JP3598423B2 - Linear voice coil for dual gap - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a voice coil used in an electroacoustic transducer, and more particularly to a dual-gap linear voice coil having no output fluctuation due to amplitude.
[0002]
[Prior art]
FIG. 2 is a half sectional view of a magnetic circuit and a voice coil according to Conventional Example 1. In the drawing, 1 is a magnet, 2 is a top plate having a plate thickness Tp installed on the upper part of the magnet 1, 14 is a yoke located on the lower part and the outer periphery of the magnet 1, 15 is a top plate 2 This is a magnetic gap between the yokes 14. Reference numeral 17 denotes a voice coil inserted and arranged in the magnetic gap 15. The winding width Lc of the voice coil 17 is substantially the same as or slightly smaller than the thickness Tp of the top plate 2.
[0003]
The magnetic flux generated by the magnet 1 goes around the top plate 2 → the magnetic gap 15 → the yoke 14 → the magnet 1 to form a magnetic circuit. Here, when a current is applied to the voice coil 17, the voice coil 17 is driven up and down according to the direction of the current according to Fleming's law.
Here, assuming that the magnetic flux in the magnetic gap 15 is b,
Since the winding width of the voice coil 17 inserted in the magnetic gap 15 is Lc,
The driving force of the voice coil 17 is proportional to b · Lc.
[0004]
In the first conventional example, the magnetic flux is effectively used. However, since the driving force fluctuates according to the amplitude of the voice coil 17 and the magnetic flux density distribution in the magnetic gap 15 is asymmetric in the vertical direction, it is inserted into the magnetic gap 15. The operation of the shifted voice coil 17 differs between the case where it moves upward and the case where it moves downward, and the second harmonic distortion occurs in the low range of the speaker. Further, in the voice coil 17, the impedance in the high frequency range is increased, which adversely affects the high frequency characteristics of the speaker.
[0005]
FIG. 3 is a half sectional view of a magnetic circuit and a voice coil according to Conventional Example 2 in which the above-described disadvantages of Conventional Example 1 are improved. In the drawing, reference numeral 1 denotes the same magnet as that of the conventional example 1, reference numeral 2 denotes the same top plate as that of the conventional example 1 installed above the magnet 1, and reference numeral 14 denotes the same magnet as that of the conventional example 1 located at the lower part and the outer periphery of the magnet 1. The same yoke 15 is a magnetic gap between the top plate 2 and the yoke 14. Reference numeral 27 denotes a voice coil including an upper voice coil 27a and a lower voice coil 27b inserted and arranged in the magnetic gap 15. The winding width of the upper voice coil 27a and the lower voice coil 27b is the same as that of the voice coil 17 of the first conventional example. It is half Lc / 2, which is approximately half the thickness Tp of the top plate 2. However, the winding directions of the upper voice coil 27a and the lower voice coil 27b are opposite to each other, and are connected to each other.
The sum of the lower part of the upper voice coil 27a and the upper part of the lower voice coil 27b inserted in the magnetic gap 15 is Lc / 2.
[0006]
The magnetic flux generated by the magnet 1 goes around the top plate 2 → the magnetic gap 15 → the yoke 14 → the magnet 1 to form a magnetic circuit. Here, when a current is applied to the upper voice coil 27a and the lower voice coil 27b, the coil is driven up and down according to the direction of the current according to Fleming's law, and the total width of the voice coils in the magnetic gap 15 regardless of the amplitude. Is constant at Lc / 2, and the driving force of the voice coil 27 does not fluctuate.
Here, assuming that the magnetic flux in the magnetic gap 15 is b,
Since the total winding width of the voice coil 27 inserted in the magnetic gap 15 is Lc / 2,
The driving force of the voice coil 27 is constant in proportion to 0.5b · Lc.
