Apparatus for exhaust gas aftertreatment having a slotted matrix

Abstract

The invention relates to an apparatus for the aftertreatment of exhaust gases, in particular exhaust gases of an internal combustion engine, wherein the apparatus can be arranged within an exhaust gas tract through which the exhaust gas can flow and through which said flow can pass in a main flow direction defined by a plurality of flow channels formed in the matrix (8) from a gas inlet side to a gas outlet side, wherein the matrix (8) is formed from a plurality of metal foils (1, 6), which are stacked on top of one another to form a layer stack and are wound around at least one rotation point, wherein the matrix (8) has an axial extent running along the main flow direction and a radial extent running transversely to the axial extent, wherein all the metal foils (1, 6) have a plurality of slots (2), wherein the slots (2) of the individual metal foils (1, 6) are congruent with one another in the wound state and run in the circumferential direction of the matrix (8).

Description

[0001] Exhaust gas aftertreatment device with a slotted matrix

[0002] The invention relates to a device for the aftertreatment of exhaust gases, in particular exhaust gases from an internal combustion engine. The device is arranged or can be arranged within an exhaust gas path through which the exhaust gas can flow, and can flow along a main flow direction defined by a plurality of flow channels formed in the matrix, from a gas inlet side to a gas outlet side. The matrix is ​​formed from a plurality of metal foils stacked one on top of the other to form a layer stack and wound around at least one pivot point. The matrix has an axial extension running along the main flow direction and a radial extension running transversely to the axial extension.

[0003] For the purpose of exhaust gas aftertreatment of an internal combustion engine, and in particular for converting the pollutants contained in the exhaust gas, various catalysts can be installed in the exhaust system. These catalysts typically comprise a honeycomb structure through which flow can occur along a plurality of flow channels. This structure has a catalytically active surface where the chemical reaction of the pollutants into non-critical products takes place.

[0004] Metallic honeycomb bodies are known which are formed from a plurality of metal foils stacked on top of one another to form a layer stack and cut to a defined length. The stacked metal foils are at least partially wound or wound 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 throughout are used for the honeycomb body, which are preferably stacked alternately on top of one another. The so-called cells form between the metal foils and form flow channels of the honeycomb body through which flow can take place along a main flow direction from a gas inlet side to a gas outlet side. The honeycomb body thus produced, 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 at least partially structured metal foils extend continuously across the entire axial extent of the honeycomb body. It is also possible to create a carrier matrix entirely from structured metal foils, with the structures, for example, positioned at an angle to each other so that the metal foils do not interlock.

[0005] A particular disadvantage of the designs known in the prior art is that the known honeycomb bodies are designed as a single piece along their axial extent and therefore have only limited flexibility.

[0006] It was also discovered that during rapid heating or cooling, due to the heat capacity of the metal foils and the support tube, both radial and axial temperature differences arise within the honeycomb body. These temperature gradients result in torsional loading of the honeycomb body between the axially cold and warm regions, which is transmitted via the metal foils in the form of tangential shear forces.

[0007] In particular, at high temperature loads, a temperature gradient develops along the axial extent 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 failure of the component. Therefore, the object of the present invention is to at least partially solve the problems described with reference to the prior art and, in particular, to create a device with a honeycomb body which has a design in which, in particular, the temperature-induced torsion of the matrix is ​​reduced or even mitigated and / or counteracts structural damage to the matrix.

[0008] The object of the device is achieved by a device having the features of claim 1. Advantageous further developments are specified in the dependent claims. The features individually recited in the claims can be combined with each other and / or with the facts of the description as desired. The description, particularly in conjunction with the figures, explains the invention and provides additional embodiments.

[0009] A device for the aftertreatment of exhaust gases, in particular exhaust gases from an internal combustion engine, contributes to this, wherein the device is arranged or can be arranged within an exhaust gas path through which the exhaust gas can flow and can flow along a main flow direction defined by a plurality of flow channels formed in 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 one another to form a layer stack and wound or wound around at least one pivot point, wherein the matrix has an axial extent running along the main flow direction and a radial extent running transversely to the axial extent. All metal foils have a plurality of slits, wherein the slits of the individual metal foils are congruent with one another in the wound or wound state and run in the circumferential direction of the matrix.

