Transducer and driving method thereof, and system

Abstract

To provide a transducer capable of varying a resonance frequency of a vibration body.SOLUTION: A transducer comprises: a piezoelectric element; and a film body including a film support portion having a hollow portion, and a vibration film connected to the film support portion and displaceable in a film thickness direction, where the piezoelectric element is stacked over the vibration film. The piezoelectric element includes: a first stacked body that comprises a first pair of electrodes and a first piezoelectric film sandwiched between the first pair of electrodes; and a second stacked body that comprises a second pair of electrodes and a second piezoelectric film sandwiched between the second pair of electrodes and is separated from the first stacked body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present embodiment relates to a transducer, a driving method thereof, and a system thereof. [Background technology]

[0002] 2. Description of the Related Art Transducers that transmit or receive sound waves or ultrasonic waves are known. Transducers are used, for example, as speakers that transmit sound waves, and are mounted in earphones, wearable devices, and the like.

[0003] For example, Patent Document 1 discloses a sound generating device suitable for earphones. This sound generating device includes a coil that generates a magnetic field and a magnet that interacts with the magnetic field generated by the coil to vibrate a diaphragm.

[0004] Speakers that use a coil and a magnet require a current to flow through the coil to generate a magnetic field, resulting in high power consumption. Therefore, speakers that use a piezoelectric element consisting of a piezoelectric film sandwiched between a pair of electrodes have been attracting attention (see, for example, Patent Document 2). Speakers of this type are manufactured using MEMS (Micro Electro Mechanical Systems), a semiconductor manufacturing technology that enables microfabrication. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-170592 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-105170 Summary of the Invention [Problem to be solved by the invention]

[0006] By repeatedly applying a drive voltage to the pair of electrodes of the piezoelectric element, the diaphragm, together with the piezoelectric element, alternately displaces upward and downward. Specifically, the tip of the diaphragm is displaced so as to bend. The vibration of the diaphragm vibrates the air around the diaphragm, and the vibration of the air is output as sound waves. The properties of the output sound waves depend on the resonant frequency of the vibrating body (e.g., the diaphragm), which is determined by the properties such as strength and size (diameter and length) of the vibrating body.

[0007] If the resonant frequency of the vibrator is not optimal on the receiving side that receives the output sound waves, the receiving sensitivity will decrease. Furthermore, in order to adjust the resonant frequency of the vibrator, it is necessary to change the design of the vibrator. Therefore, once the design of the vibrator is decided, the resonant frequency of the vibrator is fixed, and readjusting this resonant frequency requires a great deal of time and effort.

[0008] One aspect of this embodiment provides a transducer capable of varying the resonant frequency of a vibrating body. Another aspect of this embodiment provides a method for driving the transducer. Still another aspect of this embodiment provides a system for adjusting the resonant frequency of a vibrating body so that the vibrating body is in a suitable state with high sensitivity. [Means for solving the problem]

[0009] One aspect of this embodiment is a transducer comprising a membrane body including a piezoelectric element, a membrane support portion having a hollow portion, and a vibration membrane connected to the membrane support portion and capable of displacement in the film thickness direction, and wherein the piezoelectric element is stacked on the vibration membrane, and the piezoelectric element comprises a first laminate including a first pair of electrodes and a first piezoelectric membrane sandwiched between the first pair of electrodes, and a second laminate including a second pair of electrodes and a second piezoelectric membrane sandwiched between the second pair of electrodes, the second laminate being spaced apart from the first laminate.

[0010] Another aspect of this embodiment is a transducer comprising: a piezoelectric element; a membrane support portion having a hollow portion; and a vibration membrane connected to the membrane support portion and capable of displacement in the film thickness direction, wherein the piezoelectric element is stacked on the vibration membrane; the piezoelectric element comprising: a first electrode; a first laminate comprising a first piezoelectric membrane and a second electrode; and a second laminate comprising a second piezoelectric membrane and a third electrode and spaced apart from the first laminate; the first piezoelectric membrane is sandwiched between the first electrode and the second electrode; and the second piezoelectric membrane is sandwiched between the first electrode and the third electrode.

[0011] Another aspect of this embodiment is a transducer comprising a membrane body including a piezoelectric element, a membrane support portion having a hollow portion, and a vibration membrane connected to the membrane support portion and capable of displacement in the film thickness direction, and wherein the piezoelectric element is stacked on the vibration membrane, wherein the piezoelectric element has a first electrode, a second electrode, a piezoelectric membrane sandwiched between the first electrode and the second electrode, and a third electrode, wherein the piezoelectric membrane is sandwiched between the first electrode and the third electrode, and the third electrode is spaced apart from the second electrode.

