JP7261429B2 - Sonar, ultrasonic transducer and manufacturing method thereof - Google Patents

Description

The present invention relates to a sonar for detecting objects such as schools of fish using ultrasonic waves, an ultrasonic transducer suitable for the sonar, and a method for manufacturing the same.

Conventionally, there is known a sonar that detects an object to be detected such as a school of fish by transmitting and receiving ultrasonic waves (see, for example, Patent Document 1). The sonar has an ultrasonic transducer that transmits and receives ultrasonic waves, and a mechanism that tilts and rotates the central axis of the ultrasonic transducer. , is designed to detect underwater. Then, the result of underwater detection is displayed on the screen as a detected image. An ultrasonic transducer generally includes a disk-shaped piezoelectric element and an acoustic matching layer bonded to the irradiation surface of the piezoelectric element.

By the way, in sonar, there is a demand for detecting objects at longer distances. For this purpose, it is necessary to make the ultrasonic transducer highly sensitive. In addition, it is necessary to increase the sound pressure of transmitted waves by driving the ultrasonic transducer with a high voltage. As a method for increasing the sensitivity of the ultrasonic transducer, as shown in FIGS. , and a composite structure in which a resin material 104 is filled between adjacent pillars 103 (see Patent Documents 2 to 4, for example). In this way, each column portion 103, which is a vibrating portion, is easily deformed, so that the piezoelectric element 102 is easily deformed at each site. That is, since the piezoelectric element 102 is easily vibrated, the sensitivity of the ultrasonic transducer 101 is increased.

Japanese Patent No. 5979537 (claim 1, FIG. 4, etc.) Japanese Patent Application Laid-Open No. 2002-22718 (Fig. 1, etc.) Japanese Patent Application Laid-Open No. 2018-113279 (Fig. 1, Fig. 4, etc.) WO2011/083611 (Fig. 3, etc.)

By the way, in order to transmit and receive ultrasonic waves from the ultrasonic transducer 101, it is necessary to form electrodes 105 on both sides of the piezoelectric element 102 and apply a voltage between the electrodes 105. FIG. However, even if the ultrasonic transducer 101 having a composite structure as in Patent Documents 2 to 4 is used, the ultrasonic transducer 101 must be applied at 1.5 kV in order to capture the reflection from a school of fish at a depth of 500 m or more. It is necessary to drive at a high voltage. However, in conventional structures such as those disclosed in Patent Documents 2 to 4, when the ultrasonic transducer 101 is continuously driven at 1.5 kV for a long period of time, the electrode 105 is damaged and separated from the piezoelectric element 102. There is a problem that the sensitivity is lowered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a sonar and an ultrasonic transducer that can prevent a decrease in sensitivity by increasing the bonding strength between a piezoelectric element and an electrode portion. That's what it is. Another object of the present invention is to provide a method of manufacturing an ultrasonic transducer that is easy to manufacture and has a high yield.

In order to solve the above problems, the invention according to claim 1 is a sonar having an ultrasonic transducer that transmits and receives ultrasonic waves and a mechanism that tilts and rotates the central axis of the ultrasonic transducer, The ultrasonic transducer is composed of a base material that also serves as an acoustic matching layer and a plurality of divided vibrating parts, and is made of a ceramic plate having a front surface joined to the base material and a back surface on the opposite side. a piezoelectric element having a shape, wherein a conductive mesh is arranged on the back surface of the piezoelectric element over the entire back surface, and the conductive mesh forms a mesh by weaving vertical and horizontal wires. In addition, the conductive mesh has an undulating shape in the thickness direction, and the conductive mesh is bonded to the piezoelectric element via a bonding material in a state where the crossing portions of the vertical and horizontal wires are in contact with the end surface of the vibrating portion . The subject matter is a sonar characterized by:

Therefore, according to the first aspect of the invention, in addition to interposing the bonding material between the conductive mesh, which is the electrode portion, and the piezoelectric element, the bonding material enters the holes of the conductive mesh, thereby A mesh is bonded to the piezoelectric element. As a result, the bonding strength between the piezoelectric element and the conductive mesh is increased, so that the conductive mesh is less likely to separate from the piezoelectric element even if the ultrasonic transducer is continuously driven for a long period of time. Therefore, it is possible to prevent a decrease in sensitivity of the ultrasonic transducer.

As the bonding material, an adhesive such as an epoxy adhesive having a relatively strong bonding force can be used. A brazing material such as solder may be used instead of the adhesive.

The invention according to claim 2 is characterized in that, in claim 1, the conductive mesh is a plain-woven wire mesh.

Therefore, according to the second aspect of the invention, the vertical and horizontal wires forming the mesh of the conductive mesh are woven into a shape in which the wires are undulated in the vertical direction. As a result, the contact pressure between the intersections of the vertical and horizontal wires and the end face of the vibrating portion increases, so that the conductive mesh can reliably function as an electrode. In addition, since fine meshes are densely packed in the conductive mesh, the bonding material is likely to enter the gaps of the meshes. Therefore, the bonding strength between the piezoelectric element and the conductive mesh is further increased. As a material for forming the conductive mesh, a metal wire having a low electric resistance such as copper or silver can be used.

The invention according to claim 3 is characterized in that, in claim 1 or 2, the bonding material solidifies in a state in which it enters both the gaps between the meshes in the conductive mesh and the gaps between the plurality of vibrating parts, The gist is that the conductive mesh is joined to the end surfaces of the plurality of vibrating portions.

Therefore, according to the third aspect of the invention, the bonding material joins the piezoelectric element and the conductive mesh by the anchor effect obtained by entering both the gaps in the mesh of the conductive mesh and the gaps between the plurality of vibrating parts. Strength is even higher. As a result, the separation of the conductive mesh from the piezoelectric element is reliably prevented, thereby dramatically improving the reliability of the ultrasonic transducer.

The invention according to claim 4 is the piezoelectric element according to any one of claims 1 to 3, wherein the plurality of vibrating portions are a plurality of pillars divided so as to extend along the thickness direction of the piezoelectric element. That is the gist of it.

Therefore, according to the fourth aspect of the invention, since the plurality of vibrating portions are the plurality of pillars divided so as to extend along the thickness direction of the piezoelectric element, each of the pillars extends in the height direction. It becomes easy to transform into. As a result, the piezoelectric element is easily deformed in the thickness direction at each part, and the piezoelectric element is easily vibrated. Therefore, even if the conductive mesh is arranged on the back surface of the piezoelectric element, the conductive mesh is easily peeled off. Therefore, by bonding the conductive mesh to the back surface of the piezoelectric element via a bonding material, the peeling of the conductive mesh can be reliably prevented. In this specification, the term "columnar section" is defined as having a maximum dimension equal to or less than the height of the vibrating section when the vibrating section is viewed from the thickness direction of the piezoelectric element.

A fifth aspect of the invention is characterized in that, in the first to fourth aspects, the plurality of vibrating portions are connected to each other at the front end portion of the piezoelectric element.

Therefore, according to the fifth aspect of the invention, even if the piezoelectric element is divided into a plurality of vibrating portions, the thickness of the portion where the vibrating portions are connected to each other at the front end of the piezoelectric element is ensured. . Therefore, the strength of the piezoelectric element can be secured.

According to a sixth aspect of the present invention, in the first to fifth aspects, the size of the mesh of the conductive mesh is smaller than the maximum size of the vibrating portion when viewed from the thickness direction of the piezoelectric element. This is the gist.

