JPH0419919Y2 - - 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 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 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 examples. A diaphragm 1 made of a polymer piezoelectric film having a diaphragm 1, a substrate 2 having a protruding adhesive frame 2a for adhering and extending the diaphragm 1, and a low-density film filled between the substrate 2 and the diaphragm 1. an elastic body 3, a plurality of presser bars 4 that apply tension to the diaphragm 1 by pressing the elastic body 3 from the upper surface at multiple locations on the diaphragm 1 at unequal intervals, and a plurality of presser bars 4 that apply tension to the diaphragm 1, and the presser bars 4 are placed on the diaphragm. It has a structure in which the diaphragm 1 is divided into a plurality of locations of different dimensions by a presser rod 4, and the frame 5 is attached to the substrate 2 so as to apply a predetermined tension to each section. have

[Function] In the piezoelectric speaker having such a structure, when the frame 5 is attached to the substrate 2, the presser rod 4 held on the frame 5 presses the diaphragm 1 from the top surface at different intervals. 3 and divides the diaphragm 1 into multiple locations with different dimensions and applies a predetermined tension to each section, so the frequency characteristics of each section are determined based on the resonant frequency and vibration mode of each section. As a result, the overall frequency characteristic obtained by combining these resonances becomes flat as each resonance cancels out, and becomes a wide band as they complement each other.

[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 two adhesion parts 2a protruding from the top surface to which the diaphragm is attached.

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, in which the diaphragm 1 is placed in three locations at unequal intervals in a square hole that exposes the diaphragm 1, and an elastic body 3 is inserted from the top surface.
Three presser rods 4 are attached for pressing.

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, so that the diaphragm 1 has a continuous waveform of cylindrical surfaces having different areas and curvatures. Each cylindrical surface portion of the diaphragm 1 is 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, the structural requirements of the present invention include changing the material of the piezoelectric polymer film or elastic body to another material with equivalent properties, the number of presser bars, and whether the presser bars are parallel or not parallel to each other. The present invention can be modified and implemented as appropriate within the scope of having the functions and effects of the present invention.

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

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 has the advantage of having flat and wide frequency characteristics and a piezoelectric speaker with excellent performance.

[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 a sticking frame 2a protruding from which the diaphragm 1 is attached and extended, and the substrate 2 and the diaphragm 1. A low-density elastic body 3 filled between the diaphragm 1 and the diaphragm 1 are pressed against the elastic body 3 from above at a plurality of locations on the diaphragm 1 at unequal intervals.
a plurality of presser rods 4 that apply tension to the presser rods 4;
The diaphragm 1 is divided into a plurality of locations with different dimensions by a presser rod 4, and the frame 5 is attached to the substrate 2 so as to apply a predetermined tension to each section. A piezoelectric speaker characterized by: