Support structure for a heating disc or a heating resistor, support system, and electric exhaust-gas heater

Abstract

The invention relates to a support structure (70) for a heating disc or a heating resistor (10) in an exhaust-gas system, which support structure comprises: a multi-part housing (35); at least one first, outer ring (40) made of a fiber material; and at least one second, inner ring (80) made of a heat-resistant material which is not electrically conducting and differs from the fiber material of the at least one first ring (40); wherein the at least one second, inner ring (80) defines a receiving space for the heating disc or the heating resistor (10).

Description

[0001] A support structure for a heating disc or a heating resistor, a support system and an electric exhaust gas heater

[0002] Field of the invention

[0003] The present invention relates generally to support structures and systems for supporting a heating element with applications particularly in exhaust aftertreatment systems.

[0004] Background of the invention (and prior art)

[0005] In light of upcoming emissions regulations (e.g., Euro 7, CN7, EU VII, CN VII), automakers are constantly seeking technologies for active thermal management of exhaust aftertreatment systems with the goal of reducing cold-start emissions while simultaneously keeping the relevant exhaust system components at operating temperature. Electric exhaust heaters, also known as e-heaters, are considered a promising technology in this context, which can help not only meet future emissions targets but also actively improve the service life of the underlying systems.

[0006] A promising approach is the use of heating elements with a cell structure, e.g., square or hexagonal, made of a high-temperature-resistant material (e.g., Ni-Cr or Fe-Cr-Al alloy), which offer very good heating performance while requiring little space.

[0007] One challenge, however, is the integration of such a heating element into a metal housing of an exhaust aftertreatment system with the following main requirements:

[0008] The heating element, such as a heating disk or a heating resistor, must be robustly mounted in the housing throughout the vehicle's service life, taking into account high exhaust temperatures and mass flows, as well as high vibration and acceleration values ​​in both axial and radial directions. Electrical insulation must also be provided to prevent short circuits or other malfunctions. In addition, thermal insulation from surrounding components and the simplest possible manufacturing processes are required.

[0009] Until now, a pair of pressed or pre-stressed rings were used to attach the heating disc, which were welded to a split tube on both sides of the heating disc.

[0010] However, during internal tests of electric heaters constructed in this manner, abrasion and erosion were observed during thermoelectric endurance runs, particularly in the worn rings. This led to deterioration of the associated support structure and a higher-level support system, as well as damage to the electric heater itself and subsequent failure. It is assumed that the cause of the observed abrasion lies primarily in the relative movement of the heating disc to the compressed rings. When the support device is compressed during the assembly process of the electric heater, some parts of the rings are pressed into a cellular structure of the heating disc. However, during operation of the electric heater—accompanying the expansion and contraction of the heating disc—these elements can break and gradually protrude from metal rings belonging to the housing.

[0011] In this context, reference is made to US 2022 / 0 186647 A1, which discloses a heating device with stabilizing elements for an exhaust system and an exhaust system. Furthermore, US 5 597 503 A discloses an axially mounted housing for electric heaters for heating an exhaust gas stream with a peripheral pressure ring that generates a diametrically balanced force. A heating element is installed in the housing with a one-piece housing wall, wherein the heating element is held between a circumferential support element and a circumferential pressure ring attached to the housing wall. Furthermore, US 6 025 578 A discloses an electrically insulating bushing with an electrocorrosion protection device. Object of the invention

[0012] It is the object of the present invention to overcome one or more of the problems or disadvantages associated with the prior art.

[0013] Summary of the invention

[0014] The above-mentioned object and other problems are solved by a support structure for a heating disk or a heating resistor, a support system, and an electric exhaust gas heater according to the main claims. The subclaims relate to preferred embodiments of the invention.

[0015] The present invention relates to a support structure for a heating disc or a heating resistor in an exhaust system, comprising the following: a multi-part housing, at least one first outer ring made of a fiber material, and at least one second inner ring made of an electrically non-conductive material that differs from the fiber material of the at least one first ring. The at least one second inner ring defines a receiving space for the heating disc or the heating resistor. The aforementioned arrangement of the support structure has, among other things, the advantage of structurally separating the at least one first outer ring from the heating disc or the heating resistor in the exhaust system. Such a separation contributes to reducing wear of the support structure due to thermal and / or mechanical stress when used in the exhaust system.