Therefore, according to the sixth aspect of the invention, the wires forming the meshes of the conductive mesh are reliably brought into contact with the end surfaces of the vibrating portions one by one. In other words, a plurality of contact points exist within each end surface. Therefore, by bonding the conductive mesh to the piezoelectric element, the conductive mesh reliably serves as a common electrode for the end surfaces of the vibrating portions.

Here, examples of the shape of the end face of the vibrating portion include a planar view polygonal shape, a planar view circular shape, and the like. For example, when the vibrating portion has a polygonal shape in plan view such as a rectangular shape or a hexagonal shape in plan view, the maximum dimension of the vibrating portion when viewed from the thickness direction is the diagonal line of the end surface (back surface) of the vibrating portion. is the length of Further, when the vibrating portion has a circular shape in a plan view, the maximum dimension when the vibrating portion is viewed from the thickness direction is the diameter of the end surface of the vibrating portion.

The invention according to claim 7 is the piezoelectric element according to any one of claims 1 to 6, wherein the front surface of the piezoelectric element is bonded to the base material via a front electrode layer, and the front electrode layer The gist of this is that it is a plain electrode layer with a sufficient thickness.

Therefore, according to the seventh aspect of the invention, since the front electrode layer is a plain electrode layer, the contact area between the piezoelectric element and the front electrode layer is increased, and the contact between the front electrode layer and the substrate is increased. area becomes larger. Therefore, the bonding strength between the piezoelectric element and the substrate is improved.

In addition, the base material can be appropriately selected in consideration of specific acoustic impedance, frequency of ultrasonic waves, mechanical strength, and the like. Suitable materials for forming the base material include, for example, glass epoxy (FR-4), glass epoxy (CEM-3), polyphenyl sulfide (PPS), Duratron (registered trademark of the QUADRANT Group), Fluorosint (QUADRANT Group (registered trademark), porous bodies of alumina, and the like.

According to an eighth aspect of the present invention, there is provided an ultrasonic transducer for transmitting and receiving ultrasonic waves, comprising a base material that also serves as an acoustic matching layer, and a plurality of divided vibrating parts, which are joined to the base material. a piezoelectric element made of a ceramic plate having a front surface and a back surface on the opposite side, a conductive mesh is disposed on the back surface of the piezoelectric element over the entire back surface, and the The conductive mesh forms a mesh by weaving vertical and horizontal wires, and has an undulating shape in the thickness direction . 1. An ultrasonic transducer characterized in that said conductive mesh is bonded to said piezoelectric element via a bonding material.

Therefore, according to the eighth aspect of the invention, in addition to interposing the bonding material between the conductive mesh, which is the electrode portion, and the piezoelectric element, the bonding material enters the holes of the conductive mesh, thereby A mesh is bonded to the piezoelectric element. As a result, the bonding strength between the piezoelectric element and the conductive mesh is increased, so that the conductive mesh is less likely to separate from the piezoelectric element even if the ultrasonic transducer is continuously driven for a long period of time. Therefore, it is possible to prevent a decrease in sensitivity of the ultrasonic transducer.

The invention according to claim 9 is the method for manufacturing the ultrasonic transducer according to claim 8, further comprising a bonding step of bonding a ceramic plate-like object to be the piezoelectric element to one side of the base material. After the joining step, a plurality of cuts are formed in the back side of the ceramic plate-like object, so that the ceramic plate-like object is connected to the plurality of vibrating portions at the end portion on the front side thereof. and after the vibrating portion forming step, a conductive mesh is arranged on the back surface of the piezoelectric element so as to be in contact with the end surfaces of the plurality of vibrating portions, and in this state, a bonding material is interposed. The gist of the method is a method for manufacturing an ultrasonic vibrator, comprising: a step of installing a mesh to join the conductive mesh.

Therefore, according to the ninth aspect of the invention, the ceramic plate is joined to the base material before the cut is formed in the ceramic plate. It becomes the "support" of the ceramic plate. As a result, even if a cut is formed, the ceramic plate-like object is less likely to break. In addition, the cut can be formed to a fairly deep position in the ceramic plate. Furthermore, after the back surface of the ceramic plate-shaped object is divided by forming the cuts, the mesh installation step is carried out so that the conductive mesh is placed in contact with the end face of each vibrating part. , multiple end faces can be easily contacted. Furthermore, in the mesh installation step, when the conductive mesh is bonded to the piezoelectric element via a bonding material, the bonding material easily enters both the gaps between the meshes of the conductive mesh and the gaps between the plurality of vibrating parts. The bonding strength between the piezoelectric element and the conductive mesh is increased. Moreover, since the bonding material enters the gaps between the vibrating portions, the vibrating portions are supported by the bonding material so as to be less likely to be damaged. In other words, it becomes easier to form cuts and to join the conductive mesh, making it easier to manufacture an ultrasonic transducer. In addition, since the ultrasonic transducers are easy to manufacture and less likely to be damaged, the rate of defective products is reduced, and the yield of the ultrasonic transducers is increased.

As described in detail above, according to the first to eighth aspects of the present invention, it is possible to prevent a decrease in the sensitivity of the ultrasonic transducer by increasing the bonding strength between the piezoelectric element and the electrode portion. Further, according to the ninth aspect of the invention, it is possible to manufacture an ultrasonic transducer that is easy to manufacture and has a high yield.

FIG. 2 is an explanatory diagram showing a ship on which the sonar of the present embodiment is mounted; FIG. 2 is a schematic configuration diagram showing a sonar, an elevating device, and a liquid crystal monitor; Schematic cross-sectional view showing a sonar. Schematic cross-sectional view showing a sonar. FIG. 2 is a schematic cross-sectional view showing an ultrasonic transducer housed in a case; FIG. 2 is a plan view showing an ultrasonic transducer; FIG. 2 is a side view showing an ultrasonic transducer; Sectional drawing which shows a column part. The perspective view which shows a column part. 2 is a block diagram showing the electrical configuration of the sonar; FIG. (a) is a cross-sectional view showing the pillar portion during expansion, and (b) is a cross-sectional view showing the pillar portion during contraction. Graph showing changes in capacitance due to continuous driving of an ultrasonic transducer. 4 is a graph showing changes in the transmission/reception sensitivity product due to continuous driving of the ultrasonic transducer. 4 is a graph showing changes in sensitivity in a running test in Comparative Example 1. FIG. FIG. 2 is a schematic perspective view showing a piezoelectric element with a 1-3 composite structure; FIG. 2 is a schematic perspective view showing a piezoelectric element having a 2-2 composite structure; FIG. 10 is a cross-sectional view of a main part showing an ultrasonic transducer according to another embodiment; FIG. 2 is a plan view of a main part showing a punching mesh; FIG. 10 is a schematic plan view showing an ultrasonic transducer in another embodiment; FIG. 10 is a schematic cross-sectional view showing an ultrasonic transducer housed in a case according to another embodiment; FIG. 2 is a plan view of a main part showing a piezoelectric element in the prior art; Sectional drawing which shows the column part in a prior art.

