Ventilation-type silencer

Abstract

Provided is a ventilation-type silencer using a porous sound absorbing material, the silencer having excellent sound deadening performance in a low frequency range. A ventilation-type silencer having an inlet-side vent pipe, an expansion section communicating with the inlet-side vent pipe and having a larger cross-sectional area than the inlet-side vent pipe, and an outlet-side vent pipe communicating with the expansion section and having a smaller cross-sectional area than the expansion section. The ventilation-type silencer further has: a porous sound absorbing material arranged in at least a part of the expansion section; a back space, of the porous sound absorbing material, which is the space in the expansion section opposite from a flow path connecting the inlet-side vent pipe and the outlet-side vent pipe; and a partition member that partitions the back space. The region partitioned by the partition member constitutes an acoustic resonator, and the acoustic resonator is acoustically coupled to the flow path.

Description

Ventilation type silencer

[0001] The present invention relates to a ventilation type silencer.

[0002] In a vent pipe that transports gas, a ventilation type silencer that is installed in the middle of the vent pipe and has an expanded section with a cross-sectional area larger than that of the vent pipe is known as a silencer that silences noise from a gas supply source or the like along the vent pipe. Also, in order to further improve the sound absorbing performance, a porous sound absorbing material is sometimes placed inside the expanded section. In a ventilation type silencer, the porous sound absorbing material is placed along the flow path so as to provide a space in the center that serves as a ventilation path.

[0003] The sound absorption performance of porous sound-absorbing materials depends on their volume, so in order to increase sound absorption performance, it is necessary to use a large amount of porous sound-absorbing material. However, if there is a large amount of porous sound-absorbing material, problems such as mold growth due to the water seeping deep into the material and preventing it from drying, the material becoming more flammable, increased costs due to material costs and the labor required for packing, and ultimately increased waste can occur. For this reason, efforts are being made to increase sound absorption performance using a small amount of porous sound-absorbing material.

[0004] For example, Patent Document 1 describes a crank box-type sound-absorbing and ventilation structure that is provided to communicate between a decorative panel and a wall that separates two spaces, the sound-absorbing and ventilation structure having a hollow sound-absorbing container arranged in the space between the decorative panel and the wall, at least two open pipe sections connected to two opposing side surfaces of the sound-absorbing container and each communicating with a space within the sound-absorbing container, sound-absorbing material provided inside the sound-absorbing container, and a covering material that covers part of the surface of the sound-absorbing material, the open pipe section on one side surface of the sound-absorbing container being arranged to communicate with the decorative panel, and the open pipe section on the other side surface of the sound-absorbing container being arranged to communicate with the wall, the open pipe section on one side surface and the open pipe section on the other side surface being arranged at different positions in the longitudinal direction of the sound-absorbing container, and the covering material exposing another part of the surface of the sound-absorbing material, configuring the exposed part as at least one contact surface that comes into contact with the space within the sound-absorbing container.

[0005] Japanese Patent Application Laid-Open No. 2019-132576

[0006] Patent document 1 describes that by covering a portion of the porous sound-absorbing material, the sound pressure at the contact surface with the ventilation channel can be increased and the particle velocity can be increased, thereby improving the sound absorption effect of the porous sound-absorbing material.

[0007] Another possible configuration for increasing the sound absorption effect with a small amount of porous sound-absorbing material is to provide a space (hereinafter referred to as a back space) on the side of the porous sound-absorbing material opposite the ventilation channel side (hereinafter also referred to as the back side). If the back side of the porous sound-absorbing material is in direct contact with the wall, sound waves that enter the porous sound-absorbing material from the ventilation channel will be reflected by the wall and return to the ventilation channel, which may prevent the sound absorption effect of the porous sound-absorbing material from being fully achieved. In contrast, by providing a back space on the back side of the porous sound-absorbing material, it is possible to prevent sound waves that enter the porous sound-absorbing material from the ventilation channel from being reflected and returning to the ventilation channel, thereby further increasing the sound absorption effect of the porous sound-absorbing material.

[0008] However, according to the investigations of the present inventors, it was found that when a back space is provided on the back side of the porous sound-absorbing material, there is a problem in that the sound-absorbing performance in the low frequency range is low.

[0009] The object of the present invention is to solve the problems of the above-mentioned conventional technology and to provide a ventilation type silencer that uses a porous sound-absorbing material and has high noise absorbing performance in the low frequency range.

[0010] To solve this problem, the present invention has the following configuration. [1] A ventilation silencer having an inlet-side vent pipe, an expansion section communicating with the inlet-side vent pipe and having a cross-sectional area larger than that of the inlet-side vent pipe, and an outlet-side vent pipe communicating with the expansion section and having a cross-sectional area smaller than that of the expansion section, the ventilation silencer comprising: a porous sound-absorbing material disposed in at least a part of the expansion section; a back space within the expansion section on the side of the porous sound-absorbing material opposite to a flow path connecting the inlet-side vent pipe and the outlet-side vent pipe; and a partition member separating the back space, the area separated by the partition member forming an acoustic resonance section, and the acoustic resonance section acoustically connected to the flow path. [2] The ventilation silencer according to [1], in which resonance in the acoustic resonance section is air column resonance. [3] The ventilation silencer according to [1], in which the partition member has a portion at an end on the porous sound-absorbing material side that protrudes toward the acoustic resonance section, and the resonance in the acoustic resonance section is Helmholtz resonance. [4] The ventilation type silencer according to any one of [1] to [3], wherein the partition member is not bonded to at least one of the two walls of the extension section that surround the acoustic resonance section and face each other. [5] The ventilation type silencer according to [4], wherein the distance between the partition member and the wall to which the partition member is not bonded is 5 mm or less. [6] The ventilation type silencer according to any one of [1] to [5], wherein the partition member is in contact with a porous sound-absorbing material. [7] The ventilation type silencer according to any one of [1] to [6], wherein at least one surface of the extension section is a flat surface. [8] The ventilation type silencer according to [7], wherein the lowest natural frequency of the flat surface section after construction including the partition member is 2000 Hz or less. [9] The ventilation type silencer according to any one of [1] to [8], wherein the partition member is formed integrally with the extension section.

[10] The ventilation type silencer according to [9], wherein the thickness of the partition member is constant or monotonically decreasing in at least one direction from the position where the partition member is joined to the wall of the expansion section to the direction away from the wall.

[11] The ventilation type silencer according to any of [1] to

[10] , wherein all sides of the partition member are straight lines.

[12] The ventilation type silencer according to any of [1] to

[11] , wherein at least one of the connecting part with the inlet side ventilation pipe and the connecting part with the outlet side ventilation pipe of the expansion section has an opening structure whose cross-sectional area gradually increases from the connecting part toward the inside of the expansion section.

[0011] According to the present invention, it is possible to provide a ventilation type silencer that uses a porous sound-absorbing material and has high noise absorbing performance in the low frequency range.

[0012] 11. A cross-sectional view conceptually showing one example of a ventilation type silencer of the present invention. A cross-sectional view taken along line B-B in FIG. 1. A cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. A perspective view of an opening structure possessed by the ventilation type silencer shown in FIG. 1. A perspective view conceptually showing another example of the opening structure. A perspective view conceptually showing another example of the opening structure. A cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. A cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. A cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. A cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. A cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. A cross-sectional view conceptually showing a ventilation type silencer of a comparative example. A cross-sectional view taken along line CC in FIG. 11. A graph showing the relationship between frequency and transmission loss. A graph showing the relationship between frequency and transmission loss. A graph showing the relationship between frequency and transmission loss. A cross-sectional view conceptually showing a ventilation type silencer of a comparative example. A graph showing the relationship between frequency and transmission loss. A graph showing the relationship between frequency and transmission loss.

