JP3185447B2 - Active duct silencer - Google Patents

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 which can reduce noise from an exhaust duct of an engine.

[0002]

2. Description of the Related Art As a conventional apparatus of this kind, for example, the apparatus shown in FIGS. 12 and 13 is known (see Japanese Patent Application Laid-Open No. 2-50332193). This device is a device that actively suppresses noise by superimposing a canceling sound on an exhaust sound of an automobile. An anti-noise chamber 2 that is coaxially opened with an opening end 1a is provided around an end of an exhaust duct 1. The loudspeaker 3 and the enclosure 4 are symmetrically arranged in the anti-noise chamber 2 to form a secondary sound generator.

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

FIG. 14 shows another example (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 a duct 1 via a waveguide 5.

In this device, the primary sound propagating in the duct 1 is superimposed on the secondary sound in the acoustic mixer 6 and released into the atmosphere after the two have completely canceled each other. It shows good silencing performance even at times.

[0006]

However, the above-mentioned 2)
Each of the two conventional devices has the following problems.
That is, in the former, if the diameter of the secondary sound outlet is increased to improve the efficiency of the speaker 3, the overall diameter becomes very large due to the double-tube structure, and the degree of freedom in design is reduced. I will. In addition, since the speaker 3 transmits the canceling sound to the position of the discharge port 1a, when the flow rate of the exhaust gas is large, the noise reduction effect obtained in the vicinity of the discharge port may be weakened. Further, the speaker 3 may be easily flooded.

In the latter case, the length of the waveguide 5 must be increased 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 extracted.

Accordingly, the present invention provides an active duct silencer capable of preventing heat damage and flooding of a speaker and effectively drawing out the efficiency of the speaker by employing a structure in which 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 silencer in which a canceling sound is superimposed on a source sound propagating in the duct to muffle the sound. An expansion chamber, a waveguide opening to the expansion chamber, and a canceling sound generating means connected to the waveguide,
A pipe is connected between the gas inlet and outlet communicating with the extension chamber by the duct, and a peripheral surface of the pipe on the side opposite to the waveguide is opened into the extension chamber.

According to a second aspect of the present invention, there is provided the active duct silencer according to the first aspect, wherein the pipe is opened into an expansion chamber as a half-split pipe.

According to a third aspect of the present invention, there is provided the active duct silencer according to the second aspect, wherein the half-shaped pipe waveguide is located downstream of the gas flow from the opening of the waveguide. A flange plate is provided between the side outer surface and the expansion room surface.

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 larger than the diameter of the duct on the inlet side. It 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 provided on a side of the expansion chamber of the waveguide.

According to a sixth aspect of the present invention, there is provided the active duct silencer according to the first aspect, wherein the pipe is opened into the expansion chamber through a plurality of through holes.

[0015]

In the apparatus according to the first aspect of the present invention, the entrance and exit of the duct to the expansion chamber are connected by a pipe, and the peripheral surface of the pipe on the side opposite to the waveguide is open to the expansion chamber. It mainly flows on the open side of the pipe and reaches the outlet duct. Therefore, it hardly turns to the waveguide side. Even if it turns around, the gas flowing in the space on the open side of the pipe will cause the open side space to be in a negative pressure state, so that the gas going to turn to the waveguide side will be pulled back, and the gas will flow to the waveguide side. It is only about stagnation. As a result, the possibility that the gas flows 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 superimposed on the canceling sound introduced from the waveguide into the expansion chamber and is eliminated.

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

In the apparatus according to the third aspect of the present invention, since the flange plate is provided on the downstream side of the opening of the waveguide, the swirling flow of gas generated on the end wall on the outlet side of the expansion chamber is at the same end as the flange plate. As a result, the flow of gas into the waveguide due to the effect of the swirling flow can be more effectively prevented.

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

In the apparatus according to the fifth aspect of the present invention, since the insulator is disposed in the portion of the waveguide near the expansion chamber where the flow of gas is small, it is expected that the sound absorbing effect or the heat shielding effect is maintained for a long time.

In the apparatus according to 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 rises. 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 denoted by the same reference numerals, and description thereof will be omitted.

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

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

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

Next, the operation will be described.

When there is no half-split pipe 16,
Exhaust gas introduced into the expansion chamber 12 from the inlet duct 11 </ b> A makes a large swirl 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 there is a half-split pipe 16 as in this embodiment, the exhaust gas flows to the outlet duct 11B only through the open side of the pipe 16. Accordingly, a weak swirl flow of the exhaust gas is generated in the expansion chamber 12, but the influence does not reach the waveguide 13 side much. 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 turn to the waveguide 13 side,
The exhaust gas is returned to the open space. Therefore, the gas almost stays in the vicinity of the opening of the waveguide 13, and the intrusion of the gas into the waveguide 13 is suppressed.

