Diaphragm of sound-generating device and sound-generating device

Abstract

The present application discloses a diaphragm of a sound-generating device and a sound-generating device. The diaphragm includes at least one modified EPDM rubber membrane layer, which is prepared by mixing inorganic hollow microspheres, additives, and a polymer synthesized from ethylene and propylene as basic monomers to form a mixed rubber, followed by a cross-linking reaction. The particle size of the inorganic hollow microspheres is 1 μm to 60 μm, and the distribution density of the inorganic hollow microspheres in the modified EPDM rubber membrane layer is 0.15 g / cm 3 ~0.9g / cm 3 The modified EPDM rubber membrane layer has a compression set of ≤55% when placed in a 130°C environment for 70 hours and at a compression rate of 25%. The diaphragm of the present application includes a modified EPDM rubber membrane layer prepared by cross-linking a rubber compound formed by mixing inorganic hollow microspheres, additives, and a polymer synthesized from ethylene and propylene as basic monomers. This not only reduces the density of the diaphragm material and improves the mid-frequency sensitivity of the sound-generating device, but also ensures that the diaphragm material has excellent rebound performance under high temperature conditions.

Description

Technical Field

[0001] The present application relates to the field of electroacoustic technology, and more specifically, to a diaphragm of a sound-generating device and a sound-generating device using the diaphragm. Background Art

[0002] With the advent of the 5G era, smart electronic devices are developing rapidly, and people's demands for the sound quality and acoustics of these devices are becoming increasingly stringent. This means that the standards for speaker sound quality and stability are becoming increasingly stringent. As a key component of speaker components, the performance of the diaphragm significantly impacts the speaker's sound quality and stability. Rubber diaphragms are inherently soft and elastic, offering excellent low-frequency performance, higher loudness, and a more comfortable listening experience, making them popular. However, due to the high density of rubber materials, rubber diaphragms increase the mass of the vibration system, resulting in low mid-frequency sensitivity in speaker products.

[0003] In addition, the mechanical properties of conventional EPDM diaphragms will decline under harsh environments such as high temperatures, reducing the resilience of the diaphragm and thus affecting the acoustic performance of the sound-generating device.

[0004] Therefore, a new technical solution is needed to solve the above problems. Summary of the Invention

[0005] One object of the present application is to provide a diaphragm for a sound-generating device.

[0006] Another object of the present application is to provide a sound-generating device composed of the above-mentioned diaphragm.

[0007] In order to achieve the above objectives, this application provides the following technical solutions.

[0008] According to the diaphragm of the sound-emitting device of the first embodiment of the present application, the diaphragm includes at least one modified EPDM rubber membrane layer, which is prepared by mixing inorganic hollow microspheres, additives, and a polymer synthesized from ethylene and propylene as basic monomers to form a mixed rubber and then undergoing a cross-linking reaction; wherein the particle size of the inorganic hollow microspheres is 1 μm to 60 μm, and the distribution density of the inorganic hollow microspheres in the modified EPDM rubber membrane layer is 0.15 g / cm 3 ~0.9g / cm 3 The modified EPDM rubber film layer is placed in an environment of 130° C. for 70 hours and has a compression permanent deformation of ≤55% under a compression rate of 25%.

[0009] According to some embodiments of the present application, the density of the modified EPDM rubber film layer is 0.4 g / cm 3 ~1.1g / cm 3 .

[0010] According to some embodiments of the present application, the tensile strength of the modified EPDM rubber film layer is 3 MPa to 35 MPa.

[0011] According to some embodiments of the present application, the content of the inorganic hollow microspheres accounts for 5 wt % to 40 wt % of the total amount of the rubber mix.

[0012] According to some embodiments of the present application, the compressive strength of the inorganic hollow microspheres is ≥10 MPa.

[0013] According to some embodiments of the present application, the glass transition temperature of the modified EPDM rubber film layer is ≤-20°C.

[0014] According to some embodiments of the present application, a coupling agent is provided on the surface of the inorganic hollow microspheres, and the coupling agent performs surface modification on the inorganic hollow microspheres so that the inorganic hollow microspheres are interface-bonded with the matrix of the polymer synthesized with ethylene and propylene as basic monomers; wherein the coupling agent is at least one of a silane coupling agent, a titanate coupling agent and an aluminate coupling agent.

[0015] According to some embodiments of the present application, the content of the coupling agent accounts for 1 wt% to 10 wt% of the added amount of the inorganic hollow microspheres.

[0016] According to some embodiments of the present application, the additives include a cross-linking agent, a reinforcing agent and an antioxidant, wherein the cross-linking agent is at least one of a sulfur and an organic peroxide vulcanization system; the reinforcing agent is at least one of carbon black, white carbon black, graphene oxide, montmorillonite, talc, clay, mica powder, feldspar powder, sodium alginate, magnetic powder, and diatomaceous earth; the antioxidant is at least one of antioxidant N-445, antioxidant 246, antioxidant 4010, antioxidant SP, antioxidant RD, antioxidant ODA, antioxidant OD, and antioxidant WH-02.

[0017] According to some embodiments of the present application, the content of the crosslinking agent accounts for 0.5wt% to 4.5wt% of the rubber mix, the content of the reinforcing agent accounts for 5wt% to 65wt% of the rubber mix, and the content of the antioxidant accounts for 0.1wt% to 5wt% of the rubber mix.

[0018] According to some embodiments of the present application, the diaphragm is a single-layer structure, and the diaphragm is composed of a layer of the modified ethylene propylene rubber membrane.

[0019] According to some embodiments of the present application, the diaphragm is a composite layer structure, and the diaphragm further includes a membrane layer made of at least one of a thermoplastic elastomer, an engineering plastic, and a thermosetting elastomer.

[0020] According to the second aspect of the embodiment of the present application, the sound-producing device includes a vibration system and a magnetic circuit system coordinated with the vibration system, the vibration system includes a diaphragm and a voice coil coupled to one side of the diaphragm, the magnetic circuit system drives the voice coil to vibrate to drive the diaphragm to produce sound, and the diaphragm is the diaphragm according to the above-mentioned embodiment of the present application.

[0021] According to the third aspect of the present application, the sound-producing device includes a shell and a magnetic circuit system and a vibration system arranged in the shell. The vibration system includes a voice coil, a first diaphragm and a second diaphragm. The top of the voice coil is connected to the first diaphragm. The magnetic circuit system drives the voice coil to vibrate to drive the first diaphragm to produce sound. The two ends of the second diaphragm are respectively connected to the shell and the bottom of the voice coil. The second diaphragm is the diaphragm according to the above-mentioned embodiment of the present application.