[0012] Another aspect of this embodiment is a method for driving a transducer having a membrane body including a piezoelectric element, a membrane support portion having a hollow portion, and a vibrating membrane connected to the membrane support portion and capable of displacement in the film thickness direction, and the piezoelectric element is stacked on the vibrating membrane, wherein the piezoelectric element has a lower electrode, a piezoelectric membrane on the lower electrode, and a plurality of upper electrodes spaced apart from each other on the piezoelectric membrane, one end of the plurality of upper electrodes having a first region closest to the membrane support portion, and the method performs one of the following selected from the group consisting of applying a control voltage to the upper electrode in the first region, opening the upper electrode, and opening the lower electrode, and independently applying a control voltage or a waveform voltage to the remaining upper electrodes, opening the upper electrode, and opening the lower electrode, thereby changing the resonant frequency of the vibrating body including the piezoelectric element and the membrane body.

[0013] Another aspect of this embodiment is a system having a membrane body comprising a piezoelectric element, a membrane support portion having a hollow portion, and a vibrating membrane connected to the membrane support portion and capable of displacement in the membrane thickness direction, and wherein the piezoelectric element is stacked on the vibrating membrane, wherein the piezoelectric element has a lower electrode, a piezoelectric membrane on the lower electrode, and a plurality of upper electrodes on the piezoelectric membrane that are spaced apart from each other, and one end of the plurality of upper electrodes has a first region that is closest to the membrane support portion, and the system performs one of the following operations selected from the group consisting of applying a control voltage to the upper electrode in the first region, opening the upper electrode, opening the lower electrode, and extracting a signal generated by the vibration of the membrane body, and independently applying a control voltage to the remaining upper electrodes, opening the upper electrode, opening the lower electrode, and extracting a signal generated by the vibration of the membrane body, so as to achieve the highest reception efficiency for signals from outside. [Effects of the Invention]

[0014] According to this embodiment, it is possible to provide a transducer capable of varying the resonant frequency of the vibrating body, a method for driving the transducer, and a system for adjusting the resonant frequency of the vibrating body so that the vibrating body is in a suitable state with high sensitivity. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a transducer according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the transducer when the diaphragm vibrates. [Figure 3] FIG. 3 is a top view of the transducer according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of the transducer according to the first embodiment. [Figure 5] FIG. 5 is a top view of a transducer according to a first modified example. [Figure 6]FIG. 6 is a cross-sectional view of a transducer according to a first modified example. [Figure 7] FIG. 7 is a top view of a transducer according to a second modified example. [Figure 8] FIG. 8 is a cross-sectional view of a transducer according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] Next, this embodiment will be described with reference to the drawings. In the drawings described below, identical or similar parts are designated by identical or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and planar dimensions of each component may differ from the actual relationship. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships and ratios.

[0017] Furthermore, the embodiments shown below are merely examples of devices and methods for embodying the technical ideas, and do not specify the materials, shapes, structures, arrangements, etc. of each component part. Various modifications can be made to the present embodiments within the scope of the claims.

[0018] A specific aspect of this embodiment is as follows.

[0019] <1> A transducer comprising: a membrane body including a piezoelectric element, a membrane support portion having a hollow portion, and a vibration membrane connected to the membrane support portion and capable of displacement in the film thickness direction, with the piezoelectric element stacked on the vibration membrane, wherein the piezoelectric element comprises a first laminate including a first pair of electrodes and a first piezoelectric membrane sandwiched between the first pair of electrodes, and a second laminate including a second pair of electrodes and a second piezoelectric membrane sandwiched between the second pair of electrodes, the second laminate being spaced apart from the first laminate.

[0020] <2> the piezoelectric element further includes a third laminate including a third pair of electrodes and a third piezoelectric film sandwiched between the third pair of electrodes, the third laminate being sandwiched between the first laminate and the second laminate and being spaced apart from the first laminate and the second laminate; <1> The transducer according to claim 1.

[0021] <3> A transducer comprising: a piezoelectric element; a membrane support portion having a hollow portion; and a vibration membrane connected to the membrane support portion and capable of displacement in a film thickness direction, wherein the piezoelectric element is stacked on the vibration membrane; wherein the piezoelectric element has a first electrode, a first laminate comprising a first piezoelectric membrane and a second electrode, and a second laminate comprising a second piezoelectric membrane and a third electrode and spaced apart from the first laminate; wherein the first piezoelectric membrane is sandwiched between the first electrode and the second electrode, and the second piezoelectric membrane is sandwiched between the first electrode and the third electrode.

[0022] <4> the first piezoelectric film and the second piezoelectric film are located on the first electrode; <3> The transducer according to claim 1.

[0023] <5> the piezoelectric element further includes a third laminate including a third piezoelectric film and a fourth electrode, the third laminate being sandwiched between the first laminate and the second laminate and spaced apart from the first laminate and the second laminate; <3> or <4> The transducer according to claim 1.

[0024] <6> an end portion of the second laminate has a region that overlaps with the membrane support portion when viewed from a normal direction to the vibration membrane; <1> ~ <5> 10. A transducer according to any one of claims 1 to 9.

[0025] <7> The first stack is surrounded by the second stack. <1> ~ <6> 10. A transducer according to any one of claims 1 to 9.

[0026] <8> A transducer comprising: a membrane body including a piezoelectric element, a membrane support portion having a hollow portion, and a vibration membrane connected to the membrane support portion and capable of displacement in a thickness direction, with the piezoelectric element stacked on the vibration membrane, wherein the piezoelectric element has a first electrode, a second electrode, a piezoelectric membrane sandwiched between the first electrode and the second electrode, and a third electrode, the piezoelectric membrane being sandwiched between the first electrode and the third electrode, and the third electrode being spaced apart from the second electrode.

[0027] <9> an end of the third electrode has a region that overlaps with the membrane support portion when viewed from a normal direction to the vibration membrane; <8> The transducer according to claim 1.

[0028] <10> the piezoelectric film is located on the first electrode; <8> or <9> The transducer according to claim 1.

[0029] <11> the piezoelectric element further has a fourth electrode, the piezoelectric film is sandwiched between the first electrode and the fourth electrode, the fourth electrode is sandwiched between the second electrode and the third electrode, and is spaced apart from the second electrode and the third electrode; <8> ~ <10> 10. A transducer according to any one of claims 1 to 9.

[0030] <12> The second electrode is surrounded by the third electrode. <8> ~ <11> 10. A transducer according to any one of claims 1 to 9.

[0031] <13> The vibration membrane has a doubly supported beam shape. <1> ~ <12> 10. A transducer according to any one of claims 1 to 9.

[0032] <14> the piezoelectric element has a function of changing the resonance frequency of a vibrating body including the piezoelectric element and the film body; <1> ~ <13> 10. A transducer according to any one of claims 1 to 9.

[0033] <15> A method for driving a transducer having a membrane body including a piezoelectric element, a membrane support portion having a hollow portion, and a vibrating membrane connected to the membrane support portion and capable of displacement in the film thickness direction, and in which the piezoelectric element is stacked on the vibrating membrane, wherein the piezoelectric element has a lower electrode, a piezoelectric membrane on the lower electrode, and a plurality of upper electrodes spaced apart from each other on the piezoelectric membrane, one end of the plurality of upper electrodes having a first region closest to the membrane support portion, and the method comprises performing one of the following operations selected from the group consisting of applying a control voltage to the upper electrode in the first region, opening the upper electrode, and opening the lower electrode, and independently applying a control voltage or a waveform voltage to the remaining upper electrodes, opening the upper electrode, and opening the lower electrode, thereby changing the resonant frequency of the vibrating body including the piezoelectric element and the membrane body.

[0034] <16> the first region overlaps with the membrane support portion when viewed from a normal direction to the vibration membrane, and a waveform voltage is applied to an upper electrode having a second region that is farthest from the first region; <15> A method for driving the transducer according to claim 1.

[0035] <17> the upper electrode in the second region is surrounded by the upper electrode in the first region; <16> A method for driving the transducer according to claim 1.

[0036] <18> the control voltage is applied to the upper electrode closest to the second region and all upper electrodes sandwiched between the upper electrode in the first region; <16> or <17> A method for driving the transducer according to claim 1.

[0037] <19> The piezoelectric film is provided in plurality so as to be spaced apart from each other. <15> ~ <18> 10. A method for driving a transducer according to any one of claims 1 to 9.

[0038] <20> The lower electrode is provided in plurality and spaced apart from each other. <19> A method for driving the transducer according to claim 1.

[0039] <21> A system having a membrane body comprising a piezoelectric element, a membrane support portion having a hollow portion, and a vibrating membrane connected to the membrane support portion and capable of displacement in the membrane thickness direction, and wherein the piezoelectric element is stacked on the vibrating membrane, wherein the piezoelectric element has a lower electrode, a piezoelectric membrane on the lower electrode, and a plurality of upper electrodes on the piezoelectric membrane that are spaced apart from each other, one end of the plurality of upper electrodes has a first region that is closest to the membrane support portion, and the system performs one of the following selected from the group consisting of applying a control voltage to the upper electrode in the first region, opening the upper electrode, opening the lower electrode, and extracting a signal generated by the vibration of the membrane body, and independently applying a control voltage to the remaining upper electrodes so as to achieve the highest reception efficiency for external signals, opening the upper electrode, opening the lower electrode, and extracting a signal generated by the vibration of the membrane body.

[0040] <22> The first region overlaps with the membrane support portion when viewed from a normal direction of the vibration membrane, and a signal generated by vibration of the membrane body is extracted in a second region that is farthest from the first region. <21> The system described in

[0041] <23> the upper electrode in the second region is surrounded by the upper electrode in the first region; <22> The system described in

[0042] <24> the control voltage is applied to the upper electrode closest to the second region and all upper electrodes sandwiched between the upper electrode in the first region; <22> or <23> The system described in

[0043] <25> The piezoelectric film is provided in plurality so as to be spaced apart from each other. <21> ~ <24> 10. The system according to claim 1, wherein

[0044] <26> The lower electrode is provided in plurality and spaced apart from each other. <25> The system described in

[0045] (First embodiment) The configuration of the transducer according to this embodiment will be described with reference to the drawings. As shown in Fig. 1, the transducer 10 according to this embodiment is mainly composed of a piezoelectric element 50 and a film body 15. In the following description, the up and down directions are defined based on the state of the transducer 10 shown in Fig. 1, but this does not limit the direction in which the transducer 10 is used.

