Ultrasonic transducer and parametric speaker including the same

Abstract

The first diaphragm (110) has at least one diaphragm portion (111) extending in the longitudinal direction. At least one support (120) has a shaft portion (121) extending in the longitudinal direction and is joined to the first diaphragm (110). At least one ultrasonic vibrator (130) is respectively attached to at least one support (120) over the entire longitudinal length of the shaft portion (121), and faces at least one diaphragm portion (111) with a first gap (Rg) interposed therebetween through at least one support (120). In the short direction orthogonal to the longitudinal direction, the short dimension of the shaft portion (121) is smaller than the short dimensions of each of at least one diaphragm portion (111) and at least one ultrasonic vibrator (130). At least one diaphragm portion (111) resonates and vibrates in a reverse phase to at least one ultrasonic vibrator (130) in a direction orthogonal to at least one diaphragm portion (111). The longitudinal dimension of the shaft portion (121) in the longitudinal direction is 4 times or more the short dimension of at least one ultrasonic vibrator (130).

Description

Technical Field

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

Background Art

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

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

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

Means for Solving the Problems

[0007] The ultrasonic transducer according to the present invention includes a first diaphragm, at least one support, and at least one ultrasonic vibrator. The first diaphragm has at least one diaphragm portion extending in the longitudinal direction. At least one support has a shaft portion extending in the longitudinal direction and is joined to the first diaphragm. At least one ultrasonic vibrator is respectively attached to at least one support over the entire length of the shaft portion in the longitudinal direction, and faces at least one diaphragm portion with a first gap therebetween across at least one support. In the short direction orthogonal to the longitudinal direction, the short dimension of the shaft portion is smaller than the short dimensions of each of at least one diaphragm portion and at least one ultrasonic vibrator. At least one diaphragm portion resonates and vibrates in a reverse phase to at least one ultrasonic vibrator in a direction orthogonal to at least one diaphragm portion. The longitudinal dimension of the shaft portion in the longitudinal direction is 4 times or more the short dimension of at least one ultrasonic vibrator.

Effects of the Invention

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

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Hereinafter, the ultrasonic transducer according to each embodiment of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated. The present invention is applicable to applications that require high sound pressure ultrasonic waves such as ultrasonic transducers for parametric speakers, ultrasonic sensors, or non-contact haptics. In the following embodiments, the ultrasonic transducer for a parametric speaker will be exemplified and described, 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 the ultrasonic transducer according to Embodiment 1 of the present invention. FIG. 2 is an exploded perspective view showing the configuration of the ultrasonic transducer according to Embodiment 1 of the present invention. As shown in FIGS. 1 and 2, the ultrasonic transducer 100 according to Embodiment 1 of the present invention includes a first diaphragm 110, a 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 the first direction (X-axis direction) and a long side direction along the second direction (Y-axis direction). The first diaphragm 110 has at least one diaphragm portion 111 extending in the long side direction. In the present embodiment, the first diaphragm 110 has one diaphragm portion 111.

[0013] The first diaphragm 110 is made of an aluminum alloy such as jeralmin containing aluminum, or a metal such as stainless steel. In the present embodiment, the first diaphragm 110 is made of stainless steel. The thickness 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 the present embodiment, on both outer sides of the shaft portion 121 in the second direction (Y-axis direction), a pair of restraint plate portions 122 extending in the first direction (X-axis direction) are formed on the support 120. That is, the support 120 has an H-shaped configuration. One end of the support 120 in the third direction (Z-axis direction) is joined to the first diaphragm 110 by an adhesive made of, for example, an epoxy resin. Specifically, one end of the entire shaft portion 121 in the third direction (Z-axis direction) is joined to the first diaphragm 110 by an adhesive. One end of at least a part or the whole of each of the pair of restraint plate portions 122 in the third direction (Z-axis direction) may be joined to the first diaphragm 110 by an adhesive.

[0015] The support 120 is formed of a metal such as an aluminum alloy or stainless steel, glass epoxy, or resin. From the viewpoint of suppressing characteristic changes due to temperature changes of the ultrasonic transducer 100, it is preferable that the support 120 be made of metal. On the other hand, from the viewpoints of reducing the frequency of the ultrasonic waves transmitted or received by the ultrasonic transducer 100 and miniaturizing the ultrasonic transducer 100, it is preferable that the support 120 be made of resin. In the present embodiment, the support 120 is made of stainless steel.

[0016] The thickness dimension T2 of the support 120 is, for example, not less than 0.15 mm and not more than 0.4 mm. When 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 joined to each other by the oozing adhesive. When 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 shaft portion 121 is larger than the short-side dimension W3 of the ultrasonic vibrator 130. In the present embodiment, the longitudinal dimension L1 of the shaft portion 121 is not less than 4 times the short-side dimension W3 of the ultrasonic vibrator 130. From the viewpoint of increasing the sound pressure level of the ultrasonic wave transmitted by the ultrasonic transducer 100, the longitudinal dimension L1 is, for example, not less than 20 mm. The short-side dimension W2 of the shaft portion 121 is smaller than each of the short-side dimension W1 of the diaphragm portion 111 and the short-side dimension W3 of the ultrasonic vibrator 130. The short-side dimension W2 of the shaft portion 121 is, for example, not more than 1 mm, and preferably not less than 0.3 mm and not more than 0.6 mm from the viewpoint of maintaining the joining strength. When the short-side dimension W2 of the shaft portion 121 exceeds 1 mm, 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 vibrator 130.

[0018] In the present embodiment, the shaft portion 121 is joined to the central portion of the diaphragm portion 111 in the first direction (X-axis direction). That is, 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 in the first direction (X-axis direction) are substantially the same. However, the shaft portion 121 may be joined at a position deviated from the central portion of the diaphragm portion 111 in the first direction (X-axis direction).

[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 diaphragm portion 111 with a gap Rg therebetween across the support 120. 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 diaphragm portion 111 with the support 120 therebetween. In the present embodiment, the ultrasonic vibrator 130 is attached to one end of the entire shaft portion 121 in the third direction (Z-axis direction) and at least a part or the whole of each of the pair of restraint plate portions 122 at the other end in the third direction (Z-axis direction). Each of the pair of restraint plate portions 122 is joined to both longitudinal ends of the ultrasonic vibrator 130, respectively.

[0020] FIG. 3 is a cross-sectional view showing the configuration of the ultrasonic vibrator included in the ultrasonic transducer according to Embodiment 1 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 the present embodiment, the ultrasonic vibrator 130 includes two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are different from each other. Specifically, the polarization directions Dp of the two piezoelectric bodies 131 face each other in the third direction (Z-axis direction). The two piezoelectric bodies 131 are sandwiched between the first electrode 132 and the 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, 0.2 mm or more and 0.4 mm or less.

