JP2007158889A - Electrostatic ultrasonic transducer, method for manufacturing the electrostatic ultrasonic transducer, and ultrasonic speaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic ultrasonic transducer which can flexibly and easily correspond to changes in the size of fixed electrodes, the number of through holes and electrode thickness, and that can significantly reduce the manufacturing cost. <P>SOLUTION: As fixed electrode base materials 1 and 2, conductive pipes 11 are arranged in a honeycomb shape, an outer circumference is bundled by a holding member 12, and gaps among the conductive pipes 11 are fixed by a fixing material 13 to be united into a single body, which manufactures bundled pipes. Then, the fixed electrode base materials 1 and 2 are cut with desired thickness, to manufacture a fixed electrode member (base member for manufacturing a fixed electrode). Here, the inside diameter of a conductive pipe 11 is matched with the diameter of a through hole of the fixed electrode, and the outside diameter of the conductive pipe 11 is matched with the pitch length of the through hole. In addition, the mold material of a resin system or a conductive resin is used for the fixing material 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic ultrasonic transducer, a method of manufacturing an electrostatic ultrasonic transducer, and an ultrasonic speaker, and in particular, flexibly and easily responds to changes in the size of fixed electrodes, the number of through holes, and electrode thickness. The present invention relates to an electrostatic ultrasonic transducer, a manufacturing method of an electrostatic ultrasonic transducer, and an ultrasonic speaker that can significantly reduce manufacturing costs.

  The ultrasonic transducer can reproduce a sound having a sharp directivity by outputting a modulated wave obtained by modulating a carrier wave in an ultrasonic band with an acoustic signal in an audible band.

  FIG. 8 is a diagram illustrating a configuration example of a conventional ultrasonic transducer. Most conventional ultrasonic transducers are resonant types using piezoelectric ceramics. The piezoelectric ultrasonic transducer shown in FIG. 8A uses a piezoelectric ceramic as a vibration element to convert an electric signal to an ultrasonic wave and to convert an ultrasonic signal to an electric signal (transmission and reception of ultrasonic waves). Do both. The bimorph type ultrasonic transducer shown in FIG. 8A is composed of two piezoelectric ceramics 61 and 62, a cone 63, a case 64, leads 65 and 66, and a screen 67. The piezoelectric ceramics 61 and 62 are bonded to each other, and a lead 65 and a lead 66 are connected to a surface opposite to the bonded surface, respectively.

  Since the piezoelectric ultrasonic transducer utilizes the resonance phenomenon of piezoelectric ceramic, the transmission and reception characteristics of ultrasonic waves are good in a relatively narrow frequency band around the resonance frequency. However, since the piezoelectric transducer utilizes the sharp resonance characteristics of the element, a high sound pressure can be obtained, but the frequency band is very narrow. For this reason, an ultrasonic speaker using a piezoelectric transducer has a narrow reproducible frequency band, and there is a tendency that reproduced sound quality is poor as compared with a loudspeaker.

  Unlike the piezoelectric transducers described above, electrostatic ultrasonic transducers are conventionally known as broadband oscillation ultrasonic transducers that can generate high sound pressure over a high frequency band. FIG. 8B shows a configuration example of a broadband oscillation type electrostatic ultrasonic transducer. This electrostatic ultrasonic transducer is called a pull type because it works only in the direction in which the vibrating membrane is attracted to the fixed electrode side.

  The electrostatic ultrasonic transducer shown in FIG. 8B uses a dielectric 131 (insulator) such as PET (polyethylene terephthalate resin) having a thickness of about 3 to 10 μm as a vibrating body (vibrating film). . An upper electrode 132 formed as a metal foil such as aluminum is integrally formed on the upper surface of the dielectric 131 by a process such as vapor deposition, and a lower electrode 133 formed of brass is formed on the lower surface of the dielectric 131. It is provided so that it may contact a part. The lower electrode 133 is connected to a lead 152 and fixed to a base plate 135 made of bakelite or the like.

  The upper electrode 132 is connected to a lead 153, and the lead 153 is connected to the DC bias power supply 150. A DC bias voltage for attracting the upper electrode of about 50 to 150 V is constantly applied to the upper electrode 132 by the DC bias power source 150, and the upper electrode 132 is attracted to the lower electrode 133 side. Reference numeral 151 denotes a signal source.

  The dielectric 131, the upper electrode 132, and the base plate 135 are caulked by the case 130 together with the metal rings 136, 137, and 138 and the mesh 139.