[0022] According to the diaphragm of the sound-emitting device in the embodiment of the present application, a modified ethylene-propylene rubber membrane layer is prepared by cross-linking reaction after mixing inorganic hollow microbeads, additives and a polymer synthesized from ethylene and propylene as basic monomers to form a mixed rubber. This diaphragm material can not only reduce the density of the diaphragm material and improve the mid-frequency sensitivity of the sound-emitting device, but also make the diaphragm material have excellent mechanical properties and temperature resistance, so that the diaphragm still has excellent rebound performance under high temperature conditions, thereby effectively improving the use effect of the diaphragm and the acoustic stability of the sound-emitting device.

[0023] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0025] Figure 1 is a graph showing changes in the fracture strain of the diaphragm of the sound-generating device according to an embodiment of the present application as a function of the mass ratio of the inorganic hollow microspheres;

[0026] Figure 2 : The intermediate frequency Fr curve of the modified EPDM rubber membrane layer with different densities of the diaphragm of the sound-generating device according to the embodiment of the present application;

[0027] Figure 3 Schematic diagram of the overall structure of the sound-generating device according to an embodiment of the present application;

[0028] Figure 4 is a schematic diagram of a partial structure of a sound-generating device according to an embodiment of the present application;

[0029] Figure 5is a cross-sectional view of a sound-generating device according to an embodiment of the present application;

[0030] Figure 6 1 is an exploded view of a sound-generating device according to an embodiment of the present application.

[0031] Reference numerals

[0032] Sound-generating device 100;

[0033] Housing 10; voice coil 11; first diaphragm 12; second diaphragm 13; magnetic circuit system 14;

[0034] Diaphragm 15 ; surround 151 ; dome 152 . DETAILED DESCRIPTION

[0035] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0036] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0037] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0038] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0039] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0040] The diaphragm of the sound-emitting device according to the embodiment of the present application is described in detail below with reference to the accompanying drawings.

[0041] According to the diaphragm of the sound-generating device of the embodiment of the present application, the diaphragm includes at least one modified EPDM rubber membrane layer, which is prepared by mixing inorganic hollow microspheres, additives, and a polymer synthesized from ethylene and propylene as basic monomers to form a rubber compound, followed by a cross-linking reaction. The particle size of the inorganic hollow microspheres is 1 μm to 60 μm, and the distribution density of the inorganic hollow microspheres in the modified EPDM rubber membrane layer is 0.15 g / cm 3 ~0.9g / cm 3The modified EPDM rubber film layer is placed in an environment of 130℃ for 70h and the compression rate is 25%, and the compression permanent deformation is ≤55%.

[0042] The diaphragm of the sound-emitting device according to the embodiment of the present application can be composed of at least one layer of modified EPDM rubber membrane layer. Specifically, the diaphragm in the present application can be a single-layer structure or a multi-layer composite structure. When the diaphragm is a single-layer structure, that is, the diaphragm is made of a layer of modified EPDM rubber membrane layer of the present application. When the diaphragm is a multi-layer composite structure, the diaphragm includes at least one layer of modified EPDM rubber membrane layer, and the diaphragm is composed of a modified EPDM rubber membrane layer and a membrane layer of other materials. Optionally, when the diaphragm contains multiple layers of modified EPDM rubber membrane layers, two adjacent modified EPDM rubber membrane layers can be spaced apart, that is, a membrane layer of other materials can also be set between two adjacent modified EPDM rubber membrane layers. Of course, two adjacent modified EPDM rubber membrane layers can also be set in close contact with each other. The setting can be selected according to actual usage requirements, and the present application does not impose specific restrictions on this.

[0043] Specifically, the molecular structure of the polymer synthesized from ethylene and propylene as basic monomers can be represented by the following formula (I).

[0044]

[0045] In formula (I), m and n are natural numbers.

[0046] Polymers synthesized from ethylene and propylene as base monomers can form ethylene-propylene rubber (EPR). The ethylene and propylene monomers are randomly arranged in the main chain of the EPR molecule, losing the regularity of the polyethylene or polypropylene structure, thus forming an elastomer. EPR includes ethylene-propylene diene monomer (EPM), which is copolymerized with the monoolefins ethylene and propylene, and ethylene-propylene diene monomer (EPDM), which is copolymerized with ethylene, propylene, and a small amount of non-conjugated diene monomers. The mass ratio of ethylene monomer to propylene monomer ranges from 0.25 to 4, and the content of non-conjugated diene monomer is 1% to 15% of the total content of ethylene and propylene monomers.

[0047] For the convenience of description, a polymer synthesized from ethylene and propylene as basic monomers is defined as a base polymer.

[0048] The modified EPDM rubber membrane layer is made by adding inorganic hollow microspheres to a base polymer. By mixing the inorganic hollow microspheres, additives, and base polymer, a rubber mix can be formed. After vulcanization, the rubber mix can form a modified EPDM rubber membrane layer. In other words, the base polymer can form EPDM rubber, which acts as a base material. After mixing the inorganic hollow microspheres with the base polymer, the inorganic hollow microspheres can be dispersed in the base material. Because the density of inorganic hollow microspheres is lower than that of rubber, adding inorganic hollow microspheres to the rubber can reduce the density of the diaphragm material, resulting in a low-density diaphragm.

[0049] Under the condition that the EPDM diaphragm material with inorganic hollow microspheres added and the EPDM diaphragm material without inorganic hollow microspheres have the same hardness, the diaphragm of the present application has a lower diaphragm density, which can reduce the vibration mass of the vibration system. The mid-frequency region of the frequency response of the sound-generating device is the vibration system quality control area. The lower the vibration mass, the higher the mid-frequency sensitivity. By adding inorganic hollow microspheres to the base polymer, the present application can effectively reduce the vibration mass of the vibration system and improve the mid-frequency sensitivity of the vibration system.

[0050] Therefore, the mid-frequency sensitivity of a sound-generating device using the diaphragm of the present application is significantly improved compared to that of a sound-generating device using a conventional EPDM diaphragm material. That is, the diaphragm of the present application can improve the mid-frequency response of the sound-generating device, thereby giving the sound-generating device a higher mid-frequency sensitivity.

[0051] It's important to note that frequency response (Fr) is used in electronics to describe the differences in an instrument's ability to process signals of varying frequencies. Like distortion, Fr is a very important parameter. Frequency response, also known as the gain curve, is the curve showing how gain changes with frequency. Any audio device or carrier (the object that records sound signals) has a frequency response curve.

[0052] Inorganic hollow microspheres are hollow, thin-walled, hard, and lightweight spheres with a high strength-to-density ratio. The addition of inorganic hollow microspheres to the diaphragm of the sound-generating device in this application effectively reduces the density and weight of the rubber, thereby reducing the overall weight of the diaphragm, lowering the vibration mass of the vibration system, and improving the sensitivity of the sound-generating device.

