JP4617463B2 - CPU cooling device using plasma synthetic jet - Google Patents

Description

  The present invention relates to a cooling device, and more particularly to a cooling device for a CPU of a computer.

The operating speed of a computer is mainly determined by the clock frequency of the CPU, but recently, there is a tendency to increase the processing speed of the computer, and therefore the clock frequency of the CPU reaches several gigahertz. As the CPU clock frequency increases, the amount of heat generated by the CPU increases. Therefore, it is necessary to increase the cooling capacity of the CPU.
As shown in FIG. 4, the CPU cooling device is provided with a heat sink made of a material having a high thermal conductivity so that heat is transmitted to the outer periphery of the CPU, and in particular, a fin portion is formed outside the heat sink to transfer heat. It is common to increase the heat transfer area, blow air from the side and cool by heat exchange.

In order to increase the cooling capacity of the cooling device, it is necessary to increase the heat transfer area by increasing the heat transfer area and by forced convection of a fan or the like. In order to increase the heat transfer area, it is possible to increase the area per fin and increase the number.
However, since the size of the CPU is small and the space for mounting the CPU in a computer having a compact configuration is limited, there is a restriction that the heat sink and fins cannot be so large. In addition, when the number of sheets is increased, the gap between the fins decreases, the air resistance increases, and the flow becomes weaker with the same blowing force. After all, there was a limit to improving the cooling efficiency as a whole.

As a conventional technique for a cooling device such as a CPU, there is the following.
JP 2003-163317 A JP 2001-352020 A

Patent Document 1 discloses providing a rectifier for guiding air supplied from a blower to a heat sink in which fins are formed in order to cool a heat generating element such as a CPU.
In Patent Document 2, in order to increase the heat dissipation efficiency of a heat sink for cooling a heat generating element such as a CPU, an aluminum material plate is clad on a copper material plate, and aluminum is formed only at the tip by cutting and raising from above. It discloses that a skive fin made of a copper material having a portion made of a material is formed.

The rectifying body in Patent Document 1 also prevents air stagnation in the heat sink to some extent, but it does not sufficiently increase the cooling efficiency of the entire heat sink. Also in Patent Document 2, the cooling efficiency is improved by the fin material. It means that it can be raised to some extent, and still not enough.
On the other hand, a plasma synthetic jet actuator (PSJA) has recently attracted attention for flow control along a wing body, a flat plate, and the like, and is disclosed in the following documents.

Proceedings of the Japan Opportunity Society (B), Vol. 69, No. 686, pp 2237-2242, October 2003, Vol. 70, No. 700, pp 50-56. Non-Patent Document 1 discloses that a plasma synthetic jet actuator (PSJA) suppresses separation around an aircraft wing and reduces drag while maintaining high lift. However, no attempt has been made to apply this technique to a cooling device such as a CPU.

  In a cooling device for a part that generates a large amount of heat with a small size like a CPU of a conventional computer, the cooling device can be efficiently cooled without increasing the size of the cooling device or increasing the power of the fan so much. The reality is that it is difficult, and even if the cooling area is increased by narrowing the gap between the fins, the air flow velocity at the fin surface of the heat sink will decrease, and as a result, the cooling efficiency will not increase that much. It was. Therefore, a cooling device with high cooling efficiency is desired even with a heat sink in which fins having relatively small dimensions are formed.

The present invention solves such a problem in the prior art. A CPU is attached to a base, and a plurality of fins made of a conductive material formed integrally with the base are integrally formed. A cooling device having a heat sink, wherein an electrode is attached along an edge of the tip of each of the plurality of fins with an insulator interposed therebetween, and a rear edge side edge of the electrode with respect to a surface of the fin 50-120 be one having a step of microns, which was set to give rise to air flow along the surface of the fin by the plasma synthetic jet action by applying an AC voltage between said fins and said electrode Te It is.

The AC voltage is preferably at a frequency of 0.5 to 1.20 kHz, and the voltage is preferably 700 to 1000 V, and the electrode is made of aluminum and circulates along the edge of each tip of the plurality of fins. attached to, the insulator is preferably made of polyimide tape.
The rear edge of the electrode preferably has a step of 50 to 120 microns with respect to the fin surface.

  In the present invention, an anode electrode is provided along the edge of the tip of the fin in the heat sink of the cooling device, and PSJA that applies an AC voltage to the cathode (fin) is applied to each fin. It is possible to increase the cooling efficiency of the entire heat sink by reducing the interval between the fins while maintaining the heat radiation efficiency of each, and increasing the number of fins, that is, the heat radiation area.

(Description of basic technology)
The present invention uses a technique of a plasma synthetic jet actuator (PSJA) as a fluid control device that has been attracting attention in recent years as an effective fluid control device in order to increase the cooling efficiency of a heat sink in which fins are formed. First, PSJA will be described.

PSJA is an electrical fluid device control that utilizes an electrohydrodynamic effect in the air in the vicinity of an electrode by applying an alternating voltage between electrodes sandwiching an insulator, and as a result a jet is induced. is there.
The effect of PSJA occurs, for example, in an electrode structure having a shape as shown in a sectional view in FIG. The central needle-like electrode 2 provided on the wall surface of the wing body 1 or the like is a nichrome-plated wire, and a voltage of 750 V and a frequency of 0 is provided between the washer-like electrode 4 surrounding the tip with an insulator 3 interposed therebetween. When an AC voltage of .5 to 1.20 kHz is applied, several discharge paths with a blue-violet emission are generated radially from the needle-like electrode, and a three-dimensional vortex is induced with it. The vortex is visualized by incense smoke, etc., but the flow velocity is on the order of several cm / s.

