JPH07189645A - Active silencing device - Google Patents

Abstract

PURPOSE:To obtain silencing effect effectively, while maintaining a speaker at a sufficient low temperature. CONSTITUTION:An active muffler device is constitution by a nearly cylindrical insulator 13 by which an exhaust pipe 11 is enclosed, a nearly cylindrical extended pipe 12 by which the insulator 13 is enclosed, a close part 14 for closing the insulator 13 and the extended pipe 12, a speaker box 15, and a speaker 16. The insulator 13 is maintained in a low temperature without directly heating by radiating heat of an exhaust pipe 11 since outside air passed in an outside air passage 18. Therefore, the speaker 16 is maintained in a low temperature sufficiently. Since an acoustic passage 19 is formed in a shape having the inclining angle which the close part 14 is 45+ or -5 deg. in relation to the shaft of the exhaust pipe 11, noise which is generated from the speaker 16 achieves in an interaction region without deteriorating output characteristic, so that silencing is achieved effectively.

Description

Detailed Description of the Invention

The present invention relates to an active silencer attached to an exhaust pipe that emits exhaust noise.

[0002]

[Industrial applications]

[0003]

2. Description of the Related Art Heretofore, as an active silencer attached to an exhaust pipe that emits exhaust noise, for example, Japanese Patent Laid-Open No. Hei 4
The one disclosed in No. -350314 is known. That is, as shown in FIG. 9, a duct 102 that collects sound waves emitted from the speaker 101 on the front surface of the speaker 101.
And the opening 103 at the tip of the duct 102 is connected to the exhaust pipe 10.
The ventilation hole 105 is provided at a position away from the exhaust gas flow (solid arrow) of the exhaust pipe 104, and the speaker 101 is cooled by sucking out the air in the duct 102 by the exhaust gas flow. A structure is disclosed.

In this active muffler, the opening 10
3 has a structure that forms an ejector by the exhaust gas flow and sucks out the air in the duct 102.
Needs to be designed smaller. In addition, the air flows into the duct 102 through the ventilation inlet 106, and then the ventilation hole 10
5 and flows out from the opening 103. The inflow and outflow paths of air are shown by the dotted arrows.

According to this, the speaker 101 is cooled by the inflow and outflow of air, and the speaker 101 is exhausted by the exhaust pipe 1.
Since it does not come into contact with the exhaust gas flow discharged from 04, deterioration due to its heat or a specific corrosive component is prevented to some extent.

[0006]

By the way, the speaker 1
01 is a speaker box 1 provided inside the duct 102
Since it is attached to No. 07, not only the cone portion 101a but also the coil portion 101b may be in a high temperature state. In order to cool the speaker 101 having a high temperature in this way, a considerable cooling efficiency is required.

However, in the conventional active silencer, although the speaker 101 is cooled by the inflow and outflow of air, the air must be turned at the ventilation inlet 106 when the air flows into the duct 102. That is, since the ventilation hole 105 and the opening 103 are smaller than the volume of the duct 102, the flow rate of air is limited, and the cone portion 101a and the coil portion 101b are protected against radiant heat from the exhaust gas passage immediately after operation under high load. It is difficult to efficiently cool the speaker 101 due to insufficient conditions.

As a result, the speaker 101 is exposed to a high temperature state for a long time, and various performances such as sound output characteristics may be deteriorated in the normal speaker 101 not subjected to the heat resistance treatment. Therefore, it is necessary to use an expensive speaker that has been subjected to a heat treatment.

On the other hand, in this active silencer, the characteristics of the antiphase sound emitted from the speaker 101 may deteriorate in the duct 102 before they interfere with the exhaust sound. As a result, there is a problem in that an effective silencing effect cannot be obtained. The present invention has been made in order to solve the above problems, and an object of the present invention is to provide an active silencer capable of maintaining a speaker at a sufficiently low temperature and obtaining an effective silence effect.

[0010]

In order to solve the above problems, an active silencer of the present invention is a substantially cylindrical insulator that surrounds the rear end of an exhaust pipe that emits exhaust noise, and a substantially cylindrical insulator that surrounds the insulator. Of the expansion pipe, the front peripheral portion of the insulator and the front peripheral portion of the expansion pipe are closed, the closed portion formed at a predetermined inclination angle with respect to the axis of the exhaust pipe, and the outer peripheral surface of the exhaust pipe And an outside air flow path formed by the inner peripheral surface of the insulator, and the outside pipe of the expansion pipe through a communication pipe that communicates with a gap between the outer peripheral surface of the insulator and the inner peripheral surface of the expansion pipe. And a speaker for outputting a sound having a phase opposite to that of the exhaust sound into the gap.

