WO2021082244A1

WO2021082244A1 - Vibration diaphragm for miniature sound production device, and miniature sound production device

Info

Publication number: WO2021082244A1
Application number: PCT/CN2019/128039
Authority: WO
Inventors: 惠冰; 凌风光; 李春; 刘春发
Original assignee: 歌尔股份有限公司
Priority date: 2019-10-31
Filing date: 2019-12-24
Publication date: 2021-05-06
Also published as: CN110784805A

Abstract

Disclosed are a vibration diaphragm for a miniature sound production device, and a miniature sound production device. The vibration diaphragm is made of a natural rubber comprising a polyisoprene. The mass fraction of the polyisoprene in the natural rubber is 90%-95%. The vibration diaphragm has a glass transition temperature ranging from -95 to -30ºC. The vibration diaphragm provided in the present invention has a better structural stability, polarization resistance capability and low-frequency sensitivity; and the miniature sound production device provided in the present invention has a better acoustic performance.

Description

Vibration diaphragm for miniature sounding device and miniature sounding device

Technical field

The present invention relates to the technical field of electronic products, in particular, the present invention relates to a diaphragm for a miniature sounding device and a miniature sounding device.

Background technique

With the advancement of science and technology, the application of electronic products has become more and more extensive, especially the increasingly miniaturized personal consumer electronics market such as smart phones, tablet computers, and smart watches. Along with this, there is an increasing demand for micro-sounding devices used in personal consumer electronic products.

Most of the existing miniature sounding devices use single-layer or multi-layer composite engineering plastics or thermoplastic elastomers as the diaphragm material. Play the role of supporting the vibrating part and providing elasticity. However, due to the limitation of the vibration space, the total thickness of the existing diaphragm usually needs to be controlled within 100 μm, while the thickness of the single-layer membrane in the composite diaphragm usually needs to be controlled within 20 μm.

If the diaphragm of the diaphragm is thin, the diaphragm is prone to stress concentration points during the vibration process, and in the case of repeated vibration, the stress concentration position of the diaphragm will become extremely fragile. At locations where the stress is concentrated, the diaphragm is not only prone to deformation but also prone to breakage of the diaphragm, resulting in deterioration of the acoustic performance of the diaphragm or complete failure of the entire diaphragm. In addition, the conventional diaphragm has poor high temperature resistance. In harsh environments, the material performance decreases and the vibration state becomes worse.

It can be seen that the overall performance of the above-mentioned diaphragm is poor and cannot meet the overall performance requirements of the miniature sound generating device. Therefore, providing a diaphragm for a miniature sounding device with strong comprehensive performance and high reliability has become a major technical problem faced by the technical field.

Summary of the invention

An object of the present invention is to provide a diaphragm for a micro-sounding device and a micro-sounding device, the diaphragm having better structural stability, anti-polarization ability and low-frequency sensitivity; the micro-sounding device has better acoustics performance.

According to the first aspect of the present invention, there is provided a diaphragm for a miniature sounding device, the diaphragm is made of natural rubber, the natural rubber includes polyisoprene, and the polyisoprene in the natural rubber The mass fraction of the diene is 90-95%, and the glass transition temperature of the diaphragm is -95 to -30°C.

Optionally, the natural rubber is mixed with a vulcanizing agent, the vulcanizing agent includes at least one of sulfur, peroxide, and resin, the natural rubber itself is 100 parts by mass, and the vulcanizing agent itself The number of parts by mass is 0.5-15 parts.

Optionally, the mass parts of the vulcanizing agent itself is 0.5-5 parts.

Optionally, the natural rubber is mixed with a reinforcing agent, and the reinforcing agent includes at least one of carbon black, silicon dioxide, calcium carbonate, barium sulfate, organic montmorillonite, and unsaturated carboxylic acid metal salt The mass parts of the natural rubber itself is 100 parts, and the mass parts of the reinforcing agent itself is 2-80 parts.

Optionally, the hardness of the natural rubber diaphragm is 30-85A.

Optionally, the elongation at break of the natural rubber diaphragm is greater than 150%.

Optionally, when the constant elongation rate of the diaphragm is 25%, the elastic recovery rate of the diaphragm is greater than 90%.

Optionally, the loss factor of the natural rubber diaphragm at room temperature is greater than 0.06.