[0053] Inorganic hollow microspheres can be hollow glass microspheres, hollow ceramic microspheres, and the like. Hollow glass microspheres are composed of inorganic materials such as silicon dioxide, aluminum oxide, zirconium oxide, magnesium oxide, and sodium silicate, along with an enclosed gas. The main component of the hollow glass microsphere shell is borosilicate, which has the characteristics of high rigidity, good chemical stability, and a high melting point. When filled into rubber, it can effectively prevent rubber aging caused by light and heat, thereby improving the temperature resistance of the rubber material. Furthermore, hollow glass microspheres are excellent thermal insulation materials that can effectively block external heat and effectively slow down the damage to the internal network structure of the rubber caused by external heat.

[0054] In other words, adding inorganic hollow microspheres to EPDM effectively improves its aging and temperature resistance. Low-density rubber diaphragms incorporating inorganic hollow microspheres maintain excellent acoustic performance even in harsh, high-temperature environments. Furthermore, the high compressive strength of the inorganic hollow microspheres prevents them from being crushed during the mixing process.

[0055] Furthermore, the particle size of the inorganic hollow microspheres can be selected within the range of 1 μm to 60 μm, preferably 5 μm to 30 μm. For example, the particle size of the inorganic hollow microspheres can be 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or 60 μm. In other words, inorganic hollow microspheres of different particle sizes can be selected according to the thickness of the diaphragm to ensure that the inorganic hollow microspheres are evenly dispersed in the substrate.

[0056] In addition, as the size of the inorganic hollow microspheres decreases, the distribution density of the inorganic hollow microspheres in the modified EPDM rubber film layer will increase. By selecting the appropriate size of the inorganic hollow microspheres, the distribution density of the inorganic hollow microspheres in the modified EPDM rubber film layer can be controlled at 0.15 g / cm 3 ~0.9g / cm 3 For example, the distribution density of inorganic hollow microspheres can be 0.15 g / cm 3 , 0.2g / cm 3 , 0.35g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 or 0.9g / cm 3 To ensure that the inorganic hollow microspheres can effectively reduce the density of the diaphragm, the distribution density of the inorganic hollow microspheres is preferably 0.35 g / cm 3 ~0.8g / cm 3 .

[0057] The addition of inorganic hollow microspheres to EPDM effectively improves the rubber's heat resistance. At high temperatures, the modified EPDM membrane's internal network structure is minimally damaged. When subjected to external loads, the modified EPDM membrane exhibits higher internal network recovery and greater resilience than conventional EPDM membranes.

[0058] It should be noted that rebound resilience is an important indicator for measuring the acoustic vibration stability of rubber diaphragm products. The better the rebound resilience of the diaphragm material, the better the acoustic vibration stability of the sound-generating device, and the higher the acoustic quality of the sound-generating device.

[0059] Specifically, by subjecting the modified EPDM rubber film to compression at 130°C for 70 hours and a pre-compression rate of 25%, the modified EPDM rubber film achieved a compression set of ≤55%. Table 1 shows the test results for the compression set of modified EPDM rubber films containing varying amounts of inorganic hollow microspheres. The inorganic hollow microspheres used here are hollow glass microspheres. It should be noted that hollow glass microspheres are a type of inorganic hollow microsphere. Whether using hollow glass microspheres or other inorganic hollow microspheres can equally demonstrate the role played by the inorganic hollow microspheres in the material.

[0060] Test index: compression permanent deformation

[0061] Test method: The compression set value of EPDM vulcanizate was tested in accordance with GB / T7759-1996 (Method B). The test conditions were: test temperature 130°C, placement time of the modified EPDM rubber film layer 70h, and pre-compression rate of the modified EPDM rubber film layer 25%. The same sample was tested three times and the average value was taken.

[0062] The influence of the content of inorganic hollow microspheres in the diaphragm material on the rebound performance of the diaphragm material is as follows:

[0063] Table 1

[0064]

[0065]

[0066] As shown in Table 1, the compression set of EPDM rubber with zero hollow glass microspheres added is 65%, which is greater than 55%. As the amount of hollow glass microspheres added increases, the compression set of the modified EPDM rubber membrane gradually decreases. This indicates that the addition of inorganic hollow microspheres effectively reduces the destructive effects of high temperatures on the rubber's internal network structure. When subjected to load, the membrane still exhibits excellent recovery properties, reducing the compression set of the modified EPDM rubber membrane. In other words, by adding a certain amount of inorganic hollow microspheres to the base polymer as a diaphragm material, the resilience of the modified EPDM rubber membrane can be effectively improved.

[0067] Furthermore, diaphragms of modified EPDM rubber membrane layers with different contents of inorganic hollow microspheres and diaphragms of conventional EPDM rubber membrane layers were baked at 120°C for 168 hours and then applied to speakers for relevant acoustic tests. The test results are shown in Table 2.

[0068] Test index: Speaker module F0 (resonance frequency) change

[0069] Table 2

[0070] Hollow glass microsphere mass percentage (wt%) 0 10 30 40 120℃*168h Speaker F0 change (Hz) 31 20 15 13

[0071] The EPDM membrane layer with zero hollow glass microspheres is a conventional EPDM membrane layer. As shown in Table 2, as the amount of hollow glass microspheres added increases, the F0 variation of the speaker module with the modified EPDM membrane layer significantly decreases. This indicates that after high-temperature baking of the diaphragm, the speaker using the modified EPDM membrane layer of this application has better F0 stability.

[0072] In other words, the modified EPDM membrane layer has superior resilience compared to conventional EPDM membrane layers. The diaphragm of this application can maintain consistent mechanical properties even in harsh environments, allowing sound-generating devices using this diaphragm to maintain stable acoustic performance in even harsher temperature environments, thereby improving the reliability of the sound-generating device in extreme environments.

[0073] Therefore, according to the embodiment of the present application, the diaphragm of the sound-emitting device is made of a modified ethylene-propylene rubber membrane layer prepared by cross-linking reaction after mixing inorganic hollow microbeads, additives and a polymer synthesized from ethylene and propylene as basic monomers to form a mixed rubber. This not only reduces the density of the diaphragm material and improves the mid-frequency response of the sound-emitting device, but also makes the diaphragm material have excellent temperature resistance and deformation resistance. The diaphragm still has excellent rebound performance under high temperature conditions, thereby effectively improving the use effect of the diaphragm and the acoustic stability of the sound-emitting device.

[0074] It should be noted that the conventional EPDM rubber membrane layer is a membrane layer made of EPDM rubber without adding inorganic hollow microbeads.

[0075] According to one embodiment of the present application, the compressive strength of the inorganic hollow microspheres is ≥10 MPa.

[0076] In other words, the high compressive strength of inorganic hollow microspheres not only prevents them from being crushed during the mixing process, but also effectively increases the tensile strength of the modified EPDM membrane when added to the EPDM. The high mechanical strength of the diaphragm prevents it from overstretching due to excessive driving forces in extreme environments, further ensuring the effectiveness of the diaphragm.

