JPH05137196A - Speaker magnetic circuit - Google Patents

Abstract

PURPOSE:To make constituting materials thin and to uniformize the magnetic flux density distribution in an air gap part. CONSTITUTION:A center pole 2 is stuck in the center part on the upper face of a yoke 1 like a disk, and an annular magnet 3 is coaxially attached in the vicinity of the peripheral edge on the upper face of the center pole 2. A top plate 21 is attached on the magnet 3. Such taper face is formed in the edge part of the top plate 21 so that the air gap facing the side face of the center pole 2 is linearly changed. Since the magnetic flux from the magnet 3 is sparser in the part where the air gap is smaller, a uniform magnetic field is obtained for voice coil part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker magnetic circuit in an acoustic output device.

[0002]

2. Description of the Related Art A structure including a magnetic circuit of a conventional speaker will be described. FIG. 5 is a sectional view showing a configuration example of an outer magnet type speaker. At the center of the upper surface of the yoke 1 formed of a disk-shaped magnetic body, a center pole 2 which is a cylindrical magnetic body is provided.
Is attached, and an annular magnet 3 is attached coaxially therewith in the vicinity of the outer peripheral edge of the upper surface of the yoke 1. A top plate 4 is attached to the upper portion of the magnet 3 so as to face the side surface of the center pole 2 and maintain a predetermined gap. Further, a conical frame 5 having a plurality of cutout openings is fixed to the upper portion of the top plate 4.

On the other hand, the space formed by the center pole 2 and the end portion of the top plate 4 is called a magnetic gap portion, and the voice coil portion 7 is provided in this gap portion. A suspension 6 is held inside the frame 5, and a voice coil portion 7 is vibratably supported in a central opening thereof. The conical diaphragm 8 is fixed to the voice coil section 7 and driven by the electromagnetic force of the magnetic gap section.
In the voice coil unit 7, a coil 7b is wound around the side surface of a cylindrical movable body 7a, and the movable body 7a vibrates while being held by a suspension 6 having a wavy cross section. Also, the diaphragm 8
A dome-shaped dust cap 9 is attached to the central part of the.

In the speaker having such a structure, the yoke 1, the center pole 2, the magnet 3, and the top plate 4 constitute a magnetic circuit of the voice coil section 7.
Due to the magnetic flux between the center pole 2 and the top plate 4,
The voice coil unit 7 is responsive to the drive current flowing through the coil 7b.
Receives electromagnetic force.

A specific configuration example of a conventional speaker magnetic circuit will be described with reference to FIGS. 6 (a) and 6 (b). Figure 6
(A) is sectional drawing which shows the structure of the external magnet type magnetic circuit used for the conventional speaker. The structure is the same as that described in FIG. 5, and the magnet 3 is located at the outer peripheral portion of the magnetic circuit. The top plate 4 has a predetermined thickness in order to maintain a constant gap (air gap) only in the portion facing the center pole 2 in order to reduce the material cost of the magnetic body. The plate thickness of the portion joined to the magnet 3 is thin.

Next, FIG. 6 (b) is a sectional view showing the structure of an inner magnet type speaker magnetic circuit. The yoke 11 is a magnetic body in which a hollow cylindrical portion, a disk portion that shields the lower end of the hollow cylindrical portion, and an annular portion located at the upper end thereof are integrally formed, and the annular portion is formed on the inner edge of the annular portion. A cylindrical surface deeper than the wall thickness is formed.
At the center of the inner surface of the yoke 3, a cylindrical Macnet 12 is attached as a part of the center pole. A disc-shaped pole piece 13 is fixed on the same axis as the magnet 12 so as to face the annular portion of the yoke 11.

The space formed by the pole piece 13 and the end of the yoke 11 constitutes a magnetic gap portion,
A voice coil portion (not shown) is inserted into this gap portion. The shape of the yoke 11 of the magnetic gap portion is designed to have a predetermined thickness in order to reduce the material cost of the magnetic body and to hold the magnetic gap portion having a constant gap only in the portion facing the pole piece 13. However, the plate thickness of other parts is thin.

[0008]

FIG. 7 is an explanatory diagram showing the relationship between the shape of the magnetic gap portion and the magnetic flux density distribution. In this figure, the center pole 2 and the top plate 4 are shown by solid lines, and the magnetic flux density is high in the region Y1 of the thick width in the space of the portion closely facing the center pole 2 In the bent lower region Y2, the magnetic flux density decreases with increasing distance from the thick width portion, and it is difficult to ensure a uniform magnetic flux density. Therefore, the magnetic flux density is as shown by the curve A in FIG. Therefore, when the voice coil located in the magnetic gap performs piston movement with a large amplitude,
There was a problem that the linearity of vibration with respect to the input power was lost.

