MXPA99009074A - Element of escape gas conduction and method for the manufacture of a gas conduction element of esc - Google Patents

Abstract

The exhaust gas conduction element (11) comprises an exhaust elbow (12) with at least two intake ducts (15) for example still a catalyst (13) and a wall with two composite wall elements (23, 24). ). The two wall elements (23, 23) enclose together in cross section the interior spaces of all the intake ducts (15) and eventually also also the catalytic agents (41) of the catalyst (13). Each wall element (23, 24) comprises two concave metal plates (25, 26) in one piece and a layer (35) of heat insulating material disposed therebetween, so that each wall element (23, 24) provides good insulation thermal. When a wall element (23, 24) is manufactured, the concave plates (25, 26) that correspond to it and the layer (35) of insulating material disposed between them are plastically deformed together. This allows an economical manufacture of the wall. (Fig

Description

ESCAPE GAS CONDUCTION ELEMENT AND METHOD FOR THE MANUFACTURE OF AN EXHAUST GAS CONDUCTION ELEMENT Description of the invention The invention relates to an exhaust gas conducting element or an exhaust system with at least two intake ducts to connect with an internal combustion engine and a wall. The exhaust gas conduction element serves as part of an exhaust system of an internal combustion engine, for conducting and eventually catalytically treating and purifying exhaust gas. In the case of the internal combustion engine, it can be, for example, a gasoline engine of a motor vehicle or other motor vehicles for roads. The known escape elbows have two or more intake ducts that can be connected to an internal combustion engine, and a common outlet for those, the various ducts being constituted by tubes with simple metal walls. Such walls are heated during the operation of the internal combustion engine at elevated temperatures which are normally at least 700 ° C, so that such exhaust elbows and in particular their intake ducts emit a lot of heat to their surroundings. The great heat emitted by radiation, thermal conduction and convection causes unwanted heating of parts and / or thermosensitive spaces that are near the exhaust elbow, such as electrical, electronic components and / or comprising synthetic materials, the fuel tank, a spare wheel and / or the passenger cabin. Therefore, in practice it is often necessary to mount heat shield plates close to the exhaust elbows that make the automotive vehicle expensive, take up a lot of space and can cause noise problems due to the vibrations generated by the engine. It is also known to surround the gas conducting parts of an exhaust elbow or catalyst with a double-walled cooling jacket. The latter has an intermediate space through which water is conducted during the operation. However, such a cooling jacket requires an additional cooling system to keep the heated water in the cooling jacket circulating and cooling, or the expansion of a cooling system that serves primarily to cool the motor. This increases space needs and costs. US 3 751 920 A discloses a non-catalytic exhaust gas reactor with a box and intake ducts which at points distributed along the cylindrical sleeve of the box open into the interior space of the box through the jacket. That is, this exhaust gas reactor does not form an exhaust elbow and generates a great back pressure during the operation. The intake ducts of the exhaust gas reactor obviously have metal walls and therefore emit a lot of heat to their surroundings. The shirt has an outer wall that you obviously made of metal. This encloses an insulating layer that has perforations in the mouths of the intake ducts as well as the exhaust duct, and fittings inside, outside, at the ends and next to the perforations. Insulating layers are also disposed on the inner sides of the end walls. That is, these insulating layers and their fittings must be manufactured and mounted additionally to the cylindrical metal exterior wall, the flat metal end walls and the intake ducts. In order to form this box, the intake ducts and the insulating layers it is necessary to manufacture and assemble many independent parts. Otherwise the materials of the insulating layers and of the linings are not indicated. Document FR 2 238 585 A discloses a composite material consisting of fiberglass fabric arranged between two metal sheets and serving in particular to form boxes of silencers. To make one of these, two plates of the composite material are formed to form half-shells and then joined together along the edges. Document FR 2 238 585 A does not reveal escape elbows. Additionally, the fiberglass weave is obviously extremely thin, and also only has a low resistance to pressure. However, in order to form a flat plate of composite material in order to form an exhaust elbow having relatively small radii of curvature, it is necessary to apply high pressure forces on the plate by means of which the fiberglass fabric would be very strongly compressed. . According to the tests carried out, the thickness of the fiberglass fabric in the finished exhaust elbow would probably be at most approximately 20% to 35% of the original thickness, and already less than about 1 mm. By this the emission of heat from an exhaust elbow could only be reduced insufficiently. US 4 215 093 A discloses a catalyst and two intake ducts for connecting an internal combustion engine to the catalyst. The latter has a box with two walls of which each consists of two concave plates and between which there is an intermediate space containing air. However, the intake ducts only have simple metal walls that during the operation are heated to high temperatures and emit a lot of heat. Additionally, the investigations carried out on motor vehicle catalysts with a similar double-walled box demonstrate that despite the intermediate space containing air, the outer wall of the boxes of this type is heated to elevated temperatures which are typically approximately 500 ° C. at 600 ° C. Therefore, a catalyst of this nature also emits a lot of heat to its environment. The exhaust device known from US 4 215 093 A also has the disadvantages that it is necessary to assemble many independent parts in order to manufacture it, which makes the manufacture of the exhaust system more expensive. Additionally, the screw connection of the concave plates that form the outer wall takes a lot of place. Similar problems can also occur in the case of an independent escape elbow. Accordingly, the object of the invention is to create an exhaust gas line or an exhaust system for catalytic exhaust gas to be catalysed and optionally treated, which respectively eliminates the disadvantages of the exhaust gas supply elements and / or known exhaust devices with an exhaust elbow and / or catalyst with at least two intake ducts, and provide a good thermal insulation, but can nevertheless be manufactured and assembled economically, and occupy only a small place. According to the invention, this