EP0953741A1 - Catalytic converter and acoustic treatment apparatus of a dual flow exhaust line - Google Patents

Abstract

The device comprises a single metal housing (8), fed by two exhaust pipes (17a,17b), containing two catalytic converter units (14a,14b) and two silencers (15'a,15'b), positioned alternately so that each silencer lies alongside one converter and end to end with the other. The converters and silencers are held in place inside the housing by supports (13a,13b,16a,16b) and are fitted with guides (18a,19b,20a,20b) for the gas flows.

Description

The invention relates to a catalytic converter and acoustic treatment a double flow exhaust line.

To improve the performance of internal combustion engines motor vehicles, we tried to favor filling at admission and the exhaust emptying of the engine cylinders by acoustic effects, or at least to limit the unfavorable effects on performances, of a transmission of a pressure wave to the exhaust, between the engine cylinders.

For this, it has been proposed to connect the pipes together. cylinder exhaust, in a specific configuration, for lead into two separate conduits which are themselves joined in only one conduit after a certain route. For example, in the case of four-cylinder engines, pipes can be connected together exhaust cylinders 1 and 3 on the one hand and 2 and 4 on the other. In the in the case of six-cylinder V-shaped engines, it has been proposed to connect them the tubing of the cylinders of each of the cylinder lines.

Such exhaust lines have two exhaust ducts which run in parallel over a length which should generally be as large as possible and are called dual exhaust lines flux.

In addition, the exhaust systems of motor vehicles must include exhaust gas cleaning devices such as catalytic converters and sound treatment devices for gases such as mufflers, to reduce exhaust noise, or such than interference devices, to improve engine performance.

The exhaust lines of internal combustion engines can therefore have a complex structure and a large size, particularly in the case of double flow lines. It is therefore necessary to provide under the vehicle floor, a space extending in the direction longitudinal of the vehicle, called tunnel, in which the conduits are housed and the active components of the exhaust system. Because it takes provide a ground clearance of the motor vehicle greater than a certain fixed limit, the tunnel can be projecting over a relatively high important inside the passenger compartment of the motor vehicle.

It is desirable, especially in the case of high vehicles range, to have the flattest floor possible, to improve comfort passengers, especially at the rear of the vehicle. It is therefore desirable to remove the tunnel or at least reduce the height as much as possible of the projecting part of the floor delimiting the tunnel.

In the case of dual-flow exhaust systems, in particular, there components need to be kept as small as possible of the exhaust line, while preserving the performance of the line exhaust regarding the elimination of pollutants and acoustic treatments exhaust gases and ensuring good protection of these components.

The object of the invention is therefore to propose a catalytic converter and acoustic treatment of an exhaust line with two parallel conduits ensuring the arrival at the catalytic converter of a first and a second flow of gas from an internal combustion engine which is the most compact possible and which ensures effective catalytic and acoustic treatment of gas as well as protection of the components of the exhaust line.

For this purpose, the following catalytic converter and acoustic treatment the invention comprises, inside a first section of a metal casing outside of the catalytic converter, between an inlet end of the envelope and a central zone, a first catalyst and a first muffler and, in a second section of the envelope, between the middle zone and a casing outlet end, a second catalyst and a second muffler, as well as means for holding catalysts and mufflers in the metal casing and means for channeling the flows gaseous connected to catalysts, silencers and exhaust pipes, so as to impose on the first gas flow a circulation path inside the envelope successively crossing the first catalyst and the second silencer and the second gas flow, a course of circulation successively passing through the first silencer and the second catalyst.

In order to clearly understand the invention, we will describe as example, with reference to the attached figures, an embodiment a catalytic converter and acoustic treatment for a line dual flow exhaust according to the invention.

Figure 1 is a perspective view of part of the line dual flow exhaust including catalytic converter and treatment acoustic.

FIG. 2 is an exploded perspective view of the catalytic converter and acoustic treatment according to a first embodiment.

FIG. 3 is a view in longitudinal section of the catalytic converter and acoustic treatment according to a second embodiment.

Figure 4 is a perspective view of an end cover of the pot shown in one of Figures 2 and 3.

Figure 5 is a perspective view of a holding cup a catalyst and a silencer in the envelope of the pot and guiding gas flow.

Figure 6 is a perspective view of a cup constituting a partition of the first and second sections of the catalytic converter.

In Figure 1, we see part of a double exhaust line flow of a motor vehicle generally designated by the reference 1.

The dual-flow exhaust line, or twin-tube line, includes two conduits 2a, 2b, connected at one of their ends (in the direction of the arrow 3) to the exhaust pipes of an internal combustion engine. For example, each of the conduits 2a and 2b can be connected to three pipes exhaust of three cylinders from a cylinder line of an engine V6.

