JP2003269130A - Muffler for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffler having improved noise reduction property. <P>SOLUTION: A porous pipe 25 having a plurality of pores is provided between an inlet 24 and an outlet 26 of an exhaust fluid and a chamber 21 is provided with an interior space storing the porous pipe and communicating with the pores. An inner pipe portion 27 having a predetermined length is inserted into the porous pipe 25 and an opening portion 27a is provided therein for guiding the exhaust fluid introduced from the inlet into the porous pipe into a gap space S formed between the porous pipe and the inner pipe portion. Preferably, the gap space S has a relatively wider inlet portion but an outlet portion relatively narrower or in a throttled or closed condition. The guide of the exhaust fluid from the opening portion into the gap space promotes the oscillating wave diffusing and interfering operation of the exhaust fluid through the pores and improves the noise reduction effects. The throttled outlet of the gap space promotes the compression of the exhaust fluid in the gap space and improves the noise reduction effects. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler for an internal combustion engine such as an automobile engine, and more particularly to a muffler capable of improving sound deadening performance.

[0002]

[Prior art]

[Patent Document 1] JP-B-46-36670

[Patent Document 2] JP-A-47-6804

[Patent Document 3] JP-A-47-14169

[Patent Document 4] Japanese Utility Model Publication No. 14-11446

[Patent Document 5] Japanese Utility Model Publication No. 44-31526 As an example of a conventional muffler for an automobile, ones shown in FIGS. 13 and 14 are known. The muffler 1 shown in FIG. 13 has four partitioned chambers 2, 3, 4, and 5, and exhaust gas discharged from an engine (not shown) is introduced into the chamber via an introduction pipe 6. 4, flows from the chamber 4 into the chamber 2 through the communication pipe 7 having a large number of small holes, and further flows from the chamber 2 into the outlet pipe 8 and is discharged. Further, the chamber 4 communicates with the chamber 5 via the pipe 9. With this configuration, expansion, resonance, interference, resistance, etc. of sound waves occur, and exhaust noise can be silenced in a predetermined frequency band.

The muffler 10 shown in FIG. 14 is provided with a perforated pipe 13 in which an inlet pipe 11 and an outlet pipe 12 communicate with each other in a straight line. The perforated pipe 13 is covered with a filter 14, and the periphery thereof is covered. The room is filled with a sound absorbing material 15 such as glass wool. In this case, sound absorption in the predetermined frequency band is performed by the sound absorption characteristics of the sound absorbing material 15.

[0004]

In the muffler 1 shown in FIG. 13, the sound pressure level is reduced by making the exhaust path complicated and long. Therefore,
Although the sound deadening characteristics are good, on the other hand, loss and resistance of exhaust pressure are increased, and significant adverse effects occur at high rotation and high load. On the other hand, the muffler 10 shown in FIG. 14 is a low exhaust pressure loss type because it can be exhausted in a straight line, but it can only muffle a specific frequency band of the sound absorbing material, and particularly in the low frequency band. I could not mute. In particular, it was not possible to muffle sound in the band of 70 Hz to 90 Hz, which is the vibration frequency of the vehicle interior cavity resonance. Further, since the sound absorbing material easily absorbs moisture, there is a problem that the metal of the pipe line or the muffler body is easily corroded and durability is poor.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a muffler for an internal combustion engine which has a good muffling characteristic. Furthermore, it is an object of the present invention to provide a muffler capable of improving durability. Furthermore,
It is intended to provide a muffler that can achieve both low exhaust pressure loss characteristics and improvement of noise reduction characteristics.

[0006]

A muffler for an internal combustion engine according to the present invention comprises an inlet for introducing exhaust fluid,
A muffler body having a chamber provided inside and an outlet for leading out the exhaust fluid to the outside, and the exhaust fluid passes through the pipe housed in the muffler body. And a first tube portion including a perforated tube portion having a plurality of small holes communicating with the chamber, and a given length inserted into the first tube portion at a location corresponding to the perforated tube portion. A second pipe portion having an inner pipe portion that forms a gap space between the outer peripheral surface of the inner pipe portion and the inner peripheral surface of the perforated pipe portion. The given length of the inner tube portion corresponds to a length range in which the plurality of small holes are present in the perforated tube portion, and
When the exhaust fluid flows through the first pipe portion extending between the inlet and the outlet, the end of the inner pipe portion near the exhaust upstream is open to the internal space of the first pipe portion. Exhaust fluid is allowed to smoothly pass through the inner pipe portion, and the gap space formed between the outer peripheral surface of the inner pipe portion and the inner peripheral surface of the perforated pipe portion is At least near the exhaust upstream side, the exhaust sound waves are communicated with the internal space of the first pipe portion so as to be able to enter the gap space, and the first pipe portion is at least from the introduction port to the internal space. It is characterized in that it extends continuously without interruption in the path leading to the exhaust upstream end of the pipe portion.

