Cooling unit and method for manufacturing the same

Abstract

To provide a cooling unit having satisfactory reliability that can secure joint strength between a unit main body and a sealing body, and a manufacturing method for a cooling unit.SOLUTION: A cooling unit comprises a unit main body having a bottom part and a peripheral wall part standing up from a peripheral edge of the bottom part, and a sealing body sealing an opening of the unit main body. A plasticized area is formed at a butted part between the unit main body and the sealing body, and an air void is formed closer to the unit main body than the center of the plasticized area.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cooling unit used for cooling in-vehicle equipment and other electronic devices, and a method for manufacturing the cooling unit. [Background technology]

[0002] In recent years, as the performance of power conversion semiconductor devices used for inverter control in vehicle chargers, air conditioners, air conditioning equipment, personal computers, and other electronic devices has improved, the amount of heat generated by the electronic components (heat generating elements) installed in them has increased, making cooling of the electronic components important.

[0003] Electric vehicles and plug-in hybrid vehicles are equipped with an on-board charger for charging the battery, which is a storage battery. Typically, the on-board charger is provided with a cooling unit to prevent components from burning out due to a rise in temperature while the battery is being charged (see, for example, Patent Documents 1 and 2). In particular, Patent Document 2 discloses a manufacturing method for maintaining the watertightness and airtightness of a liquid-cooled cooling unit, in which a jacket body and a sealing body, which are metallic components, are joined by friction stir welding. Friction stir welding (FSW) is a method of joining metal components in a solid state by moving a rotating tool along the butt joint between the metal components while rotating, and causing the metal in the butt joint to plastically flow due to the frictional heat between the rotating tool and the metal components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5572678 [Patent Document 2] JP 2015-131321 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the liquid cooling jacket disclosed in Patent Document 2, the jacket body has a complex shape and is therefore made of, for example, a cast aluminum alloy material, whereas components such as the sealing body, which have a relatively simple shape, are made of a wrought aluminum alloy material. In this way, when manufacturing a liquid cooling jacket by joining aluminum alloy components of different materials, the jacket body is generally harder than the sealing body, and when the two are joined by friction stir welding, the material resistance that the stirring pin, which is a rotating tool, experiences from the jacket body side is greater than the material resistance that it experiences from the sealing body side. Therefore, when the size of the liquid cooling jacket increases and the dimensional variation between the jacket body and the sealing body increases, and when the shape variation occurs, such as the occurrence of a gap at the butt joint, it becomes difficult to mix the different materials in a balanced manner using the stirring pin, and there is a risk of voids occurring in the plasticized region after joining. Here, the plasticized region refers to the region where the rotating tool is pressed into the butt joint to stir, and the region around it where plastic flow occurs due to stirring. Furthermore, in the plasticized region, there is a stress concentration area when water pressure is applied by the cooling water flowing through the liquid cooling jacket, and if there is a void near the stress concentration area, it may trigger crack growth and reduce the joining strength.

[0006] An object of the present disclosure is to provide a cooling unit and a method for manufacturing the cooling unit that can ensure the bonding strength between the unit body and the sealing body and have good reliability. [Means for solving the problem]

[0007] The cooling unit according to the present disclosure comprises: a unit body having a bottom and a peripheral wall rising from a peripheral edge of the bottom; a seal for sealing the opening of the unit body, a plasticized region is formed at the butt joint between the unit body and the sealing body, A void is formed on the unit body side from the center of the plasticized region. And, The size of the gap in at least one of a direction parallel to and a direction perpendicular to the bottom of the unit body is 0.3 mm or more and 1.0 mm or less.

[0008] A method for manufacturing a cooling unit according to the present disclosure includes: a first step of processing a unit body having a bottom and a peripheral wall rising from a peripheral edge of the bottom to form a step portion on an inner peripheral edge of the peripheral wall, the step portion being composed of a step bottom surface and a step side surface rising from the step bottom surface toward an opening of the unit body; a second step of placing a sealing body that seals the opening of the unit body on the bottom surface of the step with a side surface of the sealing body butting against the step side surface to form an abutting portion having a gap between the side surface of the sealing body and the step side surface; A third step of performing friction stir welding by inserting a rotating tool into the butted portion and moving the rotating tool along the butted portion while rotating the rotating tool; Including fruit, In the third step, the rotation direction and movement direction of the rotating tool are set so that a gap is formed on the unit body side of the center of the plasticized region formed by the friction stir welding, and the rotation speed and movement speed of the rotating tool are set so that the size of the gap in at least one of the directions parallel to and perpendicular to the bottom of the unit body is 0.3 mm or more and 1.0 mm or less. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a cooling unit and a method for manufacturing a cooling unit that can ensure the bonding strength between the unit body and the sealing body and have good reliability. [Brief description of the drawings]

[0010] [Figure 1] 1A and 1B are perspective views showing a configuration of a cooling unit according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a joined state of the cooling unit according to the embodiment. [Diagram 3] 3A to 3D are diagrams illustrating a manufacturing process of the cooling unit according to the embodiment. [Figure 4] 4A to 4C are diagrams illustrating the mechanism by which a gap is formed in the cooling unit according to the embodiment. [Diagram 5] FIG. 5 is a cross-sectional view showing a modified example of the bonded body of the cooling unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of a cooling unit according to the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiment described below.

