JP2850382B2 - Electroacoustic transducer - Google Patents

Description

The present invention relates to an electromagnetic induction type speaker.

B. Summary of the Invention The present invention relates to an electromagnetic induction type loudspeaker, in which a secondary coil positioned in a DC magnetic field of a magnetic circuit unit is mounted and supported so as to be able to move forward and backward, and opposed to the secondary coil. A primary coil is provided, and at least one of these coils is formed of a superconducting material, so that heat generation of each coil can be suppressed, and sufficient sound can be faithfully and sufficiently generated for a signal input over a wide frequency band. Realizes pressure sound reproduction.

C. Prior Art Conventionally, as an electroacoustic transducer, a conductive speaker in which a voice coil is mounted on a diaphragm and a driving current corresponding to an acoustic signal is supplied to the voice coil to drive the voice coil has been widely used. I have. Since the conductive type speaker supplies power to the voice coil via a tinsel wire belonging to the voice coil, when the diaphragm vibrates, the tinsel wire becomes a load, and stable vibration of the diaphragm becomes stable. Hindered, making it impossible to obtain good reproduction characteristics. Further, since an extremely thin conductive wire is used for the tinsel wire, there is a possibility that the wire may be broken due to vibration.

In order to solve the problems caused by using such a tinsel wire, an electromagnetic induction type speaker configured without using a tinsel wire has been proposed.

As an electromagnetic induction type speaker, there is one described in Japanese Patent Publication No. 56-27039. The loudspeaker described in this publication includes a magnetic circuit unit that forms a DC magnetic field by a magnetic flux generated from a magnet, a secondary coil attached to a diaphragm, arranged in the DC magnetic field, and both ends of which are short-circuited. A primary coil disposed concentrically outside the secondary coil. In this loudspeaker, when a driving current corresponding to an acoustic signal is supplied to a primary coil, a secondary current is induced in a secondary coil by electromagnetic induction, and the action of the secondary current induced in the secondary coil and a DC magnetic field is performed. Thereby, the diaphragm is driven.

D. Problems to be Solved by the Invention By the way, as described above, an electromagnetic induction type speaker in which a secondary current is induced by electromagnetic induction to drive a diaphragm has sufficient sound over a wide frequency band. It is difficult to obtain pressure. In this speaker, when the drive current supplied to the primary coil is increased to increase the sound pressure level, the amount of heat generated in the primary coil increases, and the electrical resistance increases. Therefore, it becomes difficult to increase the drive current and increase the sound pressure level.

Further, when the heat generation amount of the primary coil increases, the entire speaker is heated, and the speaker may be damaged.

Since the primary coil acts as a high-pass filter, it is impossible to reproduce a frequency band lower than the low-frequency cutoff frequency. In order to lower the low cut-off frequency of the primary coil, it is necessary to increase the inductance by increasing the number of turns of the primary coil. When the number of turns of the primary coil is increased, the electric resistance increases and it becomes difficult to supply a sufficient drive current.

Therefore, the present invention is proposed in view of the above-described circumstances, and can faithfully reproduce sound with sufficient sound pressure over a wide frequency band, and can suppress heat generation due to driving. It is intended to provide a speaker.

E. Means for Solving the Problems In order to solve the above problems and achieve the above object, a speaker according to the present invention has a magnet and a yoke on which the magnet is mounted and a magnetic gap is formed, A magnetic circuit unit that forms a DC magnetic field by a magnetic flux generated from a magnet; a primary coil attached to the yoke and supplied with a signal from a sound source; and a primary coil opposed to the primary coil and disposed in the magnetic gap. A vibrating plate to which a secondary coil whose both ends are short-circuited is attached, and supporting means for supporting the vibrating plate so as to vibrate freely, wherein at least one of the primary coil and the secondary coil is superconductive. It is formed of a material.

The speaker according to the present invention is further provided with cooling means for cooling the one coil.

F. Function The speaker according to the present invention is configured such that when a signal is supplied from a sound source to a primary coil, an induced current is induced in a secondary coil whose both ends are short-circuited, and the induced current induced in the secondary coil and a magnetic circuit are induced. The diaphragm is driven by the action of the DC magnetic field of the section.

G. Embodiment Hereinafter, a speaker according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the loudspeaker according to the present invention includes an outer-magnet type magnetic circuit unit 1 and a primary coil 2 to which a drive current according to an acoustic signal from a sound source is supplied. Have been. On the diaphragm 4 side, a secondary coil 3 in which both ends where an induced current is induced is short-circuited is provided.

The magnetic circuit part 1 has a cylindrical center pole 5 at the center.
Is provided with a yoke 6 which is integrally provided. The center pole 5 and the yoke 6 are formed of a highly magnetically permeable material such as a metal, and a ring-shaped magnet 7 is arranged on the yoke 6 so as to surround the center pole 5. This magnet 7 is formed of a neodymium-based magnetic material,
It is formed slightly lower than the center pole 5. A ring-shaped top plate 8 made of the same material as the yoke 6 is provided on the upper surface of the magnet 7. The inner diameter of the top plate 8 is smaller than the inner diameter of the magnet 7, the inner peripheral surface 8 a projects from the inner peripheral surface 7 a of the magnet 7 toward the enter pole 5, and the inner peripheral surface 8 a A magnetic gap 9 is formed between them. A DC magnetic field is formed in the magnetic gap 9 by a magnetic flux generated from the magnet 7 as shown by an arrow B in FIG.

The diaphragm 4 is supported by the magnetic circuit unit 1 configured as described above via the support member 10. The support member 10 is formed of a material having an appropriate rigidity such as a metal, and is formed in a substantially cylindrical shape whose diameter at the distal end is enlarged.
It is fixed and attached to.

The diaphragm 4 is made of metal, synthetic resin, paper, or a composite material thereof, and has a sound-emitting portion 4 a formed in a conical shape substantially corresponding to the support member 10 and a central portion of the sound-emitting portion 4 closed. And a dome portion 4b joined to the sound emitting portion 4a. The diaphragm 4 supports the outer peripheral edge of the sound emitting portion 4a with a support member.
1 is supported via a connecting member 11 formed of a flexible material at a tip side thereof so as to be able to advance and retreat in a direction orthogonal to the magnetic flux in the magnetic gap 9 in the direction of arrow F in FIG. Further, a damper 12 is provided between the diaphragm 4 and the support member 10. The damper 12 is formed in a ring shape from a material having a certain flexibility, elasticity and internal loss. The outer peripheral side is supported by the support member 10, and the inner peripheral side is supported by the diaphragm 4. 4 is held at the midpoint position, and a constant attenuation is given to the moving direction of the diaphragm 4 in the direction of arrow F in FIG.

The secondary coil 3 is disposed on the base end side of the diaphragm 4 inserted into the magnetic gap 9. The secondary coil 3
A conductive wire made of a conductive material such as copper is wound in a ring shape and supported on the base end side of the diaphragm 4 and located in the magnetic gap 9. The secondary coil 3 is short-circuited at the beginning and end of the conducting wire.

The primary coil 3 is disposed on the outer peripheral surface of the center pole 5 so as to face the secondary coil 3 concentrically. The primary coil 2 is configured by winding a conductive wire around the outer peripheral surface on the distal end side of the center pole 5. This primary coil 2 is made of Bi-based material such as Nb ₃ Sn, YBa ₂ Cu ₃ O ₇ −x or Bi ₂ Sr ₂ Ca ₂ Cu ₃ Ox, or Tl ₂ Ba ₂ Ca ₂ Cu ₃ Ox or the like.
Superconducting materials such as Tl-based materials are used. The primary coil 2 has one end 2a and the other end 2b of the primary coil 2.
A driving current corresponding to the acoustic signal is supplied through the power supply unit.

The primary coil 2 is cooled by liquid nitrogen or liquid helium. The speaker is provided with a cooling device 13 for cooling the center pole 5 and the primary coil 2 by circulating a cooling liquid made of liquid nitrogen or liquid helium around the center pole 5.

The cooling device 13 includes a pump device 15 driven by a drive motor 14, and a storage tank 16 that stores a cooling liquid.
The cooling liquid is sent out onto the yoke 6 via the transport pipe 17. A partition 18 is provided on the yoke 6 between the outer peripheral surface of the center pole 5 and the inner peripheral surface 7a of the magnet 7.
The cooling liquid sent upward circulates through a circulation path formed by the upper surface of the yoke 6, the outer peripheral surface of the center pole 5, the inner peripheral surface 7a of the magnet 7, and the partition wall 18, thereby cooling the center pole 5 and the like. , Are radiated into the air through predetermined discharge holes, and the primary coil 2 is cooled. Since the magnet 7 is formed of a neodymium-based material, the magnet 7 has a small demagnetizing effect even when cooled.