[0077] In some specific embodiments of the present application, the content of the inorganic hollow microspheres accounts for 5 wt % to 40 wt % of the total rubber mix.

[0078] In other words, a modified EPDM rubber membrane layer can be prepared by adding inorganic hollow microspheres in an amount of 5wt% to 40wt% of the total rubber mix to the base polymer. As the amount of inorganic hollow microspheres added increases, the density of the modified EPDM rubber membrane layer decreases. By controlling the density of the inorganic hollow microspheres added, a diaphragm material with desired performance can be obtained. The content of the inorganic hollow microspheres can be any value between 5wt% and 40wt%, for example, the content of the inorganic hollow microspheres can be 5wt%, 10wt%, 15wt%, 20wt%, 30wt% or 40wt%.

[0079] It should be noted that because the distribution density of inorganic hollow microspheres is much lower than that of rubber, the density of the rubber material will significantly decrease as the amount of inorganic hollow microspheres added increases. Specifically, when the content of inorganic hollow microspheres is low (less than 5wt%), the density of the diaphragm material is not significantly affected, and the diaphragm still has a relatively high density.

[0080] When the content of inorganic hollow microspheres is too high (greater than 40wt%), the mass proportion of the inorganic hollow microspheres is too high, the rubber content is reduced, the material modulus is increased, and the fracture strain is reduced, causing the modified EPDM rubber membrane layer to lose the rubber's inherent soft elasticity. Due to its excessive mechanical strength, the maximum amplitude that can be achieved by the prepared diaphragm under the same driving force is reduced, resulting in a decrease in the low-frequency Fr of the sound-generating device. In addition, the excessive addition of inorganic hollow microspheres will significantly reduce the density of the modified EPDM rubber membrane layer, resulting in low elongation and strength at break, and prone to reliability issues such as collapse and rupture.

[0081] Therefore, by using a modified EPDM rubber membrane layer prepared by adding 5wt% to 40wt% of inorganic hollow microbeads to the total rubber mix as the diaphragm material, the density and strength of the diaphragm can be achieved at the same time, effectively ensuring the excellent mid-frequency and low-frequency performance of the diaphragm.

[0082] According to one embodiment of the present application, the surface contact angle between the modified EPDM rubber film layer and water is ≥85°.

[0083] It should be noted that the rubber film phenomenon is caused by the precipitation of small molecule compounding agents inside the rubber. During the high-temperature molding process of the rubber material diaphragm, the small molecule compounding agents inside the rubber migrate to the surface and adhere to the mold. Multiple molding will cause the accumulation of small molecule compounding agents on the mold to increase. On the one hand, it causes corrosion of the mold. On the other hand, the surface of the rubber diaphragm product forms a physical bond with the small molecule compounding agents accumulated on the mold. The combined effect of these two aspects causes severe rubber film. Rubber film is an unavoidable problem in the rubber processing process. Rubber film has a very large impact on the molding state of the diaphragm product. The film will cause poor dimensional stability of the rubber and cause corrosion to the mold. Severe film will cause extremely thin diaphragms to have reliability problems such as pulling deformation, film breakage and dimensional instability, resulting in poor molding of the diaphragm product.

[0084] Because mucosal properties are related to surface polar groups, the degree of mucosal properties of a diaphragm can be characterized by measuring the surface contact angle. The smaller the surface contact angle, the higher the mucosal properties of the diaphragm. To evaluate the mucosal properties of the modified EPDM rubber film layer, the applicant conducted surface contact angle tests on the surfaces of diaphragm materials produced under the same molding conditions and containing varying amounts of inorganic hollow microspheres.

[0085] It should also be noted that if the surface contact angle between a substance and water is less than 90°, it means that the surface of the substance is hydrophilic, that is, liquid can easily wet the substance, and the smaller the angle, the better the wettability; if the surface contact angle between a substance and water is greater than 90°, it means that the surface of the substance is hydrophobic, that is, liquid cannot easily wet the substance and can easily move on the surface.

[0086] Table 3 shows the effect of adding different contents of inorganic hollow microspheres to the diaphragm material formed by EPDM rubber on the surface contact angle of the diaphragm material.

[0087] The effect of the content of inorganic hollow microspheres in the diaphragm material on the mucosal properties of the diaphragm is as follows:

[0088] The test method is: measuring the contact angle of rubber diaphragms with different hollow glass microbead contents and the corresponding mold surface after 30 molding cycles; testing is carried out according to the GGS1616 water drop angle standard, and ten points are measured for each sample to obtain the average value.

[0089] It should be noted that EPDM conventional rubber + xwt% hollow glass microspheres refers to EPDM conventional rubber with xwt% hollow glass microspheres added, that is, modified EPDM rubber membrane layers with different hollow glass microsphere contents, where x is 10, 30, or 40.

[0090] Table 3

[0091] Rubber diaphragm product material Surface contact angle EPDM conventional rubber diaphragm material 75° Diaphragm material of EPDM conventional rubber + 10wt% hollow glass microspheres 87° Diaphragm material of EPDM conventional rubber + 30wt% hollow glass microspheres 96° Diaphragm material of EPDM conventional rubber + 40wt% hollow glass microspheres 103°

[0092] As shown in Table 3, the surface contact angle between EPDM and water without hollow glass microspheres is 75°, less than 90°, indicating high mucosal properties. As the amount of hollow glass microspheres added to the EPDM increases, the surface contact angle of the rubber diaphragm material increases significantly, indicating a significant improvement in the mucosal properties of the modified EPDM film.

[0093] In other words, because low-density inorganic hollow microspheres are smooth and sufficiently rigid inorganic fillers, adding them to rubber can, on the one hand, reduce the rubber's own adhesion, and on the other hand, effectively improve the surface migration of small molecule compounding agents within the rubber, thereby improving the rubber's sticking phenomenon. This ensures the molding quality of the diaphragm product.

[0094] According to one embodiment of the present application, the tensile strength of the modified EPDM rubber film layer is 3 MPa to 35 MPa.

[0095] In some specific embodiments of the present application, the tear strength of the modified EPDM rubber film layer is 15 N / mm to 85 N / mm.

[0096] That is to say, by adding inorganic hollow microbeads to the base polymer to form a low-density rubber diaphragm material, its tensile strength can be controlled within the range of 3MPa to 35MPa, and its tear strength can be controlled within the range of 15N / mm to 85N / mm. For example, the tensile strength of the modified EPDM rubber membrane layer can be 3MPa, 6MPa, 10MPa, 16MPa, 20MPa, 25MPa, 30MPa or 35MPa. The tear strength of the modified EPDM rubber membrane layer can be 15N / mm, 30N / mm, 45N / mm, 50N / mm, 70N / mm, 80N / mm or 85N / mm. That is, the modified EPDM rubber membrane layer can have suitable mechanical properties, and the diaphragm prepared therefrom is not prone to problems such as membrane breakage during the use of the sound-generating device, effectively ensuring the reliability of the diaphragm.

