DE102016120432B4 - Exhaust system and associated method of operating the exhaust system to protect a gasoline particulate filter - Google Patents

Abstract

Method for protecting a particle filter (20) in a main exhaust line (a) of an exhaust system (100) of an Otto internal combustion engine (M) during an overrun phase (II; Δt) occurring during operation of the internal combustion engine (M), in which the internal combustion engine ( M) is operated without fuel and the particulate filter (20) is subjected to a fresh air mass flow (ṁF), so that the exhaust gas mass flow (ṁM) is subjected to an increase in the oxygen concentration, with the particulate filter (20) being subjected to the fresh air mass flow (ṁF ) is prevented during the overrun phase (II; Δt) by the fresh air mass flow (ṁF) during the overrun phase (II; Δt) being routed around the particle filter (20) via a bypass circuit within the exhaust system (100), whereby the Particulate filter (20) in the overrun phase (II; Δt) due to the redirection of the fresh air mass flow (ṁF) via a bypass line (b) of the bypass circuit, no oxygen is available, the bypass line (b) being the bypass - Circuit activated depending on a critical component temperature of the particle filter (20) and depending on a loading value of the particle filter (20) and the fresh air mass flow (ṁF) in the main exhaust line (a) during the overrun phase (II; Δt) around the particle filter (20) into the bypass line (b), characterized in that the fresh air mass flow (ṁF) is diverted during the overrun phase (II; Δt) only when the particle filter ( 20) has a critical component temperature that is too high and a critical load value that is too high at the same time.

Description

The invention relates to an exhaust system and an associated method for protecting a particle filter in a main exhaust system of the exhaust system of an internal combustion engine.

The pamphlet DE 101 30 633 B4 discloses a method for regenerating a diesel particle filter, in which the diesel particle filter is arranged in combination with an oxidation catalytic converter (CRT) in the exhaust gas flow of an internal combustion engine, with the oxidation of the soot particles taking place with the NO ₂ formed in the oxidation catalytic converter. Provision is made for the particle filter to be regenerated continuously. A soot balance is continuously created, with the soot balance being set negative again in the event of a positive development of the soot balance as a result of measures on the internal combustion engine and/or countermeasures on the diesel particle filter. The publication describes in detail the procedure for creating the soot balance. The filter temperature is a significant influencing factor for the maximum achievable conversion on the particle filter, the so-called soot burn-off. The filter temperature is determined by the exhaust gas temperature and the mass flow rate through the particle filter as well as the heat dissipation on the surface of the system and the energy supply through external sources (heating). The method provides that cooling of the diesel particle filter is prevented in certain operating phases (overrun, idling, low load) if the exhaust gas temperature of the exhaust gas flow is lower than the component temperature of the diesel particle filter in the phases mentioned.

In the pamphlet DE 10 2010 039 013 A1 a method is described which uses a lambda measurement upstream and downstream of an Otto particle filter (OPF) to determine oxygen consumption and thus the soot conversion and the resulting thermal load on the Otto particle filter. If a thermal load that is too high is detected, the soot conversion is stopped by switching to sub-stoichiometric operation. In the method mentioned, it is also described that the particle filter is at risk from locally high temperature gradients, which can occur, for example, as a result of too rapid regeneration with a high soot load and high temperatures at the same time. Critical states of this kind are reached above all in the case of already controlled active regeneration and a sudden significant increase in the oxygen concentration. For this reason, it is advantageous if fuel cut-off is prevented during the controlled, active regeneration phase.

There are also the pamphlets US 2003/0 196 429 A1 and DE 10 2009 015 900 A1 as well as DE 11 2009 000 112 B4 , DE 100 05 623 A1 and DE 11 2009 000 235 T5 called.

The object of the invention is to provide an exhaust system and a method for operating an Otto particle filter which prevents critical states of the Otto particle filter during an overrun phase occurring during operation of the internal combustion engine.

The starting point of the invention is a method for protecting a particle filter in a main exhaust system of an exhaust system of an Otto internal combustion engine during an overrun phase occurring during operation of the internal combustion engine, in which the internal combustion engine is operated without fuel and the particle filter is subjected to a fresh air mass flow, so that an increase in the oxygen concentration occurs in the exhaust gas mass flow, the loading of the particle filter with the fresh air mass flow during the overrun phase being prevented by the fresh air mass flow being routed around the particle filter via a bypass circuit within the exhaust system during the overrun phase, whereby the particle filter in no oxygen is available during the overrun phase due to the redirection of the fresh air mass flow via a bypass line of the bypass circuit, with the bypass line activating the bypass circuit depending on a critical component temperature of the particle filter and depending on a load value of the particle filter and the Fresh air mass flow in the main exhaust line is routed around the particle filter into the bypass line during the overrun phase.

Provision is made for the fresh air mass flow to be diverted during the overrun phase only if the particle filter has a critical component temperature that is too high and a critical loading value that is too high at the same time.

