Battery pack

Abstract

According to the present invention, a flammable gas within a battery pack is safely discharged to the outside from the battery pack, while suppressing breakage of a fitting connection part of a case due to increase of the internal pressure.　A battery pack according to the present invention contains a battery unit (10) in an outer package case (2) that is composed of a first case (2A) and a second case (2B). The first case (2A) and the second case (2B) are connected to each other by having stacking plates of a first peripheral wall (4A) and a second peripheral wall (4B) stacked upon each other at opening ends. The first peripheral wall (4A) connects a first stacking plate (5A) that is stacked on the outer surface, while the second peripheral wall (4B) connects a second stacking plate (5B) that is stacked on the inner surface. The first stacking plate (5A) has plural arrays of reinforcement ribs (6) that protrude from the inner surface; the second stacking plate (5B) has a fitting part that is composed of plural arrays of slits or grooves into which the reinforcement ribs (6) are to be guided; and the first case (2A) and the second case (2B) are connected to each other by guiding the reinforcement ribs (6) into the fitting part.

Description

[Technical Field]

[0001] The present invention relates to a battery pack. [Background technology]

[0002] Battery packs, which consist of multiple secondary battery cells connected in series and parallel, are used as power sources for portable electric devices such as electric cleaners and power tools; as stationary power storage devices for server backup power supplies; and as power sources for home, office, and factory use. They are also used as driving power sources for assisted bicycles, electric scooters, electric carts, and vehicles such as hybrid and electric vehicles. Lithium-ion secondary batteries are generally used as secondary battery cells in such battery packs. However, lithium-ion secondary batteries can be subject to unsafe conditions, such as the emission of smoke or fire, due to an abnormality such as bolt penetration during a collision. If an unsafe condition were to occur in a battery pack, there is a risk that the fire from the internal secondary battery cells could be released outside the battery pack.

[0003] Such battery packs have a structure in which a battery unit including multiple secondary battery cells is housed in a resin outer case. The outer case often has a structure in which a box-shaped first case and a second case, each with a peripheral wall around a bottom plate, are connected to each other through an opening. For example, some such outer cases use a fitting structure in which a stepped portion with a thin wall thickness is formed on the inner surface of the opening of one case and on the outer surface of the opening of the other case, and the two cases are connected by a stacked portion that is fitted together by fitting the stepped portion (see Patent Documents 1 and 2). This structure has the advantage that the thickness of the stacked portion of the first case and the second case is the same as the thickness of the other peripheral wall portion, and the first case and the second case can be accurately connected to each other.

[0004] However, in a battery pack equipped with such an outer case, if a thermal runaway or other abnormality occurs in a stored secondary battery cell and high-temperature, high-pressure gas is released, the gas fills the interior of the outer case, creating a flow path 94 that leads from the mating connection portion 93 of the outer case 92 to the outside, as shown by the arrow in Figure 16. From this flow path, high-temperature, high-pressure gas can be sprayed outside the case, potentially leading to a fire leak. In particular, because the stacked portions 95 of the mating connection portion 93 of the outer case are formed thin, when high-pressure gas passes through the boundary of the mating connection portion 93, the outer stacked portion 95 is likely to deform outward due to the gas pressure, as shown by the chain line in Figure 16. This can cause a large amount of flammable gas to be released to the outside all at once, potentially resulting in a fire. For this reason, conventional battery packs have had to reinforce the mating connection portion of the outer case with expensive fire-resistant sheets or other materials to prevent fires from igniting through the mating connection portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-10591 [Patent Document 2] Japanese Patent Application Publication No. 10-241647 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention was developed with the aim of overcoming the above drawbacks, and one of the objects of the present invention is to provide a battery pack that can improve safety by safely releasing flammable gases inside the battery pack to the outside of the battery pack while preventing the failure of the mating connection of the case due to an increase in internal pressure of the battery pack caused by gases emitted due to a battery abnormality.

[0007] A battery pack according to a first aspect of the present invention is a battery pack comprising an outer case housing a battery unit, the outer case comprising a first case having a first peripheral wall around a first surface plate and a second case having a second peripheral wall around a second surface plate, the first and second cases being connected at their open ends to house the battery unit within a closed structure. Furthermore, the first and second peripheral walls integrally connect stacked plates formed by stacking the inner and outer surfaces of each other along the open end. The first peripheral wall connects the first stacked plates stacked on the outer surface, and the second peripheral wall connects the second stacked plates stacked on the inner surface. The first stacked plates have multiple rows of reinforcing ribs extending from the open end toward the first peripheral wall and projecting to the inner surface, and the second stacked plates have fitting portions formed by multiple rows of slits or grooves that guide the reinforcing ribs. 1 of Reinforcement ribs 1 each Guided by the fitting portion, the first stacking plate and the second stacking plate are stacked together, connecting the first case and the second case.

[0008] The above configuration has the advantage that, even when the internal pressure of the exterior case rises due to gas discharged due to a battery abnormality, failure of the mating connection of the cases can be suppressed, and flammable gas inside the battery pack can be safely released outside the battery pack, improving safety. This is because the above battery pack connects the first case and the second case by stacking a first stacking plate connected to the first peripheral wall of the first case and a second stacking plate connected to the second peripheral wall of the second case, the first stacking plate stacked on the outer surface has multiple rows of reinforcing ribs protruding to the inner surface, and the second stacking plate stacked on the inner surface has fitting portions consisting of multiple rows of slits or grooves that guide the reinforcing ribs, and the first stacking plate and the second stacking plate are stacked with the reinforcing ribs guided into the fitting portions to connect the first case and the second case. This structure provides multiple rows of reinforcing ribs on the inner surface of the outer first laminate plate, increasing the rigidity of the first laminate plate and preventing it from deforming outward due to gas pressure. This effectively prevents flammable gases inside the case from bursting through the mating connection and being suddenly released to the outside when the internal pressure of the outer case rises, preventing flames from leaking to the outside. Furthermore, by providing a mating portion for the reinforcing ribs on the second laminate plate, the reinforcing ribs are guided into the mating portion to connect the first and second laminate plates using a mating structure. This allows the first laminate plate to be reinforced while still properly connecting them without increasing the thickness of the laminated portions of the first and second laminate plates.

