JPH0239800A - Piezoelectric loudspeaker - Google Patents

Abstract

PURPOSE:To prevent the lowering of sound pressure between a first-order resonance and a second-order resonance by fitting not only a piezoelectric sounding body to generate the first resonance and the second resonance but also another piezoelectric sounding body having the resonance frequency between the first-order resonance and the second-order resonance to a diaphragm and oscillating the diaphragm. CONSTITUTION:Piezoelectric sounding bodies 4 having the same characteristic with each other are fitted to five parts of a rectangular diaphragm 3, which are the center and near the four corners of the diaphragm 3, two types of piezoelectric sounding bodies 5 and 6 respectively having different characteristics from that of the piezoelectric sounding bodies 4 are fitted to the diaphragm 3, and all the sounding bodies are connected in parallel. Since the first resonance mode of the diaphragm 3 appears in its longitudinal direction and in its cross direction, and respective oscillations have nodes I and J, each of which generates partitioned oscillations at its both sides, between centers E and F and edges G and H, the piezoelectric sounding bodies 4 near the four corners are fitted to intersections where the segments (i) of the nodes I and the segments (j) of the nodes J intersect and arranged so that the partitioned oscillations are never generated actually. For the piezoelectric sounding bodies 5 and 6, the sounding bodies having the resonance frequencies between the first resonance frequency and the second resonance frequency generated in the diaphragm 3 with the respective piezoelectric sounding bodies 4 are used, and as the result, the lowering of the sound pressure between the first resonance and the second resonance can be eliminated, and a low sound can be sounded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric speaker, and in particular, to a piezoelectric speaker that includes a diaphragm supported by a frame via an elastic support piece, and a piezoelectric sounding body attached to the diaphragm. The present invention relates to a piezoelectric speaker driven by a piezoelectric speaker.

As the above-mentioned piezoelectric speaker, the applicant has
We have proposed what is shown in the figure (sectional view taken along the VT-VT line in Figure 5). This is because the outer peripheral part of the diaphragm 3 is supported by the frame 1 via the elastic support piece 2, and one or more, for example, five piezoelectric sounding bodies 4 are fixed to the diaphragm 3 via the support part 3c. The piezoelectric sounding body 4 drives the diaphragm 3 to emit sound. 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 drives the diaphragm 3 by bending a pair of piezoelectric bodies 4a, 4a and a metal plate 4b sandwiched between them. Therefore, sound is emitted from the piezoelectric speaker. Note that a plurality of piezoelectric sounding bodies 4 are connected to one diaphragm 3.
The reason for providing the piezoelectric sounding body 4 is to improve the sound pressure level compared to the case where only one piezoelectric sounding body 4 is used.

However, even if the sound pressure level is improved in this way, if the plurality of piezoelectric sounding bodies 4 all have the same characteristics, the sound pressure frequency characteristics of the piezoelectric speaker will not be as shown in FIG. As shown by the broken line, a low sound pressure frequency band appeared widely between the primary resonance A and the secondary resonance B of the piezoelectric sounding body 4, so no bass was produced. In addition, a low sound pressure frequency band appears widely between the secondary resonance B and the tertiary resonance C, and even between higher resonance frequencies, resulting in a problem of poor sound quality over the entire frequency band. was there.

In piezoelectric speakers, it is generally difficult to reproduce bass sounds due to their characteristics, so they are designed to make the primary resonance frequency as low as possible to ensure bass sounds. There is a situation in which the sound pressure level in a frequency band exceeding the primary resonance frequency (A) becomes low, and even if the primary resonance frequency is designed to be low, it is not very effective.

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 that produces good bass sounds and has good sound quality over the entire frequency band.

In the present invention, a piezoelectric sounding body is attached to a diaphragm supported by a frame via an elastic support piece, and the piezoelectric sounding body causes the diaphragm to vibrate, and the piezoelectric sounding body causes the diaphragm to vibrate. Another piezoelectric sounding body having a resonance frequency between the frequency of the primary resonance and the frequency of the secondary resonance that occurs is attached to the diaphragm, and the diaphragm is also vibrated by this other piezoelectric sounding body to generate sound. Characterized by what has been done.

In the present invention, in addition to the piezoelectric sounding body that causes primary resonance and secondary resonance in the diaphragm, a piezoelectric sounding body that has a resonant frequency between the primary resonance and the secondary resonance is provided. Since the piezoelectric sounding body is attached to the diaphragm and the diaphragm is vibrated, it is possible to prevent the sound pressure from decreasing between the primary resonance and the secondary resonance.

One embodiment of the present invention will be described below. Fig. 1 is a front view (partially cut away) of the speaker of the present invention, and Fig. 2 is a - of Fig. 1.
This is a cross-sectional view taken along line 2, and the same parts as in FIGS. 6 and 7 are given the same numbers. In the speaker of the present invention, piezoelectric sounding bodies 4 having the same characteristics are attached at five locations, including the center of a rectangular diaphragm 3 and near the four corners, and two piezoelectric sounding bodies 4 having different characteristics from this are attached.
Different types of piezoelectric sounding bodies 5, 6 are attached to the diaphragm 3.

The piezoelectric sounding bodies 4 near the four corners mentioned above are attached at the following positions. That is, only one piezoelectric sounding body 4 is placed in the center of the diaphragm 3.
is installed, the primary resonance mode of the diaphragm 3 at this time appears in the vertical and horizontal directions as shown in Fig. 3, and the respective vibrations occur between the center E, F and both ends G, H. , there are nodes I and J where split vibration occurs on both sides, so in this example, the piezoelectric sounding bodies 4 near the four corners are attached to the intersections of the line segment i of the node ■ and the line segment j of the node J, In reality, the arrangement is such that the split vibration does not occur.

The piezoelectric sounding body 5 is located on a diagonal line connecting the central piezoelectric sounding body 4 and the two piezoelectric sounding bodies 4 sandwiching it, and is located between the central piezoelectric sounding body 4 and the outer piezoelectric sounding body 4. The other piezoelectric sounding body 6 is located on the diagonal line connecting the center piezoelectric sounding body 4 and the remaining two piezoelectric sounding bodies 4 sandwiching it, and They are arranged at two locations between the outer piezoelectric sounding body 4 and the outer piezoelectric sounding body 4. Note that the piezoelectric sounding body 4 does not necessarily need to be attached at five locations, and may be attached only at the center.

The piezoelectric sounding bodies 5 and 6 are those having a resonance frequency between the frequency of the primary resonance and the frequency of the secondary resonance generated in the diaphragm 3 by the piezoelectric sounding body 4, for example. Diameter: 80mm, the diameter of the piezoelectric sounding body 5 is 7011 mm, and the diameter of the other piezoelectric sounding body 6 is 6011 mm.
The basic configuration is the same as the piezoelectric sounding body 4.

Further, the piezoelectric sounding bodies 4, 5.6 are all connected in parallel.

Therefore, the sound pressure increases at the resonance frequency of each of the piezoelectric sounding bodies 5 and 6.

Therefore, as shown by the solid line in FIG.
．． There is a sound pressure peak at each resonance frequency due to each resonance frequency, and as a result, the sound pressure drop between the primary resonance and the secondary resonance disappears, and a bass sound is produced. Also, secondary resonance B and 3
There is no appearance of a frequency band with low sound pressure between the next resonance C and even between resonance frequencies higher than this, and therefore the sound quality is improved over the entire frequency band. In addition, the measurement data in Fig. 4 shows that the size of frame 1 is
The width of the grave is near 28m, height: 514mm, depth: 251, and the size of the diaphragm 3 is near width 04mm, height:
The values are shown when the width is 490 mm and the depth is 18 mm.

Note that the piezoelectric sounding bodies 5.6 do not necessarily need to be disposed diagonally, and may be disposed at arbitrary positions on the diaphragm 3.

Furthermore, in the above embodiment, two piezoelectric sounding elements having different characteristics from the piezoelectric sounding element 4 are used.
Although the piezoelectric sounding body 5.6 of different types is attached to the diaphragm 3 separately from the piezoelectric sounding body 4, the present invention is not limited to this, and as long as the requirements of the present invention are satisfied, the piezoelectric sounding body 5. One type or three or more types of piezoelectric sounding bodies may be attached.

As described in detail above, in the case of the present invention, in addition to the piezoelectric sounding body that causes primary resonance and secondary resonance in the diaphragm, there is a Another piezoelectric sounding body with a resonant frequency is attached to the diaphragm and the diaphragm vibrates, so
It is possible to prevent the sound pressure from decreasing between the primary resonance and the secondary resonance, thereby making it possible to provide a piezoelectric speaker with good sound quality and good bass sound.

[Brief explanation of the drawing]

Fig. 1 is a front view (partially cut away) of the speaker of the present invention, Fig. 2 is a sectional view taken along line n-n in Fig. 1, and Fig. 3 is a 1st view of the diaphragm.
An explanatory diagram of the next resonance mode, FIG. 4 is a graph showing the sound pressure frequency characteristics (solid line) in the case of the present invention and sound pressure frequency characteristics (broken line) in the conventional case, and FIG. 5 is a front view of the conventional product ( FIG. 6 is a cross-sectional view taken along the -Vl line in FIG. 5. DESCRIPTION OF SYMBOLS 1... Frame, 2... Elastic support piece, 3... Vibration plate, 4, 5. 6...Piezoelectric sounding body. Patent distributor Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] (1) A piezoelectric sounding body is attached to a diaphragm supported by an elastic support piece on a frame, and the piezoelectric sounding body causes the diaphragm to vibrate, and the frequency of primary resonance generated in the diaphragm by the piezoelectric sounding body Another piezoelectric sounding body having a resonance frequency between the frequency of the diaphragm and the frequency of the secondary resonance is attached to the diaphragm, and the diaphragm is also vibrated by this other piezoelectric sounding body to emit sound. piezoelectric speaker.