Battery pack manufacturing method

Abstract

To prevent the formation of air gaps between the battery cells and the thermal conductive material when mounting the battery module into the case. [Solution] A method for manufacturing a battery pack, comprising: step S1 of applying a thermal conductive material to the mounting surface of a lower case; step S2 of starting to apply vibration to the lower case after the application of the thermal conductive material to the mounting surface is completed; and step S3 of mounting a battery module to the mounting surface while the thermal conductive material is being vibrated and the thermal conductive material is compressed on the bottom surface of the battery cell to form a thermal conductive material layer between the battery cell and the lower case, wherein the vibration applied to the lower case is a high-frequency vibration in a plane direction parallel to the mounting surface.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a battery pack.

Background Art

[0002] In Patent Document 1, as a method for manufacturing a battery pack, after forming a heat transfer layer between a battery cell and a case and assembling the battery module to the case, vibration due to Lorentz force is generated in the heat transfer layer to break the void formed between the battery cell and the case.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the method described in Patent Document 1, since the heat transfer layer is vibrated after a plurality of battery cells are assembled to the case, the number of post-assembly steps increases, and an alternating current generator and a direct current magnetic field generator are required, increasing the manufacturing cost. Further, the method described in Patent Document 1 breaks a large void once generated between the battery cell and the heat transfer layer into small voids, and does not suppress the generation of voids when the battery module is mounted on the case.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a battery pack capable of suppressing the generation of voids between a battery cell and a heat conductive material when the battery module is mounted on a case.

Means for Solving the Problems

[0006] The present invention relates to a method for manufacturing a battery pack in which a thermal conductive material layer is interposed between a battery module, which is made up of a plurality of stacked battery cells, and a cooler, comprising: a coating step of applying a thermal conductive material to a mounting surface of a lower case; a starting step of starting to apply vibration to the lower case after the application of the thermal conductive material to the mounting surface is completed; and a mounting step of mounting the battery module to the mounting surface while forming a thermal conductive material layer between the battery cells and the lower case by crushing the thermal conductive material at the bottom surface of the battery cells while the lower case and the thermal conductive material are vibrating, wherein the vibration applied to the lower case is a high-frequency vibration in a plane direction parallel to the mounting surface. [Effects of the Invention]

[0007] In this invention, it is possible to suppress the occurrence of air gaps between the battery cells and the thermal conductive material when mounting the battery module in a case. [Brief explanation of the drawing]

[0008] [Figure 1] This is an exploded view showing the battery pack in an embodiment. [Figure 2] This is a flowchart illustrating the manufacturing method of a battery pack. [Figure 3] This is a diagram illustrating the mounting process. [Figure 4] This is a schematic diagram illustrating the state of a heat conductive material in vibration. [Figure 5] This diagram illustrates the contact point between the bottom surface of the battery cell and the thermal conductive material. [Modes for carrying out the invention]

[0009] The following describes in detail the method for manufacturing a battery pack according to embodiments of the present invention. However, the present invention is not limited to the embodiments described below.

[0010] Figure 1 is an exploded view showing a battery pack in an embodiment. The battery pack 1 is to be mounted in an electric vehicle. The battery pack 1 comprises a battery module 3 in which a plurality of battery cells 2 are stacked, a lower case 4 that houses the battery module 3, a heat conductive material 5, and a cooler 6 that cools the battery cells 2.

[0011] The battery module 3 is a battery pack having multiple battery cells 2. The battery module 3 comprises a laminate formed by stacking multiple battery cells 2 and multiple separators, a pair of end plates positioned at both ends of the laminate in the stacking direction, and a restraining member extending to connect the pair of end plates. The laminate is restrained in a compressed state in the stacking direction by the pair of end plates and the restraining member. The end plates are provided with fastening holes through which bolts are inserted when fastening the battery module 3 to the lower case 4 with bolts.

[0012] The lower case 4 is a metal case that houses multiple battery modules 3. The battery modules 3 are mounted inside the lower case 4. The lower case 4 has a mounting surface 4a on which the battery modules 3 are placed. A thermal conductive material layer made of thermal conductive material 5 is formed on the mounting surface 4a at the position where the battery cells 2 are placed.

