JPH0417770Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an exhaust silencer structure provided in an exhaust passage of an engine.

[Conventional technology]

Conventionally, this type of silencer is known to have a perforated pipe with a large number of small holes formed in the peripheral wall, and a sound absorbing material provided on the outer periphery of the perforated pipe (for example, in practical applications). (See Publication No. 59-165520).
In a silencer with this configuration, exhaust gas discharged from the engine's exhaust manifold is released into the atmosphere through a perforated pipe, while sound waves generated by the exhaust gas are absorbed by a sound absorbing material provided outside the perforated pipe. That's what I do.

Furthermore, Japanese Utility Model Application Publication No. 60-194117 proposes a configuration in which a perforated pipe is arranged inside the exhaust passage forming pipe, and a sound absorbing material is arranged outside the exhaust passage forming pipe via a perforated plate. . With this configuration, noise can be muted by adjusting the dimensions of a large number of perforated plates or perforated tubes.

[The problem that the idea attempts to solve]

In the structure described in the above-mentioned Japanese Utility Model Publication No. 59-165520,
Although most of the exhaust gas passes through the perforated pipe,
A part of the exhaust gas is sent into the sound absorbing material through the small holes of the perforated pipe, and a flow is generated where it is discharged from the small holes again. Therefore, as time passes, the sound absorbing material near the outer peripheral surface of the porous pipe flows out of the holes and scatters due to this flow, and the sound absorbing material is no longer able to maintain its initial sound absorbing effect.

Also, in the structure described in Japanese Utility Model Application Publication No. 60-194117, a part of the exhaust gas passes through the small hole of the internal porous pipe and the small hole of the exhaust path forming pipe near the entrance of the exhaust forming pipe. A flow is generated that is sent into the sound absorbing material through the holes in the plate and then discharged again through the small holes. As a result, as time passes, the sound absorbing material near the outer circumferential surface of the porous pipe flows out of the small holes and scatters, causing the same problem as above that the sound absorbing material is no longer able to maintain its initial sound absorbing effect. is left in.

This invention was made in order to eliminate such conventional drawbacks, and aims to provide an engine exhaust silencer that can maintain the sound absorption effect of the sound absorbing material.

[Means to solve the problem]

This idea consists of a perforated tube with an exhaust inlet formed at one end, an exhaust outlet formed at the other end, and a large number of small holes formed in the peripheral wall, and an annular space formed around the outer periphery of this perforated tube. an inner tube arranged concentrically with the porous tube around the outer periphery of the porous tube, a sound absorbing material placed on the outer periphery of the inner tube, an outer tube covering the outer peripheral surface of the sound absorbing material, and one end A guide pipe is attached to the outer periphery of the porous pipe and extends between the porous pipe and the inner pipe to near the other end, and is open at the other end, and the inner pipe has a large number of small holes. The guide pipe is formed of a pipe without holes.

[Effect]

In the above configuration, most of the exhaust gas fed into the perforated pipe is exhausted through the perforated pipe, but some of the exhaust gas passes through the small holes on the inlet side of the perforated pipe and reaches the outer periphery of the perforated pipe. There, it is guided by a guide pipe toward the outlet side, and on the outlet side, it passes through the small hole again, enters the porous tube, and is discharged. Then, only the sound waves generated by the exhaust gas are transmitted from the rear end opening of the guide pipe to the space outside the guide pipe, and are transmitted to the sound absorbing material through the small holes of the inner pipe, where the sound is absorbed.

〔Example〕

FIG. 2 is a configuration diagram of an exhaust system equipped with an exhaust silencer for an engine showing an embodiment of this invention.
The inlet of the catalytic converter 2 is connected via a,
The outlet of the catalytic converter 2 is connected to the inlet of the pre-stage exhaust silencer 3 via an exhaust pipe 5b.
In addition, an exhaust pipe 5c is provided at the outlet of the front exhaust silencer 3.
The inlet of the main exhaust silencer 4 is connected via the
An outlet of the main exhaust silencer 4 is connected to an exhaust pipe 5d.

