JP2002010391A - Speaker, electronic device having it and reduction method of its leakage flux - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speaker, an electronic device having it and a reduction method of its leakage flux capable of improving the shild performance with more precise cancellation of the leakage flux. SOLUTION: The speaker comprises a first magnet 30 fixed to a plate 32 and to a yoke 36 opposed via a voice coil 18, a second magnet 40 opposed to the first magnet 30 via the yoke 36 and also fixed to the yoke 36, the plate 32, a magnetic circuit formed with the yoke 36 and also giving flux for vibrations to the voice coil 18, an magnetic shield 20 covering the circuit and a third magnet 60 mounted at the shield 20 and having smaller magnetism than that of the first and second magnet 30, 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loudspeaker capable of reducing magnetic flux leakage even in a loudspeaker having a magnetic shield, an electronic device having the loudspeaker, and a method of reducing magnetic flux leakage in a loudspeaker.

[0002]

2. Description of the Related Art Loudspeakers, especially low-leakage magnetic flux type speakers, are used in, for example, various audio equipment and video equipment. This type of conventional speaker has a structure as shown in FIG. The magnetic shield cover 1000 is a plate 100
1, a main magnet 1002, a yoke 1003, and another magnet 1004 are accommodated. The plate 1001 is fixed to the frame 1005 of the speaker. A voice coil 1006 is arranged in a hole in the plate 1001 to vibrate a diaphragm (not shown).

[0003]

In this type of loudspeaker, when the voice coil 1006 is energized to output sound, the magnetic flux Fa generated by the main magnet 1002 generates
A canceling magnet 1004 is used to cancel the leakage of magnetic flux outside through the magnetic shield cover 1000. However, even if such a canceling magnet 1004 is used, the leakage magnetic flux Fa may not be sufficiently canceled and a slight leakage magnetic flux may be generated. This leakage magnetic flux (also referred to as leakage magnetic flux) Fa
May be in the opposite direction to the arrow shown in FIG. 6, depending on the strength of the magnetic field of the canceling magnet 1004. As described above, even if the canceling magnet 1004 is present, a small amount of leakage magnetic flux is generated. Therefore, for example, this kind of speaker cannot be used for video equipment, audio equipment, and the like that have strict requirements for leakage magnetic flux. There are also problems. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems and to provide a speaker, an electronic device having the speaker, and a method of reducing the leakage magnetic flux in the speaker, which can cancel the leakage magnetic flux more reliably and improve the magnetic shielding performance.

[0004]

According to a first aspect of the present invention, a first magnet fixed to a plate and a yoke opposed to each other via a voice coil, the first magnet opposed to the first magnet via the yoke, and A magnetic circuit formed from the second magnet fixed to the yoke, the plate, and the yoke and providing a magnetic flux for vibration to the voice coil; a magnetic shield covering the magnetic circuit; 2
A low-leakage magnetic flux type loudspeaker comprising a third magnet having a magnetic force weaker than a magnet. In the first aspect, the third magnet has a weaker magnetic force than the first magnet and the second magnet, and the third magnet is provided on the magnetic shield.
Thereby, the third magnet can surely cancel the leakage magnetic flux slightly leaking from the magnetic shield, and the magnetic shield performance of the speaker can be improved.

According to a second aspect of the present invention, in the loudspeaker according to the first aspect, the first magnet, the second magnet, and the third magnet are arranged substantially at the same center. According to the second aspect, the effect of preventing magnetic leakage can be made uniform.

According to a third aspect of the present invention, in the speaker according to the second aspect, a vent hole is formed in a center portion of the magnetic shield. According to the third aspect, since the ventilation hole is formed in the center of the magnetic shield, it is possible to improve bass reproduction in the speaker.

According to a fourth aspect of the present invention, there is provided an electronic apparatus having a speaker, wherein the speaker has a first magnet fixed to a plate and a yoke facing each other via a voice coil, and the first magnet via the yoke. A second magnet opposed to the magnet and fixed to the yoke, a magnetic circuit formed from the plate and the yoke and applying a magnetic flux for vibration to the voice coil, and a magnetic shield covering the magnetic circuit; , Provided on the magnetic shield,
And a third magnet having a magnetic force weaker than that of the second magnet. In claim 4, the third magnet is composed of the first magnet and the second magnet.
It has a weaker magnetic force than the magnet, and this third magnet is provided on the magnetic shield. Thereby, the third magnet can surely cancel the leakage magnetic flux slightly leaking from the magnetic shield, and the magnetic shield performance of the speaker can be improved. In particular, it is effective to use this kind of speaker when it is desired to prevent the characteristics of the electronic device from being affected by the leakage magnetic flux.

