Ultrasonic transducer and parametric speaker provided with same

Abstract

According to the present invention, the dimension of the inside of at least one frame body (120) in the long-side direction is at least four times the dimension of the inside of the at least one frame body (120) in the short-side direction orthogonal to the long-side direction, and is greater than the minimum dimension (Lm) of at least one ultrasonic transducer (130) in the long-side direction. An average distance (L3) in the long-side direction of a gap between at least one end edge (120e) of an inner peripheral surface (120s) of the at least one frame body (120) in the long-side direction and at least one end edge (130e) of a surface (130s) on the frame body (120) side of the at least one ultrasonic transducer (130) in the long-side direction is 1.3 times or less the dimension (L2) of the inside of the at least one frame body (120) in the short-side direction.

Description

Ultrasonic transducer and parametric speaker including same

[0001] The present invention relates to an ultrasonic transducer and a parametric speaker including the same.

[0002] Prior documents disclosing the configuration of an ultradirectional acoustic device include Japanese Patent Laid-Open No. 2003-47085 (Patent Document 1) and Japanese Patent No. 6333480 (Patent Document 2). The ultradirectional acoustic device described in Patent Document 1 is configured by deploying multiple ultrasonic transducers on a single printed circuit board and arranging them so that the outer periphery is approximately circular. The multiple ultrasonic transducers are divided into two groups installed at different heights.

[0003] The ultradirectional acoustic device described in Patent Document 2 includes a first ultrasonic emitter and a second ultrasonic emitter. The second ultrasonic emitter is disposed on the axis of the first ultrasonic emitter and in front of the radiation surface. The phase of the carrier signal radiated by the second ultrasonic emitter is opposite to the phase of the carrier signal contained in the signal radiated by the first ultrasonic emitter.

[0004] JP 2003-47085 A Japanese Patent No. 6333480

[0005] The superdirectional acoustic device described in Patent Document 1 has a complex configuration, with multiple ultrasonic transducers arranged in two groups at different installation heights.The superdirectional acoustic device described in Patent Document 2 has a second ultrasonic emitter arranged outside the first ultrasonic emitter, which increases the size of the device.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide an ultrasonic transducer and a parametric speaker equipped with the same that can increase the sound pressure level while reducing power consumption with a simple and compact configuration.

[0007] An ultrasonic transducer according to the present invention comprises a first diaphragm, at least one frame body, and at least one ultrasonic vibrator. The at least one frame body extends in a longitudinal direction and is bonded to the first diaphragm. The at least one ultrasonic vibrator is attached to the at least one frame body and faces the first diaphragm at a distance. The first diaphragm vibrates in an antiphase with the at least one ultrasonic vibrator in a direction perpendicular to the first diaphragm. The longitudinal dimension inside the at least one frame body is at least four times the lateral dimension inside the at least one frame body perpendicular to the longitudinal direction and is larger than the minimum longitudinal dimension of the at least one ultrasonic vibrator. The average longitudinal distance of a gap between at least one longitudinal edge of an inner peripheral surface of the at least one frame body and at least one longitudinal edge of a surface of the at least one ultrasonic vibrator facing the frame body is not more than 1.3 times the lateral dimension inside the at least one frame body.

[0008] According to the present invention, it is possible to increase the sound pressure level while reducing power consumption with a simple and compact configuration in an ultrasonic transducer.

[0009] 1 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. 2 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. 3 is a perspective view showing the configuration of a frame included in the ultrasonic transducer according to a first embodiment of the present invention. 4 is a view of the ultrasonic transducer of FIG. 2 as viewed from the direction of arrow IV. 5 is a sectional view showing the configuration of an ultrasonic vibrator included in the ultrasonic transducer according to a first embodiment of the present invention. 6 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to the first embodiment of the present invention is transmitting or receiving ultrasonic waves. 7 is a sectional view of the ultrasonic transducer of FIG. 6 as viewed from the direction of the arrows VII-VII. 8 is a graph obtained by simulating and analyzing, using the finite element method, the transition of the resonance frequency of the first diaphragm when the longitudinal dimension is changed while the lateral dimension inside the frame is fixed. 9 is a graph obtained by simulating and analyzing, using the finite element method, the transition of the sound pressure of ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension is changed while the lateral dimension inside the frame is fixed. 10 is a graph obtained by simulating and analyzing, using the finite element method, the transition of the sound pressure of ultrasonic waves transmitted from the ultrasonic transducer when the minimum dimension in the second direction (Y-axis direction) of the ultrasonic vibrator is changed. 1 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a first comparative example, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 20 mm, transmits or receives ultrasonic waves. FIG. 2 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a first embodiment, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 15 mm, transmits or receives ultrasonic waves. FIG. 3 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a second embodiment, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 14.5 mm, transmits or receives ultrasonic waves. FIG. 4 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a second comparative example, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 14 mm, transmits or receives ultrasonic waves.23 is a rear view of the ultrasonic transducer shown in FIG. 23 from the direction of the arrows XV-XV. FIG. 24 is a cross-sectional view of the ultrasonic transducer of FIG. 14, taken from the direction of the arrows XV-XV. FIG. 25 is a view of an ultrasonic transducer according to a first modified example of embodiment 1 of the present invention, viewed from the ultrasonic vibrator side. FIG. 26 is a cross-sectional view of an ultrasonic transducer according to a second modified example of embodiment 1 of the present invention, viewed from the ultrasonic vibrator side. FIG. 27 is a cross-sectional view of an ultrasonic vibrator according to a third modified example. FIG. 28 is a cross-sectional view of an ultrasonic vibrator according to a fourth modified example. FIG. 29 is a cross-sectional view of an ultrasonic vibrator according to a fifth modified example. FIG. 29 is a longitudinal cross-sectional view of an ultrasonic transducer according to a sixth modified example of embodiment 1 of the present invention. FIG. 29 is a longitudinal cross-sectional view of an ultrasonic transducer according to a seventh modified example of embodiment 1 of the present invention. FIG. 29 is a side view of an ultrasonic transducer according to a second embodiment of the present invention. FIG. 29 is a rear view of the ultrasonic transducer shown in FIG. 23, taken from the direction of the arrows XXIV. FIG. 29 is an exploded perspective view showing a stacked state in a step of stacking and bonding the components of the ultrasonic transducer according to embodiment 2 of the present invention. FIG. 29 is a plan view showing the positional relationship in the first direction (X-axis direction) in a step of cutting the piezoelectric body of the ultrasonic transducer according to embodiment 2 of the present invention. FIG. 29 is a perspective view of an ultrasonic transducer according to embodiment 3 of the present invention, viewed from the second diaphragm side. 10 is a perspective view showing an ultrasonic transducer according to a first modified example of embodiment 3 of the present invention, viewed from the second diaphragm side. FIG. 11 is a cross-sectional view showing the configuration of an ultrasonic transducer according to embodiment 4 of the present invention.

