Heating disc for exhaust line heating element

Abstract

Heating disc for exhaust line heating element The invention relates to a heating disc (1) for an exhaust line heating element, capable of being arranged across the passage section of the heating element so as to substantially close it, comprising an electrically insulating crown (2), an electrically conductive wafer (3) permeable to exhaust gases, disc-shaped and arranged in the insulating crown (2), at least two electrodes (8-9) for circulating a current through the wafer (3), further comprising at least one electrically insulating divider (4) separating the wafer (3) into equal sectors (5, 6). Abstract figure: Figure 2

Description

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

[0001] The invention relates to a heating disc for an exhaust line heating element. Prior art

[0002] An exhaust line collects the exhaust gases from a heat engine. Its function is to transport these exhaust gases from the engine to a cannula opening into the open air. It also has the function of purifying them before releasing them into the atmosphere.

[0003] Purification is typically carried out by a catalyst which allows a nitrogen oxide reduction reaction. The proper functioning of such a catalyst requires a minimum operating temperature. This operating temperature of the catalyst is generally obtained by heating using the exhaust gases themselves. During the cold engine start-up phase, the exhaust gases are not hot enough to perform this function.

[0004] Also, it is known to use a heating element, in order to heat the exhaust gases, typically arranged across the passage section of the exhaust line, porous, so as to be crossed by the exhaust gases and to heat them during their passage.

[0005] According to one embodiment, illustrated in [Fig.l], such a heating element 20 is made from a wafer 21 made of metal foam, in order to be porous and permeable to exhaust gases. This wafer 21 is housed in an insulating ring 22, here made in two halves. The wafer 21 and its ring 22 form a heating disc. The latter is housed in a housing 23 whose section merges with the section of the exhaust line. The wafer 21 comprises cutouts 28, alternately opening out, preventing the current from passing, so as to form a coil, guiding the current. At both ends of the coil, there are contact points 24, 25. To each contact point 24, 25 is connected an electrode 26, 27.Between the electrodes 26, 27 is connected a power supply, in order to circulate a current in the coil, so as to heat the wafer 21 / the heating disc 20, by Joule effect and thus heat the exhaust gases passing through it.

[0006] The problem that arises with such a heating disc 20 is that the metal foam does not have high mechanical resistance. Also, and in particular when the dimension of the passage section increases, as is the case for a line industrial or commercial vehicle exhaust, this embodiment becomes too fragile.

[0007] The invention presents a new innovative embodiment which makes it possible to produce a heating disc having increased mechanical resistance. Summary of the invention

[0008] The subject of the invention is a heating disc for an exhaust line heating element, capable of being arranged across the passage section of the heating element so as to substantially close it, comprising an electrically insulating crown, an electrically conductive wafer, permeable to exhaust gases, discoidal and arranged in the insulating crown, at least two electrodes allowing a current to flow through the wafer, where the heating disc further comprises at least one divider, electrically insulating, and separating the wafer into equal sectors.

[0009] Particular characteristics or embodiments, usable alone or in combination, are:

[0010] - the number of sectors is between 2 and 10,

[0011] - a sector is made of metal foam,

[0012] - a sector, comprises a plurality of cutouts, substantially flat according to a plane substantially parallel to an axis of the heating disc, substantially parallel to each other, passing through according to the thickness, radially emerging alternately on one side or the other of the sector, so as to form a coil,

[0013] - the cutouts are substantially parallel to the bisector plane of the sector,

[0014] - an electrode is connected to each end of the coil,

[0015] - two sectors, advantageously all the sectors of a wafer, are connected in parallel, each sector comprising two electrodes connected to a power supply,

[0016] - two sectors, advantageously all the sectors of a wafer, are connected in series, a first electrode of a first sector being connected to a second electrode of a second sector, excluding two extreme electrodes connected to the power supply,

[0017] - the first electrode of a first sector and the second adjacent electrode of a second adjacent sector, are merged and connected by a junction, crossing the divider.

