Battery case

Abstract

[Problem] To provide a battery case capable of reducing destruction of a core part by suppressing local breakage thereof even when a local load is input to a sandwich panel. [Solution] In a battery case 10 for housing a traction battery 12, at least one of an upper panel part 13, a lower panel part 14, and a side panel part 15 is composed of a sandwich panel 20. The sandwich panel includes: an outer peripheral frame 21; a bar member 22 that partitions an inner space 30 surrounded by the outer peripheral frame into a plurality of chambers 31; a core part 23 stored in each of the chambers; and a first panel 24 and a second panel 25 that sandwich the outer peripheral frame, the bar member, and the core part.

Description

Battery case

[0001] The present invention relates to a battery case that houses a battery for driving a vehicle.

[0002] Electric vehicles, hybrid vehicles, and the like are equipped with a battery for driving the vehicle. The battery for driving the vehicle is housed in a battery case. To reduce the weight of the battery case, a battery case using a sandwich panel is known (see Patent Document 1). The sandwich panel has a core and a pair of panels that sandwich the core.

[0003] Japanese Patent Application Laid-Open No. 2019-110003

[0004] The core of a sandwich panel is relatively weak against localized deformation. Therefore, if a localized force is applied to the sandwich panel, the core may be locally damaged, causing shear deformation of the pair of panels sandwiching the core. As a result, the battery case may be destroyed, and the battery may not be adequately protected.

[0005] Therefore, an object of the present invention is to provide a battery case that can suppress localized damage to the core portion and reduce destruction even when a localized input occurs to the sandwich panel.

[0006] In order to achieve the above object, the present invention provides a battery case for storing a battery for driving, in which at least one of the upper panel portion, lower panel portion, and side panel portion is composed of a sandwich panel having an outer peripheral frame, bar members that divide the inner space surrounded by the outer peripheral frame into multiple chambers, core portions stored in each of the chambers, and first and second panels that sandwich the outer peripheral frame, the bar members, and the core portions.

[0007] The battery case uses bar members to separate the inner space surrounded by the outer frame, allowing the outer frame and bar members to reinforce the core. The outer frame and bar members, functioning as reinforcing members, distribute the load in the longitudinal direction when a localized force is applied to the sandwich panel. This improves the sandwich panel's resistance to localized force. Even when a localized force is applied to the sandwich panel, localized damage to the core can be suppressed, and shear deformation of the pair of panels sandwiching the core can be suppressed. As a result, the battery case is less likely to be destroyed.

[0008] 1 is a cross-sectional view of a main portion of a battery case according to an embodiment; FIG. 2 is a plan view showing an outer peripheral frame, bar members, and a core portion of a sandwich panel constituting a lower panel portion; FIG. 3 is a view showing a honeycomb core constituting the core portion; FIG. 4 is a perspective view schematically showing a connection state between a sandwich panel constituting a lower panel portion and a battery member; FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 2; FIG. 6 is a cross-sectional view of a battery case according to a first modification, corresponding to FIG. 5; FIG. 7 is a cross-sectional view of a battery case according to a second modification, corresponding to FIG. 5; FIG. 8 is a cross-sectional view of a battery case according to a third modification, corresponding to FIG. 5; FIG. 9 is a cross-sectional view of a main portion of a battery case to which modifications 2 and 3 are applied, corresponding to FIG. 1; FIG. 10 is a cross-sectional view of a battery case according to a fourth modification, corresponding to FIG. 5; FIG. 11 is a perspective view showing a main portion of a sandwich panel according to a fourth modification; FIG. 12 is a schematic view showing an example of an arch curve of an arch portion and a recess of a transmission portion; FIG. 13 is a schematic view showing another example of an arch curve of an arch portion and a recess of a transmission portion; FIG. 14 is a schematic view showing yet another example of an arch curve of an arch portion and a recess of a transmission portion; FIG. 15 is a perspective view showing a main portion of a sandwich panel according to a sixth modification;

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments shown here are merely examples for embodying the technical concept of the present invention and are not intended to limit the present invention. Therefore, all other embodiments, examples, and operational techniques that can be conceived by those skilled in the art without departing from the spirit of the present invention are included in the scope and spirit of the present invention, as well as in the scope of the inventions set forth in the claims and their equivalents.

