JP7747481B2 - Ultrasound probe - Google Patents

Description

The present invention relates to an ultrasound probe.

Patent Document 1 discloses an example of an ultrasonic probe. The ultrasonic probe disclosed in Patent Document 1 has an ultrasonic transmission medium filled between the ultrasonic probe and the acoustic radiation window, and oil is used as the ultrasonic transmission medium.

Japanese Patent Application Laid-Open No. 2002-345819

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

The present invention was developed based on the above circumstances, and aims to provide an ultrasonic probe that can reduce defects between the piezoelectric element and the ultrasonic wave emitting surface and can reduce ultrasonic wave attenuation.

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.

In the ultrasonic probe described above, the gaps between multiple acoustic transmission members or between the piezoelectric element and the acoustic transmission member are not bonded, which prevents problems that would otherwise occur if these gaps were bonded with adhesive (for example, element cracking due to residual stress in the adhesive or poor performance due to adhesive thickness). Furthermore, because a liquid is present in these gaps, ultrasonic attenuation can be reduced compared to configurations in which a gas with a high ultrasonic attenuation rate is used instead of adhesive.

In the above ultrasonic probe, the liquid may have a lower ultrasonic attenuation rate than air.

This ultrasonic probe reduces the attenuation of ultrasound passing through the liquid compared to when air is present at the liquid location.

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

This ultrasonic probe is advantageous in optimizing acoustic impedance because it can adjust the acoustic impedance using both liquid and solid particles.

In the above-mentioned ultrasonic probe, the elastic member may have a conductor and form a path for transmitting signals to the piezoelectric element.

This ultrasonic probe uses the elastic member not only as a member that presses the piezoelectric element against the acoustic transmission member, but also as a path for transmitting signals, thereby reducing the number of parts compared to configurations that require a separate, dedicated signal transmission path.

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

This ultrasonic probe uses two types of liquid with different acoustic impedances, so the liquid can be placed at multiple locations to further reduce ultrasonic attenuation while still allowing the acoustic impedance to vary at each location.

The ultrasonic probe may have a partition separating a first region containing the first liquid from a second region containing the second liquid. The partition may be configured to block movement of the liquid between the first region and the second region.

This ultrasonic probe can more reliably separate the first liquid and the second liquid while placing the first liquid and the second liquid in different positions.

The ultrasonic probe, which is one aspect of the present invention, can reduce defects between the piezoelectric element and the ultrasonic wave emitting surface caused by bonding, and can also reduce ultrasonic wave attenuation.

FIG. 1 is a cross-sectional view that schematically illustrates an ultrasonic probe according to a first embodiment. FIG. 2 is an explanatory diagram illustrating some steps of a method for manufacturing the ultrasonic probe of FIG. FIG. 3 is an explanatory diagram illustrating a process subsequent to the process of FIG. 2 in the method of manufacturing the ultrasonic probe of FIG. FIG. 4 is an explanatory diagram illustrating a process subsequent to the process of FIG. 3 in the method of manufacturing the ultrasonic probe of FIG. 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 from the step shown in FIG. FIG. 6 is an explanatory diagram illustrating a step subsequent to the step in FIG. FIG. 7 is an explanatory diagram showing a simplified experimental setup for confirming the effect. FIG. 8 is a graph illustrating the results of an experiment to confirm the effect. FIG. 9 is a cross-sectional view schematically illustrating an ultrasonic probe according to the second embodiment.

First Embodiment
1. Configuration of Ultrasound Probe P The following description relates to the ultrasound 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.

As shown in FIG. 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.

In the following description, as shown in Figure 1, the thickness direction of the piezoelectric element 10 is the up-down direction. One side of the thickness direction of the piezoelectric element 10 is the lower side, and the other side of the thickness direction of the piezoelectric element 10 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 Figure 1) is the lower side. Figure 1 shows a schematic cross section of the ultrasonic probe P cut along the central axis X.

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 plate-shaped with a predetermined thickness. The piezoelectric element 10 is cylindrical, more specifically, disk-shaped, with the central axis X as its center. 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 cylindrical.

The piezoelectric element 14 is made of PZT (lead zirconate titanate) or similar material. The piezoelectric element 14 is in the shape of a disk with a predetermined thickness.

