JPS6272149A - Heat dissipation fin with piezoelectric fan - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat dissipation fin, and more particularly to a heat dissipation fin with a piezoelectric fan intended to efficiently dissipate heat using a piezoelectric fan.

The heat radiation fin with a piezoelectric fan according to the present invention is applied to, for example, a heat radiation fin of a power transistor, a heat radiation means of various electronic devices, and the like.

[Prior Art] In recent years, the integration of electronic circuits and the miniaturization of devices have progressed, and as a result, heat dissipation measures for circuits and appliances have become important. This is because insufficient heat dissipation measures can cause circuit malfunctions and pose a major hindrance to improving reliability.

Conventionally, as heat dissipation measures such as this, power transistors are fixed on heat dissipation fins made of aluminum or the like, and the heat dissipation fins are placed so that they can easily come in contact with the outside air. Remove to. This method was commonly used.

[Problems to be Solved by the Invention] However, as the density of circuits increases and the output of power transistors increases, the amount of heat generated tends to increase. This problem has to be solved by increasing the surface area of the heat dissipation part of the heat dissipation fin to increase the heat dissipation efficiency, which requires a space to incorporate the large heat dissipation fin, making it extremely difficult to downsize the entire device. On the other hand, if an attempt is made to downsize the device, the size of the heat radiation fins is limited, making it impossible to obtain a sufficient heat radiation effect and reducing the reliability of the device due to heat accumulation. In any case, conventional heat dissipation fins have not been able to solve these problems.

[Means for Solving the Problems] A heat dissipation fin with a piezoelectric fan according to the present invention is characterized in that a piezoelectric fan is provided on a heat dissipation plate and air is blown to the heat dissipation plate.

[Function] In this way, by providing the piezoelectric fan on the heat sink, which is the heat dissipation part of the heat dissipation fin, and blowing air, forced cooling can be performed and the heat dissipation effect can be greatly enhanced. Furthermore, by providing the piezoelectric fan on the heat sink, the heat from the heat sink can be directly transferred to the piezoelectric fan, and the air flow can be automatically adjusted using the temperature characteristics of the piezoelectric element.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a perspective view of an embodiment of a heat radiation fin with a piezoelectric fan according to the present invention.

In the figure, an opening 2 is formed in each of the plurality of heat sinks l of the heat sink, and a piezoelectric fan 3 is installed in the opening 2 facing upward. The pressure fan 3 has an elastic plate 4
and a piezoelectric element 5, and one end of the piezoelectric element 5 is connected to a heat sink 1.
It is fixed directly or via an elastic material with good heat conduction. Therefore, by applying an alternating current voltage of an appropriate frequency to the piezoelectric element 5, the piezoelectric fan 3 can be driven to blow air onto the heat sink 1 from below, thereby increasing the heat radiation effect.

Moreover, as shown in FIG. 2, various transverse effect type piezoelectric elements can be used as the piezoelectric element 5. As shown in FIG.

21'S 2 'Ill (A) to (D) are schematic cross-sectional views of piezoelectric elements having unimorph, heimorph, laminated unimorph, and laminated bimorph structures.

In FIG. 2(A), a piezoelectric ceramic 52 and a t-pole 53 are formed on one side of the metal plate 51, and in FIG. 2(B), they are formed on both sides of the metal plate 51.

In the same figure (C), a laminated part 54 of piezoelectric ceramics and electrodes is formed on one side of the metal plate 51, and in the same figure (B)
Here, a laminated portion 54 is formed on the H side of the metal plate 51. By laminating piezoelectric ceramics and electrodes in this manner, the distance between internal electrodes can be shortened, and the piezoelectric element can be driven at low voltage. Note that the metal plate 51 is extended to form the elastic plate 4.
may be configured.

Furthermore, in this embodiment, piezoelectric ceramics are used in which the temperature coefficient of the piezoelectric constant d31 is positive and is greater than or equal to 1o00pPl/''C, and the blowing force of the piezoelectric fan 3 is automatically divided into 31 nodes depending on the temperature of the heat sink 1. Configured.

The relationship between the piezoelectric constant d31 and the displacement amount and driving force of the piezoelectric element 5 will be explained below.

FIG. 3 is a perspective view of the piezoelectric element for explaining the relationship between the piezoelectric constant d31, the amount of displacement, and the driving force in the piezoelectric element having a bimorph structure.

