JPS5925556B2 - Diaphragm for speakers - Google Patents

Description

[Detailed description of the invention] The present invention relates to the structure of a soft dome-shaped diaphragm.

Conventionally, as a medium tuning fork, a so-called soft dome type speaker using a soft dome type diaphragm has been frequently used as a high frequency speaker.

Since the diaphragm in this type of speaker itself has relatively low rigidity, split vibrations occur at relatively low frequencies, and the interference between the split vibrations and internal loss are large, resulting in a steep Although it has a flat frequency characteristic with few peaks or dips, it has the disadvantage of low acoustic radiation efficiency because the vibration system is heavy.

As shown in Figure 1a, the above-mentioned diaphragms have conventionally been impregnated with or coated with a thermosetting resin solution such as phenol, epoxy, polyester, or urea resin as a filler to give shape retention to fabric made of natural fibers. Note 1) In the figure, set this to 100°.
Leave the thermosetting resin in an atmosphere of ~150° C. for 3 to 5 minutes (2) in the figure to bring the thermosetting resin into a semi-hardened state.

This is pressed for about 25 seconds using a press heated to 200 DEG -240 DEG C. (3 in the figure) to completely cure the thermosetting resin and to form it into the shape of a diaphragm.

This is coated with or impregnated with a loss material such as NBR, SBR, methyl methacrylic, etc. (4 in the figure) to complete the diaphragm in order to seal the internal loss and the texture.

Or phenol impregnation (1 in the figure) as shown in Figure 1.
After drying (2 in the figure), apply or impregnate the loss material (4 in the figure).
), after drying to the touch (4a in the figure), press molding (3 in the figure) may be performed to obtain a diaphragm.

The cross-sectional structure of the diaphragm obtained by the above-mentioned manufacturing method is as shown in Figure 3a, where the warp 31a and the weft of the fabric are connected.

At the junction with the thread 31b, each of the threads 31a and 31b
The fibers are bonded together by a thermosetting resin 32 covering the threads, and a loss material 33 is filled between the threads.

Furthermore, there is also a method in which a loss material film is bonded under heat instead of coating or impregnating the loss material, but they have almost the same structure.

In any case, in the conventional structure, since the fabric used as the material does not have self-shape retention, it was necessary to impart shapeability with a thermosetting resin, which caused an increase in weight.

Furthermore, as mentioned above, after impregnating with phenol, the thermosetting resin is dried to a semi-hardened state and press-molded to completely cure it, but in the actual manufacturing process, the pressed material (phenol-impregnated fabric) is Normally, it is left to stand until a certain amount remains, but during this time hardening progresses, albeit gradually.

Therefore, since the hardening state of each material differs during press molding, diaphragms with different hardening states will be manufactured if press molding is performed under the same conditions.

When such a diaphragm is incorporated into a speaker, variations in frequency characteristics such as jo occur, which poses a quality problem.

Furthermore, if press conditions are set according to the can material, a uniform product can be obtained, but in the manufacturing process of mass production, it is economically impossible to change the conditions each time.

Also, it is 200° to 24° to completely cure phenol.
Although a pressing temperature of 0° C. is required, the types of fabrics that do not deteriorate under such temperatures are limited, and there is little freedom in design.

Furthermore, various problems have occurred such as adhesion on the mold surface due to temporary melting of the thermosetting resin during the pressing process.

This invention is a diaphragm in which a woven or knitted fabric made of thermoplastic resin fibers as a self-shape-retaining fabric is used as a diaphragm base material, and a loss material is coated or impregnated on this diaphragm, without using a thermosetting resin. By forming the diaphragm in this way, the drawbacks of the conventional example described above are solved, and will be explained in detail below along with the manufacturing process.

The process shown in Figure 2a is press molding of thermoplastic resin fabric such as polyethylene terephthalate, vinylidene difluoride, polyamide, acrylic resin, etc. into the shape of a diaphragm (3 in the figure, the pressing temperature is 20°C higher than the melting temperature of the fabric). The temperature is appropriate.

) and then coat or impregnate it with a resin solution with large internal loss such as SBR, NBR, methyl methacrylic resin (4 in the figure)
It is completed by doing so.

Also, Figure 2 shows the finished product by coating or impregnating the cloth with a loss material (4 in the figure), drying it (4a in the figure), and press-forming (3 in the figure).

Alternatively, an equivalent diaphragm can be obtained by overlapping a film made of a loss material on a cloth and press-molding the same.

As shown in FIG. 3, the cross-sectional structure of the diaphragm of the present invention obtained through this process is such that the warp threads 41a and the weft threads 41b are melted at the contact portion by the temperature of the press mold, and are integrated and bonded by the press pressure. .

Further, the thread softened in the press mold is stretched in the mold, and when it is cooled, it hardens and maintains the shape of the diaphragm.

A loss material 42 is filled between the threads for sealing and providing internal loss.

As mentioned above, since the present invention is made of cloth that has self-shape retention properties, there is no need for excipients such as phenol as in the past, so the weight of the diaphragm can be reduced and the acoustic radiation efficiency can be improved. In addition, the manufacturing process is extremely simple, and the various problems caused by using thermosetting resins do not occur at all, making it extremely suitable for mass production.

Example Polyethylene terephthalate resin monofilament with a wire diameter of 45μ is plain woven in a grid pattern, and SB is applied to a 200 mesh, 75μ thick, 0.372g/100crA fabric.
Impregnated with R to obtain a sheet of 0.652 g/100 crA.

This is press-molded for 10 seconds using a press mold maintained at a temperature of 260 to 280°C to obtain a dome-shaped diaphragm having a diameter of 25φ.

FIG. 4 shows the frequency characteristics of a speaker incorporating a conventional diaphragm of the same diameter and a speaker incorporating the diaphragm of the present invention.

(The solid line in the figure is the characteristic of this invention, and the dashed line is the characteristic of the conventional example.) As is clear from the figure, it is possible to achieve the objective of this invention, which is to improve the acoustic radiation efficiency, and to expand the high-frequency sound reproduction range. .

Further, when the diaphragm of the present invention was left in an atmosphere at 135° C. for 4 hours, no deformation or change in rigidity was observed.

As explained above, the present invention is a diaphragm made of a fabric made of thermoplastic resin fibers, which is heat-molded without adding a thermosetting resin, and in which the mesh of the fabric is filled with a loss material. Therefore, in terms of performance, it is an extremely useful invention in practical terms, as it increases sound pressure and expands the high frequency range, and in terms of manufacturing, it can provide diaphragms in large quantities with stable quality.

Note that the fabric is not limited to plain weave, and the same effect can be obtained using various woven or knitted fabrics or paper-made fabrics.

[Brief explanation of the drawings] Figure 1 a and b are process diagrams showing the conventional manufacturing process. Figure 2 a
, b is a process diagram showing the manufacturing process of this invention, FIG. 3a is a conventional soft diaphragm, and an enlarged view of the soft diaphragm of this invention, and FIG. 4 is a diagram showing the conventional and this invention diaphragms. It is a frequency characteristic diagram of the built-in speaker.

Claims (1)

[Claims] 1. A diaphragm base made of a thermosetting resin fiber fabric that is heat-molded without applying a thermosetting resin and the intersection portions of the fibers are fused to each other, and a loss material filled in the fabric of the base. A speaker diaphragm characterized by: