Battery pack and method for manufacturing same

Abstract

The present invention makes it possible to fix secondary battery cells to a battery holder with high reliability. A battery pack 100 includes: a plurality of secondary battery cells 1 each of which has an outer can with a cylindrical shape and has end faces of the cylindrical shape that are cell end faces; and a battery holder 2 including a holder body 10 having a plurality of storage parts 14 that are each for storing one of the plurality of secondary battery cells 1, and a holder lid 20 fixed to the holder body 10 via an adhesive layer 40 in a state where the secondary battery cells 1 are stored in the storage parts 14 of the holder body 10. The battery holder 2 includes, at at least a part of a bonding interface where the end edge of each storage part 14 of the holder body 10 and the holder lid 20 face each other, a protrusion 30 protruding in a direction intersecting the bonding interface. The adhesive layer 40 is formed at the bonding interface between each protrusion 30 and the holder body 10.

Description

Battery pack and manufacturing method thereof

[0001] The present disclosure relates to a battery pack and a method for manufacturing the same.

[0002] Battery packs are used to power electrical devices such as power tools, or to power electrically driven mobile objects such as vehicles and construction machinery, by connecting multiple rechargeable secondary battery cells, such as lithium-ion secondary batteries, in series or parallel (see, for example, Patent Document 1). Some secondary battery cells used in such battery packs are housed in a battery holder.

[0003] As shown in the perspective views of FIGS. 7 and 8 , the battery holder 702 may be divided into a holder main body 710 and a holder lid 720 to facilitate the storage of the secondary battery cells 701. In such a configuration, an adhesive 742 may be used to secure the holder main body 710 and the holder lid 720 to form the battery holder 702. For example, this may be used to waterproof the joint interface between the holder main body 710 and the holder lid 720. A method of securing the battery holder 702 using the adhesive 742 involves storing the secondary battery cells 701 in the holder main body 710, partially applying the adhesive 742 to the periphery of the secondary battery cell 701 on the holder main body 710 side, as shown in black in the plan view of FIG. 9 , and then closing the holder main body 710 with the holder lid 720 as shown in FIG. 10 . The adhesive 742 is then spread in the gap between the holder main body 710 and the holder lid 720 to bond and secure the interface between the holder lid 720 and the holder main body 710.

[0004] 11 , the adhesive 742 is not uniformly spread, resulting in blank areas BK where no adhesive layer is formed in the adhesive layer 740 formed after the adhesive 742 hardens. When the adhesive 742 is uneven around the secondary battery cell 701 in this way, the adhesive 742 is unable to exert a uniform bonding force, which may result in a decrease in strength and reliability.

[0005] Japanese Patent Application Laid-Open No. 2018-6275

[0006] One object of one embodiment of the present disclosure is to provide a battery pack and a manufacturing method thereof that enable rechargeable battery cells to be reliably fixed to a battery holder. Another object of another embodiment is to provide a battery pack and a manufacturing method thereof that enable adhesive to be uniformly applied. Note that the description of these objects and problems of the present disclosure does not preclude the existence of other objects and problems. Furthermore, it is not necessary for one embodiment of the present disclosure to solve all of these problems. Furthermore, problems other than these may be extracted from the description of the specification, drawings, and claims of the present disclosure.

[0007] A battery pack according to one embodiment of the present disclosure is a battery pack comprising: a battery holder including a plurality of secondary battery cells, each having a cylindrical outer can with each end face of the cylinder as a cell end face; a holder main body having a plurality of storage sections for storing the plurality of secondary battery cells, respectively; and a holder lid that is fixed to the holder main body via an adhesive layer when the secondary battery cells are stored in the storage sections of the holder main body, wherein the battery holder has a protrusion that protrudes in a direction intersecting the joint interface between the edge of the storage section of the holder main body and the holder lid, and the adhesive layer is formed at the joint interface between the protrusion and the holder main body.

[0008] A manufacturing method of a battery pack according to another aspect is a manufacturing method of a battery pack including a battery holder including a plurality of secondary battery cells, each having a cylindrical outer can and each end face of the cylindrical can as a cell end face, a holder main body having a plurality of storage sections for storing the plurality of secondary battery cells, and a holder lid fixed to the holder main body via an adhesive layer in a state in which the secondary battery cells are stored in the storage sections of the holder main body, wherein a protrusion is formed in a direction intersecting the bonding interface at at least a part of a bonding interface where an edge of the storage section of the holder main body and the holder lid face each other. the step of preparing the battery holder on which the protrusions are formed; the step of discretely applying uncured adhesive to the bonding interface between the protrusions and the holder body at positions corresponding to the protrusions; the step of bonding the holder lid to the holder body and spreading the uncured adhesive discretely applied to the bonding interface with the protrusions, thereby diffusing the uncured adhesive so that it is continuously connected to each other at the bonding interface; and the step of curing the uncured adhesive to form an adhesive layer at the bonding interface between the protrusions and the holder body.

