Ultrasonic transducer

Abstract

This invention provides a technology that, while utilizing a square piezoelectric element, allows for the first contact point to be brought into contact with or joined to the diaphragm at a node, and the second contact point to be brought into contact with or joined to the piezoelectric element. [Solution] The piezoelectric element 11 of the ultrasonic transducer 1 is positioned such that its center of gravity 11G is offset from the center of gravity 10G of the diaphragm 10, avoiding a position that overlaps with the first contact portion 15C in the thickness direction, and is positioned so that it overlaps with a part of the node 20 when viewed from the thickness direction.

Description

Technical Field

[0001] This disclosure relates to an ultrasonic transducer.

Background Art

[0002] Patent Document 1 discloses an ultrasonic transducer. This ultrasonic transducer includes a diaphragm, a piezoelectric element, a first wiring portion, and a second wiring portion. The first wiring portion has a first contact portion. The second wiring portion has a second contact portion. The piezoelectric element is disposed at a position overlapping a part of a node of vibration when viewed from the thickness direction. The first contact portion is in contact with or joined to the diaphragm at a position overlapping the node when viewed from the thickness direction. The second contact portion is in contact with or joined to the piezoelectric element at a position overlapping the node when viewed from the thickness direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Considering from the viewpoint that the shape of the piezoelectric element is difficult to have vibration bias, it is preferably square. However, when a square piezoelectric element is disposed at the center of the diaphragm, it is difficult to make the first contact portion contact or join the diaphragm at a position overlapping the node, and make the second contact portion contact or join the piezoelectric element at a position overlapping the node. For this reason, in Patent Document 1, the shape of the piezoelectric element is different from a square.

[0005] An object of this disclosure is to provide a technique capable of making the first contact portion contact or join the diaphragm on the node and making the second contact portion contact or join the piezoelectric element on the node while using a square piezoelectric element.

Means for Solving the Problems

[0006] The ultrasonic transducer of this disclosure is A vibrator having a disc-shaped conductive diaphragm and a piezoelectric element joined to a part of the first surface on one side in the thickness direction of the diaphragm, and vibrating to generate annular nodes, A first wiring section having a first contact portion that contacts or joins to the first surface of the diaphragm, A second wiring portion having a second contact portion that contacts or joins to the second surface of the piezoelectric element opposite to the diaphragm side, Equipped with, The first contact portion is in contact with or joined to the first surface of the diaphragm at a position that overlaps with the node when viewed from the thickness direction. The second contact portion is in contact with or joined to the second surface of the piezoelectric element at a position that overlaps with the node when viewed from the thickness direction. The piezoelectric element is an ultrasonic transducer whose shape is square when viewed from the thickness direction, The piezoelectric element is positioned such that, in the thickness direction, its center of gravity is offset from the center of gravity of the diaphragm, avoiding a position that overlaps with the first contact portion, and is positioned so as to overlap with a part of the node when viewed from the thickness direction. [Effects of the Invention]

[0007] According to this disclosure, even while using a square piezoelectric element, a first contact portion can be brought into contact with or joined to the diaphragm at a node, and a second contact portion can be brought into contact with or joined to the piezoelectric element. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of the ultrasonic transducer of the first embodiment, cut along the X-axis. [Figure 2] Figure 2 is a cross-sectional view taken along line AA in Figure 1. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] The embodiments of this disclosure are listed and illustrated below.

[0010] [1] A vibrator having a disc-shaped conductive diaphragm and a piezoelectric element joined to a part of the first surface on one side in the thickness direction of the diaphragm, which vibrates to generate annular nodes, A first wiring section having a first contact portion that contacts or joins to the first surface of the diaphragm, A second wiring portion having a second contact portion that contacts or joins to the second surface of the piezoelectric element opposite to the diaphragm side, Equipped with, The first contact portion is in contact with or joined to the first surface of the diaphragm at a position that overlaps with the node when viewed from the thickness direction. The second contact portion is in contact with or joined to the second surface of the piezoelectric element at a position that overlaps with the node when viewed from the thickness direction. The piezoelectric element is an ultrasonic transducer whose shape is square when viewed from the thickness direction, The piezoelectric element is positioned such that, in the thickness direction, its center of gravity is offset from the center of gravity of the diaphragm, avoiding a position that overlaps with the first contact portion, and is positioned so as to overlap with a part of the node when viewed from the thickness direction. Ultrasonic transducer.

[0011] In this configuration, the center of gravity of the piezoelectric element is positioned offset from the center of gravity of the diaphragm. Therefore, even while using a square piezoelectric element, it is possible to make the first contact point in contact with or join the diaphragm and the second contact point in contact with or join the piezoelectric element at the node.

