Heating device and method of manufacturing a heating device
The heating device achieves efficient and cost-effective heating of exhaust gases by using a conductive foam to create a symmetrical current path for electrodes, addressing the challenge of angular positioning and hot spots in catalytic converter heating devices.
Patent Information
- Application Number
- FR2022005093
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2021-05-27
- Filing Date
- 2022-05-27
- Publication Date
- 2025-10-03
- Estimated Expiration
- 2042-05-27
AI Technical Summary
Existing heating devices for catalytic converters in exhaust systems face challenges in arranging electrodes at angles less than 120° due to the need for homogeneous temperature distribution, which is crucial for efficient operation.
A heating device design that incorporates a conductive foam divided into sections with current-conducting paths and electrodes positioned at less than 180°, utilizing a conductive foam to create a symmetrical and efficient current path, ensuring homogeneous heating and preventing hot spots.
The solution enables efficient and homogeneous heating of exhaust gases, enhancing catalytic converter performance by allowing electrodes to be positioned at desired angles while minimizing hot spots and reducing manufacturing and assembly costs.
Smart Images
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Abstract
Description
Title of the invention: Heating device and method of manufacturing a heating device
[0001] The invention relates to a heating device for an exhaust system and to a method of manufacturing such a heating device.
[0002] Catalytic converters are usually provided in the exhaust systems of internal combustion engines to reduce emissions.
[0003] For rapid starting of the catalytic converter after a cold start of the internal combustion engine, it is known to provide heating devices which heat the catalytic converter to a reaction temperature.
[0004] The heating device may be provided in the form of a heating device through which exhaust gases pass, which is arranged upstream of the catalytic converter and is arranged so as to heat the exhaust gases before they pass through the catalytic converter.
[0005] It is already known here to provide heating elements (for example heating grids, heating wires or heating foams) for heating inside the heating device. These heating elements are electrical resistance heating means to which a heating current is applied by means of two electrodes.
[0006] In a known embodiment of the heating foam, the latter has a serpentine shape in cross section in which the electrodes are arranged at the ends of the serpentine shape. This embodiment makes it possible to obtain a particularly homogeneous temperature distribution over the section over which a flow flows, which is, on the other hand, important for high efficiency of the catalytic converter.
[0007] To achieve a homogeneous temperature distribution, the heating foam extends uniformly and symmetrically in the heating device, so that the ends of the coiled heating foam are at least almost opposite each other. The electrodes must therefore be arranged at an angle of almost 180°, but at least at an angle of 120° to each other. US 5,695,722 A1 is cited here solely as an example.
[0008] For the integration of such heating devices into an upper system, however, mounting angles of less than 120° are most often required.
[0009] The aim of the present invention is therefore to create a heating device in which the two electrodes can be arranged at an angular distance of less than 120°.
[0010] The object is achieved, according to the invention, by a heating device for an exhaust system of a motor vehicle, comprising an electrically conductive heating foam which is divided, by interruptions, into sections which, seen in cross-section, are arranged next to each other so that a current path is predefined, which extends from a current inlet point of the heating device to a current outlet point, for example from one side of the heating device to the other, two electrodes which are electrically connected to the current inlet point or to the current outlet point, the heating foam being provided on the outer side, at least in sections, with a current-conducting foam which forms current-conducting sections connecting adjacent sections of the electrically heating foam to each other,and one of the current inlet point or the current outlet point being provided as a connecting section which is made of the current-conducting foam, extends in the circumferential direction along at least one current-conducting section but is electrically insulated from it, the connecting section being electrically connected to one of the sections of the heating foam and to one of the electrodes, so that the two electrodes are spaced apart from each other by less than 180°, in particular by less than 120° in the circumferential direction, and the other of the current inlet point or the current outlet point being provided as a second connecting section which is made of the current-conducting foam and is connected to the second electrode. The invention is based on the basic idea of creating, by means of the current-conducting foam which is in any case present, a contact section for an electrode,which extends along the heating foam so that the electrode can be arranged at the desired location.
[0011] The current-conducting foam used in addition to the heating foam makes it possible to reliably attach the electrodes to the more solid current-conducting foam. The current-conducting sections can also be made thin, since the critical limit surface area of the cross-section at which the formation of hot spots is just not yet reached is smaller than in the case of undensified foam due to the densification.
