JPS6059799B2 - Diaphragm for speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diaphragm for speakers, and particularly to a diaphragm having a sandwich structure in which a thin paper film is pasted on both sides of the opening of a core material of a continuous plurality of cylindrical bodies, which has good airtightness and is excellent in mass production. This relates to a diaphragm.

In general, the physical properties required for a direct radiation type dynamic speaker diaphragm are: first, a high elastic modulus-to-density ratio (hereinafter referred to as E/δ); and second, a high loss coefficient (hereinafter referred to as tanδ). The third reason is that the airtightness is high.

The reason why E/δ is required to be high is the frequency band in which the diaphragm vibrates as a unit without dividing into vibrations.

This is to make the area (hereinafter referred to as piston area) as wide as possible and expand the reproduction band. The reason why it is necessary for tan δ to be large is that it is important for damping the resonance when the diaphragm performs split vibration and exhibits a resonance phenomenon. Furthermore, the reason why airtightness is necessary is to eliminate third-order distortion due to nonlinearity of air passing through the diaphragm. In response to such demands, recently a honeycomb-shaped core made of metal, polymeric material, or paper is used as the core material 1, and thin films of metal, polymeric material, or paper, etc. are pasted on both sides of the core material to form the skin 3. A diaphragm with a sandwich structure as shown in Fig. 1 has come into practical use.

Note that in this figure, 2 indicates a unit core (cell). Since the sandwich-structured diaphragm described here has (a) a large specific elastic modulus E/δ, it is possible to have a wide piston area with good acoustic performance.

The structure combines a honeycomb core that is resistant to compression and a skin that is resistant to expansion and contraction, so it has high bending rigidity, is less prone to splitting vibrations, and has low distortion in acoustic output. This has great advantages as a speaker diaphragm.

Among them, a honeycomb structure diaphragm with a core made of a honeycomb core made of paper foil made of sanded natural fibers and a skin made by pasting thin paper films on both sides has the advantage of having an appropriate tan δ.
This makes it especially excellent as a speaker diaphragm. The manufacturing method of this honeycomb sandwich structure diaphragm has conventionally been carried out mainly by applying a liquid adhesive to the skin and then overlapping it with a honeycomb core. However, since the honeycomb diaphragm manufactured in this manner uses paper foil as the skin, it is breathable, so the third-order distortion was large.

In order to improve this problem, it was necessary to attach a non-breathable film to the front or back of the diaphragm, or to treat the paper foil of the skin to make it airtight. However, when these treatments are carried out, the weight of the diaphragm increases, which has the disadvantage that the above-mentioned E/δ decreases. In addition, liquid adhesives generally take a long time to cure and take time to assemble, making them unsuitable for mass production.

This invention was made in view of the above-mentioned problems, and its purpose is to provide a paper thin film on both sides of the opening of the core material of a continuous plurality of paper cylinders, which has high airtightness, short manufacturing time, and is excellent in mass production. An object of the present invention is to provide a speaker diaphragm to which a diaphragm is attached.

That is, the present invention uses a cylindrical body made of paper foil made from natural fibers or a paper foil reinforced by impregnating and hardening a polymer material as a core material, and has a shape in which the circumferential side thereof is continuous. A thin film of paper made from natural fibers is integrated on both sides of the opening using a film-like hot-melt adhesive. The film-like hot-melt adhesive used in this invention is an adhesive formed into a film of ethylene/vinyl acetate copolymer, polyamide resin, polyester resin, etc., and the film is sandwiched between adherends. After the adhesive is melted by heat pressing, the adhesive solidifies as it cools, completing the bonding.