The present invention has been made in view of the above conventional problems, and in a speaker having an outer magnet type and an inner magnet type magnetic circuit, the magnetic gap portion has a uniform magnetic flux density distribution, An object of the present invention is to realize a speaker magnetic circuit in which the linearity of the vibration with respect to the input power is sufficiently secured even if the coil makes a piston movement with a large amplitude.

[0010]

According to a first aspect of the present invention, a disk-shaped yoke, a cylindrical center pole fixed to the central portion of the upper surface of the yoke, and a fixed center pole on the yoke coaxial with the center pole. An annular magnet that is attached at a distance, and an annular member that is attached to the upper part of the magnet, the inner peripheral portion of which is made thick, and the magnetic gap portion between the outer peripheral side surface of the center pole and the top surface of the top plate. To a lower surface side, the top plate having a taper surface with a gap between the ends becoming smaller continuously is provided.

According to a third aspect of the present invention, there is provided a disk-shaped yoke, a center pole which is a cylindrical member having a lower surface attached to a central portion of an upper surface of the yoke, and a tapered surface formed at an edge of an outer periphery of the upper surface. , A ring-shaped magnet mounted on the yoke coaxially with the center pole at regular intervals,
And a top plate attached to the upper part of the magnet and having a cylindrical surface facing the tapered surface of the center pole.

The invention of claim 5 of the present application is a member in which a hollow cylindrical portion, a disk portion for shielding the lower end thereof and an annular portion located at the upper end thereof are integrally formed, and the inside of the annular portion The yoke having a tapered surface whose opening diameter becomes continuously smaller along the lower side, the cylindrical magnet attached to the upper surface of the disk portion of the yoke, and the yoke attached to the upper surface of the magnet coaxially with the yoke. And a pole piece having a cylindrical surface in the magnetic gap portion facing the annular portion.

According to a sixth aspect of the present invention, there is provided a member in which a hollow cylindrical portion, a disc portion that shields the lower end of the hollow cylindrical portion, and an annular portion located at the upper end of the hollow cylindrical portion are integrally formed. A yoke having a cylindrical surface deeper than the annular portion, a columnar magnet attached to the central portion of the upper surface of the yoke, and an upper surface of the magnet that is coaxial with the yoke and faces the annular portion of the yoke. And a pole piece in which a taper surface whose diameter increases downward is formed in the magnetic gap portion.

[0014]

According to the invention of claim 1 of the present application having such characteristics, the distance between the disk-shaped yoke, the columnar center pole, the ring-shaped magnet, and the magnetic gap is small toward the lower surface side. A magnetic circuit is constituted by the top plate formed so as to have the shape described above. Therefore, the magnetic flux is reduced in the portion where the magnetic flux is small, so that the magnetic flux density in this portion is approximately the same as that in the portion where the magnetic gap is large. Further, since a long and uniform magnetic flux density can be obtained along the axial direction, the voice coil portion of the outer magnet type speaker is driven with a uniform magnetic flux density.

Further, according to the invention of claim 3 of the present application, a disk-shaped yoke, a cylindrical center pole having a tapered surface at its tip, a ring-shaped magnet, and a top having a cylindrical surface at an edge portion. A magnetic circuit is formed by the plate and the plate. For this reason, since the magnetic flux gap is made larger in the portion where the magnetic flux is large, the magnetic flux density in this portion is about the same as that in the portion where the magnetic gap is small. Further, since a long and uniform magnetic flux density can be obtained along the axial direction, the voice coil portion of the outer magnet type speaker is driven with a uniform magnetic flux density.

Further, according to the invention of claim 5 of the present application, a magnetic circuit is formed by the columnar pole piece, the columnar magnet, and the yoke formed such that the gap between the magnetic gap portions becomes smaller toward the lower surface side. Composed. Therefore, the magnetic flux is reduced in the portion where the magnetic flux is small, so that the magnetic flux density in this portion is approximately the same as that in the portion where the magnetic gap is large. Further, since a long and uniform magnetic flux density can be obtained along the axial direction, the voice coil portion of the inner magnet type speaker is driven with a uniform magnetic flux density.