[0010] In addition, for the convenience of illustration and ease of understanding, the drawings attached to this specification may be represented schematically with the scale, aspect ratio, shape, etc. appropriately changed from the actual product, but these are merely examples and do not limit the interpretation of the present invention.

[0011] In this specification, ordinal numbers such as "first," "second," etc. may be used. However, unless otherwise specified, these ordinal numbers are used to identify components for the sake of convenience, and do not specify the number or order.

[0012] <Embodiment> Fig. 1 is a cross-sectional view of a main portion of a battery case 10 according to an embodiment. Fig. 2 is a plan view showing the outer frame 21, bar members 22, and core portion 23 of a sandwich panel 20 constituting the lower panel portion 14. Fig. 3 is a diagram showing a honeycomb core 23a constituting the core portion 23. Fig. 4 is a perspective view showing a schematic diagram of the connection between the sandwich panel 20 constituting the lower panel portion 14 and the battery member 12a of the battery 12. Fig. 5 is a cross-sectional view taken along line 5-5 in Fig. 2. In the figure, the X axis indicates the longitudinal direction of the vehicle, the Y axis indicates the lateral direction of the vehicle, and the Z axis indicates the vertical direction of the vehicle.

[0013] As shown in FIG. 1 , the battery case 10 has a storage compartment 11. A driving battery 12 is stored in the storage compartment 11. The battery case 10 has an upper panel portion 13, a lower panel portion 14, and a side panel portion 15. In the illustrated example, the upper panel portion 13, the lower panel portion 14, and the side panel portion 15 are each composed of a sandwich panel 20. The upper panel portion 13 and the side panel portion 15 are integrally formed. The outer periphery of the lower panel portion 14 is fixed to a first connection plate 14a. The lower end of the side panel portion 15 is fixed to a second connection plate 15a. The first connection plate 14a and the second connection plate 15a are fixed to a vehicle body panel 17 via bolts 16 or the like.

[0014] As shown in Figures 2, 3, 4, and 5, the sandwich panel 20 has an outer peripheral frame 21, bar members 22 that divide the inner space 30 surrounded by the outer peripheral frame 21 into multiple chambers 31, core portions 23 housed in each of the chambers 31, and a first panel 24 and a second panel 25 that sandwich the outer peripheral frame 21, the bar members 22, and the core portion 23.

[0015] The outer perimeter frame 21 forms the outer perimeter of the sandwich panel 20. The inner space 30 surrounded by the outer perimeter frame 21 has a relatively large area. When viewed in a cross section perpendicular to the longitudinal direction, the outer perimeter frame 21 has a rectangular cross section (see FIG. 5 ). The outer perimeter frame 21 may be solid, but is preferably hollow from the perspective of weight reduction. The material from which the outer perimeter frame 21 is formed is not particularly limited. The outer perimeter frame 21 is formed, for example, from aluminum.

[0016] The bar members 22 divide the inner space 30 surrounded by the outer frame 21. The bar members 22 include a first bar 22a extending in the left-right direction in FIG. 2 and a second bar 22b extending in the up-down direction. The outer frame 21 and the bar members 22 function as reinforcing members that reinforce the core portion 23. When viewed in a cross section perpendicular to the longitudinal direction, the bar members 22 have a rectangular cross section (see FIG. 5). The bar members 22 may be solid, but are preferably hollow from the perspective of reducing weight. The material from which the bar members 22 are formed is not particularly limited. The bar members 22 are formed, for example, from aluminum.

[0017] The core portion 23 is made of, for example, a honeycomb core 23a (see FIG. 3). Instead of the honeycomb core 23a, the core portion 23 can be made of a foam material such as foamed polyurethane.

[0018] The first panel 24 and the second panel 25 constitute surface layers on both the front and back sides of the core portion 23. The first panel 24 and the second panel 25 are attached to the core portion 23, for example, with an adhesive, but the fixing method is not particularly limited. The first panel 24 constitutes the surface layer on the storage chamber 11 side of the battery case 10. The second panel 25 constitutes the outer surface layer of the battery case 10. The materials forming the first panel 24 and the second panel 25 are not particularly limited. The first panel 24 and the second panel 25 are formed, for example, from a metal material such as aluminum, glass fiber reinforced plastic (GFRP), or the like. The materials forming the first panel 24 and the second panel 25 may be different materials. For example, the first panel 24 can be formed from aluminum, and the second panel 25 can be formed from GFRP.

[0019] In the sandwich panel 20 of the present invention, the inner space 30 of the peripheral frame 21 is divided by bar members 22. The sandwich panel 20 of the present invention does not include a configuration formed by arranging multiple small-area sandwich panel pieces. Therefore, in the sandwich panel 20 of the present invention, the inner space 30 of the peripheral frame 21 is divided into at least two chambers 31 by at least one bar member 22.

[0020] In the battery case 10 configured as described above, the bar members 22 separate the inner space 30 surrounded by the outer peripheral frame 21, allowing the outer peripheral frame 21 and the bar members 22 to reinforce the core portion 23. The outer peripheral frame 21 and the bar members 22 function as reinforcing members to distribute the load in the longitudinal direction when a localized force is applied to the sandwich panel 20. This improves the sandwich panel 20's resistance to the localized force. Even when a localized force is applied to the sandwich panel 20, localized damage (damage due to shear deformation or compressive deformation) to the core portion 23 can be suppressed, and shear deformation of the pair of panels sandwiching the core portion 23 can be suppressed. As a result, the battery case 10 is less likely to be destroyed.

[0021] Components of the battery 12 or vehicle body components (such as the vehicle body panel 17) are fixed to the outer perimeter frame 21 or bar members 22 of the sandwich panel 20. FIG. 4 shows a state in which a battery member 12a, a component of the battery 12, is fixed to the outer perimeter frame 21. The battery member 12a is also simply referred to as a "member." The battery member 12a collectively refers to a battery cross member 12b extending in the lateral direction of the vehicle (indicated by the Y axis) and a battery side member 12c extending in the longitudinal direction of the vehicle (indicated by the X axis). With this configuration, the lightweight sandwich panel 20 can easily protect the battery case 10 and the housed battery 12 from input forces to the sandwich panel 20.

[0022] The core portion 23 is composed of a honeycomb core 23a. The honeycomb core 23a is a lightweight, strong reinforcing material. By configuring the core portion 23 in this manner, the weight of the sandwich panel 20 can be reduced by reducing the weight of the core portion 23. Furthermore, the strength and rigidity of the core portion 23 can be improved.

[0023] <Modifications 1-3> Fig. 6A is a cross-sectional view of the battery case 10 of Modification 1, corresponding to Fig. 5. Fig. 6B is a cross-sectional view of the battery case 10 of Modification 2, corresponding to Fig. 5. Fig. 6C is a cross-sectional view of the battery case 10 of Modification 3, corresponding to Fig. 5.

[0024] Although the peripheral frame 21 and the bar members 22 in the embodiment have a rectangular cross-sectional shape (see FIG. 5), the cross-sectional shapes of the peripheral frame 21 and the bar members 22 can be changed as appropriate.

