Heating element for exhaust line

Abstract

Heating element for exhaust line The invention relates to a heating element (1) for an exhaust line comprising a tubular housing (2) aligned with and / or merging with a pipe (3) of the exhaust line, a wafer (4) arranged across the housing (2), occupying substantially the entire passage section, comprising a metal disc (5), substantially of the same volume as the wafer (4) and at least two electrodes (6, 7) electrically connected to the disc (5), where the disc (5) is made of three-dimensional metal mesh. Figure for 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 of an internal combustion engine. Prior art

[0002] It is known to produce a heating element for an exhaust line. According to one embodiment, such a heating element is heated electrically, for example by the Joule effect. Such a heating element is typically arranged across the exhaust pipe. The function of such a heating element is to heat the exhaust gas passing through it. This advantageously makes it possible to heat a catalyst, arranged downstream of the heating element in order to allow it to reach its minimum operating temperature.

[0003] It is also known to produce such a heating element by producing a tubular housing aligned and / or merging with a pipe of the exhaust line. In this housing is arranged a wafer, across the passage section of the housing, the wafer occupying substantially the entire passage section. The wafer comprises a metal disc, substantially of the same volume as the wafer. The heating element also comprises at least two electrodes electrically connected to the wafer in order to be able to circulate a current in the metal disc and thus cause it to heat up. Summary of the invention

[0004] The invention proposes a new and original way of producing the metal disc using a three-dimensional metal mesh.

[0005] The invention relates to a heating element for an exhaust line comprising a tubular housing aligned and / or merging with a pipe of the exhaust line, a wafer arranged across the housing, occupying substantially the entire passage section, comprising a metal disc, substantially of the same volume as the wafer and also at least two electrodes electrically connected to the disc, where the disc is made of three-dimensional metal mesh.

[0006] Particular characteristics or embodiments, usable alone or in combination, are:

[0007] - the three-dimensional metal mesh is knitted, from a metal wire of diameter between 0.2 and 3 mm, preferably in stainless steel, even more preferably in FeNiAl steel, in order to produce a mesh with dimensions between 1 and 20 mm,

[0008] - the wafer also comprises a metal plate for each electrode, in electrical continuity with the disc, secured to the disc preferably by welding, arranged on the periphery of the disc substantially parallel to the surface of the housing, in order to allow electrical connection with an electrode,

[0009] - the disc comprises at least two cutouts, substantially flat, substantially pa aligned with the axis of the housing and substantially parallel to each other, a cutout having one end opening out at the periphery of the disc and another non-opening end, alternating the ends of one cutout with its neighbor, so as to form a serpentine,

[0010] - a metal plate, capable of allowing electrical connection with an electrode, is preferably arranged at one end of the possible coil,

[0011] - the ends of the coil are diametrically opposed, relative to the disc and each facing an electrode,

[0012] - a non-opening end is widened, preferably by a cy drilling lindrique along an axis parallel to the axis, preferably with a diameter at least 5 times greater than the width of a cut,

[0013] - the wafer also includes an electrical insulator, covering the edge of the disc,

[0014] - the heating element further comprises at least one annular support, capable of blocking axially the wafer and to be fixed to the housing, preferably by welding.

[0015] In a second aspect of the invention, an exhaust line comprising at least one such heating element. Brief description of the drawings

[0016] 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:

[0017] [Fig-1] shows, in perspective view, a heating element,

[0018] [Fig.2] shows, in exploded perspective view, the heating element of [Fig.l],

[0019] [Fig.3A], [Fig.3B], [Fig.3C] show three examples of three-dimensional metal mesh monthly. Description of the embodiments

[0020] With reference to figures 1 or 2, the invention relates to a heating element 1 for an exhaust line (not shown). This heating element 1 comprises a tubular housing 2. This housing 2 has a passage section of any shape, for example as shown, circular. The housing 2 is aligned with a pipe 3 of the exhaust line. Thus, all the exhaust gas which passes through the pipe 3 circulates through the heating element 1. The housing 2 merges with the pipe 3 in that it is connected to the latter at its upstream and downstream or in that it is housed in an uninterrupted pipe 3.

[0021] The heating element 1 comprises a substantially discoidal wafer 4. The wafer 4 is arranged across the housing 2. In order for the entire flow of exhaust gas to pass through the wafer 4, the latter has a section substantially identical to the passage section and such that it occupies substantially the entire passage section of the housing 2.

[0022] The main volume of the wafer 4 is occupied by a disc 5. This disc 5 is metallic in order to be able to conduct a current through it and heat up accordingly, by the Joule effect.

