GB2386083A

GB2386083A - Honeycomb body having a segmented sheathing tube

Info

Publication number: GB2386083A
Application number: GB0306460A
Authority: GB
Inventors: Rolf Brueck; Katrin Schaper; Joerg-Roman Konieczny
Original assignee: Emitec Gesellschaft fuer Emissionstechnologie mbH
Current assignee: Vitesco Technologies Lohmar Verwaltungs GmbH
Priority date: 2000-09-13
Filing date: 2001-08-31
Publication date: 2003-09-10
Also published as: JP2004509263A; CN1454287A; AU2001287707A1; DE10193874D2; DE10045502A1; WO2002023020A1; GB0306460D0

Abstract

The invention relates to a honeycomb body (1) held inside a housing (2), whereby the honeycomb body (1) has an axial (5) length (6) and is surrounded by segments (9) that are interspaced (8) in a circumferential direction (7). Each of the segments is joined to the housing (2) in at least one partial section (10) and to the honeycomb body (1) in at least one partial area (11) by using joining techniques, and the at least one partial section (10) and the at least one partial area (11) are axially (5) interspaced (30). The inventive honeycomb body that is held inside a housing can thermally expand in relation to the housing in a nearly unimpeded manner, whereby a long-lasting fixing of the honeycomb body is ensured inside the housing, in particular, inside the housing of an exhaust gas system of an internal combustion engine. The invention is particularly important for honeycomb bodies having a high channel density of 800 cpsi and sheet metal thicknesses of thinner than 0.025 mm.

Description

- Honeycomb body with segmented tubular casing The invention concerns a

honeycomb body which is held in a housing, as set forth in the classifying portion of claim 1. Such honeycomb bodies are used in particular in an exhaust system of an internal combustion engine.

Such a honeycomb body is known from DE 39 30 680. Described therein is a 5 catalytic converter for cleaning motor vehicle engines comprising a metallic honeycomb body and a metallic housing. In that arrangement the honeycomb body is not brazed to the housing over the entire periphery but is elastically suspended on the housing by two or more mountings. The mountings are of such a nature that they can accommodate the relative movements between the housing and the honeycomb body, 10 which occur due to the rise in temperature and growth of the honeycomb body, in a radial direction, or, upon the increase in the periphery of the honeycomb body which occurs as a result, in the tangential direction. The mountings comprise leaf springs which are distributed uniformly on the periphery of a casing ring surrounding the honeycomb body. In regard to the fixed mounting the leaf springs are connected to 15 the casing ring and the housing by a procedure involving intimate joining of the materials concerned. The loose mounting additionally has a sliding ring, in which respect the leaf springs are connected to the casing ring and the sliding ring by a procedure involving intimate joining of the materials involved and the sliding ring is axially movably supported in the housing. Welding the springs to the casing ring and 20 to the sliding ring and the housing respectively provides that the honeycomb body is always guided centrally as all springs act uniformly on the honeycomb body. The honeycomb body is held by the mounting arrangement at a spacing of two to ten millimetres from the housing. In that arrangement the annular gap which is produced in that case has to be sealed off again by further structural measures in order to 25 prevent exhaust gases from flowing through the annular gap. It is further proposed that the casing ring should be replaced by four segments in the form of portions of a

circle, thereby improving the expansibility of the honeycomb body in the peripheral direction. That holding arrangement with a plurality of casing rings or segments, a plurality of leaf springs, at least one sliding ring and seals for the annular gap requires a high level of production and assembly expenditure in order for the holding 5 arrangement to withstand the thermal and dynamic loadings in an exhaust system.

Based thereon, the object of the present invention is to provide a honeycomb body which is disposed in a housing and which has a holding arrangement of a simple configuration, wherein long-duration fixing of the honeycomb body in the housing is ensured in spite of differing thermal expansion characteristics on the part of the 10 individual components.

That object is attained by a honeycomb body held in a housing, as set forth by the features of claim 1. Advantageous developments and particularly preferred embodiments are described in the appendant claims. The holding arrangement, which is proposed herein, for the honeycomb body, is used in particular for fixing a 15 honeycomb body in a housing of an exhaust system of an internal combustion engine.

