FR3085428A1 - DEVICE FOR HEATING EXHAUST GAS, PARTICULARLY FOR A COMBUSTION ENGINE - Google Patents

Abstract

The heating device (10) comprises a support frame (14) delimiting a passage for gases, and at least one conductive element (18) extending between two ends and arranged in the passage, each conductive element (18) being connected at each of its ends to a respective electrode (20). It comprises at least one plate (26, 28, 30) for supporting each conductive element (18), secured to the support frame (14).

Description

Exhaust gas heating device, in particular for a combustion engine

The present invention relates to an exhaust gas heating device, in particular for a combustion engine. Such a heating device is intended to heat the exhaust gases and a catalyst, in order to optimize the catalytic conversion of the polluting gases, in a moving vehicle, such as a motor vehicle, a truck, a ship, or in a stationary engine such as a generator.

More particularly, the invention relates to an exhaust gas heating device, comprising a support frame delimiting a passage for the gas, and at least one conductive element extending between two ends and arranged in the passage, each conductive element being connected at each of its ends to a respective electrode.

The conductive element is subject to relatively difficult living conditions, since it is in the passage of exhaust gases. More particularly, the conductive element is notably subjected to a high temperature, chemical reactions, impacts with particles, etc.

The object of the invention is in particular to ensure effective fixing of each conductive element, despite these difficult living conditions.

To this end, the invention particularly relates to an exhaust gas heating device, comprising a support frame delimiting a passage for gases, and at least one conductive element extending between two ends and arranged in the passage , each conductive element being connected at each of its ends to a respective electrode, characterized in that it comprises at least one electrically insulating support plate for each conductive element, secured to the support frame.

Advantageously, the invention applies to a heating device comprising an electrode device, the two terminals of which are arranged on the same side, unlike devices known from the state of the art in which the terminals are diametrically opposite. , which has a larger footprint outside the pollution control unit. Such an electrode device, the two terminals of which are arranged on the same side, is therefore more compact.

For example, the distance between the terminals is less than 10 cm, preferably less than 5 cm, and even more preferably between 3 and 4 cm.

A heating device according to the invention may include one or more of the following characteristics, taken alone or in any technically conceivable combination.

- Each support plate comprises, for each conductive element, at least one respective slot for passage of this conductive element, each passage slot extending between an open end and a closed end, and comprising a shoulder between the open and closed ends , the conductive element being disposed between the closed end and the shoulder.

- The heating device comprises a plurality of support plates, among which:

- a first central plate, secured to the support frame,

- at least a second plate, extending between a first end connected to the support frame, and a second end provided with a slot engaged on the first central plate.

- The heating device comprises at least one pair of second plates, preferably two pairs of second plates, the second plates of the same pair intersecting at their second ends at the level of the central plate.

- Each support plate is connected to the support frame, by inserting at least one end of this support plate in a slot made for this purpose in the support frame.

- Each support plate is made of electrically insulating material and resistant to temperatures above 500 ° C, for example mica.

- The support frame has an interior surface delimiting said passage, and an exterior surface, the exterior surface being provided with at least one wedging element, intended to be interposed between the support frame and an interior wall of a housing of exhaust line.

- The support frame is formed by the housing.

- The heating device comprises at least one conductive element intended to be arranged in an exhaust gas passage, and configured to heat the exhaust gases circulating in this passage, each conductive element extending in a predefined direction between a first and second end, and a first positive electrical terminal and a second negative electrical terminal, and first and second connection parts made of conductive material, such that each connection part comprises: a first substantially planar longitudinal part, extending in a longitudinal direction, a second connection part, connected to the first part extending transversely to this first part, the second part being connected to a respective one of the terminals, at least a third part, connected to the first part by extending transversely to this first part, each conduc element tor having one of its ends connected to the second or third part of one of the connecting parts, and the other of its ends connected to the second or third part of the other connecting part.

- The heating device comprises at least two conductive elements, preferably arranged in parallel with one another.

- At least one of the conductive elements has its first end connected to the first terminal and its second end connected to the second terminal, so that a first electric current flows in this conductive element, in a first direction of flow, at at least one other of the conductive elements has its first end connected to the second terminal and its second end connected to the first terminal, so that a second electric current flows in this conductive element in a second direction of flow opposite to the first direction.

- The heating device comprises means for keeping the ends of each conductive element in contact with the connection pieces, the holding means comprising for example a clamp or a stud passing through the conductive elements and the second and third parts of the pieces of connection.

- Each third part of each connecting part is arranged, in the longitudinal direction, either between the second part and a third part adjacent to this second part of the other connecting part, or between two third adjacent parts of the other part of connection.

