WO2008025599A1

WO2008025599A1 - Filter element for a soot particle filter and method for producing a filter element

Info

Publication number: WO2008025599A1
Application number: PCT/EP2007/056924
Authority: WO
Inventors: Joachim Frangen; Ruediger Herr; Juergen Goetz
Original assignee: Robert Bosch Gmbh
Priority date: 2006-08-30
Filing date: 2007-07-09
Publication date: 2008-03-06
Also published as: DE102006040643A1

Abstract

The invention relates to a method which allows the filter bodies (36) of filter elements to be improved to give a filter element having entry channels (28) and exit channels (30) by simply placing a first closing disk (42) and a second closing disk (34) on said filter bodies.

Description

description

title

Filter element for a soot particle filter and method for producing a filter element

State of the art

The invention relates to a soot particle filter according to the preamble of the independent claims 1 and 4.

If the filter elements are made of a ceramic material, this is usually done by extrusion. This means that the filter body is initially a prismatic structure with a plurality of mutually parallel channels. So that the exhaust gas is forced through the filter walls located between the channels, the so-called inlet channels are closed at the outlet surface of the filter body, while the outlet channels are closed at the inlet surface of the filter body. The closing of the inlet channels takes place after the extrusion. The inlet and outlet channels are closed by sealing plugs made of the same or a similar ceramic material from which the filter body was also extruded. These plugs are pressed into the respective channels. As a filter element partially several hundred channels are present and all channels are closed at one end by a plug, therefore, several hundred plugs must be introduced into the channels. This method is naturally very time-consuming and thus cost-intensive. It also contains a large error rate. Disclosure of the invention

The invention is based on the object to provide a method for producing a filter element, which works more effectively and cost-effectively and also with a lower error rate than the conventional method for producing a filter element.

Furthermore, the invention is based on the object to provide a filter element whose hydraulic properties are improved and in which the filter performance is increased over conventional filter elements.

This object is achieved in a method according to the invention for producing a filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, with an inlet surface and an outlet surface, with inlet channels and with outlet channels, wherein the inlet channels begin at the inlet surface and are closed at the outlet surface, wherein the outlet channels are closed at the entrance surface and terminate at the exit surface, and wherein the inlet channels and the outlet channels are separated by filter walls of an open-pored material by the following method steps.

Extruding a prismatic filter body, forming at least one first closure disk for the entry surface, forming at least one second closure disk for the

Exit surface, placing the first closure disc on the entrance surface and the second closure disc on the exit surface, and thermally treating the filter element.

By forming a closure disk, which is designed so that it closes the outlet channels or the inlet channels at the inlet surface or at the outlet surface of the filter body, it is possible by placing only one closure disc on the entry surface and a closure disc on the exit surface all channels in the right way to close. This results in a very high time savings when closing the channels and also reduces the reject rate when closing the channels.

If the first or the second closure disk for manufacturing reasons or other reasons must be made so thin that they can not withstand the prevailing pressures and temperatures during operation, can according to the invention several layers of Closing discs are placed on both the entrance surface and on the exit surface. As a result, the required strength can be achieved and it results in a better connection between the filter walls or the inlet and the outlet surfaces of the filter body and the closure discs.

Furthermore, it has proved to be advantageous if the filter element composed of filter body and closure disks is subjected to a heat treatment after drying, in particular by sintering.

The inventive task is also in a filter element with a Eintrittsfiäche and with an exit surface, with inlet channels and outlet channels, wherein the inlet channels begin at the entrance surface and are closed at the Austrittsfiäche, the outlet channels are closed at the Eintrittsfiäche and terminate at the exit surface, and wherein the inlet channels and the outlet channels are separated by filter walls from an open-pored material, achieved in that at least one closure disc is present at the entrance surface and / or the outlet surface, and that the closure disc serves to close the inlet channels and / or the outlet channels.

The filter element according to the invention, consisting of the filter body and the closure disks, is much easier to handle in terms of production technology than conventional filter elements and has a lower error rate.

It is self-evident that the at least one closure disk has openings at the entrance surface where the inlet channels begin and that the at least one closure disk has openings at the outlet opening where the outlet channels terminate.

For many geometries of filter bodies, even the closure disks for the entrance surface and the exit surfaces can be identically shaped. You just need to be twisted differently or shifted to each other on the Eintrittsfiäche or the exit surface are placed.

Further advantages and advantageous embodiments of the invention are the following Drawing, the description and the claims can be removed.

Brief description of the drawings

Show it:

Figure 1 is a schematic representation of an internal combustion engine with an exhaust aftertreatment device according to the invention;

Figure 2 shows a filter element in longitudinal section and

Figure 3 shows an exemplary embodiment of an inventive filter element.

Embodiments of the invention

In Figure 1, an internal combustion engine carries the reference numeral 10. The exhaust gases are discharged via an exhaust pipe 12, in which a filter device 14 is arranged. With this, soot particles are filtered out of the exhaust gas flowing in the exhaust pipe 12. This is particularly necessary in diesel internal combustion engines to comply with legal requirements.

The filter device 14 comprises a cylindrical housing 16, in which a rotationally symmetrical in the present embodiment, a total also cylindrical filter element 18 is arranged. Between the housing 16 and the filter element 18 is a mat (see reference numeral 38 in Figure 3) is provided, which serves to attach the filter element 18 in the housing and at the same time prevents exhaust gases flowing through the annular gap between the housing 16 and the filter element 18.

FIG. 2 shows a cross section through a filter element 18 according to the prior art. The filter element 18 may, for example, be produced as an extruded shaped body of a ceramic material, such as cordierite. The filter element 18 is flowed through in the direction of the arrows 20 of not shown exhaust gas. An entrance surface has the reference numeral 22 in FIG. 2, while an exit surface in FIG. 2 has the reference numeral 24.

Parallel to a longitudinal axis 26 of the filter element 18 extend a plurality of inlet channels 28 in alternation with outlet channels 30. The inlet channels 28 are closed at the outlet surface 24. The sealing plugs are shown in FIG. 2 without reference numerals. In contrast, the outlet channels 30 are open at the outlet surface 24 and closed in the region of the inlet surface 22.

The flow path of the unpurified exhaust gas thus leads into one of the inlet channels 28 and from there through a filter wall 31 into one of the outlet channels 30. This is illustrated by arrows 32 by way of example.

By reversing the flow direction of the exhaust gas, the surface 24 becomes the inflow surface and the surface 22 becomes the exit surface. As a result, the channels 28 become outlet channels, while the channels 30 become inlet channels. The reversal of the flow direction of the exhaust gas can be achieved by changing the mounting position of the filter element 18 in the housing 16 in the simplest way. In the embodiments described below, for the sake of clarity, only one direction of flow and consequently a function of the channels 28 and 30 are assumed, although the function of the channels 28 and 30 can also be changed by turning the filter element 18 in the housing 16.

The problem of the gas-tight and play-free attachment of the filter element 18 and the body for a catalyst in the housing 16 is identical.

FIG. 3 shows an exemplary embodiment of a filter element 18 according to the invention. In the right part of Figure 3, a second shutter plate 34 according to the invention is shown in a front view. In a cylindrical filter body 36 whose channels 28 and 30 each have a square cross-section, the second shutter disk 34 has the shape shown in the right part of Figure 3. The hatched areas 38, of which not all have been provided with reference numerals for reasons of clarity, consist of the same Material as the filter body 36. Between the closure surfaces 38 openings 40 are recessed.

The second closure plate 34 is then placed on the filter body 36 such that the closure surfaces 38 close the inlet channels 28 at the outlet surface 24 and the openings 40 release the outlet channels 30 at the outlet surface 24.

Similarly, a first closure plate 42 disposed on the entrance surface 22 seals the exit channels 30 while having openings 40 at the beginning of the entrance channels 28.

The fact that the first closure plate 42 and the second closure plate 34 are formed as a separate molded part, it is possible by the placement of only a first closure plate 22 and a second closure plate 24, the filter body 36 so that the inlet channels 28 are closed at the exit surface 24 and the exit channels 30 are closed at the entrance surface 22. This results in a considerable acceleration of the production process. The erroneous closing of channels becomes almost impossible.

