Stacked composite transducer and underwater active sonar

Abstract

To provide a laminate type composite vibrator that is suitable for mounting in a limited space and widens an in-use frequency band.SOLUTION: A laminate type composite vibrator 400 includes a first composite vibrator 41 and a second composite vibrator 42 laminated on an acoustic radiation surface 40. The second composite vibrator 42 functions as an acoustic matching layer at an in-use frequency of the first composite vibrator 41.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated composite vibrator, and more particularly to a composite vibrator that achieves a broader frequency band. [Background technology]

[0002] Until now, underwater active sonars have employed an array of transducers with multiple different bands on the same radiation surface, making them broadband and multifunctional. These underwater active sonars acquire information about objects in the water or on the bottom by using sound waves with multiple different bands propagating through the water. However, arranging transducers with multiple different bands is limited by the mounting space. Furthermore, miniaturization of underwater active sonars is essential for mounting them on unmanned vehicles, including UUVs (Unmanned Underwater Vehicles). Therefore, it has been difficult to miniaturize underwater active sonars while maintaining performance by arranging transducers with multiple bands.

[0003] Patent Document 1 relates to an underwater transducer using a bolt-clamped Langevin transducer, and proposes bonding an acoustic matching layer to the acoustic radiation surface of the front mass of the bolt-clamped Langevin transducer.

[0004] Patent Document 2 relates to an ultrasound probe that transmits and receives ultrasound to and from a test subject such as a living body to obtain an ultrasound image. Patent Document 2 proposes forming a laminated ultrasound transducer by alternately laminating composite piezoelectric materials and monolithic piezoelectric materials, thereby obtaining high-resolution ultrasound images of the test subject such as a living body. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-178700 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-142880 Summary of the Invention [Problem to be solved by the invention]

[0006] Various methods have been investigated for broadening the usable frequency band, such as using an acoustic matching layer, as shown in Patent Document 1. However, simply using an acoustic matching layer is not sufficient to broaden the usable frequency band, and further broadening is desired. Furthermore, in recent years, the size of mounted devices has been reduced, and with mounting space being limited, it is desired to achieve miniaturization while maintaining the previous performance.

[0007] As mentioned above, Patent Document 2 proposes constructing a laminated ultrasonic transducer by alternately laminating composite piezoelectric material and monolithic piezoelectric material, but it is not intended to broaden the usable frequency band, nor does it describe a composite transducer suitable for use in underwater active sonar. Therefore, while the ultrasonic probe in Patent Document 2 can obtain images of subjects such as living organisms, it is difficult to achieve miniaturization while maintaining the same performance as before.

[0008] In view of the above problems, an object of the present invention is to provide a laminated composite vibrator that is suitable for installation in a limited space and that can realize a wide frequency band for use. [Means for solving the problem]

[0009] In order to achieve the above object, the laminated composite vibrator according to the present invention comprises: a first composite transducer and a second composite transducer stacked on an acoustic radiation surface; The second composite transducer functions as an acoustic matching layer at the operating frequency of the first composite transducer.

[0010] An underwater active sonar according to the present invention includes the laminated composite transducer having the above characteristics and the above acoustic radiation surface. [Effects of the Invention]

[0011] The laminated composite vibrator of the present invention is suitable for installation in a limited space and can realize a wide frequency band for use. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a side view illustrating a laminated composite vibrator according to an embodiment of the present invention; [Figure 2] FIG. 1 is a side view illustrating a layered composite vibrator according to a first embodiment of the present invention. [Figure 3] 4 is a graph for explaining the frequency characteristics of the layered composite vibrator according to the first embodiment of the present invention. [Figure 4] 4 is a graph for explaining the frequency characteristics of the layered composite vibrator according to the first embodiment of the present invention. [Figure 5] FIG. 10 is a side view illustrating a layered composite vibrator according to a second embodiment of the present invention. [Figure 6] 10 is a graph illustrating the frequency characteristics of the layered composite vibrator according to the second embodiment of the present invention. [Figure 7] A conceptual diagram of a ship equipped with an underwater active sonar. DETAILED DESCRIPTION OF THE INVENTION

[0013] Before describing specific embodiments of the present invention, a laminated composite vibrator according to a general embodiment of the present invention will be described. Fig. 1 is a side view illustrating a laminated composite vibrator according to a general embodiment of the present invention.

