Piezoelectric sounder

Abstract

To reproduce a wide frequency band at a high sound pressure.SOLUTION: A piezoelectric sounder 10 of the present disclosure includes a plate-shaped piezoelectric ceramic 20 having one surface and the other surface, a metal plate 30 having an inner peripheral part 31 bonded to one surface of the piezoelectric ceramic 20 and an outer peripheral part 32 located on the outer peripheral side of the inner peripheral part 31, a vibration plate 40 having a covering part 43 covering the metal plate 30 from the side opposite to the piezoelectric ceramic 20 in which an opening edge part 42 of an opening 41 of the covering part 43 that opens toward the metal plate 30 extends toward the outer peripheral part 32 and a part of the covering part 43 is bonded to the metal plate 30, and a fixing part 50 that fixes the other surface of the piezoelectric ceramic 20. According to such a configuration, a diaphragm 40 can be driven by the outer peripheral part 32 of the metal plate 30. Since the diaphragm 40 is driven by bending of the metal plate 30 and the change in a radial direction, a sound in a wide band can be generated with a high sound pressure. In addition to characteristics of the piezoelectric sounder 10 itself, arbitrary acoustic characteristics can be obtained depending on the material and shape of the diaphragm 40.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a piezoelectric sounding body. [Background technology]

[0002] Conventionally, a piezoelectric speaker device using a piezoelectric element is known, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-304598 (Patent Document 1 below). Among such piezoelectric speaker devices, a speaker device specialized for high frequencies is known, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-299194 (Patent Document 2 below). This speaker for ultra-high frequencies includes a substantially disk-shaped piezoelectric ceramic vibrator formed by bonding a piezoelectric ceramic to a metal substrate, a dome-shaped diaphragm attached to the piezoelectric ceramic vibrator, and a panel that fixes the outer periphery of the piezoelectric ceramic vibrator. An opening in the panel exposes essentially only the dome portion to the outside. The panel covers the front of the outer periphery of the piezoelectric ceramic vibrator, blocking sound from there. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-304598 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-299194 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned ultra-high frequency speakers are suitable for reproducing ultra-high frequencies, but because the outer periphery of the diaphragm is fixed to the panel, there is no stroke and they cannot reproduce a wide frequency range at high sound pressure. [Means for solving the problem]

[0005] The piezoelectric speaker of the present disclosure is a piezoelectric speaker comprising: a plate-shaped piezoelectric ceramic having one side and another side; a metal plate having an inner peripheral portion bonded to the one side of the piezoelectric ceramic and an outer peripheral portion located outer than the inner peripheral portion; a diaphragm having a cover portion covering the metal plate from the side opposite the piezoelectric ceramic, the opening edge of the opening of the cover portion that opens toward the metal plate extending toward the outer peripheral portion, and a fixing portion that fixes the other side of the piezoelectric ceramic; [Effects of the Invention]

[0006] According to the present disclosure, a wide frequency band can be reproduced with high sound pressure. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a front view of the piezoelectric sounding body of the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the internal structure of the piezoelectric sounding body of the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing a state in which the outer periphery of the metal plate is bent upward. [Figure 4] FIG. 4 is a cross-sectional view showing a state in which the outer periphery of the metal plate is bent downward. [Figure 5] FIG. 5 is a graph showing the frequency characteristics of the piezoelectric sounding body. [Figure 6] FIG. 6 is a front view of the piezoelectric sounding body of the second embodiment. [Figure 7] FIG. 7 is a front view of the piezoelectric sounding body of the third embodiment. [Figure 8] FIG. 8 is a front view of the piezoelectric sounding body of the fourth embodiment. [Figure 9] FIG. 9 is a front view of the piezoelectric sounding body of the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) The piezoelectric speaker of the present disclosure comprises a plate-shaped piezoelectric ceramic having one surface and another surface, a metal plate having an inner peripheral portion bonded to the one surface of the piezoelectric ceramic and an outer peripheral portion located on the outer periphery side of the inner peripheral portion, a cover portion covering the metal plate from the side opposite the piezoelectric ceramic, the opening edge of the opening of the cover portion facing the metal plate extending toward the outer periphery, and a vibration plate in which a portion of the cover portion is bonded to the metal plate, and a fixing portion fixing the other surface of the piezoelectric ceramic.

