Battery pack and method for manufacturing same

Abstract

In the present invention, reliability of bond strength between an exterior case and a battery core fixated inside the exterior case is enhanced. A battery pack 100 comprises: a battery core 2 which holds a plurality of secondary battery cells 1; and an exterior case 10 which has at least one surface opened and is connected from an opening end 13 to define a storage space 14 for storing the battery core 2 thereinside. The exterior case 10 comprises a suspension structure for suspending the battery core 2 in the storage space 14. A fixed gap GP1 is formed between the bottom surface of the battery core 2 suspended in the storage space 14 by the suspension structure and the inner bottom surface of the exterior case 10, and an adhesive layer 40 is interposed in the gap GP1.

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 drive electric vehicles such as vehicles and construction machinery, or electric devices such as power tools, by connecting multiple rechargeable secondary battery cells such as lithium-ion secondary batteries in series or parallel and storing them in an exterior case (see, for example, Patent Document 1). In such battery packs, the battery core is stored in the exterior case.

[0003] When fixing such an outer case and battery core with adhesive, the adhesive is applied to the bottom of the outer case before the battery core is inserted. However, when the weight of the battery core presses against the adhesive, the thickness of the adhesive between the outer case and battery core is not uniform, which creates the problem of making it difficult to achieve uniform fixing strength.

[0004] Furthermore, the battery core could not be inserted into the bottom of the battery core unless there was a large clearance between the exterior case and the battery core, making it difficult to position the battery core. In particular, in a configuration in which a connector or the like is provided on the top surface of the battery core, it is necessary to position the connector that is exposed to the outside of the exterior case, but this position cannot be uniquely determined.

[0005] Japanese Patent Application Laid-Open No. 2005-347233

[0006] One object of one embodiment of the present disclosure is to provide a battery pack and a manufacturing method thereof that improve the reliability of the joint strength between the battery core fixed inside the outer case and the outer case. Another object of another embodiment is to provide a battery pack and a manufacturing method thereof that allows the outer case and the battery core to be positioned. 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 core that holds a plurality of secondary battery cells, and an outer case that has at least one open side and is connected to the open end to define a storage space for storing the battery core therein, wherein the outer case has a suspension structure that suspends the battery core in the storage space, and a fixed gap is formed between the bottom surface of the battery core suspended in the storage space by the suspension structure and the inner bottom surface of the outer case, and an adhesive layer is interposed in the gap.

[0008] In addition, a manufacturing method for a battery pack according to another embodiment of the present disclosure is a manufacturing method for a battery pack including a battery core that holds a plurality of secondary battery cells and an outer case that defines a storage space for storing the battery core therein, and includes the steps of applying uncured adhesive to the bottom surface of the storage space of the outer case, suspending the battery core in the storage space with a suspension structure that suspends the battery core in the storage space of the outer case, forming a fixed gap between the bottom surface of the battery core and the inner bottom surface of the outer case, and arranging the uncured adhesive in the fixed gap, and curing the adhesive to form an adhesive layer in the fixed gap.

[0009] According to a battery pack according to one embodiment of the present disclosure, the bottom surface of the battery core is raised by a suspension structure to form a gap of a certain height, which can be filled with adhesive to form an adhesive layer of uniform thickness, thereby increasing the reliability of the bonding strength between the battery core and the outer case.

[0010] 1 is a perspective view showing a battery pack according to an embodiment; FIG. 1 is an exploded perspective view showing a state in which a lid portion of the battery pack of FIG. 1 has been removed; FIG. 2 is an exploded perspective view showing a state in which a battery core has been further removed from an exterior case; FIG. 1 is a vertical cross-sectional view of the battery pack of FIG. 1 taken along line IV-IV with an enlarged view of a main portion; FIG. 1 is a horizontal cross-sectional view of the battery pack of FIG. 1 taken along line V-V; FIG. 1 is a vertical cross-sectional view of a battery pack according to Comparative Example 1; FIG. 2 is an exploded cross-sectional view of a battery pack according to Comparative Example 2 with an enlarged view of a main portion; FIG. 2 is an enlarged perspective view of a main portion of the battery pack of FIG. 8; FIG. 4 is an enlarged exploded cross-sectional view of a main portion of a lower portion of the battery pack of FIG. 4; FIG. 4 is an enlarged cross-sectional view of a main portion showing a suspension structure of the battery pack of FIG. 4; FIG. 2 is a plan view of the battery pack of FIG. 2; FIG. 12 is an enlarged plan view of a main portion of a first corner of the battery pack of FIG. 12; FIG. 12 is an enlarged plan view of a main portion of a second corner of the battery pack of FIG. 12; FIG. 12 is an enlarged plan view of a main portion of a third corner of the battery pack of FIG. 12; FIG. 12 is an enlarged vertical cross-sectional view of a main portion showing a suspension structure of the battery pack according to an embodiment; FIG. 12 is a vertical cross-sectional view of a battery pack according to an embodiment with an enlarged view of a main portion.

