JPH09223618A - Bonded soft magnetic substance for speaker magnetic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonded soft magnetic substance suited to reduce the distortion with a magnetic circuit of a speaker and improve the quality of sound. SOLUTION: Production of bonded soft magnetic substance uses at least one of Fe or Fe base alloy powders produced by the atomizing, electrolytic or reduction method and the surface treatment is applied to the powder, using an aminosilane coupling agent. An epoxy resin combined with a hardening agent is used and its content is 5-30vol.%. A metal soap is added as needed. The resultant mixture is compression molded and heat treated to obtain a bonded soft magnetic substance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved speaker magnetic circuit, and more particularly to a bond soft magnetic material used in an improved speaker magnetic circuit for reducing high frequency distortion of speaker sound.

[0002]

2. Description of the Related Art A magnetic circuit is an important constituent element of a driving source of a speaker unit. In a relatively large speaker, a ferrite magnet having a high electric resistance is used as a permanent magnet, but in a small speaker, a sintered rare earth magnet having a low electric resistance is used, and an iron, which is a metal component, is used for a yoke. Since there are many metal parts like this, eddy currents are induced in these metal parts when the voice coil is activated, and this eddy current causes distortion of the voice and also a factor that hinders the high-speed response of the voice coil and causes deterioration of sound quality. Has become. As a method for improving this, (1) a method of depositing a copper ring on a magnetic gap forming portion of an iron yoke forming a magnetic circuit, (2)
There is a method of suppressing the generation of eddy current by using non-metal components of the magnetic circuit. In the case of (1), the voice coil driving force is reduced due to an increase in cost due to an increase in the number of parts, a large magnetic gap width in the magnetic circuit, and a decrease in gap magnetic flux density. In the case of (2), typical examples of the non-metal yoke are soft ferrites such as MnZn ferrite and NiZn ferrite. These soft ferrites have a saturation magnetic flux density B which is one of the important characteristics of the yoke material.
Since s is about 5000 G, which is as low as about 1/4 of that of iron material, the gap magnetic flux density of the magnetic circuit cannot be increased, sufficient voice coil driving force cannot be obtained, and there are drawbacks limited to low-output speakers.

[0003]

DISCLOSURE OF THE INVENTION According to the present invention, by producing a bond soft magnetic material having a high saturation magnetic flux density and a high electric resistance, the inside of the yoke due to the magnetic field generated from the voice current flowing in the voice coil is produced. By preventing the generation of eddy currents, deterioration of sound quality due to distortion is prevented, and at the same time, depending on the structure of the yoke material and the magnetic circuit having a high gap magnetic flux density that can be applied to a high output speaker, a permanent magnet is also used. The pole material used is provided.

[0004]