As an electrode structure, it has been confirmed that two thin strips 6 and 7 separated by a solid insulator 5 are installed on the wall surface of the wing body 1 or the like. The strip had a specific direction along the wall when an AC voltage of 1/0 kV and a frequency of 0.5 to 1.20 kHz was applied to an electrode using aluminum tape, copper tape, etc., and Kapton tape as an insulator. A jet is induced.
In this way, the action by PSJA has been actually confirmed, and it is considered that the dielectric force proportional to the energy density gradient is an important factor for the mechanism of such action. However, it has not been clarified yet.

  Although the effect of PSJA has already been confirmed, and it has been studied to install on the wing surface of an aircraft and suppress separation, it is difficult to install on the fin of the cooling device, No specific attempt has been made to apply to the cooling of a computer CPU or the like.

  In the present invention, PSJA is applied to a cooling device such as a CPU using a heat sink in which fins are formed to increase the cooling efficiency. The heat dissipation heat sink of the CPU to which PSJA is applied has a configuration as shown in FIG. 2A. The CPU 11 is attached to the base 13 of the heat sink 12 and a plurality of thin fins 14 are formed integrally with the base 13. The fin 14 serves as a cathode electrode in PSJA. An anode electrode 16 is provided along the edge of the tip of each fin 14 via an insulator 15.

  FIG. 2B is a perspective view of the tip side of one fin. The fin 14 is made of a material having good thermal conductivity, such as aluminum, and is integrally formed with the heat sink. The insulator 15 attached with an appropriate adhesive around the edge of the tip of the fin is made of mercapto. Further, an anode electrode 16 formed of a material such as aluminum having a shape that circulates around the insulator 15 is attached with an appropriate adhesive. An adhesive having insulating properties is preferable.

  The anode electrode 16 shown in FIGS. 2 (a) and 2 (b) circulates around the edge of the tip of the fin 14, and the anode electrode 16 has a streamlined tip as shown in cross section in FIG. 2 (c). In this case, it is preferable that the disturbance of the flow when the air flow from the front is supplied is reduced, and that the height of the edge on the rear end side is 50 to 120 microns with respect to the surface of the fin 14. This step is important for obtaining the effect of PSJA when an AC voltage is applied between the anode electrode 16 and the fin 14.

  FIG. 3 shows an example of a drive circuit for driving PSJA. This drive circuit is configured, for example, by connecting a switching device 22 such as an FET to the input terminal side of a transformer 21 that boosts the voltage on the input side of 12 V to 1 kV, and has a square wave with an input voltage of about 1 kHz and a duty ratio of 50%. As a result, when an alternating current of about 1 kHz and 1 kV is obtained on the output side of the transformer 21 and the output 24 of the alternating current is applied to the cathode (fin 14) and the output 23 to the anode electrode 16, the PSJA acts as a part of the electrode. From there, an air flow along the surface of the fin occurs.

In order to obtain the effect of PSJA, it is necessary to apply a considerably high alternating voltage. Therefore, when cooling the CPU, it is preferable to carefully shield the periphery of the CPU in order to prevent the influence of electromagnetic noise.
In the conventional heat sink, if the fin spacing is smaller than about 5 mm, the heat dissipation efficiency is reduced even by forced convection, so there is a restriction that the fin spacing is about 5 mm. For example, even if the distance between the fins is about 2 mm, the heat radiation efficiency does not decrease so much, and as a result, the heat radiation area can be greatly increased, and the cooling capacity of the heat sink is greatly increased.

It is a figure which shows the structure of PSJA. (A) It is sectional drawing which shows the cooling device by the Example of this invention. (B) A perspective view of one fin. (C) It is sectional drawing to which the front end side part of one fin was expanded. It is a figure which shows the example of the drive circuit of PSJA. It is sectional drawing of the cooling device which has the heat sink in which the conventional fin was formed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wing body 2 Electrode 3 Insulator 4 Washer-like electrode 5 Solid insulator 6, 7 Strip 11 CPU
12 heat sink 13 base 14 fin 15 insulator 16 anode electrode 21 transformer 22 switching device 23 output 24 output

Claims (3)

A cooling device having a heat sink in which a CPU is attached to a base and a plurality of fins made of a conductive material formed integrally with the base are integrally formed , each of the tips of the plurality of fins An electrode is attached along an edge of the electrode with an insulator interposed therebetween, and a rear edge of the electrode has a step of 50 to 120 microns with respect to the surface of the fin, and the electrode and the electrode A cooling device for a CPU, wherein an AC voltage is applied between the fins to generate an air flow along the surface of the fins by a plasma synthetic jet action. 2. The CPU cooling device according to claim 1, wherein the AC voltage has a frequency of 0.5 to 1.20 kHz and a voltage of 700 to 1000V. The electrode according to claim 1 or 2, wherein the electrode is made of aluminum and is attached so as to go around the edge of each of the plurality of fins, and the insulator is made of polyimide tape. The CPU cooling device according to any one of the above.

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