Ultrasonic transducer array and manufacturing method thereof

Abstract

To provide a manufacturing method of efficiently forming an element at low cost in an ultrasonic transducer array constituting a parametric speaker, and realize an operating temperature range (high temperature characteristic) required under a usage condition of the parametric speaker.SOLUTION: In an ultrasonic transducer array constituting the parametric speaker, a plurality of ultrasonic transducers are formed in a matrix on a plane, and the ultrasonic transducer is a monomorph piezoelectric element having a vibrating plate, and a piezoelectric material used for the piezoelectric element is porous ceramics, and is formed by using a solgel method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic transducer array, a method for manufacturing an ultrasonic transducer array, a parametric speaker using an ultrasonic transducer array, and a method for using a parametric speaker using an ultrasonic transducer array. [Background technology]

[0002] A parametric speaker is an acoustic system that uses ultrasonic waves to achieve sharp directionality. It can selectively deliver sound to people in a specific narrow area, making it particularly effective for conveying information in special environments such as road construction sites.

[0003] A typical ultrasonic speaker (transducer) has a directivity of only about 60 to 70 degrees by itself, but when multiple transducers are arranged on a flat surface to form a parametric array, the directivity becomes extremely sharp. Due to the straight-line nature of ultrasonic waves and the parametric effect of arranging multiple transducers, parametric speakers have the characteristics of being super-directional and making the sound sound like it is coming from close to your ears. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-89621 A [Patent Document 2] JP 2019-186836 A [Patent Document 3] JP 2019-68313 A [Patent Document 4] Japanese Patent Application Publication No. 11-262084 [Non-patent literature]

[0005] [Non-Patent Document 1] M.Kobayashi, TROlding, M.Sayer, C.-K.Jen, “Piezoelectric thick film ultrasonic transducers fabricated by a sol-gel spray technique”, Proceedings of Ultrasonics, Volume 39, Issue 10, October 2002, PP. 675-680 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the ultrasonic transducer array that makes up a parametric speaker can usually only be constructed by arranging multiple individual ultrasonic transducers, which poses a cost issue. Furthermore, for use in the special environments described above, there is the issue that the heat resistance is low compared to the required specifications, which has hindered its widespread use.

[0007] For this reason, there is a demand for a manufacturing method that can form elements efficiently and at low cost in the ultrasonic transducer array that makes up a parametric speaker, as well as a demand for realizing the operating temperature range (high temperature characteristics) required for the usage conditions of the parametric speaker.

[0008] In addition, conventionally, the ultrasonic element (ultrasonic transducer) used in the radiating section, which is the main component of parametric speakers used in highway warning speakers, can only be applied with a maximum voltage of about 80V, making it difficult to increase the output, and the directivity of a single unit is wide at 60 to 70 degrees, so the only way to sharpen the directivity is to arrange multiple ultrasonic elements in a row, which poses a cost issue. Furthermore, the components that make up the ultrasonic element are made up of multiple parts such as piezoelectric ceramics, metal plates, and cone-shaped resonators inside a resin case, making them complex and with low heat resistance, and there is an issue that the heat resistance is low compared to the required specifications for use in special environments such as highways where the heat is high in summer, which has hindered their widespread use. [Means for solving the problem]

[0009] The present invention relates to an ultrasonic transducer array, a method for manufacturing an ultrasonic transducer array, a parametric speaker using an ultrasonic transducer array, and a method for using a parametric speaker using an ultrasonic transducer array.

[0010] The present invention relates to an ultrasonic transducer array that constitutes a parametric speaker, the ultrasonic transducer being a monomorph piezoelectric element having a diaphragm, the piezoelectric body used in the piezoelectric element being a porous ceramic formed using a sol-gel method, and a parametric speaker that uses such an ultrasonic transducer array.

