JP6189648B2 - Piezoelectric vibration element, piezoelectric vibration device using the same, and portable terminal - Google Patents

Description

  The present invention relates to a piezoelectric vibration element, a piezoelectric vibration device using the same, and a portable terminal.

  2. Description of the Related Art Conventionally, a piezoelectric vibration device is known that vibrates a diaphragm by fixing a plate-like piezoelectric bimorph element to the diaphragm and vibrating the piezoelectric bimorph element (see, for example, Patent Document 1).

JP 2006-238072 A

  However, in the above-described conventional piezoelectric vibration device, the amplitude of the diaphragm changes abruptly at a specific frequency, and the sound information to be transmitted is distorted when the sound information is transmitted by the vibration of the diaphragm. There was a problem.

  The present invention has been devised in view of such problems in the prior art, and an object of the present invention is to provide a piezoelectric vibration element capable of realizing a vibration device in which an abrupt change in amplitude at a specific frequency is reduced, and It is to provide a piezoelectric vibration device and a portable terminal using the same.

The piezoelectric vibration element of the present invention has at least a plurality of piezoelectric layers and a plurality of electrodes, and each of the piezoelectric layers is a portion sandwiched between the electrodes connected to different potentials. It has a vibrating part that is a part that receives a signal and undergoes stretching vibration, and has a rectangular parallelepiped shape having a length direction along the stretching direction, along a direction perpendicular to the stretching direction of the stretching vibration in the vibrating part. The piezoelectric layers and the electrodes are alternately arranged, and the expansion and contraction in the expansion / contraction vibration are reversed on one side and the other side in the direction perpendicular to the expansion / contraction direction, and the electric signal is A piezoelectric vibration element that receives input and flexurally vibrates, wherein a position of a center of the expansion / contraction direction in the vibration part of each piezoelectric layer changes along a direction perpendicular to the expansion / contraction direction. It is what.

  The piezoelectric vibration device of the present invention includes at least the piezoelectric vibration element and a vibration plate bonded to a surface on one side in a direction perpendicular to the expansion / contraction direction of the piezoelectric vibration element. An average position of the plurality of piezoelectric layers in the expansion / contraction direction in the vibration part of the layer is different from a central position of the diaphragm in the expansion / contraction direction. .

  The portable terminal according to the present invention includes at least the piezoelectric vibration device and an electronic circuit that generates an electric signal input to the piezoelectric vibration element.

According to the piezoelectric vibration element of the present invention, it is possible to obtain a piezoelectric vibration element capable of realizing a vibration device in which an abrupt change in amplitude at a specific frequency is reduced. According to the piezoelectric vibration device of the present invention, it is possible to obtain a piezoelectric vibration device in which a sudden change in amplitude at a specific frequency is reduced. According to the mobile terminal of the present invention, it is possible to obtain a mobile terminal capable of transmitting audio information with small distortion.

1 is a perspective view schematically showing a piezoelectric vibration element of a first example of an embodiment of the present invention. (A)-(e) is a top view for demonstrating the structure of the piezoelectric vibration element shown in FIG. It is a figure for demonstrating the structure of the piezoelectric vibration element shown in FIG. It is sectional drawing for demonstrating the structure of the piezoelectric vibration element shown in FIG. It is a perspective view which shows typically the piezoelectric vibration apparatus of the 2nd example of embodiment of this invention. FIG. 6 is a sectional view taken along line D-D ′ in FIG. 5. It is a perspective view which shows typically the portable terminal of the 3rd example of embodiment of this invention. FIG. 8 is a cross-sectional view taken along line A-A ′ in FIG. 7. FIG. 8 is a sectional view taken along line B-B ′ in FIG. 7.

  Hereinafter, a piezoelectric vibration element of the present invention, a piezoelectric vibration device using the same, and a portable terminal will be described in detail with reference to the accompanying drawings.

