JP2001231097A - Electromagnetic electric-acoustic transducer and portable terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic electric-acoustic transducer that can attain low sound frequency reproduction and high sound pressure and low distortion reproduction. SOLUTION: The electromagnetic electric-acoustic transducer is provided with a 1st diaphragm that is placed to be capable of vibration, a 2nd diaphragm being a magnetic substance that is placed in the middle of the 1st diaphragm, a yoke placed in opposition to the 1st diaphragm, a center pole placed between the yoke and the 1st diaphragm, a coil placed around the centre pole, a 1st magnet placed to surround the coil, and a 2nd magnet placed at an opposite side of the center pole with respect to the 1st diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mobile phone,
Installed in portable terminals such as pagers (registered trademark),
The present invention relates to an electro-acoustic transducer used for reproducing an alarm sound, a melody sound, and a voice when a call arrives.

[0002]

2. Description of the Related Art FIG. 18A is a plan view of a conventional electromagnetic electroacoustic transducer, and FIG.
The conventional electromagnetic electroacoustic transducer 200 has a cylindrical housing 1.
07, and a disk-shaped yoke 106 arranged so as to cover the bottom surface of the housing 107. A center pole 10 integrally formed with the yoke is provided at the center of the yoke 106.
3 are provided. A coil 104 is wound around the center pole 103. An annular magnet 105 is provided on the outer periphery of the coil 104.
4 and the inner peripheral surface of the magnet 105 have an appropriate interval over the entire circumference. The outer peripheral surface of the magnet 105 is in contact with the inner peripheral surface of the housing 107. A disk-shaped first diaphragm 100 is supported on the upper end of the casing 107, and an appropriate gap is provided between the first diaphragm 100, the magnet 105, the coil 104, and the center pole 103. Is provided. At the center of the first diaphragm 100, a second diaphragm 101, which is a disk-shaped magnetic body, is provided concentrically with the first diaphragm 100.

The operation and effect of the electromagnetic electroacoustic transducer 200 configured as described above will be described.

In an initial state where no current flows through the coil 104, a magnetic path is formed by the magnet 105, the second diaphragm 101, the center pole 103, and the yoke 106, and the second diaphragm 101 is connected to the magnet 105 and the center. The first diaphragm 100 is sucked by the pole 103 and displaced until it becomes equal to the elastic force of the first diaphragm 100. When an AC current flows through the coil 104 in such an initial state, an AC magnetic field is generated in the magnetic path, and an AC driving force is generated in the second diaphragm 101. When such an AC driving force is generated in the second diaphragm 101, the second diaphragm 101
Vibrates from the initial state together with the fixed first diaphragm 100 due to the interaction with the static suction force generated by the vibration. The vibration is emitted as sound.

[0005]

The resonance frequency of the electromagnetic electro-acoustic transducer 200 having the above-described structure is determined by the elastic force of the first diaphragm 100 and the second force of the magnet 105.
Depends on the deformed shape in a state where the static suction force generated on the vibration plate 101 is balanced.

FIG. 19 shows a force-displacement curve of the first diaphragm 100 and the second diaphragm 101 by the magnet 105.
Shows the relationship with the static suction force that occurs in the above. The vertical axis represents force, and the horizontal axis represents diaphragm displacement. The intersection A shown in FIG.
The force-displacement curve of the first diaphragm 100 and the magnet 10
5 is an intersection with a curve indicating a static suction force generated in the second diaphragm 101. That is, the intersection A represents a point at which the elastic force and the static suction force balance, and the resonance frequency is determined by the elastic constant of the first diaphragm 100 at the intersection A.

In order to lower the resonance frequency, it is necessary to increase the mass of the vibration system or reduce its elastic constant. However, increasing the mass of the vibration system is not desirable because it leads to lower efficiency. On the other hand, if the elastic constant of the vibration system is too small, the force-displacement curve of the first diaphragm 100 has a characteristic shown as a dotted line in FIG. 19, and the force-displacement curve of the first diaphragm 100 and the magnet Since there is no longer an intersection with the static suction force generated by the first diaphragm 105, the second diaphragm 101
Along with 0, it is attracted to the magnetic circuit unit without being balanced at any position.

In other words, the lower limit of the designable resonance frequency is naturally determined from the condition that the elastic constant must be within the range where the intersection with the static suction force exists. It is also possible to reduce the elastic constant by reducing the static suction force, but in that case, the generated AC driving force also decreases, so that a sufficient reproduction sound pressure cannot be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and it is possible to reproduce low-frequency sound without changing the size of the first magnet and the first and second diaphragms.
It is an object of the present invention to provide an electromagnetic electro-acoustic transducer capable of reproducing high sound pressure and low distortion by increasing an AC driving force.

[0010]

According to the present invention, there is provided an electromagnetic electro-acoustic transducer according to the present invention, comprising: a first vibrating plate arranged so as to vibrate;
A second diaphragm made of a magnetic material, provided at the center of the diaphragm, and a yoke provided facing the first diaphragm;
A center pole provided between the yoke and the first diaphragm, a coil disposed to surround the center pole, a first magnet disposed to surround the coil, and a first diaphragm A second magnet disposed on the opposite side of the center pole to achieve the above object.

[0011] The apparatus may further include a first housing supporting the first diaphragm and a second housing provided with a second magnet.

The shape of the second magnet may be a disk.

The shape of the second magnet may be annular.

When the shape of the second magnet is a disk, the outer diameter of the second magnet may be smaller than the outer diameter of the second diaphragm. When the shape of the second magnet is annular The outer diameter of the second magnet may be equal to or larger than the outer diameter of the second diaphragm.

[0015] A third magnet may be further provided at the center of at least one surface of the first diaphragm or the second diaphragm.

[0016] The magnetization direction of the second magnet may be the same as the magnetization direction of the first magnet.

The magnetization direction of the second magnet may be a radial direction with reference to a center axis passing through the center of the center pole.

The thickness of the second diaphragm may be a thickness that causes magnetic saturation when approaching the center pole side by a predetermined distance.

The material of the first diaphragm may be a magnetic material.