[0009] In a battery pack according to a second aspect of the present invention, the fitting portion is a slit, and the height of the reinforcing rib is equal to the thickness of the second stacking plate. With this configuration, the upper end surface of the reinforcing rib of the first stacking plate and the inner surface of the second stacking plate are flush with each other, and the inner surface of the case is flat, allowing the first stacking plate and the second stacking plate to be securely fitted together.

[0010] A battery pack according to a third aspect of the present invention has a second stacking plate provided with multiple rows of second reinforcing ribs that extend from the opening end toward the second peripheral wall and protrude toward the outer surface, and a first stacking plate provided with a second fitting portion consisting of multiple rows of slits or grooves that guide the second reinforcing ribs, guiding the second reinforcing ribs into the second fitting portion, stacking the first stacking plate and the second stacking plate, and connecting the first case and the second case.

[0011] According to the above configuration, by providing a reinforcing rib on the first lamination plate and a second reinforcing rib on the second lamination plate, the rigidity of both the first lamination plate and the second lamination plate is increased, and the lamination plates are prevented from deforming outward due to gas pressure, which would otherwise cause the mating connection to break. This allows flammable gases inside the battery pack to be safely released to the outside of the battery pack when the internal pressure of the outer case increases, effectively preventing flames from leaking to the outside. Furthermore, by providing a second mating portion on the first lamination plate, the reinforcing rib and the second reinforcing rib can be mated and connected to the mating portion and the second mating portion, respectively. This allows the first lamination plate and the second lamination plate to be reinforced while being properly connected without increasing the thickness of the laminated portions of the first lamination plate and the second lamination plate.

[0012] In a battery pack according to a fourth aspect of the present invention, the second fitting portion is a slit, and the height of the second reinforcing rib is equal to the thickness of the first laminated plate. With this configuration, the second reinforcing rib is placed in the slit provided in the first laminated plate and exposed to the outside, and the upper end surface of the second reinforcing rib is flush with the outer surface of the first laminated plate, thereby achieving a beautiful appearance and a pleasant feel.

[0013] In a battery pack according to a fifth aspect of the present invention, the mating portion and the second mating portion are slits, and a refracted flow path for passing gas from the inside to the outside of the outer case is formed between the adjacent mating portion and the second mating portion. With this configuration, by fitting a reinforcing rib into the slit in the second stacking plate and fitting the second reinforcing rib into the slit in the first stacking plate, a refracted flow path for passing gas is formed between the adjacent mating portion and the second mating portion. Therefore, gas that fills the outer case due to a battery malfunction can be smoothly discharged to the outside of the outer case via the multiple refracted flow paths formed in the stacking plate. In particular, by forming the mating portion and the second mating portion into slits, the overall lengths of the inlet and outlet portions of the refracted flow paths formed on the inner and outer surfaces of the stacking plate can be increased, allowing gas within the outer case to be safely discharged to the outside. In this way, by suppressing the amount of high-temperature gas discharged to the outside of the outer case, flames can be effectively prevented from leaking to the outside.

[0014] In a battery pack according to a sixth aspect of the present invention, the second stacking plate is provided with multiple rows of second reinforcing ribs that extend from the opening end toward the second peripheral wall and protrude inward, and the first stacking plate and the second stacking plate are stacked to connect the first case and the second case.

[0015] According to the above configuration, by providing a reinforcing rib on the first lamination plate and a second reinforcing rib on the second lamination plate, the rigidity of both the first lamination plate and the second lamination plate is increased, and the lamination plates are more effectively prevented from being deformed outward due to gas pressure, causing the mating connection to break. Therefore, when the internal pressure of the outer case increases, flammable gas inside the battery pack can be more safely released to the outside of the battery pack, effectively preventing flames from leaking to the outside. Furthermore, because the second mating portion protrudes from the inner surface of the second lamination plate, the impact of the second reinforcing rib on the second lamination plate on the first lamination plate is reduced.

[0016] In a battery pack according to a seventh aspect of the present invention, the first and second stacking plates have a thickness that is half the thickness of the peripheral wall. With this configuration, a stable connection state can be achieved by making the thickness of the first and second stacking plates equal, and the thickness of the stacked portions of the first and second stacking plates can be made equal to the thickness of the peripheral wall, making the inner and outer surfaces of the stacked portions flush with the surface of the peripheral wall.

[0017] In a battery pack according to an eighth aspect of the present invention, the first case and the second case have peripheral walls with a rectangular cross-sectional shape, a laminated plate is provided around the entire periphery of the opening edge of the peripheral wall, and a reinforcing rib and a fitting portion are provided on the laminated plate located on the long side of the peripheral wall that is rectangular in cross section.

