Title of Invention	METALLIC HONEYCOMB BODY COMPRISING AT LEAST PARTIALLY PERFORATED SHEET-METAL LAYERS
Abstract	This invention relates to a metallic honeycomb having an axial length (L) composed of sheet-metal layers (1; 10, 11) which are structured in such a way that a fluid, in particular the exhaust gas from an internal combustion engine, can flow through the honeycomb body in a direction of flow (S) from an inflow end side (12) to an outflow end side (13), the sheet-metal layers (1; 10, 11), at least in partial regions, having a multiplicity of openings (6), the honeycomb body furthermore having holes (6) in all the sheet metal layers (1; 10,11) in a partial volume (T) which forms at least 55% of the axial length (L) and has a radial dimension (22) of at least 20 mm, and in which honeycomb body: the holes (6) each have a surface area of between 1 and 120 mm2; in the partial volume (T), the sheet-metal layer surface area is reduced by 10 to 80%, preferably 35 to 60%, by the holes (6) compared to a sheet-metal layer without holes, the partial volume (T) is in each case at a distance (R2, R3) from the end sides (12,13) of the honeycomb body, so that no-holes (6) touch or cut through the end-side edges of the sheet-metal layers.

Title of Invention

METALLIC HONEYCOMB BODY COMPRISING AT LEAST PARTIALLY PERFORATED SHEET-METAL LAYERS

Abstract

This invention relates to a metallic honeycomb having an axial length (L) composed of sheet-metal layers (1; 10, 11) which are structured in such a way that a fluid, in particular the exhaust gas from an internal combustion engine, can flow through the honeycomb body in a direction of flow (S) from an inflow end side (12) to an outflow end side (13), the sheet-metal layers (1; 10, 11), at least in partial regions, having a multiplicity of openings (6), the honeycomb body furthermore having holes (6) in all the sheet metal layers (1; 10,11) in a partial volume (T) which forms at least 55% of the axial length (L) and has a radial dimension (22) of at least 20 mm, and in which honeycomb body: the holes (6) each have a surface area of between 1 and 120 mm2; in the partial volume (T), the sheet-metal layer surface area is reduced by 10 to 80%, preferably 35 to 60%, by the holes (6) compared to a sheet-metal layer without holes, the partial volume (T) is in each case at a distance (R2, R3) from the end sides (12,13) of the honeycomb body, so that no-holes (6) touch or cut through the end-side edges of the sheet-metal layers.