When iron is pure (for example, impurities are 0.05% or less), the maximum magnetic permeability is extremely large, reaching 2 × 10 ⁵ , but according to the conductivity of the metal. The electric resistance is as small as 10 μΩcm, for example, and it cannot be said that the material is suitable for the magnetic core including the yoke and the pole.
Conventionally, metals with high magnetic permeability, such as iron or permalloy (Fe-Ni-Mo), sendust (Fe-Si-A)
l) Other iron-based alloy powders are added to substances with high electrical resistance,
For example, a magnetic body made into a green compact by binding with an organic or inorganic binder such as Bakelite or water glass is disclosed in, for example, Japanese Patent No. 887.
It has long been known as described in Japanese Patent No. 79, Japanese Patent No. 112235, and Japanese Patent No. 122714. The above-mentioned conventional powder magnetic material is, for example, carbonyl iron powder is pressure-bonded with an organic insulator at a relatively low temperature to form a powder magnetic core, or other iron-based alloy powder is mixed with an insulating material and added. It is formed by pressure molding. Since the generation of eddy current increases as the electric resistance value decreases as described above, it is necessary that each of the particles of iron or iron-based alloy powder be insulated by a resin or the like. As described in No. 22515, there is proposed a method of increasing the electric resistance value by dissolving polyphenyl oxide in toluene and mixing it with iron powder. Also, in the old days
As described in Japanese Patent No. 9941, it is proposed that a surface of iron powder is treated with unsaturated ammonium sulfide to form a sulfide film on the surface of the particle, and this is pressed together with an electrically insulating substance. In recent years, various aminosilane coupling agents and titanium-based coupling materials have been developed and are known to be used as surface treatment agents for magnetic particles of rare earth-based bonded magnets and ferrite-based bonded magnets. . On the other hand, the magnetic flux density of the bond soft magnetic material is affected by the true density of iron or an iron-based alloy. That is, when the true density is high, the saturation magnetic flux density is high, and when the true density is low, the saturation magnetic flux density is low. The true density is related to the compactability of the powder and the molding pressure. It is desirable that the powder is as good as possible. It is desirable that the molding pressure is also high, but it is not necessary that the pressure is high enough to increase the coercive force of the iron or iron-based alloy powder by increasing the coercive force of the iron or iron-based alloy powder due to the adverse effects caused by the later-described crimping of the powder or the extreme distortion. Absent. If the molding pressure is too high, the iron or iron-based alloy powder particles are pressed against each other and bonded to each other, so that the electric resistance is lowered and a large amount of eddy current is generated. Therefore, in the present invention, as shown in Examples to be described later, after the epoxy resin is added to the iron or iron-based alloy powder together with the curing agent to sufficiently insulate the particles from each other, pressure bonding is performed to form the bond soft magnetic material. obtain. In order to further increase the electric resistance and strengthen the bond between the particles and the resin, the surface of the iron or iron-based alloy powder particles is previously coated with an aminosilane coupling agent to form an insulating coating. However, if a large amount of epoxy resin is added to sufficiently insulate the iron or iron-based alloy powder particles one by one, the bond soft magnetic material of the iron or iron-based alloy will increase even if the electric resistance of the bond soft magnetic material increases. As a result, the true density as a factor, so-called space factor, decreases, resulting in a decrease in saturation magnetic flux density. On the other hand, if the amount of epoxy resin added is too small, it becomes impossible to insulate each other sufficiently by containing iron or iron-based alloy powder particles one by one, and the electrical resistance will decrease, resulting in a large eddy current generation. Become.
In addition, in a general powder compact not added with an epoxy resin, by exposing it to a high temperature, diffusion is caused between particles to be integrated, but when an epoxy resin is added as described above, iron or iron The mutual diffusion of the base alloy powder cannot be expected, and the strength after the integration must be maintained by the adhesive force of the epoxy resin. From this point as well, if the amount of resin is too small, it is not possible to obtain a bond soft magnetic material having a strength that can withstand practical use. The reason for coating the particle surface with the aminosilane coupling agent is to improve the mechanical strength in addition to increasing the electric resistance. That is, the aminosilane coupling agent has hydrophilicity and lipophilicity. The hydrophilic alkoxysilane portion is strongly adsorbed to the hydrophilic iron or iron-based alloy powder. On the other hand, the part of the alkyl group exhibiting lipophilicity is strongly bonded between the iron or iron-based alloy powder and the epoxy resin via the aminosilane coupling agent in order to firmly bond the lipophilic epoxy resin. Due to such strong adhesion, it is possible to obtain a bond soft magnetic material having a high electrical resistance value and strong mechanical strength. The reason why an epoxy resin is used as an insulator is that its properties are excellent in adhesive strength with a metal, the resin itself has high strength, high temperature resistance, and good weather resistance. As a resin having good adhesiveness to a metal, a phenol resin, a silicone resin, etc. are known in addition to an epoxy resin. The comparison of these mechanical properties is as follows.

