Ultrasonic transducer and parametric speaker including the same

Abstract

The first diaphragm (110) resonates in a reverse phase to at least one unimorph piezoelectric vibrator (130) in a direction orthogonal to the first diaphragm (110). The longitudinal dimension (L1) inside at least one frame body (120) is 4 times or more the dimension in the short direction orthogonal to the longitudinal direction inside at least one frame body (120). The second diaphragm (135) is located within a region sandwiched by both end edges (120s1, 120s2) in the short direction on the inner peripheral surface of at least one frame body (120) in the short direction when viewed from a direction orthogonal to the first diaphragm (110), and the average distance (D1) in the short direction between one end edge (120s1) in the short direction on the inner peripheral surface of at least one frame body (120) and one end edge (135s1) in the short direction of the second diaphragm (135), and the average distance (D2) in the short direction between the other end edge (120s2) in the short direction on the inner peripheral surface of at least one frame body (120) and the other end edge (135s2) in the short direction of the second diaphragm (135) are each 1 / 6 or less of the dimension (L2) in the short direction inside at least one frame body (120).

Description

Technical Field

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

Background Art

[0002] As prior art documents disclosing the configuration of a superdirective acoustic device, there are JP-A-2003-47085 (Patent Document 1) and Patent No. 6333480 (Patent Document 2). The superdirective acoustic device described in Patent Document 1 is configured by arranging a plurality of ultrasonic transducers on a single printed circuit board so that its outer periphery has a substantially circular shape. The plurality of ultrasonic transducers are divided into two groups with different installation heights.

[0003] The superdirective 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 wave signal radiated by the second ultrasonic emitter is opposite to the phase of the carrier wave signal included in the signal radiated by the first ultrasonic emitter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the superdirective acoustic device described in Patent Document 1, a plurality of ultrasonic transducers are arranged in two groups with different installation heights, and the configuration is complicated. In the superdirective acoustic device described in Patent Document 2, the second ultrasonic emitter is arranged outside the first ultrasonic emitter, and the device becomes large-sized.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide an ultrasonic transducer and a parametric speaker including the same, which can increase the sound pressure level with a simple and downsized configuration.

Means for Solving the Problems

[0007] The ultrasonic transducer according to the present invention includes a first diaphragm, at least one frame body, and at least one unimorph piezoelectric vibrator. The at least one frame body extends in the longitudinal direction and is joined to the first diaphragm. The at least one unimorph piezoelectric vibrator is respectively attached to the at least one frame body. 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 opposite to the frame body side of the piezoelectric body. The first diaphragm resonates and vibrates in a reverse phase to the at least one unimorph piezoelectric vibrator in a direction orthogonal to the first diaphragm. The dimension in the longitudinal direction inside the at least one frame body is 4 times or more the dimension in the short direction orthogonal to the longitudinal direction inside the at least one frame body. The second diaphragm is located in a region sandwiched between both end edges in the short direction on the inner peripheral surface of the at least one frame body in the short direction when viewed from a direction orthogonal to the first diaphragm. Each of the average distance in the short direction between one end edge in the short direction on the inner peripheral surface of the at least one frame body and one end edge in the short direction of the second diaphragm, and the average distance in the short direction between the other end edge in the short direction on the inner peripheral surface of the at least one frame body and the other end edge in the short direction of the second diaphragm is 1 / 6 or less of the dimension in the short direction inside the at least one frame body.

Effects of the Invention

[0008] According to the present invention, the sound pressure level can be increased with a simple and downsized configuration in the ultrasonic transducer.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Hereinafter, the ultrasonic transducer according to each embodiment 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 are denoted by the same reference numerals, and the description thereof will not be repeated. The present invention is applicable to applications that require 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 exemplified and described, but the use of the ultrasonic transducer is not limited thereto.

[0011] (Embodiment 1) FIG. 1 is a longitudinal sectional view showing the configuration of the 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, the ultrasonic transducer 100 according to Embodiment 1 of the present invention includes a first diaphragm 110, a frame body 120, and a unimorph type 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 germalmin containing aluminum, or a metal such as stainless steel. In the present embodiment, the first diaphragm 110 is made of an aluminum alloy. Since the aluminum alloy has a small Young's modulus, by forming the first diaphragm 110 of the aluminum alloy, the stress generated in the first diaphragm 110 during driving of the ultrasonic transducer 100 can be reduced. The thickness of the first diaphragm 110 is, for example, 0.05 mm or more and 0.2 mm or less.

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

[0014] The frame body 120 is formed of a metal such as an aluminum alloy, an iron-nickel alloy (42Ni-Fe), or stainless steel, a glass epoxy, or a resin. From the viewpoint of suppressing characteristic changes due to temperature changes of the ultrasonic transducer 100, it is preferable that the frame body 120 is made of metal. On the other hand, from the viewpoints of reducing the frequency of the ultrasonic waves transmitted or received by the ultrasonic transducer 100 and miniaturizing the ultrasonic transducer 100, it is preferable that the frame body 120 is made of resin. In the present embodiment, the frame body 120 is made of stainless steel. The thickness of the frame body 120 is, for example, 0.2 mm or more and 0.6 mm or less.

[0015] FIG. 3 is a perspective view showing the configuration of a frame body included in the ultrasonic transducer according to Embodiment 1 of the present invention. As shown in FIG. 3, the frame body 120 has a pair of long side portions 121 extending in the second direction (Y-axis direction) and a pair of short side portions 122 extending in the first direction (X-axis direction). The pair of long side portions 121 and the pair of short side portions 122 are continuous to form the inner peripheral surface of the frame body 120. The average interval between the short side portions 122 is 4 times or more the shortest interval between the long side portions 121. That is, the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 is 4 times or more the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0016] Note that the corner portions sandwiched between the long side portions 121 and the short side portions 122 may be chamfered. Further, the short side portions 122 are not limited to being linear when viewed from the third direction (Z-axis direction), and may be convex arc-shaped on the inner side of the frame body 120 or convex arc-shaped on the outer side of the frame body 120.

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

[0018] The longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 is 4 times or more the short-side dimension L2, and from the viewpoint of increasing the sound pressure level of the ultrasonic waves transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, 20 mm or more.

[0019] FIG. 4 is a view of the ultrasonic transducer of FIG. 2 as seen from the direction of arrow IV. As shown in FIGS. 1 and 4, the unimorph piezoelectric vibrator 130 is attached to the frame body 120. The unimorph piezoelectric vibrator 130 includes a piezoelectric body 131 facing the first diaphragm 110 with a gap therebetween and a second diaphragm 135 provided on the side of the piezoelectric body 131 opposite to the frame body 120 side. The piezoelectric body 131 has a rectangular parallelepiped shape. The thickness of the piezoelectric body 131 is, for example, 0.1 mm or more and 0.2 mm or less. The piezoelectric body 131 is, for example, a piezoelectric ceramic.

[0020] The second diaphragm 135 is formed of a metal such as an aluminum alloy, an iron-nickel alloy (42Ni-Fe), or stainless steel, glass epoxy, or ceramic. In the present 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 joined 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 W of the second diaphragm 135 in the first direction (X-axis direction) satisfies the relationship of (2 / 3)L2 ≤ W < L2 with respect to the short-side dimension L2 of the inside of the frame body 120 in the first direction (X-axis direction). The thickness of the second diaphragm 135 is, for example, 0.2 mm or more and 0.4 mm or less. When the shape of the second diaphragm 135 is not rectangular but elliptical or the like when viewed from the third direction (Z-axis direction), the short-side dimension W is the average value.

[0021] As shown in FIG. 4, when the second diaphragm 135 is viewed from the third direction (Z-axis direction) orthogonal to the first diaphragm 110, it is located within a region sandwiched between both end edges 120s1 and 120s2 in the first direction (X-axis direction) of the inner peripheral surface of the frame body 120 in the first direction (X-axis direction).

[0022] As shown in FIG. 1, in the second diaphragm 135, the average distance D1 in the first direction (X-axis direction) between one end edge 120s1 in the first direction (X-axis direction) of the inner peripheral surface of the frame body 120 and one end 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 end edge 120s2 in the first direction (X-axis direction) of the inner peripheral surface of the frame body 120 and the other end 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 of the inside of the frame body 120 in the first direction (X-axis direction).

[0023] As shown in Fig. 4, the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame 120 is larger than the minimum dimension Lm of the piezoelectric body 131 in the second direction (Y-axis direction) of the unimorph piezoelectric vibrator 130. Here, the minimum dimension Lm of the piezoelectric body 131 in the second direction (Y-axis direction) of the unimorph piezoelectric vibrator 130 is the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body with the shortest length in the second direction (Y-axis direction) among the plurality of piezoelectric bodies when the unimorph piezoelectric vibrator 130 has a laminated structure in which a plurality of piezoelectric bodies are laminated. For example, when the unimorph piezoelectric vibrator 130 has a laminated structure in which two piezoelectric bodies 131 are laminated, the polarization directions Dp 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 in which the two piezoelectric bodies 131 bend and vibrate in the same manner is configured.

[0024] Fig. 4 shows a state in which the piezoelectric body 131 and the second diaphragm 135 are overlapped without displacement in the second direction (Y-axis direction). In the present embodiment, the length of the piezoelectric body 131 in the second direction (Y-axis direction) is shorter than the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame 120, but it is not limited thereto, and it may be equal to or greater than the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame 120.

[0025] The average distance L3 in the second direction (Y-axis direction) between at least one edge 120e in the second direction (Y-axis direction) on the inner peripheral surface of the frame 120 and at least one edge 130e in the second direction (Y-axis direction) on the surface 130s of the piezoelectric body 131 on the frame 120 side of the unimorph piezoelectric vibrator 130 shown in Fig. 2 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame 120.

[0026] In the present embodiment, the average distance L3 in the second direction (Y-axis direction) between the edge 120e on one side in the second direction (Y-axis direction) of the inner peripheral surface of the frame body 120 and the edge 130e on one side in the second direction (Y-axis direction) of the surface 130s on the frame body 120 side of the piezoelectric body 131 in the unimorph piezoelectric vibrator 130 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, and the average distance L3 in the second direction (Y-axis direction) between the edge 120e on the other side in the second direction (Y-axis direction) of the inner peripheral surface of the frame body 120 and the edge 130e on the other side in the second direction (Y-axis direction) of the surface 130s on the frame body 120 side of the piezoelectric body 131 in the unimorph piezoelectric vibrator 130 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 the unimorph piezoelectric vibrator included in the ultrasonic transducer according to Embodiment 1 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 ends in the third direction (Z-axis direction) of each of the pair of long-side portions 121 of the frame body 120, and faces the first diaphragm 110 with the inner space of the frame body 120 therebetween.

[0028] As shown in FIGS. 1, 2, and 5, the unimorph piezoelectric vibrator 130 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 5, in the present embodiment, the piezoelectric body 131 is sandwiched between the first electrode 132 and the 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 capable of applying an AC voltage.

[0029] FIG. 6 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 1 of the present invention transmits or receives ultrasonic waves. FIG. 7 is a cross-sectional view of the ultrasonic transducer of FIG. 6 viewed from the direction of the arrow VII-VII. As simulation analysis conditions, the thickness of the first diaphragm 110 was set to 0.1 mm, the thickness of the piezoelectric body 131 was set to 0.1 mm, the thickness of the second diaphragm 135 was set to 0.2 mm, the longitudinal dimension L1 inside the frame body 120 was set to 20 mm, the lateral dimension L2 was set to 1.8 mm, and the thickness of the frame body 120 in the third direction (Z-axis direction) was set to 0.4 mm.

[0030] As shown in FIGS. 6 and 7, in the vibration mode of the ultrasonic transducer 100 according to Embodiment 1 of the present invention, the first diaphragm 110 resonates in a reverse phase to the unimorph piezoelectric vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 110. That is, as shown in FIG. 7, the displacement direction of the resonance vibration Bm of the first diaphragm 110 and the displacement direction of the resonance vibration Bp of the unimorph piezoelectric vibrator 130 are opposite to each other in the third direction (Z-axis direction). In the present embodiment, the resonance frequencies of the first diaphragm 110 and the unimorph piezoelectric vibrator 130 are 100 kHz or higher.

[0031] In the first diaphragm 110, an intermediate portion 110c located above the middle in the longitudinal direction inside the frame body 120 becomes an antinode of resonance vibration, and end portions 110e located at both ends in the longitudinal direction inside the frame body 120 become nodes of resonance vibration. That is, the portion of the first diaphragm 110 located above the inner space of the frame body 120 becomes a vibration region that resonates. The longitudinal dimension of the vibration region of the first diaphragm 110 is the same as the longitudinal dimension L1 inside the frame body 120, and the lateral dimension of the vibration region of the first diaphragm 110 is the same as the lateral dimension L2 inside the frame body 120.

[0032] Here, the relationship between the resonance frequency of the first diaphragm 110 and the longitudinal dimension L1 inside the frame body 120 will be described.

[0033] FIG. 8 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the resonance frequency of the first diaphragm when the longitudinal dimension is changed while fixing the lateral dimension inside the frame. In FIG. 8, the vertical axis represents the resonance frequency (kHz) of the first diaphragm 110, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame 120. As a simulation analysis condition, the lateral dimension L2 inside the frame 120 was fixed at 2 mm.

[0034] As shown in FIG. 8, when the longitudinal dimension L1 inside the frame 120 is 2 mm, the resonance frequency of the first diaphragm 110 is 220 kHz. As the longitudinal dimension L1 increases up to 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 increases, the resonance frequency of the first diaphragm 110 decreases to 122 kHz. Thereafter, even when the longitudinal dimension L1 inside the frame 120 becomes larger than 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 becomes even larger, the resonance frequency of the first diaphragm 110 becomes substantially constant at 122 kHz.

[0035] That is, the resonance frequency of the first diaphragm 110 is determined by the speed of sound of the first diaphragm 110 and the reflection of the vibration with the frame 120 as a fixed end. However, when the longitudinal dimension L1 inside the frame 120 exceeds four times the lateral dimension L2, the influence of the lateral dimension L2 becomes dominant with respect to the reflection of the vibration, indicating that the state of the reflection of the vibration does not change even when the longitudinal dimension L1 becomes even larger than four times the lateral dimension L2.

[0036] Next, the results of a simulation analysis using the finite element method on the relationship between the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 100 and the longitudinal dimension L1 inside the frame 120 will be described.

