JP2001268686A - Diaphragm for electroacoustic transducer and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diaphragm for an electroacoustic transducer which is lightweight and highly rigid, has adequate internal loss and superior watertightness, excellent sound quality, and superior productivity by forming the diaphragm of synthetic resin by using a molding method which reduces independent spaces as much as possible and increasing the cavity capacity of a structure close to a paper-made diaphragm after injection and compression. SOLUTION: The diaphragm for the electroacoustic transducer is molded out of a resin material, obtained by mixing synthetic resin and glass fiber, by expanding the cavity capacity after injection and compression. The resin material has continuous gaps 13 formed inside by using the reaction force of the glass fiber when the resin material expands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diaphragm for an electroacoustic transducer and a method for manufacturing the same. More specifically, the present invention relates to a synthetic resin diaphragm for an electroacoustic transducer manufactured by using a molding method for expanding a cavity volume after injection compression, and a method for manufacturing the same.

[0002]

2. Description of the Related Art The physical properties required of a diaphragm for an electroacoustic transducer such as a speaker (sometimes simply referred to as a diaphragm), particularly a diaphragm for the low to mid-range or all bands, are specific elastic modulus (E).
/ Ρ) and the specific bending rigidity (E / ρ ³ ) are large (that is,
High elastic modulus, low density), moderate internal loss, high mechanical fatigue resistance and good weatherability. Furthermore, in recent years, waterproofness has become one of the important characteristics mainly for use in vehicles. In order to respond to such demands, various materials such as various metals, ceramics, synthetic resins, synthetic fibers, and natural fibers have been conventionally proposed, processed using various processing methods, and used.

[0003]

Among materials that have been used in the past, metals and ceramics have relatively high elasticity but high density and small internal loss, and are therefore relatively excellent for high-frequency reproduction. However, it is unsuitable for low to mid-range or all bands where light weight and high rigidity are required. In addition, the so-called paper diaphragm using cellulose fibers such as wood pulp as the main raw material has a relatively low density, has a sufficient elastic modulus for general performance, and a moderate internal loss, so It has been used for many things since ancient times. However, this paper diaphragm also has problems such as poor water resistance, natural fibers as a main raw material, and large changes in physical properties in response to changes in manufacturing conditions, resulting in unstable product performance.

On the other hand, a synthetic resin diaphragm is formed mainly by injection molding, in which a filler such as mica or carbon fiber is mixed based on an olefin resin such as polypropylene. This synthetic resin diaphragm made by injection molding has excellent waterproof properties, has a relatively high elastic modulus, and can be produced with little variation.In these respects, it can be said that the diaphragm is superior to a paper diaphragm. Since the density is higher than that of a paper diaphragm, if the weight is reduced to about the same level as a paper diaphragm, the diaphragm becomes too thin, and a sufficient bending rigidity cannot be obtained.

[0005] In view of the above, in order to obtain an excellent diaphragm for the low to mid-range and all bands that can be used in vehicles or the like that require waterproofness, it is necessary to apply a waterproof treatment to a paper diaphragm. It is necessary to reduce the density of the synthetic resin diaphragm by injection molding. Regarding waterproofing of paper diaphragms, various methods have been proposed for filling a resin such as silicone or fluorine, or forming a film of synthetic resin on the diaphragm surface, but the waterproofness is not sufficient. , Causing an increase in mass,
Products vary widely, costs are high,
And none were perfect.

In order to reduce the density of a synthetic resin diaphragm by injection molding, Japanese Patent Application Laid-Open No. 8-340594 proposes a method in which cells are formed using a foaming agent and voids are provided in the diaphragm. ing. The diaphragm by this method is excellent when the physical properties (specific bending stiffness, etc.) are evaluated as a structure (plate). However, the diaphragm for the electroacoustic transducer has an independent space by cells, Furthermore, because the film is thin and the cell system becomes relatively large,
There is a disadvantage that the cell resonates and consequently deteriorates the sound quality of the speaker. In addition, when the molding is performed as thin as a diaphragm, there is a disadvantage that the cell diameter varies due to minute variations in molding conditions, and the acoustic performance varies greatly.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to eliminate the space as much as possible and to increase the cavity volume after injection and compression of a structure close to a paper diaphragm (fiber three-dimensional structure). By using a synthetic resin diaphragm by the method, it is light weight, high rigidity, moderate internal loss, excellent waterproofness, good sound quality, and excellent productivity for electroacoustic transducers An object of the present invention is to provide a diaphragm and a method for manufacturing the diaphragm.

