JP7576834B2 - Sonar - Google Patents

Description

The present invention relates to a sonar that uses ultrasonic waves to detect objects such as schools of fish.

Conventionally, sonars that detect objects to be detected, such as schools of fish, by transmitting and receiving ultrasonic waves are known. The sonar includes an ultrasonic transducer that transmits and receives ultrasonic waves, and a drive mechanism that causes the ultrasonic transducer to perform a rotational motion around a rotation axis oriented in the vertical direction and a tilting motion around a tilting axis perpendicular to the rotation axis. By transmitting and receiving ultrasonic waves while moving the ultrasonic transducer, it is possible to detect underwater (see, for example, Patent Documents 1 to 4). The detection results detected underwater are displayed on a screen as a detection image. The ultrasonic transducer generally includes an acoustic matching layer and a piezoelectric element bonded to the acoustic matching layer.

By the way, there is a demand for sonar to detect objects at longer distances. To this end, it is necessary to make the ultrasonic transducer highly sensitive. As a method for making the ultrasonic transducer highly sensitive, as shown in Figs. 38 and 39, a structure has been proposed in which the piezoelectric element 102 constituting the ultrasonic transducer 101 is composed of a plurality of (for example, 100 or more) vibration parts 103 arranged vertically and horizontally as viewed from the thickness direction, and a filler 104 is filled between the adjacent vibration parts 103 (see, for example, Patent Documents 5 and 6). In this way, each vibration part 103 is easily deformed in the height direction of the vibration part 103, so that the piezoelectric element 102 is easily deformed at each part. In other words, the piezoelectric element 102 is easily vibrated, so that the sensitivity of the ultrasonic transducer 101 is increased. In addition, the filler 104 enters the gaps between the vibration parts 103, so that the vibration parts 103 are mutually reinforced.

Japanese Patent No. 5979537 (Claim 1, FIG. 4, etc.) JP 2013-221791 A (paragraph [0036], Figures 1 to 6, etc.) Japanese Patent Publication No. 01-025435 (drawings, etc.) Japanese Patent Publication No. 63-042755 (Fig. 1, etc.) JP 2016-213666 A (FIG. 4B, etc.) JP 2012-182758 A (FIG. 6, etc.)

However, when the filler 104 is filled between the adjacent vibration parts 103, each vibration part 103 becomes difficult to deform (vibrate) in the height direction, which causes a problem of reducing the sensitivity of the ultrasonic transducer 101. It is possible to secure the sensitivity by removing the filler 104, but each vibration part 103 has a thin rod shape and low strength. Therefore, if the ultrasonic transducer 101 is driven for a long period of time without the filler 104, cracks are likely to occur due to fatigue failure. In other words, if the filler 104 is not filled, there is a problem of reducing the reliability of the ultrasonic transducer 101.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sonar that can obtain a highly reliable ultrasonic transducer by preventing a decrease in strength of the vibration part while maintaining sensitivity. Another object of the present invention is to provide a sonar that can obtain an ultrasonic transducer that is easy to manufacture and has low manufacturing costs.

In order to solve the above problems, the invention described in claim 1 is a sonar comprising an ultrasonic transducer for transmitting and receiving ultrasonic waves, and a drive mechanism for causing the ultrasonic transducer to perform a rotational motion about a rotation axis oriented in a vertical direction and a tilting motion about a tilting axis perpendicular to the rotation axis, the ultrasonic transducer comprising a substantially disk-shaped piezoelectric element having a front surface and a rear surface on the opposite side, the piezoelectric element having a plurality of grooves formed therein that extend in the surface direction so as not to intersect with each other, a plurality of band-shaped vibration parts disposed via the grooves, the length of the vibration parts becoming shorter as the distance from the center of the piezoelectric element increases, and the ultrasonic transducer is disposed so that the grooves form an angle of 60° to 120° with respect to the tilting axis. The ultrasonic transducer has a substantially circular substrate that also serves as an acoustic matching layer, the front surface of the piezoelectric element is bonded to the substrate, the plurality of vibration parts are connected to each other at the ends on the front surface side of the piezoelectric element, the plurality of vibration parts are composed of a pair of outer vibration parts that are farthest from the center of the piezoelectric element and a plurality of inner vibration parts that are arranged between the pair of outer vibration parts, the width of the outer vibration parts is greater than the width of the inner vibration parts, and the ultrasonic transducer is contained within a sonar dome that is filled with an ultrasonic propagation liquid that propagates ultrasonic waves, and a portion of the ultrasonic propagation liquid flows into the groove portion, which is an empty space, thereby filling the groove portion.
Another invention (reference invention) for solving the above problem is a sonar including an ultrasonic transducer for transmitting and receiving ultrasonic waves, and a drive mechanism for causing the ultrasonic transducer to perform a rotational motion about a rotation axis oriented in a vertical direction and a tilting motion about a tilt axis perpendicular to the rotation axis, the ultrasonic transducer including a substantially disk-shaped piezoelectric element having a front surface and a back surface on the opposite side, the piezoelectric element having a plurality of grooves formed therein that extend in the surface direction so as not to intersect with each other, and a plurality of band-shaped vibration parts disposed through the grooves, the length of the vibration parts becoming longer as the distance from the center of the piezoelectric element increases, The gist of the sonar is that the ultrasonic transducer is arranged so that the groove portion is short and forms an angle of 60° to 120° with respect to the tilt axis, and the drive mode of the ultrasonic transducer when performing the rotational motion with the ultrasonic transducer tilted with respect to the rotation axis can be switched to either a full drive mode in which all of the vibration parts are driven to narrow the directional angle in the vibration part arrangement direction, or a partial drive mode in which a portion of the vibration parts located in the central region of the piezoelectric element is driven to widen the directional angle in the vibration part arrangement direction to three to five times that of the full drive mode.

Therefore, according to the invention described in claim 1, a band-shaped vibration part is formed on the piezoelectric element. Therefore, since the vibration part is longer in the planar direction than the columnar vibration part, the vibration part has a stable shape that is less likely to fall, and the strength of the vibration part is prevented from decreasing. As a result, even if the grooves are not filled with a filler, the occurrence of cracks in the vibration part can be prevented, and the reliability of the ultrasonic vibrator can be improved. Moreover, in claim 1, since the band-shaped vibration part is obtained by forming grooves extending in the planar direction so as not to intersect with each other, the number of times that the grooves are formed required to form the vibration part is reduced compared to the case where the columnar vibration part is obtained by forming grooves extending vertically and horizontally. Therefore, since the grooves are easily formed, the manufacturing cost of the ultrasonic vibrator can be reduced. In addition, since the number of times that the grooves are formed is reduced, the number of divisions of the electrode is also reduced, and the effort required to connect each of the divided electrodes with a conductive member is also reduced. Note that, compared to the case where a columnar vibration part is obtained by forming grooves extending vertically and horizontally, the vibration amplitude of the vibration part is reduced due to the influence of the vibration parts being connected in a band shape. However, the reduction in vibration amplitude is compensated for by the increase in vibration amplitude due to not filling the grooves with filler and the increase in the area of the electrodes described above, so that the transmission and reception sensitivity of the ultrasonic transducer is maintained at the same level as when a columnar vibration section is obtained.

Furthermore, in claim 1, the longer the distance from the center of the piezoelectric element, the shorter the length of the vibration part. In this case, since the outer shape of the entire vibration part approaches a circle, the directional characteristics of the ultrasonic waves irradiated in the perpendicular direction of the piezoelectric element approach axial symmetry. As a result, the ultrasonic beam becomes spotlight-like, making it easier to recognize the area being ultrasonically scanned. In addition, since the piezoelectric element is approximately disk-shaped, the outer shape of the ultrasonic transducer can be made circular. Note that, when the ultrasonic transducer is stored in a hemispherical sonar dome, a circular outer shape of the ultrasonic transducer can ensure a larger vibration part area, so that a small and highly sensitive ultrasonic transducer can be suitably obtained. In addition, in claim 1, the ultrasonic transducer is arranged so that the groove part forms an angle of 60° to 120° with respect to the tilt axis. Accordingly, the multiple vibration parts arranged through the groove part are strip-shaped extending in a direction approximately perpendicular to the tilt axis. In particular, if the ultrasonic transducer is disposed so that the grooves form an angle of 90° with respect to the tilt axis, each vibration portion will have a strip shape extending in a direction perpendicular to the tilt axis.

Note that the term "approximately disk-shaped piezoelectric element" includes not only disk-shaped piezoelectric elements, but also elliptical plate-shaped piezoelectric elements, oval plate-shaped piezoelectric elements, etc. In other words, it is preferable to use a piezoelectric element whose periphery is partly or entirely arc-shaped.

According to the above-mentioned reference invention, when the ultrasonic transducer is driven in the full drive mode in which all the vibration parts are driven, the external shape of the entire vibration part is approximately circular, so that the directional characteristics of the ultrasonic waves irradiated in the perpendicular direction of the piezoelectric element approach axial symmetry. On the other hand, when the ultrasonic transducer is driven in the partial drive mode in which some of the vibration parts are driven, the ultrasonic waves irradiated from the belt-shaped vibration part of the ultrasonic transducer alone have a relatively narrow directional angle in the longitudinal direction of the vibration part, but a relatively wide directional angle in the width direction of the vibration part (the arrangement direction of each vibration part). Therefore, for example, when scanning all around, if the drive mode of the ultrasonic transducer is switched to the partial drive mode, the directional angle of the ultrasonic waves in the scanning direction can be made wider. As a result, the step angle during the scanning operation can be made coarse, so that the detection time can be shortened compared to the full drive mode.

In the above invention , it is preferable that the width of the vibration portion is smaller than the thickness of the piezoelectric element.

Therefore, according to the above configuration , since the width of the vibration part is smaller than the thickness of the piezoelectric element, the vibration part can be made elongated with a width smaller than the height. As a result, when the vibration part contracts in the height direction, the vibration part is easily deformed so as to become thicker by the contracted volume, and when the vibration part expands in the height direction, the vibration part is easily deformed toward the center of the vibration part along the width direction. In other words, the vibration part has a shape that easily vibrates in the height direction, and the electromechanical coupling coefficient is increased, so the sensitivity of the ultrasonic transducer can be increased.

In the above invention , it is preferable that the width of the vibration portion is greater than or equal to one-quarter and less than or equal to one-half the thickness of the piezoelectric element.

Therefore, according to the above configuration , since the width of the vibration part is equal to or more than one-fourth the thickness of the piezoelectric element, it is possible to prevent the strength of the vibration part from decreasing. Also, since the width of the vibration part is equal to or less than one-half the thickness of the piezoelectric element, the vibration part has an elongated shape that is easy to vibrate in the height direction, and the electromechanical coupling coefficient is reliably increased, thereby reliably increasing the sensitivity of the ultrasonic transducer .

As described above in detail, according to the first aspect of the present invention, a highly reliable ultrasonic transducer can be obtained by preventing a decrease in strength of the vibrating portion while maintaining sensitivity.

FIG. 1 is an explanatory diagram showing a ship equipped with a sonar according to a first embodiment. FIG. 2 is a schematic diagram showing a sonar, an elevator device, and a monitor. Schematic cross-sectional view showing a sonar. Schematic cross-sectional view showing a sonar. FIG. 4 is a side view showing the ultrasonic transducer housed in the case. FIG. 4 is a schematic cross-sectional view showing an ultrasonic transducer housed in a case. Back view showing the case. FIG. FIG. FIG. FIG. 4A is a perspective view showing an outer vibration part, and FIG. FIG. 2 is a block diagram showing the electrical configuration of the sonar. 1A is a cross-sectional view showing the vibrating part during expansion, and FIG. 1B is a cross-sectional view showing the vibrating part during contraction. FIG. 11 is a plan view showing an ultrasonic transducer according to a second embodiment. FIG. 11 is a perspective view conceptually showing an ultrasonic transducer driven in all drive modes in the second embodiment. FIG. 13 is a perspective view conceptually showing the propagation state of ultrasonic waves in all drive modes. FIG. 11 is an impedance characteristic diagram showing the results of a piezoelectric harmonic analysis simulation in all driving modes. 1 is a diagram showing a simulation of the propagation state of ultrasonic waves in the XZ plane of a piezoelectric element in all drive modes. 1 is a diagram showing a simulation of the propagation state of ultrasonic waves in the YZ plane of a piezoelectric element in all drive modes. 11 is a graph showing simulation results of ultrasonic directionality in all driving modes. FIG. 11 is a perspective view conceptually showing an ultrasonic transducer driven in a partial drive mode in a second embodiment. FIG. 13 is a perspective view conceptually showing the propagation state of ultrasonic waves in a partial drive mode. FIG. 11 is an impedance characteristic diagram showing the results of a piezoelectric harmonic analysis simulation in a partial drive mode. 13 is a diagram showing a simulation of the propagation state of ultrasonic waves in the XZ plane of a piezoelectric element in a partial drive mode. 13 is a diagram showing a simulation of the propagation state of ultrasonic waves in the YZ plane of a piezoelectric element in a partial drive mode. 13 is a graph showing a simulation result of ultrasonic directionality in a partial drive mode. FIG. 13 is a perspective view conceptually showing an ultrasonic transducer to be driven in a comparative example. FIG. 11 is an impedance characteristic diagram showing the results of a piezoelectric harmonic analysis simulation in a comparative example. 11 is a diagram showing a simulation of the propagation state of ultrasonic waves in the YZ plane of a piezoelectric element in a comparative example. 11 is a graph showing a simulation result of ultrasonic wave directivity in a comparative example. FIG. 11 is an explanatory diagram showing the number of scans in all driving modes. FIG. 11 is an explanatory diagram showing the number of scans in a partial drive mode. 13A to 13C are schematic plan views showing an ultrasonic transducer according to another embodiment. 13A to 13D are schematic plan views showing an ultrasonic transducer according to another embodiment. FIG. 11 is a plan view showing an ultrasonic transducer according to another embodiment. FIG. 11 is a plan view showing an ultrasonic transducer according to another embodiment. FIG. 11 is a plan view showing an ultrasonic transducer according to another embodiment. FIG. 1 is a plan view showing a main portion of a piezoelectric element according to a conventional technique. FIG. 11 is a cross-sectional view showing a vibrating portion in the prior art.

[First embodiment]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will now be described in detail 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 for use. The sonar 11 is a device that detects an object to be detected S0, such as a school of fish, present in the water by emitting ultrasonic waves U1 into the water. As shown in Fig. 2, the sonar 11 is attached to a lifting device 12. The lifting device 12 is a device that raises and lowers the sonar 11 to make the sonar 11 appear and disappear into the water from the bottom of the ship. Furthermore, 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 wheelhouse of the ship 10, and has an operation unit 14 and a display unit 15.

As shown in Fig. 3 and Fig. 4, the sonar 11 includes a sonar dome 20. The sonar dome 20 is made of a resin material such as ABS resin (acrylonitrile butadiene styrene resin) and is composed of an upper case 21, a lower case 22, and a lid 23. The upper case 21 is a cylindrical case with a bottom that opens at the bottom, and the lower case 22 is a cylindrical case with a bottom that opens at the top. The lower end of the lower case 22 is dome-shaped (hemispherical). The lid 23 is disk-shaped and serves to close the lower end opening of the upper case 21 and the upper end opening of the lower case 22. The lid 23 and the upper case 21 form an upper storage space 24, and the lid 23 and the lower case 22 form a lower storage space 25.

The sonar dome 20 also contains an ultrasonic transducer 41 for transmitting and receiving ultrasonic waves U1, a case 40 for housing the ultrasonic transducer 41, and a drive mechanism 30 for moving the ultrasonic transducer 41. The drive mechanism 30 includes a scan motor 31 and a tilt motor 32. The scan motor 31 is installed in the center of the lid 23 in the upper housing space 24. A stepping motor is used as the scan motor 31 in this embodiment. The rotation shaft 31a of the scan motor 31 extends along the vertical direction and protrudes into the lower housing space 25 through a through hole 33 provided in the center of the lid 23. Furthermore, the tip of the rotation shaft 31a is connected to the center of a disk-shaped support plate 34, and a support frame 35 is attached to the lower surface of the support plate 34. The support frame 35 is U-shaped with a pair of arms 35a.

