Surface acoustic wave device

Abstract

This surface acoustic wave device (10) comprises an ultrasonic wave generation source (11), a reflection unit (12), and a surface wave generation unit (13). The reflection unit (12) comprises a reflection surface (20) formed to generate transverse waves by reflecting an ultrasonic wave generated from the ultrasonic wave generation source (11). The surface wave generation unit (13) generates a surface acoustic wave on a target surface (30) in accordance with introduction of the transverse waves generated on the reflection surface (20). The reflection surface (20) is curved so that the transverse waves generated on the reflection surface (20) converge at a focal point. When a flat region in a base end portion of the targe surface (30) in the propagation direction of the surface acoustic wave is defined as a base end surface (31), the reflection surface (20) and the base end surface (31) are arranged in a positional relationship that falls within a range of angles of 0° or more and less than 90° between a traveling direction (TD1) where the surface acoustic wave travels along the base end surface (31) and directions where at least some of the transverse waves generated on the reflection surface (20) are directed.

Description

Surface Acoustic Wave Devices

[0001] The present disclosure relates to surface acoustic wave devices.

[0002] Patent Document 1 discloses an ultrasonic vibrator that generates surface acoustic waves. Devices that generate surface acoustic waves are expected to be applied to actuators, atomization devices, sensors, cell culture devices, microchannel devices, motors that move drivers, and the like.

[0003] Japanese Patent Application Publication No. 7-222286

[0004] The technique of Patent Document 1 does not take into consideration how to make it easier to generate surface acoustic waves, and there is room for improvement in this regard.

[0005] The present disclosure aims to provide a technique that makes it easy to generate surface acoustic waves.

[0006] The surface acoustic wave device of the present disclosure is a surface acoustic wave device comprising: an ultrasonic generating source that generates ultrasonic waves; a reflecting section having a reflecting surface that reflects ultrasonic waves generated from the ultrasonic generating source at the reflecting surface to generate shear waves; and a surface wave generating section having a target surface that generates surface acoustic waves at the target surface in response to the introduction of the shear waves generated at the reflecting surface, wherein the reflecting surface is curved so that the shear waves generated at the reflecting surface are focused, and when a flat region of the target surface at a base end in the propagation direction of the surface acoustic wave is defined as a base end surface, the reflecting surface and the base end surface are positioned in a positional relationship such that the angle between the direction in which at least a portion of the shear waves generated at the reflecting surface are directed and the propagation direction in which the surface acoustic wave propagates along the base end surface is within a range of 0° or more and less than 90°.

[0007] According to the present disclosure, it is possible to provide a technique that makes it easy to generate a surface acoustic wave.

[0008] FIG. 1 is a perspective view of a surface acoustic wave device according to a first embodiment. FIG. 2 is a cross-sectional view of the surface acoustic wave device according to the first embodiment. FIG. 3 is an explanatory diagram conceptually illustrating how ultrasonic waves are propagated. FIG. 4 is a graph illustrating the relationship between the angle of incidence and the energy conversion rate from longitudinal waves to shear waves. FIG. 5 is a cross-sectional view of a surface acoustic wave device according to a second embodiment. FIG. 6 is a cross-sectional view of a surface acoustic wave device according to a third embodiment. FIG. 7 is a cross-sectional view of a surface acoustic wave device according to a fourth embodiment. FIG. 8 is a cross-sectional view taken along line A-A in FIG. 7. FIG. 9 is a cross-sectional view of a surface acoustic wave device according to a fifth embodiment. FIG. 10 is a cross-sectional view of a surface acoustic wave device according to a sixth embodiment. FIG. 11 is a cross-sectional view of a surface acoustic wave device according to a seventh embodiment. FIG. 12 is a plan view of a surface acoustic wave device according to the seventh embodiment. FIG. 13 is a cross-sectional view of a surface acoustic wave device according to an eighth embodiment. FIG. 14 is a cross-sectional view of a surface acoustic wave device according to a ninth embodiment. FIG. 15 is a cross-sectional view of a surface acoustic wave device according to a tenth embodiment.

[0009] [Description of Embodiments of the Present Disclosure] In the following, embodiments of the present disclosure are listed and illustrated.

[0010] [1] A surface acoustic wave device comprising: an ultrasonic generating source that generates ultrasonic waves; a reflecting section having a reflecting surface that reflects ultrasonic waves generated from the ultrasonic generating source at the reflecting surface to generate shear waves; and a surface wave generating section having a target surface that generates surface acoustic waves at the target surface in response to the introduction of the shear waves generated at the reflecting surface, wherein the reflecting surface is curved so that the shear waves generated at the reflecting surface are focused, and when a flat region at a base end of the target surface in the propagation direction of the surface acoustic waves is defined as a base end surface, the reflecting surface and the base end surface are positioned in a positional relationship such that the angle between the direction in which at least a part of the shear waves generated at the reflecting surface are directed and the propagation direction in which the surface acoustic waves propagate along the base end surface is within a range of 0° or more and less than 90°.

[0011] In the surface acoustic wave device, transverse waves generated on the reflecting surface are focused toward a focal point. Moreover, the angle between the direction of at least some of the transverse waves and the traveling direction is within the range of 0° to 90°. Therefore, the transverse waves generated at various points on the reflecting surface have a concentrated effect on the target surface, generating surface acoustic waves on the target surface. In other words, the surface acoustic wave device is easy to generate surface acoustic waves.

[0012] [2] The surface acoustic wave device according to [1], wherein the focal point is located between the reflecting surface and the base end surface in a direction parallel to the base end surface, and the shortest distance between the focal point and the base end surface in the direction parallel to the base end surface is shorter than the shortest distance between the focal point and the reflecting surface.

[0013] With this configuration, the transverse waves generated at the reflecting surface tend to be concentrated near the base end surface, making it easier to generate surface acoustic waves.

[0014] [3] The surface acoustic wave device according to [1] or [2], wherein a portion of the target surface is at the same height as the highest point of the reflecting portion in a height direction perpendicular to the base end surface, or higher than the highest point of the reflecting portion.

[0015] According to this configuration, the reflecting portion is unlikely to be an obstacle when processing the portion, such as polishing, and therefore the portion can be easily processed.

[0016] [4] The surface acoustic wave device according to any one of [1] to [3], wherein the target surface has a curved target surface that has a curved shape when cut along the traveling direction.

[0017] This configuration makes it possible to change the direction in which the surface acoustic wave travels.

[0018] [5] A surface acoustic wave device according to any one of [1] to [4], comprising a suppression section having suppression surfaces arranged on both sides of the target surface in a direction perpendicular to the traveling direction, the suppression surfaces being continuous with the target surface and curved so that their height positions relative to the target surface become lower as they move away from the target surface.

[0019] According to this configuration, the suppression surface can suppress the surface acoustic wave from leaking to both sides from the target surface, thereby improving the propagation efficiency of the surface acoustic wave.

[0020] [6] The surface acoustic wave device according to any one of [1] to [5], wherein the ultrasonic wave generating source generates longitudinal ultrasonic waves.

[0021] According to this configuration, ultrasonic waves with higher energy can be generated compared to a configuration in which the ultrasonic generator generates transverse waves.

[0022] [7] The surface acoustic wave device according to any one of [1] to [6], wherein the reflecting surface and the base end surface are arranged in a positional relationship such that the angle between the direction in which at least a portion of the transverse wave generated at the reflecting surface travels and the propagation direction is within a range of 30° to 80°.

[0023] This configuration makes it easier to generate surface acoustic waves on the target surface.

[0024] [8] The surface acoustic wave device according to any one of [1] to [7], wherein the reflecting surface and the base end surface are arranged in a positional relationship such that transverse waves generated at the reflecting surface are focused onto the focal point from both sides in a direction perpendicular to the base end surface.

[0025] In a configuration in which shear waves are focused on a focal point from only one side, the shear waves pass through the focal point and are reflected near the base end face, which may reduce the efficiency of forming surface acoustic waves.In the above-mentioned surface acoustic wave device, shear waves are focused on a focal point from both sides, so the above problem caused by the interaction of the shear waves focusing from both sides is less likely to occur, and as a result, surface acoustic waves can be formed with high efficiency.

[0026] [9] The surface acoustic wave device according to any one of [1] to [8], further comprising a vibration absorber provided at a tip end of the surface wave generating section in the propagation direction of the surface acoustic wave.

[0027] With this configuration, the surface acoustic waves propagated to the tip end of the surface wave generating section in the propagation direction of the surface acoustic waves can be absorbed by the vibration absorber, thereby suppressing the reflection of the surface acoustic waves at the tip end and preventing the surface acoustic waves reflected at the tip end from interfering with the surface acoustic waves propagating from the base end side.

[0028]

[10] A surface acoustic wave device according to any one of [1] to [9], wherein the reflecting portion is annular, the ultrasonic wave generating source is annularly arranged along the reflecting portion, and the target surface is arranged inside the inner periphery of the reflecting portion.

[0029] With this configuration, transverse waves for generating surface acoustic waves on the target surface can be generated over the entire circumferential direction, making it even easier to generate surface acoustic waves.

[0030] [Details of the Embodiments of the Present Disclosure] The surface acoustic wave device of the present disclosure is used in, for example, an atomization device, an actuator, a sensor, a cell culture device, a microchannel device, and the like.

[0031] 1 and 2 disclose a surface acoustic wave device 10. The surface acoustic wave device 10 generates a surface acoustic wave. The surface acoustic wave device 10 includes an ultrasonic wave generating source 11, a reflecting unit 12, and a surface wave generating unit 13.

[0032] The ultrasonic wave generating source 11 generates ultrasonic waves. The ultrasonic wave generating source 11 is configured, for example, by a piezoelectric element. The piezoelectric element has a piezoelectric body made of piezoelectric ceramics and electrodes arranged on both sides of the piezoelectric body. The piezoelectric body is configured, for example, by lead zirconate titanate (PZT) or potassium sodium niobate (KNN). The ultrasonic wave generating source 11 is plate-shaped. The ultrasonic wave generating source 11 has a thickness. The thickness direction of the ultrasonic wave generating source 11 is the stacking direction of the piezoelectric body and the electrodes. The ultrasonic wave generating source 11 generates ultrasonic waves when an electrical signal is received from a signal transmission / reception circuit (not shown). The ultrasonic wave generating source 11 generates ultrasonic waves at a frequency of, for example, 30 kHz or more and 100 MHz or less. The ultrasonic wave generating source 11 generates ultrasonic waves in its thickness direction. In this embodiment, the ultrasonic wave generating source 11 generates longitudinal ultrasonic waves.

[0033] The reflecting unit 12 is made of, for example, metal (e.g., duralumin). The reflecting unit 12 has a reflecting surface 20. When the longitudinal waves generated by the ultrasonic wave generating source 11 are reflected by the reflecting surface 20, longitudinal waves and transverse waves are generated. The reflection angle of the longitudinal waves generated by the reflecting surface 20 is the same as the incident angle of the longitudinal waves incident on the reflecting surface 20. The reflection angle of the transverse waves generated by the reflecting surface 20 is smaller than the incident angle on the reflecting surface 20. The transverse waves generated by the reflecting surface 20 are directed toward the surface wave generating unit 13.

[0034] As shown in Figure 3, the reflecting surface 20 is curved so that the transverse waves generated on the reflecting surface 20 converge at a focal point F1. For example, the reflecting surface 20 has a shape along an ellipse, and the ratio of the major axis to the minor axis of the ellipse satisfies the condition of the following formula (1). Major axis: minor axis = CD: √(CD ２ -CT ２ ) Equation (1) CD is the propagation velocity of the longitudinal wave incident on the reflecting surface 20. CT is the propagation velocity of the transverse wave generated at the reflecting surface 20. According to this configuration, the transverse wave generated at the reflecting surface 20 is concentrated at the focal point F1.

[0035] The surface wave generating unit 13 is formed of, for example, metal (e.g., duralumin). The surface wave generating unit 13 may be integrated with the reflecting unit 12 or may be separate. The surface wave generating unit 13 has a target surface 30. The target surface 30 is a flat surface. The target surface 30 is arranged facing in the same direction as the irradiation surface 11A of the ultrasonic generating source 11 that irradiates ultrasonic waves. The surface wave generating unit 13 generates surface acoustic waves on the target surface 30 in response to the introduction of transverse waves generated on the reflecting surface 20.

[0036] The target surface 30 has a base end surface 31. The base end surface 31 is a flat surface located at the base end of the target surface 30 in the propagation direction of the surface acoustic wave. The reflecting surface 20 and the base end surface 31 are arranged in a positional relationship such that the angles formed between the direction of the shear wave generated at the reflecting surface 20 and the propagation direction TD1 in which the surface acoustic wave propagates along the base end surface 31 are both within a range of 0° or more and less than 90°. Note that if the base end of the target surface 30 in the propagation direction of the surface acoustic wave is rounded, the rounded portion is not included in the base end surface 31, and the flat surface is defined as the base end surface 31.

[0037] 3, the angle θ1 between the direction of the transverse wave TW1 generated at the reflecting surface 20 and the traveling direction TD1 is within the range of 0° or more and less than 90°. Also, the angle θ2 between the direction of the transverse wave TW2 generated at the reflecting surface 20 and the traveling direction TD1 is within the range of 0° or more and less than 90°.

[0038] In this way, the transverse waves generated at various points on the reflecting surface 20 have a concentrated effect on the target surface 30, generating a surface acoustic wave SAW1 on the target surface 30. In other words, the surface acoustic wave device 10 is likely to generate a surface acoustic wave SAW1. In particular, the angle θ2 is within the range of 30° to 80°. Therefore, the surface acoustic wave SAW1 is more likely to be generated on the target surface 30 by the transverse wave TW2.

[0039] The focal point F1 is located between the reflecting surface 20 and the base end surface 31 in a direction parallel to the base end surface 31. In the direction parallel to the base end surface 31, the shortest distance D1 between the focal point F1 and the base end surface 31 is shorter than the shortest distance D2 between the focal point F1 and the reflecting surface 20 (see FIG. 3 ). With this configuration, transverse waves generated at the reflecting surface 20 tend to concentrate near the base end surface 31, making it easier to generate surface acoustic waves. It is preferable that the shortest distance D1 between the focal point F1 and the base end surface 31 be 20% or less of the shortest distance D2 between the focal point F1 and the reflecting surface 20.

[0040] The shortest distance D2 between the focal point F1 and the reflecting surface 20 is preferably equal to or less than one wavelength of the shear wave that is focused at the focal point F1.

[0041] The reflecting surface 20 includes a reflection point 21 where the energy conversion rate from longitudinal waves to shear waves is 50% or more (see FIG. 3 ). As shown in FIG. 4 , the energy conversion rate varies depending on the Poisson's ratio of the material constituting the reflecting surface 20. For example, when the Poisson's ratio is 0.17 or more and 0.34 or less, the energy conversion rate from longitudinal waves to shear waves is 50% or more at a reflection point (e.g., reflection point 21) where the incident angle of the longitudinal waves generated by the ultrasonic wave generating source 11 is 40° or more and 85° or less. As a result, the conversion efficiency of converting the longitudinal waves generated by the ultrasonic wave generating source 11 to shear waves is easily improved. Note that, from the viewpoint of further improving the energy conversion rate, it is more preferable that the incident angle of the longitudinal waves be 50° or more.

[0042] The reflecting surface 20 and the base end surface 31 are positioned such that transverse waves (e.g., transverse waves TW1 and TW2) generated on the reflecting surface 20 are focused onto a focal point F1 from both sides in a direction perpendicular to the base end surface 31. In a configuration in which transverse waves are focused onto a focal point from only one side, the transverse waves may pass through the focal point and be reflected near the base end surface 31, reducing the efficiency of forming surface acoustic waves. In the surface acoustic wave device 10, the transverse waves are focused onto the focal point F1 from both sides, making it less likely that the above-mentioned problems will occur due to the interaction of the transverse waves focusing from both sides, and as a result, surface acoustic waves can be formed with high efficiency.

[0043] The ultrasonic wave generating source 11, the reflecting section 12, and the surface wave generating section 13 are arranged continuously over a wide range in an orthogonal direction (a direction orthogonal to the cross section of FIG. 2 ) that is orthogonal to the direction in which ultrasonic waves are generated by the ultrasonic wave generating source 11. Therefore, the surface acoustic wave device 10 can generate surface acoustic waves over a wide range in the orthogonal direction.

[0044] Second Embodiment In the first embodiment, an example in which the ultrasonic wave generating source generates longitudinal waves has been described, whereas in the second embodiment, an example in which the ultrasonic wave generating source generates transverse waves will be described.

[0045] 5, a surface acoustic wave device 210 according to the second embodiment includes an ultrasonic wave generating source 211, a reflecting section 212, and a surface wave generating section 213. The ultrasonic wave generating source 211, the reflecting section 212, and the surface wave generating section 213 are continuously arranged over a wide range in an orthogonal direction (a direction orthogonal to the cross section of FIG. 5) that is orthogonal to the direction in which the ultrasonic wave generating source 211 generates ultrasonic waves.

[0046] The ultrasonic wave generating source 211 generates ultrasonic waves of transverse waves. In other respects, the ultrasonic wave generating source 211 is the same as the ultrasonic wave generating source 11 of the first embodiment.

[0047] The reflecting section 212 is formed of, for example, a metal (e.g., duralumin). The reflecting section 212 has a reflecting surface 220. When a shear wave generated from the ultrasonic wave generating source 211 is reflected by the reflecting surface 220, a longitudinal wave and a shear wave are generated. The reflection angle of the shear wave generated by the reflecting surface 220 is the same as the incident angle of the shear wave incident on the reflecting surface 220. The shear wave generated by the reflecting surface 220 travels toward the surface wave generating section 213.

[0048] The reflecting surface 220 is curved so that the transverse waves generated on the reflecting surface 220 converge at a focal point F2. The reflecting surface 220 is, for example, a paraboloid.

[0049] The surface wave generating unit 213 is formed of, for example, metal (e.g., duralumin). The surface wave generating unit 213 may be integrated with the reflecting unit 212 or may be separate. The surface wave generating unit 213 has a target surface 230. The target surface 230 is a flat surface. The surface wave generating unit 213 generates a surface acoustic wave on the target surface 230 in response to the introduction of a transverse wave generated on the reflecting surface 220.

[0050] The target surface 230 has a base end surface 231. The base end surface 231 is a flat surface located at the base end in the propagation direction of the surface acoustic wave on the target surface 230. The reflecting surface 220 and the base end surface 231 are arranged in a positional relationship such that the angles formed between the direction of the shear wave generated on the reflecting surface 220 and the propagation direction TD2 in which the surface acoustic wave propagates along the base end surface 231 are both within a range of 0° or more and less than 90°.

[0051] 5, the angle θ21 between the direction of the transverse wave TW21 generated at the reflecting surface 220 and the traveling direction TD2 is within the range of 0° to 90°. Also, the angle θ22 between the direction of the transverse wave TW22 generated at the reflecting surface 220 and the traveling direction TD2 is within the range of 0° to 90°.

[0052] In this way, the transverse waves generated at various points on the reflecting surface 220 have a concentrated effect on the target surface 230, generating a surface acoustic wave SAW2 on the target surface 230. In other words, the surface acoustic wave device 210 is likely to generate a surface acoustic wave SAW2.

[0053] The focal point F2 is located between the reflecting surface 220 and the base end surface 231 in a direction parallel to the base end surface 231. In the direction parallel to the base end surface 231, the shortest distance D21 between the focal point F2 and the base end surface 231 is shorter than the shortest distance D22 between the focal point F2 and the reflecting surface 220. With this configuration, transverse waves generated at the reflecting surface 220 tend to concentrate near the base end surface 231, making it easier to generate surface acoustic waves. It is preferable that the shortest distance D21 between the focal point F2 and the base end surface 231 be 20% or less of the shortest distance D22 between the focal point F2 and the reflecting surface 220.

[0054] Third Embodiment In the first embodiment, an example in which the entire target surface is flat is described. In contrast, in the third embodiment, an example in which the target surface is a curved target surface that is curved in the direction in which the surface acoustic wave travels is described. In the third embodiment, the same components as in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0055] 6, a surface acoustic wave device 310 according to the third embodiment includes an ultrasonic wave generating source 11, a reflecting section 12, and a surface wave generating section 313. The ultrasonic wave generating source 11, the reflecting section 12, and the surface wave generating section 313 are continuously arranged over a wide range in an orthogonal direction (a direction orthogonal to the cross section of FIG. 6) that is orthogonal to the direction in which the ultrasonic wave generating source 11 generates ultrasonic waves.

[0056] The surface wave generating unit 313 is formed of, for example, metal (e.g., duralumin). The surface wave generating unit 313 may be integrated with the reflecting unit 12 or may be separate from it. The surface wave generating unit 313 has a target surface 330. The surface wave generating unit 313 generates a surface acoustic wave on the target surface 330 in response to the introduction of a transverse wave generated on the reflecting surface 20.

[0057] The target surface 330 has a base end surface 331, a flat target surface 332, and a curved target surface 333. The base end surface 331 is a flat surface located at the base end of the target surface 330 in the propagation direction of the surface acoustic wave. The reflecting surface 20 and the base end surface 331 are arranged in a positional relationship such that the angles formed between the direction of the shear wave generated at the reflecting surface 20 and the propagation direction TD3 in which the surface acoustic wave propagates along the base end surface 331 are both within a range of 0° or more and less than 90°.

[0058] 6, the angle θ31 formed between the direction of the transverse wave TW1 generated at the reflecting surface 20 and the traveling direction TD3 is within the range of 0° or more and less than 90°. Also, the angle θ32 formed between the direction of the transverse wave TW2 generated at the reflecting surface 20 and the traveling direction TD3 is within the range of 0° or more and less than 90°.

[0059] In this way, the transverse waves generated at various points on the reflecting surface 20 have a concentrated effect on the target surface 330, generating a surface acoustic wave SAW3 on the target surface 330. In other words, the surface acoustic wave device 310 is likely to generate a surface acoustic wave SAW3. In particular, the angle θ32 is within the range of 30° to 80°. This makes it easier for the transverse wave TW2 to generate a surface acoustic wave SAW3 on the target surface 330.

[0060] The focal point F3 is located between the reflecting surface 20 and the base end surface 331 in a direction parallel to the base end surface 331. In the direction parallel to the base end surface 331, the shortest distance D31 between the focal point F3 and the base end surface 331 is shorter than the shortest distance D32 between the focal point F3 and the reflecting surface 20. With this configuration, transverse waves generated at the reflecting surface 20 tend to concentrate near the base end surface 331, making it easier to generate surface acoustic waves. It is preferable that the shortest distance D31 between the focal point F3 and the base end surface 331 be 20% or less of the shortest distance D32 between the focal point F3 and the reflecting surface 20.

[0061] The flat target surface 332 is arranged on the tip side in the propagation direction of the surface acoustic wave relative to the base end surface 331. The flat target surface 332 is provided at the tip of the target surface 330 in the propagation direction of the surface acoustic wave. The flat target surface 332 is a flat surface. The flat target surface 332 is arranged at the same height as the highest point HP of the reflecting section 12 in a height direction perpendicular to the base end surface 331. With this configuration, the reflecting section 12 is less likely to get in the way when processing the flat target surface 332, such as polishing, making it easier to process the flat target surface 332.

[0062] The curved target surface 333 is disposed on the distal side of the base end surface 331 in the propagation direction of the surface acoustic wave. The curved target surface 333 is disposed between the base end surface 331 and the flat target surface 332 in the propagation direction of the surface acoustic wave. The curved target surface 333 has a curved shape when cut along the propagation direction of the surface acoustic wave. With this configuration, the propagation direction of the surface acoustic wave along the target surface 330 can be changed.

[0063] Fourth Embodiment In a fourth embodiment, an example will be described in which suppression surfaces are arranged on both sides of a target surface. Note that in the fourth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0064] 7 and 8, a surface acoustic wave device 410 of the fourth embodiment includes an ultrasonic wave generating source 411, a reflecting unit 412, and a surface wave generating unit 413. The ultrasonic wave generating source 411, the reflecting unit 412, and the surface wave generating unit 413 differ from the ultrasonic wave generating source 11, the reflecting unit 12, and the surface wave generating unit 13 of the first embodiment in that they are short in length in the depth direction (the direction perpendicular to the direction in which the ultrasonic wave generating source 11 generates ultrasonic waves), but are common in other respects.

[0065] The surface wave generating unit 413 has a target surface 430. The target surface 430 is a flat surface. The target surface 430 has a base end surface 431. The base end surface 431 is a flat surface located at the base end of the target surface 430 in the propagation direction of the surface acoustic wave.

[0066] The surface acoustic wave device 410 further includes a suppression unit 414. The suppression unit 414 has suppression surfaces 441 and 442. The suppression surfaces 441 and 442 are arranged on both sides of the target surface 430 of the surface wave generating unit 413 in a direction perpendicular to the propagation direction TD4 in which the surface acoustic wave propagates along the base end surface 431. The suppression surfaces 441 and 442 are continuous with the target surface 430 and are curved so that their height positions relative to the target surface 430 decrease with increasing distance from the target surface 430. The surface acoustic wave SAW4 is less likely to propagate along a curved surface in a direction perpendicular to the propagation direction TD4. In other words, with this configuration, the suppression surfaces 441 and 442 can suppress leakage of the surface acoustic wave SAW4 from the target surface 430 to both sides. As a result, the propagation efficiency of the surface acoustic wave SAW4 can be improved.

[0067] Fifth Embodiment In a fifth embodiment, a configuration including a vibration absorber will be described. In the fifth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0068] 9, a surface acoustic wave device 510 according to the fifth embodiment includes a vibration absorber 541 in addition to the configuration of the surface acoustic wave device 10 according to the first embodiment. The vibration absorber 541 is made of a well-known material such as urethane synthetic rubber.

[0069] The vibration absorber 541 is provided at the tip of the surface wave generating unit 13 in the propagation direction of the surface acoustic wave SAW1. The surface wave generating unit 13 has a tip surface 32 provided at the tip in the propagation direction of the surface acoustic wave SAW1. The tip surface 32 is connected to the target surface 30 via a bent portion 33. The vibration absorber 541 is provided on the tip surface 32.

[0070] According to this configuration, the surface acoustic wave SAW1 propagated to the tip end of the surface wave generating unit 13 in the propagation direction of the surface acoustic wave SAW1 can be absorbed by the vibration absorber 541. This suppresses reflection of the surface acoustic wave SAW1 at the tip end, and suppresses interference between the surface acoustic wave reflected at the tip end and the surface acoustic wave SAW1 propagating from the base end side.

[0071] Sixth Embodiment In the sixth embodiment, a configuration including a vibration absorber will be described, which is different from that of the fifth embodiment. In the sixth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0072] 10 , a surface acoustic wave device 610 according to the sixth embodiment includes an ultrasonic wave generating source 11, a reflecting unit 12, and a surface wave generating unit 613. The ultrasonic wave generating source 11, the reflecting unit 12, and the surface wave generating unit 613 are continuously arranged over a wide range in an orthogonal direction (a direction orthogonal to the cross section of FIG. 10 ) that is orthogonal to the direction in which the ultrasonic wave generating source 11 generates ultrasonic waves.

[0073] The surface wave generating unit 613 is formed of, for example, metal (e.g., duralumin). The surface wave generating unit 613 may be integrated with the reflecting unit 12 or may be separate from it. The surface wave generating unit 613 has a target surface 630. The surface wave generating unit 613 generates a surface acoustic wave SAW6 on the target surface 630 in response to the introduction of a transverse wave generated on the reflecting surface 20.

[0074] The target surface 630 has a base end surface 31, a first flat target surface 632, a curved target surface 633, and a second flat target surface 634. The base end surface 31, the first flat target surface 632, the curved target surface 633, and the second flat target surface 634 are arranged in this order from the base end side to the tip end side in the propagation direction of the surface acoustic wave SAW6 in the surface wave generating unit 613. The first flat target surface 632 is flush with the base end surface 31. The curved target surface 633 is continuous with the first flat target surface 632. The second flat target surface 634 is continuous with the curved target surface 633 and is arranged along a direction perpendicular to the first flat target surface 632.

[0075] The surface acoustic wave device 610 includes a vibration absorber 641. The vibration absorber 641 is formed of a well-known material, such as urethane synthetic rubber. The vibration absorber 641 is provided at the tip of the surface acoustic wave generating unit 613 in the propagation direction of the surface acoustic wave SAW6. The surface acoustic wave generating unit 613 has a tip surface 635 provided at the tip of the surface acoustic wave SAW6 in the propagation direction. The tip surface 635 is connected to the target surface 630 via a bent portion 636. The vibration absorber 641 is provided on the tip surface 635.

[0076] According to this configuration, the surface acoustic wave SAW6 propagated to the tip end of the surface wave generating unit 613 in the propagation direction of the surface acoustic wave SAW6 can be absorbed by the vibration absorber 641. This suppresses reflection of the surface acoustic wave SAW6 at the tip end, and suppresses interference between the surface acoustic wave reflected at the tip end and the surface acoustic wave SAW6 propagating from the base end side.

[0077] Seventh Embodiment In a seventh embodiment, a surface acoustic wave device having a body of revolution will be described. In the seventh embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0078] As shown in FIGS. 11 and 12, a surface acoustic wave device 710 according to the seventh embodiment includes an ultrasonic wave generating source 711, a reflecting section 712, and a surface wave generating section 713.

[0079] The reflecting portion 712 has an annular shape (more specifically, a circular ring shape) centered on the axis Z. The reflecting portion 712 has a reflecting surface 720. The reflecting surface 720 has an annular shape (more specifically, a circular ring shape) centered on the axis Z. The ultrasonic generating source 711 is arranged in an annular shape (more specifically, a circular ring shape) along the reflecting portion 712. The ultrasonic generating source 711 has an annular shape (more specifically, a circular ring shape) centered on the axis Z. The surface wave generating portion 713 has a target surface 730. The surface wave generating portion 713 and the target surface 730 are arranged inside the annular reflecting portion 712. In other words, the surface wave generating portion 713 and the target surface 730 are arranged radially inside the reflecting portion 712.

[0080] The surface wave generating unit 713 has a base 714 and a shaft 715. The base 714 is continuous around the entire inner periphery of the annular reflecting unit 712. The base 714 has a base surface 714A. The base surface 714A is arranged facing the same direction as the irradiation surface 711A of the ultrasonic generating source 711 that irradiates ultrasonic waves. The shaft 715 is rod-shaped and extends from the base surface 714A of the base 714. The shaft 715 extends along the axis Z. The shaft 715 protrudes in the direction in which the irradiation surface 711A faces. The outer circumferential surface 715A of the shaft 715 is continuous with the base surface 714A via a curved surface 716. The target surface 730 of the surface wave generating unit 713 is formed by the base surface 714 A, the curved target surface 716 , and the outer peripheral surface 715 A of the shaft portion 715 .

[0081] Longitudinal waves and transverse waves are generated when longitudinal waves generated from the ultrasonic wave generating source 711 are reflected by the reflecting surface 720. The transverse waves generated all around the periphery of the reflecting surface 720 each travel toward the surface wave generating unit 713. As shown in Fig. 11, the reflecting surface 720 is curved so that the transverse waves generated by the reflecting surface 720 converge at a focal point F7.

[0082] The surface wave generating unit 713 generates surface acoustic waves (SAW7) around the entire circumference of the target surface 730 in response to the introduction of shear waves generated around the entire circumference of the reflecting surface 720. The target surface 730 (more specifically, the base surface 714A) of the surface wave generating unit 713 has a base end surface 731. The base end surface 731 has an annular (more specifically, annular) shape centered on the axis Z. The surface acoustic waves (SAW7) generated around the entire circumference of the base end surface 731 travel from the base surface 714A toward the shaft portion 715 on the radially inner side, propagate via the curved target surface 716 to the outer peripheral surface 715A of the shaft portion 715, and then propagate from the base end side to the tip end side of the shaft portion 715 on the outer peripheral surface 715A of the shaft portion 715.

[0083] According to this configuration, it is possible to generate transverse waves in the entire circumferential direction to generate the surface acoustic wave SAW7 on the target surface 730. This makes it even easier to generate the surface acoustic wave SAW7.

[0084] Eighth Embodiment In the seventh embodiment, an example in which the surface wave generating section is solid has been described. In contrast, in the eighth embodiment, an example in which the surface wave generating section is cylindrical will be described. In the eighth embodiment, the same components as in the seventh embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0085] As shown in Figure 13, the surface acoustic wave device 810 of the eighth embodiment corresponds to the surface acoustic wave device 710 of the seventh embodiment, in which a through hole is formed that penetrates the surface wave generating portion 713 (more specifically, the base portion 714 and the shaft portion 715) along the axis Z.

[0086] The surface acoustic wave device 810 includes an ultrasonic wave generating source 711, a reflecting section 712, and a surface wave generating section 813. The surface wave generating section 813 has a cylindrical shape centered on the axis Z. The surface wave generating section 813 has a base section 814 and a shaft section 815.

[0087] The base 814 has a cylindrical shape centered on the axis Z. The base 814 is continuous with the inner periphery of the annular reflecting part 712 over the entire circumference. The base 814 has a base surface 814A. The base surface 814A is disposed facing the same direction as the irradiation surface 711A of the ultrasonic generation source 711.

[0088] The shaft portion 815 protrudes from the base surface 814A of the base portion 814 in the direction toward the irradiation surface 711A. The shaft portion 815 extends along the axis Z. The shaft portion 815 is cylindrical with the axis Z as its center. The internal space of the shaft portion 815 is connected to the internal space of the base portion 814. The surface wave generating portion 813 has a through-hole 817 that penetrates the surface wave generating portion 813 (more specifically, the base portion 814 and the shaft portion 815) along the axis Z. The outer peripheral surface 815A of the shaft portion 815 is connected to the base surface 814A via the curved target surface 816. The target surface 830 of the surface wave generating portion 813 is formed by the base surface 814A, the curved target surface 816, and the outer peripheral surface 815A of the shaft portion 815.

[0089] The surface wave generating unit 813 generates surface acoustic waves (SAW8) all around the target surface 830 in response to the introduction of shear waves generated all around the reflecting surface 720. The target surface 830 (more specifically, the base surface 814A) of the surface wave generating unit 813 has a base end surface 831. The base end surface 831 has an annular (more specifically, annular) shape centered on the axis Z. The surface acoustic waves (SAW8) generated all around the base end surface 831 travel from the base surface 814A toward the shaft portion 815 on the radially inner side, propagate via the curved target surface 816 to the outer peripheral surface 815A of the shaft portion 815, and then propagate from the base end side to the tip end side of the shaft portion 815 on the outer peripheral surface 815A of the shaft portion 815.

[0090] Even in this configuration, it is possible to generate transverse waves in the entire circumferential direction to generate the surface acoustic waves SAW8 on the target surface 830. This makes it even easier to generate the surface acoustic waves SAW8.

[0091] Ninth Embodiment In the eighth embodiment, an example was described in which the outer peripheral surface of the shaft portion was used as the target surface. In contrast, in the ninth embodiment, an example will be described in which the inner peripheral surface of the shaft portion is used as the target surface. In the ninth embodiment, the same components as in the eighth embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0092] As shown in FIG. 14, a surface acoustic wave device 910 according to the ninth embodiment includes an ultrasonic wave generating source 711, a reflecting section 712, and a surface wave generating section 913.

[0093] The surface wave generating unit 913 has a cylindrical shape centered on the axis Z. The surface wave generating unit 913 has a base 914 and a shaft 915.

[0094] The base 914 has a cylindrical shape centered on the axis Z. The base 914 is continuous around the entire inner periphery of the annular reflecting part 712. The base 914 has a first surface 914A facing in the same direction as the irradiation surface 711A of the ultrasonic generating source 711, and a second surface 914B provided on the opposite side to the first surface 914A.

[0095] The shaft portion 915 protrudes from the second surface 914B of the base portion 914. The shaft portion 915 extends along the axis Z. The shaft portion 915 has a cylindrical shape centered on the axis Z. The internal space of the shaft portion 915 communicates with the internal space of the base portion 914.

[0096] The surface wave generating unit 913 has a through hole 917 formed therein, which penetrates the surface wave generating unit 913 (more specifically, the base 914 and the shaft 915) along the axis Z. An inner circumferential surface 917A of the through hole 917 is connected to the first surface 914A via the curved target surface 916. The target surface 930 of the surface wave generating unit 913 is formed by the first surface 914A, the curved target surface 916, and the inner circumferential surface 917A of the through hole 917.

[0097] The surface wave generating unit 913 generates surface acoustic waves (SAW9) all around the target surface 930 in response to the introduction of shear waves generated all around the reflecting surface 720. The target surface 930 (more specifically, the first surface 914A) of the surface wave generating unit 913 has a base end surface 931. The base end surface 931 has an annular (more specifically, annular) shape centered on the axis Z. The surface acoustic waves (SAW9) generated all around the base end surface 931 propagate from the first surface 914A toward the through hole 917 on the radially inner side, and then propagate from the base end side to the tip end side of the shaft portion 915 on the inner circumferential surface 917A of the through hole 917.

[0098] According to this configuration, a surface acoustic wave SAW 9 can be generated on the inner peripheral surface 917 A of the through-hole 917 .

[0099] Tenth Embodiment In the tenth embodiment, an example will be described in which the target surface is arranged facing in the opposite direction to the irradiation surface of the ultrasonic wave generating source. Note that in the tenth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0100] 15 , a surface acoustic wave device 1010 according to the tenth embodiment includes an ultrasonic wave generating source 11, a reflecting unit 12, and a surface wave generating unit 1013. The surface wave generating unit 1013 has a target surface 1030. The target surface 1030 is disposed facing in the opposite direction to the irradiation surface 11A of the ultrasonic wave generating source 11.

