A noise reduction structure for an air duct, an air duct, an air conditioner and a vehicle

Abstract

The application discloses a noise reduction structure for an air duct, an air duct integrating the same, an air conditioner and a vehicle. The noise reduction structure comprises an inner layer piece, an outer layer piece, a partition plate, a communication hole and a short pipe. The partition plate is arranged along the airflow direction, and separates the annular gap between the inner layer piece and the outer layer piece into a closed annular cavity. The communication hole penetrates the wall surface of the inner layer piece, and the short pipe extends into the cavity and has a length less than the thickness of the cavity. The structure solves the problems of the prior art, such as large volume, difficulty in adapting to narrow space, easy vibration noise under high-speed airflow and narrow noise reduction frequency band. The thickness of the cavity is less than or equal to 10 mm to adapt to the space under the vehicle instrument panel. Multiple cavities are connected in series and the parameters can be adjusted to achieve wide frequency noise reduction (sound insulation amount 8-12 dB) of 450-1560 Hz. The air duct integrates the noise reduction structure, the air conditioner is in sealed communication with the air duct, and the vehicle is equipped with the air conditioner. When the vehicle is idling and the air conditioner is in the 7th gear, the sound pressure level at the head of the driver is less than or equal to 55 dB, and the driving comfort is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of noise reduction technology, and more specifically, to a noise reduction structure for air ducts, air ducts, air conditioners, and vehicles. Background Technology

[0002] Air conditioning ducts generate noise during airflow, primarily including fan noise and airflow turbulence noise. This noise propagates through the ducts into indoor or vehicle interiors, impacting environmental comfort. Existing noise reduction technologies suffer from several drawbacks: traditional porous sound-absorbing materials require significant thickness, making them unsuitable for narrow duct spaces; resonant silencing structures have narrow bandwidths and tend to increase airflow resistance; some acoustic metasurface structures have uneven surfaces, easily inducing additional aerodynamic noise, and their internal components have poor stability, making it impossible to maintain noise reduction performance over the long term. Therefore, there is an urgent need for a highly efficient noise reduction solution that is adaptable to narrow spaces, has low aerodynamic interference, and high stability. Summary of the Invention

[0003] The technical problem this invention aims to solve is that traditional resonant cavity noise reduction structures require a large volume to achieve low-frequency noise reduction, making them unsuitable for the limited installation space of air ducts (especially automotive air ducts); composite sound-absorbing structures rely on multi-layer stacking designs, which are not only thick and complex but also inconvenient to maintain; thin and lightweight noise reduction structures such as micro-perforated plates lack strength and are prone to flow-induced vibration noise under the action of high-speed airflow in the air duct, which exacerbates the noise problem; at the same time, most existing technologies have narrow noise reduction bandwidth and poor adjustment flexibility, making it difficult to match the actual wideband noise requirements of air ducts. Ultimately, existing technologies cannot achieve a balance between space constraints, noise reduction effect, structural stability and bandwidth adaptability, and cannot meet the actual application requirements of air ducts (especially automotive air conditioning ducts).

[0004] To address the aforementioned technical problems, a noise reduction structure for an air duct is provided, comprising: an inner layer having an inner channel for airflow; an outer layer surrounding the inner layer and forming an annular gap between them; at least two partition plates spaced apart along the airflow direction of the inner channel, with both ends of the partition plates sealed to the outer wall of the inner layer and the inner wall of the outer layer, respectively, to divide the annular gap into at least two sealed surrounding cavities; and at least one connecting hole is provided on the wall of the inner layer, one end of which communicates with the inner channel, and the other end extends into the surrounding cavity to form a short tube, the length of which is less than the radial thickness of the surrounding cavity along the inner layer.

[0005] As an optional technical solution of the present invention, the maximum thickness of the surrounding cavity along the radial direction of the inner layer is ≤10mm.

[0006] As an optional technical solution of the present invention, the partition plate is also arranged at intervals along the circumference of the inner layer component, further dividing the single surrounding cavity into at least two circumferential sub-cavities, each circumferential sub-cavity corresponding to a different wall surface of the inner layer component.

[0007] As an optional technical solution of the present invention, the number of connecting holes corresponding to a single surrounding cavity is 1-4, and the cross-sectional shape of the connecting holes is circular, triangular or rectangular.

[0008] As an optional technical solution of the present invention, the free end of the short tube away from the inner layer is provided with a chamfer structure, the chamfer angle of the chamfer structure is 30-45°, and the chamfer radius is 0.5-1mm.

