JP3308699B2 - Magnetic circuit structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic circuit structure such as a speaker and a voice coil type actuator, and more particularly to an inner magnet type magnetic circuit structure.

[0002]

2. Description of the Related Art The magnetic circuit structure of a typical conventional speaker is roughly divided into an outer magnet type and an inner magnet type. Generally, the outer magnet type refers to a magnet having a configuration in which a permanent magnet is disposed outside and a magnetic gap in which a voice coil is suspended is formed between an inner peripheral surface of a plate and an outer peripheral surface of a pole piece. At this time, the permanent magnet is held between the plate and the flange provided at the bottom of the pole piece.

[0003] The prior art of the outer magnet type is disclosed in Japanese Utility Model Application Laid-Open No. 63-92.
494;
92800 and the like.

Japanese Utility Model Application Laid-Open Nos. 63-92494 and 62
The prior art shown in US Pat.
FIG. 1 of JP-A 2494 and Japanese Utility Model Application Laid-Open No. 62-155597.
As shown in FIG. 4 of the publication, a recess is provided in a portion where the pole piece faces the bottom of the voice coil. By providing the recess, the amplitude of the voice coil can be increased.

In the prior art disclosed in Japanese Patent Application Laid-Open No. 4-192800, a through hole is provided in a pole piece as shown in FIG. 1 of Japanese Patent Application Laid-Open No. 4-192800. By providing the through holes, the air in the bobbin of the voice coil can be freely circulated to the outside, thereby improving the bass reproduction characteristic.

[0006] On the other hand, the prior art of the inner magnet type has a structure shown in FIG.
, A conventional technique shown in Japanese Utility Model Application Laid-Open No. 4-102397, and a conventional technique shown in FIG.

The prior art shown in FIG. 4 shows the characteristics of the most typical inner-magnet type magnetic circuit. A magnetic gap in which the voice coil 1 is suspended has an outer peripheral surface of the plate 2 and a yoke surrounding the plate 2. 3 is formed between the top and the inner peripheral surface. A permanent magnet 4 is provided inside between the plate 2 and the bottom of the yoke 3.

In the prior art shown in Japanese Utility Model Laid-Open No. 4-102397, the bottom plate of the yoke and the yoke main body are separated from each other as shown in FIGS. A permanent magnet having a diameter larger than the inside diameter of the insertion hole of the voice coil provided at the top can be mounted in the yoke main body.

In the prior art shown in FIG. 5, the diameter of the permanent magnet 4 is increased by enlarging the bottom of the plate 2.

In general, a ferrite magnet is used as a permanent magnet in an outer-magnet type magnetic circuit structure, and an alnico-based magnet or samarium cobalt is used as a permanent magnet in an inner-magnet type magnetic circuit structure.
A rare earth magnet such as neodymium is used. Rare earth magnets are more expensive than ferrite magnets and have a large magnetizing force at the optimum operating point. Therefore, it is preferable to make the shape as flat as possible.In the internal magnet type magnetic circuit structure, the thickness of the permanent magnet is set to be small. Is done.

[0011]

Problems to be Solved by the Invention
4, Japanese Utility Model Application Laid-Open No. 62-155597 and JP-A-4-192.
In the prior art shown in FIG. 800, since the external magnet type uses a ferrite magnet as the permanent magnet, the size of the magnetic circuit,
In particular, the outer diameter is larger than that of the inner-magnet type magnetic circuit structure, and is not suitable for miniaturization.

In the typical prior art of the internal magnet type shown in FIG. 4, the thickness of the permanent magnet 4, which is a rare earth magnet, is reduced in order to reduce the cost and the like. Is small. For this reason, when a low tone occurs in which the amplitude of the voice coil 1 increases, there is a problem that the bottom of the voice coil 1 collides with the bottom of the yoke 3 and the voice coil 1 is damaged. Therefore, the prior art shown in FIG. 4 cannot be used for generating bass. Also in the prior art shown in Japanese Utility Model Laid-Open No. 4-102397, the distance between the bottom of the voice coil and the upper surface of the permanent magnet is small, and the voice coil collides with the permanent magnet when a low tone is generated.

In the prior art shown in FIG.
Increases, the voice coil contacts the inclined surface at the bottom of the plate 2. In order to increase the amplitude of the voice coil 1, a method of increasing the thickness of the portion of the plate 2 facing the magnetic gap or increasing the thickness of the permanent magnet 4 can be mentioned. However, there is a problem that the magnetic flux density in the magnetic air gap becomes small, and there is a problem that if the permanent magnet 4 is made thick, the cost becomes high.

4 and 5 and FIG.
97, the voice coil is covered by the yoke, so that when a high-output sound is continuously generated, heat generated from the voice coil is trapped in the yoke. . If heat is trapped in the yoke, the voice coil is overheated, and the insulating varnish fixing the voice coil is melted, and the voice coil may be damaged or burnt.

The prior art shown in the above-mentioned Japanese Patent Application Laid-Open No. 4-129800 is an external magnet type not suitable for miniaturization, and the through holes provided in the pole pieces are not for releasing heat.

An object of the present invention is to solve the above-mentioned problems, and to provide a magnetic circuit structure which can vibrate a voice coil with a large amplitude, is small and has improved input resistance.

[0017]

According to the present invention, a magnetic gap in which a voice coil is suspended is formed between an outer peripheral surface of a plate and an inner peripheral surface of a yoke surrounding the plate. In the inner-magnet type magnetic circuit structure in which a permanent magnet is provided between the permanent magnet and the bottom, the permanent magnet is plate-like, the top magnetic pole surface is joined to the bottom surface of the plate, and the yoke projects from the bottom, and the permanent magnet A connection portion that is magnetically connected to the bottom magnetic pole surface is formed, and the outer diameter of the permanent magnet and the outer diameter of the connection portion are equal to or smaller than the outer diameter of the plate.
A magnetic circuit structure is characterized in that a bottomed hole that opens on the bottom side of the yoke is formed.

Further, according to the present invention, a magnetic gap in which the voice coil is suspended is formed between the outer peripheral surface of the plate and the inner peripheral surface of the yoke surrounding the plate, and is provided between the plate and the bottom of the yoke. In an inner-magnet type magnetic circuit structure provided with a permanent magnet, the permanent magnet is plate-shaped, a top magnetic pole surface is joined to a bottom surface of the plate, and a yoke is projected from the bottom, and a magnetic field is applied to the bottom magnetic pole surface of the permanent magnet. The outer diameter of the permanent magnet and the outer diameter of the connection part are equal to or less than the outer diameter of the plate, and the upper surface of the plate rises from the outside toward the center. A magnetic circuit structure having a curved surface shape.

[0019]

According to the present invention, a magnetic gap in which a voice coil is suspended is formed between the outer peripheral surface of the plate and the inner peripheral surface of the top of the yoke surrounding the plate. In the structure, a connection portion protruding from the bottom of the yoke is formed in the yoke. The top magnetic pole surface of the plate-shaped permanent magnet, which is a magnetic flux source, is magnetically connected to the bottom surface of the plate, and the bottom magnetic pole surface is magnetically connected to the upper surface of the connection portion at the bottom of the yoke, and the permanent magnet is sandwiched between the plate and the connection portion. . The outer diameter of the permanent magnet and the outer diameter of the connection portion are set to be equal to or less than the outer diameter of the plate.

Therefore, the distance between the bottom of the voice coil and the bottom of the yoke facing the bottom of the voice coil can be increased without increasing the thicknesses of the plate and the permanent magnet. As a result, when the magnetic circuit structure of the present invention is applied to a speaker or the like, the amplitude of the voice coil increases as the generated sound changes from a treble to a bass, but the distance between the voice coil and the bottom of the yoke is increased. Since it is enlarged, bass can be reproduced in a good condition. A connection portion provided at the bottom of the yoke has a bottomed hole that opens to the bottom side of the yoke.
Therefore, the surface area of the outer surface of the yoke can be increased, and the heat generated from the voice coil can be efficiently released to the outside of the yoke.

Further, according to the present invention, by raising the upper surface of the plate, it is possible to increase the cross-sectional area of the central portion of the plate in the thickness direction. Since the cross-sectional area of the central portion is enlarged, the saturation of the magnetic flux can be prevented even at the central portion of the plate, and the magnetic flux generated from the permanent magnet can be efficiently guided.

[0022]

FIG. 1 is a sectional view showing the configuration of an inner magnet type magnetic circuit 11 according to one embodiment of the present invention. Magnetic circuit 11
Generally includes a yoke 12, a voice coil 14 wound around a bobbin 13, a plate-shaped plate 15, and a plate-shaped permanent magnet 16. Yoke 12 surrounding voice coil 14, plate 15 and permanent magnet 16
Is configured to include a top portion 20, a cylindrical portion 21, a bottom portion 22, and a connection portion 23 formed on the bottom portion 22. Top 20
Is formed so as to project inward from the upper end of the cylindrical portion 21 and has an inner peripheral surface surrounding the voice coil 14. The connection portion 23 is formed so as to protrude upward from the bottom portion 22 and has a connection surface having a predetermined height from the bottom portion 22.

The permanent magnet 16 is connected to the plate 15 and the connecting portion 2.
3 and is sandwiched. At this time, the top pole face of the permanent magnet 16 is connected to the bottom face of the plate 15, and the bottom pole face is connected to the connection face of the connection portion 23. A magnetic gap 24 is formed at a uniform interval between the outer peripheral surface of the plate 15 and the inner peripheral surface of the top 20 of the yoke 12. The voice coil 14 is provided in the magnetic gap 24 by the bobbin 13.
Is suspended. Since the rare earth magnet used for the permanent magnet 16 is expensive and has a large magnetizing force at the optimum operating point, the thickness of the permanent magnet 16 is set to be small in order to use it in a flat shape. If the thickness of the plate 15 is too large, the magnetic flux density in the magnetic gap 24 becomes small, so that the thickness is set to an appropriate thickness.

The permanent magnet 16 and the connecting portion 23 have the same cross-sectional shape, for example, a circular shape, and the outer peripheral surface of the plate 15 is correspondingly uniform from the outer peripheral surface of the permanent magnet 16 and the connecting portion 23. It protrudes somewhat outward. In the present embodiment, it is assumed that the cross-sectional shape of the permanent magnet 16, the connecting portion 23, and the plate 15 is circular, but the outer shape of the yoke 12 is not limited to a circle, but may be other shapes such as a square. There may be. Here, since the outer peripheral surfaces of the permanent magnet 16 and the connecting portion 23 are recessed inward from the outer peripheral surface of the plate 15, the voice coil 1
4 vibrates up and down in the figure, the inner peripheral surface of the bobbin 13 is less likely to contact the permanent magnet 16 and the connecting portion 23,
The voice coil 14 can be vibrated well.

The yoke 12 and the plate 15 are formed of a ferromagnetic metal material having a high magnetic permeability such as iron. York 1
Since the connecting portion 23 projecting upward from the bottom portion 22 is formed on the bottom portion 22 of the second plate 2, the plate 15 and the permanent magnet 1
The distance L3 between the bottom of the voice coil 14 and the bottom of the yoke 12 can be increased while maintaining the thickness of the voice coil 6 at an appropriate thickness. By increasing the distance L3, the amplitude of the voice coil 14 can be increased. Thus, when the magnetic circuit 11 is applied to a speaker or the like, the amplitude of the voice coil 14 increases as the generated sound changes from a treble to a bass, but the bottom of the voice coil 14 is , And high to low tones can be satisfactorily generated without touching the sound.

