Ultrasonic transducer and parametric speaker including the same

Abstract

The present invention comprises a first vibration plate (110), at least one frame body (120), and at least one ultrasonic vibrator (130). The at least one frame body (120) extends in the longitudinal direction and is joined to the first vibration plate (110). The at least one ultrasonic vibrator (130) is attached to the at least one frame body (120), and faces the first vibration plate (110) with an interval therebetween. The first vibration plate (110) resonantly vibrates in antiphase with the at least one ultrasonic vibrator (130) in a direction orthogonal to the first vibration plate (110). The dimension of the at least one frame body (120) on the inside thereof in the longitudinal direction is greater than the dimension of the at least one frame body (120) on the inside thereof in the short direction orthogonal to the longitudinal direction. This ultrasonic transducer is provided with at least one opening which connects between an external space on the side opposite to the at least one frame body (120) across the first vibration plate (110) and an internal space inside the at least one frame body.

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 Japanese 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 the outer periphery thereof is substantially circular. The plurality of ultrasonic transducers are divided into two groups having 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 disposed 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 having different installation heights, and the configuration is complicated. In the superdirective acoustic device described in Patent Document 2, the second ultrasonic emitter is disposed 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 while reducing internal stress with a simple and miniaturized 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 ultrasonic vibrator. The at least one frame body extends in the longitudinal direction and is joined to the first diaphragm. The at least one ultrasonic vibrator is respectively attached to the at least one frame body and faces the first diaphragm with a gap therebetween. The first diaphragm resonates and vibrates in a reverse phase to the at least one ultrasonic vibrator in a direction orthogonal to the first diaphragm. The dimension in the longitudinal direction inside the at least one frame body is larger than the dimension in the short direction orthogonal to the longitudinal direction inside the at least one frame body. The ultrasonic transducer is provided with at least one opening that communicates an external space on the side opposite to the at least one frame body with respect to the first diaphragm and an internal space inside the at least one frame body.

Effects of the Invention

[0008] According to the present invention, it is possible to increase the sound pressure level while reducing internal stress with a simple and miniaturized configuration in the ultrasonic transducer.

Brief Description of the Drawings

[0009]

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Embodiments 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 description of the following 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-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 120, and an ultrasonic vibrator 130.

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

[0013] The frame body 120 has a rectangular annular shape. The frame body 120 has a short side direction along 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 epoxy resin or the like.

[0014] The frame body 120 is formed of a metal such as an aluminum alloy or stainless steel, glass epoxy, or 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 0.8 mm or less.

[0015] FIG. 3 is a perspective view showing the configuration of the 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 average distance between the short side portions 122 is 4 times or more the shortest distance 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 portion sandwiched between the long side portion 121 and the short side portion 122 may be chamfered. Further, the short side portion 122 is 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 more, 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 larger than the short-side dimension L2, and from the viewpoint of increasing the sound pressure level of the ultrasonic wave transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, 20 mm or more.

[0019] FIG. 4 is a cross-sectional view showing the configuration of an ultrasonic vibrator included in the ultrasonic transducer according to Embodiment 1 of the present invention. As shown in FIG. 1, the ultrasonic vibrator 130 is attached to the frame body 120 and faces the first diaphragm 110 with a gap therebetween. Specifically, the ultrasonic vibrator 130 is attached to the other end of the frame body 120 in the third direction (Z-axis direction), and faces the first diaphragm 110 with the internal space IS inside the frame body 120 interposed therebetween.

[0020] The ultrasonic transducer 100 is provided with at least one opening that communicates the external space ES on the side opposite to the frame body 120 with respect to the first diaphragm 110 and the internal space IS inside the frame body 120. In the present embodiment, as shown in FIG. 2, two openings are formed in the first diaphragm 110. Note that the opening is not limited to being formed in the first diaphragm 110, and a portion where the first diaphragm 110 does not cover a part of the inside of the frame body 120 may be formed as an opening due to the dimension of the first diaphragm 110 in the second direction (Y-axis direction) being smaller than the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120.

[0021] Each of the two openings is a slit 110s extending in the first direction (X-axis direction). Each of the two slits 110s extends by at least the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120. In the present embodiment, 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.

[0022] As shown in FIGS. 1, 2, and 4, the ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 4, in the present embodiment, the ultrasonic vibrator 130 includes two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are different from each other. Specifically, the polarization directions Dp of the two piezoelectric bodies 131 face each other in the third direction (Z-axis direction). The two piezoelectric bodies 131 are sandwiched between a first electrode 132 and a second electrode 133, and an intermediate electrode 134 is disposed between the two piezoelectric bodies 131. The first electrode 132 and the second electrode 133 are electrically connected to a processing circuit 140 capable of applying an AC voltage. The ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator. The total thickness of the two piezoelectric bodies 131 is, for example, 0.5 mm or more and 0.85 mm or less.

[0023] FIG. 5 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 is transmitting or receiving ultrasonic waves. FIG. 6 is a cross-sectional view of the ultrasonic transducer of FIG. 5 viewed from the direction of the arrow along line VI-VI. As simulation analysis conditions, the thickness of the first diaphragm 110 was set to 0.1 mm, the combined thickness of the two piezoelectric bodies 131 was set to 0.8 mm, the longitudinal dimension L1 inside the frame body 120 was set to 20 mm, the lateral dimension L2 was set to 2 mm, and the thickness of the frame body 120 in the third direction (Z-axis direction) was set to 0.4 mm. Two slits 110s each having a length dimension of 20 mm 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). That is, the width dimension of the two slits 110s was set to 0.5 mm.

[0024] As shown in FIGS. 5 and 6, in the vibration mode of the ultrasonic transducer 100 according to Embodiment 1 of the present invention, the first diaphragm 110 resonates and vibrates in a reverse phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 110. That is, as shown in FIG. 6, the displacement direction of the resonance vibration Bm of the first diaphragm 110 and the displacement direction of the resonance vibration Bp of the ultrasonic vibrator 130 are opposite to each other in the third direction (Z-axis direction). In the present embodiment, the resonance frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 are 100 kHz or higher.

[0025] A portion of the first diaphragm 110 that is located above the internal space IS inside the frame body 120 and is located between the slits 110s in the second direction (Y-axis direction) becomes a vibration region that resonates and vibrates. The longitudinal dimension of the vibration region of the first diaphragm 110 is the dimension between the slits 110s, 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. In the first diaphragm 110, an intermediate portion 110c located above the middle in the longitudinal direction inside the frame body 120 is largely displaced, and an end portion 110e located outside the slits 110s in the second direction (Y-axis direction) is hardly displaced.

[0026] Here, the relationship between the resonance frequency of the first diaphragm 110 and the longitudinal dimension L1 inside the frame 120 will be described.

[0027] FIG. 7 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 short transverse dimension inside the frame in the ultrasonic transducer according to Embodiment 1 of the present invention. In FIG. 7, 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 short transverse dimension L2 inside the frame 120 was fixed at 2 mm.

[0028] As shown in FIG. 7, regardless of the change in the longitudinal dimension L1 inside the frame 120, the resonance frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 became substantially constant at 130 kHz. That is, the resonance frequency of the first diaphragm 110 is determined by the sound velocity of the first diaphragm 110 and the reflection of the vibration with the frame 120 as a fixed end. However, regardless of the longitudinal dimension L1 inside the frame 120, the influence of the short transverse dimension L2 on the vibration reflection is dominant, indicating that the state of the vibration reflection does not change even when the longitudinal dimension L1 increases.

[0029] 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.

[0030] FIG. 8 is a graph obtained by performing simulation analysis using the finite element method on the transition of the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer according to Embodiment 1 of the present invention when the longitudinal dimension is changed while fixing the lateral dimension inside the frame. In FIG. 8, 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 simulation analysis conditions, the lateral 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.