[0046] The piezoelectric element 50 is composed of a plurality of pairs of electrodes 11, 12 and a piezoelectric film 13 sandwiched between the pairs of electrodes 11, 12. The pairs of electrodes 11, 12 and the piezoelectric film 13 have shapes corresponding to the shape of a vibration film 16 described later, and are circular in the example shown in Figs. 3 and 4 described later.

[0047] Each of the pair of electrodes 11, 12 is formed using a thin film of a conductive metal such as platinum, molybdenum, iridium, or titanium. One electrode 11 is located above the piezoelectric film 13 and is connected to an electrode pad, which is a circuit pattern for applying a drive voltage to the electrode 11. The other electrode 12 is located below the piezoelectric film 13 and is connected to an electrode pad, which is a circuit pattern for applying a drive voltage to the electrode 12.

[0048] The piezoelectric film 13 is made of, for example, lead zirconate titanate (PZT). In addition to lead zirconate titanate, the piezoelectric film 13 can also be made of aluminum nitride (AlN), zinc oxide (ZnO), lead titanate (PbTiO3), or the like.

[0049] The membrane 15 is made up of a vibrating membrane 16 and a membrane support portion 17. The membrane 15 is made of, for example, silicon (Si). By etching the back surface of the membrane 15, the vibrating membrane 16 and the membrane support portion 17 are integrally formed.

[0050] The diaphragm 16 is made of a thin film and is configured to be displaceable in the film thickness direction, i.e., in the normal direction to the diaphragm 16 (the up-down direction on the paper in FIG. 1). When observed from a plane parallel to the diaphragm 16, the diaphragm 16 has a substantially circular shape.

[0051] The membrane support part 17 has a cylindrical inner peripheral surface that forms a hollow part (cavity). The vibrating membrane 16 is connected to the inner peripheral surface of the membrane support part 17 around the entire circumference so that the vibrating membrane 16 is in contact with the inner peripheral surface of the membrane support part 17, and thus the periphery of the vibrating membrane 16 is supported by the membrane support part 17. The vibrating membrane 16 is connected to the upper end side of the membrane support part 17.

[0052] Furthermore, the membrane support portion 17 has an area that overlaps with the end portion 51 of the piezoelectric element 50 (electrode 11, electrode 12, and piezoelectric membrane 13) when viewed from the normal direction to the vibration membrane 16, and the vibration membrane 16 has a doubly supported beam shape with both ends fixed by the membrane support portion 17. However, the vibration membrane 16 is not limited to this, and may have a cantilever shape that extends from the membrane support portion 17 and the tip portion of the vibration membrane 16 is configured as a free end. Furthermore, the vibration membrane 16 may have an annular shape and a structure in which the outside of the annular vibration membrane 16 is fixed by the membrane support portion 17, or a structure in which the outside of the vibration membrane 16 is fixed by the membrane support portion 17 and the vibration membrane 16 has one or more holes. In this specification, the term "end portion" refers to the part farthest from the center of a patterned object in each single direction.

[0053] Furthermore, the membrane support portion 17 does not have to overlap the end portion 51 of the piezoelectric element 50 when viewed from the normal direction to the vibrating membrane 16, as long as it does not impair the effect of the transducer according to this embodiment, which will be described later. For example, the end portion of the membrane support portion 17 and the end portion 51 of the piezoelectric element may be aligned, or the end portion 51 of the piezoelectric element 50 may be located slightly closer to the center than the membrane support portion 17. When the end portion 51 of the piezoelectric element 50 is located closer to the center than the membrane support portion 17, for example, the end portion 51 of the piezoelectric element 50 may be located about 10 times the thickness of the vibrating membrane 16 from the end portion of the membrane support portion 17 towards the center.

[0054] 2 shows a cross-sectional view of the area surrounding the region overlapping with the end of the piezoelectric element 50 when viewed from the normal direction to the vibrating membrane 16 while the vibrating membrane 16 is vibrating. The vibrating membrane 16 has an inflection point 18, and the end of the piezoelectric element 50 is disposed closer to the membrane support portion 17 than the inflection point 18. By disposing it in this manner, the peripheral portion of the vibrating membrane 16 can be effectively constrained by applying a control voltage. Furthermore, the end of the piezoelectric element 50 and the membrane support portion 17 do not need to overlap with each other when viewed from the normal direction to the vibrating membrane 16, as long as the above-mentioned effect is not impaired.