This adhesive has the characteristics that uniform adhesion is possible and adhesion time is short. Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a part of a sectional view of a cone-shaped diaphragm having a diameter of 22 cm, which is an embodiment of the present invention. Core material 1 that makes up this diaphragm
A large number of hexagonal cylindrical unit cores (cells) 2 are arranged adjacent to each other to form a honeycomb shape. The core material 1 is made of paper foil having a thickness of 0.05mm and is arranged in three heights, and the minimum diameter of the hollow portion of the cell 2 is set to 9wn.
The thin film 3 that is in contact with the front and back surfaces of the core material 1 is made from natural fibers into a cone shape and has a thickness of 0.277177! paper foil. 4 is a film-like hot-melt adhesive made of ethylene/vinyl acetate copolymer, which has a melting point of 100°C and a thickness of 50μ.

By the way, in the case of conventional sandwich-structured diaphragms in which paper thin films are attached to both the front and back sides of a paper core material using liquid adhesive, the third-order distortion is quite large due to the lack of airtightness. .

In order to improve this problem, it was necessary to attach a film-like material to the front or back of the diaphragm. On the other hand,
In the diaphragm of this invention, the adhesive itself is airtight, and because it fulfills this role, no extra film is required, making it possible to reduce the weight of the diaphragm. Next, an example of a method for manufacturing a speaker diaphragm according to the present invention will be explained. As shown in Fig. 3, a female mold is formed by laminating a cone-shaped thin film, an adhesive, a honeycomb-shaped core adhesive, and a thin film in this order, and has a cone-shaped upper inner surface and a heater 5 on the circumferential side. 6 is heated to about 200°C by the heater 5 and placed on the female mold 6, the lower outer surface is formed into a cone shape corresponding to the female mold 6, the heater 7 is placed on the circumferential side, and the upper surface is placed on the female mold 6. A male mold 9 having a pressurizing device 8 is heated to about 20°C by a heater 7.
It is heated to 0° C., placed on the top of the laminated diaphragm material, and heated and pressurized by the pressurizing device 8 for about 1 minute.

Thereafter, the molds 6 and 9 are taken out, and as shown in FIG. 4, the molds 10 and 11 are fitted between the molds 10 and 11, which are similar to the female mold 6 and the male mold 9, except that they do not each have a heater. The mixture is then cooled at room temperature for about 1 minute while being pressurized using a pressurizing device 8.
When both molds 10 and 11 are then removed, the adhesive has cooled and solidified at this point, so the adhesion is complete. Therefore, assembly work can be completed within 5 minutes, and mass productivity is excellent. In the above embodiment, a cone-shaped diaphragm has been described, but the present invention is not limited to this, and can also be applied to a flat diaphragm or a diaphragm whose cross-sectional shape along a conical generatrix has an arbitrary curve.

Further, the cylinder shape of the continuous plurality of cylinders is limited to a hexagonal honeycomb shape, but any shape such as a circle, a square, a pentagon, etc. is not restricted.

As described above, this invention uses a film-like hot-melt adhesive to adhere paper thin films to both sides of the openings of a continuous plurality of paper cylindrical core members, thereby creating an integrated sandwich-structured diaphragm. Therefore, it has higher airtightness than conventional paper diaphragms of the same type, and is also suitable for mass production.

[Brief explanation of the drawing]

Fig. 1 is a cutaway plan view showing the main parts of a speaker diaphragm with a honeycomb structure, Fig. 2 is a sectional view showing the main parts of an embodiment of the present invention, and Fig. 3 is a method for manufacturing the diaphragm of the invention. FIG. 4 is a vertical cross-sectional view of the bonding process showing the method, and FIG. 4 is a vertical cross-sectional view showing the cooling process of the manufacturing method. In the figure, the same reference numerals indicate the same or equivalent parts, 1 is a honeycomb-shaped core material, 2 is a unit core, 3 is a thin film, 4 is a film-like hot-melt adhesive, 5 is a heater, 6 is a female mold, 7 is a heater, 8 is a pressurizing device, 9 is a male mold, 10 is a female mold, and 11 is a male mold.

Claims (1)

[Claims] 1. The core material is made of paper foil made from natural fibers or paper foil reinforced by impregnating and hardening a polymeric material, with a cylindrical body continuous on its circumferential side. A diaphragm for a speaker, characterized in that a thin film of paper made from natural fibers is integrated with a film-like hot-melt adhesive.