Honeycomb body for exhaust gas aftertreatment with slotted metal foils

Description

Technical field

[0001] The invention relates to a honeycomb body for the aftertreatment of exhaust gases from an internal combustion engine, wherein the honeycomb body is formed from a plurality of metal foils which are stacked on top of one another to form a layer stack and are wound around at least one pivot point, wherein the layer stack is formed alternately from smooth and at least partially structured metal foils, wherein the metal foils have a foil width and a foil length, wherein the width of the foils runs along the main flow direction of the honeycomb body from a gas inlet side to a gas outlet side and the foil length runs transversely to this direction. State of the art

[0002] 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 are installed in the exhaust system. These catalysts typically comprise a honeycomb structure through which flow can occur along a plurality of flow channels. This honeycomb structure has a catalytically active surface where the chemical reaction of the pollutants into non-critical products takes place.

[0003] 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 wound around at least one pivot point, thereby forming the honeycomb body. Both smooth, unstructured metal foils and metal foils that are structured at least in sections and are preferably stacked alternately on top of one another are used for the honeycomb body. The so-called cells form between the metal foils and form the 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 resulting honeycomb body, also known as a support matrix, is then pressed into a housing known as a support tube and soldered to it. In known catalyst designs, both the completely smooth metal foils and the metal foils that are structured at least in sections extend continuously over the entire axial length of the honeycomb body.

[0005] Honeycomb bodies are known from the following publications: EP 0 569 400 B2, EP 0 682 742 B1, EP 0 705 962 A1 or US 5 791 043 A.

[0006] A particular disadvantage of the designs known in the prior art is that the known honeycomb bodies are constructed in one piece along their axial extent, thus exhibiting only limited flexibility in the axial direction. During rapid heating or cooling, both radial and axial temperature differences arise within the honeycomb body due to the heat capacity of the metal foils and the support tube. 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 applications subject to high thermal stress, the reduction of tangential shear forces upon exceeding the respective yield strength of the metal foil material leads to plastic deformation of the metal foils. This deformation occurs primarily in the radial edge region of the honeycomb body or in its center, but also in the intermediate regions between the center and the radial edge region. As a result of this plastic deformation, the conversion rate of the catalyst can be reduced due to the flaking of the catalytically active coating. Furthermore, engine performance can be negatively affected by the increased backpressure in the honeycomb body.In addition, this can lead to a functional restriction and, in the worst case, to the destruction of downstream components in the flow direction, since parts of the flaked-off catalytically active coating, in particular the precious metals contained therein, can trigger undesirable chemical interactions with the downstream components. Description of the invention, task, solution, advantages

[0008] Therefore, the object of the present invention is to provide a honeycomb body which has increased flexibility in the axial direction, thereby reducing the plastic deformation of the metal foils in thermally highly stressed applications.

[0009] The problem with regard to the honeycomb body is solved by a honeycomb body having the features of claim 1.

[0010] One embodiment of the invention relates to a honeycomb body for the aftertreatment of exhaust gases from an internal combustion engine, wherein the honeycomb body is formed from a plurality of metal foils which are stacked on top of one another to form a layer stack and are wound around at least one pivot point, wherein the layer stack is formed alternately from smooth and at least partially structured metal foils, wherein the metal foils have a foil width and a foil length, wherein the width of the foils runs along the main flow direction of the honeycomb body from a gas inlet side to a gas outlet side and the foil length runs transversely to this direction, wherein at least individual metal foils have at least individual slits which divide the respective metal foil into a plurality of segments.

[0011] The foils are formed from thin metal sheets that have a length and a width that are significantly longer than the thickness of the respective sheet. In the honeycomb body according to the invention, the width of the metal foil refers to the extension in the axial direction of the wound honeycomb body. The length of the metal foil runs in a direction orthogonal to the width and, in the wound honeycomb body, runs in the circumferential direction of the honeycomb body. The metal foils have slits that sever the metal foils at least in sections, thus creating a segmentation of the metal foil and thus of the honeycomb body. The slits mechanically decouple the individual segments from one another, thereby increasing the flexibility of the honeycomb body, while at the same time ensuring the structural integrity of the honeycomb body because the honeycomb body is not completely severed.

[0012] According to the invention, the slits run in the direction of the film length.

[0013] The slits run along the length of the foil, resulting in segmentation that creates several segments arranged in an axial direction. By rolling up the metal foils, the slits in the honeycomb body run in the circumferential direction of the honeycomb body. The axial segments are advantageous, in particular, for creating increased flexibility of the honeycomb body, for compensating for thermally induced stresses in the honeycomb body, and, in particular, for preventing the washcoat applied to the metal foils, i.e., the catalytically active coating, from cracking and breaking off.

[0014] It is also advantageous if the slots are arranged parallel to each other along the film width and spaced apart from each other along the film length.

