JPH0714240B2 - Multilayer dust cap and its molding method - Google Patents

Description

The present invention relates to a speaker dust cap for a cone type speaker.

[Prior Art] As is well known, the dust cap of the cone type speaker is
It is located near the center of the speaker diaphragm and has the function of blocking foreign matter such as dust. Especially, the dust cap connected to the root of the diaphragm affects the vibration mode of the diaphragm. The vibration absorbing force for suppressing abnormal resonance of the diaphragm is required to be relatively large. Further, since the dust cap is in the vicinity of the voice coil and is affected by the heat generation of the voice coil, it is necessary that the dust cap has high heat resistance in order to increase the input resistance of the speaker.

A typical structure of a conventional dust cap having a smooth surface or superposing different materials is, for example, (1)
Molded polypropylene film, (2) Base material made of woven cloth and thermoplastic vibration-absorbing material such as thermoplastic urethane elastomer film fused by heat and pressure, (3) Base material made of woven cloth and thermoplastic vibration absorption A material in which a heat-sealing adhesive film having a lower melting point than the thermoplastic vibration-absorbing material film is sandwiched between material films and heat-press molded is put into practical use.

[Problems to be Solved] In a conventional dust cap having such a structure,
The dust cap belonging to (1) above has a smooth and beautiful surface, but has a large thermal deformability and a low input resistance, (2),
The dust cap belonging to (3) has design restrictions because irregularities of fibers appear on the surface and a smooth surface cannot be obtained. In the dust cap belonging to (3), the weight of the adhesive film makes the dust cap heavy, and it is difficult to manufacture because air residue is likely to occur between layers during molding, and a slight air residue expands over time, causing partial peeling. There was a problem to be solved, such as swelling.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional example, and to provide a dust cap having a smooth and beautiful surface, excellent heat resistance, high productivity, and high reliability over time.

[Means for Solving the Problems] A dust cap and a method for molding the same according to the present invention for achieving the above-mentioned object are obtained by coating the surface of a fine first woven fabric composed of small-diameter yarns with a vibration-absorbing material, A multilayer dust cap, characterized in that a second woven fabric having a rigidity higher than that of the first woven fabric is overlaid and formed on the back side of the vibration-absorbing coated woven fabric coated with a heat-sealable adhesive. Cloth
A multilayer dust cap, characterized in that it is made of fibers that are thicker and have higher rigidity than the first woven fabric, and the second woven fabric is
A multilayer dust cap characterized by being a woven fabric impregnated or coated with a rigidity-imparting material or a shape-imparting material, wherein the method for molding the multilayer dust cap is a heat-sealing adhesive surface of a first woven cloth, By stacking the second woven fabric, clamping the outer periphery, and heat-pressing the second woven fabric so that the convex mold of the heating mold comes into contact with the second woven fabric, the heat from the second woven fabric causes the back surface of the first woven fabric to disappear. In the method for molding a multilayer dust cap, the heat-sealing adhesive is softened and melted, and at the same time, the heat-sealing adhesive is press-fitted into the texture holes of the second woven fabric.

The reason why the second woven fabric has a large diameter fiber is to increase the rigidity and to secure a sufficient volume of the weft holes to be filled with the softening-melted and heat-fusible adhesive.

[Operation] In the dust cap having such a structure, since the volume of the weave holes of the first woven fabric is small, the surface of the weave can be smoothed by closing the weave holes with a small amount of vibration-absorbing material. Since the heat-sealing adhesive on the back surface of the vibration-absorbing coated woven fabric melts, the heat-sealing adhesive penetrates into the weft holes of the second woven fabric. Moreover, since the second woven fabric is made of high-rigidity and thick-diameter fiber and is impregnated with or applied with the rigidity-imparting material or the shape-imparting material, the rigidity can be adjusted.

[Embodiment] An embodiment of the present invention will be described in detail with reference to Figs. FIG. 1 shows an internal configuration diagram of the dust cap of the embodiment, and FIG. 2 shows an explanatory diagram of the dust cap molding method of the embodiment.