[0012] <Cooling unit 1 structure> 1A and 1B are perspective views showing a configuration of a cooling unit 1 according to an embodiment. Fig. 1A shows an exploded view of the cooling unit 1 before bonding, and Fig. 1B shows the cooling unit 1 in the middle of bonding. Fig. 2 is a cross-sectional view showing the bonding state of the cooling unit 1.

[0013] 1A and 1B, the cooling unit 1 includes a unit body 10 and a sealing body 20. The sealing body 20 is joined so as to close the opening 14 of the unit body 10, thereby forming an enclosed space through which cooling water flows. The cooling unit 1 is provided, for example, in an on-board charger, and prevents components from burning out due to a rise in temperature during charging of the battery. Although not shown, a circulation flow path that circulates cooling water in the enclosed space is connected to the cooling unit 1.

[0014] The unit body 10 is a box member having a bottom 11 and a peripheral wall portion 12 rising from the peripheral edge of the bottom portion 11. The unit body 10 has, for example, a rectangular box shape having a rectangular opening 14 in a plan view. The unit body 10 also has a step portion 13 consisting of a step bottom surface 131 and a step side surface 132 on the inner peripheral edge of the peripheral wall portion 12 on the opening 14 side. The step side surface 132 is formed to rise from the step bottom surface 131 toward the opening 14.

[0015] The sealing body 20 is a flat plate member that closes the opening 14, and has a size and shape that conform to the opening 14. The sealing body 20 is placed on the step bottom surface 131 with the side surface 21 of the sealing body 20 butting against the step side surface 132, and is joined to the unit body 10 by friction stir welding. A plasticized region 33 is formed at the joint between the unit body 10 and the sealing body 20. A friction stir welding rotary tool 40 is used for the friction stir welding. The rotary tool 40 is made of, for example, tool steel, and has a cylindrical shoulder portion 41 and a stirring pin 42 protruding from the lower end surface of the shoulder portion 41 (see FIG. 3C).

[0016] In this embodiment, the void 34 generated by friction stir welding is formed on the unit body 10 side of the center C of the plasticized region 33, specifically, inside the peripheral wall portion 12 of the unit body 10. In other words, when cooling water flows through the cooling unit 1 and water pressure is applied, a stress concentration portion 35 is formed on the sealing body 20 side of the plasticized region 33, but no void 34 is present in the vicinity of this stress concentration portion 35. Therefore, it is possible to prevent cracks from propagating starting from the void 34 and reducing the joint strength.

[0017] Here, even if the void 34 is located closer to the unit body 10 than the center C of the plasticized region 33, the mechanical strength of the cooling unit 1 may be reduced depending on the size of the void 34. Therefore, it is desirable that the size of the void 34 is 0.3 mm or more and 1.0 mm or less in the direction perpendicular to the step side surface 132, or 0.3 mm or more and 1.0 mm or less in the direction perpendicular to the step bottom surface 131. This allows the mechanical strength of the cooling unit 1 to be maintained.

[0018] The size of the gap 34 is controlled by the size of the gap 32 formed between the sealing body 20 and the unit body 10, and the rotation speed and moving speed of the rotating tool 40. For example, when the rotation speed and moving speed of the rotating tool 40 are constant, the size of the gap 34 depends on the size of the gap 32.

[0019] Moreover, the unit body 10 and the sealing body 20 are formed of, for example, an aluminum alloy, which can provide the thermal conductivity and mechanical strength required for the cooling unit 1 and reduce the weight of the cooling unit 1.

[0020] In particular, the first aluminum alloy forming the unit body 10 is a material type having a higher hardness than the second aluminum alloy forming the sealing body 20. This can increase the durability of the cooling unit 1.

[0021] Furthermore, the unit body 10 is preferably formed from an aluminum alloy casting material. This can improve the castability, strength, machinability, etc. of the unit body 10. Furthermore, the sealing body 20 is preferably formed from an aluminum alloy wrought material. This can improve the processability and thermal conductivity.

[0022] <Method of manufacturing cooling unit 1> The above-described cooling unit 1 is manufactured, for example, by the steps shown below. Figures 3A to 3D are diagrams showing the manufacturing steps of the cooling unit 1. Furthermore, the mechanism by which the gap 34 is formed in the cooling unit 1 is shown in Figures 4A to 4C.

