Ultrasonic transducer and parametric speaker including same

Abstract

The supports have a shaft portion (221) extending in the longitudinal direction, and are arranged to be aligned in a lateral direction perpendicular to the longitudinal direction. The ultrasonic transducers (130) are attached to the supports over the entire length of the shaft portion (221) in the longitudinal direction, and are arranged at intervals from each other in the lateral direction. The back resonance plate (410) is arranged on the opposite side of the supports with respect to the ultrasonic transducers (130), and faces each of the ultrasonic transducers (130) with a first gap (Rk) therebetween. The lateral dimension of the shaft portion (221) in the lateral direction is smaller than the lateral dimension of each of the ultrasonic transducers (130). The longitudinal dimension of the shaft portion (221) in the longitudinal direction is larger than the lateral dimension of each of the ultrasonic transducers (130). If the wavelength converted from the drive frequency of the multiple ultrasonic transducers (130) is λ, the rear resonance board (410) can generate air resonance of λ in the short direction in the first gap (Rk).

Description

[Technical field]

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

[0002] Prior documents disclosing the configuration of an ultradirectional acoustic device include Japanese Patent Application 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 substantially circular. The multiple ultrasonic transducers are divided into two groups with different installation heights.

[0003] The superdirectional acoustic device described in Patent Document 2 includes a first ultrasonic emitter and a second ultrasonic emitter. The second ultrasonic emitter is disposed on the axis of the first ultrasonic emitter and in front of the radiation surface. The phase of the carrier signal emitted by the second ultrasonic emitter is inverse to the phase of the carrier signal included in the signal emitted by the first ultrasonic emitter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-47085 A [Patent Document 2] Patent No. 6333480 Summary of the Invention [Problem to be solved by the invention]

[0005] In the superdirectional acoustic device described in Patent Document 1, a plurality of ultrasonic transducers are arranged in two groups with different installation heights, resulting in a complex configuration. In the superdirectional acoustic device described in Patent Document 2, a second ultrasonic emitter is arranged outside a first ultrasonic emitter, resulting in a large device.

[0006] The present invention has been made in consideration of the above problems, and has an object to provide an ultrasonic transducer and a parametric speaker equipped with the same that can increase the sound pressure level with a simple and compact configuration. [Means for solving the problem]

[0007] The ultrasonic transducer according to the present invention includes a plurality of supports, a plurality of ultrasonic vibrators, and a back-side resonating plate. The supports have an axis extending in the longitudinal direction, and are arranged so as to be aligned in a short-side direction perpendicular to the longitudinal direction. The ultrasonic vibrators are attached to the supports over the entire length of the axis in the longitudinal direction, and are arranged at intervals from each other in the short-side direction. The back-side resonating plate is arranged on the opposite side of the supports with respect to the ultrasonic vibrators, and faces each of the ultrasonic vibrators with a first gap. The short-side dimension of the axis in the short-side direction is smaller than the short-side dimension of each of the ultrasonic vibrators. The long-side dimension of the axis in the longitudinal direction is larger than the short-side dimension of each of the ultrasonic vibrators. If the wavelength converted from the driving frequency of the ultrasonic vibrators is λ, the back-side resonating plate can generate air resonance of λ in the short-side direction in the first gap. Effect of the Invention

[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. [Brief description of the drawings]

[0009] [Figure 1] 1 is a longitudinal sectional view showing a configuration of an ultrasonic transducer according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is an exploded perspective view showing a configuration of an ultrasonic transducer according to a first embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view showing a configuration of an ultrasonic vibrator included in an ultrasonic transducer according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view showing a displacement state obtained by simulation analysis using a finite element method when the ultrasonic transducer according to the first embodiment of the present invention transmits or receives ultrasonic waves. [Diagram 5] 5 is a cross-sectional view of the ultrasonic transducer of FIG. 4 as viewed from the direction of the arrow VV. [Figure 6] 13 is a graph showing a result of simulation analysis using a finite element method of the change in the resonance frequency of the first diaphragm when the longitudinal dimension of the shaft part of the support body is changed while the transverse dimension of the ultrasonic transducer is fixed. [Figure 7] 13 is a graph showing a simulation analysis using a finite element method of the change in the sound pressure of ultrasonic waves transmitted from an ultrasonic transducer when the longitudinal dimension of the shaft portion of the support is changed while the transverse dimension of the ultrasonic vibrator is fixed. [Figure 8] FIG. 2 is a diagram showing a sound pressure distribution obtained by simulation analysis using a finite element method when air resonance of λ / 4 occurs in the ultrasonic transducer according to the first embodiment of the present invention. [Figure 9] FIG. 11 is a cross-sectional view showing the configuration of an ultrasonic transducer according to a first modified example. [Figure 10] FIG. 11 is a cross-sectional view showing the configuration of an ultrasonic transducer according to a second modified example. [Figure 11] FIG. 11 is a cross-sectional view showing the configuration of an ultrasonic transducer according to a third modified example. [Figure 12] FIG. 11 is an exploded perspective view showing a configuration of an ultrasonic transducer according to a fourth modified example of the first embodiment of the present invention. [Figure 13] FIG. 11 is a plan view of an ultrasonic transducer according to a fourth modified example of the first embodiment of the present invention, as viewed from the first diaphragm side. [Figure 14] FIG. 11 is a perspective view showing a displacement state obtained by simulation analysis using a finite element method when an ultrasonic transducer according to a fourth modified example of the first embodiment of the present invention transmits or receives ultrasonic waves. [Figure 15] FIG. 11 is an exploded perspective view showing a configuration of an ultrasonic transducer according to a fifth modified example of the first embodiment of the present invention. [Figure 16]FIG. 11 is a perspective view showing a displacement state obtained by simulation analysis using a finite element method when an ultrasonic transducer according to a fifth modified example of the first embodiment of the present invention transmits or receives ultrasonic waves. [Figure 17] 17 is a cross-sectional view of the ultrasonic transducer of FIG. 16 as viewed in the direction of the arrows indicated by the lines XVII-XVII. [Figure 18] FIG. 13 is an exploded perspective view showing a configuration of an ultrasonic transducer according to a sixth modified example of the first embodiment of the present invention. [Figure 19] FIG. 13 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the sixth modified example of the first embodiment of the present invention transmits or receives ultrasonic waves. [Figure 20] 20 is a cross-sectional view of the ultrasonic transducer of FIG. 19 taken along the line XX-XX. [Figure 21] FIG. 4 is a side view showing the configuration of an ultrasonic transducer according to a second embodiment of the present invention. [Figure 22] 22 is a rear perspective view of the ultrasonic transducer shown in FIG. 21, as viewed in the direction of arrow XXII. [Figure 23] FIG. 11 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a second embodiment of the present invention. [Figure 24] FIG. 11 is a perspective view showing a displacement state obtained by simulation analysis using a finite element method when an ultrasonic transducer according to a second embodiment of the present invention transmits or receives ultrasonic waves. [Diagram 25] 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. [Figure 26] FIG. 11 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a third embodiment of the present invention. [Figure 27] 11 is a side view showing the positional relationship between the cutting positions of a piezoelectric body and a resonance plate portion of an ultrasonic transducer according to a third embodiment of the present invention. FIG. [Figure 28] 13 is a plan view showing a configuration of a plurality of supports according to a modified example. FIG. [Figure 29]FIG. 11 is a perspective view showing a displacement state simulated and analyzed by using a finite element method when an ultrasonic transducer according to a third embodiment of the present invention transmits or receives ultrasonic waves. [Diagram 30] 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. [Diagram 31] FIG. 11 is a diagram showing a sound pressure distribution obtained by simulation analysis using the finite element method when air resonance of λ / 2 occurs in the ultrasonic transducer according to the third embodiment of the present invention. [Diagram 32] FIG. 11 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fourth embodiment of the present invention. [Diagram 33] FIG. 11 is a diagram showing a sound pressure distribution obtained by simulation analysis using a finite element method when air resonance of λ occurs in an ultrasonic transducer according to a fourth embodiment of the present invention. [Diagram 34] FIG. 11 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a fifth embodiment of the present invention. [Diagram 35] FIG. 11 is a diagram showing a sound pressure distribution obtained by simulation analysis using a finite element method when air resonance of λ occurs in an ultrasonic transducer according to a fifth embodiment of the present invention. [Diagram 36] FIG. 11 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a sixth embodiment of the present invention. [Figure 37] FIG. 13 is a diagram showing a sound pressure distribution obtained by simulation analysis using a finite element method when λ air resonance and λ / 4 air resonance occur in an ultrasonic transducer according to a sixth embodiment of the present invention. [Figure 38] FIG. 11 is an exploded perspective view showing the configuration of an ultrasonic transducer according to a seventh embodiment of the present invention. [Figure 39] FIG. 13 is a diagram showing a sound pressure distribution obtained by simulation analysis using a finite element method when air resonance of λ and air resonance of λ / 2 occur in an ultrasonic transducer according to a seventh embodiment of the present invention. [Diagram 40] FIG. 1 is an exploded perspective view showing a configuration of an ultrasonic transducer according to a comparative example. [Diagram 41] 1 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 a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an ultrasonic transducer according to each embodiment of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings are given the same reference numerals, and the description thereof will not be repeated. The present invention is applicable to applications requiring ultrasonic waves with high sound pressure, 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 an 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 direction along a first direction (X-axis direction) and a long side direction 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 dimension 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, the support 120 has a pair of constraint plate portions 122 extending in the first direction (X-axis direction) formed on both outer sides of the shaft portion 121 in the second direction (Y-axis direction). 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 by a bonding agent made of epoxy resin or the like. Specifically, one end of the entire shaft portion 121 in the third direction (Z-axis direction) is bonded to the first diaphragm 110 by a bonding agent. At least a part or the entire one end of the pair of constraint plate portions 122 in the third direction (Z-axis direction) may be bonded to the first diaphragm 110 by a 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, it is preferable that the support 120 is made of a 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, it is preferable that the support 120 is made of a 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 transducer 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 transducer 130 may be hindered.

[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 four times or more the transverse dimension W3 of the ultrasonic vibrator 130, and from the viewpoint of increasing the sound pressure level of the ultrasonic waves transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, 20 mm or more. The transverse dimension W2 of the stem 121 is smaller than each of 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 from the viewpoint of maintaining the bonding strength, it is preferable that it is 0.3 mm or more and 0.6 mm or less. If the transverse dimension W2 of the stem 121 exceeds 1 mm, it may hinder the vibration of the ultrasonic vibrator 130. The dimension of each of the pair of restraining plate portions 122 in the first direction (X-axis direction) is equal to the short side dimension W3 of the ultrasonic transducer .

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

[0019] As shown in FIG. 1, the ultrasonic transducer 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, sandwiching the support 120 therebetween. Specifically, the ultrasonic transducer 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 transducer 130 is attached to one end of the entire shaft portion 121 in the third direction (Z-axis direction), and to at least a part of or the other end of the entire pair of constraint plate portions 122 in the third direction (Z-axis direction). Each of the pair of constraint plate portions 122 is joined to both ends of the ultrasonic transducer 130 in the longitudinal direction, respectively.