(First example of embodiment)
FIG. 1 is a perspective view schematically showing a piezoelectric vibration element 14 which is a first example of an embodiment of the present invention. 2A to 2E are plan views schematically showing the shapes of the electrodes 21 to 25 included in the piezoelectric vibration element 14 shown in FIG. 2A to 2D show a state seen from the + z direction side, and FIG. 2E shows a state seen from the −z direction side. FIG. 3 is a diagram schematically showing the positional relationship between the electrodes 21 to 25 in the z-axis direction and the state of polarization of the piezoelectric layer 27 disposed between the electrodes 21 to 25. In FIG. 3, the stacked body 20, the first to third terminal electrodes, and the piezoelectric layer 27 are not shown.

  The piezoelectric vibration element 14 of this example has a rectangular parallelepiped shape in which the z-axis direction is the thickness direction, the x-axis direction is the length direction, and the y-axis direction is the width direction. In addition, the piezoelectric vibration element 14 includes the multilayer body 20, a first terminal electrode 41, a second terminal electrode 42, and a third terminal electrode (not shown).

  A first terminal electrode 41 and a second terminal electrode 42 are disposed on the end face on the + x direction side of the stacked body 20 so as to straddle both end faces in the z-axis direction. A third terminal electrode (not shown) is disposed on the end surface on the −x direction side of the stacked body 20.

  The laminated body 20 is configured by alternately arranging a plurality of piezoelectric layers 27 polarized in the z-axis direction and a plurality of flat electrodes 21 to 25 along the z-axis direction. The electrode 23 is disposed on the surface of the stacked body 20 on the + z direction side. The electrode 25 is disposed on the surface of the stacked body 20 on the −z direction side. A plurality of electrodes 21, electrodes 22, and electrodes 24 are arranged inside the stacked body 20. And the electrode 21 or the electrode 22, and the electrode 23 or the electrode 24 or the electrode 25 are alternately arranged in the z-axis direction (in the laminated body 20, the electrode 21 or the electrode 22 and the electrode 24 are Are alternately arranged in the z-axis direction). On the + z direction side, the electrodes 23 or 24 and the electrodes 21 are alternately arranged, and on the −z direction side, the electrodes 24 or the electrodes 25 and the electrodes 22 are alternately arranged.

The electrode 21 has a structure in which one end of a rectangular lead portion 21b is connected to one end of a rectangular main body portion 21a formed at a distance from the side surface of the laminate 20. Drawer 21
The other end of b is connected to the first terminal electrode 41. The electrode 22 has a structure in which one end of a rectangular lead portion 22b is connected to one end of a rectangular main body portion 22a formed at a distance from the side surface of the laminate 20. The other end of the lead portion 22 b is connected to the second terminal electrode 42. Each of the electrodes 23, 24, 25 has a rectangular shape in which only one end in the length direction is exposed on the side surface of the stacked body 20. One end in the length direction of each of the electrodes 23, 24, and 25 is connected to a third terminal electrode (not shown).

  The piezoelectric layer 27 disposed between the electrodes 21 to 25 is polarized in the direction indicated by the arrow in FIG. In other words, the + z direction side is polarized in the direction from the electrode 21 toward the electrodes 23 and 24, and the −z direction side is polarized in the direction from the electrodes 24 and 25 toward the electrode 22. When the piezoelectric vibration element 14 is vibrated, for example, the electrodes 21 and 22 are at the same potential, the electrodes 23, 24 and 25 are at the same potential, and between the electrodes 21 and 22 and the electrodes 23, 24 and 25. An electric signal (alternating voltage) is applied so that a potential difference is generated between the two. Thereby, the direction of polarization with respect to the direction of the electric field applied at a certain moment is reversed between the piezoelectric layer 27 located on the + z direction side and the piezoelectric layer 27 located on the −z direction side.

  Therefore, when an electric signal is applied and the piezoelectric layer 27 positioned on the + z direction side extends in the x-axis direction at a certain moment, the piezoelectric layer 27 positioned on the −z direction side contracts in the x-axis direction. It is supposed to be. As a result, the piezoelectric vibration element 14 bends and vibrates in the z-axis direction so that the amplitude changes along the x-axis direction when an electric signal is input. Thus, the piezoelectric vibration element 14 is configured by a piezoelectric body (piezoelectric bimorph element) having a bimorph structure.