In that case the honeycomb body is of an axial length and is surrounded by segments which are spaced from each other in the peripheral direction. The segments are respectively connected by a procedure involving intimate joining of the materials involved to the housing in at least one partial portion and to the honeycomb body in at 20 least one partial region. The honeycomb body which is held in accordance with the invention is distinguished in that the at least one partial portion and the at least one partial region are axially spaced from each other.

As the segments are arranged distributed at a predeterminable spacing relative to each other on the periphery of the honeycomb body, that holding arrangement 25 permits relatively unimpeded expansion or shrinkage of the honeycomb body in the peripheral direction. The axially mutually spaced connection of the segments to the honeycomb body and the housing respectively permits low-stress expansion of the honeycomb body in the radial direction. Axial expansion freedom of the honeycomb body is ensured in that the honeycomb body is not connected over the entire length to 30 the segments. In that case the segments themselves serve as bending springs which

are connected on the one hand to the honeycomb body and on the other hand to the housing. This therefore affords a holding arrangement, of a particularly simple structure, for holding a honeycomb body in a housing, wherein virtually unimpeded expansion of the honeycomb body due to thermal stresses is ensured.

5 It is particularly advantageous in that respect that the segments are of a cross section which is preferably in the Loran of a portion of a circle and the outsides of the segments are connected directly to the housing and the insides are connected directly to the honeycomb body, involving intimate joining of the materials concerned. A cross-section in the form of a portion of a circle guarantees that the honeycomb body, 10 in the at least one partial region, bears against the segments in such a way as to ensure that the segment and the honeycomb body are intimately joined together over the largest possible surface area. That enhances the service life of such a honeycomb body holding arrangement, precisely in regard to the pressure fluctuations occurring in a flow of exhaust gas. If the honeycomb body, the segments and the housing at least 15 in part are of a similar geometry at the periphery and in addition are arranged in mutually coaxial relationship, then in each case the honeycomb body can be directly connected to the inside of the segments and the outside of the segments can be directly connected to an inside surface of the housing. That arrangement always ensures that the intimate joins in the partial region and the partial portion respectively are such as 20 to afford long-term fixing of the honeycomb body in the housing. The connection afforded by intimate joining of the materials involved in preferably made by a welding or brazing operation.

It is further proposed that the outsides bear substantially against the housing and the insides bear substantially against the honeycomb body. This means on the one 25 hand that the outsides of the segments are in bearing contact in the region with the intimate joins in order to ensure a connection of large area, while on the other hand this also ensures that a by-pass flow of the exhaust gas is prevented in operation of the exhaust system.

In accordance with a further configuration the axial extent of the segments is 30 smaller than the axial extent of the honeycomb body. This ensures that the

honeycomb body can expand or contract unimpededly at least in some portions. If in that case the segments are arranged in such a way that they do not extend as far as the end of the honeycomb body, through which for example a hot exhaust gas to be cleaned enters, heat dissipation by way of the segments is not possible, thereby 5 ensuring that the honeycomb body heats up particularly quickly. If the honeycomb body additionally heats a catalytically active coating, then it very quickly reaches its starting temperature for catalytic conversion of pollutants in the exhaust gas.

A smaller axial extent on the part of the segments with respect to the length of the honeycomb body also permits the advantageous design configuration that at least 10 two segments are arranged in axial succession. In that way for example the spacings of the segments in the peripheral direction and thus also unimpeded expansibility in that direction can be increased. In that respect it is particularly advantageous that the at least two segments are additionally arranged in mutually displaced relationship in the peripheral direction. It is thus possible to arrange the segments in such a way that, 15 over the entire periphery of the honeycomb body, there are partial regions for connection of the honeycomb body to the segments. Besides the increase in stabi},r of the holding arrangement, that also has a sealing function as a by-pass flow past the honeycomb body and therethrough is greatly impeded.

