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JP2009094977

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DESCRIPTION JP2009094977
PROBLEM TO BE SOLVED: To provide a configuration of an external-magnet type electrodynamic
electroacoustic transducer having a simple structure, being thin, excellent in sounding efficiency,
and having good productivity, and a method of manufacturing the same. SOLUTION: Two rod-like
permanent magnets are arranged in parallel on the outer side of a voice coil which is held on a
diaphragm fixed at the periphery and has two straight sides, and the outer edge is on the outer
side of the permanent magnet. An electro-dynamic electroacoustic transducer comprising a yoke
having a cross-sectional shape in which an intermediate portion substantially covers an upper
surface excluding at least a central portion of the diaphragm and an inner edge portion descends
toward the inside of the voice coil, A frame-shaped member having a thickness in contact with
the inner surface of the outer edge of the yoke and the outer surface of each of the rod-shaped
permanent magnets, each of the rod-shaped permanent magnets being fixed to the inner surface
of the frame-shaped member. Also, at the time of assembly, the rod-like permanent magnet
should be fixed in advance to the frame-like member. [Selected figure] Figure 1
Electro-acoustic transducer and method of manufacturing the same
[0001]
The present invention relates to a structure and a manufacturing method of an electrodynamic
electroacoustic transducer having a function as a speaker or a microphone and suitable for being
mounted on a relatively small portable electronic device.
[0002]
In recent years, mobile phones and other small information devices that handle images and
voices are becoming increasingly multifunctional, and image information is required to have a
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large area, and additional functions such as cameras are also required, and electro-acoustic
conversion for voices. In spite of the strict requirements for both sound quality and volume for
the device, the space allocated within the device is becoming increasingly compressed.
[0003]
Heretofore, small dynamic electrodynamic speakers have been used for this purpose.
These are only 10 mm in diameter and several mm in thickness, for example. However, in
addition to further downsizing and thinning, planar shapes such as rectangles that can be easily
arranged around the image display device are also strongly sought. It is supposed to be
In the latter horizontal speaker, a so-called external magnet type magnetic circuit, which is
disposed outside the voice coil, is often used to increase the volume of the permanent magnet.
[0004]
There are many proposals for such external magnet type speakers, but there are, for example, the
following examples. Patent No. 3841222 (hereinafter referred to as conventional example 1) JPA-2004-266337 (hereinafter referred to as prior art 2). JP-A-2005-51283 (hereinafter referred
to as prior art 3). )
[0005]
FIG. 6 is a cross-sectional view taken along the short diameter of the speaker of Conventional
Example 1, and corresponds to FIG. 21 of Patent Document 1. As shown in FIG. 43 is a boxshaped yoke, the planar shape of which is a rectangular shape in which the major axis direction,
that is, the depth direction of the screen is deep, or the shape of a track of an athletics consisting
of parallel equal-length two straight lines and two half arcs To make a track-like). The voice coil
44 also has a track-like planar shape, and the coil wire is wound along the track direction.
[0006]
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2
Each of the first magnet 41 and the two second magnets is in the shape of a long bar in the depth
direction of the screen, and is disposed parallel to the two straight sides of the voice coil 44 and
is magnetized in the illustrated direction. A magnetic field is formed across the entire length of
the magnet so as to cross the coil 44 in a crosswise manner in an inward and outward direction.
A yoke 43 made of a soft magnetic material forms part of a magnetic circuit. A diaphragm 45 has
a voice coil 44 mounted thereon. If a voice current is supplied to the voice coil 44, the diaphragm
45 vibrates in the vertical direction in the figure to emit sound.
[0007]
FIG. 7 is a cross-sectional view taken along the minor axis of the speaker of Conventional
Example 2, and corresponds to FIG. 2 of Patent Document 2. As shown in FIG. Reference numeral
21 denotes two rod-like magnets long in the depth direction of the screen, which are considered
to be magnetized in the vertical direction of the cross section. An upper plate 22 made of a soft
magnetic material and a lower plate 23 made of a soft magnetic material have a projection
serving as a magnetic pole at the center. The central projections of the two upper and lower
plates 22 and 23 have substantially the same length as the parallel linear portions of the tracklike voice coil 28.