[0011] The present invention is also a method for manufacturing an ultrasonic transducer array constituting a parametric speaker, the ultrasonic transducer being formed on a substrate in a plurality of ultrasonic transducers, the ultrasonic transducer being a monomorph piezoelectric element having a diaphragm, the piezoelectric body used in the piezoelectric element being a porous ceramic, the piezoelectric body being formed by a sol-gel method, the forming method being formed by spraying a piezoelectric material solution on the surface of an object to construct a piezoelectric film, and then baking the piezoelectric material solution. The present invention is also a method for manufacturing an ultrasonic transducer array, the spray system for spraying the piezoelectric material solution includes a spray unit for spraying the piezoelectric material solution on the surface of the object, a holding unit for holding the piezoelectric material solution, a stirring unit for stirring the piezoelectric material solution held in the holding unit, and a circulation unit for supplying the piezoelectric material solution held by the holding unit to the spray unit using a supply path from the holding unit to the spray unit, and the circulation unit is configured to recover the piezoelectric material solution supplied to the spray unit using a recovery path from the spray unit to the holding unit when the spray unit is not spraying.

[0012] The present invention is also characterized in that the piezoelectric material solution used in the piezoelectric element is a composite of lead zirconate titanate (PZT) sol-gel solution and PZT powder.The present invention is also characterized in that the piezoelectric material solution used in the piezoelectric element is a composite of lead zirconate titanate (PZT) sol-gel solution and PZT powder, and in the piezoelectric material solution, the mass ratio of PZT powder to PZT sol-gel solution is 1.25 or less.

[0013] The present invention is also characterized in that a plurality of ultrasonic transducers are formed on a substrate in a linear, matrix or diagonal pattern.

[0014] The present invention is also characterized in that the substrate used in the ultrasonic transducer also serves as a diaphragm.The present invention is also characterized in that the substrate used in the ultrasonic transducer also serves as a diaphragm and further functions as an electrode.

[0015] The present invention is also characterized in that the substrate used in the ultrasonic transducer is a metal, and further characterized in that the substrate used in the ultrasonic transducer is a stainless steel thin plate. Further characterized in that the thickness of the substrate used in the ultrasonic transducer is 1 mm or more and 5 mm or less.

[0016] In addition, the present invention is characterized in that each of the ultrasonic transducers forming the ultrasonic transducer array is formed in a region having a substantially circular, substantially elliptical or substantially polygonal shape.

[0017] The present invention is also characterized in that each ultrasonic transducer forming the ultrasonic transducer array is formed in a region of a substantially circular, elliptical or polygonal shape, and that a part of the periphery of the region is cut out, and that each ultrasonic transducer is held by a beam.Furthermore, the present invention is characterized in that each ultrasonic transducer forming the ultrasonic transducer array is held by a beam, and that the beams are formed in 2 to 6 places for each ultrasonic transducer.

[0018] The present invention is also characterized in that each ultrasonic transducer forming the ultrasonic transducer array is formed into a non-planar shape, and the present invention is further characterized in that each ultrasonic transducer forming the ultrasonic transducer array is formed into a non-planar shape, and the shape is approximately spherical, approximately ellipsoidal, or approximately parabolic.

[0019] Furthermore, the present invention is characterized in that the piezoelectric body used in each ultrasonic transducer forming the ultrasonic transducer array is a porous ceramic, and the thickness of the piezoelectric body is 10 μm or more and 50 μm or less.

[0020] Furthermore, the present invention is characterized in that the piezoelectric body used in each ultrasonic transducer forming the ultrasonic transducer array is a porous ceramic, and the thickness of the piezoelectric body is 10 μm or more and 50 μm or less.

[0021] In the present invention, each of the ultrasonic transducers forming the ultrasonic transducer array has a counter electrode formed on a piezoelectric body.

[0022] The present invention also relates to a method for using a parametric speaker that uses the ultrasonic transducer array, characterized in that it is used for transmitting information in special environments including road construction sites, railway construction sites, and tunnel construction sites.