[0009] According to a battery pack of one embodiment of the present disclosure, when the holder lid is adhered to the holder body, the uncured adhesive that has been partially applied to the joint interface is pushed out by the protrusion and diffused to the surrounding area, allowing the adhesive to be distributed evenly over the joint interface, preventing uneven areas where the adhesive is not applied and improving the reliability of the adhesion.

[0010] 1 is a perspective view showing a battery pack according to an embodiment; FIG. 1 is a vertical cross-sectional view taken along line II-II of the battery pack of FIG. 1; FIG. 2 is an exploded perspective view showing the assembled state of the battery pack of FIG. 3; FIG. 4 is an exploded perspective view showing the battery pack of FIG. 3 when viewed obliquely from below; FIG. 5 is an exploded cross-sectional view showing how the holder lid is bonded to the holder body of FIG. 4; FIG. 6 is a perspective view of a battery pack according to a comparative example; FIG. 7 is an exploded perspective view showing the assembled state of the battery pack of FIG. 7; FIG. 8 is a plan view showing the top surface of the holder body of FIG. 8; FIG. 9 is an exploded cross-sectional view showing how the holder lid is bonded to the holder body of FIG. 8; FIG. 10 is a cross-sectional view taken along line XI-XI of the battery pack of FIG. 7; FIG. 11 is an enlarged cross-sectional view of a main part of the battery pack of FIG. 2; FIG. 12 is an enlarged cross-sectional view of a main part of the battery pack according to an embodiment; FIG. 13 is a plan view showing a state in which an adhesive material has been applied to the top surface of the holder body of FIG. 4; FIG. 16A to FIG. 16I are enlarged views showing protrusions of the battery packs according to the respective embodiments; FIG. 16B is a perspective plan view of the battery pack of FIG. 4; FIG. 17 is a horizontal cross-sectional view taken along line XVIII-XVIII of the battery pack of FIG. 1;

[0011] The embodiments of the present disclosure may be specified by the following configurations and features.

[0012] In a battery pack according to another aspect of the present disclosure, in the above aspect, the protrusion is formed on the holder lid. With this configuration, uncured adhesive can be applied to the edge of the storage section of the holder body and spread by the protrusion of the holder lid, so that the adhesive can be distributed almost uniformly at the bonding interface.

[0013] In addition, in the battery pack according to another aspect of the present disclosure, in any of the above aspects, the protrusion has an inclined surface. With this configuration, by pressing the inclined surface of the protrusion against the uncured adhesive, the adhesive can be easily spread laterally along the inclined surface and diffused.

[0014] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the protrusion has the inclined surfaces formed symmetrically with respect to the protruding direction of the protrusion. With this configuration, the inclined surfaces of the protrusion formed symmetrically can spread the uncured adhesive evenly around the protrusion, making it easier to diffuse the adhesive.

[0015] In a battery pack according to still another aspect of the present disclosure, in any of the above aspects, the protrusion has a curved surface. With this configuration, by pressing the inclined surface of the protrusion against the uncured adhesive, the adhesive can be easily spread laterally along the curved surface and diffused.

[0016] In a battery pack according to still another aspect of the present disclosure, in any of the above aspects, the protrusion is formed in any one of a cone shape, a truncated cone shape, a pyramid shape, and a truncated pyramid shape. By forming the protrusion in a flared shape, the uncured adhesive can be easily spread and diffused evenly around the protrusion.

[0017] In a battery pack according to still another aspect of the present disclosure, in any of the above aspects, the holder main body is configured so that the plurality of storage sections that respectively store the plurality of cylindrical secondary battery cells hold the plurality of secondary battery cells in a stacked state with adjacent storage sections arranged in a staggered manner, and the bonding interface is provided in the gap between three adjacent secondary battery cells arranged in the staggered manner. With this configuration, it is possible to apply uncured adhesive to the area surrounded by the three staggered secondary battery cells, thereby stably bonding the holder main body and the holder lid.

[0018] In a battery pack according to yet another aspect of the present disclosure, in any of the above aspects, the storage compartment is open at both ends, a pair of holder lids are provided to close each open end of the storage compartment, and the protrusions are provided at each bonding interface between each holder lid and the holder body. This configuration enables stable bonding of each holder lid to the holder body in a structure in which each cell end face of a secondary battery cell stored in a holder tube is closed by the holder lid.

[0019] In a battery pack according to yet another aspect of the present disclosure, in any of the above aspects, the holder main body has a guide portion formed around the open end of the storage compartment. With this configuration, adhesive can be guided through the guide portion to the side surface of the secondary battery cell inserted into the storage compartment, thereby firmly fixing the holder lid and holder main body to the holder tube.