In accordance with still a further embodiment the at least one partial portion 20 for intimate joining to the housing is arranged substantially centrally with respect to the end faces of the segments, wherein preferably at least two partial regions for intimate joining to the honeycomb body are arranged near the end faces. Such a holding arrangement in particular promotes the substantially symmetrical cooling characteristics of a honeycomb body. As the honeycomb body mostly cools down by 25 way of its ends, shrinkage also starts firstly and to an increased degree in that zone while in the central region it occurs markedly more slowly, by virtue of the lack of cooling effect. This embodiment of the holding arrangement accommodates that as the zones of the honeycomb body, which are active in terms of expansion, are only very slightly impeded by the partial regions while the bonding of the segments to the

housing in the partial portion has more sluggish expansion or cooling characteristics and thus ensures stable fixing.

In a further advantageous embodiment the at least one partial region for intimate joining of the holding arrangement to the honeycomb body is arranged 5 substantially centrally with respect to the end faces, wherein preferably at least two partial portions for intimate joining to the housing are arranged near the end faces.

This has the advantage that the intimate joins in the at least two partial regions, near the end faces of the segments, prevent a by-pass flow. In addition the central bonding of the honeycomb body to the segments again guarantees virtually unimpeded 10 expansion freedom of the honeycomb body in the zones which are active in terms of expansion. In accordance with a further embodiment the segments each have at least one transverse slot which extend substantially in the peripheral direction The transverse slots narrow the segments in that region and thereby influence the flexural stiffness of 15 the segments. The flexural stiffness of the segments decreases with an increasing number of transverse slots. In that respect the flexural stiffness is to be so set that on the one hand relatively unimpeded expansion of the honeycomb body when thermal stresses occur is guaranteed, while on the other hand severe vibration and oscillation of the honeycomb body by virtue of pressure fluctuations occurring in the flow of 20 exhaust gas is prevented. Depending on whether the transverse slots only extend between side faces of the segments or extend from a side face, the transverse slots have two end regions or one end region. In that respect it is particularly advantageous that the at least one end region of the transverse slot has a cut-out. In that case the cut-

out is to be of a substantially round configuration and serves to prevent notches which 25 can occur for example due to high dynamic loading in the end regions of the transverse slots.

In accordance with a further embodiment the segments are held at a spacing in the peripheral direction by means of a support structure. A support structure of that kind is so designed that the expansion characteristics of the honeycomb body are not 30 substantially adversely affected. The purpose of the support structure is to fix the

segments relative to each other avidity and in the peripheral direction in particular during assembly.

In accordance with a further embodiment the honeycomb body has sheet metal layers which are so structured that they have passages through which an exhaust gas 5 can flow. In that respect the honeycomb body should involve in particular a passage density of at least 800 cpsi (cells per square inch). The consequence of that relatively high passage density is that a relatively large surface area is available in the exhaust gas. If that surface is provided for example with a catalytically active coating that guarantees particularly effective conversion of pollutants in exhaust gas from the 10 internal combustion engine. For that purpose the sheet metal layers are preferably constructed with sheets of a sheet thickness of less than 0.025 mm. Those small sheet thicknesses ensure that the honeycomb body has a surface-specific thermal capacity which is also low, thereby speeding up in particular the process of heating the honeycomb body.

15 In a further advantageous configuration the honeycomb body, at least near one end, has a sleeve portion which is connected to the ends of the sheet metal layers by a procedure involving intimate joining of the materials concerned. To produce such a honeycomb body for example smooth and corrugated sheets are stacked and then twisted or wound in such a way that the shape of the honeycomb body is formed. To 20 retain that shape the sheet metal layers are connected by a procedure invoking intimate joining, in particular brazing, at least from one end. In order to prevent the ends of the sheet metal layers coming loose by virtue of the thermal and dynamic stresses on the honeycomb body during operation, they are advantageously surrounded by a sleeve portion. A sleeve portion of that kind can be made for example from a 25 metal sheet of a similar thickness to the sheets of the sheet layers of the honeycomb body. That therefore ensures that the sleeve portion and the honeycomb body have the same thermal expansion characteristics, thereby avoiding thermal stresses.