[0031] As shown in FIG. 8, 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 the slits 110s 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.

[0032] 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. In addition, since there are node points at both longitudinal ends, these two ends can be supported or fixed, so that the ultrasonic transducer 100 can be easily mounted.

[0033] Here, an ultrasonic element array according to a first comparative example for obtaining a high sound pressure by arranging high-frequency ultrasonic elements side by side will be described.

[0034] FIG. 9 is a perspective view showing the configuration of the ultrasonic element array according to the first comparative example. As shown in FIG. 9, in the ultrasonic element array according to the first comparative example, a plurality of ultrasonic elements 800 are arranged side by side at intervals in the second direction (Y-axis direction). In such an ultrasonic element array, since there is a space where no sound pressure is generated between the ultrasonic elements 800, the efficiency is low. Further, for example, since the ultrasonic element 800 having a high frequency of 100 kHz or more has a small size, it takes time and effort to configure an ultrasonic element array by arranging a plurality of ultrasonic elements 800 side by side.

[0035] Hereinafter, the thickness of the first diaphragm 110 included in the ultrasonic transducer 100 according to one embodiment of the present invention will be described in detail.

[0036] The first diaphragm 110 and the ultrasonic vibrator 130 resonate and vibrate in opposite phases to each other, and have a vibration mode like a tuning fork vibration. From the viewpoint of maintaining the physical balance between the first diaphragm 110 and the ultrasonic vibrator 130, assuming that the transverse wave sound velocity of the first diaphragm 110 is Cv, the transverse wave sound velocity of the piezoelectric body 131 is Cp, the thickness dimension of the first diaphragm 110 is Tv, and the thickness dimension of the piezoelectric body 131 is Tp, it is preferable to satisfy the relationship of 0.7CpTp / Cv ≤ Tv ≤ 1.3CpTp / Cv. The transverse wave sound velocity Cv of the first diaphragm 110 is determined by the material constituting the first diaphragm 110. The transverse wave sound velocity Cp of the piezoelectric body 131 is determined by the material constituting the piezoelectric body 131. When a plurality of piezoelectric bodies 131 are laminated in the ultrasonic vibrator 130, the thickness dimension Tp of the piezoelectric body 131 is the total value of the thicknesses of the plurality of piezoelectric bodies 131.

[0037] By satisfying the relationship of 0.7CpTp / Cv ≦ Tv ≦ 1.3CpTp / Cv, the physical balance during the vibration of the first diaphragm 110 and the ultrasonic vibrator 130 can be maintained, the amplitude of the resonant vibration of the first diaphragm 110 can be increased, the sound pressure can be increased, and vibration leakage can be suppressed. It is more preferable to satisfy the relationship of Tv = CpTp / Cv. From the perspective of maintaining the physical balance, when Tp = 0.8, it is ideal for the thickness dimension Tv of the first diaphragm 110 to be 0.4 according to the relational expression of Tv = 0.8Cp / Cv.

[0038] FIG. 10 is a graph obtained by performing simulation analysis using the finite element method regarding the relationship between the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer and the thickness of the first diaphragm. In FIG. 10, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the thickness (mm) of the first diaphragm. As the simulation analysis condition, the total value Tp of the thicknesses of the two piezoelectric bodies 131 was set to 0.8 mm. As shown in FIG. 10, when the thickness of the first diaphragm 110 was 0.4 mm, the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer became maximum.

[0039] FIG. 11 is a graph obtained by performing simulation analysis using the finite element method regarding the relationship between the internal stress in the third direction (Z-axis direction) generated in the ultrasonic transducer (value normalized per sound pressure) and the thickness of the first diaphragm. In FIG. 11, the vertical axis represents the internal stress in the third direction (Z-axis direction) per sound pressure, and the horizontal axis represents the thickness (mm) of the first diaphragm.

[0040] As shown in Fig. 11, the thinner the thickness of the first diaphragm 110, the smaller the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100. In particular, when the thickness of the first diaphragm 110 is 0.24 mm or less, the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100 is significantly reduced. By reducing the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100, it is possible to suppress the occurrence of cracks due to the internal stress at each of the joint between the first diaphragm 110 and the frame 120, and the joint between the frame 120 and the ultrasonic vibrator 130. On the other hand, when the thickness of the first diaphragm 110 becomes thinner than 0.1 mm, the first diaphragm 110 becomes too soft and is no longer suitable as a vibrating body for generating ultrasonic waves.

[0041] That is, from the viewpoint of suppressing the occurrence of cracks due to internal stress and generating high sound pressure ultrasonic waves, it is preferable to satisfy the relationship of 0.25CpTp / Cv ≦ Tv ≦ 0.6CpTp / Cv. In the present embodiment, by setting the thickness of the first diaphragm 110 to be 0.1 mm or more and 0.2 mm or less, it is possible to drive the ultrasonic transducer 100 in a state where the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100 is lowered.

[0042] Here, the results of simulation analysis using the finite element method for the driving efficiency of the ultrasonic transducer when the ultrasonic vibrator is a bimorph type piezoelectric vibrator and when it is a unimorph type piezoelectric vibrator will be described. As simulation analysis conditions, in order to match the conditions with the bimorph type ultrasonic vibrator 130 shown in Fig. 1, the unimorph type ultrasonic vibrator also has a structure in which two piezoelectric bodies 131 are bonded together as shown in Fig. 1, and a driving voltage is applied only to one of the two piezoelectric bodies 131, and the other piezoelectric body 131 serves as a second diaphragm to which no driving voltage is applied.

[0043] Specifically, in the ultrasonic transducer of the first modification, a driving voltage is applied to the piezoelectric body 131 adjacent to the frame body 120, and the piezoelectric body 131 not adjacent to the frame body 120 becomes a second diaphragm to which no driving voltage is applied. In the first modification, the second diaphragm is provided on the side opposite to the frame body side of the piezoelectric body 131 to which the driving voltage is applied.

[0044] In the ultrasonic transducer of the second modification, a driving voltage is applied to the piezoelectric body 131 not adjacent to the frame body 120, and the piezoelectric body 131 adjacent to the frame body 120 becomes a second diaphragm to which no driving voltage is applied. In the second modification, the second diaphragm is provided on the frame body side of the piezoelectric body 131 to which the driving voltage is applied.

[0045] FIG. 12 is a graph obtained by performing a simulation analysis using the finite element method on the relationship between the displacement of the first diaphragm and the frequency of the ultrasonic vibrator in the ultrasonic transducer according to the present embodiment, the ultrasonic transducer according to the first modification, and the ultrasonic transducer according to the second modification. In FIG. 12, the vertical axis represents the displacement of the first diaphragm 110, and the horizontal axis represents the frequency (kHz) of the ultrasonic vibrator 130. The data of the ultrasonic transducer 100 according to the present embodiment are shown by a solid line, the data of the ultrasonic transducer according to the first modification are shown by a dotted line, and the data of the ultrasonic transducer according to the second modification are shown by a dashed-dotted line.

[0046] As shown in FIG. 12, when the displacement of the first diaphragm 110 in the ultrasonic transducer 100 according to the present embodiment is set to 100%, the displacement of the first diaphragm 110 of the ultrasonic transducer according to the first modification is 85.6%, and the displacement of the first diaphragm 110 of the ultrasonic transducer according to the second modification is 23.5%. When the free capacitance of the piezoelectric element in the ultrasonic transducer 100 according to the present embodiment is set to 100%, the free capacitance of the piezoelectric element of the ultrasonic transducer according to the first modification is 53.5%, and the free capacitance of the piezoelectric element of the ultrasonic transducer according to the second modification is 60.5%.