The material of the first diaphragm may be a non-magnetic material.

A first magnetic thin plate provided between the first magnet and the first diaphragm may be further provided.

The shape of the first magnetic thin plate may be annular. The second magnetic thin plate provided on the second magnet may be further provided.

The shape of the second magnetic thin plate may be a disk shape.

The shape of the second magnetic thin plate may be annular.

The shape of the first diaphragm may be a shape having a non-linearity which cancels out the non-linearity of the AC driving force generated in the second diaphragm.

The relationship between the resultant force obtained by adding the first static suction force and the second static suction force and the distance between the second diaphragm and the center pole is substantially linear. Static suction force
A static attraction force generated on the second diaphragm by a magnetic circuit composed of the first magnet, the center pole and the yoke, and the second static attraction force is generated by the second magnet by the second magnet. The first vibrating plate may be bonded to the first housing by a static suction force generated in the first case.
May be fixed.

The first diaphragm may be fixed by sandwiching the first diaphragm between the first housing and the second housing.

[0028] The second housing may be a cover for protecting the first and second diaphragms.

According to the present invention, there is provided a portable terminal device provided with the above-mentioned electromagnetic electroacoustic transducer.

The portable terminal device may further include a third housing having a sound hole, and the electromagnetic electroacoustic transducer may be provided such that the first and second diaphragms face the sound hole.

[0031] A second magnet may be provided on the third housing.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) An electromagnetic electro-acoustic transducer 1000 according to Embodiment 1 of the present invention will be described with reference to FIGS.

FIGS. 1 (a) and 1 (b) are a plan view and a sectional view of an electromagnetic electro-acoustic transducer 1000 according to Embodiment 1 of the present invention.

FIG. 2 is a magnetic flux vector diagram of the electromagnetic electro-acoustic transducer 1000 according to Embodiment 1 of the present invention.
The magnetic flux vector diagram shown in FIG. 2 shows only one half of the center axis of electromagnetic electro-acoustic transducer 1000 in the first embodiment of the present invention.

As shown in FIG. 1B, the electromagnetic electro-acoustic transducer 1000 according to the first embodiment of the present invention
It has a cylindrical first housing 7 and a disk-shaped yoke 6 arranged so as to cover the bottom surface of the first housing 7.
A center pole 3 integrally formed with the yoke is provided at the center of the yoke 6. A coil 4 is wound around the center pole 3. An annular magnet 5 is provided on the outer periphery of the coil 4, and an appropriate interval is provided between the coil 4 and the inner peripheral surface of the magnet 5 over the entire circumference. The outer peripheral surface of the magnet 5 and the inner peripheral surface of the first housing 7 are provided with an appropriate interval over the entire circumference. First
A first diaphragm 1, which is a disk-shaped magnetic material, is supported on the upper end of the housing 7 so as to be able to vibrate.
An appropriate distance is provided between the coil 4 and the center pole 3. At the center of the first diaphragm 1, a second diaphragm 2, which is a disk-shaped magnetic body, is provided concentrically with the first diaphragm 1. Further, a cylindrical second housing 10 is provided so as to cover the upper surface of the first housing 7, and the second magnet 9 is positioned such that the second magnet 9 is positioned above the second diaphragm 2. The second housing 10 is provided. The second magnet 9 has a disk shape as shown in FIG. The first diaphragm 1 may be bonded to, for example, the first housing 7, or may be fixed between the first housing 7 and the second housing 10.

As shown in FIG. 1A, the second casing 10 emits sound from the first diaphragm 1 and the second diaphragm 2 to the outside of the second casing 10. For this purpose, a plurality of air holes 12 are provided. The second housing 10 also serves as a cover for protecting the first and second diaphragms 1 and 2 from external impact. The yoke 6 has a space between the coil 4 and the inner peripheral surface of the magnet 5 and the first diaphragm 1.
A plurality of air holes 8 communicating with the outside of the space between the air gap and the yoke 6 are provided at appropriate intervals in the circumferential direction.
Each air hole 8 discharges air from the space between the coil 4 and the inner peripheral surface of the magnet 5 to the outside, so that an acoustic load applied to the first diaphragm 1 is reduced.

The operation and effects of the electromagnetic electro-acoustic transducer 1000 configured as described above will be described.

In the present embodiment, in the initial state where no current flows through the coil 4, as shown in FIG. 2, the first magnet 5, the first diaphragm 1, the second diaphragm 2, the center pole 3 and the yoke 6 form a first magnetic path, and the second magnet 9 and the second diaphragm 2 form a second magnetic path.

In such a configuration, the second diaphragm 2
Above, the downward static attraction generated by the first magnetic path and the upward static attraction generated by the second magnetic path cancel each other. Therefore, the first diaphragm 1
Is hardly displaced by the downward static attraction force generated by the magnetic path.

Next, when an AC current flows through the coil 4, an AC magnetic field is generated, and an AC driving force is generated on the second diaphragm 2. When such an AC driving force is generated in the second diaphragm 2, the second diaphragm 2 interacts with the fixed first diaphragm 1 due to the interaction with the static attraction generated by the magnet 5. Vibrates from the initial state. The vibration is emitted as sound.

In this case, since the first diaphragm 1 is hardly displaced by the downward static attraction force generated by the first magnetic path, the force of the first diaphragm shown in FIG. The resonance frequency depends on the elastic constant near the origin on the displacement curve. Therefore, the electromagnetic electro-acoustic transducer 1000 of the present embodiment is
The elastic constant is smaller and the resonance frequency is lower than in the state where there is an initial deflection as seen at 0. For example, in an electromagnetic electroacoustic transducer having a diameter of 15 mm, when the first diaphragm 1 and the second diaphragm 2 are each made of permalloy and have a thickness of 30 μm and 150 μm, respectively,
By providing the second magnet 9, the resonance frequency becomes 1.6
It can be reduced from kHz to 1 kHz.

