Cooling device

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

[Technical Field]

[0001] The present invention relates to a cooling device, and more particularly to a cooling device including a heat sink on which a plasma actuator is formed. [Background technology]

[0002] 2. Description of the Related Art A power conversion device such as a converter includes electronic components that generate heat, such as semiconductors, capacitors, and coils, and a heat sink is attached to cool these electronic components.

[0003] In recent years, there has been a demand for smaller and more powerful power conversion devices. When electronic components are densely arranged and made smaller, the density of heat-generating elements within the power conversion device increases. In addition, the amount of heat generated by the heat-generating elements increases as the power increases, so it is necessary to improve the performance of the heat sinks that cool these elements.

[0004] 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. Therefore, if the heat sink itself is enlarged to improve its cooling performance, the entire power conversion device will become larger, making it difficult to miniaturize the power conversion device.

[0005] Patent document 1 discloses that by shaping the fins of a heat sink in a desired shape relative to the direction of flow of the cooling air, the flow of the cooling air can be disrupted over the entire area from the base to the tip of the fin, thereby improving the heat dissipation performance of the heat sink. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-290004 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the heat sink in Patent Document 1 has fins that disrupt the flow of cooling air, resulting in large pressure losses. In order to fully utilize the cooling performance of the heat sink, the flow of cooling air needs to be strengthened, requiring a large fan, making it difficult to further miniaturize the power conversion device.

[0008] The present invention has been made in view of the problems inherent in the prior art, and an object of the present invention is to provide a cooling device with high cooling efficiency. [Means for solving the problem]

[0009] As a result of extensive research into achieving the above object, the inventors discovered that the above object could be achieved by forming a plasma actuator on a heat sink, and thus completed the present invention.

[0010] That is, the cooling device of the present invention comprises 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; The metal heat sink and a power supply connected to the electrode are provided to generate an induced flow. The metal heat sink has an electric field concentration portion that concentrates an electric field at one end of the electrode on the side in the direction in which the induced flow flows, The power supply device is made of the metal Hi The device is characterized in that an AC voltage is applied between the heat sink and the electrode to generate an induced flow. [Effects of the Invention]

[0011] According to the present invention, since a plasma actuator is formed on the heat sink, an airflow can be generated on the surface of the heat sink, which promotes heat dissipation and provides a cooling device with high cooling efficiency. [Brief explanation of the drawings]

[0012] [Figure 1] 1A and 1B are diagrams illustrating the operating principle of a plasma actuator. [Figure 2] FIG. 1 is a perspective view illustrating an example of a heat sink. [Figure 3] 3 is a schematic cross-sectional view of the heat sink of FIG. 2, taken along the ZX plane at a location where an electrode is present. [Figure 4] FIG. 10 is a diagram illustrating the flow of an induced flow that occurs on the ZY plane when a plasma actuator is formed on a flat fin. [Figure 5] 1 is a schematic cross-sectional view showing an example of a ZX plane in which the heat sink of the present invention is cut at a location where an electrode is present. [Figure 6] 10 is a schematic cross-sectional view showing another example of the heat sink of the present invention cut along the ZX plane at the location where the electrodes are present. FIG. [Figure 7] FIG. 10 is a schematic cross-sectional view showing yet another example of the heat sink of the present invention cut along the ZX plane at the location where the electrodes are present. [Figure 8] FIG. 10 is a schematic cross-sectional view showing yet another example of the heat sink of the present invention cut along the ZX plane at the location where the electrodes are present. [Figure 9] FIG. 1 is a diagram illustrating an induced flow that flows on a heat sink of the present invention. [Figure 10] 10A and 10B are diagrams illustrating a state in which fins are joined to a base plate. [Figure 11] FIG. 1 is a schematic diagram illustrating an example of a heat sink having corrugated fins. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Cooling device> The cooling device of the present invention will now be described in detail. This cooling device is equipped with a heat sink on which a plasma actuator is formed, and uses the electrohydrodynamic action generated by atmospheric pressure barrier discharge to induce a gas flow, which is then used for cooling.

[0014] Specifically, low-temperature plasma is generated by atmospheric pressure barrier discharge. As shown in Figure 1, this low-temperature plasma is in a state where the molecules that make up the atmospheric gas are ionized into positive ions and electrons. For example, positive ions are accelerated by the electric field when the voltage is increased, and collide with air molecules, causing the momentum of the positive ions to be transferred to the air molecules, resulting in an air flow (hereinafter sometimes referred to as an "induced flow") that is utilized.

[0015] The cooling device comprises 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 unit, with the metal heat sink body serving as the counter electrode to the electrode formed on the surface of the dielectric layer, and an AC voltage being applied between the electrode and the metal heat sink to generate an induced flow.

[0016] That is, by applying an AC voltage between the metal heat sink and the electrode sandwiching the dielectric layer, they function as a plasma actuator.

[0017] The cooling device of the present invention will be described using the heat sink shown in FIG. 2 as an example. This heat sink has a plurality of flat fins that are arranged in parallel and stand on a base plate.