[0018] According to the above configuration, by providing reinforcing ribs and fitting portions on the laminated plates located on the long sides of the first case and the second case, whose peripheral walls have a rectangular cross-sectional shape, the peripheral walls on the long sides, which are prone to deformation relative to the short sides, are reinforced with reinforcing ribs, which has the advantage of effectively preventing failure of the fitting connection portions of the outer case. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a battery pack according to a first embodiment of the present invention. [Figure 2] 2 is a partially enlarged exploded perspective view of the battery pack of FIG. 1 as seen from the left side. [Figure 3] 2 is a partially enlarged exploded perspective view of the battery pack of FIG. 1, seen from the right side. [Figure 4] FIG. 3 is an exploded perspective view of a battery unit of the battery pack shown in FIG. 2. [Figure 5] 2 is an enlarged cross-sectional view of the battery pack taken along line VV in FIG. 1. [Figure 6] 6 is an enlarged exploded cross-sectional view of the battery pack taken along line VI-VI in FIG. 1. [Figure 7] FIG. 10 is an enlarged exploded cross-sectional view showing another example of a stacking plate of an outer case. [Figure 8]FIG. 10 is an enlarged exploded perspective view of a portion of an exterior case of a battery pack according to a second embodiment of the present invention. [Figure 9] FIG. 10 is an enlarged cross-sectional view of an exterior case of a battery pack according to a second embodiment of the present invention. [Figure 10] FIG. 11 is a partially enlarged exploded perspective view of an exterior case of a battery pack according to a third embodiment of the present invention. [Figure 11] FIG. 10 is an enlarged cross-sectional view of an exterior case of a battery pack according to a third embodiment of the present invention. [Figure 12] FIG. 10 is a perspective view showing a battery pack according to a fourth embodiment of the present invention. [Figure 13] 13 is an enlarged exploded perspective view of a part of the exterior case of the battery pack shown in FIG. 12. FIG. [Figure 14] 13 is an enlarged cross-sectional view of the exterior case of the battery pack shown in FIG. 12. [Figure 15] 13 is a cross-sectional perspective view showing a state in which the battery pack shown in FIG. 12 is discharging gas from the inside to the outside of the exterior case. FIG. [Figure 16] FIG. 10 is an enlarged cross-sectional perspective view showing a state in which a fitting connection portion of an outer case of a conventional battery pack breaks. DETAILED DESCRIPTION OF THE INVENTION

[0020] Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concept of the present invention, and the present invention is not limited to these. Furthermore, this specification in no way specifies the components set forth in the claims as components of the embodiments. The dimensions, materials, shapes, and relative positions of components described in the embodiments are not intended to limit the scope of the present invention, and are merely illustrative unless otherwise specified. The size and relative positions of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate identical or similar components, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present invention may be configured with the same components, so that one component serves multiple functions, or conversely, the function of one component may be shared by multiple components.

[0021] The battery pack of the present invention can be used as a power source for portable electric devices such as electric cleaners and power tools, or as a backup power source for servers in stationary power storage applications, or as a power source for homes, offices, and factories, and further as a power source for driving electric-powered bicycles, electric scooters, electric carts, or vehicles such as hybrid cars and electric automobiles. Hereinafter, a battery pack used as a power source for portable electric devices will be described as one embodiment of the present invention.

[0022] [Embodiment 1] A battery pack 100 according to a first embodiment of the present invention is shown in Figures 1 to 5. Figure 1 is an external perspective view of the battery pack, Figures 2 and 3 are exploded perspective views of the battery pack of Figure 1, Figure 4 is an exploded perspective view of a battery unit of the battery pack shown in Figure 2, Figure 5 is an enlarged cross-sectional view of the exterior case shown in Figure 1 taken along line VV, and Figure 6 is an enlarged cross-sectional view of the exterior case shown in Figure 1 taken along line VI-VI. The battery pack 100 shown in these figures has a battery unit 10, which contains a plurality of secondary battery cells, housed in an exterior case 2.

[0023] (Battery unit 10) The battery unit 10 houses multiple secondary battery cells 1 in fixed positions inside a battery holder 11. The battery unit 10 is housed inside an outer case 2, and the outer shape of the battery holder 11 is formed to be slightly smaller than the inner shape of the outer case 2. An exploded perspective view of the battery holder 11 is shown in Figure 4. This battery holder 11 holds the secondary battery cells 1 and a circuit board 60. The battery holder 11 with the secondary battery cells 1 and circuit board 60 set in it forms the battery unit 10. The circuit board 60 is placed on one side of the battery holder 11 and fixed in place.

[0024] The battery holder 11 holds multiple secondary battery cells 1. The battery holder 11 is divided into two sub-holders 11A and 11B, which sandwich and hold the multiple secondary battery cells 1 lengthwise. Each of the sub-holders 11A and 11B forms a cylindrical storage space 13 for storing the secondary battery cells 1. In this example, four secondary battery cells 1 are stacked and held in a 2-row by 2-column configuration. The number and stacking method of the secondary battery cells 1 are not limited to this configuration; three or fewer, or five or more, may be held. The number of secondary battery cells 1 is not limited to two layers; it may be one layer, in which all the secondary battery cells are arranged on the same plane, or three or more layers. In addition to a matrix arrangement, the cells may be arranged in a staggered pattern, alternating between layers. For example, the thickness of the battery holder can be reduced by forming two storage spaces with offset cylindrical centers between the upper and lower layers. The battery holder 11 is made of a material with excellent insulating and heat-resistant properties, such as a resin such as polycarbonate or ABS.

[0025] (Secondary battery cell 1) Each secondary battery cell 1 is a cylindrical secondary battery cell whose outer can is cylindrical. The cylindrical secondary battery cell has electrode surfaces on both end faces. One of the electrode surfaces is also equipped with a safety valve. The safety valve is a component that opens to release internal gas when the internal pressure of the outer can increases. Although the safety valve is generally provided on the positive electrode side, the present invention does not limit the location of the safety valve to the positive electrode side; it may be provided in another position, for example, on the negative electrode side. The battery holder 11 also has a slit 14 formed in it so that gas discharged from the safety valve can be released to the outside of the battery holder 11 when the safety valve opens.

[0026] Cylindrical lithium-ion secondary batteries are suitable for use as such secondary battery cells 1. However, the battery pack of the present invention does not limit the secondary battery cells to cylindrical batteries, nor does it limit them to lithium-ion secondary batteries. Any rechargeable battery, such as nickel-metal hydride batteries or nickel-cadmium batteries, can be used as the secondary battery cells.

[0027] (reed plate) Lead plates (not shown) are fixed to the end faces of the secondary battery cells 1. Multiple secondary battery cells 1 are connected in series or parallel via the lead plates. The lead plates are made of metal plates and are welded to the secondary battery cells 1. Lead positioning guides that follow the outline of the lead plates are formed on the inner surface of the battery holder 11 to position the lead plates in a predetermined position. The lead plates may be placed on the outer surface of the battery holder rather than the inner surface. In this case, after the secondary battery cells are inserted into the storage space of the battery holder, the lead plates are fixed to the electrode surfaces of the secondary battery cells that are exposed from the battery holder. The output of the battery unit 10, which is made up of secondary battery cells 1 connected in series or parallel via the lead plates in this way, is output from the battery pack 100.