[0025] As shown in Figures 6A, 6B, and 6C, in Modifications 1-3, the perimeter frame 21 has a cross-sectional shape with an arch portion 40 equipped with a transmission unit 50 that transmits an input load, forming a closed cross section when viewed in a cross section perpendicular to the longitudinal direction. The transmission unit 50 in the perimeter frame 21 includes a wall portion 50b covering the upper side of the perimeter frame 21, a wall portion 50c covering the lower side of the perimeter frame 21, and a wall portion 50d that closes the opening in the direction in which the protruding portion 41 of the arch portion 40 protrudes. In the illustrated example, the wall portion 50b is formed by extending the first panel 24, the wall portion 50c is formed by extending the second panel 25, and the wall portion 50d is formed by bending the first panel 24 and connecting it to the second panel 25. Note that the walls 50b, 50c, and 50d of the transmission unit 50 are not limited to the above configuration and can be formed from plate members separate from the first panel 24 and the second panel 25. Furthermore, the wall portion 50d of the transmission portion 50 can be formed from the end of the first connecting plate 14a or the end of the second connecting plate 15a (see FIG. 1). In Modification 1, the bar member 22 has a rectangular cross-sectional shape when viewed in a cross section perpendicular to the longitudinal direction, as in the embodiment. In Modifications 2 and 3, the bar member 22 also has a cross-sectional shape with an arch portion 40 equipped with a transmission portion 50 that transmits an input load, forming a closed cross section when viewed in a cross section perpendicular to the longitudinal direction. The transmission portion 50 of the bar member 22 also has wall portions 50e and 50f that cover the sides of the outer frame 21 and a wall portion 50g that closes the opening in the direction in which the protrusion 41 of the arch portion 40 protrudes. The ends of the wall portions 50e and 50f are connected to the first panel 24 and the second panel 25. In the illustrated example, the wall portion 50g of Modification 2 is formed by the second panel 25, and the wall portion 50g of Modification 3 is formed by the first panel 24.

[0026] With this configuration, when a localized input is applied to the sandwich panel 20, the outer peripheral frame 21 and bar members 22, which function as reinforcing members, efficiently distribute the load in the longitudinal direction via the transmission unit 50. This further improves the sandwich panel 20's resistance to localized input, further improving the strength of the sandwich panel 20 and reducing the risk of the battery case 10 being destroyed.

[0027] In Modifications 1, 2, and 3, the convex portions 41 of the arch portions 40 of the outer periphery frames 21 protrude outward when viewed from the center of the battery case 10. Referring to FIG. 2 , in the left and right outer periphery frames 21 extending in the longitudinal direction of the vehicle (indicated by the X axis), the convex portions 41 of the arch portions 40 protrude laterally, as indicated by arrows 61 and 62, to enhance strength against a side collision. In the front outer periphery frame 21 extending laterally, as indicated by the Y axis, the convex portions 41 of the arch portions 40 protrude forward, as indicated by arrow 63, to enhance strength against a frontal collision. In the rear outer periphery frame 21 (not shown), the convex portions 41 of the arch portions 40 protrude rearward, as indicated by arrow 64, to enhance strength against a rearward collision. 6A, 6B, and 6C, the convex portions 41 of the arch portions 40 of the left and right outer peripheral frames 21 protrude laterally toward the vehicle body, as indicated by arrows 61 and 62. With this configuration, when a localized force is applied to the sandwich panel 20 from the outside toward the center of the battery case 10, the outer peripheral frames 21 efficiently distribute the load in the longitudinal direction. This improves the strength of the sandwich panel 20 and reduces the risk of the battery case 10 being destroyed.

[0028] In Modifications 2 and 3, the protruding direction of the convex portions 41 of the arch portions 40 of the bar members 22 can be set arbitrarily. For example, in Modification 2, the convex portions 41 of the arch portions 40 of the bar members 22 protrude downward (see FIG. 6B ). In Modification 3, the convex portions 41 of the arch portions 40 of the bar members 22 protrude upward (see FIG. 6C ). This configuration allows the protruding direction of the convex portions 41 of the bar members 22 to be determined according to the design. When the sandwich panel 20 is applied to the lower panel portion 14, the protruding direction of the convex portions 41 of the bar members 22 can be set downward in consideration of impacts from below the lower panel portion 14 (see Modification 2 in FIG. 6B ). The protruding direction of the convex portions 41 of the bar members 22 can be set upward in consideration of the weight of the battery 12 to be accommodated (see Modification 3 in FIG. 6C ). Depending on the position where the bar members 22 are arranged, bar members 22 with the protrusions 41 projecting in an upward direction and bar members 22 with the protrusions 41 projecting in a downward direction can be used in combination.

[0029] 6D is a cross-sectional view corresponding to FIG. 1 , showing a battery case 10 to which Modifications 2 and 3 are applied. In a sandwich panel 20 applied to the lower panel portion 14, the convex portions 41 of the arch portions 40 of the outer peripheral frame 21 protrude outward (to the right in the figure) when viewed from the center of the battery case 10. In addition, in a sandwich panel 20 applied to the upper panel portion 13, the convex portions 41 of the arch portions 40 of the outer peripheral frame 21 protrude outward (to the right in the figure) when viewed from the center of the battery case 10. The convex portions 41 of the arch portions 40 of the bar members 22 protrude in any direction.

