U.S. patent application number 10/505110 was filed with the patent office on 2005-10-13 for internal combustion engine silencer.
This patent application is currently assigned to Sango Co. Ltd.. Invention is credited to Mizuno, Fumihiko, Yokoi, Masayuki.
Application Number | 20050224283 10/505110 |
Document ID | / |
Family ID | 27759647 |
Filed Date | 2005-10-13 |
United States Patent
Application |
20050224283 |
Kind Code |
A1 |
Yokoi, Masayuki ; et
al. |
October 13, 2005 |
Internal combustion engine silencer
Abstract
A muffler for internal combustion engines, in order to achieve a
high attenuating effect without reducing the attenuating effect in
the high revolution range of the engine, comprising one or more
expanding chambers 11 through 13 formed in a muffler 1, an inlet
pipe 5 which opens into a expanding chamber 11 and introduces
exhaust gas into the muffler 1, and an outlet pipe 6 which opens
into other expanding chamber 13 and introduces exhaust gas out of
the muffler 1. In the muffler, the exhaust gas discharged through
an aperture 5a of this inlet pipe 5 is inverted once or more times
in the muffler 1 and is introduced into an aperture 6a of the
outlet pipe 6. In a contraflow area L2 in which the flowing
direction C of exhaust gas flowing in the expanding chambers 11
through 13 and the flowing direction E of exhaust gas flowing in
the outlet pipe 6 are not the same, interference holes 7 composing
of a plurality of small holes communicating with the expanding
chambers 11 through 13 are bored in the outlet pipe 6. The aperture
area of the small holes 7 is kept at not less than 1% but not more
than 5% of the surface area of the outlet pipe in the contraflow
area L2.
Inventors: |
Yokoi, Masayuki; (Aichi,
JP) ; Mizuno, Fumihiko; (Aichi, JP) |
Correspondence
Address: |
Stevens Davis
Miller & Mosher
Suite 850
1615 L Street NW
Washington
DC
20036
US
|
Assignee: |
Sango Co. Ltd.
3-1, Mutsuno 1-chome, Atsuta-ku
Aichi
JP
|
Family ID: |
27759647 |
Appl. No.: |
10/505110 |
Filed: |
August 19, 2004 |
PCT Filed: |
February 19, 2003 |
PCT NO: |
PCT/JP03/01815 |
Current U.S.
Class: |
181/268 ;
181/269 |
Current CPC
Class: |
F01N 3/00 20130101; F01N
2470/02 20130101; F01N 1/10 20130101; F01N 2260/10 20130101; F01N
1/084 20130101; F01N 2470/20 20130101; F01N 2470/18 20130101; F01N
13/1888 20130101; F01N 2470/04 20130101; F01N 1/06 20130101; F01N
2470/10 20130101; F01N 13/1872 20130101; F01N 1/089 20130101 |
Class at
Publication: |
181/268 ;
181/269 |
International
Class: |
F01N 001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2002 |
JP |
2002-43286 |
Nov 20, 2002 |
JP |
2002-335913 |
Claims
1. A muffler for internal combustion engines comprising at least
one expanding chamber formed within the muffler, an inlet pipe
opening into said expanding chamber to introduce exhaust gas into
the muffler, and an outlet pipe opening into said expanding chamber
to introduce exhaust gas out of the muffler, in which exhaust gas
discharged from an opening in said inlet pipe is inverted once or
more and then introduced into an opening in said outlet pipe,
wherein, in a contraflow area in which a flowing direction of
exhaust gas flowing in said expanding chamber and a flowing
direction of exhaust gas flowing in said outlet pipe are different,
interference holes composed of a plurality of small holes
communicating with said expanding chamber are bored in said outlet
pipe, and the total aperture area of said interference holes is not
less than 1% but not more than 5% of a surface area of said outlet
pipe in said contraflow area.
2. The muffler for internal combustion engines as claimed in claim
1, wherein said at least one expanding chamber is a plurality of
expanding chambers, said inlet pipe is disposed to open into one of
them to introduce exhaust gas into the muffler, and said outlet
pipe is disposed to open into other one to introduce exhaust gas
out of the muffler.
3. The muffler for internal combustion engines as claimed in claim,
wherein said interference holes are disposed in a range of not less
than 75% of a length of said outlet pipe in said contraflow
area.
4. The muffler for internal combustion engines as claimed in claim
1, wherein bypass holes composing of a plurality of small holes
communicating with said expanding chamber are bored downstream from
a part of said outlet pipe in said contraflow area, and a total
aperture area of said interference holes and said bypass holes
together is not greater than a sectional area of a passage in said
outlet pipe.
5. The muffler for internal combustion engines as claimed in claim
1, wherein interference holes composing of a plurality of small
holes communicating with said expanding chamber are bored in said
contraflow section of said inlet pipe.
Description
TECHNICAL FIELD
[0001] The present invention relates to an international combustion
engine silencer, or a muffler for internal combustion engines.
BACKGROUND ART
[0002] Among mufflers to be disposed on the exhaust line of an
internal combustion engine are conventionally known ones having a
U-turn structure in which exhaust gas is inverted once or more in
the muffler. As a muffler having such a U-turn structure, the
muffler illustrated in FIG. 11, for instance, is disclosed in the
Japanese Utility Model Unexamined Publication JP-U-61-194718.
[0003] The muffler, as shown in FIG. 11, is provided within its
housing 101, successively from the upstream side (left side in the
drawing) onward, a first expanding chamber 102, a second expanding
chamber 103, a third expanding chamber 104 and a resonator chamber
105 partitioned from one another. In the third expanding chamber
104 opens an inlet pipe 106 for introducing exhaust gas into the
muffler, and the first expanding chamber 102 is provided with,
opening into it, an outlet pipe 109 for discharging exhaust gas out
of the muffler. Between the first expanding chamber 102 and the
third expanding chamber 104 is disposed, opening into them, a
conduit 107 to make possible communication between the two chambers
102 and 104. Further in the second expanding chamber 103, a small
hole 111 is provided in the inlet pipe 106, a small hole 112 in the
outlet pipe 109 and a small hole 113 in the conduit 107, to enable
part of exhaust gas to be discharged out of or let into the second
expanding chamber 103, to cause elements of sound wave energy in
exhaust gas to interfere with one another and thereby to reduce
exhaust noise.
[0004] In the above-described conventional muffler, there is an
antinomic relationship that, in order to cause elements of sound
wave energy in exhaust gas to interfere with one another in the
second expanding chamber 103 section and the resultant interfering
action to achieve a significant attenuating effect, the open area
ratios of the small holes 111, 112 and 113 should be increased
while raising the open area ratios of the small holes would reduce
the attenuating effect in the high revolution range of the
engine.
DISCLOSURE OF THE INVENTION
[0005] The present invention, therefore, is intended to provide a
muffler capable of achieving a high attenuating effect without
reducing the attenuating effect in the high revolution range of the
engine.
[0006] In order to solve the problems noted above, the invention
provides a muffler for internal combustion engines equipped with at
least one expanding chamber formed within the muffler, an inlet
pipe opening into the expanding chamber to introduce exhaust gas
into the muffler, and an outlet pipe opening into the expanding
chamber to introduce exhaust gas out of the muffler, in which
exhaust gas discharged from an opening in the inlet pipe is
inverted once or more and introduced into an opening in the outlet
pipe, wherein in a contraflow area of the muffler where the flowing
direction of exhaust gas flowing in the expanding chamber and the
flowing direction of exhaust gas flowing in the outlet pipe are not
the same, interference holes composed of a plurality of small holes
communicating with the expanding chamber are provided in the outlet
pipe and the total aperture area of the interference holes is not
less than 1% but not more than 5% of the surface area of the outlet
pipe in the contraflow area.
[0007] With this configuration, exhaust noise flowing in the
expanding chamber in one direction flows into the outlet pipe
through the interference holes bored in the outlet pipe, interferes
with exhaust noise flowing in the outlet pipe in the direction
reverse to the flowing direction in the expanding chamber, and is
attenuated by that interfering action.
[0008] According to the invention, at least one expanding chamber
may be a plurality of expanding chambers, the inlet pipe is
disposed to open into one of them and to introduce exhaust gas into
the muffler, and the outlet pipe is disposed to open into other one
and to introduce exhaust gas out of the muffler.
[0009] According to the invention, the range in which the
interference holes are provided may as well be not less than 75% of
the length of the outlet pipe in the contraflow area.
[0010] As this configuration causes various route differences to
give rise to the interference, noise in a broad revolution range of
the engine is attenuated.
[0011] Thus, as the route (distance) from the opening of the inlet
pipe as the starting point to the interfering point differs with
whether it runs via the opening of the outlet pipe or it runs via
an interference hole, the time of arrival differs as much as this
difference in route.
