Title of Invention

HONEYCOMB BODY WITH THERMAL INSULATION

Abstract

The present invention concerns a honeycomb body comprising a plurality of honeycombs and thermal insulation (43) which has a plurality of stacked and/or wound insulating sheet layers (4; 34) which are in mutually supporting relationship by means of microstructures (5) provided in the insulating sheet layers (34) so that intermediate spaces exist between the insulating sheet layers (4; 34), wherein the microstructures (5) are of a height of from 10 µm to 250 µm. In that way the honeycomb body has only slight heat losses to the environment.

Full Text

-1A- The present invention concerns a honeycomb body having a plurality of honeycombs, preferably for use as a catalyst carrier body in motor vehicles. A coating of catalytic material applied to walls of the honeycombs permits conversion of exhaust gases from internal combustion engines. WO 90/08249 and WO 96/09892 describe honeycomb bodies with macrostructures which determine the honeycomb form. The honeycomb bodies additionally have microstructures which influence the flow of exhaust gas passing through the honeycombs. The honeycomb walls comprise for example metal. A possible way of producing honeycomb bodies with such honeycomb walls includes soldering or welding. Suitable kinds of welds are known for example from WO 89/07488. It is known from EP 0 229 352 to use a heat radiation guard or protection device. The heat radiation guard or protection device comprises, one or more sheet layers which are arranged outside a tubular casing. That arrangement uses the same sheet layers which also form the honeycomb structure within the tubular casing. Particularly in the automobile industry, the requirements imposed in terms of the properties of an exhaust gas catalytic converter are becoming ever increasingly strict. In the course of ever increasing strictness in relation to exhaust gas standards, in particular the cold-start and restart characteristics have to be continually improved. When an engine is re-started after a stoppage time, it is important that the honeycomb body of the catalytic converter is still at a temperature which is as high as possible. WO 96/07021 describes a catalytic reactor for the conversion of exhaust gases which has a thermal insulation both within and also outside a casing. An air gap and an insulating mat are mentioned as examples of such insulations. In the above-mentioned state of the art the insulation effect is achieved by air or by means of a solid insulation material. Admittedly air at rest has a lower level of thermal conductivity than known solid insulating materials, but it only extremely slightly impedes the transportation of heat due to radiation. In contrast a plurality of sheet layers, as have been proposed in WO 96/07021, considerably reduce the amount of heat radiation. Due to their contact locations however the sheet layers form thermal bridges, with the result that once again a considerable degree of heat transportation can occur due to heat conduction. The problem of the present invention is so to develop a honeycomb body that it has only low heat losses to the environment. 2 According to the invention that problem is solved by a honeycomb body having the features recited in claim 1. Advantageous developments are the subject-matter of the appendant claims. The honeycomb body according to the invention is distinguished in that it has a thermal insulation with a plurality of stacked and/or wound insulating sheet layers which are in mutually supporting relationship by virtue of microstructures provided in the insulating sheet layers so that intermediate spaces exist between the insulating sheet layers. The microstructures are approximately of a height of from 15 µm to 250 µm. They are therefore substantially lower than the structures known from EP 0 229 352 for forming honeycomb-like passages through which exhaust gas can flow. Microstructures of that height are known from WO 96/09892 in which they have been proposed for intermixing exhaust gas flowing in a laminar flow in the honeycomb-like passages. In the case of a honeycomb body according to the invention however, the properties of such microstructures are used in a completely different manner. Because of their small height it is possible for a multiplicity of insulating sheet layers to be disposed in mutually stacked or stratified relationship in a small space, whereby heat transportation due to heat radiation through the stack is considerably reduced. As the reduction depends to a good approximation solely on the number of insulating sheet layers, it is possible to save space or achieve a higher level of insulation effect, in comparison with the state of the art. The greater stack density however has still another advantage. By virtue of a suitable configuration of the microstructures, for example in such a way that they have narrow, sharp-edged crests or ridges the contact surface area between each two insulating sheet layers can be considerably reduced. In that way it is also possible markedly to reduce the transmission of heat due to heat conduction. In particular in order effectively to protect the honeycomb body with its plurality of honeycombs from heat losses, it is desirable if the insulating sheet layers enclose the honeycombs in an as closed configuration as possible. It will be appreciated that in the case of honeycomb bodies for use as exhaust gas catalyst carrier bodies, openings for the intake and outlet of