阅读说明：本技术 用于废气还原剂的混合器 (Mixer for exhaust gas reducing agent ) 是由 洛朗·普安索 阿兰·昂热尔 菲利普·罗兰 于 2021-05-19 设计创作，主要内容包括：本发明涉及一种混合废气和还原剂的混合器(1),其包括：除入口(3)和出口(4)外封闭且密封的箱体(2),废气在该箱体中从入口(3)流向出口(4)；以及还原剂喷射器(5),其被设置为使得还原剂能够被喷射到废气流中,箱体(2)为基本上圆柱体的形状,具有底部(6)、盖体(7)、外壁(8)和偏转器(9),底部(6)和盖体(7)基本上是平面的、基本上平行地叠置并形成圆柱体的面部,外壁(8)将底部(6)和盖体(7)的周边接合并且形成圆柱体的母线,盖体(7)和外壁(8)一起被形成为单件,偏转器(9)是将底部(6)和盖体(7)基本上垂直地接合的内壁,并且底部(6)和偏转器(9)一起被形成为单件。(The invention relates to a mixer (1) for mixing an exhaust gas and a reducing agent, comprising: a closed and sealed housing (2) except for an inlet (3) and an outlet (4), in which housing the exhaust gases flow from the inlet (3) to the outlet (4); and a reductant injector (5) arranged to enable reductant to be injected into the exhaust gas stream, the tank (2) being substantially cylindrical in shape, having a base (6), a cover (7), an outer wall (8) and a deflector (9), the base (6) and the cover (7) being substantially planar, superimposed substantially parallel and forming a face of the cylinder, the outer wall (8) joining the peripheries of the base (6) and the cover (7) and forming a generatrix of the cylinder, the cover (7) and the outer wall (8) being formed together as a single piece, the deflector (9) being an inner wall joining the base (6) and the cover (7) substantially perpendicularly, and the base (6) and the deflector (9) being formed together as a single piece.)

1. A mixer (1) for mixing an exhaust gas and a reducing agent, comprising: a closed and sealed housing (2) except for an inlet (3) and an outlet (4), in which housing exhaust gases flow from the inlet (3) to the outlet (4); and a reductant injector (5) arranged to enable reductant to be injected into the exhaust gas stream, the tank (2) being in the shape of a cylinder having a base (6), a cover (7), an outer wall (8) and a deflector (9), the base (6) and the cover (7) being substantially planar, superimposed substantially parallel and forming a face of the cylinder, the outer wall (8) joining a periphery of the base (6) and a periphery of the cover (7) and forming a generatrix of the cylinder, the cover (7) and the outer wall (8) being formed together as a single piece, the deflector (9) being an inner wall joining the base (6) and the cover (7) substantially perpendicularly, characterised in that the base (6) and the deflector (9) are formed together as a single piece.

2. The mixer (1) according to claim 1, characterized in that the inlet (3) is formed in the outer wall (8) and the outlet (4) is formed in the bottom (6).

3. The mixer (1) according to claim 1, characterized in that the reducing agent injector (5) is arranged in the outer wall (8).

4. A mixer (1) according to claim 1, wherein the reductant injector (5) and the inlet (3) are provided in a common duct in the outer wall (8).

5. Mixer (1) according to claim 1, characterized in that the lower junction (10) between the deflector (9) and the bottom (6) has a chamfer with a radius at least equal to 2 mm.

6. The mixer (1) according to claim 1, characterized in that said deflector (9) has a substantially rectilinear or substantially "U" -shaped section along a plane parallel to said base (6) and to said cover (7).

7. Mixer (1) according to claim 6, characterized in that said cross-section of the deflector is "U" -shaped, said deflector (9) further comprising a top (11) connecting in a sealed manner the two branches of the "U" -shape by means of a plate substantially parallel to the cover (7).

8. Mixer (1) according to claim 7, characterized by the fact that at least one part of the surface of the top (11) is shaped to abut against the cover (7).

9. The mixer of claim 8, wherein the portion of the surface is proximate the inlet.

10. The mixer of claim 8, wherein the portion of the surface extends over the entire surface.

11. Mixer (1) according to claim 7 or 8, characterized in that the top (11) is formed in one piece with the deflector (9) and wherein the upper junction (12) between the deflector (9) and the top (11) has a rounded corner with a radius at least equal to 2 mm.

