JP2987188B2 - Magnetic circuit for speaker - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic circuit for driving a speaker, and more particularly to a magnetic circuit for a speaker that is lightweight and has a high magnetic flux density in a gap.

(Prior art) Speakers incorporated in audio systems, etc.
It converts an electric signal from the amplifier into an acoustic signal and outputs sound to the outside.

At present, a dynamic loudspeaker that converts an electric signal into an acoustic signal by the action of a magnetic flux and an electromagnetic force has become a mainstay.

Such dynamic speakers include a cone speaker, a dome speaker, a horn speaker, a flat speaker, and the like.

FIG. 15 shows a cone type speaker as an example of a dynamic type speaker.

As shown in FIG. 1, a yoke 1 of a cone type speaker is provided with a columnar pole portion 2 and a yoke base 3. A ring-shaped plate 4 is arranged on the yoke base 3, and a magnet 5 is held between the plate 4 and the yoke base 3. In a magnetic gap G formed by a gap between the plate 4 and the pole portion 2, a columnar voice coil 6 is disposed so as to be movable in the directions of arrows ab.

The frame 4 is attached to the plate 4. A diaphragm 9 is arranged between the edge 8 of the frame 7 and the voice coil 6. The voice coil 6 is held at a fixed position in the magnetic gap by a damper 10. In the figure, reference numeral 11 indicates a terminal, and reference numeral 12 indicates a lead wire.

When the voice coil 6 moves in the direction of the arrow a or b due to the action of the magnetic flux from the magnet 5 and the electromagnetic force from the voice coil 6, the diaphragm 9 vibrates, whereby sound is radiated to the outside.

(Problems to be Solved by the Invention) In the above-described magnetic circuit of the conventional cone-type speaker, for example, as shown in FIG. 16, the cross-sectional shapes of the yoke 1, the magnet 5, and the plate 4 are each rectangular. It has been.

For this reason, the efficiency of the magnetic flux φD to the magnetic gap G, which is originally required, is reduced due to the generation of the leakage magnetic fluxes φA, φB, and φC.

The outer circumference of the magnet 5 has leakage magnetic fluxes φA and φB
, But the contribution of the upper and lower corners is small.

That is, the lines of magnetic force from the magnet 5 pass through the yoke 1, the plate 4, and the inside of the magnet 5. At this time, the leakage magnetic fluxes φA, φB, and φC spreading around the yoke 1, the plate 4, and the magnet 5 have a large magnetic flux density.

For this reason, the magnetic flux φ to the magnetic gap, which is originally required,
The efficiency of D becomes low due to the generation of the leakage magnetic fluxes φA, φB, and φC, which causes a decrease in the conversion efficiency.

As a means for preventing such a decrease in conversion efficiency, for example, Japanese Utility Model Publication No. 46-8272 discloses a magnetic circuit in which a taper 13 is provided in a yoke base 3 as shown in FIG.

However, in such a magnetic circuit, although the leakage magnetic fluxes φA and φB are reduced by providing the taper 13 in the yoke base 3, the conversion efficiency of the magnetic flux φD to the magnetic gap, which is originally required, is increased. Has limitations. Furthermore, since the shape is simply provided with the taper 13, there is a limit in reducing the weight and cost of the magnetic circuit.

That is, despite the provision of the taper 13 in the yoke base 3, the leakage magnetic flux φB is still generated from the outer peripheral edge of each yoke base 3 and the plate 4. Although it is possible to reduce the weight and cost to some extent by adjusting the taper angle of the taper 13, considering the distribution state of the magnetic flux density inside the iron material,
This is because a portion having a small magnetic flux density, that is, a useless portion still remains, and it is not possible to obtain an optimum shape in consideration of weight reduction and cost reduction.

Note that regardless of the magnetic circuit shown in FIGS. 16 and 17,
Some other magnetic circuits have a hollow portion provided along the axial direction of the pole portion 2.

This hollow portion is, for example, a bolt hole for coaxially mounting another speaker in a coaxial composite speaker. In a large-diameter speaker, a ventilation hole is provided to improve the movement of the diaphragm.

