JP2873149B2 - Electromagnetic sound transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic acoustic transducer, and more particularly to an electromagnetic acoustic transducer having high sound pressure sensitivity.

[0002]

2. Description of the Related Art As shown in FIG. 4, an electromagnetic acoustic transducer 40 includes a diaphragm 30 and a coil 4 inside a container composed of a lower container 1 and an upper container (hereinafter referred to as a lid) 2. And a magnetic flux generating means in which the magnet 50 is combined.

[0003] A sound leakage hole 11 to which an acoustic resistance cloth 12 is attached is formed on the bottom surface of the lower container 1. At the center of the lid 2, a protruding portion 21 protruding toward the inside of the container 1 is formed.

The diaphragm 30 is made of thin aluminum,
A small disk-shaped armature 31 made of a non-magnetic material such as SUS304 and made of a 42Ni-Fe alloy or the like is arranged in order to improve the magnetization efficiency due to the magnetic flux emitted from the protrusion 21 of the lid 2. This amateur 31
Is generally affixed and fixed to the center of the diaphragm 30 via an adhesive layer made of spot welding or an epoxy resin adhesive.

The coil 4 and the magnet 50 are fixed to a coil bobbin body 6 made of plastic.
Is fixed by winding a wire around the coil bobbin 61, and the magnet 50 is adhered around the coil bobbin 61.

In the electromagnetic acoustic transducer 40 described above, the diaphragm 30 and the coil bobbin 6 are fixed to the lower container 1 via an adhesive, and the lid 2 is closed so as to close the opening of the lower container 1. It was fixed with an adhesive or a mechanical structure.

As a result, the inside of the container 1 is separated by the diaphragm 30 into the sound-emitting side space (front air chamber A) and the back side space (rear air chamber B).
, Which is generated from the coil 4 and the magnet 50 arranged on the sound emitting side and is made of a magnetic material such as iron.
The magnetic flux emitted from the projection 21 of the
0, especially its amateur 31 will be magnetized.

When an AC signal corresponding to an audio signal is applied to the coil 4, the intensity of the magnetic flux emitted from the projecting portion 21 of the cover 2 and the direction in which the magnetic flux is generated fluctuate. It will bend and vibrate.

Accordingly, the air in the front air chamber A and the air in the rear air chamber B vibrate, and a sound signal of a predetermined frequency is emitted from the sound emission hole 22. Note that a magnetic flux corresponding to the audio signal leaks to the outside of the sound emitting side of the outer peripheral container 1, and a hearing impaired person can obtain an audio signal by capturing the leaked magnetic flux with a pickup coil or the like.

In the electromagnetic acoustic transducer 40 described above, a non-magnetic material has been used as the material of the diaphragm 30. This is because the vibration coefficient is relatively good and the frequency of the acoustic characteristic can be easily adjusted.

[0011]

However, since the diaphragm 30 is made of a non-magnetic material, the coil 4 and the magnet 50 can be easily adjusted even if the frequency is easily adjusted in terms of acoustic characteristics.
The magnetic force generated by the magnetic force was weak, and the sound pressure level was particularly low in terms of acoustic characteristics.

The armature 31 is attached to the diaphragm 30 in order to increase the holding force and increase the sound pressure level. However, considering the effect of the attachment of the armature 31 on the vibration of the diaphragm 30, the armature 31 is attached. However, there is a limit to the size and thickness of the magnet, and the amount of leakage magnetic flux is still large. Eventually, the magnetic force of the magnet 50 as the magnetic flux generating means is increased.

That is, a magnet 50 made of crystalline ferrite or the like formed by sintering with a magnetic force of about 1500 to 2000 Gauss has been used.

As described above, the magnet 50 made of crystalline ferrite is expensive, and since it is a sintered body, chips and cracks are liable to be generated due to mechanical impact, so that care must be taken in handling. .