[0028] Furthermore, the upper surface of the battery holder 11 serves as a mounting surface 15 on which a substrate 60 is placed. A frame for holding the substrate 60 may be formed on the mounting surface 15. Alternatively, a substrate holder for holding the substrate may be provided separately. (Substrate 60)

[0029] Electronic circuits such as a voltage detection circuit that detects the total potential and intermediate potential of the battery assembly in which the secondary battery cells 1 are connected in series or parallel, a control circuit that controls charging and discharging, and a safety circuit are mounted on the substrate 60. The substrate 60 is formed in a rectangular shape.

[0030] (Outer case 2) The exterior case 2 that houses the battery unit 10 is formed in the shape of a rectangular parallelepiped box. In the example shown in Figure 1, the exterior case 2 is divided into a first case 2A and a second case 2B, and the battery unit 10 is housed between them, sandwiched from the left and right. The direction in which the first case 2A and the second case 2B are separated is at a right angle to the direction in which the battery holder 11 is separated into sub-holders 11A and 11B, which increases resistance to impact.

[0031] The first case 2A and the second case 2B have a peripheral wall 4 around the surface plate 3, giving them an overall box shape with an opening on one side and a bottom. The first case 2A has a first peripheral wall 4A around the first surface plate 3A, and the second case 2B has a second peripheral wall 4B around the second surface plate 3B. The first and second cases 2A and 2B have their first and second peripheral walls 4A and 4B connected at their open ends, and the battery unit 10 is housed inside the closed structure.

[0032] The first case 2A and second case 2B shown in Figures 1 to 3 use a metal plate 16 as the surface plate 3. The first case 2A and second case 2B shown in the figures have an open box-shaped bottom, and this opening is closed with a metal plate 16 to form the surface plate 3. The metal plate 16 shown in the figures has multiple through-holes 17, which prevent gas from being released from any of the secondary battery cells 1 housed inside the battery pack 100 from suddenly escaping to the outside, thereby preventing flames from leaking outside the battery pack 100. The main body of the first case 2A and second case 2B, excluding the metal plate 16, is made of a highly insulating material, such as a resin such as polycarbonate or ABS. Although the exterior case 2 shown in the figures has the metal plate 16 covering almost the entire surface plate 3, the metal plate can be provided only partially on the surface plate, or the entire case can be made of resin without a metal plate.

[0033] 2 and 3, a first case 2A and a second case 2B are provided with laminated plates 5 laminated on the inner and outer surfaces of each case along the open edge of their peripheral walls 4, which are connected to form an integral structure. In the illustrated exterior case 2, the peripheral walls 4 of the first case 2A and the second case 2B have a generally rectangular cross section, and laminated plates 5 are provided around the entire perimeter of the open edge of the peripheral walls 4. The first peripheral wall 4A connects the first laminated plates 5A laminated on the outer surfaces, and the second peripheral wall 4B connects the second laminated plates 5B laminated on the inner surfaces.

[0034] As shown in FIG. 3 , the first lamination plate 5A extends from the open end of the first case 2A toward the first peripheral wall 4A and is integrally molded to protrude from the leading edge of the first peripheral wall 4A in the direction of extension of the peripheral wall 4. The first lamination plate 5A is thinner than the first peripheral wall 4A, with its outer surface flush with the outer surface of the first peripheral wall 4A and its inner surface lower than the inner surface of the first peripheral wall 4A, forming a stepped shape. To increase the strength of the first lamination plate 5A, which is thinner than the peripheral wall 4, the first lamination plate 5A has multiple rows of reinforcing ribs 6 protruding from its inner surface. The reinforcing ribs 6 shown in the figure are ridges integrally molded with the first lamination plate 5A and extend from the leading edge of the first lamination plate 5A to the leading edge surface 4a of the first peripheral wall 4A. The first stacking plate 5A in this structure has multiple rows of reinforcing ribs 6 protruding from its inner surface, which increase the moment of inertia in the bending direction in the cross section and suppress outward deformation. Therefore, even if gas is released from one of the secondary battery cells 1 housed inside the exterior case 2 and passes to the outside through the boundary between the first stacking plate 5A and the second stacking plate 5B, the first stacking plate 5A is suppressed from deforming outward, allowing the flammable gas inside the battery pack to be safely released to the outside of the battery pack and effectively preventing the gas from being suddenly ejected to the outside.

[0035] The reinforcing rib 6 shown in FIG. 5 is a convex strip with a rectangular cross section. A reinforcing rib 6 of this shape has the advantage of being able to improve strength with a simple structure. However, the reinforcing rib does not have to have a rectangular cross section, and can also have a triangular cross section or a shape with a curved upper end surface. Furthermore, the reinforcing rib 6 with a rectangular cross section is formed so that its upper end surface in the height direction (the lower end surface in FIG. 5) is positioned on the same plane as the inner surface of the first peripheral wall 4A.

[0036] As shown in the partially enlarged view of Figure 3 and the exploded cross-sectional view of Figure 6, the first lamination plate 5A has a thickness (t1) of 0.5 to 1.5 mm, a protrusion (L1) from the first peripheral wall 4A of 1.5 to 5.0 mm, a width (d1) of the reinforcing rib 6 of 0.2 to 1.0 mm, a height (h1) of 1.0 to 3.0 mm, and a center-to-center distance (M1) between adjacent reinforcing ribs of 3.0 to 5.0 mm. The total length (H1) of the reinforcing rib is approximately equal to the protrusion (L1) of the first lamination plate 5A, so that the first lamination plate 5A can be reinforced. However, the total length (H1) of the reinforcing rib can also be shorter than the protrusion (L1) of the first lamination plate 5A.