  FIG. 4 is a schematic cross-sectional view for explaining the structure of the piezoelectric vibration element shown in FIG. 1 in more detail. In FIG. 4, for ease of illustration, the first to third terminal electrodes are not shown, and the piezoelectric layer 27 has only four layers 27a, 27b, 27c, and 27d. 21 shows a state in which there is only one electrode 22 and one electrode 24.

  The piezoelectric layers 27a to 27d are arranged in the order of 27a, 27b, 27c, and 27d from the + z direction side, and the electrodes 21 to 25 are arranged in the order of 23, 21, 24, 22, and 25 from the + z direction side. Yes. That is, the electrode 23 is disposed on the surface of the piezoelectric layer 27a on the + z direction side, the electrode 21 is disposed between the piezoelectric layers 27a and 27b, and the electrode 24 is composed of the piezoelectric layers 27b and 27c. The electrode 22 is disposed between the piezoelectric layers 27c and 27d, and the electrode 25 is disposed on the surface of the piezoelectric layer 27d on the −z direction side.

  Therefore, in the piezoelectric layer 27a, a portion sandwiched between the electrode 23 and the electrode 21 becomes a vibrating portion 28a that is a portion that expands and contracts in the x-axis direction when an electric signal is input, and in the piezoelectric layer 27b, the electrode The portion sandwiched between 21 and the electrode 24 becomes a vibrating portion 28b that is a portion that expands and contracts in the x-axis direction when an electric signal is input. In the piezoelectric layer 27c, the portion sandwiched between the electrode 24 and the electrode 22 The vibration portion 28c is a portion that expands and contracts in the x-axis direction when an electric signal is input. In the piezoelectric layer 27d, the portion sandwiched between the electrode 22 and the electrode 25 receives the electric signal and is in the x-axis direction. It is a vibration part 28d which is a part that expands and contracts.

Then, the position of the center 29a in the x-axis direction in the vibration portion 28a of the piezoelectric layer 27a located closest to the + z direction side in the piezoelectric vibration element 14 and the piezoelectric layer located second from the + z direction side in the piezoelectric vibration element 14 The position of the center 29b in the x-axis direction of the vibrating portion 28b of 27b is different, and the center in the x-axis direction of the vibrating portion 28c of the piezoelectric layer 27c located third from the + z direction side in the piezoelectric vibrating element 14 is different. The position of 29c is different from the position of the center 29d in the x-axis direction in the vibrating portion 28d of the piezoelectric layer 27d located fourth from the + z direction side in the piezoelectric vibration element 14. That is, the positions of the centers 29a to 29d in the expansion / contraction direction (x-axis direction) in the vibrating portions 28a to 28d of the piezoelectric layers 27a to 27d change along the direction perpendicular to the expansion / contraction direction (z-axis direction). Yes. Thus, “the position of the center of the expansion / contraction direction in the vibration part of each piezoelectric layer changes along the direction perpendicular to the expansion / contraction direction” means that the piezoelectric vibration element is perpendicular to the expansion / contraction direction. This means that the position of the center in the expansion / contraction direction of the vibration part of the piezoelectric layer changes depending on the position of the piezoelectric layer in the direction.

  As described above, the piezoelectric vibration element 14 of this example includes at least the plurality of piezoelectric layers 27 and the plurality of electrodes 21 to 25, and each piezoelectric layer 27 is an electrode connected to a different potential. The vibration portions 28a to 28d are portions that are sandwiched between and vibrate when an electric signal is input, and in the expansion / contraction direction (stretching direction) of the expansion / contraction vibration in each of the vibration portions 28a to 28d. The piezoelectric layers 27 and the electrodes 21 to 25 are alternately arranged along the vertical direction (z-axis direction), and stretching vibration occurs on one side and the other side in the direction perpendicular to the stretching direction (z-axis direction). The piezoelectric vibration element 14 that is reversely expanded and contracted and receives an electric signal to bend and vibrate in the z-axis direction, and the expansion and contraction directions (in the vibration portions 28a to 28d of the piezoelectric layers 27a to 27d) center in the x-axis direction) Position of 9a~29d is altered along the vertical direction (z axis direction) in the stretch direction. Thus, an electric signal is input, and the piezoelectric vibration element 14 is in a direction perpendicular to the expansion / contraction direction of the vibration units 28a to 28d so that the amplitude changes along the expansion / contraction direction (x-axis direction) of the vibration units 28a to 28d. When bending vibration occurs in the z-axis direction, the standing wave in the x-axis direction in the bending vibration of the piezoelectric vibration element 14 can be dispersed. Therefore, when a piezoelectric vibration device is configured in which the vibration plate is vibrated by the vibration of the piezoelectric vibration element 14 by joining the principal surface of the vibration plate to the bent surface (surface in the z-axis direction) of the piezoelectric vibration element 14. A sudden change in amplitude in frequency can be reduced. That is, it is possible to realize a piezoelectric vibration device having vibration characteristics with little sudden change in amplitude according to a change in frequency. Therefore, when sound is generated by the vibration of the diaphragm, it is possible to generate sound with little sudden change in sound thickness according to the change in frequency.

