EP1801378B1 - Process for the manufacture of a precisely shaped honeycomb body - Google Patents

Description

The present invention relates to a method for producing a honeycomb body comprising a honeycomb structure arranged in a housing. Such honeycomb bodies are used in particular for the aftertreatment of exhaust gases.

Such honeycomb bodies regularly comprise a metallic housing by arranging a ceramic or metallic honeycomb structure. Part of the manufacturing process is to introduce the honeycomb structure in a suitable manner in the housing and ultimately form a joining connection between the housing and honeycomb structure.

For this it is necessary that the contact of the honeycomb structure with the housing is as uniform as possible. In addition, it should be ensured that the honeycomb body is produced with a desired roundness or shape accuracy. This is of particular interest, since ultimately an integration of the honeycomb body, for example, in the exhaust system of a mobile internal combustion engine as in a vehicle to be made. The housing often offers contact surface for further positive or non-positive connections. An inaccuracy in terms of the outer shape means that under certain circumstances sealing compounds for subsequent adjustment of shape tolerances, elaborate reworking steps or other, time-consuming and expensive measures are required.

The WO-A1-98 / 15354 describes a method for producing metallic honeycomb bodies, wherein structured sheet metal strips are folded and placed in a housing before they are joined together. With the method described there, in particular the durability of honeycomb bodies with folded sheet metal strips is to be improved.

The EP - A2 - 0 897 749 discloses a method for producing a metallic honeycomb body in which stacks of structured and smooth plates are wound and introduced into a jacket tube. In this case, the stack is pressed with a punch in the jacket tube, so that the diameter of the coiled stack is reduced. This should be accompanied by an improved conditioning of the plates on the jacket tube.

From the US Pat. No. 5,055,274 For example, a method for producing a catalytic converter is known, in which a ceramic honeycomb structure is pressed via a bearing mat with a housing. For structuring or diameter reduction of the housing, a tool is proposed which has radially movable punches with respect to the housing.

Is still on the WO - A1 - 2005/001251 to the applicant, which indicates a particularly effective production of small honeycomb bodies. In this case, a limited number of layers and metal foils are specified, which are separated and wound together in a forming and cutting tool with a predetermined length.

The problems with regard to a dimensional accuracy occur, in particular, in honeycomb bodies which, for example, have a metallic honeycomb structure which is to be introduced in a non-cylindrical cross section of the housing. In this case, it may happen that act from the honeycomb structure in the circumferential direction of the housing, various forces or pressures on the housing. This can already lead to a small deformation, especially with thin-walled housings. In addition, with such an uneven pressure distribution, it has been observed that this effect is enhanced during later thermal treatments of the honeycomb body. This can lead to a further deformation of the housing and / or to a non-uniform connection of the honeycomb body to the housing.

The object of the present invention is to at least partially solve the problems described with reference to the prior art. In particular, a method for producing a dimensionally accurate honeycomb body is to be specified.

These objects are achieved with a method for producing a honeycomb body according to the features of claim 1.Further advantageous embodiments of the invention are specified in the dependent formulated claims. It should be noted that the features listed individually in the claims can be combined with each other in any technologically meaningful way, and show further embodiments of the invention.

1. a) Ausbilden einer Wabenstruktur,
2. b) Einfügen der Wabenstruktur in ein Gehäuse,
3. c) Durchführen einer thermischen Behandlung der Wabenstruktur mit Gehäuse,

wobei zumindest während Schritt b) und Schritt c) ein außen bereichsweise anliegendes Formteil vorgesehen ist, dessen Anlageflächen eine gewünschte Außenkontur des Gehäuses abbilden.The inventive method for producing a honeycomb body having a honeycomb structure arranged in a housing comprises at least the following steps:

1. a) forming a honeycomb structure,
2. b) inserting the honeycomb structure into a housing,
3. c) performing a thermal treatment of the honeycomb structure with housing,

wherein at least during step b) and step c) an externally partially applied mold part is provided, the contact surfaces of which form a desired outer contour of the housing.

