JP2009222019A - Piezoelectric fan device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device for an electronic device, excellent in cooling performance for locally cooling around an IC chip and the like within the electronic device of various types. <P>SOLUTION: The piezoelectric fan device is provided with a piezoelectric fan part 110 comprising a plate-shaped piezoelectric element 111, and a flat elastic vibration plate 112 having longer length than the plate-shaped piezoelectric element 111, on which it is fixed. The piezoelectric fan part 110 is fixed on one end side or at a middle part to be supported in an overhanging way by a support part. It is also provided with an AC circuit to apply AC voltage to the plate-shaped piezoelectric element 111. The elastic vibration plate 112 comprises a comb teeth part 112b of large width. The plate-shaped piezoelectric element 111 is provided on the free end side of the comb teeth part 112b on at least every other tooth. The substantial length of the elastic vibration plate can thus be long. The amplitude is increased, noise is reduced, and a blow range is enlarged. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

    The present invention relates to a piezoelectric fan device including a piezoelectric element that locally cools the periphery of a chip such as an LSI or a CPU in various electronic devices.

Since chips such as LSIs and CPUs incorporated in various electronic devices are local heat sources, depending on the product, it is necessary to cool them appropriately.
As a response to such a demand, a simple heat radiating body (plate) having a large number of heat radiating pieces is also used, but a small piezoelectric element (ceramic element) that can be cooled more efficiently is used. A piezoelectric fan device is provided (for example, cited document 1).
JP 2000-323882 A

The schematic structure of the piezoelectric fan device is as shown in FIGS. In these apparatuses, one or two plate-like piezoelectric elements (usually ceramic elements made of PZT or the like) 11 are placed on one or both sides of a longer elastic metal plate (blade) 12 via an adhesive layer 13. Pasted. The plate-like piezoelectric element 11 is usually provided with electrodes 14 and 14 on both sides thereof, and is integrated with the elastic metal plate 12 as the piezoelectric fan unit 10.
An AC circuit 20 for applying an AC voltage to the piezoelectric fan unit 10 is connected to the piezoelectric fan unit 10 so as to be energized between the electrodes 14 and 14 of the plate-like piezoelectric element 11, while one end (center, etc.) of the piezoelectric fan unit 10 is connected. Is also supported and fixed as a cantilever type by a support part 30 which is a fixed part. In addition, a single plate-like piezoelectric element 11 is called a monomorph type (unimorph type), and a two-sheet piezoelectric element 11 is called a bimorph type.

  In the case of such a piezoelectric fan device, when an AC voltage is applied, the plate-like piezoelectric element 11 expands or contracts, so that the piezoelectric fan unit 10 is bent alternately in the forward and reverse directions as a whole. Therefore, if the piezoelectric fan device is assembled around a chip such as an LSI or CPU in an electronic device and a sine wave having a resonance frequency is applied as an AC voltage, the free end (free end) side of the elastic metal plate 12 is a fan shape. Cooling air is generated. That is, a desired fan function can be obtained.

  In addition, when there are two plate-like piezoelectric elements 11, when one plate-like piezoelectric element 11 extends, the other plate-like piezoelectric element 11 shrinks. Conversely, when one plate-like piezoelectric element 11 shrinks, the other Since the plate-like piezoelectric element 11 is extended, the bending motion in the forward and reverse directions is amplified. For this reason, larger cooling air is generated. That is, a better fan function can be obtained.

  In the piezoelectric fan device having such a structure, in order to increase the cooling performance, in order to obtain larger high vibration of the elastic metal plate 12, the length of the elastic metal plate 12 is increased or the voltage to be energized is increased. It will be necessary.

  However, in recent years, with the downsizing of electronic equipment, the space for installing a piezoelectric fan device, which is a cooling component, has also been limited, and it has become difficult to increase the size of the device. On the other hand, the power consumption of electronic devices has increased due to the progress of multi-functionalization, and it has become difficult to drive the piezoelectric fan device at a high voltage.

  That is, there is a need for a piezoelectric fan device having a size equivalent to that of the conventional structure and higher cooling performance. Furthermore, there is a need for a piezoelectric fan device that has the same cooling performance even in a smaller size than the conventional structure.

  Therefore, the present inventors have focused on the elastic metal plate 12 that is an elastic diaphragm, and has a shape having a wide comb tooth portion, and a plate-like piezoelectric element is provided on a part of the comb tooth portion. The left and right comb teeth adjacent to the comb teeth where the plate-like piezoelectric element is installed function as a continuous folded piece, and the length of the elastic diaphragm is substantially increased. Thus, it has been found that a higher amplitude can be obtained. It has also been found that the resonance frequency of the elastic diaphragm is lowered and noise can be reduced. Furthermore, two portions on the base end portion (folded portion) side of the comb tooth portion where the plate-like piezoelectric element is installed and the free end side of the comb tooth portion of the folded piece become vibration portions, and air is obtained at two locations. I also understood that.