[0013] The ventilation silencer of the present invention will be described in detail below. The following description of the components will be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, "perpendicular" and "parallel" are intended to include the range of error generally accepted in the technical field to which the present invention pertains. For example, "perpendicular" and "parallel" mean a range of less than ±10° from strict perpendicular or parallel, and the error from strict perpendicular or parallel is preferably 5° or less, and more preferably 3° or less. In this specification, terms such as "same" and "identical" are intended to include the range of error generally accepted in the technical field.

[0014] [Ventilation type silencer] The ventilation type silencer of the present invention is a ventilation type silencer having an inlet side ventilation pipe, an expansion section that communicates with the inlet side ventilation pipe and has a larger cross-sectional area than the inlet side ventilation pipe, and an outlet side ventilation pipe that communicates with the expansion section and has a smaller cross-sectional area than the expansion section, and the ventilation type silencer has a porous sound-absorbing material arranged in at least a part of the expansion section, a back space that is a space within the expansion section on the opposite side of the porous sound-absorbing material to the flow path that connects the inlet side ventilation pipe and the outlet side ventilation pipe, and a partition member that separates the back space, wherein the area separated by the partition member constitutes an acoustic resonance section, and the acoustic resonance section is acoustically connected to the flow path.

[0015] The configuration of the ventilation type silencer of the present invention will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing an example of an embodiment of the ventilation type silencer of the present invention. Fig. 2 is a cross-sectional view taken along line B-B of Fig. 1.

[0016] The ventilation type silencer 10 shown in FIG. 1 has a cylindrical inlet side ventilation pipe 12, an expansion section 14 connected to one open end face of the inlet side ventilation pipe 12, a cylindrical outlet side ventilation pipe 16 connected to the end face of the expansion section 14 opposite the inlet side ventilation pipe 12, a porous sound-absorbing material 30 arranged in a partial area within the expansion section 14, a back space 14a on the opposite side of the ventilation pipe, which is a space in which the porous sound-absorbing material 30 of the expansion section 14 is not arranged, and a partition member 34 that separates the back space 14a.

[0017] 1 has a first opening structure 20 disposed at a connection portion with the inlet-side ventilation pipe 12 in the expansion portion 14, and a second opening structure 24 disposed at a connection portion with the outlet-side ventilation pipe 16 in the expansion portion 14. Hereinafter, the first opening structure 20 and the second opening structure 24 will also be collectively referred to as the opening structure.

[0018] The inlet vent pipe 12 is a cylindrical member that transports gas flowing in from one open end face to the expansion section 14 connected to the other open end face.

[0019] The outlet vent pipe 16 is a cylindrical member that transports gas flowing in from one open end surface connected to the expansion section 14 to the other open end surface.

[0020] The cross-sectional shape of the inlet vent pipe 12 and the outlet vent pipe 16 (hereinafter collectively referred to as the vent pipes) may be various shapes, such as circular, rectangular, triangular, etc. Furthermore, the cross-sectional shape of the vent pipe does not have to be constant in the axial direction of the central axis of the vent pipe. For example, the diameter of the vent pipe may vary in the axial direction.

[0021] The inlet vent pipe 12 and the outlet vent pipe 16 may have the same cross-sectional shape and cross-sectional area, or may have different shapes and / or cross-sectional areas. In the example shown in Fig. 1, the inlet vent pipe 12 and the outlet vent pipe 16 are arranged so that their central axes coincide, but this is not limiting. As shown in Fig. 8, which will be described later, the central axes of the inlet vent pipe 12 and the outlet vent pipe 16 may be misaligned.

[0022] The sizes (cross-sectional area, etc.) of the inlet side ventilation pipe 12 and the outlet side ventilation pipe 16 may be set appropriately depending on the size of the equipment in which the ventilation type silencer is used, the required ventilation performance, etc.

[0023] The expansion section 14 is disposed between the inlet ventilation pipe 12 and the outlet ventilation pipe 16 and transports the gas flowing in from the inlet ventilation pipe 12 to the outlet ventilation pipe 16 .

[0024] The cross-sectional area of ​​the expansion section 14 perpendicular to the flow path direction is larger than that of the inlet-side vent pipe 12 and also larger than that of the outlet-side vent pipe 16. That is, for example, if the cross-sectional shapes of the inlet-side vent pipe 12, the outlet-side vent pipe 16, and the expansion section 14 are circular, the diameter of the cross section of the expansion section 14 is larger than the diameters of the inlet-side vent pipe 12 and the outlet-side vent pipe 16.

[0025] The cross-sectional shape of the expansion section 14 may be various shapes such as circular, rectangular, triangular, etc. Furthermore, the cross-sectional shape of the expansion section 14 does not have to be constant in the axial direction of the central axis of the expansion section 14. For example, the diameter of the expansion section 14 may vary in the axial direction.

[0026] The size (length, cross-sectional area, etc.) of the extension portion 14 may be set appropriately depending on the size of the equipment in which the ventilation type silencer is used, the required noise reduction performance, etc.

[0027] 1 and 2, the expansion section 14 has a hollow rectangular parallelepiped shape, with the inlet vent pipe 12 connected to one of the two opposing faces with the smallest area, and the outlet vent pipe 16 connected to the other. Also, as shown in Fig. 2, each vent pipe is connected at a position offset from the center of the face to which it is connected. Specifically, in Fig. 2, the vent pipe is connected at a position close to the left face in the left-right direction and close to the lower face in the up-down direction.

[0028] A porous sound-absorbing material 30 is disposed inside the expansion portion 14. The porous sound-absorbing material 30 absorbs sound by converting the sound energy of sound waves passing through the inside into thermal energy.

[0029] 1, the porous sound-absorbing material 30 is arranged along the region that forms the flow path connecting the inlet-side vent pipe 12 and the outlet-side vent pipe 16 within the expansion section 14. In the illustrated example, as a preferred embodiment, the first opening structure 20 is provided at the connection portion with the inlet-side vent pipe 12 within the expansion section 14, and the second opening structure 24 is provided at the connection portion with the outlet-side vent pipe 16 within the expansion section 14, so that the region that linearly connects the end face of the first opening structure 20 on the outlet-side vent pipe 16 side and the end face of the second opening structure 24 on the inlet-side vent pipe 12 side forms a flow path, and the porous sound-absorbing material 30 is arranged to surround this flow path. More specifically, as shown in Fig. 2, the porous sound-absorbing material 30 is disposed in the entire area between the upper largest surface of the extension section 14 and the first opening structure 20 and the second opening structure 24, i.e., the flow path, in Fig. 2, the entire area between the right side surface of the extension section 14 and the first opening structure 20 and the second opening structure 24 (flow path) in Fig. 1, and in the area along the flow path on the first opening structure 20 and the second opening structure 24 side between the left side surface of the extension section 14 and the first opening structure 20 and the second opening structure 24 (flow path) in Fig. 1. As a result, the porous sound-absorbing material 30 is disposed so as not to block the ventilation pipe when viewed from the flow path direction. Therefore, the area surrounded by the porous sound-absorbing material 30 acts as a flow path (ventilation channel).