[0018] In this example, as shown in FIG. 3, a dielectric layer and an electrode are formed on the surface of each fin, and an induced flow is generated in the in-plane direction (ZY plane) of the fin.

[0019] In this case, even if a plasma actuator is formed on the fin of the heat sink, the fin is generally flat, so as shown in Figure 4, the distance between the electrode and the fin is constant and no bias occurs in the electric field, so plasma is generated equally on both sides of the electrode, and as shown by the arrows in Figure 4, the induced flows flow in both directions and cancel each other out, making it difficult to improve cooling efficiency.

[0020] In the present invention, the electrodes are arranged so that the distance between the electrodes and the fins in the in-plane direction is shorter at one end of the electrode and longer at the other end. This allows the electric field to be concentrated at one end of the electrode, and the induced flow to be controlled to flow in a fixed direction, thereby improving cooling efficiency. Although the electrodes are shown in FIG. 3 to explain the electrode positions, the electrodes do not need to be exposed on the end surfaces.

[0021] The direction of the induced flow, i.e., the position where the electric field is concentrated, can be controlled by the shape of the fin. For example, by providing a protrusion on part of the fin, or by 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 the desired direction, and the direction of the induced flow can be controlled.

[0022] Methods for providing a protrusion on a part of the fin include, for example, increasing the thickness of a part of the fin so that it protrudes toward the dielectric layer, as shown in Figure 5, or bending a part of the fin so that it protrudes toward the dielectric layer, as shown in Figure 6.

[0023] If an electrode is provided at a position offset from the convex portion on the dielectric layer, the thickness of the dielectric layer is reduced by the convex portion of the fin, so that the distance between the electrode and the fin is closer to one end of the convex portion and farther to the other end of the electrode. As a result, the electric field is concentrated at one end of the electrode, generating plasma, and the direction of the induced flow can be controlled.

[0024] Furthermore, when forming through-holes or notches in the fins, the through-holes may be left as they are in the flat fins as shown in Figure 7, or the edges of the through-holes may be bent toward the electrode as shown in Figure 8. Bending the edges toward the electrode concentrates the electric field, generating a strong plasma and allowing the flow of the induced flow to be controlled to suit the required cooling characteristics.

[0025] 7 and 8, the fins are shown divided into left and right halves, but they are connected in the front or back direction of the paper and have the same potential.

[0026] Furthermore, if the electrode and the protrusion of the fin overlap, or if the electrode protrudes from a through-hole in the fin and overlaps with the fin, the point where the distance between the electrode and the fin is shortest will have width, and an electric field will also be generated in a direction perpendicular to the in-plane direction of the fin.

[0027] The electric field generated in a direction perpendicular to the in-plane direction of the fin does not contribute to the generation of an induced flow, so the efficiency of generating an induced flow decreases and power consumption increases.

[0028] Therefore, it is preferable that the electrodes provided on the dielectric layer are positioned in a Y coordinate position that does not overlap with the convex shape of the fins or that corresponds to the range of the through holes or notches of the fins, thereby reducing power consumption.

[0029] As described above, a plurality of plasma actuators formed by electrodes and convex shapes or through holes provided on the fins can be provided for one fin.

[0030] On the surface of the fin, the airflow speed slows down as it moves downstream due to friction between the fin and the gas (fluid). Therefore, by installing multiple plasma actuators on one fin and generating an induced flow again, the cooling efficiency can be improved.

[0031] It is preferable that the electrode provided on the dielectric layer and the dielectric layer are flush, as shown in Figures 5 and 8, and that the surface of the fin opposite the electrode is similarly flat. By having a flat, even surface and back surface of the fin, the induced flow generated upstream is not disturbed by unevenness, thereby suppressing pressure loss.

[0032] The cooling device of the present invention further includes a main airflow generating device such as a fan, and can send airflow in the in-plane direction (ZY plane) of the fins.

[0033] As shown in Figure 9, the airflow from the main flow generator flows in the same direction as the induced flow, i.e., from the other end of the electrode to one end (Y-axis direction), which, in combination with the induced flow, further improves the cooling efficiency.

[0034] On the surface of the fin, not only does the airflow speed slow down as it moves downstream as described above, but a boundary layer with a slow gas flow speed is formed on the surface side of the fin. Therefore, even if the airflow is sent by a mainstream generator, the airflow slows down near the surface of the fin, and heat conduction from the fin to the gas decreases, making it difficult to dissipate heat efficiently.

[0035] However, in the present invention, an induced flow is generated on the surface of the fin, suppressing the generation of a boundary layer, thereby preventing a decrease in cooling efficiency due to the boundary layer. In FIG. 9, the notches in the fins hidden by the dielectric layer are shown by dotted lines in order to explain the positional relationship between the notches in the fins and the electrodes.

[0036] <Preparation of cooling device> The cooling device can be fabricated by forming a dielectric layer and electrodes on fins of a desired shape, bonding the resulting structure to a base plate, and connecting the fins and electrodes to a power source.