[0010] Hereinafter, ultrasonic transducers according to embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their description will not be repeated. The present invention is applicable to applications requiring high sound pressure ultrasonic waves, such as ultrasonic transducers for parametric speakers, ultrasonic sensors, or non-contact haptics. In the following embodiments, an ultrasonic transducer for a parametric speaker will be described as an example, but the use of the ultrasonic transducer is not limited to this.

[0011] (Embodiment 1) Fig. 1 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to embodiment 1 of the present invention. Fig. 2 is an exploded perspective view showing the configuration of the ultrasonic transducer according to embodiment 1 of the present invention. As shown in Figs. 1 and 2, an ultrasonic transducer 100 according to embodiment 1 of the present invention includes a first diaphragm 110, a frame 120, and an ultrasonic vibrator 130.

[0012] The first diaphragm 110 has a flat plate shape. The first diaphragm 110 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, the first diaphragm 110 is made of stainless steel. The thickness of the first diaphragm 110 is, for example, 0.1 mm or more and 0.2 mm or less.

[0013] The frame body 120 has a rectangular annular shape. The frame body 120 has a short side direction along a first direction (X-axis direction) and a long side direction along a second direction (Y-axis direction). The frame body 120 extends in the second direction (Y-axis direction). The axial direction of the frame body 120 is along a third direction (Z-axis direction). One end of the frame body 120 in the third direction (Z-axis direction) is bonded to the first diaphragm 110 with a bonding agent made of epoxy resin or the like.

[0014] The frame body 120 is formed from a metal such as an aluminum alloy or stainless steel, glass epoxy, or resin. From the viewpoint of suppressing changes in the characteristics of the ultrasonic transducer 100 due to temperature changes, the frame body 120 is preferably made of metal. On the other hand, from the viewpoint of lowering the frequency of the ultrasonic waves transmitted or received by the ultrasonic transducer 100 and from the viewpoint of miniaturizing the ultrasonic transducer 100, the frame body 120 is preferably made of resin. In this embodiment, the frame body 120 is made of stainless steel. The thickness of the frame body 120 is, for example, 0.2 mm or more and 0.8 mm or less.

[0015] 3 is a perspective view showing the configuration of a frame body included in the ultrasonic transducer according to the first embodiment of the present invention. As shown in FIG. 3, the frame body 120 has a pair of long side portions 121 extending in the second direction (Y-axis direction) and a pair of short side portions 122 extending in the first direction (X-axis direction). The pair of long side portions 121 and the pair of short side portions 122 are continuous to form an inner peripheral surface 120s of the frame body 120. The average distance between the short side portions 122 is four or more times the shortest distance between the long side portions 121. In other words, the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 is four or more times the lateral dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0016] The corners between the long side portion 121 and the short side portion 122 may be chamfered. Furthermore, the short side portion 122 does not have to be linear when viewed from the third direction (Z-axis direction), and may have an arc shape that is convex toward the inside of the frame body 120 or an arc shape that is convex toward the outside of the frame body 120.

[0017] The resonant frequency of the first diaphragm 110 can be adjusted by changing the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120. For example, when the resonant frequency of the first diaphragm 110 is set to 100 kHz or higher, the short-side dimension L2 is 1.5 mm or more and 3 mm or less.

[0018] The longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 is four times or more the short dimension L2, and from the viewpoint of increasing the sound pressure level of the ultrasound transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, 20 mm or more.

[0019] FIG. 4 is a view of the ultrasonic transducer of FIG. 2 as viewed from the direction of arrow IV. As shown in FIG. 4, the ultrasonic vibrator 130 has a rectangular outer shape. The longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame 120 is greater than the minimum dimension Lm of the ultrasonic vibrator 130 in the second direction (Y-axis direction). Here, when the ultrasonic vibrator 130 has a layered structure in which multiple piezoelectric elements are stacked, as described below, the minimum dimension Lm of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is the minimum dimension in the second direction (Y-axis direction) of the piezoelectric element with the shortest length in the second direction (Y-axis direction) among the multiple piezoelectric elements. FIG. 4 shows a layered structure in which multiple piezoelectric elements are stacked without any misalignment in the second direction (Y-axis direction).

[0020] The average distance L3 in the second direction (Y-axis direction) of the gap between at least one edge 120e in the second direction (Y-axis direction) of the inner surface 120s of the frame body 120 and at least one edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame body 120 side of the ultrasonic vibrator 130 shown in Figure 2 is 1.3 times or less the short side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0021] In this embodiment, the average distance L3 in the second direction (Y-axis direction) of the gap between the edge 120e on one side in the second direction (Y-axis direction) of the inner surface 120s of the frame body 120 and the edge 130e on one side in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 facing the frame body 120 is 1.3 times or less the short side dimension L2 in the first direction (X-axis direction) inside the frame body 120, and the average distance L3 in the second direction (Y-axis direction) of the gap between the edge 120e on the other side in the second direction (Y-axis direction) of the inner surface 120s of the frame body 120 and the edge 130e on the other side in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 facing the frame body 120 is 1.3 times or less the short side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0022] 5 is a cross-sectional view showing the configuration of an ultrasonic vibrator included in the ultrasonic transducer according to embodiment 1 of the present invention. As shown in Fig. 1, the ultrasonic vibrator 130 is attached to the frame body 120 and faces the first diaphragm 110 with a gap therebetween. Specifically, the ultrasonic vibrator 130 is attached to the other end in the third direction (Z-axis direction) of each of the pair of long side portions 121 of the frame body 120, and faces the first diaphragm 110 with the internal space of the frame body 120 sandwiched therebetween.

