Cooling structure

Abstract

To improve the heat dissipation performance of a cooling structure.SOLUTION: The present invention relates to a cooling structure that forms a refrigerant flow passage for circulating a refrigerant inside. The cooling structure includes: a fin base thermally connected to a heat dissipation target member and having a plurality of heat dissipation fins; a frame including an opening closed in a liquid-tight manner by the fin base and configured to hold the fin base so as to be relatively displaceable in a standing direction of the plurality of heat dissipation fins; and a flow path cover covering the fin base and liquid-tightly coupled to the frame on the outer peripheral side of the fin base. The flow path cover includes a curved part having a radius of curvature at least equal to a predetermined value at a position opposing the tip of the outermost heat dissipation fin of the plurality of heat dissipation fins. The flow path cover further includes a pressing part recessed toward the fin base beyond the vertex of the curved part and being into contact with tips of some of the plurality of heat dissipation fins. The flow path cover includes, in a cross section perpendicular to the refrigerant flow direction, a plurality of inflection points between the curved part and the pressing part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a cooling structure. [Background technology]

[0002] Power converters that convert DC power and AC power mutually through the switching operation of semiconductor elements are widely used in electric vehicles, hybrid vehicles, and other vehicles. The semiconductor elements in power converters generate heat through their switching operation, requiring high heat dissipation performance for their cooling structure. A power module incorporating semiconductor elements includes a heat dissipation member that cools the heat generated by the semiconductor elements. The heat dissipation member has heat dissipation fins, and the cooling structure includes a water channel that passes through the heat dissipation fins. Patent Document 1 discloses a semiconductor element comprising: multiple power modules each including semiconductor elements; multiple heat dissipation bases each having heat dissipation fins, and a frame with multiple openings; and a cover that covers the heat dissipation bases and the frame to form a refrigerant flow path. The multiple heat dissipation bases each close the multiple openings, and the cover has elastic biasing portions on the surfaces that contact the heat dissipation fins, and biases the heat dissipation bases toward the power modules by applying pressure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-073861 Summary of the Invention [Problem to be solved by the invention]

[0004] The invention described in Patent Document 1 leaves room for improvement in the cooling structure. [Means for solving the problem]

[0005] A cooling structure according to a first aspect of the present invention is a cooling structure that forms a refrigerant flow path for circulating a refrigerant therethrough, and includes: a fin base that is thermally connected to a heat-receiving member and has a plurality of heat dissipation fins; a frame that has an opening that is liquid-tightly closed by the fin base and holds the fin base so that it can be relatively displaced in the vertical direction of the plurality of heat dissipation fins; and a flow path cover that covers the fin base and is liquid-tightly connected to the frame on the outer periphery of the fin base, wherein the flow path cover has a curved portion with a curvature radius of a predetermined value or more at a position opposite to the tip of the outermost heat dissipation fin of the plurality of heat dissipation fins, and the flow path cover has a pressing portion that is recessed toward the fin base from the apex of the curved portion and abuts against the tips of some of the heat dissipation fins of the plurality of heat dissipation fins, and the flow path cover has a plurality of inflection points between the curved portion and the pressing portion in a cross section perpendicular to the flow direction of the refrigerant. [Effects of the Invention]

[0006] According to the present invention, the heat dissipation performance of the cooling structure can be improved. [Brief explanation of the drawings]

[0007] [Figure 1] Exploded perspective view of a power conversion device [Figure 2] Cross-sectional view showing the cooling structure of the power conversion device [Figure 3] Cross-sectional view showing the cooling structure of the power conversion device [Figure 4] 1 is a cross-sectional view of a comparative example power conversion device. [Figure 5] 10A and 10B are diagrams showing a method for manufacturing a power conversion device according to a second embodiment; [Figure 6] FIG. 10 is a diagram showing a cooling structure of a power conversion device according to a third embodiment. [Figure 7] FIG. 10 is a diagram showing a cooling structure of a power conversion device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural. The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0009] -First embodiment- A first embodiment of the cooling structure will be described below with reference to FIGS.

