Ultrasound probe

Abstract

To suppress trouble between a piezoelectric element and an ultrasonic wave emission surface and also to suppress an ultrasonic wave from attenuating.SOLUTION: An ultrasonic probe P has an elastic member 40 which presses a piezoelectric element 10 against to acoustic wave transmission members, and liquid 70. The ultrasonic probe P has the piezoelectric element 10 and an ultrasonic emission surface not joined in a gap between a plurality of acoustic transmission members or between the piezoelectric element 10 and the acoustic transmission members, and the liquid 70 is present in the no-joining gap.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasound probe. [Background technology]

[0002] An example of an ultrasonic probe is disclosed in Patent Document 1. In the ultrasonic probe disclosed in Patent Document 1, an ultrasonic transmission medium is filled between an ultrasonic probe and an acoustic radiation window, and oil is used as the ultrasonic transmission medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-345819 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional technologies including the technology of Patent Document 1, a configuration is used in which an acoustic transmission member that transmits ultrasonic waves generated by a piezoelectric element is fixed to the piezoelectric element by a medium such as an adhesive or a resin mold. However, with this configuration, there is a concern that problems may occur in the piezoelectric element due to causes attributable to the medium (residual stress or poor characteristics).

[0005] The present invention was completed based on the above circumstances, and aims to provide an ultrasonic probe that can suppress defects between the piezoelectric element and the ultrasonic wave emitting surface and can suppress the attenuation of ultrasonic waves. [Means for solving the problem]

[0006] The ultrasonic probe according to the present invention is a piezoelectric element that generates ultrasonic waves; an ultrasonic transmission unit having one or more acoustic transmission members that transmit ultrasonic waves generated by the piezoelectric element, supporting the piezoelectric element on one side thereof and having the other side thereof serving as an ultrasonic wave emitting surface; An ultrasound probe having an elastic member that generates a force that presses the piezoelectric element toward the acoustic transmission member; Liquid and and Between the piezoelectric element and the ultrasonic wave emitting surface, gaps between the plurality of acoustic transmission members or between the piezoelectric element and the acoustic transmission member are not joined, and the liquid is present in the gaps.

[0007] In the ultrasonic probe described above, the gaps between the plurality of acoustic transmission members or between the piezoelectric element and the acoustic transmission member are not bonded, so that it is possible to prevent problems caused by bonding these gaps with an adhesive (for example, problems such as element cracking caused by residual stress in the adhesive or poor characteristics due to the thickness of the adhesive). Moreover, because a liquid is present in these gaps, it is possible to suppress the attenuation of ultrasonic waves compared to a configuration in which a gas with a high ultrasonic attenuation rate is present instead of an adhesive.

[0008] In the ultrasonic probe, the liquid may have a lower ultrasonic attenuation rate than air.

[0009] This ultrasonic probe can reduce attenuation of ultrasonic waves passing through the liquid position compared to when air is present at the liquid position.

[0010] In the ultrasonic probe, the liquid may contain solid particles smaller than the width of the gap.

[0011] This ultrasonic probe is advantageous in terms of optimizing the acoustic impedance because the acoustic impedance can be adjusted by both liquid and solid particles.

[0012] In the ultrasonic probe, the elastic member may have a conductor and form a path for transmitting a signal to the piezoelectric element.

[0013] This ultrasonic probe uses the elastic member not only as a member for pressing the piezoelectric element toward the acoustic transmission member, but also as a path for transmitting signals, thereby reducing the number of parts compared to a configuration that requires a separate, dedicated signal transmission path.

[0014] The ultrasonic probe may have a plurality of the acoustic transmission members. The liquid may include a first liquid present in any one of gaps between the plurality of acoustic transmission members or between the piezoelectric element and the acoustic transmission member, and a second liquid present in another gap. The acoustic impedance of the first liquid may be different from that of the second liquid.

[0015] This ultrasonic probe uses two types of liquid with different acoustic impedances, so it is possible to place the liquid at multiple positions to further reduce ultrasonic wave attenuation while also making the acoustic impedance different at each position.

[0016] The ultrasonic probe may have a partition that separates a first region containing the first liquid from a second region containing the second liquid, and the partition may be configured to block movement of the liquid between the first region and the second region.

[0017] This ultrasonic probe can separate the first liquid and the second liquid more reliably while arranging the first liquid and the second liquid at different positions. [Effects of the Invention]

[0018] The ultrasonic probe according to the present invention can suppress defects between the piezoelectric element and the ultrasonic wave emitting surface due to bonding, and can also suppress attenuation of ultrasonic waves. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view that schematically illustrates an ultrasonic probe according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram illustrating some steps of a method for manufacturing the ultrasonic probe of FIG. [Figure 3] FIG. 3 is an explanatory diagram illustrating a step subsequent to the step in FIG. 2 in the method of manufacturing the ultrasonic probe in FIG. [Figure 4] FIG. 4 is an explanatory diagram illustrating a step subsequent to the step in FIG. 3 in the method of manufacturing the ultrasonic probe in FIG. [Figure 5] FIG. 5 is an explanatory diagram illustrating some steps of a method for manufacturing an ultrasonic probe according to a modified example, which is an explanatory diagram illustrating a modified step of the step shown in FIG. [Figure 6] FIG. 6 is an explanatory diagram illustrating a step subsequent to the step in FIG. [Figure 7] FIG. 7 is an explanatory diagram showing a simplified experimental setup for confirming the effect. [Figure 8] FIG. 8 is a graph illustrating the results of an experiment conducted to confirm the effect. [Figure 9] FIG. 9 is a cross-sectional view schematically illustrating an ultrasonic probe according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] First Embodiment 1. Configuration of ultrasonic probe P The following description relates to the ultrasonic probe P of the first embodiment. The ultrasonic probe P of the first embodiment shown in Fig. 1 is used in a medical or industrial ultrasonic device. The ultrasonic probe P transmits and receives ultrasonic waves.

[0021] 1, the ultrasonic probe P includes a piezoelectric element 10, an acoustic matching layer 30, an elastic member 40, a support member 50, and a case 90. The ultrasonic probe P is electrically connected to a control device (not shown) and can receive electrical signals from the control device. The ultrasonic probe P can also transmit electrical signals to the control device. In the configuration of FIG. 1, the acoustic matching layer 30 and the case 90 correspond to an example of an acoustic transmission member.

