| Title of Invention | METHOD AND TOOL FOR PRODUCING STRUCTURED SHEET METAL LAYERS AND CATALYST CARRIER |
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| Abstract | The invention relates to a method for multiple structure sheet metal foils(1) which comprises the steps of (A) forming the sheet metal foil (1).thereby producing a primary structure (4) having a first primary structure width (5).ID forming the sheet metal foil (1) which has been provided with a primary stucture (4). thereby producing a secondary structure (6); C1 formating the structured sheet metal foil(1), thereby producing a second primary structure width (7) that is smaller than the first primary structure width(5). The invention also relates to a support which comprises multiple structured sheet metal foil for exhaust gas purification and to a tool for producing multiple structured sheet metal foils. |
| Full Text | Method and tool for producing structured sheet metal layers; arid catalyst carrier The present invention relates tc a method for producing structured sheet metal foils, to a catalyst carrier comprising multiple-structured sheet metal foils for exhaust systems of mobile internal combustion engines and to a tool for producing multiple-structured sheet metal foils. In the exhaust emission treatment of mobile internal combustion angines, such as spark-ignition and diesel engines, for: example, the arrangement of components or structures providing a relatively large surface in the exhaust lin-s is already known. These components are usually provided with an adsorbent, catalytically active or (-similar coating, the large surface of the components -ensuring a close contact with the exhaust gas flowing past. Such components include, for example, filter elements for filtering out particulates contained in the exhaust gas, adsorbers for at least temporary storage of pollutants (such as N0x) contained in the exhaust gae, catalytic converters (for example, three-way catalytic converters, oxidation-type catalytic converters, reduction-type converters, etc.), diffusers fcr influencing the flow and swirling of the exhaust gas flowing through, or heating elements, which heat the e>iiaust gas to a predetermined temperature just after cold starting of the internal combustion engine. The following carrier substrates have basically proved suitable for the conditions of use prevailing in the exhaust system of an automobile: ceramic honeycomb monoliths, extruded honeycomb monoliths and honeycomb monoliths made from metal foils. The fact that these carrier substrates can always be adapted to suit their functions means that high tempe::ature-resistant and corrosion-resistant - 2 - sheet metal foils are especially well-suited to service as basic na:erial. Producing honeycomb monoliths with a multiplicity of at least partially structured sheet metal foils, which are then inserted into a casing to form a catalyst carrier, which can be provided with one or more of the aforementioned coatings, is already known. The at least partially structured sheet metal foils are arranged so as to form ducts arranged basically parallel to one another. In order to ensure this, some of the shei»t metal foils, for example, are provided with a prinary structure, one of the distinguishing features of which is a regular, recurring frfcruoture, in particular % type of sinusoidal-shaped corrugation, a saw-tooth .structure, a rectangular corrugation, a triangular corrugation, an omega-shaped corrugation or the like. These sheet metal foils provided with a primary stricture are then stacked one on top of the other (poos ibly alternating with smooth interlayers), connected tc>gether and inserted into a casing. In this way a hone;'comb monolith is formed, which has ducts basically parallel to one another. Also known is the incorporation into such sheet metal foils of a second structure, which is intended to prevent a Liminar flow forming immediately the exhaust gas enters the honeycomb monolith, with the result that no exchange of gas takes place between those areas of the partial exhaust gas flow situated at the center of such a duct and the, for example, catalytically active duct wall areas. This secondary structure accordingly provides sui'faces for the incident flow, which result in a form oil swirling of the partial exhaust gas flows inside such a duct. This leads to an intensive mixing of the partial exhaust gas flows themselves, so that a close contact of the pollutants contained in the exhaust gas with the duct wall is ensured. It is - 3 - furtbenuox*e possible, using such secondary structures, to form flow passages transversely to the duct, which will permit an exchange of gas between partial exhaust gas flows ii adjacent ducts. For this reason secondary ducts are known, which comprise, for example, baffles, microstructures, protrusions, projections, vanes, plates, hoJes or the like. In this respect, this results in a significantly greater variety in the manufacture of such metal honeycomb monoliths, compared to those of ceramic material, since in the latter case such a complex duct wall can be achieved only at an exceptionally high technical cost, if at all. It is also particularly important in exhaust emission treatment that the pollutants contained in the exhaust gas should be converted with virtually no delay after starting tt.e engine. This should be done with a particularly high efficiency in accordance with the statutory regulations or guidelines. For this reason the metal foils used have in the past become thinner and thinner. Very thin sheet metal foils mean that the surface-specific heat capacity is very low. That is to say relatively little is extracted from the passing exhaust: gas flow and the sheet metal foils themselves experience a temperature increase relatively rapidly. This is important because the catalytically active coatings currently used in the exhaust system start to convert the pollutants only from a certain starting temperature in the order of 230»C to 270°C, with the aim of converting the pollutants with an efficiency of at least 9('% after just a few seconds, sheet metal foils have been used, which have a foil thickness of less than 20 urn, for example. The objectives stated above, however, give rise to a number of production and application problems. The production of such filigree structures, in particular the secondary structures, requires high-precision - 4 - tooling, which is usually very expensive and which should accordingly have a long service life, At the same time account mpst be taken of the fact that both forming aid sometimes also cutting production operations have to be performed. In order to save tooling cosi;s, as many machining operations as possible have been integrated in one tool, increasing tool wear been observed resulting from the design of the secondary structure. There is also the problem that the relatively thin sheet metal foils have to be fed at a suitable rate, if possible without being exposed to any undesir«ible cold deformation. The strain hardening can have an adverse effect on the forming properties of the sheet netal foils. Owing to the low material thickness fcaere is moreover the risk of an increased tendency to creasing and/or rolling up on the part of the sheet matal foil. The creases mean, for example, that ducts may possibly become clogged or cracks may form, which owing