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

[0012] In the power supply device according to another aspect of the present disclosure, in the above-described aspect, the suspension structure is provided above the storage space and also serves as a structure for positioning the battery core within the storage space. This configuration has the advantage that the suspension structure can also position the battery core.

[0013] In addition, in a power supply device according to another aspect of the present disclosure, in any of the above aspects, the exterior case has a rectangular outer shape, and the suspension structure is provided in an upper corner of the storage space. With this configuration, by providing the suspension structure at a corner of the rectangular exterior case, it is possible to prevent the outer shape of the battery core from becoming smaller due to the provision of the suspension structure, thereby preventing a reduction in battery capacity.

[0014] In addition, in a power supply device according to another aspect of the present disclosure, in any of the above aspects, the suspension structure includes a core-side locking portion protruding from a shoulder portion of the battery core, and a case-side locking portion protruding from an upper portion of the outer case to the interior thereof for locking the core-side locking portion. With this configuration, the shoulder portion of the battery core can be locked to the core-side locking portion of the outer case, making it easy to suspend the battery core within the storage space.

[0015] In addition, in the power supply device according to another aspect of the present disclosure, in any of the above aspects, the case-side locking portion includes a base portion that protrudes into the storage space and a pin portion that protrudes from the upper surface of the base portion, and the core-side locking portion includes a protruding piece that is disposed on the base portion and is thinner than the height of the pin portion, and a hole that opens in the protruding piece and into which the pin portion can be inserted. With the above configuration, a suspension structure can be realized with a simple configuration in which the pin portion is inserted into the hole portion.

[0016] In yet another aspect of the power supply device of the present disclosure, in any of the above aspects, the suspension structure is provided at each of the four corners of the upper portion of the storage space of the rectangular outer case, and the first hole of the first core-side locking part located at a first corner of the four corners has a first clearance between the first pin inserted into the first hole and the first clearance between the first pin inserted into the first hole and the pin inserted into the hole of the core-side locking part located at the other corner. With this configuration, the hole at the first corner positions the battery core and the outer case, while the clearances at the other holes are increased to accommodate component tolerances and manufacturing tolerances.

[0017] In yet another aspect of the power supply device of the present disclosure, in any of the above aspects, the second hole of the second core-side locking portion located adjacent to one side of the first corner of the four corners is formed in a circular shape, and the second hole is formed with an inner diameter larger than that of the first hole. With this configuration, the hole at the first corner positions the battery core and the outer case, while the second hole provides a larger clearance to accommodate component tolerances and manufacturing tolerances.

[0018] In yet another aspect of the power supply device of the present disclosure, in any of the above aspects, the suspension structure is provided at each of the four corners of the upper portion of the storage space of the exterior case having a rectangular outer shape, and the first hole of the first core-side locking part located at a first corner of the four corners is formed in a circular shape, and the third hole of the third core-side locking part located at a third corner diagonally opposite to the first corner is formed in an elongated hole elongated in the diagonal direction. With the above configuration, it is possible to position the battery core in the rotational direction while accommodating component tolerances and manufacturing tolerances.

[0019] Furthermore, in the power supply device according to another aspect of the present disclosure, in any of the above aspects, the height of the pin portion is 5 mm to 20 mm.

[0020] In addition, in the power supply device according to any one of the above aspects, the gap between the bottom surface of the battery core and the inner bottom surface of the exterior case is 0.8 mm to 4 mm.

[0021] Furthermore, in the power supply device according to another aspect of the present disclosure, in any one of the above aspects, the pin portion has a screw hole formed therein.

[0022] The battery pack further includes a screw portion that is screwed into the screw hole.

[0023] The pin is inserted into the hole, and the screw is threaded into the screw hole to secure the core-side locking portion to the case-side locking portion, with the protruding piece locked to the base. With this configuration, the battery core is secured in a suspended state within the storage space of the outer case, improving stability.