The exhaust line 1 further comprises a catalytic converter and acoustic treatment according to the invention, designated by the reference 4. The conduits exhaust 2a and 2b lead into an inlet portion of the pot 4. Des exhaust ducts 5a and 5b connected to the outlet of the pot 4 run at parallel to a fitting 6 allowing the flows transported by the two conduits 5a and 5b in the form of a single flow opening into a terminal part 7 of the exhaust line.

The length of the part of the dual flow exhaust line between the engine manifolds and the fitting 6 is determined, taking into account the characteristics of pot 4, to optimize the acoustic behavior of gases exhaust and engine performance.

The pot 4 according to the invention comprises a metallic external envelope 8 of generally cylindrical shape closed at its ends by a first cup 8a closing the inlet part of the casing 8 and by a second cup 8b closing the outlet part of the envelope 8. The cups 8a and 8b are crimped onto the end parts of the cylindrical casing 8.

The two inlet conduits 2a and 2b pass through the cup 8a to lead to the inside of the pot 4, by means of tips 9a and 9b of cylindrical or cylindrical-frustoconical shape projecting outwards from the cup 8a. Similarly, the conduits 5a and 5b open into the volume internal of the pot 4, by means of tips 10a and 10b of cylindro-frustoconical shape projecting outwards from the cup 8b.

In FIGS. 2 and 3, which represent the pot 4 according to the invention, in a first embodiment and in a second embodiment, respectively, the corresponding elements have been designated by the same references.

In both embodiments, the outer casing 8 of the pot is constituted by a cylindrical steel ferrule closed at its ends by an inlet cup 8a and an outlet cup 8b.

The internal volume of the envelope 8 of the pot 4 is divided into a first section 11a and in a second section 11b, by a partition 12 constituted by a cup fixed inside the envelope 8, in an inclined arrangement at an angle other than 90 °, relative to the longitudinal axis of the pot 4.

The section 11a disposed on the side of the inlet of the pot 4 is between the inlet cup 8a and the inclined cup 12. The second section or section outlet 11b is between the inclined cup 12 and the cup exit 8b.

Inside the inlet section 11a of the pot 4 are arranged a first catalyst 14a and a first silencer 15a (in the case of the first embodiment shown in Figure 2) or 15'a (in the case of the second embodiment shown in Figure 3). Indeed, the two modes of making the pot 4 differ only in the making of the silencers, as will be explained later.

The second section 11b, or outlet section of the pot 4, contains a second catalyst 14b and a second silencer 15b (in the case of the first embodiment shown in Figure 2) or 15'b (in the case of the second embodiment shown in Figure 3).

The first section 11a and the second section 11b of the catalytic converter are identical with regard to the mounting of the silencers and catalysts in envelope 8 and are placed in the extension of one another, in a reverse layout.

Catalysts 14a and 14b and silencers 15a and 15b or 15'a and 15'b are held inside the casing 8, by respective cups 13a and 13b at their ends near the inlet end and the outlet end of the pot 4, respectively.

Catalysts 14a and 14b and silencers 15a and 15b or 15'a and 15'b are also held in the casing 8, at their opposite ends at the inlet or outlet of pot 4, respectively, by spacers respective which may be constituted by cups 16a and 16b.

Catalysts 14a and 14b and silencers 15a and 15b or 15'a and 15'b have a generally cylindrical or tubular shape and are arranged inside the casing 8 so that the first catalyst 14a and the second silencer 15b or 15'b are located in the extension one of the other in the longitudinal direction of the pot 4 along which the first circulates exhaust gas flow diagrammed by arrows 17a.

Similarly, the first silencer 15a or 15'a and the second catalyst 14b are arranged in the extension of one another, in the direction longitudinal circulation of the second flow of exhaust gas shown diagrammatically by arrows 17b.

The end cup 8a (or 8b), the entry holding cup 13a (or the outlet holding cup 13b) and the inclined cup 12 constituting the intermediate wall of the pot 4 have been shown respectively in Figures 4, 5 and 6.

We will refer to all of Figures 2, 3, 4, 5 and 6 to describe the different cups of pot 4 as well as their arrangement on pot 4 and their functions.

The cups 8a, 8b, 13a, 13b and 12 can be produced by cutting and stamping of a metal flank or in mechanically welded form, by attaching and fixing by welding to a metal sidewall having a stamped peripheral part, cylindrical shaped tips or cylindrical-frustoconical, according to openings cut in the side metallic.

