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JP2010258856

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DESCRIPTION JP2010258856
PROBLEM TO BE SOLVED: To provide a thin-type acousto-electro-mechanical transducer capable
of surely obtaining better acoustic characteristics than ever by improving a diaphragm.
SOLUTION: A flat speaker 10 as a thin-type acousto-electrical mechanical converter according to
the present invention has a front cover 22 as a housing. The vibrating membrane 12 is
accommodated in the hollow portion 58 of the front cover 22. The outer peripheral edge of the
vibrating membrane 12 is surrounded by the inner circumferential wall of the hollow portion 58,
whereby the displacement in the in-plane direction is restricted, and the vibrating membrane 12
can vibrate only in the thickness direction. Furthermore, the four corners 34, 34, ... of the
vibrating membrane 12 are chamfered in a straight line. As a result, when the vibrating
membrane 12 is incorporated into the hollow portion 58, the possibility that the four corners 34,
34,... Of the vibrating membrane 12 will protrude from the hollow portion 58 is low even if socalled positional displacement occurs. Therefore, the vibrating membrane 12 vibrates as
expected and thus good acoustic characteristics can be obtained. [Selected figure] Figure 10
Thin-type electro-mechanical transducer
[0001]
The present invention relates to a thin acousto-electromechanical transducer such as a flat
speaker.
[0002]
Conventionally, as a flat speaker, for example, one disclosed in Patent Literature 1 is known.
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1
According to this prior art, inside the flat rectangular parallelepiped case main body with one
surface opened, a square plate-like front (surface) side permanent magnet plate and a square
sheet-like front side buffer sheet from the opening side A rectangular sheet-shaped vibrating film,
a rectangular sheet-shaped back surface (back surface) side buffer sheet, and a rectangular plateshaped back surface permanent magnet plate are accommodated in this order. In this state, the
opening of the case body is closed by the substantially rectangular plate-like back cover. Here, a
meandering conductive pattern as a coil is formed on the surface of the diaphragm. Then, a striplike N pole and a strip-like S pole alternately appear on the surface of each permanent magnet
plate facing the vibrating membrane so that a magnetic field crossing the linear portion of the
coil at a right angle is generated. A striped multipole magnetization pattern is formed.
Furthermore, a large number of vent holes are provided in the boundary region between the N
pole and the S pole of the front permanent magnet plate so as to penetrate the permanent
magnet plate. Similarly to this, a large number of vent holes are provided on the main surface of
the case main body so as to penetrate the main surface. Each buffer sheet has air permeability
and flexibility, and as such a buffer sheet, for example, one or more non-woven fabrics are
adopted.
[0003]
That is, according to this configuration, when current flows in the coil, a mechanical force
(electromagnetic force) along the thickness direction of the vibrating film acts on the coil
according to Fleming's left-hand rule. Along with this, the vibrating membrane vibrates, and as a
result, a sound wave is generated. Specifically, the sound waves are emitted to the outside
through the vent holes provided in the front permanent magnet plate and the vent holes
provided in the main surface of the case body. When the vibrating membrane vibrates, the
vibrating membrane may collide with each permanent magnet plate to generate noise (abnormal
sound), but a buffer sheet is provided between them. So such concerns are wiped out. Further,
particularly, the front side buffer sheet also functions as a dustproof one. Furthermore, since the
back side is in a closed state, it is said that good acoustic characteristics (sound pressure
characteristics) can be obtained in the high sound range.
[0004]
Unexamined-Japanese-Patent No. 2006-86733
[0005]
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2
By the way, in the above-mentioned prior art, it is important that the vibrating membrane
vibrates only in its thickness direction and is not displaced in the in-plane direction.
For this reason, in the related art, as schematically shown in FIG. 14A, the outer peripheral edge
of the vibrating membrane 1 is surrounded by the inner peripheral wall 3 of the case main body
2. Further, both are as close as possible so as not to form an extra space (play) between the outer
peripheral edge of the vibrating membrane 1 and the inner peripheral wall 3 of the case main
body 2.
