EP0292784A2 - Device for catalytic purification of exhaust gases - Google Patents

Abstract

A device for catalytic purification of exhaust gases, especially from internal-combustion engines, is specified in which a catalyser support, arranged in a housing, is supported against the housing by a corrugated part of temperature and corrosion-resistant metal wire. In this arrangement, the corrugation of the part is constructed in an omega-shape, such that, in the installed state, the mutually facing flank parts of the respective adjacent corrugation peaks and troughs are located on one another. <IMAGE>

Description

The invention relates to a device for the catalytic purification of exhaust gases, in particular internal combustion engines, with a housing provided with an exhaust gas inlet and an exhaust gas outlet and at least one catalyst carrier mounted therein, the catalyst carrier being mounted between the outer contour thereof, which is essentially parallel to the flow direction of the exhaust gas, and the associated housing wall at least one corrugated part, which completely surrounds the catalyst carrier transversely to the direction of the exhaust gas flow, is made of temperature and corrosion-resistant metal wire.

Such devices can be circular, but also oval or one transverse to the direction of flow of the exhaust gas otherwise have a suitable cross-section, with the design depending on the installation conditions, in particular on the underside of a motor vehicle. The housing is generally composed of two half-shells arranged parallel to the exhaust gas flow during the course of the assembly, the half-shells being welded to one another or otherwise connected to one another along their parting line. Of course, other suitable designs of the housing, in particular without a shell construction, are also conceivable and are intended to be included in the invention.

With regard to the catalyst carrier, it is important to store it firmly but sufficiently cushioned in the housing. This is because the catalyst carrier is known to be extremely sensitive to hard impact loads, such as those resulting from the driving movements of a motor vehicle and the vibrations of the exhaust gas flow. On the other hand, this is because the temperature-related thermal expansions of the catalyst carrier on the one hand and the housing on the other are different and must therefore be compensated for.

In the known case, the corrugated part which surrounds the catalyst carrier and supports it in relation to the housing wall, the corrugation of which has an approximately sinusoidal shape, serves this purpose. However, it is disadvantageous here that such a corrugation results in a relatively soft suspension, so that the corrugated part is unable to hold the catalyst carrier sufficiently. Try that, for example To counteract by placing the shells forming the housing more firmly only cause the individual shafts to turn laterally in an unordered form and thus create unmanageable and asymmetrical conditions with regard to the mounting of the catalyst carrier, which can even lead to the catalyst carrier under vibrations occurring in seeks to move in a preferred direction within the housing. If one increases the strength with which the housing is put on, this finally leads to largely flattened shafts and a sudden increase in the spring stiffness of the corrugated part, so that the mounting of the catalyst carrier in the housing is now too rigid and quickly leads to damage to the catalyst carrier . These circumstances cannot be met even by very careful handling with the intention of finding the cheapest middle ground, since the manufacturing tolerances of the parts to be assembled here are in a larger range and their respective effect on the sum is not sufficiently predictable.

Attempts have therefore also been made to design the corrugated part in multiple layers in order to give the individual shafts greater stability and durability of their shape. Even with this, however, the above-described basic behaviors of the corrugated part could not be eliminated, and a negative phenomenon which is associated with the known corrugated parts and which consists in the fact that it behaves was intensified The "sharp-edged" apex of the shafts coming into contact with the catalyst carrier work into the material of the catalyst carrier, as a result of which the catalyst carrier is destroyed relatively quickly and the spring pretension of the corrugated part generated during assembly is likewise reduced.

The object of the invention is to provide a construction of a device of the type mentioned above with regard to the corrugated part which, while eliminating the above-mentioned defects, permits a fixed, uniformly oriented storage of the catalyst carrier in the housing which is independent of manufacturing tolerances and excludes damage to the catalyst carrier, whereby Compared to the known designs, no additional effort, be it material, or should it arise with regard to the other production costs.

This object is achieved in that the corrugation of the part is omega-shaped, such that in the installed state the flank parts of the adjacent wave crests and wave troughs which are directed towards one another lie against one another.

This measure has the effect that when assembling the device, the wave crests or wave troughs can be pressed more or less flat within manageable and predeterminable limits without the individual waves tending to flip sideways or lay flat, so that the symmetrical structure of the corrugated part is retained and thus a one-sided migration tendency of the catalyst carrier cannot arise.

In addition, the size of the spring preload changes, depending on how strongly the corrugated part is compressed during assembly. However, this change is linear, so that unexpected progression or degression of the spring preload during assembly is eliminated.

