Sandwich structure acoustic material and preparation method and wrapping device thereof

Abstract

The invention discloses a sandwich structure acoustic material and a preparation method and a wrapping device thereof, and belongs to the technical field of acoustic materials, the sandwich structure acoustic material sequentially comprises an EVA hard layer, a sound absorption outer layer, an aluminum foil damping layer and a sound absorption inner layer from outside to inside, the sound absorption outer layer and the sound absorption inner layer are both made of PU foaming materials, and the sound absorption outer layer and the sound absorption inner layer wrap the aluminum foil damping layer. The outer sound absorption layer is fixedly adhered to the inner side of the EVA hard layer, the aluminum foil is light in weight, high in strength, low in cost and convenient to manufacture, the sandwich structure of the sound absorption layer-damping layer-sound absorption layer formed by the acoustic material is simple in process, and low-frequency energy of 600-1000 Hz can be effectively dissipated, so that the required sound absorption and reduction index is achieved, and the light weight of the structure is kept.

Description

Technical Field

[0001] This invention belongs to the field of acoustic materials technology, and more specifically, relates to a sandwich structure acoustic material, its preparation method, and its encapsulation device. Background Technology

[0002] In existing technologies, the acoustic wrapping materials for automotive parts such as electric compressors mostly adopt the structure of EVA+PU or PET+non-woven fabric+two-component sound-absorbing cotton. These materials mainly have good sound absorption effects in the high frequency range above 1000Hz, but in the low frequency range of around 600Hz, not only is the sound absorption effect poor, but it may even lead to noise amplification due to the cavity reverberation effect. This cannot meet the NVH performance requirements of the whole vehicle, such as noise, vibration and acoustic roughness. Therefore, there is a need for an acoustic wrapping material with good sound absorption performance in the low frequency range and that is not prone to noise amplification. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a sandwich structure acoustic material based on damping material, its preparation method and its encapsulation device, which can meet the requirements of good sound absorption performance in the low frequency band and not easily generating noise amplification.

[0004] This invention discloses a sandwich-structured acoustic material, its preparation method, and its encapsulation device. From the outside to the inside, it comprises an EVA rigid layer, a sound-absorbing outer layer, an aluminum foil damping layer, and a sound-absorbing inner layer. Both the sound-absorbing outer and inner layers are made of PU foam material. The sound-absorbing outer and inner layers are wrapped around the aluminum foil damping layer, and the sound-absorbing outer layer is fixedly bonded to the inner side of the EVA rigid layer. The aluminum foil is lightweight, strong, low-cost, and easy to manufacture. The sandwich structure of the acoustic material—sound-absorbing layer-damping layer-sound-absorbing layer—is simple to manufacture and can effectively dissipate low-frequency energy of 600-1000Hz, thereby achieving the required sound absorption and insulation while maintaining a lightweight structure.

[0005] As a further improvement of the present invention, the density of the sound-absorbing outer layer and the sound-absorbing inner layer is 60-70 kg / m³, which balances the sound absorption performance and mechanical strength of the material, ensuring that the material has broadband sound absorption characteristics that meet the sound absorption requirements, while maintaining the flexibility and fit of the wrapping material.

[0006] As a further improvement of the present invention, the thickness of the EVA rigid layer is 2.5±0.5mm and the density is 6±1kg / m². It supports the overall acoustic material, provides rigidity and strength to the entire sandwich structure, facilitates installation and fixation, and can effectively resist external impacts and protect the internal aluminum foil damping layer and sound-absorbing layer.

[0007] As a further improvement of the present invention, the total thickness is 11±1mm, wherein the thickness of the EVA rigid layer accounts for 20%-30% of the total thickness, and the thickness of the aluminum foil damping layer accounts for 0.5%-1% of the total thickness, which facilitates the bonding of the aluminum foil with the PU foam material during processing, while ensuring effective dissipation of vibration energy in the target low-frequency band.

[0008] As a further improvement of the present invention, a method for preparing the sandwich structure acoustic material based on damping material includes the following steps: Step 1: Place EVA material into the same mold and foam it to form a rigid EVA layer; Step 2: Place aluminum foil in the mold beforehand; Step 3: The PU foam material is extruded into the mold described in Step 2 by low-pressure injection to foam, so that the PU foam material fills the space between the EVA rigid layer and the aluminum foil; Step 4: During the PU foaming process, it adheres to the inner side of the rigid EVA layer formed in Step 1 to form an integrated structure; By sequentially completing aluminum foil positioning, PU foam layer molding, and EVA layer molding and sandwich structure bonding in the same mold, the three-layer material is integrated into a single molding process, ensuring the firmness and consistency of the interlayer bonding, avoiding delamination problems that may occur during secondary lamination, improving production efficiency and significantly reducing production costs.

