Method for manufacturing battery pack

Abstract

To provide a manufacturing method of a battery pack capable of suppressing cost increase of the battery pack.SOLUTION: A method for manufacturing a battery pack is a method for manufacturing a battery pack having a tray for accommodating a battery, and includes a first step of placing a metal insert material to be a flat portion of the tray at a predetermined position in a cavity formed by a mold, and a second step of introducing molten metal into the cavity after the first step and then solidifying the molten metal to form an insert material to be a frame-shaped portion of the tray. The method for manufacturing a battery pack further includes a third step of joining the planar portion and the frame-shaped portion after the second step.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present 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 housing batteries. [Background technology]

[0002] An example of a battery pack to be mounted on an electric vehicle or the like is disclosed in Patent Document 1.

[0003] The battery pack described in Patent Document 1 comprises a box-shaped tray that houses batteries and is open at the top, and an outer frame welded along the outside of the side wall surface of the tray. The outer frame is made of a plate-shaped member or a combination thereof, and has a first protrusion welded to the outer bottom surface of the tray, a second protrusion that is located above the first protrusion and protrudes outward from the tray, an outer portion that connects the first protrusion and the second protrusion at a position spaced outward from the side wall surface of the tray, and an inner portion that extends from the second protrusion toward the first protrusion and is welded to the outer surface of the tray. The first protrusion, the second protrusion, and the inner portion form part of a closed cross section, and the outer portion has an opening through which a welding gun can be inserted to weld the side wall surface of the tray to the inner portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-170452 Summary of the Invention [Problem to be solved by the invention]

[0005] The tray of the battery pack described in Patent Document 1 is provided with many components. When manufacturing such a battery pack, many components are required, and many welding processes are required to join them to the tray. Therefore, the technology described in Patent Document 1 has the problem of possibly increasing the cost of the battery pack.

[0006] The present disclosure has been made to solve such problems, and aims to provide a method for manufacturing a battery pack that can prevent the cost of the battery pack from increasing. [Means for solving the problem]

[0007] A manufacturing method for a battery pack according to one embodiment is a manufacturing method for a battery pack having a tray for accommodating batteries, and includes a first step of placing a metal insert material that will become the flat surface of the tray at a predetermined position in a cavity formed by a mold, and a second step of introducing molten metal into the cavity after the first step, and then solidifying the molten metal to form a cast-in insert material that will become the frame-shaped portion of the tray. [Effects of the Invention]

[0008] The present disclosure makes it possible to provide a method for manufacturing a battery pack that can prevent the cost of the battery pack from increasing. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a battery pack according to a first embodiment. [Figure 2] 3 is a flowchart showing a manufacturing method of the battery pack according to the first embodiment. [Figure 3] FIG. 2 is a schematic cross-sectional view illustrating a first step and a second step. [Figure 4] FIG. 10 is a schematic cross-sectional view illustrating a first example of a third step. [Figure 5] FIG. 10 is a schematic cross-sectional view illustrating a second example of the third step. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiment 1 Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate for clarity of explanation.

[0011] Fig. 1 is a perspective view showing a battery pack according to a first embodiment. The battery pack 1 shown in Fig. 1 is mounted on an electric vehicle such as a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV). The battery pack 1 supplies power to a motor and electrical components mounted on the electric vehicle.

[0012] 1, the battery pack 1 includes a tray 10 and a cover 20. The tray 10 and the cover 20 are made of a metal such as aluminum, an aluminum alloy, or a magnesium alloy. From the viewpoint of reducing the weight and cost of the battery pack 1, aluminum or an aluminum alloy is preferred as the metal.

[0013] The tray 10 is formed in a box shape with an open top. A flange portion 11 is provided around the opening of the tray 10, to which the cover 20 is joined. The flange portion 11 is formed so as to protrude outward from the opening. The cover 20 is formed in a box shape with an open bottom. A flange portion 21 is provided around the opening of the cover 20, to which the tray 10 is joined. The flange portion 21 is formed so as to protrude outward from the opening.

[0014] The battery pack 1 also has a gasket 30 provided between the tray 10 and the cover 20. The gasket 30 is provided between the upper surface of the flange portion 11 and the lower surface of the flange portion 21. The gasket 30 is made of an elastic material such as rubber. The gasket 30 fills a gap that occurs between the tray 10 and the cover 20 when the tray 10 and the cover 20 are fastened together.

[0015] The battery pack 1 accommodates multiple batteries in an accommodation space formed inside the tray 10. Then, by assembling a cover 20 onto the top of the tray 10, the accommodation space accommodating the multiple batteries is closed by the cover 20.

[0016] The tray 10 is provided with bracket-shaped fastening portions for fastening multiple batteries to the tray 10, reinforcing portions for suppressing deformation of the battery pack 1 in the event of a collision of the electric vehicle, partition portions for dividing the storage space, and the like.

[0017] One method for manufacturing a battery pack 1 having such a complicatedly shaped tray 10 is to join a large number of components corresponding to fastening portions, reinforcing portions, partition portions, etc. to a tray formed by press molding. However, joining a large number of components to a tray increases the number of parts, and requires a large amount of welding to join the large number of components to the tray, which may increase the cost of the battery pack 1.

[0018] Another method for manufacturing the battery pack 1 is to integrally mold a tray having a complex shape by die casting. However, the die-casting machine required to perform the die-casting process must have a higher capacity as the projected area of ​​the die-cast product to be molded increases. Therefore, when integrally molding the tray by die casting, a large die-casting machine is required, which may result in an increase in the cost of the battery pack 1.

[0019] Therefore, the manufacturing method of the battery pack according to the first embodiment (hereinafter also referred to as the present manufacturing method) has a first step (step S1) and a second step (step S2) shown in Figures 2 and 3. Figure 2 is a flowchart showing the manufacturing method of the battery pack according to the first embodiment. Figure 3 is a schematic cross-sectional view illustrating the first step and the second step.

[0020] 2 and 3, the first step is to place a metal insert 120, which will become the flat portion 12 of the tray 10, at a predetermined position in a cavity 54 formed by a mold 51. The second step is to introduce molten metal M into the cavity 54 after the first step, and then solidify the molten metal M to form a cast-in insert 130, which will become the frame-shaped portion 13 of the tray 10.

[0021] This manufacturing method is performed using, for example, a die-casting apparatus 50 shown in FIG. 3. The die-casting apparatus 50 shown in FIG. 3 has a mold 51 including a fixed mold 52 and a movable mold 53 that correspond to each other. The fixed mold 52 can hold the insert material 120 by, for example, reduced pressure suction. The movable mold 53 can move relative to the fixed mold 52. After the fixed mold 52 holds the insert material 120, the movable mold 53 moves toward the fixed mold 52 to clamp the mold 51, thereby forming a cavity 54 between the fixed mold 52 and the movable mold 53 that has a shape corresponding to the shape of the tray 10, and placing the insert material 120 at a predetermined position in the cavity 54. The movable mold 53 is provided with an ejector pin 60 that ejects the tray 10 molded by the mold 51.

[0022] In a manufacturing method of a battery pack 1 using such a die-casting apparatus 50, first, in a first step, as shown in S1-1 of Fig. 3, an insert material 120 is held in a fixed mold 52 of an opened mold 51. Here, the insert material 120 is a rectangular aluminum plate. Then, as shown in S1-2 of Fig. 3, the movable mold 53 is moved toward the fixed mold 52 holding the insert material 120, thereby clamping the mold 51 to align the movable mold 53 with the fixed mold 52. As a result, a cavity 54 having 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.

[0023] Next, in a second step, as shown in S2-1 of Fig. 3, molten metal M that will become the cast-in insert material 130 is introduced into the cavity 54. In this case, the molten metal M is molten aluminum. In this way, the insert material 120 that will become the flat portion 12 of the tray 10 is cast-in inserted into the cast-in insert material 130 that will become the frame-shaped portion 13 of the tray 10. Then, as shown in S2-2 of Fig. 3, after the molten metal M has solidified, the mold 51 is opened to separate the movable mold 53 from the fixed mold 52. Thereafter, the molded tray 10 is ejected from the movable mold 53 by the ejector pin 60, and the molded product, tray 10, is removed from the mold 51.

[0024] The first and second steps produce a tray 10 in which the flat portion 12 is integrated with the frame portion 13. The resulting tray 10 is composed of the frame portion 13, which is formed by die-casting, and the flat portion 12, which is insert-molded into the frame portion 13. The bottom surface of the tray 10 is formed by the flat portion 12, and a pair of side surfaces and a pair of end surfaces are formed by the frame portion 13. As a result, the tray 10 is surrounded by the flat portion 12 and the frame portion 13, and is formed in the shape of a box with an open top.

[0025] This manufacturing method can reduce the number of parts compared to a method in which multiple components are joined to the tray 10, and therefore can manufacture the battery pack 1 at low cost. Furthermore, if the die-cast product is only the insert material 130 that becomes the frame portion 13 that is part of the tray 10, the projected area of ​​the die-cast product is smaller than if the die-cast product were the entire tray 10. Therefore, this manufacturing method realizes downsizing of the die-casting apparatus 50 and can manufacture the battery pack 1 at low cost. Therefore, this manufacturing method can prevent the cost of the battery pack 1 from increasing.

[0026] Furthermore, the present manufacturing method preferably includes a third step of joining the flat portion 12 and the frame-shaped portion 13 after the second step. By joining the flat portion 12 and the frame-shaped portion 13, crevice corrosion between the flat portion 12 and the frame-shaped portion 13 can be suppressed. Examples of joining methods for joining the flat portion 12 and the frame-shaped portion 13 include friction stir welding, welding such as arc welding and laser welding, and bonding using an adhesive or the like. As joining methods for joining the flat portion 12 and the frame-shaped portion 13, bolt joining combined with a sealant to eliminate gaps between the flat portion 12 and the frame-shaped portion 13, rivet joining combined with a sealant, or the like may also be used.

[0027] Furthermore, when the present manufacturing method includes the third step, the flat portion 12 and the frame portion 13 are preferably joined by friction stir welding, thereby obtaining a tray 10 with improved joining strength, joining precision, and airtightness between the flat portion 12 and the frame portion 13.

[0028] Here, Fig. 4 is a schematic cross-sectional view illustrating a first example of the third step. As shown in the upper side of Fig. 4, the tray 10 before joining is formed so that the flat portion 12 and the frame-shaped portion 13 overlap with the upper surface of the peripheral portion 12a of the flat portion 12 in contact with the lower surface of the frame-shaped portion 13. In the first example of the third step, the overlapping portions of the flat portion 12 and the frame-shaped portion 13 are joined by friction stir welding. Then, as shown in the lower side of Fig. 4, the joined tray 10 has a joint 14 formed at the joined portions of the flat portion 12 and the frame-shaped portion 13.

[0029] On the other hand, after joining, the tray 10 may have an unjoined portion 15 around the joint portion 14, where the flat portion 12 and the frame portion 13 are not joined. In such an unjoined portion 15, crevice corrosion between the flat portion 12 and the frame portion 13 may occur.

[0030] Therefore, as shown in FIG. 5, in the third step, it is preferable to join the butted surfaces 12s, 13s of the flat portion 12 and the frame-shaped portion 13 together.

[0031] Fig. 5 is a schematic cross-sectional view illustrating a second example of the third step. As shown in the upper part of Fig. 5, the tray 10 before bonding is formed so that the peripheral edge 12a of the flat portion 12 and the end 13a (lower end) of the frame-shaped portion 13 are abutted against each other, and the flat portion 12 is fitted into the recess 13b of the frame-shaped portion 13. 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. The end 13a of the frame-shaped portion 13 is formed so as to extend downward along the outer peripheral surface of the frame-shaped portion 13. The end 13a of the frame-shaped portion 13 surrounds the recess 13b.

[0032] In a second example of the third step, the butted surfaces 12s, 13s of the flat portion 12 and the frame-shaped portion 13 are joined by friction stir welding. Then, as shown in the lower part of Fig. 5, the joined tray 10 has a joint 16 formed at the butted surfaces 12s, 13s of the flat portion 12 and the frame-shaped portion 13.

[0033] In the second example of the third step, by joining the butting surfaces 12s, 13s of the flat portion 12 and the frame-shaped portion 13, it is possible to suppress gap corrosion between the flat portion 12 and the frame-shaped portion 13 that may occur when the overlapping portions of the flat portion 12 and the frame-shaped portion 13 are joined.

[0034] Furthermore, it is preferable that the abutting surface 12s of the flat portion 12 is the outer peripheral surface of the flat portion 12, and the abutting surface 13s of the frame-shaped portion 13 is the inner peripheral surface of the end portion 13a that surrounds the recess 13b of the frame-shaped portion 13 into which the flat portion 12 is fitted. This makes it possible to eliminate any gap that may occur between the flat portion 12 and the frame-shaped portion 13, thereby obtaining a tray 10 with improved bonding strength, bonding accuracy, and airtightness between the flat portion 12 and the frame-shaped portion 13.

[0035] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present disclosure. For example, the battery pack 1 is not limited to being mounted on an electric vehicle, but may also be mounted on other devices such as a self-propelled robot. [Explanation of symbols]

[0036] 1 battery pack 10 Tray 11 Flange 12: Flat portion; 12a: Peripheral portion; 12s: Butting surface 13 Frame-shaped portion 13a End portion 13b Recessed portion 13s Butting surface 14 Joint part 15 Unjoined part 16 Joint part 20 Cover 21 Flange 30 gaskets 50 Die-casting device 51 Mold 52 Fixed mold 53 Movable mold 54 Cavity 60 Ejector pin 120 Insert material 130 Cast-in material M molten metal

Claims

1. A method for manufacturing a battery pack having a tray for accommodating batteries, comprising: a first step of placing a metal insert material that will become a flat surface of the tray at a predetermined position in a cavity formed by a mold; a second step of introducing a molten metal into the cavity after the first step and then solidifying the molten metal to form a cast-in insert material that will become a frame-shaped portion of the tray; A method for manufacturing a battery pack having the above structure.

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

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

4. The method for manufacturing a battery pack according to claim 2 , wherein in the third step, the butting surfaces of the flat portion and the frame-shaped portion are joined together.

5. the abutting surface of the flat portion is an outer peripheral surface of the flat portion, The method for manufacturing a battery pack according to claim 2 , wherein the abutting surface of the frame-shaped portion is an inner peripheral surface of an end portion surrounding a recess of the frame-shaped portion into which the flat portion is fitted.

Images