JPH0270196A - Magnetic circuit for speaker - Google Patents

Abstract

PURPOSE:To suppress the influence of AC magnetic flux, and to stabilize the operation of a magnetic circuit by filling conductive wool into respective spaces surrounded by a top plate, a first and a second magnets, a bottom plate and a shield cover. CONSTITUTION:The conductive wool 10a is filled in the space surrounded by the top plate 5, the first magnet 4, the bottom plate 1,the second magnet 6 and the shield cover 7, and besides, the conductive wool 10b is filled in the space surrounded by the plate 1, the magnet 6 and the cover 7. In the magnetic circuit of a speaker, the flow of AC magnetic flux has four loops phi1 to phi4. By arranging the wool 10a, 10b on the routes or in the vicinity of the routes of the magnetic fluxes phi3, phi4 among these routes of the AC magnetic circuit, the magnetic fluxes phi3, phi4 are consumed as an eddy current by the wool 10a, 10b. Thus, the modulation of the DC magnetic flux density of a magnetic gap 9 and the modulation of the magnetic flux density of an operating point of the magnet 6 can be suppressed, and the stable magnetic circuit can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic circuit for a speaker.

[Prior Art] FIG. 7(a) is a sectional view showing a half part of a magnetic circuit of a conventional speaker disclosed in, for example, Japanese Utility Model Application Publication No. 61-72993, and FIG. Kaisho 47-1292
FIG. 3 is a sectional view showing a half portion of a magnetic circuit of a conventional speaker disclosed in Publication No. 3; In the figure, 1 is a bottom plate having a center pole 2, 4 is a first magnet fixed on the bottom plate 1, 5 is a top plate fixed on the first magnet 4, 3 is near the center pole 2, and a conductive ring sandwiched between the bottom plate 1 and the top plate 5; 6 is a second magnet fixed to the bottom surface of the bottom plate 1 with the magnetization direction opposite to that of the first magnet 4; 7 is a second magnet; A shield cover 8 is fixed to the lower surface of the magnet 6 to form a bowl shape, and the upper edge of the cover faces the outer periphery of the top plate 5. Reference numeral 8 indicates the center pole 2.
and the top plate 5.
This is the voice coil inserted inside.

FIG. 8 is an explanatory diagram showing the flow of AC magnetic flux in the magnetic circuit of FIG. 7(a), and FIG. 9 is an explanatory diagram showing AC magnetic lines of force in the magnetic circuit of FIG. 7(a).

Next, the operation of the magnetic circuit of the above conventional speaker will be explained. In the above magnetic circuit, the first magnet 4.
A DC magnetic flux is formed in the magnetic gap 9 by the second magnet 6 . When a voice current flows through the voice coil 8 inserted into the magnetic gap 9, AC magnetic flux is generated, and this AC magnetic flux modulates the DC magnetic flux.

As shown in FIG. 8, as a result of analyzing the flow of AC magnetic flux in the magnetic circuit using the finite element method, it was found that the flow of AC magnetic flux had four loops. In FIG. 8, Φ1 is the alternating magnetic flux of the loop that revolves around the magnetic gap 9, and Φ2 is the center pole 2. Bottom plate l, first magnet4. The alternating current magnetic flux of the loop around the top plate 5,
Φ3 is center pole 2, bottom plate 1. AC magnetic flux of loop rotating around shield cover 7 and top plate 5, φ
4 is center pole 2. Bottom plate l.

This is an alternating current magnetic flux in a loop that revolves around the second magnet 6, shield cover 7, and top plate 5.

FIG. 9 shows the distribution of AC magnetic lines of force as a result of analyzing the AC magnetic flux of the magnetic circuit using the finite element method.

This analysis shows the distribution of AC magnetic lines of force when a human power equivalent to IW is applied to the voice coil 8 at 50 Hz. Here, in the above magnetic circuit, for example, the diameter of the center pole 2 is a6 mm, and the diameter of the first magnet 4 is 90 x 50 mm.
mm, the diameter of the second magnet 6 is 80 x 32 mm,)
The thickness of the tongue plate 5 is 8 mm, and the length of the magnetic gap 9 is 1°2 mm.