The first conductive layer 11 is disposed on one surface (top surface) of the piezoelectric body 14. The second conductive layer 12 is disposed on the other surface (bottom 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 other methods of depositing gold, silver, copper, tin, or the like. The first conductive layer 11 is disposed so as to cover the entire top surface of the piezoelectric body 14. The second conductive layer 12 is disposed so as to cover the entire bottom surface of the piezoelectric body 14. The top surface 11A of the first conductive layer 11 and the bottom surface 12B of the second conductive layer 12 are parallel. Both the top surface 11A and the bottom surface 12B are perpendicular to the central axis X.

The first conductive layer 11 is the first electrode on the upper surface side of the piezoelectric element 10. The 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.

The second conductive layer 12 is a second electrode on the underside of the piezoelectric element 10. The underside 12B of the second conductive layer 12 is the other main surface (bottom surface) of the piezoelectric element 10. The piezoelectric element 10 is placed on the acoustic matching layer 30. The underside 12B of the second conductive layer 12 is supported by the upper surface of the acoustic matching layer 30, with a liquid 70 (described below) 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.

The piezoelectric element 10 can transmit an electrical 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 electrical signal from the control device. The piezoelectric element 10 generates ultrasonic waves in response to an AC voltage being applied between the first conductive layer 11 and the second conductive layer 12.

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 the ultrasonic waves generated by the piezoelectric element 10. In the example of FIG. 1, multiple acoustic transmission members (acoustic matching layer 30 and bottom wall 92A) make up the ultrasonic transmission unit 20. The ultrasonic transmission unit 20 supports the piezoelectric element 10 with one of its surfaces, the upper surface 30A of the acoustic matching layer 30, and its other surface, the lower surface of the bottom wall 92A (more specifically, the lower surface 96A of the lens portion 96), serves as the ultrasonic wave emission surface.

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.

The acoustic matching layer 30 is cylindrical and centered on the central axis X. Both the top surface 30A and the bottom surface 30B of the acoustic matching layer 30 are flat. The outer edges of both the top surface 30A and the bottom 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 in a planar direction perpendicular to the central axis X with respect to the case 90 is determined by the inner 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 is configured such that 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.

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.

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 the 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 surface of the peripheral wall 92B surrounds the outer surface of the acoustic matching layer 30. In the configuration shown in FIG. 1, the acoustic matching layer 30 is fitted inside the peripheral wall 92B. Both the inner and outer surfaces of the peripheral wall 92B are cylindrical surfaces centered on the central axis X.

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 at the central axis X. The lens portion 96 and the acoustic matching layer 30 are stacked in a coaxial positional relationship, with their center at the central axis X.

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 with a relatively small inner diameter and a second inner circumferential portion 99 with a larger inner diameter than the first inner circumferential portion 98. The first inner circumferential portion 98 is positioned above the second inner circumferential portion 99. The inner circumferential surface 98A of the first inner circumferential portion 98 and the inner circumferential surface 99A of the second inner circumferential portion 99 form a step.

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 shown in Figure 1, the mating 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 mating portion 52. The first inner circumferential portion 98 surrounds the mating portion 52 to prevent the mating portion 52 from moving in a plane perpendicular to the central axis X, and forms an up and down passage that allows the mating portion 52 to move up and down along the direction of the central axis X.

The inner surface 99A of the second inner circumferential portion 99 is a cylindrical surface centered on the central axis X. In the configuration shown in Figure 1, the circumferential wall 92B fits inside the second inner circumferential portion 99. The gap between the second inner circumferential portion 99 and the circumferential wall 92B is sealed.

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 has a fitting portion 52 and a pressing portion 54 that is positioned below the fitting portion 52. The fitting portion 52 and the pressing portion 54 are integrally formed.

The fitting portion 52 is cylindrical. In the example shown in Figure 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 peripheral 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 peripheral portion 98 are fitted together, the support member 50 is not permitted to move relative to the case 90 in a direction perpendicular to the central axis X, and is only permitted to move relative to the case 90 in a direction along the central axis X.

The pressing portion 54 is positioned to block the lower end of the fitting portion 52. In other words, the space inside the fitting portion 52 is blocked by the pressing portion 54. The upper surface 54A of the pressing portion 54, which is positioned 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 is pressed downward by the elastic member 40 due to the elastic force of the elastic member 40. The pressing portion 54 is, for example, cylindrical 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 formed 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.

The lower end of the pressing portion 54 is provided with a restricting portion 56 that 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 circumferential surface of the piezoelectric element 10 near the upper end. The annular portion 56A engages with a portion of the piezoelectric element 10 (at least a portion including the upper end) and restricts movement of the piezoelectric element 10 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 that continuously presses downward near the outer edge of the upper surface 11A of the piezoelectric element 10 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 impact or stress, the support member 50 is allowed to move upward against the bias of the elastic member 40 to absorb or release this force.