[0008]

In order to achieve the above object, a diaphragm for an electroacoustic transducer according to the present invention is formed by injection molding a resin material obtained by mixing a synthetic resin and glass fiber, and then expanding and molding the cavity volume. In the diaphragm for an electroacoustic transducer, the resin material has a continuous void formed by utilizing a reaction force of the glass fiber when the resin material expands.

According to the diaphragm for an electroacoustic transducer having this configuration, since it has continuous voids formed of glass fiber and resin inside, the density is lower than that of a general diaphragm made of synthetic resin. Since the glass fiber and the resin are firmly bound, the weight and the rigidity are increased. In addition, although the internal loss due to foaming cannot be expected with a normal foam structure, the diaphragm for an electroacoustic transducer according to the present invention has a large thermal conversion rate of energy due to the movement of glass fibers, and thus has not been expanded. The internal loss can be improved as compared with that of the above. Furthermore, since a skin layer is formed on the diaphragm surface by the injection compression molding method, that is, since a skin layer / expansion layer / skin layer is formed in the thickness direction in order, the waterproof property is excellent and the production is stable. It is possible to obtain a diaphragm for an electro-acoustic transducer having excellent properties, and since there is no cell resonance that tends to occur in a foamed product, a high-quality sound quality with little feeling of distortion can be obtained.

In the above, when the resin material expands, the average expansion magnification of the entire diaphragm is 1.1 to 4.0 times,
Preferably it is 1.5 to 3.0 times. Expansion ratio is 1.1
If the ratio is less than twice, the specific elastic modulus is further improved, but the specific bending rigidity cannot be sufficiently obtained. On the other hand, when the expansion ratio exceeds 4.0 times, the specific bending rigidity is further improved, but the specific elastic modulus cannot be sufficiently obtained, and further, a good appearance cannot be obtained.

The content of the glass fiber is 15 to 70.
% By weight, preferably 20 to 50% by weight. When the content of glass fiber is less than 15% by weight, the expandability, strength, rigidity and heat resistance are not sufficient, and when the content of glass fiber exceeds 70% by weight, the fluidity at the time of melting decreases, Expandability and moldability are reduced, and a good appearance cannot be obtained.

The diaphragm of the present invention is made of a thermoplastic resin containing 15 to 70% by weight of a fiber having a weight average fiber length of 0.5 to 4 mm and a main part having a thickness of 1.2 m.
m and a porosity of 10 to 75% are preferable.

The weight reduction of the diaphragm depends on the type and content of the contained fiber and the required characteristics of the target molded product, but the porosity (average) is 10 to 75%, preferably 20 to 60%. Is selected in the range. If the porosity is less than 10%, the effect of weight reduction is small, and if it exceeds 75%, the smoothness of the surface is reduced, the dense skin layer on the surface is thinned, and the strength is also weak. The porosity (%) can be expressed as [(volume of molded article−volume without voids) / volume of molded article] × 100.

The weight average glass fiber length in the molded article after molding is in the range of 0.5 to 10 mm, preferably 0.5 to 4 mm. It is advantageous to keep the glass fiber length as long as possible in terms of strength and springback properties. For example, in the case of a thin diaphragm such as a diaphragm of an embodiment to be described later, the length is 0.3 mm before expansion and the expansion is 0.3 mm. 0.6 later
mm, it is difficult to hold the glass fiber to 10 mm or more, and the appearance is slightly deteriorated. In consideration of the strength, the springback property, and the appearance, it is preferable to keep the thickness at 4 mm or less. If it is less than 0.5 mm, it is difficult to expand.

According to the method of manufacturing a diaphragm for an electroacoustic transducer of the present invention, in order to achieve the above object, the glass fiber content is 1%.
5 to 70% by weight, the glass fibers are parallel to each other in parallel and the glass fiber-containing thermoplastic resin pellets having a length of 2 to 100 mm, or the glass fiber content is 15 to 9
0% by weight, the glass fibers are parallel and parallel to each other,
A mixture containing a glass fiber-containing thermoplastic resin pellet having a length of 2 to 100 mm and a thermoplastic resin other than the above, such that the glass fiber content in the glass fiber-containing thermoplastic resin pellet is 15 to 70% by weight of the whole. Is melt-kneaded, and the molten resin is injected into a mold that is opened so as to be larger than the mold cavity volume corresponding to the final molded product. The mold is filled with molten resin by advancing the movable mold to a position where it becomes smaller than the volume of the final molded product, and then the movable mold is retracted to a position corresponding to the volume of the final molded product. And