[0037] As shown in FIG. 2, the second lamination plate 5B extends from the open end of the second case 2B toward the second peripheral wall 4B. It is integrally molded to protrude from the leading end surface 4b of the second peripheral wall 4B in the direction of extension of the peripheral wall 4. The second lamination plate 5B is thinner than the second peripheral wall 4B. The inner surface of the second lamination plate 5B is flush with the inner surface of the second peripheral wall 4B, and the outer surface of the second lamination plate 5B is formed in a stepped shape that is lower than the outer surface of the second peripheral wall 4B. Furthermore, the second lamination plate 5B has a fitting portion 7 that guides the reinforcing ribs 6 provided on the first lamination plate 5A. The fitting portion 7 shown in the figure is a plurality of rows of slits 7A provided in the second lamination plate 5B. The slits 7A shown in the figure are provided in a position that extends from the leading end of the second lamination plate 5B to the leading end surface of the second peripheral wall 4B. The fitting portion 7, which is the slit 7A, is formed in a size and shape that allows the reinforcing ribs 6 to be fitted into the fitting portion 7 at a position opposite the reinforcing ribs 6 provided on the first stacking plate 5A.

[0038] 2, the second lamination plate 5B is divided into a plurality of divided plate portions 5b by a plurality of rows of slits 7A. The divided plate portions 5b are connected in place by fitting into mating recesses 5a formed by a plurality of rows of reinforcing ribs 6 protruding from the inner surface of the first lamination plate 5A and the leading end surface 4a of the first peripheral wall 4A. That is, the reinforcing ribs 6 on the inner surface of the first lamination plate 5A are guided into the mating recesses 7 on the second lamination plate 5B, and the divided plate portions 5b of the second lamination plate 5B are guided into the mating recesses 5a on the first lamination plate 5A, so that the open ends of the first case 2A and the second case 2B are reliably connected to each other by a mating structure.

[0039] 3 and 6, the first lamination plate 5A has chamfered corners between its tip surface and inner surface, and between its tip surface and upper end surface of the reinforcing rib 6. Furthermore, the second lamination plate 5B has chamfered corners between its tip surface and inner surface, and the opening edge of the slit 7A, as shown in FIGS. 2 and 6. This reduces the contact between the first lamination plate 5A and the second lamination plate 5B when the first case 2A and the second case 2B are connected, making it easier to guide the divided plate portions 5b of the second lamination plate 5B into the fitting recesses 5a of the first lamination plate 5A and to fit the reinforcing rib 6 into the slit 7a.

[0040] 2, the thickness (t2), protrusion (L2) from the second peripheral wall 4B, width (d2) of the slits 7A, center-to-center distance (M2) between adjacent slits, and total length (H2) of the slits can be adjusted to optimal sizes to connect the second lamination plate 5B with the first lamination plate 5A having the reinforcing rib 6 in an interlocking structure. For example, the thickness (t2) of the second lamination plate 5B can be set equal to the height (h1) of the reinforcing rib 6, the protrusion (L2) from the second peripheral wall 4B can be set equal to the protrusion (L1) of the first lamination plate 5A, the width (d2) of the slits 7A can be set slightly larger than the width (d1) of the reinforcing rib 6, and the total length (H2) of the slits 7A can be set equal to the total length (H1) of the reinforcing rib 6.

[0041] In the illustrated outer case 2, the thickness (t1) of the first lamination plate 5A and the thickness (t2) of the second lamination plate 5B are equal and approximately half the thickness (s) of the peripheral wall 4. This structure ensures that when opposing lamination plates 5 are stacked on top of each other, the thickness (t1 + t2) of the laminated portion is equal to the thickness (s) of the peripheral wall 4. However, the first lamination plate and the second lamination plate do not necessarily have to be the same thickness; they can also be different thicknesses. For example, the first lamination plate can be formed thicker than the second lamination plate. Because the first lamination plate is stacked on the outside of the second lamination plate, a structure that makes the first lamination plate thicker can more effectively prevent the first lamination plate from deforming outward when gas pressure inside the outer case increases. Even if the thicknesses of the first and second stacking plates are different, it is preferable that the thickness (t1+t2) of the stacked portion of the first and second stacking plates is equal to the thickness (s) of the peripheral wall.

[0042] Furthermore, the first lamination plate 5A and the second lamination plate 5B shown in the figures have a constant thickness from their leading edge to their rear edge. However, the first lamination plate 5A and the second lamination plate 5B can also be formed to be thinner from their rear edge to their leading edge, as shown in Figure 7. This structure allows the leading edge of the mating recess 5a formed in the first lamination plate 5A to be deeper, while the leading edge of the divided plate portion 5b of the second lamination plate 5B inserted into the mating recess 5a can be thinner. This has the advantage that the first lamination plate 5A and the second lamination plate 5B can be smoothly connected when mated with each other from their leading edges.

[0043] In the first case 2A and second case 2B constructed as described above, the reinforcing rib 6 on the first lamination plate 5A is guided through the slit 7A on the second lamination plate 5B, thereby stacking and connecting the first lamination plate 5A and the second lamination plate 5B. The structure using the slit 7A as the mating portion 7 allows the height (h1) of the reinforcing rib 6 to be equal to the thickness (t2) of the second lamination plate. This allows the upper surface of the reinforcing rib 6 and the inner surface of the second lamination plate 5B, which are connected to each other, to be positioned on the same plane, making the inner surface of the laminated portion flat. However, the height (h1) of the reinforcing rib 6 can also be greater than the thickness (t2) of the second lamination plate 5B. This structure further increases the strength of the first lamination plate 5A.

[0044] [Embodiment 2] In the above-described exterior case 2, the fitting portion 7 of the second lamination plate 5B is a slit 7A, but the fitting portion formed in the second lamination plate can also be a groove. In the exterior case 2 shown in FIGS. 8 and 9, the second lamination plate 5B of the second case 2B has multiple rows of grooves 7B formed in positions facing the reinforcing ribs 6 provided on the first lamination plate 5A of the first case 2A, forming the fitting portion 7. The grooves 7B shown in the figures are provided in an orientation extending from the tip of the second lamination plate 5B to the tip surface 4a of the second peripheral wall 4B, and are formed in a size and shape that allows the reinforcing ribs 6 provided on the first lamination plate 5A to fit into them. The depth (h2) of the grooves 7B is smaller than the thickness (t2) of the second lamination plate 5B and is approximately equal to the height (h1) of the reinforcing ribs 6 of the first lamination plate 5A. The reinforcing ribs 6 formed on the first lamination plate 5A are formed lower than the reinforcing ribs 6 shown in Fig. 3, and are formed so that their upper end faces are lower than the inner surface of the first peripheral wall 4A. In this way, the structure in which the fitting portions 7 are grooves 7B has the advantage that the second lamination plate 5B is integrally connected without being divided into multiple parts, and the first lamination plate 5A can be reinforced by the reinforcing ribs 6 while the multiple rows of reinforcing ribs 6 of the first lamination plate 5A are connected to the multiple rows of grooves 7B by a fitting structure.

[0045] [Embodiment 3] The above-described exterior case 2 is structured to suppress deformation due to gas released from the secondary battery cells 1 housed inside the exterior case 2 by reinforcing the first stacking plate 5A with reinforcing ribs 6, but reinforcing ribs can also be provided on the second stacking plate. In the exterior case 2 shown in Figures 10 and 11, the second stacking plate 5B of the second case 2B is provided with multiple rows of second reinforcing ribs 8 that protrude inward. The first case 2A shown in the figures has the same structure as the first case 2A shown in Figures 1 to 4 described above, and the second case 2B also has the same structure as the second case 2B shown in Figures 1 to 4 described above, except that second reinforcing ribs 8 are provided on the inner surface of the second stacking plate 5B.

[0046] The second case 2B shown in Figures 10 and 11 has multiple rows of second reinforcing ribs 8 integrally molded on the inner surface of the second lamination plate 5B. The second reinforcing ribs 8 are located at the center of the multiple divided plate sections 5b separated by the fitting sections 7, which are slits 7A, and extend from the open end of the second case 2B toward the second peripheral wall 4B. The second reinforcing ribs 8 shown in the figures extend from the leading edge of the second lamination plate 5B, past the rear end of the second lamination plate 5B, to the leading edge of the second peripheral wall 4B, with a total length (H3) greater than the protrusion (L2) of the second lamination plate 5B. This structure, in which the second reinforcing ribs 8 extend from the second lamination plate 5B to the second peripheral wall 4B, can more effectively suppress deformation of the second lamination plate 5B. Furthermore, the second reinforcing ribs 8 shown in the figures are convex stripes with a semicircular cross section. The second reinforcing rib 8 of this shape has the advantage of being able to reliably reinforce the second stacking plate 5B while ensuring good contact with the battery unit 10 and other components housed in the exterior case 2.

[0047] The second stacking plate 5B described above has multiple rows of second reinforcing ribs 8 protruding from its inner surface, which increases the moment of inertia in the cross section and suppresses deformation due to gas pressure. As a result, even if gas is released from any of the secondary battery cells 1 housed inside the exterior case 2, the first stacking plate 5A and the second stacking plate 5B are suppressed from deforming outward, more effectively preventing the fitting connection of the exterior case from failing.

[0048] [Embodiment 4] Furthermore, the exterior case 2 can also have the structure shown in Figures 12 to 14. The exterior case 2 shown in these figures has multiple rows of reinforcing ribs 6 on the inner surface of the first stacking plate 5A of the first case 2A, and the second stacking plate 5B of the second case 2B has fitting portions 7 consisting of multiple rows of slits 7A that guide the reinforcing ribs 6 of the first stacking plate 5A, and further has multiple rows of second reinforcing ribs 8 on the outer surface of the second stacking plate 5B of the second case 2B, and the first stacking plate 5A of the first case 2A has second fitting portions 9 consisting of multiple rows of slits 9A that guide the second reinforcing ribs 8 provided on the second stacking plate 5B.

[0049] The second lamination plate 5B is provided with a second reinforcing rib 8 that is integrally molded and protrudes from the center of the outer surface of the divided plate portion 5b, which is divided into multiple pieces by fitting portions 7 that are slits 7A, and extends from the tip surface of the divided plate portion 5b to the tip surface 4b of the second peripheral wall 4B. The second reinforcing rib 8 provided on the second lamination plate 5B can be of the same shape and size as the reinforcing rib 6 provided on the first lamination plate 5A.

[0050] The first lamination plate 5A is divided into a plurality of divided plate portions 5c by fitting portions 9 which are slits 9A, and a reinforcing rib 6 is formed so as to protrude from the center of the inner surface of each divided plate portion 5c. The second fitting portions 9 which are slits 9A provided in the first lamination plate 5A can be made to have the same shape and size as the fitting portions 7 which are slits 7A provided in the second lamination plate 5B.

[0051] The first case 2A and second case 2B of this structure are connected to each other by guiding the reinforcing rib 6 of the first stacking plate 5A into the fitting portion 7 of the second stacking plate 5B, and guiding the second reinforcing rib 8 of the second stacking plate 5B into the second fitting portion 9 of the first stacking plate 5A. At this time, the divided plate portion 5b of the second stacking plate 5B is guided into the fitting recess 5a of the first stacking plate 5A, and the divided plate portion 5c of the first stacking plate 5A is guided into the fitting recess 5d formed between the second reinforcing ribs 8 on the outer surface of the second stacking plate 5B.

[0052] 12, in this exterior case 2, second reinforcing ribs 8 are exposed on the outer surface of the first case 2A from second fitting portions 9, which are slits 9A formed in the first stacking plate 5A. In this exterior case 2, the height (h3) of the second reinforcing ribs 8 is equal to the thickness (t1) of the first stacking plate 5A. This allows the upper surfaces, which are the outer surfaces of the second reinforcing ribs 8 that are connected to each other, to be flush with the outer surface of the first stacking plate 5A, giving the outer surface of the stacked portion a flat, beautiful appearance and a pleasant feel.

