JP2023124384A - piezoelectric vibration device - Google Patents

Abstract

To provide a long life piezoelectric vibration device.SOLUTION: A disclosed piezoelectric vibration device 100 includes: a piezoelectric element 120; a diaphragm 110 joined to the piezoelectric element 120; a first protective layer 151 coating the piezoelectric element 120 and the diaphragm 110 on the side where piezoelectric element 120 is joined; and a second protective layer 152 coating the diaphragm 110 on the side opposite to the first protective layer 151. The diaphragm 120 has a base layer 111 and a surface layer 112 laminated on the base layer 111 and bonded to the piezoelectric element 120.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a piezoelectric vibration device having a piezoelectric element and a diaphragm.

As shown in FIGS. 9(a) and 9(b), a thin piezoelectric speaker 400 has been developed in which a disk-shaped piezoelectric element 420 is bonded to a conductive flat plate-shaped diaphragm 410. . An electrode 431 is attached to the surface of the piezoelectric element 420 opposite to the surface bonded to the diaphragm 410 . Another electrode 432 is attached to the diaphragm 410 .

In the piezoelectric speaker 400 shown in FIG. 9A , a positive voltage is applied to the electrode 431 while a negative voltage is applied to the electrode 432 . This voltage application expands the piezoelectric element 420 in the radial direction. At this time, diaphragm 410 is elastically curved so as to be convex toward piezoelectric element 420 . When the voltage applied to the electrodes 431 and 432 is removed, the diaphragm 410 restores to its original flat plate shape.

In the piezoelectric speaker 400 shown in FIG. 9(b), the polarities of the voltages applied to the electrodes 431 and 432 are opposite to the polarities of the voltages shown in FIG. 9(a). In this state, the piezoelectric element 420 contracts in the radial direction, and the vibration plate 410 is elastically curved so as to protrude on the side opposite to the piezoelectric element 420 .

By applying an AC voltage to the electrodes 431 and 432, the state shown in FIG. 9(a) and the state shown in FIG. 9(b) are repeated. In other words, the vibration plate 410 vibrates by repeating bending deformation to become convex toward the piezoelectric element 420 and bending deformation to become convex toward the side opposite to the piezoelectric element 420 . When the diaphragm 410 vibrates in this way, if the polarity of the voltage is switched at the timing when the diaphragm 410 restores its original flat plate shape, the diaphragm 410 enters a resonance state, and the amplitude of the diaphragm 410 increases. becomes larger. If the diaphragm 410 vibrates with a large amplitude, the piezoelectric speaker 400 can emit a loud sound.

In order to further increase the vibration amplitude of diaphragm 410 under the same energy, it is conceivable to reduce the weight of diaphragm 410 . By reducing the thickness of the diaphragm 410, the weight of the diaphragm 410 can be reduced, but the restoring force when the diaphragm 410 returns to the flat plate shape from the curved deformation state is reduced. The vibration of diaphragm 410 shown in FIG. 9B cannot be obtained. For this reason, in Patent Document 1, as shown in FIGS. 10A and 10B, the diaphragm 410 is made lighter while maintaining the thickness required for vibration of the diaphragm 410 .

Specifically, the diaphragm 410 of the piezoelectric speaker 400 of Patent Document 1 has a three-layer structure, and the central layer is a base layer 411 having a lower density than the other layers. The thickness of the base layer 411 is set so that the diaphragm 410 has a certain degree of restoring force. A surface layer 412 is laminated on the surface of the base layer 411 on the piezoelectric element 420 side. The surface layer 412 is made of a conductive material with a higher density than the base layer 411 , and the piezoelectric element 420 is bonded to the surface layer 412 . The piezoelectric element 420 is bonded to the base layer 411 via the surface layer 412 for the following reasons.

Since the base layer 411 has a low density, the base layer 411 is likely to be deformed such that the molecules forming the base layer 411 are brought closer to each other, that is, the base layer 411 is likely to be shrunk. Therefore, if the piezoelectric element 420 shrinks while the piezoelectric element 420 is directly bonded to the base layer 411, only the portion bonded to the piezoelectric element 420 shrinks in accordance with the shrinkage of the piezoelectric element 420. As a result, the amount of bending deformation of the base layer 411 can be reduced. Therefore, in Patent Document 1, a surface layer 412 having a higher density than the base layer 411 is provided, and the piezoelectric element 420 is bonded to this surface layer 412 .

Another surface layer 413 is laminated to the base layer 411 on the side opposite to the surface layer 412 . The other surface layer 413 is made of the same material as the surface layer 412 and has approximately the same thickness as the surface layer 412 . As a result, the bending rigidity of the diaphragm 410 is symmetrical between the surface layer 412 side and the surface layer 413 side, and the vibration amplitude of the diaphragm 410 on the piezoelectric element 420 side and the vibration amplitude on the opposite side are substantially equal. By making these vibration amplitudes substantially equal, distortion of the sound emitted from the piezoelectric speaker 400 is suppressed.

It is possible to configure a piezoelectric vibration sensor that detects vibration of a detection target by using a structure that is substantially the same as the structure of the piezoelectric speaker 400 shown in FIGS. 9A to 10B. That is, if diaphragm 410 is arranged to receive the vibration of the object to be detected, diaphragm 410 vibrates. The piezoelectric element 420 expands and contracts in response to this vibration, and a voltage corresponding to the amount of expansion and contraction of the piezoelectric element 420 is output from the piezoelectric element 420, so that the piezoelectric element 420 can function as a vibration detection sensor. By monitoring the voltage output from the piezoelectric element 420, the vibration of the detection target can be detected and analyzed.

Japanese Patent Application Laid-Open No. 2003-230193

Since the piezoelectric speaker 400 of FIGS. 9( a ) to 10 ( b ) is thin, it can be mounted on various devices (for example, smart phones or washing machines), but the device mounted with the piezoelectric speaker 400 was placed Depending on the environment, its life can be shortened. For example, if the piezoelectric speaker 400 of FIGS. 9(a) to 10(b) is installed in a washing machine, the life of the piezoelectric speaker 400 may be shortened by moisture. A similar problem can also arise with piezoelectric vibration sensors.

An object of the present invention is to provide a technique for extending the life of a piezoelectric vibration device that can function as a piezoelectric speaker and a piezoelectric vibration sensor.

The piezoelectric vibration device according to the present disclosure includes a diaphragm and a vibration plate that expands and contracts under the application of an AC voltage to generate sound by vibrating the diaphragm while bending and deforming the diaphragm, or by bending and deforming the diaphragm. a piezoelectric element bonded to one surface of the diaphragm so as to generate a voltage signal by expanding and contracting following the vibration of the diaphragm in a state of vibrating while the piezoelectric element and the one surface of the diaphragm are connected to each other; a first protective layer that protects the piezoelectric element and the diaphragm by covering a second protective layer that protects the diaphragm by covering the other surface of the diaphragm opposite to the first protective layer; It has The first protective layer and the second protective layer can bend and deform together with the diaphragm. The vibration plate includes a base layer having a thickness that generates a restoring force to restore from a curved and deformed state; and a surface layer made of a material of The second protective layer is bonded to the base layer without being bonded to the surface layer.