According to the method of manufacturing a diaphragm for an electroacoustic transducer having this configuration, a glass fiber-containing thermoplastic resin pellet or a mixture containing glass fiber-containing thermoplastic resin pellets is melt-kneaded and a widely opened mold is provided. The molten resin is injected into the cavity, and then the movable mold is advanced to a position where the volume of the mold cavity becomes smaller than the volume of the final molded product immediately before, immediately after, or at the completion of the injection of the molten resin. Thus, after the mold cavity is filled with the molten resin, the movable mold is retracted, and the volume of the mold cavity is increased to a position corresponding to the volume of the final molded product.
Then, the molten thermoplastic resin expands to an enlarged volume due to a springback phenomenon caused by the entanglement of the glass fibers contained therein, so that a diaphragm having continuous voids inside is obtained.

Here, as the molding material, the average fiber length of the glass fibers is 2 to 100 mm, preferably 4 to 50 mm.
More preferably, it is 5 to 20 mm, and has a length equal to this total length, and is 15 to 20 arranged in parallel with each other.
Molding comprising fiber-reinforced thermoplastic resin pellets containing 90% by weight, preferably 20-80% by weight of glass fibers, wherein the glass fibers make up 15-70% by weight, preferably 20-50% by weight of the total molding material. Use materials. That is, the fiber-reinforced thermoplastic resin pellets can be used alone, or can be a mixture with another thermoplastic resin.

If the fiber-reinforced thermoplastic resin pellets are used, even if plasticization and kneading are performed with a screw of an injection device,
Fiber breakage is unlikely to occur, and the dispersibility is also good. Further, the springback phenomenon of the molten resin in the cavity is improved, and the fiber length remaining in the final molded product is increased, whereby the physical properties and the surface appearance are improved.
In addition, as a plasticizing screw of an injection molding machine, use of a relatively low type having a compression ratio of 2.3 or less, particularly 2 or less is preferable in terms of suppressing fiber breakage.

As the molding die, for example, a molding die capable of reducing and enlarging the volume of the mold cavity (die interval) is used. In this case, the structure is not limited to the structure in which the entire surface of the cavity is compressed and expanded, but may be a structure in which only the main part moves forward and backward depending on the shape of the molded product. When manufacturing the diaphragm by reducing or enlarging the volume of the mold cavity, the distance between the mold cavities in the main part of the mold at the start of resin filling is 0.2 to 1
It is desirable to use a mold cavity that is 0 mm, preferably 3 to 5 mm, and narrows to 0.1 to 1.1 mm when the resin is full. Here, the diaphragm may not always be a uniform plate-shaped molded product, and the interval between the main parts is set within the above range. Also, this mold cavity spacing is
It can be appropriately determined by performing an inverse calculation from the target thickness and apparent density of the diaphragm.

In the above conditions, when the mold temperature is a crystalline resin, (Tc−50) based on the crystallization temperature (Tc).
° C) to (Tc), or (Tg-50 ° C) to (Tg) based on the glass transition temperature (Tg) in the case of an amorphous resin.
It is desirable to carry out molding under the above temperature range and under molding conditions in which the injection filling time is within 1 second. That is, the mold temperature is set to a relatively higher temperature than in the case of general molding. From the viewpoint of the cooling efficiency after shaping and the molding cycle, it is desirable that the temperature of the mold is lower in the case of a normal molded product, but in the molding of the diaphragm of the present invention, the mold temperature is relatively high. It is desirable to set the temperature to increase the expandability.

The crystallization temperature of the crystalline thermoplastic resin can be measured according to JIS K7121. Specifically, DSCs manufactured by Perkin-Elmer
Using -7, the crystalline thermoplastic resin is heated at a heating rate of 10 ° C./min, kept at 230 ° C. for 3 minutes, and then cooled at a cooling rate of 10 ° C./min. In addition, the glass transition temperature of the amorphous thermoplastic resin is determined by a known method, for example, as a gradient in measurement of a relationship between specific volume and temperature, that is, as a change point of a temperature coefficient of specific volume.

The mold temperature is appropriately determined in consideration of other manufacturing conditions such as the type of molding material, fiber content, melt flowability, cavity spacing during injection filling, and degree of weight reduction. You. For example, when a polypropylene resin is used as the thermoplastic resin, the temperature is from 75 ° C. to the crystallization temperature (Tc), preferably from 80 ° C. to 120 ° C.

