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 an EHC, from the English "Electrically Heated Catalyst". Prior art

[0002] Such a heating element is conventionally used for the treatment of exhaust gases from combustion within an engine, circulating in an exhaust system. The treatment of nitrogen oxides (NOx), polluting compounds resulting from the combustion of hydrocarbons, is most often achieved by a catalytic reduction reaction. This reaction requires a catalyst, comprising precious metals. A hot catalyst transforms the NOx contained in the exhaust gases, along with a reducing fluid, generally an aqueous urea solution, into non-polluting nitrogen (N2) and water (H2O).

[0003] For the reduction reaction to be effective, the catalyst must be very hot. This is ensured under steady-state conditions, as the catalyst is heated by the very hot exhaust gases from 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 embodiment of such a heating element is a heating disc, perforated to allow the passage of exhaust gases. The heating disc is positioned across the cross-section of the exhaust line. The heating disc is heated so as to heat the exhaust gases as they pass through.

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

[0007] It has recently become apparent that, in terms of performance and durability, it is advantageous to create a heating element with more than one heating disc, connected in series, both fluidly and electrically. This then raises issues 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, wherein 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] Specific features 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 ring, substantially conforming to the periphery of the exhaust gas passage section, a hub adapted to support the central electrode and spokes connecting the ring 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 one arm of the L arranged radially and the other branch of the L arranged axially, the radial branch of the L forming a first bearing surface capable of bearing axially against the periphery of a first disk of said at least two disks,

[0013] - the first wheel flange is disposed outside said at least two discs, the with the radial arm of the L resting against the adjacent disc and the axial arm of the L pointing outwards,

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

[0015] - a first insulating ring is arranged axially between said at least two discs and the hub are electrically isolated relative to the central electrode.

[0016] - the first wheel flange is disposed between said at least two discs, the arm with the radial arm of the L resting against a first disk and the axial arm of the L pointing towards a second disk,

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

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

[0019] - the connector means further comprises a simple flange comprising a crown presenting 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 bearing against the periphery of a second disc of said at least two discs and isolated electrically connected to said second disk by a third axially interposed insulating ring,

[0020] - the single flange is electrically isolated from the housing radially by a second Peripheral mat

[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 ring, substantially conforming to the periphery of the passage section for the exhaust gases, a hub and spokes connecting the ring to the hub, a hub being electrically connected to the respective center of the adjacent disc and a ring being electrically isolated from the adjacent disc by an axially interposed insulating ring,

[0022] - the connector means comprises a cylindrical slice of metallic 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 metallic foam being preferably coated to produce a catalytic effect,

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

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

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

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

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

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

[0029] [Fig-1] shows, in a cross-sectional view along its axis, a heating element along a first method of implementation,

[0030] [Fig.2] shows, in perspective view, the heating element of the [Fig.1],

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

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

[0033] [Fig. 5] shows, in a cross-sectional view along its axis, a heating element along a third method of implementation,

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

[0035] [Fig.7] shows, in a cross-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 the [Fig.7],

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

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

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

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

[0041] Throughout this document, the terms "radial" and "axial" are understood to mean relative to the axis of the exhaust line or housing. The term "axial" describes an element substantially aligned with said axis, while "radial" describes 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 into or forming a section of the exhaust line, defining a passage cross-section for the exhaust gases. This housing 2 accommodates at least two heating discs 3, 4 arranged across the passage cross-section so as to force the exhaust gases to pass through said at least two heating discs 3, 4.

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

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

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

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

[0047] According to one feature, used in several embodiments, more particularly 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 ring 9, substantially conforming to the periphery of the exhaust gas passage section, a hub 10, preferably central, and spokes 11 connecting the ring 9 to the hub 10. The hub 10 receives and retains 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 allows for the production of an inexpensive part and control over its manufacture and supply. Consequently, this wheel flange 8 is conductive. In order to prevent short circuits, appropriate electrical insulation must be provided.

[0050] According to another feature, the ring 9 of the first wheel flange 8 has an L-shaped cross-section. One arm of the L is arranged radially. The other arm of the L is arranged axially. The radial arm of the L thus forms a first bearing surface 13. It is therefore able to bear axially against the periphery of a first disk 3 among said at least two disks 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 disposed outside said at least two discs 3, 4. The radial arm of the L bears against a disc 3 which is referred to as the neighboring disc 3. The axial arm of the L points outwards from said at least two discs 3, 4.

[0052] According to another feature of the first embodiment, the first wheel flange 8 is welded directly to the adjacent disc 3. This provides mechanical reinforcement from the first wheel flange 8, which stiffens and thus supports the adjacent 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 necessary to electrically isolate said at least two disks 3, 4 at judiciously chosen points. For this purpose, according to another feature of the first embodiment, a first insulating ring 14 is arranged axially between said at least two disks 3, 4. This first insulating ring 14 is peripheral and covers at least the respective periphery of the disks 3, 4. Furthermore, in order to complete the electrical isolation scheme and to define the current flow path, the hub 10 is insulated electrically relative to the central electrode 12. This first insulating ring 14 is, for example, made of rope, typically of glass fibers.

