JPS643440B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a diaphragm or vibrating member for a speaker by thermoforming using a sheet-like material.

Conventional configurations and their problems Paper cones are commonly used as speaker diaphragms because paper has excellent physical properties as a speaker diaphragm, but paper cones are Another major advantage was that because the diaphragm was manufactured, the thickness and density of the diaphragm were uniform over the entire surface. However, paper cones have disadvantages in that their manufacturing process is complicated, their productivity is poor, and their properties change significantly over time due to poor moisture resistance.

In recent years, in order to solve these drawbacks of paper cones, polymer composite materials, which can be continuously thermoformed, are suitable for mass production, and have excellent environmental resistance, have been used as cone materials. . Among these, those using thermoplastic resins containing high elastic fibers such as carbon fibers, aramid fibers, and glass fibers as reinforcing materials have been put into practical use because they have properties superior to those of paper cones and can be easily mass-produced. However, a drawback of thermoforming is that the thickness of the diaphragm after molding becomes sloped, resulting in the fh (high frequency limit) as a speaker.
The drawbacks were a decrease in performance and variations in properties. A conventional method for molding this type of cone is shown in FIG. 1 is a first mold, 2 is a second mold of the same type as the first mold 1, and the molding material 3, which has been preheated to an appropriate temperature, is cold-pressed and molded using these. Molded products tend to become thinner toward the center. Figure 2 shows a cross-sectional view of a typical molded product. As shown in FIG. 2, the thickness of the outer periphery of the cone 4 maintains approximately the same thickness as before molding, but the thickness of the central portion becomes 50 to 80% of the thickness of the outer periphery, depending on the depth of the cone. When the central portion becomes thinner in this way, the rigidity of the diaphragm decreases, and when a voice coil is connected to the central portion and is driven, the fh of the speaker decreases.

When a sheet-shaped fiber-reinforced resin material is thermoformed using the conventional method, mass productivity is improved, but the inherent physical properties of the material cannot be effectively utilized as speaker characteristics.

To solve these problems, a sheet of fiber-reinforced resin material was placed between low-hardness silicone rubber heated above the melting point of the resin and a mold heated to the same temperature. A molding method has been devised in which silicone rubber is press-fitted into a mold. In this way, the fiber-reinforced resin material first contacts the surface of the silicone rubber and is heated uniformly, and then when pressurized, it stretches as the silicone rubber deforms, making it possible to make the thickness of the molded product almost uniform. I can do it.

However, there was a drawback that the fiber length of the fibers mixed as a reinforcing material affected the moldability and physical properties of the material after molding. In other words, if the fiber length is too long, it becomes difficult to stretch uniformly due to the entanglement of the fibers.
On the other hand, if the length was too short, the physical properties of the material would deteriorate.

OBJECTS OF THE INVENTION The present invention eliminates the conventional drawbacks as described above, and is a method for manufacturing a diaphragm that can effectively exhibit the physical properties of the material with a uniform thickness.

Structure of the Invention The method for manufacturing a diaphragm of the present invention involves heating a sheet-like fiber-reinforced resin material mixed with reinforcing fibers with a defined fiber length to the same temperature as low-hardness silicone rubber heated above the melting point of the resin. The silicone rubber is placed in the middle of the formed mold and pressurized to force the silicone rubber into the mold.

In this way, the fiber-reinforced resin material first comes into contact with the surface of the silicone rubber and is heated uniformly, and when pressurized, the material is molded as the silicone rubber deforms. At this time, since the fiber length of the reinforcing fibers is regulated, it can be molded to a uniform thickness.
Moreover, the physical properties of the material can be effectively exhibited.

Description of examples Examples of the present invention will be described below.

FIG. 3 shows a first embodiment of the present invention,
5 is carbon fiber with a fiber length of 0.2 to 1.0 mm (diameter 6 μm)
This fiber-reinforced resin material is made by cutting a 200 μm thick sheet of polyethylene containing 90 W/W% or more into the required size. This is placed on a mold 6, and a low hardness silicone rubber 7 is placed on top of it.
(Rubber hardness 6: Toray Silicon Co., Ltd. DX-35-053)
is placed and pressurized together with the presser plate 8.

This pressurization is performed within the cylinder 9 to prevent the silicone rubber 7 from flowing out. Furthermore, the surfaces of the mold 6 and the silicone rubber 7 are heated to a uniform temperature. As a result, the fiber-reinforced resin material 5 is uniformly heated and expands as the silicone rubber 7 is deformed, so that a molded product of uniform thickness can be obtained.

FIG. 4 shows a cross section of the cone 10 molded by the manufacturing method of this example. Outer periphery 10 of cone 10
The thicknesses of a and the inner peripheral portion 10b are molded with a thickness accuracy of within ±6%, and a diaphragm that effectively exhibits the physical properties of the material can be obtained.

Figure 5 shows the fiber length of the carbon fibers mixed in and the Young's modulus after heating.

FIG. 6 shows the relationship between the fiber length and the elongation rate of the sheet (the elongation rate immediately before breaking) in each case.

From FIG. 5 and FIG. 6, it can be seen that when the fiber length is 0.2 mm or less, the Young's modulus decreases, and when the fiber length is 1.0 mm or more, the elongation rate of the material decreases and the moldability tends to decrease. Therefore, the fiber length should be 0.2 to 1.0.
By setting it within the range of mm, moldability is good and deterioration in physical properties can be minimized.

FIG. 7 shows an example of a speaker diaphragm obtained by the method of the present invention.

In FIG. 7, reference numeral 12 denotes a core material having a shape in which a plurality of fan-shaped small pieces with a zigzag cross section are assembled, and surface materials 11a and 11b are provided on both sides of the core material.
is attached to form a flat speaker diaphragm.

The core material 12 is molded by the method shown in the above embodiment using a mold of the same shape, and has the advantage that a complex shape can be integrally molded in a short time.

This allows the currently expensive flat diaphragm to be manufactured at low cost, and the quality is also stable.

Effects of the Invention As described above, according to the present invention, sheet-like fiber-reinforced resin materials, which were conventionally difficult to mold to a uniform thickness, can be molded to a uniform thickness, and complex shapes can be integrally molded. Therefore, by applying this to the core material of cone-shaped, dome-shaped diaphragms, dust caps, and flat plate diaphragms with a sandwich structure, the physical properties of the material can be utilized to the maximum.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional molding method, Fig. 2 is a sectional view of a diaphragm formed by the conventional method, Fig. 3 is a sectional view showing an embodiment of the forming method according to the present invention, and Fig. 4 is a cross-sectional view of a diaphragm formed by the method of the present invention, FIG. 5 is a diagram showing the relationship between the fiber length of the reinforcing material and Young's modulus, FIG. 6 is a diagram showing the relationship between the fiber length and the elongation rate of the material, and FIG. FIG. 7 is a partially cutaway perspective view showing an example of a speaker diaphragm obtained by the method of the present invention. 5... Fiber reinforced resin material, 6... Molding mold, 7...
...Silicone rubber, 6...pressing plate, 10...cone.

Claims (1)

[Claims] 1. A sheet-like fiber-reinforced resin material obtained by mixing high elastic fibers such as carbon fibers, aramid fibers, and glass fibers as reinforcing materials with synthetic resin fibers is placed between heated silicone rubber and a heated mold,
This is pressurized and the silicone rubber is press-fitted into the mold, and the reinforcing fibers are 0.2 to 1.0 mm in proportion to 90W/W% or more.
1. A method of manufacturing a speaker diaphragm having a fiber length of .