EP0415101B1 - Exhaust system, in particular, device for the purification of exhaust gas - Google Patents

Description

The invention relates to an exhaust gas device with an at least partially double-shell metal housing, the gas-carrying metallic inner housing being supported by an elastic mineral fiber mat in the metallic outer housing, in particular exhaust gas cleaning device having an outer housing consisting of two half-shells, in which an elastic bearing mat, preferably a so-called. Swell mat, at least one honeycomb-structured support body and on the input and output side inner shielding funnels and, if appropriate, shielding rings are mounted between successive support bodies.

In such exhaust gas devices (EP-A-0275565 and EP-A-0193072) with a double-shell housing, there is basically the problem of compensating for the thermal expansion differences between the inner shell and the outer shell, which has considerable temperature differences during operation due to the thermal shielding by the mineral fiber mat . To compensate for the thermal expansion differences, it is usually assumed that a sliding seat is installed on at least one side (EP-A-0193072). This results in the unfortunate situation that two different thermal expansion differences have to be taken into account, namely radial expansion differences between the inner shell and the outer shell and secondly axial expansion differences between the inner lining funnel and, for example, the mostly ceramic carrier body which is in contact with it. Even if one tries to compensate for these radial expansion differences by dividing the segments, it has been shown in practice that the overlapping areas in which the expansion displacement should take place often do so at the high operating temperatures strongly adhere to one another, that in reality a functioning sliding seat does not come into being and thus lining funnels and other spacer rings create correct folds, which leads to considerable tension and a great risk of breakage of the ceramic monoliths. But also in the case of exhaust gas devices without built-in mineral carrier bodies, such as for example in the case of insulated double shell manifolds, the problem of absorbing the expansion differences of the gas-carrying inner manifold shells compared to the load-bearing outer manifold shells is relevant in the same way.

The invention is therefore based on the object of designing an exhaust gas device of the type mentioned in such a way that the problems with axial and radial expansion differences are solved with a simple structure, and moreover with a favorable transition to any ceramic parts, without the occurrence of stress peaks and the risk of wrinkles can be.

To achieve this object it is provided according to the invention that the inner housing is formed from a close-meshed and inherently sliding wire mesh mat and is fixed on both ends either on the outer housing or on a carrier body mounted therein.

Through the configuration according to the invention, a number of special problems can be solved in one. On the one hand, such a wire mesh mat - mesh fabrics with a mesh width of <0.5 mm are particularly suitable - can be processed very easily in press or deep-drawing molds, so that even very complicated shell structures can be produced. On the other hand, such shielding parts made of a wire mesh mat are provided with a very high degree of elasticity, both in the longitudinal direction and radially and in the transverse direction, so that the expansion differences mentioned at the beginning can be easily absorbed in the wire mesh in both the axial direction and the radial direction.

In a preferred embodiment of an exhaust gas cleaning device designed according to the invention with an outer housing consisting of two half-shells, in which at least one honeycomb-shaped support body and input and output-side inner shielding funnels and optionally shielding rings between successive support bodies are mounted via an elastic bearing mat, such that the one in the connecting piece jammed or welded shielding funnels clampingly encompasses the front end of the carrier body, any shielding rings should clamp around the neighboring carrier body ends in a corresponding manner, with the compensation of the expansion tolerance there is also an absolute certainty that due to any different expansions excessive stress peaks occur that lead to could destroy the thin-walled ceramic.

The special properties of a wire mesh mat also clearly prevent any risk of creasing at different expansions, for example of the shielding funnel produced from such a wire mesh mat and of the ceramic support body which is subsequently clamped around. As extensive tests have shown, the porosity of a shielding funnel made of a wire mesh mat does not interfere with the dense design of a shielding funnel that is deep-drawn from sheet metal, since with a sufficiently small mesh size, sufficient elasticity of the inner shielding component produced therefrom is still guaranteed on the one hand, and on the other hand due to the occurring mesh opening neither damage to the mineral fiber mat can take place, which in practice is more heat-resistant anyway is as metal, but on the other hand also blowing out or falling out parts from the mineral fiber mat can be reliably prevented.

Fig. 1

einen Längsschnitt durch eine erfindungsgemäß ausgebildete Abgasreinigungsvorrichtung,

Fig. 2

einen Schnitt längs der Linie II - II in Fig. 1,

Fig. 3

einen Längsschnitt durch einen isolierten Doppelschalenkrümmer mit aus einer Drahtgewebematte gebildetem Innengehäuse und

Fig. 4

einen Querschnitt längs der Linie IV - IV in Fig. 3.

Further advantages, features and details of the invention result from the following description of an exemplary embodiment and from the drawing. Show:

Fig. 1

2 shows a longitudinal section through an exhaust gas cleaning device designed according to the invention,

Fig. 2

2 shows a section along the line II-II in FIG. 1,

Fig. 3

a longitudinal section through an insulated double shell manifold with an inner housing formed from a wire mesh mat and

Fig. 4

3 shows a cross section along the line IV-IV in FIG. 3.