task is solved with an exhaust gas guiding element with the features of claim 1. The invention also relates to a method for the manufacture of an exhaust gas conducting element, being that the method according to the invention has the characteristics of the claim 14. Advantageous improvements of the exhaust gas conducting element and the method are derived from the dependent claims. The layer of heat insulating material that according to the invention is between the concave plates of each wall element provides good thermal insulation. This ensures that the heat carried by the exhaust gas remains largely in the exhaust gas and / or in the interior of the exhaust gas line or exhaust system. The heat that remains in the exhaust gas is transported by it and at least in large part is spread to the environment along with the exhaust gas. Accordingly, each outer concave plate of the exhaust gas conduit element or the exhaust device is heated only at a relatively low temperature during the operation. Additionally, the exhaust gas conduction element emits little heat to its surroundings. Therefore, it is also not necessary to protect the thermosensitive parts or spaces which are close to the exhaust gas supply element against the heat radiated or otherwise emitted by the exhaust gas supply element by means of thermal protection plates. In an advantageous embodiment of the exhaust gas guiding element, this has an exhaust elbow forming the intake ducts and, arranged downstream of the elbow also a catalyst with catalytic agents for the catalytic treatment of the exhaust gas which together with that form a unit. Both wall elements of the exhaust elbow can then, for example, also completely enclose an interior space of the catalyst, and in particular catalytic agents, in the cross section. Instead, two additional wall elements can be provided for the catalyst, each having two metal concave plates and a layer of heat insulating material disposed therebetween. Then the two additional wall elements can together completely enclose the catalytic agents in the cross section and, for example, be directly, immediately, rigidly and hermetically joined to the wall elements belonging to the exhaust elbow. By means of this configuration of the exhaust gas guide element, the catalyst and its connection with the exhaust elbow are also very well thermally isolated. In addition, it is possible to manufacture such a unit in a particularly economical manner. The wall elements are preferably designed in such a way that they are firm and substantially rigid, as well as connected to one another in a substantially rigid and at least partially or completely airtight manner, which are self-supporting and together form a self-supporting part of the wall. At least one essential part of the wall of the exhaust gas supply element can then be constituted exclusively by the wall elements connected to one another. It is then only necessary, for example, to provide connecting and / or connecting elements on the wall at most at the entrance and / or exit of the exhaust gas supply element for connecting the exhaust gas supply element. with the internal combustion engine and a part of the exhaust system disposed downstream of the exhaust gas conduction element. The connection and / or connection elements can have, for example, a common connection flange for all the intake ducts or at least two connection flanges which are associated with different intake ducts. In addition, the wall elements can then form the outer limit of the exhaust gas supply element for at least the majority of the wall. The elements of the wall can be configured and united in such a way with each other that they only take up little space. The concave plates, for example, have a thickness of about 0.5 mm to 1 mm. In the finished exhaust gas guiding element, the heat-insulating layer generally has a thickness of at most 10 mm, preferably substantially at least 2 mm, and for example from at least approximately 3 mm to maximum 5 mm. The temperatures of the external concave plates of the wall elements will then be, for example, at most approximately 50% of the temperature of the exhaust gas measured from 0 ° C and / or of the temperatures resulting in the outer surface of a simple metallic wall to otherwise the same configuration of the exhaust gas conduit element or of the exhaust device. The heat insulating insulating material will preferably be inorganic, fireproof and heat-resistant at least up to the operating temperature of the exhaust gas conducting element and up to the exhaust gas temperature, for example to at least 800 ° C. Each layer of insulating material is constituted, for example, by a plate and / or microporous sheets (s) continuous (s), more or less firm (s), in particular especially resistant (s) to pressure. By "microporous" it is meant that the layer or plate has pores with sizes of about 1 μm or some, but less than 10 μm or less than 1 μm. Each heat insulating layer is formed, for example, by a material that originally had the form of particles that at least in the majority consisted of grains, which eventually still had fibers, and which were compact by pressure as well as by heat treatment and / or a chemical reaction Accordingly, each layer of this type has, for example, grains that adhere to each other with greater or lesser firmness, and eventually still fibers that serve as reinforcement. The proportion of fiber is, for example, at most about 10% by weight, so that the layer or plate has at least a large part, and for example, in large part a granular structure. The insulating material, and in particular its granular components, are constituted, for example, substantially by oxidic materials. The insulating material contains, for example, silicic acid and / or at least one silicate and / or aluminum oxide ceramic, specifically at least 50% by weight of highly dispersed silicic acid. The fibers are constituted, for example, by a mineral and / or ceramic material of aluminum oxide. Such microporous insulating materials are described, for example, in EP 0 029 227 A and the corresponding US 4 985 163 A, and are obtained, for example, under the trademark WACKER DS through the company Wacker-Chemie GmbH, Munich, Federal Republic of Germany. In order to manufacture the wall, for each or each wall element, two pieces of flat metal sheet metal can be molded to form concave plates, and to join them together. For this purpose it is possible to mold joints in pairs during at least a large part of the forming process, with a layer of heat insulating material disposed therebetween, the two pieces of sheet metal that are required to form a pair of concave plates. This makes possible an economical manufacture of the wall. The shaping can be carried out, for example, by deep drawing. During forming a considerable force of pressure is exerted on the pieces of sheet metal or concave plates, and on the layer of heat insulating material disposed between them. When this happens, the thermoinsulating layer is compressed.

