Vibration device and piezoelectric vibrator

Abstract

To provide a vibration device and a piezoelectric vibrator that can improve the sound pressure and suppress the distortion of the waveform by suppressing the high-order vibration mode.SOLUTION: A vibration device 1 includes a piezoelectric element 4, a vibration unit 5 to which the piezoelectric element 4 is fixed and causes bending vibration by driving the piezoelectric element 4, a fixing unit 3 that fixes the vibration unit 5, and a vibration limiting unit 6 that has a bending rigidity equal to or higher than that of the vibration unit 5 and limits a part of the bending vibration generated in the vibration unit 5. The vibration limiting unit 6 is located at least in a region between the piezoelectric element 4 and the fixing unit 3 in the plan view of the vibration unit 5, and is arranged apart from the central portion C of the fixing unit 3 and the piezoelectric element 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a vibration device and a piezoelectric vibrator.

Background Art

[0002] As a conventional vibration device, for example, there is a transparent speaker described in Patent Document 1. This conventional vibration device is configured by fixing a piezoelectric element to a vibrating portion. In this vibration device, the vibration of the piezoelectric element is amplified by the vibrating portion, and a bending vibration is generated in the vibrating portion, so that a desired acoustic output can be obtained.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a configuration that uses the bending vibration of the vibrating portion, such as the vibration device of Patent Document 1 described above, the vibration transmissibility from the piezoelectric element to the vibrating portion is excellent. On the other hand, in a vibration device assuming acoustic use, a plurality of vibration modes exist in the effective frequency region, and higher-order vibration modes corresponding to an integer multiple of the input frequency may occur. For example, it is assumed that there are a plurality of higher-order vibration modes for a single input frequency, or that the basic vibration mode becomes a higher-order vibration mode according to the input frequency. Since the bending vibration is non-linear, even if the input is a sine wave, the output (vibration displacement or measured sound pressure) can be a waveform other than a sine wave. Therefore, when higher-order vibration modes exist in the effective frequency region, there is a possibility that the sound pressure may decrease due to the vibrations canceling each other out, or that the waveform may be distorted.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a vibration device and a piezoelectric vibrator in which improvement of sound pressure and suppression of waveform distortion are achieved by suppressing higher-order vibration modes.

Means for Solving the Problems

[0006] A vibration device according to one aspect of the present disclosure includes a piezoelectric element, a vibration part to which the piezoelectric element is fixed and which generates bending vibration by driving the piezoelectric element, a fixing part for fixing the vibration part, and a vibration restricting part having a bending rigidity equal to or higher than that of the vibration part and restricting a part of the bending vibration generated in the vibration part. The vibration restricting part is located in at least a region between the piezoelectric element and the fixing part in a plan view of the vibration part, and is arranged so as to be separated from the central portions of the fixing part and the piezoelectric element.

[0007] In this vibration device, in a plan view of the vibration part, the vibration restricting part is arranged in at least a region between the piezoelectric element and the fixing part and is separated from the central portions of the fixing part and the piezoelectric element. By this arrangement of the vibration restricting part, the natural frequency of the vibration part can be shifted to the high-frequency side. Therefore, it is possible to suppress the generation of higher-order vibration modes in the effective frequency region, and it is possible to suppress a decrease in sound pressure and waveform distortion caused by the vibrations canceling each other out. In this vibration device, since the vibration restricting part is separated from the fixing part, the bending vibration starting from both ends of the diaphragm is maintained, and since it is separated from the central portion of the piezoelectric element, it is also possible to avoid the amplitude of the vibration mode to be taken out as an output from being inhibited. Therefore, improvement of sound pressure can be achieved.

[0008] The end portion on the fixing part side in the vibration restricting part may be located on the fixing part side rather than at the position of the antinode of the vibration waveform of the higher-order vibration mode of the bending vibration. With such a configuration, the vibration restricting part is arranged at the position of the antinode of the vibration waveform of the higher-order vibration mode, and the generation of the higher-order vibration mode in the effective frequency region can be effectively suppressed.

[0009] The end portion on the piezoelectric element side in the vibration limiting portion may overlap with the edge portion of the piezoelectric element in a plan view of the vibrating portion. With such a configuration, the vibration limiting portion is disposed at the position of the antinode of the vibration waveform of the higher-order vibration mode, and the generation of the higher-order vibration mode in the effective frequency region can be effectively suppressed.