Further, according to the invention of claim 6 of the present application, a pole piece having a tapered surface, a columnar magnet,
A magnetic circuit is formed by the yoke having an edge portion having a cylindrical surface. For this reason, since the magnetic flux gap is made larger in the portion where the magnetic flux is large, the magnetic flux density in this portion is about the same as that in the portion where the magnetic gap is small. Further, since a long and uniform magnetic flux density can be obtained along the axial direction, the voice coil portion of the inner magnet type speaker is driven with a uniform magnetic flux density.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. FIG. 1A is a cross-sectional view showing the configuration of an external magnet type speaker magnetic circuit in this embodiment. still,
The same parts as those in FIG. 6 showing the conventional example are designated by the same reference numerals and detailed description thereof will be omitted. A cylindrical center pole 2 is attached to the central portion of the upper surface of the disk-shaped yoke 1, and an annular magnet 3 is attached coaxially with the center pole 2 in the vicinity of the outer peripheral edge of the upper surface of the yoke 1. A top plate 21 is attached to the top of the magnet 3. The top plate 21 has a taper surface in the gap portion between the outer peripheral side surface of the center pole 2 and the gap distance which continuously decreases from the upper surface side to the lower surface side. This tapered surface is the edge 21a of the top plate 21.
Is formed in a conical shape so that the gap decreases along the arrow B direction. The gap formed by the center pole 2 and the end portion of the top plate 21 constitutes a magnetic gap portion, and the voice coil portion of a speaker (not shown) is inserted therein.

FIG. 2 is an explanatory view showing the relationship between the shape of the magnetic gap portion and the magnetic flux density distribution. In such a configuration, the region Y1 has a large air gap and a high magnetic resistance as shown in the figure, but is a portion where the magnetic flux from the magnet 3 is concentrated. On the other hand, the region Y2 has a small air gap and a low magnetic resistance, but is a portion where the magnetic flux from the magnet 3 is dispersed. Then, the edge portion 21 is provided to make the magnetic resistance uniform.
Since a is a tapered surface, the actual magnetic flux density is curve C
As shown by, the distribution is almost uniform in both regions Y1 and Y2.

FIG. 1B is a sectional view showing the structure of the outer magnet type speaker magnetic circuit in the second embodiment. In this embodiment, the part different from the first embodiment is that the yoke and the center pole are integrally formed. In the figure, the yoke 22 with a center pole is a magnetic body whose cross-sectional shape including the central axis has an inverted T shape. The yoke 22 with a center pole is composed of a columnar member that serves as a center pole in the center thereof and a disc-shaped member below the center pole. An annular magnet 3 is fixed to the outer periphery of the yoke 22 with a center pole. A top plate 21 having the same shape as that shown in FIG. 1A is attached to the top of the magnet 3. The top plate 21 has a tapered surface such that an edge portion facing the side surface of the yoke 23 with a center pole becomes smaller along the B direction. Also in this case, a uniform magnetic flux density similar to that in FIG. 1 can be obtained.

FIG. 3A is a sectional view of an external magnet type speaker magnetic circuit according to the third embodiment of the present invention. That is, the yoke 1, magnet 3 and top plate 4 are the same as those shown in FIG. The center pole 23 has a tapered surface at a portion facing the top plate 4,
Similar to the magnetic gap portion shown in (1), the magnetic gap portion is formed so that the gap becomes smaller along the arrow B direction.

In this structure, the magnetic flux from the magnet 3 is concentrated in the portion where the air gap is large and the magnetic resistance is high. On the other hand, in the portion where the air gab is small and the magnetic resistance is small, the magnetic flux from the magnet 3 is dispersed. Therefore, the actual magnetic flux density has a substantially uniform distribution in both the regions Y1 and Y2 as shown by the curve C in FIG.

FIG. 3B is a sectional view showing the configuration of an outer magnet type speaker magnetic circuit in the fourth embodiment. In this embodiment, a part different from the third embodiment is that the yoke and the center pole are integrally formed. In the figure, the yoke 24 with a center pole is a magnetic body having an inverted T-shaped cross section including the central axis. Yoke with center pole 2
Reference numeral 4 is composed of a cylindrical member that serves as a center pole in the center thereof and a disc-shaped member below the cylindrical member. An annular magnet 3 is fixed to the outer peripheral portion of the yoke 24 with the center pole. The upper part of the magnet 3 is shown in FIG.
The top plate 4 having the same shape as (a) is attached. The cylindrical member of the yoke 24 with a center pole is
A tapered surface is formed so that the air gap facing the edge of the top plate 4 becomes smaller along the B direction. Also in this case, a uniform magnetic flux density similar to that in FIG. 1 can be obtained.

FIGS. 4 (a) and 4 (b) are sectional views showing the configurations of the inner magnet type speaker magnetic circuits in the fifth and sixth embodiments, respectively. In FIG. 4 (a), the magnet 12 and the pole piece 13 are the same as those shown in FIG. 6 (b), and the yoke 25 has a taper surface formed on the inner edge facing the side surface of the pole piece 13, The gap is configured to linearly decrease along the arrow B direction. This magnetic gap portion is similar to that of the first embodiment, and a uniform magnetic flux density can be obtained.