to the high thermal and dynamic stresses wiM later spread through the exhaust system of an automobile, thereby jeopardizing the structural integrity oi: the honeycomb monolith. It must also be remembered that such creased or deformed primary and/or secondary structures present undesirable opposition to the exhaust gas, so that an increased backpressure may possibly be" noted upstream of the honeycomb monolith, which can lead to a reduction in engine power output. Proceeding from this, an object of the present invention :.s to overcome the technical problems previously described. One object in particular is to specify a method for producing multiple-structured sheet metal foils, which is economic and preferably continuous, which avoids excessive strain hardening of the sheet nw»tal foils, allows t.tie design of different secondary structures and generates a primary structure that is suited to the production of in the exhaust systems of mobile internal coirimstion engines, this - 5 - catalyst carrier being intended to have a very low flow resistance, especially in the case of high duct densities and an integrated secondary structure. It is further intended to specify a tool for producing multiple-structured sheet metal foils, which is suitable for introducing particularly complex and aerodynamicilly favorable structures into thin sheet metal foils and to modifying these. These objects are achieved by a method for producing multiple-structured sheet metal foils according to the features of claim 1, a catalyst carrier for exhaust systems of nobile internal combustion engines according to the feat.ures of claim 22 and a tool for producing multiple-st::uctured sheet metal foils according to the features of claim 23. Particularly advantageous developments are described in the respective dependent claims, the features disclosed therein being capable of any suitable combination with one another. The method according to the invention for producing multiple-st:ructured sheet metal foils comprises at least the following steps: A) Forming of the sheet metal foil, thereby producing a primary structure having a first primary structure width; B) Forming of the sheet metal foil provided with a primary structure, thereby producing a secondary structure; C) Forming of the structured sheet metal foil, thereby producing a second primary structure width which is less than the first primary structure width. In so doing it is particularly advantageous if, prior to step A) multiple separating edges are introduced - 6 - into an inner area of the basically plane sheet metal foil (step a)) . In order to avoid repetition, the individual steps of the method will hereafter be denoted solely by the corresponding letters. It must be noted from the outset that tne invention departs from the idea, based on cost grounds, of configuring the production method so that as many forming operations as possible are performed simultaneously and/or in one tool. In this respect the steps a), A) to C) described are to be thought of as steps in the method which, in particular, run independently and separately from one another. This also means, in particular, that first (only) the separating edges, then the prinary structure followed by the secondary structure and then the reduced primary structure width are produced in sequence. Such a sequential, step-by-step production means, for example, that any premature fatigue of the sheet metal foil whilst still in service in the exhaust system of an automobile is avoided, since strain hardening due to high degrees of deformation occurs to a significantly lesser extent. It is also to be noted that this results "in reduced stressing of the tool, so that wear to the tending and forming edges thereof is significant:.y reduced. At the same time it should again be clearly stated that even with a method of producing multiple-structured sheet metal foils in just two or three separately performed operations, a sheet metal foil is ultimately produced which has a primary structure having a second primary structure width and a secondary structure. For this reason none of the said steps a), Al to C) is ultimately omitted entirely, the steps beintj rather combined with one another or performed simultaneously with one another, for example in one tool. - 7 - Especially preferred variants of the method for producing maltiple-structured sheet metal foils will be described :>elow, the bracketed letter combinations representing combined or simultaneously performed steps: a+JUB+C; (a+A)+B+C; (a+A) + (B+C) ; a+A+(B+C) ; (a+A+B)+C; a+(A+B)+C. With regard to step a) it should again be pointed out that this can possibly be integrated directly into step B), that is to say precisely when the sheet metal foil provided with a primary structure is being formed, in such a way that the separation of material occurs, that ie to say the separating edges are produced simultaneously with the secondary structure. In this case the following variants of the method would be particularly preferred: A+a/B+C; (A+a/B)+C, the term rta/B" representing the simultaneous; production of separating edges and secondary structure. In principle a two-stage structuring of the individual operations is particularly preferred, at precisely which point1 it should be ensured that the steps B) and C) are not undertaken together in one step or in one operation, but rather that each step B) and "-C) is performed at another etace or using another tool or at another time. The following detailed points should be noted with regard to the steps in the method: On a) With regard to this, a basically uniormed sheet metal foil :.s to be assumed, by which it is meant that this sheet metal foil is preferably drawn off directly from a coil. The sheet metal foil comprises a temperature-resistant, corrosion-resistant material preferably having relatively high proportions of aluminum, chromium, molybdenum or equivalent constituents. The term "plane" is in this context taken to mean that no structure has yet been introduced, and the sheet metal foil therefore extends - 8 - basically in two dimensions. In view of the fact that the steps in the method for producing multiple-structured sheet metal foils are performed at least largely wit.iout any interruption, a sheet metal foil is here intended to imply a so-called ncontinuous" sheet metal foil, that is to say a sheet metal foil which doe s not yet have the dimeas ions which it wi 11 ultimately have when in use, for example as catalyst carrier foi catalytically active coatings. In this respect the introduction of separating edges is not to be taken to mean that this "continuous" sheet metal foil is here cut to shape, but rather that the sheet metal foil largely retains its length. Instead of the complete separation of partial areas of the sheet metal foil it is iiere proposed to provide multiple separating edges in an inner area. This means that at least some of the separating edges are completely enclosed by the material of the sheet metal foil, that is to say forming a t.ype of slit, crack, opening, hole or the like. The separating edges are at the same time preferably arranged in a regular pattern, fox example in lines or columns at regular distances, it being in turn possibLe to construct these patterns differently in partial sections of the sheet metal foil, that is, for example, to allow greater distances