  On the surface of the lower electrode 133 on the dielectric 131 side, a plurality of minute grooves (uneven portions) having a non-uniform shape of about several tens to several hundreds of μm are formed. Since this minute groove becomes a gap between the lower electrode 133 and the dielectric 131, the electrostatic capacity distribution between the upper electrode 132 and the lower electrode 133 changes minutely. These random minute grooves are formed by manually roughing the surface of the lower electrode 133 with a file. An electrostatic ultrasonic transducer has a wide frequency characteristic by forming innumerable capacitors having different gap sizes and depths (Patent Documents 1 and 2).

  As described above, the electrostatic ultrasonic transducer shown in FIG. 8 is conventionally known as a broadband ultrasonic transducer (Pull type) capable of generating a relatively high sound pressure over a wide frequency band. .

  However, the maximum value of the sound pressure is slightly low, for example, the sound pressure is as low as 120 dB or less, and the sound pressure is slightly insufficient for use as an ultrasonic speaker. An ultrasonic sound pressure of 120 dB or more is necessary for the parametric effect to sufficiently appear in an ultrasonic speaker. However, it is difficult to achieve this numerical value with an electrostatic ultrasonic transducer (pull type). Polymer piezoelectric elements such as ceramic piezoelectric elements and PVDF have been used as ultrasonic transmitters. However, since the piezoelectric element has a sharp resonance point regardless of the material, and is practically used as an ultrasonic speaker by being driven at the resonance frequency, the frequency region where a high sound pressure can be secured is extremely narrow. That is, it can be said that it is a narrow band.

  In order to solve such a problem, the present applicant has previously proposed an electrostatic ultrasonic transducer as shown in FIG. 9 (Japanese Patent Application No. 2004-173946). Such a structure is generally referred to as a push-pull type, and has the ability to satisfy both high bandwidth and high sound pressure at the same time as compared to a pull type electrostatic ultrasonic transducer. .

  In FIG. 9, a push-pull type electrostatic ultrasonic transducer includes a pair of fixed electrodes 20 and 21 including a conductive member formed of a conductive material that functions as an electrode, and a pair of fixed electrodes. (Vibration membrane electrode) It has the vibration membrane 22 which has 221 and a support member 25 which hold | maintains a pair of fixed electrodes 20 and 21 and the vibration membrane 22. FIG.

  The vibration film 22 includes an insulating layer 220 and a conductive layer 221 formed of a conductive material, and the conductive layer 221 has a single polarity (positive or negative polarity) by a DC bias power source 26. DC bias voltage) may be applied.

  The pair of fixed electrodes 20, 21 have the same number and a plurality of through holes 24 A, 24 B at positions facing each other with the vibrating membrane 22, and a signal source is provided between the conductive members of the pair of fixed electrodes 20, 21. An AC signal is applied by 28A and 28B. Capacitors are formed on the fixed electrode 20 and the conductive layer 221, and on the fixed electrode 21 and the conductive layer 221, respectively.

  In the above configuration, in the electrostatic ultrasonic transducer, a single polarity (positive polarity in this example) DC bias voltage is applied to the conductive layer 221 of the vibration film 22 by the DC bias power supply 26. On the other hand, an AC signal is applied to the pair of fixed electrodes 20 and 21 by the signal sources 28A and 28B. As a result, in the positive half cycle of the AC signal output from the signal sources 28A and 28B, since a positive voltage is applied to the fixed electrode 20, the surface portion 23A not sandwiched between the fixed electrodes of the vibrating membrane 22 is applied. The electrostatic repulsive force acts, and the surface portion 23A is pulled downward in FIG. At this time, since a negative voltage is applied to the opposing fixed electrode 21, an electrostatic attraction force acts on the back surface portion 23B that is the back surface side of the surface portion 23A of the vibration film 22, The back surface portion 23B is pulled further upward in FIG.

  Accordingly, the membrane portion of the vibrating membrane 22 that is not sandwiched between the pair of fixed electrodes 20 and 21 receives an electrostatic repulsive force and an electrostatic repulsive force in the same direction. Similarly, in the negative half cycle of the AC signal output from the signal sources 28A and 28B, the surface portion 23A of the vibration film 22 has an electrostatic attraction force on the upper side in FIG. 9, and the back surface portion 23B. In FIG. 9, an electrostatic repulsive force acts on the upper side, and the film portion not sandwiched between the pair of fixed electrodes 20 and 21 of the vibration film 22 receives the electrostatic repulsive force and the electrostatic repulsive force in the same direction. In this way, the direction in which the electrostatic force changes alternately while the vibrating membrane 22 receives the electrostatic repulsive force and the electrostatic repulsive force in the same direction according to the change in the polarity of the AC signal. An acoustic signal having a sound pressure level sufficient to obtain a parametric array effect can be generated.