[0030] <Modification 4> Fig. 7A is a cross-sectional view of a battery case 10 of Modification 4, corresponding to Fig. 5. Fig. 7B is a perspective view showing a main part of a sandwich panel 20 of Modification 4.

[0031] Modification 4 differs from modifications 1-3 in that it modifies the configuration of transmission unit 50. As shown in Figures 7A and 7B, transmission unit 50 of modification 4 differs from transmission unit 50 of modifications 1-3 in that it further includes rib portions 51 that are arranged along the outside of arch portion 40 and extend in the direction in which convex portion 41 of arch portion 40 protrudes.

[0032] The rib portions 51 are erected in the same direction as the protruding direction of the convex portions 41. The transmission portion 50 has recesses 50a that match the shape of the convex portions 41 of the arch portion 40. The spacing between the rib portions 51 can be determined appropriately depending on the design. The transmission portion 50 further including the rib portions 51 in this manner can efficiently distribute the load in the longitudinal direction of the outer peripheral frame 21 and the bar members 22 when a localized input occurs to the sandwich panel 20. As a result, the outer peripheral frame 21 and the bar members 22, which function as reinforcing members, can increase the amount of energy absorption while suppressing an increase in mass.

[0033] 8A, 8B, and 8C are schematic diagrams showing the arch curves of the arch portion 40 and the recessed portion 50a of the transmission portion 50. FIG.

[0034] The arch curve shown in FIG. 8A represents a catenary curve. The arch portion 40 has an arch shape that follows the catenary curve. The recessed portion 50a of the transmission portion 50 has a shape that follows the catenary curve and matches the shape of the arch portion 40. The arch curve shown in FIG. 8B represents a uniform radius of curvature. The arch portion 40 has an arch shape that follows the uniform radius of curvature. The recessed portion 50a of the transmission portion 50 has a shape that follows the uniform radius of curvature and matches the shape of the arch portion 40. The arch curve shown in FIG. 8C represents a quadratic curve. The arch portion 40 has an arch shape that follows the quadratic curve. The recessed portion 50a of the transmission portion 50 has a shape that follows the quadratic curve and matches the shape of the arch portion 40.

[0035] When the transmission part 50 is subjected to a uniformly distributed load as shown by the arrow, only compressive force along the arch curve occurs in the catenary curve. Therefore, the catenary curve has the greatest strength among the three arch curves shown in the figure.

[0036] Therefore, it is preferable that the arch portion 40 has an arch shape that follows a catenary curve, and the transmission portion 50 has a recess 50a that matches the outer shape of the arch portion 40. With this configuration, the transmission portion 50 can efficiently transmit the input load to the arch portion 40 as a compressive load that follows the tangent direction of the arch shape. As a result, the outer peripheral frame 21 and bar members 22, which function as reinforcing members, can further increase their energy absorption capacity, thereby further suppressing an increase in mass.

[0037] <Modification 5> FIG. 9 is a perspective view showing a main part of a sandwich panel 20 according to Modification 5. As shown in FIG.

[0038] Variation 5 differs from Variation 4 in that the configuration of the transmission unit 50 has been modified. The transmission unit 50 of Variation 5 further includes a foamed resin 52 arranged along the outer side of the arch portion 40. The foamed resin 52 may be, for example, foamed polyurethane or foamed polystyrene. The foamed resin 52 may optionally be filled inside the arch portion 40. When a localized force is applied to the sandwich panel 20, the transmission unit 50 configured with the foamed resin 52 receives the load over the entire longitudinal direction of the transmission unit 50, thereby efficiently distributing the load along the longitudinal direction of the outer perimeter frame 21 and the bar members 22. As a result, the outer perimeter frame 21 and the bar members 22, which function as reinforcing members, can increase their energy absorption capacity while suppressing an increase in mass.

[0039] <Sixth Modification> FIG. 10 is a perspective view showing a main part of a sandwich panel 20 according to a sixth modification.