[0016] The support structure is optionally designed such that the at least one first ring comprises two rings and / or that the at least one second ring comprises two rings, wherein the receiving space for the heating disk or the heating resistor is preferably defined between the two second rings. Such a design can simplify assembly of the support structure and installation into a higher-level structure, depending on the application. In the support structure, the multi-part housing optionally has at least two metal rings or two metal halves, which are preferably designed to apply a predefined clamping pressure of up to approximately 15 bar to the first and second rings. This pressure is particularly preferably approximately 2 to 4 bar, depending on the respective application and / or the underlying installation size.The values ​​stated are in addition to generally applicable tolerances for components in exhaust system construction for metallic housing parts and for ceramic fiber materials in catalyst bearings.

[0017] The fiber material of the at least one first ring of the support structure is optionally a ceramic material, preferably Al2O3, SiO2 or a mullite ceramic material, the latter being a mixture of Al2O3 and SiO2 and more precisely Al2Al2+2xSi2-2xO -x with x = oxygen vacancies per unit cell.

[0018] The fiber material of the at least one first ring of the support structure optionally further comprises fibers with a diameter in the range of approximately 3 to 12 pm, preferably 5 to 10 pm. Additionally or alternatively, the fibers of the fiber material are present in a length-to-diameter ratio greater than 3 to 1.

[0019] Furthermore, the at least one first ring or the two first rings of the support structure are optionally compressible, preferably by a factor in the range of 2 to 5 in the installed state.

[0020] The material of the at least one second ring or the two second rings optionally also has at least one of the following properties: It is temperature-resistant up to 1100°C, preferably in a temperature range between -40°C and 1100°C. Additionally or alternatively, it is compressible, flexible and / or pliable, wherein in particular the compressibility is preferably lower than that of the material of the at least one first ring and is in the low percentage range, particularly preferably at most 20%. Furthermore or alternatively, it is formable, preferably in a ring, oval or elliptical shape. In addition, there are optional aspects of erosion resistance and / or resistance to exhaust gases and / or chemical resistance, preferably to substances that can occur in exhaust gas aftertreatment systems.

[0021] The material of the at least one second ring or the two second rings of the support structure is optionally mica, also known internationally as “mica.” Preferably, the material of the at least one second ring or the two second rings of the support structure is a layered silicate, particularly preferably phlogopite, muscovite, a potassium-magnesium aluminosilicate with optional fluorine or hydroxide ions, a non-organic binder, or a combination thereof. The material can be selected according to the application: Due to its high temperature resistance, phlogopite is particularly suitable for applications with extremely hot exhaust gases, for example in connection with gasoline applications or with internal combustion engines. In comparison, muscovite is suitable for somewhat lower temperature ranges, such as those that can occur in diesel applications.

[0022] At least one of the first and / or second rings of the support structure can optionally be at least two-part in the circumferential direction. Depending on the application, installation space and / or the need for corresponding pre-assembly of the support structure, a symmetrical subdivision, for example at 180° in each case, is preferred. Alternatively, however, an asymmetrical subdivision or even an uneven subdivision is conceivable, wherein moreover only one of the said rings can be subdivided once or multiple times. A potential influencing factor in this context is, for example, the number and / or arrangement of electrodes on the heating disk or the heating resistor used. An independent influencing factor and thus a technical advantage can lie in the fact that retrofitting the support structure according to the invention into an existing support system is also possible due to the fact that the rings present have a correspondingly adapted division.At the same time or alternatively, at least one of the first and / or second rings can optionally have an L-shaped, U-shaped, round, or rectangular cross-section. This encompasses any combination of rings and cross-sections that have a corresponding influence on aspects such as the installability or retrofittability of the support structure according to the invention, as well as on economic aspects, for example, with regard to the availability of the raw materials underlying the materials used.

[0023] The at least one second ring or the two second rings of the support structure can optionally be present as a coating on a corresponding side of the at least one first ring or the respective first ring. At the same time or alternatively, the at least one second ring or the two second rings can optionally have a thickness of approximately 0.1 mm to 1.5 mm, preferably approximately 0.1 mm to 0.8 mm.

[0024] Furthermore, the at least one second ring or at least one of the two second rings can optionally have a metal mesh insert.

[0025] In addition, the at least one first ring or the at least two first rings of the support structure can optionally have a continuous outer contour or alternating recesses and / or elevations.