The piezoelectric vibration device described above has a long life.

A plan view of a portion of a piezoelectric vibration device that functions as a piezoelectric speaker. Schematic cross-sectional view of the piezoelectric vibration device along line II-II in FIG. Schematic representation of bending deformation of diaphragm A plan view of a part of the piezoelectric vibration device Schematic cross-sectional view of the piezoelectric vibration device along line VV in FIG. Schematic cross-sectional view of piezoelectric vibration device Schematic cross-sectional view of piezoelectric vibration device Schematic cross-sectional view of a piezoelectric vibration device functioning as a piezoelectric vibration sensor Schematic cross-sectional view of a conventional piezoelectric speaker Schematic cross-sectional view of a conventional piezoelectric speaker

Hereinafter, the first embodiment and the second embodiment will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters or redundant descriptions of substantially the same configurations may be omitted. This is to avoid the following description from becoming more redundant than necessary and to facilitate understanding by those skilled in the art. It should be noted that the accompanying drawings and the following description are provided to allow those skilled in the art to fully understand the present disclosure and are not intended to limit the claimed subject matter thereby.

(First embodiment)
FIG. 1 is a schematic plan view of part of a piezoelectric vibration device 100 that functions as a piezoelectric speaker. FIG. 2 is a schematic cross-sectional view of the piezoelectric vibration device 100 (cross-sectional view taken along line II-II in FIG. 1). The structure of the piezoelectric vibration device 100 will be described with reference to FIGS. 1 and 2. FIG.

(Structure of piezoelectric vibration device)
The piezoelectric vibration device 100 includes a substantially square diaphragm 110, a flat piezoelectric element 120 joined to the diaphragm 110, a surrounding layer 113 surrounding the diaphragm 110 in the circumferential direction, and and a laminated rigid layer 140 .

The piezoelectric element 120 is a disk having a thickness of approximately 30 μm to 50 μm, and one surface of the piezoelectric element 120 is bonded to the vibration plate 110 . Piezoelectric element 120 may be adhered to diaphragm 110 using, for example, an acrylic adhesive. The piezoelectric element 120 has the characteristic of expanding and contracting in the radial direction when an AC voltage is applied to both surfaces of the piezoelectric element 120 . In addition, the piezoelectric element 120 has a characteristic of expanding and contracting more as the voltage applied to both surfaces of the piezoelectric element 120 increases.

In the present embodiment, when a positive voltage is applied to one surface of the piezoelectric element 120 (upper surface in FIG. 2) and a negative voltage is applied to the other surface, the piezoelectric element 120 is as shown in FIG. As shown in (a), it has the characteristic of extending in the radial direction. Further, as shown in FIG. 3B, when the polarity of the voltage is reversed from the state shown in FIG. Such a piezoelectric element 120 can be formed using, for example, a piezoelectric material such as PZT (lead zirconate titanate).

Note that if the piezoelectric element 120 is turned upside down and joined to the diaphragm 110, the expansion/contraction characteristics are opposite to those shown in FIGS. 3(a) and 3(b). That is, in a state in which a negative voltage is applied to one surface (upper surface in FIG. 2) of the piezoelectric element 120 and a positive voltage is applied to the other surface, the piezoelectric element 120 expands in the radial direction. characteristics. In this case, the piezoelectric element 120 has the characteristic of contracting in the radial direction due to the polarity reversal of the applied voltage.

The vibration plate 110 is a thin plate member (for example, a member having a thickness of about 40 μm) that bends and deforms as the piezoelectric element 120 expands and contracts. The diaphragm 110 has a two-layer structure, and is composed of a base layer 111 and a surface layer 112 bonded to the base layer 111 on the piezoelectric element 120 side. A piezoelectric element 120 is bonded to the surface layer 112 .

Base layer 111 is made of a material with a lower density than surface layer 112 . For example, the base layer 111 may be a resin film layer or an aluminum layer. When the base layer 111 is made of resin, polyethylene terephthalate, polyethylene, polypropylene, polyurethane, polyamide, or polyimide may be used. Alternatively, the base layer 111 may be made of styrene-butadiene-based rubber, butadiene-based rubber, butyl-based rubber, or ethylene-propylene-based rubber.

The base layer 111 obtains a restoring force for returning from the curved state shown in FIGS. 3A and 3B to the flat state shown in FIG. and is thicker than the surface layer 112 . For example, base layer 111 has a thickness of 30 μm, while surface layer 112 has a thickness of approximately 10 μm. As described above, the base layer 111 is thicker than the surface layer 112, but as described above, it is made of a material with a lower density than the surface layer 112, so an increase in the weight of the diaphragm 110 is suppressed.

The surface layer 112 is made of a conductive material and used for voltage application to the piezoelectric element 120 . Also, the surface layer 112 is made of a material with a higher density than the base layer 111 . For example, surface layer 112 may be a layer of 42 alloy (42Ni--Fe) or a layer of copper (Cu). The surface layer 112 is bonded to the base layer 111 by van der Waals force. Alternatively, surface layer 112 and base layer 111 may be joined by an adhesive.

The surface layer 112 has an overall rectangular shape in a plan view, but is partially cut out. A portion of the base layer 111 is exposed from the surface layer 112 at this notch portion. This notch portion is used for arranging an electrode 132 for applying a voltage to the piezoelectric element 120 .

The surface layer 112 is made of a material with a higher density than the base layer 111, and when the piezoelectric element 120 expands and contracts in the radial direction, the surface layer 112 protrudes toward the piezoelectric element 120 as shown in FIGS. It bends and deforms in the direction of convexity in the direction and the opposite direction. Following the bending deformation of the surface layer 112, the base layer 111 joined to the surface layer 112 also bends and deforms.

As shown in FIG. 2, the surface layer 112 is bonded only to the surface of the base layer 111 on the side of the piezoelectric element 120 and is not provided on the side opposite to the piezoelectric element 120 . Therefore, diaphragm 110 has high rigidity on the surface layer 112 side and low rigidity on the opposite side.

The surrounding layer 113 is integrally formed with the base layer 111 so as to surround the base layer 111 in the circumferential direction. That is, the material of the surrounding layer 113 is the same material as that of the base layer 111, and the surrounding layer 113 and the base layer 111 constitute one resin layer or aluminum layer. As shown in FIG. 2 , when the piezoelectric vibration device 100 is arranged with the vibration plate 110 overlapping the rectangular opening 310 provided in the device 300 , the surrounding layer 113 is formed around the opening 310 . is the part that overlaps with In this state, the surrounding layer 113 is fixed to the device 300 together with other layers (third protective layer 153 and fourth protective layer 154 to be described later) for protecting the surrounding layer 113 .