Full Text	E-80893 Metallic honeycomb body comprising at least partially perforated sheet-metal layers The present invention relates to a metallic honeycomb body, in particular to a honeycomb body for an exhaust system of an internal combustion engine. Honeycomb bodies of this type are used as supports for catalytically active material and/or for adsorber material and similar applications. In particular metallic honeycomb bodies used for the purification of exhaust gases in internal combustion engines have to satisfy very different demands, and in some cases compromises have to be made between contradictory requirements. First of all, honeycomb bodies of this type should provide the maximum possible surface area at which the desired catalytic reactions or adsorption processes can take place. In many applications, a low heat capacity is desired, so that the honeycomb body is either quickly heated to its desired operating temperature or should also have a high heat capacity, so that it can remain at operating temperature for a longer time but cannot be heated to excessively high temperatures too quickly. Of course, an arrangement of this type must in general terms be mechanically stable, i.e. must be able to withstand a pulsating gas flow and also mechanical loads caused by the movement of the vehicle. Its material must be resistant to high-temperature corrosion and it must also be possible to machine this material in such a way that the desired honeycomb structures can be produced easily and at low cost. In many cases, particular structures are also required within the honeycomb body in order to influence flow, for example to improve contact with the surface or to effect -1- cross-mixing. Finally, it must be possible for a suitable honeycomb body to be produced at low cost in mass production. Individual aspects of the above problems have been described extensively in numerous documents which form part of the prior art. A distinction is drawn in particular between two typical forms of metallic honeycomb bodies. An early form, of which DE 29 02 779 A1 shows typical examples, is the helical form in which substantially one smooth and one corrugated sheet-metal layer are laid on top of one another and are wound helically. In another form, the honeycomb body is composed of a multiplicity of alternately arranged smooth and corrugated or differently corrugated sheet-metal layers, the sheet-metal layers initially forming one or more stacks which are wrapped together. In this case, the ends of all the sheet-metal layers come to lie on the outside and can be connected to a housing or tubular casing, resulting in numerous connections, which increase the durability of the honeycomb body. Typical examples of these forms are described in EP 0 245 737 B1 or WO 90/03220. It has also long been known to equip the sheet-metal layers with additional structures in order to influence the flow and/or to achieve cross-mixing between the individual flow passages. Typical examples of configurations of this type are WO 91/01178, WO 91/01807 and WO 90/08249. Finally, there are also honeycomb bodies in conical form, if appropriate including with further additional structures for influencing flow. A honeycomb body of this type is described, for example, in WO 97/49905. Furthermore, it is also known to form a recess for a sensor, in particular for accommodating a lambda sensor, in a honeycomb body. One example of this is described in DE 88 16 154 U1. -2- It has also long been known to use slotted metal sheets, in particular expanded metal and similar slot structures, for honeycomb bodies. An overview of various forms and arrangements of openings in sheet-metal layers of catalyst support bodies is given in US 5,599,509 together with the prior art cited therein. This makes targeted use of openings to reduce the heat capacity in the front region of a honeycomb body compared to the rear region. Although the extensive prior art allows many different directions to be pursued in development, some further development trends have emerged. One of these trends is the development toward ever thinner metal foils in order to be able to provide a large surface area while using small amounts of material and achieving a low heat capacity. An obvious drawback of this development trend is that the thin foils become increasingly mechanically sensitive and the honeycomb bodies produced therefrom are less durable. At the same time, a trend has evolved toward ever higher cell densities, which to a certain extent is caused by the ever thinner foils being used. To improve mass transfer with the surfaces of a honeycomb body, structures for influencing flow were introduced into the surfaces, in particular what are known as transverse structures, or flow-guiding surfaces or additional inflow edges were created in the interior of a honeycomb body. Although the advantages of openings in the sheet-metal layers for cross-mixing are known, the systematic provision of openings through which a fluid can freely pass in the majority of the catalytic converter volume has not hitherto been considered in practice, since this runs contrary to the trend toward providing ever greater surface areas within increasingly small volumes. While slots and/or flow-guiding surfaces and similar structures do not reduce the surface area in a honeycomb body, the use of a large number of holes does -3- considerably reduce the surface area and, moreover, at least if the holes are formed by removing material, means an increased consumption of starting material without a corresponding increase in surface area, which likewise runs contrary to prevailing trends. Therefore, holes have only been considered if they are supposed to have a specific function at a certain location in the honeycomb body, for example the function of cross-mixing or reducing the heat capacity compared to other regions. Although this consideration, when seen in isolation, was certainly applicable to a metallic honeycomb body, one should not lose sight of the fact that a metallic honeycomb body is subsequently coated with a coating material, which in many cases also contains expensive precious metals as a catalytically active component. Consequently, a large surface area always also means a large quantity of expensive coating material. Surprisingly, tests have shown that for certain dimensions of size, distribution and density of a large number of holes over a honeycomb body, the catalytic conversion properties can be as good, with a smaller surface area, as in a honey comb body without holes and with a larger quantity of coating material. Therefore, it is an object of the present invention to provide a metallic honeycomb body which, by having a suitable number, dimensions and distribution of holes, is particularly suitable as a support for a coating, in particular for economical deployment of the coating material. A metallic honeycomb body in accordance with the features of the invention is used to achieve this object. This honeycomb body having an axial length composed of sheet-metal layers which are structured in such a way that a fluid, in particular the exhaust gas from an .. 4 internal combustion engine, can flow through the honeycomb body in a direction of flow from an inflow end side to an outflow end side, the sheet-metal layers, at least in partial regions, having a multiplicity of openings, is distinguished, according to the invention, by the fact that the honeycomb body has holes in all the sheet-metal layers in a partial volume which forms at least 55% of its axial length and has a radial dimension of at least 20 mm, and in which honeycomb body: the holes each have a hole surface area of between 1 and 12 0 mm2, in the partial volume, the sheet-metal layer surface area is reduced by 10 to 80%, preferably 35 to 60%, by the holes compared to a sheet-metal layer without holes, the partial volume is in each case at a distance from the end sides of the honeycomb body, so that no holes touch or cut through the end-side edges of the sheet-metal layers. Tests have shown that a honeycomb body with holes according to the invention, on account of the improved flow properties in its interior and the resultant improved mass transfer properties between flow and surface, has an effectiveness which is comparable to and under certain circumstances even superior to a honeycomb body without holes, even though less coating material is used. The holes are so large that firstly they are not closed up by coating material during coating and secondly they also do not become blocked by particles in a fluid which is to be purified. Therefore, these are not holes similar to those used in a filter for retaining particles, but rather openings through which a fluid which is to be purified, in particular an exhaust gas from an internal combustion engine, can flow freely. For manufacture and technology reasons and with a view to the subsequent durability, it is important for the end-side edges not to be eaten into by holes -5- or parts of holes, and consequently the holes should be at a distance from the end sides. As has already been stated, the holes have more advantages than disadvantages, and consequently the partial volume provided with holes should amount to more than 60%, preferably more than 90%, of the total honeycomb body volume. This makes it possible to exploit the positive effect to its maximum extent. For mechanical and fluid dynamic reasons, it is expedient if the holes each have a surface area of from 5 to 60 mm2. With a size of this type, they are easy to produce, do not disrupt a coating process and bring about the above advantages of improved mass transfer. Holes of this size allow good cross-mixing and also allow dissipation of heat from the interior of the honeycomb body outward, not only by thermal conduction but also by thermal radiation, which passes through the holes into regions laying further toward the outside. Of course, the larger the total area of the holes compared to the total area of the heat-metal layers which remain, the stronger these effects become. For comparable applications, the prior art has almost exclusively described openings in the sheet-metal layers which have polygonal contours. From a mechanical point of view, this is not advantageous under high and fluctuating loads, since cracks can form starting from the corners of the holes. Consequently, in the present invention it is preferable to use rounded contours of the holes, so that the boundary lines of the holes do not have any corners, in particular do not have any acute angles. The holes should particularly preferably be round, oval or elliptical, in which case it is recommended, in -6- the case of shapes which are not round, not to exceed a maximum diameter to minimum diameter ratio of two. However, holes of this type cannot be produced in a material-saving manner, as is possible, for example, with expanded metal, but rather have to be produced by removal of the material from a full-area sheet-metal layer. However, the material, which is preferably removed by stamping or cutting, can be reused to produce new sheet-metal layers. Depending on the way in which the sheet-metal layer is produced, the holes may also be removed as early as during the production process, an option which is suitable in particular for materials produced by galvanoplastic means. In the case of a production process in which first of all an inexpensive material is produced and the quality of this material is subsequently improved by coating, e.g. with aluminum and/or chromium, it is recommended to produce the holes before the material is improved with these further materials. A further advantage of the invention is that the heat capacity of a honeycomb body with holes is, of course, lower than the heat capacity of a honeycomb body without holes. On the other hand, this enables honeycomb bodies according to the invention to be produced from thicker sheet-metal layers without the heat capacity increasing compared to honeycomb bodies made from unperforated, thinner sheet-metal layers. According to the invention, the thickness of the sheet-metal layers may be between 20 and 80 µm, but a thickness of from 40 to 60 µm is preferred. The preferred range leads to improved mechanical stability, in particular at the end sides of a honeycomb body, and makes it possible to use tried-and-tested production processes which can no longer readily be applied to very thin foils. Nevertheless, the heat capacity of the honeycomb bodies -7- which form is less than or equal to that of honeycomb bodies made from thinner foils without holes. To ensure mechanical stability of a honeycomb body according to the invention, the holes should have a minimum spacing of 0.5 mm, with the distances between the holes preferably in each case being approximately equal, so that no mechanical weak points are formed. Foils configured in this way can be corrugated without problems and then used in the remaining working steps for production of helical or coated and wrapped honeycomb bodies. A honeycomb body according to the invention, like most which are known in the prior art, particularly preferably comprises alternately arranged smooth and corrugated sheet-metal layers or comprises alternating differently corrugated sheet-metal layers. Structures of this type produce the typical flow passages in a honeycomb body. On account of the positive effects of the holes, for the catalytic converters which are subsequently produced from the honeycomb bodies to have good conversion properties, it is not necessary for honeycomb bodies according to the invention to have an extremely high cell density. According to the invention, cell densities of between 200 and 1000 cpsi (cells per square inch), in particular cell densities of from 400 to 800 cpsi, are preferred. The inventive use of holes in the sheet-metal layers does not adversely affect the usability of the sheet-metal layers for most previously disclosed additional structures for influencing flow as have been mentioned in the description of the prior art. In particular, the perforated sheet-metal layers can also be provided with transverse structures, with -8- projections and/or with flow-guiding surfaces. In general, the holes even assist the action of structures of this-type,since any pressure differences which occur in the passages can be compensated for by the openings, additional turbulence is generated and the flow profile within the honeycomb body is made more uniform. The configuration of a honeycomb body according to the invention has particularly positive effects when a sensor, in particular a lambda sensor, which has been introduced into a cavity in a honeycomb body is used as proposed in the prior art. Since a measurement sensor, in particular an oxygen measurement sensor, is intended to measure a value for the fluid flowing in the honeycomb body which is as representative as possible, cross-mixing upstream of the sensor is highly advantageous. Therefore, honeycomb bodies according to the invention are particularly suitable for applications in which a lambda sensor is to be introduced into a cavity in the honeycomb body. In manufacturing technology terms, this requires a certain level of outlay in production of the sheet-metal layers, so that after assembly they subsequently form a suitable cavity. However, nowadays this outlay is manageable by using NC manufacturing installations. This at the same time makes it possible not to position any holes close to the edges of the sheet-metal layers which delimit the cavity, in order to prevent the edges from being attacked at this location too. Therefore, it is particularly preferable for there to be no holes in a region of from 1 to 5 mm around the cavity for a measurement sensor. For the durability of a honeycomb body, it is advantageous if the individual sheet-metal layers are connected to one another -9- by joining, preferably by brazing, which typically takes place at the end sides of a honeycomb body. This is also a reason why no holes should intersect the end-side edge regions of the sheet-metal layers. On the other hand, the holes can also very deliberately prevent adhesive which has been applied to the end sides or solder which has been applied to the end sides from penetrating into the interior of the honeycomb body along the contact lines between the sheet-metal layers, which is often undesirable for mechanical reasons. Here, holes end the capillary effect, so that the distance between the holes and the end sides of a honeycomb body can also be used very deliberately to limit a region which is connected by soldering. A similar statement also applies to the attachment of the sheet-metal layers to a tubular