DE102021211453A1 - Honeycomb body for the purpose of exhaust aftertreatment with slotted metal foils - Google Patents

Abstract

The invention relates to a honeycomb body (9) for after-treatment of exhaust gases from an internal combustion engine, the honeycomb body (9) being formed from a plurality of metal foils (1) which are stacked on top of one another to form a stack of layers and are wound around at least one pivot point, the stack of layers alternating is formed from smooth and at least partially structured metal foils (1), the metal foils (1) having a foil width (5) and a foil length (3), the width (5) of the foils (1) being along the main flow direction of the honeycomb body (9 ) runs from a gas inlet side (11) to a gas outlet side (12) and the foil length (3) transversely to this direction, wherein at least individual metal foils (1) have at least individual slots (2, 13) which the respective metal foil (1) into several segments (8, 14, 17, 18, 20).

Description

technical field

The invention relates to a honeycomb body for after-treatment of exhaust gases from an internal combustion engine, the honeycomb body being formed from a plurality of metal foils which are stacked on top of one another to form a stack of layers and wound around at least one pivot point, the stack of layers being formed alternately from smooth and at least partially structured metal foils , wherein the metal foils have a foil width and a foil length, the width of the foils running along the main flow direction of the honeycomb body from a gas inlet side to a gas outlet side and the foil length running transversely to this direction.

State of the art

Different catalytic converters are installed in the exhaust line for the purpose of after-treating the exhaust gases of an internal combustion engine and in particular for converting the pollutants contained in the exhaust gas. The catalytic converters regularly have a honeycomb body through which flow can take place along a large number of flow channels, which has a catalytically active surface on which the chemical reaction of the pollutants to form non-critical products takes place.

Metallic honeycomb bodies are known which are formed from a plurality of metal foils stacked on top of one another to form a stack of layers and cut to a defined length. The metal foils stacked on top of one another are wound up around at least one pivot point, as a result of which the honeycomb body is formed. For the honeycomb body, both smooth, unstructured metal foils are used, as well as metal foils that are structured at least in sections, which are preferably stacked alternately on top of one another. The so-called cells form between the metal foils, which form the flow channels of the honeycomb body through which flow can occur along a main flow direction from a gas inlet side to a gas outlet side.

The honeycomb body produced in this way, which is also known as a carrier matrix, is then pressed into a housing known as a carrier tube and soldered to it. In known catalytic converter 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.

A particular disadvantage of the designs hitherto known in the prior art is that the known honeycomb bodies are designed in one piece along their axial extension and they therefore have only limited flexibility in the axial direction. In the event of rapid heating or rapid cooling, temperature differences arise both radially and axially in the honeycomb body due to the heat capacity of the metal foils and the support tube. These temperature gradients result in a torsional load on the honeycomb body between the cold and warm areas in the axial direction, which are transmitted in the form of tangential shear forces via the metal foils.

In the case of thermally highly stressed applications, the dissipation of the tangential shear forces when the respective yield point of the material of the metal foils is exceeded leads to plastic deformation of the metal foils. These occur primarily in the radial edge area of the honeycomb body or in its center, but also in the intermediate areas lying between the center and the radial edge area. As a result of this plastic deformation, the conversion rate of the catalyst can be reduced due to the flaking off of the catalytically active coating. In addition, engine performance can be adversely affected by the increase in back pressure in the honeycomb. In addition, there may be a functional limitation and, in the worst case, destruction of downstream components in the direction of flow, since parts of the catalytically active coating that has flaked off, in particular the noble metals contained therein, can trigger undesirable chemical interactions with the downstream components.

Presentation of the invention, task, solution, advantages

It is therefore the object of the present invention 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 subject to high thermal stress.

The object with regard to the honeycomb body is achieved by a honeycomb body having the features of claim 1.

One exemplary embodiment of the invention relates to a honeycomb body for the aftertreatment of exhaust gases from an internal combustion engine, the honeycomb body being 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, the layer stack being composed alternately of smooth and at least partially structured metal foils is formed, the metal foils having a foil width and a foil length have, the width of the foils running along the main flow direction of the honeycomb body from a gas inlet side to a gas outlet side and the foil length running transversely to this direction, with at least individual metal foils having at least individual slots which divide the respective metal foil into a plurality of segments.

The foils are formed from thin sheets of metal having a length and width substantially greater than the thickness of each sheet. In the honeycomb body according to the invention, the width of the metal foil designates 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 runs in the circumferential direction of the honeycomb body in the wound honeycomb body. The metal foils have slits which cut through the metal foils at least in sections and thus produce a segmentation of the metal foil and thus of the honeycomb body. A mechanical decoupling of the individual segments from one another takes place through the slits, as a result of which the flexibility of the honeycomb body is increased, while at the same time the structural integrity of the honeycomb body remains guaranteed, since the honeycomb body is not completely severed.