[0053] Furthermore, in the above-described exterior case 2, the fitting portion 7 provided on the second lamination plate 5B and the second fitting portion 9 provided on the first lamination plate 5A are formed as slits 7A and 9A, and as shown in Figures 14 and 15, when the first lamination plate 5A and the second lamination plate 5B are stacked together, a refracted flow path 19 is formed between the adjacent fitting portion 7 and second fitting portion 9, allowing gas to pass from the inside to the outside of the exterior case 2. This refracted flow path 19 is a gas flow path formed between the first lamination plate 5A and the second lamination plate 5B, which are stacked together, and allows gas that flows in between the slit 7A formed on the inner surface of the second lamination plate 5B and the reinforcing rib 6 to pass through the stacking surfaces of the second lamination plate 5B and the first lamination plate 5A, and then flows out to the outside between the slit 9A formed on the outer surface of the first lamination plate 5A and the second reinforcing rib 8. Although the refracted flow paths 19 are not always open, if an abnormality occurs in one of the stored secondary battery cells 1, causing high-temperature, high-pressure gas to be released and increasing internal pressure, the gas is passed from the inside of the exterior case 2 to the outside and discharged. In this way, by providing a large number of refracted flow paths 19, which are narrow gaps with a long creepage distance between the first and second stacking plates 5A, 5B, which are stacked and fitted together, and by passing gas through these refracted flow paths 19, the internal gas can be safely discharged while suppressing the amount of discharged gas, without being discharged all at once. In particular, by forming the fitting portion 7 and the second fitting portion 9 into slits 7A, 9A and lengthening the overall lengths of the inlet portions 19a and outlet portions 19b of the refracted flow paths 19 formed on the inner and outer surfaces of the stacking plates 5, the gas passage resistance can be adjusted, allowing the gas inside the exterior case 2 to be safely discharged to the outside.

[0054] In the outer case 2 according to the first to fourth embodiments described above, the cross-sectional shape of the peripheral walls of the first case 2A and the second case 2B is substantially rectangular, and reinforcing ribs 6 and fitting portions 7 are provided only on the laminating plates 5 located on the long sides of the rectangular peripheral wall 4. This structure effectively prevents failure of the fitting connections of the outer case 2 by reinforcing the first laminating plate 5A on the long side, which is more likely to deform relative to the short sides, with the reinforcing ribs 6. However, the outer case can also be provided with reinforcing ribs and fitting portions on the laminating plates located on the short sides of the rectangular peripheral wall. This structure reinforces the first laminating plate with reinforcing ribs around the entire perimeter of the peripheral wall, more effectively preventing failure of the fitting connections of the outer case. [Industrial Applicability]

[0055] The battery pack according to the present invention can be suitably used as a power source for portable electrical devices such as electric cleaners and power tools, and can also be suitably used as a power source device for mobile objects such as assisted bicycles and electric carts. [Explanation of symbols]

[0056] 100...Battery pack 1... Secondary battery cell 2...Outer case 2A...First case 2B...Second case 3...Surface plate 3A...First surface plate 3B...First surface plate 4...Peripheral wall 4A...First wall 4a…Tip surface 4B...Second wall 4b…Tip surface 5...Laminated plate 5A...First stacking plate 5a...Mating recess 5c...Divided plate section 5B...Second stacking plate 5b...Divided plate section 5d...Mating recess 6...Reinforcing rib 7...Mating part 7A...Slit 7B…Groove 8...Second reinforcing rib 9...Second fitting portion 9A...Slit 10...Battery unit 11...Battery holder 11A, 11B...Sub holder 13...Storage space 14...Slit 15...Placement surface 16...Metal plate 17...Through hole 19...Bent flow path 19a...Inflow part 19b...Outflow part 60...Substrate 92...Outer case 93...Fitting connection part 94...Flow path 95...Laminated section

Claims

1. A battery pack having a battery unit housed in an exterior case, The outer case is a first case having a first peripheral wall around a first surface plate; a second case having a second peripheral wall around the second surface plate; and The first case and the second case have the first peripheral wall and the second peripheral wall connected at an open end, and the battery unit is housed inside a closed structure; and the first peripheral wall and the second peripheral wall are formed by connecting stacked plates formed by stacking the plates on the inner and outer surfaces of each other along the opening edge into an integral structure, the first peripheral wall is formed by connecting first stacked plates stacked on an outer surface thereof, the second peripheral wall is formed by connecting second stacked plates stacked on an inner surface thereof, the first lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the first peripheral wall and protruding on an inner surface; the second lamination plate has a fitting portion formed of a plurality of rows of slits or grooves that guide the reinforcing ribs, A battery pack in which one of the reinforcing ribs is guided into one of the fitting portions, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected.

2. A battery pack having a battery unit housed in an exterior case, The outer case is a first case having a first peripheral wall around a first surface plate; a second case having a second peripheral wall around the second surface plate; and The first case and the second case have the first peripheral wall and the second peripheral wall connected at an open end, and the battery unit is housed inside a closed structure; and the first peripheral wall and the second peripheral wall are formed by connecting stacked plates formed by stacking the plates on the inner and outer surfaces of each other along the opening edge into an integral structure, the first peripheral wall is formed by connecting first stacked plates stacked on an outer surface thereof, the second peripheral wall is formed by connecting second stacked plates stacked on an inner surface thereof, the first lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the first peripheral wall and protruding on an inner surface; the second lamination plate has a fitting portion formed of a plurality of rows of slits or grooves that guide the reinforcing ribs, the second stacked plate is divided into a plurality of divided plate portions by a plurality of rows of the fitting portions, the divided plate portions are fitted into all of the fitting recesses formed by the plurality of rows of reinforcing ribs protruding from the inner surface of the first stacking plate and the tip end surface of the first peripheral wall, and are connected in fixed positions, The reinforcing rib is guided into the fitting portion, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected to form a battery pack.

3. A battery pack having a battery unit housed in an exterior case, The outer case is a first case having a first peripheral wall around a first surface plate; a second case having a second peripheral wall around the second surface plate; and The first case and the second case have the first peripheral wall and the second peripheral wall connected at an open end, and the battery unit is housed inside a closed structure; and the first peripheral wall and the second peripheral wall are formed by connecting stacked plates formed by stacking the plates on the inner and outer surfaces of each other along the opening edge into an integral structure, the first peripheral wall is formed by connecting first stacked plates stacked on an outer surface thereof, the second peripheral wall is formed by connecting second stacked plates stacked on an inner surface thereof, the first lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the first peripheral wall and protruding on an inner surface; the second lamination plate has a fitting portion formed of a plurality of rows of slits or grooves that guide the reinforcing ribs, The slits are each formed to have a width, an overall length, and a thickness, The thickness of the slit is equal to or greater than the thickness and width of the second stacking plate, The grooves are each formed to have a width, an overall length, and a depth, The depth of the groove is equal to or greater than the width, The reinforcing rib is guided into the fitting portion, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected to form a battery pack.

4. A battery pack having a battery unit housed in an exterior case, The outer case is a first case having a first peripheral wall around a first surface plate; a second case having a second peripheral wall around the second surface plate; and The first case and the second case have the first peripheral wall and the second peripheral wall connected at an open end, and the battery unit is housed inside a closed structure; and the first peripheral wall and the second peripheral wall are formed by connecting stacked plates formed by stacking the plates on the inner and outer surfaces of each other along the opening edge into an integral structure, the first peripheral wall is formed by connecting first stacked plates stacked on an outer surface thereof, the second peripheral wall is formed by connecting second stacked plates stacked on an inner surface thereof, the first lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the first peripheral wall and protruding on an inner surface; the second lamination plate has a fitting portion formed of a plurality of rows of grooves that guide the reinforcing rib, The reinforcing rib is guided into the fitting portion, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected to form a battery pack.

5. A battery pack having a battery unit housed in an exterior case, The outer case is a first case having a first peripheral wall around a first surface plate; a second case having a second peripheral wall around the second surface plate; and The first case and the second case have the first peripheral wall and the second peripheral wall connected at an open end, and the battery unit is housed inside a closed structure; and the first peripheral wall and the second peripheral wall are formed by connecting stacked plates formed by stacking the plates on the inner and outer surfaces of each other along the opening edge into an integral structure, the first peripheral wall is formed by connecting first stacked plates stacked on an outer surface thereof, the second peripheral wall is formed by connecting second stacked plates stacked on an inner surface thereof, the first lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the first peripheral wall and protruding on an inner surface; the second lamination plate has a fitting portion formed of a plurality of rows of slits that guide the reinforcing rib, the reinforcing rib is guided into the fitting portion, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected together; a reinforcing rib having a height equal to a thickness of the second laminate plate;

6. A battery pack having a battery unit housed in an exterior case, The outer case is a first case having a first peripheral wall around a first surface plate; a second case having a second peripheral wall around the second surface plate; and The first case and the second case have the first peripheral wall and the second peripheral wall connected at an open end, and the battery unit is housed inside a closed structure; and the first peripheral wall and the second peripheral wall are formed by connecting stacked plates formed by stacking the plates on the inner and outer surfaces of each other along the opening edge into an integral structure, the first peripheral wall is formed by connecting first stacked plates stacked on an outer surface thereof, the second peripheral wall is formed by connecting second stacked plates stacked on an inner surface thereof, the first lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the first peripheral wall and protruding on an inner surface; the second lamination plate has a fitting portion formed of a plurality of rows of slits or grooves that guide the reinforcing ribs, the reinforcing rib is guided into the fitting portion, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected together; the second lamination plate has a plurality of rows of second reinforcing ribs extending from an open end toward the second peripheral wall and protruding toward an outer surface; the first lamination plate has a second fitting portion formed of a plurality of rows of slits or grooves that guide the second reinforcing rib; The second reinforcing rib is guided into the second fitting portion, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected to form a battery pack.

7. 7. The battery pack according to claim 6, The battery pack according to claim 1, wherein the second fitting portion is a slit, and the height of the second reinforcing rib is equal to the thickness of the first stacking plate.

8. 8. The battery pack according to claim 6 or 7, a battery pack characterized in that the fitting portion and the second fitting portion are slits, and a bending flow path that allows gas to pass from the inside to the outside of the outer case is formed between the fitting portion and the second fitting portion that are adjacent to each other.

9. A battery pack having a battery unit housed in an exterior case, The outer case is a first case having a first peripheral wall around a first surface plate; a second case having a second peripheral wall around the second surface plate; and The first case and the second case have the first peripheral wall and the second peripheral wall connected at an open end, and the battery unit is housed inside a closed structure; and the first peripheral wall and the second peripheral wall are formed by connecting stacked plates formed by stacking the plates on the inner and outer surfaces of each other along the opening edge into an integral structure, the first peripheral wall is formed by connecting first stacked plates stacked on an outer surface thereof, the second peripheral wall is formed by connecting second stacked plates stacked on an inner surface thereof, the first lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the first peripheral wall and protruding on an inner surface; the second lamination plate has a fitting portion formed of a plurality of rows of slits or grooves that guide the reinforcing ribs, the reinforcing rib is guided into the fitting portion, the first stacking plate and the second stacking plate are stacked, and the first case and the second case are connected together; the second lamination plate has a plurality of rows of reinforcing ribs extending from an open end toward the second peripheral wall and protruding inward; The battery pack is formed by stacking the first stacking plate and the second stacking plate, and connecting the first case and the second case.

10. The battery pack according to any one of claims 1 to 9, The battery pack according to claim 1, wherein the thickness of the first stacking plate and the second stacking plate is half the thickness of the peripheral wall.

11. The battery pack according to any one of claims 1 to 10, The first case and the second case have peripheral walls each having a rectangular cross section, and the stacking plate is provided around the entire periphery of the opening edge of the peripheral wall, The battery pack has the reinforcing rib and the fitting portion provided on the stacking plate located on a long side of the peripheral wall having a rectangular cross section.

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