JPS63263999A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To improve the sound pressure level of a low area frequency by constituting an acoustic cavity of a sounding body and a case to be adhered with a piezoelectric element and an oscillator and drilling a sound releasing hole at a diaphragm. CONSTITUTION:A piezoelectric element 1 to be baked and formed an electrode at both surfaces of a piezoelectric magnetic base and a sounding body 3 to be stuck and constituted a metallic shallow tray-shaped diaphragm 2 are linked by adhesives to a case 5 in a marginal part so that a cavity 4 can be intermediately formed. At the diaphragm 2, the part of the piezoelectric element is avoided and a sound releasing hole 6 is drilled. When an electric oscillation is impressed to the piezoelectric element 1, the sounding body supported in the marginal part is bent and oscillated, a higher harmonic characteristic is controlled by the design of the resonance frequency of the sounding body 3 and the resonance frequency of a forward cavity 4, and thus, the hole diameter, the number of pieces and position of the sound releasing hole 6 in the diaphragm 2 are suitably selected and the low area resonance frequency in the cavity 4 can be set.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric speaker using a piezoelectric sounding body in which a piezoelectric element is bonded to a diaphragm.

[Problems with conventional technology]

A piezoelectric sounding body, in which a piezoelectric element made of ceramic is attached to a diaphragm, can be made thin, making it convenient for making speakers thinner; however, as a conventional piezoelectric speaker, A piezoelectric element is coupled to a diaphragm made of paper cone, etc., and the diaphragm is driven by the vibration of the piezoelectric element, or a cavity is formed by the space surrounded by the case and the sounding body, and the thickness of the case is 9.
The cavity frequency is set through acoustic design based on the selection of the distance from the sounding body, the outer diameter, the size of the sound emitting hole provided in the case, etc.

Although ceramic type piezoelectric elements have relatively good sound pressure frequency characteristics on the high frequency side, the sound pressure on the low frequency side is extremely low, so even when used in speakers, the sound pressure on the low frequency side The pressure was low, making it unsuitable for use as a dynamic speaker.

[Purpose of the invention]

An object of the present invention is to provide a piezoelectric speaker that improves the sound pressure at low frequencies while keeping the speaker itself thin and has sound pressure-frequency characteristics that are averaged over a wide band. The aim is to provide a thin tweeter.

[Failure to solve problems]

This device is characterized in that an acoustic cavity is formed so as to be surrounded by a case and a sounding body in which a piezoelectric element and a diaphragm are bonded together, and a sound emitting hole is formed in the diaphragm.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention illustrated in the drawings will be described in detail.

The embodiments shown in FIGS. 1 and 2 include a piezoelectric element with electrodes baked on both sides of a piezoelectric ceramic base, and a diaphragm shaped like a residual tray made of metal such as brass, stainless steel, or metal. 2
The sounding body 3 is bonded to the case 5 at the periphery with an adhesive so that a cavity 4 is formed in the middle. A sound emitting hole 6 is formed, so that when electric vibration is applied to the piezoelectric element 1, the sounding body 3 supported at the periphery vibrates bending, and the resonance frequency of the sounding body 3 and the front The low-frequency resonance frequency in the cavity 4 is set by controlling the harmonic characteristics by designing with the resonance frequency of the cavity 4, and by appropriately selecting the number and number of hole diameters of the sound emission holes 6 in the diaphragm 2. It is possible,
Therefore, while the conventional piezoelectric speaker has a frequency characteristic as shown by the dotted line in FIG. 4, this embodiment has a frequency characteristic as shown by the chain line in FIG. 4.

Further, in the embodiment shown in FIG.
The cases 5a and 5b are adhesively bonded to each other so that the sounding body 3 is surrounded by the cases 5a and 5b while being held at its peripheral edge so that cavities 4a and 4b are formed on both front and rear surfaces of the case 5a and 5b. is provided with a sound emission hole 7, so that one of the cavities 4a and 4b, for example, cavity 4a, can raise the cavity frequency to 400.
Hz, and the frequency of the other cavity 4b is set to 5 to 6 KHz to improve the sound pressure level of frequencies close to that frequency, and the sound emitting hole 6 of the sounding body 3 is set to 5 to 6 KHz. The low frequency sound pressure level is further improved by making the frequency match the set frequency, thereby making it possible to obtain a flat sound pressure-frequency characteristic in a wide band as shown by the solid line in FIG.

It is desirable that both cases 5a and 5b in the embodiment shown in FIG. It is possible to equalize the conditions.

In both of the above embodiments, the shape of the diaphragm 2 is in the shape of a residual tray, but it may also be flat or dish-shaped, and the piezoelectric element 1 may also be of the Unimo #7 fJh type or the bimorph type. It goes without saying that it can be applied and may also be flat or dish-shaped.

〔Effect of the invention〕

As explained above, according to the present invention, in a piezoelectric speaker consisting of a case and a sounding body formed by pasting a piezoelectric element and a diaphragm, the diaphragm itself is provided with sound emission holes. Despite keeping the speaker thin with a thickness of about 2 to 3 mm and a small diameter of about 20 to 40 mm, the sound pressure level in the low frequency range is improved and a flat frequency range over a wide range is achieved. If the characteristics can be obtained and the case is configured on only one side, there is no problem even if the case side is brought close together during installation, and it is suitable as a tweeter.

Furthermore, by providing a case so that acoustic cavities are formed on both sides of the sounding body, the sound pressure level at low frequencies can be further improved, making it possible to adapt it to a wide range of applications.

[Brief explanation of drawings]

In the drawings, FIGS. 1 and 2 are a perspective view and a vertical side view showing a piezoelectric speaker of the present invention in one embodiment, respectively, FIG. 3 is a vertical side view showing another embodiment, and FIG. 4 is a sound It is a pressure-frequency characteristic diagram. 1...Piezoelectric element 2...Diaphragm 3...Sounding body 4.4a, 4b, fist φ capacity 5.5a, 5b...Case 6...Sound emission hole 7...Sound emission hole 8...Concavity for preventing adhesion

Claims (1)

[Claims] 1. A sounding body in which a piezoelectric element and a diaphragm are bonded together and a case are combined so that an acoustic cavity surrounded by both is formed, and the piezoelectric element is bonded to the diaphragm. A piezoelectric speaker characterized in that a sound emitting hole is formed avoiding the mounting part. 2. A patent claim characterized in that the case is joined to surround the sounding body from both sides so that an acoustic cavity is formed on both sides of the sounding body, and the case is provided with a sound emitting hole. The piezoelectric speaker according to the range 1 above. 3. The piezoelectric speaker according to claim 2, wherein a recess for preventing contact is provided on the surface of the case.