[0022] In the following description, the thickness direction of the piezoelectric element 10 is the up-down direction, as shown in Fig. 1. One side of the piezoelectric element 10 in the thickness direction is the lower side, and the other side of the piezoelectric element 10 in the thickness direction is the upper side. Specifically, with respect to the piezoelectric element 10, the elastic member 40 side is the upper side, and the opposite side (the acoustic matching layer 30 side in Fig. 1) is the lower side. Fig. 1 schematically shows a cross section of the ultrasonic probe P cut along the central axis X.

[0023] The piezoelectric element 10 is an element that generates ultrasonic waves. The piezoelectric element 10 has a piezoelectric body 14, a first conductive layer 11, and a second conductive layer 12. The piezoelectric element 10 is in the form of a plate with a predetermined thickness. The piezoelectric element 10 is in the form of a cylinder centered on a central axis X, more specifically, a disk. The outer edges of the upper surface 11A and the lower surface 12B of the piezoelectric element 10 are both circular, and the outer circumferential surface is a cylindrical surface.

[0024] The piezoelectric body 14 is made of PZT (lead zirconate titanate) etc. The piezoelectric body 14 is in the shape of a disk with a predetermined thickness.

[0025] The first conductive layer 11 is disposed on one plate surface (upper surface) of the piezoelectric body 14. The second conductive layer 12 is disposed on the other plate surface (lower surface) of the piezoelectric body 14. The first conductive layer 11 and the second conductive layer 12 are conductive electrode layers formed by vapor deposition, plating, sputtering, paste printing, baking, or the like of gold, silver, copper, tin, or the like. The first conductive layer 11 is disposed so as to cover the entire upper surface of the piezoelectric body 14. The second conductive layer 12 is disposed so as to cover the entire lower surface of the piezoelectric body 14. The upper surface 11A of the first conductive layer 11 and the lower surface 12B of the second conductive layer 12 are parallel to each other. Both the upper surface 11A and the lower surface 12B are perpendicular to the central axis X.

[0026] The first conductive layer 11 is a first electrode on the upper surface side of the piezoelectric element 10. An upper surface 11A of the first conductive layer 11 is one of the main surfaces (upper surface) of the piezoelectric element 10. The first conductive layer 11 is electrically connected to the elastic member 40 by a conductive member (not shown). The first conductive layer 11 is electrically connected to a substrate (not shown) via the elastic member 40, and transmits signals between this substrate. For example, the same voltage as that applied to the elastic member 40 is applied to the first conductive layer 11.

[0027] The second conductive layer 12 is a second electrode on the lower surface side of the piezoelectric element 10. The lower surface 12B of the second conductive layer 12 is the other main surface (lower surface) of the piezoelectric element 10. The piezoelectric element 10 is placed on the acoustic matching layer 30. The lower surface 12B of the second conductive layer 12 is supported by the upper surface of the acoustic matching layer 30, with a liquid 70 (described later) interposed therebetween. The second conductive layer 12 is electrically connected to the substrate via a conductive member (not shown), and transmits signals between the second conductive layer 12 and the substrate. For example, the same voltage as that applied to the conductive member is applied to the second conductive layer 12.

[0028] The piezoelectric element 10 can transmit an electric signal to a control device (not shown) via the first conductive layer 11 and the second conductive layer 12. Furthermore, the piezoelectric element 10 can receive an electric signal from the control device. The piezoelectric element 10 generates an ultrasonic wave in response to an AC voltage being applied between the first conductive layer 11 and the second conductive layer 12.

[0029] An ultrasonic transmission unit 20 is provided below the piezoelectric element 10. The ultrasonic transmission unit 20 includes one or more acoustic transmission members that transmit ultrasonic waves generated by the piezoelectric element 10. In the example of FIG. 1, a plurality of acoustic transmission members (acoustic matching layer 30 and bottom wall 92A) form the ultrasonic transmission unit 20. The ultrasonic transmission unit 20 supports the piezoelectric element 10 by using one of its surfaces, namely the upper surface 30A of the acoustic matching layer 30, and the other surface, namely the lower surface of the bottom wall 92A (more specifically, the lower surface 96A of the lens portion 96), serves as an ultrasonic wave emission surface.

[0030] The acoustic matching layer 30 is a member that transmits ultrasonic waves generated by the piezoelectric element 10. The acoustic matching layer 30 is disposed below the piezoelectric element 10 and is sandwiched between the piezoelectric element 10 and the bottom wall 92A in the vertical direction. The acoustic matching layer 30 is disk-shaped. The upper surface 30A of the acoustic matching layer 30 is a support surface that supports the lower surface 12B of the piezoelectric element 10 and supports the piezoelectric element 10 from below. The lower surface 30B of the acoustic matching layer 30 is a surface that is supported from below by the bottom wall 92A. The acoustic impedance of the acoustic matching layer 30 is intermediate between the acoustic impedance of the piezoelectric element 10 and the acoustic impedance of the bottom wall 92A, which functions as an acoustic lens.

[0031] The acoustic matching layer 30 has a cylindrical shape centered on the central axis X. Both the upper surface 30A and the lower surface 30B of the acoustic matching layer 30 are flat. The outer edges of both the upper surface 30A and the lower surface 30B of the acoustic matching layer 30 are circular and centered on the central axis X. The relative position of the acoustic matching layer 30 with respect to the case 90 in a planar direction perpendicular to the central axis X is determined by the inner circumferential surface of the peripheral wall 92B. Because the acoustic matching layer 30 is surrounded by the peripheral wall 92B, relative movement in the planar direction is restricted, preventing significant positional deviation in the planar direction. The acoustic matching layer 30 and the piezoelectric element 10 are stacked in a coaxial positional relationship centered on the central axis X. Because the ultrasonic probe P has a configuration in which the acoustic matching layer 30 is interposed between the bottom wall 92A and the piezoelectric element 10, ultrasonic waves are efficiently propagated to the bottom wall 92A.

