DE102008000688A1 - Filter device, in particular for an exhaust system of an internal combustion engine - Google Patents

Abstract

A filter element is proposed whose cross-section is composed of hexagonal unit cells (35) with inlet channels (28) and outlet channels (30).

Description

State of the art

The The invention relates to a filter element, in particular for an exhaust system of an internal combustion engine, according to the preamble of Claim 1 and a filter device with a filter element according to the independent claim. 7

From the DE 10 2006 026 161 A1 For example, a filter element is known having an entrance surface and an exit surface, a plurality of inlet channels and a plurality of outlet channels, the inlet channels and the outlet channels having a hexagonal cross-section, and wherein the inlet channels and the outlet channels are separated from an open-pore material by a filter wall are.

filter elements often consist of a ceramic material and are usually produced by extrusion. This means that the Blank of the filter element a prismatic body with a plurality of mutually parallel channels is. The channels of a blank are initially on open at both ends.

In order to the exhaust gas to be cleaned flows through the walls of the filter, becomes part of the channels at the rear end of the filter element closed while another part of the channels is closed at the front end of the filter element. This will be formed two groups of channels, namely the so-called Inlet ducts, which are closed at the rear end, and the so-called exit channels, which at the beginning of Filter element are closed.

Between the inlet channels and the outlet channels consists solely of the porous walls the filter element (hereinafter filter walls) a flow connection, so that the exhaust gas can only flow through the filter element, by leaving the entrance channels through the walls of the filter element flows into the outlet channels.

With of time are deposited on the upstream surfaces the filter walls of the filter elements soot particles from. These soot particles reduce the permeability the filter walls and thereby increase the passage the gas flow through the filter walls occurring pressure drop. Accordingly, the so-called "exhaust back pressure" increases the filter device. If the exhaust back pressure of this one particular Exceeds the limit, the filter is regenerated by the separated soot particles are burned. It will Heat released, causing a temperature increase in the filter element leads. So this temperature increase does not lead to stress cracks in filter element, becomes a sought uniform loading of the filter element with soot.

at the filter element known from the prior art is by suitable cross-sectional geometries of the filter elements equalize reached the loading of the filter elements with soot.

Disclosure of the invention

Of the Invention is based on the object, further improved geometries the filter elements which, with regard to soot loading, Temperature distribution during regeneration and manufacturing advantages compared to the prior art ..

These Object is according to the invention in a filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, with an entrance surface and with an exit surface, with a variety of entry channels and with a variety of Outlet channels, wherein the inlet channels and the Outlet channels through filter walls of an open-pore Material are separated and where the cross-sectional areas all entrance channels larger than the Cross-sectional area of all outlet channels is and where the filter element in cross section of several hexagonal unit cells is composed, solved by the fact that at the corners and arranged at the center of the unit cell exit channels are, and that between two adjacent and at the vertices arranged outlet channels at least a first filter wall is provided.

Thereby it is possible between the at the corners of the hexagon located outlet channels and the center of the Hexagonal outlet channel at least one annular inlet channel train. Furthermore it is possible to do this at least a first filter wall flat, kinked and / or curved train. By the number of first filter walls between two adjacently arranged outlet channels and their Design can be the ratio between cross-sectional area of inlet channels and outlet channels as well the number of entrance channels also within Limits are controlled. As a result, the soot loading can thereby of the filter element can be further improved so that the temperature-induced Thermal stresses during regeneration on be reduced.

The inventive design of the channels of the filter element allows a greater asymmetry of the ratio of the cross-sectional areas of the inlet channels to the cross-sectional areas of the outlet channels, without causing the flow Resistance of the outlet channels increases too much. Due to the enlarged in the filter element according to the invention surfaces of the inlet channels, the storage capacity for ashes increases, which has a positive effect on the life of the filter element.

The Ratio between the number of entry channels and the number of exit channels can be further controlled thereby Be that, starting from one concentric to the center the unit cell arranged outlet channel limiting filter wall a plurality of substantially radially extending second filter walls are provided. This filter walls allow it, the number of entry channels within wide limits to vary and thereby the flow conditions within the filter element also within wide limits.

It has proven to be beneficial when between six (6) and nine (9) radially extending filter walls per unit cell available are. If six or more radially extending second filter walls are present, is the ratio of the number of entrance channels to the number of outlet channels greater than 2 and thus assumes a favorable value.

A Further advantageous embodiment of the invention provides that the exit channels a circular or polygonal Have cross-section.

A Particularly advantageous embodiment of the invention provides that the cross section of a filter element of several embodiments of the invention composed of unit cells. This makes it possible for example, in the center of the filter element other channel geometries to provide as at the periphery of the filter element. In this way can different soot loading and different Flow and pressure conditions over the cross section of the filter element be taken into account.

Further Advantages and advantageous embodiments of the invention are the subsequent drawing, the description and the claims removable. All in the drawing, the description and the claims disclosed features can be used individually as well as in any Combination with each other essential to the invention.

It demonstrate:

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

2 a filter element according to the invention in longitudinal section and

3 to 8th Cross sections through embodiments of inventive filter elements.

In 1 an internal combustion engine carries the reference number 10 , The exhaust gases are via an exhaust pipe 12 derived in which a filter device 14 is arranged. With this soot particles from the exhaust pipe 12 filtered exhaust gas filtered out. The filter device 14 comprises a prismatic, in particular cylindrical housing 16 in which a rotationally symmetrical in the present embodiment, a total also cylindrical filter element 18 is arranged.

In 2 is a longitudinal section through a filter element according to the invention 18 shown. The filter element 18 For example, may be prepared as an extruded molded article of a ceramic material, such as cordierite.

The filter element 18 will be in the direction of the arrows 20 flows through not shown exhaust gas. An entrance area has in 2 the reference number 22 while an exit surface in 2 the reference number 24 Has.

Parallel to a longitudinal axis 26 of the filter element 18 run several inlet channels 28 in alternation with outlet channels 30 , The entrance channels 28 are at the exit surface 24 locked. The sealing plugs are in 2 shown without reference number. In contrast, the exit channels 30 at the entrance area 22 locked.

In the filter elements according to the invention, the cross section of the filter element is set 18 from hexagonal unit cells whose boundary is in the 3 pictured, together.

In the 3a is an embodiment of a unit cell according to the invention 35 whose border is indicated by a dashed line 33 is indicated, shown greatly enlarged. The unit cell 35 has six corners 37 of which in 3a only two have been provided with reference numerals. Furthermore, the unit cell has 35 a center 39 ,

How out 3a good to see is on every corner 37 and in the center 39 the unit cell 35 in each case a circular outlet channel 30 available.

Again, for reasons of clarity, not all channels and all filter walls 31 provided with reference numerals.

Between the concentric to the corners 37 arranged outlet channels 30 is a first filter wall 31.1 available. At the in 3a Darge First embodiment of a unit cell of a filter element according to the invention connect the first filter walls 31.1 the shortest way to the exit channels 30 belonging filter walls 31 , They run in the illustrated embodiment on the borderline 33 the unit cell 35 ,

Furthermore, in the embodiment according to 3a a total of six second filter walls 31.2 provided, which extend radially and in each case the filter walls 31 of the focus 39 arranged outlet channel 30 with the filter walls 31 the one at the corners 37 the unit cell arranged outlet channels 30 combines.

The filter walls 31.1 . 31.2 and the circle segments of the outlet channels 30 limiting filter walls 31 limit a total of six entrance channels 28 ,

In 3b a total of three such unit cells have been joined together. This pattern, consisting of a plurality of unit cells with the same edge lengths, can be continued until the desired diameter of the filter element 18 is reached.

If you look at the number of exit channels 30 and the number of entry channels is related to each other, in this embodiment, the number of entry channels 28 twice as large as the number of exit channels 30 , The example of 3a this can also be illustrated.