The present invention has been made in view of the above-mentioned problems, and has as its object to replace the material of the diaphragm with a magnetic material to increase the magnetic flux holding capacity and to increase the sound pressure level of the acoustic characteristics. And an electromagnetic acoustic transducer that can obtain predetermined characteristics even when the magnetic force of the magnetic flux generating means is relatively small.

[0016]

According to the present invention, there is provided a container comprising a sound emitting side front air chamber having a sound emitting hole, and a back side rear air chamber having a sound leaking hole, separated by a diaphragm made of a magnetic material. An electromagnetic acoustic transducer in which a coil for generating a magnetic flux for vibrating the diaphragm and a rubber magnet are accommodated and arranged in the sound-emitting side front air chamber.

[0017]

According to the present invention, since the diaphragm is made of a magnetic material, all the magnetic force from the coil and the rubber magnet as the magnetic flux generating means can affect the diaphragm, and the leakage magnetic flux is substantially eliminated. . That is, the holding force on the diaphragm is increased, the amplitude of the diaphragm is large, and the sound pressure level on the acoustic characteristics is greatly improved.

Further, in order to maintain the predetermined sound pressure level, the magnetic force on the magnetic flux generating means side for applying vibration to the diaphragm from the magnetic material can be reduced. A rubber magnet in which a magnet steel component or the like is mixed with about 500 gauss of rubber can be used. As a result, the cost can be significantly reduced, and the handling of the rubber magnet is eased.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The electromagnetic acoustic transducer of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an external view of an electromagnetic acoustic transducer, FIG. 2 is an exploded sectional view thereof, and FIG. 3 is an exploded sectional view thereof. The same parts as those in the conventional art are denoted by the same reference numerals.

The electromagnetic acoustic transducer 10 of the present invention comprises a lower container 1 serving as a container, a lid 2 also serving as a yoke plate, a diaphragm 3, a coil 4, and a rubber magnet 5.

The lower container 1 is made of ABS plastic or the like, and has a diameter of 20 to 25 mm and a thickness of 3 to 4 as a whole.
It has a bottomed cylindrical shape of mm. A sound leak hole 1
1 is formed, and an acoustic resistance cloth 12 for closing the sound leakage hole 11 is attached to the surface of the inner bottom surface.

The inner side wall has three steps 13 to 13.
15 are provided. From the upper part on the opening side, the first step portion 13 is for mounting and fixing the lid 2, and the second step portion 14 is for mounting and fixing the coil bobbin body 6. The step portion 15 is for mounting and fixing the diaphragm 3.

The lid 2 is made of a magnetic metal material such as Ni-plated iron, and has a shape fitted to the first step portion 13. A projecting portion 21 projecting toward the inside of the container is formed at the center of the lid 2. In addition, this protrusion 2
1 is a yoke part. A plurality of sound emission holes 22 are formed on the surface of the lid 2.

The diaphragm 3 is mounted and fixed on the third step 15 and is made of a magnetic metal material such as SUS430, Ni--Fe alloy, and has a shape of, for example, a diameter of 1 mm.
The thickness is 8 mm and the thickness is 0.1 mm. Further, an armature 31 made of, for example, a 42Ni-Fe alloy and having a diameter of 4.8 mm and a thickness of 0.2 mm is bonded and fixed to a central portion of the diaphragm 3 with a relatively soft adhesive.

The coil 4 and the rubber magnet 5 are wound or mounted on the coil bobbin 6, respectively.

The coil bobbin body 6 is placed on the second step portion 14 of the lower container 1, and a bobbin portion 61 having a through hole is formed at a central portion.
Is projected from a part of the outside. And
In this part, lead terminals 62 and 63 extending to the outside are formed.

The coil 4 is formed by winding a wire around the bobbin 61 of the coil bobbin body 6.

The rubber magnet 5 is formed by mixing and solidifying a rubber component and a magnetic steel component such as Fe-Al-Ni-Co or Cu-Ni-Fe.
It is formed in a ring shape so as to be disposed around. Such a rubber magnet 5 has a magnetic force of about 300 to 1000 Gauss.