[0023] As shown in FIGS. 1, 2, and 5, the ultrasonic transducer 130 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 5, in this embodiment, the ultrasonic transducer 130 has a layered structure in which a plurality of piezoelectric bodies 131 are stacked. Specifically, the ultrasonic transducer 130 includes two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are different from each other. Specifically, the polarization directions Dp of the two piezoelectric bodies 131 face each other in the third direction (Z-axis direction). The two piezoelectric bodies 131 are sandwiched between a first electrode 132 and a second electrode 133, and an intermediate electrode 134 is disposed between the two piezoelectric bodies 131. The first electrode 132 and the second electrode 133 are electrically connected to a processing circuit 140 capable of applying an AC voltage. The ultrasonic transducer 130 is a so-called series-type bimorph piezoelectric transducer. The piezoelectric body 131 has a rectangular parallelepiped shape. The total thickness of the two piezoelectric bodies 131 is, for example, 0.5 mm or more and 0.85 mm or less. The piezoelectric body 131 is, for example, a piezoelectric ceramic.

[0024] Fig. 6 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to embodiment 1 of the present invention transmits or receives ultrasonic waves. Fig. 7 is a cross-sectional view of the ultrasonic transducer of Fig. 6 as viewed from the direction of the arrow VII-VII. The simulation analysis conditions were as follows: the thickness of the first diaphragm 110 was 0.1 mm, the combined thickness of the two piezoelectric bodies 131 was 0.8 mm, the longitudinal dimension L1 inside the frame body 120 was 20 mm, the lateral dimension L2 was 2 mm, and the thickness of the frame body 120 in the third direction (Z-axis direction) was 0.4 mm.

[0025] 6 and 7, in the vibration mode of the ultrasonic transducer 100 according to the first embodiment of the present invention, the first diaphragm 110 resonates in an opposite phase to the ultrasonic vibrator 130 in a third direction (Z-axis direction) perpendicular to the first diaphragm 110. That is, as shown in Fig. 7, the displacement direction of the resonant vibration Bm of the first diaphragm 110 and the displacement direction of the resonant vibration Bp of the ultrasonic vibrator 130 are opposite to each other in the third direction (Z-axis direction). In this embodiment, the resonant frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 are 100 kHz or higher.

[0026] In first diaphragm 110, middle portion 110c located at the middle in the longitudinal direction inside frame body 120 becomes the antinode of the resonant vibration, and end portions 110e located at both ends in the longitudinal direction inside frame body 120 become nodes of the resonant vibration. In other words, the portion of first diaphragm 110 located above the internal space of frame body 120 becomes the vibration region that resonates. The longitudinal dimension of the vibration region of first diaphragm 110 is the same as longitudinal dimension L1 inside frame body 120, and the lateral dimension of the vibration region of first diaphragm 110 is the same as lateral dimension L2 inside frame body 120.

[0027] Here, the relationship between the resonance frequency of the first diaphragm 110 and the longitudinal dimension L1 inside the frame 120 will be described.

[0028] Fig. 8 is a graph showing the results of a simulation analysis using the finite element method of the change in the resonant frequency of the first diaphragm 110 when the longitudinal dimension is changed while the transverse dimension inside the frame is fixed. In Fig. 8, the vertical axis represents the resonant frequency (kHz) of the first diaphragm 110, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame 120. As a condition for the simulation analysis, the transverse dimension L2 inside the frame 120 was fixed at 2 mm.

[0029] 8, when the longitudinal dimension L1 inside the frame 120 is 2 mm, the resonant frequency of the first diaphragm 110 is 220 kHz, and when the longitudinal dimension L1 increases to 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 increases, the resonant frequency of the first diaphragm 110 decreases to 122 kHz. Thereafter, even when the longitudinal dimension L1 inside the frame 120 exceeds 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 further increases, the resonant frequency of the first diaphragm 110 remains substantially constant at 122 kHz.

[0030] In other words, the resonant frequency of the first vibration plate 110 is determined by the speed of sound of the first vibration plate 110 and the reflection of vibration with the frame body 120 as the fixed end, but once the longitudinal dimension L1 inside the frame body 120 exceeds four times the lateral dimension L2, the influence of the lateral dimension L2 becomes dominant with respect to the reflection of vibration, and the state of vibration reflection does not change even if the longitudinal dimension L1 becomes even larger than four times the lateral dimension L2.

[0031] Next, the results of a simulation analysis using the finite element method on the relationship between the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 and the longitudinal dimension L1 inside the frame body 120 will be described.

[0032] 9 is a graph showing the results of a simulation analysis using the finite element method of the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension is changed while the lateral dimension inside the frame body is fixed. In FIG. 9, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame body 120. As a simulation analysis condition, the lateral dimension L2 inside the frame body 120 was fixed at 2 mm, and the sound pressure (Pa) was calculated at a position 30 cm away in the third direction (Z-axis direction) from the first diaphragm 110 on the front side of the ultrasonic transducer 100.

[0033] 9, as the longitudinal dimension L1 inside the frame body 120 increases, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 increases. This means that even when the longitudinal dimension of the vibration region of the first diaphragm 110 is increased, the entire vibration region of the first diaphragm 110 between both end portions 110e vibrates. In other words, the area of ​​the vibration region can be increased by the amount that the vibration region of the first diaphragm 110 is longer, and as a result, the change in air pressure due to the vibration of the first diaphragm 110 can be increased, thereby obtaining a high sound pressure.

[0034] In this way, the ultrasonic transducer 100 according to this embodiment can increase the sound pressure while maintaining a substantially constant resonant frequency by increasing the longitudinal dimension of the vibration region of the first diaphragm 110. Furthermore, since there are nodal points at both ends in the longitudinal direction, the ends can be supported or fixed, making it easy to mount the ultrasonic transducer 100.

[0035] Next, the results of a simulation analysis using the finite element method on the relationship between the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer and the minimum dimension Lm of the ultrasonic vibrator in the second direction (Y-axis direction) will be described.

