EP3039257B1 - Silencer intended to be fitted to an exhaust line of a heat engine - Google Patents

Description

The present invention relates to a silencer intended to equip an exhaust line of a heat engine. The invention also relates to an exhaust line of the type comprising such a silencer, as well as the vehicle that embodies it.

Vehicles powered by a combustion engine, also called internal combustion, have at least one exhaust line of the combustion gases. In order to reduce noise pollution and to meet the rules of acoustic approval of vehicles, the exhaust line comprises in known manner a silencer. It is fixed under the vehicle body and terminates at one of its ends by a discharge pipe, also called cannula, which sometimes slightly exceeds the rear bumper when it comes to vehicles powered solely by a heat engine .

Especially in the case where the vehicle is also powered by a second power unit using an energy other than heat, such as an electric machine (hybrid electric vehicle) or a hydraulic motor (hybrid-air vehicle), or when the heat engine is connected to a compressed air tank (pneumatic hybrid vehicle), or when the heat engine also uses gaseous fuel of the natural gas type, it is necessary to house one or more additional tanks / devices in the vehicle, in particular under the box. We then try to shorten, to compact the exhaust line and bodies of the silent type that it integrates. The line can then be shortened in such a way that the exhaust pipe which terminates it, at the outlet of the silencer, is under the body, at the front of the rear axle of the vehicle, for example at the second row of the vehicle. seats in the passenger compartment of the vehicle. It is ensured that the exhaust gases do not come up in the passenger compartment because, at the standstill, with the hybrid-type vehicles, the engine does not operate and in fact does not emit any gas. exhaust, and that in driving conditions, the speed makes the exhaust gas circulate under the body and evacuate without difficulty towards the rear of the vehicle.

However, shortening and compacting the exhaust line can be tricky, since the design of the exhaust line has an impact on the operation of the heat engine, especially on its filling air / fuel mixture, and that it seems desirable not to have to modify too significantly the control control of the engine according to whether it is the only means of propulsion of the vehicle or not. It is also important to maintain the same type of acoustic reflection for the muffler, especially the portion usually referred to as the intermediate muffler. It is known from the document US5,726,397 a system of three silencers distributed along the length of the exhaust line, including a silencer defining a path of the exhaust gas in return, with a gas inlet at one end of the silencer and a gas evacuation by its opposite end.

The object of the invention is then the development of an improved engine exhaust system silencer. These include designing a muffler more compact, or at least more adaptable dimensionally, while having acoustic performance at least as good. Incidentally, we seek to design a silencer with improved acoustic performance for a shortened exhaust line, compared to the performance of a silencer of a conventional exhaust line, the acoustic source with a shortened exhaust line being closer the ears of the occupants.

• un conduit d'alimentation amenant les gaz d'échappement depuis le moteur dans le volume intermédiaire en traversant le volume amont,
• un conduit de trajet dit « aller » conduisant les gaz d'échappement depuis le volume intermédiaire dans le volume aval,
• un conduit de trajet dit « retour » conduisant les gaz d'échappement depuis le volume aval vers le volume amont en traversant le volume intermédiaire, et
• un conduit d'évacuation conduisant les gaz d'échappement hors du silencieux,
• soit par un trajet dit « aller » depuis le volume amont vers le volume aval d'où il débouche vers l'extérieur,
• soit par un trajet dit « aller-retour » depuis le volume amont vers le volume aval puis à nouveau vers le volume amont d'où il débouche vers l'extérieur.

The invention relates to a silencer intended to equip an exhaust line of a heat engine, and which comprises one or more envelope (s) which delimits (s) three said volumes upstream, intermediate and downstream, arranged successively and traversed by a plurality of conduits, of which:

• a supply duct bringing the exhaust gases from the engine into the intermediate volume through the upstream volume,
• a "go" path line leading the exhaust gases from the intermediate volume to the downstream volume,
• a "return" path line leading the exhaust gases from the downstream volume to the upstream volume through the intermediate volume, and
• an exhaust duct leading the exhaust gases out of the silencer,
• either by a so-called "go" path from the upstream volume to the downstream volume from which it opens outwards,
• either by a so-called "round trip" from the upstream volume to the downstream volume and then back to the upstream volume from which it opens outwards.

