Ultrasonic Transducer

Abstract

At least one unimorph piezoelectric vibrator (130) includes a piezoelectric body (131) facing the first vibrating plate (110) with a gap therebetween, and a second vibrating plate (135) provided on the side of the piezoelectric body (131) opposite the frame body (120). The first vibrating plate (110) has a plurality of openings (110s) formed at both ends of the longitudinal direction inside each of the plurality of frame bodies (120). The first vibrating plate (110) resonates and vibrates in an opposite phase to the at least one unimorph piezoelectric vibrator (130) in a direction perpendicular to the first vibrating plate (110). Regarding the dimensions inside each of the plurality of frame bodies (120), the longitudinal dimension (L1) in the longitudinal direction is between 4 and 11 times the transverse dimension (L2) in the transverse direction perpendicular to the longitudinal direction. The plurality of frames 120 have substantially the same short-side dimension (L2). The difference in the long-side dimension (L1) between adjacent frames 120 in the longitudinal direction is equal to or less than the short-side dimension (L2).

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic transducer. [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 an object of the present invention is to provide an ultrasonic transducer that has a simple and compact configuration and can reduce internal stress while increasing the sound pressure level. [Means for solving the problem]

[0007] An ultrasonic transducer according to the present invention comprises a first diaphragm, a plurality of frame bodies, and at least one unimorph piezoelectric vibrator. The plurality of frame bodies each extend in a longitudinal direction, are adjacently arranged in a line in the longitudinal direction, and are joined to the first diaphragm. The at least one unimorph piezoelectric vibrator is attached to the plurality of frame bodies. The at least one unimorph piezoelectric vibrator includes a piezoelectric body facing the first diaphragm with a gap therebetween and a second diaphragm provided on the side of the piezoelectric body opposite the frame body side. The first diaphragm has a plurality of openings formed at both ends of the longitudinal direction inside each of the plurality of frame bodies. The first diaphragm resonates and vibrates in an antiphase with the at least one unimorph piezoelectric vibrator in a direction perpendicular to the first diaphragm. Regarding the dimensions inside each of the plurality of frame bodies, the longitudinal dimension in the longitudinal direction is between 4 and 11 times the transverse dimension in a transverse direction perpendicular to the longitudinal direction. The transverse dimensions of the plurality of frame bodies are approximately the same as each other. The difference in the longitudinal dimension between adjacent frame bodies in the longitudinal direction among the plurality of frame bodies is equal to or less than the widthwise dimension. [Effects of the Invention]

[0008] According to the present invention, it is possible to increase the sound pressure level while reducing the internal stress in an ultrasonic transducer with a simple and compact configuration. [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 a unimorph type piezoelectric vibrator included in an ultrasonic transducer according to a first embodiment of the present invention. [Figure 6] 1 is a perspective view showing a displacement state obtained by simulation analysis using a finite element method when the ultrasonic transducer according to the first embodiment of the present invention transmits or receives ultrasonic waves. FIG. [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] FIG. 1 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Comparative Example 1. [Figure 11] 10 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Comparative Example 1 transmits or receives ultrasonic waves. FIG. [Figure 12] This is a graph showing actual measurements of the applied voltage and sound pressure level changes by the processing circuit for an ultrasonic transducer according to Example 1, which has two frame bodies and has a dimension of 30 mm between the first short sides in the second direction (Y-axis direction), and an ultrasonic transducer according to Comparative Example 1. [Figure 13] 10 is a graph showing a simulation analysis using a finite element method of the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer when the dimension of the opening in the short side direction is changed. [Figure 14]This is a perspective view showing the displacement state simulated and analyzed using the finite element method when the ultrasonic transducer of sample 1, in which the ratio of the short-side dimension of the opening to the short-side dimension of the frame body is 0%, is transmitting or receiving ultrasonic waves. [Figure 15] This is a perspective view showing the displacement state simulated and analyzed using the finite element method when the ultrasonic transducer of sample 2, in which the ratio of the short-side dimension of the opening to the short-side dimension of the frame body is 33%, is transmitting or receiving ultrasonic waves. [Figure 16] This is a perspective view showing the displacement state simulated and analyzed using the finite element method when the ultrasonic transducer of sample 3, in which the ratio of the short-side dimension of the opening to the short-side dimension of the frame body is 100%, is transmitting or receiving ultrasonic waves. [Figure 17] FIG. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Comparative Example 2. [Figure 18] 10 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Comparative Example 2 transmits or receives ultrasonic waves. FIG. [Figure 19] 10 is a graph showing a simulation analysis using a finite element method of the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer of Comparative Example 2 when the dimension of the opening in the short side direction is changed. [Figure 20] FIG. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Comparative Example 3. [Figure 21] FIG. 10 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to Comparative Example 3 transmits or receives ultrasonic waves at a frequency of 150 kHz. [Figure 22] FIG. 10 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Comparative Example 3 transmits or receives ultrasonic waves at a frequency of 150.4 kHz. [Figure 23]FIG. 10 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Comparative Example 4 transmits or receives ultrasonic waves. [Figure 24] FIG. 1 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a first modification of the first embodiment of the present invention. [Figure 25] 10 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Modification 1 transmits or receives ultrasonic waves. FIG. [Figure 26] FIG. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a second modification of the first embodiment of the present invention. [Figure 27] FIG. 10 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Modification 2 transmits or receives ultrasonic waves. [Figure 28] FIG. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a third modification of the first embodiment of the present invention. [Figure 29] FIG. 11 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Modification 3 transmits or receives ultrasonic waves. [Figure 30] 30 is a view of the ultrasonic transducer of FIG. 29 as seen from the direction of arrow XXX. [Figure 31] FIG. 10 is a view of an ultrasonic transducer according to Modification 3, viewed from the second diaphragm side. [Figure 32] FIG. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fourth modification of the first embodiment of the present invention. [Figure 33] FIG. 11 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when an ultrasonic transducer according to Modification 4 transmits or receives ultrasonic waves. [Figure 34] 34 is a view of the ultrasonic transducer of FIG. 33 as seen from the direction of arrow XXXIV. [Figure 35] FIG. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fifth modification of the first embodiment of the present invention. [Figure 36] FIG. 11 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when an ultrasonic transducer according to Modification 5 transmits or receives ultrasonic waves. [Figure 37] FIG. 37 is a view of the ultrasonic transducer of FIG. 36 as seen from the direction of arrow XXXVII. [Figure 38] FIG. 11 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer of Comparative Example 5, in which the unimorph piezoelectric vibrator is vibrating in a bending mode resonant vibration, transmits or receives ultrasonic waves. [Figure 39] FIG. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a second embodiment of the present invention. [Figure 40] FIG. 40 is a rear view of the ultrasonic transducer shown in FIG. 39 as seen from the direction of arrow XL. [Figure 41] 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. 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 plurality of frame bodies 120, and a unimorph piezoelectric 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 an aluminum alloy. Since aluminum alloys have a small Young's modulus, making the first diaphragm 110 out of an aluminum alloy can reduce stress generated in the first diaphragm 110 when the ultrasonic transducer 100 is driven. The thickness of the first diaphragm 110 is, for example, not less than 0.05 mm and not more than 0.2 mm.