As an example, the inner pipe portion is in close contact with the perforated pipe portion at a predetermined position of the inner pipe portion on the downstream side of the exhaust gas. As an example, the gap is closed at a predetermined position on the downstream side of the exhaust gas. As an example, the gap is set so as to gradually narrow as it goes from the upstream side to the downstream side of the exhaust gas, and the relative relationship between the outer diameter of the inner pipe portion and the inner diameter of the perforated pipe portion is set to change. It is characterized by

As an example, a sound absorbing member is housed in the chamber. As an example, in the muffler body, the inlet and the outlet are arranged substantially in a straight line, and the first pipe portion is arranged so as to form a substantially straight exhaust passage therebetween.

According to the present invention, the exhaust sound wave of the exhaust fluid passing through the first pipe portion is constituted by a large number of small holes of the perforated pipe portion in the first pipe portion communicating with the internal space of the chamber of the muffler body. Diffuse into the space inside the room through the small holes, and effects such as diffusion and interference of exhaust sound waves, thereby contributing to silencing in a predetermined frequency band (for example, a middle-high frequency band). In particular, it comprises a second tube section having an inner tube section of a given length inserted into the first tube section at a location corresponding to the perforated tube section, Since the pipe portion and the inner pipe portion of the second pipe portion arranged inside the pipe portion have a double pipe structure, a gap space is formed between the outer peripheral surface of the inner pipe portion and the inner peripheral surface of the porous pipe portion. Are formed, and the exhaust sound waves are compressed in this gap space, whereby diffusion, interference, etc. of the exhaust sound waves through the small holes of the perforated pipe are promoted, and therefore, the sound deadening effect can be further promoted. It has an excellent effect that it can.

In particular, the gap space formed between the outer peripheral surface of the inner pipe portion and the inner peripheral surface of the perforated pipe portion communicates with the inner space of the first pipe portion at least near the exhaust upstream side. With the configuration in which the exhaust sound waves can enter the gap space, there is an advantage that diffusion and interference of the exhaust sound waves can be surely promoted. Also,
The end portion of the inner pipe portion near the exhaust upstream has a relatively large diameter and opens into the internal space of the first pipe portion, and exhausts the inside of the first pipe portion that extends between the inlet and the outlet. When the fluid flows, the exhaust fluid can smoothly pass through the inner pipe portion, so that the exhaust fluid can be smoothly discharged, engine exhaust pressure can be reduced, and engine efficiency can be reduced. Has the advantage of not.

By way of example, the preferred form of the gap space can be provided in various forms. For example, the inner pipe portion may be brought close to the perforated pipe portion at a predetermined portion of the inner pipe portion on the downstream side of the exhaust gas so that the clearance space is minimized. Alternatively, the inner pipe portion may be in close contact with the perforated pipe portion at a predetermined position of the inner pipe portion on the downstream side of the exhaust gas to close the gap space. Alternatively, the gap space may be structured so as to be throttled in the downstream side of the exhaust gas or closed in the downstream side of the exhaust gas. Alternatively, the clearance space on the upstream side of the exhaust gas may be wider than that on the downstream side of the exhaust gas. Alternatively, the clearance space is set so that it gradually narrows as it goes from the upstream side of the exhaust gas to the downstream side, and the relative relationship between the outer diameter of the inner pipe portion and the inner diameter of the perforated pipe portion is changed. Good. This change in the clearance space may be gradual. Alternatively, the relative space between the outer diameter of the inner pipe portion and the inner diameter of the perforated pipe portion is set so that the clearance space is substantially constant in a predetermined range from the upstream side of the exhaust gas and is narrowed at the end portion. May be. Alternatively, the gap space may be changed by changing at least one of the outer diameter of the inner pipe portion and the inner diameter of the perforated pipe portion. Various other variations are possible.

[0012] Overall, considering a preferable mode of the gap space formed between the perforated pipe portion and the inner pipe portion inside thereof, the end of the inner pipe portion closer to the inlet (closer to the exhaust upstream) is considered. The cross-sectional area or partial volume of the space between this part and the inner wall of the perforated pipe (provisionally this is called the gap space inlet) is between the end of the inner pipe part near the outlet (closer to the exhaust downstream) and the inner wall of the perforated pipe. It is characterized in that it is larger than the cross-sectional area or partial volume of the space (provisionally, this is called the gap space outlet). That is, the gap space inlet is wider than the gap space outlet-in other words, the gap space outlet is relatively narrowed or closed-, so that the perforated pipe and the inner pipe portion have a double pipe structure. The exhaust sound waves that enter the gap space are compressed by the narrowed outlet, so that the diffusion and interference of the exhaust sound waves through the small holes of the perforated pipe are further promoted. Therefore, a preferable mode of such a clearance space is to further promote the sound deadening effect.

