Ultrasonic transducer and parametric speaker provided with same

Abstract

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

Description

Technical Field

[0001] The present invention relates to an ultrasonic transducer and a parametric loudspeaker having the ultrasonic transducer. Background Art

[0002] As existing documents that disclose the structure of a super-directional acoustic device, there are Japanese Patent Publication No. 2003-47085 (Patent Document 1) and Japanese Patent No. 6333480 (Patent Document 2). The super-directional acoustic device described in Patent Document 1 is configured by spreading a plurality of ultrasonic vibrators on a printed substrate and arranging them in a substantially circular shape. The plurality of ultrasonic vibrators are divided into two groups with different installation heights.

[0003] The super-directional acoustic device described in Patent Document 2 includes a first ultrasonic emitter and a second ultrasonic emitter. The second ultrasonic emitter is arranged 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 inversely proportional to the phase of the carrier signal included in the signal radiated by the first ultrasonic emitter.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-47085

[0007] Patent Document 2: Japanese Patent No. 6333480 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] In the super-directional acoustic device described in Patent Document 1, a plurality of ultrasonic transducers are arranged in two groups at different heights, resulting in a complicated structure. In the super-directional acoustic device described in Patent Document 2, a second ultrasonic emitter is arranged outside the first ultrasonic emitter, resulting in a large-scale device.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an ultrasonic transducer and a parametric speaker including the ultrasonic transducer which can reduce power consumption and improve sound pressure level with a simple and compact structure.

[0011] Solutions for solving problems

[0012] The ultrasonic transducer according to the present invention comprises a first vibration plate, at least one frame and at least one ultrasonic vibrator. The at least one frame extends in the long-side direction and is bonded to the first vibration plate. The at least one ultrasonic vibrator is respectively mounted on the at least one frame and is spaced apart from the first vibration plate. The first vibration plate resonates and vibrates in a direction orthogonal to the first vibration plate with a phase opposite to that of the at least one ultrasonic vibrator. The dimension of the inner side of the at least one frame in the long-side direction is more than 4 times the dimension of the inner side of the at least one frame in the short-side direction orthogonal to the long-side direction, and is larger than the minimum dimension of the at least one ultrasonic vibrator in the long-side direction. The average distance in the long-side direction of the gap between at least one end edge of the inner peripheral surface of the at least one frame in the long-side direction and at least one end edge of the surface of the at least one ultrasonic vibrator on the frame side is less than 1.3 times the dimension of the inner side of the at least one frame in the short-side direction.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to reduce power consumption and improve the sound pressure level in an ultrasonic transducer with a simple and compact structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a longitudinal sectional view showing the structure of the ultrasonic transducer according to the first embodiment of the present invention.

[0016] Figure 2 It is an exploded perspective view showing the structure of the ultrasonic transducer according to the first embodiment of the present invention.

[0017] Figure 3 It is a perspective view showing the structure of a housing included in the ultrasonic transducer according to the first embodiment of the present invention.

[0018] Figure 4 Observed from the direction of arrow IV Figure 2 Diagram of an ultrasonic transducer.

[0019] Figure 5 This is a cross-sectional view showing the structure of an ultrasonic vibrator included in the ultrasonic transducer according to the first embodiment of the present invention.

[0020] Figure 6 This 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.

[0021] Figure 7 Observe from the direction of the arrow on line VII-VII Figure 6 Cross-sectional view of an ultrasonic transducer.

[0022] Figure 8 This is a graph obtained by simulation analysis using the finite element method of the change in the resonance frequency of the first diaphragm when the short side dimension inside the frame is fixed and the long side dimension is changed.

[0023] Fig. 9 This is a graph showing a simulation analysis using the finite element method of the change in the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer when the short side dimension inside the frame is fixed and the long side dimension is changed.

[0024] Fig.10 This is a graph obtained by simulation analysis using the finite element method of the change in the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer when the minimum dimension of the ultrasonic transducer in the second direction (Y-axis direction) is changed.

[0025] Fig.11 This is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer of the 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.

[0026] Fig.12 This is a perspective view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer of 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.

[0027] Fig.13 This is a perspective view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer of the 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.

[0028] Fig.14 This is a perspective view showing a displacement state obtained by simulation analysis 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.

[0029] Fig.15 Observe from the direction of the arrow on line XV-XV Fig.14 Cross-sectional view of an ultrasonic transducer.

[0030] Fig.16 This is a diagram showing an ultrasonic transducer according to a first modified example of Embodiment 1 of the present invention as viewed from the ultrasonic vibrator side.

[0031] Fig.17 This is a diagram showing an ultrasonic transducer according to a second modified example of the first embodiment of the present invention as viewed from the ultrasonic vibrator side.

[0032] Fig.18 It is a cross-sectional view showing the structure of an ultrasonic transducer according to a third modified example.

[0033] Fig.19 It is a cross-sectional view showing the structure of an ultrasonic transducer according to a fourth modified example.

[0034] Fig. 20 It is a cross-sectional view showing the structure of an ultrasonic transducer according to a fifth modification.

[0035] Fig.21 It is a longitudinal sectional view showing the structure of an ultrasonic transducer according to a sixth modified example of embodiment 1 of the present invention.

[0036] Fig. 22 It is a longitudinal sectional view showing the structure of an ultrasonic transducer according to a seventh modified example of embodiment 1 of the present invention.

[0037] Fig.23 It is a side view showing the structure of an ultrasonic transducer according to Embodiment 2 of the present invention.

[0038] Fig.24 Observed from the direction of arrow XXIV Fig.23 Rear view of the ultrasonic transducer shown.

[0039] Fig.25 This is an exploded perspective view showing a stacking state in the process of stacking and bonding the components of the ultrasonic transducer according to the second embodiment of the present invention.

[0040] Fig.26 It 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 the second embodiment of the present invention.

[0041] Fig. 27 This is a perspective view showing the ultrasonic transducer according to Embodiment 3 of the present invention as viewed from the second vibration plate side.

[0042] Fig.28 This 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.

[0043] Fig.29 It is a cross-sectional view showing the structure of an ultrasonic transducer according to Embodiment 4 of the present invention. DETAILED DESCRIPTION

[0044] Hereinafter, the ultrasonic transducer of each embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the embodiments, the same reference numerals are marked on the same parts or equivalent parts in the figures, and the description thereof will not be repeated. The present invention can be applied to ultrasonic transducers for parametric speakers, ultrasonic sensors, or non-contact tactile applications that require ultrasonic waves with high sound pressure. In the following embodiments, an ultrasonic transducer for a parametric speaker is exemplified for description, but the use of the ultrasonic transducer is not limited to this.