[0013] Each of the multiple frame bodies 120 has a rectangular ring shape. Each of the multiple frame bodies 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). Each of the multiple frame bodies 120 extends in the second direction (Y-axis direction). The axial direction of each of the multiple frame bodies 120 is along a third direction (Z-axis direction). The multiple frame bodies 120 are adjacently arranged so as to be aligned in the longitudinal direction. In the example shown in FIG. 2, two frame bodies 120 are adjacently arranged in the second direction (Y-axis direction). However, the number of frame bodies 120 adjacently arranged in the second direction (Y-axis direction) is not limited to two and may be three or more. One end of each of the multiple frame bodies 120 in the third direction (Z-axis direction) is bonded to the first diaphragm 110 by a bonding agent such as epoxy resin.

[0014] The frame 120 is formed from a metal such as an aluminum alloy, an iron-nickel alloy (42Ni-Fe), 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 an aluminum alloy. The thickness of the frame 120 is, for example, 0.2 mm or more and 0.6 mm or less.

[0015] Fig. 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, each of the multiple frame bodies 120 has a pair of long side portions 121 extending in the second direction (Y-axis direction) and a first short side portion 122 and a second short side portion 123 extending in the first direction (X-axis direction). The first short side portions 122 are both end portions located at both ends of the multiple frame bodies 120 in the second direction (Y-axis direction). The second short side portions 123 are connecting end portions that connect the multiple frame bodies 120 adjacent to each other in the second direction (Y-axis direction).

[0016] A pair of long side portions 121, a first short side portion 122, and a second short side portion 123 are continuous to form the inner peripheral surface of the frame body 120. The average distance between the first short side portion 122 and the second short side portion 123 is 4 to 11 times the shortest distance between the long side portions 121. That is, among the dimensions on the inside of each of the multiple frame bodies 120, the longitudinal dimension L1 in the second direction (Y-axis direction) is 4 to 11 times the lateral dimension L2 in the first direction (X-axis direction). 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, 19 mm to 22 mm. The difference in the longitudinal dimension L1 between adjacent frame bodies 120 in the second direction (Y-axis direction) is equal to or less than the lateral dimension L2. In this embodiment, the longitudinal dimensions L1 of the plurality of frame bodies 120 adjacent to each other in the second direction (Y-axis direction) are substantially the same.

[0017] The dimension La between the first short side portions 122 in the second direction (Y-axis direction) is the sum of the longitudinal dimension L1 of each of the multiple frames 120 and the width dimension W of each of the second short side portions 123 in the second direction (Y-axis direction). In the example shown in Fig. 3, the relationship La = L1 × 2 + W is satisfied. The width dimension W of the second short side portion 123 is, for example, not less than 0.3 mm and not more than 1 mm.

[0018] Note that corners between the first short side portion 122 or the second short side portion 123 and the long side portion 121 may be chamfered. Furthermore, each of the first short side portion 122 and the second short side portion 123 is not limited to being linear when viewed from the third direction (Z-axis direction), and may be an arc-shaped portion that convex toward the inside of the frame body 120 or an arc-shaped portion that convex toward the outside of the frame body 120.

[0019] The resonant 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, if the resonant 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. The short-side dimension L2 of multiple frame bodies 120 is approximately the same.

[0020] Fig. 4 is a view of the ultrasonic transducer of Fig. 2 as viewed from the direction of arrow IV. As shown in Figs. 1 and 4, unimorph piezoelectric vibrators 130 are attached to a plurality of frame bodies 120. The unimorph piezoelectric vibrators 130 include a piezoelectric body 131 that faces the first vibration plate 110 with a gap therebetween, and a second vibration plate 135 that is provided on the side of the piezoelectric body 131 opposite the frame body 120 side. The piezoelectric body 131 has a rectangular parallelepiped shape. The thickness of the piezoelectric body 131 is, for example, not less than 0.1 mm and not more than 0.2 mm. The piezoelectric body 131 is, for example, a piezoelectric ceramic.

[0021] The second diaphragm 135 is made of a metal such as an aluminum alloy, an iron-nickel alloy (42Ni-Fe), or stainless steel, glass epoxy, or ceramic. In this embodiment, the second diaphragm 135 is made of an iron-nickel alloy (42Ni-Fe). The second diaphragm 135 has a rectangular parallelepiped shape. The second diaphragm 135 is bonded to the piezoelectric body 131. The length of the second diaphragm 135 in the second direction (Y-axis direction) is equal to the length of the piezoelectric body 131 in the second direction (Y-axis direction). The short-side dimension of the second diaphragm 135 in the first direction (X-axis direction) is equal to or greater than (2 / 3)L2 and less than L2, where L2 is the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120. The thickness of the second diaphragm 135 is, for example, equal to or greater than 0.2 mm and equal to or less than L2. When the shape of second diaphragm 135 is not rectangular but elliptical when viewed from the third direction (Z-axis direction), the short side dimension of second diaphragm 135 is set to the average value.

[0022] As shown in FIG. 4, when viewed from a third direction (Z-axis direction) perpendicular to the first diaphragm 110, the second diaphragm 135 is located within a region sandwiched between both end edges 120s1, 120s2 in the first direction (X-axis direction) on the inner circumferential surface of each of the multiple frame bodies 120.

[0023] As shown in FIG. 1, in the second diaphragm 135, the average distance D1 in the first direction (X-axis direction) between one edge 120s1 in the first direction (X-axis direction) on the inner peripheral surface of the frame body 120 and one edge 135s1 in the first direction (X-axis direction) of the second diaphragm 135, and the average distance D2 in the first direction (X-axis direction) between the other edge 120s2 in the first direction (X-axis direction) on the inner peripheral surface of the frame body 120 and the other edge 135s2 in the first direction (X-axis direction) of the second diaphragm 135, are each 1 / 6 or less of the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0024] As shown in FIG. 4, the dimension La between the first short side portions 122 in the second direction (Y-axis direction) is larger than the minimum dimension Lm of the piezoelectric body 131 of the unimorph piezoelectric vibrator 130 in the second direction (Y-axis direction). Here, when the unimorph piezoelectric vibrator 130 has a layered structure in which multiple piezoelectric bodies are stacked, the minimum dimension Lm of the piezoelectric body 131 in the second direction (Y-axis direction) of the piezoelectric body with the shortest length in the second direction (Y-axis direction) among the multiple piezoelectric bodies. For example, when the unimorph piezoelectric vibrator 130 has a layered structure in which two piezoelectric bodies 131 are stacked, the polarization directions of the two piezoelectric bodies 131 face each other in the third direction (Z-axis direction). Since the electric fields applied to the two piezoelectric bodies 131 are also opposite to each other in the third direction (Z-axis direction), a unimorph piezoelectric vibrator is configured in which the two piezoelectric bodies 131 flexurally vibrate in the same way.

[0025] 4 shows a state in which the piezoelectric body 131 and the second vibration plate 135 are stacked together without any misalignment in the second direction (Y-axis direction). In this embodiment, the length of the piezoelectric body 131 in the second direction (Y-axis direction) is shorter than the dimension La between the first short sides 122 in the second direction (Y-axis direction), but is not limited to this and may be equal to or greater than the dimension La between the first short sides 122 in the second direction (Y-axis direction).