casing. In this case too, on account of the very stable connection to the tubular casing which is desired, it is more favorable if the edge regions are not intersected by holes. In this case too, furthermore, the holes ensure that the solder cannot penetrate too far into the interior of the honeycomb body by means of capillary action, but rather remains precisely where it is used to secure the sheet-metal layers. The size of the honeycomb body volume in catalytic converters (sum of the volumes of the sheet-metal layers and also the passages, openings, holes, etc. which are formed or enclosed) is dependent, for example, on the positioning in the exhaust section: if it is arranged in the engine compartment or in the immediate vicinity of the engine (within a distance of up to 0.5 m) , this size is usually less than the capacity of the engine, e.g. less than 50% of the capacity, in particular less than 1 liter or 0.5 liter. If it is arranged in the underbody of a passenger car, the honeycomb body volume may also be -40- greater than the capacity of the engine, preferably between 1 and 5 liters. Different sizes may also result in other applications, such as for example for use in trucks, motorcycles, lawnmowers, hand-held appliances (hedge clippers, power saws, etc.) or the like, in which case the corresponding person skilled in the art can make suitable modifications. A similar statement is true for honeycomb bodies which are used as heat exchangers, flow mixers, adsorbers, particle traps, particulate filters, electrical heaters in exhaust systems. In these cases too, the person skilled in the art is aware of a range of tests which allow the honeycomb body volume to be suitably adapted. When designing or configuring the pattern of holes in the sheet-metal layer, account should also be taken of the desired application of the honeycomb bodies. Since in this context it has not been possible to make use of knowledge gained from experience, tests have shown that the effects of the mixing or catalytic conversion combined, at the same time, with a considerably reduced deployment of catalytic material were surprisingly good in sheet-metal foils with holes whose maximum extent was greater than the structure width of the corrugation, in particular with holes in which even the shortest distance between opposite contours of the holes was still greater than the structure width. This preferably applies to the holes in the at least partially structured sheet-metal layers, so that the holes are superimposed on the corrugation or structure. It is particularly advantageous for all the holes in the at least one partial volume to have an extent which is greater than the structure width. Surprisingly good results can be achieved with a honeycomb body in whose sheet-metal foils the size of the hole is at least twice, preferably four times, in particular six times, as great as the structure width. -11- According to an advantageous refinement of the honeycomb body, at least some of the holes are designed as slots whose maximum extent in each case extends in the direction of a dedicated main axis, the holes designed as slots being arranged in such a way that the honeycomb body has zones of different rigidities. In this context, a slot is understood as meaning in particular a hole which has two opposite rounded, preferably semicircle-like tip regions, the maxima or turning points of which define the main axis, the slot preferably having edges which run parallel to one another between these tip regions. The maximum extent in the direction of the main axis is preferably greater by at least a factor of two than the extent perpendicular to the main axis. The result of this is that webs are formed between adjacent slots. In this context, it is now proposed for these slots to be oriented in such a way with respect to the direction of the circumference, the radius, the center axis of the honeycomb body or of the sheet-metal layer or at least two of these directions in such a way that the rigidity of the honeycomb body differs in a plurality of zones. In this context, the term rigidity is to be understood as meaning the extent to which the zones yield to external forces in at 1east one of the abovementioned directions. This means, for example, that in a first (in particular gas entry side) and if appropriate also in a third (in particular gas exit side) zone, the slots are arranged in such a way that the honeycomb body has a very low rigidity, while in a second (in particular inner) zone the honeycomb body is designed to be relatively rigid. By way of example, if the thermal expansion characteristics of honeycomb bodies of this type in the exhaust system of an automobile are considered, it is established that the end sides expand and contract to a considerably greater extent on account of the fluctuating thermal loads than central regions of the -12- honeycomb body. The different zones make it possible to compensate for or interrupt differential thermal expansions of this type or different levels of forces introduced (e.g. as a result of pulses in the exhaust gas flow). In this context, it is preferable for the holes which are designed as slots to be at least partially offset with respect to one another in the direction of a circumference and/or a radius and/or a center axis and/or to be arranged at an angle in terms of their main axes. This means, for example, that: - the holes are arranged in lines parallel to the edge region, and that the lines (or groups of adjacent lines) which are adjacent in the direction parallel to the attachment region are offset with respect to one another in the direction of the edge region (with an identical or variable spacing between one another); - the holes are arranged in lines parallel to the attachment region, and that the lines (or groups of adjacent lines) which adjoin one another in the direction parallel to the edge region are offset with respect to one another in the direction of the attachment region (with an identical or variable distance between one another); - the holes are oriented obliquely with respect to one another, in particular with main axes which are not at a right angle with respect to the orientation of the edge or attachment regions; - at least in partial regions of the zones, the holes form a type of latticework; - the holes generate different thicknesses of webs and/or different orientations of the webs with respect to the honeycomb body; or - the holes are arranged in accordance with partial combinations as mentioned here, in order to produce differing -13- rigidities of the honeycomb body over its axial extent and/or its radius and/or its circumference. Exemplary embodiments and details of the invention, to which the invention is not, however, limited, are explained in more detail below with reference to the drawings, in which: Fig. 1 shows a sheet-metal layer for the production of a honeycomb body according to the invention. Fig. 2 shows a perspective, partially cut-away view of a honeycomb body according to the invention, Fig. 3 shows a partially cut-away catalytic converter having a honeycomb body according to the invention and a cavity for a lambda sensor in a diagrammatic side view, Fig. 4 shows a diagrammatic and perspective illustration of a corrugated sheet-metal layer with holes, Fig. 5 diagrammatically depicts the sequence of a process for producing a honeycomb body according to the invention, Fig. 6 diagrammatically depicts a configuration of a sheet-metal layer with slots, and Fig. 7 diagrammatically depicts a honeycomb body with a plurality of zones of different rigidity. Fig. 1 shows a sheet-metal layer 1, which may be either smooth or corrugated, as used to construct a honeycomb body 15 according to the invention. This sheet-metal layer 1 has a width L which subsequently determines the axial length L of a honeycomb body 15 produced therefrom. The size of the sheet- -14- metal layer 1 in the other direction is dependent on the construction type of the honeycomb body 15 which is to be produced. It may be very long if a helically wound honeycomb body 15 is to be produced therefrom or relatively short if it forms part of a stack of a plurality of sheet-metal layers 1 of this type which is subsequently wrapped to form a honeycomb body 15. The thickness 26 of the sheet-metal layer 1 may be between 20 and 80 µm, preferably between 40 and 60 µm. In a partial region {in this case characterized as section 29), the sheet-metal layer 1 has a large number of holes 6 which each have a hole surface area 23 of between 1 and 120 mm2. Holes 6 with a diameter of between 3 and 8 mm, preferably between 4 and 6 mm, are preferred. At least in regions, these holes 6 are arranged in a regular pattern and are preferably at identical distances D7 from one another. However, it is also possible to vary the pattern from the inflow end side 12 to the outflow end side 13, in which case, by way of example, the number of holes, the diameter of the holes and/or the distances D7 are increased. This increase may take place continuously or in steps. It is also advantageous, after these values have been increased in a central region, for them to be reduced again toward the outflow end side 13 for certain applications. It is preferable for the holes 6 to be round or elliptical or oval with a maximum diameter R6 of up to 8 mm. The distances D7 between the holes 6 are selected in such a way that the sheet-metal layer surface area 24 is reduced by from 10 to 80%, preferably 3 0 to 60%, compared to an unperforated surface. The sheet-metal layer 1 has an inflow-side edge region 2 which is free of holes 6. It is preferable for an outflow-side edge region 3 likewise to be free of holes 6. This simplifies processing of the sheet-metal layer 1, makes it possible to -15- connect sheet-metal layers to one another in this edge region and prevents irregularly shaped (jagged) inflow end sides 12 or outflow end sides 13 from being formed during construction of a honeycomb body 15. The inflow-side edge region has a width R2 of from 1 to 5 mm, and the outflow-side edge region 3 has a width R3 of from 1 to 5 mm. Moreover, the sheet-metal layer 1 has at least one attachment region 4, by means of which the sheet-metal layer 1 can subsequently be secured to a tubular casing 14. This attachment region 4, having the width R4, is preferably also free of holes 6. For designs of honeycomb bodies 15 in which the sheet-metal layers 1 are secured to a tubular casing 14 at both ends, a second attachment region 5 with a width R5 is also free of holes 6. If the sheet-metal layer 1 is to be used to produce a honeycomb body 15 which has a cavity 7 for accommodating a measurement sensor 9, a corresponding cavity 7 is to be provided in the sheet-metal layer 1. According to the invention, this cavity is surrounded by a hole-free edge 8, which is once again used to make the sheet-metal layer 1 easier to process and to facilitate production of a uniform cavity 7. The subsequent direction of flow S of a fluid which can flow through the honeycomb body 15 is indicated by arrows in the figures. The path length B of the hole-free edge 8 is preferably at least 1 mm over the entire circumference of the cavity. Figure 2 shows a perspective view of a honeycomb body 15 according to the invention in which the dimension 22 of the perforated partial volume T is diagrammatically indicated. In this case, the dimension 22 starts from the center of the cross section of the honeycomb body, but it is also possible for the partial volume T to be formed as a type of inner, annular hollow cylinder in which the dimension 22 forms any -16- desired part of the diameter or radius of the cross section. The honeycomb body 15 which is shown by way of example is wound helically from a smooth sheet-metal layer 10 and a corrugated sheet-metal layer 11, which in an attachment region 4 are connected to a tubular casing 14. Figure 3 diagrammatically depicts a partially cut-away side view of a catalytic converter 28 with a cavity 7 for receiving a lambda sensor 9. An exhaust gas can flow through the catalytic converter 2 8 in the direction of flow S starting from the inflow end side 12 to the outflow end side 13. At the inflow end side 12 there is a hole-free edge region 2, and at the outflow end side there is a hole-free edge region 3. Between these edge regions is the perforated partial volume T which therefore extends over virtually the entire axial length L of the honeycomb body 15. The honeycomb body 15 has a cavity 7, which was produced either after the honeycomb body 15 had been completed or before this by suitable positioning of cavities 7 in the individual sheet-metal layers 10, 11. A measurement sensor 9, in particular an oxygen measurement sensor 9, can be introduced into this cavity 7. To ensure uniform edges of the cavity 7, a hole-free edge 8, in which the sheet-metal layers 10, 11 do not have any holes 6, surrounds the cavity 7. The combination of a honeycomb body 15 with holes 6 and a cavity 7 for a measurement sensor 9 which is illustrated here is particularly advantageous because the holes 6 upstream of the measurement sensor 9 allow cross-mixing in the honeycomb body 15 and consequently the measurement sensor 9 can measure a representative measured value for the composition of the fluid in the honeycomb body 15 as a whole. Fig. 4 shows a diagrammatic and perspective illustration of a corrugated sheet-metal layer 1 with holes 6. The corrugations -17- or structure of the sheet-metal layer 1 can be described, for example, by a structure height H and structure width A. The abovementioned advantages, in particular with regard to the cross-mixing of the exhaust-gas stream and the inexpensive production of a honeycomb body 15 of this type, can be achieved particularly successfully if the maximum extent R6 of a hole 6 is greater than the structure width A. In the exemplary embodiment illustrated, the holes 6 have an extent R6 or a diameter which corresponds to approximately three times the structure width A of the sinusoidal corrugation of the sheet-metal layer 1. In this case, the holes 6 are arranged in such a way that there is a regular pattern in which each corrugation peak or corrugation valley is interrupted at least by one hole 6 over the axial length within the section 29 which is delimited by the unperforated edges R3, R2, R5 (R4 not shown) of the sheet-metal layer 1 and forms the partial volume T in the honeycomb body 15. With regard to the proportion of the sheet-metal layer surface area 24 which is taken up by the holes 6, it should be noted that in particular the sheet-metal layer surface area 24 within the section 29 is reduced by 30 - 60%, and preferably the overall sheet-metal layer surface area 24 (i.e. including the edges) is reduced by 20 - 40%. To achieve the maximum possible amount of perforation in the section 29, it is advantageous, as illustrated in Fig. 4, for the distances D7 between the holes to be designed to be no greater than a few structure widths A, in particular less than 5, preferably less than 3 structure widths A of the sheet-metal layer 1. For stability reasons, for particular applications of the honeycomb body 15 it is under certain circumstances also possible for the distances D7 in different directions (e.g. in the longitudinal and transverse directions) to be designed to differ from one another in terms -18- of their size, in which case it is preferable for a uniform distance D7 between the holes 6 to be maintained in one direction. Moreover, in the vicinity of the edge R2, the figure shows a microstrueture 27, the height of which is considerably less than the structure height H. It is used, for example, to delimit the attachment region, since in this way a small gap is formed between the sheet-metal layers 1 arranged adjacent to one another, and this gap, during a soldering process, prevents the liquid solder from accumulating in the section 29 as a result of capillary effects, where it may produce undesirable connections. Fig. 5 diagrammatically depicts a possible particularly suitable process for producing a catalytic converter. In a first step, the holes 6 are introduced into the sheet-metal layer 1, this step in this case being carried out mechanically by means of a stamping device 16. In the next step, the structures are produced in the perforated sheet-metal layer 1 by means of two meshing profiling tools 17, so that corrugated sheet-metal layers 11 with a structure height H and a structure width A are formed. These corrugated, at least partially perforated sheet-metal layers 11 are then stacked with smooth sheet-metal layers 10 (perforated or unperforated) to form a honeycomb body 15. These sheet-metal layers 10, 11 are