Next, the injection filling time of the molten resin containing the glass fiber into the mold cavity is not particularly limited, but is 1 second or less, preferably 0.5 second or less, more preferably 0.1 second or less. is there. The injection filling time is a time from the start of injection of the molten resin into the mold cavity until the molten resin is completely filled in the mold cavity. This time can be appropriately selected according to factors such as other various molding conditions as in the case of the mold temperature. However, if it exceeds 1 second, even if the temperature of the molding die is set higher, the amount of resin is small, the cooling is easy, and the interval between the molding cavities is very narrow. Due to the retreat, the expansion of the mold cavity is not sufficient, and the expandability is not sufficient, and it may be difficult to manufacture a preferable diaphragm.

With respect to the fluidity of the thermoplastic resin, it is preferable to use a resin having a melt index (MI) equal to or higher than a super-high fluidity grade among conventional injection molding materials. In particular, a resin having low molecular weight and ultrahigh fluidity, which itself has low strength and cannot be used for injection molding, can be used in the present invention. This MI
, The measurement conditions are different depending on each thermoplastic resin, but under the general measurement conditions of each thermoplastic resin, MI is 8
0 to 800 g / 10 min, preferably 100 to 600 g /
10 minutes. This MI can be determined from the resin or raw material resin in the fiber-reinforced thermoplastic resin pellets, and the MI of other pellets.

In the case of a polypropylene resin to which the present invention can be preferably applied, MI is specifically 80 to 800 g / g.
It is 10 minutes, preferably 100 to 600 g / 10 minutes, and more preferably 200 to 500 g / 10 minutes. MI is 80
If the flow rate is less than g / 10 minutes, the fluidity may be reduced and the formation of the diaphragm may be difficult, and if the MI exceeds 800 g / 10 minutes, the strength of the diaphragm may be insufficient. In addition,
The measurement of MI of the polypropylene resin is performed according to JIS K72.
10 (230 ° C., 2.16 kg load) (hereinafter the same).

Here, the ultra-high-flowability polypropylene resin used in the present invention is based on the type of fiber contained,
MI should be appropriately selected according to length, content, temperature of molding die, cavity interval during injection or injection compression, cavity shape, flow length (area) from nozzle (gate), other molding conditions, etc. Can be. In this case, resins having different MIs may be mixed and used. But M
As for I, there is no need to use an extremely large one as long as the formability is satisfied.

The synthetic resin used in the present invention is not particularly limited. For example, polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, polyolefin resin such as polyethylene, polystyrene, rubber-modified Impact-resistant polystyrene, polystyrene resin such as polystyrene having a syndiotactic structure, ABS resin, polyvinyl chloride resin, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, polyaromatic ether or thioether resin Thermoplastic resins such as resins, polyaromatic ester resins, polysulfone resins, and acrylate resins can be employed. Here, the thermoplastic resin may be used alone, or two or more kinds may be used in combination.

Among such thermoplastic resins, polypropylene resins such as polypropylene, block copolymers of propylene and other olefins, random copolymers, and mixtures thereof are preferred. The polypropylene resin is preferably a polypropylene resin containing an acid-modified polyolefin resin modified with an unsaturated carboxylic acid such as maleic anhydride or fumaric acid, or a derivative thereof. In addition, high-density polyethylene, low-density polyethylene, ethylene-α
-Other thermoplastic resins such as olefin copolymer resins and polyamide resins, and elastomers for improving impact strength, such as ethylene-α-olefin copolymer elastomers, can also be blended.

Also, phenol-based, phosphorus-based, sulfur-based antioxidants, light stabilizers, ultraviolet absorbers, weathering agents, crosslinking agents, nucleating agents, coloring agents, fillers such as short fibers, talc, calcium carbonate and the like. Can also be added. These additives are
In general, apart from the fiber-reinforced thermoplastic resin pellets, it is added as another thermoplastic resin or as another additive master batch.

As the glass fiber, E-glass or S
-Glass fiber of glass having an average fiber diameter of 25
μm or less, preferably in the range of 3 to 20 μm can be preferably employed. When the diameter of the glass fiber is less than 3 μm, the glass fiber does not blend with the resin during the production of the glass fiber reinforced pellet, and it becomes difficult to impregnate the resin.
If it exceeds μm, cutting and chipping tend to occur during melt-kneading. Using these thermoplastic resins and glass fibers, when producing pellets by a pultrusion method, etc., the glass fibers are surface-treated with a coupling agent,
Depending on the sizing agent, 100 to 10000, preferably 15
It is desirable to bundle them in the range of 0 to 5000.

The coupling agent can be appropriately selected from so-called silane coupling agents and titanium coupling agents which have been conventionally used. In particular, it is preferable to employ an amino silane compound.

