JP2023018985A - Cooling device - Google Patents

Abstract

To provide a cooling device with high cooling efficiency.SOLUTION: A cooling device comprises: a metal heat sink; a dielectric layer which covers at least a portion of a surface of the metal heat sink; an electrode which is formed on a portion of a surface of the dielectric layer; and a power supply device. The electrode is disposed at such a position that a distance to the metal heat sink may be shorter on one end side in the in-plane direction of the heat sink. By applying an AC voltage between the metal heat sink and the electrode, the heat sink functions as a plasma actuator so as to generate an induced flow with a controlled flow direction, thereby improving cooling efficiency.SELECTED DRAWING: Figure 5

Description

The present invention relates to a cooling device, and more particularly, to a cooling device having a heat sink with plasma actuators formed thereon.

A power converter such as a converter includes electronic components that generate heat, such as semiconductors, capacitors, and coils, and heat sinks are attached to cool these electronic components.

In recent years, there has been a demand for smaller power converters and higher power. As the heat output of the elements increases, so too must the performance of heat sinks to cool them.

The cooling performance of a heat sink generally depends on its volume (heat capacity), material (thermal conductivity), and surface area (heat transfer area) depending on its shape. If the size is increased, the size of the power conversion device as a whole is increased, so it is difficult to reduce the size of the power conversion device.

Patent Document 1 discloses that the fins of the heat sink are formed in a desired shape with respect to the flow direction of the cooling air, so that the flow of the cooling air can be disturbed over the entire region from the base to the tip of the fins, thereby dissipating heat from the heat sink. It is disclosed that the performance is improved.

JP 2009-290004 A

However, since the heat sink of Patent Document 1 disturbs the flow of cooling air with fins, the pressure loss is large. is required, it is difficult to further reduce the size of the power converter.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a cooling device with high cooling efficiency.

As a result of earnest studies to achieve the above object, the inventors found that the above object can be achieved by forming a plasma actuator on a heat sink, and completed the present invention.

That is, the cooling device of the present invention includes a metal heat sink, a dielectric layer covering at least a portion of the surface of the metal heat sink, an electrode formed on a portion of the surface of the dielectric layer, a power supply device, Prepare.
The electrode is arranged at a position where the distance from the metal heat sink is shorter at one end in the in-plane direction, and an AC voltage is applied between the metal sheet sink and the electrode.

According to the present invention, since the plasma actuator is formed on the heat sink, it is possible to generate an airflow on the surface of the heat sink, thereby promoting heat dissipation and providing a cooling device with high cooling efficiency.

It is a figure explaining the operating principle of a plasma actuator. It is a perspective view showing an example of a heat sink. FIG. 3 is a schematic cross-sectional view of a portion of the heat sink of FIG. 2 where electrodes are present, taken along the ZX plane; FIG. 10 is a diagram for explaining the flow of induced currents generated on the ZY plane when plasma actuators are formed on flat fins; FIG. 2 is a schematic cross-sectional view showing an example of the ZX plane of the heat sink of the present invention cut at a location where electrodes are present; FIG. 4 is a schematic cross-sectional view showing another example of the ZX plane of the heat sink of the present invention cut at the location where the electrodes are present; FIG. 4 is a schematic cross-sectional view showing still another example of the ZX plane of the heat sink of the present invention cut at a location where electrodes are present; FIG. 5 is a schematic cross-sectional view showing yet another example of the ZX plane of the heat sink of the present invention cut at the location where the electrodes are present; It is a figure explaining the induced flow which flows on the heat sink of this invention. It is a figure explaining the state which joins a fin to a base plate. FIG. 2 is a schematic diagram illustrating an example of a heat sink with corrugated fins;

<Cooling device>
The cooling device of the present invention will be explained in detail.
This cooling device includes a heat sink in which a plasma actuator is formed, and uses an electrohydrodynamic effect caused by atmospheric pressure barrier discharge to induce a gas flow, which is used for cooling. This is the equipment used.

Specifically, low-temperature plasma is generated by atmospheric pressure barrier discharge. As shown in FIG. 1, this low-temperature plasma is a state in which molecules forming the atmosphere gas are ionized into positive ions and electrons. Then, for example, the positive ions are accelerated by the electric field when the voltage rises, collide with the air molecules, and the momentum of the positive ions is transported to the air molecules. It is what I did.

The cooling device includes a metal heat sink, a dielectric layer covering at least a portion of the surface of the metal heat sink, an electrode formed on a portion of the surface of the dielectric layer, and a power supply device. A metal heat sink body is used as a counter electrode for the electrode formed on the surface of the dielectric layer, and an AC voltage is applied between the electrode and the metal heat sink to generate an induced flow.

That is, by applying an AC voltage between the metal heat sink and the electrodes sandwiching the dielectric layer, they function as a plasma actuator.

