JP3606492B2 - Diaphragm for electroacoustic transducer - Google Patents

Description

【００１５】
図２は、本発明による振動板を使用したスピーカの音圧とポリプロピレン１００％の振動板を使用したスピーカの音圧の周波数特性図である。
図における実線Ａは、先に説明した繊維長３ｍｍにカットされた引張弾性率２５０ＧＰａのポリパラフェニレンベンズビスオキサゾール（ＰＢＯ）繊維２０重量％とポリプロピレン（三菱ポリプロＢＣ２Ａ）８０重量％からなる本発明による振動板を用いた口径１３ｃｍのスピーカの音圧−周波数特性である。
また、破線Ｂは、フィラーの全く入っていないポリプロピレン（三菱ポリプロＢＣ２Ａ）１００％を用いて作製した同形状の振動板を用いた口径１３ｃｍのスピーカの音圧−周波数特性である。
実線Ａは破線Ｂに対し、比弾性率が大きいため、高域の再生限界が延びている。
【００１６】
図３は、本発明による振動板を使用したスピーカの音圧とカーボン繊維２０％，ポリプロピレン８０％の振動板を使用したスピーカの音圧の周波数特性図である。
図における実線Ａは、先に説明した繊維長３ｍｍにカットされた引張弾性率２５０ＧＰａのポリパラフェニレンベンズビスオキサゾール（ＰＢＯ）繊維２０重量％とポリプロピレン（三菱ポリプロＢＣ２Ａ）８０重量％からなる本発明による振動板を用いた口径１３ｃｍのスピーカの音圧−周波数特性である。
また、破線Ｃは、ＰＢＯ繊維の代わりにカーボン繊維（三菱ダイアリードＫ２２３，引張弾性率２２０ＧＰａ）を用いて同一工程にて作製した同形状の振動板を用いた口径１３ｃｍのスピーカの音圧−周波数特性である。
両者の比弾性率に殆ど差がないため、高域の再生限界はほぼ同じだが、実線Ａの方が内部損失が大きいため、よりフラット（平坦）なレスポンスを得ている。
【００１７】
【発明の効果】
以上説明したように、本発明による電気音響変換器用振動板は、ポリオレフィン系重合体にポリベンザゾール繊維を５重量％以上混合し、射出成形法により成形したので、
また、本発明による電気音響変換器用振動板は、前記ポリオレフィン系重合体がポリプロピレン、ポリ（４−メチルペンテン−１）、ポリエチレン等の脂肪族オレフィンの重合体もしくはこれらのアロイ、さらには上記重合体の構成モノマーを主成分とする共重合体であるので、
さらに、本発明による電気音響変換器用振動板は、前記ポリベンザゾール繊維が引張強度４．０ＧＰａ以上で、初期引張弾性率１４０ＧＰａ以上であるので、比弾性率が大きく、内部損失も比較的大きいため、分割振動がおきにくく、低域から高域まで平坦で、高域再生限界の高いスピーカを得ることができ、また、導電性がないため、スピーカ製造時に絶縁処理が不要となり、製造コストが安価となる。さらに、振動板の製造においては、カーボン繊維の様な折れが発生しないため、物性のバラツキの少ない安定した振動板が得られる。
【図面の簡単な説明】
【図１】本発明による振動板の片側断面の正面図である。
【図２】本発明による振動板を使用したスピーカの音圧とポリプロピレン１００％の振動板を使用したスピーカの音圧の周波数特性図である。
【図３】本発明による振動板を使用したスピーカの音圧とカーボン繊維２０％，ポリプロピレン８０％の振動板を使用したスピーカの音圧の周波数特性図である。
【符号の説明】
１ 振動板
２ エッジ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diaphragm for an electroacoustic transducer such as a speaker or a microphone used in an electroacoustic transducer, and more specifically, the vibration for an electroacoustic transducer having a large specific elastic modulus, an appropriate internal loss, and excellent weather resistance. Regarding the board.
[0002]
[Prior art]
Physical properties required for diaphragms for electroacoustic transducers used in speakers, microphones, etc., such as high specific elastic modulus, appropriate internal loss, low mechanical fatigue, and excellent weather resistance Is mentioned. In order to meet these demands, materials such as various metals, ceramics, synthetic resins, synthetic fibers, plant cellulose (wood, non-wood pulp), and microbial cellulose fibers have been proposed and processed using various processing methods. Have been used.
[0003]
Among them, although metal and ceramics have a large elastic modulus, they are relatively excellent for high-frequency reproduction because of their high density and low internal loss, but they are suitable for medium to low frequencies and all bands where lightweight and high rigidity is required. Is inappropriate.
[0004]
In addition, paper diaphragms mainly composed of various cellulose fibers have appropriate internal loss, but their specific elastic modulus is not so large and they are weak against water and humidity. In addition, there was a problem for in-vehicle use that requires water during cleaning.
[0005]
On the other hand, a diaphragm using synthetic fibers is formed into a sheet of a synthetic resin alone or a base resin mixed with a filler, an alloy with other resins, and the like (mainly). Vacuum molded) and pellets that have been injection molded with an injection molding machine. These resin diaphragms have a relatively high performance because they have a high specific elastic modulus, have an appropriate internal loss, are resistant to water and humidity, and have little variation during mass production. It can be said.
[0006]