  As described above, the ultrasonic transducer shown in FIG. 9 is called a push-pull type because the vibrating membrane 22 receives a force from the pair of fixed electrodes 20 and 21 and vibrates. The push-pull type electrostatic ultrasonic transducer is capable of simultaneously satisfying wide bandwidth and high sound pressure compared to the pull type electrostatic ultrasonic transducer that only acts on the vibrating membrane. have.

  In the electrostatic ultrasonic transducer shown in FIG. 9, the fixed electrodes 20 and 21 may be made of a conductive material. For example, SUS, brass, iron, or nickel may be used alone. In addition, since it is necessary to reduce the weight, a desired hole processing is performed on a glass epoxy substrate or a paper phenol substrate generally used for circuit boards, and then plating is performed with nickel, gold, silver, copper, or the like. It is also possible. In this case, in order to prevent warping after molding, it is also effective to devise plating on the both surfaces. However, in consideration of insulation, it is desirable that some kind of insulation treatment be performed on the vibration film side of each fixed electrode. For example, a convex portion insulated with a liquid solder resist, a photosensitive film, a photosensitive coating material, a non-conductive paint, an electrodeposition material, or the like is formed.

  As described above, in the push-pull type electrostatic ultrasonic transducer, a high voltage DC bias voltage is applied to the vibration film, and an AC voltage is applied to the fixed electrode, so that the fixed electrode-vibration film The membrane part vibrates due to the electrostatic force (attraction and repulsive force) acting on. In this case, in order to realize the vibration of the ultrasonic band, it is necessary to make the diameter of the vibrating portion a few mm or less, and by providing a large number of vibrating holes, it is necessary to configure a transducer with high followability and high output There is.

  FIG. 10 is a diagram for explaining a configuration of a fixed electrode used in the push-pull type electrostatic ultrasonic transducer shown in FIG. 9 and a manufacturing process thereof.

  As described above, the fixed electrode needs a through-hole for emitting sound waves, and in many cases, 1000 or more holes are required. Although machining is appropriate in terms of machining accuracy, machining by etching is applied because it is not cost effective. However, the diameter of the through hole vacated by the etching is limited in relation to the thickness. For example, it is difficult to manufacture a fixed electrode that satisfies a desired processing accuracy with a through-hole diameter of 0.75 mm and a thickness of 1.5 mm only by etching.

  Therefore, as shown in FIG. 10A, a desired through hole 203 is formed in a conductor (usually metal, using copper or stainless steel) 202 having a thickness sufficiently smaller than the diameter of the through hole, for example, 0.25 mm. Etching is performed by covering the mask member 201 to be formed, and a plurality of conductors 202 having through holes 203 are prepared.

  Then, as shown in FIG. 10B, when the total thickness is 1.5 mm, six of these conductors 202 are stacked so that the positions of all the through holes 203 coincide. Then, as shown in FIG. 10 (C), the laminated conductor 202 is pressed from both sides and subjected to thermocompression bonding or diffusion bonding treatment, and the result is a fixed electrode integrated (metal bonded) with a thickness of 1.5 mm. Is completed. (The example shown in FIG. 10 shows an example in which a rectangular fixed electrode is manufactured. However, in the case of manufacturing a circular fixed electrode as shown in FIG. 9, the conductor 202 is circular.)

However, in the above process, when the size of the fixed electrode and the number of through holes are changed, it is necessary to manufacture a mask member for etching each time. In addition, a positioning jig and an alignment process for aligning the center positions of all the through holes are required for stacking. Furthermore, in the thermocompression bonding or diffusion bonding process, the number of processes per process is limited and the process cost is expensive, so that the manufacturing cost is large. In addition, when changing the thickness, it is necessary to prepare several thickness levels for correcting the thickness, and it is necessary to manufacture and join the lamination jig each time. (In the joining process, it is very difficult to simultaneously manufacture different thicknesses.)
JP 2000-50387 A JP 2000-50392 A

  As described above, in the manufacturing process of the fixed electrode by etching, it is necessary to manufacture a mask member for etching each time the size of the fixed electrode and the number of through holes are changed. In addition, a positioning jig and an alignment process for aligning the center positions of all the through holes are required for the lamination. Furthermore, in the thermocompression bonding or diffusion bonding process, the number of processes per process is limited and the process cost is expensive, so that the manufacturing cost is large. In addition, when changing the thickness, it is necessary to prepare several thickness levels for correcting the thickness, and there is a problem that production and joining processing of a lamination jig is necessary each time.

