Ultrasonic transducer and parametric speaker comprising same

Abstract

A first vibration plate (110) has at least one vibration plate part (111) that extends in a long direction. At least one support body (120) has a shaft part (121) that extends in the long direction, and is joined to the first vibration plate (110). At least one ultrasonic vibrator (130) is attached to the at least one support body (120) over the entire length of the shaft part (121) in the long direction, and faces the at least one vibration plate part (111) with the at least one support body (120) therebetween so as to leave a first gap (Rg) between the at least one ultrasonic vibrator (130) and the at least one vibration plate part (111). The short dimension of the shaft part (121) in a short direction orthogonal to the long direction is smaller than the short dimension of each of the at least one vibration plate part (111) and the at least one ultrasonic vibrator (130). The at least one vibration plate part (111) vibrates resonantly in the opposite phase from the at least one ultrasonic vibrator (130) in a direction orthogonal to the at least one vibration plate part (111). The long dimension of the shaft part (121) in the long direction is at least four times the short dimension of the at least one ultrasonic vibrator (130).

Description

Ultrasonic transducer and parametric speaker including same

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

[0002] Prior documents disclosing the configuration of an ultradirectional acoustic device include Japanese Patent Laid-Open No. 2003-47085 (Patent Document 1) and Japanese Patent No. 6333480 (Patent Document 2). The ultradirectional acoustic device described in Patent Document 1 is configured by deploying multiple ultrasonic transducers on a single printed circuit board and arranging them so that the outer periphery is approximately circular. The multiple ultrasonic transducers are divided into two groups installed at different heights.

[0003] The ultradirectional acoustic device described in Patent Document 2 includes a first ultrasonic emitter and a second ultrasonic emitter. The second ultrasonic emitter is disposed on the axis of the first ultrasonic emitter and in front of the radiation surface. The phase of the carrier signal radiated by the second ultrasonic emitter is opposite to the phase of the carrier signal contained in the signal radiated by the first ultrasonic emitter.

[0004] JP 2003-47085 A Japanese Patent No. 6333480

[0005] The superdirectional acoustic device described in Patent Document 1 has a complex configuration, with multiple ultrasonic transducers arranged in two groups at different installation heights.The superdirectional acoustic device described in Patent Document 2 has a second ultrasonic emitter arranged outside the first ultrasonic emitter, which increases the size of the device.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an ultrasonic transducer and a parametric speaker including the same that can increase the sound pressure level with a simple and compact configuration.

[0007] An ultrasonic transducer according to the present invention comprises a first diaphragm, at least one support, and at least one ultrasonic vibrator. The first diaphragm has at least one vibrating plate portion extending in a longitudinal direction. The at least one support has a shaft portion extending in the longitudinal direction and is joined to the first diaphragm. The at least one ultrasonic vibrator is attached to the at least one support over the entire length of the shaft portion in the longitudinal direction, and faces the at least one vibrating plate portion with a first gap therebetween, sandwiching the at least one support therebetween. The lateral dimension of the shaft portion in a lateral direction perpendicular to the longitudinal direction is smaller than the lateral dimensions of the at least one vibrating plate portion and the at least one ultrasonic vibrator. The at least one vibrating plate portion resonates in an antiphase with the at least one ultrasonic vibrator in a direction perpendicular to the at least one vibrating plate portion. The longitudinal dimension of the shaft portion in the longitudinal direction is at least four times the lateral dimension of the at least one ultrasonic vibrator.

[0008] According to the present invention, it is possible to increase the sound pressure level in an ultrasonic transducer with a simple and compact configuration.

[0009] 1 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. 2 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a first embodiment of the present invention. 3 is a sectional view showing the configuration of an ultrasonic vibrator included in the ultrasonic transducer according to a first embodiment of the present invention. 4 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to a first embodiment of the present invention is transmitting or receiving ultrasonic waves. 5 is a sectional view of the ultrasonic transducer of FIG. 4 as viewed from the direction of the arrow V-V. 6 is a graph showing a simulation analysis, using the finite element method, of the transition in the resonance frequency of the first diaphragm when the longitudinal dimension of the shank of the support is changed while the lateral dimension of the ultrasonic vibrator is fixed. 7 is a graph showing a simulation analysis, using the finite element method, of the transition in the sound pressure of ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension of the shank of the support is changed while the lateral dimension of the ultrasonic vibrator is fixed. 8 is a diagram showing a sound pressure distribution simulated and analyzed using the finite element method when λ / 4 air resonance occurs in the ultrasonic transducer according to a first embodiment of the present invention. 9 is a sectional view showing the configuration of an ultrasonic vibrator according to a first modified example. 10 is a sectional view showing the configuration of an ultrasonic vibrator according to a second modified example. 11 is a sectional view showing the configuration of an ultrasonic vibrator according to a third modified example. 16 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fourth modified example of embodiment 1 of the present invention. FIG. 17 is a plan view of the ultrasonic transducer according to the fourth modified example of embodiment 1 of the present invention, viewed from the first diaphragm side. FIG. 18 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to the fourth modified example of embodiment 1 of the present invention is transmitting or receiving ultrasonic waves. FIG. 19 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fifth modified example of embodiment 1 of the present invention. FIG. 19 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to the fifth modified example of embodiment 1 of the present invention is transmitting or receiving ultrasonic waves. FIG. 19 is a cross-sectional view of the ultrasonic transducer of FIG. 16, viewed from the direction of the arrows along line XVII-XVII. FIG. 19 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a sixth modified example of embodiment 1 of the present invention.24 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a sixth modified example of the first embodiment of the present invention transmits or receives ultrasonic waves. This is a cross-sectional view of the ultrasonic transducer of FIG. 19 as seen from the direction of the arrows XX-XX. This is a side view showing the configuration of an ultrasonic transducer according to a second embodiment of the present invention. This is a rear perspective view of the ultrasonic transducer shown in FIG. 21 as seen from the direction of the arrows XXII. This is an exploded perspective view showing the configuration of an ultrasonic transducer according to the second embodiment of the present invention. This is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to the second embodiment of the present invention transmits or receives ultrasonic waves. This is a cross-sectional view of the ultrasonic transducer of FIG. 24 as seen from the direction of the arrows XXV-XXV. This is an exploded perspective view showing the configuration of an ultrasonic transducer according to a third embodiment of the present invention. This is a side view showing the positional relationship between the cutting position of the piezoelectric body and the resonance plate portion of the ultrasonic transducer according to the third embodiment of the present invention. This is a plan view showing the configuration of a plurality of support bodies according to a modified example. This is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to the third embodiment of the present invention transmits or receives ultrasonic waves. This is a cross-sectional view of the ultrasonic transducer of FIG. 29 as seen from the direction of the arrows XXX-XXX. 1 is a diagram showing a sound pressure distribution simulated and analyzed using the finite element method when air resonance of λ / 2 occurs in the ultrasonic transducer according to embodiment 3 of the present invention. FIG. 2 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 4 of the present invention. FIG. 3 is a diagram showing a sound pressure distribution simulated and analyzed using the finite element method when air resonance of λ occurs in the ultrasonic transducer according to embodiment 4 of the present invention. FIG. 4 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 5 of the present invention. FIG. 5 is a diagram showing a sound pressure distribution simulated and analyzed using the finite element method when air resonance of λ occurs in the ultrasonic transducer according to embodiment 5 of the present invention. FIG. 6 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 6 of the present invention.1 is a diagram showing a sound pressure distribution simulated and analyzed using the finite element method when air resonance of λ and air resonance of λ / 4 occur in an ultrasonic transducer according to embodiment 6 of the present invention. FIG. 2 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 7 of the present invention. FIG. 3 is a diagram showing a sound pressure distribution simulated and analyzed using the finite element method when air resonance of λ and air resonance of λ / 2 occur in an ultrasonic transducer according to embodiment 7 of the present invention. FIG. 4 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a comparative example. FIG. 5 is a graph showing the results of actual measurements of the output of ultrasonic waves radiated from the ultrasonic transducers according to examples 1 to 3 and the comparative example.

[0010] Hereinafter, ultrasonic transducers according to embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their description will not be repeated. The present invention is applicable to applications requiring high sound pressure ultrasonic waves, such as ultrasonic transducers for parametric speakers, ultrasonic sensors, or non-contact haptics. In the following embodiments, an ultrasonic transducer for a parametric speaker will be described as an example, but the use of the ultrasonic transducer is not limited to this.

[0011] (Embodiment 1) Fig. 1 is a longitudinal sectional view showing the configuration of an ultrasonic transducer according to embodiment 1 of the present invention. Fig. 2 is an exploded perspective view showing the configuration of the ultrasonic transducer according to embodiment 1 of the present invention. As shown in Figs. 1 and 2, an ultrasonic transducer 100 according to embodiment 1 of the present invention includes a first diaphragm 110, a support 120, and an ultrasonic vibrator 130.

[0012] The first diaphragm 110 has a rectangular flat plate shape. The first diaphragm 110 has a short side along a first direction (X-axis direction) and a long side along a second direction (Y-axis direction). The first diaphragm 110 has at least one diaphragm portion 111 extending in the long side direction. In this embodiment, the first diaphragm 110 has one diaphragm portion 111.

[0013] The first diaphragm 110 is made of an aluminum alloy such as aluminum-containing duralumin, or a metal such as stainless steel. In this embodiment, the first diaphragm 110 is made of stainless steel. The thickness T1 of the first diaphragm 110 is, for example, 0.05 mm or more and 0.2 mm or less. The short side dimension W1 of the diaphragm portion 111 is, for example, 1 mm or more and 2 mm or less.

[0014] The support 120 has a shaft portion 121 extending in the second direction (Y-axis direction). In this embodiment, a pair of constraining plate portions 122 extending in the first direction (X-axis direction) are formed on both outer sides of the shaft portion 121 in the second direction (Y-axis direction) on the support 120. That is, the support 120 has an H-shape. One end of the support 120 in the third direction (Z-axis direction) is bonded to the first diaphragm 110 with a bonding agent such as epoxy resin. Specifically, one end of the entire shaft portion 121 in the third direction (Z-axis direction) is bonded to the first diaphragm 110 with the bonding agent. At least a portion or the entire end of each of the pair of constraining plate portions 122 in the third direction (Z-axis direction) may be bonded to the first diaphragm 110 with the bonding agent.

[0015] The support 120 is made of a metal such as an aluminum alloy or stainless steel, glass epoxy, or resin. From the viewpoint of suppressing changes in the characteristics of the ultrasonic transducer 100 due to temperature changes, the support 120 is preferably made of metal. On the other hand, from the viewpoint of lowering the frequency of the ultrasonic waves transmitted or received by the ultrasonic transducer 100 and from the viewpoint of miniaturizing the ultrasonic transducer 100, the support 120 is preferably made of resin. In this embodiment, the support 120 is made of stainless steel.

[0016] The thickness dimension T2 of the support 120 is, for example, 0.15 mm or more and 0.4 mm or less. If the thickness dimension T2 of the support 120 is less than 0.15 mm, the diaphragm portion 111 and the ultrasonic vibrator 130 may be bonded to each other by the seeping adhesive. If the thickness dimension T2 of the support 120 exceeds 0.4 mm, the vibration of the ultrasonic vibrator 130 may be inhibited.

[0017] The longitudinal dimension L1 of the stem 121 is greater than the transverse dimension W3 of the ultrasonic vibrator 130. In this embodiment, the longitudinal dimension L1 of the stem 121 is at least four times the transverse dimension W3 of the ultrasonic vibrator 130. From the viewpoint of increasing the sound pressure level of the ultrasonic waves transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, 20 mm or greater. The transverse dimension W2 of the stem 121 is smaller than both the transverse dimension W1 of the diaphragm portion 111 and the transverse dimension W3 of the ultrasonic vibrator 130. The transverse dimension W2 of the stem 121 is, for example, 1 mm or less, and is preferably 0.3 mm or greater and 0.6 mm or less from the viewpoint of maintaining bonding strength. If the transverse dimension W2 of the stem 121 exceeds 1 mm, there is a possibility that the vibration of the ultrasonic vibrator 130 may be inhibited. The dimension of each of the pair of restraint plate portions 122 in the first direction (X-axis direction) is equal to the short side dimension W3 of the ultrasonic transducer 130.

[0018] In this embodiment, the shaft portion 121 is joined to the center in the first direction (X-axis direction) of the diaphragm portion 111. That is, in the first direction (X-axis direction), the shortest distance L2 between one end of the shaft portion 121 and one end of the diaphragm portion 111 is substantially the same as the shortest distance L3 between the other end of the shaft portion 121 and the other end of the diaphragm portion 111. However, the shaft portion 121 may be joined to a position shifted from the center in the first direction (X-axis direction) of the diaphragm portion 111.

[0019] As shown in FIG. 1 , the ultrasonic vibrator 130 is attached to the support 120 over the entire length of the shaft portion 121 in the longitudinal direction, and faces the vibration plate portion 111 with a gap Rg therebetween, with the support 120 sandwiched therebetween. Specifically, the ultrasonic vibrator 130 is attached to the other end of the support 120 in the third direction (Z-axis direction), and faces the vibration plate portion 111 with the support 120 sandwiched therebetween. In this embodiment, the ultrasonic vibrator 130 is attached to one end of the entire shaft portion 121 in the third direction (Z-axis direction), and to the other end of at least a portion or the entire third direction (Z-axis direction) of each of the pair of constraint plate portions 122. Each of the pair of constraint plate portions 122 is joined to both longitudinal ends of the ultrasonic vibrator 130.

[0020] FIG. 3 is a cross-sectional view showing the configuration of an ultrasonic vibrator included in the ultrasonic transducer according to the first embodiment of the present invention. As shown in FIGS. 1, 2, and 3, the ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. As shown in FIG. 3, in this 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 T3 of the two piezoelectric bodies 131 shown in FIG. 1 is, for example, not less than 0.2 mm and not more than 0.4 mm.

[0021] The resonant frequency of the first diaphragm 110 can be adjusted by changing the short side dimension W3 of the ultrasonic vibrator 130. For example, when the resonant frequency of the first diaphragm 110 is set to 100 kHz or more and 200 kHz or less, the short side dimension W3 is 1.5 mm or more and 3 mm or less.

[0022] Fig. 4 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to embodiment 1 of the present invention transmits or receives ultrasonic waves. Fig. 5 is a cross-sectional view of the ultrasonic transducer of Fig. 4 as viewed from the direction of the arrow V-V. The simulation analysis conditions were as follows: thickness T1 of first diaphragm 110 was 0.05 mm, combined thickness T3 of two piezoelectric bodies 131 was 0.4 mm, thickness T2 of support body 120 was 0.2 mm, and longitudinal dimension L1 of shaft portion 121 was 20 mm.

[0023] As shown in Figures 4 and 5, in the vibration mode of the ultrasonic transducer 100 according to the first embodiment of the present invention, the vibration plate portion 111 of the first vibration plate 110 resonates in an opposite phase to the ultrasonic vibrator 130 in a third direction (Z-axis direction) perpendicular to the first vibration plate 110. That is, as shown in Figure 5, the displacement direction of the resonant vibration Bm of the first vibration plate 110 and the displacement direction of the resonant vibration Bp of the ultrasonic vibrator 130 are opposite to each other in the third direction (Z-axis direction). The ultrasonic vibrator 130 vibrates in a bending mode in the third direction (Z-axis direction) when viewed from the second direction (Y-axis direction). In this embodiment, the resonant frequency of the first vibration plate 110 and the ultrasonic vibrator 130 is 100 kHz or higher.

[0024] In first diaphragm 110, the displacement of the resonant vibration is greatest at intermediate portion 110c of diaphragm portion 111 located at the longitudinal midpoint of shaft portion 121, and the end portion located on constraining plate portion 122 becomes node point 110e. That is, in first diaphragm 110, diaphragm portion 111 located on shaft portion 121 between constraining plate portions 122 becomes the vibration region that resonates. The longitudinal dimension of the vibration region of first diaphragm 110 is the same as longitudinal dimension L1 of shaft portion 121.

[0025] Here, the relationship between the resonance frequency of first diaphragm 110 and longitudinal dimension L1 of shaft portion 121 will be described.