The method advantageously prevents the introduction of oxygen into the particle filter and allows the overrun cut-off function to be maintained without injecting fuel, so that no unexpected vehicle behavior occurs when fuel is injected in the overrun phase, since when the method is carried out, the oxygen-consuming Injection can be deactivated in overrun.

The method can be carried out with different exhaust system configurations, as explained in more detail in the detailed description.

The method is preferably further characterized in that the bypass branch is opened at a first point in time at the end of a phase of operation of the internal combustion engine with a positive load requirement on the internal combustion engine and the start of the overrun phase, while the overrun phase is open for a period of time, and is closed again at a second point in time when the overrun phase ends. This procedure is activated either in each overrun phase or, as explained above, as a function of a critical component temperature of the particulate filter and as a function of a loading value of the gasoline particulate filter.

The method can be carried out with an exhaust system for protecting a particle filter in a main exhaust line of the exhaust system of an internal combustion engine, the exhaust system being characterized in that it has a bypass circuit with a switching element with which a bypass line can be activated, so that the fresh air mass flow of the main exhaust line is routed around the particle filter into the bypass line, with the particle filter not having any oxygen available in the overrun phase due to the redirection of the fresh air mass flow via the bypass line of the bypass circuit, with the The bypass line of the bypass circuit is activated depending on a critical component temperature of the particle filter and depending on a load value of the particle filter and the fresh air mass flow in the main exhaust line is routed around the particle filter into the bypass line during the overrun phase, and the diversion of the Fresh air mass flow is only carried out during the overrun phase if the particle filter has too high a critical component temperature and a too high critical loading value at a coincidence in time.

In a preferred embodiment, the switching element can be brought into a first switching position by means of a switching mechanism, in which the main exhaust line is open and the bypass line is closed, and into a second switching position, in which the main exhaust line is closed and the bypass line is open .

Provision is made for the switching element to be arranged at the inlet of the bypass line in the main exhaust line of the particulate filter, with the bypass line branching off from a first main exhaust sub-line of the main exhaust line and bypassing a second main exhaust sub-line of the main exhaust line, in which the Otto particle filter is located. In this exhaust system configuration, the exhaust system has only the particle filter, such as in FIG 7 is shown.

In other exhaust system configurations, it is provided that viewed in the flow direction of the exhaust gas, at least one three-way catalytic converter is arranged in the first main partial exhaust line and the particle filter is arranged in the second main partial exhaust line, such as in 3 and 5 is shown.

A further exhaust system configuration is characterized in that viewed in the direction of flow of the exhaust gas, a first three-way catalytic converter is arranged in the first main partial exhaust line and a second further three-way catalytic converter and the particle filter are arranged in the second main partial exhaust line, as in FIG 6 is made clear.

But it is also in a preferred embodiment of the invention according to 9 and 10 It is possible for the particle filter and the three-way catalytic converter, or vice versa, to be arranged in the second main partial exhaust line, viewed in the direction of flow of the exhaust gas.

In addition, a further exhaust system configuration is provided such that several three-way catalytic converters and the particle filter are arranged in the second main partial exhaust line, as seen in the direction of flow, as in FIG 11 is shown.

Finally, according to the 8th Another preferred system configuration is proposed, which is characterized in that in the second main partial exhaust line, seen in the flow direction of the exhaust gas, the particle filter and in a subsequent third main partial exhaust line behind the junction of the bypass line with the main exhaust line at the end of the second Main exhaust branch at least one three-way catalytic converter are arranged.

In a preferred embodiment of the exhaust system according to the invention, it is set up to carry out the method according to the invention for protecting the particle filter. For this purpose, the exhaust system includes, in particular, a control device in which a computer-readable program algorithm for executing the method and any necessary characteristic diagrams are stored.