[0032] The case 90 has a lower case body 92 and an upper case body 94. The case 90 is made of, for example, a resin material. The inside of the case 90 contains the piezoelectric element 10, the acoustic matching layer 30, the elastic member 40, the support member 50, the liquid 70, etc.

[0033] The lower case body 92 has a bottom wall 92A and a peripheral wall 92B. The bottom wall 92A and the peripheral wall 92B are integrally formed, for example, from the same material. The bottom wall 92A is generally disk-shaped, and its outer edge is circular when viewed from above or below. The bottom wall 92A covers the entire lower surface of the case 90. The upper surface of the bottom wall 92A is a support surface that supports the acoustic matching layer 30 from below. The lower surface of the bottom wall 92A is an outer surface exposed to the outside of the ultrasonic probe P. The peripheral wall 92B is connected around the entire outer edge of the bottom wall 92A and rises upward from the bottom wall 92A. The peripheral wall 92B is cylindrical. In the example of FIG. 1 , the peripheral wall 92B is a cylinder centered on the central axis X. The upper end of the peripheral wall 92B is open, forming a circular opening. The inner peripheral surface of the peripheral wall 92B is a surface that surrounds the outer peripheral surface of the acoustic matching layer 30. In the configuration of Fig. 1, the acoustic matching layer 30 is fitted inside the peripheral wall 92B. Both the inner peripheral surface and the outer peripheral surface of the peripheral wall 92B are cylindrical surfaces centered on the central axis X.

[0034] The lens portion 96, which forms part of the bottom wall 92A of the case 90, is an acoustic lens that focuses ultrasonic waves. The lower surface 96A of the lens portion 96 is a curved surface and forms part of the lower surface of the bottom wall 92A. The upper surface of the lens portion 96 is a flat surface and forms part of the upper surface of the bottom wall 92A. The outer edge of the lens portion 96 (the outer edge of the lower surface 96A (curved surface)) is circular, with its center on the central axis X. The lens portion 96 and the acoustic matching layer 30 are laminated in a coaxial positional relationship, with their center on the central axis X.

[0035] The upper case body 94 functions as a lid that closes the opening at the upper end of the lower case body 92. The upper case body 94 has an upper wall 94A and a peripheral wall 94B. The upper wall 94A and the peripheral wall 94B are integrally formed, for example, from the same material. The upper wall 94A is generally disk-shaped. The upper wall 94A covers the entire upper surface of the case 90. The lower surface of the upper wall 94A is a support surface that supports the elastic member 40 from above. The lower surface of the upper wall 94A is pressed upward by the elastic member 40. The peripheral wall 94B is connected around the entire outer edge of the upper wall 94A and extends downward from the upper wall 94A. The peripheral wall 94B is cylindrical. The lower end of the peripheral wall 94B is open, forming a circular opening. Both the inner and outer circumferential surfaces of the peripheral wall 94B are cylindrical surfaces centered on the central axis X. The inner circumferential portion of the peripheral wall 94B has a first inner circumferential portion 98 having a relatively small inner diameter and a second inner circumferential portion 99 having a larger inner diameter than the first inner circumferential portion 98. The first inner circumferential portion 98 is disposed above the second inner circumferential portion 99. An inner circumferential surface 98A of the first inner circumferential portion 98 and an inner circumferential surface 99A of the second inner circumferential portion 99 form a step shape.

[0036] The inner circumferential surface 98A of the first inner circumferential portion 98 is a cylindrical surface centered on the central axis X. In the configuration of FIG. 1 , the fitting portion 52 of the support member 50 is fitted inside the first inner circumferential portion 98. The first inner circumferential portion 98 is an inner wall portion that restricts the movement direction of the fitting portion 52. The first inner circumferential portion 98 surrounds the fitting portion 52 to prevent the fitting portion 52 from moving in a plane perpendicular to the central axis X, and forms an up and down passage that allows the fitting portion 52 to move up and down along the direction of the central axis X.

[0037] An inner peripheral surface 99A of the second inner peripheral portion 99 is a cylindrical surface centered on the central axis line X. In the configuration of Fig. 1, a peripheral wall 92B is fitted inside the second inner peripheral portion 99. The gap between the second inner peripheral portion 99 and the peripheral wall 92B is sealed.

[0038] The support member 50 is a member that presses the piezoelectric element 10 from above. The support member 50 is made of, for example, a resin material. The support member 50 includes a fitting portion 52 and a pressing portion 54 that is disposed below the fitting portion 52. The fitting portion 52 and the pressing portion 54 are integrally formed.

[0039] The fitting portion 52 is configured in a cylindrical shape. In the example of FIG. 1 , the fitting portion 52 is a cylinder centered on the central axis X. The fitting portion 52 can slide up and down while fitted with the first inner circumferential portion 98. A portion of the elastic member 40 is disposed in the space inside the fitting portion 52. Because the fitting portion 52 and the first inner circumferential portion 98 are fitted with each other, the support member 50 is not allowed to move relative to the case 90 in a direction perpendicular to the central axis X, but is only allowed to move relative to the case 90 in a direction along the central axis X.

[0040] The pressing portion 54 is disposed so as to close the lower end of the fitting portion 52. That is, the space inside the fitting portion 52 is closed by the pressing portion 54. An upper surface 54A of the pressing portion 54, disposed inside the fitting portion 52, is a support surface that supports the elastic member 40 from below. The upper surface 54A of the pressing portion 54 receives pressure based on the elastic force of the elastic member 40 and is pressed downward by the elastic member 40. The pressing portion 54 is configured, for example, in a cylindrical shape and protrudes downward beyond the fitting portion 52. The outer peripheral surface 54B of the pressing portion 54 is a cylindrical surface centered on the central axis X. The diameter (outer diameter) of the outer peripheral surface 54B of the pressing portion 54 is smaller than the inner diameters of the first inner peripheral portion 98 and the second inner peripheral portion 99 and is smaller than the inner diameter of the peripheral wall 92B. A space is defined between the outer peripheral surface 54B of the pressing portion 54 and the inner peripheral surface of the peripheral wall 92B, and this space contains a portion of the liquid 70 described below.

