DE102009010307A1 - Exhaust gas treatment device and method for operating an exhaust gas treatment device - Google Patents

Abstract

The invention relates to an exhaust gas treatment device for an internal combustion engine, comprising a first particle filter and a second particle filter (6) arranged downstream of the first particle filter in the flow direction of the exhaust gas through the exhaust gas treatment device. The second particle filter (6) comprises at least one carrying device (16) through which the exhaust gas can flow, to which a filter unit (17) is arranged. In this case, a pore size of the filter unit (17) is smaller than a pore size of the at least one carrying device (16). Furthermore, the invention relates to a method for operating an exhaust gas treatment device for an internal combustion engine.

Description

The The invention relates to an exhaust gas treatment device for an internal combustion engine, with a first particle filter and one in the flow direction of the exhaust gas through the exhaust gas treatment device arranged downstream of the first particulate filter second Particulate filter. Furthermore, the invention relates to a method for operating such an exhaust gas treatment device.

The WO 2008/043422 A1 describes an exhaust treatment device for an internal combustion engine. In this case, a second particle filter is arranged downstream of a first particle filter. A volume of the second particulate filter is preferably less than 30% of the first particulate filter, so that the second particulate filter has a lower particle absorption capacity than the first particulate filter. Additionally or alternatively, a lower porosity of the second particle filter compared to the first particle filter can lead to a reduced particle absorption capacity of the second particle filter. Due to the comparatively low particle absorption capacity of the second particle filter, an increase in the loading of the second particle filter can be detected relatively quickly. A malfunction of the first particulate filter or a reduced degree of separation of the particles on the first particulate filter can be detected so that measures for restoring the functionality of the first particulate filter can be taken.

task It is the object of the present invention to provide an exhaust gas treatment device or to provide a method of the type mentioned, by means of which or by means of which an even more rapid impairment the functionality of the first particulate filter detectable is.

These The object is achieved by an exhaust gas treatment device having the features of claim 1. Furthermore this task becomes solved by a method having the features of claim 17. Advantageous embodiments with appropriate Further developments of the invention are dependent on the respective Claims specified.

The Exhaust treatment device according to the invention for an internal combustion engine has a first particle filter and one in the flow direction of the exhaust gas through the exhaust gas treatment device arranged downstream of the first particulate filter second Particle filter on. The second particulate filter comprises at least a carrying device through which the exhaust gas can flow, on which a filter unit is arranged, wherein a pore size the filter unit is less than a pore size the at least one carrying device.

Of the Invention is based on the finding that in one of the Prior art known second particulate filter reduction its particle absorbency by providing a particularly small volumes of the same limits are set. At one too small Sizing of the second particulate filter is namely its mechanical stability is limited. present ensures the exhaust flow through the exhaust, porous carrying device the sufficient mechanical stability of the second particulate filter. This allows the second filter unit, which compared to the support lower pore size has, relatively delicate and on the most effective Deposition of particles to be optimized optimized.

For example is the filter unit as applied to the support filter membrane educated. A loading of the filter membrane then decreases damage, such as a crack, of the first particulate filter very quickly too. A period until the impairment is determined the functionality of the first particulate filter is then especially low. This is a particularly high accuracy upon determining a reduction in a degree of separation of the first Particulate filter achievable. Furthermore, this training the second particulate filter whose space requirements, weight and cost especially low. In addition, the second one increases Particle filter the back pressure of the exhaust treatment device only slightly.

In an advantageous embodiment of the invention the pore size of the filter unit at least the Half, in particular half to one tenth, the pore size of the at least one support device. The pore size of the filter unit may also be, for example one-fifth of the pore size of at least a carrying device amount. This is especially effective too ensure that the retention of the particles in the exhaust stream through the filter unit. So can an increase the loading of the second particulate filter particularly quickly and accurately be recorded.

When Furthermore, it has been shown to be advantageous if the filter unit for Retention of particles by surface filtration is trained. As a result, the filter unit from the exhaust gas with a flowed through very low pressure loss. However, you can Soot particles do not penetrate into the filter unit, but are retained on the surface of the filter unit.

The Filter unit can in particular have microfiltration properties, so that soot particles of less than 10 μm diameter, in particular soot particles with a diameter of 10 microns to 0.1 μm, particularly well retained by the filter unit become.