[0012] The connected sections of the heating foam can then form the predefined current path of the heating foam, the connecting section which is electrically connected to a first electrode being in contact with one of the outer ends of the current path inside the heating foam, and the second connecting section which is electrically connected to the second electrode being in contact with the second outer end of the current path inside the heating foam. By maximizing the length of the current path in the heating foam, a particularly homogeneous heating of the gas flow exhaust is obtained and the heated surface is enlarged, thanks to which the operation of the catalytic converter can be even more efficient.
[0013] According to one embodiment, the second connecting section, like the first connecting section, extends in the circumferential direction along at least one current-conducting section, but is electrically insulated from it. By arranging the second connecting section also along a current-conducting section, it is possible to design a symmetrical embodiment in which the two connecting sections have the same length, a symmetrical current input and current output being thus achieved.
[0014] According to one embodiment of the invention, it is provided that the current-conducting foam has a hollow cylindrical, in particular annular, shape and does not have any structures projecting from the outer or inner face of the shape, said at least one electrical insulation between the connection section and a current-conducting section being able to be achieved by recesses inside the hollow cylindrical, in particular annular, shape. The manufacturing and assembly costs are low due to the constructive implementation without projecting structures. This embodiment is also particularly compact.
[0015] The current-conducting foam preferably has a hollow circular cylindrical shape, and the connecting sections and the current-conducting sections do not protrude below or above the inner or outer diameter of the current-conducting foam. The hollow circular cylindrical shape offers even lower manufacturing costs and allows easy installation of the heating device in a higher assembly, for example a housing for receiving, the geometry of which can also be made hollow circular cylindrical, whereby the total manufacturing cost is further reduced.
[0016] According to another embodiment, the current-conducting foam has a hollow circular cylindrical basic shape, and at least one connecting section or current-conducting section is located outside or inside the basic shape and projects above or below the outer or inner diameter of the basic shape. By means of this embodiment, it is possible to save material and space with at the same time connecting sections or current-conducting sections made reinforced in their overlapping areas which prevent the formation of a hot spot.
[0017] The above-mentioned object is further achieved by a method of manufacturing a heating device of the type mentioned in the introduction, the manufacturing method comprising the following steps:
[0018] a) manufacturing a heating foam and forming the outer contour of the foam heating,
[0019] b) manufacturing an outer current-conducting foam and forming the inner contour of the current-conducting foam,
[0020] c) inserting the heating foam into the current conduction foam,
[0021] d) assembly of the heating foam and the current conduction foam in an oven, and
[0022] e) creating a serpentine-shaped current path and producing the connecting sections and the current-conducting sections in the current-conducting foam by incising the heating foam and the current-conducting foam.
[0023] The particular advantage of this method is that the connecting sections and the current-conducting sections are only produced by incising the heating foam and the current-conducting section after the heating foam and the current-conducting foam have been joined together. Thus, it is not necessary at any time to work with a plurality of individual components and it is also not necessary to join many individual components together.
[0024] According to one variant, the manufacture of the external current-conducting foam comprises pre-densification of the foam-shaped starting material. By pre-densifying the current-conducting foam, it is possible to use the same starting material for the heating foam and the current-conducting foam, thereby simplifying the purchase of materials and reducing storage costs.
[0025] The invention is explained in the following with the aid of various exemplary embodiments which are shown in the accompanying drawings. These show:
[0026] - [Fig.l] [Fig.l] is a perspective view of a heating device according to the invention in a first embodiment, manufactured according to a method according to the invention,
[0027] - [Fig.2] [Fig.2] is a cross-section of the heating device of [Fig.l] , the electrodes not being shown in section,
[0028] - [Fig.3] [Fig.3] is a perspective view of a heating device according to the invention in a second embodiment, manufactured according to a method according to the invention,
[0029] - [Fig.4] [Fig.4] is a cross-section of the heating device of [Fig.3] , the electrodes not being shown in section,
[0030] - [Fig.5] [Fig.5] is a perspective view of a heating device according to the invention in a third embodiment, manufactured according to a method according to the invention,
[0031] - [Fig.6] [Fig.6] is a cross-section of the heating device of [Fig.5] , the electrodes not being shown in section,
[0032] - [Fig.7] [Fig.7] is a perspective view of a heating device according to the invention in a fourth embodiment, manufactured according to a method according to the invention,
[0033] - [Fig.8] [Fig.8] is a cross-section of the heating device of [Fig.7] , the electrodes not being shown in section,
[0034] - [Fig.9] [Fig.9] is a perspective view of a detail of a heating device according to the invention in a fifth embodiment, manufactured according to a method according to the invention,
[0035] - [Fig. 10] [Fig. 10] is a cross-section of the detail of the heating device of [Fig.9], the electrodes not being shown in section,
[0036] - [Fig. 11] [Fig. 11] is a perspective view of a detail of a device of heating according to the invention in a sixth embodiment, manufactured according to a method according to the invention,
[0037] - [Fig. 12] [Fig. 12] is a cross-section of the detail of the heating device of [Fig.11], the electrodes not being shown in section.