[0009] As an optional technical solution of the present invention, the thickness of the surrounding cavity is variable along the circumference of the inner layer, and the thickness difference at each position is ≤3mm.

[0010] As an optional technical solution of the present invention, multiple surrounding cavities are arranged in series along the airflow direction, the spacing between the partition plates between two adjacent surrounding cavities is 3-6mm, and the size of the connecting hole and the length of the short tube corresponding to different surrounding cavities are different in at least one of them.

[0011] As an optional technical solution of the present invention, the series-connected surround cavity forms a broadband noise reduction unit. The effective noise reduction frequency band of the broadband noise reduction unit is 450-1560Hz, and the sound insulation in this frequency band is 8-12dB.

[0012] As an optional technical solution of the present invention, the inner layer is made of ABS engineering plastic, and the outer layer and the partition are made of PP plastic; the inner layer has a wall thickness of 1.5-2mm, and the outer layer has a wall thickness of 1-1.5mm.

[0013] On the other hand, as an optional technical solution of the present invention, this disclosure also provides an air duct, including an air duct body and the aforementioned noise reduction structure; the inner layer component encloses and forms the main airflow channel of the air duct body, and the airflow direction of the main airflow channel is consistent with the airflow direction of the inner channel of the inner layer component. As an optional technical solution of the present invention, the cross-section of the air duct body is rectangular.

[0014] As an optional technical solution of the present invention, the airflow velocity of the main airflow channel under rated working conditions is 20-25m / s, and the pressure loss of the main airflow channel is ≤5Pa.

[0015] As an optional technical solution of the present invention, the noise reduction structure is detachably connected to at least one section of the air duct body to replace the corresponding section of the air duct body; the cross-sectional shape of the air duct body is rectangular, circular, elliptical or trapezoidal, and the cross-sectional shapes of the inner layer and the outer layer are the same or different.

[0016] As an optional technical solution of the present invention, the spacing between the partition plates between each surrounding cavity is gradually distributed along the airflow direction.

[0017] On the other hand, as an optional technical solution of the present invention, this disclosure also provides an air conditioner, including an air conditioner body and the above-mentioned air duct; the air conditioner body is provided with an air supply device, and the air outlet of the air supply device is sealed and connected to the main airflow channel of the air duct to deliver airflow to the main airflow channel.

[0018] As an optional technical solution of the present invention, the air supply device is a centrifugal fan or an axial fan; the effective noise reduction frequency band of the air conditioner is consistent with the effective noise reduction frequency band of the noise reduction structure.

[0019] As an optional technical solution of the present invention, the air conditioner body is further provided with a temperature regulating component, the air outlet of the temperature regulating component is connected to the air inlet of the air supply device, and the minimum distance between the outer wall of the outer layer of the air duct and the temperature regulating component is ≥5mm.

[0020] On the other hand, as an optional technical solution of the present invention, this disclosure also provides a vehicle, including a body and the aforementioned air conditioner.

[0021] The beneficial effects of this disclosure are as follows: The invention achieves effective noise reduction in confined spaces (such as under a vehicle dashboard) through a design combining a double-layered surround cavity and a short tube, significantly improving space utilization; the use of a solid wall with scattered openings and partition support structure avoids flow-induced vibration noise caused by high-speed airflow, ensuring structural stability; the noise reduction frequency band can be flexibly adjusted by adjusting the cavity spacing, opening parameters, and short tube length to meet the wide-frequency noise requirements of the air duct; the overall structure is simple and detachable, facilitating production and maintenance; and when finally applied to vehicles via air ducts and air conditioning, it can significantly reduce air duct noise and effectively improve driving comfort. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a partial structural diagram of some embodiments of the present invention. Figure 1 ;

[0024] Figure 2 This is a partial structural diagram of some embodiments of the present invention. Figure 2 ;

[0025] Figure 3This is a partial structural diagram of some embodiments of the present invention. Figure 3 ;

[0026] The reference numerals in the accompanying drawings are as follows: 100, air duct; 1, noise reduction structure; 11, inner layer component; 12, outer layer component; 13, partition plate; 14, connecting hole; 15, short pipe. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0028] The following details a noise reduction structure for an air duct, an air duct, an air conditioner, and a vehicle according to the present disclosure.