[0026] Fig. 6 is a graph showing the results of a simulation analysis using the finite element method of the transition of the resonant frequency of the first diaphragm when the longitudinal dimension of the shaft portion of the support body is changed while the transverse dimension of the ultrasonic vibrator is fixed. In Fig. 6, the vertical axis represents the resonant frequency (kHz) of the first diaphragm 110, and the horizontal axis represents the longitudinal dimension L1 (mm) of the shaft portion 121 of the support body 120. As a condition for the simulation analysis, the transverse dimension W3 of the ultrasonic vibrator 130 was fixed at 2 mm.

[0027] 6 , when the longitudinal dimension L1 of the shaft portion 121 of the support 120 is 2 mm, the resonant frequency of the first diaphragm 110 is 200 kHz. When the longitudinal dimension L1 is increased to 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 is increased, the resonant frequency of the first diaphragm 110 decreases to 112 kHz. Thereafter, even when the longitudinal dimension L1 of the shaft portion 121 of the support 120 exceeds 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 is further increased, the resonant frequency of the first diaphragm 110 remains substantially constant at 112 kHz. In other words, the resonant frequency of the first diaphragm 110 becomes substantially constant when the longitudinal dimension L1 of the shaft portion 121 of the support 120 exceeds four times the lateral dimension W3 of the ultrasonic vibrator 130.

[0028] Next, the results of a simulation analysis using the finite element method on the relationship between the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer 100 and the longitudinal dimension L1 of the shaft portion 121 of the support 120 will be described.

[0029] 7 is a graph showing the results of a simulation analysis using the finite element method of the transition of the sound pressure of the ultrasonic waves transmitted from the ultrasonic transducer when the longitudinal dimension of the shaft portion of the support body is changed while the lateral dimension of the ultrasonic vibrator is fixed. In Fig. 7, the vertical axis represents the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis represents the longitudinal dimension L1 (mm) of the shaft portion 121 of the support body 120. As a simulation analysis condition, the lateral dimension W3 of the ultrasonic vibrator 130 was fixed at 2 mm, and the sound pressure (Pa) was calculated at a position 30 cm away in the third direction (Z-axis direction) from the first diaphragm 110 on the front side of the ultrasonic transducer 100.

[0030] 7, as the longitudinal dimension L1 of the shaft portion 121 of the support 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 node points 110e vibrates. In other words, the area of ​​the vibration region can be increased by the amount that the vibration region of the first diaphragm 110 is longer, and as a result, the change in air pressure due to the vibration of the first diaphragm 110 can be increased, thereby obtaining a high sound pressure.

[0031] In this way, the ultrasonic transducer 100 according to this embodiment can increase the sound pressure while maintaining a substantially constant resonant frequency by increasing the longitudinal dimension of the vibration region of the first diaphragm 110. Furthermore, since there are nodal points at both ends in the longitudinal direction, the ends can be supported or fixed, making it easy to mount the ultrasonic transducer 100.

[0032] 8 is a diagram showing a sound pressure distribution obtained by simulation analysis using the finite element method when λ / 4 air resonance occurs in the ultrasonic transducer according to the first embodiment of the present invention. In Fig. 8, the sound pressure increases as the color changes from black to white in the area where air is present. In the state shown in Fig. 8, the sound pressure is high in the gap Rg between the diaphragm portion 111 and the ultrasonic vibrator 130, and low in the region Rf directly above the first diaphragm 110.

[0033] The vibration plate portion 111 vibrates in a resonant manner in the opposite phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 110, so that air is repeatedly compressed and expanded in the gap Rg.

[0034] Air resonance occurs depending on the shortest distance L2 between one end of the shaft portion 121 and one end of the diaphragm portion 111, and the shortest distance L3 between the other end of the shaft portion 121 and the other end of the diaphragm portion 111. Specifically, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance can occur in the gap Rg when at least one of the shortest distances L2 and L3 is close to λ / 4. That is, the area near the shaft portion 121 becomes a fixed end and a node of the air resonance, and the area outside the gap Rg becomes an open end and a loop of the air resonance. As a result, air resonance of λ / 4 occurs in the gap Rg in the first direction (X-axis direction).

[0035] For example, when the thickness dimension T2 of the support 120 is 0.2 mm and at least one of the shortest distances L2 and L3 is approximately 0.5 mm or more and 0.7 mm or less, air resonance with a frequency of 100 kHz can occur in the gap Rg. When the thickness dimension T2 of the support 120 is 0.2 mm and at least one of the shortest distances L2 and L3 is approximately 0.3 mm or more and 0.5 mm or less, air resonance with a frequency of 150 kHz can occur in the gap Rg. The reason why the dimensions of the shortest distances L2 and L3 have a certain range for the air resonance frequency is because the state in which air resonance occurs changes depending on the configuration around the ultrasonic transducer 100.

[0036] In this embodiment, the ultrasonic vibrator 130 is a so-called series-type bimorph piezoelectric vibrator, but the ultrasonic vibrator 130 may be another type of piezoelectric vibrator. Hereinafter, an ultrasonic vibrator of an ultrasonic transducer according to a modification of the first embodiment of the present invention will be described.

[0037] Fig. 9 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a first modified example. As shown in Fig. 9, an ultrasonic vibrator 130a according to the first modified example is a piezoelectric element including two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are the same. The ultrasonic vibrator 130a is a so-called parallel bimorph piezoelectric vibrator.

[0038] Fig. 10 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to the second modification. As shown in Fig. 10, an ultrasonic vibrator 130b according to the second modification is a piezoelectric element including four stacked piezoelectric bodies 131. The polarization directions Dp of the two outermost piezoelectric bodies 131 of the four piezoelectric bodies 131 face one side of the third direction (Z-axis direction), and the polarization directions Dp of the two innermost piezoelectric bodies 131 of the four piezoelectric bodies 131 face the other side of the third direction (Z-axis direction). The ultrasonic vibrator 130b is a so-called multimorph piezoelectric vibrator.

[0039] Fig. 11 is a cross-sectional view showing the configuration of an ultrasonic vibrator according to a third modified example. As shown in Fig. 11, an ultrasonic vibrator 130c according to the third modified example is a piezoelectric element including one piezoelectric body 131. Specifically, the piezoelectric body 131 is sandwiched between a first electrode 132 and a second vibration plate 135 made of metal. The ultrasonic vibrator 130c is a so-called unimorph piezoelectric vibrator.

[0040] FIG. 12 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fourth modified example of the first embodiment of the present invention. FIG. 13 is a plan view of the ultrasonic transducer according to the fourth modified example of the first embodiment of the present invention, viewed from the first diaphragm side. As shown in FIGS. 12 and 13 , the ultrasonic transducer 100a according to the fourth modified example of the first embodiment of the present invention includes a first diaphragm 110a, a support 120, and an ultrasonic vibrator 130. The first diaphragm 110a has a constricted portion 113 formed at a position longitudinally outward of the diaphragm portion 111, the constricted portion 113 being narrower than the lateral dimension W2 of the shaft portion 121 of the support 120. Specifically, the first diaphragm 110a has a pair of constricted portions 113 formed between both longitudinal end portions 112 and the diaphragm portion 111. Note that only one constricted portion 113 may be formed.

[0041] Both end portions 112 of the first diaphragm 110a are respectively joined to a pair of restraint plate portions 122 of the support body 120. In the ultrasonic transducer 100a according to the fourth modification of the first embodiment of the present invention, when the first diaphragm 110a and the support body 120 are joined to each other, the first diaphragm 110a can be placed on the support body 120 while checking that the constricted portion 113 of the first diaphragm 110a is positioned above the center in the first direction (X-axis direction) of the shaft portion 121 of the support body 120. This makes it possible to reduce assembly errors of the ultrasonic transducer 100a.

[0042] 14 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the fourth modification of the first embodiment of the present invention transmits or receives ultrasonic waves. As shown in FIG. 14, the ultrasonic transducer 100a according to the fourth modification of the first embodiment of the present invention also exhibits a vibration mode equivalent to that of the ultrasonic transducer 100 according to the first embodiment of the present invention.

[0043] Fig. 15 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fifth modified example of embodiment 1 of the present invention. As shown in Fig. 15, an ultrasonic transducer 100b according to the fifth modified example of embodiment 1 of the present invention includes a first diaphragm 110, a support 120b, and an ultrasonic vibrator 130. The support 120b is composed of only a shaft portion 121.

[0044] Fig. 16 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a fifth modification of the first embodiment of the present invention transmits or receives ultrasonic waves. Fig. 17 is a cross-sectional view of the ultrasonic transducer of Fig. 16 as viewed from the direction of the arrows along line XVII-XVII. The simulation analysis conditions were as follows: thickness T1 of first diaphragm 110 was 0.05 mm, combined thickness T3 of two piezoelectric bodies 131 was 0.4 mm, thickness T2 of support body 120b was 0.2 mm, and longitudinal dimension L1 of shaft portion 121 was 20 mm.

[0045] 16 and 17 , in the vibration mode of the ultrasonic transducer 100b according to the fifth modification of the first embodiment of the present invention, the vibration plate portion 111 of the first vibration plate 110 resonates and vibrates in the opposite phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 110. The ultrasonic vibrator 130 vibrates in the bending mode in the third direction (Z-axis direction) when viewed from the second direction (Y-axis direction).

[0046] However, in the ultrasonic transducer 100b according to the fifth modification of the first embodiment of the present invention, since there is no constraint plate portion 122, there are no node points at the longitudinal end portions of the shaft portion 121. In addition, an unnecessary vibration mode occurs in which the displacement of the resonant vibration changes at regular intervals in the second direction (Y-axis direction), and the characteristics of the ultrasonic transducer 100b tend to become unstable.

[0047] FIG. 18 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a sixth modified example of the first embodiment of the present invention. As shown in FIG. 18, the ultrasonic transducer 100c according to the sixth modified example of the first embodiment of the present invention includes a first diaphragm 110, a support 120b, an ultrasonic vibrator 130, and a pair of constraining plates 120c. The support 120b is composed only of a shaft 121. The pair of constraining plates 120c are composed of separate members from the support 120b. The pair of constraining plates 120c extend in the first direction (X-axis direction) and are respectively joined to both longitudinal ends of the ultrasonic vibrator 130. Note that the pair of constraining plates 120c are not limited to being joined to both longitudinal ends of the ultrasonic vibrator 130, but may also be joined to positions approximately 2 mm inward from both longitudinal ends of the ultrasonic vibrator 130. That is, the pair of restraint plate portions 120c may be joined to positions near both ends of the ultrasonic transducer 130 in the longitudinal direction.

[0048] Fig. 19 is a perspective view showing a displacement state simulated and analyzed using the finite element method when an ultrasonic transducer according to a sixth modification of the first embodiment of the present invention transmits or receives ultrasonic waves. Fig. 20 is a cross-sectional view of the ultrasonic transducer of Fig. 19 as viewed from the direction of the arrows along the line XX-XX. The simulation analysis conditions were as follows: thickness T1 of first diaphragm 110 was 0.05 mm; combined thickness T3 of two piezoelectric bodies 131 was 0.4 mm; thickness T2 of support body 120b was 0.2 mm; longitudinal dimension L1 of shaft portion 121 was 20 mm; thickness of constraining plate portion 120c was 0.2 mm; and the dimension of constraining plate portion 122 in the first direction (X-axis direction) was the same as widthwise dimension W3 of ultrasonic vibrator 130.

[0049] As shown in FIGS. 19 and 20, it was confirmed that the ultrasonic transducer 100c according to the sixth modified example of the first embodiment of the present invention also has a vibration mode equivalent to that of the ultrasonic transducer 100 according to the first embodiment of the present invention.

[0050] The ultrasonic transducer 100 according to the first embodiment of the present invention includes a first diaphragm 110, at least one support 120, and at least one ultrasonic vibrator 130. The first diaphragm 110 has at least one diaphragm portion 111 extending in the longitudinal direction. The at least one support 120 has a shaft portion 121 extending in the longitudinal direction and is joined to the first diaphragm 110. The at least one ultrasonic vibrator 130 is attached to the at least one support 120 over the entire length of the shaft portion 121 in the longitudinal direction, and faces the at least one diaphragm portion 111 with a gap Rg therebetween, with the at least one support 120 sandwiched therebetween. A lateral dimension W2 of the shaft portion 121 in a lateral direction perpendicular to the longitudinal direction is smaller than the lateral dimensions of the at least one diaphragm portion 111 and the at least one ultrasonic vibrator 130. At least one diaphragm portion 111 resonates in an opposite phase to at least one ultrasonic vibrator 130 in a direction perpendicular to the at least one diaphragm portion 111. The longitudinal dimension L1 of the shaft portion 121 in the longitudinal direction is four or more times the lateral dimension W3 of at least one ultrasonic vibrator 130. This allows the ultrasonic transducer 100 to increase the sound pressure level with a simple and compact configuration.

[0051] In the ultrasonic transducer 100 according to the first embodiment of the present invention, at least one ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. This allows the ultrasonic transducer to have a simple and compact configuration.

[0052] In the ultrasonic transducer 100 according to the first embodiment of the present invention, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance of λ / 4 can be generated in the first direction (X-axis direction) in the gap Rg. When air resonance of λ / 4 is generated, the ultrasonic transducer 100 can emit ultrasonic waves at a high sound pressure level due to the superposition of sound pressure caused by the air resonance.

[0053] The ultrasonic transducer 100 according to the first embodiment of the present invention includes a pair of constraining plates 122 extending in a first direction (X-axis direction) and joined to both longitudinal ends of the ultrasonic vibrator 130. This allows for nodal points at both longitudinal ends, making it possible to support or fix these ends, facilitating the mounting of the ultrasonic transducer 100. Furthermore, the generation of unwanted vibration modes can be suppressed, stabilizing the characteristics of the ultrasonic transducer 100. Furthermore, since the support body 120 includes the pair of constraining plates 122, the number of components of the ultrasonic transducer 100 can be reduced compared to when the pair of constraining plates are configured as separate members from the support body 120.

[0054] In a parametric speaker including the ultrasonic transducer 100 according to the first embodiment of the present invention, it is possible to reproduce audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 100 through modulation driving of the ultrasonic transducer 100. Modulation methods include an AM modulation method (amplitude modulation method) and an FM modulation method (frequency modulation method).

[0055] (Embodiment 2) An ultrasonic transducer according to embodiment 2 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 2 of the present invention differs from the ultrasonic transducer according to embodiment 1 of the present invention in that a plurality of ultrasonic vibrators are arranged in an array, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 1 of the present invention will not be repeated.

[0056] Fig. 21 is a side view showing the configuration of an ultrasonic transducer according to embodiment 2 of the present invention, Fig. 22 is a rear perspective view of the ultrasonic transducer shown in Fig. 21 as seen from the direction of arrow XXII.

[0057] 21 and 22 , in an ultrasonic transducer 200 according to embodiment 2 of the present invention, the ultrasonic transducers 100 according to embodiment 1 are arranged in an array in a first direction (X-axis direction) and are integrally constructed. The ultrasonic transducer 200 includes a first diaphragm 210, a plurality of supports 220, and a plurality of ultrasonic vibrators 130. The first diaphragm 210 and the plurality of supports 220 are bonded together, and the plurality of ultrasonic vibrators 130 are bonded to the plurality of supports 220, respectively.

[0058] Fig. 23 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 2 of the present invention. As shown in Fig. 23, a first diaphragm 210 has a plurality of diaphragm portions 211 that extend in a second direction (Y-axis direction) and are arranged side by side in a first direction (X-axis direction) at intervals from each other. Diaphragm portions 211 adjacent to each other in the first direction (X-axis direction) on the first diaphragm 210 are connected at both ends 212 of the first diaphragm 210 in the second direction (Y-axis direction).

[0059] The first diaphragm 210 is made of an aluminum alloy such as duralumin containing aluminum, or a metal such as stainless steel. In this embodiment, the first diaphragm 210 is made of stainless steel.

[0060] The multiple supports 220 have shaft portions 221 extending in the second direction (Y-axis direction) and are arranged side by side in the first direction (X-axis direction). In this embodiment, the multiple supports 220 adjacent to each other in the first direction (X-axis direction) are connected to each other at both ends in the second direction (Y-axis direction). Specifically, the shaft portions 221 of the supports 220 adjacent to each other in the first direction (X-axis direction) are connected to each other at both ends in the second direction (Y-axis direction) by a pair of restraining plate portions 222. That is, in this embodiment, the support 220 is formed with the shaft portion 221 and the pair of restraining plate portions 222.

[0061] The longitudinal dimension L1 of the stem 221 is greater than the transverse dimension W3 of the ultrasonic vibrator 130. In this embodiment, the longitudinal dimension L1 of the stem 221 is at least four times the transverse dimension W3 of the ultrasonic vibrator 130. From the viewpoint of increasing the sound pressure level of the ultrasonic waves transmitted by the ultrasonic transducer 200, the longitudinal dimension L1 is, for example, 20 mm or greater. The transverse dimension W2 of the stem 221 is smaller than both the transverse dimension W1 of the diaphragm portion 211 and the transverse dimension W3 of the ultrasonic vibrator 130. The transverse dimension W2 of the stem 221 is, for example, 1 mm or less, and is preferably 0.3 mm or greater and 0.6 mm or less from the viewpoint of maintaining bonding strength. If the transverse dimension W2 of the stem 221 exceeds 1 mm, there is a possibility that the vibration of the ultrasonic vibrator 130 may be hindered.

[0062] Each of the plurality of supports 220 is formed from a metal such as an aluminum alloy or stainless steel, glass epoxy, resin, etc. In this embodiment, the plurality of supports 220 are formed from a single thin plate, but this is not limiting, and the plurality of supports 220, each formed from a plurality of thin plates, may be joined together to form an integrated body.

[0063] In this embodiment, each of the multiple ultrasonic vibrators 130 includes two stacked piezoelectric bodies 131. As shown in Fig. 23, the two piezoelectric bodies 131 constituting the multiple ultrasonic vibrators 130 are stacked and bonded in the form of two thin plates. The multiple ultrasonic vibrators 130 are attached to the multiple supports 220 over the entire length of the shaft portion 221 in the second direction (Y-axis direction), and are arranged at intervals from each other in the first direction (X-axis direction). The multiple ultrasonic vibrators 130 face the multiple vibration plate portions 211 with the gap Rg therebetween, with a corresponding support 220 among the multiple supports 220 sandwiched therebetween.

[0064] Fig. 24 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to embodiment 2 of the present invention transmits or receives ultrasonic waves. Fig. 25 is a cross-sectional view of the ultrasonic transducer of Fig. 24 as viewed from the direction of the arrows along line XXV-XXV. The simulation analysis conditions were as follows: thickness T1 of first diaphragm 210 was 0.05 mm, thickness T3 of two piezoelectric bodies 131 combined was 0.4 mm, thickness T2 of support body 220 was 0.2 mm, and longitudinal dimension L1 of shaft portion 221 was 20 mm.

[0065] 24 and 25 , in the vibration mode of the ultrasonic transducer 200 according to the second embodiment of the present invention, the vibration plate portion 211 of the first vibration plate 210 resonates and vibrates in the opposite phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 210. The ultrasonic vibrator 130 vibrates in the bending mode in the third direction (Z-axis direction) when viewed from the second direction (Y-axis direction).

[0066] In the first diaphragm 210, the displacement of the resonant vibration is greatest at the middle portion 210c of the diaphragm portion 211 located at the longitudinal midpoint of the shaft portion 221, and both end portions 212 located on the restraint plate portion 222 become node points 210e.

[0067] The ultrasonic transducer 100 according to the first embodiment has node points 110e at both ends in the second direction (Y-axis direction), which is the longitudinal direction, and therefore even if the ultrasonic transducers 100 according to the first embodiment are connected to each other at the both ends to form an array to form the ultrasonic transducer 200 according to the second embodiment, the resonant vibration of each ultrasonic transducer 100 is not inhibited. Therefore, by increasing the number of ultrasonic transducers 100 that form the ultrasonic transducer 200 according to the second embodiment, the sound pressure level can be easily increased.

[0068] In a parametric speaker equipped with the ultrasonic transducer 200 according to the second embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 200 by modulating the ultrasonic waves to reproduce audible sounds.

[0069] A parametric speaker equipped with the ultrasonic transducer 200 according to this embodiment, which transmits ultrasonic waves at high frequencies of 100 kHz or higher, can reproduce audible sound only in a limited space, suppressing sound from traveling unnecessarily far and sound leakage due to unnecessary reflections. Furthermore, the ultrasonic transducer 200 can increase the attenuation of audible sound over the propagation distance without requiring a configuration for transmitting an opposite-phase carrier wave, as in Patent Document 2, allowing for a simple and compact configuration. Furthermore, because ultrasonic waves at high frequencies of 100 kHz or higher are outside the audible range of animals such as dogs and cats, the effects on these animals can be suppressed.

[0070] In order for audible sound to attenuate after a propagation distance of 30 cm, the Rayleigh distance must be within 30 cm. The Rayleigh distance R0 is given by R0 = (k × a 2 ) / 2, where k is the wave number and a is the radius of the sound source. Therefore, if the speed of sound in air is 340 m / s, when the ultrasonic frequency is 100 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 36 mm or less, when the ultrasonic frequency is 150 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 29.4 mm or less, and when the ultrasonic frequency is 200 kHz, the longitudinal dimension of the vibration region of first diaphragm 210 is 25.5 mm or less. When the ultrasonic frequency is 100 kHz or more, the longitudinal dimension L1 is between 4 and 24 times the lateral dimension L2.

[0071] The ultrasonic transducer 200 according to this embodiment can be used as a phased array system.

[0072] In the ultrasonic transducer 200 according to the second embodiment of the present invention, a plurality of supports 220 are arranged in the short-side direction and joined to the first vibration plate 210, and the supports 220 adjacent to each other in the short-side direction are connected to each other at both ends in the long-side direction by a pair of restraining plate portions 222. This makes it possible to easily increase the sound pressure level.

[0073] (Embodiment 3) An ultrasonic transducer according to embodiment 3 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 3 of the present invention differs from the ultrasonic transducer according to embodiment 2 of the present invention in that a resonating plate portion is provided, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 2 of the present invention will not be repeated.

[0074] Fig. 26 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 3 of the present invention. As shown in Fig. 26, the ultrasonic transducer 300 according to embodiment 3 of the present invention includes a first diaphragm 310, a plurality of supports 220, and a plurality of ultrasonic vibrators 130. The first diaphragm 310 and the plurality of supports 220 are bonded together, and the plurality of ultrasonic vibrators 130 are bonded to the plurality of supports 220, respectively.

[0075] The first diaphragm 310 is provided with a plurality of resonance plate portions 311 which are disposed between the vibration plate portions 211 adjacent to each other in the first direction (X-axis direction) and extend in the second direction (Y-axis direction) and face, with a gap therebetween, each of the ultrasonic vibrators 130 which are adjacent to each other in the first direction (X-axis direction) among the plurality of ultrasonic vibrators 130. Each of the plurality of resonance plate portions 311 is connected to both end portions 212 of the first diaphragm 310 in the second direction (Y-axis direction). In this embodiment, the resonance plate portions 311 are formed on the first diaphragm 310, but this is not limiting, and the resonance plate portions 311 may be formed on a member separate from the first diaphragm 310.

[0076] 27 is a side view showing the positional relationship between the cutting positions of the piezoelectric bodies of the ultrasonic transducer according to embodiment 3 of the present invention and the resonance board portion. As shown in Fig. 27, the two stacked piezoelectric bodies 131 are cut and divided by a dicer or the like along multiple cut lines LC that are located approximately at the center of the resonance board portion 311 in the first direction (X-axis direction) and extend in the second direction (Y-axis direction). As a result, the multiple ultrasonic vibrators 130 attached to the multiple supports 220 are arranged at intervals from each other in the first direction (X-axis direction).

[0077] FIG. 28 is a plan view showing the configuration of multiple supports according to a modified example. As shown in FIG. 28 , multiple supports 320 according to the modified example are arranged side by side in the first direction (X-axis direction) while having shafts 321 extending in the second direction (Y-axis direction). Supports 320 adjacent to each other in the first direction (X-axis direction) are connected at both ends in the second direction (Y-axis direction). Specifically, the shafts 321 of supports 320 adjacent to each other in the first direction (X-axis direction) are connected at both ends in the second direction (Y-axis direction) by a pair of restraining plates 322. That is, in this embodiment, the support 320 is formed with a shaft 321 and a pair of restraining plates 322. In each of the pair of restraining plates 322, portions with a larger width and a smaller width in the second direction (Y-axis direction) are alternately arranged in the first direction (X-axis direction), and the portion connected to the shaft 321 is the portion with a larger width in the second direction (Y-axis direction).

