JPS5856318B2 - piezoelectric speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sounding body using a piezoelectric vibrator, and more particularly to a piezoelectric speaker in which the shape of the vibrator is specified and reproduction frequency characteristics are improved.

In recent years, as audio equipment such as radios and tape recorders have become smaller, piezoelectric speakers, which are thin and feature low power consumption, are being considered as compact speakers.

However, since piezoelectric speakers utilize the mechanical resonance of a piezoelectric vibrator as a driving source, the frequency characteristics of the acoustic output are not flat, so they have not yet been put into practical use.

In view of the above-mentioned points, the present invention provides a piezoelectric speaker suitable for practical use.In a piezoelectric vibrator having a cantilever structure, the width of the metal plate part is set to the width of the main vibrating part on the vibrating tip side of the piezoelectric vibrator. This is a piezoelectric speaker consisting of a auxiliary vibration section that is discontinuously narrowed, and a diaphragm is connected to the auxiliary vibration section.

Here, to explain the conventional typical shape of a piezoelectric vibrator with a cantilever configuration, a piezoelectric plate of a similar shape is attached to a rectangular metal plate, one end of the metal plate is fixed, and the other end is The piezoelectric speaker has a structure in which the vibrating tip is connected to the center of a paper cone, for example, and assembled into a piezoelectric speaker.

Next, regarding the piezoelectric vibrator and speaker according to the present invention,
A specific example will be explained based on the drawings.

First, the piezoelectric vibrator is made by combining a semicircular piezoelectric plate 2 with a metal plate 1 in which a rectangular part is connected to the semicircular circumferential part, and the connected rectangular part is the fixed side, and the vibrating tip side of the metal plate 1 is A rectangular metal plate is provided protruding from the center of the straight line portion to serve as an auxiliary vibration section 3.

To assemble the speaker, the rectangular part on the fixed side is fixed to, for example, the support base 4 of the speaker case, and the center point of the cone-shaped diaphragm 5 and the auxiliary vibration part 3 are connected. ), the circumferential end of the diaphragm 5 is fixed to the opening circumferential portion 6 of the speaker case.

With this configuration, the semicircular part of the metal plate 1 becomes the main vibrating part that serves as a drive source for piezoelectrically vibrating the diaphragm, and the auxiliary vibrating part 3 has a widthwise dimension relative to the main vibrating part. By narrowing discontinuously, it has the function of preventing the vibration node from moving to the connection point between this vibrator and the diaphragm 5 provided on the auxiliary vibrator 3. The frequency characteristics of the reproduced sound are flattened.

For further details, the vibration mode of the vibrator will be explained as an example.

FIG. 2 shows a vibrator for comparison consisting of only a semicircular main vibrating section with the auxiliary vibrating section 3 removed from the vibrator according to the present invention described above.

When the above-mentioned vibrator is used, when high-order resonance occurs, it is excited in a vibration mode (vibration <16 kHz, as will be made clear in the following example), for example, as shown in the figure with the nodal position of vibration indicated by a broken line. When this happens, the piezoelectric plate 2 and the diaphragm 5 on the vibrating side tip of the vibrator, that is, the semicircular straight part in this case are usually connected, but the vibration node is Since the coupling point is located on or near the position, the vibration is not transmitted to the diaphragm 5, resulting in a sharp valley in the acoustic output.

Furthermore, even at frequencies that are off resonance, when the vibration mode shifts from a low-order mode to a high-order vibration mode, the contact point moves to the coupling point, resulting in a sharp valley in the acoustic output, similar to the case described above.

In contrast, in the vibrator of the present invention, the widthwise dimension (W2) of the vibrating tip portion where the connection point with the vibrating plate 5 is located, that is, the auxiliary vibrating portion 3, is discontinuous in the vibrator length direction (4). The vibration node position in the same vibration mode as in Figure 2 is shown with a broken line in Figure 1, but the vibration node moves to the auxiliary vibration part 3 during high-order resonance. Never.

Therefore, no vibration nodes are generated at the connection point with the diaphragm 5 (black dots in the figure), so there is no valley in the acoustic output.
The frequency characteristics are flattened.

The gist of this invention is to reduce the vibration node position by coupling the diaphragm and the oscillator by a configuration in which the width (Wl) dimension of the oscillator is discontinuously narrowed in the length direction toward the vibrating tip side. The point is not to move it to a point.

Therefore, the width of the auxiliary vibration part (W2) with respect to the main vibration width (Wl) of the vibrator is important, and the dimension ratio of w2/W1 must be less than /3, and the width of the auxiliary vibration part exceeds this range. The above-mentioned nodes occur, and the effect of flattening the frequency characteristics is reduced.

Furthermore, since the effects of the present invention are obtained by discontinuously changing the width of the auxiliary vibrating part in the length direction of the vibrator as described above, the main vibrating part of the vibrator can have an arbitrary shape. That's fine.

For example, like the semicircular shape shown in Figure 1 or the hexagonal shape shown in Figure 3 a, the width of the main vibrating part on the vibration side is made wider than the fixed side width, and the minimum resonance force in the width direction is It is also possible to adopt a configuration in which the acoustic output in the low frequency range is improved by increasing the .

Further, as shown in FIG. 3B, the auxiliary vibration section according to the present invention may be constructed in a conventional rectangular vibrator.

In particular, as shown in Fig. 3C, by forming the auxiliary vibration section 3 within the tip of the main vibration section, the effective length of the main vibration section can be increased, so that the lower limit frequency of the sound reproduced by the speaker can be increased. It can be lowered.

Regarding the basic structure of the piezoelectric vibrator, it is possible to obtain the same effect with the so-called asymmetric vibrator in which the piezoelectric plate is bonded to only one side of the metal plate, as well as in the symmetrical vibrator in which the piezoelectric plate is bonded to both sides. It goes without saying.

Examples according to the present invention will be shown below to clarify its effects.

Here, a case will be explained in which the main vibrating section shown in FIG. 1 is a semicircular piezoelectric vibrator.

For the metal plate 1, an iron-chromium metal material with a thickness of 0.15 mm and a low mechanical Q value is used, and the shape of the main vibration part is set to a radius of 13 mm.
mm semicircle, the auxiliary vibration part 3 has a width of 2 mm and a length of 3 mm,
The part fixed to the support base 4 was formed to have a width of 0 mm and a length of 3 mm, and a semicircular piezoelectric plate 2 with a radius of 13 mm made of zircon-lead titanate porcelain was adhered thereon to produce a piezoelectric vibrator. .

Next, for the diaphragm 5, a cone-shaped diaphragm with a diameter of 25 mm made of a polyimide film with a thickness of 75 μm is used.The center point of the cone shape is glued to the auxiliary vibration part, and the circumferential part of the diaphragm 5 is attached to the speaker. It was fixed to the opening 6 of the frame with adhesive to create a piezoelectric speaker.

Next, for comparison, a substantially semicircular vibrator without an auxiliary vibrating part as shown in FIG. 2 was used and assembled into a piezoelectric speaker similar to the above.

In manufacturing, the above-mentioned vibrator according to the present invention was used, with the auxiliary vibrating part cut off.

An alternating voltage with an effective value of 1 .mu.m was applied to the two types of speakers shown above, and the sound pressure level at an on-axis position of 10 Cr/L was measured.

FIG. 4 shows the frequency characteristics of a speaker using a vibrator for comparison without an auxiliary vibrating section, and FIG. 5 shows the frequency characteristics of a speaker according to the present invention.

As is clear from Figure 4, in the case of the comparative example, the frequency was approximately 8kHz, 1
The sound pressure level drops significantly at 1 KHz and 16 KHz, and a sharp valley appears.

On the other hand, when a vibrator according to the present invention having an auxiliary vibrating section is used even if the main vibrating section is the same, the sound pressure level does not drop and exhibits flat frequency characteristics.

This is because, as described above, the vibration node on the main vibration section cannot move to the connection point with the diaphragm, that is, to the auxiliary vibration section.

By the way, the vibration node position indicated by the broken line in Figures 1 and 2 is 16.
KL! This corresponds to the vibration of z.

As is clear from the above embodiments, the speaker using the piezoelectric vibrator according to the present invention is capable of reproducing a wide band with one speaker unit, and is an excellent wide band piezoelectric speaker that can be used for moderate practical purposes. be.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a piezoelectric speaker according to the present invention and a plan view of a vibrator, FIG. 2 is a vertical cross-sectional view of a piezoelectric speaker and a plan view of a vibrator for comparison, and FIG. 3 is a piezoelectric vibration according to the present invention. FIG. 4 is a diagram showing the frequency characteristics of the piezoelectric speaker for comparison in the example;
FIG. 5 is a chart showing the frequency characteristics of a speaker according to the present invention in an example. In the figure 1...Metal plate, 2...Piezoelectric plate, 3
...Auxiliary vibration section, 4...Support stand, 5.
...Diaphragm, 6...Aperture circumference.

Claims (1)

[Claims] 1 A piezoelectric vibrator made by combining a piezoelectric plate with a metal plate and fixing one end of the metal plate is used as a drive source, and an auxiliary vibrating part with a width dimension of 1/3 or less of the width of the main vibrating part is provided on the vibrating tip side. A piezoelectric speaker with a diaphragm coupled to the auxiliary vibration part.