[0038] Figures 1 and 2 show a heating device 1 for heating the exhaust gas flow of an internal combustion engine.
[0039] The heating device 1 comprises a heating foam 10, a current-conducting foam 20, a first electrode 30 and a second electrode 32. The current-conducting foam 20 is connected to the heating foam 10 and surrounds the heating foam 10. The two electrodes 30, 32 are arranged on a first or second connecting section 24, 26 on the outer periphery of the current-conducting foam 20.
[0040] The heating foam 10 is composed of several sections 12 which are made by incisions in the heating foam 10.
[0041] These sections 12 have the function of heating the flow of exhaust gas passing through the heating device 1.
[0042] The current-conducting foam 20 has two functions: On the one hand, it is mechanically and electrically connected to the electrodes 30, 32, by means of which the heating current is introduced. Due to its higher mechanical strength, the current-conducting foam 20 is well suited for this, without the need for contact sheets etc. On the other hand, the current-conducting foam 20 serves to connect the individual sections 12 of the heating foam 10 electrically to one another. The current-conducting foam 20 forms a respective current-conducting section 22 between the individual sections 12, so that overall, a predefined current path 40 (shown in dotted lines) is produced through the heating device 1, which extends from one electrode 30, 32 to the other.
[0043] The current conduction foam 20 is distinguished from the heating foam 10 by that the starting material of the current-conducting foam 20 has been pre-densified. Due to the higher density of the current-conducting foam 20, it has a lower resistivity, so that no heat is generated (or at least not in significant quantity) in the current-conducting foam 20. Thanks to the lower resistivity, it is further ensured that hot spots do not form in the current-conducting sections 22.
[0044] It is generally possible to produce the current-conducting foam 20 with higher electrical conductivity in a manner other than by means of a higher density.
[0045] The current path 40 extends from the first electrode 30, via the first connecting section 24, the first section 14 of the heating foam 10, the current conducting sections 22 and the other sections 12 of the heating foam 10 to the last section 16 of the heating foam 10 and the second connecting section 26 to the second electrode 32. The current path shows which sections 12 of the heating foam 10 are potentially suitable for heating.
[0046] In the first embodiment according to Figures 1 and 2, the first connecting section 24 is electrically conductively connected to the first current-conducting section 25, and the second connecting section 26 is electrically conductively connected to the last current-conducting section 27. Since the current chooses the path of least resistance, the first and last sections 14, 16 of the heating foam 10 are bypassed and not heated by this embodiment. Bypassing the sections 14, 16 reduces the inert mass of the heating foam 10 to be heated and leads to an accelerated heating of the remaining sections with an identical heating power.
[0047] The particular embodiment and the particular arrangement of the connection sections 24, 26 allows the electrodes 30, 32 to be positioned relative to each other on the outer periphery of the current conduction foam 20 at an angle of less than 120°.
[0048] According to [Fig.2], the first connection section 24 extends on the outer face of the current conduction foam 20 along two current conduction sections 22. The connection section 24 is electrically insulated from the current conduction sections 22.
[0049] In this embodiment, the second connecting section 26 is arranged in a manner known from the prior art, the connecting section 26 not extending along at least one current-conducting section 22, but being arranged in the circumferential direction next to the current-conducting sections 22. In this embodiment, an asymmetrical arrangement is achieved due to the two 24, 26 different connection sections.
[0050] The current-conducting foam 20 can take different embodiments. The first embodiment according to FIGS. 1 and 2 has a current-conducting foam 20 with a hollow circular cylindrical shape, in which the insulation between the current-conducting sections 22 and the connecting sections 24, 26 is achieved by recesses, here in the form of slots.
[0051] Figures 3 and 4 show a heating device 1 according to a second embodiment. The same reference numbers are used for the components and features known from the first embodiment, and reference is made to the explanations above.