• 1A ein v/t-Diagramm nach dem Stand der Technik zur Verdeutlichung des unterschiedlichen Geschwindigkeitsverhaltens eines Fahrzeuges jeweils ausgehend von einem Fahrverhalten eines Fahrers des Fahrzeuges mit einer positiven Lastanforderung im Übergang zu einem Schubabschalten entweder mit gleichzeitiger Einspritzung von Kraftstoff oder ohne Einspritzung von Kraftstoff;
• 1B eine Abgasanlage nach dem Stand der Technik;
• 2 in einer oberen Abbildung ein λ/t-Diagramm, in einer mittleren Abbildung ein T_vorOPF/t-Diagramm und in einer unteren Abbildung ein ṁ_OPF/t-Diagramm zur Verdeutlichung der Lambda-Werte λ über der Zeit t, der Temperatur vor einem Otto-Partikelfilter über der Zeit und des durch den Otto-Partikelfilter strömenden Massenstroms ṁ_OPF über der Zeit t einer erfindungsgemäßen Abgasanlage und des zugehörigen Verfahrens im Vergleich zu einer Abgasanlage gemäß 1B und dem Verfahren nach dem Stand der Technik;
• 3 die erfindungsgemäße Abgasanlage in einer ersten Ausführungsvariante gemäß der Erfindung;
• 4 die erfindungsgemäße Abgasanlage in der ersten Ausführungsvariante gemäß 3 in einer oberen Abbildung zum Zeitpunkt einer positiven Lastanforderung, in einer mittleren Abbildung im Übergang zu dem ohne Kraftstoffeinspritzung durchgeführten Schubabschalten und in einer unteren Abbildung im Übergang zu einer erneuten positiven Lastanforderung;
• 5 eine erfindungsgemäße Abgasanlage in einer zweiten Ausführungsvariante;
• 6 eine erfindungsgemäße Abgasanlage in einer dritten Ausführungsvariante;
• 7 eine erfindungsgemäße Abgasanlage in einer vierten Ausführungsvariante;
• 8 eine erfindungsgemäße Abgasanlage in einer fünften Ausführungsvariante;
• 9 eine erfindungsgemäße Abgasanlage in einer sechsten Ausführungsvariante;
• 10 eine erfindungsgemäße Abgasanlage in einer siebenten Ausführungsvariante;
• 11 eine erfindungsgemäße Abgasanlage in einer achten Ausführungsvariante.

The invention is explained in more detail below with reference to the associated drawings. Show it:

• 1A a v / t diagram according to the prior art to illustrate the different speed behavior of a vehicle, each starting from a driving behavior of a driver of the vehicle with a positive load requirement in the transition to an overrun cut either at the same time tiger injection of fuel or without injection of fuel;
• 1B a prior art exhaust system;
• 2 a λ/t diagram in an upper figure, a T _vorOPF /t diagram in a middle figure and a ṁ _OPF /t diagram in a lower figure to illustrate the lambda values λ over time t, the temperature in front of a Otto particle filter over time and the mass flow ṁ _OPF flowing through the Otto particle filter over time t of an exhaust system according to the invention and the associated method in comparison to an exhaust system according to 1B and the prior art method;
• 3 the exhaust system according to the invention in a first embodiment according to the invention;
• 4 the exhaust system according to the invention in the first embodiment 3 in an upper figure at the time of a positive load request, in a middle figure in the transition to the overrun cut-off carried out without fuel injection and in a lower figure in the transition to a renewed positive load request;
• 5 an exhaust system according to the invention in a second embodiment;
• 6 an exhaust system according to the invention in a third embodiment;
• 7 an exhaust system according to the invention in a fourth embodiment;
• 8th an exhaust system according to the invention in a fifth embodiment;
• 9 an exhaust system according to the invention in a sixth embodiment;
• 10 an exhaust system according to the invention in a seventh variant;
• 11 an exhaust system according to the invention in an eighth variant.

Future emissions legislation places high demands on engine raw emissions and on the exhaust aftertreatment of internal combustion engines (Otto engines) operated with Otto fuel.

With the introduction of the Euro 6 standard, a particle number (PN) limit value is prescribed. Under certain circumstances, this means that the use of an Otto particle filter (OPF) is necessary in some vehicles.

When driving, a petrol particle filter can become loaded with petrol soot. So that the exhaust back pressure level does not increase too much, it must be regenerated continuously or periodically. In order to carry out a thermal oxidation with oxygen, a sufficient temperature level is necessary with the simultaneous presence of residual oxygen in the exhaust gas.

When the vehicle is in operation, however, loading conditions also occur in which an uncontrolled flow of oxygen through the particle filter is not desired. If the loading level of the Otto particle filter reaches a critical level, an overrun phase showing an excess of oxygen, for example, together with a high temperature of the Otto particle filter, can lead to uncontrolled soot conversion. The exothermic oxidation of the carbon results in high temperatures in the Otto particle filter, which can damage it. Therefore, the inventive idea of the present invention consists in preventing the entry of oxygen into the Otto particle filter in critical situations, in particular when an overrun is switched off.

The method previously provided for limiting the oxygen input in Otto particle filters with high loading quantities and sufficiently high temperatures for uncontrolled regeneration is to prevent overrun cut-off.

In a motorized vehicle, overrun is the driving condition in which the engine is dragged through the vehicle, i.e. kept rotating, if the traction is not disconnected (e.g. if the clutch is not pressed).

In the case of overrun cut-off within the meaning of the present invention, the fuel supply is interrupted during overrun operation. In phases in which no torque is required from the engine, it goes into overdrive. Here, the engine is dragged by the rolling vehicle. In this case, the so-called overrun cut-off, the injection of fuel is prevented by an engine control unit that is part of the exhaust system. As a result, the engine pumps the intake air through the exhaust system and the oxygen content in the exhaust system thus rises to the level of the fresh air.