[0012] Therefore, as the phase of exhaust noise having entered into
the outlet pipe via the opening of the outlet pipe differs from the
phase of exhaust noise having entered into the outlet pipe via the
interference holes (phase difference), they interfere with each
other and the noise is attenuated.
[0013] Since the efficiency of attenuating is high at a phase
difference of 180 degrees, in order to effectively attenuate noises
of many different frequencies (noises in a broad revolution range
of the engine), interference should be caused to occur at a variety
of route differences.
[0014] According to the invention, since a variety of route
differences are set by providing interference holes in a range of
75% or more of the length of the outlet pipe in the contraflow area
(long range), noise in a broad revolution range of the engine is
attenuated.
[0015] Further, according to the invention, bypass holes composed
of a plurality of small holes communicating with the expanding
chamber may be bored downstream from the part of the outlet pipe in
the contraflow area, and the total aperture area of the
interference holes and the bypass holes together may be kept not
greater than the sectional area of the passage in the outlet
pipe.
[0016] This configuration proves effective in attenuating noise in
the low revolution area by virtue of its bypass holes.
[0017] Further, according to the invention, interference holes
composed of a plurality of small holes communicating with the
expanding chamber may be bored in the contraflow section of the
inlet pipe.
[0018] With this configuration, an even greater attenuating effect
can be achieved without reducing the attenuating effect in the high
revolution range of the engine by boring the interference holes in
the inlet pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a side sectional view showing a first embodiment
according to the present invention;
[0020] FIG. 2A and FIG. 2B are front views of separators in FIG. 1,
respectively;
[0021] FIG. 3 is a diagram showing a result of analysis simulating
a primary component of exhaust noise by varying a total aperture
area of interference holes relative to a surface area of the outlet
pipe in its contraflow area L2 in the embodiment of FIG. 1;
[0022] FIG. 4 is a diagram showing a result of analysis simulating
a relationship of an average attenuate level to an opening area
ratio of the interference holes in the embodiment of FIG. 1;
[0023] FIG. 5 is a side sectional view showing a second embodiment
of the invention;
[0024] FIG. 6 is a front view of a separator in FIG. 5;
[0025] FIG. 7 is a side sectional view showing a third embodiment
of the invention;
[0026] FIG. 8 is a side sectional view showing a fourth embodiment
of the invention;
[0027] FIG. 9 is a sectional view taken along a line IX-IX in FIG.
8;
[0028] FIG. 10 is a side sectional view showing a fifth embodiment
of the invention; and
[0029] FIG. 11 is a side sectional view showing a conventional
muffler.
BEST MODES FOR CARRYING OUT THE INVENTION
[0030] Embodiments according to the present invention will be
described with reference to FIG. 1 through FIG. 10.
[0031] FIG. 1 and FIG. 4 show a first embodiment of the
invention.
[0032] In FIG. 1, a housing 2 in a muffler 1 is constituted of a
metallic cylinder of which both ends are reduced in diameter to
form constrictions 2a and 2b.
[0033] In the housing 2, a separator 3 in which a plurality of
through holes 3a and two burring holes 3b and 3c are bored as shown
in FIG. 2A and a separator 4 in which a plurality of through holes
4a and two burring holes 4b and 4c are bored as shown in FIG. 2B
are fixed with a prescribed spacing L1 between them, and they
partition the housing 2 in the lengthwise direction into a first
expanding chamber 11, a second expanding chamber 12 and a third
expanding chamber 13.
[0034] In the housing 2, forcing into its constriction 2a and the
burring holes 3b and 4b of the separators 3 and 4, an inlet pipe 5
for introducing exhaust gas into the muffler 1 is disposed, and its
downstream side aperture 5a opens into the first expanding chamber
11. Incidentally, an upstream side aperture 5b is connected to an
upstream side exhaust pipe.
[0035] Further, in the housing 2, forcing into its constriction 2b
and the burring holes 3c and 4c of the separators 3 and 4, an
outlet pipe 6 to discharge exhaust gas out of the muffler 1 is
disposed, and its upstream side aperture 6a opens into the third
expanding chamber 13. Incidentally, a downstream side aperture 6b
is connected to a downstream side exhaust pipe.
[0036] In this muffler, with the range from the downstream side
aperture 5a of the inlet pipe 5 to the upstream side aperture 6a of
the outlet pipe 6 being assumed to be a contraflow area L2, the
interference holes 7 constituted of a plurality of small holes
communicating with the first through third expanding chambers 11
through 13 are bored, positioned in this contraflow area L2, in the
outlet pipe 6.
