Plate-shaped elastic body type silencer

Abstract

To provide a silencer that is easy to manufacture and easily adjusted according to a frequency.SOLUTION: In the present invention relating to a silencer 1 fitted to a main pipe 2 in which a fluid flows, a plate-like elastic body 3 provided, at a plate-like base part 4, with a plurality of first ribs 5 extending in a first direction and a second rib 6 extending between adjacent first ribs 5 in a second direction orthogonal to the first direction is inserted into the main pipe 2 with the first ribs 5 and the second rib 6 out and also with the first ribs 5 bent cylindrically to an axial direction. The first ribs 5 and the second rib 6 are in contact with an inner surface of the main pipe 2 because of elasticity of the plate-like elastic body 3. Silencing spaces (side branch chambers) 7a and 7b surrounded with the first ribs 5 and the second rib 6 are formed between the inner surface of the main pipe 2 and the plate-like base part 4 of the plate-like elastic body 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention is directed to a device for inserting into a refrigerant pipe, an exhaust pipe, etc. of an air conditioning system for a vehicle. Plate-shaped elastic body type Regarding silencers. [Background technology]

[0002] In automotive air conditioners, mechanical noise from the compressor and noise caused by refrigerant cavitation are transmitted through the piping to the evaporator and then to the driver through the air outlet, or they are transmitted along the piping through the engine compartment and then to the driver via the vehicle body. For this reason, muffler-type silencers or insert-type silencers are installed in the piping of automotive air conditioners. Muffler-type silencers are large and heavy, and brazing them increases costs, so insert-type silencers have become more common in recent years.

[0003] For example, Patent Document 1 describes a device in which spiral fins are provided on the outer surface of an inner tube. In this device, a phase difference occurs due to the difference in the length of the inner and outer flow passages, which causes sound interference and produces a noise reduction effect, but it is difficult to adjust the flow passage length.

[0004] Patent Document 2 describes a silencer that is inserted into a tubular main body, with a resonator chamber provided between the silencer and the main body, and a flow path in the main body connected to the resonator chamber via a connecting channel. Patent Document 3 also describes a sound-absorbing device in which an outer member surrounding an inner member is a bellows, a cavity is formed between the inner and outer members, and an opening of the inner member is open to the cavity. Both of these are resonance types, and the resonance frequency is determined by the shape of the resonator, making it difficult to adjust according to the frequency of the sound source. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Publication EP2138750A1 [Patent Document 2] Patent No. 5785173 specification [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-84693 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned problems of the conventional art, and an object of the present invention is to provide a silencer that is easy to manufacture and can be easily adjusted according to frequency. [Means for solving the problem]

[0007] As a means for solving the above problems, the present invention provides: (1) A silencer attached to a main pipe through which a fluid flows, a plate-like elastic body having a plate-like base portion provided with a plurality of first ribs extending in a first direction and second ribs extending between adjacent first ribs in a second direction perpendicular to the first direction, the plate-like elastic body being inserted into the main pipe with the first ribs and the second ribs facing outward and the first ribs bent in a cylindrical shape in the axial direction; The elasticity of the plate-shaped elastic body causes the first rib and the second rib to come into close contact with the inner surface of the main pipe, A sound-absorbing space surrounded by the first rib and the second rib is formed between the inner surface of the main pipe and the plate-shaped base of the plate-shaped elastic body.

[0008] In this type of silencer, fluid enters the inside of the cylindrical, bent elastic plate from the upstream side of the main pipe, passes through the inside of the elastic plate, and flows out to the downstream side of the main pipe. Sound waves that enter the silencing space surrounded by the main pipe and the plate-like base of the elastic plate are silenced in the silencing space. Due to this feature, the silencer can be easily manufactured by simply bending a plate-shaped elastic body, which has first and second ribs already provided, into a cylindrical shape and inserting it into the main pipe, as the first and second ribs of the plate-shaped elastic body will adhere closely to the inner surface of the main pipe.

[0009] (2) The silencing space is preferably a side branch chamber having an inlet and outlet opening at the axial end edge of the plate-like base. (3) The axial end edge of the plate-shaped elastic body is closed by a third rib, The silencing space is preferably a side branch chamber having an entrance and exit formed in the plate-like base near the second rib or the third rib. (4) Two of the second ribs are provided opposite each other between the adjacent first ribs, The silencing space is preferably a resonance chamber surrounded by the adjacent first rib and the two second ribs and having an opening in the plate-like base. (5) The axial end edge of the plate-shaped elastic body is closed by a third rib, The silencing space is preferably a resonance chamber surrounded by the adjacent first rib, second rib, and third rib and having an opening in the plate-like base. In this way, by adding the second rib and / or the third rib and forming an entrance or an opening in the plate-like base, it is possible to form a side branch chamber or a resonating chamber. Also, by changing the position of the second rib according to the frequency of the noise, it is possible to adjust the length of the side branch and also the volume of the resonating chamber.