[0018] According to a second aspect of the invention, a heating element comprising such a heating disc.

[0019] According to a third aspect of the invention, an exhaust line comprising such a heating element. Brief description of the drawings

[0020] 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:

[0021] [Fig-1] already described, shows, in perspective view, a heating element according to the art prior,

[0022] [Fig.2] shows, in perspective view, a first embodiment according to the invention,

[0023] [Fig.3] shows, in perspective view, another embodiment according to the invention. Description of the embodiments

[0024] With reference to [Fig.2] or 3, the invention relates to a heating disc 1 for an exhaust line heating element.

[0025] Such a heating disc 1 is capable of being placed in a heating element 20, similar to that of the prior art, as illustrated in [Fig.l].

[0026] Such a heating disc 1 is conventionally arranged across the passage section of the heating element so as to substantially close it by occupying the entire passage section. This heating disc 1 advantageously comprises an electrically insulating crown 2. The heating disc 1 is intended to be inserted into a metal housing arranged across or merging with the passage section of an exhaust line.

[0027] The wafer 3 is discoidal and is arranged in the insulating ring 2 which separates it from the housing. The wafer 3 is electrically conductive and is designed to be traversed by a current, in order to heat up by the Joule effect. The insulating ring 2 prevents said current from circulating in the housing and in the exhaust line.

[0028] The heating disc 1 substantially closes the passage section in order to allow the entire flow of exhaust gas to pass through. However, the wafer 3 is permeable to the exhaust gases, in order to allow them to pass through, and thus to heat up in contact with the heated wafer 3.

[0029] The heating disc 1 further comprises at least two electrodes 8-9. These electrodes 8-9, electrically connected to the wafer 3, allow, by placing an electrical power supply between them, to circulate a current through the wafer 3, and thus to heat the wafer 3 by Joule effect.

[0030] According to one characteristic, the heating disk 1 further comprises at least one divider 4. This divider 4 separates the wafer 3 into sectors 5, 6, preferably equal. The sectors 5, 6 all end at the center of the wafer 3. The contours of the sectors 5, 6 have any shape, but preferably identical from one sector to another, so that the shape and the surface of the sectors 5, 6 are equal. Also, the divider 4 has the shape of a regular star. According to a simple embodiment, between two sectors 5, 6, a branch of the divider 4 has a radial and rectilinear shape. Also, the divider 4 has the shape of a regular cross comprising as many branches that there are sectors 5, 6.

[0031] The separator 4 is electrically insulating, so as to electrically isolate each sector 5, 6 from its neighbors.

[0032] The relative fragility of a wafer 21 according to the prior art is linked to the low mechanical resistance of the permeable material constituting the wafer 21 in combination with a large span, linked to the size of the passage section, and increasing with the section of the wafer 3. The insertion of a divider 4, more mechanically resistant, and reducing the size of the wafer 21 to the size of the sectors 5, 6, i.e. a span at least divided by 2, advantageously significantly increases the resistance of the wafer 3.

[0033] The number of sectors 5, 6, and therefore of branches of the separator 4 is at least equal to 2. The maximum number of sectors 5, 6 is a compromise between increasing mechanical resistance and reducing complexity. It does not seem relevant to divide into more than 10 sectors 5, 6.

[0034] According to another characteristic, a sector 5, 6 is made of metal foam. This advantageously makes it possible to produce a metal wafer 3, therefore electrically heatable by the Joule effect, while being porous in order to allow the exhaust gases to pass through.

[0035] According to another characteristic, a sector 5, 6 is shaped like a serpentine, in order to circulate the current as uniformly as possible in substantially the entire surface of the sector 5, 6. For this, a sector 5, 6 comprises a plurality of cutouts 7. These cutouts 7 are substantially flat along a plane substantially parallel to an axis A of the heating disc 1. They are substantially parallel to each other. They pass through the thickness of the sector 5, 6. They are radially emerging on only one side of the sector 5, 6. This emerging side is alternately on one side or the other of the sector 5, 6, between a cutout 7 and the immediately adjacent cutout. Thus, all of the cutouts 7 cut out the sector 5, 6, so as to form a serpentine.

[0036] According to another characteristic, the cutouts 7 are substantially parallel to the bisector plane of the sector 5, 6. They are also arranged symmetrically relative to the bisector plane of the sector 5, 6.

[0037] Thus, a coil is formed. This coil forms a path for the current to flow through the sector 5, 6. According to another characteristic, for the current to flow, an electrode 8-12 is connected to each end of the coil. A current is applied between these two electrodes 8-12.

[0038] The wiring of the electrodes 8-12 of each sector 5, 6 can be carried out independently for each pair of sectors 5, 6 or in a recurring manner for each pair of sets of sectors 5, 6, either in series or in parallel.

[0039] According to another characteristic, two sectors 5, 6 of a wafer 3 are connected in parallel. These may be adjacent or non-adjacent sectors 5, 6. As more particularly illustrated in [Fig.2], each sector 5, 6 comprises two electrodes 8, 9. These electrodes are connected, either each to a power supply, or preferably in parallel to the same power supply. This is applicable to all or part of sectors 5, 6.

[0040] The resistance rl of a sector 5, 6 is equal to the resistance R of a wafer 21 not divided into sectors, divided by the number n of sectors 5, 6, i.e. rl = R / n.

[0041] Also, the resistance r2 of a pair of sectors 5, 6 connected in parallel is equal to half of rl, r2=rl / 2, or R / 2n. This reduction in the equivalent resistance results, for the same applied voltage, in an increase in the heating power, relative to a wafer 21 not divided into sectors.

[0042] Thus, in [Fig.2], it is possible to connect all the first electrodes 8 together to a first pole of a power supply and all the second electrodes 9 to a second pole of a power supply. Thus, advantageously, all the sectors 5, 6 of a wafer 3 are connected in parallel.

[0043] In this case, the equivalent resistance of the n sectors 5, 6 connected in parallel is equal to rl / n, or R / n2 where n is the number of sectors 5, 6 connected in parallel. This reduction in the equivalent resistance results, for the same applied voltage, in an increase in the heating power, relative to a wafer 3 not divided into sectors. This increase in power is equal to the heating power of an undivided wafer 21, multiplied by the number n of sectors 5, 6.

[0044] Also, the division into sectors 5, 6, associated with a parallel connection makes it possible to modify the resistance of the wafer 3 and therefore the heating power of a wafer 3. The parameter number n of sectors 5, 6 thus makes it possible to vary the resistance of the wafer 3.

[0045] According to another characteristic, two sectors 5, 6 of a wafer 3 are connected in series. These may be adjacent sectors 5, 6 or not. As more particularly illustrated in [Fig.3], a first electrode 8 of a first sector 5 is connected to a second electrode 9 of a second sector 6. The two remaining electrodes, namely the second electrode 9 of the first sector 5 which is also called the first end electrode 11 and the first electrode 8 of the second sector 6 which is also called the second end electrode 12 are then connected to a power supply.

[0046] The resistance rl of a sector 5, 6 is equal to the resistance R of a wafer 3 not divided into sectors, divided by the number n of sectors 5, 6, i.e. rl = R / n.

[0047] Also, the resistance r3 of a pair of sectors 5, 6 connected in series is equal to the sum of the resistances rl of the two sectors 5, 6, i.e. r3=rl+rl= 2rl, i.e. 2R / 2=R.

[0048] Thus, in [Fig. 3], it is possible to connect in series all the sectors 5, 6 by connecting the end electrodes 11, 12 to a power supply. Thus, advantageously, all the sectors 5, 6 of a wafer 3, are connected in series.

[0049] In this case, the equivalent resistance of the n sectors 5, 6 connected in series is equal to n.rl, i.e. R where n is the number of sectors 5, 6 connected in series. Also, a series connection does not modify the resistance R and the heating power, relative to an undivided wafer 21.