[0006]
However, as the outer peripheral wall of the vibrating membrane 1 and the inner peripheral wall
3 of the case main body 2 approach each other in this way, as shown, for example, in FIG. There
is a problem that so-called misalignment easily occurs when the. That is, the flat speaker may be
assembled in a state where at least a part of the four corners of the vibrating membrane 1
protrudes from the inside of the case body 2. In such a case, the vibration of the vibrating
membrane 1 is naturally inhibited, and the expected acoustic characteristics can not be obtained.
[0007]
Also, even if the positional deviation does not occur, the related art has another problem. That is,
it is assumed that the vibrating membrane 1 is properly incorporated in the case body 2 as
shown in FIG. 14 (a). As a result, as shown in an enlarged view in FIG. 15, the displacement
amount of the vibrating membrane 1 is suppressed to Da or less in the longitudinal direction of
the vibrating membrane 1 (vertical direction in FIG. 15). It is assumed that the displacement
amount of the diaphragm 1 is suppressed to Db or less in the side direction (left and right
direction in FIG. 15). However, in other directions, for example, in the diagonal direction of the
vibrating membrane 1, the maximum displacement Dc of the vibrating membrane 1 is larger than
the maximum displacements Da and Db in the longitudinal direction and the short side direction
(Dc = ( Da <2> + Db <2>) <1/2>). That is, there is a problem that the vibrating film 1 is largely
displaced depending on the direction in which the vibrating film 1 is displaced.
[0008]
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Furthermore, the prior art also has the following problems. That is, as described above, the
vibrating membrane 1 vibrates accompanying the coil formed on the surface thereof. Therefore,
when the vibrating membrane 1 is observed in detail, the portion of the vibrating membrane 1 in
which the coil is formed vibrates with high responsiveness, and the portion without the response
is low in responsiveness. The low response portion includes the four corners of the vibrating
membrane 1. Moreover, the four corner portions do not contribute so much to the conversion
into sound waves because they are accompanied by a large deflection when vibrating. Then,
when viewed from the entire vibrating membrane 1, the four corners are merely a load, and on
the contrary, they become an obstacle. This also greatly affects the acoustic characteristics,
particularly the characteristics in the low range.
[0009]
Then, an object of this invention is to provide the thin-shaped acousto-electro-mechanical
transducer which can acquire a more favorable acoustic characteristic than before by improving
a vibrating membrane.
[0010]
In order to achieve this object, the present invention comprises a housing having a hollow
portion, and a vibrating membrane provided in the hollow portion of the housing.
Here, the hollow portion of the housing has a substantially rectangular opening, and is in the
form of a substantially rectangular parallelepiped whose entire surface is the opening. Then, the
outer peripheral edge of the vibrating membrane is surrounded by the inner peripheral wall of
the hollow portion of the housing, so displacement in the in-plane direction is restricted, and
displacement is made possible only in the thickness direction (out-plane direction) There is.
Furthermore, the vibrating membrane has flexibility, and a coil is formed on its surface. The coil
has a portion extending in a direction transverse to the magnetic field formed in the hollow
portion of the housing. In such a thin acousto-electro-mechanical transducer, in the present
invention, the four corners of the vibrating membrane are further formed in a chamfered shape,
and the four corners of the inner peripheral wall of the hollow portion are shaped according to
the four corners of the vibrating membrane. It is
[0011]
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That is, according to this configuration, for example, when current flows in the coil, mechanical
force along the thickness direction of the vibrating membrane acts on the coil according to
Fleming's left-hand rule. Then, along with the coil, the vibrating membrane vibrates along its
thickness direction, and as a result, a sound wave is generated. In other words, a converter for
converting electric energy, which is current, into mechanical energy, which is mechanical force,
and thus, sound waves, so-called speakers, is realized. On the contrary, when a mechanical force
acts on the vibrating film by the sound wave striking the vibrating film, the vibrating film
vibrates along its thickness direction, and the coil also vibrates accordingly. As a result, current
flows in the coil according to Fleming's right-hand rule. In other words, a converter for
converting mechanical energy, which is generated when the sound wave strikes the diaphragm,
into electrical energy, that is, a so-called microphone is realized.