[0037] The contraflow area L2, as will be further described
afterwards, means a range in the muffler, similarly to the inlet
pipe 5, the range in which the flowing direction of exhaust gas in
the outlet pipe 6 is not identical with the flowing direction of
exhaust gas in the expanding chambers.
[0038] Next will be described the actions of the first
embodiment.
[0039] A greater part of exhaust gas having circulated through the
upstream side exhaust pipe not shown in FIG. 1, after circulating
within the inlet pipe 5 in the direction of an arrow A and flowing
into the first expanding chamber 11 from the aperture 5a, inverts
its flowing direction as indicated by an arrow B into the flowing
direction indicated by arrow C, enters into the second expanding
chamber 12 via the through holes 3a bored in the separator 3, and
flows within the second expanding chamber 12 in the direction of
the arrow C, i.e. upstream from the outlet pipe 6. It further flows
into the third expanding chamber 13 via the through holes 4a bored
in the separator 4, then inverts its flowing direction as indicated
by an arrow D, circulates within the outlet pipe 6 from the
aperture 6a of the outlet pipe 6 in the direction of an arrow E,
reverse to its direction in the second expanding chamber 12, and
then is discharged out of the muffler 1.
[0040] Exhaust noise, like the exhaust gas described above,
circulates within the muffler and is attenuated by the expanding
chambers 11 through 13 by their expansive actions.
[0041] Further, part of exhaust gas enters into the outlet pipe 6
from the expanding chambers 11 through 13 via the interference
holes 7 constituted of small holes bored in the outlet pipe 6.
Exhaust noises having then entered via the interference holes 7
together with the exhaust gas, mutually interfere with exhaust
noise circulating in the outlet pipe 6 and are attenuated by this
interfering action.
[0042] To add, by boring the interference holes 7 in as large a
part of the contraflow area L2 as practicable, interference will be
caused to occur with many different route differences, and
accordingly this will exert an attenuating effect on noise in a
broad revolution range of the engine. Therefore, it is preferable
for an area L3 in which the interference holes 7 of FIG. 1 are
bored to correspond to 75% or more of the length of the contraflow
area L2.
[0043] The result of analysis simulating the primary component of
exhaust noise during acceleration by varying the total aperture
area S2 (open area ratio) of the interference holes 7 relative to
the surface area S1 of the outlet pipe 6 in the contraflow area L2
is shown in FIG. 3.
[0044] From this result, it is seen that a greater attenuating
effect can be achieved by increasing the open area ratio. At the
same time, however, it is also seen that if the open area ratio is
excessively increased, the attenuating effect in the high
revolution range of the engine deteriorates.
[0045] Further, the result of analysis simulating the relationship
of the average attenuate level (the average of the attenuate levels
at different frequencies of revolution) to the open area ratio with
respect to an aperture ratio of 0% by varying the open area ratio
more finely is shown in FIG. 4.
[0046] From the result shown in FIG. 4, it is found preferable for
the open area ratio to be not less than 1% but not more than 5%. It
is even more preferable for the ratio to be not less than 1.5% but
not more than 3.5%.
[0047] FIG. 5 and FIG. 6 show a second embodiment of the
invention.
[0048] Referring to FIG. 5, the housing of a muffler 21 is composed
of a shell 22 cylindrically formed of a steel plate and outer
plates 23 and 24 caulk-coupled to both ends of the shell 22. Within
the housing, a separator 31 in which a plurality of through holes
31a and a burring hole 31b are bored as shown in FIG. 6 is fixed,
and the housing is partitioned by the separator 31 into a first
expanding chamber 29 and a second expanding chamber 30.
[0049] An inlet pipe 25, positioned on the first expanding chamber
29 side, is inserted into a burring hole 22a of the shell 22, with
its end being blocked by a cap 27 disposed in the opposite position
to the burring hole 22a.
[0050] Further, in the side face of the inlet pipe 25 are bored
discharge ports (apertures) 28 so that exhaust gas in the inlet
pipe 25 can flow into the first expanding chamber 29 via the
discharge ports 28.
[0051] An outlet pipe 26 is inserted into a burring hole 24a of an
outer plate 24 and the burring hole 31b of the separator 31, so
that an aperture 26a on the upstream side open into the second
expanding chamber 30.
