JP2020077945A - Vibration detection element and ultrasonic sensor - Google Patents

Abstract

To provide a vibration detection element capable of easily forming a three-dimensional curved shape.SOLUTION: A vibration detection element 2 includes a piezoelectric body 11 made of polymer piezoelectric material having film-like flexibility and one or more strips of low rigidity portions 13 that detect the potential difference between the front and back of the piezoelectric body 11 by a pair of electrodes 12a and 12b stacked on the front and back of the piezoelectric body 11, and extend inward from its outer edge. The plurality of low rigidity portions 13 are smoothly curved or bent in a direction perpendicular to the extending direction of the low rigidity portion 13 while absorbing an excess portion of a sheet.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vibration detecting element and an ultrasonic sensor.

  For example, an ultrasonic sensor is used to inspect the heat-sealing property of a food package, the presence or absence of air bubbles in a storage battery, a fuel cell, or the like. This ultrasonic sensor is provided so as to face the ultrasonic transmitter across the subject, and detects the ultrasonic waves transmitted from the ultrasonic transmitter and transmitted through the subject to inspect the adhesive state of the heat seal. Configured to be possible.

  This ultrasonic sensor is composed of a piezoelectric element, and has an ultrasonic wave receiving surface that faces the ultrasonic wave transmitter with the subject interposed therebetween. The ultrasonic wave receiving surface has, for example, a concave curved surface shape whose focus is on the subject (see Japanese Patent Application Laid-Open No. 2013-127400).

  In this ultrasonic sensor, for example, a piezoelectric element is stacked on the upper surface of a back surface addition material curved in a concave shape in one direction, and a pressure plate having an inverted shape of the upper surface of the back surface addition material is pressed from above the piezoelectric element. (Refer to JP 2010-258602 A). As this piezoelectric element, a relatively expensive inorganic piezoelectric body made of lead zirconate titanate (PZT) or the like and having a pair of electrodes laminated on both sides is used.

JP, 2013-127400, A JP, 2010-258602, A

  On the other hand, in order to inspect the heat-sealing property or the like of the subject with high accuracy, the ultrasonic wave transmitting surface of the ultrasonic wave transmitter and the ultrasonic wave receiving surface of the ultrasonic wave sensor have three-dimensional curved shapes (for example, the same focal point). It is desired to form a bowl shape.

  However, if the conventional ultrasonic sensor is formed in a three-dimensional curved shape, wrinkles may occur in a region where an ultrasonic wave is detected, and an appropriate inspection may not be performed.

  The present invention has been made under such circumstances, and an object of the present invention is to provide a vibration detection element and an ultrasonic sensor capable of easily forming a three-dimensional curved shape.

  The present invention made to solve the above-mentioned problems includes a film-shaped piezoelectric body and a pair of electrodes laminated on the front and back of the piezoelectric body, and includes one or a plurality of belt-shaped low-rigidity portions extending inward from the outer edge thereof. It is a vibration detecting element having.

  It is preferable that the vibration detection element has a base portion in an in-plane region thereof, and the low-rigidity portion radially extends from an outer peripheral edge of the base portion.

  It is preferable that the low-rigidity portion is a thin portion in which the electrode is not laminated on at least one surface of the piezoelectric body.

  It is preferable that the low-rigidity portion has a slit.

  Further, the present invention made to solve the above-mentioned problems is an ultrasonic sensor in which the vibration detection element is the low-rigidity portion, and is curved or bent in a direction perpendicular to the extending direction of the low-rigidity portion. is there.

  In the ultrasonic sensor, the vibration detection element may have a bowl shape.

  The ultrasonic sensor is preferably formed with a fold in the low-rigidity portion.

  The ultrasonic sensor may further include a support member having an inverted shape of the back surface of the vibration detection element and having a mounting surface on which the vibration detection element is mounted from the back surface side.

  It is preferable that the support member has one or a plurality of through holes penetrating in the thickness direction and reaching the vibration detection element.

  In the ultrasonic sensor, the vibration detection element may be partially bonded to the mounting surface by the one or more low-rigidity portions.

  In the present invention, "front" means the side that receives vibration, and "back" means the opposite side. The "extending direction of the low-rigidity portion" means a direction perpendicular to the width of the low-rigidity portion at any point. The “bowl shape” means a shape that is three-dimensionally concave and has a blunt bottom (rounded or flat bottom). The “fold” means a wrinkle formed by overlapping, folding, or the like.

  In the vibration detecting element according to the present invention, one or a plurality of low-rigidity portions are formed and arranged in a desired shape, and the low-rigidity portions bend or bend in a direction perpendicular to the extending direction of the low-rigidity portions. Thus, it can be easily formed into a three-dimensional curved shape.

FIG. 1 is a schematic perspective view of an ultrasonic sensor including a vibration detection element according to an embodiment of the present invention. FIG. 2 is a schematic end view of the ultrasonic sensor of FIG. 1 taken along the line AA. FIG. 3 is a schematic AA line enlarged cross-sectional view of the vibration detection element of the ultrasonic sensor of FIG. 1. FIG. 4 is a schematic front view of the ultrasonic sensor of FIG. FIG. 5 is a schematic rear view showing a bonded state between the vibration detection element and the support member of the ultrasonic sensor of FIG. FIG. 6 is a schematic front view showing the arrangement of the through holes of the supporting member of the ultrasonic sensor of FIG. FIG. 7 is a schematic front view showing an ultrasonic sensor according to an embodiment different from the ultrasonic sensor of FIG. FIG. 8 is a schematic front view showing a vibration detecting element of an ultrasonic sensor according to an embodiment different from the ultrasonic sensors of FIGS. 1 and 7. FIG. 9 is a schematic front view showing a vibration detecting element of an ultrasonic sensor according to an embodiment different from the ultrasonic sensors of FIGS. 1, 7 and 8. FIG. 10 is a schematic front view showing the vibration detection element of the ultrasonic sensor according to the comparative embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[First embodiment]
<Ultrasonic sensor>
The ultrasonic sensor 1 of FIGS. 1 and 2 includes a vibration detecting element 2 which itself constitutes the present invention, and a support member 3 which supports the vibration detecting element 2 from the back surface side. The ultrasonic sensor 1 is used in an inspection device for ultrasonically inspecting the heat sealability of a food package and the presence or absence of bubbles in a storage battery or a fuel cell. In the ultrasonic sensor 1, the surface of the vibration detecting element 2 constitutes an ultrasonic receiving surface that faces an ultrasonic transmitter (not shown) with the subject in between. The ultrasonic wave transmitting surface of the ultrasonic wave transmitter is formed as a quadratic curve rotating surface, a rotating parabolic surface, or the like so as to focus the ultrasonic wave toward one point of the subject.

(Vibration detection element)
As shown in FIG. 3, the vibration detecting element 2 includes a film-shaped piezoelectric body 11 and a pair of electrodes laminated on the front and back of the piezoelectric body 11 (the first electrode 12 a and the piezoelectric body 11 laminated on the surface of the piezoelectric body 11). Has a second electrode 12b) laminated on the back surface of the. The vibration detecting element 2 has a sheet shape as a whole.

  Examples of the piezoelectric material forming the piezoelectric body 11 include flexible polymer piezoelectric materials. Examples of the polymeric piezoelectric material include polyvinylidene fluoride (PVDF), vinylidene fluoride-3 fluoroethylene copolymer (P (VDF / TrFE)), vinylidene cyanide-vinyl acetate copolymer (P (VDCN / VAc)) and the like. Further, by using these polymeric piezoelectric materials as the porous film, the flexibility is further increased, and the bendability and bendability of the vibration detection element 2 can be enhanced.

  In addition, as the piezoelectric body 11, for example, polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), etc., which do not have piezoelectric characteristics, are formed with a large number of flat pores to form a corona discharge. For example, it is possible to use one having piezoelectric characteristics by polarizing the opposite surfaces of the flat pores and charging them by the above method.

  The lower limit of the average thickness of the piezoelectric body 11 is preferably 10 μm, more preferably 50 μm. On the other hand, the upper limit of the average thickness of the piezoelectric body 11 is preferably 500 μm, more preferably 200 μm. If the average thickness of the piezoelectric body 11 is less than the lower limit, the strength of the piezoelectric body 11 may be insufficient. On the other hand, if the average thickness of the piezoelectric body 11 exceeds the upper limit, it may be difficult to form the vibration detection element 2 into a desired curved or bent shape when the vibration detection element 2 is laminated on the support member 3.