[0036] Fig. 10 is a graph obtained by simulating and analyzing using the finite element method the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer when the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is changed. In Fig. 10, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer, and the horizontal axis represents the minimum dimension Lm (mm) of the ultrasonic vibrator in the second direction (Y-axis direction).

[0037] The simulation analysis conditions were as follows: the outer dimension of the frame body 120 in the second direction (Y-axis direction) was 24 mm, the dimension in the first direction (X-axis direction) was 2.6 mm, the thickness of the frame body 120 in the third direction (Z-axis direction) was 0.4 mm, and the longitudinal dimension L1 and lateral dimension L2 inside the frame body 120 were 20 mm and 2 mm, respectively. The outer dimensions of the first vibration plate 110 were the same as those of the frame body 120, and the thickness of the first vibration plate 110 was 0.1 mm. The ultrasonic vibrator 130 was a unimorph piezoelectric vibrator in which only the piezoelectric body 131 on the frame body 120 side of the two stacked piezoelectric bodies 131 was driven, and the dimension of the piezoelectric body 131 in the first direction (X-axis direction) was 2.9 mm, and the combined thickness of the two piezoelectric bodies 131 was 0.8 mm. The two stacked piezoelectric bodies 131 were arranged so as to be positioned point-symmetrically with respect to the center of the frame body 120 when viewed from the third direction (Z-axis direction). The sound pressure (Pa) was calculated at a position 30 cm away in the third direction (Z-axis direction) from the first diaphragm 110 on the front side of the ultrasonic transducer.

[0038] FIG. 11 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a first comparative example, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 20 mm, transmits or receives ultrasonic waves. FIG. 12 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a first example, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 15 mm, transmits or receives ultrasonic waves. FIG. 13 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a second example, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 14.5 mm, transmits or receives ultrasonic waves. FIG. 14 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a second comparative example, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 14 mm, transmits or receives ultrasonic waves. FIG. 15 is a cross-sectional view of the ultrasonic transducer of FIG. 14 as viewed from the direction of the arrows XV-XV.

[0039] 11 and 12, in the ultrasonic transducer 900 according to the first comparative example and the ultrasonic transducer 101 according to the first example, in which the minimum dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 15 mm or more, the first diaphragm 110 vibrated in a tuning-fork vibration mode in which the middle portion 110c of the first diaphragm 110 serves as an antinode of the resonant vibration. As shown in FIG. 13, in the ultrasonic transducer 102 according to the second example, in which the minimum dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 14.5 mm, the first diaphragm 110 vibrated in a vibration mode in which large displacement portions 110p with the largest displacement appeared near each of both longitudinal ends of the first diaphragm 110 inside the frame 120. However, the two large displacement portions 110p vibrated in the same phase, and the vibrations in the first diaphragm 110 were in the same phase.

[0040] 14 and 15 , in the ultrasonic transducer 800 according to the second comparative example in which the minimum dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 14 mm, the first diaphragm 110 vibrated in a vibration mode in which reverse displacement portions 110b displacing in a displacement direction Ds opposite to the displacement direction Dm of the intermediate portion 110c appeared in the first diaphragm 110 near each of both longitudinal end portions inside the frame body 120. That is, in the first diaphragm 110, vibrations of an opposite phase to that of the intermediate portion 110c occurred in the first diaphragm 110 near each of both longitudinal end portions inside the frame body 120.

[0041] As a result, as shown in Figure 10, the sound pressure of the ultrasound transmitted from the ultrasonic transducer 800 of the second comparative example, in which the minimum dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 14 mm, was approximately half the sound pressure of the ultrasound transmitted from the ultrasonic transducer 101 of the first embodiment, in which the minimum dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 15 mm.

[0042] In the ultrasonic transducer 800 according to the second comparative example, the average distance L3 in the second direction (Y-axis direction) of the gap between at least one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame body 120 and at least one edge 130e in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 facing the frame body 120 is 3 mm, which is 1.5 times the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120. In other words, when the average distance L3 is 1.5 times the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, antiphase vibrations are generated in the first diaphragm 110.

[0043] Although slight variations occur when the length dimension in the second direction (Y-axis direction) of the ultrasonic vibrator 130 and the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120 are changed, it has been confirmed by simulation analysis using the finite element method that, as long as the average distance L3 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, no anti-phase vibrations occur in the first diaphragm 110. In other words, as long as the average distance L3 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, it is possible to reduce power consumption while maintaining a high sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer.

[0044] Here, we will explain the power consumption of an ultrasonic transducer. The piezoelectric body 131 that constitutes the ultrasonic vibrator 130, particularly piezoelectric ceramic, has a large dielectric constant and electrical characteristics similar to those of a capacitor. The impedance of a capacitor is proportional to 1 / ωC, where ω is the frequency of the AC current and C is the capacitance. Therefore, as the frequency of the voltage applied to the piezoelectric body 131 increases, the impedance of the piezoelectric body 131 decreases, and current consumption increases. On the other hand, if the area of ​​the piezoelectric body 131 is reduced, the capacitance decreases, and current consumption decreases.

[0045] In the ultrasonic transducer 900 according to the first comparative example, in which the minimum dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 20 mm, the length of the ultrasonic vibrator 130 in the second direction (Y-axis direction) and the longitudinal dimension L1 inside the frame body 120 are the same at 20 mm, but as shown in Fig. 11, in the first diaphragm 110, the ends 110e located on both ends in the longitudinal direction inside the frame body 120 become nodes of the resonant vibration and hardly vibrate. In other words, both ends of the ultrasonic vibrator 130 in the second direction (Y-axis direction) hardly vibrate and do not work.

[0046] Therefore, in this embodiment, as shown in Fig. 4, the minimum dimension Lm in the second direction (Y-axis direction) of the ultrasonic vibrator 130 is made smaller than the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 so that a gap is formed between at least one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame body 120 and at least one edge 130e in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 on the frame body 120 side shown in Fig. 2. This makes it possible to eliminate both ends in the second direction (Y-axis direction) of the ultrasonic vibrator 130, which are parts that consume power but do not work as shown in Fig. 11, and therefore the power consumption of the ultrasonic vibrator 130 can be reduced and efficiency can be improved.

