

24

second exhaust gas flow

26

first particle filter

28

second particle filter

30

Control element / exhaust flap

32

first exhaust flap

34

second exhaust flap

36

branch

38

Secondary air source

40

Secondary air pump

42

first secondary air pump

44

second secondary air pump

46

inlet point

48

first discharge point

50

second discharge point

52

first section

54

second part

p _G

Exhaust backpressure

p _max

maximum permissible exhaust gas back pressure

p _s

Threshold of exhaust back pressure

p ₁

Exhaust back pressure with open first exhaust gas flow

p _{1 + 2}

Exhaust back pressure at both open exhaust gas flows

P _N

Rated power of the internal combustion engine

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10241898 A1 [0003]
• DE 102008063809 A1 [0004]

Claims (15)

Exhaust gas aftertreatment system (12) for an internal combustion engine (10), wherein an exhaust passage (20) downstream of an outlet (14) of the internal combustion engine (10) has a first section (52) in which the exhaust passage (20) is designed to be single inlet and in which Three-way catalyst (18) is arranged, characterized in that the exhaust passage (20) downstream of the three-way catalyst (18) has a second portion (54), at which the single-flow exhaust duct (20) at a branch (36) into a first exhaust gas flow (22) and a second exhaust gas flow (24), wherein in the first exhaust gas flow (22) a first particulate filter (26) and in the second exhaust gas flow (24) a second particulate filter (28) is arranged. Exhaust after-treatment system (12) according to Claim 1 , characterized in that in the exhaust passage (20) downstream of the three-way catalyst (18) at least one adjusting element (30, 32, 34) is arranged, with which an exhaust gas flow of the internal combustion engine (10) substantially through the first exhaust gas flow (22 ), through the second exhaust gas flow (24) or through both exhaust gas passages (22, 24) can be passed. Exhaust after-treatment system (12) according to Claim 2 , characterized in that the adjusting element (30) is arranged at the branch (36). Exhaust after-treatment system (12) according to Claim 2 , characterized in that in the first exhaust gas flow (22) a first exhaust valve (32) and in the second exhaust gas flow (24) a second exhaust valve (34) is arranged, with which the respective exhaust gas flows (22, 24) can be disabled or released , Exhaust after-treatment system (12) according to one of Claims 1 to 4 , characterized in that downstream of the three-way catalyst (18) at least one introduction point (46, 48, 50) for introducing secondary air into the exhaust gas passage (20) is provided. Exhaust after-treatment system (12) according to Claim 5 , characterized in that the introduction point (46) in the single-flow section of the exhaust passage (20) upstream of the branch (36). Exhaust after-treatment system (12) according to Claim 5 , characterized in that in each of the exhaust gas flows (22, 24) downstream of the branch (36) and upstream of the respective particulate filter (26, 28) a discharge point (48, 50) for introducing secondary air into the exhaust passage (20) is provided. Exhaust after-treatment system (12) according to Claim 7 , characterized in that the inlet points (48, 50) in the different exhaust gas flows (22, 24) via a common secondary air source (38) are supplied. A method for loading and / or regeneration of at least two particulate filters (26, 28) in an exhaust aftertreatment system (12) of an internal combustion engine (10), in which downstream of an outlet (14) of the internal combustion engine (10) of the exhaust passage (20) is designed to be single-flow and the exhaust gas of the internal combustion engine (10) is passed through a three-way catalytic converter (18), characterized in that the exhaust gas duct (20) downstream of the three-way catalytic converter (18) branches off into a first exhaust gas flow (22). and a second exhaust gas flow (24), wherein in each of the two exhaust gas flows (22, 24) each have a particle filter (26, 28) is arranged, and wherein in a normal operation of the internal combustion engine (10) at least one of the particulate filters (26, 28) is loaded with the resulting during combustion in the internal combustion engine (10) soot particles. Method according to Claim 9 , characterized in that the exhaust gas flow through the particulate filters (26, 28) is controlled by at least one control element (30) in the exhaust system downstream of the three-way catalytic converter (18). Method according to Claim 10 , characterized in that in a first operating state of the internal combustion engine (10), in particular in a partial load operation of the internal combustion engine (10), one of the exhaust gas flows (22, 24) is open and the respective other exhaust gas flow (22, 24) is closed. Method according to one of Claims 9 to 11 , characterized in that in a second operating state, in particular in a regeneration of the particulate filter (26, 28), the exhaust gas flow (22, 24) with the more heavily loaded particulate filter (26, 28) is open, and the respective other exhaust gas flow (22, 24 ) is closed with the less heavily loaded particulate filter (26, 28). Method according to Claim 12 , characterized in that the exhaust gas flow (22, 24) is opened with the less heavily loaded particulate filter (26, 28) when the combustion engine (10) is operated in a third operating condition with a higher load than in the second operation condition, and the power of the internal combustion engine (10) or the exhaust back pressure in the exhaust gas flow (22, 24) with the more heavily loaded particulate filter (26, 28) exceeds a threshold value (S _P , S _D ). Method according to one of Claims 12 or 13 , characterized in that in a fourth Operating state, in particular in a coasting phase of the internal combustion engine (10) at high particulate filter temperatures of the more heavily laden particulate filter (26, 28), the exhaust gas flow (22, 24) with the more heavily loaded particulate filter (22, 24) is closed and the exhaust gas flow over the other exhaust gas flow with the substantially unloaded particulate filter (26, 28) is passed. Method according to Claim 10 , characterized in that after an operating phase in which the exhaust gas flow of the internal combustion engine (10) is passed in parallel through both exhaust gas flows (22, 24) and both particulate filters (26, 28) are loaded with soot particles regeneration of the particulate filter (26, 28) time sequentially, and the other particulate filter (26, 28) by a position of the adjusting element (30) or the adjusting elements (32, 34) is coupled out of the exhaust gas stream of the internal combustion engine (10).

Images