JP2005220871A - Muffler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffler in which a sound absorbing material is filled between an outer pipe and an inner pipe and high flow speed air near a center is brought into contact with the surrounding sound absorbing material. <P>SOLUTION: Large noise gas flow is introduced from the air outlet of an internal combustion engine or the like to an inlet port 8a. The introduced noise gas impinge on a first rectification net 6 perpendicularly arranged in the inside pipe 3 of the muffler, air is disturbed and enters the inner pipe 3, a part of air enters many punched holes and is brought into contact with a glass wool 4 forming the sound absorbing material, and acoustic wave is absorbed. Acoustic wave reflected from the surface of the inner pipe 3 reenters the other hole and is absorbed into the glass wool 4. After repeating the above process, air enters a second rectification net 5, and here, air is disturbed, reenters the punched hole, and is brought into contact with the glass wool 4 forming the sound absorbing material, and acoustic wave is absorbed. Acoustic wave reflected from the surface of the inner pipe 3 reenters the other hole, and absorbed into the glass wool 4. After repeating the above process, air is finally discharged from the air outlet 7a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a silencer for suppressing noise, and more particularly to a cylindrical silencer for eliminating high-pitched sounds of internal combustion engines such as automobiles, motorcycles and airplanes.

With the integration of the residential environment and the working environment, noise from internal combustion engines and air conditioning equipment has become a problem. Noise is improved by a source, a sound insulation effect by an enclosure, and a noise reduction measure by a sound absorbing material. In an internal combustion engine or the like, exhaust is silenced by a muffler.
Regulated according to the Noise Prevention Law and the Noise Regulation Law by local regulations, noise pollution has a large sensory factor, and not only displays the intensity of the sound in dB, but also the frequency distribution intensity of the sound. Depending on how it is, the degree of noise is different. The human ear can usually be heard from 16 Hz to 20000 Hz, but not all of them can be heard with uniform sensitivity, and the frequency analysis sound level meter measures from 30 Hz to 8000 Hz at the center frequency. Treble is also a problem.
The Fletcher-Munson audibility curve and the noise example show a curve where the audibility decreases slightly around 4000 Hz, 90 dB in the subway car, and 110 dB under the train passage guard, showing a uniform intensity level over the entire frequency range. Yes.

  As a kind of silencer, there are an enclosure type, a muffler type, a sound absorption duct type, and the like. The enclosure type is a system in which a sound source is covered with a sound insulation wall, and a sound absorbing material is attached to the inside as a material of a partition wall. This format can handle a relatively wide frequency band, but noise leaks from ventilation openings. The muffler type attenuates noise generated from the fluid in the flow path, and is effective in reducing the level of a specific frequency. However, it is difficult to obtain a uniform silencing effect over a wide frequency band. The structure guides a fluid that generates noise to a space of a certain size and consumes sound energy by utilizing a resonance phenomenon in this portion. It is necessary to sufficiently increase the ratio of the cross-sectional area of the cavity and the cross-sectional area of the exhaust pipe. The sound-absorbing duct type has a structure in which a sound-absorbing material is attached to the inner wall of the duct, but a cell or splitter made of sound-absorbing material is placed in the flow path to increase the contact area between the sound-absorbing material and the fluid, thereby increasing the attenuation Can be made. It is effective to use a thick steel plate as the duct material.

FIG. 2 shows a cross section of a muffler-type and duct-type muffler.
An outer tube 12 made of a metal cylinder, an inner tube 13 made of a metal cylinder with a hole punched out, and a glass wool 14 as a sound absorbing material is filled between the outer tube 12 and the inner tube 13, and a flange is formed on the intake port 18a side. 18 includes a duct 11 having a flange 17 on the exhaust port 17a side.
A fluid that generates noise is introduced from the intake port 18a, and sound waves enter a large number of holes punched into the tube wall in the flow path in the inner tube 13, and are absorbed into the fiber of the glass wool 14 as a sound absorbing material and muffled. . On the other hand, the sound wave that does not enter the hole is reflected inside the inner tube 13, and the reflected sound enters another hole and is absorbed by the glass wool 14. The sound wave that does not enter the other hole by the first reflected sound is reflected inside the inner tube 13, enters the other hole again, and is absorbed by the glass wool 14. The fluid that has been reduced in sound repeatedly flows from the exhaust port 17a to the outside. As a characteristic of the duct type structure, reflection and sound absorption are repeated, and the sound wave energy is attenuated by the sound absorbing material of the glass wool 14 around the cylinder. Furthermore, as a characteristic of the muffler type structure, the space due to the diameter and length of the inner tube 13 Depending on the size of the exhaust port 17a, a sound wave in a specific frequency region is attenuated using a sound resonance phenomenon. The sound is silenced by the action of both.
Also, an apparatus for actively controlling noise has been devised. This method reduces the noise in the duct without increasing the size of the duct. A noise detection microphone is provided upstream and downstream of the duct, a control sound source is provided between them, and the control sound is controlled by a signal from the microphone. This is a method of irradiating a control sound with the same sound pressure and anti-phase from the decrease. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 2002-186085 (page 9, FIG. 1)

