Manufacturing method of battery pack

Abstract

To provide a manufacturing method of a battery pack which enables improvement of cooling efficiency.SOLUTION: A manufacturing method of a battery pack including a battery case and a cooler disposed below the battery case includes: a forming step in which the battery case and the cooler are adhered through a heat conduction member to form a battery pack structure; and a structure paint step in which antirust coating is applied to a surface of the battery pack structure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a battery pack. [Background technology]

[0002] As described in Patent Document 1, a battery pack mounted on an electric vehicle is known. The battery pack needs to be provided with a cooling structure to prevent deterioration of the battery due to an increase in temperature of the battery cells. Conventionally, in a manufacturing method of such a battery pack, a battery case that houses the battery cells is first coated with an anti-rust paint, and then a thermally conductive material is applied to the battery case, and the battery case and a cooler are assembled. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 185849 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above manufacturing method, an anti-rust coating film is interposed between the adhesive surface of the battery pack and the cooler, and this anti-rust coating film has a high thermal resistance, which causes a problem of reduced cooling efficiency. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] According to one embodiment of the present disclosure, there is provided a method for manufacturing a battery pack including a battery case and a cooler disposed below the battery case, the method including a forming step of bonding the battery case and the cooler via a thermally conductive member to form a battery pack structure, and a structure coating step of coating a surface of the battery pack structure with an anti-rust coating. According to this embodiment, after forming a battery pack structure in which the battery case and the cooler are integrated in the forming step, the entire surface of the battery pack structure is coated with an anti-rust coating in the structure coating step. In other words, since the battery case alone is not coated with an anti-rust coating, there is no anti-rust coating layer between the adhesive surfaces of the battery case and the cooler. Therefore, the thermal resistance between the battery case and the cooler can be reduced, and efficient heat exchange can be achieved. [Brief description of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing a portion of a battery pack in a first embodiment of the present disclosure. [Diagram 2] 4 is a flowchart showing a process procedure in a manufacturing method of a battery pack. [Diagram 3] 6 is a cross-sectional view showing a portion of a battery pack in a second embodiment of the present disclosure. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A. First embodiment: A1. Battery pack 1 configuration: Fig. 1 is a cross-sectional view showing a part of a battery pack 1 in a first embodiment of the present disclosure. Fig. 1 is a diagram for explaining the structure of an adhesion portion between a lower case 21 and a cooler 30 described later in the battery pack 1, and does not show all the members constituting the battery pack 1. The battery pack 1 is mounted on a hybrid vehicle capable of running using at least one of the power of a motor and an engine, or an electric vehicle that runs using driving force obtained from electric energy. The battery pack 1 is mounted, for example, below a floor panel of the vehicle.

[0009] As shown in Fig. 1, the battery pack 1 includes a battery case 20, a cooler 30, and a heat conductive member 40. The battery case 20 is a case that houses a plurality of battery stacks (not shown), and is configured to have an upper case and a lower case 21 (not shown). Note that only the lower case 21 is shown in Fig. 1.

[0010] The upper case is located above the lower case 21. The upper case has a generally box-like shape that is open downward. The upper case may be made of a metal material. Also, to reduce weight, the upper case may be made of a resin material.

[0011] The lower case 21 has a generally box-like shape that is open upward. The lower case 21 is made of a metal material. The lower case 21 preferably has good thermal conductivity. The lower case 21 has a bottom 22. A plurality of battery stacks are placed on an upper surface 22a of the bottom 22.

[0012] Each of the multiple battery stacks includes multiple battery cells (not shown). The battery cells are, for example, secondary batteries such as nickel-metal hydride batteries or lithium-ion batteries. The battery cells have, for example, a rectangular shape. The battery cells may use a liquid electrolyte or a solid electrolyte. Furthermore, the battery cells may be unit capacitors configured to be capable of storing electricity.