[0008]
The central projections of the two upper and lower plates 22 and 23 generate a magnetic field in
which the magnetic flux crosses in and out of the parallel linear portions of the track-like voice
coil 28 inside the magnetic gaps. 27 is a diaphragm, 29 is a protector that has an elongated
sound emission hole and protects the front surface. The frame 26 combines each component and
serves as an exterior.
[0009]
FIG. 8 is a central cross-sectional view of a circular external magnetic speaker according to
Conventional Example 3, corresponding to FIG. 4 (D) of Patent Document 3. As shown in FIG.
This example is a speaker provided with a ring-shaped permanent magnet and a voice coil. A
magnet body 210, an inner yoke 220, and an outer yoke 230 are all ring-shaped. 400 is a
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circular diaphragm, 500 is a voice coil wound directly on the cylindrical vertical wall of the
diaphragm, the magnetic body 300 has a ring shape, and the outer periphery is fitted to the
upper flange of the outer yoke 230 And the inner periphery is located over and above the voice
coil 500.
[0010]
An assembly jig 600 has a gap positioning portion 620 projecting in a ring shape on the top
surface thereof. When assembling the speaker, the magnet portion consisting of the magnet body
210, the inner yoke 220, and the outer yoke 230 is placed on the jig surface on the outer side of
the gap positioning portion 620 so as to fit therein, and then adhered to the flange surface of the
outer yoke The agent is supplied to assemble the diaphragm 400 and the magnetic body 300.
[0011]
Conventional Example 1 has a relatively simple structure but requires three magnets. Also, the
magnetic flux leakage to the upper surface is considered to be large. In Conventional Example 2,
since the magnetization of the magnet is in the vertical direction, upper and lower plates are
further stacked on the magnet, and a protector is provided on the front surface, so it is difficult to
reduce the overall thickness small.
[0012]
Conventional Example 3 has a configuration close to that of the present invention, but has a
flange portion in which the outer yoke and the magnetic body are fitted, so the outer diameter of
the speaker tends to be large. Due to the presence of the inner yoke, the volume of the magnet
body can not be made sufficiently large. In addition, if the diaphragm is made of a thin material
with small rigidity, the diaphragm is easily deformed and the voice coil is also deformed, which
makes it difficult to maintain the positional accuracy in the magnetic gap.
[0013]
An object of the present invention is to provide a configuration of an external-magnet type
electrodynamic electroacoustic transducer having a simple structure, a thin shape, excellent in
sounding efficiency, and good productivity, and a method of manufacturing the same.
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[0014]
The electroacoustic transducer of the present invention has any of the following features (1) to
(4).
(1) Two rod-like permanent magnets are provided on the outside of the voice coil having two
straight sides, which are held on a diaphragm which is fixed at its periphery and which can be
displaced in the vertical direction, and each of the permanent magnets is It is disposed parallel to
the outside of each of the two linear sides of the voice coil and is magnetized so as to generate a
magnetic flux crossing the voice coil inward and outward, the outer edge is outside the
permanent magnet and the middle part is An electro-dynamic electroacoustic transducer
comprising: a yoke having a cross-sectional shape substantially covering an upper surface
excluding at least a central portion of the diaphragm and having an inner edge portion having a
step portion hanging down toward the inside of the voice coil, The electro-acoustic transducer
further includes a frame-like member having a thickness in contact with the inner surface of the
outer edge of the yoke and the outer surface of each of the rod-like permanent magnets, each of
the rod-like permanent magnets being On the inner surface of the frame member That you are
wearing. (2) In the above (1), the frame-like member is made of a magnetic material. (3) In the
above (1), the frame-like member is made of a resin material. (4) In any one of the above (1) to
(3), the voice coil is provided inside the stepped portion.