1 and 2 comprises, in a manner known per se, a two-shell outer housing 1, the two half-shells 1a and 1b of which are welded together on their flanges 2 and 3 running in the parting plane. In the exemplary embodiment shown, two honeycomb-shaped ceramic carrier bodies 4 u. 4 'with the aid of a mineral fiber mat 5 which is continuous over the entire length of the exhaust gas cleaning device and which is spaced apart in the middle. The inner shielding funnel 7, which covers the inlet cone 6 and the outlet cone (not shown), consists of a wire mesh mat which is fastened in the connecting piece both on the inlet side - which is achieved in the present case by jamming - and also fixed on the opposite side is. To this In the exemplary embodiment shown, the shielding funnel 7, which consists of a wire mesh mat, is resiliently stretched onto the end of the carrier body 4, an additional holding effect also being provided by the pressure of the surrounding mineral fiber mat 5. In the same way, the shielding ring 10 for the gap 11 between the adjacent carrier bodies 4 u. 4 'made of a wire mesh mat and clamped onto the ends of the carrier body. With this design, the inner shielding cylinder can not only be placed very easily around complicated inner structures, as must be the case with the complex-shaped carrier body 4 (FIG. 2), but there can be neither thermally induced stress peaks nor warping or wrinkling Shielding funnels or shielding rings, neither in the radial nor in the axial direction. It goes without saying that before applying the outer shells 1a and. 1b the shielding funnel 7 placed around the carrier body 4 does not initially lie completely into the upper trough 8, at least not when it is clamped onto the carrier body 4 with pretension. With the compression of the two shell halves 1a u. 1b of the outer housing, however, any lifting off at this point is corrected again.

3 and 4, using an insulated double shell manifold with a metallic outer housing 1 'and an inner housing 9, shows how the inventive construction of the inner housing from a wire mesh mat in a very simple and effective form can also be used with other types of exhaust gas devices, to avoid the otherwise usual complicated sliding seats in the area of the inner housing and / or outer housing. There is, as usual, a mineral fiber mat 5 'between the outer housing 1' and that of the wire mesh mat Shaped inner housing 9 is provided, the mineral fiber mat 5 'is preferably composed of divided blanks, which preferably abut against one another with their abutting edges because of the complicated structure.

The invention is not restricted to the exemplary embodiments shown. In particular, it would also be possible to form the shielding funnels and rings from two layers of wire mesh mats separated by a thermally insulating intermediate layer, which can preferably be done in such a way that the intermediate layer consists of ceramic fiber material in the form of a fabric, paper, blankets or fleece .

This design can namely be provided in the area of the shielding funnels or rings that the elastic bearing mat is completely eliminated over large sections, which in turn has the advantage that no high compressive forces of this elastic fiber mat have to be absorbed by the wire mesh shielding funnels and shielding rings . The production from the wire mesh mat instead of the usual metal sheets has the advantage that, for example, damage to the monolith is eliminated by the encompassing edge of the shielding funnel or shielding ring. Due to the thermally insulating intermediate layer, excessive thermal heating of the outer shell is avoided even without pulling the bearing mat over the area of the rings and shielding funnels, and on the other hand - in particular if the thermally insulating intermediate layer is used as paper, film or the like. is made of thermally resistant material - prevents hot exhaust gases from getting into the space between the inner shell and the outer shell, so that they are neither there heating or blowing out the elastic mineral fiber mat present in the area of the monolith at the latest.

In this context, it should finally be pointed out that due to the mostly existing asymmetry of wire mesh mats with regard to their sliding elasticity in different directions, the orientation of the mats when installing as a shielding funnel or shielding ring will of course be chosen such that the greatest sliding elasticity is also expected in the greatest direction of expansion to be expected consists.

Claims (5)

1. An exhaust gas device with a metallic housing (1, 7, 10; 1', 9) having a double shell at least in sections, the gas-conducting metallic inner housing (7, 10; 9) being mounted via an elastic mineral fibre mat in the metallic outer housing (1, 1'), characterised in that the inner housing (7, 10; 9) is formed by fine-mesh and intrinsically slide-elastic woven wire matting and is fixed at both ends either to the outer housing (1, 1') or a support element (4, 4') mounted therein.
2. An exhaust gas cleaning device according to claim 1 with an outer housing, which comprises two half shells and in which at least one honeycomb-stuctured support element, inlet and outlet inner shield funnels and optionally shield rings between succesive support elements are mounted via an elastic bearing mat, characterised in that the shield funnel (7) wedged or welded in the connection socket encloses the end-face end of the support element (4, 4') in a clamping fashion.
3. An exhaust gas cleaning device according to claim 2, characterised in that the shield rings (10) enclose the adjacent support element ends in a clamping fashion.
4. An exhaust gas cleaning device according to claim 2 or 3, characterised in that the shield funnels (7) and shield rings (10) are formed by two layers of woven wire matting separated by a thermally insulating intermediate layer.
5. An exhaust gas cleaning device according to claim 4, characterised in that the intermediate layer is made of ceramic fibre material in the form of a fabric, paper, blanker or fleece.

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