JP7798341B2 - Sound deadening structure - Google Patents

Description

The present invention relates to a sound-absorbing structure that suppresses resonance of air columns within a space and reduces noise.

Conventionally, structures that ensure breathability, such as ducts, mufflers, and ventilation sleeves, allow gas, wind, or heat to pass through while also allowing sound to pass through and/or generate sound, and therefore often require noise control measures. A known noise control measure involves placing a sound absorber equipped with a diaphragm inside a duct (see, for example, Patent Document 1). In such a sound absorber, for example, when sound waves from a sound source are received, the diaphragm resonates (vibrates) in a resonant frequency band. This causes the air layer inside the sound absorber to repeatedly compress and expand, converting sound energy into thermal energy and absorbing the sound. Therefore, a sound absorber with a peak sound absorption frequency that matches the frequency band of the incoming sound is installed inside the duct.

JP 2016-170194 A

However, the sound absorbing material in Patent Document 1 has a significantly reduced sound absorbing effect for sounds at frequencies other than the peak sound absorption frequency. This means that in order to muffle sound over a wide frequency band, it is necessary to arrange many different types of sound absorbing material, which makes it difficult to install them inside the duct. In addition, if the duct is enlarged to accommodate the sound absorbing material, the location where the duct can be installed is limited. Another problem is that placing sound absorbing material inside the duct reduces breathability.

The present invention was developed through extensive research by the inventors in light of the above-mentioned problems, and aims to provide a means of achieving sound deadening effects over a wide frequency range while ensuring ventilation and without increasing the size of the flow space, using a simple structure.

The sound-absorbing structure of the present invention comprises a flow space within which gas can flow, surrounded by a partition wall that defines an interior and an exterior, and having openings at both ends that directly or indirectly communicate with the interior and exterior, and an expanded diameter portion formed by expanding the cross-sectional area of the flow space , wherein the ratio of the cross-sectional area of the inner diameter of the expanded diameter portion to the cross-sectional area of the inner diameter of the flow space is large enough to suppress resonance of the air column in the flow space .

The sound-absorbing structure of the present invention is also characterized in that the enlarged diameter portion is disposed at the end of the wall.

The sound-absorbing structure of the present invention is also characterized in that the expanded diameter portion is disposed at a location including an opening on the downstream side in the gas flow direction.

The sound-absorbing structure of the present invention is also characterized in that the expanded diameter portion has multiple regions with different inner diameters.

The sound-absorbing structure of the present invention is also characterized in that the multiple regions of different inner diameters of the expanded diameter section are arranged in ascending order of diameter from the upstream side to the downstream side in the gas flow direction.

The sound-absorbing structure of the present invention is also characterized in that the multiple regions of different inner diameters of the expanded diameter portion are arranged in descending order of diameter from the upstream side to the downstream side in the gas flow direction.

The sound deadening structure of the present invention is also characterized by having a flow generating section for causing gas to flow, the flow generating section having a fan that rotates in the internal space of the expanded diameter section.

The sound-absorbing structure of the present invention is also characterized in that the maximum outer diameter of the fan is larger than the inner diameter of the wall and smaller than the inner diameter of the expanded diameter portion.

The sound-absorbing structure of the present invention is also characterized in that the height of the fan is shorter than the length of the expanded diameter portion.

The present invention uses a simple structure to ensure breathability and achieve a sound-deadening effect over a wide frequency range without increasing the size of the flow space.

1 is a cross-sectional view showing a tubular body that is a sound-absorbing structure of the present invention. 10A and 10B are diagrams showing other examples of the expanded diameter portion. FIG. 1 is a perspective view showing a toxic target reduction device. FIG. 1 is a cross-sectional view showing a toxic target reduction device. 1 is a cross-sectional view showing a tunnel that serves as the sound-absorbing structure of the present invention.

Embodiments of the sound-absorbing structure of the present invention will be described below with reference to the drawings. Figure 1 is a cross-sectional view showing a tubular body 1, which is a sound-absorbing structure of the present invention. The tubular body 1 is open at both ends and allows gas (air) to flow downward inside. The tubular body 1 has a flow space 4 that allows gas to flow inside and is surrounded by a partition wall 2 that separates the inside and outside, with both ends having openings that directly or indirectly communicate with the inside and outside, and an expanded diameter section 6 formed in the partition wall 2 between the openings at both ends to change the cross-sectional area of the flow space and form a sound-absorbing structure that suppresses resonance of the air column generated in the flow space.

