JPS60212099A - Speaker - Google Patents

Abstract

PURPOSE:To reduce an impedance of a voice coil without a short ring and then to decrease the secondary harmonic distortion by forming a magnet for comprising a magnet constituting a magnetic circuit by means of a conductive ferrite containing divalent Fe. CONSTITUTION:An annular magnet 1 consisting of a conductive ferrite at an outer periphery, a yoke 2, a plate 3 and a circular pole 4 are arranged, thereby constituting a speaker. Furthermore a voice coil 8 is arranged in a magnetic gap 5. Here, the yoke 2, the plate 3 and the pole 4 are made of a pure iron including 99.4% Fe, 0.3% Si, 0.2% Mn and the like. In the magnet 1 divarent Fe<2+> is produced and the conductive ferrite whose electric resistance is substantially reduced is used. As a result, the magnet 1 itself serves as a short ring, and the impedance of the voice coil is decreased, whereby the distortion seldom occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a speaker device, and more particularly to an improvement in a magnet constituting a magnetic circuit.

[Background technology and its problems]

Conventionally, as a magnet constituting a magnetic circuit of a speaker device, for example, Fe A/Ni-C has been used.

Metal magnets such as Alnico-based alloys (so-called alnico magnets) are mainly used, but since this type of metal magnet is a natural metal and has limited resources and is expensive, ferrite magnets are used instead. is becoming widely used. Since this ferrite magnet is inexpensive and easily available, it is extremely useful in reducing the cost of speaker devices.

By the way, generally speaking, a speaker device has a magnetic circuit made up of, for example, a magnet, a pole, a plate, etc., and a voice coil coupled to a diaphragm is located within the magnetic gap of this magnetic circuit. By supplying an audio signal as a current to the voice coil, the voice coil is vibrated according to Fleming's left-hand rule, and the signal is converted from the electrical system to the acoustic system. However, when the audio current flows through the voice coil, the above-mentioned Alternating current magnetic flux is generated in the magnetic circuit, and the nonlinearity of the magnetic permeability of the magnetic material that makes up the magnetic circuit, especially the magnetization structure with a hysteresis loop, can cause distortion in the current and generate sound pressure distortion. Are known.

In particular, in the case of a so-called long voice coil in which the voice coil is longer than the same width as the gap so that the magnetic flux in the magnetic gap and the voice coil are always 100% interlinked in the vibration range, a large amount of magnetic flux passing through the magnet is generated. Therefore, second harmonic distortion tends to increase.

Therefore, it is possible to prevent the generation of current distortion by canceling the alternating current magnetic flux generated by the voice current using the conductivity of the magnet and reducing the apparent inductance of the voice coil. However, the ferrite magnet is an insulator. Since it is close to , no effect can be expected.

For this reason, conventionally, a short ring such as a copper ring or an aluminum ring is provided inside the magnet formed by the ferrite magnet, and this short ring acts as a secondary winding of the voice coil to short-circuit the voice coil. A method of reducing the inductance of the coil is being considered. By providing this short ring, even if there is nonlinearity in the magnetic material constituting the magnetic circuit, the amount of change in inductance is reduced, current distortion is reduced, and second harmonic distortion can be suppressed.

However, using the above-mentioned short ring increases the number of parts and the associated assembly man-hours, which is disadvantageous in terms of manufacturing costs.In addition, the above-mentioned ferrite magnet has considerable dimensional errors in the sintered state. Problems also arise in terms of workability, such as difficulty in adjusting dimensions with the short ring.

[Purpose of the invention]

Therefore, the present invention was proposed in order to eliminate the drawbacks of the above-mentioned conventional devices, and it is possible to reduce the inductance of the voice coil without using a short ring, thereby reducing the second harmonic distortion. The purpose of the present invention is to provide a speaker device that is easy to use.