It is particularly advantageous if the slits run in the direction of the length of the film. The slits run along the length of the foil, as a result of which the segmentation takes place in such a way that several segments are formed in a row in the axial direction. As a result of the metal foils being rolled up, the slots in the honeycomb body run in the circumferential direction of the honeycomb body. The axial segments are advantageous in order in particular to generate 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, ie the catalytically active coating, from breaking up and breaking off.

It is also advantageous if the slits are arranged parallel to one another along the width of the film and spaced apart from one another along the length of the film.

A number of slits running along the length of the film form a row of slits. The slits within a row of slits are spaced apart from one another, so that the metal foil is not completely severed.

Several rows of slits are spaced apart from one another along the width of the film and are arranged parallel to one another, as a result of which the individual axial segments are formed in the rolled-up honeycomb body.

A preferred exemplary embodiment is characterized in that a plurality of slits are arranged in a row running along the length of the film, spaced apart from one another by a web. The web helps to ensure that the slits do not cut through the entire length of the metal foil and the metal foil becomes unstable or is destroyed as a result. The strength of the respective metal foil can be influenced via the web width.

It is also preferable if a plurality of rows of slots are arranged spaced apart from one another along the main flow direction, with preferably 1 to 20 rows of slots being provided, particularly preferably 1 to 12 rows of slots.

Honeycomb bodies for the area of exhaust aftertreatment of passenger cars regularly have an axial length of 30mm to 180mm, which is why extensive investigations 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 ensure sufficient flexibility on the one hand produce in order to prevent the catalytically active coating from breaking up and on the other hand to have sufficient stability in the stack of layers that the mechanical process of rolling up around the winding mandrel or the winding mandrels does not lead to damage to the metal foils.

In addition, it is advantageous if the webs arranged between the slits of a row of slits have a length of 0.5 mm to 20 mm, particularly preferably 1 mm to 10 mm. This dimension has also turned out to be particularly advantageous with regard to the sizes usually used for honeycomb bodies, in order to achieve the balance between flexibility and stability.

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.

It is also expedient if the slit width in the direction of the film width is less than 2 mm, particularly preferably less than 1 mm. Since the purpose of the slits is primarily to interrupt the shear forces occurring under thermal stress and, moreover, the slits should not have any exhaust-gas-conducting effect, it is expedient to keep the slits as narrow as possible.

The slits can advantageously be produced, for example, by means of a partially interrupted rolling knife. Alternatively, a rolling knife can also be made by controlled immersion in the plane of the film. The slots can also be produced by means of laser welding.

In addition, it is advantageous if the rows of slits are unevenly distributed along the width of the film. An uneven distribution of the rows of slots makes it particularly easy to react to specific installation situations. Different temperature profiles can thus be achieved on different honeycomb bodies, so that the interruption of the shear forces in individual areas of the honeycomb body must take place to a greater extent than in other areas. By arranging the rows of slots in a targeted manner, a solution that is individually tailored to the application can be achieved.

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.

This is particularly advantageous since the temperatures that occur on the gas inlet side and the gas outlet side can deviate from one another. Although the temperature equalizes over the operating time, higher temperatures initially occur more quickly on the gas inlet side than on the gas outlet side, which is why there is an additional temperature gradient here.

A further advantage of the slits is a reduction in the axial heat conduction through the honeycomb body, as a result of which better heating behavior of the honeycomb body is achieved.

The slitting process is preferably integrated directly into the production process of the conventional honeycomb body and can be carried out on the individual metal foils that have been cut to size or on an endless metal foil. Particularly preferably, both the smooth metal foils and the metal foils that are structured at least in sections are provided with slits. In the case of metal foils that are structured at least in sections, the slitting process precedes the structuring process. In particular in the case of the metal foils which are 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.

Advantageous developments of the present invention are described in the dependent claims and in the following description of the figures.

character list

• 1 eine Aufsicht auf eine Metallfolie wobei die Schlitzreihen beabstandet entlang der Folienbreite und die innerhalb der Schlitzreihe entlang der Folienlänge angeordneten Schlitze gezeigt sind,
• 2 eine Schnittansicht durch einen Wabenkörper in einem Trägerrohr wobei mehrere entlang der Hauptdurchströmungsrichtung gleichmäßig beabstandete Schlitzreihen angeordnet sind,
• 3 eine Schnittansicht durch einen Wabenkörper in einem Trägerrohr wobei mehrere entlang der Hauptdurchströmungsrichtung ungleichmäßig beabstandete Schlitzreihen angeordnet sind, und
• 4 eine Schnittansicht durch einen Wabenkörper in einem Trägerrohr wobei mehrere entlang der Hauptdurchströmungsrichtung ungleichmäßig beabstandete Schlitzreihen angeordnet sind wobei die Abstände der Schlitzreihen an Gaseintrittsseite und Gasaustrittsseite unterschiedlich sind.

