Metallic honeycomb body with adhesion improving microstructures

Abstract

A metallic honeycomb body with channels through which a gas may flow, made up of layers of at least partially structured sheet metal, the layers of sheet metal having at least in subregions at least two different structures, of which the first structure, with a greater structure height (H), determines the size of the channels and the second structure has a much smaller structure height (h) between troughs and peaks and the form and/or the structure height (H) of the second structure being chosen such that a ceramic coating applied later may fill the troughs of the second structure on average to at least 10%, in particular at least 50%, of their structure height (h). With the honeycomb body according to the invention, more coating material per unit of volume is durably attached in a metallic honeycomb body without excessively increasing the pressure loss. This is of advantage particularly for applications for reducing nitrogen oxides (NOx) in diesel exhaust gases.

Claims

1. A metallic honeycomb body, comprising: a plurality of channels through which a gas may flow; a plurality of layers of at least partially structured sheet metal, each of the plurality of channels being made from the plurality of layers of at least partially structured sheet metal; a plurality of subregions being part of the plurality of layers of at least partially structured sheet metal; a first plurality of structures, the first plurality of structures being of a first type and having a first height, the height of each of the first plurality of structures determining the size of each of the plurality of channels; a second plurality of structures, each of the second plurality of structures having a corresponding trough and a corresponding peak, the second plurality of structures being of a second type and having a second height (h) which is less than the first height, the second height (h) of each of the second plurality of structures extending between each corresponding trough and each corresponding peak; and a ceramic coating applied to each of the plurality of second structures such that the ceramic coating fills the troughs; wherein the ceramic coating on average fills the troughs of each of the plurality of second structures to at least 10%, preferably at least 20%, particularly preferably at least 30%, in particular at least 50%, of the second height (h) of each of the plurality of second structures.

2. The metallic honeycomb body of claim 1, wherein each of the second plurality of structures further comprising: a plurality of flanks, each of the flanks extending between one of the corresponding troughs and one of the corresponding peaks; and a zigzag corrugation with at least one trough and at least one peak which, considered on average, form an acute angle (α) between flanks forming at least one of the corresponding troughs and one of the corresponding peaks, preferably an angle (α) of less than 75°, in particular less than 50°.

3. The metallic honeycomb body of claim 1, wherein the ceramic coating fills the troughs of the second structure to at least 20% of the second height (h), preferably to at least 30%, in particular at least 50%.

4. The metallic honeycomb body of claim 1, further comprising a coating applied to the honeycomb body for the removal of NOx from a gas stream.

5. The metallic honeycomb body of claim 1, wherein the second height (h) being of such a size that each of the second plurality of structures is partially covered by a coating, in particular at least 10%, preferably at least 30%, of the second height (h) remains after the coating is applied.

6. The metallic honeycomb body of claim 1, wherein the honeycomb body is wound from the plurality of layers of at least partially structured sheet metal, the plurality of layers of at least partially structured sheet metal being soldered to one another at a multiplicity of points of contact.

7. The metallic honeycomb body of claim 6, wherein at least one of the plurality of layers of at least partially structured sheet metal is smooth in the region of each of the points of contact.

8. The metallic honeycomb body of claim 1, wherein the first height of each of the first plurality of structures is between 1 mm and 4 mm.

9. The metallic honeycomb body of claim 1, wherein the second height (h) of each of the second plurality of structures is between 0.1 mm and 0.8 mm.

10. The metallic honeycomb body of claim 1, wherein the ratio of the first height of each of the first plurality of structures to the second height (h) of each of the second plurality of structures is generally greater than 1.3.

11. The metallic honeycomb body of claim 1, wherein the ratio of the first height of each of the first plurality of structures to the second height of each of the second plurality of structures is generally greater than 1.5.

12. The metallic honeycomb body of claim 1, further comprising a periodicity of the second plurality of structures, wherein the periodicity is between 0.05 and 0.2 mm.

13. The metallic honeycomb body of claim 1, wherein the ceramic coating converts nitrogen oxides (NOx) and/or hydrocarbons (CHx), of at least 200 g/l (grams per liter of volume of the honeycomb body), preferably at least 250 g/l, in particular approximately 300 g/l.