Since the closure discs 42 and 34 are placed on the entry surface 22 and 24, and not, as in conventional filter elements, closed by in the channels 28, 30 pressed-in sealing plug, the effective filter area of the filter body 36 is not shortened. This results in the same length of the filter body 36, a larger filter area and thus a more efficient filter element 18. Since the thickness of the closure discs 42 and 24 is also smaller than the length of the sealing plug, which are usually inserted into the channels 28 and 30, is can also be the total length of the filter element 18, consisting of filter body 36 and shutter disks 42 and 34, can be reduced.

The placement of the closure disks 42 and 34 on the filter body 36 takes place when both the filter body 36 and the closure disks 42 and 34 are still wet, so that the closure disks 42 and 34 connect to the filter body 36 during the subsequent drying operation. This compound is made by a subsequent heat treatment, such as sintering, further strengthened, so that the result is a very stable connection between the closure disks 42 and 34 and filter body 36 results.

Another not to be underestimated advantage of the filter element according to the invention can be seen in the fact that the closure disks 42 and 34 are relatively small in thickness D, so that the difference between the thickness D of the shutter disks 42 and 34 to the thickness of the filter walls 31 is relatively low is. As a result, the thermal stresses resulting from unequal temperature distributions in the region of the entrance surfaces 22 and the exit surface 24 are less than conventional filter elements in which in the region of the entrance surface 24 and the exit surface 24 through the sealing plug a relatively large accumulation of ceramic Material is located in the smallest space.

Claims

claims

1. A method for producing a filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, with an inlet surface (22) and with an outlet surface (24), with inlet channels (28) and with outlet channels (30), wherein the inlet channels (28) on the Begin entrance surface (22) and are closed at the exit surface (24), wherein the

Outlet channels (30) are closed at the entry surface (22) and terminate at the exit surface (24), and wherein the inlet channels (28) and the outlet channels (30) are separated by filter walls (31) from an open-pored material, characterized by the following method steps :

Extruding a prismatic filter body (36),

Forming at least one first closure disk (42) for the entry surface (22),

Forming at least one second shutter disk (34) for the exit surface (24),

Placing the first closure disc (42) on the entry surface (22),

- Setting the second shutter disc (34) on the Austrittsfiäche (24) and

- Heat treatment, in particular drying, of the filter element (18).

2. The method according to claim 1, characterized in that more than a first or second shutter disc (42, 34) on the entry surface (22) and / or on the exit surface (24) is placed.

3. The method according to claim 1 or 2, characterized in that the filter element (18) after drying a heat treatment, in particular by sintering, is subjected.

4. filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, with an entrance surface (22) and with an outlet surface (24), with inlet channels (28) and with outlet channels (30), wherein the inlet channels (28) begin at the inlet surface (22) and are closed at the outlet surface (24) the outlet channels (30) are closed at the inlet surface (22) and terminate at the outlet surface (24), and wherein the inlet channels (28) and the outlet channels (30) are separated from an open-pored material by filter walls (31), characterized at least one closure disk (42, 34) is present on the entry surface (22) and / or the exit surface (24), and in that the closure disk (42, 34) closes the inlet channels (28) and / or the exit channels (30) serves.

5. Filter element according to claim 4, characterized in that the at least one closure disc at the entry surface (22) there openings (40), where the

Start entry channels (28).

6. Filter element according to claim 4 or 5, characterized in that the at least one closure disc at the outlet surface (22) there openings (40), where the outlet channels (28) terminate.

7. Filter element according to one of claims 4 to 6, characterized in that the

Entry channels (28) begin at the entry surface (22) and are closed at the exit surface (24), and that the exit channels (30) are closed at the entry surface (22) and terminate at the exit surface (24).

8. Filter element (18) according to one of claims 4 to 7, characterized in that the filter element (18) made of a ceramic or a glass-ceramic material, in particular of cordierite, aluminum titanate or silicon carbide, is produced.