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JP2006311156

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DESCRIPTION JP2006311156
The reduction in volume of a permanent magnet, the reduction in the effective wire length of a
voice coil, and the increase in stiffness of a diaphragm decrease the acoustic characteristics as
the speaker is miniaturized. An end face of a voice coil having a relatively large diameter is joined
to the lower surface of an expansion member, and is joined to a diaphragm at a portion inside the
coil on the upper surface of the expansion member. With this configuration, it is possible to
secure the area of the outer peripheral dome of the diaphragm and prevent the increase in
stiffness while increasing the effective wire length of the coil and the volume of the permanent
magnet, and realize excellent acoustic characteristics even with a small speaker. be able to.
[Selected figure] Figure 3
Electro-acoustic transducer
[0001]
The present invention relates to an electroacoustic transducer used in acoustic equipment and
information communication equipment. In particular, it relates to a small-sized speech speaker.
[0002]
In recent years, in electronic devices equipped with acoustic functions, information
communication devices, in particular mobile phones, due to the diversification and multifunctionalization of models, the speaker, which is a type of electro-acoustic transducer, is an
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important part, but downsizing It is required. For example, it is necessary that the outer shape is
15 mm or less when the shape (planar shape) of the diaphragm is circular, and the short side is
10 mm or less when the diaphragm is oval (flat speaker). In addition to the miniaturization,
maintenance and improvement of acoustic characteristics must be achieved.
[0003]
A typical loudspeaker has the form of a so-called electrokinetic acoustic transducer. That is, a
voice coil (a winding is made approximately parallel to the surface of the diaphragm, making a
thin cylindrical shape) is placed in the magnetic field created by the permanent magnet and the
magnetic pole, and a voice current flows through the voice coil to vibrate. And drive the
diaphragm.
[0004]
First, factors that affect the acoustic characteristics of the speaker will be described. Among the
main acoustic characteristics of the speaker, the sound pressure P and the low-pass resonant
frequency f0 are: P = A × B × L × I / (S0 × M0) (1) f0 = (1 / 2π) √ (S0 / M0) It is expressed
by the expression of (2). Here, A is a constant specific to the speaker, B is the magnetic force of
the permanent magnet (the strength of the magnetic field), L is the diameter of the voice coil (or
the effective line length in the magnetic field), I is the current, and S0 is the vibration of the
diaphragm Toughness (rigidity), M0 is the mass of the vibration system.
[0005]
As can be seen from the above equations (1) and (2), in the case of a circular speaker, when the
outer diameter is reduced, the voice coil is also miniaturized and the effective wire length is
reduced. It becomes smaller, and the space of the outer peripheral portion giving elasticity to the
diaphragm becomes smaller and the stiffness S0 becomes larger. As a result of these, a decrease
in sound pressure P (decrease in sound volume) and an increase in f0 (decrease in flatness of
frequency characteristics) tend to occur. The reduction of the shape also results in the
characteristic change of the same tendency in the speaker having the oval or rectangular
diaphragm. In particular, the impact of shortening the short side dimension is significant.
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[0006]
Next, the structure of an example of a conventional speaker will be described using FIGS. 17 to
22. FIG. This is a speaker having an oblong diaphragm, and FIGS. 17-20 are a plan view, a bottom
view, a sectional view including a major axis, and a sectional view including a minor axis,
respectively. 21 and 22 are a plan view and a bottom view of the diaphragm (with the voice coil
fixed). Note that in order to simplify the drawing and make the structure easy to see, in the crosssectional view, the illustration of a part of the horizontal line that should be originally appeared
due to the part behind the page is omitted. Also, the structure of a speaker having a circular
diaphragm can be analogized from these figures.
[0007]
In each of the above figures, an oblong, flat columnar shape and a permanent magnet 3
magnetized in the thickness direction are fixed (adhered) at the inner center of the lower frame 2
made of soft magnetic material and substantially cup-shaped. On the upper surface of the
permanent magnet 3, an oval plate-shaped pole piece made of a soft magnetic material is
adhered (bonded). The lower frame 2, the permanent magnet 3, and the pole piece 4 constitute a
magnetic circuit, and a ring-shaped air gap (approximately uniform width and oval shape formed
in the gap between the upper end of the lower frame 2 and the side surface of the pole piece 4).
A strong radial magnetic field is generated in the shape).
