JPH11119783A - Speaker for silencer - Google Patents

Abstract

(57) [Problem] To provide a speaker for a silencer capable of preventing a diaphragm portion from becoming high temperature by radiant heat and improving durability. SOLUTION: The surface of a diaphragm 21 of a speaker 4A (4B) is subjected to infrared reflection processing. As infrared reflection processing,
It is painted with a color having a high infrared reflectance such as white, or is coated with gold, silver, aluminum, or a dielectric reflection film having a high infrared reflectance, by vapor deposition or the like. This can prevent the diaphragm 21 from becoming high temperature,
And the drive unit 22 can be prevented from being damaged, and the durability of the speakers 4A and 4B can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a speaker for a silencer using an active noise control (ANC) technique.

[0002]

2. Description of the Related Art In recent years, silencers using active noise control technology have been widely known, and have been used for silencing control of noise flowing through a sound absorbing duct of a blower or an exhaust pipe of an engine generator system. Among them, a muffling speaker (hereinafter simply referred to as a "speaker") for generating muffling sound waves having the same amplitude and opposite phase to noise is provided in a casing surrounding the periphery of the exhaust pipe, so that the front surface of the speaker and the outer wall surface of the exhaust pipe are provided. By forming an air chamber between the air pipe and the air chamber, one end of which communicates with the exhaust pipe concentrically with the exhaust pipe, the noise radiated from the exhaust pipe and the sound-absorbing sound wave radiated from the acoustic pipe are reduced. There is a device that interferes with the sound to obtain a noise-reducing effect. This is configured to resonate at the main frequency of the noise by the stiffness of the air in the air chamber and the air mass inside the acoustic tube, and to efficiently generate a sound-absorbing sound wave having a large sound pressure.

[0003]

However, in the above-described configuration, when the noise source is an engine accompanied by high-temperature exhaust gas, the exhaust pipe through which the noise and the exhaust gas flow has a considerably high temperature. The front surface of the speaker disposed so as to face the outer wall surface of the exhaust pipe, that is, the surface of the diaphragm portion receives the radiant heat from the exhaust pipe and becomes high temperature, and the speaker is damaged or deteriorated, There is a problem that the durability is deteriorated.

The present invention has been made in view of the above problems, and has as its object to provide a speaker for a silencer capable of preventing the diaphragm from being heated to a high temperature by radiant heat and improving durability.

[0005]

SUMMARY OF THE INVENTION The above object is achieved by a muffling signal generator based on the output of a noise detector for detecting noise from a noise source and the output of a muffling deviation detector for detecting a muffling deviation. A muffling device speaker, comprising: a driving unit that receives a muffling signal, and a diaphragm that is driven by the driving unit based on the muffling signal and that generates a sound wave having the same magnitude as the noise and having an opposite phase. The problem is solved by a speaker for a silencer, wherein infrared reflection processing is performed on a surface of the diaphragm portion.

That is, according to the present invention, the surface of the diaphragm is subjected to infrared reflection processing to protect the surface of the diaphragm from heat applied from the outside, thereby improving the durability of the speaker.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.
A noise detector 2 for detecting a noise P from a noise source (an engine in an engine generator system in the present embodiment) 9 is provided inside the exhaust pipe 1. A silencing deviation detector 3 for detecting a silencing deviation level is provided outside. The muffling signal generator 5 receiving the output x of the noise detector 2 and the output e of the muffling deviation detector 3 is for generating muffling sound waves having the same phase as the noise P and having opposite phases from the speakers 4A and 4B. A mute signal y is formed.

In the present embodiment, speakers 4A and 4A
B, a casing 6 defining an air chamber 10 is provided between the front surface of the exhaust pipe 1 and the outer wall surface of the exhaust pipe 1.
A sound pipe 7 whose one end communicates with the opening end 1a of the exhaust pipe 1
Are provided concentrically. Speaker 4A,
The back space of 4B is defined by back casings 8A and 8B. The loudspeakers 4A and 4B vibrate the air chamber 10 on the front face, resonate at a main frequency of noise by the stiffness of the air in the air chamber 10 and the air mass in the acoustic pipe 7, and open the end 7a of the acoustic pipe 7. Sound and noise P emitted from the opening end 1a of the exhaust pipe 1.
, The noise P is silenced.

FIG. 3 shows details of the muffling signal generator 5. The output x of the noise detector 2 is supplied through an amplifier 11 and an A / D converter 12 to an adaptive filter (hereinafter referred to as A
Abbreviated as DF. ) 14 and the delay filter 13. The ADF 14 has N taps, the coefficients of which are updated by the output of the coefficient calculator 15. The delay filter 13 has an acoustic transfer characteristic corresponding to a path from the speakers 4A and 4B to the air chamber 10 to the acoustic tube 7 to the silencing deviation detector 3. That is, the coefficient of the delay filter 13 is determined in consideration of the time delay, and is measured or identified in advance. The output e of the silencing deviation detector 3 is supplied to the amplifier 16 and the A / D converter 1.
7 is supplied to the coefficient calculator 15. Coefficient calculator 1
Reference numeral 5 denotes an adaptive algorithm for sequentially calculating an optimum coefficient to be given to the ADF 14. The muffling signal y formed by the ADF 14 is supplied to the speakers 4A and 4B via the D / A converter 18 and the amplifier 19, and generates noise-reducing sound waves having the same magnitude as the noise P and having the opposite phase. .
The muffling signal generator 5 has a configuration using the above-described well-known ANC control technology.