[0052] Referring to FIG. 5, with the range from the discharge ports
28 of the inlet pipe 25 to the upstream side aperture 26a in the
outlet pipe 26 being assumed to be a contraflow area L4,
interference holes 32 constituting of a plurality of small holes
communicating with the first and second expanding chambers 29 and
30 are bored, positioned in this contraflow area L4, in the outlet
pipe 26.
[0053] Next will be described the actions of the second
embodiment.
[0054] Referring to FIG. 5, exhaust gas having circulated in the
inlet pipe 25 as indicated by an arrow F flows into the first
expanding chamber 29 via the discharge ports 28 of the inlet pipe
25; then a greater part of the exhaust gas flows into the first
expanding chamber 29 as indicated by an arrow G, flows into the
second expanding chamber 30 via the through holes 31a of the
separator 31, and flows within the second expanding chamber 30 as
indicated by an arrow H; then after inverting its flowing direction
as indicated by an arrow I, flows into the outlet pipe 26 via the
upstream side aperture 26a of the outlet pipe 26, and circulates
within the outlet pipe 26 in the direction of an arrow J, which is
reverse to the flowing directions G and H within the first and
second expanding chambers 29 and 30.
[0055] Then, part of exhaust gas circulating in the first expanding
chamber 29 and the second expanding chamber 30 flows into the
outlet pipe 26 via the interference holes 32 constituting of small
holes bored in the outlet pipe 26. Exhaust noise having entered
into the outlet pipe 26 via the interference holes 32 together with
this exhaust gas mutually interferes with exhaust noise flowing
within the outlet pipe 26 in the direction inverse to the flowing
directions in the two expanding chambers 29 and 30, thereby
attenuating the exhaust noise.
[0056] This second embodiment can achieve a similar effect to the
first embodiment by keeping the open area ratio of the interference
holes 32 not less than 1% but not more than 5% or, more preferably,
not less than 1.5% but not more than 3.5%.
[0057] Further, it is preferable for an area L5 in which the
interference holes 32 are bored to correspond to 75% or more of the
length of the contraflow area L4 shown in FIG. 5.
[0058] FIG. 7 shows a third embodiment of the invention.
[0059] Referring to FIG. 7, the housing 42 of a muffler 41 is
constituted of a metallic cylinder of which both ends are coaxially
reduced in diameter to form a constriction 42a and a constriction
42b.
[0060] In the housing 42, the separator 3 in which through holes 3a
are bored as shown in the first embodiment and the separator 4 in
which the through holes 4a are bored are fixed with the prescribed
spacing L1 between them, and they partition the housing 42 in the
longitudinal direction into a first expanding chamber 51, a second
expanding chamber 52 and a third expanding chamber 53.
[0061] In the housing 42, as in the foregoing embodiment, an inlet
pipe 45 for introducing exhaust gas into the muffler 41 is
disposed, held by the constriction 42a and the separators 3 and 4,
and an aperture 45a on its downstream side opens into the first
expanding chamber 51. Incidentally, an aperture 45b on its upstream
side is connected to an upstream exhaust pipe.
[0062] In the housing 42, as in the foregoing embodiment, an outlet
pipe 46 for discharging exhaust gas out of the muffler 41 is
disposed, held by the constriction 42b and the separators 3 and 4,
and an aperture 46a at its upstream end opens into the third
expanding chamber 53. Incidentally, an aperture 46b on the its
downstream side is connected to a downstream exhaust pipe.
[0063] Both the inlet pipe 45 and the outlet pipe 46 are disposed
in a bent form to be shifted to each other in the muffler 41 as
shown in FIG. 7.
[0064] Referring to FIG. 7, with the range from an aperture 45a at
the downstream end of the inlet pipe 45 to an aperture 46a at the
upstream end of the outlet pipe 46 being assumed to be the
contraflow area L2, interference holes 47 composed of a plurality
of small holes communicating with the first through third expanding
chambers 51 through 53 are bored, positioned in the contraflow area
L2, in the outlet pipe 46.
[0065] Further in the outlet pipe 46 are bored, positioned
downstream of the contraflow area L2, bypass holes 48 composed of a
plurality of small holes communicating with the first expanding
chamber 51. Incidentally, it is preferable for the bypass holes 48
to be as far downstream of the outlet pipe 46 as practicable.
[0066] Also, it is preferable for the total aperture area of the
interference holes 47 and the bypass holes 48 together to be kept
not greater than the passage area of the outlet pipe 46.