Although the conventional silencer is configured as described above, the air near the center of the inner tube 13 has a high flow velocity and passes through without contacting the inner tube 13 and the glass wool 14. For this reason, there is a structural problem that noise is not sufficiently absorbed.
On the other hand, when the diameter of the inner tube 13 is reduced and the length is increased, there are a problem in installation space and a problem that the conduit resistance increases with respect to the fluid and the exhaust capacity decreases. For this reason, there is a demand for sufficient noise absorption in the current shape.
The present invention has been made in view of such circumstances, and a sound-absorbing material in which a sound-absorbing material is filled between an outer tube and an inner tube so that air having a large flow velocity near the center is in contact with the surrounding sound-absorbing material. The purpose is to provide a vessel.

In order to achieve the above-described object, the silencer of the present invention is configured such that a duct through which air flows is formed into a double pipe composed of an outer pipe and a perforated inner pipe, and a sound absorbing material is filled between the double pipes. In the silencer, the rectifier network for rectifying air is provided inside the inner pipe.
The silencer of the present invention is the one according to claim 1, wherein the rectifying network is provided perpendicular to the axial direction of the duct.
Moreover, the silencer of the present invention is the one according to claim 1, wherein a rectifying network is provided at a plurality of locations.

The silencer of the present invention is configured as described above, is configured as a double tube, and is filled with a glass wool as a sound absorbing material between the outer tube and the inner tube in which the hole is punched, and is connected to the flow path of the inner tube. A rectification network is provided perpendicular to the direction at two or a plurality of locations in the middle of the entrance.
With such a structure, when the air passes through the rectifying network, the air is disturbed and the flow velocity distribution is made uniform. Thereby, since the quantity which contacts glass wool increases, the silencing effect improves.

  The silencer of the present invention is configured as described above, and is a rectifying network provided vertically at a plurality of locations in the inner tube, where the high-speed portion at the center is disturbed and enters the peripheral hole and contacts the glass wool. . In the conventional silencer, air with a high flow velocity in the center passes through and is not silenced, but the air disturbed by the installation of the rectifying network hits the surroundings, and is reflected by the surface of the inner tube to reduce energy and holes. Since the sound wave that enters and comes into contact with the glass wool is silenced more than before, the silencing effect is improved. In addition, by installing the rectifying network, the resonance phenomenon of the duct moves to the high sound range, and the attenuation of the high sound band becomes large. Thereby, the silencing effect can be improved with the current dimensions without enlarging the outer dimension.

  The silencer of the present invention realizes a small silencer in which a sound absorbing material is punched into the circumference and held in a cylindrical portion, and a portion with a fast central flow velocity is silenced by a vertical rectifier network. .

An embodiment of the silencer of the present invention will be described with reference to FIG. FIG. 1 is a view showing a cross-sectional structure of a silencer of the present invention.
The silencer of the present invention is a sound absorbing material that fills the space between the outer tube 2 and the inner tube 3, the metal outer tube 2 forming the silencer, the metal inner tube 3 punched out of the hole. Glass wool 4 of material, a plurality of rectifying networks 5 and 6 provided in the inner tube 3 perpendicular to the axial direction, a flange 8 having a gas inlet 8a, and a gas outlet 7a It is comprised from the flange 7 provided with.

