JP4008559B2 - Method for manufacturing diaphragm for electroacoustic transducer and diaphragm for electroacoustic transducer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a diaphragm for an electroacoustic transducer such as a speaker or a microphone, which is a kind of acoustic equipment, and a diaphragm for an electroacoustic transducer manufactured by the manufacturing method .
[0002]
[Prior art]
The physical properties required for this type of electroacoustic transducer diaphragm include a high specific elastic modulus, an appropriate internal loss, little mechanical fatigue, and excellent weather resistance. In order to meet these demands, materials such as various metals, ceramics, synthetic resins, synthetic fibers, vegetable cellulose (wood, non-wood pulp), carbon fibers, aramid fibers, etc. have been proposed and used various processing methods. Processed and used.
[0003]
[Problems to be solved by the invention]
Among them, metals and ceramics have a high elastic modulus, but because of their high density and low internal loss, they can be used for high-frequency reproduction, but are not suitable for mid-low frequencies and all bands where lightweight and high rigidity is required. It is. In addition, for synthetic resin, a synthetic resin alone or a base resin mixed with filler, or an alloy with other resin is made into a sheet, which is molded (mainly Vacuum molded), and pelletized and injection molded with an injection molding machine, etc. These resin diaphragms have a high specific modulus and appropriate internal loss, and have little variation during mass production. Therefore, it has a relatively excellent property, but it is weak to heat and its thickness is not easy to control, so it has a drawback in that the degree of freedom in design is small.
[0004]
On the other hand, a paper diaphragm obtained by papermaking using cellulose fibers of various plants has a high degree of freedom in design and has an appropriate internal loss, but the specific modulus is not so large. In order to improve the above, various synthetic fibers, in particular, aramid fibers, carbon fibers, and ceramic fibers are proposed and put into practical use.
[0005]
There is also a diaphragm in which a woven fabric using only aramid fibers and a woven fabric using only carbon fibers are impregnated with resin, and not molded with plant cellulose fibers. These diaphragms have high strength and high specific elastic modulus. In particular, a carbon fiber woven fabric has a higher specific modulus than that of an aramid fiber.
[0006]
However, although carbon fiber has a high specific modulus, it has a drawback that internal loss is not so large. In addition, the conductivity of carbon needs to be insulated during speaker production, which is an obstacle in terms of cost.
[0007]
Aramid fibers have an appropriate internal loss, but the specific elastic modulus does not reach that of carbon fibers. Furthermore, compared to diaphragms using plant cellulose fibers, both woven fabrics of aramid fibers and woven fabrics of carbon fibers have a higher specific gravity. In particular, the resin covers the front and back of the woven fabric during molding. In the case of a molding method using a prepreg of the type that is performed simultaneously, there is a drawback that the mass of the diaphragm increases and the efficiency of the speaker tends to decrease.
[0008]
The present invention has been made in view of the above points. The purpose of the present invention is to compensate for the above-mentioned conventional drawbacks, and the elastic modulus is substantially the same as that of carbon fibers (about twice that of aramid fibers), and internal loss. Large woven fabric using polyparaphenylene benzobisoxazole (PBO) fiber, which is an organic fiber having high strength and high heat resistance, and has a large specific elastic modulus, large internal loss, and good sound quality. An object of the present invention is to provide a method for manufacturing an electroacoustic transducer diaphragm that is obtained and can be reduced in weight and cost, and an electroacoustic transducer diaphragm manufactured by the manufacturing method .
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1 is applied to a woven fabric made of polyparaphenylene benzobisoxazole fibers having a tensile strength of 4.0 GPa or more and an initial tensile elastic modulus of 140 GPa or more. , Impregnated with a thermosetting resin made of phenolic resin or melamine resin in a dry weight percentage of 3% or more and 20% or less with respect to the weight of the fabric , molded into a predetermined shape, and then an acrylic emulsion or vinyl acetate type on one side It is characterized by coating an emulsion resin comprising an emulsion or a styrene / butadiene emulsion .