[0009] As a further improvement of the present invention, an acoustic enclosure made of the acoustic material can be applied to motors, compressors, and water pumps commonly used in automobiles, and can specifically solve the problem of low-frequency noise absorption of components in automobile drive systems and air conditioning systems, thereby improving the quietness and comfort of the entire vehicle.

[0010] As a further improvement of the present invention, the overall weight of the acoustic package does not exceed 800g, ensuring lightweight structure, reducing costs, reducing the burden on the vehicle, and improving the overall vehicle energy efficiency.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: the sandwich structure of the acoustic material forming the sound-absorbing layer-damping layer-sound-absorbing layer is simple to manufacture, and can effectively dissipate low-frequency energy of 600-1000Hz to achieve the required sound absorption and insulation while maintaining the lightweight of the structure; the aluminum foil is lightweight, strong, low-cost, and easy to manufacture; by sequentially completing the aluminum foil positioning, PU foam layer molding, and EVA layer molding and sandwich structure bonding in the same mold, the three-layer material is integrated into a single molding process, ensuring the firmness and consistency of the interlayer bonding, avoiding delamination problems that may occur during secondary lamination, improving production efficiency and significantly reducing production costs; The outer and inner sound-absorbing layers have a density of 60-70 kg / m³, balancing the material's sound absorption performance and mechanical strength to ensure the material possesses wideband sound absorption characteristics that meet sound absorption requirements, while maintaining the flexibility and fit of the wrapping material. The EVA rigid layer has a thickness of 2.5±0.5 and a density of 6±1 kg / m², supporting the overall acoustic material, providing rigidity and strength for the entire sandwich structure, facilitating installation and fixation, and effectively resisting external impacts while protecting the inner aluminum foil damping layer and sound-absorbing layer. The EVA rigid layer accounts for 20%-30% of the total thickness, and the aluminum foil damping layer accounts for 0.5%-1% of the total thickness, facilitating the bonding of the aluminum foil with the PU foam material during processing, while ensuring effective dissipation of vibration energy in the target low-frequency band. The overall weight of the acoustic wrapping made of the material does not exceed 800g, ensuring lightweight structure, reducing costs, and reducing the vehicle's load to improve overall vehicle energy efficiency. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the exploded structure of the present invention; Figure 3 This is a schematic diagram comparing the changes in the average sound pressure level at four points in the 1 / 3 octave band coordinate system at 8000 rpm and in the case without a sound packet, according to the present invention. Figure 4 This is a schematic diagram comparing the changes in the average sound pressure level at four points with and without a sound envelope, when the compressor rotor speed is between 1000-11000 rpm. Figure 5 A schematic diagram comparing the changes in the average sound pressure level at 4 points in the 1 / 3 octave band coordinate system at 8000 rpm with and without a sound packet. Figure 6 This is a schematic diagram comparing the changes in the average sound pressure level of the existing sound package at four points with the compressor rotor speed ranging from 1000 to 11000 rpm.

[0013] Explanation of the labels in the diagram: 1. EVA rigid layer; 2. Sound-absorbing outer layer; 3. Aluminum foil damping layer; 4. Sound-absorbing inner layer; 5. Compressor; 51. Controller side; 52. Exhaust side; 53. Directly above; 54. Motor side; 6. Bracket. Detailed Implementation

[0014] Specific Implementation Example 1: Please refer to... Figure 1-4This invention relates to a sandwich-structured acoustic material, its preparation method, and its encapsulation device. From the outside to the inside, it comprises an EVA rigid layer 1, a sound-absorbing outer layer 2, an aluminum foil damping layer 3, and a sound-absorbing inner layer 4. Both the sound-absorbing outer layer 2 and the sound-absorbing inner layer 4 are made of PU foam material. The sound-absorbing outer layer 2 and the sound-absorbing inner layer 4 cover the aluminum foil damping layer 3, and the sound-absorbing outer layer 2 is fixedly bonded to the inside of the EVA rigid layer 1. The aluminum foil is lightweight, strong, low-cost, and easy to manufacture, avoiding the amplification of low-frequency noise and effectively absorbing sound.

[0015] In a further embodiment, the density of the sound-absorbing outer layer 2 and the sound-absorbing inner layer 4 is 60-70 kg / m³, balancing the sound absorption performance and mechanical strength of the material, ensuring that the material has broadband sound absorption characteristics that meet the sound absorption requirements, while maintaining the flexibility and fit of the wrapping material.

[0016] In a further embodiment, the total thickness is 12mm, the thickness of the EVA rigid layer 1 is 3mm, the density is 6kg / m², it supports the overall acoustic material, provides rigidity and strength for the entire sandwich structure, facilitates installation and fixation, and can effectively resist external impacts and protect the internal aluminum foil damping layer 3, sound-absorbing outer layer 2 and sound-absorbing inner layer 4.

[0017] In a further embodiment, the aluminum foil damping layer 2 has a thickness of 0.12 mm and a density of 2.7 kg / m³, which facilitates the bonding of the aluminum foil with the PU foam material during processing, while ensuring effective dissipation of vibration energy in the target low-frequency band.

[0018] In a further embodiment, a method for preparing the sandwich structure acoustic material based on damping material includes the following steps: Step 1: Place the EVA material into the same mold and foam it to form the rigid EVA layer 1; Step 2: Place aluminum foil in the mold beforehand; Step 3: The PU foam material is extruded into the mold described in Step 2 by low-pressure injection, so that the PU foam material fills the space between the EVA rigid layer 1 and the aluminum foil; Step 4: During the PU foaming process, it adheres to the inner side of the EVA rigid layer 1 formed in Step 1 to form an integrated structure.

[0019] In a further embodiment, the acoustic material is used to make an acoustic package with an overall weight of no more than 800g. It can be used on motors, compressors, and water pumps commonly used in automobiles. It can specifically solve the problem of low-frequency noise absorption of components in automobile drive systems and air conditioning systems, ensuring lightweight structure, reducing costs, and reducing the burden on automobiles to improve overall vehicle energy efficiency.

[0020] In a further embodiment, such as Figure 2As shown, according to the test method in GBT+22068-2018 Automotive Air Conditioning Electric Compressor Assembly 6.4, the operating noise difference between two types of acoustic enclosure compressors—one without acoustic enclosure and the other with an acoustic enclosure made of sandwich-structured acoustic material containing damping material—was compared. The compressor 5 was fixed on the bracket 6. A microphone was placed 30cm away from the compressor controller side 51, the exhaust side 52, directly above it 53, and the motor side 54 to collect noise, and the average energy of the sound pressure level at the four microphones was calculated. In a further embodiment, such as Figure 3 As shown, the X-axis represents the one-third octave band frequency band variation, and the Y-axis represents the corresponding average sound pressure level variation within that frequency band. The blue bars represent the average sound pressure level of the acoustically encased compressor in each frequency band, and the green bars represent the average sound pressure level of the acoustically encased compressor without acoustic encasing in each frequency band. According to the chart, from 630Hz to 22387Hz, the four-point average sound pressure level of the acoustically encased compressor is lower than that of the acoustically encased compressor without acoustic encasing, and the four-point average sound pressure level of the acoustically encased compressor is 3-7 dB lower on average than that of the acoustically encased compressor without acoustic encasing. Furthermore, from... Figure 3 It can be seen that the acoustic wrapping described in this invention significantly reduces the average sound pressure level at 630Hz, thus achieving sound absorption and insulation effects to absorb low-frequency noise.

[0021] In a further embodiment, such as Figure 4 As shown, the X-axis represents the rotational speed of the acoustically encased compressor rotor, and the Y-axis represents the change in the average sound pressure level at four points. The green curve represents the average sound pressure level of the acoustically encased compressor at the rotor speed, while the red curve represents the average sound pressure level of the acoustically encased compressor at the rotor speed. According to the chart, when the compressor is pulled from 1000 rpm to 11000 rpm with an intake pressure of 0.3 MPa and an exhaust pressure of 1.5 MPa, the average sound pressure level at four points of the acoustically encased compressor is 4-8 dB lower than that of the acoustically encased compressor.