If the heat insulating material is constituted by a precompacted microporous plate or sheet, then the thickness of the heat insulating layer is only reduced, for example, by less than 50% during forming, specifically in general approximately 20% to 40%. That is, before the shaping, it is only necessary that the thickness of the layer is relatively a little greater than in the finished exhaust gas guiding element. Eventually each heat insulating layer, instead of being constituted by a microporous plate or sheet, can be at least for the most part by a fiber material, for example a single layer or multilayer fabric. The fibers can consist, for example, of aluminum oxide ceramic and / or mineral wool, basaltic wool, glass wool and / or any other mineral material. However, the fiber material is compressed considerably harder during shaping than a precompacted microporous sheet or sheet, so that the thickness is reduced during shaping, for example, about 65% to 80%. The object of the invention is explained below in more detail based on the exemplary embodiments shown in the drawing. In the drawing, FIG. 1 shows a schematic diagonal view of an internal combustion engine with an exhaust gas line element having an exhaust elbow and a catalyst, FIG. 2 the exhaust gas line element illustrated partially in longitudinal section and partly in side elevation, figure 3 a cross section through a catalyst area along the line lililí of figure 2, on a larger scale, figure 4 a cross section through the element of The line IV-IV of FIG. 2 is enlarged on a larger scale, FIG. 5 is a cross-section through two pieces of sheet metal used for the formation of the two concave plates of the gas supply element. outlet located below in figures 3, 4, and a shaping device for forming the sheet metal parts, represented schematically, figure 6 a cross section through an area of both pieces of sheet metal 'or concave plates drawn in figure 5 after the partial shaping of these, and a cutting device represented schematically, figure 7 a cutting device for cutting out areas of metal sheets which are intended for the formation of the concave plates that are located above in figures 3, 4, figure 8 a longitudinal section through an area of another exhaust gas conduction element, figure 9 a diagonal view of parts of another exhaust gas conducting element, the heat insulating wall being omitted, Figure 10 a simplified longitudinal section through the exhaust gas conduit element according to Figure 9, with the heat insulating wall, and the 11 shows a diagonal view of an exhaust gas conducting element having only one exhaust elbow. The internal combustion engine 1 partially drawn in schematic form in Figures 1 and 2 comprises a crankcase 2 of the engine, several cylinders and at least two exhaust gas outlets 3 with respectively an opening. Each exhaust gas outlet 3 defines an axis 4 straight. The motor has, for example, on each side three exhaust gas outlets 3 whose axes 4 are parallel to each other, for example in a common plane and inclined downwards away from the engine crankcase. An exhaust system comprises an exhaust device 11 or an exhaust gas conduction element 11, which can be seen in figures 1 to 4. The exhaust device or exhaust gas conduction element 11 forms an elbow 12. and a catalytic converter 13. The exhaust elbow 12 has at least two and specifically three intake ducts 15 bent in their longitudinal directions at least partially or at some points to communicate the exhaust gas outlets 3 with the catalyst 13. The exhaust elbow 12 has connecting elements and / or connection with a common connection flange 17 for all the intake ducts 15. The flange has an opening for each intake duct 15. The catalyst 13 has a box 21. This in the direction of flow of the exhaust gas comprises in sequence an input section 21a, a main section 21b, an exit section 21c and a neck 21d. The main section 21b is substantially parallel to an axis 22 defined by it, as well as generally cylindrical and of cross section, for example, generally approximately oval and / or elliptical. The inlet section 21a communicates the three intake ducts 15 with the main section 21b and widens for example in at least one longitudinal cut to the main section 21b. The outlet section 21c has a general funnel shape and narrows away from the central section 21b. The neck 21d delimits a circular opening. The axis 22 encloses with the axes 4 parallel to each other, for example, an obtuse angle a. The exhaust elbow 12 and the case 21 of the catalyst 13 have a common wall with two multi-layer wall elements 23, 24 and / or continuous heat insulating compounds along the flow path. Each wall element 23, 24 forms in cross section about half the wall and has a continuous main section without interruptions in cross section forming approximately half the body wall and an area of the end sections of the conduits 15 of the wall. admission joined with the box 21. Furthermore, each wall element has three finger-shaped sections extending from its main section to the joint flange 17, which in the cross section are separated from each other by free intermediate spaces and they are respectively associated with one of the intake conduits 15. The two wall elements enclose an interior space completely in cross section. Each multi-layer and / or composite wall element 23, 24 comprises a pair of one-piece metallic concave plates made of steel, specifically an external concave or outer plate 25 and an inner concave plate 26 or 28. The two concave plates 25, 26 or 27, 28 belonging to the same wall element have central sections 25a, 26a, 27a, 28a separated one from the other by an intermediate space and edge sections that are in contact with each other as along the entire circumference of the concave plate. The outer edge sections of the four concave plates 25, 26, 27, 28 which extend from the inlets of the intake ducts 15 generally in the longitudinal direction along the exhaust gas flow path to the outlet of the exhaust pipe. Catalyst are designated 25a 26a, 27a, 28a in Figures 3, 4. The central sections 25a, 26a, 27a, 28a have a convex and at least partially curved cross section. In both concave plates 27, 28 which in FIGS. 3, 4 are below, the sections 27b, 28b of the edge protrude outwardly away from the central sections 27a, 28a, have an approximately angular cross section and / or approximately linear shape . The sections 25b, 26b of the edge of the two concave plates 25 and 26 which in FIGS. 3, 4 are above are curved at most a little with respect to the central section 25a or 26a and protrude inwards from the necks formed by the sections 28b of the edge of the inner lower concave plates 28. The sections 25b of the edge of the outer upper concave plate 25 are in contact with the sections 28b of the edge of the inner lower concave plate 28. Each finger-shaped section of a concave plate is formed in its cross-section analogously as the sections of the concave plates belonging to the body. At the inlets of the intake ducts 15 and at the outlet of the catalyst the sections of the edges of the concave plates belonging to the same wall element are in contact with each other in the manner shown in Figure 2. The sections of the edge of the various concave plates abut one another at the contact points, where in each case they are in direct contact with each other at least two sections of the edge. The edge sections of the concave plates that belong to the same wall element are firmly attached, specifically welded substantially rigidly and inseparably and hermetically to one another along the entire circumference of the concave plates and partly also to other parts. In sections 25b, 26, 27b, 28b, of the edges visible in FIGS. 3, 4 extending generally in the longitudinal direction, all four sections 25b, 26b, 27b, 28b which are in contact with one another by The pairs are joined to one another by a common welded joint 33 produced in a single welding process. The corresponding is valid for the sections of the edges between the finger-shaped sections of the concave plates. The intermediate space between the central sections 25a, 26a of the concave plates 25 or 26 contains a layer 35 of insulating material. The intermediate space between the central sections 27a, 28a of the concave plates 27 or 28 contains a layer 36 of insulating material. The layers 35, 36 of insulating material fill substantially all of said intermediate spaces. The insulating material can be constituted by any of the insulating materials described in the introduction, for example a microporous plate or sheet. The main section 21b of the box 21 contains catalytic agents 41 for the treatment and catalytic purification of the exhaust gas. The catalytic agents 41 have for example a catalyst body 42 of approximately oval and / or substantially cylindrical elliptical cross section with an inlet surface 42a of the exhaust gas as well as an exhaust outlet surface 42b. The surfaces 42a, 42b are flat and perpendicular to the axis 22. The catalyst body comprises, for example, a ceramic substrate with a multitude of axial passages for the exhaust gas.