An embodiment embodying the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the sonar 11 of this embodiment is mounted on the bottom of a ship 10 and used. The sonar 11 is a device that detects an object to be detected S1 such as a school of fish existing in water by irradiating the water with ultrasonic waves W1. Also, as shown in FIG. 2, the sonar 11 is attached to the lifting device 12 . The elevating device 12 is a device that causes the sonar 11 to appear and disappear from the bottom of the ship and into the water by elevating the sonar 11 . Further, a liquid crystal monitor 13 is electrically connected to the sonar 11 and the lifting device 12 . The liquid crystal monitor 13 is installed in the steering room of the ship 10 and has an operation section 14 and a display section 15 .

As shown in FIGS. 3 and 4, sonar 11 includes sonar dome 20 . The sonar dome 20 is made of a resin material such as ABS resin (acrylonitrile-butadiene-styrene resin), and includes an upper case 21 , a lower case 22 and a lid 23 . The upper case 21 is a bottomed cylindrical case that is open at its lower end, and the lower case 22 is a bottomed cylindrical case that is open at its upper end. The lower end of the lower case 22 is dome-shaped (hemispherical). The cover 23 is disc-shaped and serves to close the lower opening of the upper case 21 and the upper opening of the lower case 22 . An upper housing space 24 is formed by the lid 23 and the upper case 21 , and a lower housing space 25 is formed by the lid 23 and the lower case 22 .

Further, the sonar dome 20 accommodates an ultrasonic transducer 41 that transmits and receives the ultrasonic wave W1, and a tilting and rotating mechanism 30 that tilts and rotates the central axis O1 of the ultrasonic transducer 41. As shown in FIG. The tilt rotation mechanism 30 includes a scan motor 31, a tilt motor 32, a case 40 that houses an ultrasonic transducer 41, and the like. The scan motor 31 is installed in the center of the lid 23 inside the upper accommodation space 24 . A stepping motor is used as the scan motor 31 of this embodiment. An output shaft 31 a of the scan motor 31 is inserted through a through hole 33 provided in the central portion of the lid 23 and protrudes into the lower accommodation space 25 . Further, the tip of the output shaft 31a is connected to the central portion of a disk-shaped support plate 34, and a support frame 35 is attached to the lower surface of the support plate 34. As shown in FIG. The support frame 35 is U-shaped with a pair of arms 35a.

As shown in FIGS. 3 and 4, the case 40 is made of a resin material such as ABS resin and is formed into a bottomed cylindrical shape with one end open. It is attached to the connecting rotating shaft 36 . Therefore, when the output shaft 31a of the scan motor 31 rotates, the support plate 34, the support frame 35, the case 40, and the ultrasonic transducer 41 (the central axis O1 thereof) rotate about the output shaft 31a. Along with this, the irradiation direction of the ultrasonic wave W1 output from the ultrasonic transducer 41 changes along the circumferential direction of the output shaft 31a.

Also, the tilt motor 32 is attached to the upper end of the support frame 35 . A stepping motor is used as the tilt motor 32 of this embodiment. The output shaft 32a of the tilt motor 32 is arranged parallel to the rotary shaft 36, and a pinion gear 32b is attached to the tip of the output shaft 32a. The pinion gear 32 b meshes with a substantially semicircular tilt gear 37 attached to the case 40 . Therefore, when the output shaft 32a of the tilt motor 32 rotates, the pinion gear 32b and the tilt gear 37 rotate, causing the case 40 and the ultrasonic transducer 41 (the central axis O1 thereof) to incline ( Rotate. Along with this, the irradiation angle of the ultrasonic wave W1 output from the ultrasonic transducer 41 also changes as the ultrasonic transducer 41 rotates.

As shown in FIGS. 5 to 7, the ultrasonic transducer 41 has a substrate 42 and a piezoelectric element 43. As shown in FIG. The base material 42 is a resin plate-like object formed using glass epoxy (FR-4), which is a material that also serves as an acoustic matching layer, and has a disk shape with a thickness t2 (see FIG. 7) of 3.0 mm. is making Further, the specific acoustic impedance of the base material 42 is 2.3×10 ⁶ (Pa·s/m) or more and 14×10 ⁶ (Pa·s/m) or less, preferably 3×10 ⁶ (Pa·s/m) or less. ) or more and 9×10 ⁶ (Pa·s/m) or less. By doing so, the transmittance of the ultrasonic wave W1 at the boundary portion between the base material 42 and the piezoelectric element 43 is increased, so that the transmission/reception sensitivity of the ultrasonic transducer 41 is further increased.

As shown in FIGS. 6 and 7, four overhanging portions 44 are provided on the outer peripheral portion of the base material 42, and each of the overhanging portions 44 is provided with a screw hole 45. As shown in FIGS. Each screw hole 45 is arranged at equal angular intervals with the central axis O1 of the ultrasonic transducer 41 as a reference. Then, a screw (not shown) is inserted through each screw hole 45 , and the tip of the inserted screw is screwed into the case 40 . As a result, the ultrasonic transducer 41 is fixed to the case 40 (see FIG. 5).

The piezoelectric element 43 is, for example, a ceramic plate made of lead zirconate titanate (PZT), which is a piezoelectric ceramic, and has a specific acoustic impedance of 32×10 ⁶ (Pa·s/m). It has become. The piezoelectric element 43 has a disc shape with a thickness t1 (see FIG. 7) of 7.2 mm. Since the outer diameter of the piezoelectric element 43 is smaller than the outer diameter of the base material 42 , the area of the piezoelectric element 43 is smaller than the area of the base material 42 . The piezoelectric element 43 also has a front surface 51 bonded to the substrate 42 , a rear surface 52 opposite to the front surface 51 , and an outer peripheral surface 53 perpendicular to the front surface 51 and the rear surface 52 . Furthermore, as shown in FIGS. 5 and 8, a front electrode layer 54 is formed on the front surface 51 of the piezoelectric element 43 and a rear electrode layer 55 is formed on the rear surface 52 of the piezoelectric element 43 . In this embodiment, the entire front surface 51 of the piezoelectric element 43 is bonded to the substrate 42 via the front electrode layer 54 and the adhesive layer 56 (see FIG. 8). It is a plain electrode layer of uniform thickness.

As shown in FIGS. 5 to 9, the piezoelectric element 43 is composed of a plurality of divided columnar portions 57 (vibrating portions) extending along the thickness direction of the piezoelectric element 43. As shown in FIG. Each column portion 57 is configured by forming a plurality of first cuts K1 and a plurality of second cuts K2 orthogonal to the first cuts K1 in the back surface 52 of the piezoelectric element 43 . In this embodiment, the first cuts K1 are arranged parallel to each other, and the second cuts K2 are also arranged parallel to each other. Therefore, among the pillars 57, the pillars 57 that do not constitute the outer peripheral surface 53 are formed in the shape of a regular quadrangular prism. The columns 57 are arranged on a straight line along the X direction (see FIG. 6), and are also arranged on a straight line along the Y direction (see FIG. 6).

The columns 57 are connected to each other at the ends of the piezoelectric elements 43 on the front surface 51 side. The height H1 (thickness) of the column portion 57 is equal to the depth of the cuts K1 and K2. Here, the height H1 is 6.7 mm, which is approximately 93% (≈6.7/7.2×100) of the thickness t1 (7.2 mm) of the piezoelectric element 43 . Therefore, the thickness t<b>2 (3.0 mm) of the base material 42 described above is smaller than the height H<b>1 of the column portion 57 . Further, the thickness H2 of the portion where the columnar portions 57 are connected to each other in the piezoelectric element 43 is a value calculated from the formula t1-H1, and is smaller than the thickness t2 of the base material .