[0029] In optional embodiments of this disclosure, such as Figure 1-3 The noise reduction structure 1 includes an inner layer 11, an outer layer 12, at least two partition plates 13, a connecting hole 14, and a short pipe 15. The inner layer 11 is a hollow structure, forming an inner channel for airflow. The cross-sectional shape of the inner channel is adapted to the airflow requirements of the duct (e.g., rectangular or circular). The outer layer 12 surrounds the outer periphery of the inner layer 11, with a pre-reserved annular gap between it and the outer wall of the inner layer 11. The width of the annular gap (i.e., the radial thickness of the subsequent surrounding cavity) is designed according to the installation space. The partition plates 13 are spaced apart along the airflow direction of the inner channel, and their ends are respectively connected to the outer wall of the inner layer 11 and the inner wall of the outer layer 12 by ultrasonic welding or high-temperature resistant sealant. The wall-sealed connection ensures that the annular gap is divided into at least two independent sealed surrounding cavities, preventing airflow crosstalk between cavities from affecting the resonance effect. The inner layer 11 has at least one connecting hole 14 on its wall surface (e.g., upper, lower, left, and right walls). One end of the connecting hole 14 extends through to the inner channel, and the other end extends into the surrounding cavity to form a short tube 15. The short tube 15 is integrally formed with the inner layer 11, and its length is less than the radial thickness of the surrounding cavity along the inner layer 11, ensuring that the short tube 15 does not exceed the cavity's range and avoids interference with the inner wall of the outer layer 12. This "inner layer + outer layer + surrounding cavity" structure forms the basic structure for resonance noise reduction. The design of the short tube 15 reduces the resonance frequency without increasing the cavity volume. Simultaneously, the sealed surrounding cavity prevents airflow leakage, ensuring noise reduction efficiency. The overall structure has no unnecessary protrusions, making it suitable for confined installation spaces.

[0030] In optional embodiments of this disclosure, such as Figure 1-3According to the noise reduction structure 1 described above, the maximum radial thickness of the surround cavity along the inner layer 11 is ≤10mm. In specific implementation, the radial thickness of the surround cavity can be designed to be 5-10mm (e.g., 8mm). For example, in a space of 5-8mm under a car dashboard, the distance between the outer wall of the outer layer 12 and the wiring and vehicle components below the dashboard can be maintained at more than 3mm. The design with a thickness of ≤10mm is fully adaptable to narrow spaces such as those in vehicles, avoiding interference with surrounding components (such as wiring and sensors) and solving the problem that traditional resonant cavities (thickness ≥15mm) cannot be installed.

[0031] In optional embodiments of this disclosure, such as Figure 1-3 According to the noise reduction structure 1 described above, the partition plate 13 is also arranged circumferentially along the inner layer 11, further dividing the single surrounding cavity into at least two circumferential sub-cavities, each corresponding to a different wall surface of the inner layer 11. The circumferential partition plate intersects the flow direction partition plate perpendicularly, for example, dividing the single surrounding cavity into two sub-cavities corresponding to the upper and lower walls of the inner layer 11, or four sub-cavities corresponding to the upper, lower, left, and right walls. The volume of each sub-cavity is designed according to the noise intensity of the corresponding wall surface (e.g., the sub-cavity volume corresponding to the lower wall with stronger noise is slightly larger).

[0032] In optional embodiments of this disclosure, such as Figure 1-3 Each periodic unit contains eight noise reduction units 1. The reflection phase difference between two adjacent noise reduction units 1 is π / 4. Through the gradient design of the eight units, a complete phase coverage of 0 to 2π can be formed, ensuring precise control of the sound wave reflection direction. This achieves circumferential zoned noise reduction, avoiding the problem of local wall noise of the inner layer component 11 not being covered. For example, for strong noise generated by airflow impact on the lower wall of the air duct, noise reduction can be enhanced through corresponding sub-cavities, improving the overall noise reduction uniformity.

[0033] In optional embodiments of this disclosure, such as Figure 1-3 According to the noise reduction structure 1 described above, the number of connecting holes 14 corresponding to a single surround cavity is 1-4, and the cross-sectional shape of the connecting holes 14 is circular, triangular, or rectangular. The number of connecting holes 14 is adjusted according to the cavity volume (3-4 for large cavities, 1-2 for small cavities); the diameter of the circular holes is 0.6-1.4mm (e.g., 1mm), the side length of the triangular holes is 0.8-1.2mm, and the aspect ratio of the rectangular holes is 1:1-2:1. The edges of all holes are smoothed (roughness Ra≤0.8μm). By adjusting the number and shape of the holes, the resonance requirements of different cavities can be adapted. For example, circular holes are easy to process and have low airflow resistance, while triangular holes offer more flexible adjustment of the resonance frequency, avoiding the problem of poor adaptability of a single hole type.

