Silencer for a motor vehicle exhaust system, and its method of mounting
A silencer for a vehicle engine exhaust system, wherein the silencer is constituted by at least one duct which acts as a guide for exhaust gas and as an acoustic attenuator for exhaust noise, and which comprises at least one porous internal metal tubular element, intermediate thermal and acoustic lagging, and a leaktight outer covering of polymer material, and wherein the outer covering is connected in leaktight manner to two tubular metal connection devices via two metal caps.
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The invention relates to a silencer for a motor vehicle exhaust system, and also to its method of mounting.
BACKGROUND OF THE INVENTIONIn the prior art, an exhaust system comprises in succession, going away from the exhaust manifold of the power unit: a decoupling hose, a catalytic converter, and/or a particle filter, and often two silencers. An exhaust system silencer is of large volume (h=150 millimeters (mm)×L=400 mm×w=200 mm, for example) and it is fixed to the vehicle body by resilient straps, thereby leading to considerable size constraints.
OBJECTS AND SUMMARY OF THE INVENTIONAn object of the invention is to devise an exhaust system having a novel type of silencer making it possible to reduce weight, cost, and size in order to mitigate the drawbacks of a conventional exhaust system.
To this end, the invention provides a silencer for a vehicle engine exhaust system, wherein the silencer is constituted by at least one duct which acts as a guide for exhaust gas and as an acoustic attenuator for exhaust noise, and which comprises at least one porous internal metal tubular element, intermediate thermal and acoustic lagging, and a leaktight outer covering of polymer material, and wherein the outer covering is connected in leaktight manner to two tubular metal connection devices via two metal caps.
The internal metal tubular element may be constituted by a flat spring with overlapping turns, by a sheet metal tube with single or double seam joints, or by a flexible or rigid metal tube, each of which elements may be pierced with openings for acoustic reasons.
Advantageously, the internal tubular element may be coated in a refractory fabric possessing a certain degree of porosity, the refractory fabric possibly being made of ceramic, basalt, or glass fibers.
The duct, which may be flexible, may also include leaktight annular volumes arranged longitudinally in the thermal and acoustic lagging, each leaktight intermediate volume being defined by two compression rings, each compression ring being resilient and made of silicone, for example.
The duct may also include acoustic baffles interposed in the internal tubular element.
In general, in order to reduce the temperature of exhaust gases, a tubular metal connection device can be placed at the entrance to the duct, the device presenting external and/or internal cooling fins, and/or a diffuser-forming device may be placed at the exit from the duct.
In an embodiment of the silencer in accordance with the invention, the outer covering of the duct may form a box having the internal metal element passing therethrough, the thermal and acoustic lagging filling said box in which the internal metal element may form at least one bend.
Advantageously, the wall of the box presents at least one resonance surface in the form of a membrane, for example, having resonant frequency(ies) corresponding to certain frequencies of the frequency spectrum that is to be attenuated.
The invention also provides a method of mounting a silencer of the invention in a motor vehicle exhaust system, the method consisting in manufacturing, storing, and transporting the silencer in rectilinear shape, and in deforming it to comply with a given geometrical shape at its mounting site using the corrugations formed by the outer covering of the duct.
BRIEF DESCRIPTION OF THE DRAWINGSOther advantages, characteristics, and details of the invention appear from the additional description below made with reference to the accompanying drawings, given purely by way of example, and in which:
The exhaust system 1 shown in
In the exhaust system 10 of the invention and as shown in
In an embodiment of the invention shown in
In general, the duct 14 is constituted by at least one internal tubular element 16 of flexible or rigid type which is preferably made of metal so as to be capable of withstanding the temperature of exhaust gas, and which is porous, in particular for acoustic reasons. The internal tubular element 16 is made to be porous by piercing openings through it over substantially its entire length.
As an example shown in
In the embodiment of a silencer of the invention that is shown in
In the embodiment shown in
In the embodiment shown in
In the embodiment shown in
In general, the exhaust gas must be rejected to the atmosphere at a temperature of less than 200° C., for example, whereas on the entry to the duct 14 it may be at a temperature of about 500° C. When the cooling fins 77 of the connection device 70 at the entrance of the duct 14 (
In a variant embodiment of the invention as shown in
Advantageously, and as shown in
In the examples described above, the duct 14 presents a porous internal metal element 16 extending over substantially its entire length, however the duct 14 could also be made as a plurality of portions assembled together in pairs by substantially smooth tubular metal elements connected to two adjacent porous metal elements 16, where a smooth element is suitable for being bent and is optionally covered in a refractory fabric 30, in lagging 18, and in the outer covering 20.
