JP2005260546A - Speaker diaphragm and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a speaker diaphragm that is ecologically friendly, is free in color tone, can put a shine on its surface, and is superior in design. <P>SOLUTION: The speaker diaphragm 10 is made of both the materials of biodegradable plastic and kenaf fiber, and the ratio of the weight of the kenaf fiber to the total weight of both the materials is 5% or higher and 20% or smaller. Preferably, the biodegradable plastic is polylactic acid. Further, the manufacturing method of the speaker diaphragm 10 includes a mixing process for mixing the biodegradable plastic with the kenaf fiber, so that the ratio of the weight of the kenaf fiber to the total weight of both the materials becomes a prescribed value ranging from 5% or higher and 20% or smaller in the state of a forming body; a process for fusing the mixture after the mixing process; a process for putting the fused mixture into the mold of the speaker diaphragm; and a process for curing the mixture put into the mold. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a speaker diaphragm that is a sound wave generation part of a speaker used in an acoustic device and the like, and a method for manufacturing the speaker diaphragm.

  The speaker diaphragm is manufactured from a material that takes into consideration the functionality such as density, sound speed, elastic modulus, and internal loss, economy, workability, and design. Typical materials for the speaker diaphragm include industrial plastics such as polypropylene or polystyrene, wood pulp, or kenaf pulp (see, for example, Patent Document 1).

  When manufacturing speaker diaphragms with industrial plastics, heat-melted fluid industrial plastics are injected from the injection device into a molding die under high pressure, and cooled to cure the industrial plastics. The speaker diaphragm is obtained by taking out the mold.

  Also, when producing speaker diaphragms with natural fibers such as wood pulp or kenaf pulp, the trees or kenaf were harvested, dried thoroughly, ground to a size of several centimeters, dispersed in water, and finished. Thereafter, the speaker diaphragm is obtained by drying with hot air as it is or by performing hot press processing.

JP-A-6-253390 (abstract)

  Speaker diaphragms made from industrial plastics such as polypropylene or polystyrene are difficult to recycle and are therefore often landfilled and discarded after use. The industrial plastic speaker diaphragm buried in the ground is not decomposed by underground microorganisms and remains in the ground for a long period of time. Therefore, the environmental evaluation of the industrial speaker speaker diaphragm is low.

  On the other hand, loudspeaker diaphragms made of fibers such as wood pulp or kenaf pulp are decomposed by microorganisms in the ground even if they are disposed of in landfills, so that their environmental evaluation is high. However, it is difficult for such natural fiber speaker diaphragms to obtain a free color tone by coloring due to the addition of pigments in the manufacturing process or coloring by surface coating after manufacturing due to the nature of the fiber itself. . Also, the fiber speaker diaphragm is difficult to mold. For this reason, it is difficult to give the fiber speaker diaphragm the high glossiness of the surface of the industrial plastic speaker diaphragm obtained by molding with a mirror mold.

  The present invention has been made in view of the above problems, and is an environmentally friendly speaker diaphragm and speaker diaphragm that is excellent in design and can impart a free color tone and high glossiness to the surface thereof. An object is to provide a manufacturing method.

  In order to achieve the above object, the speaker diaphragm of the present invention is composed of both biodegradable plastic and kenaf fiber, and the ratio of the weight of kenaf fiber to the total weight of both materials is 5% or more and 20% or less. It is. The biodegradable plastic may employ a configuration that is polylactic acid. Moreover, the structure whose thickness of a speaker diaphragm is 0.2 mm or more and 0.4 mm or less is employable.

  In the method for manufacturing the speaker diaphragm of the present invention, the ratio of the weight of the kenaf fiber to the total weight of both materials in the state of the molded body of the biodegradable plastic and the kenaf fiber is in the range of 5% to 20%. A mixing step of mixing so as to be a predetermined value, a step of melting the mixture after the mixing step, a step of putting the molten mixture into a mold of a speaker diaphragm, a step of curing the mixture put in the mold, It is what has. Further, prior to the mixing step, there is a step of producing a biodegradable plastic pellet, and a method of mixing a colorant in the step of producing the pellet can be employed.

  According to the present invention, it is possible to obtain a loudspeaker diaphragm that is environmentally friendly and has an excellent design that can give a free color tone and high glossiness to the surface.

  Hereinafter, embodiments of a speaker diaphragm and a method for manufacturing the speaker diaphragm according to the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a speaker 12 having a speaker diaphragm 10 according to an embodiment of the present invention. In addition to the speaker diaphragm 10, the speaker 12 includes a magnetic circuit 14, a voice coil 16, a damper 18, and a frame 20.

  The magnetic circuit 14 includes a first plate 22, a magnet 24, and a second plate 26. The first plate 22 has a shape in which a donut disk is joined to the outside of one open end of the cylinder.

  The magnet 24 is a ring-shaped magnetic body that surrounds the center pole 28 that is the cylindrical portion of the first plate 22 in a non-contact manner. The magnet 24 is supported by being bonded and fixed to the first plate 22.

  The second plate 26 has a ring shape surrounding the center pole 28 of the first plate 22 in a non-contact manner, and is bonded and fixed to the magnet 24.

  The voice coil 16 is a coil formed by winding a conductive wire, and is disposed between the outer wall of the center pole 28 of the first plate 22 and the inner wall of the second plate 26 in a noncontact manner.

  The damper 18 has a donut shape having a concentric uneven surface on the surface. Further, the damper 18 supports the voice coil 16 at the inner periphery so that the voice coil 16 can swing in the central axis direction of the voice coil 16. The outer periphery of the damper 18 is connected to the inner wall of the frame 20.

  The speaker diaphragm 10 has a megaphone-like cylindrical shape having one end opened with a small circle and the other end opened with a large circle. The speaker diaphragm 10 is connected to the voice coil 16 at the opening end of a small circle. The large circular opening end of the speaker diaphragm 10 is bent outward toward the small circular opening end and fixed to the front panel 29.

  The frame 20 includes a cup-shaped first frame 30 on the rear side of the speaker 12 and a megaphone-shaped second frame 32 on the front side of the speaker 12. The first frame 30 functions as a housing that surrounds the first plate 22, the magnet 24, and the second plate 26.

  The second frame 32 has one end fixed to the second plate 26 and the other end fixed to the front panel 29. The second frame 32 functions as a housing that covers the damper 18 and the speaker diaphragm 10.

  Next, the operation of the speaker 12 will be described.

  An acoustic signal current is input to the voice coil 16 from the outside of the speaker 12. The voice coil 16 swings in the direction of the central axis of the voice coil 16 according to the current value input to the voice coil 16. With the amplitude of the voice coil 16, the speaker diaphragm 10 also vibrates. The vibration of the speaker diaphragm 10 generates sound waves by vibrating the surrounding air.

  Therefore, since the speaker diaphragm 10 is a member that affects the acoustic characteristics, the selection of the material is important. In addition, the speaker diaphragm 10 must be selected from a material that takes into consideration not only the acoustic characteristics, but also the design and the environmental load in recent years.

  The speaker diaphragm 10 according to the embodiment of the present invention is made of both materials of biodegradable plastic and kenaf fiber, and is manufactured by molding a mixture of these materials. Even if the speaker diaphragm 10 is discarded in the ground, it is decomposed into water and carbon dioxide by microorganisms, so that the evaluation of the speaker diaphragm 10 with respect to the environment is high.

  Further, depending on the surface shape of the speaker diaphragm 10, the surface of the speaker diaphragm 10 can be a high gloss surface, a semi-matt surface, or a matte surface (matt surface). The speaker diaphragm 10 may be manufactured by other than molding, for example, by placing a molten material thinly on a base, peeling it off after curing, and cutting it into the shape of the speaker diaphragm 10.