[0050] It appears to the person skilled in the art that it is possible to combine the two preceding embodiments, series and parallel, and to connect a first set of sectors 5, 6 according to a first mode, a second set of sectors 5, 6 according to a second mode, identical to or different from the second mode and then to connect the first set and the second set according to any one of the two modes. These connections can also be reproduced, as desired, on the sets newly formed by the preceding connections, in a recurrent manner.

[0051] It is thus possible by combining series connections and parallel connections between sectors 5, 6, to vary the resistance of the wafer 3, relative to an undivided wafer 21, and this without modifying the dimensional characteristics of the wafer 3, such as its thickness.

[0052] According to another characteristic, more particularly illustrated in [Fig.3], for two adjacent sectors 5, 6, it is possible to simplify their connection in series. For this, the first electrode 8 of a first sector 5 and the adjacent electrode, i.e. the second electrode 9 of the second sector 6, adjacent to the first sector 5, are merged into a junction 10. The junction 10 connects the first electrode 8 of the first sector 5 and the second electrode 9 of the second sector 6. Advantageously, the junction 10 passes through the divider 4, in its branch arranged between the first sector 5 and the second adjacent sector 6.

[0053] The invention also relates to a heating element comprising a heating disc 1 as previously described.

[0054] The invention also relates to an exhaust line comprising such a heating element.

[0055] 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

[0056] A: axis,

[0057] 1: heating disc,

[0058] 2, 22: crown,

[0059] 3, 21: pancake,

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] 4: divider, 5, 6: sector, 7, 28: cutout, 8, 9, 26, 27: electrode, 10: junction, 11,12: end electrode, 20: heating element, 23: housing, 24, 25: contact point

Claims

Claims

1. Heating disc (1) for an exhaust line heating element, capable of being arranged across the passage section of the heating element so as to substantially close it, comprising an electrically insulating crown (2), an electrically conductive wafer (3), permeable to exhaust gases, discoidal and arranged in the insulating crown (2), at least two electrodes (8-9) allowing a current to flow through the wafer (3), characterized in that it further comprises at least one divider (4), electrically insulating, and separating the wafer (3) into equal sectors (5, 6).

2. Heating disc (1) according to the preceding claim, where the number of sectors is between 2 and 10.

3. Heating disc (1) according to any one of the preceding claims, wherein a sector (5, 6) is made of metal foam.

4. Heating disc (1) according to any one of the preceding claims, where a sector (5, 6) comprises a plurality of cutouts (7), substantially flat along a plane substantially parallel to an axis (A) of the heating disc (1), substantially parallel to each other, passing through the thickness, radially emerging alternately on one side or the other of the sector (5, 6), so as to form a serpentine.

5. Heating disc (1) according to the preceding claim, where the cutouts (7) are substantially parallel to the bisector plane of the sector (5, 6).

6. A heating disc (1) according to any one of the two preceding claims, wherein an electrode (8-12) is connected to each end of the coil.

7. Heating disc (1) according to any one of the preceding claims, wherein two sectors (5, 6), advantageously all sectors (5, 6) of a wafer (3), are connected in parallel, each sector (5, 6) comprising two electrodes (8-9) connected to a power supply.

8. Heating disc (1) according to any one of the preceding claims, wherein two sectors (5, 6), advantageously all sectors (5, 6) of a wafer (3), are connected in series, a first electrode (8) of a first sector (5) being connected to a second electrode (9) of a second sector (6), excluding two end electrodes (11-12) connected to the power supply.

9. Heating disc (1) according to the preceding claim, wherein the first electrode (8) of a first sector (5) and the second electrode (9) adjacent to a second adjacent sector (6), are merged and connected by a junction (10), crossing the divider (4).

10. Heating element, characterized in that it comprises a heating disc (1) according to any one of the preceding claims.

11. Exhaust line, characterized in that it comprises a heating element according to the preceding claim.

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