In a further advantageous embodiment of the invention a thickness of the at least one support means is a multiple of one Thickness of the filter unit. As a result, the filter unit compared in comparison is designed to be particularly thin to the support device, has the filter unit for the exhaust good flow through on. Alternatively, but preferably in addition, amounts a porosity of the at least one support means Multiple of the porosity of the filter unit. The thus in the Compared to the carrying device few and comparatively fine Pore-containing filter unit is thus in a damage of the first particulate filter, for example if this is due to repeated Temperature changes or due to a long service life one Crack or a hole, very fast too. An accompanying one Significantly increase the pressure drop across the second particulate filter is also with little sensitive and thus particularly robust pressure detection means very easy and clearly detectable.

at a further advantageous embodiment of the invention is a minimum extension of at least one Carrying device transverse to the flow direction of the exhaust gas a multiple, in particular at least a fivefold, a thickness of the at least one support device. For example as a porous round disc trained carrying device Thus, the diameter is a multiple, in particular five times or ten times the thickness of the carrying device. By this flat design of the support device whose flow resistance especially low.

When Furthermore, it has proved to be advantageous if the at least one Carrying device and the filter unit at least partially a same material are formed. This causes tensions between the carrying device and the filter unit due to a different Expansion behavior at a temperature increase avoidable. This is a particularly high durability of the second particulate filter associated.

at the material forming the supporting device and the filter unit it may in particular be a metallic or ceramic material act. For example, the support means as metallic Knitted wire, as a single-layer or multi-layer sieve or as a metal foam component be educated. For example, designed as a filter membrane Filter unit can then be a dense metal fiber fleece. Prefers For example, such a non-woven fabric of metal fibers has a felt-like structure on. Fibers of the nonwoven fabric can be used in the manufacture of the filter unit and / or of the second particulate filter, for example by sintering together be connected. In particular, can also be a connection of support means and filter unit by sintering done. To connect the separately However, manufactured filter unit with the support means can Soldering or welding are used. Instead of a separate manufacturing of the filter unit and an application on the carrying device in a downstream process can alternatively carrying device and filter unit in the same manufacturing process be prepared.

is the support means formed of a ceramic material, such as As a highly porous ceramic component, so is the preferred filter unit also formed from a porous ceramic material.

For the carrying device and the filter unit used metallic or ceramic materials are advantageously high temperature resistant, so that an arrangement in close proximity to the first Particulate filter can be provided. Such high temperature resistant Materials withstand a temperature load of 900 ° C, in particular from 1200 ° C to 1300 ° C, without damage. This is particularly advantageous when regenerating the Particulate filter, so when burning off on the particulate filter deposited soot, high temperatures in the exhaust treatment device occur.

The at least one carrying device can be downstream and / or be arranged upstream of the filter unit. If the Carrying device both upstream and downstream the filter unit is arranged, so can a material connection the filter unit with at least one of the support devices omitted, because the filter unit by the support means arranged on both sides is fixable in their position.

If the at least one support device upstream of the filter unit is arranged, the support means may additionally to their support function a Abscheidefunktion for Take over particles. Here then points the second particle filter Also properties of a depth filter, as a separation of Particles both in channels and / or pores of the support device as well as on the surface of the filter unit.

is arranged the filter unit between two support means, so can the two support devices with regard to the for each material used and / or terms their structure and / or their porosity and / or their Distinguish pore size.

The second particle filter may be arranged at least substantially perpendicular or inclined to the flow direction of the exhaust gas in the exhaust gas treatment device. By arranging inclined to the flow direction of the exhaust gas in the exhaust gas treatment device is an increase in the effective area for the deposition of particles of the second particulate filter achievable. When installed perpendicular to the flow direction, however, a particularly small space requirement is given.

To the Setting the second particulate filter on an inner wall of the exhaust treatment device can the support means with the inner wall by welding or Be connected soldering. Complementary or alternative can between the inner wall of the exhaust treatment device and the least one support means a fiber mat or the like provided be, wherein the support means by a clamping action of the fiber mat is fixed in position in the exhaust gas treatment device. This clamping effect in particular by an expansion of the fiber mat at elevated Improved temperature of the exhaust treatment device.

To the Increasing an effective filter area of the second particulate filter, the second particulate filter at least have a survey. The survey is preferred here opposite the flow direction of the exhaust gas aligned to accumulate of particles in a throat region of the second particulate filter to prevent. In particular, a plurality of concentric Surveys should be provided. In addition or alternatively can the second particulate filter has a plurality of mutually parallel ones Have elevations, so that the second particle filter in longitudinal section has a corrugated profile.

When Furthermore, it has proved to be advantageous if the second particle filter regenerable by a heat transfer in the Exhaust tract is arranged, the heat transfer over by means of a thermal regeneration of the first particle filter is feasible. This can ensure that a burn off of soot, which by means of the first particulate filter the exhaust gas is deposited, to burn off soot leads to the second particle filter. On a separate regeneration of the second particulate filter can be dispensed with.