Specific embodiments of the inner tube portion and the perforated tube portion forming the double tube structure may be designed in various ways. For example, in a predetermined range from the exhaust upstream side to the exhaust downstream side,
It may include a tapered tube structure whose diameter gradually changes. Alternatively, the diameter may be changed stepwise within a predetermined range from the upstream side to the downstream side of the exhaust gas. Alternatively, the diameters of both pipe portions may be substantially constant in a range over substantially the entire clearance space, and the two may be close or close to each other so as to narrow or close the clearance space at the terminal end of the clearance space. . A desired mode of changing the clearance space may be realized by changing the diameters of both the inner pipe part and the perforated pipe part, or a desired mode of changing the clearance space may be changed by changing either one of the diameters. May be realized. Further, the cross-sectional shape of the tube is not necessarily circular, but may be any shape such as an ellipse or a polygon. Therefore, the size of the pipe diameter in the present invention is synonymous with the size of the cross-sectional area.

The muffler according to the present invention is only required to have the double tube structure as described above at least in part, and any structure may be added thereto. One preferable embodiment is to combine the exhaust passage in which the exhaust inlets and outlets in the muffler body are arranged in a substantially straight line with the double pipe structure as described above. As a result, a configuration (low exhaust pressure loss type) capable of significantly suppressing the resistance and loss exerted on the exhaust pressure can be made, which can greatly contribute to fuel saving and improvement of power performance. In that case, due to the above-mentioned improvement in sound deadening performance due to the double pipe structure, it is possible to obtain the necessary sound deadening performance even if the sound absorbing material required by the conventional straight pipe structure muffler is not provided. . Therefore, by not providing a large amount of sound absorbing material, it is possible to solve the problem of corrosion of metal due to moisture absorption by the sound absorbing material and deterioration of durability due to the corrosion.

Of course, in order to further improve the silencing performance,
A sound absorbing material may be used in combination with the double pipe structure as described above. For example, a sound absorbing material may be filled in the sound absorbing chamber. Then, the sound absorption characteristic of the sound absorbing material enables the sound to be effectively damped in the predetermined frequency band, and the sound deadening effect can be further enhanced. Further, providing the sound deadening material along at least a part of the wall surface in the sound absorbing room reduces the amount of the sound deadening material used, and moreover,
When combined with the double pipe structure, it is advantageous because it contributes to removing exhaust sound vibration waves in a specific frequency band that cannot be removed by the double pipe structure. In practicing the present invention, the various embodiments described above and below may be partially combined in various ways.

[0016]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. A muffler 20 according to an embodiment of the present invention shown in FIG.
It has two chambers partitioned by a partition 23, namely a first chamber 21 and a second chamber 22. Exhaust gas from an engine (not shown) is introduced into the muffler body via an introduction pipe 24 (corresponding to an introduction port), and a discharge pipe 26 (corresponding to a discharge port).
And is discharged from the muffler body via. A perforated pipe 25 having a large number of small holes 33 on its side surface is linearly connected to the introduction pipe 24, and the perforated pipe 25 is linearly communicated with the outlet pipe 26. Therefore, since the exhaust gas linearly passes through the muffler 20, it has an extremely efficient exhaust pressure low loss structure.

The perforated pipe 25 is provided so as to correspond to the first chamber 21, and the inner space of the perforated pipe 25 not only communicates with the inlet pipe 24 and the outlet pipe 26 as described above, but also on the side surface thereof. It communicates with the first chamber 21 through a large number of small holes 33 provided. As a result, diffusion (expansion), interference, etc. of the exhaust sound vibration wave occur in the chamber 21 via the large number of small holes 33, and the sound of a predetermined middle and high range (for example, air flow sound) is silenced by the porous resonance type silencing effect. Can be done.

Inside the perforated pipe 25, an inner pipe portion 27 made of a pipe having a predetermined length is fixedly provided, and has a double pipe structure. The inner pipe portion 27 is characterized in that its pipe diameter is larger at the pipe end portion 27b near the outlet port than at the exhaust fluid inlet port 27a. To show this, A- in FIG.
An enlarged sectional view taken along the line A is shown in FIG. 2A, and an enlarged sectional view taken along the line BB is shown in FIG. 2B. The gap space S between the perforated pipe 25 and the inner pipe portion 27 is relatively large upstream of the flow of the exhaust fluid as shown in FIG. 2 (a), and relatively large downstream thereof as shown in FIG. 2 (b). You can see that it is small (or closed).