[0020] In addition, in a battery pack according to another aspect of the present disclosure, in any of the above aspects, the protrusions are formed at positions corresponding to the application positions of the adhesive material that forms the adhesive layer. With this configuration, the protrusions formed at the positions corresponding to the applied adhesive material can efficiently spread the adhesive material and distribute it evenly around the periphery of the storage portion and the interface between the holder lid, thereby increasing the bonding strength and improving reliability.

[0021] In yet another aspect of the present disclosure, in the method for manufacturing a battery pack according to any of the above aspects, in the step of preparing the battery holder, the protrusions are formed on the holder lid, and in the step of discretely applying the uncured adhesive, the uncured adhesive is applied to the edge of the storage section of the holder main body. This allows the uncured adhesive to be applied to the edge of the storage section of the holder main body and then spread by the protrusions of the holder lid, so that the adhesive is distributed almost uniformly at the bonding interface. In particular, when the uncured adhesive is applied to the side of the holder main body where the secondary battery cell is inserted and the holder lid is advanced toward this side to crush the adhesive, the protrusions formed on the holder lid spread the uncured adhesive and diffuse it around, making it possible to apply the adhesive evenly, exerting adhesive strength and improving reliability.

[0022] Embodiments of the present disclosure will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concepts of the present disclosure, and the present disclosure is not limited to the following. Furthermore, this specification does not in any way specify the components set forth in the claims to be those of the embodiments. The dimensions, materials, shapes, relative positions, etc. of components described in the embodiments are not intended to limit the scope of the present disclosure, and are merely illustrative examples, unless otherwise specified. The size and positional relationships of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate components that are identical or of the same quality, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present disclosure may be configured with the same components, such that multiple elements are served by a single component, or conversely, the functions of a single component may be shared by multiple components.

[0023] The battery pack of the present disclosure can be used as a power source for portable electrical devices such as power tools and electric cleaners, as a driving power source for mobile objects such as electric carts, electric scooters, and assisted bicycles, as a backup power source for servers in stationary power storage applications, as a battery pack for home, office, or factory use, and as a driving power source for vehicles such as hybrid cars and electric cars. Hereinafter, as one embodiment of the present invention, a battery pack used as a driving power source for power tools used at construction sites, such as earth compactors, will be described. [Embodiment 1]

[0024] A battery pack 100 according to a first embodiment of the present disclosure is shown in FIGS. 1 to 6. In these figures, FIG. 1 is a perspective view showing the battery pack 100 according to the embodiment, FIG. 2 is a vertical cross-sectional view of the battery pack 100 of FIG. 1 taken along line II-II, FIG. 3 is an exploded perspective view of the battery pack 100 of FIG. 1, FIG. 4 is an exploded perspective view showing the assembled state of the battery pack 100 of FIG. 3, FIG. 5 is an exploded perspective view of the battery pack 100 of FIG. 4 seen obliquely from below, and FIG. 6 is an exploded cross-sectional view showing how the holder lid 20 is attached to the holder main body 10 of FIG. 4. The battery pack 100 shown in these figures includes multiple rechargeable battery cells 1 and a battery holder 2. The battery pack 100 of FIG. 1 has a box-shaped exterior and houses multiple rechargeable battery cells 1 inside the battery holder 2. In the battery pack, the electrodes of each rechargeable battery cell are connected to lead plates. The lead plates are also connected to a circuit board. Furthermore, the battery pack is housed in an outer case as needed, and the secondary battery cells are discharged and charged via output terminals drawn out from the surface of the outer case (secondary battery cells 1).

[0025] In the examples of Figures 2 and 3, cylindrical secondary battery cells are used as the secondary battery cells 1, each with a cylindrical outer can. Each cylindrical secondary battery cell has a cell end face on each end face of the cylinder, and is provided with a cell electrode. The cell electrodes are connected to lead plates (not shown) and are connected in series or parallel to adjacent secondary battery cells 1. In the example of Figure 3, 12 secondary battery cells 1 are connected in a 4-parallel x 3-series configuration. However, the number of secondary battery cells, the number of series connections, and the number of parallel connections are not limited to this example and can be designed as appropriate according to the required specifications.

[0026] In the example shown in FIG. 1 etc., cylindrical secondary battery cells 1 are arranged horizontally in a staggered pattern inside the outer can. The arrangement of the secondary battery cells is not limited to this example, and any arrangement can be used as appropriate. For example, cylindrical secondary battery cells can be arranged in rows and columns or in a matrix. Known secondary batteries, such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, can be used as such secondary battery cells 1.

[0027] Each secondary battery cell 1 has a positive and a negative cell electrode. The positive or negative cell electrode terminal is preferably provided on one cell end surface of the secondary battery cell 1. In the example of FIG. 3, the positive terminal is provided on one cell end surface of the secondary battery cell 1, and the other surface of the outer can serves as the negative terminal. (Battery holder 2)

[0028] The battery holder 2 holds multiple secondary battery cells 1 in a position where the end faces of each cell are flush with one another. The end faces of adjacent secondary battery cells 1 are offset from each other, with the centers of the circles shifted.

