case

Abstract

This invention provides a case made of resin that combines mechanical strength, heat dissipation, and electromagnetic shielding properties. [Solution] The case comprises a metal case and a resin part. The metal case has a bottom and a side wall with a plurality of through holes. The resin part covers the metal case and has a first opening that partially exposes the outer surface of the side wall, a plurality of second openings that partially expose the inner surface of the bottom, and a plurality of connecting parts that fill the plurality of through holes and connect the inner and outer parts of the side wall.

Description

Technical Field

[0001] The present invention relates to a case for housing electronic components.

Background Art

[0002] In electric vehicles, while engines and transmissions mounted in conventional vehicles become unnecessary, it is necessary to mount a large-capacity battery, so the total weight tends to increase. On the other hand, in electric vehicles, it is preferable to be lightweight in order to improve electricity costs and increase the cruising range. In electric vehicles, in order to reduce weight, it is effective to change the mounted metal members to members using lightweight materials such as resin.

[0003] Under such circumstances, for the PCU (Power Control Unit) essential for electric vehicles, miniaturization, weight reduction, and high functionality of electronic components have been promoted, and a case for housing an inverter or the like of the PCU is also expected to be switched from an aluminum die-cast product to a resin molded product. Resin molded products are lighter than aluminum die-cast products, but are inferior in mechanical strength, heat dissipation, and electromagnetic shielding properties.

[0004] On the other hand, Patent Document 1 discloses a technique for improving the heat dissipation of a multilayer substrate by providing an interlayer heat transfer layer in an inner layer of the multilayer substrate on which electronic components are mounted. Patent Document 2 discloses a technique for improving the electromagnetic shielding property of a resin member by embedding an iron wire mesh in the resin member. Patent Document 3 discloses a technique for improving the mechanical strength and electromagnetic shielding property of a resin layer by embedding punching metal in the resin layer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] Even when applying the above technology to cases for housing electronic components, it is difficult to achieve a configuration that is lightweight and also possesses mechanical strength, heat dissipation, and electromagnetic shielding properties.

[0007] In view of the above circumstances, the object of the present invention is to provide a case made of resin that combines mechanical strength, heat dissipation, and electromagnetic shielding properties. [Means for solving the problem]

[0008] To achieve the above objective, a case according to one embodiment of the present invention comprises a metal case and a resin part. The metal case has a bottom and a side wall portion in which a plurality of through holes are formed. The resin part covers the metal case and has a first opening that partially exposes the inner surface of the bottom, a plurality of second openings that partially expose the outer surface of the side wall, and a plurality of connecting parts that fill the plurality of through holes and connect the inner surface portion and the outer surface portion of the side wall.

[0009] In this case, the inner surface of the bottom of the metal case exposed at the first opening functions as a heat absorption section, and the outer surface of the side wall of the metal case exposed at the second opening functions as a heat dissipation section. In other words, the heat generated by the electronic components held in the heat absorption section located inside the case is released to the outside of the case through the heat dissipation section via the bottom and side walls of the metal case. Furthermore, in this case, the inner and outer portions of the resin part are continuous via connecting parts filled in multiple through-holes in the metal case, and the resin part is continuous with the outer surface of the side wall of the metal case in portions other than the second opening, thus providing a reinforcing effect from the resin part. Moreover, in this case, electromagnetic shielding is achieved through the action of the metal case. Therefore, this case combines mechanical strength, heat dissipation, and electromagnetic shielding properties.

[0010] The electronic component is held within the first opening on the inner surface of the bottom, and the maximum diameter of the plurality of through holes may be less than or equal to half the wavelength of the electromagnetic waves emitted by the electronic component. In this case, electromagnetic waves emitted by the electronic components can be prevented from being released to the outside through multiple through-holes in the metal case. Therefore, the electromagnetic shielding performance is further improved in this case.

[0011] In at least a portion of the outer surface of the side wall portion, the plurality of second openings may be arranged regularly so that the resin portion forms a planar filling structure. The aforementioned planar tethering structure may be a honeycomb structure. In these cases, the reinforcing effect of the resin portion on the outer surface of the side wall is more effectively achieved. Therefore, in these cases, the mechanical strength is further improved.

[0012] The side wall portion may have an uneven region in which an uneven shape is formed on both the inner and outer surfaces. In this case, high mechanical strength is obtained in the side walls of the metal case. Therefore, the mechanical strength is further improved in this case.