As shown in FIGS. 6 to 9, the tip surface 58 (back surface 52) of the column portion 57 has a square shape in plan view, and the lengths L1 and L2 of the sides forming the tip surface 58 are equal to each other. They are equal and 2.4 mm each. The widths of the cuts K1 and K2 described above are equal to each other and are 100% or less, preferably 17% or more and 30% or less of the lengths L1 and L2. Moreover, the length of the diagonal line of the tip surface 58 is about 3.39 mm, and the length of this diagonal line is the maximum dimension L3 (see FIG. 9) when the column portion 57 is viewed from the thickness direction. The maximum dimension L3 is 80% or less, preferably 60% or less (approximately 51% (≈3.39/6.7×100) in this embodiment) of the height H1 of the column portion 57 . In this case, since the flexural vibration of the column portions 57 is reduced, each column portion 57 can be easily vibrated along the thickness direction of the piezoelectric element 43 . Further, the total area of the tip surface 58 of each column 57 is 25% or more and 80% or less, or 60% or more and 80% or less of the area of the front surface 51 (back surface 52) of the piezoelectric element 43 .

Furthermore, the piezoelectric element 43 of the present embodiment is made of lead zirconate titanate (PZT), and the center frequency of the ultrasonic wave W1 that maximizes the sensitivity is 160 kHz or more and 200 kHz or less. The ratio (fractional band) is 27% or more and 52% or less. In this embodiment, the sound speed c1 (4160 m/s) of the longitudinal wave (ultrasonic wave W1) propagating in the piezoelectric element 43, the sound speed c2 (2460 m/s) of the longitudinal wave (ultrasonic wave W1) propagating in the base material 42, s), the thickness t1 (7.2 mm) of the piezoelectric element 43 and the thickness t2 (3.0 mm) of the base material 42 are (c2×t1)/(c1×t2)=0.8 or more and 1.7 or less. meet the relationship. By doing so, the relative band of the ultrasonic wave W1 can be widened, and the sensitivity of the ultrasonic transducer 41 is also increased.

As shown in FIGS. 5, 6, 8 and 9, a copper mesh 91 (conductive mesh) is arranged over the entire back surface 52 of the piezoelectric element 43 . The copper mesh 91 of the present embodiment is a plain weave wire mesh and is composed of a plurality of meshes 92 . Each mesh 92 has a square shape in plan view, and is composed of a pair of first wires 93 and a pair of second wires 94 orthogonal to both first wires 93 . Each first wire 93 is a copper wire extending in the X direction (see FIG. 6) and arranged parallel to each other. In addition, the pitch p1 (see FIG. 9) between adjacent first wires 93 is one-third or less of the pitch P1 between adjacent first cuts K1, and the side length L1 It is about one-fifth of (2.4 mm). Similarly, each second wire 94 is also a copper wire extending along the Y direction (see FIG. 6) and arranged parallel to each other. In addition, the pitch p2 (see FIG. 9) between adjacent second wires 94 is one-third or less of the pitch P2 between adjacent second cuts K2, and the length L2 of the side forming tip surface 58 is It is about one-fifth of (2.4 mm). Therefore, the dimensions (pitches p1, p2) of the meshes 92 are equal to each other and are finer than the maximum dimension L3 (approximately 3.39 mm) when the column portion 57 is viewed from the thickness direction. Further, the total area of the gaps of the meshes 92 is 10% or more and 30% or less of the area of the back surface 52 (front surface 51) of the piezoelectric element 43. FIG.

As shown in FIG. 8, the copper mesh 91 has vertical and horizontal wires 93 and 94 that are woven into a shape in which the wires 93 and 94 are undulated. Therefore, the copper mesh 91 is formed with the joining material 90 (eg, epoxy It is bonded to the back side electrode layer 55 on the back side 52 via an adhesive). In addition, the bonding material 90 enters both the gaps between the meshes 92 in the copper mesh 91 and part of the gaps K0 (cuts K1 and K2) between the columns 57 (openings on the back surface 52 side of the piezoelectric element 43). The copper mesh 91 is joined to the tip end face 58 of each column portion 57 by solidifying in the bare state. As a result, a plurality of (36 in this embodiment) crossing portions A1 are in reliable contact with each of the back side electrode layers 55 on the tip surface 58 of each column portion 57, so that the copper mesh 91 By joining, the copper mesh 91 becomes a common electrode for the tip surface 58 of each column portion 57 .

A first lead wire 62 is connected to the front electrode layer 54 and a second lead wire 63 is connected to the copper mesh 91, as shown in FIG. The first lead wires 62 are connected by soldering or the like to side terminals (not shown) extending outward from the front electrode layer 54 . The second lead wire 63 is connected to the outer periphery of the copper mesh 91 by soldering or the like. The first lead wire 62 and the second lead wire 63 are bound by a wiring tube 64 and pulled out of the case 40 . Although the first lead wire 62 is connected to the side terminal, a metal foil (not shown) such as copper foil is attached on the front side electrode layer 54 or on the surface 42a of the substrate 42 so that the metal foil is connected to the side terminal. Alternatively, the first lead wire 62 may be connected by soldering or the like. A sheet-like soundproof material 65 (backing material) is attached on the copper mesh 91 . The soundproof material 65 is for suppressing reverberation, and is attached to the inner peripheral surface of the case 40 as well. As the soundproof material 65, a resin material or rubber containing particles or fibers made of metal or ceramics, or a resin material having dispersed holes (sponge or the like) is used. can be used.

The sonar dome 20 shown in FIGS. 3 and 4 is filled with an ultrasonic wave propagating liquid (not shown) for propagating the ultrasonic wave W1. Further, part of the ultrasonic wave propagating liquid flows into the case 40 through a liquid passage (not shown) provided in the case 40, and the gap K0 (notch K1, K2) and fills the air gap K0. The ultrasonic wave propagating liquid of this embodiment is liquid paraffin and has a specific acoustic impedance of 1.2×10 ⁶ (Pa·s/m). Therefore, the intrinsic acoustic impedance (2.3 to 14×10 ⁶ (Pa·s/m)) of the substrate 42 described above is the intrinsic acoustic impedance (32×10 ⁶ (Pa·s/m)) of the piezoelectric element 43. and larger than the specific acoustic impedance of ultrasonic propagating liquid and the specific acoustic impedance of water (1.5×10 ⁶ (Pa·s/m)).

Next, the electrical configuration of the sonar 11 will be described.

As shown in FIG. 10, the liquid crystal monitor 13 of the sonar 11 has a control device 70 that controls the entire device. The control device 70 is composed of a well-known computer including a CPU 71, a ROM 72, a RAM 73, and the like.

The CPU 71 is electrically connected to the scan motor 31 and the tilt motor 32 via the motor driver 81, and controls them by various drive signals. Also, the CPU 71 is electrically connected to the ultrasonic transducer 41 via the transmission/reception circuit 82 . The transmission/reception circuit 82 outputs an oscillation signal to the ultrasonic transducer 41 to drive the ultrasonic transducer 41 . As a result, the ultrasonic transducer 41 irradiates (transmits) the ultrasonic wave W1 toward the water. Further, the transmitting/receiving circuit 82 is adapted to receive an electrical signal representing the ultrasonic waves W1 (reflected waves W2) received by the ultrasonic transducer 41 . Further, the CPU 71 is electrically connected to the lifting device 12, the operating section 14, the display section 15, and the GPS (Global Positioning System) receiving section 83, respectively.