[0045] (Implementation Method 1)

[0046] Figure 1 It is a longitudinal sectional view showing the structure of the ultrasonic transducer according to the first embodiment of the present invention. Figure 2 FIG. 2 is an exploded perspective view showing the structure of an ultrasonic transducer according to Embodiment 1 of the present invention. Figure 1 and Figure 2 As shown, the ultrasonic transducer 100 according to the first embodiment of the present invention includes a first vibration plate 110 , a frame 120 , and an ultrasonic vibrator 130 .

[0047] The first vibration plate 110 has a flat plate shape. The first vibration plate 110 is formed of an aluminum alloy such as duralumin containing aluminum, or a metal such as stainless steel. In the present embodiment, the first vibration plate 110 is formed of stainless steel. The thickness of the first vibration plate 110 is, for example, 0.1 mm or more and 0.2 mm or less.

[0048] The frame 120 has a rectangular ring shape. The frame 120 has a short side direction along the first direction (X-axis direction) and a long side direction along the second direction (Y-axis direction). The frame 120 extends in the second direction (Y-axis direction). The axial direction of the frame 120 is along the third direction (Z-axis direction). One end of the frame 120 in the third direction (Z-axis direction) is bonded to the first vibration plate 110 using a bonding agent, and the bonding agent is composed of epoxy resin or the like.

[0049] The frame 120 is formed of a metal such as an aluminum alloy or stainless steel, a glass epoxy material or a resin. From the viewpoint of suppressing the characteristic change of the ultrasonic transducer 100 caused by the temperature change, the frame 120 is preferably formed of a metal. On the other hand, from the viewpoint of lowering the frequency of the ultrasonic wave transmitted or received by the ultrasonic transducer 100 and miniaturizing the ultrasonic transducer 100, the frame 120 is preferably formed of a resin. In the present embodiment, the frame 120 is formed of stainless steel. The thickness of the frame 120 is, for example, not less than 0.2 mm and not more than 0.8 mm.

[0050] Figure 3 FIG. 1 is a perspective view showing the structure of a frame body of the ultrasonic transducer according to the first embodiment of the present invention. Figure 3As shown, the frame 120 has a pair of long sides 121 extending in the second direction (Y-axis direction) and a pair of short sides 122 extending in the first direction (X-axis direction). The pair of long sides 121 and the pair of short sides 122 are continuous to form the inner peripheral surface 120s of the frame 120. The average interval between the short sides 122 is more than 4 times the shortest interval between the long sides 121. That is, the long side dimension L1 of the inner side of the frame 120 in the second direction (Y-axis direction) is more than 4 times the short side dimension L2 of the inner side of the frame 120 in the first direction (X-axis direction).

[0051] In addition, the corners sandwiched by the long side 121 and the short side 122 may also be chamfered. In addition, the short side 122 is not limited to a straight line when viewed from the third direction (Z-axis direction), and may also be an arc convex to the inside of the frame 120, or an arc convex to the outside of the frame 120.

[0052] The resonance frequency of the first vibration plate 110 can be adjusted by changing the short side dimension L2 in the first direction (X-axis direction) inside the frame 120. For example, when the resonance frequency of the first vibration plate 110 is set to 100 kHz or more, the short side dimension L2 is set to 1.5 mm or more and 3 mm or less.

[0053] The long side dimension L1 in the second direction (Y-axis direction) inside the frame 120 is at least 4 times the short side dimension L2. From the perspective of increasing the sound pressure level of the ultrasonic wave transmitted by the ultrasonic transducer 100, the long side dimension L1 is, for example, at least 20 mm.

[0054] Figure 4 Observed from the direction of arrow IV Figure 2 Figure 1 shows an ultrasonic transducer. Figure 4 As shown, the ultrasonic vibrator 130 has a rectangular shape. The long side dimension L1 of the inner side of the frame 120 in the second direction (Y-axis direction) is larger than the minimum dimension Lm of the ultrasonic vibrator 130 in the second direction (Y-axis direction). As described later, when the ultrasonic vibrator 130 has a stacked structure in which a plurality of piezoelectric bodies are stacked, 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 body having the shortest length in the second direction (Y-axis direction) among the plurality of piezoelectric bodies. Figure 4 , a stacked structure is shown in which a plurality of piezoelectric bodies are stacked without being offset in the second direction (Y-axis direction).

[0055] At least one end edge 120e of the inner peripheral surface 120s of the frame body 120 in the second direction (Y-axis direction) and Figure 2The average distance L3 in the second direction (Y-axis direction) of the gap between at least one end edge 130e of the surface 130s of the ultrasonic vibrator 130 on the side of the frame 120 is less than 1.3 times the short side dimension L2 in the first direction (X-axis direction) of the inner side of the frame 120.

[0056] In the present embodiment, an average distance L3 in the second direction (Y-axis direction) of a gap between an edge 120e on one side of an inner circumferential surface 120s of the frame body 120 and an edge 130e on one side of a surface 130s on the frame body 120 side of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 1.3 times or less of a short side dimension L2 of the inner side of the frame body 120 in the first direction (X-axis direction), and an average distance L3 in the second direction (Y-axis direction) of a gap between an edge 120e on the other side of the inner circumferential surface 120s of the frame body 120 and an edge 130e on the other side of the surface 130s on the frame body 120 side of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 1.3 times or less of a short side dimension L2 of the inner side of the frame body 120 in the first direction (X-axis direction).

[0057] Figure 5 FIG. 1 is a cross-sectional view showing the structure of an ultrasonic vibrator included in the ultrasonic transducer according to Embodiment 1 of the present invention. Figure 1 As shown, the ultrasonic vibrator 130 is mounted on the frame 120 and faces the first vibration plate 110 at a distance. Specifically, the ultrasonic vibrator 130 is mounted on the other end of each of the pair of long sides 121 of the frame 120 in the third direction (Z-axis direction), and faces the first vibration plate 110 with the inner space of the frame 120 interposed therebetween.