[0026] The average distance L3 in the second direction (Y-axis direction) of the gap between the edge 120e on the first short side portion 122 side of the inner surface of the frame body 120 and the edge 130e in the second direction (Y-axis direction) of the surface 130s of the piezoelectric body 131 on the frame body 120 side of the unimorph type piezoelectric vibrator 130 shown in Figure 2 is 1.3 times or less the short side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0027] Fig. 5 is a cross-sectional view showing the configuration of a unimorph piezoelectric vibrator included in the ultrasonic transducer according to the first embodiment of the present invention. As shown in Fig. 1, the unimorph piezoelectric vibrator 130 is attached to the frame body 120 and faces the first diaphragm 110 with a gap therebetween. Specifically, the unimorph piezoelectric 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 and second short side portions 123 of each frame body 120, and faces the first diaphragm 110 with the inner space of each frame body 120 sandwiched therebetween.

[0028] 1, 2, and 5, the unimorph piezoelectric vibrator 130 is a piezoelectric element including a piezoelectric body 131. As shown in Fig. 5, in this embodiment, the piezoelectric body 131 is sandwiched between a first electrode 132 and a second electrode 133. The polarization direction Dp of the piezoelectric body 131 is along the third direction (Z-axis direction). 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.

[0029] 2 and 4, first diaphragm 110 is formed with a plurality of openings 110s that open to both ends in the second direction (Y-axis direction) inside each of the plurality of frame bodies 120. That is, first diaphragm 110 has two openings 110s that open to both ends in the second direction (Y-axis direction) inside each of the frame bodies 120, and in the example shown in FIG. 2, a total of four openings 110s are formed in first diaphragm 110.

[0030] Each of the multiple frames 120 extends in a first direction (X-axis direction). In this embodiment, the dimension SL of each of the multiple openings 110s in the first direction (X-axis direction) is 67% to 94% of the short-side dimension L2 in the first direction (X-axis direction) inside the frame 120. However, the dimension SL of each of the multiple openings 110s in the first direction (X-axis direction) may be less than 67% of the short-side dimension L2 or may exceed 94% of the short-side dimension L2.

[0031] In this embodiment, the width dimension SW of each of the plurality of openings 110s is 0.4 mm or more and 0.6 mm or less. The openings 110s are formed from a position on the edge of the inner peripheral surface of the frame 120 in the second direction (Y-axis direction) to a position inward in the second direction (Y-axis direction) by the width dimension SW.

[0032] The smaller the width dimension SW of the opening 110s in the second direction (Y-axis direction), the better, from the viewpoint of increasing the area of ​​the vibration region of the first diaphragm 110. When the first diaphragm 110 and the frame body 120 are joined with an adhesive, the width dimension SW of the opening 110s in the second direction (Y-axis direction) is preferably 0.4 mm or more and 0.6 mm or less, in order to prevent the opening 110s from being blocked by the adhesive that has seeped into the opening 110s formed near the edge of the inner peripheral surface of the frame body 120 in the second direction (Y-axis direction).

[0033] Alternatively, it is preferable that the opening 110s is formed with a width of 0.2 mm to 0.4 mm inward in the second direction (Y-axis direction) from a position 0.2 mm inward in the second direction (Y-axis direction) from a position on the edge in the second direction (Y-axis direction) on the inner peripheral surface of the frame 120. That is, in this case, the width SW is 0.2 mm to 0.4 mm.

[0034] From the viewpoint of suppressing the decrease in sound pressure of ultrasonic waves generated on the frame body 120 side of the first vibration plate 110 due to their emission from the opening 110s, if the driving frequency of the ultrasonic transducer 100 is f (kHz), and the width dimension SW (mm) in the second direction (Y-axis direction) of the opening 110s satisfies the relationship f×SW≦90, the decrease in sound pressure of ultrasonic waves due to their emission from the opening 110s can be suppressed to 10% or less.

[0035] Furthermore, when the opening 110s is formed at a position on the edge of the inner surface of the frame body 120 in the second direction (Y-axis direction), the amount of stacking misalignment between the first vibration plate 110 and the frame body 120 and the amount of adhesive that has seeped out to the inside of the frame body 120 can be visually confirmed through the opening 110s, so the opening 110s can be used to improve the assembly accuracy of the ultrasonic transducer 100.

[0036] Furthermore, since the opening 110s is formed, the internal space inside the frame body 120 is connected to the external space outside the frame body 120 through the opening 110s, and therefore, for example, pressure changes in the internal space when the adhesive that bonds the first vibration plate 110 and the frame body 120 is heated and hardened can be reduced, thereby preventing internal stress within the ultrasonic transducer 100 from increasing.

[0037] Fig. 6 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to the first embodiment of the present invention 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 arrows VII-VII. The simulation analysis conditions were as follows: the thickness of first diaphragm 110 was 0.1 mm, the thickness of piezoelectric body 131 was 0.1 mm, the thickness of second diaphragm 135 was 0.2 mm, the longitudinal dimension L1 inside frame body 120 was 9.85 mm, the lateral dimension L2 was 1.8 mm, the thickness of frame body 120 in the third direction (Z-axis direction) was 0.2 mm, the dimension La between first short side portions 122 in the second direction (Y-axis direction) was 20 mm, the minimum dimension Lm of piezoelectric body 131 was 19 mm, the dimension of second diaphragm 135 in the second direction (Y-axis direction) was 19 mm, and the dimension of second diaphragm 135 in the first direction (X-axis direction) was 1.5 mm. Four openings 110s with a dimension SL of 1.42 mm in the first direction (X-axis direction) were formed from a position on the edge in the second direction (Y-axis direction) on the inner peripheral surface of the frame body 120 to a position 0.5 mm inward in the second direction (Y-axis direction). In other words, the width dimension SW of the four openings 110s was set to 0.5 mm.

[0038] 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 unimorph piezoelectric 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 unimorph piezoelectric 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 unimorph piezoelectric vibrator 130 are 100 kHz or higher.

[0039] In first diaphragm 110, peak portion 110p located at the middle in the longitudinal direction inside frame body 120 becomes the antinode of the resonant vibration, and end portions located on 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.

[0040] Here, the relationship between the resonance frequency of first diaphragm 110 and longitudinal dimension L1 inside frame body 120 will be described.

[0041] 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 simulation analysis conditions, only one frame 120 was provided, and the lateral dimension L2 inside frame 120 was fixed at 2 mm.

[0042] 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.

[0043] 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.

[0044] 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 longitudinal dimension L1 inside the frame body 120 will be described.

[0045] 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 is fixed. In Fig. 9, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame 120. As simulation analysis conditions, only one frame 120 was provided, and the lateral dimension L2 inside the frame 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 of the ultrasonic transducer.

[0046] 9, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer increased as the longitudinal dimension L1 inside the frame body 120 increased. 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 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.

[0047] Here, the relationship between the longitudinal dimension L1 inside the frame and the structural stability of the ultrasonic transducer will be described.

[0048] Fig. 10 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Comparative Example 1. As shown in Fig. 10, the ultrasonic transducer 900 according to Comparative Example 1 includes a first diaphragm 910, one frame 920, and a unimorph piezoelectric vibrator 130. Regarding the dimensions inside the frame 920, the longitudinal dimension L1 is 30 mm, and the lateral dimension L2 is 1.8 mm. No opening is formed in the first diaphragm 910. Other than the above, the configuration of the ultrasonic transducer 900 is the same as that of the ultrasonic transducer 100.

[0049] Fig. 11 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to Comparative Example 1 transmits or receives ultrasonic waves. As shown in Fig. 11, in the first diaphragm 910 of the ultrasonic transducer 900 according to Comparative Example 1, a peak portion 910p located at the middle in the longitudinal direction inside the frame body 920 becomes an antinode of the resonant vibration, and ends located on both ends in the longitudinal direction inside the frame body 920 become nodes of the resonant vibration.

[0050] 11 shows a state in which no deformation occurs in frame body 920, but if the longitudinal dimension L1 is, for example, 30 mm or longer, the rigidity of frame body 920 decreases, and therefore, when frame body 920 and piezoelectric body 131 are pressurized and crimped together, frame body 920 may be deformed so that the transverse dimension L2 increases at a position offset in the second direction (Y-axis direction) of frame body 920. In this case, the position of peak portion 910p shifts in the second direction (Y-axis direction) from the center position in the longitudinal direction inside frame body 920, the resonance frequency of first diaphragm 910 decreases, and the phase of the displacement of first diaphragm 910 relative to the voltage applied by the processing circuit shifts.

[0051] 12 is a graph showing actual measurements of the applied voltage and sound pressure level transitions by the processing circuit for an ultrasonic transducer according to Example 1, which has two frames and a dimension La between the first short sides in the second direction (Y-axis direction) of 30 mm, and an ultrasonic transducer according to Comparative Example 1. In FIG. 12, the vertical axis represents sound pressure level (dB) and the horizontal axis represents applied voltage. The data for the ultrasonic transducer according to Example 1 is shown by a solid line, and the data for the ultrasonic transducer 900 according to Comparative Example 1 is shown by a dotted line. The sound pressure level is the value of the sound pressure level of an audible sound with a frequency of 3 kHz at a point 30 cm away from the front of the ultrasonic transducer in the third direction (Z-axis direction). The applied voltage is a normalized value. The configuration of the ultrasonic transducer according to Example 1, other than the dimension La, is the same as that of the ultrasonic transducer 100 according to Embodiment 1.

[0052] 12, the ultrasonic transducer 900 according to Comparative Example 1 has a lower sound pressure level over the entire range of applied voltage compared to the ultrasonic transducer according to Example 1. In the ultrasonic transducer 900 according to Comparative Example 1, when the applied voltage by the processing circuit 140 exceeds a threshold value, the joint between the first diaphragm 910 and the frame body 920 peels off, and the sound pressure level does not increase even when the applied voltage increases.

[0053] In the ultrasonic transducer 900 of Comparative Example 1, when the longitudinal dimension L1 was set to 20 mm, which is approximately 11 times the lateral dimension L2, no peeling occurred at the joint between the first vibration plate 910 and the frame body 920 over the entire range of applied voltage, and the sound pressure level increased as the applied voltage increased.

[0054] Therefore, in the ultrasonic transducer 100 of this embodiment, the inner dimensions of each of the multiple frame bodies 120 are such that the longitudinal dimension L1 in the second direction (Y-axis direction) is between 4 and 11 times the lateral dimension L2 in the first direction (X-axis direction), thereby suppressing peeling at the joint between the first vibration plate 110 and the multiple frame bodies 120 and increasing the sound pressure while maintaining the resonance frequency of the first vibration plate 110 approximately constant.

[0055] Here, we will explain 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 ratio of the short-side dimension SL of the opening to the short-side dimension L2 of the frame body.

[0056] Fig. 13 is a graph showing the transition of the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer when the dimension of the opening in the short-side direction is changed, as a result of simulation analysis using the finite element method. In Fig. 13, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer, and the horizontal axis represents the ratio (%) of the dimension SL of the opening in the short-side direction to the dimension L2 of the frame. The simulation analysis conditions were as follows: the longitudinal dimension L1 inside the frame 120 was fixed at 9.85 mm, the short-side dimension L2 was fixed at 1.8 mm, and the dimension La between the first short sides 122 in the second direction (Y-axis direction) was set at 20 mm. The sound pressure (Pa) was calculated at a position 30 cm away from the first diaphragm on the front of the ultrasonic transducer in the third direction (Z-axis direction). The dotted line indicates the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer 900 according to Comparative Example 1, in which the longitudinal dimension L1 is 20 mm and the first diaphragm 910 does not have an opening.

[0057] FIG. 14 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer of sample 1, in which the ratio of the lateral dimension of the opening to the lateral dimension of the frame is 0%, transmits or receives ultrasonic waves. FIG. 15 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer of sample 2, in which the ratio of the lateral dimension of the opening to the lateral dimension of the frame is 33%, transmits or receives ultrasonic waves. FIG. 16 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer of sample 3, in which the ratio of the lateral dimension of the opening to the lateral dimension of the frame is 100%, transmits or receives ultrasonic waves. In samples 1 to 3, the configurations other than the ratio of the lateral dimension SL of the opening to the lateral dimension L2 of the frame are the same as those of the ultrasonic transducer 100 according to embodiment 1 shown in FIG. 6.

[0058] As shown in Figure 14, in the ultrasonic transducer 901 of sample 1 in which the ratio of the short-side dimension SL of the opening to the short-side dimension L2 of the frame body is 0% and no opening is formed in the first vibration plate 911, the displacement of the peak portion 911p of the first vibration plate 911 is small, and therefore, as shown in Figure 13, the sound pressure of the transmitted ultrasonic waves is lower than that of the ultrasonic transducer 900 of comparative example 1.

[0059] As shown in Figure 15, in the ultrasonic transducer 902 of sample 2, in which an opening 912s is formed in the first vibration plate 912, and the ratio of the short-side dimension SL of the opening to the short-side dimension L2 of the frame body is 33%, the displacement of the peak portion 912p of the first vibration plate 912 is small, so that the sound pressure of the transmitted ultrasonic waves is lower than that of the ultrasonic transducer 900 of comparative example 1, as shown in Figure 13.

[0060] As shown in Fig. 6, in the ultrasonic transducer 100 according to embodiment 1, in which the first diaphragm 110 is formed with an opening 110s in which the ratio of the dimension SL of the opening in the short-side direction to the dimension L2 of the frame is 79%, the displacement of the peak portion 110p of the first diaphragm 110 is large, and as shown in Fig. 13, the sound pressure of the transmitted ultrasonic waves is higher than that of the ultrasonic transducer 900 according to comparative example 1. As shown in Fig. 13, when the ratio of the dimension SL of the opening in the short-side direction to the dimension L2 of the frame is in the range of 67% or more and 94% or less, the entire vibration region of the first diaphragm vibrates, and a higher sound pressure can be obtained than that of the ultrasonic transducer 900 according to comparative example 1.

[0061] As shown in Figure 16, in the ultrasonic transducer 903 of sample 3, in which an opening 913s is formed in the first vibration plate 913, and the ratio of the short-side dimension SL of the opening to the short-side dimension L2 of the frame body is 100%, the peak portion 913p of the first vibration plate 913 is located near the opening 913s, and stress is concentrated and acts on the joint between the first vibration plate 913 and the frame body 120, which is located near the opening 913s, and as shown in Figure 13, the sound pressure of the transmitted ultrasonic waves is lower than that of the ultrasonic transducer 900 of comparative example 1.

[0062] Therefore, in the ultrasonic transducer 100 of this embodiment, the ratio of the above-mentioned short-side dimension SL of the opening to the short-side dimension L2 of the frame body is 67% or more and 94% or less, so that the entire vibration area of ​​the first vibration plate 110 can be vibrated to obtain high sound pressure, and stress concentration at the joint between the first vibration plate 110 and the frame body 120 located near the opening 110s can be suppressed.

[0063] Here, we will explain the results of a simulation analysis using the finite element method regarding the relationship between the sound pressure of the ultrasound transmitted from the ultrasonic transducer of Comparative Example 2, in which two openings are formed so that one corresponds to each of the two frame bodies 120, and the ratio of the short-side dimension SL of the opening to the short-side dimension L2 of the frame body.

[0064] FIG. 17 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Comparative Example 2. As shown in FIG. 17, an ultrasonic transducer 904 according to Comparative Example 2 includes a first diaphragm 914, two frame bodies 120, and a unimorph piezoelectric vibrator 130. Two openings 914s are formed in the first diaphragm 914, one for each of the two frame bodies 120. Specifically, one opening 914s is formed so as to open to one side of the inside of the frame body 120 located on one side in the second direction (Y-axis direction), and the other opening 914s is formed so as to open to the other side of the inside of the frame body 120 located on the other side in the second direction (Y-axis direction). The ultrasonic transducer 904 is otherwise similar in configuration to the ultrasonic transducer 100.

[0065] FIG. 18 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Comparative Example 2 transmits or receives ultrasonic waves.

[0066] 19 is a graph showing the results of a simulation analysis using the finite element method to show the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer of Comparative Example 2 when the dimension of the opening in the short-side direction is changed. In FIG. 19, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer, and the horizontal axis represents the ratio (%) of the dimension SL of the opening in the short-side direction to the dimension L2 of the frame. The simulation analysis conditions were as follows: the longitudinal dimension L1 inside the frame 120 was fixed at 9.85 mm, the short-side dimension L2 was fixed at 1.8 mm, and the dimension La between the first short sides 122 in the second direction (Y-axis direction) was set at 20 mm. The sound pressure (Pa) was calculated at a position 30 cm away from the first diaphragm on the front of the ultrasonic transducer in the third direction (Z-axis direction). The dotted line indicates the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 900 of Comparative Example 1, in which the longitudinal dimension L1 is 20 mm and the first diaphragm 910 does not have an opening.

[0067] As shown in Figure 18, in the ultrasonic transducer 904 of Comparative Example 2, the peak portion 914p of the first vibration plate 914 is located near the opening 914s, and stress is concentrated and acts on the joint between the first vibration plate 914 and the frame body 120, which is located near the opening 914s.In addition, as shown in Figure 19, when the ratio of the short-side dimension SL of the opening 914s to the short-side dimension L2 of the frame body is 60% or more, the sound pressure of the transmitted ultrasonic waves is lower than that of the ultrasonic transducer 900 of Comparative Example 1.

[0068] From the above results, it was confirmed that when two openings 914s are formed, one for each of the two frame bodies 120, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer cannot be increased even if the ratio of the short-side dimension SL of the opening 914s to the short-side dimension L2 of the frame body is increased to 60% or more.

[0069] Next, we will explain the results of a simulation analysis using the finite element method on the resonant vibration of the first diaphragm in the ultrasonic transducer of Comparative Example 3, in which two openings are formed corresponding to one of the two frame bodies 120 and one opening is formed corresponding to the other of the two frame bodies 120.

[0070] FIG. 20 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Comparative Example 3. As shown in FIG. 20, the ultrasonic transducer 905 according to Comparative Example 3 includes a first diaphragm 915, two frame bodies 120, and a unimorph piezoelectric vibrator 130. The first diaphragm 915 has one opening 915s formed corresponding to one of the two frame bodies 120, and two openings 915s formed corresponding to the other of the two frame bodies 120. Specifically, one opening 915s is formed so as to open to one side of the inside of the frame body 120 located on one side in the second direction (Y-axis direction), and two openings 915s are formed so as to open to both ends in the second direction (Y-axis direction) of the inside of the frame body 120 located on the other side in the second direction (Y-axis direction). The ultrasonic transducer 905 has the same configuration as the ultrasonic transducer 100 except for the above.

[0071] Fig. 21 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to Comparative Example 3 transmits or receives ultrasonic waves at a frequency of 150 kHz. Fig. 22 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to Comparative Example 3 transmits or receives ultrasonic waves at a frequency of 150.4 kHz.

[0072] As shown in Figure 21, when the ultrasonic transducer 905 of Comparative Example 3 is transmitting or receiving ultrasonic waves at a frequency of 150 kHz, the peak portion 915p of the first vibration plate 915 located at the middle of the longitudinal direction inside the frame body 120 located on the other side in the second direction (Y-axis direction) becomes the antinode of the resonant vibration, and the vibration area covering the inside of the frame body 120 located on one side in the second direction (Y-axis direction) has a small displacement.

[0073] As shown in Figure 22, when the ultrasonic transducer 905 of Comparative Example 3 is transmitting or receiving ultrasonic waves at a frequency of 150.4 kHz, in the first vibration plate 915, the peak portion 915p of the vibration region covering the inside of the frame body 120 located on one side in the second direction (Y-axis direction) is located near the opening 915s, and the displacement of the vibration region covering the inside of the frame body 120 located on the other side in the second direction (Y-axis direction) is reduced.

[0074] As shown in Figures 21 and 22, in the ultrasonic transducer 905 of Comparative Example 3, in which two openings are formed corresponding to one of the two frame bodies 120 and one opening is formed corresponding to the other of the two frame bodies 120, the vibration modes and displacements of the vibration regions covering the two frame bodies 120 in the first vibration plate 915 are different from each other, and therefore the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 905 could not be increased.

[0075] Therefore, in the ultrasonic transducer 100 of this embodiment, the first vibration plate 110 is formed with a plurality of openings 110s that are open at both ends in the second direction (Y-axis direction) inside each of the plurality of frame bodies 120, so that the vibration modes and displacements of the vibration regions that cover the plurality of frame bodies 120 in the first vibration plate 110 can be matched with each other, thereby increasing the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100.

[0076] Here, we will explain the results of a simulation analysis using the finite element method on the resonant vibration of the first diaphragm in an ultrasonic transducer according to Comparative Example 4, in which the difference in the longitudinal dimension L1 between adjacent frame bodies in the second direction (Y-axis direction) exceeds the transverse dimension L2.

[0077] 23 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to Comparative Example 4 transmits or receives ultrasonic waves. As shown in FIG. 23, an ultrasonic transducer 906 according to Comparative Example 4 includes a first diaphragm 916, frame bodies 920a and 920b, and a unimorph piezoelectric vibrator 130. The simulation analysis conditions were as follows: the longitudinal dimension L1 on the inside of frame body 920a was 11.8 mm, the longitudinal dimension L1 on the inside of frame body 920b was 8.2 mm, and the transverse dimension L2 of each of frame bodies 920a and 920b was 1.8 mm. The remaining configuration of ultrasonic transducer 906 is the same as that of ultrasonic transducer 100.