[0023] The heating element 1 further comprises at least two electrodes 6, 7 electrically connected to the disc 5. These electrodes 6, 7 make it possible to circulate a current through the metal disc 5 and thus, via its electrical resistance, cause it to heat up.

[0024] According to an important characteristic of the invention, the disc 5 is made of three-dimensional metal mesh. Such a three-dimensional metal mesh is made by knitting a metal wire, generally by machine. After knitting, the rigidity of the assembly can be increased by brazing the meshes in contact.

[0025] Such a three-dimensional metal mesh offers a substantially homogeneous, rigid structure, as well as at least one spatial periodicity. Figures 3A, 3B and 3C show three different examples of three-dimensional metal mesh. It is possible to vary the type of three-dimensional metal mesh by modifying the knitting program and thus the mesh obtained.

[0026] Another advantage of such a three-dimensional metal mesh is that its structure is known and predictable, knowing its basic module, the latter being repeated periodically. This makes it possible to simplify modeling, in particular finite element modeling, for both mechanics and thermal aspects. This is advantageous, relative to the metal foams previously used in the prior art and whose structure is not known deterministically and must be approximated statistically or globally.

[0027] The disc 5 can be simply produced by cutting a slice, substantially flat, from a block of three-dimensional metal mesh and cutting a disc with a section substantially equal to the passage section in said slice.

[0028] According to another characteristic, the three-dimensional metal mesh is knitted from a metal wire. The diameter of this wire is advantageously between 0.2 and 3 mm. The material of this wire is preferably stainless steel. A preferred choice of stainless steel is FeCrAl steel. The wire is knitted so as to produce a mesh with a dimension of between 1 and 20 mm.

[0029] In order to allow the connection of an electrode 6, 7, according to another characteristic, a metal plate 8 is advantageously affixed to each electrode 6, 7. full and continuous in electrical continuity with the disc 5. This plate 8 is arranged on the surface of the three-dimensional metal mesh, secured to said three-dimensional metal mesh, for example by welding. This welding can be brazing. It is arranged on the periphery of the disc 5, substantially parallel to the surface of the housing 2, i.e. on the edge of the disc 5, in order to allow electrical connection with an electrode 6, 7.

[0030] As described above, the disc 5 is extracted from a solid piece of three-dimensional metal mesh. In order to create the longest possible electrical path and running substantially over the entire surface of the disc 5, in order to distribute heating evenly over said surface, according to another characteristic, the disc 5 is advantageously cut. This cutting comprises at least two cutouts 10. According to a possible embodiment, these cutouts 10 are substantially planar, substantially parallel to the axis A of the housing 2 and substantially parallel to each other. A cutout passes through the thickness of the disc 5. In a direction contained in a plane parallel to the disc 5, or contained in a plane perpendicular to the axis A, a cutout 10 emerges along only one of its ends. Thus, a cutout 10 has an emerging end 11 at the periphery of the disc 5 and another non-emerging end 12.A non-emerging end 12 is however close to the periphery of the disc 5. The length of a cutout 10, in the plane of the disc 5, relative to a complete double-emerging cutout, exceeds a ratio of 80%. The cutting pattern is alternated from one cutout 10 to its neighbor. If a cutout 10 has its emerging end 11 on the right, the immediately neighboring cutout 10 has its emerging end 11 on the left and vice versa. Thus, by alternating the cutouts 10, the disc 5 is cut so as to form a serpentine. This is particularly illustrated in Figures 1 and 2.

[0031] The width of a cutout 10 is such that it completely isolates the three-dimensional metal mesh on one side of the cutout 10 from that on the other side of the cutout 10. However, it remains reduced so as not to cause too much exhaust gas leakage. In order to take into account possible deformations of the disc 5, for example under the effect of thermal expansion, said width is preferably between 0.5 and 5 mm, and is preferably equal to 2 mm.

[0032] According to another characteristic, a metal plate 8, capable of allowing electrical connection with an electrode 6, 7, is preferably arranged at one end of the possible coil. This is particularly visible in [Fig.2], where the position of a metal plate 8 is shown.

[0033] According to another characteristic, the cutouts 10 are made in such a way that the two ends of the coil are diametrically opposed, relative to the disc 5. Advantageously, each end of the coil is located opposite a electrode 6, 7.

[0034] This embodiment advantageously makes it possible to arrange all the electrodes 6, 7 at the periphery of the disk 5 / of the wafer 4, advantageously avoiding a central electrode, which is more complex to implement and causes an additional loss of charge.