[0015] Several slits running along the length of the foil form a slit row. The slits within a slit row are spaced apart from each other so that the metal foil is not completely severed.

[0016] Several rows of slots are spaced apart along the film width and arranged parallel to each other, forming the individual axial segments in the rolled-up honeycomb body.

[0017] A preferred embodiment is characterized in that several slits are arranged in a row running along the length of the foil, spaced apart by a web. The web helps ensure that the slits do not sever the entire length of the metal foil, thereby rendering the metal foil unstable or destroyed. The strength of the respective metal foil can be influenced by the web width.

[0018] It is also preferable if several rows of slots are arranged at a distance from one another along the main flow direction, wherein preferably 1 to 20 rows of slots are provided, particularly preferably 1 to 12 rows of slots.

[0019] Honeycomb bodies for the exhaust gas aftertreatment of cars regularly have an axial length of 30mm to 180mm, which is why extensive studies have shown that a number of 1 to 20 rows of slots or preferably 1 to 12 rows of slots is particularly advantageous in order to create sufficient flexibility to prevent the catalytically active coating from breaking up and to have sufficient stability in the layer stack so that the mechanical process of rolling up around the winding mandrel or mandrels does not lead to damage to the metal foils.

[0020] Furthermore, it is advantageous if the webs arranged between the slots in a row have a length of 0.5 mm to 20 mm, particularly preferably 1 mm to 10 mm. This dimension has also proven particularly advantageous in terms of the commonly used sizes for honeycomb bodies, achieving a balance between flexibility and stability.

[0021] Furthermore, it is advantageous if the length of the webs in the center and / or at the edge area of ​​the respective metal foil is longer than the length of the webs between the center and edge area of ​​the metal foil.

[0022] It is also advisable for the slot width along the film width to be less than 2 mm, particularly preferably less than 1 mm. Since the primary purpose of the slots is to interrupt the shear forces that occur under thermal stress and, furthermore, the slots are not intended to exert any exhaust gas conducting effect, it is advisable to keep the slots as narrow as possible.

[0023] The slits can advantageously be created, for example, using a partially interrupted rolling knife. Alternatively, a rolling knife can be created by controlled immersion into the film plane. The slits can also be created using laser welding.

[0024] Furthermore, it is advantageous if the rows of slots are distributed unevenly across the film width. This uneven distribution of the rows of slots makes it particularly easy to respond to specific installation situations. This allows different temperature profiles to be achieved on different honeycomb structures, meaning that the interruption of shear forces must occur to a greater extent in certain areas of the honeycomb structure than in other areas. By precisely arranging the rows of slots, a solution can be achieved that is individually tailored to the application.

[0025] Furthermore, it is expedient if the distances between the rows of slots in the area of ​​the gas inlet side are different from the distances between the rows of slots on the gas outlet side.

[0026] This is particularly advantageous because the temperatures occurring at the gas inlet and outlet sides can differ from each other. Although the temperature will equalize over time, initially higher temperatures occur more quickly at the gas inlet side than at the gas outlet side, resulting in an additional temperature gradient.

[0027] A further advantage of the slots is a reduction in axial heat conduction through the honeycomb body, which results in better heating behavior of the honeycomb body.

[0028] The slitting process is preferably integrated directly into the manufacturing process of the conventional honeycomb body and can be performed on the cut individual metal foils or on a continuous metal foil. Particularly preferably, both the smooth metal foils and the metal foils structured at least in sections are provided with slits. In the case of metal foils structured at least in sections, the slitting process precedes the structuring process. Especially in the case of metal foils structured at least in sections, the slits and web lengths are adapted to the shortening factor applicable to the respective structure, for example, a corrugation.

[0029] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures. Short description of the drawings

[0030] The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings: Fig. 1 is a plan view of a metal foil, wherein the rows of slots are shown spaced apart along the foil width and the slots arranged within the row of slots along the foil length, Fig. 2 is a sectional view through a honeycomb body in a support tube, wherein several rows of slots are arranged evenly spaced along the main flow direction, Fig. 3 is a sectional view through a honeycomb body in a support tube, wherein several rows of slots are arranged unevenly spaced along the main flow direction, and Fig. 4 is a sectional view through a honeycomb body in a support tube, wherein several rows of slots are arranged unevenly spaced along the main flow direction, wherein the distances between the rows of slots are different on the gas inlet side and the gas outlet side. Preferred embodiment of the invention

[0031] The Figure 1shows a top view of a metal foil 1. The metal foil 1 shown is a smooth metal foil without a structure. What is described below for this smooth metal foil 1 can also apply to a metal foil that is structured at least in sections.

