JPH0419920Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to the structure of a piezoelectric speaker using a polymeric piezoelectric film as a diaphragm in the field of electroacoustic equipment.

[Prior Art] In the conventional structure of a piezoelectric speaker, which uses a flexible polymer piezoelectric film as a diaphragm with electrodes on both sides, when an electric signal is applied to the electrodes, the polymer piezoelectric film Since the vibration stretches and contracts in the direction, the acoustic conversion efficiency is extremely low if left as is.Therefore, for the purpose of converting the vibration in the plane direction into the vibration in the direction perpendicular to the plane, a typical structure is shown in Figure 3 as a representative example. As seen in the specification and drawings of Japanese Patent Publication No. 54-12213, a diaphragm 21 made of a polymeric piezoelectric film is assembled with a frame 22 and a substrate 23 so as to have a cylindrical surface or a shape of a combination of cylindrical surfaces. By holding and forming a cylindrical surface, expansion and contraction in the surface direction is converted into deviation in a direction perpendicular to the surface. and,
In order to prevent split vibration of the diaphragm and to efficiently convert such vibration modes, the inside of the cylindrical diaphragm is filled with a low-density elastic material 24 such as foamed resin or glass wool to form the diaphragm 21. gives a certain tension to.

[Problem to be solved] The frequency characteristics of the piezoelectric speaker with the conventional structure described above depend on the tension and dimensions of the diaphragm, but on the other hand, the diaphragm has tension caused by the expansion force of the elastic body filled inside. Therefore, as long as the dimensions of the diaphragm are constant, the frequency characteristics of a speaker with such a structure will be affected by the vibration of the eigenmode of the diaphragm, such as the lowest resonant frequency, and the reproduction band can also be wide. There was a drawback that I couldn't do it.

Therefore, the present invention aims to eliminate the drawbacks of the conventional example and improve the method of supporting a single diaphragm to obtain a piezoelectric speaker with flat frequency characteristics and a wide band. With the goal.

[Means for Solving the Problems] The structure of the piezoelectric speaker according to the present invention for achieving the above object will be explained with reference to FIGS. 1 and 2 showing embodiments. a diaphragm 1 made of a polymer piezoelectric film having By pressing the elastic body 3 of the above-mentioned adhesive frame 2 at the intermediate portion corresponding to the adhesive frame excluding both ends of the adhesive frame 2 from the upper surface of the diaphragm 1 to the adhesive frame 2a, the adhesive frames 2a are mutually bonded. It consists of a presser rod 4 that applies tension to the diaphragm 1 between the diaphragms 1 and a frame 5 that presses and holds the diaphragm 4 on the diaphragm.
It has a structure in which the frame body 5 is attached to the substrate 2 so as to be divided into a plurality of locations having different dimensions, and to apply a unique tension to each section.

[Function] In the piezoelectric speaker having such a structure, when the frame 5 is attached to the substrate 2, the presser rod 4 held by the frame 5 and each adhesion frame 2a of the substrate 2 are attached to the diaphragm 1.
Since it is divided into multiple locations with different dimensions and a predetermined tension is applied to each section independently,
The frequency characteristics of each section are different based on the resonant frequency and vibration mode of each section, and the overall frequency characteristics of each section are flat because each resonance cancels each other out, and when they complement each other, it becomes a wide band. .

Moreover, since the boundary between the sections is almost fixed by the adhesive frame 2a and the presser bar 4, there is no mechanical vibration interference between adjacent sections, and there is no cross-modulation distortion. Prevents abnormal vibrations and improves the quality of reproduced sound.

[Example] In Figs. 1 and 2, reference numeral 1 denotes a flexible diaphragm having electrodes formed by vapor-depositing metal on both sides of a polarized polyvinylidene fluoride film.

Reference numeral 2 denotes a substrate for holding the diaphragm 1 in an extended manner, and has five sticking portions 2a protruding from the top surface to which the diaphragm is attached.

The mutual spacing between the five adhesive parts 2a is different, and in this embodiment, the closer to the center the more narrow the width.

The diaphragm 1 has both sides attached to the adhesive part 2 so as to be bridged.
It is attached and held on a.

A low-density elastic body 3 is placed between the substrate 2 and the diaphragm 1.
The diaphragm 1 is filled with glass wool in an amount sufficient to apply tension to the diaphragm 1.

Reference numeral 5 denotes a frame body, and the diaphragm 1 is exposed at three positions corresponding to the adhesive part 2a excluding both ends of the square hole part exposing the diaphragm 1.
3 for pressing the diaphragm 1 onto the adhesive frame 2a from the top surface
A book presser bar 4 is attached.

The frame body 5 is attached to the substrate 2 with screws 6, etc., and the three presser rods 4 press the diaphragm 1 at three locations, making the diaphragm 1 a continuous waveform of cylindrical surfaces with different areas and curvatures. . Each cylindrical surface portion of the diaphragm 1 is individually given tension by the expansion force of the filled elastic body 3 made of glass wool.

Although typical embodiments of the present invention have been described in detail above, the structure of the piezoelectric speaker of the present invention is not limited to the above embodiments. For example, changing the material of the piezoelectric polymer film or elastic body to another material with equivalent properties, increasing or decreasing the number of presser bars, whether the presser bars are parallel or not parallel to each other, etc. The present invention has the constituent elements defined in the present invention, and can be modified and implemented as appropriate within the scope of having the functions and effects of the present invention.

[Effects] In the piezoelectric speaker according to the present invention described above, the diaphragm 1 is pressed against the adhesive part using presser rods arranged at different intervals, and the diaphragm 1 is divided into a plurality of sections with different dimensions, and the frequency of each section is adjusted. Since the characteristics are different, the overall frequency characteristic, which is a combination of these characteristics, is flat and wideband.

Furthermore, since cross-modulation distortion and abnormal vibrations due to mechanical vibration mutual interference of the divided sections do not occur, it is possible to obtain reproduced sound of extremely high quality.

FIG. 4 shows the frequency characteristics of the example. The solid line shows an embodiment of the present invention in which the presser bars are spaced at different intervals, and the dotted line shows the characteristics of the speaker in which the spacing is equal.

From this result, the speaker structure according to the present invention is effective in making the frequency characteristics flat and broadband.
This has the advantage that a piezoelectric speaker with excellent performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a piezoelectric speaker according to the present invention, FIG. 2 is a partially cutaway perspective view, FIG. 3 is a sectional view of a conventional example, and FIG. 4 is a frequency characteristic diagram of an embodiment. 1 is a diaphragm, 2 is a substrate, 3 is an elastic body, 4 is a presser bar, and 5 is a frame body.

Claims (1)

[Scope of utility model registration request] A diaphragm 1 made of a flexible polymeric piezoelectric film with electrodes on both sides; a substrate 2 with adhesion frames 2a protruding from multiple locations to which the diaphragm 1 is attached;
A low-density elastic body 3 filled between the substrate 2 and the diaphragm 1, and a location on the diaphragm 1 corresponding to the middle part of the adhesion frame excluding both ends of the adhesion frame 2a. It consists of a presser bar 4 that applies tension to the diaphragm 1 between the adhesion frames 2a by being press-fitted to the adhesion frame 2a from the top surface, and a frame body 5 that presses and holds the presser bar 4 on the diaphragm 1. The diaphragm 1 is divided into a plurality of locations with different dimensions using the adhesive frame 2a and the presser bar 4, and the frame body 5 is attached to the substrate 2 so as to apply a unique tension to each section.
A piezoelectric speaker characterized by being attached to.