[0047] Furthermore, since the gap is formed, the internal space inside the frame body 120 communicates with the external space outside the frame body 120. This reduces pressure changes in the internal space when, for example, an adhesive bonding the first diaphragm 110 and the frame body 120 is heated and cured, thereby preventing an increase in internal stress within the ultrasonic transducer 100. When the first diaphragm 110 and the frame body 120 are bonded together with an adhesive, the average distance L3 of the gap in the second direction (Y-axis direction) is preferably 0.2 mm or more to prevent the gap from being blocked by the adhesive that has been applied to the long side portion 121 of the frame body 120 and has penetrated into the gap. That is, the average distance L3 of the gap in the second direction (Y-axis direction) is preferably 0.2 mm or more and 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0048] 16 is a view of an ultrasonic transducer according to a first modification of embodiment 1 of the present invention as viewed from the ultrasonic vibrator side. As shown in Fig. 16, in the ultrasonic transducer 103 according to the first modification of embodiment 1 of the present invention, the average distance L3 in the second direction (Y-axis direction) of the gap between the edge 120e on one side in the second direction (Y-axis direction) of the inner circumferential surface 120s of the frame body 120 and the edge 130e on one side in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 facing the frame body 120 is 1.3 times or less the short side dimension L2 in the first direction (X-axis direction) on the inside of the frame body 120, and no gap is formed between the edge 120e on the other side in the second direction (Y-axis direction) of the inner circumferential surface 120s of the frame body 120 and the edge 130e on the other side in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 facing the frame body 120. That is, only one of the two ends in the second direction (Y-axis direction) of the ultrasonic transducer 130, which is the part that consumes power but does not work as shown in FIG. 11, may be removed.

[0049] Fig. 17 is a view of an ultrasonic transducer according to a second modification of embodiment 1 of the present invention, viewed from the ultrasonic vibrator side. As shown in Fig. 17, in the ultrasonic transducer 104 according to the second modification of embodiment 1 of the present invention, when viewed from the third direction (Z-axis direction), at least one edge 130e in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 on the frame body 120 side is not positioned parallel to at least one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame body 120. In such a case, the average distance L3 in the second direction (Y-axis direction) of the gap between at least one edge 120e in the second direction (Y-axis direction) on the inner surface 120s of the frame body 120 and at least one edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame body 120 side of the ultrasonic vibrator 130 shown in Figure 2 is the average value of the shortest distance between the edge 120e and the edge 130e, which changes depending on the position in the first direction (X-axis direction), and it is sufficient if the average distance L3 is 1.3 times or less the short side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0050] In this embodiment, the ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator, but the ultrasonic vibrator 130 may be another type of piezoelectric vibrator. Hereinafter, an ultrasonic vibrator of an ultrasonic transducer according to a modification of the first embodiment of the present invention will be described.

[0051] Fig. 18 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a third modified example. As shown in Fig. 18, an ultrasonic vibrator 130a according to the third modified example is a piezoelectric element including two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are the same. The ultrasonic vibrator 130a is a so-called parallel bimorph piezoelectric vibrator.

[0052] Fig. 19 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a fourth modification. As shown in Fig. 19, an ultrasonic vibrator 130b according to the fourth modification is a piezoelectric element including four stacked piezoelectric bodies 131. The polarization directions Dp of the two outermost piezoelectric bodies 131 of the four piezoelectric bodies 131 face one side of the first direction (Z-axis direction), and the polarization directions Dp of the two innermost piezoelectric bodies 131 of the four piezoelectric bodies 131 face the other side of the first direction (Z-axis direction). The ultrasonic vibrator 130b is a so-called multimorph piezoelectric vibrator.

[0053] Fig. 20 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to the fifth modification. As shown in Fig. 20, an ultrasonic vibrator 130c according to the fifth modification is a piezoelectric element including one piezoelectric body 131. Specifically, the piezoelectric body 131 is sandwiched between a first electrode 132 and a second vibration plate 135 made of metal. The ultrasonic vibrator 130c is a so-called unimorph piezoelectric vibrator.

[0054] Fig. 21 is a longitudinal cross-sectional view showing the configuration of an ultrasonic transducer according to a sixth modified example of the first embodiment of the present invention. As shown in Fig. 21, the ultrasonic transducer 100a according to the sixth modified example of the first embodiment of the present invention includes a first diaphragm 110, a frame body 120a, and an ultrasonic vibrator 130. The frame body 120a has a cylindrical shape with a bottom. The frame body 120a is made of metal. A piezoelectric body 131 is attached to the outer bottom surface of the frame body 120a, thereby forming an ultrasonic vibrator that is a unimorph type piezoelectric vibrator.

[0055] FIG. 22 is a longitudinal cross-sectional view showing the configuration of an ultrasonic transducer according to a seventh modification of the first embodiment of the present invention. As shown in FIG. 22, the ultrasonic transducer 100b according to the seventh modification of the first embodiment of the present invention includes a first diaphragm 110, a frame 120, and an ultrasonic vibrator 130. The ultrasonic vibrator 130 is a piezoelectric element including two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 face each other in the third direction (Z-axis direction). The electric fields applied to the two piezoelectric bodies 131 are also opposite each other in the third direction (Z-axis direction), thereby forming an ultrasonic vibrator that is a unimorph piezoelectric vibrator in which the two piezoelectric bodies 131 flexurally vibrate in the same manner. A second diaphragm 135 is attached to the piezoelectric body 131 located on the opposite side from the frame 120 of the two piezoelectric bodies 131.

[0056] The ultrasonic transducer 100 according to the first embodiment of the present invention includes a first diaphragm 110, at least one frame body 120, and at least one ultrasonic vibrator 130. The at least one frame body 120 extends in the longitudinal direction and is bonded to the first diaphragm 110. The at least one ultrasonic vibrator 130 is attached to the at least one frame body 120 and faces the first diaphragm 110 at an interval. The first diaphragm 110 resonates in an opposite phase to the at least one ultrasonic vibrator 130 in a direction perpendicular to the first diaphragm 110. A longitudinal dimension L1 inside the at least one frame body 120 is four or more times a lateral dimension L2 inside the at least one frame body 120 that is perpendicular to the longitudinal direction, and is larger than a minimum dimension Lm in the longitudinal direction of the at least one ultrasonic vibrator 130. An average distance L3 in the longitudinal direction of a gap between at least one edge 120e in the longitudinal direction of the inner peripheral surface 120s of the at least one frame body 120 and at least one edge 130e in the longitudinal direction of the surface 130s of the at least one ultrasonic vibrator 130 facing the frame body 120 is 1.3 times or less the dimension L2 in the lateral direction inside the at least one frame body 120. This makes it possible to increase the sound pressure level while reducing power consumption with a simple and compact configuration in the ultrasonic transducer.

[0057] In the ultrasonic transducer according to the fifth modification of the first embodiment of the present invention, at least one ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. This allows the ultrasonic transducer to have a simple and compact configuration.

[0058] In the ultrasonic transducer according to the fifth modification of the first embodiment of the present invention, the ultrasonic vibrator 130c is a unimorph piezoelectric vibrator, and a second diaphragm 135 is provided on the side opposite to the frame body side of the piezoelectric body 131. This makes it possible to maintain a high displacement of the first diaphragm 110 while reducing power consumption, thereby improving the efficiency of the ultrasonic transducer.

[0059] In a parametric speaker including the ultrasonic transducer 100 according to the first embodiment of the present invention, it is possible to reproduce audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 100 through modulation driving of the ultrasonic transducer 100. Modulation methods include an AM modulation method (amplitude modulation method) and an FM modulation method (frequency modulation method).

[0060] (Embodiment 2) An ultrasonic transducer according to embodiment 2 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 2 of the present invention differs from the ultrasonic transducer according to embodiment 1 of the present invention in that a plurality of ultrasonic vibrators are arranged in an array, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 1 of the present invention will not be repeated.

[0061] Fig. 23 is a side view showing the configuration of an ultrasonic transducer according to embodiment 2 of the present invention, and Fig. 24 is a rear view of the ultrasonic transducer shown in Fig. 23 as seen from the direction of arrow XXIV.

[0062] 23 and 24 , in an ultrasonic transducer 200 according to embodiment 2 of the present invention, ultrasonic transducers 100 according to embodiment 1 arranged in an array in a first direction (X-axis direction) are integrally configured. The ultrasonic transducer 200 includes a first diaphragm 210, a plurality of frame bodies 220, and a plurality of ultrasonic vibrators 130. A plurality of frame bodies 220 are bonded to the first diaphragm 210, and a plurality of ultrasonic vibrators 130 are bonded to the plurality of frame bodies 220, respectively.

[0063] Here, a description will be given of a manufacturing method of the ultrasonic transducer 200. Fig. 25 is an exploded perspective view showing a stacked state in the process of stacking and bonding the components of the ultrasonic transducer according to the second embodiment of the present invention.

[0064] 25 , the first diaphragm 210 has a flat plate shape, and a plurality of slits 211 extending in the second direction (Y-axis direction) are formed at intervals in the first direction (X-axis direction). The first diaphragm 210 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, the first diaphragm 210 is made of stainless steel. The plurality of slits 211 are formed by etching, cutting, or the like.

[0065] Each of the multiple frame bodies 220 has a rectangular ring shape. Each of the multiple frame bodies 220 has a short side direction along a first direction (X-axis direction) and a long side direction along a second direction (Y-axis direction). Each of the multiple frame bodies 220 extends in the second direction (Y-axis direction). The axial direction of each of the multiple frame bodies 220 is along a third direction (Z-axis direction). Each of the multiple frame bodies 220 has a pair of long side portions 221 extending in the second direction (Y-axis direction) and a pair of short side portions 222 extending in the first direction (X-axis direction). The shortest distance between the long side portions 221 is four or more times the shortest distance between the short side portions 222.

[0066] The multiple frame bodies 220 are arranged side by side in a first direction (X-axis direction). A slit 223 is formed between adjacent frame bodies 220 in the first direction (X-axis direction). The multiple slits 223 are formed by etching, cutting, or the like. Adjacent long side portions 221 of adjacent frame bodies 220 in the first direction (X-axis direction) are separated from each other by the slits 223.

[0067] The frame bodies 220 adjacent to each other in the first direction (X-axis direction) are connected to each other at the short side portions 222. That is, among the multiple frame bodies 220, the frame bodies 220 adjacent to each other in the short side direction are connected to each other at both ends in the longitudinal direction.

[0068] Each of the plurality of frame bodies 220 is formed from a metal such as an aluminum alloy or stainless steel, glass epoxy, resin, etc. In this embodiment, the plurality of frame bodies 220 are formed from a single thin plate, but this is not limiting, and the plurality of frame bodies 220, each formed from a plurality of thin plates, may be integrated by joining the short side portions 222 of the frame bodies 220 together.

[0069] In this embodiment, each of the plurality of ultrasonic vibrators 130 includes two stacked piezoelectric bodies 131. As shown in Fig. 25, the two piezoelectric bodies 131 constituting the plurality of ultrasonic vibrators 130 are stacked and joined in the form of two thin plates.

[0070] 26 is a plan view showing the positional relationship in the first direction (X-axis direction) in the step of cutting the piezoelectric body of the ultrasonic transducer according to embodiment 2 of the present invention. In FIG. 26, only one piezoelectric body 131 is shown.

[0071] 26, the slits 211 and 223 are arranged at the same position in the first direction (X-axis direction) so as to overlap with each other in the third direction (Z-axis direction). The piezoelectric body 131 is cut and divided by a dicer or the like along a plurality of cut lines LC extending in the second direction (Y-axis direction) so as to overlap with the slits 211 and 223 in the third direction (Z-axis direction). As a result, the ultrasonic transducer 200 shown in FIGS. 23 and 24 is formed.

[0072] The ultrasonic transducer 100 according to the first embodiment has nodal points at both ends in the second direction (Y-axis direction), which is the longitudinal direction, and therefore even if the ultrasonic transducers 100 according to the first embodiment are connected to each other at the both ends to form an array to form the ultrasonic transducer 200 according to the second embodiment, the resonant vibration of each ultrasonic transducer 100 is not inhibited. Therefore, by increasing the number of ultrasonic transducers 100 that form the ultrasonic transducer 200 according to the second embodiment, the sound pressure level can be easily increased.

