Friction stir welding method and battery pack

Abstract

To provide a friction stir welding method capable of improving welding strength at a terminal end portion of friction stir welding, and a battery pack welded by the friction stir welding method.SOLUTION: A friction stir welding method for joining metallic members M1 and M2 by overlapping the metallic members M1 and M2 and moving a joining tool 10 includes: a terminal end portion forming process for forming a closed space at a terminal end portion of a joining line 20 which is a moving locus of the joining tool 10, and a drawing process for moving the joining tool 10 to the inside of the closed space and drawing the joining tool 10 from the metallic members M1 and M2.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a friction stir welding method and a battery pack formed by the friction stir welding method. [Background technology]

[0002] Friction stir welding (FSW) is known as a method for joining metal members together. In this friction stir welding, two metal members to be joined are overlapped, and a joining tool is pressed against one of the metal members while rotating, softening the one metal member with frictional heat and penetrating it, while the one metal member and the other metal member are stirred by the rotational force of the joining tool to cause plastic flow. The plastically flowed material then rapidly loses frictional heat and cools and solidifies, thereby joining the one metal member and the other metal member.

[0003] Incidentally, in this friction stir welding method, a hole (hereinafter, probe hole) is formed at the terminal end when the welding tool is withdrawn.

[0004] Fig. 1 is a cross-sectional view showing a state in which the joining tool 10 has been removed from the terminal end, and Fig. 2 is a schematic diagram of a joining end portion when the joining tool 10 has been moved linearly and removed from the terminal end. In Fig. 2 (also in Figs. 3 and 4), reference numeral 11A denotes a joining mark made by the shoulder 11, and reference numeral 12A denotes a probe hole portion formed when the probe 12 is removed. The thick solid line in the figure denotes a joining line 20, which is the movement trajectory of the axis of the probe 12. Note that the joining line 20 is an imaginary line for the purpose of explanation, and does not generally remain after joining.

[0005] As shown in Fig. 1, the welding tool 10 has a probe (projection) 12 that projects along the axis from the tip of a cylindrical shoulder 11. As shown in Fig. 2, when the welding tool 10 is moved linearly as shown by arrow Y1 and pulled out at the end of a welding line 20, a probe hole 12A in the shape of the probe 12 is formed at the welding end. When the probe hole 12A is formed, the interface between one metal member M1 and the other metal member M2 is exposed (see Fig. 1). In addition, the welding area around the probe hole 12A is narrow, and the welding strength is weak.

[0006] In order to solve such problems, Patent Document 1 describes a method in which, as shown in FIG. 3, the joining tool 10 is moved linearly as indicated by the arrow Y2, and then the joining tool is moved in an arc at the end of the joining line 20, more specifically, in a J-shape, to form a joining end portion. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-152759 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, even the bonding method described in Patent Document 1 had room for improvement in terms of bonding strength. In particular, when forming a flow path between two bonded members, water pressure acts around the probe hole, and water leakage occurs if the bonding strength is weak.

[0009] The present invention provides a friction stir welding method capable of improving the joint strength at an end portion of friction stir welding, and a battery pack joined by the friction stir welding method. [Means for solving the problem]

[0010] The present invention relates to A friction stir welding method in which at least two workpieces are overlapped and the workpieces are joined together by moving a welding tool, an end forming step of forming a closed space at an end of a welding line which is a moving trajectory of the welding tool; and a withdrawal process of moving the welding tool to the inside of the closed space and withdrawing the welding tool from the workpieces.

[0011] The present invention also provides a method for producing a semiconductor device comprising the steps of: a battery module in which a plurality of battery cells are stacked; a battery case that houses the battery module; a plate member that is joined to the battery case to form a flow path between the battery case and the plate member, through which a fluid for adjusting a battery temperature flows; At least one of the battery case and the plate member has a protrusion protruding toward the other, The protruding portion is joined by friction stir welding to form a joint, The joint portion has a linear portion extending in an extension direction of the protruding portion and a circular portion formed at one of the ends of the linear portion, The width of the circular portion is greater than the width of the linear portion. Effect of the Invention

[0012] According to the present invention, the welding tool can improve the welding strength at the end portion of the welding line. [Brief description of the drawings]

