JP2005299593A - Silencer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silencer sufficiently absorbing sound with a saved space. <P>SOLUTION: This silencer comprises a pipe 1a forming a flow passage 2 for a gas including sound wave, a porous plate 3 extending in the axial direction of the pipe 1a and partitioning the flow passage 2 so as to form an auxiliary flow passage, through holes 3a formed in a porous plate 3 to pass a gas therethrough, and a reflection plate 4 reflecting a part of the sound wave propagating so that the sound pressure difference of the sound wave occurs on the front and rear sides of the through holes 3a and installed in the auxiliary passage making nonuniform the distribution of the sound pressure in the cross sectional direction of the pipe 1a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a silencer that silences a sound wave superimposed on a fluid flow.

  So far, various structures have been proposed to absorb noise contained in air. For example, Patent Document 1 describes a sound absorbing structure using resonance (Helmholtz principle). The sound absorbing structure described in Patent Literature 1 has a small hole provided in a pipe through which air flows and a hollow larger than the small hole. Then, when the circulating air enters the hollow through the small hole, the air in the hollow acts as a spring, whereby the air enters and exits vigorously in the small hole portion. As a result, sound absorption is achieved by converting acoustic energy into thermal energy due to viscous damping at the wall surface of the small hole when air passes through the small hole and pressure loss when air enters and exits the small hole. is doing.

Japanese Patent Laid-Open No. 2001-1992287 (FIG. 4)

  However, the structure of Patent Document 1 has a problem in that a hollow for causing resonance, that is, an air layer needs to be provided in the pipe, and the structure itself becomes large.

  Therefore, an object of the present invention is to propose a silencer that can sufficiently absorb sound in a small space.

Means and effects for solving the problems

  The present invention provides a pipe that forms a flow path of a fluid containing sound waves, a partition member that extends in the axial direction of the pipe and partitions the flow path so as to form a sub-flow path, and the partition member. Provided in a sub-flow path that reflects a part of the propagating sound wave and makes the sound pressure distribution non-uniform in the cross-sectional direction of the pipe so that a sound pressure difference between the sound wave of the sound wave occurs between the through hole and the front and back of the through hole. A reflective member.

  According to this configuration, by reflecting a part of the propagating sound wave, the sound pressure distribution becomes non-uniform in the cross-sectional direction of the pipe, that is, a sound pressure difference is generated between the front and back of the through hole, and the fluid is accompanied accordingly. Moves through the through hole. And a noise can be absorbed when a fluid passes a through-hole. In addition, in order to allow the fluid to pass through the through-hole using the sound pressure difference generated by providing the reflecting member, the structure of silencing using the principle of resonance (Helmholtz), that is, the structure of providing a back air layer in the pipe In contrast, the piping space can be reduced.

  It is preferable that the reflecting member of the present invention is disposed on the partition member and / or the pipe. According to this, the installation position of the reflecting member can be appropriately changed depending on the workability and the like.

  In another aspect, the present invention provides a pipe that forms a flow path of a fluid containing sound waves, a partition member that extends in the axial direction of the pipe and partitions the flow path so as to form a sub-flow path, and a partition member A through-hole through which the fluid passes; and a reflecting member that is provided in the pipe and / or the partition member and reflects a part of the sound wave propagating through the sub-flow path.

  In the present invention, two or more reflecting members are provided in each of the two or more sub-flow channels, and the interval in the axial direction of the reflecting member disposed in the same sub-flow channel is different for each sub-flow channel. It is preferable. According to this, a difference in sound pressure between the front and back of the through hole is more likely to occur by changing the interval of the reflecting member for each sub-channel, and the sound absorption performance can be improved.

  In the present invention, the interval in the axial direction of the reflecting members disposed in the same sub-flow path may be non-uniform. According to this configuration, the sound absorption band can be widened by setting the sound absorption frequency band determined by the interval between the reflecting members to various frequencies.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, a first embodiment of the present invention will be described. The silencer 1 according to the present embodiment includes a moving device including a driving mechanism such as an engine, and a driving mechanism such as a motor and a gear inside, such as an automobile, a railway vehicle, a construction vehicle, a ship, and an automatic transfer device. To exhaust pipes that contain noise, that is, when exhausting airflow (gas) with superimposed noise, or pipes that transmit noise superimposed on the flow of compressed gas, such as compressors, etc. Preferably used. In the present embodiment, the fluid flowing through the silencer 1 is described as a gas, but it may be a liquid such as water or oil.

  As shown in FIGS. 1 (a) and 1 (b), the silencer 1 includes a long pipe 1a having a square cross section that forms a flow path 2 through which an air flow superimposed with sound waves such as noise flows. And a plate-like perforated plate 3 (partition member) and a plate-like reflector 4 (reflecting member). These pipes 1a, the perforated plate 3, and the reflecting plate 4 are made of a metal such as iron or aluminum or a synthetic resin. The pipe 1a, the perforated plate 3 and the reflecting plate 4 are preferably formed of the same material so as to eliminate the separation process at the time of recycling.

  The perforated plate 3 extends in the axial direction of the pipe 1a and divides the flow path 2 into two sub flow paths 2a and 2b. The perforated plate 3 has a through-hole 3a through which gas passes, and the gas can move between the sub-flow channels 2a and 2b through the through-hole 3a. It should be noted that parameters such as the plate thickness of the perforated plate 3, the opening ratio of the through hole 3a, and the hole diameter are set so as to produce a damping effect due to viscous action and pressure loss on the gas passing through the through hole 3a. It is preferable.

  Further, when the gas is air at normal temperature and normal pressure, the hole diameter of the through hole 3a is not particularly limited, but is desirably 1 mm or less. And when the hole diameter of the through-hole 3a is set to 1 mm or less in this way, viscous action and pressure loss can be reliably generated in the gas flowing through the through-hole 3a.

  In addition, it is preferable that the lower limit of the diameter of the through-hole 3a is 0.2 mm. The reason for this is that when the diameter of the through hole 3a approaches 0, the peak of the sound absorption coefficient is theoretically 1.0, but in reality, it does not reach 1.0, and the diameter is 0.2 mm or less. This is because, if it is extremely small, the viscosity of the air in the through hole 3a becomes too large, so that the resistance to the air flow in the through hole 3a increases and the sound absorption rate is considered to decrease. In addition, if the diameter is extremely small, such as 0.2 mm or less, the manufacturing becomes significantly difficult, and the through-hole 3a is likely to be blocked by dust or dust depending on the use environment. In addition, the diameter of the through-hole 3a is not limited to the above-mentioned numerical value, What is necessary is just to determine a suitable numerical value by the state of a gas, a characteristic, the frequency of the sound wave to silence, etc.

  Moreover, the through-hole 3a may be oval, rectangular, polygonal, or slit-shaped, may be set to the same size and shape, or may be mixed in various sizes and shapes. good. When various sizes and shapes are mixed, the frequency bandwidth that exhibits sufficient sound absorption performance can be expanded.

  The reflection plate 4 reflects a part of the sound wave propagating through the sub-channels 2a and 2b so that the sound pressure distribution is not uniform in the cross-sectional direction of the pipe 1a, that is, the pipe 1a is shielded from the propagating sound wave. It is arranged perpendicular to the inner wall. A plurality of the reflecting plates 4 are arranged on the wall surface facing the perforated plate 3 at equal intervals in the axial direction in the sub-channels 2a and 2b. The reflectors 4 arranged on the sub-channel 2a side are arranged at the interval La, and the reflectors 4 arranged on the sub-channel 2b side are arranged at the interval Lb. Here, the arrangement interval L (La · Lb) of the reflection plate 4 is set to be approximately L = c / 2f. Here, c is the speed of sound, and f is the frequency of sound waves contained in the gas flowing through each sub-flow channel. That is, the interval between the reflecting plates 4 is approximately half the wavelength of the sound wave.

  By providing the reflecting plate 4, a part of the sound wave propagating through the sub-channels 2a and 2b is reflected, so that the sound pressure distribution of the sound wave contained in the gas is shown in FIG. It looks like a curve. A difference in sound pressure between the sub-channels 2a and 2b causes a difference in sound pressure between the front and back of the through hole 3a. Here, the front surface of the through hole 3a refers to the sub flow channel 2a side, and the back surface of the through hole 3a refers to the sub flow channel 2b side.

  Due to the difference in sound pressure between the front and back of the through-hole 3a, the air moves from the higher sound pressure to the lower one as shown by the arrows in FIG. Therefore, the gas flowing through the sub flow channel 2a moves to the sub flow channel 2b through the through hole 3a due to the sound pressure difference. For this reason, gas can be allowed to pass through the through-hole 3a, and sound can be absorbed by the viscous action and pressure loss between the through-hole 3a and the gas.