[Summary of the invention]

The present inventors have completed the present invention by focusing on the extremely low electrical resistance of ferrite containing divalent iron. A speaker device in which a voice coil is disposed in a magnetic gap of a magnetic circuit is characterized in that the magnet is made of conductive ferrite containing divalent iron.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of essential parts showing the configuration of a speaker device to which the present invention is applied.

The speaker device according to the present invention has an annular magnet 1 made of conductive ferrite arranged on the outer periphery, a yoke 2 on the bottom, a plate 3 on the top, and a cylindrical pole 4 in the center. Furthermore, a voice is wound around the circumferential surface of the voice coil bobbin 7 coupled to the diaphragm 6 within the gap formed between the inner circumferential surface of the plate 3 and the outer circumferential surface of the pole 4, that is, the magnetic gap 5. It is arranged so that the coil 8 is located.

Here, the yoke 2, plate 3, and pole 4 are made of commonly used materials, such as Fe 99.
4%, SiO, 3%, Mn 0.2 q6, etc.

On the other hand, as the magnet 1, barium ferrite BaO.□Pe2's or strontium ferrite Sr0.6Fe20s is usually used.
Since it is a polycrystalline material consisting of the following particles and has a high electrical resistance of approximately 10Ω·cm, conductive ferrite is used here, in which divalent iron (Fe 2 ) is generated to significantly reduce the electrical resistance.

As a method to lower the electrical resistance of the barium ferrite and strontium ferrite mentioned above, first, 2×102Ω・c
It is conceivable to precipitate FezOa having an electrical resistance of about m, but since this Fe20g is non-extractive, it would reduce the magnetic properties of the ferrite, such as coercive force Hc and residual magnetic flux density Br. . On the other hand, when divalent iron Fe is generated as FeaO+, the electromechanical resistance of Fea04 is about 7×1OΩ・cm, so it is possible to significantly lower the electrical resistance of the ferrite. Moreover, it does not have any adverse effect on magnetic properties.

By the way, in order to generate divalent iron Fe as FeaO+ in the barium ferrite or strontium ferrite, the ferrite is treated at a high temperature of about 1370°C to proceed with the reaction 1370'C 3FezOa →2 Ii''e804+102. However, especially in the presence of BaO or SrO, this reaction is difficult to proceed and higher temperatures are required. At such high temperatures, FezOg crystal grains grow and the coercive force Hc of the resulting ferrite decreases significantly. Normally, when creating the above-mentioned barium ferrite and strontium ferrite, BaO or S
The presence of BaO or SrO is unavoidable because the firing is performed with an excess of rO.

Therefore, in order to manufacture the conductive ferrite containing the divalent iron Fe2+, the following manufacturing method may be used.

First, raw materials EaO or SrO and Fe2es are prepared and mixed at a predetermined mixing ratio. At this time,
In order to advance the ferrite reaction during calcination described later, the Ba
O or SrO is blended so that it is slightly in excess of the stoichiometric composition.

Next, the above mixture is calcined to advance the ferrite reaction, and then pulverized. The ferrite reaction obtained at this time,
Pure ao/6Fe208 or Sr0/5 FezOa
In addition, excessive amounts of aO and SrO exist alone as impurities with a weight of about 5%.

If this BaO or SrO exists, as mentioned above, the temperature conditions for producing Fe 804 will be high and there is a risk that the coercive force Hc' will decrease due to the growth of Fezes crystal grains. must be removed in advance.

Next, the pulverized material is washed with water to remove excess BaO or 8rO.

Since the above-mentioned BaO or SrO is water-soluble, the content of BaO or SrO can be reduced to 0.05 weight coefficient or less by, for example, boiling and cleaning.

After washing and removing the impurities BaO or SrO in this way, Fe20a is added and further heat treatment is performed to generate FeBO4. The FezO8 to be added may be heat-treated to precipitate an appropriate amount of Fe before addition. In addition, the amount of Fe20a added is 2 to 10% by weight, that is, Fe2O8
The molar ratio of to BaO or SrO is 6.14 to 6.
．． It may be set to about 69. Furthermore, the above heat treatment is preferably carried out under a low 02 partial pressure so that the formation of Fe3O4 proceeds rapidly at low temperatures. Just process it.