According to a fifth aspect of the present invention, there is provided a first magnet constituting a magnetic circuit for driving the diaphragm, a second magnet for canceling a magnetic flux by the magnetic circuit, and a magnetic shield covering the magnetic circuit. A method of reducing leakage magnetic flux in a speaker, wherein a third magnet having a weaker magnetic force than the first magnet and the second magnet is provided on the magnetic shield, and a magnetic flux leaking out of the magnetic shield is canceled to reduce the leakage magnetic flux. This is a method for reducing leakage magnetic flux in a loudspeaker, characterized in that the magnetic flux is reduced. According to claim 5, a third magnet having a lower magnetic force than the first magnet and the second magnet is provided on the magnetic shield,
The magnetic flux leaking out of the magnetic shield is canceled by the third magnet to reduce the magnetic flux leaking. Thereby, the magnetic shielding performance of the speaker can be improved.

According to a sixth aspect of the present invention, in the method for reducing a magnetic flux leakage in a loudspeaker according to the fifth aspect, the first magnet, the second magnet, and the third magnet are arranged such that their centers are substantially the same. I have. According to the sixth aspect, the effect of preventing magnetic leakage can be made uniform.

According to a seventh aspect of the present invention, in the method of the sixth aspect, a vent hole is formed in a center portion of the magnetic shield. Claim 7
In this case, since a ventilation hole is formed in the center of the magnetic shield, it is possible to improve bass reproduction in a speaker.

[0011]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 is a perspective view having a partial cross section showing a preferred embodiment of the speaker of the present invention. The speaker 10 shown in FIG. 1 is a so-called low-leakage magnetic flux type speaker, and is most suitable for use in various video equipment and various audio equipment. The speaker 10 is provided in, for example, a television receiver. This speaker 10 is generally a frame 1
2, a diaphragm 14, a damper 16, a voice coil 18, a magnetic shield cover (also referred to as an electromagnetic shield cover or a magnetic shield cover) 20 as a magnetic shield, and the like. The frame 12 has a terminal member 22. The terminal member 22 is a portion for electrically connecting a speaker drive circuit (not shown) to the voice coil 18.

A cap 24 is provided at the center of the diaphragm 14. The frame 12 is a frame of the outer frame and supports the diaphragm 26 of the diaphragm 14. The diaphragm 26 supports the diaphragm 14 easily in the direction E. The vibration plate 14 is, for example, cone paper, and is a portion that vibrates air in the E direction. The damper 16 includes a voice coil 18
It is a part that supports the movement easily. Voice coil 18
A magnetic force is generated by an audio current supplied from the outside via the terminal member 22, and magnetically attracts or repels with the main magnet 30, thereby transmitting vibration to the diaphragm 14. The diaphragm 14 vibrates air to reproduce sound (generate sound waves).

FIG. 2 shows a structural example of each element housed in the magnetic shield cover 20 of FIG. Magnetic shield cover 2
Numeral 0 is a cylindrical container having, for example, a bottom portion 20A made of, for example, iron or other magnetic material, for example, iron rolled steel plate (SPCC, SPCD) or nickel, cobalt, or permalloy. Magnetic shield cover 2
The zero contains a plate 32, a main magnet 30, a center pole 34, a yoke 36, a canceling magnet 40, and the like. As the frame 12, for example, a mold frame made of resin can be employed. The frame 12 is fixed to an outer surface of the plate 32.

