JPH0321119Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to an improvement of a diaphragm which is a main part of the vibration system of a dome-shaped speaker, and particularly relates to a dome speaker having a diaphragm made of a material that is very easily molded. In general, the diaphragm of a speaker is designed to have a high divided vibration frequency to widen the speaker reproduction bandwidth, and to make the diaphragm as light as possible and highly rigid in order to improve the frequency characteristics within the band. In order to achieve this, efforts have been made to use composite materials with high Young's modulus based on highly rigid fibers, or to improve the apparent rigidity by devising shapes.
Particularly in dome-shaped speakers, there is a tendency to increase the diameter of the diaphragm in order to increase efficiency in the mid-to-high range, but in this case, the size of the magnet is limited by price, so the diameter of the driving voice coil is generally Since the diameter of the diaphragm is smaller than that of the diaphragm, it is difficult to drive the entire surface of the diaphragm uniformly due to the lack of rigidity of the diaphragm, which requires driving the middle part of the dome portion. In recent years, synthetic resins reinforced with carbon fiber have been used and put into practical use in speaker diaphragms, primarily to increase the rigidity of the material, but these are once organized into a flat shape as woven or non-woven fabrics. Since the diaphragm is impregnated and molded with a thermosetting resin using a diaphragm as a base material, it is difficult to mold a complex-shaped diaphragm having, for example, reinforcing ribs provided to increase rigidity. This idea is a lightweight composite material obtained by mixing montmorillonite with a curing agent or curing accelerator adsorbed between the layers, a thermosetting resin, and short carbon fibers.
This is a dome-shaped speaker with a diaphragm heat-molded to a shape that increases rigidity. Montmorillonite, which is used as a material for the diaphragm of this invention, is a type of hydrated silicate mineral and has the composition Al ₂ O ₃ 4SiO ₂・nH ₂ O. It is also called bentonite, and has two layers, upper and lower. between the silicate layers of the surrounding materials and adsorbed.
It has a three-layer structure with an ionic layer consisting of interlayer ions such as Na ⁺ and Ca ⁺ , and due to the presence of the interlayer ions, other ions and water can be adsorbed between the silicate layers, and the adsorbed substances can be heated. It has the function of emitting by In the embodiment of the present invention, the montmorillonite is immersed (at 60° C. for several hours) in a solution containing a hardening agent or hardening accelerator in a suitable solvent. This allows the curing agent or curing agent accelerator to be adsorbed between the silicate layers of the montmorillonite. After solution washing, this is dried to obtain a composite with a curing agent or curing accelerator. Next, the above composite (adsorbed diaminodiphenylmethane as a curing agent) was added to a 6-part epoxy resin monomer (trade name: Araldite).
6071) 29 parts Hardening agent (diaminodiphenylsulfone) 4.2 parts Mold release agent (zinc stearate) 1 part Short carbon fibers (polyacrylonitrile carbon fiber, average length 0.35 mm) A mixture consisting of 60 parts was heated (85 ℃) to mix uniformly, then cooled and pulverized to obtain a powdered composite material. Next, this composite material is heated using a mold with a predetermined shape.
A diaphragm was obtained by press molding at 160° C., a press pressure of 50 kg/cm ² , and a molding time of 10 minutes. As shown in FIG. 1, the predetermined shape of the diaphragm is such that radial ribs 3 and cylindrical ribs 4 are integrally formed inside a dome portion 2 of the diaphragm. In the diaphragm of the present invention, the epoxy resin melts once in the press mold, becomes low viscosity, and flows.
The curing agent adsorbed between the layers of montmorillonite does not leach out until a certain temperature (150°C), so it maintains a low viscosity fluid state, and as a result, even if the mold has a complex shape, it is filled to every corner, and then the metal When the molding temperature of the mold is reached, the curing agent adsorbed on the montmorillonite leaches out and hardens the epoxy resin. At this time, since the liquid is cured after it has flowed into every corner of the mold, a diaphragm with high shape and size accuracy can be obtained. The vibration system obtained by bonding the voice coil 5 to the lower end of each of the ribs and the edge 6 to the peripheral part of the diaphragm obtained in this way is as shown in FIG. The voice coil 5 is held in the air gap. In addition, in the present invention, when molding the diaphragm, the cylindrical rib 4 is extended and used as a voice coil winding frame by taking advantage of the good fluidity of the molding material as described above, and the edge 6 It is also possible to integrally mold the parts at the same time (FIG. 3) or to limit the radial ribs to only between the outer surface of the cylindrical rib and the inner surface of the dome part. Next, Table 1 shows the Young's modulus E, density ρ, and specific strength E/ρ of the diaphragm according to the embodiment of the present invention and the conventional diaphragm made of reinforced plastic made of polypropylene resin mixed with 15 wt% carbon fiber. .

[Table] As is clear from Table 1, the E/ρ of the diaphragm of this invention is extremely high. The reason for the remarkable increase in the Young's modulus of the diaphragm of the present invention is that the montmorillonite composite is dispersed to fill the spaces in the carbon fibers, and the epoxy polymer and montmorillonite are tightly bonded between the layers of the montmorillonite. This seems to be because a polymer is formed and the blended polymer is organized into a three-dimensional network structure so as to entangle the carbon fibers. FIG. 4 is a frequency characteristic diagram of the embodiment shown in Table 1 above and the conventional example. The effect of the diaphragm in the present invention is clear from the fact that the characteristics of the embodiment (solid line) are compared with the conventional example (dotted line), and the width of the flat band of frequency characteristics due to the piston vibration of the diaphragm is narrower. As explained above, this invention uses montmorillonite with a curing agent or curing accelerator adsorbed between the layers, a thermosetting resin monomer, and carbon fiber as the main materials, and the above composite material is lightweight and has high rigidity. This is a dome-shaped speaker that has a diaphragm that has been heat-molded into a similar shape, and it is possible to easily manufacture a speaker that has excellent frequency characteristics even with a dome-shaped diaphragm that has a relatively large diameter in order to reproduce low frequencies. It has excellent effects that could not be achieved conventionally.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway exploded perspective view of a vibration system according to an embodiment of the present invention, Fig. 2 is a sectional view of a dome speaker of the present invention, and Fig. 3 is a partially cutaway perspective view of a vibration system according to another embodiment. FIG. 4 is a frequency characteristic diagram. 1 is a diaphragm, 2 is a dome portion of the diaphragm, 3 is a radial rib, 4 is a cylindrical rib, and 5 is a voice coil.

Claims (1)

[Claims for Utility Model Registration] 1. The main materials are montmorillonite with a hardening agent or hardening accelerator adsorbed between the layers, a thermosetting resin monomer, carbon fiber, or silicon carbide whiskers, and the above materials are uniformly mixed. It is made of a heat-cured composite material, and a dome part 2;
Radial ribs 3 formed inside the dome portion 2
A dome-shaped speaker characterized by having a vibration system in which a voice coil bobbin having a voice coil 5 wound thereon is fixed to the lower end of each rib of a dome-shaped diaphragm 1 which is integrally formed with a cylindrical rib 4 and a cylindrical rib 4. 2. The dome-shaped speaker according to claim 1, which is a registered utility model, characterized in that the cylindrical rib 4 is extended and a voice coil 5 is wound around the end thereof.