[0013] [Figure 1] 4 is a cross-sectional view showing a state in which the joining tool 10 has been pulled out at the terminal end portion. FIG. [Diagram 2] 1 is a schematic diagram of a weld end portion when the welding tool 10 is moved linearly and then pulled out at the end portion. FIG. [Diagram 3] 1 is a schematic diagram of a weld end portion when the welding tool 10 is moved linearly, and then moved in a circular arc (J-shape) at the end portion and then pulled out. [Figure 4] 1 is a schematic diagram of a weld end portion when the welding tool 10 is moved linearly, and then moved in a circular motion at the end portion and then pulled out. [Diagram 5] FIG. 5 is a schematic diagram showing the joint end portion of FIG. 4. [Figure 6] 2 is a perspective view showing the inside of a battery pack 50. FIG. [Figure 7] 13 is a diagram showing a cover plate 70 that is friction stir welded to a bottom plate 61 of a battery case 60. FIG. [Figure 8] 13 is a diagram showing the bottom surface of the battery case 60 to which the cover plate 70 is joined. [Figure 9] 9 is a cross-sectional view taken along line AA in FIG. 8. [Figure 10] FIG. 9 is an enlarged view of part B in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of a friction stir welding method and a battery pack formed by the friction stir welding method of the present invention will be described with reference to the drawings.

[0015] FIG. 4 is a schematic diagram showing one embodiment of the friction stir welding method of the present invention, in which the welding tool 10 is moved linearly, and then moved in a circular motion at the end portion and then pulled out.

[0016] The friction stir welding method of this embodiment includes an end formation process for forming a closed space at the end of the welding line 20, which is the movement trajectory of the probe 12 of the welding tool 10, and a withdrawal process for moving the welding tool 10 into the inside of this closed space and withdrawing the welding tool 10.

[0017] In the terminal end forming process, as shown in Fig. 4, the probe 12 of the joining tool 10 is moved, for example, linearly as indicated by the arrow Y11, and then moved from a position (position P1 in the figure) before the target extraction position G in a circular motion with the target extraction position G as its center. Note that dashed line Q1 in the figure indicates the shoulder 11 when the probe 12 is at position P1. Position P1 is, as an example, the point where the shoulder 11 reaches the target extraction position G. The target extraction position G is a target position that corresponds to the axis of the probe 12 when the joining tool 10 is extracted.

[0018] To explain the processing in the terminal end formation process more specifically, the joining tool 10 is moved counterclockwise around the target extraction position G at the terminal end so that the probe 12 moves from position P1 → position P2 → position P3 → position P4 → position P5 (position P1), for example, as shown by arrows Y12 and Y13.

[0019] By moving the welding tool 10 in a circular motion around the target withdrawal position G, a circular closed space is formed at the welding line 20. If the diameter of this circular closed space is D1 and the diameter of the probe 12 is D2, it is preferable that D1>D2 be satisfied.

[0020] Moreover, it is preferable that the closed space is formed so as to overlap a part of the welding line 20. That is, in this embodiment, the trajectory of the probe 12 from position P5 to position P6 overlaps a part of the trajectory of the probe 12 from position P1 to position P2. In this manner, by moving the welding tool 10 so that a part of the welding line 20 overlaps, it is possible to reliably form the closed space.

[0021] However, if the overlap amount is too large, the time required for the joining process will increase, so the overlap amount is preferably 180° or less, more preferably 90° or less, and even more preferably 60° or less, centered on the target extraction position G.

[0022] Next, the probe 12 is moved inside the circular closed space to the target extraction position G.

[0023] In the withdrawal process, the welding tool 10 is withdrawn after the probe 12 reaches the target withdrawal position G. At this time, by setting the diameter D1 of the closed space to be larger than the diameter D2 of the probe 12, the probe 12 of the welding tool 10, which becomes the probe hole portion 12A after the welding tool 10 is withdrawn, can be positioned inside the closed space.

[0024] In this way, by withdrawing the welding tool 10 inside the closed space formed at the end of the welding line 20, a welding region of the two workpieces is formed outside the withdrawal position (target withdrawal position G). In FIG. 5, only the region of the welding region that does not overlap with the shoulder 11 of the welding tool 10 during withdrawal is hatched. That is, the welding region in which the metal members M1 and M2 are stirred and plastically flowed is formed outside the probe hole 12A. Therefore, even if the welding strength of the welding region at the withdrawal position (target withdrawal position G) is low, the welding strength can be improved because the welding is strong outside the probe hole 12A.