[0010] The vibration limiting portion may further have a connecting portion that connects the portion located on one side of the piezoelectric element and the portion located on the other side of the piezoelectric element. In this case, the bending rigidity in the vibration limiting portion can be further sufficiently ensured. The generation of the higher-order vibration mode in the effective frequency region can be effectively suppressed.

[0011] The piezoelectric vibrator according to one aspect of the present disclosure includes a piezoelectric element, a vibrating portion to which the piezoelectric element is fixed and that generates bending vibration by driving the piezoelectric element, and a vibration limiting portion having a bending rigidity equal to or higher than that of the vibrating portion and that limits a part of the bending vibration generated in the vibrating portion. The vibration limiting portion is disposed at least apart from the central portion of the piezoelectric element in a plan view of the vibrating portion.

[0012] In this piezoelectric vibrator, in a plan view of the vibrating portion, the vibration limiting portion is disposed at least apart from the central portion of the piezoelectric element. By this arrangement of the vibration limiting portion, the natural frequency of the vibrating portion can be shifted to the high-frequency side. Therefore, it becomes possible to suppress the generation of the higher-order vibration mode in the effective frequency region, and it is possible to suppress a decrease in sound pressure and distortion of the waveform due to the vibrations canceling each other out. Since the vibration limiting portion is apart from the central portion of the piezoelectric element, it is also possible to avoid the bending vibration itself in the vibrating portion from being inhibited, and an improvement in sound pressure can be achieved.

Advantages of the Invention

[0013] According to the present disclosure, by suppressing the higher-order vibration mode, an improvement in sound pressure and suppression of waveform distortion can be achieved.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0015] Hereinafter, with reference to the drawings, preferred embodiments of a vibration device and a piezoelectric vibrator according to one aspect of the present disclosure will be described in detail. [First Embodiment]

[0016] FIG. 1 is a schematic plan view showing the configuration of the vibration device according to the first embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. 1. The vibration device 1 shown in FIGS. 1 and 2 is a device used as an acoustic device such as a speaker, and can be mounted on an electronic device that emits sound, such as a television or a smartphone. As shown in FIGS. 1 and 2, the vibration device 1 includes a piezoelectric vibrator 2 and a fixing portion 3.

[0017] The piezoelectric vibrator 2 includes a piezoelectric element 4 and a vibrating portion 5. The piezoelectric element 4 has, for example, a piezoelectric body and a pair of external electrodes (not shown). The piezoelectric body is composed of a stack of a plurality of piezoelectric body layers. In the examples of FIGS. 1 and 2, the piezoelectric body has a rectangular shape in plan view. Each piezoelectric body layer is formed of a piezoelectric material. In the present embodiment, each piezoelectric body layer is made of a piezoelectric ceramic material. Examples of the piezoelectric ceramic material include PZT [Pb(Zr,Ti)O3], PT (PbTiO3), PLZT [(Pb,La)(Zr,Ti)O3], and barium titanate (BaTiO3).

[0018] Each piezoelectric body layer is composed of, for example, a sintered body of a ceramic green sheet containing the above-described piezoelectric ceramic material. In an actual piezoelectric body, each piezoelectric body layer is integrated to such an extent that the boundary between the piezoelectric body layers cannot be recognized. A plurality of internal electrodes (not shown) are disposed in the piezoelectric body. Each internal electrode is formed of a conductive material. Examples of the conductive material include Ag, Pd, and Ag-Pd alloys.

[0019] A wiring member (not shown), such as a flexible printed circuit board, is electrically connected to the pair of external electrodes of the piezoelectric element 4. One end side of the wiring member is electrically and physically connected to the pair of external electrodes of the piezoelectric element 4, and the other end side of the wiring member is electrically and physically connected to an electronic device on which the vibration device 1 is mounted.

[0020] The vibrating portion 5 is a portion that generates bending vibration by driving the piezoelectric element 4. The vibrating portion 5 is formed in a thin plate shape, for example, by a metal material, and extends in one direction with a certain width. Hereinafter, the one direction in which the vibrating portion 5 extends is referred to as the extending direction D. Also, the direction orthogonal to the one direction is referred to as the width direction W. Examples of the metal material include Ni-Fe alloy, Ni, brass, stainless steel, etc. The vibrating portion 5 may be composed of a resin material. Examples of the resin material include PC (polycarbonate), PPS (polyphenylene sulfide), etc. Here, the vibrating portion 5 has a rectangular shape in plan view, and has a long side along the extending direction D and a short side orthogonal to the extending direction D. The rectangular shape may include, for example, a shape with chamfered corners and a shape with rounded corners.