[0009] With this configuration, the diaphragm can be driven by the outer periphery of the metal plate. Because the diaphragm is driven by the bending and radial changes of the metal plate, it is possible to generate sounds over a wide frequency range with high sound pressure. Furthermore, in addition to the characteristics of the piezoelectric sounding body itself, desired acoustic characteristics can be obtained by changing the material and shape of the diaphragm.

[0010] (2) The fixing portion preferably fixes the center of the other surface of the piezoelectric ceramic. By fixing the center of the other surface of the piezoelectric ceramic, the outer periphery of the metal plate vibrates, making it easier to drive the entire diaphragm.

[0011] (3) The diaphragm may have any shape driven by the outer periphery of the metal plate, but it is preferable that the diaphragm be, for example, a cone shape, an arc-shaped dome shape, a hemispherical dome shape, a spherical dome shape, or a cylindrical box shape. These diaphragms can increase sound pressure by driving the entire diaphragm.

[0012] [Details of the embodiments of the present disclosure] Embodiments 1 to 5 of the present disclosure will be described with reference to Figures 1 to 9. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the following description, when multiple identical components are used, only some of the components may be designated by reference numerals, and the reference numerals for other components may be omitted.

[0013] <Embodiment 1> As shown in Fig. 1, the piezoelectric sounding body 10 of embodiment 1 is fixed to the upper surface of a base 11. The base 11 is a support member that supports the piezoelectric sounding body 10. Any material can be used for the base 11, such as wood, resin, or metal. As shown in Fig. 2, the piezoelectric sounding body 10 includes a piezoelectric ceramic 20, a metal plate 30, a diaphragm 40, and a fixed portion 50.

[0014] The piezoelectric ceramic 20 is a small, circular, and general-purpose piezoelectric ceramic that is widely used. A voltage is applied to the piezoelectric ceramic 20 via an electric wire 60. When a voltage is applied, the piezoelectric ceramic 20 expands and contracts in the radial direction. The piezoelectric ceramic 20 has an upper surface 21 and a lower surface 22. Piezoelectric ceramics of any material, shape, and thickness can be used as the piezoelectric ceramic 20. The upper surface 21 corresponds to "one surface" in this disclosure, and the lower surface 22 corresponds to "the other surface" in this disclosure.

[0015] The metal plate 30 is a circular, flat metal plate. The piezoelectric ceramic 20 is disposed in the center of the metal plate 30. The metal plate 30 is bonded to the upper surface 21 of the piezoelectric ceramic 20. Any metal plate of any material, shape, and thickness can be used as the metal plate 30. The piezoelectric ceramic 20 and the metal plate 30 constitute a monomorph type piezoelectric ceramic vibrator. In addition to the monomorph type, bimorph type and stacked type piezoelectric ceramic vibrators can also be used as the piezoelectric ceramic vibrator.

[0016] The metal plate 30 has a larger diameter than the piezoelectric ceramic 20. The portion of the metal plate 30 that is fixed to the upper surface 21 of the piezoelectric ceramic 20 is referred to as an inner peripheral portion 31, and the portion located on the outer peripheral side of the inner peripheral portion 31 is referred to as an outer peripheral portion 32. The outer peripheral portion 32 protrudes radially outward beyond the outer edge of the piezoelectric ceramic 20.

[0017] The diaphragm 40 is a flat metal plate formed into a conical shape. The diaphragm 40 has a cover portion 43 that covers the metal plate 30. The cover portion 43 is arranged coaxially with the piezoelectric ceramic 20 and the metal plate 30. The diaphragm 40 has an opening 41 that opens downward. The opening edge 42 of the opening 41 extends toward the outer periphery 32 of the metal plate 30, and a portion of the cover portion 43 is bonded to the metal plate 30. The metal plate 30 and the diaphragm 40 are bonded together with an adhesive (not shown). This bonding allows vibrations to propagate from the metal plate 30 to the diaphragm 40, and the diaphragm 40 vibrates in response to the vibrations of the metal plate 30. The diaphragm 40 can be made of any material, including resin, metals such as aluminum, and paper. The characteristics and tone of the piezoelectric speaker 10 can be adjusted by changing the material, shape, and thickness of the diaphragm 40.

[0018] The fixing portion 50 fixes the center of the lower surface 22 of the piezoelectric ceramic 20 to the upper surface of the base 11. The maximum dimension of the fixing portion 50 is preferably equal to or less than one-fifth the diameter of the metal plate 30. Any material such as resin or metal can be used for the fixing portion 50. The fixing portion 50 of this embodiment is a metal cylinder.

[0019] <Example> When a voltage is applied to the piezoelectric speaker 10, the piezoelectric ceramic 20 expands and contracts, causing the outer periphery 32 of the metal plate 30 to bend and deform in the vertical direction. FIG. 3 shows the state in which the outer periphery 32 is bent and deformed upward, and FIG. 4 shows the state in which the outer periphery 32 is bent and deformed downward. The outer periphery 32 quickly alternates between the state shown in FIG. 3 and the state shown in FIG. 4, causing the diaphragm 40 to vibrate in the vertical direction. The opening edge 42 of the diaphragm 40 is fixed to the outer periphery 32 of the metal plate 30, and is vibrated in the vertical direction by the outer periphery 32, so the entire cover 43 of the diaphragm 40 vibrates in the vertical direction. This allows for a significantly higher sound pressure than a piezoelectric speaker alone without the diaphragm 40.

[0020] Figure 5 is a graph showing the sound pressure corresponding to the frequency band for three piezoelectric sounders: a piezoelectric sounder alone, a piezoelectric sounder using a small conical diaphragm made of paper (small paper cone), and a piezoelectric sounder using a large conical diaphragm made of paper (large paper cone). The diameter of the small diaphragm is equal to the diameter of the metal plate, while the diameter of the large diaphragm is larger than the diameter of the metal plate.

[0021] It can be seen that in the frequency range above 1000Hz, the sound pressure is higher when a paper cone is attached to the piezoelectric speaker alone than when it is the piezoelectric speaker alone. It can also be seen that the frequency at which the sound pressure increases varies depending on the size of the cone, and it can be seen that the sound pressure and frequency characteristics can be controlled by changing the shape and size of the diaphragm attached to the piezoelectric speaker (in this case, the cone diaphragm).

[0022] <Effects of the First Embodiment> As described above, the piezoelectric speaker 10 of embodiment 1 comprises a plate-shaped piezoelectric ceramic 20 having an upper surface 21 and a lower surface 22, a metal plate 30 having an inner peripheral portion 31 bonded to the upper surface 21 of the piezoelectric ceramic 20 and an outer peripheral portion 32 located outer than the inner peripheral portion 31, a vibration plate 40 having a cover portion 43 that covers the metal plate 30 from the side opposite the piezoelectric ceramic 20, and an opening edge portion 42 of an opening 41 that opens toward the metal plate 30 in the cover portion 43 extending toward the outer peripheral portion 32, and a fixing portion 50 that fixes the lower surface of the piezoelectric ceramic 20.

[0023] With this configuration, the diaphragm 40 can be driven by the outer periphery 32 of the metal plate 30. Because the diaphragm 40 is driven by bending and radial changes of the metal plate 30, it is possible to generate sounds over a wide frequency range with high sound pressure. Furthermore, in addition to the characteristics of the piezoelectric sounding body itself, any desired acoustic characteristics can be obtained by changing the material and shape of the diaphragm 40.

[0024] The fixing portion 50 fixes the center portion of the lower surface 22 of the piezoelectric ceramic 20. In this way, the outer peripheral portion 32 of the metal plate 30 vibrates, making it easier to drive the entire diaphragm 40.

[0025] The advantages over piezoelectric speakers include the following: -High sound pressure. -Frequency characteristics are flattened. -The structure is simple. High degree of freedom in designing required characteristics (characteristics and tone can be adjusted by changing the diaphragm material, shape, thickness, etc.).

[0026] The advantages over magnetic speakers include the following: ·light. No leakage magnetic flux. -Can be made thin. High degree of freedom in shape.

