Device for heating an exhaust gas flow with a tolerance compensation

Abstract

The invention relates to a device for heating an exhaust gas flow in an exhaust gas section, comprising an electrically heatable heating matrix (1) and a support structure (3, 8) which is connected to the heating matrix (1) via multiple support pins (2), wherein the device can be inserted into a housing of an exhaust gas section, The heating matrix (1) has a plurality of flow channels, through which exhaust gas can flow along the main flow direction from an end surface that forms the inflow side to an end surface that forms the outflow side. The support structure (3, 8) is designed in the form of a grid, and the heating matrix (1) is mounted upstream and / or downstream thereof. The support pins (2) are inserted into the heating matrix (1) and are bonded to the support structure (3, 8) while protruding beyond the inflow side and / or the outflow side. The support structure (3) has solder reservoirs (6, 7, 9, 10) on the surface facing the heating matrix (1), the free end (4, 5) of each support pin (2) being inserted into a respective solder reservoir.

Description

[0001] Description

[0002] Device for heating an exhaust gas stream with tolerance compensation

[0003] Technical area

[0004] The invention relates to a device for heating an exhaust gas flow in an exhaust gas line, with an electrically heatable heating matrix, with a support structure which is connected to the heating matrix via a plurality of support pins, wherein the device can be inserted into a housing of an exhaust gas line, wherein the heating matrix has a plurality of flow channels through which flow can be carried along the main flow direction from an end face forming the inflow side to an end face forming the outflow side, wherein the support structure is designed in the manner of a grid and is arranged upstream and / or downstream of the heating matrix, wherein the support pins which are inserted into the heating matrix and protrude beyond the inflow side and / or the outflow side are integrally connected to the support structure.

[0005] State of the art

[0006] Electric heating elements are now routinely used to heat exhaust gases in an exhaust system downstream of a combustion engine or the exhaust gas flowing through an exhaust system. The goal here is to more quickly reach a temperature threshold at which effective conversion of the pollutants carried in the exhaust can occur. This is necessary because the catalytically active surfaces of the catalysts installed in the exhaust system used for exhaust gas aftertreatment only allow sufficient conversion of the respective pollutants above a minimum temperature, the so-called light-off temperature.

[0007] Known solutions in the prior art include so-called heating catalysts, which have a metallic structure connected to a voltage source or a metallically coated ceramic structure which can be heated by utilizing the ohmic resistance.

[0008] The heatable metallic structures can, for example, consist of a honeycomb body made of metal foils. For this purpose, a plurality of smooth and / or at least partially structured metal foils are stacked on top of one another and wound around at least one pivot point to form a honeycomb body. The matrix formed from the metal foils can be electrically contacted and heated using the ohmic resistance.

[0009] For this purpose, the matrix must be arranged in an exhaust gas line and be located upstream or downstream of a catalyst designed for exhaust gas aftertreatment in the flow direction of the exhaust gas.

[0010] To position the matrix in the exhaust system and, in particular, to protect it against mechanical and thermal loads, a support structure must be provided. The support structure must be designed to absorb and withstand the alternating thermal loads and the strong and irregular mechanical loads in the exhaust system. The support structure itself is attached to the exhaust system housing.

[0011] To create a materially bonded connection between the heating matrix and the support structure, so-called support pins are used. These are inserted into cells of the heating matrix and connected to the support structure. All components have certain manufacturing tolerances; additional tolerances can be introduced during the assembly process, so that individual tolerances can accumulate to form negative tolerance chains, resulting in an unacceptable overall tolerance that jeopardizes the structural integrity of the component.

[0012] A particular disadvantage of the known solutions in the prior art is that there are currently no suitable means that allow the connection of the support pins to the support structure to be represented in a process-reliable manner, even if higher tolerances sometimes occur and the final position of the support pins relative to the support structure does not correspond to the actually planned position.