If this is not desired, for example, when the filter is critically loaded, this overrun cut-off can be prevented by what is known as “fired overrun”. Then, due to the uninterrupted supply of fuel, even during the overrun phase, the intake air in the engine is throttled at an air ratio of lambda = 1 implemented with fuel. This means that no excess oxygen gets into the exhaust system and uncontrolled soot conversion in the filter can be effectively prevented. The disadvantage of this method is that 1 illustrated changed engine behavior. Due to the continued combustion in the overrun phase, the engine braking torque is significantly lower than in unfired overrun and the vehicle decelerates less. Disadvantageously, this represents unexpected vehicle behavior for the driver, and fuel consumption also disadvantageously increases, since combustion continues even during overrun.

In the 1A a diagram is shown with the speed v on the ordinate and the time t on the abscissa.

A first graph G1 (continuous line) and a second graph G2 (dash-dotted line) are shown in three successive phases I, II, III.

The first graph G1 is associated with the (unfired) overrun cut-off without fuel supply during the overrun phase, while the second graph is associated with the fired overrun with fuel supply during the overrun phase.

Phase I corresponds to normal driving with a positive load request from the driver, in which the exhaust gas is passed through the exhaust gas aftertreatment components (cf 1B) a conventional exhaust system 1 in an exhaust line a, in particular through a close-coupled three-way catalytic converter 10, and an Otto particle filter 20 is passed. The Otto engine as an internal combustion engine is marked with the reference symbol M.

At the end of the first phase according to 1A at the first point in time t ₁ no load is requested by the driver.

The second phase II follows, in which, according to graph G2, the engine braking torque is significantly lower due to the continued combustion in the fired overrun than in the case of unfired overrun cut-off according to graph G1, so that the vehicle decelerates less in phase II than at the higher speed v ₂ > v ₁ (v ₂ greater than v ₁ ) of the graph G2 compared to the graph G1 becomes clear. As already mentioned, this effect of the lower deceleration of the vehicle in phase II disadvantageously represents an unexpected vehicle behavior for the driver.

In phase III from the second point in time t2, the driver switches to normal driving with a new load request.

The idea according to the invention is to prevent the entry of oxygen into the Otto particle filter 20, whereby the function of the (unfired) overrun cut-off can be maintained, so that the unexpected vehicle behavior described does not occur, so that the fired overrun according to the graph G2 in 1A activated injection can be deactivated.

In other words, the inventively provided diversion of the fresh air mass flow ṁ _F present during the unfired overrun fuel cut-off via a bypass line b avoids the effect perceived as negative by the driver and at the same time the Otto particle filter 20 is effectively protected against damage that occurs during of the unfired overrun cut-off with a significant increase in the oxygen concentration in the exhaust gas mass flow ṁ, as shown below using the 2 until 11 explained in detail in a synopsis.

An exhaust system configuration 100 preferred according to the invention is shown in FIG 3 a close-coupled three-way catalytic converter 10 and an Otto particle filter 20 in a position remote from the engine. The Otto particle filter 20 can optionally be designed with or without an active catalytic three-way coating. This applies to all embodiment variants that are described and not described in this patent application. According to the invention, provision is made for a bypass line b to be assigned to the Otto particle filter 20 arranged in the exhaust line a, as in a first preferred embodiment variant in FIG 3 is shown. The exhaust line a is referred to below as the main exhaust line a.

The three-way catalytic converter 10 is arranged in a first main exhaust gas branch a1 close to the engine and the Otto particle filter 20 is arranged in a second main exhaust gas branch a2 remote from the engine, the outlet of the bypass branch b marking the start of the second main Exhaust sub-branch a2 and the beginning of the bypass line b marked.

Viewed in the direction of flow, the bypass line b finally opens into the main exhaust line a, bypassing the Otto particle filter 20, and marks the end of the second main exhaust line a2 and the beginning of a third main line in the access to the main exhaust line a. Partial exhaust line a3 and the end of the bypass line b.

According to the invention, it is provided that the bypass branch b can be switched, ie it can be switched on and off. About the bypass line b, the fresh air mass flow ṁ _F of the engine M to the Otto particle filter 20 are redirected, whereby an inventive method is created, which based on the synopsis of 2 and 4 is explained.

To switch the bypass line b, a switching element 12 with a switching mechanism is arranged at the input of the bypass line b, which is designed, for example, as a flap.

The switching element 12 can assume a first switching position 12a, in which the main exhaust line a is open and the bypass line b is closed, see 4 top and bottom figure.

The switching element 12 can assume a second switching position 12b, in which the main exhaust line a is closed from the outlet of the bypass line b and the bypass line a is open, compare 4 middle figure. The second and third main exhaust gas sections a2, a3 are thus separated from the first main exhaust gas sections a1 on the flow side.