[0055] The transducer according to this embodiment will be described in more detail with reference to Figures 3 and 4. The piezoelectric element 50 has a plurality of electrodes 11 (in this embodiment, for example, upper electrodes 11a, 11b, 11c, and 11d), a plurality of piezoelectric films 13 (in this embodiment, for example, piezoelectric films 13a, 13b, 13c, and 13d), and a plurality of electrodes 12 (in this embodiment, for example, lower electrodes 12a, 12b, 12c, and 12d). In this embodiment, the electrodes 11, the piezoelectric films 13, and the electrodes 12 are collectively referred to as a laminate (for example, laminates 30a and 30d).

[0056] The laminate 30d is the end 51 of the piezoelectric element 50, is closest to the membrane support portion 17, and is located closer to the membrane support portion 17 than the inflection point of the vibrating membrane 16. The laminate 30a is the laminate farthest from the laminate 30d, and is located at the center of the vibrating membrane 16 in this embodiment. When the vibrating membrane 16 has a substantially circular shape, the laminate 30a has a substantially circular structure, and the laminates other than the laminate 30a (for example, the laminate 30d) have an annular structure. In other words, the laminate 30a is surrounded by the laminates other than the laminate 30a (for example, the laminate 30d).

[0057] The multiple laminates are spaced apart from one another. That is, the multiple upper electrodes are spaced apart from one another, the multiple piezoelectric films are spaced apart from one another, and the multiple lower electrodes are spaced apart from one another. Furthermore, the laminate 30d, which is the end 51 of the piezoelectric element 50, has a region that is closest to the membrane support portion 17 (overlapping when viewed from the normal direction to the vibration membrane 16 in FIGS. 3 and 4). Although four laminates are illustrated in FIGS. 3 and 4, the number of laminates is not limited to this and may be two or more. For example, the piezoelectric element may include two, three, or five laminates. Furthermore, the end 51 of the piezoelectric element 50 and the membrane support portion 17 do not need to overlap with each other when viewed from the normal direction to the vibration membrane 16, as long as the above-described effect is not impaired.

[0058] Each electrode 11 and each electrode 12 is electrically connected to an electrode pad via wiring. Specifically, upper electrode 11a is electrically connected to electrode pad 21a, upper electrode 11b is electrically connected to electrode pad 21b, upper electrode 11c is electrically connected to electrode pad 21c, upper electrode 11d is electrically connected to electrode pad 21d, lower electrode 12a is electrically connected to electrode pad 22a, lower electrode 12b is electrically connected to electrode pad 22b, lower electrode 12c is electrically connected to electrode pad 22c, and lower electrode 12d is electrically connected to electrode pad 22d. The wiring is routed and arranged symmetrically with respect to the center of gravity of diaphragm 16. In this specification, "electrically connected" includes a case where the electrodes are connected via "something having some electrical effect." Here, "something having some electrical effect" is not particularly limited as long as it enables the exchange of electrical signals between the connected objects. For example, "something that has some kind of electrical action" includes electrodes, wiring, switching elements, resistive elements, inductors, capacitive elements, and other elements that have various functions.

[0059] When a driving voltage is applied to the electrode 11 and the electrode 12, a potential difference occurs between the electrode 11 and the electrode 12. The potential difference causes the vibration membrane 16 to be displaced.

[0060] By repeatedly applying a drive voltage to electrodes 11 and 12, diaphragm 16 alternately displaces upward and downward. The vibration of diaphragm 16 vibrates the air around diaphragm 16, and the vibration of the air is output as a sound wave.

[0061] In this embodiment, the piezoelectric element 50 has a plurality of laminates including the electrodes 11 and 12, and a drive voltage is applied to each laminate. By appropriately adjusting the drive voltage for each laminate, it is possible to change the physical properties such as the effective size and hardness of the vibrating body including the piezoelectric element 50 and the vibrating membrane 16, and it is possible to change the resonant frequency (natural frequency) of the vibrating body.

[0062] Specifically, a waveform voltage is applied to the stack 30a, a control voltage is applied to the stack 30d, or the upper electrode 11d of the stack 30d is opened, and a control voltage or waveform voltage is applied independently to the remaining stacks, or the upper electrodes of the stacks are opened. The control voltage can be, for example, 0 V or any other voltage. The waveform voltage can be any desired waveform, such as a 0 to 5 V sine wave, a monopolar pulse, a bipolar pulse, a burst wave, or a continuous wave. Furthermore, "opening the electrodes" refers to interrupting the path of current flowing through the electrodes.

[0063] In addition, although the above example illustrates the case where the upper electrode is open, the present invention is not limited to this, and the lower electrode may be open, or both the upper electrode and the lower electrode may be open.

[0064] Furthermore, the voltage applied to the electrodes can be modulated using a filter or the like, for example, by modulating the voltage applied to one electrode and then applying the modulated voltage to another electrode. This can reduce the number of electrode pads and the types of driving voltages to be applied, making the manufacturing process simpler.