[0012]
In the present invention, as described above, the outer peripheral edge of the vibrating
membrane is surrounded by the inner peripheral wall of the hollow portion of the casing in order
to regulate the displacement of the vibrating membrane in the in-plane direction. That is, the two
are as close as possible to each other so that an extra space is not formed between the outer
peripheral edge of the vibrating membrane and the inner peripheral wall of the hollow portion of
the housing. Therefore, when the vibrating membrane is incorporated into the hollow portion of
the housing, the above-mentioned positional deviation is likely to occur, and therefore, it is feared
that the four corners of the vibrating membrane may protrude from the hollow portion. However,
in the present invention, since the four corners of the vibrating membrane are formed in a
chamfered shape, the possibility of the four corners protruding from the hollow portion is low,
and there is no such concern.
[0013]
Further, in the above-mentioned prior art, when the vibrating membrane vibrates, there is a
concern that the four corners become an obstacle and the acoustic characteristics are
deteriorated as a result, but in the present invention, there is no such concern. That is, in the
present invention, since the four corners of the vibrating membrane are formed in a chamfered
shape, the four corners do not get in the way, and hence the acoustic characteristics are not
deteriorated due to this.
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[0014]
The four corners of the vibrating membrane may be chamfered, for example, by being eliminated
linearly. Moreover, it may be made into the said chamfered shape by being excluded by R shape,
for example, forming in a quarter circle shape. Furthermore, it may be chamfered by being
excluded in a polygonal shape.
[0015]
In addition, in the present invention, the four corners of the inner peripheral wall of the hollow
portion in which the vibrating membrane is accommodated are also shaped according to the four
corners of the vibrating membrane. Thereby, also in the directions of the four corners, as in the
other directions, the displacement of the vibrating film is finely regulated, and better acoustic
characteristics can be obtained.
[0016]
The present invention is suitable for a speaker. In particular, the larger the diaphragm, the better.
That is, in the above-described prior art, the tendency of the four corners of the vibrating film to
interfere with the acoustic characteristics becomes worse as the vibrating film becomes larger.
The present invention is extremely effective for a speaker having a large diaphragm which causes
such an unwilling tendency.
[0017]
As described above, according to the present invention, when the diaphragm is incorporated into
the hollow portion of the housing, the four corners of the diaphragm do not protrude from the
hollow portion even if positional deviation occurs. Therefore, unlike the prior art in which the
acoustic characteristic may be deteriorated due to the positional deviation, the acoustic
characteristic as expected can be surely obtained. Further, in the prior art, there is a concern that
the four corners of the vibrating film may be in the way and this may also deteriorate the
acoustic characteristics, but the present invention does not have such a concern. Furthermore, in
the present invention, better acoustic characteristics can be obtained by forming the four corners
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of the inner circumferential wall of the hollow portion in which the vibrating membrane is
accommodated according to the four corners of the vibrating membrane. As described above,
according to the present invention, better acoustic characteristics can be reliably obtained than
in the prior art.
[0018]
It is a figure which shows schematic structure of the flat speaker which concerns on one
Embodiment of this invention. It is an assembly drawing of the same plane speaker. It is an
illustration figure which shows the diaphragm which comprises the same plane speaker. It is an
illustration figure showing the shock absorbing member by the side of the front which
constitutes the flat speaker. It is an illustration figure which shows the shock absorbing member
by the side of the back which constitutes the flat speaker. It is an illustration figure showing the
permanent magnet board by the side of the front which constitutes the coplanar speaker. It is an
illustration figure which shows the permanent magnet board by the side of the back which
comprises the flat speaker. It is an illustration figure which shows the front cover which
comprises the coplanar speaker. It is an illustration figure which shows the backplate which
comprises the coplanar speaker. It is an illustration figure which shows the positional
relationship of the front cover which comprises the same plane speaker, and a vibrating
membrane. It is an illustration figure which expands and shows the upper right part of FIG. FIG. 6
is an illustrative view showing a vibrating membrane in a mode different from FIG. 3 in a
partially enlarged manner; FIG. 13 is an illustrative view showing a vibrating membrane in a
further different mode from FIG. 12; It is an illustration figure for demonstrating the problem in a
prior art. It is an illustration figure for demonstrating another problem in a prior art.
[0019]
One embodiment of the flat speaker 10 to which the present invention is applied will be
described below.
[0020]
As shown in FIG. 1, the flat speaker 10 according to the present embodiment is a flat,
substantially rectangular parallelepiped in appearance.