[0007]
[Problems to be solved by the invention]
However, the driving force of the voice coil including two voice coils, one upper and the lower part, in one magnetic gap of the conventional example 2 is reduced to half the driving force as compared with the case where one voice coil is used in one magnetic gap. Is bad.
[0008]
The present invention has been made in view of such a point, and an object of the present invention is to provide a dual-gap linear voice coil in which the driving force does not change regardless of the amplitude and the efficiency is improved.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the dual gap linear voice coil of the present invention is composed of two voice coils, an upper voice coil and a lower voice coil, whose winding directions are opposite to each other and whose width is equal to or smaller than the thickness of the top plate. That is, the dual gap magnetic circuit is inserted and arranged in two magnetic gaps whose magnetic flux directions are opposite to each other. The lower part of the upper voice coil inserted in the upper magnetic gap has the same width as the upper part of the lower voice coil inserted in the lower magnetic gap, and the total width of one voice coil is one. The driving force of the dual gap linear voice coil does not fluctuate, and the efficiency is further improved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
In the dual-gap linear voice coil of the present invention, a top plate 2 and a bottom plate 3 having the same plate thickness are provided on the upper and lower portions of the magnet 1, respectively. And a dual gap magnetic circuit that forms a gap 5 having a lower magnetic gap 5b.
The upper voice coil 7a and the lower voice coil 7b are connected to each other and have the same winding width and opposite winding directions. The winding width is equal to or smaller than the thickness of the top plate 2, and is inserted into the upper magnetic gap 5a. The width of the lower portion of the upper voice coil 7a and the upper portion of the lower voice coil 7b inserted into the lower magnetic gap 5b are the same, and the total is the same as the width of one voice coil. There is a characteristic in that there is.
[0011]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a half sectional view of a dual gap magnetic circuit and a dual gap linear voice coil according to the present invention. In the figure, 1 is the same magnet as the conventional example, 2 is the same top plate as the conventional example installed above the magnet 1, and 3 is the bottom plate with a plate thickness Tp installed below the magnet 1. It is. Reference numeral 4 denotes a yoke provided on the outer periphery of the magnet 1, the top plate 2, and the bottom plate 3, 5a denotes an upper magnetic gap between the top plate 2 and the yoke 4, and 5b denotes a lower magnetic gap between the bottom plate 3 and the yoke 4. The gap 5 has an upper magnetic gap 5a and a lower magnetic gap 5b.
[0012]
Reference numeral 7 denotes a dual-gap linear voice coil composed of an upper voice coil 7a and a lower voice coil 7b inserted and arranged in the gap 5. The winding width Lc of the upper voice coil 7a and the lower voice coil 7b is set to the plate of the top plate 2. Although it is equal to or smaller than the thickness Tp, it is desirably substantially the same as the plate thickness Tp. However, the winding directions of the upper voice coil 7a and the lower voice coil 7b are opposite to each other, and they are connected to each other.
[0013]
The magnetic flux generated by the magnet 1 goes around the top plate 2 → the upper magnetic gap 5a → the yoke 4 → the lower magnetic gap 5b → the magnet 1 to form a magnetic circuit. Here, when a current is applied to the upper voice coil 7a and the lower voice coil 7b, the coil is driven vertically according to the direction of the current according to Fleming's law. The lower part of the upper voice coil 7a inserted in the upper magnetic gap 5a has the same winding width as the upper part of the lower voice coil 7b inserted in the lower magnetic gap 5b, and the total is one voice. By making the coil width equal to the coil width, the sum of the voice coil widths in the two magnetic gaps 5a and 5b is constant at Lc regardless of the amplitude, and the driving force of the dual gap linear voice coil 7 varies. And the efficiency is further improved.
[0014]
In the embodiment shown in FIG. 1, for comparison with the conventional examples 1 and 2, the magnet and the top plate are the same as those of the conventional example, and the units of the winding width of the voice coil are also equal. In the embodiment, there are two magnetic gaps, and the magnetic flux density is reduced by that much compared to the conventional example. Here, the magnetic flux in the upper magnetic gap 5a and the lower magnetic gap 5b is set to 0.9 of the magnetic gap 15 in the conventional example, and the total winding length of each of the upper voice coil 7a and the lower voice coil 7b is shortened to reduce the effective winding width. It is set to 0.8.