[0040] Variation 6 differs from Variations 4 and 5 in that the configuration of the transmission unit 50 has been modified. The transmission unit 50 of Variation 6 further includes a lattice structure 53 arranged along the outer side of the arch portion 40. As is well known, the lattice structure 53 is a structure in which multiple lattice-shaped cells 53a are stacked three-dimensionally and periodically. The shape of the cells 53a to be applied is not particularly limited. The lattice structure 53 can be optionally filled inside the arch portion 40. When a localized input occurs to the sandwich panel 20, the transmission unit 50 configured with the lattice structure 53 receives the load over the entire longitudinal direction of the transmission unit 50 and further distributes the load through the cells 53a of the lattice structure 53 themselves, thereby efficiently distributing the load in the longitudinal direction of the outer perimeter frame 21 and the bar members 22. As a result, the outer perimeter frame 21 and the bar members 22, which function as reinforcing members, can increase their energy absorption capacity while suppressing an increase in mass.

[0041] The above describes embodiments and modifications of the battery case 10 of the present invention, but the present invention is not limited to the configurations described in the above-mentioned embodiments and modifications, and can be modified as appropriate based on the claims.

[0042] For example, although the embodiment has been shown in which each of the upper panel portion 13, the lower panel portion 14, and the side panel portion 15 is made of a sandwich panel 20, the present invention is not limited to this case. At least one of the upper panel portion 13, the lower panel portion 14, and the side panel portion 15 can be made of a sandwich panel 20.

[0043] The following embodiments are also included within the scope of the present invention: a battery case 10 according to claim 2 having the features of claim 4; a battery case 10 according to claim 9 having the features of claim 10.

[0044] REFERENCE SIGNS LIST 10 Battery case 11 Storage compartment 12 Battery 12a Battery member 13 Upper panel portion 14 Lower panel portion 14a First connection plate 15 Side panel portion 15a Second connection plate 16 Bolt 17 Vehicle body side panel 20 Sandwich panel 21 Peripheral frame 22 Bar member 22a First bar 22b Second bar 23 Core portion 23a Honeycomb core 24 First panel 25 Second panel 30 Inner space 31 Chamber 40 Arch portion 41 Convex portion 50 Transmission portion 50a Concave portion 51 Rib portion 52 Foamed resin 53 Lattice structure 53a Cell

Claims

1. A battery case for storing a battery for driving, wherein at least one of the upper panel portion, lower panel portion, and side panel portion is composed of a sandwich panel having an outer peripheral frame, bar members that divide the inner space surrounded by the outer peripheral frame into multiple chambers, core portions housed in each of the chambers, and first and second panels that sandwich the outer peripheral frame, bar members, and core portions.

2. A battery case as described in claim 1, wherein the outer peripheral frame has a cross-sectional shape having an arch portion equipped with a transmission portion for transmitting input loads when viewed in a cross section perpendicular to the longitudinal direction, forming a closed cross section.

3. A battery case as described in claim 2, wherein the bar member has a cross-sectional shape having an arch portion equipped with a transmission portion that transmits input loads when viewed in a cross section perpendicular to the longitudinal direction, forming a closed cross section.

4. The battery case according to claim 3, wherein the protrusions of the arch portions of the outer peripheral frame protrude outward when viewed from the center of the battery case.

5. The battery case according to claim 4, wherein the arch portion has an arch shape that follows a catenary curve, and the transmission portion has a recess that matches the outer shape of the arch portion.

6. The battery case according to claim 4, wherein the transmission portion has a rib portion disposed along the outside of the arch portion and extending in the direction in which the convex portion of the arch portion protrudes.

7. The battery case according to claim 4, wherein the transmission portion has a foamed resin disposed along the outside of the arch portion.

8. The battery case according to claim 4, wherein the transmission portion has a lattice structure arranged along the outside of the arch portion.

9. A battery case according to any one of claims 1 to 8, wherein a component of the battery or a vehicle body member is fixed to the outer peripheral frame or the bar member of the sandwich panel.

10. The battery case according to any one of claims 1 to 8, wherein the core portion is made of a honeycomb core.

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