  Since the speaker diaphragm 10 made only of biodegradable plastic has a high density, the sound pressure of the sound wave generated from the speaker diaphragm 10 is reduced. When the sound pressure is low, the sound volume at the sound wave generation source is attenuated before reaching the listener. On the other hand, the speaker diaphragm 10 made of a material in which kenaf fiber is added to biodegradable plastic is lighter than the speaker diaphragm 10 made only of degradable plastic, so that the sound wave generated from the speaker diaphragm 10 Sound pressure does not decrease.

  A material having biodegradable plastic and kenaf fiber has an additive for improving molding processability, an additive for reinforcing the material, an additive for facilitating mold release, or a colorant such as pigment or dye. You may do it.

  The ratio of the weight of kenaf fiber to the total weight of biodegradable plastic and kenaf fiber, that is, the weight of kenaf fiber / (weight of biodegradable plastic + weight of kenaf fiber) is 5% or more and 20% or less. Preferably there is.

  When the ratio of the weight of the kenaf fiber to the total weight of the biodegradable plastic and the kenaf fiber exceeds 20%, the mold processability by the mold is deteriorated and the influence of the color of the kenaf fiber is increased. The degree of freedom of color tone decreases.

  If the ratio of the weight of the kenaf fiber to the total weight of the biodegradable plastic and the kenaf fiber is less than 5%, the speaker diaphragm 10 cannot be reduced in weight. The ratio of the weight of the kenaf fiber to the total weight of the more preferable biodegradable plastic and kenaf fiber is 15%.

  The biodegradable plastic used as the material of the speaker diaphragm 10 includes (1) chemical synthesis such as polylactic acid, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, polybutylene succinate carbonate or polybutylene succinate terephthalate. Aliphatic polyesters and copolymers thereof, (2) biopolyesters such as polyhydroxybutyrate produced by microorganisms, biocellulose, polysaccharides or polyamino acids, (3) modified starches or natural polymers produced by microorganisms, Etc. can be used.

  Of these, polylactic acid is inexpensive, readily available, excellent in moldability by mold, has material strength, is transparent, and can be easily adjusted in color by coloring. Therefore, it is preferable to use polylactic acid as the biodegradable plastic as the material of the speaker diaphragm 10.

  Moreover, it is preferable that the thickness of the speaker diaphragm 10 is 0.2 mm or more and 0.4 mm or less. This is because the speaker diaphragm 10 thinner than 0.2 mm or thicker than 0.4 mm is inferior in acoustic characteristics. The weight of the kenaf fiber in the total weight of the biodegradable plastic and the kenaf fiber as the material of the speaker diaphragm 10 is 20% or less, so that the thickness is 0.2 mm or more and 0.4 mm or less. The diaphragm 10 can be manufactured in a short time by molding. If this ratio exceeds 20%, the viscosity of the molten material becomes high, and the molten material becomes difficult to spread inside the mold having a depth of 0.4 mm or less, resulting in poor production efficiency.

  Next, a method for manufacturing the speaker diaphragm 10 according to the embodiment of the present invention will be described.

  First, biodegradable plastic and kenaf fiber are uniformly mixed and processed into a pellet. Next, the pellet of the biodegradable plastic and kenaf fiber mixture is heated and melted. Next, the molten biodegradable plastic and kenaf fiber mixture is filled into an injection device. Next, high-pressure injection of a melted mixture of biodegradable plastic and kenaf fibers into the mold of the speaker diaphragm 10 is performed from an injection device.

  As the mold, a mold, a ceramic mold, or a resin mold having a melting point higher than the melting temperature of the mixture of biodegradable plastic and kenaf fiber can be used. Among these, it is preferable to use a mold in consideration of the cost of the material, the workability of the material, the durability of the mold, the ease of extraction of the molded body from the mold, and the like.

  Next, the mixture of biodegradable plastic and kenaf fiber injected into the mold is cooled and cured. And the speaker diaphragm 10 can be obtained by taking out the mixture of the hardened biodegradable plastic and kenaf fiber from a type | mold.