[0065] Furthermore, it is preferable that the control voltage be applied to the stack 30d and all stacks sandwiched between the stack 30d and the stack 30a that is closest to the stack 30a, which are also subjected to the control voltage, thereby reducing the number of types of driving voltages and simplifying the manufacturing process.

[0066] This configuration provides a transducer capable of varying the resonant frequency of the vibrator. Furthermore, the more laminates included in the piezoelectric element, the greater the gradation of the resonant frequency of the vibrator. Therefore, the receiver can output sound waves using a more optimal resonant frequency of the vibrator. Furthermore, by applying various voltages to the control voltage, the control voltage can be gradually and continuously changed, allowing adjustments to be made using a scanning operation to find the optimal value for the resonant frequency of the vibrator.

[0067] The transducer according to this embodiment is not limited to the above-described configuration, and various modifications are possible. Modifications of the transducer according to this embodiment will be described below.

[0068] <First Modification> The configuration of the transducer according to this modification will be described using Figures 5 and 6. The transducer 10A according to this modification differs from the transducer 10 shown in Figures 3 and 4 in that a lower electrode 12e is used instead of the lower electrodes 12a, 12b, 12c, and 12d. The above explanation will be used to refer to the points common to the transducer 10 shown in Figures 3 and 4 in this modification, and only the points of difference will be described below.

[0069] The piezoelectric element 50A has a plurality of electrodes 11 (in this modification, for example, upper electrodes 11a, 11b, 11c, and 11d), a plurality of piezoelectric films 13 (in this modification, for example, piezoelectric films 13a, 13b, 13c, and 13d), and a lower electrode 12e. The lower electrode 12e can be made of the same material as the electrode 12. In this modification, the electrodes 11 and the piezoelectric films 13 are collectively referred to as a laminate (for example, laminates 40a and 40d).

[0070] The laminate 40d is an end portion 51A of the piezoelectric element 50A, and is disposed closer to the membrane support portion 17 than the inflection point of the vibrating membrane 16. The laminate 40a is the laminate farthest from the laminate 40d, and is disposed at the center of the vibrating membrane 16 in this modification. When the vibrating membrane 16 has a substantially circular shape, the laminate 40a has a substantially circular structure, and the laminates other than the laminate 40a (for example, the laminate 40d) have an annular structure. In other words, the laminate 40a is surrounded by the laminates other than the laminate 40a (for example, the laminate 40d).

[0071] The multiple laminates are spaced apart from one another. That is, the multiple upper electrodes are spaced apart from one another, and the multiple piezoelectric films are spaced apart from one another. Furthermore, the laminate 40d, which is the end 51A of the piezoelectric element 50A, has a region that overlaps with the membrane support portion 17 when viewed from the normal direction to the vibration membrane 16. Furthermore, the end 51A of the piezoelectric element 51 and the membrane support portion 17 do not need to overlap with each other when viewed from the normal direction to the vibration membrane 16, as long as the above-mentioned effect is not impaired.

[0072] Each electrode 11 is electrically connected to an electrode pad via a wiring. Specifically, upper electrode 11a is electrically connected to electrode pad 21a, upper electrode 11b is electrically connected to electrode pad 21b, upper electrode 11c is electrically connected to electrode pad 21c, upper electrode 11d is electrically connected to electrode pad 21d, and lower electrode 12e is electrically connected to electrode pad 22e. The wiring is routed and arranged symmetrically with respect to the center of gravity of diaphragm 16.

[0073] With this configuration, a potential difference is generated between the upper electrodes of the multiple stacked bodies and the lower electrodes 12e. The lower electrodes 12e are paired with the upper electrodes of the multiple stacked bodies, and the lower electrodes 12e are shared by each pair. By sharing the lower electrodes 12e, the number of electrode pads and the types of driving voltages to be applied can be reduced, and the manufacturing process can be simplified.

[0074] <Second Modification> The configuration of the transducer according to this modification will be described using Figures 7 and 8. The transducer 10B according to this modification differs from the transducer 10A shown in Figures 5 and 6 in that a piezoelectric film 13e is used instead of the piezoelectric films 13a, 13b, 13c, and 13d. The above explanation will be used to refer to the points common to the transducer 10A shown in Figures 5 and 6 in this modification, and only the points of difference will be described below.

[0075] The piezoelectric element 50B has a plurality of electrodes 11 (in this modification, for example, upper electrodes 11a, 11b, 11c, and 11d), a piezoelectric film 13e, and a lower electrode 12e. The piezoelectric film 13e can be made of the same material as the piezoelectric film 13.

[0076] Upper electrode 11d is an end portion 51B of piezoelectric element 50B, and is disposed closer to membrane support portion 17 than the inflection point of vibrating membrane 16. Upper electrode 11a is the upper electrode farthest from upper electrode 11d, and is disposed at the center of vibrating membrane 16 in this modification. When vibrating membrane 16 has a substantially circular shape, upper electrode 11a has a substantially circular structure, and upper electrodes other than upper electrode 11a (for example, upper electrode 11d) have an annular structure. In other words, upper electrode 11a is surrounded by upper electrodes other than upper electrode 11a (for example, upper electrode 11d).

[0077] The upper electrodes 11d, which is the end 51B of the piezoelectric element 50B, have a region that overlaps with the membrane support portion 17 when viewed from the normal direction to the vibration membrane 16.

[0078] With this configuration, a potential difference is generated between the multiple upper electrodes and the lower electrode 12e. The lower electrode 12e is paired with each of the multiple upper electrodes, and the lower electrode 12e is shared by each pair. By sharing the lower electrode 12e, the number of electrode pads and the types of driving voltages to be applied can be reduced, making the manufacturing process simpler.

[0079] As mentioned above, although several modifications have been described, the descriptions and drawings forming part of the disclosure should be understood as illustrative and not restrictive. From this disclosure, various alternative modifications and operating techniques will become apparent to those skilled in the art.

[0080] (Second embodiment) The system according to this embodiment will be described. The system according to this embodiment includes the above-mentioned piezoelectric element and a film 15. The vibrating body including the piezoelectric element and the film 15 can change the resonance frequency.

[0081] The system has a function of selecting the drive voltages to be applied to the electrodes 11 and 12 of the piezoelectric element 50, respectively, and selecting the combination that provides the highest efficiency in response to an external input (such as a sound wave). For example, in the piezoelectric element of the first embodiment, a vibrating body, in which electrodes 11 and 12 are stacked to apply a sine wave of 0 to 5 V, is vibrated by an external input. When the vibrating body receives the vibration, a signal (electrical signal) is generated between the electrodes 11 and 12 due to the positive piezoelectric effect, and the signal is extracted. In other words, the electrodes 11 and 12 are used as a vibration sensor for sensing the electrical signal. Generally, the receiving frequency at which a vibration sensor is most sensitive is the resonant frequency of the vibrating body that serves as the sensing device. The system can achieve the highest sensitivity and a more optimal state in response to an external input by adjusting the resonant frequency of the vibrating body itself, which serves as a vibration sensor.

[0082] The method of combining (selecting) drive voltages is, for example, by having the user input transmitter information (such as the transmission frequency) into the system, and the system's control unit selects the optimal combination. This selection allows the vibrator to be in the most optimal state with the highest sensitivity.

[0083] With this configuration, it is possible to provide a system that adjusts the resonant frequency of the vibrator so that the vibrator is in the most optimal state with the highest sensitivity to external input.

[0084] (Other embodiments) Although several embodiments have been described above, the descriptions and drawings forming part of the disclosure are illustrative and should not be understood as limiting. From this disclosure, various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art.

[0085] The present invention is related to the subject matter of Japanese Patent Application No. 2020-088169, filed on May 20, 2020, the entire disclosure of which is incorporated herein by reference. [Explanation of symbols]

[0086] 10, 10A, 10B transducers 11 electrodes 11a, 11b, 11c, 11d Upper electrode 12 electrodes 12a, 12b, 12c, 12d, 12e bottom electrode 13, 13a, 13b, 13c, 13d, 13e Piezoelectric film 15 Membrane body 16. Vibration membrane 17 Membrane support part 18 Inflection Point 21a, 21b, 21c, 21d, 22a, 22b, 22c, 22d, 22e Electrode pads 30a, 30d, 40a, 40d laminate 50, 50A, 50B Piezoelectric element 51, 51A, 51B end

Claims

1. a piezoelectric element; a membrane body including a membrane support part having a hollow part, and a vibration membrane connected to the membrane support part and displaceable in a thickness direction, and the piezoelectric element is laminated on the vibration membrane; The piezoelectric element is a first laminate including a first pair of electrodes and a first piezoelectric film sandwiched between the first pair of electrodes; A transducer comprising: a second stack comprising a second pair of electrodes; a second piezoelectric film sandwiched between the second pair of electrodes; and a second stack spaced apart from the first stack.

2. the piezoelectric element further includes a third laminate including a third pair of electrodes and a third piezoelectric film sandwiched between the third pair of electrodes; The transducer of claim 1 , wherein the third stack is sandwiched between the first stack and the second stack and spaced apart from the first stack and the second stack.

3. a piezoelectric element; a membrane body including a membrane support part having a hollow part, and a vibration membrane connected to the membrane support part and displaceable in a thickness direction, and the piezoelectric element is laminated on the vibration membrane; The piezoelectric element is a first electrode; a first laminate including a first piezoelectric film and a second electrode; a second laminate comprising a second piezoelectric film and a third electrode, the second laminate being spaced apart from the first laminate; the first piezoelectric film is sandwiched between the first electrode and the second electrode; The second piezoelectric film is sandwiched between the first electrode and the third electrode.

4. The transducer of claim 3 , wherein the first piezoelectric film and the second piezoelectric film are located on the first electrode.