Specifically, the tubular body 1 has a partition wall 2 that separates the inside from the outside, and openings 3a and 3b that are open at both ends, and its cross section perpendicular to the extension direction is endless. Furthermore, air flows into the flow space 4 surrounded by the partition wall 2 from the outside through one opening 3a, and the flowing air can flow down toward the other opening 3b. Of course, the tubular body 1 can also be used so that air can flow in from the outside through the other opening 3b and flow down toward the one opening 3a.

Although the tubular body 1 has a straight pipe shape, it may have a curved pipe shape or the like.
The tubular body 1 has a substantially uniform inner diameter from the opening 3a to a point excluding the expanded diameter portion 6 near the opening 3b. The expanded diameter portion 6 is disposed at the end near the opening 3b, expanding the inner diameter and thereby expanding the cross-sectional area of the flow space 4 at that point.

The enlarged diameter section 6 functions to suppress resonance noise that may occur inside the tubular body 1. It is desirable to place the enlarged diameter section 6 on the most downstream side in the direction of air flow. Therefore, here it is placed at the end of the tubular body 1 on the opening 3b side. Of course, the enlarged diameter section 6 may also be placed midway between openings 3a and 3b.

Furthermore, the cross-sectional shape and radial dimensions of the expanded diameter section 6 can be set as appropriate as long as the shape expands the cross-sectional area of the flow space. However, it should be noted that if the ratio of the cross-sectional area of the flow space in the expanded diameter section 6 or the cross-sectional area of the inner diameter of the expanded diameter section 6 to the cross-sectional area of the inner diameter of the tubular body 1 is too small, the noise reduction or silencing effect will be insufficient.

As described above, the tubular body 1 has an expanded diameter section 6 that discontinuously expands its cross-sectional area, resulting in a significant reduction in the energy density of sound waves and a reduction in sound pressure level. Furthermore, the expansion of the tubular body 1 creates a semi-open end near the expanded diameter section 6, shifting the frequency (resonant frequency) at which the tubular body 1 can resonate in the flow space 4. This suppresses air column vibration at that frequency and reduces the generation of resonance sounds (noise). By simply providing the tubular body 1 with the expanded diameter section 6, sound deadening effects can be achieved across a wide frequency band while still ensuring breathability and without increasing the overall size of the tubular body 1.

The shape of the enlarged diameter portion 6 may be stepped (see, for example, Figure 1) in which the inner diameter of the tubular body 1 is suddenly enlarged, or may be a shape in which the inner diameter of the tubular body 1 is gradually enlarged as shown in Figure 2(a), i.e., an enlarged diameter portion 6 having a shape in which the diameter is enlarged in an approximately inverted taper shape.
The shape of the expanded diameter portion 6 may be set so that the inner diameter is expanded in multiple stages. That is, as shown in Fig. 2(b), the expanded diameter portion 6 may be formed to have a first expanded diameter region 6a whose diameter is larger than the inner diameter of the tubular body 1 and a second expanded diameter region 6b whose diameter is larger than that of the first expanded diameter region 6a.
Of course, when the diameter expansion section 6 is made multi-stage, the number of stages (number of diameter expansion regions) may be three or more and is not particularly limited. Furthermore, the arrangement of the diameter expansion regions in the diameter expansion section 6 can be set appropriately. For example, the diameter expansion regions can be arranged in ascending (or descending) order of inner diameter from the upstream side to the downstream side in the gas flow direction.

The tubular body 1 can be applied to a variety of components. An example of application of the tubular body 1 to a toxic target elimination device is shown below. Figure 3 is a perspective view of the toxic target elimination device 10, and Figure 4 is a cross-sectional view of the toxic target elimination device 10. The toxic target elimination device 10 is used in a vertical position with the axis of the tubular body 1 oriented approximately vertically. The toxic target elimination device 10 takes in air from outside the device through the suction port 12 and causes it to flow downward in an approximately vertical direction, reducing (e.g., decomposing, inactivating, sterilizing, etc.) toxic targets in the air. The air with the toxic targets removed is then discharged to the outside through the exhaust port 14.

Toxic substances include pathogenic microorganisms such as bacteria and viruses, as well as harmful molecules such as formaldehyde, sulfur dioxide gas, and nitrous acid gas, which are at least toxic to the human body and travel with the air.