[0073] In a parametric speaker equipped with the ultrasonic transducer 200 according to the second embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 200 by modulating the ultrasonic waves to reproduce audible sounds.

[0074] A parametric speaker equipped with the ultrasonic transducer 200 according to this embodiment, which transmits ultrasonic waves at high frequencies of 100 kHz or higher, can reproduce audible sound only in a limited space, suppressing sound from traveling unnecessarily far and sound leakage due to unnecessary reflections. Furthermore, the ultrasonic transducer 200 can increase the attenuation of audible sound over the propagation distance without requiring a configuration for transmitting an opposite-phase carrier wave, as in Patent Document 2, allowing for a simple and compact configuration. Furthermore, because ultrasonic waves at high frequencies of 100 kHz or higher are outside the audible range of animals such as dogs and cats, the effects on these animals can be suppressed.

[0075] In order for audible sound to attenuate after a propagation distance of 30 cm, the Rayleigh distance must be within 30 cm. The Rayleigh distance R0 is given by R0 = (k × a 2 ) / 2, where k is the wave number and a is the radius of the sound source. Therefore, if the speed of sound in air is 340 m / s, when the ultrasonic frequency is 100 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 36 mm or less, when the ultrasonic frequency is 150 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 29.4 mm or less, and when the ultrasonic frequency is 200 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 25.5 mm or less. When the ultrasonic frequency is 100 kHz or more, the longitudinal dimension L1 is between 4 and 24 times the lateral dimension L2.

[0076] The ultrasonic transducer 200 according to this embodiment can be used as a phased array system.

[0077] In the ultrasonic transducer 200 according to the second embodiment of the present invention, at least one frame body 220 is arranged in a plurality of rows in the short side direction and joined to the first vibration plate 210, and adjacent frame bodies 220 in the short side direction of at least one frame body 220 are connected to each other at both ends in the long side direction. This makes it possible to easily increase the sound pressure level.

[0078] (Embodiment 3) An ultrasonic transducer according to embodiment 3 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 3 of the present invention differs from the ultrasonic transducer according to the fifth modified example of embodiment 1 of the present invention in that a portion of the surface of the piezoelectric body opposite to the frame body side is exposed, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to the fifth modified example of embodiment 1 of the present invention will not be repeated.

[0079] 27 is a perspective view showing an ultrasonic transducer according to a third embodiment of the present invention, as viewed from the second diaphragm side. As shown in FIG. 27 , an ultrasonic transducer 100c according to the third embodiment of the present invention includes a first diaphragm 110, a frame 120, an ultrasonic vibrator 130, and a second diaphragm 135. The ultrasonic vibrator 130 is a unimorph piezoelectric vibrator. The ultrasonic vibrator 130c is a piezoelectric element including at least one piezoelectric body 131. The average distance L3 in the second direction (Y-axis direction) of the gap between at least one edge 120e in the second direction (Y-axis direction) on the inner peripheral surface of the frame 120 and at least one edge 130e in the second direction (Y-axis direction) on the surface of the ultrasonic vibrator 130 facing the frame 120 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame 120. This allows the ultrasonic transducer 100c to have a simple, compact configuration, reduce power consumption, and increase the sound pressure level.

[0080] The second vibration plate 135 is provided on the side of the piezoelectric body 131 opposite to the frame body 120 side. The dimension of the second vibration plate 135 in the second direction (Y-axis direction) is smaller than the minimum dimension Lm of the ultrasonic vibrator 130 in the second direction (Y-axis direction). A portion of the surface 131b of the piezoelectric body 131 opposite to the frame body 120 side is not covered by the second vibration plate 135. This makes it possible to easily connect wiring 10 for supplying power to the piezoelectric body 131 to the portion of the surface 131b of the piezoelectric body 131 opposite to the frame body 120 side that is not covered by the second vibration plate 135.

[0081] 28 is a perspective view showing an ultrasonic transducer according to a first modified example of embodiment 3 of the present invention, as viewed from the second diaphragm side. As shown in FIG. 28, in an ultrasonic transducer 200c according to a first modified example of embodiment 3 of the present invention, ultrasonic transducers 100c according to embodiment 3 arranged in an array in a first direction (X-axis direction) are integrally configured. The ultrasonic transducer 200c includes a first diaphragm 210, a plurality of frame bodies 220, a plurality of ultrasonic vibrators 130, and a plurality of second diaphragms 135. A plurality of frame bodies 220 are bonded to the first diaphragm 210, a plurality of ultrasonic vibrators 130 are bonded to the plurality of frame bodies 220, respectively, and a plurality of second diaphragms 135 are bonded to the plurality of ultrasonic vibrators 130, respectively. By increasing the number of ultrasonic transducers 100c constituting the ultrasonic transducer 200c according to the first modified example of embodiment 3, the sound pressure level can be easily increased.

[0082] (Embodiment 4) An ultrasonic transducer according to embodiment 4 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 4 of the present invention differs from the ultrasonic transducer according to embodiment 1 of the present invention in that a portion of the surface of the piezoelectric body opposite to the frame body side is exposed, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 1 of the present invention will not be repeated.

[0083] Fig. 29 is a cross-sectional view showing the configuration of an ultrasonic transducer according to embodiment 4 of the present invention. As shown in Fig. 29, the ultrasonic transducer 100d according to embodiment 4 of the present invention includes a first diaphragm 110, a frame 120, and an ultrasonic vibrator 130. The ultrasonic vibrator 130 is a unimorph type piezoelectric vibrator. The ultrasonic vibrator 130c has a layered structure in which a plurality of piezoelectric bodies 131 are stacked.

[0084] The average distance L3 in the second direction (Y-axis direction) of the gap between at least one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface of the frame body 120 and at least one edge 130e in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 facing the frame body 120 is 1.3 times or less the short side dimension L2 in the first direction (X-axis direction) inside the frame body 120. This enables the ultrasonic transducer 100d to increase the sound pressure level while reducing power consumption with a simple and compact configuration.