[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 FIG. 1, FIG. 2, and FIG. 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 laminated 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 transducer 130. For example, when the resonant frequency of the first diaphragm 110 is set to be 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 the first embodiment of the present invention transmits or receives ultrasonic waves. Fig. 5 is a cross-sectional view of the ultrasonic transducer in Fig. 4 as seen from the direction of the VV line arrow. The simulation analysis conditions were as follows: thickness T1 of first vibration plate 110 is 0.05 mm, combined thickness T3 of two piezoelectric bodies 131 is 0.4 mm, thickness T2 of support body 120 is 0.2 mm, and longitudinal dimension L1 of shaft portion 121 is 20 mm.

[0023] As shown in Fig. 4 and Fig. 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 the third direction (Z-axis direction) perpendicular to the first vibration plate 110. That is, as shown in Fig. 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 more.

[0024] In the first diaphragm 110, the displacement of the resonant vibration is maximum at the middle part 110c of the diaphragm part 111 located at the middle of the shaft part 121 in the longitudinal direction, and the end part located on the constraining plate part 122 becomes the node point 110e. That is, in the first diaphragm 110, the diaphragm part 111 located on the shaft part 121 between the constraining plate parts 122 becomes the vibration region that resonates. The longitudinal dimension of the vibration region of the first diaphragm 110 is the same as the longitudinal dimension L1 of the shaft part 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 a simulation analysis using the finite element method of the transition of the resonance frequency of the first vibration plate when the longitudinal dimension of the shaft part of the support is changed while the transverse dimension of the ultrasonic transducer is fixed. In Fig. 6, the vertical axis shows the resonance frequency (kHz) of the first vibration plate 110, and the horizontal axis shows the longitudinal dimension L1 (mm) of the shaft part 121 of the support 120. As a simulation analysis condition, the transverse dimension W3 of the ultrasonic transducer 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 resonance frequency of the first vibration plate 110 is 200 kHz, and when the longitudinal dimension L1 is increased to 8 mm and the longitudinal dimension of the vibration region of the first vibration plate 110 is increased, the resonance frequency of the first vibration plate 110 drops to 112 kHz. Thereafter, even when the longitudinal dimension L1 of the shaft portion 121 of the support 120 becomes larger than 8 mm and the longitudinal dimension of the vibration region of the first vibration plate 110 becomes further larger, the resonance frequency of the first vibration plate 110 becomes approximately constant at 112 kHz. In other words, the resonance frequency of the first vibration plate 110 becomes approximately constant when the longitudinal dimension L1 of the shaft portion 121 of the support 120 exceeds four times the short-side dimension W3 of the ultrasonic transducer 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] Fig. 7 is a graph showing a simulation analysis using the finite element method of the transition of the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer when the longitudinal dimension of the shaft part of the support is changed while the transverse dimension of the ultrasonic vibrator is fixed. In Fig. 7, the vertical axis shows the sound pressure (Pa) transmitted from the ultrasonic transducer 100, and the horizontal axis shows the longitudinal dimension L1 (mm) of the shaft part 121 of the support 120. As a simulation analysis condition, the transverse dimension W3 of the ultrasonic vibrator 130 is fixed at 2 mm, and the sound pressure (Pa) 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 is calculated.

[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 of the first diaphragm 110 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 caused by the vibration of the first diaphragm 110 can be increased to obtain a high sound pressure.

[0031] In this way, the ultrasonic transducer 100 according to this 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 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] Fig. 8 is a diagram showing a sound pressure distribution obtained by simulation analysis using a finite element method when air resonance of λ / 4 occurs in the ultrasonic transducer according to the first embodiment of the present invention. Fig. 8 shows that the sound pressure increases as the color changes from black to white in the portion where air exists. In the state shown in Fig. 8, the sound pressure is high in the gap Rg between the vibration plate part 111 and the ultrasonic vibrator 130, and the sound pressure is low in the region Rf directly above the first vibration plate 110.

[0033] Since the diaphragm portion 111 resonates and vibrates in the opposite phase to the ultrasonic transducer 130 in the third direction (Z-axis direction) perpendicular to the first diaphragm 110, 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 transducer 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. That is, the vicinity of the shaft portion 121 becomes a fixed end and becomes a node of air resonance, and the area outside the gap Rg becomes an open end and becomes an antinode of 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 distance L2 and the shortest distance L3 is about 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 distance L2 and the shortest distance L3 is about 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 there is a certain range for the dimensions of the shortest distance L2 and the shortest distance L3 with respect to the frequency of air resonance is because the occurrence state of air resonance 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 type 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 transducer according to a first modification. As shown in Fig. 9, an ultrasonic transducer 130a according to a first modification is a piezoelectric element including two laminated piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are the same. The ultrasonic transducer 130a is a so-called parallel bimorph type piezoelectric transducer.

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

[0039] Fig. 11 is a cross-sectional view showing the configuration of an ultrasonic transducer according to a third modified example. As shown in Fig. 11, an ultrasonic transducer 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 transducer 130c is a so-called unimorph type piezoelectric transducer.

[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 an ultrasonic transducer according to a fourth modified example of the first embodiment of the present invention, seen from the first diaphragm side. As shown in FIG. 12 and FIG. 13, an ultrasonic transducer 100a according to a fourth modified example of the first embodiment of the present invention includes a first diaphragm 110a, a support 120, and an ultrasonic vibrator 130. A constricted portion 113 that is narrower than the short side dimension W2 of the shaft portion 121 of the support 120 is formed in the first diaphragm 110a at a position outside the diaphragm portion 111 in the longitudinal direction. Specifically, a pair of constricted portions 113 are formed in the first diaphragm 110a between both ends 112 in the longitudinal direction and the diaphragm portion 111. Only one constricted portion 113 may be formed.

[0041] Both ends 112 of the first diaphragm 110a are respectively joined to a pair of restraining plate portions 122 of the support 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 120 are joined to each other, the first diaphragm 110a can be placed on the support 120 while checking that the constricted portion 113 of the first diaphragm 110a is positioned on the center of the shaft portion 121 of the support 120 in the first direction (X-axis direction). This makes it possible to reduce assembly errors of the ultrasonic transducer 100a.

[0042] Fig. 14 is a perspective view showing a displacement state analyzed by simulation 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 has 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 the first embodiment of the present invention. As shown in Fig. 15, an ultrasonic transducer 100b according to the fifth modified example of the first embodiment 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 seen from the direction of the arrows XVII-XVII line. The simulation analysis conditions were as follows: thickness T1 of first vibration plate 110 is 0.05 mm, thickness T3 of two piezoelectric bodies 131 combined is 0.4 mm, thickness T2 of support body 120b is 0.2 mm, and longitudinal dimension L1 of shaft portion 121 is 20 mm.

[0045] 16 and 17, in the vibration mode of the ultrasonic transducer 100b according to the fifth modified example 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 transducer 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 110. The ultrasonic transducer 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 is no node point at the longitudinal end of the shaft portion 121. Also, 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 vibration plate 110, a support 120b, an ultrasonic vibrator 130, and a pair of constraint plate parts 120c. The support 120b is composed of only an axis part 121. The pair of constraint plate parts 120c are composed of a separate member from the support 120b. The pair of constraint plate parts 120c extend in a first direction (X-axis direction) and are respectively joined to both ends of the ultrasonic vibrator 130 in the longitudinal direction. Note that the pair of constraint plate parts 120c are not limited to being joined to both ends of the ultrasonic vibrator 130 in the longitudinal direction, but may be respectively joined to positions about 2 mm inward from both ends of the ultrasonic vibrator 130 in the longitudinal direction. That is, the pair of restraining 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 by the finite element method when the ultrasonic transducer according to the 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 seen from the direction of the arrows along the line XX-XX. The simulation analysis conditions were as follows: thickness T1 of the first vibration plate 110 was 0.05 mm, thickness T3 of the two piezoelectric bodies 131 combined was 0.4 mm, thickness T2 of the support body 120b was 0.2 mm, longitudinal dimension L1 of the shaft portion 121 was 20 mm, thickness of the constraining plate portion 120c was 0.2 mm, and the dimension of the first direction (X-axis direction) of the constraining plate portion 122 was the same as the short-side dimension W3 of the ultrasonic transducer 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 had 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 vibration plate 110, at least one support 120, and at least one ultrasonic vibrator 130. The first vibration plate 110 has at least one vibration plate 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 vibration plate 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 vibration plate portion 111 with a gap Rg therebetween, with the at least one support 120 sandwiched therebetween. A short-side dimension W2 of the shaft portion 121 in a short-side direction perpendicular to the longitudinal direction is smaller than the short-side dimensions of the at least one vibration plate portion 111 and the at least one ultrasonic vibrator 130. At least one diaphragm portion 111 resonates and vibrates in an opposite phase to at least one ultrasonic vibrator 130 in a direction perpendicular to 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, then 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 radiate ultrasonic waves at a high sound pressure level by superimposing the sound pressure due to air resonance.

[0053] The ultrasonic transducer 100 according to the first embodiment of the present invention includes a pair of constraining plate parts 122 extending in a first direction (X-axis direction) and joined to both ends of the ultrasonic vibrator 130 in the longitudinal direction. As a result, since there are nodal points at both ends in the longitudinal direction, the both ends can be supported or fixed, and therefore the ultrasonic transducer 100 can be easily mounted. In addition, the generation of unnecessary vibration modes can be suppressed, and the characteristics of the ultrasonic transducer 100 can be stabilized. Furthermore, since the support body 120 has the pair of constraining plate parts 122, the number of parts of the ultrasonic transducer 100 can be reduced compared to the case where the pair of constraining plate parts 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 an audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 100 through modulation driving of the ultrasonic transducer 100. As the modulation method, there are an AM modulation method (amplitude modulation method) and an FM modulation method (frequency modulation method).

[0055] (Embodiment 2) Hereinafter, an ultrasonic transducer according to a second embodiment of the present invention will be described with reference to the drawings. The ultrasonic transducer according to the second embodiment of the present invention differs from the ultrasonic transducer according to the first embodiment of the present invention in that a plurality of ultrasonic vibrators are arranged in an array, and therefore the description of the same configuration as the ultrasonic transducer according to the first embodiment 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 viewed 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 arranged in an array in a first direction (X-axis direction) are integrally configured. The ultrasonic transducer 200 includes a first diaphragm 210, a plurality of supports 220, and a plurality of ultrasonic vibrators 130. The first diaphragm 210 and the plurality of supports 220 are bonded to each other, 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 parts 211 arranged to extend in a second direction (Y-axis direction) and be aligned in a first direction (X-axis direction) at intervals from each other. Diaphragm parts 211 adjacent to each other in the first direction (X-axis direction) in the first diaphragm 210 are connected to each other 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, etc. 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 a pair of restraining plate portions 222.

[0061] The longitudinal dimension L1 of the shaft portion 221 is larger than the short-side dimension W3 of the ultrasonic vibrator 130. In this embodiment, the longitudinal dimension L1 of the shaft portion 221 is four times or more the short-side dimension W3 of the ultrasonic vibrator 130, and 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 more. The short-side dimension W2 of the shaft portion 221 is smaller than each of the short-side dimension W1 of the diaphragm portion 211 and the short-side dimension W3 of the ultrasonic vibrator 130. The short-side dimension W2 of the shaft portion 221 is, for example, 1 mm or less, and from the viewpoint of maintaining the bonding strength, it is preferable that it is 0.3 mm or more and 0.6 mm or less. If the short-side dimension W2 of the shaft portion 221 exceeds 1 mm, the vibration of the ultrasonic vibrator 130 may be hindered.

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

[0063] In this embodiment, each of the ultrasonic transducers 130 includes two laminated piezoelectric bodies 131. As shown in Fig. 23, the two piezoelectric bodies 131 constituting the ultrasonic transducers 130 are laminated and bonded in the form of two thin plates. The ultrasonic transducers 130 are attached to the 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 ultrasonic transducers 130 face the vibration plate portions 211 with the above-mentioned gap Rg therebetween, sandwiching the corresponding support 220 among the supports 220.

[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 the second embodiment of the present invention transmits or receives ultrasonic waves. Fig. 25 is a cross-sectional view of the ultrasonic transducer in Fig. 24 as seen from the direction of the arrows along the line XXV-XXV. The simulation analysis conditions were as follows: thickness T1 of first vibration plate 210 was 0.05 mm, combined thickness T3 of two piezoelectric bodies 131 was 0.4 mm, thickness T2 of support 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 transducer 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 210. The ultrasonic transducer 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 maximum at the middle portion 210c of the diaphragm portion 211 located on the longitudinal middle of the shaft portion 221, and both end portions 212 located on the restraint plate portions 222 become node points 210e.

[0067] Since 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, 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 in each ultrasonic transducer 100 is not inhibited. Therefore, by increasing the number of ultrasonic transducers 100 constituting the ultrasonic transducer 200 according to the second embodiment, the sound pressure level can be easily increased.

[0068] In a parametric speaker including the ultrasonic transducer 200 according to the second embodiment of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 200 through modulation driving of the ultrasonic transducer 200.

[0069] In a parametric speaker including the ultrasonic transducer 200 according to the present embodiment, which transmits ultrasonic waves of high frequencies of 100 kHz or more, it is possible to suppress sound from reaching unnecessarily far and sound leakage due to unnecessary reflection, and to reproduce audible sound only in a limited space. In addition, in the ultrasonic transducer 200, since it is possible to increase the attenuation of audible sound due to the propagation distance without providing a configuration for transmitting a carrier wave of an opposite phase as in Patent Document 2, it is possible to have a simple and compact configuration. Furthermore, since ultrasonic waves of high frequencies of 100 kHz or more are outside the audible range of animals such as dogs and cats, it is possible to suppress the influence on these animals.

[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 R0 = (k × a 2 ) / 2, where k is the wave number and a is the radius of the sound source. Thus, assuming that the speed of sound in air is 340 m / s, when the frequency of the ultrasonic waves 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 waves is 150 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 29.4 mm or less, and when the frequency of the ultrasonic waves is 200 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 25.5 mm or less. When the frequency of the ultrasonic waves is 100 kHz or more, the longitudinal dimension L1 is 4 times or more and 24 times or less than the transverse 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 longitudinal direction by a pair of restraining plate parts 222. This makes it possible to easily increase the sound pressure level.

[0073] (Embodiment 3) Hereinafter, an ultrasonic transducer according to a third embodiment of the present invention will be described with reference to the drawings. The ultrasonic transducer according to the third embodiment of the present invention differs from the ultrasonic transducer according to the second embodiment of the present invention in that a resonating plate part is provided, and therefore the description of the same configuration as that of the ultrasonic transducer according to the second embodiment 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, an ultrasonic transducer 300 according to embodiment 3 of the present invention includes a first vibration plate 310, a plurality of supports 220, and a plurality of ultrasonic vibrators 130. The first vibration plate 310 and the plurality of supports 220 are joined, and the plurality of ultrasonic vibrators 130 are joined to the plurality of supports 220, respectively.

[0075] The first vibration plate 310 is provided with a plurality of resonance plate portions 311 disposed between the vibration plate portions 211 adjacent to each other in the first direction (X-axis direction), extending in the second direction (Y-axis direction) and facing each of the ultrasonic transducers 130 adjacent to each other in the first direction (X-axis direction) with a gap therebetween. Each of the plurality of resonance plate portions 311 is connected to both ends 212 of the first vibration plate 310 in the second direction (Y-axis direction). In this embodiment, the resonance plate portion 311 is formed on the first vibration plate 310, but is not limited thereto, and the resonance plate portion 311 may be formed on a member separate from the first vibration plate 310.

[0076] Fig. 27 is a side view showing the positional relationship between the cutting positions of the piezoelectric body of the ultrasonic transducer according to the third embodiment of the present invention and the resonance plate part. As shown in Fig. 27, the two laminated piezoelectric bodies 131 are cut and divided by a dicer or the like at multiple cut lines LC that are located approximately at the center of the resonance plate part 311 in the first direction (X-axis direction) and extend in the second direction (Y-axis direction). As a result, multiple ultrasonic vibrators 130 respectively attached to 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 a plurality of supports according to a modified example. As shown in FIG. 28, a plurality of supports 320 according to a modified example are arranged to be aligned in a first direction (X-axis direction) while having a shaft portion 321 extending in a second direction (Y-axis direction). The supports 320 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 321 of the supports 320 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 322. That is, in this embodiment, the support 320 is formed with a shaft portion 321 and a pair of restraining plate portions 322. In each of the pair of restraining plate portions 322, a portion with a wide width in the second direction (Y-axis direction) and a portion with a narrow 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 portion 321 is the portion with a wide 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 the third embodiment of the present invention transmits or receives ultrasonic waves. Fig. 30 is a cross-sectional view of the ultrasonic transducer in Fig. 29 as seen from the direction of the arrows along the line XXX-XXX. The simulation analysis conditions were as follows: thickness T1 of first vibration plate 310 was 0.05 mm, combined thickness T3 of two piezoelectric bodies 131 was 0.4 mm, thickness T2 of support 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 transducer 130 in the third direction (Z-axis direction) perpendicular to the first vibration plate 310. The ultrasonic transducer 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 maximum at the middle part 310c of the diaphragm part 211 located on the longitudinal center of the shaft part 221, and the both end parts 212 located on the restraint plate part 322 become the node points 310e. The resonant plate part 311 hardly vibrates.

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

[0082] Since the diaphragm portion 211 resonates and vibrates in the opposite phase to the ultrasonic transducer 130 in the third direction (Z-axis direction) perpendicular to the first diaphragm 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 transducer 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] The resonant vibration of the ultrasonic vibrator 130 causes repeated compression and expansion of air in the gap Rh between the resonator plate 311 and the ultrasonic vibrator 130. Air resonance occurs depending on the short side dimension of the resonator plate 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 side dimension of the resonator plate 311 in the first direction (X-axis direction) is a dimension 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 plate 311 in the first direction (X-axis direction) becomes the antinode of air resonance, and the position directly below the end of the resonator plate 311 in the first direction (X-axis direction) becomes the node of air resonance.

[0085] For example, when the thickness dimension T2 of the support 220 is 0.2 mm and the short side dimension in the first direction (X-axis direction) of the resonance board 311 is about 1.3 mm, air resonance with a frequency of 100 kHz can be generated in the gap Rh. When the thickness dimension T2 of the support 220 is 0.2 mm and the short side dimension in the first direction (X-axis direction) of the resonance board 311 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, when the wavelength converted from the drive frequency of the ultrasonic vibrator 130 is λ, air resonance of λ / 2 can be generated in the first direction (X-axis direction) in the gap Rh. When air resonance of λ / 2 is generated in the ultrasonic transducer 300, sound pressure due to air resonance is superimposed, and ultrasonic waves of 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 pressure due to air resonance of λ / 2 and air resonance of λ / 4 are superimposed, and ultrasonic waves of a high sound pressure level can be emitted.

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

[0088] In a parametric speaker including the ultrasonic transducer 300 according to the third embodiment of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 300 through modulation driving of the ultrasonic transducer 300.

[0089] (Embodiment 4) Hereinafter, an ultrasonic transducer according to a fourth embodiment of the present invention will be described with reference to the drawings. The ultrasonic transducer according to the fourth embodiment of the present invention differs from the ultrasonic transducer according to the third embodiment of the present invention in that a rear resonance plate is provided, and therefore the description of the same configuration as that of the ultrasonic transducer according to the third embodiment 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 the fourth embodiment of the present invention. As shown in FIG. 32, the ultrasonic transducer 400 according to the fourth embodiment of the present invention includes a first vibration plate 310, a plurality of supports 220, a plurality of ultrasonic vibrators 130, a back-side resonance plate 410, and a spacer 420. The first vibration plate 310 and the plurality of supports 220 are joined, and the plurality of ultrasonic vibrators 130 are respectively joined to the plurality of supports 220, and the back-side resonance plate 410 is disposed opposite each of the plurality of ultrasonic vibrators 130 via the spacer 420. The spacer 420 is joined to the back-side resonance plate 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 gap between the ultrasonic transducers 130 formed by cutting along the cut line LC.

[0092] Fig. 33 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 the fourth embodiment of the present invention. Fig. 33 shows that the sound pressure increases as the color changes from black to white in the part where air exists. In the state shown in Fig. 33, the sound pressure is high in the gap Rg between the diaphragm part 211 and the ultrasonic vibrator 130 and the gap Rk between the ultrasonic vibrator 130 and the rear resonance board 410, and is low in the gap Rh between the resonance board part 311 and the ultrasonic vibrator 130, the gap Rm between the ultrasonic vibrators 130, and the area Rj directly above the resonance board part 311.

[0093] Since the diaphragm portion 211 resonates and vibrates in the opposite phase to the ultrasonic transducer 130 in the third direction (Z-axis direction) perpendicular to the first diaphragm 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 transducer 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 plate 311 and the ultrasonic vibrator 130. Air resonance occurs depending on the short dimension of the resonance plate 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 plate 311 in the first direction (X-axis direction) is a dimension 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 transducer 130 also causes repeated compression and expansion of air in the gap Rk between the ultrasonic transducer 130 and the rear resonance board 410. By making the thickness of the spacer 420 about 0.1 mm and securing the gap Rk between the ultrasonic transducer 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 transducer 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 transducer 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, when 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. In the ultrasonic transducer 400 when air resonance of λ is generated, 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, and ultrasonic waves of a high sound pressure level can be emitted. Furthermore, in the ultrasonic transducer 400 when air resonance of λ / 4 is generated in the first direction (X-axis direction) in the gap Rg, the sound pressure due to air resonance of λ and air resonance of λ / 4 are superimposed, and ultrasonic waves of a high sound pressure level can be emitted. Furthermore, in the ultrasonic transducer 400 when air resonance of λ / 2 is generated in the first direction (X-axis direction) in the gap Rh, the sound pressure due to air resonance of λ, air resonance of λ / 2, and air resonance of λ / 4 are superimposed, and ultrasonic waves of a high sound pressure level can be emitted.

[0098] In a parametric speaker including the ultrasonic transducer 400 according to the fourth embodiment of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 400 through modulation driving of the ultrasonic transducer 400.

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

[0100] 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 a finite element method when air resonance of λ occurs in the ultrasonic transducer according to the fifth embodiment of the present invention. Fig. 35 shows that in the part where air exists, the sound pressure increases as the color changes from black to white.

[0102] As shown in FIG. 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 plate 410.

[0103] In the ultrasonic transducer 500 according to the fifth 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 500 can radiate ultrasonic waves with a high sound pressure level with a simple and compact configuration by air resonance of λ radiated to the front side of the ultrasonic transducer 500 through the gap Rm.

[0104] In a parametric speaker including the ultrasonic transducer 500 according to the fifth embodiment of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 500 through modulation driving of the ultrasonic transducer 500.

[0105] (Embodiment 6) Hereinafter, an ultrasonic transducer according to a sixth embodiment of the present invention will be described with reference to the drawings. The ultrasonic transducer according to the sixth embodiment of the present invention differs from the ultrasonic transducer according to the fourth embodiment of the present invention in that it does not include a resonating plate portion, and therefore the description of the same configuration as that of the ultrasonic transducer according to the fourth embodiment 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 a finite element method when λ air resonance and λ / 4 air resonance occur in an ultrasonic transducer according to embodiment 6 of the present invention. Fig. 37 shows that in the part where air exists, the sound pressure increases as the color changes from black to white.

[0108] As shown in Fig. 37, in the ultrasonic transducer 600 according to the sixth embodiment of the present invention, where 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. In the ultrasonic transducer 600 when air resonance of λ is generated, the sound pressure due to air resonance of λ radiated to the front side of the ultrasonic transducer 600 through the gap Rm is superimposed, and ultrasonic waves of a high sound pressure level can be emitted. Furthermore, in the ultrasonic transducer 600 when air resonance of λ / 4 is generated in the first direction (X-axis direction) in the gap Rg, the sound pressure due to air resonance of λ and air resonance of λ / 4 are superimposed, and ultrasonic waves of a high sound pressure level can be emitted.

[0109] In a parametric speaker including the ultrasonic transducer 600 according to the sixth embodiment of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 600 through modulation driving of the ultrasonic transducer 600.

[0110] (Embodiment 7) Hereinafter, an ultrasonic transducer according to a seventh embodiment of the present invention will be described with reference to the drawings. The ultrasonic transducer according to the seventh embodiment of the present invention differs from the ultrasonic transducer according to the fourth embodiment of the present invention in that it does not include a diaphragm portion, and therefore the description of the same configuration as the ultrasonic transducer according to the fourth embodiment 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, an 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 resonance board 710 is formed with a plurality of resonance board portions 711 extending in the second direction (Y-axis direction) and facing, with a gap therebetween, each of the ultrasonic transducers 130 adjacent in the first direction (X-axis direction) among the plurality of ultrasonic transducers 130. Each of the plurality of resonance board portions 711 is connected to both ends 712 of the front-side resonance 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 a finite element method when air resonance of λ and air resonance of λ / 2 occur in the ultrasonic transducer according to the seventh embodiment of the present invention. Fig. 39 shows that in the part where air exists, the sound pressure increases as the color changes from black to white.

[0114] As shown in Fig. 39, in the ultrasonic transducer 700 according to the seventh embodiment of the present invention, when 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. In the ultrasonic transducer 700 when air resonance of λ is generated, the sound pressure due to air resonance of λ radiated to the front side of the ultrasonic transducer 700 through the gap Rm is superimposed, and ultrasonic waves of a high sound pressure level can be emitted. Furthermore, in the ultrasonic transducer 700 when air resonance of λ / 2 is generated in the first direction (X-axis direction) in the gap Rh, the sound pressure due to air resonance of λ and air resonance of λ / 2 are superimposed, and ultrasonic waves of a high sound pressure level can be emitted.

[0115] In a parametric speaker including the ultrasonic transducer 700 according to the sixth embodiment of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic waves emitted from the ultrasonic transducer 700 through modulation driving of the ultrasonic transducer 700.

[0116] (Experimental Example) 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 the fourth embodiment as Example 1, the ultrasonic transducer 300 according to the third embodiment as Example 2, the ultrasonic transducer 500 according to the fifth embodiment 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 of Example 1 was 13 times higher, that of Example 2 was 7 times higher, and that of Example 3 was 4 times higher.

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

[0120] <1> A plurality of supports each having a shaft portion extending in a longitudinal direction and arranged to be aligned in a lateral direction perpendicular to the longitudinal direction; A plurality of ultrasonic transducers are attached to the plurality of supports over the entire length of the shaft portion in the longitudinal direction and are arranged at intervals in the lateral direction; a back resonance plate disposed on the opposite side of the plurality of ultrasonic transducers from the plurality of supports and facing each of the plurality of ultrasonic transducers with a first gap therebetween; A short side dimension of the shaft portion in the short side direction is smaller than a short side dimension of each of the plurality of ultrasonic transducers, a longitudinal dimension of the shaft portion in the longitudinal direction is greater than a transverse dimension of each of the plurality of ultrasonic transducers, An ultrasonic transducer, wherein, when a wavelength converted from a drive frequency of the plurality of ultrasonic vibrators is λ, the rear resonance plate is capable of generating air resonance of λ in the short direction in the first gap.

[0121] <2> The plurality of ultrasonic transducers are piezoelectric elements including a piezoelectric body. <1> 2. The ultrasonic transducer according to claim 1 .

[0122] <3> Adjacent supports in the short side direction among the plurality of supports are connected to each other at both ends in the long side direction. <1> or <2> 2. The ultrasonic transducer according to claim 1 .

[0123] <4> The device further includes a first diaphragm having a plurality of diaphragm portions extending in the longitudinal direction and arranged in the lateral direction at intervals from each other, and joined to the plurality of supports; the ultrasonic transducers are opposed to the vibration plate portions with second gaps therebetween, with corresponding supports among the supports interposed therebetween; the plurality of vibration plate portions resonate and vibrate in an opposite phase to the plurality of ultrasonic transducers in a direction perpendicular to the plurality of vibration plate portions, The longitudinal dimension of the shaft portion in the longitudinal direction is four or more times the short dimension of each of the plurality of ultrasonic transducers. <1> from <3> 2. An ultrasonic transducer according to claim 1 .

[0124] <5> When the wavelength converted from the drive frequency of the plurality of ultrasonic transducers is λ, air resonance of λ / 4 can be generated in the short side direction in the second gap. <4> 2. The ultrasonic transducer according to claim 1 .

[0125] <6> At least one resonant plate portion is disposed between the vibration plate portions adjacent to each other in the short side direction, extends in the longitudinal direction, and faces each of the ultrasonic transducers adjacent to each other in the short side direction with a third gap therebetween, When a wavelength converted from the drive frequency of the plurality of ultrasonic transducers is λ, the at least one resonance plate portion can generate air resonance of λ / 2 in the short side direction in the third gap. <1> from <5> 2. An ultrasonic transducer according to claim 1 .

[0126] <7> <1> from <6> The ultrasonic transducer according to any one of the above items is provided, A parametric speaker that reproduces audible sound by modulating the ultrasonic transducer.

[0127] In the above description of the embodiments, configurations that can be combined may be combined with each other.

[0128] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0129] 100, 100a, 100b, 100c, 200, 300, 400, 500, 600, 700, 900 Ultrasonic transducer, 110, 110a, 210, 310 First vibration plate, 110c, 210c, 310c Middle portion, 110e, 210e, 310e Node point, 111, 211 Vibration plate portion, 112, 212, 712 Both ends, 113 Narrowed 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, resonator section, 410, rear resonator, 420, spacer, 710, front resonator.

Claims

1. A plurality of supports each having a shaft portion extending in a longitudinal direction and arranged to be aligned in a lateral direction perpendicular to the longitudinal direction; A plurality of ultrasonic transducers are attached to the plurality of supports over the entire length of the shaft portion in the longitudinal direction and are arranged at intervals in the lateral direction; a back resonance plate disposed on the opposite side of the plurality of ultrasonic transducers from the plurality of supports and facing each of the plurality of ultrasonic transducers with a first gap therebetween; A short side dimension of the shaft portion in the short side direction is smaller than a short side dimension of each of the plurality of ultrasonic transducers, a longitudinal dimension of the shaft portion in the longitudinal direction is greater than a transverse dimension of each of the plurality of ultrasonic transducers, An ultrasonic transducer, wherein the wavelength converted from the drive frequency of the plurality of ultrasonic vibrators is λ, and the rear resonance plate is capable of generating air resonance of λ in the short direction in the first gap.

2. The ultrasonic transducer according to claim 1 , wherein the plurality of ultrasonic vibrators are piezoelectric elements including a piezoelectric body.

3. The ultrasonic transducer according to claim 1 , wherein adjacent supports in the short side direction among the plurality of supports are connected to each other at both ends in the long side direction.

4. The device further includes a first diaphragm having a plurality of diaphragm portions extending in the longitudinal direction and arranged in the lateral direction at intervals from each other, and joined to the plurality of supports; the ultrasonic transducers are opposed to the vibration plate portions with second gaps therebetween, with corresponding supports among the supports interposed therebetween; the plurality of vibration plate portions resonate and vibrate in an opposite phase to the plurality of ultrasonic transducers in a direction perpendicular to the plurality of vibration plate portions, The ultrasonic transducer according to claim 1 , wherein a longitudinal dimension of the shaft portion in the longitudinal direction is four or more times a lateral dimension of each of the plurality of ultrasonic transducers.

5. The ultrasonic transducer according to claim 4 , wherein, when a wavelength converted from a drive frequency of the plurality of ultrasonic vibrators is λ, air resonance of λ / 4 can be generated in the short direction in the second gap.

6. At least one resonant plate portion is disposed between the vibration plate portions adjacent to each other in the short side direction, extends in the longitudinal direction, and faces each of the ultrasonic transducers adjacent to each other in the short side direction with a third gap therebetween, An ultrasonic transducer as described in any one of claims 1 to 5, wherein, when the wavelength converted from the driving frequency of the plurality of ultrasonic transducers is λ, at least one of the resonant plate portions is capable of generating air resonance of λ / 2 in the short direction in the third gap.

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

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