As the first woven fabric, 50 denier warp yarn, 75 denier weft yarn, 110 warp yarns / inch, 81 weft yarns / inch,
On a Tetoron woven fabric 1a with a weight of 50 g / m ² and a small weft hole,
Acrylic resin 1a emulsion is coated as a vibration absorbing material and dried with hot air at 130 ° C. for 10 minutes. On this back surface, a heat-fusion adhesive 1c made of a copolymer emulsion of ethylene vinyl acetate and acrylic is applied and dried with hot air.
A vibration-absorbing coated woven fabric 1 of g / m ² was prepared. Next, weft 60 ×
60 pieces / inch, 96g / m ² of meta type aramid fiber woven cloth 2a,
Phenol resin 2b is immersed in a 30% methanol solution,
It was squeezed with a rotary roller and dried with hot air to prepare 116 g / m ² of phenol resin-impregnated woven fabric 2. This is superposed on the heat-sealable adhesive 1c surface of the vibration-absorbing coated woven fabric 1 so that the phenolic resin-impregnated woven fabric 2 surface is in contact with the convex die 3a of the dome-shaped heating die, and the temperature is about 205 ° C. Heat and press mold at 3 kg / cm ^{2 for} about 30 seconds. As a result, the convex mold is lowered and comes into contact with the surface of the phenol resin-impregnated woven fabric 2 and heat is transferred from the convex mold 3a to the phenol resin-impregnated woven fabric 2 layers and then to the heat fusion adhesive 1c layer. The heat-sealable adhesive 1c is softened from the 2nd side of the phenol resin-impregnated woven cloth, and the Tetoron woven cloth 1a
Of the phenol resin-impregnated woven fabric 2 without penetrating into the slight gaps. Heat-sealing adhesive for vibration-absorbing woven fabric 1
When 1c becomes sufficiently soft, the vibration-damping coated woven fabric 1 and the phenol resin-impregnated woven fabric 2 come into close contact with each other, and the convex mold 3a
Has reached the bottom dead center, so the heat fusion adhesive due to pressure
After the movement of 1c is completed, the inner surface of the vibration-absorbing coated woven fabric 1 hardly changes, and most of the heat-sealable adhesive 1c penetrates into the stitch holes of the phenol resin-impregnated woven fabric 2, and at the same time, the vibration-absorbing coated woven fabric. 1
The air on the superposed surface of the woven fabric 2 and the phenol resin-impregnated woven fabric 2 escapes to the outside through the gap between the convex mold 3a and the woven fabric 2 impregnated with the phenol resin, so that the air is adhered without remaining air. Next, in about 27 seconds while the convex upper mold 3a and the concave lower mold 3b are tightened, the heat-sealable adhesive 1c is fused to the phenol resin-impregnated woven fabric 2 and the phenol resin of the phenol resin-impregnated woven fabric 2 is melted. 2b
Is hardened and is not deformed by an external force at the time of mold release, the acrylic resin 1b is also firmly adhered to the inside, and crosslinking progresses to obtain a dust cap having a smooth and beautiful surface.

The physical properties of the dust caps obtained in the examples of the present invention and the results of leaving them in a thermostat of 130 ° C for 12 hours as a heat resistance test are shown in Table 1. The dust caps have a cone type diaphragm with an outer diameter of 25 cm. FIG. 3 shows the frequency characteristics of the speaker used in the above. For comparison, as a first conventional example, a dust cap made of polypropylene mixed with carbon powder having the same shape and substantially the same weight, and as a second example, between a phenol resin-impregnated woven cloth and a polypropylene elastomer having a thickness of 50 μm, Physical properties of a dust cap in which a phenol resin-impregnated woven fabric and a polypropylene elastomer are heat-sealed at the same time as molding at a mold temperature of about 230 ° C and a lower mold temperature of about 130 ° C by sandwiching a 50 μm-thick heat-sealing adhesive film. The results of the heat resistance test and the frequency characteristics are shown in Table 1 and FIG. 3, respectively.

As described above, the multilayer dust cap according to the present invention and the molding method thereof have been described in detail based on the considered typical examples.
The embodiment of the present invention, even in the case of woven fabrics and resin materials,
The present invention is not limited to the above-mentioned examples, and may be implemented with appropriate modifications as long as it has the constituents described in the above-mentioned claims, exhibits the function of the present invention, and has the effects described below. It is a thing.

[Effect] Dust cap according to apparent as the present invention from Table 1, not decreased Young's modulus lightweight, since a large thickness, Et ³
The rigidity represented by is large. In addition, it has excellent heat resistance, does not deform due to heat generation of the voice coil, and there is no air remaining during molding, so it is also excellent in productivity and reliability over time, and it is impregnated or coated with a rigidity-imparting material or a shape-imparting material. Since it is possible to impart appropriate rigidity, the internal loss is large, the unevenness in the high frequency range of the frequency characteristics is small, and the surface is smooth and beautiful, which greatly improves the design.

[Brief description of drawings]

FIG. 1 is an internal configuration diagram of the dust cap of the embodiment, FIG. 2 is an explanatory diagram of a dust cap molding method of the embodiment, and FIG. 3 is a frequency characteristic diagram of a speaker using the dust cap of the embodiment and the conventional example. . 1 is a vibration-absorbing coated woven fabric, 1a is a Tetoron woven fabric, 1b is an acrylic resin, 1c is a heat-fusion adhesive, 2 is a phenol resin-impregnated woven fabric, 2a is a meta-type aramid fiber woven fabric, 2b is a phenol resin, 3a Is a convex type and 3b is a concave type.

Claims (4)

[Claims] 1. A vibration absorbing coated woven fabric having a surface of a fine first woven fabric made of small-diameter yarns coated with a vibration absorbing material and a back face coated with a heat-sealable adhesive is provided on the back side of the woven fabric higher than the first woven fabric. A multi-layer dust cap made by stacking and molding a rigid second woven fabric. 2. The multi-layer dust cap according to claim 1, wherein the second woven fabric is made of a fiber thicker and more rigid than the first woven fabric. 3. The multilayer dust cap according to claim 2 or 1, wherein the second woven fabric is a woven fabric impregnated with or applied with a rigidity imparting material or a shape imparting material. 4. The method for molding the multilayer dust cap, wherein the heat-sealable adhesive surface of the first woven cloth and the second woven cloth are overlapped and the outer circumference is clamped, and the second woven cloth surface is heated by a heating mold. By heat and pressure molding so that the convex molds come into contact with each other, heat from the second woven cloth softens and melts the heat-sealable adhesive on the back surface of the first woven cloth, and at the same time, weave holes in the second woven cloth. A method for molding a multi-layer dust cap, characterized in that the heat-fusion adhesive is press-fitted into.