[0010] The arrangement of the slits in all metal foils is particularly advantageous because it prevents the foils from experiencing different levels of force, in particular torsional moments, due to a different number of slits and / or a twisted position relative to one another, thus leading to a critical stress state in the matrix.

[0011] The number and arrangement of the slots in each of the metal foils is therefore identical in order to create a uniform stress state across the individual metal foils as a result of thermal loads. The slots primarily serve to mechanically relieve the stress on the metal foils and are intended to prevent the generation of high torsional moments or to reduce the effects of torsional moments on the matrix. The slots do not pursue the (primary) purpose of promoting the overflow of exhaust gas between different (parallel or adjacent) flow channels. Therefore, 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.

[0012] The matrix may comprise a plurality of layer stacks. The at least one layer stack may be wound and / or twisted around at least one pivot point,

[0013] 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 wound (or wound up). "Congruent" also means, in particular, that the slots or an equal number of slots in the metal foils overlap in radial direction when the metal foils are wound (or wound up). The overlapping slots can together form one or more slot gaps in the matrix.

[0014] The wound state is particularly present when the metal foils or matrix are attached in the housing or carrier tube.

[0015] The circumferential direction is particularly characterized by the orientation of the metal foils in the wound (or wound) state, perpendicular to the axial extent of the matrix. The slots are preferably at least 20 times longer than they are wide. Particularly preferably, the slots are even 50 times longer than they are wide. However, in an advantageous embodiment, the slots can also be 500 times or more longer than they are wide.

[0016] 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 one another are arranged in the axial direction / extension.

[0017] The slit pattern refers in particular to the number and relative position of the slits, especially in a metal foil. A slit pattern in the circumferential direction therefore describes how many slits are formed in a predetermined axial plane, spaced apart from one another in the circumferential direction. Several such slit patterns in the circumferential direction can be provided axially spaced apart in a metal foil. The totality of the slit patterns in the circumferential direction of a metal foil can be referred to as the overall slit pattern of the metal foil.

[0018] A number of two slots in each circumferential direction is advantageous because it specifically increases the flexibility of the matrix, which allows for the compensation of disruptive forces within the elastic deformation. At the same time, the durability and stability of the matrix, which is required for use in an exhaust system, are not excessively reduced.

[0019] It is also advantageous if the two slits of the slit pattern are separated from each other by a central web and each by an edge web from the respective edge of the metal foil. The central web and edge web are formed from the metal foil material. By placing an edge web at the layer outlet or end of the metal foil in the circumferential direction, i.e., before and after the slits in the circumferential direction, it is ensured that the individual metal foils have sufficient stability to prevent tearing during assembly and to avoid structural damage during use.

[0020] A preferred embodiment is characterized in that the individual metal foils, particularly depending on their position in the layer stack, have slits of varying lengths in the circumferential direction. The slit lengths are selected such that, in the wound (or wound) state of the matrix, the slits of the individual metal foils are congruent with one another.

[0021] By winding or coiling the metal foils to form the matrix, areas of different bending radii are created within the metal foils. This refers to the (overarching) path of the metal foils and not the (inherent) structuring of the metal foil. An area closer to the center of the matrix has a smaller bending radius than an area at the radial edge of the matrix. If the metal foils all have slots of exactly the same length, the winding process will sometimes result in offsets 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 one in the area of ​​a smaller bending radius.

[0022] By adjusting the slot lengths in the circumferential direction, this phenomenon can be counteracted and it can be ensured that the slots are arranged exactly congruently when wound up.

[0023] In other words, this means that the slot lengths are selected depending on a bending radius of the metal foil in the area of ​​the slot in the wound state.