  In this manufacturing method, by changing the surface shape of the mold, the surface of the speaker diaphragm 10 can be made a high gloss surface, a semi-matt surface or a matte surface (matt surface). In addition, in the manufacturing method, the biodegradable plastic and the kenaf fiber are uniformly mixed and processed into a pellet form. If a colorant is added, the speaker diaphragm 10 can be colored easily and with a desired color tone. can do. As the colorant, pigments or dyes can be used.

  The acoustic characteristics of the speaker diaphragm 10 can be evaluated by measuring density, sound speed, elastic modulus, internal loss, and the like.

  Examples of the present invention will be described below. First, 85% by weight of polylactic acid (“Lacia M151” from Mitsui Chemicals, Inc.), which is a biodegradable plastic, and 15% by weight of kenaf fiber were uniformly mixed to form mixed resin pellets.

  Next, this mixed resin pellet was dried and then heated and melted. Next, the molten mixed resin was filled into an injection apparatus. Next, the molten mixed resin was injected from the injection device into the mold of the heated speaker diaphragm 10 at a high pressure.

  Next, the mold was cooled to cure the mixed resin in the mold, and then the cured mixed resin was taken out of the mold. In this manner, a speaker diaphragm 10 having a thickness of 0.3 mm made of 85% by weight of polylactic acid and 15% by weight of kenaf fibers of the example was obtained.

  As Comparative Example 1, a speaker diaphragm 10 was manufactured by molding only polylactic acid. As Comparative Example 2, the speaker diaphragm 10 was manufactured by molding an industrial plastic made of 85% by weight of polypropylene and 15% by weight of mica.

  The speaker diaphragm 10 obtained in Example, Comparative Example 1 and Comparative Example 2 was processed into a strip shape, and the density, sound speed, elastic modulus, and internal loss, which are indicators of acoustic characteristics, were measured by the vibration lead method. The measurement results are shown in the table.

  The speaker diaphragm 10 of the example was about 30% smaller in density than the speaker diaphragm of the first comparative example. Therefore, the sound pressure with the sound wave generated from the speaker diaphragm 10 of the embodiment is larger than the sound pressure with the sound wave generated from the speaker diaphragm 10 of the comparative example 1.

  The speaker diaphragm 10 of the example was slightly larger in density than the speaker diaphragm 10 of the comparative example 2, but not as large as the speaker diaphragm 10 of the comparative example 1. In addition, the speaker diaphragm 10 of the example was equal to or higher in sound speed, elastic modulus, and internal loss than the speaker diaphragm 10 of Comparative Example 2. Therefore, it is considered that the speaker diaphragm 10 of the example has acoustic characteristics suitable as a speaker diaphragm.

  INDUSTRIAL APPLICATION This invention can be used for the speaker diaphragm which is a sound wave generation part of the speaker used for an audio equipment etc., and its manufacture.

It is sectional drawing of the speaker which provided the speaker diaphragm which concerns on embodiment of this invention.

Explanation of symbols

10 Speaker diaphragm 12 Speaker 14 Magnetic circuit 16 Voice coil 18 Damper 20 Frame 22 First plate 24 Magnet 26 Second plate 28 Center pole 29 Front panel

Claims (5)

  A speaker diaphragm comprising a biodegradable plastic and a kenaf fiber, wherein a ratio of the weight of the kenaf fiber to a total weight of the both materials is 5% or more and 20% or less.   The speaker diaphragm according to claim 1, wherein the biodegradable plastic is polylactic acid.   The speaker diaphragm according to claim 1 or 2, wherein the thickness is 0.2 mm or more and 0.4 mm or less. A mixing step of mixing the biodegradable plastic and the kenaf fiber so that the ratio of the weight of the kenaf fiber to the total weight of both materials in a molded body is a predetermined value in the range of 5% to 20%. When,
Melting the mixture after the mixing step;
Placing the molten mixture into a speaker diaphragm mold;
Curing the mixture placed in the mold,
A method of manufacturing a speaker diaphragm, comprising:   5. The method for manufacturing a speaker diaphragm according to claim 4, further comprising a step of producing pellets of the biodegradable plastic prior to the mixing step, wherein a colorant is mixed in the step of producing the pellets.

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