[0025] In this embodiment, the welding tool 10 is moved counterclockwise around the target withdrawal position G, but it goes without saying that the welding tool 10 may be moved clockwise. Also, the closed space is not limited to a circle as long as it is a closed space when viewed from above, and may be a polygon such as a triangle or a rectangle, or may be an ellipse.

[0026] Next, a battery pack to which the above-mentioned friction stir welding method is applied will be described with reference to Figs. 6 to 8. In the following description, for convenience, a coordinate system consisting of a front-rear direction, a left-right direction, and an up-down direction that are mutually perpendicular will be used. In the drawings, the front is indicated as Fr, the rear as Rr, the left side as L, the right side as R, the upside as U, and the downside as D. However, these directions are unrelated to the direction in which the battery pack is mounted on the device. For example, when the battery pack is mounted on a vehicle, the up-down direction of the battery pack may face the traveling direction of the vehicle when mounted on the vehicle, or may face the vehicle width direction.

[0027] FIG. 6 is an oblique view showing the inside of the battery pack 50, FIG. 7 is a diagram showing a cover plate 70 that is friction stir welded to a bottom plate 61 of a battery case 60, FIG. 8 is a diagram showing the bottom surface of the battery case 60 to which the cover plate 70 is joined, FIG. 9 is a cross-sectional view along line AA in FIG. 8, and FIG. 10 is an enlarged view of portion B in FIG. 8.

[0028] As shown in Fig. 6, the battery pack 50 includes a battery module 51 in which a plurality of battery cells are stacked, and a battery case 60 that houses the battery module 51. Note that Fig. 5 illustrates only two battery modules 51, and does not illustrate the other battery modules 51. The number and arrangement of the battery modules 51 housed in the battery case 60 can be set as appropriate.

[0029] As shown in FIG. 6, the battery case 60 includes a rectangular bottom plate 61 on which a plurality of battery modules 51 are mounted, a side wall 62 standing upright from the outer edge of the bottom plate 61, and a plurality of cross members 63.

[0030] The battery case 60 is formed, for example, from an aluminum alloy containing aluminum. More specifically, the bottom plate 61, the side walls 62, and the multiple cross members 63 of the battery case 60 are formed by aluminum die casting. The aluminum die casting is formed by melting an aluminum alloy, filling it at high speed into a mold using a die casting machine, and then applying high pressure. By forming the battery case 60 from an aluminum alloy, the weight of the battery pack 50 can be reduced.

[0031] As shown in Fig. 7, the bottom plate 61 of the battery case 60 is covered with a plate-shaped cover plate 70 arranged below by friction stir welding. The cover plate 70 is, for example, a press-molded product made of iron. Referring also to Fig. 8, a refrigerant flow path 80 is formed between the bottom plate 61 and the cover plate 70 of the battery case 60. The battery module 51 accommodated inside the battery case 60 is cooled and / or heated by the refrigerant flowing through the refrigerant flow path 80, and the temperature of the battery can be adjusted.

[0032] More specifically, projections and recesses are provided on each of the bottom plate 61 and the cover plate 70. The bottom plate 61 is provided with a projection 611 that projects toward the outside of the battery case 60, i.e., toward the cover plate 70 side, and a recess 612 that is recessed on the opposite side of the cover plate 70 from the projection 611.

[0033] The cover plate 70 is provided with a protrusion 701 protruding toward the bottom plate 61 side, and a recess 702 recessed on the opposite side of the bottom plate 61 from the protrusion 701 .

[0034] 8, in friction stir welding, the joining tool 10 is moved along the extension direction of the convex parts 611, 701 while the convex parts 611 of the bottom plate 61 and the convex parts 701 of the cover plate 70 are in contact with each other. At this time, the aforementioned end forming process of forming a closed space at the end part of the joining line 20, which is the movement trajectory of the probe 12 of the joining tool 10, and the withdrawal process of moving the joining tool 10 into the inside of this closed space and withdrawing the joining tool 10 are performed.