[0021] The vibrating portion 5 has one surface 5a and the other surface 5b which is the opposite surface of the one surface 5a. A fixing region of the above-described piezoelectric element 4 is provided at the central portion of the one surface 5a of the vibrating portion 5. For example, an adhesive is used for fixing the one surface 5a of the vibrating portion 5 and the piezoelectric element 4. In the examples of FIGS. 1 and 2, the long side and the short side of the piezoelectric element 4 in plan view are smaller than the long side and the short side of the vibrating portion 5 in plan view. In the plan view of the vibrating portion 5, the long side of the piezoelectric element 4 is along the long side of the vibrating portion 5, and the short side of the piezoelectric element 4 is along the short side of the vibrating portion 5. Also, in the plan view of the vibrating portion 5, the center position of the piezoelectric element 4 coincides with the center position of the vibrating portion 5. As a result, in the plan view of the vibrating portion 5, the entire piezoelectric element 4 overlaps the vibrating portion 5, and the piezoelectric element 4 does not protrude from the edge of the vibrating portion 5 (see FIG. 1).

[0022] Both end portions 5c, 5c in the extending direction D of the vibrating portion 5 are fixed by the fixing portion 3. Specifically, both end portions 5c, 5c in the extending direction D of the vibrating portion 5 are in a state of being buried in the fixing portion 3. Thereby, both end portions 5c, 5c in the extending direction D of the vibrating portion 5 are the fixed ends of the bending vibration generated in the vibrating portion 5 by the piezoelectric element 4. In the examples of FIGS. 1 and 2, the entire edge portion on the short side of the vibrating portion 5 is buried in the fixing portion 3. In a plan view of the vibrating portion 5, a certain interval is provided between the piezoelectric element 4 and the fixing portion 3 in the extending direction D. The both end portions 5c, 5c do not necessarily include the edges in the extending direction D of the vibrating portion 5, and the fixed ends of the bending vibration generated in the vibrating portion 5 may be located slightly closer to the center in the extending direction D than the edges in the extending direction D of the vibrating portion 5.

[0023] Next, the piezoelectric vibrator 2 described above will be described in more detail.

[0024] As shown in FIGS. 1 and 2, the piezoelectric vibrator 2 is provided with a vibration restricting portion 6 that restricts a part of the bending vibration generated in the vibrating portion 5 by the piezoelectric element 4. In the present embodiment, the vibration restricting portion 6 is fixed to the surface on the opposite side of the surface of the vibrating portion 5 where the piezoelectric element 4 is fixed, that is, the other surface 5b. For example, an adhesive is used for fixing between the other surface 5b of the vibrating portion 5 and the piezoelectric element 4.

[0025] The vibration restricting portion 6 has a bending rigidity equal to or higher than that of the vibrating portion 5. The bending rigidity of the vibration restricting portion 6 is preferably 1 to 130 times the bending rigidity of the vibrating portion 5. For example, when the bending rigidity of the vibrating portion 5 is 7.7×10 -3 Pa·m 4 , the bending rigidity of the vibration restricting portion 6 is preferably 7.7×10 -3 Pa·m 4 ~9.7×10 -1 Pa·m 4 . The bending rigidities of the vibrating portion 5 and the vibration restricting portion 6 can be measured, for example, by a tensile test or a resonance method.

[0026] Examples of the constituent material of the vibration limiting part 6 include metal materials. Examples of the metal materials include Ni-Fe alloys, Ni, brass, stainless steel, etc. The vibration limiting part 6 may be made of a resin material. Examples of the resin materials include PC (polycarbonate), PPS (polyphenylene sulfide), etc. The constituent material of the vibration limiting part 6 may be the same as or different from the constituent material of the vibrating part 5. In the present embodiment, the vibration limiting part 6 is formed of the same material as the material constituting the vibrating part 5 and has the same thickness as the vibrating part 5. For example, when the vibrating part 5 is formed of stainless steel (SUS304) with a thickness of 0.2 mm, the vibration limiting part 6 is also formed of stainless steel (SUS304) with a thickness of 0.2 mm.