  The present invention was made to solve such problems, and its purpose is to flexibly and easily respond to changes in the size of fixed electrodes, the number of through-holes, and electrode thickness, greatly reducing manufacturing costs. An electrostatic ultrasonic transducer, a method for manufacturing an electrostatic ultrasonic transducer, and an ultrasonic speaker are provided.

The present invention has been made to solve the above problems, and an electrostatic ultrasonic transducer according to the present invention includes a first fixed electrode in which a plurality of through holes are formed, the first fixed electrode, A second fixed electrode in which a plurality of through-holes forming a pair are formed; a vibration film sandwiched between the pair of fixed electrodes and having a conductive layer to which a DC bias voltage is applied; and the pair of pairs An electrostatic ultrasonic transducer having a fixed electrode and a support member for holding the vibrating membrane, wherein an AC signal is applied between the pair of fixed electrodes, the first and second fixed electrodes being The base material is a conductive pipe, and the outer periphery is held by a holding member so as to be bundled in a state where a plurality of the conductive pipes are arranged, and the gap between the bundled conductive pipes is fixed by a fixing material. By cutting the fixed electrode base material with a desired thickness, Serial first, characterized in that the second fixed electrode is formed.
With such a configuration, when manufacturing a fixed electrode of an electrostatic ultrasonic transducer, the fixed electrode base material is arranged in parallel (for example, in a honeycomb shape) with a desired conductive pipe, and the outer periphery is bound by a holding member. The gap between the conductive pipes is formed by a bundling pipe that is solidified by a fixing material and integrated. Then, the fixed electrode base material (bundling pipe) is cut at a desired thickness to manufacture the fixed electrode.
Thus, when manufacturing fixed electrodes for electrostatic ultrasonic transducers, by selecting the number of conductive pipes to be arranged in parallel, the size of the fixed electrodes, the number of through-holes, and the electrode thickness can be changed. It can respond flexibly and easily. In addition, the manufacturing cost of the electrostatic ultrasonic transducer can be greatly reduced.

The electrostatic ultrasonic transducer according to the present invention is characterized in that the conductive pipes are bundled in a state of being arranged in a honeycomb shape.
With such a configuration, the conductive pipes are bundled in a state of being arranged in a honeycomb shape (honeycomb shape). Accordingly, the size and number of the conductive pipes are selected, and the conductive pipes are formed in a honeycomb shape. A fixed electrode having a desired size, the number of through-holes, and an electrode thickness can be easily manufactured simply by bundling and fixing them side by side.

The electrostatic ultrasonic transducer according to the present invention is characterized in that an inner diameter of the conductive pipe is matched with a through-hole diameter of a fixed electrode, and an outer diameter of the conductive pipe is matched with a pitch length of the through-hole. To do.
With such a configuration, the inner diameter of the conductive pipe is matched with the through-hole diameter of the fixed electrode, and the outer diameter of the conductive pipe is matched with the pitch length of the through-hole. By selecting the conductive pipe having, it is possible to easily manufacture a fixed electrode having a desired through-hole diameter and a through-hole pitch length.

The electrostatic ultrasonic transducer according to the present invention is characterized in that the fixing material is formed of a resin-based molding material or an adhesive.
With this configuration, a resin-based molding material (or conductive resin) or adhesive is used as the fixing material for the conductive pipe, so that a plurality of conductive pipes can be fixed easily. Can do. Further, since the gaps in the conductive pipe are filled with a resin having a low density, the weight of the fixed electrode can be reduced. Furthermore, when a conductive resin is used, an electrical contact to the fixed electrode can be easily provided.

