Heat sink and inverter equipped with the heat sink

Abstract

The present invention provides a heat sink that can reduce the difference in cooling capacity between the upstream and downstream sides of the heat sink caused by the temperature rise of the refrigerant. [Solution] The heat sink of the present invention is equipped with a triple-period minimal curved surface structure within the refrigerant flow path. Furthermore, the triple-periodic minimal curved surface structure has a constant thickness from the upstream end to the downstream end of the refrigerant flow path, and the period in at least one direction selected from the length, width, and height directions of the refrigerant flow path is shorter on the downstream side than on the upstream side. Therefore, it is possible to provide a heat sink with a small difference in cooling capacity between the upstream and downstream sides that occurs as the temperature of the refrigerant rises.

Description

Technical Field

[0001] The present invention relates to a heat sink and an inverter provided with the heat sink, and more particularly to a heat sink having a triply periodic minimal surface in which a periodic pattern continues three-dimensionally and an inverter provided with the heat sink.

Background Art

[0002] A triply periodic minimal surface (TPMS) structure such as a gyroid in which a periodic pattern is arranged three-dimensionally has a large surface area per unit volume and can improve the heat transfer rate, so it is used for heat sinks and the like.

[0003] Patent Document 1 discloses that a heat sink having a gyroid structure with a thickness increasing from the upstream side to the downstream side suppresses the pressure drop on the downstream side and improves the cooling performance compared to a heat sink with a uniform thickness.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the heat sink of Patent Document 1, since the thickness of the gyroid structure becomes thicker on the downstream side and the flow path width becomes narrower, the pressure loss increases and the surface area on the downstream side becomes smaller, so the advantage of a triply periodic minimal surface with a large surface area per unit volume is not utilized.

[0006] Furthermore, when cooling semiconductor elements that generate a large amount of heat, such as power semiconductor elements used in inverters that drive motors in electric vehicles, the temperature of the refrigerant rises, resulting in a difference in cooling capacity between the upstream and downstream sides within the heat sink.

[0007] Therefore, in order to keep the temperature of the downstream portion of the semiconductor element below its heat resistance temperature, the cooling capacity of the heat sink must be based on the downstream portion where the cooling capacity has decreased, rather than the average cooling capacity of the entire heat sink. This results in waste, as the cooling capacity of the upstream portion becomes excessive.

[0008] This invention has been made in view of the problems of the prior art, and its objective is to provide a heat sink that can reduce the difference in cooling capacity between the upstream and downstream sides of the heat sink caused by the temperature rise of the refrigerant. [Means for solving the problem]

[0009] As a result of diligent research to achieve the above objective, the inventors have discovered that by making the period on the downstream side of the triple-period minimal curved surface structure placed in the refrigerant flow path shorter than that on the upstream side, the surface area on the downstream side of the triple-period minimal curved surface structure increases, thereby achieving the above objective, and have completed the present invention.

[0010] In other words, the heat sink of the present invention is equipped with a triple-periodic minimal curved surface structure within the refrigerant flow path. Furthermore, the triple-periodic minimal curved surface structure is characterized in that its thickness is constant from the upstream end to the downstream end of the refrigerant flow path, and the period in at least one direction selected from the length, width, and height directions of the refrigerant flow path is shorter on the downstream side than on the upstream side.

[0011] Furthermore, the inverter of the present invention is an inverter in which multiple semiconductor elements cooperate to drive the drive motor of an electric vehicle. Furthermore, the invention features a heat sink in which multiple triple-period minimal surface structures are arranged in series within a refrigerant flow path, the average period between the multiple triple-period minimal surface structures is shorter for the triple-period minimal surface structures located downstream than for the triple-period minimal surface structures located upstream, and the semiconductor elements are arranged at locations corresponding to each triple-period minimal surface structure. [Effects of the Invention]

[0012] According to the present invention, by making the period of the downstream side of the triple-period minimal curved surface structure in the refrigerant flow path shorter than that of the upstream side, and by making the surface area of ​​the triple-period minimal curved surface structure larger on the downstream side, it is possible to provide a heat sink in which the difference in cooling capacity between the upstream and downstream sides that occurs as the temperature of the refrigerant rises is small. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing an example of the heat sink of the present invention. [Figure 2] This figure shows an example of a triple-periodic minimal surface structure. [Figure 3] This is a cross-sectional view of a gyroid structure. [Figure 4] This is a schematic diagram showing an example of a heat sink having multiple triple-periodic minimal surface structures. [Modes for carrying out the invention]

[0014] <Heat sink> The heat sink of the present invention will be described in detail. As shown in Figure 1, the heat sink 1 of the present invention includes a triple-period minimal curved surface structure 3 that abuts against the inner wall of the refrigerant flow path 2, and heat exchange occurs between the refrigerant and the heat sink as the refrigerant flows through this triple-period minimal curved surface structure.