The fact that adjacent wave crests or troughs of the corrugated part according to the invention are supported against each other parallel to the surface of the catalyst carrier, results in a much better or more stable support of the catalyst carrier in the longitudinal direction or parallel to its surface compared to the known designs, so that the corrugated Partly fulfills a function not only essentially radially to the catalyst carrier.

Furthermore, the formation of the wave crests or wave troughs according to the invention leads to a comparatively large-area system with respect to the catalyst carrier, so that point or line loads and correspondingly no more destructive influences can no longer occur due to the fact that the material of the catalyst carrier is locally destroyed or destroyed is removed.

Since it can be seen that the part corrugated in the manner according to the invention is inherently firmer or more stable, the manufacturing tolerances of the parts to be assembled can be Keep the device closer in the range of a certain size, since the corrugated part now builds up the spring preload over a shorter distance compared to the known designs, so there is no need for greater installation clearance, which ultimately also makes assembly easier and especially also in terms of automation is more manageable.

Depending on the circumstances of the individual case, the corrugated part can extend over the entire length of the catalyst carrier, but in the other case there is also the possibility that several parts are arranged along the length of the catalyst carrier, but then at least depending on the flow direction of the exhaust gas a part must be arranged at the beginning and end of the respective catalyst carrier. In the latter case, use has already been made of the fact that the design according to the invention results in a much firmer and more secure mounting of the catalyst carrier, so that one can be satisfied with individual corrugated sections distributed over the length of the catalyst carrier for mounting. Then the remaining space between the catalyst carrier and the housing can be filled with an economical storage, that is a simpler and cheaper material that would not be suitable for storing the catalyst carrier alone. For this purpose, for example, a metal fiber fleece can be sufficient, with which a resilient support alone would not be possible. The waves of the corrugated part can cross the direction of flow of the exhaust gas around the kata lysatorträger be circumferential, but there is also the possibility that the waves of the part run parallel to the flow direction of the exhaust gas. Which of these options is preferred depends in turn on the respective structural and load-related circumstances.

Another possibility can be that the waves of the corrugated part are arranged obliquely to the flow direction of the exhaust gas.

In all cases, the corrugated part can consist of a knitted, woven or braided wire, i.e. materials that can be machined evenly with a very good internal bond. In the case of the forms with corrugation lying transversely or parallel to the flow direction of the exhaust gas, the corrugated part can simultaneously be produced as a seamlessly closed stocking, for example in the form of a knitted stocking which is subsequently subjected to the corrugation in the form according to the invention.

In the case of the corrugation running obliquely to the flow direction of the exhaust gas, it is expedient to design the corrugated part as a helically wound mat around the catalyst carrier, which contains the corrugation according to the invention, whereby it is expedient that the corrugations of such a mat-shaped part are transverse, oblique or are arranged parallel to the longitudinal direction of the mat, whereby the production of the corrugation is facilitated.

Furthermore, it appears advantageous that the corrugated part protrudes above the catalyst carrier at the respective end. Here, reference is made to the fact that the housing containing the catalyst carrier generally tapers in a funnel shape, starting from the contour surrounding the catalyst carrier, towards the exhaust gas inlet and exhaust gas outlet. If the corrugated part is now guided beyond the ends of the catalyst carrier, it comes to lie on the end faces of the catalyst carrier between the latter and the conically tapering housing wall and can thus also serve to provide axial support for the front edges of the catalyst carrier.

Furthermore, it may be appropriate for the corrugated part to be provided with a flow-inhibiting filler, in particular in the form of mica or ceramic fibers. This measure prevents unpleasant amounts of exhaust gas from bypassing the catalyst carrier on the way over the undulating part and consequently not participating in the catalytic cleaning in the desired manner.

Finally, it should be emphasized that the corrugated part according to the invention can be formed in one layer, which simplifies and reduces the cost of manufacture and assembly.

• Fig. 1 den axialen Halbschnitt einer Vorrichtung zur katalytischen Reinigung von Abgasen und
• Fig. 2 die perspektivische Ansicht einer Abwand­lung der Ausführungsform gemäß Fig. 1 oh­ne Gehäuse.

Further features and details of the invention result from the following description of embodiments with reference to the drawing. The drawing shows:

• Fig. 1 shows the axial half-section of a device for the catalytic purification of exhaust gases and
• Fig. 2 is a perspective view of a modification of the embodiment of FIG. 1 without a housing.

1, a catalyst housing 1 has an exhaust gas inlet 2 and an exhaust gas outlet 3, from which the housing widens conically into the space accommodating the catalyst carrier 4.

In the present case, the catalyst carrier 4 and corresponding to the housing space receiving it is circular cylindrical.