[0012] [2] When viewed from the thickness direction, both ends of the side of the piezoelectric element opposite to the side facing the first contact portion are positioned on the outer edge of the diaphragm. The ultrasonic transducer described in [1].

[0013] When the square piezoelectric element is arranged avoiding the position overlapping with the first contact portion, the bonding area of the piezoelectric element with respect to the diaphragm tends to be small. In this regard, in the ultrasonic transducer, since both ends of the side opposite to the side of the piezoelectric element facing the first contact portion are arranged on the outer peripheral edge of the diaphragm, compared with the configuration in which both ends are arranged inside the outer peripheral edge, the bonding area of the piezoelectric element with respect to the diaphragm becomes large, and the output of the piezoelectric element also becomes large.

[0014] 〔3〕The square which is the shape of the piezoelectric element as viewed from the thickness direction has a first side facing the first contact portion and a second side orthogonal to the first side. The first contact portion is arranged at a position overlapping with the X-axis which is parallel to the second side and passes through the center of gravity of the diaphragm when viewed from the thickness direction. The ultrasonic transducer according to 〔1〕 or 〔2〕.

[0015] According to this configuration, the first contact portion can be arranged at a node and at one end on one side of the X-axis, and the piezoelectric element can be arranged on the other side of the X-axis with respect to the first contact portion. That is, while arranging the first contact portion on the node, a large arrangement area of the piezoelectric element can be secured, so that the bonding area of the piezoelectric element with respect to the diaphragm becomes large, and the output of the piezoelectric element also becomes large.

[0016] 〔4〕The node includes a protruding portion protruding only from one side of the piezoelectric element when viewed from the thickness direction. The first contact portion is in contact with or bonded to the first surface of the diaphragm at a position overlapping with the protruding portion when viewed from the thickness direction. The ultrasonic transducer according to any one of 〔1〕 to 〔3〕.

[0017] According to this configuration, since the region where the piezoelectric element overlaps with the node in the thickness direction can be increased, the degree of freedom in the position where the second contact portion is arranged can be increased.

[0018] [Details of Embodiments of the Present Disclosure] 1. First Embodiment The ultrasonic transducer 1 shown in Figure 1 is used, for example, in medical or industrial ultrasonic devices. The ultrasonic transducer 1 generates ultrasound when a drive signal is applied and converts the ultrasound into an electrical signal when it is received.

[0019] The ultrasonic transducer 1 comprises a transducer 9, an intervening member 13, a base portion 14, a first wiring portion 15, a second wiring portion 16, and a case 17. The transducer 9 has a diaphragm 10, a piezoelectric element 11, and a resonator 12.

[0020] The diaphragm 10 is disc-shaped. The diaphragm 10 is conductive. The diaphragm 10 is made of metal, for example, 42 alloy (42Ni-Fe). The diameter of the diaphragm 10 is greater than the width (maximum width) of the resonator 12, the intervening member 13, and the piezoelectric element 11.

[0021] The diaphragm 10 has a piezoelectric element 11 bonded to one of its first surfaces 21 in the thickness direction, and a resonator 12 bonded to the other surface. The thickness direction refers to the direction of the plate thickness. In this specification, when simply referred to as "thickness direction," it means the thickness direction of the diaphragm 10. In this specification, "bonding" is a concept that includes not only configurations where components are directly bonded, but also configurations where components are bonded via other members.

[0022] The piezoelectric element 11 is plate-shaped. The shape of the piezoelectric element 11 is square when viewed from the thickness direction. The piezoelectric element 11 is bonded to the diaphragm 10 in a stacked manner. The piezoelectric element 11 is bonded to a part of the first surface 21 of the diaphragm 10. In other words, the first surface 21 of the diaphragm 10 includes a part to which the piezoelectric element 11 is bonded and a part that is not bonded. The piezoelectric element 11 is bonded to the diaphragm 10 with a heat-curing epoxy adhesive or the like.

[0023] The piezoelectric element 11 comprises a plate-shaped piezoelectric body 31 and electrodes 32 and 33 provided on both sides of the piezoelectric body 31 in the thickness direction. The piezoelectric body 31 is made of ceramics such as lead zirconate titanate (PZT) or potassium sodium niobate (KNN). One of the electrodes 32 and 33 provided on both sides of the piezoelectric element 11, electrode 32, is joined to the diaphragm 10 and electrically connected to the first wiring section 15 via the diaphragm 10. The other electrode 33 provided on both sides of the piezoelectric element 11, electrode 33, is electrically connected to the second wiring section 16. A base section 14 is joined to the second surface 22 of the piezoelectric element 11, opposite to the diaphragm 10 side, via an intervening member 13.