[0032] The metal foil 1 has a plurality of slits 2 running along the foil length 3. The individual slit rows 4 are arranged parallel to one another and spaced apart in the direction of the foil width 5. The slit rows 4 divide the metal foil 1 into segments 8. The segments 8 are arranged adjacent to one another in the axial direction of the finished honeycomb body.

[0033] Between the individual slots 2 of a slot row 4, webs 6, 7 are arranged. The webs 6 in the center of the metal foil 1 and at the outer edge areas are in the embodiment of the Figure 1wider than the webs 7 in the intermediate area The metal foil 1 forms a single layer in the layer stack, which is then wound up to form the honeycomb body.

[0034] Figure 2 shows a sectional view through a honeycomb body 9, which is arranged in a casing tube 10. The honeycomb body 9 can be flowed through from a gas inlet side 11 to the gas outlet side 12 along the flow channels 16 formed by the metal foils. The reference numeral 13 represents the slots that divide the honeycomb body 9 into several segments 14. In the embodiment of the Figure 2 the rows of slots 15 are arranged equidistantly over the axial extent of the honeycomb body 9.

[0035] Figure 3 shows a honeycomb body 9 in a casing tube 10. The honeycomb body 9 corresponds to the structure of the Figure 2 shown honeycomb body 9. The reference numerals are the same for identical elements.

[0036] In contrast to Figure 2 the rows of slots 15 are unevenly distributed, so that in the area of ​​the gas inlet side 11 a narrow segment 17 is formed, to which several equally wide segments 18 are connected.

[0037] Figure 4 shows an alternative design of a honeycomb body 9. The rows of slots 19 are arranged such that the segments 20 become continuously wider from the gas inlet side 11 to the gas outlet side 12.

[0038] The different features of the individual embodiments can also be combined with one another. The arrangement of the rows of slots can also differ from the embodiments shown here. For example, the segments can become wider or narrower from the gas outlet side to the gas inlet side.

[0039] The examples of the Figures 1 to 4In particular, they are not restrictive and serve to clarify the inventive concept. List of reference symbols

[0040] 1.Metal foil 2.Slot 3.Foil length 4.Row of slots 5.Foil width 6.Web 7.Web 8.Segment 9.Honeycomb body 10.Support tube 11.Gas inlet side 12.Gas outlet side 13.Slot 14.Segment 15.Row of slots 16.Flow channels 17.Segment 18.Segment 19.Row of slots 20.Segment

Claims

1. Honeycomb body (9) for the aftertreatment of exhaust gases from an internal combustion engine, wherein the honeycomb body (9) is formed from a plurality of metal foils (1) which are stacked on one another to form a layer stack and are wound around at least one center of rotation, wherein the layer stack is formed alternatingly from smooth and at least partially structured metal foils (1), wherein the metal foils (1) have a foil width (5) and a foil length (3), wherein the width (5) of the foils (1) runs along the main throughflow direction of the honeycomb body (9) from a gas inlet side (11) to a gas outlet side (12), and the foil length (3) runs transversely to this direction, wherein at least some metal foils (1) have at least some slots (2, 13) which divide the respective metal foil (1) into a plurality of segments (8, 14, 17, 18, 20), characterized in that the slots (2, 13) run in the direction of the foil length (3).

2. Honeycomb body (9) according to one of the preceding claims, characterized in that the slots (2, 13) are arranged parallel to one another along the foil width (5) and are spaced from one another along the foil length (3).

3. Honeycomb body (9) according to one of the preceding claims, characterized in that a plurality of slots (2, 13) in a row running along the foil length (3) are spaced from one another by a connecting piece (6, 7).

4. Honeycomb body (9) according to one of the preceding claims, characterized in that a plurality of slot rows (4, 15, 19) are spaced from one another along the main throughflow direction, wherein preferably 1 to 20 slot rows (4, 15, 19) are provided, particularly preferably 1 to 12 slot rows (4, 15, 19).

5. Honeycomb body (9) according to one of the preceding claims, characterized in that the connecting pieces (6, 7) between the slots (2, 13) of a slot row (4, 15, 19) have a length of 0.5 mm to 20 mm, particularly preferably of 1 mm to 10 mm.

6. Honeycomb body (9) according to one of the preceding claims, characterized in that the length of the connecting pieces (6) in the center and / or at the edge region of the metal foil (1) in question is longer than the length of the connecting pieces (7) between the center and the edge region of the metal foil (1).

7. Honeycomb body (9) according to one of the preceding claims, characterized in that the slot width in the direction of the foil width (5) is less than 2 mm, particularly preferably less than 1 mm.

8. Honeycomb body (9) according to one of the preceding claims, characterized in that the slot rows (15, 19) are distributed unevenly along the foil width (5).

9. Honeycomb body (9) according to one of the preceding claims, characterized in that the spacings of the slot rows in the region of the gas inlet side (11) are different from the spacings of the slot rows on the gas outlet side (12).