Battery pack manufacturing method

Abstract

The invention relates to a manufacturing method of a battery pack. Provided is a method for manufacturing a battery pack capable of suppressing an increase in cost of the battery pack. This method for manufacturing a battery pack is a method for manufacturing a battery pack having a tray for accommodating a battery, and has a first step in which a metal insert serving as a flat surface part of the tray is provided at a predetermined position in a cavity formed by a mold, and a second step in which a melt is introduced into the cavity after the first step, and then the metal insert is inserted into the cavity after the second step. The molten liquid is solidified to form a casting ladle which forms a frame-shaped part of the tray. The method for manufacturing the battery pack further includes a third step in which the flat portion and the frame-shaped portion are joined after the second step.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing a battery pack, and more particularly to a method for manufacturing a battery pack having a tray for storing batteries. Background Technology

[0002] Patent Document 1 discloses an example of a battery pack mounted on an electric vehicle or the like.

[0003] The battery pack described in Patent Document 1 includes a box-shaped tray for storing batteries and formed as an open top, and an outer frame welded along the outer side of the side wall of the tray. The outer frame is composed of plate-shaped members or a combination thereof, and has a first protrusion welded to the outer bottom surface of the tray, a second protrusion located above the first protrusion and extending outward from the tray, an outer side portion connecting the first protrusion and the second protrusion at a position separated from the side wall of the tray outward, and an inner side portion extending from the second protrusion toward the first protrusion and welded to the outer side surface of the tray. The first protrusion, the second protrusion and the inner side portion form a part of a closed section, and an opening is provided on the outer side portion for inserting a welding torch for welding the side wall of the tray and the inner side portion.

[0004] [Prior Technology Documents]

[0005] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2015-170452 Summary of the Invention

[0007] The battery pack tray described in Patent Document 1 has multiple components. Manufacturing such a battery pack requires multiple components, and numerous welds are needed to attach them to the tray. Therefore, the technology described in Patent Document 1 has the potential to lead to high costs for the battery pack.

[0008] This disclosure was made to solve such a problem, and its purpose is to provide a method for manufacturing a battery pack that can suppress the high cost of the battery pack.

[0009] One embodiment of the battery pack manufacturing method is a battery pack manufacturing method having a tray for storing batteries, comprising a first step and a second step. In the first step, a metal insert that will become the flat part of the tray is set at a predetermined position in a cavity formed by a mold. In the second step, after molten liquid is introduced into the cavity following the first step, the molten liquid is solidified to form a casting that becomes the frame part of the tray.

[0010] According to this disclosure, a method for manufacturing a battery pack that can suppress the high cost of the battery pack can be provided. Attached Figure Description

[0011] Figure 1 This is a perspective view showing the battery pack of Embodiment 1.

[0012] Figure 2 This is a flowchart illustrating a method for manufacturing a battery pack according to Embodiment 1.

[0013] Figure 3 This is a rough cross-sectional diagram illustrating the first and second processes.

[0014] Figure 4 This is a schematic cross-sectional view illustrating the first example of the third process.

[0015] Figure 5 This is a schematic cross-sectional view illustrating the second example of the third process.

[0016] Explanation of reference numerals in the attached figures

[0017] 1: Battery pack;

[0018] 10: Tray; 11: Flange;

[0019] 12: Planar part; 12a: Peripheral part; 12s: Dating surface;

[0020] 13: Frame-shaped part; 13a: End; 13b: Recess; 13s: Mutation surface;

[0021] 14: Joint; 15: Unjoined; 16: Joint;

[0022] 20: Cover; 21: Flange;

[0023] 30: Gasket;

[0024] 50: Die-casting device; 51: Mold; 52: Fixed mold; 53: Movable mold; 54: Chamber;

[0025] 60: ejector pin;

[0026] 120: Insert; 130: Casting;

[0027] M: Molten liquid. Detailed Implementation

[0028] Implementation Method 1

[0029] The following detailed description of specific embodiments in which the present invention is applied is based on the accompanying drawings. However, the present invention is not limited to the following embodiments. Furthermore, for clarity, the following description and drawings are appropriately simplified.

