Device for aftertreatment of exhaust gases

Abstract

The present invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a metal matrix (5) through which the gases can flow along a main flow direction and which is inserted into a casing pipe (1, 11), the matrix (5) being formed from a layer stack made up of a plurality of metal foils wound around at least one center of rotation, at least some of the metal foils being at least partially structured, so that a plurality of channels are formed between the metal foils, which channels can flow along the main flow direction from the gas inlet side to the gas outlet side of the matrix (5), an inner tube (6) being arranged between the casing pipe (1, 11) and the matrix (5), and an air gap (7) being formed between the inner tube (6) and the casing pipe (1, 11).

Description

[Technical Field]

[0001] The present invention relates to an apparatus for the aftertreatment of exhaust gases from an internal combustion engine, comprising a metal matrix through which the gases can flow along the main flow direction and which is inserted into a casing tube. The matrix is ​​formed from a layer stack made of several metal foils wound around at least one center of rotation. At least some of the metal foils are at least partially structured, so that several channels are formed between the metal foils, which can flow along the main flow direction from the gas inlet side to the gas outlet side of the matrix. [Background technology]

[0002] A honeycomb body for a catalytic converter for the aftertreatment of exhaust gases from an internal combustion engine has a plurality of flow channels through which a flow can pass along the main flow direction. The honeycomb body, in particular a metallic honeycomb body, is formed by a plurality of smooth and / or at least partially structured metal foils, which are stacked on top of each other and wound and / or twisted to form the final honeycomb body. The matrix formed from the metal foils is inserted into a housing and permanently connected to the housing for stabilization and 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 which 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 typically lies flat against the casing and is connected to the casing by a brazed joint, which means that the matrix cannot flexibly move radially or axially. In addition, the essentially full surface contact between the matrix and the casing forms a highly thermally conductive bridge, which conducts thermal energy through the matrix to the casing and ultimately to the environment. This results in a delay in reaching the activation temperature. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is therefore to at least partially solve the problems described in relation to the prior art, in particular to provide an apparatus for exhaust gas aftertreatment with improved thermal insulation between the matrix and the casing. [Means for solving the problem]

[0007] 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.

[0008] This is achieved by an apparatus for the aftertreatment of exhaust gases from an internal combustion engine, comprising a metal matrix through which gases can flow along the main flow direction and inserted into a casing tube. The matrix is ​​formed from (at least) one layer stack formed from a plurality of metal foils, which layer stack is partially or completely wound or coiled around at least one center of rotation. At least some of the metal foils are at least partially structured, so that a plurality of channels are formed between the metal foils, through which gases can flow along the main flow direction from the gas inlet side to the gas outlet side of the matrix. Furthermore, an inner tube is arranged between the casing tube and the matrix, and an air gap is formed between the inner tube and the casing tube.

[0009] A matrix inserted into and connected to the inner pipe is disposed within the casing pipe, and a circumferentially extending gap is formed at least partially between the inner pipe and the casing pipe, which gap provides insulation and thereby reduces the transfer of heat energy from the matrix to the (radially outer) casing pipe.

[0010] The voids are designed in particular to radially space the inner pipe from the casing pipe. The voids extend in the circumferential direction of the matrix or inner pipe, in particular by at least 20%, preferably at least 40%, or particularly preferably at least 60%. Several voids may be formed, which may be axially spaced apart or parallel.

[0011] The inner tube may have a significantly lower material thickness than the casing tube and may essentially serve to stabilize the matrix formed from the multiple metal foils.

[0012] It is particularly advantageous if the air gap is formed circumferentially (completely) around the inner tube and extends axially at least along a section of the device. Preferably, the circumferentially extending air gap extends axially over at least a partial region of the device. It is advantageous if the air gap extends from the gas inlet side toward the center of the device along the main flow direction. The air gap preferably extends from the gas inlet side toward the center. Particularly high temperatures occur in the gas inlet side region during operation, so heat transfer to the casing tube should be reduced particularly in this region.

[0013] The inner tube may have a material thickness of less than 1.0 mm (millimeter), preferably less than 0.6 mm, particularly preferably less than 0.5 mm. The material thickness is preferably at least 0.3 mm.