As a result, the exhaust gas does not damage the speaker 15 and the need for using a special secondary sound source such as a heat-resistant speaker is eliminated. Further, the length of the waveguide 13 can be shortened and the area of the opening to the expansion chamber 12 can be increased, so that the efficiency of the speaker 15 can be sufficiently obtained. Further, since the sound is superposed and silenced in the expansion chamber 12, the silencing performance does not deteriorate even when the flow rate 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
This increases the degree of freedom in design such as the mounting position of the device, and can reliably solve problems such as flooding. In addition, since the expansion chamber 12 is arranged in the middle of the duct 11, the diameter of the opening end side of the duct can be reduced, and the degree of freedom in design is widened.

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

In the apparatus of the second embodiment, a flange plate 17 is newly added to the apparatus 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 side of the waveguide 13. The inner periphery is in contact with the outer surface of the pipe 16, and the outer periphery is in contact with the inner surface of the expansion chamber 12. Wave tube 13
Is located downstream of the gas flow from the opening position of the expansion chamber 12, and faces the outlet-side end wall 12a of the expansion chamber 12 at an interval.

The provision of the flange plate 17 prevents the influence of the swirling flow from reaching the opening of the waveguide 13. That is, the swirling flow is mainly generated by the gas flowing through the pipe 16 hitting the outlet side end wall 12a of the expansion chamber 12, and the swirling flow is generated by the presence of the flange plate 17 and the flange plate 17 and the end wall 12a. Is regulated between. 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 further increases,
Intrusion of the exhaust gas into the waveguide 13 is further suppressed.

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

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

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

<< Fourth Embodiment >> A fourth embodiment (the sixth embodiment) of the present invention will be described with reference to FIGS.

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

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

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

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

Conventionally, when a sound absorbing material or the like is provided at this position, the sound absorbing material is deteriorated with time due to the flow of the exhaust gas. However, in the apparatus 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 (a 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.
1 will be described.

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, and the height of the speaker 15 is set to be substantially the same as the height of the extension room 12. The opening 13 a of the waveguide 13 is provided diagonally above the peripheral wall of the expansion chamber 12, and the open side 16 a of the pipe 16 is set obliquely downward, opposite to the opening 13 a of the waveguide 13.

In the case of the apparatus of this embodiment, the degree of freedom in designing the layout can be increased, and at the same time, flooding can be effectively prevented. Here, the efficiency of the loudspeaker 15 will be affected by setting the waveguide 13 to be slightly longer. However, since the presence of the pipe 16 allows the aperture 13a of the waveguide 13 to be set wider, the efficiency is reduced. Will not fall.

[0045]

As described above, according to the first aspect of the present invention, gas intrusion into the waveguide can be suppressed, so that the canceling sound generator can be prevented from being damaged by heat.
It is not necessary to use a heat-resistant speaker or the like. Further, the length of the waveguide can be shortened, and the area of the opening to the expansion chamber can be widened, so that the efficiency of the speaker can be maximized. In addition, since the source sound and the canceling sound are superimposed in the expansion chamber, the sound deadening performance does not deteriorate when the gas flow velocity increases.

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

According to the second aspect of the present invention, the above-mentioned effects can be obtained by the half-pipe, and the structure is simplified.

According to the third aspect of the present invention, the inflow of gas into the waveguide can be prevented by the flange plate, and the heat damage of the canceling sound generating means can be more effectively prevented.

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

According to the fifth aspect of the invention, a long-term sound absorbing effect,
A heat shielding effect can be expected, and maintenance costs can be reduced.

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

[Brief description of the 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 line III-III of FIG. 2;

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.

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5;

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.

FIG. 13 is a sectional view taken along the arrow XIII-XIII in FIG. 12;

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Duct 11A Entrance side duct 11B Exit side duct 12 Expansion room 12 Exit side end wall 13 Waveguide 14 Enclosure (cancellation sound generation device) 15 Speaker (cancellation sound generation device) 16 Pipe 17 Flange plate 20 Sound absorbing material 26 Pipe 26a Penetration Hole

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-43806 (JP, A) JP-A-57-97989 (JP, A) JP-A-6-14420 (JP, U) 503219 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G10K 11/178 F01N 1/00 F16L 55/04 G10K 11/16

Claims (6)

(57) [Claims] 1. An active duct silencer for muffling by superimposing a canceling sound on a source sound propagating in a duct, comprising: an expansion chamber provided in the middle of the duct; and a conductor opening into the expansion chamber. A waveguide, and a canceling sound generating means connected to the waveguide, wherein the duct is connected by a pipe between gas inlets and outlets communicating with the expansion chamber, and a circumference of the pipe on a side opposite to the waveguide is provided. An active duct silencer characterized in that a surface is opened into the expansion chamber. 2. The active duct silencer according to claim 1, wherein the pipe is opened into an expansion chamber as a half-pipe. 3. The active duct silencer according to claim 2, further comprising: a waveguide-side outer surface of the half-split pipe and the expansion at a gas flow downstream of the waveguide opening. An active duct silencer wherein a flange plate is provided between the duct and an indoor 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 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 said pipe is opened into said expansion chamber through a plurality of through holes.