[0058] like Figure 1 , Figure 2 as well as Figure 5 As shown in FIG. 1 , the ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. Figure 5As shown, in the present embodiment, the ultrasonic vibrator 130 has a stacked structure formed by stacking a plurality of piezoelectric bodies 131. 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 are opposite to each other in the third direction (Z-axis direction). The two piezoelectric bodies 131 are sandwiched by a first electrode 132 and a second electrode 133, and an intermediate electrode 134 is arranged 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 dual-chip piezoelectric vibrator. The piezoelectric body 131 has a rectangular parallelepiped shape. The total thickness of the two piezoelectric bodies 131 is, for example, greater than 0.5 mm and less than 0.85 mm. The piezoelectric body 131 is, for example, a piezoelectric ceramic.

[0059] Figure 6 This 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 Observe from the direction of the arrow on line VII-VII Figure 6 As simulation analysis conditions, the thickness of the first vibration plate 110 is set to 0.1 mm, the thickness of the two piezoelectric bodies 131 added together is set to 0.8 mm, the inner long side dimension L1 of the frame 120 is set to 20 mm, the short side dimension L2 is set to 2 mm, and the thickness of the frame 120 in the third direction (Z-axis direction) is set to 0.4 mm.

[0060] like Figure 6 and Figure 7 As shown, in the vibration mode of the ultrasonic transducer 100 according to the first embodiment of the present invention, the first vibration plate 110 resonates and vibrates in a third direction (Z-axis direction) orthogonal to the first vibration plate 110 with a phase opposite to that of the ultrasonic vibrator 130. Figure 7 As shown, the displacement direction of the resonance vibration Bm of the first vibration plate 110 and the displacement direction of the resonance vibration Bp of the ultrasonic vibrator 130 are opposite to each other in the third direction (Z-axis direction). In this embodiment, the resonance frequency of the first vibration plate 110 and the ultrasonic vibrator 130 is greater than 100 kHz.

[0061] In the first vibration plate 110, the middle portion 110c located in the middle of the long side direction of the inner side of the frame 120 becomes the antinode of the resonant vibration, and the end portions 110e located at both ends of the long side direction of the inner side of the frame 120 become the nodes of the resonant vibration. That is, the portion of the first vibration plate 110 located above the inner space of the frame 120 becomes the vibration region of the resonant vibration. The long side dimension of the vibration region of the first vibration plate 110 is the same as the long side dimension L1 of the inner side of the frame 120, and the short side dimension of the vibration region of the first vibration plate 110 is the same as the short side dimension L2 of the inner side of the frame 120.

[0062] Here, the relationship between the resonance frequency of the first vibration plate 110 and the inner long side dimension L1 of the frame body 120 will be described.

[0063] Figure 8 This is a graph showing the change in the resonance frequency of the first vibration plate when the short side dimension of the inner side of the frame is fixed and the long side dimension is changed, using the finite element method. Figure 8 In FIG. 1 , the vertical axis represents the resonance frequency (kHz) of the first vibration plate 110, and the horizontal axis represents the inner long side dimension L1 (mm) of the frame body 120. As a simulation analysis condition, the inner short side dimension L2 of the frame body 120 is fixed at 2 mm.

[0064] like Figure 8 As shown, when the long side dimension L1 of the inner side of the frame 120 is 2 mm, the resonance frequency of the first vibration plate 110 is 220 kHz. When the long side dimension L1 increases to 8 mm and the long side dimension of the vibration region of the first vibration plate 110 increases, the resonance frequency of the first vibration plate 110 decreases to 122 kHz. Thereafter, even if the long side dimension L1 of the inner side of the frame 120 is larger than 8 mm and the long side dimension of the vibration region of the first vibration plate 110 further increases, the resonance frequency of the first vibration plate 110 is substantially constant at 122 kHz.

[0065] That is, although the resonant frequency of the first vibration plate 110 is determined by the speed of sound in the first vibration plate 110 and the reflection of the vibration with the frame 120 set as the fixed end, the following situation occurs when the long side dimension L1 on the inner side of the frame 120 is larger than 4 times the short side dimension L2. The influence of the short side dimension L2 becomes dominant for the reflection of the vibration, and the state of the reflection of the vibration remains unchanged even if the long side dimension L1 becomes further larger than 4 times the short side dimension L2.

[0066] Next, the relationship between the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 100 and the inner long side dimension L1 of the housing 120 will be described using the results of a simulation analysis using the finite element method.

[0067] Fig. 9This is a graph showing the change in the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer when the short side dimension of the inner side of the frame is fixed and the long side dimension is changed, using the finite element method. Fig. 9 In FIG. 1 , the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the inner long side dimension L1 (mm) of the frame 120. As a simulation analysis condition, the inner short side dimension L2 of the frame 120 is fixed at 2 mm, and the sound pressure (Pa) at a position separated by 30 cm from the first vibration plate 110 on the front side of the ultrasonic transducer 100 in the third direction (Z-axis direction) is calculated.

[0068] like Fig. 9 As shown in FIG. 1 , as the long side dimension L1 of the inner side of the frame 120 increases, the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 100 increases. This means that even when the long side dimension of the vibration region of the first vibration plate 110 is increased, the entire vibration region of the first vibration plate 110 between the two end portions 110e will vibrate. That is, the area of ​​the vibration region can be increased by the amount by which the vibration region of the first vibration plate 110 becomes longer, and as a result, the pressure change of the air caused by the vibration of the first vibration plate 110 can be increased to obtain a higher sound pressure.

[0069] In this way, the ultrasonic transducer 100 of this embodiment can increase the sound pressure while maintaining the resonance frequency substantially constant by increasing the long side dimension of the vibration region of the first vibration plate 110. In addition, since there are nodes at both ends in the long side direction, the two ends can be supported or fixed, so the ultrasonic transducer 100 is easy to install.

[0070] Next, the relationship between the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer and the minimum dimension Lm of the ultrasonic transducer in the second direction (Y-axis direction) will be described using the results of simulation analysis using the finite element method.

[0071] Fig.10 This is a graph showing the change in the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer when the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) is changed by simulation using the finite element method. Fig.10 In FIG. 1 , 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 transducer in the second direction (Y-axis direction).

