Ultrasonic Transducers

Abstract

To provide an ultrasonic transducer that makes it easy to adjust the directivity.SOLUTION: A bottom portion 22 has an inner surface 22a facing an accommodation space, and an outer surface 22b facing the inner surface 22a. A piezoelectric element is arranged on the inner surface 22a. The bottom portion 22 includes a first portion 22c and at least one second portion 22d. The first portion 22c has a first distance T1 between the inner surface 22a and the outer surface 22b in a direction in which the inner surface 22a and the outer surface 22b face each other. The at least one second portion 22d has a second distance T2 between the inner surface 22a and the outer surface 22b in a direction in which the inner surface 22a and the outer surface 22b face each other. The second distance T2 is less than the first distance T1.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to an ultrasonic transducer. [Background technology]

[0002] A known ultrasonic transducer includes a piezoelectric element and a case that houses the piezoelectric element (see, for example, Patent Document 1). The case has a bottom that defines a space that houses the piezoelectric element. The piezoelectric element is disposed on the bottom. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-32594 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have conducted extensive research into the directionality of ultrasonic waves output from ultrasonic transducers. As a result, the inventors have discovered that the shape of the bottom of the case, through which vibrations propagate from the piezoelectric element, is related to the directionality of ultrasonic waves. In ultrasonic transducers according to the above-mentioned prior art, the bottom vibrates almost uniformly due to the vibrations propagating from the piezoelectric element. Therefore, the ultrasonic waves output are unlikely to have directionality, and the directionality of the ultrasonic waves is difficult to adjust.

[0005] An object of one aspect of the present invention is to provide an ultrasonic transducer whose directivity can be easily adjusted. [Means for solving the problem]

[0006] An ultrasonic transducer according to one embodiment includes a case defining an accommodation space, a piezoelectric element disposed in the accommodation space, and a wiring member electrically connected to the piezoelectric element. The case has a bottom having an inner surface facing the accommodation space and an outer surface facing the inner surface, and a side portion extending in a direction intersecting the bottom and defining the accommodation space together with the bottom. The piezoelectric element is disposed on the inner surface. The bottom portion includes a first portion having a first distance between the inner surface and the outer surface in a direction in which the inner surface and the outer surface face each other, and at least one second portion having a second distance between the inner surface and the outer surface that is smaller than the first distance in a direction in which the inner surface and the outer surface face each other.

[0007] In the one aspect, the second distance of the second part is smaller than the first distance of the first part. Therefore, the vibration propagating from the piezoelectric element to the bottom is less likely to attenuate in the second part before it propagates to the outer surface of the bottom compared to the first part. That is, the vibration propagating from the piezoelectric element to the bottom is more likely to attenuate in the first part before it propagates to the outer surface of the bottom compared to the second part. The vibration propagating in the first part tends to attenuate before it propagates to the outer surface compared to the vibration propagating in the second part. As a result, in the one aspect, the ultrasonic waves output from the ultrasonic transducer have a directivity corresponding to the strength of the vibration reaching the outer surface of the bottom. In the one aspect, for example, the directivity of the ultrasonic waves output from the ultrasonic transducer is adjusted by adjusting the shapes of the first part and the second part. Effect of the Invention

[0008] One aspect of the present invention provides an ultrasonic transducer whose directivity is easily adjustable. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing an ultrasonic transducer according to a first embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing the ultrasonic transducer according to the first embodiment. [Diagram 3]FIG. 3 is a diagram showing a cross-sectional configuration of the ultrasonic transducer according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing the ultrasonic transducer according to the first embodiment. [Diagram 5] FIG. 5 is a perspective view showing the ultrasonic transducer according to the first embodiment. [Figure 6] FIG. 6 is a perspective view showing the ultrasonic transducer according to the first embodiment. [Figure 7] FIG. 7 is a perspective view showing a piezoelectric element. [Figure 8] FIG. 8 is a plan view showing an acoustic matching member. [Figure 9] FIG. 9 is a plan view showing the piezoelectric element and the acoustic matching member. [Figure 10] FIG. 10 is a diagram showing a cross-sectional configuration taken along line XX in FIG. [Figure 11] FIG. 11 is a plan view showing a modified example of the acoustic matching member. [Figure 12] FIG. 12 is a diagram showing a cross-sectional configuration taken along line XXII-XXII in FIG. [Figure 13] FIG. 13 is a plan view showing another modified example of the acoustic matching member. [Figure 14] FIG. 14 is a diagram showing a cross-sectional structure of the acoustic matching member shown in FIG. [Figure 15] FIG. 15 is a diagram showing a cross-sectional configuration of another modified example of the acoustic matching member. [Figure 16] FIG. 16 is a diagram showing a cross-sectional configuration of still another modified example of the acoustic matching member. [Figure 17] FIG. 17 is a perspective view showing an ultrasonic transducer according to the second embodiment. [Figure 18] FIG. 18 is an exploded perspective view showing an ultrasonic transducer according to the second embodiment. [Figure 19] FIG. 19 is a diagram showing a cross-sectional configuration taken along line XIX-XIX in FIG. [Figure 20] FIG. 20 is a diagram showing a cross-sectional configuration taken along line XIX-XIX in FIG. [Figure 21] FIG. 21 is a plan view showing a flexible substrate and a piezoelectric element. [Figure 22] FIG. 22 is a plan view showing the relay board and the case. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and duplicated description will be omitted.

[0011] First embodiment The configuration of an ultrasonic transducer 1 according to this embodiment will be described with reference to Figs. 1 to 7. Fig. 1 is a perspective view showing an ultrasonic transducer according to this embodiment. Fig. 2 is an exploded perspective view showing an ultrasonic transducer according to this embodiment. Fig. 3 is a view showing a cross-sectional configuration of an ultrasonic transducer according to this embodiment. Figs. 4 to 6 are perspective views showing an ultrasonic transducer according to this embodiment. Fig. 4 shows a state in which a frame member and a filling member are removed from the ultrasonic transducer. Fig. 5 shows a state in which an acoustic matching member is further removed from the state shown in Fig. 4. Fig. 6 shows a state in which a resin member is further removed from the state shown in Fig. 5. Fig. 7 is a perspective view showing a piezoelectric element. The ultrasonic transducer 1 includes an acoustic matching member 2, a frame member 3, a piezoelectric element 4, a pair of wires 5, at least one terminal metal fitting 6, a resin member 7, and a filling member 8.

[0012] The ultrasonic transducer 1 is an ultrasonic transmission / reception device that emits ultrasonic waves or detects received ultrasonic waves by a piezoelectric element 4. When the ultrasonic transducer 1 emits ultrasonic waves, for example, an AC voltage is applied to the piezoelectric element 4, and the piezoelectric element 4 is continuously displaced by the AC voltage. Ultrasonic waves are emitted from the ultrasonic transducer 1 in response to the displacement of the piezoelectric element 4. When the ultrasonic transducer 1 detects ultrasonic waves, for example, an electromotive force is generated in the piezoelectric element 4 due to the displacement of the piezoelectric element 4 caused by the received ultrasonic waves. Whether or not ultrasonic waves have been received is detected by the generation of the electromotive force, and the sound pressure or sound pressure level of the ultrasonic waves is detected by the magnitude of the generated electromotive force.

[0013] The acoustic matching member 2 forms an accommodation space S in which the piezoelectric element 4 is accommodated. In this embodiment, for example, the acoustic matching member 2 constitutes a case that defines the accommodation space S. The acoustic matching member 2 covers at least a part of the piezoelectric element 4 and at least a part of the terminal fitting 6 to adjust the acoustic impedance of the piezoelectric element 4. The acoustic matching member 2 matches the acoustic impedance of the piezoelectric element 4 with the impedance of a medium present around the acoustic matching member 2 by its shape, structure, and material. The medium includes, for example, air or a gas other than air. The acoustic matching member 2 is formed, for example, from an epoxy resin. The acoustic matching member 2 is formed, for example, by foam molding of a composite material in which glass beads are mixed into an epoxy resin. The acoustic matching member 2 has a bottomed tubular shape. The acoustic matching member 2 has a bottom 22 and a side portion 23. In this embodiment, the bottom 22 and the side portion 23 are integrally formed.

