JP2003113706A - Muffler for engine exhaust system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler that can appreciably suppress generation of noise resulting from a resonance phenomenon. SOLUTION: A sub muffler 15 comprises an inner pipe 21 having a plurality of holes 20 in a pipe wall, and an outer pipe 22 connected to the inner pipe 21 to cover a perforated portion 21 of the pipe wall with a clearance. The perforated portion 21a of the inner pipe 21 is extended in a cantilever relation into the outer pipe 22 from a connection 24 between the inner pipe 21 and the outer pipe 22, and the end of the extended perforated portion 21a is mounted with a deadweight 23. An opening at the end of the perforated portion 21a of the inner pipe 21 is closed with a cap 25.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a muffler used in an exhaust system of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a muffler of this type, a sub-muffler (for example, an actual flatbed 2) provided separately from the main muffler in an exhaust system for the purpose of eliminating a lack of muffling of the main muffler.
-19820)).

Generally, such a sub-muffler has the following structure, for example. That is, as shown in FIG. 8, the sub-muffler includes an inner pipe 101 having a large number of small holes 100, and an outer pipe 102 that covers the outer circumference of the inner pipe 101 with a predetermined gap. The outer pipe 102 has a large diameter portion 103 formed at the center in the longitudinal direction thereof.
Small diameter portions 105 are formed on both ends of 03 via the gradually changing portions 104.

Then, one end 101a of the inner pipe 101 and one end 102a of the outer pipe 102 are externally fitted and welded to the downstream end of the upstream exhaust pipe 106. Also, the outer tube 10
The other end 102b of No. 2 is externally fitted and welded to the upstream end of the downstream exhaust pipe 107. Also, the inner pipe 1
The wire mesh ring 108 is attached to the other end portion 101b of 01.
And the other end portion 101 b of the inner pipe 101 is fitted to the other end portion 10 of the outer pipe 102 via the wire mesh ring 108.
It is supported by the inner peripheral wall of 2b.

By providing such a sub-muffler in the exhaust system, when the exhaust gas from the internal combustion engine flows in the sub-muffler, a part of the exhaust gas flows from the inside of the inner pipe 101 to the small hole 10.
Through 0, it expands and flows into the space 109 between the outer circumference of the inner pipe 101 and the inner circumference of the outer pipe 102. Due to this expansion, the acoustic energy of the exhaust gas is attenuated, and the exhaust sound can be reduced.

Further, since the wire mesh ring 108 supporting the other end portion 101b of the inner pipe 101 can be deformed relatively freely, the other end portion 101b of the inner pipe 101 can be deformed relatively.
It is possible to move (slide) relative to 2 in the axial direction. Therefore, even if a difference in thermal expansion occurs between the inner pipe 101 and the outer pipe 102 when the high-temperature exhaust gas flows through the sub-muffler, the inner pipe 101 moves relatively to the outer pipe 102. , The difference in thermal expansion comes to be absorbed.

[0007]

As described above, the inner pipe 101 is
By providing the wire mesh ring 108 between the outer pipe 102 and the outer pipe 102, the difference in thermal expansion between the pipes 101 and 102 is absorbed, and damage to the pipes 101 and 102 due to thermal stress is appropriately suppressed. You can By the way, in the exhaust system of the internal combustion engine such as the sub-muffler, a resonance phenomenon may occur due to the pulsation of the exhaust gas caused by the intermittent combustion explosion of the engine. In the conventional sub-muffler described above, when such a resonance phenomenon occurs, the contact noise of each tube 101, 102 can be suppressed by the wire mesh ring 108, but each tube 101, 102 is suppressed by the resonance.
The radiated sound generated from 102 could not be dealt with, and there was still room for improvement in this respect.

The present invention has been made in view of such circumstances, and an object thereof is to provide a muffler which can suitably suppress the generation of noise due to a resonance phenomenon.

[0009]

[Means for Solving the Problems] Means for attaining the above-mentioned objects and their effects will be described below. The invention according to claim 1 is a muffler including an inner pipe having a hole in a part of a pipe wall and an outer pipe connected to the inner pipe and covering a perforated portion of the pipe wall with a gap. The gist of the invention is that the perforated portion extends from the connecting portion of each pipe into the inside of the outer pipe in a cantilever shape, and a weight is attached to the extended portion.

According to the above construction, the weight functions as the mass of the dynamic damper, while the portion of the extending portion of the inner pipe between the attachment portion of the weight and the connecting portion functions as a spring and a dashpot in the dynamic damper. Come to do. Therefore, even if the exhaust pulsation is transmitted to the muffler of the engine exhaust system, the resonance is suppressed by the damping action of the dynamic damper.

Further, the mass of the muffler is increased by the weight, and the weight also functions as a mass damper. Therefore, even when the muffler resonates and vibrates, its vibration amplitude can be suppressed to a small value by the action of the mass damper.

As a result, it is possible to suitably suppress the generation of noise due to the resonance phenomenon in the muffler of the engine exhaust system. A second aspect of the present invention is based on the muffler of the first aspect, wherein the weight is attached to an end of the elongated perforated portion.

According to the above construction, the interval between the portion where the weight is attached and the connecting portion becomes large in the extending portion of the inner pipe. For this reason, this extended portion is likely to vibrate and functions properly as a spring and a dashpot in the dynamic damper, so that the resonance suppressing effect of the dynamic damper can be further enhanced.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the muffler described in (1), the gist of the perforated portion of the inner tube is that the extended end portion is closed. The invention according to claim 4 is the muffler according to any one of claims 1 to 3, wherein the perforated portion of the inner pipe is set to have a smaller passage cross-sectional area than other portions. Use as a summary.

Further, the invention according to claim 5 includes an inner pipe having a hole in a part of a pipe wall, and an outer pipe connected to the inner pipe and covering a perforated portion of the pipe wall with a gap. It is a muffler provided, and the gist is that the perforated portion is extended from the connecting portion of each of the pipes to the inside of the outer pipe, and the extended end portion is closed.

The invention according to claim 6 includes an inner tube having a hole in a part of the tube wall, and an outer tube connected to the inner tube and covering a holed part of the tube wall with a gap. It is a muffler provided, wherein the perforated portion is extended from the connecting portion of each of the pipes to the inside of the outer pipe, and the passage cross-sectional area thereof is set to be smaller than other portions. .

With these configurations, the ventilation resistance when the exhaust gas flows through the muffler increases. As a result, in the muffler of the engine exhaust system, the exhaust exhausted from the engine combustion chamber to the exhaust system is located upstream of the closed extended end of the inner pipe and the perforated portion where the passage cross-sectional area is reduced. It becomes easy to stay in the exhaust gas, and the exhaust gas that stays and the exhaust gas that is discharged thereafter interfere with each other. As a result, the exhaust pulsation and eventually the acoustic energy of the exhaust are reduced, and it is possible to preferably suppress the generation of noise due to the resonance phenomenon in the muffler of the engine exhaust system.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the muffler of the present invention is applied to a sub-muffler provided in an exhaust system of an on-vehicle internal combustion engine will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 1, in the exhaust pipe 17 which constitutes the exhaust system 12, the exhaust manifold 13 and the catalytic converter 1 are arranged in this order from the upstream side in the exhaust flow direction.
4, a sub muffler 15 and a main muffler 16 are arranged.

In the exhaust system 12 thus constructed, the exhaust gas discharged from the internal combustion engine 11 passes through the exhaust manifold 13, the catalytic converter 14, the sub muffler 15 and the main muffler 16 and is discharged to the outside. On this occasion,
The exhaust is silenced by the sub muffler 15 in addition to the main muffler 16.

As shown in FIG. 2, the sub-muffler 15 has an inner pipe 2 in which a plurality of holes 20 are formed in a part of the pipe wall.
1 and an outer pipe 22 connected to the inner pipe 21 and covering the perforated portion 21a of the inner pipe 21 with a gap therebetween.

The inner pipe 21 is formed by reducing the diameter of the downstream end of the upstream exhaust pipe 17a (see FIG. 1) arranged upstream of the sub muffler 15. On the other hand, the outer tube 2
2 is formed by expanding the diameter of the upstream end of the downstream exhaust pipe 17b (see FIG. 1) arranged downstream of the sub muffler 15.

The downstream end of the upstream exhaust pipe 17a is inserted from the opening of the upstream end of the downstream exhaust pipe 17b, and the upstream end of the downstream exhaust pipe 17b is further connected to the upstream exhaust pipe 17a. It is welded to the outer periphery of the non-reduced portion of the. The upstream exhaust pipe 17a and the downstream exhaust pipe 17b are connected by this welding. In this way, in the state where the upstream side exhaust pipe 17a and the downstream side exhaust pipe 17b are connected to each other, the perforated portion 21a of the inner pipe 21 is
From the connection portion 24 between the outer tube 22 and the outer tube 22, the outer tube 22 extends in a cantilever shape. Also, this perforated portion 21a
The cross-sectional area of the passage is set smaller than that of the other portion of the inner pipe 21 by the diameter reduction process.

Further, as shown in FIG. 2, the inner pipe 21
An annular weight 23 is attached to the outer periphery of the distal end of the elongated perforated portion 21a. Here, the weight 23 is set to have a mass corresponding to the resonance frequency of the exhaust system 12. Furthermore, the extended end of the perforated portion 21a is the cap 2
It is blocked by 5. The cap 25 is fixed to the extending end portion by, for example, press fitting.

In the sub-muffler 15 having such a structure, when the exhaust gas flows through the sub-muffler 15, the exhaust gas flows from the inside of the inner pipe 21 through the hole 20 to the outer surface of the inner pipe 21 and the inner surface of the outer pipe 22. It expands and flows into the space 26 between them. Due to this expansion, the acoustic energy of the exhaust gas is attenuated, and the exhaust sound can be reduced.

Further, in the sub muffler 15, the inner pipe 2
Since the extended end of the perforated portion 21a of No. 1 is closed by the cap 25, the exhaust gas from the internal combustion engine 11 always flows through the hole 20 of the inner pipe 21. As a result, the ventilation resistance when the exhaust gas flows through the sub-muffler 15 increases, and the exhaust gas discharged from the internal combustion engine 11 to the exhaust system 12 is upstream of the extended end portion of the inner pipe 21 in the exhaust system 12. It becomes easy to stay in the system, and the exhaust that stays and the exhaust that is discharged thereafter interfere with each other. As a result, the exhaust pulsation, and eventually the acoustic energy of the exhaust, can be suitably reduced, and the noise can be further reduced.

Further, in the sub muffler 15, the inner pipe 21
Since the weight 23 is arranged at the extended end of the inner pipe 21, the weight 23 functions as the mass of the dynamic damper, while the tip of the perforated portion 21a of the inner pipe 21 and the connecting portion 2 are connected.
The portion between 4 and 4 functions as a spring and a dashpot in the dynamic damper. Therefore, even if the exhaust pulsation is transmitted from the internal combustion engine 11 to the sub muffler 15, the resonance is suppressed by the damping action of the dynamic damper. As a result, it is possible to preferably suppress the generation of noise due to the resonance phenomenon.

In particular, the weight 23 is replaced by the perforated portion 21a of the inner pipe 21.
Since it is attached to the end of the inner pipe 21,
The distance between the end of the connector and the connecting portion 24 increases. As a result, the extended portion of the inner pipe 21 is likely to vibrate, and it suitably functions as a spring and a dashpot in the dynamic damper, so that the resonance suppressing effect of the dynamic damper can be further enhanced. Therefore, the noise caused by the resonance phenomenon can be reduced more preferably.

The mass of the sub-muffler 15 is increased by the weight 23, and the weight 23 also functions as a mass damper. Therefore, even if the muffler resonates and vibrates, its vibration amplitude can be suppressed to a small value by the action of the mass damper, and further noise reduction can be achieved.