exhaust gas have to be kept free. In a particular configuration however the nature of a thermal insulation, in accordance with the invention is also suitable for protecting heat-sensitive articles in the vicinity of a honeycomb body. In that case the thermal insulation only partially encloses the honeycombs so that a thermal insulation effect is achieved in solid angle regions which are limited, as viewed from the honeycombs. In a preferred configuration of a honeycomb body according to the 3 invention the insulating sheet layers of the thermal insulation are at least partially connected together by a procedure involving the intimate joining of the materials, preferably soldered or welded. An advantage is the mechanical stability of the thermal insulation, which can be achieved in that way. In an advantageous configuration the honeycombs have metal honeycomb walls. In alternative configurations in which insulating sheet layers adjoining the honeycombs are also metal, solder or welded connections of the honeycombs to each other and honeycombs to insulating sheet layers can be produced at the same time in the same soldering or welding process. As an alternative however other materials such as ceramic materials are also used for the honeycomb walls, or different materials are combined. A particular configuration is achieved if insulating sheet layers are applied to a green ceramic with a plurality of honeycombs and then the ceramic is fired. In an alternative configuration thereof the insulating sheet layers are secured to the green ceramic by virtue of their microstructures as they are impressed into the green ceramic. In the case of metal honeycomb walls, the requirements made in regard to the resistance to corrosion thereof are high. A honeycomb body according to the invention which is suitably provided with catalytically active material is suitable for the conversion of exhaust gases of an internal combustion engine, in particular an Otto-cycle engine. The exhaust gas temperature of such engines is typically over 800°C. A honeycomb body for that purpose of use must withstand corrosion phenomena at those temperatures over thousands of operating hours. The same requirements however do not have to be made in terms of the thermal insulation. The thermal insulation is not exposed to such high temperatures as the honeycomb walls. With a good insulation effect at most insulating sheet layers adjacent the honeycomb walls reach similarly high temperatures. In a preferred embodiment of a honeycomb body according to the invention the thermal insulation also does not come into contact with corrosive gases, particularly in an embodiment in which the thermal insulation is closed off in relation to any intake of gas into the intermediate spaces. In a further embodiment a honeycomb body has a tubular casing, in the tubular interior of which are disposed honeycombs. Such a configuration is advantageous for reasons of mechanical stability but also for reasons relating to manufacturing procedure. There are various different configurations of such a honeycomb body. In one of them a thermal insulation as described above is also disposed in the tubular interior. In other alternative configurations, instead or in addition, such a thermal insulation is disposed outside the tubular casing. In that respect for 4 example an outermost insulating sheet layer which is particularly thick or a second outer tubular casing affords protection from mechanical damage. In the case of alternative constructions involving metal tubular casings, connections between thermal insulation and the tubular casings are advantageously at least partially brazed or welded. In another embodiment the insulating sheet layers of the thermal insulation are parts of a continuous sheet strip which is wound in a spiral. In a specific alternative configuration the thermal insulation has precisely two sheet strips, with the microstructures being provided in at least one. The two sheet strips are twisted together in a spiral winding. Such a winding configuration can be produced for example by the two sheet strips firstly being laid one upon the other, then secured at one end to each other and/or to another part of the honeycomb body, for example to a tubular casing, and then wound. Other variants use more than two sheet strips. Spiral windings are advantageous inter alia for the reason that they are particularly easy to produce. It is however also possible to use annular insulating sheet layers which are closed in themselves. Completely different shapes in respect of the thermal insulation are also possible for specific purposes, while retaining the construction principle involved. In order to protect individual sensitive items outside the honeycomb body from heat radiation, a stack of slightly bent insulating sheet layers is arranged for example on a limited part of the surface of the honeycomb body. In a further embodiment the honeycombs are at least partially heatable. By virtue of the thermal insulation the heatable region can be rapidly brought without substantial heat losses to a desired operating temperature. The thermal insulation helps to be easy on the power source, for example a battery of a motor vehicle. In various design configurations the thermal insulation has ends at which there are edges of a plurality of insulating sheet layers. If for example air flows against an end of such a honeycomb body, then an undesirable cooling action can occur due to an air flow through the