Perimeter layer 113 itself may not be rigid enough to be attached to device 300 since it is of the same low density material as base layer 111 . For this reason, the rigid layer 140 is laminated on the peripheral layer 113 to increase the rigidity of the laminated portion. That is, by laminating the rigid layer 140 on the surrounding layer 113, a rigidity suitable for the attachment portion to the device 300 can be obtained.

The rigid layer 140 is substantially C-shaped in plan view, and is laminated so as to surround the diaphragm 110 in the circumferential direction. In this embodiment, the rigid layer 140 is laminated on the surface of the resin layer or aluminum layer formed by the surrounding layer 113 and the base layer 111 on which the surface layer 112 is provided. The rigid layer 140 has an opening in the same direction as the notch portion of the surface layer 112 , and this opening portion is used for arranging electrodes 131 and 132 for applying voltage to the piezoelectric element 120 .

The material of the rigid layer 140 may be the same material as the surface layer 112 . Rigid layer 140 may also have the same thickness as surface layer 112, provided it is sufficiently rigid for attachment to device 300. FIG. It should be noted that the rigid layer 140 may be thicker than the surface layer 112 in order to improve the rigidity of the attachment portion to the device 300 . As shown in FIGS. 3A and 3B, the rigid layer 140 is arranged to overlap the entire length of the peripheral edge of the opening 310 when the piezoelectric vibration device 100 is attached to the device 300, In this state, it may be secured to device 300 .

The inner edge of rigid layer 140 is spaced a substantially constant distance from the outer edge of surface layer 112 over its entire length. Therefore, an inner edge portion 114 of the surrounding layer 113 along the outer edge of the base layer 111 appears between the inner edge of the rigid layer 140 and the outer edge of the surface layer 112 . In other words, rigid layer 140 is laminated to perimeter layer 113 on the outside of inner edge portion 114 of perimeter layer 113 .

Neither the surface layer 112 having a relatively high rigidity nor the rigid layer 140 are laminated on the inner edge portion 114 of the peripheral layer 113 . Therefore, when the diaphragm 110 is curved and deformed as shown in FIGS. 3(a) and 3(b), the inner edge portion 114 is allowed to be greatly deformed due to the curved deformation.

Also, the inner edge portion 114 of the surrounding layer 113 has a substantially constant width. Therefore, the vibration plate 110 is not in a state in which it is likely to specifically vibrate in any direction in the radial direction of the piezoelectric element 120 . That is, the inner edge portion 114 of the surrounding layer 113 can be expanded and contracted in four directions of the substantially square diaphragm 110 substantially uniformly.

As described above, the electrodes 131 and 132 are arranged using the opening portion of the rigid layer 140 and the cutout portion of the surface layer 112 . The electrode 131 is formed integrally with the surface layer 112 and laminated on the surrounding layer 113 . Electrode 131 is electrically conductive, as is surface layer 112 .

On the other hand, the electrode 132 is laminated not only on the surrounding layer 113 but also on the base layer 111 in the cutout region of the surface layer 112 . The electrode 132 is bonded to the surface of the piezoelectric element 120 opposite to the side to which the surface layer 112 is bonded using a conductive and stretchable bonding material. Since the bonding material has a certain degree of stretchability, even when the piezoelectric element 120 is deformed, the connecting portion between the piezoelectric element 120 and the electrode 132 is less likely to break. As the bonding material, for example, a silver paste in which a resin material is mixed with silver may be used, or a paste material in which conductors such as copper, gold, nickel, and carbon are added as fillers to this silver paste. may Further, as the resin material of the bonding material, a resin binder having a nitrile group (for example, acrylonitrile rubber), a resin binder containing an epoxy resin, and/or a resin binder containing a urethane resin may be used. good. As another resin material, a thermoplastic polyester-based resin binder may be used. If such a resin binder is used, a bonding material having flexibility can be obtained.

In order to protect the diaphragm 110, the piezoelectric element 120, the rigid layer 140 and the electrodes 131, 132 from environmental degradation factors such as moisture, as shown in FIG. is provided. The first protective layer 151 to the fourth protective layer 154 may be made of acrylic resin, epoxy resin, or urethane resin that is polymerized and cured by thermal drying. Alternatively, the first protective layer 151 to the fourth protective layer 154 may be made of a material that is photopolymerized and cured by ultraviolet rays (eg, urethane acrylate resin, epoxy acrylate resin, or polyester acrylate resin).

The first protective layer 151 is provided to protect the surface layer 112 of the diaphragm 110 and the piezoelectric element 120 . That is, the first protective layer 151 is provided so as to be laminated on the surface layer 112 and the piezoelectric element 120 on the surface layer 112 and the piezoelectric element 120 side, and covers them. The third protective layer 153 is formed so as to surround the first protective layer 151 in the circumferential direction so as to form one resin layer together with the first protective layer 151 and is laminated on the surrounding layer 113 . The third protective layer 153 is provided to protect the rigid layer 140 and the electrodes 131 and covers them. Also, the other electrode 132 is covered with a first protective layer 151 and a third protective layer 153 .

The second protective layer 152 is provided on the side opposite to the first protective layer 151 in the thickness direction of the diaphragm 110 (vertical direction in FIG. 2), and covers the base layer 111 . That is, the second protective layer 152 is bonded to the base layer 111 without being bonded to the surface layer 112 . In addition, the fourth protective layer 154 is formed so as to surround the second protective layer 152 in the circumferential direction so as to form one resin layer together with the second protective layer 152, and is formed around the opposite side of the third protective layer 153. Laminated on the surface of layer 113 . As a result, the base layer 111 and the surrounding layer 113 are protected by the second protective layer 152 to the fourth protective layer 154. FIG.

The thicknesses of the resin layers constituting the first to fourth protective layers 151 to 154 follow the bending deformation of the vibration plate 110 and the piezoelectric element 120 shown in FIGS. 3(a) and 3(b). , the first protective layer 151 to the fourth protective layer 154 are set so as to be curved and deformable.

The second protective layer 152 is made of the same material as the first protective layer 151 , but is thicker than the first protective layer 151 so as to have higher rigidity than the first protective layer 151 . The thickness of the second protective layer 152 may be set so that the flexural rigidity of the second protective layer 152 is close to the flexural rigidity of the laminate composed of the first protective layer 151 and the surface layer 112. . In other words, the two layers sandwiching the base layer 111 (that is, the layer of the laminate of the first protective layer 151 and the surface layer 112, and the second protective layer 152) may have approximately the same flexural rigidity.

(Description of operation)
When an AC voltage is applied to the electrodes 131 and 132, the piezoelectric element 120 and the diaphragm 110 vibrate by repeatedly bending and deforming as shown in FIGS. 3(a) and 3(b).

In the state shown in FIG. 3A, a positive voltage is applied to one surface (upper surface) of the piezoelectric element 120 through the electrode 132, and the other surface (lower surface) of the piezoelectric element 120 is applied through the electrode 131 and the surface layer 112. is applied with a negative voltage. In the state shown in FIG. 3B, a negative voltage is applied to one surface (upper surface) of the piezoelectric element 120 through the electrode 132, and the other surface (lower surface) of the piezoelectric element 120 is applied through the electrode 131 and the surface layer 112. A positive voltage is applied to .

In both the state shown in FIG. 3A and the state shown in FIG. 3B, a potential difference is generated between both surfaces of the piezoelectric element 120, and the piezoelectric element 120 expands and contracts due to this potential difference. In the state shown in FIG. 3A, the piezoelectric element 120 extends in the radial direction due to the potential difference between the two surfaces, and the diaphragm 110 is curved so as to be convex on the piezoelectric element 120 side. On the other hand, in the state shown in FIG. 3B, the piezoelectric element 120 contracts in the radial direction due to the potential difference between the two surfaces, and the diaphragm 110 is curved so as to be convex on the side opposite to the piezoelectric element 120. there is

If the states shown in FIGS. 3A and 3B are alternately repeated at a predetermined frequency, the diaphragm 110 vibrates at the predetermined frequency. As a result of the vibration of diaphragm 110 , the air surrounding diaphragm 110 vibrates and a sound corresponding to the vibration frequency of diaphragm 110 is generated. By changing the frequency of the AC voltage applied to the piezoelectric element 120, the vibration frequency of the diaphragm 110 is changed, making it possible to change the frequency of the sound generated from the piezoelectric vibration device 100. FIG.

After the voltage is applied as shown in FIG. 3(a), when the voltage is removed, the diaphragm 110 returns to the plate-like state shown in FIG. At this time, when the voltage pole is switched as shown in FIG. , the diaphragm 110 can be greatly bent and deformed. In this manner, the frequency of the AC voltage applied to the piezoelectric element 120 is adjusted so that the deformation direction of the diaphragm 110 due to the restoring force of the base layer 111 and the deformation direction of the diaphragm 110 due to expansion and contraction of the piezoelectric element 120 are aligned. Then, the diaphragm 110 is in a resonant state. In this state, the diaphragm 110 vibrates with a large amplitude, and the piezoelectric vibration device 100 can emit a loud sound.

When the diaphragm 110 is vibrating as shown in FIGS. 3A and 3B, the inner edge portion 114 of the surrounding layer 113 is also bent vertically in FIG. transform. Therefore, the vibration amplitude of diaphragm 110 increases by the amount of deformation of inner edge portion 114 of surrounding layer 113, and piezoelectric vibration device 100 can emit a loud sound.

In the above-described embodiments, the first protective layer 151 and the second protective layer 152 protect the diaphragm 110, the piezoelectric element 120, and the rigid layer 140, so that the piezoelectric vibration device 100 has a long life.

In the above-described embodiments, the surface layer 112 is provided only on one side of the base layer 111 . Therefore, the step of forming the surface layer 112 is more necessary than the conventional diaphragm 410 (diaphragm 410 having a base layer 411 sandwiched between a pair of surface layers 412 and 413) shown in FIGS. less.

As a result of providing the surface layer 112 only on one surface of the base layer 111, the diaphragm 110 has high bending rigidity on the surface layer 112 side and low bending rigidity on the opposite side. Due to such a distribution of bending rigidity, the easiness of bending of the diaphragm 110 itself differs between the direction in which the diaphragm 110 protrudes toward the piezoelectric element 120 and the direction in which the vibration plate 110 protrudes on the opposite side. Even if the first protective layer 151 and the second protective layer 152 having the same flexural rigidity are laminated on the diaphragm 110, the above-described difference in bendability is not resolved. Therefore, the vibration amplitude of the laminate of the diaphragm 110, the first protective layer 151, and the second protective layer 152 is different between the convex direction toward the piezoelectric element 120 and the opposite direction. This difference in vibration amplitude can cause sound distortion.

On the other hand, in the above-described embodiment, the flexural rigidity of the second protective layer 152 is higher than the flexural rigidity of the first protective layer 151, and the flexural rigidity of the laminate of the first protective layer 151 and the surface layer 112 is values are close. That is, the two layers sandwiching the base layer 111 (that is, the laminate layer of the first protective layer 151 and the surface layer 112 and the second protective layer 152) have approximately the same flexural rigidity. As a result, the easiness of bending of the laminated body of the diaphragm 110, the first protective layer 151, and the second protective layer 152 is substantially equal between the convex direction toward the piezoelectric element 120 and the opposite direction. In other words, in these directions, the vibration amplitude of the laminate of diaphragm 110, first protective layer 151, and second protective layer 152 becomes substantially equal, and sound distortion is suppressed.

In the embodiments described above, the first protective layer 151 and the second protective layer 152 are made of the same material. Alternatively, the second protective layer 152 may be made of a material harder than the material forming the first protective layer 151 . In this case, even if the thickness of the second protective layer 152 is less than the thickness of the first protective layer 151, the flexural rigidity of the second protective layer 152 is the same as that of the laminate composed of the first protective layer 151 and the surface layer 112. The condition of being approximately equal to the bending stiffness can be satisfied. Therefore, by forming the second protective layer 152 using a relatively hard material, it is possible to reduce the thickness of the piezoelectric vibration device 100 .

The rigid layer 140 may be laminated to the surrounding layer 113 on the side opposite to the piezoelectric element 120, as shown in FIGS. In the piezoelectric vibration device 100 shown in FIGS. 4 and 5,
The rigid layer 140 is laminated on the lower surface of the surrounding layer 113, whereas the electrodes 131 and 132 are laminated on the upper surface of the surrounding layer 113, and interference between the rigid layer 140 and the electrodes 131 and 132 occurs. do not have. Therefore, the rigid layer 140 does not need to be provided with opening regions for disposing the electrodes 131 and 132 , and may be formed so as to completely surround the diaphragm 110 . For example, as shown in FIGS. 4 and 5, the rigid layer 140 may be formed in a substantially square frame shape instead of a C shape in plan view.

In the piezoelectric vibration device 100 shown in FIGS. 4 and 5, the rigid layer 140 is laminated on the lower surface of the resin layer or the aluminum layer constituted by the surrounding layer 113 and the base layer 111, whereas the surface layer 112 is , is laminated on the upper surface of the resin layer or the aluminum layer. In this case, the rigid layer 140 may be formed by a lamination process different from the lamination process of laminating the surface layer 112 on the base layer 111 . If a lamination process separate from the lamination process for the surface layer 112 is provided for forming the rigid layer 140, the surface layer 112 and the rigid layer 140 can be formed from a material different from that of the surface layer 112. The effort for forming layer 140 is not much different. Therefore, the rigid layer 140 may be formed harder than the surface layer 112, for example.

In the piezoelectric vibration device 100 shown in FIGS. 4 and 5, the third protective layer 153 that protects the rigid layer 140 is provided so as to form one resin layer together with the second protective layer 152 . That is, the third protective layer 153 is formed so as to surround the second protective layer 152 in the circumferential direction and is laminated on the surrounding layer 113 . On the other hand, the fourth protective layer 154 is laminated on the surrounding layer 113 so as to surround the first protective layer 151 in the circumferential direction, and forms one resin layer together with the first protective layer 151 .

In the piezoelectric vibrator 100 shown in FIGS. 1 to 5, the first protective layer 151 to the fourth protective layer 154 entirely cover both sides of the resin layer or aluminum layer constituted by the base layer 111 and the surrounding layer 113. ing. In this case, the first protective layer 151 to the fourth protective layer 154 can exhibit an excellent protective function for the piezoelectric vibration device 100, while also acting to suppress deformation of the inner edge portion 114 of the surrounding layer 113. do. In order to reduce this suppression effect, the resin layers of the first protective layer 151 to the fourth protective layer 154 may be formed so as not to constrain the inner edge portion 114 . For example, as shown in FIG. 6, gaps 155 may be formed between the first protective layer 151 and the third protective layer 153 and between the second protective layer 152 and the fourth protective layer 154 . In this case, the gap 155 is formed at a position corresponding to the inner edge portion 114 of the surrounding layer 113, so the inner edge portion 114 is not constrained by the first protective layer 151 to the fourth protective layer 154. FIG. Note that the piezoelectric vibration device 100 shown in FIG. 6 has the same configuration as the piezoelectric vibration device 100 shown in FIGS. 1 and 2 except that an air gap 155 is formed.

In the piezoelectric vibration device 100 shown in FIG. 6, the inner edge portion 114 is not covered with the first protective layer 151 to the fourth protective layer 154, so the deformation of the inner edge portion 114 is caused by the first protective layer 151 to the fourth protective layer 154. Therefore, diaphragm 110 can vibrate with a larger amplitude than when air gap 155 is not formed.

In the piezoelectric vibration device 100 shown in FIG. 6, the gap 155 is formed both between the first protective layer 151 and the third protective layer 153 and between the second protective layer 152 and the fourth protective layer 154. . Alternatively, the air gap 155 may be formed only on one side as long as the amplitude difference of the diaphragm 110 between the piezoelectric element 120 side and the opposite side is not excessively large. In this case, the vibration amplitude of diaphragm 110 can be smaller than the vibration amplitude of piezoelectric vibration device 100 shown in FIG. 6, but the protective effect of first protective layer 151 to fourth protective layer 154 can be enhanced.

The air gap 155 may be formed in the piezoelectric vibration device 100 shown in FIGS. 4 and 5. FIG. Even if the gap 155 is formed in the piezoelectric vibration device 100 shown in FIGS. 4 and 5, the vibration amplitude of the vibration plate 110 can be increased.

The piezoelectric vibrating device 100 shown in FIGS. 1-6 includes a rigid layer 140 . Alternatively, if the stack of surrounding layer 113, third protective layer 153 and fourth protective layer 154 are sufficiently rigid for attachment to the device 300, the piezoelectric vibrating device 100 is shown in FIG. , the rigid layer 140 may not be provided. The piezoelectric vibration device 100 shown in FIG. 7 has the same configuration as the piezoelectric vibration device 100 shown in FIGS. 1 and 2 except that the rigid layer 140 is not provided.

The piezoelectric vibration device 100 according to one aspect of the above-described embodiment vibrates the diaphragm 110 while expanding and contracting under the application of an AC voltage to bend and deform the diaphragm 110 to generate sound. Alternatively, when the diaphragm 110 vibrates while bending and deforming, it expands and contracts following the vibration of the diaphragm 110 to generate a voltage signal. a first protective layer 151 that protects the piezoelectric element 120 and the diaphragm 110 by covering one surface of the piezoelectric element 120 and the diaphragm 110; and a second protective layer 152 that protects the diaphragm 110 by covering the other surface of the diaphragm 110 . The first protective layer 151 and the second protective layer 152 can bend and deform together with the diaphragm 110 . The vibration plate 110 includes a base layer 111 having a thickness that generates a restoring force to restore from a curved and deformed state, a surface of the base layer 111 on the side of the first protective layer 151 and the piezoelectric element 120 that is joined to the base layer 111 . and a surface layer 112 of higher density material than layer 111 . The second protective layer 152 is bonded to the base layer 111 without being bonded to the surface layer 112 .

According to the above configuration, when an AC voltage is applied to the piezoelectric element 120, the piezoelectric element 120 causes the diaphragm 110 to bend and deform, thereby vibrating the diaphragm 110 to generate sound. 100 may function as a piezoelectric speaker. On the other hand, if the piezoelectric element 120 expands and contracts following the vibration of the diaphragm 110 while the diaphragm 110 vibrates while bending and deforming, the piezoelectric element 120 generates a voltage signal. It can function as a piezoelectric vibration sensor that detects vibrations.

The piezoelectric element 120 and the vibration plate 110 are protected by being covered with the first protective layer 151 and the second protective layer 152, and the piezoelectric vibration device 100 has a long life. The second protective layer 152 is bonded to the base layer 111 without being bonded to the surface layer 112, and the surface layer 112 is interposed between the second protective layer 152 and the base layer 111. do not have. Therefore, compared to the conventional diaphragm in which the base layer 111 is sandwiched between the pair of surface layers 112, the number of steps for forming the surface layer 112 is reduced, and the manufacturing process of the piezoelectric vibration device 100 can be simplified.

In the configuration described above, the bending rigidity of the second protective layer 152 may be greater than the bending rigidity of the first protective layer 151 .

When the relatively high-rigidity surface layer 112 is laminated only on one surface of the base layer 111, the diaphragm 110 has high rigidity on the surface layer 112 side and low rigidity on the opposite side. Due to such a rigidity distribution, the easiness of bending differs between when the diaphragm 110 itself is bent toward the surface layer 112 side and when it is bent toward the opposite side. Even if the first protective layer 151 and the second protective layer 152 having the same flexural rigidity are laminated on the diaphragm 110, the above-described difference in ease of bending cannot be eliminated. This difference in ease of bending appears as a difference between the amplitude of the diaphragm 110 curved and deformed toward the surface layer 112 side and the amplitude of the diaphragm 110 curved and deformed toward the opposite side. If the piezoelectric vibration device 100 is used as a piezoelectric speaker in this state, the sound emitted by the piezoelectric vibration device 100 may be distorted. Further, if the piezoelectric vibration device 100 is used as a piezoelectric vibration sensor, the vibration detection accuracy differs between when the vibration plate 110 bends toward the surface layer 112 and when it bends toward the opposite side. obtain.