As shown in Fig. 3 and Fig. 4, the case 40 is formed of a resin material such as ABS resin into a cylindrical shape with one end open and a bottom. The case 40 is provided with a tilting shaft 36 perpendicular to the rotation shaft 31a. The tilting shaft 36 is divided into two tilting shaft parts 36a, and the two tilting shaft parts 36a protrude in opposite directions from both sides of the case 40 (left side and right side in Fig. 4 and Fig. 7). The two tilting shaft parts 36a are fitted into through holes provided in both arms 35a of the support frame 35 via bearings (not shown). Therefore, when the rotation shaft 31a of the scan motor 31 rotates, the support plate 34, the support frame 35, the case 40, and the ultrasonic transducer 41 perform a revolving motion around the rotation shaft 31a. Accordingly, the irradiation direction of the ultrasonic waves U1 output from the ultrasonic transducer 41 changes along the circumferential direction of the rotation shaft 31a.

5 and 7, four bosses 46 are provided on the outer periphery of the case 40, and each boss 46 is provided with a screw hole 47. The screw holes 47 are disposed at equal angular intervals with respect to the center C1 of the case 40.

As shown in Fig. 3 and Fig. 4, 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 in this embodiment. The output shaft 32a of the tilt motor 32 is arranged parallel to a pair of tilt shaft parts 36a, and a pinion gear 32b is attached to the tip of the output shaft 32a. The pinion gear 32b is engaged with a tilt gear 37 that is substantially semicircular and 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, and the case 40 and the ultrasonic transducer 41 perform a tilting motion around the tilt shaft 36 (tilt shaft part 36a). Accordingly, the irradiation angle of the ultrasonic wave U1 output from the ultrasonic transducer 41 also changes with the tilt of the ultrasonic transducer 41.

As shown in Figs. 5, 6, 8 and 9, the ultrasonic transducer 41 includes a substrate 42 and a piezoelectric element 43. The substrate 42 is a disk-shaped resin plate-like object that also serves as an acoustic matching layer. Four protruding parts 44 are provided on the outer periphery of the substrate 42, and each protruding part 44 is provided with a screw hole 45. The screw holes 45 are arranged at equal angular intervals with respect to the center O1 of the piezoelectric element 43 (ultrasonic transducer 41). In addition, the opening of each screw hole 45 on the back surface 42b side of the substrate 42 is countersunk. Therefore, even if a screw (not shown) is inserted into the screw hole 45, the head of the screw does not protrude from the back surface 42b of the substrate 42, so that interference between the screw and the sonar dome 20 that houses the ultrasonic transducer 41 can be avoided.

Then, a screw is inserted into each screw hole 45, and the tip of the inserted screw is screwed into a screw hole portion 47 provided in a boss 46 of the case 40. As a result, the ultrasonic vibrator 41 is fixed to the case 40 as shown in Figures 5 and 6. The boss 46 protrudes downward from the lower end surface 40a of the case 40 by 0.5 mm to 1 mm. Therefore, when the ultrasonic vibrator 41 is fixed to the case 40, a gap is generated between the case 40 and the base material 42. This gap becomes a communication port 48 that communicates between the inside and outside of the case 40.

The piezoelectric element 43 is a substantially circular ceramic plate-like object formed, for example, using lead zirconate titanate (PZT) which is a piezoelectric ceramic. As shown in Figs. 6, 8 and 9, the outer diameter of the piezoelectric element 43 is smaller than the outer diameter of the substrate 42, so that the area of the piezoelectric element 43 is smaller than the area of the substrate 42. The piezoelectric element 43 has a front surface 51 bonded to the substrate 42, a back surface 52 on the opposite side of the front surface 51, and an outer peripheral surface 53 perpendicular to the front surface 51 and the back surface 52. As shown in Figs. 6 and 10, a front surface electrode 54 is formed on the front surface 51 of the piezoelectric element 43, and a back surface electrode 55 is formed on the back 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 surface electrode 54 and an adhesive layer 56 (see Fig. 10). In addition, the piezoelectric element 43 is polarized in the thickness direction by applying a voltage between the front electrode 54 and the rear electrode 55 .

As shown in FIG. 6 and FIG. 8 to FIG. 11, the piezoelectric element 43 is composed of a plurality of vibration parts 90 divided to extend along the thickness direction of the piezoelectric element 43. Each vibration part 90 is formed by forming a plurality of grooves K1 on the back surface 52 of the piezoelectric element 43. Each groove K1 extends in one direction (Y direction in FIG. 8) along the surface direction so as not to intersect with each other. Therefore, each vibration part 90 is arranged in a direction (X direction in FIG. 8) perpendicular to the direction in which the groove K1 extends through the groove K1. In addition, each groove K1 is arranged parallel to each other and at an angle of 60° to 120° (90° in this embodiment) with respect to the central axis A1 of the tilt shaft 36 (see FIG. 8). That is, each groove K1 is perpendicular to the central axis A1 of the tilt shaft 36. Furthermore, in this embodiment, the center O1 of the piezoelectric element 43 (ultrasonic vibrator 41) is located on the groove K1 located in the center of each groove K1. The width of each groove K1 is smaller than the width of the vibration part 90, and in this embodiment, it is between one tenth and one third of the width of the vibration part 90. The widths of each groove K1 are equal to each other. Furthermore, since no filler such as a resin material (epoxy resin, urethane resin, silicone resin, etc.) or an adhesive (epoxy-based adhesive, etc.) is filled in each groove K1, each groove K1 is an empty space K0 overall.

As shown in Figs. 8 to 11, each vibration part 90 is composed of a pair of outer vibration parts 91 located at both ends (left end and right end in Fig. 8) and a plurality of inner vibration parts 92 arranged between the outer vibration parts 91. Each vibration part 90 is in the form of a strip when viewed from the rear. Specifically, as shown in Fig. 11(a), the surface 93a (back surface 52) of the outer vibration part 91 is composed of two sides 94a and 94b, the side 94a is in the form of an arc when viewed from the rear, and the side 94b is in the form of a straight line when viewed from the rear. Also, as shown in Fig. 11(b), the surface 93b (back surface 52) of the inner vibration part 92 is composed of four sides 95a, 95b, 95c, and 95d, the sides 95a and 95c are in the form of an arc when viewed from the rear, and the sides 95b and 95d are in the form of straight lines when viewed from the rear. The outer surfaces 96 of both outer vibrating portions 91 and both end surfaces 97 of each inner vibrating portion 92 form the outer circumferential surface 53 of the piezoelectric element 43 .

In this embodiment, among the vibration parts 90, the vibration part 90 located at the center (the inner vibration part 92) has the longest length and is approximately equal to the outer diameter of the piezoelectric element 43. The longer the distance from the center O1 of the piezoelectric element 43, the shorter the length of the vibration part 90. The width W1 of the outer vibration part 91 is larger than the width W2 of the inner vibration part 92.

As shown in FIG. 8 to FIG. 11, both outer vibration parts 91 and each inner vibration part 92 are connected to each other at the end part on the front surface 51 side of the piezoelectric element 43. The length of the outer vibration part 91 is smaller than the length of the inner vibration part 92. Furthermore, the length of the outer vibration part 91 is larger than the height H1 of the outer vibration part 91, and the height H1 of the outer vibration part 91 is larger than the width W1 of the outer vibration part 91. That is, the minimum value of the length of the vibration part 90 is larger than the height H1 of the vibration part 90. Similarly, the length of the inner vibration part 92 is larger than the height H1 of the inner vibration part 92, and the height H1 of the inner vibration part 92 is larger than the width W2 of the inner vibration part 92. The height H1 of the vibration parts 91, 92 is equal to the depth of the groove part K1. Furthermore, the thickness of the above-mentioned base material 42 is smaller than the height H1 of the vibration parts 91, 92. Furthermore, the thickness H2 of the portion of the piezoelectric element 43 where the vibration parts 91, 92 are connected to each other is smaller than the thickness of the substrate 42. The thickness H3 of the piezoelectric element 43 (the height H1 of the vibration parts 91, 92) is determined arbitrarily, but is determined, for example, so that the "longitudinal vibration" of the vibration parts 91, 92 has a desired resonant frequency.

Furthermore, in the piezoelectric element 43 of this embodiment, the width W of the vibration part 90 (specifically, the width W1 of the outer vibration part 91 or the width W2 of the inner vibration part 92) is smaller than the thickness H3 of the piezoelectric element 43, specifically, it is more than one-quarter and less than one-half of the thickness H3. In addition, in the piezoelectric element 43 of this embodiment, the width W of the vibration part 90 and the minimum value L of the outer diameter of the piezoelectric element 43 (in this embodiment, the diameter of the piezoelectric element 43) satisfy the relationship of 0.05≦W/L≦0.1, particularly the relationship of 0.07≦W/L≦0.1. This indicates that the piezoelectric element 43 has 10 or more vibration parts 90. In this way, the composite vibration is reduced and the sensitivity of the specific part is increased, and the sensitivity near the specific part is also increased accordingly, and the relative band of the ultrasonic wave U1 is widened.