[0008]
The upper frame 5 is a shallow dish-like member made of nonmagnetic material (resin, metal),
and has an oval hole at the center of the bottom, which is fitted to the top of the lower frame 2
and mutually positioned It is fixed. The upper end portion of the upper frame 5 has an oblong
stepped portion inside, and the fixed portion 1a which occupies the outer periphery of the
diaphragm 1 in an edge shape is mounted and fixed on the stepped portion. In addition, in the
upper frame, there are opened several back holes 5a for distributing the air under the diaphragm
1 to the outside. Further, a terminal processing portion 5b to which two terminal wires 6a of the
voice coil 6 are soldered, and a terminal 5c having a pattern electrically connected to them
respectively are provided on the lower surface side.
[0009]
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The diaphragm 1 is a flexible member formed by forming a thin resin film into a substantially
concentric uneven shape. A thin, flat fixing portion 1a which is oblong and is fixed to the upper
frame as described above in order from the outside, which occupies the inside of the thin flat
fixing portion 1a, and which gives elasticity for the diaphragm to move flexibly in the vertical
direction And an outer peripheral dome 1b having a convex shape on the upper side, and a flat
and oval joint portion 1c which occupies the inner side and has a width of, for example, about 0.5
mm, and a central dome 1d forming the entire inner side. Become. The central dome 1d gives
rigidity to the central portion of the diaphragm and has the function of causing the diaphragm to
perform parallel motion in the vertical direction as much as possible.
[0010]
The voice coil 6 is formed by winding a single layer or several layers so as to form an oval
cylindrical shape. The upper end face is adhered to the lower surface of the joint portion 1 c of
the diaphragm 1. When the diaphragm 1 is fixed to the outer frame 5, the voice coil 6 is inserted
into the ring-shaped space formed between the lower frame 2 and the pole piece 4 without
touching the periphery, and the current flowing to the voice coil 6 The diaphragm 1 is driven in
the vertical axis direction by the interaction of the magnetic field and the magnetic field. The
terminal wire 6 a of the voice coil 6 is drawn to the outside of the diaphragm 1 by winding the
lower surface of the outer peripheral dome 1 b of the diaphragm 1, and is connected to the
terminal processing unit 5 b provided on the lower surface of the upper frame 5. This is the end
of the description of the conventional example.
[0011]
In the above structure, in order to prevent the reduction of the low-pass resonant frequency f0 of
equation (2), that is, not to make the stiffness of the diaphragm excessive, even if the speaker
becomes small (especially the minor diameter of the diaphragm), A certain limit must be ensured
for the width of the peripheral dome 1b. Then, the joint 1c has to be provided inside, and as
shown in FIGS. 3 and 4, since the length and width (especially width) of the rod-like permanent
magnet 3 are of the inner magnet type, the voice coil 6 is formed. It is not possible to provide a
sufficiently large volume, and the magnetic force B, that is, the strong magnetic field in the air
gap can not be obtained. Further, since the voice coil 6 is also miniaturized at the same time, the
effective winding length L is reduced. These will synergistically reduce the sound pressure P
according to equation (1). Although the material of the permanent magnet is examined to avoid
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the problems associated with the miniaturization, there is a limit to the reduction in diameter.
[0012]
There are also structural proposals (other conventional examples) for overcoming the above
problems. An example is shown. JP, 2004-266337, A This example is the structure of the
speaker which has an oval diaphragm, and two rod-shaped permanent magnets are arranged
along the two long sides outside of the voice coil whose width became narrow, This invention is
an invention in which a pole piece is placed inside to make an external magnet type magnetic
circuit, and the volume of the permanent magnet is comprehensively increased to increase the
magnetic force. However, this proposal increases the parts cost and assembly cost because the
magnet is increased, the leakage flux is large due to the external magnet type, the magnetic
efficiency is poor, and the structure is limited to the oval speaker (that is, the circular speaker
There is a drawback such as not becoming a measure to miniaturize.
[0013]
The object of the present invention is to provide a speaker structure that does not cause
deterioration in acoustic characteristics (typified by a decrease in sound pressure or deterioration
in frequency characteristics) even if the speaker is miniaturized, or that the deterioration can be
mitigated. It is to be. More specifically, an object of the present invention is to provide a speaker
structure capable of preventing increase or decrease of the volume of a permanent magnet and
the wire length of a voice coil while preventing an increase in stiffness of the diaphragm as much
as possible. .
[0014]
In order to achieve the above object, the acoustic transducer of the present invention has the
following features. (1) A magnetic circuit including a permanent magnet, a cylindrical voice coil
inserted in the air gap of the magnetic circuit, and a bent cross-sectional shape, a part of which is
joined to the voice coil, and the voice coil In the electro-acoustic transducer provided with a
driven diaphragm, the diaphragm is indirectly joined to a fixed portion on the outer periphery, an
outer peripheral dome to the inner side of the fixed portion, and the voice coil to the inner side of
the outer peripheral dome. A joint is provided, and at least a part of a diameter of the voice coil is
made larger than a diameter of the joint, and an expansion member fixed to both the voice coil
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and the joint is provided.
[0015]
The acoustic transducer of the present invention may further have any of the following features.
(2) The expansion member is flat.
[0016]
(3) The expansion member has a ring shape having an outer shape substantially including the
outer shape of the voice coil and having a hole on the inner periphery, and the inner periphery
reaches the joint.
[0017]
(4) The diaphragm includes a central dome inside the outer peripheral dome or inside the joint,
and the expansion member also includes a central dome shaped to fit the central dome of the
diaphragm.
[0018]
(5) The diaphragm has a hole inside the joint, and the expansion member has a central dome
shaped to fit in the hole of the diaphragm.
[0019]
(6) Almost all of the inside of the outer peripheral dome of the diaphragm forms a joint.
[0020]
(7) The expansion member is configured by connecting a plurality of members.
(8) The end face shape of the cylindrical voice coil is any one of a ring-like circle, an ellipse, an
oval, a rectangle, and a polygon, and a cross-sectional shape of the joint portion is a ring shape, a
flat shape or a dome shape It has a curved shape, and the planar shape of the outer shape is any
of a circle, an ellipse, an oval, a rectangle, and a polygon.
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[0021]
According to the present invention, it is possible to obtain an electroacoustic transducer which is
free from or less in deterioration of acoustic characteristics due to miniaturization and which is
easy to manufacture.
In other words, the internal magnet type electricity does not increase or decrease the rigidity of
the diaphragm even if it is miniaturized, and does not reduce the volume of the permanent
magnet or the size of the voice coil. The configuration of the acoustic transducer can be obtained.
Alternatively, it is possible to obtain an electroacoustic transducer with improved acoustic
characteristics while maintaining the external dimensions substantially.
[0022]
An expansion member, which is a relatively lightweight and rigid member, having a
predetermined width on the outer peripheral dome of the diaphragm, forming a joint on the
inner side thereof, and the joint and a voice coil having a larger shape than the joint. Join
through.
A voice coil is a speaker that is inserted into the air gap of an internal magnetic type magnetic
circuit consisting of a permanent magnet, a lower frame, and a pole piece.
[0023]
The structure of a loudspeaker according to a first embodiment of the present invention will be
described with reference to FIGS. 1 to 6. This example is also a speaker having an oval
diaphragm, and FIGS. 1-4 are a plan view, a bottom view, a cross-sectional view including a long
axis, and a cross-sectional view including a short axis, respectively. 5 and 6 are a plan view and a
bottom view of the diaphragm (with the voice coil fixed). The arrangement order of the
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respective drawings is the same as that of the conventional example. As in the conventional
example, a part of the horizontal line is omitted in the sectional view to improve the visibility of
the structure. Also, the embodiment of the circular speaker is not shown for simplicity. The same
reference numerals as in the conventional example are given to the components that are
substantially common, and the descriptions and duplication are avoided as already described.
[0024]
The main point of the structural difference between the present invention and the conventional
example is that the width in the minor axis direction and the length in the major axis direction of
the voice coil 6 are larger than in the conventional example, and the stiffness of the upper end
face and the diaphragm 1 is maintained. Because the same width as the conventional example is
given to the outer peripheral dome 1b, the diameter is small as in the conventional example. The
lower surface of the joint portion 1c is joined (bonded) via the thin extension member 7 as a thin
plate member. It is what you did.
[0025]
The extension member 7 must have sufficient rigidity to faithfully transmit the driving force of
the voice coil 6 to the diaphragm 1.
Moreover, in order not to deteriorate the acoustic characteristic in Formula (1) and (2), it is
desirable that it is lightweight. As long as they are, it can form using arbitrary materials. In this
example, for weight reduction, the central portion of the expansion member 7 (the portion
substantially overlapping the central dome 1d inside the joint portion 1c) has an oval outer shape
(slightly larger than the outer shape of the voice coil 6) for weight reduction. A hole has been
punched out. Therefore, the planar shape of the extension member is an oval ring shape.
[0026]
As a material of the extension member used for a miniaturized speaker to the extent used in a
mobile phone, for example, a metal plate (preferably light metal), a polymer film material (PET
etc.), or a glass epoxy resin plate Any one is suitable as a material. Naturally, other materials may
be used as long as the characteristics are satisfied.
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[0027]
Comparing FIG. 4 which is a cross sectional view in the first embodiment and FIG. 20 which is
the same cross sectional view of the conventional example, the permanent magnet 3 which can
be used is an internal magnet type even if the dimensions in the minor axis direction of the
diaphragm are almost equal. Therefore, the thickness of the present invention is much larger,
and a strong magnetic force can be obtained. Further, since the width of the voice coil 6 itself is
thicker in the present invention, the length per winding turn is longer than in the conventional
example, and it is obvious that the effective wire length placed in the magnetic field is also longer
in the present invention. is there. In addition, the increase in vibrational mass and the ability to
transmit force by the expansion member can be within the satisfactory range. These features
make it possible to obtain a small speaker maintaining the acoustic characteristics in a preferable
range. In addition, the structure is not complicated, the increase in manufacturing cost is small,
and since the internal magnet type is used, effects such as less leakage of magnetic flux can be
obtained.
[0028]
The structure of a loudspeaker according to a second embodiment of the present invention will
be described with reference to FIGS. 7 to 12. This example is also a speaker having an oval
diaphragm, and FIGS. 7-10 are a plan view, a bottom view, a cross-sectional view including a
major axis, and a cross-sectional view including a minor axis, respectively. 11 and 12 are a plan
view and a bottom view of the diaphragm (with the voice coil fixed). The partial omission in the
cross-sectional view, the arrangement order of the drawings, and the sharing of reference
numerals are the same as in the first embodiment and the conventional example.
[0029]
The difference between the second embodiment and the first embodiment described above is that
the width (dimension in the minor axis direction) of the voice coil 6 is equal to that in the first
embodiment, but the length (dimension in the major axis direction) is the same as the
conventional example. It does not change and is equal to the length of the junction 1c. Even in
this case, the width of at least the permanent magnet 3 can be increased as in the first
embodiment, so that the volume of the permanent magnet 3 can be increased to obtain a
sufficient magnetic force. The effects obtained are also in accordance with Example 1.
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[0030]
In the following figures, in order to further explain the main parts of the present invention from
FIG. 13 to FIG. 16, various structures are focused on parts (vibration system) related to the
diaphragm, the expansion member, and the voice coil. As a schematic cross-sectional view, but in
more detail. Let them be Examples 3, 4, 5 and 6. Each figure is a sectional view of the diaphragm
alone (a), a sectional view of the voice coil extension member (b), and a sectional view of the
combination of the two (c). The horizontal lines appearing in the back of the paper are shown
without omission for each of these figures. The code is also standardized. In each of these
embodiments, the speaker to be applied may be circular or flat.
[0031]
The effects obtained by applying these structures to a speaker are basically the same as in the
first and second embodiments. That is, the outer peripheral dome 1b is sufficiently large to
prevent the hardening (increase in stiffness) of the diaphragm, and the volume of the permanent
magnet (not shown) increases in accordance with the expansion of the voice coil 6 by the
expansion member 7 The effective wire length of the voice coil 6 is increased.
[0032]
Example 3 is shown in FIG. The third embodiment is basically the same as the structure of the
vibration system (FIGS. 5, 6, 11, 12) used for the speaker of the first or second embodiment. The
extension member 7 is flat and has a hole 7c at the center (it was provided for weight reduction,
but it can also be made without a hole in view of the characteristics). Is fixed by the adhesive
layer 7a and the lower surface of the connection portion 1c of the diaphragm by the adhesive
layer 7b.
[0033]
Example 4 is shown in FIG. The expanding member 7 in this example has a central dome 7d,
which is shaped to match the central dome 1d of the diaphragm. When the vibration system is
assembled as shown in the figure (c), the central dome of the vibration system is doubled, and the
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rigidity of the central portion is further enhanced. Incidentally, at the time of assembly and
adhesion, the adhesive 7b may be used on the lower surface of the joint portion 1c as in the third
embodiment, but the central domes 1d and 7d may be adhered as illustrated in (c). In this case,
since the joint portion 1d is not necessary for contact wear, it may be used to reduce the
diaphragm stiffness by further increasing the area of the outer peripheral dome 1b by narrowing
or eliminating the width. (Of course, the diameter of the speaker may be reduced. )
[0034]
Example 5 is shown in FIG. The expansion member 7 in this example has a central dome 7d, and
the diaphragm 1 does not have a central dome, and instead a hole 1e is opened. As shown in the
small figure (c), in the assembled state of the vibration system, the central dome 7d of the
expansion member substitutes for the central dome 1d of the missing diaphragm.
[0035]
Example 6 is shown in FIG. The diaphragm 1 of this example has no central dome, and the
central portion is flat and the whole is a joint 1 c. A flat plate-like expansion member 7 is
centered and attached to this portion. There is no dome at the center of the vibration system, but
it will be a laminated adhesive of multiple parts and sufficient rigidity can be obtained. The main
effect of this example is that the area of the peripheral dome can be extended to the limit, and
the diaphragm stiffness can be further improved (or the speaker can be miniaturized).
[0036]
Although not shown, other structures and modified examples are collectively described as a
seventh embodiment. For example, the shape of the expansion member may be, for example, a
bowl shape at its peripheral portion to increase rigidity. Alternatively, it may be a composite
member. For example, a thin rigid plate (such as a metal plate) may be laminated outside with a
lightweight plate inside. Also, a thin plate ring for adjusting the height of the voice coil may be
used in combination. Further, the bonding between the expansion member and the diaphragm
may be performed by a method other than the adhesive, such as ultrasonic welding or laser
welding. In addition, the outer peripheral dome of the diaphragm is not necessarily in the outer
(upper) convex ring shape, and other bent shapes can be used. The same is true for the central
dome. Various other arbitrary modifications will be possible. Although each example in which the
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present invention is applied to a speaker is shown, there is room for applying the present
invention to other electroacoustic transducers such as a microphone. Further, it goes without
saying that the device to which the electroacoustic transducer of the present invention is applied
is not limited to a mobile phone.
[0037]
Since the present invention realizes the acoustic characteristics of an excellent electroacoustic
transducer and can be miniaturized, the industrial applicability is extremely large.
[0038]
It is a top view of Example 1 in the speaker of the present invention.
It is a bottom view of Example 1 in the speaker of the present invention. It is sectional drawing
along the long axis of Example 1 in the speaker of this invention. It is sectional drawing along the
short axis of Example 1 in the speaker of this invention. It is a top view of the diaphragm used for
Example 1 in the speaker of this invention. It is a bottom view of a diaphragm used for Example 1
in a speaker of the present invention. It is a top view of Example 2 in the speaker of the present
invention. It is a bottom view of Example 2 in the speaker of the present invention. It is sectional
drawing along the long axis of Example 2 in the speaker of this invention. It is sectional drawing
along the short axis of Example 2 in the speaker of this invention. It is a top view of the
diaphragm used for Example 2 in the speaker of this invention. It is a bottom view of the
diaphragm used for Example 2 in the speaker of this invention. It is typical sectional drawing of
Example 3 in the diaphragm of this invention, (a) is a diaphragm, (b) is an expansion member
with a voice coil, (c) is both combined body. It is typical sectional drawing of Example 4 in the
diaphragm of this invention, (a) is a diaphragm, (b) is the expansion member with a voice coil, (c)
is both combined body. It is typical sectional drawing of Example 5 in the diaphragm of this
invention, (a) is a diaphragm, (b) is an expansion member with a voice coil, (c) is both combined
body. It is typical sectional drawing of Example 6 in the diaphragm of this invention, (a) is a
diaphragm, (b) is the expansion member with a voice coil, (c) is both combined body. It is a top
view of the speaker of a prior art example. It is a bottom view of the speaker of a conventional
example. It is sectional drawing along the long axis of the speaker of a prior art example. It is
sectional drawing along the short axis of the speaker of a prior art example. It is a top view of the
diaphragm used for the speaker of a prior art example. It is a bottom view of the diaphragm used
for the speaker of a prior art example.
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Explanation of sign
[0039]
DESCRIPTION OF SYMBOLS 1 diaphragm 1a fixed part 1b outer periphery dome 1c joint part 1d
center dome 1e hole 2 lower frame 3 permanent magnet 4 pole piece 5 upper frame 5a back
hole 5b terminal processing part 5c terminal 6 voice coil 6a terminal wire 7 expansion member
7a, 7b adhesive layer 7c hole 7d central dome
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