JPH02299396A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To strengthen the rigidity of a piezoelectric driver support section while vibrating a piezoelectric driver sufficiently in response to the input level by forming a tapered projection to the middle of an annular groove in a diaphragm while being swollen. CONSTITUTION:A diaphragm 22 consists of two foamed resin plates 25, 26 and the annular grooves 25a, 26a somewhat larger than the size of a piezoelectric driver 21 are formed to the middle of the opposed faces of the plates 25, 26. Thus, the piezoelectric driver accommodating space larger than the driver 21 is formed. Furthermore, tapered and truncated cone shaped projections 25b, 26b are formed in the middle of the slots 25a, 26a while being swollen and the driver 21 is supported by using an adhesives or the like. Moreover, the height of the projections 25b, 26b is somewhat shorter than the depth of the grooves 25a, 26a and formed while being swollen from the circumferential ridge of the grooves 25a, 26a. Since the volume of the projections 25b, 26b is increased, while the driver 21 is vibrated sufficiently in response to the input level, the rigidity of the piezoelectric driver support 40 is strengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric speaker in which a piezoelectric driver is attached to a diaphragm made of a foamable resin.

Conventional Q Figure 3 shows a conventional example of this type of piezoelectric speaker. This piezoelectric speaker has a diaphragm 3 formed by facing two foamed resin plates 4.5 made of foamed polystyrene, foamed polyethylene, etc., and a piezoelectric driver 6 held between the foamed resin plates 4.5. It has a structure.

Specifically, annular grooves 4a and 5a are formed in the center of the facing surface of the foamed resin plate 4.5.
It has a structure in which a piezoelectric driver 6 is held between cylindrical projections 4b and 5b remaining at the center of a.

The piezoelectric driver 6 is of a bimorph type, in which piezoelectric plates 6a, 6a (made of PZT, etc., for example) are concentrically attached to both sides of a circular metal plate 6b.

I! By the way, in the piezoelectric speaker described above, in order to vibrate the piezoelectric driver 6 sufficiently according to the input level, the contact area between the protrusions 4b and 5b holding the piezoelectric driver 6 and the piezoelectric driver 6 is adjusted. It needs to be made as small as possible. Therefore, if the protrusions 4b, 5b are made cylindrical as described above, the volumes of the protrusions 4b, 5b will be reduced. In addition, grooves 4a, 5a
Thickness dimension t of the foamed resin plates 4 and 5 at the part where is formed
.

is getting smaller. From these facts, the protrusions 4b, 5
foamed resin plate 4 in the area where grooves 4a and 5a are formed.
- The rigidity of the piezoelectric driver support part 8 (shown with diagonal lines in the figure) consisting of 5 and 5 becomes weak. Therefore, the piezoelectric driver 6
It becomes difficult for the vibrations to be transmitted to the entire diaphragm 3, and so-called split vibrations, where only the piezoelectric driver support part 8 vibrates strongly and the vibrations of other parts become weaker, tend to occur.

As a result, there have been problems in that the frequency characteristics are not flat and the sound pressure level is low.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide a piezoelectric speaker that can eliminate the above-mentioned drawbacks.

In order to achieve the above object, the present invention comprises a piezoelectric driver that vibrates in accordance with an applied signal, and two foamed resin plates that are butted against each other in a facing manner. In the piezoelectric speaker, the piezoelectric speaker has a diaphragm in which recesses are formed on each side, and a storage space for accommodating the piezoelectric driver is formed by these recesses, in the center of both the recesses.
The piezoelectric driver is characterized in that a protrusion having a tapered shape and a height slightly shorter than the depth of the recess is formed in a raised manner, and the piezoelectric driver is held under pressure by this protrusion.

As with the above configuration (if the protrusions formed in the center of the four parts are formed in a tapered shape, the contact area between the protrusions and the piezoelectric driver remains small, and the volume of the protrusions can be greatly reduced). Therefore, it is possible to increase the rigidity of the piezoelectric driver support part while sufficiently vibrating the piezoelectric driver according to the input level.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view showing a piezoelectric speaker according to the present invention;
FIG. 2 is an enlarged sectional view showing the main part.

In the piezoelectric speaker, a diaphragm 22 in which a piezoelectric driver 21 is housed is connected to a frame 2 through an elastic support piece 23.
This configuration is fixed at 4. Specifically, the above frame 2
Reference numeral 4 has a frame shape, and the peripheral edge of the diaphragm 22 is inserted and connected to a groove 24a having a U-shaped cross section formed over the entire length of the inner peripheral surface.

