Ultrasonic transducer and parametric speaker including 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

[Technical Field]

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

[0002] Prior documents disclosing the configuration of an ultradirectional acoustic device include Japanese Patent Laid-Open Publication 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 emitted by the second ultrasonic emitter is opposite to the phase of the carrier signal included in the signal emitted by the first ultrasonic emitter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-47085 [Patent Document 2] Patent No. 6333480 Summary of the Invention [Problem to be solved by the invention]

[0005] In the superdirectional acoustic device described in Patent Document 1, a plurality of ultrasonic transducers are arranged in two groups at different installation heights, resulting in a complex configuration. In the superdirectional acoustic device described in Patent Document 2, a second ultrasonic emitter is arranged outside a first ultrasonic emitter, resulting in an increased 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. [Means for solving the problem]

[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 joined 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 a direction perpendicular to the first diaphragm in an antiphase with the at least one ultrasonic vibrator. The longitudinal dimension inside the at least one frame body is four or more 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 1.3 or less times the lateral dimension inside the at least one frame body. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. [Figure 2]1 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. [Figure 3] 1 is a perspective view showing the configuration of a frame body included in an ultrasonic transducer according to a first embodiment of the present invention. [Figure 4] 4 is a view of the ultrasonic transducer of FIG. 2 as seen from the direction of arrow IV. [Figure 5] 1 is a cross-sectional view showing the configuration of an ultrasonic vibrator included in an ultrasonic transducer according to a first embodiment of the present invention. [Figure 6] FIG. 2 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the first embodiment of the present invention transmits or receives ultrasonic waves. [Figure 7] 7 is a cross-sectional view of the ultrasonic transducer of FIG. 6 as viewed from the direction of the arrows VII-VII. [Figure 8] 10 is a graph showing a simulation analysis using a finite element method of the change in the resonance frequency of the first diaphragm when the longitudinal dimension is changed while the lateral dimension inside the frame is fixed. [Figure 9] 10 is a graph showing a simulation analysis using a finite element method of the change in the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer when the longitudinal dimension is changed while the lateral dimension inside the frame body is fixed. [Figure 10] 10 is a graph showing 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 minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is changed. [Figure 11] FIG. 10 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. [Figure 12]FIG. 10 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, in which the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is 15 mm, transmits or receives ultrasonic waves. [Figure 13] FIG. 10 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. [Figure 14] FIG. 10 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. [Figure 15] 15 is a cross-sectional view of the ultrasonic transducer of FIG. 14 as viewed from the direction of the arrows along line XV-XV. [Figure 16] FIG. 2 is a diagram showing an ultrasonic transducer according to a first modified example of the first embodiment of the present invention, viewed from the ultrasonic vibrator side. [Figure 17] FIG. 10 is a diagram showing an ultrasonic transducer according to a second modified example of the first embodiment of the present invention, viewed from the ultrasonic vibrator side. [Figure 18] FIG. 10 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a third modified example. [Figure 19] FIG. 10 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a fourth modified example. [Figure 20] FIG. 11 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a fifth modified example. [Figure 21] FIG. 10 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a sixth modified example of the first embodiment of the present invention. [Figure 22] FIG. 10 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a seventh modified example of the first embodiment of the present invention. [Figure 23] FIG. 10 is a side view showing the configuration of an ultrasonic transducer according to a second embodiment of the present invention. [Figure 24]FIG. 24 is a rear view of the ultrasonic transducer shown in FIG. 23 as seen from the direction of arrow XXIV. [Figure 25] FIG. 10 is an exploded perspective view showing a stacked state in a step of stacking and bonding components of an ultrasonic transducer according to a second embodiment of the present invention. [Figure 26] 10 is a plan view showing the positional relationship in a first direction (X-axis direction) in a step of cutting a piezoelectric body of an ultrasonic transducer according to a second embodiment of the present invention. FIG. [Figure 27] FIG. 10 is a perspective view showing an ultrasonic transducer according to a third embodiment of the present invention as viewed from the second diaphragm side. [Figure 28] FIG. 10 is a perspective view showing an ultrasonic transducer according to a first modified example of the third embodiment of the present invention, viewed from the second diaphragm side. [Figure 29] FIG. 10 is a cross-sectional view showing the configuration of an ultrasonic transducer according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE 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, not less than 0.1 mm and not more than 0.2 mm.