Around a particularly efficient heat transfer from effect the first particulate filter on the second particulate filter For example, the second particulate filter may be within a first particulate filter be arranged surrounding housing. This can be a distance of a few centimeters between the first particle filter and the be provided second particulate filter. Alternatively, at least in some areas a touch contact of the first particle filter and second particulate filter.

alternative The second particulate filter can be housed in a separate housing be accommodated, which upstream compared to an area of the exhaust tract this separate housing an enlarged Cross section has. By placing the second particulate filter in the housing surrounding the first particulate filter, or in the separate housing, the second particulate filter So a particularly large flow-through cross-section and thus a particularly low flow resistance exhibit.

Thereby, in that, when regenerating the first particle filter, the second particle filter is also regenerated, can be a continuous increase in Loading the second particulate filter as a result of operating the intact first particle filter can be avoided. So long as that first particulate filter is intact and one to comply with legal Regulations has sufficient particle absorption capacity, At the second particulate filter, there will be no significant increase in Exhaust Backpressure be observable.

According to one Further advantageous embodiment of the invention, the exhaust gas treatment device Pressure sensing means and an evaluation, wherein means the evaluation device, a difference in pressure between a Position upstream of the second particulate filter and a location downstream of the second particulate filter with respect to a state of the first particulate filter is evaluable. The difference can in this case by means of a differential pressure sensor or by means of two Absolute pressure sensors are determined. Exceeds the value the difference a threshold, may be due to damage of the first Particle filters are closed. In contrast, at falling below the threshold value to a non-critical state of the first particulate filter are closed.

One such evaluation of the difference with regard to the state of first particulate filter is particularly safe and fast. An additional or alternatively predictable evaluation of a temperature rise at second particulate filter during thermal regeneration of the same would however, a detection of a damage of the first particulate filter only during regeneration allow. As the thermal regeneration in different time intervals performed is a damage of the first particulate filter then not always immediately detectable. In contrast, can when detecting the pressure drop across the second particulate filter, if necessary an already existing measuring device for detecting the pressure drop on the first particulate filter, in particular a measuring line, shared become.

It has proven to be advantageous in this case if a reference value of the difference characterizing the state of the first particle filter is stored in a memory. The memory can in this case be arranged in the evaluation device. Preferably, the reference value characterizes the difference in initial start-up of the exhaust treatment device, a new condition of the first and the second particulate filter. If, compared to the reference value for the new condition of the first particulate filter, a value of the difference is detected which is greater than a threshold value, it is possible to conclude an erroneous condition of the first particulate filter by means of the evaluation device. Such a faulty state of the first particulate filter can be communicated in particular via a communication device, for example in the form of an optical and / or acoustic alarm signal or a display or the like.

Prefers is the characterizing state of the first particulate filter Reference value as a function of aging of the first Particle filter variable. The reference value may be in the form of a Characteristic stored in the memory, which is an operating period the exhaust gas treatment device and / or an exhaust gas flow rate the exhaust treatment device and / or a fuel flow rate the internal combustion engine having the exhaust gas treatment device and / or in an exhaust gas treatment device arranged in a vehicle considered a covered distance of the vehicle. Additionally or alternatively, temperature profiles the exhaust treatment device for characterizing the aging be used of the first particulate filter.

Around to prevent a short-term crossing of the Threshold for detecting damage to the first particulate filter leads, the value of the difference formed from measured values steamed and / or, in particular using a Low-pass filter, filtered processed in the evaluation or the evaluation device is subdued or filtered become.

Of the Pressure drop across the second particulate filter can be particularly continuous be evaluated. In this case, a standardization is preferably carried out to a value independent of the volume of exhaust gas flow to obtain.

In a further advantageous embodiment of the invention, the Exhaust treatment device Pressure detection device for detecting the pressure upstream and downstream of the first particulate filter on. As a result, the loading state of the first particulate filter in response to a pressure drop across the first particulate filter be determined. Here, a differential pressure sensor can be used come. Also can be upstream and downstream the first particulate filter is provided in each case an absolute pressure sensor be.

In an alternative embodiment is merely an absolute pressure sensor at a location upstream of the first particulate filter present, and the pressure downstream of the first particulate filter is calculated by a model.