[0005]

[Table 1]

On the other hand, the relationship between the mechanical strength and the temperature required for continuous use of the speaker must be such that the continuous use up to a maximum of about 130 ° C. gives a large mechanical strength in consideration of mounting on a vehicle. So 1 phenol resin
Silicone resin cannot withstand continuous use at 30 ° C. or higher, and silicone resin can withstand use at 130 ° C. or higher, but its mechanical strength is significantly inferior to that of epoxy resin. Epoxy resin is also suitable in terms of weather resistance. Further, the epoxy resin is used as a liquid or a fine powder depending on the kind of the curing agent in order to carry out uniform mixing or kneading, and the viscosity is preferably 100 poise or less in the case of a liquid. It is also an advantage that the viscosity can be easily adjusted and that a predetermined amount of a desired curing agent can be uniformly mixed in the form of fine powder. The reason why the epoxy resin content is limited to 5 to 30% by volume as shown in FIG. 1 is that the bending strength is 10 at 5% or less.
Kg / mm or less, and if it is 30% or more, addition of more than that does not contribute to strength. Further, the effective electric resistance value depends on the added amount, and as shown in FIG. 2, the effective electric resistance value extremely decreases at an added amount of 4% or less, so that the addition amount more than this is required. On the other hand, the magnetic flux density B ₁₀₀₀ naturally increases as the added amount decreases, but as shown in FIG. 3, when the volume ratio exceeds 30%, the magnetic flux density B ₁₀₀₀ becomes about 7,000 G or less, and in order to obtain the required magnetic flux amount. Will increase in volume. Of course, the value of B ₁₀₀₀ 7000G is, MnZn ferrite, exhibit higher than B ₁₀₀₀ 5000 G of soft magnetic oxide materials represented by NiZn ferrite, B ₁₀₀₀
Since it is desirable to suppress the volume increase as much as possible in the speaker magnetic circuit for practical use of ≧ 10,000 G, it is limited to 30%.

The iron or iron-based alloy powder used for the bond soft magnetic material is greatly affected by its manufacturing method. FIG. 4 shows the rising of the magnetization with respect to the applied magnetic field in the first quadrant of the bond soft magnetic body produced in Example 1 described later by the magnetic flux density B. As aforementioned,
Although the maximum magnetic permeability of pure iron reaches 2 × 10 ⁵ , the magnetic permeability is remarkably lowered by the accumulation of impurities, lattice defects, dislocations, strains, etc. contained in the crystal, and the coercive force Hc is also increased, resulting in a soft magnetic field. Application as a magnetic material becomes difficult. In FIG. 4, 1 is an iron powder of 100 mesh or less produced by the atomizing method, and 2 is an iron powder of 100 mesh or less produced by mechanical grinding. Value of B when a magnetic field of 1000 Oe is applied to both
Comparing B ₁₀₀₀ , 1 shows B ₁₀₀₀ = 15 KG, while 2 shows B ₁₀₀₀ = 9.1 KOe, which is a low value despite the same iron powder / resin volume ratio. Further, 1 is almost saturated in a magnetic field of 1.5 KOe, but 2 is not saturated even when a magnetic field of 5 KOe is applied. The cause of the decrease in B is not due to impurities but to the accumulation of dislocations and strains in the crystal during the mechanical crushing process. By the way, the iron powder of _{2 is} 650 to 7 in N ₂ gas flow.
By performing so-called strain relief firing at 00 ° C. for several hours,
B recovers to the extent of 1. However, since heat treatment equipment and heat treatment costs are added, it cannot be denied that the cost will increase. Therefore, the production of iron powder or iron-based alloy powder in which the occurrence of transformation and strain is prevented as much as possible is essential from a practical viewpoint, and the preferred powder is one produced by an atomizing method, a hydrogen reduction method and an electrolysis method. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Eddy current generated when a voice current flows through a voice coil for a speaker is generated in a surface layer (surface effect of eddy current) of an iron yoke around a voice coil of a magnetic circuit. Therefore, by forming at least a portion of the yoke facing the magnetic gap with a bond soft magnetic material having a large electric resistance instead of iron, it is possible to suppress the generation of an eddy current that causes audio distortion. . The bond soft magnetic material required for that purpose is a surface of iron powder or iron-based alloy powder that is treated with a silane coupling material in order to enhance the insulating property and strengthen the binding force with the resin, and at the same time Each one must be well insulated by the resin. Epoxy resin is desirable as the resin because it has excellent mechanical strength, heat resistance and weather resistance. By using the bond soft magnetic material formed in this manner, it is possible to suppress the generation of eddy currents and to configure a magnetic circuit for a speaker excellent in sound.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Example 1) 4 kg of iron powder (1) mechanically pulverized by a vibration mill having a grain size of 100 mesh or less and iron powder (2) of the same grain size produced by an atomizing method were prepared. For each of these iron powders (1) and (2), 4 g of γ-glycidoxypropyltrimethoxysilane was added to n-hexane 800 g.
The mixed solution dispersed in ml was added, mixed with a Henschel mixer, and then surface-treated in a thermostat at 100 ° C. for 1 h. Then, liquid epoxy resin (Epicoat 807) 100 is added to each of 4 kg of iron powder (1) and (2) after the surface treatment.
After adding 100 g of a resin solution in which 10 parts of 4,4′-diaminodiphenylmethane was previously dissolved as a curing agent, kneading was performed by a kneader at 100 ° C., and the epoxy resin was polymerized at 120 ° C. After the obtained iron powder epoxy solid was crushed to 60 mesh or less, 20 g of dimethyldiphenyl sulfone having 325 mesh or less was added to 4 Kg of the crushed powder, and they were sufficiently mixed by a Henschel mixer. 0.1 wt% of calcium stearate, which is a metallic soap, is mixed with this mixture, and the molding pressure is 3.5 t / c.
After pressure-molding at room temperature under m ² , the pressure-molded body was heat-cured at 150 ° C. for 2 hours to obtain a bond soft magnetic body. The magnetic flux densities obtained from the iron powders (1) and (2) are as shown in FIG. 4, and as described above, the iron powder (2) having almost no occurrence of strain, defects, etc. exhibits excellent characteristics. In this example, the volume fraction of the resin component was approximately 15 vol% and the electrical resistance was 10 ⁻¹ Ω · cm.
It agrees well with the preliminary examination result of. Since the electric resistance value of the conventional iron yoke is about 10 ⁻⁵ Ω · cm, the electric resistance of the bond soft magnetic material of this embodiment is 10 ⁴ times as large. As a comparative example, when the iron powders (1) and (2) not subjected to the surface treatment with γ-glycidoxypropyltrimethoxysilane were used, the magnetic flux density had a value equivalent to that of FIG. 4, but the electric resistance value was 10 ^{It is −3} Ω · cm, which is 100 times lower than that of the iron yoke, which has a value 100 times higher than that of the iron yoke. From this fact,
It can be seen that the surface treatment with the aminosilane coupling agent has a remarkable effect in increasing the electric resistance.

(Example 2) In Example 1, a liquid resin is used as the epoxy resin. The viscosity of the liquid epoxy resin can be adjusted by the molecular weight or an organic solvent such as acetone, and a homogeneous mixture can be obtained. However, in mass production, the fluidity of the compound, which is a mixture of iron powder and resin, is an important issue during pressure molding. That is, when pressure-molding a compound composed of a liquid epoxy resin containing a curing agent and iron powder, the fluidity is poor,
Continuous supply into the mold cavity is impossible. Therefore, in Example 1, 4,4′-diaminodiphenylmethane was used as a curing agent, after kneading with iron powder, the primary curing was performed to solidify the epoxy resin to ensure fluidity, and By a two-step curing method using dimethyldiphenyl sulfone as a secondary curing agent after pressure molding,
Enables continuous molding of soft magnetic materials. However, this method requires a lot of energy and time due to heating for producing the compound. Therefore, in this embodiment, a fine powder of epoxy resin is used. That is, 3 containing dicyandiamide and its derivative as a curing agent
An epoxy resin fine powder having a size of 25 mesh or less (Epiform EPX-6136) was used. Iron powder is 100 each
Atomized powder below the mesh, electrolytic iron powder, and reduced iron powder from oxides were used. 4 kg of each iron powder was surface-treated with γ-glycidoxypropyltrimethoxysilane in the same manner as in Example 1. 120 kg of Epiform EPX-6136 resin mixture was added to 4 kg of each iron powder after surface treatment.
g, and mixed with a Henscel mixer. 0.2 wt% of calcium stearate was mixed with the mixture, and pressure molding and heat curing treatment were performed in the same manner as in Example 1. The mixing time of the iron powder and the resin varies depending on the shape of the mixer, the number of revolutions, and the amount of treatment, but it is considered appropriate to be about 10 minutes or less, preferably 5 minutes or less. The reason is that the resin adheres to the iron powder surface due to the collision between the iron powder and the resin portion during mixing, but the impact heat at that time suppresses the polymerization accompanied by the local temperature rise of the resin portion as much as possible. . The electric resistance value of each of the obtained bond soft magnetic materials was 10 ^-1 Ω · c.
As shown in FIG. 5, the atomization powder (1), the electrolytic iron powder (2), and the reduced iron powder (3) both showed high values suitable for the bond soft magnetic material. Therefore, it can be seen that all of these iron powders are powders with little distortion. From the above, by using a finely powdered epoxy resin containing or mixed with a curing agent, the time for producing the compound can be shortened and energy can be saved.