intermediate spaces. In a desirable development therefore the insulating sheet layers are at least partially connected together in the proximity of the end or the ends so that a flow of air or another flow of gas between the intermediate spaces and the atmosphere surrounding the thermal insulation is impeded or blocked. For example the insulating sheet layers are soldered or welded together in the proximity of the end, they are provided with a filling material at the end, or an additional closure portion is mounted at the end. The efficiency of a thermal insulation arrangement is increased by the intermediate spaces between the insulating sheet layers being all or 5 partially sealed off in relation to air, and evacuated. Besides the reduction in overall thermal conductivity, that also prevents . the penetration under some circumstances of corrosive gases into the thermal insulation. The heat radiation within the thermal insulation and/or the radiant heat emission from the honeycomb body outwardly is further reduced if at least a part of the insulating sheet layers of the thermal insulation, in particular at least one outer insulating sheet layer, is provided with a surface which has a degree of emission of less than 0.1. In an embodiment the insulating sheet layers consist throughout of a material with the desired emission properties, while in another embodiment disposed at the surface is a material layer comprising a different material from the predominant part of the insulating sheet layer in other respects. The layer may for example be applied by vapour deposition. Further features and advantages of honeycomb bodies according to the invention are described with reference to the drawing. The invention however is not limited to the embodiments set forth therein. In the individual Figures of the drawing: Figure 1 is a perspective view of a cylindrical honeycomb body with a wound thermal insulation, Figure 2 is a view in section through a honeycomb body with two tubular casings, Figure 3 shows a honeycomb body with a thermal insulation comprising a sheet strip, Figure 4 shows a honeycomb body with a thermal insulation comprising two sheet strips, Figure 5 shows a portion of an insulating sheet layer with microstructure and with an anti-emission layer, Figure 6 shows an insulating sheet layer with parallel microstructures which are raised towards both sides of the insulating sheet layer, Figure 7 shows an insulating sheet layer with crossed microstructures, Figure 8 shows an insulating sheet layer with microstructures parallel to an end edge, Figure 9 shows a partial section through a honeycomb body with a heat insulation comprising insulating sheet layers with and without microstructures, and Figure 10 shows a partial section through a honeycomb body with a thermal insulation having insulating sheet layers which are microstructured on two sides. Figure 1 shows a preferred embodiment 1 of a honeycomb body according to the invention. The core comprises a plurality of honeycombs 2 which are formed by wound, smooth and corrugated sheet layers. The honeycombs form 6 passages connecting the ends 10. The core is embraced by a cylindrical tubular casing 6 which in turn is embraced by a thermal insulation 43. In this embodiment the thermal insulation 43 has insulating sheet layers of which one 4 is smooth and another 34 is microstructured at two sides as indicated at 5. Figure 1 shows a snapshot at a moment just before the two insulating sheet layers 4 and 34 are wound completely around the core. Figure 2 shows a honeycomb body with a core as in Figure 1, which is embraced by an inner tubular casing 6. The thermal insulation 3 which externally adjoins the inner tubular casing 6 is of substantially greater thickness than the embodiment shown in Figure 1, in relation to the diameter of the core. The thermal insulation 3 is embraced by a second, outer tubular casing 6. Figure 3.shows a specific structure of a thermal insulation 23. The insulating sheet layers 24 are parts of a continuous, spirally wound sheet strip 11 with microstructures 5 which are raised at the inward side of the sheet strip 11. The sheet strip 11 is connected at its beginning 8 to the tubular casing 6. At its end 9 it is secured to another portion of itself. Figure 4 shows another possible structure of a thermal insulation. This structure is similar to that shown in Figure 1 but here the microstructures 5 of the sheet strip 11 extend in a direction approximately parallel to the passages whereas in the example of Figure 1 they extend approximately transversely relative thereto. In contrast to the thermal insulation 23 in Figure 3 the thermal insulation 33 comprises two sheet strips 11; 12 of which one 12 is smooth, that is to say it does not have any microstructures 5. Two details of an insulating sheet layer 14 can be explained with reference to Figure 5. At its microstructure 5 the insulating sheet layer 14 is of approximately the same thickness as elsewhere. Such a microstructure is produced for example by bending or stamping the insulating sheet layer 14. Another possible way of producing the microstructures involves applying additional material to an insulating sheet layer. The insulating sheet layer 14 is built up in a laminate manner. The thinner anti-emission layer 15 forms a continuous surface on one side of the insulating sheet layer 14. It is carried by the base material 16. An anti-emission layer 15 can be applied for example galvanically to the base material 16. Figure 6 shows an insulating sheet layer 34 in which the microstructures 5 have an array of ridges or crests which extend line-like in mutually parallel relationship. The ridges or crests are raised alternately towards both sides of the insulating sheet layer 34. The microstructures 5 meet the end edge 10 of the insulating sheet layer 34 in perpendicular relationship. 7 A particularly advantageous structure for a thermal insulation 3 can be achieved by combining such an insulating sheet layer 34 with insulating sheet layers of the same kind. When that is done the insulating sheet layers are stacked one upon the other with their ridges or crests extending in mutually crossed directions. The ridges or crests which extend in mutually crossed relationship only contact each other at approximately point-like contact locations at double the spacing of the parallel microstructures 5. Contact locations of an insulating sheet layer 34 in relation to a lower and an upper neighbour in the stack are disposed at the spacing of the parallel microstructures 5. Values of between 1 mm and 20 mm are advantageous in terms of the spacings of parallel microstructures, with values of between 5 mm and 15 mm being preferred. Heat which is conducted in a general direction perpendicularly to the insulating sheet layers 34 therefore flows along considerable detour routes. By virtue of those detour routes and by virtue of the point-like contact locations, the level of thermal insulation effect achieved is particularly high. The embodiment shown in Figure 7 of an insulating sheet layer 44 with microstructures 5 is mechanically particularly stable because of the ridges or crests which extend in mutually crossed directions. Depending on the desired bending radius, it can possibly be bent only in given directions and wound around a honeycomb body core. As the crests or ridges are raised towards precisely one side of the insulating sheet layer 44 the insulating sheet layer 44 is advantageously combined on the other side with insulating sheet layers 14; 24; 34; 44 which also have microstructures. The combination with insulating sheet layers without microstructures would result, on one side, in contact over an undesirably large surface area. An advantageous combination is in particular that with insulating sheet layers 14; 24; 34 in which the overall image of the microstructures differs in terms of the shape, angle of intersection and/or spacing of the microstructures, from the overall image of the insulating sheet layer 44. In that way it is possible to prevent the microstructures of one insulating sheet layer from engaging in positively locking relationship into the microstructures of another insulating sheet layer. Figure 8 shows an insulating sheet layer with microstructures 5 which is suitable for an advantageous combination with the insulating sheet layer shown in Figure 7. Figures 9 and 10 each show views in section of respective portions of a honeycomb body core and a thermal insulation 43; 53. The transition from the core to the thermal insulation 43; 53 is by way of an insulating sheet layer 4 without microstructures (Figure 9) or by way of an insulating sheet layer 34 with microstructures (Figure 10). The insulating sheet layers 4; 34 each form a respective stack, but with a different stacking sequence. 8 In Figure 10 all insulating sheet layers 34 are microstructured on both sides. In Figure 9 the insulating sheet layers 34 with the microstructures have at least one insulating sheet layer 4 without microstructures as the closest successive neighbour. The cylindrical spatial configuration shown in Figure 1 or the circular cross-sections shown in further Figures are in no way the only options in regard to the shape of a honeycomb body according to the invention. Examples of other shapes are a conical spatial configuration or a polygonal cross-section. A thermal insulation 3; 23; 33; 43; 53 with microstructured insulating sheet layers may also be arranged relative to honeycombs 2 differently from the configurations shown in the Figures. For example it may only semilaterally embrace the honeycombs 2 or honeycombs 2 may also be disposed outside of it. 9 List of references 1 honeycomb body 2 honeycombs 3 thermal insulation 4 smooth insulating sheet layer 5 microstructure 6 tubular casing 7 insulating sheet layer as damage protection 8 sheet strip beginning 9 sheet strip end 10 end 11 sheet strip with microstructure 12 sheet strip without microstructure 14 insulating sheet layer with anti-emission layer 15 anti-emission layer 16 base material 23 thermal insulation comprising a sheet strip 24 single-sidedly microstructured insulating sheet layer 33 thermal insulation comprising two sheet strips 34 double-sidedly microstructured insulating sheet layer 43 thermal insulation with microstructured and smooth sheet layers 44 insulating sheet layer with single-sided crossed microstructures 53 thermal insulation comprising microstructured sheet layers 10 We Claim 1. A honeycomb body with thermal insulation comprising a plurality of honeycombs and thermal insulation characterized in that, the thermal insulation (3; 23; 33; 43; 53) has a plurality of stacked and / or wound insulating sheet layers (4; 7; 14; 24; 34; 44) which are in mutually supporting relationship by virtue of microstructures (5) provided in the insulating sheet layers (14; 24; 34; 44) so that intermediates spaces exist between the insulating sheet layers (4; 7; 14; 24; 34; 44) wherein the microstructures (5) are of a height of from 15 µm to 250 µm. 2. A honeycomb body as claimed in claim 1 wherein the thermal insulation (3; 23; 33; 43; 53) only partially surrounds the honeycombs (2). 