The ferrite obtained by the above heat treatment has
There is a possibility that some crystal grains of F"ezQa may have grown due to this heat treatment, so this is crushed again, and the crushed product is pressure-molded and sintered to obtain conductive ferrite.The resulting conductive ferrite The electrical resistance of is about 1-10 BΩ, cm.

As described above, by forming the magnet 1 constituting the magnetic circuit from conductive ferrite containing divalent iron (Fe) and having low electrical resistance, the inductance of the voice coil is reduced and the speaker device generates extremely little distortion. is obtained. FIG. 2 shows the second harmonic distortion frequency characteristic of the obtained speaker device, and FIG. 3 shows the third harmonic distortion frequency characteristic of the obtained speaker device in comparison with the conventional one. In addition, in these figures 2 and 3,
Curve a represents the characteristics of the speaker device to which the present invention is applied, and curve A represents the characteristics of the conventional speaker device. From FIG. 2, the second harmonic distortion is significantly reduced in the speaker device to which the present invention is applied, and from FIG.
It can be seen that the harmonic distortion is also slightly improved.

Furthermore, in the above embodiment, the electric resistance of the magnet 1 itself is lowered to serve as a short ring, and assembly is easy because no special member (short ring such as a copper ring or aluminum ring) is required. Also, there is no increase in manufacturing costs due to an increase in the number of parts.

By the way, in order to further reduce the electrical resistance and improve the thermal conductivity of the magnet 1 constituting the magnetic circuit of the above-described speaker device, the magnet 1 is formed of conductive ferrite containing divalent iron, and This surface may be plated with metal.

That is, after degreasing and cleaning the surface of the magnet 1 formed of the conductive ferrite, and further acid cleaning,
After neutralization, Cu electroless plating is applied to deposit a Cu base film on the surface. Then, a desired metal is electrolytically plated on this base film. The type and thickness of the metal to be electrolytically plated are arbitrary, and the part to be plated may be the entire surface of the magnet 1 or a part thereof.

In this way, by forming the magnet 1 with conductive ferrite containing divalent iron and further plating its surface with metal, it is possible to further reduce the electrical resistance and suppress the occurrence of distortion. At the same time, since the thermal conductivity of the magnet 1 is improved, it is also possible to improve the input resistance of the speaker device.

Note that the present invention is applicable not only to the speaker device having the configuration shown in the above embodiment, but also to any structure, such as an internal magnet type or an external magnet type, as long as the speaker device has a magnetic circuit composed of at least a magnet or a yoke. It is possible to do so.

〔Effect of the invention〕

As is clear from the description of the embodiments above, in the present invention, the magnet constituting the magnetic circuit is formed of conductive ferrite containing divalent iron, so special members such as short rings are used. Therefore, the inductance of the voice coil can be reduced without any distortion, and a speaker device with less distortion and easy assembly can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main parts showing the configuration of a speaker device to which the present invention is applied, Fig. 2 is a characteristic diagram showing its second harmonic distortion frequency characteristics in comparison with a conventional one, and Fig. 3 is a 3rd harmonic distortion frequency characteristic. FIG. 3 is a characteristic diagram showing harmonic distortion frequency characteristics in comparison with a conventional one. 1...Magnet 2...Yoke 5...Magnetic gap 8...Voice coil patent applicant Sony Corporation Tohoku Metal Industry ■ Agent Patent attorney Kodo Koike 1) Sakae Mura - Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a speaker device comprising a magnetic circuit composed of at least a magnet and a yoke, and a voice coil disposed in a magnetic gap of the magnetic circuit, the magnet constituting the magnetic circuit is formed of conductive ferrite containing divalent iron. A speaker device characterized by: