Title of Invention	FILTER ASSEMBLY AND PROCESS FOR PRODUCING IT
Abstract	This invention relates to a fitter assembly (1), through which a fluid can flow and which comprises at least one covering layer (2) formed of an at least partially porous material having at least one boundary region (3), and at least one fiber layer (4) made from a fiber fabric, characterized in that the at least one covering layer (2) forms a sleeve (31) which surrounds the fiber layer (4), so that the fiber layer (4) is captively held inside the at least one covering layer (2), and in that the at least one covering layer (2) is a metal foil with a thickness (5) of less than 0.04 mm, in particular less than 0.03 mm or even less than 0.02 mm.

Title of Invention

FILTER ASSEMBLY AND PROCESS FOR PRODUCING IT

Abstract

This invention relates to a fitter assembly (1), through which a fluid can flow and which comprises at least one covering layer (2) formed of an at least partially porous material having at least one boundary region (3), and at least one fiber layer (4) made from a fiber fabric, characterized in that the at least one covering layer (2) forms a sleeve (31) which surrounds the fiber layer (4), so that the fiber layer (4) is captively held inside the at least one covering layer (2), and in that the at least one covering layer (2) is a metal foil with a thickness (5) of less than 0.04 mm, in particular less than 0.03 mm or even less than 0.02 mm.