Layers of electrically insulating material are inserted between the connection pieces, each layer of insulating material being inserted between a respective one of the third parts of one of the connection pieces and the second part of the other connection piece, or between one of the respective third parts of one of the connecting pieces and a respective one of the third parts of the other connecting piece.

- Each end of each conductive element is fixed to a respective one of the second or third parts of a respective one of the connection pieces, between this second or third part and the layer of insulating material this second or third part.

- The insulating material is mica.

- The heating device comprises first, second, third and fourth substantially parallel conductive elements and all extending in the same plane, such as: the first external conductive element surrounds all the other conductive elements, the second conductive element surrounds the third and fourth conductive elements, the third conductive element surrounds the fourth conductive element, the first ends of the first and fourth conductive elements are connected to the first positive terminal and their second ends are connected to the second negative terminal, and the first ends of the second and third conductive elements are connected to the second negative terminal and their second ends are connected to the first positive terminal.

The invention also relates to a combustion engine exhaust line, comprising an exhaust line housing, characterized in that it comprises a heating device as defined above, housed in the housing.

The invention also relates to a motor vehicle, comprising an exhaust line as defined above.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the appended figures, among which:

- Figure 1 is a perspective view of a heating device according to an exemplary embodiment of the invention;

- Figures 2 and 3 partially show, from above, a support plate of the heating device of Figure 1, respectively with a tab in the closed position and the folded tab in the open position.

FIG. 1 shows a device 10 for heating exhaust gases according to an exemplary embodiment of the invention. The heating device 10 is arranged in an exhaust line casing 12, through which the exhaust gases are intended to circulate, near a catalyst.

The housing 12 has for example a generally cylindrical shape with a circular base.

The heating device 10 includes a support frame 14, defining a passage for the exhaust gases. The support frame 14 has for example a generally cylindrical shape with a circular base, preferably coaxial with the housing 12.

The support frame 14 has an inner surface defining said passage, and an outer surface facing the housing 12. The outer surface is provided with at least one wedging element 16, intended to be interposed between the support frame 14 and a inner wall of the exhaust line housing 12. The wedging elements 16 therefore define a circular space between the support frame 14 and the housing 12.

The wedging elements 16 are fixed to the support frame 14 on the one hand, and to the housing 12 on the other hand, for example by welding.

In the example described, the wedging elements 16 are formed by tongues. Alternatively, one could arrange a single wedging element, formed by a thermally insulating sheet.

According to a variant not shown, the support frame is directly formed by the housing 12.

The heating device 10 also comprises at least one conductive element 18 extending between two ends, and arranged in the passage.

In the example described, the heating device 10 comprises four conductive elements 18 arranged in parallel. By considering a median plane of the heating device 10, each conductive element 18 has its ends on either side of this median plane.

The heater 10 has two electrodes 20, one forming a negative terminal and the other forming a positive terminal. Each end of each conductive element 18 is connected to a respective one of the electrodes 20. Each conductive element 18 is fixed to the electrodes 20 by means of a connection member, for example by a screw / nut system, by welding or by soldering.

An electric current is therefore likely to flow in the conductive element 18, which has the effect of increasing its temperature by the Joule effect. This makes it possible to heat the exhaust gases passing through the heating device 10.

According to a variant, one of the electrodes is formed by the housing 12. In this case, the device 10 comprises a positive electrode 20, and the housing 12 forms a negative electrode or a ground.

Advantageously, at least one of the conductive elements 18, preferably each conductive element 18, comprises two curved lateral parts, for example in an arc of a circle, and a central part comprising two substantially straight portions, each extending one of the lateral parts. , and converging towards each other. This shape increases the length of the conductive element 18, compared to a conductive element which would be circular.

For example, at least one of the conductive elements 18, preferably each conductive element 18, has a length greater than 100 mmm, and preferably greater than 250 mm.

According to another example, at least one of the conductive elements 18, preferably each conductive element 18, has a length less than or equal to the circumference of the housing 12.

According to yet another example, at least one of the conductive elements 18, preferably each conductive element 18, has a length greater than or equal to the circumference of the housing 12.

Indeed, the efficiency of the conductive elements 18 increases with their length, the exchange surface between the exhaust gases and the conductive elements 18, as well as the resistance, increasing with this length. The heating capacity therefore increases with the length of the conductive elements.

According to the example described, at least one of the conductive elements 18, preferably each conductive element 18, is formed by a strip, having a width less than its length, and a thickness much less than its width.

For example, the width of at least one of the conductive elements 18, preferably of each conductive element 18, is less than 10mm, preferably approximately equal to 5mm. Indeed, the efficiency of the conductive elements 18 increases when their width decreases, their resistance and therefore their ability to rise in temperature increases.