FIG. 3 shows the relationship between the outer diameter of the second magnet 2 and the static attraction force and the AC driving force. The vertical axis represents the static attraction force and the AC driving force, and the horizontal axis represents the second magnet 2.
Shows the outer diameter of the. The solid line is the static suction force, and the broken line is the AC driving force. If the static suction force is negative, the second diaphragm 2
Is attracted to the second magnet 9 side.
Further, the diameter of the second diaphragm 2 in this embodiment is 4 mm.
And

As shown in FIG. 3, the static suction force is the second
When the outer diameter of the magnet 9 substantially coincides with the outer diameter of the second diaphragm 2, the value becomes 0, and the vertical static attraction acting on the second diaphragm 2 is balanced. If the outer diameter of the second magnet is larger than that, it can be seen that the second magnet 9 is more strongly attracted to the center pole side despite the increase in volume. Conversely, when the outer diameter of the second magnet decreases, it can be seen that the second diaphragm 2 is attracted to the second magnet 9 side. From this result, it is understood that the smaller the outer diameter of the second magnet, the more strongly the second diaphragm 2 is attracted to the second magnet 9 side.

From the result, the second magnet 9
When the outer diameter of the second magnet 9 is reduced, the second diaphragm 2 is attracted to the second magnet 9 more than necessary depending on the outer diameter. In this case, the thickness of the second magnet 9 is reduced. The static suction force can be adjusted by changing the thickness to a smaller value or a smaller energy product. As described above, when the thickness of the second magnet 9 is changed to be thin or a product having a small energy product, the volume of the electromagnetic electro-acoustic transducer is reduced, and the electromagnetic electro-acoustic transducer is not connected to the outside. Leakage magnetic flux is reduced.

From the above, the outer diameter of the second magnet 9 is
It is desirable that the diameter be equal to or less than the outer diameter of the second diaphragm 2.

In this embodiment, the magnetizing direction of the second magnet 9 is the same as that of the first magnet 5, but the magnetizing may be performed in the opposite direction.

(Embodiment 2) An electromagnetic electro-acoustic transducer 2000 according to Embodiment 2 of the present invention will be described with reference to FIG.

FIG. 4 is a sectional view of an electromagnetic electro-acoustic transducer 2000 according to Embodiment 2 of the present invention.

The electromagnetic electroacoustic transducer 20 shown in FIG.
In 00, the third magnet 11 is provided on the second diaphragm 2. The third magnet 11 can be provided on the second diaphragm 2 by, for example, bonding. First magnet 405 and second magnet 409
Has the same effect as the first magnet 5 and the second magnet 9 shown in the first embodiment of the present invention,
The energy products are adjusted to form an appropriate magnetic path with the third magnet 11. Other configurations are the same as those of the electromagnetic electro-acoustic transducer 1000 according to Embodiment 1 of the present invention shown in FIG. The magnetization direction of the third magnet 11 is the same as that of the first magnet 4.
05 and the direction of magnetization of the second magnet 409 are opposite to each other.

The operation of electromagnetic electro-acoustic transducer 2000 according to the second embodiment of the present invention configured as described above is substantially the same as that of electromagnetic electro-acoustic transducer 1000 according to the first embodiment of the present invention. . The difference from the first embodiment of the present invention is that the third magnet 11 is provided on the second diaphragm 2. The third magnet 11 is the first magnet 4
05 and the second magnet 409, when the first diaphragm 1 bends or vibrates, the first diaphragm 1 is repelled by the third magnet 11 by the repulsive force. In addition, it is possible to prevent the second diaphragm 2 from adsorbing to the first magnet 405 and the second magnet 409.

Therefore, even when the electromagnetic electroacoustic transducer is used for a long time and the elastic force of the first diaphragm 1 changes, the first diaphragm 1 and the second diaphragm 2 It is possible to realize an electromagnetic electro-acoustic transducer in which the first magnet 405 and the second magnet 409 are not attracted, that is, have excellent durability.

Although the third magnet 11 is provided on the second diaphragm 2 in the present embodiment, it may be provided on the lower center or on both sides of the first diaphragm 1.

(Embodiment 3) An electromagnetic electroacoustic transducer 3000 according to Embodiment 3 of the present invention will be described with reference to FIGS.

FIGS. 5 and 6 are a sectional view and a magnetic flux vector diagram of an electromagnetic electroacoustic transducer 3000 according to the third embodiment of the present invention, respectively. The magnetic flux vector diagram of FIG. 6 shows only one half with respect to the center axis of the electromagnetic electro-acoustic transducer 3000 according to the third embodiment of the present invention.

The electromagnetic electroacoustic transducer 30 shown in FIG.
In 00, the second magnet 29 is supported by the second housing 10 so as to be located above the second diaphragm. The second magnet 29 is magnetized in the radial direction with reference to an axis passing through the center of the second diaphragm 2. Other configurations are the same as those of the electromagnetic electro-acoustic transducer 1000 according to Embodiment 1 of the present invention shown in FIG.

In the electromagnetic electro-acoustic transducer 3000 according to Embodiment 3 of the present invention having the above-described configuration, as shown in FIG.
A first magnetic path is formed by the diaphragm 1, the second diaphragm 2, the center pole 3, and the yoke 6, and a second magnetic path is formed by the second magnet 29 and the second diaphragm 2. You. The formation of the first magnetic path and the second magnetic path is basically the same as that of the electromagnetic electro-acoustic transducer 1000 according to the first embodiment of the present invention. The operation of the electromagnetic electro-acoustic transducer 3000 according to the third embodiment of the present invention is basically the same as the operation of the electromagnetic electro-acoustic transducer 1000 according to the first embodiment of the present invention.

The difference from the first embodiment is the magnetization direction of the second magnet 29. As shown in FIG. 6, the direction is opposite to the direction of the magnetic flux vector on the second diaphragm 2.
By radially magnetizing the second magnet 29,
A magnetic path can be formed more efficiently. As a result, magnetic flux leakage is reduced, as can be seen from comparison with the magnetic flux vector diagram in the first embodiment as shown in FIG.

Since the magnetic path is formed efficiently, the thickness of the second magnet 29 can be reduced. For example, when the second magnet 29 is designed using radially magnetized ferrite, the thickness of the second magnet 29 for obtaining the same effect as that of the first embodiment is the second magnet 29 of the first embodiment. The thickness is about 1/3 of that of the magnet 9.

