Device for aftertreatment of exhaust gases

Abstract

The invention relates to a device (1) for the aftertreatment of exhaust gases from an internal combustion engine, comprising a metal matrix (2) through which a flow can pass along the main flow direction, the matrix (2) being formed by a plurality of metal foils that are stacked on top of each other to form a layer stack and that are wound to form the matrix (2), with a plurality of flow channels formed between the metal foils, the matrix (2) being housed in a casing tube (4, 6, 7), an inner tube (3) being arranged between the matrix (2) and the casing tube (4, 6, 7), the inner tube (3) having a structuring (5), whereby contact between the inner tube (3) and the matrix (2) and / or the casing tube (4) is only partially formed.

Description

[Technical Field]

[0001] The present invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a metal matrix through which a flow can pass along a main flow direction, the matrix being formed by a plurality of metal foils that are stacked on top of each other to form a layer stack and that are wound or twisted to form the matrix, with a plurality of flow channels formed between the metal foils, and the matrix being housed in a casing tube. [Background technology]

[0002] Honeycomb bodies for catalytic converters for exhaust gas aftertreatment of internal combustion engines have a plurality of flow channels through which a flow can pass along the main flow direction. Honeycomb bodies, especially metallic honeycomb bodies, can be formed from a number of smooth and / or at least partially structured metal foils, which are stacked on top of each other and wound or (at least partially) twisted to form the final honeycomb body. The matrix (honeycomb body) formed from the metal foils is inserted into a housing and permanently connected to the housing for stabilization, especially for protection against mechanical disturbances.

[0003] In the simplest case, the housing is formed by a tube designed to accommodate the matrix inside. A further function of the housing is to ensure the flow of gases through the honeycomb body, in particular to prevent exhaust gases from bypassing the honeycomb body.

[0004] The matrix must be permanently fixed within the housing, which is why brazed joints are regularly formed between the matrix and the casing.

[0005] A particular drawback of prior art devices is that the matrix abuts the entire surface of the casing and is connected to the casing by a brazed joint, which means that the matrix cannot flexibly move radially or axially. Even a partial connection between the matrix and the casing is problematic because brazing material can be carried over when the matrix is ​​pressed into the casing, and capillary forces between the casing and the matrix can cause the brazing material to flow into unwanted areas during the brazing process.

[0006] Furthermore, the essentially full-surface abutment of the matrix with the casing does not create a thermally insulating connection, but leads to an increase in the thermal mass in the edge regions of the matrix and therefore to an increase in heat transfer through the casing to the environment. Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is therefore to solve at least some of the problems described in relation to the prior art, and in particular to create a matrix housed in a casing that allows flexible movement of the matrix to compensate for thermally induced forces and / or that can reduce heat transfer from the matrix to the casing. [Means for solving the problem]

[0008] The object of the device is achieved by a device having the features of claim 1. Advantageous further embodiments are specified in the dependent claims. The features individually recited in the claims may be combined in any manner with each other and / or with the features of the description. The description, particularly in conjunction with the drawings, explains the invention and specifies further embodiments.

[0009] This is supported by a device for the aftertreatment of exhaust gases from an internal combustion engine, which has a metal matrix through which a flow can pass along the main flow direction, the matrix being formed by a plurality of metal foils which are stacked on top of each other to form a layer stack and which are wound or coiled (e.g. at least partially twisted) to form the matrix. Channels (especially multiple channels) are formed between the metal foils, and the matrix is ​​housed in a casing tube. An inner tube is arranged between the matrix and the casing tube, the inner tube having a structuring such that contact between the inner tube and the matrix and / or the casing tube is only partial.

[0010] Honeycomb bodies or matrices of this type are already known in many forms. The matrix is ​​formed from multiple metal foils, at least some of which are at least partially structured. The metal foils are stacked on top of each other. The layer stack thus formed is then wound, coiled, or twisted around at least one center of rotation. This creates cells between the individual metal foils, which can flow along the main flow direction extending along the axial extension of the matrix. Depending on the intended application, the metal foils can be provided with a catalytically active coating, including a so-called washcoat, which may carry catalytically active material for converting pollutants in exhaust gases. As a result, the medium (exhaust gas) flowing along the formed channels can be chemically converted, for example, on the surface of the matrix.