Therefore, in the above configuration, the bending rigidity of the second protective layer 152 laminated on the diaphragm 110 is made higher than the bending rigidity of the first protective layer 151 . In this case, the difference between the bending rigidity of the laminate of the first protective layer 151 and the surface layer 112 and the bending rigidity of the second protective layer 152 can be reduced. That is, the flexural rigidity of the two layers sandwiching the base layer 111 (that is, the layer of the laminate of the first protective layer 151 and the surface layer 112 and the second protective layer 152) has a similar value, and the bending direction of the diaphragm 110 The difference in bendability due to is suppressed.

In the above configuration, the material of the second protective layer 152 may be the same as the material of the first protective layer 151 . The second protective layer 152 may be thicker than the first protective layer 151 .

According to the above configuration, since the first protective layer 151 and the second protective layer 152 are made of the same material, the piezoelectric vibration device 100 can be easily manufactured. In this case, by making the second protective layer 152 thicker than the first protective layer 151 , the bending rigidity of the second protective layer 152 can be made higher than the bending rigidity of the first protective layer 151 .

In the configuration described above, the second protective layer 152 may be made of a harder material than the first protective layer 151 and may have a thickness less than that of the first protective layer 151 .

According to the configuration described above, the second protective layer 152 is made of a harder material than the first protective layer 151 . Therefore, even if the second protective layer 152 has a thickness less than the thickness of the first protective layer 151, Bending stiffness can be close to the value.

In the above-described configuration, the piezoelectric vibration device 100 is configured to surround the base layer 111 in the circumferential direction with the same material as the base layer 111, and has a surrounding layer 113 integrally formed with the base layer 111 and a vibrating layer 113. By being laminated on the surface of the surrounding layer 113 facing in the same direction as one surface or the other surface of the plate 110, the rigidity around the diaphragm 110 is increased, and the piezoelectric vibration device 100 can be attached to another device 300. It may further include a rigid layer 140 that enables the transmission, and a third protective layer 153 that protects the rigid layer 140 by covering the rigid layer 140 .

According to the above configuration, the portion of the peripheral layer 113 where the rigid layer 140 is laminated has high rigidity, and therefore can be used for attaching the piezoelectric vibration device 100 to another device 300 . The rigid layer 140 is protected by being covered with a third protective layer 153 .

In the configurations described above, the perimeter layer 113 may have an inner edge portion 114 along the outer edge of the base layer 111 . Rigid layer 140 may be laminated to peripheral layer 113 outside inner edge portion 114 to allow inner edge portion 114 to deform following vibration of diaphragm 110 . The third protective layer 153 may cover the rigid layer 140 so as not to constrain the inner edge portion 114 .

According to the above configuration, the surrounding layer 113 is made of the same material as the base layer 111, so it has a relatively low density, and the inner edge portion 114 of the surrounding layer 113 along the outer edge of the base layer 111 is , can be deformed following the vibration of the diaphragm 110 . If the inner edge portion 114 of the surrounding layer 113 is greatly deformed following the vibration of the diaphragm 110, the vibration amplitude of the diaphragm 110 can be increased. When the diaphragm 110 vibrates with a large amplitude, the diaphragm 110 can generate a loud sound when the piezoelectric vibration device 100 is used as a piezoelectric speaker. Moreover, when the piezoelectric vibration device 100 functions as a piezoelectric vibration sensor, the voltage signal can be increased to increase the vibration detection accuracy. Therefore, the formation positions of the rigid layer 140 and the third protective layer 153 are set so that the inner edge portion 114 of the surrounding layer 113 can be largely deformed. That is, since the rigid layer 140 of the surrounding layer 113 is laminated to the surrounding layer 113 outside the inner edge portion 114 of the surrounding layer 113, the inner edge portion 114 of the surrounding layer 113 can vibrate without being hindered by the rigid layer 140. It can be deformed by following the vibration of the plate 110 . In addition, since the third protective layer 153 covers the rigid layer 140 so as not to constrain the inner edge portion 114 of the surrounding layer 113 , the inner edge portion 114 can move the diaphragm 110 without being hindered by the third protective layer 153 . It can be deformed following vibration.

(Second embodiment)
The piezoelectric vibration device 100 shown in FIGS. 1 to 7 can also function as a piezoelectric vibration sensor that detects vibration of a detection target. That is, when the vibration of the object to be detected is transmitted to diaphragm 110, diaphragm 110 vibrates. When the diaphragm 110 vibrates, the piezoelectric element 120 joined to the diaphragm 110 expands and contracts, and a potential difference corresponding to the amount of expansion and contraction of the piezoelectric element 120 can occur in the piezoelectric element 120 . Vibration of the object to be detected can be detected by detecting the potential difference generated in the piezoelectric element 120 . In the second embodiment, a case where the piezoelectric vibration device 100 shown in FIGS. 1 and 2 functions as a piezoelectric vibration sensor will be described with reference to FIG.

The piezoelectric vibration device 100 is attached to a device 300 (for example, a washing machine) that is a detection target. The device 300 has a substantially square opening 310 wider than the diaphragm 110 so as not to interfere with the vibration of the diaphragm 110 .

The piezoelectric vibrating device 100 is secured to the device 300 such that the rigid layer 140 overlaps the portion of the device 300 around the opening 310 while the entire inner region of the rigid layer 140 overlaps the opening 310 . In this state, if the device 300 vibrates, this vibration is transmitted to the piezoelectric vibration device 100, and the vibration plate 110 and the inner edge portion 114 inside the rigid layer 140 also vibrate. As a result, the diaphragm 110 can be deformed as shown in FIGS. 3(a) and 3(b).

In the state shown in FIG. 3A, the diaphragm 110 is curved and deformed in a convex direction toward the piezoelectric element 120 side. Following this bending deformation, the piezoelectric element 120 expands in the radial direction, and a potential difference is generated between both surfaces of the piezoelectric element 120 . Further, the greater the amount of bending deformation of the vibration plate 110, the greater the amount of expansion of the piezoelectric element 120, and the greater the potential difference generated in the piezoelectric element 120. FIG. On the other hand, as shown in FIG. 3B, when the diaphragm 110 is curved and deformed in the opposite direction, the piezoelectric element 120 contracts. In this case, the greater the amount of bending deformation of diaphragm 110, the greater the amount of contraction of piezoelectric element 120 and the greater the potential difference generated in piezoelectric element 120. FIG.

In the state shown in FIG. 3A, one surface (upper surface) of the piezoelectric element 120 has a positive potential and the other surface (lower surface) of the piezoelectric element 120 has a negative potential. On the other hand, in the state shown in FIG. 3B, a state occurs in which the other surface (lower surface) of the piezoelectric element 120 has a positive potential and one surface (upper surface) of the piezoelectric element 120 has a negative potential. there is Since the electrodes 131 and 132 are connected to both surfaces of the piezoelectric element 120, the information on the potential difference generated in the piezoelectric element 120 is output from the electrodes 131 and 132 as voltage signals. Electrodes 131 and 132 may be electrically connected to a vibration analyzer (eg, microcomputer). In this case, the vibration analyzer can acquire information about the vibration frequency of the piezoelectric vibrating device 100 and, in turn, the device 300, based on the frequency of switching between the positive and negative poles of the voltage signal. Also, from the magnitude of the voltage signal, the vibration analyzer can obtain information about the vibration amplitude of the piezoelectric vibration device 100 and thus the device 300 .

When the piezoelectric vibrating device 100 has the structure shown in FIG. 6, gaps 155 are formed in the first protective layer 151 and the second protective layer 152 . Since the surrounding layer 113 can be greatly deformed in the region where the air gap 155 is formed, the vibration plate 110 vibrates with a larger amplitude, and the expansion and contraction amount of the piezoelectric element 120 increases. In this case, under the condition that the vibration amplitude of the detection target (apparatus 300) is equal, the vibration amplitude of the detection target when the gap 155 is formed is greater than when the gap 155 is not formed. A larger voltage signal is output with respect to Therefore, the formation of the air gap 155 makes it possible to detect the vibration amplitude of the object to be detected with higher accuracy.

A piezoelectric vibration device 100 according to one aspect according to the second embodiment, similarly to the first embodiment, expands and contracts under the application of an AC voltage to bend and deform the vibration plate 110 . The diaphragm 110 vibrates to generate a sound, or expands and contracts to follow the vibration of the diaphragm 110 in a state where the diaphragm 110 vibrates while bending and deforming to generate a voltage signal. a first protective layer 151 that protects the piezoelectric element 120 and the diaphragm 110 by covering the piezoelectric element 120 and one surface of the diaphragm 110; and a second protective layer 152 that protects the diaphragm 110 by covering the other surface of the diaphragm 110 opposite to the protective layer 151 . The first protective layer 151 and the second protective layer 152 can bend and deform together with the diaphragm 110 . The vibration plate 110 includes a base layer 111 having a thickness that generates a restoring force to restore from a curved and deformed state, a surface of the base layer 111 on the side of the first protective layer 151 and the piezoelectric element 120 that is joined to the base layer 111 . and a surface layer 112 of higher density material than layer 111 . The second protective layer 152 is bonded to the base layer 111 without being bonded to the surface layer 112 .

In the above configuration, the flexural rigidity of the second protective layer 152 may be greater than the flexural rigidity of the first protective layer 151, as in the first embodiment.

In the above configuration, the material of the second protective layer 152 may be the same material as that of the first protective layer 151, as in the first embodiment. The second protective layer 152 may be thicker than the first protective layer 151 .

In the above configuration, the second protective layer 152 is made of a harder material than the first protective layer 151 and has a thickness less than that of the first protective layer 151, as in the first embodiment. You may have

In the above-described configuration, the piezoelectric vibration device 100 is configured so as to surround the base layer 111 in the circumferential direction with the same material as the base layer 111, and is integrally formed with the base layer 111, as in the first embodiment. and the surface of the surrounding layer 113 facing in the same direction as the one surface or the other surface of the diaphragm 110, the rigidity around the diaphragm 110 is increased, and the piezoelectric vibration device is formed. It may further include a rigid layer 140 that enables attachment of 100 to other devices 300 and a third protective layer 153 that protects rigid layer 140 by covering rigid layer 140 .

In the configuration described above, the surrounding layer 113 may have an inner edge portion 114 along the outer edge of the base layer 111 as in the first embodiment. Rigid layer 140 may be laminated to peripheral layer 113 outside inner edge portion 114 to allow inner edge portion 114 to deform following vibration of diaphragm 110 . The third protective layer 153 may cover the rigid layer 140 so as not to constrain the inner edge portion 114 .

(effects, etc.)
The piezoelectric vibration device 100 according to the above-described embodiment has the following features and the following effects.

A piezoelectric vibration device according to one aspect of the above-described embodiment includes a diaphragm and a vibrating diaphragm that expands and contracts under the application of an AC voltage to bend and deform the diaphragm so as to generate sound by vibrating the diaphragm. Alternatively, a piezoelectric element bonded to one surface of the diaphragm so as to generate a voltage signal by expanding and contracting following the vibration of the diaphragm while the diaphragm vibrates while bending and deforming; and one surface of the diaphragm to protect the piezoelectric element and the diaphragm, and the diaphragm by covering the other surface of the diaphragm opposite to the first protective layer and a second protective layer for protection. The first protective layer and the second protective layer can bend and deform together with the diaphragm. The vibration plate includes a base layer having a thickness that generates a restoring force to restore from a curved and deformed state; and a surface layer made of a material of The second protective layer is bonded to the base layer without being bonded to the surface layer.

According to the above configuration, when an AC voltage is applied to the piezoelectric element, the piezoelectric element vibrates the diaphragm while bending and deforming the diaphragm to generate sound. can function as On the other hand, if the piezoelectric element expands and contracts following the vibration of the diaphragm while the diaphragm vibrates while bending and deforming, the piezoelectric element generates a voltage signal. It can function as a vibration sensor.

The piezoelectric element and the diaphragm are protected by being covered with the first protective layer and the second protective layer, and the piezoelectric vibration device has a long life. The second protective layer is joined to the base layer without being joined to the surface layer, and no surface layer is interposed between the second protective layer and the base layer. Therefore, the number of steps for forming the surface layers is reduced as compared with the conventional diaphragm in which the base layer is sandwiched between the pair of surface layers, and the manufacturing process of the piezoelectric vibration device can be simplified.

In the above configuration, the flexural rigidity of the second protective layer may be greater than the flexural rigidity of the first protective layer.

