JPS63103600A - Piezoelectric electroacoustic transducer - Google Patents

Abstract

PURPOSE:To improve the electroacoustic conversion efficiency by coupling a recessed ridge of a piezoelectric film having an electrode formed to both sides and shaped as rugged stripes with a support base having a curved face. CONSTITUTION:In the piezoelectric element 1, a polyfluoride vinylidene film is formed while its cross section is a waving shape rugged stripe and a conductor foil is laminated to both sides to form the electrode and the low ridge line is coupled with a curved face of the support base 2 having a curved face constituting a part of a cylinder wall face. For example, in applying one polarity signal, the piezoelectric element 1 is expanded in the fatial direction and the peak of the waveform is increased and expanded and in applying the signal of the other polarity, the contraction, expansion and contraction are repeated conversely to obtain an acoustic output. Moreover, since the fatial direction expansion/contraction of the piezoelectric element efficiently is transduced into the forward/backward vibration, the acoustic radiation efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to piezoelectric electroacoustic transducers, particularly those using piezoelectric films.

[Prior Art] Conventionally, an electroacoustic transducer, such as a speaker, using a synthetic resin film having a pressure-to-electricity conversion function, such as polyvinylidene fluoride, is a piezoelectric transducer formed in a curved surface that forms part of a cylindrical wall surface. Acoustic output is produced by fixing both ends of the film, applying an AC signal between the electrodes formed on both surfaces of the piezoelectric film, and driving the curved surface in the radial direction by expanding and contracting the piezoelectric film in the plane direction. Two piezoelectric films with different configurations and polarization directions are laminated, the cross section of which is bent into a wave shape, and both edges of the film are fixed, and the electrode portion formed at the bent part of the wave shape is By applying an alternating current signal, adjacent wall surfaces of the waveform are driven in opposite directions, and the air between them is emitted and sucked, thereby obtaining acoustic output.

[Problems to be Solved by the Invention] The above-mentioned conventional piezoelectric film speaker has a serious problem in that the vibration amplitude cannot be maintained, that is, the electroacoustic conversion efficiency is significantly lower than that of electrodynamic speakers, etc. was.

Means for Solving the Problem] The present invention comprises a support substrate having a curved surface constituting a part of a cylindrical wall surface, and a piezoelectric film formed into uneven stripes and having electrode portions formed on both sides. The piezoelectric electroacoustic transducer includes a concave ridgeline portion of a piezoelectric film coupled to the support substrate.

[Operation] Acoustic output is obtained by converting the expansion and contraction of the piezoelectric film in the plane direction into vibrations in the height direction of the uneven shape.

[Example] This invention will be described below with reference to Examples.

Fig. 1 shows an embodiment of the present invention, and 1 is a piezoelectric element in which a polyvinylidene fluoride film is formed into a corrugated cross-sectional shape, and conductive foil is laminated on both sides to form an electrode part. . The direction of the uneven stripes is perpendicular to the stretching direction of the film, and converts the large expansion and contraction in the stretching direction into a change in wave height. The trough ridgeline of the piezoelectric element 1 is connected to the supporting substrate 2 having a curved surface forming a part of the cylindrical wall surface.
is connected to the corresponding curved surface. Then, an AC signal is applied to electrode portions formed on both sides of the piezoelectric element.

According to the above configuration, as shown in FIG. 2, when a signal of one polarity is applied, for example, the piezoelectric element 1 expands in the plane direction and the wave height of the waveform increases, as shown by the dashed line in the figure. When a signal of one polarity is applied to the other, it contracts as shown by the dotted line. The sound output is increased by 1q due to the expansion and contraction movements. Further, since the expansion and contraction of the piezoelectric element in the plane direction can be efficiently converted into vibration in the front-rear direction, the acoustic radiation efficiency can be improved.

FIG. 3 shows another embodiment, which is an electroacoustic transducer using a piezoelectric element having a concavo-convex strip portion 1a formed with a corrugated cross-sectional shape, that is, with different amplitudes and/or periods. According to the embodiment shown in FIG. 1, the effect of flattening the frequency characteristics is obtained by dispersing the resonance due to the same specific frequency that can be formed in the simple shape.

Further, a means for preventing unnecessary resonance may be used together by arranging a damping material between the piezoelectric element 1 and the support substrate 2 or at a desired location. In addition, the signal supply means has a configuration in which supply lead wires are directly connected to both sides of the piezoelectric element, respectively.
A conceivable configuration is to use the support substrate as part of the supply means by making at least the curved surface of the support substrate conductive and bonding the curved surface and the piezoelectric element with a conductive adhesive. In general, the cross-sectional shape of each driving portion is not limited to a waveform, and other shapes such as a trapezoid can be adopted.

[Effects of the Invention] According to the present invention, a significant increase in acoustic output can be achieved in a vibrating element using a piezoelectric film, and unnecessary resonance can be suppressed, resulting in electroacoustic conversion with flatter frequency characteristics. We were able to provide equipment.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts of an embodiment of the invention, FIG. 2 is a side view showing the operation of the embodiment of the invention, and FIG. 3 is a side view of another embodiment of the invention. 1 is a piezoelectric film, and 2 is a support substrate.

Claims (1)

[Claims] Support substrate (2
) and a piezoelectric film (1) having electrode parts formed on both sides and formed into uneven stripes, the piezoelectric film (1)
2. A piezoelectric electroacoustic transducer, characterized in that the ridgeline portion of the concave portion (2) is coupled to the support substrate (2).