[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 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 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 120 is preferably made of resin. In this embodiment, the frame 120 is made of stainless steel. The thickness of the frame 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 with each other 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. The short side portion 122 is not limited to being linear when viewed from the third direction (Z-axis direction), and may be an arc-shaped portion that is convex toward the inside of the frame body 120 or an arc-shaped portion that is convex toward the outside of the frame body 120.

[0017] The resonance frequency of first diaphragm 110 can be adjusted by changing short-side dimension L2 in the first direction (X-axis direction) inside frame body 120. For example, when the resonance frequency of first diaphragm 110 is set to 100 kHz or higher, 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 or more times the short dimension L2, and from the viewpoint of increasing the sound pressure level of the ultrasonic waves transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, 20 mm or more.

[0019] 4 is a view of the ultrasonic transducer of FIG. 2 as viewed from the direction of arrow IV. As shown in FIG. 4, ultrasonic vibrator 130 has a rectangular outer shape. A longitudinal dimension L1 in the second direction (Y-axis direction) inside frame body 120 is greater than a minimum dimension Lm of ultrasonic vibrator 130 in the second direction (Y-axis direction). Here, when ultrasonic vibrator 130 has a layered structure in which multiple piezoelectric bodies are stacked, as will be described later, the minimum dimension Lm of ultrasonic vibrator 130 in the second direction (Y-axis direction) is the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body that has the shortest length in the second direction (Y-axis direction) among the multiple piezoelectric bodies. FIG. 4 shows a layered structure in which multiple piezoelectric bodies 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 of the ultrasonic vibrator 130 on the frame body 120 side 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] Fig. 5 is a cross-sectional view showing the configuration of an ultrasonic vibrator included in the ultrasonic transducer according to the first embodiment 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 inner space of the frame body 120 sandwiched therebetween.

[0023] As shown in FIGS. 1, 2, and 5, the ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 5, in this embodiment, the ultrasonic vibrator 130 has a layered structure in which a plurality of piezoelectric bodies 131 are stacked. Specifically, the ultrasonic vibrator 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 to which an AC voltage can be applied. The ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator. 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 bodies 131 are, for example, piezoelectric ceramics.

[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 first diaphragm 110 was 0.1 mm, the combined thickness of two piezoelectric bodies 131 was 0.8 mm, the longitudinal dimension L1 inside frame body 120 was 20 mm, the lateral dimension L2 was 2 mm, and the thickness of 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 inner 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 first diaphragm 110 and longitudinal dimension L1 inside frame body 120 will be described.

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

[0029] 8, when the longitudinal dimension L1 inside the frame body 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 body 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 approximately constant at 122 kHz.

[0030] In other words, the resonant frequency of the first diaphragm 110 is determined by the speed of sound in the first diaphragm 110 and the reflection of vibrations 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 in terms of vibration reflection, 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] Fig. 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 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 frame body 120 in the third direction (Z-axis direction) was 0.4 mm, the longitudinal dimension L1 inside frame body 120 was 20 mm, and the lateral dimension L2 inside frame body 120 was 2 mm. The outer dimensions of first diaphragm 110 were the same as those of frame body 120, and the thickness of first diaphragm 110 was 0.1 mm. Ultrasonic vibrator 130 was a unimorph piezoelectric vibrator in which only the piezoelectric body 131 on the frame body 120 side of two stacked piezoelectric bodies 131 was driven, the dimension of 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 becomes 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 end portions inside the frame body 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 FIG. 10, the sound pressure of the ultrasonic waves transmitted from 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, was approximately half the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 101 according to 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, vibrations of opposite phases are generated in the first diaphragm 110.

[0043] Although there are some variations due to changes in the length dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) and the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, 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 properties 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 the current consumption increases. On the other hand, if the area of ​​the piezoelectric body 131 is reduced, the capacitance decreases, and the 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 end portions 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 of the ultrasonic transducer 130 in the second direction (Y-axis direction) 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 transducer 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 transducer 130, which are parts that consume power but do not work as shown in Fig. 11, and thus it is possible to reduce the power consumption of the ultrasonic transducer 130 and improve efficiency.

[0047] Furthermore, since the gap is formed, the internal space inside frame body 120 communicates with the external space outside frame body 120 through the gap, and this reduces pressure changes in the internal space when, for example, an adhesive bonding first diaphragm 110 and frame body 120 is heated and cured, thereby suppressing an increase in internal stress within ultrasonic transducer 100. When first diaphragm 110 and frame body 120 are bonded 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 long side portion 121 of frame body 120 and seeped 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 frame body 120.

[0048] 16 is a view of an ultrasonic transducer according to a first modification of the first embodiment 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 the first embodiment 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 end portions in the second direction (Y-axis direction) of the ultrasonic transducer 130, which is the portion consuming power but not performing work as shown in FIG. 11, may be removed.

[0049] Fig. 17 is a view of an ultrasonic transducer according to a second modified example of embodiment 1 of the present invention, viewed from the ultrasonic vibrator side. As shown in Fig. 17, in ultrasonic transducer 104 according to the second modified example 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 surface 130s of 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 inner circumferential surface 120s of 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 distances between the edges 120e and 130e, which vary depending on the position in the first direction (X-axis direction), and it is sufficient that 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. An ultrasonic vibrator of an ultrasonic transducer according to a modification of the first embodiment of the present invention will be described below.

[0051] Fig. 18 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a third modification. As shown in Fig. 18, ultrasonic vibrator 130a according to the third modification is a piezoelectric element including two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are the same. 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, 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 piezoelectric bodies 131 located on the outer sides of the four piezoelectric bodies 131 face one side of the first direction (Z-axis direction), and the polarization directions Dp of the two piezoelectric bodies 131 located on the inner sides of the four piezoelectric bodies 131 face the other side of the first direction (Z-axis direction). 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 a fifth modified example. As shown in Fig. 20, ultrasonic vibrator 130c according to the fifth modified example is a piezoelectric element including one piezoelectric body 131. Specifically, piezoelectric body 131 is sandwiched between a first electrode 132 and a second vibration plate 135 made of metal. 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 piezoelectric vibrator.

[0055] 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 configuring 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 of the two piezoelectric bodies 131 located on the opposite side from the frame 120.

[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 joined 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 and vibrates 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 short side direction on the inside of 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 AM modulation (amplitude modulation) and FM modulation (frequency modulation).

[0060] (Embodiment 2) An ultrasonic transducer according to a second embodiment of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to the second embodiment of the present invention differs from the ultrasonic transducer according to the first embodiment of the present invention in that a plurality of ultrasonic vibrators are arranged in an array, and therefore, description of the same configuration as the ultrasonic transducer according to the first embodiment 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, 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. The plurality of frame bodies 220 are bonded to the first diaphragm 210, and the plurality of ultrasonic vibrators 130 are bonded to the plurality of frame bodies 220, respectively.

[0063] Here, we will explain the method for manufacturing 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, first diaphragm 210 has a flat plate shape, and a plurality of slits 211 extending in a second direction (Y-axis direction) are formed at intervals in a first direction (X-axis direction). First diaphragm 210 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, 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 annular 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 plurality of 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 to each other.

[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 bonded 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 including 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 and driving the ultrasonic transducer 200, thereby reproducing audible sounds.

[0074] A parametric speaker including the ultrasonic transducer 200 according to this embodiment, which transmits ultrasonic waves with high frequencies of 100 kHz or higher, can suppress sound from traveling unnecessarily far and sound leakage due to unnecessary reflections, thereby reproducing audible sound only in a limited space. Furthermore, the ultrasonic transducer 200 can increase the attenuation of audible sound over the propagation distance without providing 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 with 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 diaphragm 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 a third embodiment of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to the third embodiment of the present invention differs from the ultrasonic transducer according to the fifth modified example of the first embodiment 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 same configuration as that of the ultrasonic transducer according to the fifth modified example of the first embodiment 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] Second vibration plate 135 is provided on the side of piezoelectric body 131 opposite to frame body 120. The dimension of second vibration plate 135 in the second direction (Y-axis direction) is smaller than the minimum dimension Lm of ultrasonic vibrator 130 in the second direction (Y-axis direction). A portion of surface 131b of piezoelectric body 131 opposite to frame body 120 is not covered by second vibration plate 135. This makes it possible to easily connect wiring 10 for supplying power to piezoelectric body 131 to the portion of surface 131b of piezoelectric body 131 opposite to frame body 120, which is not covered by second vibration plate 135.

[0081] FIG. 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 a fourth embodiment of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to the fourth embodiment of the present invention differs from the ultrasonic transducer according to the first embodiment of the present invention in that a part of the surface of the piezoelectric body opposite to the frame body side is exposed, and therefore, description of the same configuration as the ultrasonic transducer according to the first embodiment 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, an 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 makes it possible to increase the sound pressure level while reducing power consumption with a simple and compact configuration in the ultrasonic transducer 100d.

[0085] A portion of a surface 131b of the piezoelectric body 131 located closest to the frame body 120 in the laminated structure, opposite 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, opposite 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 opposite the frame body 120 side, which is not covered by the other piezoelectric body 131. The dimension in the second direction (Y-axis direction) of the other piezoelectric bodies 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 laminated structure.

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

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

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

[0089] <3> The at least one ultrasonic transducer has a laminated structure in which a plurality of the piezoelectric bodies are laminated, a part of a surface opposite to the frame body side of the piezoelectric element positioned closest to the frame body in the laminated structure is not covered by at least one other piezoelectric element other than the piezoelectric element positioned closest to the frame body in the laminated structure; <2> 2. The ultrasonic transducer according to claim 1 .

[0090] <4> the at least one ultrasonic transducer is a unimorph type piezoelectric transducer, A second vibration plate is provided on the opposite side of the piezoelectric body from the frame body side, <2> 2. The ultrasonic transducer according to claim 1 .

[0091] <5> a part of the surface of the piezoelectric body opposite to the frame body side is not covered by the second diaphragm; <4> 2. The ultrasonic transducer according to claim 1 .

[0092] <6> a plurality of the at least one frame members are arranged in the short-side direction and joined to the first diaphragm; The at least one frame body has two adjacent frame bodies in the short side direction connected to each other at both ends in the long side direction. <1> from <5> 10. The ultrasonic transducer according to claim 9, wherein the ultrasonic transducer is a piezoelectric element.

[0093] <7> <1> from <6> The ultrasonic transducer according to any one of the above items is provided, A parametric speaker that reproduces audible sound by modulating 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. [Explanation of symbols]

[0096] 10 Wiring, 100, 100a, 100b, 100c, 100d, 101, 102, 103, 104, 200, 200c, 800, 900 Ultrasonic transducer, 110, 210 First diaphragm, 110b Reverse displacement portion, 110c Middle portion, 110e End portion, 110p Large displacement portion, 120, 120a, 220 Frame body, 120e, 130e Edge, 120s Inner 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 diaphragm, 140 processing circuits, 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 vibrator attached to each of the at least one frame bodies and facing the first vibration plate with a gap therebetween; the first vibration plate vibrates in a direction perpendicular to the first vibration plate in an antiphase with the at least one ultrasonic vibrator; In the first diaphragm, a middle portion located at a middle point in the longitudinal direction inside the at least one frame body becomes an antinode of the resonant vibration, a longitudinal dimension inside the at least one frame body is four times or more a lateral dimension orthogonal to the longitudinal direction inside the at least one frame body, and is larger than a minimum dimension in the longitudinal direction of the at least one ultrasonic transducer; 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 vibrator is 1.3 times or less 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 the surface opposite the frame body side of the piezoelectric element located closest to the frame body in the laminated structure is not covered by at least one other piezoelectric element other than the piezoelectric element located closest to the frame body in the laminated structure.

4. the at least one ultrasonic transducer is a unimorph type piezoelectric transducer, 3. The ultrasonic transducer according to claim 2, further comprising a second diaphragm provided on the side of said piezoelectric body opposite to the frame body side.

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

6. a plurality of the at least one frame members are arranged 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, and reproducing an audible sound by modulating and driving the ultrasonic transducer.

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