DE102015221495A1 - Method and apparatus for regeneration of a particulate filter - Google Patents

Abstract

The invention relates to a method and a device for regenerating a particulate filter (20) in the exhaust passage (12) of an internal combustion engine (10), wherein a loading state of the particulate filter (20) is determined by a loading model, wherein the particulate filter (20) for modeling in at least two filter elements (32, 34) is divided, and wherein for each filter element (32, 34) separately a loading state and / or a temperature distribution is determined. The invention further relates to a device for regeneration of a particulate filter (20) in the exhaust passage (12) of an internal combustion engine (10), wherein a control device (16) is provided, which has a computer-readable program algorithm for controlling a method according to the invention as well as possibly required maps and the like.

Description

The invention relates to a method and a device for the regeneration of a particulate filter in an exhaust passage of an internal combustion engine.

The current and increasingly stringent emissions legislation in the future places high demands on the engine raw emissions and the exhaust aftertreatment of internal combustion engines. With the introduction of the emission standard EU6 for gasoline engines a limit value for the particle emission is prescribed, so that it can come also with gasoline engines to the necessity of the employment of a particle filter. The particle filter is loaded while driving a motor vehicle with particles, the exhaust back pressure in the exhaust duct increases with the load. This loading of the particulate filter can be determined for example by means of a differential pressure measurement in the exhaust gas duct before and after the particulate filter or a modeling in a control unit of the internal combustion engine. So that the exhaust back pressure level does not rise too far, the particle filter must be regenerated continuously or periodically. In order to carry out a thermal oxidation of the soot particles on the particle filter with oxygen, a sufficient regeneration temperature and the simultaneous presence of residual oxygen in the exhaust gas are necessary. The Rußaustrag from the particulate filter can be mapped to the load of the particulate filter also via a back pressure measurement in the exhaust duct or a modeling.

From the DE 42 30 180 A1 a method for the regeneration of a particulate filter is known in which for determining the loading state of a particulate filter, a pressure value, an exhaust gas flow rate through the particulate filter and the speed of the combustion engine occurring at the determined exhaust gas volumetric flow are measured. Taking these measured values into account, an actual characteristic value is determined and compared with a limit value, with a regeneration of the particle filter being initiated given a sufficiently small difference between the actual characteristic value and the limit value.

From the DE 199 45 372 A1 For example, a method for controlling the regeneration of a particulate filter is known in which the regeneration of the particulate filter is carried out via a characteristic map or a model. The model includes a load value of the particulate filter, in which the travel time and the distance traveled since the last regeneration. The load value is used to determine a condition code that, if exceeded, performs a regeneration.

Even though these methods already take several parameters into account, they nevertheless assume a uniform temperature distribution over the particle filter and a uniform loading of the particle filter.

From the DE 103 49 134 A1 a method for the regeneration of a particulate filter is known in which a distribution of the surface temperature is determined by means of a thermographic camera and is attempted on the basis of the present temperature distribution to achieve the most uniform temperature distribution over the cross section of the particulate filter by selecting appropriate engine parameters or a corresponding flow of the particulate filter ,

However, this method is very expensive and expensive, so it is primarily suitable for use on a test bench and not for use in a motor vehicle. In addition, due to the soot in the exhaust gas, the viewing window for the thermographic camera may become dirty, so that this influence must be additionally compensated and the measurement duration is limited.

The invention is based on the object to provide a method for regenerating a particulate filter, which radial and axial temperature gradients on the particulate filter and the resulting different conversion rates in a regeneration of the particulate filter takes into account even under unfavorable operating conditions effective component protection measures for the particulate filter or active regeneration measures to be able to initiate the particulate filter.

According to the basic idea of the invention, it is provided that the loading state of the particulate filter is determined by a loading model, wherein the particulate filter is subdivided into at least two filter elements for modeling, wherein a loading state and / or a temperature distribution is determined for each filter element. Due to radial and / or axial temperature differences on the particle filter may be present by the resulting different conversion rates after a partial regeneration of the particulate filter different specific loadings of the particulate filter with soot particles. However, precise knowledge of this is necessary in order to be able to initiate effective component protection measures or active regeneration measures for the particle filter even under unfavorable operating conditions. By dividing the particle filter into a plurality of filter elements, local loads can be modeled here, whereby a more accurate component load for the particle filter can be determined and damage to the particle filter can be avoided.

In a preferred embodiment of the invention it is provided that the particle filter for Modeling in the axial direction is divided into several filter levels. As a result, it is possible to model the loading state and / or the temperature along the flow direction through the particle filter, ie in the axial direction through the particle filter, so that the particle entry or the particle discharge at different points of the particle filter along the flow direction of the exhaust gas can be determined by the particle filter. It is particularly advantageous if the filter planes are disc-shaped. By modeling with several in the flow direction of the exhaust gas through the particle filter successively arranged disc-shaped filter elements a particularly simple modeling of the loading state in the axial direction is possible. In this case, the filter elements preferably extend radially outwards starting from a central axis of the particle filter and in each case have the same diameter or the same radius.

According to a further advantageous embodiment of the method, it is provided that the particle filter for modeling is divided radially into several rings. Thus, radial temperature differences and different loading states of the particulate filter in the radial direction can be modeled in a simple manner, wherein among other things it can be taken into account that the radially outer regions of the particulate filter are generally colder than the radially inner regions of the particulate filter. Furthermore, it has been shown that in the axial direction, the temperature in the radially outer regions of the particulate filter decreases faster than in the radially inner regions. By a corresponding modeling of the temperature distribution, a significantly more accurate modeling of the particle entry and / or of the particle discharge into or out of the particle filter can take place, for example via a back pressure measurement via the particle filter or a model based on a homogeneous distribution of the soot particles on the soot particle filter , is possible.

If the particle filter is subdivided both axially and radially into a plurality of filter elements, a particularly accurate modeling of the loading state of the particle filter is possible by a radial division of the particle filter into rings and an axial division of the particle filter into slices. This is the preferred embodiment of the present invention.

According to a further development of the method, it is provided that in each case one component temperature of the particle filter is determined per filter element. This can also be done by modeling or by local temperature measurements, for example by embedded in the particulate filter thermocouples. By determining the local temperatures in the individual filter elements of the particulate filter, a more accurate forecast of soot input and / or soot discharge into the respective filter element or from the respective filter element is possible, whereby the model formation is further refined and improved.

Alternatively, it is advantageously provided that the component temperature of the particulate filter is measured only on selected filter elements and the temperatures of the other filter elements are determined by means of modeling. In the simplest case, the modeling can be done by simple interpolation or extrapolation of the temperature distribution along a series of measuring elements. As a result, the accuracy of the modeling of the soot entry into the particle filter and / or of the soot discharge from the particle filter can likewise be improved and thus the quality of the loading model of the particle filter can be further improved.

Alternatively, the temperature can also be determined without temperature measuring elements on or in the particle filter by means of a suitable calculation model. This can be done for example by means of a flow simulation in the exhaust duct, preferably supplemented by a combustion model for modeling the combustion chamber temperature in the internal combustion engine. Alternatively, it is also possible to measure a temperature at a position spaced apart from the particle filter in the exhaust gas duct and from this a temperature distribution on the particle filter can be modeled.

According to a further improvement of the method, provision is made for measures for component protection of the particulate filter to be initiated when determining an unfavorable loading state of the particulate filter. This can prevent that local load peaks for the particulate filter occur, which can lead to damage or destruction of the particulate filter. It is particularly advantageous if, upon detection of an unfavorable loading state of the particulate filter, the internal combustion engine is operated with a stoichiometric or rich mixture, so that no oxygen enters the exhaust duct. Particularly critical in this context are overrun phases of the internal combustion engine in vehicle operation, in which the fuel injection is adjusted, the cylinders of the internal combustion engine compress air and convey this air into the exhaust duct. At sufficiently high temperatures, this can lead to an uncontrolled Rußverbrennnung on the particulate filter, which can lead to damage or destruction of the particulate filter. To avoid this, fuel is in the combustion chamber of the component protection even in such deceleration phases Internal combustion engine injected to protect the particulate filter from uncontrolled Rußabbrand.

Further, the invention provides a device for regenerating a particulate filter in the exhaust passage of an internal combustion engine having a control device, in particular a control unit (the engine control unit), which has a computer-readable program algorithm for controlling the method according to the invention and which is suitable to carry out the inventive method. The control device may also have any required maps and the like. By means of a corresponding control device, the internal combustion engine can be controlled or regulated in a simple manner such that regeneration of the particle filter is initiated and component damage to the particle filter, in particular thermal damage to the particle filter, can be avoided.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

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

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 an internal combustion engine with an exhaust duct and a particle filter, in which a method according to the invention for the regeneration of the particulate filter can be carried out,

2 a diagram of a simple loading model for determining the loading state of a particulate filter,

3 a sketch for the distribution of axial and radial temperature levels in a particle filter,

4 a diagram for the axial and radial temperature distribution on a particle filter,

5 a schematic representation of a loading and regeneration of a particulate filter,

6 an inventive subdivision of the particulate filter into filter elements for modeling the particle loading of the particulate filter.