[0034] In optional embodiments of this disclosure, such as Figure 1-3According to the aforementioned noise reduction structure 1, the free end of the short tube 15 away from the inner layer 11 is provided with a chamfered structure. The chamfer angle is 30-45°, and the chamfer radius is 0.5-1mm. The chamfered structure is integrally formed by injection molding to avoid burrs generated during subsequent processing. The chamfer angle is preferably 45°, and the radius is preferably 0.8mm to ensure that there is no sharp edge impact when the airflow passes through the end of the short tube 15. This eliminates airflow vortices at the free end of the short tube 15, reduces flow-induced noise (by 2-3dB), and solves the problem of additional noise caused by airflow impact in traditional non-chamfered structures.

[0035] In optional embodiments of this disclosure, such as Figure 1-3 According to the aforementioned noise reduction structure 1, the thickness of the surround cavity is variable along the circumference of the inner layer 11, and the thickness difference at each position is ≤3mm. This allows for flexible adaptation to irregular installation spaces, avoiding the inability to arrange the cavity due to localized narrow spaces. Simultaneously, the thickness difference of ≤3mm ensures balanced resonance at each position, eliminating significant noise reduction dead zones.

[0036] In optional embodiments of this disclosure, such as Figure 1-3 According to the noise reduction structure 1 described above, multiple surround cavities are arranged in series along the airflow direction. The spacing between the partition plates 13 between two adjacent surround cavities is 3-6 mm, and at least one of the dimensions of the connecting holes 14 and the length of the short tubes 15 is different for each surround cavity. The number of cavities connected in series is 50-70 (e.g., 64). The spacing between adjacent partition plates 13 gradually changes from the airflow inlet to the outlet (e.g., 5 mm at the inlet and 3 mm at the outlet). The diameter of the connecting holes 14 of some cavities is 1 mm and the length of the short tubes 15 is 2 mm, while the diameter of the short tubes 15 of others is 0.8 mm and the length of the short tubes 15 is 3 mm. By connecting cavities with different parameters in series, wide frequency coverage (e.g., 450-1560 Hz) is achieved, solving the problem that traditional single-parameter cavities can only cover the 100-200 Hz frequency band. The 3-6 mm spacing between adjacent cavities ensures that there is no significant pressure change when the airflow passes through.

[0037] In optional embodiments of this disclosure, such as Figure 1-3 According to the noise reduction structure 1 above, the series-connected surround cavity forms a broadband noise reduction unit. The effective noise reduction frequency band of the broadband noise reduction unit is 450-1560Hz, and the sound insulation in this frequency band is 8-12dB.

[0038] In optional embodiments of this disclosure, such as Figure 1-3Through semi-anechoic chamber testing, the sound insulation was 8dB at 450Hz, 10dB at 1000Hz, and 12dB at 1560Hz, completely covering the main noise frequency band of automotive air conditioning ducts (450-1560Hz). The 8-12dB sound insulation can reduce in-vehicle duct noise from 65dB to 53-57dB, achieving a comfortable noise level for driving and riding, effectively addressing the deficiency of traditional technologies with only 3-5dB sound insulation in this frequency band.

[0039] In optional embodiments of this disclosure, such as Figure 1-3 According to the aforementioned noise reduction structure 1, the inner layer 11 is made of ABS engineering plastic, while the outer layer 12 and the partition plate 13 are made of PP plastic. The inner layer 11 has a wall thickness of 1.5-2mm, and the outer layer 12 has a wall thickness of 1-1.5mm. The tensile strength of ABS engineering plastic is ≥40MPa, which can withstand the pressure of airflow of 25m / s in the duct (≤5Pa) and avoid deformation. The temperature resistance range of PP plastic is -40℃ to 120℃, which is suitable for the working environment of air conditioning ducts from -30℃ to 80℃, and it is not prone to aging. The material selection takes into account both strength and temperature resistance. The 1.5-2mm wall thickness of the inner layer 11 ensures structural stability, while the 1-1.5mm wall thickness of the outer layer 12 controls the overall weight (40% lighter than metal structures), while avoiding the decay of noise reduction effect due to material aging, and extending the service life to more than 5 years.