[0035] In the terminal end forming process, the welding tool 10 is moved so as to draw a circle centered on the target extraction position G, so that, as shown in Fig. 10, the joint on the protrusions 611, 701 is provided with a linear portion 21 extending in the extension direction of the protrusions 611, 701 and a circular portion 22 formed at the terminal end, which is one of the ends of the linear portion 21. The width, i.e., the diameter, of the circular portion 22 is larger than the width of the linear portion 21 extending linearly.

[0036] Then, in the withdrawal process, the joining tool 10 is moved inside the circular portion 22, which is a closed space, and then the probe 12 withdraws the joining tool 10 at the target withdrawal position G, thereby forming a probe hole portion 12A in the center of the circular portion 22 (see Figure 5).

[0037] As shown in Figs. 7, 8, and 10, in the convex portions 611, 701, the width T1 of the region R1 where the linear portion 21 is formed is smaller than the width T2 of the convex portions 611, 701 in the region R2 where the circular portion 22 is formed. In principle, it is preferable to minimize the width of the convex portions 611, 701 in consideration of the heat capacity of the refrigerant flow path 80. On the other hand, in order to perform the above-mentioned terminal portion forming step and drawing step, the convex portions 611, 701 are required to have a width larger than that of the circular portion 22. Therefore, by increasing only the width of the terminal portion of the convex portions 611, 701 where the circular portion 22 is formed, it is possible to form the circular portion 22 in the terminal portion forming step and drawing step while ensuring the heat capacity of the refrigerant flow path 80.

[0038] In this way, by applying the above-described friction stir welding method to the manufacture of the battery pack 50 and forming the refrigerant flow path 80 between the bottom plate 61 and the cover plate 70 of the battery case 60, it is possible to improve the bonding strength between the bottom plate 61 and the cover plate 70. Furthermore, by improving the bonding strength between the bottom plate 61 and the cover plate 70, it is possible to prevent the refrigerant from leaking even if the water pressure of the refrigerant flowing between the bottom plate 61 and the cover plate 70 acts on the bonding area.

[0039] In the present embodiment, the convex portion 611 of the bottom plate 61 and the convex portion 701 of the cover plate 70 are brought into contact with each other and friction stir welded to form the coolant flow path 80 by the concave portions 612, 702, but the present invention is not limited to this. For example, only one side may be a convex portion and the other side may be a flat portion, and the coolant flow path 80 may be formed between the flat portion and the concave portion.

[0040] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present invention. Furthermore, the components in the above-mentioned embodiments may be arbitrarily combined within the scope of the invention.

[0041] For example, the battery pack 50 has been given as an example of an application of the friction stir welding method described above, but the present invention is not limited to this, and can be applied to at least two metal members that are members to be welded together.

[0042] This specification describes at least the following items. Note that, in parentheses, components corresponding to those in the above-mentioned embodiment are shown, but the present invention is not limited to these.

[0043] (1) A friction stir welding method in which at least two workpieces (metal members M1, M2) are overlapped and the workpieces are joined together by moving a welding tool (welding tool 10), a terminal end forming process for forming a closed space at a terminal end of a welding line (welding line 20) which is a moving trajectory of the welding tool; and a withdrawal process of moving the welding tool to the inside of the closed space and withdrawing the welding tool from the workpieces. Friction stir welding method.

[0044] According to (1), by withdrawing the welding tool inside the closed space formed at the end of the welding line, which is the moving path of the welding tool, the welding area can be formed outside the withdrawal position, so that the welding strength can be improved. Also, when the space between the two workpieces is made to be an enclosed space, the sealing performance can be improved.

[0045] (2) The friction stir welding method according to (1), The closed space is circular, The welding tool has a cylindrical shape with a protrusion (probe 12) at the tip, the joining line is a movement path of the axis of the protrusion, The diameter (diameter D1) of the closed space is larger than the diameter (diameter D2) of the protrusion of the welding tool. Friction stir welding method.

[0046] According to (2), the projection of the joining tool, which becomes the hole after extraction, can be positioned inside the closed space, so that the joining strength and sealing performance can be appropriately improved.

[0047] (3) A friction stir welding method according to (1) or (2), In the end portion forming step, the closed space is formed so that a part of the joining line overlaps. Friction stir welding method.

[0048] According to (3), by moving the welding tool so that the welding lines partially overlap, a closed space can be reliably formed.

[0049] (4) The friction stir welding method according to (3), The amount of overlap of the bond lines is 180° or less. Friction stir welding method.

[0050] According to (4), by making the overlapping amount of the joining lines 180° or less, the time required for the joining process can be shortened.

[0051] (5) a battery module (battery module 51) in which a plurality of battery cells are stacked; a battery case (battery case 60) that houses the battery module; a plate member (cover plate 70) that is joined to the battery case to form a flow path (refrigerant flow path 80) between the battery case and the plate member, through which a fluid for adjusting the battery temperature flows; At least one of the battery case and the plate member has a protrusion (protrusion 611, 701) protruding toward the other, The protruding portion is joined by friction stir welding to form a joint, The joint portion has a linear portion (linear portion 21) extending in the extension direction of the protruding portion, and a circular portion (circular portion 22) formed at one of the ends of the linear portion, The width of the circular portion is greater than the width of the linear portion. Battery pack.

[0052] According to (5), the joint between the battery case and the plate member has a circular portion having a width larger than that of the linear portion at one of the ends of the linear portion, thereby improving the joint strength and the sealing performance of the flow path formed between the battery case and the plate member through which the battery temperature control fluid flows.

[0053] (6) The battery pack according to (5), The circular portion is formed with a hole portion (probe hole portion 12A) recessed from the plate member side to the battery case side. Battery pack.

[0054] According to (6), since there is a circular portion around the hole through which the welding tool is withdrawn, the welding strength around the hole can be improved.

[0055] (7) A battery pack according to (5) or (6), a width (width T1) of the convex portion in a region (region R1) where the linear portion is formed is smaller than a width (width T2) of the convex portion in a region (region R2) where the circular portion is formed; Battery pack.

[0056] According to (7), while ensuring the heat capacity of the flow path through which the battery temperature control fluid flows, a circular portion having high joining strength can be formed at one end of the linear portion by friction stir welding. [Explanation of symbols]

[0057] 10 Joining tools 12 Probe (protrusion) 12A Probe hole (hole) 20 Joining line 21 Linear section 22 Circular part 50 Battery Pack 51 Battery Module 60 Battery case 70 Cover plate (plate member) 80 Coolant flow path (flow path) D1 Diameter (diameter of closed space) D2 diameter (diameter of protrusion) R1 Region where linear part is formed R2 Region where the circular part is formed T1 Width T2 width

Claims

1. A friction stir welding method in which at least two workpieces are overlapped and the workpieces are joined together by moving a welding tool, an end forming step of forming a closed space at an end of a welding line which is a moving trajectory of the welding tool; and a withdrawal process of moving the welding tool to the inside of the closed space and withdrawing the welding tool from the workpieces. Friction stir welding method.

2. The friction stir welding method according to claim 1, The closed space is circular, The welding tool has a cylindrical shape with a protrusion at a tip end, the joining line is a movement path of the axis of the protrusion, The diameter of the closed space is larger than the diameter of the projection of the welding tool. Friction stir welding method.

3. The friction stir welding method according to claim 1 or 2, In the end portion forming step, the closed space is formed so that a part of the joining line overlaps. Friction stir welding method.

4. The friction stir welding method according to claim 3, The amount of overlap of the bond lines is 180° or less. Friction stir welding method.

5. a battery module in which a plurality of battery cells are stacked; a battery case that houses the battery module; a plate member that is joined to the battery case to form a flow path between the battery case and the plate member, through which a fluid for adjusting a battery temperature flows; At least one of the battery case and the plate member has a protrusion protruding toward the other, The protruding portion is joined by friction stir welding to form a joint, The joint portion has a linear portion extending in an extension direction of the protruding portion and a circular portion formed at one of the ends of the linear portion, The width of the circular portion is greater than the width of the linear portion. Battery pack.

6. 6. The battery pack according to claim 5, The circular portion is formed with a hole recessed from the plate member side to the battery case side. Battery pack.

7. 7. The battery pack according to claim 5, a width of the protrusion in a region where the linear portion is formed is smaller than a width of the protrusion in a region where the circular portion is formed; Battery pack.

Images