[0014] The laminated composite vibrator 400 of FIG. 1 includes a first composite vibrator 41 and a second composite vibrator 42 stacked on an acoustic radiation surface 40. The second composite vibrator 42 functions as an acoustic matching layer at the operating frequency of the first composite vibrator 41. An acoustic matching layer is generally used to efficiently transmit ultrasonic waves from an ultrasonic transmitter into a gas. The acoustic matching layer is provided between a piezoelectric vibrator, which vibrates at an ultrasonic frequency, and the gas to efficiently transmit the vibration of the piezoelectric vibrator into the gas. For example, an acoustic matching layer is inserted between the vibrator and the acoustic wave transmission medium when there is a large difference between the acoustic impedance of the vibrator and the acoustic impedance of the sound wave transmission medium. Inserting an acoustic matching layer can minimize the reflection of sound waves. Note that the specifications of the first composite vibrator 41 and the second composite vibrator 42 differ from each other in the operating frequency bands.

[0015] In the embodiment of the present invention, a first composite vibrator 41 and a second composite vibrator 42, which have specifications for different usable frequency bands, are stacked on the acoustic radiation surface 40. This makes it possible to ensure two frequency bands: one usable frequency band when the second composite vibrator 42 is driven alone, and one usable frequency band when the first composite vibrator 41 is driven over a wide band. The usable frequency band when the first composite vibrator 41 is driven over a wide band is achieved by operating the second composite vibrator 42 as an acoustic matching layer for the first composite vibrator 41. As a result, the stacked composite vibrator 400 according to the embodiment of the present invention enables an expansion of the usable frequency band, and can be miniaturized even in a limited mounting space while still ensuring the same usable frequency band.

[0016] Furthermore, by adjusting the transducers to be stacked, the performance of the laminated composite transducer 400 can be changed. Furthermore, by using composite transducers as the transducers to be stacked, the number of parameters to be adjusted is reduced. By adopting a composite transducer as the transducer to be stacked in this way, performance can be changed more easily than with other transducers such as a bolt-clamped Langevin transducer (described in Patent Document 1), which has the advantage of reducing design costs. More specific embodiments of the present invention will be described in detail below with reference to the drawings.

[0017] [First embodiment] Next, a description will be given of a laminated composite vibrator according to a first embodiment of the present invention. Fig. 2 is a side view for explaining the laminated composite vibrator according to the first embodiment of the present invention.

[0018] The laminated composite vibrator 100 of FIG. 2 mainly includes a composite vibrator 1 and a composite vibrator 2. The composite vibrator 1 and the composite vibrator 2 are laminated together. One end face of the composite vibrator 1 of FIG. 2 is fixed to the composite vibrator 2. The composite vibrator 2 is selected to also function as an acoustic matching layer in the frequency band used by the composite vibrator 1. The composite vibrator 2 is formed with a thickness that functions as an acoustic matching layer for the composite vibrator 1, thereby giving the composite vibrator 1 wideband characteristics. As described above, an acoustic matching layer is inserted between the vibrator and the sound-transmitting medium when there is a large difference between the acoustic impedance of the vibrator and the sound-transmitting medium. Inserting an acoustic matching layer can minimize the reflection of sound waves.

[0019] FIG. 3 shows the transmission voltage sensitivity obtained by finite element analysis using a three-dimensional analysis model that simply simulates each embodiment of the composite vibrator. In FIG. 3, the vertical axis represents the transmission voltage sensitivity, and the horizontal axis represents the frequency. The frequency characteristics of composite vibrator 1 alone are shown by a solid line, the frequency characteristics of composite vibrator 2 are shown by a dashed line, and the frequency characteristics of composite vibrator 1 when composite vibrator 2 is used as an acoustic matching layer are shown by a dotted line. As shown by the solid line in FIG. 3, composite vibrator 1 has a band 12. As shown by the dashed line in FIG. 3, composite vibrator 2 has a band 14. That is, stacked composite vibrator 100 includes composite vibrator 1 having a band 12 and composite vibrator 2 having a band 14 and also serving as an acoustic matching layer for composite vibrator 1. In this specification, a band is defined as a portion 10 dB down from the peak of the transmission voltage sensitivity.

