JP2005020646A - Damper for speaker, manufacturing method thereof, and speaker using damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a damper for speaker which has superior durability and reliability, is applicable to mass production, and can obtain a speaker having superior sound quality. <P>SOLUTION: This damper for speaker is molded of a thermoplastic resin foam, and the average diameter of a bubble of this foam is 0.1-10 μm. Preferably, the cellular density of this foam is 10<SP>9</SP>-10<SP>15</SP>pcs./cm<SP>3</SP>, the specific gravity is less than 1.0 g/cm<SP>3</SP>, the tensile strength is 700 MPa or more, and the flexural modulus is 800 MPa or more. The thermoplastic resin constituting this foam is selected from a group consisting of a PET resin, PC resin, PPS resin, PETG resin, PBT resin, PS resin, thermoplastic elastomer and alloys of these materials. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３１】
（比較例１）
発泡ガスを用いなかったこと以外は実施例１と同様にして、図１のようなダンパーを作製した。得られたダンパーを用いて、口径１２ｃｍのスピーカーを作製し、音圧周波数特性を測定した。測定結果を実施例１の結果と併せて図２に示す。また、内部損失を通常の方法で測定したところ０．０３であった。さらに、実施例１と同様にして、耐久性の評価に供した。結果を上記表１に示す。
【００３２】
図２から明らかなように、実施例１のスピーカーは、比較例１のスピーカーに比べて、全帯域において音圧が高く、かつ、２ｋＨｚ付近のピークディップが顕著に改善されていることがわかる。これは、実施例１のダンパーが比較例１のダンパーに比べて軽量であること、および、発泡構造を有するために共振が起こりにくいことに起因すると考えられる。さらに、表１から明らかなように、実施例１のスピーカーは、比較例１のスピーカーに比べて耐久性が格段に優れている。これは、実施例１のダンパーが微細な発泡構造を有することに起因して、アーム部の応力集中が緩和するためであると考えられる。加えて、内部損失の測定結果から明らかなように、実施例１のダンパーは、比較例１のダンパーに比べて不要な音の放射が格段に少ないことがわかる。
【００３３】
【発明の効果】
以上のように、本発明によれば、平均径が０．１〜１０μｍという微小な気泡を有する発泡体を用いてダンパーを形成することにより、優れた耐久性および信頼性を有し、量産に適用可能であり、かつ、優れた音質を有するスピーカーが得られるダンパーを提供することができる。
【図面の簡単な説明】
【図１】本発明の好ましい実施形態によるダンパーの一例である蝶ダンパーを説明するための概略図である。
【図２】本発明の実施例のダンパーを用いたスピーカーと比較例のスピーカーについて音圧周波数特性を比較して示すグラフである。
【図３】本発明と同様の方法で得られた発泡体の気泡の状態を説明するＳＥＭ写真の模式図である。
【符号の説明】
１ 外周部
２ 内周部
３ アーム部
１００ 蝶ダンパー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a damper for a speaker. More specifically, the present invention relates to a damper that has a characteristic with little change with time, has excellent durability and reliability, can be applied to mass production, and provides a speaker having excellent sound quality.
[0002]
[Prior art]
The basic characteristics of speaker dampers are excellent retention stability of the voice coil bobbin, reciprocating the diaphragm faithfully according to the stress generated by the voice coil, and no sound from the damper. Desired. As an example of a conventional damper, a woven fabric impregnated with a thermosetting resin has been proposed. As the woven fabric, cotton, aramid fiber, a woven fabric made of a blended yarn of para-type aramid fiber and meta-type aramid fiber, or the like is used. As the thermosetting resin, a phenol resin is typically used. Such a damper is obtained by dipping a thermosetting resin on a woven fabric and molding and curing it in a heating mold.
[0003]
However, in such a damper, all the thermosetting resins used for shape imparting have low elasticity, are very brittle, and have low affinity with fibers, so they are hard immediately after molding and vibrate when used. Will gradually become softer. That is, there is a problem that the characteristics change with time. In addition, the deformation of bending and bending cannot be followed because of its low elasticity, and if it is used for a long time, the intersection of the woven fabric will crack. That is, such a damper has insufficient durability. Furthermore, the uncured part of the thermosetting resin may remain due to uneven temperature during molding, in such a case, the adhesion between the fibers constituting the woven fabric becomes insufficient, as a result, There is also a problem that the linearity of the load / amplitude of the damper is insufficient. In addition, the woven fabric damper has a large surface area due to its structure, so there is a problem in that unnecessary sound radiated when vibrating following the voice coil is increased, resulting in a sense of distortion. is there.