[0097] According to one embodiment of the present application, the room temperature storage modulus of the modified EPDM rubber membrane layer is 0.5 MPa to 35 MPa. By adding inorganic hollow microspheres to the base polymer to form a low-density rubber diaphragm material, the room temperature storage modulus of the modified EPDM rubber membrane layer can be within the range of 0.5 MPa to 35 MPa, ensuring the diaphragm has good resilience.

[0098] In other words, the diaphragm made with this modified EPDM rubber membrane layer has excellent damping performance and resilience, effectively suppressing polarization during the vibration and sound generation process, and achieving greater consistency in the vibration system. The diaphragm of this application achieves greater vibration consistency across its various components, effectively reducing distortion in the sound-generating device.

[0099] In some specific embodiments of the present application, the hardness of the modified EPDM rubber film layer is 35A to 80A.

[0100] It should be noted that the sound-producing device can be a loudspeaker. The loudspeaker includes a vibration system and a magnetic circuit system that cooperates with the vibration system. The vibration system includes the diaphragm provided in this application, which can be a ring-shaped diaphragm or a flat diaphragm. Loudspeakers using the diaphragm provided in this application have advantages such as good sound quality and durability.

[0101] The F0 (resonant frequency) of the speaker is proportional to the Young's modulus and thickness (see equations (1) to (3)). The F0 can be changed by changing the thickness and Young's modulus of the speaker diaphragm. The specific adjustment principle is as follows:

[0102]

[0103] In formula (1), Mms is the equivalent vibration mass of the loudspeaker, and Cms is the equivalent compliance of the loudspeaker.

[0104]

[0105] In formula (2), Cms1 is the elastic wave compliance, and Cms2 is the diaphragm compliance. When there is no elastic wave design, the equivalent compliance of the loudspeaker is the diaphragm compliance.

[0106]

[0107] In formula (3), W is the total width of the diaphragm surround; t is the diaphragm thickness; dvc is the outer diameter of the diaphragm voice coil; E is the Young's modulus of the diaphragm material; and u is the Poisson's ratio of the diaphragm material.

[0108] It can be seen that the F0 of the speaker is proportional to the modulus and thickness, while the modulus of rubber is proportional to its hardness, so hardness can be used instead of its modulus. For example, when you want to get full bass and a comfortable listening experience, the diaphragm should have sufficient stiffness and damping while having a low F0. Therefore, the size of the speaker's F0 can be adjusted by adjusting the hardness and thickness of the speaker diaphragm. When the hardness of the diaphragm material is controlled within the range of 35A to 80A and the room temperature storage modulus is within the range of 0.5MPa to 35MPa, the F0 of the speaker can reach 500Hz to 1500Hz, which makes the speaker have excellent low-frequency performance.

[0109] In some specific embodiments of the present application, the glass transition temperature of the modified EPDM rubber film layer is ≤-20°C.

[0110] That is to say, by adding inorganic hollow microbeads to the base polymer to form a low-density rubber diaphragm material, and then adjusting the amount of inorganic hollow microbeads added, the glass transition temperature of the diaphragm can be controlled to ≤-20°C. For example, -20°C, -23°C, -25°C, -30°C, etc. Preferably, the glass transition temperature of the modified EPDM rubber membrane layer can be ≤-30°C. A lower glass transition temperature can enable the diaphragm to maintain good rubber elasticity in a low-temperature environment, so that the sound-generating device can produce sound normally in extreme environments, further improving the acoustic performance and reliability of the sound-generating device.

[0111] Therefore, by adding inorganic hollow microbeads to EPDM rubber, the glass transition temperature of the diaphragm of the present application can be controlled to ≤-20°C, which can enable the modified EPDM rubber film layer to maintain a high elastic state at room temperature, so that the diaphragm has good resilience. When the operating temperature of the diaphragm is lower than 0°C, the speaker diaphragm can always maintain good rubber elasticity during operation, so that the speaker exhibits higher sound quality. At the same time, the risk of damage to the speaker diaphragm in a low temperature environment is reduced, and the reliability is higher. In addition, a diaphragm with a lower glass transition temperature can enable the diaphragm material to have a high modulus consistency when working above the glass transition temperature, and the F0 of the diaphragm prepared from the diaphragm material has better stability in the entire temperature range.

[0112] According to one embodiment of the present application, the density of the modified EPDM rubber film layer is 0.4 g / cm 3 ~1.1g / cm 3 .

[0113] In other words, by adding inorganic hollow microspheres to the base polymer to form a low-density rubber diaphragm material, and then by adjusting the amount of inorganic hollow microspheres added, the density of the diaphragm can be controlled at 0.4g / cm 3 ~1.1g / cm 3 For example, the density of the diaphragm can be 0.4g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1g / cm 3 or 1.1 g / cm 3 Thus, through the above-mentioned setting, the weight of the modified EPDM rubber membrane layer can be reduced by 30%-50%, which has a good weight reduction effect and greatly improves the sound sensitivity of the diaphragm.

[0114] Table 4 shows the effect of different addition amounts of inorganic hollow microspheres on the density of the modified EPDM rubber film. Hollow glass microspheres are used as the inorganic hollow microspheres. It should be noted that hollow glass microspheres are a type of inorganic hollow microspheres. Using hollow glass microspheres or other inorganic hollow microspheres can equally demonstrate the role played by inorganic hollow microspheres in the material.

[0115] As shown in Table 4, with the increase of the addition amount of inorganic hollow microspheres, the density of the modified EPDM rubber film layer gradually decreases.

[0116] By measuring the fracture strain of the modified EPDM rubber film layer with different contents of hollow glass microspheres, a graph showing the fracture strain of the modified EPDM rubber film layer as a function of the mass proportion of the hollow glass microspheres can be obtained. Figure 1 As shown in the figure, as the amount of inorganic hollow microspheres added increases, the fracture strain gradually decreases. When the mass proportion of the added inorganic hollow microspheres is too high, the rubber content decreases, and the inorganic hollow microspheres and the rubber matrix will separate into phases, resulting in poor mechanical properties. The fracture strain will be greatly reduced, and the elasticity of the modified EPDM rubber film layer will deteriorate. This can easily cause reliability issues such as film breakage during processing, making it difficult to meet the performance requirements of the diaphragm.

