Support structure for heating disc

Abstract

The invention relates to a device for the aftertreatment of exhaust gases of an internal combustion engine, with a flow path which is spatially delimited by a housing and through which exhaust gas is able to flow, with a metallic heating matrix (10, 16) which has a plurality of flow channels formed between a plurality of metal foils that are stacked on top of one another and are wound about at least one axis of rotation, wherein the exhaust gas is able to flow through the flow channels from a gas inlet side to a gas outlet side along a main through-flow direction, wherein the heating matrix (10, 16) is connectable to a voltage source and is heatable using the ohmic resistance, and with a support structure (1, 7, 17) which is connected to the housing in an integrally bonded manner and is connected to the heating matrix (10, 16) by means of a plurality of coupling elements (18), wherein the support structure (1, 7, 17) has an annular region (2) which bears on an inner face of the housing and has a plurality of arms (3) projecting from this annular region (2) to the centre of the housing, wherein the arms (3) end in a closed circular region (4, 8) at the centre of the housing.

Description

[0001] Description

[0002] Support structure for heating disc

[0003] Technical area

[0004] The invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, with a flow path spatially delimited by a housing, through which exhaust gas can flow, with a metallic heating matrix which has a plurality of flow channels which are formed between a plurality of metal foils stacked on top of one another and wound around at least one axis of rotation, wherein the exhaust gas can flow through the flow channels along a main flow direction from a gas inlet side to a gas outlet side, wherein the heating matrix can be connected to a voltage source and can be heated by utilizing the ohmic resistance, with a support structure which is integrally connected to the housing and is connected to the heating matrix by means of a plurality of coupling elements.

[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] 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.

[0011] A particular disadvantage of the known solutions in the state of the art is that the structures are very complex and therefore not cost-optimal.

[0012] Description of the invention, task, solution, advantages

[0013] Therefore, the object of the present invention is to provide a device which enables a safe and durable positioning of a heating matrix in an exhaust gas flow path.

[0014] The object of the device is achieved by a device having the features of claim 1. An embodiment of the invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a flow path spatially delimited by a housing through which exhaust gas can flow, comprising a metallic heating matrix having a plurality of flow channels formed between a plurality of metal foils stacked on top of one another and wound around at least one rotational axis, wherein the exhaust gas can flow through the flow channels along a main flow direction from a gas inlet side to a gas outlet side, wherein the heating matrix is ​​connectable to a voltage source and can be heated using the ohmic resistance, comprising a support structure which is integrally connected to the housing and is connected to the heating matrix by means of a plurality of coupling elements,wherein the support structure has an annular region which abuts an inner surface of the housing and has a plurality of arms projecting from this annular region towards the center of the housing, the arms terminating in a closed, circular region in the center of the housing.

[0015] The annular region preferably extends in the circumferential direction of the housing as a completely closed ring. The width of the ring in the radial direction of the housing is preferably 2 mm to 10 mm, particularly preferably 4 mm to 6 mm. The thickness of the ring in the axial direction of the housing is preferably 1 mm to 6 mm, particularly preferably 2 mm to 4 mm.

[0016] The design of the support structure is selected such that vibrations out of the plane of the support structure or the heating matrix are minimized as much as possible. In particular, movements out of this plane along the main flow direction should be avoided. Furthermore, the natural frequency of the support structure and the heating matrix should be as high as possible, preferably above 800 Hz for cars and above 400 Hz for trucks, in order to keep the overlap with the vibrations occurring during operation as low as possible. The support structure preferably has between six and twelve arms that run from the annular area on the housing towards the center. The arms have an arcuate or involute-like shape and are preferably bent in a direction that also corresponds to the winding direction of the heating matrix. The arcuate design of the arms should enable a defined torsional movement of the support structure.

[0017] It is particularly advantageous if the arms extend in an arc shape in the plane of the support structure, with the arms curved in the same direction in the circumferential direction. The bending of the arms creates a spiral design. Preferably, the bending of the arms is adapted to the spiral shape of the heating matrix, so that the arms follow the course of the individual winding layers of the heating matrix as closely as possible.

[0018] It is also advantageous if the closed, circular area located in the center has a cross brace that follows the path of the metal foils forming the heating matrix. Since the heating matrix is ​​preferably wound around two winding mandrels, this forms a so-called S-shaped winding pattern, which describes the S-shaped winding of the layer stack around the two winding mandrels. To best stabilize the center of the heating matrix, the cross brace follows the layer stack in this central area, allowing the area to be directly connected via coupling elements.

[0019] A preferred embodiment is characterized in that the arcs of the arms are oriented in the same direction as the metal foils of the heating matrix are wound. This helps absorb torsional forces that may arise as a result of heating. Due to the self-heating or external heating of the spiral-shaped heating matrix, it will thermally expand and thereby perform a torsional movement. If the support structure cannot sufficiently follow this movement, the coupling elements would shear off at a certain rotational movement, or the heating matrix and / or the support structure would be damaged. It is also preferable if the coupling elements do not exceed a maximum distance of 80 mm from one another.This results in an asymmetrical distribution of the coupling elements across the cross-section of the heating matrix, with fewer coupling elements arranged in the outer region, which is closest to the housing, and a higher number of coupling elements relative to the area in the center. This is advantageous because the heating matrix has a greater curvature in the center due to the winding, which preferably requires support from winding layer to winding layer, i.e., with as tight a mesh as possible, to ensure the heating matrix is ​​mounted particularly stably there.