[0013] In the aforementioned uneven region, the inner surface of the side wall portion may have a dimple shape. In this case, electromagnetic waves are less likely to be emitted to the outside due to diffuse reflection of electromagnetic waves on the inner surface of the side wall. Therefore, in this case, the electromagnetic shielding performance is further improved.

[0014] The outer surface of the side wall portion may protrude within the plurality of second openings. In this case, since the heat dissipation portion protrudes, the heat dissipation performance is further improved.

[0015] The resin portion may cover the inner surface of the side wall portion without any gaps. In this case, it is possible to prevent the heat generated by the electronic component held by the heat absorption portion at the bottom of the metal case exposed at the first opening from returning inside at the side wall portion. Therefore, in this case, the heat dissipation performance is further improved.

[0016] The resin portion may be injection molded integrally with the metal case. In this case, the above configuration can be realized quickly and easily.

Effects of the Invention

[0017] As described above, the present invention can provide a case that has mechanical strength, heat dissipation performance, and electromagnetic shielding performance in a configuration using resin.

Brief Description of the Drawings

[0018] [Figure 1] It is a perspective view of a case according to an embodiment of the present invention. [Figure 2] It is a plan view of the above case. [Figure 3] It is a perspective view showing a cross-sectional view along the line A - A' of FIG. 1 of the above case. [Figure 4] It is a perspective view showing the metal case of the above case. [Figure 5] It is a view showing models of cases according to Examples and Comparative Examples. [Figure 6] It is a view showing the results of thermal conductivity analysis of models of cases according to Examples and Comparative Examples.

Modes for Carrying Out the Invention

[0019] [Introduction] Embodiments of the present invention will be described below with reference to the drawings. The drawings show mutually orthogonal X, Y, and Z axes. The X, Y, and Z axes are a fixed coordinate system fixed to case 100 and are common to all drawings. In this specification, the upper and lower directions along the Z axis in each drawing may also be simply referred to as the upper and lower directions.

[0020] [Configuration of Case 100] Figures 1 and 2 show a case 100 according to one embodiment of the present invention. Figure 1 is a perspective view of case 100. Figure 2 is a plan view of case 100. Case 100 is configured as a box with an open top, and is a rectangular parallelepiped with the X-axis direction as the longitudinal direction, the Y-axis direction as the width direction, and the Z-axis direction as the height direction. Figure 2 shows case 100 as viewed from above, that is, the interior of case 100. The upward and downward directions along the Z-axis are sometimes simply referred to as upward and downward.

[0021] Case 100 is used to house electronic components that emit heat and electromagnetic waves. The electronic components housed in Case 100 are primarily those that emit electromagnetic waves in the frequency band of 500 Hz to 79 GHz. Examples of such components include inverters, DC-DC converters, and ECUs (Electronic Control Units) for Power Control Units (PCUs).

[0022] Case 100 comprises a metal case 110 and a resin part 120. The metal case 110 has a bottom portion 110a and side wall portions 110b. The bottom portion 110a is rectangular in shape, having two sides parallel to the X-axis and two sides parallel to the Y-axis. The side wall portions 110b extend upward in a cylindrical shape from the four sides of the bottom portion 110a. The metal case 110 can be made of, for example, aluminum, copper, magnesium, etc. In case 100, from the viewpoint of reducing weight while ensuring mechanical strength, the thickness of the bottom portion 110a and side wall portions 110b of the metal case 110 is preferably 0.5 mm or more and 4.0 mm or less, and more preferably 1.0 mm or more and 2.0 mm or less.

[0023] The resin portion 120 covers the metal case 110, exposing only specific parts of the inner and outer surfaces of the metal case 110. The resin portion 120 can be formed from thermoplastic resins such as polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), polyamide (PA), liquid crystal polymer (LCP), polycarbonate (PC), and polyetheretherketone (PEEK), or from composite resins in which various fillers such as heat-resistant fillers and reinforcing fillers are filled into these thermoplastic resins. In the case 100, the thickness of the resin portion 120 on the surface (inner or outer surface) of the metal case 110 is preferably 0.5 mm to 5.0 mm, and more preferably 2.0 mm to 3.0 mm.

[0024] The resin part 120 is provided with a first opening 121 and a second opening 122 that expose the surface of the metal case 110. The first opening 121 is located in the center of the X-axis and Y-axis directions on the inner surface of the bottom portion 110a of the metal case 110. The second opening 122 is located two-dimensionally on the outer surface of the side wall portion 110b of the metal case 110. The resin part 120 exposes the inner surface of the metal case 110 only through the first opening 121, and exposes the outer surface of the metal case 110 only through the second opening 122.

[0025] In case 100, the area within the first opening 121 of the resin part 120 on the inner surface of the bottom 110a of the metal case 110 is configured as a heat absorption section 111. In case 100, the area within the second opening 122 of the resin part 120 on the outer surface of the side wall 110b of the metal case 110 is configured as a heat dissipation section 112. In case 100, the electronic components to be housed are held in the heat absorption section 111 which constitutes the inner surface of the bottom 110a of the metal case 110. In case 100, the electronic components may be held directly in the heat absorption section 111, or they may be held between the heat absorption section 111 and the heat absorption section 111 via thermal grease, thermal sheets, etc.

[0026] Figure 3 is a perspective view showing a cross-section of case 100 along the line A-A' in Figure 1. In the metal case 110, the heat-absorbing section 111 is a plane parallel to the XY plane and protrudes slightly upward at the bottom 110a. As shown in the cross-section of case 100 in Figure 3, the bottom 110a and side walls 110b of the metal case 110 form a heat transfer path that thermally connects the heat-absorbing section 111 and each heat-dissipating section 112.

[0027] Therefore, in case 100, the heat generated by the electronic components held in the heat absorption section 111 is transferred to each heat dissipation section 112, and efficiently released to the outside in each heat dissipation section 112. In addition, in case 100, since the inner surface of the side wall section 110b of the metal case 110 is covered without gaps by the resin section 120, the heat absorbed in the heat absorption section 111 does not return to the inside, and heat dissipation in each heat dissipation section 112 is promoted.

[0028] Furthermore, in case 100, the outer surface of the side wall portion 110b of the metal case 110 is covered with the resin portion 120 in areas other than the heat dissipation portion 112, meaning that the resin portion 120 is two-dimensionally continuous in areas other than the second opening 122. As a result, in case 100, the reinforcing effect of the resin portion 120 on the outer surface of the side wall portion 110b of the metal case 110 is obtained, improving the mechanical strength. Therefore, in case 100, even if the side wall portion 110b of the metal case 110 is made thinner to reduce weight, sufficient mechanical strength can be easily ensured by the reinforcing effect of the resin portion 120.

[0029] Furthermore, in case 100, each second opening 122 of the resin part 120 is hexagonal, and multiple second openings 122 are regularly arranged on the outer surface of the side wall portion 110b of the metal case 110, so that the resin part 120 forms a honeycomb structure. As a result, the reinforcing effect of the resin part 120 is enhanced in case 100, and further weight reduction can be achieved by further thinning of the side wall portion 110b of the metal case 110.

[0030] As shown in Figure 3, the side wall portion 110b of the metal case 110 is provided with a plurality of through holes 113 that penetrate in the thickness direction. The resin portion 120 has a plurality of connecting portions 123 that are filled in the plurality of through holes 113 of the side wall portion 110b, and the inner side portion and the outer side portion of the side wall portion 110b are connected via the plurality of connecting portions 123. As a result, in the case 100, the resin portion 120 is firmly fixed to the metal case 110, thereby improving the mechanical strength. In the case 100, in order to obtain even higher mechanical strength, it is preferable that the plurality of through holes 113 are provided at positions corresponding to the nodes of the honeycomb structure formed by the resin portion 120 in the side wall portion 110b of the metal case 110. The plurality of through holes 113 can have various cross-sectional shapes, for example, they can have circular, elliptical, or square cross-sectional shapes.

[0031] In case 100, high electromagnetic shielding performance is obtained due to the action of the metal case 110. In this regard, it is preferable that in case 100, electromagnetic waves emitted by the electronic components housed inside are suppressed from being emitted to the outside through the multiple through holes 113 in the side wall portion 110b of the metal case 110. From this viewpoint, in case 100, it is preferable that the maximum hole diameter (for example, the major axis if the cross-sectional shape is elliptical) of the multiple through holes 113 formed in the side wall portion 110b of the metal case 110 is half or less of the wavelength of the electromagnetic waves emitted by the electronic components to be housed. As a result, the electromagnetic waves hardly diffract in the multiple through holes 113, so that the electromagnetic waves cannot pass outward through the multiple through holes 113. Furthermore, the electromagnetic waves are attenuated by interference in the multiple through holes 113. For this reason, even higher electromagnetic shielding performance can be obtained in case 100. In case 100, it is preferable that the maximum diameter of the multiple through holes 113 formed in the side wall portion 110b of the metal case 110 is 3.0 mm or more and 8.0 mm or less.