between the separating edges in one section than in another. The separating edges themselves may have different functions. Thus these separating edges, for example, may serve to ensure a gentle engagement of the forming tool for forming the secondary structure. The separating edge may further be used to align the sheet metal foil in relation to the succeeding forming tools. It is particularly advantageous, however, for the separate prc-duction to result in very precisely aligned and executec separating edges. In this way creases and deformations of the sheet metal foil in subsequent machining operations are avoided. _ 9 - On A) The forming of the sheet; metal foil so that a primary structure having a f:Lrst primary structure width is produced is preferably continuous. Two production methods in particular, corrugation rolling and roller bending, lend themselves to the production of such a primary structure. In these methods of bend forming, rotating or turning profile rolls are used, which mesh tfith one another as the sheet metal foil is fed through them. in corrugation rolling the sheet metal foil is in contact with the flanks of both intermeshincf profile teeth throughout the forming process, whereas in roller bending a mutual contact generally occurs only in the ar«a of the profile tooth tip or the profile tooth base. In each case a primary structure is generated, the bending plane of which is basically perpendicular to the axis of the rotating tools. This step in the method is generally performed in such a way that during the forming of the sheet metal foil very small, if any, tensile forces are introduced into the sheet metal foil, the forming process therefore being largely attributable to pure bending. This is achieved, for example, in that a gap is provided between the forming tools through which the sheet metal foil is fed, the gap being greater in extent than the thickness of the sheet metal foil. This can sei-ve to prevent the sheet metal foil becoming -jammed at aiy point, thus obstructing the feed. As a result, the formed sheet metal foil will have no material defects, which might be a cause of premature failure, particularly when used as a catalyst carrier. The preferred method of executing the forming processes without introducing tensile forces is, in particular, also to be followed when performing at least one of the succeeding steps B) and C). Oa B) According to step B) the pretreated sheet metal foil already provided with a primary structure is now - 10 - provided with a secondary structure. The secondary structure :.e superimposed on the primary structure, that is to say it locally modifies or breaks up the primary structure. Thus it is possible, for example, for the primary structure to be at least partially undone, replaced by another and/or intensified. The position on or in the sheet metal foil may serve as a criteria fcr distinguishing between primary structure and seconcUxy structure. The primary structure can generally b3 recognized simply by looking at the edge of the sheet metal foil which extends parallel to the direction of the "continuous" ;*heet metal foil. The basic shape or primary structure is usually clearly discernible from this edge. The secondary structure, on the other hand, is often more readily discernible from the edges of the metal foil running perpendicular thereto as a modification to the basically straight edge, this being particularly true of intermittent, that is to stay locally recurring secondary structures. On C) In this forming step the primary structure of the sheet netal foil, now already provided with two structures, is machined yet again. As a result of this forming step the primary structure acquires a second _ primary structure width, which is less than the first primary structure width after the forming step A}. In other words, the structure is forced together, gathered. up, more tightly compressed or telescoped etc. A primary structure width is here taken to mean the distance between two identically aligned extremes of the structure adjacent to one another. If the primary Structure in a corrugation with peaks and valleys, for example, th«s primary width is the distance between two peaks which directly succeed ones another in the course of the corrugation. The main effect of reducing the primary structure width is to shift the extremes closer together, the sheet metal foil areas lying between the extremes falling and rifling more steeply. - 11 " Producing the primary structure in two steps has advantages particularly with regard to superimposition of the secondary structure. Producing the primary structure sud the secondary structure simultaneously, particularly with very small primary structure widths, requires vary delicate tools, since the secondary structure is largely arranged in the area of the extremes o! the primary structure. Small primary structure widths also result in relatively confined extremes, ;?o that additional separating or forming steps have to be performed at the slender end faces of the filigree tools. This leads to increased wear of the tool eid faces and owing to the high degree of deformation of the sheet metal foil harbors the risk of creasing. Gathering up or pushing the primary structure together at a subsequent stage means that more solid tools can be used to produce the secondary Structure, thereby significantly increasing the service life of th3 tools, so that significantly more sheet metal foils can be machined using the same tool. According t) a further development of the method it is proposed that the introduction of the separating edges be achieved using at least one of the following " production methods A) Cutting B) Pressing C) Stamping D) Drilling E) Etching thereby producing multiple passages. To clarify, it should be Jioted here that the passages are at least partially defined by the separating edges. In this case the term passages preferably relates to basically rounded contours, such as circular, elliptical or - 12 - similar, relatively large holes. The passages preferably have a maximum distance ranging from 0.2 to 6 mm in relation to opposing separating edges. It is advantageous to select one of the aforementioned methods according, in particuleir, to the material of the sheet metal foil and the size and/or number of the passages. In cutting the sheet metal foil is subjected to cutting forces by a cutting punch, a cutting plate into which the e it ting punch can penetrate being provided on the side remote from the cutting punch, increasing the force acting on the sheet metal foil causes the cutting punch to penetrate into the foil, the material being plastically deformed. When the fluidity of the material i:i the shear zone is exhausted, cracks generally emanating from the cutting plate occur, which lead to separating of the material through fracture and hence to th«i formation of separating edges. In pres sin With thicke:: materials, or where multiple sheet metal foils together are to be provided with separating edges, drilling with a rotary tool may also be used as production rrethod. If especially small passages are to be produced, particularly in very thin foils, this can also be done, for example by a hole mask, which is placed on the sheet metal foil, an etching medium then being applied - 13 - to the sheet metal foil through this hole foil, resulting In a chemical