Although an example in which ferrite is used as the material of the second magnet 29 has been described here, neodymium or the like may be used in order to further reduce the thickness of the second magnet 29. In addition, samarium cobalt may be used as the material of the second magnet 29 in consideration of heat resistance.

(Embodiment 4) An electromagnetic electroacoustic transducer 4000 according to Embodiment 4 of the present invention will be described with reference to FIGS.

FIG. 7 is a sectional view of an electromagnetic electro-acoustic transducer 4000 according to Embodiment 4 of the present invention.

The electromagnetic electro-acoustic transducer 40 shown in FIG.
In 00, the first diaphragm 31, which is a non-magnetic material, is fixed by being sandwiched between the first housing 7 and the second housing 10.
The first diaphragm 31 is made of, for example, titanium. Further, the shape of the first diaphragm 31 is a shape in which a part of the disk shape is raised in a direction perpendicular to the diameter direction. First magnet 705 and second magnet 709
Has the same effect as the first magnet 5 and the second magnet 9 shown in the first embodiment of the present invention,
In consideration of the fact that the first diaphragm 31 is a non-magnetic material, the energy products are adjusted in order to form an appropriate magnetic path. Other configurations are the same as those of the electromagnetic electro-acoustic transducer 1000 according to Embodiment 1 of the present invention shown in FIG.

The operation and effects of the electromagnetic electro-acoustic transducer 4000 configured as described above will be described. The basic operation is the same as in the first embodiment.

When the first diaphragm 31 is a non-magnetic material,
The static suction force and the AC driving force generated in the second diaphragm 2 are constant irrespective of the shape of the first diaphragm 31.

In general, when a current is input to the coil 4 as a sine wave, the AC driving force generated on the second diaphragm 2 is the driving force acting on the plus side (the direction in which the diaphragm moves away from the magnetic circuit portion) and the minus side. (The direction in which the diaphragm approaches the magnetic circuit)
In the driving force acting on the sine waves, the sine waves do not always have the same amplitude. For example, the ratio between the plus side and the minus side is 0.85: 1.00, and the driving force is biased to the minus side. Such non-linearity causes harmonic distortion.

Therefore, in the fourth embodiment, the first
Is designed so that the force-displacement characteristic of the first diaphragm 31 is the reverse characteristic of the biased driving force characteristic, thereby canceling the non-linearity of the driving force.

FIG. 8 shows a force-displacement curve of the first diaphragm 31 shown in FIG. The shape of the first diaphragm 31 has different elastic constants when deformed to the plus side and the minus side, and its force-displacement characteristics are opposite to the biased drive characteristics as described above. It is designed to. As a result, in the entire system in which the driving force and the elasticity of the first diaphragm 31 are considered, the force-displacement of the first diaphragm 31 becomes almost linear, and low distortion reproduction becomes possible.

In the fourth embodiment, the shape of the first diaphragm 31 is a shape in which a part of the disk shape is protruded in a direction perpendicular to the diameter direction. Any achievable shape is applied as the shape of the first diaphragm 31. For example, a part of the first diaphragm 31 may have a waveform.

Although the material of the first diaphragm 31 is made of a non-magnetic material to facilitate the design, a magnetic material may be used to further increase the driving force. Further, the first diaphragm is fixed by being sandwiched between the first case 7 and the second case 10, but may be fixed by bonding.

(Embodiment 5) An electromagnetic electroacoustic transducer 5000 according to Embodiment 5 of the present invention will be described with reference to FIGS.

FIG. 9A is a sectional view of an electromagnetic electro-acoustic transducer 5000 according to the fifth embodiment of the present invention.

The magnetic flux vector diagram shown in FIG. 10 shows the electromagnetic electroacoustic transducer 500 according to the fifth embodiment of the present invention.
Only one half is displayed with respect to the central axis of 0.

In the electromagnetic electroacoustic transducer 5000 shown in FIG. 9A, the first diaphragm 41, which is a non-magnetic material,
It is fixed by being sandwiched between the first housing 7 and the second housing 10. The shape of the first diaphragm 41 is a shape in which a part of the disk shape is raised in a direction perpendicular to the diameter direction.
In the center of the first diaphragm 41, a second diaphragm 22, which is a disk-shaped magnetic material, is provided concentrically with the first diaphragm 41. Further, an annular second magnet 19 as shown in FIG. 9B is provided in the second housing 10 so as to be located above the second diaphragm 22, and an annular magnetic thin plate is provided. 13 is provided on the surface of the first magnet 905 facing the first diaphragm 41. A concave portion for providing the magnetic thin plate 13 is provided on the inner peripheral side portion of the first magnet 905.

In the present embodiment, the first diaphragm 41
Is titanium, which is a non-magnetic material, and its thickness is 15
μm. The material of the second diaphragm 22 is permalloy, and its thickness is 50 μm. The thickness of the second diaphragm 22 is such that the first diaphragm 41 is
This is the thickness that causes magnetic saturation when flexing to the side. The magnetization direction of the second magnet 19 is the same as that of the first magnet 9.
The height direction is the same as 05. Other configurations are the same as those of electromagnetic electro-acoustic transducer 4000 according to the fourth embodiment of the present invention shown in FIG.

The operation and effect of the electromagnetic electro-acoustic transducer 5000 configured as described above will be described.

In the present embodiment, in the initial state where no current flows through coil 4, as shown in FIG.
905, magnetic thin plate 13, second diaphragm 2
2, a first magnetic path is formed by the center pole 3 and the yoke 6, and a second magnetic path is formed by the second magnet 19 and the second diaphragm 22.

As shown in FIG. 9A, by providing the magnetic thin plate 13, it is possible to efficiently supply the AC magnetic flux to the second diaphragm 22, and as a result, the AC driving force is increased. Therefore, the reproduction sound pressure can be increased.

In the fifth embodiment, since titanium, which is a non-magnetic material, is used for the first diaphragm 41, FIG.
The first diaphragm 41 is not shown in the magnetic flux vector diagram shown in FIG.