  In addition, the change (piezoelectric direction) of the positions of the centers 29a to 29d in the expansion / contraction direction (x-axis direction) of the vibrating portions 28a to 28d of the piezoelectric layers 27a to 27d is perpendicular to the expansion / contraction direction (z-axis direction). When the difference between the body layers is increased, the effect of reducing a sudden change in amplitude at a specific frequency is increased, but the intensity of the generated vibration is reduced overall. Therefore, the amount of change in the positions of the centers 29a to 29d in the expansion / contraction direction (x-axis direction) in the vibration units 28a to 28d is appropriately set according to desired characteristics.

  In addition, the piezoelectric vibration element 14 of this example has the vibrations of the piezoelectric layers 27b and 27c other than the piezoelectric layers 27a and 27d positioned on the outermost side in the direction (z-axis direction) perpendicular to the expansion / contraction direction of the vibration portions 28a to 28d. The positions of the centers 29b and 29c in the expansion / contraction direction (x-axis direction) of the portions 28b and 28c are made equal, and the expansion / contraction direction (x-axis direction) of the vibrating portions 28a and 28d of the piezoelectric layers 27a and 27d located on the outermost side. Only the positions of the centers 29a and 29d are different. As a result, when a vibration device is configured by attaching a diaphragm to the surface in the direction perpendicular to the expansion / contraction direction of the piezoelectric vibration element 14 (z-axis direction), the piezoelectric device reduces the sudden change in amplitude at a specific frequency. A decrease in the vibration intensity of the vibration element 14 can be reduced.

  Moreover, since the piezoelectric vibration element 14 of this example has a long shape in the expansion / contraction direction (x-axis direction) in the vibration portions 28a to 28d, the effect of reducing a sudden change in amplitude according to a change in frequency. Can be further enhanced.

Further, in the piezoelectric vibration element 14 of this example, the position C1 obtained by averaging the positions of the centers 29a to 29d in the expansion / contraction direction (x-axis direction) of the vibration portions 28a to 28d of each piezoelectric layer 27 with respect to the plurality of piezoelectric layers 27. Is different from the center position C2 of the piezoelectric vibration element 14 in the expansion / contraction direction (x-axis direction). Thus, an electric signal is input, and the piezoelectric vibration element 14 is in a direction perpendicular to the expansion / contraction direction of the vibration units 28a to 28d so that the amplitude changes along the expansion / contraction direction (x-axis direction) of the vibration units 28a to 28d. When bending vibration occurs in the (z-axis direction), the standing wave in the x-axis direction in the bending vibration of the piezoelectric vibration element 14 can be further dispersed. Therefore, when a piezoelectric vibration device is configured in which the vibration plate is vibrated by the vibration of the piezoelectric vibration element 14 by joining the principal surface of the vibration plate to the bent surface (surface in the z-axis direction) of the piezoelectric vibration element 14. A sudden change in amplitude in frequency can be further reduced.

