Device for heating exhaust gas

Abstract

The invention relates to a device for heating an exhaust gas flow in an exhaust gas section, comprising: a heating substrate which can be electrically heated; a support structure (4) which is connected to the heating substrate (5); the invention relates to a heating device (1), comprising a heating base body (5), which has a main flow direction, and a housing (1), which spatially delimits an exhaust section and through which a flow can flow in the main flow direction of the housing (1), the heating base body (5) having a plurality of flow channels, through which a flow can flow in the main flow direction of the housing (1), the housing (1) having at least one projection (2, 6, 7, 8, 9) on the inner surface thereof, which projection (2, 6, 7, 8, 9) surrounds at least partially in the circumferential direction, the protrusion protrudes inward in a radial direction from the inner surface.

Description

Technical Field

[0001] The present invention relates to a device for heating an exhaust gas flow in an exhaust section / exhaust passage, the device having: an electrically heatable heating substrate; a support structure connected to the heating substrate; and a housing that spatially defines the exhaust section and can be flowed through along the main flow direction, wherein the heating substrate has a plurality of flow channels that can be flowed through along the main flow direction of the housing. Background Art

[0002] In order to heat the exhaust gas in the exhaust section downstream of an internal combustion engine or the exhaust gas flowing in the exhaust section, electric heating elements are generally used nowadays. Here, the aim is to reach a temperature threshold more quickly, above which the harmful substances carried in the exhaust gas can be converted more effectively. This is necessary because the catalytically active surface for the exhaust gas aftertreatment of the catalytic converter installed in the exhaust section can only achieve sufficient conversion of the corresponding harmful substances above a minimum temperature, i.e., the so-called light-off temperature.

[0003] Known solutions in the prior art include so-called heated catalytic converters, which have a metal structure connected to a voltage source or a ceramic structure with a metal coating that can be heated using ohmic resistance.

[0004] The heatable metal structure can, for example, include a honeycomb body made of metal foil. For this purpose, a plurality of smooth and / or at least partially structured metal foils are stacked together and wound around at least one pivot point to form a honeycomb body. The substrate formed by the metal foil can be electrically contacted and heated using ohmic resistance.

[0005] For this purpose, the substrate must be arranged in the exhaust section and be located upstream or downstream of the catalytic converter designed for exhaust gas aftertreatment along the flow direction of the exhaust gas.

[0006] In order to position the substrate in the exhaust section and support the substrate, especially against mechanical and thermal loads, a bracket must be provided, which can especially withstand the high thermal cyclic loads and strong and irregular mechanical loads in the exhaust section, especially in the exhaust section of a motor vehicle.

[0007] The disadvantages of the known solutions in the prior art are especially that the known connection types cannot achieve an optimal connection between the support structure and the housing, and especially need to be improved in terms of durability. Summary of the Invention

[0008] Therefore, an object of the present invention is to provide a device for heating exhaust gas, which can reliably and durably position the heating substrate in the housing of the exhaust section and durably fix it in the housing of the exhaust section.

[0009] The object associated with the device is achieved by a device having the features of claim 1.

[0010] An embodiment of the invention is designed as a device for heating an exhaust gas flow in an exhaust section, the device having: a heating substrate that can be electrically heated; a support structure that is connected to the heating substrate; and a housing that spatially delimits the exhaust section and can be flowed through along the main flow direction, wherein the heating substrate has a plurality of flow channels that can be flowed through along the main flow direction of the housing, and wherein the housing has at least one circumferentially at least partially surrounding projection on its inner surface, the projection protruding inward in the radial direction from the inner surface.

[0011] The housing of the exhaust section is typically formed by a pipe having a circular cross-section, especially in automotive manufacturing. The heating substrate is formed, for example, by a metal honeycomb body that is formed by a plurality of metal foils. Here, the metal foils are smooth and / or at least partially structured, especially corrugated, and are stacked on top of each other to form a laminate and wound around at least one turning point. Thereby, a honeycomb body is formed that forms a plurality of flow channels between the metal foils. The honeycomb body can be energized through corresponding electrical contacts and heated by means of ohmic resistance. The exhaust gas flowing through the honeycomb body is heated, so that other catalysts downstream in the exhaust section in the flow direction can be heated more quickly and reach their respective light-off temperatures, from which full exhaust gas conversion, i.e., catalytic conversion, takes place.

