JP2008099164

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DESCRIPTION JP2008099164
An electrostatic ultrasonic transducer is provided which can secure the flatness of a flat plate
fixed electrode and improve the sandwiching property of a vibrating membrane. A first support
member for supporting a first flat plate fixed electrode having a plurality of through holes, and a
second flat plate having a plurality of through holes paired with the through holes of the first flat
plate fixed electrode The flat fixed electrode includes a second support member for supporting
the fixed electrode, and a vibrating membrane having a vibrating electrode and sandwiched by
the pair of flat fixed electrodes, to which a DC bias voltage is applied to the vibrating electrode.
And the gap between the flat plate fixed electrode and the supporting member is provided in the
outer peripheral region from the fixed portion toward the outer peripheral portion, and the pair
of flat plates is provided. An alternating current signal is applied between the fixed electrodes to
vibrate the diaphragm. [Selected figure] Figure 1
Electrostatic ultrasonic transducer, method of manufacturing electrostatic ultrasonic transducer,
ultrasonic speaker, display device, and directional acoustic system
[0001]
The present invention makes it easy to ensure the flatness of a flat plate fixed electrode of an
electrostatic ultrasonic transducer, and significantly improves the sandwiching property of a
vibrating film, manufacturing an electrostatic ultrasonic transducer and an electrostatic
ultrasonic transducer. The present invention relates to a method, an ultrasonic speaker using the
electrostatic ultrasonic transducer, a display device including the ultrasonic speaker, and a
directional acoustic system.
[0002]
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1
FIG. 8 is a view showing a basic configuration (cross-sectional view) and a driving method of an
electrostatic ultrasonic transducer to which the present invention is applied.
The configuration and operation of the electrostatic ultrasonic transducer will be described
below with reference to FIG.
[0003]
In FIG. 8, the electrostatic ultrasonic transducer 1 has a pair of flat fixed electrodes consisting of
a front flat fixed electrode 10A and a back flat fixed electrode 10B (a front flat fixed electrode
10A and a rear flat When the fixed electrode 10B is generically referred to as a flat fixed
electrode 10). Further, the front side flat plate fixed electrode 10A is provided with a plurality of
through holes 13A, and the back side flat plate fixed electrode 10B has the same shape at a
position facing each through hole 13A provided in the front side flat plate fixed electrode 10A.
The through holes 13B are provided (when the through holes 13A and the through holes 13B are
collectively referred to as the through holes 13).
[0004]
The front side flat plate fixed electrode 10A and the back side flat plate fixed electrode 10B are
supported by the counter electrode forming body 11 with a predetermined gap from the
vibrating membrane 12, respectively, and the vibrating membrane 12 and the flat plate fixed
electrode 10 are partially voided. The counter electrode forming body 11 is formed to face each
other via. The vibration space of the vibrating membrane 12 is formed by the counter electrode
forming body 11. The vibrating film 12 is formed so as to sandwich the vibrating electrode 121
vapor-deposited by Al (aluminum) between the dielectric films 120.
[0005]
With the above configuration, the two flat plate fixed electrodes 10 constituting the vibration
space of the vibration film 12 sandwich the Al-deposited vibration film 12 therebetween, and the
DC bias power supply 14 applies DC to the + side of the vibration electrode 121 of the vibration
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film 12. By applying an alternating current signal (reference condition 250 Vpp) 15 so that a bias
(reference condition 250 V) is given and the opposite plate fixed electrode 10 is in reverse phase,
a positive AC signal is applied to one plate fixed electrode During this time, a negative AC signal
is applied to the other flat plate fixed electrode, so electrostatic attraction and repulsive force
always act between the vibrating membrane 12 and the flat plate fixed electrode 10. As a result,
the vibrating membrane 12 vibrates in response to the alternating current signal to generate a
sound wave, and the sound wave is emitted in both directions of the flat plate fixed electrode 10.
Thus, the electrostatic ultrasonic transducer shown in FIG. 8 is called a Push-Pull type
electrostatic transducer because electrostatic attraction and electrostatic repulsion always act on
the vibrating film 12. ing.
[0006]
Here, in the conventional ultrasonic transducer, as shown in FIG. 9, a method in which the flat
fixed electrode 10 is fixed to the support member 31 is fixed to the case member 41. The fixed
portion (for example, screw fixing portion or the like) 22 of the flat plate fixed electrode 10 and
the support member 31 is a central portion of four sides, and the fixed portion 32 of the support
member 31 and the case member 41 is a corner of four corners.
[0007]
When fixed in this manner, a fixing stress is applied to the central portion of the flat plate fixed
electrode 10, the tendency of the four corners of the flat plate fixed electrode 10 to rise is
increased, and the flatness of the electrode can not be secured. As a result, when the vibrating
membrane 12 (see FIG. 8) is sandwiched by the flat plate fixed electrode 10 in such a state, the
four corner edges of the flat plate fixed electrode 10 bite into the vibrating membrane 12 and the
flat plate fixed electrode 10 and the vibrating electrode 121 And the insulation between them
significantly lowers, making it prone to dielectric breakdown.
[0008]
In order to solve this problem, as shown in FIG. 10, the conventional flat plate fixed electrode 10
is formed into a flat plate fixed electrode 21 having fixing portions (for example, screw fixing
portions etc.) 22 provided at four corners. Although it is essential to fix the fixed electrode 21 to
the support member 31 at the four corners, depending on the position of the fixing hole and the
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way of applying stress due to the contact state with the support member 31, as shown in FIG. A
dent of a distance d is generated at the central portion of the electrode 21. As a result, a gap is
generated between the flat plate fixed electrode 21 and the vibrating film, and it becomes
impossible to secure stable vibration characteristics. Therefore, it is necessary to add a member
having a function of pressing the central portion of the flat plate fixed electrode 21 from both
sides, or to change the electrode structure to be able to configure a fixed portion at the central
portion of the electrode. It has been difficult to secure the electrode processing accuracy, and has
been a factor to increase the manufacturing cost.
[0009]
As described above, in the conventional method of attaching the flat plate fixed electrode, there is
a tendency that the four corners of the flat plate fixed electrode are lifted or dents are generated
in the central portion of the flat plate fixed electrode, and the flatness of the electrode is It was
not easy to secure.
[0010]
The present invention has been made to solve such problems, and its object is to make it easy to
secure the flatness of a flat plate fixed electrode, greatly improve the sandwiching property of the
vibrating membrane, and to provide vibration and sound pressure characteristics. In addition to
the improvement, it is possible to prevent the deflection of the vibrating membrane by
preventing the warpage of the corner of the flat fixed electrode, which has been a big problem in
the related art, and to remove the sound pressure improvement countermeasure part
conventionally required. Patent application title: Capable electrostatic ultrasonic transducer,
method of manufacturing electrostatic ultrasonic transducer, ultrasonic speaker using the
electrostatic ultrasonic transducer, display device including the ultrasonic speaker, and
directional acoustic system It is.
[0011]
The present invention has been made to solve the above-mentioned problems, and an
electrostatic ultrasonic transducer according to the present invention comprises: a first flat plate
fixed electrode having a plurality of through holes; and a penetration of the first flat plate fixed
electrode. A second flat plate fixed electrode having a plurality of through holes paired with a
hole, a first support member for supporting the first flat plate fixed electrode by a fixed portion,
and a second flat fixed electrode by a fixed portion It is sandwiched by a pair of flat plate fixed
electrodes which have a second support member to support and a vibrating electrode and which
comprises the first flat plate fixed electrode and the second flat plate fixed electrode, and a DC
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bias voltage is applied to the vibrating electrode Between the flat plate fixed electrode and the
support member in the outer peripheral region from the fixed portion toward the outer
peripheral portion, while the fixed portion is disposed in a portion close to the outer peripheral
portion of the flat plate fixed electrode. Create a gap Configured urchin, an AC signal is applied
between the pair of flat plates fixing the electrode to vibrate the vibrating membrane, and
wherein the city.