then wound together and introduced into a tubular casing 14. After the sheet-metal layers 10, 11 have been stacked and/or wound, the way in which the holes 6 in the adjacent sheet-metal layers 10, 11 are arranged with respect to one another may be of importance. In principle, it is possible for the holes to be oriented in such a way with respect to one another that they (almost completely) overlap one another. This may be advantageous, for example, if high levels of -19- pressure losses (as may occur with a very turbulent flow) are to be avoided. On the other hand, if the flow is substantially uniform when it enters the honeycomb body 15, it is advantageous for the maximum possible number of inflow edges which lead to swirling to be provided in the interior of the honeycomb body 15. In the latter case, therefore, it is expedient for the holes 6 in the adjacent sheet-metal layers 10, 11 to be arranged offset with respect to one another. In addition to the possible variations with regard to the relative position of the holes 6 with respect to one another, it is also advantageous to consider using different forms of holes 6 even when the holes 6 are superimposed or overlap. For example, different distances D7 between the holes, different maximum extents R6 or different contours 25 of the holes 6 themselves, as well as the relative position with respect to one another in the sheet-metal layers 10, 11 arranged adjacent to one another can be combined with one another. After a soldering process in which in particular the unperf orated regions or edges R1, R2, R3, R4 are provided with solder material (not shown), the sheet-metal layers with one another and also with the tubular casing 14 are subjected to a heat treatment in a furnace 18, in particular are subjected to high-temperature soldering in vacuo and/or under a shielding gas atmosphere. The support body 19 produced in this way can then also be provided with a catalytically active coating 20 in order to enable it ultimately to be used as a catalytic converter in the exhaust system of a motor vehicle. The support body 19 is coated with what is known as washcoat, which has a very rugged surface. This rugged surface on the one hand ensures that sufficient space is available for fixing a catalyst (e.g. platinum, rhodium, etc.) and is secondly used to swirl up the exhaust gas flowing through, producing -20- particularly intensive contact with the catalyst. The washcoat usually consists of a mixture of an aluminum oxide from the transition series and at least one promoter oxide, such as for example rare earth oxides, zirconium oxide, nickel oxide, iron oxide, germanium oxide and barium oxide. The washcoat layer with a large surface area which promotes catalysis is applied in a known way by the honeycomb body 15 or the support body 19 being immersed in or sprayed with a liquid washcoat dispersion. However, particularly in the case of the perforated sheet-metal layers 11, there is a risk of the washcoat dispersion covering and closing up the holes 6. This would lead to the level of perforation in the partial volume T of the honeycomb body 15 being lower than desired, with the result that firstly the cross-mixing between the exhaust-gas part-streams which are formed as a result of the exhaust gas coming into contact with the honeycomb-like form of the end side 12 of the honeycomb body 15 is reduced and secondly too much washcoat dispersion is required. For this reason, the coating operation is carried out using a vibratory installation 21, which generates relative motion between the washcoat dispersion and the support body 19. This relative motion comprises in particular continuous and/or discontinuous vibration, pulsed excitation (e.g. similar to a hammer blow) or similar stimulation of the support body 19, which may also be combined with one another in any desired sequence and/or in different directions. If the washcoat dispersion is excited directly, by way of example a frequency in the ultrasound range has proven particularly advantageous. The excitation took place in a frequency range from 2 0 kHz to 10 MHz. In particular in the case of indirect excitation, i.e. for example brought about by vibration of the support body 19, frequencies in the audible -21- range have proven appropriate, in which case in particular excitation at a frequency of between 20 Hz and 15 kHz has ensured a drop in the viscosity of the washcoat dispersion over a very prolonged period. The result of this is that a uniform distribution of the dispersion is ensured. Furthermore, it has proven particularly advantageous for the support body 19 to be excited one final time in a pulse-like manner, in particular after it has emerged from the coating bath, in order to ensure that there are no longer any holes 6 covered over by the washcoat dispersion. After the excess washcoat dispersion has been removed, the washcoat is dried in the honeycomb body and finally calcined at temperatures which are generally above 450°C. During the calcining, the volatile constituents of the washcoat dispersion are forced out, so that a temperature-resistant, catalysis-promoting layer with a high specific surface area is produced. If appropriate, this operation was repeated a number of times in order to achieve a desired layer thickness. Fig. 6 diagrammatically depicts a configuration of a sheet-metal layer 1 with holes 6 which are formed as slots. This figure illustrates the sheet-metal layer 1 including its attachment regions 4, 5 and its edge regions 2, 3; in this context, it should be noted that the holes 6 do not have to extend over the entire length and/or width of the sheet-metal layer 1. The sheet-metal layer 1 is diagrammatically divided into four sectors {denoted by I, II, III and IV). The holes 6 which are designed as slots and the maximum extent R6 of which in each case extends in the direction of a dedicated main axis 3 0 are arranged differently with respect to one another in the sectors. The holes 6 designed as slots are at least in some cases offset with respect to one another in the direction of a circumference 37 and/or a radius 36 and/or a center axis 35 -22- and/or are arranged at an angle 31 in terms of their main axes 30. In the first sector, their main axes 3 0 have the same orientation, and accordingly they are parallel to one another. The lines of holes 6 illustrated may be repeated constantly within a zone 32, 33, 34, but it is also possible for the lines to be arranged obliquely with respect to one another and/or for the holes 6 in the lines to be offset with respect to one another. In the second sector, the slots are illustrated with a different orientation from those in the first sector, the lines within the second sector being offset with respect to one another. In the third sector, it can be seen that combinations of the arrangements of these slots described are also possible. The fourth sector illustrates a relatively rigid arrangement of the slots: a latticework. The main axes 3 0 of the adjacent holes 6 are at an angle 31 with respect to one another, this angle preferably lying in a range from 30° to 60°. A latticework of this type can also be formed by the holes 6 which are designed as slots being oriented in lines and, in terms of their main axes 30, obliquely with respect to the edge regions 2, 3, in which case all the slots within the line have the same orientation, while the adjacent lines running parallel are arranged offset, with the slots at a different angle with respect to the edge regions 2, 3. It is preferable for the slots of the adjacent lines to be arranged in such a way that the main axes of the holes 6 in a first line are oriented perpendicular with respect to the main axes of the slots arranged in the adjacent cells and/or the main axes of the slots in the first line intersect the center of the slots of the adjacent slots. The arrangement of the holes 6 means that the sheet-metal layer 1 reacts to external forces with different levels of -23- sensitivity in the sectors. In the first sector, it is relatively rigid with respect to forces from the direction of the attachment regions 5, 4 but more elastic with regard to forces perpendicular thereto. The exact opposite is true of sector II. Accordingly, the rigidity characteristics of the honeycomb body 15 can be set in a zoned manner 32, 33, 34 according to the orientation of the holes 6. The zones 32, 33, 34 can divide the honeycomb body in the direction of the axial length L, the circumference 37 or the radius 36. Although Fig. 7 shows only three zones, under certain circumstances it is also possible to provide two or more zones. The present invention allows a high coating effectiveness for the treatment of a fluid to be achieved in most known forms of honeycomb bodies with a reduced usage of coating material while nevertheless enabling properties relating to mechanical stability, heat capacity, thermal conductivity and the like of a honeycomb body to be specifically matched to the requirements of individual applications. -24- List of reference symbols 1 Sheet-metal layer 2 Inflow-side edge region 3 Outflow-side edge region 4 Attachment region 5 Attachment region 6 Hole 7 Cavity 8 Hole-free edge 9 Lambda sensor 10 Smooth sheet-metal layer 11 Corrugated sheet-metal layer 12 Inflow end side 13 Outflow end side 14 Tubular casing 15 Honeycomb body 16 Stamping device 17 Profiling tool 18 Furnace 19 Support body 20 Coating 21 Vibratory installation 22 Dimension 23 Hole surface area 24 Sheet-metal layer surface area 25 Contour 26 Thickness 27 Microstructure 28 Catalytic converter 29 Section 30 Main axis 31 Angle 32 First zone -25- 33 Second zone 34 Third zone 35 Center axis 3 6 Radius 3? Circumference 38 Web 39 Offset A Structure width H Structure height B Path L Axial length R2 Width of the inflow-side edge region R3 Width of the outflow-side edge region R4 Width of the attachment region R5 Width of the attachment region R6 Maximum extent of a hole D7 Distance between two holes 6 S Direction of flow T Partial volume -26- WE CLAIM 1. A metallic honeycomb body (15) having an axial length (L) composed of sheet-metal layers (1; 10, 11) which are structured in such a way that a fluid, in particular the exhaust gas from an internal combustion engine, can flow through the honeycomb body (15) in a direction of flow (S) from an inflow end side (12) to an outflow end side (13), the sheet-metal layers (1; 10, 11), at least in partial regions, having a multiplicity of openings (6), characterized in that the honeycomb body (15) has holes (6) in all the sheet-metal layers (1; 10, 11) in a partial volume (T) which forms at least 55% of the axial length (L) and has a radial dimension (22) of at least 20 mm, and in which honeycomb body; - each of the holes (6) has a hole surface area (23) of between 1 and 120 mm2, - in the partial volume (T), the sheet-metal layer surface area (24) is reduced by 10 to 80%, preferably 35 to 60% by the holes (6) compared to a sheet-metal layer without holes, - the partial volume (T) is in each case at a distance (R2, R3) from the end sides (12, 13) of the honeycomb body, so that none of the holes (6) touches or cuts through the end-side edges of the sheet- metal layers. 27 2. The honeycomb body (15) as claimed in claim 1, wherein the partial volume (T) amounts to more than 60%, preferably more than 90% of the total honeycomb body volume (W). 3. The honeycomb body (15) as claimed in claim 1 or 2, wherein each of the holes (6) each has a hole surface area (23) of from 5 to 60 mm2. 4. The honeycomb body (15) as claimed in claim 1, 2 or 3, wherein the holes (6) have rounded contours (25). 5. The honeycomb body (15) as claimed in claim 1, 2 or 3, wherein the holes (6) are round, oval or elliptical. 6. The honeycomb body (15) as claimed in one of the preceding claims, wherein the holes (6) are produced by removing material from a full-area sheet-metal layer (1). 7. The honeycomb body (15) as claimed in one of claims 1 to 5, wherein the holes (6) are formed during production of the sheet-metal layer (1). 8. The honeycomb body (15) as claimed in one of the preceding claims, wherein the thickness (26) of the sheet-metal layers (1; 10, 11) is 20 to 80 urn, preferably 40 to 60 urn. 28 9. The honeycomb body (15) as claimed in one of the preceding claims, wherein the holes (6) are each at a minimum distance of 0.5 mm from one another, preferably with all the distances (D7) between the holes being approximately equal. 10.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) comprises alternating smooth (10) and corrugated (11) sheet-metal layers or comprises alternating differently corrugated sheet-metal layers. 11.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) has a cell density of 200 to 1000 cpsi (cells per square inch), preferably of 400 to 800 cpsi. 12.The honeycomb body (15) as claimed in one of the preceding claims, wherein the sheet-metal layers (1, 10, 11) have additional microstructures (27) for influencing flow, in particular transverse structures and/or projections and/or flow-guiding surfaces. 13.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) has a cavity (7) for accommodating a sensor, in particular a lambda sensor (9), the cavity (7) being arranged within the partial volume (T) or downstream of the partial volume (T). 14.The honeycomb body (15) as claimed in claim 13, wherein those edges (8) of the sheet-metal layers (1, 10,11) which adjoin the cavity (7) are free of holes over a path (B) of from 1 to 5 mm to the cavity (7). 29 15.The honeycomb body (15) as claimed in one of the preceding claims, wherein the sheet-metal layers (1; 10, 11), at least in partial regions at the end sides (12, 13) are connected to one another by joining, preferably by brazing, in particular in the edge regions (2,3) without holes. 16.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) is arranged in a tubular casing (14), to which attachment regions (4,5) of the sheet-metal layers (1; 10, 11) are internally secured by joining, in particular by brazing, the partial volume (T) not touching the tubular casing (14), that is to say, no hole (6) being present in the attachment regions (4,5) of the sheet-metal layers (1; 10,11) which bear against the tubular casing (14). 17.The honeycomb body (15) as claimed in one of the preceding claims, wherein the maximum extent (R6) of a hole (6) is greater than the structure width (A), in particular each extent (R6) is greater than the structure width (A). 18.The honeycomb body (15) as claimed in claim 17, wherein all the holes (6) in the at least one partial volume (T) have an extent (R6) which is greater than the structure width (A). 19.The honeycomb body (15) as claimed in one of claims 17 or 18, wherein the extent (R6) of the hole (6) is at least twice, preferably four times, in particular six times, as great as the structure width (A). 30 20.The honeycomb body (15) as claimed in one of the preceding claims, wherein at least some of the holes (6) are designed as slots whose maximum extent (R6) in each case extends in the direction of a dedicated main axis (30), the holes (6) which are designed as slots being arranged in such a way that the honeycomb body (15) has zones (32,33, 34) of different rigidities. 21.The honeycomb body (15) as claimed in claim 20, wherein the holes (6) which are designed as slots are at least in part offset with respect to one another in the direction of a circumference (37) and/or a radius (36) and/or a center axis (35) and/or are arranged at an angle (31) in terms of their main axes (30). Dated this 2nd day of February, 2005 31 This invention relates to a metallic honeycomb having an axial length (L) composed of sheet-metal layers (1; 10, 11) which are structured in such a way that a fluid, in particular the exhaust gas from an internal combustion engine, can flow through the honeycomb body in a direction of flow (S) from an inflow end side (12) to an outflow end side (13), the sheet-metal layers (1; 10, 11), at least in partial regions, having a multiplicity of openings (6), the honeycomb body furthermore having holes (6) in all the sheet metal layers (1; 10,11) in a partial volume (T) which forms at least 55% of the axial length (L) and has a radial dimension (22) of at least 20 mm, and in which honeycomb body: the holes (6) each have a surface area of between 1 and 120 mm2; in the partial volume (T), the sheet-metal layer surface area is reduced by 10 to 80%, preferably 35 to 60%, by the holes (6) compared to a sheet-metal layer without holes, the partial volume (T) is in each case at a distance (R2, R3) from the end sides (12,13) of the honeycomb body, so that no-holes (6) touch or cut through the end-side edges of the sheet-metal layers.

