Exhaust line heating element

Abstract

Exhaust line heating element. The invention relates to an exhaust line heating element (1), comprising a substantially tubular housing (2) defining a passage cross-section for the exhaust gases, accommodating at least two heating discs (3, 4) arranged transversely across the passage cross-section so as to force the exhaust gases to pass through said at least two discs (3, 4), wherein the heating element (1) further comprises a connector means supporting said at least two discs (3, 4) and ensuring an electrical connection between said at least two discs (3, 4). Figure for the abstract: Figure 1

Description

Title of the invention: Heating element for exhaust line Technical field

[0001] The invention relates to a heating element for an exhaust line. Such a heating element is conventionally heated electrically. It is also called EHC, from the English "Electrically Heated Catalyst" Prior art

[0002] Such a heating element is conventionally used for the depollution of exhaust gases resulting from combustion within an engine, circulating in an exhaust line. The depollution of nitrogen oxides, NOx, polluting compounds resulting from the combustion of a hydrocarbon, is most often carried out by a catalytic reduction reaction. This reaction requires a catalyst, comprising precious metals. A hot catalyst transforms the NOx, contained in the exhaust gases, added to a reducing fluid, generally an aqueous solution of urea, into nitrogen N2 and water H20, non-polluting.

[0003] For the reduction reaction to be effective, it is essential that the catalyst be very hot. This is ensured in steady state, the catalyst being heated by the very hot exhaust gases from the combustion. However, this is not the case in the initial phases, following engine start-up.

[0004] Also, it is known to have, in an exhaust line, upstream of a catalyst, a heating element capable of heating the exhaust gases passing through it, in order to also heat the catalyst itself.

[0005] One possible principle for producing such a heating element is a heating disc, perforated so as to allow the passage of exhaust gases. The heating disc is arranged across the passage section of the exhaust line. The heating disc is heated so as to heat the exhaust gases as they pass.

[0006] According to a possible embodiment, the heating is carried out by applying an electric current between two extreme points of the metal heating disc, in order to heat it by the Joule effect.

[0007] It has recently become interesting, in terms of performance and durability, to produce a heating element with more than one heating disc, connected in series, both fluidically and electrically. This raises problems of mechanical support for said heating discs and their electrical connection.

[0008] The invention proposes several embodiments ensuring optimized mechanical support and electrical connection. Summary of the invention

[0009] The invention proposes to provide a heating element for an exhaust line, comprising a substantially tubular housing defining a passage section for the exhaust gases, accommodating at least two heating discs arranged across the passage section so as to force the exhaust gases to pass through said at least two heating discs, where the heating element further comprises a connector means supporting said at least two discs and ensuring an electrical connection between said at least two discs.

[0010] Particular characteristics or embodiments, usable alone or in combination, are:

[0011] - the connector means comprises a first wheel flange and a central electrode, the first wheel flange comprising a crown, substantially matching the periphery of the passage section for the exhaust gases, a hub capable of supporting the central electrode and spokes connecting the crown to the hub, the central electrode electrically connecting the respective centers of said at least two discs,

[0012] - the crown of the first wheel flange has an L-shaped section, with a branch of the L arranged radially and the other branch of the L arranged axially, the radial branch of the L forming a first bearing face capable of pressing axially against the periphery of a first disc of said at least two discs,

[0013] - the first wheel flange is arranged outside said at least two discs, the radial branch of the L resting against the neighboring disc and the axial branch of the L pointing outwards,

[0014] - the first wheel flange is welded to the neighboring disc,

[0015] - a first insulating crown is arranged axially between said at least two discs and the hub is electrically insulated relative to the central electrode,

[0016] - the first wheel flange is arranged between said at least two discs, the branch radial of the L being supported against a first disc and the axial branch of the L pointing towards a second disc,

[0017] - the first wheel flange is electrically insulated from said first disc by a second axially intercalated insulating crown,

[0018] - the first wheel flange is electrically insulated from the housing radially by a first peripheral carpet,

[0019] - the connector means also comprises a simple flange comprising a crown having an L-shaped section, inverted relative to the section of the crown of the first wheel flange so as to form a second bearing face capable of pressing against the periphery of a second disc of said at least two discs and electrically insulated from said second disc by a third axially insulating crown intercalary,

[0020] - the single flange is electrically insulated from the housing radially by a second peripheral carpet,