The plate 32 includes a main magnet 30,
The yoke 36 and the magnetic shield cover 20 form a magnetic circuit. This magnetic circuit gives the voice coil 18 a magnetic flux for vibration. The plate 32 is made of, for example, iron or another magnetic material, for example, an iron rolled steel plate, or nickel, cobalt, or permalloy. The plate 32 is a disk-shaped member, and has a hole 32A in the center.
Are formed. This hole 32A has a center pole 3
4 is located on top. The voice coil 18 is located between the upper part of the center pole 34 and the inner peripheral surface of the plate 32. The center pole 34 is a cylindrical portion, a part of the yoke 36, and is integrated with the yoke 36. The center pole 34 and the yoke 36 are made of, for example, iron or other magnetic material, for example, an iron rolled steel plate,
In addition, it is made of nickel, cobalt and permalloy. The voice coil 18 is wound around the center pole 34. In the center of the center pole 34 is a through hole 34A
Are formed in the axial direction. The center position of the through hole 34 </ b> A is centered on the center axis CL of the magnetic shield cover 20. The yoke 36 is, for example, a circular portion, and a ring-shaped main magnet 30 is provided between the yoke 36 and the plate 32.
Is arranged. When the audio current flows through the voice coil 18, the main magnet 30 corresponds to a first magnet constituting the above-described magnetic circuit for driving the diaphragm according to the magnitude of the audio current. The main magnet 30 is fixed to the plate 32 and the yoke 36 facing each other via the voice coil 18.

On the other hand, the canceling magnet 40 is fixed to the yoke 36 and corresponds to a second magnet for canceling the magnetic flux leaking out of the magnetic shield 20 by the main magnet 30. The canceling magnet 40 is connected to the main magnet 30 via the yoke 36.
And is fixed to the yoke 36. The main magnet 30, the canceling magnet 40, and the additional magnet 60 to be described later are made of, for example, a rubber magnet, a ferrite magnet, neodymium, or alnico. Although the canceling magnet 40 is a ring-shaped magnet, the magnetic force of the canceling magnet 40 is set smaller (weaker) than the magnetic force of the main magnet 30.

At the center of the bottom 20A of the magnetic shield cover 20,
A ventilation hole 50 is formed. The inner diameter of the ventilation hole 50 is set, for example, slightly larger than the inner diameter of the through hole 34A. The center of the ventilation hole 50 is arranged approximately the same as the center of the through hole 34A and the central axis CL of the magnetic shield cover 20. The reason why the central axes of the through hole 34A and the vent hole 50 are substantially coincident with the central axis CL of the magnetic shield cover 20 is to achieve a uniform magnetic leakage prevention effect. The through hole 34A, the ventilation hole 50 and the corresponding ventilation hole 70
Is provided, the flow of air when the diaphragm vibrates is facilitated, and bass reproduction in the speaker 10 can be improved. That is, an air chamber formed of the cap 24 and the center pole 34 is generated, and the air chamber expands and contracts due to the amplitude of the diaphragm 14, which hinders the amplitude of the diaphragm 14.
It is reduced by providing a through hole.

As shown in FIGS. 2, 3 and 4, on the outside of the magnetic shield cover 20, an additional magnet 60 as a third magnet is further provided.
However, the outer surface 20A of the magnetically
It is fixed to. The additional magnet 60 has, for example, a ring shape, and has a ventilation hole 70 formed at the center as shown in FIG. The inside diameter of the ventilation hole 70 is slightly larger than the inside diameter of the ventilation hole 50, for example. Ventilation holes 70,
The center of the ventilation hole 50 and the through hole 34A is
It is arranged approximately identically to the center axis CL of 0. The reason why the centers of the ventilation holes 70, the ventilation holes 50, and the through holes 34A are aligned with the central axis CL is to allow the air to flow smoothly.

FIG. 3 shows how an additional magnet (also called an additional magnet) 60 is fixed by an adhesive layer 80. As the adhesive layer 80, for example, an epoxy or acrylic adhesive can be used. Additional magnet 60
Is weaker than the magnetic force of the main magnet 30 and the canceling magnet 40.

Next, a magnetic circuit including the main magnet 30 and the canceling magnet 40 will be described with reference to FIG. As shown in FIG. 5, a magnetic circuit indicated by a magnetic flux F1 is formed between the plate 32, the yoke 36, the main magnet 30, and the magnetic shield cover 20. The magnetic shield 20 covers the magnetic circuit. The magnetic circuit applies a magnetic flux for vibration to the voice coil 18. A magnetic circuit indicated by a magnetic flux F2 is formed between the main magnet 30, the yoke 36, the magnetic shield cover 20, and the canceling magnet 40. Furthermore, the bottom 20A of the magnetic shield cover 20
A leakage magnetic flux F3 may be formed from the side toward the plate 32. Referring to FIG. 6, since the magnetic shield cover 20 has the ventilation holes 50, a leakage magnetic flux F <b> 4 may be formed from the magnetic shield cover 20 through the ventilation holes 50.