The cooling device of the present invention will be described by taking the heat sink shown in FIG. 2 as an example.
This heat sink has a plurality of flat plate-shaped fins, and these fins are arranged in parallel and erected on a base plate.

In this example, as shown in FIG. 3, a dielectric layer and an electrode are formed on the surface of each fin to generate an induced flow in the in-plane direction (ZY plane) of the fin.

At this time, even if the plasma actuator is formed on the fins of the heat sink, since the fins are generally flat plates, the distance between the electrodes and the fins is constant as shown in FIG. , plasma is generated on both sides of the electrode in the same way, and as indicated by the arrows in FIG.

In the present invention, the electrodes are arranged so that the distance between the electrodes and the fins is short on one end side of the electrodes and long on the other end side in the in-plane direction. Since it can be controlled to flow in a certain direction, the cooling efficiency can be improved.
Although the electrodes are shown in FIG. 3 to explain the positions of the electrodes, the electrodes need not be exposed on the end faces.

The direction in which the induced current flows, that is, the position where the electric field is concentrated can be controlled by the shape of the fins. For example, by providing a protrusion in a part of the fin, forming a through hole or a notch, and adjusting the position where the electrode and the fin are close to each other, a barrier discharge is generated in a desired direction, resulting in an induced current. can control the direction of

As a method of providing a convex portion on a part of the fin, for example, as shown in FIG. Another method is to bend a portion of the fin to protrude toward the dielectric layer.

When the electrode is provided at a position shifted from the convex portion on the dielectric layer, the thickness of the dielectric layer is reduced by that amount due to the convex portion of the fin. The one end side and the one end side of the convex portion are close, and the other end side of the electrode and the other end side of the convex portion are distant. Therefore, since the electric field is concentrated on one end side of the electrode and plasma is generated, the direction in which the induced current flows can be controlled.

When through holes or notches are formed in the fins, as shown in FIG. 7, the through holes may be formed in the flat plate fins. Alternatively, as shown in FIG. You may bend to the electrode side. By bending the edge toward the electrode, the electric field can be concentrated to generate a strong plasma, and the flow of the induced current can be controlled according to the required cooling characteristics.

In FIGS. 7 and 8, the fins are divided into left and right fins, but the fins are connected in the front or back direction of the paper and have the same potential.

Also, if the electrode and the fin overlap each other, or if the electrode protrudes from the through hole of the fin and overlaps the fin, the part where the distance between the electrode and the fin is the shortest has a width, and the fin has a width. An electric field is also generated in the direction orthogonal to the in-plane direction of the .

Since the electric field generated in the direction orthogonal to the in-plane direction of the fins does not contribute to the generation of the induced flow, the generation efficiency of the induced flow decreases and the power consumption increases.

Therefore, the position of the electrode provided on the dielectric layer is preferably a position that does not overlap the convex shape of the fin or a position that corresponds to the range of the through hole or notch of the fin on the Y coordinate. Thereby, power consumption can be reduced.

As described above, a plurality of plasma actuators formed by electrodes and convex shapes or through holes provided in the fin can be provided for one fin.

On the surface of the fins, due to the friction between the fins and the gas (fluid), the flow speed of the airflow becomes slower as it goes downstream. can be improved.

The electrodes provided on the dielectric layer and the dielectric layer are preferably flush with each other, as shown in FIGS. preferable. Since the front and back surfaces of the fins are flat without irregularities, pressure loss can be suppressed without disturbing the flow of the induced flow generated upstream by the irregularities.

The cooling device of the present invention further includes a mainstream generator such as a fan, and can send airflow in the in-plane direction (ZY plane) of the fins.

As shown in FIG. 9, the airflow from the main stream generator flows in the same direction as the flow direction of the induced flow, that is, in the direction from the other end side to the one end side (Y-axis direction) of the electrodes, thereby generating an induced flow. Together, the cooling efficiency can be further improved.

On the surface of the fins, not only does the flow velocity of the air flow become slower as it goes downstream as described above, but also a boundary layer in which the flow velocity of the gas is slow is formed on the surface side of the fins. However, in the vicinity of the surface of the fins, the flow of the air current slows down and the heat transfer from the fins to the gas decreases, so it is difficult to dissipate the heat efficiently.

However, in the present invention, since an induced flow is generated on the surface of the fins to suppress the generation of the boundary layer, it is possible to prevent the deterioration of the cooling efficiency due to the boundary layer.
In FIG. 9, the cutouts of the fins hidden by the dielectric layer are indicated by dotted lines in order to explain the positional relationship between the cutouts of the fins and the electrodes.

<Production of cooling device>
The cooling device can be manufactured by forming a dielectric layer and electrodes on fins of a desired shape, bonding this to a base plate, and connecting the fins and electrodes to a power source.