In the figure, when a DC voltage V is applied between the metal plate 51 and the pole 53 of the bimorph piezoelectric element in a free state, the displacement X and the driving force F of the piezoelectric element are expressed by the following equation.

x = 3 (L/T)2 @dH* VF = (T
W/L) ・(d:u/SthE) *V However, L, 'it, and T represent the height, width, and thickness of the piezoelectric element, respectively, and 5llE represents the total elastic compliance when the electric field is zero. .

As is clear from the above equations, when the piezoelectric constant d31 of the piezoelectric ceramic increases as the temperature increases,
Both the displacement end X and the driving force F of the bimorph piezoelectric element 5 increase. Conversely, if the temperature decreases and the value of the piezoelectric constant dll of the compact ceramic becomes smaller, the displacement amount X and the driving force F decrease.

As already mentioned, one end of the bimorph piezoelectric element 5 is fixed to the heat sink 1 either directly or via an elastic material with good heat conduction, so that the heat of the heat sink 1 is immediately transferred to the bimorph piezoelectric element 5. Ru. Therefore, when the piezoelectric element is driven, the temperature of the element itself rises, but if the temperature of the heat sink 1 rises above that temperature, the piezoelectric constant d31 of the piezoelectric ceramic of the bimorph piezoelectric element 5 increases, and the piezoelectric constant d31 of the piezoelectric ceramic of the bimorph piezoelectric element 5 increases. The displacement M x and the driving force F increase and the piezoelectric fan 3
The sending force of will increase. As a result, the heat dissipation effect of the heat sink l increases, and the cooling capacity increases. Further, if the temperature of the heat sink 1 decreases, the displacement X and the driving force F of the bimorph pressure 'if element' f-5 decrease, and the air force sent by the piezoelectric fan 3 decreases.

In this way, the temperature coefficient of the piezoelectric constant d31 is positive and 1
By providing the bimorph piezoelectric element 5 using piezoelectric ceramics with a temperature of 000PP/°C or higher on the heat sink 1, the air force of the piezoelectric fan 3 can be automatically adjusted according to the temperature of the heat sink 1 without using any special temperature detection means. Can be adjusted. Of course, similar effects can be obtained using not only the bimorph structure but also various piezoelectric elements shown in FIG.

The reason why the temperature coefficient of the piezoelectric constant d31 of the piezoelectric ceramic is set to be equal to or higher than toopp■/° C. is to effectively change the blowing force of the piezoelectric fan in accordance with the temperature change of the heat sink 1.

Furthermore, although the position d of the piezoelectric fan 3 is not limited to this embodiment, it is clear that it is desirable to place it below the heat sink I in terms of the heat radiation effect. Furthermore, it is desirable to drive the piezoelectric fans 3 provided on the plurality of heat sinks 1 by alternately swinging them in opposite directions, etc., in order to prevent unnecessary vibrations.

[Effects of the Invention] As explained in detail above, the piezoelectric fan 71 according to the present invention
=t M radiating fin ilD [Since the fan is provided on the radiating plate, which is the heat radiating part of the radiating fin, to blow air, the heat radiating effect can be greatly enhanced by forced cooling. Therefore, the surface of the radiation fins can be reduced in size, and it is possible to promote downsizing of equipment that requires heat radiation means.

In addition, by installing a piezoelectric fan on the heat sink, the heat from the heat sink can be directly transferred to the piezoelectric fan, and the temperature characteristics of the piezoelectric constant of the piezoelectric element can be used to automatically control the air flow. can.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of a heat dissipation fin with a piezoelectric fan according to the present invention. 3 is a perspective view of the piezoelectric element for explaining the relationship between the piezoelectric constant d31, the amount of displacement, and the driving force in the piezoelectric element having a bimorph structure. 1... Heat dissipation plate 3... Piezoelectric fan 4... Elastic plate 5... Piezoelectric element agent Patent attorney Minoru Yamashita Figure 2 (A) (B) (C) (D) Figure 3 Mouth one one two eleven

Claims (2)

[Claims] (1) A heat dissipation fin with a piezoelectric fan, characterized in that a piezoelectric fan is provided on a heat dissipation plate, and air is blown to the heat dissipation plate. (2) The piezoelectric element of the piezoelectric fan has a piezoelectric constant d_3_
Claim 1, characterized in that a piezoelectric ceramic having a positive temperature coefficient of 1000 ppm/°C or more is used.
Heat dissipation fin with piezoelectric fan as described in section.