  The first electrode 12a and the second electrode 12b have a thin film shape. The first electrode 12a and the second electrode 12b are used to detect the potential difference between the front surface and the back surface of the piezoelectric body 11. Therefore, the first electrode 12a and the second electrode 12b are connected to a detection circuit (not shown).

  The first electrode 12a and the second electrode 12b may be made of any material having conductivity, and examples thereof include metals such as aluminum, copper and nickel, and carbon.

  The method for laminating the first electrode 12a and the second electrode 12b on the piezoelectric body 11 is not particularly limited, and examples thereof include vapor deposition of metal, printing of carbon conductive ink, and coating and drying of silver paste.

  The average thickness of the first electrode 12a and the second electrode 12b may be, for example, 0.1 μm or more and 30 μm or less, depending on the stacking method. If the average thickness is less than the lower limit, the strength of the first electrode 12a and the second electrode 12b may be insufficient. On the contrary, when the average thickness exceeds the upper limit, there is a possibility that the followability to the curved surface shape in the state where the vibration detecting element 2 is curved or bent is deteriorated.

  The vibration detecting element 2 has a plurality of belt-shaped low-rigidity portions 13 extending inward from the outer edge thereof. The vibration detecting element 2 is smoothly curved or bent in a direction perpendicular to the extending direction of the low-rigidity portion 13 while absorbing the excess portion of the sheet in the plurality of low-rigidity portions 13. The vibration detecting element 2 is also curved or bent in the direction along the extending direction of the plurality of low-rigidity portions 13. That is, the vibration detecting element 2 is curved or bent three-dimensionally by the plurality of low-rigidity portions 13. The “strip shape” means a shape whose width is smaller than its length.

  The plurality of low-rigidity portions 13 are formed with the outer edge of the vibration detection element 2 as one end in the extending direction. The plurality of low-rigidity portions 13 are thin portions in which the first electrode 12a and the second electrode 12b are not laminated on both surfaces of the piezoelectric body 11. The vibration detecting element 2 is patterned in the same shape in plan view so that the first electrode 12a and the second electrode 12b face each other in the thickness direction of the piezoelectric body 11. In the vibration detecting element 2, the non-patterning regions of the first electrode 12a and the second electrode 12b form the low rigidity portion 13. That is, the piezoelectric body 11 has an exposed region where neither the first electrode 12a nor the second electrode 12b is laminated at a position facing each other in the thickness direction, and this exposed region constitutes the low-rigidity portion 13. ing. The ultrasonic sensor 1 has a vibration detection unit in which first electrodes 12a and second electrodes 12b are laminated on both surfaces of a piezoelectric body 11, and a first electrode 12a and second electrodes 12b are laminated on both surfaces of the piezoelectric body 11. And has a non-vibration detection unit that does not detect vibration. In the ultrasonic sensor 1, the plurality of low-rigidity portions 13 are non-vibration detecting portions that do not detect vibration.

  Since the vibration detecting element 2 has the low-rigidity portion 13, the low-rigidity portion 13 absorbs the excess portion of the sheet (while the excess portion of the sheet due to bending or bending is overlapped with the low-rigidity portion 13). Can be curved to More specifically, the vibration detecting element 2 in the expanded state has a surplus portion in the seat surface direction with respect to the curved or bent state. This excess portion is likely to be formed as a fold in a curved or bent state. At this time, if the low-rigidity portion 13 does not exist, a plurality of folds are likely to occur randomly (no principle) in the vibration detection portion in which the first electrode 12a and the second electrode 12b are laminated on the piezoelectric body 11. On the other hand, when the vibration detecting element 2 has the low-rigidity part 13, the low-rigidity part 13 whose rigidity is smaller than that of the vibration detection part is likely to be selectively folded. In other words, since the vibration detection element 2 has the low-rigidity portion 13, it is possible to prevent the low-rigidity portion 13 from forming a fold in the vibration detection portion. Therefore, in the ultrasonic sensor 1, since the vibration detection element 2 has the low-rigidity portion 13, it is possible to suppress the decrease in the detection sensitivity due to the folds in the vibration detection portion and appropriately detect the vibration. You can In order to further suppress the occurrence of folds in the vibration detecting portion, it is preferable that the low-rigidity portions 13 arranged radially are arranged at a uniform pitch in the circumferential direction. By arranging the low-rigidity portions 13 at a uniform pitch, it is possible to form folds of the same degree on all the low-rigidity portions 13.