A fin having a convex shape can be produced by joining a metal piece to a flat plate, pressing, or the like. Further, fins having through holes and notches can be produced by punching a flat plate into a desired shape.

A dielectric film and an electrode are laminated on the fin and pressed, and the fin is joined to the base plate as shown in FIG.

The fins and the base plate may be electrically connected by soldering, brazing, or the like, or may be insulated by an insulator such as grease or adhesive.

If the fins and baseplate are electrically bonded, the electrodes and baseplate can be connected to a power supply.

As a material for the metal heat sink, a material having electrical conductivity and excellent heat conductivity can be used, and for example, metal materials such as copper, aluminum, and iron can be used.

Moreover, as the material of the electrodes, the same material as the metal material can be used, and the material may be the same as or different from the metal heat sink.
The thickness of the electrode is preferably 10 μm to 500 μm, and a copper tape, tungsten wire, or the like can be preferably used.

In addition, as a dielectric that forms the dielectric layer, a material having insulating properties can be used. In addition to resins such as , metal oxides such as alumina and ceramics can be used.

The thickness of the dielectric layer is preferably 5 μm to 500 μm, depending on the type of dielectric. The thin dielectric layer facilitates air flow over the surface of the metal heat sink without impeding air flow.

The power supply is an AC power supply that applies an AC voltage between the metal heat sink and the electrodes. The AC voltage to be applied is preferably 1 kVp to 10 kVp, and the AC frequency is preferably 5 kHz to 20 kHz.

(Modification)
The cooling device of the present invention has been described as an example of a heat sink in which a plurality of flat plate-like fins are arranged in a comb-like shape on a base plate. It is not particularly limited.

The metal heat sink may be a single flat base plate without fins, or may have base plates on both the upper and lower sides of the fins.

Further, the fins may be arranged obliquely with respect to the base plate, and the cross section (ZX plane) when viewed from the Y-axis direction may be curved or curved. Furthermore, as shown in FIG. 11, the convex portions of the corrugated fins may be bonded to the base plate to form flow paths between them. The XY plane of this heat sink viewed from the corrugated fin side is the same as in FIG. 9 except that the broken lines are not shown.

Such curved fins can be formed by pressing after forming the dielectric layer and the electrode, or by laminating the dielectric layer and the electrode and pressing them simultaneously.

Also, the intervals between the fins joined to the base plate may be constant or different, and can be changed according to the number of objects to be cooled, the amount of heat generated, and the mounting positions thereof.

In addition to generating an induced current on one side of the fin, it is possible to generate an induced current on both sides of the fin by forming dielectric layers and electrodes on both sides of the fin with the fin as the center.

REFERENCE SIGNS LIST 1 metal heat sink 2 base plate 3 fins 31 projections 32 through holes/notches 4 dielectric layer 5 electrodes 6 mainstream generator 61 mainstream A molecules of gas in the atmosphere P plasma I induced flow C channel

Claims (11)

a metal heatsink and
a dielectric layer covering at least a portion of the metal heat sink surface;
an electrode formed on a portion of the surface of the dielectric layer;
A cooling device comprising a power supply,
The electrode is arranged at a position where the distance from the metal heat sink is shorter on one end side in the in-plane direction,
A cooling device, wherein an alternating voltage is applied between the metal sheet sink and the electrode to generate an induced flow. The metal heat sink has a convex shape on the dielectric layer side,
2. The cooling device according to claim 1, wherein the convex shape is formed by increasing the thickness of the metal heat sink. The metal heat sink has a convex shape on the dielectric layer side,
2. The cooling device according to claim 1, wherein the convex shape is formed by bending a metal heat sink. 2. Cooling device according to claim 1, characterized in that the metal heat sink has through holes and/or notches. 5. The cooling device according to claim 4, wherein the metal heat sink has edges of the through holes and/or cutouts that are bent toward the electrodes. The cooling device according to any one of claims 2 to 5, wherein the electrode is provided at a position that does not overlap with the convex shape or at a position that overlaps with the through hole and/or the notch. . In addition, it has a mainstream generator that generates airflow,
7. The main stream generator according to claim 1, wherein the main flow generator generates an airflow in the in-plane direction of the surface of the metal heat sink on which the dielectric layer and the electrodes are formed. Cooling system. 8. The cooling device according to claim 7, wherein the one end side of the electrode is located downstream of the airflow, and the induced current flows in the same direction as the airflow. The metal heat sink is formed with a base plate and fins,
The cooling device according to any one of claims 1 to 8, wherein the dielectric layer and the electrodes are provided on the fins. 10. The cooling device according to claim 9, wherein a plurality of flat plate-like fins are erected in parallel on the base plate. 10. The cooling device according to claim 9, wherein the fins are wave-shaped, and the wave-shaped projections are joined to the base plate to form flow paths with the base plate.

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