WO2005093231A1

WO2005093231A1 - Particle filter

Info

Publication number: WO2005093231A1
Application number: PCT/EP2005/051315
Authority: WO
Inventors: Karl-Heinz Effenberger; Wolfgang Maurischat; Klaus Prescha
Original assignee: Robert Bosch Gmbh
Priority date: 2004-03-29
Filing date: 2005-03-22
Publication date: 2005-10-06
Also published as: DE102004015698A1

Abstract

The inventive particle filter for cleaning exhaust gases of internal combustion engines comprises a filter body (4) consisting of at least one filter belt (18) which is wound around the longitudinal axis (19) of the filter body (4) and radially form interspaced filtering walls (21, 22, 24, 26) which separate a first filtering space (23) situated in the flow direction upstream of said filtering walls (21, 22, 24, 26) from a second filtering space (27) situated downstream thereof, wherein the first filtering space (23) is open on the input side towards the first frontal face (12) of the filter body (4) and is closed on the output side towards the second frontal face thereof. Said invention is characterised in that a radial distance (A) between the radially limited filtering walls (21, 22, 24, 26) of one of the filtering space (23, 27) in the area of one of the frontal faces (12, 13) is greater than the radial distance (a) between the radially limited filtering walls (21, 22, 24, 26) of the other filtering spaces (27, 23).

Description

particulate Filter

State of the art

The invention is based on a particle filter with the features of the preamble of claim 1 or 20,

Such a particle filter is known from the published patent application DE 10223452 AI. This particle filter has a filter body arranged in a housing, which is constructed from filter pockets through which the exhaust gas flows, which are arranged radially around a longitudinal axis of the filter body and each form a wedge-shaped filter space between them in pairs.

A disadvantage of the particle filter is, on the one hand, the relatively complex production. The filter bags must be manufactured individually and then connected to the filter body are assembled. The surfaces of the filter bags themselves form relatively long seams that have to be welded or closed in some other way. As a result of the different material thickness in the area of the seams, the use of the particle filter for exhaust gas cleaning can result in undesirable warping of the filter surfaces or in the seams due to the self-cleaning that takes place at high temperatures, which can lead to a reduction in the service life of the particle filter ,

A spiral filter is known from the patent specification CH 226682, which consists of two paper webs spirally wound around a core, which are connected to one another at their edges with profile cords. This filter is not suitable for exhaust gas cleaning due to the lack of temperature and pressure resistance.

An exhaust gas filter is known from EP 1256369 A2, which consists of a spirally wound body with two spaced-apart web-shaped filter layers, between which there is a corrugated web-shaped spacer. The filter layers are alternately closed on the front. The filter layers are parallel to each other, resulting in filter spaces with the same volume and flow cross-section.

Filter systems currently used for particles in exhaust gases from internal combustion engines are designed either as ceramic filters with a catalytic coating or as metallic filters. The filter walls of the particle filters have one Microporous structure, which in particular retains carbon particles in the exhaust gas flow, the particles accumulating on the surface of the filter and thus gradually increasing the differential pressure in the exhaust system. The particle filter must therefore be regenerated from time to time, which in the case of metallic filters takes place through targeted burning cycles. Ceramic filters require the addition of additives whose storage volume is limited for cleaning. Metallic filters are therefore superior to ceramic filters in terms of service life.

For large series applications, it is desirable to find a filter design that is easy to manufacture and is less prone to deformation, even with large temperature fluctuations. In addition, the particle filter should be optimized so that the largest possible filter area can be accommodated in a given construction volume. If the filter area is larger, the differential pressure in the exhaust system increases more slowly, so that the particle filter has to be regenerated less frequently.

After regeneration, residual ash remains in the particle filter, which must be collected in a suitable manner within the filter body, so that the filter function of the particle filter is not impaired.

Advantages of the invention

The particle filter according to the invention with the characterizing features of patent claim 1 has the advantage of having an improved inflow crossflow compared to the prior art. cut and to have a higher collection capacity for residual ash. In addition, the design of the particle filter according to the invention enables an increased ratio of filter area to housing volume. This means that a larger flue gas volume can be cleaned with a comparable housing volume. The seam length required to close the filter edge is considerably shortened.