[0011] The matrix made from metal foil is inherently unstable and is therefore inserted into a so-called casing tube to protect it from mechanical damage. This casing tube often also serves to guide the exhaust gases, forming an exhaust gas passage through which they can flow.

[0012] It is proposed here that the matrix is ​​accommodated in an inner tube, and that the matrix accommodated in the inner tube is finally inserted into a casing tube, the inner tube being particularly made of metal foil, and structured so that the matrix with its radially outwardly facing surface and / or the casing tube with its radially inwardly facing surface rests against a structure of the inner tube extending from the cylindrical base surface.

[0013] The inner pipe may be a separate component. The structuring may be formed by a plurality of structures, in particular of the same type, adjacent to one another or spaced apart from one another. The inner pipe may be provided with structures over (almost) the entire inner and / or outer surface of the inner pipe, so that the inner pipe is designed with structuring over a large area or over most of it. The structuring may include protrusions and / or recesses in the radial direction or towards the casing pipe and / or matrix. The protrusions and / or recesses may be arranged alternately in the axial and / or circumferential direction of the inner pipe. In particular, only recesses and protrusions are provided in the structured region of the inner pipe, so that, for example, only a smooth, possibly cylindrical, inner pipe edge is formed outside this region.

[0014] The contact between the inner tube and the matrix and / or casing tube is only partial, resulting in a small contact area relative to the entire surface of the inner tube. The contact surface may be (essentially) linear, with the contact line preferably extending at least partially (or mostly) in the circumferential direction and / or at an angle of less than 90° to the circumferential direction. The area where contact exists may be less than 20%, in particular less than 10%, of the outer or inner surface of the inner tube.

[0015] It is particularly advantageous if the inner tube has a material thickness less than that of the casing tube. The inner tube is also formed from a thin metal foil, preferably with a thickness of 0.01 mm to 2.0 mm, more preferably 0.05 mm to 0.5 mm, and particularly preferably 0.08 mm to 0.3 mm. In particular, the material thickness of the inner tube can be significantly smaller than that of the casing tube, so that the casing tube has a thickness at least two times, particularly at least ten times, greater than the selected material thickness of the inner tube.

[0016] The inner tube may have protrusions and recesses that protrude or are recessed radially from the main casing surface of the inner tube.

[0017] Preferably, the metal foil forming the inner tube is structured. This means that the metal foil has convex and concave portions (roughness) protruding from the cylindrical basic shape formed by the smooth metal foil or from the main housing surface formed by a cylinder. Preferably, hexagonal structures are embossed into the metal foil in cross section. Such hexagonal structures may comprise a hexagonally protruding / recessed frame and recessed / protruding curved portions enclosed therein. Alternatively, the individual structures may have different cross sections.

[0018] The projections and recesses extending from the base surface form contact surfaces or lines, or simply contact points, against which the casing tube rests on the one hand and the outer surface of the matrix rests on the other hand.

[0019] Contact between the inner tube and the matrix and / or casing tube may be formed only in the areas of the protrusions and / or recesses.

[0020] This is advantageous because the contact surface between the inner tube and the casing tube or matrix is ​​significantly smaller than in the case of full-surface contact, as in the case of honeycomb bodies or matrices known from the prior art. This reduces heat transfer from the matrix to the casing tube, thereby reducing heat loss. The contact points or surfaces defined by the structures ensure a very clear connection between the matrix and the inner tube, and between the inner tube and the casing tube. This prevents carryover or capillary action of the brazing material between the matrix and the inner tube and / or between the inner tube and the casing tube, which could cause displacement of the brazing material.

[0021] An air-filled chamber can be formed between the matrix and / or casing tube (on the one hand) and the inner tube (on the other hand), through which the respective components are spaced apart from each other in some areas.