[0041] A restricting portion 56 is provided at the lower end of the pressing portion 54, which holds down the piezoelectric element 10 while restricting its movement. The restricting portion 56 includes an annular portion 56A and a pressing portion 56B. The annular portion 56A is disposed around the vicinity of the upper end of the piezoelectric element 10, surrounding the outer peripheral surface of the piezoelectric element 10 near the upper end. The annular portion 56A fits into a portion of the piezoelectric element 10 (at least a portion including the upper end) and restricts the piezoelectric element 10 from moving in a plane perpendicular to the central axis X. The pressing portion 56B is annularly disposed so as to press downward near the outer edge of the upper surface 11A of the piezoelectric element 10. The pressing portion 54 is biased downward by the elastic member 40 and is continuously pressed downward by the elastic member 40. Therefore, a force continuously pressing downward near the outer edge of the upper surface 11A is continuously generated in the pressing portion 56B, thereby continuously pressing the piezoelectric element 10 from above. However, if an upward force is applied to the pressing portion 54 due to an impact or stress, the support member 50 is allowed to move upward against the bias of the elastic member 40 so as to absorb or release this force.

[0042] The elastic member 40 generates a force that presses the piezoelectric element 10 toward the acoustic transmission member. The elastic member 40 has a coil spring wound around the central axis X. The elastic member 40 functions as a compression spring. When the elastic member 40 is contracted, it is sandwiched between the lower surface of the upper wall 94A and the upper surface 54A of the pressing portion 54. The lower end of the elastic member 40 contacts the upper surface 54A of the pressing portion 54, and the lower end continuously presses the pressing portion 54 downward based on its own elastic force. Therefore, the pressing portion 54 continuously generates a force that presses the upper surface of the piezoelectric element 10 downward. The elastic member 40 has a conductor. In the configuration shown in FIG. 1, the entire elastic member 40 is made of a conductor such as a conductive elastic material. The elastic member 40 is electrically connected to the first conductive layer 11 and forms a path for transmitting signals to the piezoelectric element 10.

[0043] The liquid 70 is a medium interposed in gaps between the plurality of acoustic transmission members or between the piezoelectric element 10 and the acoustic transmission members. In this configuration, the gaps between the plurality of acoustic transmission members and between the piezoelectric element 10 and the acoustic transmission member are not bonded between the piezoelectric element 10 and the ultrasound emission surface (lower surface 96A), and the liquid 70 is interposed in these gaps. The liquid 70 may be any liquid in the broad sense. The liquid 70 may be a sol or a gel, or a liquid other than a sol or a gel. The liquid 70 does not solidify or volatilize and is not lost in the environment in which the ultrasonic probe P is used (e.g., room temperature). In the following description, a configuration in which glycerin is used as the liquid 70 will be described as a representative example. In the configuration of FIG. 1, the lower surface 12B of the piezoelectric element 10 and the upper surface 30A of the acoustic matching layer 30 are not bonded, and the liquid 70 is interposed by filling the gap between the lower surface 12B and the upper surface 30A. Because the lower surface 12B and the upper surface 30A are not bonded to each other, the lower surface 12B is allowed to move slightly relative to the upper surface 30A. Therefore, even if stress, deformation, impact, etc. occurs in either the piezoelectric element 10 or the acoustic matching layer 30, the effects are unlikely to extend to the other. Furthermore, a liquid 70 is interposed by being filled in the gap between the lower surface 30B of the acoustic matching layer 30 and the upper surface of the bottom wall 92A. Because the lower surface 30B and the upper surface of the bottom wall 92A are not bonded to each other, the lower surface 30B is allowed to move slightly relative to the upper surface of the bottom wall 92A. Therefore, even if stress, deformation, impact, etc. occurs in either the acoustic matching layer 30 or the bottom wall 92A, the effects are unlikely to extend to the other. Furthermore, the liquid 70 leaking from these gaps is contained in the space outside the gaps within the case 90.

[0044] 1, a storage space 80 for storing a portion of the liquid 70 is formed outside the outer peripheral surface of the piezoelectric element 10 and outside the pressing portion 54. The storage space 80 communicates with the gap between the lower surface 12B of the piezoelectric element 10 and the upper surface 30A of the acoustic matching layer 30. The storage space 80 also communicates with the gap between the lower surface 30B of the acoustic matching layer 30 and the upper surface of the bottom wall 92A. Note that, although the configuration of FIG. 1 shows that only a portion of the storage space 80 is the area for the liquid 70, the liquid 70 may be stored so as to fill the entire storage space 80.

[0045] The liquid 70 has a lower ultrasonic attenuation rate than air. Furthermore, the liquid 70 contains solid particles whose diameters are smaller than the width of the gap. The diameters of the solid particles are smaller than the gap between the lower surface 12B and the upper surface 30A. The gap between the lower surface 12B and the upper surface 30A is the vertical distance between the lower surface 12B and the upper surface 30A at the position where the vertical distance is greatest. The diameters of the solid particles are smaller than the gap between the lower surface 30B and the upper surface of the bottom wall 92A. The gap between the lower surface 30B and the upper surface of the bottom wall 92A is the vertical distance between the lower surface 30B and the upper surface of the bottom wall 92A at the position where the vertical distance is greatest. In other words, the size of the solid particles contained in the liquid 70 is such that they can enter the gap between the lower surface 12B and the upper surface 30A, and also the gap between the lower surface 30B and the upper surface of the bottom wall 92A.

[0046] For example, if the acoustic impedance of one of the piezoelectric element 10 and the acoustic matching layer 30 is Z1 and the acoustic impedance of the other is Z2, where Z1>Z2, then it is desirable that the acoustic impedance Za of the medium present in the gap between the lower surface 12B and the upper surface 30A satisfy Z1>Za>Z2. For example, if only liquid 70 is present in the gap between the lower surface 12B and the upper surface 30A and the acoustic impedance of the liquid 70 is Za, it is desirable that Z1>Za>Z2. For example, if the liquid 70 containing solid particles is present in the gap between the lower surface 12B and the upper surface 30A and the acoustic impedance of the liquid 70 containing solid particles is Za, it is desirable that Z1>Za>Z2.