[0072] As the simulation analysis conditions, the dimension of the outer shape of the frame 120 in the second direction (Y-axis direction) was set to 24 mm, the dimension in the first direction (X-axis direction) was set to 2.6 mm, the thickness of the frame 120 in the third direction (Z-axis direction) was set to 0.4 mm, the inner long side dimension L1 of the frame 120 was set to 20 mm, and the short side dimension L2 was set to 2 mm. The outer shape dimensions of the first vibration plate 110 were set to be the same as the outer shape dimensions of the frame 120, and the thickness of the first vibration plate 110 was set to 0.1 mm. The ultrasonic vibrator 130 was set to be a unimorph type piezoelectric vibrator in which only the piezoelectric body 131 on the frame 120 side of the two stacked piezoelectric bodies 131 was driven, the dimension of the piezoelectric body 131 in the first direction (X-axis direction) was set to 2.9 mm, and the thickness of the two piezoelectric bodies 131 added together was set to 0.8 mm. The two stacked piezoelectric bodies 131 are arranged so as to be point-symmetrical about the center of the frame 120 when viewed from the third direction (Z-axis direction). The sound pressure (Pa) at a position 30 cm away from the first vibration plate 110 on the front side of the ultrasonic transducer in the third direction (Z-axis direction) is calculated.

[0073] Fig.11 This is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer of the 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 This is a perspective view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer of 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. Fig.13 This is a perspective view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer of the 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.14 This is a perspective view showing a displacement state obtained by simulation analysis 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 Observe from the direction of the arrow on line XV-XV Fig.14 Cross-sectional view of an ultrasonic transducer.

[0074] like Fig.11 and Fig.12As shown, in the ultrasonic transducer 900 of the first comparative example and 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 or more, the first vibration plate 110 vibrates in a tuning fork vibration mode in which the middle portion 110c of the first vibration plate 110 becomes an antinode of the resonant vibration. Fig.13 As shown, in the ultrasonic transducer 102 of the second embodiment in which the minimum dimension of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is 14.5 mm, the first vibration plate 110 vibrates in the following vibration mode: large displacement portions 110p having the largest displacement appear near each of the two end portions in the long-side direction of the inner side of the frame 120 of the first vibration plate 110. The two large displacement portions 110p vibrate in the same phase, and the vibration in the first vibration plate 110 is in the same phase.

[0075] like Fig.14 and Fig.15 As shown, in 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, the first vibration plate 110 vibrates in the following vibration mode: the reverse displacement portion 110b that is displaced in the displacement direction Ds opposite to the displacement direction Dm of the middle portion 110c appears near each of the two end portions in the long-side direction inside the frame 120 of the first vibration plate 110. That is, in the first vibration plate 110, vibrations of a phase opposite to that of the middle portion 110c are generated near each of the two end portions in the long-side direction inside the frame 120.

[0076] The results, such as Fig.10 As shown, the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 800 of the second comparison example in which the minimum dimension in the second direction (Y-axis direction) of the ultrasonic vibrator 130 is 14 mm becomes approximately half the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 101 of the first embodiment in which the minimum dimension in the second direction (Y-axis direction) of the ultrasonic vibrator 130 is 15 mm.

[0077] In the ultrasonic transducer 800 of the second comparative example, the average distance L3 in the second direction (Y-axis direction) of the gap between at least one end edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame 120 and at least one end edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame 120 side of the ultrasonic vibrator 130 is 3 mm, which is 1.5 times the short side dimension L2 in the first direction (X-axis direction) of the inner side of the frame 120. That is, when the average distance L3 is 1.5 times the short side dimension L2 in the first direction (X-axis direction) of the inner side of the frame 120, vibrations of opposite phases are generated in the first vibration plate 110.

[0078] Through simulation analysis using the finite element method, it was confirmed that although the length of the ultrasonic transducer 130 in the second direction (Y-axis direction) and the short side dimension L2 in the first direction (X-axis direction) of the inner side of the frame 120 slightly changed due to the change, if the average distance L3 is 1.3 times or less of the short side dimension L2 in the first direction (X-axis direction) of the inner side of the frame 120, no anti-phase vibration is generated in the first vibration plate 110. In other words, if the average distance L3 is 1.3 times or less of the short side dimension L2 in the first direction (X-axis direction) of the inner side of the frame 120, the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer can be maintained high and the power consumption can be reduced.

[0079] Here, the power consumption of the ultrasonic transducer is described. The piezoelectric body 131, especially the piezoelectric ceramic, which constitutes the ultrasonic vibrator 130 has a large dielectric constant and has electrical characteristics like a capacitor. If each frequency of the alternating current is set to ω and the capacitance is set to C, the impedance of the capacitor is proportional to 1 / ωC. Therefore, if the frequency of the applied voltage to the piezoelectric body 131 becomes higher, 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, so the current consumption decreases.

[0080] In the ultrasonic transducer 900 of 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 inner long side dimension L1 of the frame 120 are both 20 mm. Fig.11 As shown, the ends 110e of the first vibration plate 110 located at both ends of the longitudinal direction inside the frame 120 become nodes of resonance vibration and hardly vibrate. That is, the ends of the ultrasonic vibrator 130 in the second direction (Y-axis direction) hardly vibrate and do not operate.

[0081] Therefore, in this embodiment, if Figure 4 As shown, at least one end edge 120e of the inner peripheral surface 120s of the frame body 120 in the second direction (Y-axis direction) is connected to Figure 2 In the manner shown, a gap is formed between at least one end edge 130e of the surface 130s of the ultrasonic vibrator 130 on the side of the frame 120 in the second direction (Y-axis direction), so that the minimum dimension Lm of the ultrasonic vibrator 130 in the second direction (Y-axis direction) is smaller than the long side dimension L1 of the inner side of the frame 120 in the second direction (Y-axis direction). Fig.11 The two end portions of the ultrasonic vibrator 130 in the second direction (Y-axis direction), which are shown as portions that consume power and do not operate, can reduce the power consumption of the ultrasonic vibrator 130 and improve efficiency.