[0014] The bottom 22 has a disk shape. The bottom 22 is a part that emits ultrasonic waves in response to the displacement of the piezoelectric element 4, or receives ultrasonic waves from the outside and transmits vibrations to the piezoelectric element 4. The bottom 22 has an inner surface 22a located so as to face the storage space S, and an outer surface 22b located so as to face the medium. The inner surface 22a and the outer surface 22b face each other in the first direction D1, as shown in FIG. 3. In this embodiment, the first direction D1 coincides with the direction perpendicular to the inner surface 22a and coincides with the direction perpendicular to the outer surface 22b. The inner surface 22a and the outer surface 22b have, for example, a circular shape when viewed from the first direction D1. The inner surface 22a defines the storage space S of the acoustic matching member 2. In this embodiment, the inner surface 22a is approximately flat. The outer surface 22b constitutes the ultrasonic wave transmission surface and reception surface of the ultrasonic transducer 1. A tapered portion 22e is provided on the bottom portion 22. The tapered portion 22e tapers from the inner surface 22a toward the outer surface 22b.

[0015] The side portion 23 has a tubular shape. In this embodiment, the side portion 23 has a cylindrical shape. The side portion 23 extends from the bottom portion 22 in a direction intersecting the bottom portion 22. In this embodiment, the side portion 23 extends in a first direction D1. An inner surface 23a of the side portion 23, together with an inner surface 22a of the bottom portion 22, defines an accommodation space S.

[0016] The frame member 3 is attached to the acoustic matching member 2. The frame member 3 is formed of, for example, rubber. The frame member 3 forms an accommodation space S together with the acoustic matching member 2. The frame member 3 has a main body portion 31 and a flange portion 32. The main body portion 31 and the flange portion 32 are formed integrally.

[0017] The main body 31 has a generally cylindrical shape. The main body 31 is attached to the side portion 23 of the acoustic matching member 2. The main body 31 surrounds the outer peripheral surface of the upper portion of the side portion 23 and is disposed on the upper portion of the side portion 23. The main body 31 forms an opening K that communicates with the accommodation space S. The inner diameter of the main body 31 is smaller than the inner diameter of the side portion 23 of the acoustic matching member 2. The flange portion 32 is provided at the upper end portion of the main body 31. The flange portion 32 has a circular frame shape. The flange portion 32 protrudes radially outward from the outer peripheral surface of the main body 31.

[0018] 7, the piezoelectric element 4 has a piezoelectric body 40 and a pair of electrodes 41, 42. The piezoelectric body 40 has a disk shape. The piezoelectric body 40 has a pair of principal surfaces 40a, 40b facing each other, and a side surface 40c connecting the principal surfaces 40a and 40b. The pair of principal surfaces 40a, 40b face each other in a first direction D1. The principal surfaces 40a, 40b have a circular shape.

[0019] The piezoelectric element 40 is configured by stacking a plurality of piezoelectric layers (not shown). Each piezoelectric layer is made of a piezoelectric material. In this embodiment, each piezoelectric layer is made of a piezoelectric ceramic material. For example, PZT [Pb(Zr,Ti)O3], PT(PbTiO3), PLZT [(Pb,La)(Zr,Ti)O3], or barium titanate (BaTiO3) is used as the piezoelectric ceramic material. Each piezoelectric layer is made of, for example, a sintered ceramic green sheet containing the above-mentioned piezoelectric ceramic material. In the actual piezoelectric element 40, each piezoelectric layer is integrated to such an extent that the boundaries between the piezoelectric layers cannot be recognized. A plurality of internal electrodes (not shown) may be arranged in the piezoelectric element 40. Each internal electrode is made of a conductive material. For example, Ag, Pd, or an Ag-Pd alloy is used as the conductive material.

[0020] The electrode 41 is disposed on the principal surface 40a, the principal surface 40b, and the side surface 40c. The electrode 41 is disposed across the principal surface 40a, the side surface 40c, and the principal surface 40b. The portion of the electrode 41 disposed on the principal surface 40a has a substantially circular shape. The electrode 42 is disposed on the principal surface 40b. The electrode 42 has a shape that is a circle with a portion cut out.

[0021] The electrodes 41 and 42 are spaced apart from each other. When viewed from the opposing direction of the principal surfaces 40a and 40b, the area of ​​the portion of the electrode 41 disposed on the principal surface 40b is smaller than the area of ​​the portion of the electrode 42 disposed on the principal surface 40b. The electrodes 41 and 42 are made of a conductive material. For example, Ag, Pd, or an Ag-Pd alloy is used as the conductive material. The electrodes 41 and 42 are formed, for example, as a sintered body of a conductive paste containing the conductive material.

[0022] The pair of wirings 5 ​​are electrically indirectly connected to the electrodes 41, 42 of the corresponding piezoelectric element 4. The pair of wirings 5 ​​each include a lead wire 51, 52. The lead wires 51, 52 extend from the accommodation space S formed by the acoustic matching member 2 and the frame member 3 to the outside of the accommodation space S through an opening K of the frame member 3. The lead wire 51 is electrically indirectly connected to the electrode 41. The lead wire 52 is electrically indirectly connected to the electrode 42.

[0023] The terminal metal fitting 6 is electrically connected to the piezoelectric element 4. In this embodiment, the terminal metal fitting 6 includes two terminal metal fittings 61 and 62. The terminal metal fittings 61 and 62 are provided on the main surface 40b of the piezoelectric element 4 along the edge of the main surface 40b. Each of the terminal metal fittings 61 and 62 has a first portion 63 and a second portion 64. The first portion 63 and the second portion 64 are electrically connected to each other. In this embodiment, the first portion 63 and the second portion 64 are integrally connected. The material of the terminal metal fittings 61 and 62 is conductive and made of a metal. The metal constituting the terminal metal fittings 61 and 62 is, for example, phosphor bronze, oxygen-free copper, or a copper alloy. In this embodiment, the terminal metal fittings 61 and 62 are lead frames.

[0024] The first portion 63 of the terminal fittings 61 and 62 is physically connected to the wiring 5 and is spaced apart from the piezoelectric element 4. The first portion 63 extends in a direction intersecting the principal surfaces 40a and 40b. The first portion 63 extends in the opposing direction of the principal surfaces 40a and 40b, or in a direction away from the center of gravity of the piezoelectric element 4 as viewed from the opposing direction. In this embodiment, the first portion 63 extends in the opposing direction of the principal surfaces 40a and 40b. The wiring 5 is physically connected to the first portion 63 at a distance from the piezoelectric element 4 and the second portion 64. In this embodiment, the first portion 63 of the terminal fitting 61 is physically connected to the conductor portion of the lead wire 51, and the first portion 63 of the terminal fitting 62 is physically connected to the conductor portion of the lead wire 52. In this specification, "physically connected" includes a case where the two are directly abutted against each other, as well as a case where the two are connected via a conductive adhesive material such as solder or conductive resin, but does not include a case where the two are connected via a member other than the conductive adhesive material.

[0025] The first portion 63 and the second portion 64 each include a plate-shaped plate portion 65, 66. The first portion 63 includes the plate portion 65, and the second portion 64 includes the plate portion 66. The plate portion 65 and the plate portion 66 extend in directions intersecting each other. The plate portion 65 extends in a direction away from the electrodes 41, 42. In this embodiment, the plate portion 65 and the plate portion 66 extend in directions perpendicular to each other. In other words, in this embodiment, the terminal fittings 61, 62 are L-shaped. The plate portion 65 extends in the opposing direction of the main surfaces 40a, 40b. The plate portion 66 extends along the main surface 40b. The plate portion 66 of the second portion 64 has a rectangular shape when viewed from the opposing direction of the main surfaces 40a, 40b. When viewed from the opposing direction of the principal surfaces 40a, 40b, the area of ​​the plate portion 66 is smaller than the area of ​​the portion of the electrode 41 disposed on the principal surface 40b. The plate portions 66 of the terminal fittings 61, 62 are physically connected to the electrodes 41, 42, respectively, by soldering. The terminal fitting 61 is physically and electrically connected to the electrode 41, and the terminal fitting 62 is physically and electrically connected to the electrode 42. Therefore, the wiring member 9 is connected to the electrodes 41, 42. That is, the wiring member 9 is electrically connected to the piezoelectric element 4.