Further, as described above, since the amplitude mode is generated between the reflection plates 4 by setting the interval between the reflection plates 4 to be approximately half the wavelength of the sound wave, a sound pressure difference is easily generated between the front and back of the through hole 3a, and the sound absorption force is increased. It is getting bigger. In addition, it is not necessary to make the space | interval of the reflecting plate 4 into the half wavelength of a sound wave completely, What is necessary is just the space | interval which a sound pressure difference produces in the front and back of the through-hole 3a by reflecting a sound wave. For example, the arrangement interval L is 1/3 octave range around the frequency f of the acoustic wave, that is, if the value of the frequency of the sound wave is determined as a range from f × ^-6 √2 of f × ⁶ √2 The sound pressure difference tends to occur between the front and back of the through hole 3a.

  As described above, the silencer 1 of the present embodiment is configured so that the pipe 1a that forms the flow path of the gas containing the sound wave and the axial direction of the pipe 1a are extended to form the auxiliary flow paths 2a and 2b. A perforated plate 3 that divides the flow path 2, a through hole 3 a that is provided in the perforated plate 3, and a sub-flow path that is provided in the perforated plate 3, reflects a part of the propagating sound wave, and the sound pressure distribution of the pipe 1 a It has a structure having a reflector that makes it non-uniform in the cross-sectional direction.

  As a result, a sound pressure difference is generated between the front and back of the through hole. Accordingly, the gas moves through the through hole, and noise can be absorbed by the gas passing through the through hole. In addition, in order to allow the gas to pass through the through-hole 3a using the sound pressure difference generated by providing the reflecting plate 4, in comparison with the structure of silencing using resonance, that is, the structure of providing a back air layer in the pipe, The space of the pipe 1a can be reduced.

  Moreover, when the reflecting plate 4 of this embodiment is arrange | positioned at the perforated plate 3 and / or the piping 1a, it becomes possible to change the installation position of the reflecting plate 4 suitably by workability etc. Further, in the present embodiment, two or more reflectors 4 are provided in each of the sub-channels 2a and 2b, and the interval in the axial direction of the reflectors 4 disposed in the same sub-channel is determined as the sub-stream. By being different for each road, the sound pressure difference between the front and back of the through hole 3a is more likely to occur, and the sound absorption performance can be improved.

  Furthermore, in this embodiment, the axial interval L of the reflectors 4 disposed in the same sub-flow path is c, the sound speed is c, and the frequency of sound waves contained in the gas flowing through the sub-flow path is f. Is set so as to satisfy approximately L = c / 2f. Thereby, by setting the interval between the reflection plates 4 to be approximately half the wavelength of the sound wave, an amplitude mode is generated between the reflection plates 4, and a sound pressure difference between the front and rear of the through hole 3 a is more likely to occur, thereby improving sound absorption performance. Can do.

  In addition, although this invention was demonstrated based on suitable embodiment, this invention can be changed in the range which does not exceed the meaning.

  That is, the reflecting plate 4 is disposed only on the inner wall of the pipe 1a, but is not limited thereto. For example, as shown in FIG. 3, the reflecting plate 4 may be provided on the front and back surfaces of the porous plate 3, or as shown in FIG. 4, the reflecting plate 4 may be provided on both the pipe 1a and the porous plate 3. May be. The flow path 2 is divided into two sub flow paths 2a and 2b by the perforated plate 3. However, the flow path 2 may be divided into three flow paths, or the flow path 2 may not be divided completely. Two sub-channels may be formed. Furthermore, the pipe 1a may have a cylindrical shape, or the flow path 2 may be divided using a cylindrical perforated plate.

  Further, the reflecting plate 4 may not be plate-shaped as long as it can reflect sound waves. Further, the reflectors 4 are arranged at intervals that substantially satisfy L = c / 2f. However, the present invention is not limited to this, and a structure in which only one reflector 4 is provided may be used. . In the present embodiment, the case where the sound wave to be silenced has a single frequency has been described. However, when the sound wave has a plurality of frequencies, the reflector 4 is spaced at intervals L obtained for each of the plurality of frequencies. May be installed in the secondary flow path.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The silencer 5 according to the present embodiment is different from the first embodiment in that the interval between the reflecting plates 4 disposed in the sub-flow paths 2a and 2b is not uniform, that is, not constant. As shown in FIG. 5, the reflecting plate 4 disposed on the inner wall of the pipe 5a facing the sub-flow channel 2a is gradually spaced from the left side (point A) in the figure toward the right side (point B) in the figure. Is arranged to be large. Further, the reflecting plate 4 disposed on the inner wall of the pipe 5a facing the sub flow path 2b is disposed so that the interval gradually decreases from the point A toward the point B. By making the arrangement interval of the reflectors 4 constant, irregular sound pressure distribution is generated in each sub-flow channel, so that the frequency bandwidth that exhibits sufficient sound absorption performance can be expanded.

  As described above, the silencer 5 according to the present embodiment has the effect of being able to absorb broadband sound waves in addition to the effects of the first embodiment.

  In order to confirm the effect of the silencer 1 according to the first embodiment, the following test was performed. That is, noise of various frequencies is put on the gas flowing from the left side (point A) in the drawing to the right side (point B) in the silencer 1 shown in FIG. The difference from the noise level at point B was measured. FIG. 2 is a graph showing the noise frequency (unit: Hz) on the horizontal axis and the reduction amount of the noise amount at point A and the noise amount at point B on the vertical axis from the above test results. Moreover, the silencer 1 used in the present embodiment is arranged at intervals at which the reflector 4 absorbs noise having a frequency of 1300 Hz, the axial length of the pipe 1a is 1 m, and the thickness of the porous plate 3 is 1 mm. The through hole 3a has a hole diameter of 1 mm and an aperture ratio of 20%.

  In the vertical axis of FIG. 2, the sound absorption effect is improved as it goes upward (in the direction in which the reduction amount increases). Therefore, when no silencer 4 is provided in the silencer 1, the noise reduction amount is 0 dB, and no sound is absorbed. As can be seen from the figure, when the frequency of the noise of the gas flowing through the silencer 1 is about 1300 Hz, the noise of about 20 dB can be reduced.

  Next, in order to confirm the effect of the silencer 5 according to the second embodiment, the same test as in Example 1 was performed. In the silencer 5, the interval between the reflecting plates 4 arranged in the sub-channel 2a is 90, 110 mm, the interval between the reflecting plates 4 arranged in the sub-channel 2b is 50, 70 mm, and the others are the same as in the first embodiment. Is set to FIG. 6 shows a test result curve 61 of the silencer 5 used in the present embodiment and a test result curve 62 of the silencer 1 used in the first embodiment. The curve 62 shows that the amount of noise reduction gradually decreases from around the frequency of 1300 Hz, and the sound absorbing effect disappears near the frequency of 1500 Hz, whereas the curve 61 has a sound absorbing effect in a wide band. Can be read.

  The present invention can be applied not only to the above-described apparatus but also to a construction machine or a press machine using hydraulic pressure, a pipe portion where a liquid such as a pump circulates, or the like.

(A) It is side surface perspective drawing of the silencer concerning the 1st Embodiment of the present invention. (B) It is a front view of the silencer concerning a 1st embodiment of the present invention. (C) It is an enlarged view of the through-hole in Fig.1 (a). It is a graph which shows the test result done using the silencer as described in Drawing 1 (a). It is a figure which shows the modification of the 1st Embodiment of this invention. It is a figure which shows another modification of the 1st Embodiment of this invention. It is side surface perspective drawing of the silencer which concerns on the 2nd Embodiment of this invention. It is a graph which shows the test result performed using the silencer of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silencer 2 Channel 2a, 2b Subchannel 3 Perforated plate 3a Through hole 4 Reflector

Claims (5)

Piping that forms a flow path for fluid containing sound waves;
A partition member extending in the axial direction of the pipe and partitioning the flow path so as to form a sub-flow path;
A through hole provided in the partition member through which the fluid passes;
A reflection provided in the sub-flow path that reflects a part of the propagating sound wave so that a sound pressure difference between the sound waves occurs on the front and back sides of the through hole and makes the sound pressure distribution non-uniform in the cross-sectional direction of the pipe. And a silencer. The reflective member is
The silencer according to claim 1, wherein the silencer is disposed on the partition member and / or the pipe. Piping that forms a flow path for fluid containing sound waves;
A partition member extending in the axial direction of the pipe and partitioning the flow path so as to form a sub-flow path;
A through hole provided in the partition member through which the fluid passes;
A silencer, comprising: a reflection member that is provided in the pipe and / or the partition member and reflects a part of a sound wave propagating through the sub-flow channel.   Two or more reflective members are provided in each of the two or more secondary flow paths, and the interval between the reflective members arranged in the same secondary flow path in the axial direction is different for each secondary flow path. The silencer according to any one of claims 1 to 3, wherein the silencer is different.   The silencer according to any one of claims 1 to 4, wherein intervals in the axial direction of the reflection members arranged in the same sub-flow path are non-uniform.

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