Among them, especially those in which a fibrous filler is mixed with a synthetic resin based on a polyolefin polymer (mainly polypropylene) uses a fiber orientation in injection molding and has a particularly excellent performance. Have gained. Furthermore, since the performance (mainly elastic modulus) depends on the performance of the filler to be added, at present, the one using carbon fiber is a relatively excellent diaphragm.
[0007]
[Problems to be solved by the invention]
However, in the case of using carbon fiber, although the conductivity of carbon is not fatal in itself due to the structure of the speaker, the insulation treatment at the time of manufacturing the speaker is an obstacle in terms of cost. Further, many high-elasticity carbon fibers have insufficient strength, and there is a problem that fiber breakage often occurs during mixing with resin and injection molding, resulting in product variations.
[0008]
This invention is made | formed in view of such a point, and provides the diaphragm for electroacoustic transducers using the fiber which has a high elastic modulus, high intensity | strength, high internal loss, high toughness, and has no electroconductivity. For the purpose.
[0009]
[Means for Solving the Problems]
Polyparaphenylene benzbisthiazole (PBT) and polyparaphenylene benzbisoxazole (PBT), which are organic fibers that have almost the same modulus of elasticity as carbon fibers (about twice that of aramid fibers) and have high strength, high internal loss, and high toughness. A polybenzazole (PBZ) fiber such as PBO) is mixed with a polyolefin polymer, and a diaphragm for an electroacoustic transducer is formed using an injection molding method.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The diaphragm for an electroacoustic transducer according to the present invention is characterized in that 5% by weight or more of polybenzazole fiber is mixed with a polyolefin polymer and molded by an injection molding method.
[0011]
In the electroacoustic transducer diaphragm according to the present invention, the polyolefin polymer is a polymer of an aliphatic olefin such as polypropylene, poly (4-methylpentene-1) or polyethylene, or an alloy thereof, or the above polymer. It is characterized in that it is a copolymer comprising as a main component a constituent monomer of
[0012]
Further, the electroacoustic transducer diaphragm according to the present invention is characterized in that the polybenzazole fiber has a tensile strength of 4.0 GPa or more and an initial tensile elastic modulus of 140 GPa or more.
[0013]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view of one-side cross section of a diaphragm according to the present invention. Reference numeral 1 is a diaphragm, and 2 is an edge.
1. 20% by weight of polyparaphenylene benzbisoxazole (PBO) fibers with a tensile modulus of 250 GPa cut to a fiber length of 3 mm and 80% by weight of polypropylene (Mitsubishi Polypro BC2A) are melt-mixed at 230 ° C. using a single screw extruder and pellets Was made.
2. The pellets obtained in 1 above are injection molded into a predetermined shape (this time the cone shape in FIG. 1) at a resin temperature of 240 ° C., an injection pressure of 100 MPa, an injection time of 1 second, a mold temperature of 60 ° C., and a cooling time of 10 seconds. did.
3. The edge 2 was attached to the diaphragm 1 obtained in 2 above.
[0014]
The speed of sound (square root of specific elastic modulus) and internal loss (tan δ) were measured for three types of pellets (20% by weight of PBO fiber, 20% by weight of carbon fiber, and 100% of polypropylene) prepared at the time of manufacturing the diaphragm. Table 1 shows the values. This time, a corn-shaped diaphragm was produced, but a dome-shaped diaphragm, a flat diaphragm, a center cap, etc. can also be produced. The measurement method is a vibration lead method.

