JPS6133433B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a diaphragm for audio equipment such as a speaker. Conventionally, as a measure to prevent the split vibration of the diaphragm, the diaphragm itself has been made of a material with a large internal loss, or the diaphragm has been coated with a piscolloid-like substance. However, materials with high internal loss have a low sound velocity through the diaphragm, so when split vibration occurs, the resonance sharpness is low, but Young's modulus is generally low, which causes split vibration from low frequencies. It was hot. On the other hand, a diaphragm coated with a viscolloid material has problems in that its characteristics change over time and that a sufficient damping effect cannot be obtained because the viscolloid material has a low Young's modulus. This invention was made in view of such conventional problems, and by attaching a damping material that has a large damping effect and is easy to mold to appropriate parts of the diaphragm body, the mass of the entire diaphragm structure is not significantly increased. It is an object of the present invention to provide a diaphragm for an audio device that can lower the resonance sharpness of divided vibration without causing vibration. In general, when a damping material is partially attached to a diaphragm body that can be used as a diaphragm, the following is required. (a) Density ρ must be small This is because if the density of the damping material is high, its adhesion will prevent the smooth vibration of the diaphragm body. (b) Large internal loss tan δ and Young's modulus E. Large internal loss improves absorption of vibration energy, and large Young's modulus increases resistance to bending deformation due to split vibration of the diaphragm body. The synergistic effect of the two can lower the resonance sharpness of the split vibration and increase the damping effect. In other words, the resonance sharpness Q of the divided vibration of the diaphragm body
is given as 1/Q=E×tanδ/E′E′;Young's modulus of the diaphragm body.Increasing E×tanδ naturally lowers the resonance sharpness Q. Based on the above considerations, the inventor researched a damping material with a relatively low density and a large Young's modulus and internal loss, and found that the Young's modulus could be improved by mixing and orienting a flaky inorganic substance into a thermoplastic resin. At the same time, they discovered that the internal loss could be improved without lowering Young's modulus by adding a relatively large amount of plasticizer, and this kneaded material could be partially attached to appropriate parts of the diaphragm body as a damping material. This is intended to improve vibration characteristics. This invention will be explained in detail below based on the drawings of embodiments. The damping material consists of a thermoplastic resin, especially a resin such as vinyl chloride resin that is easily mixed with Wyler, a flaky inorganic material such as flaky graphite powder or mica powder, a relatively large amount of plasticizer, and an appropriate amount of stable material. It is made by mixing and kneading the ingredients with a coupling agent and a coupling agent, and then forming the mixture into a sheet by rolling or pressing. The damping material can be formed into a sheet by extrusion molding or other methods, but roll rolling is most preferred in order to orient the flaky inorganic material and increase Young's modulus. An example of a damping material is 10 parts of vinyl chloride resin, 20 parts of flaky graphite powder, an appropriate amount of stabilizer and coupling agent, and a plasticizer (BPBG).
The relationship between the amount of plasticizer added and the Young's modulus E or internal loss tan δ of a composition in which a certain amount of was added was as shown in FIG. As is clear from Figure 1, when the amount of plasticizer is up to 20 phr, Young's modulus E and internal loss tan
There is almost no change in both δ, but when it exceeds 20 phr
tan δ increases and E decreases. However, the degree of decrease in E is gradual, and the manner in which tan δ increases is rapid. For example, if the plasticizer is 40 phr,
Young's modulus E≒3×10 ¹⁰ N/m ² , which is only about 1/2 lower than when the amount of plasticizer is small, but the internal loss tan
δ is 0.18, which is about 7 times higher than when there is less plasticizer. The physical properties of this damping material when the plasticizer is 40 phr are compared with other diaphragm materials as shown in the table below. As is clear from the table, the internal loss of this damping material is smaller than that of butyl rubber, but the Young's modulus is greater than that of butyl rubber by more than four orders of magnitude. Furthermore, both internal loss and Young's modulus exceed paper diaphragms. Furthermore, the density ρ is 1.8, which is a relatively small value. From this, it can be seen that this damping material has a large E×tan δ and a small density ρ, making it excellent as a damping material. Regarding vinyl chloride resin, a damping material with extremely good properties can be obtained by using 5 to 40 parts of flaky graphite and 20 phr or more of plasticizer to 10 parts of resin.

[Table] The damping material having the above characteristics is attached to the diaphragm body as shown in FIGS. 2 and 3. In the figure,
1 is a damping material, and 2 is a diaphragm body. The damping material 1 is attached to the diaphragm body 2 by adhesive or
A method using thermocompression bonding is used. Further, it is preferable to select the portion where the damping material 1 is attached by examining the divided vibration mode of the diaphragm body 2 and selecting the portion where the amount of deformation is the largest. Moreover, it is also possible to attach it to two or more places as necessary. Furthermore, the shape may be a band shape as shown in FIG. 2, a shape divided along the circumference of the diaphragm body 2 as shown in FIG. 2, or any other suitable shape. Not limited. The material of the diaphragm body is not limited;
Although it can be applied to various types of diaphragms that are normally used as diaphragms, it is most effective for metals and plastics with fillers mixed in.
In particular, for the diaphragm body with filler mixed in, vinyl chloride resin, vinylidene chloride resin, or a mixture thereof is mixed with a flaky inorganic material such as flaky graphite, kneaded, and then rolled into a sheet shape. When using a product obtained by molding this, a thermocompression bonding method can be applied to attach the damping material, and since the materials are similar, the bond can be strengthened and the characteristics can be further improved. As described above, this invention uses a sheet material made of thermoplastic resin mixed with flaky inorganic material and further added with a relatively appropriate amount of plasticizer and kneaded, and used as a damping material. Moreover, due to the addition of a large amount of plasticizer, a damping material that does not significantly reduce the Young's modulus and has a large internal loss is attached to the diaphragm body, and the partial adhesion of the damping material increases the mass too much. This has the advantage that the resonance sharpness of the divided vibration can be effectively lowered without causing any interference, and the sound pressure characteristics can be flattened over a wide band.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the amount of plasticizer added to the damping material used in one embodiment of the present invention, Young's modulus, and internal loss.
The figure is a sectional view of one embodiment of the invention, and FIG. 3 is a bottom view of another embodiment. 1...braking material, 2...diaphragm body.

Claims (1)

[Scope of Claims] 1. An audio device comprising a sheet-shaped damping material made of a thermoplastic resin mixed with a flake-like inorganic material and a relatively large amount of plasticizer, which is partially adhered to appropriate locations on a diaphragm body. diaphragm. 2. The diaphragm for an audio device according to claim 1, wherein the thermoplastic resin is a vinyl chloride resin, and the damping material is a material obtained by adding 20 phr or more of a plasticizer and kneading it.