[0014] It is proposed that the air gap has a radial width of more than 1.0 mm (millimeter), preferably more than 2.0 mm, particularly preferably more than 3.0 mm and less than 5.0 mm. The wider the air gap, the greater the insulating effect of the air gap. The air gap is preferably largest in the region of the device in the exhaust system of the combustion engine where the thermal load during operation is high or maximum.

[0015] In an advantageous embodiment, the gap or its width may vary along the axial extension of the device so that an appropriately thick gap is created for each expected temperature level.

[0016] It may be envisaged that no voids are formed in certain areas of the device, for example in the area on the gas outlet side.

[0017] The casing pipe may have (at least partially) an insulating layer on its radially inwardly facing surface. The insulating layer is particularly advantageous for further reducing the transfer of thermal energy. Preferably, the insulating layer has a low thermal mass (compared to the casing pipe). In a preferred embodiment, the insulating layer can be formed by a ceramic coating of the casing pipe. Alternatively, the insulating layer can be formed by a plurality of thin metal foils that are at least partially (in some sections) spaced apart from one another by spacers (by insulating air layers).

[0018] The spacers can be formed, for example, by the formation of irregularities and specific shaping of the metal foil, the irregularities having dimensions of, for example, several tenths of a millimeter. Alternatively, the metal foil can have other structures, such as corrugations, which form air chambers or air layers between the individual metal foils and thus provide thermal insulation.

[0019] Furthermore, it may be advantageous if the casing pipe has a cross-sectional taper in the gas inlet region, with the inside of the casing pipe abutting the outside of the inner pipe. The cross-sectional taper can be produced, for example, by a notch made in the casing pipe from the outside. The notch is preferably pointed (e.g., has a pointed end region), which means that the surface facing the inner pipe is as small as possible. This reduces the contact area of ​​the casing pipe with the inner pipe, which reduces heat transfer from the inner pipe to the casing pipe. The notch or reduction in the cross-section of the casing pipe is intended to prevent or minimize the ingress of washcoat into voids during the coating process of the device and / or to prevent hot exhaust gases from entering the voids.

[0020] Instead of a notch, an alternative design may provide a shoulder that extends circumferentially around the inner surface. [Brief explanation of the drawings]

[0021] 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.

[0022] [Figure 1] 1 is a cross-sectional view of an apparatus in which an insulating layer comprising a plurality of metal foils is disposed on the inner surface of a casing tube. [Figure 2] 1 is a cross-sectional view of a device in which a ceramic layer is disposed on the inner surface of the casing tube as a thermal insulating layer. [Figure 3] 1 is a cross-sectional view of a device in which the casing tube has a notch and the casing tube abuts the outer surface of the inner tube at the tip of the notch. [Figure 4] 1 shows a perspective view of an apparatus for after-treating exhaust gases with a matrix in a casing tube. DETAILED DESCRIPTION OF THE INVENTION

[0023] FIG. 1 shows a cross section of a casing pipe (jacket pipe, Mantelrohr) 1. The casing pipe 1 has an insulating layer 2 on its inner-facing surface. In the embodiment shown in FIG. 1, the insulating layer 2 is formed by a plurality of metal foils 3 (concentric or radially adjacent layers) stacked on top of each other. The metal foils 3 have (respectively circumferential) irregularities (ridges, grooves, Sicken) 4 that separate the metal foils 3 from each other. The metal foils 3 have a low overall thermal mass and are well suited to preventing or at least reducing the transport of thermal energy from the interior of a matrix 5 into the casing pipe 1.

[0024] The metal foil 3 forming the thermal insulation layer 2 may essentially correspond in terms of material, material thickness etc. to that of the (also) metal foil forming the channel 13 or layer stack.

[0025] The matrix 5 is arranged in the center of the casing pipe 1 and is housed in an inner pipe 6. An air gap 7 is formed between the inner pipe 6 and the insulating layer 2. This air gap 7 extends in the axial direction 8 over the entire device in at least some regions. The air gap 7 is preferably formed in the region on the gas inlet side and extends from there towards the center of the device.

[0026] The inner tube 6 has a thickness 9 that is significantly smaller than the casing tube 1 .

[0027] Figure 2 shows a cross section of a device with a structure similar to that of the example of Figure 1. In contrast to Figure 1, the thermal insulation layer 10 is formed by a ceramic coating. The remaining components are the same as in the embodiment of Figure 1.

