JPH11113093A - Piezoelectric speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sound quality and the sound pressure of a piezoelectric speaker. SOLUTION: A throughhole is formed to the front side and the rear side of a case in which a diaphragm adhered with a piezoelectric ceramic plate is housed and the case is fitted to a box 10 that has a cavity 16 in its inside. The case is fitted to the surface of the box 10 so that the throughhole of the rear side of the case connects to the cavity 16. Vibration of the diaphragm is conducted to the cavity 16 of the box 10 and the cavity 16 also acts like a vibration space.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric speaker, and more particularly to a structure of a piezoelectric speaker capable of improving sound quality and sound pressure.

[0002]

2. Description of the Related Art Generally, a speaker which generates vibration electromagnetically is used as a speaker, but a piezoelectric speaker which generates vibration by a piezoelectric element is also used for the purpose of miniaturization and low-current driving. This piezoelectric speaker generates a sound by applying a voltage to a piezoelectric ceramic plate attached to a diaphragm to generate vibration. There is also an advantage that magnetostriction does not occur, for example, when used in combination with a liquid crystal display device.

[0003] A diaphragm made of piezoelectric ceramic has a problem that the sound quality is poor and harsh because the natural vibration frequency is located at a higher frequency than the audible frequency. In order to solve this problem, attempts have been made to reduce the thickness, to make the shape rectangular, and to make corrections by selecting an attachment method and a material, but none of them has been satisfactory.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric speaker capable of improving sound quality in a low frequency band and improving sound pressure.

[0005]

According to the present invention, the vibration space is expanded by combining with a box having a hollow portion.
This is to solve the above problem.

That is, a metal plate on which a piezoelectric ceramic plate whose front and rear electrodes are connected to a drive circuit is fixed in a housing having through holes formed in the front and rear surfaces, and this housing has a hollow portion therein. Is characterized in that the through-hole on the back surface of the housing is attached to the box body having

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A piezo-electric ceramic plate is stuck in a housing and housed and fixed in a diaphragm. Through holes are formed in the front and back surfaces of the housing. This housing is mounted on the surface of a box made of wood, plastic, or the like having a cavity therein. The vibration of the diaphragm is transmitted to the inside of the cavity from the back of the housing, and the cavity also acts as a vibration space.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a front sectional view of a vibration generating portion of the piezoelectric speaker used in the present invention. The vibrating element is fixed in a rectangular or circular metal case. The metal case 21 has a space for accommodating elements, and has through holes 22 formed on the front and back surfaces. After accommodating the elements and the like, the upper plate and the lower plate are fixed by bonding or caulking. Even when a case other than metal is used, almost the same structure can be obtained.

A diaphragm 23 made of a 42 alloy or the like having a thickness of about 0.1 mm is arranged in a case 21 and a 0.1 m thick
A piezoelectric ceramic plate 24 of about m is attached. Electrodes of silver or the like are formed on both surfaces of the piezoelectric ceramic plate 24, and lead wires (not shown) are connected to the respective electrodes. The connection of the electrodes on the surface to be attached to the diaphragm 23 can be performed by soldering lead wires to the diaphragm 23. It is also possible to adopt a structure in which a metal plate is adhered to the diaphragm using polycarbonate or the like, and a piezoelectric ceramic plate is disposed thereon.
The peripheral portion of the diaphragm 23 is sandwiched by the foamed resin 25.

FIG. 1 is a front sectional view showing an embodiment of the present invention. The device shown in FIG. 2 is attached to a box. The box 10 made of a material such as wood or plastic has a cavity 16 inside.

The box 10 is made of three plates in this example. The back plate 11 and the front plate 12 are connected by a spacer 13, and a cavity 16 is formed inside. The spacer 13 is arranged so as to cover the entire periphery, and the cavity 16 is
It is connected to the external space at 12 openings 17. In addition, you may form a through-hole in a part of box.

In this example, a step is provided on the surface side of the opening 17 of the surface plate, and the housing 20 is housed in a recess formed by the step. Through hole on the back of the housing 20 (22 in FIG. 2)
Faces the opening 17 and is connected to the cavity 16. Housing
20 is fixed to the surface plate 12 of the box body 10 by screwing or the like.

A part of the vibration of the vibration plate caused by the voltage applied to the piezoelectric ceramic plate in the housing is transmitted from the through hole on the back surface of the housing to the cavity 16, and the cavity 16 becomes a part of the vibration space. . This vibration is transmitted to the outside through the box.

As described above, since the cavity is used as a vibration space, the vibration space becomes wider as compared with a conventional piezoelectric speaker in which only the inside of the housing is a vibration space. In the past, the restriction was imposed in a narrow space, but the restriction is removed, and vibration in a wide frequency band can be obtained. As a result, the frequency characteristic becomes flat and the sound quality is improved.

The present invention is not limited to the above example, and the structure of the box can be arbitrarily selected. Also,
The material can be appropriately changed according to the application. In addition, pictures, characters, and the like can be displayed or pasted as panels on the box body.

[0017]

According to the present invention, it is possible to improve the sound quality in the low frequency range which has not been obtained conventionally. Further, the high frequency side is conventionally strong and uncomfortable, but the high frequency side is relatively suppressed, and good characteristics can be obtained in a wide band.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention.

FIG. 2 is a partial front sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 10: Box 16: Cavity 20: Housing

Claims (2)

[Claims] 1. A metal plate on which a piezoelectric ceramic plate having electrodes on the front and back surfaces connected to a drive circuit is fixed in a housing having through holes formed on the front and back surfaces, and the housing has a hollow portion inside. A piezoelectric speaker is attached to a box having the following so that the through hole on the back surface of the housing faces the cavity. 2. A metal plate to which a piezoelectric ceramic plate having electrodes on the front and back surfaces connected to a driving circuit is fixed in a housing having through holes formed on the front and back surfaces, and the housing has a hollow portion inside. A piezoelectric speaker comprising: a housing having a concave portion connected to the through hole on the surface and having a concave portion connected to the through hole on a rear surface of the housing;