Full Text	Filter assembly and process for producing it The invention relates to a filter assembly through which a fluid can flow, and to a filter body for purifying an exhaustgas stream from an internal combustion engine constructed using the filter assembly according to the invention. Furthermore, the invention describes a process for producing a filter assembly. If new vehicle registrations in Germany are considered, it will be found that in 2000 around one third of all newly registered vehicles have diesel engines. By tradition, this percentage is significantly higher than in, for example, France and Austria. This increased interest in diesel vehicles stems, for example, from the relatively low fuel consumption, the currently relatively low prices of diesel fuel, but also from the improved driving properties of vehicles of this type. A diesel vehicle is also very attractive from environmental aspects, since it has a significantly reduced emission of CO2 compared to gasoline-powered vehicles. However, it should be noted that the level of soot particulates produced during combustion is well above that of gasoline-powered vehicles. If the purification of exhaust gases, in particular of diesel engines, is considered, it is possible for hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas to be oxidized in a known way by, for example, being brought into contact with a catalytically active surface. However, it is more difficult to reduce nitrogen oxides (NOX) under oxygen-rich conditions. A three-way catalytic converter, as is used, for example, in spark-ignition engines, does not provide the desired effects. For this reason, the selective catalytic reduction (SCR) process has been developed. Furthermore, N0x adsorbers have been tested for use for the reduction of nitrogen oxides. Discussions have long been ongoing as to whether particulates or long-chain hydrocarbons have an adverse effect on human health, but to date no definitive verdict has been reached. Irrespective of this, it is clearly desirable that emissions of this nature should not be released to the environment above a certain tolerance range. In this respect, the question arises as to what filtering efficiency is actually required in order to be able to comply with the well known statutory guidelines even in the future. If current exhaust emissions from commercially available vehicles in the Federal Republic of Germany are considered, it can be concluded that most passenger automobiles certified under EU III in 1999 are also able to satisfy the requirements of EU IV if they are equipped with a filter with an efficiency of at least 30 to 40%. To reduce the levels of particulate emissions, it is known to use particulate traps which are constructed from a ceramic substrate. They have passages, so that the exhaust gas which is to be purified can flow into the particulate trap. The adjacent passages are alternately closed off, so that the exhaust gas enters the passage on the inlet side, passes through the ceramic wall and escapes again through the adjacent passage on the outlet side. Filters of this type achieve an efficiency of approx. 95% over the entire range of particulate sizes which occur. In addition to chemical interactions with additives and special coatings, the reliable regeneration of the filter in the exhaust system of an automobile still constitutes a problem. It is necessary to regenerate the particulates trap, since the increasing accumulation of particulates in the passage wall through which the gas is to flow leads to a constantly increasing pressure loss which has adverse effects on engine performance. The regeneration substantially comprises brief heating of the particulates trap and the particulates which have accumulated therein, so that the soot particulates are converted into gaseous constituents. However, this high thermal loading of the particulates trap has adverse effects on the service life. To avoid this discontinuous regeneration, which is a major factor in promoting thermally induced wear, a system for the continuous regeneration of filters has been developed (CRT: continuous regeneration trap). In a system of this type, the particulates are burnt by means of oxidation with NO2 at temperatures which are already over 200°C. The NO2 which is required for this purpose is often generated by an oxidation catalytic converter arranged upstream of the particulates trap. However, in particular for use in motor vehicles using diesel fuel, this gives rise to the problem that there is only an insufficient level of nitrogen monoxide (NO) which can be converted into the desired nitrogen dioxide (N02) in the exhaust gas. Consequently, it has not hitherto been possible to ensure that continuous regeneration of the particulates trap in the exhaust system will occur. Furthermore, it should be borne in mind that, in addition to non-convertible particulates, oil or additional residues of additives also accumulate in a particulates trap and cannot readily be regenerated. For this reason, known filters have to be replaced and/or washed at regular intervals. Filter systems of plate-like structure attempt to solve this problem by allowing vibration-like excitation which leads to these constituents being removed from the filter. However, this means that the non-regeneratable fraction of the particulates in some cases passes directly into the environment without any further treatment. In addition to a minimum reaction temperature and a specific residence time, it is necessary to provide sufficient nitrogen oxide for the continuous regeneration of particulates using NO2. Tests relating to the dynamic emission of nitrogen monoxide (NO) and particulates have clearly demonstrated that the particulates are emitted in particular when there is no or only a very small amount of nitrogen monoxide in the exhaust gas, and vice versa. What this means is that a filter with true continuous regeneration substantially has to function as a compensator or store, so that it is ensured that the two reaction partners are present in the filter in the required quantities at a given instant. Furthermore, the filter is to be arranged as close as possible to the internal combustion engine in order to be able to reach temperatures which are as high as possible immediately after a cold start. To provide the required nitrogen dioxide, an oxidation catalytic converter is to be connected upstream of the filter, so as to react carbon monoxide (CO) and hydrocarbons (HC) and in particular also to convert nitrogen monoxide (NO) into nitrogen dioxide (N02) . If this system comprising oxidation catalytic converter and filter is arranged close to the engine, a suitable position is in particular upstream of a turbocharger which is often used in diesel motor vehicles to increase the boost pressure in the combustion chamber. If these basic considerations are looked at, the question arises, for actual deployment in automotive engineering, as to how a filter of this type, which in such a position and in the presence of extremely high thermal and dynamic loads has a satisfactory filtering efficiency, is constructed. In this context, account should be taken in particular of the spatial conditions, which require a new design of filters. Whereas the maximum possible volume was to the fore in the case of conventional filters, which were arranged in the underbody of a motor vehicle, in order to ensure a long residence time of the as yet unreacted particulates in the filter and therefore a high efficiency, if the filters are arranged close to the engine, there is not sufficient space or room available. For this purpose, a new concept has been developed, mainly referred to by the term "open filter system" . These open filter systems are distinguished by the fact that there is no need for the filter passages to be alternately closed off by structural means. In this context, it is provided that the passage walls be constructed at least in part from porous or highly porous material and that the flow passages of the open filter have diverting or guiding structures. These internal fittings cause the flow and the particulates contained therein to be diverted toward the regions made from porous or highly porous material. Surprisingly, it has emerged that the particulates, as a result of being intercepted and/or impacting, are retained on and/or in the porous passage wall. The pressure differences in the flow profile of the flowing exhaust gas are of importance to this effect occurring. The diversion additionally makes it possible to produce local reduced pressure or excess pressure conditions, leading to a filtration effect through the porous wall, since the abovementioned pressure differences have to be compensated for. The particulate trap, unlike the known closed screen or filter systems, is open, since there are no flow blind alleys. This property can therefore also be used to characterize particulate filters of this type, so that, for example, the "freedom of flow" parameter is suitable for describing the systems. By way of example, a "freedom of flow" of 20% means that, when viewed in cross section, it is possible to see through approx. 20% of the surface area. In the case of a particulate filter with a passage density of approx. 600 cpsi (cells per square inch) with a hydraulic diameter of 0.8 mm, this freedom of flow would correspond to an area of over 0.1 mm2. To realize an open filter system of this nature, it is also an object of the present invention to provide a filter material which is particularly suitable in particular for use in the context of continuous regeneration, with the resulting demands. In this respect, the filter system has to be able to withstand the high thermal and dynamic loads in the exhaust system of a passenger automobile, which stem from the pulsed emission of very hot exhaust gas. Furthermore, it is intended to provide a corresponding filter body which is suitable for significantly reducing the levels of particulates in the exhaust system. In addition, it is intended to provide a process for producing the filter material. These objects are achieved by a filter assembly having the features of patent claim 1, a filter body for purifying an exhaust-gas stream from an internal combustion engine having the features of patent claim 12, and a process for producing a filter assembly in accordance with the features of patent claim 14. Further advantageous configurations are described in the respective dependent claims, in which context the particular features may occur individually or in any desired and appropriate combination. A fluid can flow through the filter assembly according to the invention, and this filter assembly comprises at least one covering layer made from at least partially porous or highly porous material, and at least one fiber layer made from a fiber fabric. Moreover, the covering layer has at least one boundary region. The filter assembly is distinguished by the fact that the at least one covering layer forms a sleeve which surrounds the fiber layer, so that the fiber layer is arranged captively inside the at least one covering layer. In this context, a sleeve is to be understood as meaning an arrangement of the at least one covering layer in which the at least one covering layer also, at least in part, extends beyond the periphery of the fiber layer, in particular completely surrounds the fiber layer. In this respect, at least in part a sleeve is formed over the entire periphery of the fiber layer. This arrangement whereby the covering layer engages around the periphery of the fiber layer accordingly means that a relative movement of the fiber layer with respect to the at least one covering layer is impeded in a positively locking manner in at least one direction. The design of a filter assembly of this type combines a number of advantages which are of importance in particular for the arrangement of a filter assembly of this type close to the engine. The at least one covering layer constitutes a type of protective sleeve which protects the inner fiber layer from the pressure shocks and temperature peaks which occur. The fiber layer represents a significantly looser assembly of fibers than the covering layer. In this context, it should be noted that the term "fiber fabric" encompasses all conceivable arrangements of fibers in bonded assemblies, knitted fabrics or the like. There are also numerous possible alternatives for the material, such as for example ceramic fibers, metal fibers, sintered materials or the like. The fiber layer may have a very high porosity, since the presence of a protective covering layer means that it does not have to be designed primarily for strength. In particular, it is possible to realize particularly large free spaces, pores or the like in the fiber layer. This is boosted in particular by the fact that the at least one covering layer is constructed in a form similar to a strip or sheet, i.e. offers a relatively large bearing surface area. Consequently, in this case it is possible to use fiber materials which are packed significantly more loosely than, for example, in known wire meshes which have hitherto been used to ensure the dimensional stability of the filter layers. Since then, sandwich structures of this type have been designed in such a way that there is in each case one supporting structure arranged on both sides of the filter material (in particular braided wire fabrics), and this sandwich has then been bent or deformed into the desired shape. These sandwich structures have been arranged in the exhaust-gas stream in such a way that the periphery (or end face) of the filter material was exposed to the pulsating exhaust-gas stream without protection. This led to detachment phenomena in particular in chese end regions. To ensure that the fiber material is fixed between the wire fabrics for a prolonged period of time, this sandwich structure had to be pressed together under a high pressure, which, on account of the resultant very small pores or free spaces, led to the accumulation of particulates, with noticeable adverse effects on the efficiency of the filter material. This is avoided in a simple way in the filter assembly according to the invention, since the fact that the at least one covering layer engages around the periphery of the fiber layer means that the fiber layer is arranged captively in the interior. According to a further configuration, the sleeve which protects the fiber layer is formed from a covering layer, the latter having at least one boundary region and an opposite deformation region, and the covering layer being connected to itself by joining in the at least one boundary region. Consequently, the dimensions of the covering layer allow the covering layer to be arranged around the fiber layer once, with the covering layer being deformed (bent, folded or the like) in the vicinity of a periphery of the fiber layer and being soldered or welded onto itself, for example, on the opposite side in a boundary region. The arrangement of a filter assembly of this type in the exhaust-gas stream from an internal combustion engine is preferably such that the exhaust gas which flows onto the filter assembly strikes either the boundary region with the connection by joining or the deformation region. Consequently, an offset or relative movement of the fiber layer with respect to the covering layer as seen in the direction of flow of the exhaust gas is not possible, since a positively locking barrier is formed here. In a direction perpendicular to this, the filter assembly can make do without the covering layer engaging around it, since the forces which are active here are relatively low. Rather, this ensures, for example, that the different thermal expansion coefficients of covering layer and fiber layer can be compensated for. As an alternative, it is also proposed that the sleeve be formed with at least two covering layers, in which case the covering layers are connected to one another by joining in at least one boundary region, and the fiber layer is arranged captively between these interconnected covering layers. Accordingly, what is described here is a sandwich structure in which the fiber layer is arranged between at least two covering layers. The sleeve is in this case produced by the externally arranged covering layers each having boundary regions which overlap the fiber layer and are connected to one another by joining (soldering, welding, sintering, adhesive bonding) . These boundary