[0024] In yet another aspect of the power supply device of the present disclosure, in any of the above aspects, the exterior case is formed in a box shape, and of the vertical, horizontal, and height directions that form the box-shaped solid, the height direction, which is the direction in which the battery core is inserted from the opening end into the storage space, is formed to be the longest. With this configuration, since the battery core is inserted in the height direction, which is the longest direction, it would be difficult to position it in the height direction, but positioning is achieved by a suspension structure.

[0025] In a power supply device according to still another aspect of the present disclosure, in any of the above aspects, the battery core has a connector portion on its top surface. With this configuration, the bottom surface of the battery core can be fixed, while the connector portion on the top surface, which requires positioning, can be connected to the exterior case in a suspended structure while being positioned thereon.

[0026] 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.

[0027] The battery pack of the present disclosure can be used as a driving power source for mobile devices such as electric carts, electric scooters, and assisted bicycles, as a power source for portable electrical devices such as power tools and electric cleaners, 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 an electric forklift will be described. [Embodiment 1]

[0028] A battery pack 100 according to a first embodiment of the present disclosure is shown in FIGS. 1 to 5. In these figures, FIG. 1 is a perspective view showing the battery pack 100 according to the embodiment, FIG. 2 is an exploded perspective view showing the battery pack 100 of FIG. 1 with the lid removed, FIG. 3 is an exploded perspective view showing the battery pack 100 of FIG. 2 with the battery core 2 further removed from the outer case 10, FIG. 4 is a vertical cross-sectional view of the battery pack 100 of FIG. 1 taken along line IV-IV with an enlarged view of a main portion, and FIG. 5 is a horizontal cross-sectional view of the battery pack 100 of FIG. 1 taken along line V-V. The battery pack 100 shown in these figures includes an outer case 10 and a battery core 2. It also includes a circuit board 3 and a connector 4 as needed. (Outer case 10)

[0029] The exterior case 10 houses the battery core 2 and circuit board 3. The exterior shape of the exterior case 10 can be any shape that has an internal storage space 14. However, a rectangular shape is preferable from the standpoints of outer diameter stability and ease of storage of the battery core 2. Here, the exterior case 10 is formed into a box shape with its exterior extending vertically. Of the three sides that form the box-shaped solid, the height is the longest. In this example, the height of the exterior case 10 is 200 mm to 400 mm, the horizontal width (i.e., the width of the bottom surface) is 20 mm to 50 mm, and the vertical depth (i.e., the depth of the bottom surface) is 20 mm to 50 mm.

[0030] 1 to 3, the box-shaped outer case 10 is composed of two separate pieces: a lid case 11 and a main case 12. The lid case 11 and the main case 12 are fastened together by screwing or the like. However, the present disclosure is not limited to this configuration, and the outer case may be divided into three or more pieces.

[0031] The exterior case 10 is preferably made of a material with excellent insulating properties, such as a resin such as polycarbonate or PC-ABS alloy, but may also be made of a metal material such as aluminum or its alloy.

[0032] Furthermore, the exterior case 10 has an open end 13 on one side thereof. The open end 13 is in communication with the interior space. In the examples shown in Figures 3 and 4, the open end 13 is formed on the top surface of the main case 12 of the exterior case 10, and the battery core 2 is inserted into the storage space 14 from above. (Battery Core 2)

[0033] The battery core 2, also known as a core pack, houses multiple rechargeable battery cells 1. The battery core 2 may also be composed of multiple battery blocks, each housing multiple rechargeable battery cells 1. In the example shown in FIG. 5, the battery core 2 is divided into two in the front-to-rear direction, and the two battery blocks form the battery core 2. The top plate 2a of the battery core 2 is made of a material strong enough to withstand the suspension of a heavy load of multiple rechargeable battery cells, such as a resin such as polycarbonate or PC-ABS alloy, or a metal member such as aluminum or its alloy. (Battery holder 5)

[0034] Each battery core 2 includes a battery holder 5, a rechargeable battery cell 1, and lead plates. The battery holder 5 has multiple cylindrical holder sections, into which the rechargeable battery cells 1 are inserted and held. The battery holder 5 may house all of the rechargeable battery cells 1 as a whole, or may be divided into multiple sub-holders, each of which may house only a few of the multiple rechargeable battery cells. The battery holder may also be divided in the length direction of the rechargeable battery cells. The battery holder 5 is made of a material with excellent insulating properties. Preferably, it is made of a resin such as polycarbonate or PC-ABS alloy.