The substrate surfaces delimiting the passages are provided with coatings which for the most part consist of porous aluminum oxide and also comprise at least one catalytically active material, for example platinum. The main section 21b of the box 21 further contains an intermediate layer 43 resistant to temperature which is disposed between the surface of the jacket of the body 42 of the catalyst and the internal surface of the inner wall 32, which encloses the body of the catalyst in cross section and also keeps it isolated from vibrations. The intermediate layer 43 is constituted by a material in the form of a heat-resistant, heat-insulating and, for example, elastically deformable layer, in particular radially compressible. The intermediate layer 43 is constituted for example by a mat with inorganic fibers, mineral plates that are inflated during the first heating, and a binding agent. The intermediate layer, however, could also have at least one layer of an interlaced wire or wire mesh and a thermally insulating material. The wall formed by both wall elements 23, 24 encloses a funnel-shaped inlet and / or inlet wall 45 in cross section. This is disposed at the transition from the exhaust elbow to the catalyst and is for the most part inside the inlet section 21a of the box but also still protrudes into the interior space area of the exhaust gas guiding element that belongs to the escape elbow. The inner collector and / or inlet wall 45 encloses an internal collector space in cross section. The final section of the exhaust elbow disposed downstream and the transition section thereof to the catalyst also form a collector or collecting section of the exhaust gas conducting element. At the end which is closest to the joining flange 17 along the flow path, the inner and / or inlet wall 45 has a final section with an inlet opening 45a which can be seen with particular clarity in Figure 4, a central section that widens in the direction of the stream, and at its downstream end a substantially cylindrical short end section of approximately oval and / or elliptical cross section with an outlet opening. This end section extends to at least near the inlet surface of the exhaust gas of the body 42 of the catalyst, has an external surface aligned at least approximately with the surface of the jacket or the circumference of the catalyst body and is enclosed at least partially by the intermediate layer 43. The inner collector and / or inlet wall 45 is constituted by two concave plates 46, 47 of a metallic material, specifically steel. The concave plates 46, 47 have a convex cross-section and are curved at some points and welded together in the vicinity of their edges. Each intake duct 15 has an internal duct 51. The latter is constituted by a tube of a single piece of a metallic material, specifically steel curved at least in some parts. The connection flange 17 comprises, for example, two flat plates adjoining one another. The finger-shaped sections of the four concave plates 25 to 28 associated with the intake ducts have edge sections projecting inwards from openings in the joint flange 17 and are there welded together, with both plates of the flange of union and with extreme sections of the internal conduits. The connecting flange 17 is removably attached to the engine casing 2 with fastening elements 53 having for example bolts, and communicating the intake duct inlets hermetically with the exhaust gas outlets 3 of the internal combustion engine. The outlet end sections of the inner conduits 51 remote from the flange 17 protrude side by side towards the inside opening 45a of the internal collector and / or inlet wall 45 with at most a small clearance, so that together they fill at least approximately the entry aperture 45a in cross section, they can be displaced for example in their longitudinal direction with respect to the inner collector and / or inlet wall 45 and produce a connection at least approximately hermetic internal conduits 51 of the intake ducts 15 with the internal wall 45 collecting and / or inlet. An internal, generally funnel-shaped outlet wall 55 is disposed downstream of the catalytic agents 41 in the box 27, and is for the most part in the outlet section 21c of the box 21. The inner wall 55 of The outlet has at its end which is upstream a short end section of approximately oval and / or elliptical cross section that abuts at least approximately with the body 42 of the catalyst, which has an external surface aligned approximately with the surface of the jacket and / or of the circumference thereof and which at least is partially surrounded by the intermediate layer 43. To this cylindrical end section follows a narrowing central section, which is followed by an approximately cylindrical short end section extending approximately to the end of the box 21 arranged downstream, delimits a circular opening and together with the neck 21d of the box 21 forms the exhaust gas outlet of the common catalytic converter for all intake ducts. The inner exit wall 55 is constituted by a one-piece body of a metallic material, specifically steel. An outlet conduit 57 consisting of a tube of a metallic material, specifically steel is tightly and tightly joined, specifically welded to the inner exit wall 55 and the neck 2Id of the box 21 formed by the edge sections of the concave plates. , 26, 27, 28. A metallic bushing made of steel has an axial through hole with an internal thread, protrudes through perforations of the concave plates 25, 26 and 46 disposed upstream of the catalytic agents 41 and is hermetically sealed with these concave plates. A lambda probe 60 is screwed into the internal thread of the bushing 59 and protrudes through it into the internal area enclosed by the inner entrance wall 45. A bushing 61 is welded in a bore of the conduit 57 downstream of the catalytic agents 41 and also has an axial through hole with an internal thread in which a lambda probe 67 is screwed protruding into the outlet conduit 57. The output of the catalyst 13 can be coupled with other parts of an exhaust system, in particular with a silencer through the outlet conduit 57. The inner collector and / or inlet wall 45 is rigidly connected to the wall 22 composed by the bushing 59 as well as further maintained in a centered and limitedly mobile manner by at least one flange or the like, or possibly is rigidly connected with the elements of composite wall 23, 24 by means of additional joining elements. The internal ducts 51 of the intake ducts 15 are separated from the inner concave plates 26, 28 of the composite wall elements 23, 24 substantially and for the most part - ie by omitting their end sections attached to the joint flange - by an intermediate space 65 continuous. The intermediate space 65 also separates most of the internal collector and / or funnel-shaped entrance wall 45 from the composite wall elements 23, 24. The funnel-shaped exit inner wall 55 is substantially and substantially separated. most of the wall elements 23, 24 by an intermediate space 67. The intermediate spaces 65, 67 are substantially