It is particularly advantageous to use an at least simply longitudinally folded filter web, in which case a filter space which is closed in the area of the fold is obtained between two adjacent filter webs.

Furthermore, it is advantageous if the input-side filter space of the filter body exposes the largest possible opening cross-section and tapers towards the output side of the filter body. In this way, good flow properties and a good ash collecting capacity can be combined.

Furthermore, the method according to the invention for producing a particle filter with the features of claim 18 has the advantage of making production easier.

Further advantages and advantageous embodiments of the object according to the invention can be found in the description, the drawing and the patent claims. drawing

Several exemplary embodiments of a particle filter according to the invention are shown schematically simplified in the drawing and are explained in more detail in the following description. FIG. 1 shows a side view of a particle filter according to the invention in a tubular design with a cut-away inlet side of the filter body; FIG. 2 shows a side view of the tubular particle filter according to FIG. 1 with the cut-out outlet side of the filter body; FIG. 3 shows a side view of a particle filter in a pot-shaped design with the cut-in input side of the filter body; FIG. 4 shows a side view of the cup-shaped particle filter according to FIG. 3 with a longitudinally cut filter body; FIG. 5 shows a perspective side view of a filter body; FIG. 6 shows a detail of an enlarged sectional view through a filter body with a simply folded filter web; FIG. 7 shows a detail of an enlarged sectional view through a filter body with a triple-folded filter web;

FIG. 8 shows an illustration for the production of a triple-folded filter web according to FIG. 7;

FIG. 9 is an illustration of a simply folded filter web loosely pre-wound into a filter spiral; and FIG. 10 shows the filter spiral according to FIG. 9 compressed to form a filter body; FIG. 11 shows a filter body with a triangular basic shape with rounded edges; FIG. 12 shows an illustration of a filter body with two filter webs which are wound offset from one another around an oval core.

Description of the embodiments

A particle filter 1 is shown in FIG. 1, which is integrated in an exhaust pipe 2 of an internal combustion engine (not shown). In the example, the exhaust pipe 2 forms a cup-shaped extension 3 with a funnel-shaped transition 14, into which a cylindrical filter body 4 is inserted. The filter body 4 is provided with an annular flange 5 which can be connected to a corresponding holding flange 6 at the end of the cup-shaped extension 3. The particle filter 1 is followed by a funnel-shaped constriction 7, which is connected to the flange 5 via a corresponding counter flange 8 and opens into an exhaust pipe 9. The arrows 10 and 11 describe the direction of flow of the exhaust gas from the internal combustion engine via the exhaust pipe 2 and the particle filter 1 to the exhaust pipe 9. The unfiltered exhaust gas enters the filter body 4 via a first end 12 on the input side. The particle filter 1 is arranged concentrically in line with the exhaust pipe 2 and the exhaust pipe 9, which allows, for example, an arrangement under the vehicle floor. The filter body 4 has an overall length L and a diameter D. In the example of FIGS. 1 and 2, the ratio of diameter D to length L is less than 1, which results in an elongated, tubular arrangement of the particle filter 1. gives. FIG. 2 shows an outlet-side second end 13 of the filter body 4 opposite the first end 12, from which the filtered exhaust gas emerges from the particle filter 1 and is directed via the funnel-shaped constriction 7 to the exhaust pipe 9. Alternatively, the particle filter 1 could also be provided with its own housing, which is arranged between the exhaust pipe 2 and the exhaust pipe 9.

Figure 3 shows a second possible embodiment of the arrangement of the particle filter 1. The same and equivalent parts are identified by the same reference numerals. The exhaust pipe 2 and the exhaust pipe 9 are here offset in parallel and the particle filter 1 is perpendicular to it. This arrangement is preferably suitable for a particle filter 1 in which the ratio of D to L is greater than or equal to 1, which results in a pot-shaped, bulbous design. In the installed position, the first end face 12 is preferably at the bottom and the opposite outlet side 13 is at the top, so that particles retained by the filter body 4 and the residual ash remaining after self-cleaning of the particle filter can fall out of the filter body 4 favored by gravity and vibrations downwards. This design is particularly suitable for placement in places without narrow diameter restrictions, such as in the engine compartment. In Figure 4, the filter body 4 is shown cut in the longitudinal direction. The second end face 13 is in the installation position above. Figure 5 shows the filter body 4 in a perspective side view. The filter body 4 has a core 20 which extends along a longitudinal axis 19 of the filter body 4, around which a filter web 18 extends in a spiral in a plurality of windings. The individual windings of the filter web 18 are spaced apart in the radial direction, so that a filter space 23, 27 results between the windings (see also FIG. 6). The filter web 18 forms the filter space 23, 27 in the radial direction delimiting, permeable filter walls through which the exhaust gas must pass. A first filter chamber 23 is opened axially to the first end face 12 on the inflow side, so that the uncleaned exhaust gas can penetrate into the filter body 4 there.

