Patent Application
20210363907
This application is a U.S. non-provisional application claiming the benefit of French Application No. 20 05029, filed on May 19, 2020, which is incorporated herein by reference in its entirety.
The disclosure relates to the field of reduction mixers for exhaust gases.
A reduction mixer is typically arranged in an exhaust line of an internal combustion engine. Its function is to mix a reducing fluid, typically an aqueous urea solution: AdBlue, DEF, with the exhaust gas, in preparation for treatment of the mixture by a selective catalytic reductor (SCR) in order to reduce nitrogen oxides.
Different architectures are known for the making such a mixer. In one possible embodiment, a mixer comprises a closed and sealed box except for an inlet and an outlet. The exhaust gas flows through the box from the inlet to the outlet. The mixer further comprises a sprayer capable of spraying a reducer into the box, so that the sprayed reducer mixes with the exhaust gas flowing through the box.
It is also known that, in order to optimize the mixing of the reducer with the exhaust gas, the reducer is sprayed into a gas stream of the longest possible length, so as to increase the common circulation time of the two components and thus improve the mixing. For this purpose, while the space available in an engine and/or exhaust compartment is generally limited, it is still known to use a deflector, arranged in the box, and capable of deflecting the exhaust gas flow, in order to create the longest possible circulation path in the restricted volume allocated to the mixer.
According to one embodiment, the box has a substantially cylindrical shape. The faces of the cylinder form the bottom of the mixer and its cover, respectively. The faces are substantially flat, of the same shape, and are superimposed in a substantially parallel manner. The generator of the cylinder forms an outer wall, joining the perimeter of the bottom and the perimeter of the cover, substantially perpendicular to the bottom and the cover.
It is also known to make the cover in a single piece with the wall. This makes it possible to make it by stamping a single part, ensuring the wall function and simultaneously the cover function.
The deflector, as known, can be an internal wall, arranged in the box, joining the bottom and the cover, substantially perpendicularly, inside the perimeters of the bottom and the cover.
Due to the high temperature induced by the exhaust gas, a mixer and all its components are usually made of metallic material. Due to the temperature, the main way of joining the different components is by welding.
In order to ensure a gas-tight seal, a welded assembly is possible. It is quite simple to weld on the outside of the box. Also, sealing with the outside of the box can be achieved.
However, it can be more difficult to weld components inside the box, especially the deflector assembly with the cover. This can compromise the interior seal. If a leak occurs, the exhaust gas will have a shortcut and will be able to flow more quickly between the inlet and the outlet. This can cause the exhaust gas to contact the reducer and disrupt the function of the mixer.
The alternative to welding to achieve a seal is to make contact/support between the two parts to be sealed, one against the other. This requires precise manufacturing tolerances.
With punching, forming and stamping techniques, it is difficult to obtain precise tolerances. It is also difficult to achieve a seal by simple contact between two parts, due to dimensional dispersions. Furthermore, if a weld is used, it can lead to a deformation of a part which in turn can compromise contact between two parts and thus the sealing.
Also, other paradigms are sought to ensure sealing, primarily at the deflector, both at its lower interface with the bottom, and at its upper interface with the cover.
A mixer is provided for mixing an exhaust gas and a reducer, the mixer comprising a closed and sealed box excluding an inlet and an outlet, in which the exhaust gas flows from the inlet to the outlet. A reducer sprayer is arranged to be able to spray the reducer into an exhaust gas flow. The box has a substantially cylindrical shape with a bottom, a cover, an outer wall, and a deflector. The bottom and the cover are substantially flat, are overlapping substantially parallel, and form faces of a cylinder. The outer wall joins perimeters of the bottom and the cover and forms a generator of the cylinder. The cover and the outer wall are made together in a single piece. The deflector is an inner wall joining the bottom and the cover substantially perpendicularly, and the bottom and the deflector are made together of one single piece.
Particular features or embodiments, usable alone or in combination, are:
In a second aspect of the disclosure, an exhaust line comprises at least one such mixer.
In a third aspect of the disclosure, a motor vehicle comprises such an exhaust line.
The disclosure will be better understood from the following description, made only by way of example, and with reference to the appended Figures in which:
A mixer 1 is designed to mix an exhaust gas and a reducing fluid, in order to prepare a catalytic reaction aimed at reducing nitrogen oxides, NOx, in order to depollute the exhaust gas.
For this purpose, with reference to
According to one embodiment, the box 2 has a substantially cylindrical shape. Substantially cylindrical is understood as a generalized cylinder shape obtained by translating a base shape, which may be any shape, substantially parallel to itself. Such a generalized cylinder comprises a first face, substantially flat, reproducing the basic shape, a second face, substantially parallel and identical to the first face. The surface obtained by scanning/translating the base surface, here perpendicular to the base surface, is called the generating surface.