[0035] The battery core 2 also includes lead plates for electrically connecting the rechargeable battery cells 1 to each other. The lead plates are preferably arranged on the outer surface of the battery holder 5. The lead plates are electrically connected to the terminals of the rechargeable battery cells 1 exposed through electrode windows opened in the battery holder 5. Each lead plate connects the electrodes on the cell end faces of the rechargeable battery cells 1 to each other, thereby connecting multiple rechargeable battery cells 1 to each other. The lead plates are made of metal plates with excellent conductivity, such as aluminum, nickel, or copper. Multiple rechargeable battery cells 1 are connected in series or in parallel via the lead plates. The number of series connections or parallel connections can be set as desired according to the required specifications. The number of rechargeable battery cells and the connection configuration, i.e., the number of series connections or parallel connections, are set appropriately according to the required specifications. (Secondary Battery Cell 1)

[0036] As shown in Figures 4 and 5, each battery block 30 houses rechargeable battery cells 1 in a battery holder 5. Each rechargeable battery cell 1 can be cylindrical or rectangular. In the example shown in Figure 4, the cylindrical rechargeable battery cells 1 are arranged horizontally in a staggered pattern. The number and arrangement of the rechargeable battery cells 1 are not limited to this example, and any number and arrangement can be used. For example, cylindrical rechargeable battery cells can be arranged in a matrix. Known rechargeable batteries, such as lithium-ion rechargeable batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, can be used as the rechargeable battery cells 1.

[0037] Each secondary battery cell 1 has a positive electrode and a negative electrode. The positive or negative electrode terminal is preferably provided on one cell end face of the secondary battery cell 1. In the example of FIG. 5, a positive terminal is provided on one cell end face of the secondary battery cell 1, and the other face of the outer casing serves as the negative electrode. The battery holder 5 stacks multiple secondary battery cells 1 in multiple vertical tiers with the cell end faces on the same plane. In addition, the cell end faces of adjacent secondary battery cells 1 in the vertical tiers are offset with the centers of the circles shifted. (Circuit board 3)

[0038] The battery core 2 is connected to the circuit board 3 via lead plates. The circuit board 3 is equipped with a charge / discharge circuit that charges and discharges the secondary battery cells 1, and a protection circuit that monitors the voltage and temperature of the secondary battery cells 1 and cuts off the current in the event of an abnormality. The circuit board 3 is made of a glass epoxy board or the like. A board holder may also be provided as a member to hold the circuit board 3. (Connector 4)

[0039] Furthermore, the circuit board 3 has a connector 4 on its top surface. The connector 4 is exposed from the top surface of the exterior case 10 for electrical connection with external devices. (Suspension structure)

[0040] The exterior case 10 also has a suspension structure that suspends the battery core 2 in the storage space 14. This suspension structure forms a constant gap GP1 between the bottom surface of the battery core 2 suspended in the storage space 14 and the inner bottom surface of the exterior case 10. Furthermore, an adhesive layer 40 is interposed in the gap GP1. By using this suspension structure to raise the bottom surface of the battery core 2 and form a gap GP1 of a constant height, an adhesive can be filled in this gap to form an adhesive layer 40 of uniform thickness, thereby improving the reliability of the bonding strength between the battery core 2 and the exterior case 10.

[0041] In a battery pack that is long in the vertical direction, it is difficult to fix the battery core to the outer case by passing bolts or the like through the top and bottom. Therefore, it is possible to adopt a structure in which the bottom surface of the battery core is adhered to the inner surface of the outer case with adhesive. In this case, uncured adhesive is applied to the bottom surface of the outer case before inserting the battery core.

[0042] However, when the battery core's own weight presses the adhesive, the thickness of the adhesive between the exterior case and the battery core is not uniform, resulting in a problem of inconsistent fixation strength. For example, depending on the position of the battery core's center of gravity, weight balance, and the battery core's posture during insertion, the battery core 602 may be tilted within the exterior case 610, as in the battery pack 600 of Comparative Example 1 shown in Figure 6 . It is particularly difficult to insert the battery core 602 into a deep exterior case 610 while maintaining its bottom parallel to the bottom of the exterior case 610. Furthermore, uncured adhesive has a certain degree of viscosity and tends to form lumps, making it difficult to apply it to the bottom of a deep exterior case 610 with a uniform thickness. As a result, if the adhesive is applied in a partially thickened state, the battery core 602 may tilt. As a result, the thickness of the adhesive layer 640 that fixes the battery core 602 varies in parts, resulting in uneven bonding strength and making it difficult to maintain a stable fixation state.