[0022] Air-filled chambers are formed by the above-mentioned protrusions and recesses. The air-filled chambers can be separated or delimited from one another by the protrusions and recesses. In the structural maxima of the inner tube, on the one hand, it abuts against the casing tube and, on the other hand, against the outer surface of the matrix. In the remaining areas of each structured section, air chambers are formed between the inner tube and the casing tube or between the inner tube and the matrix. The air-filled chambers can form a thermal insulation or barrier for these components.

[0023] The contact area between the inner tube and the casing pipe and between the inner tube and the matrix can be significantly smaller than in the case of a matrix of the same size lying flat against the casing pipe. This is achieved by the reduced contact area resulting from the structuring. The reduced contact area ensures lower heat transfer from the flowing exhaust gas through the matrix to the casing pipe, which reduces heat loss and therefore improves the efficiency of the exhaust gas aftertreatment device. The matrix also heats up more quickly, which is beneficial for quickly reaching the required operating temperature, known as the activation temperature.

[0024] Furthermore, it may be assumed that the casing pipe has at least two sections with different inner diameters, and the contact surface between the inner pipe and the casing pipe is formed in the region of the section with the smaller inner diameter.

[0025] The stepped casing pipe, having sections with different internal diameters, allows for the formation of an air gap at least partially, which extends around the circumference and provides additional thermal insulation. The casing pipe preferably contacts the inner pipe in the section with the smallest internal diameter. Sections with larger diameters are free from contact with the inner pipe.

[0026] The casing pipe may be designed as a single piece or (alternatively) as multiple pieces.

[0027] It may also be useful to arrange at least one sealing element between the casing pipe and the inner pipe to form a seal at least in the axial direction of the device. The sealing element may, for example, be formed by or together with (at least) one sealing ring arranged between the inner pipe and the casing pipe. The sealing ring must be temperature stable and prevent exhaust gases from entering the gap formed between the casing pipe and the inner pipe.

[0028] In addition, it may be advantageous if the sealing element is produced by forming the inner tube and / or the casing tube.

[0029] Alternatively, the axial seal can also be produced by selectively shaping the casing tube and / or the inner tube, for example, an axial end of the casing tube or the inner tube can be bent in such a way that there is (only) a flat abutment between the casing tube and the inner tube at this axial end.

[0030] Furthermore, it may be advantageous if the casing pipe is designed in multiple sections, the casing pipe being formed from multiple pipe sections with different internal diameters.

[0031] The present invention and its contents are described in detail below with reference to schematic drawings and examples of embodiments. It should be noted that elements designated by the same reference signs in the drawings may have the same characteristics unless otherwise expressly stated in this specification. Elements shown in the drawings may be further characterized by features from other drawings and / or descriptions and / or claims (and vice versa), unless expressly excluded below. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a perspective view of an apparatus having a structured inner tube and a casing tube extending axially over a portion of the inner tube. [Figure 2] 2 is a perspective view of the device according to FIG. 1, in which two further sections of the casing tube are arranged around the inner tube. [Figure 3] 1 is a cross-sectional view of a device having a matrix, an inner tube, and a casing tube with sections of different inner diameters. DETAILED DESCRIPTION OF THE INVENTION

[0033] FIG. 1 shows a device 1 formed by a through-flowable matrix 2, an inner pipe 3 and a casing pipe (jacket pipe, Mantelrohr) 4.

[0034] The casing tube 4 is only partially shown. In particular, the axial length L of the casing tube 4 corresponds to the axial length of the matrix 2 and of the inner tube 3.

[0035] In particular, sections of the casing tube 4 are shown that abut against structures 5 formed in the inner tube 3 and that are in contact with the inner tube 3 in the region of the largest structure of the structures extending towards the casing tube 4. The structures 5 of the inner tube 3 have a hexagonal cross section and extend alternately in the direction of the matrix 2 and the casing tube 4.