[0021] - the connector means comprises a first wheel flange and a second flange wheel, mounted head to tail between two of said at least two discs, electrically connected to each other, a wheel flange comprising a crown, substantially matching the periphery of the passage section for the exhaust gases, a hub and spokes connecting the crown to the hub, a hub being electrically connected to the respective center of the adjacent disc and a crown being electrically insulated from the adjacent disc by an axially interposed insulating crown,

[0022] - the connector means comprises a cylindrical slice of metal foam, arranged between a first disc and a second disc of said at least two discs, electrically connected with the first center of the first disc and with the second center of the second disc, axially electrically insulated from the rest of the first disc by a second insulating ring and axially electrically insulated from the rest of the second disc by a third insulating ring, the metal foam being preferentially coated to produce a catalytic effect,

[0023] - the heating element also comprises for each of said at least two discs, a peripheral electrode electrically connected to the periphery of said disc,

[0024] - a puddle wheel also includes a mixer,

[0025] - the connector means comprises a connector of substantially tubular shape, conforming, from the inside, to the shape of the housing, so as to ensure an electrical connection between the respective peripheries of said at least two discs,

[0026] - the heating element also comprises for each of said at least two discs, a central electrode respectively electrically connected to the center of the disc, from the outside,

[0027] - the connector means further comprises a catalytic brick arranged between said at least two discs. Brief description of the drawings

[0028] The invention will be better understood on reading the following description, given solely by way of example, and with reference to the appended figures in which:

[0029] [Fig-1] shows, in a sectional view along its axis, a heating element according to a first embodiment,

[0030] [Fig.2] shows, in perspective view, the heating element of [Fig.l],

[0031] [Fig.3] shows, in a sectional view along its axis, a heating element according to a second embodiment,

[0032] [Fig.4] shows, in perspective view, the heating element of [Fig.3],

[0033] [Fig.5] shows, in a sectional view along its axis, a heating element according to a third embodiment,

[0034] [Fig.6] shows, in perspective view, the heating element of [Fig.5],

[0035] [Fig.7] shows, in a sectional view along its axis, a heating element according to a variant of the third embodiment,

[0036] [Fig.8] shows, in perspective view, the heating element of [Fig.7],

[0037] [Fig.9] shows, in a sectional view along its axis, a heating element according to a fourth embodiment,

[0038] [Fig. 10] shows, in perspective view, the heating element of [Fig.9],

[0039] [Fig. 11] shows, in a sectional view along its axis, a heating element according to a fifth embodiment,

[0040] [Fig.12] shows, in perspective view, the heating element of [Fig.11]. Description of the embodiments

[0041] Throughout the present document, the terms "radial" and "axial" are understood to mean relative to the axis of the exhaust line or the housing. The term "axial" qualifies an element substantially aligned with said axis, while "radial" qualifies an element substantially perpendicular to said axis.

[0042] The invention relates to a heating element 1 for an exhaust line. Such a heating element 1 comprises a housing 2, substantially tubular, integrated or forming a section of the exhaust line, defining a passage section for the exhaust gases. This housing 2 accommodates at least two heating discs 3, 4 arranged across the passage section so as to force the exhaust gases to pass through said at least two heating discs 3, 4.

[0043] According to one characteristic, the heating element 1 further comprises a connector means. This connector means provides two functions: mechanical support and electrical connection. The connector means provides mechanical support for said at least two discs 3, 4. It further provides an electrical connection between said at least two discs 3, 4.

[0044] In order to heat, the discs 3, 4 must be electrically connected at two points, preferably at extremes, so that the electric current passes through, as uniformly as possible, the entire surface of said at least two discs 3, 4. According to a characteristic retained here, a first point is located at the center 5, 6 of the disc 3, 4 and the other point is located at the periphery of the disc 3, 4. This allows a substantially uniform radial circulation of the electric current between the two points.

[0045] The two discs 3, 4 are advantageously electrically connected in series.

[0046] Several embodiments of this connector and support means are envisaged.

[0047] According to a characteristic, used in several embodiments, more particu As illustrated in Figures 1-4, the connector means comprises a first wheel flange 8 and a central electrode 12.