[0023] The present invention also relates to a method of using a parametric speaker that employs the ultrasonic transducer array, characterized in that it is used for permanent or vehicle-mounted warning purposes on expressways, warning purposes in voice guidance at toll booths, or warning purposes to prevent falls on station platforms. Effect of the Invention

[0024] The present invention can form a uniform piezoelectric film on a large-area target, and furthermore, since it is possible to define the formation area, it is possible to form multiple ultrasonic elements integrally, which allows for overwhelming cost reduction. In addition, conventional ultrasonic elements have a low maximum applied voltage, can only be manufactured in a planar structure, and have a directivity of 60 to 70 degrees per unit, so it is necessary to arrange multiple ultrasonic elements on a plane to form a parametric array to sharpen the directivity, which resulted in high costs. The newly developed ultrasonic element is porous, has a high coercive electric field, can improve the applied voltage, and can be manufactured in shapes such as curved surfaces, making it possible to achieve directivity per unit and realizing low costs. In addition, the PZT thin film generated by the piezoelectric film spray coating technology is porous with an air layer, has a high Curie temperature, and is highly heat-resistant because the parts that make up the element are metal. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a photograph showing an example of an ultrasonic transducer array according to the present invention. [Diagram 2] FIG. 2 is a conceptual diagram showing an example of a method for generating a piezoelectric curtain by a sol-gel method in a method for manufacturing an ultrasonic transducer array according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present invention relates to an ultrasonic transducer array, a method for manufacturing an ultrasonic transducer array, a parametric speaker using an ultrasonic transducer array, and a method for using a parametric speaker using an ultrasonic transducer array.

[0027] The present invention is an ultrasonic transducer array constituting a parametric speaker, in which a plurality of ultrasonic transducers are formed in a matrix on a plane, the ultrasonic transducer is a monomorph piezoelectric element having a diaphragm, the piezoelectric body used in the piezoelectric element is a porous ceramic, and is characterized by being formed by a sol-gel method, and a parametric speaker using such an ultrasonic transducer array. Conventional ultrasonic elements have a low maximum applied voltage, can only be manufactured in a planar structure, and have a directivity of 60 to 70 degrees per unit, so it is necessary to arrange multiple ultrasonic elements on a plane to form a parametric array to sharpen the directivity, which is expensive, but the newly developed ultrasonic element is porous, has a high coercive electric field, can improve the applied voltage, and can be manufactured in a shape such as a curved surface, so that directivity can be achieved by a unit and low cost can be achieved. In addition, the PZT thin film generated by the piezoelectric film spray coating technology is porous with an air layer, has a high Curie temperature, and the parts constituting the element are metal, which allows high heat resistance to be achieved.

[0028] The present invention is also a method for manufacturing an ultrasonic transducer array constituting a parametric speaker, the ultrasonic transducer being formed on a substrate in a plurality of ultrasonic transducers, the ultrasonic transducer being a monomorph piezoelectric element having a diaphragm, the piezoelectric body used in the piezoelectric element being a porous ceramic, the piezoelectric body being formed by a sol-gel method, the forming method being formed by spraying a piezoelectric material solution on the surface of an object to construct a piezoelectric film, and then baking the piezoelectric material solution. The present invention is also a method for manufacturing an ultrasonic transducer array, the spray system for spraying the piezoelectric material solution includes a spray unit for spraying the piezoelectric material solution on the surface of the object, a holding unit for holding the piezoelectric material solution, a stirring unit for stirring the piezoelectric material solution held in the holding unit, and a circulation unit for supplying the piezoelectric material solution held by the holding unit to the spray unit using a supply path from the holding unit to the spray unit, and the circulation unit is configured to recover the piezoelectric material solution supplied to the spray unit using a recovery path from the spray unit to the holding unit when the spray unit is not spraying. The manufacturing method of the ultrasonic transducer array according to the present invention is capable of forming a uniform piezoelectric film on a large-area object and further allows the formation area to be specified, making it possible to integrally form multiple ultrasonic elements and enabling dramatic cost reduction.

[0029] The present invention is also characterized in that the piezoelectric material solution used in the piezoelectric element is a composite of lead zirconate titanate (PZT) sol-gel solution and PZT powder. The present invention is also characterized in that the piezoelectric material solution used in the piezoelectric element is a composite of lead zirconate titanate (PZT) sol-gel solution and PZT powder, and in the piezoelectric material solution, the mass ratio of PZT powder to PZT sol-gel solution is 1.25 or less. With this configuration, stable film formation is achieved, and high heat resistance can be achieved by being porous with an air layer and having a high Curie temperature.