[0030] Figure 1This is a perspective view showing the battery pack of Embodiment 1. Figure 1 The battery pack 1 shown is used, for example, in electric vehicles such as hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs). The battery pack 1 supplies power to the motor and electrical components of the electric vehicle.

[0031] like Figure 1 As shown, the battery pack 1 has a tray 10 and a cover 20. The materials constituting the tray 10 and the cover 20 are metals such as aluminum, aluminum alloy, and magnesium alloy. From the viewpoint of achieving lightweight and low cost of the battery pack 1, aluminum or aluminum alloy is preferred as the metal.

[0032] The tray 10 is formed as a box with an opening at the top. A flange 11, which engages with the cover 20, is provided around the opening of the tray 10. The flange 11 is formed to extend outward from the opening. The cover 20 is formed as a box with an opening at the bottom. A flange 21, which engages with the tray 10, is provided around the opening of the cover 20. The flange 21 is formed to extend outward from the opening.

[0033] Additionally, the battery pack 1 has a gasket 30 disposed between the tray 10 and the cover 20. The gasket 30 is disposed between the upper surface of the flange 11 and the lower surface of the flange 21. The gasket 30 is formed of an elastomer such as rubber. The gasket 30 fills the gap between the tray 10 and the cover 20 by fastening the tray 10 and the cover 20.

[0034] The battery pack 1 stores multiple batteries in a storage space formed inside the tray 10. Furthermore, by assembling a cover 20 on the upper part of the tray 10, the storage space storing the multiple batteries is blocked by the cover 20.

[0035] Furthermore, the tray 10 is provided with a bracket-shaped fastening part for securing multiple batteries to the tray 10, a reinforcing part for suppressing deformation of the battery pack 1 in the event of an electric vehicle collision, and a partition part for separating the storage space.

[0036] As a method for manufacturing a battery pack 1 with such a complex shape as a tray 10, one consideration is to join multiple components corresponding to fasteners, reinforcing parts, partitions, etc., to the tray formed by compression molding. However, in the method of joining multiple components to the tray, not only does the number of components increase, but also many welds are required to join multiple components to the tray, which may lead to a high cost for the battery pack 1.

[0037] As another method for manufacturing battery pack 1, it is possible to integrally form the complex-shaped tray by die casting. However, the larger the projected area of ​​the formed die-cast product, the higher the capacity of the die-casting equipment required. Therefore, in the case of integrally forming the tray by die casting, a large die-casting equipment is required, which may lead to high costs for battery pack 1.

[0038] Therefore, the battery pack manufacturing method of Embodiment 1 (hereinafter also referred to as the manufacturing method) has Figure 2 and Figure 3 The first process (step S1) and the second process (step S2) are shown. Figure 2 This is a flowchart illustrating a method for manufacturing a battery pack according to Embodiment 1. Figure 3 This is a simplified cross-sectional diagram illustrating the first and second processes.

[0039] like Figure 2 and Figure 3 As shown, the first process is to place a metal insert 120, which will become the flat part 12 of the tray 10, at a predetermined position in the cavity 54 formed by the mold 51. The second process is to solidify the molten liquid M after introducing it into the cavity 54 after the first process to form a casting 130 that becomes the frame part 13 of the tray 10.

[0040] This manufacturing method, for example, uses... Figure 3 The die-casting apparatus 50 shown is used for this process. Figure 3 The die-casting apparatus 50 shown has a mold 51 comprising a fixed mold 52 and a movable mold 53 that correspond to each other. The fixed mold 52 can hold the insert 120 by decompression suction or the like. The movable mold 53 can move relative to the fixed mold 52. The mold 51 closes by moving the movable mold 53 toward the fixed mold 52 after the insert 120 is held in the fixed mold 52, forming a cavity 54 between the fixed mold 52 and the movable mold 53 with a shape corresponding to the shape of the tray 10, and placing the insert 120 in a predetermined position in the cavity 54. A push rod 60 is provided in the movable mold 53 to push out the tray 10 formed by the mold 51.

[0041] In the manufacturing method of the battery pack 1 using such a die-casting device 50, firstly, in the first step, as... Figure 3 As shown in S1-1, the insert 120 is held in the fixed mold 52 of the mold 51 after it has been opened. The insert 120 is a rectangular plate-shaped aluminum plate. Then, as... Figure 3As shown in S1-2, the mold 51, which aligns the movable mold 53 with the fixed mold 52, is closed by moving the movable mold 53 toward the fixed mold 52 that holds the insert 120. As a result, a cavity 54 with a shape corresponding to the shape of the tray 10 is formed between the fixed mold 52 and the movable mold 53, and the insert material 120 is placed at a predetermined position in the cavity 54.

[0042] Next, in the second process, as Figure 3 As shown in S2-1, molten metal M, which becomes the casting ladle 130, is introduced into chamber 54. Molten metal M is molten aluminum here. Thus, the insert 120, which will become the flat portion 12 of tray 10, is cast into the casting ladle 130, which becomes the frame-shaped portion 13 of tray 10. Then, as... Figure 3 As shown in S2-2, after the molten liquid M is solidified, the mold 51 is opened to separate the movable mold 53 from the fixed mold 52. Then, the tray 10 formed by the movable mold 53 is pushed out by the push rod 60 to remove the tray 10 as a molded product from the mold 51.

[0043] Through the first and second processes, a tray 10 is obtained in which the flat portion 12 and the frame portion 13 are integrated. The resulting tray 10 is constructed using a frame portion 13 cast by die casting and a flat portion 12 embedded in the frame portion 13. The tray 10 has a bottom surface formed by the flat portion 12 and a pair of side surfaces and a pair of end surfaces formed by the frame portion 13. Thus, the tray 10 is formed into a box shape that is enclosed by the flat portion 12 and the frame portion 13 and has an opening at the top.

[0044] Compared to methods that join multiple components to the tray 10, this manufacturing method reduces the number of components, thus enabling the battery pack 1 to be manufactured at a lower cost. Furthermore, if the die-cast product is merely a casting 130 that forms part 13 of the frame-like portion 13 as part of the tray 10, the projected area of ​​the die-cast product is smaller compared to the case where the die-cast product is an integral part of the tray 10. Therefore, this manufacturing method enables the miniaturization of the die-casting apparatus 50 and the manufacture of the battery pack 1 at a lower cost. Thus, according to this manufacturing method, the high cost of the battery pack 1 can be mitigated.

[0045] Furthermore, this manufacturing method preferably includes a third step after the second step, in which the planar portion 12 and the frame-shaped portion 13 are joined. By joining the planar portion 12 and the frame-shaped portion 13, crevice corrosion between the planar portion 12 and the frame-shaped portion 13 can be suppressed. Examples of joining methods for joining the planar portion 12 and the frame-shaped portion 13 include friction stir welding, arc welding, laser welding, and welding using a bonding agent. Other joining methods for joining the planar portion 12 and the frame-shaped portion 13 include bolt joining using a sealant to eliminate the gap between the planar portion 12 and the frame-shaped portion 13, and riveting joining using a sealant.

[0046] Furthermore, in the case where the manufacturing method includes a third step, the planar portion 12 and the frame-shaped portion 13 are preferably joined by friction stirring. This results in a tray 10 with improved joint strength, joint accuracy, and airtightness between the planar portion 12 and the frame-shaped portion 13.

[0047] Here, Figure 4 This is a schematic cross-sectional view illustrating the first example of the third process. (For example...) Figure 4 As shown on the upper side, the tray 10 before joining is shaped such that the planar portion 12 and the frame-shaped portion 13 overlap in a state where the upper surface of the peripheral portion 12a of the planar portion 12 contacts the lower surface of the frame-shaped portion 13. In the first example of the third process, the overlapping portions of the planar portion 12 and the frame-shaped portion 13 are joined by friction stirring joining. Moreover, as Figure 4 As shown on the lower side, a joining portion 14 is formed on the joined tray 10, which joins the overlapping portions of the planar portion 12 and the frame-shaped portion 13.

[0048] On the other hand, in the joined tray 10, sometimes an unjoined portion 15 is formed around the joint 14, where the planar portion 12 and the frame-shaped portion 13 are not joined. In such an unjoined portion 15, gap corrosion between the planar portion 12 and the frame-shaped portion 13 may occur.

[0049] Therefore, as Figure 5 As shown, in the third step, it is preferable to join the mating surfaces 12s of the planar portion 12 and the mating surfaces 13s of the frame portion 13 together.

[0050] Figure 5 This is a schematic cross-sectional view illustrating the second example of the third process. (For example...) Figure 5 As shown on the upper side, the tray 10 before joining is formed such that the flat portion 12 is inserted into the recess 13b of the frame-shaped portion 13 with the peripheral portion 12a of the flat portion 12 abutting the end portion 13a (lower end portion) of the frame-shaped portion 13. Furthermore, the recess 13b of the frame-shaped portion 13 is formed on the lower surface of the frame-shaped portion 13. The recess 13b is recessed upward from the lower surface of the frame-shaped portion 13. In addition, the end portion 13a of the frame-shaped portion 13 is formed to extend downward along the outer peripheral surface of the frame-shaped portion 13. The end portion 13a of the frame-shaped portion 13 surrounds the recess 13b.

[0051] In the second example of the third process, the mating surfaces 12s of the flat portion 12 and the mating surfaces 13s of the frame-shaped portion 13 are joined together by friction stirring. Furthermore, as... Figure 5 As shown on the lower side, a joint portion 16 is formed on the joined tray 10, which joins the mating surfaces 12s of the flat portion 12 and the mating surfaces 13s of the frame portion 13 to each other.

[0052] In the second example of the third process, by joining the mating surfaces 12s of the planar portion 12 and the mating surfaces 13s of the frame portion 13 to each other, it is possible to suppress the gap corrosion between the planar portion 12 and the frame portion 13 that may occur when the overlapping parts of the planar portion 12 and the frame portion 13 are joined together.

[0053] Furthermore, preferably, the mating surface 12s of the flat portion 12 is the outer peripheral surface of the flat portion 12, and the mating surface 13s of the frame-shaped portion 13 is the inner peripheral surface of the end portion 13a, which surrounds the recess 13b of the frame-shaped portion 13 into which the flat portion 12 is embedded. This eliminates any gaps that may occur between the flat portion 12 and the frame-shaped portion 13, thus resulting in a tray 10 with further improved joint strength, joint accuracy, and airtightness between the flat portion 12 and the frame-shaped portion 13.

[0054] Furthermore, this disclosure is not limited to the above-described embodiments, and appropriate modifications can be made without departing from its spirit. For example, the battery pack 1 is not limited to a battery pack mounted on an electric vehicle, but may also be a battery pack mounted on other devices such as a self-propelled robot.

Claims

1. A method of manufacturing a battery pack having a tray that houses a battery, comprising: a first step of disposing a metal insert that becomes a flat portion of the tray at a prescribed position of a cavity formed by a mold; and a second step of introducing a molten metal into the cavity after the first step and solidifying the molten metal to form a casting insert that becomes a frame portion of the tray.

2. The method of manufacturing a battery pack according to claim 1, further comprising a third step of joining the flat portion and the frame portion after the second step.

3. The method of manufacturing a battery pack according to claim 2, wherein the flat portion and the frame portion are joined by friction stir joining.

4. The method of manufacturing a battery pack according to claim 2, wherein, in the third step, a joining surface of the flat portion and a joining surface of the frame portion are joined to each other.

5. The method of manufacturing a battery pack according to claim 2, wherein the joining surface of the flat portion is an outer peripheral surface of the flat portion, and the joining surface of the frame portion is an inner peripheral surface of an end portion of the frame portion that surrounds a recess of the frame portion into which the flat portion is inserted. ​ ​ ​ ​

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