JPS6139800A - Diaphragm for speaker - Google Patents

Abstract

PURPOSE:To obtain an excellent specific elesticity modulus with high rigidity and an excellent physical property and to smoothen the frequency characteristics at an audible frequency band by forming, on a metallic base material, a coating layer made of a mixture of the metallic oxide and silicon nitride whisker. CONSTITUTION:On the surface of an aluminum foil 1 as a metallic base material, a coating layer 2 is formed by flame-spraying a mixture of the powder of alumina Al2O3 as a metallic oxide and the silicon nitride whisker, for instance, by the plasma spraying. As the first step, said foil is blast-treated by spraying with polishing powder on its surface, after the 40mu-thick aluminum foil formed into a desired diaphragm shape is degreased and cleaned, for instance, with trichloroethylene, etc. In the second step, a material obtained by mixing the alumina Al2O3 powder with 5wt% silicon nitride whisker is sprayed onto the surface of the aluminum foil by a plasma spraying device 3, and the coating layer 2 which is approximately 35-45mu in thickness and is made of Al2O3- Si3N4 35-45mu in thickness, is formed.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a diaphragm for a speaker.

[Technical background of the invention and its problems] The diaphragm material generally used for speakers has the following characteristics: +1) The density p is as small as possible; (2)
Various conditions are required, such as a large elastic modulus E, a large vibration propagation velocity, a wide frequency range, and (3) an appropriately large internal loss.

Conventional diaphragm manufacturing materials for satisfying these conditions include diaphragms made of paper, plastics, metal, and the like. Although speaker diaphragms made from these materials have many features, they also have drawbacks, and to compensate for these drawbacks, they are very rarely used alone, and many of them are combined with other materials. It is used as a mixture or composite with other materials.

・In recent years, metal oxides such as alumina (for example, alumina) have been applied to metal substrates.
We are currently developing speaker diaphragms that are plasma-sprayed with materials such as Al・03), titania (T i O・), and zirconia ('Z'rO2). These metal oxides have high rigidity as a single substance and exhibit excellent physical properties, but
When we measured the physical properties after thermal spraying, we found that they were significantly inferior to the physical properties of the material alone.

For example, alumina on aluminum foil (All2'03)
The physical properties of the product with a coating layer applied by plasma spraying are as follows: 2 degrees ρ is 2.1 (g/cJ), the elastic modulus E is 11.9 X l O” (dyn/c+J), and the specific elastic modulus E/ ρ is 5.7 x 10” (c+a/s
ec 2), whereas in the case of single reminium (All), the density ρ is 2.7 (g/cJ), the elastic modulus E is 7.2X10" (dyn/cJ), and the specific elastic modulus E/ρ is 2.7 x 10” (cffl/5eC
2), and also alumina ('A II 2'l
O3,) has a density ρ of 3.9 (g/cJ) and an elastic modulus E of 38. OX 10” (dyn/cJ),
Specific elastic modulus E/p is 9.7 x 10"(C>/sec 2)
This is significantly inferior to alumina alone.

[Purpose of the invention]

This invention was made in view of the above points, and its purpose is to form a metal oxide mixed with silicon nitride whiskers on a metal base material.
An object of the present invention is to provide a speaker diaphragm with improved physical properties.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be explained for each manufacturing process in accordance with one embodiment with reference to the drawings.

(2) is an aluminum foil as a metal base material, and (2) is alumina (An2) as a metal oxide on the surface of the aluminum foil 1.
03. ) and silicon nitride whiskers (silicon nitride in the form of high-purity acicular single crystals) is sprayed by, for example, a plasma spraying method.

To explain each manufacturing process of this coating N2, the first step is to degrease and clean the 40 μm aluminum foil molded into the desired diaphragm shape with trichlorethylene, etc., and then spray abrasive powder onto the surface. Perform plast treatment.

Next, as a second step, alumina (A120i) powder is coated with a material having a diameter of 0.2 to 0.5 μm and a length of 50 to 300 μm, for example.
, density 1)+ is 3.18 g/cJ, tensile strength 14
00 kg/m%, elastic modulus E+3.85XlOkg/
A material mixed with 5 wt.
A coating layer 2 of about 35 to 45 μm of 3 S Ig N4 is formed.

Also, in the same way as in the above manufacturing method, A1. (A 12"03). By spraying a mixture containing 10% by weight of silicon oxide whiskers (powder) onto an aluminum foil 1 as a metal base material, the coating layer 2 formed on the surface of the aluminum foil 1 and the coating layer 2 formed on the surface of the aluminum foil 1 as a metal base material and Comparing the physical properties such as density ρ, elastic modulus E, and specific elastic modulus E/ρ of the coating layer 2 formed with those of aluminum (Aj alone) and titanium (Ti) alone, the following Table N is obtained. .

Table (I) From Table (I) above, the coating layer 2 made of A6203 Si3N4 formed on the surface of the metal base material by mixing silicon nitride whiskers with Al2O3 as a metal oxide is:
Among the physical properties, both the elastic modulus E and the specific elastic modulus E/ρ are improved compared to aluminum alone or titanium alone. In addition, the Al1203513N4 coating N2 contains Si3N4, which has electrical insulation and heat resistance, and is mixed with AN203, which is a metal oxide with high hardness, so it has very strong thermal shock and fire resistance, and is mechanically It has high physical strength and hardness, excellent rigidity, very small thermal expansion, is chemically stable and corrosion resistant, and has excellent electrical insulation properties, so these properties do not deteriorate even at high temperatures. in this case,
The reason why metal oxides such as alumina (AN20a) were used to mix Si3N4 was because it was coated after thermal spraying! 2
This is to stabilize the bond with 3i3N4.

In the above example, aluminum foil is used as the metal base material, but in addition to aluminum foil, titanium,
Other metal foils such as magnesium alloy and beryllium may also be used. Also, as a metal oxide, alumina AJ! 203 is used in the above example, but in addition to alumina An203, titania (Ti02), zirconia (Zr02)
,? A material having heat resistance and low thermal expansion, such as gnesia (MgO) or herria (B e O), may be used.

Further, in the above embodiment, plasma solvent is used to form the coating layer 2, but the coating N2 may be formed by other means. Either double-sided thermal spraying as shown in FIG. 3 or single-sided thermal spraying as shown in FIG. 3 may be used.

(Effects of the Invention) As described above, the present invention has a structure in which a coating layer made of a mixture of a metal oxide and a silicon nitride whisker is formed on a metal base material. A speaker diaphragm with excellent physical properties such as high rigidity and specific elastic modulus, large internal loss, and high peeling strength can be obtained, and is capable of piston movement up to the high frequency range, allowing for high frequency division. The vibration frequency increases, the frequency characteristics in the audible frequency band can be made flat, and this can contribute to improving the efficiency of the speaker.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention using double-sided thermal spraying, Fig. 2 is a sectional view showing an example of the manufacturing method for manufacturing the diaphragm of the above embodiment, and Fig. 3 is single-sided thermal spraying. FIG. 3 is a sectional view showing another embodiment of the present invention.

Claims (1)

[Claims] A diaphragm for a speaker, characterized in that a coating layer of a mixture of metal oxide and silicon nitride whiskers is formed on a metal base material.