Heating disc for exhaust pipeline heating element

Abstract

The present disclosure relates to a heating tray for an exhaust line heating element. The invention relates to a heating plate (1) for a heating element of an exhaust line, which is adapted to be arranged across a flow region of the heating element so as to substantially seal the flow region, the invention relates to a heating disc (1) for a motor vehicle, comprising an electrically insulating ring (2), a disc-shaped electrically conductive wafer (3) which is permeable to exhaust gas and which is arranged in the insulating ring (2), at least two electrodes (8-9) which enable an electric current to flow through the wafer (3), and at least one electrically insulating shunt (4) which divides the wafer (3) into equal sectors (5, 6).

Description

Technical Field

[0001] The present invention relates to a heating plate for a heating element of an exhaust pipe line. Background Art

[0002] The exhaust pipe line collects the exhaust gases leaving the internal combustion engine. Its function is to convey these exhaust gases from the engine to a sleeve leading to the outside air. The exhaust pipe line also purifies the exhaust gases before releasing them into the atmosphere.

[0003] Purification is usually carried out by a catalyst, which enables the reaction of reducing nitrogen oxides. To enable this catalyst to work properly, a minimum operating temperature is required. The operating temperature of this catalyst is usually achieved by heating the exhaust gases themselves. When the engine is cold-started, the exhaust gases are not hot enough to perform this function.

[0004] It is also known to use a heating element to heat the exhaust gases, which is usually arranged across the flow area of the exhaust pipe line and is porous so as to be traversed by the exhaust gases and heat them as the exhaust gases pass through.

[0005] According to Figure 1 One embodiment shown, such a heating element 20 is produced from a metal foam wafer 21 so as to be porous and permeable to the exhaust gases. The wafer 21 is received in an insulating ring 22, which is here made in two halves. The wafer 21 and its ring 22 form a heating plate. The latter is received in a housing 23, the cross-section of which converges with the cross-section of the exhaust pipe line. The wafer 21 has alternately open cutouts 28 to prevent the flow of current, thus forming a serpentine shape to direct the current. At the two ends of the serpentine are contact points 24, 25. Electrodes 26, 27 are connected to each contact point 24, 25. A power supply is connected between the electrodes 26, 27 to circulate current through the serpentine, thereby heating the wafer 21 / the heating plate 20 by the Joule effect and thus heating the exhaust gases passing through it.

[0006] The problem with such a heating plate 20 is that the metal foam does not have good mechanical strength. Moreover, and especially when the size of the channel cross-section increases, as is the case for the exhaust pipe lines of industrial or commercial vehicles, this embodiment becomes too fragile.

[0007] The present invention proposes a novel and innovative embodiment for manufacturing a heating plate with increased mechanical strength. Summary of the Invention

[0008] The object of the present invention is a heating disk for a heating element of an exhaust pipe line, the heating disk being adapted to be arranged across the flow region of the heating element so as to substantially seal the flow region, the heating disk comprising an electrically insulating ring, a disk-shaped and exhaust-permeable conductive wafer arranged in the insulating ring, and at least two electrodes enabling an electric current to flow through the wafer, wherein the heating disk further comprises at least one electrically insulating diverter dividing the wafer into equal sectors.

[0009] Specific features or embodiments that can be used alone or in combination are:

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

[0011] - The sectors are made of metal foam,

[0012] - The sectors include a plurality of cuts which are substantially planar, substantially parallel to each other, extend through the sectors according to different thicknesses, and open radially alternately on one side or the other side of the sectors so as to form a serpentine shape in a plane substantially parallel to the axis of the heating disk.

[0013] - The cuts are substantially parallel to the bisecting plane of the sector.

[0014] - The electrodes are connected to each end of the serpentine wire.

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

[0016] - Two sectors of the wafer, advantageously all sectors, are connected in series, and the first electrode of the first sector is connected to the second electrode of the second sector, excluding the two end electrodes connected to the power supply.

[0017] - The first electrode of the first sector and the adjacent second electrode of the adjacent second sector are connected in combination through a joint passing through the diverter.

[0018] According to a second aspect of the present invention, the heating element comprises such a heating disk.

[0019] According to a third aspect of the present invention, the exhaust pipe line comprises such a heating element. Description of the Drawings

[0020] The present invention will be better understood by reading the following description given by way of example only and by referring to the drawings, in which:

[0021] What has been described Figure 1 shows a heating element according to the prior art in perspective view,

[0022] Figure 2 shows a first embodiment according to the present invention in perspective view, ​

[0023] Figure 3 shows another embodiment according to the present invention in a perspective view. Detailed Description

[0024] Reference Figure 2 to FIGS. 2 or 3, the present invention relates to a heating plate 1 for a heating element of an exhaust pipe line.

[0025] Such a heating plate 1 is adapted to be installed in a heating element 20 similar to a heating element of the prior art as Figure 1 shown.

[0026] Such a heating plate 1 is generally arranged to span the flow area of the heating element so as to substantially seal it by occupying the entire said flow area. The heating plate 1 advantageously includes an electrical insulation ring 2. The heating plate 1 is designed to be inserted into a metal housing which is arranged to span or converge with the flow area of the exhaust pipe line.

