Patent Application
20240418115
The disclosure 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 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, wherein the metal foils have a foil width and a foil length, wherein the width of the foils runs along the main throughflow direction of the honeycomb body from a gas inlet side to a gas outlet side, and the foil length runs transversely to this direction.
For the purpose of exhaust-gas aftertreatment of the exhaust gases from an internal combustion engine and in particular for the conversion of the pollutants present in the exhaust gas, various catalytic converters are installed in the exhaust-gas line. The catalytic converters generally have a honeycomb body through which flow can pass along a plurality of flow ducts and which has a catalytically active surface on which the chemical reaction of the pollutants into harmless products takes place.
Metallic honeycomb bodies are known which are formed from a plurality of metal foils, which are stacked on one another to form a layer stack and are cut to a defined length. The metal foils stacked on one another are wound at least around a center of rotation, as a result of which the honeycomb body is formed. For the honeycomb body, both smooth, unstructured metal foils and metal foils, which are structured at least in some sections are used, which metal foils are preferably stacked alternatingly on one another. The so-called cells are formed between the metal foils and form the flow ducts of the honeycomb body through which flow can pass along a main throughflow direction from a gas inlet side to a gas outlet side.
The honeycomb body produced in this way, which is also known as a support matrix, is then pressed into a housing known as a support pipe and soldered thereto. In known catalytic converter designs, both the completely smooth metal foils and the metal foils which are structured at least in some sections extend continuously over the full axial length of the honeycomb body.
The designs previously known in the prior art are disadvantageous in particular in that the known honeycomb bodies are designed in one piece along their axial extent and therefore have only limited flexibility in the axial direction. During rapid heating and rapid cooling, temperature differences, caused by the heat capacity of the metal foils and of the support pipe, occur both radially and axially in the honeycomb body. These temperature gradients result in torsional loading of the honeycomb body between the cold and warm regions in the axial direction, which are transmitted in the form of tangential shear forces via the metal foils.
In applications with high thermal loading, the reduction of the tangential shear forces when the particular yield point of the material of the metal foils is exceeded results in plastic deformation of the metal foils. This occurs primarily in the radial edge region of the honeycomb body or in the center thereof, 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 catalytic converter can decrease, because the catalytically active coating flakes off. Moreover, the engine power can be negatively affected by the increase in the counterpressure in the honeycomb body. Moreover, components downstream in the flow direction can be functionally impaired and in the worst case destroyed, since parts of the flaked-off catalytically active coating, in particular the precious metals present therein, can trigger undesirable chemical interactions with the downstream components.
The object of one aspect of the present invention is therefore to create a honeycomb body which has increased flexibility in the axial direction, as a result of which the plastic deformation of the metal foils is reduced in applications with high thermal loading.
An exemplary aspect 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 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, wherein the metal foils have a foil width and a foil length, wherein the width of the foils runs along the main throughflow 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 some metal foils have at least some slots which divide the respective metal foil into a plurality of segments.
The foils are formed from thin metal sheets, which have a length and a width which are substantially longer than the thickness of the sheet in question. In the honeycomb body according to one aspect of the invention, the width of the metal foil refers to the extent in the axial direction of the wound-up honeycomb body. The length of the metal foil runs in an orthogonal direction to the width and, in the wound-up honeycomb body, runs in the circumferential direction of the honeycomb body. The metal foils have slots which cut through the metal foils at least in some sections and in this way produce a segmentation of the metal foil and thus of the honeycomb body. Owing to the slots, the individual segments are mechanically decoupled from one another, as a result of which the flexibility of the honeycomb body is increased, and at the same time the structural integrity of the honeycomb body remains ensured, since the honeycomb body is not cut through completely.
It is particularly advantageous when the slots run in the direction of the foil length. The slots run along the foil length, as a result of which the segmentation takes place such that a plurality of segments lined up in the axial direction are produced. When the metal foils are rolled up, the slots in the honeycomb body run in the circumferential direction of the honeycomb body. The axial segments are advantageous in particular to produce an increased flexibility of the honeycomb body, to compensate for thermally induced stresses in the honeycomb body, and in particular to prevent the washcoat applied to the metal foils, i.e., the catalytically active coating, from breaking up and breaking off.
It is also advantageous when the slots are arranged parallel to one another along the foil width and are spaced from one another along the foil length.
A plurality of slots running along the foil length form a slot row. The slots in a slot row are spaced from one another, so the metal foil is not cut through completely.
A plurality of slot rows are spaced from one another and arranged parallel to one another along the foil width, as a result of which the individual axial segments are formed in the rolled-up honeycomb body.