The toxic target reduction device 10 comprises an external air intake section 11 with an intake port 12 at the top and an air exhaust section 13 with an exhaust port 14 at the bottom, sandwiched between a tubular body 1, and each section is connected to connect the internal spaces of each section. In other words, each section is connected so that air introduced from the intake port 12 passes through the inside of the tubular body 1 and is exhausted from the exhaust port 14.

Of course, the positions of the outside air intake section 11 and the air exhaust section 13 are not limited to this; the outside air intake section 11 can be located at the bottom of the tubular body 1, and the air exhaust section 13 can be located at the top of the tubular body 1. It goes without saying that the toxic target reduction device 10 can also be used in a horizontal position other than a vertical position. In other words, the orientation of the tubular body 1 can be set as appropriate, and it can also be used in an orientation tilted from the vertical direction.

As shown in Figure 5, the interior of the toxic target elimination device 10 contains an ultraviolet light emitter 16 as a toxic target elimination means, a flow generator 18 that generates air flow within the device, and other components. Specifically, the ultraviolet light emitter 16 is arranged within the tubular body 1 so as to extend parallel to the axis of the tubular body 1.

The flow generating unit 18 can be arranged so that the fan 18a, which has multiple blades, can rotate within the internal space of the expanded diameter section 6. That is, the flow generating unit 18 is located within the air discharge section 13, and the fan 18a is arranged so that it is surrounded by the expanded diameter section 6. Of course, the position of the flow generating unit 18 can be set as appropriate, and the fan 18a may be located near the tubular body 1, downstream of the expanded diameter section 6 in the air flow direction.

The outside air intake section 11 is connected to the upper end of the tubular body 1 and has an intake port 12 at the top, as well as louvers 20 that prevent ultraviolet rays emitted from the ultraviolet emitting section 16 (described below) from leaking outside the device through the intake port 12.

The air discharge section 13 is a member that can accommodate the lower end of the tubular body 1 so as to surround the expanded diameter section 6 of the tubular body 1, and is equipped with the flow generating section 18 and a power supply section (not shown) for supplying power to each section. The air discharge section 13 also has outlets 14 on its circumferential surface. Multiple outlets 14 are provided, and the opening area and number of each outlet are set so that the total opening area exceeds the opening area of the suction port 12. In other words, the air discharge section 13 has a generally rectangular shape when viewed axially, and multiple outlets 14 are provided on each of the four outer peripheral surfaces.

The position of the exhaust port 14 along the axial direction can be set appropriately, but if it is set above the lower end of the tubular body 1, a guide path or the like may be provided within the air exhaust section 13 to guide the flow of air from the tubular body 1 to the exhaust port 14.

The ultraviolet light emitter 16 uses ultraviolet light to reduce or eliminate toxic substances, such as by decomposing, inactivating, disinfecting, sterilizing, sterilizing, or sterilizing the target. The ultraviolet light emitter 16 has an ultraviolet light source such as a germicidal lamp, ultraviolet lamp, or ultraviolet LED, and is shaped like a long, straight tube, emitting ultraviolet light in a generally radial pattern when viewed in the axial direction. Note that the shape of the ultraviolet light emitter 16 is not limited to a straight tube shape, and can be, for example, a light bulb shape, a ring shape, a curved shape, or the like.

The ultraviolet light emitted from the ultraviolet light emitter 16 preferably has a wavelength of approximately 100 to 400 nm, and more preferably around 250 to 270 nm. Of course, the ultraviolet light may be near ultraviolet light (UV-C) with a wavelength of less than 260 nm, far ultraviolet light (wavelength 10 to 200 nm), extreme ultraviolet light (wavelength 10 to 121 nm), etc., as long as it is capable of at least neutralizing toxic substances. Near ultraviolet light (UV-A, UV-B) with a wavelength of more than 300 nm may also be used, and a combination of these may also be used.

The flow generating unit 18 has a fan structure for generating air flow within the device. That is, the flow generating unit 18 is composed of a fan with multiple blades around a rotation shaft, a drive motor for rotating the rotation shaft, etc. Therefore, the flow generating unit 18 can be an axial flow fan, centrifugal fan, mixed flow fan, centrifugal axial flow fan, vortex fan, cross flow fan, etc.