  Further, in the vibration detecting element 2, the low rigidity portion 13 is the thin portion described above. As a result, the first electrode 12a and the second electrode 12b are separated by the piezoelectric body 11, and a short circuit between the first electrode 12a and the second electrode 12b can be prevented. More specifically, for example, in the place where both the first electrode 12a and the second electrode 12b are formed (that is, the vibration detection portion described above), a slit penetrating in the thickness direction of the vibration detection element instead of the low-rigidity portion 13. When a curved shape or a bent shape is formed by overlapping the portions on both sides sandwiching the slit, the first electrode and the second electrode are connected at the overlapping portion, and a short circuit occurs. Further, as shown in FIG. 10, a cutout 103 that penetrates in the thickness direction of the vibration detection element 102 is provided in place of the low-rigidity portion 13, and the cutout 103 is not overlapped even when both sides of the cutout 103 are not overlapped. A conductive member may adhere to the end surface cut by 103, or conductive dust may adhere, resulting in a short circuit between the first electrode and the second electrode. On the other hand, in the vibration detecting element 2, the piezoelectric body 11 is provided with a thin portion where the first electrode 12a and the second electrode 12b are not laminated, thereby preventing a short circuit between the first electrode 12a and the second electrode 12b. can do.

  The vibration detecting element 2 has a shape corresponding to the shape of the ultrasonic wave transmitting surface of the ultrasonic wave transmitter described above. The vibration detecting element 2 is formed in a concave shape that is recessed on the back surface side. In this embodiment, the vibration detecting element 2 has a bowl shape. Since the vibration detecting element 2 has a bowl shape, the ultrasonic sensor 1 can easily and surely detect defects such as adhesion failure and bubbles by ultrasonic waves.

  As shown in FIG. 4, the vibration detecting element 2 has a base 2a in a region within its surface. The base 2a has a circular shape in plan view, more specifically, a perfect circular shape in plan view. The base portion 2a constitutes a part of a vibration detecting portion in which the first electrode 12a and the second electrode 12b are laminated on the piezoelectric body 11. The base portion 2a is located at the center portion (that is, the bottom portion) of the vibration detection element 2. The outer peripheral edge of the base portion 2a and the outer peripheral edge of the vibration detecting element 2 are formed in a concentric shape in a plan view. The vibration detecting element 2 has a plurality of low-rigidity portions 13 radially extending from the outer peripheral edge of the base portion 2a. The plurality of low-rigidity portions 13 extend linearly in the radial direction of the vibration detection element 2. In the vibration detection element 2, the plurality of low-rigidity portions 13 radially extend from the outer peripheral edge of the base portion 2a, so that the plurality of low-rigidity portions 13 extend in the extending direction (in the present embodiment, the diameter of the vibration detection element 2). It is possible to easily bend or bend in the direction perpendicular to the extending direction of the plurality of low-rigidity portions 13 while absorbing the excess portion of the sheet over the (direction). The “circle” includes not only a perfect circle but also an ellipse and an oval. The base portion 2a is not limited to a circular shape in plan view, and may be a polygonal shape, a star shape, or the like.

  The base portion 2a is a region that does not absorb the surplus portion of the sheet in a curved or bent state, and is formed in a relatively small area of the central portion of the vibration detection element 2 as shown in FIG. The lower limit of the ratio of the average radius R2 of the vibration detecting element 2 (the length along the curved or bent surface) to the average radius R2 of the base 2a (the length along the curved or bent surface) is preferably 0.1, and the lower limit is 0.1. 3 is more preferable. On the other hand, the upper limit of the ratio is preferably 0.5, more preferably 0.4. If the ratio is less than the lower limit, the area ratio of the plurality of low-rigidity portions 13 becomes relatively large, which may unnecessarily reduce the area of the vibration detection portion. On the other hand, if the ratio exceeds the upper limit, the plurality of low-rigidity portions 13 cannot sufficiently absorb the excess portion of the sheet, and there is a possibility that the vibration detection portion may be pleated.