[0026] The present invention further relates to a support system for an electric heating device, comprising the support structure according to the invention and a heating disc or a heating resistor, preferably with two sides, a cellular structure, and / or a plurality of slots. The heating disc or the heating resistor is arranged in the receiving space of the at least one second ring or between the two second rings. In the support structure according to the invention or in the support system according to the invention, the respective first and second rings are optionally pre-assembled, preferably glued or sewn to one another. Alternatively or simultaneously, the heating disc or the heating resistor is optionally pre-assembled on both sides to the corresponding side of the respective second ring, preferably glued or sewn. Accordingly, aspects such as dimensional stability and assembly accuracy can be improved in the assembled state.Furthermore, optional pre-assemblies of individual components can facilitate the assembly of the support structure or the support system according to the invention.

[0027] The support structure or the support system can optionally have a plurality of pins configured for positioning, supporting, and holding the heating disc or the heating resistor and / or for electrical insulation between partial regions of the heating disc or the heating resistor (10), wherein the plurality of pins are preferably spacer elements, and wherein particularly preferably some of the spacer elements are designed as holding means positioned in a corresponding recess in the housing, wherein at least one end of the holding means is directly mechanically connectable to the housing; and / or wherein at least some of the spacer elements are positioned, preferably clamped, between the two second rings (80). The pins can optionally assume the function of electrical insulation between the partial regions (meander-shaped heating loops) of the heating disc.

[0028] Furthermore, the at least one second ring or the two second rings of the support system optionally contact only an edge region of the heating disc or the heating resistor in the circumferential direction, wherein the edge region is not actively heated. Such a mounting of the heating disc or the heating resistor simultaneously allows the heating disc or the heating resistor to be mounted slidingly or in a sliding fit in the support system during a heating or cooling process. The present invention also relates to an electric exhaust gas heater comprising a support system according to the invention and a heater housing, preferably made of metal, which is positioned in an exhaust line of an exhaust gas aftertreatment system and is configured to receive the support system.

[0029] Short description of the drawings

[0030] The invention, as well as further details and advantages thereof, are explained below using preferred embodiments with reference to the figures, wherein like designations refer to like elements. They show:

[0031] Fig. 1 is an isometric view of an electric exhaust gas heater with two electrodes;

[0032] Fig. 2 is a partially sectioned side view and a plan view of an electric exhaust gas heater;

[0033] Fig. 3 is a sectional view of an electric exhaust gas heater, a section AA from Fig. 2, as well as a detailed view B from this sectional view;

[0034] Fig. 4 shows an assembly according to the invention consisting of an L-shaped first ring and a flat second ring in different views;

[0035] Fig. 5 is a sectional view of the electric exhaust gas heater, a section AA from Fig. 2 and a detailed view from the sectional view;

[0036] Fig. 6 shows a flat second ring according to the invention in two views;

[0037] Fig. 7 is a sectional view of the electric exhaust gas heater, a section AA from Fig. 2 and a detailed view from the sectional view.

[0038] Detailed description of the invention

[0039] In this description, the terms top, bottom, right, and left, as well as similar designations, refer to the orientations or arrangements shown in the figures and are used only to describe the exemplary embodiments. These terms may indicate preferred arrangements but are not to be understood in a limiting sense.

[0040] Furthermore, the terms "substantially", "approximately", "about" and similar expressions mean that deviations of + / -10%, preferably + / -5%, from the stated value are permissible.

[0041] The following describes the use of a plurality of rings, for example, at least one first ring, at least one second ring, or metal rings. The term "ring" is a generic term for a respective component that does not necessarily have to have a round shape. Rather, geometric adaptability to other design parameters is possible and encompassed by the term, with particular consideration given to the shape of the housing and / or the heating element used.

[0042] This description, and the accompanying figures, illustrate the use or installation of a heating element in various embodiments of the present invention. The properties mentioned below apply equally to all embodiments, even if they are shown, illustrated, or specifically described, for example, only in a round and / or disc-shaped form.

[0043] Fig. 1 shows an isometric view of an electric exhaust gas heater 1, 2, 3 with two electrodes. In the illustration shown here, a heating element, more precisely a heating disc 10, and a multi-part heater housing are also shown from the outside, whereby initially only an outer side 20 is visible here. The heating disc 10 has an exemplary configuration with a plurality of slots and two electrodes for the power supply, which are preferably attached directly to the heating disc 10, for example by means of laser welding. A heating element, more precisely a heating disc or a heating resistor, as used in the present invention, preferably consists of a regular cell or honeycomb structure which has differently shaped cells, for example square or hexagonal cells, and / or of a high-temperature-resistant material (e.g.Ni-Cr or Fe-Cr-Al alloy) and / or offers excellent heating performance with a small installation space requirement. The heating element can have a round cross-section and / or be disc-shaped.

