| Title of Invention | A CATALYTIC EXHAUST GAS PURIFICATION DEVICE" |
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| Abstract | The invention relates to a catalytic exhaust purification device (1) and a corresponding compensation layer (4), especially for motor vehicles. The inventive device reliably protects a swell ing mat (5) from strongly pulsating streams of exhaust Qasee, even at very high ambient temperatures. To this end, a compensation layer (4) comprising the swelling mat (5) and an insulating mat (6) is provided between an outer housing (3) and a honeycomb (2). An edging (7) is produced preferably by folding round the insulating mat (6). Said edging (7) is thicker in the area of at least one face of the honeycomb (2) than in the remaining inner area (8) of the insulating mat (6). Next to the side of the inner area (8) facing away from the honeycomb (2) the swelling mat (5) is arranged so that the thicker area of the edging (7) of the insulating mat (6) covers those edge areas of the swelling mat (5) which are at risk of abrasion. The compensation layer (4) preferably consists of composite material which can be wound. The invention is characterized by its especially simple and effective construction and is also suitable for use in devices within motor vehicle exhaust gas cleaning systems (1) which are situated close to the engine, even when thin-walled-ceramic honeycombs are used. |
| Full Text | The present invention relates to a catalytic exhaust-gas purification device and to an associate comprising layer in particular for motor vehicles. Exhaust-gas purification devices - differing in each case in construction and/or the type of catalytically active surface coating - are required both for diesel-powered motor vehicles, where one of the concerns is afterburning of soot, and for detoxifying the exhaust gases of petrol engines. One significant problem in all cases is providing" durable, secure and, in particular, shock-damped mounting, in a metallic casing, for fragile ceramic honeycomb elements of the type frequently used in exhaust-gas purification devices, this problem being exacerbated further by the fact that the casing expands much more than the honeycomb element when the temperature increases. Particularly advantageous properties of the exhaust-gas purification devices are obtained when so-called swelling mats are used in a compensating layer between the casing and the honeycomb element since it is possible in this way to absorb the above-described large differences in thermal expansion particularly advantageously. The swelling mat is capable of swelling up to fill the cavities which form due to the differences in the behavior of the casing and the honeycomb element and due to manufacturing tolerances and thus ensures secure mounting over a long period of operation. Swelling mats generally contain particles of mica, which, to the extent -1- that there is sufficient space around them, absorb water and swell in the process. However, it is a disadvantage of swelling mats of this kind, and indeed of mats based on aluminum silicate fiber preferably used in such cases, that they are abraded very easily by pulsating exhaust-gas flows. In order to prevent this, a number of solutions have been proposed to deal with the problems which arise from pulsating exhaust gases. To stabilize such swelling mats, DE 80 19 813 Ul has already proposed to integrate a corrugated wire mesh mat into the swelling mat, for example. To protect the swelling mat from abrasion at the ends of the honeycomb element, gas-sealing rings are to be provided at the ends of the honeycomb element to cover the gap filled by the swelling mat. Another solution for providing protection against abrasion envisages so-called shielding funnels made of metal, which are arranged at a minimum distance in front of the end of a ceramic honeycomb element,this minimum distance being determined by thermally induced changes in length. An advantageous development of this solution provides shielding funnels made of ceramic material, whose ends then rest directly against the ceramic honeycomb element since the coefficients of expansion are the same. DE 297 09 180 Ul discloses a mounting mat with a ply of "intumescent" material, that is to say presumably having a swelling agent, which mat, for the purpose of protecting it against abrasion, is provided with at least one insert of elastic, flexible material which is not intumescent or is less so. -2- Since, furthermore, honeycomb elements in exhaust-gas systems heat up to 900°C and more in operation, and components arranged in the vicinity of the exhaust-gas purification device should be protected from this high temperature, it is also known practice to provide a thermally insulating layer between the casing and the honeycomb element. This thermally insulating layer can be a layer of air, which insulates the casing by virtue of the low heat conduction and heat convection properties of air against the high temperatures which occur in the honeycomb element during the use of the catalytic exhaust-gas purification device. As an alternative or supplement to insulation by a layer of air, the prior art includes the provision of an insulating layer composed of a ceramic material. Here too, there is thermal insulation of the external casing from the honeycomb element by virtue of the low heat conduction and heat convection properties of the ceramic materials provided. Since the above-mentioned swelling mats for holding honeycomb elements release water at a very high ambient temperature of, for example, over 800°C and shrink in the process, with the result that the honeycomb element may come loose in the casing, swelling mats must be thermally insulated from the honeycomb element in certain exhaust-gas purification devices subject to high stresses, for which purpose it is already known first of all to provide the honeycomb element with a so-called insulating mat, that is to say with a thermally insulating layer, preferably made of ceramic material, and only then to surround it with a swelling mat. However, there is still the problem of protecting the swelling mat from abrasion due to pulsating exhaust-gas flows and, — 3 — according to the prior art described above, this protection can only be adequately ensured by means of complicated covers and/or of integral reinforcements or inserts. Faced with this situation, the object underlying the invention is to achieve, with a more simple construction, reliable shielding of the swelling mat from strongly pulsating exhaust-gas flows, even at very high ambient temperatures. This object is achieved by an exhaust-gas purification device according to the features of the invention and by a compensating layer, Advantageous refinements and developments are described in the respectively associated dependent claims. Since the insulating mat has a thicker border in the region of at least one end of the honeycomb element than in the remaining inner region, a swelling mat being arranged in such a way near to the side of the inner region of the insulating mat which faces away from the honeycomb element that the thicker region of the border of the insulating mat covers the border regions of the swelling mat, which are at risk from abrasion, the swelling mat is advantageously shielded from strongly pulsating exhaust gases and thermally insulated in terms of heat conduction and heat convection. Moreover, any cavities which remain in production or form during operation between the casing and the honeycomb element are advantageously sealed by the swelling mat, the swelling mat sealing cavities adjacent to it by swelling when it absorbs water. This ensures durable, secure and, in particular, shock-damped mounting of the fragile ceramic honeycomb element. -4 - According to a particularly advantageous development of the invention, the thicker region of the border can be produced by folding over the insulating mat. Another refinement of the compensating layer comprising a swelling mat and an insulating mat, said refinement being advantageous in terms of production, is obtained if the mat and the swelling mat are designed as a composite material. This material is preferably capable of being wound at least once or else, in the case of higher requirements on the insulation, more than once around a honeycomb element, for example, in the circumferential direction. As an alternative, the compensating layer designed as a composite material can be assembled from prefabricated cylindrical or oval segments or segments that are matched to some other contour of the casing, in particular segments in the form of half shells. Further features, advantages and refinements of the present invention will be described in the following description with reference to the accompanying drawing, in which: Fig. 1 shows a portion of an exhaust-gas purification device, partially in section, and Fig, 2 shows a compensating layer in the form of a composite material comprising a swelling mat and an insulating mat. Fig. 1 shows a partially sectioned portion of an exhaust-gas purification device 1 according to the invention. Arranged in this, in a casing 3, is a honeycomb element 2, which is wrapped in a compensating layer 4. —5 — The honeycomb element 2 is preferably a monolithic ceramic honeycomb element, in particular one made of so-called thin-walled ceramic. However, honeycomb elements 2 constructed from thin metal sheets can also be held in a similar manner, the aim likewise being thermal insulation relative to the, preferably metallic, casing 3. In the exemplary embodiment under consideration, retention and insulation is achieved by means of a compensating layer 4 comprising a ply of ceramic material, preferably a swelling mat 5, and another, thermally insulating layer, a so-called insulating mat 6. Together, these two plies form the compensating layer 4 which, on the one hand, holds the honeycomb element 2 securely in the casing 3 and, on the other hand, ensures very good thermal insulation. The insulating mat 6 is composed of a