[0012] The heating substrate and the support structure are durably connected, for example, by means of support pins. Here, depending on the application, the heating substrate can be electrically insulated from the support structure. The support structure itself has a grid-like structure that has sufficient connection points for the heating substrate in the cross-section of the heating substrate in order to be able to reliably support the heating substrate and protect the heating substrate from mechanical and thermal loads. At the same time, the support structure is constructed such that the pressure loss generated by the flowing exhaust gas is as small as possible.

[0013] The support structure also has an annular region from which struts protrude radially inward. The annular region and the struts together form a grid-like structure. The annular region can preferably be constructed as a closed ring that completely surrounds. This region is used to connect the support structure to the housing.

[0014] According to the invention, the housing has a circumferentially at least partially surrounding projection. The projection serves as a abutment point for the support structure, especially for the annular region of the support structure. The support structure can abut against the projection during assembly into the housing and be connected to the projection of the housing, for example, by means of a soldering process. The projection can preferably be constructed at a precisely defined position and enables precise positioning of the support structure and thus of the heating substrate.

[0015] Particularly advantageously, the protrusions are configured to surround the entire circumference. A protrusion that completely surrounds the circumference of the housing in the circumferential direction of the housing is advantageous in order to create as large a contact surface as possible between the support structure and the protrusion and thus to create a particularly stable connection. This particularly helps the support structure and thus protects the heating substrate from strong vibrations and the severe temperature changes that inevitably occur in the exhaust section. In addition, the vibration states of the heating substrate and the support structure can be reduced by a particularly firm connection, which is determined, for example, by the respective natural frequencies of the bodies.

[0016] Equally advantageously, the protrusions are formed by an inner tube that is installed in the housing. Preferably, an inner tube with a correspondingly smaller outer diameter can be pressed into the tube forming the housing. In this way, the protrusions serving as contact points are formed in a simple manner. By means of a controlled press-fit, the position of the protrusions can be determined very precisely, and in particular, an unfavorable tolerance chain can be avoided.

[0017] When selecting materials, it is preferred that the housing and the inner tube are made of the same material. This prevents negative effects, such as different thermal expansion coefficients that can lead to mechanical stress, for example.

[0018] The preferred embodiment is characterized in that the protrusions are produced by a shaping process on the housing. Alternatively, the protrusions can be formed by a shaping process on the housing. For this purpose, for example, ribs can be embossed into the housing from the outside. Here, the ribs can be formed completely or only partially in the circumferential direction. In particular, a plurality of ribs can be formed at intervals from each other in the circumferential direction.

[0019] Equally preferably, the housing has two protrusions that are spaced apart from each other along the main flow direction. This is produced in a simple manner by a pressed-in inner tube that forms two protrusions oriented in opposite directions. Thus, the protrusions formed by the tube have a contact surface along the main flow direction and a contact surface oriented opposite to the main flow direction. The advantage of the two protrusions is that the heating substrate can be supported doubly by forming support structures on both sides of the heating substrate.

[0020] Furthermore, it is advantageous that the support structure has a first annular outer region whose outer diameter is smaller than the inner diameter of the housing, wherein the inner diameter of the section of the housing formed by the protrusions is smaller than the outer diameter of the first annular outer region of the support structure. Thus, the support structure can be simply inserted into the housing and positioned on the formed protrusions. By means of the corresponding dimensional relationships, it is possible to prevent the support structure from slipping off the protrusions. This simplifies manufacturability. In addition to the protrusions, components for positioning the support structure can be provided in the tube of the housing, which are formed, for example, by protrusions.

[0021] Furthermore, it is advantageous that the support structure has a second annular outer region, wherein the first annular outer region is arranged upstream of the heating matrix in the main flow direction, and the second annular outer region is arranged downstream of the heating matrix in the main flow direction. This enables an improved positioning and fixation of the heating matrix relative to the tube. For assembly purposes, the heating matrix can be connected to a half of the support structure and then inserted into the housing. Then, the heating matrix is connected to the second half of the support structure, which abuts against a second projection in the housing during the connection to the heating matrix. Finally, the two halves of the support structure can be connected to the projections of the housing by means of a suitable method.

[0022] Equally suitable is that the housing is formed with a plurality of projections, wherein the plurality of projections are arranged spaced apart from each other in a cross-section of the housing in the circumferential direction of the housing.