  When calculating the position C1 obtained by averaging the positions of the centers 29a to 29d in the expansion / contraction direction (x-axis direction) of the vibration portions 28a to 28d of each piezoelectric layer 27 with respect to the plurality of piezoelectric layers 27, the expansion / contraction direction is calculated. It is necessary to obtain an average after weighting by the area of the vibrating portions 28a to 28d when viewed in plan from the direction perpendicular to the z-axis direction (z-axis direction). For example, in the piezoelectric layers 27a to 27d, the distances from one end in the expansion / contraction direction (x-axis direction) of the piezoelectric vibration element 14 to the centers 29a to 29d of the vibration portions 28a to 28d are x1, x2, x3, and x4, respectively. When the areas of the vibration units 28a to 28d in plan view are s1, s2, s3, and s4, respectively, the distance x5 from one end in the expansion / contraction direction (x-axis direction) of the piezoelectric vibration element 14 is x5 = ( The position of x1s1 + x2s2 + x3s3 + x4s4) / (s1 + s2 + s3 + s4) is defined as the position of C1.

  Increasing the amount of positional deviation of C1 with respect to C2 increases the effect of reducing a sudden change in amplitude at a specific frequency, but reduces the strength of the generated vibration as a whole. Therefore, the amount of misalignment of C1 with respect to C2 is set as appropriate according to the desired characteristics.

  In the piezoelectric vibration element 14 of this example, the laminate 20 can have a length of about 18 mm to 28 mm, a width of about 1 mm to 6 mm, and a thickness of about 0.2 mm to 1.0 mm, for example. The lengths of the electrodes 21 to 25 can be set to, for example, about 17 mm to 25 mm, and the widths of the electrodes 21 to 25 can be set to, for example, about 0.5 mm to 1.5 mm.

  The piezoelectric layer 27 constituting the laminate 20 is preferably made of, for example, lead-free piezoelectric material such as lead titanate (PT), lead zirconate titanate (PZT), Bi layered compound, tungsten bronze structure compound, or the like. However, other piezoelectric materials may be used. The thickness of one layer of the piezoelectric layer 27 can be set to, for example, about 0.01 to 0.1 mm. The electrodes 21, 22, and 24 can be formed by suitably using, for example, a ceramic component or a glass component in addition to a metal component such as silver or an alloy of silver and palladium. You may form using a known metal material. The electrodes 23 and 25 and the first to third terminal electrodes desirably contain a metal component made of silver and a glass component, but may be a metal other than silver.

  Such a piezoelectric vibration element 14 can be manufactured by the following method, for example. First, a binder, a dispersant, a plasticizer, and a solvent are added to the piezoelectric material powder, and the mixture is agitated to produce a slurry. The obtained slurry is formed into a sheet shape to produce a green sheet. Next, a conductive paste is printed on the green sheet to form electrode patterns to be the electrodes 21, 22, and 24. The green sheets on which the electrode patterns are formed are stacked and pressed using a press device to form a laminated molded body Is made. Then, degreasing and baking are performed, and a laminated body is obtained by cutting to a predetermined dimension. Next, after printing the conductor paste for forming the electrodes 23 and 25, the first terminal electrode 41, the second terminal electrode 42, and the third terminal electrode (not shown) and baking them at a predetermined temperature The piezoelectric layer 27 is polarized by applying a DC voltage through the first to third terminal electrodes. In this way, the piezoelectric vibration element 14 can be obtained.

In addition, for example, when a problem occurs when the electrode is exposed on the end face in the direction perpendicular to the expansion / contraction direction of the stacked body 20 (z-axis direction), a protective layer made of a piezoelectric body or the like may be provided. In that case, it is desirable to sufficiently reduce the thickness of the protective layer.

(Second example of embodiment)
FIG. 5 is a perspective view schematically showing a piezoelectric vibration device 15 according to a second example of the embodiment of the present invention. FIG. 6 is a cross-sectional view taken along the line DD ′ in FIG. 5 and 6, the detailed structure of the piezoelectric vibration element 14 is not shown in order to facilitate drawing. Moreover, in this example, a different point from the 1st example of embodiment mentioned above is demonstrated, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted. The piezoelectric vibration device 15 of this example includes the piezoelectric vibration element 14 and the diaphragm 12 of the first example of the above-described embodiment.