[0010] FIG. 1 is an exploded perspective view of a power converter 1. The power converter 1 includes a power module 2, a heat dissipation member 3, a frame 4, and a flow path cover 5. In the example shown in FIG. 1, the power converter 1 has 24 power modules 2 (six sets of four modules) arranged side by side. The power modules 2 are mounted on a substrate 6. In addition to the power modules 2, electronic components, positioning holes, and fixing bosses are also mounted on the substrate 6, but these are not shown in FIG. 1. The power modules 2 generate a large amount of heat, so heat dissipation is required for stable operation. The power converter 1 has a cooling structure for cooling the power modules 2. Because the power modules 2 require heat dissipation, they can also be called "heat-receiving members."

[0011] The power module 2 contains semiconductor elements and lead wires sealed with a sealing material, but the sealing material is not shown in Fig. 1. Also, insulating material is installed inside or outside the power module 2, but the insulating material is not shown in Fig. 1. Both sides of the power module 2 are heat dissipation surfaces that dissipate heat generated by the switching operation of the semiconductor elements. Thermally conductive material 7 (see Fig. 2), such as thermally conductive grease or a thermally conductive sheet, is installed on both sides of the power module 2.

[0012] The heat dissipation member 3 includes a fin base 31 and a plurality of heat dissipation fins 32. A total of six heat dissipation members 3 are provided, one for each of four power modules 2. The fin base 31 is thermally connected to the heat dissipation surface of the power module 2, which is the member to be dissipated, via a heat conduction member 7. Note that although the heat dissipation fins 32 are shown as cylindrical pin fins, they may have other shapes and the shape of the heat dissipation fins 32 is not limited.

[0013] The frame 4 is formed with openings 41, the same number as the heat dissipation members 3, and the heat dissipation members 3 are fitted into these openings 41. Details of the state in which the heat dissipation members 3 are fitted into the openings 41 will be described later with reference to FIGS. 2 and 3. The flow path cover 5 forms a closed space by covering the heat dissipation members 3 and the frame 4. This closed space will be referred to as the refrigerant flow path below. The flow path cover 5 is equipped with an inlet pipe 93 and an outlet pipe 94, and the refrigerant flows from the inlet pipe 93 to the outlet pipe 94, i.e., from left to right in the figure. The refrigerant passes through the heat dissipation fins 32, allowing efficient heat transfer from the heat dissipation fins 32 to the refrigerant. Details of the flow path cover 5 will be described later with reference to FIGS. 2 and 3. In FIG. 1, the lower side of the substrate 6 is not shown in the exploded perspective view, but a refrigerant flow path is formed therein, similar to the upper side. The upper and lower refrigerant flow paths are connected by a connecting pipe 95.

[0014] Although the power conversion device 1 shows an example in which 24 power modules 2 (6 sets of 4) are arranged, the number of power modules 2 is arbitrary. Furthermore, in this embodiment, an example in which the heat dissipation members 3 are arranged on both sides of the power module 2 will be described, but the heat dissipation members 3 may be arranged on one side of the power module 2. In this case, a housing or mounting member is arranged on the other side of the power module 2, and the other side of the power module 2 is fixed to this housing or mounting member with a fixing member.

[0015] 2 and 3 are cross-sectional views showing the cooling structure of the power conversion device 1. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and is illustrated as a cross section parallel to the direction of refrigerant flow. FIG. 3 is a cross-sectional view taken along line III-III in FIGS. 1 and 2, and is illustrated as a cross section perpendicular to the direction of refrigerant flow. FIG. 2 shows a state in which the heat dissipation members 3, frames 4, flow path covers 5, etc. are attached to both sides of the power module 2 via heat conduction members 7. FIG. 3 shows a state in which the heat dissipation members 3, frames 4, flow path covers 5, etc. are attached to both sides of the power module 2 via heat conduction members 7.