[0047] When the piezoelectric element is driven with the same voltage, the smaller the free capacitance of the piezoelectric element, the smaller the power consumption. The ultrasonic transducer according to the first modification can displace the first diaphragm 110 by nearly 80% of the ultrasonic transducer 100 according to the present embodiment with about half the power consumption of the ultrasonic transducer 100 according to the present embodiment, and it has been found that the efficiency is good.

[0048] In the present embodiment, the ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator, but the ultrasonic vibrator 130 may be another type of piezoelectric vibrator. Hereinafter, the ultrasonic vibrator of the ultrasonic transducer according to the modification of Embodiment 1 of the present invention will be described.

[0049] FIG. 13 is a cross-sectional view showing the configuration of the ultrasonic vibrator according to the third modification. As shown in FIG. 13, the ultrasonic vibrator 130a according to the third modification is a piezoelectric element including two laminated piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are equal to each other. The ultrasonic vibrator 130a is a so-called parallel-type bimorph piezoelectric vibrator.

[0050] FIG. 14 is a cross-sectional view showing the configuration of the ultrasonic vibrator according to the fourth modification. As shown in FIG. 14, the ultrasonic vibrator 130b according to the fourth modification is a piezoelectric element including four laminated piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 located on the outside among the four piezoelectric bodies 131 face one side in the first direction (Z-axis direction), and the polarization directions Dp of the two piezoelectric bodies 131 located on the inside among the four piezoelectric bodies 131 face the other side in the first direction (Z-axis direction). The ultrasonic vibrator 130b is a so-called multimorph piezoelectric vibrator.

[0051] FIG. 15 is a cross-sectional view showing the configuration of the ultrasonic vibrator according to the fifth modification. As shown in FIG. 15, the ultrasonic vibrator 130c according to the fifth modification is a piezoelectric element including one piezoelectric body 131. Specifically, the piezoelectric body 131 is sandwiched between the first electrode 132 and the second diaphragm 135 made of metal. The ultrasonic vibrator 130c is a so-called unimorph piezoelectric vibrator.

[0052] FIG. 16 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a sixth modification of Embodiment 1 of the present invention. As shown in FIG. 16, an ultrasonic transducer 100a according to a sixth modification of Embodiment 1 of the present invention includes a first diaphragm 110, a frame body 120a, and an ultrasonic vibrator 130. The frame body 120a has a bottomed cylindrical shape. The frame body 120a is formed of metal. A piezoelectric body 131 is attached to the outer bottom surface of the frame body 120a, and an ultrasonic vibrator, which is a unimorph type piezoelectric vibrator, is configured.

[0053] Here, the formation position and size of the slit will be described in detail. FIG. 17 is a perspective view showing a displacement state obtained by performing simulation analysis using the finite element method when an ultrasonic transducer according to a seventh modification of Embodiment 1 of the present invention, in which the formation positions of each of the two slits are shifted by 2 mm closer to the center in the longitudinal direction inside the frame, is transmitting or receiving ultrasonic waves. In the ultrasonic transducer 100b according to the seventh modification of Embodiment 1 of the present invention, the slit 110sb is formed from a position 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 body 120 to a position 0.5 mm inward. That is, each of the two slits 110s has a length dimension of 20 mm and a width dimension of 0.5 mm. Other simulation analysis conditions are the same as those of the ultrasonic transducer 100 shown in FIG. 5.

[0054] As shown in FIG. 17, in the ultrasonic transducer 100b according to the seventh modification of Embodiment 1 of the present invention, a portion of the first diaphragm 110 that is located above the internal space IS inside the frame body 120 and between the slits 110sb in the second direction (Y-axis direction) becomes a vibration region that resonantly vibrates. In the first diaphragm 110, an intermediate portion 110c located on the middle in the longitudinal direction inside the frame body 120 is largely displaced, and an end portion 110e located outside the slit 110sb in the second direction (Y-axis direction) is hardly displaced.

[0055] Therefore, compared with the ultrasonic transducer 100 according to the first embodiment of the present invention, the ultrasonic transducer 100b according to the seventh modification of the first embodiment of the present invention has a reduced area of the vibration region of the first diaphragm 110, and the pressure change of air due to the vibration of the first diaphragm 110 becomes smaller, resulting in a smaller sound pressure. Therefore, like the ultrasonic transducer 100 according to the first embodiment of the present invention, it is preferable that the slit 110s is formed near the position on the edge in the second direction (Y-axis direction) on the inner peripheral surface of the frame body 120.

[0056] From the viewpoint of preventing fixed ends from appearing at both ends in the second direction (Y-axis direction) in the vibration region that resonates and vibrates in the first diaphragm 110, the length dimension of the slit 110s in the first direction (X-axis direction) is preferably not less than the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120.

[0057] From the viewpoint of increasing the area of the vibration region of the first diaphragm 110, the smaller the width dimension of the slit 110s in the second direction (Y-axis direction), the more preferable. When the first diaphragm 110 and the frame body 120 are joined with an adhesive, in order to prevent the slit 110s from being blocked by the adhesive that has penetrated into the slit 110s formed near the position on the edge in the second direction (Y-axis direction) on the inner peripheral surface of the frame body 120, the width dimension of the slit 110s in the second direction (Y-axis direction) is preferably not less than 0.4 mm and not more than 0.6 mm. Alternatively, it is preferable that the slit 110s is formed from a position 0.2 mm inward in the second direction (Y-axis direction) from the position on the edge in the second direction (Y-axis direction) on the inner peripheral surface of the frame body 120, with a width dimension of not less than 0.2 mm and not more than 0.4 mm inward in the second direction (Y-axis direction). When the slit 110s is formed at the position on the edge in the second direction (Y-axis direction) on the inner peripheral surface of the frame body 120, through the slit 110s, the amount of lamination displacement between the first diaphragm 110 and the frame body 120, and the amount of adhesive oozing out inside the frame body 120 can be visually recognized. Therefore, the slit 110s can be used to improve the assembly accuracy of the ultrasonic transducer 100.

[0058] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, a first diaphragm 110, at least one frame body 120, and at least one ultrasonic vibrator 130 are provided. The at least one frame body 120 extends in the longitudinal direction and is joined to the first diaphragm 110. The at least one ultrasonic vibrator 130 is respectively attached to the at least one frame body 120 and faces the first diaphragm 110 with a gap therebetween. The first diaphragm 110 resonates and vibrates in a reverse phase to the at least one ultrasonic vibrator 130 in a direction orthogonal to the first diaphragm 110. The dimension L1 in the longitudinal direction inside the at least one frame body 120 is larger than the dimension L2 in the short hand direction orthogonal to the longitudinal direction inside the at least one frame body 120. The ultrasonic transducer 100 is provided with at least one opening that communicates an external space ES on the side opposite to the at least one frame body 120 with respect to the first diaphragm 110 and an internal space IS inside the at least one frame body 120.

[0059] Thereby, since the internal space IS and the external space ES communicate with each other through the opening, for example, when heating and curing the adhesive that joins the first diaphragm 110 and the frame body 120, the pressure change in the internal space IS can be reduced, and it is possible to suppress the internal stress in the ultrasonic transducer 100 from becoming high. Further, since the portion adjacent to the opening becomes the free end of the first diaphragm 110 that resonates and vibrates and is likely to be 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 downsized configuration.

[0060] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, at least one opening is formed in the first diaphragm 110. Thereby, it becomes possible to appropriately set the position where the opening is provided.

[0061] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, at least one opening is a slit 110s extending in the short side direction. Thereby, it is possible to suppress a decrease in the area of the vibration region of the resonant vibration due to the provision of the slit 110s, and to obtain a high sound pressure.

[0062] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, at least one opening is equal to or greater than the short side dimension L2 in the first direction (X-axis direction) inside at least one frame body 120. Thereby, it is possible to make the free end of the first diaphragm 110 that is resonantly vibrating at a location adjacent to the opening, and to make it easier for the first diaphragm 110 to be displaced. As a result, the sound pressure level can be increased.

