JPS6133432B2 - - 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 a diaphragm, the diaphragm itself has been made of a material with a large internal loss, or the diaphragm has been coated with a viscolloid-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 the above-mentioned problems in the prior art, and it avoids increasing the mass of the entire diaphragm too much by attaching a damping material that has a large damping effect and is easy to mold to appropriate parts of the diaphragm body. An object of the present invention is to provide a diaphragm for an audio device that can reduce the resonance sharpness of divided vibration without any problem. 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 by mixing a rubber material and carbon black, and by partially attaching this mixed material to appropriate parts of the diaphragm body as a damping material, the vibration characteristics could be improved. This is an improvement. This invention will be explained in detail below based on the drawings of embodiments. Braking materials are made of thermoplastic resins, especially resins such as vinyl chloride resins that are easily mixed with fillers, NBR,
A rubber material such as SBR or NR, a flaky inorganic material such as flaky graphite powder or mica powder, and carbon black are mixed, thoroughly kneaded, and rolled into a sheet. If necessary, an appropriate amount of plasticizer or stabilizer may be added to facilitate kneading. In this case, the reason why the damping material is rolled into a sheet with rolls is that roll rolling will orient the flaky inorganic material and increase Young's modulus. For example, when formed into a sheet using an extrusion molding machine, the orientation of the flake-like inorganic substances is low, and the Young's modulus is less than 1/2 that when formed into a sheet by roll rolling. An example of a braking material is vinyl chloride resin.
10wt%, NBR20wt%, flake graphite 30wt%,
A well-kneaded mixture of 30wt% carbon black and 10wt% additives (plasticizers, stabilizers) was rolled into a sheet, and its physical properties were evaluated for use with other damping materials and diaphragm materials. The comparison is as shown in the table below.

[Table] As can be seen from this table, the internal loss tan δ of the damping material of this example is slightly lower than that of butyl rubber alone, but
Young's modulus E is 4 orders of magnitude larger than that of butyl rubber, and E
It is also extremely excellent in terms of xtanδ. Furthermore, the density ρ is relatively small at approximately 1.8 g/cm ³ . In addition, even in cases other than the above-mentioned compounding ratio, the total amount of vinyl chloride resin and rubber material is 10 to 10% of the total.
It is effective in a range of 60 wt%, a weight ratio of vinyl chloride resin to rubber material of 10 to 90%, and a weight ratio of flake graphite to carbon black of 30 to 70%. The damping material having the above characteristics is attached to the diaphragm body as shown in FIGS. 1 and 2. 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. 1, 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 containing filler, 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 a thermoplastic resin mixed with a flaky inorganic substance, and further mixed with a rubber material and carbon black, and used as a braking material. A damping material with a high damping rate and a large internal loss due to the mixture of carbon black and rubber-based materials and a large damping effect is attached to the diaphragm body, and the partial adhesion of the damping material reduces the mass. The resonance sharpness of the divided vibration can be effectively lowered without increasing it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the invention, and FIG. 2 is a bottom view of another embodiment. 1...braking material, 2...diaphragm body.

Claims (1)

[Scope of Claims] 1. A sheet damping material made of a kneaded material whose main components are a thermoplastic resin, a rubber material, a flake-like inorganic material, and carbon black is partially adhered to the appropriate positions of the diaphragm body. Characteristic diaphragm of audio equipment. 2. The diaphragm for an audio device according to claim 1, wherein the thermoplastic resin is a vinyl chloride resin, and the flaky inorganic material is flaky graphite.