1 shows an internal combustion engine 10 with an exhaust duct 12 and one in the exhaust passage 12 arranged particulate filter 20 , The internal combustion engine 10 is preferably designed as an internal combustion engine for driving a motor vehicle, particularly preferably as a gasoline engine. The internal combustion engine preferably has a direct fuel injection in which fuel is injected directly into the cylinders of the internal combustion engine. The combustion processes in the internal combustion engine 10 be via a control unit 16 controlled or regulated. The internal combustion engine 10 is preferably formed as a supercharged internal combustion engine, which via a turbocharger 14 or a compressor is supplied with air. Alternatively, the internal combustion engine 10 also as a naturally aspirated or internal combustion engine 10 be formed of another genus. In the exhaust duct 12 the internal combustion engine 10 is preferably a three-way catalyst 18 arranged.

In operation of the internal combustion engine 10 becomes the particle filter 20 with particles from the combustion process of the internal combustion engine 10 loaded. This loading is done by means of a modeling in the control unit 16 certainly. So that the exhaust back pressure level of the internal combustion engine 10 does not rise too far, must the particle filter 20 be regenerated continuously or periodically. The particle filter 20 may additionally comprise a catalytically active coating, for example a three-way catalytically active coating or a coating for the selective catalytic reduction of nitrogen oxides. To a thermal oxidation of the in the particle filter 20 To carry out retention of soot particles with oxygen, a sufficient temperature level is necessary in the presence of residual oxygen in the exhaust gas. The soot discharge from the particle filter 20 is also done by means of a modeling in the control unit 16 determined.

In 2 is a simple modeling of the loading state of the particulate filter 20 shown. The currently on the particulate filter 20 present load is by an integral of the sum of particle entry and particle discharge in the particle filter 20 or from the particle filter 20 educated. The soot entry is, for example, via a raw emission model of the internal combustion engine 10 calculated, which in the control unit 16 the internal combustion engine 10 is stored.

A decisive factor for the soot discharge is the temperature of the particulate filter 20 , Assuming a homogeneous temperature distribution, uniform soot turnover would occur over all areas of the particulate filter 20 to adjust. Under real conditions, however, occur both in the radial direction, starting from a central axis 30 the particle filter as well as in the axial direction of temperature gradients, resulting in inhomogeneous conversion rates of the particle filter 20 retained soot lead. These radial and axial temperature gradients lead especially in the case of large particle filters, for example in the case of large-volume passenger car engines or in engines in commercial vehicles, in the event of an incomplete regeneration of the particulate filter 20 Uneven soot loadings in the individual areas of the particulate filter 20 to adjust. Such an uneven loading of the particulate filter 20 is in 5 shown.

In 3 is a schematic representation of the radial and axial temperature distribution through the particulate filter 20 shown. This is the particle filter 20 in different filter levels 22 . 24 . 26 . 28 divided, wherein the first filter plane in the flow direction of an exhaust gas through the exhaust passage 22 has a higher temperature than that in the flow direction downstream of the first filter plane 22 lying further filter levels 24 . 26 . 28 , As in 4 it can be seen that the temperature decrease in the axial direction in the radially outer regions r1 and r2 is greater than a decrease in temperature in the axial direction along the central axis r0, 30 of the particulate filter 20 , Furthermore, it is off 3 to recognize that the temperature in the radial direction, starting from the central axis r0, 30 decreases in the radial direction, so that a lower temperature occurs in the edge region r2 than in an eccentric region r1 and in both regions r1, r2 a lower temperature than in the region of the central axis r0, 30 of the particulate filter 20 , By a division of the particle filter 20 modeling in radial rings and in slices in the axial direction can accurately model the loading state of the particulate filter 20 and / or the temperature distribution on the particulate filter 20 be determined.

