JPH08246843A - Silencer - Google Patents

Abstract

PURPOSE: To eliminate an air current noise while reducing exhaust pressure in a silencer having an S-shaped bend in a silencer main body. CONSTITUTION: A silencer main body 17 inside which a sound absorbing material 19 is filled and plural communicating holes 21 which are arranged in this silencer main body 17 and communicate with the inside of the silencer main body 17, are formed. A porous pipe part 27 having S-shaped bending parts 23 and 25 and an exhaust pipe 29 which is communicated with this porous pipe part 27 and in which exhaust gas from an engine flows, are provided. Then, the bending parts 23 and 25 of the porous pipe part 27 are covered with a sound absorbing material 31 whose density is higher than the sound absorbing material 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer for silencing exhaust noise of exhaust gas from an engine.

[0002]

2. Description of the Related Art In Japanese Utility Model Laid-Open No. 59-102921 and Japanese Utility Model Laid-Open No. 63-21716, expansion type silencers are proposed. This expansion type muffler forms a plurality of expansion chambers in the muffler body and expands high-temperature, high-pressure exhaust gas from the engine to reduce the pressure and muffle the sound.

However, in such an expansion-type silencer, since the exhaust gas once expands in the expansion chamber and then contracts until it flows into the next expansion chamber, the exhaust gas is discharged into the silencer body. The pressure of gas, so-called exhaust pressure, becomes high, and exhaust gas cannot be quickly released into the atmosphere.

Therefore, as shown in FIG. 6, there has been proposed a silencer 1 having a structure in which exhaust gas smoothly flows in the exhaust pipe to suppress exhaust pressure to a low level. In this muffler 1, the exhaust pipe 3 through which exhaust gas from the engine flows is circulated through an S-shaped bent portion 9 in the expansion chamber 7 of the muffler body 5, and then to the outside of the expansion chamber 7. Has been pulled out. Further, in the expansion chamber 7, a large number of communication holes 11 are formed in the exhaust pipe 3,
A sound absorbing material 13 is filled in the expansion chamber 7.

Exhaust gas from the engine flows through the exhaust pipe 3, passes through the bent portion 9 in the expansion chamber 7, and is then discharged. In the expansion chamber 7, it is released from the communication hole 11 into the expansion chamber 7 and expands. As a result, the exhaust sound of the exhaust gas is silenced.

Further, since the exhaust pipe 3 is bent into an S shape in the expansion chamber 7, the exhaust gas smoothly flows and the waste gas can be quickly released into the atmosphere, and the exhaust pressure can be reduced. Can be done.

[0007]

However, when the exhaust pulsating flow from the engine enters the silencer body 5, the exhaust pulsating flow is guided to the exhaust pipe and is greatly changed into an S-shape, and is discharged into the atmosphere from the exhaust port. However, since the flow direction is largely deflected at the S-shaped bent portion, the flow is greatly disturbed and airflow sound (a sound range of about 1.5 KHz) is generated with separation from the inner wall of the exhaust pipe.

Therefore, an object of the present invention is to provide a muffler having an S-shaped bend in the muffler body, which is capable of suppressing air pressure noise while suppressing exhaust pressure.

[0009]

To achieve the above object, the invention according to claim 1 is characterized in that a silencer body having a sound absorbing material filled therein, and a silencer body provided in the silencer body. A silencer having a plurality of communicating holes formed therein and having a S-shaped bent portion, and an exhaust pipe communicating with the porous pipe portion and through which exhaust gas from an engine is circulated. The bent portion of the perforated pipe portion is covered with a sound absorbing material having a higher density than the sound absorbing material.

The invention according to claim 2 is the invention according to claim 1, wherein the bent portion of the perforated pipe is housed in a sound absorbing box filled with a sound absorbing material having a higher density than the sound absorbing material. Is characterized by.

The invention according to claim 3 is the invention according to claim 3, characterized in that the sound absorbing box is provided with a plurality of communication holes communicating with the inside of the silencer body.

The invention according to claim 4 is the invention according to claim 3, wherein the silencer main body, the sound absorbing box, and a communication hole provided in the sound absorbing box form a multi-stage expansion structure. I am trying.

The invention according to claim 5 is the invention according to claim 2 or 3, wherein the sound absorbing box is composed of an upper box body and a lower box body.

[0014]

According to the invention of claim 1, the exhaust gas from the engine flows through the exhaust pipe, passes through the perforated pipe portion, and is exhausted. Exhaust gas passing through the perforated pipe portion is discharged from the communication hole into the silencer body and is expanded to reduce the pressure to be silenced. In this case, since the sound absorbing material is filled in the main body of the muffler, the muffling effect is enhanced.

Further, the exhaust gas passing through the perforated pipe portion smoothly flows and the rise of exhaust pressure is suppressed. Further, in the S-shaped bent portion, the exhaust gas is largely deflected in its flow path and is separated from the inner wall of the pipe portion to generate airflow noise. However, the S-shaped bent portion is covered with a high-density sound absorbing material. Therefore, this air flow noise is silenced by the sound absorbing material.