Throughout this text, the terms "upstream" and "downstream" are understood by reference to the general direction of flow of the exhaust gases from the exhaust manifold of the engine to the outside of the vehicle. In the same way, "successively" is to be understood according to this direction of general flow. All the present text includes "low", "high" and "vertical" spatial positioning indications such as the indications relating to the positioning of the muffler once mounted in the vehicle, itself positioned at a standstill. horizontal plane.

The silencer according to the invention therefore has the particularity of implanting the acoustic schema of the silencer with at least three separate volumes, connected by ducts that provide the guiding of the exhaust gases inside these volumes.

Preferably, the exhaust duct can define a so-called "round-trip" path by presenting a bend in the downstream volume: in this configuration, the exhaust gases enter the exhaust duct in the upstream volume and remain guided in the duct to lead directly to the outside of the silencer at the same volume upstream.

Preferably, the silencer has three volumes divided into one, two or three envelopes.

With the multi-envelope embodiment, the exhaust gases will go back and forth via predefined ducts (as detailed below), the ducts then fulfilling their usual role of guiding the exhaust gases in closed volumes in order to mitigate the sound impact. But these conduits, or at least some of them, also play a mechanical role of linking the two envelopes together. This ensures coherence of the assembly without having to foresee (in any case more compulsorily) specific mechanical means to maintain correct relative positioning of the envelopes relative to each other

According to one embodiment, the volumes of the silencer are distributed in several envelopes delimited by lateral walls and transverse end walls called cups, said envelopes being connected to each other by at least two ducts passing through at least two cups next to two successive envelopes.

According to one variant, the evacuation duct opens up from the upstream cup of the envelope defining the upstream volume of the silencer (configuration with the so-called "round-trip" path of the evacuation duct). This variant is particularly suitable when the muffler is intended to be oriented substantially along the longitudinal axis of the vehicle, and for example at least partially housed in the tunnel of the vehicle body.

According to another variant, the evacuation duct opens out from the transverse wall of the envelope defining the upstream volume of the silencer (configuration with the so-called "round trip" path of the evacuation duct). This variant is particularly suitable in the case where the silencer is in transverse position, that is to say disposed perpendicular to the longitudinal axis of the vehicle, to facilitate the connection of the silencer to the rest of the exhaust line in part swallows.

Naturally, this same type of connection can be provided between the silencer and the exhaust line in the upstream part, the supply duct can thus enter the upstream volume not by its upstream cup but through its side wall.

Always if the silencer is mounted in transverse configuration, it is also possible to maintain arrivals of the supply and evacuation ducts via the cups, in a more conventional way, by elbowing the ducts coming out of the ducts. volumes to allow the connection with the exhaust line which can, she, usually have an orientation along the longitudinal axis of the vehicle.

The silencer according to the invention may comprise several, in particular two, "go" and / or several path ducts, in particular two, "return" path ducts, and / or more, in particular two, evacuation ducts, in particular parallel ducts. them on at least a part of their lengths.

It is indeed possible to split each of the muffler ducts, in particular to give more flexibility in the sizing of the muffler as a whole. The ducts thus split will advantageously have a smaller section than a unit duct, so as to keep the same pipe capacity gas flow rate given, and keep a similar pressure drop.

Advantageously, the silencer according to the invention has its intermediate volume substantially equal to or adjacent to the downstream volume.

Advantageously, the silencer according to the invention has its upstream volume is substantially twice as large as the intermediate volume and / or the downstream volume. It is thus preferably equal to the sum of the intermediate and downstream volumes.

According to a preferred embodiment, the silencer according to the invention has a so-called "go" path duct of a length less than that of the so-called "return" path duct, which itself is shorter than the duct length. evacuation. This choice (according to the conventions of acoustic diagrams) is optimal in terms of acoustic performance for the proposed silencer architecture.