Full Text

E-80893
Metallic honeycomb body comprising at least partially perforated sheet-metal layers
The present invention relates to a metallic honeycomb body, in particular to a honeycomb body for an exhaust system of an internal combustion engine. Honeycomb bodies of this type are used as supports for catalytically active material and/or for adsorber material and similar applications.
In particular metallic honeycomb bodies used for the purification of exhaust gases in internal combustion engines have to satisfy very different demands, and in some cases compromises have to be made between contradictory requirements. First of all, honeycomb bodies of this type should provide the maximum possible surface area at which the desired catalytic reactions or adsorption processes can take place. In many applications, a low heat capacity is desired, so that the honeycomb body is either quickly heated to its desired operating temperature or should also have a high heat capacity, so that it can remain at operating temperature for a longer time but cannot be heated to excessively high temperatures too quickly. Of course, an arrangement of this type must in general terms be mechanically stable, i.e. must be able to withstand a pulsating gas flow and also mechanical loads caused by the movement of the vehicle. Its material must be resistant to high-temperature corrosion and it must also be possible to machine this material in such a way that the desired honeycomb structures can be produced easily and at low cost. In many cases, particular structures are also required within the honeycomb body in order to influence flow, for example to improve contact with the surface or to effect
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cross-mixing. Finally, it must be possible for a suitable honeycomb body to be produced at low cost in mass production.
Individual aspects of the above problems have been described extensively in numerous documents which form part of the prior art.
A distinction is drawn in particular between two typical forms of metallic honeycomb bodies. An early form, of which DE 29 02 779 A1 shows typical examples, is the helical form in which substantially one smooth and one corrugated sheet-metal layer are laid on top of one another and are wound helically. In another form, the honeycomb body is composed of a multiplicity of alternately arranged smooth and corrugated or differently corrugated sheet-metal layers, the sheet-metal layers initially forming one or more stacks which are wrapped together. In this case, the ends of all the sheet-metal layers come to lie on the outside and can be connected to a housing or tubular casing, resulting in numerous connections, which increase the durability of the honeycomb body. Typical examples of these forms are described in EP 0 245 737 B1 or WO 90/03220. It has also long been known to equip the sheet-metal layers with additional structures in order to influence the flow and/or to achieve cross-mixing between the individual flow passages. Typical examples of configurations of this type are WO 91/01178, WO 91/01807 and WO 90/08249. Finally, there are also honeycomb bodies in conical form, if appropriate including with further additional structures for influencing flow. A honeycomb body of this type is described, for example, in WO 97/49905. Furthermore, it is also known to form a recess for a sensor, in particular for accommodating a lambda sensor, in a honeycomb body. One example of this is described in DE 88 16 154 U1.
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It has also long been known to use slotted metal sheets, in particular expanded metal and similar slot structures, for honeycomb bodies. An overview of various forms and arrangements of openings in sheet-metal layers of catalyst support bodies is given in US 5,599,509 together with the prior art cited therein. This makes targeted use of openings to reduce the heat capacity in the front region of a honeycomb body compared to the rear region.
Although the extensive prior art allows many different directions to be pursued in development, some further development trends have emerged. One of these trends is the development toward ever thinner metal foils in order to be able to provide a large surface area while using small amounts of material and achieving a low heat capacity. An obvious drawback of this development trend is that the thin foils become increasingly mechanically sensitive and the honeycomb bodies produced therefrom are less durable. At the same time, a trend has evolved toward ever higher cell densities, which to a certain extent is caused by the ever thinner foils being used. To improve mass transfer with the surfaces of a honeycomb body, structures for influencing flow were introduced into the surfaces, in particular what are known as transverse structures, or flow-guiding surfaces or additional inflow edges were created in the interior of a honeycomb body. Although the advantages of openings in the sheet-metal layers for cross-mixing are known, the systematic provision of openings through which a fluid can freely pass in the majority of the catalytic converter volume has not hitherto been considered in practice, since this runs contrary to the trend toward providing ever greater surface areas within increasingly small volumes. While slots and/or flow-guiding surfaces and similar structures do not reduce the surface area in a honeycomb body, the use of a large number of holes does
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considerably reduce the surface area and, moreover, at least if the holes are formed by removing material, means an increased consumption of starting material without a corresponding increase in surface area, which likewise runs contrary to prevailing trends. Therefore, holes have only been considered if they are supposed to have a specific function at a certain location in the honeycomb body, for example the function of cross-mixing or reducing the heat capacity compared to other regions.
Although this consideration, when seen in isolation, was certainly applicable to a metallic honeycomb body, one should not lose sight of the fact that a metallic honeycomb body is subsequently coated with a coating material, which in many cases also contains expensive precious metals as a catalytically active component. Consequently, a large surface area always also means a large quantity of expensive coating material. Surprisingly, tests have shown that for certain dimensions of size, distribution and density of a large number of holes over a honeycomb body, the catalytic conversion properties can be as good, with a smaller surface area, as in a honey comb body without holes and with a larger quantity of coating material.
Therefore, it is an object of the present invention to provide a metallic honeycomb body which, by having a suitable number, dimensions and distribution of holes, is particularly suitable as a support for a coating, in particular for economical deployment of the coating material.
A metallic honeycomb body in accordance with the features of the invention is used to achieve this object. This honeycomb body having an axial length composed of sheet-metal layers which are structured in such a way that a fluid, in particular the exhaust gas from an ..
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internal combustion engine, can flow through the honeycomb body in a direction of flow from an inflow end side to an outflow end side, the sheet-metal layers, at least in partial regions, having a multiplicity of openings, is distinguished, according to the invention, by the fact that the honeycomb body has holes in all the sheet-metal layers in a partial volume which forms at least 55% of its axial length and has a radial dimension of at least 20 mm, and in which honeycomb body:
the holes each have a hole surface area of between 1 and 12 0 mm2, in the partial volume, the sheet-metal layer surface area is reduced by 10 to 80%, preferably 35 to 60%, by the holes compared to a sheet-metal layer without holes, the partial volume is in each case at a distance from the end sides of the honeycomb body, so that no holes touch or cut through the end-side edges of the sheet-metal layers.
Tests have shown that a honeycomb body with holes according to the invention, on account of the improved flow properties in its interior and the resultant improved mass transfer properties between flow and surface, has an effectiveness which is comparable to and under certain circumstances even superior to a honeycomb body without holes, even though less coating material is used. The holes are so large that firstly they are not closed up by coating material during coating and secondly they also do not become blocked by particles in a fluid which is to be purified. Therefore, these are not holes similar to those used in a filter for retaining particles, but rather openings through which a fluid which is to be purified, in particular an exhaust gas from an internal combustion engine, can flow freely. For manufacture and technology reasons and with a view to the subsequent durability, it is important for the end-side edges not to be eaten into by holes
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or parts of holes, and consequently the holes should be at a distance from the end sides.
As has already been stated, the holes have more advantages than disadvantages, and consequently the partial volume provided with holes should amount to more than 60%, preferably more than 90%, of the total honeycomb body volume. This makes it possible to exploit the positive effect to its maximum extent.
For mechanical and fluid dynamic reasons, it is expedient if the holes each have a surface area of from 5 to 60 mm2. With a size of this type, they are easy to produce, do not disrupt a coating process and bring about the above advantages of improved mass transfer. Holes of this size allow good cross-mixing and also allow dissipation of heat from the interior of the honeycomb body outward, not only by thermal conduction but also by thermal radiation, which passes through the holes into regions laying further toward the outside. Of course, the
larger the total area of the holes compared to the total area of the heat-metal layers which remain, the stronger these effects become.
For comparable applications, the prior art has almost exclusively described openings in the sheet-metal layers which have polygonal contours. From a mechanical point of view, this is not advantageous under high and fluctuating loads, since cracks can form starting from the corners of the holes. Consequently, in the present invention it is preferable to use rounded contours of the holes, so that the boundary lines of the holes do not have any corners, in particular do not have any acute angles. The holes should particularly preferably be round, oval or elliptical, in which case it is recommended, in
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the case of shapes which are not round, not to exceed a maximum diameter to minimum diameter ratio of two.
However, holes of this type cannot be produced in a material-saving manner, as is possible, for example, with expanded metal, but rather have to be produced by removal of the material from a full-area sheet-metal layer. However, the material, which is preferably removed by stamping or cutting, can be reused to produce new sheet-metal layers.
Depending on the way in which the sheet-metal layer is produced, the holes may also be removed as early as during the production process, an option which is suitable in particular for materials produced by galvanoplastic means. In the case of a production process in which first of all an inexpensive material is produced and the quality of this material is subsequently improved by coating, e.g. with aluminum and/or chromium, it is recommended to produce the holes before the material is improved with these further materials.
A further advantage of the invention is that the heat capacity of a honeycomb body with holes is, of course, lower than the heat capacity of a honeycomb body without holes. On the other hand, this enables honeycomb bodies according to the invention to be produced from thicker sheet-metal layers without the heat capacity increasing compared to honeycomb bodies made from unperforated, thinner sheet-metal layers. According to the invention, the thickness of the sheet-metal layers may be between 20 and 80 µm, but a thickness of from 40 to 60 µm is preferred. The preferred range leads to improved mechanical stability, in particular at the end sides of a honeycomb body, and makes it possible to use tried-and-tested production processes which can no longer readily be applied to very thin foils. Nevertheless, the heat capacity of the honeycomb bodies
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which form is less than or equal to that of honeycomb bodies made from thinner foils without holes.
To ensure mechanical stability of a honeycomb body according to the invention, the holes should have a minimum spacing of 0.5 mm, with the distances between the holes preferably in each case being approximately equal, so that no mechanical weak points are formed. Foils configured in this way can be corrugated without problems and then used in the remaining working steps for production of helical or coated and wrapped honeycomb bodies.
A honeycomb body according to the invention, like most which are known in the prior art, particularly preferably comprises alternately arranged smooth and corrugated sheet-metal layers or comprises alternating differently corrugated sheet-metal layers. Structures of this type produce the typical flow passages in a honeycomb body.
On account of the positive effects of the holes, for the catalytic converters which are subsequently produced from the honeycomb bodies to have good conversion properties, it is not necessary for honeycomb bodies according to the invention to have an extremely high cell density. According to the invention, cell densities of between 200 and 1000 cpsi (cells per square inch), in particular cell densities of from 400 to 800 cpsi, are preferred.
The inventive use of holes in the sheet-metal layers does not adversely affect the usability of the sheet-metal layers for most previously disclosed additional structures for influencing flow as have been mentioned in the description of the prior art. In particular, the perforated sheet-metal layers can also be provided with transverse structures, with
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projections and/or with flow-guiding surfaces. In general, the holes even assist the action of structures of this-type,since any pressure differences which occur in the passages can be compensated for by the openings, additional turbulence is generated and the flow profile within the honeycomb body is made more uniform.
The configuration of a honeycomb body according to the invention has particularly positive effects when a sensor, in particular a lambda sensor, which has been introduced into a cavity in a honeycomb body is used as proposed in the prior art. Since a measurement sensor, in particular an oxygen measurement sensor, is intended to measure a value for the fluid flowing in the honeycomb body which is as representative as possible, cross-mixing upstream of the sensor is highly advantageous. Therefore, honeycomb bodies according to the invention are particularly suitable for applications in which a lambda sensor is to be introduced into a cavity in the honeycomb body.
In manufacturing technology terms, this requires a certain level of outlay in production of the sheet-metal layers, so that after assembly they subsequently form a suitable cavity. However, nowadays this outlay is manageable by using NC manufacturing installations. This at the same time makes it possible not to position any holes close to the edges of the sheet-metal layers which delimit the cavity, in order to prevent the edges from being attacked at this location too. Therefore, it is particularly preferable for there to be no holes in a region of from 1 to 5 mm around the cavity for a measurement sensor.
For the durability of a honeycomb body, it is advantageous if the individual sheet-metal layers are connected to one another
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by joining, preferably by brazing, which typically takes place at the end sides of a honeycomb body. This is also a reason why no holes should intersect the end-side edge regions of the sheet-metal layers. On the other hand, the holes can also very deliberately prevent adhesive which has been applied to the end sides or solder which has been applied to the end sides from penetrating into the interior of the honeycomb body along the contact lines between the sheet-metal layers, which is often undesirable for mechanical reasons. Here, holes end the capillary effect, so that the distance between the holes and the end sides of a honeycomb body can also be used very deliberately to limit a region which is connected by soldering.
A similar statement also applies to the attachment of the sheet-metal layers to a tubular casing. In this case too, on account of the very stable connection to the tubular casing which is desired, it is more favorable if the edge regions are not intersected by holes. In this case too, furthermore, the holes ensure that the solder cannot penetrate too far into the interior of the honeycomb body by means of capillary action, but rather remains precisely where it is used to secure the sheet-metal layers.
The size of the honeycomb body volume in catalytic converters (sum of the volumes of the sheet-metal layers and also the passages, openings, holes, etc. which are formed or enclosed) is dependent, for example, on the positioning in the exhaust section: if it is arranged in the engine compartment or in the immediate vicinity of the engine (within a distance of up to 0.5 m) , this size is usually less than the capacity of the engine, e.g. less than 50% of the capacity, in particular less than 1 liter or 0.5 liter. If it is arranged in the underbody of a passenger car, the honeycomb body volume may also be
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greater than the capacity of the engine, preferably between 1 and 5 liters. Different sizes may also result in other applications, such as for example for use in trucks, motorcycles, lawnmowers, hand-held appliances (hedge clippers, power saws, etc.) or the like, in which case the corresponding person skilled in the art can make suitable modifications. A similar statement is true for honeycomb bodies which are used as heat exchangers, flow mixers, adsorbers, particle traps, particulate filters, electrical heaters in exhaust systems. In these cases too, the person skilled in the art is aware of a range of tests which allow the honeycomb body volume to be suitably adapted.
When designing or configuring the pattern of holes in the sheet-metal layer, account should also be taken of the desired application of the honeycomb bodies. Since in this context it has not been possible to make use of knowledge gained from experience, tests have shown that the effects of the mixing or catalytic conversion combined, at the same time, with a considerably reduced deployment of catalytic material were surprisingly good in sheet-metal foils with holes whose maximum extent was greater than the structure width of the corrugation, in particular with holes in which even the shortest distance between opposite contours of the holes was still greater than the structure width. This preferably applies to the holes in the at least partially structured sheet-metal layers, so that the holes are superimposed on the corrugation or structure. It is particularly advantageous for all the holes in the at least one partial volume to have an extent which is greater than the structure width. Surprisingly good results can be achieved with a honeycomb body in whose sheet-metal foils the size of the hole is at least twice, preferably four times, in particular six times, as great as the structure width.
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According to an advantageous refinement of the honeycomb body, at least some of the holes are designed as slots whose maximum extent in each case extends in the direction of a dedicated main axis, the holes designed as slots being arranged in such a way that the honeycomb body has zones of different rigidities. In this context, a slot is understood as meaning in particular a hole which has two opposite rounded, preferably semicircle-like tip regions, the maxima or turning points of which define the main axis, the slot preferably having edges which run parallel to one another between these tip regions. The maximum extent in the direction of the main axis is preferably greater by at least a factor of two than the extent perpendicular to the main axis. The result of this is that webs are formed between adjacent slots. In this context, it is now proposed for these slots to be oriented in such a way with respect to the direction of the circumference,
the radius, the center axis of the honeycomb body or of the

