Support structure for a heating matrix

Abstract

The invention relates to a support structure (1) for positioning a heating matrix in an exhaust gas section which is spatially delimited by a housing. The heating matrix is made of a honeycomb body that has a plurality of flow channels through which exhaust gas can flow along a main flow direction, and the heating matrix is supported against the inner surface of the housing by the support structure (1). The matrix is fixed relative to the support structure (1) by means of a plurality of coupling elements (4), and the coupling elements (4) are plugged into individual heating matrix cells formed by the flow channels and are durably connected thereto. The free end of each coupling element (4) is directly or indirectly connected to the support structure (1), and a respective tolerance compensating element is provided which compensates for a positional tolerance of the coupling element (4) in at least two spatial directions by means of a connecting element (5) with at least one elongated hole. The invention additionally relates to a method for connecting the support structure to a heating matrix.

Description

[0001] Description

[0002] Support structure for a heating matrix

[0003] Technical area

[0004] The invention relates to a support structure for positioning a heating matrix in an exhaust gas path spatially delimited by a housing. The heating matrix is ​​formed by a honeycomb body having a plurality of flow channels through which flow can occur along a main flow direction. The heating matrix is ​​supported by the support structure relative to the inner surface of the housing, and the matrix is ​​fixed relative to the support structure by means of a plurality of coupling elements. The coupling elements are inserted into individual cells of the heating matrix formed by the flow channels and are permanently connected to them. The invention also relates to a method for connecting a support structure to a heating matrix.

[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 that can be heated using ohmic resistance. 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 ohmic resistance.

[0008] 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.

[0009] In order to position the matrix in the exhaust system and to support it in particular against mechanical and thermal loads, a support must be provided, which in particular occurs with the high thermal alternating loads and also with the strong and irregular mechanical loads in an exhaust system, in particular the exhaust system of a motor vehicle.

[0010] The connection between the support structure and the heating matrix is ​​achieved via a plurality of coupling elements. Since all components are subject to certain manufacturing tolerances due to production, tolerance compensation must be created to enable stress-free assembly. A particular disadvantage of the known solutions in the prior art is that the tolerance compensation of the known coupling elements is insufficient.

[0011] Description of the invention, task, solution, advantages

[0012] Therefore, the object of the present invention is to provide a support structure for a heating matrix, which has advantageous coupling elements that allow sufficient tolerance compensation. Furthermore, the object of the invention is to provide a method for connecting the support structure to the heating matrix. The object with regard to the support structure is achieved by a support structure having the features of claim 1.

[0013] One embodiment of the invention relates to a support structure for positioning a heating matrix in an exhaust gas path spatially delimited by a housing, wherein the heating matrix is ​​formed by a honeycomb body which has a plurality of flow channels through which flow can be carried along a main flow direction, wherein the heating matrix is ​​supported relative to the inner surface of the housing by the support structure and the matrix is ​​fixed relative to the support structure by means of a plurality of coupling elements, wherein the coupling elements are inserted into individual cells of the heating matrix formed by the flow channels and are permanently connected to these, wherein the respective free end of a coupling element is connected directly or indirectly to the support structure, wherein in each case a tolerance compensation element is provided which compensates for a positional tolerance of the coupling element in at least two spatial directions.

[0014] Tolerance compensation is necessary because all components are subject to tolerances due to production. Therefore, compensation is essential for precise assembly. In addition to the production-related tolerances, a tolerance arises from the fact that the coupling elements must be inserted into the cells of the honeycomb body. Slight deviations can sometimes occur here. Furthermore, a coupling element can deviate slightly from its basic position due to a shape tolerance of the honeycomb body.

[0015] Tolerance compensation is preferably provided in the area of ​​the connection of the coupling element to the support structure, since the connection to the honeycomb body offers practically no compensation options.

[0016] The coupling element, which may be formed, for example, by a support pin known in the prior art or, depending on the need for electrical insulation, may also be formed by a simple metal pin, may be connected directly to the support structure or using an intermediate element.

[0017] Two of the three spatial directions in which tolerance compensation must take place span the plane in which the support structure lies. The third spatial direction runs as a surface normal to this plane. In the first two spatial directions, a positional tolerance of the coupling element is compensated for, for example, if the coupling element is inserted into a neighboring cell of the actual target cell or if the honeycomb body has a manufacturing tolerance in this area. In the third spatial direction, which is the direction in which the coupling elements are inserted into the honeycomb body, a tolerance in the axial direction of the exhaust system is compensated for. Usually, the tolerance in the third direction is smaller than in the first two directions because the insertion depth into the honeycomb body is controlled very precisely by machine and the deviations are therefore small.