The configuration of the above-described embodiment can be appropriately changed as follows. In the above-described embodiment, as shown in FIG. 2, the length of the perforated portion 21a of the inner pipe 21 is the perforated portion of the inner pipe 21 with the upstream exhaust pipe 17a and the downstream exhaust pipe 17b being connected. Part 2
The length of the end portion 1a is set to the downstream side of the outer tube 22.
However, the length of the perforated portion 21a of the inner pipe 21 can be arbitrarily set. For example, as shown in FIG.
With the exhaust pipes 17a and 17b connected, the perforated portion 2
The downstream end of 1a may be set to be located upstream of the outer pipe 22, or may be set to be located in a portion of the downstream exhaust pipe 17b where diameter expansion processing is not performed. . In the latter case, the inner pipe 21 and the weight (not shown in FIG. 3) are prevented from coming into contact with the downstream exhaust pipe 17b so that the inner diameter of the inner pipe 21 of the downstream exhaust pipe 17b or the outer portion of the inner pipe 21 does not contact the downstream exhaust pipe 17b. It is necessary to set the diameter.

In the above embodiment, a substantially U-shaped cut is provided in the peripheral wall of the inner pipe 21, and, for example, in the mode shown in FIG.
The hole 20 may be formed by bending the peripheral wall of the cut portion outward to form the louver 30.

In the above embodiment, the inner pipe 21 is formed integrally with the upstream exhaust pipe 17a, while the outer pipe 22 is formed integrally with the downstream exhaust pipe 17b. However, only one or both of the inner pipe 21 and the outer pipe 22 is connected to the exhaust pipe 17
It may be formed separately from a and 17b. In the above embodiment, the inner pipe 21 and the outer pipe 22 are the exhaust pipes 17a and 17b, respectively, which are opposite to each other, that is, the inner pipe 21 is at the upstream end of the downstream exhaust pipe 17b, while the outer pipe 22 is at the upstream side. The exhaust pipe 17a may be provided at the downstream end.

The perforated portion 21a of the inner pipe 21 is not necessarily limited to one in which the passage cross-sectional area is set smaller than that of the other portion of the inner pipe 21. In the above embodiment, a through hole may be provided in the wall surface of the cap 25 orthogonal to the flow direction of the exhaust gas in the exhaust system 12, and the extended end of the perforated portion 21a of the inner pipe 21 may not be completely closed.

In the above embodiment, the end of the perforated portion 21a of the inner pipe 21 is closed by the cap 25. However, instead of providing the cap 25 on the inner pipe 21, for example, in the mode shown in FIG.
The end opening of 1a may be closed by pressing or the like.

Further, as shown in FIGS. 6 and 7, for example, the passage cross-sectional area of the end portion (see FIG. 6) of the perforated portion 21a of the inner pipe 21 or in the vicinity thereof (see FIG. 7) is the inner pipe 21. The structure may be formed so as to be smaller than the passage cross-sectional area of other portions.

Even in such a case, the ventilation resistance when the exhaust gas flows through the sub muffler 15 increases, and the exhaust system 1
2, upstream of the extended end portion of the inner pipe 21, the exhaust gas already discharged from the internal combustion engine 11 to the exhaust system 12 interferes with the exhaust gas discharged thereafter. As a result, the exhaust pulsation, and eventually the acoustic energy of the exhaust, can be suitably reduced, and the noise can be further reduced.

In the above embodiment, the cap 25 may also function as the weight 23. If you do this,
It is possible to simplify the configuration while suppressing the occurrence of resonance in the resonance system of the exhaust system 12.

In the above embodiment, the position of the weight 23 fixed to the inner pipe 21 is arbitrary. Further, it is not necessary to provide the weight 23 over the entire circumference of the inner pipe 21, and the weight 23 may be provided only in a part of the inner pipe 21 in the circumferential direction.

The number of weights 23 fixed to the inner pipe 21 is not limited to one. The weight 23 may be provided in two or more in the longitudinal direction of the inner pipe 21, or may be provided so as to be divided into a plurality in the circumferential direction of the inner pipe 21.