[0117] The influence of the content of inorganic hollow microspheres in the diaphragm material on the density of the diaphragm is as follows:

[0118] Determination method: Direct determination by density balance

[0119] Table 4

[0120] Hollow glass microsphere mass percentage (wt%) 0 5 10 40 50 <![CDATA[Rubber density (g / cm 3 )]]> 1.1 1.04 0.98 0.57 0.47

[0121] The influence of the content of inorganic hollow microspheres in the diaphragm material on the intermediate frequency Fr of the diaphragm is as follows:

[0122] like Figure 2 As shown in the figure, by testing the mid-frequency (Fr) of sound-generating devices with diaphragm densities of different sizes, it was found that as the diaphragm density increases, the mid-frequency performance of the sound-generating device gradually decreases. In other words, by adding inorganic hollow microbeads to a diaphragm material composed of a polymer based on ethylene and propylene, the density of the diaphragm can be reduced, thereby improving the mid-frequency sensitivity of the sound-generating device.

[0123] It should be noted that when the density of the low-density rubber is low (less than 0.4 g / cm 3 ), the content of inorganic hollow microspheres is high, the mechanical properties are deteriorated, the fracture strain of the prepared diaphragm is low, and reliability problems such as collapse and rupture are prone to occur. When the content of inorganic hollow microspheres is low and the diaphragm density is high (>1g / cm 3 ), the prepared diaphragm has a lower quality than ordinary conventional diaphragms at the same thickness, and the improvement of the mid-frequency sensitivity of the sound-generating device is not obvious.

[0124] According to one embodiment of the present application, a coupling agent is provided on the surface of the inorganic hollow microspheres. The coupling agent modifies the surface of the inorganic hollow microspheres to allow for interfacial bonding between the inorganic hollow microspheres and a matrix of a polymer synthesized from ethylene and propylene as primary monomers. The coupling agent is at least one of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent.

[0125] Inorganic hollow microspheres are polar, insoluble substances, while ethylene propylene diene monomer (EPM) and ethylene propylene diene monomer (EPDM) are relatively low-polar rubbers. This polarity difference results in poor compatibility between the two. Directly or excessively filling EPDM with inorganic hollow microspheres can degrade the mechanical properties of the rubber, adversely affecting its performance. Therefore, a coupling agent is required to surface-modify the inorganic hollow microspheres.

[0126] In other words, the inorganic hollow microspheres need to be surface-modified with a coupling agent to achieve good interfacial bonding with the rubber matrix (EPDM), thereby ensuring uniform dispersion of the inorganic hollow microspheres within the rubber matrix. The coupling agent can be selected from at least one of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent. Inorganic hollow microspheres inherently possess advantages such as high rigidity, good chemical stability, a high melting point, and excellent thermal insulation. Further surface modification with a coupling agent enables good interfacial bonding with the rubber matrix, further enhancing the rubber's temperature resistance.

[0127] In some specific embodiments of the present application, the content of the coupling agent accounts for 1 wt% to 10 wt% of the added amount of the inorganic hollow microspheres.

[0128] That is, the amount of the coupling agent added can be controlled within the range of 1 wt% to 10 wt% of the amount of the inorganic hollow microspheres added. Preferably, the amount of the coupling agent added is 3 wt% to 7 wt% of the amount of the inorganic hollow microspheres added.

[0129] It should be noted that if the coupling agent addition level is too low, the surface modification of the inorganic hollow microspheres will not be achieved, making it difficult to ensure uniform dispersion of the inorganic hollow microspheres in the rubber matrix. If the coupling agent addition level is too high, the coupling agent itself will undergo coupling and crosslinking, resulting in unsatisfactory surface modification of the inorganic hollow microspheres. Only by adjusting the coupling agent content within the appropriate range can a good interfacial bonding between the inorganic hollow microspheres and the rubber matrix be ensured, achieving a reinforcing effect.

[0130] Therefore, by controlling the content of the coupling agent within the range of 1wt% to 10wt% of the added amount of inorganic hollow microspheres, it is possible to ensure that the inorganic hollow microspheres have a good interface bond with the base polymer, and the inorganic hollow microspheres can be evenly dispersed in the rubber matrix, thereby achieving a good reinforcement effect on the rubber matrix, so that the diaphragm of the present application has good mechanical properties and temperature resistance.

[0131] According to one embodiment of the present application, the additives include a crosslinking agent, a reinforcing agent, and an antioxidant. The crosslinking agent is at least one of a sulfur-based and organic peroxide-based vulcanization system; the reinforcing agent is at least one of carbon black, white carbon black, graphene oxide, montmorillonite, talc, clay, mica powder, feldspar powder, sodium alginate, magnetic powder, and diatomaceous earth; and the antioxidant is at least one of antioxidant N-445, antioxidant 246, antioxidant 4010, antioxidant SP, antioxidant RD, antioxidant ODA, antioxidant OD, and antioxidant WH-02.

[0132] In some specific embodiments of the present application, the content of the crosslinking agent is 0.5wt% to 4.5wt% of the rubber mix, the content of the reinforcing agent is 5wt% to 65wt% of the rubber mix, and the content of the antioxidant is 0.1wt% to 5wt% of the rubber mix.

[0133] The crosslinking agent content accounts for 0.5wt% to 4.5wt% of the rubber mix, preferably 1wt% to 3wt%. The amount of crosslinking agent used directly determines the degree of crosslinking. When the crosslinking agent content in the system is less than 0.5wt%, the rubber has a low degree of crosslinking, low mechanical strength, and the material's mechanical properties fail to meet product requirements. When the crosslinking agent content exceeds 4.5wt%, the rubber has a high degree of crosslinking, low elongation at break, and insufficient toughness, making it prone to brittle fracture during long-term use.

[0134] Antioxidants should be present in a range of 0.1-5% by weight of the rubber mix. Over time, as rubber molecules break down over time, they generate free radicals, accelerating their aging. Adding antioxidants can inhibit the generation of autocatalytic free radicals in rubber products. Too little antioxidant content will not extend the product's service life, while too much antioxidant content will be difficult to dissolve in the elastomer, leading to a decrease in mechanical properties and a tendency to surface precipitation over time.

[0135] The reinforcing agent accounts for 5% to 65% of the rubber mix. The reinforcing agent interacts with the rubber molecular chains through entanglement, van der Waals forces, or hydrogen bonds. When the material is subjected to stress, the molecular chains easily slide on the reinforcing agent surface but are difficult to separate from the reinforcing agent. The rubber molecules and the reinforcing agent form a strong bond that allows sliding, increasing the mechanical strength. However, excessive reinforcing agent significantly increases the tensile strength of the material and sharply reduces the elongation at break, which cannot meet product requirements.

[0136] According to one embodiment of the present application, the diaphragm is a single-layer structure, and the diaphragm is composed of a modified ethylene propylene rubber membrane layer.

[0137] In some specific embodiments of the present application, the diaphragm is a composite layer structure, and the diaphragm further includes a membrane layer made of at least one of a thermoplastic elastomer, an engineering plastic, and a thermosetting elastomer.