[0030] The porous sound-absorbing material 30 is not particularly limited, and conventionally known sound-absorbing materials can be used as appropriate. For example, foams, foam materials (urethane foam (e.g., "Calmflex F Series" by Inoac Corporation, urethane foam by Hikarisha, "MIF" by Tokai Rubber Industries, etc.), soft urethane foam, ceramic particle sintered material, phenol foam, melamine foam ("Basotect" by BASF (Japanese name: "Basotect"), polyamide foam, etc.), nonwoven fabric sound-absorbing materials (microfiber nonwoven fabric (e.g., "Thinsulate" by 3M, "Milife MF" by ENEOS Techno Material Corporation, "Micromat" by Taihei Felt Industry Co., Ltd., etc.), polyamide foam, etc.), etc. Various known sound-absorbing materials can be used, including polyester nonwoven fabrics (e.g., "White Q-on" by Tokyo Bouon Co., Ltd., "QonPET" by Bridgestone KBG Corporation, and "Synthfiber" by Toray Industries, Inc.), plastic nonwoven fabrics such as acrylic fiber nonwoven fabrics, natural fiber nonwoven fabrics such as wool and felt, metal nonwoven fabrics, glass nonwoven fabrics, cellulose nonwoven fabrics, and other materials containing minute air bubbles (glass wool, rock wool, nanofiber fiber sound-absorbing materials (silica nanofiber, acrylic nanofiber (e.g., "XAI" by Mitsubishi Chemical Corporation)). Alternatively, a sound-absorbing material having a two-layer structure consisting of a thin, high-density surface nonwoven fabric and a low-density back nonwoven fabric may be used.

[0031] The size and type of the porous sound-absorbing material may be appropriately determined depending on the silencing performance (silencing frequency, silencing volume), ventilation volume, etc. required for the ventilation type silencer.

[0032] A back space 14a, which is the space within the extension section 14, is formed on the side of the porous sound-absorbing material 30 opposite to the flow path (hereinafter also referred to as the back side). Specifically, in Fig. 1, the back space 14a, in which no porous sound-absorbing material 30 is arranged, is formed between the left surface of the extension section 14 and the first opening structure 20 and second opening structure 24 (flow path) on the side of the first opening structure 20 and second opening structure 24.

[0033] As mentioned above, if the back side of the porous sound-absorbing material is in direct contact with a wall, sound waves that enter the porous sound-absorbing material from the ventilation passage will be reflected by the wall and return to the passage, which may result in insufficient sound-absorbing effect from the porous sound-absorbing material. In contrast, by providing a back space 14a on the back side of the porous sound-absorbing material 30, sound waves that enter the porous sound-absorbing material 30 from the passage can be prevented from being reflected and returning to the passage, thereby enhancing the sound-deadening effect of the porous sound-absorbing material 30. Furthermore, because the sound-absorbing effect can be increased even with a reduced amount of porous sound-absorbing material 30, problems that arise when a large amount of porous sound-absorbing material is used, such as mold growth when wet with water, flammability, increased costs due to material costs, and increased waste, can be reduced.

[0034] In the present invention, a partition member 34 is disposed within the rear space 14a to separate the rear space 14a. In the illustrated example, the partition member 34 is a flat, plate-like member that separates the rear space 14a into two spaces in the flow path direction (the up-and-down direction in FIG. 1 ). The partition member 34 is disposed so that its largest surface is perpendicular to the largest surface of the expansion section 14 and is also perpendicular to the flow path direction. The partition member 34 is also disposed in a position such that the volumes of the two separated spaces are different.

[0035] One of the two spaces in the rear space 14a separated by the partition member 34 functions as an acoustic resonance portion 36. In the example shown in FIG. 1 , of the two spaces in the rear space 14a separated by the partition member 34, the upper space with the smaller volume functions as the acoustic resonance portion 36. As shown in the figure, the acoustic resonance portion 36 is open on the porous sound-absorbing material 30 side and is acoustically connected to the flow path via the porous sound-absorbing material 30. Note that, of the two spaces separated by the partition member, the space with the larger volume may function as an acoustic resonance portion, and the space with the smaller volume may function as the rear space.

[0036] For example, the acoustic resonator 36 acts as an air column resonator by generating standing waves in a space having an opening. The air column resonator can muffle sounds of a certain frequency by adjusting its resonant frequency to the frequency of the sound to be muffled.

[0037] As mentioned above, when a porous sound-absorbing material has a back space on the back side, there is a problem that the sound-absorbing performance is low in the low frequency range. Specifically, when a porous sound-absorbing material has a back space on the back side, it has been found that the transmission loss (sound absorption performance) decreases in a certain frequency band and in the low frequency range due to the influence of the back space.

[0038] In contrast, the ventilation type silencer 10 of the present invention has a partition member 34 that separates the back space 14a disposed within the back space 14a, and the area separated by the partition member 34 acts as an acoustic resonance portion 36. By adjusting the resonance frequency of the acoustic resonance portion 36 to the frequency of the sound to be silenced, i.e., the frequency at which transmission loss decreases due to the influence of the back space, it is possible to silence the sound of that frequency and improve the sound silencing performance.

[0039] In addition, since porous sound-absorbing material 30 is arranged between the partition member 34 (acoustic resonance section 36) and the flow path, the wind flowing through the flow path does not come into direct contact with the partition member 34 (opening of the acoustic resonance section 36), thereby suppressing pressure loss and the generation of wind noise.

[0040] In addition, although the frequency band of sound deadening by a resonator is generally narrow, since the porous sound-absorbing material 30 is arranged to cover the opening of the acoustic resonance unit 36, the frequency band of sound deadening by the acoustic resonance unit 36 ​​can be widened (broadened).

[0041] Furthermore, by providing a partition member 34 inside the expansion section 14 and bonding or integrating the partition member 34 with the housing (wall) of the expansion section 14, the strength of the expansion section 14, which has a large space, can be increased. As a result, even if the expansion section 14 is made of resin, sufficient strength can be ensured.

[0042] The thickness of the porous sound-absorbing material 30 in the direction perpendicular to the flow path direction may be appropriately set to a thickness that provides the desired sound-absorbing performance depending on the flow resistance, porosity, tortuousity, etc. of the porous sound-absorbing material 30. From the viewpoint of sound-absorbing performance, the thickness of the porous sound-absorbing material 30 in the direction perpendicular to the flow path direction is preferably 3 mm to 50 mm, more preferably 10 mm to 30 mm, and most preferably 9 mm to 20 mm.

[0043] From the viewpoint of sound-absorbing performance, the depth of the back space 14a in the direction perpendicular to the flow path direction is preferably 30 mm to 400 mm, and more preferably 50 mm to 200 mm. From the viewpoint of sound-absorbing performance, the depth of the back space 14a is preferably 2 to 20 times, and more preferably 3 to 10 times, the thickness of the porous sound-absorbing material 30.

[0044] Here, in the example shown in Figures 1 and 2, the partition member 34 is a flat plate-like member, but this is not limited to this, and it is sufficient if it can form an acoustic resonance section 36 that has a sound-deadening effect in a desired frequency band.For example, it may have a shape that is at least partially curved, a shape that has a bent section, a zigzag shape, a complex maze-like shape, etc.

[0045] In the example shown in FIG. 1 , the resonance in the acoustic resonator 36 is air column resonance, but this is not limiting and the resonance in the acoustic resonator may be Helmholtz resonance. Helmholtz resonance is a structure in which the air in the internal space acts as a spring due to thermodynamic expansion and compression, and the air in the opening acts as a mass, causing mass-spring resonance and absorbing sound due to thermoviscous friction near the wall of the opening. Resonance can be generated even with various opening shapes, such as circular, rectangular, or slit-shaped. Furthermore, there may be multiple openings.

[0046] When the resonance in the acoustic resonator is Helmholtz resonance, as shown in the example of FIG. 3 , the partition member 34 preferably has a portion at the end closest to the porous sound-absorbing material 30 that protrudes toward the acoustic resonator 36b. The partition member 34 in the illustrated example has a plate-like member 34b, the width of which is the same as that of the plate-like member 34a in the direction perpendicular to the paper surface in FIG. 3 , standing on the acoustic resonator 36b side, at the end closest to the porous sound-absorbing material 30. The end face of the plate-like member 34b opposite the plate-like member 34a is not in contact with the wall of the extension section 14 (the upper wall in FIG. 3 ), and an opening is formed therein. In the example of FIG. 3 , the opening of the acoustic resonator 36b is narrowed by the plate-like member 34b, as compared to the example of FIG. 1 . By narrowing the opening of the acoustic resonator 36b in this way, the resonance in the acoustic resonator 36b can be Helmholtz resonance.

[0047] The resonant frequency of air column resonance depends on the length of the resonance tube, and lowering the frequency requires increasing the length of the resonance tube, resulting in an increase in size. On the other hand, the resonant frequency of Helmholtz resonance depends on the volume of the internal space and the area and length of the opening. Therefore, Helmholtz resonance is preferable because it allows the resonant frequency to be lowered without increasing the size by appropriately setting the volume of the internal space and the area and length of the opening.

[0048] The size (depth, width, volume, etc.) of the acoustic resonance section 36 formed by being partitioned by the partition member 34 and the size of the opening may be set appropriately depending on the size and shape of the expansion section 14, the type of resonance by the acoustic resonance section 36, the resonance frequency, etc. In other words, the partition member 34 may be positioned so that the size of the acoustic resonance section 36 and the size of the opening are the desired sizes.

[0049] The resonance frequency of the acoustic resonance portion is preferably 2000 Hz or less, more preferably 100 Hz to 1800 Hz, and even more preferably 200 Hz to 1500 Hz.

[0050] 1 and 3, in a preferred embodiment, the partition member 34 is in contact with the porous sound-absorbing material 30. This allows the partition member 34 to support the porous sound-absorbing material 30, so that the porous sound-absorbing material 30 can be maintained in an appropriate position even in a configuration having a back space 14a.

[0051] Furthermore, the ventilation type silencer of the present invention is preferably configured so that at least one of the walls constituting the extension portion 14 vibrates to silence the sound of the natural frequency of this vibration.

[0052] At least one of the walls constituting the extension section 14 vibrates, particularly at the natural frequency of the wall. By adjusting the natural frequency of the wall to the frequency of the sound to be silenced, the sound of that frequency can be silenced, improving sound-silencing performance.

[0053] The natural frequency of a wall can be adjusted by appropriately setting the thickness, hardness, size, fixing method, etc. The natural frequency can also be adjusted by attaching a weight to the wall.

[0054] The lowest natural frequency of the wall is preferably a low frequency of 2000 Hz or less, more preferably 100 Hz to 1500 Hz, and even more preferably 200 Hz to 1000 Hz, thereby improving the sound absorbing performance in the low frequency range that is difficult to drown out with the porous sound-absorbing material 30.

[0055] The vibrating wall is preferably the wall with the largest area among the walls constituting the extension section 14. This allows the silencing frequency due to the vibration of the wall to be lowered. In the example shown in Figures 1 and 2, it is preferable that the upper or lower wall in Figure 2 vibrates.

[0056] In addition, the vibrating wall is preferably a flat surface from the viewpoint of being easily vibrated. As mentioned above, the cross-sectional shape of the extension section 14 can be various shapes such as a circle, a rectangle, a triangle, etc., and the wall of the extension section 14 may be curved, but since curved walls are difficult to vibrate, it is preferable to have a flat wall.

[0057] Furthermore, from the viewpoint of not restricting the vibration of the wall and lowering the natural frequency, it is preferable that the partition member 34 is not adhered to at least one of the two walls of the expansion section 14 that surround and face the acoustic resonance section 36.

[0058] In the example shown in FIG. 2 , a gap 35 is provided between the upper wall and the partition member 34, and they are not bonded. In FIG. 2 , the upper wall is a wall that surrounds the acoustic resonance unit 36 ​​and faces a lower wall that also surrounds the acoustic resonance unit 36. This lower wall is bonded or integrally formed with the partition member 34. In the example shown in FIG. 2 , the upper and lower walls are the largest surfaces of the walls that make up the expansion section 14. Because the partition member 34 and the upper wall are not bonded, the vibration of the upper wall is not restricted, making it more likely to vibrate. Furthermore, the natural frequency of the upper wall can be lowered, and the vibration of this upper wall can muffle low-frequency sounds (sound at the natural frequency of the wall). Furthermore, as shown in the example, it is preferable that the surface with the largest area is not bonded.

[0059] The distance between the partition member 34 and the unbonded wall (the vertical width of the gap 35 in FIG. 2) is preferably 5 mm or less, and more preferably 1 mm to 3 mm. If the gap is small, sound will not pass easily due to thermoviscous acoustics (thermal friction caused by vibration). This allows acoustic resonance to be maintained. Therefore, 5 mm or less is desirable. On the other hand, if the gap is too small, there is a risk that the housing will collide with vibration and rattle, causing noise or damage. Therefore, 1 mm or more is preferable.

[0060] If the distance between the partition member 34 and the unbonded wall is not constant, the distance may be measured at five or more equally spaced points, and the average value may be within the above range.

[0061] The partition member 34 may also be bonded (integrated) to both of the two walls of the extension section 14 that face each other and surround the acoustic resonance section 36. In this case, it is preferable that the lowest natural frequency of the flat surface section (wall) after construction including the partition member is 2000 Hz or less.

[0062] 1 and 3 , the acoustic resonator 36 is preferably formed on one end of the expansion section 14 in the flow path direction, but this is not limiting. The acoustic resonator 36 may be formed at any position in the expansion section 14 in the flow path direction. In other words, the example shown in FIGS. 1 and 3 includes one partition member 34, and the acoustic resonator 36 is defined as a space formed by the partition member 34 and walls surrounding the expansion section 14 on four sides. However, this is not limiting. For example, in FIG. 1 , the expansion section 14 may include another partition member that is parallel to the partition member 34 but offset in the flow path direction, and the acoustic resonator 36 may be defined as a space formed by the two partition members and walls surrounding the expansion section 14 on three sides.

[0063] By configuring the acoustic resonance section 36 to be formed on one end side of the expansion section 14 in the flow path direction, it becomes less likely to restrict the vibration of the wall to which the partition member 34 is bonded or integrated, and the size of the surface that can actually vibrate can be increased, making it possible to lower the natural frequency of the wall.

[0064] The expansion section 14 may be formed, for example, by arranging multiple (six in the example shown in FIG. 1 ) plate materials in a box shape and joining adjacent plate materials together using adhesive, pressure-sensitive adhesive, solder, fusion, etc. Alternatively, the expansion section 14 may be divided into two pieces, and each piece may be produced by injection molding, a 3D printer, etc., and the pieces may be combined to form the expansion section 14. Furthermore, the partition member 34 and the wall of the expansion section 14 may be joined by adhesive, pressure-sensitive adhesive, solder, fusion, etc., or may be integrally formed. For example, when the pieces of the expansion section 14 are produced by injection molding, a 3D printer, etc., the partition member 34 may be integrated with the pieces of the expansion section 14, and the integrated pieces may be produced by injection molding, a 3D printer, etc.

[0065] For example, when integrating the extension section 14 and the partition member 34 of the ventilation type silencer 10 shown in Figures 1 and 2, in Figure 2, the plate material that will become the upper wall of the extension section 14 and the other part are divided into two pieces, and a fragment that integrates the part of the extension section 14 excluding the upper wall with the partition member 34 is produced by injection molding, a 3D printer, etc., and the plate material that will become the upper wall is joined to this fragment, thereby making it possible to produce the extension section 14 in which the partition member 34 is arranged.

[0066] When the partition member 34 and the expansion section 14 are integrated, it is preferable that the thickness of the partition member 34 is constant or monotonically decreasing in at least one direction from the position where the partition member 34 is joined to the wall of the expansion section 14 toward the direction away from the wall.

[0067] For example, in the example shown in Figure 2, when the portion of the expansion section 14 excluding the upper wall is formed integrally with the partition member 34, it is preferable that the thickness of the partition member 34 is constant or monotonically decreases in the direction away from the lower wall joined to the partition member 34, i.e., toward the upward direction in Figure 2.

[0068] This makes it possible and easy to remove the fragment from the mold when, for example, producing by injection molding a fragment in which the portion of the extension section 14 excluding the upper wall and the partition member 34 are integrated together. Also, for example, when producing by a 3D printer a fragment in which the portion of the extension section 14 excluding the upper wall and the partition member 34 are integrated together, it becomes easy to stack layers, making production easier.

[0069] Furthermore, from the viewpoint of facilitating production using injection molding or a 3D printer, it is preferable that at least one surface of the extension portion 14 be a flat surface.

[0070] Furthermore, from the viewpoint of facilitating production using injection molding or a 3D printer, it is preferable that all sides of the partition member 34 are straight lines.

[0071] In addition, the partition member 34 may be manufactured as a separate member from the expansion section 14 and glued to the wall of the expansion section 14, or a claw portion or groove, etc. may be provided on the wall of the expansion section 14 and the partition member 34 may be fitted into the claw portion or groove, etc.

[0072] Materials for forming the ventilation pipe, the extension portion, and the partition member include metal materials, resin materials, reinforced plastic materials, carbon fiber, etc. Metal materials include, for example, aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, nichrome molybdenum, and alloys thereof. Examples of resin materials include acrylic resin (PMMA), polymethyl methacrylate, polycarbonate, polyamide, polyarylate, polyetherimide, polyacetal, polyetheretherketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate (PET), polyimide, triacetyl cellulose (TAC), polypropylene (PP), polyethylene (PE), polystyrene (PS), ABS resin (acrylonitrile, butadiene, styrene copolymer synthetic resin), flame-retardant ABS resin, ASA resin (acrylonitrile, styrene, acrylate copolymer synthetic resin), PVC (polyvinyl chloride) resin, and PLA (polylactic acid) resin. Examples of reinforced plastic materials include carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP).

[0073] From the viewpoint of weight reduction and ease of molding, it is preferable to use a resin material as the material for forming the ventilation type silencer.

[0074] It is desirable that these materials have non-combustible, flame-retardant and self-extinguishing properties. It is also desirable that the entire ventilation type silencer has non-combustible, flame-retardant and self-extinguishing properties.

[0075] 1 and 2 has, as a preferred embodiment, an opening structure in which the cross-sectional area gradually increases from the connecting portion to the inlet side ventilation pipe 12 of the expansion portion 14 and the connecting portion to the outlet side ventilation pipe 16 toward the inside of the expansion portion 14. Fig. 4 shows a perspective view of the opening structure (20, 24).

[0076] The first opening structure 20 is positioned adjacent to the connection with the inlet side ventilation pipe 12 within the expansion section 14, and is a tapered cylindrical member whose opening area gradually expands from the inlet side ventilation pipe 12 side toward the outlet side ventilation pipe 16 side.

[0077] In the illustrated example, the shape and area of ​​the opening of the first opening structure 20 on the inlet-side vent pipe 12 side (hereinafter also referred to as the base end side) generally match the cross-sectional shape and cross-sectional area of ​​the inlet-side vent pipe 12. Furthermore, the shape and area of ​​the opening of the end face of the first opening structure 20 on the outlet-side vent pipe 16 side (hereinafter also referred to as the tip end side) generally match the cross-sectional shape and cross-sectional area of ​​the substantially rectangular flow path surrounded by the porous sound-absorbing material 30 and the wall of the extension section 14. In other words, the end face of the first opening structure 20 on the outlet-side vent pipe 16 side generally contacts the porous sound-absorbing material 30 and the wall of the extension section 14.

[0078] As shown in FIG. 4, the first opening structure 20 is a trumpet-shaped tubular member whose cross-sectional area gradually increases from the base end side toward the tip end side.

[0079] The second opening structure 24 is positioned adjacent to the connection with the outlet side ventilation pipe 16 within the expansion section 14, and is a tapered cylindrical member whose opening area gradually decreases from the inlet side ventilation pipe 12 side toward the outlet side ventilation pipe 16 side.

[0080] In the illustrated example, the shape and area of ​​the opening of the second opening structure 24 on the outlet-side vent pipe 16 side (hereinafter also referred to as the base end side) generally match the cross-sectional shape and cross-sectional area of ​​the outlet-side vent pipe 16. Furthermore, the shape and area of ​​the opening of the end face of the second opening structure 24 on the inlet-side vent pipe 12 side (hereinafter also referred to as the tip end side) generally match the cross-sectional shape and cross-sectional area of ​​the substantially rectangular flow path surrounded by the porous sound-absorbing material 30 and the wall of the extension section 14. In other words, the end face of the second opening structure 24 on the inlet-side vent pipe 12 side generally contacts the porous sound-absorbing material 30 and the wall of the extension section 14.

[0081] As shown in FIG. 4, the second opening structure 24 is a trumpet-shaped tubular member whose cross-sectional area gradually increases from the base end side toward the tip end side.

[0082] The ventilation type silencer 10 having the expansion section 14 can enhance the silencing effect by placing a horn-shaped member (opening structure) at the entrance and exit to the expansion section 14, whose cross-sectional area gradually expands toward the inside of the expansion section 14, thereby suppressing turbulence in the flow of air flowing into or being discharged from the expansion section 14.

[0083] 4, the first opening structure 20 and the second opening structure 24 are horn-shaped tubular members whose cross-sectional area gradually increases from the base end side to the tip end side, but this is not limited thereto. The shape of the opening structure is not particularly limited as long as it has a configuration in which the cross-sectional area gradually changes. Other examples of the first opening structure 20 and the second opening structure 24 will be described below.

[0084] The opening structure 20b shown in Fig. 5 has two curved plate-like members, and the width between the two plate-like members gradually increases from one end to the other. The opening structure 20b is open in the vertical direction in the figure, and may be configured to contact, for example, the wall of the extension section 14 or the porous sound-absorbing material 30. The opening structure may also be only one of the structures shown in Fig. 5. By configuring one side as a wall and one side as a curved plate-like member, an opening structure with a gradually changing cross-sectional area can be realized.

[0085] In this way, the opening structure may be configured such that the cross section at the end on the other vent pipe side is not blocked, i.e., the first opening structure may be configured such that the cross section at the end on the outlet vent pipe side is not blocked, and the second opening structure may be configured such that the cross section at the end on the inlet vent pipe side is not blocked.

[0086] 6 has a rectangular cross-sectional shape, and has a shape in which the cross-sectional area expands along the central axis while maintaining a similar shape. That is, the opening structure 20c has a truncated quadrangular pyramid shape and has an opening that penetrates from the upper base to the lower base.

[0087] Furthermore, the opening structure is not limited to a cross-sectional shape that expands as in the above-described examples. It may also be configured such that the thickness of the opening structure (20d, 24d) gradually decreases at the end, as in the ventilation silencer shown in FIG. 7 . That is, the first opening structure 20d has the same cross-sectional shape as the inlet-side vent pipe 12, and the thickness of the end on the outlet-side vent pipe 16 side gradually decreases toward the outlet-side vent pipe 16 side. The second opening structure 24d has the same cross-sectional shape as the outlet-side vent pipe 16, and the thickness of the end on the inlet-side vent pipe 12 side gradually decreases toward the inlet-side vent pipe 12 side. The first opening structure 20d and the inlet-side vent pipe 12 may be integrally formed. The second opening structure 24d and the outlet-side vent pipe 16 may also be integrally formed.