[0010] (6) The second rib is characterized in that the thickness of the tip side is thinner than the thickness of the base side. (7) The second rib has a smaller elastic modulus than the plate-like base and the first rib. Due to these characteristics, when the plate-shaped elastic body is bent into a cylindrical shape, the second rib can easily stretch in the circumferential direction, reducing resistance and enabling the body to be bent correctly into a cylindrical shape.

[0011] (8) The tip end surface of the second rib is curved convexly with respect to a plane formed by the tip end of the first rib before the plate-like elastic body is bent. Due to this feature, even if the second rib stretches circumferentially when the plate-shaped elastic body is bent into a cylindrical shape, no gap is created between the tip of the second rib and the inner surface of the main pipe, ensuring the airtightness of the sound-absorbing space.

[0012] (9) The plate-shaped elastic body is characterized in that both ends in the second direction are bent in advance so as to fit along the inner surface of the main pipe. Due to this feature, when the plate-shaped elastic body is bent into a cylindrical shape, both ends in the second direction are in close contact with the inner surface of the main pipe, so no gaps are created between both ends in the second direction of the plate-shaped elastic body and the inner surface of the main pipe, ensuring the airtightness of the sound-absorbing space.

[0013] (10) The present invention is characterized in that a biasing member is provided inside the plate-shaped elastic body to press the plate-shaped elastic body against the main pipe. Due to this feature, the plate-shaped elastic body is pressed against the main pipe from the inside by the biasing member, so that no gaps are created between the tips of the first and second ribs and the inner surface of the main pipe, thereby ensuring better airtightness of the sound-absorbing space. [Effects of the Invention]

[0014] According to the invention of claim 1, the silencer can be easily manufactured by simply bending a plate-shaped elastic body, which has first and second ribs already provided, into a cylindrical shape and inserting it into the main pipe, so that the first and second ribs of the plate-shaped elastic body come into close contact with the inner surface of the main pipe.

[0015] According to the inventions of claims 2 to 5, by adding the second rib and / or the third rib and forming an entrance or an opening in the plate-like base, it is possible to form a side branch chamber or a resonating chamber. Also, by changing the position of the second rib according to the frequency of the noise, it is possible to adjust the length of the side branch and also the volume of the resonating chamber.

[0016] According to the inventions of claims 6 and 7, when the plate-shaped elastic body is bent into a cylindrical shape, the second rib is easily stretched in the circumferential direction, reducing resistance and enabling the plate-shaped elastic body to be bent correctly into a cylindrical shape.

[0017] According to the invention of claim 8, even if the second rib stretches circumferentially when the plate-shaped elastic body is bent into a cylindrical shape, no gap is created between the tip of the second rib and the inner surface of the main pipe, ensuring the airtightness of the sound-absorbing space.

[0018] According to the invention of claim 9, when the plate-shaped elastic body is bent into a cylindrical shape, both ends in the second direction are in close contact with the inner surface of the main pipe, so no gaps are created between both ends in the second direction of the plate-shaped elastic body and the inner surface of the main pipe, ensuring the airtightness of the sound-absorbing space.