[0016] The flow path cover 5 and the frame 4 are joined by brazing or the like at joints 10 on the outer periphery of the fin base 31, thereby maintaining the liquid tightness of each. Also, similar to joints 10, fastening parts 11 are provided on the outer periphery of the fin base 31, and by fastening with bolts or the like, the frame 4 and the flow path cover 5 are held above and below the substrate 6.

[0017] The fin base 31 is fitted into the opening 41 of the frame 4 via the first seal member 81, thereby ensuring liquid tightness. The first seal member 81 is an elastic member such as a liquid seal, and the fin base 31 is elastically supported by the frame 4. In other words, the fin base 31 is held so as to be relatively displaceable in the erection direction of the heat dissipation fins 32, i.e., in the vertical direction in the figure.

[0018] With the configuration described above, refrigerant flow paths 90, which cover the heat dissipation member 3 and the frame 4 with the flow path cover 5, are formed above and below the substrate 6. The refrigerant flow paths 90 include an upper flow path 91 and a lower flow path 92. An inlet pipe 93, which serves as an inlet for the refrigerant, is installed in the flow path cover 5 on the upper side of the substrate 6, and an outlet pipe 94, which serves as an outlet for the refrigerant, is installed on the opposite side of the inlet pipe 93. In addition, a connecting pipe 95 is connected in a liquid-tight state by a second sealing member 82 such as an O-ring, and connects the upper flow path 91 and the lower flow path 92.

[0019] The refrigerant is supplied from an inlet pipe 93 by a pump (not shown) and distributed to an upper flow path 91 and a lower flow path 92 via a connecting pipe 95. The distributed refrigerant passes through the heat dissipation fins 32, passes from the lower flow path 92 through the connecting pipe 95, rejoins the upper flow path 91, and is discharged from an outlet pipe 94. However, the refrigerant flow described here is an example and is not limited to this.

[0020] As shown in Fig. 3, the flow path cover 5 has curved portions 51 at positions facing the tips of the outermost fins of the multiple heat dissipation fins 32. The flow path cover 5 also has pressing portions 52 that come into contact with the tips of some of the multiple heat dissipation fins 32. The height of the heat dissipation fins 32 is approximately constant, and the distance between the heat dissipation fins 32 and the flow path cover 5 is determined by the shape of the flow path cover 5. The pressing portions 52 have a convex shape that is recessed by a predetermined value or more toward the fin base 31 from the apex of the curved portions 51. The flow path cover 5 is made of an elastic member such as aluminum, and is fastened by bolts or the like at the fastening portions 11, so that a fastening force is applied from above and below in directions toward the power module 2.

[0021] The pressing portion 52 of the flow path cover 5 presses the tips of the heat dissipation fins 32 that it abuts, urging the heat dissipation member 3 toward the heat dissipation surface of the power module 2. This urging applies surface pressure from the fin base 31 to the heat conduction member 7. Because a reaction force is applied to the curved portion 51 when the tips of the heat dissipation fins 32 are pressed, the curved portion 51 has a curvature radius equal to or greater than a predetermined value to suppress stress concentration in a local area of ​​the curved portion 51. With this configuration, in a cross section perpendicular to the refrigerant flow direction shown in FIG. 3 , a bypass portion 96 is formed between the curved portion 51 and pressing portion 52 of the flow path cover 5 and the tips of the multiple heat dissipation fins 32. Part of the refrigerant flows into the bypass portion 96 without passing between the multiple heat dissipation fins 32.

[0022] In a cross section perpendicular to the refrigerant flow direction shown in FIG. 3, the flow path cover 5 has a first inflection point 53a, a second inflection point 53b, and a third inflection point 53c between the curved portion 51 and the pressing portion 52. An inflection point is a point where, when the cross section of the water channel cover viewed in a cross section perpendicular to the refrigerant flow direction is considered as a curve, the shape changes from an upward convex to a downward convex. The presence of multiple inflection points indicates that the flow path cover 5 has a shape that is bent multiple times up and down or a multi-stage structure with multiple recessed portions. The first inflection point 53a to the third inflection point 53c are closer to the tips of the multiple heat dissipation fins 32 than the apex of the curved portion 51.