[0029] The battery holder 2 is divided into a holder body 10 and a holder lid 20. In the example shown in the exploded perspective view of Figure 3, the battery holder 2 is composed of three pieces, with the holder lid 20 fixed to the top and bottom of the holder body 10. With the rechargeable battery cells 1 inserted into the holder body 10, the battery holder 2 holds the rechargeable battery cells 1 by covering the ends of the rechargeable battery cells 1 that protrude from the top and bottom of the holder body 10 with the holder lid 20, as shown in Figure 2 and other figures. However, the battery holder may be divided into three, two, four or more parts.

[0030] In this configuration where the battery holder 2 is divided into multiple pieces, a fixing structure is required to fix each piece together. In this case, adhesive 42 is used to form an adhesive layer 40 at the joint interface between each piece (holder body 10).

[0031] The holder body 10 has a box-like outer shape with a top surface 11, a bottom surface 12, and side surfaces 13. The holder body 10 is hollow and has multiple storage sections 14 for storing multiple rechargeable battery cells 1, respectively. The top surface 11, the bottom surface 12, and the side surfaces 13 are each formed in a plate shape. As shown in the exploded perspective view of FIG. 3 , the storage sections 14 are formed by storage windows opened in the box-like top surface 11 and bottom surface 12. The storage windows are opened along the outer shape of the rechargeable battery cells 1. If the rechargeable battery cells 1 are cylindrical, the storage windows are slightly larger and have a circular shape. By passing the rechargeable battery cells 1 through the storage windows in the top surface 11 and the bottom surface 12, the upper and lower parts of the rechargeable battery cells 1 are held by the top surface 11 and the bottom surface 12 of the holder body 10, respectively. The side surfaces of the rechargeable battery cells 1 are exposed. Furthermore, by partially opening the side surfaces 13 of the holder body 10 and exposing the side surfaces of the rechargeable battery cells 1, heat dissipation can be improved. As shown in Figures 2, 4, 6, etc., when a rechargeable battery cell 1 is inserted into the holder body 10, the top and bottom portions of each rechargeable battery cell 1 protrude from the holder body 10. These protruding top and bottom portions of the rechargeable battery cell 1 are held by the holder lid 20. Furthermore, to make it easier to position the holder lid 20, the holder body 10 has protruding wall portions 15 around the top surface 11 and bottom surface 12, and the holder lid 20 is positioned inside the area surrounded by the wall portions 15. The wall portions 15 are formed by extending the side surfaces 13 of the holder body 10. (Holder lid 20)

[0032] The holder lid 20 is fixed to the holder body 10 via an adhesive layer 40 when the rechargeable battery cells 1 are stored in the storage compartments 14 of the holder body 10. The adhesive 42 and adhesive layer 40 are not shown in the exploded perspective view of FIG. 3 . As shown in FIGS. 2 , 5 , 6 , etc., the holder lid 20 has recesses 21 into which the upper and lower ends of the rechargeable battery cells 1 are inserted. An opening window 22 is formed in the bottom surface 12 of the recess 21, exposing the cell ends of each rechargeable battery cell 1 stored in the battery holder 2. This allows the cell ends of the rechargeable battery cells 1 stored in the battery holder 2 to be connected to lead plates or the like.

[0033] The holder body 10 and the holder lid 20 are made of a material with excellent insulating properties, preferably a resin such as polycarbonate or PC-ABS alloy. (Protrusion 30)

[0034] The battery holder 2 has a protrusion 30 formed on at least a portion of the joint interface between the edge of the storage section 14 of the holder body 10 and the holder lid 20, protruding in a direction intersecting this joint interface. With this configuration, when the holder lid 20 is bonded to the holder body 10, the uncured adhesive 42 partially applied to the joint interface is spread by the protrusion 30 and diffused to the surrounding area, allowing the adhesive 42 to be distributed evenly across the joint interface, preventing areas where the adhesive 42 is not applied and improving the reliability of the bond.

[0035] As mentioned above, when a battery holder is divided into multiple pieces, such as a holder body and a holder lid, a fixing structure is required to fasten the pieces together. Fixing structures include, for example, threaded engagement using screws, or engagement or press-fitting using pins or bosses. However, to use these fixing structures, it is necessary to form screw holes or boss holes in the partition wall of the storage section that stores the secondary battery cells in the holder body, and then fix the holder lid.

[0036] On the other hand, in recent years, there has been a strong demand for smaller and lighter battery packs to make them easier to carry and improve fuel efficiency. This has led to a demand for thinner partition walls, making it difficult to make them thicker. Therefore, one approach to fixating the partition wall joint interface with an adhesive is to secure the partition wall while keeping it thin. Fixing with an adhesive not only provides waterproofing, but also fixes the rechargeable battery cell to the storage section, thereby preventing the rechargeable battery cell from rotating inside the storage section and damaging the joint between the lead plate and the battery cell.

