EP0387422A1 - Apparatus for catalytic or other purification of exhaust gases of internal combustion engines, with two exhaust gas treating bodies and a protection ring between them - Google Patents

Abstract

Apparatus for catalytic purification of or removal of particulates from exhaust gases of internal combustion engines, having a housing (2), which has two open end regions (4) connected to an exhaust pipe (6) and a throughflow passage for the exhaust gas between the end regions (4), having two exhaust gas treating bodies (8), which are mounted in series in the housing (2) in the direction of flow, at a mutual spacing, and through which the gas can flow, and having a rigid protection ring (12) composed of ceramic material which encircles the clearance space between the two exhaust gas treating bodies (8). The protection ring (12) is held positively in the housing (2) in the axial direction by means of a holding element (10) which surrounds it on the outside, an axial gap (24) existing between the protection ring (12) and at least one of the two exhaust gas treating bodies (8) in the installed state. <IMAGE>

Description

The invention relates to a device for catalytic detoxification or for the de-combustion of internal combustion engine exhaust gases, with a housing which has two open end regions connected to an exhaust gas line and a flow passage for the exhaust gas between the end regions, with two in the flow direction in succession and in mutual Distance in the housing, flowable exhaust gas treatment bodies, and with a rigid protective ring made of ceramic material that delimits the space between the two exhaust gas treatment bodies on the outside.

A device for catalytic exhaust gas detoxification, in which the exhaust gas treatment bodies are ceramic monoliths with a catalytically active coating, is known from DE-A 36 26 728. There, among other things, a rigid protective ring made of ceramic material is described, the end faces of which bear against the two adjoining exhaust gas treatment bodies and the cylindrical outer circumferential surface of which is flush with the outer circumferential surfaces of the two adjoining exhaust gas treatment bodies.

A ceramic protective ring has the advantage over a protective ring made of sheet metal that it has much less thermal expansion and heat conduction.

According to the invention, the device is characterized in that the protective ring is held in the housing in a form-fitting manner in the axial direction by means of a holding element which surrounds it, with an axial gap between the protective ring and at least one of the two exhaust gas treatment bodies in the installed state.

An axial gap is preferably provided on both sides of the protective ring.

In the invention, the protective ring is largely decoupled from the two exhaust gas treatment bodies and is independently held in a form-fitting manner in the housing. Edge pressures between the protective ring and the treatment bodies and the need to adhere to tight manufacturing and assembly tolerances are avoided. Since the axial gap or the two axial gaps is or are preferably narrow, the effect of the hot exhaust gases acting through the axial gap is kept within reasonable limits. The invention makes available a protective ring solution which is more favorable in terms of behavior at changing temperatures and in terms of production technology.

Preferred, specific means for the form-fitting fixing of the protective ring are at least one peripheral bulge or at least one peripheral recess on the outside of the protective ring. The actual housing, on which the holding element bears on the outside, can also be designed, for example by at least one peripheral bead which is embossed outwards or inwards, in such a way that the holding element and thus the protective ring are reliably axially fixed. The device is structurally particularly favorable when the holding element is part of a holding mat holding the two exhaust gas treatment bodies. Specifically, the construction can also be such that the retaining element of the protective ring, which is designed as a mounting mat, also axially surrounds the two adjoining exhaust gas treatment bodies only to a certain extent, and that a further mounting mat is provided axially next to each exhaust gas treatment body. The mounting mat is preferably made of ceramic fibers or is designed as a so-called swelling mat, the volume of which increases as the temperature rises. Swelling mats are commercially available. The holding element can also consist of wire mesh.

Even if the holding element is not part of a longer mat, it can consist of the same material as is known for swelling mats.

Particularly in the case of the protective ring being held by swelling mat material, the ceramic material of the protective ring is preferably selected in the sense of comparatively good thermal conductivity. This has the advantage that the swelling mat material of the holding element actually becomes hot enough for swelling through the protective ring.

The protective ring is preferably surrounded by an intermediate layer over at least part of its axial length. This intermediate layer can act as an assembly aid to make it easier for the protective ring, and possibly also the exhaust gas treatment body, to slip into the correct installation position when the device is being assembled. Furthermore, the intermediate layer can serve as additional protection in the contact area between the protective ring and the subsequent exhaust gas treatment body or in the area of the axial gap there against the action of the hot exhaust gases.