The 2 shows another diagram in the top figure, in which lambda λ is plotted on the ordinate and time t is plotted on the abscissa. Graphs G1 and G2 show the lambda values in phases I, II, III, which correspond to the previous explanations in relation to the speed/time behavior in the unfired overrun phase (graph G1) and the fired overrun phase (graph G2). 1A are equivalent to.

The 2 shows another diagram in the center figure, in which a temperature T _vorOPF in front of the Otto particle filter 20 is plotted on the ordinate and the time t is plotted on the abscissa. The graphs G1 and G2 show the temperature values T _vorOPF in phases I, II, III, which correspond to the previous explanations in relation to the speed/time behavior in the unfired overrun phase (graph G1) and the fired overrun phase (graph G2). 1A are equivalent to.

The 2 shows a further diagram in the figure below, in which a mass flow ṁ _OPF flowing through the Otto particle filter 20 is plotted on the ordinate and the time t is plotted on the abscissa. The graphs G1 and G2 show the values of the mass flow ṁ _OPF over the Otto particle filter 20 in phases I, II, III, which correspond to the previous explanations in relation to the speed/time behavior in the unfired overrun phase (Graph G1) and the fired overrun phase (Graph G2) according to 1A are equivalent to.

The illustrations in the 2 each show a third graph G3 (dotted line), which shows the lambda values λ, the temperature values T _{in front of OPF} and the values of the mass flow ṁ _OPF flowing through the Otto particle filter 20 in phases I, II, III.

It is made by comparing the graphs in the illustrations of the 2 clearly that the graphs G1 and G2 differ from the graph G3, especially in the overrun phase II; Δt, differ from each other, as follows in a synopsis with the 3 and 4 is explained.

In phase I of the illustrations of the 2 is again analogous to the 1A , 1B the normal operation with a positive load request by the driver is shown, in which the exhaust gas mass flow ṁ _M of the exhaust gas through the main exhaust line a via the close-coupled three-way catalytic converter 10 and as an exhaust gas mass flow ṁ _M; ṁ _OPF is passed through the Otto particle filter 20. The exhaust gas is converted in the three-way catalytic converter 10 and the Otto soot particles are separated in the Otto particle filter 20 .

If the Otto particle filter 20 reaches a load value that is above a limit load to be defined, which is only 3g/l, for example, the conventional procedure can be used if the exhaust gas temperature is sufficient, at which soot burn-off takes place as desired, in the subsequent unfired thrust phase II; At the Otto particle filter 20 are damaged due to an excessively high temperature for the Otto particle filter 20, which is caused by the uncontrolled exothermic reaction of the soot burn-off.

In order to prevent this undesired critical state, according to the graph G3 in the illustrations of 2 according to the invention at a critical component temperature of the Otto particle filter 20 and a loading value of the Otto particle filter 20 as well as an overrun phase II requested during driving; .DELTA.t activated during the unfired overrun cut-off of the bypass line b, that is opened. The switching element 12 is switched over from the first switching position 12a to the second switching position 12b (cf 4 , middle figure).

The component temperature of the Otto particle filter 20 is determined via sensors (not shown) or via an exhaust gas temperature model.

The load value is determined via a differential pressure measurement across the Otto particle filter 20 or a load model.

To open the bypass line b, the switching element 12 is thus via the actuating mechanism brought into the switching position 12b, see 4 , middle figure.

This achieves the effect that oxygen-rich exhaust gas is routed around Otto particle filter 20 during unfired overrun fuel cut-off II.

According to the invention, the diameter of the bypass line b is designed to be significantly smaller than the main exhaust line a, since the fresh air mass flow ṁ _F of the engine M is significantly lower in the case of an unfired overrun fuel cutoff II. The small dimensioning of the bypass line b is in the 3 until 11 however not shown.

Out of 2 The upper figure makes it clear that the desired stoichiometric air ratio (λ=1) for combustion in the Otto particle filter 20, represented by the lambda values λ over time t according to graph G3 in the upper figure 2 also in the unfired thrust phase II; Δt is retained, which reliably prevents unwanted oxidation of the soot. In other words, in phase II, during the unfired overrun cut-off, the unwanted lambda value λ = ∞, which indicates an excess of oxygen, according to graph G1 in the upper figure in 2 avoided.

In order to avoid the oxygen excess, it is therefore not necessary according to the invention to use a fired thrust according to graph G2 in the upper figure in 2 to be selected, since this mode of operation has the disadvantage described in the introduction.

At the end of push phase II; Δt, as soon as the driver switches to normal driving with a new load request, the bypass line b is brought back into the switching position 12a via the switching element 12 by means of the actuating mechanism, so that the bypass line b following the unfired overrun phase II; Δt is closed again at the second point in time t ₂ in phase III. The switching element 12 is switched over from the second switching position 12b to the first switching position 12a (cf 4 , lower figure).