hollow and contain air and / or at least approximately stationary exhaust gas. In the manufacture of the exhaust device or exhaust gas conducting element 11, the one-piece flat sheet metal parts intended for the manufacture of the concave plates 25, 26, 27, 28, 46, 47, and the inner output wall 55 are cut out, for example by punching. The further processing of the sheet metal parts intended for the formation of the two concave plates 27, 28 which are located below in figures 3 and 4 is explained in more detail based on figures 5 and 6. The sheet metal parts and their sections are designated with the same reference numbers as the finished concave plates and their sections. During the further processing, the sheet part for the formation of the external concave plate 27 is provided by means of a preforming, for example, a flat recess in which the layer 36 of still flat insulation material is placed. The still flat piece 28 is then placed on the sheet piece 27 and inserted together with the latter into the shaping device 71 shown schematically in FIG. 5. This is designed as a deep-drawing device and comprises, for example, a tool 72 of molding configured as a die, a clamping element 73 and a molding tool 74, specifically a die. The edge sections 27b, 28b of both sheet metal parts 27 and 28 are retained for conformation between the molding tool 72 configured as a die and the clamping element 73.

When the molding tool 74 serving as a die is moved downwards in the manner indicated by the arrows, the pieces of sheet intended for the formation of the concave plates 27, 28 and the layer 36 of insulating material arranged between them are formed simultaneously by deep drawing. The sheet pieces suffer in this a plastic deformation and bend. The layer 36 of insulating material is deformed, folded and compressed more or less plastically - depending on its composition. During the shaping, that is to say the deep drawing, the central sections 27a, 28a of both sheet metal parts or concave plates 27, 28 obtain the desired shapes for the finished concave plates shown in FIG. 6. A cutting device 75 represented schematically in figure 6 it comprises two cutting tools 76, 77 of which for example the tool 76 has a stationary blade and the tool 77 is configured as a movable blade 77. After forming the central sections 27a, 28a the non-needed areas of the edge sections 27b, 28b are eliminated by cutting with the cutting device 75. After this the remaining edge sections 27b, 28b are angled together upward in an additional shaping step so as to obtain their final shape. The originally planar sheet metal parts for the formation of the two concave plates 25, 26 which are located above in FIG. 3, 4 are formed analogously as described for the concave plates 27, 28 on the basis of FIG. 5. sheet metal pieces for the formation of the concave plates 25, 26 in this case they are in particular shaped in large part together with the layer 35 of insulating material disposed therebetween. After this the edge sections of the sheet pieces which are held by the die and the fastening element during the deep drawing are cut as close as possible to the shaped areas of the sheet parts with the cutting device 79 arranged in figure 7. The concave plates 25, 26 thus obtain their finished shape so that in the case of these concave plates no further bending and / or angulation of the edge sections is necessary. When the concave plates 25, 26, 27, 28 and layers 35 and 36 of insulating material arranged between them have been formed, the two pairs of concave plates are joined and welded together according to figures 1 to 4. The welding is carried out for example with an electrode, where welding material is applied and the edge sections 25b, 26b, 27b, 28b of all four concave plates that adjoin each other in pairs are simultaneously welded together. . By doing this, the aforementioned welded joint 33 is formed. In other words, during the series production the two multi-layer and / or composite wall elements 23, 24 can be formed with relatively few shaping processes from originally planar sheet metal parts and layers of originally planar insulating material, and join then one with another through few welding processes. It is also possible to form the entire exhaust system or the entire exhaust gas supply element 11 from relatively few originally independent parts and assemble it quickly, easily and economically. When the internal combustion engine 1 produces hot exhaust gas during the operation, it flows through the steps delimited by the internal conduits 51 of the intake ducts 15 and the internal area and / or passage to the inlet surface 42a. the exhaust gas of the body 42 catalyst of the catalytic agents 41, delimited by the inlet interior wall 45 which widens in the direction of flow. The internal funnel-shaped collecting and / or inlet wall 45 serves in this to collect the exhaust gas coming from various intake ducts and to distribute it over the inlet surface 42a for exhaust gas of the body 42 of the catalyst. For this, the internal and / or inlet wall 45 conducts the exhaust gas in general and in particular in the central area, ie in the vicinity of the axis 22, parallel to this as well as approximately perpendicularly with respect to the inlet surface 42a for the exhaust gas, against the latter. The exhaust gas then flows through the passages of the catalyst body and in doing so is treated and catalytically purified. The exhaust gas flowing out of the body 36 of the catalyst via the exhaust surface 42b for exhaust gas then flows through the interior space of the interior outlet wall 55 in the shape of a funnel tapering in the direction of the stream to the exit conduit 57. The two lambda probes 60 and 62 can measure the oxygen content of the exhaust gas upstream and downstream of the catalytic agents 41. The compactly designed exhaust gas guiding element 11 only takes up little space and allows the catalyst 13 to be arranged close to the internal combustion engine 1 and connected to it by relatively short intake ducts. The layers of insulating material 35, 36 of the wall elements 23, 24, the intermediate layer 43 as well as the intermediate spaces 65, 67 containing the more or less stationary air and / or exhaust gas produce a good thermal insulation and insulate thermally against the environment the gas conducting parts of the exhaust elbow and the catalyst. The good thermal insulation also ensures that the exhaust gas only suffers little cooling between the internal combustion engine and the catalytic agents. In the case of a cold start this results in the advantage that catalytic agents that are originally at room temperature are rapidly heated to a temperature required for effective catalytic treatment and purification of the exhaust gas. During the operation, the hot exhaust gas causes temporary and different heating and dilatations of the parts of the exhaust gas conduction element 11. The design as well as the manner of assembly of the gas conducting parts make it possible to absorb the various dimensional changes caused