Therefore, the magnetic flux in the magnetic gaps 5a and 5b is 0.9b,
Since the total winding width of the upper voice coil 7a and the lower voice coil 7b inserted in the magnetic gaps 5a and 5b is 0.8Lc,
The driving force of the dual gap linear voice coil 7 is proportional to 0.72b · Lc and constant.
[0015]
When the conventional example 1 (see FIG. 2) has one magnetic gap and one voice coil winding portion, the driving force of the voice coil is the product of the magnetic flux b and the coil winding width Lc, that is, b · Lc. Proportional.
In the conventional example 2 (see FIG. 3) having one magnetic gap and two voice coil windings, the driving force of the voice coil is the product of the magnetic flux b and the total effective coil width Lc / 2, In other words, it becomes constant in proportion to 0.5b · Lc.
In the embodiment of the present invention (see FIG. 1), when the magnetic gap is two and the voice coil has two winding portions, the driving force of the voice coil is a magnetic flux 0.9b and a total effective coil width of 0.8Lc. Is constant in proportion to 0.72b · Lc, and the efficiency is improved as compared with the conventional example.
[0016]
【The invention's effect】
The dual-gap linear voice coil of the present invention is connected to each other, and includes an upper voice coil 7a and a lower voice coil 7b having the same winding width and opposite winding directions, and the winding width is the same as the plate thickness of the top plate 2. The lower part of the upper voice coil 7a inserted in the upper magnetic gap 5a and the upper part of the lower voice coil 7b inserted in the lower magnetic gap 5b have the same winding width, and Is the same as the width of one voice coil,
Even if the dual-gap linear voice coil 7 swings, the driving force can be kept constant, and the current flowing through the upper voice coil 7a and the current flowing through the lower voice coil 7b are in opposite directions. It is possible to suppress an increase in impedance at a high frequency, thereby improving high-frequency characteristics and reducing current distortion. In addition, compared to the conventional example in which a coil having two winding portions is provided in one magnetic gap, the present invention is more efficient because two winding portions are provided in each of the two magnetic gaps.
[Brief description of the drawings]
FIG. 1 is a half sectional view of a dual gap magnetic circuit and a dual gap linear voice coil according to the present invention.
FIG. 2 is a half sectional view of a magnetic circuit and a voice coil according to Conventional Example 1.
FIG. 3 is a half sectional view of a magnetic circuit and a voice coil according to a second conventional example.
[Explanation of symbols]
1 Magnet 2 Top plate 3 Bottom plate 4, 14 Yoke 5, 15 Gap 5a Upper magnetic gap 5b Lower magnetic gap 7 Linear voice coil 7a, 27a for dual gap Upper voice coil 7b, 27b Lower voice coil 17, 27 Voice coil

Claims (1)

A top plate (2) and a bottom plate (3) having the same plate thickness are provided on the upper and lower portions of the magnet (1), respectively, and a yoke (4) is provided on the outer periphery thereof to form an upper magnetic gap (5a). A dual gap magnetic circuit for forming a gap (5) having a lower magnetic gap (5b) is provided. In a dual gap linear voice coil (7) inserted and arranged in the gap (5),
An upper voice coil (7a) and a lower voice coil (7b) connected to each other and having the same winding width and opposite winding directions,
The winding width is equal to or smaller than the thickness of the top plate (2),
The lower part of the upper voice coil (7a) inserted in the upper magnetic gap (5a) has the same winding width as the upper part of the lower voice coil (7b) inserted in the lower magnetic gap (5b). A dual-gap linear voice coil, wherein the total is the same as the winding width of one voice coil.

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