U.S. patent application number 11/036554 was filed with the patent office on 2005-08-04 for silencer for a motor vehicle exhaust system, and its method of mounting.
This patent application is currently assigned to Hutchinson. Invention is credited to Simon, Jean-Michel.
Application Number | 20050167192 11/036554 |
Document ID | / |
Family ID | 34639810 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050167192 |
Kind Code |
A1 |
Simon, Jean-Michel |
August 4, 2005 |
Silencer for a motor vehicle exhaust system, and its method of
mounting
Abstract
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.
Inventors: |
Simon, Jean-Michel;
(Chatillon, FR) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
100 E WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Assignee: |
Hutchinson
Paris
FR
|
Family ID: |
34639810 |
Appl. No.: |
11/036554 |
Filed: |
January 14, 2005 |
Current U.S.
Class: |
181/256 ;
181/222; 181/252 |
Current CPC
Class: |
F01N 13/1816 20130101;
F01N 2530/22 20130101; F01N 13/20 20130101; F01N 1/083 20130101;
F01N 1/006 20130101; F01N 1/10 20130101; F01N 13/02 20130101; F01N
2310/02 20130101; F01N 3/055 20130101; F01N 2260/02 20130101; Y02T
10/20 20130101; F01N 1/22 20130101; F01N 2470/24 20130101; Y02T
10/12 20130101; F01N 13/16 20130101 |
Class at
Publication: |
181/256 ;
181/252; 181/222 |
International
Class: |
F01N 001/24; F01N
001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2004 |
FR |
0400894 |
Claims
What is claimed is:
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.RTM., 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.
Description
[0001] The invention relates to a silencer for a motor vehicle
exhaust system, and also to its method of mounting.
BACKGROUND OF THE INVENTION
[0002] In 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).times.L=400 mm.times.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 INVENTION
[0003] An 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] The duct may also include acoustic baffles interposed in the
internal tubular element.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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 DRAWINGS
[0013] Other 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:
[0014] FIG. 1 is a perspective view of a prior art exhaust system,
mentioned in the introduction;
[0015] FIG. 2 is a perspective view of an exhaust system including
a silencer in accordance with the invention;
[0016] FIG. 3 is a fragmentary longitudinal section view of an
embodiment of the FIG. 2 silencer with a flexible duct comprising
at least one internal tubular element, thermal and acoustic
lagging, and an outer covering;
[0017] FIGS. 4a to 4e are diagrams showing variant embodiments of
the internal tubular element of the flexible duct of FIG. 3;
[0018] FIG. 5 is a section view of an embodiment of the external
covering of the duct;
[0019] FIG. 6 is a fragmentary longitudinal section view showing
compression rings mounted in the thermal and acoustic lagging of
the duct of FIG. 3;
[0020] FIG. 7 is a fragmentary longitudinal section view showing
acoustic baffles interposed in the internal tubular element of the
duct of FIG. 3;
[0021] FIG. 8 is a fragmentary longitudinal section view of a
device enabling exhaust gas to enter into the FIG. 3 duct;
[0022] FIG. 8a is a view seen looking along arrow VIIIa of FIG.
8;
[0023] FIG. 9 is a longitudinal section view of a device enabling
exhaust gas to exit from the duct of FIG. 3;
[0024] FIG. 10 shows a variant embodiment of FIG. 9;
[0025] FIG. 10a is a section view on line Xa-Xa of FIG. 10;
[0026] FIG. 11 is a diagram showing another embodiment of the duct
of the invention;
[0027] FIG. 12 is a perspective view of FIG. 11; and
[0028] FIGS. 13 and 14 are perspective views for showing the method
of mounting a silencer of the invention.
MORE DETAILED DESCRIPTION
[0029] The exhaust system 1 shown in FIG. 1 shows the state of the
art mentioned in the introduction, the system 1 comprising in
succession, from a multitube exhaust manifold 3 at the outlet from
a power unit 4: a decoupling hose 5; a catalytic converter 6; and
two rigid silencers 7 secured to the vehicle body by resilient
straps 8; and interconnected by tubes 9 of stainless steel.
[0030] In the exhaust system 10 of the invention and as shown in
FIG. 2, the two silencers 7 have been eliminated and replaced by at
least one silencer 12 constituted by a duct 14 which is fastened by
rigid fastening tabs 15 to the body of the vehicle and which acts
as a guide for exhaust gas and as an acoustic attenuator for
exhaust noise, as described below with reference to FIGS. 2 to
9.