The holding element is preferably installed with a radial preload so that the protective ring is securely held even with increasing radial dimensions of the annular space between the protective ring and the housing under high temperatures. It is preferably a non-rigid, resilient, but nevertheless fixing-tight holder.

It goes without saying that more than two exhaust gas treatment bodies can also be present in succession in the flow direction in the housing of the device, protective rings according to the invention preferably being provided in all spacing spaces between two adjacent exhaust gas treatment bodies.

Typical examples of proposed exhaust gas treatment bodies are ceramic monoliths with longitudinal channels and catalytically active coating for exhaust gas detoxification and sieve-shaped soot filter bodies, which can consist of ceramic material, but also of metallic material.

AlTiO, SiO₂, ZrO₂ and cordierite may be mentioned as typical, suitable ceramic materials for the protective ring. Silicon carbides and silicon nitrides may be mentioned as typical, cheaply usable ceramic materials for the case of desired, high thermal conductivity on the scale of the ceramic materials. Ceramic fabrics are particularly suitable for the intermediate layer.

Ceramic protective rings with practically any sectional profile can be produced in particular by a process known as slip casting. Within the scope of the invention, however, it is preferred to give the protective ring such a shape that it can be produced by the much cheaper pressing method. A particularly important prerequisite for the producibility of the protective ring by the pressing process is that, as preferred according to the invention, its inner circumference is designed such that the inner molded part or the inner molded parts of the manufacturing press mold in the axial direction can be pulled out. Or in other words: the inner circumference of the protective ring should, at least starting from the parting plane between two inner molded parts, not have any undercuts which would make it impossible to pull out the inner molded parts. In contrast, the design of the outer circumference of the protective ring is less critical since one can work there, for example, with the outer molded parts being moved radially away.

In a further development of the invention, it is further preferred that the protective ring has at least one area distributed over the circumference of at least one end face, in which the protective ring face has a greater radial height than next to the area in question. These end face areas with greater radial extension can serve as more effective contact surfaces for spacer plates. These are inserted between the protective ring and the adjacent exhaust gas treatment body during assembly of the device, so that the protective ring between the two exhaust gas treatment bodies is not aligned. The spacer plates preferably consist of a material, in particular a plastic, which burns at a higher temperature when the exhaust gas treatment device is operated for the first time. It is expedient to provide such end face regions with a greater radial height on both end faces of the protective ring and in a larger number than two distributed over the respective circumference.

In an embodiment of the invention it is possible to give the guard ring a cutting profile which changes as the guard ring progresses in the circumferential direction. This variant is particularly favorable if the protective ring is not circular, but in particular oval, rounded-triangular or the like. Then, for example, the protective ring can be given a profile in those circumferential areas where it has a comparatively smaller radius of curvature, which gives greater strength to the bending moments acting on it.
In the case of circular protective rings in particular, it can preferably be provided that the protective ring has a projecting nose at least at one point on its outer circumference in order to secure the protective ring in the circumferential direction in the housing. The lug (s) can (most conveniently) lie in one division plane of the housing.

• Fig. 1 eine Abgas-Vorrichtung im Längsschnitt;
• Fig. 2 weitere Schutzringkonfigurationen in größerem Maßstab und im Längsschnitt, und zwar vier unter­schiedliche Varianten links oben, rechts oben, links unten und rechts unten;
• Fig. 3 zwei weitere Schutzringkonfigurationen in einer Darstellung wie in Fig. 2, und zwar unterschied­liche Varianten oben und unten in der Zeichnung;
• Fig. 4 bis 8 weitere Schutzringkonfigurationen im Längsschnitt-Ausschnitt;
• Fig. 9 und 10 eine weitere Schutzringkonfiguration im Längsschnitt und in der Stirnansicht;
• Fig. 11 eine weitere Schutzringkonfiguration in Stirn­ansicht;
• Fig. 12 und 13 den Schutzring von Fig. 11 in einem Längs­schnitt gemäß 12-12 bzw. 13-13 in Fig. 11;
• Fig. 14 eine weitere Schutzringkonfiguration in Stirn­ansicht.