According to the second aspect of the present invention, the sound absorbing box serves as an expansion chamber by accommodating the bent portion in the sound absorbing box.
The exhaust gas discharged from the communication hole of the bent portion is expanded, and the sound deadening effect is enhanced together with the sound deadening by the high-density sound absorbing material.

According to the invention of claim 3, since the sound absorbing box is provided with a plurality of communication holes communicating with the silencer body, the inside of the silencer body becomes an air layer behind the sound absorbing box, and a Helmholtz type resonator. Acts as. Therefore, the sound deadening effect is further enhanced.

According to the invention of claim 4, the exhaust gas flowing through the perforated pipe portion is discharged into the sound absorbing material in the sound absorbing box, further passes through the communication hole, and is discharged into the silencer body. Therefore, the exhaust noise is silenced by the multi-stage expansion structure.

According to the invention of claim 5, in the sound absorbing box, the bent portion is accommodated by sandwiching the bent portion between the upper box body and the lower box body.

[0020]

Embodiments of the silencer according to the present invention will be described below with reference to the drawings. FIG. 1 shows the muffler 15 and is a perspective view of the inside of the muffler body 17 seen through. FIG. 2 is a sectional view showing the inside of the silencer body 17.

As shown in FIGS. 1 and 2, the silencer 15
Is a silencer body 17 having a sound absorbing material 19 filled therein,
A plurality of communication holes 21 provided in the muffler body 17 and communicating with the muffler body 17 are formed, and a perforated pipe portion 27 having S-shaped bent portions 23 and 25, and the perforated pipe portion The exhaust pipe 29 communicates with the exhaust pipe 27 and through which exhaust gas from the engine flows. In addition, in the muffler 15 of this embodiment, the bent portions 23 and 25 of the perforated pipe portion 27 are made of the sound absorbing material 19.
It is covered with a higher density sound absorbing material 31.

The muffler body 17 has an expansion chamber 33 formed therein. Inside the expansion chamber 33, the sound absorbing material 19 is filled and the perforated pipe portion 27 is arranged.

The perforated tube portion 27 is bent into an S-shape as a whole, and two U-shaped bent portions 23 and 25 are formed. Then, one side of the perforated pipe section 27 is in communication with the exhaust pipe 29, and the other side is in communication with the outlet pipe 35.
Further, a plurality of communication holes 39 that communicate with the inside of the silencer body 17 are formed on the entire outer circumference of the perforated pipe portion 27. Further, the bent portions 23 and 25 are housed in the sound absorbing box 37. The sound absorbing box 37 is filled with a sound absorbing material 31 having a higher density than the sound absorbing material 19. Therefore, the bent portion 2
3, 25 are covered with a high-density sound absorbing material 31, housed in a sound absorbing box 37, and further covered with a sound absorbing material 19.

The sound absorbing box 37 includes an upper box 37a and a lower box 37.
b and flange portions 38a, 3 formed on both
It is formed into a box by bonding with 8b. Further, the bent portions 23 and 25 are housed in the sound absorbing box 37 by sandwiching the bent portions 23 and 25 between the upper box 37a and the lower box 37b. Further, the upper box body 37a and the lower box body 37b are formed with communication holes 39 in the entire outer circumference.

Next, the operation of the muffler 15 will be described.

Exhaust gas from the engine flows through the exhaust pipe, passes through the perforated pipe portion 27, and is discharged from the outlet pipe 35 into the atmosphere. In this case, since the perforated pipe portion 27 is bent into an S-shape, the exhaust gas from the engine is perforated into the perforated pipe portion 27.
It smoothly circulates inside and is discharged into the atmosphere from the outlet pipe.
Therefore, the exhaust pressure of the exhaust gas from the engine is reduced.

Further, since the exhaust gas flowing through the perforated pipe portion 27 is discharged from the communication hole 21 to the sound absorbing material 19 inside the silencer body 17, the exhaust gas is expanded and the exhaust sound is absorbed by the sound absorbing material 1.
Sound is absorbed at 9, and the sound is muted.

Further, in the curved portions 23 and 25, the flow path of the exhaust gas is largely deflected and the flow is greatly disturbed, and the curved portion 2
Airflow noise is generated by being separated from the inner walls of 3, 25, but since the bent portions 23, 25 are covered with the high-density sound absorbing material 31, the airflow noise is silenced. Further, since the bent portions 23 and 25 are housed in the sound absorbing box 37,
Part of the exhaust gas passing through the bent portions 23 and 25 is discharged into the sound absorbing box 37. Therefore, the sound absorbing box 37 serves as an expansion chamber to reduce the pressure of exhaust gas.

Further, the sound absorbing box 37 has a plurality of communication holes 39.
Therefore, the inside of the muffler body 17 serves as a back air layer against the effect of the sound absorbing material 31 in the sound absorbing box 37 and acts as a Helmholtz type resonator to enhance the sound absorbing effect.