[0021] By changing the short-side dimension W3 of the ultrasonic vibrator 130, the resonance frequency of the first diaphragm 110 can be adjusted. For example, when the resonance frequency of the first diaphragm 110 is set to 100 kHz or more 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 obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 1 of the present invention is transmitting or receiving ultrasonic waves. FIG. 5 is a cross-sectional view of the ultrasonic transducer of FIG. 4 viewed from the direction of the V-V line arrow. As simulation analysis conditions, the thickness T1 of the first diaphragm 110 was set to 0.05 mm, the combined thickness T3 of the two piezoelectric bodies 131 was set to 0.4 mm, the thickness T2 of the support 120 was set to 0.2 mm, and the longitudinal dimension L1 of the shaft portion 121 was set to 20 mm.

[0023] As shown in FIGS. 4 and 5, in the vibration mode of the ultrasonic transducer 100 according to Embodiment 1 of the present invention, the diaphragm portion 111 of the first diaphragm 110 resonates in a reverse phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 110. That is, as shown in FIG. 5, the displacement direction of the resonant vibration Bm of the first diaphragm 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 the present embodiment, the resonant frequencies of the first diaphragm 110 and the ultrasonic vibrator 130 are 100 kHz or more.

[0024] In the first diaphragm 110, the displacement of the resonant vibration becomes maximum at the intermediate portion 110c of the diaphragm portion 111 located on the middle in the longitudinal direction of the shaft portion 121, and the end portion located on the restraint plate portion 122 becomes the node point 110e. That is, in the first diaphragm 110, the diaphragm portion 111 located on the shaft portion 121 between the restraint plate portions 122 becomes the vibration region where the resonant vibration occurs. The longitudinal dimension of the vibration region of the first diaphragm 110 is the same as the longitudinal dimension L1 of the shaft portion 121.

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

[0026] FIG. 6 is a graph obtained by performing a simulation analysis using the finite element method on the transition of the resonance frequency of the first diaphragm when the longitudinal dimension of the shaft portion of the support is changed while fixing the short dimension of the ultrasonic vibrator. In FIG. 6, the vertical axis represents the resonance 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 120. As a simulation analysis condition, the short dimension W3 of the ultrasonic vibrator 130 was fixed at 2 mm.

[0027] As shown in FIG. 6, when the longitudinal dimension L1 of the shaft portion 121 of the support 120 is 2 mm, the resonance frequency of the first diaphragm 110 is 200 kHz. As the longitudinal dimension L1 increases up to 8 mm and the longitudinal dimension of the vibration region of the first diaphragm 110 increases, the resonance frequency of the first diaphragm 110 decreases to 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 diaphragm 110 becomes even larger, the resonance frequency of the first diaphragm 110 becomes substantially constant at 112 kHz. That is, the resonance 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 short dimension W3 of the ultrasonic vibrator 130.

[0028] Next, the results of a simulation analysis using the finite element method for the relationship between the sound pressure of the ultrasonic wave 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 obtained by performing a simulation analysis using the finite element method on the transition of the sound pressure of the ultrasonic wave transmitted from the ultrasonic transducer when the longitudinal dimension of the shaft portion of the support is changed while fixing the short dimension of the ultrasonic vibrator. 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 120. As a simulation analysis condition, the short dimension W3 of the ultrasonic vibrator 130 was fixed at 2 mm, and the sound pressure (Pa) at a position 30 cm away from the first diaphragm 110 on the front surface of the ultrasonic transducer 100 in the third direction (Z-axis direction) was calculated.

[0030] As shown in FIG. 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. That is, the area of the vibration region can be increased by the amount that the vibration region of the first diaphragm 110 becomes longer. As a result, the pressure change of the air due to the vibration of the first diaphragm 110 can be increased to obtain a high sound pressure.

[0031] Thus, the ultrasonic transducer 100 according to the present embodiment can increase the sound pressure while maintaining it substantially constant with respect to the resonance frequency by increasing the longitudinal dimension of the vibration region of the first diaphragm 110. In addition, since there are node points at both longitudinal ends, both ends can be supported or fixed, so that the ultrasonic transducer 100 can be easily mounted.

[0032] FIG. 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 Embodiment 1 of the present invention. In FIG. 8, in the portion where air exists, it is shown that the sound pressure increases as the color changes from black to white. 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 the sound pressure is low in the region Rf directly above the first diaphragm 110.

[0033] Since the diaphragm portion 111 resonantly vibrates in a reverse phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 110, compression and expansion of the air are repeated in the gap Rg.

[0034] 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, air resonance may occur. Specifically, assuming that the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, when at least one of the shortest distance L2 and the shortest distance L3 is a dimension near λ / 4, air resonance can occur in the gap Rg. That is, the vicinity of the shaft portion 121 becomes a fixed end and a node of air resonance, and the region outside the gap Rg becomes an open end and an antinode of air resonance. As a result, air resonance with a wavelength of λ / 4 in the first direction (X-axis direction) occurs in the gap Rg.

[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 in the dimensions of the shortest distance L2 and the shortest distance L3 with respect to the frequency of air resonance is that the occurrence situation of air resonance changes depending on the configuration around the ultrasonic transducer 100.

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

[0037] FIG. 9 is a cross-sectional view showing the configuration of the ultrasonic vibrator according to the first modification. As shown in FIG. 9, the ultrasonic vibrator 130a according to the first modification is a piezoelectric element including two stacked piezoelectric bodies 131. The polarization directions Dp of the two piezoelectric bodies 131 are equal to each other. The ultrasonic vibrator 130a is a so-called parallel-type bimorph piezoelectric vibrator.

[0038] FIG. 10 is a cross-sectional view showing the configuration of the ultrasonic vibrator according to the second modification. As shown in FIG. 10, the ultrasonic vibrator 130b according to the second modification is a piezoelectric element including four stacked piezoelectric bodies 131. Of the four piezoelectric bodies 131, the polarization directions Dp of the two piezoelectric bodies 131 located on the outer side 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 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 type piezoelectric vibrator.

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

[0040] FIG. 12 is an exploded perspective view showing the configuration of the ultrasonic transducer according to the fourth modification of Embodiment 1 of the present invention. FIG. 13 is a plan view of the ultrasonic transducer according to the fourth modification of Embodiment 1 of the present invention as viewed from the first diaphragm side. As shown in FIGS. 12 and 13, the ultrasonic transducer 100a according to the fourth modification of Embodiment 1 of the present invention includes a first diaphragm 110a, a support 120, and an ultrasonic vibrator 130. In the first diaphragm 110a, a constricted portion 113 that is thinner than the short-side dimension W2 of the shaft portion 121 of the support 120 is formed at a position outside the diaphragm portion 111 in the longitudinal direction. Specifically, a pair of constricted portions 113 are formed between both end portions 112 in the longitudinal direction and the diaphragm portion 111 in the first diaphragm 110a. Note that only one constricted portion 113 may be formed.