The method of manufacturing an electrostatic ultrasonic transducer according to the present invention includes a first fixed electrode having a plurality of through holes and a plurality of through holes that are paired with the first fixed electrodes. Two fixed electrodes, a vibration film sandwiched between the pair of fixed electrodes and having a conductive layer to which a DC bias voltage is applied to the conductive layer, a support member for holding the pair of fixed electrodes and the vibration film, A method of manufacturing an electrostatic ultrasonic transducer in which an AC signal is applied between the pair of fixed electrodes, wherein the first and second fixed electrodes have a base material as a conductive pipe, A fixed electrode base material formed by holding the outer periphery with a holding member so as to bind the conductive pipes in a state where a plurality of the conductive pipes are arranged and fixing a gap between the bound conductive pipes with a fixing material. 1st process of forming a fixed electrode member by cutting in length A mask member that masks the through hole of the fixed electrode member and a region in the vicinity of the through hole is placed on one surface of the fixed electrode member, and the surface of the fixed electrode member on which the mask member is placed A counter electrode forming material for forming an insulating counter electrode forming body is set thereon, and the counter electrode forming material is applied to a portion of the surface of the fixed electrode member that is not masked by the mask member. In the second step and the second step, a third step of removing the mask member after completion of the application of the counter electrode forming material and drying the counter electrode forming body formed on the surface of the fixed electrode member. And is produced by the following.
By such a method, a fixed electrode member (a base member for manufacturing a fixed electrode) is prepared by cutting a fixed electrode base material in which a plurality of conductive pipes are bundled with a predetermined thickness. Then, a screen plate (mask member for forming the counter electrode) that masks the through hole and the area near the through hole is set on one surface of the fixed electrode member, and the counter electrode forming material is masked by moving the squeegee. Apply to areas not covered. This counter electrode forming material can be configured as a counter electrode forming body permanently and is non-conductive, for example, used as a liquid solder resist or a sand blast resist for packages generally used in circuit boards. For example, masking ink. Then, after the application is completed, the screen plate for forming the counter electrode is removed, and the counter electrode forming body is dried to obtain a desired fixed electrode.
Thus, when manufacturing fixed electrodes for electrostatic ultrasonic transducers, by selecting the number of conductive pipes to be arranged in parallel, the size of the fixed electrodes, the number of through-holes, and the electrode thickness can be changed. It can respond flexibly and easily. Further, the counter electrode forming body can be easily formed on the surface of the fixed electrode member. For this reason, the manufacturing cost of the electrostatic ultrasonic transducer can be greatly reduced.

In addition, the method for manufacturing an electrostatic ultrasonic transducer according to the present invention is characterized in that the conductive pipes are bundled in a state of being arranged in a honeycomb shape.
By such a method, the conductive pipes are bundled in a state of being arranged in a honeycomb shape (honeycomb shape). Thus, the size and number of the conductive pipes are selected, and the conductive pipes are formed in a honeycomb shape. A fixed electrode having a desired size, the number of through-holes, and an electrode thickness can be easily manufactured simply by bundling and fixing them side by side.

In the method of manufacturing an electrostatic ultrasonic transducer according to the present invention, the inner diameter of the conductive pipe is matched with the through-hole diameter of the fixed electrode, and the outer diameter of the conductive pipe is matched with the pitch length of the through-hole. It is characterized by.
By such a method, the inner diameter of the conductive pipe is matched with the through-hole diameter of the fixed electrode, and the outer diameter of the conductive pipe is matched with the pitch length of the through-hole. By selecting the conductive pipe having, it is possible to easily manufacture a fixed electrode having a desired through-hole diameter and a through-hole pitch length.

In the method of manufacturing an electrostatic ultrasonic transducer according to the present invention, the fixing material is formed of a resin-based molding material or an adhesive.
By using such a method, resin-based molding material (or conductive resin) or adhesive is used as the fixing material for the conductive pipe, so that a plurality of conductive pipes can be fixed easily. Can do. Further, since the gaps in the conductive pipe are filled with a resin having a low density, the weight of the fixed electrode can be reduced. Furthermore, when a conductive resin is used, an electrical contact to the fixed electrode can be easily provided.

In addition, an ultrasonic speaker according to the present invention includes any one of the electrostatic ultrasonic transducers described above.
This makes it possible to flexibly and easily respond to changes in the size of fixed electrodes, the number of through-holes, and electrode thickness when manufacturing fixed electrodes for electrostatic ultrasonic transducers used in ultrasonic speakers. It can be greatly reduced. In addition, since the fixed electrode can be reduced in weight, the entire ultrasonic speaker can be reduced in weight.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram (cross-sectional view) showing a configuration example of a fixed electrode base material. The fixed electrode base materials 1 and 2 are base materials for manufacturing the fixed electrode of the electrostatic ultrasonic transducer of the present invention. It will be. 1A shows an example of a fixed electrode base material 1 having a square cross-sectional shape, and FIG. 1B shows an example of a fixed electrode base material 2 having a circular cross-sectional shape. In the fixed electrode base materials 1 and 2, the conductive pipes 11 are arranged in a honeycomb (Honeycomb) shape, and a holding member 12 is arranged on the outer periphery thereof, and the conductive pipes 11 are bound and held so as not to be displaced in the radial direction. To do. The holding member 12 may be a metal or a resin (glass epoxy, PEEK, etc.) as long as it has a suitable mechanical strength.

  Further, a fixing material 13 is disposed in the gap between the conductive pipes 11 and is completely fixed. Here, as the fixing material 13, a resin-based molding material or an adhesive is suitable, but application of a conductive resin is also effective. For example, when a resin that is an insulating material is used for the holding member 12, it is troublesome to arrange the electrode contacts of the fixed electrode on the conductive pipe 11. An electrical contact can be easily obtained by arranging a conducting wire and filling and solidifying it with a conductive resin.