14. The metallic honeycomb body of claim 1, wherein the ceramic coating is applied to each of the plurality of second structures such that the ceramic coating fills the troughs on average to at least 10% of the second height (h).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention, to which the invention is however not restricted, are explained in more detail below on the basis of the drawing, in which:

(2) FIG. 1 schematically shows in an end-on view part of a honeycomb body according to the invention with a microstructure on all of the layers of sheet metal,

(3) FIG. 2 shows a layer of sheet metal with a microstructure according to the invention,

(4) FIG. 3 shows a schematic cross section of a cell of a honeycomb body according to the invention with second structures only at subregions of the channel walls,

(5) FIG. 4 shows a detail from FIG. 3 with an applied coating, and

(6) FIG. 5 shows a portion of a layer of sheet metal with a microcorrugation, in which acute angles form even in the case of wide corrugation troughs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

(8) FIG. 1 schematically shows a honeycomb body 1 wound from layers of sheet metal 2 or laminated in a way known per se, it being immaterial for the invention which form of construction is used. What is important, however, is that the layers of sheet metal have at least in subregions a first structure 3 with a greater structure height H, which substantially determines the size of channels 4 in the honeycomb body 1. These channels 4 are flowed through by a gas in a direction of flow S and the first structure 3 is typically a corrugation running transversely in relation to the direction of flow. Furthermore, the layers of sheet metal 3 have at least in subregions a second structure 5 with a smaller structure height h, which serves the purpose of durably fixing more coating material in the honeycomb body. The second structure forms troughs 6 and peaks 7, which typically run in the direction of flow. The second structure 5 is therefore usually also a corrugation running transversely in relation to the direction of flow S. It is important for the adherence of coating material that the second structure 5 in the lower region of the troughs 6 is designed such that an acute angle, preferably even an angle below 75°, in particular even below 50°, forms. Then, the structure there resembles an interstice between corrugated and smooth layers of sheet metal, in which typically a particularly great amount of coating material is deposited.

(9) FIG. 2 schematically shows a portion of a layer of sheet metal 2 with a first structure 3 and a second structure 5, in the present case a zigzag corrugation. A honeycomb body 1 according to the invention may be designed completely in this way, but it is also possible to alternately use smooth layers of sheet metal and those described here.

(10) FIG. 3 schematically shows as an exemplary embodiment of the invention the cross section of a channel 4 of a honeycomb body 1 according to the invention in which second structures 5 are only present in subregions of the channel walls. The greater structure height H of a layer of sheet metal 2 corrugated with a first structure 3, which is arranged between two layers of smooth sheet metal 2, determines the size of the channel 4. The layers of sheet metal 2 touch at points of contact 9, where they may, if appropriate, also be soldered to one another. A second structure 5 with a smaller structure height h is present in subregions of the channel walls, and here forms troughs 6 and peaks 7. It should be noted here that a trough 6 in one channel 4 forms a peak 7 in a respectively adjacent channel, and vice versa.

(11) FIG. 4 shows an enlarged detail from FIG. 3 after the application of a coating 8. This coating has a thickness D, which however is not the same everywhere. The coating is thicker in the interstices in the vicinity of the point of contact 9 and in the troughs 6 of the second structure 5 than in other regions. The coating partly fills the troughs 6, as a result of which considerably more coating material is durably attached in the honeycomb body 1 than without the second structure 5. It is important for the at least partial filling of the troughs 6 with coating 8 that in a lower end region the flanks 10 of the troughs form in relation to one another an acute angle α (alpha), which is preferably less than 75°, in particular less than 50°.

(12) FIG. 5 illustrates that it is not absolutely necessary for the invention that the troughs 6 of the second structure 5 are delimited by straight flanks 10. It is sufficient if conditions such as occur in an interstice at points of contact of smooth and corrugated metal sheets are established in a lower end region of the flanks. Then good retention is obtained even for a greater thickness D of a coating 8.

(13) The present invention is suitable in particular for the durable fixing of coatings in a honeycomb body for the elimination of nitrogen oxides (NOx) from a gas stream, in particular in the exhaust gas cleaning of diesel engines, where not only the contact surface that is present in relation to the gas stream is important but also for example, because of the storage capability for oxygen, nitrogen oxides and/or ammonia, the thickness of the coating.

(14) The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.