[0041] Both end portions 112 of the first diaphragm 110a are joined to a pair of restraint plate portions 122 of the support 120, respectively. In the ultrasonic transducer 100a according to the fourth modification of the first embodiment of the present invention, when joining the first diaphragm 110a and the support 120 to each other, while confirming 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 120, the first diaphragm 110a can be arranged on the support 120. Thereby, it is possible to reduce the assembly error of the ultrasonic transducer 100a.

[0042] FIG. 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 is transmitting or receiving ultrasonic waves. As shown in FIG. 14, also in the ultrasonic transducer 100a according to the fourth modification of the first embodiment of the present invention, a vibration mode equivalent to that of the ultrasonic transducer 100 according to the first embodiment of the present invention was confirmed.

[0043] FIG. 15 is an exploded perspective view showing the configuration of the ultrasonic transducer according to the fifth modification of the first embodiment of the present invention. As shown in FIG. 15, the ultrasonic transducer 100b according to the fifth modification 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 the shaft portion 121.

[0044] FIG. 16 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to the fifth modification of the first embodiment of the present invention is transmitting or receiving ultrasonic waves. FIG. 17 is a cross-sectional view of the ultrasonic transducer of FIG. 16 as viewed from the direction of the arrow XVII-XVII. As simulation analysis conditions, the thickness T1 of the first diaphragm 110 was set to 0.05 mm, the combined thickness T3 of the two piezoelectric bodies 131 was set to 0.4 mm, the thickness T2 of the support 120b was set to 0.2 mm, and the longitudinal dimension L1 of the shaft portion 121 was set to 20 mm.

[0045] As shown in FIGS. 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 diaphragm portion 111 of the first diaphragm 110 resonates and vibrates in a reverse phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 110. 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).

[0046] However, in the ultrasonic transducer 100b according to the fifth modification of the first embodiment of the present invention, since the restraint plate portion 122 does not exist, no node points exist at the longitudinal ends of the shaft portion 121. Also, an unnecessary vibration mode in which the displacement of the resonant vibration changes at regular intervals in the second direction (Y-axis direction) occurs, 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 the sixth modification of the first embodiment of the present invention. As shown in FIG. 18, the ultrasonic transducer 100c according to the sixth modification of the first embodiment of the present invention includes a first diaphragm 110, a support 120b, an ultrasonic vibrator 130, and a pair of restraint plate portions 120c. The support 120b is composed of only the shaft portion 121. The pair of restraint plate portions 120c are formed as separate members from the support 120b. The pair of restraint plate portions 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 restraint plate portions 120c are not limited to being joined to both longitudinal ends of the ultrasonic vibrator 130, and may be joined to positions about 2 mm inside from both longitudinal ends of the ultrasonic vibrator 130, respectively. That is, the pair of restraint plate portions 120c may be joined to positions near both longitudinal ends of the ultrasonic vibrator 130, respectively.

[0048] FIG. 19 is a perspective view showing a displacement state obtained by performing simulation analysis using the finite element method when the ultrasonic transducer according to the sixth modification of Embodiment 1 of the present invention is transmitting or receiving ultrasonic waves. FIG. 20 is a cross-sectional view of the ultrasonic transducer of FIG. 19 viewed from the direction of the XX-XX line arrow. As simulation analysis conditions, the thickness T1 of the first diaphragm 110 is 0.05 mm, the combined thickness T3 of the two piezoelectric bodies 131 is 0.4 mm, the thickness T2 of the support 120b is 0.2 mm, the longitudinal dimension L1 of the shaft portion 121 is 20 mm, the thickness of the restraint plate portion 120c is 0.2 mm, and the dimension of the restraint plate portion 122 in the first direction (X-axis direction) is the same as the short-side dimension W3 of the ultrasonic vibrator 130.

[0049] As shown in FIGS. 19 and 20, in the ultrasonic transducer 100c according to the sixth modification of Embodiment 1 of the present invention, a vibration mode equivalent to that of the ultrasonic transducer 100 according to Embodiment 1 of the present invention was also confirmed.

[0050] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, a first diaphragm 110, at least one support 120, and at least one ultrasonic vibrator 130 are provided. 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 respectively attached to the at least one support 120 over the entire length of the shaft portion 121 in the longitudinal direction, and faces at least one diaphragm portion 111 with a gap Rg therebetween across the at least one support 120. The short-side dimension W2 of the shaft portion 121 in the short-side direction orthogonal to the longitudinal direction is smaller than the short-side dimension of each of the at least one diaphragm portion 111 and the at least one ultrasonic vibrator 130. The at least one diaphragm portion 111 resonantly vibrates in a reverse phase to the at least one ultrasonic vibrator 130 in a direction orthogonal to the at least one diaphragm portion 111. The longitudinal dimension L1 of the shaft portion 121 in the longitudinal direction is 4 times or more the short-side dimension W3 of the at least one ultrasonic vibrator 130. Thereby, in the ultrasonic transducer 100, the sound pressure level can be increased with a simple and miniaturized configuration.

[0051] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, the at least one ultrasonic vibrator 130 is a piezoelectric element including a piezoelectric body 131. Thereby, the ultrasonic transducer can have a simple and miniaturized configuration.

[0052] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, when the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, it is possible to generate an air resonance of λ / 4 in the first direction (X-axis direction) in the gap Rg. In the ultrasonic transducer 100 when the air resonance of λ / 4 occurs, the sound pressure due to the air resonance is superimposed and ultrasonic waves with a high sound pressure level can be radiated.

[0053] In the ultrasonic transducer 100 according to Embodiment 1 of the present invention, a pair of restraint plate portions 122 extending in the first direction (X-axis direction) and joined to both longitudinal ends of the ultrasonic vibrator 130 are provided. As a result, since there are node points at both longitudinal ends, both ends can be supported or fixed, so that the ultrasonic transducer 100 can be easily mounted. In addition, generation of unnecessary vibration modes can be suppressed, and the characteristics of the ultrasonic transducer 100 can be stabilized. Further, since the support 120 has a pair of restraint plate portions 122, the number of parts of the ultrasonic transducer 100 can be reduced as compared with the case where the pair of restraint plate portions are formed of separate members from the support 120.

[0054] In a parametric speaker including the ultrasonic transducer 100 according to Embodiment 1 of the present invention, it is possible to reproduce an audible sound by modulating the ultrasonic wave radiated from the ultrasonic transducer 100 by modulation driving of the ultrasonic transducer 100. As modulation methods, there are an AM modulation method (amplitude modulation method) and an FM modulation method (frequency modulation method).

[0055] (Embodiment 2) Hereinafter, the ultrasonic transducer according to Embodiment 2 of the present invention will be described with reference to the drawings. The ultrasonic transducer according to Embodiment 2 of the present invention is different from the ultrasonic transducer according to Embodiment 1 of the present invention in that a plurality of ultrasonic vibrators are arranged in an array, and thus the description of the same configuration 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 the 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] As shown in FIGS. 21 and 22, in the ultrasonic transducer 200 according to Embodiment 2 of the present invention, ultrasonic transducers 100 according to Embodiment 1 arranged in an array along the 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 joined, and the plurality of ultrasonic vibrators 130 are respectively joined to the plurality of supports 220.

[0058] FIG. 23 is an exploded perspective view showing the configuration of the ultrasonic transducer according to Embodiment 2 of the present invention. As shown in FIG. 23, the first diaphragm 210 has a plurality of diaphragm portions 211 arranged side by side in the first direction (X-axis direction) while extending in the second direction (Y-axis direction) with a space therebetween. In the first diaphragm 210, the diaphragm portions 211 adjacent to each other in the first direction (X-axis direction) are connected at both end portions 212 in the second direction (Y-axis direction) of the first diaphragm 210.

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

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

[0061] The longitudinal dimension L1 of the shaft portion 221 is larger than the short dimension W3 of the ultrasonic vibrator 130. In the present embodiment, the longitudinal dimension L1 of the shaft portion 221 is 4 times or more the short 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 dimension W2 of the shaft portion 221 is smaller than each of the short dimension W1 of the diaphragm portion 211 and the short dimension W3 of the ultrasonic vibrator 130. The short 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 preferably 0.3 mm or more and 0.6 mm or less. If the short dimension W2 of the shaft portion 221 exceeds 1 mm, the vibration of the ultrasonic vibrator 130 may be inhibited.

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

[0063] In the present embodiment, each of the plurality of ultrasonic vibrators 130 includes two stacked piezoelectric bodies 131. As shown in FIG. 23, the two piezoelectric bodies 131 constituting the plurality of ultrasonic vibrators 130 are stacked and joined in a state of two thin plates. The plurality of ultrasonic vibrators 130 are respectively attached to the plurality of supports 220 over the entire length in the second direction (Y-axis direction) of the shaft portion 221, and are arranged at intervals in the first direction (X-axis direction). The plurality of ultrasonic vibrators 130 face the plurality of diaphragm portions 211 with the corresponding supports 220 among the plurality of supports 220 interposed therebetween, with the gap Rg therebetween.

[0064] FIG. 24 is a perspective view showing a displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 2 of the present invention is transmitting or receiving ultrasonic waves. FIG. 25 is a cross-sectional view of the ultrasonic transducer of FIG. 24 as viewed from the direction of the XXV-XXV line arrow. As simulation analysis conditions, the thickness T1 of the first diaphragm 210 was 0.05 mm, the combined thickness T3 of the two piezoelectric bodies 131 was 0.4 mm, the thickness T2 of the support 220 was 0.2 mm, and the longitudinal dimension L1 of the shaft portion 221 was 20 mm.

[0065] As shown in FIGS. 24 and 25, in the vibration mode of the ultrasonic transducer 200 according to Embodiment 2 of the present invention, the diaphragm portion 211 of the first diaphragm 210 resonates in a reverse phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 210. The ultrasonic vibrator 130 vibrates in a bending mode in the third direction (Z-axis direction) as viewed from the second direction (Y-axis direction).

[0066] In the first diaphragm 210, the displacement of the resonant vibration becomes maximum at the intermediate portion 210c of the diaphragm portion 211 located on the intermediate in the longitudinal direction of the shaft portion 221, and both end portions 212 located on the restraint plate portion 222 become node points 210e.

[0067] Since the ultrasonic transducer 100 according to Embodiment 1 has node points 110e at both ends in the longitudinal second direction (Y-axis direction), even if the ultrasonic transducers 100 according to Embodiment 1 are connected to each other at the both ends to form an array to constitute the ultrasonic transducer 200 according to Embodiment 2, 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 Embodiment 2, the sound pressure level can be easily increased.

[0068] In the parametric speaker including the ultrasonic transducer 200 according to Embodiment 2 of the present invention, it is possible to modulate the ultrasonic wave radiated from the ultrasonic transducer 200 by modulating driving of the ultrasonic transducer 200 and reproduce an audible sound.

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

[0070] In order to cause the audible sound to attenuate when the propagation distance is 30 cm or more, it is necessary to set the Rayleigh distance to 30 cm or less. The Rayleigh distance R0 satisfies the relationship of R0 = (k × a 2 ) / 2. k is the wave number, and a is the radius of the sound source. Therefore, assuming that the speed of sound in air is 340 m / s, when the frequency of the ultrasonic wave is 100 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 36 mm or less, when the frequency of the ultrasonic wave is 150 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 29.4 mm or less, and when the frequency of the ultrasonic wave is 200 kHz, the longitudinal dimension of the vibration region of the first diaphragm 210 is 25.5 mm or less. When the frequency of the ultrasonic wave is 100 kHz or more, the longitudinal dimension L1 is 4 times or more and 24 times or less the lateral dimension L2.

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

[0072] In the ultrasonic transducer 200 according to Embodiment 2 of the present invention, a plurality of supports 220 are arranged side by side in the short side direction and joined to the first diaphragm 210. Among the plurality of supports 220, the supports 220 adjacent to each other in the short side direction are connected by a pair of restraint plate portions 222 at both ends in the longitudinal direction of each other. Thereby, the sound pressure level can be easily increased.

[0073] (Embodiment 3) Hereinafter, the ultrasonic transducer according to Embodiment 3 of the present invention will be described with reference to the drawings. Since the ultrasonic transducer according to Embodiment 3 of the present invention is different from the ultrasonic transducer according to Embodiment 2 of the present invention in that a resonance plate portion is arranged, the description of the configuration similar to 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 the 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 joined, and the plurality of ultrasonic vibrators 130 are respectively joined to the plurality of supports 220.

