JPH08186894A - Electromagnetic acoustic converter - Google Patents

Abstract

PURPOSE: To provide the electromagnetic acoustic converter improved in sound pressure level. CONSTITUTION: In the electromagnetic acoustic converter where the diaphragm 3 made of magnetic material is placed on and fixed to the step part 13 formed at the internal surrounding of a container 1 and the coil 4 and the magnet 5 vibrating the diaphragm 3 are arranged, plural projection parts 13a to 13d are intermittently formed on the step part 13 on which the diaphragm 3 is placed and the tip part of the diaphragm 3 is adhered/fixed to the step part 13 via rubber-like adhesive material 31.

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 An electromagnetic acoustic transducer 40 has a lower container (hereinafter, simply referred to as a container), as shown in the sectional view of FIG.
A vibrating plate 30, a magnetic flux generating means combining a coil 4 and a magnet 5 are arranged inside a container body composed of 1 and an upper container (hereinafter referred to as a lid) 2.

The container 1 has a sound leakage hole 11 having an acoustic resistance cloth 12 attached to the bottom surface thereof, and the inner wall thereof has a first step portion 13 on which a vibration plate 30 is mounted from the bottom surface side, and a coil. Coil bobbin body 6 that integrates 4 and magnet 5
Is formed, and a third step portion 15 on which the lid 2 is placed is formed.

A diaphragm 30 made of a magnetic material or a non-magnetic material, to which an armature 31 is adhered, is placed on the first step portion 13 if necessary and fixed by an adhesive.

A coil bobbin body 6 made of plastic, on which the coil 4 and the magnet 5 are mounted, is mounted on the second step portion 14.
Is placed and fixed with an adhesive such as epoxy resin. A tubular penetrating body (bobbin portion) 61 is formed in the central portion of the coil bobbin body 6, and a wire material constituting the coil 4 is wound around the bobbin portion 61, and a magnet 5 is adhered around the wire material. There is.

The lid 2 made of a magnetic metal material such as iron plated with Ni is placed on the third step portion 15,
It is fitted and fixed with an adhesive such as epoxy resin. A projecting portion 21 that projects toward the container 2 is formed in the center of the lid body 2, and the bobbin portion 6 of the coil pobbin body 6 is formed.
1 is inserted into the inside of the device 1 so as to be close to the vibration plate 30. The projecting portion acts as a yoke portion that concentrates the magnetic flux generated from the coil 4 and the magnet 5 and increases the influence on the diaphragm 30. A plurality of sound emitting holes 22 ... Are formed on the surface of the lid 2.

As a result, in the container 1, the sound emitting side space (front air chamber A) and the back side space (rear air chamber B) are formed by the vibrating plate 30.
The magnetic flux generated from the coil 4 and the magnet 5 that are partitioned into the sound emitting side and are emitted from the yoke portion 21 is magnetized to magnetize the diaphragm 30 and the armature 31. At this time, when an AC signal corresponding to the audio signal is applied to the coil 4, the intensity of the magnetic flux emitted from the protruding portion 21 of the lid 2 and the direction in which the magnetic flux is generated fluctuate, and the diaphragm 30 flexurally vibrates accordingly. Then, the air in the front air chamber A and the air in the rear air chamber B vibrate, and the sound signal of the predetermined frequency is emitted from the sound output hole 22.

A magnetic flux corresponding to a voice signal leaks to the outside of the sound output side of the container 1, and a person with a hearing loss can obtain a voice signal by capturing the leaked magnetic flux with a pickup coil or the like. .

[0009]

However, the vibrating plate 30 is mounted on the first step portion 13 provided around the inner wall surface of the container 1, and the step portion is formed at the entire peripheral end of the vibrating plate 30. 13 is in surface contact.

Therefore, when the diaphragm 3 vertically vibrates due to the magnetic flux of the coil 4 and the magnet 5, particularly when the vibration direction of the diaphragm 3 is in the direction of abutting the first step portion 13, on the contrary, A force for bending the diaphragm 30 in the opposite direction is generated from the step portion 13 of No. 1 and stress is applied to the diaphragm 30, and as a result, the sound pressure in the low frequency range is reduced.