[0082] In addition, by forming the above-mentioned gap, the internal space inside the frame 120 and the external space outside the frame 120 are connected through the above-mentioned gap. Therefore, for example, when the adhesive material that joins the first vibration plate 110 and the frame 120 is heated and cured, the pressure change in the above-mentioned internal space can be reduced, thereby suppressing the internal stress in the ultrasonic transducer 100 from increasing. In the case where the first vibration plate 110 and the frame 120 are joined by the adhesive material, in order to suppress the above-mentioned gap from being blocked by the adhesive material applied to the long side portion 121 of the frame 120 and entering the above-mentioned gap, the average distance L3 of the above-mentioned gap in the second direction (Y-axis direction) is preferably 0.2 mm or more. That is, the average distance L3 of the above-mentioned gap in the second direction (Y-axis direction) is preferably 0.2 mm or more and is 1.3 times or less of the short side dimension L2 of the inside of the frame 120 in the first direction (X-axis direction).

[0083] Fig.16 This is a diagram of an ultrasonic transducer according to a first variation of the first embodiment of the present invention as viewed from the ultrasonic vibrator side. Fig.16 As shown, in the ultrasonic transducer 103 of the first variant 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 of the inner peripheral surface 120s of the frame 120 and the edge 130e on one side of the surface 130s on the frame 120 side in the second direction (Y-axis direction) is 1.3 times or less of the short side dimension L2 of the inner side of the frame 120 in the first direction (X-axis direction), and the gap between the edge 120e on the other side of the inner peripheral surface 120s of the frame 120 and the edge 130e on the other side of the surface 130s on the frame 120 side in the second direction (Y-axis direction) is not formed. That is, it is also possible to eliminate only the gap. Fig.11 One of the two end portions of the ultrasonic transducer 130 in the second direction (Y-axis direction) is shown as a portion that consumes power and does not operate.

[0084] Fig.17 This is a diagram of an ultrasonic transducer according to a second variation of the first embodiment of the present invention as viewed from the ultrasonic vibrator side. Fig.17 As shown, in the ultrasonic transducer 104 of the second modified example of the first embodiment of the present invention, when viewed from the third direction (Z-axis direction), at least one end edge 130e of the surface 130s of the ultrasonic vibrator 130 on the side of the frame 120 in the second direction (Y-axis direction) is located at a position that is not parallel to at least one end edge 120e of the inner peripheral surface 120s of the frame 120 in the second direction (Y-axis direction). In this case, at least one end edge 120e of the inner peripheral surface 120s of the frame 120 in the second direction (Y-axis direction) is parallel to the inner peripheral surface 120s of the frame 120. Figure 2The average distance L3 in the second direction (Y-axis direction) of the gap between at least one end edge 130e in the second direction (Y-axis direction) of the surface 130s of the ultrasonic vibrator 130 on the side of the frame 120 shown is set to the average value of the shortest distance between the end edge 120e and the end edge 130e that changes according to the position in the first direction (X-axis direction), and the average distance L3 can be less than 1.3 times the short side dimension L2 of the inner side of the frame 120 in the first direction (X-axis direction).

[0085] In this embodiment, the ultrasonic vibrator 130 is a so-called tandem bimorph piezoelectric vibrator, but the ultrasonic vibrator 130 may be another type of piezoelectric vibrator. Hereinafter, the ultrasonic vibrator of the ultrasonic transducer according to the modification of the first embodiment of the present invention will be described.

[0086] Fig.18 FIG. 4 is a cross-sectional view showing the structure of an ultrasonic vibrator according to a third modified example. Fig.18 As shown in FIG. 1 , the ultrasonic transducer 130a of 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. The ultrasonic transducer 130a is a so-called parallel bimorph piezoelectric transducer.

[0087] Fig.19 4 is a cross-sectional view showing the structure of an ultrasonic vibrator according to a fourth variant. Fig.19 As shown in FIG. 1 , the ultrasonic transducer 130b of the fourth modified example is a piezoelectric element including four stacked piezoelectric bodies 131. The polarization direction Dp of the two piezoelectric bodies 131 located on the outer side of the four piezoelectric bodies 131 faces one side of the first direction (Z-axis direction), and the polarization direction Dp of the two piezoelectric bodies 131 located on the inner side of the four piezoelectric bodies 131 faces the other side of the first direction (Z-axis direction). The ultrasonic transducer 130b is a so-called polycrystalline piezoelectric transducer.

[0088] Fig. 20 1 is a cross-sectional view showing the structure of an ultrasonic vibrator according to the fifth variant. Fig. 20 As shown, the ultrasonic vibrator 130c of 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 formed of metal. The ultrasonic vibrator 130c is a so-called unimorph type piezoelectric vibrator.

[0089] Fig.21 FIG. 2 is a longitudinal sectional view showing the structure of an ultrasonic transducer according to a sixth variation of the first embodiment of the present invention. Fig.21As shown, the ultrasonic transducer 100a of the sixth variation of the first embodiment of the present invention includes a first vibration plate 110, a frame 120a, and an ultrasonic vibrator 130. The frame 120a has a bottomed cylindrical shape. The frame 120a is formed of metal. A piezoelectric body 131 is attached to the bottom surface of the outer side of the frame 120a, constituting an ultrasonic vibrator as a single crystal type piezoelectric vibrator.

[0090] Fig. 22 1 is a longitudinal sectional view showing the structure of an ultrasonic transducer according to a seventh variation of the first embodiment of the present invention. Fig. 22 As shown, the ultrasonic transducer 100b of the seventh variation of the first embodiment of the present invention includes a first vibration plate 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 are opposite to each other in the third direction (Z-axis direction). The electric field applied to the two piezoelectric bodies 131 also becomes opposite to each other in the third direction (Z-axis direction), thereby constituting an ultrasonic vibrator as a single-crystal piezoelectric vibrator in which the two piezoelectric bodies 131 bend and vibrate in the same manner. The second vibration plate 135 is attached to the piezoelectric body 131 located on the side opposite to the side where the frame 120 is located.

[0091] The ultrasonic transducer 100 according to the first embodiment of the present invention includes a first vibration plate 110, at least one frame 120, and at least one ultrasonic vibrator 130. The at least one frame 120 extends in the longitudinal direction and is bonded to the first vibration plate 110. The at least one ultrasonic vibrator 130 is mounted on the at least one frame 120 and faces the first vibration plate 110 with a gap therebetween. The first vibration plate 110 resonates and vibrates in a direction orthogonal to the first vibration plate 110 in a phase opposite to that of the at least one ultrasonic vibrator 130. The dimension L1 of the inner side of the at least one frame 120 in the longitudinal direction is at least 4 times the dimension L2 of the inner side of the at least one frame 120 in the lateral direction orthogonal to the longitudinal direction, and is larger than the minimum dimension Lm of the at least one ultrasonic vibrator 130 in the longitudinal direction. The average distance L3 in the long-side direction of the gap between at least one end edge 120e in the long-side direction of the inner peripheral surface 120s of the at least one frame 120 and at least one end edge 130e in the long-side direction of the surface 130s on the frame 120 side of the at least one ultrasonic vibrator 130 is 1.3 times or less of the dimension L2 in the short-side direction of the inner side of the at least one frame 120. Thus, in the ultrasonic transducer, power consumption can be reduced and the sound pressure level can be improved with a simple and miniaturized structure.