[0030] The present invention is also characterized in that a plurality of ultrasonic transducers are formed on a substrate in a linear, matrix, or diagonal pattern. According to the present invention, it is possible to integrally form a plurality of ultrasonic elements, which enables a dramatic reduction in costs.

[0031] The present invention is also characterized in that the substrate used in the ultrasonic transducer also serves as a diaphragm.The present invention is also characterized in that the substrate used in the ultrasonic transducer also serves as a diaphragm and further functions as an electrode.

[0032] The present invention is also characterized in that the substrate used in the ultrasonic transducer is a metal, and further characterized in that the substrate used in the ultrasonic transducer is a stainless steel thin plate. Further characterized in that the thickness of the substrate used in the ultrasonic transducer is 1 mm or more and 5 mm or less. With this configuration, it is possible to integrally form a plurality of ultrasonic elements, and at the same time, high heat resistance is achieved by using a metal substrate.

[0033] In addition, the present invention is characterized in that each ultrasonic transducer forming the ultrasonic transducer array is formed in a region having a substantially circular, substantially elliptical or substantially polygonal shape. Such a shape contributes to improving the performance of each ultrasonic transducer.

[0034] The present invention is also characterized in that each ultrasonic transducer forming the ultrasonic transducer array is formed in a region of a substantially circular, elliptical or polygonal shape, and that a part of the periphery of the region is cut out, and that each ultrasonic transducer is held by a beam.Furthermore, the present invention is characterized in that each ultrasonic transducer forming the ultrasonic transducer array is held by a beam, and that the beams are formed in 2 to 6 places for each ultrasonic transducer.

[0035] The present invention is also characterized in that each ultrasonic transducer forming the ultrasonic transducer array is formed in a non-planar shape, and the present invention is further characterized in that each ultrasonic transducer forming the ultrasonic transducer array is formed in a non-planar shape, and the shape is a substantially spherical, substantially elliptical, or substantially parabolic surface, which can further improve directionality and achieve high efficiency.

[0036] The present invention is also characterized in that the piezoelectric body used in each ultrasonic transducer forming the ultrasonic transducer array is a porous ceramic, and the thickness of the piezoelectric body is 10 μm to 50 μm. The PZT thin film generated by the piezoelectric film spray coating technology is porous with an air layer, has a high Curie temperature, and can achieve high heat resistance.

[0037] In addition, the present invention is characterized in that each ultrasonic transducer forming the ultrasonic transducer array has a counter electrode formed on a piezoelectric body. This configuration also contributes to the integral formation of the ultrasonic transducer array, making it possible to dramatically reduce costs.

[0038] The present invention also relates to a method for using a parametric speaker using the ultrasonic transducer array, which is characterized by being used for transmitting information in special environments including road construction sites, railway construction sites, and tunnel construction sites. The present invention also relates to a method for using a parametric speaker using the ultrasonic transducer array, which is characterized by being used for permanent or vehicle-mounted warning on expressways, warning in voice guidance at toll booths, or warning to prevent falls on station platforms. The parametric speaker using the ultrasonic transducer array of the present invention is extremely effective in special environments such as those described above due to its characteristics of super-directivity, high heat resistance, and high efficiency. EXAMPLES

[0039] An ultrasonic transducer array according to the present invention will be described below based on an embodiment. Fig. 1 is a photograph substituted for a drawing showing an example of an ultrasonic transducer array according to the present invention.

[0040] In this embodiment, a plurality of ultrasonic transducers are formed on a substrate, and the ultrasonic transducers are monomorph piezoelectric elements having a vibration plate. The piezoelectric material used in the piezoelectric elements is porous ceramics, and the piezoelectric material is formed using a sol-gel method, in which a piezoelectric material solution is sprayed onto the surface of an object using an injection system to build a piezoelectric film on the surface, followed by firing.

[0041] In this embodiment, five ultrasonic transducer elements are formed linearly on a substrate, each element having a circular shape, and each element is supported by beams at two locations.