  FIG. 2 is a diagram showing a method of cutting out a fixed electrode member 3 (member serving as a basis for manufacturing a fixed electrode) 3 from the fixed electrode base material 2. FIG. 2A shows an overview of the fixed electrode base material 2, and FIG. 2B shows a state cut into a form used as the fixed electrode member 3.

  The fixed electrode base material 2 can be formed as long as the conductive pipe 11 can be manufactured, and the fixed electrode base material 2 is cut out from the fixed electrode base material 2 with a desired thickness to produce the fixed electrode member 3. A large number of fixed electrode members 3 can be cut out from the material 2 at a plurality of thickness levels. If the cut surface of the fixed electrode member 3 cut out is subjected to a double-side polishing process, an electrode surface free of burrs can be formed.

  FIG. 3 is a diagram for explaining a counter electrode forming body of fixed electrodes. FIG. 3A shows a fixed electrode member (member serving as a basis for manufacturing the fixed electrode) in a state cut from the fixed electrode base material, and FIG. 3B shows the fixed electrode after the counter electrode forming body 14 is arranged. It is a top view (completion state after processing a fixed electrode member).

  As shown in FIG. 3B, in a state where the counter electrode forming body 14 is arranged on the fixed electrode member, the predetermined range on the inner peripheral side of the conductive pipe 11 is only exposed as the counter electrode portion 15. All other regions are covered with a counter electrode forming body 14 made of an insulating material. Moreover, the hole of the electroconductive pipe 11 is comprised so that itself may function as the through-hole 16 which radiates | emits a sound wave.

  FIG. 4 is a diagram showing a configuration example of an electrostatic ultrasonic transducer according to the present invention. FIG. 4A is a cross-sectional view of the electrostatic ultrasonic transducer, and FIG. 4B is a diagram showing details of the counter electrode unit 15.

  As shown in FIG. 4 (A), the counter electrode forming body 14, the counter electrode portion 15 formed to be covered with the counter electrode forming body 14, the through hole 16, the holding member 12, and the fixing electrode 13. 20 and 21 are arranged so that the surfaces on which the counter electrode forming bodies 14 are arranged face each other. Further, the fixed electrodes 20 and 21 are arranged so that the center positions of all the through holes 16 coincide. The pair of fixed electrodes 20 and 21 sandwich the vibration film 22 (vibration film composed of the conductive layer 221 and the insulating layer 220) to constitute an electrostatic ultrasonic transducer. The operation principle of this electrostatic ultrasonic transducer is the same as that of the electrostatic ultrasonic transducer shown in FIG. 9, and the description thereof is omitted.

Here, as an example of each dimension value constituting the counter electrode part 15, as shown in FIG. 4B, the outer peripheral diameter of the counter electrode part 15 is D1, the through hole diameter is D2, and the adjacent counter electrode part 15 When the distance between the outer peripheries is G and the center pitch of the through holes 16 is P,
The relationship is defined as D1 = D2 × 2, P = D1 + G (unit: mm).
Here, the distance G between the outer peripheries is about 10% of the outer perimeter diameter D1 of the counter electrode portion 15.

FIG. 5 is a diagram for explaining the outer diameter of the conductive pipe. As shown in FIG. 5, the outer diameter D3 of the conductive pipe 11 necessary for realizing the fixed electrodes 20 and 21 maintaining the relationship of D1, D2, G, and P described above is
D3 = D2 × 2 + G = P (unit: mm), and the conductive pipe 11 may be manufactured by adjusting the outer diameter to the pitch of the through holes.

  FIG. 6 is a diagram for explaining a manufacturing process of the fixed electrode of the electrostatic ultrasonic transducer according to the present invention. Hereinafter, the manufacturing process of the fixed electrode will be described with reference to FIG.

  First, as shown in FIG. 6 (A), a fixed electrode member 3 cut as shown in FIG. 2 (B) with a predetermined thickness and having a cut surface is prepared.

  Next, as shown in FIG. 6B, on one surface of the fixed electrode member 3, a screen plate (a mask member for forming a counter electrode) 19 for forming the counter electrode forming body 14 and a liquid counter plate are formed. The electrode forming material 18 is set, the squeegee 17 is moved, and the counter electrode forming material 18 is applied to the portion where the mask is not applied.

  The counter electrode forming material 18 considered to be effective can be permanently configured as the counter electrode forming body 14 and is non-conductive. For example, a liquid solder resist for a package generally used for a circuit board or for sandblasting Masking ink used as a resist. 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 various conductors (such as conductive resins) including metals, and is a polymer film. It is very effective for sandwiching a vibrating membrane made of

  Then, as shown in FIG. 6C, when the counter electrode forming screen plate (counter electrode forming mask member) 19 is removed after the application of the counter electrode forming material 18 is completed, the other parts excluding the counter electrode portion 15 are removed. The non-conductive layer (= counter electrode forming body 14) remains on the substrate, and is dried to obtain a desired fixed electrode.

  FIG. 7 is a diagram showing a configuration example of an ultrasonic speaker using the electrostatic ultrasonic transducer of the present invention. An ultrasonic speaker applies AM modulation to an ultrasonic wave called a carrier wave with an audio signal (audible area signal), and when it is released into the air, the original audio signal is self-reproduced in the air due to air nonlinearity. It is. In other words, since the sound wave is a close-packed wave that is transmitted using air as a medium, in the process in which the modulated ultrasonic wave propagates, a dense part and a sparse part of the air appear prominently, and the dense part has a high sound speed, Since the sound speed is slow in the sparse 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 is generally called the pametric array effect.

  The ultrasonic speaker 30 shown in FIG. 7 includes an audio frequency signal source (audio signal source) 31 that generates a signal wave in the audio frequency band, and a carrier wave signal source 32 that generates and outputs a carrier wave in the ultrasonic frequency band. A modulator 33, a power amplifier 34, and an electrostatic ultrasonic transducer 35.

  In the above configuration, the modulation signal obtained by modulating the carrier wave in the ultrasonic frequency band output from the carrier wave signal source 32 by the modulator 33 using the audio signal wave output from the audible frequency signal source 31 and then amplifying it by the power amplifier 34. Thus, the electrostatic ultrasonic transducer 35 is driven. As a result, the modulated signal is converted into a sound wave of a finite amplitude level by the electrostatic ultrasonic transducer 35, and this sound wave is radiated into the medium (in the air), and the original audible frequency band due to the nonlinear effect of the medium (air). The signal sound is regenerated.

  The embodiment of the present invention has been described above. However, when the above-described electrostatic ultrasonic transducer of the present invention and the manufacturing method thereof are used, the following effects can be obtained.

As a first effect, it is easy to change the size of the fixed electrode, the number of through holes, and the electrode thickness.
That is, in the current manufacturing method (etching + diffusion bonding), when changing the size of the electrode or the number of through holes, it was necessary to remanufacture the mask member for etching. If it is used, it is only necessary to change the number of conductive pipes to be bundled.

  Further, in the current manufacturing method (etching + diffusion bonding), for example, when an etched material having only a thickness of 0.25 mm is prepared, the electrode thickness is an intermediate thickness (for example, 0.2 mm). 9 mm, 1.2 mm, etc.), a 0.1 mm thick one must be additionally manufactured. However, if the manufacturing method of the present invention is used, how the fixed electrode base material is cut? Can also change the thickness. Moreover, when manufacturing a laminated board by diffusion bonding, it is not possible to simultaneously manufacture products having different thicknesses in a single process. Therefore, in order to prepare several kinds of thickness levels, it is necessary to perform diffusion bonding by the number of the levels, which is very expensive, but this problem can be solved by using the manufacturing method of the present invention.

As a second effect, the manufacturing cost can be reduced.
The conductive pipe may be carbon steel or stainless steel, which is used as a general material, and the material cost can be kept low. The fixed electrode member (the basic member for manufacturing the fixed electrode) can be obtained by bundling these, molding, and cutting. ) Can be manufactured, so that a stacking fixture for diffusion bonding as in the current manufacturing method (etching + diffusion bonding) and the expensive diffusion bonding itself are not required, so that the manufacturing cost can be greatly reduced.

As a third effect, the fixed electrode can be reduced in weight.
In the current manufacturing method (etching + diffusion bonding), the entire fixed electrode is made of metal. However, in the fixed electrode according to the present invention, the void portion of the conductive pipe is filled with a low-density resin so that the weight can be reduced. Significantly contributes to weight reduction.

  Although the embodiments of the present invention have been described above, the electrostatic ultrasonic transducer of the present invention is not limited to the above-described illustrated examples, and various modifications can be made without departing from the scope of the present invention. Of course, it can be added.

