Battery pack

Abstract

To inhibit high temperature heat from a battery of a battery pack to the other battery.SOLUTION: A battery pack 1 includes: multiple batteries 20 each having a gas discharge part 2; a housing 12 which houses the batteries 20; and a member 30 which is provided adjacent to the batteries 20 between the batteries 20 of the housing 12. A heat insulation material 50 is provided at the member 30 located adjacent to the batteries 20.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In a floor structure of an electric vehicle having a lower floor separated from an upper floor below the upper floor, a placement portion for a battery is partitioned by members arranged in a lattice pattern on the lower floor, and a frame that can be attached to and detached from below the upper floor is provided around this placement portion (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, when high-temperature gas is released from a battery cell in a battery pack, the heat of the gas may be transmitted to a cross member, and then the heat may be transmitted to other adjacent battery cells through the cross member.

[0005] An object of the present invention is to suppress the transmission of high-temperature heat from a battery in a battery pack to other batteries.

Means for Solving the Problems

[0006] The present invention includes a plurality of batteries having gas discharge portions, and a housing having a member that defines a housing chamber for housing the batteries. The member has a closed cross-section, and a heat insulating material is provided inside the closed cross-section. In a battery pack, The aforementioned insulating material has an H-shaped cross-section, with both ends provided along a pair of opposing inner surfaces of the member and a connecting portion connecting the central parts of both ends, and the centers of both ends are convex toward the center of the member. This solves the above problems.

Effects of the Invention

[0007] According to the present invention, it is possible to suppress the transfer of high-temperature heat from one battery in a battery pack to other batteries. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of a battery pack according to an embodiment of the present invention, viewed from the upper left front. [Figure 2] Figure 1 is an exploded perspective view showing the structure of the battery pack. [Figure 3] Figure 1 is an exploded perspective view showing the structure of the battery module. [Figure 4] This is a schematic partial cross-sectional view along line AA in Figure 2, showing the cross member and thermal insulation material (expanded graphite) of a battery pack according to the first embodiment of the present invention. [Figure 5] This is a schematic partial cross-sectional view corresponding to Figure 3, illustrating the operation of a battery pack according to the first embodiment of the present invention. [Figure 6] This is a schematic partial cross-sectional view along line AA in Figure 2, showing the cross member and thermal insulation material (expanded graphite) of a battery pack according to a second embodiment of the present invention. [Figure 7] This is a schematic partial cross-sectional view along line AA in Figure 2, showing the cross member and thermal insulation material (expanded graphite) of a battery pack according to a third embodiment of the present invention. [Figure 8] This is a schematic partial cross-sectional view along line AA in Figure 2, showing the cross member and thermal insulation material (expanded graphite) of a battery pack according to a fourth embodiment of the present invention. [Figure 9] This is a schematic partial cross-sectional view along line AA in Figure 2, showing a cross member and thermal insulation material (expanded graphite) of a battery pack according to yet another embodiment of the present invention. [Modes for carrying out the invention]

[0009] The following description will explain a battery pack according to an embodiment of the present invention with reference to the drawings. Figure 1 is a perspective view of the battery pack 1 according to an embodiment of the present invention, viewed from the upper left front of the vehicle, and Figure 2 is an exploded perspective view showing the structure of the battery pack 1. In each figure, FR indicates the front of the vehicle in the longitudinal direction, LH indicates the left side of the vehicle in the lateral direction, and UP indicates the upper side of the vehicle in the vertical direction. In the following description, the front and rear of the vehicle in the longitudinal direction, the left and right sides of the vehicle in the lateral direction, and the upper and lower sides of the vehicle in the vertical direction will be referred to as "vehicle front," "vehicle rear," "vehicle left," "vehicle right," "vehicle upper," and "vehicle lower," respectively. Furthermore, parts having the same function will be denoted by the same reference numerals, and if there is duplication, the explanation will be omitted.

[0010] The battery pack 1 according to this embodiment is not particularly limited, but as an example, it can be used as a vehicle drive battery for an electric vehicle (EV).

[0011] As shown in Figures 1 and 2, the battery pack 1 according to this embodiment comprises a housing 10 having an upper case 11 and a lower case 12, a battery module 20, and a cross member 30 disposed in the lower case 12.

[0012] The battery pack 1 comprises a housing 10, which is a hollow, rectangular box-shaped component, and a battery module 20 housed inside. The housing 10 has a flattened shape, where the vertical dimension of the vehicle is smaller than the horizontal dimension of the vehicle, and the horizontal dimension of the vehicle is smaller than the vertical dimension of the vehicle. The shape of the battery pack 1 is not limited to the shape shown in Figure 1, and can be made into an appropriate shape depending on the location of the vehicle in which the battery pack 1 is installed. In this embodiment, the battery pack 1 is installed over almost the entire surface of the underside of the vehicle floor, from the front floor to the rear floor, and therefore has a flattened shape which is preferable for placement over the entire underside of the vehicle floor.

[0013] The housing 10 has an upper case 11 and a lower case 12, both of which are made of metal materials such as aluminum or steel. At the bottom of the lower case 12, multiple cross members 30, also made of metal materials such as aluminum or steel, or composite or resin materials, are arranged extending in the left-right direction of the vehicle. These multiple cross members 30 define the lower case 12 into multiple storage compartments 32, and multiple battery modules 20 are arranged in these defined storage compartments 32 along the left-right direction of the vehicle. As will be described in detail later, each battery module 20 is made up of one or more battery cells 21 stacked on top of each other. Although not particularly limited, in the example shown in Figure 2, four cross members 30 provided on the lower case 12 divide the lower case 12 into five spaces in the front-rear direction of the vehicle, and each battery module 20 is arranged in one of these spaces.

[0014] As shown in Figure 2, the upper case 11 and the lower case 12 are fastened together at their periphery by fasteners (not shown). A rubber sealing member may be interposed at the periphery contact area between the upper case 11 and the lower case 12.

[0015] The lower case 12 is a box-shaped member with a bottom that opens at the top of the vehicle, and the battery module 20 is arranged in a housing chamber 32 defined by a cross member 30 at the bottom. As shown in Figure 2, on the front side of the lower case 12, a total of eight battery modules 20 are arranged in two rows in the left-right direction and four rows in the front-rear direction of the vehicle. On the rear side of the lower case 12, a total of eight battery modules 20 are arranged in two rows in the up-down direction, two rows in the left-right direction and two rows in the front-rear direction of the vehicle.

[0016] Also, in the longitudinal direction of the vehicle, a cross member 30 is disposed at the bottom of the lower case 12 in the vehicle width direction so as to separate the battery modules 20 from each other. By doing so, when an external force is applied to the battery pack 1, the cross member 30 restricts the area where the battery module 20 can move, and it is possible to suppress contact between the battery modules 20 or between the battery cells 21. Note that the form of partitioning the lower case 12 by the cross member 30 shown in FIG. 2 is an example and is not particularly limited, and can be made into an appropriate form according to the shape and quantity of the battery module 20.

[0017] FIG. 3 is an exploded perspective view showing the structure of the battery module 20 of the present embodiment. The battery module 20 of the present embodiment is a module component in which a plurality of flat battery cells 21 are stacked and electrically connected by wiring members such as a bus bar unit (not shown). The battery cell 21 is, for example, a lithium-ion secondary battery or the like, which is configured by laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween and sealing them with an exterior member made of a material such as aluminum together with an electrolyte.

[0018] The battery cell 21 in the present embodiment is a lithium-ion secondary battery, and it is well known to those skilled in the art that when the battery cell 21 is placed in a high-temperature situation, there is a risk of generating high-temperature gas. Therefore, as shown in FIG. 3, the battery cell 21 has a gas release portion 22. In the illustrated example, the gas release portion 22 is provided at one location on the upper side of the vehicle. The gas release portion 22 has the role of a ventilation hole for releasing the gas when gas is generated inside the battery cell 21. By providing such a structure, abnormal expansion of the battery cell 21 due to gas generation can be suppressed.

[0019] The gas release section 22 can be, for example, an explosion-proof valve that opens to release the gas when the internal pressure of the battery cell 21 exceeds a predetermined value, or a sealing member that ruptures to release the gas. In the illustrated example, the gas release section 22 is circular in shape, but it may also be elliptical, rectangular, or polygonal. The number and position of the gas release sections 22 in the battery cell 21 can be appropriately set according to the performance, shape, and dimensions of the battery pack 1, battery module 20, battery cell 21, or gas release section 22. In this embodiment, a single battery module 20 is constructed by stacking multiple flattened battery cells 21, and multiple battery modules 20 are arranged in the housing 10. However, the battery pack 1 of the present invention is not particularly limited in its form and may consist only of battery cells 21. The battery cell 21 and battery module 20 together are referred to as the battery.