  The vibration plate 12 has a rectangular thin plate shape, and has one main surface (on the −z direction side in the drawing) on the surface on one side (+ z direction side) perpendicular to the expansion / contraction direction of the piezoelectric vibration element 14. Are joined using an adhesive or the like. Such a diaphragm 12 can be preferably formed using a material having high rigidity and elasticity, such as acrylic resin or glass. Moreover, the thickness of the diaphragm 12 is set to about 0.4 mm to 1.5 mm, for example. The piezoelectric vibration device 15 of this example having such a configuration functions as a piezoelectric vibration device that vibrates the diaphragm 12 by bending vibration of the piezoelectric vibration element 14 by applying an electric signal.

  In the piezoelectric vibration device 15 of this example, the position C1 obtained by averaging the center positions in the expansion / contraction direction (x-axis direction) of the vibration portions of the piezoelectric layers 27 for all the piezoelectric layers 27 is the expansion / contraction direction. This is different from the center position C3 of the diaphragm 12 in the (x-axis direction). As a result, the standing wave in the x-axis direction generated in the vibration of the diaphragm 12 can be dispersed, so that a sudden change in amplitude at a specific frequency can be reduced in the vibration of the diaphragm 12. That is, according to the piezoelectric vibration device 15 of the present example, it is possible to obtain a piezoelectric vibration device having vibration characteristics with little abrupt change in amplitude according to a change in frequency.

  In addition, the piezoelectric vibration device 15 of this example has a position C1 in which the center position in the expansion / contraction direction (x-axis direction) in the vibration part of each piezoelectric layer 27 is averaged for all the piezoelectric layers 27, and the expansion / contraction direction. The central position C2 of the piezoelectric vibration element 14 in the (x-axis direction) and the central position C3 of the diaphragm 12 in the expansion / contraction direction (x-axis direction) are all different. Thereby, the standing wave in the x-axis direction generated in the vibration of the diaphragm 12 can be further dispersed, so that a sudden change in amplitude at a specific frequency can be further reduced.

  Increasing the amount of misalignment of C1 with respect to C3 increases the effect of reducing the level of a peak occurring at a specific frequency in the vibration characteristics of the diaphragm 12, but the intensity of the generated vibration is reduced overall. . Therefore, the amount of positional deviation of C1 with respect to C3 is appropriately set according to the desired characteristics.

(Third example of embodiment)
FIG. 7 is a perspective view schematically showing a mobile terminal according to a third example of the embodiment of the present invention. 8 is a cross-sectional view taken along line AA ′ in FIG. 9 is a cross-sectional view taken along line BB ′ in FIG. 8 and 9, the detailed structure of the piezoelectric vibration element 14 is not shown. Moreover, in this example, a different point from the 2nd example of embodiment mentioned above is demonstrated, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted. The portable terminal of this example includes the piezoelectric vibration device 15 of the second example of the embodiment shown in FIGS. 5 and 6, an electronic circuit 17, a display 18, and a housing 19.

The electronic circuit 17 generates an electrical signal that is input to the piezoelectric vibration element 14. The electronic circuit 17 may include other circuits such as a circuit for processing image information to be displayed on the display 18 and a communication circuit. The electronic circuit 17 and the piezoelectric vibration element 14 are connected via a wiring (not shown).

  The display 18 is a display device having a function of displaying image information. For example, a known display such as a liquid crystal display, a plasma display, and an organic EL display can be suitably used. The display 18 may have an input device such as a touch panel.

  The housing 19 has a box shape with one surface opened. The housing 19 can be preferably formed using a material such as a synthetic resin having high rigidity and elasticity, but may be formed using another material such as a metal.

  In the portable terminal of this example, the diaphragm 12 is disposed outside the display 18 and integrated with the display 18, and functions as a cover that protects the display 18. Further, the diaphragm 12 has only one main surface (main surface on the −z direction side in the figure) around the casing 19 joined to the casing 19 with an adhesive or the like, and is attached to the casing 19 so as to vibrate. . The diaphragm 12 may have an input device such as a touch panel.