A section of the filter body 4 is shown in longitudinal section in FIG. The filter body 4 consists of the filter web 18, which in the example is simply folded in the middle in the longitudinal direction at a fold point 17 and placed one above the other. The bending of the filter web 18 that results at the fold point 17 can have a radius as well as be angular. The two-layer filter web resulting from the folding is then wound spirally around the core 20. As a result of the folding, a pair of filter walls with filter walls 21, 22 is created, which is closed in the area of the first end face 12 and extends approximately V-shaped to the second end face 13. After winding by an angle of more than 360 degrees, a further layer of a filter wall pair with filter walls 24, 26 is created. The opposing filter walls 22, 24 of two adjacent filter wall pairs have on the first end face 12 a radial distance A from each other and form between them the first filter chamber 23, which is open to the inflow side of the filter body 4. Each additional winding by at least 360 degrees accordingly leads to a further pair of filter walls. The radial distance A of the filter walls 22 and 24 from one another decreases with increasing axial distance from the first end face 12 until the two filter walls 22, 24 touch at a connection point 28 and thus close the first filter chamber 23 towards the second end face 13.

A second filter chamber 27 is formed between the filter walls 21 and 22, or 24 and 26 of a pair of filter walls, which is closed to the first end face 12 (inflow side) and is open to the second end face 13 (outflow side). The filter walls 21, 22 and 24, 26 have a distance a from one another on the first end face 12 that is smaller than the distance A. The distance between the filter walls 21, 22 and 24, 26 increases with increasing axial distance from the first Front 12 to the second

End face 13 to. At the same time, the distance A decreases accordingly. The increase in distance a or the decrease in distance A can run continuously, but also discontinuously, as shown in FIG. 6.

The second filter chamber 27 forms a rear side of the filter body 4, since the exhaust gas has to flow through the filter walls 21, 22, 24, 26 of the filter web 18 in order to get there and is filtered in this way. As a result, less soot or ash is produced on the output side of the filter body 4. For this reason, the filter walls 21, 22, 24, 26 can also advantageously be arranged such that the first filter space 23 has a larger volume than the second filter space 27, so that the ash collection capacity of the first filter space 23 increases.

At the connection points 28, the windings of the filter web 18 are connected to one another with the next winding in each case. The connection points 28 can be produced by welding, pressing, flanging or in some other way. An additional connecting part can also be applied to the filter web 18. It is important that there is a sufficiently tight connection at the connection point 28. The connection points 28 can also be provided on the first end face 12.

Another exemplary embodiment of a filter body 4 is shown in FIG. Instead of a single-folded filter web 18, a triple-folded filter web 18 is wound spirally, so that one winding forms four filter walls 21, 22, 24, 26 which are integrally connected in a double V-shape (see also FIG. 8). With the same radial distance between the connection points 28 as in the exemplary embodiment according to FIG. 6, this results in a denser packing of the filter body 4, so that an even larger filter area can be accommodated in a given construction volume.

The filter web 18 can be coated with filter material before folding and winding, in that a metallic sintered material is sintered onto a non-rusting metallic carrier. The connection to the core 20 can for example, by welding or stapling. A steel tube, for example, is suitable as the core 20, the material properties of which correspond to the conditions of use with regard to temperature resistance, thermal expansion and corrosion. The core 20 must be closed at least on the inflow side.