[0019] According to the invention of claim 10, the plate-shaped elastic body bent into a cylindrical shape is pressed against the main pipe by the biasing member from the inside of the plate-shaped elastic body, so that no gaps are created between the tips of the first and second ribs and the inner surface of the main pipe, thereby ensuring better airtightness of the sound-absorbing space. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a partially cutaway perspective view of a side branch type silencer according to a first embodiment of the present invention. [Figure 2] 2A and 2B are perspective views of the plate-shaped elastic body of the noise absorbing device of FIG. 1 before and after bending, respectively. [Figure 3] FIG. 2 is a cross-sectional view of the silencer of FIG. 1. [Figure 4] FIG. 2 is a longitudinal cross-sectional view of the silencer of FIG. 1. [Figure 5] 1. FIG. 4 is an enlarged cross-sectional view showing a first modified example of the second rib of the silencer of FIG. [Figure 6] 1. FIG. 4 is an enlarged cross-sectional view showing a second modified example of the second rib of the silencer of FIG. [Figure 7] 1. FIG. 4 is an enlarged cross-sectional view showing a third modified example of the second rib of the silencer of FIG. [Figure 8] 1. FIG. 4 is a diagram showing a modified example of the silencing space of the silencing device of FIG. [Figure 9] 1. FIG. 4 is a diagram showing a modified example of the plate-shaped elastic body of the noise suppressor of FIG. [Figure 10] FIG. 5 is a partially cutaway perspective view of a side branch type silencer according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0022] First Embodiment FIG. 1 shows a silencer 1 according to a first embodiment of the present invention. The silencer 1 is provided in a pipe through which a refrigerant of a vehicle air conditioner flows. Specifically, the silencer is attached to a pipe (hereinafter referred to as a "main pipe") 2 on the outlet side of an evaporator or compressor in a vehicle air conditioner that includes a compressor, a condenser, an expansion valve, and an evaporator (not shown). The main pipe 2 is formed of a material that has elasticity and flexibility, such as rubber or synthetic resin, but is not limited to these, and an inflexible material such as aluminum may also be used. A fluid (hereinafter referred to as a "refrigerant") flows through the main pipe 2 from the upstream side on the left side to the downstream side on the right side in FIG. 1.

[0023] The main pipe 2 is designed to have a silencer 1 attached to the inside.

[0024] 2(a), the noise suppressor 1 is made of a rectangular elastic plate 3 made of rubber such as IIR or synthetic resin such as PA6, and has elasticity that tends to return to its original shape when bent. The elastic plate 3 has a plate-like base 4, a first rib 5, and a second rib 6, and is integrally molded by injection molding or the like.

[0025] The plate-shaped base 4 has a rectangular shape with short sides 4a and long sides 4b. The short sides 4a define the axial length of the silencer 1, and the long sides 4b are shorter than the inner circumferential length of the main pipe 2. The direction of the short sides 4a of the plate-shaped base 4 is called the first direction, and the direction of the long sides 4b is called the second direction. When the plate-shaped base 4 is bent into a cylindrical shape, the short sides 4a are in the axial direction, and the long sides 4b are in the circumferential direction. The thickness of the plate-shaped base 4 is arbitrary, but as long as it does not deform due to the influence of the fluid, a thickness of 2 to 3 mm is preferred for soft materials such as rubber, and a thickness of 1 to 2 mm is preferred for hard materials such as synthetic resin.

[0026] The first ribs 5 extend in a first direction parallel to the short sides 4a of the plate-like base 4 and reach both long sides 4b. A plurality of first ribs 5 are provided at predetermined intervals in a second direction parallel to the long sides 4b. The thickness of the first ribs 5 is also arbitrary, but since they are less susceptible to the influence of fluid, it is sufficient if they are equal to or less than the thickness of the plate-like base 4. For soft materials such as rubber, a thickness of 1 to 3 mm is preferred, and for hard materials such as synthetic resin, a thickness of 0.5 to 2 mm is preferred. The height of the first ribs 5 and the spacing between the first ribs 5 may be determined based on the desired cross-sectional area of ​​the silencing space, which will be described later.

[0027] The second ribs 6 are located between adjacent first ribs 5 and extend in the second direction of the plate-shaped base 4. The thickness of the second ribs 6 can also be arbitrary, but since they are easily affected by fluids, it is sufficient if they are equal to or greater than the thickness of the plate-shaped base 4. For soft materials such as rubber, a thickness of 2 to 4 mm is preferred, and for hard materials such as synthetic resin, a thickness of 1 to 3 mm is preferred. The height of the second ribs 6 is approximately the same as that of the first ribs 5. The position of the second ribs 6 in the first direction can be determined based on the desired length of the silencing space on both sides of the second rib 6.

[0028] As shown in Figure 2(b), the plate-shaped elastic body 3 is inserted into the main pipe 2 with the first rib 5 and the second rib 6 facing outward and the first rib 5 bent axially into a cylindrical shape. When the plate-shaped elastic body 3 is bent, the outer diameter of the plate-shaped elastic body 3, i.e., the outer diameter formed by the tips of the first rib 5 and the second rib 6, is made smaller than the inner diameter of the main pipe 2, and both ends of the plate-shaped elastic body 3 in the second direction are spaced apart without overlapping.

