JP2008099164A - Electrostatic ultrasonic transducer, method for manufacturing the electrostatic ultrasonic transducer, ultrasonic speaker, display device and directional acoustic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic ultrasonic transducer for securing flatness of a plate fixed electrode, and for improving the pinching characteristics of a vibrating film. <P>SOLUTION: The electrostatic ultrasonic transducer has a first support member for supporting the first plate fixed electrode having a plurality of through-holes; a second support member for supporting a second plate fixed electrode, having a plurality of through-holes making a pair with the through-holes of the first plate fixed electrode; and a vibrating film interposed in between the pair of plate fixed electrodes, and equipped with a vibrating electrode to which a DC bias voltage is applied. The fixed site is arranged near the outer peripheral section of the plate fixed electrode, and a gap is arranged between the plate fixed electrode and the support member in an outer peripheral region, going from the fixed site to the outer peripheral section. An AC signal is applied to the gap between the pair of plate fixed electrodes so that the vibrating film is vibrated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention makes it easy to ensure the flatness of a plate-fixed electrode of an electrostatic ultrasonic transducer, and greatly improves the sandwichability of a vibrating membrane, and manufacture of 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.

  FIG. 8 is a diagram showing a basic configuration (cross-sectional view) and a driving method of an electrostatic ultrasonic transducer to which the present invention is applied. Hereinafter, the configuration and operation of the electrostatic ultrasonic transducer will be described with reference to FIG.

  In FIG. 8, the electrostatic ultrasonic transducer 1 has a pair of flat plate fixed electrodes composed of a front plate fixed electrode 10A and a back plate fixed electrode 10B (the front plate fixed electrode 10A and the back plate). When the fixed electrode 10B is generically called, it is called the flat plate fixed electrode 10). The front plate fixing electrode 10A has a plurality of through holes 13A, and the back plate fixing electrode 10B has the same shape at a position facing each through hole 13A provided in the front plate fixing electrode 10A. Through-holes 13B are provided (when the through-hole 13A and the through-hole 13B are collectively referred to as the through-hole 13).

  The front side flat plate fixed electrode 10A and the back side flat plate fixed electrode 10B are respectively supported by the counter electrode forming body 11 with a predetermined gap from the vibration film 12, and the vibration film 12 and the flat plate fixed electrode 10 are partially spaced. The counter electrode forming body 11 is formed so as to face each other. The counter electrode formation body 11 forms a vibration space of the vibration film 12. The vibration film 12 is formed so that the vibration electrode 121 deposited with Al (aluminum) is sandwiched between the dielectric films 120.

  With the above configuration, the Al-deposited vibration film 12 is sandwiched between the two flat plate fixed electrodes 10 constituting the vibration space of the vibration film 12. By applying a bias (reference condition 250 V) and applying an AC signal (reference condition 250 Vpp) 15 to the opposite plate fixing electrode 10 so as to have an opposite phase, a positive AC signal is applied to the plate fixing electrode on one side. In the meantime, since a negative AC signal is applied to the other flat plate fixed electrode, an electrostatic attractive force and an electrostatic 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 accordance with the AC signal, generates a sound wave, and is radiated in both directions of the flat plate fixed electrode 10. As described above, the electrostatic ultrasonic transducer shown in FIG. 8 is called a push-pull type electrostatic transducer because the electrostatic attractive force and the electrostatic repulsive force always act on the vibration film 12. ing.

  Here, in the conventional ultrasonic transducer, as shown in FIG. 9, a method in which the flat plate fixed electrode 10 fixed to the support member 31 is fixed to the case member 41. The fixed portion (for example, screw fixing portion) 22 between the flat plate fixing electrode 10 and the support member 31 is the central portion of the four sides, and the fixing portions 32 between the support member 31 and the case member 41 are the corners of the four corners.

  When fixed in this way, a fixing stress is applied to the central portion of the flat plate fixed electrode 10, and the tendency of the four corners of the flat plate fixed electrode 10 to rise increases, and the flatness of the electrode cannot be ensured. As a result, when the vibrating membrane 12 (see FIG. 8) is sandwiched between the flat plate fixing electrodes 10 in such a state, the four corner edges of the flat plate fixing electrode 10 bite into the vibrating membrane 12, and the flat plate fixing electrode 10 and the vibrating electrode 121 are cut. The insulation between the two is remarkably lowered, and the dielectric breakdown is likely to occur.

  In order to solve this problem, as shown in FIG. 10, the conventional flat plate fixing electrode 10 is formed into a flat plate fixing electrode 21 having fixing portions (for example, screw fixing portions) 22 provided at four corners. It is essential to fix the fixed electrode 21 to the support member 31 at four corners. However, depending on the position of the fixing hole and the state of contact with the support member 31, depending on how stress is applied, as shown in FIG. A dent having a distance d is generated in the central portion of the electrode 21. As a result, a gap is generated between the flat plate fixed electrode 21 and the vibration membrane, and stable vibration characteristics cannot be ensured. Therefore, it is necessary to take measures such as adding a member having a function of pushing the central portion of the flat plate fixed electrode 21 from both sides, or changing to an electrode structure in which the fixed portion can be configured in the central portion of the electrode, increasing the manufacturing process, It has been a factor that makes it difficult to ensure electrode processing accuracy and increases manufacturing costs.

  As described above, in the conventional method for attaching the flat plate fixed electrode, the four corners of the flat plate fixed electrode tend to rise, or the center portion of the flat plate fixed electrode tends to be dented. It was not easy to secure.

  The present invention has been made to solve such problems, and its purpose is to facilitate the securing of the flatness of the plate-fixed electrode, to greatly improve the sandwichability of the vibrating membrane, and to improve the vibration / sound pressure characteristics. As well as improving, it is possible to prevent the warping of the corner of the flat plate fixed electrode, which has been a big problem in the past, to prevent the vibration membrane from being damaged, and to eliminate the sound pressure improvement parts that were required in the past An electrostatic ultrasonic transducer, a method for manufacturing the electrostatic ultrasonic transducer, an ultrasonic speaker using the electrostatic ultrasonic transducer, a display device including the ultrasonic speaker, and a directional acoustic system are provided. There is.

The present invention has been made to solve the above problems, and an electrostatic ultrasonic transducer according to the present invention includes a first flat plate fixing electrode having a plurality of through holes, and a through hole of the first flat plate fixing electrode. A second flat plate fixing electrode having a plurality of through holes paired with a hole; a first support member that supports the first flat plate fixing electrode by a fixed portion; and the second flat plate fixing electrode by a fixed portion. A second support member to be supported, a vibration electrode, and sandwiched between a pair of flat plate fixed electrodes including the first flat plate fixed electrode and the second flat plate fixed electrode, and a DC bias voltage is applied to the vibration electrode. The fixed portion is disposed in a portion close to the outer peripheral portion of the flat plate fixed electrode, and in the outer peripheral region from the fixed portion toward the outer peripheral portion, between the flat plate fixed electrode and the support member. 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 fixing electrode and the support member are fixed by the fixing portion. For example, when the flat plate fixing electrode is rectangular, screws are fixed at four corners. During the fixing, a gap is provided between the flat plate fixing electrode and the support member in the outer peripheral region of the fixing portion. Then, for example, the gap is adjusted according to the material and thickness of the flat plate fixing electrode, and further, the tightening torque to the support member of the flat plate fixing electrode is adjusted, and the displacement amount (protrusion amount) of the central portion of the flat plate fixing electrode is desired. Adjust to the size of.
This makes it easy to ensure the flatness of the plate-fixed electrode, greatly improves the sandwichability of the vibrating membrane, improves the vibration and sound pressure characteristics, and the corners of the plate-fixed electrode, which has been a big problem in the past Can be prevented, the diaphragm can be prevented from being damaged, and the sound pressure improvement component that has been required in the past can be eliminated.

In the electrostatic ultrasonic transducer according to the present invention, the flat plate fixing electrode is formed in a square shape, and the fixing portions are four corners of the flat plate fixing electrode.
With such a configuration, when the flat plate fixing electrode is rectangular, fixing portions are provided at the four corners. For example, the flat plate fixing electrode and the support member are fixed with screws at four corners. During the fixing, a gap is provided between the flat plate fixing electrode and the support member in the outer peripheral region of the fixing portion. Then, for example, the gap is adjusted according to the material and thickness of the flat plate fixing electrode, and further, the tightening torque to the support member of the flat plate fixing electrode is adjusted, and the displacement amount (protrusion amount) of the central portion of the flat plate fixing electrode is desired. Adjust to the size of.
This makes it easy to ensure the flatness of the rectangular plate-shaped fixed electrode, greatly improves the sandwichability of the diaphragm, improves the vibration and sound pressure characteristics, and has been a major problem in the past. Can prevent warping of the corner of the diaphragm, breakage of the diaphragm, and can eliminate the conventionally required sound pressure improvement countermeasure parts.

The electrostatic ultrasonic transducer according to the present invention is characterized in that the size of the gap is set in accordance with the material and thickness of the flat plate fixing electrode.
With such a configuration, the size of the gap is set according to the material and thickness of the flat plate fixing electrode, and the flat plate fixing electrode is fixed to the support member with an appropriate tightening torque. The displacement amount (projection amount) can be adjusted to a desired size.

In the electrostatic ultrasonic transducer according to the present invention, the gap between the flat plate fixed electrode and the support member may be formed by providing a step in the support member from the center portion to the outer peripheral portion of the fixed portion. Features.
With such a configuration, the gap between the flat plate fixed electrode and the support member is formed by providing a step on the support member from the center portion of the fixed portion toward the outer peripheral portion.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by performing surface processing to a supporting member.

In the electrostatic ultrasonic transducer according to the present invention, the gap between the flat plate fixed electrode and the support member may be formed by providing an inclination from the center of the fixed part toward the outer periphery of the support member. Features.
With such a configuration, the gap between the flat plate fixed electrode and the support member is formed by providing an inclination on the support member from the center portion of the fixed portion toward the outer peripheral portion.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by performing surface processing to a supporting member.

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 center portion of the fixed portion to the outer peripheral portion of the support member. Features.
With such a configuration, the gap between the flat plate fixed electrode and the support member is formed by providing a groove on the support member from the center portion to the outer peripheral portion of the fixed portion.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by performing surface processing to a supporting member.

In addition, the electrostatic ultrasonic transducer according to the present invention forms a thickened portion having a predetermined thickness on a surface of the flat plate fixed electrode in contact with the support member, and has an outer periphery from a fixed portion on the flat plate fixed electrode surface. In the outer peripheral area toward the portion, the fleshed portion is not formed and the surface of the flat plate fixed electrode is exposed.
With such a configuration, a thickened portion is provided, for example, by plating at the peripheral portion on the flat plate fixed electrode surface. And in the part of the outer peripheral area | region of the fixing | fixed site | part on a flat plate fixed electrode surface, a flat plate fixed electrode surface is exposed, without providing a fleshing part.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by surface-treating to the peripheral part on a flat plate fixed electrode surface.

The electrostatic ultrasonic transducer according to the present invention is characterized in that the thinned portion is formed by applying nickel plating to the surface of the flat plate fixed electrode or applying a conductive paste material.
As a result, a thickened portion having a desired shape and thickness can be easily formed on the surface of the flat plate fixed electrode.

In addition, the electrostatic ultrasonic transducer according to the present invention is configured such that the fixing method of the flat plate fixing electrode to the support member is screw fixing, and the protruding amount of the central portion of the flat plate fixing electrode is adjusted by the tightening torque. It is characterized by that.
With such a configuration, for example, when the flat plate fixing electrode has a rectangular shape or the like, screws are fixed to the support member at the four corners. At this time, the protruding amount of the central portion of the flat plate fixing 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 fixing electrode can be adjusted to a desired size by the tightening torque of the flat plate fixing electrode, greatly improving the clamping property of the vibrating membrane, and vibration / sound pressure The characteristics can be improved. In addition, it prevents the warping of the corner of the flat plate fixed electrode, which has been a big problem in the past, prevents the diaphragm from being damaged, and further eliminates the sound pressure improvement parts that were required in the past. A highly reliable and low-cost ultrasonic transducer can be provided.

The method for manufacturing an electrostatic ultrasonic transducer according to the present invention includes a first flat plate fixing electrode having a plurality of through holes and a plurality of through holes that are paired with the through holes of the first flat plate fixing electrode. A second flat plate fixed electrode; a first support member that supports the first flat plate fixed electrode by a fixed portion; a second support member that supports the second flat plate fixed electrode by a fixed portion; and a vibrating electrode And a vibrating membrane sandwiched between a pair of flat plate fixing electrodes comprising the first flat plate fixing electrode and the second flat plate fixing electrode, and applying a DC bias voltage to the vibrating electrode. A method of manufacturing an electrostatic ultrasonic transducer in which an AC signal is applied between the flat plate fixed electrodes to vibrate the vibration membrane, and the fixed portion is disposed in a portion near the outer peripheral portion of the flat plate fixed electrode; , Said flat A step of fixing the fixed electrode to the support member by the fixing portion and fixing the fixing electrode so as to provide a gap between the flat plate fixing electrode and the supporting member in the outer peripheral region from the fixing portion toward the outer peripheral portion. It is characterized by.
By such a procedure, a fixed part is provided on the flat plate fixing electrode, and the flat plate fixing electrode and the support member are fixed by this fixing part. For example, when the flat plate fixing electrode is rectangular, screws are fixed at four corners. At the time of this fixing, a clearance is provided between the flat plate fixing electrode and the support member in the outer peripheral region of the fixing part. Then, for example, the gap is adjusted according to the material and thickness of the flat plate fixing electrode, and further, the tightening torque to the support member of the flat plate fixing electrode is adjusted, and the displacement amount (protrusion amount) of the central portion of the flat plate fixing electrode is desired. Adjust to the size of.
This makes it easy to ensure the flatness of the plate-fixed electrode, greatly improves the sandwichability of the vibrating membrane, improves the vibration and sound pressure characteristics, and the corners of the plate-fixed electrode, which has been a big problem in the past Can be prevented, the diaphragm can be prevented from being damaged, and the sound pressure improvement component that has been required in the past can be eliminated.

The method for manufacturing an electrostatic ultrasonic transducer according to the present invention is characterized in that the flat plate fixing electrode is formed in a square shape and the fixing portions are provided at four corners of the flat plate fixing electrode.
According to such a procedure, when the flat plate fixing electrode is rectangular, fixing portions are provided at the four corners. For example, the flat plate fixing electrode and the support member are fixed with screws at four corners. During the fixing, a gap is provided between the flat plate fixing electrode and the support member in the outer peripheral region of the fixing portion. Then, for example, the gap is adjusted according to the material and thickness of the flat plate fixing electrode, and further, the tightening torque to the support member of the flat plate fixing electrode is adjusted, and the displacement amount (protrusion amount) of the central portion of the flat plate fixing electrode is desired. Adjust to the size of.
This makes it easy to ensure the flatness of the rectangular plate-shaped fixed electrode, greatly improves the sandwichability of the diaphragm, improves the vibration and sound pressure characteristics, and has been a major problem in the past. Can prevent warping of the corner of the diaphragm, breakage of the diaphragm, and can eliminate the conventionally required sound pressure improvement countermeasure parts.

In addition, the method for manufacturing an electrostatic ultrasonic transducer according to the present invention includes a step of setting the size of the gap according to the material and thickness of the flat plate fixing electrode.
By such a procedure, the size of the gap is set according to the material and thickness of the flat plate fixing electrode, and the flat plate fixing electrode is fixed to the support member with an appropriate tightening torque. The displacement amount (projection amount) can be adjusted to a desired size.

Further, in the method for manufacturing an electrostatic ultrasonic transducer according to the present invention, the gap between the flat plate fixing electrode and the support member is formed by providing a step from the center portion of the fixing portion of the support member toward the outer peripheral portion. It is characterized by including.
By such a procedure, the gap between the flat plate fixed electrode and the support member is formed by providing a step on the support member from the center portion to the outer peripheral portion of the fixed portion.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by performing surface processing on a supporting member.

Further, in the method of manufacturing an electrostatic ultrasonic transducer according to the present invention, the gap between the flat plate fixing electrode and the support member is formed by providing an inclination from the center portion to the outer peripheral portion of the fixing 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 center portion of the fixed portion toward the outer peripheral portion on the support member.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by performing surface processing on a supporting member.

Further, in the method of manufacturing an electrostatic ultrasonic transducer according to the present invention, the gap between the flat plate fixing electrode and the support member is formed by providing a groove from the center portion to the outer peripheral portion of the fixing portion of the support member. It is characterized by including.
According to such a procedure, the gap between the flat plate fixing electrode and the support member is formed by providing a groove on the support member from the center portion of the fixed portion toward the outer peripheral portion.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by performing surface processing on a supporting member.

In the method of manufacturing an electrostatic ultrasonic transducer according to the present invention, a fixed portion having a predetermined thickness is formed on a surface of the flat plate fixed electrode that is in contact with the support member, and fixed on the flat plate fixed electrode surface. In the outer peripheral region from the part to the outer peripheral part, the procedure includes exposing the surface of the flat plate fixing electrode without forming the fleshing part.
By such a procedure, a thickened portion is provided, for example, by plating at the peripheral portion on the flat plate fixed electrode surface. And in the part of the outer peripheral area | region of the fixing | fixed site | part on a flat plate fixed electrode surface, a flat plate fixed electrode surface is exposed, without providing a fleshing part.
Thereby, the clearance gap between a flat plate fixed electrode and a supporting member can be easily formed by surface-treating to the peripheral part on a flat plate fixed electrode surface.

Moreover, the manufacturing method of the electrostatic ultrasonic transducer according to the present invention includes a procedure for forming the fleshed portion by applying nickel plating to the surface of the flat plate fixed electrode or applying a conductive paste material. It is characterized by that.
As a result, a thickened portion having a desired shape and thickness can be easily formed on the surface of the flat plate fixed electrode.

The method of manufacturing the electrostatic ultrasonic transducer according to the present invention is a procedure in which the fixing method of the flat plate fixing electrode to the support member is screw fixing, and the projection amount of the central portion of the flat plate fixing electrode is adjusted by the tightening torque. It is characterized by including.
By such a procedure, for example, when the flat plate fixing electrode has a rectangular shape or the like, screws are fixed to the support member at the four corners. At this time, the protruding amount of the central portion of the flat plate fixing 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 fixing electrode can be adjusted to a desired size by the tightening torque of the flat plate fixing electrode, greatly improving the clamping property of the vibrating membrane, and vibration / sound pressure The characteristics can be improved. In addition, it prevents the warping of the corner of the flat plate fixed electrode, which has been a big problem in the past, prevents the diaphragm from being damaged, and further eliminates the sound pressure improvement parts that were required in the past. A highly reliable and low-cost ultrasonic transducer can be provided.

The ultrasonic speaker according to the present invention includes an audible frequency signal source that generates an audible frequency band signal wave, a carrier wave signal source that generates and outputs an ultrasonic frequency carrier wave, and the audible carrier wave. An ultrasonic wave comprising: a modulator that modulates a signal wave in a frequency band; a power amplifier that amplifies and outputs a modulation signal output from the modulator; and an electrostatic ultrasonic transducer that is driven by the power amplifier. The electrostatic ultrasonic transducer in the ultrasonic speaker includes a plurality of penetrations paired with a first flat plate fixing electrode having a plurality of through holes and a through hole of the first flat plate fixing electrode. A second flat plate fixing electrode having a hole; a first support member for supporting the first flat plate fixing electrode by a fixing portion; and a second support for supporting the second flat plate fixing electrode by a fixing portion. And a vibrating membrane having a vibrating electrode and sandwiched between a pair of flat plate fixing electrodes comprising the first flat plate fixing electrode and the second flat plate fixing electrode, and a DC bias voltage is applied to the vibrating electrode. The fixing portion is disposed in a portion near the outer peripheral portion of the flat plate fixing electrode, and a gap is provided between the flat plate fixing electrode and the support member in an outer peripheral region from the fixing portion toward the outer peripheral portion. It is comprised, It is comprised so that an alternating current signal may be applied between a pair of said flat plate fixed electrodes, and a vibration film may be vibrated.
With such a configuration, in the electrostatic ultrasonic transducer used in the ultrasonic speaker, when the flat plate fixing electrode is attached to the support member, the flat plate fixing electrode is disposed in the outer peripheral region of the fixing portion (for example, a screw fixing portion). A gap is provided between the support member and the support member. And the displacement amount (protrusion amount) of the center part of a flat plate fixed electrode is adjusted to a desired magnitude | size by fixing a flat plate fixed electrode to a support member with an appropriate fastening torque.
As a result, in an electrostatic ultrasonic transducer used for an ultrasonic speaker, it is easy to ensure the flatness of the plate-fixed electrode, greatly improve the clamping property of the vibrating membrane, and improve the vibration and sound pressure characteristics. Can do.

The display device of the present invention modulates a carrier wave signal in an ultrasonic frequency band with an audio signal supplied from an acoustic source, and drives an electrostatic ultrasonic transducer with the modulated signal to generate a signal sound in an audible frequency band. A display device comprising: an ultrasonic speaker to be reproduced; and a projection optical system that projects 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 fixing electrode, a second flat plate fixing electrode having a plurality of through holes that are paired with the through holes of the first flat plate fixing electrode, and a first portion that supports the first flat plate fixing electrode by a fixing portion. A pair of flat plates having a vibration electrode and comprising the first flat plate fixing electrode and the second flat plate fixing electrode. Fixed A vibrating membrane sandwiched between poles and applied with a DC bias voltage to the vibrating electrode, and the fixing portion is disposed in a portion near the outer peripheral portion of the flat plate fixing electrode, and from the fixing portion to the outer peripheral portion. In the outer peripheral area toward the surface, 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 vibrating membrane. It is characterized by.
With such a configuration, in an electrostatic ultrasonic transducer in an ultrasonic speaker used in a display device including a projection optical system for projecting an image, when a flat plate fixing electrode is attached to a support member, a fixing portion (for example, In the outer peripheral region of the screw fixing portion or the like, a gap is provided between the flat plate fixing electrode and the support member. And the displacement amount (protrusion amount) of the center part of a flat plate fixed electrode is adjusted to a desired magnitude | size by fixing a flat plate fixed electrode to a support member with an appropriate fastening torque.
As a result, in the ultrasonic speaker used in the display device, it is easy to ensure the flatness of the plate-fixed electrode of the electrostatic ultrasonic transducer, greatly improves the sandwichability of the vibrating membrane, and has the vibration / sound pressure characteristics. Can be improved.

Further, the directional acoustic system of the present invention modulates a carrier wave signal in an ultrasonic frequency band with a signal in a first sound range among audio signals supplied from an acoustic source, and an electrostatic ultrasonic transducer is modulated with the modulated signal. An ultrasonic speaker that drives and reproduces signal sound in an audible frequency band; and a low-frequency sound reproduction speaker that reproduces a signal in a second sound range lower than the first sound range among sound signals supplied from the acoustic source; The electrostatic ultrasonic transducer in the ultrasonic speaker includes: a first flat plate fixing electrode having a plurality of through holes; and a through hole of the first flat plate fixing electrode. A second flat plate fixing electrode having a plurality of pairs of through holes, a first support member that supports the first flat plate fixing electrode by a fixing portion, and the second flat plate fixing electrode by a fixing portion. A second supporting member to be held, a vibration electrode, and sandwiched between a pair of flat plate fixing electrodes including the first flat plate fixing electrode and the second flat plate fixing electrode, and a DC bias voltage is applied to the vibrating electrode. The fixed portion is disposed in a portion close to the outer peripheral portion of the flat plate fixed electrode, and in the outer peripheral region from the fixed portion toward the outer peripheral portion, between the flat plate fixed electrode and the support member. A gap is provided between the pair of flat plate fixed electrodes, and an AC signal is applied between the pair of flat plate fixed electrodes to vibrate the vibrating membrane.
With such a configuration, when attaching the flat plate fixed electrode to the support member in the electrostatic ultrasonic transducer used in the ultrasonic speaker that reproduces the signal in the first sound range among the audio signals supplied from the acoustic source. A gap is provided between the flat plate fixing electrode and the support member in the outer peripheral region of the fixing portion (for example, a screw fixing portion). And the displacement amount (protrusion amount) of the center part of a flat plate fixed electrode is adjusted to a desired magnitude | size by fixing a flat plate fixed electrode to a support member with an appropriate fastening torque.
As a result, in the ultrasonic speaker used in the directional acoustic system, it is easy to ensure the flatness of the plate fixed electrode of the electrostatic ultrasonic transducer, greatly improve the clamping property of the vibrating membrane, and the vibration / sound pressure The characteristics can be improved.

  In the electrostatic ultrasonic transducer of the present invention, a gap is provided between the flat plate fixing electrode and the support member in the outer peripheral region of a fixing portion (for example, a screw fixing portion) that fixes the flat plate fixing electrode to the support member.

  For example, when the flat plate fixing electrode is rectangular, it is screwed to the support member at the four corners. During this fixing, a gap is provided between the flat plate fixing 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 electrode material and thickness, the center portion of the flat plate fixing electrode is protruded with a desired dimension, and the holding property of the vibrating membrane when the flat plate fixing electrode is opposed is enhanced.

The best mode for carrying out the present invention will be described below with reference to the drawings.
In the example of the embodiment described below, an example in which the flat plate fixing electrode is square and screws are fixed to the support member at four corners is shown. However, the shape of the flat plate fixing electrode is not limited to the square shape. Various shapes such as a circular shape and an oval shape can be used. The fixing parts are not limited to the four corners, and the fixing method is not limited to screw fixing.

[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.

  In the first embodiment of the present invention, as shown in FIG. 10, the fixed portions 22 of the flat plate fixing electrode 21 and the support member 31 are set to four locations at four corners of the flat plate fixing electrode, and the minimum mechanical strength is obtained. Place it as far as possible within the range that can be secured.

  FIG. 1 is a view showing a method of attaching a flat plate fixed electrode to a support member according to the present invention. As shown in FIG. 1 (A), a step 33 is provided as a gap in the outer peripheral area of the fixing part of the support member 31 (outer area from the fixing part toward the outer peripheral part), or as shown in FIG. 1 (B). An inclination 34 is provided as a gap. The starting point of the step 33 or the slope 34 is near the center of the fixed portion 22, and as a result, an appropriate gap is generated between the flat plate fixed electrode 21 and the support member 31 in the outer region of the fixed portion 22.

  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 one step higher, like the groove 35 shown in FIG. A structure in which the groove 35 is dug on the plane of the support member 31 may be used, and this structure requires fewer processing steps and can reduce the cost.

  In such a configuration, the fastening force due to fixation acts as a bending stress in the outer region (outer peripheral region) of the fixing portion 22 of the flat plate fixing electrode 21. Therefore, the flat plate fixing electrode 21 bends in the tightening direction in the outer region of the fixing portion 22. On the other hand, in the inner region of the fixed portion 22, the flat plate fixing electrode 21 bends in the direction opposite to the tightening direction. As a result, the central portion of the flat plate fixing electrode 21 protrudes and the corner portion of the flat plate fixing electrode 21 is bent.

  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 plate fixing electrode 21 can be adjusted by a gap provided between the flat plate fixing electrode 21 and the support member 31 and a tightening force (tightening load) of the flat plate fixing electrode 21. .

Moreover, FIG. 2 is a figure which shows the other attachment method to the supporting member of the flat fixed electrode by this invention.
In the example shown in FIG. 2, the support member 31 is not provided with a gap such as a step 33 as shown in FIG. This is an example in which an exposed portion (a portion where the surface of the flat plate fixed electrode 21 is exposed from the flesh portion 23) 24 is provided. In this manner, by providing the flesh portion 23 and the exposed portion 24, the same effect as when the gap is provided in the support member 31 can be obtained.

  The meat portion 23 can be easily formed on the flat plate fixed electrode 21 by, for example, nickel plating or applying a conductive paste material.

  Next, an example in which a simulation is performed in order to verify the relationship between the protruding amount of the central portion of the flat plate fixing electrode 21 and the tightening force at the fixed portion of the flat plate fixing electrode 21 will be described. For the simulation, structural analysis software “I-DEAS (registered trademark)” is used.

In this simulation,
As the “analysis model”, a flat plate fixed electrode (with a through hole), a shell element, a thickness of 1.0 mm / 1.5 mm / 2.0 mm, an element number of 23221, and a node number of 13235 are used.
There are two types of “material conditions”: aluminum and stainless steel.
As the “constraint condition”, the flat plate 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”, a tightening force converted from the tightening torque is applied to the flat plate fixed electrode screw fixing range in terms of surface pressure.

  In addition, the characteristic values of each material are as shown in FIG. 4A, and four conditions were applied as analytical model load conditions as shown in FIG. 4B. The load condition was 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.

  FIG. 4C shows the protrusion amount of the central portion of the flat plate fixed electrode obtained by the above analysis model and analysis conditions. Further, the bending amount of the flat plate fixed electrode corner is shown in FIG.

  FIG. 5 is a graph showing the amount of protrusion at the center of the flat plate fixed electrode. As can be seen from FIG. 5, for each electrode thickness, a linear relationship is established between the tightening force and the protrusion amount. Therefore, if the material and thickness of the flat plate fixing electrode 21 are determined, the tightening force necessary to obtain a desired amount of displacement is determined, and therefore the tightening torque of the fixing screw may be adjusted.

  Moreover, when only the electrode thickness is determined and it is desired to secure a desired amount of protrusion, an appropriate material is selected and the tightening force is adjusted. For example, when the electrode thickness is 1.5 mm and the desired displacement is 5 μm, aluminum is selected as the material from the table shown in FIG. 4C (or the graph shown in FIG. 5), and tightening is performed. The force may be 25 kg (10 cN / m). If the electrode thickness is 1.0 mm and the desired displacement is 5 μm, stainless steel is selected as the material and the tightening force is 25 kg (10 cN / m).

  Here, in the case of an aluminum electrode having an electrode thickness of 1.5 mm, in order to obtain a displacement of 5 μm, it is shown in FIG. You can see from the table. A gap larger than this must be provided between the flat plate fixed electrode and the support member. However, since the amount of bending can be adjusted by tightening torque, the gap may be slightly larger (several tens of μm). There is no problem, so that the processing accuracy can be relaxed and the manufacturing cost can be reduced.

  FIG. 6 shows an electrostatic ultrasonic transducer configured based on the manufacturing method of the present invention, FIG. 6 (A) is a top view thereof, and FIG. 6 (B) is a cross-sectional view taken along line AA ′. It is. The electrostatic ultrasonic transducer 2 shown in FIG. 6 opposes the front side flat plate fixed electrode 21A fixed to the support member 31A and the back side flat plate fixed electrode 21B fixed to the support member 31B in the same manner. The vibration film 12 fixed by the film frame 33 is disposed and sandwiched between the vibration films 12.

  The front plate fixing electrode 21A corresponds to the first plate fixing electrode described above, the support member 31A corresponds to the first supporting member described above, and the rear plate fixing electrode 21B corresponds to the second plate fixing electrode described above. The support member 31B corresponds to the electrode, and corresponds to the second support member described above. Further, the front side flat plate fixed electrode 21A and the back side flat plate fixed electrode 21B are collectively referred to as the flat plate fixed electrode 21, and the support member 31A and the support member 31B are collectively referred to as the support member 31.

  The basic configuration and operation of the electrostatic ultrasonic transducer 2 shown in FIG. 6 are the same as those of the electrostatic ultrasonic transducer 1 shown in FIG. That is, as shown in FIG. 8, the vibration film 12 is formed so that the vibration electrode 121 deposited with Al (aluminum) is sandwiched between the dielectric films 120. In addition, the two flat plate fixed electrodes 21 constituting the vibration space of the vibration film 12 sandwich the vibration film 12 deposited with Al, and the vibration electrode 121 of the vibration film 12 is positively biased with a DC bias (reference) by a DC bias power source. Condition 250V) and applying an AC signal (reference condition 250Vpp) so as to be in opposite phase to the opposing flat plate fixing electrode 21, while a positive AC signal is applied to the flat plate fixing electrode on one side, Since a negative AC signal is applied to the other flat plate fixing electrode, an electrostatic attractive force and an electrostatic repulsive force always act between the vibrating membrane 12 and the flat plate fixing electrode 21. As a result, the vibrating membrane 12 vibrates in accordance with the AC signal, generates a sound wave, and is radiated in both directions of the flat plate fixed electrode 21.

  FIG. 7 is a view for explaining a process for manufacturing a flat plate fixed electrode of the electrostatic ultrasonic transducer according to the present invention. Hereinafter, with reference to FIG. 7, the manufacturing process of the flat plate fixed electrode will be described.

  First, as shown in FIG. 7A, a flat plate fixed electrode base material made of a conductor 51 in which a through hole 13 is formed by machining, pressing, or etching and bonding is prepared.

  Next, as shown in FIG. 7B, a counter electrode forming mask serving as a screen plate for forming the counter 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, the squeegee 54 is moved, and the counter electrode forming material 53 is applied to a portion where no mask is applied.

  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 in a circuit board. And masking inks used as sandblast resists.

  In particular, the solder resist for flexible printed circuit boards is relatively soft (pencil hardness is about HB to 3H), so it has excellent adhesion strength with metals and various conductors (such as conductive resins), and is a polymer film. The vibration film made of

  Then, as shown in FIG. 7C, when the counter electrode forming mask member 52, which is a screen plate for forming the counter electrode, is removed after the application of the counter electrode forming material 53 is completed, the other portions except the counter electrode portion are removed. A non-conductive layer (= counter electrode forming body) remains and is dried to obtain a desired flat plate fixed electrode.

  As described above, in the electrostatic ultrasonic transducer according to the present invention, a gap is provided between the flat plate fixing electrode and the support member in the outer peripheral region of the fixing portion where the flat plate fixing electrode is fixed to the support member. For example, the flat plate fixing electrode has a rectangular shape, and when the screws are fixed to the support member at the four corners, a gap is provided between the flat plate fixing 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 fixing electrode, and further adjusting the tightening torque to the support member of the flat plate fixing electrode, the displacement amount (protrusion amount) of the central portion of the flat plate fixing electrode is desired. Adjust to the size of. As a result, the sandwichability of the vibration membrane can be greatly improved, and the vibration / sound pressure characteristics can be improved. In addition, it prevents the warping of the corner of the flat plate fixed electrode, which has been a big problem in the past, prevents the diaphragm from being damaged, and further eliminates the sound pressure improvement parts that were required in the past. A highly reliable and low cost ultrasonic transducer can be provided.

[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.

  FIG. 12 is a diagram 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 the audio frequency band, and a carrier wave signal source 102 that generates and outputs a carrier wave in the ultrasonic frequency band. , A modulator 103 and a power amplifier 104.

  The ultrasonic speaker performs AM modulation on an ultrasonic wave called a carrier wave with an audio signal (audible area signal), and when this is emitted into the air, the original audio signal is self-reproduced in the air due to the nonlinearity of air. That's it. In other words, since sound waves are coarse and dense waves that propagate using air as a medium, the dense and sparse portions of the air appear prominently in the process of the modulated ultrasonic waves propagating, and the dense portions have high sound speed and sparseness. Since the speed of sound is slow in this part, the modulation wave itself is distorted. As a result, the waveform is separated into a carrier wave (ultrasonic wave) and an audible wave (original audio signal), and we humans audible sound (original audio signal) below 20 kHz. This is the principle that only listening can be heard, and it is generally called the parametric array effect.

  In the above configuration, the carrier wave in 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 modulated signal amplified in step 1 is applied to both ends of the primary winding of the output transformer T.

  One terminal on the secondary side of the output transformer T is connected to the front plate fixing electrode 21A of the electrostatic ultrasonic transducer 2 (see FIG. 6) of the present invention, and the other terminal is connected to the back plate fixing electrode 21B. Has been. A center tap is provided in the secondary winding of the output transformer T, and a DC bias voltage VB is applied to the vibration electrode 121 of the electrostatic ultrasonic transducer 2 with the center tap as a reference.

  As shown in FIG. 12, by connecting the output transformer T and the electrostatic ultrasonic transducer 2, an alternating voltage having the same amplitude with reversed phases is applied to the front plate fixing electrode 21 </ b> A and the rear plate fixing electrode 21 </ b> B. Therefore, a sound wave with small distortion can be output.

  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 plate fixed electrode 21 of the electrostatic ultrasonic transducer 2 is These are attached to the support member 31 by the method shown in FIG. 1 or FIG. As a result, the sandwichability of the vibration membrane can be greatly improved, and the vibration / sound pressure characteristics can be improved. In addition, the corners of the plate-fixed electrode are prevented from warping, the diaphragm is prevented from being damaged, and the sound pressure improvement parts that were required in the past have been deleted, providing high performance, high reliability, and low cost. A sound wave speaker can be provided.

[Third Embodiment]
Next, as a third embodiment of the present invention, an example of a display device including an ultrasonic speaker using the electrostatic ultrasonic transducer of the present invention will be described.

  FIG. 13 shows an example of a display device in which a projector incorporating an ultrasonic speaker is taken as an example, and its use state is shown. As shown in the figure, the projector 201 is installed behind the viewer 203, projects an image on a screen 202 installed in front of the viewer 203, and uses an ultrasonic speaker mounted on the projector 201 to screen 202. A virtual sound source is formed on the projection plane and the sound is reproduced. Note that an acoustic device using an ultrasonic speaker that forms a virtual sound source on a projector screen, a projector with a built-in ultrasonic speaker, and the like are also called a directional acoustic system.

An external configuration of the projector 201 is shown in FIG. The projector 201 includes a projector main body 220 including a projection optical system that projects an image on a projection surface such as a screen, and electrostatic ultrasonic transducers 224A and 224B that can oscillate sound waves in an ultrasonic frequency band. And an ultrasonic speaker that reproduces a signal sound in an audible frequency band from an audio signal supplied from the audio signal. In the present embodiment, in order to reproduce a stereo audio 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 low-pitched sound reproduction speaker 223 is provided on the bottom surface of the projector main body 220. Reference numeral 225 denotes a height adjusting screw for adjusting the height of the projector main body 220, and reference numeral 226 denotes an air cooling fan exhaust port.

  As described above, the projector 201 includes an ultrasonic speaker using an electrostatic ultrasonic transducer, and thereby oscillates an acoustic signal in a wide frequency band (sound wave in the ultrasonic frequency band) with high sound pressure. Can do. Then, by controlling the spatial reproduction range of the reproduction signal in the audible frequency band by changing the frequency of the carrier wave, the acoustic effect that can be obtained in a stereo surround system or 5.1ch surround system is conventionally required. Thus, it is possible to realize a projector that can be realized without requiring a large-scale sound system and is easy to carry.

  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 static An ultrasonic speaker including electric ultrasonic transducers 224A and 224B, a high-pass filter 217A and 217B, a low-pass filter 219, a mixer 221, a power amplifier 222C, a low-frequency sound reproduction speaker 223, and a projector main body 220. ing. The electrostatic ultrasonic transducers 224A and 224B are electrostatic ultrasonic transducers in which the flat plate fixing electrode is fixed to the support member by the method shown in FIG. 1 or FIG.

  The projector main body 220 includes a video generation unit 232 that generates a video, and a projection optical system 233 that projects the generated video onto 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.

  The operation input unit 210 has various function keys including a numeric keypad, numeric keys, and a power key for turning the power on and off. The reproduction range setting unit 212 can input data for specifying the reproduction range of a reproduction signal (signal sound) by the user operating the operation input unit 210 with a key. The frequency of the carrier wave that defines the reproduction range of the signal is set and held. The reproduction range of the reproduction signal is set by designating a distance that the reproduction signal reaches in the radial axis direction from the sound wave emitting surfaces of the electrostatic ultrasonic transducers 224A and 224B.

The reproduction range setting unit 212 can set the frequency of the carrier wave by a control signal output from the audio / video signal reproduction unit 214 according to the video content.
Also, the reproduction range control processing unit 213 refers to the setting contents of the reproduction range setting unit 212, and changes the carrier wave frequency generated by the carrier wave oscillation source 216 so as to be within 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 the internal information of the reproduction range setting unit 212, the carrier wave oscillation source 216 is controlled to oscillate at 50 kHz.

The reproduction range control processing unit 213 previously stores a table indicating the relationship between the distance that the reproduction signal reaches in the radial axis direction from the sound wave emitting surfaces of the electrostatic ultrasonic transducers 224A and 224B that define the reproduction range and the frequency of the carrier wave. A storage unit is stored. The data in this table is 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 table based on the setting content of the reproduction range setting unit 212, and oscillates the carrier wave so as to be the frequency. Control the source 216.

The audio / video signal reproducing unit 214 is, for example, a DVD player that uses a DVD as a video medium, and among the reproduced audio signals, the R channel audio signal is sent to the modulator 218A via the high-pass filter 217A. The signal is output to the modulator 218B via the high-pass filter 217B, and the video signal is output to the video generation unit 232 of the projector main body 220.
The R channel audio signal and the L channel audio signal output from the audio / video signal reproduction unit 214 are combined by the mixer 221 and input to the power amplifier 222C via the low pass filter 219. . The audio / video signal reproduction unit 214 corresponds to an acoustic source.

The high-pass filters 217A and 217B have characteristics that allow only the frequency components in the middle and high frequencies in the R-channel and L-channel audio signals to pass, and the low-pass filters are low-frequency filters in the R-channel and L-channel audio signals. It has the characteristic of passing only the frequency component of the sound range.
Accordingly, the mid-high range audio signals of the R channel and L channel audio signals are reproduced by the electrostatic ultrasonic transducers 224A and 224B, respectively, and the low range audio signals of the R channel and L channel audio signals are reproduced. The signal is reproduced by the bass reproduction speaker 223.

  The audio / video signal playback unit 214 is not limited to a DVD player, and may be a playback device that plays back a video signal input from the outside. In addition, the audio / video signal reproduction unit 214 instructs the reproduction range setting unit 212 to dynamically change the reproduction range of the reproduction sound in order to produce an acoustic effect according to the scene of the reproduced video. Has a function of outputting a control signal.

The carrier wave oscillation source 216 has a function of generating a carrier wave having a frequency in the ultrasonic frequency band designated by the reproduction range setting unit 212 and outputting the carrier wave to the modulators 218A and 218B.
Modulators 218A and 218B AM modulate the carrier wave supplied from carrier wave oscillation source 216 with an audio signal in an audible frequency band output from audio / video signal reproduction unit 214, and each of the modulated signals is power amplifier 222A. , 222B.

  The electrostatic ultrasonic transducers 224A and 224B are driven by the modulation signals output from the modulators 218A and 218B via the power amplifiers 222A and 222B, respectively, and convert the modulation signals into sound waves of a finite amplitude level. It has a function of emitting signal sound (reproduction signal) in the audible frequency band.

The video generation unit 232 includes a display such as a liquid crystal display and a plasma display panel (PDP), a drive circuit that drives the display based on a video signal output from the audio / video signal reproduction unit 214, and the like. A video 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 the display onto a projection surface such as a screen installed in front of the projector main body 220.

  Next, the operation of the projector 201 having the above configuration will be described. First, data (distance information) for instructing the reproduction range of the reproduction signal is set in the reproduction range setting unit 212 from the operation input unit 210 by the user's key operation, and a reproduction instruction is given to the audio / video signal reproduction unit 214.

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 carrier wave oscillation source 216 is controlled so as to obtain the frequency of the carrier wave corresponding to the set distance information with reference to the set table and to generate the carrier wave of the frequency.
As a result, the carrier wave oscillation source 216 generates a carrier wave having 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.

  On the other hand, the audio / video signal reproduction unit 214 outputs the R channel audio signal to the modulator 218A via the high pass filter 217A and the L channel audio signal to the modulator 218B via the high pass filter 217B. In addition, the R channel audio signal and the L channel audio signal 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.

Accordingly, the high-pass filter 217A inputs the mid-high range audio signal of the R channel audio signal to the modulator 218A, and the high-pass filter 217B converts the mid-high range audio signal of the L channel audio signal to the modulator 218B. Is input.
The R channel audio signal and the L channel audio signal are combined by the mixer 221, and the low frequency audio signal of the R channel audio signal and the L channel audio signal is input to the power amplifier 222 C by the low pass filter 219. Is done.

The video generation unit 232 generates a video by driving the display based on the input video signal, and displays the video. The video displayed on the display is projected onto a projection surface, for example, the screen 202 shown in FIG. 13 by the projection optical system 233.
On the other hand, the modulator 218A AM-modulates the carrier wave output from the carrier wave oscillation source 216 with the mid to high frequency audio signal in the R channel audio signal output from the high pass filter 217A, and outputs the result to the power amplifier 222A. .
The modulator 218B AM-modulates the carrier wave output from the carrier wave oscillation source 216 with the mid-high range audio signal in the L-channel audio signal output from the high-pass filter 217B, and outputs the result to the power amplifier 222B. .

The modulation signals amplified by the power amplifiers 222A and 222B are respectively converted into front-side flat plate fixed electrodes (upper electrodes) 21A and rear-side flat plate fixed electrodes (lower electrodes) 21B (see FIG. 6) of the electrostatic ultrasonic transducers 224A and 224B. The modulation signal is converted into a sound wave (acoustic signal) of a finite amplitude level, radiated to a medium (in the air), and the electrostatic ultrasonic transducer 224A receives the signal of the R channel. An audio signal in the middle and high range in the audio signal is reproduced, and an audio signal in the middle and high range in the L channel audio signal is reproduced from the electrostatic ultrasonic transducer 224B.
In addition, the low-frequency sound signal in the R channel and the L channel amplified by the power amplifier 222C is reproduced by the low sound reproduction speaker 223.

  As described above, in the propagation of ultrasonic waves radiated into a medium (in the air) by an electrostatic ultrasonic transducer, the sound speed increases at a portion where the sound pressure is high, and at a portion where the sound pressure is low. The speed of sound slows down. As a result, waveform distortion occurs.

  When a signal (carrier wave) in the radiated ultrasonic band is modulated (AM modulation) with a signal in the audible frequency band, the signal wave in the audible frequency band used for modulation is super It is formed so as to be self-demodulated separately from the carrier wave in the sonic frequency band. At this time, the spread of the reproduction signal becomes a beam shape due to the characteristics of ultrasonic waves, and the sound is reproduced only in a specific direction completely different from that of a normal speaker.

  Beam-shaped reproduction signals output from the electrostatic ultrasonic transducers 224A and 224B constituting the ultrasonic speaker are radiated toward a projection plane (screen) on which an image is projected by the projection optical system 233, and are projected on the projection plane. Reflected and diffused. In this case, in accordance with the frequency of the carrier wave set in the reproduction range setting unit 212, the reproduction signal from the carrier wave in the radial axis direction (normal direction) from the sound wave emission surface of the electrostatic ultrasonic transducers 224A and 224B. Since the distance until the two are separated and the beam width (beam divergence angle) of the carrier wave are different, the reproduction range changes.

  FIG. 16 shows a state in which a reproduction signal is reproduced by an ultrasonic speaker including the electrostatic ultrasonic transducers 224A and 224B in the projector 201. In the projector 201, when the electrostatic ultrasonic transducer is driven by the modulation signal obtained by modulating the carrier wave with the audio signal, if the carrier frequency set by the reproduction range setting unit 212 is low, the electrostatic ultrasonic wave The distance from the sound wave emission surface of the transducers 224A and 224B to the separation of the reproduction signal from the carrier wave in the radial axis direction (normal direction of the sound wave emission surface), that is, the distance to the reproduction point is increased.

  Accordingly, the reproduced reproduction signal beam in the audible frequency band reaches the projection surface (screen) 202 without being relatively expanded, and is reflected on the projection surface 202 in this state. Therefore, the reproduction range is as shown in FIG. , The audible range A is indicated by a dotted arrow, and a playback signal (playback sound) can be heard only in a relatively far and narrow range from the projection plane 202.

  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 emitted from the sound wave emitting surfaces of the electrostatic ultrasonic transducers 224A and 224B has a low carrier frequency. Although it is more narrowed down, the distance until the reproduction signal is separated from the carrier wave in the radial axis direction (normal direction of the acoustic wave emission surface) from the sound wave emission surface of the electrostatic ultrasonic transducers 224A and 224B, that is, The distance to the playback point is shortened.

  Therefore, the reproduced reproduction signal beam in the audible frequency band spreads to reach the projection surface 202 before reaching the projection surface 202, and is reflected on the projection surface 202 in this state. 16, an audible range B indicated by a solid arrow is obtained, and a playback signal (reproduced sound) can be heard only in a relatively close and wide range from the projection surface 202.

  Although the display device (projector or the like) 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 fixed plate electrode of the electrostatic ultrasonic transducer. The support member is fixed by the method shown in FIG. 1 or FIG. Thereby, in the ultrasonic speaker in the display device, the sandwichability of the vibration film can be greatly improved, and the vibration / sound pressure characteristics can be improved. In addition, the corners of the plate-fixed electrode are prevented from warping, the diaphragm is prevented from being damaged, and the sound pressure improvement parts that were required in the past have been deleted, providing high performance, high reliability, and low cost. A sound wave speaker can be provided.

  The projector described above is used for viewing images on a large screen. Recently, large-screen liquid crystal televisions and large-screen plasma televisions are rapidly spreading, and those large-screen televisions are also used. The ultrasonic speaker using the electrostatic transducer of the present invention can be used effectively.

  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.

  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 illustrated examples described above, and the gist of the present invention is described. Of course, various changes can be made without departing from the scope.

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 fixed electrode. The figure which shows the example of the 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 fixed electrode. The figure which displayed the simulation result in the graph. 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 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 fixed electrode. The figure which shows the example of the curvature 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. FIG. 3 is a diagram illustrating a usage state of the projector according to the embodiment of the invention. FIG. 14 is a diagram showing an external configuration of the projector shown in FIG. 13. 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 signal by an electrostatic type ultrasonic transducer.

Explanation of symbols

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 membrane, 13, 13A, 13B ... penetrating Hole 14, bias power source 21, flat plate fixed electrode, 21 A, front side flat plate fixed electrode, 21 B, back side flat plate fixed electrode, 22, fixed portion, 23, flesh portion, 24, exposed portion, 31, 31 A, 31 B DESCRIPTION OF SYMBOLS ... Support member, 32 ... Fixed part, 33 ... Step, 34 ... Inclination, 35 ... Groove, 41 ... Case member, 51 ... Conductor, 52 ... Counter electrode forming mask member, 53 ... Counter electrode forming material, 54 ... Squeegee DESCRIPTION OF SYMBOLS 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 ... reproduction range setting unit, 213 ... reproduction range control processing unit, 214 ... audio / video signal reproduction unit, 216 ... carrier wave oscillation source, 217A, 217B ... high-pass filter, 218A, 218B ... modulator, 219 ... low-pass filter, 220 ... projector body, 221 ... mixer, 222A, 222B ... power amplifier, 222C ... power amplifier, 223 low-frequency sound reproduction speaker, 224A, 224B ... electrostatic type Ultrasonic transducer, 231 ... projector lens, 232 ... video generation unit, 233 ... projection optical system

Claims (21)

A first flat plate fixed electrode having a plurality of through holes;
A second flat plate fixing electrode having a plurality of through holes paired with the through holes of the first flat plate fixing electrode;
A first support member for supporting the first flat plate fixed electrode by a fixed portion;
A second support member for supporting the second flat plate fixed electrode by a fixed portion;
A vibrating membrane having a vibrating electrode and sandwiched between a pair of flat plate fixed electrodes comprising the first flat plate fixed electrode and the second flat plate fixed electrode, and a DC bias voltage applied to the vibrating electrode;
Have
While arranging the fixed part in a portion near the outer peripheral portion of the flat plate fixed electrode,
In the outer peripheral region from the fixed part toward the outer peripheral part, it is configured to provide a gap between the flat plate fixed electrode and the support member,
An AC signal is applied between the pair of flat plate fixed electrodes to vibrate the vibrating membrane;
An electrostatic ultrasonic transducer characterized by the above. The flat plate fixed electrode is configured in a square shape,
The electrostatic ultrasonic transducer according to claim 1, wherein the fixed parts are four corners of the flat plate fixed electrode. The electrostatic ultrasonic transducer according to claim 1 or 2, wherein a size of the gap is set according to a material and a thickness of the flat plate fixed electrode. 4. The gap between the flat plate fixed electrode and the support member is formed by providing a step in the support member from the center portion to the outer peripheral portion of the fixed portion. 5. Electrostatic ultrasonic transducer. 4. The gap between the flat plate fixing electrode and the support member is formed by providing an inclination from the center portion to the outer peripheral portion of the fixed portion in the support member. 5. Electrostatic ultrasonic transducer. 4. The gap between the flat plate fixed electrode and the support member is formed by providing a groove from the center portion to the outer peripheral portion of the fixed portion in the support member. 5. Electrostatic ultrasonic transducer. On the surface of the flat plate fixed electrode in contact with the support member, a thickened portion having a predetermined thickness is formed,
4. The structure according to claim 1, wherein in the outer peripheral region from the fixed portion on the flat plate fixed electrode surface toward the outer peripheral portion, the surface of the flat plate fixed electrode is exposed without forming the flesh portion. The electrostatic ultrasonic transducer according to any one of the above. The electrostatic ultrasonic transducer according to claim 7, wherein the thinned portion is formed by performing nickel plating on a surface of the flat plate fixed electrode or applying a conductive paste material. The fixing method of the flat plate fixing electrode to the support member is screw fixing, and the protruding amount of the central portion of the flat plate fixing electrode is adjusted by the tightening torque. An electrostatic ultrasonic transducer according to claim 1. A first flat plate fixed electrode having a plurality of through holes;
A second flat plate fixing electrode having a plurality of through holes paired with the through holes of the first flat plate fixing electrode;
A first support member for supporting the first flat plate fixed electrode by a fixed portion;
A second support member for supporting the second flat plate fixed electrode by a fixed portion;
A vibrating membrane having a vibrating electrode and sandwiched between a pair of flat plate fixed electrodes comprising the first flat plate fixed electrode and the second flat plate fixed electrode, and a DC bias voltage applied to the vibrating electrode;
With
An electrostatic ultrasonic transducer for applying an alternating current signal between the pair of flat plate fixed electrodes to vibrate the vibration membrane,
A procedure for disposing the fixing portion in a portion near the outer peripheral portion of the flat plate fixing electrode;
When fixing the flat plate fixing electrode to the support member by the fixing portion, in the outer peripheral region from the fixing portion toward the outer peripheral portion, a procedure for fixing the flat plate fixing electrode so as to provide a gap between the flat plate fixing electrode and the support member;
A method for manufacturing an electrostatic ultrasonic transducer, comprising: The method of manufacturing an electrostatic ultrasonic transducer according to claim 10, comprising a step of forming the flat plate fixing electrode in a square shape and providing the fixing portions at four corners of the flat plate fixing electrode. The method for manufacturing an electrostatic ultrasonic transducer according to claim 10, further comprising a step of setting a size of the gap according to a material and a thickness of the flat plate fixed electrode. 13. The method according to claim 10, further comprising a step of forming a gap between the flat plate fixing electrode and the support member by providing a step from a center portion of the fixing portion of the support member toward an outer peripheral portion. The manufacturing method of the electrostatic ultrasonic transducer of description. 13. The method according to claim 10, further comprising: forming a gap between the flat plate fixed electrode and the support member by providing an inclination from a center portion of the fixing portion of the support member toward an outer peripheral portion. The manufacturing method of the electrostatic ultrasonic transducer of description. 13. The method according to claim 10, further comprising a step of forming a gap between the flat plate fixed electrode and the support member by providing a groove from a center portion of the fixing portion of the support member toward an outer peripheral portion. The manufacturing method of the electrostatic ultrasonic transducer of description. On the surface of the flat plate fixed electrode in contact with the support member, a thickened portion having a predetermined thickness is formed,
13. The method according to claim 10, further comprising a step of exposing the surface of the flat plate fixed electrode without forming the flesh portion in the outer peripheral region from the fixed portion on the flat plate fixed electrode surface toward the outer peripheral portion. A method for producing the electrostatic ultrasonic transducer according to claim 1. The electrostatic ultrasonic wave according to claim 16, further comprising a step of forming the thinned portion by performing nickel plating on a surface of the flat plate fixed electrode or applying a conductive paste material. A method for manufacturing a transducer. 18. The method according to claim 10, further comprising the step of: fixing the flat plate fixing electrode to the support member by screw fixing, and adjusting the protrusion amount of the central portion of the flat plate fixing electrode by the tightening torque. The manufacturing method of the electrostatic ultrasonic transducer of description. An audible frequency signal source that generates an audible frequency band signal wave, a carrier wave signal source that generates and outputs a carrier wave in an ultrasonic frequency band, and a modulator that modulates the carrier wave with the audible frequency band signal wave And an ultrasonic speaker comprising: a power amplifier that amplifies and outputs a modulation signal output from the modulator; and an electrostatic ultrasonic transducer driven by the power amplifier,
The electrostatic ultrasonic transducer in the ultrasonic speaker is:
A first flat plate fixed electrode having a plurality of through holes;
A second flat plate fixing electrode having a plurality of through holes paired with the through holes of the first flat plate fixing electrode;
A first support member for supporting the first flat plate fixed electrode by a fixed portion;
A second support member for supporting the second flat plate fixed electrode by a fixed portion;
A vibrating membrane having a vibrating electrode and sandwiched between a pair of flat plate fixed electrodes comprising the first flat plate fixed electrode and the second flat plate fixed electrode, and a DC bias voltage applied to the vibrating electrode;
Have
While arranging the fixed part in a portion near the outer peripheral portion of the flat plate fixed electrode,
In the outer peripheral region from the fixed part toward the outer peripheral part, it is configured to provide a gap between the flat plate fixed electrode and the support member,
An ultrasonic speaker, wherein an alternating current signal is applied between the pair of flat plate fixed electrodes to vibrate the vibrating membrane. An ultrasonic speaker that modulates a carrier wave signal in an ultrasonic frequency band with an audio signal supplied from an acoustic source, and drives an electrostatic ultrasonic transducer with the modulated signal to reproduce a signal sound in an audible frequency band;
A projection optical system that projects an image onto a projection surface;
A display device comprising:
The electrostatic ultrasonic transducer in the ultrasonic speaker is:
A first flat plate fixed electrode having a plurality of through holes;
A second flat plate fixing electrode having a plurality of through holes paired with the through holes of the first flat plate fixing electrode;
A first support member for supporting the first flat plate fixed electrode by a fixed portion;
A second support member for supporting the second flat plate fixed electrode by a fixed portion;
A vibrating membrane having a vibrating electrode and sandwiched between a pair of flat plate fixed electrodes comprising the first flat plate fixed electrode and the second flat plate fixed electrode, and a DC bias voltage applied to the vibrating electrode;
Have
While arranging the fixed part in a portion near the outer peripheral portion of the flat plate fixed electrode,
In the outer peripheral region from the fixed part toward the outer peripheral part, it is configured to provide a gap between the flat plate fixed electrode and the support member,
A display device, wherein an alternating current signal is applied between the pair of flat plate fixed electrodes to vibrate the vibrating membrane. The carrier signal in the ultrasonic frequency band is modulated by the signal in the first sound range among the sound signals supplied from the acoustic source, and the electrostatic ultrasonic transducer is driven by the modulated signal to reproduce the signal sound in the audible frequency band. An ultrasonic speaker,
A low-frequency sound reproduction speaker for reproducing a signal in a second sound range lower than the first sound range among the sound signals supplied from the acoustic source;
A directional acoustic system comprising:
The electrostatic ultrasonic transducer in the ultrasonic speaker is:
A first flat plate fixed electrode having a plurality of through holes;
A second flat plate fixing electrode having a plurality of through holes paired with the through holes of the first flat plate fixing electrode;
A first support member for supporting the first flat plate fixed electrode by a fixed portion;
A second support member for supporting the second flat plate fixed electrode by a fixed portion;
A vibrating membrane having a vibrating electrode and sandwiched between a pair of flat plate fixed electrodes comprising the first flat plate fixed electrode and the second flat plate fixed electrode, and a DC bias voltage applied to the vibrating electrode;
Have
While arranging the fixed part in a portion near the outer peripheral portion of the flat plate fixed electrode,
In the outer peripheral region from the fixed part toward the outer peripheral part, it is configured to provide a gap between the flat plate fixed electrode and the support member,
A directivity acoustic system configured to apply an AC signal between the pair of flat plate fixed electrodes to vibrate the vibrating membrane.

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