[0023] First, in a first step, the unit body 10 is processed to form the step portion 13 on the inner peripheral edge of the peripheral wall portion 12 on the opening 14 side, as shown in FIG. 3A.

[0024] 3B, the sealing body 20 is placed on the step bottom surface 131 with the side surface 21 of the sealing body 20 and the step side surface 132 butted against each other. Then, an abutting portion 31 is formed between the side surface 21 of the sealing body 20 and the step side surface 132. At this time, due to dimensional variations between the unit body 10 and the sealing body 20, a gap 32 is formed between the step side surface 132 and the side surface 21 of the sealing body 20. The width of the gap 32 is 0.1 mm or more and 1.0 mm or less.

[0025] 3C and 3D, a rotating tool 40 is pressed into the butt joint 31 and moved along the butt joint 31 while rotating to perform friction stir welding. Note that the start and end points of friction stir welding do not have to be located on the butt joint 31.

[0026] 4A, the rotation direction R and the moving direction M of the rotation tool 40 are set so that the unit body 10 side is the advancing side (AS) in the rotation direction R of the rotation tool 40 and the sealing body 20 side is the retreating side (RS) in the rotation direction R of the rotation tool 40. In addition, the rotation speed and the moving speed of the rotation tool 40 are set so that the voids 34 remain in the unit body 10 and are formed outside the plasticized region 33, as will be described later.

[0027] When the rotary tool 40 is moved along the butt joint 31, the sealing body 20 on the retreating side in the rotation direction R flows and fills the rear part of the rotary tool 40 in the moving direction M. At this time, a gap 32 is formed between the sealing body 20 and the unit body 10, causing an insufficient supply of material, resulting in a void 34 occurring in the rear part of the rotary tool 40. 4C, the voids 34 move toward the unit body 10 on the advancing side due to the rotation of the rotary tool 40, but as the voids 34 move toward the unit body 10, centrifugal force is generated in the voids 34, so that the voids 34 gradually move away from the rotary tool 40. Then, the moving speed of the voids 34 slows down, and the voids 34 remain in the unit body 10 on the advancing side and are formed outside the plasticized region 33.

[0028] After the rotary tool 40 has been rotated once along the butt joint 31, the rotary tool 40 is pulled out, completing the joining of the unit body 10 and the sealing body 20. The void 34 is continuously formed along the traveling direction M of the rotary tool 40. In the above process, the plasticized region 33 is formed along the butt joint 31 in the cooling unit 1. In addition, the void 34 is formed on the unit body 10 side of the center of the plasticized region 33.

[0029] Thus, the cooling unit 1 according to the embodiment includes a unit body 10 having a bottom 11 and a peripheral wall portion 12 rising from the peripheral edge of the bottom 11, and a sealing body 20 that seals an opening 14 of the unit body 10. The unit body 10 has a step portion 13 on the inner peripheral edge of the peripheral wall portion 12, which is composed of a step bottom surface 131 and a step side surface 132 rising from the step bottom surface 131 toward the opening 14, and the sealing body 20 is placed on the step bottom surface 131 with the side surface 21 of the sealing body 20 butted against the step side surface 132. In addition, a plasticized region 33 is formed at the butted portion between the unit body 10 and the sealing body 20, and a gap 34 is formed on the unit body 10 side of the center of the plasticized region 33.

[0030] The manufacturing method of the cooling unit 1 also includes a first step (see FIG. 3A) of processing the unit body 10 having the bottom 11 and the peripheral wall portion 12 rising from the peripheral edge of the bottom 11 to form a step portion 13 consisting of a step bottom surface 131 and a step side surface 132 rising from the step bottom surface 131 toward the opening 14 of the unit body 10 on the inner peripheral edge of the peripheral wall portion 12; a second step (see FIG. 3B) of placing the sealing body 20 that seals the opening 14 of the unit body 10 on the step bottom surface 131 with the side surface 21 of the sealing body 20 butted against the step side surface 132 to form a butt joint portion 31 having a gap between the side surface 21 of the sealing body 20 and the step side surface 132; and a third step (see FIGS. 3C and 3D) of pressing a rotating tool 40 into the butt joint portion 31 and moving it along the butt joint portion 31 while rotating it to perform friction stir welding.

[0031] According to the cooling unit 1 and the manufacturing method for the cooling unit 1, even if the cooling unit becomes large or the structure becomes complicated, the bonding strength between the unit body 10 and the sealing body 20 can be ensured, and the reliability can be improved. More specifically, even if the size of the cooling unit 1 increases and the dimensional variation between the unit body 10 and the sealing body 20 increases, resulting in a shape variation such as a gap at the butt joint 31, since the void 34 is located away from the stress concentration portion 35, it is possible to prevent cracks from progressing from the void 34 as a starting point, and the joining strength can be ensured.