[0020] Referring to FIG. 2, composite vibrator 1 is provided with electrodes 3 and 4 on both sides in the vibration direction. Furthermore, composite vibrator 1 is provided with flexible substrate 6 on electrode 3 and flexible substrate 7 on electrode 4 as means for inputting electrical signals to each electrode. The vibration direction of composite vibrator 1 is the direction indicated by arrow 11 in FIG. 2, and composite vibrator 1 is polarized in that direction. By inputting AC electrical signals to flexible substrate 6 and flexible substrate 7, electromechanical conversion (conversion of electrical signals into mechanical vibration) is performed in composite vibrator 1. Furthermore, one end face of composite vibrator 1 is fixed to composite vibrator 2 via flexible substrate 7.

[0021] The composite vibrator 2 has electrodes 4 and 5 on both sides in the vibration direction. The composite vibrator 2 also has a flexible substrate 7 on electrode 4 and a flexible substrate 8 on electrode 5 as means for inputting electrical signals to each electrode. The vibration direction of the composite vibrator 2 is indicated by arrow 11 in FIG. 2 , and the composite vibrator 2 is polarized in that direction. By inputting AC electrical signals to the flexible substrates 7 and 8, the composite vibrator 2 performs electromechanical conversion (converting electrical signals into mechanical vibrations). The composite vibrator 2 has an acoustic emitting surface 9 made of rubber or the like bonded to the side opposite the surface bonded to the composite vibrator 1. The acoustic emitting surface 9 is one element of a mounting device on which a laminated composite vibrator according to an embodiment of the present invention is mounted. The surface of the acoustic emitting surface 9 opposite the surface bonded to the composite vibrator 2 is in contact with the surface of water 10. Note that water 10 is an example of an acoustic wave transmission medium containing a target object from which information is to be acquired.

[0022] In the laminated composite vibrator according to the embodiment of the present invention, a flexible substrate is used to input an electric signal to the electrodes of the composite vibrator, but the wiring can also be implemented by using lead wires, etc. Furthermore, the laminated composite vibrators according to the embodiment of the present invention may be arranged in plural on the surface of the above-mentioned acoustic radiation surface 9, or may be arranged in plural arrays.

[0023] (Operation of the embodiment) The operation of the layered composite vibrator 100 of this embodiment will be described with reference to FIGS.

[0024] Figures 3 and 4 are graphs for explaining the frequency characteristics of the laminated composite vibrator according to the first embodiment of the present invention. Figures 3 and 4 show the comparison results of the transmitted wave voltage sensitivity obtained by finite element method analysis using a three-dimensional analysis model that simply simulates the laminated composite vibrator according to the embodiment shown in Figure 2. The horizontal axis represents frequency and the vertical axis represents transmitted wave voltage sensitivity. The horizontal axis has a scale of 10 kHz, and the vertical axis has a scale of 10 dB.

[0025] The laminated composite vibrator 100 in Fig. 2 includes a composite vibrator 1 having a band 12 in Fig. 3 and a composite vibrator 2 having a band 14 in Fig. 3 and serving as an acoustic matching layer for the composite vibrator 1. In this specification, the band is defined as the portion 10 dB down from the peak of the transmission voltage sensitivity.

[0026] The solid line in Figure 3 shows the frequency characteristics when composite vibrator 1 is operated alone, the dashed line in Figure 3 shows the frequency characteristics of composite vibrator 2, and the dotted line in Figure 3 shows the frequency characteristics of composite vibrator 1 when composite vibrator 2 is used as an acoustic matching layer.

[0027] The solid line in Fig. 4 indicates the frequency characteristics when the composite vibrator 1 is operated independently, and the dashed line in Fig. 4 indicates the frequency characteristics of the composite vibrator 2. Furthermore, the dotted line in Fig. 4 indicates the frequency characteristics of the composite vibrator 1 when the composite vibrator 2 is used as an acoustic matching layer, and the dashed line in Fig. 4 indicates the frequency characteristics when the composite vibrator 1 and the composite vibrator 2 are driven simultaneously.

[0028] 2, when an AC electric signal is input between the flexible substrate 6 and the flexible substrate 7, the above-mentioned electromechanical conversion occurs in the composite vibrator 1, causing the composite vibrator 1 to expand and contract. The energy from this expansion and contraction is transmitted through the composite vibrator 2 and the acoustic emitting surface 9, and is radiated into the water 10 as an acoustic signal.

