JPS6237600B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric speaker whose diaphragm is driven by the bending motion of a piezoelectric element.

FIG. 1 shows a conventional piezoelectric speaker. In the piezoelectric speaker shown in the figure, the top of a cone-shaped diaphragm 2 is adhesively bonded to the center of the upper surface of a disk-shaped piezoelectric element 1.
The back surface of this piezoelectric element is flexibly held at the bottom of a frame 4 via a flexible material 3 such as moltoprene.

According to such a conventional structure, the bending force of the piezoelectric element is
The signal is transmitted only from the center to the top of the diaphragm 2.

However, this piezoelectric element 1 has a limit on its maximum bending amount due to structural constraints consisting of bonding a piezoelectric ceramic and a brass plate, and therefore there is also a limit on the maximum amplitude of the diaphragm 2. Ta.

For this reason, with conventional piezoelectric speakers, as is clear from the relationship curve between the amplitude of the diaphragm and the reproduction frequency in Figure 2, the low frequency range that requires a large amplitude is not reproduced, and the audio band (300Hz to Even in the midrange (3000Hz), we were unable to obtain sufficient sound pressure.
It was mainly used as a speaker for high frequency reproduction.

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 in which the amplitude of the diaphragm is increased, and the sound pressure in the mid-low range of reproduction frequencies is increased.

FIG. 3 shows an embodiment of the piezoelectric speaker of the present invention. Note that Figure a is a front view thereof, and Figure b is a cross-sectional view thereof. In these diagrams, 4 is positive 12
It is a rectangular diaphragm, and has a wavy shape formed by alternately folding back 12 center lines connecting the center and 12 peripheral vertices as ridge line portions 5, 5, . . . . still,
The materials used for the diaphragm 4 include a plastic sheet such as polyester film, a thin metal plate such as aluminum, and valve paper. 6 and 7 are disc-shaped first and second piezoelectric elements arranged concentrically on the upper and lower sides of the vibration plate 4, respectively, and the diameters of both piezoelectric elements 6 and 7 are such that It is approximately 1/3 of the diameter of plate 4. The center part of the first piezoelectric element 6 and the center part of the diaphragm 4 are connected by a first spacer 8, and the peripheral part of the element 6 and the 6 part protruding above the diaphragm 4 are connected to each other by a first spacer 8. Approximately 1/3 of the center of the ridge line portion 5 of the book is connected by six first stays 9. Furthermore, the second piezoelectric element 7 is similarly connected at its center to the center of the diaphragm 4 by the spacer 10, and its peripheral portion is connected below the diaphragm 4 by the six stays 11. It is connected to six protruding ridge line parts 5. 12 is a frame, which includes the diaphragm 4, both piezoelectric elements 6, 7, spacers 8, 10,
A vibration system consisting of stays 9...11... is housed, and the center part of the lower surface of the second piezoelectric element 7 and this frame 12
is connected to the bottom central portion of the holder 1 by a third spacer 13.

The operation of the piezoelectric speaker of the present invention having such a configuration will be described in detail with reference to FIG.

FIG. 4a shows a case where a constant voltage is applied so that both piezoelectric elements 6 and 7 are bent upward in a concave shape, and FIG. 4b shows a case where both piezoelectric elements 6 and 7 are both concavely bent downward. As is clear from these figures, the center of the diaphragm 4, which is connected to the center of both piezoelectric elements 6 and 7 by the spacers 8 and 10, serves as a fulcrum, and the 12 stays 9...11... Both piezoelectric elements 6 and 7
The point of action is about 1/3 from the center of the ridge line part 5 of the diaphragm 4 connected to the peripheral part of the diaphragm 4.
The displacement x of the periphery of both piezoelectric elements 6 and 7 is approximately three times larger than that of the periphery of both piezoelectric elements 6 and 7.

In FIG. 5, the operation of the diaphragm 4 itself will be described, taking as an example a case where one piezoelectric element 7' is disposed only on the lower surface side of the diaphragm 4. As shown in Figure b, the piezoelectric element 7'
is bent, each ridge line portion 5 of the diaphragm 4
The folding angle α' at... is smaller than the folding angle α when the piezoelectric element 7' is not bent, as shown in FIG. Therefore, in case b of the same figure, that is,
Corresponding to FIG. 4a, when the diaphragm 4 expands the bending motion of the piezoelectric element 7' and bends upward in a concave manner as described above, the diaphragm 4 itself also makes a waving motion in the tangential direction, so that it protrudes upward. The ridge line portions 5... are pushed upward, and the swing width near the upper ridge line portions 5 is further expanded.