3. A honeycomb body as claimed in claim 1 or claim 2 wherein: it is being mounted as a catalytic a converter for the catalytic conversion of exhaust gases, in particular exhaust gases from internal combustion engines, in particular otto-cycle engines. 4. A honeycomb body as claimed in claim 1, claim 2 or claim 3 wherein the insulating sheet layers (4; 7; 14; 24; 34; 44) are at least partially connected together by a procedure involving intimate joining of materials, preferably soldered or welded. 5. A honeycomb body as claimed in one of claims 1 to 4 wherein the honeycombs (2) have metal honeycomb walls. 6. A honeycomb body as claimed in claim 5 wherein the metal honeycomb walls are at least partially connected together by a procedure involving intimate joining of materials, preferably soldered or welded. 11 7. A honeycomb body as claimed in claim 5 or claim 6 wherein the material of the metal honeycomb walls and the material of the insulating sheet layers (4; 7; 14; 24; 34; 44) differ from each other, wherein in particular the former is resistant to corrosion at temperatures over 800°C and the latter is less resistant to corrosion. 8. Ahoneycomb body as claimed in claims 5 to 7 wherein a part of the honeycomb walls is connected to one of the insulating sheet layers (4; 14; 24; 34 44) by a procedure involving intimate joining of the materials, preferably soldered or welded. 9. A honeycomb body as claimed in one of claims 1 to 8 wherein it has tubular casing (6), in the tubular interior of which are disposed the honeycombs (2). 10. A honeycomb in one of claims 1 to 9 wherein it has a tubular casing (6) and that the thermal insulation (3; 23; 33; 43; 53) lies outside the tubular casing (6). 11. A honeycomb body as claimed in one of claims 1 to 10 wherein the outermost insulating sheet layer (7) is thicker than the insulating sheet layers (4; 14; 24; 34; 44) which are disposed within same. 12. A honeycomb body as claimed in one of claims 1 to 11 wherein it has a tubular casing (6) in the tubular interior of which the thermal insulation (3; 23; 33; 43; 53) is disposed. 13. A honeycomb body as claimed in one of claims 1 to 12 wherein the insulating sheet layers (4; 14; 24; 34; 44) are parts of a continuous, spirally wound sheet strip (11; 12). 12 14. A honeycomb body as claimed in claim 13 wherein the thermal insulation (33) has two sheet strips (11; 12), wherein the microstructures (5) are formed in at least one, and that the two sheet strips (11; 12) are twisted together in a spiral winding. 15. A honeycomb body as claimed in claims 1 to 14 wherein the honeycombs (2) have walls, which are heatable. 16. A honeycomb body as claimed in one of claims 1 to 15 wherein the thermal insulation (3; 23; 33; 43; 53) has an end (10) at which there are edges of a plurality of the insulating sheet layers (4; 7; 14; 24; 34; 44) and that the insulating sheet layers (4; 7; 14; 24; 34; 44) are connected together in the proximity of the end (10) so that an air flow between the intermediate spaces and the surroundings of the thermal insulation (3; 23; 33; 43; 53) is impeded or blocked. 17. A honeycomb body as claimed in one of claims 1 to 16 wherein the intermediate spaces are all or partially sealed off in relation to air and evacuated. 18. A honeycomb body as claimed in one of claims 1 to 17 wherein, in particular at least one insulating sheet layer (4; 7; 24; 34; 44) at an outward side of the thermal insulation (3; 23; 33; 43; 53) has an emission degree of less than 0.1 for the emission of heat radiation. 19. A honeycomb body as claimed in claim 18 wherein, disposed at the surface of such an insulating sheet layer (14) is an anti-emission material layer (15) which comprises a different material from the predominant part of the insulating sheet layer in other respects (16). 13 20. A honeycombbody as claimed in claims 1 to 19 wherein, in the case of at least one but preferably in the case of all insulating sheet layers (14; 24; 34; 44) with the microstructures (5) the microstructures (5) have an array of ridges which extend linelike in mutually parallel relationship. 21. A honeycomb body as claimed in claim 20 wherein, the microstructures (5) of a respective array are at spacings of between 1 mm and 20 mm from each other, preferably from 5 to 15 mm. 22. A honeycomb body as claimed in claim 20 or claim 21 wherein, the microstructures (5) have two such arrays with ridges extending in mutually crossed directions. 23. A honeycomb body as claimed in claim 20 or claim 21 wherein, with a pair of insulating sheet layers (4; 7; 14; 24; 34; 44) which have a common intermediate space, characterized in that the pair are in mutually supporting relationship by respectively precisely one such array, the ridges extending in mutually crossed directions. The present invention concerns a honeycomb body comprising a plurality of honeycombs and thermal insulation (43) which has a plurality of stacked and/or wound insulating sheet layers (4; 34) which are in mutually supporting relationship by means of microstructures (5) provided in the insulating sheet layers (34) so that intermediate spaces exist between the insulating sheet layers (4; 34), wherein the microstructures (5) are of a height of from 10 µm to 250 µm. In that way the honeycomb body has only slight heat losses to the environment.

