FR3048450A1 - CATALYTIC POST-PROCESSING DEVICE OF A MOTOR VEHICLE HAVING A DEFLECTOR - Google Patents

Abstract

The invention proposes a motor vehicle combustion engine exhaust after-treatment device (10) comprising an enclosure delimited by a tubular wall defining an internal tubular chamber, a deflector element (16) arranged inside. of the enclosure, substantially in the center of the tubular chamber, at least two arms (36) for fixing the deflector element (16), each of which is of generally radial orientation and has an inner radial end (38) attached to the deflector element (16) and an outer radial end (40) fixed to the concave inner face (30) of the tubular wall, characterized in that it comprises at least one deformable fixing arm (36) whose length is greater than at the radial distance (DR) separating its inner radial end (38) from the concave inner face (30) of the tubular wall.

Description

"Cataiytic after-treatment device for an automobile vehicle with a deflector"

TECHNICAL FIELD OF THE INVENTION The invention relates to a catalytic after-treatment device for a motor vehicle.

STATE OF THE ART

A catalytic aftertreatment device for a motor vehicle, commonly called a catalytic converter, is connected to the exhaust outlet of a heat engine in order to receive the exhaust gases thereof and to treat them by catalytic oxidation in order to transform pollutants in water, nitrogen and carbon dioxide.

A catalytic converter operates in a wide range of temperatures up to high values, of the order of 700 ° C to 800 ° C.

These high operating temperatures and the vibrations of the vehicle strongly affect the structure of the catalytic converter and its components.

In general, a catalytic converter comprises a metal casing, usually designated by the English word "canning", defining an internal chamber in which is housed a catalytic block, for example in the form of a monolith, containing the catalyst. The inner chamber is substantially tubular and may have a circular or elliptical base.

The exhaust gases enter the catalytic converter through an inlet at an axial end and are conducted to the catalytic block, for example to the monolith, by a flared portion which forms an inlet cone. This entry cone is generally a separate part of the envelope and partially covers one end of the envelope, to which it is fixed by means of a clamp.

In order to improve the distribution of the exhaust gases from the inlet cone to the catalytic block, especially when the distance between the inlet of the catalytic converter and the catalytic block is short, there is generally a deflector inside the entrance cone, in a central area thereof.

This deflector is usually generally conical or frustoconical, of dimensions smaller than those of the entry cone, and it is for example fixed to the entry cone by radial fixing and centering arms - made in the form of strips of rectilinear plates which extend in an axial plane-whose inner radial ends are welded directly to the inlet cone and whose outer radial ends are welded directly to the concave inner face of the wall of the enclosure.

The various components of the catalytic converter are generally made of stainless steel, resistant to temperatures and conditions of use.

An exemplary design of such a device is for example illustrated in WO-A2-2005 / 094253.

Due to the high temperatures mentioned above, these materials are subjected to significant expansions which can lead to permanent deformations and cracks on the deflector fixed by welding, and buckling phenomena of the fixing arms.

There is therefore a need for an arrangement of a baffle inside an inlet cone which is more resistant to severe use conditions of a post-treatment device, and in particular to expansion phenomena. and in particular of differential expansion (s). For this purpose, in WO-A1-201 5/1 10738, a solution was proposed to modify the connection of the outer radial ends of the attachment arms with the enclosure in order to offer a capacity for absorbing variations. dimensions at these links.

The present invention aims at proposing another solution making it possible in particular to preserve the industrial techniques of fixing and assembling by welding the radial ends of the fixing arms.

BRIEF SUMMARY OF THE INVENTION

For this purpose, the invention proposes an aftertreatment device for motor vehicle combustion engine exhaust gas comprising: an enclosure delimited by a tubular wall defining an internal tubular chamber; a deflector element arranged inside the enclosure, substantially in the center of the tubular chamber; at least two attachment arms of the deflector element, each of which is of generally radial orientation and has an inner radial end fixed to the deflector element and an outer radial end attached to the inner face of the tubular wall, characterized in that it comprises at least one deformable fixing arm whose total length is greater than the radial distance separating its radial inner end from the concave inner face of the tubular wall, so as to have a deformation capacity to absorb the dimensional variations due to dilation.