[0101] According to this configuration, the surface acoustic wave SAW 10 can be generated on the surface of the ultrasonic wave generating source 11 facing away from the irradiation surface 11A.

[0102] <Other Embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments are also included within the technical scope of the present invention. Furthermore, various features of the above-mentioned embodiments and the embodiments to be described later may be combined in any manner as long as they are not contradictory.

[0103] (1) In the first to third embodiments, the ultrasonic wave generating source, the reflecting unit, and the surface wave generating unit are configured to be continuously arranged in an orthogonal direction perpendicular to the direction in which the ultrasonic wave generating source generates ultrasonic waves. In contrast, the ultrasonic wave generating source may be made up of multiple members and arranged intermittently in the orthogonal direction. The reflecting unit may be made up of multiple members and arranged intermittently in the orthogonal direction. The surface wave generating unit may be made up of multiple members and arranged intermittently in the orthogonal direction.

[0104] (2) In the third embodiment, the flat target surface is disposed at the same height as the highest point of the reflecting portion. However, the flat target surface may be disposed at a position higher than the highest point of the reflecting portion.

[0105] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims.

[0106] 10,210,310,410,510,610,710,810,910,1010...Surface acoustic wave device 11,211,411,711...Ultrasonic wave generating source 11A,711A...Irradiation surface 12,212,412,712...Reflecting section 13,213,313,413,613,713,813,913,1013...Surface wave generating section 20,220,720...Reflecting surface 21...Reflection point 30,230,330,430,630,730,830,930,1030...Target surface 31,231,331,431,731,831,931...Base end surface 32,635...Tip surface of surface wave generating section 33, 363...Bending portion 332...Flat target surface 333, 633, 716, 816, 916...Curved target surface 414...Suppression portion 441, 442...Suppression surface 541, 641...Vibration absorber 632...First flat target surface 634...Second flat target surface 714, 814, 914...Base portion 714A, 814A...Base surface 715, 815, 915...Shaft portion 715A, 815A...Outer surface of shaft portion 817, 917...Through hole D1, D2, D21, D22, D31, D32...Shortest distance F1, F2, F3, F7...Focus point HP...Highest point SAW1, SAW2, SAW3, SAW4, SAW6, SAW7, SAW8, SAW9, SAW10... Surface acoustic waves TD1, TD2, TD3, TD4... Direction of propagation TW1, TW2, TW21, TW22... Transverse waves θ1, θ2, θ21, θ22, θ31, θ32... Angle

Claims

1. A surface acoustic wave device comprising: an ultrasonic generating source that generates ultrasonic waves; a reflecting section having a reflecting surface that reflects ultrasonic waves generated from the ultrasonic generating source at the reflecting surface to generate transverse waves; and a surface wave generating section having a target surface that generates surface acoustic waves on the target surface in response to the introduction of the transverse waves generated at the reflecting surface, wherein the reflecting surface is curved so that the transverse waves generated at the reflecting surface are focused, and when a flat area at the base end of the target surface in the propagation direction of the surface acoustic wave is taken as a base end surface, the reflecting surface and the base end surface are positioned in a positional relationship such that the angle between the direction in which at least a part of the transverse waves generated at the reflecting surface are directed and the propagation direction in which the surface acoustic wave propagates along the base end surface is within the range of 0° or more and less than 90°.

2. The surface acoustic wave device according to claim 1, wherein the focal point is located between the reflecting surface and the base end surface in a direction parallel to the base end surface, and the shortest distance between the focal point and the base end surface in the direction parallel to the base end surface is shorter than the shortest distance between the focal point and the reflecting surface.

3. A surface acoustic wave device according to claim 1 or 2, wherein a portion of the target surface is at the same height as the highest point of the reflecting portion in a height direction perpendicular to the base end surface, or is higher than the highest point of the reflecting portion.

4. The surface acoustic wave device according to claim 1 or 2, wherein the target surface has a curved target surface that has a curved shape when cut along the traveling direction.

5. A surface acoustic wave device as claimed in claim 1 or 2, further comprising a suppression section having suppression surfaces arranged on both sides of the target surface in a direction perpendicular to the propagation direction, the suppression surfaces being continuous with the target surface and curved such that their height positions with respect to the target surface decrease with increasing distance from the target surface.

6. The surface acoustic wave device according to claim 1 or 2, wherein the ultrasonic wave generating source generates ultrasonic waves of a longitudinal wave type.

7. A surface acoustic wave device as described in claim 1 or 2, wherein the reflecting surface and the base end surface are arranged in a positional relationship such that an angle between the direction in which at least a portion of a transverse wave generated at the reflecting surface travels and the propagation direction is within a range of 30° or more and 80° or less.

8. A surface acoustic wave device according to claim 1 or 2, wherein the reflecting surface and the base end surface are arranged in a positional relationship such that a transverse wave generated at the reflecting surface is focused onto the focal point from both sides in a direction perpendicular to the base end surface.

9. The surface acoustic wave device according to claim 1 or 2, further comprising a vibration absorber provided at a tip end of the surface wave generating section in a propagation direction of the surface acoustic wave.

10. A surface acoustic wave device as claimed in claim 1 or claim 2, wherein the reflecting portion is annular, the ultrasonic generating source is annularly arranged along the reflecting portion, and the target surface is arranged inside the inner circumference of the reflecting portion.

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