[0092] In the ultrasonic transducer according to the fifth modified example of the first embodiment of the present invention, at least one ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. Thus, the ultrasonic transducer can be made into a simple and compact structure.

[0093] In the ultrasonic transducer of the fifth variation of the first embodiment of the present invention, the ultrasonic vibrator 130c is a unimorph piezoelectric vibrator, and the second vibration plate 135 is provided on the side opposite to the side where the frame is located of the piezoelectric body 131. Thus, it is possible to reduce power consumption and maintain the displacement of the first vibration plate 110 high, thereby improving the efficiency of the ultrasonic transducer.

[0094] In the 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 radiated from the ultrasonic transducer 100 through modulation driving of the ultrasonic transducer 100. As modulation methods, there are AM modulation method (amplitude modulation method) and FM modulation method (frequency modulation method).

[0095] (Implementation Method 2)

[0096] Hereinafter, an ultrasonic transducer according to Embodiment 2 of the present invention will be described with reference to the accompanying drawings. In the ultrasonic transducer according to Embodiment 2 of the present invention, a plurality of ultrasonic vibrators are arranged in an array, which is different from the ultrasonic transducer according to Embodiment 1 of the present invention. Therefore, the same structure as that of the ultrasonic transducer according to Embodiment 1 of the present invention will not be described repeatedly.

[0097] Fig.23 It is a side view showing the structure of an ultrasonic transducer according to Embodiment 2 of the present invention. Fig.24 Observed from the direction of arrow XXIV Fig.23 Rear view of the ultrasonic transducer shown.

[0098] like Fig.23 and Fig.24 As shown, in the ultrasonic transducer 200 according to the second embodiment of the present invention, the ultrasonic transducer 100 according to the first embodiment arranged in an array in the first direction (X-axis direction) is integrally configured. The ultrasonic transducer 200 includes a first vibration plate 210, a plurality of frames 220, and a plurality of ultrasonic vibrators 130. The plurality of frames 220 are bonded to the first vibration plate 210, and the plurality of ultrasonic vibrators 130 are bonded to the plurality of frames 220, respectively.

[0099] Here, a method for manufacturing the ultrasonic transducer 200 will be described. Fig.25 This is an exploded perspective view showing a stacking state in the process of stacking and bonding the components of the ultrasonic transducer according to the second embodiment of the present invention.

[0100] like Fig.25 As shown, the first vibration plate 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 vibration plate 210 is formed of an aluminum alloy such as duralumin containing aluminum, or a metal such as stainless steel. In this embodiment, the first vibration plate 210 is formed of stainless steel. The plurality of slits 211 are formed by etching or cutting.

[0101] The plurality of frames 220 each have a rectangular ring shape. The plurality of frames 220 each have a short side direction along the first direction (X-axis direction) and a long side direction along the second direction (Y-axis direction). The plurality of frames 220 each extend in the second direction (Y-axis direction). The axial direction of each of the plurality of frames 220 is along the third direction (Z-axis direction). The plurality of frames 220 each have a pair of long sides 221 extending in the second direction (Y-axis direction) and a pair of short sides 222 extending in the first direction (X-axis direction). The shortest interval between the long sides 221 is more than 4 times the shortest interval between the short sides 222.

[0102] The plurality of frames 220 are arranged in a first direction (X-axis direction). Slits 223 are formed between the frames 220 adjacent to each other along the first direction (X-axis direction). The plurality of slits 223 are formed by etching or cutting. The adjacent long sides 221 of the frames 220 adjacent to each other along the first direction (X-axis direction) are separated from each other by the slits 223.

[0103] 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, the frame bodies 220 adjacent to each other in the short side direction among the plurality of frame bodies 220 are connected to each other at both ends in the long side direction.

[0104] The plurality of frames 220 are respectively formed of metals such as aluminum alloy or stainless steel, glass epoxy materials or resins, etc. In the present embodiment, the plurality of frames 220 are formed of one thin plate, but the present invention is not limited thereto, and the plurality of frames 220 respectively formed of a plurality of thin plates may be joined to form a single body.

[0105] In this embodiment, each of the plurality of ultrasonic vibrators 130 includes two stacked piezoelectric bodies 131. Fig.25 As shown, two piezoelectric bodies 131 constituting the plurality of ultrasonic vibrators 130 are stacked and bonded in the form of two thin plates.

[0106] Fig.26 1 is a plan view showing the positional relationship in the first direction (X-axis direction) in the process of cutting the piezoelectric body of the ultrasonic transducer according to the second embodiment of the present invention. Fig.26In the figure, only one piezoelectric body 131 is shown.

[0107] like Fig.26 As shown in FIG. 1 , the slits 211 and slits 223 are arranged at the same position in the first direction (X-axis direction) so as to overlap each other in the third direction (Z-axis direction). The piezoelectric body 131 is cut and divided by a cutting machine or the like at a plurality of cutting lines LC extending along the second direction (Y-axis direction) so as to overlap the slits 211 and slits 223 in the third direction (Z-axis direction). As a result, Fig.23 and Fig.24 An ultrasonic transducer 200 is shown.

[0108] The ultrasonic transducer 100 of the first embodiment has nodes at both ends in the second direction (Y-axis direction) which is the long-side direction. Therefore, even if the ultrasonic transducers 100 of the first embodiment are connected to each other at the both ends to form an array to constitute the ultrasonic transducer 200 of the second embodiment, the resonant vibration in each ultrasonic transducer 100 is not hindered. Therefore, the sound pressure level can be easily increased by increasing the number of ultrasonic transducers 100 constituting the ultrasonic transducer 200 of the second embodiment.

[0109] In the parametric speaker including the ultrasonic transducer 200 according to the second embodiment of the present invention, it is possible to reproduce audible sound by modulating the ultrasonic waves radiated from the ultrasonic transducer 200 through modulation driving of the ultrasonic transducer 200 .

[0110] In the parametric speaker of the ultrasonic transducer 200 of the present embodiment that transmits high-frequency ultrasonic waves of 100kHz or more, it is possible to suppress the sound from reaching an unnecessary distance, and to suppress the sound leakage caused by unnecessary reflection, so that the audible sound can be reproduced only in a limited space. In addition, in the ultrasonic transducer 200, it is possible to increase the attenuation of the audible sound by the propagation distance without providing a structure that transmits a carrier wave of opposite phase as in Patent Document 2, so that a simple and miniaturized structure can be provided. Moreover, the high-frequency ultrasonic waves of 100kHz or more are outside the audible range of animals such as dogs and cats, so the influence on these animals can be suppressed.

[0111] In order to attenuate the audible sound after the propagation distance is 30 cm, the Rayleigh distance needs to be set within 30 cm. The Rayleigh distance R0 satisfies R0 = (k × a 2) / 2. k is the wave number, and a is the radius of the sound source. Therefore, when the speed of sound in the air is set to 340m / s, when the frequency of the ultrasonic wave is 100kHz, the long side dimension of the vibration area of ​​the first vibration plate 210 is less than 36mm, when the frequency of the ultrasonic wave is 150kHz, the long side dimension of the vibration area of ​​the first vibration plate 210 is less than 29.4mm, and when the frequency of the ultrasonic wave is 200kHz, the long side dimension of the vibration area of ​​the first vibration plate 210 is less than 25.5mm. When the frequency of the ultrasonic wave is above 100kHz, the long side dimension L1 is more than 4 times and less than 24 times the short side dimension L2.

[0112] The ultrasonic transducer 200 of this embodiment can be used as a phased array system.

[0113] In the ultrasonic transducer 200 according to the second embodiment of the present invention, a plurality of at least one frame 220 are arranged in the short-side direction and bonded to the first vibration plate 210, and the frame 220 adjacent to each other in the short-side direction of at least one frame 220 are connected to each other at both ends in the long-side direction. Thus, the sound pressure level can be easily increased.

[0114] (Implementation method 3)

[0115] Hereinafter, an ultrasonic transducer according to Embodiment 3 of the present invention will be described with reference to the accompanying drawings. In the ultrasonic transducer according to Embodiment 3 of the present invention, a part of the surface of the piezoelectric body on the side opposite to the side where the frame is located is exposed, which is different from the ultrasonic transducer according to the fifth variation of Embodiment 1 of the present invention. Therefore, the same structure as that of the ultrasonic transducer according to the fifth variation of Embodiment 1 of the present invention will not be described repeatedly.

[0116] Fig. 27 This is a perspective view showing the ultrasonic transducer according to Embodiment 3 of the present invention as viewed from the second vibration plate side. Fig. 27 As shown, the ultrasonic transducer 100c of the third embodiment of the present invention includes a first vibration plate 110, a frame 120, an ultrasonic vibrator 130, and a second vibration plate 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 end edge 120e of the inner peripheral surface of the frame 120 in the second direction (Y-axis direction) and at least one end edge 130e of the surface of the ultrasonic vibrator 130 on the side of the frame 120 in the second direction (Y-axis direction) is 1.3 times or less of the short side dimension L2 of the inner side of the frame 120 in the first direction (X-axis direction). As a result, in the ultrasonic transducer 100c, it is possible to reduce power consumption and improve the sound pressure level with a simple and compact structure.

[0117] The second vibration plate 135 is provided on the side of the piezoelectric body 131 opposite to the side where the frame 120 is located. The dimension of the second vibration plate 135 in the second direction (Y-axis direction) is smaller than the minimum dimension Lm in the second direction (Y-axis direction) of the ultrasonic vibrator 130. A portion of the surface 131b of the piezoelectric body 131 on the side opposite to the side where the frame 120 is located is not covered by the second vibration plate 135. Thus, the wiring 10 for supplying power to the piezoelectric body 131 can be easily connected to the portion of the surface 131b of the piezoelectric body 131 on the side opposite to the side where the frame 120 is located that is not covered by the second vibration plate 135.

[0118] Fig.28 This is a perspective view showing the ultrasonic transducer according to the first modified example of the third embodiment of the present invention as viewed from the second vibration plate side. Fig.28 As shown, in the ultrasonic transducer 200c of the first modified example of the third embodiment of the present invention, the ultrasonic transducer 100c of the third embodiment arranged in the first direction (X-axis direction) in an array shape is integrally configured. The ultrasonic transducer 200c includes a first vibration plate 210, a plurality of frames 220, a plurality of ultrasonic vibrators 130, and a plurality of second vibration plates 135. The plurality of frames 220 are joined to the first vibration plate 210, the plurality of ultrasonic vibrators 130 are joined to the plurality of frames 220, and the plurality of second vibration plates 135 are joined to the plurality of ultrasonic vibrators 130. The sound pressure level can be easily increased by increasing the number of ultrasonic transducers 100c constituting the first modified example of the third embodiment.

[0119] (Implementation 4)

[0120] Hereinafter, an ultrasonic transducer according to a fourth embodiment of the present invention will be described with reference to the accompanying drawings. In the ultrasonic transducer according to the fourth embodiment of the present invention, a part of the surface of the piezoelectric body on the side opposite to the side where the frame is located is exposed, which is different from the ultrasonic transducer according to the first embodiment of the present invention. Therefore, for the same structure as that of the ultrasonic transducer according to the first embodiment of the present invention, the description will not be repeated.

[0121] Fig.29 4 is a cross-sectional view showing the structure of an ultrasonic transducer according to Embodiment 4 of the present invention. Fig.29 As shown, the ultrasonic transducer 100d according to the fourth embodiment of the present invention includes a first vibration plate 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 stacked structure in which a plurality of piezoelectric bodies 131 are stacked.

[0122] The average distance L3 in the second direction (Y-axis direction) of the gap between at least one end edge 120e in the second direction (Y-axis direction) of the inner peripheral surface of the frame 120 and at least one end edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame 120 side of the ultrasonic vibrator 130 is 1.3 times or less of the short side dimension L2 in the first direction (X-axis direction) of the inner side of the frame 120. Thus, in the ultrasonic transducer 100d, it is possible to reduce power consumption and improve the sound pressure level with a simple and compact structure.