decomposition of the sheet metal foil in a desired area. It should fce noted with regard to this that the person skilled in the art will be familiar with these production methods and will be in a position to select a suitable production method A to E specific to the application. According to a further development it is proposed that during the first forming step A) the sheet metal foil should be bent by means of intermeshing profile teeth so that a basically regular, recurring corrugation is produced an primary structure. These intermeshing profile teeth are preferably part of rotating tools, which produce the primary structure by the corrugation roiling or corrugation bending production method, A basically sinusoidal form of corrugation /*s preferably produced in the process. It is fur:her proposed^ that steps a) and A) be performed by means of a firut tool, the step a) preferably comprising the cutting production method and/or the primary structure being produced in step A) by the coirugation rolling production method. The combination of steps a) and A) here proposed is of particular interest from the cost and time standpoints. Neither of the steps requires any degree of forming of the sheet m - 14 - particular less than 80%, preferably less than 55%, is produced during the second forming step B) . This means that the secondary structure does not extend over an entire prirrary structure width, it being worth noting here that the primary structure width and the secondary structure vldth are arranged parallel to one another. This relates in particular to secondary structures which form separate edges for the incident flow, baffles, vaies and the like. According :o yet another development the secondary structure is of striated design, preferably extending along extremes of the primary structure. Such striated secondary structures extending along the extremes, that is to say peaks or valleys, serve, for example, to increase ths structural integrity, to set the positions of metal foils arranged adjacently to one another or to define coating areas. It is also advantageous if the secondary structure is of intermittent design, preferably extending parallel to extremes of the primary structure. This means that more than one and in particular a plurality of secondary utructures, which are preferably arranged equidistant from one another, is situated on one extreme of the primary structure. A parallel arrangement is here taken to mean both the arrangement directly along the extremes and also parallel thereto in an area of the sheet metal foil between adjacent extremes. Such intermittent secondary structures serve in particular to influence ttie partial exhaust gas flows when 3ueh a sheet metal foil is used to produce a catalyst carrier. According to a further development of the method the secondary structure is designed so that this forms passages in the sheet metal foil. This (nay mean, on the one hand, that the secondary structure is at least - 15 - partially defined by the passages, although it is also possible fcr passages to be situated in an inner area of the secondary structure. To illustrate this, reference should be made to a secondary structure like that represented in Fig. l, for example. The secondary structure siown there takes the form of a baffle, which forms a passage. In this case it is a passage at least partially defined by the secondary structure. A passage in the secondary structure itself would be created it the baffle shown were again provided with a hole or the like. With regard to the production method it is possible in this case for the separating edges produced during step a) to constitute holes, which ultimately occur in the baffle itself, whilst a further passage, tiat shown in Fig. 1, is formed when generating t:he actual secondary structure. According to a further advantageous development of the method the forming step C) gives rise to a second primary structure width, which is less than 80%, in particular 50% of the first primary structure width. It is furthermore advantageous for the forming step C) to produce a first primary structure height,, which is less than 80%, in particular 60%, of the second primary structure lieight. The degree of deformation is determined on the basis of the change in the primary structure w:.dth and the primary structure height. The same or a different percentage modification may occur in each casa, according to the desired second primary structure width or second primary structure height. According to a further advantageous development of the method, during forming step C) segments of a second tool intezTtwish in the primary structure formed by the extremes. Thi s means, in part icular, that a guided compression or reduction of the primary structure width takes place here. This permits an especially gentle forming of the sheet metal foil. - 16 - It is further proposed that the forming step C) should be performed simultaneously with the forming step B), preferably by means of just one second tcvl. This is advantageous for reasons similar to those given for combining steps a) and A) of the method. Reference should be wide inasmuch to the explanations above. According to yet another development of the method the multiple-st:ructured sheet metal foils are produced from high temp - 18 - also means that the areas of the sheet metal foil between the extremes run relatively steeply. One particular result of this is that only very small gussets are formed close to the contact areas of the adjoining (sheet metal foils. In the production of catalyst carriers, these gussets are preferably used for the uniform distribution of solder material. For this purpose the honeycomb monolith of the desired design is isunersed by its end face in a liquid solder, the solder in the gussets wetting the gussets right through the entire honeycomb monolith due to capillary action, even against the force of gravity, provided that no passivation agents are used, which interrupt this capij-lary action. The development of the primary structure hare proposed means that the capillaries are very small, so that only a relatively small quantity of solder collscts in proximity to the contact areas of the sheet metal foils arranged adjacently to one another. A smaller quantity of solder is thereby ultimately distributed in the interior of the honeycomb monolith. ;."n addition to cost advantages this also has the positive effect that a honeycomb monolith or a catalyst carrier having a particularly long service life even under extremely corrosive conditions can be produced in a highly reliable process. The reason for this is that the small quantity of solder does not attack the tiheet metal foils, as normally occurs due to the affinity for alloy elements of the sheet metal foil, thereby possibly leading to local depletion of alloys in the sheet metal foil. This effect, which is even more markedly apparent when sheet metal foils are used which have a foil thickness of less than 20 um, for example, is avoided by the multiple-structured sheet metal foils proposed here. However, the smaller gussets not only have an advantageous effect on the joining technique but can - 19 - also serve to reduce the quantity of coating on the catalyst c.irrier. The coating is applied to the surface of the carrier structure in a similar way to the liquid solder. Owing to the smaller capillaries a reduced quantity of wash coat and catalytically active elements (platinum, rhodium, etc.) also suffices here, whilst at the same time still producing a uniformly thin coatJ.ng and without adversely affect the efficiency with regard to. the conversion of pollutants contained in the exhaust gas. Instead th»s effects described above give rise to another effect, that is to say a reduced pressure loss or back pressure upstream of the carrier structure. The fact that both solder and ccating are positioned in the ducts results in a larger duct flow cross-section for the same duct density. This also means that the secondary .-structure projecting into the duct, for example, is less subject to stresses, that is to say it will withstand for longer the ambient conditions in the exhaust system. At the same time the intensive contact of the exhaust gas with the duct wall coated with catalytical.'.y active substances next to the secondary structure is also assisted by the relatively narrow design of the duct-. The reason for this is that each partial exhaust gas flow inside such a duct: flows past relatively close to one or two opposing duct walls running virtually parallel or at a shallow angle to one another. This greatly increases the probability of contact betueen the pollutants contained in the exhaust gas and the catalysts, resulting in their conversion. According to a further aspect of the invention a tool for producing multiple-structured sheet metal foils is proposed, whereby a sheet metal foil having a primary structure can be fed to the tool. In this case the tool has segments, which are arranged at an interval from and preferably parallel to one another in the - 20 - direction of the primary structure, the tool comprising means for ndjusting the interval. That is to say in other words that the tool is suitable for seating and guiding an already pre-structured sheet metal foil. The seat or guide, which is here designed with segments, serves among other things to advance or convey the sheet metal foil through the tool. As already described above with reference to the method, this tool forms the already structured sheet metal foil in such a way that a second primary structure width is produced, which is less than the first primary structure width of the already structured sheet metal foil. The segments here described are brought into engagement with the existing primary structure, that is to say in particular that the segments are in contact with a multiplicity of the extremes, in particular with each extreme in one alignment (that is, for example, corrugation peaks or corrugation valleys) in - 21 - corrugation valleys of the primary structure of the sheet metal foil (only) from above, it will be seen that these* are basically at an interval which corresponds to the first primary structure width of the sheet metal foil. Now, with the aid of various means such as a drive, springs, a guide or stops, the segments are moved towards one another, so that the interval between them is reduced. In the case shown here, in which the first interval basically corresponds to the fir;tt primary structure width, the interval is reduced to the same extent as the desired reduction in the primary structure width. That is to say that after the forming step the segments are at an interval from one another which basically corresponds to the second primary stiucture width. It will be clear from this example that, given an arrangement of the segments prior to the forming step with a multiple of the first primary structure width or a fraction of the first primary structure width, the intervals from one another will simply also vary correspondingly. In this way it is in particular possible to obtain sheet rmetul foils or catalyst carriers having particularly steep duct walls, which have the advantages already explained above. Such a guided partially interlocking reduction of the primary structure width is particularly gentle, so that this forming st«p can be used for especially thin sheet metal foils, in particular those having a foil thickness oE less than 30 urn. According to a development of the tool the interval between the segments can be reduced by at least 15%, in particular at least 25% and preferably even by at least 35%. That is to say the segments during the forming step can mcve towards one another, a greater reduction of the interval at the same time producing a greater deformation of the structured sheet metal foils so - 17 - than 1.5. The multiple-structured sheet metal foils are in particular produced according to one of the developments outlined above of the method for producing a multiple-structured sheet metal foil. As already explained in the introductory part, such catalyst carriers usually have a multiplicity of ducts basically arranged parallel to one another, though which an e: - 22 - that, in particular, significantly smaller ratios of the second primary structure width to the second primary structure height, ranging from l.o to 1.3, for example, ca:i also be produced. According to an advantageous development of the tool the segments are at the same interval from one another over their extent. That is to say, for example, that the center axes of the segments are arranged parallel to one another and are therefore at the same interval from one ar.other. At the same time the segments are preferably aligned so that the center axes are oriented perpendicular to the sheet metal foil in the contact area. According to a further development the tool, preferably at least some of the segments, has at leaet one embossing e Lenient for producing a secondary structure in the sheel: metal foil already provided with a primary structure. This means that the tool described here is able, in particular, to perform the aforementioned steps B) ar.d C) of the method simultaneously. This applies, in particular, where the secondary structures are arranged, in the area of the extremes of the primary structure, siince in this area the segments are already in contact with the sheet metal foil. The embossing element itself may take the form of a projection, protrusion or other elevation-in the material of the tool or the segment, although it is also possible to provide a special pin, stud, punch or some similar element, which permits a relative movement in relation to the segment. This means, for example, that in a first step ;he segments come into engagement with the primary stricture, before the punches are traversed in order to foam the secondary structure, and the primary structure width of the sheet metal foil is then finally reduced, - 23 - The invention will be explained in more detail below with reference to the drawings. It should be pointed out here that the drawings represent particularly preferred exemplary embodiments, but that the invention is not limited to these. In the drawings: Fig. 1 shows a first embodiment of a multiple-structured sheet metal fell; Fig. 2 shows in schematic form the sequence in a method for producing a multiple-structured sheet metal foil? Fig. 3 shows a schematic perspective view of an emboliment of a first tool for producing a primary structure in a sheet metal foil; Fig. 4 show3 a schematic representation of an exhaust system of an automobile; Fig, 5 shows a schematic perspective view of an exemplary embodiment of a catalyst carrier for the treatment of exhaust