  The present invention has been invented by paying attention to this point. The elastic diaphragm (blade) has a shape having a wide comb tooth portion, and a plate-like piezoelectric element is provided on a part of the comb tooth portion. The present invention provides an excellent piezoelectric fan device capable of obtaining a high amplitude (improving cooling performance) and at the same time having a low vibration frequency (noise reduction) and blowing air at two sites (expanding the air blowing area). .

According to a first aspect of the present invention, there is provided a piezoelectric fan comprising a single plate-like piezoelectric element and a plate-like elastic vibration plate having a length longer than that of the plate-like piezoelectric element. In the piezoelectric fan device provided with an AC circuit for applying an AC voltage to the plate-like piezoelectric element while supporting and fixing one end side or the middle of the part in a cantilevered manner with a support part,
In the piezoelectric fan device, the elastic diaphragm has a shape having a wide comb-tooth portion, and at least every other plate-like piezoelectric element is provided on the free end side of the comb-tooth portion.

  The present invention according to claim 2 is characterized in that the elastic diaphragm has three wide comb teeth and the plate-like piezoelectric element is provided on the free end side of the center comb teeth. The piezoelectric fan device according to claim 1.

  The present invention according to claim 3 is characterized in that the elastic diaphragm has three wide comb teeth, and the plate-like piezoelectric elements are provided on both surfaces of the free end of the central comb teeth. The piezoelectric fan device according to claim 1.

  The invention according to claim 4 is characterized in that the elastic diaphragm has three wide comb teeth and the plate-like piezoelectric elements are provided on the free ends of the left and right comb teeth. The piezoelectric fan device according to claim 1.

  The invention according to claim 5 is characterized in that the elastic diaphragm has three wide comb teeth and the plate-like piezoelectric elements are provided on both sides of the free ends of the left and right comb teeth. The piezoelectric fan device according to claim 1.

  According to a sixth aspect of the present invention, in the piezoelectric fan device according to the first, second, third, fourth or fifth aspect, the elastic diaphragm is an elastic metal plate or an elastic resin plate.

  According to the piezoelectric fan device of the present invention, in the monomorph type or bimorph type, the elastic diaphragm has a shape having a wide comb tooth portion, and a plate-like piezoelectric element is provided on a part of the comb tooth portion. The non-installed comb-teeth portion of the adjacent plate-like piezoelectric element becomes a folded piece, the length of the elastic diaphragm is substantially increased, and higher amplitude, that is, improvement in cooling performance can be obtained. In other words, the length of the elastic diaphragm can be shortened in obtaining equivalent cooling performance. That is, the apparatus can be downsized.

  Moreover, since the length of the elastic diaphragm is substantially increased, the vibration frequency (resonance frequency) of the elastic diaphragm is lowered, and noise can be reduced. Furthermore, since the two portions on the base end portion (folded portion) side of the comb tooth portion where the plate-like piezoelectric element is installed and the free end side of the comb tooth portion of the folded piece are vibration portions, these two portions (portions) In this case, the air can be obtained and the air blowing area can be enlarged. As a result, the cooling performance is improved. Further, when the cooling performance is improved, it is not particularly necessary to increase the energization voltage, so that high voltage driving is not required.

  FIG. 1 shows an example of a piezoelectric fan device according to the present invention, FIG. 2 shows its main part, and FIG. 3 shows an elastic diaphragm. In the figure, reference numeral 100A denotes a monomorph type piezoelectric fan device, and 110 denotes the piezoelectric fan unit. The piezoelectric fan unit 110 includes a plate-like piezoelectric element (PZT or the like) 111, which is longer than this, for example, an elastic vibration plate (hardness of a steel material such as SUS or an elastic metal plate such as a brass material). A high elastic resin plate or the like is also possible). It is attached to one side of 112 via an adhesive layer 113. In addition, electrodes 114 and 114 are provided on both surfaces of the plate-like piezoelectric element 111. 120 is an AC circuit for applying an AC voltage to the plate-like piezoelectric element 111, and 130 is a support portion made of a fixed component that supports one end side of the piezoelectric fan portion 110 (in the middle or the like) in a cantilever manner. is there.

  The elastic diaphragm 112 has a shape having a plurality (for example, three, four or more, or two) of wide comb teeth 112b by slits 112a such as cuts. In this example, three comb teeth 112b are provided, and a plate-like piezoelectric element 111 is provided on the free end side of the center comb teeth 112b. The formation of the slit 112a is not limited to cutting, and may be formed by, for example, pressing or molding.