A preferred exemplary aspect is characterized in that a plurality of slots in a row running along the foil length are spaced from one another by a connecting piece. The connecting piece helps to ensure that the slots do not cut through the entire metal foil along its length with the result that the metal foil becomes unstable or is destroyed. The strength of the metal foil in question can be influenced via the connecting piece width.
It is also preferable when a plurality of slot rows are spaced from one another along the main throughflow direction, wherein preferably 1 to 20 slot rows are provided, particularly preferably 1 to 12 slot rows.
Honeycomb bodies for exhaust-gas aftertreatment in cars generally have an axial length of 30 mm to 180 mm, for which reason it has been found in extensive experiments that a number of 1 to 20 slot rows or preferably 1 to 12 slot rows is particularly advantageous on the one hand to produce sufficient flexibility to prevent the catalytically active coating from breaking up and on the other hand to have sufficient stability in the layer stack so that the mechanical process of rolling up around the winding mandrel(s) does not result in damage to the metal foils.
Furthermore, it is advantageous when the connecting pieces between the slots of a slot row have a length of 0.5 mm to 20 mm, particularly preferably of 1 mm to 10 mm. This measure has been found to be particularly advantageous also with regard to the usually used sizes for honeycomb bodies to achieve the balance between flexibility and stability.
Furthermore, it is advantageous when the length of the connecting pieces in the center and/or at the edge region of the metal foil in question is longer than the length of the connecting pieces between the center and the edge region of the metal foil.
It is also expedient when the slot width in the direction of the foil width is less than 2 mm, particularly preferably less than 1 mm. Since the purpose of the slots is primarily to interrupt the shear forces occurring under thermal loading, and the slots are not intended to have any exhaust-gas-conducting effect, it is expedient to keep the slots as narrow as possible.
The slots can advantageously be produced by a partially interrupted rolling blade, for example. Alternatively, a rolling blade can also be effected by controlled penetration into the foil plane. The slots can also be produced by laser welding.
Furthermore, it is advantageous when the slot rows are distributed unevenly along the foil width. Specific installation situations can be reacted to particularly simply by an uneven distribution of the slot rows. Different temperature profiles can thus be achieved on different honeycomb bodies, so the interruption of the shear forces in some regions of the honeycomb body must take place to a greater extent than in other regions. In this case, a solution tailored to the use case can be achieved by the targeted arrangement of the slot rows.
Furthermore, it is expedient when the spacings of the slot rows in the region of the gas inlet side are different from the spacings of the slot rows on the gas outlet side.
This is particularly advantageous, since the temperatures occurring on the gas inlet side and the gas outlet side can differ from one another. Although the temperature equalizes over the operating time, higher temperatures initially occur more rapidly on the gas inlet side than on the gas outlet side, which is why an additional temperature gradient occurs here.
A further advantage of the slots is a reduction in the axial thermal conduction through the honeycomb body, as a result of which a better heating-up behavior of the honeycomb body is achieved.
The slotting process is preferably integrated directly in the process of manufacturing the conventional honeycomb body and can be carried out on the individual metal foils which have been cut to size or on an endless metal foil. Particularly preferably, both the smooth metal foils and the metal foils, which are structured at least in some sections are provided with slots. In the case of the metal foils which are structured at least in some sections, the slotting process is carried out before the structuring process. In particular in the case of the metal foils which are structured at least in some sections, the slots and connecting piece lengths are adapted to the shortening factor applicable to the structure in question, for example a corrugation.
Advantageous developments of the present invention are described in the dependent claims and in the following description of the figures.
Aspects of the invention will be explained in more detail below with reference to the drawings, in which:
The metal foil 1 has a plurality of slots 2, which run along the foil length 3. The individual slot rows 4 are spaced from one another and arranged parallel to one another in the direction of the foil width 5. The metal foil 1 is divided into segments 8 by the slot rows 4. The segments 8 are arranged adjacently to one another in the axial direction of the finished honeycomb body.
Connecting pieces 6, 7 are arranged between the individual slots 2 of a slot row 4. In the exemplary embodiment of
The metal foil 1 forms a single layer in the layer stack, which is then wound up to form the honeycomb body.
In contrast to
The different features of the individual exemplary embodiments can also be combined with one another. The slot rows can also be arranged differently from the exemplary embodiments shown here. For instance, the segments can also get wider or narrower from the gas outlet side to the gas inlet side.
The exemplary embodiments of
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 211 453.9 | Oct 2021 | DE | national |
This is a U.S. national stage of Application No. PCT/EP2022/076784 filed Sep. 27, 2022. Priority is claimed on German Application No. DE 10 2021 211 453.9 filed Oct. 11, 2021, the content of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/076784 | 9/27/2022 | WO |