[0138] That is, when the diaphragm is a composite diaphragm, it includes at least one modified EPDM membrane layer. It may include a single modified EPDM membrane layer or multiple modified EPDM membrane layers. The multiple modified EPDM membrane layers may be arranged adjacent to each other or spaced apart. The specific arrangement method can be selected based on the specific design requirements of the sound-generating device.

[0139] The thermoplastic elastomer is at least one of a thermoplastic polyester elastomer, a thermoplastic polyurethane elastomer, a thermoplastic polyamide elastomer, and a silicone elastomer; the engineering plastic is at least one of polyetheretherketone, polyarylate, polyetherimide, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyethylene terephthalate, and polybutylene terephthalate; and the thermosetting elastomer is at least one of natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), chlorinated nitrile rubber (HNBR), ethylene-propylene rubber (EPDM), silicone rubber (Q), fluorosilicone rubber, fluororubber (FPM), polyurethane rubber (AU), acrylate rubber (ACM), ethylene-acrylate rubber (AEM), ethylene-vinyl acetate rubber (EVM), chlorosulfonated polyethylene rubber (CSM), epichlorohydrin rubber (CO), and polysulfide rubber.

[0140] Furthermore, when the diaphragm is a composite diaphragm, the composite diaphragm can be composed of a film layer made of at least one of a thermoplastic polyester elastomer, a thermoplastic polyurethane elastomer, a thermoplastic polyamide elastomer, and a silicone elastomer, and a modified ethylene propylene rubber film layer. The raw materials for the plastic polyurethane elastomer, thermoplastic polyamide elastomer, and silicone elastomer can be selected from a variety of sources and can be selected based on specific needs. The composite diaphragm composed of a film layer made of a plastic polyurethane elastomer, a thermoplastic polyamide elastomer, and a silicone elastomer and a modified ethylene propylene rubber film layer has excellent mechanical properties, maintaining a certain level of mechanical strength while also having a high damping value.

[0141] In summary, the diaphragm of the sound-emitting device according to the embodiment of the present application is prepared by adopting the modified EPDM rubber membrane layer as the raw material, and by controlling the amount of added inorganic hollow microbeads, not only the density of the diaphragm is reduced and the intermediate frequency Fr of the sound-emitting device is improved, but also the diaphragm can have excellent rebound resilience, and the vibration system has good vibration stability during the vibration and sound-emitting process. Furthermore, the sound-emitting device using the diaphragm of the present application can still maintain excellent acoustic performance under more harsh environments (high temperatures).

[0142] It should be noted that the diaphragm provided herein can be incorporated into any sound-generating device, such as the following typical sound-generating device: It includes a vibration system and a magnetic circuit system that cooperates with the vibration system. The vibration system includes a diaphragm and a voice coil coupled to one side of the diaphragm. When the sound-generating device is in operation, the voice coil is energized and, under the influence of the magnetic field of the magnetic circuit system, vibrates up and down, driving the diaphragm to vibrate. This vibration of the diaphragm produces sound.

[0143] According to an embodiment of the second aspect of the present application, a sound-producing device includes a vibration system and a magnetic circuit system coordinated with the vibration system. The vibration system includes a diaphragm and a voice coil coupled to one side of the diaphragm. The magnetic circuit system drives the voice coil to vibrate, thereby driving the diaphragm to produce sound. The diaphragm is the diaphragm of the aforementioned embodiment. Specifically, when the sound-producing device is in operation, after power is applied to the voice coil, the magnetic force of the magnetic circuit system causes the voice coil to vibrate up and down, driving the diaphragm to vibrate. The vibration of the diaphragm produces sound.

[0144] like Figure 3 and Figure 4 As shown, the sound-generating device includes a diaphragm 15 prepared according to the above-described embodiment of the present application. The diaphragm 15 can be composed of a rim portion 151 and a dome portion 152. A modified EPDM rubber membrane layer can be applied to the rim portion 151 of the diaphragm. Those skilled in the art can make corresponding adjustments based on actual product requirements, such as increasing the rim portion 151 toward the voice coil 11, positioning the dome portion 152 on the lower surface of the rim portion 151, and adding a centering support to the vibration system.

[0145] like Figure 5 and Figure 6As shown, the sound-producing device 100 according to the third embodiment of the present application includes a shell 10 and a magnetic circuit system 14 and a vibration system arranged in the shell 10. The vibration system includes a voice coil 11, a first diaphragm 12 and a second diaphragm 13. The top of the voice coil 11 is connected to the first diaphragm 12. The magnetic circuit system 14 drives the voice coil 11 to vibrate to drive the first diaphragm 12 to produce sound. The two ends of the second diaphragm 13 are respectively connected to the bottom of the shell 10 and the voice coil 11. The second diaphragm 13 is the diaphragm of the above embodiment.

[0146] That is, the sound-generating device 100 according to the embodiment of the present application may further include two diaphragms prepared according to the above-described embodiment of the present application, namely, a first diaphragm 12 and a second diaphragm 13. The first diaphragm 12 can be used to vibrate and produce sound, and the second diaphragm 13 can be used to balance the vibration of the voice coil 11. Specifically, when the sound-generating device 100 is in operation, after the voice coil 11 is energized, the magnetic field force of the magnetic circuit system 14 causes the voice coil 11 to vibrate up and down, thereby driving the first diaphragm 12 to vibrate. The vibration of the first diaphragm 12 can produce sound. The second diaphragm 13 can also vibrate up and down following the voice coil 11. Since the two ends of the second diaphragm 13 are respectively connected to the housing 10 and the bottom of the voice coil 11, the second diaphragm 13 can balance the vibration of the voice coil 11, prevent polarization of the voice coil 11, and thus improve the sound quality of the sound-generating device 100.

[0147] It should be noted that the first diaphragm 12 and the second diaphragm 13 may simultaneously adopt the diaphragms of the above embodiment of the present application, or one of the first diaphragm 12 and the second diaphragm 13 may adopt the diaphragm of the above embodiment of the present application. The present application does not impose any specific restrictions on this.

[0148] The diaphragm of the sound-generating device of the present application is described in detail below with reference to specific embodiments.

[0149] Comparative Example 1

[0150] The formula, calculated by mass, is shown in Table 5. After mixing according to this formula, a cross-linking reaction is performed to form the diaphragm material. The ethylene monomer content in the EPDM is 51%, and the third monomer, ENB (ethylidene norbornene), has a content of 7.7%.

[0151] Table 5

[0152] formula Dosage (parts by mass) EPDM (polymer synthesized from ethylene and propylene as basic monomers) 100 sulfur 1.5 Accelerator 2-mercaptobenzothiazole (M) 1.5 Accelerator zinc dibutyldithiocarbamate (BZ) (BZ) 1.5 zinc oxide 5 stearic acid 2 Silica 30 Coupling agent Si-69 2 paraffin oil 20 Antioxidant 4010 3

[0153] Example 1

[0154] The formula, calculated by mass, is shown in Table 6. After mixing according to the formula, a cross-linking reaction is performed to form the diaphragm material. The hollow glass microspheres have a size of 18 μm.