FIG. 11 shows the static attraction generated on the second diaphragm 22 with and without the second magnet 19. The vertical axis indicates the static suction force, and the horizontal axis indicates the distance from the zero point of the second diaphragm 22. The zero point indicates the position of the second diaphragm 22 when the vertical static attraction acting on the second diaphragm 22 by the first magnet 905 and the second magnet 19 is balanced. The solid line shows the case where the second magnet 19 is provided, and the broken line shows the case of the conventional electromagnetic electroacoustic transducer without the second magnet 19.

In the case where the second magnet 19 is not provided in FIG. 11, the second diaphragm 22 is connected to the first magnet 90.
The value of the static suction force is always positive because it is sucked by 5.

On the other hand, when the second magnet 19 is provided, a static attractive force is also generated in the direction opposite to the center pole 3. Accordingly, the value of the static suction force can be both positive and negative with respect to the zero point at which the static suction force is balanced in the second diaphragm 22.

The second diaphragm 22 has a thickness of 50 μm.
This makes it possible to suppress the phenomenon that the static attraction force suddenly increases as approaching the center pole 3 as in a conventional electromagnetic type electro-acoustic transducer.

As a result of the above configuration, the change in the static suction force has a substantially linear characteristic with respect to the distance from the zero point as shown in FIG. As a result, it is possible to reduce the stiffness of the entire system obtained from the difference between the elastic force of the first diaphragm 41 and the static suction force, and it is possible to lower the resonance frequency determined by the stiffness.

Further, if the elastic force of the first diaphragm 41 is linear, the stiffness of the entire system is constant regardless of the distance, so that the resonance frequency does not change due to the applied voltage, and the harmonic distortion does not occur. Also less.

FIG. 12 shows the AC driving force generated on the second diaphragm 22 with and without the second magnet 19. The vertical axis indicates the AC driving force, and the horizontal axis indicates the distance from the center pole 3. FIG.
Similarly to the above, the solid line shows the case where the second magnet 19 is provided, and the broken line shows the case of the conventional electromagnetic electro-acoustic transducer without the second magnet 19.

In FIG. 12, when the second magnet 19 is not provided, magnetic saturation occurs due to the use of the second diaphragm 22 having a small thickness, and a sufficient AC driving force cannot be obtained.

Therefore, the second magnet 19 is added, and the magnetic flux generated in the second diaphragm 22 is canceled by the first magnet 905 to reduce the magnetic saturation.
As a result, the AC magnetic flux as the driving force can efficiently flow into the second diaphragm 22, and the obtained AC driving force increases. That is, a sufficient AC driving force can be obtained even with a thin diaphragm that easily causes magnetic saturation. Also, by reducing the thickness, the weight of the vibration system is reduced, so that the reproduced sound pressure can be further increased.

FIG. 13 shows the relationship between the outer diameter of the second magnet 22 and the static attraction force and the AC driving force. The vertical axis indicates the static attraction force and the AC driving force, and the horizontal axis indicates the outer diameter of the second magnet. The solid line is the static suction force, and the broken line is the AC driving force. The larger the static suction force, the more the second diaphragm 2
2 indicates that the center pole 3 is being sucked.
Further, the diameter of the second diaphragm 22 in this embodiment is set to 4 m.
m.

As shown in FIG. 13, the change in the static attraction force is caused by the fact that the outer diameter of the second magnet 19 is smaller than the second diaphragm 22.
Is smaller than the outer diameter of the second magnet 19, but when the outer diameter of the second magnet 19 whose respective outer diameters match is larger than 4 mm, the change in the static attractive force also increases, and the position of the static attractive force is balanced. It is approaching zero.

From the results, in the range shown in FIG. 13, as the outer diameter of the second magnet 19 increases, the static attraction force acting on the second diaphragm 22 toward the second magnet 19 and the center pole It can be seen that the static suction force on the third side is easily balanced.

On the other hand, the AC driving force is maximized when the outer diameter of the second diaphragm 22 is about 4.5 mm, although the AC driving force is slightly different, but the AC driving force significantly changes due to the change in the outer diameter of the second magnet 19. Is not seen.

From the above, it is desirable that the outer diameter of the second magnet 19 be equal to or larger than the outer diameter of the second diaphragm 22.

In this embodiment, the first diaphragm 41 can be designed without considering the heat resistance and the influence of the magnetic field.
Although non-magnetic titanium was used for the above, permalloy may be used like the second diaphragm 22. In this case, the materials of the first diaphragm 41 and the second diaphragm 22 are the same type. Therefore, joining becomes easy. In addition, a non-metallic resin material may be used for the first diaphragm 41, and in this case, the shape of the first diaphragm 41 is easily formed.

In the present embodiment, the second diaphragm 22
Is reduced to 50 μm so that magnetic saturation easily occurs. However, when magnetic saturation is not taken into account as described in the first embodiment of the present invention, the thickness of the second diaphragm 22 may be large. Good. In this case, since the AC driving force does not decrease due to saturation near the center pole as shown in FIG. 12, it is advantageous to design the second diaphragm 22 to be used near the center pole. The same effect is obtained by the second diaphragm 22
Can be obtained by using pure iron as the material.

In the present embodiment, the magnetic thin plate 13 is provided on the first magnet 905. However, the magnetic thin plate 13 is not provided when a sufficient AC driving force can be obtained only by the magnet or when the space is difficult to install. You may.

Further, in the present embodiment, the static attraction generated in the second diaphragm 22 by the magnetic path formed by the first magnet 905, the center pole 3 and the yoke 6 and the second magnet 19 is reduced. In order to make the second diaphragm substantially linear with respect to the distance from the center pole 3, the thickness of the second diaphragm was reduced to cause magnetic saturation, but this is not limited as long as the same effect can be obtained. For example, by setting the shape of the second diaphragm 22 arbitrarily, such as providing a notch or a hole in the second diaphragm 22, the static suction force and the distance from the center pole 3 as described above can be reduced. May be linear.

(Embodiment 6) An electromagnetic electro-acoustic transducer 6000 according to Embodiment 6 of the present invention will be described with reference to FIGS.