[0013] The thermal conductive material 5 is an insulating gel-like component. The thermal conductive material 5 is made of an adhesive resin. The thermal conductive material 5 includes a module-side thermal conductive material 5 provided between the battery module 3 and the lower case 4, and a cooler 6-side thermal conductive material 5 provided between the lower case 4 and the cooler 6. The thermal conductive material 5 forms a thermal conductive material layer between the components. The thermal conductive material layer is formed in layers such that the thermal conductive material 5 has a predetermined target width and target thickness. In the battery pack 1, a thermal conductive material layer is interposed between the battery cell 2 and the cooler 6. The battery pack 1 has a first thermal conductive material layer interposed between the cooler 6 and the lower case 4, and a second thermal conductive material layer interposed between the lower case 4 and the battery cell 2.

[0014] The cooler 6 is located outside the lower case 4 and cools the battery cell 2 through the lower case 4. The cooler 6 is positioned below the lower case 4 and is integrated with the lower case 4. The cooler 6 is attached to the outer surface of the lower case 4 opposite to the mounting surface 4a.

[0015] Since the battery pack 1 configured in this way will be installed in an electric vehicle, the required battery capacity will increase, and consequently the amount of heat generated by the battery will also increase, so an improvement in cooling performance is desirable. In order to improve the cooling performance of the battery pack 1, it is necessary to increase the contact area between the heat conductive material 5 applied between the various components and the components themselves.

[0016] Therefore, in the battery pack 1, the thermal conductive material 5 is formed with a narrower width and greater thickness during the manufacturing process compared to the target width and thickness of the thermal conductive material layer at the time of completion. Then, when assembling the battery module 3, the thermal conductive material 5 is compressed and spread out by the battery cell 2, thereby ensuring a sufficient contact area between the battery cell 2 and the thermal conductive material layer.

[0017] However, in a battery module 3 in which multiple battery cells 2 are stacked, positional displacement (height displacement) occurs where the positions of the battery cells 2 shift in the height direction. In particular, in battery packs 1 installed in electric vehicles, the number of stacked battery cells 2 is large, so the amount of waviness (height displacement) of the battery module 3 becomes large. Therefore, it is necessary to absorb the height displacement of the battery cells 2 in the battery module 3 with a thermal conductive material layer and to ensure close contact between the battery cells 2 and the thermal conductive material layer. In order to effectively absorb the height displacement of the battery cells 2, it is desirable that the thermal conductive material layer be of a certain thickness and have low viscosity.

[0018] On the one hand, in order to ensure the cooling performance of the battery pack 1, the thickness of the heat conductive material layer should be as thin as possible. That is, although it is better to increase the thickness of the heat conductive material layer to absorb the undulations of the battery module 3 and bring the lower case 4 into close contact with the battery module 3, there is a contradiction in that it is better to make the heat conductive material layer thinner to improve the cooling performance. Therefore, in the embodiment, a manufacturing method of the battery pack 1 capable of efficiently increasing the contact area between the heat conductive material layer and the battery cell 2 is adopted so as to ensure the cooling performance while absorbing the undulations of the battery module 3.

[0019] FIG. 2 is a flowchart showing a manufacturing method of the battery pack. The manufacturing method of the battery pack 1 includes a coating step (step S1), a start step of starting the application of vibration (step S2), a mounting step (step S3), a fastening step (step S4), and an end step of ending the application of vibration (step S5).

[0020] The coating step is a step of coating the heat conductive material 5 on the mounting surface 4a in the lower case 4 (step S1). As shown in FIG. 3, in the coating step, the heat conductive material 5 is coated at a position corresponding to the battery cell 2 of the battery module 3 on the mounting surface 4a. In the coating step, the heat conductive material 5 is coated in a shape with a narrow width and a thick thickness with respect to the target width and target thickness in the heat conductive material layer.