[0037] FIG. 9 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer when the longitudinal dimension is changed while fixing the short-side dimension inside the frame. In FIG. 9, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame 120. As a simulation analysis condition, the short-side dimension L2 inside the frame 120 was fixed at 2 mm, and the sound pressure (Pa) at a position 30 cm away from the first diaphragm 110 on the front surface of the ultrasonic transducer 100 in the third direction (Z-axis direction) was calculated.

[0038] As shown in FIG. 9, as the longitudinal dimension L1 inside the frame 120 increases, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 increases. This means that even when the longitudinal dimension of the vibration region of the first diaphragm 110 is increased, the entire vibration region of the first diaphragm 110 between both end portions 110e vibrates. That is, the area of the vibration region can be increased by the amount that the vibration region of the first diaphragm 110 becomes longer, and as a result, the pressure change of the air due to the vibration of the first diaphragm 110 can be increased to obtain a high sound pressure.

[0039] Thus, the ultrasonic transducer 100 according to the present embodiment can increase the sound pressure while maintaining the resonance frequency substantially constant by increasing the longitudinal dimension of the vibration region of the first diaphragm 110. Further, since there are node points at both end portions in the longitudinal direction, both end portions can be supported or fixed, so that the ultrasonic transducer 100 can be easily mounted.

[0040] Next, the results of a simulation analysis using the finite element method for the relationship between the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer and the minimum dimension Lm of the piezoelectric body 131 in the second direction (Y-axis direction) will be described.

[0041] FIG. 10 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer when the minimum dimension in the second direction (Y-axis direction) of the ultrasonic vibrator is changed. In FIG. 10, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer, and the horizontal axis represents the minimum dimension Lm (mm) of the piezoelectric body in the second direction (Y-axis direction).

[0042] As simulation analysis conditions, the dimension in the second direction (Y-axis direction) of the outer shape of the frame body 120 was set to 24 mm, the dimension in the first direction (X-axis direction) was set to 2.6 mm, the thickness in the third direction (Z-axis direction) of the frame body 120 was set to 0.4 mm, the longitudinal dimension L1 inside the frame body 120 was set to 20 mm, and the short-side dimension L2 was set to 1.8 mm. The dimensions of the outer shape of the first diaphragm 110 were the same as those of the outer shape of the frame body 120, and the thickness of the first diaphragm 110 was set to 0.1 mm. The dimension of the piezoelectric body 131 in the first direction (X-axis direction) was set to 2.4 mm, and the thickness of the piezoelectric body 131 was set to 0.1 mm. The piezoelectric body 131 was arranged so as to be point-symmetric with respect to the center of the frame body 120 when viewed from the third direction (Z-axis direction). The dimension of the second diaphragm 135 in the first direction (X-axis direction) was set to 1.5 mm, and the thickness of the second diaphragm 135 was set to 0.2 mm. The dimensions of the piezoelectric body 131 and the second diaphragm 135 in the second direction (Y-axis direction) were made the same. The sound pressure (Pa) at a position 30 cm away from the first diaphragm 110 on the front surface of the ultrasonic transducer in the third direction (Z-axis direction) was calculated.

[0043] 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 a first embodiment, in which a minimum dimension in a second direction (Y-axis direction) of a piezoelectric body is 24 mm, is transmitting or receiving ultrasonic waves. FIG. 12 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 embodiment, in which a minimum dimension in the second direction (Y-axis direction) of the piezoelectric body is 16 mm, is transmitting or receiving ultrasonic waves. FIG. 13 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when an ultrasonic transducer according to a third embodiment, in which a minimum dimension in the second direction (Y-axis direction) of the piezoelectric body is 15 mm, is transmitting or receiving ultrasonic waves. FIG. 14 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when an ultrasonic transducer according to a fourth embodiment, in which a minimum dimension in the second direction (Y-axis direction) of the piezoelectric body is 14.5 mm, is transmitting or receiving ultrasonic waves. FIG. 15 is a cross-sectional view of the ultrasonic transducer of FIG. 14 as viewed from the direction of the arrow XV-XV.

[0044] As shown in FIGS. 11 and 12, in the ultrasonic transducer 101 according to the first embodiment and the ultrasonic transducer 102 according to the second embodiment, in which the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body 131 is 16 mm or more, the first diaphragm 110 vibrates in a tuning fork vibration mode in which the intermediate portion 110c of the first diaphragm 110 becomes an antinode of resonance vibration. As shown in FIG. 13, in the ultrasonic transducer 103 according to the third embodiment, in which the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body 131 is 15 mm, the first diaphragm 110 vibrates in a vibration mode in which large displacement portions 110p where displacement is the largest appear in the vicinity of each of both longitudinal ends inside the frame body 120. However, the two large displacement portions 110p vibrate in the same phase, and the vibration in the first diaphragm 110 is in the same phase.

[0045] As shown in FIGS. 14 and 15, in the ultrasonic transducer 104 according to the fourth embodiment in which the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body 131 is 14.5 mm, in the first diaphragm 110, near each of both longitudinal ends inside the frame body 120, an anti-displacement portion 110b that displaces in a displacement direction Ds opposite to the displacement direction Dm of the intermediate portion 110c appears, and the first diaphragm 110 is vibrating in a vibration mode. That is, in the first diaphragm 110, vibrations with a phase opposite to that of the intermediate portion 110c occurred near each of both longitudinal ends inside the frame body 120.

[0046] As a result, as shown in FIG. 10, the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 104 according to the fourth embodiment in which the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body 131 is 14.5 mm is about half of the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 102 according to the second embodiment in which the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body 131 is 16 mm.

[0047] In the ultrasonic transducer 104 according to the fourth embodiment, the average distance L3 in the second direction (Y-axis direction) between at least one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame body 120 and at least one edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame body 120 side of the unimorph piezoelectric vibrator 130 is 2.75 mm, which is about 1.5 times the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120. That is, when the average distance L3 is about 1.5 times the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, vibrations with a phase opposite to each other occur in the first diaphragm 110.

[0048] By changing the dimension of the length of the unimorph piezoelectric vibrator 130 in the second direction (Y-axis direction) and the short dimension L2 in the first direction (X-axis direction) inside the frame 120, although there are some fluctuations, if the average distance L3 is 1.3 times or less the short dimension L2 in the first direction (X-axis direction) inside the frame 120, it was confirmed by simulation analysis using the finite element method that reverse-phase vibration does not occur in the first diaphragm 110. That is, if the average distance L3 is 1.3 times or less the short dimension L2 in the first direction (X-axis direction) inside the frame 120, it is possible to reduce the power consumption while maintaining a high sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer.

[0049] Here, the power consumption of the ultrasonic transducer will be described. The piezoelectric body 131 that constitutes the unimorph piezoelectric vibrator 130, particularly the piezoelectric ceramic, has a large dielectric constant and electrical characteristics like a capacitor. The impedance of a capacitor is proportional to 1 / ωC, where ω is the frequency of the alternating current and C is the capacitance. Therefore, when the frequency of the voltage applied to the piezoelectric body 131 increases, the impedance of the piezoelectric body 131 decreases and the consumption current increases. On the other hand, when the area of the piezoelectric body 131 is reduced, the capacitance decreases, so the consumption current decreases.

[0050] In the ultrasonic transducer 101 according to the first embodiment where the minimum dimension in the second direction (Y-axis direction) of the unimorph piezoelectric vibrator 130 is 24 mm, as shown in FIG. 11, at both ends in the longitudinal direction inside the frame 120 of the first diaphragm 110, the end portions 110e located thereon become nodes of resonant vibration and hardly vibrate. That is, both end portions in the second direction (Y-axis direction) of the unimorph piezoelectric vibrator 130 hardly vibrate and do not perform work.

[0051] Therefore, in the present embodiment, as shown in FIG. 4, the minimum dimension Lm of the piezoelectric body 131 in the second direction (Y-axis direction) is made smaller than the longitudinal dimension L1 of the inner side of the frame body 120 in the second direction (Y-axis direction) so that a gap is formed between at least one edge 120e of the inner peripheral surface 120s of the frame body 120 in the second direction (Y-axis direction) and at least one edge 130e of the surface 130s on the frame body 120 side of the piezoelectric body 131 shown in FIG. 2. As a result, both ends of the unimorph piezoelectric vibrator 130 in the second direction (Y-axis direction), which is a portion that consumes power but does not perform work as shown in FIG. 11, can be eliminated, and the power consumption of the unimorph piezoelectric vibrator 130 can be reduced and the efficiency can be improved.

[0052] Further, since the above gap is formed and the internal space inside the frame body 120 and the external space outside the frame body 120 communicate with each other through the above gap, for example, when heating and curing the adhesive joining the first diaphragm 110 and the frame body 120, the pressure change in the internal space can be reduced, and the increase in the internal stress in the ultrasonic transducer 100 can be suppressed. When the first diaphragm 110 and the frame body 120 are joined with an adhesive, in order to prevent the gap from being blocked by the adhesive applied to the long side portion 121 of the frame body 120 and entering the gap, the average distance L3 in the second direction (Y-axis direction) of the gap is preferably 0.2 mm or more. That is, the average distance L3 in the second direction (Y-axis direction) of the gap is preferably 0.2 mm or more and 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) of the inner side of the frame body 120.

[0053] FIG. 16 is a view of the ultrasonic transducer according to the fifth embodiment of Embodiment 1 of the present invention as seen from the ultrasonic vibrator side. As shown in FIG. 16, in the ultrasonic transducer 105 according to the fifth embodiment of Embodiment 1 of the present invention, the edge 120e on one side in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame 120 and the piezoelectric body 131 in the unimorph piezoelectric vibrator 130 The average distance L3 in the second direction (Y-axis direction) of the gap between the edge 130e on one side in the second direction (Y-axis direction) of the surface 130s on the frame 120 side is the short side dimension L2 in the first direction (X-axis direction) inside the frame 120 It is 1.3 times or less, and the edge 120e on the other side in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame 120 and the piezoelectric body 131 in the unimorph piezoelectric vibrator 130 The gap between the edge 130e on the other side in the second direction (Y-axis direction) of the surface 130s on the frame 120 side is not formed. That is, only one of both ends in the second direction (Y-axis direction) of the unimorph piezoelectric vibrator 130, which is a portion that consumes power and does not perform work as shown in FIG. 11, may be eliminated.

[0054] FIG. 17 is a view of the ultrasonic transducer according to the sixth embodiment of Embodiment 1 of the present invention as seen from the ultrasonic vibrator side. As shown in FIG. 17, in the ultrasonic transducer 106 according to the sixth embodiment of Embodiment 1 of the present invention, when viewed from the third direction (Z-axis direction), the piezoelectric body 131 in the unimorph piezoelectric vibrator 130 The edge 130e on one side in the second direction (Y-axis direction) of the surface 130s on the frame 120 side is not parallel to at least one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame 120. In such a case, at least one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame 120 and the piezoelectric body 131 in the unimorph piezoelectric vibrator 130 shown in FIG. 2 The average distance L3 in the second direction (Y-axis direction) of the gap between the edge 130e on one side in the second direction (Y-axis direction) of the surface 130s on the frame 120 side is the average value of the shortest distance between the edge 120e and the edge 130e that changes depending on the position in the first direction (X-axis direction), and the average distance L3 is the frame It suffices that it is 1.3 times or less of the short side dimension L2 in the first direction (X-axis direction) inside 120.

[0055] FIG. 18 is a cross-sectional view showing the configuration of an ultrasonic transducer according to a seventh embodiment of Embodiment 1 of the present invention. As shown in FIG. 18, the average distance L3 in the second direction (Y-axis direction) between at least one edge 120e in the second direction (Y-axis direction) on the inner peripheral surface of the frame 120 and at least one edge 130e in the second direction (Y-axis direction) on the surface 130s on the frame 120 side of the unimorph piezoelectric vibrator 130 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame 120. Thereby, in the ultrasonic transducer 100d, it is possible to increase the sound pressure level while reducing power consumption with a simple and downsized configuration.

[0056] A part of the surface 131b of the piezoelectric body 131 on the side opposite to the frame 120 side is not covered by the second diaphragm 135. Specifically, since the second diaphragm 135 is displaced in the second direction (Y-axis direction) with respect to the piezoelectric body 131, a part of the surface 131b of the piezoelectric body 131 on the side opposite to the frame 120 side is exposed without being covered by the second diaphragm 135. Thereby, it becomes possible to easily connect the wiring 10 for supplying power to the piezoelectric body 131 to a part of the surface 131b of the piezoelectric body 131 on the side opposite to the frame 120 side that is not covered by the second diaphragm 135. Note that the dimension of the second diaphragm 135 in the second direction (Y-axis direction) may be larger, smaller, or the same as the dimension of the piezoelectric body 131 in the second direction (Y-axis direction).

[0057] Here, the relationship between each of 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 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 120 and the other edge 135s2 in the first direction (X-axis direction) of the second diaphragm 135, and the displacement of the first diaphragm 110 will be described with respect to the results of a first experimental example obtained by simulation analysis.

[0058] FIG. 19 is a graph showing the transition of the displacement of the first diaphragm when the short-side dimension W of the second diaphragm is changed while fixing the center position of the second diaphragm in the first direction (X-axis direction) in the first experimental example, obtained by simulation analysis using the finite element method. In FIG. 19, the displacement (μm) of the first diaphragm 110 is shown on the vertical axis, and the short-side dimension W (mm) of the second diaphragm is shown on the horizontal axis.

[0059] As the simulation analysis conditions in the first experimental example, the thickness of the first diaphragm 110 in the third direction (Z-axis direction) is 0.1 mm, the longitudinal dimension of the piezoelectric body 131 in the second direction (Y-axis direction) is 18 mm, the thickness of the piezoelectric body 131 in the third direction (Z-axis direction) is 0.1 mm, the longitudinal dimension L1 inside the frame body 120 is 20 mm, the short-side dimension L2 is 1.8 mm, the thickness of the frame body 120 in the third direction (Z-axis direction) is 0.4 mm, the thickness of the second diaphragm 135 in the third direction (Z-axis direction) is 0.2 mm, and the longitudinal dimension of the second diaphragm 135 in the second direction (Y-axis direction) is 18 mm. The material of the first diaphragm 110 is an aluminum alloy, the material of the frame body 120 is stainless steel, and the material of the second diaphragm 135 is an iron-nickel alloy (42Ni-Fe). The center position of the second diaphragm 135 in the first direction (X-axis direction) is made to coincide with the center position of the inner space of the frame body 120 in the first direction (X-axis direction).

[0060] FIG. 20 is a cross-sectional view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the first comparative example, in which the short-side dimension W in the first direction (X-axis direction) of the second diaphragm is 1 mm and each of the average distances D1 and D2 is 0.4 mm, in the first experimental example is transmitting or receiving ultrasonic waves.