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 Figure 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.

Liquid 70 is a medium interposed in the gaps between multiple acoustic transmission members or between the piezoelectric element 10 and the acoustic transmission member. In this configuration, the gaps between the multiple 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 liquid 70 is interposed in these gaps. Liquid 70 may be any liquid in the broad sense. Liquid 70 may be a sol or gel, or a liquid other than a sol or gel. Liquid 70 does not solidify or volatilize in the environment in which the ultrasonic probe P is used (e.g., room temperature). The following explanation uses a configuration in which glycerin is used as liquid 70 as a representative example. In the configuration shown in 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 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, liquid 70 is interposed by filling 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, liquid 70 that leaks from these gaps is contained in the space outside the gaps within the case 90.

In the configuration of FIG. 1, a storage space 80 that contains a portion of the liquid 70 is configured outside the outer peripheral surface of the piezoelectric element 10 and outside the pressing portion 54. The storage space 80 is connected to the gap between the lower surface 12B of the piezoelectric element 10 and the upper surface 30A of the acoustic matching layer 30. Furthermore, the storage space 80 is connected to 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 in the configuration of FIG. 1, only a portion of the storage space 80 is used as the area for the liquid 70, the liquid 70 may be contained so that it fills the entire storage space 80.

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 diameter of the solid particles is 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 diameter of the solid particles is 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 the gap between the lower surface 30B and the upper surface of the bottom wall 92A.

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.

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 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.

2. Method for Manufacturing 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. 2A 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. The amount of liquid 70 injected in the first injection step is desirably an amount sufficient to cover most or all of the upper surface of the bottom wall 92A.

After the first injection step shown in FIG. 2(A), the first placement step shown in FIG. 2(B) is performed. In the first placement step, the acoustic matching layer 30 is placed on top of the liquid 70 injected in the first injection step. After the first placement 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.

The first placement step shown in FIG. 2(B) is followed by the 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 placement step. It is desirable that the amount of liquid 70 injected in the second injection step be sufficient to cover most or all of the upper surface of the acoustic matching layer 30.

After the second injection step shown in FIG. 2(C), the second placement step shown in FIG. 3(A) is performed. In the second placement step, the piezoelectric element 10 is placed on the liquid 70 injected in the second injection step. In performing the second placement step, the piezoelectric element 10 with the predetermined structure described above is formed in advance before the second placement step, and the piezoelectric element 10 thus formed is placed in the second placement step. After the second placement 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.

The second placement process shown in FIG. 3(A) is followed by the conductive path connection process shown in FIG. 3(B). In the conductive path connection process, wiring 101 forming a first conductive path is electrically connected to the 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 the second conductive layer 12 arranged on the other side of the piezoelectric element 10. The structure connecting the first conductive layer 11 and wiring 101 may be any structure that allows mutual conduction. The structure connecting the second conductive layer 12 and wiring 102 may be any structure that allows mutual conduction. Wiring 101 and wiring 102 may be configured as separate signal transmission paths.

3B, the pressing portion placement process shown in FIG. 4 is performed. In this embodiment, the pressing portion that presses the piezoelectric element 10 is formed by the support member 50 and elastic member 40 described above. In the pressing portion placement process, the pressing portion is placed on the structure after the conductive path connection process. In the pressing portion placement process, the support member 50 is first placed on the piezoelectric element 10. The support member 50 is placed so that the annular portion 56A fits into the vicinity of the upper end of the piezoelectric element 10 and the pressing portion 56B presses against the vicinity of the peripheral edge on the upper surface of the piezoelectric element 10. Furthermore, in the pressing portion placement process, the elastic member 40 is placed on the support member 50 placed on the piezoelectric element 10. The wiring 101, 102 connected in the conductive path connection process are placed in predetermined positions to ensure a signal path. For example, one of the wires 101 is electrically connected to the elastic member 40 via a wiring placement portion (e.g., a hole) formed in the support member 50. The other wire 102 is also 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 further passes through the elastic member 40.

After the pressure unit placement process is performed in this manner, a sealing process is performed so that the upper case body 94 of the predetermined shape described above is placed, thereby obtaining the ultrasonic probe P shown in Figure 1. Note that while the wiring 101 and 102 are not shown in Figure 1, it is sufficient that the wiring 102 is placed so that it straddles the inside and outside of the case 90 via a lead-out portion (hole, etc.) not shown. Furthermore, with regard to the signal path on the elastic member 40 side, it is sufficient that the conductor electrically connected to the elastic member 40 is placed so that it straddles the inside and outside of the case 90 via a lead-out portion (hole, etc.) not shown.

