JPH0233300A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric speaker whose sound pressure level is flat with excellent sound quality by fitting a piezoelectric sounding body to the node of the primary resonance mode in a diaphragm so as to vibrate the entire face of the diaphragm. CONSTITUTION:A diaphragm 3 made of a square foamed resin or the like is supported to a frame 1 by an elastic support and a piezoelectric sounding body 4 is fitted to four positions deviated toward the center a little from four corners of the diaphragm 3. The piezoelectric sounding body 4 consists of a couple of circular piezoelectric substances a, 4a made of a material such as PZT adhered to both sides of a circular metallic plate 4b having a larger diameter than that of the substance 4a. The primary resonance mode of the diaphragm 3 appears in longitudinal and lateral directions, the respective vibration has nodes I, J between the centers E, F and both ends G, H and the piezoelectric sounding body 4 is fitted to a cross point between a line segment (i) of the node I and a line segment (j) of the node J.

Description

[Detailed description of the invention] Children's Work ■Shaku■ Branch The present invention relates to piezoelectric speakers.

As a piezoelectric speaker to prevent disasters, the applicant has proposed the following as shown in Fig. 8 (front view).
What is proposed is shown in FIG. 9 (a sectional view taken along line IX-IX in FIG. 8). This is because the outer peripheral part of the diaphragm 3 is supported by the frame 1 via the elastic support piece 2, and the piezoelectric sounding body 4 is fixed to this diaphragm 3 via the support part 3c. The configuration is such that the diaphragm 3 is driven.

The diaphragm 3 is made by pasting together two foamed resin plates 3a and 3b, one large and one small, with the larger one 3a disposed on the front side. The piezoelectric sounding body 4 includes a pair of piezoelectric bodies 4a, 4a, and a metal plate 4b sandwiched between the piezoelectric bodies 4a, 4a.
The diaphragm 3 is driven by bending the metal plate 4b. Therefore, sound is emitted from the piezoelectric speaker.

FIG. 10 shows the sound pressure frequency characteristics in the case of a piezoelectric speaker in which the piezoelectric sounding body 4 is provided in the center of the diaphragm 3. In this case, first-order resonance of the diaphragm 3 appears in the frequency range A where the peak exists, and large peaks and troughs occur in the sound pressure near this resonance frequency.

Therefore, there is a problem in that the sound quality of the speaker deteriorates at the peaks and troughs of the sound pressure caused by the resonance of the diaphragm 3 that appear in the frequency range A. Note that the peak in the frequency range B is due to the first-order resonance of the piezoelectric sounding body 4, and the plurality of peaks in the frequency range C or higher are due to the higher-order resonance.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a piezoelectric speaker with good sound quality by preventing the occurrence of primary resonance of the diaphragm.

The present invention provides a piezoelectric speaker in which a diaphragm supported by a frame via an elastic support piece is driven by a piezoelectric sounding body attached to the diaphragm, in which the piezoelectric sounding body generates vibrations. It is characterized by being attached to the node of the primary resonance mode in the plate.

In the present invention, since the piezoelectric sounding body is attached to the node of the primary resonance mode of the diaphragm, the node is driven by the piezoelectric sounding body together with other parts of the diaphragm. The entire surface of the diaphragm vibrates.

One embodiment of the present invention will be described with reference to FIGS. 1 to 3. Fig. 1 is a front view showing the speaker of the present invention, and Fig. 2 is a front view showing the speaker of the present invention.
FIG.
The same parts as in Figure 9 are given the same numbers. This speaker is the same as the conventional speaker except for the mounting position and number of piezoelectric sounding elements 4. That is, in frame 1,
A square-shaped diaphragm 3 made of foamed resin, for example, foamed polystyrene, is supported via an elastic support piece made of an elastic material such as urethane foam, rubber, or leather.
Piezoelectric sounding elements 4 are placed at 4 positions slightly closer to the center than the four corners of the
are installed respectively. This piezoelectric sounding body 4 has a structure in which a pair of circular piezoelectric bodies 4a, 4a made of, for example, PZT or the like are adhered to both sides of a circular metal plate 4b having a larger diameter.

The mounting position of the piezoelectric sounding body 4 is determined as follows. That is, in the case of the square-shaped diaphragm 3,
The primary resonance mode of the diaphragm 3 appears in the vertical and horizontal directions as shown in FIG.
Section 1 between H. J, the intersection point where line segment i of node I intersects line segment j of node J, that is, the point at which split vibration occurs is set as the boundary.

FIG. 4 shows the sound pressure frequency characteristics of the speaker of the present invention in which the piezoelectric sounding body 4 is attached to the above-mentioned intersection. In this case, since the piezoelectric sounding body 4 is driven starting from the point where split vibration occurs, split vibration does not actually occur, and the diaphragm 3 resonates in the frequency range A where the peak shown by the broken line conventionally occurred. disappears, and the sound pressure near frequency range A becomes uniform.

Next, a case where the present invention is applied to a piezoelectric speaker having a disc-shaped diaphragm will be described. FIG. 5 is a front view thereof, and FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. In this speaker, a frame 15, an elastic support piece 2, and a diaphragm 3 are each formed in a circular shape, and piezoelectric sounding bodies 4 are attached to the circular diaphragm 3 at three equally spaced positions around the center.

The mounting position is determined as follows. That is, in the case of a circular diaphragm 3, the primary resonance mode of the diaphragm 3 is as shown in FIG. exists continuously in the circumferential direction at a position of about 70% of the diameter, so it is basically a point on the circular line r of the node R. However, if only one or two piezoelectric sounding bodies 4 are attached on the circular line r, the entire surface of the diaphragm 3 cannot be driven evenly, so it is preferable to attach three or more piezoelectric sounding bodies 4.

Therefore, in this embodiment, three are installed.

Main Effects As described in detail above, in the case of the present invention, a piezoelectric sounding body is attached to the node of the primary resonance mode of the diaphragm. This makes it possible to vibrate the entire surface of the diaphragm, eliminating resonance in the diaphragm's primary resonance mode, making it possible to provide a piezoelectric speaker with good sound quality and a flat sound pressure level. It has excellent effects.

[Brief explanation of the drawing]

Fig. 1 is a front view showing the speaker of the present invention, Fig. 2 is a sectional view taken along line mu in Fig. 1, Fig. 3 is a diagram showing the generation state of the primary resonance mode of the diaphragm, and Fig. 4 is A graph showing sound pressure frequency characteristics according to the present invention, FIG. 5 is a front view when the present invention is applied to a piezoelectric speaker having a disc-shaped diaphragm, and FIG. 6 is a line VI-VI in FIG. 5. 7 is a diagram showing the generation state of the primary resonance mode of the circular diaphragm, FIG. 8 is a front view showing an example of a conventionally proposed piezoelectric speaker, and FIG.
The figure is a cross-sectional view taken along line IX-IX in FIG. 8, and FIG. 10 is a graph showing the sound pressure frequency characteristics in that case. DESCRIPTION OF SYMBOLS 1... Frame, 2... Elastic support piece, 3... Vibration plate, 4... Piezoelectric sounding body.

Claims (1)

[Claims] (1) In a piezoelectric speaker in which a diaphragm supported by a frame via an elastic support piece is driven by a piezoelectric sounding body attached to the diaphragm, the piezoelectric sounding body drives the first resonance mode of the diaphragm. A piezoelectric speaker characterized by being attached to a node.