The cups 8a and 8b have a cylindrical peripheral edge for connection to the casing 8, a cylindrical-frustoconical end piece 9a (or 10b) and a cylindrical end piece 9b (or 10a) which project on the same side of the cup wall.

The cups 13a and 13b have an outer peripheral edge of cylindrical shape for fixing the cup on the inner surface of the casing 8, a cylindrical-frustoconical end piece 18a (or 19b) and a tip cylindrical 18b (or 19a) projecting on either side of the wall of the cup.

As can be seen in Figures 2, 3 and 6, the cup 12 has an elliptical wall and, around its wall, a peripheral edge having the shape of a cylinder section between two planes inclined with respect to to the cylinder axis, through which the cup 12 can be fixed inside the cylindrical casing 8 of the pot 4, in an arrangement inclined relative to the axis of the cylindrical casing 8, at a different angle 90 °.

As can be seen in FIG. 6, the cup 12 has two end caps cylindrical-frustoconical 20a and 20b projecting on either side of the wall of the cup 12.

The cups 16a and 16b serving as spacers for maintaining the catalysts and silencers each have a peripheral edge of attachment to the inner surface of the casing 8, an opening and a nozzle of engagement and maintenance of a catalyst and an opening and a tip for engaging and holding a silencer.

Catalysts 14a and 14b each consist of a catalyst body substantially cylindrical with channels covered with precious metal with catalytic functions and a metal shell cylindrical surrounding the lateral surface of the catalyst body.

One of the end faces of the catalyst body constitutes a face inlet and opposite side an outlet side of the gases passing through the catalyst in its axial direction, as shown by the arrows 17a and 17b.

In the embodiment shown in particular in Figures 3 and 5, the cup 13a or 13b for holding the inlet end or the outlet end of the catalyst 14a or 14b, respectively, has a tapered end piece 18a or 19b which is arranged inside the end piece frustoconical 9a or 10b of the end cup 8a or 8b (with a certain spacing) and which also receives the end of the inlet duct 2a of the first flow line or the outlet conduit 5b of the second line of stream, respectively.

In this way, the first flow 17a of exhaust gas enters in the catalyst 14a by its entry face, being guided by the nozzle frustoconical 18a. The second exhaust gas flow 17b leaves the second catalyst 14b by the outlet face of the catalyst being guided by the frustoconical end 19b of the cup 13b, to reach the conduit 5b outlet which is engaged in the cylindrical end of the nozzle 19b.

In addition, the frustoconical ends 9a and 18a on the one hand and 10b and 19b on the other hand, which are placed one inside the other with a certain spacing, constitute a double wall surrounding the gas inlet or outlet first or second flow exhaust. The double wall thus formed insulates the first flow or the second gas flow exhaust on entering or leaving the catalytic converter 4.

As explained above, the frustoconical tips 18a and 19b of guidance of the exhaust gases at their entry or exit can be made in one piece with the corresponding cups 13a and 13b, in a stamping or independently formed manufacturing process and attached to the cups 13a and 13b at the level of the openings having a diameter substantially equal to the outside diameter of the catalyst. It is also possible to provide end caps 18a and 18b of form frustoconical formed by an end portion of the cylindrical envelope external of catalysts 14a and 14b.

In the case of the first embodiment of the catalytic converter and acoustic treatment shown in FIG. 2, the silencers 15a and 15b consist of a cylindrical body on which is placed in derivation, piping, respectively 21a and 21b opening into the internal space of section 11a or 11b of the casing 8 of the pot 4 which constitutes a volume depreciation. The bypass piping 21a of the silencer 15a is connected to the outlet part of the body of the silencer 15a placed in the first section 11a and the pipe 21b of the silencer 15b is fixed to the part of the main body of the silencer 15b placed in the second section 11b of pot 4. In either case, the volume of acoustic damping consists of the volume of the section 11a (or 11b) formed around the catalyst 14a (or 14b) and the corresponding silencer body 15a (or 15b) which do not fill all the internal space of the first and second sections from pot 4. The silencer constitutes a resonator.

In the case of the second embodiment shown in FIG. 3, the first 15'a muffler and the second 15'b muffler consist of a tubular body whose wall is traversed by a plurality of circular openings 22a (or 22b). The openings 22a or 22b put in communication the internal space of the tubular body of the silencer in which the second circulates or the first exhaust gas flow, with the part of the internal volume of the first section 11a or of the second section 11b of the casing 8 of the pot 4, outside the catalyst 14a (or 14b) and the corresponding silencer. This part of the internal space of the first or second section of the pot 4 constitutes an acoustic damping volume.