FIG. 14 is a sectional view of an electromagnetic electro-acoustic transducer 6000 according to Embodiment 6 of the present invention.

The magnetic flux vector diagram shown in FIG. 15 shows the electromagnetic electroacoustic transducer 600 according to the sixth embodiment of the present invention.
Only one half is displayed with respect to the central axis of 0.

The electromagnetic electroacoustic transducer 6 shown in FIG.
In 000, an annular second magnet 39 provided in the second housing 10 is magnetized in a radial direction based on an axis passing through the center of the second diaphragm 22. Other configurations are the same as those of electromagnetic electro-acoustic transducer 5000 according to the fifth embodiment of the present invention shown in FIG.

In the present embodiment, in the initial state where no current flows through coil 4, as shown in FIG.
905, magnetic thin plate 13, second diaphragm 2
The first magnetic path is formed by the center pole 3 and the yoke 6, and the second magnetic path is formed by the second magnet 39 and the second diaphragm 22 as in the fifth embodiment. is there. The operation is the same as that of the fifth embodiment.

The difference from the fifth embodiment lies in the direction of magnetization of the second magnet 39. As shown in FIG.
By radially magnetizing the second magnet 39 so as to be in the direction opposite to the direction of the magnetic flux vector on the diaphragm 22, the magnetic path can be formed more efficiently. As a result, magnetic flux leakage is reduced as can be seen from comparison with the magnetic flux vector diagram in the fifth embodiment as shown in FIG.

Since the magnetic path is formed efficiently, the thickness of the second magnet 39 can be reduced. For example, when the second magnet 39 is designed using radially magnetized ferrite, the thickness of the second magnet 39 for obtaining the same effect as that of the fifth embodiment is the second magnet 39 of the fifth embodiment. The thickness is about ／ of that of the magnet 19.

Here, an example in which ferrite is used as the material of the second magnet 39 has been described, but neodymium or the like may be used in order to make the thickness of the second magnet 39 thinner. In addition, samarium cobalt may be used as the material of the second magnet 39 in consideration of heat resistance.

(Embodiment 7) An electromagnetic electroacoustic transducer 7000 according to Embodiment 7 of the present invention will be described with reference to FIG.

FIG. 16 is a sectional view of an electromagnetic electro-acoustic transducer 7000 according to the seventh embodiment of the present invention.

In the electromagnetic electroacoustic transducer 7000 shown in FIG. 16A, the upper surface of the second magnet 619 is
An annular second magnetic thin plate 33 as shown in FIG. 16B is provided. The second housing 610 is newly provided with a concave portion for accommodating the second magnetic thin plate 33. The second housing 610 includes the first diaphragm 41.
Further, a plurality of air holes 612 for radiating the sound from the second diaphragm 22 to the outside of the second housing 610 are provided. By providing the second magnetic thin plate 33 on the upper surface of the second magnet 619, the magnetic path is changed to the second magnet 61.
9, the second magnetic thin plate 33 and the second diaphragm 22. The first magnet 605 and the second magnet 619 are effective in the fifth embodiment of the present invention.
The first magnet 905 and the second magnet 19 are the same as those described above, but an appropriate magnetic path is formed in consideration of the fact that the magnetic flux of the second magnet 619 is guided to the second magnetic thin plate 33. Energy products have been adjusted to achieve this. Other configurations are the same as those of electromagnetic electro-acoustic transducer 5000 according to the fifth embodiment of the present invention shown in FIG.

As shown in FIG. 16, the second magnetic thin plate 3
By providing 3, the magnetic resistance of the magnetic path configured as described above decreases because the magnetic flux of the second magnet 619 is guided by the second magnetic thin plate 33. Therefore, compared with the case where the second magnetic thin plate 33 is not provided,
Energy product of the magnet 619 can be reduced. Furthermore, since the magnetic flux of the second magnet 619 is guided into the second magnetic thin plate 33, the leakage magnetic flux to the outside of the electromagnetic electro-acoustic transducer 7000 of the present embodiment is reduced.

In this embodiment, the shape of the second magnetic thin plate 33 is annular as shown in FIG. 16 (a), but it is disc-shaped as shown in FIG. 16 (c). The second magnetic thin plate 34 may be provided on the upper surface of the second magnet 619.

The second magnetic thin plate 3 is attached to the disk-shaped second magnet as shown in the first to fourth embodiments of the present invention.
3 or 34 may be provided.

In this embodiment, the second magnetic thin plate 33
(For example, the fifth embodiment of the present invention), the second magnet 19 has an energy product of 26 MGOe,
By providing the second magnetic thin plate 33, the effect of the static attractive force corresponding to a thickness of 0.7 mm can be realized by the second magnet 619 having an energy product of 22 MGOe and a thickness of 0.5 mm. it can.

FIG. 17 is a partially broken perspective view of a portable telephone as an example of a portable terminal provided with the electromagnetic electro-acoustic transducer of the present invention. Any of the electromagnetic electro-acoustic transducers 1000 to 7000 described in Embodiments 1 to 7 of the present invention is applied to the electromagnetic electro-acoustic transducer 64 used in this mobile phone.

The portable telephone 61 has a housing 62, and a sound hole 63 is provided on one side of the housing 62. An electromagnetic electroacoustic transducer 64 is provided inside the housing 62.
The first diaphragm is provided so as to face the sound hole 63. The mobile phone 61 has a built-in signal processing circuit (not shown) for converting a calling signal for receiving a signal and inputting the signal to the electromagnetic electro-acoustic transducer 64. When the signal processing circuit of the mobile phone 61 receives the signal indicating the incoming call, the signal is input to the electromagnetic electroacoustic transducer 64,
A ringtone plays. As a result, the user can know the incoming call. Subsequently, the audio signal is input to the electromagnetic electro-acoustic transducer 64, and the user can receive the sound by reproducing the audio.

Many of the electromagnetic electroacoustic transducers built in portable terminals typified by conventional portable telephones have high resonance frequencies and have been used only for ringing tone reproduction.