[0011]

The active muffler of the present invention having the above structure is attached to an exhaust pipe of an automobile or the like. Although the exhaust pipe is in a high temperature state during traveling of an automobile or the like, in the active silencer of the present invention, the outside air passes from the front to the rear of the outside air flow path at a speed substantially equal to the vehicle speed, so that the air cooling efficiency is high. Therefore, the radiant heat of the exhaust pipe is not directly conducted to the insulator, which prevents the insulator itself from reaching a high temperature. Since the speaker is arranged outside the insulator, the insulator is surely protected from heat damage.

Further, the speaker is arranged outside the expansion tube via a communication tube. Therefore, the radiant heat of the exhaust pipe does not reach the entire speaker including the cone portion and the coil portion. Therefore, according to the active silencer of the present invention, the speaker can be kept at a sufficiently low temperature by the outside air passing through the outside air flow path.

Further, since the speaker does not come into contact with the exhaust gas flow, it does not corrode due to corrosive components contained in the exhaust gas flow. On the other hand, the sound output from the speaker passes through the gap between the insulator and the expansion pipe when reaching the vicinity of the end portion of the exhaust pipe that interferes with the exhaust sound. This gap is less likely to deteriorate the sound output characteristics before reaching the end of the exhaust pipe. The reason for this is not clear, but it is presumed that the closed portion is formed in a shape having a predetermined inclination angle with respect to the axis of the exhaust pipe.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below in detail with reference to the drawings. 1 to 4 are diagrams showing the first embodiment,
1 is a plan view in which an active muffler of the first embodiment is attached to an exhaust pipe of an engine, FIG. 2 is a partial front view of the same, and FIG. 3 is a vertical sectional view of FIG. Further, FIG. 4 is a cross-sectional view taken along the line AA of FIG.

The active silencer 10 of the first embodiment is
Mainly, the expansion pipe 12, the insulator 13, and the closing portion 1
4, a speaker box 15 and a speaker 16. The expansion tube 12 is formed in a substantially tubular shape with a throttle in the middle from the front to the rear. This expansion tube 12
As shown in FIG. 2, the terminal peripheral edge portion (hereinafter, referred to as “terminal portion”) 12a of the exhaust pipe 11 is inclined forward from the upper side to the lower side similarly to the terminal peripheral portion (hereinafter, referred to as “terminal portion”) 11a of the exhaust pipe 11. Is formed. In addition, the expansion tube 12
The end portion 12a of the exhaust pipe 11 is disposed rearward from the end portion 11a of the exhaust pipe 11 by a distance d (see FIG. 2, d = 15 mm). On the other hand, the front peripheral portion 12b of the expansion pipe 12 has the exhaust pipe 1
It is formed with a predetermined inclination angle with respect to one axis. In this embodiment, this inclination angle is set within the range of 45 ± 5 °. Further, a communication hole 12c is provided on the outer peripheral surface of the expansion tube 12. A short communication pipe 17 is connected to the communication hole 12c.

The insulator 13 is arranged at an intermediate position between the outer peripheral surface of the exhaust pipe 11 and the inner peripheral surface of the expansion pipe 12, and is formed in a substantially cylindrical shape. A terminal peripheral edge portion (hereinafter, referred to as “terminal portion”) 13a of the insulator 13 is formed at a position in front of the terminal portion 11a of the exhaust pipe 11 so as to be substantially orthogonal to the axis of the exhaust pipe 11. . The front peripheral portion 13b of the insulator 13 is formed with the same inclination angle as the expansion pipe 12 with respect to the axis of the exhaust pipe 11.

The closing portion 14 is formed in a substantially annular shape so as to cover and close the front peripheral edge portion 13b of the insulator 13 and the front peripheral edge portion 12b of the expansion tube 12. The surface of the closing portion 14 is also formed with the same inclination angle with respect to the axis of the exhaust pipe 11 as that of the expansion pipe 12.

The speaker box 15 is connected to the communication pipe 17 and is located outside the expansion pipe 12. In this speaker box 15, a speaker 16 has a cone 16
It is installed so that a is substantially parallel to the surface of the exhaust pipe 11 and faces the communication hole 12c. The opening area of the communication hole 12c is designed to be smaller than the area of the cone 16a so as not to impair the sound output characteristics of the speaker 16.

The outside air passage 18 is formed by the outer peripheral surface of the exhaust pipe 11 and the inner peripheral surface of the insulator 13. In the outside air flow path 18, outside air flows in from a front inlet 18a, and outside air flows out from a rear outlet 18b. The acoustic passage 19 is a gap formed by the outer peripheral surface of the insulator 13 and the inner peripheral surface of the expansion pipe 12, and is a path through which the sound output from the speaker 16 moves to the periphery of the end portion 11 a of the exhaust pipe 11. is there.