Claims
1. A silencer for a vehicle engine exhaust system, wherein the silencer is constituted by at least one duct which acts as a guide for exhaust gas and as an acoustic attenuator for exhaust noise, and which comprises at least one porous internal metal tubular element, intermediate thermal and acoustic lagging, and a leaktight outer covering of polymer material, and wherein the outer covering is connected in leaktight manner to two tubular metal connection devices via two metal caps.
2. A silencer according to claim 1, in which the duct is flexible.
3. A silencer according to claim 1, in which the internal metal tubular element is constituted by a flat spring having overlapping turns.
4. A silencer according to claim 1, in which the internal metal tubular element is constituted by a sheet metal tube with single or double seam joints.
5. A silencer according to claim 1, in which the flexible or rigid internal metal tubular element is pierced by openings.
6. A silencer according to claim 5, in which the openings are of diameter that increases in the flow direction of the exhaust gas.
7. A silencer according to claim 6, in which the openings are subdivided into a plurality of series of openings, the openings in each series having substantially the same diameter.
8. A silencer according to claim 5, in which the internal metal tubular element is constituted by at least two concentric tubes, an inner tube and an outer tube, both pierced by openings.
9. A silencer according to claim 8, in which the inner metal tube extends over a portion only of the total length of the silencer.
10. A silencer according to claim 1, in which the internal tubular element is covered in a refractory fabric presenting a degree of porosity.
11. A silencer according to claim 10, in which the refractory fabric is made of ceramic, basalt, or glass fibers.
12. A silencer according to claim 1, in which the outer covering of the duct is made on the basis of a thermoplastic material such as polyamide 66, or on the basis of an elastomer material such as Vamac®, or a silicone.
13. A silencer according to claim 1, in which the outer covering of the duct is formed by a blow extrusion operation.
14. A silencer according to claim 1, in which leaktight annular volumes are formed that are spaced apart longitudinally in the thermal and acoustic lagging.
15. A silencer according to claim 14, in which each leaktight intermediate volume in the thermal and acoustic lagging is defined by two compression rings.
16. A silencer according to claim 15, in which each compression ring is resilient and made of silicone, for example.
17. A silencer according to claim 1, in which acoustic baffles are interposed in the internal tubular element of the flexible duct.
18. A silencer according to claim 17, in which an acoustic baffle is constituted by three disks mounted perpendicularly to the exhaust gas flow axis, and by two connection tubes presenting holes that are coaxial with the internal tubular element and that are of smaller diameter.
19. A silencer according to claim 1, in which the leakproof outer covering presents at least one outwardly-directed projection to create an additional volume which is filled with the material forming the lagging.
20. A silencer according to claim 19, in which the inside wall of the projection is covered in an absorbent lining.
21. A silencer according to claim 20, in which the absorbent lining is a cellular silicone foam.
22. A silencer according to claim 1, in which the flexible duct has its entrance connected to a flared tubular metal connection device presenting internal and/or external cooling fins to reduce the temperature of the exhaust gas.
23. A silencer according to claim 1, in which the flexible duct is connected at its exit to a diffuser-forming device for reducing the exit temperature of the exhaust gas.
24. A silencer according to claim 23, in which the diffuser-forming exit device comprises at least one generally conical element that is pierced by holes, and a tubular exit element which surrounds and extends the element, and having a wall that presents at least one opening for enabling ambient air to enter therein.
25. A silencer according to claim 23, in which the diffuser-forming exit device comprises at least one star-shaped element and an exit tubular element which surrounds and extends the element, and having a wall that presents at least one opening for allowing ambient air to enter therein.
26. A silencer according to claim 1, in which the leakproof outer covering of the silencer forms a box through which the internal metal tubular element passes, the intermediate thermal and acoustic lagging filling said box.
27. A silencer according to claim 26, in which the internal metal tubular element forms at least one bend inside the box.
28. A silencer according to claim 26, in which the box presents in its wall, at least one surface formed by a resonant membrane which is tuned to at least one frequency in the frequency spectrum to be attenuated.
29. A silencer according to claim 1, in which the silencer comprises at least two ducts connected to each other by an optionally bent tubular metal element.
30. A silencer according to claim 29, in which the tubular metal element is smooth.
31. A method of mounting a silencer as defined in claim 1 in a motor vehicle exhaust system, the method consisting in manufacturing, storing, and transporting the silencer in rectilinear shape, in deforming it to take up a given configuration at the time it is mounted in the exhaust system, and in fastening it to the vehicle body by means of rigid fastening tabs.
32. A method according to claim 31, in which the duct is bent at a corrugated zone of the duct.
33. A method according to claim 31, in which the leakproof outer covering of the duct is made by a blow extrusion operation.
Type: Application
Filed: Jan 14, 2005
Publication Date: Aug 4, 2005
Applicant: Hutchinson (Paris)
Inventor: Jean-Michel Simon (Chatillon)
Application Number: 11/036,554