In the magnetic circuit 11, the voice coil 14
The height of the connection portion 24 from the bottom 22 is adjusted in accordance with the amplitude of the voice coil 14 and the bottom of the yoke 12.
Can be set to an appropriate length. By setting the distance L3 to an appropriate length, it is possible to reduce the extra thickness of the magnetic circuit 11 in the up-down direction, thereby realizing miniaturization and cost reduction of the magnetic circuit 11.

In the magnetic circuit 11, the yoke 12
The top 20, the tubular portion 21, and the bottom 22 may be separate, and the bottom 22 and the connecting portion 23 may be separate. For example, the top 20, the cylinder 21 and the bottom 2
By forming the connection part 23 and the connecting part 23 separately, the yoke 12 can be manufactured at low cost by punching or bending by pressing.

FIG. 2 is a sectional view showing the configuration of an inner magnet type magnetic circuit 11a according to another embodiment of the present invention. 2, portions corresponding to those of the magnetic circuit 11 shown in FIG. 1 are denoted by the same reference numerals. A feature of the magnetic circuit 11 a is that a bottomed hole 25 that opens to the bottom surface side of the bottom 22 of the yoke 12 is formed in the connection portion 23 of the yoke 12.

When the hole 25 is formed, the yoke 1
2 can increase the surface area of the outer surface. As a result, even when the magnetic circuit 11a is applied to a speaker or the like and continuously generates a large output sound, the heat generated from the voice coil 14 can be efficiently released to the outside of the yoke 12, and the voice Overheating of the coil 14 can be prevented. Since the overheating of the voice coil 14 is prevented in this manner, the deterioration of the voice coil 12 caused by the overheating of the voice coil 14 can be prevented, and the input resistance of the magnetic circuit 11a can be improved.

In the magnetic circuit 11a, the hole 25 is formed in the yoke 12 so as to open from the inside of the connection portion 23 to the bottom portion 22, so that the entire yoke 12 can be made substantially uniform in thickness. Therefore, the bottom portion 22 of the yoke 12 and the connection portion 23
If the magnetic circuit 11 of the previous embodiment needs to be processed by cutting or casting, it is suitable for mass production because the magnetic circuit 11a of this embodiment has a uniform thickness. Pressing can also be performed.

In this embodiment, the hole 25 formed in the connecting portion 23 is assumed to be circular in cross section when cut in a plane parallel to the horizontal plane. Other shapes suitable for heat dissipation such as a mold may be used.

FIG. 3 is a sectional view showing the configuration of an inner-magnet type magnetic circuit 11b according to still another embodiment of the present invention. 3, parts corresponding to the magnetic circuit 11 shown in FIG. 1 are denoted by the same reference numerals. A feature of the magnetic circuit 11b is that the upper surface 26 of the plate 15 has a curved surface shape that rises from the outer periphery toward the center. By raising the upper surface 26 of the plate 15, it is possible to increase the cross-sectional area of the central portion of the plate 15 in the thickness direction.

In the magnetic material used for the plate 15, the upper limit of the magnetic flux density from the permanent magnet 16 to the magnetic gap via the plate 15 is determined by the magnetic saturation amount inherent to the magnetic material. Is easily saturated, but since the cross-sectional area of the central portion is enlarged, the saturation of the magnetic flux can be prevented even at the central portion of the plate 15.
Thus, the magnetic flux generated from the permanent magnet 16 can be efficiently guided.

In the first to third embodiments, it is assumed that the magnetic circuits 11, 11a and 11b are applied to a speaker. It may be applied to a type of actuator or the like, and may be used for moving a magnetic head such as a magnetic disk storage device.

[0035]

As described above, according to the present invention, the connecting portion projecting upward from the bottom of the yoke is formed on the yoke which surrounds and holds the plate and the permanent magnet. The permanent magnet is sandwiched between the plate and the connection. Therefore, conventionally, the distance between the bottom of the voice coil and the bottom of the yoke has been increased by increasing the thickness of the plate and the permanent magnet. While maintaining the thickness,
The distance between the bottom of the voice coil and the bottom of the yoke can be increased.