As shown in Figs. 8 and 10, rear electrodes 55 are formed on the surfaces 93a of both outer vibration parts 91 and the surfaces 93b of each inner vibration part 92. A wire 60 (conductive member) made of a conductive metal with low electrical resistance such as copper, silver, or tin (copper in this embodiment) is joined so as to bridge each of the multiple rear electrodes 55. The wire 60 is disposed at a position shifted from the center O1 of the piezoelectric element 43 (ultrasonic transducer 41). The wire 60 in this embodiment has an undulating shape (wavy). The wire 60 is connected to each rear electrode 55 via solder 61. The connection of the wire 60 makes the wire 60 a common electrode for the surfaces 93a of both outer vibration parts 91 and the surfaces 93b of each inner vibration part 92.

As shown in FIG. 6, a first lead wire 62 is connected to the front electrode 54, and a second lead wire 63 is connected to the back electrode 55. The first lead wire 62 is connected to a side terminal (not shown) extending outward from the front electrode 54 by soldering or the like. The second lead wire 63 is connected to any one of the multiple back electrodes 55 by soldering or the like. The first lead wire 62 and the second lead wire 63 are bound by a wiring tube 64 and are drawn out of the case 40 through a wiring insertion hole 49 provided in the upper part of the case 40. Although the first lead wire 62 is connected to the side terminal, a metal foil such as copper foil (not shown) may be attached to the front electrode 54 or the surface 42a of the base material 42, and the first lead wire 62 may be connected to the metal foil by soldering or the like. Also, as shown in FIG. 4, the wiring insertion hole 49 is disposed on the opposite side of the tilt gear 37 through the center C1 of the case 40. This makes it possible to prevent interference between the wiring tube 64 passing through the wiring insertion hole 49 and the tilt gear 37. In addition, the wiring insertion hole 49 is disposed near the tilt shaft portion 36a. This makes it possible to prevent flapping of the wiring tube 64 (the first lead wire 62 and the second lead wire 63) when the ultrasonic transducer 41 performs a tilting motion.

6, a sheet-like soundproofing material 65 (backing material) is attached to the back surface 52 side of the piezoelectric element 43. The soundproofing material 65 is for suppressing reverberation, and is also attached to the inner peripheral surface of the case 40. Note that the soundproofing material 65 may be a resin material or rubber containing particles or fibers made of metal or ceramics, or a resin material with dispersed pores (such as a sponge).

The sonar dome 20 shown in Fig. 3 and Fig. 4 is filled with an ultrasonic wave propagation liquid (not shown) that propagates ultrasonic waves U1. A part of the ultrasonic wave propagation liquid flows into the case 40 through the communication port 48 provided in the case 40, and flows into the gap K0 (groove portion K1) between the adjacent vibration parts 90 in the piezoelectric element 43, filling the gap K0. The ultrasonic wave propagation liquid in this embodiment is liquid paraffin. The specific acoustic impedance of the above-mentioned base material 42 is smaller than the specific acoustic impedance of the piezoelectric element 43, and is larger than the specific acoustic impedance of the ultrasonic wave propagation liquid and the specific acoustic impedance of water.

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

12, the liquid crystal monitor 13 of the sonar 11 is provided with a control device 70 that performs overall control of the entire device. The control device 70 is configured with a well-known computer that includes a CPU 71, a ROM 72, a RAM 73, etc.

The CPU 71 is electrically connected to the scan motor 31 and the tilt motor 32 via a motor driver 81, and controls them by various drive signals. The CPU 71 is also electrically connected to the ultrasonic transducer 41 via a 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) ultrasonic waves U1 into the water. The transmission/reception circuit 82 is also configured to receive an electrical signal indicating the ultrasonic waves U1 (reflected waves U2) received by the ultrasonic transducer 41. The CPU 71 is also electrically connected to the lifting device 12, the operation unit 14, the display unit 15, and a GPS (Global Positioning System) receiving unit 83.

12 controls the transmitting/receiving circuit 82 to emit ultrasonic waves U1 from the ultrasonic transducer 41, and also controls the lifting device 12. The CPU 71 controls the motor driver 81 to drive the scan motor 31 and the tilt motor 32. Position information of the ship 10 received by the GPS receiving unit 83 is input to the CPU 71.

Furthermore, the CPU 71 receives a reception signal generated when the ultrasonic transducer 41 receives the reflected wave U2 via the transmission/reception circuit 82. The CPU 71 then generates detection image data based on the received reception signal, and stores the generated detection image data in the RAM 73. The CPU 71 performs control to display a detection image on the display unit 15 based on the detection image data stored in the RAM 73.

Next, a method for detecting the object S0 to be detected using the sonar 11 will be described.

First, the power supplies (not shown) of the sonar 11, the lifting device 12, and the liquid crystal monitor 13 are turned on. At this time, position information indicating the position of the ship 10 is input from the GPS receiving unit 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, and drives the ultrasonic transducer 41. At this time, each vibration part 90 of the piezoelectric element 43 repeats contraction (see FIG. 13(b)) and expansion (see FIG. 13(a)). When the vibration part 90 contracts in the height direction, the vibration part 90 deforms in the width direction, specifically, toward the outer periphery of the vibration part 90 (see arrow F1 in FIG. 13(b)), so as to become thicker by the contracted volume. Then, when the vibration part 90 expands in the height direction, the vibration part 90 deforms in the width direction, specifically, toward the center of the vibration part 90 (see arrow F2 in FIG. 13(a)). As a result, the piezoelectric element 43 vibrates, and ultrasonic waves U1 are emitted (transmitted) into the water from the ultrasonic transducer 41. Then, when the ultrasonic waves U1 reach the object to be detected S0 (see FIG. 1), the ultrasonic waves U1 are reflected by the object to be detected S0 and become reflected waves U2, which propagate toward the sonar 11 and are input (received) by the ultrasonic transducer 41. The ultrasonic waves U1 (reflected waves U2) received by the ultrasonic transducer 41 are then converted into a received signal and input to the CPU 71 via the transmission/reception circuit 82. At this point, the object to be detected S0 is detected.

Furthermore, the CPU 71 controls the driving of the scan motor 31 via the motor driver 81, causing the ultrasonic transducer 41 to perform a rotational motion around the rotation axis 31a. The CPU 71 also controls the driving of the tilt motor 32 via the motor driver 81, causing the ultrasonic transducer 41 to perform a tilting motion around the tilt axis 36. As a result, the direction of irradiation of the ultrasonic waves U1 gradually changes, and the detection range also gradually changes accordingly. After that, when the operator turns off the power, the control device 70 stops the transmission/reception circuit 82, and the irradiation of the ultrasonic waves U1 and the reception of the reflected waves U2 end.

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

First, the substrate 42 is prepared. Specifically, a resin plate made of glass epoxy (FR-4) or the like is cut into a circular shape. A ceramic plate to become the piezoelectric element 43 is also prepared. Specifically, a disk-shaped ceramic sintered body made of lead zirconate titanate (PZT) is produced, and then the surface is polished to obtain a ceramic plate. Next, an electrode formation step is performed to form a front electrode 54 on the front surface 51 of the ceramic plate, and a back electrode 55 on the back surface 52 of the ceramic plate. Specifically, silver paste is applied to the front surface 51 and the back surface 52 of the ceramic plate, respectively, and the applied silver paste is fired to form the electrodes 54 and 55. Then, a voltage is applied between the front electrode 54 and the back electrode 55 to perform a polarization process in which the ceramic plate is polarized in the thickness direction.

In the subsequent bonding step, a ceramic plate-like object is bonded to one surface of the substrate 42 via the front electrode 54. Specifically, an adhesive (such as an epoxy adhesive) that serves as an adhesive layer 56 is applied to either the surface of the front electrode 54 or the surface 42a of the substrate 42, and the ceramic plate-like object is bonded and fixed to the substrate 42. Note that brazing may be performed using solder or the like instead of applying an adhesive.