[0029] The desired acoustic signal can be obtained by changing the frequency and voltage of the AC electrical signal. Here, composite vibrator 2 has an acoustic impedance intermediate between that of composite vibrator 1 and water, and functions as an acoustic matching layer for composite vibrator 1. In this case, the laminated composite vibrator of Figure 2 has a bandwidth 13 as shown in Figure 3. This allows the laminated composite vibrator of Figure 2 to obtain wider bandwidth characteristics than the bandwidth 12 obtained when composite vibrator 1 is driven alone.

[0030] 2, when an AC electric signal is input between the flexible substrate 7 and the flexible substrate 8, the above-mentioned electromechanical conversion occurs in the composite vibrator 2, causing the composite vibrator 2 to expand and contract. The energy generated by this expansion and contraction is transmitted through the acoustic emitting surface 9 and radiated into the water 10 as an acoustic signal.

[0031] By changing the frequency and voltage of the AC electric signal, a desired acoustic signal can be obtained. As shown in Fig. 3, a band 14 can be obtained by the composite vibrator 2, which, together with the band 13, becomes a band 15, and the laminated composite vibrator according to the first embodiment of the present invention achieves an even wider band characteristic.

[0032] Furthermore, when an AC electric signal is input between flexible substrate 6 and flexible substrate 7, and between flexible substrate 7 and flexible substrate 8, and composite vibrator 1 and composite vibrator 2 are simultaneously driven, composite vibrator 1 and composite vibrator 2 perform an expansion and contraction motion. Energy from this expansion and contraction motion is transmitted through acoustic radiation surface 9 and radiated into water 10 as an acoustic signal. Band 17 can be obtained as shown in FIG. 4, and together with band 16, band 18 is obtained, thereby realizing an even wider band characteristic for the stacked composite vibrator according to the first embodiment of the present invention.

[0033] (Effects of the embodiment) In the laminated composite vibrator of this embodiment, composite vibrator 1 and composite vibrator 2 are laminated on an acoustic radiation surface 9, and composite vibrator 2 is laminated so as to also function as an acoustic matching layer in the frequency band used by composite vibrator 1.

[0034] By stacking the composite vibrator 1 and the composite vibrator 2, the occupied area of ​​the laminated composite vibrator can be made smaller than when they are mounted separately on the acoustic radiation surface. Furthermore, by stacking the composite vibrator 1 and the composite vibrator 2, the usable frequency band can be made wider than the frequency band in which the composite vibrator alone operates, due to the effect of using the composite vibrator 2 as an acoustic matching layer. Furthermore, when the usable frequency band of the composite vibrator 2 is also included, it can be understood that the usable frequency band of the laminated composite vibrator of this embodiment is even wider.

[0035] Furthermore, in a laminated composite vibrator having such a configuration, by simultaneously driving composite vibrator 1 and composite vibrator 2, the band is expanded to band 17 in Figure 4, and together with band 16, the usable frequency band can be widened.

[0036] By laminating the composite vibrator 1 and the composite vibrator 2, the frequency band becomes wider than the frequency band in which the composite vibrator operates alone without laminating the composite vibrators, due to the effect of using the composite vibrator 2 as an acoustic matching layer. Furthermore, when the frequency band used by the composite vibrator 2 is also included, it can be seen that the laminated composite vibrator of this embodiment has an even wider band.

[0037] Second Embodiment Next, a laminated composite vibrator according to a second embodiment of the present invention will be described. In the above-described first embodiment, the laminated composite vibrator is described, the main feature of which is that the composite vibrator 1 and the composite vibrator 2 are laminated on the sound emitting surface 9, but the laminated composite vibrator of the present invention is not limited to this.

[0038] 5 is a side view for explaining a layered composite vibrator according to a second embodiment of the present invention, in which detailed explanations of elements similar to those of the first embodiment will be omitted.

[0039] The laminated composite vibrator 200 in Fig. 5 mainly includes a composite vibrator 19, a composite vibrator 20, and a composite vibrator 21. The composite vibrators 19, 20, and 21 are laminated. One end face of the composite vibrator 19 in Fig. 5 is fixed to the composite vibrator 20.