Although the method can basically be used with any type of honeycomb structures, step a) preferably comprises the formation of a metallic honeycomb structure. For this purpose, at least partially structured metal foils are layered and then wound together. In this case, a spiral, an S-shaped or a similar structure of the honeycomb structure can be achieved. The honeycomb structure regularly comprises a multiplicity of channels arranged essentially parallel to one another, through which an exhaust gas can flow. Usually, the honeycomb structure is prepared separately from the housing and now inserted by means of step b) in a housing.

With regard to step b), the honeycomb structure is preferably inserted into a housing (in particular in the circumferential direction). For this purpose, it may be advantageous to provide a so-called insertion cone, which is placed on the housing and through which the honeycomb structure is passed, wherein the honeycomb structure is reduced by slight compressions on the internal dimension of the housing.

Step c) relates in particular to a coating and / or a bonding process. With regard to the bonding method, those in which sintered, brazed and / or welded joints are formed within the honeycomb structure or between the honeycomb structure and the housing are preferred.

The molding in particular has the task of substantially maintaining a desired shape of the housing during the manufacturing process. With regard to the specific embodiment of the molded part, reference is made to the following explanations. At this point, however, it should already be noted that the molding is usually made more stable than the housing and partially applied in the circumferential direction of the housing. The contact surfaces are arranged in particular where an increased stress of the housing due to the introduced honeycomb structure is to be expected. This concerns in particular the areas which have a smaller distance to the center of the honeycomb body and / or in areas of curvature sections of the housing with a large radius of curvature. In principle, it is also possible to provide a plurality of molded parts on a housing.

The method is particularly advantageous if a honeycomb body having a non-circular cross-section of the housing is produced. By "non-circular" is meant in particular oval, "race-track" -like, angular or other non-round cross-sections. These regularly have different radii of curvature, some of which can go to infinity (straight housing section). It is precisely here that the different stress states described above can occur during the thermal treatment of the honeycomb body, so that, in particular, such honeycomb bodies can be produced in a dimensionally accurate manner with the method described here.

Therefore, according to a development of the method, it is particularly advantageous to bring the molded part into contact with the housing outside step b) and to remove it again after step c). In other words, that the composite honeycomb structure and housing by means of the molded part as long as supported or retained in shape until a joining technology connection between sub-components of the honeycomb structure and the housing is actually generated.

• Beloten des Wabenkörpers,
• Beschichten des Wabenkörpers,
• Transport des Wabenkörpers.

Furthermore, it is advantageous if the molded part is also provided on the housing at least during one of the following machining processes:

• Belote the honeycomb body,
• Coating the honeycomb body,
• Transport of the honeycomb body.

When Belote the honeycomb body powdered hard solder is preferably supplied via an end face of the honeycomb body. In addition, it is possible that the honeycomb body is previously immersed in the front side of an adhesive liquid to which the brazing material should later adhere defined. When coating the honeycomb body in particular a so-called washcoat coating is provided, the z. B. doped with precious metals and then calcined. With regard to the transport of the honeycomb body is to be noted that this fixation of the honeycomb body by means of the molding z. B. is maintained between the individual processing stations or for temporary storage.

Furthermore, a molded part for carrying out a method of the type described above in accordance with the invention is also proposed, a frame having a plurality of inwardly directed abutment surfaces being provided for a desired outer contour of the housing. The frame is preferably closed in the circumferential direction, for example in the manner of a frame. Most notably Preferably, the frame is stirred in one piece. The inner contour of the frame accordingly has a plurality of inwardly directed contact surfaces, that is to say that the contact surfaces comprise the part of the inner contour of the frame that projects furthest inward. The contact surfaces are aligned with one another or designed such that they essentially correspond to the desired outer contour of the housing. In other words, this means that the contact surfaces form part of the outer contour of the housing. In principle, however, it is possible that a part of the contact surfaces are also beveled, so that, for example, a simplified insertion of the housing is made possible in the frame.