[0023] The effects of this embodiment will be described. In this embodiment, the flow path cover 5 has a first inflection point 53a, a second inflection point 53b, and a third inflection point 53c between the curved portion 51 and the pressing portion 52. These three inflection points are closer to the tips of the heat dissipation fins 32 than the apex of the curved portion 51. This allows the cross-sectional area of ​​the bypass portion 96 formed between the curved portion 51 and the pressing portion 52 of the flow path cover 5 and the tips of the heat dissipation fins 32 to be reduced. Because the refrigerant passing through the bypass portion 96 does not contribute to the dissipation of heat generated by the power module 2, increasing the amount of refrigerant passing through the bypass portion 96 deteriorates the heat dissipation performance. By reducing the cross-sectional area of ​​the bypass portion 96, the flow resistance of the bypass portion 96 increases, reducing the amount of refrigerant passing through the bypass portion 96, and thereby increasing the amount of refrigerant passing through the heat dissipation fins 32. This improves the heat dissipation performance of the cooling structure of the power conversion device 1.

[0024] Other effects of this embodiment will be described. In this embodiment, the pressing portion 52 has a convex shape that is recessed by a predetermined value or more toward the fin base 31 from the apex of the curved portion 51. This improves the ability to adapt to variations in the thickness of the power modules 2. Therefore, it is possible to apply a uniform and large surface pressure to each of the heat conduction members 7 installed on multiple power modules 2 that have thickness variations. This allows the thickness of the heat conduction members 7 to be reduced to a predetermined value or less, and the thermal resistance of the heat conduction members 7 to be reduced. This improves the heat dissipation performance of the cooling structure of the power conversion device 1.

[0025] FIG. 4 is a cross-sectional view of a comparative power conversion device 1Z, which is a comparative example. FIG. 4 is taken from the same perspective as FIG. 3. Comparative power conversion device 1Z has a structure similar to that of power conversion device 1, but comparative power conversion device 1Z does not have first inflection point 53a, second inflection point 53b, or third inflection point 53c. Because comparative power conversion device 1Z does not have first inflection point 53a, second inflection point 53b, or third inflection point 53c, the cross-sectional area of ​​bypass section 96 is larger than that of power conversion device 1. Therefore, comparative power conversion device 1Z has a cooling structure with lower heat dissipation performance than power conversion device 1.

[0026] In contrast, the flow path cover 5 in this embodiment has a plurality of inflection points, namely, a first inflection point 53a, a second inflection point 53b, and a third inflection point 53c, between the curved portion 51 and the pressing portion 52. The first inflection point 53a to the third inflection point 53c are located closer to the tips of the plurality of heat dissipation fins 32 than the apex of the curved portion 51, thereby making it possible to reduce the cross-sectional area of ​​the bypass portion 96.

[0027] According to the first embodiment described above, the following advantageous effects can be obtained. (1) The cooling structure of the power conversion device 1 forms a refrigerant flow path through which a refrigerant flows. The power conversion device 1 includes a fin base 31 thermally connected to a power module 2, which is a heat-receiving member, and having multiple heat dissipation fins 32; a frame 4 having an opening 41 liquid-tightly closed by the fin base 31 and holding the fin base 31 so as to be relatively displaceable in the vertical direction of the multiple heat dissipation fins 32; and a flow path cover 5 covering the fin base 31 and liquid-tightly coupled to the frame 4 on the outer periphery of the fin base 31. The flow path cover 5 has a curved portion 51 with a curvature radius equal to or greater than a predetermined value, positioned opposite the tip of the outermost heat dissipation fin among the multiple heat dissipation fins. The flow path cover 5 has a pressing portion 52 recessed toward the fin base from the apex of the curved portion 51 and abutting against the tip of some of the multiple heat dissipation fins. The flow path cover 5 has multiple inflection points between the curved portion 51 and the pressing portion 52 in a cross section perpendicular to the flow direction of the refrigerant. Therefore, the cross-sectional area of ​​the bypass portion 96 is reduced, and the amount of refrigerant passing through the plurality of heat dissipation fins 32 increases, so that the heat dissipation performance of the cooling structure of the power conversion device 1 can be improved.