[0031] In an embodiment of the invention shown in FIG. 3, the duct
14 is constituted by at least one internal tubular element 16 which
is porous, thermal and acoustic lagging 18, and a flexible and
leakproof external covering 20 of elastomer material that
withstands high temperature, the covering 20 possibly being made
out of a thermoplastic material such as PA 66, or an elastomer
material such as Vamac.RTM., or silicone, for example.
[0032] 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.
[0033] As an example shown in FIG. 4a, the internal tubular element
16 is constituted by a metal tube 25 pierced by openings 27.
Advantageously, the openings 27 can be formed by a plurality of
series of openings, e.g. three series 27a, 27b, and 27c which are
of flow sections or diameters that increase going in the flow
direction of the exhaust gas, in particular to avoid any risk of
the exhaust gas flowing in the reverse direction through the
lagging 18, and as shown in FIG. 4b. These three series of openings
27a, 27b, and 27c may have diameters of 1 mm, 2 mm, and 3 mm
respectively, for example. In a first variant embodiment shown in
FIG. 4c, the internal tubular element 16 is constituted by two
concentric tubes, an inner tube 25a and an outer tube 25b, the
inner tube 25a extending over a fraction only of the length of the
silencer, for example, e.g. over 5% to 30%, so as to create
interference suitable for canceling the soundwaves from the flow of
exhaust gases. In a second variant embodiment of the invention, the
internal tubular element 16 is made of sheet metal with single or
double seam joints (FIG. 4d, FIG. 4e) or by a spring having
overlapping turns (FIG. 3), all of which elements present
communication passages independently of any additional openings
that may be pierced in the same manner as for the metal tubes of
FIGS. 4a or 4b.
[0034] In the embodiment of a silencer of the invention that is
shown in FIG. 3, the internal tubular element 16 is made in the
form of a flat spring 29 having overlapping turns, however the
element 16 could be replaced by an element as shown in any of the
embodiments of FIGS. 4a to 4e. Advantageously, a refractory fabric
30 can be wound around all or part of the internal tubular element
16, said fabric presenting sufficient porosity to enable the
lagging 18 to damp acoustic waves, while limiting any direct
passage of exhaust gas through the lagging 18 so as to avoid
damaging the outer covering 20. The fabric 30 may be made of
ceramic, basalt, or glass fibers, for example.
[0035] In the embodiment shown in FIG. 5, the duct 14 may present
at least one outwardly-extending projection 32 formed in its outer
covering 20 to create an additional volume 33 that is filled with
the material constituting the lagging 18. Advantageously, an
absorbent lining 34 having a very low index of reflection can be
received against the inside wall of the projection 32 so as to
obtain better noise absorption. This is made possible by the low
temperature level in the vicinity of the projection 32, and would
be impossible to do with a metal silencer of the prior art. The
lining 34 may be made of a cellular silicone foam, for example.
[0036] In the embodiment shown in FIG. 6, compression rings 40 are
provided in the lagging 18 to compress it, thereby defining a
plurality of volumes V that are matched to the frequencies that are
to be countered. These rings 40 are resilient, being spaced apart
regularly from one another, e.g. being made of silicone, and they
bear against the outer covering 20. Thus, compressing the
insulating material on one side and pressing against the outer
covering 30 on the other side, they serve to define a leaktight
volume V which acts as an acoustic resonant volume. Such rings 40
thus create an incompressible zone suitable for supporting the
weight of the internal tubular element 16 without any risk of the
insulating material suffering creep.
[0037] In the embodiment shown in FIG. 7, acoustic baffles 45 are
interposed inside the internal tubular element 16 of the duct 14. A
baffle 45 may be constituted by an assembly of three metal disks,
two end disks comprising an upstream disk 47 and a downstream disk
49, and a middle disk 51, all three disks being disposed
perpendicularly to the flow direction of the exhaust gases, and two
connecting metal tubes 53 and 55 pierced by holes 52 and mounted
coaxially inside the internal tubular element 16, being of smaller
diameter. More precisely, the upstream end disk 47 presents a
central opening 57 having the diameter of the two connection tubes
53 and 55, and openings 59 distributed around the central opening,
while the downstream end disk 49 has only one central opening 57 of
the diameter of the two connection tubes 53 and 55. The middle disk
51 is solid in its central portion so as to prevent direct
communication between the two connection tubes 53 and 55, however
it does present openings 61 in its periphery. This defines a first
volume V.sub.1 inside the connection tube 53, a second volume
V.sub.2 that is annular around the connection tube 53, a third
volume V.sub.3 that is annular around the connection tube 55, and a
fourth volume V.sub.4 inside the connection tube 55. Thus, the
exhaust gas penetrates directly firstly into the first volume
V.sub.1 via the central opening 57 in the upstream disk 47, and
then into the second volume V.sub.2 through the holes 52 in the
connection tube 53, and secondly into the volume V.sub.2 through
the holes 59 in the upstream disk 47. The exhaust gas passes from
the second volume V.sub.2 to the third volume V.sub.3 through the
openings 61 in the middle disk 51, and then penetrates into the
fourth volume V.sub.4 through the openings 52 in the connection
tube 55 prior to escaping from the baffle 45 via the central
opening 57 in the downstream disk 49. A plurality of baffles 45 may
be interposed inside the internal tubular element 16 of the duct
14.