Further, structurally, as can be understood from the assembly drawing shown in FIG. 2, one
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vibrating membrane 12 and two buffer members 14 and 16 provided so as to sandwich both
sides of the vibrating membrane 12; It consists of two permanent magnet plates 18 and 20
provided so as to sandwich these buffer members 14 and 16 from the outside, and a front cover
22 and a back plate 24 as a housing.
[0021]
The vibrating membrane 12 comprises a substantially rectangular thin film 26 and meandering
coils 28 and 30 formed on the front and back of the thin film 26, as also shown in FIG. Among
them, the thin film 26 is, for example, a resin film having a thickness of about 30 [μm] and
flexibility. Examples of such resinous films include polyethylene terephthalate films and aromatic
polyimide films. A concave notch 32 is provided at the center of the upper end edge of the thin
film 26, for example. Furthermore, the four corners 34, 34, ... of the thin film 26 are chamfered
in a straight line. The chamfering dimension of these four corners 34, 34, ..., in detail, the
chamfering dimension h in the longitudinal direction of the thin film 26 (vibration film 12) is
appropriately determined in accordance with the side dimension H of the longitudinal direction
of the thin film 26 It is set to about 1/20 to 1/5 of the side dimension H of the direction. The
chamfering dimension w in the short side direction of the thin film 26 is also appropriately
determined in accordance with the short side dimension W of the thin film 26, and is, for
example, about 1/20 to 1/5 of the short side dimension W. In the present embodiment, the side
dimension H in the longitudinal direction of the thin film 26 is about 290 [mm], and the
chamfering dimension h in the longitudinal direction is about 30 [mm], that is, about 1/10 of the
long side dimension H , And is. The short side dimension W of the thin film 26 is about 200 mm,
and the chamfering dimension w in the short side direction is about 30 mm, that is, about 1/7 of
the short side dimension W.
[0022]
On the other hand, coils 28 and 30 are, for example, copper foil patterns with a thickness of 20
μm to 50 μm formed by printed wiring technology, and through holes 36 provided in the
vicinity of the lower end edge of thin film 26 Are connected in series with one another. The end
38 of the coil 28 on the front side is provided as a plus terminal in the vicinity of the side edge of
the notch 32, and the end 40 of the coil 30 on the back side is opposite to the notch 32 as a
minus terminal. Near the side edge of the In the front side coil 28, a large number of straight
portions provided so as to extend along the horizontal direction and a large number of straight
portions similarly provided in the back side coil 30 Sandwiching, they overlap each other. And
the linear part of coil 28 by the side of these fronts and the linear part of coil 30 by the side of a
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8
back are in a mutually conjugate relation. That is, when current flows between the plus terminal,
which is the end 38 of the front side coil 28, and the minus terminal, which is the end 40 of the
back side coil 30, the current flows in the respective straight portions Flow in the same direction
as each other.
[0023]
Referring back to FIGS. 1 and 2, the front cushioning member 14 is a substantially rectangular
sheet of substantially the same size as the vibrating membrane 12 (thin film 26), and is formed of
a material having flexibility and air permeability. . Examples of such a material include nonwoven
fabric and Japanese paper. Further, as also shown in FIG. 4, the four corners 42, 42,... Of the
buffer member 14 on the front side are chamfered in a straight line like the vibrating film 12.
Although not shown in detail, the chamfering dimensions of the four corners 42, 42, ... of the
buffer member 14 are substantially the same as or slightly larger than the chamfering
dimensions h and w of the four corners 34, 34, ... of the vibrating membrane 12 It is considered
to be smaller. Moreover, FIG. 4 is a figure which shows the front surface of the buffer member
14, However, since the back surface is the same as the said front surface, it abbreviate | omits
also about the illustration.
[0024]
Similarly to this, the back side buffer member 16 is also a substantially rectangular sheet of
substantially the same size as the vibrating membrane 12, and is formed of, for example, nonwoven fabric or Japanese paper. Further, as also shown in FIG. 5, the four corners 44, 44,... Of
the back side cushioning member 16 are also chamfered in a straight line. Furthermore, a notch
46 similar to the vibrating membrane 12 (thin film 26) is provided at the center of the upper end
edge. Although FIG. 5 is a view showing the front surface of the buffer member 14, the back
surface is the same as the front surface, so the illustration thereof is omitted.