In principle, it is also possible that the molded part is designed so that the relative position of the contact surfaces is adjustable to each other. This allows a particularly flexible use of the molding for different contours of the housing. In addition, there is the advantage that with such movable contact surfaces easier removal of the housing or the honeycomb body, for example, after performing a thermal treatment is possible.

Further, it is also proposed that radially outwardly directed recesses space the inwardly directed abutment surfaces. The recesses preferably extend substantially parallel to the contact surfaces and limit these at least partially. By means of such recesses prevents excessive pressure of the housing to the frame occurs. This makes the housing easier to remove after processing.

For this reason too, it is particularly advantageous if the contact surfaces of the molded part cover between 50% and 80% of the circumference of the housing. This ensures on the one hand a sufficient fixation of the housing to achieve a dimensional stability and on the other hand allows a safe removal of the housing also as part of a series production. In this case, the recesses may be designed, for example, suitable for gripping tools.

It is particularly advantageous if the molded part is made of a high-temperature-resistant and corrosion-resistant metal. The molding is very particularly preferably made from an at least similar material as the housing in order to ensure a uniform thermal expansion behavior, in particular during a thermal treatment of the honeycomb body. At a minimum, the metal should be able to withstand the thermal conditions during a brazing process.

According to one embodiment of the molded part, the contact surfaces are at least partially executed with a coating. Alternatively or in combination, the contact surfaces can also be provided at least partially with a structured surface. These measures are used, for example, to avoid connections between the molded part and the housing, as they may possibly take place at high temperatures (for example, sintered connections). Likewise, the contact surface between the molded part and the housing is further reduced by the structured surface of the contact surface, whereby the Entfembarkeit of the housing is improved according to the manufacturing process of the honeycomb body. Although these measures may be only partially provided in the contact surfaces, the application for all contact surfaces in the same way is preferred.

The provision of an exhaust gas treatment unit comprising a honeycomb body with a housing having a thickness of at most 1.5 mm is preferably realized according to the method described according to the invention.

Fig. 1:

Einen nicht-zylindrischen Wabenkörper,

Fig. 2:

eine Ausgestaltung eines Formteils,

Fig. 3:

ein Detail eines in einem Formteil angeordneten Wabenkörpers, und

Fig. 4:

ein Abgassystem für ein Fahrzeug.

The invention and the technical environment will be explained in more detail with reference to FIGS. The figures also show particularly preferred embodiments of the invention, to which, however, this is not limited. Show it:

Fig. 1:

A non-cylindrical honeycomb body,

Fig. 2:

an embodiment of a molded part,

3:

a detail of a arranged in a molding honeycomb body, and

4:

an exhaust system for a vehicle.

Fig. 1 schematically shows in a front view of a honeycomb body 2, which has an inner honeycomb structure 3 and an outer housing 1. The housing 1 has a non-circular cross-section 12, in which the honeycomb structure 3 is arranged. The cross section 12 is substantially oval, almost in the nature of a so-called "race track", having a first extent 13 and a second extent 14 different from each other. The illustration shows that the honeycomb body 2 is designed at the top and bottom with a larger radius of curvature than left and right.

The honeycomb structure 3 is constructed with a plurality of structured and smooth metal foils 18 that are wound in an S-shape and that form essentially parallel channels 15. In particular, in this arrangement, starting from the metal foils 18, different voltages act on the housing 1, which could possibly influence the outer contour 6 of the housing 1. To avoid deviations from the outer contour 6, the use of a molding is proposed, which in a preferred embodiment for such a honeycomb body in Fig. 2 is shown.