[0020] Furthermore, it is advantageous if the support structure has receiving points to which the coupling elements are connected to the support structure. Receiving points can, for example, be holes in the support structure into which the coupling elements are inserted and connected to the support structure. Holes preferably have a diameter of 4 mm to 10 mm. Alternatively, elongated holes can be provided which enable tolerance compensation of the heating matrix, the coupling elements or the support structure itself. Elongated holes have a significantly larger clear opening width than the diameter of the free end of the coupling elements. The elongated holes preferably have a width of 2 mm to 4 mm and a length of 4 mm to 10 mm. Alternatively, the receiving points can be formed by depressions in the support structure, which serve, for example, as a solder reservoir and thus enable simple connection to the coupling elements by soldering.The recesses can also have a larger clear opening width than the coupling elements in order to allow for tolerance compensation.

[0021] Furthermore, it is advantageous if a support structure is arranged upstream of the heating matrix and downstream of the heating matrix in the direction of flow. The support structures can be identical or different. A support structure only on one side would preferably be arranged on the gas inlet side of the heating matrix. As a result, the support structure itself does not act as a heat sink, and the flow distribution in the flow path is not impaired by a structure arranged downstream of the heating matrix. It is also expedient if the support structure is cambered. A convex shape of the support structure is particularly advantageous. The support structure is convexly protruding from its actual plane with its center.This is helpful to achieve a further shift of the natural frequency of the support structure towards safe frequency ranges, and thus to shift the natural frequencies out of the frequency ranges typically occurring during operation.

[0022] Furthermore, it is advantageous if a support structure is arranged upstream and downstream of the heating matrix in the flow direction, wherein the support structures are cambered in the same direction or in opposite directions to each other.

[0023] Furthermore, it is expedient for the heating matrix to be formed from a layer stack consisting of a plurality of stacked metal foils, wherein the layer stack is wound spirally by means of two rotating mandrels, with the windings of the layer stack being spaced from each other by an air gap. The spacing of the winding layers from each other is necessary to create a targeted current path along the heating matrix and to achieve the most uniform heating of the heating matrix possible.

[0024] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures.

[0025] Short description of the drawings

[0026] The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings:

[0027] Fig. 1 is a perspective view of a support structure with a plurality of arms extending in an arc from the outer ring region to the inner ring region, Fig. 2 is a perspective view of an alternatively designed support structure,

[0028] Fig. 3 is a schematic view of a support structure with curved arms and a schematic view of an S-shaped wound heating matrix, and

[0029] Fig. 4 is a view of a heating matrix accommodated between two support structures, showing different crownings of the support structures.

[0030] Preferred embodiment of the invention

[0031] Figure 1 shows a support structure 1 comprising an annular region 2 designed to be connected to the inner surface of the housing, which spatially defines the flow path. Several arms 3 project from the annular region 2 and are directed radially inward in a curved shape. The arms 3 terminate in the center at a circular region 4 of the support structure 1. The arms 3 are all curved in a blade-like manner and aligned in the same direction, so that the arms 3 have an arrangement similar to a paddle wheel.

[0032] The circular region 4 has a cross strut 5, which connects two points, preferably opposite points, of the circular region 4 through the center of the support structure 1. In the example of the figure, the cross strut 5 is bent in an S-shape and thus follows in particular the so-called S-bend of the heating disc (not shown), which arises when a stack of layers of metal foils is wound around two winding mandrels. This has the advantage that the center of the heating disc (not shown), which forms a significant portion of the total mass of the heating disc, can also be supported multiple times relative to the support structure 1. In an alternative embodiment, the circular region and in particular the cross strut can also follow a different shape, which is preferably adapted to the course of the layers of the heating disc.The support structure 1 has a plurality of recesses 6, which serve as connection points for the coupling elements, via which the heating disc can be connected to the support structure 1. In the embodiment of Figure 1, the recesses 6 are designed like elongated holes. The recesses 6 can also be used as a solder reservoir and for tolerance compensation. As a solder reservoir, the recesses 6 are pre-filled with a solder, so that inserting the heating disc with the coupling elements leads to the free ends of the coupling elements being immersed in the recesses 6, whereby they are also immersed in the solder. During a subsequent soldering process, the coupling elements are permanently connected to the support structure 1.

[0033] Due to the slot-like design of the recesses 6, these can compensate for a positional tolerance for the coupling element, at least along the longer extent of the recess 6, which can arise from a production tolerance of the heating disc, the coupling elements, the support structure 1 or from a tolerance resulting from the assembly.

[0034] The support structure 1 can be made of a cast part, a sheet metal, or another metallic material. The exemplary embodiment in Figure 1 shows a support structure 1 with a circular cross-section, which is adapted for a housing with a circular cross-section.