[0026] The first portion 63 further includes a grip portion 67 connected to the plate portion 65, an engagement portion 68, a check terminal portion 69, and a contact portion 70. The grip portion 67, the engagement portion 68, the check terminal portion 69, and the contact portion 70 are integrally connected to the plate portion 65 and are bent relative to the plate portion 65. In other words, the grip portion 67, the engagement portion 68, the check terminal portion 69, and the contact portion 70 protrude from the plate portion 65.

[0027] The gripping portion 67 grips the wiring 5. The gripping portion 67 of the terminal fitting 61 grips the tip portion of the lead wire 51, and the gripping portion 67 of the terminal fitting 62 grips the tip portion of the lead wire 52. In this embodiment, the gripping portion 67 grips the wiring 5 by crimping. The gripping portion 67 includes a plurality of pin portions, and grips the wiring 5 by bending each pin portion. The conductor portion of the lead wire 51 of the wiring 5 is physically connected to the plate portion 65 of the terminal fitting 61 by the gripping portion 67. The conductor portion of the lead wire 52 of the wiring 5 is connected to the plate portion 65 of the terminal fitting 62 by the gripping portion 67. In this embodiment, the gripping portion 67 grips the conductor portion of the wiring 5 by at least one pin portion, and the conductor portion is also connected to at least one pin portion.

[0028] The engaging portion 68 includes a pair of pin portions and engages with the resin member 7. The terminal fittings 61, 62 are fixed to the resin member 7 by the engagement between the resin member 7 and the engaging portion 68. In this specification, "fixed" includes a state in which the terminal fittings are engaged with some play.

[0029] The check terminal portion 69 is a terminal for checking the electrical continuity of the wiring 5. After the terminal fittings 61, 62 are placed on the piezoelectric element 4, a terminal of a tester or the like is brought into contact with the check terminal portion 69, whereby it can be confirmed whether the terminal fittings 61, 62 are connected to the electrodes 41, 42 or not.

[0030] The contact portion 70 protrudes in a direction intersecting the opposing direction of the principal surfaces 40a, 40b. The contact portion 70 protrudes toward the acoustic matching member 2 and elastically abuts against the acoustic matching member 2. In this embodiment, the piezoelectric element 4 is positioned relative to the acoustic matching member 2 via the terminal fittings 61, 62 by the abutment between the contact portion 70 and the inner surface 23a of the acoustic matching member 2.

[0031] The resin member 7 is accommodated in the accommodation space S formed by the acoustic matching member 2 and the frame member 3. The resin member 7 has a frame shape. The thickness direction of the resin member 7 coincides with the opposing direction of the main surfaces 40a, 40b. The resin member 7 is formed around an axis extending in the opposing direction of the main surfaces 40a, 40b. The outer periphery of the resin member 7 is surrounded by the acoustic matching member 2. The resin member 7 is provided along the outer periphery of the piezoelectric element 4. The resin member 7 extends along the edge of the main surface 40b of the piezoelectric element 4. The resin member 7 extends so as to surround the center of gravity of the main surface 40b when viewed from the opposing direction of the main surfaces 40a, 40b.

[0032] The resin member 7 has missing portions 7a, 7b. The engagement portion 68 of the terminal fitting 61 engages with the edge of the missing portion 7a. The engagement portion 68 of the terminal fitting 62 engages with the edge of the missing portion 7b. This causes the multiple terminal fittings 61, 62 to be fixed to the resin member 7. In this embodiment, the resin member 7 is sandwiched between the engagement portion 68 and the plate portion 66. The engagement portion 68 limits the movement of the resin member 7 in the outer circumferential direction relative to the terminal fitting 6, and the engagement portion 68 and the plate portion 66 limit the movement of the resin member 7 in the thickness direction. The material of the resin member 7 includes a thermoplastic molding material such as PBT or LCP.

[0033] The filling member 8 is filled in the accommodation space S formed by the acoustic matching member 2 and the frame member 3. Therefore, the accommodation space S accommodates the piezoelectric element 4, part of the wiring 5, the terminal fittings 6, the resin member 7, and the filling member 8. The filling member 8 contacts the acoustic matching member 2, the frame member 3, the piezoelectric element 4, part of the wiring 5, the terminal fittings 6, and the resin member 7. The filling member 8 is filled after the piezoelectric element 4, part of the wiring 5, the terminal fittings 6, and the resin member 7 are accommodated in the accommodation space S. The filling member 8 covers the piezoelectric element 4, part of the wiring 5, the terminal fittings 6, and the resin member 7. The filling member 8 includes at least one of an epoxy resin and a urethane resin, for example.

[0034] Next, the configurations of the piezoelectric element 4 and the bottom portion 22 will be described with reference to Fig. 8 to Fig. 10. Fig. 8 is a plan view showing an acoustic matching member. Fig. 9 is a plan view showing an acoustic matching member and a piezoelectric element. Fig. 10 is a diagram showing a cross-sectional configuration along line XX in Fig. 9. In Fig. 10, the pair of electrodes 41, 42 is omitted. The bottom 22 includes a first portion 22c and a plurality of second portions 22d. In this embodiment, the bottom 22 includes two second portions 22d. That is, the bottom 22 includes at least one second portion 22d. In this embodiment, the thickness of the first portion 22c is different from the thickness of each second portion 22d. Therefore, the outer surface 22b has a step corresponding to the difference between the first distance T1 and the second distance T2.

[0035] As shown in FIG. 10, the first portion 22c has a first distance T1 between the inner surface 22a and the outer surface 22b in the first direction D1. The two second portions 22d have a second distance T2 between the inner surface 22a and the outer surface 22b in the first direction D1, the second distance T2 being smaller than the first distance T1. The second distance T2 is substantially constant in each of the second portions 22d. The second distances T2 in each of the second portions 22d are, for example, equal. The second distances T2 in each of the second portions 22d may be different from each other. The first distance T1 and the second distance T2 are, for example, defined by the shortest distance between the inner surface 22a and the outer surface 22b. The first distance T1 is, for example, 1 to 4 mm. The second distance T2 is, for example, 0.5 to 3.5 mm. In this embodiment, the first distance T1 is 4 mm, and the second distance T2 is 3.5 mm. The ratio (T2 / T1) of the first distance T1 to the second distance T2 is, for example, 0.5 to 0.875 In this embodiment, the ratio (T2 / T1) is 0.875.

[0036] As shown in FIG. 8, the two second parts 22d are positioned so as to be spaced apart from each other with the first part 22c therebetween, as viewed from the first direction D1. In this embodiment, the two second parts 22d are positioned so as to be spaced apart from each other in the second direction D2. The two second parts 22d are positioned so as to be point-symmetrical with respect to the center C of the outer surface 22b, as viewed from the first direction D1. For example, the two second parts 22d are line-symmetrical with respect to a virtual line L1 passing through the center C along a second direction D2 perpendicular to the first direction D1. The two second parts 22d are also line-symmetrical with respect to a virtual line L2 passing through the center C along a third direction D3 perpendicular to the first direction D1 and the second direction D2. The two second parts 22d are point-symmetrical with respect to the center C of the outer surface 22b. The two second parts 22d are positioned so that the entire circumference of each of them is surrounded by the first part 22c, as viewed from the first direction D1. As viewed from the first direction D1, the position of the center C of the outer surface 22b coincides with the position of the center of the inner surface 22a.

[0037] As shown in FIG. 8 and FIG. 9, the width of the two second portions 22d increases with increasing distance from the center C of the outer surface 22b when viewed from the first direction D1. The width of each second portion 22d is defined by, for example, a length in the third direction D3. The widths of the two second portions 22d may be equal to each other or may be different from each other. The widths of the two second portions 22d may increase continuously or stepwise with increasing distance from the center C of the outer surface 22b. In this embodiment, the two second portions 22d have a fan shape having an arc on the edge side of the bottom 22 when viewed from the first direction D1. Each second portion 22d may have a triangular shape when viewed from the first direction D1. The central angle of each second portion 22d is, for example, 10 to 45 degrees. The radius of each second portion 22d is, for example, 2 to 6 mm. In this embodiment, the central angle of each second portion 22d is 45 degrees, and the radius of each second portion 22d is 5.3 mm.