[0037] Fins with a convex shape can be produced by joining a metal piece to a flat plate or by press working, etc. Fins with through holes or notches can be produced by punching a flat plate into the desired shape, etc.

[0038] A dielectric film and an electrode are laminated and pressed onto the fin, and the fin is then joined to a base plate as shown in FIG.

[0039] The fins and the base plate may be electrically joined by soldering or brazing, or may be insulated from each other by an insulator such as grease or adhesive.

[0040] If the fins and the base plate are electrically joined, the electrodes and the base plate can be connected to a power supply.

[0041] The material of the metal heat sink can be one that has electrical conductivity and excellent thermal conductivity, such as copper, aluminum, iron, or other metal materials.

[0042] The material of the electrodes can be the same as the metal material described above, and may be the same material as the metal heat sink or a different material. The thickness of the electrode is preferably 10 μm to 500 μm, and copper tape, tungsten wire, or the like can be preferably used.

[0043] Furthermore, a material having insulating properties can be used as the dielectric forming the dielectric layer. From the viewpoint of high insulation and resistance to high voltages of several kV, for example, resins such as fluororesin, polyimide, nylon, and silicon, as well as metal oxides such as alumina and ceramics can be used.

[0044] The thickness of the dielectric layer is preferably 5 μm to 500 μm, although it depends on the type of dielectric, etc. A thin dielectric layer allows air to flow easily over the surface of the metal heat sink without being obstructed.

[0045] The power supply is an AC power supply that applies an AC voltage between the metal heat sink and the electrode. The applied AC voltage is preferably 1 kVp to 10 kVp, and the AC frequency is preferably 5 kHz to 20 kHz.

[0046] (Variation) The cooling device of the present invention has been described using as an example a heat sink having a base plate with multiple flat fins arranged in a comb-like pattern, but the shape of the heat sink is not particularly limited as long as it has a surface that is aligned with the direction in which the induced flow flows.

[0047] The metal heat sink may be a single flat base plate without fins, or may have base plates both above and below the fins.

[0048] The fins may also be arranged at an angle to the base plate, and the cross section (ZX plane) when viewed from the Y-axis direction may be curved or arc-shaped. Furthermore, as shown in Figure 11, the convex portions of the corrugated fins may be joined to the base plate to form a flow path between them. The XY plane of this heat sink viewed from the corrugated fin side is the same as that shown in Figure 9, except that the broken lines are not shown.

[0049] Such curved fins can be formed by pressing after forming the dielectric layer and the electrodes, or by laminating the dielectric layer and the electrodes and simultaneously pressing them together.

[0050] The spacing between the fins joined to the base plate may be constant or may vary depending on the number of objects to be cooled, the amount of heat generated, and their mounting positions.

[0051] Furthermore, by forming a dielectric layer and an electrode on both sides of the fin, rather than just generating an induced flow on one side of the fin, an induced flow can be generated on both sides of the fin. [Explanation of symbols]

[0052] 1 metal heat sink 2 base plates 3 Fins 31 Convex part 32 Through holes / cutouts 4 Dielectric Layer 5 electrodes 6 Mainstream Generator 61 mainstream A Gas molecules in the atmosphere P plasma I. Induced flow C flow path

Claims

1. 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 cooling device that generates an induced flow, comprising the metal heat sink and a power supply connected to the electrode, the metal heat sink has an electric field concentration portion that concentrates an electric field on one end side of the electrode in the direction in which the induced flow flows, The cooling device is characterized in that the power supply applies an AC voltage between the metal heat sink and the electrode to generate an induced flow.

2. 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.

3. 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.

4. 2. The cooling device according to claim 1, wherein the metal heat sink has a through hole and / or a notch.

5. 5. The cooling device according to claim 4, wherein the metal heat sink has an edge of the through hole and / or the notch bent toward the electrode.

6. 4. The cooling device according to claim 2, wherein the electrode is provided at a position that does not overlap with the convex shape.

7. 6. The cooling device according to claim 4, wherein the electrode is provided at a position overlapping with the through hole and / or the notch.

8. Furthermore, it is equipped with a mainstream generator that generates airflow, The cooling device according to any one of claims 1 to 7, wherein the main flow generating device generates an airflow in an in-plane direction of a surface on which the dielectric layer and the electrodes of the metal heat sink are formed.

9. 9. The cooling device according to claim 8, wherein one end of the electrode is located downstream of the airflow, and the induced flow flows in the same direction as the airflow.

10. the metal heat sink is formed of a base plate and fins; 10. The cooling device according to claim 1, wherein the dielectric layer and the electrode are provided on the fin.

11. 11. The cooling device according to claim 10, wherein a plurality of flat fins are provided in parallel and standing on the base plate.

12. 11. The cooling device according to claim 10, wherein the fins are wavy, and protrusions of the wavy shape are joined to the base plate, forming a flow path between the fins and the base plate.

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