When a relatively high-rigidity surface layer is laminated only on one surface of the base layer, the diaphragm has high rigidity on the surface layer side and low rigidity on the opposite side. Due to such a rigidity distribution, the easiness of bending differs between when the diaphragm itself is bent toward the surface layer side and when it is bent toward the opposite side. Even if a first protective layer and a second protective layer having the same flexural rigidity are laminated on such a diaphragm, the above-described difference in ease of bending cannot be eliminated. This difference in ease of bending appears as a difference between the amplitude of the diaphragm curvedly deformed toward the surface layer side and the amplitude of the diaphragm curvedly deformed toward the opposite side. If the piezoelectric vibration device is used as a piezoelectric speaker in this state, the sound emitted by the piezoelectric vibration device may be distorted. Further, if the piezoelectric vibration device is used as a piezoelectric vibration sensor, the vibration detection accuracy may differ between when the diaphragm bends toward the surface layer side and when it bends toward the opposite side.

Therefore, in the above configuration, the bending rigidity of the second protective layer laminated on the diaphragm is made higher than the bending rigidity of the first protective layer. In this case, the difference between the flexural rigidity of the laminate of the first protective layer and the surface layer and the flexural rigidity of the second protective layer can be reduced. That is, the flexural rigidity of the two layers sandwiching the base layer (that is, the layer of the laminate of the first protective layer and the surface layer and the second protective layer) has a similar value, and the ease of bending depending on the bending direction of the diaphragm. Differences are suppressed.

In the above configuration, the material of the second protective layer may be the same as that of the first protective layer. The second protective layer may be thicker than the first protective layer.

According to the above configuration, since the first protective layer and the second protective layer are made of the same material, the piezoelectric vibration device can be easily manufactured. In this case, by making the second protective layer thicker than the first protective layer, the bending rigidity of the second protective layer can be made higher than the bending rigidity of the first protective layer.

In the above configuration, the second protective layer may be made of a harder material than the first protective layer and have a thickness less than that of the first protective layer.

According to the above configuration, the second protective layer is made of a harder material than the first protective layer, so the thickness of the second protective layer is less than that of the first protective layer. Also, the flexural rigidity of the laminate of the first protective layer and the surface layer and that of the second protective layer can be close to each other.

In the above configuration, the piezoelectric vibration device is configured to surround the base layer with the same material as that of the base layer in the circumferential direction. Alternatively, a rigid layer that is laminated on the surface of the surrounding layer that faces the same direction as the other surface increases the rigidity around the diaphragm so that the piezoelectric vibration device can be attached to other devices, and the rigid layer. A third protective layer that protects the rigid layer by covering it may further be provided.

According to the above configuration, the portion of the peripheral layer where the rigid layer is laminated has high rigidity, and thus can be used to attach the piezoelectric vibration device to another device. The rigid layer is protected by being covered with a third protective layer.

In the configurations described above, the peripheral layer may have an inner edge portion that follows the outer edge of the base layer. The rigid layer may be laminated to the surrounding layer outside the inner edge portion to allow the inner edge portion to deform following vibration of the diaphragm. The third protective layer may cover the rigid layer so as not to constrain the inner edge portion.

According to the above configuration, since the surrounding layer is made of the same material as the base layer, it has a relatively low density, and the inner edge portion of the surrounding layer along the outer edge of the base layer is the vibration of the diaphragm. can be deformed according to If the inner edge part is greatly deformed following the vibration of the diaphragm, the vibration amplitude of the diaphragm can be increased. If the diaphragm vibrates with a large amplitude, the diaphragm can generate a loud sound when the piezoelectric vibration device is used as a piezoelectric speaker, and when the piezoelectric vibration device functions as a piezoelectric vibration sensor, By increasing the voltage signal, the vibration detection accuracy can be improved. For this reason, the formation positions of the rigid layer and the third protective layer are set so that a large deformation of the inner edge portion of the surrounding layer can be obtained. That is, since the rigid layer is laminated on the surrounding layer outside the inner edge portion of the surrounding layer, the inner edge portion of the surrounding layer can deform following the vibration of the diaphragm without being hindered by the rigid layer. can. Further, since the third protective layer covers the rigid layer so as not to constrain the inner edge portion, the inner edge portion of the surrounding layer deforms following the vibration of the diaphragm without being hindered by the third protective layer. be able to.

As described above, the first embodiment and the second embodiment have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments with modifications, replacements, additions, omissions, and the like. Further, it is also possible to combine the constituent elements described in the above-described first and second embodiments to form a new embodiment.

INDUSTRIAL APPLICABILITY The present disclosure is suitably used in technical fields requiring sound generation and in technical fields requiring vibration detection.

REFERENCE SIGNS LIST 100 Piezoelectric vibration device 110 Diaphragm 111 Base layer 112 Surface layer 113 Surrounding layer 114 Inner edge portion 120 Piezoelectric element 140 Rigid layer 151 First protective layer 152 Second protective layer 153 Third protective layer 300 ·Device

Claims (6)

a diaphragm;
The vibration is generated by vibrating the diaphragm while bending and deforming the diaphragm by expanding and contracting under the application of an AC voltage, or in a state where the diaphragm vibrates while bending and deforming. a piezoelectric element bonded to one surface of the diaphragm so as to expand and contract following vibration of the plate to generate a voltage signal;
a first protective layer that protects the piezoelectric element and the diaphragm by covering the piezoelectric element and the one surface of the diaphragm;
a second protective layer that protects the diaphragm by covering the other surface of the diaphragm opposite to the first protective layer;
The first protective layer and the second protective layer are capable of bending and deforming together with the diaphragm,
The diaphragm includes a base layer having a thickness that generates a restoring force to restore from a curved and deformed state, a surface of the base layer on the side of the first protective layer, and a surface of the base layer that is joined to the piezoelectric element and the base. a surface layer of material having a higher density than the layer;
The piezoelectric vibration device, wherein the second protective layer is bonded to the base layer without being bonded to the surface layer. The piezoelectric vibration device according to claim 1, wherein the second protective layer has a higher bending rigidity than the first protective layer. The material of the second protective layer is the same material as the first protective layer,
3. The piezoelectric vibration device according to claim 2, wherein said second protective layer is thicker than said first protective layer. 3. The piezoelectric vibration device according to claim 2, wherein said second protective layer is made of a harder material than said first protective layer and has a thickness less than that of said first protective layer. . a peripheral layer made of the same material as the base layer and configured to surround the base layer in the circumferential direction and integrally formed with the base layer;
By being laminated on the surface of the surrounding layer facing in the same direction as the one surface or the other surface of the diaphragm, the rigidity around the diaphragm is increased, and the piezoelectric vibration device can be used as another device. a rigid layer that allows attachment to the
The piezoelectric vibration device according to any one of claims 1 to 4, further comprising a third protective layer that protects the rigid layer by covering the rigid layer. The surrounding layer has an inner edge portion along the outer edge of the base layer,
The rigid layer is laminated on the peripheral layer outside the inner edge portion so as to allow the inner edge portion to follow the vibration of the diaphragm and deform,
6. The piezoelectric vibration device according to claim 5, wherein said third protective layer covers said rigid layer so as not to constrain said inner edge portion.

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