The invention also relates to the body structure of a motor vehicle comprising a cockpit floor having a tunnel, such that said tunnel houses at least a portion of the silencer described above. The muffler thus has a configuration where the single envelope or the successive envelopes can be aligned longitudinally along the axis of the tunnel, which is coincident with or parallel to the longitudinal axis of the vehicle.

As already mentioned, the silencer can also be provided for transverse implantation in the vehicle.

Optionally, the envelope, or at least one of the envelopes in the case where there are several, may be doubled, preferably internally, a soundproofing layer of a material supporting high temperatures. It may for example be glass wool or rock wool.

A great advantage of the silencer according to the invention is that it can easily be arranged in the tunnel (in its longitudinal implantation). The space between the two envelopes, in the configuration with several envelopes, which, in fact, makes in this area the quieter muffler in its section (its bulk was defined only by the section of the ducts which connect the two envelopes ), can be exploited to accommodate for example internal mechanical reinforcements of the tunnel, for example. And it is compact enough to occupy only a part of the length of the available tunnel, which makes it possible to consider also housing in the tunnel other organs, such as gas tanks or electrical machines.

The invention also relates to any motor vehicle, comprising the body structure described above, and a heat engine associated with another mode of propulsion such as an electric machine, a hydraulic motor, or a hybrid heat-pneumatic engine or an engine operating on gaseous fuel.

• la figure 1 présente une coupe longitudinale d'un premier exemple de silencieux selon l'invention ;
• la figure 2 présente une coupe longitudinale d'un deuxième exemple de silencieux selon l'invention ;
• la figure 3 présente une vue en perspective d'un troisième exemple de silencieux selon l'invention ;
• la figure 4 représente le schéma acoustique correspondant aux silencieux des figures précédentes.

Other advantages and features of the invention will become apparent from the following description of several embodiments of the invention, given by way of non-limiting examples, with reference to the following figures:

• the figure 1 has a longitudinal section of a first example of silencer according to the invention;
• the figure 2 has a longitudinal section of a second example of silencer according to the invention;
• the figure 3 shows a perspective view of a third example of a silencer according to the invention;
• the figure 4 represents the acoustic diagram corresponding to the silencers of the preceding figures.

These figures are schematic, and do not necessarily respect the scale. From one figure to another, the same references correspond to the same components.

The Figures 2 and 3 are examples of silencers - respectively referenced S2 and S3 - according to the invention integrated in an exhaust line L of a heat engine M of a hybrid vehicle having another means of non-thermal propulsion. The arrow F indicates the general flow direction of the exhaust gases from the engine M, the terms "upstream" and "downstream" referring to said general direction of flow. These examples of silencers according to the invention incorporate what is generally referred to in the field of mufflers under the terms of intermediate silencer and rear silencer. Various methods can be used to manufacture the envelopes and ducts of the examples of silencers, described below, which are made of metal: one can use the technique of stamping, or the so-called "rolled-crimped" technique.

Naturally, the invention is not limited to an application to hybrid vehicles, and is also advantageously applicable for vehicles only equipped with a heat engine.

The figure 1 represents a first example of S1 silencer according to the state of the art which comprises two envelopes: an upstream envelope E1 and a downstream envelope E2, both substantially aligned and arranged along the longitudinal axis of the vehicle. The upstream envelope E1 comprises a side wall which defines a so-called upstream volume 1a substantially parallelepipedic, and which is closed at its transverse ends by upstream end 3 and downstream transverse transverse partitions 4, also called cups. The envelopes define a substantially parallelepipedal volume, with a substantially rectangular or square section, here slightly frustoconical. Alternatively, their section can be circular for define a cylindrical volume, or be oval or have another shape, as long as the envelope in question defines an elongated geometric shape for accommodating conduits.