According to other characteristics of the invention: each fixing arm is a deformable fixing arm whose length is greater than the radial distance separating its radial inner end from the internal face of the tubular wall; each deformable fixing arm comprises at least one curved section; the curved section is an arcuate section; each deformable fixing arm is a curved arm in an arc of a circle; each fixing arm is a sheet metal strip extending generally in an axial plane; the device comprises three fastening arms distributed angularly in a regular manner; the two radial ends of each fixing arm are aligned axially; the enclosure comprises a tubular casing intended to house a catalytic block and an inlet front cone of which a rear axial end tubular section is attached to a front axial end section of the casing; - The outer radial end of each attachment arm is fixed to the inner face of the tubular rear axial end section of the cone.

BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: FIG. 1 is an axial sectional view, along the line 1-1 of Figure 2 which shows a catalytic post-treatment device according to an embodiment of the invention; FIG. 2 is a cross-sectional view along line 2-2 of FIG. 1; and FIG. 3 is an enlarged detail view of part of FIG. 2.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 shows a device 10 for catalytic post-treatment, in particular for treating the exhaust gas of a motor vehicle combustion engine.

The device 10 consists essentially of an enclosure 12 of generally circular shape around a main axis A of generally tubular shape with circular section. The chamber 12 defines an internal tubular chamber 14 inside which are arranged in particular a deflector element 16 and a catalytic treatment block 18, also called monolith containing an oxidation catalyst. The tubular enclosure 12 comprises in particular a central tubular casing 20 in which is housed the catalytic block 18 and an inlet front cone 22.

Considering the flow direction of the flow F of the exhaust gas inside the device 10, the cone 22 comprises a front tubular section 24 inlet, a frustoconical intermediate section 26 and a rear axial end tubular section 28 .

According to the embodiment illustrated in the figures, and without limitation, the baffle element 16 is here arranged axially in the chamber 12 inside the rear axial tubular end portion 28 of the cone 22. The axial arrangement of the deflector element 16 inside the front cone 22 and its attachment to the latter has the advantage of allowing the production and manufacture of a subassembly incorporating the deflector element 16 which can then be fixed on the envelope 12.

The rear section 28 of the cone 22 is delimited internally by a concave tubular inner face 30.

In known manner, the rear section 28 of the cone 22 is fixed on a front axial end section 32 of the tubular envelope 20. The tubular envelope 20 is delimited internally by a concave inner face 34.

In the usual and known manner, all the components of the enclosure 10 are preferably made of stainless steel. The deflector element 16 is here a generally frustoconical element whose convexity is oriented towards the front and which is delimited by a frustoconical outer face 36. The deflector element 16 is arranged inside the enclosure 12 substantially in the center of the tubular chamber 14, that is to say that it is centered on the general axis A of the device 10.

In known manner, the deflector element 16 is positioned and fixed inside the chamber 14 by means of several fixing arms 36 which, in a non-limiting manner, are three in number and which are angularly distributed in a regular manner, at 120 degrees of angle around the axis A, as can be seen in Figure 2.

According to this generally symmetrical design, the identical constitution of the three attachment arms 36 and their uniform angular distribution is intended in particular to keep the deflector element 16 in its radial position centered on the axis A which is also the central axis of the flow F of the exhaust gas entering the device 10.

Each fixing arm 36 is constituted by a sheet metal strip, preferably made of stainless steel, which extends in an axial plane of the device 10.

In known manner, each of the two ends of a fixing arm 36 is fixed by welding to the deflector element 16 and to the tubular wall of the enclosure 12.

More specifically, an inner radial end 38 of each attachment arm 36 is fixed by welding to the outer convex frustoconical face 35 of the deflector element 16, while its outer radial end 40 is also fixed by welding to the concave inner face of the the tubular wall of the casing 12, and more specifically to the inner face 30 of the rear axial end portion 28 of the front cone 22 of the device 10.

In order to facilitate welding assembly and fixing operations, the outer radial end 40 of each arm 36 is extended by a tab 41 folded substantially at a right angle which matches the profile of the internal face 30.

As can be seen in particular in Figure 2, the two inner radial ends 38 and outer 40 of attachment of each attachment arm 36 are here aligned in the same radius.

As can be seen in FIG. 1, these two radial inner 38 and outer 40 ends of each attachment arm 36 are also axially aligned, that is to say that they lie generally in the same radial plane corresponding to line 2-2 of Figure 1.