[0015]
FIG. 2 is a frequency characteristic diagram of the sound pressure of a speaker using a diaphragm according to the present invention and the sound pressure of a speaker using a diaphragm made of 100% polypropylene.
The solid line A in the figure is according to the present invention comprising 20% by weight of polyparaphenylene benzbisoxazole (PBO) fiber having a tensile modulus of 250 GPa cut to a fiber length of 3 mm, and 80% by weight of polypropylene (Mitsubishi Polypro BC2A). It is a sound pressure-frequency characteristic of a speaker having a diameter of 13 cm using a diaphragm.
A broken line B is a sound pressure-frequency characteristic of a speaker having a diameter of 13 cm using a diaphragm having the same shape manufactured using 100% polypropylene (Mitsubishi Polypro BC2A) containing no filler.
Since the solid line A has a higher specific elastic modulus than the broken line B, the reproduction limit in the high range is extended.
[0016]
FIG. 3 is a frequency characteristic diagram of the sound pressure of the speaker using the diaphragm according to the present invention and the sound pressure of the speaker using the diaphragm made of 20% carbon fiber and 80% polypropylene.
The solid line A in the figure is according to the present invention comprising 20% by weight of polyparaphenylene benzbisoxazole (PBO) fiber having a tensile modulus of 250 GPa cut to a fiber length of 3 mm, and 80% by weight of polypropylene (Mitsubishi Polypro BC2A). It is a sound pressure-frequency characteristic of a speaker having a diameter of 13 cm using a diaphragm.
A broken line C indicates a sound pressure-frequency of a speaker having a caliber of 13 cm using a diaphragm having the same shape manufactured in the same process using carbon fiber (Mitsubishi Dialead K223, tensile elastic modulus 220 GPa) instead of PBO fiber. It is a characteristic.
Since there is almost no difference in the specific elastic modulus between them, the reproduction limit in the high range is almost the same, but since the internal loss is larger in the solid line A, a flat (flat) response is obtained.
[0017]
【The invention's effect】
As described above, the diaphragm for an electroacoustic transducer according to the present invention is a mixture of 5 wt% or more of polybenzazole fibers in a polyolefin polymer and molded by an injection molding method.
In the electroacoustic transducer diaphragm according to the present invention, the polyolefin polymer is a polymer of an aliphatic olefin such as polypropylene, poly (4-methylpentene-1) or polyethylene, or an alloy thereof, or the above polymer. Because the copolymer has a constituent monomer of
Furthermore, since the polybenzazole fiber has a tensile strength of 4.0 GPa or more and an initial tensile elastic modulus of 140 GPa or more, the electroacoustic transducer diaphragm according to the present invention has a large specific elastic modulus and a relatively large internal loss. In addition, it is difficult to generate divided vibrations, and it is possible to obtain a speaker that is flat from low to high and has a high reproduction limit. Also, since there is no electrical conductivity, there is no need for insulation when manufacturing the speaker, and the manufacturing cost is low. It becomes. Furthermore, in the manufacture of the diaphragm, since a fold like carbon fiber does not occur, a stable diaphragm with little variation in physical properties can be obtained.
[Brief description of the drawings]
FIG. 1 is a front view of one-side cross section of a diaphragm according to the present invention.
FIG. 2 is a frequency characteristic diagram of the sound pressure of a speaker using a diaphragm according to the present invention and the sound pressure of a speaker using a diaphragm made of 100% polypropylene.
FIG. 3 is a frequency characteristic diagram of sound pressure of a speaker using a diaphragm according to the present invention and sound pressure of a speaker using a diaphragm made of 20% carbon fiber and 80% polypropylene.
[Explanation of symbols]
1 Diaphragm 2 Edge

Claims (3)

A diaphragm for an electroacoustic transducer, wherein 5% by weight or more of polybenzazole fiber is mixed with a polyolefin-based polymer and molded by an injection molding method. The polyolefin polymer is a polymer of an aliphatic olefin such as polypropylene, poly (4-methylpentene-1), polyethylene, or an alloy thereof, and further a copolymer having a constituent monomer of the polymer as a main component. The diaphragm for an electroacoustic transducer according to claim 1. The diaphragm for an electroacoustic transducer according to claim 1, wherein the polybenzazole fiber has a tensile strength of 4.0 GPa or more and an initial tensile elastic modulus of 140 GPa or more.

Images