[0024] The resonator 12 resonates with the vibration of the diaphragm 10 to generate ultrasonic waves. The resonator 12 has the function of increasing the efficiency of sound wave emission by the diaphragm 10, which is excited in accordance with the periodic supply of power to the piezoelectric element 11. The resonator 12 is made of metal, such as an aluminum alloy. The resonator 12 is joined to the diaphragm 10. The joining method is not limited and may be bonded with an adhesive such as epoxy adhesive, or it may be soldered, ultrasonically welded, laser welded, etc. The resonator 12 is cone-shaped. The inner surface of the resonator 12 is tapered, widening towards the side opposite to the diaphragm 10.

[0025] As shown in Figure 2, the transducer 9 vibrates to generate an annular (more specifically, circular) node 20. The transducer 9 generates only one annular node 20. The node 20 is the part of the diaphragm 10 where the displacement in the thickness direction is smallest or where there is no vibration. The position of the node 20 is uniquely determined by the shape and material of the transducer 9 (more specifically, the diaphragm 10, piezoelectric element 11, and resonator 12). The piezoelectric element 11 is significantly smaller than the diaphragm 10 and resonator 12. Therefore, the position of the node 20 is generally determined by the shape and material of the diaphragm 10 and resonator 12, and the shape and material of the piezoelectric element 11 have little influence on the determination of the node 20's position. The outer edge of the diaphragm 10 is a free end. In other words, the ultrasonic transducer 1 is a so-called open type and is more prone to vibration compared to a closed type where the outer edge of the diaphragm 10 is fixed. Node 20 occurs in a plane perpendicular to the thickness direction of the diaphragm 10, inside the outer edge of the diaphragm 10 and outside the center. The vibration of the diaphragm 10 increases as you move from node 20 towards the outer edge and also increases as you move from node 20 towards the center.

[0026] As shown in Figure 1, the intervening member 13 is positioned between the piezoelectric element 11 and the base portion 14, and is joined to both the piezoelectric element 11 and the base portion 14. The intervening member 13 is insulating and elastic. The intervening member 13 has a lower Young's modulus than the base portion 14. The intervening member 13 is made of, for example, rubber such as silicone rubber or resin such as a silicone-based adhesive. The intervening member 13 is positioned along the node 20. The intervening member 13 is annular (more specifically, circular). The axial direction of the intervening member 13 is along the thickness direction of the diaphragm 10, and more specifically, it is the same as the thickness direction of the diaphragm 10.

[0027] The base portion 14 is made of synthetic resin and is configured as a resin base. The base portion 14 is plate-shaped. The thickness direction of the base portion 14 is aligned with the thickness direction of the diaphragm 10, or more specifically, it is the same as the thickness direction of the diaphragm 10.

[0028] The first wiring section 15 has a metal first terminal 15A and a first coil spring 15B. The base section 14 has a first base through-hole 14A that penetrates in the thickness direction. The first wiring section 15 is inserted through the first base through-hole 14A. The first terminal 15A is fixed to the base section 14 in a position that closes the opening of the first base through-hole 14A on the side opposite to the diaphragm 10. The direction of expansion and contraction of the first coil spring 15B is along the thickness direction of the diaphragm 10, or more specifically, the same as the thickness direction. The first coil spring 15B is positioned sandwiched between the diaphragm 10 and the first terminal 15A, and is positioned in a compressed state by being pressed by the diaphragm 10 and the first terminal 15A. One end of the first coil spring 15B is in contact with the first surface 21 of the diaphragm 10, and the other end is in contact with the first terminal 15A. The first wiring section 15 has a first contact portion 15C that contacts the first surface 21 of the diaphragm 10. The first contact portion 15C is annular (more specifically, circular). The first wiring section 15 is electrically connected to one of the conductive paths, the positive electrode conductive path and the negative electrode conductive path (e.g., ground).

[0029] The second wiring section 16 has a metal second terminal 16A and a second coil spring 16B. The base section 14 has a second base through-hole 14B that penetrates in the thickness direction. The second wiring section 16 is inserted through the second base through-hole 14B. The second terminal 16A is fixed to the base section 14 in a position that closes the opening of the second base through-hole 14B on the side opposite to the diaphragm 10. The direction of expansion and contraction of the second coil spring 16B is along the thickness direction of the diaphragm 10, or more specifically, the same as the thickness direction. The second coil spring 16B is positioned sandwiched between the piezoelectric element 11 and the second terminal 16A, and is positioned in a compressed state by being pressed by the piezoelectric element 11 and the second terminal 16A. One end of the second coil spring 16B contacts the second surface 22 of the piezoelectric element 11 opposite to the diaphragm 10 (i.e., the electrode 33 of the piezoelectric element 11), and the other end contacts the second terminal 16A. The second wiring section 16 has a second contact portion 16C that contacts the second surface 22 of the piezoelectric element 11. The second contact portion 16C is annular (more specifically, circular). The second wiring section 16 is electrically connected to the other conductive path of the positive electrode side and the negative electrode side (e.g., ground).