[0032] The disclosure by the inventors has been specifically described above based on the embodiments, but the present disclosure is not limited to the above-described embodiments and can be modified within the scope of the gist thereof.

[0033] For example, the location where the void 34 is formed may be closer to the unit body 10 than the center of the plasticized region 33, and may be formed inside the plasticized region 33 as shown in Fig. 5. In this case, the same effect as that of the cooling unit 1 described in the embodiment can be obtained. For example, in the friction stir welding process, the rotation speed or movement speed of the rotating tool 40 can be increased to position the voids 34 inside the plasticized region 33. In other words, when the rotation speed or movement speed of the rotating tool 40 is increased, the followability of the sealing body 20 on the retreating side when it flows and fills the rear part of the rotating tool 40 becomes poor, and the movement speed of the voids 34 becomes even slower than the movement speed of the rotating tool 40. Therefore, the voids 34 do not move to the unit body 10 on the advancing side, but are formed inside the plasticized region 33.

[0034] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Industrial Applicability]

[0035] The cooling unit 1 of the present disclosure is suitable for use in electronic devices equipped with a high-performance power module used for inverter control in on-board chargers, air conditioners, and the like. [Explanation of symbols]

[0036] 1 Cooling unit 10 Unit body 11 Bottom 12 Peripheral wall section 13 Step 131 Bottom of step 132 Step Side 14 Aperture 20 Sealing body 21 Side 31 Butt joint 32 Gap 33 Plasticization region 34 void 35 Stress concentration area

Claims

1. a unit body having a bottom and a peripheral wall rising from a peripheral edge of the bottom; a seal for sealing the opening of the unit body, a plasticized region is formed at the butt joint between the unit body and the sealing body, A void is formed on the unit main body side from the center of the plasticized region, The gap has a size of 0.3 mm or more and 1.0 mm or less in at least one of a direction parallel to and a direction perpendicular to the bottom of the unit body. Cooling unit.

2. The size of the gap in a direction parallel to and perpendicular to the bottom of the unit body is 0.3 mm or more and 1.0 mm or less. The cooling unit of claim 1 .

3. The void is formed in the peripheral wall portion outside the plasticized region.

3. A cooling unit according to claim 1 or 2.

4. The void is formed in a plasticized region.

3. A cooling unit according to claim 1 or 2.

5. the unit body is formed of a first aluminum alloy, the sealing body is formed of a second aluminum alloy, The first aluminum alloy is a material having a higher hardness than the second aluminum alloy. A cooling unit according to any one of claims 1 to 4.

6. The unit body is formed of an aluminum alloy casting material, The sealing body is formed of an aluminum alloy wrought material.

6. The cooling unit of claim 5.

7. a first step of processing a unit body having a bottom and a peripheral wall rising from a peripheral edge of the bottom to form a step portion on an inner peripheral edge of the peripheral wall, the step portion being composed of a step bottom surface and a step side surface rising from the step bottom surface toward an opening of the unit body; a second step of placing a sealing body that seals the opening of the unit body on the bottom surface of the step with a side surface of the sealing body butting against a side surface of the step, and forming an abutting portion having a gap between the side surface of the sealing body and the side surface of the step; A third step of performing friction stir welding by inserting a rotating tool into the butted portion and moving the rotating tool along the butted portion while rotating the rotating tool; Including, In the third step, a rotation direction and a movement direction of the rotation tool are set so that a gap is formed on the unit body side from a center of a plasticized region formed by the friction stir welding, and a rotation speed and a movement speed of the rotation tool are set so that a size of the gap in at least one of a direction parallel to and a direction perpendicular to the bottom of the unit body is 0.3 mm or more and 1.0 mm or less. A method for manufacturing a cooling unit.

8. In the third step, the rotation speed or the moving speed is set to be slower than a threshold value, and the void is formed in the peripheral wall portion that is outside the plasticized region. A method for manufacturing the cooling unit according to claim 7.

9. In the third step, the rotation speed or the movement speed is set to be faster than a threshold value, and a void is formed inside the plasticized region. A method for manufacturing the cooling unit according to claim 7.

10. In the second step, the butt joint is formed so as to be perpendicular to the bottom of the unit body, In the third step, the rotary tool is pushed in from directly above the butted portion so as to come into contact with both the unit body and the sealing body. A method for manufacturing a cooling unit according to any one of claims 7 to 9.

11. The width of the gap formed between the side surface of the sealing body and the step side surface is 0.1 mm or more and 1.0 mm or less. A method for manufacturing a cooling unit according to any one of claims 7 to 10.

12. In the third step, a rotation direction and a traveling direction of the rotation tool are set so that the unit body is on an advancing side in a rotation direction of the rotation tool and the sealing body is on a retreating side in the rotation direction. A method for manufacturing a cooling unit according to any one of claims 7 to 11.

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