[0040] In optional embodiments of this disclosure, such as Figure 1-3 The air duct 100 includes the air duct body and any of the aforementioned noise reduction structures 1. The outer periphery of the inner layer 11 is fitted against the inner wall of the air duct body. The inner channel formed by the inner layer 11 is the main airflow channel of the air duct body. The axis of the main airflow channel is consistent with the airflow direction of the inner channel of the inner layer 11 (e.g., horizontal flow). Both ends of the air duct body are connected to other air duct sections via flanges or clips. This achieves the integrated function of "airflow delivery + noise reduction" in the air duct, eliminating the need for additional noise reduction components outside the air duct, simplifying the air duct system structure. Simultaneously, the main airflow channel is compatible with the inner layer 11, ensuring that the airflow delivery efficiency is not reduced (airflow loss ≤2%).

[0041] In optional embodiments of this disclosure, such as Figure 1-3 Based on the aforementioned air duct 100, the airflow velocity in the main airflow channel under rated operating conditions is 20-25 m / s, and the pressure loss in the main airflow channel is ≤5 Pa. The rated operating condition is air conditioning fan speed setting 7 (the highest setting commonly found in automotive air conditioning). Through CFD simulation and actual testing, the airflow velocity within the main airflow channel is uniform (deviation ≤1 m / s), and the pressure loss is controlled at 3-5 Pa, far below the industry-permitted upper limit of 10 Pa. While meeting the high airflow requirements of air conditioning (20-25 m / s), the low pressure loss avoids increased energy consumption of the air conditioning fan (energy consumption increase ≤3%), solving the problem of increased fan load caused by high airflow resistance in traditional noise reduction structures.

[0042] In optional embodiments of this disclosure, such as Figure 1-3 According to the aforementioned air duct 100, the noise reduction structure 1 is detachably connected to at least one section of the air duct body to replace the corresponding section of the air duct body. The cross-sectional shape of the air duct body is rectangular, circular, elliptical, or trapezoidal, and the cross-sectional shapes of the inner layer 11 and the outer layer 12 may be the same or different. The noise reduction structure 1 is connected to the air duct body by bolts or slots, and can be replaced simply by unscrewing the bolts or loosening the slots. For example, if the air duct body is rectangular (60mm × 40mm), the inner layer 11 is also rectangular, and the outer layer 12 is elliptical (major axis 76mm, minor axis 56mm), it can fit irregular spaces under the dashboard. The detachable design facilitates later maintenance (replacement time ≤ 10 minutes) without replacing the entire air duct; the cross-sectional shape is flexible to adapt to different air duct scenarios, avoiding installation difficulties caused by cross-sectional mismatch.

[0043] In optional embodiments of this disclosure, such as Figure 1-3 According to the aforementioned air duct 100, the spacing of the partition plates 13 between each surrounding cavity is gradually distributed along the airflow direction. The spacing of the partition plates 13 gradually changes from 6mm at the airflow inlet end to 3mm at the outlet end. For example, the spacing of the 64 cavities is 6mm, 5.8mm, ..., 3mm respectively, with a uniform gradient interval (the spacing decreases by 0.5mm every 10 cavities). The gradual spacing allows for a smooth transition of the resonant frequency of each cavity (e.g., from 1560Hz to 450Hz), avoiding frequency band breaks and ensuring no noise reduction blind spots in the 450-1560Hz frequency band.

[0044] In optional embodiments of this disclosure, such as Figure 1-3 The air conditioner includes the main unit and any of the aforementioned air ducts 100. The air outlet of the air supply device (such as a fan) of the main unit is sealed and connected to the main airflow channel inlet of the air duct 100 via a sealing ring. The sealing ring is made of heat-resistant rubber (-40℃ to 120℃) to ensure no airflow leakage. When the air supply device is working, it delivers airflow to the main airflow channel. This achieves system integration of "temperature control + air supply + noise reduction" for the air conditioner. The noise reduction effect of the air duct 100 is adapted to the air supply parameters of the air conditioner, avoiding additional noise during operation and improving the user experience.