Becomes even the pressure drop detected on the first particulate filter, it can Size to plausibility of over the Measuring the pressure drop at the second particulate filter certain state be used of the first particulate filter. About that In addition, the downstream of the first particulate filter arranged Measuring point of the pressure detecting means for determining the pressure drop at the first particulate filter and for determining the pressure drop be used on the second particle filter.

at a supplementary or alternative embodiment the invention, wherein the exhaust gas treatment device pressure sensing means and an evaluation device, the pressure detection means to be used, a ratio of a difference the pressure between a location upstream of the second Particulate filter and a point downstream of the second Particulate filter to a difference in pressure between a point upstream the first particulate filter and a downstream location to determine the first particle filter. An based on the pressure sensing means certain ratio can be determined by means of the evaluation device compared with a stored in a memory ratio and evaluated with respect to a state of the first particulate filter become.

The stored in memory ratio is ordinary in the new state of the exhaust treatment device largest and decreases with increasing operating time of the exhaust treatment device from. On a damage of the first particulate filter can by means of Evaluation be closed when determined by the pressure sensing means Ratio during the operation of the exhaust treatment device increases again.

In a further advantageous embodiment of the invention is the Evaluation designed to the basis of the pressure sensing means certain ratio depending on one evaluate thermal regeneration of at least the first particulate filter. This is based on the knowledge that the data stored in memory, characterizing the new condition of the exhaust gas treatment device Relationship most likely then achievable if the first Particle filter and the second particle filter just regenerated were. So it can be provided that on the basis of the pressure sensing means evaluate certain ratio whenever just one thermal regeneration of at least the first particulate filter takes place is. Here, for example, an average value of the ratio be determined within a given time window.

After all it has proven to be advantageous if the exhaust gas treatment device branching off downstream of the second particulate filter, in particular a throttle device having, exhaust gas recirculation line includes. Here then the second particle filter serves a retention of particles originating from the first particle filter which are there possibly as a result of injury or because of Preparation of the first particulate filter present.

Especially, when the exhaust gas recirculation line upstream a compressor of an exhaust gas turbocharger in an intake of the Internal combustion engine opens, serves the second particulate filter a protection of the compressor from damage by such Particles. In addition, the upstream carries arranged the diversion of the exhaust gas recirculation line second particulate filter does not increase the backpressure the exhaust gas recirculation line, so that the exhaust gas recirculation line has an undiminished effective flushing gradient. By placing the second particulate filter upstream the branch of the exhaust gas recirculation line is the Further, it avoids one associated with operating the exhaust treatment device increasing loading of the second particulate filter with intact first Particle filter to a deterioration of the functionality the exhaust gas recirculation leads.

According to one Another aspect of the invention, the above object is achieved by a method of operating an exhaust treatment device for an internal combustion engine, in which exhaust by means of a first particulate filter and by means of one in the flow direction the exhaust gas through the exhaust treatment device downstream of the first particulate filter arranged second particulate filter is filtered. This flows through the means of the second Particulate filter exhaust filtered at least one support device and a filter unit arranged on the at least one carrying device, wherein a pore size of the filter unit is lower is as a pore size of the at least one support device. The for the exhaust gas treatment device according to the invention described preferred embodiments and advantages also apply to the invention Method for operating an exhaust gas treatment device.

The features and feature combinations mentioned above in the description as well as the below mentioned in the figure description and / or in the figures alone shown features and feature combinations are not only in the specified combination, but also usable in other combinations or in isolation, without to leave the scope of the invention.

Further Advantages, features and details of the invention will become apparent the claims, the following description is more preferred Embodiments and with reference to the drawings. Showing:

1 a schematic representation of an internal combustion engine of a vehicle having an air supply tract and an exhaust tract, which comprises an exhaust gas treatment device with a first particulate filter and a second particulate filter arranged downstream of the first particulate filter;

2 Sectional views of three alternative designs of the second particulate filter;

3 in a sectional view, a first type of arrangement of the second particulate filter in the exhaust system;

4 in a sectional view, an alternative way of arranging the second particulate filter in the exhaust tract, wherein the second particulate filter has an alternative design;

5 in a sectional view of a further design of the disposed in the exhaust tract second particulate filter;

6 a sectional view and a plan view in the flow direction of the exhaust gas to another design of the second particulate filter;

7 a sectional view and a plan view in the flow direction of the exhaust gas on a to the design in 6 alternative design of the second particulate filter;

8th a section of the exhaust tract according to 1 with a first example of an arrangement of pressure detecting means;

9 a section of the exhaust tract according to 1 with a second example of an arrangement of pressure detecting means;

10 a section of the exhaust tract according to 1 with a third example of an arrangement of pressure detecting means;

11 a section of the exhaust tract according to 1 with a fourth example of an arrangement of pressure detecting means;

12 a section of the exhaust tract according to 1 with a fifth example of an arrangement of pressure detecting means;

13 a section of the exhaust tract according to 1 with a sixth example of an arrangement of pressure detecting means;

14 a section of the exhaust tract according to 1 with a seventh example of an arrangement of pressure detecting means; and

15 a section of the exhaust tract according to 1 with an eighth example of an arrangement of pressure detecting means.