  The difference between the silencer of the present invention and the conventional silencer is that the conventional silencer is a double silencer in which glass wool 14 is filled between an outer tube 12 and an inner tube 13 having a hole punched as shown in FIG. In contrast to this, the silencer is provided with a plurality of rectifying networks 6 and 5 in the inner tube 3 to disturb the air having a high flow velocity in the center, and to the surrounding glass wool 4. It is comprised with the duct 1 which silences by contacting air. The installation of the rectifying network 6 and the rectifying network 5 greatly improves the silencing effect with the same outer dimensions, and the silencing effect in the high sound range is particularly great.

Next, each component of the silencer will be described.
The outer pipe 2 and the inner pipe 3 usually have a lot of exhaust gas from an internal combustion engine or the like in an air flow having noise, and vibrations of the internal combustion engine or the like are transmitted simultaneously at high temperature and high pressure. Therefore, a material that is resistant to vibration, temperature, and pressure is selected. Usually, a steel plate is used, and the outer tube 2 is provided with flanges 7 and 8 at both ends in order to make a mechanically strong structure. Since the high temperature gas, NOx, suspended particulate matter (SPM) and the like flow into the inner tube 3, a heat-resistant steel material is used. The inner tube 3 is a muffler type and has an effect of reducing the level of a specific frequency. Since the energy of sound can be consumed by utilizing a resonance phenomenon in this portion, a steel plate having a large transmission loss is used.
Glass wool 4 is used as the sound absorbing material, and the sound wave entering from the hole punched into the inner tube 3 is attenuated by the glass fiber. The effect varies depending on the degree of filling, and a medium filled with moderate compression has a good balance between the contact rate and the attenuation rate of air. It also affects the thickness of the glass fiber.
The rectifying network 6 and the rectifying network 5 are made of a heat-resistant steel net because high-temperature gas, NOx, suspended particulate matter (SPM), and the like flow in the same manner as the inner pipe 3. And it arrange | positions in several places perpendicular | vertical to the axial direction of the inner side pipe | tube 3. FIG. The first rectifying network 6 is installed at the inlet of the inner tube 3 in order to disturb the air having a high flow velocity at the center of the inner tube 3. Then, the second rectification network 5 is installed in the middle. The air disturbed by the rectifying network 6 is absorbed by the glass wool 4 in the direction toward the hole of the surrounding inner tube 3. The air flow that has not been disturbed by the first rectifying network 6 enters the second rectifying network 5 again, where the air flow is turbulent, and is absorbed by the glass wool 4 inside toward the hole of the surrounding inner tube 3. The rectifying networks 5 and 6 may be provided in a plurality of locations in the inner pipe 3.

Next, the operation of the silencer will be described.
High-temperature gas having noise from an internal combustion engine or the like is introduced into the intake port 8a. The introduced gas having noise collides with the rectifying network 6 provided at the inlet. There, the air is turbulent, part of the turbulent air travels forward, part of it is reflected by the surface of the inner tube 3 to attenuate energy, and part of it enters a hole punched into the inner tube 3, The energy of sound waves is attenuated in the filled glass wool 4. The air that has advanced in front of the former and the air reflected by the surface of the inner tube 3 collide with the second rectifying network 5 again. There, the air is turbulent, part of the turbulent air travels forward, part of it is reflected by the surface of the inner tube 3 to attenuate energy, and part of it enters a hole punched into the inner tube 3, Sound is absorbed by the filled glass wool 4. Then, the reflection on the surface of the inner tube 3 and the sound that enters the hole punched out in the inner tube 3 are absorbed and the air is finally silenced from the exhaust port 7a.

It is explanatory drawing which showed one Example of the silencer of this invention. It is explanatory drawing which showed the conventional silencer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Duct 2 Outer tube 3 Inner tube 4 Glass wool 5 Rectification network 6 Rectification network 7 Flange 7a Exhaust port 8 Flange 8a Inlet port 11 Duct 12 Outer tube 13 Inner tube 14 Glass wool 17 Flange 17a Exhaust port 18 Flange 18a Inlet port

Claims (3)

  A silencer in which a duct through which air flows is configured as a double pipe composed of an outer pipe and a perforated inner pipe, and a sound absorbing material is filled between the double pipes to mute the sound. A silencer characterized in that it is provided with a rectifying network for rectifying air.   The silencer according to claim 1, wherein the rectifying network is provided perpendicular to the axial direction of the duct.   The silencer according to claim 1, wherein a rectifying network is provided at a plurality of locations.

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