The catalysts and the bodies of the silencers are engaged by their end parts respectively opposite to their entry part or to their outlet part, in openings and ends of the holding cups 16a and 16b. In addition, the outlet end portion of the tubular body of the muffler 15'a and the inlet part of the tubular body of the silencer 15'b are engaged and crimped in the respective frustoconical ends 20b and 20a of the cup 12 separating the sections 11a and 11b from the pot 4.

At the outlet of the first catalyst 14a, the exhaust gases from the first gas flow 17a are received in a collector whose volume expansion results from the inclination of the cup 12 and the presence of the frustoconical end piece 20a, then penetrate inside the body of the silencer 15b (or 15'b).

Likewise, the exhaust gases from the second gas flow 17b penetrate, at the outlet of the body of the silencer 15a (or 15'a) in a collector, before entering the second catalyst 14b.

The entry end of the tubular body of the first muffler (15a, 15'a) is engaged directly on the end of the inlet pipe (2b) of the second gas flow (17b) in the pot (4) and the outlet end of the body tubular second silencer (15b, 15'b) is engaged directly on the outlet pipe (5a) of the first gas flow (17a).

The gases of the first flow 17a are guided so as to pass through first the first catalyst 14a then the second silencer 15b (or 15'b). The gases of the second exhaust gas flow 17b pass successively the first silencer 15a (or 15'a) and the second catalyst 14b. Of this way the first exhaust stream undergoes inside the pot 4 a treatment for removing pollutants and an acoustic treatment, following a sequence reversed with respect to the second stream.

In order to improve the conditions for the elimination treatment of pollutants in contact with the catalysts, it may be advantageous to place the pot 4 as close as possible to the exhaust gas outlet pipes of the motor, which can be easily achieved due to the compactness of the pot 4 and also due to the fact that pot 4 is double flow and that at the outlet of pot 4, the exhaust gases are also taken up by two conduits running in parallel. We can therefore move the connector 6 between the parallel conduits output of the desired length to obtain satisfactory acoustic chords which can be identical to those obtained when two lines are used separate exhaust pipes under the vehicle, each with a catalytic converter, a silencer and possibly an interference device. Optimizing acoustic chords allows gain engine torque, in particular in the vicinity of the speeds for which a decrease in the torque is observed, that is to say in the vicinity of 2000 and 3000 rpm.

In addition, the pot 4 according to the invention makes it possible to carry out a treatment very effective attenuation acoustics for exhaust gas flows.

First, as explained above, the entry and exit cones exhaust gas outlet in the catalysts are double walled, this which limits the emission of noise from exhaust gas flows. One can also provide a double wall for the metal casing cylindrical of the catalytic converter, so as to reduce noise emission to outside.

The use of the interior volume of the envelope of pot 4 as volume damping, both in the case where the silencers are made in the form of resonators, as shown in FIG. 2, and in the form of drilled tubes, as shown in Figure 3, allows obtain very good efficiency in terms of acoustic attenuation while limiting the total volume of the components of the exhaust line.

In addition, catalysts 14a and 14b, which are located entirely at inside the metal casing 8 of the pot 4, are protected against thermal shock or corrosive attack that occurs when the metal shell of the catalyst is likely to come into direct contact with the external environment in which the motor vehicle circulates. This therefore increases the strength of the metal casings of the catalysts.

One of the most important advantages of the device according to the invention is the compactness of this device which brings together in a small volume the components required for anti-pollutant treatment and treatment acoustics of exhaust gas flows. In addition, the catalytic converter and acoustic treatment according to the invention can be carried out with a number of stamped and welded parts reduced, compared to an exhaust line classic. This gives a very good price-performance ratio during manufacture of the pot according to the invention. We also get a weight gain of 10 to 15%, for the entire exhaust line, compared to one line classic dual flow exhaust.

The resumption of efforts between the entry and exit of the pot according to the invention is ensured by cups internal to the envelope of the pot. Others cups can be crimped and can allow the pot to expand catalytic in service, in the same way as in an exhaust pipe conventional.

The invention is not limited to the embodiments which have been described.

The end cups and internal cups for holding the catalysts and silencers can be made in a different form.

The silencers can be of any type.

Finally, the catalytic converter and acoustic treatment according to the invention can be used on any type of motor vehicle with a line dual flow exhaust.