Optionally, the diaphragm is a single-layer diaphragm, and the single-layer diaphragm is composed of a natural rubber film layer;

Alternatively, the diaphragm is a composite diaphragm, the composite diaphragm includes two, three, four or five diaphragm layers, and the composite diaphragm includes at least one natural rubber diaphragm.

Optionally, the thickness of the natural rubber film layer is 10-200 μm.

According to a second aspect of the present invention, there is provided a micro sounding device, comprising a micro sounding device main body and the diaphragm, the diaphragm being arranged on the micro sounding device main body, the diaphragm being configured to be capable of Vibration sounds.

The technical effect of the present invention is that the present invention discloses a diaphragm for a micro-sound device and a micro-sound device. The diaphragm is made of natural rubber, and the diaphragm has better structural stability and anti-polarization. Ability and low-frequency sensitivity; the miniature sound generating device has better acoustic performance.

Through the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, other features and advantages of the present invention will become clear.

Description of the drawings

The drawings incorporated in the specification and constituting a part of the specification illustrate the embodiments of the present invention, and together with the description are used to explain the principle of the present invention.

Figure 1 is a test curve of vibration displacement at different frequencies for different parts of the diaphragm of a miniature sounding device according to an embodiment of the present invention;

Figure 2 is the test curve of the vibration displacement of different parts of the conventional diaphragm at different frequencies;

Fig. 3 is a harmonic distortion (THD) test curve of a diaphragm and a conventional PEEK diaphragm according to an embodiment of the present invention;

Fig. 4 is a stress-strain curve of a diaphragm and a conventional PEEK diaphragm according to an embodiment of the present invention;

Fig. 5 is a test curve (SPL curve) of loudness at different frequencies of a diaphragm and a conventional diaphragm according to an embodiment of the present invention.

Detailed ways

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

The following description of at least one exemplary embodiment is actually only illustrative, and in no way serves as any limitation to the present invention and its application or use.

The technologies, methods, and equipment known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be regarded as part of the specification.

In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiment may have different values.

It should be noted that similar reference numerals and letters indicate similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

The main component of natural rubber is polyisoprene, and the rest are non-rubber substances such as protein, fatty acid, ash, and sugars. Because polyisoprene has low molecular cohesive energy and relatively flexible molecular chain, natural rubber material itself has good elasticity and excellent low temperature resistance. The diaphragm can ensure that the diaphragm has good resistance to deformation Ability and has excellent anti-fatigue properties. The natural rubber diaphragm can not only maintain excellent elasticity during long-term vibration, but also has excellent anti-fatigue properties, so it has excellent reliability.

The invention provides a diaphragm for a miniature sounding device, and the diaphragm is made of natural rubber. The natural rubber includes polyisoprene, and the mass fraction of polyisoprene in the natural rubber is 90-95%.

Specifically, the molecular structure of the polyisoprene is as follows:

In the above formula, n is a natural number.

The natural rubber diaphragm provided by the present invention is in a highly elastic state at room temperature, the molecular chain is easy to move, the friction between molecules is large, and it has good damping performance, and its loss factor at room temperature is greater than 0.06, preferably greater than 0.1.

Excellent damping performance, so that the diaphragm has a lower quality factor Q. The damping of the diaphragm is improved, the vibration system has a strong ability to suppress the polarization phenomenon during the vibration process, and the vibration consistency is good. The commonly used engineering plastic diaphragm has low damping, and its loss factor is generally less than 0.01, and the damping is small.

Fig. 1 is a test curve for the vibration displacement of different parts of the diaphragm of a miniature sounding device at different frequencies according to an embodiment of the present invention. Figure 2 is the test curve of the vibration displacement of different parts of the conventional diaphragm at different frequencies.

Among them, the diaphragm is a rectangular folded ring diaphragm. The abscissa is the frequency (Hz), and the ordinate is the loudness displacement (mm). Take points at the edge position and the center position of the center of the diaphragm for testing.

It can be seen that the curves in Figure 1 are more concentrated, while the curves in Figure 2 are more scattered. This shows that the vibration consistency of each part of the diaphragm in the embodiment of the present invention is better, and during the vibration process, the vibration of the diaphragm is less, and the sound quality and listening stability are more excellent.

Compared with engineering plastics, the natural rubber diaphragm provided by the present invention has a wider elastic area. When the strain of the diaphragm occurs in this area, after the external force is removed, the diaphragm has excellent resilience. When the elongation is 25%, the elastic recovery rate is greater than 90%. During the vibration process of the diaphragm, there is less swinging vibration, and the sound quality and listening stability are better.