[0044] The heating disc can have a plurality of slots, which are preferably wider than 1 mm, wherein their width is particularly preferably in the range between 1 and 5 mm. Between individual slots of the plurality of slots, there are optionally 2 to 10, preferably 4 to 5 cells, particularly preferably 3 or even only 2 cells next to one another, wherein this number can vary depending on the application, positioning of the plurality of slots and / or the required electrical resistance. The individual cells are optionally between 1.2 and 1.3 mm, preferably 1.27 mm, wide or wide. Their wall thickness is in the range of 150 μm. A cell structure used in the context of the present invention particularly preferably has a cell density of between 50 and 400 CPSI (CPSI = cells per square inch), i.e., between 8 and 62 cells per cm 2Depending on the arrangement of the individual slots on the heating disc, this results in, for example, an arrangement of connected cells in meandering heating loops, which are connected to each other at their respective ends and arranged between the adjacent slots. Such heating loops serve, in particular, to prevent electrical short circuits.

[0045] Heating discs used in the present invention usually have sharp edges, for example, around continuous sharp edges, due to manufacturing and / or shape-related factors depending on the cell and slot structure. Preferred manufacturing processes fall into the field of additive manufacturing techniques, generative manufacturing techniques, and rapid technologies, which are also generally referred to below as 3D printing processes. However, the support structures, support systems, and / or electric exhaust gas heaters of the present invention are also compatible with heating discs or resistors manufactured elsewhere, which also makes the present invention usable for retrofit systems. Examples of alternative manufacturing processes include extruded heating discs or heating discs made from soldered, welded, or molded thin sheets, as well as cast or stamped heating discs.The thickness of a heating disc used in the present invention is preferably between 3 and 15 mm, particularly preferably between 4 and 8 mm, although other dimensions are also conceivable depending on the application.

[0046] Fig. 2 is a partially sectioned side view and a top view of an electric exhaust gas heater 1, 2, 3 with a basic configuration like the electric exhaust gas heater 1, 2, 3 shown in Fig. 1. In the top right partial section of the electric exhaust gas heater 1, 2, 3 in Fig. 2, a pin or pin 60 is shown which is embedded in the heating disk 10 and is one of a plurality of pins 60. The pins 60 are used to position, support and / or hold the heating disk or the heating resistor 10 in a housing of a support structure (not yet shown in detail here). The pins 60 are preferably spacer elements, optionally with a metal core and preferably ceramically coated, which are designed to keep partial areas of the heating disk 10 at a distance.Particularly preferably, at least some of the spacer elements are designed as holding means positioned in a corresponding recess in the housing, with at least one end of the holding means being mechanically connectable directly to the housing. They can also fulfill the aforementioned function as spacers by maintaining constant distances between individual segments of the overall arrangement, thereby preventing potential short circuits.

[0047] The plan view of the electric exhaust gas heater 1, 2, 3 below the sectional view again shows the outer side 20 of the heater housing as well as a cover 50 belonging to the heater housing. Together with an inner side (not yet shown here), this results in a purely exemplary arrangement that can be adapted depending on the application.

[0048] Fig. 3 shows a sectional view of an electric exhaust heater 1, a section AA from Fig. 2, as well as a detailed view B of this sectional view. The electric exhaust heater 1 of Fig. 3 has the heating disc 10. In addition, additional housing parts or corresponding divisions may be required, for example, due to installation space, the type and sequence of assembly of the overall arrangement, etc.

[0049] The electric exhaust gas heater 1 of Fig. 3 has a support structure 70 according to the invention for the heating disk 10, wherein the support structure 70 has the following elements: A multi-part housing 35, shown here in two-part form and preferably made as rings and / or from metal. The multi-part housing 35 of the support structure 70, as shown in Fig. 3, can be part of the heater housing of the electric exhaust gas heater 1, 2, 3 according to Fig. 1. Accordingly, in Fig. 3, an inner side 30 of the heater housing coincides with one side of the housing 35 of the support structure 70.

