Battery pack manufacturing method

Abstract

To easily determine whether a heat conduction member satisfies a quality standard.SOLUTION: A method for manufacturing a battery pack according to an embodiment includes the steps of: arranging a heat conduction material between a battery pack case having groove parts and an adjacent member adjacent to the battery pack case in a state where the groove parts are visible, and applying a load; detecting the heat conduction material flowing into the groove parts; and estimating the quality of the heat conduction material by using information on the detected heat conduction material. The adjacent member includes at least one battery module. The battery pack case includes a housing part that houses the battery module and is formed of a bottom part and wall parts.SELECTED DRAWING: Figure 1

Description

Technical Field

[0006] , ,

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

Background Art

[0002] As a battery pack mounted on an electric vehicle such as a BEV (Battery Electric Vehicle) or a PHEV (Plug-in Hybrid Electric Vehicle), there is known a battery pack including a plurality of batteries, a cooler that circulates a cooling medium therein to cool these batteries, and a heat conduction member disposed between the plurality of batteries and the cooler to transfer the heat of the batteries to the cooler.

[0003] As the heat conduction member, for example, a viscoelastic layer formed between the heat dissipation surface of the battery and the cooling surface of the cooler using a thermally conductive sheet having flexibility that can be elastically deformed is used. Patent Document 1 discloses a technique for suppressing the thickness of the viscoelastic layer from becoming thin as the battery pack is used, making it difficult to cool the battery with the cooler. The battery pack described in Patent Document 1 includes a spread regulation portion that regulates the spread of the viscoelastic layer interposed between the heat dissipation surface and the cooling surface, thereby preventing the thickness of the viscoelastic layer from becoming thin.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0007] A method for manufacturing a battery pack according to one aspect of the present invention comprises the steps of: placing a heat conductive material between a battery pack case having a groove and an adjacent member adjacent to the battery pack case in a manner that allows the groove to be visually observed, and applying a load; detecting the heat conductive material that has flowed into the groove; and estimating the quality of the heat conductive material using the detected information about the heat conductive material. [Effects of the Invention]

[0008] According to the present invention, it becomes possible to easily determine whether or not a heat conductive member meets quality standards. [Brief explanation of the drawing]

[0009] [Figure 1] This is an exploded perspective view schematically showing the configuration of the battery pack according to this embodiment. [Figure 2] Figure 1 is a disassembled cross-sectional view of a portion of the battery pack. [Figure 3] This figure shows the configuration of the top surface of the battery pack case, as shown in Figure 1. [Figure 4] This is a diagram illustrating the manufacturing method of a battery pack. [Figure 5] This diagram illustrates the process for estimating the quality of a thermal conductive material. [Figure 6] This figure shows the configuration of the bottom surface of the battery pack case, as shown in Figure 1. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. For clarity of explanation, the following descriptions and drawings have been omitted and simplified as appropriate. In addition, the same elements are denoted by the same reference numerals in each drawing, and redundant explanations are omitted as necessary. In the following embodiments, when numbers such as the number of elements, quantities, amounts, or ranges are mentioned, the number is not limited to the number mentioned unless it is specifically stated or clearly defined in principle. Furthermore, structures and the like described in the embodiments shown below are not necessarily essential to the technical concept of this disclosure unless they are specifically stated or clearly defined in principle.

[0011] This disclosure relates to a method for manufacturing a battery pack used in electric vehicles such as BEVs. In such automotive battery packs, a water-cooled cooler is usually used because the battery cells generate a lot of heat. In the event of a coolant leak, the cooler is placed on the outside of the battery pack case to prevent the coolant from entering the battery pack, and the battery pack is cooled via a thermal conductive material.

[0012] Figure 1 is an exploded perspective view schematically showing the configuration of a battery pack according to one embodiment of the present disclosure. As shown in Figure 1, the battery pack 1 comprises a plurality of battery modules 10, a battery pack case 20, and a cooler 30. Here, the direction in which each battery module 10 extends is defined as the W direction, the direction in which the plurality of battery modules 10 are aligned is defined as the L direction, and the direction in which the battery modules 10, battery pack case 20, and cooler 30 are stacked is defined as the H direction. The L direction is perpendicular to both the W direction and the H direction. In the following description, the battery modules 10, battery pack case 20, and cooler 30 may be collectively referred to as a workpiece. In Figure 1, the top surface of each component of the battery pack 1 as viewed from the battery module 10 side and the bottom surface as viewed from the cooler 30 side.

[0013] Each battery module 10 has, for example, multiple battery cells arranged in two rows in the W direction. Examples of battery cells include lithium-ion batteries. The multiple battery modules 10 are arranged with spacing in the L direction. In the example shown in Figure 1, five battery modules 10 are provided. Note that the battery pack 1 may have only a single battery module 10.

