JPH0738996A - Speaker - Google Patents

Abstract

PURPOSE:To reduce the electromagnetic coupling between plural coaxial coils and to uniformize the magnetic flux density in a gap. CONSTITUTION:A center yoke 7 is arranged to a center hole of a yoke 4, a magnetic field by a magnet 5 is obtained in a gap G1 and a magnetic field by a cancel magnet 8 is obtained in a gap G2. In this case, an upper end 4a of the yoke 4 is designed to be higher than an upper end 7a of the center yoke 7. Furthermore, taper faces TP1, TP2 spread downward are adopted for the inner circumferential face of the yoke 4 thereby making the width of the gap G2 spread downward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker having a plurality of magnetic circuits such as an MFB speaker and a two-way speaker.

[0002]

2. Description of the Related Art An MFB speaker is provided with a voice coil for driving a vibration system and a detection coil for detecting the vibration and providing an output for feedback to an amplifier. Then, magnetic circuits are formed respectively. Also, in a coaxial two-way speaker in which a woofer and a tweeter are coaxially arranged, a woofer voice coil and a tweeter voice coil may be provided and are driven by corresponding magnetic circuits.

FIG. 9 shows an example of the structure of an MFB speaker. Three
1 is a vibration plate, 32 is a voice coil for driving the vibration plate 31, 33 is a detection coil for detecting vibration, 34 is a yoke, 35 is a magnet arranged on the flange portion on the outer peripheral side of the yoke, and 36 is , A plate which is stacked above the magnet 35 and forms a gap G ₁ with the yoke 34. Voice coil 3 is placed in this gap G _1.
2 is inserted.

Reference numeral 37 denotes a yoke (hereinafter referred to as a center yoke) arranged in the central hole of the yoke 34, and 38 denotes a magnet arranged below the center yoke 37. A gap G ₂ is formed between the inner peripheral surface of the yoke 34 and the outer peripheral surface of the center yoke 37, and the detection coil 33 is inserted in the gap G ₂ . A cancel magnet 38 is provided below the flange portion of the yoke 34 and serves as a magnetic shield.

In this case, the magnet 35 and the plate 3
6, the yoke 34 forms a magnetic circuit for generating a magnetic field in the gap G ₁ , and the voice coil 32 is driven.
Further, the magnet 38, the yoke 34, the center yoke 3
7 a magnetic circuit for generating a magnetic field in the gap G ₂ is formed by, disposed in the gap G _2, the voice coil 3
It is possible to obtain a vibration detection signal from the detection coil 33 which is adapted to be linked with the second coil.

[0006]

However, when the two coils (the voice coil 32 and the detection coil 33) are coaxially arranged at the close positions in this manner, the voice coil 3
There is a problem that magnetic flux enters from 2 to the detection coil 33 side, and electromagnetic coupling between the voice coil 32 and the detection coil 33 increases. This makes accurate MFB operation difficult.

Also, the gap G for the detection coil 33
_With respect to No. 2, it is desired to make the magnetic flux density uniform in a relatively long range in the vertical direction in accordance with the stroke of the detection coil 33, but there is a problem in that this is extremely difficult to realize. Especially in the case of such an MFB speaker, the gap G
_If the magnetic flux density of ₂ is not uniform, the detection accuracy will decrease and distortion will easily occur.

A coaxial two-way speaker can also have the same structure (a voice coil for driving a tweeter is provided in place of the detection coil), but in this case as well, electromagnetic coupling between the coils and a gap are eliminated. A similar situation occurs with respect to the magnetic flux density.

[0009]

The present invention has been made in view of the above problems, and an object thereof is to reduce the electromagnetic coupling between a plurality of coils and to make the magnetic flux density in the gap uniform. And

Therefore, the second yoke is arranged in the central hole of the first yoke, and the first magnet is provided in the first gap formed on the outer periphery of the first yoke in correspondence with the first coil. In the second gap formed by the first yoke and the second yoke, the magnetic field generated by the second magnet is obtained corresponding to the second coil. The upper end of the second yoke is higher than the upper end of the second yoke.

Similarly, a second hole is formed in the central hole of the first yoke.
The first yoke formed on the outer periphery of the first yoke
A magnetic field from the first magnet corresponding to the first coil in the gap of the second coil, and a second magnetic field corresponding to the second coil in the second gap formed by the first yoke and the second yoke. When it is configured to obtain the magnetic field by the magnet, the inner peripheral surface forming the central hole of the first yoke and / or the outer peripheral surface of the second yoke are tapered surfaces that spread downward, and The gap 2 is formed so as to widen downward.

At this time, the tapered surface is formed to have a linear cross section, or all or a part of the tapered surface is formed to have a curved cross section.

[0013]

The magnetic circuit formed on the outer circumference of the first yoke and the magnetic circuit formed on the inner circumference of the first yoke by making the upper end of the first yoke higher than the upper end of the second yoke. It is possible to reduce the penetration of magnetic flux between the two. Further, by forming the second gap so as to widen downward, the magnetic flux density in the second gap can be made uniform.

[0014]

EXAMPLE An example of the present invention will be described below by taking an MFB speaker as an example. FIG. 1 shows the configuration of the MFB speaker of the first embodiment. 1 is a diaphragm, 2 is a diaphragm 1
A voice coil 3 fixed to and driving the diaphragm 1 is a detection coil for detecting vibration. 4 is a yoke, 5
Is a magnet arranged on the flange portion on the outer peripheral side of the yoke, and 6 is a plate which is stacked above the magnet 5 and forms a gap G ₁ with the yoke 4.
The voice coil 2 is inserted in the gap G ₁ . The magnet 5 is magnetized so that the plate side is S and the flange portion side of the yoke 4 is N.

Reference numeral 7 is a center yoke arranged in the central hole of the yoke 4, and the lower portion thereof is a flange portion.
A gap G ₂ is formed between the inner peripheral surface of the yoke 4 and the outer peripheral surface of the center yoke 7, and the detection coil 3 is inserted in this gap G ₂ . A cancel magnet 8 having a magnetic-shielding function is arranged between the flange portion of the yoke 4 and the flange portion of the center yoke 7. The cancel magnet 8 is magnetized so that the yoke 4 side is N and the center yoke 7 side is S.

In this case, the magnetic circuit portion is enlarged to show the magnet 5, the yoke 4, the gap G ₁ ,
The plate 6 forms a magnetic circuit shown as M ₁ in the figure, and the voice coil 2 is inserted in the gap G _1.
Is driven. In addition, by the cancel magnet 8, the yoke 4, the gap G ₂ , and the center yoke 7,
A magnetic circuit shown as ₂ is formed so that a vibration detection signal can be obtained from the detection coil 3 which is inserted into the gap G ₂ and is interlocked with the voice coil 2.

In the case of this embodiment, as can be seen by comparing with FIG. 9 described above as a conventional example, the cancel magnet 8 is used as the magnet constituting the magnetic circuit with respect to the gap G ₂ . Therefore, the magnet 38 shown in FIG. 9 is unnecessary, and the manufacturing cost can be reduced.

As can be seen from FIGS. 1 and 2, the upper end 4a of the yoke 4 is set to be higher than the upper end 7a of the center yoke 7 by the amount indicated by H in FIG. , Electromagnetic coupling between the voice coil 2 inserted in the gap G ₁ and the detection coil 3 inserted in the gap G ₂ can be reduced. That is, it is possible to effectively reduce the inflow of magnetic flux as shown by the arrow J in FIG.

Further, the gap G ₂ is formed to be relatively long vertically so as to cover the stroke of the detection coil 3. However, as shown in FIG. 2, the inner peripheral surface of the yoke 4 has a vertical central portion at the first stage. Is a tapered surface TP ₁ having a linear cross section, and the lower side thereof is a tapered surface TP ₂ having a linear cross section in the second step, whereby the gap G ₂ becomes wider as it goes downward. ing.

[0020] Thus the lower gap G ₂ by the tapered surface TP _1, TP ₂ (i.e., cancel magnet 8 side) by extending the can to uniform the magnetic flux density in the gap G ₂ in the vertical direction. In such an embodiment, as shown in FIG. 2, the lower end position of the gap G ₂ is 0,
When the position in the height direction is represented by setting the position of the upper end surface 4a of the yoke 4 to Z in the upper end direction, the magnetic flux density is as shown in FIG. 3, that is, the magnetic flux density is almost within the stroke range of the detection coil 3. It was possible to make it uniform.

For comparison, as shown in FIG. 4, the case where the tapered surface is not provided and the width of the gap G ₂ is uniform in the vertical direction is taken as an example (the conventional example of FIG. 9 is also of this type). Magnetic flux density is as shown in FIG. 5, and the gap G ₂
It was going to drop considerably towards the upper side of. In other words, it is understood that in this embodiment, the magnetic flux density can be homogenized very effectively.

By the way, although the homogenization of the magnetic flux density is almost realized as shown in FIG. 3, it can be seen that the magnetic flux density is slightly lowered at the approximate center position of the gap as shown by C in FIG. A second embodiment for improving this and realizing further homogenization is shown in FIG.

As can be seen from FIG. 6, the inner peripheral surface of the yoke 4 has a tapered surface TP ₁ having a linear section in the first step and a tapered surface TP _{2 having a} linear section in the second step, as in the above embodiment. Is formed so that the gap G ₂ becomes wider toward the lower side, but the tapered surface TP
The predetermined position on ₁ (that is, the position corresponding to C in FIG. 3) is
It is a convex portion TP ₁₁ which seems to be slightly swollen. By partially adjusting the width of the gap G ₂ by this convex portion TP ₁₁ , it was possible to obtain a magnetic flux density distribution that was almost completely uniform as shown in FIG. 7.

FIG. 8 shows a third embodiment. In this case, the inner peripheral surface of the yoke 4 is a tapered surface TP _R having a curved cross section from the central part in the vertical direction to the lower part. As described above, by making the width of the gap G ₂ widen downward by the tapered surface TP _{R having a} curved cross-section, it is possible to realize a uniform magnetic flux density distribution as shown in FIG. 7.

In each of the above embodiments, the gap G ₂
In order to widen the width of the center yoke 7 toward the lower side (closer to the cancel magnet 8), the outer peripheral surface of the center yoke 7 may be tapered, or both the inner peripheral surface of the yoke 4 and the outer peripheral surface of the center yoke 7 may be formed. It may be a tapered surface. Further, although the MFB speaker is taken as an example in the embodiment, it goes without saying that the present invention can be similarly applied to a coaxial two-way speaker.

[0026]

As described above, in the speaker of the present invention, the second yoke is arranged in the central hole of the first yoke, and the first yoke is provided.
A magnetic field generated by a first magnet corresponding to the first coil in a first gap formed on the outer periphery of the second yoke, and a second gap formed by the first yoke and the second yoke. When the magnetic field of the second magnet is obtained corresponding to the second coil, the upper end of the first yoke is set higher than the upper end of the second yoke. There is an effect that the electromagnetic coupling between the two coils can be effectively reduced.

Further, one or both of the inner peripheral surface of the first yoke and the outer peripheral surface of the second yoke is a tapered surface that expands downward so that the second gap expands downward. The effect of uniforming the magnetic flux density in the second gap can be obtained by forming the above.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a speaker that is a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a magnetic circuit portion of the first embodiment.

FIG. 3 is an explanatory diagram of a magnetic flux density distribution in the first embodiment.

FIG. 4 is an explanatory diagram of a magnetic circuit portion for comparison of magnetic flux density equalizing effects.

FIG. 5 is an explanatory diagram of a magnetic flux density distribution for comparison of magnetic flux density equalizing effects.

FIG. 6 is an explanatory diagram of a magnetic circuit portion according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram of a magnetic flux density distribution in the second embodiment.

FIG. 8 is an explanatory diagram of a magnetic circuit portion according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram of a conventional MFB speaker.

[Explanation of symbols]

1 Vibration Plate 2 Voice Coil 3 Detection Coil 4 Yoke 5 Magnet 6 Plate 7 Center Yoke 8 Cancel Magnet G ₁ , G ₂ Gap

Claims (4)

[Claims] 1. A second yoke is arranged in a central hole of the first yoke, and a first magnet corresponding to the first coil is provided in a first gap formed on the outer periphery of the first yoke. And a second gap corresponding to the second coil in the second gap formed by the first yoke and the second yoke. The upper end of the first yoke is higher than the upper end of the second yoke. 2. A second yoke is arranged in a central hole of the first yoke, and a first magnet is provided in a first gap formed on an outer circumference of the first yoke in correspondence with the first coil. And a second gap corresponding to the second coil in the second gap formed by the first yoke and the second yoke. The inner peripheral surface forming the central hole of the first yoke and / or the outer peripheral surface of the second yoke is a tapered surface that expands downward, so that the second gap expands downward. A speaker characterized by being formed in the following manner. 3. The speaker according to claim 2, wherein the tapered surface has a linear cross section. 4. The speaker according to claim 2, wherein all or part of the tapered surface is formed in a curved cross section.