The CPU 71 shown in FIG. 10 controls the transmitting/receiving circuit 82 to irradiate the ultrasonic wave W1 from the ultrasonic transducer 41 and controls the driving of the lifting device 12 . The CPU 71 controls the motor driver 81 to drive the scan motor 31 and the tilt motor 32 respectively. The positional information of the ship 10 received by the GPS receiver 83 is input to the CPU 71 .

The CPU 71 also receives, via the transmission/reception circuit 82, a reception signal generated when the ultrasonic transducer 41 receives the reflected wave W2. Then, the CPU 71 generates detected image data based on the received signal, and stores the generated detected image data in the RAM 73 . The CPU 71 controls the display unit 15 to display the detected image based on the detected image data stored in the RAM 73 .

Next, a method for detecting the object S1 to be detected using the sonar 11 will be described.

First, power sources (not shown) of the sonar 11, the lifting device 12 and the liquid crystal monitor 13 are turned on. At this time, positional information indicating the position of the vessel 10 is input from the GPS receiver 83 to the CPU 71 of the control device 70 . Next, the CPU 71 controls the transmission/reception circuit 82 to output an oscillation signal to the ultrasonic transducer 41 to drive the ultrasonic transducer 41 . At this time, each column portion 57 of the piezoelectric element 43 repeats contraction (see FIG. 11(b)) and expansion (see FIG. 11(a)). Note that when the column portion 57 contracts in the height direction, the column portion 57 deforms in the width direction, specifically, so as to escape to the outer peripheral side of the column portion 57 (see arrow F1 in FIG. 11B). do. When the column portion 57 expands in the height direction, the column portion 57 deforms in the width direction, specifically, toward the central portion of the column portion 57 (see arrow F2 in FIG. 11A). As a result, the piezoelectric element 43 vibrates, and the ultrasonic wave W1 is irradiated (transmitted) from the ultrasonic transducer 41 to the water. Then, when the ultrasonic wave W1 reaches the object S1 (see FIG. 1) to be detected, the ultrasonic wave W1 is reflected by the object S1 to become a reflected wave W2, propagates toward the sonar 11, and reaches the ultrasonic transducer 41. is input (received) to After that, the ultrasonic wave W1 (reflected wave W2) received by the ultrasonic transducer 41 is converted into a received signal and input to the CPU 71 via the transmitting/receiving circuit 82 . At this point, the object to be detected S1 is detected.

Further, the CPU 71 performs control to drive the scan motor 31 via the motor driver 81 to rotate the central axis O1 of the ultrasonic transducer 41 . As a result, the irradiation direction of the ultrasonic waves W1 gradually changes, and the detection range also gradually changes accordingly. After that, when the operator turns off the power, the transmission/reception circuit 82 is stopped by the control device 70, and the irradiation of the ultrasonic wave W1 and the reception of the reflected wave W2 are finished.

Next, a method for manufacturing the ultrasonic transducer 41 will be described.

First, the base material 42 is prepared. Specifically, a resin plate made of glass epoxy (FR-4) is cut into a circular shape. Also, a ceramic plate-like object to be the piezoelectric element 43 is prepared. Specifically, after producing a disk-shaped ceramic sintered body made of lead zirconate titanate (PZT), the surface is polished to obtain a ceramic plate. Next, an electrode layer forming step is performed to form a front electrode layer 54 on the front surface 51 of the ceramic plate and a rear electrode layer 55 on the back surface 52 of the ceramic plate. Specifically, the electrode layers 54 and 55 are formed by applying a silver paste to the front surface 51 and the back surface 52 of the ceramic plate, respectively, and firing the applied silver paste. After the electrode layer forming process, a polarization treatment process is further performed. In the polarization treatment step, a voltage is applied between the front-side electrode layer 54 and the back-side electrode layer 55 to polarize the ceramic plate in the thickness direction.

In the subsequent joining step, a ceramic plate is joined to one side of the substrate 42 via the front electrode layer 54 . Specifically, an adhesive (such as an epoxy-based adhesive) that forms the adhesive layer 56 is applied to either the surface of the front-side electrode layer 54 or the surface 42 a of the base material 42 , and the base material 42 is The piezoelectric element 43 is fixed by bonding. Brazing using solder or the like may be performed instead of applying the adhesive.

In the pillar portion forming step (vibrating portion forming step) after the bonding step, a plurality of cuts K1 and K2 are formed on the back side of the ceramic plate-like object by cutting or the like. At this time, the cuts K1 and K2 are formed so as to have a depth of 80% or more and less than 100% of the thickness t1 (7.2 mm) of the ceramic plate. As a result, the ceramic plate is divided into a plurality of columnar portions 57, and the back side electrode layer 55 formed on the back surface 52 of the piezoelectric element 43 is also divided into a plurality (the same number as the columnar portions 57). At this point, the piezoelectric element 43 is completed. Since the columns 57 are connected to each other at the ends of the piezoelectric elements 43 on the front surface 51 side and divided, the front electrode layer 54 formed on the front surface 51 is not divided.

In the mesh installation process after the pillar forming process, the copper mesh 91 is placed on the back surface 52 of the piezoelectric element 43, and a pressing force is applied to the copper mesh 91 so that the copper mesh 91 is attached to the tip surface 58 of each pillar 57. make contact. Then, the bonding material 90 is solidified in a state in which it enters both the gaps between the meshes 92 of the copper mesh 91 and part of the gaps K0 (cuts K1 and K2) between the columns 57 . As a result, the copper mesh 91 is joined to the back side electrode layer 55 , and the copper mesh 91 becomes a common electrode for the tip surface 58 of each pillar 57 . At this point, the ultrasonic transducer 41 is completed.

After the ultrasonic transducer 41 is completed, the first lead wire 62 is connected to the front electrode layer 54 via side terminals (not shown) by soldering or the like, and the copper mesh 91 is connected to the first lead wire 62 by soldering or the like. A second lead wire 63 is connected by soldering or the like. Next, a soundproof material 65 for suppressing reverberation is attached to the back surface 52 side of the piezoelectric element 43 . A soundproof material 65 is also attached to the inner surface of the case 40 . After that, the piezoelectric element 43 of the ultrasonic transducer 41 is housed in the case 40 . In this state, screws (not shown) are inserted through the plurality of screw holes 45 provided in the base material 42 , and the tips of the inserted screws are screwed into the case 40 . As a result, the ultrasonic transducer 41 is fixed to the case 40 (see FIG. 5). Furthermore, the case 40 to which the ultrasonic transducer 41 is fixed is attached to the rotating shaft 36 inside the sonar dome 20 . Then, the sonar dome 20 is filled with an ultrasonic propagation liquid (not shown). At this time, part of the ultrasonic wave propagating liquid flows into the case 40 through a liquid passage (not shown) provided in the case 40, and flows into the gap K0 between the adjacent pillars 57 in the piezoelectric element 43. . At this point, the ultrasonic transducer 41 is incorporated into the sonar dome 20 and the sonar 11 is completed.

Next, an evaluation method and results of the ultrasonic transducer will be described.

