JPH06266369A - Active duct sound elimination device - Google Patents

Abstract

PURPOSE:To prevent exhaust gas from entering a waveguide as much as possible. CONSTITUTION:The active duct sound elimination device, which eliminates a source sound propagated in a duct by superposing a canceling sound on the source sound, is equipped with an expanded chamber 12 provided halfway in the duct 11, the waveguide 13 which is open to the expanded chamber 12, and a canceling sound generating means 14 which is connected to the waveguide 13, and, an intake and an outlet for the gas, which communicate with the expanded chamber 12 of the duct 11 are linked by a pipe 16 and the peripheral surface of the pipe 16 on the opposite side to the waveguide 13 is open to the expanded chamber 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active duct silencer capable of reducing noise from an exhaust duct of an engine.

[0002]

2. Description of the Related Art As a conventional device of this type, for example, one shown in FIGS. 12 and 13 is known (see Japanese Patent Application Laid-Open No. 5032193/1990). This device is a device that actively cancels noise by superimposing a canceling sound on the exhaust sound of an automobile, and an anti-noise chamber 2 that is opened coaxially with the opening end 1a is provided on the outer circumference of the end of the exhaust duct 1. A speaker 3 and an enclosure 4 are symmetrically arranged in the anti-noise chamber 2 to form a secondary sound generator.

In this device, since the anti-noise chamber 2 is provided outside the exhaust duct 1 with a double pipe structure, the speaker 3 at the open end 1a can be avoided while avoiding problems such as heat damage to the speaker 3 due to exhaust gas. The exhaust sound can be silenced by the secondary sound from (canceling sound).

Another example is shown in FIG. 14 (see Japanese Patent Publication No. 3-25679). In this device, a secondary sound generating device including a speaker 3 and an enclosure 4 is connected to an acoustic mixer 6 at the end of the duct 1 via a waveguide 5.

In this device, the primary sound propagating in the duct 1 is superposed on the secondary sound in the acoustic mixer 6, and the two are completely canceled each other and then released into the atmosphere, so that the flow velocity of the medium increases. It also exhibits good silencing performance over time.

[0006]

[Problems to be Solved by the Invention] However, the above 2
Each of the two conventional devices had the following problems.
That is, in the former case, if the pipe diameter of the secondary sound outlet is increased in order to improve the efficiency of the speaker 3, the overall pipe diameter becomes extremely large due to the double pipe structure, and the degree of freedom in design becomes small. I will end up. Further, since the speaker 3 propagates the canceling sound to the position of the discharge port 1a, when the flow velocity of the exhaust gas is high, the silencing effect obtained near the discharge port may be diminished. Further, the speaker 3 may be easily flooded.

In the latter case, the length of the waveguide 5 must be large in order to avoid heat damage to the speaker 3.
Therefore, the sound wave from the speaker 3 is considerably attenuated in the waveguide 5 portion, and the efficiency of the speaker 3 cannot be effectively obtained.

Therefore, the present invention provides an active duct silencer capable of preventing the heat damage and flooding of the speaker and effectively drawing out the efficiency of the speaker by providing the structure in which the exhaust gas does not easily enter the waveguide. The purpose is to provide.

[0009]

According to a first aspect of the present invention, there is provided an active duct muffler for silencing a source sound propagating in a duct by superimposing a canceling sound on the source sound, which is provided in the middle of the duct. An expansion chamber, a waveguide opening to the expansion chamber, and a canceling sound generation means connected to the waveguide,
The duct connects the inlet and outlet of gas communicating with the expansion chamber with a pipe, and the peripheral surface of the pipe on the side opposite to the waveguide is opened into the expansion chamber.

A second aspect of the present invention is the active duct silencer according to the first aspect, wherein the pipe is opened in the expansion chamber as a half-split pipe.

A third aspect of the present invention is the active duct silencer according to the second aspect, wherein the waveguide of the half-split pipe is located downstream of the gas flow with respect to the opening of the waveguide. A collar plate is provided between the outer side surface and the inner surface of the expansion chamber.

According to a fourth aspect of the present invention, in the active duct silencer according to the second aspect, the diameter of the duct on the outlet side of the expansion chamber is made larger than the diameter of the duct on the inlet side. Is characterized by.