Next, the exhaust pipe 1 of the active silencer 10
The structure for attaching to 1 will be described. As shown in FIG.
A stay 21 is attached to the outer peripheral surface of the exhaust pipe 11, and a bolt 22 that penetrates the extension pipe 12 and the insulator 13
Is screwed into a nut 23 arranged inside the stay 21. An insulating washer 24 is provided between the stay 21 and the insulator 13, between the insulator 13 and the expansion tube 12, and between the expansion tube 12 and the head of the bolt 22, respectively.
a, 24b, 24c are arranged. Therefore, this mounting structure prevents the heat of the exhaust pipe 11 from being directly conducted to the insulator 13, the expansion pipe 12, and the bolt 22.

As shown in FIG. 1, the speaker box 15 is attached to the stay 25 attached to the outer peripheral surface of the exhaust pipe 11 by bolts 26 or the like via an insulating washer (not shown) as in the above. Has been. Therefore,
The heat of the exhaust pipe 11 is prevented from being directly conducted to the speaker box 15.

Next, the operation of the active silencer 10 will be described. When an engine (not shown) connected to the exhaust pipe 11 starts up and rotates, an exhaust sound is formed by an explosion sound generated according to an explosion in each cylinder. Further, the exhaust pipe 11 is gradually heated to a high temperature. On the other hand, when the rotation signal synchronized with the rotation of the engine is input, the speaker 16 is driven according to the rotation signal.

Then, the cone 16a of the speaker 16 vibrates at a predetermined frequency, and sound is output in the acoustic passage 19. This sound is synthesized in an opposite phase to the exhaust sound so as to interfere with the exhaust sound and cancel each other out. The sound output into the acoustic passage 19 reaches the periphery of the end portion 11a of the exhaust pipe 11 and is silenced by interfering with the exhaust sound.

With respect to the above operation, low temperature outside air flows into the outside air flow path 18 from the inflow port 18a and flows out from the outflow port 18b at a speed substantially equal to the vehicle speed. As a result, the inner peripheral surface of the insulator 13 is efficiently cooled, so that the exhaust pipe 1
It is not directly heated by the radiant heat of 1, but the insulator 13 itself is kept at a low temperature. This insulator 13 reliably protects the speaker 16 from heat damage.

Since the speaker 16 is located outside the expansion tube 12 via the communication tube 17, the speaker 16
The coil portion 16b is also reliably shielded from heat. Further, since the communication hole 12c communicating with the acoustic passage 19 is designed to be smaller than the area of the cone, the predetermined portion of the cone 16a which does not face the communication hole 12c is exhausted by the expansion pipe 12 and the speaker box 15 as well. Heat is shielded from 11.

Furthermore, since the distance d between the end portion 11a of the exhaust pipe 11 and the end portion 12a of the expansion pipe 12 is set to 15 mm, the high temperature exhaust gas flow only contacts the expansion pipe 12 in a narrow range, The expansion tube 12 does not become extremely hot. Therefore, the speaker 16 is less likely to be heated by the heat conduction from the expansion tube 12.

With the above operation, the speaker 1 of the first embodiment
6 can be kept at a low temperature. Further, in the first embodiment, since the distance d is set to 15 mm, the sound interference area is comparatively large, and it is possible to obtain a sufficient volume reduction in a wide frequency area. Specific data are shown in FIG.
FIG. 7 is a graph of the volume of noise reduction with respect to engine speed and frequency, and the first embodiment is indicated by Δ. As is apparent from FIG. 7, the first embodiment provides a sound deadening level of 20 dB or more.

Note that, if the distance d is increased, the maximum volume of sound is 2
Increase to about 5 dB, but conversely exhaust gas flow and expansion pipe 1
There is a drawback in that the contact range with 2 becomes large and the speaker 16 tends to be in a high temperature state. Considering these, the distance d is preferably set to 25 mm or less.

Further, since the sound passage 19 is formed so that the closing portion 14 has an inclination angle with respect to the axis of the exhaust pipe 11, the sound emitted from the speaker 16 does not deteriorate its output characteristics. It reaches the vicinity of the end portion 11a of the exhaust pipe 11. Specific data are shown in FIG. FIG. 8 is a graph showing sound volume with respect to frequency, and the output characteristic of the first embodiment is shown by a solid line. It is to be noted that what is indicated by a dotted line in FIG. 8 is an active silencer having a shape in which the closed portion 34 is substantially orthogonal to the axis of the exhaust pipe 11 (hereinafter,
This is the output characteristic of "reference example" (see FIG. 5).
In the reference example, the volume of the acoustic passage 39 is about twice that of the first embodiment. Active mufflers typically use the 75-800 Hz frequency range to muffle exhaust noise. As is clear from FIG. 8, in the reference example, the originally flat shape collapses in this frequency region, and in particular, 600 to
The sound volume is greatly reduced in the 800 Hz region. On the other hand, in the first embodiment, although the originally flat shape is also broken, the sound volume is improved by 10 to 15 dB in the region of 600 to 800 Hz as compared with the reference example. For this reason, in the first embodiment, it is possible to perform silencing more efficiently than in the reference example.