[0037] For example, consider a configuration in which the holder main body 710 and the holder lid 720 are fixed together with adhesive 742 in a battery pack 700 according to a comparative example shown in the perspective views of Figures 7 and 8. In this case, with a secondary battery cell 701 stored in the storage section 714 of the holder main body 710, uncured adhesive 742 is applied partially around the secondary battery cell 701 on the holder main body 710 side, as shown in black in the plan view of Figure 9. Then, as shown in Figure 10, the holder lid 720 is closed, and the adhesive 742 is forced to spread in the gap between the holder main body 710 and the holder lid 720, thereby adhering and fixing the interface between the holder lid 720 and the holder main body 710.

[0038] However, with this configuration, the adhesive 742 is not uniformly spread, and as shown in Fig. 11, blank areas BK may appear in the adhesive layer 740 formed after the adhesive 742 hardens. When the adhesive 742 becomes uneven around the secondary battery cell 701 in this way, the adhesive 742 is unable to exert a uniform bonding force, which may result in a decrease in strength and reliability.

[0039] Therefore, in the battery pack 100 according to this embodiment, as shown in Figures 4 and 5, a protrusion 30 is formed at the interface between the holder lid 20 and the holder body 10 of the battery holder 2. Uncured adhesive 42 is applied to the positions corresponding to the protrusions 30, and the tips of the protrusions 30 spread and distribute the adhesive 42 around the periphery, ensuring uniform distribution of the adhesive 42 and preventing unevenness. This results in a stable adhesive layer 40 and improved reliability. For the sake of explanation, Figures 4 and 5 show the upper holder lid 20 being fastened to the holder body 10. However, a similar technique can be used to fasten the lower holder lid 20 to the holder body 10. The following mainly describes the structure for fastening the upper holder lid 20 to the holder body 10.

[0040] In the example of Fig. 5, protrusions 30 are formed on the back surface of the holder lid 20. Furthermore, uncured adhesive 42 is applied to the holder main body 10 side as shown in Fig. 4. As shown in Fig. 6, by applying uncured adhesive 42 to the edge of the storage section 14 of the holder main body 10 and then spreading it with the protrusions 30 of the holder lid 20, it is possible to distribute the adhesive 42 almost uniformly at the bonding interface. In particular, when applying uncured adhesive 42 to the side of the holder main body 10 where the secondary battery cell 1 is inserted and then moving the holder lid 20 toward this side to crush the adhesive 42, the protrusions 30 formed on the holder lid 20 spread the uncured adhesive 42 around, thereby enabling the adhesive 42 to be applied uniformly, exerting adhesive strength and improving reliability.

[0041] However, the present disclosure is not limited to this configuration. For example, protrusions may be formed on the holder body side and adhesive applied to the holder lid side. For example, while protrusions 30 are formed on the bottom side of the holder lid 20 in FIG. 6, protrusions may also be formed on the bottom side of the holder body and uncured adhesive applied to the holder lid. This has the advantage that adhesive can be applied without turning the battery holder 2 upside down, while keeping it in the same position. This is because applying uncured adhesive generally requires application to the top side of the holder lid or holder body.

[0042] The bonding area of ​​the bonding interface on the holder body 10 side, which receives the protrusion 30, is flat. This makes it easy to apply an appropriate amount of uncured adhesive 42 to the flat surface opposite the location of the protrusion 30. The bonding area on the holder body 10 side is the area surrounded by the storage windows opened in the holder body 10. For example, in a configuration in which the storage sections 14 are arranged in a staggered pattern in the holder body 10 as shown in FIG. 15 , the bonding area is a triangle surrounded by three storage sections 14, or a radial shape branching at 120°. Correspondingly, as shown in FIG. 5 , protrusions 30 are provided at the centers of the radial shapes on the bottom surface 12 side of the holder lid 20. Note that in the example of FIG. 5 , the protrusions 30 are only provided in the area of ​​the bonding interface where the rechargeable battery cells 1 are adjacent to each other, i.e., only within the end surface region 24 where the cell end faces of multiple rechargeable battery cells 1 are gathered together to form a mass. In other words, they are not formed outside the end surface region 24. Outside the end surface region 24, a wide bonding interface between the holder body 10 and the holder lid 20 is ensured, and the adhesive 42 spreads easily, so it can be sufficiently diffused without providing the protrusions 30. However, protrusions may also be provided on bonding interfaces other than the end surface region. For example, protrusions may be provided at all positions corresponding to the regions where the adhesive is applied, as shown in FIG. 15. (Inclined Surface)

[0043] The protrusions 30 preferably have inclined surfaces, so that by pressing the inclined surfaces of the protrusions 30 against the uncured adhesive 42, the adhesive 42 can be pushed and spread laterally along the inclined surfaces, facilitating diffusion.

[0044] Furthermore, it is preferable that the inclined surfaces of the protrusions 30 be formed symmetrically with respect to the protruding direction of the protrusions 30. This allows the uncured adhesive 42 to be evenly spread around the protrusions 30 and easily diffused. The example in FIG. 5 shows an example in which the protrusions 30 are conical. By forming the protrusions 30 in this shape, the spread adhesive 42 hardens and forms an adhesive layer 40, as shown in black in the enlarged cross-sectional view in FIG. 12. Note that in FIG. 5, multiple dashed auxiliary lines along the inclined surfaces of the cone are shown to indicate that the protrusions 30 are conical. However, these are merely for the purpose of creating a three-dimensional representation of the figure and do not represent a specific shape such as the sides of a pyramid.

[0045] The protrusions 30 may have curved surfaces. By pressing the inclined surfaces of the protrusions 30 against the uncured adhesive 42, the adhesive 42 can be pushed and spread laterally along the curved surfaces, facilitating diffusion. The example of FIG. 13 shows a second embodiment in which the protrusions 30B are dome-shaped. In this example, the adhesive 42 can be pushed and spread laterally in the figure, allowing the adhesive 42 to be distributed evenly.

[0046] Furthermore, the tip of the protrusion 30 may be sharp or curved, or may be flat. As an example, the protrusion 30C of the battery pack according to embodiment 3 shown in FIG. 14 has a truncated cone shape, with the tip of the cone cut off to form a flat surface 32. A truncated cone or a truncated pyramid can be used for the truncated cone. In this example, too, the adhesive 42 can be pushed outward to the left and right in the figure, allowing the adhesive 42 to be distributed evenly. Furthermore, by making the contact surface of the protrusion 30 flat, it can be stably opposed to the holder body 10.

[0047] Furthermore, the bottom surface 12 of the protrusion 30 may be circular, polygonal, elliptical, track-shaped, or the like. For example, it may be elongated depending on the width of the joining area surrounded by the storage windows of the holder main body 10. For example, in an example shown in Figure 15 where the storage sections 14 are arranged in a staggered pattern in the holder main body 10, the protrusion 30 may be formed with the bottom surface 12 being a triangular area on the holder lid 20 side that faces the triangular joining area surrounded by three storage sections 14.

[0048] In this way, the shape of the protrusion 30 can be a cone, a truncated cone, a pyramid, a truncated pyramid, etc. Examples of specific shapes of the protrusion 30 are shown in Figures 16A to 16I. 16A shows a conical protrusion 30 of the battery pack 100 according to embodiment 1, FIG. 16B shows a dome-shaped protrusion 30B of the battery pack according to embodiment 2, FIG. 16C shows a truncated cone-shaped protrusion 30C of the battery pack according to embodiment 3, FIG. 16D shows a triangular pyramid-shaped protrusion 30D of the battery pack according to embodiment 4, FIG. 16E shows a square-pyramid-shaped protrusion 30E of the battery pack according to embodiment 5, FIG. 16F shows a hexagonal pyramid-shaped protrusion 30F of the battery pack according to embodiment 6, FIG. 16G shows a triangular pyramid-shaped protrusion 30G of the battery pack according to embodiment 7, FIG. 16H shows a square-pyramid-shaped protrusion 30H of the battery pack according to embodiment 8, and FIG. 16I shows a hexagonal pyramid-shaped protrusion 30I of the battery pack according to embodiment 9. In either example, by making the protrusions 30 flared, the uncured adhesive 42 can be easily spread and evenly spread around the protrusions 30 .

[0049] Furthermore, when the holder body 10 and holder lid 20 are secured with adhesive 42, the rechargeable battery cell 1 can also be secured to the battery holder 2. In particular, when cylindrical rechargeable battery cells are stored in the storage compartment, they cannot be prevented from rotating circumferentially due to vibration or impact, raising concerns that the connection between the lead plate and the cell end face may be broken by the rotation. Therefore, securing the rechargeable battery cell 1 to the battery holder 2 reduces the risk of such breakage and improves reliability. (Guide section 16)

[0050] The holder main body 10 has a guide portion 16 formed by cutting out the periphery of the opening edge of the storage window in the top surface 11 that defines the storage window. In the example shown in the enlarged views of Figures 3 and 12, the guide portion 16 is formed by chamfering the edge of the opening edge of the storage section 14. By creating the guide portion 16 in the storage section 14 in this manner, the opening edge of the storage window is widened, making it easier to guide the uncured adhesive 42 toward the storage window. As a result, the uncured adhesive 42 pushed out from the bonding area also penetrates between the storage window and the side surface of the rechargeable battery cell 1, bonding the holder main body 10 and the rechargeable battery cell 1. In this way, the adhesive 42 continuously extends from the bonding interface to the side surface of the rechargeable battery cell 1 inserted into the storage section 14, thereby securing the holder lid 20 to the holder main body 10 and firmly fixing the rechargeable battery cell 1 to the holder tube. The adhesive layer 40 also extends from within the horizontal plane in a vertical direction that intersects this plane, forming an extension region 44. (Filling space 26)