In contrast to the known prior art designs according to which each fastening arm is a straight flat strip extending along a radius, and in accordance with the teachings of the invention, the total length of each fastening arm, measured between its radial fixing ends 38 and 40 is greater than the radial distance "DR", as indicated in Figure 2, separating the two radial ends of internal fixation 38 and internal 40. For this purpose, and not limited to , almost the entire length of the fixing arm 36 extending between its radial ends 38 and 40 is shaped as a curved arcuate arm, that is to say constituted by a curved section 44.

The total length of each attachment arm 36 greater than the radial distance DR, here obtained with the aid of at least one curved or curved section 44, is intended to enable the deformations due to the expansion phenomena to be absorbed, in particular according to the radial direction by allowing, as is illustrated in detail in Figure 3, a deformation of the curved or curved section 44 in a lateral direction generally orthogonal to a radius.

FIG. 3 shows, in solid lines, the device 10 in its cold conformation and dimensions, and the dotted line shows the same elements in their expanded and possibly "hot" deformed state, that is, say during use of the after-treatment device in operation of the combustion engine that team with the same references indexed "prime".

Considering the value RI of the mean outer radius of the deflector element 16 and the outer radius R2 of the rear end portion 28 of the cone 22, the dimensional elements and expansion values are, by way of example, the following:

Calculation of dilations and dimensional variations:

For the deflector element 16: RI = 14.34 mm Temperature = 850 ° C Coefficient of expansion of the steel = 12.10-6 Dilatation = 0.14 mm

For the front cone 22: R2 = 72.75 mm Temperature = 600 ° C Coefficient of expansion of the steel = 12.10-6 Dilation = 0.52 mm The thickness of the plates of the fixing arms is for example of the order of 1 to 1 , 5 mm.

The design of the attachment arms 36 according to the invention makes it possible, by their lateral deformation, to absorb the expansions during temperature variations without causing damage, or of the deflector element 16, or of the attachment arms 36 themselves, while allowing the fixing arms 36 to substantially recover their initial form cold. The invention is not limited to the embodiment which has just been described which is given by way of non-limiting example.

First, the number of attachment arms can vary significantly by having at least two attachment arms. The deflector element 16 can be arranged axially inside the casing 20, its fixing arms 36 then being fixed by their external radial ends 40 to the concave inner tubular face 34 of the casing 20.

Nor is it necessary for each of the attachment arms 36 to be made in accordance with the teachings of the invention and it may be sufficient for only one of the attachment arms 36 to have, for example, a curved curved section giving it the capacity to absorption of dilations by deformation.

Claims (10)

1. Aftertreatment device (10) of motor vehicle combustion engine exhaust gas comprising: - an enclosure (12) defined by a tubular wall defining an inner tubular chamber (14); a deflector element (16) arranged inside the enclosure (12), substantially in the center of the tubular chamber; at least two arms (36) for fixing the deflector element (16), each of which is of generally radial orientation and has an inner radial end (38) fixed to the deflector element (16) and an outer radial end ( 40) fixed to the concave inner face (30) of the tubular wall, characterized in that it comprises at least one deformable fixing arm (36) whose length is greater than the radial distance (DR) separating its internal radial end (38) of the concave inner face (30) of the tubular wall. 2. post-processing device (10) according to claim 1, characterized in that each fixing arm (36) is a deformable fixing arm whose length is greater than the radial distance (DR) separating its internal radial end ( 38) of the inner face (30) of the tubular wall. 3. post-processing device (10) according to claim 1, characterized in that each deformable fixing arm (36) comprises at least one curved section (44). 4. post-processing device (10) according to claim 3, characterized in that the curved section (44) is an arcuate section. 5. post-processing device (10) according to claim 4, characterized in that each deformable fixing arm is a curved arm in a circular arc. 6. post-processing device (10) according to any one of the preceding claims, characterized in that each fixing arm (36) is a sheet metal strip which extends generally in an axial plane. 7. post-processing device (10) according to any one of the preceding claims, characterized in that it comprises three fastening arms (36) distributed angularly in a regular manner. 8. post-processing device (10) according to any one of the preceding claims, characterized in that the two radial ends (38, 40) of each fixing arm (36) are axially aligned. 9. post-treatment device (10) according to any one of the preceding claims, characterized in that the enclosure (12) comprises a tubular casing (20) for accommodating a catalytic block (18) and a cone before d an inlet (22) having a rear axial end tubular section (28) attached to a front axial end section (32) of the housing (20). 10. post-treatment device (10) according to claim 9, characterized in that the outer radial end (40) of each attachment arm (38) is fixed to the inner face (30) of said tubular end section. rear axial (28).