JPH0646836B2 - Electro-acoustic transducer - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to electroacoustic transducers such as electrodynamic speakers and microphones, and more particularly to an electroacoustic transducer including a diaphragm obtained by making mica.

[Prior art]

The acoustic characteristics of electroacoustic transducers represented by electrodynamic speakers are mainly affected by the physical characteristics of the vibration system, and the diaphragm plays the most important role in the performance of the vibration system. . As the material of this diaphragm, those obtained mainly from natural fibers are often used. For example, (A) sulfate pulp (KP), sulfite pulp (SP) seed hair fiber (cotton pulp, cavoc), bast fiber (sanpei, ramie), or inorganic fiber, etc. are blended and formed into a conical shape. A resin or the like is added to this, and it is formed into a conical shape by papermaking, and is then impregnated with a solvent such as a resin. (B) There is also a diaphragm formed of a film such as polypropylene or polyethylene and formed into a predetermined shape by pressing vacuum. (C) As a light metal material, aluminum, titanium, beryllium, etc. are pressed into a conical shape, and in the spotlight in recent years, fine powders of metal oxides, nitrides, borides, etc. are sintered. There is a ceramic diaphragm. Although various diaphragms are used in this way, the physical properties required as a diaphragm material are: (a) a small density ρ to improve efficiency, and (b) a wide reproduction band. Has a large specific elastic modulus E / ρ (E: elastic modulus, ρ: density), and (c) has an appropriate internal loss in order to dampen the resonance and flatten the sound pressure-frequency characteristics. Can be mentioned.

[Problems to be Solved by the Invention]

The diaphragm obtained by the paper-making method using the raw material shown in (A) above did not completely satisfy the physical conditions described above, and it was difficult to obtain the desired sound pressure frequency characteristics. Further, since the diaphragm obtained by the molding method is made of a plastic film such as polypropylene as a material, the diaphragm has a relatively high density and the efficiency is lowered, so that the expected characteristics cannot be obtained. Furthermore, the diaphragm obtained by the pressure molding method is a light metal material, and especially the beryllium diaphragm is Is very large (about 12.3km / sec), and very good sound pressure frequency characteristics can be obtained, but its price is very high,
Hard to put to practical use. When other light metal materials are used, the density is high and the propagation velocity is high. Is less than 5.24 km / sec, and even if the structure of the diaphragm made of this kind of material is improved, it is not expected that the sound pressure frequency characteristics will be improved over the existing diaphragm. Similar to the case of using a beryllium material, a ceramic material with high characteristics can be obtained, but thermal deformation easily occurs due to the influence of heat in the manufacturing process, and a high dimensional accuracy is obtained. However, there was a drawback that the cost was high. Table 1 shows the physical characteristics of the diaphragm using the diaphragm material as described above.

[Means for solving problems]

Then, this invention aims at providing the electroacoustic transducer provided with the low-density diaphragm, maintaining suitable internal loss and rigidity, and for that purpose, the alginic acid type fiber was disperse | distributed and disaggregated. The present invention is characterized in that an organic fine powder of mica or the like is mixed with the suspension, and a vibration plate obtained by making the paper is used.