12. An exhaust pipe, characterized in that it comprises at least one mixer (1) according to claim 1.

13. A motor vehicle, characterized in that it comprises an exhaust pipe according to claim 12.

Technical Field

The present invention relates to the field of reducing mixers for exhaust gases. Such a mixer is usually arranged in the exhaust pipe of an internal combustion engine. The function of which is to mix a reducing fluid (usually aqueous urea: AdBlue, DEF) with the exhaust gases, in preparation for treating the mixture by means of a selective catalytic reduction agent (SCR) for reducing nitrogen oxides.

Background

Different configurations for constructing such mixers are known. In one possible embodiment, the mixer comprises a closed and sealed tank, except for the inlet and the outlet. Exhaust gas flows through the housing from the inlet to the outlet. The mixer also includes an injector configured to inject a reductant into the tank such that the injected reductant mixes with exhaust gas flowing through the tank.

It is also known to inject the reducing agent into the gas stream as long as possible in order to optimize the mixing of the reducing agent with the exhaust gas, in order to increase the common cycle time of the two components and thus improve the mixing. For this purpose, although the space available in the engine and/or the exhaust chamber is generally limited, it is known to use a deflector which is arranged in the tank and is capable of deflecting the exhaust gas flow so as to create as long a circulation path as possible in the limited volume allocated to the mixer.

According to one embodiment, the tank has a substantially cylindrical shape. The faces of the cylinders form the bottom of the mixer and its cover, respectively. The faces are substantially planar, have the same shape, and are stacked in a substantially parallel manner. The generatrix of the cylinder forms an outer wall that joins the perimeter of the base and cover substantially perpendicular to the base and cover.

It is also known to form the cover body as a single piece with the wall. This can be achieved by stamping a single piece, ensuring the function of the wall and at the same time the function of the cover.

As is known, the deflector may be an internal wall provided in the tank, which joins the base and the cover substantially perpendicularly inside the perimeter of the base and the cover.

Due to the high temperatures caused by the exhaust gases, the mixer and all its components are usually made of metallic materials. Due to this temperature, the main way of joining the different parts is welding.

To ensure a gas-tight seal, welded assemblies are possible. It is simple to perform the welding on the outside of the tank. Furthermore, sealing to the outside of the case can be achieved.

However, welding the components inside the case, particularly the deflector assembly and the cover, may be difficult. This may compromise the internal tightness. If a leak should occur, the exhaust gas will have a short cut and be able to flow more quickly between the inlet and the outlet. This may cause the exhaust gas to contact the reducing agent and destroy the function of the mixer.

An alternative to welding for achieving sealing is to bring two parts to be sealed into contact/support with each other between them. This requires precise manufacturing tolerances.

With punching, forming and stamping techniques, it is difficult to obtain precise tolerances. Due to dimensional deviations, it is difficult to achieve sealing by simple contact between the two parts. Furthermore, if welding is used, it may cause deformation of the parts, which in turn affects the contact between the two parts and thus the tightness.

In addition, other modes are sought to ensure sealability primarily at the deflector, at its lower interface with the base, and at its upper interface with the cover.

Disclosure of Invention

To this end, the object of the invention is a mixer for mixing an exhaust gas and a reducing agent, comprising: a closed and sealed tank in which exhaust gas flows from the inlet to the outlet, except for the inlet and the outlet; and a reductant injector arranged to enable reductant to be injected into the exhaust gas stream, the tank being substantially cylindrical in shape having a base, a cover, an outer wall and a deflector, the base and cover being substantially planar, stacked substantially parallel and forming a face of the cylinder, the outer wall joining the peripheries of the base and cover and forming a generatrix of the cylinder, the cover and outer wall being formed together as a single piece, the deflector being an inner wall joining the base and cover substantially perpendicularly, wherein the base and deflector are formed together as a single piece.

Specific features or embodiments that may be used alone or in combination are:

-the inlet is provided in the outer wall and the outlet is provided on the bottom;

-the injector is arranged in the outer wall;

the ejector and the inlet are arranged in a common duct in the outer wall;

the lower junction between the deflector and the bottom has a chamfer with a radius of at least 2mm, preferably at least 10mm, more preferably at least 20 mm;

the deflector has a substantially rectilinear or substantially U-shaped cross-section in a plane parallel to the base and the cover;

the deflector of the "U" shape also comprises a top portion connecting in a sealed manner the two branches of the "U" shape by means of a plate substantially parallel to the cover;

at least a portion of the top surface, preferably a portion close to the inlet or preferably the entire surface is shaped to be in contact with the cover;

the top part is formed in one piece from the same material together with the deflector, and the radius of the upper joint between the deflector and the top part is at least 2mm, preferably at least 10mm, more preferably at least 20 mm.