In the above embodiment, the weight 23 may be attached to a corrugated tube connected to the end of the perforated portion 21a of the inner tube 21, that is, a so-called bellows tube. -In the above embodiment, the weight 23 may be omitted,
The end of the perforated portion 21a of the inner pipe 21 may not be closed.

In the above embodiment, the sub muffler 15
May be arranged downstream of the main muffler 16 in the exhaust system 12 of the automobile. In addition, sub muffler 1
When a plurality of exhaust mufflers 5 are provided in the exhaust system 12, the sub-muffler 15 may be arranged on both the upstream side and the downstream side of the main muffler 16 in the exhaust system 12.

In the above embodiment, the exhaust system 12 of the automobile
Although the example of the sub-muffler 15 arranged in a pair with the main muffler 16 is shown in the above, the present invention can be similarly applied to the muffler provided with only one in the exhaust system 12.

In the above embodiment, the exhaust system 12 of the automobile
Although the example of the sub muffler 15 provided in the above is shown, the present invention can be similarly applied to the muffler provided in the exhaust system of a motorcycle, for example.

[Brief description of drawings]

FIG. 1 is a schematic view showing a sub-muffler and an exhaust system around the sub-muffler according to an embodiment.

FIG. 2 is a sectional view showing a sectional structure of a sub-muffler of the same embodiment.

FIG. 3 is a sectional view showing a sectional structure of a sub-muffler according to another example.

FIG. 4 is a sectional view showing a sectional structure of an inner pipe portion of a sub-muffler according to another example.

FIG. 5 is a sectional view showing a sectional structure of a sub-muffler according to another example.

FIG. 6 is a sectional view showing a sectional structure of a sub-muffler according to another example.

FIG. 7 is a sectional view showing a sectional structure of a sub-muffler according to another example.

FIG. 8 is a sectional view of a conventional sub-muffler.

[Explanation of symbols]

11 ... Internal combustion engine, 12 ... Exhaust system, 13 ... Exhaust manifold, 14 ... Catalytic converter, 15 ... Sub muffler, 16 ... Main muffler, 17 ... Exhaust pipe, 17a ... Upstream exhaust pipe, 17b ... Downstream exhaust pipe, 20 ... Hole, 21 ... Inner tube, 21a ... Perforated part, 22 ... Outer tube, 23 ... Weight, 24 ...
Connection part, 25 ... Cap, 26 ... Space, 30 ... Louver.

Claims (6)

[Claims] 1. An inner pipe having a hole in a part of a pipe wall, and an outer pipe connected to the inner pipe and covering a perforated portion of the pipe wall with a gap therebetween, wherein the perforated portion includes A muffler for an engine exhaust system, which extends in a cantilever shape from a pipe connecting portion to the inside of the outer pipe, and a weight is attached to the extending portion. 2. The muffler for an engine exhaust system according to claim 1, wherein the weight is attached to an end of the elongated perforated portion. 3. A muffler for an engine exhaust system according to claim 1, wherein the perforated portion of the inner pipe is closed at its extended end. 4. A muffler for an engine exhaust system according to claim 1, wherein the perforated portion of the inner pipe is set to have a smaller passage cross-sectional area than other portions. 5. An inner pipe having a hole in a part of a pipe wall, and an outer pipe connected to the inner pipe and covering a perforated part of the pipe wall with a gap therebetween, wherein the perforated part includes each of the above-mentioned respective parts. A muffler for an engine exhaust system, which is extended from a connecting portion of a pipe to the inside of the outer pipe and whose extended end is closed. 6. An inner pipe having a hole in a part of a pipe wall, and an outer pipe connected to the inner pipe and covering a perforated part of the pipe wall with a gap therebetween, wherein the perforated part is each of the above-mentioned respective parts. A muffler for an engine exhaust system, which extends from a connecting portion of a pipe to the inside of the outer pipe and has a passage cross-sectional area set smaller than that of other portions.