[0029] When the elastic plate 3 is inserted into the main pipe 2, the elasticity of the elastic plate 3 causes the first rib 5 and second rib 6 to adhere closely to the inner surface of the main pipe 2. As a result, side branch chambers 7a, 7b are formed as sound-absorbing spaces surrounded by the first rib 5 and second rib 6 between the inner surface of the main pipe 2 and the plate-like base 4 of the elastic plate 3. These side branch chambers 7a, 7b have a first inlet / outlet 8a and a second inlet / outlet 8b that open at the axial end edges of the plate-like base 4. The inside of the elastic plate 3 forms a main flow path 9 for the fluid flowing through the main pipe 2.

[0030] In this embodiment, a first side branch chamber 7a having a first inlet / outlet 8a opening at the upstream axial edge of the plate-shaped base 4 and a second side branch chamber 7b having a second inlet / outlet 8b opening at the downstream axial edge of the plate-shaped base 4 are formed on both axial sides of the second rib 6 of the plate-shaped elastic body 3, and further, a plurality of side branch chambers are similarly formed around the circumferential direction of the plate-shaped elastic body 3, but the positions of the respective second ribs 6 are different.

[0031] Next, the operation of the noise suppressor 1 of this embodiment will be described.

[0032] As shown in Fig. 4, the refrigerant flowing through the main pipe 2 flows from the upstream end of the elastic plate 3 into the main flow path 9 inside the plate-like base 4 of the elastic plate 3, passes through the inside of the elastic plate 3, and flows out from the downstream end of the elastic plate 3 into the main pipe 2. Sound generated from a sound source (not shown) on the upstream side of the silencer 1 (mechanical noise of the compressor and noise due to cavitation of the refrigerant) propagates downstream along with the refrigerant and enters the first side branch chamber 7a and the second side branch chamber 7b of the silencer 1 through the first inlet / outlet 8a and the second inlet / outlet 8b. Note that the sound source may be located on the downstream side, in which case the noise silencing effect will be achieved on the upstream side.

[0033] Sound waves that enter the first side branch chamber 7a from the first inlet / outlet 8a at the upstream end of the plate-shaped elastic body 3 are reflected by the second rib 6 of the side branch chamber 7a and return to the first inlet / outlet 8a, where they interfere with and are silenced in antiphase with the sound waves propagating through the plate-shaped elastic body 3. Similarly, sound waves that enter the second side branch chamber 7b from the second inlet / outlet 8b at the downstream end of the plate-shaped elastic body 3 are reflected by the second rib 6 of the side branch chamber 7b and return to the second inlet / outlet 8b, where they interfere with and are silenced in antiphase with the sound waves propagating through the plate-shaped elastic body 3.

[0034] Here, if the cross-sectional area of ​​the main pipe 2 is S, the cross-sectional area of ​​the side branch chambers 7a, 7b is Ss, the length of the side branch chambers 7a, 7b is l, the frequency of the sound wave is f, and the speed of sound is c, then the transmission loss TL through each of the side branch chambers 7a, 7b of the silencer 1 is expressed by Equation 1. The length l of the side branch chambers 7a, 7b is the distance from the inlets 8a, 8b to the second rib 6.

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[0035] In the silencer 1 of this embodiment, by changing the axial position of the second rib 6, the length la of the first side branch chamber 7a and the length lb of the second side branch chamber 7b can be adjusted, thereby increasing the noise reduction effect according to the frequency of the sound source.

[0036] 5-7 show modified examples of the second rib of the silencer of the first embodiment.

[0037] The second rib 6 shown in Fig. 5 is formed so that the thickness t1 on the tip side is thinner than the thickness t2 on the base side. The tip of the second rib 6 is pulled when the plate-shaped elastic body 3 is bent, and therefore provides resistance to bending. In this modified example, the thickness t1 on the tip side of the second rib 6 is thinner than the thickness t2 on the base side, so that when the plate-shaped elastic body 3 is bent into a cylindrical shape, the second rib 6 is more likely to stretch in the circumferential direction, reducing resistance and allowing the plate-shaped elastic body 3 to be bent correctly into a cylindrical shape.

[0038] The second rib 6 shown in Fig. 6 is made of a material having a lower elastic modulus than the plate-shaped base 4 and the first rib 5. For example, two-color molding is performed using a synthetic resin material for the plate-shaped base 4 and the first rib 5 and a rubber-based material for the second rib 6. As in this modification, the second rib 6 is made of a material having a lower elastic modulus than the first rib 5, so that when the plate-shaped elastic body 3 is bent into a cylindrical shape, the second rib 6 is more likely to stretch in the circumferential direction, reducing resistance and enabling the plate-shaped elastic body 3 to be bent correctly into a cylindrical shape.

