APPARATUS FOR EXHAUST GAS AFTERTREATMENT HAVING A SLOTTED MATRIX

[0001]The invention relates to an device for exhaust gas aftertreatment, in particular exhaust gases of an internal combustion engine, wherein the device is arranged or can be arranged in an exhaust gas path through which the exhaust gas can flow and wherein the device can be flowed through along a main flow direction defined by a plurality of flow channels formed with the matrix from a gas inlet side to a gas outlet side. The matrix is formed from a plurality of metal foils stacked on top of each other to form a layer stack and coiled around at least one pivot point, wherein the matrix has an axial extension extending along the main flow direction and a radial extension extending transversely to the axial extension.

[0002]For the purpose of exhaust gas aftertreatment of the exhaust gases of an internal combustion engine and, in particular, for the conversion of the pollutants contained in the exhaust gas, different catalysts can be installed or are installed in the exhaust gas path. The catalysts regularly have a honeycomb body through which a flow can pass along a plurality of flow channels, which has a catalytically active surface on which the chemical reaction of the pollutants to non-critical products takes place.

[0003]Metal honeycomb bodies are known, which are formed from a plurality of metal foils stacked on top of each other to form a layer stack and cut to a defined length. The metal foils stacked on top of each other are wound or coiled at least partially around a pivot point, thereby forming the honeycomb body. Both smooth or unstructured metal foils and metal foils that are structured at least in sections or continuously are used for the honeycomb body, which are preferably stacked alternately on top of each other. The so-called cells form between the metal foils, which form flow channels of the honeycomb body through which gas can flow along a main flow direction from a gas inlet side to a gas outlet side.

[0004]The honeycomb body produced in this way, which is also known as a carrier matrix, can then be pressed into a housing known as a carrier tube and soldered to it. In known configurations, both the (completely) smooth metal foils and the metal foils structured at least in sections extend continuously over the entire axial extension of the honeycomb body. It is also possible to produce a carrier matrix entirely from structured metal foils, in which case the structures are, for example, positioned at an angle to each other so that the metal foils do not become entangled.

[0005]A particular disadvantage of the configuration known in the prior art is that the known honeycomb bodies are provided in one piece along their axial extension and therefore have only limited flexibility.

[0006]It has also been found that during rapid heating or rapid cooling, due to the heat capacity of the metal foils and the carrier tube, temperature differences arise in the honeycomb body both radially and axially. These temperature gradients result in a torsional load on the honeycomb body between the cold and warm areas in the axial direction, which is transmitted in the form of tangential shear forces via the metal foils.

[0007]In particular, at high temperature loads, a temperature gradient develops along the axial extension of the matrix from a very hot gas inlet side to a relatively cold gas outlet side. This temperature difference generates a torsional moment within the matrix, whereby the hot gas inlet twists relative to the relatively cold gas outlet. If the elastic deformation is exceeded, this torsion can lead to irreversible damage to the matrix and, in the worst case, to component failure.

[0008]Therefore, the object of the present invention is to solve at least some of the problems described in relation to the prior art and, in particular, to provide an device with a honeycomb body which has a configuration that reduces or even eliminates the temperature-induced torsion of the matrix and/or counteracts structural damage to the matrix.

[0009]The object with regard to the device is achieved by a device having the features of claim 1. Advantageous further embodiments are specified in the dependent claims. The features listed individually in the claims can be combined with each other and/or with features of the description in any manner. The description, in particular in connection with the figures, explains the invention and specifies additional embodiments.

[0010]This is aided by an device for exhaust gas aftertreatment, in particular exhaust gases of an internal combustion engine, wherein the device is arranged or can be arranged in an exhaust gas path through which the exhaust gas can flow and wherein the device can be flowed through along a main flow direction defined by a plurality of flow channels formed with the matrix from a gas inlet side to a gas outlet side. The matrix is formed from a plurality of metal foils stacked on top of each other to form a layer stack and wound or coiled around at least one pivot point, wherein the matrix has an axial extension extending along the main flow direction and a radial extension extending transversely to the axial extension. All metal foils have a plurality of slots, wherein the slots of the individual metal foils are congruent with each other in the wound or coiled state and extend in the circumferential direction of the matrix.

[0011]The arrangement of the slots in all metal foils is particularly advantageous because it prevents the foils from being subjected to different forces, in particular torsional moments, due to different numbers of slots and/or a twisted position relative to each other, which would lead to a critical stress state in the matrix.