gases; and. Fig. 6 showu a schematic representation of a second tooL. for reducing the primary structure width. Fig. 1 shows a schematic, perspective view of an exemplary embodiment of a multiple-structured sheet metal foil 1. The sheet metal foil 1 shown has a primary structure 4, which here takes the form of a corrugation 10. This corrugation 10 is ir* particular of sinusoid.il shape and has various extremes 14, a corrugation peak being arranged next to a corrugation valley. In addition to this corrugation 10 the sheet metal foil 1 has a secondary structure 6. This is here formed by a baffle 47, which is partially defined by a passage 8. The baffle 47 and the passages 3 have - 24 - separating edges 2, The secondary structure 6 is formed with a secondary structure width 12, which is lees than a first primary structure width, that is to say the width of two adjacent corrugation peaks of the primary structure.. In the case of the sheet metal foil l shown, different orientations of the secondary structure 6 are selected for each line. Whilst the secondary structures 6 shown at the bottom of Fig. 1 are designed so that their baffles 47 are bent downwards from the upper extreme 14 or the corrugation peak, the secondary structures 6 shown at tht» top of Fig. 1 have an opposing orientation of the bafi.'les 47 and are directed upwards from the lower extremes 14 or the corrugation valleys. This ensures tha1: later such secondary structures 6 project in each dud: and give rise to a swirling or peeling off of partial exhaust gas flows. The arrow 48, which symbolizes .a direction of flow of the exhaust gas, is shown by wiy of: explanation. When the exhaust gas therefore fl.ows through the ducts, which are defined by a sheet metal foil 1 formed in this way, the partial exhaust gas flows will be led through the passages 8 by the baffles 47, or peeled off, and will therefore pass into adjacent ducts. In this way so-called communicating ducts are formed, which permit a relatively high level of efficiency with regard to the catalytic conversion of exhaust gases. Fig. 2 in schematic form shows a development of a method for producing multiple-structured sheet metal foils. The step a) comprises the introduction of multiple separating edges 2 into an inner area 3 of the basically p:.ane sheet metal foil 1. In the embodiment shown the separating edges 2 are arranged basically parallel to the edge 49 of the sheet metal foil 1, although tlds is not necessarily the case. The separating isdges 2 may be provided in any arrangement - 25 - relative tc one another. The separating edges 2 are here shown aot in the form of holes or the like, but as slits or similar arrangements. In the step A) the sheet meta. L f oi 1 1 i e formed for the first t ime, producing a primary structure 4 having a first primary-structure width 5. The sheet metal foil l already provided with separating edges 2 is thereafter provided with the primary structure, for example by means of corrugation rolls. The primary structure is easily recognizable by the edge 49, two similar, adjacent extremes describing the first primary structure width $* A further criterion for describing th^ primary structure 4 is the primary structure height, the first forming step giving rise to a first primary structure height 13 and the ratio of the first primary structure width 5 to the first primary structure height 13 in this phase being 2.5 or more. In a further forming step B) the secondary structure 6 is introduced into the sheet metal foil 1. The secondary structure 6 shown in turn has passages 8 and baffles 47, which are oriented in opposite directions. The primary structure 6 is superimposed on the primary structure 1, In a further forming step c) the primary structure 1 is gathered up or formed so that a second primary structure width 7 is produced, which is less than the first primary structure width 5. It can be seen from the figure that reducing the primary structure width results in a corresponding enlargement of the primary structure height, that is to say the first primary structure height 13 is less than the second primary structure height 15. With the method shown here for producing multiple-structured sheet metal foils, it is possible to produce sheet metal foils 1 having a primary stiucture 4, which has a ratio of a second - 26 - primary structure width 7 to a second primary structure height 15 of lees than 2. Fig. 3 shows a schematic perspective view of a first tool 11, which is used, in particular, for producing a primary stnicture 4 having a first primary structure width 5. The first tool 11 comprises two rolls 50 having profile teeth 9, the rolls 50 being arranged so that the profile teeth 9 of the two rolls 50 intermesh with one another. The at first basically plane or two-dimensional sheet metal foil is now pushed through between the meshing profile teeth 9 of the rolls 50, bending the sheet metal foil in different directions. In the procsss the extremes of the sheet metal foil are formed between a head 51 of the one roll 50 and the foot 52 of the other roll 50. Between the head 51 of the profile teeth 9 and the foot. 53 the profile tooth 9 has a flank 52 which is, for example, aligned parallel to the central axis 46 or which may be of involute design shapsl The sheet metal foil 1 (not shown here) is carried through the rolls 50 by the rotational movement oi the rolls 50 themselves or by a separate feed device. The rolls 50 shown here furthermore have pins 38 on the heads 51 of the profile teeth 1, which whilst in contact with the sheet meal foil l simultaneously introduce separating edges 2 into the sheet metal foil 1. This occurs in particular when the head 51 oi a profile tooth 9 of the one roll is directly opposite a foot 52 of the other roll 50. In the process the separating edges 2 become completely pervious, that is to say made right through the entire material oi: the sheet metal foil i, although it is possible merely to score the material, that is to say to make the separating edges 2 only through part of the foil thickness. Fig. 4 shows a schematic representation of an exemplary embodiment of an exhaust system 27 of an automobile 40. - 27 - The exhaust, gas generated in the internal combustion engine 28 is fed via an exhaust line 41 to various components for treatment of the exhaust gas. In the exhaust system 27 shown the following succeed one another in the direction of flow of the exhaust gas; a starting catalytic converter 42, which begins to convert pollutants just a very short time after cold-starting of the internal combustion engine 28, a filter 43 for collecting particulates contained in the exhaust gas, a catalyst carrier 26, which is provided with the sheet metal, foil 1 described where, and finally a catalytic converter 44, especially a three-way catalytic converter. Fig. 5 nhyws a schematic perspective view of an embodiment of a catalyst carrier 26. The catalyst carrier 26 comprises at least one honeycomb monolith 19 having a multiplicity of at least partially structured sheet metal foils 1, 20 together with a casing 23/ the honeycomb nonolith having at least one multiple-structured 3heet metal foil 1 with a primary structure 4 and a secondary structure 6. The primary structure 4 can be seen very clearly in a. view of the catalyst carrier 26 from the end face "54. In the embodiment shown a rtultiple-structured sheet