[0063] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, the two openings are respectively open at both ends in the second direction (Y-axis direction) inside at least one frame body 120. Thereby, regardless of the longitudinal dimension L1 inside the frame body 120, the resonant frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 can be maintained substantially constant.

[0064] In a parametric speaker including the ultrasonic transducer 100 according to Embodiment 1 of the present invention, it is possible to modulate the ultrasonic waves radiated from the ultrasonic transducer 100 by modulating the driving of the ultrasonic transducer 100 to reproduce audible sound. As modulation methods, there are an AM modulation method (amplitude modulation method) and an FM modulation method (frequency modulation method).

[0065] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, the resonant frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 are 100 kHz or more. Thereby, as will be described later, when the resonant frequency is 100 kHz or more, since the attenuation of the sound wave with respect to the propagation distance is large, a parametric speaker including the ultrasonic transducer 100 can reproduce audible sound only in a limited space.

[0066] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, when the shear wave velocity of the first diaphragm 110 is Cv, the shear wave velocity of the piezoelectric body 131 is Cp, the thickness dimension of the first diaphragm 110 is Tv, and the thickness dimension of the piezoelectric body 131 is Tp, the relationship of 0.25CpTp / Cv ≤ Tv ≤ 0.6CpTp / Cv is satisfied. Thereby, it becomes possible to drive the ultrasonic transducer 100 in a state where the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer 100 is reduced. As a result, at each of the joint between the first diaphragm 110 and the frame body 120 and the joint between the frame body 120 and the ultrasonic vibrator 130, it is possible to generate high sound pressure ultrasonic waves while suppressing the occurrence of cracks due to internal stress.

[0067] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, when the shear wave velocity of the first diaphragm 110 is Cv, the shear wave velocity of the piezoelectric body 131 is Cp, the thickness dimension of the first diaphragm 110 is Tv, and the thickness dimension of the piezoelectric body 131 is Tp, the relationship of 0.7CpTp / Cv ≤ Tv ≤ 1.3CpTp / Cv is satisfied. Thereby, while maintaining the physical balance during the vibration of the first diaphragm 110 and the ultrasonic vibrator 130, it is possible to increase the amplitude of the resonance vibration of the first diaphragm 110 to increase the sound pressure and suppress vibration leakage.

[0068] In the first modification of the ultrasonic transducer 100 according to Embodiment 1 of the present invention, the ultrasonic vibrator is a unimorph type piezoelectric vibrator, and a second diaphragm is provided on the side opposite to the frame side of the piezoelectric body 131. Thereby, it is possible to improve the efficiency of the ultrasonic transducer by maintaining a high displacement of the first diaphragm 110 while reducing power consumption.

[0069] (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 ultrasonic vibrators are arranged in an array, the description of the configuration similar to that of the ultrasonic transducer according to Embodiment 1 of the present invention will not be repeated.

[0070] FIG. 18 is a side view showing the configuration of the ultrasonic transducer according to Embodiment 2 of the present invention. FIG. 19 is a rear view of the ultrasonic transducer shown in FIG. 18 as viewed from the direction of arrow XIX.

[0071] As shown in FIGS. 18 and 19, 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 configured. The ultrasonic transducer 200 includes a first diaphragm 210, a plurality of frames 220, and a plurality of ultrasonic vibrators 130. A plurality of frames 220 are joined to the first diaphragm 210, and a plurality of ultrasonic vibrators 130 are respectively joined to the plurality of frames 220.

[0072] Here, a method for manufacturing the ultrasonic transducer 200 will be described. FIG. 20 is an exploded perspective view showing a stacked state in a process of stacking and joining each component of the ultrasonic transducer according to Embodiment 2 of the present invention.

[0073] As shown in FIG. 20, 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). In the first diaphragm 210, a plurality of slits 210s are formed as a plurality of openings that communicate an external space on the side opposite to the plurality of frames 220 with respect to the first diaphragm 210 and an internal space inside the plurality of frames 220. The positional relationship between the frame 220 and the slit 210s is the same as the positional relationship between the frame 120 and the slit 110s in Embodiment 1.

[0074] 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 and the plurality of slits 210s are formed by etching, cutting, or the like.

[0075] 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 greater than the shortest distance between the short side portions 222.

[0076] 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. In adjacent frames 220 in the first direction (X-axis direction), the adjacent long side portions 221 are separated from each other by the slit 223.

[0077] Adjacent frames 220 in the first direction (X-axis direction) are connected at the short side portions 222. That is, in the plurality of frames 220, the frames 220 adjacent to each other in the short side direction are connected at both ends in their respective long side directions.

[0078] 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 are not limited thereto, and may be integrated by joining the short side portions 222 of the plurality of frames 220 respectively formed from a plurality of thin plates.

[0079] In this embodiment, each of the plurality of ultrasonic transducers 130 includes two stacked piezoelectric bodies 131. As shown in FIG. 20, the two piezoelectric bodies 131 constituting the plurality of ultrasonic transducers 130 are stacked and joined in the state of two thin plates.

[0080] FIG. 21 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. In FIG. 21, only one piezoelectric body 131 is illustrated.

[0081] As shown in FIG. 21, 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). As a result, the ultrasonic transducers 200 shown in FIGS. 18 and 19 are formed.

[0082] FIG. 22 is a perspective view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 2 of the present invention transmits or receives ultrasonic waves.

[0083] As shown in FIG. 22, a portion of the first diaphragm 210 that is located above the internal space inside each frame body 220 and between the slits 210s in the second direction (Y-axis direction) becomes a vibration region that resonantly vibrates. The longitudinal dimension of the vibration region of the first diaphragm 210 is the dimension between the slits 210s in the second direction (Y-axis direction), and the lateral dimension of the vibration region of the first diaphragm 210 is the same as the lateral dimension inside each frame body 220. In the first diaphragm 210, an intermediate portion 210c located above the middle in the longitudinal direction inside each frame body 220 is largely displaced, and end portions 210e located at both ends in the longitudinal direction inside each frame body 220 are hardly displaced.

[0084] Since the ultrasonic transducer 100 according to Embodiment 1 has node points at both ends in the longitudinal direction (Y-axis direction), even if the ultrasonic transducers 100 according to Embodiment 1 are connected to each other at 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.

[0085] In the parametric speaker including the ultrasonic transducer 200 according to Embodiment 2 of the present invention, it is possible to modulate the ultrasonic wave radiated from the ultrasonic transducer 200 by modulating the drive of the ultrasonic transducer 200 and reproduce an audible sound.

[0086] Here, the results of simulation analysis using the finite element method will be described regarding the relationship between the frequency of the ultrasonic wave and the attenuation due to the propagation distance of the sound pressure level. As the simulation analysis conditions, the attenuation transition due to the propagation distance between an audible sound with a frequency of 4 kHz reproduced from an ultrasonic wave with a resonant frequency of 146 kHz transmitted from the ultrasonic transducer 200 according to the present embodiment and an audible sound with a frequency of 4 kHz reproduced from an ultrasonic wave with a resonant frequency of 40 kHz transmitted from the ultrasonic element array according to the second comparative example was simulated using the finite element method.

[0087] FIG. 23 is a perspective view showing the configuration of the ultrasonic element array according to the second comparative example. As shown in FIG. 23, in the ultrasonic element array according to the second comparative example, 50 ultrasonic elements 900 are arranged at intervals in a matrix.