[0038] FIG. 8 shows an embodiment of a connection device 70 mounted
at the entrance to the duct 14. In general, the exit from the
catalytic converter 6 is provided by a metal tubular element 72,
e.g. made of stainless steel, whose downstream end 72a is flared so
as to connect to the duct 14 which is of diameter greater than that
of the tubular element 72. The internal tubular element 16 is
welded to the flared end 72a of the tubular element 72, while the
outer covering 20 of the duct 12 is connected by means of a long
and thin-walled metal cap 75 that serves to protect the outer
covering 20 against high temperatures. Advantageously, external
and/or internal cooling fins 77 can be provided on or in the
tubular element 72 in order to cool the exhaust gas prior to entry
into the duct 14 of the silencer 12, and the outer covering 20 may
be corrugated. To further encourage heat exchange and to reduce the
temperature of the exhaust gas penetrating into the duct 14, the
tubular element 72 can be flattened, giving it an undulating or
corrugated shape, as can be seen in FIG. 8a.
[0039] In general, the exhaust gas must be rejected to the
atmosphere at a temperature of less than 200.degree. C., for
example, whereas on the entry to the duct 14 it may be at a
temperature of about 500.degree. C. When the cooling fins 77 of the
connection device 70 at the entrance of the duct 14 (FIG. 8) are
found to be insufficient, it is possible to mount a
diffuser-forming exit device 80 made of metal at the outlet from
the duct 14. This exit device 80, as shown in FIG. 9, may comprise
at least one element 82 of generally conical shape that is pierced
by holes 84, and a tubular exit element 86 which surrounds and
extends the element 82. Thus, the exhaust gas leaves via the holes
84 to penetrate into the tubular exit element 86 which presents at
least one opening 88 in its wall so as to allow ambient air to
enter, thereby encouraging the expulsion of exhaust gases at
moderate temperature.
[0040] FIG. 10 shows another embodiment of the exit device 80 of
FIG. 9. This exit device 80 also has an element 82, but this time
it is star-shaped, and it has an exit element 86 which surrounds
and extends the element 82, having at least one opening 88 in its
wall so as to allow air to enter.
[0041] In a variant embodiment of the invention as shown in FIG.
11, the outer covering 20 of the duct 14 can be made over at least
a portion of the duct in the form of a leaktight box 90 having the
internal metal tubular element 16 passing therethrough coated in
its refractory fabric 30. The box 90 is made of two portions that
are assembled together after the internal metal element 16 has been
inserted, the box 90 being filled with the thermal and acoustic
lagging 18. The internal metal element 16 may form at least one
C-shaped bend inside the box 90 so as to increase the acoustic
insulation of the duct 14.
[0042] Advantageously, and as shown in FIG. 12, the wall of the box
90 may include at least one resonant surface 92 in the form of a
diaphragm, for example, having one or more resonant frequencies
corresponding to certain frequencies in the frequency spectrum that
is to be attenuated. Such a surface 92, on being excited, is set
into vibration, thereby dissipating energy in such a manner as to
contribute effectively to acoustically insulating the duct 14.
[0043] FIGS. 13 and 14 show a method of mounting a silencer 12 of
the invention in an exhaust system of a motor vehicle. In general,
a silencer 12 is manufactured, stored, and transported in a
rectilinear shape. Then, on the site where the silencers 12 are
mounted, each silencer is deformed into the geometrical
configuration it is to occupy prior to being fastened to the
vehicle body via its rigid fastening tabs 15. In the example shown,
the silencer 12 presents at least two series of corrugations 14a
and 14b, and it is via these corrugations 14a and 14b that is it
possible to bend the silencer 12.
[0044] 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.
* * * * *