Further details and advantageous embodiments are described in greater detail in the accompanying drawing in which:

Figure 1 shows an embodiment of the honeycomb body according to the invention which is held in a housing, Figure 2 diagrammatically shows the structure of an exhaust system, Figure 3 diagrammatically shows a detail view of a segment according to the 5 invention, Figure 4 shows a crosssection through a honeycomb body with a sleeve portion according to a further embodiment, and Figure 5 shows a further embodiment of the honeycomb body holding arrangement. 10 Figure 1 diagrammatically shows an embodiment of the honeycomb body l according to the invention which is held in a housing 2. The honeycomb body 1 is of a length 6 which is delimited by two ends 27 of the honeycomb body 1. Arranged in the peripheral direction 7 (not shown) of the honeycomb body 1 are a plurality of segments 9 which are spaced from each other at 8. The segments 9 are each 15 connected to the honeycomb body l in two partial regions. In that respect the segments 9 have a partial portion l 0 which is arranged centrally at 18 and in which the segments 9 are connected to the housing 2 by a procedure involving intimate joining of the materials concerned. The two partial regions 11 near the end faces 17 of the segments 9 and the partial portions 10 arranged centrally at 18 are arranged spaced 20 from each other, as indicated at 30, axially as indicated at 5. In the illustrated embodiment the segments 9 are of an extent 15, in the axial direction 5, which is smaller than the length 6, in the axial direction 5, of the honeycomb body 1. That permits the honeycomb body l to heat up rapidly near the ends 27.

Figure 2 diagrammatically shows the structure of an exhaust system 3 with an 25 internal combustion engine 4. The exhaust gas produced in the internal combustion engine 4 is passed into the ambient atmosphere through the exhaust system. The exhaust system 3 includes in this case components for cleaning the exhaust gas, such as for example a catalytically actively coated honeycomb body l arranged in the housing 2 of the exhaust system 3. The illustrated honeycomb body 1 has segments 9 30 spaced in the peripheral direction.

Figure 3 diagrammatically shows a detail view of a segment g with a transverse slot 19. The segment 9 is of a cross-section 12 in the form of a portion of a circle, it has a side face 17 as well as an outside 13 and an inside 14. The outside 13 serves in particular for joining the segment 9 to the housing 2 by intimate joining of 5 the materials involved, while the inside 14 serves for bonding to the honeycomb body 1. The illustrated transverse slot 19 extends in the peripheral direction into the segment 9. Accordingly the transverse slot 19 has only an end region 20 which is provided with a cut-out to prevent notches as a consequence of a high level of dynamic loading. The transverse slots 19 serve to reduce the flexural stiffness of the 10 segments 9.

Figure Elbows a cross-section through a honeycomb body 1 with a sleeve portion 28 and a plurality of segments 9 which are spaced in the peripheral direction 7.

The honeycomb body 1 has sheet metal layers 23 which are so structured that they have passages 24 through which an exhaust gas can flow. For that purpose the sheet 15 layers 23 have smooth and corrugated sheets 25 which at least in part form the passages 24. In this arrangement the sheets are preferably of a thickness of smaller than 0.025 mm. The ends 29 of the sheet layers 23 are connected by a procedure involving intimate joining of the materials concerned, to a sleeve portion 28 surrounding the honeycomb body 1. That therefore prevents the ends 29 of the sheet 20 layers 23 becoming detached from each other.

Figure S diagrammatically shows a further embodiment of a honeycomb body 1 according to the invention, which is held in a housing 2 and which has a plurality of segments 9 arranged distributed in the peripheral direction. Near an end 27 the honeycomb body 1 has a sleeve portion 28 surrounding it. The segments 9 are here 25 arranged in succession in the axial direction 5. Each segment has a partial portion 10 for making a connection to the housing 2 and a partial region 11 for connection to the honeycomb body 1. The partial portion 10 and the partial region 11 are arranged spaced from each other at 30, in the axial direction 5. The illustrated segments 9 are arranged in succession in the axial direction 5 in such a way that a positive 30 displacement 16 is formed. A negative displacement which involves at least partial

overlap of the segments 9 in the axial direction 5 has the result that a kind of seal is formed, which prevents a by-pass flow of the exhaust gas radially outside the honeycomb body 1.

The honeycomb body which is held in a housing, in accordance with the 5 invention, can expand virtually unimpededly with respect to the housing, in which respect long-term fixing of the honeycomb body in the housing is guaranteed, in particular in the housing of an exhaust system of an internal combustion engine.