[0088] FIG. 24 is a graph showing the measured transition of attenuation of sound pressure level with propagation distance in the ultrasonic transducer according to the present embodiment and the ultrasonic transducer according to the second comparative example. In FIG. 24, the vertical axis represents the sound pressure level (dB), and the horizontal axis represents the propagation distance (cm). The data of the ultrasonic transducer 200 according to the present embodiment is shown by a solid line, and the data of the ultrasonic transducer according to the second comparative example is shown by a dotted line. The sound pressure level is a value normalized with the sound pressure level of audible sound at a frequency of 4 kHz at a point 30 cm away from the front of each of the ultrasonic transducer and the ultrasonic element array in the third direction (Z-axis direction) being 0 dB.

[0089] As shown in FIG. 24, compared with the audible sound reproduced from the ultrasonic wave at the resonance frequency of 40 kHz transmitted from the ultrasonic element array according to the second comparative example, the audible sound reproduced from the ultrasonic wave at the resonance frequency of 146 kHz transmitted from the ultrasonic transducer 200 according to the present embodiment had a greater attenuation due to the propagation distance. This is because high-frequency ultrasonic waves are easily absorbed by air as heat, so the audible sound reproduced using high-frequency ultrasonic waves as a carrier has a greater attenuation due to the propagation distance.

[0090] Thus, in the parametric speaker including the ultrasonic transducer 200 according to the present embodiment that transmits ultrasonic waves of a high frequency of 100 kHz or more, it is possible to suppress the sound reaching unnecessarily far and sound leakage due to unnecessary reflections, and reproduce the audible sound only in a limited space. Further, in the ultrasonic transducer 200, since the attenuation of the audible sound due to the propagation distance can be increased without providing a configuration for transmitting a carrier wave of opposite phase as in Patent Document 2, a simple and miniaturized configuration can be achieved. Furthermore, since ultrasonic waves of a high frequency of 100 kHz or more are outside the audible range of animals such as dogs or cats, the influence on these animals can be suppressed.

[0091] As shown in FIG. 24, in order for the audible sound to attenuate when the propagation distance is 30 cm or more, it is necessary to keep the distance within 30 cm. The Rayleigh distance R0 is R0 = (k × a2 ) It satisfies the relationship of ( ) / 2. Here, k is the wave number, and a is the radius of the sound source. Thus, 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.

[0092] The ultrasonic transducer 200 according to the present embodiment can be used as a phased array system.

[0093] In the ultrasonic transducer 200 according to Embodiment 2 of the present invention, a plurality of at least one frame body 220 are arranged side by side in the short side direction and joined to the first diaphragm 210. For the at least one frame body 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. Thereby, the sound pressure level can be easily increased.

[0094] (Embodiment 3) Hereinafter, the ultrasonic transducer according to Embodiment 3 of the present invention will be described with reference to the drawings. Since the position and number of the openings of the ultrasonic transducer according to Embodiment 3 of the present invention are different from those of the ultrasonic transducer according to Embodiment 1 of the present invention, the description of the same configuration as that of the ultrasonic transducer according to Embodiment 1 of the present invention will not be repeated.

[0095] FIG. 25 is a perspective view showing a displacement state obtained by performing simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 3 of the present invention is transmitting or receiving ultrasonic waves. As shown in FIG. 25, in the ultrasonic transducer 300 according to Embodiment 3 of the present invention, an intermediate slit 110cs is formed in the first diaphragm 110 as an opening that opens at the central portion in the longitudinal direction inside the frame body 120. The length dimension of the intermediate slit 110cs 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 intermediate slit 110cs in the second direction (Y-axis direction) is 0.2 mm or more and 0.6 mm or less. Other simulation analysis conditions were the same as those of the simulation analysis shown in FIG. 5.

[0096] FIG. 26 is a graph obtained by performing 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 short-side dimension inside the frame body in the ultrasonic transducer according to Embodiment 3 of the present invention. In FIG. 26, 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 body 120. As a simulation analysis condition, the short-side dimension L2 inside the frame body 120 was fixed at 2 mm.

[0097] As shown in FIG. 26, regardless of the change in the longitudinal dimension L1 inside the frame body 120, the resonance frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 became substantially constant at 130 kHz. 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 body 120 as a fixed end. Regardless of the longitudinal dimension L1 inside the frame body 120, the influence of the short-side dimension L2 on the reflection of the vibration is dominant, indicating that the state of the reflection of the vibration does not change even when the longitudinal dimension L1 increases.

[0098] FIG. 27 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 according to Embodiment 3 of the present invention when the longitudinal dimension is changed while fixing the short-side dimension inside the frame. In FIG. 27, 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 simulation analysis conditions, 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 300 in the third direction (Z-axis direction) was calculated.

[0099] As shown in FIG. 27, as the longitudinal dimension L1 inside the frame 120 increases, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 300 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 the slits 110s 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. As a result, the pressure change of the air due to the vibration of the first diaphragm 110 can be increased, and a high sound pressure can be obtained.

[0100] Thus, also in the ultrasonic transducer 300 according to the present embodiment, by increasing the longitudinal dimension of the vibration region of the first diaphragm 110, the sound pressure can be increased while maintaining the resonance frequency substantially constant.

[0101] Incidentally, the intermediate slit may be opened at a position deviated from the central portion in the longitudinal direction inside the frame body 120. FIG. 28 is a perspective view showing a displacement state obtained by performing simulation analysis using the finite element method when the ultrasonic transducer according to the modified example of Embodiment 3 of the present invention is transmitting or receiving ultrasonic waves. As shown in FIG. 28, in the ultrasonic transducer 300a according to the modified example of Embodiment 3 of the present invention, an intermediate slit 110as is formed in the first diaphragm 110 as an opening opened at a position deviated from the central portion in the longitudinal direction inside the frame body 120 toward the end portion.

[0102] (Embodiment 4) Hereinafter, the ultrasonic transducer according to Embodiment 4 of the present invention will be described with reference to the drawings. Since the position of the opening and the number of openings of the ultrasonic transducer according to Embodiment 4 of the present invention are different from those of the ultrasonic transducer according to Embodiment 1 of the present invention, the description of the configuration similar to that of the ultrasonic transducer according to Embodiment 1 of the present invention will not be repeated.

[0103] FIG. 29 is a perspective view showing a displacement state obtained by performing simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 4 of the present invention is transmitting or receiving ultrasonic waves. As shown in FIG. 29, in the ultrasonic transducer 400 according to Embodiment 4 of the present invention, one opening is opened at one of both end portions in the longitudinal direction inside the frame body 120. That is, only one slit 110s is formed. Other simulation analysis conditions were the same as the simulation analysis shown in FIG. 5.

[0104] FIG. 30 is a graph showing the transition of the resonance frequency of the first diaphragm when the longitudinal dimension is changed while fixing the lateral dimension inside the frame body in the ultrasonic transducer according to Embodiment 4 of the present invention, obtained by performing simulation analysis using the finite element method. In FIG. 30, 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 body 120. As a simulation analysis condition, the lateral dimension L2 inside the frame body 120 was fixed at 2 mm.

[0105] As shown in FIG. 30, in the range where the longitudinal dimension L1 inside the frame body 120 is twice or more the lateral dimension L2, the resonance frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 became substantially constant at 130 kHz. 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 body 120 as a fixed end. When the longitudinal dimension L1 inside the frame body 120 becomes twice or more 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 if the longitudinal dimension L1 becomes larger.

[0106] FIG. 31 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer when the longitudinal dimension is changed while fixing the lateral dimension inside the frame body in the ultrasonic transducer according to Embodiment 4 of the present invention. In FIG. 31, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame body 120. As a simulation analysis condition, the lateral dimension L2 inside the frame body 120 was fixed at 2 mm, and the sound pressure (Pa) at a position 30 cm away from the first diaphragm 110 on the front surface of the ultrasonic transducer 400 in the third direction (Z-axis direction) was calculated.

[0107] As shown in FIG. 31, as the longitudinal dimension L1 inside the frame body 120 increased, the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer 400 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 is vibrating. That is, the area of the vibration region can be increased by the amount corresponding to the increase in the length of the vibration region of the first diaphragm 110. 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.

[0108] Thus, also in the ultrasonic transducer 400 according to this embodiment, by making the longitudinal dimension of the vibration region of the first diaphragm 110 larger than twice the lateral dimension, it is possible to increase the sound pressure while maintaining the resonance frequency substantially constant.

[0109] (Embodiment 5) Hereinafter, the ultrasonic transducer according to Embodiment 5 of the present invention will be described with reference to the drawings. Since the position of the opening and the number of openings of the ultrasonic transducer according to Embodiment 5 of the present invention are different from those of the ultrasonic transducer according to Embodiment 1 of the present invention, the description of the configurations similar to those of the ultrasonic transducer according to Embodiment 1 of the present invention will not be repeated.

[0110] FIG. 32 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 5 of the present invention is transmitting or receiving ultrasonic waves. As shown in FIG. 32, in the ultrasonic transducer 500 according to Embodiment 5 of the present invention, one opening is formed at the central portion in the longitudinal direction inside the frame body 120. That is, only the intermediate slit 110cs is formed. Other simulation analysis conditions were the same as those of the simulation analysis shown in FIG. 5.

[0111] FIG. 33 is a graph showing the transition of the resonance frequency of the first diaphragm when the longitudinal dimension is changed while fixing the lateral dimension inside the frame body in the ultrasonic transducer according to Embodiment 5 of the present invention, obtained by simulation analysis using the finite element method. In FIG. 33, 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 body 120. As a simulation analysis condition, the lateral dimension L2 inside the frame body 120 was fixed at 2 mm.

[0112] As shown in FIG. 33, in the range where the longitudinal dimension L1 inside the frame body 120 is 4 times or more the lateral dimension L2, the resonance frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 became substantially constant at 130 kHz. 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 body 120 as a fixed end. However, when the longitudinal dimension L1 inside the frame body 120 becomes 4 times or more 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 if the longitudinal dimension L1 becomes larger.

[0113] FIG. 34 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension is changed while fixing the lateral dimension inside the frame body in the ultrasonic transducer according to Embodiment 5 of the present invention. In FIG. 34, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the longitudinal dimension L1 (mm) inside the frame body 120. As a simulation analysis condition, the lateral dimension L2 inside the frame body 120 was fixed at 2 mm, and the sound pressure (Pa) at a position 30 cm away from the first diaphragm 110 on the front surface of the ultrasonic transducer 500 in the third direction (Z-axis direction) was calculated.

[0114] As shown in FIG. 34, as the longitudinal dimension L1 inside the frame body 120 increased, the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 400 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 is vibrating. That is, the area of the vibration region can be increased by the length of the vibration region of the first diaphragm 110, 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.

[0115] Thus, also in the ultrasonic transducer 500 according to the present embodiment, by making the longitudinal dimension of the vibration region of the first diaphragm 110 four times or more larger than the short-side dimension, it is possible to increase the sound pressure while maintaining the resonance frequency substantially constant.

[0116] Note that the intermediate slit may be opened at a position deviated from the central portion in the longitudinal direction inside the frame body 120. FIG. 35 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the modification of Embodiment 5 of the present invention transmits or receives ultrasonic waves. As shown in FIG. 35, in the ultrasonic transducer 500a according to the modification of Embodiment 5 of the present invention, an intermediate slit 110as is formed in the first diaphragm 110 as an opening opened at a position deviated from the central portion in the longitudinal direction inside the frame body 120 toward the end.

[0117] (Embodiment 6) Hereinafter, the ultrasonic transducer according to Embodiment 6 of the present invention will be described with reference to the drawings. Since the minimum dimension of the ultrasonic vibrator in the second direction (Y-axis direction) of the ultrasonic transducer according to Embodiment 6 of the present invention is smaller than the longitudinal dimension inside the frame body, which is different from the ultrasonic transducer according to Embodiment 1 of the present invention, the description of the configuration similar to that of the ultrasonic transducer according to Embodiment 1 of the present invention will not be repeated.

[0118] FIG. 36 is an exploded perspective view showing the configuration of the ultrasonic transducer according to Embodiment 6 of the present invention. As shown in FIG. 36, the ultrasonic transducer 600 according to Embodiment 6 of the present invention includes a first diaphragm 110, a frame body 120, and an ultrasonic vibrator 630.

[0119] FIG. 37 is a view of the ultrasonic transducer of FIG. 36 as seen from the direction of arrow XXXVII. As shown in FIG. 37, the ultrasonic vibrator 630 has a rectangular outer shape. The longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame 120 is larger than the minimum dimension Lm in the second direction (Y-axis direction) of the ultrasonic vibrator 630. Here, when the ultrasonic vibrator 630 has a stacked structure in which a plurality of piezoelectric bodies are stacked, the minimum dimension Lm in the second direction (Y-axis direction) of the ultrasonic vibrator 630 is the minimum dimension in the second direction (Y-axis direction) of the piezoelectric body having the shortest length in the second direction (Y-axis direction) among the plurality of piezoelectric bodies. FIG. 37 shows a stacked structure in which a plurality of piezoelectric bodies are stacked without displacement in the second direction (Y-axis direction).

[0120] 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 120 and at least one edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame 120 side of the ultrasonic vibrator 630 shown in FIG. 36 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame 120.

[0121] In the present embodiment, the average distance L3 in the second direction (Y-axis direction) between one edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame 120 and one edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame 120 side of the ultrasonic vibrator 630 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame 120, and the average distance L3 in the second direction (Y-axis direction) between the other edge 120e in the second direction (Y-axis direction) of the inner peripheral surface 120s of the frame 120 and the other edge 130e in the second direction (Y-axis direction) of the surface 130s on the frame 120 side of the ultrasonic vibrator 630 is 1.3 times or less the short-side dimension L2 in the first direction (X-axis direction) inside the frame 120.

[0122] FIG. 38 is a cross-sectional view showing the configuration of the ultrasonic vibrator included in the ultrasonic transducer according to Embodiment 6 of the present invention. As shown in FIG. 37, the ultrasonic vibrator 630 is attached to the frame body 120 and faces the first diaphragm 110 with a space therebetween. Specifically, the ultrasonic vibrator 630 is attached to each of the other ends in the third direction (Z-axis direction) of a 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 interposed therebetween.

[0123] As shown in FIGS. 37 and 38, the ultrasonic vibrator 630 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 38, in the present embodiment, the ultrasonic vibrator 630 has a laminated structure in which a plurality of piezoelectric bodies 131 are laminated. Specifically, the ultrasonic vibrator 630 includes two laminated piezoelectric bodies 131. Among the two piezoelectric bodies 131, the piezoelectric body 131 in contact with the frame body 120 is polarized, and the piezoelectric body 131 not in contact with the frame body 120 is not polarized.

[0124] FIG. 39 is a perspective view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 6 of the present invention is transmitting or receiving ultrasonic waves. As simulation analysis conditions, the thickness of the first diaphragm 110 was set to 0.1 mm, the combined thickness of the two piezoelectric bodies 131 was set to 0.8 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. The length dimension of the slit 110s in the first direction (X-axis direction) was set to 80.1% of the lateral 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) was set to 0.5 mm. 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 inside 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.

[0125] As shown in FIG. 39, in the vibration mode of the ultrasonic transducer 600 according to Embodiment 6 of the present invention, the first diaphragm 110 resonates in a reverse phase to the ultrasonic vibrator 630 in the third direction (Z-axis direction) orthogonal to the first diaphragm 110. In the present embodiment, the resonance frequencies of the first diaphragm 110 and the ultrasonic vibrator 630 are approximately 150 kHz.