[0013] Description of the invention, task, solution, advantages

[0014] Therefore, it is the object of the present invention to provide a device which is improved in such a way that the connections between the support structure and the support pins can be reliably produced even under the influence of large tolerances.

[0015] The object with regard to the device is achieved by a device having the features of claim 1.

[0016] An embodiment of the invention relates to a device for heating an exhaust gas flow in an exhaust gas system, comprising an electrically heatable heating matrix, having a support structure which is connected to the heating matrix via a plurality of support pins, wherein the device can be inserted into a housing of an exhaust gas system, wherein the heating matrix has a plurality of flow channels through which flow can pass along the main flow direction from an end face forming the inflow side to an end face forming the outflow side, wherein the support structure is designed in a grid-like manner and is arranged upstream and / or downstream of the heating matrix, wherein the support pins which are inserted into the heating matrix and protrude beyond the inflow side and / or the outflow side are integrally connected to the support structure, wherein the support structure has solder reservoirs on the surface facing the heating matrix,into which the free ends of the support pins are inserted.

[0017] During the manufacture of the individual parts of the device, production-related tolerances arise that cannot be completely avoided. During assembly, the individual component tolerances can add up negatively, sometimes resulting in large tolerances. In the case of the support pins, this can lead to the support pins protruding from the heating matrix to different extents. Since the support structure is essentially a flat structure, the positional tolerances and component tolerances can result in not all support pins coming into contact with the support structure. The formation of a durable, material-locking connection between the support pins and the support structure can be impaired as a result. In extreme cases, a defective connection or no connection can occur, which can lead to loose support pins. This impairs the durability and stability of the device and, in the worst case, can lead to the destruction of the device.

[0018] According to the invention, the support structure is formed with a plurality of solder reservoirs, with each support pin being assigned a solder reservoir. The solder reservoirs serve as connection areas for the support pins to the support structure.

[0019] It is particularly advantageous if the solder reservoirs are formed by recesses in the support structure. The solder reservoirs formed as recesses in the support structure allow for positional tolerances of the support pins relative to the support structure to be compensated. In an ideal device design, the support pins all protrude the same distance from the heating matrix, so that the free ends of the support pins lie in a common plane. In reality, the free ends of most support pins lie slightly in front of or slightly behind this common plane in a somewhat random distribution.

[0020] To ensure a sufficient connection between the support structure and the support pins, the support structure is positioned relative to the free ends of the support pins so that all support pins extend a predefined length into their assigned solder reservoir. The depth of the solder reservoirs must therefore be selected to ensure sufficient penetration depth into the solder reservoir for each support pin to create a solder connection with sufficient strength.

[0021] It is also advantageous if the support pins extend into the solder reservoirs. Only when the free ends of the support pins extend into the solder reservoirs can a sufficient connection between the support pin and the support structure be created during the soldering process. Due to the positional tolerances of the support pins, the position of the respective free end of a support pin relative to the bottom of the corresponding solder reservoir of the support structure is different for each support pin. To ensure a sufficient connection, it must be ensured that a sufficient penetration depth is guaranteed even for the support pin furthest from the bottom of its solder reservoir.

[0022] A preferred embodiment is characterized in that the solder reservoirs have a clear opening width that is larger than the diameter of the support pins. By having a clear opening width of the solder reservoirs that is larger than the diameter of the free ends of the support pins, not only can the positional tolerance be compensated in the direction that forms a surface normal to the plane of the support structure be achieved, but also a tolerance in both spatial directions of the plane of the support structure be achieved. The free end of the support pin does not have to be positioned exactly centrally in the solder reservoir in the final assembled state, but can also be offset from it.

[0023] It is also preferable if the solder reservoirs are incorporated into the support structure by machining. Forming the solder reservoirs using blind holes is particularly advantageous. Furthermore, it is advantageous if the solder reservoirs are created by forming the support structure. For example, the solder reservoirs can be created by embossing them into the support structure.