With such a configuration, the flat plate fixed electrode and the support member are fixed by the
fixing portion.
For example, in the case where the flat plate fixed electrode has a rectangular shape, screws are
fixed at four corners. At the time of this fixation, a gap is provided between the flat plate fixed
electrode and the support member in the outer peripheral region of the fixed portion. Then, for
example, the gap is adjusted according to the material and thickness of the flat plate fixed
electrode, and further, the tightening torque of the flat plate fixed electrode to the support
member is adjusted, and the displacement amount (protruding amount) of the central portion of
the flat plate fixed electrode is desired. Adjust to the size of This makes it easy to secure the
flatness of the flat fixed electrode, greatly improves the sandwiching property of the vibrating
film, improves the vibration and sound pressure characteristics, and corner portions of the flat
fixed electrode, which has been a big problem in the prior art. As a result, it is possible to prevent
the vibration film from being damaged, and to remove the sound pressure improvement
countermeasure component conventionally required.
[0012]
Further, in the electrostatic ultrasonic transducer according to the present invention, the flat
plate fixed electrode is formed in a square shape, and the fixed portion is at four corners of the
flat plate fixed electrode. With such a configuration, when the flat plate fixed electrode has a
rectangular shape, fixed portions are provided at four corners. For example, the flat fixed
electrode and the support member are screwed at four corners. At the time of this fixation, a gap
is provided between the flat plate fixed electrode and the support member in the outer peripheral
region of the fixed portion. Then, for example, the gap is adjusted according to the material and
thickness of the flat plate fixed electrode, and further, the tightening torque of the flat plate fixed
electrode to the support member is adjusted, and the displacement amount (protruding amount)
of the central portion of the flat plate fixed electrode is desired. Adjust to the size of This makes it
easy to secure the flatness of the rectangular flat plate fixed electrode, greatly improves the
sandwiching property of the diaphragm, improves the vibration and sound pressure
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characteristics, and also causes a large problem in the conventional flat plate fixed electrode. As a
result, it is possible to prevent the bending of the corner portion, to prevent the damage to the
vibrating membrane, and to remove the sound pressure improvement countermeasure
component conventionally required.
[0013]
In the electrostatic ultrasonic transducer according to the present invention, the size of the gap is
set according to the material and thickness of the flat plate fixed electrode. With such a
configuration, the size of the gap is set according to the material and thickness of the flat plate
fixed electrode, and the flat plate fixed electrode is fixed to the support member with an
appropriate tightening torque, thereby The displacement amount (protrusion amount) can be
adjusted to a desired size.
[0014]
Further, in the electrostatic ultrasonic transducer according to the present invention, the gap
between the flat plate fixed electrode and the support member is formed by providing a step
from the central portion to the outer peripheral portion of the fixed portion in the support
member. It features. With such a configuration, the gap between the flat plate fixed electrode and
the support member is formed by providing a step from the central portion of the fixed portion
toward the outer peripheral portion on the support member. Thus, the gap between the flat plate
fixed electrode and the support member can be easily formed by subjecting the support member
to surface processing.
[0015]
Further, in the electrostatic ultrasonic transducer according to the present invention, the gap
between the flat plate fixed electrode and the support member is formed by providing an
inclination from the central portion to the outer peripheral portion of the fixed portion in the
support member. It features. With such a configuration, the gap between the flat plate fixed
electrode and the support member is formed by providing an inclination from the central portion
of the fixed portion toward the outer peripheral portion on the support member. Thus, the gap
between the flat plate fixed electrode and the support member can be easily formed by
subjecting the support member to surface processing.
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[0016]
Further, in the electrostatic ultrasonic transducer according to the present invention, the gap
between the flat plate fixed electrode and the support member is formed by providing a groove
from the central portion to the outer peripheral portion of the fixed portion in the support
member. It features. With such a configuration, the gap between the flat plate fixed electrode and
the support member is formed by providing a groove from the central portion of the fixed
portion toward the outer peripheral portion on the support member. Thus, the gap between the
flat plate fixed electrode and the support member can be easily formed by subjecting the support
member to surface processing.
[0017]
Further, in the electrostatic ultrasonic transducer according to the present invention, a thickened
portion having a predetermined thickness is formed on the surface of the flat plate fixed
electrode in contact with the support member, and the outer periphery from the fixed portion on
the flat plate fixed electrode surface In the outer peripheral region toward the portion, the
surface of the flat plate fixed electrode is exposed without forming the thick portion. With such a
configuration, a thickened portion is provided, for example, by plating or the like on the
peripheral portion on the flat plate fixed electrode surface. Then, the flat fixed electrode surface
is exposed in the outer peripheral region of the fixed portion on the flat fixed electrode surface
without providing the thickened portion. Thus, the gap between the flat fixed electrode and the
support member can be easily formed by surface processing the peripheral portion on the flat
fixed electrode surface.
[0018]
Further, in the electrostatic ultrasonic transducer according to the present invention, the
thickened portion is formed by performing nickel plating on the surface of the flat plate fixed
electrode or applying a conductive paste material. Thus, the thickened portion having a desired
shape and thickness can be easily formed on the surface of the flat plate fixed electrode.
[0019]
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Further, in the electrostatic ultrasonic transducer according to the present invention, the method
of fixing the flat plate fixed electrode to the support member is screw fixing, and the projection
torque of the flat plate fixed electrode central portion is adjusted by the tightening torque. It is
characterized by With such a configuration, for example, in the case where the flat plate fixed
electrode has a square shape or the like, screws are fixed to the support member at four corners.
At this time, the projection amount of the central portion of the flat plate fixed electrode is
adjusted by the tightening torque of the screw. As a result, the displacement amount (protrusion
amount) of the central portion of the flat plate fixed electrode can be adjusted to a desired size by
the tightening torque of the flat plate fixed electrode, and the sandwiching property of the
vibrating membrane is significantly improved. Characteristics can be improved. In addition, it
prevents warping of the corner of the flat fixed electrode, which has been a big problem in the
past, to prevent damage to the diaphragm, and removes the parts for improving the sound
pressure that were conventionally required. A highly reliable and low cost ultrasonic transducer
can be provided.
[0020]
In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, a first flat plate fixed electrode having a plurality of through holes and a plurality of
through holes paired with the through holes of the first flat plate fixed electrode are provided. A
second flat plate fixed electrode, a first support member supporting the first flat plate fixed
electrode by a fixed portion, a second support member supporting the second flat plate fixed
electrode by a fixed portion, a vibrating electrode And a vibrating membrane which is
sandwiched between the pair of flat plate fixed electrodes consisting of the first flat plate fixed
electrode and the second flat plate fixed electrode and to which a DC bias voltage is applied to
the vibrating electrode, A method of manufacturing an electrostatic ultrasonic transducer in
which an alternating current signal is applied between the flat plate fixed electrodes to vibrate
the vibrating membrane, and the fixing portion is disposed in a portion near the outer peripheral
portion of the flat plate fixed electrode; , Said flat And fixing the fixed electrode so as to provide a
gap between the flat plate fixed electrode and the support member in the outer peripheral region
from the fixed portion to the outer peripheral portion when fixing the fixed electrode to the
support member by the fixing portion. It is characterized by According to such a procedure, the
fixed portion is disposed on the flat plate fixed electrode, and the flat fixed electrode and the
support member are fixed by the fixed portion. For example, in the case where the flat plate fixed
electrode has a rectangular shape, screws are fixed at four corners. At the time of this fixation, a
gap is provided and fixed between the flat plate fixed electrode and the support member in the
outer peripheral region of the fixed portion. Then, for example, the gap is adjusted according to
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the material and thickness of the flat plate fixed electrode, and further, the tightening torque of
the flat plate fixed electrode to the support member is adjusted, and the displacement amount
(protruding amount) of the central portion of the flat plate fixed electrode is desired. Adjust to
the size of This makes it easy to secure the flatness of the flat fixed electrode, greatly improves
the sandwiching property of the vibrating film, improves the vibration and sound pressure
characteristics, and corner portions of the flat fixed electrode, which has been a big problem in
the prior art. As a result, it is possible to prevent the vibration film from being damaged, and to
remove the sound pressure improvement countermeasure component conventionally required.
[0021]
In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, the flat fixed electrode may be formed in a square shape, and the fixing portion may be
provided at four corners of the flat fixed electrode. According to such a procedure, when the flat
plate fixed electrode has a square shape, fixed portions are provided at four corners. For
example, the flat fixed electrode and the support member are screwed at four corners. At the
time of this fixation, a gap is provided between the flat plate fixed electrode and the support
member in the outer peripheral region of the fixed portion. Then, for example, the gap is adjusted
according to the material and thickness of the flat plate fixed electrode, and further, the
tightening torque of the flat plate fixed electrode to the support member is adjusted, and the
displacement amount (protruding amount) of the central portion of the flat plate fixed electrode
is desired. Adjust to the size of This makes it easy to secure the flatness of the rectangular flat
plate fixed electrode, greatly improves the sandwiching property of the diaphragm, improves the
vibration and sound pressure characteristics, and also causes a large problem in the conventional
flat plate fixed electrode. As a result, it is possible to prevent the bending of the corner portion, to
prevent the damage to the vibrating membrane, and to remove the sound pressure improvement
countermeasure component conventionally required.
[0022]
In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, the method further includes the step of setting the size of the gap according to the
material and thickness of the flat plate fixed electrode. According to such a procedure, the size of
the gap is set according to the material and thickness of the flat plate fixed electrode, and the flat
plate fixed electrode is fixed to the support member with an appropriate tightening torque. The
displacement amount (protrusion amount) can be adjusted to a desired size.
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[0023]
In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, the step of forming a gap between the flat plate fixed electrode and the support
member from the central portion to the outer peripheral portion of the fixed portion of the
support member is formed. It is characterized by including. According to such a procedure, the
gap between the flat plate fixed electrode and the support member is formed on the support
member by providing a step from the central portion to the outer peripheral portion of the fixed
portion. Thus, the gap between the flat plate fixed electrode and the support member can be
easily formed by subjecting the support member to surface processing.
[0024]
In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, the gap between the flat plate fixed electrode and the support member is formed by
providing a slope from the central portion to the outer peripheral portion of the fixed portion of
the support member. It is characterized by including. According to such a procedure, the gap
between the flat plate fixed electrode and the support member is formed by providing an
inclination from the central portion of the fixed portion toward the outer peripheral portion on
the support member. Thus, the gap between the flat plate fixed electrode and the support
member can be easily formed by subjecting the support member to surface processing.
[0025]
In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, the gap between the flat plate fixed electrode and the support member is formed by
providing a groove from the central portion to the outer peripheral portion of the fixed portion of
the support member. It is characterized by including. According to such a procedure, the gap
between the flat plate fixed electrode and the support member is formed by providing a groove
on the support member from the central portion to the outer peripheral portion of the fixed
portion. Thus, the gap between the flat plate fixed electrode and the support member can be
easily formed by subjecting the support member to surface processing.
[0026]
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In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, a thick portion with a predetermined thickness is formed on the surface of the flat
plate fixed electrode in contact with the support member, and the flat plate fixed electrode is
fixed on the flat plate In the outer peripheral region from the portion toward the outer peripheral
portion, the method includes a step of exposing the surface of the flat plate fixed electrode
without forming the thickened portion. According to such a procedure, a thickened portion is
provided, for example, by plating or the like on the peripheral portion on the flat plate fixed
electrode surface. Then, the flat fixed electrode surface is exposed in the outer peripheral region
of the fixed portion on the flat fixed electrode surface without providing the thickened portion.
Thus, the gap between the flat fixed electrode and the support member can be easily formed by
surface processing the peripheral portion on the flat fixed electrode surface.
[0027]
Further, the method of manufacturing an electrostatic ultrasonic transducer according to the
present invention includes the step of forming the above-mentioned thickened portion by
applying nickel plating to the surface of a flat plate fixed electrode or applying a conductive
paste material. It is characterized by Thus, the thickened portion having a desired shape and
thickness can be easily formed on the surface of the flat plate fixed electrode.
[0028]
In the method of manufacturing an electrostatic ultrasonic transducer according to the present
invention, the method of fixing the flat plate fixed electrode to the support member is screw
fixing, and the projection torque of the central portion of the flat plate fixed electrode is adjusted
by the tightening torque. It is characterized by including. According to such a procedure, for
example, when the flat plate fixed electrode has a square shape or the like, screws are fixed to
the support member at the four corners. At this time, the projection amount of the central
portion of the flat plate fixed electrode is adjusted by the tightening torque of the screw. As a
result, the displacement amount (protrusion amount) of the central portion of the flat plate fixed
electrode can be adjusted to a desired size by the tightening torque of the flat plate fixed
electrode, and the sandwiching property of the vibrating membrane is significantly improved.
Characteristics can be improved. In addition, it prevents warping of the corner of the flat fixed
electrode, which has been a big problem in the past, to prevent damage to the diaphragm, and
removes the parts for improving the sound pressure that were conventionally required. A highly
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reliable and low cost ultrasonic transducer can be provided.
[0029]
Further, the ultrasonic speaker according to the present invention comprises an audio frequency
signal source generating a signal wave in an audio frequency band, a carrier wave signal source
generating a carrier wave in an ultrasonic frequency band, and outputting the carrier wave. An
ultrasonic ultrasonic transducer comprising: a modulator that modulates with a signal wave in a
frequency band; a power amplifier that amplifies and outputs a modulated signal output from the
modulator; and an electrostatic ultrasonic transducer driven by the power amplifier A speaker,
wherein the electrostatic ultrasonic transducer in the ultrasonic speaker comprises a plurality of
through holes paired with a first flat plate fixed electrode having a plurality of through holes and
a through hole of the first flat plate fixed electrode. A second flat plate fixed electrode having a
hole, a first support member for supporting the first flat plate fixed electrode by a fixed portion,
and a second support for supporting the second flat plate fixed electrode by a fixed portion A
vibrating membrane which is sandwiched between a pair of flat plate fixed electrodes having a
vibrating electrode and the first flat plate fixed electrode and the second flat plate fixed electrode,
and a direct current bias voltage is applied to the vibrating electrode; The fixed portion is
disposed in a portion near the outer peripheral portion of the flat fixed electrode, and a gap is
provided between the flat fixed electrode and the support member in an outer peripheral region
from the fixed portion toward the outer peripheral portion. The system is characterized in that an
alternating current signal is applied between the pair of flat plate fixed electrodes to vibrate the
vibrating film. With such a configuration, in the electrostatic ultrasonic transducer used for the
ultrasonic speaker, when attaching the flat plate fixed electrode to the support member, the flat
plate fixed electrode in the outer peripheral region of the fixing portion (for example, screw
fixing portion etc.) Provide a gap between the and the support member. Then, by fixing the flat
plate fixed electrode to the support member with an appropriate tightening torque, the
displacement amount (protruding amount) of the central portion of the flat plate fixed electrode
is adjusted to a desired size. Thereby, in the electrostatic ultrasonic transducer used for the
ultrasonic speaker, it is easy to secure the flatness of the flat plate fixed electrode, greatly
improve the sandwiching property of the vibrating membrane, and improve the vibration and
sound pressure characteristics. Can.