As the sizing agent, for example, urethane type and olefin type can be adopted. Urethane sizing agents are
Usually, 50% by weight of a polyisocyanate obtained by a polyaddition reaction between a diisocyanate compound and a polyhydric alcohol
Those containing in the above proportions are preferred. On the other hand, a modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof can be used as the olefin sizing agent.

A glass fiber reinforced pellet is manufactured by attaching and impregnating a thermoplastic resin to glass fibers converged by the above-mentioned converging agent. As a method of attaching and impregnating a thermoplastic resin to a glass fiber, for example, a method of passing a fiber bundle through a molten resin and impregnating the resin with the fiber, a method of impregnating the fiber bundle through a coating die, or a method using a die A method in which the molten resin adhering around the fiber is spread and impregnated into the fiber bundle can be adopted.
Here, in order to make the fiber bundle and the resin well-fitted, that is, in order to improve the wettability, the molten resin is pulled out through the tensioned fiber bundle into the inside of the die provided with the uneven portion on the inner periphery. After impregnating with a fiber bundle, a pultrusion molding method in which a step of pressing the fiber bundle with a pressure roller is further incorporated can be adopted. If the glass fiber and the molten resin are compatible with each other and have good wettability, the molten resin can be easily impregnated into the glass fiber and the pellets can be easily manufactured. May be omitted. Here, as a method of well-matching each other, a method of imparting polarity to the resin, grafting a functional group that reacts with the coupling agent on the surface of the glass fiber, or heating the fiber bundle to the melting temperature of a molten resin such as liquid paraffin or more A method of pre-treating with a liquid having a boiling point is effective.

When a long fiber bundle (strand or the like) impregnated with a resin is cut along the longitudinal direction of the fiber by the above-described method, the fiber containing the long fiber having the same length as the entire length of the pellet is obtained. A reinforced resin pellet can be obtained. On this occasion,
As the resin pellet, the fiber bundle is made into a strand, and the cross-sectional shape is not limited to a cut resin-containing long fiber bundle having a substantially circular shape, but by arranging the fibers flat,
A sheet-shaped, tape-shaped or band-shaped resin-containing long fiber bundle may be cut into a predetermined length. Thus, a fiber-reinforced resin pellet is obtained.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the diaphragm according to the present invention will be described below with reference to the drawings. FIG. 1 is a partial sectional view showing a diaphragm according to the present embodiment. FIG. 2 is a partially enlarged sectional view of FIG. The diaphragm 10 of the present embodiment includes a cone-shaped diaphragm main body 11 made of a synthetic resin, and a rubber edge 12 attached to the outer periphery of the diaphragm main body 11.

The cone-shaped diaphragm main body 11 is formed by expanding a cavity volume after injecting and compressing a resin material in which a synthetic resin and glass fiber are mixed, that is, by retracting a movable mold, and is formed inside. When the resin material expands, continuous voids 13 formed by utilizing the reaction force of the glass fiber are formed, a skin layer (unexpanded layer) 14 is formed on the surface, and the thickness of the main part is reduced. It is formed less than 1.2 mm. Here, the void ratio (the ratio of the voids 13) is 10 to 75%.
Has been adjusted. The average expansion coefficient of the resin material when the movable mold is retracted after the injection compression is 1.1 to 4.0 times.

As the synthetic resin, the above-mentioned various materials can be used, and the MI is 80 to 800 g / 10
The unsaturated carboxylic acid-modified polyolefin-containing α-olefin-based resin is preferable. For glass fiber,
The above-mentioned materials can be used, but the weight- average glass fiber length after molding is 0.5 to 4 mm. The glass fiber content is 15 to 70% by weight, preferably 20 to 50% by weight of the whole molding material.

According to such a diaphragm, since it has a continuous space 13 made of glass fiber and resin inside, the density is lower than that of an ordinary synthetic resin diaphragm, And resin are tightly bound,
Lightweight and high rigidity. Further, although the internal loss due to foaming cannot be expected to be improved in the ordinary foamed structure, the diaphragm of the present embodiment has a large thermal conversion ratio of energy due to the movement of the glass fiber, so that compared to the unexpanded one, Internal loss can be improved. Furthermore, since a skin layer is formed on the surface of the diaphragm by the injection compression molding method, a diaphragm excellent in waterproofness and excellent in production stability can be obtained. , And a good sound quality with less distortion is obtained.