[0030] Case 17 is a component that protects the resonator 12 from contact with foreign matter. Case 17 is fixed to the base portion 14. Case 17 has a peripheral wall portion 17A that surrounds the resonator 12. Multiple openings are formed on the side of Case 17 opposite to the base portion 14 from the resonator 12, and ultrasonic waves are sent to the outside and enter Case 17 from the outside through these openings.

[0031] As shown in Figure 2, the intervening member 13 has a shape that is partially interrupted in the circumferential direction. The intervening member 13 is interrupted at two points. When the diaphragm 10 is viewed from the base portion 14 side, the intervening member 13 is positioned such that the interrupted portion of the intervening member 13 exposes a part of the node 20 that is not covered by the piezoelectric element 11, and a part of the piezoelectric element 11 that covers a part of the node 20.

[0032] The first contact portion 15C is positioned to contact a part of the node 20 that is not covered by the piezoelectric element 11. As a result, the first contact portion 15C contacts the first surface 21 of the diaphragm 10 at a position that overlaps with the node 20 when viewed from the thickness direction.

[0033] The piezoelectric element 11 is positioned such that its center of gravity 11G is offset from the center of gravity 10G of the diaphragm 10, avoiding a position in the thickness direction that overlaps with the first contact portion 15C. The piezoelectric element 11 is positioned so that it overlaps with the center of gravity 10G of the diaphragm 10 in the thickness direction. The piezoelectric element 11 is positioned so that it overlaps with a portion of the node 20 when viewed from the thickness direction. In other words, when the diaphragm 10 is viewed from the base portion 14 side, a portion of the node 20 is covered by the piezoelectric element 11.

[0034] The second contact portion 16C is positioned in contact with a portion of the piezoelectric element 11 that covers a portion of the node 20. As a result, the second contact portion 16C contacts the second surface 22 of the diaphragm 10 at a position that overlaps with the node 20 when viewed from the thickness direction.

[0035] In this configuration, the center of gravity 11G of the piezoelectric element 11 is positioned offset from the center of gravity 10G of the diaphragm 10. Therefore, while utilizing a square piezoelectric element 11, the first contact portion 15C can be brought into contact with the diaphragm 10 and the second contact portion 16C can be brought into contact with the piezoelectric element 11 on the node 20.

[0036] The piezoelectric element 11, when viewed from the thickness direction, is a square with a first side 11A, a second side 11B, a third side 11C, and a fourth side 11D. The first side 11A is the side opposite the first contact portion 15C. The piezoelectric element 11 may or may not be in contact with the first contact portion 15C. The second side 11B and the fourth side 11D are sides perpendicular to the first side 11A. The third side 11C is the side of the piezoelectric element 11 opposite to the first side 11A.

[0037] Here, the line parallel to the first side 11A and passing through the center of gravity 10G of the diaphragm 10 is defined as the X-axis, and the line parallel to the second side 11B and passing through the center of gravity 10G of the diaphragm 10 is defined as the Y-axis.

[0038] The first side 11A is positioned between the first contact point 15C and the Y-axis in a direction parallel to the X-axis. The second side 11B is positioned on one side of the Y-axis relative to the X-axis. The third side 11C is positioned on the opposite side of the Y-axis from the first contact point 15C. The fourth side 11D is positioned on the other side of the Y-axis relative to the X-axis.

[0039] Both ends of the third side 11C are positioned on the outer edge of the diaphragm 10 when viewed from the thickness direction of the diaphragm 10. Note that "on the outer edge" is not limited to the exact outer edge, but also includes the effective outer edge where the displacement is within 1% of the radius of the diaphragm 10.

[0040] With this configuration, compared to a configuration where both ends of the third side 11C are positioned inward from the outer edge, the contact area of ​​the piezoelectric element 11 with the diaphragm 10 is larger, and the output of the piezoelectric element 11 is also larger.