Note that while Figures 1 and 4 show an example in which wiring 101 is arranged so as to be electrically connected to elastic member 40, the pressing portion arrangement process may also be performed so that wiring 101 is arranged in the same manner as wiring 102, as shown in Figure 5. Furthermore, as shown in Figure 6, the sealing process may also be performed in such a way that the upper case body 94 is attached so that wiring 101, 102 can be led out through holes or the like (not shown).

3. Example of Effects The following explanation relates to an example of the effects 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 that would otherwise occur if these gaps were bonded with an adhesive (for example, problems such as element cracking due to 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.

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) with adhesives or resin molds to prevent air gaps. However, this method requires time-consuming processing, such as holding the resin at high temperatures or holding it for long periods of time to harden. Furthermore, these methods pose concerns about problems such as element cracking 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, as the element's characteristics may deteriorate as it approaches the Curie point. This problem is particularly prevalent with materials with low Curie points, so it is desirable to avoid high-temperature-curing adhesives.

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 the use of adhesive. For example, the presence of the support member 50 and elastic member 40 allows for holding without the need for a restraining force such as with simple crimping, 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 conventional structures that use adhesive.

In addition, 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 changes in thickness are less likely to occur. Furthermore, because the elastic member 40, support member 50, and case 90 are configured to stably hold the piezoelectric element 10 and acoustic matching layer 30, horizontal displacement of the piezoelectric element 10 and the acoustic transmission member in the direction perpendicular to the central axis X is also prevented.

Furthermore, because ultrasonic probe P does not generate internal residual stress caused by adhesives, etc., it is possible to suppress element cracking caused by internal residual stress, making it easier to improve yield. Furthermore, ultrasonic probe P is configured so that heat treatment (a process in which adhesive is heated to bond) is not required to fix the piezoelectric element, making it easier to use elements with low Curie points if heat treatment is not used in other processes. Furthermore, because the piezoelectric element 10 itself is not glued in 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, making it easier to reduce the burden on the environment.

Furthermore, because the liquid 70 has a lower ultrasonic attenuation rate than air, 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.

Furthermore, because the liquid 70 contains solid particles 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 within the liquid 70 in the gap, the acoustic impedance of the medium can be adjusted by the degree of solid particle content, and the density and sound speed can also be adjusted.

The ultrasonic probe P not only uses the elastic member 40 to press the piezoelectric element 10 against the acoustic transmission member, but also serves as a signal transmission path, thereby reducing the number of parts compared to a configuration that requires a separate, dedicated signal transmission path.

4. Experimental Results The following describes the results of experiments conducted to confirm the effects of this embodiment.
In this experiment, an ultrasonic probe P shown in FIG. 1 was prepared as an example. This example has the same configuration as that shown in FIG. 1 , except that glycerin is interposed between the bottom wall 92A and the acoustic matching layer 30, and that glycerin is interposed between the piezoelectric element 10 and the acoustic matching layer 30. 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 shown in FIG. 1 . The comparative example has a configuration modified from that shown in FIG. 1 , in which the bottom wall 92A and the acoustic matching layer 30 are bonded together with an adhesive, and the piezoelectric element 10 and the acoustic matching layer 30 are bonded together with an adhesive. The adhesive used in the comparative example is 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.

In the experiment, to compare the performance of the ultrasonic probes of the example and comparative example, an experimental setup like that shown in Figure 7 was used, and ultrasonic waves were transmitted and received with the ultrasonic probes of each example positioned as shown in Probe Sp in Figure 7. In each example, a sinusoidal burst voltage with an amplitude of approximately 10 V was applied to the piezoelectric element 10 by a function generator, with a duration of 10 cycles. In each example, the distance between the ultrasonic probe (Probe Sp) and the metal plate 120 was 60 mm. Ultrasound was emitted from the ultrasonic probe (Probe Sp) toward the metal plate 120 placed in water, and transmission and reception loss was measured based on the reflection from the metal plate 120 received by the ultrasonic probe. As shown in Figure 7, the transmission signal from the function generator and the reception signal from the piezoelectric element 10 were input into an oscilloscope, and transmission and reception loss was evaluated based on the signal input to the oscilloscope. In the experiment, 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 Figure 8. The transmission and reception loss of the example was comparable to that of the comparative example at the target frequency of around 2 MHz.