There are a total of six entrance channels 28 and six exit channels at the corners 37 are arranged. However, each of these exit channels belongs 30 only 1/3 each to a unit cell 35 , That's why of the six exit channels at the corners 37 the unit cell only 1/3, corresponding to two outlet channels of a unit cell assign. If you still have the exit channel 30 in the centre 39 adds up to the unit cell results in total per unit cell 35 a number of three exit channels that opposes the mentioned number of six exit channels. Thus, the number of entrance channels behaves 28 to the number of exit channels 30 like 2: 1.

If this ratio is to be increased, then, as in the 4 . 5 and 6 represented, the number of second filter walls 31.2 increase. In the 4 - 6 carries the number of second filter walls 31.2 seven, eight and nine. This results in correspondingly different ratios between the number of inlet channels and the number of outlet channels.

In the embodiment according to 7 are the first filter walls 31.1 , unlike the previous embodiments not straight, but have a kink 41 on. In addition, the first filter walls run 31.1 not on the borderline 33 , so that by joining several inventive unit cells also still another outlet channel 30.1 forms, which has a roughly diamond-shaped cross-section. An example is an exit channel 30.1 with diamond-shaped cross-section in the lower left part of the 7 shown.

This also makes the ratio of the number of cross-sectional areas between the inlet channels 28 and exit channels 30 to be influenced. In addition, the hydraulic diameter of the inlet channels 28 and the exit channel 30.1 to be controlled.

In the embodiment according to 8th have the first filter walls 31.1 also a kink on and the radially extending second filter walls 31.2 end in the bend 41 the first filter walls 31.1 , Also, the ratio of the inlet cross sections and the outlet cross sections and the hydraulic diameter is changed again.

It goes without saying that the filter elements according to the invention 18 from unit cells 35 composed of the same topology or of unit cells 35 can be composed with different topology. This makes it possible, for example, the different temperature and flow and pressure conditions over the cross section of the filter element 18 Take into account. This results in a more uniform soot loading of the filter element according to the invention and thus an improved performance.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102006026161 A1 [0002]

Claims (7)

Filter element, in particular for filtering exhaust gases of a diesel internal combustion engine, having an entry surface ( 22 ) and with an exit surface ( 24 ), with a plurality of entry channels ( 28 ) and with a plurality of exit channels ( 30 ), whereby the entry channels ( 28 ) and the exit channels ( 30 ) through filter walls ( 31 ) are separated from an open-pore material and wherein the cross-sectional area of all inlet channels ( 28 ) greater than the cross-sectional area of all exit channels ( 30 ), and wherein the filter element O in cross-section of a plurality of hexagonal unit cells ( 35 ), characterized in that at the corners ( 37 ) and in the center ( 39 ) of the unit cells ( 35 ) Exit channels ( 30 ) and that between two adjacent and at the corners ( 37 ) arranged outlet channels ( 30.1 ) at least one first filter wall ( 31.1 ) is provided. Filter element according to claim 1, characterized in that the at least one first filter wall ( 31.1 ) is flat, kinked and / or curved. Filter element according to one of the preceding claims, characterized in that starting from a filter wall ( 31 ), which are the focus ( 39 ) arranged outlet channel ( 30.2 ), a plurality of substantially radially extending second filter walls ( 31.2 ) are provided. Filter element according to claim 3, characterized in that between six and nine radially extending second filter walls ( 31.2 ) per unit cell ( 35 ) are provided. Filter element according to one of the preceding claims, characterized in that the outlet channels ( 30 . 30.1 ) have a circular or polygonal cross-section. Filter element according to one of the preceding claims, characterized in that the cross section of the filter element ( 18 ) from different unit cells ( 35 ) is composed according to one of the preceding claims. Filter device with a housing ( 16 ) and with a filter element ( 18 ), characterized in that the filter element ( 18 ) according to one of the preceding claims.