In 5 is the specific soot loading on a slice of the particulate filter 20 shown. After installation of the particulate filter 20 or after a complete regeneration of the particulate filter 20 is the particle filter 20 unladen. In modeling the loading of the particulate filter 20 It is based on the theory that the exhaust gas in the exhaust duct 12 preferably through the filter elements 32 . 34 . 36 . 38 of the particulate filter 20 flows, which have the lowest specific load, since there the flow resistance and thus the exhaust back pressure are the lowest. With a fresh particle filter 20 Therefore, initially a uniform loading of the particulate filter 20 with soot particles from the exhaust gas of the internal combustion engine 10 , Will the particle filter 20 regenerated, so has the local temperature distribution in the particulate filter 20 significant influence on the particle discharge from the particle filter 20 , Due to the fact that along the central axis r0, 30 higher temperatures than in the edge region r2 of the particulate filter 20 are present, the central region r0 of the respective disc is regenerated faster than the edge region r2 of the respective disc. This can lead to incomplete regeneration of the particulate filter 20 lead, with a re-loading of the particulate filter 20 in the edge region r2 remain unoxidized soot particles, while the central region r0 is already completely oxidized. When reloading the particle filter 20 Now, the central region r0 loaded faster with particles from the exhaust gas due to the lower flow resistance, to substantially an even distribution of the soot load of the particulate filter 20 is reached over the cross section and from this point on again a uniform loading of the particulate filter 20 he follows. If the filter elements in the edge regions r2 have reached a specific loading of the filter elements in the central region r0, they are included in the current load calculation, since they now belong to the group of filter elements 32 . 34 . 36 . 38 count with the lowest load. This process continues until a homogeneous soot distribution in the particle filter again 20 has set. Beyond this point, soot will continue to enter the particulate filter 20 registered, this takes place evenly on all filter elements 32 . 34 . 36 . 38 distributed. Should a regeneration phase be initiated again in the meantime, the soot discharge will again be for each filter element 32 . 34 . 36 . 38 is calculated individually as a function of its current load state and the prevailing temperature in the respective area.

The specific loading is in particular for the component load of the soot particle filter 20 decisive, since the exothermic reaction during Rußaustrag from the particle filter 20 by oxidation of the soot particles on the particulate filter 20 can lead to high local peak temperatures. With knowledge of the exact soot distribution can under unfavorable operating conditions and / or unfavorable loading conditions of the particulate filter 20 required component protection measures to protect the particulate filter 20 , in particular for protection against thermal damage or destruction, are initiated. In addition, active measures can be taken on the internal combustion engine 10 for regeneration of the particulate filter 20 be initiated.

In 6 is a subdivision of a particulate filter according to the invention 20 in several filter elements 32 . 34 . 36 . 38 shown, wherein the particle filter 20 in the axial direction in slices and in the radial direction is divided into rings. Alternatively, another subdivision, for example, in cells or honeycomb conceivable, wherein for each cell or honeycomb of the particulate filter 20 then a load state or a temperature is determined accordingly.

LIST OF REFERENCE NUMBERS

10

Internal combustion engine

12

exhaust duct

14

turbocharger

16

control unit

18

Three-way catalytic converter

20

particulate Filter

22

first filter level

24

second filter level

26

third filter level

28

nth filter level

30

central axis

32

first filter element

34

second filter element

36

third filter element

38

nth filter element

r0

central axis

r1

first distance from the central axis

r2

second distance from the central axis

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 4230180 A1 [0003]
• DE 19945372 A1 [0004]
• DE 10349134 A1 [0006]

Claims (10)

Process for the regeneration of a particulate filter ( 20 ) in the exhaust duct ( 12 ) an internal combustion engine ( 10 ), wherein a loading state of the particulate filter ( 20 ) is determined by a loading model, characterized in that the particulate filter ( 20 ) for modeling in at least two filter elements ( 32 . 34 ), wherein for each filter element ( 32 . 34 ) a load condition and / or a temperature distribution is determined separately. Method according to claim 1, characterized in that the particle filter ( 20 ) for modeling in the axial direction into a plurality of filter planes ( 22 . 24 . 26 ) is divided. Method according to claim 2, characterized in that the plurality of filter levels ( 22 . 24 . 26 ) are disc-shaped. Method according to one of claims 1 to 3, characterized in that the particulate filter ( 20 ) is divided radially into a plurality of rings (r1, r2) for modeling. Method according to one of claims 1 to 4, characterized in that per filter element ( 32 . 34 . 36 ) each have a component temperature of the particulate filter ( 20 ) is determined. Method according to one of claims 1 to 4, characterized in that on selected filter elements ( 32 . 34 . 36 ) a component temperature of the particulate filter ( 20 ) and the temperatures of the other filter elements ( 32 . 34 . 36 ) can be determined by means of modeling. Method according to one of claims 1 to 6, characterized in that the soot conversion for each filter element ( 32 . 34 . 36 ) is calculated individually. Method according to one of claims 1 to 7, characterized in that when determining an unfavorable loading state of the particulate filter ( 20 ) Measures for the component protection of the particulate filter ( 20 ) be initiated. A method according to claim 8, characterized in that upon detection of an unfavorable loading state, the internal combustion engine ( 10 ) is operated exclusively with a stoichiometric or rich mixture, so that no oxygen for regeneration of the particulate filter in the exhaust gas channel ( 12 ). Device for the regeneration of a particle filter ( 20 ) in the exhaust duct ( 12 ) an internal combustion engine ( 10 ), characterized in that a control device ( 16 ) is provided, which has a computer-readable program algorithm for carrying out a method according to one of claims 1 to 9.

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