Improved method for applying catalytically active coatings to honeycomb structures

Abstract

The present invention relates to a method for manufacturing an apparatus for exhaust aftertreatment and for coating a catalytically active surface coating onto a honeycomb (1) disposed in the apparatus, wherein the honeycomb (1) is formed of a plurality of at least partially structured metal foils stacked and wound together such that the honeycomb forms a plurality of flow channels capable of flowing through in the main flow direction, the honeycomb is received in and permanently connected to an inner sleeve (2), the inner sleeve (2) is disposed in and permanently connected to an outer sleeve (6) serving as a housing, and one or more gaps (7) formed between the outer sleeve (6) and components disposed in the outer sleeve (1) are filled with a filling material (8) before the catalytically active coating is applied to the flow channels formed by the honeycomb (1).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an apparatus for exhaust aftertreatment and for coating a catalytically active surface coating onto a honeycomb body disposed in the apparatus, wherein the honeycomb body is formed of a plurality of at least partially structured metal foils stacked and wound together such that the honeycomb body forms a plurality of flow channels capable of flowing through in the main flow direction, wherein the honeycomb body is received in an inner sleeve and permanently connected to the inner sleeve, wherein the inner sleeve is disposed in an outer sleeve serving as a housing and is permanently connected to the outer sleeve. Background Technology

[0002] The honeycomb structure of a catalytic converter for internal combustion engine exhaust aftertreatment has multiple flow channels that allow flow along the main flow direction. The honeycomb structure, particularly those made of metal, is formed from multiple smooth and / or at least partially structured metal foils, which are stacked and wound together to form the final honeycomb structure. A substrate formed from the metal foils is inserted into and permanently connected to the housing for stabilization and to prevent mechanical interference.

[0003] In its simplest form, the shell is formed by a tube designed to receive the substrate internally. Another function of the shell is to ensure flow through the honeycomb structure and, in particular, to prevent exhaust gas from flowing around the honeycomb structure.

[0004] On the one hand, the substrate must be permanently fixed within the housing, but at the same time, the housing should be as lightweight as possible and therefore constructed with thin walls. Some embodiments of the catalyst have an inner sleeve that directly receives the substrate. The inner sleeve is then supported relative to the housing or outer sleeve by suitable supports.

[0005] A drawback of existing devices is that voids may appear between the various elements of the catalyst, such as between the inner and outer sleeves, when the substrate is coated with a catalytically active material, i.e., a so-called carrier coating / coating, which may be added into these voids. Mechanical vibrations and thermal effects during operation can cause the material adhering to these voids to detach, leading to damage and / or catalytic deactivation of downstream exhaust aftertreatment components.

[0006] Another disadvantage is that the carrier coating applied to the gaps does not participate in the catalytic reactions on the honeycomb structure and therefore does not function. Thus, the actual amount of carrier coating required to coat the honeycomb structure could be lower. Unnecessary additional consumption is particularly detrimental if the carrier coating contains expensive precious metals. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a method that enables the coating of the honeycomb in the housing with the minimum required amount of carrier coating as precisely as possible, and in particular avoids applying the carrier coating to areas that do not participate in the catalytic reaction.

[0008] The methodological objective is achieved by a method having the features of claim 1.

[0009] One embodiment of the present invention relates to a method for manufacturing an exhaust aftertreatment device and for coating a catalytically active surface coating onto a honeycomb structure disposed in the device, wherein the honeycomb structure is formed of a plurality of at least partially structured (having a specific structure) metal foils stacked and wound together such that the honeycomb structure forms a plurality of flow channels capable of flowing through in the main flow direction, wherein the honeycomb structure is received in and permanently connected to an inner sleeve, wherein the inner sleeve is disposed in and permanently connected to an outer sleeve serving as a housing, wherein one or more gaps formed between the outer sleeve and components disposed in the outer sleeve are filled with a filler material before the catalytically active coating is applied to the flow channels formed by the honeycomb structure.