Out of 2 The middle figure makes it clear that, compared to phase I in phase II, the temperature T in front of _OPF , which normally decreases in unfired overrun cutoff according to graph G1, in front of the Otto particle filter 20 remains almost constant due to the opening of the bypass line b. As a result, no negative effects are generated for the operation of the Otto particle filter 20 .

The driving style of the Otto particle filter 20 with a constant temperature T _{in front of OPF} represents an advantage of the invention, because by the in the overrun phase II; At the fresh air mass flow ṁ _F conveyed into the Otto particle filter 20 (without switching to the bypass line b), the Otto particle filter 20 is greatly cooled. This can be prevented by opening the bypass line b using the bypass circuit. This makes subsequent controlled active regeneration easier, since minimum temperatures of -550°C are required for the soot burn-off. A further advantage is that, particularly in the case of coated Otto particle filters 20, the temperature does not fall below the light-off temperature at which an Otto particle filter 20 has the necessary temperature for its efficient function, so that conversion is still possible.

Out of 2 , the lower figure makes it clear that the fresh air mass flow ṁ _F ; ṁ _OPF in phase II through the open bypass line b (cf 4 , middle figure) according to the graph G3 equals zero (ṁ _OPF = 0). In other words, the procedure according to the invention and the design of the exhaust system 100 according to the invention avoid both the disadvantages of unfired overrun cutoff and of fired overrun according to graphs G1 and G2.

Below are in the 5 until 11 additionally described and shown variants of other possible exhaust gas aftertreatment components.

The selection of the design variants is determined in particular by the available installation space and/or by exhaust gas legislation. The exhaust gas legislation specifies the selection and/or the number of the converting components to be used. The respective arrangement of the selected components in the appropriate number is determined according to the available installation space.

5 shows an exhaust system 100 according to the invention in a second embodiment. In contrast to the exhaust system 100 as shown in FIG 3 Two three-way catalytic converters 10A, 10B are arranged in the first main exhaust gas branch a1 close to the engine. Analogously to the first embodiment variant, an Otto particle filter 20 is arranged in the second main exhaust gas branch a2.

6 shows an exhaust system 100 according to the invention in a third embodiment. In contrast to the exhaust system 100 as shown in FIG 3 and description of the first embodiment variant, a first three-way Catalyst 10A and in the second main exhaust branch a2 a second three-way catalyst 10B arranged together with the Otto particle filter 20.

7 shows an exhaust system 100 according to the invention in a fourth embodiment. In contrast to the exhaust system 100 as shown in FIG 3 and description of the first embodiment variant, a three-way catalytic converter is dispensed with in the first main exhaust gas sub-branch a1 close to the engine. In the second main exhaust gas branch line a2, analogously to the first embodiment variant, an Otto particle filter 20 is arranged, which is arranged closer to the engine than in the first embodiment variant.

8th shows an exhaust system 100 according to the invention in a fifth embodiment, which is analogous to the fourth embodiment according to FIG 7 in the second main exhaust branch a2 has an Otto particle filter 20, which compared to the variants according to the 3 , 5 , 6 is arranged closer to the engine. In this fifth embodiment variant, a three-way catalytic converter 10 is arranged in the third main partial exhaust line a3, remote from the engine behind the junction of the bypass line b in the main exhaust line a. The arrangement of the Otto particle filter 20 close to the engine results in a higher temperature level of the Otto particle filter 20 during operation, as a result of which the controlled active regeneration is facilitated.

9 shows an exhaust system 100 according to the invention in a sixth embodiment. In contrast to the exhaust system 100 as shown in FIG 8th and description of the fifth embodiment variant, an Otto particle filter 20 and a three-way catalytic converter 10 are arranged one behind the other in the same way as in the fifth embodiment variant, viewed in the direction of flow, but in contrast to the fifth embodiment variant, they are both in the second main exhaust gas branch line a2 parallel to the bypass -Strand b are arranged.

10 shows an exhaust system 100 according to the invention in a seventh embodiment variant. In contrast to the exhaust system 100 as shown in FIG 9 A three-way catalytic converter 10 and an Otto particle filter 20 are arranged one behind the other as seen in the direction of flow. Analogously to the sixth embodiment variant, both are arranged in the second main partial exhaust gas line a2 parallel to the bypass line b.

11 shows an exhaust system 100 according to the invention in an eighth variant. In contrast to the exhaust system 100 as shown in FIG 10 and description of the seventh embodiment variant, two three-way catalytic converters 10A, 10B and an Otto particle filter 20 are arranged one behind the other as seen in the direction of flow. All exhaust gas aftertreatment components 10A, 10B, 20 of the exhaust system 100 are arranged in the second main partial exhaust gas line a2 parallel to the bypass line b.

If one of the design variants shown is used, in which the bypass line ( 7 , 8th , 9 , 10 , 11 and associated description) is branched off before the first exhaust gas aftertreatment component, care must be taken to ensure that the branching off occurs after an exhaust gas turbocharger that may be installed. This ensures that the exhaust gas turbocharger is kept at speed during an overrun phase.