[0050] The support structure 70 from Fig. 3 further comprises two first outer rings 40 made of a fiber material and two second inner rings 80 made of an electrically non-conductive material that differs from the fiber material of at least the first rings 40. The two inner rings 80 define a receiving space for the heating disc 10. In the receiving space of the support structure 70 of the electric exhaust gas heater 1, the heating disc 10 is arranged between the two second inner rings 80. The two second inner rings 80 are present here in a flat embodiment. Together with the heating disc 10 and the two outer rings 40, shown here in an L-shape, as well as the two-part housing 35, they form a support system according to the invention for an electric heating device, here including the heating disc 10 by way of example. The support structure 70 clamps the heating disc 10, specifically in an edge region of the heating disc 10 that is not actively heated.Even if they are not located in the sectional plane of detail view B of Fig. 3, a plurality of pins 60 can optionally be installed at this point in the support structure 70 or in the support system, as described in connection with Fig. 2. These pins 60 can then optionally each have one end seated in the metal rings of the support structure 70 or alternatively be preloaded between the second ring(s), as shown in Fig. 3. In the axial direction, they are held in position by means of the first and second rings 40, 80. At the other end, they are clamped between conductor track parts of the heating disk 10 and the second rings 80 with axial contact. An optional combination of the support structure 70 according to the invention with the plurality of pins 60 can synergistically contribute to improving the durability of the entire arrangement against external influences.Aspects of dimensional stability, wear and temperature resistance are mentioned here purely as examples.

[0051] Fig. 4 shows various views of an assembly consisting of an L-shaped first ring 40 and a flat second ring 80. On the right side of the ring assembly, one half of the receiving space for the heating disc 10 is indicated.

[0052] Fig. 5 shows a sectional view of a second electric exhaust gas heater 2 with a basic configuration as in Fig. 1 , also a section AA from Fig. 2. In addition, there is a detailed view B from the sectional view.

[0053] In detail, the second electric exhaust heater 2 of Fig. 5 differs from the first electric exhaust heater 1 of Fig. 3 in the respective shapes of the components of the support structure 70 for the heating disk 10. Firstly, the multi-part housing 35 is also part of the heater housing 20, 30, 50 of the electric exhaust heater 2, although other variants (not shown) are also possible in which the housing 35 is separate from the heater housing 20, 30, 50. Furthermore, the two first outer rings 40 are not L-shaped, but I-shaped in cross-section. Furthermore, the two second inner rings 80 are L-shaped in cross-section, with the L being open outwards in the direction of the respective first ring 40, with which it forms a corresponding assembly. Accordingly, in the electric exhaust heater 2, the receiving space for the heating disk 10 is formed between the two second inner rings 80, into which space a heating disk 10 is also inserted.

[0054] Fig. 6 shows a second inner ring 80 according to the invention. The ring shown here is flat compared, for example, to an associated (not shown) outer ring 40. The ring 80 has a circular, round, outer peripheral edge. In addition, it has an inner peripheral edge with varying diameters, i.e., with oval to ellipsoidal portions. The ring 80 shown is point-symmetrical to the center of the outer circular peripheral edge. As the attached detailed views A and B show, the ring 80 has a rectangular cross-section and an optional recess in the outer circumference for positioning in the circumferential direction. However, such a positioning aid would be omitted if the ring 80 also had a circular inner peripheral edge with the same radius at all points. Although such a ring is not shown here, it represents an alternative embodiment of the ring 80 according to the invention.

[0055] Fig. 7 shows a sectional view of a third electric exhaust gas heater 3 with a basic configuration as in Fig. 1 , also a section AA from Fig. 2. In addition, there is a detailed view B from the sectional view.

[0056] In detail, the third electric exhaust gas heater 3 in Fig. 7 differs from the first and second electric exhaust gas heaters 1, 2 in Figs. 3 and 5 partly in terms of the shapes, number and arrangement of the components of the support structure 70 for the heating disk 10. In particular, two flat second inner rings 80 are shown here again, similar to Fig. 3. Between the two second inner rings 80 and the two first outer rings 40, Fig. 7 now shows an embodiment with optional L-shaped rings 90, which are preferably made of metal. The advantage of such a design is that it prevents fibers from the first rings 40 from escaping into the heated area of ​​the heating disk 10. In addition, such L-shaped rings 90 can be manufactured cost-effectively using common manufacturing processes in the metalworking industry.

[0057] Generally applicable or not shown features

[0058] With regard to the variants of the housing 35 shown in Figs. 3, 5 and 7, as well as the number and shapes of the inner rings 40 and the outer rings 80, it should be noted that other embodiments are also conceivable, in which any combination of a single-part or multi-part housing, a single-part or multi-part first ring 40 and a single-part or multi-part second ring 80 are possible. The cross-sections and shapes of the individual rings can also vary in this context; for example, there can be annular outer circumferential edges and, at the same time, oval inner circumferential edges, or vice versa. Rings do not necessarily have to be round, in particular if the internal heating element or the external heating housing is not round or oval.