  It is preferable that the plurality of low-rigidity portions 13 be arranged at equal angular intervals from the outer peripheral edge of the base portion 2a. By arranging the plurality of low-rigidity portions 13 at equal angular intervals, the plurality of low-rigidity portions 13 can effectively absorb the excess portion of the sheet, and it is easy to prevent the vibration detection portion from being pleated.

  As described above, the low-rigidity portion 13 has a strip shape and has a constant width. Since the low-rigidity portion 13 has a constant width, it is possible to absorb the excess portion of the sheet. The average width of the plurality of low-rigidity portions 13 can be set according to the size of the vibration detection element 2, but can be set to, for example, 0.5 mm or more and 3 mm or less.

  As shown in FIG. 4, it is preferable that the low-rigidity portion 13 be provided with a fold 13a. The folds 13a are formed by overlapping the excess sheet portions when the vibration detecting element 2 is formed into a curved shape from the expanded state. In the ultrasonic sensor 1, the folds 13a are formed in the low-rigidity portion 13, so that the vibration detection element 2 can be easily formed into a desired curved surface shape. Further, since the ultrasonic sensor 1 is formed with the folds in the low-rigidity portion 13, it becomes easy to keep the surface of the vibration detecting portion in a desired curved surface having a smooth shape, and the detection sensitivity of the vibration detecting portion is increased. The decrease can be suppressed.

(Support member)
As shown in FIG. 2, the support member 3 has an inverted shape of the back surface of the vibration detection element 2 and has a mounting surface 3a on which the vibration detection element 2 is mounted from the back surface side. Further, the support member 3 has a plurality of through holes 3b penetrating in the thickness direction (front and back directions). Since the ultrasonic sensor 1 includes the support member 3, the vibration detection element 2 can be easily formed in a shape along the curved surface shape of the mounting surface 3a.

  The support member 3 is formed of, for example, a synthetic resin as a main component. Examples of this synthetic resin include polyethylene terephthalate and polypropylene. In addition, a "main component" means a component with the largest content in terms of mass.

  As shown in FIG. 5, the ultrasonic sensor 1 has a plurality of adhesive portions 14 (a plurality of first adhesive portions 14 a and a plurality of second adhesive portions 14 b) that adhere the vibration detection element 2 and the support member 3. The plurality of adhesive portions 14 can be formed by, for example, a well-known double-sided tape or adhesive.

  The plurality of first adhesive portions 14a are laminated on the plurality of low-rigidity portions 13. As a result, the vibration detection element 2 is partially bonded to the mounting surface 3a by the plurality of low-rigidity portions 13. In the ultrasonic sensor 1, the resonance frequency of the vibration detection element 2 is affected by the support member 3 because the vibration detection element 2 is partially bonded to the mounting surface 3a by the plurality of low-rigidity portions 13. It is possible to suppress the change.

  The plurality of second adhesive portions 14b are laminated on the outer peripheral edge portion of the vibration detection element 2. In the present embodiment, the plurality of second adhesive portions 14b are laminated on the outer peripheral edge portion of the second electrode 12b (that is, the vibration detection portion). As a result, the vibration detection element 2 is partially bonded to the mounting surface 3a at the outer peripheral edge portion of the vibration detection element 2 in addition to the plurality of low-rigidity portions 13. In the ultrasonic sensor 1, the resonance frequency of the vibration detection element 2 is affected by the support member 3 because the vibration detection element 2 is partially bonded to the mounting surface 3a at the outer peripheral edge portion of the vibration detection element 2. It is possible to easily suppress the peeling of the vibration detection element 2 from the mounting surface 3a while suppressing such a change.

