JPS6247399B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a voice coil for an electroacoustic transducer such as a speaker or a microphone. A voice coil for an electroacoustic transducer is usually manufactured by winding a wire around a cylindrical coil bobbin made of paper or metal foil such as aluminum. In order for an electroacoustic transducer, particularly a speaker, to reproduce faithful sound, its diaphragm must move in a piston motion. For this purpose, it is first required that the voice coil, which is the driving source, be driven without being deformed. Furthermore, since the efficiency of a speaker is proportional to the magnetic flux density within the magnetic gap, it is desired that the width of the gap be as narrow as possible, which necessarily requires a thinner coil bobbin. However, if the coil bobbin is thin, the bending rigidity will be insufficient, and the coil bobbin will vibrate with bending or bending. Eventually, it will come into contact with the magnetic circuit plate, center pole, etc., and will no longer be driven faithfully. On the other hand, the weight of the coil bobbin also directly affects the efficiency of the speaker, so it is desirable that it be light. That is, it is advantageous to use a material for the coil bobbin that is light and hard, or in other words, has a large specific elastic modulus E/ρ, which is expressed as the ratio of Young's modulus E to density ρ. Light metals such as aluminum, titanium, and beryllium currently exist as materials that are light and have a large specific modulus of elasticity E/ρ, but currently most coil bobbins are made of aluminum due to practicality such as workability and cost. It is incorporated into loudspeakers with large diameters and high outputs. The present invention provides a method for manufacturing a voice coil that uses aluminum among the above-mentioned light metals as a coil bobbin material to increase rigidity, prevent deformation, enable faithful driving, and increase magnetic flux density between magnetic gaps. . The manufacturing method of the present invention will be explained in detail below with reference to the drawings. Increasing the rigidity of aluminum as a material can be easily achieved by oxidizing the surface of the aluminum to convert it into alumina. For reference, the density ρ and specific elastic modulus E/ρ of aluminum, alumina, and other materials are shown in the table below.

【table】

[Table] Therefore, alumina has a specific elastic modulus E/ρ that is approximately four times that of aluminum. Alumina is specifically formed by anodizing aluminum. The thickness of this alumina layer is proportional to the product of the current density to be applied and the processing time required for the treatment in the anodizing treatment, and by controlling these, an alumina layer with a desired thickness can be obtained. In this case, most of the alumina layer formed is not a dense alumina layer but a layer called a porous layer in which elongated pores are densely packed. This situation is shown in Fig. 1, in which 1 is a cylindrical aluminum that is the basis of the coil bobbin, 2 is an alumina layer formed by anodizing on both the front and back sides of the aluminum 1, 3, 3... The pores are open from both the front and back sides of the alumina layer 2 toward the center, and the diameter R of the pores 3, 3... is approximately 100 to 300 Å, and the distance D between the centers is approximately
It is 300-500 Å. Therefore, simply aluminum 1
If the alumina layer 2 is simply anodized, it has a drawback in terms of brittleness due to its porous structure, and the advantage of alumina having a large specific elastic modulus E/ρ cannot be fully utilized. The present invention further provides a dense structure in which the pores 3, 3... are filled with magnetic metals 4, 4... such as nickel, iron, cobalt, or alloys thereof using an AC electrolytic deposition method, as shown in FIG. In addition, the magnetic metals 4, 4, . . . increase the magnetic permeability between the magnetic gaps and increase the magnetic flux density. In this way, the pores 33 of the alumina layer 2 are filled with the magnetic metals 4, 4, and the outer periphery of the coil bobbin has a third
As shown in the figure, the winding is wound by a well-known method, and the winding part 5
form. Next, specific examples will be given only regarding the process of anodizing aluminum 1 and forming a coil bobbin in which pores 3, 3, . . . are filled with magnetic metals 4, 4, . . ., which is a feature of the present invention. First, aluminum 1, which is the basis of the coil bobbin, is fixed with the same aluminum jig, and then anodized in a treatment bath using this jig as an anode and a lead plate as a cathode. The composition of this treatment bath was: Γ sulfuric acid 10% (wt%) Γ oxalic acid 10 g/. The current density to be applied is 2.5 A/dm ² , and the thickness of the alumina layer 2 is controlled by appropriately changing the current application time. When electricity is applied for about 30 minutes under these conditions, alumina layers 2 with a thickness of 10 μm are formed on both sides. In this alumina layer 2, countless pores 3, 3, . . . having a diameter R of 100 to 300 Å and a distance between centers D of 300 to 500 Å as described above are formed. Next, the pores 3, 3, . . . are filled with the metals 4, 4, . . . by applying an alternating voltage in an electrolytic solution of a desired magnetic metal salt. The metals 4, 4... are deposited in the alumina layer 2 by this AC electrolytic deposition method.
The pores 3, 3...start from the bottom and gradually progress toward the surface, resulting in a dense structure. When filling nickel as the magnetic metal 4, 4..., the composition of the electrolyte is Γ nickel sulfate 300 g / Γ nickel chloride 30 g / Γ boric acid 5 g /, and an alternating current voltage with a current density of about 1.5 A/dm ² is applied. do. Filling of nickel metal 4, 4, etc. is completed in about 20 minutes to 1 hour as a processing time. In this way, a light coil bobbin with high rigidity and high magnetic permeability can be obtained, and after forming the winding portion 5, this voice coil is incorporated into a desired electroacoustic transducer. As is clear from the above description, the manufacturing method of the present invention involves anodizing aluminum to form an alumina layer having pores on its surface, and filling the pores with magnetic metal by AC electrolytic deposition. Since the winding part was formed on the coil bobbin obtained by
It is possible to obtain a product that is lighter in weight and has higher rigidity than the conventional one, and can be made thinner.Furthermore, by filling with the magnetic metal, the magnetic permeability between the magnetic gaps of the magnetic circuit can be increased. Therefore, the efficiency of the device can be improved by incorporating a voice coil manufactured in accordance with the present invention, since the magnetic flux density between the magnetic gaps can be substantially increased.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view showing the state after anodizing treatment of the manufacturing method of the present invention, Fig. 2 is a cross-sectional view showing the main part after filling with the same magnetic metal, and Fig. 3 is a partial cross-sectional view showing the state after anodizing treatment of the manufacturing method of the present invention. 1 is a perspective view showing a voice coil, in which 1 is aluminum, 2 is an alumina layer, 3 is a pore, and 4 is a magnetic metal.

Claims (1)

[Claims] 1 A process of anodizing a coil bobbin made of aluminum to form an alumina layer with pores on the surface, a process of filling the pores of the alumina layer with magnetic metal by AC electrolytic deposition, and a process of winding the coil bobbin around the outer circumference of the coil bobbin. A method for manufacturing a voice coil for an electroacoustic transducer, comprising a step of forming a wire portion.