[0061] FIG. 21 is a cross-sectional view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the eighth embodiment, in which the short-side dimension W in the first direction (X-axis direction) of the second diaphragm is 1.5 mm and each of the average distances D1 and D2 is 0.15 mm, in the first experimental example is transmitting or receiving ultrasonic waves.

[0062] FIG. 22 is a cross-sectional view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the second comparative example, in the first experimental example, has a short-side dimension W of 2 mm in the first direction (X-axis direction) of the second diaphragm and each of the average distances D1 and D2 is -0.1 mm, while transmitting or receiving ultrasonic waves. FIGS. 20 to 22 are illustrated in the same cross-sectional view as FIG. 7, and are shown in a gray scale where the higher the tensile stress in the first direction (X-axis direction), the whiter it becomes, and the higher the compressive stress in the first direction (X-axis direction), the blacker it becomes.

[0063] As shown in FIG. 19, in the first experimental example, when the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.2 mm or more and 1.8 mm or less, that is, when each of the average distances D1 and D2 is 0 mm or more and 0.3 mm or less, the displacement of the first diaphragm 110 can be ensured at a high level of 0.56 μm or more in the range of the resonance frequency of 150 kHz or more and 160 kHz or less, and the transmission sound pressure and reception sensitivity of the ultrasonic transducer 100 can be increased.

[0064] As shown in FIG. 20, when each of the average distances D1 and D2 is 0.3 mm or more, in the stress distribution within the piezoelectric body 131, the portions where tensile stress is generated and the portions where compressive stress is generated are dispersed, the vibration efficiency of the piezoelectric body 131 is reduced, and the displacement of the first diaphragm 110 is decreased.

[0065] As shown in FIG. 21, when each of the average distances D1 and D2 is 0 or more and 0.3 mm or less, in the stress distribution within the piezoelectric body 131, portions where high compressive stress is generated exist as a whole, the vibration efficiency of the piezoelectric body 131 is improved, and the displacement of the first diaphragm 110 is increased.

[0066] As shown in FIG. 22, when the second diaphragm 135 protrudes outside the region sandwiched between both end edges in the first direction (X-axis direction) on the inner peripheral surface of the frame body 120 in the first direction (X-axis direction) as viewed from the third direction (Z-axis direction) orthogonal to the first diaphragm 110, the piezoelectric body 131 is restrained and it becomes difficult to vibrate, and the stress in the piezoelectric body 131 is overall low. As a result, the vibration efficiency of the piezoelectric body 131 decreases, and the displacement of the first diaphragm 110 becomes small.

[0067] According to the operating mechanism shown in FIGS. 20 to 22, when the central position of the second diaphragm 135 in the first direction (X-axis direction) coincides with the central position of the inner space of the frame body 120 in the first direction (X-axis direction), when each of the average distance D1 and the average distance D2 in the second diaphragm 135 is 1 / 6 or less of the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, it is considered that the displacement of the first diaphragm 110 can be increased and the transmission sound pressure and reception sensitivity of the ultrasonic transducer 100 can be increased.

[0068] Hereinafter, the results of analysis with the simulation analysis conditions changed from the first experimental example will be described. Regarding the following analysis results, only the conditions changed from the first experimental example are described, and the conditions not described are the same as the analysis conditions of the first experimental example.

[0069] FIG. 23 is a graph obtained by performing simulation analysis using the finite element method on the transition of the displacement of the first diaphragm when, in the second experimental example, the thickness of the piezoelectric body is changed to 0.2 mm from the analysis conditions of the first experimental example and the short-side dimension W of the second diaphragm is changed while fixing the central position of the second diaphragm in the first direction (X-axis direction).

[0070] As shown in Fig. 23, in the second experimental example, when the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.2 mm or more and 1.8 mm or less, that is, when each of the average distance D1 and the average distance D2 is 0 mm or more and 0.3 mm or less, the displacement of the first diaphragm 110 can be ensured at a high level of 0.31 μm or more in the range of the resonance frequency of 158 kHz or more and 159 kHz or less, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 could be increased.

[0071] Fig. 24 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the displacement of the first diaphragm when, in the third experimental example, the thickness of the second diaphragm was changed to 0.3 mm from the analysis conditions of the first experimental example, and the short-side dimension W of the second diaphragm was changed while fixing the center position of the second diaphragm in the first direction (X-axis direction).

[0072] As shown in Fig. 24, in the third experimental example, when the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.2 mm or more and 1.8 mm or less, that is, when each of the average distance D1 and the average distance D2 is 0 mm or more and 0.3 mm or less, the displacement of the first diaphragm 110 can be ensured at a high level of 0.55 μm or more in the range of the resonance frequency of 150 kHz or more and 160 kHz or less, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 could be increased.

[0073] Fig. 25 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the displacement of the first diaphragm when, in the fourth experimental example, the short-side dimension inside the frame was changed to 2.2 mm from the analysis conditions of the first experimental example, and the short-side dimension W of the second diaphragm was changed while fixing the center position of the second diaphragm in the first direction (X-axis direction).

[0074] As shown in Fig. 25, in the fourth experimental example, when the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.6 mm or more and 2.2 mm or less, that is, when each of the average distance D1 and the average distance D2 is 0 mm or more and 0.3 mm or less, the displacement of the first diaphragm 110 can be ensured at a high level of 0.65 μm or more in the range of the resonance frequency of 100 kHz or more and 110 kHz or less, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 can be increased.

[0075] Fig. 26 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the displacement of the first diaphragm when, in the fifth experimental example, the thickness of the piezoelectric body is changed to 0.2 mm and the short-side dimension inside the frame is changed to 2.2 mm from the analysis conditions of the first experimental example, and the short-side dimension W of the second diaphragm is changed while fixing the center position of the second diaphragm in the first direction (X-axis direction).

[0076] As shown in Fig. 26, in the fifth experimental example, when the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.6 mm or more and 2.2 mm or less, that is, when each of the average distance D1 and the average distance D2 is 0 mm or more and 0.3 mm or less, the displacement of the first diaphragm 110 can be ensured at a high level of 0.44 μm or more at the resonance frequency of 108 kHz, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 can be increased.

[0077] Fig. 27 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the displacement of the first diaphragm when, in the sixth experimental example, the material of the second diaphragm is changed to a piezoelectric ceramic from the analysis conditions of the first experimental example, and the short-side dimension W of the second diaphragm is changed while fixing the center position of the second diaphragm in the first direction (X-axis direction).

[0078] As shown in FIG. 27, in the sixth experimental example, when the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.2 mm or more and 1.8 mm or less, that is, when each of the average distance D1 and the average distance D2 is 0 mm or more and 0.3 mm or less, the displacement of the first diaphragm 110 can be ensured at a high level of 0.55 μm or more in the range of the resonance frequency of 150 kHz or more and 160 kHz or less, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 can be increased.

[0079] Next, the transition of the displacement of the first diaphragm when the short-side dimension W of the second diaphragm is changed while shifting the center position of the second diaphragm in the first direction (X-axis direction) will be described with reference to the results of the seventh experimental example obtained by performing simulation analysis using the finite element method.