According to a fifth aspect of the present invention, in the active duct silencer according to the second aspect, an insulator is arranged on the side of the expansion chamber of the waveguide.

A sixth aspect of the present invention is the active duct silencer according to the first aspect, wherein the pipe is opened into the expansion chamber through a large number of through holes.

[0015]

In the device of the first aspect of the present invention, since the inlet / outlet of the duct to the expansion chamber is connected by a pipe and the peripheral surface of the pipe on the side opposite to the waveguide is open to the expansion chamber, the gas is not generated. It flows mainly through the open side of the pipe and reaches the outlet side duct. Therefore, it hardly turns to the waveguide side. Even if it turns, the open space becomes negative pressure due to the flow velocity of the gas flowing in the open space of the pipe, so that the gas trying to turn to the waveguide side is pulled back, and the gas on the waveguide side is It is about to settle. As a result, the possibility that the gas will flow from the opening of the waveguide to the canceling sound generating means is significantly suppressed, and the risk of heat damage to the canceling sound generating means by the gas is reduced. Since the sound wave propagating through the duct is introduced into the expansion chamber from the open side of the pipe, the sound wave is superposed with the canceling sound introduced into the expansion chamber from the waveguide and is silenced.

In the apparatus according to the second aspect of the present invention, the above operation can be achieved by the half-split pipe.

In the device of the third aspect of the present invention, since the collar plate is provided on the downstream side of the opening of the waveguide, the swirling flow of gas that strikes the outlet side end wall of the expansion chamber is the same end as the collar plate. Since it is restricted between the wall and the wall, it is possible to more effectively prevent the gas from flowing into the waveguide due to the influence of the swirling flow.

In the device of the fourth aspect of the present invention, since the diameter of the outlet duct is formed large, the gas can be discharged to the outside more smoothly. Therefore, the swirling flow inside the expansion chamber is also weakened, and the inflow of gas into the waveguide can be prevented more effectively.

In the device of the fifth aspect of the present invention, since the insulator is arranged in the portion of the waveguide on the side of the expansion chamber where the gas flow is small, it is expected to maintain the sound absorbing effect or the heat shielding effect for a long term.

In the device of the sixth aspect of the present invention, since the peripheral surface of the pipe is opened into the expansion chamber by the large number of through holes formed in the pipe, not only the swirling flow generated in the expansion chamber is weakened, but also the exhaust pressure is increased. Can also be suppressed. Therefore, invasion of gas into the waveguide can be effectively suppressed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. In each embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

<< First Embodiment >> A first embodiment of the present invention (embodiments of claims 1 and 2) will be described with reference to FIGS.

In this device, an expansion chamber 12 is provided in the middle of the exhaust duct 11. That is, 11A and 11B are an inlet side duct and an outlet side duct which are aligned in a straight line, and the expansion chamber 12 is provided between both ducts 11A and 11B. One end of the waveguide 13 is opened in the peripheral wall of the expansion chamber 12, and the other end of the waveguide 13 is provided with an enclosure 14 and a speaker 15 as canceling sound generating means. As a result, the canceling sound from the speaker 15 is introduced into the expansion chamber 12 via the waveguide 13.

Inlet duct 11A and outlet duct 11
Between the inlet and the outlet of the expansion chamber 12 of B, the pipe 1
6 is connected. This pipe 16 is an anti-waveguide 13
The peripheral surface on the side is opened to form a half-split shape.

Next, the operation will be described.

If there is no half-split pipe 16,
Exhaust gas introduced into the expansion chamber 12 from the inlet duct 11A swirls largely inside the expansion chamber 12. Therefore, a large amount of exhaust gas directly enters the inside of the waveguide 13.

On the other hand, when the half-split pipe 16 is present as in the present embodiment, the exhaust gas flows only through the open side of the pipe 16 to the outlet duct 11B. Therefore, although a weak swirling flow of the exhaust gas is generated in the expansion chamber 12, the influence thereof does not reach the waveguide 13 side. Therefore, the exhaust gas is suppressed from directly entering the waveguide 13. Further, since the exhaust gas flows on the open side of the pipe 16, the space on the open side is in a negative pressure state, and even if the exhaust gas tries to reach the waveguide 13 side,
The exhaust gas is drawn back into the open space. Therefore, the gas is almost stagnant near the opening of the waveguide 13, and the invasion of the gas into the waveguide 13 is suppressed.