sheet-metal layer or at least two of these directions in such a way that the rigidity of the honeycomb body differs in a plurality of zones. In this context, the term rigidity is to be understood as meaning the extent to which the zones yield to external forces in at 1east one of the abovementioned directions. This means, for example, that in a first (in particular gas entry side) and if appropriate also in a third (in particular gas exit side) zone, the slots are arranged in such a way that the honeycomb body has a very low rigidity, while in a second (in particular inner) zone the honeycomb body is designed to be relatively rigid. By way of example, if the thermal expansion characteristics of honeycomb bodies of this type in the exhaust system of an automobile are considered, it is established that the end sides expand and contract to a considerably greater extent on account of the fluctuating thermal loads than central regions of the
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honeycomb body. The different zones make it possible to compensate for or interrupt differential thermal expansions of this type or different levels of forces introduced (e.g. as a result of pulses in the exhaust gas flow).
In this context, it is preferable for the holes which are designed as slots to be at least partially offset with respect to one another in the direction of a circumference and/or a radius and/or a center axis and/or to be arranged at an angle in terms of their main axes. This means, for example, that: - the holes are arranged in lines parallel to the edge region, and that the lines (or groups of adjacent lines) which are adjacent in the direction parallel to the attachment region are offset with respect to one another in the direction of the edge region (with an identical or variable spacing between one another);
- the holes are arranged in lines parallel to the attachment
region, and that the lines (or groups of adjacent lines) which
adjoin one another in the direction parallel to the edge
region are offset with respect to one another in the direction
of the attachment region (with an identical or variable
distance between one another);
- the holes are oriented obliquely with respect to one
another, in particular with main axes which are not at a right
angle with respect to the orientation of the edge or
attachment regions;
- at least in partial regions of the zones, the holes form a
type of latticework;
- the holes generate different thicknesses of webs and/or
different orientations of the webs with respect to the
honeycomb body; or
- the holes are arranged in accordance with partial
combinations as mentioned here, in order to produce differing
-13-

rigidities of the honeycomb body over its axial extent and/or its radius and/or its circumference.
Exemplary embodiments and details of the invention, to which the invention is not, however, limited, are explained in more detail below with reference to the drawings, in which:
Fig. 1 shows a sheet-metal layer for the production of a honeycomb body according to the invention.
Fig. 2 shows a perspective, partially cut-away view of a honeycomb body according to the invention,
Fig. 3 shows a partially cut-away catalytic converter having a honeycomb body according to the invention and a cavity for a lambda sensor in a diagrammatic side view,
Fig. 4 shows a diagrammatic and perspective illustration of a corrugated sheet-metal layer with holes,
Fig. 5 diagrammatically depicts the sequence of a process for producing a honeycomb body according to the invention,
Fig. 6 diagrammatically depicts a configuration of a sheet-metal layer with slots, and
Fig. 7 diagrammatically depicts a honeycomb body with a plurality of zones of different rigidity.
Fig. 1 shows a sheet-metal layer 1, which may be either smooth or corrugated, as used to construct a honeycomb body 15 according to the invention. This sheet-metal layer 1 has a width L which subsequently determines the axial length L of a honeycomb body 15 produced therefrom. The size of the sheet-
-14-

metal layer 1 in the other direction is dependent on the construction type of the honeycomb body 15 which is to be produced. It may be very long if a helically wound honeycomb body 15 is to be produced therefrom or relatively short if it forms part of a stack of a plurality of sheet-metal layers 1 of this type which is subsequently wrapped to form a honeycomb body 15. The thickness 26 of the sheet-metal layer 1 may be between 20 and 80 µm, preferably between 40 and 60 µm.
In a partial region {in this case characterized as section 29), the sheet-metal layer 1 has a large number of holes 6 which each have a hole surface area 23 of between 1 and 120 mm2. Holes 6 with a diameter of between 3 and 8 mm, preferably between 4 and 6 mm, are preferred. At least in regions, these holes 6 are arranged in a regular pattern and are preferably at identical distances D7 from one another. However, it is also possible to vary the pattern from the inflow end side 12 to the outflow end side 13, in which case, by way of example, the number of holes, the diameter of the holes and/or the distances D7 are increased. This increase may take place continuously or in steps. It is also advantageous, after these values have been increased in a central region, for them to be reduced again toward the outflow end side 13 for certain applications. It is preferable for the holes 6 to be round or elliptical or oval with a maximum diameter R6 of up to 8 mm. The distances D7 between the holes 6 are selected in such a way that the sheet-metal layer surface area 24 is reduced by from 10 to 80%, preferably 3 0 to 60%, compared to an unperforated surface.
The sheet-metal layer 1 has an inflow-side edge region 2 which
is free of holes 6. It is preferable for an outflow-side edge
region 3 likewise to be free of holes 6. This simplifies processing of the sheet-metal layer 1, makes it possible to
-15-

connect sheet-metal layers to one another in this edge region and prevents irregularly shaped (jagged) inflow end sides 12 or outflow end sides 13 from being formed during construction of a honeycomb body 15. The inflow-side edge region has a width R2 of from 1 to 5 mm, and the outflow-side edge region 3 has a width R3 of from 1 to 5 mm. Moreover, the sheet-metal layer 1 has at least one attachment region 4, by means of which the sheet-metal layer 1 can subsequently be secured to a tubular casing 14. This attachment region 4, having the width R4, is preferably also free of holes 6. For designs of honeycomb bodies 15 in which the sheet-metal layers 1 are secured to a tubular casing 14 at both ends, a second attachment region 5 with a width R5 is also free of holes 6.
If the sheet-metal layer 1 is to be used to produce a honeycomb body 15 which has a cavity 7 for accommodating a measurement sensor 9, a corresponding cavity 7 is to be provided in the sheet-metal layer 1. According to the invention, this cavity is surrounded by a hole-free edge 8, which is once again used to make the sheet-metal layer 1 easier to process and to facilitate production of a uniform cavity 7. The subsequent direction of flow S of a fluid which can flow through the honeycomb body 15 is indicated by arrows in the figures. The path length B of the hole-free edge 8 is preferably at least 1 mm over the entire circumference of the cavity.
Figure 2 shows a perspective view of a honeycomb body 15 according to the invention in which the dimension 22 of the perforated partial volume T is diagrammatically indicated. In this case, the dimension 22 starts from the center of the cross section of the honeycomb body, but it is also possible for the partial volume T to be formed as a type of inner, annular hollow cylinder in which the dimension 22 forms any
-16-