Furthermore, an elongated tape-shaped elastic support piece 23 is interposed around the entire circumference of the stepped portion formed on the outer periphery of the diaphragm 22, and the diaphragm 22 is supported by the frame 24 by this elastic support piece 23. It has become.

The piezoelectric driver 21 is of a bimorph type as shown in FIG. 2, and has two piezoelectric plates 21 made of PZT or the like.
a and 21b sandwich the metal plate 21c. and,
The structure is such that when an electric signal is applied to the re-piezoelectric plates 21a and 21b, the whole including the metal plate 21C undergoes bending vibration due to the piezoelectric effect.

One ends of lead wires 27a, 27a, 27b are soldered to the electrodes of the piezoelectric plates 21a, 21b and positions near the peripheral ends of the metal plate 21c, respectively.

The other end sides of the lead wires 27a, 27a, and 27b are drawn out to the outside through the opposing surfaces of foamed resin plates 25 and 26, which will be described later.
It is connected to an amplifier (not shown) that vibrates the piezoelectric driver 21.

On the other hand, the diaphragm 22 is made up of two foamed resin plates 25.
These foamed resin plates 25 and 26 are made of, for example, foamed polystyrene, foamed polyethylene, or a copolymer of both. The above foamed resin board 25.2
Annular grooves 25a and 26a, which are somewhat larger than the piezoelectric driver 21, are formed in the center of the opposing surface of the piezoelectric driver 6. A housing space is formed. Furthermore, truncated conical protrusions 25b and 26b are formed in the center of the grooves 25a and 26a, and the piezoelectric driver 21 is held between these protrusions 25b and 26b using an adhesive or the like. For this reason, protrusion 2
The height dimensions of the protrusions 25b and 26b are slightly shorter than the depth dimensions of the grooves 25a and 26a.Also, in order to increase the volume by increasing the diameter of the bottom surface of the protrusions 25b and 26b, , the protrusions 25b and 26b are the grooves 25a and 26a.
It is raised up from the peripheral edge.

Furthermore, the diameters of the tops of the protrusions 25b and 26b are set to a size that allows the piezoelectric driver 21 to vibrate sufficiently in accordance with the input level and to sufficiently support the piezoelectric driver 21.

Here, as in the above configuration, the truncated conical projections 25b, 26
When b is raised from the peripheral edge of the grooves 25a and 26a, the protrusion 2
The volumes of 5b and 26b can be made extremely large.

Therefore, the rigidity of the piezoelectric driver support portion 40 (shown by diagonal lines in the figure), which is made up of the projections 25b, 26b and the foamed resin plates 31, 32 in the portions where the grooves 25a, 26a are formed, is increased. As a result, the vibration of the piezoelectric driver 21 is easily transmitted to the entire diaphragm 22, and so-called split vibration, in which only the piezoelectric driver support part 40 vibrates strongly and the vibrations of other parts become weaker, becomes less likely to occur.

In the above embodiment, the structure in which the lead wires are soldered to the piezoelectric plates 21a and 21b and the metal plate 21c has been described, but the present invention can be applied to a structure in which the lead wires are not soldered to the metal plate 21c. Can be applied.

Furthermore, although a bimorph type piezoelectric driver 21 is used, the piezoelectric driver 21 is not limited to this, and a unimorph type can also be used.

As described above, according to the present invention, it is possible to sufficiently vibrate the piezoelectric driver according to the input level and strengthen the rigidity of the piezoelectric driver support, so that the vibration of the piezoelectric driver spreads over the entire diaphragm. This makes it easier to transmit vibrations and makes split vibrations less likely to occur. As a result, the frequency characteristics become flat and the sound pressure level can be dramatically increased.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a piezoelectric speaker according to the present invention, FIG. 2 is an enlarged cross-sectional view showing essential parts thereof, and FIG. 3 is a longitudinal cross-sectional view showing a conventional piezoelectric speaker. 21...Piezoelectric driver, 25, 26...Foamed resin plate, 25a-26a-groove, 25b-26b・
··protrusion. Patent applicant Murata Manufacturing Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] (1) A piezoelectric driver that vibrates according to an applied signal;
A diaphragm is formed by abutting two foamed resin plates facing each other, and each of the foamed resin plates has recesses formed on the abutting surfaces, and these recesses form a storage space for accommodating the piezoelectric driver. In the piezoelectric speaker, a tapered projection having a height slightly shorter than the depth of the recess is formed in the center of both the recesses, and the piezoelectric driver is held by the projection. A piezoelectric speaker featuring