[0004]
In order to reduce the above unnecessary noise, a butterfly damper in which a thermoplastic elastomer or the like is injection-molded has been proposed. The butterfly damper is a damper having a shape in which an outer peripheral portion and an inner peripheral portion are connected by a plurality of arm portions. Since the butterfly damper mainly vibrates only at the arm portion, the surface area of the vibrating portion is small, and as a result, unnecessary sound radiation can be reduced. However, the butterfly damper concentrates stress on the arm during vibration, and breaks easily when the amplitude is large. In order to solve such a problem, dampers having arm portions having various shapes have been proposed, but all of them have a problem that sound pressure is lowered because of their high specific gravity.
[0005]
On the other hand, a foamed resin sheet is known as a lightweight and highly rigid material, and a diaphragm using such a foamed resin sheet has also been proposed (see, for example, Patent Documents 1 and 2).
[0006]
[Patent Document 1]
JP 2002-300690 A [Patent Document 2]
Japanese Patent Laid-Open No. 2003-125497
However, it is difficult to apply the techniques described in Patent Documents 1 and 2 to a damper. This is because a foam having a uniform distribution and sufficiently fine bubbles cannot be obtained. Specifically, the technique described in Patent Document 1 allows an unreacted gas to penetrate into an unstretched resin sheet under pressure, then releases the pressure to obtain a foam, and heats and pressurizes the foam to create a vacuum. A diaphragm is obtained by molding. A foam produced by such a manufacturing method can only make bubbles smaller than 10 μm at most. As a result, although it is not a problem with the diaphragm, in the case of a damper that must be formed by punching, bubbles appear on the outer surface of the arm portion. As a result, at the time of a large input, there is a high possibility that the bubble portion becomes a crack base and breaks. In addition, according to this technique, since the gas is directly permeated into the sheet, it takes a very long time to complete the permeation, and the production efficiency is extremely insufficient.
[0008]
The technique described in Patent Document 2 is to form a crystalline resin into a diaphragm shape, infiltrate gas under high pressure, release the pressure, and further heat the molded body to a softening point or higher and a melting point or lower. To obtain a foam. According to this technique, since the surface portion has a high degree of crystallinity, it does not foam so much and mainly the inside foams. Therefore, the problem of Patent Document 1 can be improved to some extent. However, even with this technique, since the bubbles can be miniaturized only up to about 10 μm, there still remains a problem that mechanical strength (particularly durability) is insufficient when applied to a damper. Furthermore, since this technique requires a large-scale high-pressure facility at the time of molding, the work efficiency is poor and it is very difficult to apply to mass production.
[0009]
As described above, there is a strong demand for a damper that can provide a speaker having excellent durability and reliability, applicable to mass production, and having excellent sound quality.
[0010]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described conventional problems, and the object thereof is excellent durability and reliability, applicable to mass production, and excellent sound quality. It is to provide a damper from which a speaker can be obtained.
[0011]
[Means for Solving the Problems]
The damper of this invention is shape | molded from the thermoplastic resin foam, and the average diameter of the bubble of this foam is 0.1-10 micrometers.
[0012]
In a preferred embodiment, the foam has a cell density of 10 ⁹ to 10 ¹⁵ cells / cm ³ .
[0013]
In a preferred embodiment, the thermoplastic resin constituting the foam is selected from the group consisting of PET resin, PC resin, PPS resin, PETG resin, PBT resin, PS resin, thermoplastic elastomer, and alloys thereof. .
[0014]
In a preferred embodiment, the foam has a specific gravity of 1.0 g / cm ³ or less, a tensile strength of 700 MPa or more, and a flexural modulus of 800 MPa or more.
[0015]
In a preferred embodiment, the damper according to the present invention includes an outer peripheral portion, an inner peripheral portion, and a plurality of arm portions that connect the outer peripheral portion and the inner peripheral portion.