When the magnetic circuit structure of the present invention is applied to a speaker or the like by increasing the distance between the voice coil and the yoke, the amplitude of the voice coil increases as the generated sound changes from high to low. However, it is possible to prevent the bottom of the voice coil from colliding with the bottom of the yoke, especially when a low tone is generated. As a result, it is possible to realize a small-sized speaker capable of favorably generating high to low tones.

Further, by adjusting the height of the connecting portion from the bottom of the yoke, the distance between the bottom of the voice coil and the bottom of the yoke can be easily adjusted in accordance with the amplitude of the voice coil. This can reduce the extra thickness of the magnetic circuit structure in the vertical direction,
The size and cost of the magnetic circuit structure can be reduced. A bottomed hole that opens to the bottom side of the yoke is formed in the connection portion. Thus, the surface area of the outer surface of the yoke can be increased, and the heat generated from the voice coil can be efficiently released to the outside of the yoke. Therefore, even when the magnetic circuit structure of the present invention is applied to a speaker or the like and a high-output sound is continuously generated, overheating of the voice coil can be prevented and sound can be generated in a good state.

Further, according to the present invention, since the upper surface of the plate has a curved shape that rises from the outside to the center, the cross-sectional area in the thickness direction of the center of the plate can be increased. . Since the cross-sectional area of the central portion is enlarged, the saturation of the magnetic flux can be prevented even at the central portion of the plate, and the magnetic flux generated from the permanent magnet can be efficiently guided.

[Brief description of the drawings]

FIG. 1 is an inner magnet type magnetic circuit 11 according to an embodiment of the present invention.
It is sectional drawing which shows a structure of.

FIG. 2 shows an inner magnet type magnetic circuit 1 according to another embodiment of the present invention.
It is sectional drawing which shows the structure of 1a.

FIG. 3 is a cross-sectional view illustrating a configuration of an inner-magnet type magnetic circuit 11b according to still another embodiment of the present invention.

FIG. 4 shows a configuration of a conventional magnetic circuit.

FIG. 5 shows a configuration of another conventional magnetic circuit.

[Explanation of symbols]

 11, 11a, 11b Magnetic circuit 12 Yoke 13 Bobbin 14 Voice coil 15 Plate 16 Permanent magnet 23 Connection part 24 Magnetic gap 25 Hole

Claims (2)

(57) [Claims] 1. A magnetic air gap in which a voice coil is suspended,
In an inner magnet type magnetic circuit structure formed between the outer peripheral surface of the plate and the inner peripheral surface of the yoke surrounding the plate and provided with a permanent magnet between the plate and the bottom of the yoke, the permanent magnet is: It is plate-shaped, the top pole face is joined to the bottom face of the plate, the yoke is formed with a connection part projecting from the bottom and magnetically connected to the bottom pole face of the permanent magnet, and the outer diameter of the permanent magnet, The magnetic circuit structure according to claim 1, wherein the outer diameter of the connecting portion is equal to or less than the outer diameter of the plate, and the connecting portion is formed with a bottomed hole that opens on the bottom side of the yoke. 2. A magnetic air gap in which a voice coil is suspended,
In an inner magnet type magnetic circuit structure formed between the outer peripheral surface of the plate and the inner peripheral surface of the yoke surrounding the plate and provided with a permanent magnet between the plate and the bottom of the yoke, the permanent magnet is: It is plate-shaped, the top pole face is joined to the bottom face of the plate, the yoke is formed with a weld that projects from the bottom and is magnetically connected to the bottom pole face of the permanent magnet, and the outer diameter of the permanent magnet, The magnetic circuit structure according to claim 1, wherein the outer diameter of the connection portion is equal to or less than the outer diameter of the plate, and the upper surface of the plate has a curved surface shape that rises from the outside toward the center.