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JP2016032240

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DESCRIPTION JP2016032240
PROBLEM TO BE SOLVED: To obtain a large sound pressure from an electro-acoustic conversion
device and to be easily assembled. SOLUTION: A fixing member having at least a flat surface and
fixed to a second cover is accommodated in a housing consisting of a first cover and a second
cover fitted to the first cover. A mounting structure of an electro-acoustic conversion device for
mounting an electro-acoustic conversion device on the fixing member, wherein the electroacoustic conversion device has a sound source for converting an electric signal into mechanical
vibration, and a central portion is opened. A support plate in which the opening is a sound hole, a
first fixing member fixing the edge of the sound hole and the sound source, and a second fixing
member fixing a partial region of the outer peripheral edge of the support plate to the fixing
member The wall surface of the second fixing member is provided such that a space between the
support plate and the fixing member forms a hole wall of a communication hole communicating
with the space in the housing on the first cover side. [Selected figure] Figure 1
Mounting structure of electro-acoustic conversion device
[0001]
The present invention relates to a mounting structure of an electro-acoustic conversion device
that converts an electrical signal into acoustic vibration.
[0002]
BACKGROUND In recent years, mobile communication terminals such as smartphones and
tablets, and electronic paper terminals for browsing books and simple Internet browsing
applications have become widespread.
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[0003]
In these terminals, sounds for reactions such as menus and as alarms are required.
Therefore, a proposal has been made in which a user is notified by providing a piezoelectric
vibrating element using a ceramic element in a housing and vibrating the housing (for example,
Japanese Patent Laid-Open No. 2004-7400, Japanese Patent Laid-Open No. 2004-7400). 200136993).
[0004]
At this time, when the piezoelectric vibrating element is attached to a thin material as much as
possible, it is easy to vibrate and a large sound pressure can be obtained.
In order to secure the acoustic performance and to lower the resonance frequency, it is necessary
to use a large (large size) piezoelectric vibration element. However, when using a large-sized
piezoelectric element, it becomes difficult to secure a mounting space. In particular, in recent
terminals, since reduction in size and weight are strongly directed, securing such space is not
easy.
[0005]
Then, the structure which adheres a piezoelectric vibration element directly to the rear cover of a
terminal is proposed. Since the piezoelectric vibrating element is directly fixed to the rear cover,
the rear cover acts as a vibrating body (ringing body), which makes it possible to obtain a large
sound pressure even with a small piezoelectric vibrating element.
[0006]
Here, the housing of the terminal is configured by assembling a rear cover and a front cover, and
a display module such as a liquid crystal device is provided on the front cover side, and an
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element that performs various control between the display module and the rear cover It is
assumed that a control board on which is mounted is disposed. Further, it is assumed that the
piezoelectric vibrating element and the control substrate are connected by a lead wire.
[0007]
At this time, if the length of the lead wire is short (set to the necessary minimum length), the
work of connecting the lead wire to the control board becomes difficult. Therefore, the length of
the lead wire needs to be set to a length with allowance given the connection workability, but in
this case, when fitting the rear cover to the front case, There is a disadvantage that biting tends
to occur.
[0008]
Further, in the configuration in which the piezoelectric vibrating element is attached to the rear
cover, when the rear cover is pulled away from the front case at the time of disassembly of the
terminal, the lead wire may be pulled and disconnected, or the piezoelectric vibrating element
may be damaged.
[0009]
This will be described with reference to FIG.
FIG. 11 is a cross-sectional view of the terminal 100 in which the piezoelectric vibrating element
109 is attached to the rear cover 101a. FIG. 11 (a) shows a state in which the rear cover 101a
and the front cover 101b are integrated, FIG. 11 (b) shows the rear cover 101a and The state
which separated the front cover 101b is shown.
[0010]
The housing 120 of the terminal 100 is a fitting of the rear cover 101a and the front cover 101b.
The display screen 102 and the display module 103 are fixed to the front cover 101 b side, and
the control substrate 104 is mounted on the back side (rear cover 101 a side) of the display
module 103. Other devices such as a battery and an antenna are not shown.
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[0011]
A piezoelectric vibrating element 109, which is an electro-acoustic conversion device, is fixed to
the rear cover 101a with a double-sided tape 108.
[0012]
Therefore, when connecting the lead wire 107 to the control substrate 104 in the state of FIG.
11B, it is difficult to secure a space into which a solder iron or the like is inserted, making it
difficult to connect the lead wire 107.