The present invention has been devised in view of the above problems, and an object thereof is to focus on the relationship between the diaphragm and the stepped portion on which the diaphragm is placed, and (EN) Provided is an electromagnetic acoustic transducer which can minimize the applied stress to prevent the sound pressure level of acoustic characteristics from deteriorating and can easily control the acoustic characteristics.

[0012]

According to the present invention, a diaphragm made of a magnetic material is placed and fixed on a step portion formed around the inner surface of a container, and a coil and a magnet for vibrating the diaphragm are arranged in an electromagnetic field. In the acoustic transducer, a plurality of protrusions are intermittently formed on the stepped portion of the container, and the end portion of the diaphragm is held by the protrusions,
It is an electromagnetic acoustic transducer fixed to a step portion via a rubber-like adhesive material.

[0013]

According to the present invention, the stepped portion on which the diaphragm is placed is provided with intermittently formed projections for substantially holding the diaphragm. Further, the diaphragm and the stepped portion are made of rubber. It is fixed with adhesive.

Therefore, the vibrating plate comes into point contact with the protrusion, and even if the vibrating plate vibrates up and down, the vibrating plate vibrates without substantially making surface contact with the step surface. No stress is generated at the end portion of the plate, the sound pressure level on the acoustic characteristics is improved in the low sound range, and the sound pressure level is also improved as a whole.

Further, since the diaphragm and the rubber-like adhesive can sandwich the diaphragm and separate it into the front air chamber and the rear air chamber, the sound pressure characteristic can be easily controlled.

[0016]

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, and FIG. 2 is an exploded sectional view thereof.

The same parts as in the prior art are designated by the same reference numerals.

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

The 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 mm as a whole.
It has a bottomed cylindrical shape. A sound leakage hole 11 is formed on the bottom surface, and an acoustic resistance cloth 12 is attached to the opening of the sound leakage hole 11 on the inner bottom surface.

The inner side wall has three stepped portions 13-1.
5 are installed around. From the lower part on the opening side, the first step portion 13 is the mounting portion of the diaphragm 3, and the second step portion 14
Is a placement portion of the coil bobbin body 6, and is the third step portion 1
Reference numeral 5 is a fixed portion of the lid body 2.

The lid body 2 is made of a magnetic metal material such as iron plated with Ni, and has a shape to be fitted into the third step portion 15. A projecting portion 21 that projects toward the inside of the container is formed in the center of the lid 2. In addition, this protrusion 2
1 is the yoke part. A plurality of sound emitting holes 22 ... Are formed on the surface of the lid 2.

The diaphragm 3 is placed on the first step portion 13 and is made of a magnetic metal material such as SUS430 or Ni--Fe alloy, and its shape is, for example, 18 mm in diameter.
Is. Further, in the central portion of the diaphragm 3, for example 42N
An amateur 31 made of an i-Fe alloy is fixed by an adhesive material.

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

The coil bobbin body 6 is placed on the second step portion 14 of the container 1, and a bobbin portion 61 having a through hole is formed in the central portion thereof. It is designed to project. Then, lead terminals 62 and 63 extending outward are formed in this portion.

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

The magnet 5 is made of, for example, a rubber component and Fe.
It is obtained by mixing and solidifying a magnetic steel component such as -Al-Ni-Co system or Cu-Ni-Fe system, and has a ring shape so as to be arranged around the bobbin portion 61.

By mounting and fixing such a coil bobbin body 6 on the second step portion 14 of the container 1, the coil 4 and the magnet 5 can be arranged at predetermined positions in the container 1.

Here, a characteristic of the present invention is that the first step portion 13 is formed with projections 13a to 13d for supporting the vibration plate 2 at three or more points. As shown, the end of the diaphragm 3 on the first step 13 is adhered and fixed by a rubber-like adhesive 37 such as silicone resin.

The projections 13a to 13d are very minute, for example, the surface shape is 1 mm square and the height is 0.03 mm.