In the vibration part forming process after the bonding process, a plurality of grooves K1 are formed on the back surface 52 side of the ceramic plate-like object by performing cutting or the like. As a result, the ceramic plate-like object is divided into a plurality of vibration parts 90, and the back surface side electrodes 55 formed on the back surface 52 of the ceramic plate-like object are also divided into a plurality (the same number as the vibration parts 90). At this point, the piezoelectric element 43 is completed. Since the vibration parts 90 are divided while being connected to each other at the end of the front surface 51 side of the piezoelectric element 43, the front surface side electrodes 54 formed on the front surface 51 are not divided. After that, the wire 60 is bonded so as to bridge each of the plurality of back surface side electrodes 55, and each back surface side electrode 55 is made a common electrode for the surfaces 93a, 93b of each vibration part 90. In this embodiment, the wire 60 is bonded to each back surface side electrode 55 by soldering, but may be bonded to each back surface side electrode 55 by other bonding methods (such as brazing or bonding with an adhesive). 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 54 via a side terminal (not shown) by soldering or the like, and the second lead wire 63 is connected to the back electrode 55 by soldering or the like. Next, a soundproofing material 65 for suppressing reverberation is attached to the back 52 side of the piezoelectric element 43. In addition, a soundproofing material 65 is also attached to the inner side surface of the case 40. Then, the piezoelectric element 43 of the ultrasonic transducer 41 is housed in the case 40. Then, in this state, screws (not shown) are inserted into the multiple screw holes 45 provided in the base material 42, and the tip of the inserted screw is screwed into the screw hole portion 47 provided in the case 40. As a result, the ultrasonic transducer 41 is fixed to the case 40 (see FIGS. 5 and 6). Furthermore, the case 40 to which the ultrasonic transducer 41 is fixed is housed in the sonar dome 20, and the pair of tilting shafts 36a of the case 40 are fitted into the through holes provided in both arms 35a of the support frame 35. Then, the sonar dome 20 is filled with an ultrasonic propagation liquid (not shown). At this time, a portion of the ultrasonic propagation liquid flows into the case 40 through the communication port 48 provided in the case 40, and flows into the gap K0 between the adjacent vibration parts 90 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.

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

(1) For example, the prior art described in Patent Document 1 discloses a sonar that scans the periphery of a ship to detect objects such as schools of fish by mechanically rotating an ultrasonic transducer around a vertically oriented rotation axis while tilting the ultrasonic transducer from a vertically downward orientation. In addition, in the past, when performing a scan (all-around scan) while rotating the ultrasonic transducer 360°, it has been required to shorten the time required for all-around scan by increasing the detection speed. However, when the ultrasonic transducer is rotated at a rotation speed (angle step) exceeding the directivity angle of the ultrasonic waves, detection misses occur.

Therefore, in the sonar 11 of this embodiment, the ultrasonic transducer 41 is arranged so that the groove K1 formed in the piezoelectric element 43 forms an angle of 90° with respect to the tilt axis 36. As a result, the multiple vibration parts 90 arranged via the groove K1 are in a strip shape extending in a direction perpendicular to the tilt axis 36. The ultrasonic waves U1 irradiated from the strip-shaped vibration part 90 of the ultrasonic transducer 41 have directivity with a wide directivity angle in the width direction of the vibration part 90 (the arrangement direction of each vibration part 90). In detail, as shown in Figures 18 and 20 described later, among the ultrasonic waves U1 irradiated from the vibration part 90 located at the center of the arrangement direction, the ultrasonic waves U1 in the straight direction do not cancel each other out very much, but the ultrasonic waves U1 spreading laterally from the straight direction cancel each other out with the ultrasonic waves U1 irradiated from the adjacent vibration part 90. Therefore, the ultrasonic waves U1 are reliably irradiated downward, not to the side of the piezoelectric element 43. On the other hand, since there are no adjacent vibration parts 90 at the vibration parts 90 at both ends in the arrangement direction, a strong side lobe is irradiated toward the side where no vibration part 90 exists. As a result, the directional angle of the ultrasonic wave U1 spreads in the arrangement direction of each vibration part 90, so in this embodiment in which each vibration part 90 extends in a direction perpendicular to the tilt axis 36, the directional angle of the ultrasonic wave U1 becomes wider in the rotation direction of the rotation axis 31a perpendicular to the tilt axis 36. As a result, the detection range in one scan becomes wider, so that the number of scans required when performing a full-circle scan can be reduced. Therefore, the detection speed can be increased without causing detection omissions, and the detection time can be shortened.

(2) For example, when a columnar vibration part is formed on the piezoelectric element of an ultrasonic transducer, if the ultrasonic transducer is driven for a long period of time, there is a high possibility that a crack will occur at the lower end of the vibration part due to fatigue failure. If the ultrasonic transducer continues to be driven at a high voltage in a state where a crack has occurred, intermittent discharge will occur from the cracked part, which will cause a decrease in the piezoelectric characteristics in other vibration parts of the piezoelectric element, resulting in a problem of a decrease in transmission and reception sensitivity. On the other hand, in this embodiment, a band-shaped vibration part 90 is formed on the piezoelectric element 43 of the ultrasonic transducer 41. In this case, the vibration part 90 is longer in the planar direction than the columnar vibration part, so that the joint area between the end part (the part where the vibration parts 90 are connected) on the front surface 51 side of the piezoelectric element 43 and the vibration part 90 is larger, and the vibration part 90 has a stable shape that is less likely to fall, so that the strength of the vibration part 90 can be prevented from decreasing. Therefore, even if the ultrasonic transducer 41 is driven for a long period of time, cracks are less likely to occur in the vibration part 90, so that the above-mentioned problems caused by the occurrence of cracks are less likely to occur. In other words, by suppressing the occurrence of cracks, the reliability of the ultrasonic transducer 41 can be improved.

Moreover, in this embodiment, the belt-shaped vibration portion 90 is obtained by forming the groove portion K1 extending in one direction. Therefore, compared to the case where the columnar vibration portion is obtained by forming groove portions extending vertically and horizontally, the number of times the groove portion K1 is formed required to form the vibration portion 90 is halved, and the formation of the groove portion K1 is facilitated. Furthermore, as the number of times the groove portion K1 is formed is reduced, the number of divisions of the back electrode 55 is also reduced, and the load of the work of connecting the wire 60 to the back electrode 55 is reduced. Therefore, the manufacturing cost of the ultrasonic transducer 41 can be reduced.

(3) For example, if the width of each groove K1 formed in the piezoelectric element 43 is increased, the area of each vibration portion 90 also decreases as the width of each vibration portion 90 decreases, resulting in a decrease in the output of the ultrasonic transducer 41. On the other hand, in this embodiment, the width of each groove K1 is between one-tenth and one-third of the width of the vibration portion 90, and is considerably smaller than the width of the vibration portion 90. As a result, the area of each vibration portion 90 is ensured, and therefore the output of the ultrasonic transducer 41 can be ensured even if the groove K1 is formed.

(4) In this embodiment, the width W1 of the outer vibration portion 91 is greater than the width W2 of the inner vibration portion 92, so that the outer vibration portion 91 is wider in the width direction than the inner vibration portion 92. This increases the strength of the outer vibration portion 91, the entire outer surface 96 of which is exposed to the outside of the piezoelectric element 43, and reliably prevents cracks from occurring in the outer vibration portion 91. This makes it possible to reinforce the piezoelectric element 43 at the outer periphery, which is exposed to the outside and therefore susceptible to the action of external forces, and further increases the reliability of the ultrasonic transducer 41.

(5) Furthermore, in this embodiment, since the vibration portion 90 is elongated in the planar direction, the vibration portion 90 has a stable shape that is unlikely to fall over, and therefore there is no need to fill the gaps K0 (grooves K1) between the vibration portions 90 with a filler. In this case, the deformation of the vibration portion 90 in the height direction is not hindered by the filler, so that it is possible to prevent a decrease in the sensitivity of the ultrasonic transducer 41 caused by the filling of the filler.

(6) The sonar 11 of this embodiment has a structure in which the ultrasonic transducer 41 equipped with a disk-shaped piezoelectric element 43 rotates inside a hemispherical portion of the sonar dome 20 (the lower end portion of the lower case 22). In other words, because both the lower end portion of the lower case 22 and the ultrasonic transducer 41 have arc-shaped portions, the inner surface of the lower end portion of the lower case 22 and the ultrasonic transducer 41 can be disposed close to each other. This reduces the dead space inside the sonar dome 20, allowing the sonar 11 to be made smaller.

(7) For example, if the groove K1 formed on the back surface 52 side of the piezoelectric element 43 is extended to the front surface 51 of the piezoelectric element 43 to completely divide the piezoelectric element 43 into a plurality of vibration parts 90, the front surface electrode 54 formed on the front surface 51 of the piezoelectric element 43 will also be divided. Therefore, even if the first lead wire 62 is connected to the front surface electrode 54 (side terminal), there is a problem that electrical continuity with the entire front surface electrode 54 cannot be achieved. On the other hand, in this embodiment, since the vibration parts 90 are connected to each other at the end on the front surface 51 side of the piezoelectric element 43, the front surface electrode 54 formed on the front surface 51 is not divided. In this case, if the first lead wire 62 is connected to the front surface electrode 54, electrical continuity with the entire front surface electrode 54 can be reliably achieved, so that the sonar 11 can be easily manufactured. In addition, by connecting the vibration parts 90 to each other at the end on the front surface 51 side of the piezoelectric element 43, the entire front surface 51 of the piezoelectric element 43 contacts the surface 42a of the base material 42, so that the contact area between the two is secured and the bonding strength between the piezoelectric element 43 and the base material 42 is improved. As a result, the reliability of the ultrasonic transducer 41 is further improved.

[Second embodiment]

A second embodiment of the present invention will be described below with reference to the drawings. Here, the differences from the first embodiment will be mainly described. That is, the ultrasonic transducer of the first embodiment has only one current supply system for the multiple vibration parts, whereas the ultrasonic transducer of this embodiment has multiple current supply systems for the multiple vibration parts.

More specifically, as shown in Fig. 14, Fig. 15, and Fig. 21, in the ultrasonic transducer 111 of this embodiment, the back side electrodes 55 formed on the surfaces (back sides) of the vibration parts 113 constituting the piezoelectric element 112 are not common electrodes of the vibration parts 113, but are electrodes divided into two or more groups. Specifically, as shown in Fig. 14, each vibration part 113 is divided into a vibration part 113a located at the center in the arrangement direction of the vibration part 113, and vibration parts 113b and 113c located at both ends in the arrangement direction. Then, a wire 60a is joined so as to bridge each of the back side electrodes 55 of each vibration part 113a, a wire 60b is joined so as to bridge each of the back side electrodes 55 of each vibration part 113b, and a wire 60c is joined so as to bridge each of the back side electrodes 55 of each vibration part 113c. Further, a second lead wire 63 (see FIG. 6) is connected to any one of the back electrodes 55 of each vibration part 113a by soldering or the like. Similarly, another second lead wire 63 is connected to any one of the back electrodes 55 of each vibration part 113b and any one of the back electrodes 55 of each vibration part 113c by soldering or the like. Although there is only one second lead wire 63 shown in FIG. 6, in this embodiment, the number of second lead wires 63 increases according to the number of divided groups. Note that the wire material 60b and the wire material 60c may be connected, and one second lead wire 63 may be connected to any one of the back electrodes 55 of each vibration part 113b, 113c. In addition, in the piezoelectric element 112 of this embodiment, the width W3 of the outer vibration part 114 located at both ends of each vibration part 113 and the width W4 of the inner vibration part 115 located between the pair of outer vibration parts 114 are equal to each other.

The CPU 71 (see FIG. 12) of this embodiment can switch the driving mode of the ultrasonic transducer 111 between a full driving mode (see FIGS. 15 and 16) which is a first mode, and a partial driving mode (see FIGS. 21 and 22) which is a second mode. The full driving mode is a mode in which all the vibration parts 113 constituting the piezoelectric element 112 are driven. On the other hand, the partial driving mode is a mode in which some of the vibration parts 113 located in the central region of the piezoelectric element 112, specifically, the four vibration parts 113a located in the central part in the arrangement direction, are driven. In this embodiment, the first electric path connected to the vibration part 113a located in the central part and the second electric path connected to the other vibration parts 113b and 113c are separate systems. Therefore, it is possible to drive some of the vibration parts 113 by passing electricity through only one of the first electric path and the second electric path, and it is also possible to drive all of the drive parts 113 by driving both of them simultaneously.

When the driving mode of the ultrasonic transducer 111 is switched to the full driving mode, the CPU 71 controls the transmission/reception circuit 82 to output an oscillation signal to each vibration unit 113 via one second lead wire 63 constituting the first electrical path and two second lead wires 63 constituting the second electrical path. As a result, all the vibration units 113 vibrate, and the ultrasonic transducer 111 irradiates (transmits) ultrasonic waves U1 into the water. On the other hand, when the driving mode of the ultrasonic transducer 111 is switched to the partial driving mode, the CPU 71 controls the transmission/reception circuit 82 to output an oscillation signal to the vibration unit 113a located in the center via one second lead wire 63 constituting the first electrical path. As a result, only the four vibration units 113a located in the center vibrate, and the ultrasonic transducer 111 irradiates ultrasonic waves U1 into the water. The vibration unit 113a that irradiates the ultrasonic wave U1 when switched to the partial drive mode is a vibration unit that is located at a shorter distance from the center O1 of the piezoelectric element 112 than the vibration units 113b and 113c among the vibration units 113. The total area of the vibration units 113a that drive in the partial drive mode is between one tenth and one half of the total area of all the vibration units 113 that drive in the full drive mode.

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

First, the measurement samples were prepared as follows. An ultrasonic transducer 121 was prepared in which a plurality of band-shaped vibration sections 123 were formed by forming a plurality of groove sections K1 extending in one direction on the back surface of the piezoelectric element 122, and this was used as the Example (see Figs. 15, 16, 21, and 22). Furthermore, an ultrasonic transducer 125 in which the groove section K1 (and the vibration section 123) were not formed in the piezoelectric element 126 was prepared, and this was used as the Comparative Example (see Fig. 27).

Next, the directivity of the ultrasonic transducers 121 and 125 was verified for each measurement sample (Example and Comparative Example). Specifically, in a state where the driving mode of the ultrasonic transducer 121 of the Example was switched to the full driving mode, ultrasonic waves U1 (see FIG. 17) having a resonant frequency of 281 kHz were emitted from the ultrasonic transducer 121, and the directivity during irradiation (transmission) was simulated. FIG. 18 is a diagram showing a simulation of the propagation state of the ultrasonic waves U1 on the X-Z plane of the piezoelectric element 122 in the full driving mode, FIG. 19 is a diagram showing a simulation of the propagation state of the ultrasonic waves U1 on the Y-Z plane of the piezoelectric element 122 in the full driving mode, and FIG. 20 is a graph showing the simulation result of the directivity of the ultrasonic waves U1 in the full driving mode. The Z axis is an axis extending in the normal direction.

In addition, in a state where the drive mode of the ultrasonic transducer 121 of the embodiment is switched to the partial drive mode, ultrasonic waves U1 (see FIG. 23) having a resonant frequency of 281 kHz are irradiated from the ultrasonic transducer 121, and the directivity during irradiation is simulated. FIG. 24 is a diagram showing a simulation of the propagation state of the ultrasonic waves U1 on the X-Z plane of the piezoelectric element 122 in the partial drive mode, FIG. 25 is a diagram showing a simulation of the propagation state of the ultrasonic waves U1 on the Y-Z plane of the piezoelectric element 122 in the partial drive mode, and FIG. 26 is a graph showing the simulation result of the directivity of the ultrasonic waves U1 in the partial drive mode.

In addition, ultrasonic waves U1 (see FIG. 28) having a resonant frequency of 278 kHz were emitted from the ultrasonic transducer 125 of the comparative example, and the directivity during irradiation was simulated. FIG. 29 is a diagram showing a simulation of the propagation state of the ultrasonic waves U1 in the Y-Z plane of the piezoelectric element 126 in the comparative example, and FIG. 30 is a graph showing the simulation results of the directivity of the ultrasonic waves U1 in the comparative example.

As a result, in a comparative example in which the vibration part 123 is not formed on the piezoelectric element 126, it was confirmed that when the ultrasonic wave U1 is irradiated from the ultrasonic transducer 125, the directivity has a narrow directivity angle, for example, in the Y-Z plane (see Figs. 29 and 30). Also, in an example in which the vibration part 123 is formed on the piezoelectric element 122, it was confirmed that when the ultrasonic wave U1 is irradiated from each vibration part 123 in the same phase (full drive mode), the directivity has a narrow directivity angle in both the X-Z plane and the Y-Z plane (see Figs. 18 to 20). That is, it was confirmed that in the full drive mode, the ultrasonic wave U1 with isotropic directivity is irradiated from the ultrasonic transducer 121 (see Fig. 16).