  In the case of this elastic diaphragm 112, the substantial length of the diaphragm is that the comb teeth 112b where the plate-like piezoelectric element 111 is installed and the left and right combs where the plate-like piezoelectric element adjacent to this is not installed. Since the tooth portion 112b is folded and continuously provided, these are additive. That is, the substantial length becomes longer.

  As a result, a higher amplitude can be obtained during driving. That is, the cooling performance can be improved. Conversely, if the same cooling performance is obtained, the length of the elastic diaphragm 112 itself may be short. That is, the apparatus can be downsized. In addition, since the substantial length of the elastic diaphragm 112 becomes long and the comb-teeth portion 112b of the folded piece also resonates, the vibration frequency (resonance frequency) decreases. That is, noise can be reduced. Furthermore, two portions on the base end portion (turned-back portion) side of the comb-tooth portion 112b where the plate-like piezoelectric element 112 is installed and the free end side of the comb-tooth portion 112b serving as the turned-up piece become vibration portions (vibration ends). Therefore, vibrations are generated at these two places (parts indicated by arrows A and B in FIG. 2). Air is obtained at these two locations. For this reason, expansion of a ventilation area, ie, the improvement of cooling performance, is obtained.

  Note that energization of the electrode 114 inside the plate-like piezoelectric element 111 is performed by a normal method. When the elastic diaphragm 112 is an elastic metal plate, it can be performed by energizing it as shown in FIG. Note that since the thickness of the adhesive layer 113 is thin, even a layer made of a normal adhesive material can be energized without any problem, but may be conductive. In the case of the conductive adhesive layer, in the present invention, the electrode 114 inside the plate-like piezoelectric element 111 can be omitted. Thereby, thickness reduction of an apparatus is obtained. When the elastic diaphragm 112 is an elastic resin plate, the lead wire on the AC circuit 120 side is directly connected to the inner electrode 114 side of the plate-like piezoelectric element 111.

FIG. 4 shows another example of the piezoelectric fan device according to the present invention, and FIG. 5 shows the main part thereof. In the figure, reference numeral 100B denotes a bimorph type piezoelectric fan device, which basically has the same structure as that shown in FIGS. 1 to 3, but the plate-like piezoelectric element 111 is installed on both surfaces of the elastic diaphragm 112. It is. The same components as those of the piezoelectric fan device 100A are denoted by the same reference numerals.
In this bimorph type piezoelectric fan device 100B, since there are two plate-like piezoelectric elements 111, 111, a larger amplitude effect of the elastic diaphragm 112 can be obtained as compared with the piezoelectric fan device 100A. That is, a greater cooling effect can be obtained.

FIG. 6 and FIG. 7 show the main parts of other examples of the piezoelectric fan device according to the present invention. The main part of the piezoelectric fan device of FIG. 6 is a monomorph type in which a plate-like piezoelectric element 111 is provided on the free end side of the left and right comb teeth 112b of the three comb teeth 112 of the elastic diaphragm 112. belongs to. The main part which becomes the piezoelectric fan apparatus of FIG. 7 is a main part of the piezoelectric fan apparatus of FIG.
These main parts are basically assembled in substantially the same manner as the piezoelectric fan devices 100A and 100B. In addition, the same code | symbol is attached | subjected to the same component as piezoelectric fan apparatus 100A, 100B.

  In the case of a piezoelectric fan device having these as a main part, in both the monomorph type and the bimorph type, the left and right comb tooth portions 112b on which the plate-like piezoelectric elements 111 are installed, the side ends (folded portions), and the folded pieces Since the two free ends of the comb-tooth portion 112b at the center become vibration portions (vibration ends), vibration occurs at these two portions (the portions indicated by arrows A and C in FIGS. 6 and 7). . Air is obtained at these two locations. In addition, since the number of plate-like piezoelectric elements that are vibration sources is large, better cooling performance can be obtained. Of course, it is possible to obtain noise reduction and expansion of the air blowing region due to a decrease in the resonance frequency.

<Examples and comparative examples>
In order to confirm the effect of the piezoelectric fan device according to the present invention, the structure is the same as that of the monomorph type piezoelectric fan device 100A of the present invention shown in FIGS. Example 1) and the same structure as the monomorph type piezoelectric fan device of the present invention shown in FIG. 6 and having the dimensions shown in FIG. 9 (Example 2) and the conventional monomorph type shown in FIG. Each sample having the structure and the size shown in FIG. 10 (Comparative Example 1) was manufactured. And the alternating voltage of +/- 12V was applied to each sample, and the amplitude test of the elastic diaphragm was performed. The results were as shown in Table 1.