The specific structure of the inner tube portion 27 may be designed in various ways. For example, as shown in the figure, the pipe end 2 near the outlet port
The diameter of 7b may be large, and other diameters may be smaller than that and have substantially the same diameter. Alternatively, without being limited to this, the pipe end portion 27a near the introduction port to the pipe end portion 27b near the outlet port
The taper pipe structure may be such that the diameter gradually increases. Alternatively, the structure may be such that the diameter gradually increases in several steps from the pipe end portion 27a near the inlet port to the pipe end portion 27b near the outlet port. In addition, the inner pipe portion 27
The pipe end portion 27b near the outlet may be in close contact with the inner wall of the perforated pipe 25 at its entire circumference to completely close the outlet of the interstitial space of the double pipe structure. The space may be opened so that the gap space outlet is not completely closed. In short, any structure may be used as long as it narrows the outlet of the gap space of the double pipe structure.

Due to the double tube structure as described above, the perforated tube 2
The cross-sectional area of the gap space S formed between the inner pipe portion 27 and the inner pipe portion 27 is the space between the pipe end portion 27a near the inlet of the inner pipe portion and the inner wall of the porous pipe 25 (provisionally referred to as the gap space inlet). Is larger than the cross-sectional area of the space (provisionally referred to as a clearance space outlet) between the pipe end portion 27b near the outlet of the inner pipe portion and the inner wall of the porous pipe 25. That is, since the gap space inlet is wider than the gap space outlet, the exhaust fluid entering the gap space of the double pipe structure of the perforated pipe 25 and the inner pipe portion 27 is compressed by the outlet being compressed. As a result, the diffusion and interference of the vibration wave of the exhaust fluid through the small holes of the perforated pipe 25 are promoted. Therefore, it is possible to further promote the sound deadening effect in a predetermined middle and high band.

Further, in the embodiment shown in FIG. 1, a communication pipe 28 communicating with the first chamber 21 and the second chamber 22 is provided.
This constitutes a Helmholtz resonator (first resonator), and contributes to silencing in a predetermined low frequency band. Further, a second communication pipe 29 that communicates with the first chamber 21 and the second chamber 22 is provided at another position. As a result, the Helmholtz resonator (second resonator)
And contributes to silencing in a predetermined low frequency band. In this way, these two types of resonators can contribute to the silencing of two types of different low frequency bands.

The pipe length and / or the pipe diameter of the inner pipe portion 27 are appropriately set, the pipe length of the perforated pipe 25, the size and the number of small holes, etc. are set appropriately, and the communicating pipe 28 constituting the resonator is formed. , 29, by appropriately setting the number of tubes, the tube length, and the tube diameter, etc., while suppressing the noise in the band of 70 Hz to 90 Hz which is the so-called muffled sound of the resonance frequency in the vehicle interior cavity, Of the low frequency band (for example, 200 Hz to 300 Hz) can be achieved, and in combination with the silencing of the mid-high range through the small holes of the perforated pipe, the silencing of a wide range from the low range to the mid-high range can be easily performed. It can be achieved by a chamber structure.

FIG. 3 is a diagram showing another embodiment of the present invention. In this embodiment, the muffler 10A is shown in FIG.
Similarly to the muffler 10 shown in FIG.
1 (corresponding to the inlet) and outlet pipe 12 (corresponding to the outlet) 1
A perforated tube 13 is provided which communicates in a straight line.
The surroundings of the above are covered with a filter 14, and a sound absorbing material 15 such as glass wool is filled in the surrounding room. Inside the perforated pipe 13, an inner pipe portion 27 having the same configuration as that of FIG. 1 is provided. In this case, the inner pipe portion 27
In addition to the sound deadening effect of the perforated tube 13 promoted by, the sound deadening property of the sound absorbing material 15 is used to muffle sound in a predetermined frequency band.

FIG. 4 is a diagram showing still another embodiment of the present invention. In this embodiment, the muffler 20A has a two-chamber structure including a first chamber 21 and a second chamber 22 as in the muffler 20 shown in FIG.
Inside the perforated pipe 25 corresponding to No. 1, an inner pipe portion 27 having the same configuration as that in FIG. 1 is provided. The pipe 30 corresponding to the second chamber 22 is a perforated pipe having a large number of small holes. Further, as in the case of FIG. 3, the inside of the second chamber 22 has a configuration in which the periphery of the tube 30 made of a perforated tube is covered with a filter 31, and the surrounding room is filled with a sound absorbing material 32 such as glass wool. Has become. In this case, a communication pipe that passes through the first chamber 21 and the second chamber 22 is not provided. Also in this case, in addition to the sound deadening effect in the first chamber 21 due to the perforated tube 25 promoted by the inner tube portion 27, the sound deadening effect in the second chamber 22 due to the sound absorbing characteristic of the sound absorbing material 32 can be obtained. In this case, the first chamber 21 and the second chamber 22 may be separated. In addition, the second chamber 22 provided with the sound absorbing material 32
May be arranged in front of the first chamber 21.