The leakage magnetic flux F shown in FIGS.
3, an additional magnet 60 shown in FIGS. 5 and 6 is provided to reduce or cancel (cancel) F4. This additional magnet 60 is connected to the bottom 2 of the magnetic shield 20.
By providing at 0A, the additional magnet 60 can cancel or reduce the leakage magnetic flux F3 shown in FIG. 5 with the magnetic flux F6 and cancel the leakage magnetic flux F4 from the vent hole 50 with the magnetic flux F5 as shown in FIG. it can. As described above, the leakage magnetic flux F leaking from the magnetic shield cover 20
3 or F4 can be canceled or reduced by providing the additional magnet 60 outside the magnetic shield cover 20. From this, it is possible to provide a low-leakage-flux-type speaker 10 having higher magnetic-shielding performance.

FIG. 7 shows another embodiment of the present invention. The speaker 10 of FIG. 7 differs from the structure of the speaker 10 of FIG. 2 in that the magnetic shield cover 20 does not have the ventilation hole 50, and the center pole 34 does not have the through hole 34A. In the case of such a structure, the additional magnet 60 is, for example, a disk-shaped magnet, and unlike the additional magnet 60 in FIG. With such a structure, the leakage magnetic flux F3 in FIG. 7 can be canceled by the magnetic flux F6 of the additional magnet 60.

In the speaker having the magnetically shielded structure according to the present invention, the leakage magnetism from the magnetically shield can be reduced by attaching another additional magnet for cancellation at the center of the bottom of the magnetically shield cover. In the center of the bottom of the outer side of the magnetic shield cover, a ring-shaped and disk-shaped additional magnet weaker than the magnetic force of the canceling magnet provided inside is provided, and the leakage magnetic flux that remains without being canceled even when using the conventional magnetic shield structure Is further canceled by the additional magnet to enhance the magnetic-shielding performance.

A hole 32A is provided in a plate 32, which is a yoke top plate, which is a component forming a magnetic circuit of the speaker, and a through hole 34A is provided in a center pole 34, thereby facilitating the flow of air and thereby reproducing bass sound. Can be improved. In order to allow air to flow in a magnetic circuit having a magnetic shield structure, it is necessary to provide a ventilation hole 50 in a part of a magnetic shield cover which is a main part for performing magnetic shield. But the vent hole 50
As a result, a gap was created in a part of the magnetic shield cover,
Leakage of magnetic flux from this part may reduce the magnetic shielding performance of the speaker. Also, in magnetic circuits with a magnetic shield structure without through holes, perfect magnetic shield performance is obtained due to subtle imbalance between the main magnet and cancel magnet, insufficient thickness of the magnetic shield cover, clearance between the plate and the magnetic shield cover, etc. Not always.

However, in each case, a minute ring-shaped additional magnet is added to the magnetic-shield type magnetic circuit in a direction to cancel the magnetic leakage, so that the magnetic-shield performance can be further improved. The magnitude of the magnetic force of the additional magnet to be added is optimally selected according to the strength of the magnetic leakage of the magnetic circuit. Leakage magnetic flux generated from the ventilation hole of the magnetic shield cover is canceled by arranging a ring-shaped additional magnet around the ventilation hole, and the leakage magnetic flux of the entire magnetic circuit is obstructed by the flow of air in the center pole hole. It becomes possible to reduce without. Even in a structure other than the structure in which the through hole is provided in the center pole, it is possible to reduce the magnetic leakage by providing a ring and a disc-shaped additional magnet. Since the additional magnet may have a weak magnetic energy, a rubber magnet can be used. By adding a weak additional magnet to the outside of the magnetic shield, it is possible to reduce the leakage magnetic flux that cannot be removed due to variations in materials and the like, thereby reducing the leakage.

By the way, the present invention is not limited to the above embodiment, and various modifications can be adopted. For example, additional magnet (additional magnet, third magnet) 6
0 is the bottom surface (outer surface) of the magnetic shield cover 20 as shown in FIG.
Instead of fixing to 20A with an adhesive, it may be fixed by mechanical fitting. Magnetic shield cover 2
It is also possible to provide a concave portion at 0 and fit the additional magnet 60 into this concave portion to fix it. Additional magnet 60
Is not limited to a ring shape or a disk shape, and other shapes can be adopted. Examples of video equipment and audio equipment to which the speaker of the present invention is applied include a portable game machine, a television receiver, and a projector. When the speaker of the present invention is provided in a television receiver or a monitor device of a computer as an example of an electronic device, there are the following advantages. If the cathode ray tube has a structure in which the electron beam is bent by the deflection yoke and hits the phosphor at the correct position, there is little or no leakage magnetic flux from the speaker, so the electron beam hits the phosphor at the correct position. . However, the conventional speaker has a large amount of leakage magnetic flux, and if it is constantly emitted, the electron beam does not hit the phosphor at the correct position, resulting in a color shift of an image on the display surface of the cathode ray tube. The leakage magnetic flux is also shown in FIGS.
May occur in a direction opposite to the direction shown in FIG.

[0027]

As described above, according to the present invention,
Leakage magnetic flux can be canceled more reliably and the magnetic-shielding performance can be enhanced.

[Brief description of the drawings]

FIG. 1 is a perspective view with a partial cross section showing a preferred embodiment of a speaker of the present invention.

FIG. 2 is a sectional view showing components and additional magnets in a magnetic shield cover of the speaker of FIG. 1;

FIG. 3 is a diagram illustrating a state in which an additional magnet is fixed to the outside of a magnetic shield cover.

FIG. 4 is a perspective view with a partial cross section showing an additional magnet, a magnetic shield cover, and the like.

FIG. 5 is a diagram showing an example of a magnetic circuit of a main magnet, a canceling magnet, and an additional magnet.

FIG. 6 is a diagram illustrating a state in which a leakage magnetic flux generated from a ventilation hole of a magnetic shield cover is canceled.

FIG. 7 is a cross-sectional view showing another embodiment of the speaker of the present invention.

FIG. 8 is a cross-sectional view showing leakage magnetic flux in a conventional speaker.

[Explanation of symbols]

10 ... speaker, 18 ... voice coil, 20
..Magnetic shield cover (magnetic shield), 30 ... Main magnet (corresponding to first magnet), 32 ... Plate, 34A ... Through hole, 36 ... Yoke, 40 ...
A canceling magnet (corresponding to the second magnet),
50: vent hole, 60: additional magnet (corresponding to third magnet), 70: vent hole

Claims (7)

[Claims] A first magnet fixed to a plate and a yoke opposed via a voice coil; a second magnet opposed to the first magnet via the yoke and fixed to the yoke; A magnetic circuit formed of the plate and the yoke and providing a magnetic flux for vibration to the voice coil; a magnetic shield covering the magnetic circuit; and a magnetic shield provided on the magnetic shield, the magnetic shield being more than the first and second magnets. A low-leakage magnetic flux type speaker comprising a third magnet having a weak magnetic force. 2. The loudspeaker according to claim 1, wherein the first magnet, the second magnet, and the third magnet are arranged at substantially the same center. 3. The speaker according to claim 2, wherein a vent hole is formed in a center of the magnetic shield. 4. An electronic apparatus having a speaker, wherein the speaker faces a first magnet fixed to a plate and a yoke facing each other via a voice coil, and faces the first magnet via the yoke. A second magnet fixed to the yoke, a magnetic circuit formed from the plate and the yoke and providing a magnetic flux for vibration to the voice coil; a magnetic shield covering the magnetic circuit; An electronic device having a low-leakage magnetic flux type speaker, comprising: a third magnet having a lower magnetic force than the first and second magnets. 5. A reduction in leakage magnetic flux in a loudspeaker comprising a first magnet constituting a magnetic circuit for driving a diaphragm, a second magnet for canceling a magnetic flux generated by the magnetic circuit, and a magnetic shield covering the magnetic circuit. A method, wherein a third magnet having a lower magnetic force than the first magnet and the second magnet is provided on the magnetic shield, and a magnetic flux leaking out of the magnetic shield is canceled to reduce a leakage magnetic flux. A method for reducing magnetic flux leakage in a speaker. 6. The method according to claim 5, wherein the first magnet, the second magnet, and the third magnet are arranged at substantially the same center. 7. The method according to claim 6, wherein a vent hole is formed in a center portion of the magnetic shield.