[0015]
The method for producing an electroacoustic transducer according to the present invention has
the following features (5) to (7). (5) Two rod-like permanent magnets are provided on the outer
side of the voice coil having two linear sides held on a diaphragm fixed at its periphery and
displaced in the vertical direction, each of the permanent magnets being It is disposed parallel to
the outside of each of the two linear sides of the voice coil and is magnetized so as to generate a
magnetic flux crossing the voice coil inward and outward, the outer edge is outside the
permanent magnet and the middle part is A yoke having a cross-sectional shape covering an
upper surface excluding at least a central portion of the diaphragm and having an inner edge
depending on the inside of the voice coil, an inner surface of an outer edge of the yoke and the
rod-like permanent magnet A method of assembling an electro-dynamic electroacoustic
transducer comprising a frame member having a thickness in contact with each outer surface,
wherein each of the rod-like permanent magnets is fixed in advance to the inner surface of the
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frame member. Step and before First, the step of incorporating a diaphragm with a voice coil
from the lower opening of the yoke, and the step of fitting the outer surface of the frame-like
member to which the permanent magnet is previously fixed to the inner surface of the outer
edge of the yoke member To have. (6) In the above (5), the magnetization of the permanent
magnet is performed in a single state before they are fixed to the frame-like member. (7) In the
above (5), the permanent magnets are magnetized after they are fixed to the frame-like member.
[0016]
The electro-acoustic transducer of the present invention has a relatively small number of parts
and a simple configuration. Moreover, it is easy to exhibit the advantage of the external magnet
type that the volume of a permanent magnet is large, and it is also easy to implement | achieve
an elongate speaker. In addition, the overlapping of parts in the vertical direction is small, which
is suitable for thinning. Moreover, not only the permanent magnet but also the area of the
diaphragm is large, and there is a design margin for securing the amplitude, and the volume can
be increased. Further, better characteristics can be obtained by disposing the voice coil inside the
stepped portion of the diaphragm. In addition, since the permanent magnet is fixed to the magnet
holding frame, the manufacturing and assembly operation is easy. A resin material etc. can also
be used for a magnet holding frame.
[0017]
Examples will be described below as the best embodiments. FIG. 1 is a central sectional view
along the minor axis of the speaker of the present invention, FIG. 2 is a central sectional view
along the major axis, and FIG. 3 is a plan view thereof. The whole is in the form of a flat box. A
yoke 1 is made of a soft magnetic material and covers the inside of an outer wall 1a rising
vertically, an upper portion 1b serving as a ceiling, a track-like inner wall 1c hanging down near
the central portion and a magnetic pole inside the magnetic gap, and an inner wall 1c. It includes
a central bridge portion 1d and several sound emitting holes 1e provided in the bridge portion
1d, and doubles as a case of a speaker. In FIG. 2 and FIG. 3, 1f is a subhole, which emits sound
from the outer edge of the diaphragm 3.
[0018]
The diaphragm 3 is formed of a thin resin plate, and the outer edge 3a fixed to the yoke 1, the
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outer dome 3b formed inside thereof, the step 3c hanging down from the inner end thereof, and
the end of the voice coil 2 are bonded. It comprises an adhesive part 3d for holding and an
innermost central dome 3e. The central dome 3e is given a rigid shape for parallel translation in
the vertical direction, and the outer dome 3b is given a curve or a wedge shape for straight
vibration. The upper ring 4 and the lower ring 5 are members for holding the outer edge portion
3 a of the diaphragm 3. The respective expansion directions of the outer dome 3b and the central
dome 3e may be thin on the front side and both may be thin and secure an amplitude space in
the vertical direction.
[0019]
Reference numeral 7 denotes rod-like permanent magnets (two) whose outer side surfaces are
fixed to the inner side surface of the magnet holding frame 6 by bonding or the like, and they are
integrated. A bottom plate 8 is provided with a bottom plate hole 8a for releasing the back
pressure of the diaphragm 3 as required. The bottom plate 8 is not an essential member. A
motherboard substrate or the like on which the speaker is mounted may also be used. Although
the use of the holding frame hole 6a provided with the magnet holding frame 6 is not limited, it
may be a mounting hole of a speaker.
[0020]
FIG. 4 is a plan view of an assembly of the magnet holding frame 6 and the permanent magnet 7
in the present embodiment, and FIG. 5 is a cross-sectional view in the major axis direction. The
permanent magnet 7 is magnetized horizontally in the inside and outside. The magnetization
process may be performed after forming the assembly by bonding, or may be performed before
bonding. By such magnetization, the inner side surface of the permanent magnet 7 becomes a
magnetic pole, and a magnetic flux crossing the linear portion of the voice coil 2 is formed in the
magnetic gap between the other magnetic pole and the inner wall 1c of the yoke 1. The magnetic
flux may be inclined due to the difference in height between the magnetic poles and may not be
perfectly horizontal.