  The plurality of through holes 3b are provided so as to reach the vibration detection element 2. In particular, in the present embodiment, as shown in FIG. 5, the plurality of through holes 3b are provided so as to reach the vibration detection element 2 at a position not overlapping the plurality of low-rigidity portions 13. Thereby, the ultrasonic sensor 1 can communicate the space on the back surface side of the vibration detection portion of the vibration detection element 2 with the space on the back surface side of the support member 3. As a result, the ultrasonic sensor 1 can suppress the resonance frequency of the vibration detection element 2 from being affected by the sealing with the mounting surface 3a.

  The arrangement of the plurality of through holes 3b will be described in detail with reference to FIG. First, as described above, the ultrasonic sensor 1 includes a plurality of low-rigidity portions 13 that are non-vibration detecting portions, and a vibration detecting portion in which the first electrode 12a and the second electrode 12b are laminated on both surfaces of the piezoelectric body 11. 15 and. The vibration detecting portion 15 has a base portion 2a and a plurality of peripheral edge portions 2b defined by a plurality of low-rigidity portions 13 outside the outer peripheral edge of the base portion 2a. The ultrasonic sensor 1 is provided with a through hole 3b corresponding to the base portion 2a and the plurality of peripheral edge portions 2b. Specifically, the through holes 3b are provided in the base portion 2a and the peripheral portions 2b, and preferably, the through holes 3b are provided in a one-to-one correspondence with the base portion 2a and the peripheral portions 2b. Thereby, the ultrasonic sensor 1 can communicate the space on the back surface side of each section of the vibration detection unit 15 with the space on the back surface side of the support member 3. As a result, the ultrasonic sensor 1 can more reliably suppress the resonance frequency of the vibration detection element 2 from being affected by the sealing with the mounting surface 3a.

<Method of manufacturing ultrasonic sensor>
The ultrasonic sensor 1 fixes the vibration detection element 2 on the mounting surface 3a while allowing the flat film-shaped (deployed state) vibration detection element 2 to follow the curved surface shape of the mounting surface 3a of the support member 3. It is formed by The method for manufacturing the ultrasonic sensor 1 includes a step of stacking the vibration detecting element 2 on the mounting surface 3a of the support member 3 (a stacking step), and mounting the vibration detecting element 2 after the stacking step or at the same time as the stacking step. The process (formation process) of forming in a shape along the curved surface of the placement surface 3a is provided. In the forming step, the vibration detection element 2 can be formed in a shape along the curved surface shape of the mounting surface 3a by suction from the back surface side of the support member 3. In the forming step, instead of suction from the back surface side of the support member 3, the vibration detection element 2 may be pressed from the front surface side by a convex member.

  In the forming step, for example, the vibration detecting element 2 is sucked toward the mounting surface 3a side by vacuuming from the plurality of through holes 3b of the supporting member 3. At this time, a plurality of folds 13a are selectively formed in the plurality of low-rigidity portions 13 of the vibration detecting element 2, whereby the vibration detecting element 2 is formed into a desired curved surface shape while absorbing the excess portion of the sheet. You can

<Advantages>
The vibration detection element 2 has a plurality of belt-shaped low-rigidity portions 13 extending inward from the outer edge thereof, and the plurality of low-rigidity portions 13 are arranged in a direction perpendicular to the extending direction of these low-rigidity portions 13. It can be curved or bent. Furthermore, since the vibration detection element 2 has the plurality of strip-shaped low-rigidity portions 13, the vibration-detection element 2 is easily bent or bent in the direction along the extending direction of the low-rigidity portions 13. Therefore, the vibration detecting element 2 can be easily formed into a three-dimensional curved shape.

  In the ultrasonic sensor 1, the vibration detection element 2 has a plurality of belt-shaped low-rigidity portions 13 extending inward from the outer edge thereof. The low-rigidity portion 13 can be curved or bent in a direction perpendicular to the extending direction. Further, in the ultrasonic sensor 1, since the vibration detection element 2 has the plurality of belt-shaped low-rigidity portions 13, the vibration detection element 2 is curved or bent in a direction along the extending direction of the low-rigidity portions 13. It's easy to do. Therefore, the ultrasonic sensor 1 can easily form the vibration detecting element 2 having a three-dimensional curved shape.

  In the ultrasonic sensor 1, since it is easy to form the vibration detecting element 2 into a desired three-dimensional curved shape corresponding to the ultrasonic wave transmitting surface of the ultrasonic wave transmitter, the ultrasonic wave detecting element 2 is used as a pair with the ultrasonic wave transmitter. It is preferably used as a sensor for detecting sound waves.