In addition, when the terminal 100 is disassembled, when the rear cover 101a is removed from
the front cover 101b, the connection portion of the lead wire 107 is disconnected, or the control
substrate 104 or the piezoelectric vibrating element 109 is damaged.
[0013]
Then, as shown in FIG. 12, the method of attaching the piezoelectric vibration element 109 to the
front cover 101b side can be considered. FIG. 12 is a cross-sectional view of the terminal 100 in
which the piezoelectric vibrating element 109 is attached to the display module 103 side. FIG. 12
(a) shows a state in which the rear cover 101a and the front cover 101b are integrated, FIG. 12
(b) is a rear cover The state which separated 101a and the front cover 101b is shown.
[0014]
In this configuration, since the lead wire 107 can be soldered to the control substrate 104 before
the rear cover 101a is fitted to the front cover 101b and assembled, the lead wire 107 may have
a minimum length. Therefore, inconveniences such as biting of the lead wire 107 are less likely
to occur, and no force is applied to the lead wire 107 even when the rear cover 101a is removed,
so that the piezoelectric vibrating element 109 and the control substrate 104 may be damaged.
Absent.
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[0015]
JP 2004-7400 JP JP 2001-36993 JP
[0016]
However, the configuration in which the piezoelectric vibrating element 109 shown in FIG. 12 is
attached to the front cover 101b has the following problems.
That is, the piezoelectric vibration element 109 is fixed to, for example, the display module 103
side, but at this time, it is necessary to fix firmly so that the fixed state is not released by an
external force (such as vibration applied to the terminal 100). As a method of firmly fixing, it is
desirable to fix the surface to be fixed uniformly with an adhesive (including double-sided tape)
or the like, and to fix to a flat surface in order to increase the fixing area.
[0017]
The sound is radiated from both surfaces of the piezoelectric vibrating element 109 (the surface
on the rear cover 101 a side and the surface on the display module 103 side). However, in the
configuration of FIG. 12 described above, the space between the piezoelectric vibrating element
109 and the display module 103 is a sealed space or a substantially sealed space by the
adhesive, so the piezoelectric vibrating element 109 on the display module 103 side Sound
radiated from the surface spreads into the internal space of the housing 120 and is not radiated,
and stagnates in the space between the piezoelectric vibrating element 109 and the display
module 103. Therefore, there is a problem that it becomes difficult to obtain a large sound
pressure.
[0018]
Therefore, a main object of the present invention is to provide a mounting structure of an electroacoustic conversion device which can obtain a large sound pressure and can be easily assembled.
[0019]
In order to solve the above-mentioned subject, in the case which consists of the 1st cover and the
2nd cover which fits with the 1st cover, the fixed member which has a flat side at least, and was
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fixed to the 2nd cover side The invention according to the mounting structure of the electroacoustic conversion device which is housed and mounts the electro-acoustic conversion device
on the fixing member, the electro-acoustic conversion device comprises a sound source for
converting an electric signal into mechanical vibration and a central portion A second fixing
member fixed to the fixing member, the first fixing member being opened and fixing the support
plate of which the opening is the sound hole, the edge of the sound hole and the sound source,
and the outer peripheral portion of the support plate A wall surface of the second fixing member
is provided so as to form a hole wall of a communication hole communicating the space between
the support plate and the fixing member with the space in the housing on the first cover side. It
features.
[0020]
According to the present invention, the electro-acoustic conversion device is mounted on the
second cover side, and the space between the support plate and the fixing member is provided in
communication with the space in the housing on the first cover side through the communication
hole. Therefore, it is possible to assemble easily and obtain a large sound pressure.
[0021]
It is sectional drawing of terminals, such as a tablet terminal mounted by the mounting structure
of the electro-acoustic transducer concerning 1st Embodiment.
It is sectional drawing at the time of disassembling a terminal.
It is a figure which shows the structure of an electro-acoustic transducer, (a) is a top view, (b) is
an AO-B sectional view in (a).
It is a figure which shows the sound pressure characteristic measurement by the mounting
structure of an electro-acoustic conversion device, (a) is a measurement block diagram for
measuring a sound pressure characteristic, (b) is the measured sound pressure characteristic. It is
the figure which compared the sound pressure when pulse frequency is specialized to 3 kHz. It is
sectional drawing of terminals, such as a tablet terminal mounted by the mounting structure of
the electro-acoustic transducer concerning 2nd Embodiment. It is a figure which shows the
sound pressure characteristic by the mounting structure of an electro-acoustic transducer. It is
the figure which compared the sound pressure when pulse frequency is specialized to 3 kHz. It is
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a figure which shows the result of having investigated the sound pressure dependence with
respect to a diaphragm distance. It is sectional drawing of terminals, such as a tablet terminal
mounted by the mounting structure of the electro-acoustic transducer concerning 3rd
Embodiment. The figure which shows the mounting structure of the electro-acoustic conversion
device at the time of attaching the piezoelectric vibration element applied to description of
related technology at the rear cover side, (a) is a state which made the rear cover and the front
cover unite, (b) These are figures which show the state which separated the rear cover and the
front cover. The figure which shows the mounting structure of the electroacoustic transducer at
the time of attaching the piezoelectric vibration element applied to description of related art to
the front cover side, (a) is the state which made the rear cover and the front cover unite, (b ) Is a
diagram showing a state in which the rear cover and the front cover are separated.