[0042] The substrate used in the ultrasonic transducer also served as a diaphragm and also as an electrode. A stainless steel thin plate having a thickness of 2 mm was used as the substrate used in the ultrasonic transducer.

[0043] Here, the ultrasonic transducer may be formed not only linearly on the substrate, but also in a matrix or diagonal pattern. It is effective that the substrate used for the ultrasonic transducer also functions as a diaphragm, and it is more preferable that the substrate also functions as a diaphragm and also as an electrode.

[0044] In addition, each ultrasonic transducer forming the ultrasonic transducer array may be formed in an area having a shape not only of a circle but also of a substantially circular, substantially elliptical, or substantially polygonal shape. It is effective that each ultrasonic transducer area has a part of its periphery cut out and each ultrasonic transducer is held by a beam. It is desirable that the beam is formed in 2 to 6 places for each ultrasonic transducer.

[0045] In this embodiment, the ultrasonic transducers are formed in a plane, but according to the method of forming a piezoelectric film using a spraying system that sprays a piezoelectric material solution using a sol-gel method according to the present invention, the ultrasonic transducers may be formed in a non-planar shape. This makes it possible to form an ultrasonic transducer array that constitutes a parametric speaker with higher directivity and efficiency. Here, the non-planar shape is preferably an approximately spherical, approximately elliptical, or approximately parabolic shape.

[0046] 2 is a conceptual diagram showing an example of a method for producing a piezoelectric film by a sol-gel method in a manufacturing method of an ultrasonic transducer array according to the present invention. The ultrasonic transducer array constituting the parametric speaker according to the present invention is formed in a matrix on a plane, and the ultrasonic transducer is a monomorph piezoelectric element having a diaphragm, and the piezoelectric body used in the piezoelectric element is porous ceramics and formed by the sol-gel method.

[0047] The formation of a piezoelectric body according to the present invention is a method of forming a piezoelectric body by spraying a piezoelectric material solution onto the surface of an object using a spray system, followed by baking the piezoelectric material solution to build a piezoelectric film on the surface of the object. The spray system for spraying the piezoelectric material solution includes a spray unit that sprays the piezoelectric material solution onto the surface of the object, a holding unit that holds the piezoelectric material solution, a stirring unit that stirs the piezoelectric material solution held in the holding unit, and a circulation unit that supplies the piezoelectric material solution held by the holding unit to the spray unit using a supply path from the holding unit to the spray unit, and the circulation unit is configured to recover the piezoelectric material solution supplied to the spray unit using a recovery path from the spray unit to the holding unit when the spray unit is not spraying.

[0048] The piezoelectric material solution used in the piezoelectric element is a composite of lead zirconate titanate (PZT) sol-gel solution and PZT powder. In the piezoelectric material solution, the mass ratio of the PZT powder to the PZT sol-gel solution is preferably 1.25 or less. In this embodiment, the mass ratio of the PZT powder to the PZT sol-gel solution was set to 1.

[0049] When spraying onto a flat surface, a uniform coating may be formed by two-dimensionally scanning the spray gun over the target. When the non-flat shape is an approximately spherical, elliptical, or parabolic surface, coating can be performed in almost the same manner as for flat shapes, but when spraying onto a free-form surface, it is effective to control a six-axis coating robot and spray based on the coating parameters established for spraying onto a flat surface.

[0050] In this example, the piezoelectric material solution was sprayed using a spray system as described above, then the piezoelectric film was pre-baked at 150 degrees Celsius for 10 minutes, sintered at 650 degrees Celsius for 5 minutes, and then polarized by corona discharge to obtain a piezoelectric film. Furthermore, a counter electrode was formed on the surface of the piezoelectric film to function as an ultrasonic transducer. The piezoelectric body was made of porous ceramics.

[0051] The present invention is not limited to the above processing conditions, and processing conditions that allow the function to be exerted can be set.

[0052] In this example, the thickness of the piezoelectric body after the sintering and polarization steps was 30 μm. Here, the thickness of the piezoelectric body is preferably 10 μm or more and 50 μm or less, and more preferably 20 μm or more and 40 μm or less.

[0053] The ultrasonic transducer array manufactured in this embodiment is preferably used for a parametric speaker. The parametric speaker using the ultrasonic transducer array according to the present invention can be used for information transmission in special environments including road construction sites, railway construction sites, and tunnel construction sites, for permanent or vehicle-mounted warning on expressways, for warning in voice guidance at toll booths, or for warning to prevent falls on station platforms. Due to its characteristics of super directivity, high heat resistance, and high efficiency, it can be extremely effective in such special environments. [Industrial Applicability]

[0054] As described above, the ultrasonic transducer array, the manufacturing method of the ultrasonic transducer array, the parametric speaker using the ultrasonic transducer array, and the method of using the parametric speaker using the ultrasonic transducer array according to the present invention make it possible to integrally form a plurality of ultrasonic elements, which allows for overwhelming cost reduction. In addition, since conventional ultrasonic elements have a low maximum applied voltage and can only be manufactured in a planar structure, and the directivity of each element is 60 to 70 degrees, it is necessary to arrange multiple ultrasonic elements on a plane to form a parametric array and sharpen the directivity, which results in high costs. The newly developed ultrasonic element is porous, has a high coercive electric field, can improve the applied voltage, and can be manufactured in shapes such as curved surfaces, making it possible to realize directivity for each element and achieving low costs. In addition, the PZT thin film generated by the piezoelectric film spray coating technology is porous with an air layer, has a high Curie temperature, and is highly heat-resistant because the parts constituting the element are metal. [Explanation of symbols]

[0055] 1 Ultrasonic transducer 2 Beam section

Claims

1. An ultrasonic transducer array that configures a parametric speaker using a plurality of ultrasonic transducers, A plurality of the ultrasonic transducers are formed on a single metal substrate, The ultrasonic transducer is a monomorph piezoelectric element in which the metal substrate also serves as a vibration plate, The piezoelectric body used in the piezoelectric element is made of porous ceramics, The metal substrate is characterized in that a part of the periphery of each region in which each ultrasonic transducer is formed is cut out, and the inside of each region is not cut out, and a plurality of beams for holding each ultrasonic transducer are formed. Ultrasound transducer array.

2. The porous ceramic is characterized in that it is formed of lead zirconate titanate (PZT).

2. The ultrasonic transducer array of claim 1.

3. The thickness of the metal substrate is 1 mm or more and 5 mm or less.

3. The ultrasonic transducer array according to claim 1 or 2.

4. The region in which the ultrasonic transducer is formed is substantially circular, substantially elliptical, or substantially polygonal in shape.

4. An ultrasonic transducer array according to claim 1.

5. The metal substrate is characterized in that it has a non-planar shape.

5. An ultrasonic transducer array according to claim 1.

6. The thickness of the piezoelectric body is 10 μm or more and 50 μm or less.

6. An ultrasonic transducer array according to claim 1.

7. A method for manufacturing an ultrasonic transducer array that configures a parametric speaker using a plurality of ultrasonic transducers, comprising: A piezoelectric material solution composed of a composite of lead zirconate titanate (PZT) sol-gel solution and PZT powder is sprayed onto a metal substrate, which also serves as the vibration plate of the ultrasonic transducer, and then fired to form a porous ceramic that will become a piezoelectric body. Each ultrasonic transducer is formed by forming a plurality of opposing electrodes corresponding to each ultrasonic transducer on the piezoelectric body, Furthermore, the metal substrate is characterized in that a part of the periphery of each region in which each ultrasonic transducer is formed is cut out, and the inside of each region is not cut out, and a plurality of beams for holding each ultrasonic transducer are formed. A method for manufacturing an ultrasonic transducer array.

8. In the piezoelectric material solution, the mass ratio of the PZT powder to the PZT sol-gel solution is 1.25 or less. A method for manufacturing the ultrasonic transducer array according to claim 7.

9. The metal substrate is formed into a non-planar shape corresponding to each ultrasonic transducer. A method for manufacturing an ultrasonic transducer array according to claim 7 or 8.

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