Thus, in the case where the hollow portion is provided along the axial direction of the pole portion 2, the weight is reduced by the hollow portion. However, the contribution of weight reduction by the hollow portion is actually insufficient.

Therefore, such a limitation hinders improvement in sound quality, reduction in weight, and reduction in cost, particularly for a small-sized speaker mounted on a vehicle.

The present invention has been made in view of such circumstances, and has as its object to provide a magnetic circuit for a speaker capable of improving sound quality, reducing weight, and reducing cost.

(Means for Solving the Problems) To achieve the above object, the present invention provides a pole section,
A yoke base integrated with the pole portion, a plate facing the yoke base, and a speaker magnetic circuit including a magnet disposed between the pole portion and the yoke base and the plate; The distance from the approximate center of the pole to the outer end of the magnet is X ₁ , the distance from the approximate center of the pole to the inner end of the magnet is X ₂ , the distance from the approximate center of the pole to the magnet is The distance from the outer end of the pole portion to the outer end of the pole portion facing the inner end is X ₃ , and the distance from the approximate center position of the pole portion to the outside of the magnet is a variable X, and X ₂ ≦ X ≦ X _{1 of the} yoke base Thickness t in the range
(X) The thickness t of the yoke base in the range of X ₃ ≦ X ≦ X ₂
(X) And the thickness t of the plate in the range of X ₂ ≦ X ≦ X ₁
(X) According to the relationship, the structure is formed so as to become thinner toward the outer direction.

Further, a recess is formed in at least one of an upper portion and a lower portion of the pole portion in a direction substantially orthogonal to a direction outside the magnet, including a substantially center position of the pole portion.

(Function) In the speaker magnetic circuit of the present invention, at least the yoke base is provided with an inwardly curved taper so that the thickness of the outer peripheral edge portion is reduced, so that it is generated from the outer peripheral edge portion of the yoke base. Since it is possible to suppress the leakage magnetic flux as much as possible, the magnetic flux density in the gap can be increased.

In addition, since at least the taper provided on the yoke base has an inwardly curved shape, at least the thickness of the yoke base contributing to weight reduction of the magnetic circuit is smaller than that of the yoke base of the magnetic circuit shown in FIG. 17, for example. Become thin. Thus, the weight of the magnetic circuit can be reduced, and the cost can be reduced at the same time.

(Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of a magnetic circuit for a speaker according to the present invention.

As shown in the figure, the yoke 15 of the magnetic circuit is provided with a columnar pole portion 16 and a yoke base 17. A ring-shaped plate 18 is arranged on the yoke base 17, and a magnet 19 is held between the plate 18 and the yoke base 17. Here, the yoke base 17 and the plate 18 are formed with tapered portions 17a and 18a, respectively, so that the outer peripheral edge portions thereof become thinner. Also,
Each of the tapers 17a and 18a has a shape curved inside the yoke base 17, respectively.

In a magnetic gap formed by the gap between the plate 18 and the pole portion 16, a columnar voice coil (not shown) is disposed so as to be movable in the vertical direction.

In the magnetic circuit having such a configuration, the thickness of the outer peripheral edge of each of the yoke base 17 and the plate 18 is reduced by the taper 17a, 18a, so that the generation of the leakage magnetic flux φB in the conventional magnetic circuit can be prevented. it can. However, the thickness of the outer peripheral edge of each of the yoke bases 17 and the plate 18 is limited by the processing accuracy and the like, so that some leakage magnetic flux φB is generated.

Here, the ideal shape of the magnetic circuit shown in FIG. 1 is, for example, as shown in FIG.

That is, the thickness of the outer peripheral edge portion of each of the yoke bases 17 and the plates 18 is reduced to such an extent that the tip ends thereof are acute.

Here, the operation of each taper 17a, 18a will be described with reference to FIG.

First, as shown in the figure, the outer diameter of the magnet 19 is x ₁ ,
The inside diameter is x ₂ , and the diameter of the pole portion 16 is x ₃ . When the magnetic flux density inside the magnet 19 is Bm, the flange thickness t of the yoke base 17 at which the internal magnetic flux density Bi of the yoke 15 becomes constant
Ask for. Here, it is assumed that there is no leakage φA, φB at the outer peripheral portion of the magnet 19, and all the magnetic flux inside the magnet 19 flows into the yoke 15.

For x ₂ ≦ x ≦ x _1, the magnetic flux present between the X～x ₁ becomes φm (x) = π (x 1 2 -x 2) Bm.

On the other hand, the flange inside the magnetic flux of the yoke 15, φi (x) = 2π · x · t · Bi becomes, [phi] m = .phi.i _{^{than, x (x 1 2 -x 2}} ) Bm = 2π · x · t · Bi ∴t ^{_{(x) = (x 1 2}} -x 2) Bm / for _{(2x · Bi) x 3 ≦} x ≦ x 2, the magnetic flux present between the x~x1 is, φm (x) = π ( x 1 2 −x ₂ ² ) Bm.

On the other hand, the magnetic flux inside the collar of the yoke 15 is given by: φi (x) = 2π · x · T · Bi∴t (x) = (x ₁ ² −x ₂ ² ) Bm / (2x · Bi) When determining the slope at _{x 1, dt (x) /} dx = Bm / (2Bi) · (-x1 2 / x 2 -1) dt (x) / dt (x = x 1) = - condition that Bm / Bi Is found.

Looking considering this condition, in the _{x 2 ≦ x ≦ x 1,} t (x) = (c1 / x) -c2 · x (c1, c2 is a constant), and the outer shape of the yoke base 17 is inwardly It has a curved shape.

When x ₃ ≦ x ≦ x ₂ , t (x) = c 3 / x (c 3 is a constant), and again, the shape of the lower surface of the yoke base 17 is inwardly curved.

Note that this value is obtained assuming that there is no leakage magnetic flux φA. Therefore, in the actual magnetic circuit, a part of the magnetic flux does not pass through the pole portion 16 due to the presence of the leakage magnetic flux φA. For this reason, the rate of increase of the brim thickness is smaller than this equation, but the condition that the shape of the lower surface of the yoke base 17 is curved inward does not change. This can be confirmed by numerical calculation such as the finite element method.
Note that the above considerations also apply to the shape of the plate 18, which results in a shape in which the taper 18a is curved inward.

FIG. 4 is a magnetic force line distribution diagram simulating magnetic force lines generated in the ideal-shaped magnetic circuit of FIG.

As can be seen from this distribution diagram, the magnetic field lines g ₁ emitted from the N pole of the magnet 19 concentrate on the outer peripheral edge of the plate 18,
The magnetic flux g ₂ transmitted through the inside of the plate 18 is guided to the magnetic gap G. Magnetic lines g ₃ exiting the magnetic gap G is introduced from the end face of the yoke 15 in the magnetic gap G side yoke 15 is guided as field lines g ₄ to the S pole side of the magnet 19.

At this time, magnetic lines g ₁ in the magnet 19 has the substantially same direction as indicated by an arrow. Further, as shown by the equal magnetic flux density lines L ₁ ~L ₃ the level of magnetic flux density, and has a very high distribution in the magnetic gap G.

On the other hand, the magnet 19, the leakage magnetic flux phi ₁ and phi ₂ extending outward of plate 18 and the yoke 15, have become very magnetic flux density is low. As a result, the magnetic flux φ passing through the magnetic gap G increases, and the lines of magnetic force act efficiently on the voice coil and the like.

In contrast, in the conventional magnetic circuit, for example, as shown in FIG. 5 and FIG. 6, the degree of concentration of magnetic field lines in the magnetic gap G by the constant magnetic flux density lines L ₁ ~L ₃ is smaller. Further, in the leakage magnetic field phi ₁ and phi ₂ has a larger in comparison with the present embodiment.

That is, for example, in a magnetic circuit including the yoke 1, the plate 4, the magnet 5, and the like having a rectangular cross section shown in FIG. 16, the leakage magnetic flux φA flowing from the plate 4 to the yoke base 3 bypassing the magnet 5, and the magnetic gap G
This is because the leakage magnetic flux φB flowing from the plate 4 to the pole portion 2 without passing through the plate 4 increases.