【Example】

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the manufacturing process of the electroacoustic transducer diaphragm will be described. A water-soluble alginic acid alkali salt or a high-viscosity solution consisting of a mixture of this and a water-soluble polymer material is used as a coagulant with a metal ion and / or an acid having a salt-forming ability insoluble in alginic acid. Continuous fibers are formed by spinning into a coagulation bath consisting of an aqueous solution containing as a main component, and the continuous fibers are then cut into short fibers. After that, the short fibers are dispersed and disaggregated so as not to damage the fiber form, foreign matters and binding fibers are removed by a screen or a cleaner, and mica is mixed with the fibers to perform papermaking to obtain a vibration plate. Alginic acid is a polysaccharide contained in brown algae,
A copolymer of D-mannuronic acid and L-glucuronic acid, β-
It is mainly composed of 1,4 bonds. When this alginic acid is made into an aqueous solution as an alkali salt such as sodium, a highly viscous alginic acid alkaline solution is obtained. Here, the water-soluble alkali alginate is a salt of alginic acid such as lithium, sodium, potassium and ammonium. Metal ions having an insoluble salt forming ability with respect to alginates are ions of typical elements and transition metals of the groups Ib, II, III, IV, VI, and VIIb of the periodic table, and specifically Ca (II), Sr (II), Ba (II), Al (III),
Sn (II), Pb (II), Mn (II), Cr (III),
Fe (III), Co (II) Ni (II), Cu (II), Z
n (II), Ag (I), etc. As the acid, inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid and organic acids such as formic acid and acetic acid are used. The short fibers cut from the continuous fibers have an aspect ratio [ratio of fiber diameter (wet) to fiber length] of 15 in order to promote self-adhesion between the short fibers and to obtain a good vibrating plate texture.
Set to 0 or less. First, alginic acid-based fibers are formed by the following spinning process. Prepare a sodium alginate solution, and add 0.08
(mm-1 mm) small diameter noble, and then spun into a calcium chloride spinning solution. At this time, the spinning solution may contain a small amount of hydrochloric acid or a cationic surfactant. When sodium alginate is contacted with the spinning solution, ion exchange takes place, and it can be converted into calcium alginate long fibers. Here, the alcal metal alginate is water-soluble,
If it is a salt of a metal having a valence of 2 or more, fibers can be obtained without being dissolved in water. Moreover, this alginic acid-based fiber has flame retardancy. As the spinning conditions for forming the alginic acid-based fibers in the examples, a 5% aqueous solution of sodium alginate having a degree of polymerization of 3.8 × 10 ⁵ dalton was used, and a discharge speed of 3.5 m was obtained using a humidity type spinning machine.
It was spun into a 5% CaCl ₂ solution from a 1000-hole nozzle having a hole diameter of 0.10 mm at a rate of 1 / min, the temperature was room temperature, the winding speed was about 2.1 to 28 rpm, and the stretching ratio was 1.3. The alginic acid-based fiber produced under the above spinning conditions is washed with water and made into a staple having a fiber length of about 3 mm. Thus, the alginic acid-based fiber, which is the raw material of the diaphragm for the electroacoustic transducer, is obtained. First, FIG. 1 shows a flow chart of the production method according to this embodiment. As a defibrating step, after putting 4 kg of alginic acid type fiber 80% into a predetermined beating machine, a stock concentration of 2.
Disintegrate and disperse to a predetermined beating degree while measuring with a beating degree measuring device by defibrating at a suitable level of 5% so as not to impair the fiber morphology of the alginate fiber. Mica (particle diameter 65 μm) is put into the dispersed alginic acid fiber, and the mica is dispersed by separating 60 with a stock concentration of 3.1%, and dyeing is performed using 5% of a predetermined basic dye. Further, in order to improve the wet strength as sizing, urea resin is added to the stock at 3% (absolute dry ratio), and a sulfuric acid band is added to adjust the pH value of the stock solution to 5.0 to 5.5. Next, the adjusted stock is adjusted to a suspension 2 having a stock concentration of 0.3% in a raw material tank 1 of a paper machine shown as a schematic sectional view in FIG. This suspension 2 is sent to a stock tank 4 of a predetermined stock machine by a transfer pump 3 via a communication pipe,
The stock tank 4 is made into a paper shape by using a stock tool 5 provided in a predetermined shape. The stock tank 4 has a suction pump 6 which causes the stock tool 5 to adsorb the stock. The paper-shaped diaphragm is taken out from the stock tank 4 and dried by a dryer 7 with hot air at about 100 ° C. Reference numeral 8 denotes a jig having a predetermined shape for the diaphragm, and 9 denotes a vacuum suction pump. By cutting the inner and outer diameter portions of the dried diaphragm with a predetermined size, a composite diaphragm of alginic acid fibers and mica can be obtained. Table 2 shows the dynamic property values of the diaphragm obtained by mixing the alginic acid fiber thus obtained and mica. As is clear from Table 2, the diaphragm using the composite material of alginic acid type fiber and mica has a lower density and a higher propagation velocity, that is, the speed of sound, and the internal loss value than the diaphragm using the conventional wood pulp fiber. Shows a relatively large value, the harmonic distortion is slight, the sound pressure frequency characteristic is flat in a wide band, and the propagation speed is inferior to that of the metal material, but the resonance has an excellent balance. It will be good. Further, in the above examples, by changing the blending ratio of the alginic acid-based fiber and the mica, it is possible to easily improve various properties of the diaphragm and easily adjust the manufacturing process to obtain desired properties. When mica is used as the inorganic fine powder, its particle size is preferably 20 to 200 μm.

【The invention's effect】

As is clear from the above description, the present invention is capable of producing a vibration plate by making a suspension in which inorganic fine powder such as mica is used as a main component of alginic acid-based fibers to obtain a diaphragm, so that rigidity is maintained and internal density is low. An acoustic transducer with large loss and significantly improved propagation speed can be obtained.Because the conventional papermaking process can be used as it is, new production equipment is not required and stable quality is obtained. To be

[Brief description of drawings]

FIG. 1 is a flow chart showing the manufacturing process of the diaphragm, and FIG. 2 is a schematic explanatory view of a paper stock machine and a dryer for manufacturing the diaphragm.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayoshi Matsuo 2-3-3 Hananomiyamachi, Takamatsu City, Kagawa Prefecture, Shikoku Institute of Industrial Technology, Institute of Industrial Technology (72) Inventor, Hiroshi Uejima Hanano, Takamatsu City, Kagawa Prefecture 2-3-3 Miyamachi, Shikoku Institute of Industrial Technology, Institute of Industrial Technology (72) Inventor Satoshi Fukuoka, 2-3-3, Hananomiyacho, Takamatsu City, Kagawa Prefecture, Shikoku Institute of Industrial Technology (72) Inventor Masanori Takahashi No. 954 Shiono, Shinmachi, Mamurogawa-cho, Mogami-gun, Yamagata Prefecture Mogami Electric Co., Ltd. (72) Inventor Kazuo Tsuchiya No. 954, Shionomachi, Mamurogawa-machi, Mogami-gun, Yamagata Prefecture Mogami Denki Co., Ltd. ( 72) Inventor Takashi Furukawa 426-10 Hanazono, Tokorozawa, Saitama Examiner Takeshi Hashimoto

Claims (2)

[Claims] 1. An electroacoustic transducer comprising a vibration plate obtained by papermaking a suspension containing alginic acid fibers and inorganic fine powder. 2. The electroacoustic transducer according to claim 1, wherein the inorganic fine powder is mica.