JPS643279Y2 - - Google Patents

Description

[Detailed explanation of the invention] Field of the invention This invention relates to a piezoelectric speaker.
In particular, the present invention relates to a piezoelectric speaker with an improved sound pressure generation source.

Description of the Prior Art Conventionally, piezoelectric speakers that are of interest to this invention have used a piezoelectric ceramic body with a unimorph or bimorph configuration, and have generated sound pressure by vibration in a bending mode.

In such a typical conventional piezoelectric speaker,
The disadvantage is that the displacement is largest near the resonance point, a sound pressure peak appears, and it is difficult to obtain an overall flat frequency characteristic. In addition, when trying to obtain a sounding body with a sound pressure peak in the low frequency range, the piezoelectric ceramic body needs to be thin and large in diameter. This makes it more likely to break and also limits the sound pressure.

Purpose of the invention Therefore, the purpose of this invention is to create a piezoelectric speaker that can obtain flat frequency characteristics and extend the usable frequency range to the lower frequency side compared to typical piezoelectric speakers. It is to provide a shaped speaker.

Summary of the invention This invention uses a cylindrical piezoelectric ceramic body.
This is a piezoelectric speaker characterized by expanding and contracting vibration in the radial direction. That is, a cylindrical piezoelectric ceramic body has electrodes formed on its inner and outer circumferential surfaces, and when a driving voltage is applied between both electrodes, the piezoelectric ceramic body expands and contracts in the radial direction. Vibrate. A closed container is disposed on the inner circumferential side of such a piezoelectric ceramic body so as to be in contact with the inner circumferential surface of the piezoelectric ceramic body, and a fluid such as oil is confined in this closed vessel. A cylinder portion is formed while being in communication with the inside of the closed container, and a piston is disposed within the cylinder portion.
It is provided so as to slide in close contact with the inner wall of the cylinder part. A diaphragm serving as a diaphragm of this speaker is fixedly attached to the piston.

Effects of the invention According to this invention, the radial expansion and contraction vibration of the cylindrical piezoelectric ceramic body is transmitted to the fluid confined in the closed container, thereby causing the piston disposed in the cylinder to make linear reciprocating motion. This causes the diaphragm to vibrate. Since such a vibration mode is used, it is possible to use the speaker in a frequency range lower than the resonance point, and the usable frequency range can be extended to the lower frequency side compared to a typical conventional piezoelectric speaker. Furthermore, since it can be used as a speaker in a manner that avoids resonance peaks and can be expected to have a damping effect due to the fluid, it is possible to obtain flat sound pressure frequency characteristics as a whole.
Furthermore, compared to conventional dynamic speakers, the effects of a normal piezoelectric speaker, such as high impedance and low power consumption, are maintained. Furthermore, by changing the dimensions of the closed container, cylinder section, etc., the voltage-sound pressure characteristics can be set arbitrarily.

DESCRIPTION OF THE EMBODIMENTS The drawings show a cross-sectional structure of an embodiment of the invention.

First, a piezoelectric ceramic body 1 constituting a part of a sound pressure generation source is placed in a frame 2. As shown in FIG. The piezoelectric ceramic body 1 has a cylindrical shape as a whole, and electrodes (not shown) are formed on its inner and outer circumferential surfaces, respectively. Such a cylindrical piezoelectric ceramic body 1 expands and contracts in the radial direction, that is, in the direction of the arrow 3, by applying a driving voltage between the above-mentioned two electrodes.

A closed container 4 is arranged on the inner peripheral side of the piezoelectric ceramic body 1. This closed container 4 is brought into contact with the inner peripheral surface of the piezoelectric ceramic body 1. A fluid 5 such as a liquid such as oil or a gas is confined within the closed container 4 . At the end of the closed container 4, a cylinder portion 6 having a relatively small diameter is provided. The cylinder part 6 is in communication with the inside of the closed container 4, and the fluid 5 is filled even into the cylinder part 6.

A piston 7 is arranged within the cylinder portion 6. The piston 7 is configured to be able to slide while being in close contact with the inner wall of the cylinder portion 6.

A cone-shaped diaphragm 8 is fixedly attached at its apex to the outer end of the piston 7. The peripheral edge of the diaphragm 8 is supported by the frame 2 in a manner that does not hinder the vibration of the diaphragm 8.

In such a piezoelectric speaker, when the piezoelectric ceramic body 1 expands and contracts in the direction of the arrow 3 as described above, this vibration is transmitted to the wall of the closed container 4, causing the fluid 5 to vibrate in the direction of the arrow 9. This vibration is transmitted to the piston 7, and the diaphragm 8 vibrates in the direction of the arrow 10 via the piston 7.
A predetermined sound wave is generated.

Although this invention has been described above in connection with the illustrated embodiment, various modifications are possible within the scope of this invention. For example, the cylinder portion 6 does not need to be provided directly at the end of the closed container 4, and may be configured by connecting an appropriate pipe to the closed container 4 directly or indirectly. Further, the shape of the diaphragm 8 may be other than the illustrated cone shape.

[Brief explanation of the drawing]

The drawing is a sectional view showing an embodiment of this invention. In the figure, 1 is a piezoelectric ceramic body, 4 is a closed container, 5 is a fluid, 6 is a cylinder part, 7 is a piston,
8 is a diaphragm.

Claims (1)

[Claims for Utility Model Registration] Electrodes are formed on the inner circumferential surface and the outer circumferential surface, respectively,
a cylindrical piezoelectric ceramic body that expands and contracts in the radial direction by applying a driving voltage between both electrodes; a closed container, a cylinder portion that is in communication with the inside of the closed container, a piston that is slidably provided in the cylinder portion while being in close contact with an inner wall of the cylinder portion, and a piston that is fixedly attached to the piston. A piezoelectric speaker comprising a diaphragm.