[0043] It is also possible to provide a step on the bottom surface of the exterior case for positioning the battery core. However, to ensure that the tip of the battery core can be smoothly inserted into a deep exterior case, a certain amount of clearance must be secured between the interior space of the exterior case and the surface of the battery core. This allows the battery core 702 to tilt within the exterior case 710, as in the battery pack 700 of the comparative example shown in Figure 7, which also leads to an uneven adhesive layer 740.

[0044] In contrast, in the battery pack 100 according to this embodiment, as shown in Figures 3, 8, 9, etc., the battery core 2 is suspended in the storage space 14 using a suspension structure, forming a constant gap GP1 between the bottom surface of the battery core 2 and the inner side of the bottom surface of the exterior case 10. By floating the bottom surface of the battery core 2 using this suspension structure, the distance between the bottom surface of the battery core 2 and the inner bottom surface of the exterior case 10 can be kept constant, and the adhesive material filled there forms an adhesive layer 40 of uniform thickness, thereby improving the reliability of the bonding strength between the battery core 2 and the exterior case 10.

[0045] The gap GP1 between the bottom surface of the battery core 2 and the bottom surface of the inner surface of the exterior case 10 is 0.8 mm to 4 mm, preferably 1 mm to 2 mm, and more preferably 1.6±0.6 mm, as shown in the enlarged cross-sectional view of FIG.

[0046] Furthermore, the suspension structure is provided above the storage space 14, i.e., above the battery core 2. This suspension structure also serves as a positioning structure for the battery core 2 within the storage space 14. This configuration is particularly advantageous in a structure in which a connector 4 for electrical connection is provided on the upper side of the storage space 14. That is, the connector 4, which connects to the battery core 2 and is exposed from the exterior case 10 for electrical connection with the outside, needs to be positioned. By positioning the storage space 14 and the upper part of the battery core 2 using the suspension structure, the connector 4 provided at the upper part of the storage space 14, i.e., the upper part of the exterior case 10, can be accurately positioned, allowing it to be exposed from the top surface of the lid case 11 of the exterior case 10. In particular, when a waterproof structure is required for the battery pack 100, the positioning of the connector 4 exposed to the outside is important. The suspension structure stably fixes the battery core 2 to the bottom surface of the outer case 10, while the position of the connector 4 exposed from the lid case 11 is uniquely determined on the top surface of the outer case 10, improving the assembly accuracy of the battery pack 100.

[0047] The suspension structure is preferably provided at the upper corner of the storage space 14. In the examples shown in Figures 8 and 9, a suspension structure is provided at each of the four rectangular corners of the opening edge 13 of the exterior case 10. The rectangular corners are dead space, but by utilizing this space to provide a suspension structure, it is possible to prevent the cross-sectional shape of the battery core 2 from becoming smaller due to the addition of the suspension structure, which would reduce battery capacity.

[0048] The suspension structure is composed of a core-side locking portion and a case-side locking portion 20. The core-side locking portion protrudes from the shoulder of the top plate 2a of the battery core 2. Meanwhile, the case-side locking portion 20 is provided so as to protrude inward from the top of the outer case 10. By locking the core-side locking portion with the case-side locking portion 20, the battery core 2 is suspended within the storage space 14. In this way, by locking the shoulder of the battery core 2 with the core-side locking portion of the outer case 10, the battery core 2 can be easily suspended within the storage space 14. Preferably, the suspension structure is provided at a corner of the top plate 2a of the rectangular battery core 2. (Case-side locking portion 20)

[0049] 8 and 9, the case-side locking portion 20 includes a base portion 21 that protrudes into the storage space 14 and a pin portion 22 that protrudes from the upper surface of the base portion 21. The base portion 21 and the pin portion 22 are preferably molded integrally with the outer case 10. (Core-side locking portion 30)

[0050] The core-side locking portion 30 is provided with a protruding piece 31 that is positioned on the base portion 21 and is the same height as or thinner than the pin portion 22, and a hole 32 that is opened in the protruding piece 31 and into which the pin portion 22 can be inserted. The protruding piece 31 is preferably formed integrally with a corner of the top plate 2a of the battery core 2.

[0051] In this way, a suspension structure can be realized with a simple configuration in which the pin portion 22 is inserted into the hole 32 of the protruding piece 31. The pin portion 22 is preferably formed in a cylindrical shape. The hole 32 is preferably formed in a circular shape that follows the outer diameter of the pin portion 22. The height of the pin portion 22 is 5 mm to 20 mm, preferably 10 mm ± 0.05 mm, as shown in the enlarged cross-sectional view of FIG. 11 . The thickness of the protruding piece 31 in which the hole 32 is formed, i.e., the depth of the hole 32, is the same as or shallower than the pin portion 22, and is 5 mm to 20 mm, preferably 9 mm ± 0.05 mm. In the example of FIG. 11 , the suspension structure is achieved by inserting the hole 32 into the pin portion 22. However, the hole 32 may be cylindrical and a rivet or the like may be pressed into the hole 32 to prevent the pin portion 22 from slipping out of the hole 32.

[0052] 12 , the suspension structures provided at the four corners of the open end 13 of the exterior case 10 include a first case-side locking portion 20a and a first core-side locking portion 30a at the first corner, a second case-side locking portion 20b and a second core-side locking portion 30b at the second corner, a third case-side locking portion 20c and a third core-side locking portion 30c at the third corner, and a fourth case-side locking portion 20d and a fourth core-side locking portion 30d at the fourth corner. The first case-side locking portion 20a, located at the first upper right corner in the figure, includes a first pin portion 22a. The first core-side locking portion 30a also includes a first hole portion 32a.

[0053] 13, the first hole 32a of the first core-side locking portion 30a has a first clearance CL1 between the first pin 22a of the first case-side locking portion 20a inserted into this first hole 32a and the first clearance CL1 between the first hole 32a and the first pin 22a of the first case-side locking portion 20a inserted into this first hole 32a and the first clearance CL1 between the first hole 32a and the pin 22 inserted into the hole 32 of the core-side locking portion 30 located at another corner. With this configuration, the battery core 2 and the outer case 10 are positioned by the first hole 32a at the first corner, while the clearances at the other hole 32 are increased to accommodate component tolerances and manufacturing tolerances.

[0054] As an example, Figure 14 shows the second clearance CL2 between the second pin portion 22b of the second case-side locking portion 20b at the second corner and the second hole portion 32b of the second core-side locking portion 30b. Here, the second pin portion 22b has the same outer diameter as the first pin portion 22a (e.g., 5 mm to 10 mm, preferably 8 mm ± 0.05 mm), while the inner diameter DM1 of the first hole portion 32a (e.g., 8.1 mm ± 0.05 mm) is designed to be smaller than the inner diameter DM2 of the second hole portion 32b (e.g., 8.7 mm ± 0.05 mm). The inner diameter of the fourth hole portion 32d at the fourth corner is also designed to be the same as the second hole portion 32b. In this way, positioning is performed at four locations, and clearances are provided in each suspension structure to accommodate design tolerances. The clearance at the first corner is reduced, allowing for positioning even with the clearance provided. The first hole 32a, the second hole 32b, and the fourth hole 32d are formed in a circular shape. The third pin 22c and the fourth pin 22d also have the same outer diameter as the first pin 22a.

[0055] On the other hand, the third hole 32c, located diagonally from the first hole 32a, is formed as an elongated hole elongated in the diagonal direction, as shown in FIG. 15 . The elongated third hole 32c has an inner diameter DM3a in the major axis direction extending diagonally and an inner diameter DM3b in the minor axis direction extending in the width direction intersecting the diagonal direction. In other words, the third clearance between the third hole 32c and the third pin portion 22c is formed such that the third clearance CL3a is wide in the diagonal direction relative to the first corner and the third clearance CL3b is narrow in the width direction perpendicular to the first corner. This configuration enables the battery core 2 to be positioned in the horizontal plane while accommodating component tolerances and manufacturing tolerances. That is, by narrowing the clearance at the first corner to position the starting point, the position of the battery core 2 in the horizontal plane becomes undefined due to the clearances at the other corners. However, by narrowing the clearance in the rotational direction at the third corner diagonal to the first corner, the battery core 2 can be positioned in the rotational direction. [Embodiment 2]

[0056] In the above example, the suspension structure is a combination of the pin portion 22 and the hole portion 32. However, the present disclosure is not limited to this configuration, and other suspension structures can be appropriately adopted. For example, the enlarged cross-sectional view of a main portion of a battery pack 200 according to embodiment 2 is shown in FIG. 16 . In this figure, components similar to those in embodiment 1 described above are assigned the same reference numerals and detailed description will be omitted. The suspension structure of the battery pack 200 according to embodiment 2 employs a threaded engagement using a screw portion 34. Specifically, the pin portion 22′ has a threaded hole 24′. The height of the pin portion 22′ is lower than the depth of the hole portion 32. In this suspension structure, the hole portion 32 is inserted into the pin portion 22′, and the protruding piece 31 is engaged with the base portion 21. Then, the screw portion 34 is threaded into the threaded hole 24′ to secure the core-side locking portion 30 to the case-side locking portion 20. This allows the battery core 2 to be fixed in a suspended state within the storage space 14 of the exterior case 10, further improving stability (adhesive 42).