[0013] The cooler 30 is a device for cooling a plurality of battery stacks. A refrigerant flow path 31 through which a refrigerant flows is provided inside the cooler 30. The cooler 30 is disposed below the bottom 22 of the lower case 21, i.e., on the lower surface 22b side of the bottom 22. The cooler 30 is made of a metal material such as aluminum.

[0014] The heat conductive member 40 is disposed between the lower surface 22b of the bottom 22 and the cooler 30. The battery stacks are cooled by the cooler 30 via the heat conductive member 40, the bottom 22, and an inner heat conductive layer (not shown) disposed on the upper surface side of the lower case 21. The heat conductive member 40 also functions as an adhesive layer that bonds the bottom 22 and the cooler 30. As the heat conductive member 40, for example, an adhesive containing a silicone resin, an acrylic resin, a urethane resin, an epoxy resin, or the like can be used.

[0015] The lower case 21 and the cooler 30 are bonded together by the heat conductive member 40 and then the integrated battery pack structure 10 is subjected to an anti-rust coating treatment. A manufacturing method of the battery pack 1 including this anti-rust treatment will be described later. Cationic coating films 51, 52 that function as anti-rust coating films are formed on the upper surface 22a of the lower case 21 and the lower surface 32 of the cooler 30, respectively.

[0016] A2. Manufacturing method of battery pack 1: Next, a method for manufacturing the battery pack 1 described above in detail will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the procedure of the method for manufacturing the battery pack 1. In the method for manufacturing the battery pack 1, as shown in Fig. 2, a lower case 21 is prepared in S101. The lower case 21 here is not coated with an anti-rust coating.

[0017] In S102, an adhesive material containing a thermally conductive material is applied and filled on the cooling surface where the lower case 21 and the cooler 30 come into contact with each other. Then, in S103, the cooler 30 is pressed against the lower case 21 so that the adhesive has a predetermined thickness, and the lower case 21 and the cooler 30 are assembled together. The cooler 30 is made of a material that does not have a sacrificial layer. In S103, the thermally conductive material is left until it becomes a hardened state in which it does not soften at the temperature of the subsequent anti-rust coating treatment (S104). Alternatively, it is hardened in an accelerated environment. By the process of S103, a battery pack structure 10 in which the lower case 21 and the cooler 30 are integrated via the thermally conductive member 40 is formed. The processes of S102 and S103 correspond to a "forming process".

[0018] Then, in a state in which the lower case 21 and the cooler 30 are bonded together by hardening of the thermally conductive material, in S104, an anti-rust coating treatment is applied to the entire surface of the battery pack structure 10. In this anti-rust coating treatment, the areas on the surface of the battery pack structure 10 that do not require coating are masked, and the entire battery pack structure 10 is immersed in an anti-rust coating liquid for electrodeposition coating. The treatment in S104 corresponds to the "structure coating step."

[0019] According to the first embodiment, in the forming steps (S102, S103), the battery pack structure 10 is formed by integrating the lower case 21 and the cooler 30, and then in the structure painting step (S104), an anti-rust coating is applied to the entire surface of the battery pack structure 10. That is, since the lower case 21 alone is not coated with an anti-rust coating, only the heat conductive member 40 is interposed between the bonding surfaces of the lower case 21 and the cooler 30, and no anti-rust coating layer is present. Anti-rust resin-based coating films such as cationic coating have a high thermal resistance, and the cooling efficiency decreases in a configuration in which this anti-rust coating layer is present.

[0020] In the first embodiment, the thermal resistance can be reduced by eliminating the rust-proof coating layer between the lower case 21 and the cooler 30, so that the temperature of the battery cells can be reduced at a lower temperature and with a smaller refrigerant flow rate. In other words, more efficient heat exchange can be achieved.

[0021] In the first embodiment, the lower surface 32 of the cooler 30 that comes into contact with the outside air is covered with the cationic coating film 52, so that the heat exchange with the outside air is reduced, and the heat reception from the high-temperature outside air is reduced when cooling is required, and the heat release from the hot water to the low-temperature outside air is reduced when heating is required. This further improves the cooling efficiency.