[0040] The composite vibrators 20 and 21 are selected so as to also function as acoustic matching layers in the frequency band used by the composite vibrator 19. The composite vibrators 20 and 21 are formed with a thickness that allows them to function as acoustic matching layers for the composite vibrator 19, thereby giving the composite vibrator 19 wideband characteristics. An acoustic matching layer is inserted between the vibrator and the sound wave transmission medium when there is a large difference between the acoustic impedance of the vibrator and the acoustic impedance of the sound wave transmission medium. By inserting an acoustic matching layer, it is possible to minimize the reflection of sound waves.

[0041] The composite vibrator 21 is also selected so as to function as an acoustic matching layer in the frequency band used by the composite vibrator 20. The composite vibrator 21 is formed with a thickness that allows it to function as an acoustic matching layer for the composite vibrator 20, thereby giving the composite vibrator 20 wideband characteristics.

[0042] In FIG. 5, a laminated composite vibrator 200 includes a composite vibrator 19, a composite vibrator 20, and a composite vibrator 21, which respectively correspond to three usable frequency bands.

[0043] Composite vibrator 19 has electrodes 22 and 23 on both sides in the vibration direction. Furthermore, composite vibrator 19 has flexible substrates 26 and 27 on electrodes 22 and 23, respectively, as means for inputting electrical signals to the respective electrodes. The vibration direction of composite vibrator 19 is the direction indicated by arrow 32 in Fig. 5, and composite vibrator 19 is polarized in that direction.

[0044] One end face of composite vibrator 19 is fixed to composite vibrator 20 via flexible substrate 27. Composite vibrator 20 has an end face opposite to the end face fixed to composite vibrator 19 fixed to composite vibrator 21.

[0045] When an AC electric signal is input between the flexible substrate 26 and the flexible substrate 27, electromechanical conversion (conversion of the electric signal into mechanical vibration) occurs in the composite vibrator 19, causing the composite vibrator 19 to expand and contract. Energy from this expansion and contraction is transmitted through the composite vibrator 20, the composite vibrator 21, and the acoustic radiation surface 30, and is radiated into the water 31 as an acoustic signal.

[0046] Composite vibrator 20 has electrodes 23 and 24 on both sides in the vibration direction, and as means for inputting electrical signals to each electrode, electrode 23 has a flexible substrate 27, and electrode 24 has a flexible substrate 28. The vibration direction of composite vibrator 20 is the direction indicated by arrow 32 in Figure 5, and composite vibrator 20 is polarized in that direction.

[0047] When an AC electric signal is input between the flexible substrates 27 and 28, electromechanical conversion (conversion of the electric signal into mechanical vibration) occurs in the composite vibrator 20, causing the composite vibrator 20 to expand and contract. Energy from this expansion and contraction is transmitted through the composite vibrator 21 and the acoustic radiation surface 30, and is radiated into the water 31 as an acoustic signal.

[0048] Composite vibrator 21 has electrodes 24 and 25 on both sides in the vibration direction, and as means for inputting electrical signals to each electrode, electrode 24 has a flexible substrate 28 and electrode 25 has a flexible substrate 29. The vibration direction of composite vibrator 21 is the direction indicated by arrow 32 in Fig. 5, and composite vibrator 21 is polarized in that direction. One end face of composite vibrator 21 is fixed to composite vibrator 20 via flexible substrate 28, and the other end face opposite is bonded via flexible substrate 29 to acoustic radiation surface 30 made of rubber or the like.

[0049] When an AC electric signal is input between the flexible substrate 28 and the flexible substrate 29, electromechanical conversion (conversion of the electric signal into mechanical vibration) occurs in the composite vibrator 21, causing the composite vibrator 21 to expand and contract. Energy from this expansion and contraction is transmitted through the acoustic radiation surface 30 and radiated into the water 31 as an acoustic signal.

[0050] The acoustic radiation surface 30 is one element of a mounting device on which a stacked composite transducer according to an embodiment of the present invention is mounted. The surface of the acoustic radiation surface 30 opposite to the surface bonded to the composite transducer 21 is in contact with the water surface of the water 31. Note that the water 31 is an example of a sound wave transmission medium in which a target object from which information is to be acquired exists.