FIG. 5 is a diagram showing still another embodiment of the present invention. In this embodiment, the first muffler portion 20
Has the same configuration as the muffler portion 20 shown in FIG. The second muffler portion 10 is provided at a stage before the first muffler portion 20. The second muffler portion 10 is
It has the same configuration as the muffler 10 of FIG. Therefore, also in this case, in addition to the silencing effect in the first muffler portion 20 by the perforated pipe 25 promoted by the inner pipe portion 27,
It is possible to obtain a sound deadening effect in the second muffler portion 10 due to the sound absorbing characteristics of the sound absorbing material 15, and it is possible to cleanly remove noise in a band that could not be removed by the embodiment of FIG. FIG. 6 shows an example of the sound deadening characteristic according to the embodiment of FIG. 5, a solid line shows an example of the sound deadening characteristic by the first muffler portion 20, and a broken line shows an example of the sound deadening characteristic by the second muffler portion 10. .

In the above embodiment, the gap space S formed between the outer peripheral surface of the inner pipe portion 27 and the inner peripheral surface of the perforated pipe 25 or 13 outside the inner pipe portion 27 is narrowed in the portion near the downstream of the exhaust gas. In order to ensure that the outer diameter of the inner pipe portion 27 is changed and the inner diameters of the perforated pipes 25 and 13 are not changed, on the contrary, the outer diameter of the inner pipe portion 27 is kept constant and The inner diameters of the perforated tubes 25, 13 may be changed appropriately. Alternatively, the outer diameter of the inner pipe portion 27 and the perforated pipe 2 outside thereof
Both the inner diameters of 5 and 13 may be changed. In short, the gap space S between the perforated pipes 25, 13 and the inner pipe portion 27 provided inside thereof is gradually or gradually narrowed toward the exhaust outlet, or at least the exhaust gas is exhausted. The space may be narrowed or narrowed or closed at the exit of the.

Further, the structure of the muffler chamber in the muffler body is not limited to the two-chamber structure or the one-chamber structure shown in FIGS. 1, 3 and 4, but various modifications are possible. Further, as shown in FIG. 7, a plurality of small holes 34 may be provided in the inner pipe portion 27 as well. As a result, the vibration wave of the exhaust sound diffuses through the plurality of small holes 34 of the inner pipe portion 27, and the exhaust sound waves are diffused and diffused even between the inner pipe portion 27 and the porous pipe 25 outside thereof. Interference is promoted, which contributes to the silencing of exhaust sound vibration waves up to a wider low frequency band.

A muffler 20B according to another embodiment of the present invention shown in FIG. 8 is one in which the diameter of the inner pipe portion 37 is made constant while the diameter of the perforated pipe 35 outside thereof is changed. is there. The perforated pipe 35 having a large number of small holes 33 on its side surface is connected to the exhaust gas introduction port 24, and an inner pipe portion 37 having a constant diameter is inserted therein. The outer perforated pipe 35 has a shape in which the middle portion is swollen, and the diameter of the perforated pipe 35 is relatively large at the portion corresponding to the end portion 37a of the inner pipe portion 37 on the exhaust upstream side (close to the introduction port). A relatively large gap space S can be formed between the inner pipe portion 37 and the inner pipe portion 37. The diameter of the perforated pipe 35 gradually decreases in the portion 35b on the exhaust downstream side (close to the outlet), and finally contacts the inner pipe portion 37 to close the gap space S. As a result, as described above, since the inlet of the gap space S is wider than the outlet, the outlet of the exhaust sound wave entering the gap space S of the double pipe structure of the outer porous pipe 35 and the inner pipe portion 37 is narrowed at the outlet. As a result, it is compressed, diffusion of exhaust sound waves through the small holes 33 of the perforated pipe 35, interference, etc. are promoted, and the sound deadening effect for a predetermined frequency band is further promoted. Is something that can be done.

Further, in the example of FIG. 8, a plurality of small holes 34 are provided in the inner pipe portion 37 as in the case of FIG. 7. This makes it possible to improve the sound deadening effect in a wider frequency band, as described above. On the contrary, as in FIG. 1, it goes without saying that the plurality of small holes 34 may be omitted in the inner tube portion 37. Further, in the example of FIG. 8, the first chamber 21 is partitioned by a partition wall 36 having a large number of small holes, and a sub chamber (or a third chamber) 21B is formed. In addition, a communication pipe 28B that connects the chamber 21 and the sub chamber 21B is also provided. Thereby, the first chamber 2 through the large number of small holes of the partition wall 36 and the communication pipe 28B.
The sound deadening effect can also be obtained by diffusing and / or interfering with exhaust sound waves from 1 (that is, the main chamber) to the sub chamber 21B.