In the structure of the present embodiment, the volume of the sound absorbing box 37 can be adjusted to provide a multi-stage expansion structure for the air flow indicated by the arrow in FIG. It is possible to enhance the sound deadening effect of the (range). That is, the relationship between the sound absorbing box 37 and the muffler body 17 described above is equivalent to a structure in which two expansion chambers 37 and 33 having different volumes are continuously connected as shown in FIG.

Next, the effect of the muffler 15 of this embodiment shown in FIGS. 4 and 5 will be described. The curve A shown in FIG. 4 is
The S-shaped curved portion shows the volume of the conventional silencer provided in the silencer body. As shown in FIG.
At 0 Hz, the volume reduction (dB) is small due to the weak expansion effect, and at volume 1000 to 2000 Hz, the volume is low due to the generation of airflow noise.

On the other hand, as indicated by the curve B shown in FIG.
Sound absorbing box 37 in which 3 and 25 are filled with high density sound absorbing material 31
Since the exhaust sound of 250 to 500 Hz is housed in the sound absorbing box 37, the sound absorbing box 37 serves as an expansion chamber and is silenced (hatched portion C in FIG. 5), and the air flow sound of 1000 to 2000 Hz (shaded line D in FIG. 5). ) Is effectively silenced by the high-density sound absorbing material 31. Therefore, the muffler 1 of this embodiment
According to 5, it is possible to muffle the airflow noise while reducing the exhaust pressure.

Further, according to this embodiment, it is possible to effectively muffle exhaust sound in the middle sound range (200 to 500 Hz), which cannot be muffled by the muffler having the S-shaped bent portion in the related art.

Further, in this embodiment, the sound absorbing box 37 is replaced by the upper box body 3.
Since it is formed by 7a and the lower box body 37b, by sandwiching the bent portions 23 and 25 between the upper box body 37a and the lower box body 37b,
It can be easily accommodated in the sound absorbing box 37.

[0035]

As described above, according to the invention of claim 1, the exhaust gas passing through the inside of the perforated pipe portion smoothly flows to suppress the increase of exhaust pressure, and the exhaust gas is exhausted at the S-shaped bent portion. The gas is largely deflected in the flow path and is separated from the inner wall of the pipe to generate air flow noise. However, since the S-shaped bent portion is covered with the high-density sound absorbing material, this air flow sound is generated by the sound absorbing material. It is muted.

According to the second aspect of the invention, the exhaust gas discharged from the communicating hole of the bent portion is expanded into the sound absorbing box, and the sound deadening effect is further enhanced.

According to the third aspect of the present invention, since the sound absorbing box is provided with a plurality of communication holes communicating with the muffler body, the inside of the muffler serves as an air layer behind the sound absorbing box and is a Helmholtz type resonator. And then work. Therefore, the sound deadening effect is further enhanced.

According to the invention of claim 4, a silencer body,
Since the sound absorbing box and the communication hole provided in the sound absorbing box form a multi-stage expansion structure, the sound deadening effect can be further enhanced.

According to the invention of claim 5, the bent portion is accommodated by sandwiching the bent portion between the upper box body and the lower box body, so that the bent portion can be easily accommodated in the sound absorbing box. Can be done.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a silencer according to the present invention.

FIG. 2 is a cross-sectional view showing the inside of the silencer body of the silencer according to the present invention.

FIG. 3 is a cross-sectional view showing a silencer according to the present invention as a multi-stage expanded structure.

FIG. 4 is a diagram showing a sound deadening volume for each frequency of exhaust sound in a conventional silencer.

FIG. 5 is a diagram showing a sound deadening volume for each frequency of exhaust sound in the muffler according to the present invention.

FIG. 6 is a cross-sectional view showing a conventional silencer.

[Explanation of symbols]

 15 silencer 17 silencer main body 19 sound absorbing material 21 communication hole 23, 25 bent portion 27 porous tube portion 29 exhaust pipe 31 sound absorbing material (high density) 37 sound absorbing box 39 communication hole

Claims (5)

[Claims] 1. A muffler body having a sound absorbing material filled therein, a plurality of communication holes provided in the muffler body and communicating with the muffler body, and having an S-shaped bent portion. In a muffler comprising a perforated pipe section having a perforated pipe section and an exhaust pipe communicating with the perforated pipe section and through which exhaust gas from an engine is circulated, a curved portion of the perforated pipe section has a higher sound absorbing material than the sound absorbing material. A silencer characterized by being covered with. 2. The silencer according to claim 1, wherein the bent portion of the perforated pipe portion is housed in a sound absorbing box filled with a sound absorbing material having a higher density than the sound absorbing material. . 3. The muffler according to claim 3, wherein the sound absorbing box is provided with a plurality of communication holes communicating with the inside of the muffler body. 4. The muffler according to claim 3, wherein the muffler body, the sound absorbing box, and a communication hole provided in the sound absorbing box form a multi-stage expansion structure. 5. The silencer according to claim 2 or 3, wherein the sound absorbing box includes an upper box body and a lower box body.