Second Embodiment
The following description relates to the ultrasonic probe P of 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.

The following 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 transmission 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 its other surface, serves as the ultrasonic wave emission 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 serves as the ultrasonic wave emission surface.

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 signals 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 signals to the first conductive layer 11, as shown in FIG. 6.

In this configuration, the gaps between the multiple acoustic transmission members and between the piezoelectric element 10 and the ultrasound emission surface (lower surface 296A) are not bonded, and liquid 270 is interposed in each gap. Specifically, the liquid 270 includes a first liquid 271 and a second liquid 272. Furthermore, 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 this gap is filled with the first liquid 271. 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 this gap is filled with the second liquid 272. The first liquid 271 and the second liquid 272 have lower ultrasound attenuation rates than air. The acoustic impedance of the first liquid 271 is preferably different from that of the second liquid 272, but may be the same.

In the example of Figure 9, a recess 232 is formed on the upper surface of the acoustic matching layer 230 so as to be recessed downward, and the piezoelectric element 10 is placed on the upper surface 236 within this recess 232. A portion of one thickness-wise side of the piezoelectric element 10 is located within the recess 232. Furthermore, a recess 293 is formed on the upper surface of the bottom wall 292A so as to be recessed downward, and the acoustic matching layer 230 is placed on the upper surface 295 within the recess 293. A portion of one thickness-wise side of the acoustic matching layer 30 is located within the recess 293.

The ultrasonic probe P includes a first region 281 including the first 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 Figure 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.

The first region 281 includes the region of the first gap and the region surrounding the piezoelectric element 10 that is connected to this gap. A first liquid 271 is contained in the region within the first gap and the region surrounding the piezoelectric element 10. The first liquid 271 is filled within the first gap and is present in the region surrounding the piezoelectric element 10, overflowing from this gap.

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

At the partition 299, the vicinity of the outer edge of the recess 293 (specifically, the inner wall portion outside the groove 298) comes into close contact with a portion of the outer surface and lower surface (near the outer edge) of the acoustic matching layer 230, and this close contact prevents liquid from passing 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.

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 described above, similar to that of 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.

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

As described above, the ultrasonic probe P of the second embodiment uses two types of liquid with different acoustic impedances, so that multiple liquids can be placed at multiple positions to further reduce ultrasonic attenuation while also differentiating the characteristics (particularly acoustic impedance) at each position.

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

<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.

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

In the above-described embodiment, a configuration in which a liquid 70 containing solid particles is interposed within the gap is illustrated, but this example is not limiting. A liquid 70 that does not contain solid particles may be interposed in the gap between multiple acoustic transmission members or between the piezoelectric element and the acoustic transmission member.

In the above-described embodiment, the bottom wall 92A of the case 90 is an acoustic lens, but this is not limited to this example, and the bottom wall of the case does not have to be an acoustic lens.

In the above-described embodiment, multiple acoustic transmission members were present, 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 present 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, pressing the piezoelectric element 10 toward the acoustic matching layer 30, and movement in a direction perpendicular to the up-down axis is limited by the acoustic matching layer 30, the case 90, etc.

In the second embodiment, a configuration having multiple liquids is exemplified, but this example is not limiting. In a configuration having multiple liquids, it is sufficient to have at least a first liquid and a second liquid, and other liquids such as a third liquid and a fourth liquid may also be included.

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 of the claims or within the scope equivalent to the claims.

P... ultrasonic probe 10... piezoelectric element 20, 220... ultrasonic transmission section 30, 230... acoustic matching layer (acoustic transmission member)
40: Elastic member; 70, 270: Liquid; 90, 290: Case (sound transmission member)
271...First liquid 272...Second liquid 281...First region 282...Second region 299...Partition portion

Claims (7)

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. The pressing portion is biased by the elastic member and presses the outer edge of the piezoelectric element.
The ultrasonic probe according to claim 1 . The ultrasonic probe according to claim 1 or 2 , wherein the liquid has a lower ultrasonic attenuation rate than air. The ultrasonic probe according to claim 1 , wherein the liquid contains solid particles smaller than a width of the gap. The ultrasonic probe according to claim 1 , wherein the elastic member has a conductor and forms a path for transmitting a signal to the piezoelectric element. 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 ultrasonic probe according to claim 1 , wherein the first liquid has a different acoustic impedance from the second liquid. 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 ultrasonic probe according to claim 6 , wherein the partition section blocks movement of the liquid between the first region and the second region.