[0052] A difference between the first and second embodiments is that in the second embodiment, the connecting sections 24, 26 are made symmetrically and both extend respectively on the outer face of the current-conducting foam 20 along two current-conducting sections 22.
[0053] Another difference compared to the first embodiment is that electrical separations 28, 29 are additionally provided, here in the form of slots, between the connection sections 24, 26 and the first or last current-conducting section 25, 27. By means of these separations 28, 29, bridging by the current-conducting foam 20 is avoided. The separations 28, 29 illustrated should, however, only be considered as examples and can also be larger and positioned at a different location, in particular to maximize the length of the current path 40.
[0054] The second embodiment according to figures 3 and 4 has, like the first embodiment, a current conduction foam 20 with a hollow circular cylindrical shape, in which the insulation between the current conduction sections 22 and the connection sections 24, 26 is achieved by recesses, here in the form of slots.
[0055] Figures 5 and 6 show a heating device 1 according to a third embodiment. The same reference numbers are used for the components and features known from the previous embodiments, and reference is made to the explanations above.
[0056] The difference between the third and the first or second embodiment is that in the third embodiment, the current-conducting foam 20 has a hollow circular cylindrical basic shape, in which the two connecting sections 24, 26 protrude beyond the outer diameter of the basic shape. The connecting sections 24, 26 and the current-conducting sections 22 have similar dimensions to avoid hot spots while eco maximizing the material. This means that for any cutting plane in which the current path 40 is normal to this cutting plane, the cross-sectional areas of the connecting sections 24, 26 and the current-conducting sections 22 have similar dimensions.
[0057] Figures 7 and 8 show a heating device 1 according to a fourth embodiment. The same reference numbers are used for the components and features known from the previous embodiments, and reference is made to the explanations above.
[0058] In the fourth embodiment, the current-conducting foam 20 has, as in the third embodiment, a hollow circular cylindrical basic shape. The difference between the fourth and third embodiments is that the two connecting sections 24, 26 protrude below the inner diameter of the basic shape. As in the third embodiment, the connecting sections 24, 26 or the current-conducting sections 22 are similarly dimensioned, the cylindrical outer shape of the heating device 1 also allowing it to be easily integrated into a higher module (e.g. a housing).
[0059] As in the second embodiment, electrical separations 28, 29, here also in the form of slots, are provided in the fourth embodiment between the connection sections 24, 26 and the first or last current conduction section 25, 27. Thus, the current path 40 passes through the first and last sections 14, 16 of the heating foam 10, which allows them to be heated as well.
[0060] Two other particularly advantageous embodiments are shown in Figures 9 to 12. These embodiments correspond substantially to the second embodiment, but unlike the latter, they comprise separations 28, 29 made in a specific manner to allow even more homogeneous heating in the peripheral zones thanks to an improved current flow in the first and last sections 14, 16 of the heating foam 10.
[0061] In the fifth embodiment according to FIGS. 9 and 10, the separations 28, 29 are made larger in the circumferential direction for this purpose, the connecting section 24 and the current-conducting section 25 as well as the connecting section 26 and the current-conducting section 27 being thus further apart from each other than, for example, in the second embodiment.
[0062] The sixth embodiment according to Figures 11 and 12 has T-shaped partitions 28, 29. In direct comparison with the second embodiment, the partitions 28, 29 are also formed by a slot extending radially through the current-conducting foam 20, this slot however dividing into two further slots which connect thereto, in the form of branches, and which extend in the circumferential direction between the current-conducting foam 20 and the heating foam 10. The current-conducting foam 20 thus remains largely round in cross-section, which makes it possible to simplify the geometry of a housing in which the current-conducting foam can be stored, and thus to facilitate standardization.
[0063] Combinations of the embodiments presented are of course also conceivable. Similarly, the current-conducting foam 20 can have any hollow cylindrical shape, in particular annular.
[0064] The manufacture of a heating device 1 will now be explained.
[0065] For this purpose, the starting material of the heating foam 10 is manufactured and its outer contour is formed. The outer contour of the heating foam 10 can be freely chosen, but must substantially correspond to the inner contour of the current-conducting foam 20 described below.
[0066] In a further step, which may take place before, after or during the preceding step, the starting material of the current-conducting foam 20 is manufactured and its inner contour is formed. The forming of the inner contour of the current-conducting foam 20 thus makes it possible to form the counterpart of the heating foam 10.