As a result, the speaker 15 is not affected by heat from the exhaust gas, and it is not necessary to use a special secondary sound source such as a heat-resistant speaker. In addition, the length of the waveguide 13 can be shortened and the opening area to the expansion chamber 12 can be increased, so that the efficiency of the speaker 15 can be sufficiently brought out. Further, since the canceling sound is superimposed and deadened in the expansion chamber 12, the deadening performance does not deteriorate even when the flow velocity of the exhaust gas increases.

Since the canceling sound generated by the speaker 15 is guided into the expansion chamber 12 through the waveguide 13, the waveguide 13
The degree of freedom in design such as the mounting position of the can be increased, and problems such as flooding can be reliably solved. Further, since the expansion chamber 12 is arranged in the middle of the duct 11, the diameter of the open end side of the duct can be reduced, and the degree of freedom in designing is expanded.

<Second Embodiment> A second embodiment of the present invention (embodiment of claim 3) will be described with reference to FIGS.

In the device of the second embodiment, a collar plate 17 is newly added to the device of the first embodiment. This collar plate 17
Is a semi-annular partition plate provided on the outer periphery of the pipe 16 on the waveguide 13 side, the inner periphery of which is in contact with the outer surface of the pipe 16 and the outer periphery of which is in contact with the inner surface of the expansion chamber 12. Wave tube 13
It is arranged on the downstream side of the gas flow from the opening position of and is opposed to the outlet side end wall 12a of the expansion chamber 12 with a space.

By providing the collar plate 17, the influence of the swirling flow can be prevented from reaching the opening of the waveguide 13. That is, the swirling flow is generated mainly by the gas flowing through the pipe 16 hitting the outlet side end wall 12a of the expansion chamber 12, but the swirling flow is caused by the existence of the collar plate 17 and the collar plate 17 and the end wall 12a. Is regulated between and. Therefore, the influence of the swirling flow does not reach the opening of the waveguide 13, and the gas stagnation effect near the opening of the waveguide 13 is further increased,
Invasion of exhaust gas into the waveguide 13 is further suppressed.

<< Third Embodiment >> A third embodiment of the present invention (embodiment of claim 4) will be described with reference to FIG.

In the device of the third embodiment, the diameter of the outlet duct 11B in the device of the first embodiment is set larger than the diameter of the inlet duct 11A.

According to this device, the exhaust gas can be discharged to the outside more smoothly, so that the swirling flow inside the expansion chamber 12 can be weakened and the heat damage can be further avoided.

<Fourth Embodiment> A fourth embodiment of the present invention (embodiment of claim 6) will be described with reference to FIGS. 8 and 9.

In the apparatus of the fourth embodiment, instead of the half-split pipe 16 used in the apparatus of the first embodiment, a semi-perforated structure having a large number of through holes 26a on the peripheral surface on the side opposite to the waveguide 13 is used. The pipe 26 is used.

According to this device, the swirling flow can be significantly weakened, and heat damage can be avoided without increasing the exhaust pressure.

<Fifth Embodiment> A fifth embodiment of the present invention (embodiment of claim 4) will be described with reference to FIG.

In the device of the fifth embodiment, a sound absorbing material (or heat shield material) 20 is provided as an insulator in the portion of the waveguide 13 in the device of the first embodiment on the side of the expansion chamber 12. .

Conventionally, when a sound absorbing material or the like is arranged at this position, it deteriorates with time due to the flow of exhaust gas, but in the device of this embodiment, the vicinity of the opening of the waveguide 13 is almost stagnant. Therefore, the sound absorbing material 20 does not scatter, and a long-term sound absorbing effect (heat insulating effect in the case of a heat insulating material) can be expected to be maintained.

<< Sixth Embodiment >> A sixth embodiment of the present invention is shown in FIG.
This will be described using 1.

In the device of the sixth embodiment, the length of the waveguide 13 in the device of the first embodiment is set to be slightly longer, the height of the speaker 15 is set to be approximately the same as the height of the expansion chamber 12, and the guiding is performed. The opening 13a of the wave tube 13 is provided obliquely above the peripheral wall of the expansion chamber 12, and accordingly, the open side 16a of the pipe 16 is set obliquely downward on the side opposite to the opening 13a of the waveguide 13.