[0027] In a plan view of the vibrating part 5, the vibration limiting part 6 is located at least in the region between the piezoelectric element 4 and the fixing part 3. Further, the vibration limiting part 6 is arranged at a distance from the central portion C of the fixing part 3 and the piezoelectric element 4. In the present embodiment, in a plan view of the vibrating part 5, the vibration limiting part 6 has a rectangular frame shape so as to surround the piezoelectric element 4. More specifically, the vibration limiting part 6 has main body parts 7, 7 located in the region between the piezoelectric element 4 and the fixing part 3, and connecting parts 8, 8 connecting the main body parts 7, 7. The main body parts 7, 7 are respectively arranged on one side and the other side of the piezoelectric element 4 in the extending direction D, and the connecting parts 8, 8 are respectively arranged on one side and the other side of the piezoelectric element 4 in the width direction W.

[0028] In a plan view of the vibrating part 5, the main body part 7 has a substantially rectangular shape. In the example of FIG. 1, the shape of the main body part 7 is a rectangular shape having a short side along the extending direction D and a long side along the width direction W. The end part 7a of the main body part 7 on the fixing part 3 side is located closer to the fixing part 3 side than the position of the antinode of the higher-order vibration waveform of the bending vibration with respect to the extending direction D. In the present embodiment, the end part 7a of the main body part 7 on the fixing part 3 side is located closer to the fixing part 3 side than the position of the antinode Na of the third-order vibration mode of the bending vibration with respect to the extending direction D, which is the antinode Na located closest to the fixing part 3 side (see FIG. 3 described later).

[0029] Further, the end portion 7b on the piezoelectric element 4 side in the main body portion 7 overlaps with the edge portion 4a in the extending direction D of the piezoelectric element 4. The overlapping width between the end portion 7b of the main body portion 7 and the edge portion 4a of the piezoelectric element 4 is, for example, about 1% to 10% of the length of the piezoelectric element 4 in the extending direction D. In the present embodiment, the end portion 7b on the piezoelectric element 4 side in the main body portion 7 is located on the piezoelectric element 4 side with respect to the position of the antinode Na of the second vibration mode of the bending vibration with respect to the extending direction D, which is closer to the piezoelectric element 4 than the position of the antinode Na closest to the fixing portion 3 side (see FIG. 3 described later).

[0030] In the present embodiment, the length of the main body portion 7 in the width direction W is larger than the length of the piezoelectric element 4 in the width direction W. That is, the end portion 7c of the main body portion 7 in the width direction W is located outside the edge portion 4b of the piezoelectric element 4 in the width direction W (see FIG. 1).

[0031] The connecting portions 8, 8 form a strip shape in a plan view of the vibrating portion 5 and extend in the extending direction D. The end portion 8a on the piezoelectric element 4 side in the connecting portion 8 overlaps with the edge portion 4b of the piezoelectric element 4 in the width direction W. There is no particular limitation on the overlapping width between the end portion 8a of the connecting portion 8 and the edge portion 4b of the piezoelectric element 4, but the overlapping width is, for example, about 1% to 10% of the length of the piezoelectric element 4 in the width direction W.

[0032] The end portion 8b on the side opposite to the piezoelectric element 4 in the connecting portion 8 is located inside the end portion 5d of the vibrating portion 5 in the width direction W. The interval between the end portion 8b of the connecting portion 8 and the end portion 5d of the vibrating portion 5 is arbitrary. In the example of FIG. 1, the end portion 8b of the connecting portion 8 is located between the edge portion 4b of the piezoelectric element 4 and the end portion 5d of the vibrating portion 5 in the width direction W, but the end portion 8b of the connecting portion 8 may overlap with the edge portion 4b of the piezoelectric element 4 or may overlap with the end portion 5d of the vibrating portion 5.

[0033] FIG. 3 is a diagram for explaining the operation of the vibration limiting section. In the example of this figure, the first vibration mode, the second vibration mode, and the third vibration mode of the bending vibration generated by the piezoelectric element 4 are respectively shown. As described above, both end portions 5c, 5c in the extending direction D of the vibrating section 5 are fixed by the fixing section 3. Therefore, in any vibration mode, both end portions 5c, 5c in the extending direction D of the vibrating section 5 serve as fixed ends of the bending vibration. The displacement amplitude amount at the position of the antinode Na in each vibration mode is the largest in the first vibration mode and becomes smaller as the vibration mode becomes higher order.