Next, the details of the speakers 4A and 4B according to the present invention will be described with reference to FIG.

A hyperbolic diaphragm 21 made of, for example, pulp or paper is accommodated as a diaphragm in a frame 26 having a plurality of openings 26a on its side surface. Is fixed to the edge. The driving unit 22 that drives the diaphragm 21 will be described. A cylindrical bobbin 27 around which a voice coil 24 is wound is integrally fixed to a lower end of the diaphragm 21. Back plate 2
The pole piece 28 fixed integrally with the fitting 9 is loosely fitted. The top plate 3 fixed to the bottom of the frame 26 at a predetermined interval concentrically with the pole piece 28.
A permanent magnet 31 is fixed between 0 and the back plate 29. Further, a spider 23 made of cloth is stretched between the inner peripheral portion of the frame 26 and the bobbin 27 to elastically support the vibration of the diaphragm 21. In the drawing, reference numeral 25 denotes a net-like dust cap.

The surface of the vibration plate 21 is subjected to infrared reflection processing. In the present embodiment, a white coating film 33 is formed on the surface of the vibration plate 21 as infrared reflection processing. That is, the surface of the diaphragm 21 is painted in white with high reflectivity, thereby reflecting infrared rays, that is, heat, radiated from the outer wall surface of the exhaust pipe 1 so as to suppress an increase in the surface temperature of the diaphragm 21. ing. In the present embodiment, processing similar to the infrared reflection processing performed on the surface of the diaphragm 21 of the speakers 4A and 4B described above is performed on the inner wall surface 6a of the casing 6.

Therefore, according to the present embodiment, it is possible to prevent the diaphragm 21 from being damaged by radiant heat from the outer wall surface of the exhaust pipe 1 and disconnection of the voice coil 24 due to the heat. Can be maintained for a long period of time, and the durability thereof can be much improved. Further, since the inner wall surface 6a of the casing 6 is also subjected to infrared reflection processing so as to suppress the temperature rise, the speaker 4 due to heat conduction from the casing 6 is formed.
Heat supply to A and 4B can be suppressed to protect the speakers 4A and 4B from heat, and the casing 6 can be safely removed when the device is maintained.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiment, the surface of the diaphragm 21 is painted in white as the infrared reflection processing. However, even if the surface of the diaphragm 21 is painted in a metallic color such as silver, the above-described embodiment can be applied. The same effect as described above can be obtained. Alternatively, the surface of the diaphragm 21 may be mirror-finished to reflect infrared light.

Further, instead of painting, a metal having high reflectivity to infrared rays, such as gold, silver or aluminum, may be coated on the surface of the diaphragm 21 by, for example, vacuum evaporation. The same effect as in the embodiment can be obtained.

Alternatively, the surface of the diaphragm 21 may be coated with a dielectric thin film having a characteristic of high reflectance to infrared rays by vapor deposition or the like. Thus, the diaphragm can be protected from infrared rays, that is, heat rays. The dielectric thin film is applied to, for example, a solar cell, and is used as a selective absorption film that absorbs light having a wavelength in the visible light range but reflects light having a wavelength belonging to the infrared region.

In the above embodiment, the diaphragm 21 having a hyperbolic shape is described as the diaphragm, but the present invention is also applicable to a dome-shaped diaphragm instead.

Further, according to the above embodiment, the speaker 4A, 4B has been described as being provided in the casing 6 surrounding the exhaust pipe 1, but the opening of the exhaust pipe 1 projecting from the inside of the building to the outside. A configuration may also be adopted in which a muffler speaker is arranged near the end 1a. That is, even if the speaker is arranged in a position where sunlight is directly irradiated, the speaker for the silencer according to the present invention can sufficiently cope with the problem.

[0021]

As described above, according to the muffler speaker of the present invention, since the surface of the diaphragm is subjected to the infrared reflection processing, the vibration applied to the surface of the diaphragm is affected by the heat applied to the surface of the diaphragm. The plate and the internal drive can be protected, thus maintaining the desired function over a long period of time and improving its durability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a speaker according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of a muffling signal generation device.

[Explanation of symbols]

 Reference Signs List 1 exhaust pipe 2 noise detector 3 silencing deviation detector 4A speaker 4B speaker 5 silencing signal generator 9 noise source 21 diaphragm 33 coating

Claims (4)

[Claims] A driving unit that receives a muffling signal generated by a muffling signal generator based on an output of a noise detector that detects noise from a noise source and an output of a muffling deviation detector that detects a muffling deviation; A speaker for a muffler, comprising: a diaphragm driven by the drive unit based on the muffling signal and having the same magnitude as the noise and generating a sound wave having an opposite phase; A speaker for a silencer, which has been subjected to reflection processing. 2. The speaker according to claim 1, wherein the surface of the diaphragm is painted white as the infrared reflection processing. 3. The speaker according to claim 1, wherein a gold, silver or aluminum film is formed on the surface of the diaphragm as the infrared reflection processing. 4. The speaker according to claim 1, wherein a dielectric thin film that reflects infrared rays is formed on the surface of the diaphragm section as the infrared reflection processing.