[0041] Furthermore, the first contact portion 15C is positioned parallel to the first side 11A and coincides with the X-axis passing through the center of gravity 10G of the diaphragm 10 when viewed from the thickness direction of the diaphragm 10. The first contact portion 15C is located on the node 20 and at one end of the X-axis. The piezoelectric element 11 is located on the other side of the X-axis from the first contact portion 15C.

[0042] With this configuration, even while arranging the first contact portion 15C on the node 20, a large area for arranging the piezoelectric element 11 can be secured, resulting in a larger contact area between the piezoelectric element 11 and the diaphragm 10, and thus a larger output from the piezoelectric element 11.

[0043] Furthermore, when viewed from the thickness direction of the diaphragm 10, it includes an overhang portion 20A that extends beyond only one side (in this embodiment, the first side 11A) of the piezoelectric element 11. The first contact portion 15C contacts the first surface 21 of the diaphragm 10 at a position that overlaps with the overhang portion 20A when viewed from the thickness direction of the diaphragm 10. With this configuration, the area in which the piezoelectric element 11 overlaps with the node 20 in the thickness direction of the diaphragm 10 can be increased, thereby increasing the degree of freedom in the position where the second contact portion 16C is placed.

[0044] <Other Embodiments> The present invention is not limited to the embodiments described above and in the drawings, and the following embodiments, for example, are also included in the technical scope of the present invention. Furthermore, the various features of the embodiments described above and those described later may be combined in any way as long as they are not contradictory.

[0045] In the first embodiment described above, the first contact portion was configured to contact the diaphragm, but the first contact portion may be configured to be joined to the diaphragm. Also, in the first embodiment, the second contact portion was configured to contact the piezoelectric element, but the second contact portion may be configured to be joined to the piezoelectric element. The joining method is not limited and may include, for example, soldering, laser welding, ultrasonic welding, etc.

[0046] In the first embodiment described above, the first wiring section and the second wiring section each had a coil spring, but they may also be configured without coil springs. For example, instead of coil springs, they may have leaf springs, lead wires, etc.

[0047] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope set forth in the claims or equivalents thereof. [Explanation of symbols]

[0048] 1… Ultrasonic transducer 9…Oscillator 10…Diaphragm 10G... Center of gravity of the diaphragm 11… Piezoelectric element 11A... First side 11B...Second side 11C...Third side 11D...Fourth side 11G... Center of gravity of the piezoelectric element 12...Resonator 13…Intervening member 14…Base section 14A…First base through hole 14B…Second base through hole 15...1st wiring section 15A…1st terminal 15B...First coil spring 15C…1st contact part 16…Second wiring section 16A…Second terminal 16B... Second coil spring 16C…Second contact part 17… Cases 17A…Peripheral wall part Section 20... 20A... protruding portion 21...Side 1 22…Second side 31... Piezoelectric material 32...Electrode 33…electrode

Claims

1. A vibrator having a disc-shaped conductive diaphragm and a piezoelectric element joined to a part of the first surface on one side in the thickness direction of the diaphragm, and vibrating to generate annular nodes, A first wiring section having a first contact portion that contacts or joins the first surface of the diaphragm, A second wiring portion having a second contact portion that contacts or joins to the second surface of the piezoelectric element opposite to the diaphragm side, Equipped with, The first contact portion is in contact with or joined to the first surface of the diaphragm at a position that overlaps with the node when viewed from the thickness direction. The second contact portion is in contact with or joined to the second surface of the piezoelectric element at a position that overlaps with the node when viewed from the thickness direction. The piezoelectric element is an ultrasonic transducer whose shape is square when viewed from the thickness direction, The piezoelectric element is positioned such that, in the thickness direction, its center of gravity is offset from the center of gravity of the diaphragm, avoiding a position that overlaps with the first contact portion, and is positioned so as to overlap with a part of the node when viewed from the thickness direction. Ultrasonic transducer.

2. When viewed from the thickness direction, both ends of the side of the piezoelectric element opposite to the side facing the first contact portion are positioned on the outer edge of the diaphragm. The ultrasonic transducer according to claim 1.

3. The square shape of the piezoelectric element as viewed from the thickness direction has a first side facing the first contact portion and a second side perpendicular to the first side. The first contact portion is positioned such that, when viewed from the thickness direction, it is parallel to the second side and coincides with the X-axis passing through the center of gravity of the diaphragm. The ultrasonic transducer according to claim 1 or claim 2.

4. The aforementioned section includes an overhang that extends beyond only one side of the piezoelectric element when viewed from the thickness direction. The first contact portion is in contact with or joined to the first surface of the diaphragm at a position that overlaps with the protruding portion when viewed from the thickness direction. The ultrasonic transducer according to claim 1 or claim 2.

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