[0047] For example, if the acoustic impedance of one of the acoustic matching layer 30 and the bottom wall 92A is Z3 and the acoustic impedance of the other is Z4, where Z3>Z4, then it is desirable that the acoustic impedance Zb of the medium present in the gap between the lower surface 30B and the upper surface of the bottom wall 92A satisfy Z3>Zb>Z4. For example, if only liquid 70 is present in the gap between the lower surface 30B and the upper surface of the bottom wall 92A and the acoustic impedance of the liquid 70 is Zb, it is desirable that Z3>Zb>Z4. For example, if the liquid 70 containing solid particles is present in the gap between the lower surface 30B and the upper surface of the bottom wall 92A and the acoustic impedance of the liquid 70 containing solid particles is Zb, it is desirable that Z3>Zb>Z4.

[0048] 2. Manufacturing method of ultrasonic probe P The ultrasonic probe P can be manufactured, for example, by the following method. In the manufacturing method of the ultrasonic probe P according to this embodiment, first, a first injection step shown in FIG. 2(A) is performed. In the first injection step, a lower case body 92 having the predetermined shape described above is prepared. The method for forming the lower case body 92 is not particularly limited, and various known methods may be used. In the first injection step, a predetermined amount of liquid 70 is injected into the prepared lower case body 92. It is desirable that the amount of liquid 70 injected in the first injection step be an amount sufficient to cover most or all of the upper surface of the bottom wall 92A.

[0049] 2(A) is followed by the first disposing step shown in Fig. 2(B). In the first disposing step, the acoustic matching layer 30 is disposed on the liquid 70 injected in the first disposing step. After the first disposing step, the liquid 70 is sandwiched between the upper surface of the bottom wall 92A and the lower surface of the acoustic matching layer 30.

[0050] 2(B) is followed by a second injection step shown in Fig. 2(C). In the second injection step, a predetermined amount of liquid 70 is injected onto the upper surface of the acoustic matching layer 30 that has been placed inside the lower case body 92 after the first injection step. The amount of liquid 70 injected in the second injection step is preferably an amount sufficient to cover most or all of the upper surface of the acoustic matching layer 30.

[0051] After the second injection step shown in Fig. 2(C), the second disposing step shown in Fig. 3(A) is performed. In the second disposing step, the piezoelectric element 10 is disposed on the liquid 70 injected in the second injection step. In performing the second disposing step, the piezoelectric element 10 having the predetermined structure described above is formed in advance before the second disposing step, and the piezoelectric element 10 thus formed is disposed in the second disposing step. After the second disposing step, the liquid 70 is sandwiched between the upper surface of the acoustic matching layer 30 and the lower surface of the piezoelectric element 10.

[0052] After the second arrangement step shown in Fig. 3(A), a conductive path connection step shown in Fig. 3(B) is performed. In the conductive path connection step, wiring 101 forming a first conductive path is electrically connected to a first conductive layer 11 arranged on one side of the piezoelectric element 10, and wiring 102 forming a second conductive path is electrically connected to a second conductive layer 12 arranged on the other side of the piezoelectric element 10. The structure connecting the first conductive layer 11 and the wiring 101 may be any structure that allows mutual conduction. The structure connecting the second conductive layer 12 and the wiring 102 may be any structure that allows mutual conduction. The wiring 101 and the wiring 102 may be configured as separate signal transmission paths.

[0053] After the conductive path connecting step shown in FIG. 3(B), a pressing portion arranging step shown in FIG. 4 is performed. In this embodiment, the pressing portion that presses the piezoelectric element 10 is configured by the support member 50 and elastic member 40 described above, and in the pressing portion arranging step, the pressing portion is arranged on the structure after the conductive path connecting step. In the pressing portion arranging step, first, the support member 50 is arranged on the piezoelectric element 10. In arranging the support member 50, the annular portion 56A is fitted into the vicinity of the upper end of the piezoelectric element 10, and the pressing portion 56B is arranged so as to press the vicinity of the peripheral portion on the upper surface of the piezoelectric element 10. Furthermore, in the pressing portion arranging step, the elastic member 40 is arranged on the support member 50 arranged on the piezoelectric element 10. Note that the wiring 101, 102 connected in the conductive path connecting step are arranged in predetermined positions to ensure a signal path. For example, one of the wires 101 is configured to pass through a wiring placement portion (e.g., a hole) formed in the support member 50 and is electrically connected to the elastic member 40. The other wire 102 is configured to pass through a wiring placement portion (e.g., a hole) formed in the support member 50 and is arranged so as to straddle from the piezoelectric element 10 side to the elastic member 40 side, and is further arranged so as to pass through the elastic member 40.

[0054] After the pressure unit arranging step is performed in this manner, a sealing step is performed so that the upper case body 94 having the predetermined shape described above is arranged, thereby obtaining the ultrasonic probe P as shown in Fig. 1. Note that although the wirings 101 and 102 are not shown in Fig. 1, the wiring 102 may be arranged so as to straddle the inside and outside of the case 90 via a lead-out portion (hole or the like) not shown. Furthermore, with regard to the signal path on the elastic member 40 side, it may be arranged so that a conductor electrically connected to the elastic member 40 straddles the inside and outside of the case 90 via a lead-out portion (hole or the like) not shown.

[0055] 1 and 4 show an example in which the wiring 101 is arranged so as to be electrically connected to the elastic member 40, but the pressing portion arrangement step may be performed so that the wiring 101 is arranged similarly to the wiring 102, as shown in Fig. 5. Then, as shown in Fig. 6, the sealing step may be performed in such a manner that the upper case body 94 is attached so that the wirings 101 and 102 can be led out through holes or the like (not shown).

[0056] 3.Example of effects The following description relates to an example of the effect of the ultrasonic probe P. In the ultrasonic probe P, the gaps between the multiple acoustic transmission members and between the piezoelectric element 10 and the acoustic transmission member are not bonded, so it is possible to prevent problems caused by bonding these gaps with an adhesive (for example, problems such as element cracking caused by residual stress in the adhesive or poor characteristics due to the thickness of the adhesive). Moreover, because the liquid 70 is present in these gaps, it is possible to reduce the attenuation of ultrasonic waves compared to a configuration in which a gas with a high ultrasonic attenuation rate is present instead of an adhesive.