  The method of manufacturing the ultrasonic sensor can easily and reliably manufacture the ultrasonic sensor 1 in which the vibration detection element 2 can be easily formed into a three-dimensional curved shape.

[Second embodiment]
The ultrasonic sensor 21 of FIG. 7 is provided with a vibration detecting element 22 which itself constitutes the present invention, and a support member 3 which supports the vibration detecting element 22 from the back surface side. The vibration detection element 22 has a plurality of belt-shaped low-rigidity portions 23 extending inward from the outer edge thereof. The low-rigidity portion 23 has a slit 13b. The ultrasonic sensor 21 may have the same configuration as the ultrasonic sensor 1 of FIG. 1 except that the low-rigidity portion 23 has the slit 13b. Therefore, only the slit 13b will be described below.

  The slit 13b extends inward from the outer edge of the vibration detection element 22. The slit 13b extends along the extending direction of the low-rigidity portion 23 at an intermediate position in the width direction of the low-rigidity portion 23 (a position that does not include both ends in the width direction). The slits 13b may be provided only in a part of the low-rigidity portions 23, but it is preferable that the slits 13b be provided in a one-to-one correspondence with each low-rigidity portion 23.

<Advantages>
Since the low-rigidity portion 23 has the slit 13b, the vibration detection element 22 is easily bent or bent by the slit 13b. In the vibration detecting element 22, since the slit 13b is formed at an intermediate position in the width direction of the low-rigidity portion 23, at least one of the first electrode 12a and the second electrode 12b is provided in a certain range on both sides of the slit 13b. A non-vibration detection part is formed in which one does not exist. Therefore, the vibration detection element 22 easily suppresses a short circuit between the first electrode 12a and the second electrode 12b.

  In the ultrasonic sensor 21, since the vibration detection element 22 has the slit 13b in the low-rigidity portion 23, the vibration detection element 22 can be easily bent or bent by the slit 13b. In the ultrasonic sensor 21, since the slit 13b is formed at the intermediate position in the width direction of the low-rigidity portion 23, it is easy to suppress a short circuit between the first electrode 12a and the second electrode 12b.

[Other Embodiments]
The above embodiment does not limit the configuration of the present invention. Therefore, in the above-described embodiment, it is possible to omit, replace, or add the constituent elements of each part of the embodiment based on the description and technical common sense of the present specification, and all of them are construed as belonging to the scope of the present invention. Should be.

  For example, even when the base portion of the vibration detecting element has a circular shape in plan view, the base portion does not necessarily have to be a perfect circle shape in plan view. For example, as shown in FIG. 8, in the ultrasonic sensor, when the vibration detecting element 32 has a bowl shape, the base 32a may have an oval shape. Further, in this case, the plurality of low-rigidity portions 33 may extend radially only from the circumferential portion of the outer peripheral edge of the base portion 32a.

  The vibration detection element may have only one low-rigidity portion that extends inward from the outer edge thereof. For example, the vibration detecting element 42 of FIG. 9 has only one low-rigidity portion 43 extending inward from its outer edge. The low-rigidity portion 43 is formed in a spiral shape from the outer edge of the vibration detection element 42 toward the inside. That is, the low-rigidity portion 43 does not extend radially from the outer peripheral edge of the base portion that is circular in plan view. Even with this configuration, the vibration detection element can bend or bend in the low-rigidity portion 43 in the direction perpendicular to the extending direction of the low-rigidity portion 43.

  In the ultrasonic sensor, the curved surface shape of the vibration detecting element can be set according to the application, and the vibration detecting element does not necessarily have to be bowl-shaped. For example, the vibration detection element may be configured in a dome shape or the like that is raised on the front surface side.

  The one or more low-rigidity portions may be composed of a thin portion in which electrodes are laminated only on one surface of the piezoelectric body. However, from the viewpoint of selectively forming a fold in one or a plurality of low-rigidity portions, it is preferable that the difference in rigidity between the low-rigidity portion and the other portion (vibration detection portion) is large. Therefore, it is more preferable that the low-rigidity portion is a thin portion in which electrodes are not laminated on both surfaces of the piezoelectric body.