by temperature changes without causing excessive stress or damage. The internal combustion engine 1 partially visible in figure 8 again comprises a crankcase 2 of the engine and exhaust gas outlets 3 with mutually parallel axes 4. In FIG. 8, a part of an exhaust device or of an exhaust gas conduit element 111 can also be seen with an exhaust elbow 112 and a catalyst 113. The catalyst housing 121 defines an axis 122. This shape again with the mutually parallel axes 4 an obtuse angle a. The exhaust elbow 112 and the catalyst 113 have two wall elements 123, 124 of multilayer and / or heat insulating composite. These enclose in cross-section, among other things, a catalyst body 142 with an inlet surface 142a for exhaust gas, an internal inlet wall 145 and internal ducts 151. The exhaust gas conducting element 111 is in general similarly configured to the exhaust gas conduit element 11, but it differs from this in that the inlet section of the box 121 and the inner wall 145 collector and In this way, they are bent and / or angled in the axially drawn section, which extend partially more or less along a straight axis parallel to the axes 4. When the exhaust gas conduction element 111 is used , the exhaust gas flows correspondingly in general and in particular more or less parallel to the axes 4 against the intake surface 142a for exhaust gas in the central area of the cross section of the internal area and / or the passage delimited by the wall 151. In other words, the exhaust gas has an internal area that is very little upstream of the inlet surface 142a for exhaust gas in general and to a large extent a flow direction that is nclined against the inlet surface 142a for exhaust gas and encloses with it approximately the angle ß, which is different by 90 ° and specifically 90 ° smaller than angle a. Figures 9 and 10 show an exhaust device or an exhaust gas conduit element 211 with an exhaust elbow 212 and a catalyst 213. The exhaust elbow has for example four intake ducts 215 and a connection flange 217 which can be detachably fixed to a motor housing with fastening means, for example screws. The catalyst 213 has a box 221 which is generally rotationally symmetrical to an axis 222 having an inlet and an outlet. The wall of the exhaust elbow 212 has in the vicinity of the catalyst 213 a main section continuous in cross section and away from it, finger-shaped sections, separated in cross section by intermediate spaces, projecting towards the connection flange 217 . The main section and the finger-shaped sections of the wall of the escape elbow are formed by two wall elements 223 and 224 of several layers and / or composite. Each of them forms in cross section about half the wall and comprises a pair of metal concave plates. Each of these pairs has an outer concave plate 225 or 227 and an inner concave plate 226 or 228. The concave plates belonging to the same pair have central sections between which a layer 235 or 236 of insulating material is arranged. . The wall 224 of the catalyst also comprises two wall elements 233 and 234 of several layers and / or composed in each case a pair of concave plates and a layer of insulating material. We still note that the four composite wall elements were omitted in Figure 9 and were only drawn in Figure 10. The wall of the catalyst box formed by the composite wall elements 233, 234 encloses an inner wall in cross section. metal of the catalyst. This extends approximately along the entire axial dimension of the composite wall elements 233, 234 and protrudes for example at the catalyst exit even slightly outside the composite wall elements 233, 234. The housing 221 and the inner wall 240 sequentially have a neck approximately parallel to the axis 222 along the exhaust gas flow path, an inlet section that widens at least in the longitudinal section shown in FIG. 10, a cylindrical main section, of approximately circular or oval cross section parallel to axis 222, a narrowing outlet section and a substantially cylindrical neck or projection. The main section of the inner wall 240 of the catalyst contains catalytic agents 241 with a body 242 of the catalyst. A deformable intermediate layer 243 is disposed between the inner wall 240 and the circumferential surface of the catalyst body. The inner wall is constituted, for example, by a piece of sheet metal in one piece, or by two pieces of sheet metal welded together. An internal wall 245 for collecting and / or metal entry, for example constituted by a one-piece sheet metal part, is at least for the most part in the internal space enclosed in the cross section of the composite wall elements 223, 224. of the exhaust elbow, and is connected to the inlet of the internal wall 240 of the catalyst, for example, hermetically welded. Each intake duct 215 has an internal duct 251 extending from the attachment flange 217 to the inner and / or inlet collector wall 245 and which is attached to it at least approximately hermetically as well as displaceably or rigidly. At its outlet the box 221 has a bushing 253 protruding inwardly between the inner concave plates of the composite wall elements 233, 234 and the inner wall 240. The four concave plates 225, 226, 227, 228 of the wall elements 223, 224 composed and the four concave plates of the wall elements 233, 234 composed of cross-sections have edge sections which are analogously shaped and welded together as in the case of the four concave plates 25 to 28 according to figures 1 to 4. The four concave plates 225 to 228 are welded on the flange 217 for connection thereto, with each other and with the internal conduits 251 of the intake ducts 215. In their edge sections which are further away downstream, the concave plates 225 to 228 are bonded in pairs to each other and directly with the edge sections of the four concave plates of the composite wall elements 233, 234 that are found. at the entrance of the box 221. The edge sections of the four concave plates of the composite wall elements 233, 234 that are located at the outlet of the box 221 are welded in pairs with each other and with the bushing 253. A metallic bushing 259 is inserted into the wall of the exhaust elbow 222 in the vicinity of the inlet of the catalyst case 221 and hermetically sealed with a pair of concave plates of this wall as well as with the inner wall 245 collecting and / or inlet . The bushing 259 has an internal thread in which a lambda probe 260 is screwed. By means of the inner wall 245 collecting and / or inlet welded therewith, the bushing and possibly other connections, the inner wall 240 of the catalyst is rigidly joined to the composite wall elements 223, 224, which in turn are rigidly bonded with the wall elements 233, 234 composed of the catalyst. The internal wall 240 of the catalyst is also centered and its axial displacement in the box 221 is limited by at least one flange or the like. A free intermediate space 265 containing air separates most of the internal conduits 251, the inner wall 245 of the inlet and the inner wall 240 of the catalyst, from the walls formed by the wall elements 223, 