regions in each case lie in the vicinity of two opposite edges of the covering layer. Even if in this context it is preferable for the boundary region with the connection by joining to be arranged substantially outside the region with the fiber layer, it may under certain circumstances also be appropriate for one of the two covering layers to be of elongated design, so that it engages around a periphery of the fiber layer and is connected to the further covering layer in the region of the fiber layer. Forming a protective sleeve in this way likewise contributes to the fiber layer being arranged captively in the interior. According to a further configuration, the at least one covering layer, in at least one boundary region, has a reduced porosity with respect to the remaining region, in particular has no porosity whatsoever there. This means that the covering layer has at least two different permeabilities with respect to an exhaust gas. Whereas the covering layer has a relatively high permeability or porosity in particular in the region of contact with the fiber layer, on account of bores, holes, openings, apertures or the like, in the boundary region it is preferably made from a material which is substantially impervious to a fluid. This applies in particular to the additional material which is used to form the connection by joining, in particular solder or welding material. This allows the covering layers which are to be connected to one another to be permanently attached even in a highly corrosive environment, as is encountered in an exhaust system. According to a further configuration, the at least one covering layer is a metal foil with a thickness of less than 0.04 mm, in particular less than 0.03 mm or even less than 0.02 mm. Making the covering layer from a metal foil has particular advantages. For example, rapid heat conduction from that surface of the covering layer which is in contact with the exhaust gas to the fiber material is possible, so that in this case too rapid regeneration of trapped and/or accumulated particulates is possible (for example after the internal combustion engine has started up). Furthermore, the proposed thickness ensures that the metal foil has only a very low surface area-specific heat capacity, so that in this case too the light-off performance and/or the rapid heating to the required minimum temperature for regeneration of soot particulates is boosted. Moreover, when selecting the specific material for a metal foil of this type, it is possible to exploit knowledge which has already been gained in connection with the development of metallic honeycomb bodies as catalyst support bodies arranged close to the engine. According to an advantageous configuration, the filter assembly has a mean porosity of greater than 7 0%, in particular even greater than 90%. The mean porosity substantially relates to the region which is actually porous, i.e. discounting boundary regions of reduced porosity. By its very nature, the fiber layer often has a porosity which is well over 70% or 90%, and consequently a certain reduction is brought about by the covering layer which delimits the fiber layer. The porosity of the covering layer is defined, for example, by the size and/or number of the apertures, openings or the like. For example, it is conceivable for the covering layer to be provided with relatively large openings (e.g. with a diameter in the range from 2 to 6 mm), in which case a relatively small number of openings are provided per unit area. If, for example, pressure differences across the filter assembly play only a subordinate role, it is also possible for openings of this type to be made significantly smaller (significantly less than 1 mm) but to be provided in large numbers per unit area. The particular configuration which leads to the desired porosity depends on a large number of parameters; in this context: mention may be made, by way of example, of the composition of the exhaust gas (particulate size, pressure fluctuations, etc.), the fiber material used and/or the strength properties of the covering layer. According to yet a further configuration, the at least one boundary region extends from an edge of the covering layer over a boundary width which amounts to between 3 mm and 15 mm, with the boundary region preferably being arranged at least at two opposite edges. This boundary width ensures that the adjacent covering layers are durably attached to one another. The given range is adapted in particular for known soldering processes or, for example, roller seam welding. In this context, it should also be noted that it is possible for the fiber material to be completely sheathed or encapsulated, in which case a soldered joint or weld seam is formed all the way around the edges of the covering layers. As has already been mentioned above, it is particularly advantageous for the connection by joining to be carried out by means of a solder. Solder has proven eminently suitable for the formation of particularly corrosion-resistant and temperature-resistant connections in the production of catalyst support bodies from metal foils. However, under certain circumstances it is also possible to use various known welding processes, sintering or adhesive bonding techniques. According to a refinement, the fiber layer has a first length and a first width, and the at least one covering layer has a second length and a second width, with the first length and/or the first width of the fiber layer being less than the second length and/or second width of the at least one covering layer. This means that, if the covering and fiber layers are arranged concentrically, the covering layers, at least in part, extend beyond the peripheries of the fiber layer. This leads to the formation of overlap sections which are preferably used to form the connection by joining (boundary region). With regard to the fiber layer, it is proposed that the latter has a dimension of from 0.01 mm to 1 mm. In this context, it is preferable to use fiber layers which have an inherent porosity of over 85%. Tests carried out using fibers which have a diameter of between 0.008 mm and 0.015 mm have proven to have particularly satisfactory results with regard to the filtration action. In particular in connection with a filter assembly of this type having what is known as the open filter, to boost the flow diversion it is proposed that at least one covering layer has at least one flow-guiding surface. This is to be understood as meaning that the covering layer is not completely planar, but rather its surface forms a structure or microstructure which provides surfaces for diverting the flow. For example, a structure running transversely with respect to the direction of flow of the exhaust gas is advantageous; under certain circumstances, a structure height of a few millimeters (less than 2 mm, in particular less than 1 mm) is sufficient. These flow-guiding surfaces contribute to having a targeted influence on the direction of flow, with the result that the overall filter efficiency is improved. A further aspect of the invention proposes a filter body which can be used to purify an exhaust-gas stream from an internal combustion engine. This filter body includes at least one filter assembly as described above, which is at least partially arranged in a casing, in such a way that passages, in particular corresponding to a honeycomb structure, are formed, with the passages preferably being at least partially narrowed. This means that the proposed filter assembly is suitable both for use in filter systems with alternately closed passages and for the production of open filter bodies in which it is possible to see through more than 20%, in particular more than 40%. With regard to an open filter body, it is possible, for example, for the filter body to be constructed from corrugated sheet-metal foils and substantially smooth filter assemblies, which are first of all stacked alternately on top of one another and then coiled and/or wound together. The corrugated sheet-metal foil in this case has diverting structures which at least partially divert the exhaust gas flowing through the filter body toward the porous filter assembly. This results in the exhaust gas at least partially flowing through the filter assembly, with in particular particulates of a size of between 20 and 200 ran being filtered out in the process. Depending on how frequently a partial stream of gas is guided through a wall of filter assembly material of this type with the aid of diverting devices of this type, an increasing filtration effect is observed as the gas flows axially through the filter body. According to a further configuration of the filter body, at least one covering layer, at least in part, has being a structure which substantially delimits the passages. In other words, the structure substantially defines the cross section of flow of the passage. It is advantageous for the covering layers and/or the fiber layer together to be provided with a structure of this type, and in this context a corrugation is particularly recommended. The process for producing a filter assembly according to the invention, as described above, according to a further aspect of the invention comprises the following steps: - forming a porosity in at least one covering layer, with at least one boundary region being left out, - arranging a fiber layer on a covering layer, - forming a sleeve using the at least one covering layer, and - forming a connection by joining in the at least one boundary region, so that the fiber layer is fixed captively within the at least one covering layer. The formation of a porosity in the covering layer may, for example, be generated even while the material for the covering layer is being produced. However, it is also possible for the porosity to be produced by retrospectively providing a fluid- impervious material with bores, openings, apertures or the like. In this case, it is possible in particular to use mechanical production processes (cutting, stamping, drilling or the like), etching processes or a heat treatment, in particular using a laser. All techniques which have been disclosed hitherto can be used to form the fiber layer, so that a knitted fabric, woven fabric or similar structure made from fiber-like material is formed. According to a refinement of the process, a sleeve is formed by deformation of a covering layer, in particular by means of bending, creasing or folding of the covering layer, in a deformation region. This process step is recommended in particular for the production of a filter assembly according to the invention which has just one covering layer. In this context, with a view to the high thermal and dynamic loads on the covering layer in use, it may be advantageous if the adjacent sections of a covering layer are additionally connected to one another by joining in the deformation region. This ensures that the fiber layer is still held captively even if the covering layer should happen to tear open in the region of the bend. Furthermore, it is proposed that a sleeve be formed by means of two covering layers, in which case the at least one fiber layer is arranged between the covering layers in such a way that the boundary regions of the covering layers are at least in part directly superimposed on one another. This means that there is no fiber material arranged between the adjacent boundary regions of the covering layers, and connection by joining in this boundary region does not cause any damage to the fiber layer. Moreover, it is ensured that the connection by joining in the boundary region is able to withstand the highly corrosive conditions in the exhaust system of the internal combustion engine for a very long period of time. According to a refinement of the process, before the fiber layer is arranged on the covering layer, a structure is introduced into at least one of the covering layers. If the filter assembly has two covering layers for forming a sleeve, it is advantageously proposed that the structure be introduced into the two covering layers successively in terms of time, and in each case a different structure be produced. By way of example, this makes it possible to form different passage densities over the cross section of the filter body, so that it is ensured that the respective cross-sectional shapes of the passages and/or passage densities are matched in a targeted fashion to the incoming flow profile of the exhaustgas stream. With regard to the configuration of the connection of the covering layers to one another by joining, as an alternative it is proposed that the connection by joining be carried out by means of a welding operation or by means of a soldering operation. These constitute particularly preferred configurations of the process; under certain circumstances, joining connections using sintering or adhesive bonding processes are also possible. According to yet another configuration of the process, the at least one covering layer is provided with a solder stop outside the at least one boundary region. The solder stop used may be known oils, paints, waxes, ceramic slips or the like which prevent the solder from penetrating into internal regions of the sleeve in which the fiber layer is arranged. This firstly ensures that the solder does not contribute to reducing the porosity of the fiber layer and secondly also ensures that the quantity of solder which has been calculated to be required for the solder connection is actually present at the location which is to be joined. The invention will now be explained in more detail on the basis of figures, which show particularly advantageous and particularly preferred configurations of the filter assembly and/or filter body. Furthermore, the figures serve to illustrate the described process according to the invention. Nevertheless, it should be noted at this point that the invention is not restricted to the exemplary embodiments illustrated in the figures. In the drawing: Fig. 1 shows a diagrammatic and perspective view of a first embodiment of the filter assembly, Fig. 2 shows a sectional view through a further embodiment of the filter assembly, Fig. 3 shows an excerpt from an embodiment of the filter body- according to the invention, Fig. 4 shows a detailed view from Fig. 3, Fig. 5 diagrammatically depicts an exhaust system, Fig. 6 shows a diagrammatic and perspective, detailed view of a further embodiment of the filter body, Fig. 7 shows a diagrammatic and perspective view of a further configuration of the filter body, and Fig. 8 shows a diagrammatic and perspective view of a further embodiment of the filter body according to the invention. Fig. 1 shows a diagrammatic and perspective view of an embodiment of the filter assembly 1 according to the invention with two covering layers 2. The covering layers 2 are composed at least in part of a porous material (of. dotted region) and each have two boundary regions 3 on opposite sides. Furthermore, the filter assembly 1 comprises a fiber layer 4 formed from a fiber fabric. The two covering layers 2 form a sleeve 31 which surrounds the fiber layer 4, so that the fiber layer 4 is arranged captively inside the two covering layers 2. The two covering layers 2 are connected to one another by joining (connection 22), in particular are soldered or welded to one another, in the boundary regions 3 close to an edge 6. The fiber layer 4 has a first length 9 and a first width 10. The covering layers 2 in each case have a second length 11 and a second width 12; in the embodiment illustrated, these are equal (equal length and equal width). In principle, the second length 11 and the second width 12 of the covering layers 2 used to form the filter assembly 1 and the sleeve 31 may also differ. The Fig. also shows that the covering layers 2 have a second length 11 which is greater than the first length 9 of the fiber layer 4. This means that the covering layers 2 overlap the fiber layer 4 in length, so that the boundary regions 3 can rest on top of one another. This makes it easier to form permanent connections 22. Fig. 2 diagrammatically depicts a sectional view through a further embodiment of a filter assembly 1, the latter having just one covering layer 2 which forms the sleeve 31. The covering layer 2 has at least one boundary region 3 and an opposite deformation region 32, the covering layer 2 being connected to itself by joining in the boundary region 3. The connection by joining is in this case ensured by means of a solder 8, with a solder stop 23 being provided outside the boundary region 3, preventing the solder 8 from reaching the vicinity of the fiber layer 4 during a heat treatment. In the embodiment illustrated, solder 8 is provided in the inside of the deformation region 32, and in this case too it is optionally possible to provide solder stop 23. The boundary region 3 extends from an edge 6 of the covering layer 2 over a boundary width 7 of preferably between 3 and 15 mm. With regard to the material thicknesses, it can be explained on the basis of Fig. 2, that the covering layer 2 is, for example, a metal foil and has a thickness 5 of less than 0.04 mm. Furthermore, it can be seen that the fiber layer 4 has a dimension 13 which is preferably in the range from 0.01 mm to 1 mm. Fig. 2 likewise shows a covering layer 2 which is provided with flow-guiding surfaces 15. This is designed in particular as a microstructure. In the embodiment illustrated, this microstructure or the flow-guiding surfaces fulfils two functions. Firstly, the exhaust gas which flows by (from a boundary region 3 to the deformation region 32 or vice versa) is diverted or swirled up, so that partial gas streams are diverted toward or penetrate through the adjacent porous wall, in particular a filter assembly according to the invention. Furthermore, it can be seen that with a microstructure of this type it is also possible to effect a clamping action with respect to the inner fiber layer 4. This improves the stability of the filter assembly 1. Moreover, this enables the porosity of the covering layer 2 to be increased, since the clamping forces which are additionally introduced already sufficiently prevent any possible detachment phenomena in the fiber layer 4. Fig. 3 diagrammatically depicts a detailed view of an embodiment of a filter body according to the invention. The filter body 16 is constructed from partitions 14, between which at least one filter assembly 1 is arranged. The filter assembly 1, like the partitions 14, is illustrated in section, with the two covering layers 2 once again forming a sleeve 31 (not shown) around the fiber layer 4. In the embodiment illustrated, the filter assembly 1 has a structure 21 which substantially performs the function of spacing the smooth partitions 14 apart from one another and forming passages 19. The passage 19 has a cross-sectional area which is substantially defined by this structure 21 of the filter assembly 1. Fig. 4 shows a highly simplified detailed view of the excerpt from Fig. 3 which is indicated by IV. The fiber layer 4 is delimited by a covering layer 2. The covering layer 2 has a multiplicity of openings 24 with an opening diameter 25. The opening diameter 25 varies considerably depending on the particular application and is preferably in the range between 2 and 6 mm. However, under certain circumstances it also conceivable for openings of this type to be designed with diameters of less than 1 mm or even 0.1 mm. As is likewise illustrated in highly simplified form, the fiber layer 4 comprises a large number of fibers 33, which are arranged so as to form a knitted fabric, a woven fabric or the like, Alternatively, these may also be metal fibers, sintered materials or wire fabrics. In the embodiment illustrated, additional elements or constituents, in particular catalysts 34, are integrated in the fiber layer 4, assisting the regeneration of accumulated soot particulates or the like even at low temperatures (for example between 200 and 300°C). Fig. 5 diagrammatically depicts the structure of an exhaust system 27 for an internal combustion engine 17 . An internal combustion engine 17 of this type is preferably designed as a diesel engine. In the direction of flow 35 of the exhaust gas, the exhaust system 27 comprises the following components: - an upstream oxidation catalytic converter 40, - a filter body 16 according to the invention, - a turbocharger 39, and - a further catalytic converter 29. The individual components may be arranged in separate casings or may be partially combined with one another in a single casing, and are connected to one another via an exhaust pipe 28. As has already been stated in the introduction, it is particularly advantageous for the filter body 16 to be arranged as close as possible to the internal combustion engine 17. A distance 26 from the internal combustion engine 17 of less than 0.7 m, in particular even less than 30 cm, is particularly suitable in this respect. With the individual components arranged in this way, first of all a sufficient quantity of nitrogen dioxide is made available with the aid of the oxidation catalytic converter 40, ensuring (continuous) regeneration of the accumulated soot particulates in the filter body 16 arranged immediately downstream. The downstream catalytic converter 29 may, for example, also be designed as a hybrid converter, in which case it has partial regions with different heat capacities. In this context, it is to be designed in such a way that its heat capacity increases in the direction of flow. Fig. 6 shows a diagrammatic and perspective illustration of a further embodiment of the filter body 16 according to the invention. The filter body 16 in this case once again comprises partitions 14, between which there is in each case a filter assembly 1 according to the invention. In the embodiment illustrated, the filter assembly 1 is formed with two covering layers 2 and a fiber layer 4 arranged between them, although the connection by joining in the boundary region cannot be seen on account of the sectional illustration. The partitions 14 are in this case provided with a structure, whereas the filter assembly 1 has a substantially smooth surface. This structure of the partitions 14 forms passages 19 through which an exhaust gas can flow in a direction of flow 35. The partitions 14 in this case have different heights 30 of the structure, so that the passages 19 which are formed are matched to the characteristics of the incoming flow of exhaust gas. The embodiment illustrated here substantially shows an open filter. This property is described by the fact that there is a freedom of flow of at least 20%. In this context, the term freedom of flow means that in any desired cross section it is possible to see through at least 20% of the area, i.e. at least 20% of the area is free of internal fittings, such as diverting surfaces 37 or the like. In other words, this also means that when a particulate filter of this type is viewed from the end side, it is possible to see through at least some of the passage, provided that the internal fittings are all in the same position, i.e. are arranged aligned one behind the other. This is typically the case with honeycomb bodies made from at least partially structured sheet-metal layers. However, the freedom of flow, in the case of internal fittings which are not aligned with one another, does not necessarily mean that it is actually possible to see through part of a honeycomb body of this type. The partitions 14 are provided with apertures 36 and diverting surfaces 37 which divert the exhaust-gas stream toward the filter assembly 1. This produces pressure differences which cause partial flows of exhaust gas to penetrate through the filter assembly 1, so that soot particulates or the like remain and accumulate in the fiber layer 4. Fig. 7 shows a slightly different configuration of a filter body according to the invention. In this case too, the passages 19 are substantially generated by a corresponding structure of the partitions 14. Furthermore, the partitions 14 have diverting surfaces 37, which in the case illustrated close off the entire cross section of the passages 19. The result of this is that the direction of flow 35 of the exhaust gas is influenced in such a manner that the particulate- containing exhaust gas is guided through the filter assembly 1. This configuration is mainly suitable for applications in which a pressure loss is not critical. In the case of mobile exhaust systems, according to current knowledge, it is preferable to use an open filter with passages 19 which are just constricted but are not closed off. Depending on the number of diverting surfaces 37 which the exhaust gas is to pass through and/or the flow through a filter assembly 1, ultimately substantially the entire exhaust-gas stream is filtered and purified even in the case of an open filter body 16, as illustrated in Fig. 6. Fig. 8 shows a diagrammatic and perspective illustration of a configuration of the filter body 16 having a filter assembly 1 and a partition 14, which are wound helically to form a honeycomb body and are arranged in a casing 18. The partition 14 has a structure 21, so that passages 19, through which the exhaust gas can flow in a direction of flow 35, are formed. The exhaust gas enters the filter body 16 via an end side 20 and, on account of the flow diversions in the interior of an open filter, adopts a flow path which is preferably longer than the extent of the passages 19 in the direction of the axis 38. The filter assembly described here and the filter body which it is used to construct is particularly suitable for installation close to the engine in mobile exhaust systems. The proposed filter assembly is able to permanently withstand the high pressure loads which occur there on account of the proximity to the combustion chamber and the high temperatures of up to 700°C, and from time to time even up to 1000°C, since the fiber layer is at least partially surrounded, in a positively locking manner, by a protective sleeve formed by at least one covering layer. This prevents the fiber layer from exhibiting detachment phenomena after even just a short time. The proposed process is very simple and can be carried out reliably and without major technical difficulties even in large-series production, as is customary for automotive engineering. 1 Filter assembly 2 Covering layer 3 Boundary region 4 . Fiber layer 5 Thickness 6 Edge 7 Boundary width 8 Solder 9 First length 10 First width 11 Second length 12 Second width 13 Dimension 14 Partition 15 Flow-guiding surface 16 Filter body 17 Internal combustion engine 18 Casing 19 Passage 20 End side 21 Structure 22 Connection 23 Solder stop 24 Opening 25 Opening diameter 26 Distance 27 Exhaust system 28 Exhaust pipe 29 Catalytic converter 30 Height 31 Sleeve 32 Deformation region 33 Fiber 34 Catalyst 35 Direction of flow 36 Aperture 37 Diverting surface 38 Axis 39 Turbo charger 40 Oxidation catalytic converter WE CLAIM 1. A fitter assembly (1), through which a fluid can flow and which comprises at least one covering layer (2) formed of an at least partially porous material having at least one boundary region (3), and at least one fiber layer (4) made from a fiber fabric, characterized in that the at least one covering layer (2) forms a sleeve (31) which surrounds the fiber layer (4), so that the fiber layer (4) is captively held inside the at least one covering layer (2), and in that the at least one covering layer (2) is a metal foil with a thickness (5) of less than 0.04 mm, in particular less than 0.03 mm or even less than 0.02 mm. 2. The filter assembly (1) as claimed in claim 1, wherein when, the sleeve (31) is formed from a covering layer (2), the covering layer (2) comprises at least one boundary region (3) and an opposite deformation region (32), the covering layer (2) being connected to itself by joining in the at least one boundary region (3). 3. The filter assembly (1) as claimed in claim 1, wherein when, at least two covering layers (2) form the sleeve (31), the covering layers (2) are connected to one another by joining in at least one boundary region (3), and the fiber layer (4) is captively held between the interconnected covering layers (2). 4. The filter assembly (1) as claimed in one of claims 1 to 3, wherein at least one covering layer (2), in at least one boundary region (3), has a reduced porosity with respect to the remaining region, in particular has no porosity whatsoever there. 5. The filter assembly (1) as claimed in one of the preceding claims, wherein it has a mean porosity of greater than 70%, in particular greater than 90%. 6. The filter assembly (1) as claimed in one of claims 2 to 5, wherein the at least one boundary region (3) extends from an edge (6) of the covering layer (2) over a boundary width (7), which amounts to between 3 mm and 15 mm, the boundary region (3) preferably being arranged at least at two opposite edges (6). 7. The filter assembly (1) as claimed in one of the preceding claims, wherein the connection by joining is produced by means of a solder (8). 8. The filter assembly (1) as claimed in one of the preceding claims, wherein the fiber layer (4) has a first length (9) and a first width (10), and wherein the at least one covering layer (2) has a second length (11) and a second width (12), the first length (9) and/or first width (10) being less than the second length (11) and/or second width (12). 9. The filter assembly (1) as claimed in one of the preceding claims, wherein the fiber layer (4) has a dimension (13) of from 0.01 mm to 1mm. 10.The filter assembly (1) as claimed in one of the preceding claims, wherein the at least one covering layer (2) has at least one flow-guiding surface (15). 11.The filter body (16) for purifying an exhaust-gas stream from an internal combustion engine (17), characterized in that at least one filter assembly (1) as claimed in one of claims 1 to 10 is at least partially arranged in a casing (18) in such a way that passage (19), in particular corresponding to a honeycomb structure, are formed, the passages (19) preferably being at least partially narrowed. 12.The filter body (16) as claimed in claim 11, wherein at least one covering layer (2), at least in part, has a structure (21) which substantially delimits the passages (19). 13.A process for producing a filter assembly (1) as claimed in one of claims 1 to 10, comprising the following steps : - forming a porosity in at least one covering layer (2), with at least one boundary region (3) left out. - arranging a fiber layer (4) on a covering layer (2), - forming a sleeve (31) using the at least one covering layer (2), and - forming a connection by joining in the at least one boundary region (3), so that the fiber layer (4) is fixed captively within the at least one covering layer (2). 14.The process as claimed in claim 13, wherein the step of forming a sleeve (31) is effected by deforming a covering layer (2), in particular by bending, creasing or folding the covering layer (2) in a deformation region (32). 15.The process as claimed in claim 13, wherein the step of forming a sleeve (31) is carried out by means of two covering layers (2), the at least one fiber layer (4) being arranged between the covering layers (2) in such a way that the boundary regions of the covering layers (2) are at least in part directly superimposed on one another. 16.The process as claimed in one of claims 13 to 15, wherein before the fiber layer (4) is arranged on the covering layer (2), a structure (21) is introduced into at least one covering layer (2). 17.The process as claimed in claim 16, wherein two covering layers (2) are used to form a sleeve (31), and wherein the structure (21) is introduced into the two covering layers (2) successively in terms of time, and in each case a different structure (21) is produced. 18.The process as claimed in one of the claims 13 to 17, wherein the connection by joining is carried out by means of a welding operation. 19.The process as claimed in one of the claims 13 to 17, wherein the connection by joining is carried out by means of a soldering operation. 20.The process as claimed in claim 19, wherein at least one covering layer (2) is provided with a solder stop (23) outside the at least one boundary region (3). Dated this 27th day of May, 2004 This invention relates to a fitter assembly (1), through which a fluid can flow and which comprises at least one covering layer (2) formed of an at least partially porous material having at least one boundary region (3), and at least one fiber layer (4) made from a fiber fabric, characterized in that the at least one covering layer (2) forms a sleeve (31) which surrounds the fiber layer (4), so that the fiber layer (4) is captively held inside the at least one covering layer (2), and in that the at least one covering layer (2) is a metal foil with a thickness (5) of less than 0.04 mm, in particular less than 0.03 mm or even less than 0.02 mm.

Full Text

Filter assembly and process for producing it
The invention relates to a filter assembly through which a
fluid can flow, and to a filter body for purifying an exhaustgas
stream from an internal combustion engine constructed
using the filter assembly according to the invention.
Furthermore, the invention describes a process for producing a
filter assembly.
If new vehicle registrations in Germany are considered, it
will be found that in 2000 around one third of all newly
registered vehicles have diesel engines. By tradition, this
percentage is significantly higher than in, for example,
France and Austria. This increased interest in diesel vehicles
stems, for example, from the relatively low fuel consumption,
the currently relatively low prices of diesel fuel, but also
from the improved driving properties of vehicles of this type.
A diesel vehicle is also very attractive from environmental
aspects, since it has a significantly reduced emission of CO2
compared to gasoline-powered vehicles. However, it should be
noted that the level of soot particulates produced during
combustion is well above that of gasoline-powered vehicles.
If the purification of exhaust gases, in particular of diesel
engines, is considered, it is possible for hydrocarbons (HC)
and carbon monoxide (CO) in the exhaust gas to be oxidized in
a known way by, for example, being brought into contact with a
catalytically active surface. However, it is more difficult to
reduce nitrogen oxides (NOX) under oxygen-rich conditions. A
three-way catalytic converter, as is used, for example, in
spark-ignition engines, does not provide the desired effects.
For this reason, the selective catalytic reduction (SCR)
process has been developed. Furthermore, N0x adsorbers have
been tested for use for the reduction of nitrogen oxides.
Discussions have long been ongoing as to whether particulates
or long-chain hydrocarbons have an adverse effect on human
health, but to date no definitive verdict has been reached.
Irrespective of this, it is clearly desirable that emissions
of this nature should not be released to the environment above
a certain tolerance range. In this respect, the question
arises as to what filtering efficiency is actually required in
order to be able to comply with the well known statutory
guidelines even in the future. If current exhaust emissions
from commercially available vehicles in the Federal Republic
of Germany are considered, it can be concluded that most
passenger automobiles certified under EU III in 1999 are also
able to satisfy the requirements of EU IV if they are equipped
with a filter with an efficiency of at least 30 to 40%.
To reduce the levels of particulate emissions, it is known to
use particulate traps which are constructed from a ceramic
substrate. They have passages, so that the exhaust gas which
is to be purified can flow into the particulate trap. The
adjacent passages are alternately closed off, so that the
exhaust gas enters the passage on the inlet side, passes
through the ceramic wall and escapes again through the
adjacent passage on the outlet side. Filters of this type
achieve an efficiency of approx. 95% over the entire range of
particulate sizes which occur.
In addition to chemical interactions with additives and
special coatings, the reliable regeneration of the filter in
the exhaust system of an automobile still constitutes a
problem. It is necessary to regenerate the particulates trap,
since the increasing accumulation of particulates in the
passage wall through which the gas is to flow leads to a
constantly increasing pressure loss which has adverse effects
on engine performance. The regeneration substantially
comprises brief heating of the particulates trap and the
particulates which have accumulated therein, so that the soot
particulates are converted into gaseous constituents. However,
this high thermal loading of the particulates trap has adverse
effects on the service life.
To avoid this discontinuous regeneration, which is a major
factor in promoting thermally induced wear, a system for the
continuous regeneration of filters has been developed (CRT:
continuous regeneration trap). In a system of this type, the
particulates are burnt by means of oxidation with NO2 at
temperatures which are already over 200°C. The NO2 which is
required for this purpose is often generated by an oxidation
catalytic converter arranged upstream of the particulates
trap. However, in particular for use in motor vehicles using
diesel fuel, this gives rise to the problem that there is only
an insufficient level of nitrogen monoxide (NO) which can be
converted into the desired nitrogen dioxide (N02) in the
exhaust gas. Consequently, it has not hitherto been possible
to ensure that continuous regeneration of the particulates
trap in the exhaust system will occur.
Furthermore, it should be borne in mind that, in addition to
non-convertible particulates, oil or additional residues of
additives also accumulate in a particulates trap and cannot
readily be regenerated. For this reason, known filters have to
be replaced and/or washed at regular intervals. Filter systems
of plate-like structure attempt to solve this problem by
allowing vibration-like excitation which leads to these
constituents being removed from the filter. However, this
means that the non-regeneratable fraction of the particulates
in some cases passes directly into the environment without any
further treatment.
In addition to a minimum reaction temperature and a specific
residence time, it is necessary to provide sufficient nitrogen
oxide for the continuous regeneration of particulates using
NO2. Tests relating to the dynamic emission of nitrogen
monoxide (NO) and particulates have clearly demonstrated that
the particulates are emitted in particular when there is no or
only a very small amount of nitrogen monoxide in the exhaust
gas, and vice versa. What this means is that a filter with
true continuous regeneration substantially has to function as
a compensator or store, so that it is ensured that the two
reaction partners are present in the filter in the required
quantities at a given instant. Furthermore, the filter is to
be arranged as close as possible to the internal combustion
engine in order to be able to reach temperatures which are as
high as possible immediately after a cold start. To provide
the required nitrogen dioxide, an oxidation catalytic
converter is to be connected upstream of the filter, so as to
react carbon monoxide (CO) and hydrocarbons (HC) and in
particular also to convert nitrogen monoxide (NO) into
nitrogen dioxide (N02) . If this system comprising oxidation
catalytic converter and filter is arranged close to the
engine, a suitable position is in particular upstream of a
turbocharger which is often used in diesel motor vehicles to
increase the boost pressure in the combustion chamber.
If these basic considerations are looked at, the question
arises, for actual deployment in automotive engineering, as to
how a filter of this type, which in such a position and in the
presence of extremely high thermal and dynamic loads has a
satisfactory filtering efficiency, is constructed. In this
context, account should be taken in particular of the spatial
conditions, which require a new design of filters. Whereas the
maximum possible volume was to the fore in the case of
conventional filters, which were arranged in the underbody of
a motor vehicle, in order to ensure a long residence time of
the as yet unreacted particulates in the filter and therefore
a high efficiency, if the filters are arranged close to the
engine, there is not sufficient space or room available.
For this purpose, a new concept has been developed, mainly
referred to by the term "open filter system" . These open
filter systems are distinguished by the fact that there is no
need for the filter passages to be alternately closed off by
structural means. In this context, it is provided that the
passage walls be constructed at least in part from porous or
highly porous material and that the flow passages of the open
filter have diverting or guiding structures. These internal
fittings cause the flow and the particulates contained therein
to be diverted toward the regions made from porous or highly
porous material. Surprisingly, it has emerged that the
particulates, as a result of being intercepted and/or
impacting, are retained on and/or in the porous passage wall.
The pressure differences in the flow profile of the flowing
exhaust gas are of importance to this effect occurring. The
diversion additionally makes it possible to produce local
reduced pressure or excess pressure conditions, leading to a
filtration effect through the porous wall, since the
abovementioned pressure differences have to be compensated
for.
The particulate trap, unlike the known closed screen or filter
systems, is open, since there are no flow blind alleys. This
property can therefore also be used to characterize
particulate filters of this type, so that, for example, the
"freedom of flow" parameter is suitable for describing the
systems. By way of example, a "freedom of flow" of 20% means
that, when viewed in cross section, it is possible to see
through approx. 20% of the surface area. In the case of a
particulate filter with a passage density of approx. 600 cpsi
(cells per square inch) with a hydraulic diameter of 0.8 mm,
this freedom of flow would correspond to an area of over 0.1
mm2.
To realize an open filter system of this nature, it is also an
object of the present invention to provide a filter material
which is particularly suitable in particular for use in the
context of continuous regeneration, with the resulting
demands. In this respect, the filter system has to be able to
withstand the high thermal and dynamic loads in the exhaust
system of a passenger automobile, which stem from the pulsed
emission of very hot exhaust gas. Furthermore, it is intended
to provide a corresponding filter body which is suitable for
significantly reducing the levels of particulates in the
exhaust system. In addition, it is intended to provide a
process for producing the filter material.
These objects are achieved by a filter assembly having the
features of patent claim 1, a filter body for purifying an
exhaust-gas stream from an internal combustion engine having
the features of patent claim 12, and a process for producing a
filter assembly in accordance with the features of patent
claim 14. Further advantageous configurations are described in
the respective dependent claims, in which context the
particular features may occur individually or in any desired
and appropriate combination.
A fluid can flow through the filter assembly according to the
invention, and this filter assembly comprises at least one
covering layer made from at least partially porous or highly
porous material, and at least one fiber layer made from a
fiber fabric. Moreover, the covering layer has at least one
boundary region. The filter assembly is distinguished by the
fact that the at least one covering layer forms a sleeve which
surrounds the fiber layer, so that the fiber layer is arranged
captively inside the at least one covering layer. In this
context, a sleeve is to be understood as meaning an
arrangement of the at least one covering layer in which the at
least one covering layer also, at least in part, extends
beyond the periphery of the fiber layer, in particular
completely surrounds the fiber layer. In this respect, at
least in part a sleeve is formed over the entire periphery of
the fiber layer. This arrangement whereby the covering layer
engages around the periphery of the fiber layer accordingly
means that a relative movement of the fiber layer with respect
to the at least one covering layer is impeded in a positively
locking manner in at least one direction.
The design of a filter assembly of this type combines a number
of advantages which are of importance in particular for the
arrangement of a filter assembly of this type close to the
engine. The at least one covering layer constitutes a type of
protective sleeve which protects the inner fiber layer from
the pressure shocks and temperature peaks which occur. The
fiber layer represents a significantly looser assembly of
fibers than the covering layer. In this context, it should be
noted that the term "fiber fabric" encompasses all conceivable
arrangements of fibers in bonded assemblies, knitted fabrics
or the like. There are also numerous possible alternatives for
the material, such as for example ceramic fibers, metal
fibers, sintered materials or the like. The fiber layer may
have a very high porosity, since the presence of a protective
covering layer means that it does not have to be designed
primarily for strength. In particular, it is possible to
realize particularly large free spaces, pores or the like in
the fiber layer. This is boosted in particular by the fact
that the at least one covering layer is constructed in a form
similar to a strip or sheet, i.e. offers a relatively large
bearing surface area. Consequently, in this case it is
possible to use fiber materials which are packed significantly
more loosely than, for example, in known wire meshes which
have hitherto been used to ensure the dimensional stability of
the filter layers.
Since then, sandwich structures of this type have been
designed in such a way that there is in each case one
supporting structure arranged on both sides of the filter
material (in particular braided wire fabrics), and this
sandwich has then been bent or deformed into the desired
shape. These sandwich structures have been arranged in the
exhaust-gas stream in such a way that the periphery (or end
face) of the filter material was exposed to the pulsating
exhaust-gas stream without protection. This led to detachment
phenomena in particular in chese end regions. To ensure that
the fiber material is fixed between the wire fabrics for a
prolonged period of time, this sandwich structure had to be
pressed together under a high pressure, which, on account of
the resultant very small pores or free spaces, led to the
accumulation of particulates, with noticeable adverse effects
on the efficiency of the filter material. This is avoided in a
simple way in the filter assembly according to the invention,
since the fact that the at least one covering layer engages
around the periphery of the fiber layer means that the fiber
layer is arranged captively in the interior.
According to a further configuration, the sleeve which
protects the fiber layer is formed from a covering layer, the
latter having at least one boundary region and an opposite
deformation region, and the covering layer being connected to
itself by joining in the at least one boundary region.
Consequently, the dimensions of the covering layer allow the
covering layer to be arranged around the fiber layer once,
with the covering layer being deformed (bent, folded or the
like) in the vicinity of a periphery of the fiber layer and
being soldered or welded onto itself, for example, on the
opposite side in a boundary region. The arrangement of a
filter assembly of this type in the exhaust-gas stream from an
internal combustion engine is preferably such that the exhaust
gas which flows onto the filter assembly strikes either the
boundary region with the connection by joining or the
deformation region. Consequently, an offset or relative
movement of the fiber layer with respect to the covering layer
as seen in the direction of flow of the exhaust gas is not
possible, since a positively locking barrier is formed here.
In a direction perpendicular to this, the filter assembly can
make do without the covering layer engaging around it, since
the forces which are active here are relatively low. Rather,
this ensures, for example, that the different thermal
expansion coefficients of covering layer and fiber layer can
be compensated for.
As an alternative, it is also proposed that the sleeve be
formed with at least two covering layers, in which case the
covering layers are connected to one another by joining in at
least one boundary region, and the fiber layer is arranged
captively between these interconnected covering layers.
Accordingly, what is described here is a sandwich structure in
which the fiber layer is arranged between at least two
covering layers. The sleeve is in this case produced by the
externally arranged covering layers each having boundary
regions which overlap the fiber layer and are connected to one
another by joining (soldering, welding, sintering, adhesive
bonding) . These boundary regions in each case lie in the
vicinity of two opposite edges of the covering layer. Even if
in this context it is preferable for the boundary region with
the connection by joining to be arranged substantially outside
the region with the fiber layer, it may under certain
circumstances also be appropriate for one of the two covering
layers to be of elongated design, so that it engages around a
periphery of the fiber layer and is connected to the further
covering layer in the region of the fiber layer. Forming a
protective sleeve in this way likewise contributes to the
fiber layer being arranged captively in the interior.
According to a further configuration, the at least one
covering layer, in at least one boundary region, has a reduced
porosity with respect to the remaining region, in particular
has no porosity whatsoever there. This means that the covering
layer has at least two different permeabilities with respect
to an exhaust gas. Whereas the covering layer has a relatively
high permeability or porosity in particular in the region of
contact with the fiber layer, on account of bores, holes,
openings, apertures or the like, in the boundary region it is
preferably made from a material which is substantially
impervious to a fluid. This applies in particular to the
additional material which is used to form the connection by
joining, in particular solder or welding material. This allows
the covering layers which are to be connected to one another
to be permanently attached even in a highly corrosive
environment, as is encountered in an exhaust system.
According to a further configuration, the at least one
covering layer is a metal foil with a thickness of less than
0.04 mm, in particular less than 0.03 mm or even less than
0.02 mm. Making the covering layer from a metal foil has
particular advantages. For example, rapid heat conduction from
that surface of the covering layer which is in contact with
the exhaust gas to the fiber material is possible, so that in
this case too rapid regeneration of trapped and/or accumulated
particulates is possible (for example after the internal
combustion engine has started up). Furthermore, the proposed
thickness ensures that the metal foil has only a very low
surface area-specific heat capacity, so that in this case too
the light-off performance and/or the rapid heating to the
required minimum temperature for regeneration of soot
particulates is boosted. Moreover, when selecting the specific
material for a metal foil of this type, it is possible to
exploit knowledge which has already been gained in connection
with the development of metallic honeycomb bodies as catalyst
support bodies arranged close to the engine.
According to an advantageous configuration, the filter
assembly has a mean porosity of greater than 7 0%, in
particular even greater than 90%. The mean porosity
substantially relates to the region which is actually porous,
i.e. discounting boundary regions of reduced porosity. By its
very nature, the fiber layer often has a porosity which is
well over 70% or 90%, and consequently a certain reduction is
brought about by the covering layer which delimits the fiber
layer. The porosity of the covering layer is defined, for
example, by the size and/or number of the apertures, openings
or the like. For example, it is conceivable for the covering
layer to be provided with relatively large openings (e.g. with
a diameter in the range from 2 to 6 mm), in which case a
relatively small number of openings are provided per unit
area. If, for example, pressure differences across the filter
assembly play only a subordinate role, it is also possible for
openings of this type to be made significantly smaller
(significantly less than 1 mm) but to be provided in large
numbers per unit area. The particular configuration which
leads to the desired porosity depends on a large number of
parameters; in this context: mention may be made, by way of
example, of the composition of the exhaust gas (particulate
size, pressure fluctuations, etc.), the fiber material used
and/or the strength properties of the covering layer.
According to yet a further configuration, the at least one
boundary region extends from an edge of the covering layer
over a boundary width which amounts to between 3 mm and 15 mm,
with the boundary region preferably being arranged at least at
two opposite edges. This boundary width ensures that the
adjacent covering layers are durably attached to one another.
The given range is adapted in particular for known soldering
processes or, for example, roller seam welding. In this
context, it should also be noted that it is possible for the
fiber material to be completely sheathed or encapsulated, in
which case a soldered joint or weld seam is formed all the way
around the edges of the covering layers.
As has already been mentioned above, it is particularly
advantageous for the connection by joining to be carried out
by means of a solder. Solder has proven eminently suitable for
the formation of particularly corrosion-resistant and
temperature-resistant connections in the production of
catalyst support bodies from metal foils. However, under
certain circumstances it is also possible to use various known
welding processes, sintering or adhesive bonding techniques.
According to a refinement, the fiber layer has a first length
and a first width, and the at least one covering layer has a
second length and a second width, with the first length and/or
the first width of the fiber layer being less than the second
length and/or second width of the at least one covering layer.
This means that, if the covering and fiber layers are arranged
concentrically, the covering layers, at least in part, extend
beyond the peripheries of the fiber layer. This leads to the
formation of overlap sections which are preferably used to
form the connection by joining (boundary region).
With regard to the fiber layer, it is proposed that the latter
has a dimension of from 0.01 mm to 1 mm. In this context, it
is preferable to use fiber layers which have an inherent
porosity of over 85%. Tests carried out using fibers which
have a diameter of between 0.008 mm and 0.015 mm have proven
to have particularly satisfactory results with regard to the
filtration action.
In particular in connection with a filter assembly of this
type having what is known as the open filter, to boost the
flow diversion it is proposed that at least one covering layer
has at least one flow-guiding surface. This is to be
understood as meaning that the covering layer is not
completely planar, but rather its surface forms a structure or
microstructure which provides surfaces for diverting the flow.
For example, a structure running transversely with respect to
the direction of flow of the exhaust gas is advantageous;
under certain circumstances, a structure height of a few
millimeters (less than 2 mm, in particular less than 1 mm) is
sufficient. These flow-guiding surfaces contribute to having a
targeted influence on the direction of flow, with the result
that the overall filter efficiency is improved.
A further aspect of the invention proposes a filter body which
can be used to purify an exhaust-gas stream from an internal
combustion engine. This filter body includes at least one
filter assembly as described above, which is at least
partially arranged in a casing, in such a way that passages,
in particular corresponding to a honeycomb structure, are
formed, with the passages preferably being at least partially
narrowed. This means that the proposed filter assembly is
suitable both for use in filter systems with alternately
closed passages and for the production of open filter bodies
in which it is possible to see through more than 20%, in
particular more than 40%.
With regard to an open filter body, it is possible, for
example, for the filter body to be constructed from corrugated
sheet-metal foils and substantially smooth filter assemblies,
which are first of all stacked alternately on top of one
another and then coiled and/or wound together. The corrugated
sheet-metal foil in this case has diverting structures which
at least partially divert the exhaust gas flowing through the
filter body toward the porous filter assembly. This results in
the exhaust gas at least partially flowing through the filter
assembly, with in particular particulates of a size of between
20 and 200 ran being filtered out in the process. Depending on
how frequently a partial stream of gas is guided through a
wall of filter assembly material of this type with the aid of
diverting devices of this type, an increasing filtration
effect is observed as the gas flows axially through the filter
body.
According to a further configuration of the filter body, at
least one covering layer, at least in part, has being a
structure which substantially delimits the passages. In other
words, the structure substantially defines the cross section
of flow of the passage. It is advantageous for the covering
layers and/or the fiber layer together to be provided with a
structure of this type, and in this context a corrugation is
particularly recommended.
The process for producing a filter assembly according to the
invention, as described above, according to a further aspect
of the invention comprises the following steps:
- forming a porosity in at least one covering layer, with at
least one boundary region being left out,
- arranging a fiber layer on a covering layer,
- forming a sleeve using the at least one covering layer, and
- forming a connection by joining in the at least one
boundary region, so that the fiber layer is fixed captively
within the at least one covering layer.
The formation of a porosity in the covering layer may, for
example, be generated even while the material for the covering
layer is being produced. However, it is also possible for the
porosity to be produced by retrospectively providing a fluid-
impervious material with bores, openings, apertures or the
like. In this case, it is possible in particular to use
mechanical production processes (cutting, stamping, drilling
or the like), etching processes or a heat treatment, in
particular using a laser. All techniques which have been
disclosed hitherto can be used to form the fiber layer, so
that a knitted fabric, woven fabric or similar structure made
from fiber-like material is formed.
According to a refinement of the process, a sleeve is formed
by deformation of a covering layer, in particular by means of
bending, creasing or folding of the covering layer, in a
deformation region. This process step is recommended in
particular for the production of a filter assembly according
to the invention which has just one covering layer. In this
context, with a view to the high thermal and dynamic loads on
the covering layer in use, it may be advantageous if the
adjacent sections of a covering layer are additionally
connected to one another by joining in the deformation region.
This ensures that the fiber layer is still held captively even
if the covering layer should happen to tear open in the region
of the bend.
Furthermore, it is proposed that a sleeve be formed by means
of two covering layers, in which case the at least one fiber
layer is arranged between the covering layers in such a way
that the boundary regions of the covering layers are at least
in part directly superimposed on one another. This means that
there is no fiber material arranged between the adjacent
boundary regions of the covering layers, and connection by
joining in this boundary region does not cause any damage to
the fiber layer. Moreover, it is ensured that the connection
by joining in the boundary region is able to withstand the
highly corrosive conditions in the exhaust system of the
internal combustion engine for a very long period of time.
According to a refinement of the process, before the fiber
layer is arranged on the covering layer, a structure is
introduced into at least one of the covering layers. If the
filter assembly has two covering layers for forming a sleeve,
it is advantageously proposed that the structure be introduced
into the two covering layers successively in terms of time,
and in each case a different structure be produced. By way of
example, this makes it possible to form different passage
densities over the cross section of the filter body, so that
it is ensured that the respective cross-sectional shapes of
the passages and/or passage densities are matched in a
targeted fashion to the incoming flow profile of the exhaustgas
stream.
With regard to the configuration of the connection of the
covering layers to one another by joining, as an alternative
it is proposed that the connection by joining be carried out
by means of a welding operation or by means of a soldering
operation. These constitute particularly preferred
configurations of the process; under certain circumstances,
joining connections using sintering or adhesive bonding
processes are also possible.
According to yet another configuration of the process, the at
least one covering layer is provided with a solder stop
outside the at least one boundary region. The solder stop used
may be known oils, paints, waxes, ceramic slips or the like
which prevent the solder from penetrating into internal
regions of the sleeve in which the fiber layer is arranged.
This firstly ensures that the solder does not contribute to
reducing the porosity of the fiber layer and secondly also
ensures that the quantity of solder which has been calculated
to be required for the solder connection is actually present
at the location which is to be joined.
The invention will now be explained in more detail on the
basis of figures, which show particularly advantageous and
particularly preferred configurations of the filter assembly
and/or filter body. Furthermore, the figures serve to
illustrate the described process according to the invention.
Nevertheless, it should be noted at this point that the
invention is not restricted to the exemplary embodiments
illustrated in the figures. In the drawing:
Fig. 1 shows a diagrammatic and perspective view of a first
embodiment of the filter assembly,
Fig. 2 shows a sectional view through a further embodiment of
the filter assembly,
Fig. 3 shows an excerpt from an embodiment of the filter body-
according to the invention,
Fig. 4 shows a detailed view from Fig. 3,
Fig. 5 diagrammatically depicts an exhaust system,
Fig. 6 shows a diagrammatic and perspective, detailed view of
a further embodiment of the filter body,
Fig. 7 shows a diagrammatic and perspective view of a further
configuration of the filter body, and
Fig. 8 shows a diagrammatic and perspective view of a further
embodiment of the filter body according to the invention.
Fig. 1 shows a diagrammatic and perspective view of an
embodiment of the filter assembly 1 according to the invention
with two covering layers 2. The covering layers 2 are composed
at least in part of a porous material (of. dotted region) and
each have two boundary regions 3 on opposite sides.
Furthermore, the filter assembly 1 comprises a fiber layer 4
formed from a fiber fabric. The two covering layers 2 form a
sleeve 31 which surrounds the fiber layer 4, so that the fiber
layer 4 is arranged captively inside the two covering layers
2. The two covering layers 2 are connected to one another by
joining (connection 22), in particular are soldered or welded
to one another, in the boundary regions 3 close to an edge 6.
The fiber layer 4 has a first length 9 and a first width 10.
The covering layers 2 in each case have a second length 11 and
a second width 12; in the embodiment illustrated, these are
equal (equal length and equal width). In principle, the second
length 11 and the second width 12 of the covering layers 2
used to form the filter assembly 1 and the sleeve 31 may also
differ. The Fig. also shows that the covering layers 2 have a
second length 11 which is greater than the first length 9 of
the fiber layer 4. This means that the covering layers 2 overlap the fiber layer 4 in length, so that the boundary
regions 3 can rest on top of one another. This makes it easier
to form permanent connections 22.
Fig. 2 diagrammatically depicts a sectional view through a
further embodiment of a filter assembly 1, the latter having
just one covering layer 2 which forms the sleeve 31. The
covering layer 2 has at least one boundary region 3 and an
opposite deformation region 32, the covering layer 2 being
connected to itself by joining in the boundary region 3. The
connection by joining is in this case ensured by means of a