[0034] The first vibration mode is the vibration mode to be taken out as the output of the vibration device 1. In the vibration waveform of the first vibration mode, there is one antinode Na with respect to the extending direction D. Assuming the position of one fixed end is 0 and the position of the other fixed end is L, in the vibration waveform of the first vibration mode, the position of L / 2 is the antinode Na, and the positions of 0 and L are the nodes Nb.

[0035] Both the second vibration mode and the third vibration mode are vibration modes to be restricted by the vibration limiting section 6. In the vibration waveform of the second vibration mode, there are two antinodes Na with respect to the extending direction D. In the vibration waveform of the second vibration mode, the positions of L / 4 and 3L / 4 are the antinodes, and the positions of 0, L / 2, and L are the nodes Nb. In the third vibration mode, there are three antinodes Na of the vibration waveform with respect to the extending direction D. In the vibration waveform of the third vibration mode, the positions of L / 6, L / 2, and 5L / 6 are the antinodes Na, and the positions of 0, L / 3, 2L / 3, and L are the nodes Nb.

[0036] In the example of FIG. 3, the end portion 7a on the fixed portion 3 side in the main body portion 7 of the vibration restricting portion 6 is located on the fixed portion 3 (fixed end) side with respect to the position of the antinode Na of the third vibration mode waveform of the bending vibration with respect to the extending direction D, which is closer to the fixed portion 3 side than the position of the antinode Na closest to the fixed portion 3 side. The end portion 7b on the piezoelectric element 4 side in the main body portion 7 of the vibration restricting portion 6 is located on the piezoelectric element 4 side with respect to the position of the antinode Na of the vibration waveform of the second vibration mode with respect to the extending direction D, which is closer to the piezoelectric element 4 side than the position of the antinode Na closest to the fixed portion 3 side. The edge portion 4b on the piezoelectric element 4 side in the main body portion 7 is located on the fixed portion 3 (fixed end) side with respect to the antinode Na of the first vibration mode waveform of the bending vibration with respect to the extending direction D.

[0037] That is, the end portion 7a on the fixed portion 3 side in the main body portion 7 is located in the range of 0 to L / 6, and the end portion 7b on the piezoelectric element 4 side in the main body portion 7 is located in the range of L / 4 to L / 2. In the present embodiment, the end portion 7a on the fixed portion 3 side in the main body portion 7 is located at L / 132, and the end portion 7b on the piezoelectric element 4 side in the main body portion 7 is located at L / 4. With such an arrangement of the vibration restricting portion 6, in the vibrating portion 5, while the amplitude at the antinode Na of the vibration waveform in the first vibration mode is not inhibited, it is possible to apply a certain limit to the amplitude at the antinode Na of the vibration waveforms in the second and third vibration modes. As a result, the vibration frequency of the vibrating portion 5 shifts to the high frequency side as compared with the case where the vibration restricting portion 6 is not arranged.

[0038] As described above, in the vibration device 1, in a plan view of the vibrating portion 5, the vibration restricting portion 6 is disposed at least in a region between the piezoelectric element 4 and the fixing portion 3 and separated from the central portion C of the fixing portion 3 and the piezoelectric element 4. By this arrangement of the vibration restricting portion 6, the natural frequency of the vibrating portion 5 can be shifted to the high frequency side. Therefore, it is possible to suppress the occurrence of higher-order vibration modes in the effective frequency region, and it is possible to suppress a decrease in sound pressure and waveform distortion caused by the vibrations canceling each other out. In this vibration device 1, since the vibration restricting portion 6 is separated from the fixing portion 3, the bending vibration starting from both end portions 5c, 5c of the vibrating portion 5 is maintained, and since the vibration restricting portion 6 is separated from the central portion C of the piezoelectric element 4, it is also possible to avoid the amplitude of the primary vibration mode to be extracted as an output from being inhibited. Therefore, an improvement in sound pressure can be achieved.

[0039] In the present embodiment, the end portion 7a on the fixing portion 3 side in the vibration restricting portion 6 is located closer to the fixing portion 3 than the position of the antinode Na of the vibration waveform of the third vibration mode of the bending vibration with respect to the extending direction D. Further, the end portion 7b on the piezoelectric element 4 side in the vibration restricting portion 6 overlaps with the edge portion 4a of the piezoelectric element 4 in a plan view of the vibrating portion 5 and is located closer to the piezoelectric element 4 than the position of the antinode Na of the vibration waveform of the second vibration mode of the bending vibration with respect to the extending direction D. By arranging the vibration restricting portion 6 at the position of the antinode Na of the vibration waveform of the higher-order vibration mode in this way, the occurrence of higher-order vibration modes in the effective frequency region can be effectively suppressed.