[0025]
The front side permanent magnet plate 18 has an appropriate thickness, and as shown in FIG. 6,
the surface thereof is substantially rectangular having substantially the same size as the vibrating
membrane 12 (thin film 26). The material is a resin magnet made of ferrite or rare earth
magnetic powder, a rubber magnet, or the like, which is not shown, but the back surface of the
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permanent magnet plate 18 (the side facing the diaphragm 12 through the buffer member 14 On
the surface of the above, a parallel stripe multipolar magnetization pattern is formed in which
strip-like N poles and strip-like S poles alternately appear along the alignment direction of each
linear portion of the front side coil 28 described above . More specifically, the boundary between
each N pole and each S pole of this multipolar magnetization pattern surface is a neutral zone,
and these neutral zones are opposed to the respective straight portions of the front side coil 28.
The multipolar magnetization pattern is formed. Furthermore, a plurality of through holes 48, 48
as sound wave emission holes are provided at appropriate positions on each neutral zone, for
example, in a zigzag form so as to penetrate the permanent magnet plate 18 from the front side
to the back side. Is provided. The configuration of the permanent magnet plate 18 including the
multipolar magnetization pattern, the positional relationship between the multipolar
magnetization pattern and the front side coil 28, and the positions of the through holes 48, 48,.
Since it is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-331596,
further detailed description will be omitted. Furthermore, the four corners (corners) 50, 50,... Of
the outer peripheral wall of the permanent magnet plate 18 are also chamfered in accordance
with the four corners 34, 34,.
[0026]
The permanent magnet plate 20 on the back side is substantially the same as the permanent
magnet plate 18 on the front side, but as shown also in FIG. 7, a notch 52 aligned with the notch
32 of the vibrating membrane 12 is in the center of the upper end edge thereof. It differs from
the permanent magnet plate 18 on the front side in that it is provided. Although not shown, a
multipolar magnetization pattern is formed on the front surface (surface facing the vibrating film
12 via the buffer member 16) of the back surface side permanent magnet plate 20. . Other than
this, it is the same as the permanent magnet plate 18 on the front side including the point that a
large number of through holes 54, 54, ... are provided and the four corners (corners) 56, 56, ...
are chamfered. Since there is, detailed explanation is omitted. Although FIG. 7 is a view of the
permanent magnet plate 20 as viewed from the front side, a view as viewed from the back side is
also the same, so a view as viewed from the back side is omitted. The same applies to FIG. 6
described above.
[0027]
The front cover 22 is made of metal of high magnetic permeability such as an iron plate, and as
shown in FIG. 8, has a substantially rectangular parallelepiped hollow portion 58 whose one
surface on the back side is an opening 57. Such a front cover 22 is formed, for example, by
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10
punching, bending or drawing. Then, all the components except the back plate 24 are
accommodated in the hollow portion 58 of the front cover 22. In particular, the front permanent
magnet plate 18 is fixed to the back surface and the inner circumferential wall of the hollow
portion 58 by the magnetic attraction force. Further, the four corners (corners) 64, 64,... Of the
inner peripheral wall of the hollow portion 58 are shaped to match the four corners 34, 34,.
Specifically, the four corners 64, 64,... Are positioned slightly outside the four corners 34, 34,...
Of the vibrating membrane 12 and fitted with the four corners 50, 50,. It is formed. And, the four
corners (corners) 68, 68, ... of the outer peripheral wall of the front cover 22 corresponding to
the back sides thereof are also chamfered in conformity with the four corners 64, 64, ... of the
inner peripheral wall of the hollow portion 58. It is supposed to be in shape. Furthermore, flangelike ears 70, 70,... Are provided on the back side of the portions corresponding to the four
corners 68, 68,... Of the outer peripheral wall so as to protrude outside the opening 57. Each ear
portion 70 is provided with a through hole 74 as a screw insertion hole through which a screw
72 shown in FIG. 1A is inserted, for example. Furthermore, the front cover 22 is also provided
with a plurality of through holes 76, 76,... As sound wave emitting holes at positions facing the
respective through holes 48, 48,.