[0030]
Further, the display device of the present invention modulates a carrier wave signal of an
ultrasonic frequency band by an audio signal supplied from an acoustic source, drives an
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electrostatic ultrasonic transducer by the modulation signal, and generates an audio frequency
band signal sound. A display apparatus comprising: an ultrasonic speaker for reproducing; and a
projection optical system for projecting an image on a projection surface, wherein the
electrostatic ultrasonic transducer in the ultrasonic speaker has a plurality of through holes A
first flat plate fixed electrode, a second flat plate fixed electrode having a plurality of through
holes paired with the through holes of the first flat plate fixed electrode, and the first flat plate
fixed electrode supported by a fixed portion A support member, a second support member for
supporting the second flat fixed electrode by a fixing portion, and a pair of flat plates having a
vibrating electrode and comprising the first flat fixed electrode and the second flat fixed
electrode Fixed A vibrating membrane which is sandwiched by the poles and to which a DC bias
voltage is applied to the vibrating electrode, and the fixed portion is disposed in a portion close
to the outer peripheral portion of the flat plate fixed electrode; In the outer peripheral region
facing the gap, a gap is provided between the flat plate fixed electrode and the support member,
and an alternating current signal is applied between the pair of flat plate fixed electrodes to
vibrate the diaphragm. It is characterized by With such a configuration, in the electrostatic
ultrasonic transducer in the ultrasonic speaker used in the display apparatus provided with the
projection optical system for projecting an image, when attaching the flat plate fixed electrode to
the support member, the fixation site (for example, In the outer peripheral region of the screw
fixing portion or the like, a gap is provided between the flat plate fixed electrode and the support
member. Then, by fixing the flat plate fixed electrode to the support member with an appropriate
tightening torque, the displacement amount (protruding amount) of the central portion of the flat
plate fixed electrode is adjusted to a desired size. As a result, in the ultrasonic speaker used for
the display device, the flatness of the flat plate fixed electrode of the electrostatic ultrasonic
transducer can be easily ensured, the sandwiching property of the vibrating film can be greatly
improved, and the vibration and sound pressure characteristics can be improved. It can be
improved.
[0031]
Further, according to the directional acoustic system of the present invention, a carrier wave
signal of an ultrasonic frequency band is modulated by a signal of a first range of an audio signal
supplied from an acoustic source, and an electrostatic ultrasonic transducer is An ultrasonic
speaker for driving to reproduce a signal sound in an audible frequency band; and a bass
reproduction speaker for reproducing a signal in a second sound range lower than the first sound
range among audio signals supplied from the acoustic source A directional acoustic system, the
electrostatic ultrasonic transducer in the ultrasonic speaker comprising: a first flat plate fixed
electrode having a plurality of through holes; and a through hole of the first flat plate fixed
electrode A second flat plate fixed electrode having a plurality of pairs of through holes, a first
support member for supporting the first flat plate fixed electrode by the fixed portion, and the
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second flat plate fixed electrode by the fixed portion It is sandwiched by a pair of flat fixed
electrodes having a second supporting member to be held, a vibrating electrode and the first flat
fixed electrode and the second flat fixed electrode, and a DC bias voltage is applied to the
vibrating electrode. Between the flat plate fixed electrode and the support member in the outer
peripheral region from the fixed site toward the outer peripheral portion, while the fixed portion
is disposed in a portion close to the outer peripheral portion of the flat plate fixed electrode A
gap is provided between the pair of flat fixed electrodes, and an alternating current signal is
applied between the pair of flat plate fixed electrodes to vibrate the vibrating film. With such a
configuration, when attaching a flat fixed electrode to a support member in an electrostatic
ultrasonic transducer used for an ultrasonic speaker that reproduces a signal of a first sound
range among sound signals supplied from an acoustic source A gap is provided between the flat
plate fixed electrode and the support member in the outer peripheral region of the fixed portion
(for example, a screw fixing portion or the like). Then, by fixing the flat plate fixed electrode to
the support member with an appropriate tightening torque, the displacement amount (protruding
amount) of the central portion of the flat plate fixed electrode is adjusted to a desired size. As a
result, in the ultrasonic speaker used for the directional acoustic system, the flatness of the flat
fixed electrode of the electrostatic ultrasonic transducer can be easily ensured, and the holding
property of the vibrating film can be greatly improved, and the vibration and sound pressure
Properties can be improved.
[0032]
In the electrostatic ultrasonic transducer of the present invention, a gap is provided between the
flat plate fixed electrode and the support member in the outer peripheral region of the fixing
portion (for example, screw fixing portion) fixing the flat plate fixed electrode to the support
member.
[0033]
For example, in the case where the flat plate fixed electrode has a rectangular shape, screws are
fixed to the support member at the four corners.
At the time of this fixation, a gap is provided between the flat plate fixed electrode and the
support member in the outer peripheral region of the screw. Then, by adjusting the tightening
torque of the screw according to the material and thickness of the electrode, the central portion
of the flat fixed electrode is made to project with a desired dimension, and the holding property
of the vibrating film when the flat fixed electrode is opposed is enhanced.
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[0034]
Hereinafter, the best mode for carrying out the present invention will be described with
reference to the drawings. In the example of the embodiment described below, the flat plate fixed
electrode has a square shape, and an example in which screw fixation is performed to the
support member at four corners is shown, but the shape of the flat plate fixed electrode is not
limited to a square. It can be made into various shapes, such as a circle and an elliptical shape,
the fixing site is not limited to four corners, and the fixing method is not limited to screw fixing.
[0035]
First Embodiment First, a configuration example of an electrostatic ultrasonic transducer
according to the present invention will be described as a first embodiment of the present
invention.
[0036]
In the first embodiment of the present invention, as shown in FIG. 10, the mechanical strength of
the flat fixed electrode 21 and the support member 31 is minimized at four locations at four
corners of the flat fixed electrode. Place as outside as possible as far as possible.
[0037]
FIG. 1 is a view showing a method of attaching a flat fixed electrode to a support member
according to the present invention.
As shown in FIG. 1A, a step 33 is provided as a gap in the outer peripheral region (outside region
from the fixed portion toward the outer peripheral portion) of the fixed portion of the support
member 31 or as shown in FIG. There is provided a slope 34 which is a gap.
The start point of the step 33 or the slope 34 is in the vicinity of the center of the fixed portion
22. As a result, in the outer region of the fixed portion 22, an appropriate gap is generated
between the flat fixed electrode 21 and the support member 31.
04-05-2019
15
[0038]
Here, the support member 3 in FIGS. 1A and 1B has a structure in which the connection portion
with the flat plate fixed electrode 21 is raised by one step, but the groove 35 shown in FIG. A
structure may be employed in which the groove 35 is dug on the plane of the support member
31. This structure requires less processing steps and can reduce cost.
[0039]
In such a configuration, the clamping force due to fixation acts as a bending stress in the outer
region (peripheral region) of the fixed portion 22 of the flat plate fixed electrode 21.
Therefore, the flat fixed electrode 21 bends in the tightening direction in the outer region of the
fixed portion 22. On the other hand, in the inner region of the fixing portion 22, the flat plate
fixed electrode 21 is bent in the direction opposite to the tightening direction. As a result, the
central portion of the flat plate fixed electrode 21 protrudes and the corner of the flat plate fixed
electrode 21 deviates.
[0040]
For example, as shown in FIG. 3, the central portion protrudes by a distance d. Here, the degree
of protrusion of the central portion of the flat fixed electrode 21 can be adjusted by the gap
provided between the flat fixed electrode 21 and the support member 31 and the tightening
force (tightening load) of the flat fixed electrode 21. .
[0041]
Moreover, FIG. 2 is a figure which shows the other attachment method to the supporting member
of the flat plate fixed electrode by this invention. In the example shown in FIG. 2, instead of
providing a gap such as a step 33 in the support member 31 as shown in FIG. 1, a thickened
portion 23 is provided around the flat fixed electrode 21 and four corners of the thickened
portion 23 Is an example in which an exposed portion (a portion in which the surface of the flat
plate fixed electrode 21 is exposed from the thickened portion 23) is provided. As described
above, by providing the thickened portion 23 and the exposed portion 24, the same effect as in
the case where a gap is provided in the support member 31 can be obtained.
04-05-2019
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[0042]
The thickened portion 23 can be easily formed, for example, by performing nickel plating or the
like on the flat plate fixed electrode 21 or applying a conductive paste material.
[0043]
Next, in order to verify the relationship between the amount of protrusion of the central portion
of the flat plate fixed electrode 21 and the tightening force at the fixed portion of the flat plate
fixed electrode 21, an example of simulation is described.
For the simulation, structural analysis software "I-DEAS (registered trademark)" is used.
[0044]
In this simulation, a flat plate fixed electrode (having a through hole), a shell element, a thickness
of 1.0 mm / 1.5 mm / 2.0 mm, the number of elements 23221, and the number of nodes 13235
are used as the analysis model . There are two types of "material conditions": aluminum and
stainless steel. As the restraint condition , the flat fixed electrode inner region is completely
fixed in the screw fixing range, and the outer peripheral side of the screw fixing range is
completely free. As the load condition , the clamping force converted from the clamping
torque is applied to the flat plate fixed electrode screw fixing range and converted to surface
pressure.
[0045]
The characteristic values of the respective materials are as shown in FIG. 4 (A), and four
conditions were applied as shown in FIG. 4 (B) as analysis model load conditions. The load
conditions were set based on the recommended tightening torque of the M2 screw used for
assembling the actual machine. In the example shown in FIG. 4B, four conditions of 5 kg, 10 kg,
25 kg and 35 kg are used as the tightening force.
04-05-2019
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[0046]
The amount of protrusion of the central portion of the flat plate fixed electrode obtained by the
above analysis model and analysis conditions is shown in FIG. Moreover, the amount of bending
of the flat plate fixed electrode corner portion is shown in FIG. 4 (D).
[0047]
FIG. 5 is a graph showing the amount of protrusion of the central portion of the flat plate fixed
electrode. As can be seen from FIG. 5, in each electrode thickness, a linear relationship holds
between the clamping force and the amount of protrusion. Therefore, if the material and
thickness of the flat plate fixed electrode 21 are determined, the tightening force necessary to
obtain a desired displacement amount is determined, so the tightening torque of the fixing screw
may be matched.
[0048]
Further, when only the electrode thickness is determined and it is desired to secure a desired
amount of protrusion, an appropriate material may be selected and the tightening force may be
combined. For example, when the electrode thickness is 1.5 mm and the desired displacement
amount is 5 μm, aluminum is selected as a material from the table shown in FIG. 4C (or the
graph shown in FIG. 5) The force should be 25 kg (10 cN / m). When the thickness of the
electrode is 1.0 mm and a desired displacement amount is 5 μm, stainless steel may be selected
as the material and the clamping force may be 25 kg (10 cN / m).
[0049]
Here, in an aluminum electrode having an electrode thickness of 1.5 mm, it is shown in FIG. 5 (D)
that a bending amount of at least 8.6 μm is required at the fixed portion of the flat plate fixed
electrode to obtain 5 μm of displacement. You can see from the table. A gap larger than this
must be provided between the flat plate fixed electrode and the support member, but the amount
of bending can be adjusted by the tightening torque, so the gap may be slightly larger (several
tens of μm). There is no problem, which makes it possible to reduce the processing accuracy and
reduce the manufacturing cost.
04-05-2019
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[0050]
6 shows an electrostatic ultrasonic transducer constructed based on the manufacturing method
of the present invention, and FIG. 6 (A) is a top view thereof, and FIG. 6 (B) is a sectional view
taken along the line A-A '. It is. In the electrostatic ultrasonic transducer 2 shown in FIG. 6, the
front side flat fixed electrode 21A fixed to the support member 31A and the back side flat fixed
electrode 21B similarly fixed to the support member 31B are opposed to each other, The
diaphragm 12 fixed by the film frame 33 is disposed, and the diaphragm 12 is held.
[0051]
The front side flat fixed electrode 21A corresponds to the above-mentioned first flat fixed
electrode, the support member 31A corresponds to the above first support member, and the back
side flat fixed electrode 21B is the above second flat fixation The support member 31B
corresponds to an electrode, and corresponds to the above-described second support member.
Further, the front side flat fixed electrode 21A and the back side flat fixed electrode 21B are
generically referred to as the flat stationary electrode 21, and the support member 31A and the
support member 31B are collectively referred to as the support member 31.
[0052]
The basic configuration and operation of the electrostatic ultrasonic transducer 2 shown in FIG. 6
are similar to those of the electrostatic ultrasonic transducer 1 shown in FIG. 8 described above.
That is, as shown in FIG. 8, the vibrating film 12 is formed so as to sandwich the vibrating
electrode 121 on which Al (aluminum) is vapor-deposited by the dielectric film 120. Further, the
two flat plate fixed electrodes 21 constituting the vibration space of the vibration film 12
sandwich the Al-deposited vibration film 12 therebetween, and the DC bias power supply is
applied to the vibration electrode 121 of the vibration film 12 by the DC bias power (reference
While applying a condition 250V) and applying an alternating current signal (reference condition
250Vpp) to the opposite flat fixed electrode 21 so as to be in opposite phase, while a positive
alternating current signal is applied to one flat fixed electrode, Since a negative AC signal is
applied to the other flat plate fixed electrode, electrostatic attraction and electrostatic repulsion
always act between the vibrating membrane 12 and the flat plate fixed electrode 21. As a result,
the vibrating membrane 12 vibrates in response to the alternating current signal to generate a
04-05-2019
19
sound wave, and the sound wave is emitted in both directions of the flat plate fixed electrode 21.
[0053]
FIG. 7 is a view for explaining the manufacturing process of the flat fixed electrode of the
electrostatic ultrasonic transducer according to the present invention. Hereafter, with reference
to FIG. 7, the manufacturing process of a flat plate fixed electrode is demonstrated.
[0054]
First, as shown in FIG. 7A, a flat plate fixed electrode base material made of the conductor 51 is
prepared, in which the through holes 13 are formed by machining, pressing, etching or bonding.
[0055]
Next, as shown in FIG. 7 (B), a mask for forming an opposing electrode to be a screen plate for
forming the opposing electrode forming body 11 (see FIG. 8) on the conductor (flat plate fixed
electrode base material) 51 The member 52 and the liquid counter electrode forming material 53
are set, and the squeegee 54 is moved to coat the counter electrode forming material 53 on the
unmasked portion.
[0056]
Here, the counter electrode forming material 53 considered to be effective can be permanently
configured as the counter electrode forming body 11 and is non-conductive, for example, a liquid
solder resist for a package generally used for a circuit board. And masking ink used as a resist for
sand blasting.
[0057]
In particular, solder resists for flexible printed circuit boards are relatively soft (HB to 3H in
pencil hardness), so they have excellent adhesion to metals and various conductors (such as
conductive resins), and they are polymer films. It is also excellent in the sandwiching property of
the diaphragm made of
[0058]
Then, as shown in FIG. 7C, when the opposing electrode forming mask member 52, which is a
screen plate for forming the opposing electrode, is removed after the application of the opposing
04-05-2019
20
electrode forming material 53 is completed, the other portion excluding the opposing electrode
portion is removed. A nonconductive layer (= counter electrode formation body) remains, which
is dried to obtain the desired flat fixed electrode.
[0059]
As described above, in the electrostatic ultrasonic transducer according to the present invention,
a gap is provided between the flat plate fixed electrode and the support member in the outer
peripheral region of the fixed portion where the flat plate fixed electrode is fixed to the support
member.
For example, when the flat plate fixed electrode has a rectangular shape and a screw is fixed to
the support member at the four corners, a gap is provided between the flat plate fixed electrode
and the support member in the outer peripheral region of the screw.
Then, by adjusting the gap according to the material and thickness of the flat plate fixed
electrode, and further adjusting the tightening torque of the flat plate fixed electrode to the
support member, the displacement amount (projection amount) of the central portion of the flat
plate fixed electrode is desired. Adjust to the size of
As a result, the sandwiching property of the vibrating membrane can be greatly improved, and
the vibration and sound pressure characteristics can be improved.
In addition, it prevents warping of the corner of the flat fixed electrode, which has been a big
problem in the past, to prevent damage to the diaphragm, and removes the parts for improving
the sound pressure that were conventionally required. An ultrasonic transducer with high
reliability and low cost can be provided.
[0060]
Second Embodiment Next, as a second embodiment of the present invention, a configuration
example of an ultrasonic speaker using the electrostatic ultrasonic transducer described in the
first embodiment will be described.
04-05-2019
21
[0061]
FIG. 12 is a view showing a configuration example of an ultrasonic speaker using the electrostatic
transducer of the present invention.
The ultrasonic speaker shown in FIG. 12 includes an audio frequency wave signal source (audio
signal source) 101 that generates a signal wave in an audio wave frequency band, and a carrier
wave signal source 102 that generates and outputs a carrier wave in an ultrasonic frequency
band. , A modulator 103, and a power amplifier 104.
[0062]
The ultrasonic speaker performs AM modulation with an audio signal (audible area signal) on an
ultrasonic wave called a carrier wave, and when this is emitted into the air, the original audio
signal is self-reproduced in the air due to air non-linearity. It is said that.
That is, since the sound wave is a compressional wave propagating through air as a medium, in
the process of propagation of the modulated ultrasonic wave, dense portions and sparse portions
of air are prominently displayed, and the dense portion has a high speed of sound and is sparse.
As the speed of sound is slowed, the modulation wave itself is distorted, so that the waveform is
separated into the carrier wave (ultrasonic wave) and the audio wave (original audio signal), and
we human beings the audible sound below 20 kHz (original audio signal) The principle is that
you can hear only, and is generally called parametric array effect.
[0063]
In the above configuration, the carrier wave of the ultrasonic frequency band output from the
carrier wave signal source 102 is modulated by the modulator 103 by the audio frequency signal
(audio signal) output from the audio frequency wave signal source 101, and the power amplifier
104 The modulation signal amplified in the above is applied to both ends of the primary side
winding of the output transformer T.
[0064]
04-05-2019
22
One terminal of the secondary side of the output transformer T is connected to the front flat
electrode 21A of the electrostatic ultrasonic transducer 2 of the present invention (see FIG. 6),
and the other terminal is connected to the rear flat electrode 21B. It is done.
Further, a center tap is provided in the secondary winding of the output transformer T, and a DC
bias voltage VB is applied to the vibrating electrode 121 of the electrostatic ultrasonic transducer
2 with reference to the center tap.
[0065]
By connecting the output transformer T and the electrostatic ultrasonic transducer 2 as shown in
FIG. 12, alternating voltages having the same amplitude but opposite in phase are applied to the
front flat electrode 21A and the rear flat electrode 21B. Therefore, it is possible to output a
sound wave with small distortion.
[0066]
As described above, the ultrasonic speaker shown in FIG. 12 includes the electrostatic ultrasonic
transducer 2 (see FIG. 6) of the present invention, and the flat fixed electrode 21 of the
electrostatic ultrasonic transducer 2 is , And is attached to the support member 31 in a manner
as shown in FIG.
As a result, the sandwiching property of the vibrating membrane can be greatly improved, and
the vibration and sound pressure characteristics can be improved. In addition, the corner of the
flat plate fixed electrode is prevented from curling up to prevent damage to the diaphragm, and
the parts for improving the sound pressure, which are conventionally required, are removed.
High performance, high reliability and low cost A sound wave speaker can be provided.
[0067]
Third Embodiment Next, as a third embodiment of the present invention, an example of a display
device provided with an ultrasonic speaker using the electrostatic ultrasonic transducer of the
present invention will be described.
[0068]
04-05-2019
23
FIG. 13 shows an example of a projector incorporating an ultrasonic speaker as an example of
the display device, and shows a state of use of the projector.
As shown in the figure, the projector 201 is installed behind the viewer 203 and projects an
image on the screen 202 installed in front of the viewer 203, and the screen 202 by the
ultrasonic speaker mounted on the projector 201. The virtual sound source is formed on the
projection plane of the to reproduce the sound. An acoustic device using an ultrasonic speaker
that forms a virtual sound source on a projector screen, a projector having an ultrasonic speaker
built-in, and the like are also called directional acoustic systems.
[0069]
The external configuration of the projector 201 is shown in FIG. The projector 201 includes a
projector main body 220 including a projection optical system for projecting an image on a
projection surface such as a screen, and electrostatic ultrasonic transducers 224A and 224B
capable of oscillating sound waves in an ultrasonic frequency band, and an acoustic source And
an ultrasonic speaker that reproduces a sound signal of an audible frequency band from an audio
signal supplied from the unit. In the present embodiment, in order to reproduce a stereo sound
signal, electrostatic ultrasonic transducers 224A and 224B are mounted on the projector main
body on the left and right with the projector lens 231 constituting the projection optical system
interposed therebetween. Further, a bass reproduction speaker 223 is provided on the bottom of
the projector body 220. Reference numeral 225 denotes a height adjustment screw for adjusting
the height of the projector body 220, and reference numeral 226 denotes an exhaust port for an
air-cooling fan.
[0070]
As described above, the projector 201 is provided with an ultrasonic speaker using an
electrostatic ultrasonic transducer, thereby oscillating a wide frequency band acoustic signal
(sound wave in the ultrasonic frequency band) at high sound pressure. Can. Then, by changing
the frequency of the carrier wave to control the spatial reproduction range of the reproduction
signal in the audio frequency band, it is necessary to conventionally obtain the acoustic effect
that can be obtained with a stereo surround system, 5.1 channel surround system, etc. It is
possible to realize a projector that can be realized without the need for a large-scale sound
system and easy to carry.
04-05-2019
24
[0071]
Next, the electrical configuration of the projector 201 is shown in FIG. The projector 201
includes an operation input unit 210, a reproduction range setting unit 212, a reproduction
range control processing unit 213, an audio / video signal reproduction unit 214, a carrier wave
oscillation source 216, modulators 218A and 218B, power amplifiers 222A and 222B, and It has
an ultrasonic speaker consisting of the electric ultrasonic transducers 224A and 224B, high pass
filters 217A and 217B, a low pass filter 219, a mixer 221, a power amplifier 222C, a speaker
223 for reproducing the bass, and a projector main body 220 ing. The electrostatic ultrasonic
transducers 224A and 224B are electrostatic ultrasonic transducers in which flat fixed electrodes
are fixed to a support member by the method shown in FIG. 1 or FIG.
[0072]
The projector body 220 includes an image generation unit 232 that generates an image, and a
projection optical system 233 that projects the generated image on a projection surface. As
described above, the projector 201 is configured by integrating the ultrasonic speaker and the
bass reproduction speaker 223, and the projector main body 220.
[0073]
The operation input unit 210 has various function keys including a ten-key pad, numeric keys,
and a power key for turning the power on and off. The reproduction range setting unit 212 can
input data specifying the reproduction range of the reproduction signal (signal sound) by the
user operating the operation input unit 210 as a key. When the data is input, reproduction is
performed. The frequency of the carrier wave that defines the reproduction range of the signal is
set and held. The setting of the reproduction range of the reproduction signal is performed by
designating the distance that the reproduction signal reaches in the radiation axis direction from
the sound wave emission surface of the electrostatic ultrasonic transducers 224A and 224B.
[0074]
04-05-2019
25
Further, the reproduction range setting unit 212 can set the frequency of the carrier wave by the
control signal output from the audio / video signal reproduction unit 214 according to the
contents of the video. Further, the reproduction range control processing unit 213 refers to the
setting contents of the reproduction range setting unit 212, and changes the frequency of the
carrier wave generated by the carrier wave oscillation source 216 so as to become the set
reproduction range. It has a function of controlling the oscillation source 216. For example, when
the distance corresponding to the carrier wave frequency of 50 kHz is set as internal information
of the reproduction range setting unit 212, the carrier wave oscillation source 216 is controlled
to oscillate at 50 kHz.
[0075]
The reproduction range control processing unit 213 sets in advance a table indicating in advance
the relationship between the distance that the reproduction signal reaches in the radiation axis
direction from the sound wave emitting surface of the electrostatic ultrasonic transducers 224A
and 224B defining the reproduction range and the frequency of the carrier wave. It has a storage
unit stored. The data of this table can be obtained by actually measuring the relationship
between the frequency of the carrier wave and the reach distance of the reproduction signal. The
reproduction range control processing unit 213 obtains the frequency of the carrier wave
corresponding to the distance information set with reference to the above-mentioned table based
on the setting contents of the reproduction range setting unit 212, and carries out carrier wave
oscillation so as to be the frequency. Control the source 216.
[0076]
The audio / video signal reproduction unit 214 is, for example, a DVD player using a DVD as a
video medium, and among the reproduced audio signals, the R channel audio signal is
transmitted to the modulator 218A via the high pass filter 217A. The signal is output to the
modulator 218 B via the high pass filter 217 B, and the video signal is output to the video
generation unit 232 of the projector main body 220. The audio signal of R channel and the audio
signal of L channel output from the audio / video signal reproduction unit 214 are synthesized
by the mixer 221 and input to the power amplifier 222 C through the low pass filter 219. . The
audio / video signal reproduction unit 214 corresponds to an audio source.
[0077]
04-05-2019
26
The high-pass filters 217A and 217B have the characteristic of passing only frequency
components in the middle and high frequency range of the R channel and L channel audio
signals, respectively, and the low pass filters have low characteristics in the R channel and L
channel audio signals. It has the property of passing only frequency components in the sound
range. Therefore, among the audio signals of the R channel and L channel, audio signals in the
middle to high range are reproduced by the electrostatic ultrasonic transducers 224A and 224B,
respectively, and the audio signals of the low frequency range among the audio signals of the R
channel and L channel are reproduced. The signal is reproduced by the bass reproduction
speaker 223.
[0078]
The audio / video signal reproduction unit 214 is not limited to a DVD player, and may be a
reproduction device that reproduces a video signal input from the outside. Also, the audio / video
signal reproduction unit 214 instructs the reproduction range setting unit 212 to change the
reproduction range of the reproduction sound dynamically in order to obtain an acoustic effect
according to the scene of the video to be reproduced. Output control signal.
[0079]
The carrier wave oscillation source 216 has a function of generating a carrier wave of the
frequency of the ultrasonic frequency band instructed by the reproduction range setting unit 212
and outputting the carrier wave to the modulators 218A and 218B. The modulators 218A and
218B AM modulate the carrier wave supplied from the carrier wave oscillation source 216 with
the audio signal of the audio frequency band output from the audio / video signal reproduction
unit 214, and respectively modulate the modulated signal with the power amplifier 222A. , 222 B
have a function to output.
[0080]
The electrostatic ultrasonic transducers 224A and 224B are driven by modulation signals output
from the modulators 218A and 218B via the power amplifiers 222A and 222B, respectively,
convert the modulation signals into sound waves of finite amplitude level, and convert the
medium It has a function of emitting inside and reproducing the signal sound of the audio
frequency band (reproduction signal).
04-05-2019
27
[0081]
The video generation unit 232 includes a display such as a liquid crystal display or a plasma
display panel (PDP), and a drive circuit that drives the display based on the video signal output
from the audio / video signal reproduction unit 214. An image obtained from the video signal
output from the audio / video signal reproduction unit 214 is generated.
The projection optical system 233 has a function of projecting an image displayed on a display
on a projection surface such as a screen installed in front of the projector main body 220.
[0082]
Next, the operation of the projector 201 configured as described above will be described. First,
data (distance information) instructing the reproduction range of the reproduction signal from
the operation input unit 210 is set in the reproduction range setting unit 212 by the key
operation of the user, and the audio / video signal reproduction unit 214 is instructed to
reproduce.
[0083]
As a result, distance information defining the reproduction range is set in the reproduction range
setting unit 212, and the reproduction range control processing unit 213 takes in the distance
information set in the reproduction range setting unit 212 and stores it in the built-in storage
unit. The frequency of the carrier wave corresponding to the set distance information is
determined with reference to the table, and the carrier wave oscillation source 216 is controlled
to generate the carrier wave of the frequency. As a result, the carrier wave oscillation source 216
generates a carrier wave of a frequency corresponding to the distance information set in the
reproduction range setting unit 212, and outputs the carrier wave to the modulators 218A and
218B.
[0084]
On the other hand, the audio / video signal reproduction unit 214 transmits an audio signal of R
channel among the reproduced audio signals to the modulator 218A via the high pass filter 217A
04-05-2019
28
and an audio signal of L channel to the modulator 218B via the high pass filter 217B. The audio
signal of the R channel and the audio signal of the L channel are output to the mixer 221, and the
video signal is output to the video generation unit 232 of the projector main body 220,
respectively.
[0085]
Therefore, the high-pass filter 217A inputs the voice signal in the middle to high range among
the voice signals of the R channel to the modulator 218A, and the high-pass filter 217B inputs
the voice signal in the middle to high range among the voice signals of the L channel. Is input to
The audio signal of the R channel and the audio signal of the L channel are synthesized by the
mixer 221, and the audio signal of the bass region among the audio signal of the R channel and
the audio signal of the L channel is input to the power amplifier 222C by the low pass filter 219.
Be done.
[0086]
The video generation unit 232 drives the display based on the input video signal to generate and
display a video. The image displayed on the display is projected by the projection optical system
233 onto the projection surface, for example, the screen 202 shown in FIG. Modulator 218A, on
the other hand, AM modulates the carrier wave output from carrier wave oscillation source 216
with the middle-to-high range audio signal of the R channel audio signal output from high-pass
filter 217A, and outputs it to power amplifier 222A. . Further, the modulator 218 B AM
modulates the carrier wave output from the carrier wave oscillation source 216 with the middle
to high frequency range audio signal of the L channel audio signal output from the high pass
filter 217 B, and outputs the AM to the power amplifier 222 B .
[0087]
The modulation signals amplified by the power amplifiers 222A and 222B are respectively the
front flat fixed electrode (upper electrode) 21A and the rear flat fixed electrode (lower electrode)
21B of the electrostatic ultrasonic transducers 224A and 224B (see FIG. 6). And the modulated
signal is converted into a sound wave (acoustic signal) of a finite amplitude level and emitted to a
04-05-2019
29
medium (in air), and from the electrostatic ultrasonic transducer 224A, the R channel is The
voice signal of middle to high range in the voice signal is reproduced, and the voice signal of
middle to high range of the voice signal of L channel is reproduced from the electrostatic
ultrasonic transducer 224B. Further, the audio signal of the bass region in the R channel and the
L channel amplified by the power amplifier 222 C is reproduced by the bass reproduction
speaker 223.
[0088]
As described above, in the propagation of the ultrasonic wave radiated into the medium (in the
air) by the electrostatic ultrasonic transducer, the speed of sound becomes high in the high
sound pressure area and the sound sound is low in the low sound pressure area. The speed of
sound is slower. As a result, waveform distortion occurs.
[0089]
When the signal (carrier wave) of the emitting ultrasonic band is modulated (AM modulated) with
the signal of the audio frequency band, the signal wave of the audio frequency band used at the
time of modulation is super It is formed to be separated from the carrier wave in the sound wave
frequency band and to be self-demodulated. At this time, the spread of the reproduction signal is
in the form of a beam due to the characteristics of the ultrasonic waves, and the sound is
reproduced only in a specific direction which is completely different from that of a normal
speaker.
[0090]
Beam-like reproduction signals output from electrostatic ultrasonic transducers 224A and 224B
constituting an ultrasonic speaker are emitted toward a projection surface (screen) on which an
image is projected by the projection optical system 233, and the projection surface It is reflected
and diffused. In this case, according to the frequency of the carrier wave set in the reproduction
range setting unit 212, the reproduction signal from the carrier wave in the radiation axis
direction (normal direction) from the sound emission surface of the electrostatic ultrasonic
transducers 224A and 224B. The reproduction range changes due to the difference in the
distance until the light source is separated and the beam width of the carrier wave (beam spread
angle).
04-05-2019
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[0091]
The state at the time of reproduction ¦ regeneration of the reproduction ¦ regeneration signal by
the ultrasonic speaker comprised including electrostatic ultrasonic transducer 224A, 224B in the
projector 201 is shown in FIG. In the projector 201, when the electrostatic ultrasonic transducer
is driven by the modulation signal in which the carrier wave is modulated by the audio signal, the
electrostatic ultrasonic wave is set if the carrier frequency set by the reproduction range setting
unit 212 is low. The distance from the acoustic wave emission surface of the transducers 224A
and 224B to the separation of the reproduction signal from the carrier wave in the radiation axis
direction (the normal direction of the sound emission surface), ie, the distance to the
reproduction point becomes long.
[0092]
Therefore, the beam of the reproduced signal of the reproduced audio frequency band reaches
the projection surface (screen) 202 without spreading relatively, and is reflected at the projection
surface 202 in this state, so that the reproduction range is as shown in FIG. The audible range A
is indicated by a dotted arrow in FIG. 2 and a reproduced signal (reproduced sound) can be heard
only in a relatively far and narrow range from the projection plane 202.
[0093]
On the other hand, when the carrier frequency set by the reproduction range setting unit 212 is
higher than the case described above, the sound wave radiated from the sound wave emitting
surface of the electrostatic ultrasonic transducers 224A and 224B has a low carrier frequency.
The distance from the acoustic wave emitting surface of the electrostatic ultrasonic transducers
224A and 224B to the separation of the reproduction signal from the carrier wave in the
radiation axial direction (normal direction of the acoustic wave emitting surface) The distance to
the playback point is shortened.
[0094]
Therefore, the beam of the reproduced signal in the audible frequency band is expanded before
reaching the projection surface 202 to reach the projection surface 202, and is reflected at the
projection surface 202 in this state, so that the reproduction range is as shown in FIG. An audible
range B indicated by a solid arrow at 16 is obtained, and a reproduced signal (reproduced sound)
can be heard only in a relatively close and wide range from the projection surface 202.
04-05-2019
31
[0095]
Although the display device (projector etc.) of the present invention has been described above,
the display device uses the ultrasonic speaker provided with the electrostatic transducer
according to the present invention, and the flat fixed electrode of this electrostatic ultrasonic
transducer Is fixed to the support member by the method shown in FIG. 1 or FIG.
As a result, in the ultrasonic speaker in the display device, the holding property of the vibrating
film can be greatly improved, and the vibration and sound pressure characteristics can be
improved.
In addition, the corner of the flat plate fixed electrode is prevented from curling up to prevent
damage to the diaphragm, and the parts for improving the sound pressure, which are
conventionally required, are removed. High performance, high reliability and low cost A sound
wave speaker can be provided.
[0096]
The above-mentioned projector is used to view an image on a large screen, but recently, a largescreen liquid crystal television and a large-screen plasma television have rapidly become
widespread, and these large-screen televisions are also widely used. An ultrasonic speaker using
the electrostatic transducer of the present invention can be effectively used.
[0097]
That is, by using an ultrasonic speaker for a large screen television, it becomes possible to radiate
an audio signal locally toward the front of the large screen television.
[0098]
The embodiment of the present invention has been described above, but the electrostatic
ultrasonic transducer, the ultrasonic speaker, and the display device of the present invention are
not limited to the above illustrated examples, and the gist of the present invention Of course,
various changes can be made without departing from the scope of the invention.
[0099]
04-05-2019
32
The figure which shows the example of the fixing method to the supporting member of a flat
plate fixed electrode.
The figure which shows the other example of the fixing method to the supporting member of a
flat plate fixed electrode.
The figure which shows the example of protrusion of the center part of a flat plate fixed
electrode.
The figure which shows the simulation result of the protrusion amount and clamping force of a
flat plate fixed electrode.
The figure which displayed the simulation result graphically. The figure which shows the
structural example of the electrostatic-type ultrasonic transducer by this invention. The figure
which shows the manufacturing method of a flat plate fixed electrode. The figure which shows
the basic composition of an electrostatic type ultrasonic transducer. The figure which shows the
example of the fixing method of the conventional flat plate fixed electrode. The figure which
shows the other example of the fixing method of a flat plate fixed electrode. The figure which
shows the example of curvature rising of the corner ¦ angular part by the fixing method of the
conventional flat plate fixed electrode. The figure which shows the structural example of the
drive circuit of an ultrasonic speaker. The figure which shows the use condition of the projector
which concerns on embodiment of this invention. FIG. 14 is a diagram showing an appearance
configuration of the projector shown in FIG. FIG. 14 is a block diagram showing an electrical
configuration of the projector shown in FIG. 13. Explanatory drawing of the reproduction ¦
regeneration state of the reproduction ¦ regeneration signal by an electrostatic type ultrasonic
transducer.
Explanation of sign
[0100]
2: Electrostatic ultrasonic transducer, 10, flat plate fixed electrode, 10A: front side flat plate fixed
electrode, 10B: back side flat plate fixed electrode, 11: counter electrode forming body, 12:
vibrating film, 13, 13A, 13B: penetrating Hole 14 14 bias power supply 21 flat plate fixed
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electrode 21A front side flat plate fixed electrode 21B back side flat plate fixed electrode 22 fixed
portion 23 meat attached portion 24 exposed portion 31, 31A, 31B ... support member, 32 ...
fixed part, 33 ... level difference, 34 ... slope, 35 ... groove, 41 ... case member, 51 ... conductor, 52
... mask member for forming counter electrode, 53 ... material for forming counter electrode, 54 ...
squeegee , 101: audio frequency wave signal source, 102: carrier wave signal source, 103:
modulator, 104: power amplifier, 120: dielectric film, 121: vibrating electrode, 201: projector,
202: screen (Projection plane) 203 Viewer: 210 Operation input unit 212: Playback range setting
unit 213: Playback range control processing unit 214: Audio / video signal playback unit 216:
Carrier wave oscillation source 217A, 217B ... high pass filter, 218A, 218B ... modulator, 219 ...
low pass filter, 220 ... projector main body, 221 ... mixer, 222A, 222B ... power amplifier, 222C ...
power amplifier, 223 bass reproduction speaker, 224A, 224B ... electrostatic type Ultrasonic
transducer, 231: Projector lens, 232: Video generator, 233: Projection optical system
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