desired part of the diameter or radius of the cross section. The honeycomb body 15 which is shown by way of example is wound helically from a smooth sheet-metal layer 10 and a corrugated sheet-metal layer 11, which in an attachment region 4 are connected to a tubular casing 14.
Figure 3 diagrammatically depicts a partially cut-away side view of a catalytic converter 28 with a cavity 7 for receiving a lambda sensor 9. An exhaust gas can flow through the catalytic converter 2 8 in the direction of flow S starting from the inflow end side 12 to the outflow end side 13. At the inflow end side 12 there is a hole-free edge region 2, and at the outflow end side there is a hole-free edge region 3. Between these edge regions is the perforated partial volume T which therefore extends over virtually the entire axial length L of the honeycomb body 15. The honeycomb body 15 has a cavity 7, which was produced either after the honeycomb body 15 had been completed or before this by suitable positioning of cavities 7 in the individual sheet-metal layers 10, 11. A measurement sensor 9, in particular an oxygen measurement sensor 9, can be introduced into this cavity 7. To ensure uniform edges of the cavity 7, a hole-free edge 8, in which the sheet-metal layers 10, 11 do not have any holes 6, surrounds the cavity 7. The combination of a honeycomb body 15 with holes 6 and a cavity 7 for a measurement sensor 9 which is illustrated here is particularly advantageous because the holes 6 upstream of the measurement sensor 9 allow cross-mixing in the honeycomb body 15 and consequently the measurement sensor 9 can measure a representative measured value for the composition of the fluid in the honeycomb body 15 as a whole.
Fig. 4 shows a diagrammatic and perspective illustration of a corrugated sheet-metal layer 1 with holes 6. The corrugations
-17-

or structure of the sheet-metal layer 1 can be described, for example, by a structure height H and structure width A. The abovementioned advantages, in particular with regard to the cross-mixing of the exhaust-gas stream and the inexpensive production of a honeycomb body 15 of this type, can be achieved particularly successfully if the maximum extent R6 of a hole 6 is greater than the structure width A. In the exemplary embodiment illustrated, the holes 6 have an extent R6 or a diameter which corresponds to approximately three times the structure width A of the sinusoidal corrugation of the sheet-metal layer 1. In this case, the holes 6 are arranged in such a way that there is a regular pattern in which each corrugation peak or corrugation valley is interrupted at least by one hole 6 over the axial length within the section 29 which is delimited by the unperforated edges R3, R2, R5 (R4 not shown) of the sheet-metal layer 1 and forms the partial volume T in the honeycomb body 15. With regard to the proportion of the sheet-metal layer surface area 24 which is taken up by the holes 6, it should be noted that in particular the sheet-metal layer surface area 24 within the section 29 is reduced by 30 - 60%, and preferably the overall sheet-metal layer surface area 24 (i.e. including the edges) is reduced by 20 - 40%.
To achieve the maximum possible amount of perforation in the section 29, it is advantageous, as illustrated in Fig. 4, for the distances D7 between the holes to be designed to be no greater than a few structure widths A, in particular less than 5, preferably less than 3 structure widths A of the sheet-metal layer 1. For stability reasons, for particular applications of the honeycomb body 15 it is under certain circumstances also possible for the distances D7 in different directions (e.g. in the longitudinal and transverse directions) to be designed to differ from one another in terms
-18-

of their size, in which case it is preferable for a uniform distance D7 between the holes 6 to be maintained in one direction.
Moreover, in the vicinity of the edge R2, the figure shows a microstrueture 27, the height of which is considerably less than the structure height H. It is used, for example, to delimit the attachment region, since in this way a small gap is formed between the sheet-metal layers 1 arranged adjacent to one another, and this gap, during a soldering process, prevents the liquid solder from accumulating in the section 29 as a result of capillary effects, where it may produce undesirable connections.
Fig. 5 diagrammatically depicts a possible particularly suitable process for producing a catalytic converter. In a first step, the holes 6 are introduced into the sheet-metal layer 1, this step in this case being carried out mechanically by means of a stamping device 16. In the next step, the structures are produced in the perforated sheet-metal layer 1 by means of two meshing profiling tools 17, so that corrugated sheet-metal layers 11 with a structure height H and a structure width A are formed. These corrugated, at least partially perforated sheet-metal layers 11 are then stacked with smooth sheet-metal layers 10 (perforated or unperforated) to form a honeycomb body 15. These sheet-metal layers 10, 11 are then wound together and introduced into a tubular casing 14. After the sheet-metal layers 10, 11 have been stacked and/or wound, the way in which the holes 6 in the adjacent sheet-metal layers 10, 11 are arranged with respect to one another may be of importance. In principle, it is possible for the holes to be oriented in such a way with respect to one another that they (almost completely) overlap one another. This may be advantageous, for example, if high levels of
-19-

pressure losses (as may occur with a very turbulent flow) are to be avoided. On the other hand, if the flow is substantially uniform when it enters the honeycomb body 15, it is advantageous for the maximum possible number of inflow edges which lead to swirling to be provided in the interior of the honeycomb body 15. In the latter case, therefore, it is expedient for the holes 6 in the adjacent sheet-metal layers 10, 11 to be arranged offset with respect to one another. In addition to the possible variations with regard to the relative position of the holes 6 with respect to one another, it is also advantageous to consider using different forms of holes 6 even when the holes 6 are superimposed or overlap. For example, different distances D7 between the holes, different maximum extents R6 or different contours 25 of the holes 6 themselves, as well as the relative position with respect to one another in the sheet-metal layers 10, 11 arranged adjacent to one another can be combined with one another.
After a soldering process in which in particular the unperf orated regions or edges R1, R2, R3, R4 are provided with solder material (not shown), the sheet-metal layers with one another and also with the tubular casing 14 are subjected to a heat treatment in a furnace 18, in particular are subjected to high-temperature soldering in vacuo and/or under a shielding gas atmosphere. The support body 19 produced in this way can then also be provided with a catalytically active coating 20 in order to enable it ultimately to be used as a catalytic converter in the exhaust system of a motor vehicle.
The support body 19 is coated with what is known as washcoat, which has a very rugged surface. This rugged surface on the one hand ensures that sufficient space is available for fixing a catalyst (e.g. platinum, rhodium, etc.) and is secondly used to swirl up the exhaust gas flowing through, producing
-20-

particularly intensive contact with the catalyst. The washcoat usually consists of a mixture of an aluminum oxide from the transition series and at least one promoter oxide, such as for example rare earth oxides, zirconium oxide, nickel oxide, iron oxide, germanium oxide and barium oxide.
The washcoat layer with a large surface area which promotes catalysis is applied in a known way by the honeycomb body 15 or the support body 19 being immersed in or sprayed with a liquid washcoat dispersion. However, particularly in the case of the perforated sheet-metal layers 11, there is a risk of the washcoat dispersion covering and closing up the holes 6. This would lead to the level of perforation in the partial volume T of the honeycomb body 15 being lower than desired, with the result that firstly the cross-mixing between the exhaust-gas part-streams which are formed as a result of the exhaust gas coming into contact with the honeycomb-like form of the end side 12 of the honeycomb body 15 is reduced and secondly too much washcoat dispersion is required. For this reason, the coating operation is carried out using a vibratory installation 21, which generates relative motion between the washcoat dispersion and the support body 19. This relative motion comprises in particular continuous and/or discontinuous vibration, pulsed excitation (e.g. similar to a hammer blow) or similar stimulation of the support body 19, which may also be combined with one another in any desired sequence and/or in different directions.
If the washcoat dispersion is excited directly, by way of example a frequency in the ultrasound range has proven particularly advantageous. The excitation took place in a frequency range from 2 0 kHz to 10 MHz. In particular in the case of indirect excitation, i.e. for example brought about by vibration of the support body 19, frequencies in the audible
-21-

range have proven appropriate, in which case in particular excitation at a frequency of between 20 Hz and 15 kHz has ensured a drop in the viscosity of the washcoat dispersion over a very prolonged period. The result of this is that a uniform distribution of the dispersion is ensured. Furthermore, it has proven particularly advantageous for the support body 19 to be excited one final time in a pulse-like manner, in particular after it has emerged from the coating bath, in order to ensure that there are no longer any holes 6 covered over by the washcoat dispersion.
After the excess washcoat dispersion has been removed, the washcoat is dried in the honeycomb body and finally calcined at temperatures which are generally above 450°C. During the calcining, the volatile constituents of the washcoat dispersion are forced out, so that a temperature-resistant, catalysis-promoting layer with a high specific surface area is produced. If appropriate, this operation was repeated a number of times in order to achieve a desired layer thickness.
Fig. 6 diagrammatically depicts a configuration of a sheet-metal layer 1 with holes 6 which are formed as slots. This figure illustrates the sheet-metal layer 1 including its attachment regions 4, 5 and its edge regions 2, 3; in this context, it should be noted that the holes 6 do not have to extend over the entire length and/or width of the sheet-metal layer 1. The sheet-metal layer 1 is diagrammatically divided into four sectors {denoted by I, II, III and IV). The holes 6 which are designed as slots and the maximum extent R6 of which in each case extends in the direction of a dedicated main axis 3 0 are arranged differently with respect to one another in the sectors. The holes 6 designed as slots are at least in some cases offset with respect to one another in the direction of a circumference 37 and/or a radius 36 and/or a center axis 35
-22-

and/or are arranged at an angle 31 in terms of their main axes 30. In the first sector, their main axes 3 0 have the same orientation, and accordingly they are parallel to one another. The lines of holes 6 illustrated may be repeated constantly within a zone 32, 33, 34, but it is also possible for the lines to be arranged obliquely with respect to one another and/or for the holes 6 in the lines to be offset with respect to one another. In the second sector, the slots are illustrated with a different orientation from those in the first sector, the lines within the second sector being offset with respect to one another. In the third sector, it can be seen that combinations of the arrangements of these slots described are also possible.
The fourth sector illustrates a relatively rigid arrangement of the slots: a latticework. The main axes 3 0 of the adjacent holes 6 are at an angle 31 with respect to one another, this angle preferably lying in a range from 30° to 60°. A latticework of this type can also be formed by the holes 6 which are designed as slots being oriented in lines and, in terms of their main axes 30, obliquely with respect to the edge regions 2, 3, in which case all the slots within the line have the same orientation, while the adjacent lines running parallel are arranged offset, with the slots at a different angle with respect to the edge regions 2, 3. It is preferable for the slots of the adjacent lines to be arranged in such a way that the main axes of the holes 6 in a first line are oriented perpendicular with respect to the main axes of the slots arranged in the adjacent cells and/or the main axes of the slots in the first line intersect the center of the slots of the adjacent slots.
The arrangement of the holes 6 means that the sheet-metal layer 1 reacts to external forces with different levels of
-23-

sensitivity in the sectors. In the first sector, it is relatively rigid with respect to forces from the direction of the attachment regions 5, 4 but more elastic with regard to forces perpendicular thereto. The exact opposite is true of sector II. Accordingly, the rigidity characteristics of the honeycomb body 15 can be set in a zoned manner 32, 33, 34 according to the orientation of the holes 6. The zones 32, 33, 34 can divide the honeycomb body in the direction of the axial length L, the circumference 37 or the radius 36. Although Fig. 7 shows only three zones, under certain circumstances it is also possible to provide two or more zones.
The present invention allows a high coating effectiveness for the treatment of a fluid to be achieved in most known forms of honeycomb bodies with a reduced usage of coating material while nevertheless enabling properties relating to mechanical stability, heat capacity, thermal conductivity and the like of a honeycomb body to be specifically matched to the requirements of individual applications.