[0014] The battery pack case 20 houses multiple battery modules 10. The battery pack case 20 is made of, for example, metal. The battery pack case 20 is a lower case positioned on the lower (heat dissipation) side of the battery module 10. The battery pack case 20 has a shape that opens upward. The battery pack case 20 includes a housing section 21 that houses each of the multiple battery modules 10. The housing section 21 includes a bottom section 22 and a wall section 23 that is erected upward from the edge of the bottom section 22.

[0015] The housing section 21 is larger than the battery module 10. The wall groove 24 (see Figure 3, not shown in Figure 1) formed in the wall section 23 becomes visible from the top when the battery module 10 is housed in the housing section 21. The wall groove 24 will be described in detail later.

[0016] In the example shown in Figure 1, only the lower case is shown, but the battery pack 1 may also include an upper case positioned on the upper side of the battery module 10. The upper case has a shape that opens downwards. The upper case, together with the battery pack case 20, encloses the multiple battery modules 10.

[0017] The cooler 30 is a device for cooling the battery module 10. The cooler 30 is located on the outside of the battery pack case 20. In the example shown in Figure 1, the cooler 30 is located on the underside of the bottom 22 of the battery pack case 20. The cooler 30 is made of a metal such as aluminum. The cooler 30 includes, for example, a frame 31 and cooling sections 32. In this embodiment, ten cooling sections 32 extending in the W direction are arranged at intervals in the L direction.

[0018] Each cooling part 32 is arranged at a position facing the columns in which the battery cells of the battery module 10 are arranged, sandwiching the battery pack case 20. The cooling part 32 has a cooling flow path through which a cooling medium (cooling water) for cooling the battery module 10 flows.

[0019] The bottom groove part 26 formed on the back surface of the bottom part 22 (see FIG. 6, not shown in FIG. 1) becomes visible from the lower surface side when the cooler 30 is installed on the lower surface side of the battery pack case 20. The bottom groove part 26 will be described in detail later.

[0020] The frame part 31 holds a plurality of cooling parts 32. The frame part 31 is formed in an annular shape surrounding the plurality of cooling parts 32. In the embodiment, the frame part 31 is substantially rectangular in a top view. The end parts of each cooling part 32 are respectively connected to the frame part 31.

[0021] FIG. 2 is an exploded cross-sectional view of a part of the battery pack 1. In FIG. 2, a cross-section of one accommodating part 21 is shown. Although not shown here, a heat conduction layer is provided in the space between the battery module 10 and the battery pack case 20, and in the space between the battery pack case 20 and the cooler 30. Here, the heat conduction layer between the battery module 10 and the battery pack case 20 is the inner heat conduction layer 11, and the heat conduction layer between the battery pack case 20 and the cooler 30 is the outer heat conduction layer 12.

[0022] As the inner heat conduction layer 11 and the outer heat conduction layer 12, a viscoelastic layer made of a flexible heat conduction material capable of elastic deformation is used. The inner heat conduction layer 11 and the outer heat conduction layer 12 have the heat conductivity necessary for efficiently dissipating the heat of the battery module 10 to the cooler 30. Also, the inner heat conduction layer 11 and the outer heat conduction layer 12 are made of a material having flexibility and freely deformable by compression. Further, the inner heat conduction layer 11 and the outer heat conduction layer 12 have adhesiveness for sticking to the battery module 10, the battery pack case 20, or the cooler 30.

[0023] The inner thermal conductive layer 11 and the outer thermal conductive layer 12 are not particularly limited as long as they have adhesive properties on their surface and can be deformed by compressive load. Examples of such materials include thermosetting, room-temperature curing, moisture-curing, and UV-curing resins. Examples of thermosetting resins include silicone resins, epoxy resins, and urethane resins. Such resins may contain fillers to improve thermal conductivity. Insulating inorganic compounds can be used as fillers.

[0024] The inner heat conductive layer 11 is positioned between the battery module 10 and the battery pack case 20 in a state where it is compressed and deformed in the thickness direction (H direction) by the load from the battery module 10. The inner heat conductive layer 11 can be formed as follows, for example. First, a heat conductive material is applied to the central part of the bottom 22 of each housing 21, away from the four walls 23. Then, the inner heat conductive layer 11 is formed by crushing the heat conductive material by applying a load through the battery module 10 and spreading it inside the housing 21.

[0025] Furthermore, the outer heat conductive layer 12 is positioned between the battery pack case 20 and the cooler 30 in a state where it is compressed and deformed in the thickness direction (H direction) by the load from the cooler 30. The outer heat conductive layer 12 can be formed as follows, for example. First, a heat conductive material is applied to the back surface of the bottom portion 22 of each housing portion 21 of the battery pack case 20. Then, by applying a load through the cooler 30, the heat conductive material is crushed and expanded to form the outer heat conductive layer 12.

[0026] Thus, when a load is applied to compress the thermal conductive material to form the inner thermal conductive layer 11 and the outer thermal conductive layer 12, the following problems arise: (1) the thickness and area of ​​the thermal conductive material inside the battery pack 1 cannot be set to the target quality standard, and (2) it is not possible to inspect whether the thermal conductive material meets the quality standard.

[0027] (1) Due to variations in the shapes of the battery module 10, battery pack case 20, and cooler 30, the volume of the space into which the thermal conductive material expands when a load is applied differs depending on the direction of expansion. As a result, it is not possible to spread the thermal conductive material uniformly, and it is possible that the inner thermal conductive layer 11 and outer thermal conductive layer 12 cannot meet the target quality standards.

[0028] (2) The inner heat conductive layer 11 is placed between the battery module 10 and the battery pack case 20. The outer heat conductive layer 12 is placed between the battery pack case 20 and the cooler 30. In this way, the heat conductive material is placed between the workpieces, so it is not possible to directly observe how the heat conductive material spreads. Therefore, the inventor devised a method that achieves both a quality control structure and a quality assurance method.

[0029] First, the inner heat conductive layer 11 will be described. Figure 3 shows the configuration of the top surface of the battery pack case 20 shown in Figure 1. In Figure 3, diagonal lines are used to clarify the position of the grooves. As shown in Figure 3, wall grooves 24 are formed in the wall portion 23. In the example shown in Figure 1, two wall grooves 24 are provided at intervals in the wall portion 23 extending in the W direction. Also, one wall groove 24 is provided in the wall portion 23 extending in the L direction. The length of the wall groove 24 in the W direction, the length in the L direction, and the length in the H direction can be changed as appropriate.

[0030] Because the thermal conductive material is a highly viscous fluid, its flowability changes due to pressure loss when it is compressed and flows between narrow workpieces. By changing the position and size of the wall grooves 24, it becomes possible to appropriately control the volume of the space in each direction in which the thermal conductive material expands to form the inner thermal conductive layer 11 when a load is applied. For example, the volume of the space in the ±W and ±L directions can be changed with respect to the center of the housing 21.

[0031] The volumes of these spaces may be different or the same, taking into account the shapes of the battery module 10, the battery pack case 20, and the cooler 30. This makes it possible to control the flow rate of the thermal conductive material.

[0032] Figure 4 illustrates a method for manufacturing a battery pack. Figure 4 shows a cross-section of the area where the wall groove 24 is formed. In this example, the wall groove 24 is formed in a part of the bottom 22 side of the wall 23. Note that the wall groove 24 is not limited to being formed in a part of the wall 23, but may penetrate from the bottom to the top of the wall 23.

[0033] As shown in the left diagram of Figure 4, first, the thermal conductive material T is applied to the center of the bottom 22 inside the housing 21, so as not to come into contact with the wall 23. Then, a load is applied via the battery module 10. As a result, as shown in the center diagram of Figure 4, the thermal conductive material T spreads out toward the wall 23 where the wall groove 24 is formed. The compressed thermal conductive material T protrudes into the gap between the battery module 10 and the wall 23.

[0034] Subsequently, as shown in the right-hand diagram of Figure 4, by applying a load through the battery module 10, the thermal conductive material T fills the wall groove 24 and overflows from the wall groove 24. As a result, the inner thermal conductive layer 11 is formed in a compressed and deformed state. Then, the thermal conductive material that has flowed into the wall groove 24 is detected, and the quality of the thermal conductive material is estimated using the detected information about the thermal conductive material.

[0035] Figure 5 illustrates the process for estimating the quality of the inner thermal conductive layer 11 in the manufacturing method of the battery pack 1. Figure 5(a) shows an example in which the inner thermal conductive layer 11 meets the quality standards, and Figure 5(b) shows an example in which the inner thermal conductive layer 11 does not meet the quality standards. The figure on the right shows the battery module 10 removed from the figure on the left, making the inner thermal conductive layer 11 formed on the lower surface of the battery module 10 visible.

[0036] In the example shown in Figure 5(b), the thermal conductive material T is completely filled in the left and lower wall grooves 24, but it is not completely filled in the upper right wall grooves 24 of the upper wall 23. In this way, when there are areas in the wall grooves 24 that are not filled with thermal conductive material T, the inner thermal conductive layer 11 does not extend to the upper right portion of the housing 21, as shown in the right diagram of Figure 5(b), and it was confirmed that the quality standards are not met.