The present inventors confirmed the suitable structure of the ultrasonic transducer by trial production. First, a sample for measurement was prepared as follows. An ultrasonic transducer (that is, the ultrasonic vibrator of the present embodiment) is manufactured by bonding a copper mesh (common electrode) to the back surface of the piezoelectric element (the tip surface of each column) via an epoxy adhesive (bonding material). Three ultrasonic transducers (the same ultrasonic transducer as the ultrasonic transducer 41) were prepared, and these were used as Examples 1A, 1B, and 1C (Example 1). On the other hand, three ultrasonic transducers were prepared by bonding a copper foil tape (common electrode) to the back surface of the piezoelectric element via a conductive tape (bonding material), and these were prepared as Comparative Examples 1A, 1B, and 1C. (Comparative Example 1). Also, three ultrasonic vibrators were prepared by bonding a copper foil (common electrode) to the back surface of the piezoelectric element via an epoxy-based adhesive (bonding material). 2C (Comparative Example 2).

Next, a running test was performed on each measurement sample (Examples 1A to 1C and Comparative Examples 1A to 1C and 2A to 2C). Specifically, first, a voltage of 1.5 kVpp was applied to the ultrasonic transducers of Examples 1A to 1C and Comparative Examples 1A to 1C and 2A to 2C, and 160 kHz ultrasonic waves (burst waves) were emitted (transmitted) continuously. Then, the capacitance of the piezoelectric element was measured every 0 days (at the start of irradiation), 1 day, 6 days, 12 days, 26 days, 50 days, and 80 days. Specifically, the capacitance was measured using an LCR meter at the ends of the two leads 62, 63 connected to the piezoelectric element. Table 1 shows capacitance values in Examples 1A to 1C and Comparative Examples 1A to 1C and 2A to 2C (the unit of numerical values in the table is (pF)). The graph of FIG. 12 shows changes in capacitance in Example 1 (see "●"), Comparative Example 1 (see "▴"), and Comparative Example 2 (see "▪").

As a result, in Comparative Examples 1A to 1C, the capacitance rapidly decreased immediately after the start of ultrasonic irradiation, and when 6 days had passed since the start of irradiation, the capacitance decreased significantly, and the capacitance decreased. It was confirmed that the rate increased. In Comparative Examples 2A to 2C, the capacitance hardly decreased until about 10 days after the start of irradiation with ultrasonic waves, but it decreased significantly after that. It was confirmed that the capacity decreased significantly and the rate of decrease in capacitance also increased. It should be noted that the decrease in capacitance indicates that the electrode area is reduced due to the peeling of the common electrode. Further, it was confirmed that when the ultrasonic vibrator was continuously driven while the electrode was peeled off, electric discharge was generated from the peeled portion, resulting in charring.

On the other hand, in Examples 1A to 1C, the capacitance hardly decreased even after 80 days from the start of ultrasonic irradiation, and it was confirmed that the rate of decrease in capacitance was extremely small. Therefore, by adopting Examples 1A to 1C in which the copper mesh is bonded to the piezoelectric element via an epoxy adhesive, the decrease in the capacitance, that is, the decrease in the electrode area due to the peeling of the common electrode can be suppressed. It was confirmed that

In addition, the transmission/reception sensitivity product of the ultrasonic transducer was calculated each time 0, 1, 6, 12, 26, 50, and 80 days passed. Specifically, ultrasonic waves were applied to a 57 mm diameter phenolic resin ball located 0.5 m away from the ultrasonic oscillator. The ultrasonic waves (reflected waves) reflected by the phenolic resin spheres are received by the ultrasonic transducer about 670 μs after transmission, and voltage signals are generated across the ultrasonic transducer. At this time, the voltage amplitude during transmission and reception of the ultrasonic transducer was measured with an oscilloscope, and the transmission/reception sensitivity product was calculated by performing calculations based on the measurement results. The transmission/reception sensitivity product is the ratio of the reception voltage amplitude _V2 to the transmission voltage amplitude _V1 , and is calculated from the formula 20×log( _V2 / _V1 ). Table 2 shows the values of the transmit/receive sensitivity in Examples 1A to 1C and Comparative Examples 1A to 1C and 2A to 2C (the unit of the numerical values in the table is (dB)). Also, the graph of FIG. 13 shows changes in the transmit/receive sensitivity product in Example 1 and Comparative Examples 1 and 2. In FIG.

As a result, it was confirmed that in Comparative Examples 1A to 1C, the transmission/reception sensitivity area rapidly decreased immediately after the start of ultrasonic irradiation, and that the transmission/reception sensitivity area significantly decreased 6 days or 12 days after the start of irradiation. was done. Further, in Comparative Examples 2A to 2C, although the transmittance/reception sensitivity hardly decreased until about 10 days after the start of ultrasonic irradiation, the transmittance/reception sensitivity decreased significantly thereafter, and 50 days after the start of irradiation, the transmittance/reception sensitivity decreased. It was confirmed that the product is greatly reduced.

On the other hand, in Examples 1A to 1C, it was confirmed that the transmission/reception sensitivity hardly decreased even after 80 days from the start of ultrasonic irradiation. Therefore, by adopting Examples 1A to 1C in which the copper mesh is bonded to the piezoelectric element via an epoxy adhesive, not only is it possible to suppress the decrease in the electrode area of the common electrode, but also the decrease in the transmission/reception sensitivity area is suppressed. It was confirmed that

Further, in Comparative Example 1, the frequency was switched in a plurality of steps between 130 kHz and 251 kHz, and ultrasonic waves were applied at each switched frequency. Then, the transmission/reception sensitivity product of the ultrasonic transducer was calculated using the above method using an oscilloscope. The transmit/receive sensitivity product was calculated at each frequency every time 0 days (initial stage), 1 day, 6 days, and 12 days passed. The graph of FIG. 14 shows changes in the transmit/receive sensitivity product in Comparative Example 1. In FIG.

As a result, in Comparative Example 1, the initial stage (see “◆” in FIG. 14) → 1 day later (see “△” in FIG. 14) → 6 days later (see “▼” in FIG. 14) → 12 days later (see “▼” in FIG. 14) It was confirmed that the graph showing the transmission/reception sensitivity product between 130 kHz and 251 kHz decreased as a whole in the order of (see "□"), that is, as the time elapsed from the start of ultrasonic irradiation. Although the graphs of Example 1 (Examples 1A to 1C) are omitted, in Example 1, even if time elapses from the start of irradiation of ultrasonic waves, the transmission/reception sensitivity product hardly decreases (see Table 2). ), and it was confirmed that the graph showing the transmission/reception sensitivity product between 130 kHz and 251 kHz also hardly changed.

Therefore, according to this embodiment, the following effects can be obtained.

(1) In the sonar 11 of the present embodiment, in addition to the bonding material 90 being interposed between the copper mesh 91 and the piezoelectric element 43, which are the electrode portions, the bonding material 90 is interposed between the meshes 92 of the copper mesh 91 and The copper mesh 91 is joined to the piezoelectric element 43 by entering both of the gaps K0 between the plurality of pillars 57 . As a result, since the bonding strength between the piezoelectric element 43 and the copper mesh 91 increases, even if the ultrasonic transducer 41 is continuously driven for a long period of time, the copper mesh 91 is less likely to separate from the piezoelectric element 43. . Therefore, a decrease in sensitivity of the ultrasonic transducer 41 can be prevented.