FIG. 9 shows a loosely pre-wound filter spiral which is wound from a simply folded filter base sheet 30. The filter base sheet 30 is preferably a fabric with a sieve structure that is gas permeable. The filter base sheet 30 is first to be connected to the core 20, preferably by welding, and to be loosely pre-wound. Such a loosely wound filter spiral can be coated with the filter material after pre-winding. For this purpose, a filter material, preferably a metallic sintered material, is applied to the web fabric, e.g. by immersing, then rotating or tumbling the filter spiral. After drying, the complete spiral basket is sintered. After completion of the coating process, the filter spiral can then be compressed by rotating the core 20 relative to an outer winding end 34, and the fully compressed spiral can then be connected to the flange 5 to form the finished filter body 4 (see FIG. 10, not to scale compared to FIG. 9) - lent).

FIG. 11 shows a filter body 4 which has an approximately triangular-shaped core 20, around which the filter web 18 extends in a spiral. The filter body 4 thereby has an approximately triangularly rounded basic shape. The core 20 has a step 35 on its outer surface, whose height corresponds approximately to the thickness of a filter winding. A winding start 33 of the filter web 18 is fastened in the area of the stage 35. This results in a step-free transition between a first and a second winding around the core 20. A corresponding recess can be provided in the flange 5 for the winding end 34.

FIG. 12 shows a filter body 4 with an oval core 20, which has two stages for the winding start 33a, 33b of two filter tracks 18a, 18b, which are offset by approximately 180 degrees to one another. The filter body 4 is thus made of two layers of filter webs 18.

In all embodiments of spiral filter bodies 4, spacers can be provided between the individual layers of the filter walls 21, 22, 24, 26. For example, beads or other material characteristics can be introduced into the filter web 18 or filter base web 30, which ensure a uniform winding distance between the filter walls when the filter web 18 is wound one on top of the other. In particular, the spacers must be suitable for preventing the filter walls from collapsing under pressure. In addition, a slope of the filter spiral should be predeterminable by means of the spacers.

Band-shaped spacers 36 (FIG. 8) can also be provided between the filter walls, which are provided with spaced-apart recesses and are welded to the filter web 18 in the region of the edges thereof, for example using known resistance welding methods or using a laser. But it is also possible to do it before, at or insert separate spacers after winding in the filter rooms 23, 27.

The invention is not restricted to the exemplary embodiments shown. The spacers 36 can also be arranged on both sides of the filter web 18. The filter body 4 can also have a conical shape. The filter walls 21, 22, 24, 26 can also be selected such that the first filter chamber 23 has a larger volume than the second filter chamber 27, so that the first filter chamber 23 has a larger ash collecting capacity. The filter body 4 can also be wound from several layers of a filter web 18, each of which are either folded or have closed connection points instead of the fold points. Thus, instead of a V-shaped folded filter web 18, two layers of flat filter webs can be arranged in a V-shape with respect to one another, wherein they are connected to one another on the closed side of the V.

In particular, the filter space 23 can be discontinuous over the length of the filter body 4, e.g. step-like, change, so that there are no too small gap dimensions between the filter walls, which would clog very quickly. The filter body 4 can also be shaped conically or discontinuously over its length, so that it adapts to the corresponding shape of the first filter winding. In this way, the core 20 can optimally support the V-shape, for example in the case of V-shaped filter webs.

The folding or bending of the filter web 18 can be carried out independently of the design of the filter body 4 and the geometrical see arrangement of the filter walls 21, 22, 24, 26 may be advantageous, since this creates a closed edge. The joining effort is thus considerably reduced.

Claims

Expectations

1. Particulate filter for cleaning exhaust gases from internal combustion engines, with a filter body (4) which consists of at least one filter web (18) spirally wound around a longitudinal axis (19) of the filter body (4), the filter walls (21, 22) being spaced apart in the radial direction , 24, 26), which forms a first filter chamber (23) lying in front of the filter walls (21, 22, 24, 26) in the flow direction, and a second filter chamber (21, 22, 24, 26) behind the filter walls (21 27), the first filter chamber (23) being open towards an upstream, first end face (12) of the filter body (4) and being closed towards an outflow end, second end face (13) of the filter body (4), characterized in that a radial distance (A) between the radially delimiting filter walls (22, 24; 24, 26) of one of the filter spaces (23, 27) in the area of one of the end faces (12, 13) is greater than a radial distance (a) between the radial limiting fil walls (24, 26; 22, 24) of the other filter space (27, 23).