[0023] Advantageous refinements of the invention are described in the dependent claims and in the description of the following figures. Description of the Drawings

[0024] The invention will be explained in detail below with reference to the drawings by means of embodiments. Among them:

[0025] Figure 1 A cross-sectional view of a housing with a pressed-in inner tube is shown,

[0026] Figure 2 A cross-sectional view of a housing with a support structure abutting on the inner tube and a heating matrix is shown, and

[0027] Figure 3 A schematic view of a housing is shown, which has different forms of projections produced by shaping the housing. Detailed Description of the Embodiment

[0028] Figure 1 A cross-sectional view of the housing 1 formed by a tube is shown. In order to produce the projection 2 for the abutment surface of a support structure (not shown), the inner tube 3 is pressed into the housing 1. The diameter of the inner tube 3 is dimensioned such that a gapless and durable retention is established between the inner tube 3 and the housing 1 by pressing in the inner tube.

[0029] Figure 2 A cross-sectional view of the housing 1 with the pressed-in inner tube 3 is shown. The support structure 4 is shown on the formed projection 2, which abuts on the abutment surface formed by the projection 2.

[0030] The support structure 4 is connected to the heating matrix 5, and the heating matrix is reliably positioned in the housing 1 by abutting on the projection 2 through the support structure 4. The support structure 4 and the inner tube 3 are preferably durably connected by a soldering process.

[0031] InFigure 2 In the embodiment, the heating substrate 5 is held on both sides of the inner tube 3 by a part of the support structure 4, and the support structure 4 abuts against two protrusions 2, 6 formed by the inner tube 3. In this way, the heating substrate 5 is fixed relative to the housing 1 at two positions.

[0032] Figure 3 Two different design schemes of the housing 1 are shown. The tube forming the housing 1 is processed by a forming process, and protrusions 7, 8, 9 are formed on the inner surface of the tube. The protrusions 7, 8, 9 are formed by ribs formed from the outside into the housing 1. Figure 3 The protrusions 7, 8 and 9 shown in cross-section in can be formed to surround the entire circumference of the housing 1 in the circumferential direction, or only in part and spaced apart from each other in the circumferential direction. But in any case, the protrusions 7, 8 and 9 are correspondingly in one cross-section.

[0033] Figures 1 to 3 The embodiments of are particularly non-limiting and are used to illustrate the concept of the present invention.

[0034] List of reference numerals:

[0035] 1 Housing

[0036] 2 Protrusion

[0037] 3 Inner tube

[0038] 4 Support structure

[0039] 5 Heating substrate

[0040] 6 Protrusion

[0041] 7 Protrusion

[0042] 8 Protrusion

[0043] 9 Protrusion

Claims

1. A device for heating an exhaust gas flow in an exhaust section, the device having: a heating matrix that can be electrically heated; a support structure (4) connected to the heating matrix (5); and a housing (1) that spatially defines the exhaust section and can be flowed through along the main flow direction, wherein, the heating matrix (5) has a plurality of flow channels that can be flowed through along the main flow direction of the housing (1), characterized in that the housing (1) has at least one circumferentially at least partially surrounding projection (2, 6, 7, 8, 9) on its inner surface, which projects radially inwards from the inner surface.

2. The device according to claim 1, characterized in that, the projection (2, 6, 7, 8, 9) is configured to surround completely.

3. The device according to any one of the above claims, characterized in that, the projection (2, 6) is formed by an inner tube (3) installed in the housing (1).

4. The device according to any one of the above claims, characterized in that, the projection (7, 8, 9) is produced by a shaping process performed on the housing (1).

5. The device according to any one of the above claims, characterized in that, the housing (1) has two projections (2, 6, 7, 8, 9) that are spaced apart from each other along the main flow direction.

6. The device according to any one of the above claims, characterized in that, the support structure (4) has a first annular outer region, the outer diameter of which is smaller than the inner diameter of the housing (1), wherein the inner diameter of the section of the housing (1) formed by the projection (2, 6, 7, 8, 9) is smaller than the outer diameter of the first annular outer region of the support structure (4).

7. The device according to any one of the above claims, characterized in that, the support structure (4) has a second annular outer region, wherein the first annular outer region is located upstream of the heating matrix (5) along the main flow direction, and the second annular outer region is located downstream of the heating matrix (5) along the main flow direction.

8. The device according to any one of the above claims, characterized in that, the housing (1) is formed with a plurality of projections (7, 8, 9), wherein these projections are arranged spaced apart from each other in a section of the housing (1) along the circumferential direction of the housing (1).

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