[0059] The at least one first ring or the two first rings used within the scope of the present invention are made of a fiber material, preferably of a ceramic material. This ceramic material is particularly preferably Al2O3, SiO2 or a mullite ceramic material based on a mixture of Al2O3 and SiO2. The at least one or the two first rings are used, among other things, for positioning or centering the heating disk and preferably have at least one flat surface which, in the assembly with at least one second ring described below, preferably has adequate static friction properties, with a corresponding friction coefficient in this case being in the range between 0.1 and 0.8. The material used is characterized, at best, by good compressibility.Depending on the application, a fiber ring can be compressed after installation to between half (factor 2) and one-fifth (factor 5), preferably to one-third (factor 3) of its original thickness. For example, a preferred fiber ring has a thickness of approximately 10 to 12 mm before installation, which is pressed, prestressed, compressed, and / or compressed to a thickness of approximately 4 mm during installation.

[0060] In addition, at least one or the first two outer rings are necessary to keep the heating disc in its original position despite external influences, such as exhaust gases in the exhaust line of an exhaust aftertreatment system. Such influences include, in particular, high operating temperatures, typically between 900 and 1100 °C, and high gas pressure, which can sometimes lead to accelerations of approximately 60 to 70 g, with 1 g = 9.80665 m / s. 2, leads to. Furthermore, due to their specific material, they act as an insulator between the heating disc and the housing, which not only helps protect the housing from the heat generated by the heating disc, but also reduces thermally induced relative movement between individual components. In particular, a relative movement between the heating disc and the bearing area is specifically permitted, despite axial preload. In this context, it is preferred that the heating disc does not come into contact with the housing by using at least one first or two first outer rings.

[0061] In applications involving support systems for heating discs in which the at least one first ring or the two first rings are in direct contact with the heating disc over time, the underlying fibers begin to wear out and / or break, which leads to corresponding damage to the at least one first or the two first outer rings and thus, in the long term, to the entire system through abrasion and / or erosion. The wear can be thermally abrasive, as the heating disc expands and contracts again during a multitude of heating and cooling processes over the course of its use. In particular, an expansion of the heating disc in the radial direction of up to 1.5 mm, measured from the center of the heating disc, can be assumed here, with the parameters described above with regard to heating discs that can be used within the scope of the present invention.A potential expansion of the heating disc in the thickness direction can therefore be neglected.

[0062] The wear of the at least one first or two first outer rings may also be caused by, or instead of, the shape of the heating disc. For example, sharp edges and / or particularly thin wall elements, such as the individual cell walls of the heating structure, contribute to the wear of the two first rings.

[0063] In order to counteract premature wear and / or destruction of the entire system at this point, the present invention provides for the installation of at least one or two additional second inner rings, the material of which differs from the material of the at least one first outer ring or the two first outer rings. Preferably, the at least one second inner ring or the two second inner rings have a thickness of approximately 0.1 to 0.8 mm. The material of at least one second inner ring or the two second inner rings meets the criteria of an electrical insulator, for example to prevent electrical short circuits. In addition, it optionally has a high temperature resistance of up to approximately 1100°C, preferably approximately -40°C to approximately 1100°C.In particular, the range from 900 to 1100 °C is particularly relevant in the context of high-temperature applications, for example when using a support structure according to the invention installed in electric exhaust gas heaters for gasoline engines.

[0064] In addition, there is increased mechanical resilience against wear. Such increased resilience can be by a factor of 10 or more compared to applications without at least one or two second inner rings. Internal comparison tests showed a failure of electric exhaust heaters without an inner ring or inner rings after approximately 3,000 test cycles and failure of electric exhaust heaters with an inner ring or inner rings after approximately 50,000 test cycles. Furthermore, it offers resistance to exhaust gases in general and / or chemical resistance, preferably against substances that can occur in exhaust gas aftertreatment systems. Furthermore, it is optionally easily formable, preferably into a ring, oval, or elliptical shape, and / or erosion-resistant.