In a second aspect of the invention, an exhaust pipe comprises at least one mixer as described above.

In a third aspect of the invention, a motor vehicle includes the exhaust pipe described above.

Drawings

The invention will be better understood from the following description, made by way of example only, with reference to the accompanying drawings, in which:

fig. 1 shows a mixer according to a first embodiment in a perspective view, with the cover cut away;

FIG. 2 shows the mixer of FIG. 1, the entire cap, in a perspective view;

FIG. 3 shows the mixer of FIG. 1 in an exploded perspective view;

fig. 4 shows a mixer according to another embodiment in a perspective view with the cover and the wall removed;

fig. 5 shows the mixer of fig. 4 in perspective view with the cover and the wall in place.

Detailed Description

The mixer 1 is designed to mix the exhaust gases and the reducing fluid in preparation for a catalytic reaction for reducing nitrogen oxides NOx, in order to purify the exhaust gases.

To this end, with reference to fig. 3, which shows a first embodiment together with fig. 1 and 2, the mixer 1 comprises a tank 2 and a reducing agent injector 5. The tank 2 is closed and sealed except for the inlet 3 and the outlet 4. Between the inlet 3 and the outlet 4 a duct is arranged which circulates the exhaust gases from the inlet 3 to the outlet 4. The reductant injector 5 is typically disposed through the housing of the tank 2 so that reductant can be injected into the exhaust gas stream within the tank 2 to effect mixing.

According to one embodiment, the tank 2 has a substantially cylindrical shape. A substantially cylindrical body is understood to be a generalized cylindrical body shape obtained by translating a basic shape (which may be any shape) substantially parallel to itself. Such a generalized cylinder comprises a substantially planar first face 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 generation surface.

Furthermore, the box 2 comprises a bottom 6, a cover 7 and an outer wall 8 for the housing. The base 6 and the cover 7 are substantially planar. They are stacked substantially in parallel and form the face of a cylinder. The wall 8 joins the periphery of the base 6 and the cover 7 and forms the generatrix of the cylinder.

In order to reduce the number of parts, the cover 7 and the wall 8 may advantageously be formed together as one single piece. The common portion joining the lid 7 and the wall 8 may be formed by welding between the lid 7 and the wall 8 or by stamping a blank.

Inside the tank 2 there is also a deflector 9, the purpose of which is to expand the exhaust gas passage as much as possible to increase the contact time with the reducing agent and thus improve the mixing both in quantity and quality.

For example, the deflector 9 is an inner wall that engages the base 6 and the cover 7 substantially vertically. The shape of the deflector 9 is such that it forms a deflector opposing the direct path of the exhaust gas from the inlet 3 to the outlet 4. Which is substantially parallel to the outer wall 8.

It is appropriate to assemble all these parts together, ensuring a hermetic seal if necessary. The tank 2 can be closed by welding the periphery of the bottom 6 to the lower edge of the facing wall 8.

The difficulty comes from the deflector 9. Which may advantageously be welded to one of the faces of the base 8 and the cover 7. But the welding of the other side is more complicated, since the area to be welded is necessarily inside the tank 2 and is therefore difficult to access. An alternative to the difficult welding of the deflector 9 on the other of the base 8 and the cover 7 is to make contact, preferably by bracing, to ensure sealing. However, welding the deflector 9 to the first side typically causes the deflector 9 to deform. The dimensional deviations thus produced prevent contact by the support on the other side and therefore do not guarantee sealing.

Furthermore, the assembly of the deflector 9 with the bottom 6 is not performed by welding. According to a feature of the invention, the bottom 6 and the deflector 9 are formed together in one single piece. This enables a manufacturing method that produces much smaller dimensional deviations. In this way, the tightness between the deflector 9 and the cover 7 can be ensured by a simple supporting contact. This contact between the deflector 9 and the cover 7 may result in a slight leakage. This leakage is much less than the main flow rate, typically less than 1%. It is also observed that the reducing agent flows out of the reducing agent injector 5 by capillary action. Although more complicated, it is also possible here to weld the cover 7 to the upper edge of the deflector 9 by means of the cover 7, for example by means of transparency.

Advantageously, the common portion joining the deflector 9 and the bottom 6 can be formed by stamping.