[0032] Figure 4 is a perspective view of the metal case 110. Each of the four flat plate sections constituting the side wall 110b of the metal case 110 is provided with an uneven region where the entire thickness direction, both on the inner and outer surfaces, is deformed by press working, resulting in an uneven shape. As a result, in the metal case 110, the rigidity is increased and stress is more easily distributed in the uneven region of the side wall 110b, thus improving the mechanical strength. Therefore, in the metal case 110, sufficient mechanical strength can be easily obtained even if the side wall 110b is made thinner to reduce weight.

[0033] As shown in Figure 4, in the metal case 110, it is preferable that the inner surface of the side wall portion 110b in the uneven region has a dimple shape with a series of shallow circular depressions. As a result, in the case 100, electromagnetic waves emitted by the housed electronic components are diffusely reflected off the inner surface of the dimple-shaped side wall portion 110b, making it less likely for them to be emitted to the outside. Therefore, the electromagnetic shielding performance of the case 100 is further improved.

[0034] Furthermore, as shown in Figures 1 and 3, in the case 100, it is preferable that the outer surface of the side wall portion 110b in the uneven region has a shape in which low circular protrusions are arranged, and each protrusion constitutes a heat dissipation portion 112. In other words, in the case 100, it is preferable that the heat dissipation portion 112 that constitutes the outer surface of the side wall portion 110b of the metal case 110 protrudes outward within the second opening 122 of the resin portion 120. As a result, in the case 100, heat dissipation in the heat dissipation portion 112 is promoted, and the heat dissipation performance is further improved.

[0035] The case 100 can be manufactured, for example, by insert molding. That is, the case 100 shown in Figure 1 can be manufactured by injection molding the resin part 120 together with the metal case 110 shown in Figure 4. This allows the case 100 with the above configuration to be manufactured quickly and easily.

[0036] [Other embodiments] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above and can be modified in various ways.

[0037] For example, in case 100, the resin part 120 does not necessarily have to form a honeycomb structure on the side wall portion 110b of the metal case 110. In case 100, the shape of the first opening 121 may be a polygon other than a hexagon (triangular, square, octagonal, etc.), and the resin part 120 may form a planar filling structure other than a honeycomb structure. In this case as well, it is preferable that the multiple through holes 113 in the side wall portion 110b of the metal case 110 are provided at positions corresponding to the nodes of the planar filling structure formed by the resin part 120.

[0038] Furthermore, in case 100, it is sufficient that a second opening 122 is formed in the resin part 120 on the side wall portion 110b of the metal case 110, and the resin part 120 does not need to form a planar filling structure. In case 100, the configuration of the resin part 120 on the outer surface of the side wall portion 110b of the metal case 110 (such as the position, shape, and size of the second opening 122) can be designed in various ways depending on the required heat dissipation and mechanical strength.

[0039] Furthermore, in case 100, it is not necessary for the side wall portion 110b of the metal case 110 to have an uneven surface. In case 100, the configuration of the side wall portion 110b of the metal case 110 can be designed in various ways depending on the required weight, mechanical strength, etc.

[0040] In addition, the case 100 may have two or more first openings 121 in the resin part 120, meaning that two or more heat-absorbing parts 111 may be provided on the inner surface of the bottom part 110a of the metal case 110. The case 100 may also house two or more electronic components. Furthermore, in the case 100, the first openings 121 of the resin part 120 can have various planar shapes depending on the configuration of the electronic components held by the heat-absorbing parts 111.

[0041] Furthermore, in case 100, as described above, it is preferable that the surface of the metal case 110 is covered without gaps by the resin part 120 except for the first opening 121 and the second opening 122, but other openings may be provided in the resin part 120 in response to requirements other than the objectives of the present invention.

[0042] Furthermore, the shape of case 100 can be varied depending on the installation space and other factors. The shape of case 100 can be varied depending on the design of the metal case 110. For example, case 100 can be cylindrical with a circular cross-section, or polygonal prism with a cross-section other than a rectangle. Also, case 100 may have a configuration in which at least a portion of the top is closed off.

[0043] [Examples] The following describes embodiments of the present invention. In this embodiment, models M1 to M5, which represent only the side walls of the case, were analyzed. Models M1 to M5 are all constructed as plate-like bodies with a thickness of 4 mm. Figures 5A to 5E show models M1 to M5. Models M2 to M5 use fiber-reinforced grade PPS with glass fibers filled in as the resin.