Documents:

01801-cal-1997 abstract.pdf

01801-cal-1997 claims.pdf

01801-cal-1997 correspondence.pdf

01801-cal-1997 description(complete).pdf

01801-cal-1997 drawings.pdf

01801-cal-1997 form-1.pdf

01801-cal-1997 form-2.pdf

01801-cal-1997 form-3.pdf

01801-cal-1997 form-5.pdf

01801-cal-1997 pa.pdf

01801-cal-1997 priority document.pdf

1801-CAL-1997-(30-8-2011)-OTHER PATENT DOCUMENT.pdf

1801-CAL-1997-FORM 27.pdf

1801-CAL-1997-FORM-27.pdf

1801-cal-1997-granted-abstract.pdf

1801-cal-1997-granted-acceptance publication.pdf

1801-cal-1997-granted-claims.pdf

1801-cal-1997-granted-correspondence.pdf

1801-cal-1997-granted-description (complete).pdf

1801-cal-1997-granted-drawings.pdf

1801-cal-1997-granted-examination report.pdf

1801-cal-1997-granted-form 1.pdf

1801-cal-1997-granted-form 2.pdf

1801-cal-1997-granted-form 3.pdf

1801-cal-1997-granted-form 5.pdf

1801-cal-1997-granted-letter patent.pdf

1801-cal-1997-granted-pa.pdf

1801-cal-1997-granted-priority document.pdf

1801-cal-1997-granted-reply to examination report.pdf

1801-cal-1997-granted-specification.pdf

1801-cal-1997-granted-translated copy of priority document.pdf