[0051] (Operation of the embodiment) The operation of the composite vibrator of this embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 6 is a graph for explaining the frequency characteristics of the laminated composite vibrator according to the second embodiment of the present invention. Fig. 6 shows a comparison result of the transmitted wave voltage sensitivity obtained by finite element method analysis using a three-dimensional analysis model that simply simulates the laminated composite vibrator according to the embodiment shown in Fig. 5. In Fig. 6, the horizontal axis represents frequency and the vertical axis represents transmitted wave voltage sensitivity.

[0052] The solid line in Fig. 6 shows the frequency characteristics of the composite vibrator 19 when the composite vibrator 20 and the composite vibrator 21 are used as acoustic matching layers. The dashed-dotted line in Fig. 6 shows the frequency characteristics of the composite vibrator 20 when the composite vibrator 21 is used as an acoustic matching layer. The dotted line in Fig. 6 shows the frequency characteristics when the composite vibrator 21 is used.

[0053] 5, the above-mentioned electromechanical conversion occurs in the composite vibrator 19, causing the composite vibrator 19 to expand and contract. The energy generated by this expansion and contraction is transmitted through the composite vibrator 20, the composite vibrator 21, and the acoustic radiation surface 30, and is radiated into the water 31 as an acoustic signal.

[0054] The desired acoustic signal can be obtained by changing the frequency and voltage of the AC electrical signal. Here, composite vibrator 20 and composite vibrator 21 have an acoustic impedance intermediate between that of composite vibrator 19 and water, and function as acoustic matching layers for composite vibrator 19. In this case, the laminated composite vibrator 200 in Fig. 5 has a bandwidth 33 as shown in Fig. 6. This allows the laminated composite vibrator 200 in Fig. 5 to obtain wider bandwidth characteristics than the bandwidth obtained when composite vibrator 19 is driven alone.

[0055] 5, when an AC electric signal is input between the flexible substrate 27 and the flexible substrate 28, the above-mentioned electromechanical conversion occurs in the composite vibrator 20, causing the composite vibrator 20 to expand and contract. The energy generated by this expansion and contraction is transmitted through the acoustic emitting surface 30 and radiated into the water 31 as an acoustic signal.

[0056] By changing the frequency and voltage of the AC electrical signal, a desired acoustic signal can be obtained. Here, composite transducer 21 has an acoustic impedance intermediate between that of composite transducer 20 and water, and functions as an acoustic matching layer for composite transducer 20. As shown in Figure 6, composite transducer 20 can obtain band 34, which, together with band 33, becomes band 35, and the laminated composite transducer according to the second embodiment of the present invention achieves even wider band characteristics.

[0057] In addition, the composite vibrator 21 can be driven by itself, and when driven, the energy generated by the expansion and contraction motion is transmitted through the acoustic radiation surface 30 and radiated as an acoustic signal into the water 31, thereby obtaining a band 36 as shown in Figure 6, making this band usable.

[0058] Furthermore, when AC electrical signals are input between flexible substrate 26 and flexible substrate 27, between flexible substrate 27 and flexible substrate 28, and between flexible substrate 28 and flexible substrate 29, and composite vibrator 19, composite vibrator 20, and composite vibrator 21 are simultaneously driven, composite vibrator 19, composite vibrator 20, and composite vibrator 21 perform expansion and contraction movements. Energy from this expansion and contraction movement is transmitted through acoustic radiation surface 30 and radiated into water 31 as an acoustic signal. When simultaneously driven in this manner, the stacked composite vibrator according to the second embodiment of the present invention achieves even wider bandwidth characteristics.

[0059] (Effects of the embodiment) In the laminated composite vibrator of this embodiment, the composite vibrator 19, the composite vibrator 20, and the composite vibrator 21 are laminated on the sound radiating surface 30. This allows the area occupied by the laminated composite vibrator to be smaller than when the composite vibrator 19, the composite vibrator 20, and the composite vibrator 21 are separately mounted on the sound radiating surface. In addition, the composite vibrators 20 and 21 are laminated so as to also function as an acoustic matching layer in the frequency band used by the composite vibrator 19. In addition, the composite vibrator 21 is laminated so as to also function as an acoustic matching layer in the frequency band used by the composite vibrator 20.

