Patent Application
20220349326
This application is a U.S. non-provisional application claiming the benefit of French Application No. 21 04417, filed on Apr. 28, 2021, which is incorporated herein by reference in its entirety.
The disclosure relates to an exhaust gas heating element, of the type comprising a metallic foam wafer capable of being heated by Joule effect.
In order to heat an exhaust gas flowing in a pipe, typically located at the exhaust of an internal combustion engine, it is known to use a metallic foam wafer.
The wafer is arranged across the pipe in which the exhaust gas flows, with the axis of the wafer merging with the axis of the pipe.
The porosity of the metal foam makes it possible for the exhaust gas to pass through the wafer. The metallic foam provides the substrate which heats up by Joule effect, by using at least two electrodes, so as to transmit its heat to the exhaust gas passing through the wafer.
However, the metal foam alone lacks mechanical strength and must be reinforced. Furthermore, in order to be able to apply an electric current to the metal foam wafer via electrodes, the wafer must be insulated electrically from the pipe, which is usually metal.
The present disclosure provides a particularly advantageous solution for achieving the functions of stiffening and electrical insulation.
The subject disclosure provides an exhaust gas heating element comprising a wafer that is substantially cylindrical with an axis and has a circular, elliptical or rectangular section with rounded corners. The wafer is made of metallic foam and extends perpendicularly to the axis in a large dimension and extends along the axis in a thickness. A flexible electrical insulating sheet covers an edge of the wafer with an overlap on each face of the wafer. A rigid assembly ring is of a same section as the wafer and is substantially cylindrical with the axis The rigid assembly ring covers the sheet with an overlap on each of the faces. A housing is substantially cylindrical with the axis, has a same section as the wafer, and is capable of accommodating the ring and two electrodes. The rigid assembly ring is made from a cylinder trunk of large dimension, of which at least a first edge is serrated so as to be able to immobilize the wafer and the flexible electrical insulating sheet in the rigid assembly ring by folding ring teeth, substantially at 90°.
Particular features or embodiments, usable alone or in combination, include:
The disclosure will be better understood upon reading the following description, made only by way of example, and with reference to the appended Figures in which:
With reference to
A cylinder is understood here and throughout the present document as a general cylinder, i.e. a volume described by translation of any section S along an axis A.
The exhaust gas flow occurs substantially parallel to the direction A.
The wafer 2 has a section S, preferably circular, elliptical, or rectangular, with rounded corners. Also, a main extension of the wafer 2 is perpendicular to the axis A, along a large dimension D. This large dimension D describes the extension of the wafer 2 generically. In the case of an elliptical section, this large dimension D is identified successively with the small or large axis of the ellipse. In the case of a circular section, this large dimension D is identified with the diameter. In the case of a rectangular section, this large dimension D is identified successively with the small or the large side.
The extension of the wafer 2 along the axis A is called a thickness E.
In order to provide electrical insulation around the wafer 2, an insulating sheet 3 covers the wafer 2 in the parts that may be in contact with metal parts: namely, on the edge of the wafer 2. In order to ensure an insulation margin, the sheet 3 is extended by at least one overlap R on each side of the wafer 2. The sheet 3 is made of a flexible textile material and can be shaped by folding. The thickness of the sheet 3 is thin enough to be negligible. Also, the dimension of the sheet 3 in place around the wafer 2 takes up substantially the dimensions of the wafer 2 namely, a general cylinder of large dimension D, section S and thickness E.
A rigid assembly ring 4 surrounds the wafer 2 and sheet 3 assembly, so as to immobilize and hold the sheet 3 in place, while also stiffening the sub-assembly which includes the ring 4, the sheet 3, and the wafer 2. This ring 4 is made of sheet metal. The thickness of the sheet metal is small. Also, the dimension of the ring 4 in place around the sheet 3 and the wafer 2 is substantially the same as the dimensions of the wafer 2: namely a general cylinder of large dimension D, section S and thickness E.
The shape of the ring 4 is substantially identical to that of the sheet 3, in order to substantially cover the latter. The ring 4 has a section S similar to that of the wafer 2, covers the wafer 2 on its edge and has an overlap R on each of the faces of the wafer 2.
The sub-assembly comprising a wafer 2, a sheet 3, and a ring 4 is then arranged in a housing 5, which is housed in the exhaust gas pipe. The latter is substantially cylindrical with axis A and the same section S as the wafer 2.
The assembly is completed by two electrodes 6, 7. The electrodes 6, 7 are preferably arranged radially in holes 8 of the housing 5. These holes 8 correspond to holes 8′ in the ring 4 and holes 8″ in the sheet 3, so that the electrodes 6, 7 can bring the electric current into contact with the wafer 2 in order to heat the wafer 2.
The disclosure focuses on the embodiment of the ring 4 in such a way as to form a subassembly, as illustrated in
According to a first feature, more particularly illustrated in
According to one advantageous feature, at least a first edge of this cylinder trunk is serrated. Thus, by folding the teeth T substantially at 90°, it is possible to form a stop capable of immobilizing the wafer 2 and the sheet 3 in the ring 4. Folding the teeth T of the upper edge produces a ring 4, as illustrated in
According to the embodiment shown in
In order to be able to clamp a wafer 2 and a sheet 3, as shown in
According to another embodiment, more particularly illustrated in
This embodiment produces a shape substantially identical to that obtained by folding the teeth T of a serrated edge. However, advantageously, it has better rigidity than its serrated counterpart.
However, only a single edge can be produced by die-cutting.
In both embodiments, at least one edge must be serrated to make it possible to place the wafer 2 and the sheet 3, with the teeth T making closure possible after placement.
According to another feature, the teeth T, both the teeth of the ring 4 and the teeth of the sheet 3, have a length substantially equal to the desired overlap R.
The sheet 3 can be made in at least two embodiments, regardless of the embodiment of the ring 4.
According to another feature, more particularly illustrated in
It should be noted that such a sheet 3 is suitable for a ring 4 according to the first embodiment, illustrated in
According to another feature, a sheet 3 can still be cut in a pattern as shown in
According to another feature, the number of teeth is between 2 and 50, preferably between 4 and 40 and even more preferably equal to 26.
According to another feature, the teeth T are folded in a folding radius of between 0.1 and 5 mm, preferably between 0.2 and 2 mm. This applies both to the teeth T of the sheet 3 and to the teeth T of the ring 4.
According to another feature, the overlap R is between 5 and 20 mm, preferably between 8 and 15 mm and even more preferably equal to 11 mm.
The disclosure has been illustrated and described in detail in the drawings and the preceding description. The latter should be considered as illustrative and given as an example and not as limiting the disclosure to this description alone. Many variant embodiments are possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21 04417 | Apr 2021 | FR | national |