Also in FIG. 4 (b), the yoke 11 and the magnet 12 are the same as those shown in FIG. 6 (b), and the pole piece 26 has a tapered surface at the portion facing the inner edge of the yoke 11. Are formed, and the air gap is configured to linearly decrease along the arrow B direction. In this case as well, a uniform magnetic flux density can be obtained as in the magnetic gap portion shown in FIG.

[0026]

As described above, according to the speaker magnetic circuit of the present invention, even if the thickness of the yoke or the top plate is reduced, a magnetic flux density distribution equivalent to that when the material is thick is obtained. A magnetic circuit that receives a uniform electromagnetic force over a wide range in the magnetic gap part of is obtained. Therefore, even when the voice coil portion of the speaker is driven with a large amplitude, the effective range of electromagnetic braking is expanded, the vibration amplitude is proportional to the exciting current of the voice coil, and the linearity with respect to the input power can be further improved. The effect is obtained. Further, it is possible to reduce the material cost of the top plate or the yoke forming the magnetic circuit.

[Brief description of drawings]

1A and 1B are cross-sectional views showing the configurations of speaker magnetic circuits according to first and second embodiments of the present invention.

FIG. 2 is an explanatory diagram showing a magnetic flux density distribution of a speaker magnetic circuit according to each embodiment of the present invention.

3 (a) and 3 (b) are cross-sectional views showing the configurations of speaker magnetic circuits according to third and fourth embodiments of the present invention.

4A and 4B are cross-sectional views showing the configurations of speaker magnetic circuits according to fifth and sixth embodiments of the present invention.

FIG. 5 is a cross-sectional view showing a configuration example of a conventional external magnet type speaker.

6A and 6B are cross-sectional views showing a configuration of a conventional speaker magnetic circuit.

FIG. 7 is an explanatory diagram showing a magnetic flux density distribution in a conventional speaker magnetic circuit.

[Explanation of symbols]

 1,11,25 Yoke 2,23 Center pole 3,12 Magnet 4,21 Top plate 13,26 Pole piece 22,24 Center pole yoke

Claims (6)

[Claims] 1. A disk-shaped yoke, a cylindrical center pole fixed to a central portion of an upper surface of the yoke, and an annular magnet mounted on the yoke coaxially with the center pole at regular intervals. An annular member attached to the upper portion of the magnet, the inner peripheral portion of which has a thick wall, and the magnetic gap portion with the outer peripheral side surface of the center pole has a continuous gap from the upper surface to the lower surface of the top plate. An outer magnet type speaker magnetic circuit, comprising: a top plate having a tapered surface with a small interval. 2. The outer magnet type speaker magnetic circuit according to claim 1, wherein the center pole and the yoke are integrally formed. 3. A disk-shaped yoke, a cylindrical member having a lower surface attached to a central portion of an upper surface of the yoke, and a center pole having a tapered surface at an outer peripheral edge portion of the upper surface, and the above-mentioned yoke on the yoke. An annular magnet that is mounted coaxially with the center pole at regular intervals; and a top plate that is mounted on the magnet and has a cylindrical surface that faces the tapered surface of the center pole. External magnet type speaker magnetic circuit. 4. The outer magnet type speaker magnetic circuit according to claim 3, wherein the center pole and the yoke are integrally formed. 5. A member in which a hollow cylindrical portion, a disc portion that shields the lower end of the hollow cylindrical portion, and an annular portion located at the upper end of the hollow cylindrical portion are integrally formed, and the opening diameter inside the annular portion is downward. And a cylindrical magnet attached to the upper surface of the disk portion of the yoke, and an annular portion of the yoke that is attached to the upper surface of the magnet coaxially with the yoke. An inner magnet type speaker magnetic circuit, comprising: a pole piece having a cylindrical surface in a magnetic gap portion facing the magnetic pole portion. 6. A member in which a hollow cylindrical portion, a disc portion that shields the lower end of the hollow cylindrical portion, and an annular portion located at the upper end thereof are integrally formed, and the meat of the annular portion is inside the annular portion. A yoke having a cylindrical surface deeper than the thickness, a columnar magnet attached to the central portion of the upper surface of the yoke, and a magnetic gap that is attached to the upper surface of the magnet coaxially with the yoke and faces the annular portion of the yoke. An inner magnet type speaker magnetic circuit, comprising: a pole piece having a tapered surface whose diameter increases in a downward direction.