JP2008172105A - Piezoelectric fan device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a strong piezoelectric fan device comprising a piezoelectric element for locally cooling the periphery of a chip such as an LSI in various kinds of electronic equipment, and having superior cooling performance. <P>SOLUTION: In the piezoelectric fan device 100, a piezoelectric fan section 110 comprises two planar piezoelectric elements 111 and an elastic metal plate 112 that is longer than the planar piezoelectric elements 111 and sandwiched between and among the elements. One end side or a middle portion of the piezoelectric fan section 110 is supported and fixed in a cantilever manner by a support section 130. The piezoelectric fan device 100 has an AC circuit 120 for applying AC voltages to an electrodes 114, 114 in both the planar piezoelectric elements 111, 111. In this case, the thickness of the support side of each planar piezoelectric element 111, 111 is made larger than that of the free end side, thus improving mechanical strength, achieving robustness, and obtaining improved cooling performance. <P>COPYRIGHT: (C)2008,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

  A schematic structure of the piezoelectric fan device is shown in FIG. In this apparatus, two plate-like piezoelectric elements (usually ceramic elements made of PZT or the like) 11 and 11 are attached to both surfaces of a longer elastic metal plate 12 via adhesive layers 13 and 13. . The both plate-like piezoelectric elements 11 and 11 have electrodes 14 and 14 formed on both surfaces thereof, and are integrated with the elastic metal plate 12 to form the piezoelectric fan portion 10. The AC circuit 20 for applying an AC voltage is connected between the outer electrodes 14 and 14 and the elastic metal plate 12, and one end of the piezoelectric fan unit 10 (in the middle or the like is also possible). It is supported and fixed as a cantilever type by a support part 30 as a fixed part.

  In the case of this piezoelectric fan device, when an AC voltage is applied, when one plate-like piezoelectric element 11 expands, the other plate-like piezoelectric element 11 contracts, and conversely, when one plate-like piezoelectric element 11 shrinks, the other plate-like piezoelectric element 11 shrinks. Since the plate-like piezoelectric element 11 extends, the piezoelectric fan unit 10 is bent and moved alternately in the forward and reverse directions as a whole.

  Therefore, when 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 alternating 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 order to enhance the fan function, a diaphragm made of a thin plate made of plastic or the like is provided on the free end side of the elastic metal plate 12 as necessary.

  The piezoelectric fan device having such a structure has no advantage of electromagnetic interference, can be installed close to a heat source such as an LSI or a CPU, and has the advantage of being small in size and simple in structure. There was a problem like this.

  That is, in this apparatus, since the piezoelectric fan unit 10 is supported and fixed in a cantilever manner by the support unit 30, when the amplitude of vibration increases, stress concentrates on the support unit 30 and the plate-like piezoelectric element 11. , 11 is easily broken. In particular, when the thickness of the plate-like piezoelectric elements 11 and 11 is reduced in order to improve the fan function, this problem becomes significant. When the thickness of the element is reduced, the mechanical strength is naturally reduced, so that although the fan function can be improved in the short term, there is a concern that the element is damaged during use. To complicate matters, even if there is damage, there is also a problem that it is difficult to detect after being incorporated in an electronic device.

  However, in recent years, electronic devices have become more and more compact, and LSIs and CPUs, which are heat sources, tend to be arranged at high density. Fan function is required.

  The present invention has been made in view of the above-described conventional problems. The feature of the present invention is that the two plate-like piezoelectric element portions of the piezoelectric fan portion are arranged on the support side of the plate-like piezoelectric element. An excellent piezoelectric fan device in which a high fan function can be obtained by making the thickness thicker than the thickness on the free end side to ensure sufficient mechanical strength on the support side, while making the free end side thin. Is to provide.