The downstream envelope E2 is disposed at a distance from the upstream envelope E1. It comprises a lateral wall and transverse end partitions or cups upstream 7 and downstream 8. It is partitioned by an intermediate partition 9, so as to define an intermediate volume 1b and a downstream volume 2.

The envelopes E1, E2 of the silencer thus define three volumes: the volume 1a of the upstream envelope E1, and the intermediate volume 1b and the downstream volume 2 of the downstream envelope E2.

For mechanical strength issues, an optional, highly perforated, non-acoustically active intermediate cup may be installed to hold the end of the "go" and "return" tubes (described later) in the middle of the envelope E1.

The silencer S1 comprises an exhaust gas supply pipe 10, which is connected upstream to the exhaust line L, and which opens into the volume 1b through the volume 1a through the cup 3 and the cup 4 of the envelope E1 then the upstream cup 7 of the envelope E2. The duct portion 10 in the volume 1b is provided with perforations 11 distributed over its substantially cylindrical periphery.

This duct 10 is extended by a "go" duct 12 which passes through the intermediate cup 9 to open inside the volume 2 of the downstream envelope E2, approximately half (between one third and two thirds) of the length of volume 2.

The silencer also comprises a "return" conduit 13 under the conduit "go" 12. It opens, downstream side, in the volume 2 of the downstream envelope E2 about half (between one third and two thirds of the length of the volume 2), in a similar way to the duct 12. It opens, upstream side, in the upstream volume 1a of the upstream envelope E1 to approximately half (between the third and the two third), the length of the volume 1a, through the intermediate partition 9, the intermediate volume 1b and the cups 7 and 4.

Finally, the silencer S1 comprises a discharge duct 14, which opens, on the upstream side to approximately half (between the third and two thirds), the length of the volume 1a of the upstream envelope E1 and downstream side to the outside the downstream casing E2, passing through the cups 4, 7, 9 and 8 successively.

When it is stated in the present description that ducts pass through walls, here, in this case cups, this means that the walls / cups have, prior to their assembly, been provided with orifices allowing the insertion of the conduits in question. . Depending on the case, the mounting may be forced or around the orifices provided with sealing means to preserve the tightness of the envelope, (especially at least one of the end cups 4, 7 which are facing) or the assembly may leave a certain clearance between the conduit and the orifice to allow a certain movement between the conduit and the wall / the cup through which it passes, which allows the whole envelopes and conduits to know slight dimensional changes in use, especially due to thermal expansion, without the whole is too mechanically stressed.

The ducts 10,12,13,14 are here all cylindrical, but their section may be of different shape, oval for example. Here, the section of the ducts 10 and 12 is identical to that of the ducts 13 and 14, in order to maintain substantially constant passage sections all along the path of the gases.

Other dimensional or positioning choices or number of conduits can be made.

Thus, one could choose to split one or more of the supply conduits 10, "go" 12, "return" 13 and evacuation 14. In this case, the section of the split ducts is reduced accordingly to maintain the same total section.

The section of the evacuation duct 14 (or the sum of the sections of the evacuation ducts when they are two) may also be greater than that of the supply ducts, "go" and "return" 10,12,13, in order to reduce the speed of the gases and therefore the associated blast sound.

It has been indicated that the duct 12 is in the extension of the duct 10, beyond the perforations 11 with which the supply duct 10 is provided. Different variants are possible: the two ducts can be one. They can be attached to each other by any known technique (welding ...) by direct contact or at a distance from each other.

The path of the exhaust gas in the silencer S1 is as follows: the gases enter the silencer S1 through the supply duct 10 in a direction represented by the arrow f1, then follow the conduit "go" 12 disposed in the extension of conduit 10. They therefore cross the volume 1a and open into the volume 1b in the conduit 10, and the conduit 12 brings them into the volume 2 of the downstream envelope E2 along a first path "go". Then, as indicated by the arrow f2, they start in the opposite direction, according to a second path "return" in the conduit "return" 13 substantially parallel to the conduits 10 and 12 in a direction represented by the arrow f3 and open into the volume 1a of the upstream envelope E1. From there, they are evacuated via the evacuation duct 14 by starting again (arrow f4) along a third "go" path (arrow f4) to exit at the end of the duct 14 out of the downstream casing E2, depending on the direction symbolized by the arrow f5, with the same orientation as the direction f1 with which the gases were entered in the silencer S1.