The support of the catalyst carrier 4 with respect to the housing 1 takes place via a corrugated part 5, which surrounds the catalyst carrier 4 over its entire circumference and is provided with a helical corrugation which runs essentially transversely to the exhaust gas flow between the nozzle 2 and nozzle 3 Catalyst carrier 4 rotates, as can be seen from the inside view of the corrugated part 5 at number 9, where the catalyst carrier 4 has broken away.

The corrugated part 5 can be, for example, a stocking made of a knitted metal wire.

As can be seen from Fig. 1, the individual waves of the part 5 are omega-shaped, so that the touch the flank parts of the adjacent wave crests 6 or wave troughs 7 which are directed towards one another and thus support one another.

At the ends of the catalyst carrier 4, the corrugated part 5 protrudes and is rolled up there in the manner shown, so as to form a cushion between the end edges of the catalyst carrier 4 and the housing 1.

The housing 1 can be composed of two half-shells in the manner not shown here, which can be welded together, for example, along the plane formed by the axis 8 perpendicular to the plane of the drawing.

FIG. 2 shows a perspective view of an insert of a modified design that can be brought into the housing 1 according to FIG. 1, a catalyst carrier 10 again being surrounded by a corrugated part 11 on the basis of a circular cross section and by this against the housing not shown in FIG. 2 is supported.

In this case, the corrugation, which is also omega-shaped, runs parallel to the exhaust gas flow, based on the example according to FIG. 1, so that the individual waves lie parallel next to one another in the circumferential direction of the catalyst carrier 10.

Here, too, the corrugated part 11 can consist of a seamless stocking made of a knitted, woven or braided metal wire, which follows its manufacture was provided with the omega-shaped curl shown.

The material of the corrugated part 5 or 11 can be provided with a flow-inhibiting filler, for example mica or ceramic fibers, in order to prevent bypassing the catalyst carrier 4 or 10 by parts of the exhaust gas flow.

The examples shown show the production of the corrugated part from continuously cylindrical material. Of course, in terms of production technology, it can be particularly simple and expedient to wrap the catalyst carrier in the manner described before the description of the figures in the form of a screw thread by means of appropriate strip material into which the omega-shaped corrugation has been introduced.

Claims (13)

1. Apparatus for the catalytic purification of exhaust gases, in particular internal combustion engines, with a housing provided with an exhaust gas inlet and an exhaust gas outlet and at least one catalyst carrier mounted therein, wherein at least one for supporting the catalyst carrier between its outer contour, which is essentially parallel to the flow direction of the exhaust gas, and the associated housing wall corrugated part of temperature and corrosion-resistant metal wire, which completely surrounds the catalyst carrier transversely to the direction of the exhaust gas flow, is arranged,
characterized,
that the corrugation (6, 7) of the part (5, 11) is omega-shaped such that in the installed state Flank parts of the respective adjacent wave crests (6) and wave troughs (7) facing each other lie against one another. 2. Device according to claim 1, characterized in that the corrugated part (5, 11) extends over the entire length of the catalyst carrier (4, 10). 3. Apparatus according to claim 1, characterized in that a plurality of corrugated parts are arranged over the length of the catalyst carrier, wherein at least one part is arranged at the beginning and end of the catalyst carrier based on the flow direction of the exhaust gas. 4. Device according to one of the preceding claims, characterized in that the waves of the corrugated part (5) transverse to the flow direction of the exhaust gas around the catalyst carrier (4) are formed circumferentially. 5. Device according to one of claims 1 to 3, characterized in that the waves of the corrugated part (11) run parallel to the flow direction of the exhaust gas. 6. Device according to one of claims 1 to 3, characterized in that the waves of the corrugated part are arranged obliquely to the flow direction of the exhaust gas. 7. Device according to one of the preceding claims, characterized in that the corrugated part (5, 11) consists of a wire mesh, woven or braid. 8. Apparatus according to claim 4 or 5 and 7, characterized in that the corrugated part (5, 11) consists of a wire stocking. 9. Apparatus according to claim 6 and 7, characterized in that the corrugated part is a helically wound around the catalyst carrier mat. 10. The device according to claim 9, characterized in that the waves of the corrugated part are arranged transversely, obliquely or parallel to the longitudinal direction of the mat. 11. Device according to one of the preceding claims, characterized in that the corrugated part (5, 11) projects beyond the catalyst carrier (4, 10) at the respective end. 12. Device according to one of the preceding claims, characterized in that the corrugated part (5, 11) is provided with a flow-inhibiting filler, in particular in the form of mica or ceramic fibers. 13. Device according to one of the preceding claims, characterized in that the corrugated part (5, 11) is formed in one layer.

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