Fig. 3 is a harmonic distortion (THD) test curve of a diaphragm of an embodiment of the present invention and a conventional PEEK diaphragm. It can be seen from Fig. 3 that the diaphragm of an embodiment of the present invention has a better performance than a conventional PEEK diaphragm. Low THD (Total Harmonic Distortion), which shows that the diaphragm of the present invention has better anti-polarization ability and better sound quality.

Optionally, the natural rubber is mixed with a vulcanizing agent, and the vulcanizing agent specifically includes at least one of sulfur, peroxide, and resin. The addition of vulcanizing agent helps to form cross-linking points in the natural rubber and improve the degree of cross-linking of the polymer. As the amount of vulcanizing agent increases, the degree of cross-linking of natural rubber increases, the movement of molecular chains is restricted, the glass transition temperature increases, and the elongation at break decreases. Therefore, when the mass parts of the natural rubber itself is 100 parts, the mass parts of the vulcanizing agent itself needs to be controlled within 0.5-15 parts. Preferably, the mass parts of the vulcanizing agent itself is 0.5-5 parts. In the case of the above mass parts, it can not only ensure that the natural rubber has an appropriate degree of crosslinking, but also meet the requirements for the glass transition temperature and mechanical properties of the natural rubber diaphragm material.

Due to the high molecular weight of natural rubber, the polyisoprene molecular cohesive energy of natural rubber is low, and its molecular chain is relatively flexible, and it has excellent low temperature resistance. On this basis, in order to keep the natural rubber diaphragm in a highly elastic state and good resilience at room temperature, its glass transition temperature needs to be controlled within the range of -95 to -30°C. In a certain range, the lower the glass transition temperature, the diaphragm can work normally at a lower temperature.

In order to ensure that the natural rubber diaphragm can always maintain good rubber elasticity when the temperature is lower than -30°C in the extreme cold area, the miniature sound device exhibits higher sound quality and reduces the risk of diaphragm damage in a low temperature environment. It is necessary to adjust the mass fraction of polyisoprene in the natural rubber to achieve the purpose of controlling the glass transition temperature of the natural rubber diaphragm in the range of -90 to -50°C.

Optionally, the natural rubber has low cohesion and excellent toughness, and by adding a suitable amount of vulcanizing agent, the elongation at break of the natural rubber can be greater than 150%, preferably greater than 200%, and has a higher elongation at break. The length ratio makes the diaphragm less prone to reliability problems such as membrane rupture when used in a miniature sounding device.

Fig. 4 is a stress-strain curve of a diaphragm and a conventional PEEK diaphragm of an embodiment of the present invention. It can be seen from Fig. 4 that under the same stress, the strain of the diaphragm provided by the embodiment of the present invention is significantly greater than that of the conventional PEEK diaphragm. membrane. This indicates that the Young's modulus of the diaphragm provided by the embodiment of the present invention is significantly smaller than that of the conventional PEEK diaphragm.

In addition, the PEEK diaphragm has an obvious yield point, which is about 0.4-0.5% strain. However, the diaphragm provided by the present invention does not have a yield point, which indicates that the diaphragm provided by the present invention has a wider elastic area and has excellent resilience performance.

The natural rubber diaphragm has good flexibility, for example, the elongation at break is ≥150%. This makes the vibration displacement of the diaphragm larger and louder. And the reliability and durability are good. The better the flexibility of the diaphragm material and the greater the elongation at break, the stronger the ability of the diaphragm to resist damage. When the diaphragm is vibrating in a state of large amplitude, the diaphragm material produces a large strain, and there is a risk of membrane fold, membrane crack or membrane rupture when vibrating for a long time. The diaphragm of the present invention using natural rubber as the base material has good flexibility and reduces the risk of damage to the diaphragm.

Optionally, since the natural rubber diaphragm material has a stable cross-linked structure, the diaphragm has a higher operating temperature range, and can work continuously for more than 3 days at 120°C, which can meet the needs of micro-sound devices for high and low temperatures. In actual use, there is no risk of structural collapse due to excessive temperature.

Optionally, the natural rubber is mixed with a reinforcing agent, and the reinforcing agent includes at least one of carbon black, silicon dioxide, calcium carbonate, barium sulfate, organic montmorillonite, and unsaturated carboxylic acid metal salt In the case where the mass parts of the natural rubber is 100 parts, the mass parts of the reinforcing agent itself is 2-80 parts. Preferably, the mass parts of the reinforcing agent itself is 5-60 parts.