FIG. 3 is a cross-sectional view of a mold conceptually showing an embodiment of a method of manufacturing a diaphragm according to the present embodiment, in which molten resin is injected into a mold cavity. This shows a state immediately after the start of filling. FIG. 4 shows a state immediately after the completion of the injection filling in which the mold cavity is reduced and the molten resin is compressed and filled. FIG. 5 shows a state where the mold cavity is enlarged and the molten resin expands to form a molded product. 3, 4 and 5, 1 is a fixed mold, 2 is a movable mold, 3 is a mold cavity, 4 is a sprue, 7 is an injection nozzle, 8 is an injection molten resin, and 9 is a diaphragm. .

In the manufacture of the diaphragm of this embodiment, as shown in FIGS. 3 to 5, the movable mold 2 is moved forward and backward with respect to the fixed mold 1 so that the distance between the mold cavities (volume). ) Can be made variable. 3 to 5 show the movable mold 2 that compresses and expands the entire surface of the cavity, but depending on the shape of the molded product, only the main part may be advanced and retracted. The movable mold can be moved back and forth between the movable plate and the movable mold, or inside the movable mold, independently of the injection molding machine. This can be implemented by incorporating a mold moving device.

Next, the manufacturing method will be described based on the movement of the mold. When the molten resin is filled by injection compression, as shown in FIG. 3, the fixed mold 1 and the movable mold 2 are set to have a cavity interval D1, and in this state, the molten resin containing glass fibers is set. Start injection. Thereafter, as shown in FIG. 4, at the same time as / after the start of injection, the movable mold 2 is advanced to compress the molten resin and fill the cavity 3. In this case, the injection amount of the molten resin is a volume corresponding to the cavity interval D2 (D1> D2).

The molding die incorporates a device (not shown) for controlling the temperature of the die on the die surface of the die cavity.
As described above, the molding die has the upper limit of each temperature based on the crystallization temperature (Tc) or the glass transition temperature (Tg) of the thermoplastic resin, and is higher than the respective temperature by 5%.
The temperature is adjusted to a relatively high temperature, which is a temperature range having a lower temperature of 0 ° C. as a lower limit. In the manufacturing method of the diaphragm of the present embodiment, the mold temperature is set relatively high because the thickness of the mold cavity is small.

When a polypropylene resin is used, the mold temperature is 70 to 120 ° C., preferably 80 to 115 ° C.
° C. If the mold temperature is lower than 70 ° C., an unfilled portion of the molten resin may be generated, or the expansion may not be uniform. If the mold temperature is too high, cooling and demolding of the molded product may be difficult. However, in this embodiment, even if the mold temperature is relatively high, the rigidity of the molded product is high, and the molded product can be molded in the same manner as a general molded product.

A molten thermoplastic resin containing glass fibers melted, kneaded, plasticized and measured is injected from the injection nozzle 7 through the sprue 4 into the mold cavity by a plasticizer (not shown). Thus, a molten resin 8 is obtained. Next, the injected molten resin usually advances the movable mold 2 so that the cavity interval becomes the position of D2 before the injection is completed, compresses the molten resin, and fills and fills the mold cavity 3.

For this purpose, a plasticized melt of a volume of the molten resin having a cavity interval corresponding to D2 is injected. In this case, the advance of the movable mold 2 may be performed by position control or may be controlled by pressure. In the case of controlling the pressure, it is preferable to leave a clearance when the movable mold 2 advances and the compression of the resin is completed. As a result, even when the volume of the injection resin is delicately changed and becomes insufficient, the compressive force of the movable mold acts and the entire cavity can be reliably filled.

In the present embodiment, as described above, it is necessary to perform injection-filling at a relatively high speed of 1 second or less, preferably 0.5 second or less, and more preferably 0.1 second or less. It is. By injection filling into the mold cavity and compression by the movable mold, the molten resin reliably transfers the shape of the mold, fine irregularities such as grain on the mold surface, and the like. Cooling of the molten resin starts from the contact portion with the mold. In this embodiment,
After the filling of the molten resin is completed, simultaneously or early,
As shown in the above, the movable mold 2 is retracted to a position where the mold cavity interval is D3 (D3> D2) and the thickness of the final molded product. Due to the retreat of the movable mold 2, the glass fiber-containing thermoplastic resin in the molten state expands due to the springback phenomenon due to the entanglement of the glass fibers contained therein, and becomes the shape of the final molded product. It is pressed against the wall and shaped. That is, a diaphragm having continuous voids formed therein by the reaction force of the glass fibers is obtained.