[0075] On the first diaphragm 310, a plurality of resonance plate portions 311 are formed between the diaphragm 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 vibrators 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 diaphragm 310 in the second direction (Y-axis direction). In the present embodiment, the resonance plate portion 311 is formed on the first diaphragm 310, but is not limited thereto, and the resonance plate portion 311 may be formed on a member different from the first diaphragm 310.

[0076] FIG. 27 is a side view showing the positional relationship between the cutting position of the piezoelectric body of the ultrasonic transducer according to Embodiment 3 of the present invention and the resonance plate portion. As shown in FIG. 27, the two laminated piezoelectric bodies 131 are cut and divided by a dicing saw or the like at a plurality of cut lines LC that extend in the second direction (Y-axis direction) while being positioned substantially at the center of the resonance plate portion 311 in the first direction (X-axis direction). As a result, a plurality of ultrasonic vibrators 130 respectively attached to the plurality of supports 220 are arranged at intervals 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 modification. As shown in FIG. 28, the plurality of supports 320 according to the modification have a shaft portion 321 that extends in the second direction (Y-axis direction) and are arranged side by side in the first direction (X-axis direction). Among the plurality of supports 320, the 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) of each other. Specifically, the shaft portions 321 of the supports 320 adjacent to each other in the first direction (X-axis direction) are connected by a pair of restraint plate portions 322 at both ends in the second direction (Y-axis direction) of each other. That is, in the present embodiment, the support 320 is formed with the shaft portion 321 and a pair of restraint plate portions 322. In each of the pair of restraint plate portions 322, a wide portion and a narrow portion 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 a wide portion in the second direction (Y-axis direction).

[0078] FIG. 29 is a perspective view showing the displacement state obtained by simulation analysis using the finite element method when the ultrasonic transducer according to Embodiment 3 of the present invention transmits or receives ultrasonic waves. FIG. 30 is a cross-sectional view of the ultrasonic transducer of FIG. 29 viewed from the direction of the XXX-XXX line arrow. As the simulation analysis conditions, the thickness T1 of the first diaphragm 310 was set to 0.05 mm, the combined thickness T3 of the two piezoelectric bodies 131 was set to 0.4 mm, the thickness T2 of the support 220 was set to 0.2 mm, and the longitudinal dimension L1 of the shaft portion 221 was set to 20 mm.

[0079] As shown in FIGS. 29 and 30, in the vibration mode of the ultrasonic transducer 300 according to Embodiment 3 of the present invention, the diaphragm portion 211 of the first diaphragm 310 resonates in a reverse phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 310. 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).

[0080] In the first diaphragm 310, the displacement of the resonant vibration becomes maximum at the intermediate portion 310c 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 portion 322 become node points 310e. The resonance plate portion 311 hardly 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. In FIG. 31, in the portion where air exists, it is shown that the sound pressure increases as it 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 resonance plate portion 311 and the ultrasonic vibrator 130, and the sound pressure is low in the region Rj directly above the resonance plate portion 311.

[0082] Since the diaphragm portion 211 resonates in a reverse phase to the ultrasonic vibrator 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 310, compression and expansion of air are repeated in the gap Rg.

[0083] 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, air resonance occurs. Specifically, when at least one of the shortest distance L2 and the shortest distance L3 is a dimension near λ / 4, where λ is the wavelength converted from the driving frequency of the ultrasonic vibrator 130, air resonance can be generated in the gap Rg. As a result, λ / 4 air resonance occurs in the first direction (X-axis direction) in the gap Rg.

[0084] Due to the resonant vibration of the ultrasonic vibrator 130, compression and expansion of air are repeated also in the gap Rh between the resonance plate portion 311 and the ultrasonic vibrator 130. Depending on the short-side dimension of the resonance plate portion 311 in the first direction (X-axis direction), air resonance occurs. Specifically, when the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, air resonance can be generated in the gap Rh when the short-side dimension of the resonance plate portion 311 in the first direction (X-axis direction) is a dimension near λ / 2. As a result, air resonance of λ / 2 in the first direction (X-axis direction) occurs in the gap Rh. In the gap Rh, the position directly below the center of the resonance plate portion 311 in the first direction (X-axis direction) becomes the antinode of the air resonance, and the position directly below the end of the resonance plate portion 311 in the first direction (X-axis direction) becomes the node of the air resonance.

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

[0086] In the ultrasonic transducer 300 according to Embodiment 3 of the present invention, when the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, air resonance of λ / 2 in the first direction (X-axis direction) can be generated in the gap Rh. In the ultrasonic transducer 300 when air resonance of λ / 2 is occurring, the sound pressure due to the air resonance is superimposed and ultrasonic waves with a high sound pressure level can be radiated. Further, in the ultrasonic transducer 300 when air resonance of λ / 4 in the first direction (X-axis direction) is occurring in the gap Rg, the sound pressures due to the air resonance of λ / 2 and the air resonance of λ / 4 are superimposed and ultrasonic waves with a high sound pressure level can be radiated.

[0087] Since the first diaphragm 310 has at least one resonance plate portion 311, the number of components of the ultrasonic transducer 300 can be reduced as compared with the case where the resonance plate portion 311 is formed of a member different from the first diaphragm 310.

[0088] In a parametric speaker including the ultrasonic transducer 300 according to Embodiment 3 of the present invention, it is possible to reproduce audible sound by modulating the ultrasonic waves radiated from the ultrasonic transducer 300 by modulation driving of the ultrasonic transducer 300.

[0089] (Embodiment 4) Hereinafter, an ultrasonic transducer according to Embodiment 4 of the present invention will be described with reference to the drawings. Since the ultrasonic transducer according to Embodiment 4 of the present invention is different from the ultrasonic transducer according to Embodiment 3 of the present invention in that a back resonance plate is arranged, the description of the same configuration 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 the 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 back resonance plate 410, and a spacer 420. The first diaphragm 310 and the plurality of supports 220 are joined together, the plurality of ultrasonic vibrators 130 are respectively joined to the plurality of supports 220, and the back resonance plate 410 is disposed to face each of the plurality of ultrasonic vibrators 130 with the spacer 420 interposed therebetween. The spacer 420 is joined to each of the back resonance plate 410 and the plurality of ultrasonic vibrators 130.

[0091] The back resonance plate 410 is disposed on the side opposite to the plurality of supports 220 with respect to the plurality of ultrasonic transducers 130, and faces each of the plurality of ultrasonic transducers 130 with a gap therebetween. The spacers 420 extend linearly in a pair along both longitudinal ends of the ultrasonic transducers 130. The space sandwiched between the plurality of ultrasonic transducers 130 and the back resonance plate 410 via the spacers 420 is connected to the gap Rh through the gap between the ultrasonic transducers 130 formed by being cut at 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 λ air resonance occurs in the ultrasonic transducer according to Embodiment 4 of the present invention. In FIG. 33, in the portion where air exists, it is shown that the sound pressure increases as it changes from black to white. In the state shown in FIG. 33, the sound pressure is high in the gap Rg between the diaphragm portion 211 and the ultrasonic transducer 130, and in the gap Rk between the ultrasonic transducer 130 and the back resonance plate 410, and the sound pressure is low in the gap Rh between the resonance plate portion 311 and the ultrasonic transducer 130, the gap Rm between the ultrasonic transducers 130, and the region Rj directly above the resonance plate portion 311.

[0093] Since the diaphragm portion 211 resonates in a reverse phase to the ultrasonic transducer 130 in the third direction (Z-axis direction) orthogonal to the first diaphragm 310, compression and expansion of air are repeated in the gap Rg.

[0094] 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, air resonance occurs. Specifically, assuming that the wavelength converted from the driving frequency of the ultrasonic transducer 130 is λ, when at least one of the shortest distance L2 and the shortest distance L3 is a dimension near λ / 4, air resonance can occur in the gap Rg. As a result, λ / 4 air resonance occurs in the first direction (X-axis direction) in the gap Rg.

[0095] Due to the resonant vibration of the ultrasonic vibrator 130, compression and expansion of air are repeated also in the gap Rh between the resonance plate portion 311 and the ultrasonic vibrator 130. Depending on the short-side dimension of the resonance plate portion 311 in the first direction (X-axis direction), air resonance occurs. Specifically, assuming that the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, when the short-side dimension of the resonance plate portion 311 in the first direction (X-axis direction) is around λ / 2, it is possible to generate air resonance in the gap Rh. As a result, air resonance of λ / 2 in the first direction (X-axis direction) occurs in the gap Rh.

[0096] Due to the resonant vibration of the ultrasonic vibrator 130, compression and expansion of air are repeated also in the gap Rk between the ultrasonic vibrator 130 and the back-side resonance plate 410. By securing the gap Rk between the ultrasonic vibrator 130 and the back-side resonance plate 410 with the thickness of the spacer 420 being about 0.1 mm, it is possible to generate air resonance in the gap Rk. Specifically, assuming that the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, air resonance of λ in the first direction (X-axis direction) occurs 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 Embodiment 4 of the present invention, when the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, it is possible to generate an air resonance of λ in the first direction (X-axis direction) in the gap Rk. In the ultrasonic transducer 400 when the air resonance of λ is occurring, the sound pressure due to the air resonance of λ radiated to the front side of the ultrasonic transducer 400 through the gap Rm is superimposed, and ultrasonic waves with a high sound pressure level can be radiated. Further, in the ultrasonic transducer 400 when an air resonance of λ / 4 is occurring in the first direction (X-axis direction) in the gap Rg, the sound pressures due to the air resonance of λ and the air resonance of λ / 4 are superimposed, and ultrasonic waves with a high sound pressure level can be radiated. Further, in the ultrasonic transducer 400 when an air resonance of λ / 2 is occurring in the first direction (X-axis direction) in the gap Rh, the sound pressures due to the air resonance of λ, the air resonance of λ / 2, and the air resonance of λ / 4 are superimposed, and ultrasonic waves with a high sound pressure level can be radiated.

[0098] In a parametric speaker including the ultrasonic transducer 400 according to Embodiment 4 of the present invention, it is possible to modulate the ultrasonic waves radiated from the ultrasonic transducer 400 by modulating the drive of the ultrasonic transducer 400 and reproduce audible sound.

[0099] (Embodiment 5) Hereinafter, the ultrasonic transducer according to Embodiment 5 of the present invention will be described with reference to the drawings. The ultrasonic transducer according to Embodiment 5 of the present invention is different from the ultrasonic transducer according to Embodiment 4 of the present invention in that it does not include a diaphragm portion and a resonance plate portion. Therefore, the description of the configuration similar to 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 the ultrasonic transducer according to Embodiment 5 of the present invention. As shown in FIG. 34, the ultrasonic transducer 500 according to Embodiment 5 of the present invention includes a plurality of supports 220, a plurality of ultrasonic vibrators 130, a back resonance plate 410, and a spacer 420.

[0101] FIG. 35 is a diagram showing a sound pressure distribution obtained by performing simulation analysis using the finite element method when λ air resonance occurs in the ultrasonic transducer according to Embodiment 5 of the present invention. In FIG. 35, in the portion where air exists, it is shown that 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 Embodiment 5 of the present invention, due to the vibration of the ultrasonic vibrator 130, compression and expansion of air are repeated in the gap Rk between the ultrasonic vibrator 130 and the back resonance plate 410.

[0103] In the ultrasonic transducer 500 according to Embodiment 5 of the present invention, when the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, it is possible to generate λ air resonance in the first direction (X-axis direction) in the gap Rk. In the ultrasonic transducer 500 when λ air resonance occurs, ultrasonic waves with a high sound pressure level can be radiated with a simple and miniaturized configuration by the λ air resonance 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 Embodiment 5 of the present invention, it is possible to modulate the ultrasonic waves radiated from the ultrasonic transducer 500 by modulating the drive of the ultrasonic transducer 500 to reproduce audible sound.

[0105] (Embodiment 6) Hereinafter, the ultrasonic transducer according to Embodiment 6 of the present invention will be described with reference to the drawings. Since the ultrasonic transducer according to Embodiment 6 of the present invention is different from the ultrasonic transducer according to Embodiment 4 of the present invention in that it does not include a resonance plate portion, the description of the same configuration 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 the ultrasonic transducer according to Embodiment 6 of the present invention. As shown in FIG. 36, the ultrasonic transducer 600 according to Embodiment 6 of the present invention includes a first diaphragm 210, a plurality of supports 220, a plurality of ultrasonic vibrators 130, a back resonance plate 410, and a spacer 420.

[0107] FIG. 37 is a diagram showing the sound pressure distribution simulated by using the finite element method when the air resonance of λ and the air resonance of λ / 4 occur in the ultrasonic transducer according to Embodiment 6 of the present invention. In FIG. 37, in the portion where air exists, it is shown that 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 Embodiment 6 of the present invention, when the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, an air resonance of λ can be generated in the first direction (X-axis direction) in the gap Rk. In the ultrasonic transducer 600 when the air resonance of λ occurs, the sound pressure due to the air resonance of λ radiated to the front side of the ultrasonic transducer 600 through the gap Rm is superimposed, and ultrasonic waves with a high sound pressure level can be radiated. Further, in the ultrasonic transducer 600 when an air resonance of λ / 4 occurs in the first direction (X-axis direction) in the gap Rg, the sound pressures due to the air resonance of λ and the air resonance of λ / 4 are superimposed, and ultrasonic waves with a high sound pressure level can be radiated.