Claims (11)

Catalytic converter and acoustic treatment of an exhaust line (1) with two parallel conduits ensuring the arrival at the catalytic converter (4) a first (17a) and a second (17b) gas stream from a internal combustion, characterized in that it comprises, inside a first section (11a) of an external metal casing (8) of the catalytic converter (4), between an inlet end of the envelope (8) and a median zone, a first catalyst (14a) and a first silencer (15a, 15'a) and, in a second section (11b) of the envelope (8), between the middle zone and an outlet end of the casing (8), a second catalyst (14b) and a second silencer (15b, 15'b), as well as means (13a, 16a, 16b, 13b) for maintenance of the catalysts (14a, 14b) and the silencers (15a, 15'a, 15b, 15'b), in the metal casing (8) and means (18a, 19b, 20a, 20b) for channeling gas flows (17a, 17b) connected to the catalysts (14a, 14b), to the silencers (15a, 15'a, 15b, 15'b) and to the exhaust ducts (2a, 2b, 5a, 5b), so as to impose on the first gas flow (17a) a path of circulation inside the envelope (8) successively passing through the first catalyst (14a) and the second silencer (15b, 15'b) and the second flow gas (17b) a circulation path successively crossing the first muffler (15a, 15'a) and the second catalyst (14b). Catalytic converter according to claim 1, characterized in that that the metal casing (8) of cylindrical shape is closed at its ends axial by an inlet cup (8a) and by an outlet cup (8b) having end pieces (9a, 9b, 10a, 10b) for passage of the first stream gas (17a) and the second gas flow (17b). Catalytic converter according to claim 2, characterized in that that the first gas flow (17a) enters the first catalyst (14a) in being guided by a frustoconical tip (18a) placed inside a tip frustoconical (9a) of the inlet cup (8a) of the metal casing (8), with a certain spacing between the frustoconical endpiece (18a) for guiding the first gas flow and the frustoconical tip (9a) of the inlet cup (8a), and that the second gas flow (17b) is guided at the outlet of the second catalyst (14b) by a frustoconical end piece (19b) disposed inside a frustoconical tip (10b) of the outlet cup (8b) with a certain spacing between the frustoconical guide end piece (19b) and the frustoconical end piece (10b) of the outlet cup (8b). Catalytic converter according to claim 3, characterized in that that the frustoconical guide ends (18a) and (19b) of the first and of the second gas flow (17a, 17b) at the inlet and outlet of the catalytic converter (4) are respectively secured to a first cup (13a) for holding the first catalyst (14a) and the first silencer (15a, 15'a) and a second cup (13b) for holding the second catalyst (14b) and the second silent (15b, 15'b). Catalytic converter according to any one of Claims 1 to 4, characterized by the fact that the cylindrical metal casing (8) of the catalytic converter (4) has a double wall. Catalytic converter according to any one of Claims 1 to 5, characterized by the fact that the first section (11a) of the metal casing (8) of the catalytic converter (4) is separated from the second section (11b) by a cup (12) having a wall and a peripheral edge surrounding its wall coming into contact with the inner surface of the metal casing (8) in its middle zone, as well as a first end piece (20a) projecting from one side of the wall of the cup (12) which is connected to the inlet of the second silencer (15b, 15'b) and a second end piece (20b) projecting from a second side of the wall of the cup (12) coming to be connected with the outlet of the second silent (15a, 15'a). Catalytic converter according to claim 6, characterized in that that the cup (12) is placed inside the envelope (8) so its elliptical wall is tilted at an angle other than 90 ° by relative to a longitudinal axis of the metal wall (8) of the pot (4). Catalytic converter according to any one of claims 6 and 7, characterized in that the first end piece (20a) and the second end piece (20b) of the separation cup (12) have a cylindrical-frustoconical shape. Catalytic converter according to any one of Claims 1 to 8, characterized by the fact that the first and second silencers (15a, 15b, 15'a, 15'b) each consist of a tubular body in which the first stream and the second stream of gas respectively, are circulated, and which communicates, through communication means (21a, 21b, 22a, 22b) with part of the volume of the first section (11a) or the second section (11b) of the internal space of the metal casing (8), respectively, which constitutes a depreciation volume, outside the first catalyst and second catalyst and body of first and second silent (15a, 15'a, 15b, 15'b), respectively. Catalytic converter according to claim 9, characterized in that that the means of communication between the first silencer and the second mufflers (15a, 15b) consist of a pipe (21a, 21b) in bypass on the tubular body of the silencer (15a, 15b), opening into the volume of the section (11a, 11b) outside the catalyst (14a, 14b) and the body of the silencer (15a, 15b). Catalytic converter according to claim 9, characterized in that that the means (22a, 22b) for bringing the tubular body of the silencer (15'a, 15'b) with the volume of the section (11a, 11b) of the catalytic converter (4) outside of the first or second catalyst (14a, 14b) are formed by a plurality of circular openings (22a, 22b) passing through the wall of the tubular body of the silencer (15'a, 15'b).

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