Further, in the example of FIG. 8, the perforated pipe (that is, the outer pipe) 35 and the inner pipe portion 37 open and terminate in the sub-chamber 21B at the exhaust downstream side, and are led out through the sub-chamber 21B. It leads to a pipe 26. Diffusion of exhaust sound waves from the sub-chamber 21B to the first chamber 21 through this opening and / or
Alternatively, the sound deadening effect can be obtained by interference. In this way, even if a part of the pipeline from the exhaust inlet 24 to the outlet 26 is removed and that portion is replaced by the sub-chamber, a straight exhaust path can be secured, so that the exhaust pressure is low loss. The characteristic exhaust can still be achieved. Further, since the main chamber 21 and the sub-chamber 21B are pressure-communicated with each other by the partition wall 36 in which a plurality of small holes are formed, the exhaust fluid is accelerated so as to be sucked into the outlet pipe 26. Not only the sound deadening effect but also the effect that the exhaust efficiency can be improved is exhibited.

A muffler 20C according to another embodiment of the present invention shown in FIG. 9 has a structure in which the diameter of the inner tube portion 37 is made constant while the diameter of the outer perforated tube 35 is changed as shown in FIG. It is a modification of the embodiment. In this example, the outer perforated pipe 35 is not directly connected to the introduction pipe 24, and its end portion 35a near the exhaust upstream is open. A short perforated pipe 38 is connected to the introduction pipe 24, and an exhaust downstream end 38b of the perforated pipe 38 substantially coaxially faces the end 35a of the perforated pipe 35 at a relatively short distance. In this way, even if the outer perforated pipes 35, 38 are partially removed and open to the chamber 21, a straight exhaust path can be secured, so exhaust with low exhaust pressure loss characteristics is achieved. There is no change in what you can do. In addition, when the exhaust pressure rises momentarily, the exhaust pressure can be instantaneously released into the chamber 21 through the openings of the perforated pipes 38, 35, so that the pressure distribution is stabilized and the silencing performance is stabilized. Can contribute to. Of course, the modified example in which a part of the outer perforated pipe on the upstream side of the exhaust gas is removed to open in the muffler chamber is also applicable to the muffler 20 having the perforated pipe 25 having a constant diameter as shown in FIG. .

A muffler 20D according to another embodiment of the present invention shown in FIG. 10 is a modification of FIG. 9, in which the diameter of the perforated pipe 38 connected to the exhaust gas introduction pipe 24 is larger than the diameter of the perforated pipe 35. Largely, one end portion 35a of the perforated pipe 35 is inserted into one end portion 38b of the perforated pipe 38, and the whole has a triple pipe structure. Even in this case, since a straight exhaust path can be secured, exhaust gas with low loss characteristics can still be achieved, and in addition, the exhaust pressure increases momentarily as described above. Perforated tube 38
Since the exhaust pressure can be instantaneously released into the chamber 21 through the opening, the pressure distribution can be stabilized and the silencing performance can be stabilized. Of course, the embodiment of such a triple pipe structure is also applicable to the muffler 20 having the perforated pipe 25 having a constant diameter as shown in FIG.

Further, in the embodiment having the two perforated tubes 35 and 38 separated as shown in FIGS. 9 and 10, the perforated tube 38 near the inlet is made relatively long, It is also possible to provide an inner pipe portion inside 38 and omit the inner pipe portion 37 on the side of the perforated pipe 35. Further, by providing an inner pipe portion in each of the perforated pipes 38 and 35, and by making the gap spaces between the outer perforated pipes 38, 35 in the respective inner pipe portions be throttled toward the exhaust downstream side, respectively, The sound deadening promoting effect according to the present invention may be obtained in two places.

Furthermore, a muffler 20E according to another embodiment of the present invention shown in FIG. 11 is a modification of FIG.
The sound absorbing materials 40 and 41 are provided on the wall surface of the chamber 21. The sound absorbing effect of the sound absorbing members 40 and 41 can muffle a predetermined band (for example, a high frequency band), and the sound absorption of the predetermined band (for example, a middle and high band) due to the double pipe structure of the perforated pipe 25 and the inner pipe portion 27 can be combined. For that reason, silencing can be achieved even in a wider band as a whole.