However, since the electromagnetic electro-acoustic transducer of the present invention can lower the resonance frequency, if the electro-magnetic electro-acoustic transducer of the present invention is used in a portable terminal, it is possible to reproduce a voice signal, and a ringing tone Both reproduction and audio signal reproduction can be performed by one electromagnetic electro-acoustic transducer.
As a result, it is possible to reduce the number of acoustic components built in the portable terminal.

In the mobile phone 61, the electromagnetic electroacoustic transducer 64 is directly mounted on the housing 62, but may be mounted on a substrate built in the mobile phone 61. Also, an acoustic port may be added to increase the sound pressure of the ringing tone.

In FIG. 17, a portable telephone is shown as an example of a portable terminal. However, the present invention is not limited to this, and is a small electromagnetic type electroacoustic transducer capable of reproducing high sound pressure, such as a pager, a notebook computer and a wristwatch. Applicable to portable terminals requiring a device.

In the first to seventh embodiments, the second
Second housings 10 and 61 for supporting the magnets 9, 409, 29, 709, 19, 39 and 619 of FIG.
However, when the electromagnetic electro-acoustic transducer according to the first to seventh embodiments is mounted on the mobile phone 61 shown in FIG. 17, for example, the second magnets 9, 409, 29, 709, 19, 39 and 61
9, the second housings 10 and 610 and the mobile phone housing 62 may be shared.

[0120]

According to the electromagnetic electro-acoustic transducer of the present invention, the first diaphragm is maintained in an equilibrium state by arranging the second magnet above the second diaphragm with a gap interposed therebetween. As a result, the resonance frequency can be lowered without changing other components, thereby enabling low-frequency reproduction. Further, since the AC driving force on the second diaphragm becomes large and the static attraction force-displacement characteristic becomes almost linear, high sound pressure and low distortion can be reproduced without changing other parts. .

Further, according to the electromagnetic electroacoustic transducer of the present invention, the second magnet can be operated efficiently by setting the magnetization direction of the second magnet to the radial direction. Of the magnet can be made smaller.

Further, according to the electromagnetic electro-acoustic transducer of the present invention, the first diaphragm has the nonlinearity that cancels the nonlinearity of the AC driving force generated on the second diaphragm. Non-linearity can be reduced in the entire system, and harmonic distortion can be reduced.

According to the electromagnetic electroacoustic transducer of the present invention, the third magnet is provided on at least one of the upper and lower portions of the first and second diaphragms.
It is possible to prevent the first and second diaphragms from being attracted to the center pole and the second magnet.

According to the electromagnetic electro-acoustic transducer of the present invention, the second diaphragm has a thickness that saturates when approaching the center pole side, so that the saturation phenomenon is easily generated, The static attraction force that is amplified as the diaphragm approaches the center pole is suppressed, and a more linear static attraction force characteristic is obtained, so that a lower frequency range of the resonance frequency can be realized.

Further, according to the electromagnetic electroacoustic transducer of the present invention, by providing the magnetic thin plate provided on the surface of the first magnet opposed to the first diaphragm, the second diaphragm is provided. In order to be able to flow AC magnetic flux efficiently
The AC driving force increases and the sound pressure can be increased.

Further, according to the portable terminal device of the present invention,
Similarly, by incorporating the electromagnetic electro-acoustic transducer of the present invention, it is possible to realize a portable terminal device capable of reproducing an alarm sound, a voice, and the like.

[Brief description of the drawings]

FIG. 1A is a plan view of a second housing of an electromagnetic electro-acoustic transducer according to Embodiment 1 of the present invention. FIG. 1B is a plan view of an electromagnetic electro-acoustic transducer according to Embodiment 1 of the present invention. Sectional view (c) is a plan view of the second magnet of the electromagnetic electro-acoustic transducer according to Embodiment 1 of the present invention.

FIG. 2 is a magnetic flux vector diagram of the electromagnetic electroacoustic transducer according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an outer diameter of a second magnet of the electromagnetic electro-acoustic transducer according to Embodiment 1 of the present invention and static attraction force and AC driving force.

FIG. 4 is a cross-sectional view of an electromagnetic electro-acoustic transducer according to Embodiment 2 of the present invention.

FIG. 5 is a sectional view of an electromagnetic electroacoustic transducer according to a third embodiment of the present invention.

FIG. 6 is a magnetic flux vector diagram of the electromagnetic electroacoustic transducer according to the third embodiment of the present invention.

FIG. 7 is a sectional view of an electromagnetic electroacoustic transducer according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing force-displacement characteristics of a first diaphragm of an electromagnetic electroacoustic transducer according to Embodiment 4 of the present invention.

9A is a sectional view of an electromagnetic electro-acoustic transducer according to Embodiment 5 of the present invention. FIG. 9B is a plan view of a second magnet of the electromagnetic electro-acoustic transducer according to Embodiment 5 of the present invention. Figure

FIG. 10 is a magnetic flux vector diagram of the electromagnetic electroacoustic transducer according to the fifth embodiment of the present invention.

FIG. 11 is a diagram showing a static attractive force generated on a second diaphragm of the electromagnetic electro-acoustic transducer according to the fifth embodiment of the present invention.

FIG. 12 is a diagram showing an AC driving force generated on a second diaphragm of the electromagnetic electro-acoustic transducer according to Embodiment 5 of the present invention.

FIG. 13 is a diagram showing a relationship between an outer diameter of a second magnet of the electromagnetic electro-acoustic transducer according to Embodiment 5 of the present invention and static attraction force and AC driving force.

FIG. 14 is a sectional view of an electromagnetic electroacoustic transducer according to a sixth embodiment of the present invention.

FIG. 15 is a magnetic flux vector diagram of the electromagnetic electroacoustic transducer according to the sixth embodiment of the present invention.

16A is a cross-sectional view of an electromagnetic electro-acoustic transducer according to Embodiment 7 of the present invention. FIGS. 16B and 16C are diagrams illustrating a second example of the electromagnetic electro-acoustic transducer according to Embodiment 7 of the present invention. Plan view of thin magnetic plate

FIG. 17 is a partially cutaway perspective view of a portable terminal equipped with the electromagnetic electro-acoustic transducer of the present invention.