[0027] <Embodiment 2> A second embodiment of the present disclosure will be described with reference to Fig. 6. The piezoelectric sounding body 12 of the second embodiment is a modification of the diaphragm 40 of the first embodiment, and other configurations are the same as the piezoelectric sounding body 10 of the first embodiment, so a description thereof will be omitted. Furthermore, the same components as those of the first embodiment will be given the same reference numerals as those of the first embodiment. The piezoelectric sounding body 12 of this embodiment comprises a diaphragm 402. The diaphragm 402 is in the shape of a circular arc dome.

[0028] <Embodiment 3> A third embodiment of the present disclosure will be described with reference to Fig. 7. The piezoelectric sounding body 13 of the third embodiment is a modification of the diaphragm 40 of the first embodiment, and other configurations are the same as the piezoelectric sounding body 10 of the first embodiment, so a description thereof will be omitted. Furthermore, the same components as those of the first embodiment will be given the same reference numerals as those of the first embodiment. The piezoelectric sounding body 13 of this embodiment includes a diaphragm 403. The diaphragm 403 is hemispherical and dome-shaped.

[0029] <Embodiment 4> A fourth embodiment of the present disclosure will be described with reference to Fig. 8. The piezoelectric speaker 14 of the fourth embodiment is a modification of the diaphragm 40 of the first embodiment, and other configurations are the same as the piezoelectric speaker 10 of the first embodiment, so a description thereof will be omitted. Furthermore, the same components as those of the first embodiment will be given the same reference numerals as those of the first embodiment. The piezoelectric speaker 14 of this embodiment comprises a diaphragm 404. The diaphragm 404 is spherical and dome-shaped.

[0030] <Embodiment 5> A fifth embodiment of the present disclosure will be described with reference to Fig. 9. The piezoelectric sounding body 15 of the fifth embodiment is a modified version of the diaphragm 40 of the first embodiment, and other configurations are the same as the piezoelectric sounding body 10 of the first embodiment, so a description thereof will be omitted. Furthermore, the same components as those of the first embodiment will be given the same reference numerals as those of the first embodiment. The piezoelectric sounding body 15 of this embodiment comprises a diaphragm 405. The diaphragm 405 is in the shape of a cylindrical box.

[0031] <Other embodiments> (1) In the first to fifth embodiments, the fixing portion 50 is fixed to the center of the lower surface 22 of the piezoelectric ceramic 20, but the fixing portion 50 may be fixed to the outer periphery of the lower surface 22 of the piezoelectric ceramic 20.

[0032] (2) In the first to fifth embodiments, the inside of the cover 43 is closed by the metal plate 30, but holes may be formed in the cover to reduce the resonant frequency peak. [Explanation of symbols]

[0033] 10, 12, 13, 14, 15: Piezoelectric sounding body 11: Base 20: Piezoelectric ceramic 21: Upper surface (one surface) 22: Lower surface (other surface) 30: Metal plate 31: Inner circumference 32: Outer circumference 40, 402, 403, 404, 405: diaphragm 41: opening 42: opening edge 43: cover 50: Fixed part 60: Electric wire

Claims

1. a plate-shaped piezoelectric ceramic having one surface and another surface; a metal plate having an inner peripheral portion bonded to the one surface of the piezoelectric ceramic and an outer peripheral portion positioned outer than the inner peripheral portion; a vibration plate having a cover portion that covers the metal plate from the side opposite to the piezoelectric ceramic, wherein an edge portion of an opening of the cover portion that opens toward the metal plate extends toward the outer periphery, and a portion of the cover portion is bonded to the metal plate; a fixing portion that fixes the other surface of the piezoelectric ceramic.

2. 2. The piezoelectric sounding body according to claim 1, wherein said fixing portion fixes a central portion of said other surface of said piezoelectric ceramic.

3. 3. The piezoelectric sounding body according to claim 1, wherein said diaphragm is conical in shape.

4. 3. The piezoelectric sounding body according to claim 1, wherein said diaphragm is in the shape of a circular arc dome.

5. 3. The piezoelectric sounding body according to claim 1, wherein said diaphragm is a hemispherical dome type.

6. 3. The piezoelectric sounding body according to claim 1, wherein said diaphragm is spherical and dome-shaped.

7. 3. The piezoelectric sounding body according to claim 1, wherein said diaphragm is in the shape of a cylindrical box.

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