[0028] (Variation 1) In the first embodiment described above, the fastening portions 11 arranged at both ends of the upper and lower flow path covers 5 sandwiching the frame 4 are fastened with bolts or the like. However, instead of fastening the fastening portions 11, the center portions of the flow path covers 5 may be pressed toward the substrate 6 with a leaf spring or the like. For example, the upper flow path cover 5 in FIG. 3 is pressed downward in the figure, and the lower flow path cover 5 in the figure is pressed upward in the figure.

[0029] --Second embodiment-- A second embodiment of the cooling structure will be described with reference to Fig. 5. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. Points that are not particularly described are the same as those in the first embodiment. This embodiment differs from the first embodiment mainly in that the manufacturing method of the power conversion device is limited.

[0030] FIG. 5 is a diagram illustrating a manufacturing method of a power converter 1A according to the second embodiment. FIG. 5 is taken from the same perspective as FIG. 3 according to the first embodiment. The upper view in FIG. 5 illustrates the state before fastening with bolts or the like, and the lower view illustrates the state after fastening with bolts or the like at the fastening portions 11. In this embodiment, fastening with the fastening portions 11 applies a fastening force from above and below toward the power module 2, and the first seal member 81 is pressed and deformed, displacing the fastening portions 11 and the frame 4 toward the substrate 6. Meanwhile, the pressing portions 52 contact and press the multiple heat dissipation fins 32, urging the heat dissipation member 3 toward the heat dissipation surface of the power module 2 and applying surface pressure from the fin base 31 to the heat conduction member 7. At this time, the pressing portions 52 and the fastening portions 11 are displaced relative to each other, causing the curved portions 51, the pressing portions 52, and the first to third inflection points 53a to 53c of the flow path cover 5 to deform in directions approaching the heat dissipation fins 32.

[0031] According to the second embodiment described above, the following advantageous effects can be obtained. (2) The fin base 31 has fastening portions that are fastened to the flow path cover 5 at its outer periphery to apply a fastening force in the erect direction of the plurality of heat dissipation fins 32. Therefore, the curved portions 51, the pressing portions 52, and the first to third inflection points 53a to 53c of the flow path cover 5 are deformed in a direction approaching the heat dissipation fins 32, thereby reducing the cross-sectional area of ​​the bypass portion 96. This improves the heat dissipation performance of the cooling structure of the power conversion device 1A, similar to the first embodiment.

[0032] -Third embodiment- A third embodiment of the cooling structure will be described with reference to Fig. 6. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. Points that are not particularly described are the same as those in the first embodiment. This embodiment differs from the first embodiment mainly in that the flow path cover 5 has a multi-stage structure.

[0033] FIG. 6 is a diagram illustrating the cooling structure of a power converter 1B according to the third embodiment. FIG. 6 corresponds to FIG. 3 according to the first embodiment. The flow path cover 5 according to the present embodiment includes a first flat portion 56, a second flat portion 57, a first inclined portion 58a, and a second inclined portion 58b between a curved portion 51 and a pressing portion 52. The first flat portion 56 and the second flat portion 57 are portions that are at a constant distance from the tips of the heat dissipation fins 32. The first inclined portion 58a and the second inclined portion 58b are portions that are inclined toward the tips of the heat dissipation fins 32.

[0034] That is, the flow path cover 5 in this embodiment has a multi-stage structure in which multiple stages approach each other toward the tip of the heat dissipation fin 32. The first inflection point 53a to the third inflection point 53c are located at points where the curve changes from an upward convex to a downward convex when the cross section of the flow path cover 5 seen in a cross section perpendicular to the flow direction of the refrigerant is regarded as a curve. The first inflection point 53a is located between the first inclined portion 58a and the second flat portion 57. The second inflection point 53b is located between the second flat portion 57 and the second inclined portion 58b. The third inflection point 53c is located between the second inclined portion 58b and the pressing portion 52.

[0035] According to the above-described third embodiment, the following advantageous effects can be obtained. (3) The flow path cover 5 has a multi-stage structure between the curved portion 51 and the pressing portion 52, with multiple stages approaching the tip of the heat dissipation fin 32. This allows the cross-sectional area of ​​the bypass portion 96 to be reduced, thereby improving the heat dissipation performance of the cooling structure of the power conversion device 1B.

[0036] --Fourth embodiment-- A fourth embodiment of the cooling structure will be described with reference to FIG. 7. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. Points that are not particularly described are the same as those in the first embodiment. This embodiment differs from the first embodiment mainly in that the flow path cover 5 has a recessed portion.

[0037] Fig. 7 is a diagram showing the cooling structure of a power conversion device 1C according to the fourth embodiment. Fig. 7 corresponds to Fig. 3 according to the first embodiment. The flow path cover 5 according to the present embodiment has a recessed portion 59 between the curved portion 51 and the inflection point 53, the recessed portion 59 having a smaller radius of curvature than the curved portion 51 and projecting in the opposite direction to the curved portion 51. The recessed portion 59 can be formed, for example, by processing the flow path cover 5 from the outside using a press or the like.

[0038] According to the above-described fourth embodiment, the following advantageous effects can be obtained. (4) The flow path cover 5 has a recessed portion 59 that has a curvature radius smaller than a predetermined value and is convex in the opposite direction to the curved portion, at a position different from the curved portion 51 and the pressing portion 52. This allows the cross-sectional area of ​​the bypass portion 96 to be further reduced, and the heat dissipation performance of the cooling structure of the power conversion device 1C to be further improved.

[0039] The present invention is not limited to the above-described embodiments, and other embodiments that are conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention as long as they do not impair the characteristics of the present invention. Furthermore, the present invention may be configured by combining the above-described embodiments with multiple modifications. Furthermore, the present invention is applicable not only to electric vehicles and hybrid vehicles, but also to power conversion devices for mobile vehicles such as railway vehicles, aircraft, and ships. [Explanation of symbols]

[0040] 1, 1A, 1B, 1C: Power conversion device 3: Heat dissipation material 4: Frame 5: Flow path cover 7: Heat conducting material 11: Fastening part 31: Fin base 32: Heat dissipation fin 41: Opening 51: Curved section 52: Pressing part 53a: 1st inflection point 53b: 2nd inflection point 53c: 3rd inflection point 56: 1st flat part 57: 2nd flat part 58a: 1st slope part 58b: 2nd slope part 59: Depression 90: Refrigerant flow path 96: Bypass section

Claims

1. A cooling structure that forms a refrigerant flow path for circulating a refrigerant therein, a fin base thermally connected to the heat-dissipating member and having a plurality of heat-dissipating fins; a frame having an opening that is liquid-tightly closed by the fin base and that holds the fin base so that the fin base can be displaced relative to the fins in an upright direction; a flow path cover that covers the fin base and is liquid-tightly coupled to the frame on the outer circumferential side of the fin base, the flow path cover has a curved portion having a radius of curvature equal to or greater than a predetermined value at a position facing a tip of an outermost heat dissipation fin among the plurality of heat dissipation fins, the flow path cover has a pressing portion that is recessed toward the fin base from an apex of the curved portion and that abuts against tips of some of the plurality of heat dissipation fins, The flow path cover has a plurality of inflection points between the curved portion and the pressing portion in a cross section perpendicular to a flow direction of the refrigerant.

2. The cooling structure according to claim 1, The fin base has a fastening portion that is fastened to the flow path cover at an outer periphery thereof to apply a fastening force in an upright direction of the plurality of heat dissipation fins.

3. The cooling structure according to claim 1, The flow path cover has a multi-stage structure between the curved portion and the pressing portion, with multiple stages approaching each other toward the tip of the heat dissipation fin.

4. The cooling structure according to claim 1, The cooling structure has a recessed portion, the recessed portion having a radius of curvature smaller than the predetermined value and projecting in an opposite direction to the curved portion, at a position different from the curved portion and the pressing portion.

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