The coil bobbin body 6 is connected to the lower container 1
The coil 4 and the rubber magnet 5 can be arranged at predetermined positions in the container 1 by mounting and fixing the second step portion 14.

To assemble the above components, first, the acoustic resistance cloth 12 is inserted into the sound leakage hole 11 on the bottom of the lower container 1 having a predetermined shape.
Is attached.

The armature 31 is bonded to the center of the diaphragm 3 with an adhesive.

Further, the bobbin portion 61 of the coil bobbin body 6
The coil 4 is formed by winding a wire rod, and both ends of the coil 4 are joined to the lead terminals 62 and 63.
A rubber magnet 5 is adhered to the periphery of 1 with an adhesive.

An adhesive is applied to the third step 15 of the lower container 1 described above, and the diaphragm 3 in which the amateur 31 is integrated is placed. Next, an adhesive is applied to the second step 14 of the outer peripheral container 1, and the coil bobbin body 41 on which the coil 4 and the rubber magnet 5 are arranged is placed.

Finally, an adhesive is applied to the first step 13 of the lower container 1, and the lid 2 is placed.

At this time, the projecting portion 21 of the yoke portion of the lid 2
Is inserted through the through hole of the bobbin portion 61 of the coil bobbin body 6, and the tip of the protruding portion 21 is close to the center of the diaphragm 3. In this state, the diaphragm 3, the coil bobbin 6, the lid 2
And the adhesive between the steps 13 to 15 is hardened to perform integration.

The electromagnetic acoustic transducer 1 thus assembled
0, the intrinsic magnetic flux of the coil 4
Is released toward the diaphragm 3 and the amateur 31 from the
The diaphragm 3 and the armature 31 are magnetized.
The distance between the protrusion 21 and the diaphragm 3 in this state is set to, for example, 0.1 to 0.5 mm.

Next, when a predetermined AC signal corresponding to an audio signal is applied to the coil 4 wound around the coil bobbin body 41, a magnetic flux is generated in the coil 4 in accordance with the direction and magnitude of the current flow. The alternating magnetic flux and the magnetic flux synthesized with the inherent magnetic flux of the rubber magnet 5 affect the diaphragm 3 and the armature 31 from the protrusion 21 of the lid 2.

Thus, the diaphragm 3 and the amateur 31
Is pulled toward the protruding portion 21 of the lid 2 and is separated therefrom, causing the diaphragm 3 to bend and vibrate.
Vibrates the air in the front air chamber A and the rear air chamber B in the container partitioned by the above.

As a result, the vibrated air in the front air chamber A is released to the outside through the sound emission hole 22 and is converted into an audible acoustic signal corresponding to the current signal. The magnetic flux alternating in the coil 4 also generates a magnetic field in the external direction via the lid 2, and if a pickup coil that captures the magnetic field is used, a hearing-impaired person can obtain an audio signal.

A feature of the present invention is that the diaphragm 3 is made of a magnetic material such as 42 alloy, SUS430, or iron. For this reason, the vibration plate 3 is generated by the magnetic flux from the coil 4 and the rubber magnet 5 which are
Since the whole is magnetized, the magnetic holding capacity increases. Therefore, the degree of influence on the diaphragm 3 is increased, and the sound pressure level of the acoustic characteristics is greatly improved.

Here, the armature 31 is for concentrating the holding force at the central portion of the diaphragm 3 to increase the effect of vibration particularly at the central portion of the diaphragm 3, and is made of a conventional non-magnetic material. It is not formed on the vibrating plate 3 to generate a holding capacity.

In addition, in the present invention, the frequency adjustment of the acoustic characteristics, which was the reason for using the diaphragm 3 made of a non-magnetic material, is facilitated by the present invention. It is adjusted by the degree of opening of the mesh 11 of the acoustic resistance cloth 12 to which it is attached.

As described above, according to the present invention, the diaphragm 3
Since the whole is magnetized, the leakage flux is substantially eliminated,
All of the magnetic flux generated from the coil 4 and the rubber magnet 5 can influence the diaphragm 3.