18A is a plan view of a conventional electromagnetic electro-acoustic transducer, and FIG. 18B is a cross-sectional view of the conventional electromagnetic electro-acoustic transducer.

FIG. 19 shows the force of the first diaphragm of the electromagnetic electro-acoustic transducer.
The figure which shows the relationship between the displacement characteristic and the static attractive force which arises in a 2nd diaphragm by a magnet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 31 1st diaphragm 2, 22 2nd diaphragm 3 Center pole 4 Coil 5 Magnet 6 Yoke 7, 10 Case 8 Air hole 13, 33 Magnetic thin plate 1000 Electromagnetic electroacoustic transducer 61 Cellular phone

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[Procedure amendment]

[Submission date] November 9, 2000 (200.11.
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010]

Means for Solving the Problems] electromagnetic transducer of the present invention comprises a first diaphragm, provided in the center portion of the first diaphragm, a second diaphragm of a magnetic material A yoke provided to face the first diaphragm, a center pole provided between the yoke and the first diaphragm, a coil arranged to surround the center pole, and a coil surrounding the coil. And a second magnet arranged on the opposite side of the center pole with respect to the first diaphragm, thereby achieving the above object.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

The thickness of the second diaphragm is such that the second diaphragm is
The thickness may be such that it is magnetically saturated when approaching the vicinity of the upper surface of the interpole .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

A shape having a force-displacement characteristic that almost cancels the nonlinearity of the AC driving force generated on the second diaphragm .
The first diaphragm may be used.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

[0026] generated in the first magnet, the center pole and the first static attraction force generated on the second diaphragm by a magnetic circuit formed by the yoke, the second diaphragm on the second magnet plus the second of the static suction force
The relationship between the resultant force and the distance between the second diaphragm and the center pole
The engagement may be substantially linear . The first diaphragm may be fixed by bonding the first diaphragm to the first housing.

Claims (25)

[Claims] A first diaphragm arranged so as to be able to vibrate, a second diaphragm made of a magnetic material provided at a center of the first diaphragm, and a first diaphragm A yoke provided to face, a center pole provided between the yoke and the first diaphragm, a coil arranged to surround the center pole, and a coil arranged to surround the coil An electromagnetic electro-acoustic transducer, comprising: a first magnet; and a second magnet disposed on the opposite side of the center pole with respect to the first diaphragm. 2. The electromagnetic electro-acoustic transducer according to claim 1, further comprising: a first housing supporting the first diaphragm; and a second housing provided with the second magnet. vessel. 3. The electromagnetic electro-acoustic transducer according to claim 1, wherein said second magnet has a disk shape. 4. The electromagnetic electro-acoustic transducer according to claim 1, wherein the shape of the second magnet is annular. 5. An outer diameter of said second magnet is equal to said second magnet.
4. The electromagnetic electro-acoustic transducer according to claim 3, wherein the diameter is equal to or less than the outer diameter of the diaphragm. 6. An outer diameter of said second magnet is equal to said second magnet.
5. The electromagnetic electroacoustic transducer according to claim 4, wherein the diameter is not less than the outer diameter of the diaphragm. 7. The electromagnetic electro-acoustic transducer according to claim 1, further comprising a third magnet at the center of at least one surface of the first diaphragm or the second diaphragm. 8. The electromagnetic electroacoustic transducer according to claim 1, wherein the magnetization direction of the second magnet is the same as the magnetization direction of the first magnet. 9. The electromagnetic electro-acoustic transducer according to claim 1, wherein the magnetization direction of the second magnet is a radial direction with respect to a center axis passing through the center of the center pole. 10. The electromagnetic electro-acoustic transducer according to claim 1, wherein the thickness of the second diaphragm is a thickness that causes magnetic saturation when approaching the center pole side by a predetermined distance. 11. The electromagnetic electro-acoustic transducer according to claim 1, wherein the material of the first diaphragm is a magnetic material. 12. The electromagnetic electroacoustic transducer according to claim 1, wherein a material of the first diaphragm is a non-magnetic material. 13. The electromagnetic electroacoustic transducer according to claim 1, further comprising a first magnetic thin plate provided between the first magnet and the first diaphragm. 14. The electromagnetic electroacoustic transducer according to claim 13, wherein the shape of the first magnetic thin plate is annular. 15. The electromagnetic electro-acoustic transducer according to claim 1, further comprising a second magnetic thin plate provided on the second magnet. 16. The electromagnetic electro-acoustic transducer according to claim 15, wherein the shape of the second magnetic thin plate is a disk shape. 17. The electromagnetic electroacoustic transducer according to claim 15, wherein the shape of the second magnetic thin plate is annular. 18. The shape of the first diaphragm is the second diaphragm.
The electromagnetic electro-acoustic transducer according to claim 1, wherein the electromagnetic electro-acoustic transducer has a shape having a non-linearity that cancels out a non-linearity of an AC driving force generated in the diaphragm. 19. The relationship between the resultant force obtained by adding the first static suction force and the second static suction force and the distance between the second diaphragm and the center pole is substantially linear. The first static attraction force is a static attraction force generated on the second diaphragm by a magnetic circuit including the first magnet, the center pole, and the yoke; The electromagnetic electro-acoustic transducer according to claim 1, wherein the static attraction force is a static attraction force generated on the second diaphragm by the second magnet. 20. The electromagnetic electro-acoustic transducer according to claim 2, wherein the first diaphragm is fixed by bonding the first diaphragm to the first housing. 21. The electromagnetic electro-acoustic transducer according to claim 2, wherein the first diaphragm is fixed by being sandwiched between the first housing and the second housing. 22. The electromagnetic electro-acoustic transducer according to claim 2, wherein the second housing is a cover for protecting the first and second diaphragms. 23. A portable terminal device comprising the electromagnetic electro-acoustic transducer according to claim 1. 24. The apparatus of claim 23, further comprising a third housing having a sound hole, wherein the electromagnetic electroacoustic transducer is provided such that the first and second diaphragms face the sound hole. A mobile terminal device according to claim 1. 25. The mobile terminal device according to claim 24, wherein the second magnet is provided on the third housing.