[0015] The above-described triple-periodic minimal surface structure has a triple-periodic minimal surface that divides space into two regions, and the pattern of the above minimal surface is repeated in three directions: the X axis, the Y axis, and the Z axis.

[0016] The heat sink of the present invention reduces the cooling capacity difference in the heat sink by changing the period of the minimal surface instead of changing the wall thickness of the above-mentioned triply periodic minimal surface structure.

[0017] That is, in the heat sink of the present invention, the wall thickness of the above-mentioned triply periodic minimal surface structure is constant from the upstream end to the downstream end of the refrigerant flow path, and the period in at least one direction selected from the length (X-axis) direction, width (Y-axis) direction, and height (Z-axis) direction of the refrigerant flow path is shorter on the downstream side than on the upstream side. In other words, the cell size formed by one period of the repeating pattern of the triply periodic minimal surface structure is smaller on the downstream side than on the upstream side.

[0018] Therefore, the surface area per unit volume of the above-mentioned triply periodic minimal surface structure becomes larger on the downstream side than on the upstream side, offsetting the decrease in cooling efficiency due to the temperature rise of the refrigerant on the downstream side in the heat sink, and reducing the cooling capacity difference between the upstream side and the downstream side in the heat sink.

[0019] According to such a heat sink of the present invention, waste of the cooling capacity on the upstream side can be saved, and the heat sink itself can be miniaturized.

[0020] The period of the above-mentioned triply periodic minimal surface structure may continuously decrease from the upstream side to the downstream side, or may decrease stepwise, and can be set according to the object to be cooled.

[0021] It is preferable that the entire circumference of the above-mentioned triply periodic minimal surface structure abuts against the inner wall of the refrigerant flow path.

[0022] Since the above-mentioned triply periodic minimal surface structure has a large surface area and a large friction with the refrigerant, if there is a gap between the inner wall of the refrigerant flow path and the triply periodic minimal surface structure, the refrigerant easily flows through the gap and hardly flows through the triply periodic minimal surface structure, reducing the cooling efficiency of the heat sink.

[0023] Because the entire circumference of the triple-periodic minimal curved surface structure, i.e., the end faces in the width and height directions, are in contact with the inner wall of the refrigerant flow path, the refrigerant flows through the triple-periodic minimal curved surface structure, thereby improving cooling efficiency.

[0024] Such a heat sink may be fabricated by fitting a triple-period minimal surface structure into the refrigerant flow path, but it is preferable to integrally mold the refrigerant flow path and the triple-period minimal surface structure using a 3D printer.

[0025] By creating a heat sink in which the refrigerant flow path and the triple-periodic minimal curved surface structure are integrally molded using a 3D printer, processes such as assembly, brazing, and welding are eliminated, preventing refrigerant leakage from joints and improving the durability and reliability of the heat sink.

[0026] Examples of the triple-periodic minimal surface structures mentioned above include the gyroid, diamond, and primitive, as shown in Figure 2.

[0027] The above gyroid is governed by a minimum surface that is governed by sin(x) cos(y) + sin(y) cos(z) + sin(z) cos(x) = 0. Furthermore, the minimum surface of the above rhombus is governed by sin(x)sin(y)sin(z)+sin(x)cos(y)cos(z)+cos(x)sin(y)cos(z)+cos(x)cos(y)sin(z)=0. Furthermore, the primitives described above are governed by a minimum surface where cos(x)+cos(y)+cos(z)=0. Among these, gyroid structures are preferable because they have a shape that provides maximum space-filling with minimal material.

[0028] In the above-described gyroid structure, it is sufficient that the period in any of the directions of the length (X-axis), width (Y-axis), and height (Z-axis) of the refrigerant flow path becomes shorter downstream. The period in all axial directions may also become shorter. However, it is preferable that the period in the width (Y-axis) and height (Z-axis) directions is constant from the upstream end to the downstream end of the refrigerant flow path, and that the period in the length (X-axis) direction is shorter downstream than upstream.

[0029] Figure 3 shows a cross-sectional view of this gyroid structure when cut along the XY or XZ plane.

[0030] As shown in Figure 3, in the above-described gyroid structure, the waveform period shortens and the surface area increases downstream of the waveform channel extending in the X-axis direction formed inside it, while the width of the waveform channel remains constant and does not narrow.

[0031] Of course, the width of the corrugated flow path extending in the Y-axis and Z-axis directions narrows downstream, but since the Y-axis and Z-axis directions are perpendicular to the direction of refrigerant flow, the reduction in the width of the corrugated flow path in these directions has little effect on pressure loss, and the effect of increasing the surface area is greater.

