JPH066959B2 - Piezoelectric fan - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric fan, and more particularly to a piezoelectric fan using a bending type piezoelectric vibrator such as a bimorph vibrator.

(Prior Art) An example of a conventional piezoelectric fan is disclosed in, for example, JP-A-59-22.
It is disclosed in Japanese Patent No. 4500. The piezoelectric fan disclosed in this publication generates a bending vibration by laminating a piezoelectric body by its lateral effect or vertical effect, and disposes an elastic plate such as plastic or metal at the tip of the cantilever structure. The air is blown while amplifying the displacement caused by the vibration.

(Problems to be Solved by the Invention) In the conventional piezoelectric fan, it is necessary to ideally fix the support portion of the cantilever, but in reality, the support portion is normally integrated with the case. The case is bolted or fixed with an adhesive. The mass of such a case is finite, so that the support and the case to which it is attached also vibrate. Such vibration not only propagates to a device equipped with a piezoelectric fan and adversely affects it, but also vibrates the support part thereof, which reduces the amplitude of the tip of the elastic plate and reduces the air volume and speed. Therefore, the conventional cantilever type piezoelectric fan is not very efficient.

Therefore, the main object of the present invention is to provide a more efficient piezoelectric fan.

(Means for Solving the Problems) Briefly, the present invention provides at least one of tuning fork type substrates.
This is a piezoelectric fan in which a piezoelectric vibrator vibrating in a base symmetrical bending mode is attached to a side, and an elastic plate formed at the tips of two sides of the tuning fork type base is caused to resonate in the base symmetrical bending mode together with the tuning fork type base.

(Operation) The piezoelectric vibrator is driven to generate fundamental symmetrical bending vibration. The vibration of this piezoelectric oscillator propagates to each side of the tuning fork type base to which it is integrally attached and to the elastic plate formed at the tip of the tuning fork type base, and the elastic plate is basically Resonates with symmetrical bending vibration,
The air is blown from the free end of the elastic plate.

(Effect of the Invention) According to the present invention, an efficient piezoelectric fan can be obtained.
That is, in the basic symmetrical bending vibration in the tuning fork type base,
The free vibration causes the node to become a substantially midpoint of its bending, and therefore, by supporting that portion, leakage of vibration from the supporting portion does not occur. Therefore, a strong supporting portion having a large mass is not required, and it can be expected to be further smaller and lighter than the conventional piezoelectric fan having a cantilever structure. Further, since the elastic plate formed at the tip of the tuning fork type expects to vibrate symmetrically, both the air volume and the wind speed are dramatically increased as compared with the piezoelectric fan having the cantilever structure. Moreover, since the leakage of vibration does not occur, it does not adversely affect other equipment such as a computer to which it is attached.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

(Embodiment) FIG. 1 is an illustrative view showing one embodiment of the present invention. The piezoelectric fan 10 includes a tuning fork type base 12. The tuning fork type base body 12 is made of a constant elastic material such as elinvar and has two sides 12a and 12b. The bent center point 12c of the tuning fork type base body 12 or its vicinity is supported by the support portion 14. The support portion 14 is fixed to, for example, a case (not shown).

A pair of piezoelectric elements 16a and 18a are attached to one side 12a of the tuning fork type base 12 with the base interposed therebetween. The piezoelectric elements 14a and 16a are made of a piezoelectric ceramic such as lead zirconate titanate (PZT),
For example, Ag, Ni or A may be provided on both main surfaces.
An electrode composed of 1 or the like is formed by a method such as printing, plating or vapor deposition. In this manner, the one side 12a of the tuning fork type base body and the pair of piezoelectric elements 16a and 18a form a bimorph oscillator. The other side 12b of the tuning fork type base body 12 also includes a pair of piezoelectric elements 16b and 1b.
A bimorph oscillator is formed together with 8b. Such a bimorph oscillator causes bending vibration in this embodiment.

Elastic plates 20a and 20b made of a resin having elasticity such as plastic or glass epoxy plate are attached to the tips of the two sides 12a and 12b of the tuning fork type base 12, respectively. And side 1
2a and 12b and elastic plates 20a and 20b
And resonate as a unit in the fundamental symmetric bending mode. By adjusting the thickness, width, length, and other dimensions of each of the elastic plates 20a and 20b, it is possible to change the amount of deflection and the angle of deflection, and by controlling these, the size and shape that maximize the wind speed. Is set to.

Piezoelectric elements 16a and 18 constituting a bimorph oscillator
Each of a, 16b and 18b is polarized in the arrow direction shown in FIG. One of the electrodes of the piezoelectric element 16a and one of the electrodes of the piezoelectric element 18a are electrically connected via one side 12a of the tuning fork type base 12. Similarly, one of the electrodes of the piezoelectric element 16b and one of the electrodes of the piezoelectric element 18b are electrically connected via the side 12b of the tuning fork type base 12. Then, these piezoelectric vibrators 16a,
The other electrode of each of 18a, 16b and 18b is
It is connected to the drive source 22.

The node point of the fundamental symmetric bending mode of a phoneme with free ends is about 0.224 l (l is the length of the phoneme) from both ends, but when the phoneme is bent, the node point becomes the second point. As shown in the figure, it is known to gradually move toward the midpoint. Then, in such a basic vibration of the tuning fork, as shown in FIG. 2, the node occurs at two points near the midpoint and sandwiching the midpoint. Therefore, if these two points are supported by the supporting portion 14 as shown in FIG. 1, the amplitude at the tip becomes equivalent to that of the conventional cantilever structure. This invention
This principle is used.