[0078] Fig. 29 is a perspective view showing a displacement state simulated and analyzed using the finite element method when the ultrasonic transducer according to embodiment 3 of the present invention is transmitting or receiving ultrasonic waves. Fig. 30 is a cross-sectional view of the ultrasonic transducer of Fig. 29 as viewed from the direction of the arrows along the line XXX-XXX. The simulation analysis conditions were as follows: thickness T1 of first diaphragm 310 was 0.05 mm, thickness T3 of two piezoelectric bodies 131 combined was 0.4 mm, thickness T2 of support body 220 was 0.2 mm, and longitudinal dimension L1 of shaft portion 221 was 20 mm.

[0079] 29 and 30 , in the vibration mode of the ultrasonic transducer 300 according to the third embodiment of the present invention, the vibration plate portion 211 of the first vibration plate 310 resonates and vibrates in the opposite phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 310. The ultrasonic vibrator 130 vibrates in the bending mode in the third direction (Z-axis direction) when viewed from the second direction (Y-axis direction).

[0080] In the first diaphragm 310, the displacement of the resonant vibration is greatest at the middle portion 310c of the diaphragm portion 211 located at the longitudinal center of the shaft portion 221, and the both end portions 212 located on the restraint plate portion 322 become node points 310e. The resonant plate portion 311 barely vibrates.

[0081] Fig. 31 is a diagram showing a sound pressure distribution obtained by simulation analysis using the finite element method when λ / 2 air resonance occurs in the ultrasonic transducer according to embodiment 3 of the present invention. Fig. 31 shows that in areas where air is present, the sound pressure increases as the color changes from black to white. In the state shown in Fig. 31, the sound pressure is high in the gap Rg between the diaphragm portion 211 and the ultrasonic vibrator 130 and in the gap Rh between the resonator portion 311 and the ultrasonic vibrator 130, and is low in the region Rj directly above the resonator portion 311.

[0082] Since the vibration plate portion 211 vibrates in a resonant manner in the opposite phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 310, air is repeatedly compressed and expanded in the gap Rg.

[0083] Air resonance occurs depending on the shortest distance L2 between one end of the shaft portion 221 and one end of the diaphragm portion 211, and the shortest distance L3 between the other end of the shaft portion 221 and the other end of the diaphragm portion 211. Specifically, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance can occur in the gap Rg when at least one of the shortest distance L2 and the shortest distance L3 has a dimension close to λ / 4. As a result, air resonance of λ / 4 occurs in the gap Rg in the first direction (X-axis direction).

[0084] Due to the resonant vibration of the ultrasonic vibrator 130, air is repeatedly compressed and expanded in the gap Rh between the resonator 311 and the ultrasonic vibrator 130. Air resonance occurs depending on the short dimension of the resonator 311 in the first direction (X-axis direction). Specifically, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance can occur in the gap Rh when the short dimension of the resonator 311 in the first direction (X-axis direction) is close to λ / 2. As a result, air resonance of λ / 2 occurs in the gap Rh in the first direction (X-axis direction). In the gap Rh, the position directly below the center of the resonator 311 in the first direction (X-axis direction) becomes the antinode of the air resonance, and the position directly below the end of the resonator 311 in the first direction (X-axis direction) becomes the node of the air resonance.

[0085] For example, when the thickness T2 of the support 220 is 0.2 mm and the short side dimension of the resonance board 311 in the first direction (X-axis direction) is about 1.3 mm, air resonance with a frequency of 100 kHz can be generated in the gap Rh. When the thickness T2 of the support 220 is 0.2 mm and the short side dimension of the resonance board 311 in the first direction (X-axis direction) is about 1.0 mm, air resonance with a frequency of 150 kHz can be generated in the gap Rh.

[0086] In the ultrasonic transducer 300 according to the third embodiment of the present invention, where λ is the wavelength converted from the drive frequency of the ultrasonic vibrator 130, air resonance of λ / 2 can be generated in the gap Rh in the first direction (X-axis direction). When air resonance of λ / 2 is generated in the ultrasonic transducer 300, sound pressure due to air resonance is superimposed, and ultrasonic waves at a high sound pressure level can be emitted. Furthermore, when air resonance of λ / 4 is generated in the first direction (X-axis direction) in the gap Rg, sound pressures due to air resonance of λ / 2 and λ / 4 are superimposed, and ultrasonic waves at a high sound pressure level can be emitted.

[0087] Since the first vibration plate 310 has at least one resonance plate portion 311, the number of parts of the ultrasonic transducer 300 can be reduced compared to when the resonance plate portion 311 is constructed as a separate member from the first vibration plate 310.

[0088] In a parametric speaker equipped with the ultrasonic transducer 300 according to the third embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 300 by modulating the ultrasonic waves to reproduce audible sounds.

[0089] (Embodiment 4) An ultrasonic transducer according to embodiment 4 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 4 of the present invention differs from the ultrasonic transducer according to embodiment 3 of the present invention in that a rear resonance plate is provided, and therefore, the description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 3 of the present invention will not be repeated.

[0090] Fig. 32 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 4 of the present invention. As shown in Fig. 32, the ultrasonic transducer 400 according to embodiment 4 of the present invention includes a first diaphragm 310, a plurality of supports 220, a plurality of ultrasonic vibrators 130, a rear resonance board 410, and a spacer 420. The first diaphragm 310 and the plurality of supports 220 are bonded together, and a plurality of ultrasonic vibrators 130 are bonded to the plurality of supports 220, respectively. The rear resonance board 410 is disposed opposite each of the plurality of ultrasonic vibrators 130 via the spacer 420. The spacer 420 is bonded to the rear resonance board 410 and each of the plurality of ultrasonic vibrators 130.

[0091] The rear resonance board 410 is disposed on the opposite side of the supports 220 with respect to the ultrasonic transducers 130, and faces each of the ultrasonic transducers 130 with a gap therebetween. The spacer 420 extends in a pair of straight lines along both longitudinal ends of the ultrasonic transducers 130. The space sandwiched between the ultrasonic transducers 130 and the rear resonance board 410 via the spacer 420 is connected to the gap Rh through the gaps between the ultrasonic transducers 130 formed by cutting along the cut lines LC.

[0092] Fig. 33 shows a sound pressure distribution obtained by simulation analysis using the finite element method when air resonance of λ occurs in the ultrasonic transducer according to embodiment 4 of the present invention. Fig. 33 shows that the sound pressure increases as the color changes from black to white in areas where air is present. In the state shown in Fig. 33, the sound pressure is high in the gap Rg between the diaphragm portion 211 and the ultrasonic vibrator 130 and in the gap Rk between the ultrasonic vibrator 130 and the rear resonance board 410, while the sound pressure is low in the gap Rh between the resonance board portion 311 and the ultrasonic vibrator 130, the gap Rm between the ultrasonic vibrators 130, and the region Rj directly above the resonance board portion 311.

[0093] Since the vibration plate portion 211 vibrates in a resonant manner in the opposite phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 310, air is repeatedly compressed and expanded in the gap Rg.

[0094] Air resonance occurs depending on the shortest distance L2 between one end of the shaft portion 221 and one end of the diaphragm portion 211, and the shortest distance L3 between the other end of the shaft portion 221 and the other end of the diaphragm portion 211. Specifically, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance can occur in the gap Rg when at least one of the shortest distance L2 and the shortest distance L3 has a dimension close to λ / 4. As a result, air resonance of λ / 4 occurs in the gap Rg in the first direction (X-axis direction).

[0095] Due to the resonant vibration of the ultrasonic vibrator 130, air is repeatedly compressed and expanded in the gap Rh between the resonance board 311 and the ultrasonic vibrator 130. Air resonance occurs depending on the short dimension of the resonance board 311 in the first direction (X-axis direction). Specifically, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance can occur in the gap Rh when the short dimension of the resonance board 311 in the first direction (X-axis direction) is close to λ / 2. As a result, air resonance of λ / 2 occurs in the gap Rh in the first direction (X-axis direction).

[0096] The resonant vibration of the ultrasonic vibrator 130 also causes repeated compression and expansion of air in the gap Rk between the ultrasonic vibrator 130 and the rear resonance board 410. By making the thickness of the spacer 420 approximately 0.1 mm and ensuring the gap Rk between the ultrasonic vibrator 130 and the rear resonance board 410, air resonance can be generated in the gap Rk. Specifically, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance of λ occurs in the first direction (X-axis direction) in the gap Rk. In the gap Rk, the position directly below the center of the ultrasonic vibrator 130 in the first direction (X-axis direction) becomes the antinode of the air resonance, and the position directly below the gap Rm becomes the node of the air resonance.

[0097] In the ultrasonic transducer 400 according to the fourth embodiment of the present invention, where λ is the wavelength converted from the drive frequency of the ultrasonic vibrator 130, air resonance of λ can be generated in the first direction (X-axis direction) in the gap Rk. When air resonance of λ is generated in the ultrasonic transducer 400, the sound pressure due to air resonance of λ radiated to the front side of the ultrasonic transducer 400 through the gap Rm is superimposed, allowing the ultrasonic transducer 400 to radiate ultrasonic waves at a high sound pressure level. Furthermore, when air resonance of λ / 4 is generated in the first direction (X-axis direction) in the gap Rg, the sound pressures due to air resonance of λ and air resonance of λ / 4 are superimposed, allowing the ultrasonic transducer 400 to radiate ultrasonic waves at a high sound pressure level. Furthermore, when air resonance of λ / 2 is generated in the first direction (X-axis direction) in the gap Rh, the sound pressures due to air resonance of λ, air resonance of λ / 2, and air resonance of λ / 4 are superimposed, allowing the ultrasonic transducer 400 to radiate ultrasonic waves at a high sound pressure level.

[0098] In a parametric speaker equipped with the ultrasonic transducer 400 according to the fourth embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 400 by modulating the ultrasonic waves to reproduce audible sounds.

[0099] (Embodiment 5) An ultrasonic transducer according to embodiment 5 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 5 of the present invention differs from the ultrasonic transducer according to embodiment 4 of the present invention in that it does not include a diaphragm portion and a resonant plate portion, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 4 of the present invention will not be repeated.

[0100] Fig. 34 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 5 of the present invention. As shown in Fig. 34, an ultrasonic transducer 500 according to embodiment 5 of the present invention includes a plurality of supports 220, a plurality of ultrasonic vibrators 130, a rear resonance plate 410, and a spacer 420.

[0101] Fig. 35 is a diagram showing a sound pressure distribution obtained by simulation analysis using the finite element method when air resonance of λ occurs in the ultrasonic transducer according to embodiment 5 of the present invention. Fig. 35 shows that in the area where air is present, the sound pressure increases as the color changes from black to white.

[0102] As shown in Figure 35, in the ultrasonic transducer 500 according to the fifth embodiment of the present invention, the vibration of the ultrasonic vibrator 130 causes repeated compression and expansion of air in the gap Rk between the ultrasonic vibrator 130 and the rear resonance board 410.

[0103] In the ultrasonic transducer 500 according to the fifth embodiment of the present invention, if the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance of λ can be generated in the first direction (X-axis direction) in the gap Rk. When air resonance of λ is generated, the ultrasonic transducer 500 can radiate ultrasonic waves at a high sound pressure level with a simple and compact configuration by the air resonance of λ radiated to the front side of the ultrasonic transducer 500 through the gap Rm.

[0104] In a parametric speaker equipped with the ultrasonic transducer 500 according to the fifth embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 500 by modulating the ultrasonic waves to reproduce audible sounds.

[0105] (Embodiment 6) An ultrasonic transducer according to embodiment 6 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 6 of the present invention differs from the ultrasonic transducer according to embodiment 4 of the present invention in that it does not include a resonating plate portion, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 4 of the present invention will not be repeated.

[0106] Fig. 36 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 6 of the present invention. As shown in Fig. 36, an ultrasonic transducer 600 according to embodiment 6 of the present invention includes a first diaphragm 210, a plurality of supports 220, a plurality of ultrasonic vibrators 130, a rear resonance plate 410, and a spacer 420.

[0107] Fig. 37 is a diagram showing a sound pressure distribution obtained by simulation analysis using the finite element method when λ air resonance and λ / 4 air resonance occur in the ultrasonic transducer according to embodiment 6 of the present invention. Fig. 37 shows that in the area where air is present, the sound pressure increases as the color changes from black to white.

[0108] 37 , in the ultrasonic transducer 600 according to the sixth embodiment of the present invention, where λ is the wavelength converted from the drive frequency of the ultrasonic vibrator 130, air resonance of λ can be generated in the first direction (X-axis direction) in the gap Rk. When air resonance of λ is generated, the ultrasonic transducer 600 can radiate ultrasonic waves at a high sound pressure level by superimposing the sound pressure due to air resonance of λ radiated to the front side of the ultrasonic transducer 600 through the gap Rm. Furthermore, when air resonance of λ / 4 is generated in the first direction (X-axis direction) in the gap Rg, the ultrasonic transducer 600 can radiate ultrasonic waves at a high sound pressure level by superimposing the sound pressure due to air resonance of λ and air resonance of λ / 4.

[0109] In a parametric speaker equipped with the ultrasonic transducer 600 according to the sixth embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 600 by modulating the ultrasonic waves to reproduce audible sounds.

[0110] (Embodiment 7) An ultrasonic transducer according to embodiment 7 of the present invention will be described below with reference to the drawings. The ultrasonic transducer according to embodiment 7 of the present invention differs from the ultrasonic transducer according to embodiment 4 of the present invention in that it does not include a diaphragm portion, and therefore, description of the configuration that is the same as that of the ultrasonic transducer according to embodiment 4 of the present invention will not be repeated.

[0111] Fig. 38 is an exploded perspective view showing the configuration of an ultrasonic transducer according to embodiment 7 of the present invention. As shown in Fig. 38, the ultrasonic transducer 700 according to embodiment 7 of the present invention includes a front resonance board 710, a plurality of supports 220, a plurality of ultrasonic vibrators 130, a rear resonance board 410, and a spacer 420.

[0112] The front-side sound board 710 is formed with a plurality of sound board portions 711 that extend in the second direction (Y-axis direction) and face, with a gap between them, each of the ultrasonic vibrators 130 that are adjacent in the first direction (X-axis direction) among the plurality of ultrasonic vibrators 130. Each of the plurality of sound board portions 711 is connected to both end portions 712 of the front-side sound board 710 in the second direction (Y-axis direction).

[0113] Fig. 39 is a diagram showing a sound pressure distribution obtained by simulation analysis using the finite element method when λ air resonance and λ / 2 air resonance occur in the ultrasonic transducer according to embodiment 7 of the present invention. Fig. 39 shows that in the area where air is present, the sound pressure increases as the color changes from black to white.

[0114] 39 , in the ultrasonic transducer 700 according to the seventh embodiment of the present invention, where λ is the wavelength converted from the drive frequency of the ultrasonic vibrator 130, air resonance of λ can be generated in the first direction (X-axis direction) in the gap Rk. When air resonance of λ is generated, the ultrasonic transducer 700 can radiate ultrasonic waves at a high sound pressure level by superimposing the sound pressure due to air resonance of λ radiated to the front side of the ultrasonic transducer 700 through the gap Rm. Furthermore, when air resonance of λ / 2 is generated in the first direction (X-axis direction) in the gap Rh, the ultrasonic transducer 700 can radiate ultrasonic waves at a high sound pressure level by superimposing the sound pressure due to air resonance of λ and air resonance of λ / 2.

[0115] In a parametric speaker equipped with the ultrasonic transducer 700 according to the sixth embodiment of the present invention, it is possible to modulate the ultrasonic waves emitted from the ultrasonic transducer 700 by modulating the ultrasonic waves to reproduce audible sounds.

[0116] (Experimental Examples) Here, the results of measuring the output of ultrasonic waves emitted from the ultrasonic transducers will be described. The output of ultrasonic waves emitted from the ultrasonic transducer 400 according to embodiment 4 as Example 1, the ultrasonic transducer 300 according to embodiment 3 as Example 2, the ultrasonic transducer 500 according to embodiment 5 as Example 3, and the ultrasonic transducer according to the comparative example were measured.

[0117] 40 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a comparative example. As shown in FIG. 40, an ultrasonic transducer 900 according to the comparative example includes a plurality of supports 220 and a plurality of ultrasonic vibrators 130.

[0118] Fig. 41 is a graph showing the results of measuring the output of ultrasonic waves emitted from the ultrasonic transducers according to Examples 1 to 3 and the comparative example. As shown in Fig. 41, compared to the ultrasonic transducer 900 according to the comparative example, the output was 13 times higher in Example 1, 7 times higher in Example 2, and 4 times higher in Example 3.

[0119] (Note) It will be understood by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.

[0120] <1> An ultrasonic transducer comprising: a first vibration plate having at least one vibration plate portion extending in a longitudinal direction; at least one support member having a shaft portion extending in the longitudinal direction and joined to the first vibration plate; and at least one ultrasonic vibrator attached to the at least one support member over the entire longitudinal length of the shaft portion and facing the at least one vibration plate portion with a first gap therebetween, with the at least one support member sandwiched therebetween; wherein a short-side dimension of the shaft portion in a short-side direction perpendicular to the longitudinal direction is smaller than each short-side dimension of the at least one vibration plate portion and the at least one ultrasonic vibrator; the at least one vibration plate portion resonates and vibrates in an opposite phase to the at least one ultrasonic vibrator in the direction perpendicular to the at least one vibration plate portion; and the long-side dimension of the shaft portion in the longitudinal direction is four or more times the short-side dimension of the at least one ultrasonic vibrator.

[0121] <2> The ultrasonic transducer according to <1>, wherein the at least one ultrasonic vibrator is a piezoelectric element including a piezoelectric body.

[0122] <3> The ultrasonic transducer according to <1> or <2>, wherein, when a wavelength converted from the drive frequency of the at least one ultrasonic vibrator is λ, an air resonance of λ / 4 can be generated in the short side direction in the first gap.

[0123] <4> The ultrasonic transducer according to any one of <1> to <3>, further comprising a pair of restraint plate portions extending in the short-side direction and joined to positions near both ends of the at least one ultrasonic vibrator in the longitudinal direction.

[0124] <5> The ultrasonic transducer according to any one of <1> to <4>, wherein a constricted portion that is narrower than a short dimension of the shaft portion is formed at a position on the outer side of the at least one vibration plate portion in the longitudinal direction of the first vibration plate.

[0125] <6> The ultrasonic transducer according to any one of <1> to <5>, wherein the at least one vibration plate portion is arranged in a plurality of positions spaced apart from each other and aligned in the short side direction, the vibration plate portions adjacent to each other in the short side direction in the first vibration plate are connected at both ends in the long side direction of the first vibration plate, the at least one support is arranged in a plurality of positions aligned in the short side direction and is joined to each of the at least one vibration plate portion, and the supports adjacent to each other in the short side direction in the at least one support are connected at both ends in the long side direction.

[0126] <7> The ultrasonic transducer according to <6>, further comprising at least one resonant plate portion arranged between adjacent vibration plate portions in the short side direction, extending in the longitudinal direction and facing each of the adjacent ultrasonic vibrators in the short side direction across a second gap, wherein, when a wavelength converted from the drive frequency of the at least one ultrasonic vibrator is λ, the at least one resonant plate portion is capable of generating air resonance of λ / 2 in the short side direction in the second gap.

[0127] <8> The ultrasonic transducer according to <6> or <7>, further comprising a rear resonance board arranged on the opposite side of the at least one support with respect to the at least one ultrasonic vibrator and facing each of the at least one ultrasonic vibrator with a third gap therebetween, wherein the at least one ultrasonic vibrator is arranged in plurality with intervals between each other in the short-side direction, and wherein, when the wavelength converted from the drive frequency of the at least one ultrasonic vibrator is λ, the rear resonance board is capable of generating air resonance of λ in the short-side direction in the third gap.

[0128] <9> A parametric speaker comprising the ultrasonic transducer according to any one of <1> to <8>, and reproducing an audible sound by modulating and driving the ultrasonic transducer.

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

[0130] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0131] 100, 100a, 100b, 100c, 200, 300, 400, 500, 600, 700, 900 Ultrasonic transducer, 110, 110a, 210, 310 First vibration plate, 110c, 210c, 310c Intermediate portion, 110e, 210e, 310e Node point, 111, 211 Vibration plate portion, 112, 212, 712 Both ends, 113 Neck portion, 120, 120b, 220, 320 Support, 120c, 122, 222, 322 Restraint plate portion, 121, 221, 321 Shaft portion, 130, 130a, 130b, 130c Ultrasonic vibrator, 131 Piezoelectric body, 132 First electrode, 133 Second electrode, 134 intermediate electrode, 135 second diaphragm, 140 processing circuit, 311, 711 soundboard section, 410 rear soundboard, 420 spacer, 710 front soundboard.

Claims

1. An ultrasonic transducer comprising: a first diaphragm having at least one diaphragm portion extending in a longitudinal direction; at least one support having an axis portion extending in the longitudinal direction and joined to the first diaphragm; and at least one ultrasonic vibrator attached to the at least one support over the entire longitudinal length of the axis portion and facing the at least one diaphragm portion with a first gap therebetween, with the at least one support in between; wherein the short side dimension of the axis portion in a short side direction perpendicular to the longitudinal direction is smaller than the short side dimensions of the at least one diaphragm portion and the at least one ultrasonic vibrator, the at least one diaphragm portion resonatingly vibrates in antiphase with the at least one ultrasonic vibrator in a direction perpendicular to the at least one diaphragm portion, and the long side dimension of the axis portion in the longitudinal direction is four or more times the short side dimension of the at least one ultrasonic vibrator.

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

3. An ultrasonic transducer as described in claim 1 or claim 2, wherein, when the wavelength converted from the driving frequency of the at least one ultrasonic vibrator is λ, air resonance of λ / 4 can be generated in the short direction in the first gap.

4. An ultrasonic transducer as described in any one of claims 1 to 3, further comprising a pair of restraint plate portions extending in the short direction and joined respectively to positions near both ends of the longitudinal direction of at least one of the ultrasonic transducers.

5. An ultrasonic transducer as described in any one of claims 1 to 4, wherein a narrowed portion that is narrower than the short dimension of the shaft portion is formed at a position outside the longitudinal direction of at least one of the vibration plate portions in the first vibration plate.

6. An ultrasonic transducer as claimed in any one of claims 1 to 5, wherein the at least one vibration plate portion is arranged in a plurality of positions spaced apart from each other in the short direction, adjacent vibration plate portions in the short direction of the first vibration plate are connected at both ends in the longitudinal direction of the first vibration plate, the at least one support is arranged in a plurality of positions in the short direction and is joined to each of the at least one vibration plate portion, and adjacent supports in the short direction of the at least one support are connected to each other at both ends in the longitudinal direction.

7. An ultrasonic transducer as described in claim 6, further comprising at least one resonant plate portion arranged between adjacent vibration plate portions in the short side direction, extending in the longitudinal direction and facing each of adjacent ultrasonic transducers in the short side direction across a second gap, wherein when the wavelength converted from the drive frequency of the at least one ultrasonic transducer is λ, the at least one resonant plate portion is capable of generating air resonance of λ / 2 in the short side direction in the second gap.

8. An ultrasonic transducer as described in claim 6 or claim 7, further comprising a rear resonance plate arranged on the opposite side of the at least one support with respect to the at least one ultrasonic vibrator and facing each of the at least one ultrasonic vibrator with a third gap therebetween, the at least one ultrasonic vibrator being arranged in a plurality of spaces apart from each other in the short direction, and the rear resonance plate being capable of generating air resonance of λ in the short direction in the third gap, where λ is the wavelength converted from the drive frequency of the at least one ultrasonic vibrator.

9. A parametric speaker comprising the ultrasonic transducer according to any one of claims 1 to 8, which reproduces an audible sound by modulating and driving the ultrasonic transducer.

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