According to a first aspect of the present invention, there is provided a piezoelectric fan comprising two plate-like piezoelectric elements and an elastic metal plate having a longer length than the two plate-like piezoelectric elements and sandwiched between these plate-like piezoelectric elements. In the piezoelectric fan device comprising an AC circuit that supports and fixes one end side or a middle of the unit in a cantilevered manner with a support unit and applies an AC voltage to the electrodes on the outer surfaces of the two plate-like piezoelectric elements. The piezoelectric fan device is characterized in that the thickness of the support portion side of the plate-like piezoelectric element is thicker than the thickness of the free end side thereof.

  According to a second aspect of the present invention, there is provided the piezoelectric fan device according to the first aspect, wherein the thickness of the plate-like piezoelectric element is gradually reduced in an inclined manner from the support portion side to the free end side.

  According to a third aspect of the present invention, there is provided the piezoelectric fan device according to the first or second aspect, wherein the thickness of the plate-like piezoelectric element is at least twice that of the free end side on the support side.

According to the piezoelectric fan device of the present invention, in the two plate-like piezoelectric element portions of the piezoelectric fan portion, the thickness of the support portion side of the plate-like piezoelectric element is made larger than the thickness of its free end side, Then, while ensuring sufficient mechanical strength, a high fan function can be obtained by thinning the free end side. That is, a strong and small high-performance piezoelectric fan device can be obtained.
In addition, when the thickness of the plate-like piezoelectric element is gradually reduced from the support side to the free end side, there is a portion (stepped portion, etc.) where stress tends to concentrate from the support side to the free end side. Therefore, better mechanical strength can be obtained. In particular, when the thickness on the support portion side is twice or more that on the free end side, the stress on the support portion side can be reduced, and a larger mechanical strength can be obtained. Higher fan performance can be obtained. That is, an ideal piezoelectric element shape can be obtained.

FIG. 1 shows an example of a piezoelectric fan device according to the present invention.
In the figure, reference numeral 100 denotes a piezoelectric fan device, 110 denotes two plate-like piezoelectric elements 111 and 111 attached to both surfaces of an elastic metal plate 112 having a longer length via adhesive layers 113 and 113, Piezoelectric fan section provided with electrodes 14 and 14 of both plate-like piezoelectric elements 111 and 111, 120 is an AC circuit for applying an AC voltage between both plate-like piezoelectric elements 111 and 111 and the elastic metal plate 112, Reference numeral 130 denotes a support portion made of a fixed component that supports one end side of the piezoelectric fan portion 110 (possibly in the middle or the like) in a cantilever manner. In order to enhance the fan function, a vibration plate made of a thin plate made of plastic or the like can be appropriately provided on the free end side of the elastic metal plate 112 as necessary.

The two plate-like piezoelectric elements 111 and 111 are made of ceramic elements such as PZT, and as shown in the figure, the thickness on the support side is larger than the thickness on the free end side. An example of the specific example is shown in FIGS. For example, the length of the two plate-like piezoelectric elements 111 and 111 is 10 mm, the width of the support portion 120 is 5 mm, and the length of the elastic metal plate 112 (from one side of the support portion 120 opposite to the free end side). when the length) is 20 mm, the width of these piezoelectric fan 110 of 4 mm, the thickness of the clear way ,, support part side from the data of examples described later (t1) is from 0.18 to 0. In the range of about 90 mm, the thickness (t2) on the free end side may be adjusted in the range of about 0.02 to 0.45 mm.

<Examples and comparative examples>
Tables 1 to 5 show the thickness (t1) on the support portion side and the free end side in the piezoelectric fan devices (Examples 1 to 30 and Comparative Examples 1 to 5) having the dimensions shown in FIGS. The relationship with the thickness (t2) is set to various values, and the value (ratio) of t1 / t2, the stress (σ) applied to the support portion side, and the amplitude of the elastic metal plate are obtained. In Comparative Examples 1 to 5, the thickness (t1) on the support portion side of the plate-like piezoelectric element is the same as the thickness (t2) on the free end side.