The figure which shows the structural example of a fixed electrode base material. The figure which shows the method of cutting out a fixed electrode member from a fixed electrode base material. The figure for demonstrating the counter electrode formation body of a fixed electrode. The figure which shows the structural example of the electrostatic type ultrasonic transducer by this invention. The figure for demonstrating the outer diameter dimension of an electroconductive pipe. The figure for demonstrating the manufacturing process of a fixed electrode. The figure which shows the structural example of an ultrasonic speaker. The figure which shows the structural example of the conventional ultrasonic transducer. The figure which shows the structural example of a push-pull type electrostatic ultrasonic transducer. The figure for demonstrating the structure of a fixed electrode, and its manufacturing process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2 ... Fixed electrode base material, 3 ... Fixed electrode member (base member for manufacturing a fixed electrode), 11 ... Conductive pipe, 12 ... Holding member, 13 ... Fixing material, 14 ... Counter electrode formation body, 15 DESCRIPTION OF SYMBOLS ... Counter electrode part, 16 ... Through-hole, 17 ... Squeegee, 18 ... Counter electrode forming material, 20, 21 ... Fixed electrode, 22 ... Vibration membrane, 24A, 24B ... Through-hole, 25 ... Support member, 26 ... DC bias power supply 28A, 28B ... signal source, 220 ... insulating layer, 221 ... conductive layer, 30 ... ultrasonic speaker, 31 ... audible frequency signal source, 32 ... carrier wave signal source, 33 ... modulator, 34 ... power amplifier, 35 ... Electrostatic ultrasonic transducer

Claims (9)

A first fixed electrode having a plurality of through holes, a second fixed electrode having a plurality of through holes paired with the first fixed electrode, and a conductive layer sandwiched between the pair of fixed electrodes A vibration film to which a DC bias voltage is applied to the conductive layer, a pair of fixed electrodes, and a support member that holds the vibration film, and an AC signal is applied between the pair of fixed electrodes. An electrostatic ultrasonic transducer, comprising:
The base material of the first and second fixed electrodes is a conductive pipe,
Holding the outer periphery with a holding member so that the conductive pipes are bundled in a state where a plurality of the conductive pipes are arranged,
By cutting the fixed electrode base material formed by fixing the gap between the bound conductive pipes with a fixing material at a desired thickness,
The electrostatic ultrasonic transducer, wherein the first and second fixed electrodes are formed. The electrostatic ultrasonic transducer according to claim 1, wherein the conductive pipes are bundled in a state of being arranged in a honeycomb shape. 3. The electrostatic according to claim 1, wherein an inner diameter of the conductive pipe is matched with a through-hole diameter of a fixed electrode, and an outer diameter of the conductive pipe is matched with a pitch length of the through-hole. Type ultrasonic transducer. The electrostatic ultrasonic transducer according to any one of claims 1 to 3, wherein the fixing material is formed of a resin-based molding material or an adhesive. A first fixed electrode formed with a plurality of through holes, a second fixed electrode formed with a plurality of through holes paired with the first fixed electrode, and a conductive layer sandwiched between the pair of fixed electrodes A vibration film to which a DC bias voltage is applied to the conductive layer, a pair of fixed electrodes, and a support member that holds the vibration film, and an AC signal is applied between the pair of fixed electrodes. A method for manufacturing an electrostatic ultrasonic transducer, comprising:
The first and second fixed electrodes are:
The base material is a conductive pipe, and the outer periphery is held by a holding member so as to be bundled in a state where a plurality of the conductive pipes are arranged, and the gap between the bundled conductive pipes is fixed by a fixing material. A first step of forming a fixed electrode member by cutting the fixed electrode base material to a desired thickness;
A mask member that masks the through hole of the fixed electrode member and a region in the vicinity of the through hole is placed on one surface of the fixed electrode member, and the surface of the fixed electrode member on which the mask member is placed A counter electrode forming material for forming an insulating counter electrode forming body is set on the second electrode, and the counter electrode forming material is applied to a portion of the surface of the fixed electrode member that is not masked by the mask member. And the process of
In the second step, a third step of removing the mask member after the application of the counter electrode forming material is completed and drying the counter electrode forming body formed on the surface of the fixed electrode member;
The manufacturing method of the electrostatic ultrasonic transducer characterized by the above-mentioned. 6. The method of manufacturing an electrostatic ultrasonic transducer according to claim 5, wherein the conductive pipes are bundled in a state of being arranged in a honeycomb shape. The electrostatic diameter according to claim 5 or 6, wherein an inner diameter of the conductive pipe is made to coincide with a through hole diameter of the fixed electrode, and an outer diameter of the conductive pipe is made to coincide with a pitch length of the through hole. Method of manufacturing type ultrasonic transducer. The method for manufacturing an electrostatic ultrasonic transducer according to claim 5, wherein the fixing material is formed of a resin-based molding material or an adhesive. An ultrasonic speaker comprising the electrostatic ultrasonic transducer according to claim 1.

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