Also, the box 2, comprises a bottom 6, a cover 7, and an outer wall 8, for the outer shell. The bottom 6 and the cover 7 are substantially flat. They are superimposed substantially parallel and form the faces of the cylinder. The wall 8 joins the perimeters of the bottom 6 and the cover 7 and forms the generator of the cylinder.
In order to reduce the number of parts, the cover 7 and the wall 8 can advantageously be made together in one single piece. The common part that joins the cover 7 and the wall 8 can be made by welding between the cover 7 and the wall 8 or by stamping a blank.
Inside the box 2, there is also a deflector 9, the purpose of which is to extend the exhaust gas channel as far as possible in order to increase the contact time with the reducer and thus improve the mixing, both quantitatively and qualitatively.
The deflector 9 is, for example, an inner wall joining the bottom 6 and the cover 7 substantially perpendicularly. The shape of the deflector 9 is such that it forms deflectors opposing a direct path of the exhaust gas from the inlet 3 to the outlet 4. It is substantially parallel to the outer wall 8.
It is appropriate to assemble all these parts together, ensuring a gas-tight seal when necessary. The box 2 can be closed by welding the periphery of the bottom 6 with the lower edge of the facing wall 8.
The difficulty comes with the deflector 9. It can advantageously be welded on one of the faces among the bottom 8 and the cover 7. But welding on the other side is more delicate in that the area to be welded is necessarily inside the box 2 and therefore difficult to access. An alternative to the difficult welding of the deflector 9 on the other of the faces among the bottom 8 and the cover 7 is a contact, preferably with a support, to ensure the sealing. However, welding the deflector 9 to the first side usually results in deformation of the deflector 9. The resulting dimensional dispersion hinders the contact with support on the other side and thus the sealing is not guaranteed.
Also, the assembly of the deflector 9 with the bottom 6 is not made by welding. According to a characteristic of the disclosure, the bottom 6 and the deflector 9 are made together in one single piece. This allows for manufacturing methods that result in a much smaller dimensional dispersion. It is then possible to ensure the sealing between the deflector 9 and the cover 7 by simple support contact. Such a contact between the deflector 9 and the cover 7 may result in a slight leakage. Such leakage is much less than the main flow rate, typically less than 1%. It is also possible to observe the reducer passing from the reducer sprayer 5 by capillarity. Even if it is more delicate, welding the cover 7 with the upper edge of the deflector 9 is possible here, for example by transparency, through the cover 7.
The common part that joins the deflector 9 and the bottom 6 can advantageously be made by stamping.
According to another feature, the inlet 3 is arranged at the edge of the box 2, i.e., in the wall 8. This is more particularly visible in
Also, the sprayer 5 is advantageously arranged in the wall 8. Advantageously, the sprayer 5 is arranged directly on the inlet pipe.
According to another feature, the outlet 4 is arranged on one of the sides, for example the bottom 6.
According to another feature, the lower junction 10, between the deflector 9 and the bottom 6, has a fillet. The radius of this fillet is at least equal to 2 mm, preferably at least equal to 10 mm and even more preferably at least equal to 20 mm. This feature facilitates the production of the common part joining the bottom and the wall 8 in that a fillet facilitates stamping, in that it reduces the force to be applied and reduces the risks of breakage by strain hardening.
According to another feature, the deflector 9 has a substantially rectilinear cross-section, in a plane parallel to the bottom 6 and the cover 7. This is illustrated by the embodiment shown in
According to another feature, the deflector 9 has a section, according to a plane parallel to the bottom 6 and to the cover 7, substantially in the shape of a “U”. This is illustrated by the embodiment shown in
According to another feature, more particularly visible in
According to another feature, the roof 11 is made of the same material as the deflector 9, together in one single piece. This feature advantageously allows a common part joining the roof 11 and the deflector 9, and thus the bottom 6, to be made, for example, by stamping.
As seen previously, a stamping embodiment benefits from a soft shape, with a certain radius, rather than a sharp edge. Also, according to another characteristic, the upper junction 12, between the deflector 9 and the roof 11, advantageously has a rounding. The radius of this rounding is at least equal to 2 mm, preferably at least equal to 10 mm, and even more preferably at least equal to 20 mm.
As seen in
The lower, rounded junction 10 between the deflector 9 and the bottom 6 can also be used to guide the exhaust and reducer mixture to the inlet 16 of the next element 17.
The disclosure further relates to an exhaust line comprising at least one such mixer 1.
The disclosure further relates to a motor vehicle comprising such an exhaust line.
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 alternative embodiments are possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 05029 | May 2020 | FR | national |