[0088] 7, when the inlet-side vent pipe 12 and the outlet-side vent pipe 16 have an inner diameter of 30 mm and a thickness of 2 mm, the ratio of the area of ​​the inner diameter (34 mm diameter) of the tip end (the other vent pipe side) of the first opening structure 20d and the second opening structure 24d to the area of ​​the inner diameter of the base end (the vent pipe side to be connected) is 1.28 times, and when the thickness is 3 mm, the ratio of the area of ​​the inner diameter of the tip end to the area of ​​the inner diameter of the base end is 1.44 times, and the first opening structure 20d and the second opening structure 24d each have a structure in which the cross-sectional area changes sufficiently. As shown in the example of FIG. 7, by configuring the first opening structure 20d and the second opening structure 24d to have a region where the thickness gradually decreases, the change in cross-sectional area can be made gentler and wind noise can be reduced. It is also desirable to maintain the outer shape of the expansion portion 14 constant and gradually widen the inside, but it may also be possible to configure the tip to be thin and pointed.

[0089] 7, the first opening structure 20d and the second opening structure 24d may have a region with a constant thickness over a certain length and a region with a gradually thinner thickness toward the tip, or may be composed of only a region with a gradually thinner thickness. Also, as in the examples shown in FIGS. 4 to 6, the opening structure may have an expanding cross-sectional shape (outline) with the thickness of the end gradually tapered.

[0090] In this way, the opening structure can have a variety of shapes as long as the cross-sectional area is gradually changed. The cross-sectional shape of the base end of the opening structure can be a shape that matches the cross-sectional shape of the ventilation pipe, and the cross-sectional shape of the tip end can be a shape that matches the cross-sectional shape of the flow path surrounded by the wall of the expansion section 14 and / or the porous sound-absorbing material 30.

[0091] The cross-sectional shape of the opening structure perpendicular to the central axis preferably has two-fold or more symmetry, and more preferably has four-fold or more symmetry.

[0092] Furthermore, the change in cross-sectional area due to the opening structure may be a monotonous change, may have a changing rate, or may change in stages.

[0093] Furthermore, the average roughness Ra of the inner surface of the aperture structure (the surface on the central axis side) is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.1 mm or less. By reducing the average roughness Ra of the inner surface of the aperture structure, it is possible to suppress the generation of wind noise caused by vortices that are generated by the wind flowing over the surface of the aperture structure being separated.

[0094] 1 and the like, the inlet-side vent pipe 12 and the outlet-side vent pipe 16 are configured so that their central axes are aligned in the same straight line, but this is not limiting. For example, as shown in the examples of FIGS. 8 and 9, the inlet-side vent pipe 12 and the outlet-side vent pipe 16 may be configured so that their central axes are not aligned in the same straight line. Even in such a configuration, a rear space 14a can be formed on the rear side of the porous sound-absorbing material 30 placed in the expansion section 14, and a partition member 34 that separates the rear space 14a can be placed within the rear space 14a.

[0095] 8 and 9 also have a first opening structure and a second opening structure as a preferred embodiment. In the examples shown in Fig. 8 and 9, the first opening structure and the second opening structure have a structure in which the cross-sectional area changes and have the function of bending the flow path.

[0096] 8, the first opening structure 20e has two plate-like members arranged facing each other, the two plate-like members are curved so as to bend the flow path in the direction connecting the inlet-side vent pipe 12 and the outlet-side vent pipe 16, and one of the plate-like members has a widened structure (curved structure) with a changing cross-sectional area at the tip side (toward the outlet-side vent pipe 16). The second opening structure 24e has two plate-like members arranged facing each other, the two plate-like members are curved so as to bend the flow path from the direction connecting the inlet-side vent pipe 12 and the outlet-side vent pipe 16 to the flow direction of the outlet-side vent pipe 16, and one of the plate-like members has a widened structure (curved structure) with a changing cross-sectional area at the tip side (toward the inlet-side vent pipe 12). In the example shown in Figure 8, the first opening structure 20e and the second opening structure 24e are configured so that one of the plate-like members has an expansive structure with a changing cross-sectional area, but both plate-like members may also be configured so that they have an expansive structure (curved structure) with a changing cross-sectional area.

[0097] Furthermore, the opening structure can be configured so that the cross-sectional area changes gradually by making the two plate-like members have different radii of curvature or by changing the lengths.

[0098] As described above, the ventilation type silencer shown in FIG. 8 has a configuration in which the inlet side ventilation pipe 12 and the outlet side ventilation pipe 16 do not have central axes that are aligned in the same straight line, and the flow path is curved due to the opening structure.

[0099] The ventilation type silencer shown in Fig. 8 has a porous sound-absorbing material 30 arranged along the flow path from the tip side of the first opening structure 20e to the tip of the second opening structure 24e within the extension portion 14. Also, a back space 14a is formed on the back surface side of the porous sound-absorbing material 30. In the example shown in Fig. 8, the back spaces 14a are formed on the upper left and lower right sides within the extension portion 14 in the drawing.

[0100] A partition member 34 that separates the rear space 14a is disposed within the rear space 14a. In the illustrated example, the partition member 34 is disposed within the rear space 14a on the upper left side of the expansion section 14 in the drawing. The partition member 34 is a flat, plate-like member that extends in the left-right direction in the drawing, and is disposed so that one end contacts the wall of the expansion section 14 and the other end contacts the porous sound-absorbing material 30.

[0101] One of the two spaces in the rear space 14a separated by the partition member 34 functions as the acoustic resonator 36. In the example shown in Fig. 8, of the two spaces in the rear space 14a separated by the partition member 34, the upper space functions as the acoustic resonator 36. As shown in the figure, the acoustic resonator 36 is open on the porous sound-absorbing material 30 side and is acoustically connected to the flow path via the porous sound-absorbing material 30. This acoustic resonator 36 acts, for example, as an air column resonator.

[0102] In the example shown in Figure 8, a partition member 34 that separates the rear space 14a is placed in one of the two rear spaces 14a, but this is not limited to this.As in the example shown in Figure 9, a partition member 34 may be placed in each of the two rear spaces 14a, and the ventilation type silencer may have two acoustic resonance sections 36.

[0103] In the examples shown in Figures 8 and 9, the partition member 34 is a flat, plate-like member, and the acoustic resonator 36 functions as an air column resonator. However, this is not limiting. As shown in the example shown in Figure 10, the partition member 34 may have a portion protruding toward the acoustic resonator 36b at the end of the porous sound-absorbing material 30. The partition member 34 in the illustrated example has a plate-like member 34b, the width of which is the same as that of the plate-like member 34a in the direction perpendicular to the paper surface in Figure 10, standing on the acoustic resonator 36b side, at the end of the largest surface of the plate-like member 34a that faces the porous sound-absorbing material 30. The end surface of the plate-like member 34b opposite the plate-like member 34a is not in contact with the wall of the extension section 14 (the upper wall in Figure 10), and an opening is formed therein. In the example shown in Figure 10, the opening of the acoustic resonator 36 is narrowed by the plate-like member 34b, as compared to the example shown in Figure 1. By narrowing the opening of the acoustic resonator 36 in this way, the resonance in the acoustic resonator 36b can be made to be Helmholtz resonance.

[0104] Furthermore, even if the central axes of the inlet side ventilation pipe 12 and the outlet side ventilation pipe 16 are not collinear, the opening structure may have a region where the thickness gradually becomes thinner, so that the cross-sectional area gradually changes.

[0105] Furthermore, it is preferable that the ventilation type silencer of the present invention does not have a punched metal between the porous sound-absorbing material and the flow path. If a punched metal is provided between the porous sound-absorbing material and the flow path, the air flowing through the flow path will come into direct contact with the steps of the holes in the punched metal, which may cause pressure loss or wind noise. Furthermore, the area of ​​contact between the porous sound-absorbing material and the sound will be reduced, which may reduce the sound-absorbing effect of the porous sound-absorbing material.