Also, the change in magnetic flux density of the magnetic gap 9 at each frequency 1ΔB, the amount of change in the magnetic flux density of the first magnet 4 ΔB, 1. Amount of change ΔBI in the magnetic flux density of the second magnet 6
The results of the analysis focusing on No. 12 are shown in FIG. 4, which will be described later. In FIG. 4, α-ri is as shown in FIG. 7(a) of conventional example 1.
E-17 shows the analysis result of the AC magnetic flux of the magnetic circuit shown in FIG. 7(b) of Conventional Example 2.

The amount of change ΔB9 in the magnetic flux density of the magnetic gap 9 is the alternating current magnetic flux φ
1. Φ2. Φ3. Controlled by Φ4. In particular, when the AC magnetic flux Φ1, which has a large influence, flows from the center pole 2 to the top plate 5 in a direction of 0, the center of the AC magnetic flux Φ1 is below the center of the magnetic gap 9, resulting in vertical asymmetricity. This will affect the amount of change ΔBg in the magnetic flux density of the gear hub 9. Further, the amount of change ΔB1 in the magnetic flux density of the first magnet 4 is controlled by the alternating current magnetic flux φ2. Further, the amount of change ΔBm2 in the magnetic flux density of the second magnet 6 is controlled by the alternating current magnetic flux φ4.

[Problems to be Solved by the Invention] Since the magnetic circuit of the conventional speaker is configured as described above, the AC magnetic flux Φ1 in the magnetic circuit constitutes an asymmetrical magnetic flux with respect to the magnetic gap 9, and the AC magnetic flux Φ1. φ
2. φ3. φ4 modulates the DC magnetic flux density of the magnetic gap 9, AC magnetic flux φ2 modulates the magnetic flux density at the operating point of the first magnet 4, AC magnetic flux Φ4 modulates the magnetic flux density at the operating point of the second magnet 6, and this This has caused a problem in that the operation of the magnetic circuit becomes unstable. Furthermore, a magnetic circuit such as the magnetic circuit shown in FIG. 7(b) in which a conductive ring 3 is sandwiched between the bottom plate l and the top plate 5 in the vicinity of the center pole 2 has also been proposed. Even in such a magnetic circuit, there is a problem that the operation of the magnetic circuit cannot be sufficiently stabilized to a satisfactory degree.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a magnetic circuit for a speaker that can suppress the influence of alternating magnetic flux and stabilize the operation of the magnetic circuit.

[Means for Solving the Problems] A magnetic circuit of a speaker according to the present invention is provided in a space surrounded by a top plate, a first magnet, a bottom plate, a second magnet, and a shield cover in the magnetic circuit, or in a space surrounded by a bottom plate. The space surrounded by the second magnet and the shield cover, or both of these spaces, is filled with conductive wool made of a conductive material.

In addition, the magnetic circuit of the speaker according to the present invention includes one or more conductive rings made of a non-magnetic material and made of a conductive material, sequentially from the bottom thereof as a center pole of the magnetic circuit, and made of a conductive material. A collection ring is formed by stacking one or more magnetic rings made of a non-magnetic material and one or more conductive rings made of a conductive material, and this collection ring is fitted onto the outer periphery of the center pole. Furthermore, the upper surface of the center pole is extended to protrude from the upper surface of the opposing top plate.

[Function] In the magnetic circuit of the speaker according to the present invention, the space of the magnetic circuit is filled, and the conductive wool made of a conductive material induces a back electromotive force by the alternating current magnetic flux φ3゜Φ4 of the magnetic circuit, and this A current flows through the conductive wool due to the back electromotive force, and the magnetic flux generated by this current returns the original alternating current magnetic flux φ3. φ4
It has the effect of canceling out. That is, the AC magnetic flux φ3 of the magnetic circuit. φ4 can be consumed as an eddy current by the conductive wool, thereby providing a stable magnetic circuit.

Further, in the magnetic circuit of the speaker according to the present invention, a conductive ring, a magnetic ring, and a conductive ring are sequentially stacked from the bottom to form a collective ring as a center pole in the magnetic circuit, and this collective ring is used as a center pole. The upper surface of the center pole is configured to protrude and extend from the upper surface of the opposing top plate, so that the vertically asymmetric AC magnetic flux φ1 in the magnetic gap of the magnetic circuit is made symmetrical. None, and the alternating current magnetic fluxes Φ1 to Φ4 can be consumed as eddy currents by the center pole having the above configuration, thereby providing a stable magnetic circuit.

[Embodiment] FIG. 1 is a sectional view showing the outside half of a magnetic circuit of a speaker according to an embodiment of the present invention. In the figure, l is the bottom plate with center pole 2, 4 is the bottom plate l
The first magnet fixed on the top, 5 is the first magnet 4
The top plate fixed on the top, 6 is the first magnet 4
A second magnet 7 is fixed to the lower surface of the bottom plate l with the magnetization direction reversed, and is fixed to the lower surface of the second magnet 6 to form a bowl shape, with its upper edge facing the outer periphery of the top plate 5. The opposing shield cover 8 is a voice coil inserted into a magnetic gap 9 formed between the center pole 2 and the top plate 5. Also, 10a
and 10b is a conductive wool made of a magnetic material constituting the magnetic circuit, generally a material with lower conductivity than iron, such as copper or aluminum, and the conductive wool 10a is made of a conductive material such as copper or aluminum. 1 magnet 4, the bottom plate 1, the second magnet 6, and the shield cover 7, and the conductive wool 101) is filled in the space surrounded by the bottom plate 1, the second magnet 6, and the shield cover 7.
It fills the space surrounded by.

Next, the operation of the magnetic circuit of the speaker according to the embodiment of the present invention shown in FIG. 1 will be explained.

In the magnetic circuit described above, the first magnet 4° and the second
A DC magnetic flux is formed in the magnetic gap 9 by the magnet 6 . However, when a voice current flows through the voice coil 8 inserted into the magnetic gap 9, an alternating current magnetic flux is generated, and this alternating current magnetic flux modulates the above-mentioned direct current magnetic flux.

As shown in FIG. 8, as a result of analyzing the flow of AC magnetic flux in the magnetic circuit using the finite element method, it was found that the flow of AC magnetic flux had four loops. This 4
The alternating current magnetic flux of the two loops is φ1. Φ2. φ3
．． It is φ4. These AC magnetic fluxes φ1 to φ4 modulate the DC magnetic flux density of the magnetic gap 9, and the AC magnetic flux Φ4 modulates the DC magnetic flux density of the magnetic gap 9.
The magnetic flux density at the operating point of the magnet 6 is modulated. By modulating the DC magnetic flux density of the magnetic gap 9, second-order or higher-order harmonic distortion occurs in the reproduced sound generated from the speaker. Further, by modulating the magnetic flux density at the operating point of the second magnet 6, the magnetic flux of the second magnet 6 is demagnetized.

This invention was made to solve the above-mentioned problems, and among the four loops of AC magnetic fluxes Φ1 to Φ4, mainly AC magnetic fluxes Φ3. This is configured to reduce Φ4. That is, as shown in FIG. 1, conductive wool 10a, 1 filled in the space of the magnetic circuit.
0 b is the AC magnetic flux φ3. By installing it in or near the path of φ4, the alternating current magnetic flux φ3. Conductive wool 10a with φ4 as eddy current.

10b. Due to their properties, the conductive wools 10a and 10b easily fit into the irregularly shaped space of the magnetic circuit and can be easily inserted. Further, the air between the conductive wools 10a and 10b or the air within the conductive wools 10a and 10b has the advantage of having a sound absorbing and vibration damping effect.

Further, FIG. 2 is a sectional view showing a hand portion of a magnetic circuit of a speaker according to an embodiment of the present invention. In the figure, 1 is a bottom plate with a center pole 2, 4 is a first magnet fixed on the bottom plate l, 5 is a top plate fixed on the first magnet 4, and 6 is the first magnet 4 and its magnetization direction. A second magnet 7 is fixed to the lower surface of the bottom plate l by inverting the second magnet 7, and is fixed to the lower surface of the second magnet 6 to form a bowl shape, and the top part 8 of the tip faces the outer periphery of the top plate 5. The shield cover 8 is a voice coil inserted into a magnetic gap 9 formed between the center pole 2 and the top plate 5. Also,
11 is a magnetic ring made of magnetic material, 12.13 is a conductive ring made of non-magnetic material and conductive material such as steel, aluminum, etc.
13, one or more conductive rings 12.13 are arranged sequentially from the bottom of the center pole 2. A collection ring 14 is formed by stacking the magnetic ring 11 and the conductive ring 13 in this order, and the collection ring 14 is fitted onto the outer periphery of the center pole 2. Furthermore, the magnetic ring 11 is positioned on a surface substantially facing the top plate 5, and the upper surface of the center pole 2 fitted on the outer periphery of the collecting ring 14 is made to protrude and extend from the upper surface of the opposing top plate 5. There is.