[0010] A basic method for manufacturing an apparatus having a honeycomb structure located within an inner sleeve (which is permanently housed within an outer sleeve) is known in the prior art. The substrate is produced by stacking multiple metal foils, at least partially structured, and by subsequently winding the resulting layers around one or more cores. After the substrate is inserted into the inner sleeve, the honeycomb substrate is joined to the inner sleeve, for example, by a welding process.

[0011] The inner sleeve is preferably designed to be very thin and is mainly used to stabilize the substrate so that the substrate does not curl up or unfold.

[0012] The honeycomb structure is then inserted into the shell, which is formed by the outer sleeve and serves as a closed portion relative to the environment, and is permanently connected to the shell, for example, by welding. The outer sleeve is much thicker than the inner sleeve and serves to guide the flow of exhaust gas, mechanically protect the honeycomb structure, and connect to other components used for exhaust gas aftertreatment.

[0013] Specifically, due to tolerances of the individual components or simply due to the geometry of the individual components, a gap may form between the inner sleeve and the outer sleeve. This gap typically forms a completely circumferential gap between the inner sleeve and the outer sleeve. In the axial direction, the gap usually extends only along the section that abuts both the inner and outer sleeves. This gap forms a cavity that can be accessed from the volume (exhaust path) enclosed by the outer sleeve.

[0014] To coat the substrate, coating material is forcibly injected or drawn into the substrate's flow channels, for example, by overpressure or negative pressure. This coats the surface of the flow channels, forming a catalytically active surface on which the exhaust gas reacts chemically. The coating material can also be applied to external structures of the substrate; in particular, it can be applied into and remain in the resulting voids. This significantly increases the amount of coating material remaining in the device. Furthermore, the coating material may detach from the voids during operation, be carried by the exhaust flow, and potentially damage downstream components used for exhaust aftertreatment. Specifically, so-called "poisoning" can occur when the catalytically active material comes into contact with other types of catalytically active materials on other cell structures. A chemical reaction can then occur, completely or at least partially damaging the downstream catalyst. Therefore, it is crucial to avoid the deposition of catalytically active coating material in uncoated areas.

[0015] To prevent the coating material from being applied into the voids, fill the voids with a filler material before applying the coating material. For example, the filler material can be applied to the voids using an injection needle.

[0016] The filler material is cured in the voids to such an extent that it will not be squeezed out by the application of the coating material and will not flow out of the voids on its own or be sucked out of the voids.

[0017] The filler material can preferably be applied into the voids through an opening in the jacket. Alternatively, the filler material can be applied directly into the voids from an open cross-section of the jacket.

[0018] Of particular advantage is that the filler material is a gel-like organic substance. The gel-like organic substance helps ensure that the entire void can be filled quickly and easily by injecting the filler material directly into the void. The filler material preferably has material properties that allow it to be injected into the void. Furthermore, the filler material is designed to achieve sufficient strength within the void so that it is not easily sucked out or extruded from the void.

[0019] Advantageously, the filler material is applied to the gaps before further heat treatment of the equipment—such as drying or calcination. This is advantageous because drying or calcination causes a significant increase in the temperature of the equipment, and the filler material preferably has limited thermal stability, so that the filler material becomes unstable or completely dissolves after being subjected to a certain temperature.

[0020] A preferred embodiment is characterized by removing the filler material from the voids after the catalytically active coating is applied. Advantageously, the filler material is removed before the equipment is put into operation. Otherwise, the filler material may detach from the voids during operation under the interaction of mechanical stress and heat, leading to blockage of flow channels or damage to components in the exhaust system.

[0021] It is also preferable to remove the filler material from the voids via a thermal process. This is advantageous because the honeycomb structure, or the entire device, typically undergoes multiple process steps subjected to intense high temperatures. Therefore, it can be ensured that the filler material is heated above its critical temperature without additional processing steps, thereby dissolving the filler material.

[0022] Furthermore, it is advantageous to fill the voids in such a way that the cross-sectional opening facing the application site is sealed by the filling material, through which the catalytically active coating is applied. This is particularly important to ensure that the coating material does not adhere to the voids. This is ensured by sealing the cross-sectional opening.