FIG. 1 is a sectional view showing a specific structure of the exhaust silencer 3 or 4 shown in FIG. 2, and in this embodiment, the exhaust silencer 4 will be explained. A perforated pipe 6 is arranged between the exhaust pipes 5c and 5d, and this perforated pipe 6 has an exhaust inlet formed at one end, an exhaust outlet formed at the other end, and a large number of small holes 6a all over the peripheral wall. It is formed. The inner tube 8 is arranged so that an annular space 7 is formed on the outer periphery of the porous tube 6.
is arranged concentrically with the porous pipe 6, a sound absorbing material 9 is arranged on the outer periphery of this inner pipe 8, and furthermore, this sound absorbing material 9
The outer circumferential surface of is covered with an outer tube 10. Each end of the porous tube 6, inner tube 8, and outer tube 10 is fixed to a flange 11. The inner tube 8 has a large number of small holes formed therein. In addition, the above sound absorbing material is
It is made of heat-resistant fibers such as glass wool.

Further, in the space 7, one end is attached to the outer circumference of the porous pipe 6, and the porous pipe 6 and the inner pipe 8 are connected to each other.
A guide pipe 12 is disposed that extends between the two ends to near the other end and opens near the other end, and the guide pipe 12 is formed of a tube without holes. Therefore, an annular space is formed between the porous pipe 6 and the guide pipe 12 that is closed on the upstream side of the exhaust gas and open on the downstream side, and an annular space is formed between the guide pipe 12 and the inner pipe 8. An annular space is also formed, and these spaces communicate with each other on the downstream side (opening 12a).

In an exhaust silencer with such a configuration,
When the exhaust gas is sent into the perforated pipe 6 through the exhaust pipe 5c, most of the exhaust gas passes through the perforated pipe 6 and is sent out to the exhaust pipe 5d, and some of the gas passes through the perforated pipe 5d as shown by the arrow in the figure. Small hole 6a near the entrance of tube 6
The gas is fed into the annular space inside the guide pipe 12 on its outer periphery, faces the exit side through this space, enters the porous pipe 6 again through the small hole 6a near the exit, and flows out to the exhaust pipe 5d. On the other hand, the sound waves generated by the exhaust gas are transmitted from the opening 12a to the space between the guide pipe 12 and the inner tube 8, and further transmitted through the small holes of the inner tube 8 to the sound absorbing material 9, where the sound is absorbed. .

In this way, the exhaust gas flows from the perforated pipe 6 to the small hole 6a.
After being sent out to the outer circumference of the porous pipe 6 through the hole, it is guided by the guide pipe 12 without holes and returned to the porous pipe 6 from the downstream side, so that it does not reach the sound absorbing material 9. The sound absorbing material is not scattered, and only the sound waves generated by the exhaust gas are transmitted from the opening 12a to the sound absorbing material 9 and absorbed.

Note that the length of the guide pipe 12, that is, the length of the space (passage) formed thereby, may be set according to the frequency of the sound to be absorbed.
A longer path is advantageous for attenuation of low frequency sounds.

[Effect of idea]

As explained above, according to this invention, most of the exhaust gas sent into the perforated pipe is exhausted through the perforated pipe, but some exhaust gas is released through the small holes on the inlet side of the perforated pipe. It is sent out to the outer periphery of the porous tube through the tube, where it is guided by a guide pipe toward the outlet side, and on the outlet side it passes through the small holes again into the porous tube and is discharged. Then, only the sound waves generated by the exhaust gas are transmitted from the rear end opening of the guide pipe to the space outside the guide pipe, and are transmitted to the sound absorbing material through the small holes of the inner pipe, where the sound is absorbed. Therefore, sound absorption is achieved well, and scattering of the sound-absorbing material is prevented, so that the sound-absorbing effect can be maintained for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an exhaust silencer for an engine according to an embodiment of this invention, and FIG. 2 is an overall configuration diagram of an exhaust system provided with this exhaust silencer. 3, 4... Exhaust silencer, 6... Porous pipe, 6
a...Small hole, 7...Space, 8...Inner tube, 9...
Sound absorbing material, 12... Guide pipe, 12a... Opening.

Claims (1)

[Scope of utility model registration request] A porous tube has an exhaust inlet formed at one end, an exhaust outlet formed at the other end, and a large number of small holes formed in the peripheral wall, and an annular space formed around the outer periphery of this porous tube. An inner tube arranged concentrically with the porous tube around the outer circumference of the porous tube, a sound absorbing material placed on the outer periphery of the inner tube, an outer tube covering the outer peripheral surface of the sound absorbing material, and one end of the porous tube. a guide pipe attached to the outer periphery, extending between the porous pipe and the inner pipe to near the other end, and opening at the other end;
An exhaust silencer structure for an engine, wherein the inner pipe is formed with a large number of small holes, and the guide pipe is formed with a pipe without holes.