[0080] FIG. 28 is a graph showing the transition of the displacement of the first diaphragm when the center position of the second diaphragm in the first direction (X-axis direction) is shifted in the seventh experimental example, obtained by performing simulation analysis using the finite element method. In FIG. 28, the displacement (μm) of the first diaphragm 110 is shown on the vertical axis, and the amount of shift (mm) of the center position of the second diaphragm in the first direction (X-axis direction) is shown on the horizontal axis. In FIG. 28, the data of the short-side dimension W of the second diaphragm is shown as a solid line for 1.5 mm, a dotted line for 1.4 mm, a one-dot chain line for 1.3 mm, and a two-dot chain line for 1.2 mm.

[0081] As the simulation analysis conditions in the seventh experimental example, other conditions are the same as those in the first experimental example. Also, the direction of shifting the center position of the second diaphragm is one of the first directions (X-axis direction), and the center position of the second diaphragm is shifted until the average distance D1 becomes 0 mm.

[0082] FIG. 29 is a cross-sectional view showing the displacement state obtained by performing simulation analysis using the finite element method when the ultrasonic transducer according to the ninth embodiment, in which the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.5 mm, the amount of shift of the center position of the second diaphragm in the first direction (X-axis direction) is 0.15 mm, the average distance D1 is 0 mm, and the average distance D2 is 0.3 mm, is transmitting or receiving ultrasonic waves in the seventh experimental example.

[0083] FIG. 30 is a cross-sectional view showing a displacement state obtained by performing simulation analysis using the finite element method when the ultrasonic transducer according to the third comparative example, in the seventh experimental example, has a short-side dimension W in the first direction (X-axis direction) of the second diaphragm of 1.2 mm, a deviation amount of the center position of the second diaphragm in the first direction (X-axis direction) of 0.3 mm, an average distance D1 of 0 mm, and an average distance D2 of 0.6 mm, and is transmitting or receiving ultrasonic waves.

[0084] As shown in FIG. 28, in the seventh experimental example, when the short-side dimension W in the first direction (X-axis direction) of the second diaphragm is 1.2 mm, when the deviation amount of the center position of the second diaphragm in the first direction (X-axis direction) is 0 mm, that is, when each of the average distance D1 and the average distance D2 is 0.3 mm, the displacement of the first diaphragm 110 can be ensured at a high level of 0.56 μm or more, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 could be increased.

[0085] When the short-side dimension W in the first direction (X-axis direction) of the second diaphragm is 1.3 mm, when the deviation amount of the center position of the second diaphragm in the first direction (X-axis direction) is within 0.1 mm, that is, when the average distance D2 is within 0.35 mm, the displacement of the first diaphragm 110 can be ensured at a high level of 0.56 μm or more, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 could be increased.

[0086] When the short-side dimension W in the first direction (X-axis direction) of the second diaphragm is 1.4 mm, when the deviation amount of the center position of the second diaphragm in the first direction (X-axis direction) is within 0.15 mm, that is, when the average distance D2 is within 0.35 mm, the displacement of the first diaphragm 110 can be ensured at a high level of 0.56 μm or more, and the transmission sound pressure and the reception sensitivity of the ultrasonic transducer 100 could be increased.

[0087] When the short-side dimension W of the second diaphragm in the first direction (X-axis direction) is 1.5 mm, and when the deviation amount of the center position of the second diaphragm in the first direction (X-axis direction) is within 0.15 mm, that is, when the average distance D2 is within 0.3 mm, the displacement of the first diaphragm 110 can be ensured at a high level of 0.56 μm or more, and the transmission sound pressure and reception sensitivity of the ultrasonic transducer 100 could be increased.

[0088] As shown in FIG. 29, when the average distance D2 is 0.3 mm, in the stress distribution within the piezoelectric body 131, high compressive stress is generated in the portion on the second diaphragm 135, and high tensile stress is generated in the portion corresponding to the average distance D2. However, the vibration mode is maintained, and no significant decrease in the displacement of the first diaphragm 110 was observed.

[0089] As shown in FIG. 30, when the average distance D2 is 0.6 mm, in the stress distribution within the piezoelectric body 131, high compressive stress is generated in the portion on the second diaphragm 135, and high tensile stress is generated in the portion corresponding to the average distance D2. The vibration mode has changed and the first diaphragm 110 is deformed into a distorted shape, and a significant decrease in the displacement of the first diaphragm 110 was observed.

[0090] According to the operating mechanism shown in FIGS. 29 and 30, when the center position of the second diaphragm 135 in the first direction (X-axis direction) is deviated from the center position of the inner space of the frame body 120 in the first direction (X-axis direction), if each of the average distance D1 and the average distance D2 is 1 / 6 or less of the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120, it is considered that the displacement of the first diaphragm 110 can be ensured at a high level of 0.56 μm or more, and the transmission sound pressure and reception sensitivity of the ultrasonic transducer 100 can be increased.

[0091] From the results of the first to seventh experimental examples described above, when viewed from the third direction (Z-axis direction) in which the second diaphragm 135 is orthogonal to the first diaphragm 110, in the first direction (X-axis direction), the second diaphragm 135 is located within a region sandwiched between both end edges in the first direction (X-axis direction) on the inner peripheral surface of the frame body 120. And in the second diaphragm 135, the average distance D1 in the first direction (X-axis direction) between one end edge 120s1 in the first direction (X-axis direction) on the inner peripheral surface of the frame body 120 and one end 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 end edge 120s2 in the first direction (X-axis direction) on the inner peripheral surface of the frame body 120 and the other end 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. It is considered that the displacement of the first diaphragm 110 can be increased and the transmission sound pressure and reception sensitivity of the ultrasonic transducer 100 can be increased.

[0092] In the parametric speaker including the ultrasonic transducer 100 according to Embodiment 1 of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic wave radiated from the ultrasonic transducer 100 by the modulation drive of the ultrasonic transducer 100. As modulation methods, there are an AM modulation method (amplitude modulation method) and an FM modulation method (frequency modulation method).

[0093] FIG. 31 is a perspective view of the ultrasonic transducer according to the first modification of Embodiment 1 of the present invention as viewed from the second diaphragm side. As shown in FIG. 31, in the ultrasonic transducer 100a according to the first modification of Embodiment 1 of the present invention, the length of the second diaphragm 135 in the second direction (Y-axis direction) is longer than the length of the piezoelectric body 131 in the second direction (Y-axis direction). Each of the frame body 120 and the second diaphragm 135 is plated with Ag or the like. The frame body 120 and the piezoelectric body 131 are electrically connected by pressure bonding, and the piezoelectric body 131 and the second diaphragm 135 are electrically connected by pressure bonding. Thereby, the wiring 10 for supplying power to the piezoelectric body 131 can be easily connected to each end in the second direction (Y-axis direction) of the frame body 120 and the second diaphragm 135.

[0094] FIG. 32 is a perspective view of the ultrasonic transducer according to the second modification of Embodiment 1 of the present invention as viewed from the first diaphragm side. As shown in FIG. 32, in the ultrasonic transducer 100b according to the second modification of Embodiment 1 of the present invention, a slit 110s extending in the first direction (X-axis direction) is formed in the first diaphragm 110. In this modification, the length dimension of the slit 110s in the first direction (X-axis direction) is the same as the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120. The width dimension of the slit 110s in the second direction (Y-axis direction) is 0.4 mm or more and 0.6 mm or less. The slit 110s is formed from a position on the edge in the second direction (Y-axis direction) of the inner peripheral surface of the frame body 120 to a position inward by the above width dimension in the second direction (Y-axis direction). The two slits 110s are each open at both ends in the second direction (Y-axis direction) inside the frame body 120.

[0095] As a result, since the internal space inside the frame body 120 and the external space outside the frame body 120 communicate with each other through the slit 110s, for example, when heating and curing an adhesive for joining the first diaphragm 110 and the frame body 120, the pressure change in the internal space can be reduced, and an increase in the internal stress in the ultrasonic transducer 100 can be suppressed. In addition, since the portion adjacent to the slit 110s becomes the free end of the first diaphragm 110 that resonates and vibrates and is easily displaced, the internal stress generated in the resonating and vibrating first diaphragm 110 can be reduced. Therefore, in the ultrasonic transducer 100, it is possible to increase the sound pressure level while reducing the internal stress with a simple and miniaturized configuration.

[0096] (Embodiment 2) Hereinafter, the ultrasonic transducer according to Embodiment 2 of the present invention will be described with reference to the drawings. Since the ultrasonic transducer according to Embodiment 2 of the present invention is different from the ultrasonic transducer according to Embodiment 1 of the present invention in that a plurality of unimorph piezoelectric vibrators are arranged in an array, the description of the same configuration as that of the ultrasonic transducer according to Embodiment 1 of the present invention will not be repeated.

[0097] FIG. 33 is a side view showing the configuration of the ultrasonic transducer according to Embodiment 2 of the present invention. FIG. 34 is a rear view of the ultrasonic transducer shown in FIG. 33 as viewed from the direction of arrow XXXIV. FIG. 35 is an exploded perspective view showing the laminated state of each component of the ultrasonic transducer according to Embodiment 2 of the present invention.

[0098] As shown in FIGS. 33 to 35, in the ultrasonic transducer 200 according to Embodiment 2 of the present invention, the ultrasonic transducers 100 according to Embodiment 1 arranged in an array side by side in the first direction (X-axis direction) are integrally formed. The ultrasonic transducer 200 includes a first diaphragm 210, a plurality of frames 220, and a plurality of unimorph piezoelectric vibrators 230. A plurality of frames 220 are joined to the first diaphragm 210, and a plurality of unimorph piezoelectric vibrators 230 are respectively joined to the plurality of frames 220.

[0099] Here, a method for manufacturing the ultrasonic transducer 200 will be described. As shown in FIG. 35, the first diaphragm 210 has a flat plate shape, and a plurality of slits 211 extending in the second direction (Y-axis direction) are formed at intervals in the first direction (X-axis direction). The first diaphragm 210 is made of an aluminum alloy such as geramine containing aluminum, or a metal such as stainless steel. In the present embodiment, the first diaphragm 210 is made of stainless steel. The plurality of slits 211 are formed by etching or cutting or the like.

[0100] Each of the plurality of frames 220 has a rectangular annular shape. Each of the plurality of frames 220 has a short side direction along the first direction (X-axis direction) and a long side direction along the second direction (Y-axis direction). Each of the plurality of frames 220 extends 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). Each of the plurality of frames 220 has a pair of long side portions 221 extending in the second direction (Y-axis direction) and a pair of short side portions 222 extending in the first direction (X-axis direction). The shortest distance between the long side portions 221 is at least four times the shortest distance between the short side portions 222.

[0101] The plurality of frames 220 are arranged side by side in the first direction (X-axis direction). A slit 223 is formed between adjacent frames 220 in the first direction (X-axis direction). The plurality of slits 223 are formed by etching, cutting, or the like. The long side portions 221 adjacent to each other in adjacent frames 220 in the first direction (X-axis direction) are separated from each other by the slit 223.

[0102] Adjacent frames 220 in the first direction (X-axis direction) are connected at the short side portions 222. That is, adjacent frames 220 in the short side direction among the plurality of frames 220 are connected at both ends in their longitudinal directions.

[0103] Each of the plurality of frames 220 is formed of a metal such as an aluminum alloy or stainless steel, glass epoxy, resin, or the like. In the present embodiment, the plurality of frames 220 are formed from a single thin plate, but the present invention is not limited thereto, and short side portions 222 of the plurality of frames 220 respectively formed from a plurality of thin plates may be joined to each other to be integrated.

[0104] FIG. 36 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 Embodiment 2 of the present invention. As shown in FIG. 36, the slit 211 and the slit 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 dicing saw or the like along a plurality of cut lines LC extending in the second direction (Y-axis direction) so as to overlap the slit 211 and the slit 223 in the third direction (Z-axis direction).

[0105] As shown in FIG. 35, the second diaphragms 235 adjacent to each other in the first direction (X-axis direction) are connected by a connecting portion 236 at positions near both ends in the second direction (Y-axis direction) of each other. The connecting portion 236 extends in the first direction (X-axis direction). The connecting portion 236 is formed by etching, pressing, cutting, or the like.

[0106] A recess 237 is formed in a portion of the connecting portion 236 that faces the gap between the piezoelectric bodies 131 adjacent to each other in the first direction (X-axis direction) among the plurality of unimorph piezoelectric vibrators 230. The recess 237 is formed by half etching, pressing, cutting, or the like.

[0107] The second diaphragm 235 is bonded to the piezoelectric body 131 with an adhesive so that the recess 237 faces the cut line LC in the third direction (Z-axis direction). As a result, as shown in FIG. 34, each of the plurality of unimorph piezoelectric vibrators 230 includes a piezoelectric body 131 facing the first diaphragm 210 with a gap therebetween and a plurality of second diaphragms 235 provided on the side opposite to the frame body 220 side of the piezoelectric body 131. The plurality of unimorph piezoelectric vibrators 230 are arranged side by side in the first direction (X-axis direction).

[0108] The recess 237 functions as a reservoir for the adhesive and suppresses the adhesive from entering the cut line LC. Thereby, it is possible to suppress the characteristics of the ultrasonic transducer 200 from deteriorating due to interference between the adjacent unimorph piezoelectric vibrators 230.

[0109] In this embodiment, each of the frame body 220 and the second diaphragm 235 is plated with, for example, Ag. The frame body 220 and the piezoelectric body 131 are electrically connected by pressure bonding, and the piezoelectric body 131 and the second diaphragm 235 are electrically connected by pressure bonding. As a result, as shown in FIG. 34, by connecting the wiring 10 for supplying power to the piezoelectric body 131 only to two locations at the ends of each of the frame body 220 and the second diaphragm 235 in the second direction (Y-axis direction), a plurality of unimorph-type piezoelectric vibrators 230 can be driven.

[0110] Since the ultrasonic transducer 100 according to Embodiment 1 has node points at both ends in the longitudinal direction, which is the second direction (Y-axis direction), even if the ultrasonic transducers 100 according to Embodiment 1 are connected to each other at these both ends to form an array and the ultrasonic transducer 200 according to Embodiment 2 is configured, the resonant vibration in each ultrasonic transducer 100 is not inhibited. Therefore, by increasing the number of ultrasonic transducers 100 that make up the ultrasonic transducer 200 according to Embodiment 2, the sound pressure level can be easily increased.

[0111] In a parametric speaker including the ultrasonic transducer 200 according to Embodiment 2 of the present invention, it is possible to modulate the ultrasonic waves radiated from the ultrasonic transducer 200 by the modulation drive of the ultrasonic transducer 200 and reproduce audible sound.