In FIG. 6, the reproduction frequency characteristic of the piezoelectric speaker of the present invention shown in FIG. 3 is shown by a solid line, and that of the conventional speaker shown in FIG. 1 is shown by a broken line. The diameter of each piezoelectric element 1, 6, and 7 used here is 21 mm, the resonance frequency is 3.8 KHz, the capacitance is 90 nF, and the outer diameter of each diaphragm 2 and 4 is approximately 50 mm. It was hot. According to the figure, it can be seen that in the piezoelectric speaker of the present invention, while the lowest resonance frequency of the conventional speaker was 4KHz, this can be shifted to the low frequency range up to 500Hz.

FIG. 7 shows another embodiment of the piezoelectric speaker of the present invention. The difference between the embodiment shown in FIG. 5 and the embodiment shown in FIG. 5 is that the peripheral part of the piezoelectric element 7' is directly adhesively bonded to the ridge line part 5 below the diaphragm 4, without using the stays 9. However, it operates in the same way as the embodiment shown in FIG.

FIG. 8 shows still another embodiment of the piezoelectric speaker of the present invention. In the embodiment shown in the figure, three piezoelectric elements 71, 72, and 73 are arranged concentrically on the lower surface of the diaphragm 4 in order from the one closest to the diaphragm 4 to the one with the smallest diameter. Then, the respective piezoelectric elements 71, 7
The center portions of the piezoelectric elements 2, 73 and the center portion of the diaphragm 4 are connected by spacers 101, 102, 103, and the peripheral portions of the respective piezoelectric elements 71, 72, 73 and the lower ridge of the diaphragm 4 are connected. The wire portions 5 are connected to each other by stays 111 . . . , 112 . . . , 113 .

According to such a configuration, the diaphragm 4 has different diameters.
That is, three piezoelectric elements 71, 7 with different resonance frequencies
The bending motion of the diaphragm 2 and 73 is expanded to vibrate, thereby increasing the vibration force of the diaphragm 4 and expanding the frequency band.

As is clear from the above description, the piezoelectric speaker of the present invention includes a diaphragm having a plurality of ridge portions folded back radially from the center, and the center of the diaphragm and the center of the disc-shaped piezoelectric element. The piezoelectric element is connected to the piezoelectric element by a spacer, and each ridge line part of the diaphragm is connected to the peripheral part of the piezoelectric element.
The diaphragm can be vibrated with an amount of displacement that is an expansion of the amount of bending displacement of the piezoelectric element, and as a result, the sound pressure in the middle range can be improved, and it can be used particularly as a speaker for generating sound.

Furthermore, since the present invention provides piezoelectric elements on both sides of the diaphragm, the diaphragm can be vibrated in a complementary manner by the two piezoelectric elements, and the vibrating force can be increased.

Furthermore, since the speaker of the present invention has an appropriate number of piezoelectric elements with different diameters arranged concentrically on one side of the diaphragm, it is possible to make the diaphragm vibrate by relying on these piezoelectric elements with different resonance frequencies. is possible,
Not only can the vibration force be increased, but the reproduction frequency band can also be expanded.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional piezoelectric speaker, Figure 2 is a cross-sectional view of a conventional piezoelectric speaker.
The figure shows a relationship curve between the amplitude of the diaphragm and the reproduction frequency.
3a and 3b are a plan view and a vertical sectional view of an embodiment of the piezoelectric speaker of the present invention, FIG. 4 is a schematic diagram showing the operation of the piezoelectric speaker of the present invention, and FIGS. A side view of the vibration system of the invention piezoelectric speaker, Figure 6 is a reproduction frequency characteristic curve diagram, Figures 7 and 8.
The figures are a sectional view and a side view of different embodiments of the piezoelectric speaker of the present invention, respectively. 1, 6, 7, 7', 71, 72, 73...piezoelectric element, 2, 4...diaphragm, 5...ridge line portion, 8, 10, 1
3, 101, 102, 103...Spacer, 9, 1
1,111,112,113... Stay.

Claims (1)

[Scope of Claims] 1. A diaphragm having a plurality of ridge portions folded back radially from a center, the center of the diaphragm and the center of a disc-shaped piezoelectric element being coupled by a spacer. A piezoelectric speaker characterized in that each ridge line portion of the diaphragm is connected to a peripheral portion of a piezoelectric element, and the diaphragm is driven by the bending motion of the piezoelectric element. 2. The piezoelectric speaker according to claim 1, wherein each ridge line portion of the diaphragm and the peripheral portion of the piezoelectric element are connected by a plurality of stays. 3. The piezoelectric speaker according to claim 1 or 2, wherein the piezoelectric elements are provided on both sides of the diaphragm, and both piezoelectric elements are caused to perform complementary bending movements. 4. Claim 1, wherein an appropriate number of piezoelectric elements having different diameters are arranged concentrically on one side of the diaphragm, and these piezoelectric elements are caused to bend in the same direction.
or the piezoelectric speaker according to item 2.