Thus, the sound pressure level on the acoustic characteristics can be dramatically improved. According to the measurement by the inventor, it was confirmed that the sound pressure level of the acoustic characteristics was improved by 12 to 20 dB only by changing the material of the diaphragm from the conventional SUS304 to SUS430, which is an example of the present invention.

This also means that a practically sufficient sound pressure level can be achieved even if the magnetic force from the magnetic flux generating means is reduced. For example, the impedance of the coil 4 can be increased as compared with the prior art. It is possible, and it is possible to employ a magnet 5 having a weak magnetic force.

Conventionally, the magnetic force of the magnet 51 is set to 1000
Since a magnet made of crystalline ferrite or the like formed by sintering is used because a magnet of about 1500 Gauss is required, in the present invention, a magnetic force of 300 to 1000 is used.
Since about Gauss is sufficient, a rubber magnet 5 that is inexpensive, resistant to mechanical shock, and lightweight can be used as the magnet.

As a result, the magnet can be easily handled, the workability is improved, the mechanical shock is strong, and an inexpensive electromagnetic acoustic transducer can be achieved.

Further, in the present invention, the impedance of the conventional coil 3 is used with an impedance of 300 Ω or less in consideration of the reduction in the generated magnetic flux in order to increase the impingement of the coil. Further, since the output impedance of the op-amp of the external drive circuit is large, it is necessary to connect a buffer transistor to reduce the output impedance.

On the other hand, in the present invention, the coil 4 is
Even if the impedance is increased to about 20Ω (for example, a coil that turns a wire having a diameter of 0.03 to 0.35 mm for 800 to 1200 turns), the sound pressure level does not pose a practical problem. Therefore, since the output impedance of the op-amp of the drive circuit can be set to follow the output impedance, the transistor for the buffer can be omitted and the drive circuit can be directly driven by the operational amplifier as in the prior art, so that the electromagnetic acoustic conversion with good sound quality can be achieved. Vessel.

In the above-described embodiment, it is possible to make various changes such as the shapes of the lid 2 and the coil bobbin 6, the fixing method, the structure of the container 1, and the like. Various changes such as bonding the coil 4 and the magnet 5 to the lid 2 are possible.

[0052]

As described above, according to the present invention, by replacing the material of the diaphragm with a magnetic material, an electromagnetic acoustic transducer having an increased sound pressure level with an increased storage capacity is achieved. it can.

As a magnet of the magnetic flux generating means,
Even if the magnetic force is relatively small, the specified characteristics can be obtained,
A lightweight, impact-resistant rubber magnet can be used, and cost reduction can be achieved.

Further, since the impedance of the coil of the magnetic flux generating means can be increased, the operation can be performed by directly connecting to the operational amplifier of the drive circuit.

[Brief description of the drawings]

FIG. 1 is an external perspective view of an electromagnetic acoustic transducer of the present invention.

FIG. 2 is a sectional structural view of the electromagnetic acoustic transducer of the present invention.

FIG. 3 is an exploded structural view of the electromagnetic acoustic transducer of the present invention.

FIG. 4 is a sectional structural view of a conventional electromagnetic acoustic transducer.

[Explanation of symbols]

 Reference Signs List 10 electromagnetic sound transducer 1 lower container 2 lid 12 sound leakage hole 11 acoustic resistance cloth 21 projecting part 22 ... Sound emission hole 3, 31 ... Vibration plate 4 ... Coil 5 ... Rubber magnet 51 ... Magnet

Claims (1)

(57) [Claims] A diaphragm made of a magnetic material includes a sound-emitting-side front air chamber having a sound-emitting hole and a rear-side air chamber having a sound-leaking hole.
An electromagnetic acoustic transducer characterized in that a coil for generating magnetic flux for vibrating the diaphragm and a rubber magnet are accommodated and arranged in the sound-emitting side front air chamber of a container partitioned by a coil.