[0048] The first wheel flange 8 has a wheel shape. It comprises a crown 9, substantially matching the periphery of the exhaust gas passage section, a hub 10, preferably central, and spokes 11 connecting the crown 9 to the hub 10. The hub 10 accommodates and holds the central electrode 12. The central electrode 12 provides an electrical connection between the center 5 of a first disc 3 and the center 6 of a second disc 4.

[0049] A wheel flange 8 is preferably made of metallic material and by stamping. This makes it possible to produce an inexpensive part and to control its manufacture and supply. It follows that this wheel flange 8 is conductive. In order to avoid short circuits, it is appropriate to provide appropriate electrical insulation.

[0050] According to another characteristic, the crown 9 of the first wheel flange 8 has an L-shaped section. One of the branches of the L is arranged radially. The other branch of the L is arranged axially. The radial branch of the L thus forms a first bearing face 13. It is thus capable of pressing axially against the periphery of a first disc 3 among said at least two discs 3, 4.

[0051] According to a first embodiment, more particularly illustrated in figures 1-2, a heating element 1 comprises a first wheel flange 8 arranged outside said at least two discs 3, 4. The radial branch of the L bears against a disc 3 which is referred to as the neighboring disc 3. The axial branch of the L points towards the outside of said at least two discs 3, 4.

[0052] According to another characteristic of the first embodiment, the first wheel flange 8 is welded directly to the neighboring disc 3. This ensures mechanical reinforcement provided by the first wheel flange 8 which stiffens and thus supports the neighboring disc 3. The first wheel flange 8 is preferably made of metallic material, it participates in the electrical circuit and in the connection between said at least two discs 3, 4.

[0053] Also, in order to avoid any short circuit, it is appropriate to electrically isolate said at least two discs 3, 4 at judiciously chosen points. For this, according to another characteristic of the first embodiment, a first insulating ring 14 is arranged axially between said at least two discs 3, 4. This first insulating ring 14 is peripheral and covers at least the respective periphery of the discs 3, 4. In addition, in order to complete the electrical insulation scheme and to define the current flow path, the hub 10 is electrically insulated relative to the central electrode 12. This first insulating ring 14 is, for example, made of rope, typically glass fibers.

[0054] According to another characteristic, described further above, each of the discs 3, 4 comprises respectively a peripheral electrode 26, 27 connecting the periphery of the disc 3, 4.

[0055] Also, the electrical circuit, for this first embodiment, enters, via a first peripheral electrode 26, through the periphery of a first disc 3, crosses radially the first disc 3 to its center 5, continues, via the central electrode 12 to the center 6 of the second disc 4, crosses the second disc 3 radially, from its center 6 to its periphery and exits via the second peripheral electrode 27, connected to said periphery. A current generator connected between the two peripheral electrodes 26, 27 thus makes it possible to circulate a current and to heat the two discs 3, 4.

[0056] According to a second embodiment, more particularly illustrated in figures 3-4, the first wheel flange 8 is arranged between said at least two discs 3, 4. In this case, the radial branch of the L bears against a first disc 3 and the axial branch of the L points towards a second disc 4.

[0057] In order not to create a short circuit via the first wheel flange 8, according to another characteristic of the second embodiment, the first wheel flange 8 is electrically insulated from said first disc 3 by a second axially interposed insulating ring 15. This second insulating ring 15 is, for example, made of rope, typically glass fibers.

[0058] According to another characteristic of the second embodiment, the first wheel flange 8 is electrically insulated from the housing 2 radially by a first radial insulating mat 17. This radial insulating mat 17 is typically a fiberglass mat also called a canning mat.

[0059] According to another characteristic of the second embodiment, the connector means further comprises a single flange 19. This single flange 19 resembles a wheel flange but without the central part. Also, the single flange 19 comprises a crown, similar to the crown 9. This crown has an L-shaped section. Said section is arranged inverted relative to the section of the crown 9 of the first wheel flange 8. Thus, the radial branch of the L forms a second bearing face 20 capable of bearing against the periphery of a second disc 4 among said at least two discs 3, 4. This single flange 19 is electrically insulated from said second disc 4 by a third axially interposed insulating crown 16. This third insulating crown 16 is, for example, made of rope, typically glass fibers.

[0060] According to another characteristic of the second embodiment, the single flange 19 is electrically insulated from the housing 2, radially by the first radial insulating mat 17. This radial insulating mat 17 is typically a fiberglass mat also called a canning mat.

[0061] In this second embodiment, due to the insulation by the first mat 17 radial insulator, it is not necessary to provide electrical insulation between the first wheel flange 8, at its hub 10, and the central electrode 12 carried by said hub 10.

[0062] Also, the electrical circuit, for this second embodiment, enters, via a first peripheral electrode 26, through the periphery of a first disc 3, crosses the first disc 3 to its center 5, continues, via the central electrode 12 to the second disc 4, crosses the second disc 4 to its periphery and exits through the second peripheral electrode 27. A current generator connected between the two peripheral electrodes 26, 27 thus makes it possible to circulate a current and to heat the two discs 3, 4.

[0063] According to a third embodiment, more particularly illustrated in Figures 5-8, the connector means comprises two substantially identical wheel flanges 8, 21. The first wheel flange 8 and the second wheel flange 21 are arranged head to tail and between two of said at least two discs 3, 4. The two wheel flanges 8, 21 are electrically connected to each other. This connection is made by contacting, possibly supplemented by welding, the crowns 9, 22. This contact is made by the respective bearing faces 13, 20.

[0064] The second wheel flange 21, like the first wheel flange 8, comprises a crown 22, substantially matching the periphery of the passage section for the exhaust gases, a hub 23 and spokes 24 connecting the crown 22 to the hub 23.

[0065] The electrical connection of each of the wheel flanges 8, 21 with each of the respective discs 3, 4 is made via the hubs 10, 23. A hub 10, 23 is electrically connected to the respective center 5, 6 of the adjacent disc 3, 4.

[0066] This is completed by electrical insulation of each of the rings 9, 22 by an axially interposed insulating ring 15, 16. These insulating rings 15, 16 are, for example, made of rope, typically glass fibers.

[0067] This is further supplemented by radial electrical insulation provided by a second radial insulating mat 18 arranged radially between the rings 9, 22 and single flanges 33, 34 in electrical contact respectively with each of the discs 3, 4, at their periphery, the single flanges 33, 34 themselves being electrically insulated by the first radial insulating mat 17.

[0068] Also, the electrical circuit, for this third embodiment, enters, via a first peripheral electrode 26, by the periphery of a first disc 3, crosses the first disc 3, up to its center 5, continues by the hub 10 of the first wheel flange 8 through the first wheel flange 8, via its spokes 11, up to its crown 9. The two crowns 9, 22 being in contact ensure the electrical connection between the two wheel flanges 8, 21. The current then passes to the second wheel flange 21, crosses the second wheel disc 21, via its spokes 24, up to its hub 23. This hub 23 is connected to the center 6 of the second disc 4. The current then passes through the second disc 4 to its periphery and exits through the second peripheral electrode 27. A current generator connected between the two peripheral electrodes 26, 27 thus makes it possible to circulate a current and heat the two discs 3, 4.

[0069] Figures 7, 8 illustrate a variant embodiment of the third embodiment. The single flanges 33, 34, associated respectively with each of the discs 3, 4, are arranged with the radial branch of the L directed outwards in the third embodiment. They are arranged with the radial branch of the L directed inwards in the variant embodiment. In addition, in the variant, the peripheral electrodes 26, 27 are arranged substantially in the same plane perpendicular to the axis. These two characteristics make it possible to produce a heating element 1 that is much more axially compact.

[0070] According to a fourth embodiment, the connector means comprises a cylindrical slice 25 of metal foam. This cylindrical slice 25 is arranged between a first disc 3 and a second disc 4 of said at least two discs 3, 4. It is electrically connected with the first center 5 of the first disc 3 and with the second center 6 of the second disc 4. It thus plays the role of the central electrode 12 in the two previous embodiments. It is, on the other hand, axially electrically insulated from the rest of the first disc 3 by a second insulating ring 15 and axially electrically insulated from the rest of the second disc 4 by a third insulating ring 16. The metal foam is, according to a preferred option, coated with catalytic materials to produce a catalyst effect.

[0071] Also, the electrical circuit, for this fourth embodiment, enters, via a first peripheral electrode 26, through the periphery of a first disc 3, crosses the first disc 3, up to its center 5, continues, via the cylindrical slice 25 of metal foam, in order to reach the center 6 of the second disc 4. The current then crosses the second disc 4 up to its periphery and exits through the second peripheral electrode 27. A current generator connected between the two peripheral electrodes 26, 27 thus makes it possible to circulate a current and to heat the two discs 3, 4.

[0072] According to another characteristic common to the first, second, third and fourth embodiments, the heating element 1 further comprises, for each of said at least two discs 3, 4, a peripheral electrode 26, 27 electrically connected to the periphery of said disc 3, 4.

[0073] In order to make the electrical connection between the electrode 26, 27 and the associated disc 3, 4, a disc 3, 4 is advantageously arranged in a simple flange 33, 34. This simple flange 33, 34 has an L-shaped profile, similar to the simple flange 19 already described, for the second embodiment. Such a simple flange 33, 34 makes it possible, by the presence of a radial L branch, to provide a disc 3, 4 with an axial bearing face. This bearing face allows the disc 3, 4 to press, for example, against an insulating ring 15, 16.

[0074] According to another characteristic, a heating element 1 according to one of the embodiments among the first, the second or the third, can comprise at least one wheel flange 8, 21 integrating a mixer. A mixer is for example obtained by shaping the spokes 11, 24 in the form of fins. These fins can thus deflect the circulation of the exhaust gases to direct them towards a more particular zone of a heating disc 3, 4 arranged downstream of the wheel flange 8, 21 or even according to a given angle of incidence. A mixer can thus deflect the exhaust gases so that they arrive on the surface of a heating disc 3, 4 with a grazing incidence.

[0075] According to a fifth embodiment, more particularly illustrated in figures 11 and 12, the connector means comprises a connector 28 of substantially tubular shape, matching, from the inside, the shape of the housing 2. This connector 28 is conductive and is shaped so as to ensure an electrical connection, on the one hand with the periphery of a first disc 3, and on the other hand with the periphery of a second disc 4. Here, the connection between the heating discs 3, 4 is made by making contact between their periphery, and not between their center 5, 6 as in the previous embodiments.

[0076] For this to work, it is appropriate to isolate the connector 28 from the housing 2, for example by a radial insulating mat 17 arranged radially between the connector 28 and the housing 2. This radial insulating mat 17 is typically a fiberglass mat also called a canning mat.

[0077] The two discs 3, 4 being connected by their periphery, it is appropriate to make the current enter and exit through their respective center 5, 6. For this, according to another characteristic, the heating element 1 further comprises, for each heating disc 3, 4, a central electrode 29, 30. Each of these central electrodes 29, 30 is respectively electrically connected to the center 5, 6 of its associated disc 3, 4. This connection is advantageously made from the outside of the set of discs 3, 4 so that the central electrode 29, 30 can easily access the disc 3, 4.

[0078] It has been seen that the connector 28 is cylindrical, and advantageously hollow. Also, the space between the heating discs 3, 4 is left free. According to another characteristic, the connector means also comprises a catalytic brick 31, arranged between the discs 3, 4. This catalytic brick 31 thus makes it possible to use the vacant space while improving pollution control.

[0079] The invention has been illustrated and described in detail in the drawings and the preceding description. The foregoing description should be considered illustrative and given by way of example and not as limiting the invention to this description alone. Numerous variations of realization are possible. List of reference signs

[0080] 1: heating element,

[0081] 2: housing,

[0082] 3, 4: heating disc,

[0083] 5, 6: center,

[0084] 8: first wheel flange,

[0085] 9: crown,

[0086] 10: hub,

[0087] 11: radius,

[0088] 12: central electrode,

[0089] 13: first support face,

[0090] 14: first insulating crown,

[0091] 15: second insulating crown,

[0092] 16: third insulating crown,

[0093] 17: first radial insulating mat,

[0094] 18: second radial insulating mat,

[0095] 19: single flange,

[0096] 20: second support face,

[0097] 21: second wheel flange,

[0098] 22: crown,

[0099] 23: hub,

[0100] 24: radius,

[0101] 25: cylindrical slice,

[0102] 26, 27: peripheral electrode,

[0103] 28: connector,

[0104] 29, 30: central electrode,

[0105] 31: catalytic brick,

[0106] 32: radial insulating mat,

[0107] 33, 34: single flange.

Claims

Claims

1. Heating element (1) for an exhaust line, comprising a substantially tubular housing (2) defining a passage section for the exhaust gases, receiving at least two heating discs (3, 4) arranged across the passage section so as to force the exhaust gases to pass through said at least two discs (3, 4), characterized in that the heating element (1) further comprises a connector means supporting said at least two discs (3, 4) and ensuring an electrical connection between said at least two discs (3, 4).

2. Heating element (1) according to claim 1, wherein the connector means comprises a first wheel flange (8) and a central electrode (12), the first wheel flange (8) comprising a crown (9), substantially matching the periphery of the passage section for the exhaust gases, a hub (10) capable of supporting the central electrode (12) and spokes (11) connecting the crown (9) to the hub (10), the central electrode (12) electrically connecting the respective centers (5, 6) of said at least two discs (3, 4).

3. Heating element (1) according to claim 2, wherein the crown (9) of the first wheel flange (8) has an L-shaped section, with one branch of the L arranged radially and the other branch of the L arranged axially, the radial branch of the L forming a first bearing face (13) capable of pressing axially against the periphery of a first disc (3) of said at least two discs (3, 4).

4. Heating element (1) according to any one of claims 2 or 3, wherein the first wheel flange (8) is arranged outside said at least two discs (3, 4), the radial branch of the L bearing against the neighboring disc (3) and the axial branch of the L pointing outwards.

5. Heating element (1) according to claim 4, wherein the first wheel flange (8) is welded to the neighboring disc (3).

6. Heating element (1) according to any one of claims 4 or 5, wherein a first insulating ring (14) is arranged axially between said at least two discs (3, 4) and wherein the hub (10) is electrically insulated relative to the central electrode (12).

7. Heating element (1) according to any one of claims 2 or 3, wherein the first wheel flange (8) is arranged between said at least two discs (3, 4), the radial branch of the L bearing against a first disc (3) and the axial branch of the L pointing towards a second disc (4).

8. Heating element (1) according to claim 7, wherein the first wheel flange (8) is electrically insulated from said first disc (3) by a second axially interposed insulating ring (15).

9. Heating element (1) according to any one of claims 7 or 8, wherein the first wheel flange (8) is electrically insulated from the housing (2) radially by a first radial insulating mat (17).

10. Heating element (1) according to any one of claims 7 to 9, wherein the connector means further comprises a simple flange (19) comprising a crown having an L-shaped section, inverted relative to the section of the crown (9) of the first wheel flange (8) so as to form a second bearing face (20) capable of pressing against the periphery of a second disc (4) of said at least two discs (3, 4) and electrically insulated from said second disc (4) by a third axially interposed insulating crown (16).

11. Heating element (1) according to claim 10, wherein the single flange (19) is electrically insulated from the housing (2) radially by the first radial insulating mat (17).

12. Heating element (1) according to claim 1, wherein the connector means comprises a first wheel flange (8) and a second wheel flange (21), mounted head to tail between two of said at least two discs (3, 4), electrically connected to each other, a wheel flange (8, 21) comprising a crown (9, 22), substantially matching the periphery of the passage section for the exhaust gases, a hub (10, 23) and spokes (11, 24) connecting the crown (9, 22) to the hub (10, 23), a hub (10, 23) being electrically connected to the respective center (5, 6) of the adjacent disc (3, 4) and a crown (9, 22) being electrically insulated from the adjacent disc (3, 4) by an axially interposed insulating crown (15, 16).

13. Heating element (1) according to claim 1, wherein the connector means comprises a cylindrical slice (25) of metal foam, arranged between a first disc (3) and a second disc (4) of said at least two discs (3, 4), electrically connected with the first center (5) of the first disc (3) and with the second center (6) of the second disc (4), axially electrically insulated from the rest of the first disc (3) by a second insulating ring (15) and axially electrically insulated from the rest of the second disc (4) by a third ring

14.

15.

16.

17. insulating (16), the metal foam being preferentially coated to produce a catalytic effect. Heating element (1) according to any one of claims 2 to 12, wherein a wheel (8, 21) further comprises a mixer. Heating element (1) according to claim 1, wherein the connector means comprises a connector (28) of substantially tubular shape, internally matching the shape of the housing (2), so as to provide an electrical connection between the respective peripheries of said at least two discs (3, 4). Heating element (1) according to claim 15, further comprising for each of said at least two discs (3, 4), a central electrode (29, 30) respectively electrically connected to the center (5, 6) of the disc (3, 4), from the outside. Heating element (1) according to any one of claims 15 or 16, wherein the connector means further comprises a catalytic brick (31), arranged between said at least two discs (3, 4).

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