[0078] 23, when the ultrasonic transducer 906 according to Comparative Example 4 is transmitting or receiving ultrasonic waves, in the first diaphragm 916, a peak portion 916p located at the middle of the longitudinal direction inside the frame body 920b located on the other side in the second direction (Y-axis direction) becomes an antinode of the resonant vibration, and the vibration region covering the inside of the frame body 920a located on one side in the second direction (Y-axis direction) has a small displacement. Therefore, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 906 is 30% lower than that of an ultrasonic transducer in which the longitudinal dimension L1 of the frame bodies 120 adjacent to each other in the second direction (Y-axis direction) is approximately the same.

[0079] In addition, when the longitudinal dimension L1 inside frame body 920a was 10.9 mm, the longitudinal dimension L1 inside frame body 920b was 9.1 mm, and the short dimension L2 of each of frame bodies 920a and 920b was 1.8 mm, the sound pressure of the ultrasound transmitted from ultrasonic transducer 906 was 15% lower than that of an ultrasonic transducer in which the longitudinal dimensions L1 of adjacent frame bodies 120 in the second direction (Y-axis direction) were approximately the same.

[0080] Therefore, in the ultrasonic transducer 100 according to this embodiment, the difference in the longitudinal dimension L1 between adjacent frame bodies 120 in the second direction (Y-axis direction) among the plurality of frame bodies 120 is equal to or less than the lateral dimension L2. This suppresses differences in the vibration modes and displacements of the vibration regions covering the plurality of frame bodies 120 in the first diaphragm 110, and makes it possible to maintain a high sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100.

[0081] Here, we will explain an ultrasonic transducer according to variant example 1 in which one of the two openings corresponding to one of the two frame bodies 120 and one of the two openings corresponding to the other frame body are shared.

[0082] FIG. 24 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Modification 1 of Embodiment 1 of the present invention. As shown in FIG. 24, the ultrasonic transducer 101 according to Modification 1 includes a first diaphragm 111, two frame bodies 120, and a unimorph piezoelectric vibrator 130. Two openings 110s and one opening 111s are formed in the first diaphragm 111. Specifically, the opening 110s is formed so as to open to one side of the inside of the frame body 120 located on one side in the second direction (Y-axis direction) of the two frame bodies 120, and the opening 110s is formed so as to open to the other side of the inside of the frame body 120 located on the other side in the second direction (Y-axis direction). The openings 111s are open to the other side of the inside of the frame body 120 located on the one side and to the one side of the inside of the frame body 120 located on the other side. The ultrasonic transducer 101 is otherwise similar in configuration to the ultrasonic transducer 100.

[0083] FIG. 25 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 modification transmits or receives ultrasonic waves.

[0084] 25, in the first diaphragm 111, a peak portion 111p located at the middle in the longitudinal direction inside the frame body 120 becomes an antinode of the resonant vibration, and end portions located on both ends in the longitudinal direction inside the frame body 120 become nodes of the resonant vibration. As with the ultrasonic transducer 100 according to the first embodiment, the ultrasonic transducer 101 according to the first modification can also increase the sound pressure level while reducing internal stress with a simple and compact configuration.

[0085] Here, an ultrasonic transducer according to Modification 2 in which the piezoelectric body is divided into frames will be described.

[0086] 26 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Modification 2 of Embodiment 1 of the present invention. As shown in FIG. 26, the ultrasonic transducer 102 according to Modification 2 includes a first diaphragm 110, two frame bodies 120, and a unimorph piezoelectric vibrator 130a. The unimorph piezoelectric vibrator 130a includes a first piezoelectric body 131a, a second piezoelectric body 131b, and a second diaphragm 135. The first piezoelectric body 131a is bonded to the frame body 120 located on one side in the second direction (Y-axis direction) of the two frame bodies 120. The second piezoelectric body 131b is bonded to the frame body 120 located on the other side in the second direction (Y-axis direction) of the two frame bodies 120. The configuration of the ultrasonic transducer 102 other than the above is the same as that of the ultrasonic transducer 100.

[0087] FIG. 27 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the second modification transmits or receives ultrasonic waves.

[0088] As shown in FIG. 27, in the first diaphragm 110, the peak portion 110p located at the middle of the longitudinal direction inside the frame body 120 becomes the antinode of the resonant vibration, and the ends located at both ends of the longitudinal direction inside the frame body 120 become the nodes of the resonant vibration.

[0089] The ultrasonic transducer 102 according to Modification 2 can also increase the sound pressure level while reducing internal stress with a simple and compact configuration, similar to the ultrasonic transducer 100 according to Embodiment 1. Furthermore, since the total volume of the first piezoelectric body 131a and the second piezoelectric body 131b can be made smaller than the volume of the piezoelectric body 131 according to Embodiment 1, the free capacitance of the unimorph piezoelectric vibrator 130a can be reduced, reducing the power consumption of the ultrasonic transducer 102 and improving efficiency.

[0090] Here, an ultrasonic transducer according to Modification 3 in which a constricted portion is formed in the second diaphragm will be described.

[0091] Fig. 28 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Modification 3 of Embodiment 1 of the present invention. As shown in Fig. 28, ultrasonic transducer 103 according to Modification 3 includes a first diaphragm 110, two frame bodies 120, and a unimorph piezoelectric vibrator 130b. Unimorph piezoelectric vibrator 130b includes a piezoelectric body 131 and a second diaphragm 135a. A constricted portion 135n is formed in second diaphragm 135a. Other configurations of ultrasonic transducer 103 are the same as those of ultrasonic transducer 100.

[0092] Fig. 29 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Modification 3 transmits or receives ultrasonic waves. Fig. 30 is a view of the ultrasonic transducer of Fig. 29 as seen from the direction of arrow XXX.

[0093] As shown in FIG. 29, in the first diaphragm 110, a peak portion 110p located at the middle of the longitudinal direction inside the frame body 120 serves as an antinode of the resonant vibration, and end portions located at both ends of the longitudinal direction inside the frame body 120 serve as nodes of the resonant vibration. As shown in FIG. 30, the piezoelectric body 131 has a node 131n at a position where it is joined to the second short side portion 123 of the frame body 120. The constricted portion 135n of the second diaphragm 135a is located on the node 131n. That is, the second diaphragm 135a is constricted so that its width in the short direction is narrowed at a position facing the second short side portion 123, which is the connection end portion between adjacent frame bodies 120 in the longitudinal direction, among the multiple frame bodies 120, and at a position facing the node 131n of the piezoelectric body 131. The constricted portion 135n is formed by pressing, cutting, or the like.

[0094] Fig. 31 is a view of an ultrasonic transducer according to Modification 3 viewed from the second diaphragm side. As shown in Fig. 31, in ultrasonic transducer 103 according to Modification 3 of Embodiment 1 of the present invention, constricted portion 135n is formed at the above-mentioned position of second diaphragm 135a. This makes it possible to easily connect power supply wiring 10 to the electrode formed at node point 131n of piezoelectric body 131 exposed by constricted portion 135n.

[0095] Here, an ultrasonic transducer according to Modification 4 in which three frame bodies 120 are formed so as to be aligned in the second direction (Y-axis direction) will be described.