[0024] The metal foils can be of different lengths along the circumferential direction of the wound matrix. This is advantageous in that, particularly in the end regions which form the foil outlet, the individual metal foils run out slightly offset in order to produce a more precise shape for the matrix. In particular with a typically circular cross-section, a more precise shape is achieved in this way. Furthermore, it is advantageous if the central web and / or the edge webs have a length of 0.5 mm to 50.0 mm [millimeters], preferably a length of 1.0 mm to 10.0 mm, particularly preferably a length of 1.5 mm to 5.0 mm. The central web and the edge webs 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 webs serve in particular to create a sufficiently high integral stability to ensure the assembly and safe operation of the matrix.

[0025] The slots can have a width of 0.1 mm to 10.0 mm [millimeters], preferably a width of 0.1 mm to 2.0 mm, particularly preferably a width of 0.1 mm to 0.5 mm. The slots are preferably very narrow or designed with a particularly narrow width as specified here. This serves in particular to prevent the exhaust gas from overflowing through these slots, or at least to keep the overflow as small as possible. The slots have no (significant or substantial) flow-guiding effect, but serve (practically) solely to create a sufficiently flexible matrix structure.

[0026] 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 bordering the slot are in direct contact with one another. Depending on the stress state in the matrix, the edges bordering the slot can be in contact with one another completely or only partially. In such a design, the base material is separated (only or in this way) when cutting the slots, without any material being removed.

[0027] The slots can divide the metal foils into several axial segments, where an axial segment has a length of 1.0 mm to 50.0 mm [millimeters], preferably from 5.0 mm to 30.0 mm, particularly preferably from 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. Central webs 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 one another.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 to avoid inhomogeneous stress states in the axial direction of the matrix.

[0028] The slot patterns (in the circumferential direction) can be arranged equidistantly, i.e., at the same distance from each other, along the axial extent. This is advantageous for achieving the most homogeneous stress distribution possible across the matrix.

[0029] The invention and its environment are explained in detail below using exemplary embodiments with reference to the schematic drawings. It should be noted that elements designated by the same reference numerals in the drawings may have the same properties, unless explicitly stated otherwise. The illustrated elements in the drawings may be further characterized by facts from other drawings and / or the description and / or the claims (and vice versa), unless explicitly excluded below. The drawings show:

[0030] Fig. 1 is a perspective view of a corrugated metal foil with a slit pattern,

[0031] Fig. 2 is a detailed view of the corrugated metal foil of Fig. 1,

[0032] Fig. 3 is a schematic view of a slotted matrix in a jacket tube, and Fig. 4 is a perspective view of a device for aftertreating exhaust gases with a matrix in a jacket tube.

[0033] Fig. 1 shows a view of a structured metal foil 1. The metal foil 1 has a length L, which corresponds to the axial extent of the wound matrix. Furthermore, the metal foil 1 has a width B, which, in the final assembled matrix, runs in the circumferential direction or perpendicular to the axial extent.

[0034] The metal foil 1 has a plurality of slots 2, which run along the width B or in the circumferential direction and are arranged equidistantly from one another along the length L. Along the width B, two slots 2 are spaced from one another by a central web 3 (see also enlarged detail). The slots 2 are each spaced from the edges or end regions of the metal foil 1 by the width of an edge web 4. The slots 2 create several axial segments 5 along the length L.

[0035] Fig. 2 shows a detailed view of the metal foil 1. Here, it can be seen that a smooth metal foil 6 is arranged beneath the corrugated metal foil 1. The metal foils 1, 6 lie congruently on top of one another. Identical slit patterns are formed in both metal foils 1, 6 and are arranged congruently with one another.

[0036] In Fig. 2, the edge webs 4 can also be clearly seen (see also enlarged detail), which are formed between the slots 2 and the end of the film.