[0022]
First Embodiment A first embodiment of the present invention will be described. FIG. 1 is a crosssectional view of a terminal 2A such as a tablet terminal mounted by the mounting structure of
the electro-acoustic conversion device 4 according to the first embodiment. FIG. 2 is a crosssectional view of the terminal 2A when it is disassembled. The terminal 2A is not limited to the
tablet terminal, and any terminal having the same configuration can be applied.
[0023]
The housing 10 of the terminal 2A is a fitting of the rear cover (first cover) 10a and the front
cover (second cover) 10b. The display screen 12 and the display module 13 are fixed to the front
cover 10 b side. Further, on the rear surface side (rear cover 10 a side) of the display module 13,
a control substrate 14 on which electronic components are mounted for controlling the terminal
2 A is mounted, and the electro-acoustic conversion device 4 is attached. A battery, an antenna,
and the like (not shown) are mounted on the back side of the display module 13.
[0024]
In the present embodiment, the electro-acoustic conversion device 4 is described as being
attached to the display module 13 side, but the present invention is not limited to such a
configuration. The electro-acoustic conversion device 4 is a member on the control substrate 14
side, and may be a fixing member fixed on the front cover 10 b side and having a flat surface.
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[0025]
FIG. 3 is a view showing the configuration of the electro-acoustic transducer 4, in which (a) is a
top view and (b) is a cross-sectional view taken along the line A-O-B in (a). The electro-acoustic
conversion device 4 includes a sound source 21, a support plate 22, a first fixing member 23,
and a second fixing member 24. In the following description, a piezoelectric vibration element is
described as an example of the sound source 21. However, other devices for converting an
electrical signal such as a dynamic speaker or a magnetic sounder into an acoustic signal may be
used.
[0026]
The sound source 21 is formed by sequentially laminating a metal plate 21a, a piezoelectric
ceramic 21b, and an electrode 21c. Then, the lead wire 26 is connected to the metal plate 21a
and the electrode 21c, and the piezoelectric ceramic 21b is bent based on the signal input from
the lead wire 26 when the user operates the terminal 2A. Generate sounds such as reaction
applications and alarms.
[0027]
The support plate 22 is a member for supporting the sound source 21, and preferably is made of
a flexible material (resin or metal) so as to efficiently propagate the vibration of the sound source
21 and is formed as thin as possible. preferable. For example, PET (polyethylene terephthalate)
having a thickness of about 0.2 mm can be exemplified as the support plate 22, and the size of
the support plate 22 is preferably larger than at least the sound source 21.
[0028]
The central region of the support plate 22 is open and this opening constitutes a sound hole 27.
The shape of the sound hole 27 may be square, rectangular, circular, oval or the like.
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[0029]
The first fixing member 23 is, for example, a double-sided tape, and fixes the sound source 21
and the support plate 22. At this time, if the first fixing member 23 is provided along the outer
peripheral edge portion of the sound source 21, it is preferable because the sound source 21 and
the support plate 22 can be firmly fixed.
[0030]
The second fixing member 24 is, for example, a double-sided tape, and fixes the support plate 22
and the display module 13. At this time, the second fixing member 24 is not provided to
surround the sound hole 27. That is, the sound hole 27 and the inside of the housing 10 are
provided in communication with each other. In the present embodiment, as shown in FIG. 3A, by
arranging the second fixing member 24 at the opposite side edge portion of the support plate 22,
the area of the side adjacent to this side forms the communication hole 25. ing. Accordingly, the
sound hole 27 and the internal space (the space on the rear cover 10 a side) of the housing 10
are in communication via the communication hole 25.
[0031]
The reason why the second fixing member 24 is provided at the opposite side edge portion of the
support plate 22 is to form the communication hole 25 to prevent the sound from being dulled.
Therefore, the present invention is not limited to the above fixing method as long as the
communication hole 25 can be secured, and may be provided on three sides of the support plate
22 or in an island shape. At this time, the wall surface of the second fixing member 24 forms the
hole wall of the communication hole 25.
[0032]
The control substrate 14 of the terminal 2A is fixed to the back side of the display module 13,
and a signal to the sound source 21 is supplied from the control substrate 14.
[0033]
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As described above, the lead wire 26 is drawn from the metal plate 21a and the electrode 21c,
and the lead wire 26 is connected to the electrode of the control board 14 by soldering or the
like.
Of course, in the present embodiment, the connection is not limited to soldering, but may be
connection by a connector.
[0034]
At this time, since the electro-acoustic conversion device 4 has a structure completely separated
from the rear cover 10a, the lead wires 26 can be easily connected without considering the
presence of the rear cover 10a. That is, the assembly can be easily performed.
[0035]
In such a configuration, a pulse waveform is applied from the control board 14 to the sound
source 21 through the lead wire 26. As a result, the piezoelectric ceramic 21b generates a sound
by repeating expansion and contraction at a cycle and an amplitude level corresponding to the
pulse waveform.
[0036]
The sound radiated from the vibration surface of the sound source 21 on the rear cover 10 a side
propagates to the internal space of the housing 10 as it is. On the other hand, the sound radiated
from the vibration plane of the sound source 21 on the display module 13 side passes through
the sound hole 27 and the communication hole 25 sequentially and propagates to the internal
space of the housing 10. Then, the sound transmitted to the internal space of the housing 10 is
radiated to the outside of the terminal 2A by vibrating the rear cover 10a and the front cover
10b. As a result, the user can recognize this sound as a reaction sound or an alarm sound.
[0037]
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Next, sound pressure characteristics according to the above configuration will be described. The
resonance frequency of the device differs depending on the size and type of the sound source 21
used, and it is preferable that the reaction sound and the alarm sound have high sound pressure
at a frequency near 3 kHz which is considered to be most easily noticed by humans.
[0038]
FIG. 4 is a diagram showing the evaluation of the sound pressure characteristics by the mounting
structure of the electro-acoustic conversion device 4, and FIG. 4 (a) is a measurement
configuration diagram for measuring the sound pressure characteristics, FIG. It is a measured
sound pressure characteristic.
[0039]
As shown in FIG. 4A, the terminal 2A is placed on the mounting table (sponge) 31 with the
display surface side down, and the microphone 32 is placed at a position 30 cm away from the
surface center of the rear cover 10a. Was measured.
At this time, a pulse waveform of 3 Vp-p was applied to the sound source 21 to change the pulse
frequency from 500 Hz to 5 kHz.
[0040]
In FIG. 4 (b), the symbol ".box-solid." Indicates the configuration shown in FIG. FIG. 12 shows the
sound pressure characteristics when the sound source 21 is directly fixed to the back side of the
display module 13 with the configuration shown in FIG. 12 (hereinafter referred to as the second
conventional structure). In addition, o indicates sound pressure characteristics when the
sound source 21 is fixed to the rear cover 10 a having the configuration according to the present
embodiment (hereinafter, referred to as a first invention structure). FIG. 5 is a diagram
comparing sound pressure when the pulse frequency is specialized to 3 kHz.
[0041]
It can be seen from FIG. 4 (b) that the first invention structure can obtain a larger sound pressure
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than the second conventional structure regardless of the frequency. Further, it can be understood
from FIG. 5 that at the frequency of 3 kHz, the first invention structure can expand the sound
pressure by about 12 dB as compared to the second conventional structure, and can obtain the
same sound pressure as the first conventional structure. .
[0042]
As described above, by applying the mounting structure of the electro-acoustic conversion device
according to the present invention to a terminal, assembly of the terminal becomes easy, and a
large sound pressure can be obtained.
[0043]
Second Embodiment Next, a second embodiment of the present invention will be described.
The same components as those of the first embodiment are denoted by the same reference
numerals, and the description thereof will be omitted as appropriate.
[0044]
In the first embodiment, the sound source 21 is fixed to the surface of the support plate 22 on
the rear cover 10 a side. On the other hand, in the second embodiment, the sound source 21 is
provided on the surface of the support plate 22 on the display module 13 side.
[0045]
FIG. 6 is a cross-sectional view of a terminal 2B such as a tablet terminal mounted by the
mounting structure of the electro-acoustic conversion device 4 according to the present
embodiment, wherein the sound source 21 is provided on the surface of the support plate 22 on
the display module 13 side. There is.
[0046]
FIG. 7 is a diagram showing sound pressure characteristics according to the mounting structure
of the electro-acoustic conversion device 4, and FIG. 8 is a diagram comparing sound pressures
when the pulse frequency is specialized to 3 kHz.
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[0047]
The figure (FIG.4 (b)) which shows the sound pressure effect in 1st Embodiment is also shown
collectively in FIG.
In FIG. 7, ■ indicates the configuration shown in FIG. 11, and sound pressure characteristics
(hereinafter referred to as the first conventional structure) when the sound source 21 is fixed to
the rear cover 10a, and 印 indicates in FIG. In the configuration, the sound pressure
characteristic when the sound source 21 is directly fixed to the back side of the display module
13 is shown (hereinafter, described as a second conventional structure).
Further, Δ indicates sound pressure characteristics (hereinafter, described as a second
invention structure) when the sound source 21 is fixed to the rear cover 10 a of the
configuration according to the second embodiment.
[0048]
According to FIG. 7, it can be seen that the second invention structure can obtain a larger sound
pressure than the second conventional structure regardless of the frequency. Further, from FIG.
8, at the frequency of 3 kHz, the first invention structure can obtain about 19 dB of sound
pressure expansion compared to the second conventional structure, and can obtain the sound
pressure performance higher than the first conventional structure. I understand that.
[0049]
From these, it can be concluded that the second invention structure is an easy-to-assemble
structure and an excellent structure.
[0050]
Third Embodiment Next, a third embodiment of the present invention will be described.
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The same components as those of the first and second embodiments are denoted by the same
reference numerals and the description thereof will be omitted as appropriate.
[0051]
In the above description, the space between the support plate 22 and the display module 13
(hereinafter referred to as the height between the support plates) is not mentioned. Hereinafter,
the height between the support plates (the distance between the support plate 22 and the display
module 13) will be referred to as the support plate distance D (see FIG. 1 or 10).
[0052]
The back surface (surface on the support plate 22 side) of the display module 13 has a relatively
hard and flat structure. Therefore, the sound from the sound source 21 is reflected on the back
surface of the display module 13. The effect due to this reflection (echo effect) depends on the
distance D between the support plates. Further, the distance D between the support plates
depends on the distance D between the support plates as well, the volume of the sound
propagating to the space on the rear cover 10 a side through the communication holes 25 in
order to define the cross-sectional area of the communication hole 25. Also, the reverberation
effect differs depending on the structure of the reflective surface from which the sound is
reflected. Therefore, in the present embodiment, first, the sound pressure dependency on the
diaphragm distance D is examined, and the sound pressure dependency due to the echo effect is
examined.
[0053]
FIG. 9 shows the result of examining the sound pressure dependency on the diaphragm distance
D. As shown in FIG. The result is the sound pressure at 3 kHz, which is most noticeable to
humans. In FIG. 9, "-" indicates the structure of the first invention in the first embodiment, and "-"
indicates the structure of the second invention in the second embodiment.
[0054]
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From FIG. 9, as the distance D between the support plates is increased, the sound pressure is also
increased. This is considered to be due to the echo effect. Of course, there are some differences in
the effects depending on the speaker used, the thickness of the diaphragm, the planar size of the
diaphragm, the back surface material of the display module 13 and the like.
[0055]
In addition, in this verification, the sound pressure became large until the distance D between
support plates D = 3 mm, and when this distance (D = 3 mm) was exceeded, a tendency to
decrease was seen. Therefore, regardless of the first and second invention structures, a large
sound pressure can be obtained by increasing the distance D between the support plates. In
practice, it is not realistic to secure a large distance D between the support plates extremely from
the thinning of the terminal 2B and the mounting restriction of the internal parts. Therefore, if a
large distance between the support plates D can be secured even within a tolerance that can
realize the thinning of the terminal 2B, a sound pressure enlargement effect can be obtained.
[0056]
Although various methods are possible to adjust the distance D between the support plates, the
most direct method is to adjust the thickness of the second fixing member 24.
[0057]
In addition, although it is a trade-off with the thickness restriction of the terminal 2B, as shown in
FIG. 10, by making the end portion of the support plate 22 into a dome-shaped or semi-domeshaped terminal 2C, a more reverberation effect of sound It is also possible to obtain
[0058]
2A to 2C Terminal 4 Sound conversion device 10 Case 10a Rear cover 10b Front cover 12
Display screen 14 Display module 14 Control board 21 Sound source 21a Metal plate 21b
Piezoelectric ceramic 21c Electrode 22 Support plate 23 First fixing member 24 Second fixing
member 25 Communication Hole 26 lead 27 sound hole
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