Here, the retreat of the movable mold depends on the molding conditions, the molding material and the shape of the mold, but it is preferable that the retreat is performed immediately after the filling step of the molten resin is completed and the surface layer is formed. That is, as the cooling progresses and the viscosity of the molten resin increases, the expansion of the molten resin becomes difficult to follow the retreat of the movable mold, and it may not be possible to reliably shape the final molded product to the volume. is there.

[0048]

EXAMPLES (1) Preparation of Material Glass fiber reinforced polypropylene pellets (Mostron L) formed by drawing and cutting to a predetermined length (8 mm in this example) and polypropylene with improved fluidity for thin-wall molding (MI = 500) and the glass fiber is 30% of the whole raw material.
Dry blending was performed so as to obtain a weight%. By using this method, molding with less fiber breakage becomes possible.In the skin layer, the reinforcing effect of the glass fiber increases, and in the core portion, a remarkable springback phenomenon causes
Since a high-magnification expansion phenomenon occurs, a diaphragm for an electroacoustic transducer having a high elastic modulus and a low density can be obtained.

(2) Molding The resin produced in the above (1) is charged into an injection compression molding machine,
The diaphragm was formed in the following procedure. The resin temperature was 200 ° C. and the mold temperature was 80 ° C. Before the injection, the movable mold was opened by a predetermined amount from the normal mold clamping position (in this example, opened by 1 mm), and the injection was waited at that position. While maintaining the mold position opened by a predetermined amount,
Inject at a speed of 0 mm / sec.
After 01 seconds), the movable mold was quickly moved to a normal mold clamping position (about 0.06 seconds) and pressed at a pressure of 50 t (490 kN). Mold gap at the end of press is 0.3m
m. The injection performance was 480 kg / c injection pressure.
m ² (4704 × 100,000 Pa), filling time 0.0
4 seconds. Immediately after the pressing, the movable mold was quickly opened by a predetermined amount before the inside of the molded product was solidified, and the molded product was expanded by the reaction force of the glass fiber. The opening time was about 0.05 seconds, and the opening amount was 0.36 mm (the product thickness was 0.6 mm). After cooling for about 8 seconds, the diaphragm was removed from the mold. The molded article had continuous voids obtained by the expansion of the glass fiber inside, and both surfaces were unexpanded layers (see FIG. 2).

(3) Incorporation into a Speaker and Performance Evaluation A rubber edge was attached to the diaphragm (diaphragm body) manufactured in (2) above, incorporated into the speaker, and frequency-sound pressure characteristics and sound quality were evaluated. For comparison, an organic blowing agent (A
A diaphragm which was approximately doubled using DCA) was used. Of course, the resin of the base, the shape of the diaphragm, and the specifications of the speaker were the same as those of the product of the present invention. [Physical properties] The two resins were molded into a flat plate having a thickness of 0.6 mm, and physical properties were measured. The performance evaluation results are as shown in Table 1 below. From Table 1, the product of the present invention is
Excellent physical properties compared to conventional products.

[0051]

[Table 1]

[Sound Pressure-Frequency Characteristics and Sound Quality] The results of measuring the sound pressure-frequency characteristics and sound quality of the product of the present invention and the conventional product are shown in FIGS. 6 and 7. The product of the present invention has a higher specific elastic modulus (sound speed), specific flexural rigidity, and internal loss than conventional products (foamed by an organic foaming agent), so that the high-range reproduction limit is extended and the sound pressure is further increased. (See FIGS. 6 and 7). In addition, the actual hearing results were good, and a natural sound quality with less distortion was obtained compared to the conventional product.

[0053]

According to the diaphragm for an electroacoustic transducer of the present invention, since it has continuous voids formed of glass fiber and resin inside, the density is lower than that of a general synthetic resin diaphragm. Further, since the glass fiber and the resin are firmly bound, the weight and the rigidity are increased. In addition, although the improvement of internal loss due to foaming cannot be expected in a normal foam structure, according to the electroacoustic transducer diaphragm of the present invention, the thermal conversion rate of energy due to the movement of glass fiber is large,
The internal loss can be improved as compared with an unexpanded one. Furthermore, since a skin layer is formed on the surface of the diaphragm during injection compression, it is possible to obtain a diaphragm for an electroacoustic transducer having excellent waterproofness and excellent production stability.
Since there is no cell resonance that tends to occur in a foamed product, good sound quality with little distortion is obtained.

[Brief description of the drawings]

FIG. 1 is a partially broken side view of a diaphragm according to the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a sectional view of a mold (showing a state of injection of a molten resin into a cavity of a molding mold) conceptually illustrating an embodiment of a method of manufacturing a diaphragm according to the present invention.