Each side 12a of the tuning fork type base 12 is driven by the drive source 22.
The bimorph oscillators formed in and 12b vibrate in the fundamental symmetrical bending mode together with the elastic plates 20a and 20b. Then, these elastic plate 20a
The tips of 20 and 20b generate a large amplitude as shown by the dotted line in FIG. And at that time, the wind vector is
As shown in FIG. That is, the vector fronts of the winds generated by the respective elastic plates 20a and 20b are aligned, and a wind having a larger air volume and wind speed is generated as compared with the conventional cantilever structure.

Next, this will be described in more detail based on the results of the experiment conducted by the inventor.

FIG. 4 shows the wind velocity distribution in the conventional cantilever beam piezoelectric fan, and FIG. 5 shows the wind velocity distribution in the embodiment of FIG. However, in the example shown in FIG. 4, the cantilever support portion is shown as being completely fixed. If the fixation is not perfect, the wind speed at each point will be further reduced.

As can be seen from FIGS. 4 and 5, when the tuning fork type base 12 and the elastic plates 20a and 20b are used as in the embodiment of FIG. 1, a conventional cantilever structure piezoelectric fan is used. Compared with, the wind speed is more than double. This is because the tuning fork type piezoelectric vibrator has a mode in which it vibrates symmetrically and uses the fundamental mode, so that it is efficient. Further, as described above, since the node exists almost in the vicinity of the support portion 14 in FIG. 1, even if the support portion 14 is not completely fixed, there is almost no decrease in the wind speed, and if the support portion is free. As a matter of fact, a wind speed of 95% or more was obtained at each point.

Furthermore, the vibration node in the tuning fork type base 12 is stable, and therefore its Q is high, so that the driving efficiency, that is, the amplitude of the elastic plate 20a and 20b corresponding to the applied voltage and the wind force obtained therefrom are large.

Further, in general, in this type of piezoelectric fan, a material in which the wind speed and the air volume are more important than the temperature characteristic of the frequency or the change with time is selected, so that the resonance frequency is not stable.
Therefore, a conventional piezoelectric fan drive source uses an oscillation circuit of self-excitation or frequency tracking type other excitation. in this case,
If the Q is high and stable as in the tuning fork type piezoelectric fan of this embodiment, the oscillation in the oscillation circuit is stable, and the effect is great especially when the self-excited oscillation circuit is used.

FIG. 6 is an illustrative view showing another embodiment of the present invention. In this embodiment, while the elastic plate 20a and 20b made of a material different from that of the tuning fork type base body 12 is used in the embodiment of FIG. 1, the elastic plate 20a 'and 20b' are
It was formed as an extension of each side 12a and 12b of the tuning fork type base 12. That is, in the embodiment of FIG. 6, the elastic plates 20a 'and 20b' are the tuning fork type base 1
It is composed of the same material as 2.

FIG. 7 is an illustrative view showing still another embodiment of the present invention. In this embodiment, one side 12a of the tuning fork type base 12 is
A bimorph oscillator is constructed only in. That is, in the embodiment shown in FIG. 7, the piezoelectric elements 16b and 18 shown in FIG.
b is omitted. As described above, even if the piezoelectric element is attached to only one side of the tuning fork type base 12, the bimorph oscillator is configured, the same effect as described above can be obtained. However, since there is only one vibration source, the amplitude and the air volume with respect to the applied voltage naturally decrease accordingly.

8 to 11 are illustrative views showing different embodiments of the present invention. The examples of FIGS. 8 and 9 differ from the example of FIG. 1 in the connection of the drive source 22, respectively.

The examples of FIGS. 10 and 11 are different from the example of FIG. 1 in the bending structure of the tuning fork type base 12, respectively.

Although the tuning fork base 12 is formed by bending a single metal plate in each of the above-described embodiments, the sides 12a and 12b and the base (folding part) may be formed separately. .

[Brief description of drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention. FIG. 2 is an illustrative view for explaining the transition of node points in the case of a tuning fork type tuning piece. FIG. 3 is an illustrative view showing the wind direction vector of the embodiment in FIG. FIG. 4 is a diagram showing a wind velocity distribution in a conventional piezoelectric fan having a cantilever structure. FIG. 5 is a diagram showing the distribution of wind speed in the embodiment of FIG. 6 to 11 are illustrative views showing different embodiments of the present invention. In the figure, 10 is a piezoelectric fan, 12 is a tuning fork type substrate, and 1
2a, 12b, the side 14 is a support portion, 16a, 16b, 1
Reference numerals 8a and 18b are piezoelectric elements, 20a and 20b are elastic plates, and 22 is a drive source.

Claims (4)

[Claims] 1. A tuning-fork type base body in which ends of two sides are bent in the same direction, a piezoelectric vibrator provided on at least one side of the tuning-fork type base body, and vibrating in a fundamental symmetrical bending mode, A piezoelectric fan, comprising an elastic plate extending from respective tips of the two sides of the tuning fork type base and resonating with the tuning fork type base in a fundamental symmetrical bending mode. 2. The piezoelectric fan according to claim 1, wherein the elastic plate is made of the same material as the tuning fork type base body. 3. The piezoelectric fan according to claim 1, wherein the elastic plate is made of a material different from that of the tuning fork type base. 4. A first support according to claim 1, further comprising a support portion for supporting a bent substantially middle point of the tuning fork type base body.
The piezoelectric fan according to any one of items 1 to 3.