[0044] Model M1 represents a structure formed by aluminum die casting using an aluminum alloy (A5052). Model M2 represents a structure formed by injection molding of PPS. Model M3 represents a structure in which layers of PPS are formed on both sides of a sheet metal (1 mm thick) of aluminum alloy (A5052) with multiple through holes formed therein, by injection molding PPS as an integral part of the sheet metal. Models M1 to M3 are comparative examples of the present invention.

[0045] Model M4 represents a configuration in which PPS is injection molded integrally with a sheet metal (1 mm thick) of aluminum alloy (A5052) with multiple through holes, and one of the PPS layers on both sides of the sheet metal has a honeycomb structure. Model M5 represents a configuration in which PPS is injection molded integrally with a sheet metal (1 mm thick) of aluminum alloy (A5052) with uneven areas and multiple through holes formed by press molding, and one of the PPS layers on both sides of the sheet metal has a honeycomb structure. Models M4 and M5 are embodiments of the present invention.

[0046] Weight and mechanical strength analyses were performed for models M1 to M5. In the mechanical strength analysis, the four sides of each model were fixed, and the maximum deformation in the thickness direction was determined when a uniformly distributed load of 1000N was applied to the entire surface from the outside. Table 1 shows the analysis results for weight and deformation for each model M1 to M5.

[0047] [Table 1]

[0048] As shown in Table 1, models M2 to M5, which use resin, were significantly lighter than model M1, which is made entirely of metal. Furthermore, model M4, which had a significantly reduced amount of resin compared to model M2, was the lightest.

[0049] Furthermore, in Model M5, which uses sheet metal with uneven surfaces and a honeycomb structured resin section, the deformation was the smallest among the resin-based Models M2 to M5, and high mechanical strength was achieved. In addition, although Model M4 had the largest deformation among the Models M1 to M5, it can be evaluated that the deformation was suppressed by the action of the honeycomb structured resin section, resulting in high mechanical strength, given that the resin section was significantly reduced compared to Model M3 to prioritize heat dissipation and weight. Model M2 showed good results in both weight and deformation, but because it does not contain metal parts, it has drawbacks such as difficulty in ensuring strength in high-temperature environments and inability to achieve heat dissipation and electromagnetic shielding.

[0050] Next, thermal conduction analysis was performed on models M2 to M5, which used resin. In the thermal conduction analysis, the in-plane temperature distribution of the surface was determined for each model M2 to M5 under the condition that the central part in the long-side direction at the short-side end was maintained at 200°C. Figures 6A to 6D are temperature distribution diagrams showing the results of the thermal conduction analysis for models M2 to M5.

[0051] In models M4 and M5, shown in Figures 6C and 6D, the temperature rise on the surface is more widespread compared to models M2 and M3, shown in Figures 6A and 6B. This indicates that M4 and M5 dissipate heat more efficiently than models M2 and M3, resulting in higher heat dissipation performance. [Explanation of symbols]

[0052] 100: Case 110: Metal case 110a: bottom 110b: Side wall part 111: Heat absorption section 112: Heat dissipation part 113: Through hole 120: Resin part 121: First opening 122: Second opening 123: Connection part

Claims

1. A metal case having a bottom and side walls formed with multiple through holes, A resin part having a first opening that covers the metal case and partially exposes the inner surface of the bottom, a plurality of second openings that partially expose the outer surface of the side wall, and a plurality of connecting parts that fill the plurality of through holes and connect the inner surface portion and the outer surface portion of the side wall, A case that possesses the following characteristics.

2. The case described in claim 1, Within the first opening, the electronic component is held on the inner surface of the bottom, The maximum diameter of the plurality of through holes is less than or equal to half the wavelength of the electromagnetic waves emitted by the electronic component. case.

3. The case described in claim 1 or 2, In at least a portion of the outer surface of the side wall portion, the plurality of second openings are arranged regularly, so that the resin portion forms a planar filling structure. case.

4. The case described in claim 3, The aforementioned planar tile structure is a honeycomb structure. case.

5. The case described in claim 1 or 2, The side wall portion has an uneven region in which an uneven shape is formed on both the inner and outer surfaces. case.

6. The case described in claim 5, In the aforementioned uneven region, the inner surface of the side wall portion has a dimple shape. case.

7. The case described in claim 6, The outer surface of the side wall portion protrudes within the plurality of second openings. case.

8. The case described in claim 1 or 2, The resin portion completely covers the inner surface of the side wall portion without any gaps. case.

9. The case described in claim 1 or 2, The resin part is injection molded integrally with the metal case. case.

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