For example, the thickness of at least one of the conductive elements 18, preferably of each conductive element 18, is less than 0.2 mm and preferably approximately equal to 0.1 mm. This small thickness makes it possible to reduce the reaction time of the device.

The dimensions defined above make it possible to optimize the efficiency of the conductive elements for a given electrical energy.

Note that the conductive elements 18 are for example made of NickelChrome (NiCr), Iron-Chromium-Aluminum (FeCrAI) or a stainless steel alloy to increase their service life.

Alternatively, the conductive elements 18 could be embossed or twisted to increase their total length in a given space.

According to a variant, the conductive elements 18 can be formed by filaments.

The heating device 10 according to the invention comprises at least one support plate for each conductive element 18, secured to the support frame 14.

Each support plate includes, for each conductive element 18, a respective slot 24 for passage of this conductive element 18.

Preferably, each passage slot 24 extends between an open end and a closed end, and comprises a shoulder between the open and closed ends. The conductive element 18 is then placed between the closed end and the shoulder, so as to be held in the passage slot 24.

Preferably, as shown in FIGS. 2 and 3, each support plate 26, 28, 30 comprises, for each slot 24, a foldable tongue 32 between an open position in which it frees access to the slot 24 ( Figure 3), and a closed position in which this tongue 32 forms said shoulder (Figure 2).

Other locking systems can be envisaged: slot closed by welding points, refractory bonding, high temperature (ceramic glue type) or non-opening slot.

Advantageously, the heating device 10 comprises a plurality 22 of support plates, among which:

- A first central plate 26, secured to the support frame 14, and extending for example in said median plane;

- At least one pair of second plates 28, 30, preferably two pairs of second plates, each second plate 28, 30 extending between a first end connected to the support frame 14, and a second end provided with an engaged slot on the first central plate 26.

Each support plate 26, 28, 30 is connected to the support frame 14, by insertion of at least one end of this support plate 26, 28, 30 into a slot made for this purpose in the support frame 14. This slot can be closed at both ends, or alternatively closed at one end and having a foldable tab at the other end.

The second plates 28, 30 of the same pair intersect at the level of the central plate 26.

The first plate 26 has a passage slot 24 for each conductive element 18.

The second plates 28 of one of the pairs each have two passage slots 24 for each conductive element 18. The second plates 30 of the other pair each have a passage slot 24 for each conductive element 18.

This plurality 22 of support plates forms a self-supporting structure, particularly robust for the environment in which the heating device 10 is arranged.

It should be noted that each support plate 26, 28, 30 is made of an electrically insulating material and resistant to temperatures above 500 ° C., for example made of mica.

Claims (10)

1. An exhaust gas heating device (10), comprising a support frame (14) delimiting a passage for gases, and at least one conductive element (18) extending between two ends and arranged in the passage, each conductive element (18) being connected at each of its ends to a respective electrode (20), characterized in that it comprises at least one electrically insulating plate (26, 28, 30) for supporting each conductive element (18) , secured to the support frame (14). 2. Heating device (10) according to claim 1, wherein each support plate (26, 28, 30) comprises, for each conductive element (18), at least one slot (24) respective passage of this conductive element (18), each passage slot (24) extending between an open end and a closed end, and comprising a shoulder between the open and closed ends, the conductive element (18) being arranged between the closed end and the 'shoulder. 3. Heating device (10) according to any one of the preceding claims, comprising a plurality (22) of support plates (26, 28, 30), among which: - a first central plate (26), secured to the support frame (14), - at least a second plate (28, 30), extending between a first end connected to the support frame (14), and a second end provided with a slot engaged on the first central plate (26). 4. Heating device (10) according to claim 3, comprising at least one pair of second plates (28, 30), preferably two pairs of second plates (28, 30), the second plates of the same pair s' intersecting at their second ends at the central plate (26). 5. Heating device (10) according to any one of the preceding claims, in which each support plate (26, 28, 30) is connected to the support frame (14), by insertion of at least one end of this support plate (26, 28, 30) in a slot provided for this purpose in the support frame (14). 6. Heating device (10) according to any one of the preceding claims, in which each support plate (26, 28, 30) is made of material 9 electrically insulating and resistant to temperatures above 500 ° C, for example mica. 7. Heating device (10) according to any one of the preceding claims, in which the support frame (14) has an interior surface delimiting said passage, and an exterior surface, the exterior surface being provided with at least one element. wedging (16), intended to be interposed between the support frame (14) and an inner wall of an exhaust line housing (12). 8. Heating device (10) according to any one of claims 1 to 6, wherein the support frame is formed by the housing (12). 9. combustion engine exhaust line, comprising an exhaust line housing (12), characterized in that it comprises a heating device (10) according to any one of the preceding claims, housed in the housing (12). 10. Motor vehicle, comprising an exhaust line according to claim 9.