[0060] By laminating the composite vibrator 19, the composite vibrator 20, and the composite vibrator 21, the usable frequency band can be broadened compared to the frequency band in which the composite vibrator alone operates, due to the effect of using the composite vibrator 20 and the composite vibrator 21 as an acoustic matching layer and the effect of using the composite vibrator 21 as an acoustic matching layer. Furthermore, when the usable frequency band of the composite vibrator 21 is also included, it can be understood that the usable frequency band of the laminated composite vibrator of this embodiment becomes even broader.

[0061] (Application of laminated composite vibrator) The laminated composite transducer of the above-described embodiment is mounted in an underwater active sonar 51 as shown in Figure 7, and the underwater active sonar 51 is mounted, for example, on a ship 50 floating on the sea. By emitting sound waves into the water from the above-described laminated composite transducer of the underwater active sonar 51 and receiving the sound waves that hit something, are reflected, and return, information about objects in the water or on the bottom of the water can be obtained. Underwater active sonars themselves are well known, and the laminated composite transducer of the above-described embodiment can be applied to underwater active sonars.

[0062] The laminated composite vibrator of the above-described embodiment can be used in underwater active sonars, passive sonars, as well as in devices that use a composite vibrator as a driving source, such as ultrasonic probes, ultrasonic cleaning layers and similar cleaning devices, ultrasonic motors, and ultrasonic surgical devices.

[0063] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto. For example, in the above-described embodiment, a flexible substrate is used to input electrical signals to the electrodes of the composite vibrator, but the present invention is not limited to a flexible substrate. For example, the wiring for inputting electrical signals to the electrodes of the composite vibrator can be implemented using lead wires or the like. Furthermore, in the laminated composite vibrator of the embodiments, the number of layers of the composite vibrator is not limited to two as in the first embodiment or three as in the second embodiment, but can be four or more. Increasing the number of layers can also be considered to achieve even wider bandwidth characteristics. Various modifications are possible within the scope of the invention as defined in the claims, and needless to say, these modifications are also included in the scope of the present invention. [Explanation of symbols]

[0064] 1, 2, 19, 20, 21, 41, 42 Composite vibrators 3, 4, 5, 22, 23, 24, 25 electrodes 6, 7, 8, 26, 27, 28, 29 Flexible PCB 9, 30, 40 Acoustic radiation surface 10, 31 underwater 100, 200, 400 laminated composite vibrator

Claims

1. a first composite transducer and a second composite transducer stacked on an acoustic radiation surface; the second composite transducer functions as an acoustic matching layer inserted between the first composite transducer and a sound wave propagation medium at a frequency used by the first composite transducer; a pair of first electrical terminals to which an AC electrical signal for driving the first composite vibrator is input are included on both end surfaces of the first composite vibrator; a pair of second electrical terminals to which an AC electrical signal for driving the second composite vibrator is input are included on both end surfaces of the second composite vibrator; the pair of first electrical terminals and the pair of second electrical terminals are configured so that the first composite vibrator and the second composite vibrator are simultaneously driven in response to AC electrical signals that are independent of each other. Layered composite vibrator.

2. the second composite transducer has an acoustic impedance intermediate between that of the acoustic wave transmission medium and that of the first composite transducer; The laminated composite vibrator according to claim 1 .

3. a thickness of the second composite transducer is set so as to function as an acoustic matching layer at a frequency used by the first composite transducer; 3. The laminated composite vibrator according to claim 1 or 2.

4. a third composite transducer stacked together with the first composite transducer and the second composite transducer on the acoustic radiation surface; the second composite transducer and the third composite transducer function as acoustic matching layers at a frequency used by the first composite transducer; The laminated composite vibrator according to any one of claims 1 to 3.

5. the second composite transducer and the third composite transducer have an acoustic impedance intermediate between that of the acoustic wave transmission medium and that of the first composite transducer; The laminated composite vibrator according to claim 4 .

6. the thicknesses of the second composite vibrator and the third composite vibrator are set so as to function as acoustic matching layers at a frequency used by the first composite vibrator; 6. The laminated composite vibrator according to claim 4 or 5.

7. the third composite transducer has an acoustic impedance intermediate between that of the acoustic wave transmission medium and that of the second composite transducer; The laminated composite vibrator according to any one of claims 4 to 6.

8. A laminated composite vibrator comprising: the laminated composite vibrator according to any one of claims 1 to 7; and the acoustic radiation surface. Underwater active sonar.

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