[0022] In a further embodiment, such as Figure 5As shown, the X-axis represents the one-third octave band frequency band variation, and the Y-axis represents the corresponding average sound pressure level variation within that frequency band. The blue bars represent the average sound pressure level of the acoustically encased compressor in each frequency band, where the existing acoustic encasing is constructed of EVA and PU materials. The green bars represent the average sound pressure level of the acoustically encased compressor without acoustic encasing in each frequency band. According to the chart, from 1250Hz to 22387Hz, the four-point average sound pressure level of the acoustically encased compressor is lower than that of the unencased compressor, and the four-point average sound pressure level of the acoustically encased compressor is 2-6 dB lower on average than that of the unencased compressor. Figure 3 The comparison of the charts concludes that the acoustically encapsulated acoustic compressor of the present invention has a higher average noise reduction value and a better noise reduction effect than the existing acoustically encapsulated acoustic compressor. In addition, at 630Hz, the four-point average sound pressure level of the existing acoustically encapsulated acoustic compressor is higher than that of the acoustic compressor without acoustic encapsulation, indicating that in the low-frequency band, the existing acoustic encapsulation not only fails to absorb noise, but also generates reverberation inside the existing acoustic encapsulation, which excites the modes of the acoustic envelope and generates additional noise.

[0023] In a further embodiment, such as Figure 6 As shown, the X-axis represents the rotational speed of the acoustic compressor rotor, and the Y-axis represents the change in the average sound pressure level at four points. The green curve represents the average sound pressure level of the acoustic compressor with existing acoustic enclosure at the rotor speed, and the existing acoustic enclosure is made of EVA and PU materials. The red curve represents the average sound pressure level of the acoustic compressor without acoustic enclosure at the rotor speed. According to the chart, when the compressor is accelerated from 1000 rpm to 11000 rpm with an intake pressure of 0.3 MPa and an exhaust pressure of 1.5 MPa, the average sound pressure level at four points of the acoustic compressor with existing acoustic enclosure is 1-4 dB lower than that of the acoustic compressor without acoustic enclosure. Moreover, the existing acoustic enclosure only maintains a sustained noise reduction effect after 2225 rpm. Figure 4 The comparison of the charts concludes that the acoustically encapsulated compressor described in this invention has a better noise reduction effect than existing acoustically encapsulated compressors, and existing acoustic encapsulation does not have sound absorption capabilities in the low-frequency range.

Claims

1. A sandwich-structure acoustic material based on damping materials, characterized in that: From the outside to the inside, it includes an EVA rigid layer (1), a sound-absorbing outer layer (2), an aluminum foil damping layer (3), and a sound-absorbing inner layer (4). The sound-absorbing outer layer (2) and the sound-absorbing inner layer (4) are both made of PU foam material. The sound-absorbing outer layer (2) and the sound-absorbing inner layer (4) are covered with the aluminum foil damping layer (3), and the sound-absorbing outer layer (2) is fixedly bonded to the inside of the EVA rigid layer (1) to form a sound-absorbing-damping-sound-absorbing sandwich composite structure.

2. The sandwich structure acoustic material based on damping material according to claim 1, characterized in that: The density of the sound-absorbing outer layer (2) and the sound-absorbing inner layer (4) is 60-70 kg / m³.

3. The sandwich structure acoustic material based on damping material according to claim 1, characterized in that: The EVA hard layer (1) has a thickness of 2.5±0.5mm and a density of 6±1kg / m².

4. The sandwich structure acoustic material based on damping material according to claim 1, characterized in that: The total thickness is 11±1mm, of which the EVA hard layer (1) accounts for 20%-30% of the total thickness and the aluminum foil damping layer (2) accounts for 0.5%-1% of the total thickness.

5. A method for preparing a sandwich-structured acoustic material based on damping materials, characterized in that: Includes the following steps: Step 1: Place the EVA material into the mold and foam it to form a rigid EVA layer (1); Step 2: Place aluminum foil in the same mold beforehand; Step 3: The PU foam material is injected into the mold described in Step 2 by low pressure injection to foam, so that the PU foam material fills the space between the EVA rigid layer (1) and the aluminum foil; Step 4: During the PU foaming process, it adheres to the inner side of the EVA rigid layer (1) formed in Step 1 to form an integrated structure.

6. An acoustic envelopment device according to claim 5, characterized in that: The aluminum foil described in step two is placed after the EVA hard layer (1) has been fully hardened.

7. An acoustic envelopment device, characterized in that: Made of the sandwich structure acoustic material according to any one of claims 1 to 4, the wrapping device acts on motors, compressors, and water pumps commonly used automotive parts.

8. An acoustic envelopment device according to claim 7, characterized in that: The overall weight of the packaging device does not exceed 800g.

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