List of references 1 honeycomb body 2 housing 3 exhaust system 5 4 internal combustion engine S axis 6 length 7 peripheral direction 8 spacing 10 9 segment 10 partial portion 11 partial region 12 crosssection 1 3 outside 15 14 inside 1 S extent 1 6 displacement 17 end face 18 centre 20 19 transverse slot 20 end region 2 1 cut-out 22 support structure 23 sheet metal layer 25 24 passage 25 metal sheet 26 sheet thickness 27 end 28 sleeve portion 30 29 end

30 distance

Claims

1. A honeycomb body (1) which is held in a housing (2), in particular of an exhaust system (3) of an internal combustion engine (4), wherein the honeycomb body (1) has an axial (5) length (6) and is surrounded by segments (9) which are spaced (8) from each other in the peripheral direction (7) and which are respectively connected by intimate joining of the materials involved to the housing (2) in at least one partial portion (10) and to the honeycomb body (1) in at least one partial region (11), characterized in that the at least one partial portion (10) and the at least one partial region (11) are spaced (30) from each other axially (5).

2. A honeycomb body (1) according to claim 1 wherein the segments (9) are of a cross-section (12) which is preferably in the form of a portion of a circle and have an outside (13) and an inside (14) characterized in that the outsides (13) of the segments (9) are connected by intimate joining of the materials involved directly to the housing (2) and the insides (14) are connected by intimate joining of the materials involved directly to the honeycomb body (1).

3. A honeycomb body (1) according to claim 2 characterized in that the outside (13) bears substantially against the housing (2) and the inside (14) bears substantially against the honeycomb body (1).

4. A honeycomb body (1) according to one of claims 1 to 3 wherein the segments (9) are each of an axial (5) extent (15) characterized in that the axial (5) extent (15) of the segments (9) is smaller than the axial (5) length (6) of the honeycomb body (1).

5. A honeycomb body (1) according to claim 4 characterized in that at least two segments (9) are arranged axially (5) in succession.

6. A honeycomb body (1) according to claim 5 characterized in that the at least two segments (9) are arranged in mutually displaced relationship (16) in the peripheral direction (7).

7. A honeycomb body (1) according to one of claims 1 to 6 wherein the segments (9) each have two end faces (17) characterized in that the at least one partial portion (10) for connection to the housing (2) by intimate joining of the materials involved is arranged substantially centrally (18) relative to the end faces (17) wherein preferably at least two partial regions (11) for connection to the honeycomb body (1) by intimate joining of the materials involved are arranged near the end faces (17).

8. A honeycomb body (1) according to one of claims 1 to 6 wherein the segments (9) each have two end faces (17) characterized in that the at least one partial region (11) for connection to the honeycomb body (1) by intimate joining of the materials involved is arranged substantially centrally (18) relative to the end faces (17) wherein preferably at least two partial portions (10) for connection to the housing (2) by intimate joining of the materials involved are arranged near the end faces (17).

9. A honeycomb body (1) according to one of claims 1 to 8 characterized in that the segments (9) each have at least one transverse slot (19) extending substantially in the peripheral direction (7).

10. A holding aranganent according to claim 9 characterized in that the at least one transverse slot (19) has at least one end region (20) having a cut-out (21).

11. A honeycomb body (I) according to one of claims 1 to 10 characterized in that the segments (9) are held spaced (8) in the peripheral direction (7) by means of a support structure (22).

I4

12. A honeycomb body (1) according to one of claims 1 to 11 characterised in that the honeycomb body (1) has sheet metal layers (23) which are so structured that they have passages (24) through which an exhaust gas can flow, wherein same has in particular a passage density of at least 800 cpsi and the sheet layers (23) are constructed with sheets (25) of a sheet thickness (26) which is preferably less than 0.03 mm, in particular less than 0.025 mm.

13. A honeycomb body (1) according to claim 12 wherein the honeycomb body (l) has two ends (27) characterised in that at least near one end (27) the honeycomb body (1) has a sleeve portion (28) which is connected to the ends (29) of the sheet layers (23) by intimate joining of the materials involved.