[0085] A portion of the surface 131b of the piezoelectric body 131 located closest to the frame body 120 in the laminated structure, on the side opposite to the frame body 120 side, is not covered by at least one other piezoelectric body 131 other than the piezoelectric body 131 located closest to the frame body 120 in the laminated structure. Specifically, because the piezoelectric bodies 131 are arranged offset in the second direction (Y-axis direction) in the laminated structure, a portion of the surface 131b of the piezoelectric body 131 located closest to the frame body 120, on the side opposite to the frame body 120 side, is exposed and not covered by the other piezoelectric body 131. This makes it possible to easily connect wiring 10 for supplying power to the piezoelectric body 131 to the portion of the surface 131b of the piezoelectric body 131 on the side opposite to the frame body 120 side, which is not covered by the other piezoelectric body 131. In addition, the dimension in the second direction (Y-axis direction) of the other piezoelectric body 131 may be larger, smaller, or the same as the dimension in the second direction (Y-axis direction) of the piezoelectric body 131 located closest to the frame body 120 in the stacked structure.

[0086] (Note) It will be understood by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.

[0087] <1> An ultrasonic transducer comprising: a first diaphragm; at least one frame body extending in a longitudinal direction and joined to the first diaphragm; and at least one ultrasonic vibrator attached to each of the at least one frame body and facing the first diaphragm with a gap therebetween, wherein the first diaphragm resonates and vibrates in an opposite phase to the at least one ultrasonic vibrator in a direction perpendicular to the first diaphragm, the longitudinal dimension inside the at least one frame body is four or more times the lateral dimension perpendicular to the longitudinal direction inside the at least one frame body and is larger than the minimum dimension of the at least one ultrasonic vibrator in the longitudinal direction, and the average distance in the longitudinal direction of a gap between at least one longitudinal edge of an inner peripheral surface of the at least one frame body and at least one longitudinal edge of a surface of the at least one ultrasonic vibrator facing the frame body is 1.3 or less times the lateral dimension inside the at least one frame body.

[0088] <2> The ultrasonic transducer according to <1>, wherein the at least one ultrasonic vibrator is a piezoelectric element including a piezoelectric body.

[0089] <3> The ultrasonic transducer according to <2>, wherein the at least one ultrasonic vibrator has a laminated structure in which a plurality of the piezoelectric bodies are laminated, and a portion of a surface opposite to the frame body side of the piezoelectric body located closest to the frame body in the laminated structure is not covered by at least one other piezoelectric body other than the piezoelectric body located closest to the frame body in the laminated structure.

[0090] <4> The ultrasonic transducer according to <2>, wherein the at least one ultrasonic vibrator is a unimorph piezoelectric vibrator, and a second vibration plate is provided on the side of the piezoelectric body opposite to the frame body side.

[0091] <5> The ultrasonic transducer according to <4>, wherein a portion of the surface of the piezoelectric body opposite to the frame body side is not covered by the second diaphragm.

[0092] <6> The ultrasonic transducer according to any one of <1> to <5>, wherein the at least one frame body is arranged in a plurality of rows in the short side direction and joined to the first vibration plate, and adjacent frame bodies in the short side direction of the at least one frame body are connected to each other at both ends in the long side direction.

[0093] <7> A parametric speaker comprising the ultrasonic transducer according to any one of <1> to <6>, and reproducing an audible sound by modulating and driving the ultrasonic transducer.

[0094] In the above-described embodiments, configurations that can be combined may be combined with each other.

[0095] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0096] 10 Wiring, 100, 100a, 100b, 100c, 100d, 101, 102, 103, 104, 200, 200c, 800, 900 Ultrasonic transducer, 110, 210 First vibration plate, 110b Reverse displacement portion, 110c Intermediate portion, 110e End portion, 110p Large displacement portion, 120, 120a, 220 Frame body, 120e, 130e Edge, 120s Inner peripheral surface, 121, 221 Long side portion, 122, 222 Short side portion, 130, 130a, 130b, 130c Ultrasonic vibrator, 131 Piezoelectric body, 132 First electrode, 133 Second electrode, 134 Intermediate electrode, 135 Second vibration plate, 140 Processing circuitry, 211, 223 slits.

Claims

1. A first diaphragm; At least one frame extending in a longitudinal direction and joined to the first diaphragm; at least one ultrasonic transducer attached to each of the at least one frame bodies and facing the first vibration plate with a gap therebetween; the first vibration plate resonates in an antiphase with the at least one ultrasonic transducer in a direction perpendicular to the first vibration plate, The longitudinal dimension of the at least one frame body on the inside is four times or more the widthwise dimension of the at least one frame body perpendicular to the longitudinal direction, and is larger than the minimum dimension of the at least one ultrasonic transducer in the longitudinal direction; An ultrasonic transducer, wherein the average distance in the longitudinal direction of the gap between at least one longitudinal edge of the inner surface of the at least one frame body and at least one longitudinal edge of the frame body side surface of the at least one ultrasonic transducer is 1.3 times or less than the short side dimension inside the at least one frame body.

2. The ultrasonic transducer according to claim 1 , wherein the at least one ultrasonic vibrator is a piezoelectric element including a piezoelectric body.

3. The at least one ultrasonic transducer has a laminated structure in which a plurality of the piezoelectric bodies are laminated, An ultrasonic transducer as described in claim 2, wherein a portion of a surface opposite the frame body side of the piezoelectric body located closest to the frame body in the laminated structure is not covered by at least one other piezoelectric body other than the piezoelectric body located closest to the frame body in the laminated structure.

4. The at least one ultrasonic transducer is a unimorph type piezoelectric transducer, The ultrasonic transducer according to claim 2 , further comprising a second diaphragm provided on a side of the piezoelectric body opposite to a side of the frame body.

5. The ultrasonic transducer according to claim 4 , wherein a portion of a surface of the piezoelectric body opposite to the frame body side is not covered by the second diaphragm.

6. The at least one frame body is arranged in a plurality of frames aligned in the short side direction and joined to the first diaphragm, 6. The ultrasonic transducer according to claim 1, wherein adjacent frame members in the short side direction of the at least one frame member are connected to each other at both ends in the long side direction.

7. A parametric speaker comprising the ultrasonic transducer according to any one of claims 1 to 5, which reproduces an audible sound by modulating and driving the ultrasonic transducer.