[0021] After the application of the heat conductive material 5 to the mounting surface 4a is completed, vibration is started to be applied to the lower case 4 (step S2). In step S2, minute vibration is applied to the lower case 4 to which the heat conductive material 5 is applied. The vibration applied to the lower case 4 is vibration in the plane direction parallel to the mounting surface 4a. In step S2, high-frequency vibration such as ultrasonic vibration is applied to the lower case 4. The vibration applied to the lower case 4 determines the conditions under which the effect can be obtained based on the material physical properties of the heat conductive material 5 and the dimensions of the heat conductive material layer. For example, the frequency of the vibration applied to the lower case 4 is preferably 30 kHz or more. As an example, ultrasonic vibration is applied to the lower case 4 by bringing a device that generates ultrasonic vibration into contact with the lower case 4. In order not to damage the battery cell 2, vibration is applied to the lower case 4 and the heat conductive material 5.

[0022] The mounting process is a process of mounting the battery module 3 on the lower case 4 while vibration is being applied to the lower case 4 (step S3). As shown in FIG. 4, in the mounting process, the battery module 3 is mounted on the mounting surface 4a by crushing the heat conductive material 5 at the bottom surface 2a of the battery cell 2 while vibrating the lower case 4 and the heat conductive material 5. In the mounting process, a heat conductive material layer made of the heat conductive material 5 is formed between the battery cell 2 and the lower case 4. In the mounting process, the heat conductive material 5 is crushed and spread by the battery cell 2 to increase the contact area between the bottom surface 2a of the battery cell 2 and the heat conductive material 5 and to form a heat conductive material layer having a target width and a target thickness.

[0023] As shown in Figure 5, when the battery module 3 is mounted with the thermal conductive material 5 vibrating slightly, shear stress is applied to the thermal conductive material 5 at the contact points between each battery cell 2 in the battery module 3 and the thermal conductive material 5, and the viscosity of the thermal conductive material 5 decreases. By starting the application of vibration in the initial step so that an amplitude is generated in the planar direction of the lower case 4, the viscosity of the thermal conductive material 5 can be effectively reduced during the mounting process, and the thermal conductive material 5 is crushed along the bottom surface 2a of the battery cell 2. Furthermore, at the new contact points beyond where it has been crushed, a decrease in the viscosity of the thermal conductive material 5 due to shear stress occurs, and by repeating this process, the thermal conductive material 5 is crushed so that it adheres tightly to the battery cell 2. In this way, the thermal conductive material 5 is crushed along the bottom surface 2a of each battery cell 2 and adheres to the bottom surface 2a of the battery cell 2 without air being trapped.

[0024] The fastening process is the process of fastening the battery module 3 to the lower case 4 while vibration is being applied to the lower case 4 (step S4). In the fastening process, the battery module 3 is fastened to the lower case 4 with fastening members such as bolts and nuts while vibration continues to be applied to the lower case 4 even after the battery cell 2 has crushed the heat conductive material 5. In the fastening process, the battery module 3 is bolted to the lower case 4 by inserting a bolt through the fastening hole of the end plate and screwing the bolt into the bolt hole provided in the lower case 4.

[0025] After the fastening process, the application of vibration to the lower case 4 is terminated (step S5). In step S5, the application of vibration to the lower case 4 is terminated after the fastening of the battery module 3 to the lower case 4 is completed. Since the positional relationship between the lower case 4 and the battery module 3 is determined when the fastening of the battery module 3 is completed, the application of vibration is continued until the fastening is complete.

[0026] Furthermore, the manufacturing method of the battery pack 1 includes an assembly step of assembling the cooler 6 into the lower case 4. The assembly step includes a first coating step, a first start step, and a mounting step.

[0027] The first coating step is to apply the thermal conductive material 5 to the outer surface of the lower case 4 opposite to the mounting surface 4a. In the assembly step, the orientation of the lower case 4 is changed so that the outer surface of the lower case 4 faces upward. In the first coating step, the thermal conductive material 5 is applied to the outer surface of the lower case 4 from above.

[0028] The first initiation step begins applying vibration to the lower case 4 after the application of the heat conductive material 5 to the outer surface is complete. The vibration applied to the lower case 4 in the first initiation step is a high-frequency vibration in a direction parallel to the outer surface, and may be the same as the vibration in step S2.