  In the vibration detecting element, the pair of electrodes may not be patterned in the same shape in plan view. In this case, a region where at least one electrode is not laminated on the piezoelectric body can be configured as a thin portion.

  In the vibration detecting element, for example, in the configuration of FIGS. 8 and 9, a slit may be formed in the low rigidity portion. Further, the slit may be formed in an inner region apart from the outer edge of the vibration detecting element. Further, in the vibration detecting element, two or more slits may be formed for one low rigidity portion.

  The vibration detecting element may be provided with a low-rigidity portion between the base portion and the plurality of peripheral portions. In other words, a thin portion where at least one electrode is not laminated on the piezoelectric body may be formed between the base portion and the plurality of peripheral portions. With this configuration, it is possible to form an array sensor in which the plurality of vibration detection units are divided by the low-rigidity portion.

  The one or more low-rigidity portions may not have a constant width along the extending direction. For example, when the vibration detection element has a plurality of low-rigidity portions radially arranged, the width of these low-rigidity portions may be gradually reduced toward the outer side in the radial direction, may be gradually increased, and the width may be gradually increased. Both the gradually decreasing area and the gradually increasing area may be included.

  The ultrasonic sensor does not necessarily need to have a fold formed on the one or more low-rigidity portions as long as the curved surface shape of the vibration detection element can be appropriately maintained.

  The ultrasonic sensor does not necessarily have to have the support member described above as long as the curved surface shape of the vibration detection element can be maintained.

  When the ultrasonic sensor includes the support member, the ultrasonic sensor may be partially bonded to the mounting surface only at the one or more low-rigidity portions. Further, in the case where the ultrasonic sensor has this supporting member, the vibration detecting element and the supporting member can be adhered and fixed at an arbitrary laminated region of the electrode if the detection accuracy is not insufficient. ..

  The ultrasonic sensor may have a configuration in which a plurality of vibration detection elements are laminated on a support member.

  As described above, since the vibration detecting element according to the present invention can be easily formed into a three-dimensional curved shape, it is preferably used as a sensor for detecting ultrasonic waves.

1, 21 Ultrasonic sensor 2, 22, 32, 42 Vibration detection element 2a, 32a Base part 2b Peripheral part 3 Support member 3a Mounting surface 3b Through hole 11 Piezoelectric body 12a First electrode 12b Second electrode 13, 23, 33, 43 Low-rigidity part 13a Fold 13b Slit 14 Adhesive part 14a First adhesive part 14b Second adhesive part 15 Vibration detection part 102 Vibration detection element 103 Notch

Claims (10)

A film-shaped piezoelectric body and a pair of electrodes laminated on the front and back of the piezoelectric body,
A vibration detecting element having one or a plurality of belt-shaped low-rigidity portions extending inward from its outer edge.   The vibration detecting element according to claim 1, further comprising a base portion in an in-plane region, wherein the low-rigidity portion extends radially from an outer peripheral edge of the base portion.   The vibration detecting element according to claim 1, wherein the low-rigidity portion is a thin portion in which the electrode is not laminated on at least one surface of the piezoelectric body.   The vibration detecting element according to claim 1, 2, or 3, wherein the low-rigidity portion has a slit.   An ultrasonic sensor in which the vibration detecting element according to any one of claims 1 to 4 is curved or bent in the low-rigidity portion in a direction perpendicular to an extending direction of the low-rigidity portion.   The ultrasonic sensor according to claim 5, wherein the vibration detecting element has a bowl shape.   The ultrasonic sensor according to claim 5 or 6, wherein a fold is formed on the low-rigidity portion.   8. The support member according to claim 5, further comprising a support member having an inverted shape of the back surface of the vibration detection element and having a mounting surface on which the vibration detection element is mounted from the back surface side. Ultrasonic sensor.   The ultrasonic sensor according to claim 8, wherein the support member has one or a plurality of through holes penetrating in the thickness direction and reaching the vibration detection element.   The ultrasonic sensor according to claim 8 or 9, wherein the vibration detecting element is partially bonded to the mounting surface by the one or more low-rigidity portions.

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