FIG. 4 is a view showing a state in which the mold cavity of FIG. 3 is reduced, and a molten resin is compressed to fill the cavity.

FIG. 5 is a view showing a state where the mold cavity of FIG. 4 is enlarged and a molten resin expands to form a molded product.

FIG. 6 is a diagram showing the results of measuring sound pressure-frequency characteristics and sound quality of the product of the present invention.

FIG. 7 is a diagram showing the results of measuring sound pressure-frequency characteristics and sound quality of a conventional product.

[Explanation of symbols]

 11 diaphragm main body 12 edge 13 air gap

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29L 31:38 B29L 31:38 (72) Inventor Kaoru Wada 1-1, Anesaki Beach, Ichihara-shi, Chiba Prefecture (72) Inventor Hashimoto Hoji Inside 512 Foster Electric Co., Ltd., Miyajima-cho, Akishima City, Tokyo (72) Inventor Hiroshi Tonegawa Inside 512 Foster Electric Corporation, Miyazawa-cho, Akishima-shi, Tokyo, Japan F term (reference) 4F206 AA03C AA03J AB25 AH39 JA07 JN33 JQ81 5D016 CA05 EA08 EC02 EC03 HA02 HA06 HA07 JA08

Claims (10)

[Claims] 1. A diaphragm for an electroacoustic transducer formed by injecting and compressing a resin material obtained by mixing a synthetic resin and glass fiber, and then expanding and molding the cavity volume. Occasionally, a diaphragm for an electroacoustic transducer is provided with a continuous void formed by utilizing the reaction force of the glass fiber. 2. The diaphragm for an electroacoustic transducer according to claim 1, wherein the average expansion ratio of the entire diaphragm is 1.1 to 4.0 times. 3. The diaphragm for an electro-acoustic transducer according to claim 1, wherein the glass fiber content is 15 to 70% by weight. 4. The diaphragm for an electroacoustic transducer according to claim 1, wherein the synthetic resin is an α-olefin-based resin containing a modified polyolefin containing unsaturated carboxylic acids. Diaphragm for acoustic transducer. 5. The diaphragm for an electroacoustic transducer according to claim 4, wherein the unsaturated carboxylic acid-modified polyolefin-containing α-olefin-based resin has a melt index of 80 to 8.
A diaphragm for an electroacoustic transducer, wherein the diaphragm has a flow rate of 00 g / 10 minutes. 6. The diaphragm for an electroacoustic transducer according to claim 1, wherein the porosity is 10 to 75%. 7. The diaphragm for an electroacoustic transducer according to claim 1, wherein a thickness of a main part is less than 1.2 mm. 8. The electroacoustic transducer according to claim 1, wherein a weight average glass fiber length after molding is 0.5 to 4 mm. Dexterous diaphragm. 9. The glass fiber content is 15 to 70% by weight.
The glass fibers are parallel and parallel to each other, and the length is 2
~ 100mm glass fiber containing thermoplastic resin pellets,
Alternatively, the glass fiber content is 15 to 90% by weight, the glass fibers are parallel to each other, and the length is 2 to 10%.
A mixture containing 0 mm glass fiber-containing thermoplastic resin pellets and other thermoplastic resin and having a glass fiber content in the glass fiber-containing thermoplastic resin pellets of 15 to 70% by weight is melt-kneaded. The molten resin is injected into an open mold so as to be larger than the mold cavity volume corresponding to the final molded product, and immediately before, immediately after, or upon completion of the injection of the molten resin, the mold cavity volume becomes equal to that of the final molded product. An electro-acoustic transducer characterized by filling the mold cavity with molten resin by advancing the movable mold to a position smaller than the volume, and then retracting the movable mold to a position corresponding to the volume of the final molded product. Manufacturing method of dexterous diaphragm. 10. The method for producing a diaphragm for an electroacoustic transducer according to claim 9, wherein the glass fiber-containing thermoplastic resin pellet or
The time from the injection of the mixture into the mold cavity to the filling of the molten resin in the mold cavity is within 1 second, and the interval between the mold cavities when the molten resin is filled is 0.1 to
When the mold temperature is 1.1 mm and the molten resin is a crystalline resin, the crystallization temperature Tc is used as a reference (Tc−5).
(0 ° C.)-(Tc), and when the molten resin is an amorphous resin, (Tg)
A method for producing a diaphragm for an electroacoustic transducer, wherein the temperature is set in a temperature range of (−50 ° C.) − (Tg).