That is, the vibrating plate 3 is supported by the projections 13a to 13d at four points, and thus does not make surface contact with the first stepped portion 13 as in the conventional case. Moreover, the end portion of the diaphragm 3 is substantially fixed by the rubber-like adhesive material. Therefore, the end portion of the outer peripheral portion of the diaphragm 3 is in a completely free end state in most regions, and the protrusions 13a to 1a
Since the portion contacting with 3d is also substantially in point contact state, even if the diaphragm 3 vibrates, it does not substantially contact the first step portion 13 and stress is applied to the end of the diaphragm 3. Stable vibration is possible because it is hard to apply. This allows
No stress is generated at the end portion of the diaphragm 3, the sound pressure level on the acoustic characteristics is improved in the low sound range, and the sound pressure level is improved as a whole.

In order to make the above-mentioned end of the diaphragm 3 substantially free end, a silicone resin or the like is used as the adhesive 32 for fixing the diaphragm 3 and the first step portion 13. It is desirable to use the rubber-like adhesive material. As a result of various studies by the present inventor, the hardness is 30 to 60 (Shore-
It has been found that a D-scale) adhesive 32 is desirable.

If the hardness is less than 30 (Shore-D scale), the bonding portion between the diaphragm 3 and the protrusions 13a to 13d is deteriorated by the vibration operation, and it is difficult to maintain sufficient adhesiveness, and the hardness is high. This is because if it exceeds 60 (Shore-D scale), the free end action of the end portion of the diaphragm 3 is impaired.

Furthermore, as described above, the stress of the diaphragm 3 is less likely to be applied, the sound pressure level in the acoustic characteristics is improved in the low sound range, the sound pressure level is improved as a whole, and the diaphragm 3 is sandwiched. Since the front air chamber A and the rear air chamber B can be separated, the acoustic characteristics can be easily controlled by adjusting the opening degree of the sound emission holes 22 formed in the lid body 2 and the mesh opening degree of the acoustic resistance cloth 12. become.

Next, in assembling the above-mentioned components, first,
The acoustic resistance cloth 1 is placed in the sound leakage hole 11 on the bottom surface of the container 1 having a predetermined shape.
Paste 2.

The armature 31 is adhered to the central portion of the diaphragm 3 with an adhesive material.

Further, the bobbin portion 61 of the coil bobbin body 6
Then, a wire is wound to form the coil 4, and both ends of the coil 4 are joined to the lead terminals 62 and 63.
The magnet 5 is attached to the periphery of 1 with an adhesive material.

A rubber-like adhesive 32 such as a silicone resin is applied to the first step portion 13 of the container 1 described above, and the vibrating plate 3 in which the armature 31 is integrated is projected from the first step portion 13 to the protruding portion 13a. 13 to 13d, and a rubber-like adhesive material 32 such as a silicone resin is supplied to the end portion of the diaphragm 3 if necessary. Here, by applying the rubber-like adhesive material 32 first, a layer of the adhesive material 32 can be formed between the diaphragm 3 and the protrusions 13a to 13d.

Next, an adhesive is applied to the second step portion 14 of the container 1, and the coil bobbin body 6 in which the coil 4 and the magnet 5 are arranged is placed.

Finally, an adhesive is applied to the third step portion 15 of the container 1 and the lid 2 is placed. At this time, the protruding portion 21 of the yoke portion of the lid body 2 has the bobbin portion 6 of the coil bobbin body 6.
1 is inserted into the through hole, and the tip of the protruding portion 21 has the vibration plate 3
Close to the central part of the.

In this state, the adhesive between the diaphragm 3, the coil bobbin body 6, the lid body 2 and the step portions 13 to 15 is cured to integrate them.

Next, in the electromagnetic acoustic transducer 10 assembled in this way, the unique magnetic flux of the coil 4 is emitted from the projecting portion 21 of the lid 2 toward the diaphragm 3 and the armature 31, and the diaphragm 3 And, the amateur 31 will be 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 a voice signal is applied to the coil 4 wound around the coil bobbin 61, a magnetic flux will be generated in the coil 4 according to the direction and magnitude of the current flow. , The alternating magnetic flux and the magnetic flux combined with the above-mentioned unique magnetic flux of the magnet 5 are combined with each other to form the protrusion 2 of the lid 2.
1 affects the diaphragm 3 and the amateur 31.

As a result, the diaphragm 3 and the amateur 31
Is attracted to and pulled away from the projecting portion 21 of the lid body 2, causing the diaphragm 3 to undergo flexural vibration, and the diaphragm 3
The air in the front air chamber A and the rear air chamber B in the container partitioned by is vibrated.

As a result, the vibrated air in the front air chamber A is released to the outside through the sound output hole 22 and is converted into an audible acoustic signal corresponding to the current signal. Further, since the magnetic flux alternating with the coil 4 extends outward through the lid body 2 to generate a magnetic field, a hearing-impaired person can obtain an audio signal by using a pickup coil that captures this magnetic field.

Generally, between the spatial distance (air gap) X between the yoke portion 21 and the diaphragm 3 and the sound pressure SPL, S is
There is a relational expression of PL = logk (1 / x), and the air gap X is 140 to 15 in the electromagnetic acoustic transducer having the structure of the present invention.
Even if it is about 0 μm, a sound pressure level of 95 dB can be obtained. On the other hand, even if the air gap X is narrowed to 120 to 130 μm in the electromagnetic acoustic transducer of the conventional structure in which the end of the diaphragm 30 directly comes into surface contact with the first step portion 13, the sound pressure level is about 93 dB. I only got it.

In other words, even if the number of windings of the coil 4 is at least and the magnetic force of the magnet 5 is relatively weak, a predetermined sound pressure characteristic is obtained, and the electromagnetic type acoustic transducer is small, lightweight and inexpensive.

The shapes of the lid body 2 and the coil bobbin body 6,
The fixing method, the structure of the container 1, and the like can be variously changed, and further, the coil bobbin body 6 can be omitted and the coil 4 and the magnet 5 can be directly bonded to the lid body 2 and various changes can be made.

[0049]

As described above, according to the present invention, the portion on which the diaphragm is substantially mounted becomes a minute protrusion, and the diaphragm and the stepped portion are fixed by the rubber-like adhesive. Since it is performed through the material, the end portion of the diaphragm is substantially in a free end state, vibration is not hindered at the end portion of the diaphragm, and stress is less likely to be applied to the end portion of the diaphragm at the same time. Furthermore, since the contact between the diaphragm and the step portion is alleviated, the electromagnetic acoustic transducer has improved sound pressure characteristics, particularly in the low frequency range.

Moreover, the acoustic characteristics can be easily controlled by the sound output holes and the acoustic resistance cloth, and the small size allows stable vibration even if the magnetic flux generated from the coil or the magnet is relatively small. It becomes a lightweight and inexpensive electromagnetic acoustic transducer.

[Brief description of 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 an electromagnetic acoustic transducer of the present invention.

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

FIG. 4 is a cross-sectional view illustrating a contact state between the protrusion of the first step portion and the diaphragm according to the present invention.

FIG. 5 is a cross-sectional structure diagram of a conventional electromagnetic acoustic transducer.

[Explanation of symbols]

 10 ... Electromagnetic acoustic transducer 1 ... Container 13 ... First step portion 13a to 13d ... Projection portion 14 ... Second step portion 15 ... Step part 3 ... Lid 21 ... Yoke 22 ... Sound emitting hole 3 ... Vibration plate 32 ... Rubber-like adhesive 4 ...・ Coil 5 ・ ・ ・ ・ ・ ・ Magnet

Claims (1)

[Claims] 1. An electromagnetic acoustic transducer in which an end portion of a diaphragm made of a magnetic material is fixed to a step formed on the inner surface of the container, and a coil and a magnet for vibrating the diaphragm are arranged. Multiple protrusions are intermittently formed on the step of
An electromagnetic acoustic transducer characterized in that an end of the diaphragm is held by the projection and fixed to a step through a rubber-like adhesive material.