[0012]The number and arrangement of the slots in each of the metal foils is therefore the same in order to create a uniform stress state across the individual metal foils as a result of thermal loads. The slots primarily serve to relieve mechanical stress on the metal foils and are intended to prevent the formation of high torsional moments or reduce the effects of torsional moments on the matrix. The slots are not primarily intended to allow exhaust gas to flow between different flow channels (arranged parallel to or adjacent to each other). For this reason, the slots are many times longer, measured in the circumferential direction of the matrix, than they are wide, measured in the axial direction/extension of the matrix.

[0013]The matrix can comprise several layer stacks. The at least one layer stack can be wound and/or twisted around at least one pivot point.

[0014]In this context, “congruent” means in particular that the slots or an equal number of slots in the metal foils are located in an axial cross-sectional plane when the metal foils are in a wound or coiled state. In this context, “congruent” also means in particular that the slots or an equal number of slots of the metal foils overlap in radial extension when the metal foils are wound or coiled. The overlapping slots can together form one or more slot gaps in the matrix.

[0015]The wound or coiled state is particularly present when the metal foils or matrix are fixed in the housing or carrier tube.

[0016]The circumferential direction is particularly characterized by the course of the metal foils in the wound or coiled state, perpendicular to the axial extension of the matrix.

[0017]The slots are preferably at least 20 times longer than they are wide. The slots are particularly preferred to be 50 times longer than they are wide. However, in an advantageous embodiment, the slots may also be 500 times or more longer than they are wide.

[0018]It is particularly advantageous if the metal foils have a slot pattern of exactly two slots in the circumferential direction, wherein a plurality of slot patterns spaced apart from each other are arranged in the axial direction/extension.

[0019]The slot pattern refers in particular to the number and position of the slots in relation to each other, especially in the case of a metal foil. A slot pattern in the circumferential direction therefore describes how many slots are spaced apart from each other in a predetermined axial plane in the circumferential direction. Several such slot patterns in the circumferential direction can be provided axially spaced apart in a metal foil. The totality of the slot patterns in the circumferential direction of a metal foil can be referred to as the total slot pattern of the metal foil.

[0020]A number of two slots in the circumferential direction is advantageous because the flexibility of the matrix is specifically increased, whereby disruptive forces within the elastic deformation can be compensated. At the same time, the durability and stability of the matrix, which is required for use in an exhaust gas path, is not reduced too greatly.

[0021]It is also advantageous if the exactly two slots of the slot pattern are separated from each other by a middle section and are separated from the respective edge of the metal foil by a respective edge section. The middle section and edge section are formed from the metal foil material. By arranging one edge section at the layer outlet or end of the metal foil in the circumferential direction, i.e., before and after the slots in the circumferential direction, it is ensured that the individual metal foils have sufficient stability so that they do not tear during the assembly process and do not suffer any structural damage during use.

[0022]A preferred embodiment is characterized in that the individual metal foils, in particular depending on their position in the layer stack, have slots of different lengths in the circumferential direction. The slot lengths are selected so that when the matrix is in a wound or coiled state, the slots of the individual metal foils are congruent with each other.

[0023]When the metal foils are wound or coiled to form the matrix, areas with different bending radii are created in the metal foils, whereby this refers to the (overall) course of the metal foils and not the (inherent) structure of the metal foil. An area located more toward the center of the matrix has a smaller bending radius than an area located at the radial edge of the matrix. If the metal foils all have slots of exactly the same length, coiling will sometimes cause misalignments between the slots of the individual metal foils because a slot in the area of a larger bending radius has a shorter arc length than in the area of a smaller bending radius. This phenomenon can be counteracted by adjusting the slot lengths in the circumferential direction, thereby ensuring that the slots are arranged exactly congruent to one another when coiled.

[0024]In other words, this means that the slot lengths are selected depending on a bending radius of the metal foil in the region of the slot in the wound state.

[0025]The metal foils can be of different lengths along the circumferential direction of the coiled matrix. This is advantageous in that, particularly in the end regions which form the foil spout, the individual metal foils are slightly offset, in order to produce a more accurate shape for the matrix. In particular, with a typically circular cross-section, a more accurate shape is achieved in this way.

[0026]Furthermore, it is advantageous if the middle section and/or the edge sections have a length of 0.5 mm to 50.0 mm [millimeters], preferably a length of 1.0 mm to 10.0 mm, and particularly preferably a length of 1.5 mm to 5.0 mm. The middle section and the edge sections are preferably very short (in particular many times shorter) compared to the extension of the metal foils in the circumferential direction and also compared to the length of the slots in the circumferential direction. The sections serve in particular to produce a sufficiently high integral stability to ensure the assembly and safe operation of the matrix.

[0027]The slots may have a width of 0.1 mm to 10.0 mm [millimeters], preferably a width of 0.1 mm to 2.0 mm, and particularly preferably a width of 0.1 mm to 0.5 mm. The slots are preferably very narrow or have a particularly small width as specified here. This serves in particular to prevent the exhaust gas from flowing over these slots, or at least to keep the overflow as low as possible. The slots have no (significant or substantial) flow-conducting effect, but serve (practically) only to create a sufficiently flexible structure for the matrix.

[0028]In an extreme design, the slots can also have a width of almost 0.0 mm (so-called zero gap). In this case, the edges bounding the slot lie directly against each other. Depending on the stress state in the matrix, the edges bounding the slot may lie completely or only partially against each other. In such a design, the base material is separated (only or in this way) when the slots are cut, without any material being removed.

[0029]The slots can divide the metal foils into several axial segments, wherein an axial segment has a length of 1.0 mm to 50.0 mm [millimeters], preferably 5.0 mm to 30.0 mm, particularly preferably 10.0 mm to 20.0 mm. The more axial segments are formed over the length of the matrix, the more flexible the matrix is and can therefore absorb higher forces without being damaged. The number of axial segments can be selected from the following group: 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0030]Middle sections between the individual slot patterns (in the circumferential direction) can be aligned in the axial direction/extension so that the slots along the axial extension are also aligned with each other. This is advantageous in order to be able to absorb the forces acting on the (wound) matrix as evenly as possible over the circumference and also to avoid inhomogeneous stress states in the axial extension direction of the matrix.

[0031]The slot patterns (in the circumferential direction) can be arranged equidistantly, i.e., at equal distances from each other, along the axial extension. This is advantageous in order to achieve a stress distribution across the matrix that is as homogeneous as possible.

[0034]FIG. 2 a detailed view of the corrugated metal foil of FIG. 1,

[0035]FIG. 3 a schematic view of a slotted matrix in a sheath tube, and

[0036]FIG. 4 a perspective view of an device for exhaust gas aftertreatment with a matrix in a sheath tube.

[0037]FIG. 1 shows a view of a structured metal foil 1. The metal foil 1 has a length L which corresponds to the axial extension of the coiled matrix. In addition, the metal foil 1 has a width B which extends in the circumferential direction or perpendicular to the axial extension in the finally assembled matrix.

[0038]The metal foil 1 has a plurality of slots 2 which extend along the width B or in the circumferential direction and are arranged equidistantly from each other along the length L. Along the width B, two slots 2 are spaced apart from each other by a middle section 3 (see also enlarged detail). The slots 2 are each spaced apart from the edges or end regions of the metal foil 1 by the width of an edge section 4. The slots 2 result in several axial segments 5 along the length L.

[0039]FIG. 2 shows a detailed view of the metal foil 1. Here it can be seen that a smooth metal foil 6 is arranged below the corrugated metal foil 1. The metal foils 1, 6 lie congruently on top of each other. Identical slot patterns are formed in both metal foils 1, 6 and are arranged congruently with each other.

[0040]FIG. 2 also clearly shows the edge sections 4 (see also enlarged detail) which are formed between the slots 2 and the end of the foil.

[0041]FIG. 3 shows a view of a matrix 8 housed in a sheath tube 7, which is formed from metal foils 1 and 6 of FIGS. 1 and 2. Along the axial extension, the axial segments 5 of the metal foils 1, 6 can be seen, which are formed or delimited by the slots 2. In addition, the edge sections 4 can be seen at the circumferentially aligned foil end.

[0042]FIG. 4 illustrates an device for exhaust gas aftertreatment, in particular exhaust gases of an internal combustion engine, which can be arranged within an exhaust gas path (indicated by a dashed line) through which the exhaust gas can flow. It comprises a matrix 8 with a large number of (parallel) flow channels 9 formed therein, through which gas can flow along a defined main flow direction (along the axial extension L) from a gas inlet side (front view) to a gas outlet side (rear view, not shown). The matrix 8 comprises a plurality of metal foils 1, 6 stacked in layer stacks and wound around at least one pivot point 10 (here S-shaped around two pivot points 10). The matrix 8 has an axial extension L extending along the main flow direction and a radial extension or circumferential direction B extending transversely to the axial extension L. circumferential direction B.

[0043]The embodiments shown in FIGS. 1 to 4 are not intended to be limiting and serve only to illustrate the concept of the invention.

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