The pamphlet DE 101 30 633 B4 discloses a method for regenerating a diesel particle filter, in which the diesel particle filter is arranged in combination with an oxidation catalytic converter in the exhaust gas stream of an internal combustion engine. Bypassing the entire system using a bypass line is proposed to minimize cooling of the diesel particle filter. In particular, it is suggested to minimize cooling of the diesel particle filter in an overrun phase, an idling phase or in a low-load phase of the internal combustion engine.

The idea of the present invention is based on other conditions.

In the case of the present invention, an Otto-fuel-air mixture of an Otto engine with a constant stoichiometric fuel ratio (λ=1) is used during combustion (cf 2 , upper figure), so that in the associated exhaust system 100 in normal driving outside of the overrun phase II; Δt, unlike an engine running on diesel fuel, there is no excess oxygen.

According to the invention, this makes it possible for at least one three-way catalytic converter 10; 10A, 10B to be used. In a regulated three-way catalytic converter, the oxidation of carbon monoxide CO and hydrocarbons C _m H _n and the reduction of nitrogen oxides NO _x take place in parallel. In other words, the at least one three-way catalytic converter can only be used in vehicles with a gasoline engine and lambda control (λ=1) in the lambda window (λ=0.97-1.03).

In diesel and lean-mix gasoline engines, the excess oxygen that is always present in the exhaust gas prevents the reduction of nitrogen oxides NO _x and makes special NO _x catalytic converters necessary. That is, the disclosure of the document DE 101 30 633 B4 does not suggest providing a bypass line to prevent oxygen from entering the diesel particle filter, because the excess oxygen present in all operating phases in the exhaust gas of the internal combustion engine operated with diesel fuel represents an issue with regard to the operation of the exhaust gas system described in the cited publication with an integrated diesel -Particle filters are not a problem.

In addition, the print stimulates DE 101 30 633 B4 also the use of a three-way catalytic converter in the exhaust system does not apply, since three-way catalytic converters, as explained above, due to the oxidation of carbon monoxide CO and hydrocarbons C _m H _n and the reduction of nitrogen oxides NO _x in parallel only in vehicles can be used with Otto engines and lambda control in the lambda window.

The advantage of the present invention is that - as soon as the loading level of the Otto particle filter 20 reaches a critical level and the Otto particle filter 20 already has a high temperature and these states coincide with the unfired overrun fuel cut-off - it is ensured according to the invention that no uncontrolled soot conversion and thus no component damage of the Otto particle filter 20 occurs, since the Otto particle filter 20 in the overrun phase II; Δt according to the invention no oxygen is available due to the redirection of the fresh air mass flow ṁ _F via the bypass line b.

It becomes clear that, in contrast to the disclosure content of the document DE 101 30 633 B4 not avoiding cooling, and therefore not maintaining the highest possible temperature T _{in front of OPF} of Otto particle filter 20 or even increasing a temperature T _{in front of OPF} of Otto particle filter 20 is the focus of the invention. The temperature T _vorOPF of the Otto particle filter 20 remains in the overrun phase II in the solution according to the invention; Δt is advantageously almost constant, since the fresh air mass flow ṁ _F of the internal combustion engine 10 is diverted via the bypass line b (cf 4 , middle panel), as indicated by graph 3 in the middle panel of the 2 is made clear.

Reference List

1

Exhaust system (state of the art)

100

exhaust system (invention)

M

internal combustion engine

10

Three-way catalytic converter

10A

first three-way catalytic converter

10B

second three-way catalytic converter

20

Otto particle filter

v

speed

v1

first speed

v2

second speed

t

Time

t1

first time

t2

second point in time

Δt

Period of a push phase

I

first phase

II

second phase (push phase)

III

third phase

G1

first graph

G2

second graph

G3

third graph

λ

lambda

ṁM

Exhaust gas mass flow of the internal combustion engine

ṁF

fresh air mass flow

ṁOPF

Mass flow before/after Otto particle filter

TvorOPF

Temperature in front of Otto particle filter

a

main exhaust line

a1

first main exhaust branch

a2

second main exhaust branch

a3

third main exhaust branch

b

bypass line

Claims (10)