metal layer 1 together with a smooth interlayer 20, which is preferably also a sheet metal foil, are helically wound into a cylindrical honeycomb monolith. In principle, however, otier cross-sectional shapes of the honeycomb monolith 1J are possible, such as polygonal and ellipsoidal monolith shapes. The adjacent arrangement of the sheei: metal foil 1 and interlayer 20 forms ducts 21, which are arranged basically parallel to one another and preferably extend over the entire length of the honeycomb monolith 19. The walls of the ducts 21 formed by the sheet metal foils 1, 20 are provided with a catalytically active coating 24, the coating 24 comprising a wash coat 25 impregnated with precious - 28 - metals. l.n the enlarged detailed view it is also possible to see the gussets 4 5, which may play a central rol.e in the joining technique for the sheet metal foils 1 and the interlayers 20 and in a subsequent coating process. On inspection the multiple-structured sheet metal foils 1 have a basically corrugated primary structure 4, this being relatively shallow here for the purposes of illustration. As secondary structure 6, openings 22 etc. are provided here, which allow exhaust gas flowing through the honeycomb monolith 19 to flow from a first duct 21 crrex to another duct 21. The honeycomb monolith 19 preferably has a duct density of more than 300 cpsi, in particular more than 650 cpsi, the multiple-st.ructured sheet metal foil 1 and also the interlayer 20 having a foil thickness 18 ranging from 0.01 to 0.0!) mm. Fig. 6 shows a schematic representation of the structure of a second tool 17 for performing the steps B) and C) of the method. This tool "17 accordingly serves for producing multiple-structured sheet metal foils 1, a sheet metal foil having a primary structure 4 (represented by dashed lines) being fed to the tool. At this point the three segments 16 shown engage in the primary structure 4 of the sheet metal foil 1, so that they come into contact with the extremes 14. For reducing th - 29 - 29 are a drive 32, springs 32, possibly also dampers, a guide 31, and possibly stops 33 for limiting the possible variations. As already stated, the sheet metal foil 1 having a primary stricture 4 and a first primary stiucture width are fed to the tool 17, The segments 16 shown at the top in Fijj. 6 engage in the low points of the corrugated 3heet metal foil 1 shown. The segments 16, which are offset in relation to these and which are shown in the lower area in Fig. 6, engage in the high points or corrugation peaks of the sheet metal foil 1. The segments 16, which are arranged on one side of the sheet metai. foil 1 have an interval 29.1, which basically corresponds to a first primary structure width 5. In reducing the primary structure width the segments 16 are run towards one another so that a new interval 29.2 is set. In the process the extremes of the sheet m«stal foil 1 are shifted closer together, the term wclose::" signifying that the extremes succeed one another more closely in the direction of the corrugated shape. In the exnbc-iiment shown the secondary structures 6 are introduced isimultaneously. This is done by providing the segment s 16 with embossing elements 35, which perform a stroke 36, at least partially perforating the surface described by the primarily deformed sheet metal foil 1. In the process the secondary structures 6 are formed, in particular at those points in the sheet metal foil 1 at which the separating edges 2 were previously introduced. For this purpose it may be necessary to provide a die 37 or a matrix, which permits a corresponding execution of the secondary structure 6, on the side of the sheet metal foil i remote from the embossing element 35. - 30 - The method for producing multiple-structured sheet metal foils hitherto described overcomes the problems described in relation to the state of the art, and an economic an5 moreover reliable method is specified for producing extremely thin sheet metal foils. For this purpose it is necessary to divide the process of forming a basically plane sheet metal foil into a multiple-structured sheet metal foil into separate steps, in order to prevent unwanted creases or fissures occurring in the sheet metal foil. Such creases and fissures might result in a reduced service life^of the sheet metal foil used to form surfaces in the carrier for catalysts for converting pollutants contained in the exhaust gas. In this respect the proposed method in particular opens up the production of specially formed catc.lyet carriers having a ratio of primary structure vidth to primary structure height of less than 2. H«sre it has proved particularly advantageous to undertake the reduction .of the primary structure width using a special tool, in which the sheet metal foil is guided over its structure. All these individual components mean that ultimately a catalyst carrier CSJI be used for exhaust emission contxol, which even only ,x short time after cold- starting of the engine has iieated up to the point that it can begin to_ function, snd which generates a low back pressure, requires smilf quantities of coatings and at the same time has a fiignificantly longer service life. - 31 - List of refsrence numerals 1. Sheet metal foil 2. Separating edge 3. Inner area 4. Primary structure 5. First primary structure width 6. Secondary structure 7. Second primary structure width 8. Passage 9. Profile tooth 10. Corrugation 11. Primary tool 12. Secondary structure width 13. First primary structure height 14. Extreme 15. Second primary structure height 16. Segment 17. Secondai.-y tool 18. Foil thickness 19. Honeycorib monolith 20. Interlayer 21. Duct 22. opening 23. Casing 24. Coating 25. Wash coat 26. Catalyst: carrier 27. Exhaust system 28. Internal, combustion engine 29. Interval. 30. Spring 31. Guide 32. Drive 33. stop 34. Extent 35. Embossing element 36. Stroke - 32 - 37. Die 38. Pin 39. Direction of rotation 40. Automobile 41. Exhaust line 42. starting catalytic converter 43. Filter 44. Converter 45. Gusset 46. Central axis 47. Baffle 4 8. Arrow 49. Edge 50. Roll 51. Head 52. Flank 53. Foot - 33 -Claims 1, A method for producing multiple-structured sheet metal foils (1), comprising at least the following steps: A) forming of the sheet metal foil (1), thereby producing a primary structure (4) having a first primary structure width (b); B) forming of the sheet metal foil (l) provided with a primary structure (4), thereby producing a secondary structure (6),- c) forming of the structured sheet metal foil (1), so that a second primary structure width (7) is produced, which is less than the first primary structure width (5). 2. The method ae claimed in claim 1, characterized in that pr:.or to step A), multiple separating edges (2) are introduced into an inner area (3) of the basically plane sheet metal foil (1) . 3. The method as claimed in claim 2, characterized in that tho introduction of the separating edges (2) is achiaved using at least one of the following production methods A) 'fitting, B) ?r€seingr C) stamping, Q) Drilling, E) etching. thereby producing a multiplicity of passages (8) . 