ceramic material and has very low thermal conductivity and thus prevents heat conduction and convection from _the honeycomb element 2 to the casing 3. The swelling mat 5 contains particles of mica, which, to the extent that there is sufficient space around them, absorb water and swell in the process. In other words, the swelling mat 5 fills the cavities which form due to the differences in the behavior of the casing 3 and the honeycomb element 2 and due to manufacturing tolerances and thus ensures that the honeycomb element 2 is mounted securely in the casing 3 over a long period of operation. Swelling mats 5 and insulating mats 6 of ceramic material are typically fiber mats, as known from the prior art for holding ceramic honeycomb elements 2, with a thickness as required for compensating manufacturing tolerances of the external casing 3 and the honeycomb element 2 and for holding over a long period of operation. It should be pointed out that a number of compensating layers 4 and/or, alternatively, merely additional plies of the thermally insulating layer 6, which follow one another radially, can be provided to improve thermal insulation, especially if the -6- exhaust-gas purification device 1 is subjected to very high operating temperatures, as occur for example in the case of arrangement close to the outlet of a combustion engine. Since, as is known, pulsating hot exhaust gases abrade the swelling mats 5 containing particles of mica, a safeguard against this is provided in the region of at least one end of the honeycomb element 2, preferably in the region of both ends of the honeycomb element 2. For this purpose, the inherently very abrasion-resistant ceramic insulating layer 6 is folded over toward the casing 3, i.e. a thick border is produced, covering the border regions of the swelling mat which are at risk from abrasion. It is particularly advantageous for the •production of exhaust-gas purification devices 1 according to the invention if the compensating layer 4 constructed in this way is designed as a composite material. Fig. 2 shows a compensating layer 4, which is designed as a composite material comprising an insulating mat 6 and a swelling mat 5 and can preferably be wound at least once around the honeycomb element 2 in the circumferential direction. In an alternative embodiment (not shown), the compensating layer 4 designed as a composite material is assembled from prefabricated cylindrical or oval segments, or segments that can be matched to some other contour of the casing 3, in particular segments in the form of half shells. If the insulating mat 6, that is to say the thermally insulating layer, is composed of long ceramic fibers, at least in the thicker region of its border 7, it is not very susceptible to abrasion by pulsating exhaust gases and the protection provided by the thicker region of the border 7 for the border regions 9 of the swelling mat 5 which are at risk from abrasion is adequate. — 7 — The present invention is distinguished by a particularly simple and, at the same time, effective construction and is suitable even for applications close to the engine in catalytic exhaust-gas purification devices 1 of motor vehicles. At the same time, it allows secure mounting of honeycomb elements 2, simultaneously provides good thermal insulation of the honeycomb element 2 in the casing 3, and protects that ply 5 of the compensating layer 4 which contains the swelling material adequately against abrasion by pulsating exhaust-gas flows. -8 - We Claim: 1. A catalytic exhaust-gas purification device (1), in particular for motor vehicles, having at least one monolithic ceramic honeycomb element (2), which is arranged in a metallic casing (3), and a compensating layer (4) arranged between the casing (3) and the honeycomb element (2), the compensating layer (4) comprising: a swelling mat (5) with border regions (9) susceptible to abrasion and - an insulating mat (6) with a border (7) and an inner region (8), characterized in that - the border (7) of the insulating mat (6) is thicker in the region of at least one end of the honeycomb element (2) than the remaining inner region (8) and in that - the swelling mat (5) being arranged near to the side of the inner region (8) of the insulating mat (6) facing away from the honeycomb element (2) such that the thicker region of the border (7) of the insulating mat (6) covers the border regions (9) of the swelling mat (5), which are susceptible to abrasion. 2. The catalytic exhaust-gas device (1) as claimed in claim 1, wherein the thicker region of the border (7) is produced by folding the insulating mat (6) toward the casing (3). 3. The catalytic exhaust-gas purification device (1) as claimed in claim 1 or 2, the insulating mat (6) contains a ceramic material which has very low heat conduction and heat convection properties. 4. The catalytic exhaust-gas purification device (1) as claimed in one of claims 1 to 3, wherein the insulating mat (6) contains long ceramic fibers, at least in the thicker region of its border (7). 