[0096] Fig. 32 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Modification 4 of Embodiment 1 of the present invention. As shown in Fig. 32, the ultrasonic transducer 104 according to Modification 4 includes a first diaphragm 114, three frame bodies 120, and a unimorph piezoelectric vibrator 130b. Two openings 114s are formed in the first diaphragm 114 so as to open to both ends in the second direction (Y-axis direction) inside each frame body 120, for a total of six openings 114s formed in the first diaphragm 114. Other configurations of the ultrasonic transducer 104 than those described above are the same as those of the ultrasonic transducer 100.

[0097] Fig. 33 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to Modification 4 transmits or receives ultrasonic waves. Fig. 34 is a view of the ultrasonic transducer of Fig. 33 as seen from the direction of arrow XXXIV. The simulation analysis conditions were as follows: the longitudinal dimension L1 on the inside of the frame body 120 was 8 mm, the lateral dimension L2 was 1.8 mm, and the width dimension W of the second short side portion 123 was 0.3 mm.

[0098] As shown in Fig. 33, the position of peak portion 114p of first diaphragm 114 is slightly shifted from the longitudinal center position inside each frame body 120. As shown in Fig. 34, piezoelectric body 131 has node points 131n at both end positions in the second direction (Y-axis direction). Thus, when the number of frame bodies 120 aligned in the second direction (Y-axis direction) is odd, both end positions in the second direction (Y-axis direction) of piezoelectric body 131 become node points 131n. Note that even when the width dimension W of second short side portion 123 was changed from 0.3 mm to 1 mm, the vibration state of first diaphragm 114 and the position of node point 131n of piezoelectric body 131 did not change.

[0099] Here, an ultrasonic transducer according to Modification 5 in which four frame bodies 120 are formed to be aligned in the second direction (Y-axis direction) will be described.

[0100] Fig. 35 is an exploded perspective view showing the configuration of an ultrasonic transducer according to Modification 5 of Embodiment 1 of the present invention. As shown in Fig. 35, ultrasonic transducer 105 according to Modification 5 includes a first diaphragm 115, four frame bodies 120, and a unimorph piezoelectric vibrator 130b. Two openings 115s are formed in first diaphragm 115 so as to open to both ends in the second direction (Y-axis direction) inside each frame body 120, for a total of eight openings 115s formed in first diaphragm 115. Other configurations of ultrasonic transducer 105 than those described above are the same as those of ultrasonic transducer 100.

[0101] Fig. 36 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to Modification 5 transmits or receives ultrasonic waves. Fig. 37 is a view of the ultrasonic transducer of Fig. 36 as seen from the direction of arrow XXXVII. The simulation analysis conditions were as follows: the longitudinal dimension L1 on the inside of the frame body 120 was 7.8 mm, the lateral dimension L2 was 1.8 mm, and the width dimension W of the second short side portion 123 was 0.3 mm.

[0102] As shown in Fig. 36, in the first diaphragm 115, the position of the peak portion 115p is located at the middle in the longitudinal direction inside each frame body 120. As shown in Fig. 37, the piezoelectric body 131 has a node point 131n at the middle position in the second direction (Y-axis direction). Thus, when the number of frame bodies 120 aligned in the second direction (Y-axis direction) is even, the node point 131n is located at the middle position in the second direction (Y-axis direction) of the piezoelectric body 131. Note that even when the width dimension W of the second short side portion 123 is changed from 0.3 mm to 1 mm, the vibration state of the first diaphragm 115 and the position of the node point 131n of the piezoelectric body 131 do not change.

[0103] Here, the relationship between the resonance frequency of the first diaphragm and the resonance frequency of the bending mode of the unimorph type piezoelectric vibrator 130 will be described.

[0104] Fig. 38 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer of Comparative Example 5, in which the unimorph piezoelectric vibrator is vibrating resonantly in bending mode, transmits or receives ultrasonic waves. The simulation analysis conditions were a thickness of 0.4 mm for the frame body 120 and a width W of the second short side portion 123 of 0.9 mm. Other than the above, the configuration of the ultrasonic transducer 907 of Comparative Example 5 is the same as that of the ultrasonic transducer 104 of Modification Example 4. Note that the displacement is exaggerated in Fig. 38.

[0105] As shown in Figure 38, when the unimorph piezoelectric vibrator 130 resonates in bending mode, the vibration modes and displacements of the vibration regions covering the multiple frame bodies 120 in the first vibration plate 114 cannot be matched to each other, so it is preferable that the resonance frequency of the first vibration plate 114 be 10 kHz or more away from the resonance frequency of the bending mode of the unimorph piezoelectric vibrator 130.

[0106] 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).

[0107] In the ultrasonic transducer 100 according to the first embodiment of the present invention, the resonant frequency of the first diaphragm 110 and the unimorph piezoelectric vibrator 130 is 100 kHz or higher. When the resonant frequency is 100 kHz or higher, the attenuation of sound waves over the propagation distance is large, so that audible sound can be reproduced only in a limited space. The resonant frequency of the first diaphragm 110 and the unimorph piezoelectric vibrator 130 may be, for example, 150 kHz or higher and 200 kHz or lower.

[0108] (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 unimorph piezoelectric 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.

[0109] Fig. 39 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 2 of the present invention, Fig. 40 is a rear view of the ultrasonic transducer shown in Fig. 39 as seen from the direction of arrow XL.

[0110] 39 and 40, 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 unimorph piezoelectric vibrators 230. The plurality of frame bodies 220 are bonded to the first diaphragm 210, and the plurality of unimorph piezoelectric vibrators 230 are bonded to the plurality of frame bodies 220, respectively.

[0111] Here, a method for manufacturing the ultrasonic transducer 200 will be described. As shown in FIG. 39, the first diaphragm 210 has a flat plate shape, and a plurality of slits 211 extending in the second direction (Y-axis direction) are formed at intervals in the first direction (X-axis direction). A plurality of openings 210s are formed in the first diaphragm 210, opening at both ends in the longitudinal direction inside each of the plurality of frame bodies 220. The first diaphragm 210 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, the first diaphragm 210 is made of stainless steel. The plurality of slits 211 and the plurality of openings 210s are formed by etching, cutting, or the like.

[0112] Each of the multiple frame bodies 220 has a rectangular ring shape. Each of the multiple frame bodies 220 has a short side direction along a first direction (X-axis direction) and a long side direction along a second direction (Y-axis direction). Each of the multiple frame bodies 220 extends in the second direction (Y-axis direction). The axial direction of each of the multiple frame bodies 220 is along a third direction (Z-axis direction). Each of the multiple frame bodies 220 has a pair of long side portions 221 extending in the second direction (Y-axis direction) and a first short side portion 222 and a second short side portion 223 extending in the first direction (X-axis direction). The first short side portions 222 are both end portions of the multiple frame bodies 220 located at both ends in the second direction (Y-axis direction). The second short side portions 223 are connecting end portions that connect adjacent frame bodies 220 in the second direction (Y-axis direction) to each other. The average distance between the first short side portion 222 and the second short side portion 223 is 4 times or more and 11 times or less the shortest distance between the long side portions 221.

[0113] The multiple frame bodies 220 are arranged in a matrix so as to line up in both a first direction (X-axis direction) and a second direction (Y-axis direction). A slit 224 is formed between adjacent frame bodies 220 in the first direction (X-axis direction). The multiple slits 224 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 224.