On the other hand, in the embodiment, when the ultrasonic wave U1 is irradiated from only one vibration part 123 in the center (partial drive mode), the directivity has a narrow directivity angle in the Y-Z plane (see Figs. 25 and 26), but the directivity has a wide directivity angle in the X-Z plane (see Figs. 24 and 26). That is, in the partial drive mode, the ultrasonic wave U1 spreads relatively in the X-Z plane but does not spread relatively in the Y-Z plane, so that the ultrasonic wave U1 with anisotropic directivity is irradiated from the ultrasonic transducer 121 (see Fig. 22). Moreover, in the partial drive mode, it was confirmed that the ultrasonic wave U1 spreads concentrically from the vibration part 123 in the center (see Figs. 24 and 26).

In the embodiment, the resonance of the radial vibration of the piezoelectric element 122 is near 40 kHz, and the harmonics of this appear periodically. However, since the groove K1 is formed in the piezoelectric element 122, each vibration portion 123 does not have a disk shape. As a result, it is confirmed that the impedance characteristics shown in Figs. 17 and 23 are obtained because the radial vibration is difficult to occur. On the other hand, in the comparative example, the groove K1 is not formed in the piezoelectric element 126, so that the radial vibration occurs. As a result, it is confirmed that the harmonics of the resonance of the radial vibration appear periodically, and the impedance characteristics are obtained as shown in Fig. 28.

Therefore, it was confirmed that if the X-axis of the piezoelectric element 122 is arranged parallel to the tilt axis 36, in other words, if the groove K1 of the piezoelectric element 122 is arranged perpendicular to the tilt axis 36, the detection range of the ultrasonic transducer 121 (direction angle of the ultrasonic wave U1) becomes wider in the horizontal direction when the ultrasonic transducer 121 is driven in the partial drive mode (see FIG. 22). Therefore, it was confirmed that when performing a scan (full-circumference scan) while rotating the ultrasonic transducer 121 360° around the rotation axis 31a facing the vertical direction, even if the number of scans is reduced and the step interval during the sector scan is increased, detection omissions are unlikely to occur. In detail, when the ultrasonic transducer 121 is driven in the full drive mode, the directivity angle of the ultrasonic wave U1 is, for example, 40°, and the number of scans in the full-circumference scan is, for example, 9 (see Z1 to Z9 in FIG. 31). On the other hand, if the ultrasonic transducer 121 is driven in the partial drive mode, the directional angle of the ultrasonic wave U1 becomes, for example, three times (120°) that of the full drive mode, so that the number of scans in the full circumference scan can be, for example, one third (three times) that of the full drive mode (see Z1 to Z3 in FIG. 32). As a result, it was confirmed that the detection time can be shortened because the number of scans is reduced.

However, if the directivity angle of the ultrasonic wave U1 remains wide, there is a drawback in that the resolution of the signal (reflected wave U2) received by the CPU 71 decreases. In this case, it has been confirmed that if the ultrasonic transducer 121 is driven in the full drive mode, the directivity angle becomes narrower and the decrease in resolution can be suppressed.

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

(8) In this embodiment, when the ultrasonic transducer 111 is driven in the full drive mode in which all the vibration parts 113 are driven, the overall outer shape of the vibration parts 113 is approximately circular, so that the directional characteristics of the ultrasonic waves U1 irradiated in the perpendicular direction of the piezoelectric element 112 approach axial symmetry (see FIG. 16). On the other hand, when the ultrasonic transducer 111 is driven in the partial drive mode in which some of the vibration parts 113 are driven, the ultrasonic waves U1 irradiated from the belt-shaped vibration part 113 alone have a relatively narrow directional angle in the longitudinal direction of the vibration part 113, but have a relatively wide directional angle in the arrangement direction of the vibration part 113 (see FIG. 22). Therefore, for example, when scanning all around, if the drive mode of the ultrasonic transducer 111 is switched to the partial drive mode, the directional angle of the ultrasonic waves U1 can be made wider in the rotation direction of the ultrasonic transducer 111. As a result, the detection range in one scan is wider, so that the number of required scans can be further reduced. Therefore, the detection speed can be increased without causing detection misses, making it possible to shorten the detection time compared to the full drive mode.

(9) In the prior art described in Japanese Patent Laid-Open Publication No. 1-295190, an ultrasonic transducer is disclosed that includes a piezoelectric element in which one circular vibration part (transmitting and receiving part) and two annular vibration parts (transmitting and receiving parts) are concentrically arranged, and the directivity is controlled by switching the driving mode of the vibration part. However, if an attempt is made to widen the directional angle of the ultrasonic wave by switching to a driving mode that drives only the circular vibration part, the following problem occurs. That is, the directional angle is widened not only in the rotation direction of the ultrasonic transducer (piezoelectric element) but also in the tilt direction (depression angle direction) of the ultrasonic transducer. As a result, unnecessary information is included in the information in the depression angle direction in the reception signal generated when the ultrasonic transducer receives a reflected wave, and the accuracy is likely to decrease. For this reason, there is a problem that the resolution of the reception signal by the CPU decreases. In addition, the area of the circular vibration part is about one-third of the total area of the vibration part, and the outer diameter of the circular vibration part is about 57% of the outer diameter of the annular vibration part located at the outermost periphery. In this case, the spread of the directivity angle is less than twice as large as when all the vibrating parts are driven, so the number of scans in the full-circle scan cannot be reduced by half. Moreover, since the vibration of the circular vibrating part and the annular vibrating part is a compound vibration (see FIG. 28), there is a problem that the electromechanical coupling coefficient is low and the sensitivity is reduced. There is also a problem that the reverberation is long.

On the other hand, in this embodiment, when the directivity angle of the ultrasonic wave U1 is widened by switching to the partial drive mode in which only the vibration part 113 in the center is driven, the directivity angle can be widened only in the rotation direction of the ultrasonic transducer 111 (piezoelectric element 112). As a result, unnecessary information is less likely to be included in the information in the depression angle direction in the reception signal generated when the ultrasonic transducer 111 receives a reflected wave. Therefore, the resolution of the reception signal by the CPU 71 can be ensured. In addition, the width of the vibration part 113 in the center, which is the driving part in the partial drive mode, is about 1/9 of the outer diameter of the piezoelectric element 112. In this case, the directivity angle is, for example, about 3 to 5 times wider than when all the vibration parts 113 are driven, so that the number of scans in the full circumference scan can be reduced to, for example, about 1/5 to 1/3 (see FIG. 31 and FIG. 32). Moreover, the width of the vibration part 113 in this embodiment is half or less of the thickness of the piezoelectric element 112, as in the first embodiment, so that the vibration part 113 has a shape that easily vibrates in the height direction, and the electromechanical coupling coefficient is increased, thereby increasing the sensitivity of the ultrasonic transducer 111. In addition, the ultrasonic wave U1 has a wide band, and the reverberation is shortened.

In this embodiment, the effect of the composite vibration is small because the lengths of the vibration parts 113 are different, and the lengths of the vibration parts 113 are different on the side closer to the center O1 of the piezoelectric element 112 and the side farther from the center O1 of the piezoelectric element 112. In this case, although the vibration parts 113 vibrate in the length direction, the resonance frequency of each vibration part 113 is different, so that the resonance phenomenon in the length direction due to a specific frequency is suppressed. In contrast, the thickness is uniform in the height direction, and the resonance frequency in the thickness direction is the same for each vibration part 113. In addition, the groove processing makes it easier for each vibration part 113 to deform in the thickness direction, so the sensitivity of the ultrasonic transducer 111 is increased.

The above embodiments may be modified as follows.

In the ultrasonic transducers 41 and 111 of the above embodiments, the grooves K1 formed in the piezoelectric elements 43 and 112 are arranged parallel to each other (i.e., without intersecting) along the surface direction and perpendicular to (the central axis A1 of) the tilting shaft 36 (at an angle of 90°). However, as long as each groove K1 forms an angle of 60° or more and 120° or less with respect to the tilting shaft 36, the arrangement of each groove K1 may be appropriately changed. For example, as shown in the ultrasonic transducer 131 of FIG. 33(a), each groove K2 may extend in a different direction from each other. Also, as shown in the ultrasonic transducer 132 of FIG. 33(b), each groove K3 may be bent, and as shown in the ultrasonic transducer 133 of FIG. 33(c), each groove K4 may be curved. Note that the grooves are preferably parallel to each other and have the same width. Also, it is preferable that each groove is configured on a straight line even if it is bent halfway.