According to another feature, the inlet 3 is provided at the edge of the tank 2, i.e. in the wall 8. This can be seen in particular in fig. 1, 2 and 5. The injector 5 is preferably arranged to inject in the exhaust gas flow in a region where the exhaust gas flow has as long a straight portion as possible in order to improve the quality of the mixture. Using as long a straight portion as possible also has the advantage that no spraying is performed against the opposite wall surface. This promotes evaporation of the reducing fluid into the exhaust gas volume before it comes into contact with the walls. This is particularly important for urea-based reducing fluids that produce parasitic deposition reactions that may solidify on the walls. Such deposition is thus minimized.

Furthermore, the injector 5 is advantageously arranged in the wall 8. Advantageously, the ejector 5 is arranged directly on the inlet duct.

According to another feature, the outlet 4 is provided on one of the sides, for example on the bottom 6.

According to another feature, the lower junction 10 between the deflector 9 and the bottom 6 has a chamfer. The radius of the chamfer is at least equal to 2mm, preferably at least equal to 10mm, more preferably at least equal to 20 mm. This feature facilitates the formation of a common part joining the bottom and the wall 8, since the chamfer facilitates the stamping, since it reduces the force to be applied and reduces the risk of breakage due to strain hardening.

According to another feature, the deflector 9 has a substantially rectilinear section in a plane parallel to the base 6 and to the cover 7. This is illustrated in the embodiments shown in fig. 4 and 5.

According to another feature, the deflector 9 has a substantially "U" shaped section according to a plane parallel to the base 6 and to the cover 7. This is illustrated in the embodiment shown in fig. 1 to 3. Such a U-shape may form a spiral to lengthen the path of the exhaust gas, thereby improving mixing of the reducing agent with the exhaust gas.

According to another feature, visible in particular in fig. 3, in the case of the deflector 9 of the "U" shape, a top 11 can be added which connects the two branches of the "U" in a sealed manner. The top 11 is a metal plate substantially parallel to the cover 7. The top portion 11 forms a surface that contacts the cover 7 and thus provides a better seal than a straight line contact. The contact surface between the top 11 and the cover 7 is advantageously the entire surface of the top 11. If the contact surface is local, a region near the inlet 3 is preferred. This feature may prevent leakage that may cause gas to bypass the deflector 9 (i.e. as close as possible to the inlet 3) as quickly as possible. With the aid of the tight adjustment made during assembly, the contact is achieved with the support. Furthermore, if the seal is imperfect and causes a leak, such a leak occurs between one branch and the other of the U-shape and is not directly associated with the outlet 4. There may be a slight leakage as with the straight line contact between the upper edge of the deflector 9 and the cover 7. Due to the contact surfaces, such leakage is still reduced with respect to a straight line contact. It is also observed that the reducing agent flows out of the injector 5 by capillary action. As already mentioned, it is also possible here, although more complicated, to weld the cover 7 with the top 11 along a straight line or on a contact surface by means of the cover 7, for example by means of transparency.

According to another feature, the top 11 is formed in a single piece with the deflector 9, from the same material. This feature advantageously allows the common portion joining the top 11 and the deflector 9 and thus the bottom 6 to be formed, for example by stamping.

As noted above, the stamped embodiments benefit from a smooth shape with a particular radius rather than a sharp edge. Furthermore, according to another feature, advantageously, the upper junction 12 between the deflector 9 and the top 11 has rounded corners. The radius of the fillet is at least equal to 2mm, preferably at least equal to 10mm, more preferably at least equal to 20 mm.

As shown in fig. 3, two vanes 13, 14 may be provided in the outlet 4 to direct the mixture of exhaust gas and reductant towards the inlet 16 of the subsequent element 17, typically an SCR catalyst. The portion 15 provides an interface with the subsequent element 17.

The circular lower junction 10 between the deflector 9 and the bottom 6 can also be used to direct the mixture of exhaust gas and reducing agent to the inlet 16 of the subsequent element 17.

The invention also relates to an exhaust pipe comprising at least one mixer 1 as described above.

The invention also relates to a motor vehicle comprising an exhaust pipe as described above.

The invention has been illustrated and described in detail in the drawings and foregoing description. The latter should be considered illustrative and given as an example and should not be considered as limiting the invention to this description only. Many alternative embodiments are possible.

List of reference numerals

1: mixing device

2: box body

3: inlet port

4: an outlet

5: ejector

6: bottom part

7: cover body

8: wall(s)

9: deflection device

10: bottom joint

11: top part

12: upper joint part

13. 14: blade

15: interface surface

16: inlet of subsequent element

17: subsequent component