Further, a muffler 20F according to another embodiment of the present invention shown in FIG. 12 has an exhaust inlet 24 and an outlet 2.
6 is not in a straight line, and the double pipe structure according to the present invention can be applied to such a non-straight structure. That is, the first perforated pipe 25A connected to the introduction pipe 24 has an end portion 25Ab near the exhaust downstream thereof.
Is open and communicates with the chamber 21, and has a large number of small holes 33 on its side surface, and the first inner pipe portion 27A is provided inside thereof. The second perforated pipe 25B has an end portion 25Ba near the exhaust gas upstream that is open to the chamber 21, and the other end thereof is connected to the outlet 26. Then, similarly to the above, a large number of small holes 33 are provided on the side surface of the outer porous tube 25B, and the second inner tube portion 27B is provided inside thereof. As for the inner pipe portions 27A and 27B, as in the case of the inner pipe portion 27 in FIG. 1, the diameter of the pipe end portion closer to the outlet is larger than the diameter of the pipe end portion closer to the inlet of the exhaust fluid. The gap spaces between the inner perforated pipes 27A and 27B and the outer perforated pipes 25A and 25B are narrowed toward the exhaust downstream side.
In some places, the sound deadening promoting effect according to the present invention can be obtained. Also in this embodiment, as shown in FIG. 8, the relationship of the relative change of the diameter between the inner pipe portion and the perforated pipe is reversed, and the inner pipe portions 27A and 27B are made to have a constant diameter, and the perforated pipes 25A and 25A are formed.
Of course, the diameter of B may be changed.

Needless to say, the partial structures of the above-described embodiments may be combined and further various modifications may be made. For example, the inner pipe portions 37, 2 in FIGS.
In 7, 27A and 27B, a plurality of small holes 34 may be provided as shown in FIG. In addition, it is needless to say that each embodiment can be modified so as to appropriately increase or decrease the number of silencing chambers. Further, even if a double pipe structure (structure consisting of an outer porous pipe part and an inner pipe part inside thereof), which is the greatest feature of the present invention, is partially applied to a part of a known exhaust pipe of a muffler structure. Of course, such partial implementation is also within the scope of the invention.

[0037]

As described above, according to the present invention, since the inner pipe portion is provided inside the perforated pipe portion of the first pipe portion, the double pipe structure is provided. A gap space is formed between the inner peripheral surface of the perforated pipe portion and the exhaust sound wave is compressed in this gap space, so that diffusion, interference, etc. of the exhaust sound wave through the small holes of the perforated pipe into the silencing chamber are prevented. As a result, the sound deadening effect is further promoted, which is an excellent effect that the sound deadening effect can be further promoted. Further, the gap space inlet is wider than the gap space outlet-in other words, the gap space outlet is relatively narrowed or closed-, so that the exhaust sound wave entering the gap space is compressed and the porous pipe Diffusion and interference of exhaust sound waves into the muffling chamber through the small holes are further promoted, and the silencing effect can be further promoted.

Particularly, the clearance space formed between the outer peripheral surface of the inner pipe portion and the inner peripheral surface of the perforated pipe portion communicates with the inner space of the first pipe portion at least near the exhaust upstream side so that the exhaust sound wave is generated. With the structure that can enter the gap space, there is an advantage that diffusion and interference of exhaust sound waves can be surely promoted. Further, the end portion of the inner pipe portion on the upstream side of the exhaust gas has a relatively large diameter and opens into the internal space of the first pipe portion, and the exhaust fluid flows through the inside of the first pipe portion extending between the inlet port and the outlet port. When exhaust gas flows, the exhaust fluid can smoothly pass through the inner pipe portion, so that the exhaust fluid is discharged smoothly, engine exhaust pressure is reduced, and engine efficiency is not reduced. Has the advantage.

Further, by adopting the exhaust pressure low loss type as described above, it is possible to greatly contribute to the improvement of fuel efficiency and power performance. Even if no sound absorbing material is provided in the sound deadening chamber, the sound absorbing performance can be improved by the double pipe structure as described above. Therefore, by not providing a large amount of sound absorbing material, the sound absorbing material absorbs moisture. It is possible to solve the problem of corrosion of metal due to the above and deterioration of durability due to it, and it is possible to improve durability. Furthermore, by providing a sound deadening material in the sound absorbing chamber in combination with the double pipe structure, it is possible to contribute to the removal of exhaust sound vibration waves in a specific frequency band that cannot be removed by the double pipe structure. Moreover, by combining with a double pipe structure and providing multiple silencing chambers to form a Helmholtz resonator, it is possible to eliminate exhaust sound vibration waves in a specific frequency band that cannot be eliminated by the double pipe structure. It has the effect of contributing.

Further, the effects of the embodiment are as follows. By providing a plurality of small holes also in the inner pipe portion, the exhaust sound waves are diffused and interfered through the small holes in the inner pipe portion, which also has the effect of enhancing the silencing effect. In addition, a relatively large opening that is opened inside the chamber is formed in a part of the perforated pipe portion, or the perforated pipe portion is divided into two, and a relatively large space opened inside the chamber at the divided portion. By forming this, the instantaneous rise in exhaust pressure can be released to the room through this opening or space, and the pressure distribution can be stabilized immediately, which contributes to stabilization of the silencing performance. Produce the effect.

Further, the sound deadening effect can be further enhanced by using a triple pipe structure including the first and second porous pipes and the inner pipe portion. In this case, if the end of the outermost perforated pipe is configured to open in the muffling chamber, the instantaneous rise in exhaust pressure is released to the chamber by this opening, and the pressure distribution is immediately stabilized, as in the above case. Can be converted into
It has an excellent effect of contributing to stabilization of the silencing performance.