[0123] A portion of the surface 131b of the piezoelectric body 131 closest to the frame 120 in the stacked structure, which is opposite to the side where the frame 120 is located, is not covered by at least one other piezoelectric body 131 in the stacked structure except for the piezoelectric body 131 closest to the frame 120. Specifically, by staggering the piezoelectric bodies 131 in the second direction (Y-axis direction) in the stacked structure, a portion of the surface 131b of the piezoelectric body 131 closest to the frame 120, which is opposite to the side where the frame 120 is located, is not covered by the other piezoelectric bodies 131 but is exposed. Thus, the wiring 10 for supplying power to the piezoelectric body 131 can be easily connected to the portion of the surface 131b of the piezoelectric body 131, which is not covered by the other piezoelectric bodies 131, which is opposite to the side where the frame 120 is located. In addition, the size of the other piezoelectric body 131 in the second direction (Y-axis direction) may be larger, smaller, or the same as the size of the piezoelectric body 131 in the second direction (Y-axis direction) located closest to the frame 120 in the stacked structure.

[0124] (appendix)

[0125] It will be understood by those skilled in the art that the above-described exemplary embodiments are specific examples of the following aspects.

[0126] <1> An ultrasonic transducer comprising:

[0127] The first vibration plate;

[0128] at least one frame extending in the longitudinal direction and joined to the first vibration plate; and

[0129] at least one ultrasonic vibrator is mounted on the at least one frame and faces the first vibration plate at a distance therefrom.

[0130] The first vibration plate resonates and vibrates in a direction orthogonal to the first vibration plate at a phase opposite to that of the at least one ultrasonic vibrator.

[0131] The dimension of the inner side of the at least one frame in the long side direction is at least 4 times the dimension of the inner side of the at least one frame in the short side direction orthogonal to the long side direction, and is larger than the minimum dimension of the at least one ultrasonic vibrator in the long side direction.

[0132] The average distance in the long side direction of the gap between at least one end edge in the long side direction of the inner peripheral surface of the at least one frame and at least one end edge in the long side direction of the surface of the at least one ultrasonic vibrator close to the frame is less than 1.3 times the dimension in the short side direction of the inner side of the at least one frame.

[0133] <2> The ultrasonic transducer according to <1>, wherein:

[0134] The at least one ultrasonic vibrator is a piezoelectric element including a piezoelectric body.

[0135] <3> The ultrasonic transducer according to <2>, wherein:

[0136] The at least one ultrasonic vibrator has a stacked structure in which a plurality of the piezoelectric bodies are stacked.

[0137] A portion of a surface of the piezoelectric body closest to the frame body in the stacked structure, which is opposite to the frame body side, is not covered by at least one other piezoelectric body in the stacked structure except the piezoelectric body closest to the frame body side.

[0138] <4> The ultrasonic transducer according to <2>, wherein:

[0139] The at least one ultrasonic vibrator is a unimorph type piezoelectric vibrator,

[0140] A second vibration plate is provided on the side of the piezoelectric body opposite to the side where the frame is located.

[0141] <5> The ultrasonic transducer according to <4>, wherein:

[0142] A portion of a surface of the piezoelectric body on a side opposite to a side where the frame body is located is not covered by the second vibration plate.

[0143] <6> The ultrasonic transducer according to any one of <1> to <5>, wherein

[0144] The at least one frame is arranged in plurality in the short-side direction and is bonded to the first vibration plate.

[0145] 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.

[0146] <7> A parametric speaker comprising the ultrasonic transducer according to any one of <1> to <6>,

[0147] Audible sound is reproduced by modulated driving of the ultrasonic transducer.

[0148] In the description of the above-mentioned embodiments, combinable structures may be combined with each other.

[0149] The embodiments disclosed this time should be considered as illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0150] Description of Reference Numerals

[0151] 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, middle portion; 110e, end portion; 110p, large displacement portion; 120, 120a, 220, frame ; 120e, 130e, end edge; 120s, inner circumference; 121, 221, long side; 122, 222, short side; 130, 130a, 130b, 130c, ultrasonic vibrator; 131, piezoelectric body; 132, first electrode; 133, second electrode; 134, intermediate electrode; 135, second vibration plate; 140, processing circuit; 211, 223, slit.

Claims

1. An ultrasonic transducer comprising: The first vibration plate; at least one frame extending in the longitudinal direction and joined to the first vibration plate; and at least one ultrasonic vibrator is mounted on the at least one frame and faces the first vibration plate at a distance therefrom. The first vibration plate resonates and vibrates in a direction orthogonal to the first vibration plate at a phase opposite to that of the at least one ultrasonic vibrator. The dimension of the inner side of the at least one frame in the long side direction is at least 4 times the dimension of the inner side of the at least one frame in the short side direction orthogonal to the long side direction, and is larger than the minimum dimension of the at least one ultrasonic vibrator in the long side direction. The average distance in the long side direction of the gap between at least one end edge in the long side direction of the inner peripheral surface of the at least one frame and at least one end edge in the long side direction of the surface of the at least one ultrasonic vibrator close to the frame is less than 1.3 times the dimension in the short side direction of the inner side of the at least one frame.

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 ultrasonic transducer according to claim 2, wherein: The at least one ultrasonic vibrator has a stacked structure in which a plurality of the piezoelectric bodies are stacked. A portion of a surface of the piezoelectric body closest to the frame body in the stacked structure, which is opposite to the frame body side, is not covered by at least one other piezoelectric body in the stacked structure except the piezoelectric body closest to the frame body side.

4. The ultrasonic transducer according to claim 2, wherein: The at least one ultrasonic vibrator is a unimorph type piezoelectric vibrator, A second vibration plate is provided on the side of the piezoelectric body opposite to the side where the frame is located.

5. The ultrasonic transducer according to claim 4, wherein: A portion of the surface of the piezoelectric body on the side opposite to the side where the frame is located is not covered by the second vibration plate.

6. The ultrasonic transducer according to any one of claims 1 to 5, wherein: The at least one frame is arranged in a plurality in the short-side direction and is bonded to the first vibration plate. 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.

7. A parametric speaker comprising the ultrasonic transducer according to any one of claims 1 to 6, Audible sound is reproduced by modulated driving of the ultrasonic transducer.

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