1 schematically shows an internal combustion engine 1 a vehicle with an air supply tract 11 and an exhaust tract 3 , The internal combustion engine 1 exiting exhaust gas flows through a turbine 2 an exhaust gas turbocharger, which is a compressor 12 drives. In the exhaust tract 3 is an exhaust treatment device 13 arranged in which present in a housing 14 a catalyst 4 , a first particle filter 5 and a second particulate filter 6 are arranged. In the flow direction of the exhaust gas, which in the exhaust tract 3 through flow arrows 15 is specified here is the first particle filter 5 downstream the catalyst 4 and the second particulate filter 6 downstream of the first particulate filter 5 arranged. That's the particle filter 5 . 6 and the catalyst 4 surrounding housing 14 shows in comparison to an area of the exhaust tract 3 upstream and downstream of this housing 14 a common cross section.

Downstream of the housing 14 has the exhaust tract 3 a branch of an exhaust gas recirculation line 8th on. In the exhaust gas recirculation line 8th is an exhaust gas cooler 9 arranged. The exhaust gas recirculation line 8th serves a low-pressure exhaust gas recirculation, wherein the recirculated exhaust gas upstream of the compressor 12 the air supply tract 11 the internal combustion engine 1 is supplied. Before entering the exhaust gas recirculation line 8th in the air supply tract 11 is a throttle device 10 for throttling the exhaust gas flow through the exhaust gas recirculation line 8th arranged. Another throttle device 7 is downstream of the branch of the exhaust gas recirculation line 8th in the exhaust tract 3 arranged.

The second particle filter 6 points in the flow direction of the exhaust gas through the housing 14 Seen a thickness several times smaller than the first particle filter 5 , A particle receiving capacity of the second particulate filter 6 is thus significantly lower than a particle absorption capacity of the first particulate filter 5 ,

The second particle filter 6 has different functions in the present case. On the one hand serves the second particle filter 6 a retention of from the first particulate filter 5 and / or the catalyst 4 originating particles, such as production residues or particles broken down in the event of damage. Such particles could otherwise enter the exhaust gas recirculation line 8th enter and so if necessary the compressor 12 of the exhaust gas turbocharger.

In addition to this component protection, the second particle filter is used 6 monitoring the functioning of the first particulate filter 5 , The second particle filter 6 That is, which has the particulate matter absorbing ability, which is particularly low in comparison with the first particulate filter, reacts very sensitively to an increase in its load, for example due to damage of the first particulate filter 5 , Such damage may be a crack and / or a hole in the first particulate filter 5 be. Indicates the first particle filter 5 such damage, and thus is limited its ability to function effectively with the retention of particles, so the loading of the second particulate filter increases 6 abruptly. The increase in the load of the second particulate filter 6 in case of damage of the first particulate filter 5 occurs due to the design of the second particulate filter 6 especially fast and reliable. The increase in load is due to a pressure drop associated with the load on the second particulate filter 6 detectable.

Three different examples of specific designs of the second particle filter 6 are in enlarged, schematic representations in 2 specified. The second particle filter 6 accordingly comprises at least one carrying device through which the exhaust gas can flow 16 , which as a support for a filter membrane 17 serves.

The carrying device 16 may be formed of a metallic wire mesh, on which the filter membrane 17 , For example, in the form of a dense metal fiber fleece, is fixed. The carrying device 16 can also be designed as, in particular single-layer or multi-layer sieve or metal foam component. Alternatively, a highly porous ceramic as a carrying device 16 imaginable. Also the filter membrane 17 is then preferred as a ceramic filter membrane 17 educated. A pore size of the filter membrane 17 in the present case is only a fraction of the pore size of the support device 16 , For example, the pore size of the filter membrane 17 half, one-fifth, or even one-tenth the pore size of the carrying device 16 be.