[0040] In the present embodiment, the vibration restricting portion 6 has a connecting portion 8 that connects the main body portion 7 located on one side of the piezoelectric element 4 and the main body portion 7 located on the other side of the piezoelectric element 4. By connecting the main body portions 7, 7 to each other by the connecting portions 8, 8, the bending rigidity in the vibration restricting portion 6 can be more sufficiently ensured. Therefore, the occurrence of higher-order vibration modes in the effective frequency region can be effectively suppressed. [Second Embodiment]

[0041] FIG. 4 is a schematic plan view showing the configuration of the vibration device according to the second embodiment. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4. As shown in the figure, the vibration device 11 according to the second embodiment is different from the vibration device 1 according to the first embodiment in that the connecting portion 8 is not provided in the vibration restricting portion 6, and the vibration restricting portion 6 is composed of only the main portion 7.

[0042] Also in the vibration device 11 having such a configuration, the natural frequency of the vibrating portion 5 can be shifted to the high-frequency side by the arrangement of the vibration restricting portion 6. Therefore, it is possible to suppress the generation of higher-order vibration modes in the effective frequency region, and it is possible to suppress a decrease in sound pressure and waveform distortion due to the vibrations canceling each other out. Also in this vibration device 11, since the vibration restricting portion 6 is separated from the fixing portion 3, the bending vibration starting from both ends 5c, 5c of the vibrating portion 5 is maintained, and since the vibration restricting portion 6 is separated from the central portion C of the piezoelectric element 4, it is also possible to avoid the amplitude of the fundamental vibration mode to be taken out as an output from being inhibited. Therefore, an improvement in sound pressure can be achieved.

[0043] Further, also in this vibration device 11, the end portion 7b on the piezoelectric element 4 side of the vibration restricting portion 6 overlaps with the edge portion 4a of the piezoelectric element 4. For this reason, the vibration restricting portion 6 is arranged at the position of the antinode Na of the vibration waveform of the higher-order vibration mode, and the generation of the higher-order vibration mode in the effective frequency region can be effectively suppressed. [Third Embodiment]

[0044] FIG. 6 is a schematic plan view showing the configuration of the vibration device according to the third embodiment. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6. As shown in the figure, the vibration device 21 according to the third embodiment is further different from the vibration device 11 according to the second embodiment in that the end portion 7b on the piezoelectric element 4 side of the vibration restricting portion 6 is separated from the edge portion 4a of the piezoelectric element 4 in a plan view of the vibrating portion 5.

[0045] Even in the vibration device 21 having such a configuration, the arrangement of the vibration restricting portion 6 can shift the natural frequency of the vibrating portion 5 to the high frequency side. Therefore, it is possible to suppress the occurrence of higher-order vibration modes in the effective frequency region, and it is possible to suppress a decrease in sound pressure and distortion of the waveform due to the vibrations canceling each other out. Also in this vibration device 21, since the vibration restricting portion 6 is separated from the fixing portion 3, the bending vibration starting from both end portions 5c, 5c of the vibrating portion 5 is maintained, and since the vibration restricting portion 6 is separated from the central portion C of the piezoelectric element 4, it is also possible to avoid the amplitude of the fundamental vibration mode to be extracted as an output from being inhibited. Therefore, an improvement in sound pressure can be achieved.

[0046] Also in this vibration device 21, it is preferable that the end portion 7b on the piezoelectric element 4 side in the vibration restricting portion 6 is located on the piezoelectric element 4 side with respect to at least the position of the antinode Na of the vibration waveform of the third-order vibration mode of the bending vibration with respect to the extending direction D, and more preferably, it is located on the piezoelectric element 4 side with respect to at least the position of the antinode Na of the vibration waveform of the second-order vibration mode of the bending vibration with respect to the extending direction D. In this case, by arranging the vibration restricting portion 6 at the position of the antinode Na of the vibration waveform of the higher-order vibration mode, the occurrence of the higher-order vibration mode in the effective frequency region can be effectively suppressed. [Modification Example]

[0047] The present disclosure is not limited to the above-described embodiment. For example, in the above-described embodiment, both end portions 5c, 5c in the extending direction D of the vibrating portion 5 are fixed by the fixing portion 3, but in addition to this, both end portions in the width direction of the vibrating portion 5 may be further fixed by the fixing portion 3. In this case, by fixing the four sides of the vibrating portion 5 by the fixing portion 3, the driving of the piezoelectric element 4 fixed to the vibrating portion 5 can be stabilized.