[0038] The piezoelectric element 4 is disposed on the inner surface 22a as shown in FIG. 9. The piezoelectric element 4 is bonded onto the inner surface 22a, for example. In this case, an adhesive layer may be present between the piezoelectric element 4 and the inner surface 22a. The piezoelectric element 4 is disposed so that the center of the piezoelectric element 4 coincides with the center C of the outer surface 22b, i.e., the center of the inner surface 22a, as viewed from the first direction D1. The piezoelectric element 4 has a diameter shorter than the inner diameter of the side portion 23, and the side surface of the piezoelectric element 4 (i.e., the side surface 40c of the piezoelectric body 40) is spaced a predetermined distance from the side portion 23 as viewed from the first direction D1. The distance in the first direction D1 between a virtual plane including the main surface 40a and the outer surface 22b is smaller in the second portion 22d than in the first portion 22c.

[0039] When viewed from the first direction D1, the terminal metal fittings 61, 62 are positioned so as not to overlap the second portion 22d. That is, the terminal metal fittings 61, 62 are positioned so as to overlap the first portion 22c. Therefore, the terminal metal fittings 61, 62 are connected to the corresponding electrodes 41, 42 at a position where they do not overlap the second portion 22d. That is, the wiring member 9 is connected to the electrodes 41, 42 at a position where they do not overlap the second portion 22d. In this embodiment, the electrode 41 is also positioned so as not to overlap the second portion 22d. Therefore, the piezoelectric element 4 is disposed on the inner surface 22a so that the electrode 41 does not overlap the second portion 22d when viewed from the first direction D1.

[0040] In the ultrasonic transducer 1, the second distance T2 is smaller than the first distance T1. Therefore, the vibration propagating from the piezoelectric element 4 to the bottom 22 is less likely to attenuate in the second portion 22d before it propagates to the outer surface 22b than in the first portion 22c. That is, the vibration propagating from the piezoelectric element 4 to the bottom 22 is more likely to attenuate in the first portion 22c before it propagates to the outer surface 22b than in the second portion 22d. The vibration propagating through the first portion 22c tends to attenuate before it propagates to the outer surface 22b than the vibration propagating through the second portion 22d. As a result, the ultrasonic waves output from the ultrasonic transducer 1 have a directivity corresponding to the strength of the vibration reaching the outer surface 22b. In the ultrasonic transducer 1, for example, the directivity of the ultrasonic waves output from the ultrasonic transducer 1 is adjusted by adjusting the shapes of the first portion 22c and the second portion 22d. The shape of the second portion 22d includes not only the contour shape of the second portion 22d when viewed from the first direction D1, but also the position of the second portion 22d when viewed from the first direction D1.

[0041] In this embodiment, the directivity angle of the ultrasonic waves output from the ultrasonic transducer 1 corresponds to the shape of each second portion 22d. The directivity angle of the ultrasonic waves output from the ultrasonic transducer 1 in the second direction D2 is larger than the directivity angle in the third direction D3. That is, the ultrasonic waves output from the ultrasonic transducer 1 have a larger spread in the second direction D2 than in the third direction D3.

[0042] Even in a configuration in which the bottom 22 does not have the first portion 22c and the second portion 22d, the directivity of the ultrasonic waves output from the ultrasonic transducer 1 can be changed, for example, by changing the shape of the piezoelectric element 4. In this case, in order to adjust the directivity of the ultrasonic waves output from the ultrasonic transducer 1, it is necessary to prepare various piezoelectric elements 4 having different planar shapes. Therefore, changing the shape of the piezoelectric element 4 in order to adjust the directivity of the ultrasonic waves output from the ultrasonic transducer 1 is not practical, and it is difficult to easily adjust the directivity.

[0043] In the configuration in which the bottom 22 has the first portion 22c and the second portion 22d, the directivity of the ultrasonic waves output from the ultrasonic transducer 1 can be easily adjusted by changing the shape of the bottom 22 (the second portion 22d) as described above. The shape of the bottom 22 can be easily changed by, for example, cutting. Acoustic matching members 2 having different shapes of the bottom 22 may be prepared by injection molding. In any case, it is easier to prepare an acoustic matching member 2 in which the bottom 22 has the first portion 22c and the second portion 22d than to prepare various piezoelectric elements 4 having different planar shapes. Of course, in order to adjust the directivity of the ultrasonic waves output from the ultrasonic transducer 1, the shape of the piezoelectric element 4 may be changed in the ultrasonic transducer 1 having the acoustic matching member 2 in which the bottom 22 has the first portion 22c and the second portion 22d.

[0044] In the ultrasonic transducer 1, the wiring member 9 is connected to each of the electrodes 41, 42 at a position that does not overlap the second portion 22d. As described above, the vibration propagating from the piezoelectric element 4 to the bottom 22 is less attenuated in the second portion 22d before propagating to the outer surface 22b than in the first portion 22c. Therefore, the configuration in which the wiring member 9 is connected to each electrode 41, 42 at a position that does not overlap the second portion 22d has a smaller effect on the vibration characteristics of the ultrasonic transducer 1 than the configuration in which the wiring member 9 is connected to each electrode 41, 42 at a position that overlaps the second portion 22d.

[0045] In a configuration in which the ratio (T2 / T1) is greater than 0.875, the vibration propagating through the second portion 22d may be attenuated before propagating to the outer surface 22b, similar to the vibration propagating through the first portion 22c. In contrast, in a configuration in which the ratio (T2 / T1) is 0.875 or less, the vibration propagating through the second portion 22d is reliably attenuated by the time it propagates to the outer surface 22b, compared to the vibration propagating through the first portion 22c. Therefore, in a configuration in which the ratio (T2 / T1) is 0.875 or less, the ultrasonic waves output from the ultrasonic transducer 1 reliably have directivity corresponding to the strength of the vibration reaching the outer surface 22b.

[0046] In a configuration in which the ratio (T2 / T1) is smaller than 0.5, the ultrasonic waves output from second portion 22d are likely to attenuate for the following reason: The ultrasonic waves output from outer surface 22b included in second portion 22d are reflected by steps in outer surface 22b. The ultrasonic waves reflected by the steps in outer surface 22b may interfere with the ultrasonic waves output from outer surface 22b included in second portion 22d and may be attenuated. In contrast, in a configuration in which the ratio (T2 / T1) is 0.5 or more, even if the ultrasonic waves output from the outer surface 22b included in the second portion 22d are reflected by a step in the outer surface 22b, the above-mentioned interference is unlikely to occur. The ultrasonic waves reflected by the step in the outer surface 22b are unlikely to be attenuated. Therefore, in a configuration in which the ratio (T2 / T1) is 0.5 or more, the ultrasonic waves output from the ultrasonic transducer 1 reliably have directionality corresponding to the strength of the vibration reaching the outer surface 22b.

[0047] The configuration of a modified acoustic matching member 2 will be described with reference to Figs. 11 and 12. Fig. 11 is a plan view showing a modified acoustic matching member. Fig. 12 is a diagram showing a cross-sectional configuration along line XXII-XXII in Fig. 11. In Fig. 12, the pair of electrodes 41, 42 is omitted. This modified example differs from the first embodiment in the configuration of the bottom 22. Below, the differences between the first embodiment and this modified example will be mainly described.

[0048] The bottom 22 includes one first portion 22c and one second portion 22d. As shown in Fig. 11, the second portion 22d has a circular shape centered on the center C of the outer surface 22b when viewed from the first direction D1. The second portion 22d is positioned such that the entire circumference of the second portion 22d is surrounded by the first portion 22c when viewed from the first direction D1. In other words, the first portion 22c is positioned such that the entire circumference of the second portion 22d is surrounded by the first portion 22c when viewed from the first direction D1.

[0049] In this modification, the directivity angle of the ultrasonic waves output from the ultrasonic transducer 1 corresponds to the shape of the second portion 22d. The directivity angles in the second direction D2 and the third direction D3 of the ultrasonic waves output from the ultrasonic transducer 1 are small. That is, in this modification, the directivity angle of the ultrasonic waves output from the ultrasonic transducer 1 is narrowed overall compared to a configuration in which the bottom 22 does not have the second portion 22d.

[0050] The configuration of another modified acoustic matching member 2 will be described with reference to Figs. 13 and 14. Fig. 13 is a plan view showing another modified acoustic matching member. Fig. 14 is a diagram showing a cross-sectional configuration of the acoustic matching member shown in Fig. 13. In Fig. 14, the pair of electrodes 41, 42 is omitted. This modified embodiment differs from the first embodiment in the configuration of the bottom portion 22. Below, the differences between the first embodiment and this modified embodiment will be mainly described.

[0051] The bottom 22 includes two first portions 22c and a second portion 22d. The positional relationship between the first portion 22c and the two second portions 22d shown in FIG. 13 is replaced with the positional relationship between the first portion 22c and the second portion 22d shown in FIG. 8. Specifically, the two first portions 22c are positioned so as to be spaced apart with the second portion 22d sandwiched between them as viewed from the first direction D1. The two first portions 22c are positioned so as to be point-symmetrical with respect to the center C of the outer surface 22b as viewed from the first direction D1. The second portion 22d is disposed at a position sandwiching the center C of the outer surface 22b. The width of the two first portions 22c increases with increasing distance from the center C of the outer surface 22b as viewed from the first direction D1. The width of the two first portions 22c may increase continuously or stepwise with increasing distance from the center C of the outer surface 22b. The width of each first portion 22c is defined, for example, by a length in the third direction D3. In this modification, the two first portions 22c have a sector shape having an arc on the edge side of the bottom portion 22. Each of the first portions 22c may have a triangular shape when viewed from the first direction D1. The two first portions 22c are positioned such that the entire periphery of each of them is surrounded by the second portion 22d when viewed from the first direction D1. That is, the second portion 22d is positioned such that it surrounds the entire periphery of the first portion 22c when viewed from the first direction D1.

[0052] In this modification, the directivity angle of the ultrasonic waves output from the ultrasonic transducer 1 corresponds to the shape of the second portion 22d. The directivity angle of the ultrasonic waves output from the ultrasonic transducer 1 in the third direction D3 is larger than the directivity angle in the second direction D2. That is, the ultrasonic waves output from the ultrasonic transducer 1 have a larger spread in the third direction D3 than in the second direction D2.

[0053] The configuration of another modified example of the acoustic matching member 2 will be described with reference to Fig. 15. Fig. 15 is a diagram showing a cross-sectional configuration of another modified example of the acoustic matching member. In Fig. 15, the pair of electrodes 41, 42 is omitted. This modified example differs from the first embodiment in the configuration of the bottom portion 22. The following mainly describes the differences between the first embodiment and this modified example. As shown in Fig. 15, the second distance T2 changes in the second portion 22d. Specifically, the second distance T2 increases as the distance from the center C of the outer surface 22b increases. As shown in Fig. 10, in the first embodiment, the second distance T2 is approximately constant regardless of the distance from the center C of the outer surface 22b.

[0054] The configuration of yet another modified example of the acoustic matching member 2 will be described with reference to Fig. 16. Fig. 16 is a diagram showing the cross-sectional configuration of yet another modified example of the acoustic matching member. In Fig. 16, the pair of electrodes 41, 42 is omitted. This modified example differs from the first embodiment in the configuration of the bottom 22. The following mainly describes the differences between the first embodiment and this modified example. 16, the second distance T2 changes in the second portion 22d. Specifically, the second distance T2 decreases as it moves away from the center C of the outer surface 22b.

[0055] Second Embodiment The configuration of an ultrasonic transducer 101 according to the second embodiment will be described with reference to Figs. 17 to 21. Fig. 17 is a perspective view showing the ultrasonic transducer according to this embodiment. Fig. 18 is an exploded perspective view showing the ultrasonic transducer according to this embodiment. Fig. 19 is a diagram showing a cross-sectional configuration along line XIX-XIX in Fig. 17. Fig. 20 is a diagram showing an enlarged portion of the cross-sectional configuration along line XIX-XIX in Fig. 17. Fig. 21 is a plan view showing a flexible substrate and a piezoelectric element. The ultrasonic transducer 101 includes a case 110, a piezoelectric element 120, a sound absorbing material 180, and a vibration isolating material 190. The ultrasonic transducer 101 is configured to be able to transmit and receive ultrasonic waves.

[0056] The case 110 defines an accommodation space S that accommodates the piezoelectric element 120. The case 110 has a bottomed cylindrical shape. The case 110 has a bottom 111 and a side 113. In this embodiment, the bottom 111 and the side 113 are integrally formed and made of the same material. The case 110 is made of, for example, aluminum (Al). The case 110 may be made of a metal other than Al. The case 110 may be made of, for example, an aluminum alloy, stainless steel, or a copper alloy. The aluminum alloy includes, for example, duralumin. The copper alloy includes, for example, brass.

[0057] The bottom 111 has an inner surface 111a located so as to face the storage space S, and an outer surface 111b facing the inner surface 111a. The inner surface 111a and the outer surface 111b face each other in a first direction D1. In this embodiment, the first direction D1 coincides with a direction perpendicular to the inner surface 111a and coincides with a direction perpendicular to the outer surface 111b. The inner surface 111a has a circular shape having a major axis and a minor axis when viewed from the first direction D1. In this embodiment, the inner surface 111a has an elliptical shape. In the inner surface 111a, a second direction D2 along the minor axis and a third direction D3 along the major axis intersect with each other. The direction along the major axis and the direction along the minor axis are, for example, perpendicular to each other. In this embodiment, the inner surface 111a is approximately flat.

[0058] The side portion 113 has a tubular shape. In this embodiment, the side portion 113 has a cylindrical shape. The side portion 113 extends from the bottom portion 111 in a direction intersecting the bottom portion 111. In this embodiment, the side portion 113 extends in a first direction D1. The side portion 113 has an inner side surface 114. The inner side surface 114 forms an accommodation space S together with an inner surface 111a of the bottom portion. A plurality of step portions 115 are formed on the inner side surface 114. In this embodiment, three step portions 15 are formed. The step portions 115 are used to position the vibration-proof material 190 relative to the case 110.

[0059] The piezoelectric element 120 is accommodated in the accommodation space S of the case 110. The piezoelectric element 120 has a piezoelectric body 121 and a pair of electrodes 123, 125 for applying an electric charge to the piezoelectric body 121. The piezoelectric element 120 is disposed on the inner surface 111a as shown in Fig. 19. The piezoelectric element 120 is fixed onto the inner surface 111a by, for example, adhesion. An adhesive layer may be present between the piezoelectric element 120 and the inner surface 111a. Piezoelectric element 120 may have one or more internal electrodes disposed within piezoelectric body 121. In this case, piezoelectric body 121 may have multiple piezoelectric layers, and the internal electrodes and the piezoelectric layers may be arranged alternately.

[0060] The piezoelectric element 121 has a rectangular parallelepiped shape and has a square shape in a plan view. In this specification, the term "rectangular parallelepiped shape" includes a rectangular parallelepiped shape with chamfered corners and ridges, and a rectangular parallelepiped shape with rounded corners and ridges. The piezoelectric element 121 has a pair of square-shaped principal surfaces 121a, 121b facing each other and a pair of side surfaces 121c, 121d facing each other. The side surfaces 121c, 121d extend in a direction in which the pair of principal surfaces 121a, 121b face each other, i.e., in a first direction D1, so as to connect the pair of principal surfaces 121a, 121b. The principal surface 121b faces the inner surface 111a. The piezoelectric element 120 is disposed on the bottom 111 so that the principal surface 121b faces the inner surface 111a. The direction in which the pair of principal surfaces 121a, 121b face each other is a direction intersecting the inner surface 111a. The direction in which the pair of principal surfaces 121a, 121b face each other may be a direction perpendicular to the inner surface 111a.

[0061] The piezoelectric element 121 is made of a piezoelectric ceramic material. The piezoelectric ceramic material includes, for example, PZT [Pb(Zr,Ti)O3], PT(PbTiO3), PLZT [(Pb,La)(Zr,Ti)O3], or barium titanate (BaTiO3). The piezoelectric element 121 is made of, for example, a sintered ceramic green sheet including the above-mentioned piezoelectric ceramic material. The thickness of the piezoelectric element 121 is, for example, 150 to 500 μm. In this embodiment, the thickness of the piezoelectric element 121 is 200 μm.

[0062] Each of the electrodes 123, 125 is in direct contact with each of the surfaces 121a to 121c of the piezoelectric element 121. The thickness of each of the electrodes 123, 125 is 1.5 μm or less. Each of the electrodes 123, 125 includes a laminate made of, for example, a chromium (Cr) layer, a nickel-copper alloy (Ni-Cu) layer, and a gold (Au) layer. Each of the electrodes 123, 125 may include silver (Ag), titanium (Ti), platinum (Pt), a silver-palladium alloy (Ag-Pd), or a nickel-chromium alloy (Ni-Cr). Each of the electrodes 123, 125 is formed on the surface of the piezoelectric element 121 by, for example, a sputtering method.

[0063] The flexible substrate 140 , the pair of first pins 150 , the relay substrate 160 , and the pair of second pins 170 constitute a wiring member that is electrically connected to the piezoelectric element 120 .

[0064] The flexible substrate 140 is disposed in the accommodation space S so as to be superimposed on the piezoelectric element 120. The flexible substrate 140 is plate-like or sheet-like, and has substantially the same shape as the inner surface 111a in a plan view. More specifically, the flexible substrate 140 is designed to be slightly smaller than the inner surface 111a in a plan view, and is disposed apart from the inner surface 114 of the case 110. The flexible substrate 140 has an upper surface facing the relay substrate 160 described later, and a lower surface facing the inner surface 111a of the case 110. The flexible substrate 140 is, for example, a flexible printed circuit board (FPC) or a flexible flat cable (FFC). That is, the flexible substrate 140 has a plurality of wirings. The flexible substrate 140 electrically connects a pair of first pins 150 and the piezoelectric element 120, respectively, by the plurality of wirings. In this embodiment, the flexible substrate 140 has a configuration in which a pair of wirings 141, 142 are provided within a resin sheet made of resin such as polyimide resin.

[0065] As shown in FIGS. 19 and 20, the flexible substrate 140 has a base portion 143 and a pair of contact portions 144 and 145.

[0066] The base portion 143 is a flat portion located in the center of the flexible substrate 140, and has a pair of principal surfaces 143a, 143b facing each other in the first direction D1. The flexible substrate 140 is disposed in the accommodation space S such that the principal surface 143b of the base portion 143 faces the piezoelectric element 121.

[0067] A rectangular opening 143c is provided in the central region of the base portion 143, and the piezoelectric element 120 is partially exposed from the opening 143c. The opening 143c can be provided so that the flexible substrate 140 does not suppress vibration of the piezoelectric element 120. The flexible substrate 140 overlaps with the electrodes 123, 125 of the piezoelectric element 120 at an edge 143d of the opening 143c extending along the second direction D2.

[0068] The contact portions 144, 145 extend continuously from the base portion 143, and are provided at positions sandwiching the base portion 143 in the third direction D3. Each of the contact portions 144, 145 has a long flat plate shape extending in the second direction D2, and is designed to be thicker on the main surface 143b side than the thickness of the base portion 143. One of the contact portions 144 is located on the side surface 121c side of the piezoelectric body 121, and the other contact portion 145 is located on the side surface 121d side of the piezoelectric body 121. No piezoelectric element 120 is interposed between each of the contact portions 144, 145 and the bottom portion 111, and each of the contact portions 144, 145 is in direct contact with the inner surface 111a.

[0069] The pair of wirings 141, 142 are arranged from an edge 143d of an opening 143c of the base portion 143 overlapping with the piezoelectric element 120 to each of the contact portions 144, 145. The pair of wirings 141, 142 have first ends 141a, 142a and second ends 141b, 142b. The first end 141a of one wiring 141 is provided over the entire width of the edge 143d of the opening 143c of the base portion 143 overlapping with the electrode 123 of the piezoelectric element 120, and is exposed from the resin sheet at the lower surface of the edge 143d, i.e., the main surface 143b, and is electrically connected to the electrode 123 of the piezoelectric element 120. The second end 141b of one wiring 141 is located at the contact portion 144, is exposed from the resin sheet at the upper surface of the contact portion 144, and is electrically connected to a first pin 150 described later. The first end 142a of the other wiring 142 is provided over the entire width of the edge 143d of the opening 143c of the base portion 143 overlapping with the electrode 125 of the piezoelectric element 120, and is exposed from the resin sheet at the lower surface of the edge 143d, i.e., the main surface 143b, and is electrically connected to the electrode 125 of the piezoelectric element 120. The second end 142b of the other wiring 142 is located at the contact portion 145, and is exposed from the resin sheet at the upper surface of the contact portion 145, and is electrically connected to the first pin 150 described later. The wiring 141 is physically and electrically connected to the electrode 123, and the wiring 142 is physically and electrically connected to the electrode 125. Therefore, the above-mentioned wiring members are connected to the electrodes 123 and 125.

[0070] The flexible substrate 140 further includes a pair of damper sections 147 and 149 adjacent to the piezoelectric element 120. Each damper section 147 and 149 is provided on the main surface 143b of the base section 143 of the flexible substrate 140, and is interposed between the flexible substrate 140 and the bottom section 111. Each damper section 147 and 149 is provided on the main surface 143b between the piezoelectric element 120 and the contact sections 144 and 145, so as to cross between the piezoelectric element 120 and the contact sections 144 and 145. More specifically, each damper section 147 and 149 is provided across the entire width of the flexible substrate 140 along the second direction D2. One damper section 147 is provided between the piezoelectric element 120 and the contact section 144, and the other damper section 149 is provided between the piezoelectric element 120 and the contact section 145. In other words, the contact parts 144 and 145 of the flexible substrate 140 are located outside the damper parts 147 and 149 when viewed from the first direction D1. Each damper part 147 and 149 is made of an insulating material, for example, an insulating resin. In this embodiment, each damper part 147 and 149 is made of a thermocompression resin film, and in this case, each damper part 147 and 149 is formed by compression bonding in a state in which the surface layer part is heated and melted. The thermocompression resin film includes, for example, a nitrile rubber-based resin film. In this embodiment, each damper part 147 and 149 is bonded to both the main surface 143b of the flexible substrate 140 and the inner surface 111a of the bottom part 111, thereby fixing the flexible substrate 140 to the bottom part 111.

[0071] The first pin 150 is a conductive member and is made of, for example, a metal. The first pin 150 is made of, for example, brass. A plating layer (not shown) may be formed on the surface of the first pin 150. The plating layer may be formed of, for example, nickel plating and tin plating. In this case, the plating layer has a two-layer structure.

[0072] As shown in FIGS. 18 and 19, the portions of the pair of first pins 150 on the flexible substrate 140 side are respectively held by a pair of sleeves 152. Of the pair of sleeves 152, one sleeve 152a holds the first pin 150a, and the other sleeve 152b holds the first pin 150b. Each of the sleeves 152a and 152b is a cylindrical member having flanges on both ends. In this embodiment, the sleeves 152a and 152b have the same shape. Each of the sleeves 152a and 152b is made of resin. Each of the sleeves 152a and 152b is made of, for example, a metal. Each of the sleeves 152a and 152b is made of, for example, phosphorus deoxidized copper (PDC) or brass. When the sleeves 152a, 152b are made of metal, connection reliability is increased because not only the first pins 150a, 150b but also the sleeves 152a, 152b can be joined to the conductor layer of the flexible substrate 140. Each of the sleeves 152a, 152b may be made of PEEK (polyether ether ketone) resin, polybutylene terephthalate resin (PBT resin), or polyphenylene sulfide (PPS) resin.

[0073] A flange on one end side of each of the sleeves 152a, 152b is joined to the flexible substrate 140. Each of the sleeves 152a, 152b is disposed at a position overlapping with the contact portions 144, 145 when viewed in the axial direction, i.e., the first direction D1. The axial length of each of the sleeves 152a, 152b is shorter than the axial length of the first pin 150.

[0074] The sound absorbing material 180 is disposed on the piezoelectric element 120. The sound absorbing material 180 is disposed between a pair of first pins 150. The sound absorbing material 180 is disposed in the accommodation space S. The sound absorbing material 180 has, for example, a rectangular parallelepiped shape. The sound absorbing material 180 overlaps the entirety of the piezoelectric element 120 in the thickness direction of the piezoelectric element 120, i.e., when viewed from the first direction D1. That is, the piezoelectric element 120 is located inside the outer edge of the sound absorbing material 180 when viewed from the first direction D1. This further reduces the reverberation of ultrasonic components. When viewed from the first direction D1, the piezoelectric element 120 is located approximately in the center of the sound absorbing material 180 in the second direction D2 and the third direction D3. The sound absorbing material 180 is, for example, made of a foam mainly made of a thermoplastic resin. The foam includes, for example, a bubble structure. The thermoplastic resin includes, for example, ethylene-propylene-diene rubber (EPDM).

[0075] The relay substrate 160 is bridged between the pair of first pins 150. The relay substrate 160 is disposed in parallel to the piezoelectric element 120 with the sound absorbing material 180 sandwiched therebetween. The relay substrate 160 is disposed within the accommodation space S. As shown in FIG. 22, the relay substrate 160 is a substantially I-shaped plate-like member extending in the third direction D3, and is made of, for example, a glass epoxy substrate. The relay substrate 160 has a plurality of conductor layers, and in this embodiment, has a pair of substantially I-shaped conductor layers 162A, 162B. The relay substrate 160 has a pair of principal surfaces 160a, 160b facing each other in the first direction D1, and the principal surface 160b faces the sound absorbing material 180. Each of the principal surfaces 160a, 160b at both ends of the relay substrate 160 is curved so as to bulge outward, and has an arc shape.

[0076] The pair of conductor layers 162a, 162b are provided to connect between the through holes 164a, 164b and the through holes 166a, 166b, respectively, and electrically connect the first pins 150a, 150b and the second pins 170a, 170b. Of the pair of conductor layers 162a, 162b, one conductor layer 162a connects the first pin 150a and the second pin 170a, and the other conductor layer 162b connects the first pin 150b and the second pin 170b.

[0077] The second pins 170a, 170b are arranged on the main surface 160a in a state spaced apart from each other in the third direction D3. The second pins 170a, 170b extend from the main surface 160a in the first direction D1 and penetrate the vibration-proof material 190. The pair of second pins 170 are arranged between the pair of first pins 150a, 150b in the third direction D3. In this embodiment, the second pins 170a, 170b have the same shape as each other. The second pin 170 is made of, for example, a metal. The second pin 170 is made of, for example, brass. A plating layer (not shown) may be formed on the surface of the second pin 170. The plating layer may be formed of, for example, nickel plating and tin plating. In this case, the plating layer has a two-layer structure.

[0078] The vibration-proofing material 190 is disposed in contact with the inner surface of the case 110, i.e., the inner side surface 114, and suppresses vibration of the case 110. The vibration-proofing material 190 is disposed around the sound-absorbing material 180. The vibration-proofing material 190 has a lid 191 and a frame 193. The lid 191 seals the opening of the case 110 in a state in which the piezoelectric element 120, the flexible substrate 140, the first pin 150, the sleeve 152, the sound-absorbing material 180, and the relay substrate 160 are housed in the case 110. The lid 191 seals the housing space S. The tips of the second pins 170 protrude from the lid 191.

[0079] The frame body 193 extends in a direction intersecting with the lid body 191. The direction intersecting with the lid body 191 may be, for example, a direction perpendicular to the lid body 191. The lid body 191 and the frame body 193 are integrally formed. The vibration-proof material 190 is a cylindrical member with one axial end closed and the other end open. The vibration-proof material 190 is fitted inside the case 110. The vibration-proof material 190 is press-fitted inside the case 110. The frame body 193 extends from the lid body 91 to the inside of the case 110 along the first direction D1. The frame body 193 is spaced from the inner surface 111a. The frame body 193 is in contact with the inner side surface 114 of the case 110.

[0080] Frame 193 surrounds sound absorbing material 180. Sound absorbing material 180 protrudes toward piezoelectric element 120 further than vibration isolating material 190 (frame 193) in the thickness direction of piezoelectric element 120, i.e., in first direction D1. The distance between frame 193 and piezoelectric element 120 in first direction D1 is longer than the distance between sound absorbing material 180 and piezoelectric element 120 in first direction D1.

[0081] The frame 193 has a pair of side portions 195 and a pair of side portions 197. The pair of side portions 195 face each other in the third direction D3 with the sound-absorbing material 80 therebetween. The pair of side portions 197 face each other in the second direction D2 with the sound-absorbing material 180 therebetween. The side portions 195 face each other and the side surfaces 180c of the sound-absorbing material 180. The side portions 195 are spaced apart from the sound-absorbing material 180.

[0082] The pair of side portions 197 sandwich and hold the sound absorbing material 180. The sound absorbing material 180 is fitted between the pair of side portions 197. The pair of side portions 197 compress the sound absorbing material 180. The sound absorbing material 180 presses the pair of side portions 197 by a repulsive force against the compression. Each side portion 197 is in contact with each side surface 180d of the sound absorbing material 180.

[0083] The vibration-proof material 190 further has a plurality of protruding portions 199 that protrude from the lid 191 toward the inner surface 114. The protruding portions 199 are provided on the lid 191 at positions corresponding to the stepped portions 115 of the case 110. The protruding portions 199 are disposed in the corresponding stepped portions 115. The vibration-proof material 190 is positioned with respect to the case 110 by the protruding portions 199 being engaged with the stepped portions 115.

[0084] The vibration-proof material 190 is an elastic body, and suppresses reverberation by its elasticity. The vibration-proof material 190 is made of resin. The vibration-proof material 190 is a non-foam body, and has a density higher than that of the sound-absorbing material 180. The vibration-proof material 190 is made of, for example, silicone rubber. The vibration-proof material 190 is made of, for example, RTV (Room Temperature Vulcanizing) silicone rubber.

[0085] Next, the configuration of the bottom portion 111 will be described with reference to Fig. 22. Fig. 22 is a plan view showing the relay board and the case. The bottom 111 includes a first portion 111c and a plurality of second portions 111d, similar to the bottom 22 in the first embodiment. In this embodiment, the bottom 111 includes two second portions 111d. That is, the bottom 111 has at least one second portion 111d. In this embodiment, the thickness of the first portion 111c is different from the thickness of each of the second portions 111d.

[0086] The first portion 111c has a first distance between the inner surface 111a and the outer surface 111b in the first direction D1, similar to the first portion 22c. The two second portions 111d have a second distance between the inner surface 111a and the outer surface 111b in the first direction D1, similar to the second portion 22d. The second distance is substantially constant in each of the second portions 111d. The second distances in each of the second portions 111d are, for example, equal. The second distances in each of the second portions 111d may be different from each other. The first distance and the second distance are defined, for example, by the shortest distance between the inner surface 111a and the outer surface 111b. The first distance is, for example, 0.9 to 2 mm. The second distance is, for example, 0.3 to 0.6 mm. In this embodiment, the first distance is 0.9 mm, and the second distance is 0.3 mm. In this embodiment as well, the first distance and the second distance are different, so that the outer surface 111b has a step corresponding to the difference between the first distance and the second distance.

[0087] As shown in FIG. 22, the two second portions 111d are positioned so as to be spaced apart with the first portion 111c therebetween, as viewed from the first direction D1. In this embodiment, the two second portions 111d are positioned so as to be spaced apart in the second direction D2. The two second portions 111d are positioned so as to be point-symmetrical with respect to the center of the outer surface 111b, as viewed from the first direction D1. The two second portions 111d are positioned so that the entire circumference of each of them is surrounded by the first portion 111c, as viewed from the first direction D1. The position of the center of the outer surface 111b coincides with the position of the center of the inner surface 111a, as viewed from the first direction D1.

[0088] The width of the two second portions 111d increases with increasing distance from the center of the outer surface 111b as viewed from the first direction D1. The width of each second portion 111d is, for example, defined by a length in the third direction D3. The widths of the two second portions 111d may be equal to each other or may be different from each other. The widths of the two second portions 111d may increase continuously or stepwise as they increase from the center of the outer surface 22b. In this embodiment, the two second portions 111d also have a fan shape having an arc on the edge side of the bottom 111 as viewed from the first direction D1. Each second portion 111d may have a triangular shape as viewed from the first direction D1. The central angle of each second portion 111d is, for example, 10 to 45 degrees. The radius of each second portion 111d is, for example, 2 to 6 mm. In this embodiment, the central angle of each second portion 111d is 45 degrees, and the radius of each second portion 111d is 5.3 mm.

[0089] When viewed from the first direction D1, the wirings 141, 142 are positioned so as not to overlap the second portion 111d. That is, the wirings 141, 142 are positioned so as to overlap the first portion 111c. Therefore, the wirings 141, 142 are connected to the corresponding electrodes 123, 125 at positions that do not overlap the second portion 111d. That is, the wiring member (flexible substrate 140) is connected to the electrodes 123, 125 at positions that do not overlap the second portion 111d. In this embodiment, the electrode 123 is also positioned so as not to overlap the second portion 111d. Therefore, the piezoelectric element 120 is disposed on the inner surface 111a so that the electrode 123 does not overlap the second portion 111d at positions that do not overlap the second portion 111d.

[0090] In the ultrasonic transducer 101, the second distance is smaller than the first distance, as in the ultrasonic transducer 1. Therefore, the vibration propagating from the piezoelectric element 120 to the bottom 111 is less likely to attenuate in the second portion 111d before it propagates to the outer surface 111b than in the first portion 111c. That is, the vibration propagating from the piezoelectric element 120 to the bottom 111 is more likely to attenuate in the first portion 111c before it propagates to the outer surface 111b than in the second portion 111d. The vibration propagating through the first portion 111c tends to attenuate before it propagates to the outer surface 111b than the vibration propagating through the second portion 111d. As a result, the ultrasonic waves output from the ultrasonic transducer 101 have a directivity corresponding to the strength of the vibration reaching the outer surface 111b. In the ultrasonic transducer 101, for example, the directivity of the ultrasonic waves output from the ultrasonic transducer 101 is adjusted by adjusting the shapes of the first portion 111c and the second portion 111d. The shape of the second portion 111d includes not only the contour shape of the second portion 111d when viewed from the first direction D1, but also the position of the second portion 111d when viewed from the first direction D1.

[0091] In this embodiment, as in the first embodiment, the directivity angle of the ultrasonic waves output from the ultrasonic transducer 101 corresponds to the shape of each second portion 111d. The directivity angle of the ultrasonic waves output from the ultrasonic transducer 101 in the second direction D2 is larger than the directivity angle in the third direction D3. That is, the ultrasonic waves output from the ultrasonic transducer 101 have a larger spread in the second direction D2 than in the third direction D3. In a configuration in which the bottom 111 has the first portion 111c and the second portion 111d, as described above, the directionality of the ultrasonic waves output from the ultrasonic transducer 101 can be easily adjusted by changing the shape of the bottom 111 (second portion 111d).

[0092] In the ultrasonic transducer 101, the wiring member (flexible substrate 140) is connected to each of the electrodes 123, 125 at a position that does not substantially overlap the second portion 111d. As described above, the vibration propagating from the piezoelectric element 120 to the bottom 111 is less attenuated in the second portion 111d before propagating to the outer surface 111b than in the first portion 111c. Therefore, the configuration in which the wiring members are connected to the electrodes 123, 125 at positions that do not substantially overlap the second portion 111d also has a smaller effect on the vibration characteristics of the ultrasonic transducer 101 than the configuration in which the wiring members are connected to the electrodes 123, 125 at positions that overlap the second portion 111d.

[0093] The configuration of the bottom 111 (the first portion 111c and the second portion 111d) is not limited to the above-mentioned configuration. For example, the bottom 111 (the first portion 111c and the second portion 111d) may have the same configuration as the bottom 22 (the first portion 22c and the second portion 22d) shown in Figures 11 to 16.

[0094] The above describes the embodiments and modifications of the present invention, but the present invention is not necessarily limited to the above-described embodiments and modifications, and various modifications are possible without departing from the spirit of the present invention.

[0095] The number of second portions 22d is not limited to one or two. For example, the number of second portions 22d may be three or more. The number of second portions 111d is not limited to two. For example, the number of second portions 111d may be one, or three or more.

[0096] In the ultrasonic transducer 1, the wiring member 9 may be connected to each of the electrodes 41, 42 at a position overlapping the second portion 22d. In a configuration in which the wiring member 9 is connected to each of the electrodes 41, 42 at a position not overlapping the second portion 22d, as described above, the influence on the vibration characteristics of the ultrasonic transducer 1 is small. In the ultrasonic transducer 101, the wiring member (flexible substrate 140) may be connected to each of the electrodes 123, 125 at a position overlapping the second portion 111d. In a configuration in which the wiring member (flexible substrate 140) is connected to each of the electrodes 123, 125 at a position that does not substantially overlap the second portion 111d, as described above, the influence on the vibration characteristics of the ultrasonic transducer 101 is small.

[0097] The second portions 22d do not have to be positioned symmetrically with respect to one another with respect to the center C of the outer surface 22b when viewed from the first direction D1. The second portions 111d do not have to be positioned symmetrically with respect to one another with respect to the center of the outer surface 111b when viewed from the first direction D1.

[0098] The width of each of the second portions 22d, 111d may be constant when viewed from the first direction D1. In this case, each of the second portions 22d, 111d may have a rectangular shape when viewed from the first direction D1.

[0099] The ultrasonic transducer 1, 101 may be an ultrasonic transmitting device that only transmits ultrasonic waves. [Explanation of symbols]

[0100] 1,101...ultrasonic transducer, 2...acoustic matching member, 4,120...piezoelectric element, 9...wiring member, 22,111...bottom, 22a,111a...inner surface, 22b,111b...outer surface, 22c,111c...first portion, 22d,111d...second portion, 40,121...piezoelectric element, 40a,40b,121a,121b...main surface, 41,42,123,125...electrodes, 110...case, 140...flexible substrate, 150...first pin, 160...relay substrate, 170...second pin, C...center of outer surface, D1...first direction, D2...second direction, D3...third direction, S...accommodation space, T1...first distance, T2...second distance.

Claims

1. a case defining a storage space; A piezoelectric element disposed in the accommodation space; a wiring member electrically connected to the piezoelectric element, The case is a bottom portion having an inner surface facing the storage space and an outer surface facing the inner surface; A side portion extending in a direction intersecting the bottom portion and defining the storage space together with the bottom portion, The piezoelectric element is disposed on the inner surface, a piezoelectric element having a pair of main surfaces facing each other in a direction in which the inner surface and the outer surface face each other; a pair of electrodes disposed on one of the pair of principal surfaces; The bottom portion is a first portion having a first distance between the inner surface and the outer surface in a direction in which the inner surface and the outer surface face each other; at least one second portion having a second distance between the inner surface and the outer surface that is smaller than the first distance in a direction in which the inner surface and the outer surface face each other; An ultrasonic transducer, wherein the wiring member is connected to the pair of electrodes at a position that does not overlap with the at least one second portion when viewed in a direction perpendicular to the inner surface.

2. the bottom portion has a plurality of second portions including the at least one second portion; The ultrasonic transducer according to claim 1 , wherein the second portions are positioned so as to be spaced apart from each other with the first portion between them when viewed in a direction perpendicular to the outer surface.

3. The ultrasonic transducer according to claim 2 , wherein the second portions are positioned point-symmetrically with respect to a center of the outer surface when viewed from the direction perpendicular to the outer surface.

4. The ultrasonic transducer of claim 3 , wherein the width of each of the second portions increases with distance from the center of the outer surface when viewed in the direction perpendicular to the outer surface.

5. An ultrasonic transducer as described in any one of claims 1 to 4, wherein the at least one second portion is positioned such that, when viewed from a direction perpendicular to the outer surface, the entire circumference of the at least one second portion is surrounded by the first portion.

6. The ultrasonic transducer of claim 1 , wherein the second distance varies in the at least one second portion.

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