[0016]
According to another aspect of the present invention, a speaker is provided. The speaker of this invention is equipped with the said damper.
[0017]
According to still another aspect of the present invention, a method for manufacturing a damper is provided. This manufacturing method includes a step of melting a thermoplastic resin, a step of adding an inert gas in a supercritical state to the molten thermoplastic resin, and maintaining the pressure of the inert gas at a critical pressure or higher. A step of lowering the temperature of the molten thermoplastic resin, and a step of injecting a predetermined amount of the thermoplastic resin having the lowered temperature into the mold and simultaneously performing molding and foaming in the mold.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The damper according to a preferred embodiment of the present invention is formed from a thermoplastic resin foam. The average cell diameter of the foam is 0.1 to 10 μm, preferably 1 to 7 μm. One of the characteristics of the present invention is to use a foam having such fine bubbles, and this makes it possible to obtain a damper that is lightweight and excellent in mechanical strength. In particular, such fine bubbles are effective in improving durability and reliability. In addition, such fine bubbles have an effect of increasing the internal loss (tan δ) that is regarded as important in the acoustic member, so that the sound emitted from the damper when the voice coil / diaphragm / damper vibrates. Can be reduced. The cell density of the foam is preferably 10 ⁹ to 10 ¹⁵ pieces / cm ³ , and more preferably 10 ¹⁰ to 10 ¹⁴ pieces / cm ³ . The expansion ratio corresponding to such bubble density is 1.2 to 3.0 times. This is because the balance between strength and weight reduction can be further improved by having the cell density in such a range. Specifically, the tensile strength is preferably 700 MPa or more, more preferably 800 MPa or more, flexural elasticity while reducing the specific gravity to preferably 1.0 g / cm ³ or less, more preferably 0.9 g / cm ³ or less. A strength of 800 MPa or more, more preferably 1000 MPa or more can be achieved. The lower limit of practical specific gravity is 0.3 g / cm ³ , the upper limit of the achievable tensile strength is 1000 MPa, and the upper limit of the flexural modulus is 1300 MPa.
[0019]
Examples of the thermoplastic resin constituting the thermoplastic resin foam include polyethylene terephthalate (PET) resin, polycarbonate (PC) resin, polyphenylene sulfide (PPS) resin, amorphous PET copolymer (PETG) resin, polybutylene terephthalate ( PBT) resin, polystyrene (PS) resin, and thermoplastic elastomer. These resins may be used alone or as two or more alloys. Preferred resins are PET resin, PC resin, and thermoplastic elastomer. This is because any resin can be finely foamed. Further, the PC resin can be easily alloyed, and various fine foam alloys can be formed depending on applications. Typical alloys using a PC resin include PC / PBT, PC / PS, PC / elastomer, and PC / PET. Note that any appropriate elastomer can be used as the thermoplastic elastomer. Typical elastomers include polyester elastomers, styrene elastomers, olefin elastomers, and urethane elastomers. Particularly preferred resins are PET resins or polyester elastomers. This is because the balance of cost, versatility and strength is excellent.
[0020]
The foam may have a single layer structure or a laminated structure. For example, it is possible to foam only the intermediate layer of the resin sheet having a three-layer structure. Since the foam obtained in this way has no air bubbles on the surface, the possibility of cracking is further reduced in damper applications, which is very preferable.
[0021]
The procedure for producing the foam is as follows: First, a resin sheet is placed in a high-pressure container at room temperature. Next, a high-pressure inert gas (typically nitrogen gas, carbon dioxide gas, or a mixed gas thereof) is sufficiently dissolved in the high-pressure vessel until a saturated dissolution amount is reached. Next, a gas supersaturated state is created in the resin sheet by rapidly reducing the gas pressure in the high-pressure vessel at room temperature. At this time, the sheet becomes thermodynamically very unstable, and bubble nuclei are generated. The sheet is heated above its softening temperature to grow cell nuclei and then cooled to obtain a foam. Alternatively, the resin sheet is placed in a high-pressure vessel at a high temperature, and an inert gas (typically nitrogen gas, carbon dioxide gas, or a mixed gas thereof) is sufficiently dissolved under a high temperature and high pressure until the saturated dissolution amount is reached. Let Next, by rapidly removing the gas, gas supersaturation, bubble nucleation and bubble growth are allowed to proceed simultaneously, followed by cooling to obtain a foam.
[0022]
Alternatively, the foam can be formed using an injection molding machine for damper molding. That is, a thermoplastic resin is melted in a cylinder of an injection molding machine (typically at 100 to 450 ° C.), and a supercritical inert gas (typically nitrogen as a foaming gas) is melted into the molten thermoplastic resin. Gas, carbon dioxide gas, or a mixed gas thereof) is added in a predetermined amount (typically, 0.1 to 30 parts by weight per 100 parts by weight of the resin). The molten thermoplastic resin and the foaming gas are kneaded while maintaining the foaming gas in the cylinder at or above the critical pressure. By maintaining the foaming gas in a supercritical state, the foaming gas enters and disperses in the molten thermoplastic resin in a very short time, and a very good compatibility state is realized. Next, after the temperature of the molten thermoplastic resin is lowered (typically to 50 to 300 ° C.), the cooled thermoplastic resin is weighed. The metering of the cooled thermoplastic resin can be controlled by calculating from the cylinder diameter and the discharge speed. By molding this resin into a mold at a predetermined temperature and pressure, the damper is molded and foamed at the same time. That is, by injection, the foaming gas in the supercritical state contained in the molten thermoplastic resin is abruptly foamed in the cavity, so that the damper is molded and foamed at the same time. It is possible to control the bubble diameter by loading any appropriate counter pressure in the mold. Note that the supercritical state refers to a state at or above the critical temperature and above the critical pressure. The critical temperature of nitrogen gas is −127 ° C., the critical pressure is 3.5 MPa, the critical temperature of carbon dioxide gas is 31 ° C., and the critical pressure is 7.4 MPa.
[0023]
The present invention can be applied to any damper, but can preferably be applied to a so-called butterfly damper. Specifically, as shown in FIG. 1, the butterfly damper 100 preferably includes an outer peripheral portion 1, an inner peripheral portion 2, and a plurality of arm portions 3 that connect the outer peripheral portion 1 and the inner peripheral portion 2. Can be applied. This is because the weight reduction not only provides a speaker having excellent sound quality, but also provides a particularly remarkable effect in improving the durability of the arm portion.
[0024]
The damper according to a preferred embodiment of the invention can be used for any type of speaker, but particularly preferably it can be used for small-diameter speakers. This is because the minimum resonance frequency is lowered due to the light weight of the foam.
[0025]
The operation of the present invention will be described below.
According to the present invention, by forming a damper using a foam having fine bubbles with an average diameter of 0.1 to 10 μm, it has excellent durability and reliability, and can be applied to mass production. And the damper which can obtain the speaker which has the outstanding sound quality can be provided. Specifically, because the foam bubbles are very fine, a damper having excellent mechanical strength can be obtained. In particular, by having such fine bubbles, the occurrence of cracks at the time of large input and deterioration during long-time use are remarkably prevented, so that a damper having extremely excellent durability and reliability can be obtained. . Moreover, since the damper obtained using the foam is lightweight, a speaker with excellent sound pressure can be obtained as a result.
[0026]
According to the manufacturing method of the present invention, it is possible to simultaneously perform injection molding and foaming of a damper using a damper injection molding machine. Such a manufacturing method is completely different from the prior art in which a foam sheet is manufactured using a large-scale high-pressure facility, and both cost and mass productivity are remarkably improved.
[0027]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Unless otherwise indicated, parts and percentages in the examples are based on weight.
[0028]
(Example 1)
The injection molding machine was set to a cylinder temperature of 230 ° C and a mold temperature of 60 ° C. A polyester elastomer (manufactured by Toray DuPont, Hytrel 2751) was placed in the cylinder and melted. Here, 15 parts of carbon dioxide in a supercritical state was added to 100 parts of the resin. Carbon dioxide was supplied into the cylinder of the injection molding machine by connecting a cylinder containing carbon dioxide gas in a supercritical state to the injection molding machine and increasing the pressure using a booster pump. The molten elastomer and the foaming gas were kneaded and then injected into the cavity, and the damper was molded and foamed simultaneously as shown in FIG.