[0029] The installation process involves attaching the cooler 6 to the outer surface while vibrating the lower case 4 and the heat conductive material 5, thereby compressing the heat conductive material 5 on the surface of the cooler 6 to form a first heat conductive material layer between the cooler 6 and the lower case 4. The installation process involves compressing and expanding the heat conductive material 5 with the cooler 6, thereby increasing the contact area between the surface of the cooler 6 and the heat conductive material 5, and forming a heat conductive material layer with the target width and target thickness.

[0030] In the manufacturing method of the battery pack 1, the mounting step is performed before the mounting step (step S3), and the start step (step S2) is performed after the mounting step. In step S2, vibration is applied to the lower case 4 to which the cooler 6 has been attached in the mounting step. Then, in the mounting step, a second thermal conductive material layer consisting of thermal conductive material 5 is formed between the battery cell 2 and the lower case 4.

[0031] As described above, according to the embodiment, it is possible to suppress the formation of air gaps between the thermal conductive material 5 and the battery cell 2 when mounting the battery module 3 in the lower case 4, and to efficiently increase the contact area between the thermal conductive material layer and the battery module 3.

[0032] Furthermore, shear stress is applied to the thermal conductive material 5 at the contact point between the bottom surface 2a of each battery cell 2 in the battery module 3 and the thermal conductive material 5, which can reduce the viscosity of the thermal conductive material 5. As a result, the thermal conductive material 5 is compressed along the bottom surface 2a of each battery cell 2 and adheres without trapping air, thus preventing the generation of air bubbles and voids at relatively low frequencies and improving the cooling efficiency of the battery. [Explanation of Symbols]

[0033] 1 Battery pack 2 battery cells 3 Battery Module 4 Lower Case 4a Mounting surface 5. Thermal conductive material

Claims

1. A method for manufacturing a battery pack in which a heat conductive material layer is interposed between a battery module, which is made up of multiple stacked battery cells, and a cooler, A coating step of applying a thermal conductive material to the mounting surface of the lower case, A starting step of starting to apply vibration to the lower case after the application of the heat conductive material to the mounting surface is completed, Mounting step: Mounting the battery module to the mounting surface while vibrating the lower case and the heat conductive material, and compressing the heat conductive material at the bottom surface of the battery cell to form a heat conductive material layer between the battery cell and the lower case. Includes, The vibration applied to the lower case is a high-frequency vibration in a plane parallel to the mounting surface. A method for manufacturing a battery pack characterized by the following:

2. The coating step involves applying the thermal conductive material in a shape that is narrower and thicker than the target width and target thickness of the thermal conductive material layer. The mounting step involves crushing and spreading the thermal conductive material on the bottom surface of the battery cell, thereby increasing the contact area between the bottom surface of the battery cell and the thermal conductive material, and forming a thermal conductive material layer with the target width and target thickness. A method for manufacturing a battery pack according to claim 1.

3. A fastening step in which the battery module is fastened to the lower case by a fastening member while the vibration continues to be applied to the lower case even after the battery cell has crushed the heat conductive material, The process includes a termination step of ending the application of vibration to the lower case after the fastening of the battery module and the lower case is completed. The method for manufacturing a battery pack according to claim 2.

4. A first coating step involves applying a thermal conductive material to the outer surface of the lower case opposite to the mounting surface, A first starting step involves starting to apply vibration to the lower case after the application of the heat conductive material to the outer surface is completed, Mounting step: While vibrating the lower case and the heat conductive material, the cooler is attached to the outer surface while the heat conductive material is compressed on the surface of the cooler to form a first heat conductive material layer between the cooler and the lower case, which is made of the heat conductive material. Includes, The vibration applied to the lower case by the first initiation step is a high-frequency vibration that is parallel to the outer surface. A method for manufacturing a battery pack according to any one of claims 1 to 3.

5. The aforementioned mounting step is performed before the aforementioned mounting step. The initiation step includes applying the vibration to the lower case to which the cooler is attached by the mounting step, The mounting step includes forming a second thermal conductive layer as the thermal conductive layer between the battery cell and the lower case. The method for manufacturing a battery pack according to claim 4.

Images