[0021]
The material of the magnet holding frame 6 is preferably a soft magnetic material to increase the
effective magnetic flux density and to reduce the leakage flux, but according to the result of the
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magnetic field analysis by the finite element method, the nonmagnetic resin material Even in the
case of using a nonmagnetic material, the reduction of the magnetic flux density is only about 5
percent, so even nonmagnetic materials are sufficiently practical. It is also possible to improve
the properties by incorporating powders, particles or flakes of magnetic material into the resin
material. Also, steel and other alloys that are not perfect soft magnetic materials may be used.
[0022]
In the electro-acoustic transducer of this embodiment, the voice coil 2 is provided inside the
stepped portion 3 c of the diaphragm 3. In the examination of the specific example, when the
arrangement of the voice coil 2 was experimentally examined on the inner side (this
embodiment) and the outer side (arrangement similar to the conventional example 3) of the
stepped portion 3c, the former (this embodiment) It was found that the arrangement provided
more stable characteristics. From the experimental results, it was found that the total harmonic
distortion (THD) was improved. The reason is not necessarily clear, but when placing the voice
coil 2 outside the step 3c, it is difficult to synchronize the vibration of the voice coil and the
vibration of the diaphragm, but the placement of the voice coil 2 is inside the step 3c It is
possible that the diaphragm in the vicinity of the voice coil 2 is easily vibrated together by setting
it as in the present embodiment.
[0023]
Next, assembly of the speaker of this embodiment will be described. The assembly is extremely
easy, the yoke 1 is set downward, and the upper ring 4, the lower ring 5, the magnet holding
frame 6 (permanent) while supplying an adhesive as needed from the opening facing upward.
The magnet 7 may be fixed) in sequence.
[0024]
Of course, the technical scope of the present invention is not limited to the above embodiments.
For example, the planar shape of the speaker may be a track type or an elliptical type. The rodlike permanent magnet may also be part of a curve instead of a straight rod. Further, the central
bridge portion 1d of the yoke 1 may be eliminated, and the entire inside of the inner wall 1c may
be formed as a large track-shaped sound output hole. If the upper ring 4 is integrally formed with
the yoke 1 and the lower ring 5 is integrally formed with the magnet holding frame 6, the
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number of parts is further reduced and the assembly is facilitated.
[0025]
Industrial Applicability The present invention has high industrial applicability because the thin
and small external magnetic electrodynamic electroacoustic transducers having excellent
characteristics can be provided at low cost.
[0026]
It is sectional drawing along the short diameter of the speaker of the Example of this invention.
It is sectional drawing along the major axis of the speaker of the example of the present
invention. It is a top view of the speaker of the example of the present invention. It is a top view
of the assembly of the magnet holding frame and permanent magnet in the Example of this
invention. It is sectional drawing of the major axis direction of the assembly of the magnet
holding frame and permanent magnet in the Example of this invention. It is sectional drawing
along the short diameter direction of the speaker of the prior art example 1. FIG. It is sectional
drawing along the short diameter direction of the speaker of the prior art example 2. FIG. FIG. 10
is a central cross-sectional view of a circular speaker of Conventional Example 3;
Explanation of sign
[0027]
Reference Signs List 1 yoke 1a outer wall 1b upper portion 1c inner wall 1d central bridge
portion 1e central hole 1f subhole 2 voice coil 3 diaphragm 3a outer edge portion 3b outer dome
3c step portion 3d bonding portion 3e central dome 4 upper ring 5 lower ring 6 magnet holding
frame 6a Holding frame hole 7 permanent magnet 8 bottom plate 8a bottom plate hole 21
magnet 22 upper plate 23 lower plate 26 frame 27 diaphragm 28 voice coil 29 protector 41 first
magnet 42 second magnet 43 yoke 44 voice coil 45 diaphragm 210 magnet body 220 inner
yoke 230 outer yoke 300 magnetic body 400 diaphragm 500 voice coil 600 assembly jig 620
gap positioning portion
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