[0114] The frame bodies 220 adjacent to each other in the first direction (X-axis direction) are connected to each other at the first 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.

[0115] 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 the present 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 first short side portions 222 of the frame bodies 220 to each other.

[0116] 41 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. As shown in Fig. 41, the slits 211 and 224 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 224 in the third direction (Z-axis direction).

[0117] 39 and 40, second diaphragms 235 adjacent to each other in the first direction (X-axis direction) are connected to each other by connecting portions 236 at positions near both ends in the second direction (Y-axis direction). Connecting portions 236 extend in the first direction (X-axis direction). Connecting portions 236 are formed by etching, pressing, cutting, or the like.

[0118] The second vibration plate 235 has a constricted portion 235n formed so as to narrow the width in the short side direction at a position facing a second short side portion 223, which is a connection end portion between adjacent frame bodies 220 in the longitudinal direction among the plurality of frame bodies 220, and at a position facing a node point of the piezoelectric body 131. The constricted portion 235n is formed by half etching, pressing, cutting, or the like.

[0119] In this embodiment, each of the frame body 220 and the second diaphragm 235 is plated with Ag or the like. The frame body 220 and the piezoelectric body 131 are electrically connected by pressure and compression, and the piezoelectric body 131 and the second diaphragm 235 are electrically connected by pressure and compression. As a result, as shown in Fig. 40, by connecting the wiring 10 for supplying power to the piezoelectric body 131 to only two locations: the end of the frame body 220 in the second direction (Y-axis direction) and the electrode of the piezoelectric body 131 exposed by the constricted portion 235n, it is possible to drive a plurality of unimorph piezoelectric vibrators 230.

[0120] The ultrasonic transducer 200 according to the second embodiment can easily increase the sound pressure level by increasing the number of ultrasonic transducers 100 included therein.

[0121] 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.

[0122] 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.

[0123] (Addendum) It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0124] <1> A first diaphragm; a plurality of frame bodies each extending in a longitudinal direction, arranged adjacent to each other in the longitudinal direction and joined to the first diaphragm; at least one unimorph type piezoelectric vibrator attached to the plurality of frames and including a piezoelectric body facing the first vibration plate with a gap therebetween and a second vibration plate provided on the piezoelectric body on the opposite side to the frame body side; a plurality of openings are formed in the first diaphragm, the openings being respectively open at both ends in the longitudinal direction inside each of the plurality of frame bodies; the first diaphragm resonates in an opposite phase to the at least one unimorph piezoelectric vibrator in a direction perpendicular to the first diaphragm; In the dimensions of each of the plurality of frame bodies on the inside, the longitudinal dimension in the longitudinal direction is 4 to 11 times the short side dimension in the short side direction perpendicular to the longitudinal direction, The short-side dimensions of the plurality of frame bodies are substantially the same, An ultrasonic transducer, wherein the difference in the longitudinal dimension between adjacent frame bodies in the longitudinal direction among the plurality of frame bodies is equal to or less than the widthwise dimension.

[0125] <2> The dimension in the short side direction of each of the plurality of openings is 67% or more and 94% or less of the short side dimension. <1> 2. The ultrasonic transducer according to claim 1 .

[0126] <3> The resonance frequency of the first diaphragm and the at least one unimorph piezoelectric vibrator is 100 kHz or more. <1> or <2> 2. The ultrasonic transducer according to claim 1 .

[0127] <4> the plurality of frames are arranged in a matrix so as to be aligned in both the longitudinal direction and the lateral direction, and are joined to the first diaphragm; Among the plurality of frame bodies, frame bodies adjacent to each other in the short side direction are connected to each other at both ends in the long side direction. <1> from <3> 10. An ultrasonic transducer according to claim 9.

[0128] <5> the second vibration plate is constricted so that its width in the short side direction is narrowed at a position facing a connection end of adjacent frame bodies in the longitudinal direction among the plurality of frame bodies and at a position facing a node point of the piezoelectric body. <1> from <4> 10. An ultrasonic transducer according to claim 9.

[0129] In the above-described embodiments, configurations that can be combined may be combined with each other.

[0130] 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]

[0131] 10 Wiring, 100, 101, 102, 103, 104, 105, 200, 900, 901, 902, 903, 904, 905, 906, 907 Ultrasonic transducer, 110, 111, 114, 115, 210, 910, 911, 912, 913, 914, 915, 916 First diaphragm, 110p, 111p, 114p, 115p, 910p, 911p, 912p, 913p, 914p, 915p, 916p Peak section, 110s, 111s, 114s, 115s, 210s, 912s, 913s, 914s, 915s Opening, 120, 220, 920, 920a, 920b Frame, 120e, 120s1, 120s2, 130e, 135s1, 135s2 Edge, 121, 221 Long side, 122, 222 First short side, 123, 223 Second short side, 130, 130a, 130b, 230 Unimorph type piezoelectric vibrator, 130s Frame side surface of piezoelectric body, 131 Piezoelectric body, 131a First piezoelectric body, 131b Second piezoelectric body, 131n Node point, 132 First electrode, 133 Second electrode, 135, 135a, 235 Second vibration plate, 135n, 235n Node portion, 140 Processing circuit, 211, 224 Slit, 236 Connection part, D1, D2, L3 average distance, Dp polarization direction, L1 long dimension, L2 short dimension, LC cut line.

Claims

1. First diaphragm and A plurality of frames extending in the longitudinal direction, arranged adjacently in the longitudinal direction and joined to the first diaphragm, The device comprises at least one unimorph type piezoelectric vibrator, which is attached to the plurality of frames and includes a piezoelectric element that faces the first diaphragm at a distance from it and a second diaphragm provided on the side of the piezoelectric element opposite to the frame side, The first diaphragm has a plurality of openings formed on the inner side of each of the plurality of frames, which are located at both ends in the longitudinal direction. The first diaphragm resonates and vibrates in a direction perpendicular to the first diaphragm, in opposite phase to the at least one unimorph type piezoelectric vibrator. In the dimensions inside each of the plurality of frames, the longitudinal dimension in the longitudinal direction is 4 times or more and 11 times or less the short dimension in the short direction perpendicular to the longitudinal direction. In the aforementioned plurality of frames, the shorter side dimensions are substantially the same to each other. An ultrasonic transducer in which, among the plurality of frames, the difference in the longitudinal dimension between adjacent frames in the longitudinal direction is less than or equal to the short dimension.

2. The ultrasonic transducer according to claim 1, wherein the dimension of each of the plurality of openings in the short-side direction is 67% or more and 94% or less of the short-side dimension.

3. The ultrasonic transducer according to claim 1 or 2, wherein the resonant frequencies of the first diaphragm and the at least one unimorph type piezoelectric vibrator are 100 kHz or higher.

4. The plurality of frames are arranged in a matrix so as to be aligned in both the longitudinal and transverse directions and are joined to the first diaphragm. The ultrasonic transducer according to claim 1 or claim 2, wherein, in the plurality of frames, adjacent frames in the short direction are connected at both ends in the longitudinal direction of each other.

5. The ultrasonic transducer according to claim 1 or 2, wherein the second diaphragm is constricted in the plurality of frames at a position facing the connection end between adjacent frames in the longitudinal direction and at a position facing the node point of the piezoelectric element, such that its width in the short direction becomes narrower.

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