The ultrasonic transducers 41, 111 in the above embodiments were provided with disk-shaped piezoelectric elements 43, 112, but the piezoelectric elements may be elliptical plate-shaped piezoelectric elements 134, 135 (see Figures 34(a) and (b)), or oval plate-shaped piezoelectric elements 136, 137 (see Figures 34(c) and (d)).

In the ultrasonic transducers 41 and 111 of the above embodiments, the grooves K1 are entirely voids K0. However, both ends of the grooves K1 may be sealed on the outer peripheral surface 53 of the piezoelectric element 43 and 112. For example, as shown in FIG. 35, both ends of each groove K1 may be sealed by wrapping a tape 141 around the outer peripheral surface 53 of the piezoelectric element 140. Also, as shown in FIG. 36, both ends of each groove K1 may be sealed by filling both ends of each groove K1 with a filler 142. Furthermore, if the density of the filler is relatively low, the entire grooves K1 may be filled with the filler.

In the first embodiment, the width W1 of the outer vibration portion 91 and the width W2 of the inner vibration portion 92 are different from each other, but the widths W1 and W2 may be equal to each other. Also, in each of the above embodiments, the widths of the grooves K1 formed in the piezoelectric elements 43 and 112 are equal to each other, but the widths of the grooves K1 may be different from each other.

The piezoelectric element 43 in the first embodiment has a structure in which the divided vibration parts 90 are connected to each other at the end on the front surface 51 side. However, the piezoelectric element may have a structure in which the vibration parts are completely divided. In this case, the ultrasonic transducer is formed by attaching each vibration part to the base material 42.

In the first embodiment, the rear electrodes 55 are formed on the surfaces 93a and 93b of the vibration parts 90, and the wires 60 are joined so as to bridge each of the rear electrodes 55. However, instead of joining the wires 60, a metal foil 143 (e.g., copper foil, brass foil, aluminum foil, etc.) which is a strip-shaped conductive member may be attached so as to bridge each of the rear electrodes 55 by a conductive metal such as solder or an adhesive containing a conventionally known conductive filler (see FIG. 37). Furthermore, instead of attaching the metal foil 143, a conductive tape (not shown) which is a strip-shaped conductive member having an adhesive layer may be attached so as to bridge each of the rear electrodes 55. In addition, both the wires 60 and the metal foil 143 may be joined so as to bridge each of the rear electrodes 55.

In the second embodiment, when the drive mode of the ultrasonic transducer 111 is switched to the partial drive mode, four vibration parts 113a located in the central region of the piezoelectric element 112 are driven. However, when the drive mode is switched to the partial drive mode, one to three vibration parts 113a located in the central region of the piezoelectric element 112 may be driven, or five or more vibration parts 113 located in the central region of the piezoelectric element 112 may be driven.

The partial drive mode of the second embodiment described above is a mode in which an AC voltage is applied to the vibration portion 113a located in the central region of the piezoelectric element 112 to drive it, and no voltage is applied to the vibration portions 113b, 113c located at both ends of the piezoelectric element 112. However, the partial drive mode may be a mode in which a voltage lower than that applied to the vibration portion 113a in the central region is applied to the vibration portions 113b, 113c on both sides, or a mode in which a voltage is applied to the vibration portions 113b, 113c on both sides in a phase different from that of the vibration portion 113a in the central region.

In the ultrasonic transducers 41 and 111 of the above embodiments, the piezoelectric elements 43 and 112 are made of lead zirconate titanate (PZT), but the material for forming the piezoelectric elements 43 and 112 is not particularly limited. For example, potassium sodium niobate (alkali niobate), barium titanate, PMN-PT (Pb(Mg
Alternatively _, a piezoelectric element made of piezoelectric ceramics such as Pb(Zn _1/3 Nb _2/3 )O ₃ —PbTiO ₃ ) single _crystal , PZNT (Pb(Zn 1/3 Nb 2/3 )O ₃ —PbTiO ₃ ) single crystal, or LiNbO ₃ single crystal may be used.

In the first embodiment, the ultrasonic transducer 41 is fixed to the case 40 by inserting the tip of a screw through the screw hole 45 on the base material 42 into the screw hole 47 on the case 40 while the piezoelectric element 43 is housed in the case 40. However, the ultrasonic transducer 41 may be fixed to the case 40 by other methods. For example, the ultrasonic transducer 41 may be fixed to the case 40 using an adhesive.

- In the first embodiment described above, an ultrasonic transducer 41 was used that consisted of a substrate 42 that also served as an acoustic matching layer and a piezoelectric element 43 bonded to the substrate 42, but an ultrasonic transducer consisting only of a piezoelectric element 43 may also be used.

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

(1) A sonar according to any one of claims 1 to 6, characterized in that the maximum length of the vibrating part is equal to the outer diameter of the piezoelectric element.

(2) A sonar according to any one of claims 1 to 6, characterized in that the minimum length of the vibrating part is greater than the height of the vibrating part.

(3) A sonar according to any one of claims 1 to 6, characterized in that the height of the vibrating part is greater than the width of the vibrating part.

(4) A sonar according to any one of claims 1 to 6, characterized in that the width of the groove portion is smaller than the width of the vibration portion.

(5) A sonar according to any one of claims 1 to 6, characterized in that, when the width of the vibrating part is W and the minimum outer diameter of the piezoelectric element is L, the relationship W/L≦0.1 is satisfied.

(6) A sonar according to any one of claims 1 to 6, characterized in that the ultrasonic transducer has a substantially circular substrate that also serves as an acoustic matching layer, the front surface of the piezoelectric element is joined to the substrate, and the multiple vibration parts are connected to each other at the ends on the front surface side of the piezoelectric element.

(7) A sonar according to any one of claims 1 to 6, characterized in that the plurality of vibration parts are composed of a pair of outer vibration parts and a plurality of inner vibration parts arranged between the pair of outer vibration parts, and the width of the outer vibration parts is larger than the width of the inner vibration parts.

(8) A sonar according to claim 3 or 4, characterized in that the electrical path connected to the vibration part located in the central region of the piezoelectric element and the electrical path connected to the vibration part other than that are separate systems.

11...Sonar 30...Drive mechanism 31a...Rotation axis 36...Tilting axis 41, 111, 131, 132, 133...Ultrasonic transducer 43, 112, 134, 135, 136, 137, 140...Piezoelectric element 51...Front surface 52 of piezoelectric element...Back surface 90, 113, 113a, 113b, 113c...Vibration section 91, 114...Outer vibration section 92, 115 as vibration section...Inner vibration section H3 as vibration section...Thickness of piezoelectric element K1, K2, K3, K4...Groove section O1...Center of piezoelectric element U1...Ultrasonic wave W...Width of vibration section

Claims (1)

A sonar comprising an ultrasonic transducer for transmitting and receiving ultrasonic waves, and a drive mechanism for causing the ultrasonic transducer to perform a rotational motion about a rotation axis oriented in a vertical direction and a tilting motion about a tilting axis perpendicular to the rotation axis,
The ultrasonic transducer includes a substantially disk-shaped piezoelectric element having a front surface and an opposite back surface;
The piezoelectric element has a plurality of grooves extending in a planar direction so as not to intersect with each other, and a plurality of band-shaped vibration parts are disposed via the grooves;
The longer the distance from the center of the piezoelectric element, the shorter the length of the vibration part.
The ultrasonic transducer is disposed so that the groove portion forms an angle of 60° or more and 120° or less with respect to the tilt axis,
The ultrasonic transducer includes a substantially disk-shaped base material that also serves as an acoustic matching layer, the front surface of the piezoelectric element is bonded to the base material, and the vibration parts are connected to each other at the end portions on the front surface side of the piezoelectric element,
the plurality of vibration parts are composed of a pair of outer vibration parts that are farthest from the center of the piezoelectric element, and a plurality of inner vibration parts that are disposed between the pair of outer vibration parts, and the width of the outer vibration parts is larger than the width of the inner vibration parts,
The ultrasonic transducer is housed in a sonar dome filled with an ultrasonic propagation liquid that propagates ultrasonic waves, and a portion of the ultrasonic propagation liquid flows into the groove, which is a gap, thereby filling the groove.

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