JP2013118548A - Manufacturing method of diaphragm for electroacoustic transducer, diaphragm prepared by the same, and electroacoustic transducer having the same - Google Patents

Abstract

Electricity that can be easily set to an optimum molding temperature by using a relatively small and simple molding apparatus, can improve the dimensional accuracy of a molded product, save energy, reduce the burden on the environment, and improve the working environment. A method for manufacturing a diaphragm for an acoustic transducer is provided.
According to the method of manufacturing a diaphragm for an electroacoustic transducer of the present invention, a resin film or a resin sheet containing ferrite powder having a function of absorbing and generating microwaves is irradiated with microwaves to be softened to a predetermined shape. It is characterized by molding.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a diaphragm for an electroacoustic transducer used for a speaker, a microphone, or the like, which is a kind of acoustic equipment, a diaphragm manufactured thereby, and an electroacoustic transducer including the diaphragm.

  In general, a diaphragm for an electroacoustic transducer is required to have low conversion vibration and good natural efficiency due to resonance. For this reason, materials with high Young's modulus, large internal loss, and light weight are used.

  Various materials are used for the diaphragm for electroacoustic transducers, such as paper, metal, polymer, ceramics, or composite materials that are a combination of these or added reinforcing materials. , Durability and cost are selected.

  A diaphragm using a polymer material is molded by heating a film-like resin and pressurizing it with a mold, for example. As a method of applying heat to the film, a method of applying from the outside of the film is common. That is, a pair of molds having a predetermined molding surface facing each other is heated, a film-like material is sandwiched between the mold surfaces and pressurized, cooled to near room temperature, and then taken out from the mold to be a diaphragm having a predetermined shape. Have gained. Alternatively, there is a method in which the film is preliminarily heated with heated air or far infrared rays and then molded with a mold.

  Resin has a material-specific temperature such as a softening point that softens as the temperature increases and a melting point that melts. Although there are thermosetting resins having no melting point, there is a temperature that becomes soft to some extent at a high temperature, and it can be deformed and molded by applying physical stress near that temperature. Therefore, the temperature at which a film made of any resin can be molded is clearly determined.

  As a method of heating the mold, a method of attaching a heater using heat generated by electric resistance is generally widely used. However, it takes time to raise the temperature and the heat distribution becomes uneven depending on the heater attachment position. There are problems such as.

  On the other hand, as a mold cooling method, there are a method in which cooling water or oil is poured into a mold or a pedestal and cooled by heat exchange, or a method using a gas such as air or carbon dioxide. However, there is a problem that the flow path processing is necessary for the mold or the pedestal, the efficiency of heat exchange is low, and cooling takes a long time.

  Patent Document 1 proposes a speaker diaphragm molding apparatus that solves such problems and can shorten the cycle time by heating and cooling the mold in a short time and a molding method using this apparatus. Yes. The molding apparatus disclosed in Patent Document 1 includes a high-frequency induction heating device and a cooling device, and can be heated in a short time by heating a molding die by high-frequency induction heating. Productivity is improved by supplying cooling water to cool the mold.

JP 2006-203695 A Japanese Patent No. 4666305

Magazine Convertec 2011.8 pp.61-63 Application of soft ferrite powder to microwave absorption heat generation

  However, in the technique described in Patent Document 1, it is necessary to provide the molding die with a high-frequency induction heating device, a cooling device, a cooling unit, and the like, which leads to an increase in scale and complexity of the molding device. In addition, since a large amount of energy is consumed to heat and cool the metal mold, the burden on the environment is large, and a large amount of heat is released around the mold, so that the working environment is deteriorated. Furthermore, when a metal mold is heated and cooled, there is a problem that the dimensional accuracy of the molded product is adversely affected due to dimensional changes due to thermal expansion and contraction.

  In addition, as a method of applying heat to the film-like material from the inside instead of from the outside, a method of heating the material of the diaphragm with a metal powder and heating it by a high-frequency induction heating method, Although the method of heating etc. can also be considered, temperature control is difficult in all, and it was difficult to set to the optimal temperature according to the material to shape | mold.

  The present invention has been proposed in view of the above, and its object is to easily set an optimum molding temperature using a relatively small and simple molding apparatus and improve the dimensional accuracy of a molded product. A method of manufacturing a diaphragm for an electroacoustic transducer capable of saving energy, reducing the burden on the environment, and improving the working environment, a diaphragm produced by the method, and an electroacoustic transducer including the diaphragm There is.