[0037] Fig. 3 shows a view of a matrix 8 accommodated in a casing tube 7, which matrix is ​​formed from metal foils 1 and 6 from Figs. 1 and 2. Along the axial extent, 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 webs 4 can be seen at the circumferentially oriented foil end. Fig. 4 illustrates a device for the aftertreatment of exhaust gases, in particular exhaust gases from an internal combustion engine, which device can be arranged within an exhaust gas path through which the exhaust gas can flow (indicated by dashed lines). It comprises a matrix 8 with many (parallel) flow channels 9 formed therein, through which flow can be carried out along a defined main flow direction (along the axial extent 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 on top of one another to form layer stacks and wound around at least one pivot point 10 (here in an S-shape around two pivot points 10). The matrix 8 has an axial extent L running along the main flow direction and a radial extent or circumferential direction B running transversely to the axial extent L.

[0038] The embodiments of Figs. 1 to 4 are in particular not restrictive in nature and serve to clarify the inventive concept.

[0039] List of reference symbols

[0040] 1 corrugated metal foil

[0041] 2 slots

[0042] 3 Central bridge

[0043] 4 edge web

[0044] 5 axial segment

[0045] 6 smooth metal foil

[0046] 7 jacket pipe

[0047] 8 Matrix

[0048] 9 Flow channel

[0049] 10 Pivot point

[0050] 11 Edge web

[0051] L Length matrix (axial extension)

[0052] B Width matrix (circumferential direction)

Claims

Patent claims 1. Device for the aftertreatment of exhaust gases, in particular exhaust gases from an internal combustion engine, wherein the device can be arranged within an exhaust gas path through which the exhaust gas can flow and can flow through it along a main flow direction defined by a plurality of flow channels (6) formed in the matrix (8) from a gas inlet side to a gas outlet side, wherein the matrix (8) is formed from a plurality of metal foils (1, 6) stacked on top of one another to form a layer stack and wound around at least one pivot point, wherein the matrix (8) has an axial extent running along the main flow direction and a radial extent running transversely to the axial extent, characterized in that all metal foils (1, 6) have a plurality of slots (2), wherein the slots (2) of the individual metal foils (1,6) in the wound state are congruent with each other and run in the circumferential direction of the matrix (8)., 2. Device according to claim 1, characterized in that the metal foils (1, 6) have a slot pattern of exactly two slots (2) in the circumferential direction, wherein a plurality of slot patterns spaced apart from one another are arranged in the axial direction.

3. Device according to claim 2, characterized in that the exactly two slots (2) of the slot pattern are separated from one another by a central web (3) and are separated from the respective edge of the metal foil (1, 6) by an edge web (4).

4. Device according to one of the preceding claims, characterized in that the individual metal foils (1, 6) have slots (2) of different lengths in the circumferential direction.

5. Device according to claim 4, characterized in that the slot lengths are selected depending on a bending radius of the metal foil (1, 6) in the region of the slot (2) in the wound state. Device according to one of the preceding claims, characterized in that the metal foils (1, 6) are of different lengths along the circumferential direction of the wound matrix (8). Device according to one of the preceding claims, characterized in that the central web (3) and / or the edge webs (4) have a length of 0.5 mm to 50 mm, preferably a length of 1 mm to 10 mm, particularly preferably a length of 1.5 mm to 5 mm. Device according to one of the preceding claims, characterized in that the slots (2) have a width of 0.1 mm to 10 mm, preferably a width of 0.1 mm to 2 mm, particularly preferably a width of 0.1 mm to 0.5 mm.Device according to one of the preceding claims, characterized in that the slots (2) divide the metal foils (1, 6) into a plurality of axial segments (5), wherein an axial segment (5) has a length of 1 mm to 50 mm, preferably of 5 mm to 30 mm, particularly preferably of 10 mm to 20 mm. Device according to one of the preceding claims, characterized in that the central webs (3) between the individual slot patterns are aligned in the axial direction, so that the slots (2) are also aligned with one another along the axial extent. Device according to one of the preceding claims, characterized in that the slot patterns are arranged equidistant from one another along the axial extent.

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