[0057] Conventionally, piezoelectric elements used in ultrasonic sensors and ultrasonic probes are typically fixed to acoustic transmission components (such as acoustic matching layers and acoustic lenses) using adhesives or resin molding to prevent gaps. However, this method requires time-consuming processes, such as holding the resin at high temperatures or holding it for a long period of time to harden. Furthermore, these methods pose concerns about problems such as cracking of the element due to residual stress during resin hardening and poor characteristics due to adhesive thickness. Furthermore, in products manufactured using high-temperature heat treatment of adhesives, the piezoelectric element itself is also exposed to high temperatures. However, heating above the Curie point is not possible because it would cause the polarization state to disappear. Even heating below the Curie point must be avoided because the element characteristics may deteriorate as the temperature approaches the Curie point. In particular, materials with low Curie points are more susceptible to these problems, so it is desirable to avoid using adhesives that cure at high temperatures.

[0058] In this regard, the ultrasonic probe P of this embodiment can achieve a structure that stably maintains the positional relationship between the piezoelectric element 10 and the ultrasonic transmission unit without using adhesive. For example, the presence of the support member 50 and the elastic member 40 allows for holding without the need for a restraining force such as in simple pressure bonding, so the free vibration of the piezoelectric element 10 is not impeded. Therefore, this ultrasonic probe P has the potential to achieve acoustic transmission and reception characteristics that are comparable to or even superior to those of conventional structures that use adhesive.

[0059] Furthermore, in the ultrasonic probe P, the elastic member 40 acts to continuously reduce the gaps that occur at each interface, thereby preventing large fluctuations in the thickness of the piezoelectric element 10 and the acoustic transmission member. Therefore, changes in characteristics due to thickness changes are unlikely to occur. Furthermore, because the elastic member 40, the support member 50, and the case 90 are configured to stably hold the piezoelectric element 10 and the acoustic matching layer 30, displacement of the piezoelectric element 10 and the acoustic transmission member in the horizontal direction perpendicular to the central axis X is also prevented.

[0060] Furthermore, since the ultrasonic probe P does not generate internal residual stress due to adhesives, etc., it is possible to suppress element cracking due to internal residual stress, which makes it easier to improve yield. Furthermore, the ultrasonic probe P is configured so that heat treatment (a process of bonding by heating the adhesive) is not required to fix the piezoelectric element, so if heat treatment is not used in other processes, it is easy to use elements with low Curie points. Moreover, since the piezoelectric element 10 itself is not glued in the ultrasonic probe P, if the piezoelectric element 10 is made of a lead-containing material such as PZT, it is easy to separate such materials after use, which makes it easier to reduce the burden on the environment.

[0061] Furthermore, the liquid 70 has a lower ultrasonic attenuation rate than air, so the attenuation of ultrasonic waves passing through this position can be reduced compared to when air is present at the position of the liquid 70.

[0062] Furthermore, because the liquid 70 contains solid particles that are smaller than the width of the gap, the acoustic impedance can be adjusted by both the liquid 70 and the solid particles. Therefore, this ultrasonic probe P is advantageous in optimizing the acoustic impedance. For example, if a medium containing the solid particles is present in the liquid 70 in the gap, the acoustic impedance of the medium can be adjusted by the degree to which the solid particles are contained, and the density and sound speed can also be adjusted.

[0063] The ultrasonic probe P not only uses the elastic member 40 as a member for pressing the piezoelectric element 10 against the acoustic transmission member, but also serves as a path for transmitting signals, thereby reducing the number of parts compared to a configuration in which a separate, dedicated signal transmission path is provided.

[0064] 4. Experimental Results The results of experiments conducted to confirm the effects of this embodiment will be described below. In this experiment, an ultrasonic probe P shown in FIG. 1 was prepared as an example. In this example, glycerin was interposed between the bottom wall 92A and the acoustic matching layer 30, and glycerin was interposed between the piezoelectric element 10 and the acoustic matching layer 30 in the configuration of FIG. 1. On the other hand, as a comparative example, a configuration was prepared in which an adhesive was used instead of the liquid 70 in the configuration of FIG. 1. In the comparative example, the configuration of FIG. 1 was modified so that the bottom wall 92A and the acoustic matching layer 30 were bonded with an adhesive, and the piezoelectric element 10 and the acoustic matching layer 30 were bonded with an adhesive. The adhesive used in the comparative example was an epoxy adhesive. In both the example and comparative example, a PZT-5A element with a target center frequency of 2 MHz was used as the piezoelectric body 14.

[0065] In the experiment, to compare the performance of the ultrasonic probes of the example and the comparative example, an experimental setup as shown in FIG. 7 was used, and the ultrasonic probe of each example was positioned as shown in the probe Sp in FIG. 7 to transmit and receive ultrasonic waves. In all examples, a sinusoidal burst wave voltage with an amplitude of approximately 10 V was applied to the piezoelectric element 10 by a function generator, and the period was set to 10 cycles. In all examples, the distance between the ultrasonic probe (probe Sp) and the metal plate 120 was 60 mm. Ultrasonic waves were emitted from the ultrasonic probe (probe Sp) toward the metal plate 120 placed in water, and the transmission and reception loss was measured based on the reflection from the metal plate 120 received by the ultrasonic probe. As shown in FIG. 7, the transmission signal from the function generator and the reception signal from the piezoelectric element 10 were input to an oscilloscope, and the transmission and reception loss was evaluated based on the signal input to the oscilloscope. In the experiment, the transmission and reception loss was confirmed every 0.1 MHz in the range of 1 to 3 MHz. The results of this experiment are shown in FIG. 8. The transmission and reception loss of the example was comparable to that of the comparative example at a target frequency of around 2 MHz.

[0066] Second Embodiment The following description relates to an ultrasonic probe P according to the second embodiment. The ultrasonic probe P of the second embodiment shown in FIG. 9 uses an acoustic matching layer 230 instead of the acoustic matching layer 30, a bottom wall 292A instead of the bottom wall 92A, a first liquid 271 and a second liquid 272 instead of the liquid 70, and the arrangement of the liquid 270 differs from that of the liquid 70 used in the first embodiment. Other than these points, the ultrasonic probe P of the second embodiment has the same configuration as the ultrasonic probe P of the first embodiment. For example, the upper case body 94, the peripheral wall 92B, the support member 50, the elastic member 40, and the piezoelectric element 10 have the same configuration as those in the first embodiment, are arranged in the same manner as those in the first embodiment, and function in the same manner as those in the first embodiment. Therefore, detailed descriptions of these components will be omitted. In the ultrasonic probe P of the second embodiment, parts having the same configuration as those in the ultrasonic probe P of the first embodiment are designated by the same reference numerals as those in the ultrasonic probe P of the first embodiment.

[0067] The following description will focus on the differences between the ultrasonic probe P of the second embodiment and the first embodiment. The ultrasonic probe P of the second embodiment has a piezoelectric element 10, an ultrasonic transmission unit 220, an elastic member 40, a support member 50, a case 290, and a liquid 270. In the case 290, the upper case body 94 is the same as the upper case body 94 of the first embodiment. The lower case body 292 has a peripheral wall 92B that is the same as the peripheral wall 92B of the first embodiment, but differs from the lower case body 92 of the first embodiment in that a bottom wall 292A is used instead of the bottom wall 92A. The ultrasonic transmission unit 220 has two acoustic transmission members (an acoustic matching layer 230 and a bottom wall 292A) that transmit ultrasonic waves generated by the piezoelectric element 10. The ultrasonic transmitting unit 220 supports the piezoelectric element 10 by the upper surface of the acoustic matching layer 230, which is one of its surfaces, and the lower surface of the bottom wall 292A, which is the other surface, is used as the ultrasonic wave emitting surface. Specifically, the bottom wall 292A is provided with a lens unit 296 similar to the lens unit 96 in the first embodiment, and the lower surface 296A of this lens unit 296 is used as the ultrasonic wave emitting surface.

[0068] In the ultrasonic probe P of the second embodiment, the elastic member 40 also generates a force that presses the piezoelectric element 10 toward the ultrasonic transmission unit 220. The elastic member 40 may form a path for transmitting a signal to the first conductive layer 11 of the piezoelectric element 10 as shown in Fig. 1, or may be configured separately from the path for transmitting a signal to the first conductive layer 11 as shown in Fig. 6.

[0069] In this configuration, the gaps between the piezoelectric element 10 and the ultrasound emission surface (lower surface 296A) are not bonded, and the gaps between the multiple acoustic transmission members and between the piezoelectric element 10 and the acoustic transmission member are not bonded, and a liquid 270 is interposed in each gap. Specifically, the liquid 270 includes a first liquid 271 and a second liquid 272. Any one of the gaps between the multiple acoustic transmission members or between the piezoelectric element 10 and the acoustic transmission member (specifically, the gap between the piezoelectric element 10 and the acoustic matching layer 230) is not bonded, and the first liquid 271 is interposed in this gap. Furthermore, another gap between the multiple acoustic transmission members or between the piezoelectric element 10 and the acoustic transmission member (specifically, the gap between the acoustic matching layer 230 and the bottom wall 292A) is not bonded, and the second liquid 272 is interposed in this gap. The first liquid 271 and the second liquid 272 have an ultrasonic attenuation rate lower than that of air. The acoustic impedance of the first liquid 271 is preferably different from that of the second liquid 272, but may be the same.

[0070] 9, a recess 232 is formed in the upper surface of acoustic matching layer 230 so as to be recessed downward, and piezoelectric element 10 is placed on an upper surface 236 within this recess 232. A portion of one thickness direction side of piezoelectric element 10 is disposed within recess 232. Furthermore, a recess 293 is formed in the upper surface of bottom wall 292A so as to be recessed downward, and acoustic matching layer 230 is placed on an upper surface 295 within recess 293. A portion of one thickness direction side of acoustic matching layer 230 is disposed within recess 293.

[0071] The ultrasonic probe P includes a first region 281 including the one gap formed between the lower surface 12B of the piezoelectric element 10 and the upper surface 236 of the acoustic matching layer 230, and a second region 282 including the other gap formed between the lower surface 12B and the upper surface 236. A partition 299 is provided to separate the first region 281 and the second region 282. In the example of Fig. 9, the acoustic matching layer 230 forms the partition 299. The partition 299 blocks the movement of liquid between the first region 281 and the second region 282.

[0072] The first region 281 includes the region of the one gap and the region around the piezoelectric element 10 that is in communication with this one gap. A first liquid 271 is accommodated in a configuration that spans the region within the one gap and the region around the piezoelectric element 10. The first liquid 271 is filled in the one gap and is present in the region around the piezoelectric element 10 as well, with the configuration being that the first liquid 271 overflows from this gap.

[0073] The second region 282 includes a region within the groove portion 298 that is configured in an annular shape, and a region of the other gap (specifically, the gap between the lower surface of the acoustic matching layer 230 inside the groove portion 298 and the upper surface 295 within the recess 293). The second liquid 272 is accommodated in a configuration that spans the region within the groove portion 298 and the region within the other gap. The groove portion 298 is a groove that is recessed downward in the upper surface 295, and is formed as an annular (specifically, circular) groove centered on the central axis line X. The second liquid 272 is filled in the other gap, and is also present in the groove portion 298 in a configuration that overflows from this gap.

[0074] At the partition 299, the vicinity of the outer edge within the recess 293 (specifically, the inner wall portion outside the groove 298) and a part (near the outer edge) of the outer circumferential surface and the lower surface of the acoustic matching layer 230 are in close contact with each other, and this contact portion blocks the passage of liquid between the first region 281 and the second region 282. Therefore, the first liquid 271 does not enter the second region 282, and the second liquid 272 does not enter the first region 281.

[0075] For example, if the acoustic impedance of one of the piezoelectric element 10 and the acoustic matching layer 230 is Z1 and the acoustic impedance of the other is Z2, where Z1>Z2, then it is desirable that the acoustic impedance Za of the medium present in the gap between the lower surface 12B and the upper surface of the acoustic matching layer 230 satisfy Z1>Za>Z2. For example, if only the first liquid 271 is present in the gap between the lower surface 12B and the upper surface of the acoustic matching layer 230 and the acoustic impedance of the first liquid 271 is Za, it is desirable that Z1>Za>Z2. Furthermore, if the first liquid 271 containing the solid particles similar to those in the first embodiment is present in the gap between the lower surface 12B and the upper surface of the acoustic matching layer 230 and the acoustic impedance of the first liquid 271 containing the solid particles is Za, it is desirable that Z1>Za>Z2.

[0076] Furthermore, when the acoustic impedance of one of acoustic matching layer 230 and bottom wall 292A is Z3 and the acoustic impedance of the other is Z4, where Z3>Z4, it is desirable that the acoustic impedance Zb of the medium interposed in the gap between the lower surface of acoustic matching layer 230 and the upper surface of bottom wall 292A satisfy Z3>Zb>Z4. For example, when only second liquid 272 is interposed in the gap between the lower surface of acoustic matching layer 230 and the upper surface of bottom wall 292A and the acoustic impedance of second liquid 272 is Zb, it is desirable that Z3>Zb>Z4. Furthermore, when second liquid 272 containing solid particles is interposed in the gap between the lower surface of acoustic matching layer 230 and the upper surface of bottom wall 292A and the acoustic impedance of second liquid 272 containing solid particles is Zb, it is desirable that Z3>Zb>Z4.

[0077] As described above, the ultrasonic probe P of the second embodiment uses two types of liquids with different acoustic impedances, and therefore, by disposing multiple liquids at multiple positions, it is possible to further reduce the attenuation of ultrasonic waves while making the characteristics (particularly the acoustic impedance) of each position different.

[0078] Furthermore, the ultrasonic probe P of the second embodiment can separate the first liquid 271 and the second liquid 272 more reliably while arranging the first liquid 271 and the second liquid 272 at different positions.

[0079] <Other embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or following embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or following embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiment may be modified as follows.

[0080] In the above-described embodiment, the gaps between the multiple acoustic transmission members and between the piezoelectric element 10 and the acoustic transmission members are not bonded, and the gaps are filled with the liquid 70. However, it is also possible to fill one of the gaps with the liquid 70 and bond the other gap with an adhesive. Even in this configuration, the effect can be produced in the gap filled with the liquid 70.

[0081] In the above-described embodiment, a configuration in which the liquid 70 containing solid particles is interposed in the gap is illustrated, but the present invention is not limited to this example. The liquid 70 containing no solid particles may be interposed in the gap between the plurality of acoustic transmission members or between the piezoelectric element and the acoustic transmission member.

[0082] In the above embodiment, the bottom wall 92A of the case 90 is an acoustic lens, but the present invention is not limited to this example, and the bottom wall of the case does not have to be an acoustic lens.

[0083] In the above-described embodiment, multiple acoustic transmission members are provided, but a single acoustic transmission member may be used. For example, the acoustic matching layer 30 may be omitted from the configuration shown in FIG. 1 . In this case, the piezoelectric element 10 is supported on the bottom wall 92A, and liquid 70 is provided in the gap between the piezoelectric element 10 and the bottom wall 92A. In addition, in the above-described embodiment, the piezoelectric element 10 is pressed toward the acoustic transmission member via the support member 50, but the support member 50 may be omitted. In this case, the elastic member 40 directly contacts the piezoelectric element 10, thereby pressing the piezoelectric element 10 toward the acoustic matching layer 30, and movement of the piezoelectric element 10 in a direction perpendicular to the vertical axis is limited by the acoustic matching layer 30, the case 90, or the like.

[0084] Although the second embodiment has been described with reference to a configuration including multiple liquids, the configuration is not limited to this example. The configuration including multiple liquids may include at least a first liquid and a second liquid, and may further include a third liquid, a fourth liquid, and the like.

[0085] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is intended to include all modifications within the scope indicated by the claims or the scope equivalent to the claims. [Explanation of symbols]

[0086] P...Ultrasonic probe 10...Piezoelectric element 20,220...Ultrasonic transmission unit 30, 230... Acoustic matching layer (acoustic transmission member) 40...Elastic member 70,270…liquid 90, 290...Case (sound transmission component) 271…First liquid 272…Second liquid 281…First area 282…Second area 299...Partition

Claims

1. a piezoelectric element that generates ultrasonic waves; an ultrasonic transmission unit having one or more acoustic transmission members that transmit ultrasonic waves generated by the piezoelectric element, supporting the piezoelectric element on one side thereof and having the other side thereof serving as an ultrasonic wave emitting surface; An ultrasound probe having an elastic member that generates a force that presses the piezoelectric element toward the acoustic transmission member; Liquid and and Between the piezoelectric element and the ultrasonic wave emitting surface, a gap between the plurality of acoustic transmission members or between the piezoelectric element and the acoustic transmission member is not joined, and the liquid is present in the gap, The piezoelectric element further includes a support member disposed between the piezoelectric element and the elastic member, the one or more acoustic transmission members have a case that houses the piezoelectric element, the elastic member, and the support member; The elastic member has a coil spring wound around a central axis, the support member is not allowed to move relative to the case in a direction perpendicular to the central axis, and is only allowed to move relative to the case in a direction along the central axis, The support member includes an annular portion and a pressing portion, the annular portion is fitted with a part of the piezoelectric element to restrict the piezoelectric element from moving in a plane perpendicular to the central axis; The pressing portion is biased by the elastic member and presses the piezoelectric element. Ultrasound probe.

2. The pressing portion is biased by the elastic member and presses the outer edge portion of the piezoelectric element. The ultrasonic probe according to claim 1 .

3. The liquid has a lower ultrasonic attenuation rate than air.

3. The ultrasonic probe according to claim 1.

4. The liquid contains solid particles smaller than the width of the gap. The ultrasonic probe according to any one of claims 1 to 3.

5. The elastic member has a conductor and forms a path for transmitting a signal to the piezoelectric element. The ultrasonic probe according to any one of claims 1 to 4.

6. a plurality of the acoustic transmission members; the liquid includes a first liquid present in any one of gaps between the plurality of acoustic transmission members or gaps between the piezoelectric element and the acoustic transmission member, and a second liquid present in another gap; The acoustic impedance of the first liquid is different from that of the second liquid. The ultrasonic probe according to any one of claims 1 to 5.

7. a partition portion that separates a first region in which the first liquid is contained from a second region in which the second liquid is contained; The partition portion blocks movement of the liquid between the first region and the second region. The ultrasonic probe according to claim 6 .

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