[0027] The wafer 3 is disc-shaped and is located in the insulation ring 2 which separates the wafer from the housing. The wafer 3 is conductive and is designed to have an electric current flowing through it so that it is heated by the Joule effect. The insulation ring 2 prevents the said current from circulating in the housing and in the exhaust pipe line.

[0028] The heating plate 1 substantially encloses the flow area such that the entire exhaust flow can pass through. However, the wafer 3 is permeable to the exhaust, which allows the exhaust to pass through and be heated when in contact with the heated wafer 3.

[0029] The heating plate 1 further includes at least two electrodes 8 - 9. These electrodes 8 - 9 are electrically connected to the wafer 3 by having an electric power source therebetween such that an electric current can flow through the wafer 3, thereby heating the wafer 3 by the Joule effect.

[0030] According to a feature, the heating plate 1 further includes at least one diverter 4. The diverter 4 divides the wafer 3 into preferably equal sectors 5, 6. Both sectors 5 and 6 terminate at the center of the wafer 3. The profiles of the sectors 5, 6 can have any shape, but are preferably the same from one sector to the other such that the shapes and surface areas of the sectors 5, 6 are equal. The diverter 4 is also a regular star shape. According to a simple embodiment, between the two sectors 5, 6, one leg of the diverter 4 is radial and straight. The diverter 4 also has a shape with regular intersections and has as many branches as the sectors 5, 6.

[0031] The separator 4 is electrically insulating in order to electrically insulate each sector 5, 6 from its adjacent sectors.

[0032] ​The relative fragility of the wafer 21 according to the prior art is related to the low mechanical strength of the permeable material forming the wafer 21 and to the large span associated with the flow area size, and increases with the cross-section of the wafer 3. The insertion of the diverter 4 advantageously greatly increases the strength of the wafer 3, which has a stronger mechanical strength and reduces the size of the wafer 21 to the size of the sectors 5, 6, i.e., a span divided by at least 2.

[0033] The number of sectors 5, 6 and thus the number of legs of the diverter 4 is at least 2. The maximum number of sectors 5, 6 is a compromise between increased mechanical strength and reduced complexity. Dividing into more than 10 sectors 5, 6 seems inappropriate.

[0034] According to another feature, the sectors 5, 6 are made of metal foam. Advantageously, this allows the production of a metal wafer 3 that can be electrically heated by the Joule effect and is at the same time porous to allow the passage of exhaust gas.

[0035] According to another feature, the shape of the sectors 5, 6 is similar to a serpentine shape in order to circulate the current as evenly as possible over substantially the entire surface of the sectors 5, 6. For this purpose, the sectors 5, 6 include a plurality of cuts 7. These cuts 7 are substantially planar in a plane substantially parallel to the axis A of the heating plate 1. They extend substantially parallel to each other. They pass through the thickness of the sectors 5, 6. They open radially only on one side of the sectors 5, 6. This open side is alternately located on one side or the other of the sectors 5, 6, between the cut 7 and the adjacent cut. In this way, the set of cuts 7 cuts the sectors 5, 6 to form a serpentine shape.

[0036] According to another feature, the cuts 7 are substantially parallel to the bisecting plane of the sectors 5, 6. They are also arranged symmetrically with respect to the bisecting plane of the sectors 5, 6.

[0037] Thus, a serpentine shape is formed. This serpentine shape forms the current flow path through the sectors 5, 6. According to another feature, electrodes 8 - 12 are connected to each end of the serpentine for current flow. A current is applied between these two electrodes 8 - 12.

[0038] The electrodes 8 - 12 of each sector 5, 6 can be independently wired for each pair of sectors 5, 6, or the wiring can be repeated in series or parallel for each pair of sector groups 5, 6.

[0039] According to another feature, two sectors 5, 6 of the wafer 3 are connected in parallel. These sectors can be or can not be adjacent sectors 5 or 6. As Figure 2 more specifically shown in, each sector 5, 6 includes two electrodes 8, 9. These electrodes are individually connected to a power source, or preferably connected in parallel to the same power source. This applies to all or part of the sectors 5 and 6.

[0040] The resistance r1 of sectors 5 and 6 is equal to the resistance R of the wafer 21 that is not divided into sectors divided by the number n of sectors 5 and 6, that is, r1 = R / n.

[0041] Moreover, the resistance r2 of a pair of sectors 5 and 6 connected in parallel is equal to half of r1, r2 = r1 / 2, that is, R / 2n. For the same applied voltage, this reduction in equivalent resistance results in an increase in heating power compared to the wafer 21 that is not divided into sectors.

[0042] For example, in Figure 2 all the first electrodes 8 can be connected together to the first pole of the power supply, and all the second electrodes 9 can be connected to the second pole of the power supply. Advantageously, all the sectors 5 and 6 of the wafer 3 are connected in parallel.

[0043] In this case, the equivalent resistance of n sectors 5 and 6 connected in parallel is equal to r1 / n, that is, R / n2, where n is the number of sectors 5 and 6 connected in parallel. For the same applied voltage, this reduction in equivalent resistance results in an increase in heating power compared to the wafer 3 that is not divided into sectors. The increase in this power is equal to the heating power of the undivided wafer 21 multiplied by the number n of sectors 5 and 6.