  And it groups (G1-5) corresponding to the thickness (0.05mm, 0.04mm, 0.03mm, 0.02mm, 0.01mm) of this element, and in this group, the support part of the element Examples 1 to 30 were obtained by changing the thickness (t1) on the side and the thickness (t2) on the free end side. In each piezoelectric fan device in each group, the comparative example and the example have the same mass (weight). Moreover, in each Table 1-Table 5, the stress ((sigma)) by the side of a support part and the amplitude of an elastic metal plate are normalized by the value of Comparative Examples 1-5. These data were obtained by the finite element method (FEM). The alternating voltage applied at that time is 200 Vpp.

According to Tables 1 to 5, in the plate-like piezoelectric element, when the thickness (t2) on the free end side is made thinner than the thickness (t1) on the support part side, the stress (σ) on the support part side is reduced. I understand that
However, it can be seen that when the ratio of t1 / t2 is less than 2.0, the amplitude of the elastic metal plate becomes smaller in the cases of Comparative Examples 1 to 5. That is, the fan function is deteriorated and good cooling performance cannot be obtained. Note that the width of the plate-like piezoelectric element, that is, the width of the piezoelectric fan portion, even if it varies slightly from about 4 mm (for example, in the range of about 2 mm to 10 mm), does not significantly affect the stress on the support side and the amplitude of the elastic metal plate. There was no.

  On the other hand, when the ratio of t1 / t2 is 2.0 or more, for example, up to about 9.0, the stress (σ) on the support portion side is further reduced, and at the same time, the amplitude of the elastic metal plate is compared with Comparative Examples 1 to 5. It can be seen that it is larger than In other words, it can be seen that the load on the support portion side is small and sufficient mechanical strength can be ensured, and that a higher fan function is obtained by the larger amplitude of the elastic metal plate. Therefore, from these, the thickness on the support portion side of the plate-like piezoelectric element is made thicker on the free end side, and the thickness is more than twice that on the free end side on the support portion side. It can be seen that an ideal piezoelectric fan device can be obtained.

  In the above description, the one end side of the piezoelectric fan portion shown in FIG. 1 is supported and fixed in a cantilever manner by the support portion. However, the present invention is not limited to this, for example, a cited document. As shown in FIG. 1, the present invention can also be applied to a case where the middle portion of the piezoelectric fan portion or the like is supported and fixed in a cantilever manner by the support portion. Also in this case, the same operation and effect as in the case of supporting and fixing one end side of the piezoelectric fan portion of FIG.

It is the schematic explanatory drawing which showed an example of the piezoelectric fan apparatus which concerns on this invention. It is the schematic perspective view which showed the dimension of the piezoelectric fan part in the apparatus of FIG. It is the elements on larger scale of the piezoelectric fan part of FIG. It is the schematic perspective view which showed the conventional piezoelectric fan apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Piezoelectric fan apparatus, 110 ... Piezoelectric fan part, 111 ... Plate-shaped piezoelectric element, 112 ... Elastic metal plate, 113 ... Adhesive layer, 114 ... Electrode, 120 ... AC circuit, 130 ... support part

Claims (3)

The piezoelectric fan section at one end or the middle of a consisting of two plate-like piezoelectric element and said have a length greater than two plate-like piezoelectric element elastic metal plate sandwiched between the plate-like piezoelectric element, In a piezoelectric fan device having an AC circuit that supports and fixes in a cantilevered manner with a support portion and applies an AC voltage to the electrodes on the outer surfaces of the two plate-like piezoelectric elements, The piezoelectric fan device is characterized in that the thickness of the piezoelectric fan is thicker than the thickness on the free end side. 2. The piezoelectric fan device according to claim 1, wherein the thickness of the plate-like piezoelectric element is gradually reduced in an inclined manner from the support portion side to the free end side. 3. The piezoelectric fan device according to claim 1, wherein the thickness of the plate-like piezoelectric element is at least twice that of the free end side on the support side.

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