[0023] In a preferred embodiment, the filler material may be designed to expand after it is applied, and if necessary, a portion of the applied filler material expands out of the voids to ensure that no coating material can enter the voids.

[0024] Advantageous improvements of the invention are described in the dependent claims and the following description of the drawings. Attached Figure Description

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Wherein:

[0026] Figure 1 A cross-sectional view of a honeycomb structure housed within an outer casing is shown, wherein the gap formed between the inner and outer casings of the honeycomb structure is filled with a filler material. Detailed Implementation

[0027] Figure 1 A cross-sectional view shows the device for exhaust aftertreatment. A honeycomb structure 1 is centrally located and formed from a metal substrate. The honeycomb structure 1 is received within an inner sleeve 2, which secures the substrate against unfolding and rolling, while also protecting it from mechanical stress. This type of honeycomb structure is known in the prior art in various ways.

[0028] exist Figure 1 In this configuration, a heating plate 3 is positioned upstream of the honeycomb cell 1 and is connected to the honeycomb cell 1 via a support pin 4. The heating plate 3 is connected to a power source via the electrical feeder 5 shown and can therefore be energized, thereby achieving heating.

[0029] The honeycomb 1 and its inner sleeve 2 are inserted into the outer sleeve 6 and permanently connected to the outer sleeve, for example, by welding. A gap 7 is formed between the outer sleeve 6 and the inner sleeve 2. This may be specifically created due to the geometry of the components, or it may be created due to tolerances between the components. In principle, it is also conceivable that gaps exist between all parts of the device.

[0030] exist Figure 1 In one embodiment, the gap 7 is filled with a filling material 8, so that it is particularly impossible to enter the gap 7 from the side facing the heating plate 3.

[0031] The carrier coating used to coat the substrate of the honeycomb 1 is for example forced into the honeycomb by overpressure and / or drawn into the honeycomb by negative pressure. The carrier coating can also be used to wash the honeycomb 1. With all these methods, if the pores 7 are not sealed, the carrier coating is likely to seep into the pores 7.

[0032] For example, an injection needle can be used to apply the filling material specifically to the voids 7 in order to fill the voids and, in particular, to fill the open cross-sections.

[0033] Figure 1 The embodiments described herein are not limiting in any particular sense and are merely illustrative of the ideas of the invention.

[0034] List of reference numerals in the attached diagram:

[0035] 01 Honeycomb

[0036] 02 Inner Sheet

[0037] 03 Heating Plate

[0038] 04 Support pin

[0039] 05 Electrical feeder

[0040] 06 Outerwear

[0041] 07 Gap

[0042] 08 Filler Material

Claims

1. A method for manufacturing an apparatus for exhaust gas aftertreatment, the method comprising coating a catalytically active surface coating onto a honeycomb (1) disposed in the apparatus, wherein, The honeycomb (1) is formed of a plurality of at least partially structured metal foils stacked and wound together such that the honeycomb forms a plurality of flow channels capable of flowing along the main flow direction, wherein the honeycomb is received in an inner sleeve (2) and permanently connected to the inner sleeve, wherein the inner sleeve (2) is arranged in an outer sleeve (6) serving as a shell and is permanently connected to the outer sleeve, characterized in that one or more gaps (7) formed between the outer sleeve (6) and the components arranged in the outer sleeve are filled with a filling material (8) before the catalytically active coating is applied to the flow channels formed by the honeycomb (1).

2. The method according to claim 1, characterized in that, The filler material (8) is a gel-like organic substance.

3. The method according to any one of the preceding claims, characterized in that, The filler material (8) is applied to the voids (7) before the equipment undergoes further heat treatment.

4. The method according to claim 3, characterized in that, The additional heat treatment is drying or calcination.

5. The method according to any one of the preceding claims, characterized in that, After the catalytically active coating is applied, the filler material (8) is removed from the voids (7).

6. The method according to any one of the preceding claims, characterized in that, The filling material (8) is removed from the voids (7) by a thermal process.

7. The method according to any one of the preceding claims, characterized in that, The voids (7) are filled in such a way that the cross-section of the opening facing the application site is closed by the filling material (8), and the catalytically active coating is applied through the application site.

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