[0067] Further in the inlet pipe 45, in its contraflow area L2, are
bored interference holes 49 composed of a plurality of small holes
communicating with the second expanding chamber 52.
[0068] Since this embodiment is similar to the first embodiment in
the rest of the structure, the same constituent parts in it are
denoted by respectively the same reference signs as the foregoing,
and their description is dispensed with.
[0069] Next will be described the actions of the third
embodiment.
[0070] This third embodiment, besides achieving similar actions and
effects to the first embodiment described above, also proves
effective in attenuating noise in the low revolution range by
virtue of the bypass holes 48 bored in the outlet pipe 46.
[0071] Further, the presence of the interference holes 49 in the
inlet pipe 45 makes it possible to achieve an even greater
attenuating effect without reducing the attenuating effect in the
high revolution range of the engine.
[0072] FIG. 8 and FIG. 9 show a fourth embodiment of the
invention.
[0073] This fourth embodiment is a version of the third embodiment
described above modified in the inlet pipe 45 and the outlet pipe
46, in which the sections of an inlet pipe 65 and an outlet pipe 66
are formed in a substantially D shape within the muffler 41 as
shown in FIG. 9, and these pipes are joined together to form a
substantially circular sectional shape.
[0074] Further, a wire mesh 74 is held between the downstream end
of the outlet pipe 66 and the constriction 42b of the housing 42 to
enable any difference in thermal expansion between the housing 42
and the outlet pipe 66 to be absorbed.
[0075] Furthermore, it is preferable for the total aperture area of
the interference holes 47 and the bypass holes 48 together to be
kept not greater than the passage area in the substantially D
shaped sectional area of the outlet pipe 46.
[0076] Since this embodiment is similar to the third embodiment in
the rest of the structure, the same constituent parts in it are
denoted by respectively the same reference signs as the foregoing,
and their description is dispensed with.
[0077] This fourth embodiment can achieve similar actions and
effects to the third embodiment described above.
[0078] Also, though the fourth embodiment described above is an
example in which the inlet pipe 65 and the outlet pipe 66 are
formed in a D sectional shape and joined together, it is also
conceivable to use a separate pipe whose inside is divided in the
radial direction with a partitioning board to form in parallel
passages each having a substantially D-shaped section and to whose
open ends the inlet pipe and the outlet pipe are joined,
respectively.
[0079] Although each of the first embodiment through the fourth
embodiment described above is provided with a plurality of
expanding chambers, only one expanding chamber may as well be
disposed in the muffler as in a fifth embodiment shown in FIG.
10.
[0080] The fifth embodiment is a modified version of the third
embodiment less the separators 3 and 4, in which a single expanding
chamber 91 is formed in the housing 42 of a muffler 81.
[0081] Incidentally, the inlet pipe 45 and the outlet pipe 46 are
supported by stays 93 and 94, respectively.
[0082] Since this embodiment is similar to the third embodiment in
the rest of the structure, the same constituent parts in it are
denoted by respectively the same reference signs as the foregoing,
and their description is dispensed with.
[0083] Further, the housing of the muffler can as well be formed by
some other known method than what was described with respect to the
foregoing first through fifth embodiments, such as joining
press-formed shells to each other, and its sectional shape can also
be selected as desired.
[0084] It is further conceivable to dispose sound absorbing
materials, thermal expansion difference absorbing mechanisms and
exhaust gas purifying mechanisms midway on the inlet pipe and the
outlet pipe.
INDUSTRIAL APPLICABILITY
[0085] Because of what has been stated so far, according to the
present invention, it is possible to achieve a high attenuating
effect without reducing the attenuating effect in the high
revolution range of the engine.
[0086] Also according to the invention, an attenuating effect in an
even broader revolution range of the engine can be achieved if
interference holes are disposed in a range of 75% or more of the
length in the contraflow area of the outlet pipe.
[0087] Further according to the invention, an attenuating effect in
the low revolution range can be achieved by boring bypass holes
communicating with the expanding chamber(s) in the downstream part
matching the contraflow area of the outlet pipe and keeping the
total aperture area of the interference holes and the bypass holes
together not greater than the sectional area of the passage in the
outlet pipe.
[0088] Also according to the invention, an even greater attenuating
effect can be achieved without reducing the attenuating effect in
the high revolution range of the engine by boring interference
holes communicating with the expanding chamber(s) in the inlet pipe
in its contraflow area.
* * * * *