The flow generating unit 18 can introduce ambient air into the device by rotating the fan 18a, causing it to flow down a predetermined flow path. In this case, for example, the maximum outer diameter of the fan 18a may be set to be larger than the inner diameter (internal dimension) of the screen wall 2 but smaller than the inner diameter (internal dimension) of the expanded diameter section 6. Furthermore, the height of the fan 18a (length perpendicular to the diameter) is set to be smaller (less) than the length of the expanded diameter section 6 along the flow direction. Of course, the size of the blades of the flow generating unit 18 can be set appropriately. For example, if the fan 18a is positioned outside the expanded diameter section 6, the outer diameter of the fan 18a may be set to be larger than the inner diameter of the expanded diameter section 6, and the height of the fan may be set to be larger (greater) than the length of the expanded diameter section 6 along the flow direction.

The tubular body 1 also has an ultraviolet reflecting surface on part or all of its inner circumferential surface that has ultraviolet reflectivity and reflects ultraviolet light from the ultraviolet light emitting section 16. Such an ultraviolet reflecting surface can be a cold mirror that reflects ultraviolet light, and can be formed, for example, from a dielectric multilayer film in which multiple layers of dielectric material are vapor-deposited on the inner circumferential surface of the tubular body 1. Alternatively, an ultraviolet reflecting surface can be provided by attaching a thin plate vapor-deposited with a cold mirror to the inner circumferential surface of the tubular body 1 or by placing it inside the tubular body 1.

A dielectric multilayer film can be formed by alternately stacking dielectric thin films of high-refractive index materials and low-refractive index materials. Examples of high-refractive index materials include titanium dioxide ( _TiO2 ), aluminum oxide ( _Al2O3 ), _and zirconium oxide ( _ZrO2 ). Examples of low-refractive index materials include silicon dioxide ( _SiO2 ), zinc peroxide ( _ZnO2 ), and magnesium fluoride ( _MgF2 ).

The location of the UV-reflective surface on the inner surface of the tubular body 1 can be set as appropriate; for example, it can be provided intermittently along the axial and/or circumferential directions on the inner surface of the tubular body 1.

The thickness of the UV-reflecting surface can be set as appropriate. When formed from a multilayer film, the thickness of each layer can be set, for example, to an integral multiple of 1/4 of the wavelength of the UV light to be reflected (an odd or even multiple of 1/4 of the UV light wavelength). Specifically, if the wavelength of the UV light to be reflected is set to 253.7 nm, the thickness of each layer can be set to approximately 63.4 nm (i.e., 1/4 of the wavelength), 126.8 nm (i.e., 2/4 of the wavelength), or 190.3 nm (3/4 of the wavelength). Of course, when the reflective layer 6 is formed from a multilayer film, the thickness of each layer can be a so-called thick film of about several tens of microns, a so-called thin film of about several microns, or a so-called ultra-thin film of less than a few nanometers.

The tubular body 1 has a substantially endless cross section that surrounds the UV-emitting portion 16, and a reflective layer is disposed on the inner surface to reflect UV rays internally at a high degree, i.e., multiple times. However, a reflective layer may also be disposed on the outer surface (outer surface) of the tubular body 1 to reflect UV rays that have passed through the base material of the tubular body 1 inward. In this case, the tubular body 1 may be formed from one or more transparent materials that transmit UV rays, infrared rays, and visible light, such as resin materials such as acrylic, polycarbonate, and polyvinyl chloride, and glass-based materials. Transparent materials may also include metallic materials, ceramic materials such as metals, hydraulic materials such as cement, and transparent materials containing carbon materials.

By providing a reflective layer on the tubular body 1 as described above, the ultraviolet rays emitted from the ultraviolet emitting section 16 are highly reflected inside the tubular body 1. As a result, a high-dose, high-density ultraviolet region is created inside the tubular body 1, where the ultraviolet rays are amplified.

The following describes the toxic target abatement process and air flow by the above-mentioned toxic target abatement device 10. First, the power switch (not shown) of the toxic target abatement device 10 is turned on, and input operations are performed to operate the ultraviolet light emitting unit 16 and the flow generating unit 18.
As a result, ultraviolet rays are emitted from the ultraviolet emitting portion 16, creating a high-dose, high-density ultraviolet region inside the tubular body 1. That is, the ultraviolet rays emitted from the ultraviolet emitting portion 16 are repeatedly reflected multiple times (high-order reflection) by the ultraviolet reflective surface inside the tubular body 1. As a result, the dose of ultraviolet rays is amplified, creating an ultraviolet region.