Retention of particles by means of the filter membrane 17 done by surface filtration. Soot particles can not enter the filter membrane 17 penetration. The filter membrane 17 furthermore has one in comparison to the carrying device 16 lower, in particular by a multiple lower, porosity. Likewise, the thickness of the filter membrane 17 in the flow direction of the exhaust gas through the second particle filter 6 several times less than a thickness of the support device 16 ,

The thin, from the carrying device 16 in the case 14 supported filter membrane 17 thereby enables a particularly rapid and accurate detection of a Russeintrags in the second particle filter 6 , This is an operating time until detection of damage of the first particulate filter 5 especially low. Nevertheless, the filter membrane points 17 due to their small thickness, a particularly good flowability for exhaust gas and thus increases the total back pressure of the exhaust gas treatment device 13 minimal if the filter membrane 17 not due to damage of the first particulate filter 5 is largely loaded.

According to a first in 2 shown design of the second particulate filter 6 is the carrying device 16 downstream of the filter membrane 17 arranged. Is alternative, as also in 2 shown the carrying device 16 upstream of the filter membrane 17 arranged, so also carries the carrying device 16 for separating particles from the exhaust gas stream, in which case in the region of the carrying device 16 Retention of particles can be done by depth filtration. According to a third in 2 shown design of the second particulate filter 6 is the filter membrane 17 as an intermediate layer between two carrying devices 16 arranged.

3 shows in a sectional view of the second particle filter 6 as he exemplifies in the case 14 can be arranged. Here is the second particle filter 6 perpendicular to the flow direction of the exhaust gas in the housing 14 arranged. In the present case is the housing 14 formed in cross-section in the region of the second particle filter. The second particle filter 6 is in the design according to 3 is also round in plan view.

4 shows an alternative shape and orientation of the second particulate filter 6 in the case 14 , Here is the second particle filter 6 formed oval and inclined to the flow direction of the exhaust gas in the housing 14 arranged. This is compared to the vertical arrangement according to 3 an enlarged filter effective area of the second particulate filter 6 provided.

In an alternative design of the second particulate filter 6 , what a 5 is shown in cross section, the second particulate filter 6 cone-shaped. This has a tip 18 of the second particulate filter 6 in a direction opposite to the flow directions of the exhaust gas direction. The summit 18 of the second particulate filter 6 in this case lies on a central axis A of the housing 14 , which at the same time a central axis of the second particle filter 6 is.

In an alternative design of the second particulate filter 6 which is in 6 is shown in a plan view in the flow direction of the exhaust gas and in a sectional view, forms the exhaust gas flow facing the filter membrane 17 of the second particulate filter 6 a plurality of concentric elevations 19 , Also the carrying device 16 has the majority of concentric elevations 19 on, leaving the second particulate filter 6 has a serrated profile in longitudinal section.

At an in 7 shown further construction of the second particulate filter 6 this has a waveform in longitudinal section. Here is a plurality of mutually parallel elevations 19 the filter membrane 17 and this supporting carrying device 16 educated.

In 8th to 15 different arrangements of pressure sensing means are shown, by which a difference in pressure between a location upstream of the second particulate filter 6 and a location downstream of the second particulate filter 6 is also detectable as a loading of the first particulate filter 5 , Depending on the space available, accessibility to the respective areas of the exhaust tract 3 and type of the selected pressure sensors, by means of these measuring arrangements, the pressure drop across the second particle filter 6 be reliably and quickly determined so as to damage the first particulate filter 5 close.

According to 8th The pressure sensing means comprise two differential pressure sensors 20 . 21 , The first differential pressure sensor 20 uses a first measuring line 22 , which upstream of the first particulate filter 5 is arranged. A downstream of the first particulate filter 5 arranged second measuring line 23 of the differential pressure sensor 20 can simultaneously from the differential pressure sensor 21 which reduces the pressure drop across the second particle filter 6 detected.

At the in 9 shown arrangement of the pressure detecting means detects the differential pressure sensor 21 the pressure downstream of the second particulate filter 6 not as in the arrangement according to 8th in the area of the housing 14 , but the second measuring line of the differential pressure sensor 21 extends in the area of the diversion of the exhaust gas recirculation line 8th in the exhaust tract 3 into it.

At the in 8th and 9 illustrated arrangements of the pressure detecting means downstream of the second particulate filter 6 In addition, an absolute pressure sensor may be provided. This is particularly useful when the absolute pressure downstream of the second particulate filter 6 as an input variable for a regulation of the low-pressure exhaust gas recirculation rate through the exhaust gas recirculation line 8th should be used.

According to 10 include the printer fibers agent instead of the differential pressure sensors 20 . 21 three absolute pressure sensors 24 , These absolute pressure sensors 24 each detect the pressure at a location upstream of the first particulate filter 5 , downstream of the first particulate filter 5 and thus upstream of the second particulate filter 6 and downstream of the second particulate filter 6 each within the housing 14 ,

In the arrangement of the pressure detecting means, which in 11 is shown is only the third absolute pressure sensor 24 not in the area of the housing 14 , but at the junction of the exhaust gas recirculation line 8th in the exhaust tract 3 arranged.