[0048] In the above embodiment, the shape of the main body portion 7 of the vibration restricting portion 6 is a rectangular shape having a short side along the extending direction D and a long side along the width direction W, but it is not limited thereto. The shape of the main body portion 7 of the vibration restricting portion 6 may be a rectangular shape having a long side along the extending direction D and a short side along the width direction W, or may be a square shape in which the side along the extending direction D and the side along the width direction W are equal. The shape of the main body portion 7 of the vibration restricting portion 6 may be circular, elliptical, or oval.

[0049] In the above embodiment, the vibration portion 5 has a rectangular shape having a long side along the extending direction D and a short side along the width direction, but it is not limited thereto. The shape of the vibration portion 5 may be a rectangular shape having a short side along the extending direction D and a long side along the width direction, or may be a square shape in which the side along the extending direction D and the side along the width direction W are equal. The shape of the vibration portion 5 may be circular, elliptical, or oval. When the vibration portion 5 is circular, for example, any one direction in the radial direction of the circle can be set as the extending direction D, and the direction orthogonal to the one direction can be set as the width direction W. When the vibration portion 5 is elliptical or oval, for example, the major axis direction can be set as the extending direction D, and the minor axis direction can be set as the width direction W.

[0050] In the above embodiment, the piezoelectric element 4 is arranged on one surface 5a side of the vibration portion 5, and the vibration restricting portion 6 is arranged on the other surface 5b side, but the vibration restricting portion 6 may be arranged on one surface 5a side of the vibration portion 5, and the piezoelectric element 4 may be arranged on the other surface 5b side. In the case of the aspect where the piezoelectric element 4 and the vibration restricting portion 6 do not overlap as in the third embodiment, the piezoelectric element 4 and the vibration restricting portion 6 may be arranged on the same surface of the vibration portion 5.

Explanation of Reference Numerals

[0051] 1... Vibration device, 2... Piezoelectric vibrator, 3... Fixing portion, 4... Piezoelectric element, 4a... Edge portion, 5... Vibration portion, 6... Vibration restricting portion, 7a... End portion, 7b... End portion, 8... Connecting portion, C... Central portion.

Claims

1. A piezoelectric element, a vibration part to which the piezoelectric element is fixed and which generates bending vibration by driving the piezoelectric element, a fixing part for fixing the vibration part, a vibration restricting part having a bending rigidity equal to or higher than that of the vibration part and restricting a part of the bending vibration generated in the vibration part, and comprising: the vibration restricting part is located in at least a region between the piezoelectric element and the fixing part in a plan view of the vibration part, and is arranged so as to be separated from the central parts of the fixing part and the piezoelectric element, the vibration restricting part has a region that does not overlap with the piezoelectric element and overlaps only the vibration part in a plan view of the vibration part. A vibration device.

2. The vibration device according to claim 1, wherein an end portion of the vibration restricting part on the fixing part side is located closer to the fixing part side than a position of an antinode of a vibration waveform of a higher-order vibration mode of the bending vibration.

3. The vibration device according to claim 1 or 2, wherein an end portion of the vibration restricting part on the piezoelectric element side overlaps an edge portion of the piezoelectric element in a plan view of the vibration part.

4. The vibration device according to any one of claims 1 to 3, wherein the vibration restricting part further has a connecting part that connects a part located on one side of the piezoelectric element and a part located on the other side of the piezoelectric element.

5. A piezoelectric element, a vibration part to which the piezoelectric element is fixed and which generates bending vibration by driving the piezoelectric element, a vibration restricting part having a bending rigidity equal to or higher than that of the vibration part and restricting a part of the bending vibration generated in the vibration part, and comprising: the vibration restricting part is arranged so as to be separated from at least a central part of the piezoelectric element in a plan view of the vibration part, the vibration restricting part has at least in an extending direction of the vibration part a region that does not overlap with the piezoelectric element and overlaps only the vibration part in a plan view of the vibration part. A piezoelectric vibrator.

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