[0029]
Using the obtained damper, a speaker with a diameter of 12 cm was produced, and the sound pressure frequency characteristics were measured. The measurement results are shown in FIG. 2 together with the results of Comparative Example 1 described later. In order to evaluate the durability of this speaker, the rate of decrease in the lowest resonance frequency before and after the continuous load test was measured. The measurement results are shown in Table 1 below together with the results of Comparative Example 1 described later. Furthermore, when the internal loss was measured by a normal method, it was 0.07. In addition, a foam flat plate was formed in the same manner as described above, and the state of the bubbles was observed with a scanning electron microscope (SEM). A schematic diagram of the photograph is shown in FIG. As a result of performing image analysis processing, the average bubble diameter was less than 9 μm.
[0030]
[Table 1]

[0031]
(Comparative Example 1)
A damper as shown in FIG. 1 was produced in the same manner as in Example 1 except that no foaming gas was used. Using the obtained damper, a speaker with a diameter of 12 cm was produced, and the sound pressure frequency characteristics were measured. The measurement results are shown in FIG. 2 together with the results of Example 1. Moreover, it was 0.03 when the internal loss was measured by the normal method. Further, in the same manner as in Example 1, the durability was evaluated. The results are shown in Table 1 above.
[0032]
As can be seen from FIG. 2, the speaker of Example 1 has a higher sound pressure in the entire band than the speaker of Comparative Example 1, and the peak dip near 2 kHz is remarkably improved. This is considered to be due to the fact that the damper of Example 1 is lighter than the damper of Comparative Example 1 and that resonance does not easily occur because it has a foamed structure. Furthermore, as is clear from Table 1, the speaker of Example 1 is much more durable than the speaker of Comparative Example 1. This is considered to be because the stress concentration in the arm portion is alleviated due to the damper of Example 1 having a fine foam structure. In addition, as is apparent from the measurement result of the internal loss, it can be seen that the damper of Example 1 has much less unnecessary sound radiation than the damper of Comparative Example 1.
[0033]
【The invention's effect】
As described above, according to the present invention, by forming a damper using a foam having fine bubbles with an average diameter of 0.1 to 10 μm, it has excellent durability and reliability, and is suitable for mass production. It is possible to provide a damper that can be applied and obtain a speaker having excellent sound quality.
[Brief description of the drawings]
FIG. 1 is a schematic view for explaining a butterfly damper which is an example of a damper according to a preferred embodiment of the present invention.
FIG. 2 is a graph showing a comparison of sound pressure frequency characteristics of a speaker using a damper according to an embodiment of the present invention and a speaker of a comparative example.
FIG. 3 is a schematic diagram of an SEM photograph explaining the state of bubbles in a foam obtained by the same method as in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Outer peripheral part 2 Inner peripheral part 3 Arm part 100 Butterfly damper

Claims (7)

A damper for a speaker, which is formed from a thermoplastic resin foam and has an average cell diameter of 0.1 to 10 μm. The speaker damper according to claim 1, wherein the foam has a cell density of 10 ⁹ to 10 ¹⁵ pieces / cm ³ . The thermoplastic resin constituting the foam is selected from the group consisting of PET resin, PC resin, PPS resin, PETG resin, PBT resin, PS resin, thermoplastic elastomer, and alloys thereof. The damper for speakers described in 1. The speaker damper according to any one of claims 1 to 3, wherein the foam has a specific gravity of 1.0 g / cm ³ or less, a tensile strength of 700 MPa or more, and a flexural modulus of 800 MPa or more. The speaker damper according to any one of claims 1 to 4, comprising an outer peripheral portion, an inner peripheral portion, and a plurality of arm portions that connect the outer peripheral portion and the inner peripheral portion. A speaker comprising the damper according to claim 1. Melting the thermoplastic resin;
Adding a supercritical inert gas to the molten thermoplastic resin;
Lowering the temperature of the molten thermoplastic resin while maintaining the pressure of the inert gas at or above a critical pressure;
A method of manufacturing a damper, comprising: injecting a predetermined amount of the thermoplastic resin with the temperature lowered into a mold, and simultaneously performing molding and foaming in the mold.

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