[0037] As shown in Figure 5(a), the thermal conductive material T completely fills each wall groove 24 of the four adjacent wall portions 23. In this way, when each wall groove 24 is 100% filled with the thermal conductive material T, it was confirmed that the inner thermal conductive layer 11 has a predetermined area and thickness that meets the quality standards, as shown in the right-hand figure of Figure 5(a).

[0038] Therefore, for example, by detecting the filling rate of the thermal conductive material T in the wall groove 24 using image recognition by a camera, it is possible to estimate whether or not the inner thermal conductive layer 11 meets the quality standards. It is also possible to estimate the quality of the inner thermal conductive layer 11 by measuring the height of the thermal conductive material T along the H direction in the wall groove 24 using a laser displacement meter or a contact gauge. Note that the wall groove 24 does not need to be completely filled with the thermal conductive material T; it is possible to determine that the inner thermal conductive layer 11 meets the quality standards as long as the filling rate is above a predetermined level.

[0039] In the example described above, a wall groove 24 was formed in the wall 23, but it is not particularly limited as long as the groove can be formed in a visible location. For example, a groove may be formed in the bottom 22 located in the gap between the battery module 10 and the wall groove 24.

[0040] Furthermore, in order to solve the problem of (1) described above, the groove may be formed at the bottom 22 of the housing portion 21 between the battery module 10 and the battery pack case 20, or it may be formed on the contact surface of the battery module 10 with the battery pack case 20.

[0041] Next, the outer heat conductive layer 12 will be described. Figure 6 shows the configuration of the lower surface of the battery pack case 20 shown in Figure 1. In Figure 6, diagonal lines are used to clarify the formation position of the bottom groove 26. The lower side of the bottom 22 is referred to as the back surface 25.

[0042] In the example shown in Figure 6, four bottom grooves 26 are formed on the back surface 25. On the back surface 25, the four bottom grooves 26 are formed at positions corresponding to the four wall portions 23 that form each of the housing portions 21. The bottom grooves 26 are formed along the W direction or L direction in which the wall portions 23 extend. That is, the four bottom grooves 26 are formed so as to surround the back surface 25 corresponding to each housing portion 21. The four bottom grooves 26 may be formed independently, or some or all of them may be formed continuously. The length of the bottom grooves 26 in the W direction, L direction, and H direction can be changed as appropriate.

[0043] By changing the position and size of the bottom groove 26, it is possible to appropriately control the volume of the space in each direction in which the heat conductive material for forming the outer heat conductive layer 12 spreads when a load is applied. This makes it possible to control the ease with which the heat conductive material flows. In order to solve the problem of (1) described above, the groove may be formed on the back surface 25 between the cooler 30 and the battery pack case 20, or it may be formed on the contact surface of the cooler 30 with the battery pack case 20.

[0044] The four bottom grooves 26 are visible when the cooler 30 is in place. Therefore, as described above, the quality of the outer heat conductive layer 12 can be estimated by detecting the filling rate of the heat conductive material in the bottom grooves 26.

[0045] As described above, according to the embodiment, it is possible to easily estimate the quality of the inner heat conductive layer 11 and the outer heat conductive layer 12 in a non-destructive manner. Furthermore, by controlling the volume of the space that expands in each direction when the heat conductive material is compressed, it is possible to control the fluidity of the heat conductive material.

[0046] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0047] 1 Battery pack 10 Battery Modules 11. Inner heat conduction layer 12. Outer thermal conductive layer 20 Battery Pack Cases 21 Storage Unit 22 Bottom 23 Wall 24 Wall groove 25 Back side 26 Bottom groove 30 Cooler 31 Frame section 32 Cooling section T Thermal conductive material

Claims

1. A step of placing a heat conductive material between a battery pack case having a groove and an adjacent member adjacent to the battery pack case in a manner that makes the groove visible, and applying a load, A step of detecting the heat conductive material that has flowed into the groove, A step of estimating the quality of the heat conductive material using the detected information about the heat conductive material, Equipped with, A method for manufacturing battery packs.

2. The adjacent member includes at least one battery module, The battery pack case comprises a housing portion formed from a bottom portion and a wall portion for housing the battery module, The step of applying the load involves housing the battery module in the housing and applying the load in a state where the groove is visible from the upper side. A method for manufacturing a battery pack according to claim 1.

3. The groove is formed in at least one of the bottom or wall portions. A method for manufacturing a battery pack according to claim 2.

4. The adjacent member includes a cooler for cooling the battery module. The process of applying the load involves placing the cooler on the back side of the bottom of the battery pack case and applying the load in a state where the groove is visible from the bottom side. A method for manufacturing a battery pack according to claim 2.

5. The step of estimating the quality of the thermal conductive material involves estimating the quality based on the filling rate of the thermal conductive material in the groove. A method for manufacturing a battery pack according to claim 1.

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