  In order to solve the above-mentioned problems, a method for manufacturing a diaphragm for an electroacoustic transducer according to the first aspect of the present invention irradiates a resin film or resin sheet 1 containing ferrite powder having a function of absorbing and generating microwaves with microwaves. Then, it is softened and molded into a predetermined shape.

  The invention according to claim 2 is the method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1, wherein the ferrite powder is mixed in the resin film or the resin sheet 1.

  The invention according to claim 3 is the method for manufacturing the diaphragm for an electroacoustic transducer according to claim 1, wherein the ferrite powder is applied or coated on at least one of the front surface or the back surface of the resin film or the resin sheet 1. It is characterized by being.

  A diaphragm for an electroacoustic transducer according to a fourth aspect of the present invention is characterized in that the diaphragm 6 is produced by the method for producing a diaphragm for an electroacoustic transducer according to any one of the first to third aspects. .

  An electroacoustic transducer according to a fifth aspect of the present invention includes the diaphragm for an electroacoustic transducer according to the fourth aspect.

  According to the first aspect of the present invention, the ferrite powder in the resin film generates heat by irradiating the resin film or resin sheet containing the microwave absorbing exothermic ferrite powder with microwaves, and the resin component receives heat. To soften. By molding in this state, the resin film or the resin sheet can be deformed to obtain a diaphragm having a predetermined shape. By adjusting the basic component composition, average particle diameter, thickness with resin film material, content, etc. of this microwave absorption exothermic ferrite powder, the rate of temperature rise of the resin film or resin sheet and its upper limit, in other words, Temperature rise time and ultimate temperature can be controlled. This makes it possible to easily control the temperature according to the basic component composition, average particle diameter, resin film material and thickness, content, etc. of the ferrite powder, even with a relatively small and simple molding apparatus. The resin sheet can be set to an optimum molding temperature. In addition, it is not necessary to repeat heating and cooling of the mold, and microwaves can be effectively converted into heat and used. Therefore, energy saving and environmental burden can be reduced. In addition, since the heat radiation to the periphery of the mold is small, the working environment can be improved. Furthermore, since the influence of dimensional change due to thermal expansion and contraction of the mold can be reduced, the dimensional accuracy of the molded product can be improved.

  According to this invention which concerns on Claim 2, a resin film or a resin sheet can be heated uniformly by mixing a ferrite powder in a resin film or a resin sheet uniformly. In addition, if it is intentionally contained in a non-uniform manner, the temperature rise time and the ultimate temperature can be partially changed, so that it is possible to cope with a precise shape and change the physical properties of the resin.

  According to the third aspect of the present invention, by applying ferrite powder to the resin film or resin sheet by coating or coating, the entire surface of the resin film or resin sheet or a partial pattern is heated. The temperature distribution and the heating temperature can be controlled relatively freely by intentionally setting the thickness to be uniform or non-uniform. In particular, it is possible to vary the temperature rise time and ultimate temperature by unevenly distributing the ferrite powder, so it is easy to deal with precision shapes and to change the physical properties of the resin (such as control of crystalline and non-crystalline regions). Can be given to.

  According to the fourth aspect of the present invention, since the thermal expansion and contraction of the mold is small, a diaphragm with high dimensional accuracy can be provided.

  According to the fifth aspect of the present invention, since the diaphragm with high dimensional accuracy is provided, an electroacoustic transducer having acoustic characteristics as designed can be provided.

It is for demonstrating the manufacturing method of the diaphragm for electroacoustic transducers based on the Example of this invention, (a) A figure shows a microwave irradiation process, (b) A figure shows a press process roughly, (c) The figure is a schematic view of a press-molded diaphragm.

  The present invention obtains a diaphragm for an electroacoustic transducer by irradiating a microwave to a resin film or resin sheet containing a ferrite powder having a function of absorbing and absorbing microwaves and heating it to form a predetermined shape. .

  When a substance is irradiated with microwaves, the electric field component of the microwave and the dielectric loss of the substance interact with each other, and the magnetic field component of the microwave and the magnetic loss of the substance interact to increase the temperature of the substance. However, since the magnetic material loses its magnetism at the Curie temperature, there is no magnetic loss in the high temperature range above the Curie temperature, and heat generation stops.

  Microwave-absorbing heat-generating ferrite powder is a material utilizing such a principle of microwave heat generation. For example, it absorbs 2.45 GHz electromagnetic waves (microwaves) and self-heats, and by adjusting its basic component composition, the heat generation temperature. It is known that the upper limit can be controlled (see, for example, Patent Document 2 and Non-Patent Document 1).

  Therefore, when a microwave is applied to the resin film or resin sheet containing the microwave absorbing exothermic ferrite powder, the ferrite powder inside the resin film or the resin sheet rapidly generates heat, and the resin component is softened by receiving heat. At this time, by using the microwave absorption exothermic ferrite powder that generates heat to a temperature suitable for molding of the resin film or resin sheet, the temperature of the resin film or resin sheet can be increased to a temperature optimal for molding in a short time. Thereafter, the diaphragm having a predetermined shape can be molded by applying a stress to the resin film with a mold having a predetermined shape.

  Embodiments of the present invention will be described below with reference to the drawings.

  1A and 1B are diagrams for explaining a method of manufacturing a diaphragm for an electroacoustic transducer according to an embodiment of the present invention. FIG. 1A schematically shows a microwave irradiation process, and FIG. 1B schematically shows a pressing process. FIG. 2C is a schematic view of a press-molded diaphragm.

  (A) As shown in the figure, the resin film (or resin sheet) 1 which is a material of the diaphragm contains microwave absorption exothermic ferrite powder and is wound around the winding shaft 2 in a roll shape. Yes. The mixing of the microwave-absorbing exothermic ferrite powder into the resin film 1 may be mixed with a liquid resin at the time of forming the resin film 1, or may be applied or coated with at least one of the front and back surfaces of the resin film 1 together with a solvent. It can also be given.

  For the microwave absorption exothermic ferrite powder, for example, MnZn ferrite, NiZn ferrite, MgZn ferrite and the like can be used. The basic component composition of the ferrite, the average particle diameter of the ferrite powder, the material and thickness of the resin film 1, the rate of temperature rise of the resin film 1 that is raised according to the frequency and output of the microwave to be irradiated, and the upper limit thereof Is set. The microwave absorption exothermic ferrite powder may contain a plurality of different types or different average particle sizes.

  When mixing the microwave absorption exothermic ferrite powder into the resin film 1, it may be mixed uniformly inside, but if it is intentionally non-uniformly contained, the temperature rise time and the ultimate temperature may be partially varied. Because it can, it can respond to precision shapes and change the physical properties of the resin. Of course, if a large amount of microwave-absorbing exothermic ferrite powder is mixed into the resin film 1, the acoustic characteristics, mechanical characteristics, physical characteristics, etc. of the formed diaphragm may be adversely affected. The amount is preferably 30 wt% or less.

  Similarly, when the microwave absorption exothermic ferrite powder is applied to the front surface, back surface, or both surfaces of the resin film 1 by coating or coating, it may be formed with a uniform thickness on the entire surface, but intentionally non-uniform. By controlling the temperature distribution during heating, the temperature distribution and temperature rise can be controlled relatively freely by making the thickness partially uniform or non-uniform in a predetermined pattern. .

  For example, in normal hot press molding, the thickness of the top portion 6a of the diaphragm 6 shown in FIG. 5 (c) tends to be thin, so if the temperature of the ferrite powder in this portion is lowered and the temperature is raised to a lower temperature, The amount of extension is smaller than this part. Thereby, the thickness of the diaphragm 6 can be made uniform.

  In this way, the ferrite powder can be distributed unevenly (content, thickness, etc.) so that the temperature rise time and ultimate temperature can be varied. , Control of the non-crystalline region, etc.) can be easily provided.

  The resin film 1 is a pair of molds 4-1 and 4-2 having opposed molding surfaces of a predetermined shape by feed rollers 3-1 and 3-2 rotating in opposite directions with the resin film 1 interposed therebetween. Sent in between. The molds 4-1 and 4-2 are formed of a material that is not affected by heat generation or the like, for example, a resin, glass, ceramics, ceramics, or the like as a main component.

  Next, the microwave is irradiated from the microwave generator 5 through the mold 4-1. As an example, the microwave frequency is 2.45 GHz and the output is 500 W. Thereby, the microwave absorption exothermic ferrite powder absorbs the microwave and generates heat, and the resin film 1 is heated. Then, when the temperature of the resin film 1 reaches a predetermined temperature, the temperature rise stops.