[0018] It is particularly advantageous if the support structure has, on its surface facing the heating matrix, cup-like chambers which are open to the heating structure and which are each designed to receive a free end of a coupling element and form the tolerance compensation elements.

[0019] The support structure, which is essentially formed from flat sheets, can have cup-like chambers. These can be formed directly on the surface of the support structure facing the heating matrix. The chambers can be formed directly into the sheet material, for example, by deep drawing or stamping. Alternatively, the chambers can also be formed by a cylindrical collar that protrudes from the support structure.

[0020] It is also advantageous if the clear opening width of the cup-like chambers is a multiple of the cross-section of a free end of a coupling element. The free end of the coupling element can then be displaced within the clear opening in the first two spatial directions. By varying the insertion depth of the free end of the coupling element, tolerance compensation can also take place in the third spatial direction. The size of the clear opening simultaneously determines the maximum possible tolerance compensation in the first two spatial directions, while the depth of the chambers essentially determines the maximum possible tolerance compensation in the third spatial direction.

[0021] A preferred embodiment is characterized in that the depth of the cup-like chambers is greater than the average insertion depth of the coupling elements. This ensures that a sufficiently large tolerance compensation is possible.

[0022] The chambers can be pre-filled with a solder so that after inserting the coupling elements, a durable connection between the support structure and the heating matrix can be created using a simple soldering process.

[0023] In an alternative embodiment, it is preferable if a connecting element is arranged between the support structure and a coupling element as a tolerance compensation element, which is permanently connected to the support structure on one side and receives the free end of the coupling element on the other side.

[0024] An additional connecting element may be advantageous to compensate for tolerances. For example, a connecting element can be formed by a hollow cylinder closed on one side, which is applied to the surface of the support structure. The hollow cylinder can also be prefilled with solder.

[0025] Furthermore, it is advantageous if the connecting element has an opening facing the coupling element, which is larger than the cross-section of the free end of the coupling element. If tolerance compensation essentially has to take place in one of the first two spatial directions, a slot-like opening can be provided. Alternatively, a circular or rectangular opening cross-section can be selected. The object with regard to the method is achieved by a method having the features of claim 8.

[0026] An embodiment of the invention relates to a method for connecting the support structure to the heating matrix, wherein the connecting elements are first permanently connected to the coupling elements and, in a subsequent step, are permanently connected to the surface of the support structure facing the heating matrix.

[0027] Depending on the selected production process, the connecting element can first be connected to the free end of the coupling element. Any positional tolerance of the coupling element is transferred to the connecting element at this point. This applies particularly to tolerances in the first two spatial directions. Tolerances in the third spatial direction can be compensated for by adjusting the insertion depth of the coupling element into the connecting element.

[0028] The coupling elements are permanently connected to the connecting elements using a suitable process. This is followed by the connection to the support structure. Since the positional tolerances have been transferred to the connecting elements, it may happen that the connecting elements deviate from the originally planned position by precisely these tolerances. This can be counteracted by making the support structure wider in the area of ​​the planned position of the respective connecting elements.

[0029] The connecting elements preferably have a smooth surface facing the support structure, via which a connection to the support structure can be made in a simple manner.

[0030] In this case, the opening width for inserting the coupling elements only needs to be slightly larger than the free ends of the coupling elements, since the tolerance compensation here only takes place in the third spatial direction and the compensation of the first two spatial directions is subsequently carried out by changing the position of the connecting element relative to the support structure.

[0031] In an alternative method, it is expedient if the connecting elements are permanently connected to the surface of the support structure facing the heating matrix in a first step, and in a subsequent step the coupling elements are inserted into the connecting elements and permanently connected to them.

[0032] Alternatively, the connecting elements are first connected to the support structure. In this case, the clear opening of the connecting elements must be large enough to allow tolerance compensation in the first two spatial directions. The third spatial direction is compensated for by adjusting the insertion depth.

[0033] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures.

[0034] Short description of the drawings

[0035] The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings:

[0036] Fig. 1 is a partial view of a support structure with a plurality of connecting elements which are attached to the support structure and have different positions relative to the support structure,

[0037] Fig. 2 is a partial view of a support structure with a plurality of connecting elements arranged at predefined positions on the support structure, Fig. 3 is a sectional view through two connecting elements, each with an inserted coupling element, wherein the coupling element is fixed by a clamp in the connecting element, and

[0038] Fig. 4 a coupling element which is accommodated in cup-shaped chambers on both sides.