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

[0055] Thus, the electrical circuit, in this first embodiment, enters, via a first peripheral electrode 26, through the periphery of a first disk 3, passes radially through the first disk 3 to its center 5, continues, via the central electrode 12 to the center 6 of the second disk 4, passes radially through the second disk 3 from its center 6 to its periphery, and exits through 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 heat the two disks 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 arm of the L is in contact with a first disc 3 and the axial arm of the L points towards a second disc 4.

[0057] In order to avoid creating a short circuit via the first wheel flange 8, according to another feature of the second embodiment, the first wheel flange 8 is electrically isolated from said first disc 3 by a second axially interposed insulating ring 15. This second insulating ring 15 is, for example, made of cord, typically glass fibers.

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

[0059] According to another feature of the second embodiment, the connector means further comprises a simple flange 19. This simple flange 19 resembles a wheel flange but without the central portion. The simple flange 19 also includes a ring, similar to the ring 9. This ring has an L-shaped cross-section. This cross-section is inverted relative to the cross-section of the ring 9 of the first wheel flange 8. Thus, the radial arm of the L forms a second bearing surface 20 suitable for bearing against the periphery of a second disk 4 among said at least two disks 3, 4. This simple flange 19 is electrically insulated from said second disk 4 by a third axially interposed insulating ring 16. This third insulating ring 16 is, for example, made of cord, typically glass fibers.

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

[0061] In this second embodiment, due to the insulation by the first radial insulating mat 17, it is not necessary to provide electrical insulation between the first wheel flange 8, at the level of 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 disk 3, passes through the first disk 3 to its center 5, continues, via the central electrode 12 to the second disk 4, passes through the second disk 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 disks 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 end-to-end, and between two of them are at least two discs 3, 4. The two wheel flanges 8, 21 are electrically connected to each other. This connection is made by bringing the rings 9, 22 into contact, optionally supplemented by welding. This contact is made through the respective bearing faces 13, 20.

[0064] The second wheel flange 21, like the first wheel flange 8, comprises a ring 22, substantially following the periphery of the passage section for the exhaust gases, a hub 23 and spokes 24 connecting the ring 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 complemented 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 cord, typically glass fibers.

[0067] This is further completed by radial electrical insulation achieved by a second radial insulating mat 18 arranged radially between the rings 9, 22 and the simple flanges 33, 34 in electrical contact respectively with each of the discs 3, 4, at the level of their periphery, the simple flanges 33, 34 being themselves 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, through the periphery of a first disc 3, passes through the first disc 3, to its center 5, continues through the hub 10 of the first wheel flange 8 through the first wheel flange 8, via its spokes 11, to its ring 9. The two rings 9 and 22, being in contact, ensure the electrical connection between the two wheel flanges 8 and 21. The current then passes to the second wheel flange 21, through the second wheel disc 21, via its spokes 24, 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 and 27 thus allows a current to flow and heat the two discs 3 and 4.

[0069] Figures 7 and 8 illustrate a variant embodiment of the third embodiment. The simple flanges 33 and 34, associated respectively with each of the discs 3 and 4, are arranged with the radial arm of the L directed outwards in the third embodiment. They are arranged with the radial arm of the L directed inwards in the variant embodiment. Furthermore, in the variant, the peripheral electrodes 26 and 27 are arranged substantially in the same plane perpendicular to the axis. These two features make it possible to create 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 metallic foam. This cylindrical slice 25 is disposed 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 fulfills the role of the central electrode 12 in the two preceding embodiments. It is, however, axially electrically isolated from the rest of the first disc 3 by a second insulating ring 15 and axially electrically isolated from the rest of the second disc 4 by a third insulating ring 16. The metallic foam is, according to a preferred option, coated with catalytic materials to produce a catalytic 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, passes through the first disc 3 to its center 5, continues, via the cylindrical slice 25 of metallic foam, to reach 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.

[0072] According to another feature 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] To establish the electrical connection between the electrode 26, 27 and the associated disk 3, 4, a disk 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, by virtue of the presence of a radial arm of the L, provides a disk 3, 4 with an axial bearing surface. This bearing surface allows the disk 3, 4 to bear, for example, against an insulating ring 15, 16.

[0074] According to another feature, a heating element 1 according to one of the embodiments first, second, or third may comprise at least one wheel flange 8, 21 incorporating a mixer. A mixer is obtained, for example, by shaping the spokes 11, 24 into fins. These fins can thus deflect the flow of exhaust gases to direct them towards a more specific area of ​​a heating disc 3, 4 disposed downstream of the wheel flange 8, 21, or at a given angle of incidence. A mixer can thus deflect the exhaust gases so that they strike the surface of a heating disc 3, 4 at a grazing angle.