[0032] Therefore, in the case of a heat sink where the difference in cooling capacity between the upstream and downstream sides is the same, shortening only the period in the X-axis direction of the gyroid structure can suppress the increase in pressure loss compared to shortening the periods in all axial directions (X, Y, and Z axes), making it possible to use a low-power pump to circulate the refrigerant.

[0033] The above heat sink can be equipped with multiple triple-periodic minimal surface structures within the refrigerant flow path. While arranging triple-periodic minimal surface structures throughout the entire length of the refrigerant flow path, from the upstream to the downstream end, improves the cooling capacity of the heat sink, it increases pressure loss, requiring a high-power pump.

[0034] When used in inverters and other devices equipped with multiple semiconductor elements, as shown in Figure 4, multiple triple-periodic minimal surface structures are arranged in series with spacing between them, and semiconductor elements are placed at each of the locations corresponding to these triple-periodic minimal surface structures. This allows for the cooling of multiple semiconductor elements with a single heat sink while suppressing an increase in pressure loss.

[0035] Furthermore, it is preferable that the average period of the triple-periodic minimal surface structures described above is shorter for the triple-periodic minimal surface structures located downstream than for the triple-periodic minimal surface structures located upstream, that is, the average volume of the cell size is smaller.

[0036] This makes it possible to reduce the difference in cooling capacity between the triple-periodic minimal curved surface structure located upstream of the refrigerant flow path and the triple-periodic minimal curved surface structure located downstream.

[0037] Furthermore, as described above, it is preferable that the triple-periodic minimal surface structure located upstream and the triple-periodic minimal surface structure located downstream have the same period in the width (Y-axis) and height (Z-axis) directions, and that only the period in the length (X-axis) direction is shorter.

[0038] <Inverter> The inverter of the present invention uses multiple semiconductor elements to drive a motor for an electric vehicle, and includes a power semiconductor element that controls the U phase of a three-phase motor, a power semiconductor element that controls the V phase, and a power semiconductor element that controls the W phase. These multiple power semiconductor elements are cooled by a heat sink in which multiple triple-periodic minimal curved surface structures are arranged in series within the refrigerant flow path.

[0039] In other words, the power semiconductor elements, which are mounted on the heat sink via an insulator, are positioned at locations corresponding to the triple-periodic minimal surface structure.

[0040] As a result, the power semiconductor elements controlling the U-phase, V-phase, and W-phase can be uniformly cooled regardless of whether they are located upstream or downstream, suppressing temperature rise. This allows for the flow of large currents, and combined with the ability to cool with a low-power pump, it makes it possible to miniaturize the motor. [Explanation of Symbols]

[0041] 1 Heatsink 2 Refrigerant flow path 3 Triple periodic minimal curved structure 31 Waveform channel 4. Heat-generating components (semiconductor devices)

Claims

1. A heat sink having a triple periodic minimal curved surface structure within the refrigerant flow path, The triple-period minimal curved surface structure described above is characterized in that its thickness is constant from the upstream end to the downstream end of the refrigerant flow path, and the period in at least one direction selected from the length, width, and height directions of the refrigerant flow path is shorter on the downstream side than on the upstream side.

2. The heat sink according to claim 1, characterized in that the triple-periodic minimal curved surface structure is in contact with the inner wall of the refrigerant flow path over its entire circumference.

3. The heat sink according to claim 2, characterized in that the above-mentioned refrigerant flow path and the above-mentioned triple-periodic minimal curved surface structure are integrally molded.

4. The heat sink according to claim 3, characterized in that the triple-periodic minimal surface structure is a gyroid structure.

5. The heat sink according to claim 4, characterized in that the gyroid structure has a constant period in the width direction and height direction from the upstream end to the downstream end of the refrigerant flow path, and the period in the length direction is shorter on the downstream side than on the upstream side.

6. Multiple triple-period minimal curved surface structures are arranged in series within the above-mentioned refrigerant flow path. The heat sink according to any one of claims 1 to 5, characterized in that the average period between the multiple triple-period minimal surface structures is shorter for the triple-period minimal surface structures located downstream than for the triple-period minimal surface structures located upstream.

7. The device comprises multiple semiconductor elements and a heat sink for cooling the multiple semiconductor elements. An inverter in which the above-mentioned multiple semiconductor elements cooperate to drive the drive motor of an electric vehicle, The heat sink is the heat sink described in claim 6. An inverter characterized in that the above-mentioned semiconductor elements are arranged at locations corresponding to each of the triple-periodic minimal surface structures.

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