Method for protecting a particle filter (20) in a main exhaust line (a) of an exhaust system (100) of an Otto internal combustion engine (M) during an overrun phase (II; Δt) occurring during operation of the internal combustion engine (M), in which the internal combustion engine ( M) is operated without fuel and the particulate filter (20) is subjected to a fresh air mass flow (ṁ _F ), so that the exhaust gas mass flow (ṁ _M ) is subjected to an increase in the oxygen concentration, with the particulate filter (20) being subjected to the fresh air mass flow (ṁ _F ) during the overrun phase (II; Δt) is prevented by the fresh air mass flow (ṁ _F ) during the overrun phase (II; Δt) being routed around the particulate filter (20) via a bypass circuit within the exhaust system (100). is, whereby the particle filter (20) in the overrun phase (II; .DELTA.t) by the redirection of the fresh air masses current (ṁ _F ) via a bypass line (b) of the bypass circuit no oxygen is available, the bypass line (b) of the bypass circuit depending on a critical component temperature of the particle filter (20) and depending on a loading value of the particle filter (20) is activated and the fresh air mass flow (ṁ _F ) in the main exhaust line (a) is routed around the particle filter (20) into the bypass line (b) during the overrun phase (II; Δt), characterized that the fresh air mass flow (ṁ _F ) is diverted during the overrun phase (II; Δt) only if the particle filter (20) has a critical component temperature that is too high and a critical load value that is too high at the same time. procedure after claim 1 , characterized in that the bypass line (b) at the end of a phase (I) of operation of the internal combustion engine (M) with a positive load requirement on the internal combustion engine (M) and the start of the overrun phase (II) at a first point in time (t ₁ ) is opened during the overrun phase (II; .DELTA.t) for a period of time (.DELTA.t) is open, and with the end of the overrun phase (II; .DELTA.t) at a second point in time (t ₂ ) is closed again. Exhaust system (100) set up to carry out the method claim 1 to protect a particle filter (20) in a main exhaust system (a) of the exhaust system (100) of an Otto internal combustion engine (M) which is operated without fuel in an overrun phase (II; Δt) and the particle filter (20) is equipped with a fresh air Mass flow (ṁ _F ) is applied, so that an increase in the oxygen concentration occurs in the exhaust gas mass flow (ṁ _M ), the exhaust system (100) having a bypass circuit with a switching element (12) with which a bypass bypasses the particle filter (20). line (b) can be activated, so that during the overrun phase (II; Δt) of the internal combustion engine, a fresh air mass flow (ṁ _F ) in the main exhaust line (a) around the particle filter (20) into the bypass line (b) and then fed back into the main exhaust line (a), so that the particulate filter (20) in the overrun phase (II; Δt) by redirecting the fresh air mass flow (ṁ _F ) via the bypass line (b) the bypass - No oxygen is available in the circuit, the bypass line (b) of the bypass circuit being activated depending on a critical component temperature of the particle filter (20) and depending on a loading value of the particle filter (20) and the fresh air mass flow (ṁ _F ) in the main exhaust line (a) during the overrun phase (II; Δt) around the particle filter (20) into the bypass line (b), and the fresh air mass flow (ṁ _F ) is diverted during the overrun phase (II; Δt) only if the particle filter (20) has a critical component temperature that is too high and a critical loading value that is too high at the same time. Exhaust system (100) after claim 3 , characterized in that the switching element (12) can be brought into a first switching position (12a) by means of a switching mechanism, in which the main exhaust line (a) is open and the bypass line (b) is closed, and in a second switching position (12b) can be brought, in which the main exhaust line (a) is closed and the bypass line (a) is open. Exhaust system (100) after claim 4 , characterized in that the switching element (12) is arranged at the inlet of the bypass branch (b) in the main exhaust branch (a) of the particle filter (20), the bypass branch (b) being connected to a first main exhaust branch (a1 ) of the main exhaust branch (a) branches off, and bypasses a second main partial exhaust branch (a2) of the main exhaust branch (a), in which the particle filter (20) is arranged. Exhaust system (100) after claim 4 , characterized in that viewed in the direction of flow of the exhaust gas, at least one three-way catalytic converter (10; 10A, 10B) is arranged in the first main partial exhaust line (a1) and the particle filter (20) is arranged in the second main partial exhaust line (a2). . Exhaust system (100) after claim 4 , characterized in that seen in the direction of flow of the exhaust gas in the first main partial exhaust line (a1) a first three-way catalytic converter (10A) and in the second main exhaust partial line (a2) a second further three-way catalytic converter (10B) and the particle filter (20) are arranged. Exhaust system (100) after claim 4 , characterized in that the particle filter (20) and the three-way catalytic converter (10) or vice versa are arranged in the second main partial exhaust line (a2) viewed in the direction of flow of the exhaust gas. Exhaust system (100) after claim 4 , characterized in that in the second main exhaust branch (a2) viewed in the direction of flow, a plurality of three-way catalytic converters (10; 10A, 10B) and the particle filter (20) are arranged. Exhaust system (100) after claim 4 , characterized in that in the second main partial exhaust line (a2) viewed in the flow direction of the exhaust gas of the particle filter (20) and in a subsequent third main partial exhaust line (a3) behind the junction of the bypass line (b) in the main Exhaust line (a) at the end at least one three-way catalytic converter (10; 10A, 10B) is arranged in the second main partial exhaust line (a2).

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