[0057] The adhesive is applied to the bottom surface of the outer case 10 before inserting the battery core 2 into the outer case 10. The amount of adhesive to be applied is set to an amount that will completely fill the gap GP1 with the adhesive layer 40, taking into consideration the size of the gap GP1, i.e., the volume of the gap GP1, and shrinkage and evaporation of the adhesive when it hardens.

[0058] For the adhesive 42, a material that can exert adhesive strength is selected according to the materials of the battery core 2 and the outer case 10. Preferably, synthetic adhesives such as silicone-based, acrylic-based, epoxy-based, and polyurethane-based adhesives can be used (second adhesive layer 42).

[0059] In the above example, a structure in which the bottom side of the battery core 2 is fixed to the bottom surface of the exterior case 10 has been described. However, the present disclosure is not limited to this configuration, and the side surfaces of the battery core may also be fixed to the exterior case in addition to the bottom surface. Such an example is shown in the cross-sectional view of FIG. 17 as a battery pack 300 according to embodiment 3, with an enlarged view of a key portion. In this figure, components similar to those in embodiment 1 and the like are designated by the same reference numerals, and detailed descriptions are omitted as appropriate. In the battery pack 300 of FIG. 17, in addition to the adhesive layer 40 formed between the bottom surface of the battery core 2 and the bottom surface of the exterior case 10, a second adhesive layer 42 is also formed in the second gap GP2 between the side surface of the battery core 2 and the side surface of the exterior case 10. The second adhesive layer 42 may be provided on only one of the four sides forming the box-shaped side surface of the battery core 2, two opposing sides, any three sides, or all four sides. The second adhesive layer 42 on the side surface is formed by filling the second gap GP2 between the outer case 10 and the battery core 2 with uncured adhesive after the battery core 2 is inserted into the outer case 10. Preferably, the adhesive is filled into the second gap GP2 on the side surface before the adhesive on the bottom surface cures. The second adhesive layer 42 does not need to cover the entire side surface, and may only cover a portion of it.

[0060] It is preferable to avoid applying adhesive to the sides of the outer case 10 before inserting the battery core 2, when uncured adhesive is already applied to the bottom of the outer case 10. This is because the adhesive applied to the sides may hinder the insertion of the battery core 2, and some of the adhesive may be scraped off from the sides and pushed out toward the bottom, resulting in an excess of adhesive on the bottom side. [Battery Pack Manufacturing Method]

[0061] The manufacturing method of the above battery pack, particularly the method for fixing the battery core 2, will now be described. First, uncured adhesive is applied to the bottom surface of the storage space 14 of the outer case 10. Next, the battery core 2 is suspended in the storage space 14 of the outer case 10 using a suspension structure, forming a fixed gap GP1 between the bottom surface of the battery core 2 and the inner bottom surface of the outer case 10. With the uncured adhesive in this gap GP1, the adhesive is cured to form an adhesive layer 40 in this gap GP1. In this way, the suspension structure raises the bottom surface of the battery core 2, forming a gap GP1 of a fixed height. This allows adhesive to be filled in this gap to form an adhesive layer 40 of uniform thickness, thereby improving the reliability of the bonding strength between the battery core 2 and the outer case 10.

[0062] 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.

[0063] The battery pack according to the present disclosure can be suitably used as a driving power source for assisted bicycles, and a driving 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 power source for portable electrical devices such as radios, electric cleaners, and power tools. It can also be used as a cooling mechanism for electrical devices with built-in heating elements, not limited to power sources. 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.

[0064] DESCRIPTION OF SYMBOLS 100, 200, 300... Battery pack 1... Secondary battery cell 2... Battery core; 2a... Top plate 3... Circuit board 4... Connector 5... Battery holder 10... Outer case 11... Lid case 12... Main body case 13... Opening edge 14... Storage space 20... Case side locking portion; 20a... First case side locking portion; 20b... Second case side locking portion; 20c... Third case side locking portion; 20d... Fourth case side locking portion; 21... Base portion 22, 22'... Pin portion; 22a... First pin portion; 22b... Second pin portion; 22c... Third pin portion; 22d... Fourth pin portion; 24'... Screw hole 30... Core side locking portion; 30a... First core side locking portion; 30b... Second core side locking portion; 30c... Third core side locking portion; 30d... Fourth core side locking portion; 31...protruding piece 32...hole portion; 32a...first hole portion; 32b...second hole portion; 32c...third hole portion; 32d...fourth hole portion; 34...screw portion 40...adhesive layer 42...second adhesive layer 600...battery pack 602...battery core 610...external case 640...adhesive layer 700...battery pack 702...battery core 710...external case 740...adhesive layer GP1...gap GP2...second gap CL1...first clearance CL2...second clearance CL3a...third clearance in diagonal direction; CL3b...third clearance in width direction DM1...inner diameter of first hole portion DM2...inner diameter of second hole portion DM3a...inner diameter of third hole portion in major axis direction DM3b...inner diameter of third hole portion in minor axis direction

Claims

1. A battery pack comprising: a battery core that holds a plurality of secondary battery cells; and an exterior case that has at least one open side and is connected to the open end to define a storage space for storing the battery core inside, wherein the exterior case has a suspension structure that suspends the battery core in the storage space, and a fixed gap is formed between the bottom surface of the battery core suspended in the storage space by the suspension structure and the inner bottom surface of the exterior case, and an adhesive layer is interposed in the gap.

2. A battery pack as claimed in claim 1, wherein the suspension structure is provided above the storage space, and the suspension structure also serves as a positioning structure for the battery core within the storage space.

3. A battery pack according to claim 2, wherein the exterior case has a rectangular outer shape, and the suspension structure is provided at an upper corner of the storage space.

4. A battery pack as claimed in any one of claims 1 to 3, wherein the suspension structure comprises a core-side locking portion protruding from a shoulder portion of the battery core, and a case-side locking portion protruding from the top of the exterior case to the interior, for locking the core-side locking portion.

5. A battery pack as claimed in claim 4, wherein the case-side locking portion comprises a base portion that protrudes into the storage space and a pin portion that protrudes from the upper surface of the base portion, and the core-side locking portion comprises a protruding piece that is positioned on the base portion and is thinner than the height of the pin portion, and a hole portion that opens in the protruding piece and into which the pin portion can be inserted.

6. A battery pack as claimed in claim 5, wherein the suspension structures are provided at the four corners of the upper part of the storage space of the outer case, which has a rectangular outer shape, and wherein the first hole of the first core-side locking part located at the first corner of the four corners has a first clearance between itself and the first pin part inserted into said first hole, which is smaller than the clearance between itself and the pin part inserted into the hole of the core-side locking part located at the other corner.

7. A battery pack as claimed in claim 6, wherein the second hole of the second core-side locking part, which is located adjacent to one side of the first corner among the four corners, is formed in a circular shape, and the second hole is formed with an inner diameter larger than that of the first hole.

8. A battery pack as claimed in claim 5, wherein the suspension structures are provided at the four upper corners of the storage space of the exterior case, which has a rectangular outer shape, and wherein the first hole of the first core-side locking part, which is located at a first corner of the four corners, is formed in a circular shape, and the third hole of the third core-side locking part, which is located at a third corner diagonally opposite the first corner, is formed in the shape of an elongated hole elongated in the diagonal direction.

9. A battery pack according to claim 5, wherein the height of the pin portion is 5 mm to 20 mm, and the gap between the bottom surface of the battery core and the bottom surface of the inner surface of the exterior case is 0.8 mm to 4 mm.

10. A battery pack as claimed in claim 5, wherein the pin portion has a screw hole formed therein, and the battery pack further comprises a screw portion that is screwed into the screw hole, and the hole portion is inserted into the pin portion, and with the protruding piece engaged with the base portion, the screw portion is screwed into the screw hole to fix the core-side locking portion to the case-side locking portion.

11. A battery pack as claimed in claim 2, wherein the exterior case is formed in a box shape, and of the vertical, horizontal and height directions that form the box-shaped solid, the height direction, which is the direction in which the battery core is inserted from the opening end into the storage space, is the longest.

12. A battery pack according to claim 11, wherein the battery core has a connector portion on its upper surface.

13. A method for manufacturing a battery pack including a battery core that holds a plurality of secondary battery cells and an outer case that defines a storage space for storing the battery core therein, the method comprising the steps of: applying uncured adhesive to the bottom surface of the storage space of the outer case; suspending the battery core within the storage space using a suspension structure that suspends the battery core in the storage space of the outer case, forming a fixed gap between the bottom surface of the battery core and the bottom surface of the inner surface of the outer case, and arranging the uncured adhesive in the fixed gap; and curing the adhesive to form an adhesive layer in the fixed gap.

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