Further, the muffling chamber is divided by a partition wall having a plurality of small holes to be divided into a main chamber and a sub chamber, and the end of the perforated pipe portion is opened to the sub chamber and to the outlet port. Since the starting end of the connecting outlet pipe is opened to the sub-chamber, the main chamber and the sub-chamber are in pressure communication with each other by the partition wall having a plurality of small holes, and the exhaust fluid is sucked into the outlet pipe. Since it accelerates like this, not only the muffling effect,
The effect that the exhaust efficiency can be improved can also be achieved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a muffler according to the present invention.

2A is a sectional view taken along the line AA of FIG. 1, and FIG. 2B is a sectional view taken along the line BB of FIG.

FIG. 3 is a schematic cross-sectional view showing another embodiment of the muffler according to the present invention.

FIG. 4 is a schematic sectional view showing still another embodiment of the muffler according to the present invention.

FIG. 5 is a schematic sectional view showing still another embodiment of the muffler according to the present invention.

6 is a diagram showing an example of the silencing characteristics of the embodiment of FIG.

FIG. 7 is an enlarged side view showing a modified example of the inner pipe portion of the muffler according to the present invention.

FIG. 8 is a schematic sectional view showing another embodiment of the muffler according to the present invention.

FIG. 9 is a schematic sectional view showing still another embodiment of the muffler according to the present invention.

FIG. 10 is a schematic sectional view showing still another embodiment of the muffler according to the present invention.

FIG. 11 is a schematic sectional view showing still another embodiment of the muffler according to the present invention.

FIG. 12 is a schematic sectional view showing still another embodiment of the muffler according to the present invention.

FIG. 13 is a schematic sectional view showing an example of a conventional muffler.

FIG. 14 is a schematic sectional view showing another example of the conventional muffler.

[Explanation of symbols]

1,10,20,10A, 20A muffler Room for muffling 23 partitions 24 Inlet pipe (inlet) 25,35,25A, 25B, 38 Perforated tube 26 Outlet pipe (outlet port) 27,37,27A, 27B Inner tube part 27a Pipe end near the inlet of the inner pipe 27b Pipe end near the outlet of the inner pipe S clearance space 28,29 communication pipe 15,32 sound absorbing material 33,34 Multiple small holes 36 Partition wall with multiple small holes 21B Sub chamber

Claims (6)

[Claims] 1. A muffler body having an inlet for introducing exhaust fluid, a chamber provided inside, and an outlet for leading out the exhaust fluid to the outside, and a muffler body housed inside the muffler body. A first pipe portion including a perforated pipe portion having a plurality of small holes communicating with the chamber, the exhaust fluid passing through the pipe, and a portion corresponding to the perforated pipe portion. It has an inner pipe portion of a given length inserted in the first pipe portion, and forms a gap space between the outer peripheral surface of the inner pipe portion and the inner peripheral surface of the perforated pipe portion. A second tube portion, wherein the given length of the inner tube portion of the second tube portion corresponds to a length range in which the plurality of small holes are present in the perforated tube portion, Further, the end portion of the inner pipe portion on the upstream side of the exhaust gas is opened to the internal space of the first pipe portion. When the exhaust fluid flows through the first pipe portion extending between the introduction port and the discharge port, the exhaust fluid can smoothly pass through the inner pipe portion. The gap space formed between the outer peripheral surface of the pipe portion and the inner peripheral surface of the perforated pipe portion communicates with the internal space of the first pipe portion at least near the exhaust upstream side, and exhaust sound waves are generated in the gap space. And the first pipe portion extends continuously without interruption at least in the path from the inlet to the end of the inner pipe portion on the upstream side of the exhaust gas. Muffler for internal combustion engine. 2. The muffler for an internal combustion engine according to claim 1, wherein the inner pipe portion is in close contact with the perforated pipe portion at a predetermined position of the inner pipe portion on the downstream side of the exhaust gas. 3. The muffler for an internal combustion engine according to claim 1, wherein the gap is closed at a predetermined position on the downstream side of the exhaust gas. 4. The relative relationship between the outer diameter of the inner pipe portion and the inner diameter of the perforated pipe portion is changed so that the gap becomes gradually narrower from the upstream side to the downstream side of the exhaust gas. The muffler for an internal combustion engine according to claim 1, wherein the muffler is set. 5. The muffler for an internal combustion engine according to claim 1, wherein a sound absorbing member is housed in the chamber. 6. In the muffler body, the inlet and the outlet are arranged in a substantially straight line, and the first pipe portion is arranged so as to form a substantially straight exhaust passage therebetween. A muffler for an internal combustion engine according to any one of Items 1 to 5.