The invention and refinements of the invention are explained in more detail below with reference to exemplary embodiments illustrated in the drawings. It shows:

• Figure 1 shows an exhaust device in longitudinal section.
• Fig. 2 further guard ring configurations on a larger scale and in longitudinal section, namely four different variants top left, top right, bottom left and bottom right;
• 3 shows two further protective ring configurations in a representation as in FIG. 2, namely different variants above and below in the drawing;
• 4 to 8 further protective ring configurations in a longitudinal section detail;
• 9 and 10 a further protective ring configuration in longitudinal section and in the end view;
• 11 shows a further protective ring configuration in front view;
• 12 and 13 the protective ring of FIG. 11 in a longitudinal section according to 12-12 and 13-13 in FIG. 11;
• 14 shows a further protective ring configuration in front view.

In some of the drawing figures, the housing and / or the holding element are omitted, since their meaningful training due to the other explanations in the present application for the expert without Difficulties is possible.

The device shown in FIG. 1 has an essentially cylindrical housing 2 which tapers towards end regions 4 on both sides. Each end area 4 is welded to the open end of an exhaust pipe 6. Two ceramic monoliths 8 with a catalytically active coating for detoxification of internal combustion engine exhaust gases are held in the housing 2 one behind the other and at a mutual distance from one another by means of a continuous swelling mat 10 laid around. A ceramic protective ring 12 is arranged axially between the two monoliths 8 serving as exhaust gas treatment bodies. In the tapered areas of the housing 2, an inner shell 14 made of high-temperature-resistant sheet metal is arranged, which ends close to the respective monolith 8. An insulating mat 16, for example made of ceramic fibers, is located between the respective inner shell 14 and the housing 2. In the direction of arrows P there is a flow passage through the device from the end of the left exhaust pipe 6 through the left inner shell 14, through longitudinal channels of the left monolith 8, through the protective ring 12, through longitudinal channels of the right monolith 8, through the right inner shell 14 to the Right exhaust pipe end 6.

The protective ring 12 has a rectangular sectional profile. There is an axial gap 24 between its two flat end edges and the outer regions of the end faces of the two adjoining monoliths 8. The outer diameter of the protective ring 12 is somewhat larger than the outer diameter of the two monoliths 8, so that the protective ring 12 digs into the swelling mat 10 in a form-fitting manner. In the arrangement area of the protective ring 12, the housing 2 has an outwardly embossed, circumferential bead 28.

At the mat transition between the respective inner shell 14 and the respective monolith 8, a dotted intermediate layer 18 made of ceramic fabric can be seen.

In the embodiment according to FIG. 2, above, the protective ring 12 has a sectional profile which forms an encircling outer bead 20. As a result, the swelling mat 10 is compressed more radially in this area.

In the embodiment according to FIG. 2, below, the protective ring 12 has a corrugated sectional profile, which results in a particularly good, positive anchoring with the swelling mat 10. In addition, on the inflow-side axial gap 24, an intermediate layer 18 made of ceramic fabric is drawn as a row of dots. The intermediate layer 18 is located between the swelling mat 2 and the peripheral end region of the monolith 8 and the left peripheral end region of the protective ring 12 in FIG. 2. A corresponding intermediate layer 18 could also be provided on the right axial gap 24 or continuously over both axial gaps 24.

Both in the embodiment of Fig. 2, above, as well as in the embodiment of Fig. 2, below, the variant is indicated in the left half of the drawing that the inner cross section of the protective ring 12 to the axial tapered towards the end. This can be provided on one or both axial ends. This results in a minimized or even completely eliminated front edge covering of the monoliths 8 by the protective ring 12.

In the embodiment according to FIG. 3, at the top, the protective ring 12 has a sectional profile which forms a central, circumferential indentation 26. At the corresponding point, the housing 2 has an inwardly embossed, circumferential bead 28, so that the swelling mat has a double S-shaped change of direction at this point.

In the embodiment according to FIG. 3, below, the sectional profile of the protective ring 12 is concave as a whole bulged inwards. The housing 2 has a corresponding, inwardly embossed, surrounding bead 28. In addition, an intermediate layer 18 made of ceramic fabric can be seen, which covers the protective ring over its entire axial length, the two axial gaps and in each case one end region of the outer circumference of the two subsequent monoliths 8.