[0028]
As shown also in FIG. 9, the back plate 24 is in the form of a rectangular flat plate, and the back
plate 24 is also formed of a high magnetic permeability metal. At the four corners of the back
plate 24, there are provided screw holes 78, 78,... In which the above-mentioned screws 72, 72,.
That is, the screws 72, 72, ... are screwed to the screw holes 78, 78, ... via the through holes 74,
74, ... as screw insertion holes on the front cover 22 side, The front cover 22 and the back plate
24 are united to form a so-called housing. Then, inside the housing, the permanent magnet plate
20 on the back side is fixed to the inner side surface of the back plate 24 by the magnetic
attraction force. At this time, between the permanent magnet plate 20 on the back side and the
permanent magnet plate 18 on the front side described above, as shown particularly in FIG. ], A
gap 80 is formed. Then, in the gap 80, the vibrating membrane 12 and the buffer members 14
and 16 intervene with an appropriate margin (play) while facing each other. Further, the back
plate 24 is also provided with a plurality of through holes 82, 82,... As sound wave emitting holes
at positions facing the respective through holes 54, 54,. Further, a terminal block 84 is provided
at the center of the upper end edge of the back plate 24.
[0029]
The terminal block 84 has a plus lead terminal 86 and a minus lead terminal 88. The positive
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terminal 38 of the vibrating membrane 12 is connected to the positive lead terminal 86 among
them, and the negative terminal 40 of the vibrating membrane 12 is connected to the negative
lead terminal 88. Although this connection is realized by a suitable conductive wire such as a
wire as shown by reference numeral 90 in FIG. 1 (d), the copper foil patterns of the respective
terminals 38 and 40 of the diaphragm 12 are terminal blocks. It may be realized by extending to
the 84 lead terminals 86 and 88. Then, in order to connect the terminals 38 and 40 of the
diaphragm 12 and the lead terminals 86 and 88 of the terminal block 84, notches 32 are
provided in the diaphragm 12 (thin film 26) as described above. A notch 46 is provided in the
cushioning member 16 on the back side, and a notch 52 is provided in the permanent magnet
plate 20 on the back side.
[0030]
According to the flat speaker 10 configured as described above, the lead terminals 86 and 88 of
the terminal block 84 are connected to external wiring (not shown). That is, an audio signal is
input between the extraction terminals 86 and 88. Then, a current according to the audio signal
flows to each of the front side coil 28 and the back side coil 30. And, particularly in the straight
sections of the respective coils 28 and 30, the current flows in a direction transverse to the
magnetic field at right angles. Then, according to Fleming's left-hand rule, mechanical force along
the thickness direction of the vibrating membrane 12 (thin film 26) acts on the coils 28 and 30
at the same time. Moreover, the direction in which the mechanical force acts is the same between
the coils 28 and 30. That is, each coil 28 and 30 vibrates simultaneously and in the same
direction. Then, accompanying the coils 28 and 30, the vibrating membrane 12 vibrates, and as a
result, a sound wave is generated. More specifically, on the front side, the through holes 48, 48
as sound wave emitting holes provided in the permanent magnet plate 18 on the front side, and
the respective holes similarly provided in the front cover 22 as sound wave emitting holes. Sound
waves are emitted to the outside through the through holes 76, 76,. Then, on the back side, the
respective through holes 54, 54, ... as sound wave emission holes provided in the permanent
magnet plate 20 on the back side, and the respective through holes provided in the back plate 24
similarly as sound wave emission holes. Sound waves are emitted to the outside through the
holes 82, 82,.
[0031]
When the vibrating film 12 vibrates, the vibrating film 12 may collide with the permanent
magnet plates 18 and 20 to generate noise (abnormal sound). However, since flexible buffer
members 14 and 16 intervene between the vibrating film 12 and the permanent magnet plates
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18 and 20, the generation of the noise is prevented. Also, there is a concern that the buffer
members 14 and 16 intervene to inhibit the emission of the sound wave to the outside, but as
described above, the buffer members 14 and 16 also have air permeability, There is no such
concern. On the other hand, since the buffer members 14 and 16 also function as dustproof
means (filters), entry of dust into the flat speaker 10 (into the gap 80) from the outside is
prevented.