[0126] In the present embodiment, as shown in FIG. 37, 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 ultrasonic vibrator 630 shown in FIG. 36 in the second direction (Y-axis direction), the minimum dimension Lm of the ultrasonic vibrator 630 in the second direction (Y-axis direction) is made smaller than the longitudinal dimension L1 in the second direction (Y-axis direction) inside the frame body 120 so that a gap is formed therebetween. Thereby, the power consumption of the ultrasonic vibrator 630 can be reduced and the efficiency can be improved. Further, since the piezoelectric body 131 not adhered to the frame body 120 is not driven, the free capacitance of the piezoelectric element can be reduced, and the first diaphragm 110 can be displaced efficiently.

[0127] Here, the relationship between the ratio of the length dimension of the slit 110s in the first direction (X-axis direction) to the short dimension L2 in the first direction (X-axis direction) inside the frame body 120 and the change rate of the internal stress (value normalized per sound pressure) in the third direction (Z-axis direction) generated in the ultrasonic transducer will be described.

[0128] FIG. 40 is a graph obtained by performing a simulation analysis using the finite element method on the relationship between the ratio of the length dimension of the slit in the first direction (X-axis direction) to the short-side dimension in the first direction (X-axis direction) inside the frame body and the change rate of the internal stress in the third direction (Z-axis direction) generated in the ultrasonic transducer (a value normalized per sound pressure). In FIG. 40, the vertical axis represents the change rate (%) of the internal stress in the third direction (Z-axis direction) per sound pressure, and the horizontal axis represents the ratio (%) of the length dimension of the slit 110s in the first direction (X-axis direction) to the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120. The change rate of the internal stress in the third direction (Z-axis direction) per sound pressure is the change rate with respect to the reference of the internal stress in the third direction (Z-axis direction) per sound pressure when the ratio of the length dimension of the slit 110s in the first direction (X-axis direction) to the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120 is 0%.

[0129] As shown in FIG. 40, when the ratio of the length dimension of the slit 110s in the first direction (X-axis direction) to the short-side dimension L2 in the first direction (X-axis direction) inside the frame body 120 is 60% or more and 95% or less, the change rate of the internal stress in the third direction (Z-axis direction) per sound pressure is -15% or more. That is, when the short-side dimension of at least one opening is 60% or more and 95% or less of the short-side dimension inside at least one frame body, the internal stress in the third direction (Z-axis direction) generated in the ultrasonic transducer 600 (a value normalized per sound pressure) can be effectively reduced. As a result, at each of the joint portions between the first diaphragm 110 and the frame body 120 and between the frame body 120 and the ultrasonic vibrator 630, it is possible to effectively suppress the occurrence of cracks due to the internal stress.

[0130] Next, for Sample 1 where the ratio of the length dimension of the slit 110s in the first direction (X-axis direction) to the short-side dimension L2 of the frame body 120 in the first direction (X-axis direction) is 0%, Sample 2 where it is 55.6%, Sample 3 where it is 77.8%, Sample 4 where it is 88.9%, and Sample 5 where it is 100%, a simulation analysis was performed using the finite element method on the relationship between the position in the longitudinal direction (Y-axis direction) of the first diaphragm 110 and the displacement of the first diaphragm 110.

[0131] FIG. 41 is a graph obtained by performing a simulation analysis using the finite element method on the relationship between the position in the longitudinal direction (Y-axis direction) of the first diaphragm and the displacement of the first diaphragm in Samples 1 to 5. In FIG. 41, the displacement (μm) of the first diaphragm is shown on the vertical axis, and the position (mm) in the longitudinal direction (Y-axis direction) of the first diaphragm is shown on the horizontal axis. The position of one edge of the first diaphragm 110 in the longitudinal direction (Y-axis direction) is set to 0 mm, and the position of the other edge of the first diaphragm 110 in the longitudinal direction (Y-axis direction) is set to 22 mm.

[0132] FIG. 42 is a perspective view showing the displacement state obtained by performing a simulation analysis using the finite element method when the ultrasonic transducer according to Sample 1 is transmitting or receiving ultrasonic waves. FIG. 43 is a perspective view showing the displacement state obtained by performing a simulation analysis using the finite element method when the ultrasonic transducer according to Sample 2 is transmitting or receiving ultrasonic waves. FIG. 44 is a perspective view showing the displacement state obtained by performing a simulation analysis using the finite element method when the ultrasonic transducer according to Sample 3 is transmitting or receiving ultrasonic waves. FIG. 45 is a perspective view showing the displacement state obtained by performing a simulation analysis using the finite element method when the ultrasonic transducer according to Sample 4 is transmitting or receiving ultrasonic waves. FIG. 46 is a perspective view showing the displacement state obtained by performing a simulation analysis using the finite element method when the ultrasonic transducer according to Sample 5 is transmitting or receiving ultrasonic waves.

[0133] As shown in FIGS. 41 and 42, in the ultrasonic transducer 700 according to Sample 1, in the first diaphragm 710, the intermediate portion 710c located on the longitudinal middle inside the frame body 120 was largely displaced, and the displacement became smaller as it approached the end portion 710e in the second direction (Y-axis direction).

[0134] As shown in FIGS. 41 and 43, in the ultrasonic transducer 600a according to Sample 2, in the first diaphragm 110, the intermediate portion 110c located on the longitudinal middle inside the frame body 120 was largely displaced, and the displacement became smaller as it approached the slit 110s in the second direction (Y-axis direction).

[0135] As shown in FIGS. 41 and 44, in the ultrasonic transducer 600b according to Sample 3, in the first diaphragm 110, the intermediate portion 110c was largely displaced, and the displacement became smaller as it approached the slit 110s in the second direction (Y-axis direction). However, compared with Samples 1 and 2, Sample 3 had a smaller difference between the displacement at the intermediate portion 110c and the displacement at the position near the slit 110s within the vibration region.

[0136] As shown in FIGS. 41 and 45, in the ultrasonic transducer 600c according to Sample 4, in the first diaphragm 110, the position near the slit 110s within the vibration region was displaced slightly more than the intermediate portion 110c.

[0137] As shown in FIGS. 41 and 46, in the ultrasonic transducer 600d according to Sample 5, in the first diaphragm 110, the position near the slit 110s within the vibration region was largely displaced, and the displacement became smaller as it approached the intermediate portion 110c in the second direction (Y-axis direction).

[0138] From the above results, it was found that as the ratio of the length dimension of the slit 110s in the first direction (X-axis direction) to the short-side dimension L2 of the frame body 120 in the first direction (X-axis direction) increases, the peak position of the displacement in the first diaphragm 110 shifts from the intermediate portion 110c in the second direction (Y-axis direction) toward both end sides.

[0139] The displacement of the first diaphragm 110 is more evenly distributed in the longitudinal direction of the frame body 120, which can reduce the maximum stress in the third direction (Z-axis direction) generated in the ultrasonic transducer during driving. Due to this mechanism of action, as shown in FIG. 40, when the ratio of the length dimension of the slit 110s in the first direction (X-axis direction) to the short-side dimension L2 of the frame body 120 in the first direction (X-axis direction) is 60% or more and 95% or less, it is considered that the internal stress in the third direction (Z-axis direction) (value normalized per sound pressure) generated in the ultrasonic transducer 600 can be effectively reduced.

[0140] In addition, when the ratio of the length dimension of the slit 110s in the first direction (X-axis direction) to the short-side dimension L2 of the frame body 120 in the first direction (X-axis direction) is 60% or more and 95% or less, the effect of effectively reducing the internal stress in the third direction (Z-axis direction) (value normalized per sound pressure) generated in the ultrasonic transducer 600 can be similarly obtained for the transducers 100 and 200 according to each of the first embodiment and the second embodiment.