The molding 4 for the in Fig. 1 illustrated honeycomb body 2 is according to a preferred embodiment in Fig. 2 shown. The molded part 4 has a plurality of inwardly directed abutment surfaces 5, which rest against the outer contour of the housing 1, which is schematically illustrated. It is also illustrated that the contact surfaces 5 cover more than half of the circumference 9 of the housing 1. Between the contact surfaces 5, designed in the manner of a frame frame 7 radially outwardly directed recesses 8. In these areas, there is no system between the frame 7 and the housing. 1

Fig. 3 shows a detail of an arrangement of a honeycomb body 2 in the interior of a molded part 4 according to a further embodiment in cross section. Left in Fig. 3 Accordingly, a part of honeycomb body 2 is illustrated, which in turn is formed with a plurality of metal foils 18, so that substantially parallel channels 15 are provided. The metal foils 18 bear against the housing 1 on the inside, the housing 1 having a thickness 16, for example in the range of up to 1.5 mm, advantageously even less than 1 mm or even 0.8 mm. Outside the housing 1, the molded part 4 abuts, wherein the abutment surface 5 is designed here with a coating 17 and a structured surface 10. The provision of the structured surface 10 ensures easy removal of the honeycomb body 2 from the molded part 4, while the coating 17 prevents the formation of sintered connections between the molded part 4 and the housing 1.

The preferred field of use for such honeycomb bodies is the automotive sector. Accordingly, the structure of an exhaust system 21 for a vehicle 19 is schematically shown in FIG Fig. 4 illustrated. The exhaust gas generated by the engine 20 is now passed through a plurality of exhaust treatment units 11 until it has been freed of pollutants so far that they are discharged to the environment can. The exhaust gas treatment unit 11 is in particular equipped with the honeycomb body described here. With the invention, in particular exhaust gas treatment units with a thin housing can be accurately produced.

LIST OF REFERENCE NUMBERS

1

casing

2

honeycombs

3

honeycomb structure

4

molding

5

contact surfaces

6

outer contour

7

frame

8th

recesses

9

scope

10

surface

11

Exhaust gas treatment unit

12

cross-section

13

First extension

14

Second extension

15

channel

16

thickness

17

coating

18

metal foil

19

vehicle

20

engine

21

exhaust system

Claims (11)

1. Method for producing a honeycomb body (2) having a honeycomb structure (3) arranged in a housing (1), which method comprises at least the following steps:

   a) forming a honeycomb structure (3),

   b) inserting the honeycomb structure (3) into a housing (1),

   c) carrying out a heat treatment operation on the honeycomb structure (3) with the housing (1),

   with a formed part (4), which is in contact in regions at the outside, being provided at least during step b) and step c), the contact faces (5) of said formed part (4) reproduce a desired outer contour (6) of the housing (1).
2. Method according to Patent Claim 1, in which a honeycomb body (2) having a non-cylindrical housing cross section (12) is produced.
3. Method according to Patent Claim 1 or 2, in which the formed part (4) is placed in contact with the housing (1) at the outside before step b), and is removed again after step c).
4. Method according to one of the preceding patent claims, in which the formed part (4) is also provided at least during one of the following machining processes on the housing (1):

   - brazing the honeycomb body (2),

   - coating the honeycomb body (2),

   - transporting the honeycomb body (2).
5. Method according to one of the preceding patent claims, in which the formed part (4) is provided with a frame (7) being provided with a plurality of inwardly directed contact faces (5) for a desired outer contour (6) of the housing (1).
6. Method according to Patent Claim 5, in which the relative position of the contact faces (5) of the formed part (4) are adjustable relative to one another.
7. Method according to Patent Claim 5 or 6, in which radially outwardly directed recesses (8) of the formed part (4) provide space apart the inwardly directed contact faces (5).
8. Method according to one of the preceding Patent Claims 5 to 7, in which the contact faces (5) of the formed part (4) cover between 50% and 80% of the periphery (9) of the housing (1).
9. Method according to one of the preceding Patent Claims 5 to 8, in which said formed part is made from a high-temperature resistant and corrosion resistant metal.
10. Method according to one of the preceding Patent Claims 5 to 9, in which with the contact faces (5) of the formed part (4) are provided at least partially with a coating (17).
11. Method according to one of the preceding Patent Claims 5 to 9, in which the contact faces (5) of the formed part (4) are provided at least partially with a structured surface (10).

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