It is pointed out that the inner shells 14 shown in FIG. 1 could alternatively also continue axially, for example the monoliths 8 could include at least one end region or could pass as a combined part over the entire housing 2. In this case, the inner shell would be the housing holding the protective ring 12. It is also pointed out that the swelling mat 10 can press a piece into the axial gap 24 in a bead-like manner, as a result of which there is a cushioning between the monolith 8 and the protective ring 12 is formed. Finally, the possibility should also be mentioned that the protective ring 12 is provided between two monoliths 8 of different cross-sectional sizes, for example essentially conically overall between two coaxial monoliths 8 of different cross-sectional sizes or asymmetrically between a first, larger-sized monolith 8 and a second, smaller-sized monolith 8, the is provided with an offset central axis.

The intermediate layer 18 can be chosen to be smoother in terms of material than the swelling mat 10. Then the protective ring 12 slips more easily in the axial direction into its correct installation position when the device is being assembled, particularly in the case of the manufacture of the housing 2 from two half-shells which are welded together at the end, whereby positive installation also helps. In view of this function, a material can be selected for the intermediate layer 18 which burns during operation of the device. If one chooses a temperature-resistant material, there is a protective effect for the mounting mat 10.

In the embodiment according to FIG. 4, the protective ring 12 has a sectional profile similar to the embodiment according to FIG. 3 above, although a ring made of knitted wire is provided as the holding element, which lies on the inside in the indentation 26 of the protective ring 12 and on the outside in one outside embossed bead 28 of the housing 2 is located. A holding element 10 made of knitted wire is particularly favorable when the heat conducted through the protective ring 12 to the outside is not sufficient to swell a swelling mat there heating up enough. However, it is entirely possible to provide a mounting mat, for example made of ceramic fiber material or swelling mat material, between the outer circumference of the wire mesh ring 10 and the housing 2.

In the embodiment according to FIG. 5, the protective ring 12 has an outer peripheral shape similar to the protective ring 12 in FIG. 2 below. However, the inner circumference of the protective ring 12 is straight in the section shown and parallel to the longitudinal axis of the device. As a result, the protective ring 12 has a radial material thickness which changes as the protective ring 12 progresses in the axial direction.

In the embodiment according to FIG. 6, the protective ring 12 has a longitudinal section profile which corresponds to a rectangle with a rounded triangle attached. The inner circumference of the protective ring 12 is designed as in the embodiment according to FIG. 5.

In the embodiment according to FIG. 7, the protective ring 12 has a longitudinal sectional profile which differs from the rectangular profile according to FIG. 1 in that both the outer circumference and the inner circumference are reduced in the axially central region. This creates an indentation 26 in the axially central region of the outer circumference. At this point, the housing has an inwardly embossed bead 28, the helix angle of which is steeper than the helix angle on the outer circumference of the protective ring 12.

The embodiments according to FIGS. 4 to 7 have in common that the protective ring 12 can be produced in each case by the inexpensive pressing method. In the embodiments according to FIGS. 5 and 6, the inner circumference of the protective ring has no undercut at all, so that the inner molded part of the manufacturing mold can be pulled out in the axial direction without any problems. In the embodiments according to FIGS. 4 and 7, one can work with two internal molded parts which are indicated in FIG. 7 with the reference numbers 30 and 32. The parting plane between the two inner molded parts 30, 32 is located at the location of the smallest inner diameter of the protective ring 12. It can be seen that the inner molded parts 30, 32 can be easily removed axially outwards when the protective ring 12 is produced by the pressing process.

In the embodiment according to FIG. 8, the special feature is illustrated that the protective ring 12 is axially longer than the clear distance between the two adjoining exhaust gas treatment bodies 8. In its two axial end regions, the protective ring 12 has such a large inner circumference that it is one piece to a large extent includes the two adjoining exhaust gas treatment bodies 8. On both sides of the protective ring 12 there are circumferential partial regions 34 which are radially further inward than the described peripheral regions and which are located opposite the end edge region of the exhaust gas treatment body 8 adjoining there. The end faces of these areas 34 can serve as contact surfaces for the spacer plates described in the introduction to the description.

In the embodiment according to FIGS. 9 and 10, the protective ring has a longitudinal sectional profile similar to the protective ring 12 according to FIG. 2 below. In its two end regions, however, the protective ring 12 is provided on the inside with a bevel 36 which widens conically outwards, namely distributed over the circumference in each case over a somewhat less than 120 ° circumferential length. In this way, three areas 38 remain between the beveled areas 36, which have the full height of the protective ring in the radial direction on the respective protective ring end face. These areas 38 can serve as contact surfaces for the spacer plates described in the introduction to the description. The bevels 36 can be produced, for example, by grinding away. As a result of the bevels 36, only a very small edge area is covered by the end faces of the two adjacent monoliths 8.