  The mobile terminal of this example having such a configuration can generate sound by vibrating the diaphragm 12 by vibrating the piezoelectric vibrating element 14. And the sound information can be transmitted to a person by this sound. In addition, audio information may be transmitted by transmitting vibration by bringing the diaphragm 12 or the casing 19 into contact with a part of a human body such as an ear directly or via another object.

  Since the portable terminal of this example transmits voice information using the piezoelectric vibration device 15 in which a sudden change in amplitude at a specific frequency is reduced, a portable terminal capable of transmitting high-quality voice information with small distortion is provided. Can be obtained.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the scope of the present invention.

  For example, in FIG. 4, the positions of the centers 29a and 29d in the x-axis direction in the vibrating portions 28a and 28d of the piezoelectric layers 27a and 27d located on the outermost side in the z-axis direction are equal, and the piezoelectric layer 27b located on the inner side. 27c has been shown in which the positions of the centers 29b and 29c in the x-axis direction of the vibrating portions 28b and 28c are equal. However, the present invention is not limited to this. For example, the center position of the vibration part in the expansion / contraction direction may be different in all the piezoelectric layers.

  3 shows an example in which the piezoelectric vibration element 14 has 16 piezoelectric layers 27. In FIG. 4, the piezoelectric vibration element 14 has four piezoelectric layers 27a to simplify the illustration. , 27b, 27c, and 27d are shown, but the present invention is not limited to this. The number of piezoelectric layers 27 can be appropriately set according to desired vibration strength and thickness.

  In the second and third examples of the above-described embodiment, the example having the piezoelectric vibration element 14 of the first example of the embodiment has been described. However, the present invention is not limited to this. You may have a piezoelectric vibration element of a form.

  Further, in the third example of the above-described embodiment, the example in which the cover of the display 18 functions as the diaphragm 12 is shown, but the present invention is not limited to this. For example, the display 18 itself may function as the diaphragm 12.

12: Diaphragm 14: Piezoelectric vibration element 15: Piezoelectric vibration device 17: Electronic circuits 21, 22, 23, 24, 25: Electrodes 27, 27a, 27b, 27c, 27d: Piezoelectric layers 28a, 28b, 28c, 28d: Vibration part

Claims (5)

Having at least a plurality of piezoelectric layers and a plurality of electrodes,
Each of the piezoelectric layers is a portion sandwiched between the electrodes that are connected to different potentials, and has a vibrating portion that is a portion that receives an electric signal and undergoes stretching vibration,
A rectangular parallelepiped shape having a length direction along the stretching direction, and the piezoelectric layers and the electrodes are alternately arranged along a direction perpendicular to the stretching direction of the stretching vibration in the vibrating portion , and A piezoelectric vibration element in which expansion and contraction in the stretching vibration are reversed between one side and the other side in a direction perpendicular to the stretching direction, and an electric signal is input to bend and vibrate,
The piezoelectric vibration element, wherein a position of a center of the expansion / contraction direction in the vibration part of each piezoelectric layer is changed along a direction perpendicular to the expansion / contraction direction.   The average position of the plurality of piezoelectric layers in the expansion / contraction direction center position of the piezoelectric layer of each piezoelectric layer is different from the central position of the piezoelectric vibration element in the expansion / contraction direction. The piezoelectric vibration element according to claim 1. The piezoelectric vibration element according to claim 1 or 2, and at least a vibration plate bonded to a surface on one side in a direction perpendicular to the expansion and contraction direction of the piezoelectric vibration element,
A position obtained by averaging the center positions in the expansion / contraction direction in the vibration part of each of the piezoelectric layers is different from the center position of the diaphragm in the expansion / contraction direction. Piezoelectric vibration device. The shape of the diaphragm in plan view is a rectangular shape having a longitudinal direction and a short direction, and the expansion / contraction direction of the piezoelectric vibration element is arranged along the short direction of the diaphragm. , the position of the center of the expansion and contraction direction of the vibrating portion of each of the piezoelectric layer, the average position for the plurality of piezoelectric layers, has a central position and different of the diaphragm in front Symbol stretching direction The piezoelectric vibration device according to claim 3.   5. A portable terminal comprising at least the piezoelectric vibration device according to claim 3 and an electronic circuit that generates an electric signal input to the piezoelectric vibration element.