[0039] Preferred embodiment of the invention

[0040] Figure 1 shows a support structure 1 having several connecting elements 3 on one of its struts 2. A coupling element 4 can be inserted into each of the connecting elements 3. The support structure 1, the connecting elements 3, and the coupling elements 4 can be permanently connected to one another using a soldering process.

[0041] In the example shown in Figure 1, the connecting elements 3 are first connected to the coupling elements 4, which in turn are inserted into cells of a heating matrix and connected to it. The positional tolerances resulting from the production-related tolerances of the heating matrix are transferred to the connecting elements 3 via the coupling elements 4. Therefore, the connecting elements 3, shown here on the middle connecting element 3, are not arranged centrally on the strut 2, but sometimes slightly offset from its center.

[0042] Figure 2 shows connecting elements 5 on a strut 2 of a support structure 1. The connecting elements 5 have a slot-like opening, which allows for tolerance compensation in one of the first two spatial directions. The connecting elements 5 are first connected to the strut 2 of the support structure 1 before the coupling elements 4 are inserted into them. Therefore, the connecting elements 5 are distributed very evenly across the strut 2.

[0043] Figure 3 shows a sectional view through a coupling element 4, which is inserted into a connecting element 6 on one side. The coupling element 4 is connected to the connecting element 6 by means of a clamp. This can be an initial fixation before a permanent connection is created by soldering.

[0044] Figure 4 shows a coupling element 4, which is inserted on both sides into hollow cylindrical receptacles 7. Here, in particular, the positional tolerance in the third spatial direction can be compensated by varying the insertion depth.

[0045] The different features of the individual embodiments can also be combined with each other.

[0046] The embodiments of Figures 1 to 4 are in particular not restrictive in nature and serve to clarify the inventive concept.

[0047] List of reference symbols

[0048] 1 . Support structure

[0049] 2. Strut 3. Connecting element

[0050] 4. Coupling element

[0051] 5. Connecting element

[0052] 6. Connecting element

[0053] 7. hollow cylindrical holder

Claims

Patent claims 1. Support structure (1) for positioning a heating matrix in an exhaust gas path spatially delimited by a housing, wherein the heating matrix is ​​formed by a honeycomb body which has a plurality of flow channels through which flow can pass along a main flow direction, wherein the heating matrix is ​​supported relative to the inner surface of the housing by the support structure (1) and the matrix is ​​fixed relative to the support structure (1) by means of a plurality of coupling elements (4), wherein the coupling elements (4) are inserted into individual cells of the heating matrix formed by the flow channels and are permanently connected to these, characterized in that the respective free end of a coupling element (4) is connected directly or indirectly to the support structure (1), wherein in each case a tolerance compensation element is provided which compensates for a positional tolerance of the coupling element (4) in at least two spatial directions.

2. Support structure (1) according to claim 1, characterized in that the support structure (1) has, on its surface facing the heating matrix, cup-like chambers which are open to the heating structure and which are each designed to receive a free end of a coupling element (4) and form the tolerance compensation elements.

3. Support structure (1) according to claim 2, characterized in that the clear opening width of the cup-like chambers is in each case a multiple of the cross section of a free end of a coupling element (4).

4. Support structure (1) according to one of the preceding claims 2 or 3, characterized in that the depth of the cup-like chambers is greater than the average insertion depth of the coupling elements (4). Support structure (1) according to claim 1, characterized in that a connecting element (3, 5, 6, 7) is arranged between the support structure (1) and a coupling element (4) as a tolerance compensation element, which connecting element is permanently connected to the support structure (1) on one side and receives the free end of the coupling element (4) on the other side. Support structure (1) according to claim 5, characterized in that the connecting element (3, 5, 6, 7) has an opening facing the coupling element, which opening is larger than the cross-section of the free end of the coupling element (4). Support structure (1) according to one of claims 5 or 6, characterized in that the connecting element (5) has a slot-like opening.Method for connecting the support structure (1) according to one of the preceding claims 5 to 7 to the heating matrix, characterized in that the connecting elements (3, 7) are first permanently connected to the coupling elements (4) and, in a subsequent step, are permanently connected to the surface of the support structure (1) facing the heating matrix. Method for connecting the support structure (1) according to one of the preceding claims 5 to 7 to the heating matrix, characterized in that the connecting elements (5, 6, 7) are permanently connected to the surface of the support structure (1) facing the heating matrix in a first step, and, in a subsequent step, the coupling elements (4) are inserted into the connecting elements (5, 6, 7) and permanently connected to them.

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