The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings show:

• 1 a plan view of a metal foil showing the rows of slits spaced along the width of the foil and the slits arranged within the row of slits along the length of the foil are shown,
• 2 a sectional view through a honeycomb body in a support tube, with several rows of slots evenly spaced along the main flow direction being arranged,
• 3 a sectional view through a honeycomb body in a support tube, with a plurality of rows of slots unevenly spaced along the main flow direction being arranged, and
• 4 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, the distances between the rows of slots on the gas inlet side and gas outlet side being different.

Preferred embodiment of the invention

The 1 shows a plan view of a metal foil 1. The metal foil 1 shown is a smooth metal foil without structure. What is described below for this smooth metal foil 1 can also apply to the same extent for a metal foil that is structured at least in sections.

The metal foil 1 has a plurality of slits 2 which run along the length 3 of the foil. The individual rows of slits 4 are arranged spaced parallel to one another in the direction of the film width 5 . The metal foil 1 is divided into segments 8 by the rows of slits 4 . The segments 8 are arranged adjacent to one another in the axial direction of the finished honeycomb body.

Webs 6 , 7 are arranged between the individual slots 2 of a slot row 4 . The ridges 6 in the center of the metal foil 1 and at the outer edge regions are in the embodiment 1 made wider 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.

2 shows a sectional view through a honeycomb body 9 which is arranged in a jacket 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 through the metal foils. The slits which divide the honeycomb body 9 into a plurality of segments 14 are shown with the reference number 13 . In the embodiment of 2 the rows of slots 15 are arranged equidistantly over the axial extent of the honeycomb body 9 .

3 shows a honeycomb body 9 in a jacket tube 10. The honeycomb body 9 corresponds to the structure of FIG 2 shown honeycomb body 9. The reference numerals match for identical elements.

In contrast to 2 the rows of slots 15 are unevenly distributed, so that a narrow segment 17 is formed in the area of the gas inlet side 11, to which several segments 18 of equal width are connected.

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

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

The exemplary embodiments 1 until 4 in particular have no restrictive character and serve to clarify the idea of the invention.

reference list

1

metal foil

2

slot

3

slide length

4

row of slots

5

film width

6

web

7

web

8th

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 (10)

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 top of one another to form a stack of layers and are wound around at least one pivot point, the stack of layers alternately consisting of smooth and at least partially structured metal foils (1), the metal foils (1) having a foil width (5) and a foil length (3), the width (5) of the foils (1) along the main flow direction of the honeycomb body (9) from a gas inlet side (11) runs towards a gas outlet side (12) and the foil length (3) transversely to this direction, characterized in that at least individual metal foils (1) have at least individual slots (2, 13) which cut the respective metal foil (1) in divide several segments (8, 14, 17, 18, 20). honeycomb body (9) after claim 1 , characterized in that the slots (2, 13) run in the direction of the film length (3). Honeycomb body (9) according to one of the preceding claims, characterized in that the slits (2, 13) are arranged parallel to one another along the film width (5) and spaced apart from one another along the film length (3). Honeycomb body (9) according to one of the preceding claims, characterized in that a plurality of slits (2, 13) are arranged spaced apart from one another by a web (6, 7) in a row running along the film length (3). Honeycomb body (9) according to one of the preceding claims, characterized in that a plurality of rows of slots (4, 15, 19) are arranged spaced apart from one another along the main flow direction, with preferably 1 to 20 slots rows (4, 15, 19) are provided, particularly preferably 1 to 12 rows (4, 15, 19) of slots. Honeycomb body (9) according to one of the preceding claims, characterized in that the webs (6, 7) arranged between the slots (2, 13) of a row of slots (4, 15, 19) have a length of 0.5 mm to 20 mm, in particular preferably from 1mm to 10mm. Honeycomb body (9) according to one of the preceding claims, characterized in that the length of the webs (6) in the center and/or at the edge area of the respective metal foil (1) is longer than the length of the webs (7) between the center and edge area of the metal foil (1). Honeycomb body (9) according to one of the preceding claims, characterized in that the slot width in the direction of the film width (5) is less than 2 mm, particularly preferably less than 1 mm. Honeycomb body (9) according to one of the preceding claims, characterized in that the rows of slots (15, 19) are unevenly distributed along the film width (5). Honeycomb body (9) according to one of the preceding claims, characterized in that the distances between the rows of slots in the region of the gas inlet side (11) differ from the distances between the rows of slots on the gas outlet side (12).

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