  In each sample piezoelectric fan device, SUS301 having a thickness t1 = 0.05 mm and a length L = 20 mm was used as the elastic diaphragm. The elastic diaphragm 112 has a width H = 12 mm, each comb tooth width h1 = 4 mm, h2 = 2 mm, h3 = 2 mm, and a base end portion (folded portion) length L2 = 2 mm of the comb tooth portion. The width H of the elastic diaphragm 12 is 4 mm. Each plate-like piezoelectric element (using PZT) 111 and 11 installed on the elastic diaphragm has a length L0 = 10 mm, a thickness t2 = 0.20 mm, and a width corresponding to the base part width of the installation part.

From the amplitude data (amplitude, resonance frequency evaluation results) in Table 1, in the case of the piezoelectric fan device using the elastic diaphragm provided with the comb-tooth portion by the slit of the present invention (Examples 1 and 2), the amplitude is large. It can also be seen that the resonance frequency is low. In contrast, in the case of a conventional piezoelectric fan device using an elastic diaphragm without a comb tooth portion (Comparative Example 1), it can be seen that the amplitude is small and the resonance frequency is high.
In other words, the piezoelectric fan device (Examples 1 and 2) of the present invention can provide better cooling performance and noise reduction at the same time as the conventional piezoelectric fan device (Comparative Example 1). I understand.

  In addition, it was confirmed that the same result was obtained when the same test as described above was performed even when the piezoelectric fan device was a bimorph type. Moreover, in the said Examples 1-2, although it was a case where the comb-tooth part of an elastic diaphragm is three pieces, this invention is not limited to this. It can be applied to the case of four or more or two. That is, in the elastic diaphragm having a shape having a wide comb-tooth portion, a structure in which at least every other plate-like piezoelectric element is provided on the free end side of the comb-tooth portion, the comb-teeth on the non-installation side of the plate-like piezoelectric element is provided. The part may be a vibrating part.

It is the general | schematic longitudinal section side view which showed an example of the piezoelectric fan apparatus which concerns on this invention. It is the perspective view which showed the principal part of the apparatus of FIG. It is a top view of the elastic diaphragm of the apparatus of FIG. It is the general | schematic longitudinal section side view which showed the other example of the piezoelectric fan apparatus which concerns on this invention. It is the perspective view which showed the principal part of the apparatus of FIG. It is the perspective view which showed the principal part of the other example of the piezoelectric fan apparatus which concerns on this invention. It is the perspective view which showed the principal part of the other example of the piezoelectric fan apparatus which concerns on this invention. It is the perspective view which showed the dimension of each part in the principal part of this invention apparatus. It is the perspective view which showed the dimension of each part in the principal part of this invention apparatus. It is the perspective view which showed the dimension of each part in the principal part of conventional piezoelectricity. It is the general | schematic longitudinal side view which showed the conventional piezoelectric fan apparatus. It is the general | schematic longitudinal side view which showed the conventional piezoelectric fan apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100A-100B ... Piezoelectric fan apparatus, 110 ... Piezoelectric fan part, 111 ... Plate-shaped piezoelectric element, 112 ... Elastic vibration board, 112a ... Slit, 112b ... Comb tooth part, 113 ... Adhesive layer, 114 ... electrode, 120 ... AC circuit, 130 ... support

Claims (6)

One plate-like piezoelectric element and the plate-like piezoelectric element are fixed, and supports one end side or the middle of a piezoelectric fan unit comprising a plate-like elastic diaphragm having a longer length than the plate-like piezoelectric element. In a piezoelectric fan device having an AC circuit for supporting and fixing in a cantilevered manner at the portion and applying an AC voltage to the plate-like piezoelectric element,
The piezoelectric fan device according to claim 1, wherein the elastic diaphragm has a shape having a wide comb-tooth portion, and at least every other plate-like piezoelectric element is provided on the free end side of the comb-tooth portion. 2. The piezoelectric fan device according to claim 1, wherein the elastic diaphragm has three wide comb teeth, and the plate-like piezoelectric element is provided on the free end side of the central comb teeth. 2. The piezoelectric fan device according to claim 1, wherein the elastic diaphragm has three wide comb-teeth portions, and the plate-like piezoelectric elements are provided on both surfaces of the free end side of the central comb-teeth portion. 2. The piezoelectric fan device according to claim 1, wherein the elastic diaphragm has three wide comb teeth, and the plate-like piezoelectric elements are provided on the free ends of the left and right comb teeth. 2. The piezoelectric fan device according to claim 1, wherein the elastic diaphragm has three wide comb teeth and the plate-like piezoelectric elements are provided on both surfaces of the left and right comb teeth. 6. The piezoelectric fan device according to claim 1, wherein the elastic diaphragm is an elastic metal plate or an elastic resin plate.

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