The surface of the reinforcing agent has groups such as hydrogen, carboxyl, lactone, free radical, and quinone that can undergo reactions such as substitution, reduction, and oxidation. After the reinforcing agent is mixed into the natural rubber, due to the strong interaction between the reinforcing agent and the natural rubber interface, when the natural rubber is stressed, the molecular chain is easier to slide on the surface of the reinforcing agent particles, but it is not easy to compensate. The strong agent particles are separated, the natural rubber and the reinforcing agent particles form a strong bond that can slide, and the mechanical strength is increased; and the addition of a small amount of the reinforcing agent increases the strength of the natural rubber cross-linking bond while strengthening the natural rubber. The degree of movement between molecular chains can effectively reduce the glass transition temperature of natural rubber and ensure the long-term normal use of natural rubber under low temperature conditions.

Taking carbon black as an example, carbon black is an amorphous structure, and particles form aggregates through physical and chemical bonding with each other. The primary structure of carbon black is composed of aggregates, and there are van der Waals forces or hydrogen bonds between the aggregates, which can aggregate into a spatial network structure, that is, the secondary structure of carbon black. Carbon black has the above-mentioned groups on the surface. Carbon black particles can form the above-mentioned relationship with the molecular chain of natural rubber to enhance the mechanical strength of natural rubber.

The strength of natural rubber materials is mainly adjusted by mixing reinforcing agents, but if the mechanical strength is too high, it will cause the resonance frequency of the miniature sound device to be too high and the low-frequency response ability to decrease. Therefore, the hardness range of the natural rubber diaphragm can be 30-85A, preferably 35-80A. The mechanical strength of the natural rubber diaphragm at room temperature can reach 0.5-50 MPa, preferably 1-30 MPa.

The resonance frequency F0 of the miniature sound device is proportional to the modulus and thickness of the diaphragm. For natural rubber, its modulus is directly proportional to its hardness. Therefore, the hardness can be used to reflect the modulus of the natural rubber diaphragm. The higher the strength and hardness of the rubber diaphragm material, the higher the F0 of the diaphragm material, which leads to a reduction in the loudness of the miniature sound device and poor bass. Table 1 shows the F0 values of diaphragms with the same thickness but different hardness. It can be seen from Table 1 that as the hardness of the diaphragm material increases, F0 increases sharply.

Table 1 F0 values of diaphragms with the same thickness but different hardness

硬度(A)Hardness (A)	3030	3535	5050	8080	8585
F0(Hz)F0(Hz)	529529	571571	694694	921921	10511051

The diaphragm for the miniature sounding device provided by the present invention is a folded ring diaphragm or a flat diaphragm. The resonant frequency F0 of the miniature sounding device is proportional to the Young's modulus and thickness of the diaphragm. The change of F0 can be achieved by changing the thickness and Young's modulus of the diaphragm. The specific adjustment principle is as follows:

Among them, Mms is the equivalent vibration mass of the miniature sounding device, and Cms is the equivalent compliance of the miniature sounding device:

Among them, C _m1 is the elastic wave compliance, and C _m2 is the diaphragm compliance. When designing without bouncing waves, the equivalent compliance of the miniature sounding device is the diaphragm compliance:

Where W is the total width of the folded ring of the diaphragm, t is the thickness of the diaphragm; dvc is the outer diameter of the diaphragm and voice coil; E is the Young's modulus of the diaphragm material; a ₁ and a ₂ are the correction coefficients, The value of a ₁ depends on the shape of the diaphragm base material, a ₂ is equal to h (height of the ring)/W; u is the Poisson's ratio of the diaphragm material.

It can be seen that, in order to obtain full bass and comfortable hearing, while the miniature sound device has a lower F0, the diaphragm should have sufficient rigidity and damping. Those skilled in the art can adjust the size of F0 by adjusting the hardness and thickness of the diaphragm. Preferably, the Shore hardness of the diaphragm is preferably 35-80A. The thickness of the diaphragm is 30-120 μm. This enables the resonance frequency F0 of the miniature sound device to reach 150-1500 Hz. The low frequency performance of the miniature sound device is excellent.

Fig. 5 is a test curve (SPL curve) of loudness at different frequencies of a diaphragm and a conventional diaphragm according to an embodiment of the present invention. The diaphragm is a folded ring diaphragm. The abscissa is frequency (Hz), and the ordinate is loudness.