[0065] The material used for one or the two second inner rings can be, for example, mica, internationally known as mica, preferably a layered silicate, particularly preferably phlogopite, muscovite, a potassium magnesium aluminosilicate with optional fluorine or hydroxide ions, an inorganic binder or a combination thereof. The material used can be of natural origin or artificially produced using suitable processes. The advantage of artificially produced materials is, for example, that desired material properties can be achieved in a targeted manner whilst at the same time impurities are avoided. Particularly worthy of mention in this context is the improved temperature resistance of synthetic mica material compared to naturally obtained material, i.e. at temperatures of up to 1000°C in long-term operation.

[0066] In this context, Table 1 shows, using an example, various criteria, standards to be met and some corresponding value ranges:

[0067] Material properties

[0068] Table 1 While Table 1 shows a specific example of the material of at least one or two second inner rings, other materials are also conceivable, especially when it comes to the aspect of temperature resistance above 1000 °C, especially in continuous operation.

[0069] Due to their specific positioning, for example, where a first outer ring or ring part is arranged between an outer part of the housing and a second inner ring or ring part, the second ring or its ring part(s) in the support structure according to the invention interact with the heating disc and the two first ring(s) as a separating layer or separating components to improve the abrasion resistance of the overall assembly. Increased abrasion resistance of the support structure reduces wear on the overall assembly, which in turn extends its service life and thus its usability.

[0070] Alternatively, the two second rings may not be present as separate components, but rather as a coating on the corresponding side of the two first rings. Furthermore, all of the rings, namely just one, two, three, or all four, may optionally be multi-part. Furthermore, all of the rings, or even just some of the rings used, may optionally have an L-shaped, U-shaped, round, or rectangular cross-section instead of a true ring. This encompasses any combination of rings and cross-sections that influence aspects such as the ability to install or retrofit the support structure according to the invention, as well as economic aspects, for example with regard to the availability of the raw materials underlying the materials used.The choice of ring shape can depend, for example, on whether edge areas of the first rings should also be protected by the second rings and / or whether edge areas of the heating disc come into contact with areas or parts of the first rings and should be protected from abrasion / heat by the second rings. In addition to the designs already described and shown, another variant is worth mentioning: the first outer ring is U-shaped and one-piece. This allows it to be combined either with two inner rings, whereby different shapes are possible, or with just one inner ring, also U-shaped and one-piece.

[0071] During the assembly process, the first and second rings can be installed as separate components. Alternatively, the respective first and second rings can be pre-assembled, preferably by gluing or sewing. Alternatively or additionally, the second rings can also be pre-assembled to the corresponding side of the heating disc, preferably by gluing or sewing.

[0072] In all of the aforementioned embodiments, the aforementioned rings, in particular the at least one first or the two first outer rings, are optionally pre-tensioned or compressed in a predefined manner in the axial direction in order to withstand the external operating conditions. In this context, homogeneous compression and / or fixation of the heating disc must be ensured over the entire circumference of the heating disc. The underlying pressure here preferably reaches up to 15 bar. This pressure is particularly preferably between 2 and 4 bar, depending on the respective application and / or the underlying installation size, plus generally applicable tolerances.

[0073] In addition to the wear mechanisms already mentioned, creep of the fibers of the two first rings has also been observed due to corresponding swelling and expansion towards the center of the heating disc. To further reduce this creep risk, the outer contour of the two first rings can be modified to create more clearance between the housing and the support structure. Instead of a constant outer diameter, the two first rings can, for example, have alternating circumferential depressions and elevations. The number of elevations can optionally vary and depend on the size of the heating disc or its diameter. Such a design optionally results in even further improved durability compared to known solutions, thereby increasing product lifespan and avoiding customer complaints.

[0074] The invention has been described with reference to preferred embodiments, whereby the individual features of the described embodiments can be freely combined and / or interchanged, provided they are compatible. Likewise, individual features of the described embodiments can be omitted unless absolutely necessary.

[0075] Numerous modifications and embodiments are possible and obvious to the person skilled in the art without departing from the spirit of the invention.

Claims

Claims 1 . A support structure (70) for a heating disc or a heating resistor (10) in an exhaust system, comprising: a multi-part housing (35); at least one first outer ring (40) made of a fiber material; and at least one second inner ring (80) made of an electrically non-conductive and temperature-resistant material that differs from the fiber material of the at least one first ring (40); wherein the at least one second inner ring (80) defines a receiving space for the heating disc or the heating resistor (10).

2. The support structure (70) according to claim 1, wherein the at least one first ring (40) comprises two rings and / or wherein the at least one second ring (80) comprises two rings; wherein the receiving space for the heating disc or the heating resistor (10) is preferably defined between the two second rings (80).