FIG. 3 is an explanatory diagram showing alternating current magnetic lines of force in the magnetic circuit of FIG. 2, and FIG. 4 is a comparison diagram of the present invention and a conventional example, showing the amount of change ΔB in the distance density of the magnetic gap at each frequency.
Q T Amount of change ΔB in the distance density of the first magnet and the second magnet, 1. It is a characteristic diagram of the result of analysis focusing on ΔB,2.

Next, the operation of the magnetic circuit of the speaker according to the embodiment of the present invention shown in FIG. 2 will be explained.

Since the basic operation of the magnetic circuit described above is the same as the magnetic circuit shown in FIG. 1, detailed explanation thereof will be omitted. Second
In the magnetic circuit shown in the figure, the upper surface of the center pole 2 is extended to protrude from the upper surface of the top plate 5, so that among the four loops of AC distance φ1 to φ4, the magnetic gap 9 of AC distance φ1 is The vertical symmetry of is improved and becomes better. Moreover, the AC distance Φ1 to φ4 is consumed as eddy current within the conductive ring 12.13. A back electromotive force is induced in this conductive ring 12.13 by the AC separation Φ1 to Φ4, and a current flows through the conductive ring 12.13 due to this back electromotive force, and the magnetic flux generated by this current returns the original AC separation. This has the effect of canceling out Φ1 to Φ4.

FIG. 3 shows the distribution of AC magnetic lines of force as a result of analyzing the AC separation of the magnetic circuit using the finite element method.

This analysis represents the distribution of AC magnetic lines of force when a human power equivalent to IW at 100 Hz is applied to the voice coil 8.

Here, copper is used for the conductive rings 12, 13.

As shown in FIG. 4, k-Isshiki shows the analysis result of the AC separation of the magnetic circuit according to the present invention shown in FIG. According to the analysis results, conventional example 1. Low
It can be seen that there is a clear improvement compared to the analysis results of the AC separation of the magnetic circuit of Conventional Example 2 shown in FIG.

Further, in the magnetic circuit according to the present invention shown in FIG. 2, the center pole 2 is straight, so that it is easy to process. In addition, since the magnetic ring 11 and conductive rings 12 and 13 forming the collective ring 14 fitted to the outer circumference of the center pole 2 are laminated using punchable thin plate materials, the top plate 5 thickness and 1st
It is also possible to apply the present invention to a magnetic circuit in which the magnet 4 has a different thickness. Further, modulation of the magnetic flux density at the operating point of the second magnet 6 is also reduced, and therefore the overall operation of the first magnet 4 and the second magnet 6 is stabilized, and demagnetization is also suppressed.

In the above embodiment, a magnetic circuit of the magnetic shield type is shown as an example, but as another embodiment of the present invention, as shown in FIG.
As shown in a) and (b), it is fully applicable to an external magnetic type magnetic circuit using a ferrite magnet as the first magnet 4, and an internal magnetic type magnetic circuit using an alnico magnet 4a and a yoke la. Therefore, the same effect as the above embodiment is achieved.

Moreover, FIGS. 6(a) and (b) show other embodiments in which the first magnet 4 is made thicker and the first magnet 4 and the top plate 5 are made thinner in the magnetic circuit shown in FIG. The structure and operation of these magnetic circuits are the same as those of the magnetic circuit shown in FIG. 2, so detailed explanation thereof will be omitted.