solder 8, with a solder stop 23 being provided outside the
boundary region 3, preventing the solder 8 from reaching the
vicinity of the fiber layer 4 during a heat treatment. In the
embodiment illustrated, solder 8 is provided in the inside of
the deformation region 32, and in this case too it is
optionally possible to provide solder stop 23. The boundary
region 3 extends from an edge 6 of the covering layer 2 over a
boundary width 7 of preferably between 3 and 15 mm.
With regard to the material thicknesses, it can be explained
on the basis of Fig. 2, that the covering layer 2 is, for
example, a metal foil and has a thickness 5 of less than 0.04
mm. Furthermore, it can be seen that the fiber layer 4 has a
dimension 13 which is preferably in the range from 0.01 mm to
1 mm.
Fig. 2 likewise shows a covering layer 2 which is provided
with flow-guiding surfaces 15. This is designed in particular
as a microstructure. In the embodiment illustrated, this
microstructure or the flow-guiding surfaces fulfils two
functions. Firstly, the exhaust gas which flows by (from a
boundary region 3 to the deformation region 32 or vice versa)
is diverted or swirled up, so that partial gas streams are
diverted toward or penetrate through the adjacent porous wall,
in particular a filter assembly according to the invention.
Furthermore, it can be seen that with a microstructure of this
type it is also possible to effect a clamping action with
respect to the inner fiber layer 4. This improves the
stability of the filter assembly 1. Moreover, this enables the
porosity of the covering layer 2 to be increased, since the
clamping forces which are additionally introduced already
sufficiently prevent any possible detachment phenomena in the
fiber layer 4.
Fig. 3 diagrammatically depicts a detailed view of an
embodiment of a filter body according to the invention. The
filter body 16 is constructed from partitions 14, between
which at least one filter assembly 1 is arranged. The filter
assembly 1, like the partitions 14, is illustrated in section,
with the two covering layers 2 once again forming a sleeve 31
(not shown) around the fiber layer 4. In the embodiment
illustrated, the filter assembly 1 has a structure 21 which
substantially performs the function of spacing the smooth
partitions 14 apart from one another and forming passages 19.
The passage 19 has a cross-sectional area which is
substantially defined by this structure 21 of the filter
assembly 1.
Fig. 4 shows a highly simplified detailed view of the excerpt
from Fig. 3 which is indicated by IV. The fiber layer 4 is
delimited by a covering layer 2. The covering layer 2 has a
multiplicity of openings 24 with an opening diameter 25. The
opening diameter 25 varies considerably depending on the
particular application and is preferably in the range between
2 and 6 mm. However, under certain circumstances it also
conceivable for openings of this type to be designed with
diameters of less than 1 mm or even 0.1 mm. As is likewise
illustrated in highly simplified form, the fiber layer 4
comprises a large number of fibers 33, which are arranged so
as to form a knitted fabric, a woven fabric or the like,
Alternatively, these may also be metal fibers, sintered
materials or wire fabrics. In the embodiment illustrated,
additional elements or constituents, in particular catalysts
34, are integrated in the fiber layer 4, assisting the
regeneration of accumulated soot particulates or the like even
at low temperatures (for example between 200 and 300°C).
Fig. 5 diagrammatically depicts the structure of an exhaust
system 27 for an internal combustion engine 17 . An internal
combustion engine 17 of this type is preferably designed as a
diesel engine. In the direction of flow 35 of the exhaust gas,
the exhaust system 27 comprises the following components:
- an upstream oxidation catalytic converter 40,
- a filter body 16 according to the invention,
- a turbocharger 39, and
- a further catalytic converter 29.
The individual components may be arranged in separate casings
or may be partially combined with one another in a single
casing, and are connected to one another via an exhaust pipe
28. As has already been stated in the introduction, it is
particularly advantageous for the filter body 16 to be
arranged as close as possible to the internal combustion
engine 17. A distance 26 from the internal combustion engine
17 of less than 0.7 m, in particular even less than 30 cm, is
particularly suitable in this respect. With the individual
components arranged in this way, first of all a sufficient
quantity of nitrogen dioxide is made available with the aid of
the oxidation catalytic converter 40, ensuring (continuous)
regeneration of the accumulated soot particulates in the
filter body 16 arranged immediately downstream. The downstream
catalytic converter 29 may, for example, also be designed as a
hybrid converter, in which case it has partial regions with
different heat capacities. In this context, it is to be
designed in such a way that its heat capacity increases in the
direction of flow.
Fig. 6 shows a diagrammatic and perspective illustration of a
further embodiment of the filter body 16 according to the
invention. The filter body 16 in this case once again
comprises partitions 14, between which there is in each case a
filter assembly 1 according to the invention. In the
embodiment illustrated, the filter assembly 1 is formed with
two covering layers 2 and a fiber layer 4 arranged between
them, although the connection by joining in the boundary
region cannot be seen on account of the sectional
illustration. The partitions 14 are in this case provided with
a structure, whereas the filter assembly 1 has a substantially
smooth surface. This structure of the partitions 14 forms
passages 19 through which an exhaust gas can flow in a
direction of flow 35. The partitions 14 in this case have
different heights 30 of the structure, so that the passages 19
which are formed are matched to the characteristics of the
incoming flow of exhaust gas.
The embodiment illustrated here substantially shows an open
filter. This property is described by the fact that there is a
freedom of flow of at least 20%. In this context, the term
freedom of flow means that in any desired cross section it is
possible to see through at least 20% of the area, i.e. at
least 20% of the area is free of internal fittings, such as
diverting surfaces 37 or the like. In other words, this also
means that when a particulate filter of this type is viewed
from the end side, it is possible to see through at least some
of the passage, provided that the internal fittings are all in
the same position, i.e. are arranged aligned one behind the
other. This is typically the case with honeycomb bodies made
from at least partially structured sheet-metal layers.
However, the freedom of flow, in the case of internal fittings
which are not aligned with one another, does not necessarily
mean that it is actually possible to see through part of a
honeycomb body of this type. The partitions 14 are provided
with apertures 36 and diverting surfaces 37 which divert the
exhaust-gas stream toward the filter assembly 1. This produces
pressure differences which cause partial flows of exhaust gas
to penetrate through the filter assembly 1, so that soot
particulates or the like remain and accumulate in the fiber
layer 4.
Fig. 7 shows a slightly different configuration of a filter
body according to the invention. In this case too, the
passages 19 are substantially generated by a corresponding
structure of the partitions 14. Furthermore, the partitions 14
have diverting surfaces 37, which in the case illustrated
close off the entire cross section of the passages 19. The
result of this is that the direction of flow 35 of the exhaust
gas is influenced in such a manner that the particulate-
containing exhaust gas is guided through the filter assembly
1. This configuration is mainly suitable for applications in
which a pressure loss is not critical. In the case of mobile
exhaust systems, according to current knowledge, it is
preferable to use an open filter with passages 19 which are
just constricted but are not closed off. Depending on the
number of diverting surfaces 37 which the exhaust gas is to
pass through and/or the flow through a filter assembly 1,
ultimately substantially the entire exhaust-gas stream is
filtered and purified even in the case of an open filter body
16, as illustrated in Fig. 6.
Fig. 8 shows a diagrammatic and perspective illustration of a
configuration of the filter body 16 having a filter assembly 1
and a partition 14, which are wound helically to form a
honeycomb body and are arranged in a casing 18. The partition
14 has a structure 21, so that passages 19, through which the
exhaust gas can flow in a direction of flow 35, are formed.
The exhaust gas enters the filter body 16 via an end side 20
and, on account of the flow diversions in the interior of an
open filter, adopts a flow path which is preferably longer
than the extent of the passages 19 in the direction of the
axis 38.
The filter assembly described here and the filter body which
it is used to construct is particularly suitable for
installation close to the engine in mobile exhaust systems.
The proposed filter assembly is able to permanently withstand
the high pressure loads which occur there on account of the
proximity to the combustion chamber and the high temperatures
of up to 700°C, and from time to time even up to 1000°C, since
the fiber layer is at least partially surrounded, in a
positively locking manner, by a protective sleeve formed by at
least one covering layer. This prevents the fiber layer from
exhibiting detachment phenomena after even just a short time.
The proposed process is very simple and can be carried out
reliably and without major technical difficulties even in
large-series production, as is customary for automotive
engineering.
1 Filter assembly
2 Covering layer
3 Boundary region
4 . Fiber layer
5 Thickness
6 Edge
7 Boundary width
8 Solder
9 First length
10 First width
11 Second length
12 Second width
13 Dimension
14 Partition
15 Flow-guiding surface
16 Filter body
17 Internal combustion engine
18 Casing
19 Passage
20 End side
21 Structure
22 Connection
23 Solder stop
24 Opening
25 Opening diameter
26 Distance
27 Exhaust system
28 Exhaust pipe
29 Catalytic converter
30 Height
31 Sleeve
32 Deformation region
33 Fiber
34 Catalyst
35 Direction of flow
36 Aperture
37 Diverting surface
38 Axis
39 Turbo charger
40 Oxidation catalytic converter
WE CLAIM
1. A fitter assembly (1), through which a fluid can flow and which comprises
at least one covering layer (2) formed of an at least partially porous
material having at least one boundary region (3), and at least one fiber
layer (4) made from a fiber fabric, characterized in that the at least one
covering layer (2) forms a sleeve (31) which surrounds the fiber layer (4),
so that the fiber layer (4) is captively held inside the at least one covering
layer (2), and in that the at least one covering layer (2) is a metal foil with
a thickness (5) of less than 0.04 mm, in particular less than 0.03 mm or
even less than 0.02 mm.
2. The filter assembly (1) as claimed in claim 1, wherein when, the sleeve
(31) is formed from a covering layer (2), the covering layer (2) comprises
at least one boundary region (3) and an opposite deformation region (32),
the covering layer (2) being connected to itself by joining in the at least
one boundary region (3).
3. The filter assembly (1) as claimed in claim 1, wherein when, at least two
covering layers (2) form the sleeve (31), the covering layers (2) are
connected to one another by joining in at least one boundary region (3),
and the fiber layer (4) is captively held between the interconnected
covering layers (2).
4. The filter assembly (1) as claimed in one of claims 1 to 3, wherein at least
one covering layer (2), in at least one boundary region (3), has a reduced
porosity with respect to the remaining region, in particular has no porosity
whatsoever there.
5. The filter assembly (1) as claimed in one of the preceding claims, wherein
it has a mean porosity of greater than 70%, in particular greater than
90%.
6. The filter assembly (1) as claimed in one of claims 2 to 5, wherein the at
least one boundary region (3) extends from an edge (6) of the covering
layer (2) over a boundary width (7), which amounts to between 3 mm and
15 mm, the boundary region (3) preferably being arranged at least at two
opposite edges (6).
7. The filter assembly (1) as claimed in one of the preceding claims, wherein
the connection by joining is produced by means of a solder (8).
8. The filter assembly (1) as claimed in one of the preceding claims, wherein
the fiber layer (4) has a first length (9) and a first width (10), and wherein
the at least one covering layer (2) has a second length (11) and a second
width (12), the first length (9) and/or first width (10) being less than the
second length (11) and/or second width (12).
9. The filter assembly (1) as claimed in one of the preceding claims, wherein
the fiber layer (4) has a dimension (13) of from 0.01 mm to 1mm.
10.The filter assembly (1) as claimed in one of the preceding claims, wherein
the at least one covering layer (2) has at least one flow-guiding surface
(15).
11.The filter body (16) for purifying an exhaust-gas stream from an internal
combustion engine (17), characterized in that at least one filter assembly
(1) as claimed in one of claims 1 to 10 is at least partially arranged in a
casing (18) in such a way that passage (19), in particular corresponding
to a honeycomb structure, are formed, the passages (19) preferably being
at least partially narrowed.
12.The filter body (16) as claimed in claim 11, wherein at least one covering
layer (2), at least in part, has a structure (21) which substantially delimits
the passages (19).
13.A process for producing a filter assembly (1) as claimed in one of claims 1
to 10, comprising the following steps :
- forming a porosity in at least one covering layer (2), with at least
one boundary region (3) left out.
- arranging a fiber layer (4) on a covering layer (2),
- forming a sleeve (31) using the at least one covering layer (2), and
- forming a connection by joining in the at least one boundary
region (3), so that the fiber layer (4) is fixed captively within the at
least one covering layer (2).
14.The process as claimed in claim 13, wherein the step of forming a sleeve
(31) is effected by deforming a covering layer (2), in particular by
bending, creasing or folding the covering layer (2) in a deformation region
(32).
15.The process as claimed in claim 13, wherein the step of forming a sleeve
(31) is carried out by means of two covering layers (2), the at least one
fiber layer (4) being arranged between the covering layers (2) in such a
way that the boundary regions of the covering layers (2) are at least in
part directly superimposed on one another.
16.The process as claimed in one of claims 13 to 15, wherein before the fiber
layer (4) is arranged on the covering layer (2), a structure (21) is
introduced into at least one covering layer (2).
17.The process as claimed in claim 16, wherein two covering layers (2) are
used to form a sleeve (31), and wherein the structure (21) is introduced
into the two covering layers (2) successively in terms of time, and in each
case a different structure (21) is produced.
18.The process as claimed in one of the claims 13 to 17, wherein the
connection by joining is carried out by means of a welding operation.
19.The process as claimed in one of the claims 13 to 17, wherein the
connection by joining is carried out by means of a soldering operation.
20.The process as claimed in claim 19, wherein at least one covering layer
(2) is provided with a solder stop (23) outside the at least one boundary
region (3).
Dated this 27th day of May, 2004
This invention relates to a fitter assembly (1), through which a fluid can flow and
which comprises at least one covering layer (2) formed of an at least partially
porous material having at least one boundary region (3), and at least one fiber
layer (4) made from a fiber fabric, characterized in that the at least one covering
layer (2) forms a sleeve (31) which surrounds the fiber layer (4), so that the
fiber layer (4) is captively held inside the at least one covering layer (2), and in
that the at least one covering layer (2) is a metal foil with a thickness (5) of less
than 0.04 mm, in particular less than 0.03 mm or even less than 0.02 mm.