[0045] In optional embodiments of this disclosure, such as Figure 1-3According to the aforementioned air conditioner, the air supply device is either a centrifugal fan or an axial fan; the effective noise reduction frequency band of the air conditioner is consistent with the effective noise reduction frequency band of noise reduction structure 1. The centrifugal fan is suitable for the high static pressure requirements of automotive air conditioners (static pressure ≥300Pa), while the axial fan is suitable for low noise requirements (fan noise ≤45dB); through testing, the noise reduction of the air conditioner in the 450-1560Hz frequency band is consistent with the sound insulation of noise reduction structure 1 (8-12dB). The type of air supply device is flexibly adaptable to different air conditioning needs, and the effective noise reduction frequency band of the air conditioner is completely matched with the noise frequency band of the air duct, avoiding the noise reduction failure problem caused by "misalignment between noise reduction frequency band and noise frequency band".

[0046] In optional embodiments of this disclosure, such as Figure 1-3 According to the aforementioned air conditioner, the main body of the air conditioner is also equipped with a temperature regulating component. The air outlet of the temperature regulating component is connected to the air inlet of the air supply device, and the minimum distance between the outer wall of the outer layer 12 of the air duct 100 and the temperature regulating component is ≥5mm. The temperature regulating component is an evaporator or a heater, and its air outlet is connected to the air inlet of the air supply device through a duct. The distance between the outer wall of the outer layer 12 of the air duct 100 and the temperature regulating component is designed to be 5-8mm to avoid the low temperature (e.g., 5℃ for the evaporator) or high temperature (e.g., 60℃ for the heater) of the temperature regulating component affecting the material performance of the air duct 100. The distance ≥5mm ensures that the temperature regulating component and the air duct 100 do not interfere with each other, avoids deformation of the air duct 100 due to sudden temperature changes (deformation ≤0.1mm), and does not affect the temperature regulation efficiency of the air conditioner (cooling / heating speed reduction ≤5%).

[0047] In optional embodiments of this disclosure, such as Figure 1-3 The vehicle includes the body and any of the aforementioned air conditioners. The air conditioner duct 100 is located below the dashboard of the vehicle body. The installation space below the dashboard contains components such as wiring and the steering column. The minimum distance between the outer layer 12 of the air duct 100 and these components is ≥3mm to ensure that the normal operation of the components is not affected after installation. By integrating air duct noise reduction into the vehicle, the sound pressure level at the driver's head (50cm from the air duct outlet) is ≤55dB when the vehicle is idling and the air conditioner is at level 7, which is far below the industry average of 65dB. This significantly improves driving comfort and solves the problem of noise from the vehicle's air conditioning duct affecting the user experience.

[0048] In optional embodiments of this disclosure, such as Figure 1-3The noise reduction structure 1 is fabricated as follows: the inner layer 11 is injection molded from ABS engineering plastic (wall thickness 2mm, cross-section 60mm×40mm), the outer layer 12 is injection molded from PP plastic (wall thickness 1.5mm, cross-section 76mm×56mm), and the partition plate 13 is made of PP plastic sheet (thickness 1mm). It is ultrasonically welded to the inner and outer layers to form 64 surrounding cavities (radial thickness 8mm). Each of the four walls of the inner layer 11 has a circular connecting hole 14 (diameter 1mm), extending to form a short pipe 15 (length 5mm, less than 8mm cavity thickness). The free end of the short pipe 15 is chamfered at 45° (radius 0.8mm). The duct 100 is assembled as follows: the duct body is rectangular (60mm×40mm). The noise reduction structure 1 is detachably connected to the duct body via a slot. The spacing of the partition plates 13 gradually changes from 6mm at the inlet to 3mm at the outlet. The main airflow channel has a velocity of 23.5m / s at wind speed 7 and a pressure loss of 4Pa. Air Conditioning Integration: The main air conditioning unit uses a centrifugal fan (static pressure 300Pa), the temperature regulating component is the evaporator, the air duct 100 is sealed to the fan outlet, the outer layer 12 is 6mm away from the evaporator, and the effective noise reduction frequency band of the air conditioning is 450-1560Hz. Vehicle Installation: The air conditioning duct 100 is placed below the dashboard, the outer layer 12 is 4mm away from the wiring, and the test shows that the sound pressure level at the driver's head is 52dB, which meets the comfort requirements.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0050] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0052] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0053] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0055] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A noise reduction structure (1) for air ducts, characterized in that, include: Inner layer (11), the inner layer (11) having an inner channel for airflow; An outer layer (12) is disposed around the inner layer (11) and forms an annular gap between the outer layer (12) and the inner layer (11); At least two partition plates (13) are arranged at intervals along the airflow direction of the inner channel, and the two ends of the partition plates (13) are respectively sealed to the outer wall of the inner layer (11) and the inner wall of the outer layer (12) to divide the annular gap into at least two closed surrounding cavities. The inner layer (11) has at least one connecting hole (14) on its wall surface. One end of the connecting hole (14) is connected to the inner channel, and the other end extends into the surrounding cavity to form a short tube (15). The length of the short tube (15) is less than the thickness of the surrounding cavity along the radial direction of the inner layer.