The diaphragm for an electroacoustic transducer according to claim 2 is manufactured by the manufacturing method according to claim 1.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a woven fabric made of polyparaphenylene benzobisoxazole (PBO) fibers having a tensile strength of 4.0 GPa or more and an initial tensile modulus of 140 GPa or more is dry weight%, and the solid content is 3% to 20%. Preferably, a diaphragm made of a woven fabric of aramid fiber and a diaphragm made of a woven fabric of carbon fiber are good by impregnating with a thermosetting resin of 10% or less and molding into a predetermined shape. In addition, a diaphragm having a higher specific elastic modulus (sound speed) and a larger internal loss and having near-ideal initial physical properties is obtained.
[0011]
In this case, compared to the type using a prepreg of the type in which the resin covers the front and back of the woven fabric at the time of molding, and the sealing is performed at the same time, only the shape is maintained at the time of molding, and the sealing is applied on one side with emulsion resin By doing so, the amount of resin can be reduced, and a lighter diaphragm can be obtained.
[0012]
Further, the solid content of the thermosetting resin is 3% to 20% as described above. If it is less than 3%, the shape cannot be maintained. This is because the difference in mass with a type such as an epoxy prepreg is reduced, and the effect of reducing the weight is reduced.
[0013]
【Example】
Next, examples of the present invention will be described. That is, in the present invention, as described above, a woven fabric using the polyparaphenylene benzobisoxazole (PBO) fiber having the above-mentioned physical properties is impregnated with resin, molded, and coated on one side to produce a diaphragm. The specific manufacturing procedure is as follows.
[0014]
1. A woven fabric made of PBO fibers having a void diameter of 25 mm or less was impregnated with a phenol resin to which a predetermined amount of a diluent solvent and a release agent were added, and a sheet having a resin amount of 10% by dry mass was produced. As the thermosetting resin, other melamine resins may be used.
[0015]
2. The sheet obtained above was dried under pressure using a mold having a predetermined shape (in this example, a cone shape) to obtain a predetermined shape. The pressure heating and drying conditions here were 700 kg, 230 ° C., and 10 seconds.
[0016]
3. One side (the back side in this example) of the molded product obtained in 2 above was coated with an acrylic emulsion resin, dried, and then punched into a predetermined shape to obtain a diaphragm main body. The resin to be coated may be vinyl acetate emulsion or styrene / butadiene emulsion resin.
[0017]
4). An edge made of synthetic rubber was attached to the outer periphery of the diaphragm main body obtained in the above 3 to obtain the diaphragm 1 of FIG. In FIG. 1, 2 is an emulsion resin and 3 is an edge.
[0018]
In this example, a cone-shaped diaphragm is manufactured, but a center cap, a dome-shaped diaphragm, and the like can also be manufactured.
[0019]
FIG. 2 shows the sound pressure characteristics with respect to the frequency of the present invention. A is the present invention, B is a conventional example, and the present invention is flat from the low range to the high range and has a high high range reproduction limit. ing.
[0020]
【The invention's effect】
As described above, according to the present invention, a woven fabric made of polyparaphenylene benzobisoxazole fibers is used, impregnated with a thermosetting resin, molded into a predetermined shape, and then coated with an emulsion resin on one side. Therefore, according to this diaphragm, since the specific elastic modulus is large and the internal loss is also relatively large, it is difficult for divided vibration to occur, and it is flat from the low range to the high range, and has a characteristic with a high high range reproduction limit. Can do.
[0021]
Further, by reducing the amount of resin used, the diaphragm can be reduced in weight and the sound pressure level of the speaker can be improved. Furthermore, since there is no electrical conductivity, no insulation treatment is required when manufacturing the speaker, and the manufacturing cost is reduced accordingly.
[Brief description of the drawings]
FIG. 1 shows an example of a diaphragm shape manufactured according to the present invention.
FIG. 2 shows sound pressure characteristics with respect to frequency according to the present invention.
[Explanation of symbols]
1 Diaphragm 2 Emulsion resin 3 Edge

Claims (2)

A thermosetting resin made of a phenol resin or a melamine resin is dried on a woven fabric made of polyparaphenylene benzobisoxazole fibers having a tensile strength of 4.0 GPa or more and an initial tensile elastic modulus of 140 GPa or more, based on the weight of the fabric. Electroacoustic conversion characterized in that it is impregnated with 3% or more and 20% or less and molded into a predetermined shape and then coated on one side with an emulsion resin comprising an acrylic emulsion, a vinyl acetate emulsion, or a styrene / butadiene emulsion. A method for manufacturing a mechanical diaphragm. The characterized in that it is produced by the process according to claim 1 electric acoustic converter diaphragm.

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