[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, conforming, internally, to the shape of the housing 2. This connector 28 is conductive and is shaped 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 heated 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 necessary 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] Since the two discs 3, 4 are connected at their periphery, the current must be supplied to and supplied from their respective centers 5, 6. To this end, according to another feature, the heating element 1 further comprises, for each heated 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 on the outside of the disc assembly 3, 4 so that the central electrode 29, 30 can easily access the disc 3, 4.

[0078] It has been seen that connector 28 was cylindrical, and advantageously hollow. Also, the space between the 3 and 4 heating discs is left free. According to another feature, the connector also includes a catalytic brick 31.

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[0107] positioned between discs 3, 4. This catalytic brick 31 thus makes it possible to use the vacant space while improving pollution control. The invention has been illustrated and described in detail in the drawings and the preceding description. This description is to be considered illustrative and given by way of example, and not as limiting the invention to this single description. Numerous embodiments are possible. List of reference signs 1: heating element, 2: Housing, 3, 4: heating disc, 5, 6: center, 8: first wheel flange, 9: crown, 10: hub, 11: radius, 12: central electrode, 13: first support face, 14: first insulating layer, 15: second insulating layer, 16: third insulating layer, 17: first radial insulating mat, 18: second radial insulating mat, 19: simple flask, 20: second support face, 21: second wheel flange, 22: crown, 23: hub, 24: radius, 25: cylindrical slice, 26, 27: peripheral electrode, 28: connector, 29, 30: central electrode, 31: catalytic brick, 32: radial insulating mat, 33, 34: simple flask.

Claims

Demands

1. A heating element (1) for an exhaust line, comprising a housing (2), substantially tubular, defining a passage section for the exhaust gases, accommodating at least two heating discs (3, 4) arranged transversely across the passage section so as to force the exhaust gases to pass through said at least two discs (3, 4), and a connector means supporting said at least two discs (3, 4) and ensuring an electrical connection between said at least two discs (3, 4), characterized in that the connector means comprises a first wheel flange (8) and a central electrode (12), the first wheel flange (8) comprising a ring (9), substantially conforming to the periphery of the passage section for the exhaust gases, a hub (10) adapted to support the central electrode (12) and spokes (11) connecting the ring (9) to the hub (10), the central electrode (12) electrically connecting the centers (5,6) respective to said at least two discs (3, 4).,

2. Heating element (1) according to claim 1, wherein the ring (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 bearing axially against the periphery of a first disc (3) of said at least two discs (3, 4).

3. Heating element (1) according to any one of claims 1 or 2, wherein the first wheel flange (8) is disposed outside said at least two discs (3, 4), the radial arm of the L being in contact with the adjacent disc (3) and the axial arm of the L pointing outwards.

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

5. Heating element (1) according to any one of claims 3 or 4, 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).

6. Heating element (1) according to any one of claims 1 or 2, wherein the first wheel flange (8) is disposed between said at least two discs (3, 4), the radial arm of the L being in support against a first disk (3) and the axial branch of the L pointing towards a second disk (4).

7. Heating element (1) according to claim 6, wherein the first wheel flange (8) is electrically isolated from said first disc (3) by a second axially intercalated insulating ring (15).

8. Heating element (1) according to any one of claims 6 or 7, wherein the first wheel flange (8) is electrically insulated from the housing (2) radially by a first radially insulating mat (17).

9. Heating element (1) according to any one of claims 6 to 8, wherein the connecting means further comprises a simple flange (19) comprising a ring having an L-shaped cross-section, inverted relative to the cross-section of the ring (9) of the first wheel flange (8) so as to form a second bearing face (20) capable of bearing 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 an axially interposed third insulating ring (16).

10. Heating element (1) according to claim 9, wherein the simple flange (19) is electrically insulated from the housing (2) radially by the first radial insulating mat (17).

11. Heating element (1) according to claim 1, wherein the connecting 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 ring (9, 22), substantially conforming to the periphery of the passage section for the exhaust gases, a hub (10, 23) and spokes (11, 24) connecting the ring (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 ring (9, 22) being electrically isolated from the adjacent disc (3, 4) by an axially intercalated insulating ring (15, 16).

12. Heating element (1) according to claim 1, wherein the connecting means comprises a cylindrical slice (25) of metallic foam, disposed 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 insulated electrically from the rest of the first disc (3) by a second insulating ring (15) and axially electrically isolated from the rest of the second disk (4) by a third insulating ring (16), the metallic foam being preferentially coated to produce a catalytic effect.

13. Heating element (1) according to any one of claims 1 to 12, wherein a wheel flange (8, 21) further comprises a mixer.

14. Heating element (1) according to claim 1, wherein the connecting means further comprises a catalytic brick (31), disposed between said at least two discs (3, 4).

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