[0051] As is clear from Figure 11 , which shows a comparative example, adhesive 42 tends to be applied relatively evenly at positions away from the cell end faces of the secondary battery cells 1, i.e., when joining flat surfaces. Conversely, in narrow joining areas, i.e., areas where the cell end faces are closely spaced, areas where adhesive 42 is not distributed evenly tend to occur. Therefore, as shown in Figure 4 , the top surface of the holder body 10 is flat, while as shown in Figure 5 , the bottom surface of the holder lid 20, i.e., the surface facing the holder body 10, has a flat outer peripheral region 25 around the end face region 24, where the cell end faces of multiple secondary battery cells 1 gather together to form a mass. However, the interior of the end face region 24, specifically the region between the cell end faces, is recessed in a stepped shape. The end face region 24 is shown by a dashed line in Figure 17 . This creates a gap between the end face region 24 and the holder body 10, forming a filling space 26 into which uncured adhesive 42 can easily spread. The filling space 26 can be filled with adhesive 42 to form a thick adhesive layer 40. The filling space 26 is shown in black in FIG.

[0052] The height of the protrusions 30 is set to be approximately equal to or slightly lower than the height of the filling space 26. This prevents the holder lid 20 from lifting up when the holder lid 20 is joined to the holder body 10, and also has the effect of spreading the uncured adhesive 42 around by using the tips of the protrusions 30. (Adhesive 42)

[0053] The adhesive 42 is selected from materials that exhibit adhesive strength depending on the materials of the holder body 10 and the holder lid 20. Synthetic adhesives such as acrylic, epoxy, silicone, and polyurethane adhesives are preferably used. [Method of Manufacturing a Battery Pack]

[0054] The method for manufacturing the above battery pack, particularly the method for fixing the battery holder, will now be described. First, a holder body 10 and a holder lid 20 are prepared as the battery holder 2. The battery holder 2 has a protrusion 30 formed on at least a portion of the joint interface between the edge of the storage section 14 of the holder body 10 and the holder lid 20, protruding in a direction intersecting this joint interface. In the example shown in Figure 5, the protrusion 30 is formed on the holder lid 20. The holder body 10 is configured so that the multiple storage sections 14, each housing a plurality of cylindrical secondary battery cells 1, hold the multiple secondary battery cells 1 in a stacked state with adjacent storage sections 14 arranged in a staggered pattern. Therefore, the joint interface is located in the gap between three adjacent secondary battery cells 1 arranged in a staggered pattern.

[0055] Next, uncured adhesive 42 is applied discretely to the bonding interface between the protrusions 30 and the holder body 10, in positions corresponding to the protrusions 30. In the example of Fig. 15, uncured adhesive 42 is applied to the edge of the storage section 14 of the holder body 10, in positions corresponding to the locations of the protrusions 30. By applying uncured adhesive 42 to the area surrounded by three secondary battery cells 1 arranged in a staggered pattern in this way, it is possible to stably bond the holder body 10 and the holder lid 20.

[0056] Then, the holder lid 20 is joined to the holder body 10, and the uncured adhesive 42 that has been applied discretely to the joining interface is spread by the protrusions 30, so that the uncured adhesive 42 is diffused so that it is continuously connected to each other at the joining interface.

[0057] Finally, the uncured adhesive 42 is cured to form an adhesive layer 40 at the bonding interface between the protrusions 30 and the holder body 10. As a result, when the holder lid 20 is bonded to the holder body 10, the uncured adhesive 42 partially applied to the bonding interface is spread and diffused by the protrusions 30, allowing the adhesive 42 to be distributed evenly across the bonding interface, preventing areas where the adhesive 42 is not applied and improving the reliability of the bond. In particular, the protrusions 30 formed at positions corresponding to the applied adhesive 42 can pinpoint and efficiently spread the adhesive 42, allowing the adhesive 42 to be distributed over the interface between the periphery of the storage section 14 and the holder lid 20.

[0058] In the above examples, the battery pack is attached to the electrical device to be driven and supplies power to the electrical device. When the remaining capacity of the battery pack becomes low or when the battery pack deteriorates over time, the battery pack can be replaced, allowing the electrical device to continue being used. However, the present invention is not limited to replaceable battery packs that mainly house secondary battery cells, but can also be applied to embodiments in which secondary battery cells are housed within the housing of the electrical device. In this disclosure, a battery pack is sufficient as long as it houses secondary battery cells within a case, and also includes battery packs in which driving secondary battery cells are built into the housing of the electrical device itself. In other words, the present invention is not limited to replaceable battery packs, but can also be applied to electrical devices that house secondary battery cells.