4. The method as claimed in any one of the preceding claims, characterized in that during the first forming step B) the sheet roe^al foil (1) is bent by means of intermeshing profile teeth (9), so that a basically regular, recurring corrugation (10) is produced as primary structure (4). - 34 5. The method as claimed in any one of claims 2 to 4, characterised in that the steps A) and B) are performed by means of a first tool (11), the step A) preferably comprising uhe cutting production method and/or the primary structure (4) being produced in step B) by the corrugation rolling production method. 6. The method as claimed in arty one of the preceding claims, characterized in that the second forming step C) produces a secondary structure (6) , which has a secondary structure width (12), which is less than a first primary structure width (13), in particular less than 80%, preferably less than 55%. 7. The met'iod as claimed in ary one of the preceding claims, characterized in that the secondary structure (6) is of striated design, preferably extending along . extremes (14) of the primary- structure (4) , 8. The method as claimed in any one of the preceding claims, characterized in that the secondary structure (6) is of intermittent design, preferably extendir.g parallel to extremes (14) of the_ primary structure (4). 9. The method as claimed in any one of the preceding claims, characterized in that the secondary structure (6) is designed so that it forns passages (8) in the sheet metal foil :1). 10. The method as claimed in any one of the preceding claims, characterized in that the forming step D) gives rd.se to a second primary structure width (7) which iti less than 80%, in particular 60%, of the first primary structure width (5). - 35 - 11. The method as claimed in any one of the preceding claims, characterized in that the forming step D) gives rise to a first primary structure height (13) which is less than 80%, in particular $0%, of the second primary structure height (15). 12. The method as claimed in any one of the preceding claims, characterized in tiiat during the forming step D) segments (16) of a second tool (17) engage through the primary structure (4) formed by the extreme.*; (14) ♦ 13. The method as claimed in any one of the preceding claims, characterized in that the forming step D) is performed simultaneously during the forming step C), preferably by means of just one eerond tool (17) . 14. The method as claimed in any one of the preceding claims, characterized in that multiple-structured sheet metal foils (1) are produced from a high temperature-resistant and corrosion-resistant material having a foil thickness (18) of less than 0.05 nun, in particular lees than C. 03 nun, preferably less than 0.015 am. 15. The method as claimed in any one of the preceding claims, characterized in that multiple-structured sheet mcttal foils (1) are produced having a second primary structure width (7) of less than 3.0 mm, in particular less than 2.6 mm, preferably less than 2.2 mm, 16. The method as claimed in any one of the preceding claims, characterized in that multiple-structured sheet metal foils (1) are produced having a second primary structure height (15) of more than 1.5 mm, - 36 - in particular more than 1.8 nun, preferably more than 2.0 nun. 17, A method for producing a metal honeycomb monolith (19) conprising at least partially structured sheet metal foils (1, 20), characterized in that at least one she 18. The method as claimed in claim 16, characterized in that tha secondary structure (6) is designed so that openings (22) to adjacent ducts (21) are formed. 19. The method as claimed in claim 16 or 17, characterized in that the sheet metal foils (1, 20) are stacked and/or wound so that a duct density per unit ar«ta of at least 300 cpsi, in particular 600 cpsi, is produced. 20. The method as claimed in any one of claims 16 to 18, characterized in that the sheet metal coils (1, - 20) forming he honeycomb monolith (19) axe joined to one another and/or to a casing (23) at least partially enclosing the honeycomb monolith (19), in particular by a soldering method. 21. The mett.od as claimed in any one of claims 16 to 19, characterized in that the sheet metal foils (l, 20) forming the honeycomb monolith (19) are at least partially provided with a coating (24), which is preferably catalytically active and in particular comprises a wash coat (25). - 37 - 22. A catalyst carrier (26) for exhaust gas systems (27) oJ: mobile internal combustion engines (28) comprising at least one honeycomb monolith (19) having a multiplicity of at least partially structured sheet metal foils (1, 20) and a casing (23), the honeycomb monolith having at least one multiple-structured sheet metal foil (1) with a primary structure (4) and secondary structure (6), characterized in that the primary structure (4) has a ratic of a primary structure width (7) to a primary structure height (15) of less than 2, in particular less than 1.5. 23. A tool (17) for producing multiple-structured sheet metal foils (1)., whereby a sheet metal foil (1) having a primary structure (4) can be fed to the tool (l'O, characterized in that the tool (17) has segment* (16), which are arranged at an interval (29) from and preferably parallel to one another in the direction of the primary structure (4), the tool (17) comprising means (30, 31, 32, 33) for varying the interval (29) . 24. The too3 (17) as claimed in claim 23, characterized in that the interval (29) between the segments (16) can be reduced by at least 15%, in particular at least 2b* and preferably even by at least 35%. 25. The tool (17) as claimed in claim 23 or 24, characterized in that the segments (16) are at the same interval (29) from one another over their extent (34). 26. The tool (17) as claimed in any one of claims 23 to 25, characterized in that the tool (17), preferably at least some of the segments (16), has at least one €sml>ossing element (35) for producing a - 38 - secondary structure ($) in the sheet metal foil (l) already provided with a primary structure (4) . The invention relates to a method for multiple structure sheet metal foils(1) which comprises the steps of (A) forming the sheet metal foil (1).thereby producing a primary structure (4) having a first primary structure width (5).ID forming the sheet metal foil (1) which has been provided with a primary stucture (4). thereby producing a secondary structure (6); C1 formating the structured sheet metal foil(1), thereby producing a second primary structure width (7) that is smaller than the first primary structure width(5). The invention also relates to a support which comprises multiple structured sheet metal foil for exhaust gas purification and to a tool for producing multiple structured sheet metal foils. |
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| Patent Number | 216057 | |||||||||
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| Indian Patent Application Number | 01558/KOLNP/2005 | |||||||||
| PG Journal Number | 10/2008 | |||||||||
| Publication Date | 07-Mar-2008 | |||||||||
| Grant Date | 06-Mar-2008 | |||||||||
| Date of Filing | 05-Aug-2005 | |||||||||
| Name of Patentee | EMITEC GESELLSCHAFT FUR EMISSIONSTECHNOLOGIE MBH | |||||||||
| Applicant Address | HAUPSTRASSE 150, 53797 LOHRNAR GERMANY | |||||||||
Inventors:
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| PCT International Classification Number | F01N 3/28 | |||||||||
| PCT International Application Number | PCT/EP2004/000788 | |||||||||
| PCT International Filing date | 2004-01-29 | |||||||||
PCT Conventions:
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