The effects of the active muffler of the first embodiment described above will be described below. Since the speaker 15 is maintained at a sufficiently low temperature, it does not need to have heat resistance. Further, since the speaker 16 does not come into contact with the exhaust gas flow, there is no fear of being corroded by the corrosive components in the exhaust gas flow. Therefore, it is not necessary to provide corrosion resistance. Therefore, a normal speaker can be used, and the cost can be reduced. Since the interference region is relatively wide, it is possible to obtain a sufficient volume reduction in a wide frequency range. Since the acoustic passage 19 is formed in a shape having an inclination angle with respect to the axis of the exhaust pipe 11, the sound output from the speaker 16 is less likely to deteriorate its output characteristics.
Therefore, it is possible to effectively mute the sound. Since the expansion tube 12 and the like have a shape that spreads from the front to the rear, it is advantageous in terms of acoustic resistance.

Next, the second embodiment will be described. As shown in the partial front view of FIG. 6 in the active muffler 50 of the second embodiment, except that the distance d between the end portion 52a of the expansion pipe 52 and the end portion 11a of the exhaust pipe 11 is set to d = 0. Is the same as in the first embodiment. Therefore, description of other components will be omitted.

FIG. 7 is a graph showing the relationship between the engine speed and frequency and the sound deadening volume. The second embodiment is indicated by a circle. As is clear from this figure, the second embodiment has a lower volume reduction by about 1 to 2 dB than the first embodiment, but it can be seen that a sufficient volume reduction can be obtained.

Further, the second embodiment has a structure in which the exhaust gas flow hardly contacts the expansion pipe 52 as compared with the first embodiment, so that the expansion pipe 52 may be heated by the exhaust gas flow and become hot. , The expansion tube 52 is kept cold.
Therefore, heat conduction from the expansion tube 12 causes the speaker 16
Is less likely to be heated.

Further, in the second embodiment, although the distance d is set to 0, the noise reduction level is reduced by about 2 dB as compared with the first embodiment, and a sufficient noise reduction level can be obtained. The second embodiment described above has an effect that the temperature of the speaker 16 is maintained at a lower temperature, in addition to the effects substantially similar to those of the first embodiment.

It is needless to say that the present embodiment is not limited to the above embodiment and can be implemented in various modes without departing from the gist of the present invention.

[0036]

As described in detail above, according to the active muffler of the present invention, the speaker can be kept at a sufficiently low temperature and an effective muffling effect can be obtained. For this reason,
The speaker does not need to have heat resistance, and the output characteristics of the speaker can be fully utilized for silencing.

[Brief description of drawings]

FIG. 1 is a plan view when a first embodiment is attached to an exhaust pipe.

FIG. 2 is a partial front view when the first embodiment is attached to an exhaust pipe.

FIG. 3 is a vertical cross-sectional view when the first embodiment is attached to an exhaust pipe.

4 is a cross-sectional view taken along the line AA of FIG.

FIG. 5 is a plan view of a reference example attached to an exhaust pipe.

FIG. 6 is a partial front view of the second embodiment when attached to an exhaust pipe.

FIG. 7 is a graph showing the volume of noise reduction with respect to engine speed and frequency.

FIG. 8 is a graph showing volume characteristics with respect to frequency.

FIG. 9 is a sectional view of a conventional active silencer.

[Explanation of symbols]

10, 30, 50 ... Active silencer, 11 ...
・ Exhaust pipe, 11a ...
..Expansion pipes, 12a ... End portions, 12
b ... front peripheral portion, 12c ... communication hole, 1
3 ... Insulator, 13a ... Terminal part,
13b ... front peripheral part, 14 ... block part,
15 ... Speaker box, 16 ... Speaker, 16a ... Cone, 17 ... Communication pipe, 18 ... Outside air flow path, 19 ... Sound passage,

Claims (1)

[Claims] 1. A substantially cylindrical insulator that surrounds a rear end portion of an exhaust pipe that emits exhaust noise, a substantially cylindrical expansion pipe that surrounds the insulator, a front peripheral edge portion of the insulator, and a front peripheral edge portion of the expansion pipe. And an external air flow path formed by the outer peripheral surface of the exhaust pipe and the inner peripheral surface of the insulator, and the insulator. A speaker that is attached to the outside of the expansion pipe through a communication pipe that communicates with the outer peripheral surface of the expansion pipe and the inner peripheral surface of the expansion pipe, and that outputs a sound in a phase opposite to the exhaust sound into the gap. An active muffler characterized by having.