[0032]
By the way, in order to obtain good acoustic characteristics, it is ideal that the vibrating film 12 is
restricted in displacement in the in-plane direction, and vibrates only in the thickness direction.
Therefore, as shown in FIG. 10A, the outer peripheral edge of the vibrating membrane 12 is
surrounded by the inner peripheral wall of the hollow portion 58 of the front cover 22 in a free
state without any contact. In particular, in order not to form an extra space between the outer
peripheral edge of the vibrating membrane 12 and the inner peripheral wall of the hollow
portion 58, both are as close as possible. In FIG. 10A, only the outline of the vibrating film 12 is
described for the convenience of description. The same applies to FIG. 10 (b) described later.
[0033]
However, as the outer peripheral edge of the vibrating membrane 12 and the inner peripheral
wall of the hollow portion 58 come close to each other as described above, there is a concern
about positional deviation as shown in FIG. However, since the four corners 34, 34,... Of the
vibrating membrane 12 in the present embodiment are chamfered, even if the positional
deviation occurs, it can be sufficiently tolerated. That is, unlike the state shown in FIG. 14B, as
shown in FIG. 10B, it is difficult for the four corners 34, 34,... Of the vibrating membrane 12 to
protrude from the hollow portion 58 (opening 57). Therefore, good acoustic characteristics can
be maintained.
[0034]
Also, even if no positional displacement occurs, in the prior art, as described with reference to
FIG. There is a problem of On the other hand, in the present embodiment, the four corners 68,
68,... Of the inner peripheral wall of the hollow portion 58 conform to the four corners 34,. It is
formed to face 34,. More specifically, as shown in an enlarged view in FIG. 11, the distance
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between the outer peripheral edge of the vibrating membrane 12 and the inner circumferential
wall of the hollow portion 58 in the longitudinal direction of the vibrating membrane 12 (vertical
direction in FIG. 11) is Dx. Assuming that the distance between the outer peripheral edge of the
vibrating film 12 and the inner circumferential wall of the hollow portion 58 in the short side
direction of the vibrating film 12 (left and right direction in FIG. 11) is Dy, For example, even in
the diagonal direction of the vibrating membrane 12, the distance between the outer peripheral
edge of the vibrating membrane 12 and the inner circumferential wall of the hollow portion 58
can be set to the same Dz. That is, the displacement of the vibrating film 12 can be suppressed to
the same degree Dx, Dy and Dz in any direction. This also contributes significantly to obtaining
good acoustic properties.
[0035]
Furthermore, in the prior art, when the vibrating membrane vibrates, there is a concern that the
four corners become a hindrance, and thus the acoustic characteristics deteriorate, but in this
embodiment, there is no such concern. That is, since the vibrating film 12 in the present
embodiment has its four corners 34, 34, ... chamfered, the four corners 34, 34, ... do not get in
the way (mere load), and hence this causes acoustic There is no deterioration in the
characteristics.
[0036]
As described above, according to the present embodiment, by chamfering the four corners 34,
34,... Of the vibrating membrane 12, better acoustic characteristics than in the prior art can be
obtained. That is, by the extremely simple improvement of chamfering the four corners 34, 34, ...
of the vibrating film 12, a great effect can be obtained.
[0037]
In the present embodiment, the four corners 34, 34,... Of the vibrating membrane 12 are linearly
rectilinear, but the present invention is not limited to this. For example, as shown in FIG. 12, it
may be chamfered in an R shape, and in particular may be chamfered in a quarter circle shape.
Moreover, as shown in FIG. 13, you may chamfer to polygonal shape. The same applies to each of
the buffer members 14 and 16.
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[0038]
Furthermore, although the coils 28 and 30 are formed on both sides of the vibrating membrane
12 (thin film 26) in the present embodiment, the present invention is not limited to this. For
example, a coil may be formed only on one side of the vibrating membrane 12, or a plurality of
coils may be formed on each of the one side or both sides.
[0039]
And, in the present embodiment, the planar speaker 10 has been described as an example, but
the present invention can be applied to a microphone that exerts the opposite action.
[0040]
Reference Signs List 10 planar speaker 12 vibrating membrane 18, 20 permanent magnet plate
22 front cover 28, 30 coil 34 four corners
11-05-2019
15
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