In the case of the apparatus of this embodiment, the degree of freedom in design in layout can be increased, and at the same time flooding can be effectively prevented. Here, the efficiency of the speaker 15 is affected by setting the waveguide 13 slightly longer. However, the presence of the pipe 16 makes it possible to set the opening 13a of the waveguide 13 wide, and thus the efficiency is improved. It doesn't fall.

[0045]

As described above, according to the present invention of claim 1, it is possible to suppress the invasion of gas into the waveguide, so that it is possible to prevent the canceling sound generation device from heat damage,
There is no need to use heat resistant speakers. Further, the length of the waveguide can be shortened and the opening area to the expansion chamber can be widened, so that the efficiency of the speaker can be maximized. Further, since the source sound and the canceling sound are superposed in the expansion chamber, the silencing performance does not deteriorate when the flow velocity of the gas increases.

Further, since the canceling sound is introduced into the expansion chamber through the waveguide, there is a high degree of freedom in design such as selection of the mounting position of the waveguide, and the problem of flooding can be solved. it can.

According to the second aspect of the present invention, the above-described operation and effect can be obtained by the half-split pipe, and the structure is simplified.

According to the third aspect of the invention, the collar plate can prevent the gas from flowing into the waveguide, and can more effectively prevent the heat damage of the canceling sound generating means.

According to the fourth aspect of the present invention, the gas is discharged more smoothly, so that the heat damage to the canceling noise generating means can be prevented more effectively.

According to the invention of claim 5, a long-term sound absorbing effect,
A heat shield effect can be expected, and maintenance costs can be reduced.

In the sixth aspect of the invention, not only can the swirling flow be weakened, but also the rise in exhaust pressure can be suppressed, and heat damage can be more effectively avoided.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 is a schematic side sectional view of the first embodiment of the present invention.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a perspective view of a second embodiment of the present invention.

FIG. 5 is a schematic side sectional view of a second embodiment of the present invention.

6 is a cross-sectional view taken along the line VI-VI of FIG.

FIG. 7 is a schematic side sectional view of a third embodiment of the present invention.

FIG. 8 is a perspective view of a fourth embodiment of the present invention.

FIG. 9 is a schematic side sectional view of a fourth embodiment of the present invention.

FIG. 10 is a schematic side sectional view of a fifth embodiment of the present invention.

FIG. 11 is a sectional view of a sixth embodiment of the present invention.

FIG. 12 is a schematic side sectional view of a conventional example.

13 is a sectional view taken along the line XIII-XIII in FIG.

FIG. 14 is a schematic side sectional view of another conventional example.

[Explanation of symbols]

 11 duct 11A inlet side duct 11B outlet side duct 12 expansion chamber 12 outlet side end wall 13 waveguide 14 enclosure (cancellation sound generator) 15 speaker (cancellation sound generator) 16 pipe 17 collar plate 20 sound absorbing material 26 pipe 26a through Hole

Claims (6)

[Claims] 1. An active duct muffler that muffles a source sound propagating in a duct by superimposing a canceling sound on the source sound, the expansion chamber being provided in the middle of the duct, and a guide opening to the expansion chamber. A wave pipe and a canceling sound generating means connected to the waveguide, the duct connects the inlet and outlet of the gas communicating with the expansion chamber with a pipe, and the circumference of the pipe on the side opposite to the waveguide. An active duct silencing device having a surface open to the expansion chamber. 2. The active duct silencer according to claim 1, wherein the pipe is opened in the expansion chamber as a half-split pipe. 3. The active duct silencer according to claim 2, wherein the pipe-side outer surface of the half-split pipe and the expansion are located downstream of the gas flow with respect to the opening of the waveguide. An active duct silencer characterized in that a collar plate is provided between the interior surface and the interior surface. 4. The active duct silencer according to claim 2, wherein the diameter of the duct on the outlet side of the expansion chamber is made larger than the diameter of the duct on the inlet side. Duct silencer. 5. The active duct silencer according to claim 2, wherein an insulator is arranged on the side of the expansion chamber of the waveguide. 6. The active duct silencer according to claim 1, wherein the pipe is opened into the expansion chamber by a number of through holes.