Documents:

714-KOLNP-2004-(27-12-2011)-CORRESPONDENCE.pdf

714-KOLNP-2004-FORM 27.pdf

714-KOLNP-2004-FORM-27.pdf

714-kolnp-2004-granted-abstract.pdf

714-kolnp-2004-granted-claims.pdf

714-kolnp-2004-granted-correspondence.pdf

714-kolnp-2004-granted-description (complete).pdf

714-kolnp-2004-granted-drawings.pdf

714-kolnp-2004-granted-examination report.pdf

714-kolnp-2004-granted-form 1.pdf

714-kolnp-2004-granted-form 18.pdf

714-kolnp-2004-granted-form 2.pdf

714-kolnp-2004-granted-form 3.pdf

714-kolnp-2004-granted-form 5.pdf

714-kolnp-2004-granted-gpa.pdf

714-kolnp-2004-granted-reply to examination report.pdf

714-kolnp-2004-granted-specification.pdf

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Patent Number

223070

Indian Patent Application Number

714/KOLNP/2004

PG Journal Number

36/2008

Publication Date

05-Sep-2008

Grant Date

03-Sep-2008

Date of Filing

27-May-2004

Name of Patentee

EMITEC GESELLSCHAFT FUR EMISSIONSTECHNOLOGIE MBH

Applicant Address

HAUPTSTRASSE 150, 53797 LOHMAR

Inventors:

#	Inventor's Name	Inventor's Address
1	BRUCK, ROLF	FROBELSTRASSE 12 51429 BERGISCH GLADBACH

PCT International Classification Number

F01N 3/022

PCT International Application Number

PCT/EP02/11683

PCT International Filing date

2002-10-18

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10153284.9	2001-10-29	Germany