[0112] In a parametric speaker including the ultrasonic transducer 200 according to this embodiment that transmits ultrasonic waves with a frequency of 100 kHz or higher, it is possible to suppress the sound from reaching unnecessarily far and the sound leakage due to unnecessary reflections, and reproduce audible sound only in a limited space. Further, in the ultrasonic transducer 200, since it is possible to significantly increase the attenuation due to the propagation distance of the audible sound without providing a configuration for transmitting a carrier wave with an inverse phase as in Patent Document 2, it is possible to achieve a simple and downsized configuration. Furthermore, since ultrasonic waves with a frequency of 100 kHz or higher are outside the audible range of animals such as dogs or cats, it is possible to suppress the influence on these animals.

[0113] In order to cause the audible sound to attenuate when the propagation distance is 30 cm or more, it is necessary to set the Rayleigh distance to 30 cm or less. The Rayleigh distance R0 satisfies the relationship of R0 = (k × a 2 ) / 2. k is the wave number, and a is the radius of the sound source. Therefore, assuming the speed of sound in air is 340 m / s, when the frequency of the ultrasonic wave is 100 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 36 mm or less. When the frequency of the ultrasonic wave is 150 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 29.4 mm or less. When the frequency of the ultrasonic wave is 200 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 25.5 mm or less. When the frequency of the ultrasonic wave is 100 kHz or higher, the longitudinal dimension L1 is 4 times or more and 24 times or less the transverse dimension L2.

[0114] (Appendix) Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following aspects.

[0115] <1> A first diaphragm, At least one frame extending in the longitudinal direction and joined to the first diaphragm, At least one unimorph piezoelectric vibrator including a piezoelectric body respectively attached to the at least one frame and spaced apart from the first diaphragm, and a second diaphragm provided on the side opposite to the frame side of the piezoelectric body. The first diaphragm resonates in a reverse phase to the at least one unimorph piezoelectric vibrator in a direction orthogonal to the first diaphragm. The dimension in the longitudinal direction inside the at least one frame is 4 times or more the dimension in the short direction orthogonal to the longitudinal direction inside the at least one frame. When viewed from a direction orthogonal to the first diaphragm, the second diaphragm is located within a region sandwiched between both end edges in the short direction on the inner peripheral surface of the at least one frame in the short direction, and the average distance in the short direction between one end edge in the short direction on the inner peripheral surface of the at least one frame and one end edge in the short direction of the second diaphragm, and the average distance in the short direction between the other end edge in the short direction on the inner peripheral surface of the at least one frame and the other end edge in the short direction of the second diaphragm are each 1 / 6 or less of the dimension in the short direction inside the at least one frame. An ultrasonic transducer.

[0116] <2> The dimension in the longitudinal direction inside the at least one frame is larger than the minimum dimension of the piezoelectric body in the longitudinal direction of the at least one unimorph piezoelectric vibrator. The average distance in the longitudinal direction of the gap between at least one end edge in the longitudinal direction on the inner peripheral surface of the at least one frame and at least one end edge in the longitudinal direction of the surface on the frame side of the piezoelectric body in the at least one unimorph piezoelectric vibrator is 1.3 times or less the dimension in the short direction inside the at least one frame. The ultrasonic transducer according to <1>.

[0117] <3> A plurality of the at least one frame are arranged side by side in the short direction and joined to the first diaphragm. The frames adjacent to each other in the short direction in the at least one frame are connected at both ends in the longitudinal direction thereof. The ultrasonic transducer according to <1> or <2>, wherein a plurality of the at least one unimorph piezoelectric vibrator are arranged side by side in the short-side direction.

[0118] <4> In the at least one unimorph piezoelectric vibrator, the second diaphragm plates adjacent to each other in the short-side direction are connected by a connecting portion extending in the short-side direction at positions near both ends in the longitudinal direction of each other. The ultrasonic transducer according to <3>, wherein a concave portion is formed in a portion of the connecting portion facing a gap between the piezoelectric bodies adjacent to each other in the short-side direction in the at least one unimorph piezoelectric vibrator.

[0119] <5> Comprising the ultrasonic transducer according to any one of <1> to <4>. A parametric speaker that reproduces audible sound by modulation driving of the ultrasonic transducer.

[0120] In the description of the above-described embodiments and examples, configurations that can be combined may be combined with each other.

[0121] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0122] 10 Wiring, 100, 100a, 100b, 100d, 101, 102, 103, 104, 105, 106, 200 Ultrasonic transducer, 110, 210 First diaphragm, 110b Reverse displacement portion, 110c Intermediate portion, 110e End portion, 110p Large displacement portion, 110s, 211, 223 Slit, 120, 220 Frame body, 120e, 120s1, 120s2, 130e, 135s1, 135s2 Edge, 120s Inner peripheral surface, 121, 221 Long side portion, 122, 222 Short side portion, 130, 230 Unimorph piezoelectric vibrator, 130s, 131b Surface, 131 Piezoelectric body, 132 First electrode, 133 Second electrode, 135, 235 Second diaphragm, 140 Processing circuit, 236 Connecting portion, 237 Recess.

Claims

1. A first diaphragm; At least one frame extending in a longitudinal direction and joined to the first diaphragm; at least one unimorph type piezoelectric vibrator attached to the at least one frame body, the vibrator 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; the first diaphragm resonates in an opposite phase to the at least one unimorph piezoelectric vibrator in a direction perpendicular to the first diaphragm, a longitudinal dimension of the at least one frame body on an inner side thereof is four times or more a lateral dimension of the at least one frame body on an inner side thereof, the lateral dimension being perpendicular to the longitudinal direction; An ultrasonic transducer in which the second vibration plate is located in an area sandwiched between both short-side edges of the inner surface of the at least one frame body in the short direction when viewed from a direction perpendicular to the first vibration plate, and the average distance in the short direction between one short-side edge of the inner surface of the at least one frame body and one short-side edge of the second vibration plate, and the average distance in the short direction between the other short-side edge of the inner surface of the at least one frame body and the other short-side edge of the second vibration plate, are each 1 / 6 or less of the short-side dimension inside the at least one frame body.

2. a longitudinal dimension inside the at least one frame body is greater than a minimum dimension of the piezoelectric body in the longitudinal direction of the at least one unimorph piezoelectric vibrator; An ultrasonic transducer as described in claim 1, wherein the average distance in the longitudinal direction of the gap between at least one longitudinal edge of the inner surface of the at least one frame body and at least one longitudinal edge of the frame body side surface of the piezoelectric body in the at least one unimorph type piezoelectric vibrator is 1.3 times or less the short side dimension inside the at least one frame body.

3. a plurality of the at least one frame members are arranged in the short-side direction and joined to the first diaphragm; The at least one frame body has two adjacent frame bodies in the short-side direction connected to each other at both ends in the long-side direction, 3. The ultrasonic transducer according to claim 1, wherein a plurality of the at least one unimorph type piezoelectric vibrators are arranged in the short side direction.

4. the second vibration plates adjacent to each other in the short-side direction in the at least one unimorph type piezoelectric vibrator are connected to each other by connecting portions extending in the short-side direction at positions near both ends in the longitudinal direction, 4. The ultrasonic transducer according to claim 3, wherein a recess is formed in a portion of the connecting portion facing a gap between the piezoelectric bodies adjacent in the short-side direction in the at least one unimorph piezoelectric vibrator.

5. The ultrasonic transducer according to claim 1, A parametric speaker that reproduces audible sound by modulating the ultrasonic transducer.

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