[0109] In a parametric speaker including the ultrasonic transducer 600 according to Embodiment 6 of the present invention, it is possible to modulate the ultrasonic waves radiated from the ultrasonic transducer 600 by modulating the drive of the ultrasonic transducer 600 to reproduce audible sound.

[0110] (Embodiment 7) Hereinafter, the ultrasonic transducer according to Embodiment 7 of the present invention will be described with reference to the drawings. Since the ultrasonic transducer according to Embodiment 7 of the present invention is different from the ultrasonic transducer according to Embodiment 4 of the present invention in that it does not include a diaphragm portion, the description of the configuration similar to 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 the 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 plate 710, a plurality of supports 220, a plurality of ultrasonic vibrators 130, a back resonance plate 410, and a spacer 420.

[0112] The front resonance plate 710 is formed with a plurality of resonance plate portions 711 that extend in the second direction (Y-axis direction) and face each of the ultrasonic vibrators 130 adjacent to each other in the first direction (X-axis direction) with a gap therebetween among the plurality of ultrasonic vibrators 130. Each of the plurality of resonance plate portions 711 is connected to both ends 712 in the second direction (Y-axis direction) of the front resonance plate 710.

[0113] FIG. 39 is a diagram showing the 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. In FIG. 39, in the portion where air exists, it is shown that the sound pressure increases as it changes from black to white.

[0114] As shown in FIG. 39, in the ultrasonic transducer 700 according to Embodiment 7 of the present invention, assuming that the wavelength converted from the driving frequency of the ultrasonic vibrator 130 is λ, it is possible to generate an air resonance of λ in the first direction (X-axis direction) in the gap Rk. In the ultrasonic transducer 700 when the air resonance of λ is occurring, the sound pressure due to the air resonance of λ radiated to the front side of the ultrasonic transducer 700 through the gap Rm is superimposed, and ultrasonic waves with a high sound pressure level can be radiated. Further, in the ultrasonic transducer 700 when an air resonance of λ / 2 is occurring in the first direction (X-axis direction) in the gap Rh, the sound pressures due to the air resonance of λ and the air resonance of λ / 2 are superimposed, and ultrasonic waves with a high sound pressure level can be radiated.

[0115] In a parametric speaker including the ultrasonic transducer 700 according to Embodiment 6 of the present invention, it is possible to modulate the ultrasonic waves radiated from the ultrasonic transducer 700 by modulating the driving of the ultrasonic transducer 700 and reproduce audible sound.

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

[0117] FIG. 40 is an exploded perspective view showing the configuration of the ultrasonic transducer according to the comparative example. As shown in FIG. 40, the 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 actually measuring the output of ultrasonic waves radiated from the ultrasonic transducers according to Examples 1 to 3 and the comparative example. As shown in FIG. 41, compared with 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] (Appendix) Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following aspects.

[0120] <1> A first diaphragm having at least one diaphragm portion extending in the longitudinal direction; At least one support having a shaft portion extending in the longitudinal direction and joined to the first diaphragm; At least one ultrasonic vibrator respectively attached to the entire longitudinal length of the shaft portion with respect to the at least one support, and facing the at least one diaphragm portion with a first gap interposed therebetween with the at least one support interposed therebetween; In the short direction orthogonal to the longitudinal direction, the short dimension of the shaft portion is smaller than the short dimensions of each of the at least one diaphragm portion and the at least one ultrasonic vibrator; The at least one diaphragm portion resonantly vibrates in a reverse phase to the at least one ultrasonic vibrator in a direction orthogonal to the at least one diaphragm portion; An ultrasonic transducer, wherein the longitudinal dimension of the shaft portion in the longitudinal direction is 4 times or more the short 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> Assuming that the wavelength converted from the driving frequency of the at least one ultrasonic vibrator is λ, the ultrasonic transducer according to <1> or <2>, which can generate an air resonance of λ / 4 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 that extend in the short-side direction and are respectively joined to positions near both ends in the longitudinal direction of the at least one ultrasonic vibrator.

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

[0125] <6> A plurality of the at least one diaphragm portion are arranged at intervals in the short-side direction. In the first diaphragm, the diaphragm portions adjacent to each other in the short-side direction are connected at both ends in the longitudinal direction of the first diaphragm. A plurality of the at least one support are arranged side by side in the short-side direction and are respectively joined to the at least one diaphragm portion. The ultrasonic transducer according to any one of <1> to <5>, wherein the supports adjacent to each other in the short-side direction are connected at both ends in their longitudinal directions.

[0126] <7> Further comprising at least one resonance plate portion that is arranged between the diaphragm 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 in the at least one ultrasonic vibrator with a second gap therebetween. When the wavelength converted from the driving frequency of the at least one ultrasonic vibrator is λ, the at least one resonance plate portion can generate an air resonance of λ / 2 in the short-side direction in the second gap. The ultrasonic transducer according to <6>.

[0127] <8> A back resonance plate is further provided, which is disposed on the side opposite to the at least one support with respect to the at least one ultrasonic vibrator and faces each of the at least one ultrasonic vibrators with a third gap therebetween. A plurality of the at least one ultrasonic vibrators are arranged at intervals in the short-side direction. When the wavelength converted from the driving frequency of the at least one ultrasonic vibrator is λ, the back resonance plate can generate an air resonance of λ in the short-side direction in the third gap. The ultrasonic transducer according to <6> or <7>.

[0128] <9> Comprising the ultrasonic transducer according to any one of <1> to <8>. A parametric speaker that reproduces audible sound by modulation driving of the ultrasonic transducer.

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

[0130] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Description of Reference Numerals

[0131] 100, 100a, 100b, 100c, 200, 300, 400, 500, 600, 700, 900 ultrasonic transducers, 110, 110a, 210, 310 first diaphragms, 110c, 210c, 310c intermediate portions, 110e, 210e, 310e node points, 111, 211 diaphragm portions, 112, 212, 712 both end portions, 113 constricted portion, 120, 120b, 220, 320 supports, 120c, 122, 222, 322 restraint plate portions, 121, 221, 321 shaft portions, 130, 130a, 130b, 130c ultrasonic vibrators, 131 piezoelectric body, 132 first electrode, 133 second electrode, 134 intermediate electrode, 135 second diaphragm, 140 processing circuit, 311, 711 resonance plate portions, 410 backside resonance plate, 420 spacer, 710 frontside resonance plate.