[0039] The second rib 6 shown in Figure 7 is curved more convexly at the center than at both ends of the tip surface that contacts the first rib 5 with respect to the plane formed by the tip of the first rib 5 before the plate-shaped elastic body 3 is bent. In this modified example, the tip surface of the second rib 6 is convexly curved, so that even if the second rib 6 stretches circumferentially when the plate-shaped elastic body 3 is bent into a cylindrical shape, no gap is created between the tip of the second rib 6 and the inner surface of the main pipe 2, ensuring the airtightness of the sound-absorbing space.

[0040] In FIG. 8, both ends of the plate-shaped elastic body 3 in the second direction are formed with bent edge portions 3 a in advance so as to fit along the inner surface of the main pipe 2 . In this way, by having the edge bending portions 3a at both ends, when the plate-shaped elastic body 3 is bent into a cylindrical shape, both ends in the second direction are in close contact with the inner surface of the main pipe 2, so that no gaps are created between both ends in the second direction of the plate-shaped elastic body 3 and the inner surface of the main pipe 2, ensuring the airtightness of the sound-absorbing space.

[0041] FIG. 9 shows a modified example of the sound absorbing space formed by the plate-shaped elastic body 3. In FIG.

[0042] 9(a), the axial end edge of the plate-shaped elastic body 3 is closed by a third rib 10, a first port 11a and a second port 11b are formed in the plate-shaped base 4 near the third rib 10, and a first side branch chamber 12a and a second side branch chamber 12b are formed on both sides of the second rib 6. The first port 11a and the second port 11b may be formed near the second rib 6.

[0043] 9(b), two second ribs 6 are provided facing each other between adjacent first ribs 5, and a resonance chamber 14 having an opening 13 is formed in the plate-shaped base 4 and surrounded by the adjacent first ribs 5 and two second ribs 6. A first side branch chamber 7a and a second side branch chamber 7b are formed on both sides of the resonance chamber 14, similar to the first embodiment.

[0044] In the silencer 1 having the resonance chamber 14 formed therein, the refrigerant flowing inside the upstream main pipe 2 flows into the main flow path 9 of the elastic plate 3 at the upstream end of the elastic plate 3, passes through the elastic plate 3, and flows out from the downstream end of the elastic plate 3 into the main pipe 2. The energy of sound waves propagated from a sound source (not shown) on the upstream side of the silencer 1 and entered the elastic plate 3 is absorbed in the resonance chamber 14 through the opening 13, and the sound is silenced.

[0045] Here, when the volume of the resonance chamber 14 is V, the cross-sectional area of ​​the opening 13 is Sr, the length of the opening 13 is l, and the sound speed is c, the resonance frequency ωr is expressed by Equation 2.

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[0046] In the plate-shaped elastic body 3 shown in Figure 9(c), the axial end edge of the plate-shaped elastic body 3 is blocked by the third rib 10, and a first resonance chamber 16a is formed which is surrounded by the adjacent first rib 5, second rib 6, and third rib 10 and has a first opening 15a in the plate-shaped base 4, and a second resonance chamber 16b is formed which is surrounded by the adjacent first rib 5, second rib 6, and third rib 10 and has a second opening 15b in the plate-shaped base 4.

[0047] Thus, the second rib 6 Change the position of And / or third rib 10 is added to form entrances 11a, 11b and openings 13, 15a, 15b in plate-like base 4, thereby forming side branch chambers 12a, 12b, resonance chambers 14, 16a, 16b, or a sound-absorbing space that is a combination of these. Also, by changing the position of second rib 6 according to the noise frequency, the length of the side branch can be adjusted, and the volume of the resonance chamber can also be adjusted.

[0048] Second Embodiment 10 shows a noise suppressor 1A according to a second embodiment of the present invention. Like the noise suppressor 1 of the first embodiment, the noise suppressor 1A has a plate-shaped elastic body 3 inserted into a main pipe 2, but also has a biasing member 17 attached to the inside of the plate-shaped elastic body 3.