[0044] Moreover, by dividing into sectors 5 and 6 and combining parallel connection, the resistance of the wafer 3 can be changed, and thus the heating power of the wafer 3 can be changed. The number n of sectors 5 and 6 is used to change the resistance of the wafer 3.

[0045] According to another feature, two sectors 5 and 6 of the wafer 3 are connected in series. These sectors may or may not be adjacent sectors 5 or 6. As Figure 3 more specifically shown in, the first electrode 8 of the first sector 5 is connected to the second electrode 9 of the second sector 6. Then the two remaining electrodes - the second electrode 9 of the first sector 5 (still called the first end electrode 11) and the first electrode 8 of the second sector 6 (still called the second end electrode 12) are connected to the power supply.

[0046] The resistance r1 of sectors 5 and 6 is equal to the resistance R of the wafer 3 that is not divided into sectors divided by the number n of sectors 5 and 6, that is, r1 = R / n.

[0047] In addition, the resistance r3 of a pair of sectors 5 and 6 connected in series is equal to the sum of the resistances r1 of the two sectors 5 and 6, that is, r3 = r1 + r1 = 2r1, or 2R / 2 = R.

[0048] For example, in Figure 3 by connecting the end electrodes 11 and 12 to the power supply, all the sectors 5 and 6 can be connected in series. Therefore, advantageously, all the sectors 5 and 6 of the wafer 3 are connected in series.

[0049] In this case, the equivalent resistance of n sectors 5, 6 connected in series is equal to n·r1, i.e., R, where n is the number of sectors 5, 6 connected in series. Moreover, with respect to the undivided wafer 21, the series connection does not change the resistance R and the heating power.

[0050] It will be apparent to those skilled in the art that the two foregoing embodiments can be combined in series and in parallel, and that a first group of sectors 5, 6 according to the first embodiment and a second group of sectors 5, 6 according to a second embodiment, identical or different from the first, can be connected, and then the first and second groups can be connected according to either of the two embodiments. These connections can be reproduced in a repetitive manner as needed on the newly formed groups resulting from the previous connections.

[0051] By mixing series and parallel connections between the sectors 5, 6, it is possible to change the resistance of the wafer 3 compared to the undivided wafer 21 without changing the dimensional characteristics of the wafer 3, such as its thickness.

[0052] According to another feature, more specifically as Figure 3 shown, for two adjacent sectors 5, 6, their series connection can be simplified. To this end, the first electrode 8 of the 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 to form 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 shunt 4 in its branch disposed between the first sector 5 and the adjacent second sector 6.

[0053] The invention also relates to a heating element including the heating disk 1 as described above.

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

[0055] The invention has been described in detail and illustrated in the drawings and the foregoing description. This must be regarded as illustrative and given by way of example and not as limiting the invention to this description only. Many alternative embodiments can be adopted.

[0056] List of reference numerals

[0057] A: axis,

[0058] 1: heating disk,

[0059] 2, 22: rings,

[0060] 3, 21: wafers,

[0061] 4: shunt,

[0062] 5, 6: sectors,

[0063] 7, 28: incision

[0064] 8, 9, 26, 27: electrode

[0065] 10: joint

[0066] 11, 12: end electrode

[0067] 20: heating element

[0068] 23: housing

[0069] 24, 25: contact point

Claims

1. A heating plate (1) for an exhaust line heating element, the heating plate being capable of being arranged across the flow area of ​​the heating element so as to substantially close the flow area, the heating plate comprising an electrically insulating ring (2), a disc-shaped conductive plate (3) permeable to exhaust gas and arranged in the insulating ring (2), at least two electrodes (8-9) enabling an electric current to flow through the chip (3), the heating plate being characterized in that it also comprises at least one electrically insulating shunt (4) separating the chip (3) into equal sectors (5, 6).

2. The heating plate (1) according to the preceding claim, wherein the number of sectors is between 2 and 10.

3. The heating plate (1) according to any one of the preceding claims, wherein the sectors (5, 6) are made of metal foam.

4. A heating plate (1) according to any of the preceding claims, wherein the sectors (5, 6) comprise a plurality of cutouts (7) which are substantially planar in a plane substantially parallel to the axis (A) of the heating plate (1), substantially parallel to one another, pass through the thickness, open radially alternately on one side or the other of the sectors (5, 6) so as to form a serpentine shape.

5. The heating plate (1) according to the preceding claim, wherein the cutout (7) is substantially parallel to a plane bisecting the sectors (5, 6).

6. The heating plate (1) according to any of the two preceding claims, wherein an electrode (8-12) is connected to each end of the serpentine line.

7. The heating plate (1) according to any 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. A heating plate (1) according to any 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 terminal electrodes (11-12) connected to the power supply.

9. The heating plate (1) according to the preceding claim, wherein the first electrode (8) of a first sector (5) and the adjacent second electrode (9) of an adjacent second sector (6) are merged and connected by a joint (10) passing through the diverter (4).

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

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

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