  In this state, as shown in FIG. 5 (b), the resin film 1 is pressed between the molding surfaces of the molds 4-1 and 4-2, and after cooling to near room temperature, the molds 4-1 and 4-2 are performed. Then, the diaphragm 6 having a predetermined shape is obtained.

  Thereafter, similarly, the microwave irradiation step and the pressing step are sequentially repeated to form the diaphragm 6 as shown in FIG.

  According to the manufacturing method as described above, the upper limit of the temperature of the resin film 1 to be heated can be controlled by adjusting the basic component composition and content of the microwave absorbing exothermic ferrite. Further, the temperature increase rate (temperature increase time) varies depending on the average particle diameter of the microwave-absorbing exothermic ferrite powder, the frequency and output of the microwave, and the like. Therefore, it is possible to easily control the temperature raising time and the reached temperature when the resin film 1 is heated. In addition, since it suffices to irradiate the resin film 1 containing the microwave-absorbing exothermic ferrite powder with microwaves, the resin film 1 can be adjusted to an optimum molding temperature with a relatively small and simple molding apparatus.

  Furthermore, since heating is performed from the inside or the surface of the resin film 1, it is not necessary to heat the molds 4-1 and 4-2, and cooling is unnecessary, so that the molding cycle can be shortened. Conventionally, when forming a diaphragm by molding a PET (Polyethylene terephthalate) film, the mold is heated to a temperature of 170 ° C., and a molding cycle is required for about 3.5 minutes.

  On the other hand, when this embodiment is applied and a diaphragm is formed by molding a PET film in the same manner, the molding cycle when a microwave with a frequency of 2.45 GHz and an output of 500 W is irradiated is up to about 20 seconds. Can be shortened.

  In addition, it is not necessary to repeat heating and cooling of the mold, and the mold is made of a material that is not affected by the heat generated by microwaves. The burden can be reduced. In addition, since the heat radiation to the periphery of the mold is small, the working environment can be improved.

  In addition, if the ferrite powder is non-uniformly contained in the resin film, the temperature rise time and temperature can be partially changed, so it has been difficult to deal with precision shapes and changes in resin properties that were difficult in the past. Can be given.

  Also, if ferrite powder is applied by coating or coating, it can be heated from the entire surface of the diaphragm or partially in a predetermined pattern, and the coating layer and coating layer can be uniformly or non-uniformly thick. By setting to, distribution and heating temperature can be controlled relatively freely. In particular, by incorporating ferrite powder in the coating layer and coating layer non-uniformly, it is possible to make a difference in the temperature rise time and the temperature reached. Crystal region control etc.) can be given more easily and finely.

  As described above, since the influence of dimensional change due to thermal expansion and contraction of the mold can be reduced, the dimensional accuracy of the diaphragm 6 can be improved, and the accuracy and acoustic characteristics of the electroacoustic transducer using this diaphragm can be improved. .

  In the above embodiment, the case where the microwave is irradiated with the resin film sandwiched between the molds is shown as an example. However, the resin film is directly irradiated with microwaves and heated before being sent to the mold. After pressurizing and cooling to near room temperature, it may be taken out from the mold to obtain a diaphragm having a predetermined shape.

  In addition, the case where press molding is performed with a resin film sandwiched between upper and lower molds has been described as an example, but other normal film and sheet molding processes such as vacuum molding, blow molding, and pressure molding may be used. Of course.

DESCRIPTION OF SYMBOLS 1 Resin film 2 Winding shaft 3-1, 3-2 Feed roller 4-1, 4-2 Mold 5 Microwave generator 6 Diaphragm 6a Top part

Claims (5)

  A method for producing a diaphragm for an electroacoustic transducer, characterized in that a resin film or a resin sheet (1) containing ferrite powder having a function of absorbing and absorbing microwaves is irradiated with microwaves to be softened and molded into a predetermined shape. .   The said ferrite powder is mixed in the resin film or resin sheet (1), The manufacturing method of the diaphragm for electroacoustic transducers of Claim 1 characterized by the above-mentioned.   The method for manufacturing a diaphragm for an electroacoustic transducer according to claim 1, wherein the ferrite powder is applied or coated on at least one of a front surface and a back surface of a resin film or a resin sheet (1).   A diaphragm for an electroacoustic transducer, wherein the diaphragm (6) is produced by the method for producing a diaphragm for an electroacoustic transducer according to any one of claims 1 to 3. An electroacoustic transducer comprising the diaphragm for an electroacoustic transducer according to claim 4.

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