[Effects of the Invention] As described above, according to the magnetic circuit of the speaker of the present invention, in the space surrounded by the top plate, the first magnet, the bottom plate, the second magnet, and the shield cover in the magnetic circuit, or Since the space surrounded by the bottom plate, the second magnet, and the shield cover, or both of these spaces, is filled with conductive wool made of a conductive material, the DC magnetic flux density of the magnetic gap can be modulated, Moreover, it is possible to suppress the modulation of the magnetic flux density at the operating point of the second magnet, thereby achieving an excellent effect that a stable magnetic circuit can be obtained.

Further, according to the magnetic circuit of the speaker of the present invention, as a center pole in the magnetic circuit, a conductive ring, a magnetic ring, and a conductive ring are sequentially stacked from the bottom to form a collective ring. The structure is such that it is fitted onto the outer periphery of the center pole, and the upper surface of the center pole is extended beyond the upper surface of the opposing top plate, so that the alternating current magnetic flux that modulates the direct current magnetic flux density in the magnetic gap can be moved up and down. This has the excellent effect of improving the asymmetry and reducing the alternating current magnetic flux itself, thereby providing a stable magnetic circuit that can improve the linearity of the reproduced sound generated from the speaker.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing the hand portion of the magnetic circuit of a speaker according to an embodiment of the present invention, FIG. 3 is an explanatory diagram showing AC magnetic lines of force in the magnetic circuit of FIG. 2, and FIG. Amount of change in the magnetic flux density of the magnetic gap at each frequency ΔBQ+ Amount of change in the magnetic flux density of the first magnet and the second magnet ΔB□1. ΔB
□Characteristic diagrams of the results of analysis focusing on 2, Figures 5 (a) and (b) and Figure 6 (a) and (b) are cross-sectional views showing modifications of the magnetic circuit in Figure 2, Figure 7(a) and (b)
) is a cross-sectional view showing the hand part of the magnetic circuit of a conventional speaker.
FIG. 8 is an explanatory diagram showing the flow of AC magnetic flux in the magnetic circuit of FIG. 7(a), and FIG. 9 is an explanatory diagram showing AC magnetic lines of force in the magnetic circuit of FIG. 7(a). In the figure, 1... bottom plate, 1a... yoke, 2... center pole, 3... conductive ring, 4
... 1st magnet, 4a... Alnico magnet, 5.
...Top plate, 6...Second magnet, 7...
・Shield cover 8... Voice coil, 9... Magnetic gap, 10a, 10b... Conductive wool, 11.
... Magnetic ring, 12.13 ... Conductive ring, 14
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Claims (1)

[Claims] 1. A bottom plate having a center pole at the center, a first magnet fixed on the bottom plate, and a voice fixed on the first magnet and between the center pole. a top plate forming a magnetic gap into which the coil is inserted; a second magnet fixed to the lower surface of the bottom plate with the magnetization direction opposite to that of the first magnet; and a second magnet fixed to the lower surface of the second magnet. A magnetic circuit comprising a bowl-shaped shield cover whose upper edge opening faces the outer periphery of the top plate or faces the lower surface of the top plate, the top plate, the first magnet, and the A conductive material is provided in a space surrounded by the bottom plate, the second magnet, and the shield cover, or in a space surrounded by the bottom plate, the second magnet, and the shield cover, or in both spaces. A speaker magnetic circuit characterized by being filled with conductive wool made of. 2. A bottom plate having a center pole in the center, a first magnet fixed on the bottom plate, and a magnetic field fixed on the first magnet with a voice coil inserted between the center pole and the bottom plate. A top plate forming a gap, a second magnet fixed to the lower surface of the bottom plate with the magnetization direction opposite to that of the first magnet, and a bowl-shaped second magnet fixed to the lower surface of the second magnet. In a magnetic circuit consisting of a shield cover whose upper edge opening faces the outer periphery of the top plate or the lower surface of the top plate, the center pole is made of non-magnetic material sequentially from the bottom, And stacking one or more conductive rings made of conductive material, one or more magnetic rings made of magnetic material, and one or more conductive rings made of non-magnetic material and conductive material. to form a collecting ring, the collecting ring is fitted onto the outer periphery of the center pole, and the upper surface of the center pole is extended to protrude from the upper surface of the opposing top plate. magnetic circuit of the speaker.