-24-

List of reference symbols

1
Sheet-metal layer
2
Inflow-side edge region
3
Outflow-side edge region
4
Attachment region
5
Attachment region
6
Hole
7
Cavity
8
Hole-free edge
9
Lambda sensor
10
Smooth sheet-metal layer
11
Corrugated sheet-metal layer
12
Inflow end side
13
Outflow end side
14
Tubular casing
15
Honeycomb body
16
Stamping device
17
Profiling tool
18
Furnace
19
Support body
20
Coating
21
Vibratory installation
22
Dimension
23
Hole surface area
24
Sheet-metal layer surface area
25
Contour
26
Thickness
27
Microstructure
28
Catalytic converter
29
Section
30
Main axis
31
Angle
32
First zone
-25-

33 Second zone
34 Third zone
35 Center axis
3 6 Radius
3? Circumference
38 Web
39 Offset
A Structure width
H Structure height
B Path
L Axial length
R2 Width of the inflow-side edge region
R3 Width of the outflow-side edge region
R4 Width of the attachment region
R5 Width of the attachment region
R6 Maximum extent of a hole
D7 Distance between two holes 6
S Direction of flow
T Partial volume
-26-

WE CLAIM
1. A metallic honeycomb body (15) having an axial length (L) composed of sheet-metal layers (1; 10, 11) which are structured in such a way that a fluid, in particular the exhaust gas from an internal combustion engine, can flow through the honeycomb body (15) in a direction of flow (S) from an inflow end side (12) to an outflow end side (13), the sheet-metal layers (1; 10, 11), at least in partial regions, having a multiplicity of openings (6), characterized in that the honeycomb body (15) has holes (6) in all the sheet-metal layers (1; 10, 11) in a partial volume (T) which forms at least 55% of the axial length (L) and has a radial dimension (22) of at least 20 mm, and in which honeycomb body;
- each of the holes (6) has a hole surface area (23) of between 1
and 120 mm2,
- in the partial volume (T), the sheet-metal layer surface area (24) is
reduced by 10 to 80%, preferably 35 to 60% by the holes (6)
compared to a sheet-metal layer without holes,
- the partial volume (T) is in each case at a distance (R2, R3) from
the end sides (12, 13) of the honeycomb body, so that none of the
holes (6) touches or cuts through the end-side edges of the sheet-
metal layers.
27

2. The honeycomb body (15) as claimed in claim 1, wherein the partial
volume (T) amounts to more than 60%, preferably more than 90% of the
total honeycomb body volume (W).
3. The honeycomb body (15) as claimed in claim 1 or 2, wherein each of the
holes (6) each has a hole surface area (23) of from 5 to 60 mm2.
4. The honeycomb body (15) as claimed in claim 1, 2 or 3, wherein the holes
(6) have rounded contours (25).
5. The honeycomb body (15) as claimed in claim 1, 2 or 3, wherein the holes
(6) are round, oval or elliptical.
6. The honeycomb body (15) as claimed in one of the preceding claims,
wherein the holes (6) are produced by removing material from a full-area
sheet-metal layer (1).
7. The honeycomb body (15) as claimed in one of claims 1 to 5, wherein the
holes (6) are formed during production of the sheet-metal layer (1).
8. The honeycomb body (15) as claimed in one of the preceding claims,
wherein the thickness (26) of the sheet-metal layers (1; 10, 11) is 20 to
80 urn, preferably 40 to 60 urn.
28

9. The honeycomb body (15) as claimed in one of the preceding claims, wherein the holes (6) are each at a minimum distance of 0.5 mm from one another, preferably with all the distances (D7) between the holes being approximately equal.
10.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) comprises alternating smooth (10) and corrugated (11) sheet-metal layers or comprises alternating differently corrugated sheet-metal layers.
11.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) has a cell density of 200 to 1000 cpsi (cells per square inch), preferably of 400 to 800 cpsi.
12.The honeycomb body (15) as claimed in one of the preceding claims, wherein the sheet-metal layers (1, 10, 11) have additional microstructures (27) for influencing flow, in particular transverse structures and/or projections and/or flow-guiding surfaces.
13.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) has a cavity (7) for accommodating a sensor, in particular a lambda sensor (9), the cavity (7) being arranged within the partial volume (T) or downstream of the partial volume (T).
14.The honeycomb body (15) as claimed in claim 13, wherein those edges (8) of the sheet-metal layers (1, 10,11) which adjoin the cavity (7) are free of holes over a path (B) of from 1 to 5 mm to the cavity (7).
29

15.The honeycomb body (15) as claimed in one of the preceding claims, wherein the sheet-metal layers (1; 10, 11), at least in partial regions at the end sides (12, 13) are connected to one another by joining, preferably by brazing, in particular in the edge regions (2,3) without holes.
16.The honeycomb body (15) as claimed in one of the preceding claims, wherein the honeycomb body (15) is arranged in a tubular casing (14), to which attachment regions (4,5) of the sheet-metal layers (1; 10, 11) are internally secured by joining, in particular by brazing, the partial volume (T) not touching the tubular casing (14), that is to say, no hole (6) being present in the attachment regions (4,5) of the sheet-metal layers (1; 10,11) which bear against the tubular casing (14).
17.The honeycomb body (15) as claimed in one of the preceding claims, wherein the maximum extent (R6) of a hole (6) is greater than the structure width (A), in particular each extent (R6) is greater than the structure width (A).
18.The honeycomb body (15) as claimed in claim 17, wherein all the holes (6) in the at least one partial volume (T) have an extent (R6) which is greater than the structure width (A).
19.The honeycomb body (15) as claimed in one of claims 17 or 18, wherein the extent (R6) of the hole (6) is at least twice, preferably four times, in particular six times, as great as the structure width (A).
30

20.The honeycomb body (15) as claimed in one of the preceding claims, wherein at least some of the holes (6) are designed as slots whose maximum extent (R6) in each case extends in the direction of a dedicated main axis (30), the holes (6) which are designed as slots being arranged in such a way that the honeycomb body (15) has zones (32,33, 34) of different rigidities.
21.The honeycomb body (15) as claimed in claim 20, wherein the holes (6) which are designed as slots are at least in part offset with respect to one another in the direction of a circumference (37) and/or a radius (36) and/or a center axis (35) and/or are arranged at an angle (31) in terms of their main axes (30).

Dated this 2nd day of February, 2005

31
This invention relates to a metallic honeycomb having an axial length (L) composed of sheet-metal layers (1; 10, 11) which are structured in such a way that a fluid, in particular the exhaust gas from an internal combustion engine, can flow through the honeycomb body in a direction of flow (S) from an inflow end side (12) to an outflow end side (13), the sheet-metal layers (1; 10, 11), at least in partial regions, having a multiplicity of openings (6), the honeycomb body furthermore having holes (6) in all the sheet metal layers (1; 10,11) in a partial volume (T) which forms at least 55% of the axial length (L) and has a radial dimension (22) of at least 20 mm, and in which honeycomb body: the holes (6) each have a surface area of between 1 and 120 mm2; in the partial volume (T), the sheet-metal layer surface area is reduced by 10 to 80%, preferably 35 to 60%, by the holes (6) compared to a sheet-metal layer without holes, the partial volume (T) is in each case at a distance (R2, R3) from the end sides (12,13) of the honeycomb body, so that no-holes (6) touch or cut through the end-side edges of the sheet-metal layers.

Documents:

00117-kolnp-2005 abstract.pdf

00117-kolnp-2005 claims.pdf

00117-kolnp-2005 correspondence.pdf

00117-kolnp-2005 correspondence_1.1.pdf

00117-kolnp-2005 correspondence_1.2.pdf

00117-kolnp-2005 correspondence_1.3.pdf

00117-kolnp-2005 correspondence_1.4.pdf

00117-kolnp-2005 description(complete).pdf

00117-kolnp-2005 drawings.pdf

00117-kolnp-2005 form-1.pdf

00117-kolnp-2005 form-18.pdf

00117-kolnp-2005 form-1_1.1.pdf

00117-kolnp-2005 form-2.pdf

00117-kolnp-2005 form-3.pdf

00117-kolnp-2005 form-5.pdf

00117-kolnp-2005 gpa.pdf

00117-kolnp-2005 international publication.pdf

00117-kolnp-2005 international search authority report.pdf

00117-kolnp-2005 others.pdf

00117-kolnp-2005 pct others.pdf

00117-kolnp-2005 pct request.pdf

00117-kolnp-2005 priority document others.pdf

00117-kolnp-2005 priority document.pdf

117-KOLNP-2005-FORM 27.pdf

117-KOLNP-2005-FORM-27.pdf

117-kolnp-2005-granted-abstract.pdf

117-kolnp-2005-granted-claims.pdf

117-kolnp-2005-granted-correspondence.pdf

117-kolnp-2005-granted-description (complete).pdf

117-kolnp-2005-granted-drawings.pdf

117-kolnp-2005-granted-examination report.pdf

117-kolnp-2005-granted-form 1.pdf

117-kolnp-2005-granted-form 18.pdf

117-kolnp-2005-granted-form 2.pdf

117-kolnp-2005-granted-form 3.pdf

117-kolnp-2005-granted-form 5.pdf

117-kolnp-2005-granted-gpa.pdf

117-kolnp-2005-granted-letter patent.pdf

117-kolnp-2005-granted-reply to examination report.pdf

117-kolnp-2005-granted-specification.pdf

117-kolnp-2005-granted-translated copy of priority document.pdf

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Patent Number

214624

Indian Patent Application Number

117/KOLNP/2005

PG Journal Number

07/2008

Publication Date

15-Feb-2008

Grant Date

13-Feb-2008

Date of Filing

02-Feb-2005

Name of Patentee

EMITEC GESELLSCHAFT FUR EMISSIONSTECHNOLOGIE MBH

Applicant Address

HAUPTSTRASSE 150 53797 LOHMAR

Inventors:

#	Inventor's Name	Inventor's Address
1	MAUS WOLFGANG	GUT HORST, 51429 BERGISCH GLADBACH
2	BRUCK,ROLF	FROBELSTRASSE 12,51429 BERGISCH GLADBACH
3	HIRTH,PETER	FORSTSTRASSE 10,51107 KOLN,

PCT International Classification Number

F01N 3/28

PCT International Application Number

PCT/EP2003/007722

PCT International Filing date

2003-07-16

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10250894.1	2002-10-31	Germany
2	10314085.9	2003-03-28	Germany
3	10237512.7	2002-08-16	Germany