The cooling device 13 cools the cooling liquid after cooling the center port 5 and the like, performs a predetermined cooling process, and then re-uses the storage tank.
You may be comprised so that it may collect | recover at 16.

In the loudspeaker according to the present invention configured as described above, when the driving current is supplied to the primary coil 2, an AC magnetic field having a frequency corresponding to the driving current supplied to the primary coil 2 is generated. The alternating magnetic field is closely linked to the secondary coil 3 attached to the diaphragm 4, and is induced in the secondary coil 3 by electromagnetic induction. This induced current flows in the secondary coil 3. The induction current of the coil has a frequency corresponding to the acoustic signal. Since the secondary coil 3 is located in the magnetic gap 9, the secondary coil 3 generates a driving force by the action of the DC magnetic field formed in the magnetic gap 9 and vibrates the diaphragm 4.

In the loudspeaker according to the present invention, since the primary coil 2 is formed of a superconducting material, the electric resistance is substantially zero, the amount of the supplied driving current can be increased, and the heat generated by the driving current is suppressed. be able to. Since the electric resistance of the primary coil 2 is substantially zero, it can be driven by a constant current drive amplifier, the current supplied to the primary coil 2 is constant over a wide frequency band, and the sound having good frequency characteristics Playback can be performed.

In the speaker according to the present invention, the secondary coil 3 may be formed of a superconducting material. In this case, as shown in FIG. 2, the cooling device 13 supplies the cooling liquid to the secondary coil 3 through a through hole 19 provided in the top plate 8 from the outer peripheral side to the inner peripheral side. It is configured to circulate around.

Further, in the speaker according to the present invention, both the primary coil 2 and the secondary coil 3 may be formed of a superconducting material.

Note that the primary coil 2 may be provided on the inner peripheral surface side of the top plate 8 so as to be outside the secondary coil 3.

Furthermore, in the speaker according to the present invention, as shown in FIG. 3, the space between the primary coil 2 and the secondary coil 3 may be filled with a magnetic fluid 20. The magnetic fluid 20 is a mixture in which a predetermined solvent and a magnetic powder are mixed in a colloidal solution. The magnetic fluid 20 makes the magnetic coupling between the primary coil 2 and the secondary coil 3 denser and makes the electromagnetic induction between these two coils more efficient. In addition, magnetic fluid 20
Is viscous, so that the diaphragm 4
To attenuate vibrations. Then, since the magnetic fluid 20 is cooled by the cooling device 13, it is held at the filling position without volatilizing in the air.

The magnetic circuit section constituting the speaker according to the present invention is not limited to the above-described outer-magnet type, but may be an inner-magnet type including a junk-type yoke and a columnar magnet.

H. Effects of the Invention As described above, the loudspeaker according to the present invention has at least one of the primary coil and the secondary coil formed of a superconducting material, so that the drive current supplied to the coil can be increased. Since heat generation can be suppressed, the diaphragm can be vibrated with high efficiency using a large driving current, and sound reproduction having good characteristics can be performed over a wide frequency band at a high sound pressure level. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a speaker according to the present invention,
FIG. 2 is a partial longitudinal sectional view showing an example of the speaker according to the present invention, and FIG. 3 is a partial longitudinal sectional view showing still another example of the speaker according to the present invention. 1 ... magnetic circuit part, 2 ... primary coil, 3 ... secondary coil, 4 ... diaphragm, 9 ... magnetic gap.

Claims (2)

(57) [Claims] 1. A magnetic circuit section having a magnet and a yoke to which the magnet is attached and having a magnetic gap formed therein, the magnetic circuit section forming a DC magnetic field by magnetic flux generated from the magnet, and a sound source attached to the yoke. A primary coil to which a signal is supplied, a diaphragm facing the primary coil, and a secondary coil disposed in the magnetic gap and having both ends short-circuited, and the diaphragm is oscillated. A loudspeaker, wherein at least one of the primary coil and the secondary coil is formed of a superconducting material. 2. The speaker according to claim 1, wherein said speaker further comprises cooling means for cooling said one coil.