Furthermore, operation of the flow generating unit 18 rotates the fan, generating a flow that causes air to pass through the intake port 12, tubular body 1, and exhaust port 14 in that order. Specifically, the rotation of the fan causes the air inside the tubular body 1 to flow toward the exhaust port 14 and be discharged to the outside. Furthermore, negative pressure is created inside the toxic target elimination device 10 (inside the tubular body 1), so external air containing toxic targets is sucked in through the intake port 12.

Therefore, an air flow path is formed inside the toxic substance reduction device 10, allowing outside air to be introduced through the intake port 12 and flow down the tubular body 1 before being discharged from the exhaust port 14. Furthermore, an ultraviolet light region is created midway through the flow path, allowing toxic substances in the air to be reduced by ultraviolet light, and the air with the reduced toxic substances discharged from the exhaust port 14.

The above-mentioned toxic target reduction device 10 generates air flow inside, which can cause the air column to resonate in the tubular body 1, but the location where the expanded diameter section 6 of the tubular body 1 is provided expands the inner diameter of the tubular body 1, creating an area with an expanded flow space, which inhibits the resonance of the air column and suppresses the generation of noise inside the tubular body 1 due to the air flow.
Furthermore, the tubular body 1 of the present invention can also reduce noise caused by a gas flow whose density changes periodically, which is generated around the flow generating unit 18 due to the rotation of the fan. That is, the vibration noise generated by the housing vibration due to the mutual interference between the housing disposed inside the toxic target reduction device 10 surrounding the flow generating unit 18 and the gas flow whose density changes periodically, and the pipe-transmitted noise generated by the transmission of this vibration noise to the tubular body 1 can be silenced or reduced by the sound silencing mechanism of the present invention.

While the sound-absorbing structure of the present invention has been described as being a tubular body, the sound-absorbing structure can be applied to structures and devices with ventilation paths such as ducts and pipes, as long as it has a flow space within which gas can flow, and can also be applied to buildings with cavities such as tunnels. For example, as shown in Figure 5, by providing an expanded diameter section 32 near the open end 30 of the tunnel, it is possible to reduce or muffle noise caused by air column resonance occurring within the tunnel.

1...tubular body, 2...wall, 4...flow space, 6...expansion section, 10...toxic target reduction device, 12...intake port, 14...exhaust port, 16...ultraviolet light emission section, 18...flow generation section, 18a...fan

Claims (9)

a flow space in which a gas can flow, the flow space being surrounded by a partition wall that defines an interior and an exterior, and having openings at both ends that directly or indirectly communicate with the interior and the exterior,
an expanded diameter portion formed by expanding the cross-sectional area of the flow space ,
A sound-absorbing structure characterized in that the ratio of the cross-sectional area of the inner diameter of the expanded diameter portion to the cross-sectional area of the inner diameter of the flow space is large enough to suppress resonance of the air column in the flow space . The sound-absorbing structure according to claim 1, characterized in that the enlarged diameter portion is arranged at the end of the wall. A sound-absorbing structure according to claim 1 or 2, characterized in that the expanded diameter portion is arranged at a location including an opening on the downstream side in the gas flow direction. A sound-absorbing structure as described in any one of claims 1 to 3, characterized in that the expanded diameter portion has multiple regions with different inner diameters. The sound-absorbing structure according to claim 4, characterized in that the expanded diameter section has multiple regions with different inner diameters arranged in ascending order of diameter from the upstream side to the downstream side in the gas flow direction. The sound-absorbing structure described in claim 4, characterized in that the expanded diameter section has multiple regions with different inner diameters arranged in order of increasing diameter from the upstream side to the downstream side in the gas flow direction. a flow generating unit for causing the gas to flow;
7. The noise reduction structure according to claim 1, wherein the flow generating portion has a fan that rotates in the internal space of the enlarged diameter portion. The sound-absorbing structure of claim 7, characterized in that the maximum outer diameter of the fan is larger than the inner diameter of the wall and smaller than the inner diameter of the expanded diameter portion. 8. The noise reduction structure according to claim 7, wherein the height of the fan is shorter than the length of the expanded diameter portion.