[0059] The battery pack and manufacturing method thereof according to the present disclosure can be suitably used as a power source for portable electrical equipment such as construction machinery such as earth compactors, power tools, radios, and electric cleaners. It can also be used as a power source for driving assisted bicycles, and as a power source for vehicles such as self-propelled delivery robots, electric carts for delivery and golf courses, electric scooters, construction machinery, hybrid vehicles, and electric vehicles. It can also be used as a stationary power storage device, for example, a battery pack for home, business, or factory use, or as a backup power source for servers.

[0060] DESCRIPTION OF SYMBOLS 100...Battery pack 1...Rechargeable battery cell 2...Battery holder 10...Holder body 11...Top surface 12...Bottom surface 13...Side surface 14...Storage section 15...Wall portion 16...Guide portion 20...Holder lid 21...Recessed portion 22...Opening window 24...End surface region 25...Outer peripheral region 26...Filling space 30, 30B, 30C, 30D, 30E, 30F, 30G, 30H, 30I...Protrusions 32...Flat surface 40...Adhesive layer 42...Uncured adhesive material 11...Top surface 12...Bottom surface 13...Side surface 14...Storage section 15...Wall portion 16...Guide portion 20...Holder lid 21...Recessed portion 22...Opening window 24...End surface region 25...Outer peripheral region 26...Filling space 30, 30B, 30C, 30D, 30E, 30F, 30G, 30H, 30I... Projection portion 32... Flat surface 40... Adhesive layer 42... Uncured adhesive material 44... Stretched region 700... Battery pack 701... Secondary battery cell 702... Battery holder 710... Holder body 714... Storage section 720... Holder lid 740... Adhesive layer 742... Adhesive BK... Blank region

Claims

1. A battery pack comprising: a battery holder comprising: a plurality of secondary battery cells, each having a cylindrical outer can with each end face of the cylinder as a cell end face; a holder body having a plurality of storage sections for storing the plurality of secondary battery cells, respectively; and a holder lid that is fixed to the holder body via an adhesive layer when the secondary battery cells are stored in the storage sections of the holder body, wherein the battery holder forms a protrusion that protrudes in a direction intersecting the bonding interface at at least a part of the bonding interface between the edge of the storage section of the holder body and the holder lid, and the adhesive layer is formed at the bonding interface between the protrusion and the holder body.

2. A battery pack according to claim 1, wherein the protrusion is formed on the holder lid.

3. A battery pack according to claim 1, wherein the protrusion has an inclined surface.

4. A battery pack according to claim 3, wherein the protrusion has the inclined surface formed symmetrically with respect to the protruding direction of the protrusion.

5. A battery pack according to any one of claims 1 to 4, wherein the protrusion is formed in any one of a cone shape, a truncated cone shape, a pyramid shape, and a truncated pyramid shape.

6. A battery pack as claimed in any one of claims 1 to 4, wherein the holder body is configured to hold the plurality of cylindrical secondary battery cells in a stacked state with the plurality of storage sections that respectively store the plurality of secondary battery cells arranged in a staggered manner with adjacent storage sections arranged in a staggered manner, and the bonding interface is provided in the gap between three adjacent secondary battery cells arranged in the staggered manner.

7. A battery pack as claimed in any one of claims 1 to 4, wherein the storage section is open at both ends, a pair of holder lids are provided to close each open end of the storage section, and the protrusions are provided at each joint interface between each holder lid and the holder body.

8. A battery pack according to any one of claims 1 to 4, wherein the holder body has a guide portion formed around the opening end of the storage portion.

9. A battery pack according to any one of claims 1 to 4, wherein the protrusion is formed at a position corresponding to the application position of the adhesive material that forms the adhesive layer.

10. A method for manufacturing a battery pack comprising: a battery holder comprising: a plurality of secondary battery cells, each having a cylindrical outer can with each end face of the cylinder as a cell end face; a holder body having a plurality of storage sections for storing the plurality of secondary battery cells, respectively; and a holder lid fixed to the holder body via an adhesive layer with the secondary battery cells stored in the storage sections of the holder body, the method comprising the steps of: preparing the battery holder, in which a protrusion is formed on at least a part of a joint interface between an edge of the storage section of the holder body and the holder lid, the protrusion protruding in a direction intersecting the joint interface; and discretely applying uncured adhesive to the joint interface between the protrusion and the holder body at a position corresponding to the protrusion. a step of joining the holder lid to the holder body, and spreading the uncured adhesive discretely applied to the bonding interface with the protrusions to diffuse the uncured adhesive so that it is continuously connected to each other at the bonding interface; and a step of curing the uncured adhesive to form an adhesive layer at the bonding interface between the protrusions and the holder body.

11. A method for manufacturing a battery pack as described in claim 10, wherein in the step of preparing the battery holder, the protrusion is formed on the holder lid, and in the step of discretely applying the uncured adhesive, the uncured adhesive is applied to the edge of the storage section of the holder body.

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