[0028] Figure 3 shows a casing pipe 11 having an irregularity 12 formed from the outside into the casing pipe 11. The irregularity 12 extends to the inner pipe 6 and forms an inward tip that contacts the inner pipe 6. The casing pipe 11 also has a heat insulating layer 10 as already shown in Figure 2. Other components are similar to the embodiment shown in Figures 1 and 2.

[0029] The irregularities 12 close the voids 7 so that, on the one hand, when the metal foil of the matrix 5 is coated, the washcoat cannot penetrate into the voids 7 from the gas inlet side and possibly block it, and, on the other hand, the hot exhaust gases cannot flow from the gas inlet side into the voids 7. The physical contact between the casing pipe 11 and the inner pipe 6 is as small as possible to keep the heat transfer to a minimum.

[0030] FIG. 4 shows an apparatus for after-treating exhaust gases, particularly exhaust gases from an internal combustion engine, that can be arranged in an exhaust gas passage (shown by dashed lines) through which the exhaust gases can flow. It includes a matrix 5 with numerous (parallel) channels 13 through which the gases can flow along a defined main flow direction (along the axial extension L) from the gas inlet side (front view) to the gas outlet side (rear view not shown). The matrix 5 includes multiple (smooth and structured) metal foils 3 stacked in layers and wound around at least one center of rotation 14 (in this illustration, S-shaped around two centers of rotation 14). The matrix 5 has an axial extension L extending along the main flow direction 8 and a circumferential direction U extending perpendicular to the axial extension L. The matrix 5 is surrounded on the outside by a casing tube 1, the special structure of which is apparent from the above description of the other figures. The details of FIGS. 1-3 are particularly apparent on the gas inlet side of the apparatus.

[0031] The embodiments shown in Figures 1-4 are not intended to be limiting, but merely serve to illustrate the concepts of the present invention. [Explanation of symbols]

[0032] 1 Casing pipe 2. Insulation layer 3 Metal foil 4 Uneven part 5. Matrix 6 Inner tube 7 void 8 Axial Direction 9 Thickness 10. Insulation layer 11 Casing pipe 12 Uneven part 13 Flow path 14 Rotation Center L Axial extension U circumferential direction

Claims

1. 1. An apparatus for the aftertreatment of exhaust gases from an internal combustion engine, comprising a metal matrix (5) through which gases can flow along a main flow direction and inserted into a casing pipe (1, 11), said matrix (5) being formed from a layer stack made up of a plurality of metal foils wound around at least one center of rotation, at least some of said metal foils being at least partially structured, whereby a plurality of channels are formed between said metal foils, said channels being able to flow along said main flow direction from a gas inlet side to a gas outlet side of said matrix (5), said apparatus being characterized in that an inner tube (6) is arranged between said casing pipe (1, 11) and said matrix (5), and an air gap (7) is formed between said inner tube (6) and said casing pipe (1, 11).

2. 2. The device according to claim 1, wherein the gap (7) is formed circumferentially around the inner tube (6) and extends axially (8) along at least one section of the device.

3. 3. The device according to claim 1 or 2, characterized in that the gap (7) extends from the gas inlet side towards the center of the device along the main flow direction.

4. 4. Device according to any one of claims 1 to 3, characterized in that the inner tube (6) has a material thickness of less than 1 mm, preferably less than 0.6 mm, particularly preferably less than 0.5 mm.

5. 5. The device according to claim 1, wherein the gap (7) has a radial width of more than 1 mm, preferably more than 2 mm, particularly preferably more than 3 mm and less than 5 mm.

6. 6. Device according to any one of claims 1 to 5, characterized in that the casing pipe (1, 11) has a thermal insulation layer (2, 10) on its radially inwardly facing surface.

7. 7. The device according to claim 6, characterized in that the thermal insulation layer (2, 10) has a lower thermal mass than the casing pipe (1, 11).

8. 8. Device according to any one of claims 1 to 7, characterized in that the thermal insulation layer (10) is formed by a ceramic coating of the casing pipe (11).

9. 9. Device according to any one of claims 1 to 8, characterized in that the thermal insulation layer (2) is formed by a plurality of thin metal foils (3) at least partially spaced apart from one another by spacers (4).

10. 10. The device according to claim 1, wherein the casing pipe (11) has a cross-sectional taper (12) in the region of the gas inlet side, and the inside of the casing pipe (11) abuts against the outside of the inner pipe (6).

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