FIG. 7 shows the performance and weight of the magnetic circuit in this embodiment in comparison with a conventional magnetic circuit.

In the figure, Bg is the magnetic flux density of the gap, φg
Indicates the magnetic flux in the gap, and φm indicates the total magnetic flux in the magnet.

As can be seen from the figure, the Bg (T) according to the present embodiment is superior to the conventional example having the best characteristics by a difference of 0.008 Tesler.

Further, the weight and the total weight of each part show extremely low values as compared with the conventional example.

FIG. 8 shows another embodiment in which the sectional shape of the magnetic circuit of FIG. 1 is changed. In the drawings described below, portions common to FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

That is, in the magnetic circuit shown in the figure, the concave portion 16a is formed below the columnar pole portion 16 of the yoke 15. Such a concave portion 16a is relatively easily obtained by forging, and it is possible to slightly reduce the weight of the magnetic circuit.

FIG. 9 shows still another embodiment in which the cross-sectional shape of the magnetic circuit of FIG. 8 is changed. A concave portion 16b is also formed on the columnar pole portion 16 of the yoke 15 on the upper side. I have.
As described above, the concave portion 16a provided on the lower side of the pole portion 16
In addition, by providing the concave portion 16b on the upper side, it is possible to further reduce the weight as compared with the magnetic circuit of FIG.

FIG. 10 shows another embodiment in which the cross-sectional shape of the magnetic circuit shown in FIG. 9 is changed. A through-hole 16c is formed in a cylindrical pole portion 16 of a yoke 15 along this axial direction. Is provided. Thus, by providing the pole portion 16 with the through hole 16c along the axial direction, it is possible to further reduce the weight as compared with the magnetic circuit of FIG.

As described above, in each of the above embodiments, the yoke base and the plate are formed such that the thickness of the outer peripheral edge is reduced.
An inwardly curved taper was provided. Therefore, it is possible to minimize the leakage magnetic flux generated from the outer peripheral edge of the yoke base as much as possible, so that the magnetic flux density in the gap can be increased.

In addition, since at least the taper provided on the yoke base has an inwardly curved shape, the thickness of at least the yoke base contributing to the weight reduction of the magnetic circuit is, for example, the same as the yoke base of the conventional magnetic circuit shown in FIG. Becomes thinner. Thus, the weight of the magnetic circuit can be reduced, and the cost can be reduced at the same time.

In each of the above embodiments, the case where the inwardly curved taper is provided in each of the yoke base and the plate is described. However, the present invention is not limited to this example, and the taper may be provided only in the yoke base. . In this case, it is possible to minimize leakage magnetic flux generated at least from the outer peripheral edge of the yoke base.

In each of the above embodiments, the case where the cross section of the magnet is rectangular has been described. However, the present invention is not limited to this example. For example, as shown in FIG. The shape may be a curved shape, or, for example, as shown in FIG. 12, the corner may be cut. As described above, by making the cross-sectional shape of the magnet a curved shape or a cut shape, the weight of the magnetic circuit can be further reduced. Also,
Since expensive magnetic materials can be saved, cost reduction of the magnetic circuit can be promoted at the same time. Furthermore, since the magnetic flux density inside the magnet is made more uniform, local occurrence of low-temperature demagnetization can be suppressed, and the magnetic flux density in the gap can be further increased.

Incidentally, the cross section of the ideal magnetic circuit in FIG. 11 and FIG. 12 has, for example, the shape shown in FIG. 13 and FIG.

In the magnetic circuits shown in FIGS. 11 and 12, only the case where the cross-sectional shape of the magnet is changed has been described, but the cross-sectional shape of the pole portion is not limited to this example, and FIGS. As shown, a concave portion and a through hole may be provided together. In this case, the weight and cost of the magnetic circuit can be further reduced.

