JPS6255500A - Piezo-electric fan - Google Patents

Abstract

PURPOSE:To improve efficiency, by furnishing a piezo-resonater to oscillate in a basic symmetric bending mode at least at one side of a tuning fork type body, and making an elastic plate formed at the tops of two sides of the tuning fork type body resonate. CONSTITUTION:At one side 12a of a tuning fork type body 12, a pair of piezo-electric elements 16a and 18a are installed and made to generate a winding oscillation. At the tops of the two sides 12a and 12b, elastic plates 20a and 20b are installed to resonate integrally in a basic symmetric bending mode. Therefore, the air is blown from the free ends of the elastic plates, and an efficient piezo-electric fan can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a piezoelectric fan, and particularly to a piezoelectric fan using a bent piezoelectric vibrator such as a bimorph vibrator.

(Prior art) An example of a conventional piezoelectric fan is disclosed in Japanese Patent Application Laid-Open No. 59-22
It is disclosed in Japanese Patent No. 4500. The piezoelectric fan disclosed in this publication has piezoelectric bodies bonded together to generate bending vibration due to their transverse or vertical effects, and an elastic plate made of plastic or metal placed at the tip of the cantilever structure. Air is blown while amplifying the displacement caused by the vibration.

(Problem to be Solved by the Invention) In conventional piezoelectric fans, the supporting portion of the cantilever beam must be ideally fixed, but in reality, the supporting portion is usually integral with the case. It is fixed to the case with bolts or adhesive. The mass of such a case is finite and therefore the support and the case to which it is attached also generate vibrations. Such vibrations not only propagate and adversely affect the equipment to which the piezoelectric fan is attached, but also cause the support portion to vibrate, thereby reducing the amplitude of the tip of the elastic plate and reducing the air volume and wind speed. Therefore, conventional cantilever type piezoelectric fans are not very efficient.

Therefore, the main objective of this invention is to provide a more efficient piezoelectric fan.

(Means for Solving the Problems) Simply put, the present invention provides at least one of the tuning fork type bases.
This is a piezoelectric fan in which a piezoelectric vibrator that vibrates in a fundamentally symmetrical bending mode is attached to a side, and elastic plates 1- formed at the tips of two sides of the tuning fork-shaped base resonate in a fundamentally symmetrical bending mode together with the tuning fork-shaped base. be.

(Function) The piezoelectric vibrator is driven to produce basic symmetrical bending vibration. The vibration of this piezoelectric vibrator is propagated to each side of the tuning fork-shaped base to which it is integrally attached, as well as to the elastic plate formed at the tip of the tuning fork-shaped base, and the elastic plate is basically attached to the tuning fork-shaped base together with the elastic plate. Resonates with symmetrical bending vibration,
Air is blown from the free end of the elastic plate.

(Effect of the invention) According to this invention, an efficient piezoelectric fan can be obtained.

In other words, in the basic symmetrical bending vibration in a tuning fork type substrate,
Free vibration causes the node to be at approximately the midpoint of the bend, so if that part is supported, vibrations will not leak from the support. therefore,
It eliminates the need for a large and strong support, and can be expected to be smaller and lighter than conventional piezoelectric fans with a cantilever structure. Further, since the elastic plate formed at the tip of the tuning fork-shaped base body vibrates symmetrically, both the air volume and the air speed are dramatically increased compared to a piezoelectric fan having a cantilever structure. Furthermore, since there is no vibration leakage, there is no adverse effect on other equipment, such as a computer, to which it is attached.

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

(Embodiment) FIG. 1 is an illustrative diagram showing an embodiment of the present invention. Piezoelectric fan 10 includes a tuning fork-shaped base 12 .

This tuning fork type base 12 is made of a constant elastic material such as Erinba, and has two sides 12a and 12b. The bent midpoint 12c of the tuning fork-shaped base 12 or its vicinity is supported by the support portion 14. This 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-shaped base 12 with the base sandwiched therebetween. The piezoelectric elements 14a and 16a are made of piezoelectric ceramic such as lead zirconate titanate (PZT),
Each amphibious surface has, for example, Ag, Ni or A.
An electrode made of β or the like is formed by, for example, printing, plating, or vapor deposition. In this way, one side 12a of the tuning fork type base and the pair of piezoelectric elements 16a and 18a
A bimorph oscillator is formed.

The other side 12b of the tuning fork type base 12 also has a pair of piezoelectric elements 16.
Together with b and 18b, it forms a bimorph oscillator. Such a bimorph oscillator produces bending vibration in this embodiment.

Elastic plates 20a and 20b made of elastic resin such as plastic or glass epoxy plates are attached to the ends of each of the two sides 12a and 12b of the tuning fork-shaped base 12. And side 1
2a and 12b and elastic plates 20a and 20b
and resonate in the fundamental symmetrical bending mode as a unit. By adjusting the dimensions such as the thickness, width, and length of each of these elastic plates 20a and 20b, the amount of deflection and angle of deflection can be changed, and by controlling these, the dimensions and shape that maximize the wind speed can be adjusted. is set to

Piezoelectric elements 16a and 18 forming a bimorph vibrator
a and 16b and 18b are respectively this first
It is polarized in the direction of the arrow shown in the figure. 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-shaped base 12. Similarly, one of the electrodes of the piezoelectric element 16b and the piezoelectric element 18
b is electrically connected to one of the electrodes b through the side 12b of the tuning fork-shaped base 12. These piezoelectric vibrators 16
The other electrode of each of electrodes a, 1.8a, 16b and 18b is connected to the drive source 22.