In this example, it is the conduits 12, 13 which ensure the mechanical attachment of the upstream envelopes E1 and downstream E2 between them.

We also see that the shape of the envelopes may vary, and adapt flexibly both to the size of the conduits that must pass through, but also to the environment of the exhaust line. Here, the silencer S1 is housed in the tunnel of a vehicle underbody, and the zone between the two envelopes, less congested, the silencer will be able, in the tunnel, exploited for example so that the ceiling or the inner sides of the tunnel accommodate mechanical reinforcements.

The figure 2 represents a first example of silencer S2 according to the invention. Other things being equal, the silencer S2 has two differences compared to the silencer S1.

On the one hand, here, the volumes 1a, 1b and 2 are delimited by a single envelope E. This single envelope E then has two intermediate partitions 9 and 9 'which partition it into three.

On the other hand, the shape of the exhaust duct 14 'is different, having a bend at the volume 2, so that the exhaust gases are guided by this duct from the volume 1a to the volume 2 in a forward path (arrow f6), then from the volume 2 to the volume 1a again (arrow f7), the conduit 14 'opening out of the envelope E through the cup 3. In this configuration, we see that the exhaust flow out of the silencer S1 in a direction (f7) opposite that (f1) with which the gases enter the silencer S2.

The figure 3 represents the second example S3 silencer which is a variant of the silencer S2. The noticeable difference from the S2 muffler lies in the way the exhaust gases enter the muffler. Here, the silencer is not intended to be disposed along the longitudinal axis of the vehicle, but along its transverse axis. We are talking about transverse implantation. The upstream part of the exhaust line L to which the silencer S3 must be connected remains orientated along the longitudinal axis of the vehicle. The upstream part of the feed duct 10 is thus bent in the volume 1a, so that the gases coming from the exhaust line along the longitudinal axis can be guided to take a 90 ° orientation (arrow f1 '). In addition, here, the conduit 10 passes through the envelope E not by its upstream cup but through its side wall, near its upstream end, by an opening made for this purpose. Alternatively, it is possible to envisage a connection via the upstream cup 3, the bend of the conduit 10 then being provided outside the envelope E. The outlet of the discharge conduit 14 out of the envelope E is through the upstream cup 3, and has a bend outside the casing to allow connection downstream to the exhaust line (arrow f8 ').

The figure 4 represents the acoustic scheme of the silencer according to the invention, with the usual conventions of this type of representation. It is optimal when the total volume corresponding to 1a + 1b + 2 is divided in three in the approximate distribution where the volume 1b is about 3 liters, the volume 2 about 3 liters also, and the volume 1a about 6 liters, so preferably with the relation 2 substantially equal to 1b, and 1a greater than 2 and 1b and approximately corresponding to the sum 2 + 1b.

Here, the ducts 12, 13 and 14 are organized in such a way that their lengths increase when the flow of exhaust gas is followed: the length of the "go" duct 12 is smaller than that of the "return" ducts. 13, which itself is smaller than that of the evacuation duct 14. This distribution makes it possible to obtain resonance frequencies of the Helmholtz resonators resulting from the coupling of the ducts (masses) and the volumes (stiffness) given, with the lengths of the duct. 12, 13 and 14 minimum for a given section. The volume is thus maximally used for the desired function of the noise filtering by these volumes, above the selected resonant frequencies. This organization of volumes and ducts makes it possible to significantly separate the three associated Helmholtz resonance frequencies, allowing the cumulation of the filtering effects of each of the resonators, thus providing a high level of acoustic performance. Nevertheless, the highest Helmholtz resonance frequency must remain lower than the first acoustic resonance of the exhaust duct 14 (first acoustic mode of the open-open duct).

It is seen from these various examples that the invention has defined an acoustic scheme allowing a great flexibility of realization, which makes it possible to adapt the external dimensioning of the silencer to environments, in particular under tunnel, varied. The particularity of the path of the exhaust gases that make a return trip in the ducts passing through the envelope or envelopes, then a last return trip through the exhaust ducts contributes to this flexibility, and, overall, to a remarkable compactness of the muffler given the acoustic performance provided by its acoustic scheme.

Claims (13)

1. A silencer (S1, S2, S3) intended to be fitted to an exhaust line (L) of a heat engine (M), characterized in that it includes one or a plurality of envelope(s) which delimit(s) three volumes (1a, 1b, 2), designated upstream (1a), intermediate (1b) and downstream (2), disposed successively and traversed by a plurality of conduits, including: - a supply conduit (10) conveying the exhaust gases from the engine (M) to the intermediate volume (1b), passing through the upstream volume (1a), - a so-called "outward" journey conduit (12), taking the exhaust gases from the intermediate volume (1b) to the downstream volume (2), - a so-called "return" journey conduit (13), taking the exhaust gases from the downstream volume (2) towards the upstream volume (1a), passing through the intermediate volume (1b), and - a discharge conduit (14) taking the exhaust gases out of the silencer, by means of a so-called "outward-return" journey from the upstream volume (1a) to the downstream volume (2) then once more to the upstream volume (1a) from which it opens to the outside.
2. The silencer (S1, S2, S3) according to the preceding claim, characterized in that the discharge conduit (14) defines a so-called "outward-return" journey, having a bend in the downstream volume (2).
3. The silencer (S1, S2, S3) according to one of the preceding claims, characterized in that the three volumes (1a, 1b, 2) are distributed in one, two or three envelopes.
4. The silencer (S1, S2, S3) according to one of the preceding claims, characterized in that the three volumes (1a, 1b, 2) are distributed in a plurality of envelopes (E1, E2) delimited by lateral walls and transverse end partitions, designated cups (3, 4, 7, 8), said envelopes being connected to one another by at least two conduits traversing at least two cups facing two successive envelopes.
5. The silencer (S1, S2, S3) according to the preceding claim, characterized in that the discharge conduit (14) opens from the upstream cup (3) of the envelope defining the upstream volume (1a) of the silencer or from the downstream cup (8) of the downstream volume (2) of the silencer.
6. The silencer (S1, S2, S3) according to one of the preceding claims, characterized in that it includes a plurality, in particular two, "outward" journey conduits (12), and/or a plurality, in particular two, "return" journey conduits (13), and/or a plurality, in particular two, discharge conduits (14, 14'), in particular parallel to one another over at least a portion of their lengths.
7. The silencer (S1, S2, S3) according to one of the preceding claims, characterized in that the intermediate volume (1b) is substantially equal to or close to the downstream volume (2).
8. The silencer (S1, S2, S3) according to one of the preceding claims, characterized in that the upstream volume (1a) is substantially twice as large as the intermediate volume (1b) and/or as the downstream volume (2).
9. The silencer (S1, S2, S3) according to one of the preceding claims, characterized in that the so-called "outward" journey conduit (12) is of a length smaller than that of the so-called "return" journey conduit (13), itself being of a length smaller than that of the discharge conduit (14).
10. An exhaust line including a silencer according to one of the preceding claims.
11. A vehicle having on board an exhaust line according to the preceding claim, characterized in that the silencer is disposed along the longitudinal axis of said vehicle.
12. The vehicle having on board an exhaust line according to Claim 10, characterized in that the silencer is disposed along the transverse axis of said vehicle.
13. The vehicle according to Claim 11 or 12, characterized in that it includes a heat engine associated with another mode of propulsion selected from an electric machine, a hydraulic motor, a hybrid heat/pneumatic engine, an engine operating with gaseous fuel.

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