[0141] (Supplementary Note) Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following aspects.

[0142] <1> A first diaphragm; At least one frame body extending in the longitudinal direction and joined to the first diaphragm; At least one ultrasonic vibrator respectively attached to the at least one frame body and facing the first diaphragm with a gap therebetween. The first diaphragm resonates in antiphase with the at least one ultrasonic vibrator in a direction orthogonal to the first diaphragm. The dimension in the longitudinal direction inside the at least one frame body is larger than the dimension in the short side direction orthogonal to the longitudinal direction inside the at least one frame body. An ultrasonic transducer provided with at least one opening for communicating an external space on the side opposite to the at least one frame body with respect to the first diaphragm and an internal space inside the at least one frame body.

[0143] <2> The ultrasonic transducer according to <1>, wherein the at least one opening is formed in the first diaphragm.

[0144] <3> The ultrasonic transducer according to <2>, wherein the at least one opening is a slit extending in the short side direction.

[0145] <4> The ultrasonic transducer according to <3>, wherein the at least one opening extends by a dimension equal to or greater than the dimension in the short side direction inside the at least one frame body.

[0146] <5> The ultrasonic transducer according to any one of <1> to <4>, wherein one opening as the at least one opening opens at one of both ends in the longitudinal direction inside the at least one frame body.

[0147] <6> The ultrasonic transducer according to any one of <1> to <4>, wherein two openings as the at least one opening open at both ends in the longitudinal direction inside the at least one frame body, respectively.

[0148] <7> The at least one ultrasonic vibrator is a piezoelectric element including a piezoelectric body, and is the ultrasonic transducer according to any one of <1> to <6>.

[0149] <8> The resonance frequencies of the first diaphragm and the at least one ultrasonic vibrator are 100 kHz or more, and it is the ultrasonic transducer according to any one of <1> to <7>.

[0150] <9> When the shear wave velocity of the first diaphragm is Cv, the shear wave velocity of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, The ultrasonic transducer according to <7>, which satisfies the relationship of 0.25CpTp / Cv ≤ Tv ≤ 0.6CpTp / Cv.

[0151] <10> When the shear wave velocity of the first diaphragm is Cv, the shear wave velocity of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, The ultrasonic transducer according to <7>, which satisfies the relationship of 0.7CpTp / Cv ≤ Tv ≤ 1.3CpTp / Cv.

[0152] <11> A plurality of the at least one frame body are arranged side by side in the short side direction and joined to the first diaphragm, The ultrasonic transducer according to any one of <1> to <10>, wherein the frame bodies adjacent to each other in the short side direction in the at least one frame body are connected at both ends in the longitudinal direction thereof.

[0153] <12> The at least one ultrasonic vibrator is a unimorph type piezoelectric vibrator, The ultrasonic transducer according to <7>, wherein a second diaphragm is provided on the side opposite to the frame body side of the piezoelectric body.

[0154] <13> The dimension in the longitudinal direction inside the at least one frame body is 2 times or more the dimension in the short transverse direction inside the at least one frame body, the ultrasonic transducer according to <5>.

[0155] <14> The dimension in the short transverse direction of the at least one opening is 60% or more and 95% or less the dimension in the short transverse direction inside the at least one frame body, the ultrasonic transducer according to any one of <1> to <13>.

[0156] <15> Comprising the ultrasonic transducer according to any one of <1> to <14>, A parametric speaker that reproduces audible sound by modulating and driving the ultrasonic transducer.

[0157] In the description of the above-described embodiments, combinable configurations may be combined with each other.

[0158] 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 scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

Explanation of Signs

[0159] 100, 100a, 100b, 200, 300, 300a, 400, 500, 500a, 600, 600a, 600b, 600c, 600d, 700 ultrasonic transducers, 110, 210, 710 first diaphragms, 110as, 110cs intermediate slits, 110c, 210c, 710c intermediate portions, 110e, 210e, 710e end portions, 110s, 110sb, 210s, 211, 223 slits, 120, 120a, 220 frames, 120e, 130e edges, 120s inner peripheral surface, 121, 221 long side portions, 122, 222 short side portions, 130, 130a, 130b, 130c, 630 ultrasonic vibrators, 130s surface on the frame side of the ultrasonic vibrator, 131 piezoelectric body, 132 first electrode, 133 second electrode, 134 intermediate electrode, 135 second diaphragm, 140 processing circuit, 800, 900 ultrasonic elements, Bm, Bp resonance vibrations, Cp, Cv sound velocities, Dp polarization direction, ES external space, IS internal space, L1 longitudinal dimension, L2 short dimension, LC cut line, R0 Rayleigh distance.

Claims

1. a first diaphragm; at least one frame extending in the longitudinal direction and joined to the first diaphragm; at least one ultrasonic vibrator respectively attached to the at least one frame and facing the first diaphragm with a space therebetween; the first diaphragm resonates in a reverse phase to the at least one ultrasonic vibrator in a direction orthogonal to the first diaphragm; the dimension in the longitudinal direction inside the at least one frame is larger than the dimension in the short transverse direction orthogonal to the longitudinal direction inside the at least one frame; an ultrasonic transducer provided with at least one opening for communicating an external space on the side opposite to the at least one frame with respect to the first diaphragm and an internal space inside the at least one frame.

2. The ultrasonic transducer according to claim 1, wherein the at least one opening is formed in the first diaphragm.

3. The ultrasonic transducer according to claim 2, wherein the at least one opening is a slit extending in the short transverse direction.

4. The ultrasonic transducer according to claim 3, wherein the at least one opening extends by a dimension equal to or greater than the dimension in the short transverse direction inside the at least one frame.

5. The ultrasonic transducer according to claim 4, wherein one opening as the at least one opening opens at one of both ends in the longitudinal direction inside the at least one frame.

6. The ultrasonic transducer according to claim 4, wherein two openings as the at least one opening open at both ends in the longitudinal direction inside the at least one frame, respectively.

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

8. The ultrasonic transducer according to claim 1, wherein the resonance frequencies of the first diaphragm and the at least one ultrasonic vibrator are 100 kHz or more.

9. When the transverse wave velocity of the first diaphragm is Cv, the transverse wave velocity of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, The ultrasonic transducer according to claim 7, which satisfies the relationship of 0.25 Cp Tp / Cv ≤ Tv ≤ 0.6 Cp Tp / Cv.

10. When the transverse wave velocity of the first diaphragm is Cv, the transverse wave velocity of the piezoelectric body is Cp, the thickness dimension of the first diaphragm is Tv, and the thickness dimension of the piezoelectric body is Tp, The ultrasonic transducer according to claim 7, which satisfies the relationship of 0.7 Cp Tp / Cv ≤ Tv ≤ 1.3 Cp Tp / Cv.

11. A plurality of the at least one frame body are arranged side by side in the short side direction and joined to the first diaphragm, and the frame bodies adjacent to each other in the short side direction in the at least one frame body are connected to each other at both ends in the longitudinal direction. The ultrasonic transducer according to claim 1.

12. The at least one ultrasonic vibrator is a unimorph type piezoelectric vibrator, The ultrasonic transducer according to claim 7, wherein a second diaphragm is provided on the side opposite to the frame body side of the piezoelectric body.

13. The ultrasonic transducer according to claim 5, wherein the longitudinal dimension inside the at least one frame body is 2 times or more the transverse dimension inside the at least one frame body.

14. The dimension in the short side direction of the at least one opening is 60% or more and 95% or less of the dimension in the short side direction inside the at least one frame body. The ultrasonic transducer according to claim 1.

15. Comprising the ultrasonic transducer according to any one of claims 1 to 14, A parametric speaker that reproduces audible sound by modulating and driving the ultrasonic transducer.

Images