[0036] Figure 2 shows the device 1 already shown in Figure 1. In addition to the casing tube 4, further subsections 6, 7 of the casing tube 4 are shown to the left and right of this casing tube 4. These subsections 6, 7 have a larger inner diameter than the central casing tube 4 and therefore do not come into contact with the structural part 5 of the inner tube 3. A circumferentially extending air gap is formed between the subsections 6, 7 and the inner tube 3.

[0037] The schematic cross section shows that the matrix 2 is formed by smooth metal foils 12 and structured metal foils 11 arranged in alternating layers, which form a plurality of channels 13. The channels 13 extend parallel to the main flow direction H.

[0038] FIG. 3 shows a cross-section of the device 1 already shown in FIG. 2. The cross-section shows the matrix 2, the structured inner tube 3, and the casing tube 4, which is formed into sections of different diameters (first diameter (inner diameter) 14 and second diameter (inner diameter) 15). The central part of the casing tube 4 has a smaller diameter than the partial sections 6, 7 and abuts the structured inner tube 3. It can be clearly seen that the contact surface with the casing tube 4 is formed only at the expanded structural maximum part of the inner tube 3. Between the partial sections 6, 7 and the inner tube 3, a circumferentially extending air gap 9 is formed, which, in addition to the air chamber 8, provides thermal insulation.

[0039] The embodiments shown in Figures 1-3 are not intended to be limiting, but merely serve to illustrate the concepts of the present invention. [Explanation of symbols]

[0040] 1 device 2. Matrix 3 Inner tube 4 Casing pipe 5 Structural part 6. Casing pipe section 7. Casing pipe section 8 Air Chambers 9 void 10 Smooth metal foil 11 Structured Metal Foil 12 Flow path 13 First Diameter 14 Second Diameter L Axial length H Main flow direction

Claims

1. 1. An apparatus (1) for the aftertreatment of exhaust gases from an internal combustion engine, comprising a metal matrix (2) through which a flow can pass along a main flow direction, said matrix (2) being formed by a plurality of metal foils that are stacked on top of each other to form a layer stack and wound to form said matrix (2), said metal foils having a plurality of flow channels formed between them, said matrix (2) being housed in a casing pipe (4, 6, 7), said apparatus being characterized in that an inner pipe (3) is arranged between said matrix (2) and said casing pipe (4, 6, 7), said inner pipe (3) having a structuring (5) so that contact between said inner pipe (3) and said matrix (2) and / or said casing pipe (4) is only partial.

2. 2. Device (1) according to claim 1, characterized in that the inner tube (3) has a lower material thickness than the casing tubes (4, 6, 7).

3. 3. The device (1) according to claim 1 or claim 2, characterized in that the inner tube (3) has protrusions and recesses formed radially from the main surface of the inner tube (3).

4. 4. The device (1) according to claim 3, characterized in that the contact between the inner tube (3) and the matrix (2) and / or the casing tube (4) is formed only in the areas of the protrusions and / or recesses.

5. 5. The device (1) according to any one of claims 1 to 4, characterized in that an air-filled chamber (8) is formed between the matrix (2) and / or the casing tubes (4, 6, 7) and the inner tube (3), through which the respective components are spaced apart from each other in several regions.

6. 6. The device (1) according to claim 1, wherein the casing pipe (4, 6, 7) has at least two sections (4, 6, 7) with different internal diameters, and the contact surface between the inner pipe (3) and the casing pipe (4) is formed in the region of the section (4) with the smaller internal diameter.

7. 7. The device (1) according to claim 6, characterized in that at least one sealing element is arranged between the casing pipes (6, 7) and the inner pipe (3), which seals at least in the axial direction of the device (1).

8. 8. Device (1) according to claim 7, characterized in that the sealing element is manufactured by deforming the inner tube (3) and / or the casing tube (6, 7).

9. 9. The device (1) according to any one of claims 1 to 8, characterized in that the casing pipe (4, 6, 7) is of a multi-part design, that is, the casing pipe (4, 6, 7) is formed from a number of pipe sections with different internal diameters.

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