[0106] Furthermore, it is preferable that the ventilation type silencer of the present invention does not have a perforated metal on the surface of the porous sound-absorbing material opposite to the flow path. In other words, it is preferable that no perforated metal is provided between the porous sound-absorbing material and the back space or the acoustic resonance portion. If a perforated metal is provided between the porous sound-absorbing material and the back space, there is a risk that the above-mentioned effect of improving the sound-absorbing performance by having a back space on the back side of the porous sound-absorbing material will not be obtained.

[0107] Furthermore, when it is assumed that the ventilation type silencer of the present invention is used in connection with a hose, it is desirable that the inlet side ventilation pipe and the outlet side ventilation pipe of the ventilation type silencer have an uneven shape and / or a bellows shape on the outer surface. When connected to the hose, they are tightly fastened, so that wind leakage, sound leakage, sound reflection, etc. can be prevented.

[0108] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0109] [Comparative Example 1] As shown in Figures 11 and 12, a ventilation type silencer 100 was produced in which porous sound-absorbing materials 130, 130b were filled in the expansion portion 114. Figure 11 is a cross-sectional view conceptually showing a ventilation type silencer of the comparative example. Figure 12 is a cross-sectional view taken along line CC in Figure 11. The ventilation type silencer 100 shown in Figures 11 and 12 has the same configuration as the ventilation type silencer 10 of the present invention shown in Figures 1 and 2, except that it does not have the partition member 34 and the porous sound-absorbing material 130b is filled in the back space 14a.

[0110] The internal dimensions of the expansion section 114 were 105 mm wide x 37 mm high x 140 mm long. The internal diameters of the connected ventilation pipes (inlet ventilation pipe 112 and outlet ventilation pipe 116) were 24 mm. A first opening structure 120 was disposed at the connection portion with the inlet ventilation pipe 112 inside the expansion section 14, and a second opening structure 124 was disposed at the connection portion with the outlet ventilation pipe 116. The first opening structure 120 and the second opening structure 124 expanded two-dimensionally in the width direction, with a base end width of 24 mm, a tip end width of 30 mm, and a maximum length in the longitudinal direction of 25 mm.

[0111] The extension section 114 was produced by injection molding two parts: a wall part and a main body part, with one of the walls in the height direction being a separate part (fragment). The two opening structures and two vent pipes were also produced by injection molding. Each part was made of ABS resin. The wall part was 2 mm thick, and the other parts were 5 mm thick. A 24 mm diameter through hole was formed in each of the two longitudinal walls of the main body part that would become the extension section 114 to connect to the vent pipe. The opening structure and vent pipe were glued to the positions of the through holes in the main body part that would become the extension section 114.

[0112] Porous sound-absorbing materials 130, 130b (QonPET manufactured by Bridgestone KBG Corporation) were packed into the space inside the main body part that would become the expansion section 114, excluding the area that would become the flow path (the area connecting the tips of the two opening structures). QonPET has a structure in which a thin, high-density nonwoven fabric layer and a thick, low-density nonwoven fabric layer are joined together, with the denser nonwoven fabric layer facing the flow path side.

[0113] After filling the expansion portion 114 with porous sound-absorbing material, the wall part was adhered to the opening surface of the main body part to produce the ventilation type silencer 100. Cemedine ABS adhesive CA-243 was used as the adhesive.

[0114] [Comparative Example 2] A ventilation type silencer was produced in the same manner as in Comparative Example 1, except that the porous sound-absorbing material 130b was omitted and a back space was formed. The porous sound-absorbing material 130b is a portion of 50 mm wide x 37 mm high x 140 mm long that is arranged on the back side of the porous sound-absorbing material 130. Therefore, the ventilation type silencer of Comparative Example 2 has a back space of 50 mm wide x 37 mm high x 140 mm long.

[0115] Example 1 A ventilation type silencer (see FIGS. 1 and 2) was produced that had the same structure as that of Comparative Example 2, except that a partition member 34 was disposed in the rear space.

[0116] The partition member 34 was a flat plate-like member having a thickness of 3 mm, a width of 50 mm, and a height of 35 mm, and was placed at a position 30 mm from the wall in the longitudinal direction of the main body part that would become the extension portion 14, and was molded integrally with the main body part that would become the extension portion 14 by injection molding. The ventilation type silencer of Example 1 was produced in the same manner as Comparative Example 1, except that the porous sound-absorbing material 130b was not placed. A gap of 2 mm was provided between the wall part and the partition member 34.

[0117] [Example 2] A ventilation type silencer having the same structure as that of Example 1 was produced, except that the height of the partition member 34 was changed to 37 mm and molded integrally with the main body part, there was no gap between the wall part and the partition member 34, and the wall part and the partition member were bonded with an adhesive.

[0118] [Evaluation] The transmission loss of the ventilation silencers fabricated in Examples 1 and 2 and Comparative Examples 1 and 2 was measured. The transmission loss was measured using a 24 mm diameter acoustic tube with a speaker and a microphone at four terminals in accordance with the transfer matrix measurement method (ASTM E2611). The measurements were performed using a homemade device, but the measurements can be reproduced using commercially available four-terminal measurement sets, such as the WinZac MTX manufactured by Nihon Onkyo Engineering Co., Ltd. and the 4206-T type transmission loss tube kit manufactured by B&K. A graph of the measurement results for Comparative Example 1 and Comparative Example 2 is shown in FIG. 13. A graph of the measurement results for Comparative Example 1 and Example 1 is shown in FIG. 14. A graph of the measurement results for Comparative Example 1 and Example 2 is shown in FIG. 15.

[0119] In the examples and comparative examples of the graphs of FIGS. 13 to 15, the large change in transmission loss near 315 Hz is due to the natural vibration of the 2 mm thick wall of the extension section 14 .

[0120] 13 shows that in Comparative Example 1, the transmission loss increases monotonically toward the higher frequency side except near 315 Hz. On the other hand, Comparative Example 2 exhibited sound deadening performance that greatly exceeded that of Comparative Example 1 near 1500 Hz, but it can be seen that there are bands where the transmission loss is lower, such as near 1000 Hz and 2000 Hz. In particular, near 1000 Hz, the transmission loss value in Comparative Example 1 was also expected to be smaller than at higher frequencies, so the sound deadening performance was reduced.

[0121] As shown in Figure 14, Example 1 exhibits significantly higher transmission loss around 1000 Hz than Comparative Example 1. In Example 1, the partition member forms an acoustic resonance section with an air column resonator structure measuring 30 mm in width, 37 mm in height, and 50 mm in length on the rear side of the porous sound-absorbing material. The length of the acoustic resonance section is 67 mm, taking into account open-end correction (calculated by determining the opening area and the circle-equivalent radius), and the corresponding resonance frequency can be calculated as 1280 Hz. This nearly coincides with the maximum transmission loss around 1000 Hz in Example 1. Therefore, it can be seen that the acoustic resonance section formed on the rear side of the porous sound-absorbing material can increase the transmission loss around 1000 Hz, which was lower in Comparative Example 2, compared to Comparative Example 1, which is filled with porous sound-absorbing material. Furthermore, it can be seen that high transmission loss can be maintained at high frequencies by leaving a large residual space due to the partition member.

[0122] From Figure 15, it can be seen that the characteristics of Example 2 above 800 Hz are almost identical to those of Example 1. However, there were differences, particularly below 500 Hz. By bonding the partition member and the wall of the extension section without any gaps, the vibration frequency at low frequencies due to the resonance of the wall became higher, and the transmission loss on the lower frequency side was smaller than that of Comparative Example 1 and Example 1. On the other hand, by bonding both ends of the partition member in the height direction to the wall of the extension section, an H-shaped structure was formed, which increased the structural strength.

[0123] [Comparative Example 3] As shown in Fig. 16, a ventilation silencer was produced having a structure in which the central axis of the inlet side ventilation pipe 112 and the central axis of the outlet side ventilation pipe 116 are not collinear, a porous sound absorbing material 130 is arranged in an area along the flow path in the expansion part 114, and a back space 114a is formed. The ventilation silencer shown in Fig. 16 has the same configuration as the ventilation silencer of the present invention shown in Fig. 8, except that it does not have the partition member 34.

[0124] The internal dimensions of the expansion section 114 were 110 mm wide (vertical direction in the figure) x 47 mm high (perpendicular to the paper surface) x 170 mm long (horizontal direction in the figure). The connected vent pipes (inlet vent pipe 112 and outlet vent pipe 116) were rectangular, measuring 24 mm x 24 mm. A first opening structure 120 was disposed at the connection point with the inlet vent pipe 112 within the expansion section 14, and a second opening structure 124 was disposed at the connection point with the outlet vent pipe 116. The first opening structure 120 and the second opening structure 124 were composed of two plate-like members curved to bend the flow path direction by 20°, and the curved structure changed the cross-sectional area of ​​the flow path at the tip end. The first opening structure 120 and the second opening structure 124 were 24 mm high in the direction perpendicular to the paper surface and were disposed adjacent to one of the walls of the expansion section 114 perpendicular to the paper surface.

[0125] The extension section 114 was made by injection molding two parts, a wall part and a main body part, with one of the walls in the height direction being a separate part (fragment). The two opening structures were molded integrally with the main body part. The two vent pipes were also made by injection molding. Each part was made of ABS resin. The wall part was 2 mm thick, and the other parts were 5 mm thick. A 24 mm x 24 mm rectangular through-hole was formed in each of the two longitudinal walls of the main body part that would become the extension section 114 to connect to the vent pipe. The vent pipe was glued to the position of the through-hole in the main body part that would become the extension section 114.

[0126] As shown in the figure, inside the main body part that becomes the expansion section 114, a porous sound-absorbing material 130 (QonPET manufactured by Bridgestone KBG Corporation) was arranged along the area that becomes the flow path (the area connecting the tips of the two opening structures) so as to form a back space. The width of the porous sound-absorbing material 130 in the direction perpendicular to the flow path direction was 15 mm. In addition, a 23 mm thick porous sound-absorbing material 130 was arranged on top of the opening structure of the main body part (direction perpendicular to the paper surface) and on top of the porous sound-absorbing material 130. QonPET has a structure in which a thin, high-density nonwoven fabric layer and a thick, low-density nonwoven fabric layer are joined together, and the denser nonwoven fabric layer was arranged facing the flow path side.

[0127] After placing the porous sound-absorbing material inside the expansion part 114, the wall part was glued to the opening face of the main body part to produce a ventilation type silencer. Cemedine ABS adhesive CA-243 was used as the adhesive.

[0128] Example 3 A ventilation type silencer (see FIG. 8) was produced that had the same structure as that of Comparative Example 3, except that a partition member 34 was placed in one of the rear spaces.

[0129] The partition member 34 is a flat, plate-like member with a thickness of 2 mm and a height of 45 mm, and is positioned 20 mm from the wall in the width direction (vertical direction in the figure) of the main body part that becomes the expansion section 14, with one end contacting one wall in the length direction of the expansion section 14 (the wall on the left in the figure) and the other end contacting the porous sound-absorbing material 30. The partition member 34 is molded integrally with the main body part. There is a gap of 2 mm between the wall part and the partition member 34.

[0130] Example 4 A ventilation type silencer (see FIG. 10 ) was fabricated in the same manner as in Example 3, except that the partition member 34 had a portion (plate-shaped member 34b) that protruded toward the acoustic resonance portion 36b at the end on the porous sound-absorbing material 30 side, and the acoustic resonance portion 36b was a Helmholtz resonator. The width of the opening of the acoustic resonance portion 36b (the distance between the plate-shaped member 34b and the upper wall of the extension portion 14 in FIG. 10 ) was 10 mm.

[0131] Example 5 A ventilation type silencer (see FIG. 9) was produced that had the same structure as Example 3, except that a partition member 34 was disposed in each of the two rear spaces 14a.

[0132] [Evaluation] The transmission loss of the prepared ventilation type silencers of Examples 3 to 5 and Comparative Example 3 was measured in the same manner as above. The graph of the measurement results of Comparative Example 3 and Examples 3 and 4 is shown in Figure 17. The graph of the measurement results of Comparative Example 3 and Example 5 is shown in Figure 18.

[0133] From Figure 17, it can be seen that in Comparative Example 3, the transmission loss is at a minimum value near 1000 Hz. In contrast, in Examples 3 and 4, by providing an acoustic resonance portion on the back side of the porous sound-absorbing material, it is possible to increase the transmission loss in the 700 Hz to 2000 Hz range and increase the amount of silencing. It can also be seen that in Example 4, the peak is shifted to the lower frequency side compared to Example 3. This shows that by narrowing the entrance, the effect of the slit Helmholtz resonator can be used to increase the transmission loss on the lower frequency side, even with an acoustic resonance portion of the same volume as in Example 3.

[0134] 18, it can be seen that in Example 5, the effect of increasing the transmission loss due to the acoustic resonance portion is large, and while the maximum value near 1000 Hz in Example 3 was 16 dB, it is greatly improved to 21 dB in the structure of Example 4. The above results clearly show the effects of the present invention.

[0135] 10, 100 Ventilation type silencer 12, 112 Inlet side ventilation pipe 14, 114 Expansion section 14a, 114a Back space 16, 116 Outlet side ventilation pipe 20, 20b to 20e, 120 First opening structure 24, 24d, 24e, 124 Second opening structure 30, 130, 130b Porous sound absorbing material 34 Partition member 34a, 34b Plate-like member 35 Gap 36 Acoustic resonance section

Claims

1. A ventilation type silencer having an inlet side ventilation pipe, an expansion part communicating with the inlet side ventilation pipe and having a larger cross-sectional area than the inlet side ventilation pipe, and an outlet side ventilation pipe communicating with the expansion part and having a smaller cross-sectional area than the expansion part, A porous sound absorbing material disposed in at least a portion of the extension portion; A back space, which is a space in the extension part of the porous sound absorbing material on the opposite side of the flow path connecting the inlet side air duct and the outlet side air duct, and A partition member that partitions the rear space, The area partitioned by the partition member constitutes an acoustic resonance portion, The acoustic resonance portion is acoustically connected to the flow path, the partition member is not bonded to at least one of two walls of the extension section that face each other and surround the acoustic resonance section, The distance between the partition member and the wall not bonded to the partition member is 1 mm or more and 5 mm or less, The wall that is not bonded to the partition member is a flat surface, A ventilation type silencer, in which the lowest natural frequency of the wall that is not bonded to the partition member after construction including the partition member is 2000 Hz or less.

2. 2. The ventilation type silencer according to claim 1, wherein the resonance in the acoustic resonance portion is an air column resonance.

3. The partition member has an end portion on the porous sound-absorbing material side that protrudes toward the acoustic resonance portion, 2. The ventilation type silencer according to claim 1, wherein the resonance in the acoustic resonance portion is a Helmholtz resonance.

4. The ventilation type silencer according to any one of claims 1 to 3, wherein the partition member is in contact with the porous sound-absorbing material.

5. The ventilation type silencer according to any one of claims 1 to 3, wherein the partition member is formed integrally with the extension portion.

6. 6. The ventilation type silencer according to claim 5, wherein the thickness of the partition member is constant or decreases monotonically in at least one direction from a position where the partition member is joined to the wall of the extension portion to a direction away from the wall.

7. 4. The ventilation type silencer according to claim 1, wherein all sides of the partition member are straight lines.

8. The ventilation type silencer according to any one of claims 1 to 3, wherein at least one of the connection part between the inlet side ventilation pipe and the connection part between the outlet side ventilation pipe of the extension part has an opening structure in which the cross-sectional area gradually expands from the connection part toward the inside of the extension part.