(2) In the present embodiment, the vertical and horizontal wires 93 and 94 forming the mesh 92 of the copper mesh 91 are woven into a shape in which the wires 93 and 94 are undulated vertically. As a result, the contact pressure between the intersections A1 of the vertical and horizontal wires 93 and 94 and the tip surface 58 of the column portion 57 increases, so that the copper mesh 91 can reliably function as an electrode. In addition, since fine meshes 92 are densely packed in the copper mesh 91 , the bonding material 90 is likely to enter the gaps between the meshes 92 . Therefore, the bonding strength between the piezoelectric element 43 and the copper mesh 91 is further increased.

(3) For example, it is conceivable to dispose the copper mesh 91 over the entire front surface 51 of the piezoelectric element 43 . However, since the ultrasonic wave W1 is irradiated from the front surface 51 of the piezoelectric element 43 and passes through the base material 42 that also serves as an acoustic matching layer, if the copper mesh 91 exists on the front surface 51 side, the ultrasonic wave W1 is transmitted through the copper mesh 91. There is a possibility that the ultrasonic waves W1 may not reach the object S1 due to the scattering of the ultrasonic waves W1. On the other hand, in the present embodiment, the copper mesh 91 is arranged over the entire rear surface 52 of the piezoelectric element 43 on the opposite side of the front surface 51, which is the irradiated surface (that is, the side not irradiated with the ultrasonic wave W1). As a result, the ultrasonic wave W1 can be emitted from the ultrasonic transducer 41 without being scattered. Further, even if the ultrasonic wave W1 leaks to the back surface 52 side of the piezoelectric element 43, the ultrasonic wave W1 is dispersed and attenuated because it passes through the copper mesh 91 on the back surface 52 side. Therefore, the copper mesh 91 can also function as a suitable backing material.

(4) Japanese Patent Application Laid-Open No. 2005-323630 proposes a technique of forming a mesh-like electrode pattern on a flexible substrate. However, the electrode pattern is a mesh pattern with a thickness of about several tens of μm formed on the surface of the substrate, and is not a wire mesh woven with wires. In this case, since the bonding material cannot enter the gaps of the mesh, the anchor effect cannot be obtained, and the bonding strength with other members cannot be increased. On the other hand, in the present embodiment, since the bonding material 90 enters the gaps between the meshes 92 of the copper mesh 91 having a thickness of about several hundred μm, an anchor effect can be obtained. can be higher.

In addition, you may change the said embodiment as follows.

- In the above embodiment, one sheet of copper mesh 91 is arranged on the back surface 52 of the piezoelectric element 43 over the entire area of the back surface 52 . However, the copper mesh 91 may be divided into a plurality of copper mesh pieces, each divided copper mesh piece may be arranged for each area of the back surface 52, and the entire area of the back surface 52 may be covered with all the copper mesh pieces. In this way, the piezoelectric elements 43 can be individually driven for each area.

- In the copper mesh 91 of the above embodiment, the pitch p1 between the adjacent first wires 93 and the pitch p2 between the adjacent second wires 94 are equal to each other. good.

- In the ultrasonic transducer 41 of the above-described embodiment, the bonding material 90 enters a part of the gap K0 between the adjacent column portions 57, but the bonding material 90 may enter the entire gap K0, or The material 90 does not have to enter. Note that when the bonding material 90 does not enter, the ultrasonic wave propagating liquid can flow into the gap K0. Moreover, when the ultrasonic wave propagating liquid does not flow, the heat in the piezoelectric element 43 can be released to the outside through the gap K0.

The piezoelectric element 43 of the above-described embodiment has a structure in which a plurality of divided pillars 57 are connected to each other at the ends on the front surface 51 side, and the copper mesh 91 is joined to the rear surface 52 side. However, as shown in FIG. 15, a piezoelectric element 113 having a 1-3 composite structure, which is completely divided into a plurality of columnar portions 111 (vibrating portions) and filled with a resin material 112 between adjacent columnar portions 111, is used. may be formed and a copper mesh may be bonded to the back surface 114 side of the piezoelectric element 113 . Further, as shown in FIG. 16, a piezoelectric element 123 having a 2-2 composite structure, which is completely divided into a plurality of wall-shaped vibrating portions 121 and filled with a resin material 122 between adjacent vibrating portions 121, is provided. may be formed and a copper mesh may be bonded to the back surface 124 side of the piezoelectric element 123 .

- In the above-described embodiment, the copper mesh 91, which is a conductive mesh, is bonded to the entire back surface 52 of the piezoelectric element 43 . However, instead of bonding the copper mesh 91 to the entire back surface 52, another conductive mesh such as a punching mesh 131 having a structure in which a plurality of holes 132 are provided in a copper foil may be bonded to the entire back surface 52 (Fig. 17, see FIG. 18). Note that the punching mesh 131 is in contact with the tip surface 58 of each column 57, and each hole 132 communicates with the gap K0 between the columns 57. are spliced. The bonding material 133 is applied onto the surface (upper surface) of the punching mesh 131 and enters both the holes 132 and the gaps K0.

In the vibrating portion of the above-described embodiment, the tip surface 58 is the column portion 57 having a square shape in plan view, but the tip surface may have other shapes such as a rectangular shape in plan view, a triangular shape in plan view, a circular shape in plan view, or the like. It may be a pillar portion. In the piezoelectric element 43 of the above-described embodiment, the front end surface 58 is divided into a plurality of pillars 57 having a square shape in plan view. 19), or may be divided into three or more vibrating portions each having a fan-like tip surface in a plan view. That is, the maximum dimension of the vibrating portion when viewed from the thickness direction of the piezoelectric element does not have to be equal to or less than the height of the vibrating portion.

In the ultrasonic transducer 41 of the above embodiment, the piezoelectric element 43 made of lead zirconate titanate (PZT) is used, but the material for forming the piezoelectric element 43 is not particularly limited. For example, potassium sodium niobate (alkaline niobate), barium titanate, PMN-PT (Pb(Mg _1/3 Nb _2/3 )O ₃ —PbTiO ₃ ) single crystal, PZNT (Pb(Zn _{1/ 3Nb 2/3} )O ₃ —PbTiO ₃ ) single crystal or LiNbO ₃ single crystal piezoelectric elements may be used.

The soundproofing material 56 of the above embodiment is attached to the back surface 52 side of the piezoelectric element 43 and the inner peripheral surface of the case 40 , but the soundproofing material 65 is also attached to the outer peripheral surface 53 of the piezoelectric element 43 . good too.

The ultrasonic transducer 41 of the above embodiment is used in the sonar 11 that mechanically changes the irradiation direction of the ultrasonic waves W1, but it can also be used in the sonar that electrically changes the irradiation direction of the ultrasonic waves W1. good. Further, the ultrasonic transducer may be used in a fish finder that does not change the irradiation direction of the ultrasonic wave W1, that is, does not have the tilt rotation mechanism 30. FIG. Further, the ultrasonic transducer may be used for measuring instruments such as depth sounders for measuring the depth of water and airborne sensors for measuring distances in the air.

In the above embodiment, with the piezoelectric element 43 housed in the case 40, the tip of the screw inserted through the screw hole 45 on the base material 42 side is screwed into the case 40, whereby the ultrasonic transducer 41 is connected to the case 40. 40, it may be fixed by other methods. For example, the ultrasonic vibrator 41 may be fixed to the case 40 using an adhesive, or a filler such as epoxy resin, polyurethane resin, or silicone resin may be poured into the case 40 and hardened to prevent ultrasonic vibration. Child 41 may be fixed to case 40 . Furthermore, the ultrasonic transducer 41 may be fixed without using the case 40 . For example, a mold is arranged on the base material 42 so as to cover the piezoelectric element 43, and a resin material (epoxy resin, urethane resin, etc.) is poured into the mold and hardened, whereby the ultrasonic transducer 41 and the resin material are bonded together. You may perform molding which integrates with.