Claims

1. a first diaphragm having at least one diaphragm portion extending in the longitudinal direction; at least one support having a shaft portion extending in the longitudinal direction and joined to the first diaphragm; at least one ultrasonic vibrator respectively attached over the entire longitudinal length of the shaft portion with respect to the at least one support, and facing the at least one diaphragm portion with a first gap therebetween across the at least one support; in the short direction orthogonal to the longitudinal direction, the short dimension of the shaft portion is smaller than the short dimensions of each of the at least one diaphragm portion and the at least one ultrasonic vibrator; the at least one diaphragm portion resonates and vibrates in a reverse phase to the at least one ultrasonic vibrator in a direction orthogonal to the at least one diaphragm portion; the longitudinal dimension of the shaft portion in the longitudinal direction is 4 times or more the short dimension of the at least one ultrasonic vibrator; the short dimension of the at least one ultrasonic vibrator is larger than the short dimension of the at least one diaphragm portion; the first gap is an ultrasonic transducer having an open end on the side opposite to the shaft portion side in the short direction.

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

3. The ultrasonic transducer according to claim 1, wherein when the wavelength converted from the driving frequency of the at least one ultrasonic vibrator is λ, an air resonance of λ / 4 can be generated in the short direction in the first gap.

4. The ultrasonic transducer according to claim 1, further comprising a pair of restraint plate portions extending in the short direction and joined to positions near both ends in the longitudinal direction of the at least one ultrasonic vibrator.

5. The ultrasonic transducer according to claim 1, wherein a constricted portion thinner than the short dimension of the shaft portion is formed at a position outside the at least one diaphragm portion in the longitudinal direction in the first diaphragm.

6. a plurality of the at least one diaphragm portion are arranged at intervals in the short direction; the diaphragm portions adjacent to each other in the short direction in the first diaphragm are connected at both ends in the longitudinal direction of the first diaphragm; A plurality of the at least one support are arranged side by side in the short-side direction and are respectively joined to the at least one diaphragm portion, In the at least one support, the supports adjacent to each other in the short-side direction are connected to each other at both ends in the longitudinal direction thereof. The ultrasonic transducer according to claim 1.

7. At least one resonance plate portion is provided, which is disposed between diaphragm portions adjacent to each other in the short-side direction, extends in the longitudinal direction, and faces each of the ultrasonic vibrators adjacent to each other in the short-side direction with a second gap therebetween in the at least one ultrasonic vibrator, When the wavelength converted from the driving frequency of the at least one ultrasonic vibrator is λ, the at least one resonance plate portion can generate an air resonance of λ / 2 in the short-side direction in the second gap. The ultrasonic transducer according to claim 6.

8. A back-side resonance plate is further provided, which is disposed on the side opposite to the at least one support with respect to the at least one ultrasonic vibrator and faces each of the at least one ultrasonic vibrators with a third gap therebetween, The at least one ultrasonic vibrator is arranged in a plurality with spaces therebetween in the short-side direction, When the wavelength converted from the driving frequency of the at least one ultrasonic vibrator is λ, the back-side resonance plate can generate an air resonance of λ in the short-side direction in the third gap. The ultrasonic transducer according to claim 6 or claim 7.

9. Comprising the ultrasonic transducer according to claim 1, A parametric speaker that reproduces audible sound by modulation driving of the ultrasonic transducer.

10. A first diaphragm having at least one diaphragm portion extending in the longitudinal direction, At least one support having a shaft portion extending in the longitudinal direction and joined to the first diaphragm, At least one ultrasonic vibrator that is respectively attached to the at least one support over the entire longitudinal length of the shaft portion with respect to the at least one support, and faces the at least one diaphragm portion with a first gap therebetween with the at least one support interposed therebetween, In the short-side direction orthogonal to the longitudinal direction, the short-side dimension of the shaft portion is smaller than the short-side dimension of each of the at least one diaphragm portion and the at least one ultrasonic vibrator, The at least one diaphragm portion resonates in a direction orthogonal to the at least one diaphragm portion in a reverse phase to the at least one ultrasonic vibrator. The longitudinal dimension of the shaft portion in the longitudinal direction is 4 times or more the short-side dimension of the at least one ultrasonic vibrator. An ultrasonic transducer capable of generating an air resonance of λ / 4 in the short-side direction in the first gap, where λ is a wavelength converted from the driving frequency of the at least one ultrasonic vibrator.

11. A first diaphragm having at least one diaphragm portion extending in the longitudinal direction. At least one support having a shaft portion extending in the longitudinal direction and joined to the first diaphragm. At least one ultrasonic vibrator attached to the at least one support over the entire longitudinal length of the shaft portion with respect to the at least one support, facing the at least one diaphragm portion with a first gap therebetween across the at least one support. In the short-side direction orthogonal to the longitudinal direction, the short-side dimension of the shaft portion is smaller than the short-side dimensions of each of the at least one diaphragm portion and the at least one ultrasonic vibrator. The at least one diaphragm portion resonates in a direction orthogonal to the at least one diaphragm portion in a reverse phase to the at least one ultrasonic vibrator. The longitudinal dimension of the shaft portion in the longitudinal direction is 4 times or more the short-side dimension of the at least one ultrasonic vibrator. An ultrasonic transducer in which a constricted portion thinner than the short-side dimension of the shaft portion is formed at a position outside the at least one diaphragm portion of the first diaphragm in the longitudinal direction.

12. A first diaphragm having at least one diaphragm portion extending in the longitudinal direction. At least one support having a shaft portion extending in the longitudinal direction and joined to the first diaphragm. At least one ultrasonic vibrator attached to the at least one support over the entire longitudinal length of the shaft portion with respect to the at least one support, facing the at least one diaphragm portion with a first gap therebetween across the at least one support. In the short-side direction orthogonal to the longitudinal direction, the short-side dimension of the shaft portion is smaller than the short-side dimensions of each of the at least one diaphragm portion and the at least one ultrasonic vibrator. The at least one diaphragm portion resonates in a reverse phase to the at least one ultrasonic vibrator in a direction orthogonal to the at least one diaphragm portion. The longitudinal dimension of the shaft portion in the longitudinal direction is 4 times or more the short-side dimension of the at least one ultrasonic vibrator. A plurality of the at least one diaphragm portion are arranged side by side in the short-side direction with a space therebetween. In the first diaphragm, the diaphragm portions adjacent to each other in the short-side direction are connected at both ends in the longitudinal direction of the first diaphragm. A plurality of the at least one support are arranged side by side in the short-side direction and are respectively joined to the at least one diaphragm portion. An ultrasonic transducer in which the supports adjacent to each other in the short-side direction in the at least one support are connected at both ends in their longitudinal directions.

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