In the 12 illustrated arrangement of the pressure detecting means is largely identical to the arrangement according to 11 , but here detects an absolute pressure sensor 24 the absolute pressure upstream of the first particulate filter 5 and the differential pressure sensor 20 over the test leads 22 . 23 the pressure drop at the first particle filter 5 , Here use the absolute pressure sensor 24 and the differential pressure sensor 20 the same measuring line 22 ,

The arrangement of the pressure detecting means according to 13 is largely analogous to the arrangement according to 12 , however, the absolute pressure sensor is detected here 24 the absolute pressure downstream of the first particulate filter 5 and works in conjunction with the differential pressure sensor 20 the measuring line 23 located at the location downstream of the first particulate filter 5 measuring the pressure in the housing 14 serves.

Also in the arrangement of the pressure detecting means according to 14 the pressure is downstream of the second particulate filter 6 as a direct measure, which by means of an absolute pressure sensor 24 is detected. However, in the arrangement according to 14 the pressure drop across the second particulate filter 6 by means of the differential pressure sensor 21 certainly. This differential pressure sensor 21 Uses in conjunction with absolute pressure sensor 24 a measuring line 25 , which downstream of the second particulate filter 6 at the height of the branch of the exhaust gas recirculation line 8th in the exhaust tract 3 extends.

At the in 15 shown arrangement of the pressure detecting means is the absolute pressure downstream of the second particulate filter 6 , which as well as in the arrangement according to 14 at the height of the branch of the exhaust gas recirculation line 8th detected as an indirect measure. Here it uses the measuring line 25 using differential pressure sensor 21 by which the pressure drop across the second particulate filter 6 is determinable, a measuring line 26 together with the absolute pressure sensor 24 , which is for detecting the absolute pressure between the first particulate filter 5 and the second particulate filter 6 serves.

If in the air supply tract 11 upstream of the compressor 12 an absolute pressure sensor is arranged, both the absolute pressure downstream of the second particulate filter 6 or the pressure gradient across the exhaust gas recirculation line 8th also be detected by means of a differential pressure sensor. Its measuring lines are then in the air supply tract 11 upstream of the compressor 12 and downstream of the second particulate filter 6 positioned. In this case, at the in 12 to 14 illustrated arrangements of the pressure sensing means measuring the absolute pressure downstream of the second particulate filter 6 omitted. In the arrangement of the pressure detecting means according to 15 can then, however, detecting the differential pressure at the second particle filter 6 by means of the differential pressure sensor 21 omitted.

The pressure drop across the second particulate filter 6 can be evaluated, in particular continuously, by means of an evaluation, which in a presently not shown control device for driving the internal combustion engine 1 can be arranged. The pressure drop is compared with a comparison value, which is a new condition of the first particulate filter 5 characterized. If the measured pressure drop exceeds the comparison value by a predetermined threshold value, an alarm is triggered in a monitoring device of the control device, which is also referred to as an OBD unit (on-board diagnosis).

In the present case, the threshold value is stored in the form of a characteristic which indicates the aging of the first particle filter 5 considered.

Additionally or alternatively, for monitoring the first particulate filter 5 the pressure drop across the second particulate filter 6 to the pressure drop across the first particulate filter 5 be put into proportion. Here, then, the measured ratio with a new condition of the exhaust gas treatment device 13 characterizing ratio compared. The alarm is triggered when the high ratio in the new state increases rather than decreases and / or exceeds the value of the new state. The ratio is preferably subsequent to a joint thermal regeneration of the particulate filters 5 . 6 formed from the measured values measured by the pressure sensing means.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - WO 2008/043422 A1 [0002]

Claims (18)

Exhaust treatment device for an internal combustion engine, with a first particle filter ( 5 ) and one in the flow direction of the exhaust gas through the exhaust gas treatment device ( 13 ) downstream of the first particulate filter ( 5 ) arranged second particle filter ( 6 ), characterized in that the second particulate filter ( 6 ) at least one support device through which the exhaust gas can flow ( 16 ), to which a filter unit ( 17 ), wherein a pore size of the filter unit ( 17 ) is less than a pore size of the at least one support device ( 16 ). Exhaust treatment device according to claim 1, characterized in that the pore size of the filter unit ( 17 ) at least half, in particular half to one tenth, of the pore size of the at least one support device ( 16 ) is. Exhaust treatment device according to claim 1 or 2, characterized in that the filter unit ( 17 ) is formed for retaining particles by means of surface filtration. Exhaust gas treatment device according to one of claims 1 to 3, characterized in that a thickness and / or a porosity of the at least one support device ( 16 ) a multiple of a thickness and / or a porosity of the filter unit ( 17 ) is. Exhaust treatment device according to one of claims 1 to 4, characterized in that a smallest extension of the at least one support device ( 16 ) transversely to the flow direction of the exhaust gas a multiple, in particular at least five times, a thickness of the at least one support device ( 16 ) is. Exhaust treatment device according to one of claims 1 to 5, characterized in that the at least one support device ( 16 ) and the filter unit ( 17 ) are at least partially formed of a same, in particular metallic or ceramic, material. Exhaust treatment device according to one of claims 1 to 6, characterized in that the at least one support device ( 16 ) downstream and / or upstream of the filter unit ( 17 ) is arranged. Exhaust treatment device according to one of claims 1 to 7, characterized in that the second particle filter ( 6 ) at least substantially perpendicular or inclined to the flow direction of the exhaust gas in the exhaust gas treatment device ( 13 ) is arranged. Exhaust treatment device according to one of claims 1 to 8, characterized in that the second particle filter ( 6 ) at least one survey ( 18 . 19 ), in particular a plurality of concentric and / or mutually parallel elevations ( 19 ), having. Exhaust treatment device according to one of claims 1 to 9, characterized in that the second particle filter ( 6 ) by a heat transfer regenerable in an exhaust tract ( 3 ), in particular within a first particle filter ( 5 ) surrounding housing ( 14 ), wherein the heat transfer by means of a thermal regeneration of the first particulate filter ( 5 ) is feasible. Exhaust treatment device according to one of claims 1 to 10, characterized in that the exhaust gas treatment device ( 13 ) Pressure sensing means ( 20 . 21 . 24 ) and an evaluation device, wherein by means of the evaluation device, a difference in pressure between a location upstream of the second particle filter ( 6 ) and a point downstream of the second particulate filter ( 6 ) with regard to a condition of the first particulate filter ( 5 ) is evaluable. Exhaust treatment device according to claim 11, characterized in that a state of the first particulate filter ( 5 ) characterizing, in particular depending on an aging of the first particulate filter ( 5 ) variable, reference value of the difference is stored in a memory. Exhaust treatment device according to one of claims 1 to 12, characterized in that the exhaust gas treatment device ( 13 ) Pressure sensing means ( 20 . 24 ) for detecting the pressure upstream and downstream of the first particulate filter (FIG. 5 ) having. Exhaust treatment device according to one of claims 1 to claim 13, characterized in that the exhaust gas treatment device ( 13 ) Pressure sensing means ( 20 . 21 . 24 ) and an evaluation device, wherein - a ratio of a difference of the pressure between a location upstream of the second particle filter ( 6 ) and a point downstream of the second particulate filter ( 6 ) to a difference in pressure between a location upstream of the first particulate filter ( 5 ) and a location downstream of the first particulate filter ( 5 ) is stored in a memory, and wherein - by means of the evaluation device on the basis of the pressure sensing means ( 20 . 21 . 24 ) determined relationship with respect to a state of the first particulate filter ( 5 ) is evaluable. Exhaust-gas treatment device according to claim 14, characterized in that the evaluation device is designed to use the pressure-sensing means ( 20 . 21 . 24 ) determined ratio as a function of a thermal regeneration of at least the first particulate filter ( 5 ). Exhaust treatment device according to one of claims 1 to 15, characterized in that the exhaust gas treatment device ( 13 ) one downstream of the second particulate filter ( 6 ) branching off, in particular a throttle device ( 10 ), exhaust gas recirculation line ( 8th ). Method for operating an exhaust gas treatment device ( 13 ) for an internal combustion engine, wherein exhaust gas by means of a first particulate filter ( 5 ) and by means of a flow direction of the exhaust gas through the exhaust gas treatment device ( 13 ) downstream of the first particulate filter ( 5 ) arranged second particulate filter ( 6 ) is filtered, characterized in that the means of the second particulate filter ( 6 ) filtered exhaust gas at least one support device ( 16 ) and one on the at least one carrying device ( 16 ) arranged filter unit ( 17 ), wherein a pore size of the filter unit ( 17 ) is less than a pore size of the at least one support device ( 16 ). A method according to claim 17, characterized in that it by means of an exhaust gas treatment device ( 13 ) according to one of claims 1 to 16.