2. The noise reduction structure (1) according to claim 1, characterized in that, The maximum thickness of the surrounding cavity along the radial direction of the inner layer (11) is ≤10mm.

3. The noise reduction structure (1) according to claim 1, characterized in that, The partition plate (13) is also arranged circumferentially along the inner layer (11) to further divide the single surrounding cavity into at least two circumferential sub-cavities, each of which corresponds to a different wall surface of the inner layer (11).

4. The noise reduction structure (1) according to claim 1, characterized in that, The number of connecting holes (14) corresponding to a single surrounding cavity is 1-4, and the cross-sectional shape of the connecting holes (14) is circular, triangular or rectangular.

5. The noise reduction structure (1) according to claim 1, characterized in that, The free end of the short tube (15) away from the inner layer (11) is provided with a chamfer structure, the chamfer angle of the chamfer structure is 30-45° and the chamfer radius is 0.5-1mm.

6. The noise reduction structure (1) according to claim 1, characterized in that, The thickness of the surrounding cavity is variable along the circumference of the inner layer (11), and the thickness difference at each position is ≤3mm.

7. The noise reduction structure (1) according to claim 1, characterized in that, Multiple surrounding cavities are arranged in series along the airflow direction. The spacing between the partition plates (13) between two adjacent surrounding cavities is 3-6 mm, and the size of the connecting hole (14) and the length of the short pipe (15) corresponding to different surrounding cavities are different in at least one of them.

8. The noise reduction structure (1) according to claim 7, characterized in that, The series-connected surround cavity forms a broadband noise reduction unit with an effective noise reduction frequency band of 450-1560Hz and a sound insulation of 8-12dB within this frequency band.

9. The noise reduction structure (1) according to claim 1, characterized in that, The inner layer (11) is made of ABS engineering plastic, and the outer layer (12) and the partition plate (13) are made of PP plastic. The inner layer (11) has a wall thickness of 1.5-2mm, and the outer layer (12) has a wall thickness of 1-1.5mm.

10. A ventilation duct (100), characterized in that, It includes the air duct body and the noise reduction structure (1) as described in any one of claims 1-9; The inner layer (11) encloses and forms the main airflow channel of the air duct body, and the airflow direction of the main airflow channel is consistent with the airflow direction of the inner channel of the inner layer (11).

11. The air duct (100) according to claim 10, characterized in that, The airflow velocity in the main airflow channel under rated operating conditions is 20-25 m / s, and the pressure loss in the main airflow channel is ≤5 Pa.

12. The air duct (100) according to claim 10, characterized in that, The noise reduction structure (1) is detachably connected to at least one section of the air duct body to replace the corresponding section of the air duct body; The cross-sectional shape of the air duct body is rectangular, circular, elliptical or trapezoidal, and the cross-sectional shape of the inner layer (11) and the outer layer (12) is the same or different.

13. The air duct (100) according to claim 10, characterized in that, The spacing between the partition plates (13) between each surrounding cavity is gradually distributed along the airflow direction.

14. An air conditioner, characterized in that, Includes an air conditioning unit and an air duct (100) as described in any one of claims 10-13; The air conditioner body is equipped with an air supply device, and the air outlet of the air supply device is sealed and connected to the main airflow channel of the air duct to deliver airflow to the main airflow channel.

15. The air conditioner according to claim 14, characterized in that, The air supply device is a centrifugal fan or an axial fan; the effective noise reduction frequency band of the air conditioner is consistent with the effective noise reduction frequency band of the noise reduction structure (1).

16. The air conditioner according to claim 14, characterized in that, The air conditioner body is also provided with a temperature regulating component. The air outlet of the temperature regulating component is connected to the air inlet of the air supply device, and the minimum distance between the outer wall of the outer layer (12) of the air duct (100) and the temperature regulating component is ≥5mm.

17. A vehicle, characterized in that, Includes the vehicle body and the air conditioner as described in any one of claims 14-16.

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