3. The support structure (70) according to claim 1 or 2, wherein the multi-part housing (35) comprises at least two metal rings or two metal halves, which are preferably configured to apply a predefined clamping pressure of up to approximately 15 bar to the first and second rings (40, 80).

4. The support structure (70) according to one of the preceding claims, wherein the fiber material is a ceramic material, preferably Al2O3, SiO2 or a mullite ceramic material made of Al2O3 and SiO2.

5. The support structure (70) according to any one of the preceding claims, wherein the fiber material comprises fibers with a diameter in the range of approximately 3 to 12 pm, preferably 5 to 10 pm; and / or where the fibers of the fiber material are present in a length to diameter ratio > 3 to 1.

6. The support structure (70) according to any one of the preceding claims, wherein the at least one first ring (40) is compressible or the two first rings (40) are compressible, preferably by a factor in the range of 2 to 5 in the installed state.

7. The support structure (70) according to one of the preceding claims, wherein the material of the at least one second ring (80) or the two second rings (80) has at least one of the following properties: temperature-resistant up to 1100 °C, preferably in a temperature range between -40 °C and 1100 °C; compressible, flexible and / or pliable; formable, preferably in a ring, oval or elliptical shape; erosion-resistant; resistant to exhaust gases; and chemically resistant, preferably to substances that can occur in exhaust gas aftertreatment systems.

8. The support structure (70) according to any one of the preceding claims, wherein the material of the at least one second ring (80) or the two second rings (80) is mica, preferably a layered silicate, particularly preferably phlogopite, muscovite, a potassium magnesium aluminosilicate with optional fluorine or hydroxide ions, a non-organic binder or a combination thereof.

9. The support structure (70) according to one of the preceding claims, wherein at least one of the first and / or second rings (40, 80) is at least two-part in the circumferential direction; and / or wherein at least one of the first and / or second rings (40, 80) has an L-shaped, U-shaped, round or rectangular cross-section.

10. The support structure (70) according to one of the preceding claims, wherein the at least one second ring (80) or the two second rings (80) are present as a coating on a corresponding side of the at least one first ring (40) or the respective first ring (40); and / or wherein the at least one second ring (80) or the two second rings (80) have a thickness of approximately 0.1 mm to 1.5 mm, preferably approximately 0.1 mm to 0.8 mm.

11. The support structure (70) according to any one of the preceding claims, wherein the at least one second ring (80) or at least one of the two second rings (80) comprises a metal mesh insert.

12. The support structure (70) according to one of the preceding claims, wherein the at least one first ring (40) or the at least two first rings (40) have a continuous outer contour; or wherein the at least one first ring (40) or the two first rings (40) have alternating recesses and / or elevations.

13. A support system for an electric heating device, comprising: the support structure (70) according to any one of the preceding claims; and a heating disc or a heating resistor (10), preferably with two sides, a cellular structure, and / or a plurality of slots; wherein the heating disc or the heating resistor (10) is arranged in the receiving space of the at least one second ring (80) or between the two second rings (80).

14. The support structure (70) according to any one of claims 1 to 12 or the support system according to claim 13, wherein the respective first and second rings (40, 80) are pre-assembled, preferably glued or sewn together; and / or wherein the heating disc or the heating resistor (10) is pre-assembled on both sides to the corresponding side of the respective second ring (80), preferably glued or sewn.

15. The support structure (70) according to one of claims 1 to 12 or 14, or the support system according to one of claims 13 or 14, further comprising: a plurality of pins (60) configured for positioning, supporting, holding the heating disc or the heating resistor (10) and / or for electrical insulation between partial regions of the heating disc or the heating resistor (10); wherein the plurality of pins (10) are preferably spacer elements; wherein particularly preferably some of the spacer elements are designed as holding means positioned in a corresponding recess in the housing (35), wherein at least one end of the holding means is mechanically connectable directly to the housing (35); and / or wherein at least some of the spacer elements are positioned, preferably clamped, between the two second rings (80).

16. The carrier system according to one of claims 12 to 15, wherein the at least one second ring (80) or the two second rings (80) contact only an edge region of the heating disc or the heating resistor (80) in the circumferential direction, wherein the edge region is not actively heated.

17. An electric exhaust gas heater comprising: the support system according to any one of claims 12 to 16; a heater housing (20, 30, 50), preferably made of metal, which is positioned in an exhaust line of an exhaust gas aftertreatment system and is adapted to receive the carrier system (70).

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