[0035] According to another characteristic, in order to avoid a hot spot at the “turnover” of the path of the electric current within a disc 5, the turning radius is increased. For this, a non-opening end 12 is widened, preferably by a cylindrical drilling along an axis parallel to the axis A. In order to significantly increase the turning radius, the drilling has a diameter at least 5 times greater than the width of a cutout 10.

[0036] The disc 5 carries a current flowing between said at least two electrodes 6, 7. This current must remain confined to the disc 5 alone. Also, according to another characteristic, the disc 5 must be electrically insulated from the housing 2. Also, the wafer 4 further comprises an electrical insulator 13, covering the edge of the disc 5, so as to avoid any electrical contact between the disc 5 and the housing 2. According to an illustrated embodiment, the electrical insulator 13 can be made in two half-crowns.

[0037] A wafer 4 comprises a disc 5, a plate 8 per electrode and an electrical insulator 13.

[0038] The wafer 4 has an external section substantially identical to the internal section of the housing 2. It is appropriate to immobilize the wafer 4 axially in the housing 2. Also, according to another characteristic, a heating element 1 further comprises at least one annular support 14. Such an annular support is capable of axially blocking the wafer 4. Also, two such annular supports 14 are advantageously arranged, each on one side of the wafer 4. An annular support 14 has an external contour substantially identical to the internal contour of the housing 2. Its occupation of the passage section is as small as possible in order to limit pressure losses. An annular support 14 advantageously has at least one surface parallel to the surface of the housing 2. It is thus possible to fix the annular support 14 to the housing 2. This is preferably achieved by welding.At least one light 15, passing through the housing 2 opposite the annular support 14, makes it possible to carry out such welding through the light 15.

[0039] The invention also relates to an exhaust line comprising at least one such heating element 1.

[0040] The invention also relates to a vehicle comprising such an exhaust line.

[0041] The invention has been illustrated and described in detail in the drawings and the preceding description. This should be considered as illustrative and given by way of example. and not as limiting the invention to this description alone. Numerous alternative embodiments are possible. List of reference signs

[0042] 1: heating element,

[0043] 2: housing,

[0044] 3: driving,

[0045] 4: pancake,

[0046] 5: disc,

[0047] 6, 7: electrode,

[0048] 8: metal plate,

[0049] 10: cutting,

[0050] 11: opening end,

[0051] 12: non-opening end,

[0052] 13: insulator,

[0053] 14: annular support,

[0054] 15: light,

[0055] A: axis

Claims

Claims

1. Heating element (1) for an exhaust line comprising a tubular housing (2) aligned with and / or merging with a pipe (3) of the exhaust line, a wafer (4) arranged across the housing (2), occupying substantially the entire passage section, comprising a metal disc (5), substantially of the same volume as the wafer (4) and at least two electrodes (6, 7) electrically connected to the disc (5), characterized in that the disc (5) is made of three-dimensional metal mesh, in that the disc (5) comprises at least two cutouts (10), substantially flat, substantially parallel to the axis (A) of the housing (2) and substantially parallel to each other, a cutout having an emerging end (11) at the periphery of the disc (5) and another non-emerging end (12), alternating the ends (11, 12) of one cutout (10) with its neighbor, so as to form a coil, and in that a metal plate (8),suitable for allowing electrical connection with an electrode (6, 7), is arranged at one end of the coil.,

2. Heating element (1) according to the preceding claim, where the three-dimensional metal mesh is knitted from a metal wire with a diameter of between 0.2 and 3 mm, preferably made of stainless steel, even more preferably made of FeCrAl steel, in order to produce a mesh with a dimension of between 1 and 20 mm.

3. Heating element (1) according to any one of the preceding claims, wherein the wafer (4) further comprises a metal plate (8) for each electrode (6, 7), in electrical continuity with the disc (5), secured to the disc (5) preferably by welding, arranged on the periphery of the disc (5) substantially parallel to the surface of the housing (2), in order to allow electrical connection with an electrode (6, 7).

4. Heating element (1) according to any one of the preceding claims, wherein the ends of the coil are diametrically opposite, relative to the disc (5) and each facing an electrode (6, 7).

5. Heating element (1) according to any one of the preceding claims, where a non-opening end (12) is widened, preferably by a cylindrical drilling along an axis parallel to the axis (A), preferably with a diameter at least 5 times greater than the width of a cutout (10).

6. Heating element (1) according to any one of the preceding claims, wherein the wafer (4) further comprises an electrical insulator (13), covering the edge of the disc (5).

7. Heating element (1) according to any one of the preceding claims, further comprising at least one annular support (14), capable of axially blocking the wafer (4) and of being fixed to the housing (2), preferably by welding.

8. Exhaust line characterized in that it comprises at least one heating element (1) according to any one of the preceding claims.

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