[0155] Table 6

[0156]

[0157]

[0158] Test indicators: breaking strength, breaking strain, compression set and density

[0159] Table 7 shows the performance test results of the diaphragm materials of Comparative Example 1 and Example 1, reflecting the effect of adding inorganic hollow microspheres on the breaking strength, breaking strain, compression permanent deformation and density of the diaphragm materials.

[0160] Test method:

[0161] (1) Tensile properties The tensile strength and elongation at break were determined according to ASTM D412-2016. The specimens were dumbbell-shaped, the tensile rate was 500 mm / min, and each group of samples was tested 5 times to obtain the average value.

[0162] (2) Test the compression set of vulcanized rubber according to GB / T7759-1996 (Method B) at a test temperature of 130°C.

[0163] The physical properties of conventional EPDM rubber and EPDM rubber with inorganic hollow microspheres added in this application are compared as follows:

[0164] Table 7

[0165]

[0166] As can be seen in Table 7, the addition of hollow glass microspheres increases the fracture strength and reduces the fracture strain of the diaphragm material of this application. In other words, the modified EPDM rubber membrane layer of this application has excellent mechanical properties, fully meeting the mechanical requirements of diaphragm processing, and the diaphragm product is less likely to experience reliability issues such as film breakage during use.

[0167] Furthermore, due to the low density of the inorganic hollow microspheres, the density of the modified EPDM rubber is significantly reduced after their addition. Furthermore, the compression set of the modified EPDM rubber film layer in Example 1 of this application is significantly less than that of the conventional EPDM rubber film layer in Comparative Example 1. Therefore, the rubber film layer in this example exhibits superior resilience compared to an EPDM rubber film layer without the addition of inorganic hollow microspheres.

[0168] That is to say, compared with conventional diaphragms, the density of the diaphragm of the present application has been greatly reduced, which not only improves the mid-frequency sensitivity of the sound-emitting device, but also the diaphragm of the present application has a smaller permanent compression deformation than conventional EPDM rubber diaphragms, indicating that it has better rebound resilience. Rebound resilience is an important indicator for measuring the acoustic vibration stability of rubber diaphragm products. The better the rebound resilience, the better its acoustic vibration stability. Therefore, the sound-emitting device using the diaphragm of the present application can still maintain excellent acoustic performance under more harsh environments (high temperature).

[0169] Although some specific embodiments of the present application have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A diaphragm of a sound-generating device, characterized in that: The diaphragm comprises at least one modified EPDM rubber membrane layer, which is prepared by mixing inorganic hollow microspheres, additives and a polymer synthesized from ethylene and propylene as basic monomers to form a mixed rubber and then undergoing a cross-linking reaction; The particle size of the inorganic hollow microspheres is 1 μm to 60 μm, and the distribution density of the inorganic hollow microspheres in the modified EPDM rubber film layer is 0.15 g / cm 3 ~0.9g / cm 3 The content of the inorganic hollow microspheres accounts for 5wt% to 40wt% of the total amount of the mixed rubber. The modified EPDM rubber film layer is placed at 130°C for 70 hours and has a compression permanent deformation of ≤55% under a compression rate of 25%.

2. The diaphragm of the sound-generating device according to claim 1, wherein: The density of the modified EPDM rubber film layer is 0.4 g / cm 3 ~1.1g / cm 3 .

3. The diaphragm of the sound-generating device according to claim 1, characterized in that The tensile strength of the modified EPDM rubber film layer is 3MPa to 35MPa.

4. The diaphragm of the sound-generating device according to claim 1, wherein: The compressive strength of the inorganic hollow microspheres is ≥10 MPa.

5. The diaphragm of the sound-generating device according to claim 1, wherein: The glass transition temperature of the modified ethylene propylene rubber film layer is ≤-20°C.

6. The diaphragm of the sound-generating device according to claim 1, characterized in that A coupling agent is provided on the surface of the inorganic hollow microspheres, and the coupling agent modifies the surface of the inorganic hollow microspheres so that the inorganic hollow microspheres are interfacially bonded to the matrix of the polymer synthesized from ethylene and propylene as basic monomers; Wherein, the coupling agent is at least one of a silane coupling agent, a titanate coupling agent and an aluminate coupling agent.

7. The diaphragm of the sound-generating device according to claim 6, characterized in that: The content of the coupling agent accounts for 1 wt% to 10 wt% of the added amount of the inorganic hollow microspheres.

8. The diaphragm of the sound-generating device according to claim 1, characterized in that The additives include cross-linking agents, reinforcing agents and antioxidants, The cross-linking agent is at least one of a sulfur and an organic peroxide vulcanization system; the reinforcing agent is at least one of carbon black, white carbon black, graphene oxide, montmorillonite, talc, clay, mica powder, feldspar powder, sodium alginate, magnetic powder, and diatomaceous earth; and the antioxidant is at least one of antioxidant N-445, antioxidant 246, antioxidant 4010, antioxidant SP, antioxidant RD, antioxidant ODA, antioxidant OD, and antioxidant WH-02.

9. The diaphragm of the sound-generating device according to claim 8, characterized in that: The content of the cross-linking agent accounts for 0.5wt% to 4.5wt% of the rubber mix, the content of the reinforcing agent accounts for 5wt% to 65wt% of the rubber mix, and the content of the antioxidant accounts for 0.1wt% to 5wt% of the rubber mix.

10. The diaphragm of the sound-generating device according to claim 1, wherein: The diaphragm is a single-layer structure, and the diaphragm is composed of a layer of modified ethylene propylene rubber membrane.

11. The diaphragm of the sound-generating device according to claim 1, wherein: The diaphragm is a composite layer structure, and the diaphragm further comprises a membrane layer made of at least one of thermoplastic elastomer, engineering plastic and thermosetting elastomer.

12. A sound-generating device, characterized in that: It includes a vibration system and a magnetic circuit system coordinated with the vibration system, the vibration system includes a diaphragm and a voice coil coupled to one side of the diaphragm, the magnetic circuit system drives the voice coil to vibrate to drive the diaphragm to make sound, and the diaphragm is the diaphragm described in any one of claims 1-11.

13. A sound-generating device, characterized in that: It includes a shell and a magnetic circuit system and a vibration system arranged in the shell, the vibration system includes a voice coil, a first diaphragm and a second diaphragm, the top of the voice coil is connected to the first diaphragm, the magnetic circuit system drives the voice coil to vibrate to drive the first diaphragm to make sound, the two ends of the second diaphragm are respectively connected to the shell and the bottom of the voice coil, and the second diaphragm is the diaphragm according to any one of claims 1 to 11.

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