The node point of the basic symmetric bending mode of a vibrating piece with both ends free is located approximately 0.2241 (/ is the length of the vibrating piece) from both ends, but as the vibrating piece is bent, the node point becomes the second As shown in the figure, it is known that the object gradually moves toward the midpoint. In such fundamental vibration of the tuning fork, the nodes occur at two points in the extreme vicinity of the midpoint and sandwiching the midpoint, as shown in FIG. Therefore, if these two points are supported by the support portion 14 as shown in FIG. 1, the amplitude at the tip will be equivalent to that of the conventional cantilever structure.

This invention utilizes such a principle.

Each side 12a of the tuning fork type base 12 is driven by the driving source 22.
The bimorph oscillator formed at 12b and 12b vibrates in a fundamental symmetrical bending mode together with the elastic plates 20a and 20b. Then, these elastic plates 20a
The tip of 20b and 20b produces a large amplitude as shown by the dotted line in FIG. At that time, the wind vector is
The result is as shown in FIG. That is, the vectors of the wind generated by the respective elastic bodies 20a and 20b are aligned in the front, and a larger amount of wind and a larger wind speed are generated than in the conventional cantilever structure.

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

FIG. 4 shows the wind speed distribution in a conventional piezoelectric fan having a cantilever structure, and FIG. 5 shows the wind speed distribution in the embodiment shown in 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-shaped base 12 and the elastic plates 20a and 20b are used as in the embodiment shown in FIG. You can get more than twice the wind speed compared to a fan. This is because the tuning fork type piezoelectric vibrator has a mode that vibrates symmetrically, and its fundamental mode is used, so it is efficient. Furthermore, as mentioned above, since the node exists almost in the vicinity of the support part 14 in FIG. However, wind speeds of 95% or higher were obtained at each point.

Further, since the vibration nodes in the tuning fork type base 12 are stable and therefore have a high Q, the drive efficiency, that is, the amplitude of the elastic plates 20a and 20b that responds to the applied voltage and the wind force obtained therefrom are large.

Furthermore, in general, in this type of piezoelectric fan, materials are selected with emphasis on wind speed and air volume rather than temperature characteristics or changes in frequency over time, so the resonant frequency is not stable.

Therefore, the drive source of conventional piezoelectric fans uses an oscillation circuit of automatic oscillation or frequency tracking type separately excited oscillation. in this case,
When the Q is high and stable as in the tuning fork type piezoelectric fan of this embodiment, the oscillation in the oscillation circuit becomes stable, and this effect is particularly great when a self-oscillation oscillation circuit is used.

FIG. 6 is an illustrative view showing another embodiment of the invention. In this embodiment, whereas the embodiment shown in FIG. 1 uses elastic plates 2oa and 20b made of a different material from the tuning fork type base 12, elastic plates 20a' and 20b' are
It was formed as an extension of each side 12a and 12b of the tuning fork type base body 12. That is, in the embodiment shown in FIG. 6, the elastic plates 20a' and 20b'
It is made 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
A bimorph oscillator is constructed only in That is, in this embodiment of FIG. 7, the piezoelectric elements 16b and 18 in FIG.
b is omitted.

In this way, even if a piezoelectric element is attached to only one side of the tuning fork type base 12 to form a bimorph vibrator, the same effect as described above can be obtained. However, since there is only one vibration source, the amplitude and air volume relative to the applied voltage naturally decrease accordingly.

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

The examples shown in FIGS. 10 and 11 are different from the embodiment shown in FIG. 1 in the bending structure of the tuning fork-shaped base 12, respectively.

In each of the above embodiments, the tuning fork base 12 is constructed by bending a single metal plate, but the sides 12a and 12b and the base (bent portion) may be constructed separately. .

[Brief explanation of the drawing]

FIG. 1 is an illustrative view showing an embodiment of the present invention. FIG. 2 is an illustrative diagram illustrating the transition of node points in the case of a tuning fork type sound piece. FIG. 3 is an illustrative diagram showing the wind direction vector of the embodiment shown in FIG. FIG. 4 is a diagram showing the wind speed distribution in a conventional piezoelectric fan having a cantilever structure. FIG. 5 is a diagram showing the wind speed distribution in the embodiment shown in FIG. FIGS. 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 base, 1
2a, 12b are sides, 14 is a support part, 16a, 16
b, 18a, 18b are piezoelectric elements, 20a. 20b is an elastic plate, and 22 is a driving source. Patent Applicant Murata Manufacturing Co., Ltd. Agent Patent Attorney Yama 1) Honorable Person (and 1 other person) No. 2 71 No. 31S1 0.2ff! /s Z et al. 5 Figure H; 7 C1 No. 91, 2 -10:=+

Claims (1)

[Scope of Claims] 1. A tuning fork-shaped base bent so that the tips of two sides are aligned in the same direction; a piezoelectric vibrator that is provided on at least one side of the tuning fork-shaped base and generates vibration in a fundamental symmetrical bending mode; and a piezoelectric fan, comprising an elastic plate extending from the tip of each of the two sides of the tuning fork type base and resonating with the tuning fork type base in a fundamentally 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-shaped base. 3. The piezoelectric fan according to claim 1, wherein the elastic plate is made of a material different from that of the tuning fork-shaped base. 4. The piezoelectric fan according to any one of claims 1 to 3, comprising a support portion for supporting a substantially midpoint of the bending of the tuning fork-shaped base.