2. Particulate filter according to claim 1, characterized in that the filter walls (22, 24) of the first filter space (23) in the region of the first end face have the greater distance (A) from one another.

3. Particulate filter according to claim 1 or 2, characterized in that a volume of the first filter space (23) is larger than a volume of the second filter space (27).

4. Particle filter according to claim 1 or 2, characterized in that the filter body (4) i is wound from an at least two-layer filter web (18).

5. Particulate filter according to claim 3, characterized in that the at least two-layer filter web (18) comprises at least one approximately V-shaped filter wall pair (21, 22; 24 27).

6. Particulate filter according to one of claims 3 or 4, characterized in that the at least two layers of the filter web (18) are made by folding or bending in the longitudinal direction of the filter web (18).

7. Particulate filter according to claim 5, characterized in that the filter web (18) has four layers and is produced by triple folding or bending the filter web (18).

8. Particulate filter according to one of the preceding claims, characterized in that the filter web (18) is wound around a core (20).

9. Particulate filter according to claim 7, characterized in that the core (20) has a substantially cylindrical cross section.

10. Particulate filter according to claim 7, characterized in that the core (20) has a non-circular, in particular oval or triangular cross-section.

11. Particulate filter according to claim 7, characterized in that the core (20) is conical in the longitudinal direction.

12. Particulate filter according to claim 7, characterized in that the core (20) has on its outer circumference a step (35) extending in the longitudinal direction, the height of which corresponds approximately to the thickness of a winding.

13. Particulate filter according to one of claims 1 to 11, characterized in that the filter body (4) is tubular with a ratio of diameter (D) to length (L) less than 1.

14. Particle filter according to one of claims 1 to 11, characterized in that the filter body (4) is cup-shaped with a ratio of diameter (D) to length (L) greater than or equal to 1.

15. Particle filter according to one of the preceding claims, characterized in that the filter walls (21, 22, 24, 26) from a gas-permeable Filt'ergrundbahn (30) are produced, on which a microporous filter material is applied.

16. Particulate filter according to claim 14, characterized in that the filter base web (30) consists of a wire mesh and the filter material is sintered after being applied to the wire mesh.

17. Particulate filter according to one of the preceding claims, characterized in that the filter web (18) is provided with spacers (36) which define a certain radial distance between filter walls (21, 22, 24, 26) after winding.

18. Particulate filter according to claim 16, characterized in that the spacers (36) are on a band applied to the filter web (18).

19. A method for producing a particle filter with a filter body (4) constructed from at least one spiral-wound filter web (18), characterized in that the filter body (4) is first loosely pre-wound from a filter base web (30) that a filter material is pre-wound on the loosely Filter base sheet (30) is applied and that the filter body (4) is then compressed with a reduction in the radial diameter of the filter body (4) by real rotation of a core (20) relative to an outer winding end (34).

20. Particulate filter for cleaning exhaust gases from internal combustion engines, with a filter body (4) which consists of at least one filter web (18) which is spirally wound around a longitudinal axis (19) of the filter body (4) and which has a plurality of spaced apart in the radial direction Forms filter walls (21, 22, 24, 26) which, seen in the flow direction, lies in front of the filter walls (21, 22, 24, 26) first filter chamber (23) and behind the filter walls (21, 22, 24, 26) Separate the second filter space (27), characterized in that the filter body (4) has at least one fold point (17) at which at least two layers of filter walls (21, 22; 24, 26) formed by reshaping the filter web (18) are connected to each other.

21. Particulate filter according to claim 19, characterized in that the filter body (4) is wound from an at least two-layer filter web (18).

22. Particle filter according to claim 20, characterized in that the at least two-layer filter web (18) comprises at least one approximately V-shaped filter wall pair (21, 22; 24 27).

23. Particulate filter according to one of claims 20 or 21, characterized in that the at least two layers of the filter web (18) are produced by folding or bending in the longitudinal direction of the filter web (18).

4. Particulate filter according to claim 22, characterized in that the filter web (18) has four layers and is produced by triple folding or bending the filter web (18).