[0067] The heating foam 10 is then inserted into the current conduction foam 20. For this, an assembly force may be necessary if the outer contour of the heating foam 10 has an oversize compared to the inner contour of the current conduction foam 20.
[0068] Then, the assembly of the heating foam 10 with the current-conducting foam 20 is carried out in a furnace. In particular, sintering processes are particularly suitable for permanently connecting the two foam components to each other.
[0069] In a further step, the serpentine current path 40 is created by making the connecting sections 24, 26 and the current-conducting sections 22 in the current-conducting foam 20 by incisions in the heating foam 10 and the current-conducting foam 20. The incision of the heating foam 10 and the current-conducting foam 20 is deliberately carried out only after the two components have been assembled in the oven, which avoids many individual parts that would otherwise have to be put in place during the subsequent assembly. This method thus offers particularly simple handling of all the components involved.
Claims
1.
2.
3. Claims Heating device (1) for an exhaust system of a motor vehicle, comprising an electrically conductive heating foam (10) which is divided, by interruptions, into sections (12) which, seen in cross-section, are arranged next to each other such that a current path (40) is predefined, which extends from a current inlet point of the heating device (1) to a current outlet point, for example from one side of the heating device (1) to the other, two electrodes (30, 32) which are electrically connected to the current inlet point or the current outlet point, the heating foam (10) being provided on the outside, at least in sections, with a current-conducting foam (20) which forms current-conducting sections (22) connecting adjacent sections (12) of the heating foam (10) electrically to each other,and one of the current inlet point or the current outlet point being provided as a connecting section (24) which is made of the current-conducting foam (20), extends in the circumferential direction along at least one current-conducting section (22), but is electrically insulated from it, the connecting section (24) being electrically connected to one of the sections (12) of the heating foam (10) and to one of the electrodes (30), so that the two electrodes (30, 32) are spaced apart from each other by less than 180°, in particular by less than 120° in the circumferential direction, and the other of the current inlet point or the current outlet point being provided as a second connecting section (26) which is made of the current-conducting foam (20) and is connected to the second electrode (32)., Heating device (1) according to claim 1, characterized in that the connected sections (12) of the heating foam (10) form the predefined current path of the heating foam (10), the connecting section (24) which is electrically connected to a first electrode (30) being in contact with one of the outer ends of the current path (40) inside the heating foam, and the second connecting section (26) which is electrically connected to the second electrode (32) being in contact with the second outer end of the current path (40) inside the heating foam. Heating device (1) according to claim 1 or 2, characterized in that the second connecting section (26), like the first connecting section (24), extends in the circumferential direction along at least one current-conducting section (22) but is electrically insulated from it.
4. Heating device (1) according to one of the preceding claims, characterized in that the current-conducting foam (20) has a hollow cylindrical, in particular annular, shape, and in that the current-conducting foam (20) does not have any structures projecting from the outer or inner face of the shape, and said at least one electrical insulation between the connecting section (24, 26) and a current-conducting section (22) is provided by recesses inside the hollow cylindrical, in particular annular, shape.
5. Heating device (1) according to claim 4, characterized in that the current-conducting foam (20) has a hollow circular cylindrical shape and in that the connecting sections (24, 26) and the current-conducting sections (22) do not protrude below or above the inner or outer diameter of the current-conducting foam (20).
6. Heating device (1) according to one of claims 1 to 3, characterized in that the current-conducting foam (20) has a hollow circular cylindrical basic shape and in that at least one connecting section (24, 26) or current-conducting section (22) is located outside or inside the basic shape and projects above or below the outer or inner diameter of the basic shape.
7. Heating device according to one of the preceding claims, characterized in that the current-conducting sections (20) have a density greater than that of the heating foam (10).
8. A method of manufacturing a heating device (1) according to one of the preceding claims, the manufacturing method comprising the following steps: a) manufacturing a heating foam (10) and forming the outer contour of the heating foam (10), b) manufacturing an outer current-conducting foam (20) and forming the inner contour of the current-conducting foam (20), c) inserting the heating foam (10) into the conduction foam current (20), d) assembling the heating foam (10) and the current conduction foam (20) in an oven, and e) creating a serpentine-shaped current path (40) and producing the connecting sections (24, 26) and the current conduction sections (22) in the current conduction foam (20) by incising the heating foam (10) and the current conduction foam (20).
9. A method according to claim 8, characterized in that the manufacture of the external current-conducting foam (20) comprises pre-densification of the foam-shaped starting material.