It can be seen from FIG. 5 that the diaphragm provided by the embodiment of the present invention is consistent with the conventional diaphragm miniature sounding device F0, and both are 830 Hz, but the low-frequency sensitivity of the diaphragm provided by this embodiment is higher than that of the conventional diaphragm. In other words, the miniature sounding device using the diaphragm of the embodiment of the present invention has higher loudness and comfort.

Optionally, the diaphragm is a single-layer diaphragm or a multi-layer composite diaphragm. The single-layer diaphragm is composed of a layer of natural rubber diaphragm; and the composite diaphragm is a diaphragm formed by successively stacking multiple layers of natural rubber diaphragm. Alternatively, the composite diaphragm may include at least one natural rubber diaphragm layer, which is laminated and composited with diaphragm layers made of other materials to form a composite diaphragm made of multiple materials. The composite diaphragm includes two layers, three layers, four layers or five layers, which is not limited in the present invention.

For the natural rubber film layer, its thickness may be 10-200 μm, preferably 30-120 μm. When the thickness of the natural rubber film layer is within this range, it can better meet the performance requirements and assembly space requirements of the miniature sounding device.

Optionally, the natural rubber diaphragm is prepared by molding-injection molding or air pressure molding. Because the natural rubber diaphragm of the present invention has a very low glass transition temperature, and the diaphragm material has good strength and toughness, It can be used for a long time at high temperature, so the diaphragm can be quickly formed by simple molding-injection molding or air pressure molding, which improves production efficiency.

The present invention also provides a micro-sounding device, comprising a micro-sounding device main body and a diaphragm made of natural rubber. The diaphragm is arranged on the micro-sounding device main body, and the diaphragm is configured to be capable of Vibration produces sound through vibration. A coil, a magnetic circuit system and other components may be arranged in the main body of the miniature sound generating device, and the diaphragm is driven to vibrate through electromagnetic induction.

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present invention. The scope of the invention is defined by the appended claims.

Claims

A diaphragm for a miniature sounding device, characterized in that the diaphragm is made of natural rubber, the natural rubber includes polyisoprene, and the mass fraction of polyisoprene in the natural rubber is 90-95%, the glass transition temperature of the vibrating diaphragm is in the range of -95 to -30°C.
The diaphragm for a miniature sounding device according to claim 1, wherein the natural rubber is mixed with a vulcanizing agent, and the vulcanizing agent includes at least one of sulfur, peroxide, and resin, The mass parts of the natural rubber itself is 100 parts, and the mass parts of the vulcanizing agent itself is 0.5-15 parts.
The diaphragm for a miniature sounding device according to claim 2, wherein the mass parts of the vulcanizing agent itself is 0.5-5 parts.
The diaphragm for a miniature sounding device according to claim 1, wherein the natural rubber is mixed with a reinforcing agent, and the reinforcing agent includes carbon black, silicon dioxide, calcium carbonate, and sulfuric acid. At least one of barium, organic montmorillonite, and unsaturated carboxylic acid metal salt, the mass parts of the natural rubber itself is 100 parts, and the mass parts of the reinforcing agent itself is 2-80 parts.
The diaphragm for a miniature sounding device according to claim 4, wherein the hardness of the diaphragm is in the range of 30-85A.
The diaphragm for a miniature sounding device according to claim 1, wherein the elongation at break of the diaphragm is greater than 150%.
The diaphragm for a miniature sounding device according to claim 1, wherein when the constant elongation rate of the diaphragm is 25%, the elastic recovery rate of the diaphragm is greater than 90%.
The diaphragm for a miniature sounding device according to claim 1, wherein the loss factor of the diaphragm at room temperature is greater than 0.06.
The diaphragm for a miniature sounding device according to claim 1, wherein the diaphragm is a single-layer diaphragm, and the single-layer diaphragm is composed of a natural rubber film layer;

Alternatively, the diaphragm is a composite diaphragm, and the composite diaphragm includes two, three, four or five diaphragm layers, and the composite diaphragm includes at least one natural rubber diaphragm.
The diaphragm for a miniature sounding device according to claim 9, wherein the thickness of the natural rubber film layer is 10-200 μm.
A miniature sounding device, comprising a main body of the miniature sounding device and the diaphragm according to any one of claims 1-10, the diaphragm being arranged on the main body of the miniature sounding device, and the diaphragm being configured To vibrate and make sound.