5. The catalytic exhaust-gas purification device (1) as claimed in claim 1, wherein the swelling mat (5) contains a ceramic material which can seal adjacent cavities by swelling when it absorbs water. 6. The catalytic exhaust-gas purification device (1) as claimed in one of claims 1 to 5, wherein the compensating layer (4) is designed as a composite material. 7. The catalytic exhaust-gas purification device (1) as claimed in claim 6, wherein the compensating layer (4) is designed as a composite material, preferably wound at least once around the honeycomb element (2) in the circumferential direction. 9. 8. The catalytic exhaust-gas purification device (1) as claimed in claim 6, wherein the compensating layer (4) designed as a composite material is assembled form prefabricated cylindrical or oval segments or segments that can be matched to some other contour of the casing (3), in particular segments in the form of half shells. 9. A compensating layer (4)/comprising - a swelling mat (5) with border regions (9) susceptible to abrasion and - an insulating mat (6) with a border (7) and an inner region (8), in particular for holding a monolithic honeycomb element (2) in a metallic casing (3) of a catalytic exhaust-gas purification device, as claimed in claim 1 - the insulating mat (6) is thicker in at least parts of its border (7) than in the remaining inner region (8) and in that - the swelling mat (5) being arranged near to one side of the inner region (8) such that the thicker region of the border (7) covers the border regions (9) of the swelling mat (5), which are susceptible to abrasion. 10. The compensating layer (4) as claimed in claim 9, wherein the thicker region of the border (7) of the insulating mat (6) can be produced by folding the insulating mat (6). 11. The compensating layer (4) as claimed in claim 9 or 10, wherein the insulating mat (6) contains a ceramic material which has very low heat conduction nad heat convection properties. 12. The compensating layer (4) as claimed in one of claims 9 to 11, wherein the insualting mat (6) contains long ceramic fibers, at least in the thicker region of its border (7). 13. The compensating layer (4) as claimed in claim 9, wherein the swelling mat (5) contains a ceramic material which can seal adjacent cavities by swelling when it absorbs water. 14. The compensating layer (4) as claimed in one of claims 9 to 13, wherein the compensating layer (4) is designed as a composite material. 10. 15. The compensating layer (4) as claimed in claim 14, wherein the compensating layer (4 ) designed as a composite material is capable of being wound. 16. The compensating layer (4) as claimed in claim 14, wherein the compensating layer (4) designed as a composite material can be assembled from prefabricated cylindrical or oval segments than can be matched to some other contour, in particular segments in the form of half shells. The invention relates to a catalytic exhaust purification device (1) and a corresponding compensation layer (4), especially for motor vehicles. The inventive device reliably protects a swell ing mat (5) from strongly pulsating streams of exhaust Qasee, even at very high ambient temperatures. To this end, a compensation layer (4) comprising the swelling mat (5) and an insulating mat (6) is provided between an outer housing (3) and a honeycomb (2). An edging (7) is produced preferably by folding round the insulating mat (6). Said edging (7) is thicker in the area of at least one face of the honeycomb (2) than in the remaining inner area (8) of the insulating mat (6). Next to the side of the inner area (8) facing away from the honeycomb (2) the swelling mat (5) is arranged so that the thicker area of the edging (7) of the insulating mat (6) covers those edge areas of the swelling mat (5) which are at risk of abrasion. The compensation layer (4) preferably consists of composite material which can be wound. The invention is characterized by its especially simple and effective construction and is also suitable for use in devices within motor vehicle exhaust gas cleaning systems (1) which are situated close to the engine, even when thin-walled-ceramic honeycombs are used. |
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| Patent Number | 202580 | ||||||||
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| Indian Patent Application Number | IN/PCT/2000/00202/KOL | ||||||||
| PG Journal Number | 09/2007 | ||||||||
| Publication Date | 02-Mar-2007 | ||||||||
| Grant Date | 02-Mar-2007 | ||||||||
| Date of Filing | 09-Aug-2000 | ||||||||
| Name of Patentee | EMITEC GESELLSCHAFT FUR EMISSIONSTECHNOLOGIE MBH | ||||||||
| Applicant Address | HAUPTSTRASSE 150, D-53797 LOHMAR GERMANY | ||||||||
Inventors:
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| PCT International Classification Number | F 01 N 3/28 | ||||||||
| PCT International Application Number | PCT/EP99/00127 | ||||||||
| PCT International Filing date | 1999-01-12 | ||||||||
PCT Conventions:
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