224, 233, 234 compound Unless otherwise stated, the exhaust gas conduit element 211 can be configured similarly to the exhaust gas conduit element 11. Additionally, the composite wall elements 223, 223, 233, 234 can be fabricated and assembled with one another in a manner similar to composite wall wall elements 23, 24. When the exhaust device or the exhaust gas conduit element 211 is used, the hot exhaust gas flows from the openings of the connection flange 217 through the internal conduits 251 to the interior space of the inner entrance wall 245. which forms an exhaust gas manifold. The exhaust gas then flows into the interior space which is delimited by the inlet section of the inner wall 240 of the broadening catalyst. Then the exhaust gas flows through the passages of the body 242 of the catalyst and then through the interior space delimited by the outlet section of the inner wall 240 of the catalyst towards the catalyst outlet. That is to say, the parts that conduct the exhaust gas are practically thermally insulated against the environment along the entire flow path of the exhaust gas, by the thermoinsulating composite wall elements 223, 224, 233, 234 and by the space intermediate 265 containing air. The catalytic elements 241 are still further optionally isolated by the intermediate layer 243. Investigations have shown that the external concave plates 225 and 227 were only heated to a temperature of approximately 230 ° C in the vicinity of the junction of the exhaust elbow with the catalyst. This temperature is at least or about 300 ° C lower than in an exhaust gas line which, instead of the thermoinsulating composite wall elements 223, 224, only has a single-layer metal wall, but also an intermediate space 265 that contains air and that otherwise is configured approximately equal to the exhaust gas conduction element 211. The free intermediate space 265 and the described arrangement of the parts that conduct the exhaust gas further ensures that the different expansions of the various parts caused during the operation due to heating do not cause excessive stress and damage. In figure 11 a part of an exhaust device or of an exhaust gas conduit element 311 is shown, which substantially consists solely of an exhaust elbow 312 and does not have a catalyst. The exhaust elbow 312 comprises several intake ducts 315, for example at least partly curved, a joint flange 317 common to all the intake ducts, a manifold or collecting section 318 and an output flange 319. The wall of the intake ducts 315 and the collector or collecting section 318 are constituted by two wall elements 323, 324 of several layers and / or composite. Each of these in turn comprises a pair of metal concave plates and a layer of insulating material, as can be seen in the open area in gap of Figure 11. Otherwise, the wall elements 323, 324 can to be configured, for example in a similar manner and to be connected to one another as well as to the connecting flange 317, as the wall elements 223, 224 shown in FIG. 10. In addition, the wall elements 323, 324 are sealed together and rigidly, specifically welded with the output flange 319 in the collector or collecting section 318 at their ends remote from the joining flange 317. The internal space enclosed by two wall elements 323, 324 contains an internal wall 345 collecting and for each intake duct an internal duct 351. The internal conduits 351 are welded with the joining flange 317 at the end of the inlet side in a manner similar to the previously described embodiments. The other ends of the internal conduits 351 are welded to the inner collector wall 345, so that the passages of the internal conduits open into the internal collector space enclosed by the internal collector wall. The internal wall 345 and the internal conduits 351 are separated for the most part from the internal concave plates of the wall elements 323, 324 by free intermediate spaces, analogously to the previously described embodiments. For example, the inner wall 345 protrudes through the opening of the exit flange 319 slightly outwardly from the interior space delimited by the wall elements 323, 324, and is separated by a free intermediate space of the internal surface that delimits the opening of the exit flange. The exhaust elbow is equipped, for example, with a lambda probe 360 which protrudes into the internal collector space enclosed by the internal collector wall 345. The outlet of the common exhaust elbow for all the intake ducts 315, which is formed by the outlet flange 319 and the end of the internal collector wall 345 projecting therefrom, is connected to the catalyst, for example through a conduit not drawn or possibly directly. The exhaust devices or exhaust gas conduction elements and their manufacture can be modified in various ways. For example it is possible to combine some with other characteristics of the different embodiments described. It is also possible to replace at least some or all of the joints by welding the sections of the edges of the concave plates of the various embodiments by other types of connections. For example, it is possible to join the edge sections to one another at least partly by beading and / or brazing and / or gluing. The internal ducts 51 of the exemplary embodiment shown in FIGS. 1 to 4 can optionally be joined rigidly, for example by welding with the concave plates of the internal intake manifold wall 45. The latter should then be able to be axially displaceable with respect to the composite wall elements 23, 24. If instead it is the case that the end sections of the inner conduits 51 can be displaced with respect to the internal collector and / or inlet wall 45, as described below for the embodiment according to 1 to 4, then the two concave plates 46, 47 of the inner wall 45 of the embodiment example shown in FIGS. 1 to 4 can instead still have edge sections protruding outwardly between the sections of the walls. edges of the concave plates 26, 28 and that they are soldán with these. Each of the joint flanges 17, 217 common to all the intake ducts could be replaced with flanges attached to one or more of the ducts 15, or 215, or 315 of admission. Additionally, catalytic agents could have two or more catalyst bodies instead of just one. In addition, the or each catalyst body could be constituted by rolled or stacked sheet metal elements, provided with wraps. During the manufacture of a wall element the insulating material can still be wrapped, held together and protected with a thin plastic wrap before being inserted between two metallic concave plates. This casing can then be decomposed and / or burned by heating after joining both concave plates, so that the material of the casing consisting of synthetic material becomes gas and escapes. It is also possible before the common shaping to join together the edge sections of the sheet metal parts intended for the formation of a wall element after insertion of the insulating material in some places by welding points or the like, in order to provisionally fix the sheet metal parts and the insulating material.