[0049] The biasing member 17 has a rectangular shape that is smaller than the elastic plate 3, is made of metal or resin, and has elasticity that causes it to return to its original shape when bent. Like the elastic plate 3, the biasing member 17 is bent into a cylindrical shape and inserted inside the elastic plate 3 attached to the main pipe 2. The elasticity of the biasing member 17 causes it to expand radially, pressing the elastic plate 3 toward the main pipe 2. This prevents gaps from forming between the tips of the first rib 5 and second rib 6 of the elastic plate 3 and the inner surface of the main pipe 2, ensuring a tight seal of the silencing space. [Explanation of symbols]

[0050] 1,1A…silencer 2…Supervisor 3...Elastic plate 3a...Edge bend 4...Plate-shaped base 5...First rib 6...Second rib 7a...First side branch chamber 7b...Second side branch chamber 8a…1st entrance / exit 8b…Second entrance / exit 9…Main flow path 10...Third rib 11a…1st entrance / exit 11b…Second entrance / exit 12a...First side branch chamber 12b...Second side branch chamber 13...Aperture 14...Resonating chamber 15a...1st opening 15b…Second opening 16a...First resonating chamber 16b...Second resonant chamber 17... Urging member

Claims

1. A silencer attached to a main pipe through which a fluid flows, a plate-like elastic body having a plate-like base portion provided with a plurality of first ribs extending in a first direction and second ribs extending between adjacent first ribs in a second direction perpendicular to the first direction, the plate-like elastic body being inserted into the main pipe with the first ribs and the second ribs facing outward and the first ribs bent in a cylindrical shape in the axial direction; the first rib and the second rib are brought into close contact with the inner surface of the main pipe by the elasticity of the plate-shaped elastic body; a sound-absorbing space surrounded by the first rib and the second rib is formed between the inner surface of the main pipe and the plate-shaped base of the plate-shaped elastic body, A noise suppressor, wherein the second rib has a modulus of elasticity smaller than those of the plate-like base and the first rib.

2. A silencer attached to a main pipe through which a fluid flows, a plate-like elastic body having a plate-like base portion provided with a plurality of first ribs extending in a first direction and second ribs extending between adjacent first ribs in a second direction perpendicular to the first direction, the plate-like elastic body being inserted into the main pipe with the first ribs and the second ribs facing outward and the first ribs bent in a cylindrical shape in the axial direction; the first rib and the second rib are brought into close contact with the inner surface of the main pipe by the elasticity of the plate-shaped elastic body; a sound-absorbing space surrounded by the first rib and the second rib is formed between the inner surface of the main pipe and the plate-shaped base of the plate-shaped elastic body, A noise suppressor characterized in that the tip surface of the second rib is curved convexly with respect to a plane formed by the tip of the first rib before the plate-shaped elastic body is bent.

3. A silencer attached to a main pipe through which a fluid flows, a plate-like elastic body having a plate-like base portion provided with a plurality of first ribs extending in a first direction and second ribs extending between adjacent first ribs in a second direction perpendicular to the first direction, the plate-like elastic body being inserted into the main pipe with the first ribs and the second ribs facing outward and the first ribs bent in a cylindrical shape in the axial direction; the first rib and the second rib are brought into close contact with the inner surface of the main pipe by the elasticity of the plate-shaped elastic body; a sound-absorbing space surrounded by the first rib and the second rib is formed between the inner surface of the main pipe and the plate-shaped base of the plate-shaped elastic body, A silencer characterized in that both end portions of the plate-shaped elastic body in the second direction are bent in advance so as to fit along the inner surface of the main pipe.

4. 4. The noise suppressor according to claim 1, wherein the silencing space is a side branch chamber having an inlet and outlet opening at an axial end edge of the plate-like base.

5. an axial end edge of the plate-shaped elastic body is closed by a third rib; 4. The noise reduction device according to claim 1, wherein the silencing space is a side branch chamber having an entrance and exit formed in the plate-like base near the second rib or the third rib.

6. Two of the second ribs are provided opposite each other between the adjacent first ribs, 4. The noise suppressor according to claim 1, wherein the silencing space is a resonance chamber surrounded by the adjacent first rib and the two adjacent second ribs and has an opening in the plate-like base.

7. an axial end edge of the plate-shaped elastic body is closed by a third rib; 4. The noise reduction device according to claim 1, wherein the silencing space is a resonance chamber surrounded by the adjacent first rib, the adjacent second rib, and the adjacent third rib, and has an opening in the plate-like base.

8. 8. The silencer according to claim 1, wherein the second rib has a thickness on a tip side that is thinner than a thickness on a base side.

9. 9. A silencer according to claim 1, wherein a biasing member is provided inside the plate-shaped elastic body to press the plate-shaped elastic body against the main pipe.

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