[0024] Furthermore, it is advantageous if the solder reservoirs are filled with solder paste and / or solder powder. The prefilled solder reservoirs can be easily melted in a subsequent soldering process to create a tight connection with the support pins engaging in the solder reservoirs.

[0025] It is also expedient if at least a first number of support pins rest on the bottom of their respective solder reservoir in the final assembled state. Depending on the available insertion depth of the solder reservoirs in relation to the respective positional tolerances of the support pins, a certain number of the support pins will be in direct contact with the bottom area of ​​the solder reservoirs in the final assembled state with their free ends. Advantageous further developments of the present invention are described in the dependent claims and in the following description of the figures.

[0026] Short description of the drawings

[0027] The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings:

[0028] Fig. 1 is a sectional view through a heating matrix with an inserted support pin, wherein the support pins engage in solder reservoirs of the upstream and downstream support structure, and

[0029] Fig. 2 two sectional views through a support structure with differently designed solder reservoirs.

[0030] Preferred embodiment of the invention

[0031] Figure 1 shows a sectional view through a heating matrix 1, from which a support pin 2 protrudes on both sides. A support structure 3 is arranged upstream and downstream of the heating matrix 1. The free ends 4, 5 of the support pin 2 protrude into solder reservoirs 6, 7 formed in the support structure 3. A soldering process melts the solder material filled into the solder reservoirs 6, 7, and a permanent connection is established between the support pins 2 protruding into the solder reservoirs 6, 7 and the support structure 3.

[0032] Figure 2 shows a sectional view through a support structure 8, with the left part of the figure showing a solder reservoir 9, which was created by machining. The right part of Figure 2 shows a solder reservoir 10, which was created by a forming process, for example, stamping. The exemplary embodiments in Figures 1 to 2 are not limiting in nature and serve to clarify the inventive concept.

[0033] List of reference symbols

[0034] 1 . Heating matrix

[0035] 2. Support pin 3. Support structure

[0036] 4. free end of the support pin

[0037] 5. free end of the support pin

[0038] 6. Lot reservoir

[0039] 7. Solder reservoir 8. Support structure

[0040] 9. Lot reservoir

[0041] 10. Lot reservoir

Claims

Patent claims 1. A device for heating an exhaust gas flow in an exhaust gas line, comprising an electrically heatable heating matrix (1), with a support structure (3, 8) which is connected to the heating matrix (1) via a plurality of support pins (2), wherein the device can be inserted into a housing of an exhaust gas line, wherein the heating matrix (1) has a plurality of flow channels through which flow can pass along the main flow direction from an end face forming the inflow side to an end face forming the outflow side, wherein the support structure (3, 8) is designed in the manner of a grid and is arranged upstream and / or downstream of the heating matrix (1), wherein the support pins (2), which are inserted into the heating matrix (1) and protrude beyond the inflow side and / or the outflow side, are integrally connected to the support structure (3, 8), characterized in that the support structure (3) has solder reservoirs (6, 7, 9,10) into which the respective free ends (4, 5) of the support pins (2) are inserted., 2. Device according to claim 1, characterized in that the solder reservoirs (6, 7, 9, 10) are formed by recesses in the support structure (3, 8).

3. Device according to one of the preceding claims, characterized in that the support pins (2) extend into the solder reservoirs (6, 7, 9, 10).

4. Device according to one of the preceding claims, characterized in that the solder reservoirs (6, 7, 9, 10) have a clear opening width which is larger than the diameter of the support pins (2).

5. Device according to one of the preceding claims, characterized in that the solder reservoirs (9) are introduced into the support structure (8) by machining.

6. Device according to one of the preceding claims, characterized in that the solder reservoirs (10) are produced by deforming the support structure (8).

7. Device according to one of the preceding claims, characterized in that the solder reservoirs (6, 7, 9, 10) are filled with solder paste and / or solder powder.

8. Device according to one of the preceding claims, characterized in that at least a first number of support pins (2) in the final assembled state rest on the bottom of their respective solder reservoir (6, 7, 9, 10).

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