Claims (15)

1. CLAIMS Exhaust gas conduction element with at least two intake ducts for connection to an internal combustion engine and a wall, characterized in that the wall comprises two wall elements with respectively two metal concave plates and between them there is a layer of heat insulating material, and that the two wall elements have edge sections joined to one another and together in cross section enclose the internal spaces of all the intake ducts.
2. Exhaust gas driving element according to claim 1, characterized in that the layer of heat insulating material is microporous and at least in large part has a granular structure.
3. Exhaust gas driving element according to claim 1 or 2, characterized in that the layer constituted by heat insulating material substantially has a thickness of at least 2 mm, and is for example 3 mm thick.
4. Exhaust gas driving element according to one of claims 1 to 3, characterized in that each concave plate is in one piece, that the concave plates belonging to the same wall element are substantially joined to one another along its entire circumference and configured in such solid that together they are self-supporting, and that at least a substantial part of the wall is constituted exclusively by the wall elements.
5. Exhaust gas driving element according to one of claims 1 to 4, characterized in that all the concave plates of the two wall elements connected to one another in the edge sections are in contact with each other in the sections of the edges at least in pairs and are joined to one another at least almost hermetically by welding and / or brazing and / or gluing and / or beading.
6. Exhaust gas driving element according to one of claims 1 to 5, characterized in that the wall elements form the outermost limitation of the exhaust gas conduction element at least in most of the wall .
7. Scape gas driving element according to one of claims 1 to 6, characterized in that each intake pipe of the exhaust elbow delimits a passage for exhaust gas, that the passages for exhaust gas of the Inlet ducts are connected to a common interior manifold space for all intake ducts, and that the two wall elements that together enclose the internal spaces of the intake ducts also enclose together in cross section at least a substantial part of the space internal collector.
8. Exhaust gas driving element according to one of claims 1 to 7, characterized in that each intake duct has an internal duct which, in a transverse section, is at least partially separated by a free intermediate space of the exhaust elements. wall that surrounds it in cross section and delimits an exhaust gas passage.
9. Exhaust gas driving element according to claim 8, characterized in that it comprises an internal collector wall that at least for the most part is separated by a free intermediate space of the wall elements that surround it in cross section and it delimits an internal collector space with which the internal conduits of all the intake conduits are connected.
10. Exhaust gas driving element according to claim 8, characterized in that the internal duct of each intake duct has an entrance section rigidly connected to both wall elements and an exit section connected to the interior wall collector, and that the outlet section of each internal conduit can be displaced with respect to the inner collector wall and / or the latter (can be moved) with respect to the wall elements.
11. Exhaust gas driving element according to one of claims 1 to 10, characterized in that in addition to the exhaust elbow it comprises a catalyst with catalytic agents for the catalytic treatment of the exhaust gas, and that the two mentioned wall elements, or two additional wall elements joined thereto, which respectively comprise a pair of metallic concave plates and a layer of thermoinsulating material existing between these enclose in cross section the catalytic agents.
12. Exhaust gas driving element according to claim 11, characterized in that the two additional wall elements are directly and rigidly connected with the wall elements that enclose the interior spaces of the intake ducts of the exhaust elbow .
13. Exhaust gas driving element according to one of claims 1 to 12, characterized in that the wall elements which together enclose interior spaces of the intake ducts have finger-shaped sections, separated by spaces free intermediate, associated in each case to one of the admission channels.
14. Method for manufacturing an exhaust gas guiding element according to one of claims 1 to 13, characterized in that two pieces of sheet metal are used for each wall element, each of which serves to form one of the concave plates, of which a layer of heat insulating material is disposed between the two pieces of sheet metal and then the two pieces of sheet metal and the layer disposed between them are formed together so that both Wall elements enclose the internal spaces of the intake ducts in cross section together.
15. 15. Method according to claim 14, characterized in that when forming the sheet metal parts and the layer arranged between them, each layer of heat insulating material is compressed so that in the finished exhaust gas conducting element the layer substantially has a thickness of at least 2 mm, and for example of at least 3 mm. Method according to claim 14 or 15, characterized in that to form two wall elements that together enclose an interior space in cross section two pairs of concave plates are formed with layers arranged between them, and that after forming the concave plates are simultaneously joined to each other the edge sections of all the concave plates of the two wall elements by welding and / or brazing and / or gluing and / or flanging.