- In the above embodiment, the ultrasonic transducer 41 is fixed to the case 40 with the base material 42 exposed. However, as shown in FIG. 20, a case 150 is constituted by a case portion 151 formed in a bottomed cylindrical shape with one end open and a lid portion 152 formed in a disk shape, and the ultrasonic transducer 41 The opening of the case portion 151 may be closed with the lid portion 152 while the entire device is housed in the case portion 151 . In this way, the entire ultrasonic transducer 41 is sealed by the case 150, so that the case 150 in which the ultrasonic transducer 41 is accommodated can be submerged in water. Therefore, the structure of FIG. 20 can be used as a fish finder. Note that the lid portion 152 is formed using chloroprene rubber, polyurethane resin, or the like, and is in contact with the entire back surface 42b of the base material 42 . The specific acoustic impedance of the lid portion 152 is smaller than the specific acoustic impedance of the base material 42 (2.3 to 14×10 ⁶ (Pa·s/m)), and the specific acoustic impedance of water (1.5×10 ⁶ (Pa·s/m)). Also, the lid portion 152 may be adhered to the base material 42 .

In the above embodiment, the ceramic plate is polarized in the thickness direction by applying a voltage between the front electrode layer 54 and the back electrode layer 55 after the electrode layer forming step and before the bonding step. It was undergoing a polarization treatment process. However, the polarization treatment process may be performed after the joining process and before the column formation process, after the column formation process and before the mesh installation process, or after the mesh installation process.

Next, in addition to the technical ideas described in the claims, technical ideas grasped by the above-described embodiments are listed below.

(1) The sonar according to any one of claims 1 to 7, wherein the maximum dimension of the column when viewed from the thickness direction is 80% or less of the height of the column. .

(2) A sonar according to any one of claims 1 to 7, characterized in that the intrinsic acoustic impedance of the base material is smaller than the intrinsic acoustic impedance of the piezoelectric element and greater than the intrinsic acoustic impedance of water. .

(3) In any one of claims 1 to 7, the intrinsic acoustic impedance of the base material is 2.3×10 ⁶ (Pa·s/m) or more and 14×10 ⁶ (Pa·s/m) or less. A sonar characterized by:

(4) In any one of claims 1 to 7, let c1 be the sound velocity of the longitudinal wave propagating in the piezoelectric element, t1 be the thickness of the piezoelectric element, and t1 be the thickness of the longitudinal wave propagating in the base material. A sonar that satisfies the following relationship: (c2×t1)/(c1×t2)=0.8 or more and 1.7 or less, where c2 is the speed of sound and t2 is the thickness of the base material.

(5) In claim 9, an electrode layer forming step of forming a front side electrode layer on the front surface of the ceramic plate-like article and forming a back side electrode layer on the back side of the ceramic plate-like article; After the electrode layer forming step and before the bonding step, a polarization treatment step of applying a voltage between the front side electrode layer and the back side electrode layer to polarize the ceramic plate in a thickness direction. A method for manufacturing an ultrasonic transducer, further comprising:

11 Sonar 30 Tilting and rotating mechanism as a mechanism 41 Ultrasonic transducer 42 Substrates 43, 113, 123 Piezoelectric elements 51 Front surfaces of plate-like objects (piezoelectric elements) made of ceramics 52, 114, 124 Made of ceramics Back surface 54 of plate (piezoelectric element) front electrode layers 57, 111 column 58 as vibrating part front end surfaces 90, 133 as end faces of vibrating part bonding material 91 copper mesh 92 as conductive mesh Meshes 121, 141 Vibrating portion 131 Punching mesh K0 as a conductive mesh Gap between a plurality of vibrating portions K1 First cut K2 Second cut L3 Vibrating portion from the thickness direction Maximum dimension when viewed O1...Center axis W1...Ultrasonic wave

Claims (9)

A sonar having an ultrasonic transducer for transmitting and receiving ultrasonic waves and a mechanism for tilting and rotating a central axis of the ultrasonic transducer,
The ultrasonic transducer is composed of a base material that also serves as an acoustic matching layer and a plurality of divided vibrating parts, and is made of a ceramic plate having a front surface joined to the base material and a back surface on the opposite side. and a piezoelectric element made of a shaped object,
A conductive mesh is disposed on the back surface of the piezoelectric element over the entire back surface, and
The conductive mesh forms a mesh by weaving vertical and horizontal wires, and has an undulating shape in the thickness direction,
A sonar according to claim 1 , wherein said conductive mesh is bonded to said piezoelectric element via a bonding material in a state in which crossing portions of said vertical and horizontal wires are in contact with an end surface of said vibrating portion. 2. A sonar as in claim 1, wherein said conductive mesh is plain weave wire mesh. The bonding material joins the conductive mesh to the end surfaces of the plurality of vibrating portions by solidifying in a state in which the bonding material enters both the gaps in the mesh of the conductive mesh and the gaps between the plurality of vibrating portions. 3. The sonar according to claim 1 or 2, characterized in that: The sonar according to any one of claims 1 to 3, wherein the plurality of vibrating sections are a plurality of divided columnar sections extending along the thickness direction of the piezoelectric element. 5. The sonar according to any one of claims 1 to 4, wherein the plurality of vibrating portions are connected to each other at the front end portion of the piezoelectric element. 6. The sonar according to any one of claims 1 to 5, wherein the mesh size of the conductive mesh is smaller than the maximum size of the vibrating portion when viewed from the thickness direction of the piezoelectric element. . 7. The piezoelectric element according to any one of claims 1 to 6, wherein the front surface of the piezoelectric element is bonded to the substrate via a front electrode layer, and the front electrode layer is a plain electrode layer having a uniform thickness. or the sonar according to item 1. An ultrasonic transducer that transmits and receives ultrasonic waves,
a base material that also serves as an acoustic matching layer;
a piezoelectric element composed of a plurality of divided vibrating portions and made of a ceramic plate having a front surface joined to the base material and a back surface on the opposite side;
A conductive mesh is disposed on the back surface of the piezoelectric element over the entire back surface, and
The conductive mesh forms a mesh by weaving vertical and horizontal wires, and has an undulating shape in the thickness direction,
An ultrasonic transducer , wherein the conductive mesh is bonded to the piezoelectric element via a bonding material in a state in which intersections of the vertical and horizontal wires are in contact with end surfaces of the vibrating portion. A method for manufacturing an ultrasonic transducer according to claim 8,
a bonding step of bonding a ceramic plate-shaped object to be the piezoelectric element to one side of the base material;
After the bonding step, by forming a plurality of cuts on the back side of the ceramic plate, the ceramic plate is attached to the plurality of vibrating portions while being connected to each other at the front end. a vibrating portion forming step to be divided;
After the vibrating portion forming step, the conductive mesh is arranged on the back surface of the piezoelectric element so as to be in contact with the end faces of the plurality of vibrating portions, and in this state, the mesh installation is performed by bonding the conductive mesh via a bonding material. A method for manufacturing an ultrasonic transducer, comprising the steps of:

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