[0022] The method of manufacturing a battery pack by applying an anti-rust coating to the lower case 21 alone and assembling the cooler 30 made of a material having a sacrificial layer is hereinafter referred to as the "comparative manufacturing method". In the above-mentioned first embodiment, since an anti-rust coating film is applied to the outer surface of the cooler 30, it is not necessary to use a sacrificial layer material for anti-rust for the cooler 30 alone. Therefore, the manufacturing cost of the cooler 30 can be reduced compared to the comparative manufacturing method. Note that the area for applying the anti-rust coating to the entire surface of the battery pack structure 10 is not significantly different from the case where the anti-rust coating is applied to the lower case 21 alone, so the coating cost does not vary significantly compared to the case where the anti-rust coating is applied to the lower case 21 alone. As a result, the total cost can be reduced compared to the comparative manufacturing method while maintaining the anti-rust ability of the battery pack 1.

[0023] B. Second embodiment: Next, a manufacturing method of the battery pack 100 according to a second embodiment of the present disclosure and the battery pack 100 will be described with reference to Fig. 3. Note that the same reference numerals are used for configurations substantially similar to those of the first embodiment, and the description thereof will be omitted. The manufacturing method of the second embodiment includes a case painting process and a forming process.

[0024] In the case painting process, an anti-rust coating is applied to the surface of the lower case 21 while a part of the underside 22b of the lower case 21, which serves as a heat transfer path between the lower case 21 and the cooler 30, is masked. This coating process is performed by immersing the lower case 21 in an electrodeposition coating liquid. Then, in a forming process, the lower case 21 and the cooler 30 are bonded together via the heat conductive member 40 to form the battery pack structure 10.

[0025] Fig. 3 is a cross-sectional view showing a part of the battery pack 100 according to the second embodiment of the present disclosure manufactured by the above manufacturing method. As shown in Fig. 3, on the lower surface 22b of the lower case 21, the cationic coating film 53 is not formed on the portion that serves as the heat transfer path with the cooler 30, i.e., the portion facing the refrigerant flow path 31 via the heat conductive member 40, due to masking in the case painting process. On the lower surface 22b of the lower case 21, the cationic coating film 53 is formed on the portion other than the portion that mainly serves as the heat transfer path.

[0026] Therefore, since an unnecessary low heat transfer layer is eliminated from the heat transfer path, the cooling efficiency can be improved. In the second embodiment, the lower surface 32 of the cooler 30 can be individually subjected to anti-rust treatment, for example, by alumina treatment or by providing a sacrificial layer film.

[0027] The present disclosure is not limited to the above-mentioned embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in each embodiment corresponding to the technical features in each form described in the Summary of the Invention column can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0028] (Additional Note) A method for manufacturing a battery pack including a battery case and a cooler disposed below the battery case, a case painting process of applying an anti-rust coating to a surface of the battery case while a part of a lower surface of the battery case, which serves as a heat transfer path between the battery case and the cooler, is masked; a forming step of forming a battery pack structure by arranging a thermally conductive member on at least a portion of the lower surface of the battery case that was masked in the case painting step, and bonding the battery case and the cooler via the thermally conductive member, after the case painting step; A manufacturing method of a battery pack comprising: [Explanation of symbols]

[0029] 1,100... battery pack, 10... battery pack structure, 20... battery case, 21... lower case, 22... bottom, 22a... upper surface, 22b... lower surface, 30... cooler, 31... refrigerant flow path, 32... lower surface, 40... heat conductive member, 51, 52, 53... cationic coating film

Claims

[Claim 1] A method for manufacturing a battery pack including a battery case and a cooler disposed below the battery case, comprising: a forming step of bonding the battery case and the cooler via a thermally conductive member to form a battery pack structure; a structure painting step of applying an anti-rust coating to a surface of the battery pack structure; A manufacturing method of a battery pack comprising:

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