Further, only the yoke base may be provided with the taper. In this case, it is possible to minimize the leakage magnetic flux generated at least from the outer peripheral edge of the yoke base as described above.

(Effect of the Invention) As described above, according to the magnetic circuit of the present invention, at least the yoke base is provided with an inwardly curved taper so that the thickness of the outer peripheral edge portion is reduced. Since the leakage magnetic flux generated from the outer peripheral edge of the yoke base can be suppressed as much as possible, the magnetic flux density of the gap can be increased.

In addition, since at least the taper provided on the yoke base has an inwardly curved shape, the thickness of at least the yoke base contributing to the weight reduction of the magnetic circuit is, for example, the same as the yoke base of the conventional magnetic circuit shown in FIG. Becomes thinner. Thus, the weight of the magnetic circuit can be reduced, and the cost can be reduced at the same time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a magnetic circuit for a speaker according to the present invention, FIG. 2 is a sectional view showing its ideal shape, and FIG.
FIG. 4 is a cross-sectional view for explaining an effect of each taper in the ideal cross-sectional shape of FIG. 2, and FIG. 4 is a diagram showing a magnetic field line distribution simulating magnetic field lines generated in the ideal-shaped magnetic circuit of FIG. 5 and 6 are diagrams showing magnetic field line distributions simulating magnetic field lines generated in a conventional magnetic circuit, and FIG. 7 is a diagram showing the performance and weight of the magnetic circuit of FIG. 1 in comparison with the conventional magnetic circuit. FIG. 8 is a cross-sectional view showing another embodiment in which the cross-sectional shape of the pole portion of the magnetic circuit of FIG. 1 is changed. FIG. 9 is a cross-sectional view of the magnetic circuit in which the cross-sectional shape of the pole portion is changed. FIG. 10 is a sectional view showing still another embodiment, FIG. 10 is a sectional view showing another embodiment in which the sectional shape of the pole portion of the magnetic circuit is changed, and FIG. 11 is a sectional view of the magnet of FIG. FIG. 12 is a cross-sectional view showing another embodiment in which 13 and 14 are sectional views showing ideal shapes of the magnetic circuit of FIGS. 11 and 12, and FIG. 15 is a sectional view showing still another embodiment in which the sectional shape of the magnet is changed. FIG. 16 and FIG. 17 are sectional views showing a cone type speaker as an example of a conventional dynamic type speaker, and FIG. 17 and FIG. 15… Yoke, 16… Pole, 16a, 16b… Recess, 16c
... through-hole, 17a, 18a ... taper, 17 ... yoke base, 18 ... plate, 19 ... magnet.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masatoshi Sato 1105 Nikko, Kuno, Tendo, Yamagata Prefecture Tohoku Pioneer Co., Ltd. (56) References JP-A-59-2500 (JP, A) JP-A-57 -23398 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04R 9/02 102

Claims (2)

(57) [Claims] 1. A pole portion, a yoke base integrated with the pole portion, a plate facing the yoke base, and a magnet disposed between the pole portion, the yoke base and the plate. In the magnetic circuit for a speaker provided, a distance from a substantially center position of the pole portion to an outer end of the magnet is X ₁ , a distance from a substantially center position of the pole portion to an inner end of the magnet is X ₂ , The distance from the substantially center position of the magnet to the outer end of the pole portion facing the inner end of the magnet is X ₃ , the distance from the substantially center position of the pole portion to the outside of the magnet is variable X, and the yoke is Base thickness t in the range of X ₂ ≦ X ≦ X ₁
(X) The thickness t of the yoke base in the range of X ₃ ≦ X ≦ X ₂
(X) And the thickness t (X) of the plate in the range of X ₂ ≦ X ≦ X ₁
Is A magnetic circuit for a loudspeaker, characterized in that the magnetic circuit has a structure formed so as to become thinner toward the outer direction in accordance with the above relationship. 2. The method according to claim 1, wherein a recess is formed in at least one of an upper portion and a lower portion of the pole portion in a direction substantially orthogonal to a direction outside the magnet, including a substantially center position of the pole portion. The magnetic circuit for a speaker according to claim 1.