[0035] Figure 2 shows an embodiment of a support structure 7, wherein the support structure 7 has a different cross-section. The remaining structure is identical to that of Figure 1. The support structure 7 has a more rectangular cross-section with rounded corners. The central circular area 8 has an oval cross-section and a straight cross strut 9.

[0036] Figure 3 shows, on the left, a schematic view of a spirally wound heating disc 10. The heating disc 10 has an S-shaped center 11. Electrical connections 13 are provided at the top and bottom ends of the stack of layers 12 forming the heating disc 10, via which the heating disc 10 can be supplied with current. Arrows 14 indicate the direction in which the wound heating disc 10 will move if it is exposed to a sufficiently large amount of heat Q. Due to its winding direction, the heating disc 10 would perform a counterclockwise torsional movement and, in effect, wind up more tightly.

[0037] In the right-hand area of ​​Figure 3, a schematic view of a support structure 1 is shown, which essentially corresponds to the support structure 1 of Figure 1. Under the influence of a quantity of heat Q, the support structure 1 will also perform a torsional movement counterclockwise in the direction of the arrows 15 due to the curved design of the arms 3.

[0038] The heating disc 10 and the support structure 1 are thus designed in such a way that they twist in the same direction under the influence of heat, whereby an excessive relative movement between the support structure 1 and the heating disc 10 is prevented and thus damage to the coupling elements, the heating disc 10 or the support structure 1 is avoided.

[0039] The left part of Figure 4 shows a sectional view of a heating disk 16 arranged between two support structures 17 and connected to the support structures 17 by coupling elements 18. The right part of Figure 4 shows three different configurations of the two support structures 17.

[0040] In the upper view, the two support structures 17 are convexly curved in the same direction and protrude from their base plane. The middle view on the right shows two convexly curved support structures 17, each of which is oriented in opposite directions. In this case, both support structures 17 are protruded away from the heating disk 16. The lower view shows a configuration with a flat support structure 17 and a convexly curved support structure 17. The exemplary embodiments of Figures 1 to 4 are not limiting in nature and serve to illustrate the inventive concept.

[0041] List of reference symbols

[0042] 1 . Support structure

[0043] 2. annular area

[0044] 3. Arms

[0045] 4. circular area

[0046] 5. Cross brace

[0047] 6. Deepenings

[0048] 7. Support structure

[0049] 8. circular area

[0050] 9. Cross brace

[0051] 10. Heating disc

[0052] 11 . S-shaped curved center

[0053] 12. Layer stack

[0054] 13. electrical connections

[0055] 14th arrow

[0056] 15th arrow

[0057] 16. Heating disc

[0058] 17. Support structure

[0059] 18. Coupling element

Claims

Patent claims 1. A device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a flow path spatially delimited by a housing through which exhaust gas can flow, comprising a metallic heating matrix (10, 16) having a plurality of flow channels formed between a plurality of stacked metal foils wound around at least one rotational axis, wherein the flow channels can be flowed through by the exhaust gas along a main flow direction from a gas inlet side to a gas outlet side, wherein the heating matrix (10, 16) is connectable to a voltage source and can be heated using the ohmic resistance, comprising a support structure (1, 7, 17) which is integrally connected to the housing and is connected to the heating matrix (10, 16) by means of a plurality of coupling elements (18), characterized in that the support structure (1, 7, 17) has an annular region (2),which rests against an inner surface of the housing and has a plurality of arms (3) projecting from this annular region (2) towards the center of the housing, the arms (3) terminating in a closed, circular region (4, 8) in the center of the housing.

2. Device according to claim 1, characterized in that the arms (3) extend in an arc shape in the plane of the support structure (1, 7, 17), wherein the arms (3) are bent in the same direction in the circumferential direction.

3. Device according to one of the preceding claims, characterized in that the closed, circular region (4, 8) arranged in the center has a cross strut (5, 9) which follows the course of the metal foils forming the heating matrix (10, 16).

4. Device according to one of the preceding claims, characterized in that the arcs of the arms (3) are aligned in the same direction as the metal foils of the heating matrix (10, 16) are wound. Device according to one of the preceding claims, characterized in that the coupling elements (18) do not exceed a maximum distance of 80 mm from one another. Device according to one of the preceding claims, characterized in that the support structure (1, 7, 17) has receiving points (6) to which the coupling elements (18) are connected to the support structure (1, 7, 17). Device according to one of the preceding claims, characterized in that a support structure (17) is arranged upstream of the heating matrix (16) and downstream of the heating matrix (16) in the direction of flow. Device according to one of the preceding claims, characterized in that the support structure (17) is cambered.Device according to one of the preceding claims, characterized in that a support structure (17) is arranged upstream and downstream of the heating matrix (16) in the flow direction, wherein the support structures (17) are cambered in the same direction or in opposite directions to one another. Device according to one of the preceding claims, characterized in that the heating matrix (10, 16) is formed from a layer stack (12) formed by a plurality of metal foils stacked one on top of the other, wherein the layer stack (12) is wound spirally by means of two rotary mandrels, wherein the windings of the layer stack (12) are spaced from one another by an air gap.

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