5. the piezoelectric element further includes a third laminate including a third piezoelectric film and a fourth electrode; The transducer according to claim 3 or 4, wherein the third laminate is sandwiched between the first laminate and the second laminate and is spaced apart from the first laminate and the second laminate.

6. 6. The transducer according to claim 1, wherein an end of the second laminate has a region that overlaps with the membrane support portion when viewed from a normal direction to the vibration membrane.

7. The transducer according to any one of claims 1 to 6, wherein the first laminate is surrounded by the second laminate.

8. a piezoelectric element; a membrane body including a membrane support part having a hollow part, and a vibration membrane connected to the membrane support part and displaceable in a thickness direction, and the piezoelectric element is laminated on the vibration membrane; The piezoelectric element is a first electrode; a second electrode; and a piezoelectric film sandwiched between the first electrode and the second electrode; a third electrode; the piezoelectric film is sandwiched between the first electrode and the third electrode, The third electrode is spaced apart from the second electrode.

9. The transducer according to claim 8 , wherein an end of the third electrode has a region that overlaps with the membrane support portion when viewed from a normal direction to the vibration membrane.

10. 10. The transducer of claim 8 or 9, wherein the piezoelectric film is located on the first electrode.

11. the piezoelectric element further has a fourth electrode; the piezoelectric film is sandwiched between the first electrode and the fourth electrode, The transducer according to any one of claims 8 to 10, wherein the fourth electrode is sandwiched between the second electrode and the third electrode and is spaced apart from the second electrode and the third electrode.

12. The transducer according to any one of claims 8 to 11, wherein the second electrode is surrounded by the third electrode.

13. 13. The transducer according to claim 1, wherein the vibration membrane has a doubly supported beam shape.

14. 14. The transducer according to claim 1, wherein the piezoelectric element has a function of changing the resonance frequency of a vibrating body including the piezoelectric element and the film body.

15. a piezoelectric element; A method for driving a transducer having a membrane body, the membrane body comprising a membrane support part having a hollow part, a vibration membrane connected to the membrane support part and displaceable in a thickness direction, and the piezoelectric element being laminated on the vibration membrane, The piezoelectric element is A lower electrode; a piezoelectric film on the lower electrode; a plurality of spaced apart upper electrodes on the piezoelectric film; one end of the plurality of upper electrodes has a first region closest to the membrane support; applying a control voltage to the upper electrode of the first region, opening the upper electrode, and opening the lower electrode; A method for driving a transducer, which changes the resonant frequency of a vibrating body comprising the piezoelectric element and the film body by applying a control voltage or a waveform voltage independently to each of the remaining upper electrodes, opening the upper electrodes, and opening the lower electrodes.

16. the first region overlaps with the membrane support portion when viewed from a normal direction to the vibration membrane, 16. The method of driving a transducer according to claim 15, further comprising applying a waveform voltage to an upper electrode having a second region furthest from the first region.

17. The method of driving a transducer according to claim 16 , wherein the upper electrode of the second region is surrounded by the upper electrode of the first region.

18. A method for driving a transducer as described in claim 16 or 17, wherein the control voltage is applied to all upper electrodes sandwiched between the upper electrode closest to the second region and the upper electrode of the first region.

19. The transducer driving method according to any one of claims 15 to 18, wherein a plurality of the piezoelectric films are provided so as to be spaced apart from each other.

20. The transducer driving method according to claim 19 , wherein the lower electrode is provided in a plurality of electrodes spaced apart from each other.

21. a piezoelectric element; A system including a membrane body including a membrane support part having a hollow part, a vibration membrane connected to the membrane support part and displaceable in a thickness direction, and the piezoelectric element stacked on the vibration membrane, The piezoelectric element is A lower electrode; a piezoelectric film on the lower electrode; a plurality of spaced apart upper electrodes on the piezoelectric film; one end of the plurality of upper electrodes has a first region closest to the membrane support; applying a control voltage to the upper electrode of the first region, opening the upper electrode, opening the lower electrode, and extracting a signal generated by vibration of the film body; A system that applies a control voltage independently to each of the remaining upper electrodes so as to maximize reception efficiency for external signals, and performs one of the following operations selected from the group consisting of opening the upper electrode, opening the lower electrode, and extracting signals generated by vibration of the membrane body.

22. the first region overlaps with the membrane support portion when viewed from a normal direction to the vibration membrane, 22. The system of claim 21, wherein the signal generated by the vibration of the membrane is picked up at a second region that is furthest from the first region.

23. 23. The system of claim 22, wherein the upper electrode of the second region is surrounded by the upper electrode of the first region.

24. 24. The system of claim 22 or 23, wherein the control voltage is applied to all upper electrodes sandwiched between the upper electrode closest to the second region and the upper electrode of the first region.

25. The system according to any one of claims 21 to 24, wherein a plurality of the piezoelectric films are provided so as to be spaced apart from each other.

26. The system of claim 25 , wherein the lower electrode is provided in a plurality of locations spaced apart from each other.

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