[0010]

By using the bond soft magnetic material produced by the present invention, the generation of eddy current can be significantly reduced. Therefore, by applying it to the magnetic circuit of the speaker, the generation of distortion can be suppressed. A speaker with improved sound quality can be provided at low cost. In addition, by utilizing both high magnetic flux density and high electric resistance value, it can be used as a magnetic circuit member such as a polar choke coil that operates by applying an asymmetric voltage, and it can be made smaller, lighter, more efficient, and have a higher switching frequency. Since high frequency can be achieved with low loss,
It is also a promising member in this field.

[Brief description of drawings]

FIG. 1 shows a change in transverse rupture strength with respect to an amount of an epoxy resin component added to a bond soft magnetic material obtained in the present invention.

FIG. 2 shows a change in effective electric resistance value with respect to an added amount of an epoxy resin component of a bond soft magnetic material obtained in the present invention.

FIG. 3 shows a change in magnetic flux density B ₁₀₀₀ with respect to the amount of the epoxy resin component added to the bond soft magnetic material obtained in the present invention.

FIG. 4 shows changes in magnetic field of magnetic flux density of bond soft magnetic material when mechanically pulverized iron powder and atomized iron powder are used as starting materials.

FIG. 5 shows changes in magnetic field of magnetic flux density of bond soft magnetic material when atomized powder, electrolytic iron powder and reduced iron powder are used as starting materials.

[Explanation of symbols]

 None

Claims (8)

[Claims] 1. A volume ratio of iron to iron-based alloy powder of 5 to 30.
% Resin is added, mixed or kneaded, then pressure-molded, and treated at a temperature sufficient to cure only the resin without exposing it to the strain-removing temperature of iron, in the frequency range of about 10 to several hundred KHZ. Bond soft magnetic material for speaker magnetic circuit with high magnetic flux density and low iron loss. 2. The bond soft magnetic material for a speaker magnetic circuit according to claim 1, wherein the resin is a combination of an epoxy resin and a curing agent, and a lubricant is contained if necessary. 3. The bond soft magnetic material for a speaker magnetic circuit according to claim 1, wherein the iron or iron-based alloy powder is produced by an electrolysis method, an atomization method and / or a hydrogen reduction method. 4. The speaker magnetic circuit according to claim 1, wherein the surface of the iron or iron-based alloy powder is surface-treated with an aminosilane coupling agent, and a coating is formed on the surface of the powder by heating. Bond soft magnetic material. 5. The bond soft magnetic material for a speaker magnetic circuit according to claim 2, wherein the combination of the epoxy resin and the curing agent is composed of an epoxy resin in powder form and a curing agent in powder or liquid form. 6. The bond soft magnetic material for a speaker magnetic circuit according to claim 2, wherein the combination of the epoxy resin and the curing agent is composed of a liquid epoxy resin and a powder or a liquid curing agent. 7. The volume of epoxy resin added is 5 to 3
It is 0%, The bond soft magnetic material for speaker magnetic circuits of Claim 2 characterized by the above-mentioned. 8. The bond soft magnetic material for a speaker magnetic circuit according to claim 2, wherein the lubricant is a water-repellent metal soap.