11 to 13 is a generally oval protective ring 12 with the special feature that the protective ring 12 has a corrugated profile according to FIG. 12 in the area of its comparatively smaller radius of curvature and an im in the area of its comparatively larger radius of curvature 13 has a substantially rectangular profile. In this way, the protective ring 12 has greater strength with respect to bending loads in the areas of the comparatively smaller radius of curvature and is more resilient to bending loads in the areas of its comparatively larger radius of curvature. Furthermore, areas 38 can again be seen as in the embodiment according to FIGS. 9 and 10.

The embodiment according to FIG. 14 shows that the protective ring 12 can have outwardly projecting lugs 42 in the parting plane 40 of the housing 2, as a result of which it is positively fixed in the circumferential direction.

It is emphasized that the protective ring 12 in the context of the invention can either be circular in the end view or have another shape, in particular oval, elliptical, rounded-triangular, rounded-square, etc.

It is further emphasized that the variants described above with regard to the longitudinal sectional profile of the protective ring 12, design and material of the holding element 10, sectional profile variation along the protective ring circumference, presence of spacer plate contact surfaces 38 etc. can be combined with one another in any manner. For example, the wire mesh retaining ring 10 shown in FIG. 4 can be used in all guard ring configurations. Furthermore, for example, the spacer plate contact areas 38 can be provided in all guard ring configurations. Finally, for example, the sectional profile variation illustrated in FIGS. 11 to 13 can also be realized along the circumference of the protective ring with other specific protective ring sectional profiles.

Finally, it is emphasized that the protective ring 12 need not be symmetrical about a central plane intersecting its axis at right angles. It can, so to speak, be designed differently on the left and right, in particular on legs of different lengths on the left and right point.

Claims (13)

1. A device for catalytic detoxification or for the de-emission of internal combustion engine exhaust gases, with a housing (2) which has two open end regions (4) connected to an exhaust line (6) and a flow passage for the exhaust gas between the end regions (4), with two flowable exhaust gas treatment bodies (8) held one behind the other in the flow direction and at a mutual distance in the housing (2), and with a rigid protective ring (12) made of ceramic material which delimits the space between the two exhaust gas treatment bodies (8) on the outside,
characterized,
that the protective ring (12) is held in the housing (2) in a form-fitting manner in the axial direction by means of a holding element (10) surrounding it, with an axial gap () in the installed state between the protective ring (12) and at least one of the two exhaust gas treatment bodies (8) 24) exists. 2. Device according to claim 1,
characterized,
that the protective ring (12) has on the outside at least one circumferential bulge (20) or at least one circumferential indentation (26). 3. Device according to claim 1 or 2,
characterized,
that the holding element (10) is positively fixed in the axial direction in the housing (2). 4. The device according to claim 3,
characterized,
that the housing (2) in the arrangement area of the protective ring (12) has at least one peripheral bead (28). 5. Device according to one of claims 1 to 4, characterized in
that the holding element is part of a holding mat (10) holding the two exhaust gas treatment bodies. 6. Device according to one of claims 1 to 5, characterized in
that the holding element (10) consists of swelling mat material. 7. Device according to one of claims 1 to 5, characterized in
that the holding element (10) consists of knitted wire. 8. The device according to claim 7,
characterized,
that the ceramic material of the protective ring (12) is selected in the sense of good thermal conductivity. 9. Device according to one of claims 1 to 8, characterized in
that the protective ring (12) is surrounded at least over part of its axial length by an intermediate layer (18). 10. Device according to one of claims 1 to 9, characterized in
that the protective ring (12) designed on the inner circumference is that the inner molded part or the inner molded parts (30, 32) of a manufacturing mold can (are) pulled out. 11. The device according to one of claims 1 to 10, characterized in that
that the protective ring (12) has at least one area (38) distributed circumferentially on at least one end face, in which the face of the protective ring face has a greater radial height than next to the area in question. 12. The device according to one of claims 1 to 11, characterized in that
that the guard ring (12) has a profile on average that changes as it progresses in the guard ring circumferential direction. 13. Device according to one of claims 1 to 12, characterized in that
that the protective ring (12) has at least at one point on its outer circumference a projecting nose (42) for secure fixing in the circumferential direction.

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