[0020] As described above, in the battery pack 1 of this embodiment, when multiple battery modules 20 are arranged in the lower case 12 as shown in Figure 2, a cross member 30 exists adjacent to the battery modules 20. Thus, in this embodiment, when high-temperature gas is released from the battery cell 21, heat is transferred to the cross member 30 before it is transferred to the other battery modules 20.

[0021] Next, the structure of the cross member 30 of this embodiment will be described. Figure 4 is a cross-sectional view showing the cross member 30 according to the first embodiment of the present invention, and is a cross-sectional view along line AA in Figure 2. As shown in Figure 4, the cross member 30 of this embodiment is a hollow member in the shape of a rectangular prism with a closed cross section 30a (both ends may be open or closed), and is manufactured, for example, by extruding an aluminum material. In the cross section shown in Figure 4, the cross member 30 of this embodiment has heat insulating material 50 provided on the four internal surfaces. Since this heat insulating material 50 extends in the longitudinal direction of the cross member 30, it extends in the left-right direction of the vehicle as part of the battery pack 1. Note that the structure of the cross member 30 is not limited to a member having a closed cross section 30a, and in cases such as when the heat insulating material 50 is provided on the external surface of the cross member 30, as in the fifth embodiment described later (see Figure 9), it may be a solid member without a closed cross section 30a. Also, the cross-sectional shape of the cross member 30 is not limited to a rectangle and may be other shapes.

[0022] The thermal insulation material 50 provided in the cross member 30 having a closed cross section 30a may be incorporated by press-fitting it into the closed cross section 30a of the cross member 30, or it may be disposed inside by a manufacturing method (resin-metal integral molding method) in which it is integrally molded with the cross member 30. Furthermore, when fixing the thermal insulation material 50 to the inner surface of the closed cross section 30a of the cross member 30, it may be fixed by fasteners such as rivets or bolts, or by bonding with an adhesive.

[0023] In the battery pack 1 of this embodiment, as shown in Figure 5, when high-temperature gas is released from the gas release section 22 of the battery cell 21, this high-temperature gas may flow along the opposing upper case 11 and other components toward the surface of the cross member 30 adjacent to the battery cell 21. However, since the cross member 30 is provided with an insulating material 50, it insulates the heat of the gas. As a result, heat transfer to the other surface of the cross member 30 opposite to the surface struck by the high-temperature gas, and consequently to the other battery module 20 (the left battery module 20 in the example of Figure 5) arranged on either side of the cross member 30, can be suppressed. Furthermore, by placing the insulating material 50 on the closed cross section 30a of the cross member 30, it contributes to saving space inside the battery pack 1.

[0024] In addition, in this embodiment of the battery pack 1, the heat insulating material 50 is applied to the cross member 30, but it can also be applied to the outer frame members 31, which have a hollow cross-section and are arranged on the four sides of the outer frame of the lower case 12. By providing the heat insulating material 50 to the outer frame members 31, it is possible to suppress the release of high-temperature gas released from the gas release section 22 to the outside of the battery pack 1. In other words, the heat insulating material 50 can be placed on any member member having a hollow cross-section that is arranged in the lower case 12.

[0025] Alternatively, as shown in Figure 9, the insulation material 50 may be placed on the outer surface of the cross member 30. In this case, the insulation material 50 placed on the outer surface of the cross member 30 directly insulates the heat of the high-temperature gas released from the gas release section 22, preventing the transfer of high-temperature heat to the wall surface of the cross member 30, thereby suppressing the transfer of heat to the other battery modules 20 placed on either side of the cross member 30.

[0026] Regarding the placement of the insulation material 50, it can be placed on the outer surface of the cross member 30, the inner surface (the inner surface of the closed section 30a), or both. Furthermore, the insulation material 50 does not necessarily need to be attached to the entire surface of the cross member 30; it may be placed partially depending on the position and direction of the gas release section 22. By placing the insulation material 50 partially, the cost of the insulation material 50 can be reduced.

[0027] Furthermore, the types of insulation materials are not particularly limited; any material with low thermal conductivity and the ability to withstand high temperatures can be used.

[0028] In this embodiment, the thermal insulation material 50 is composed of expanded graphite 50a. Expanded graphite is an intercalation compound obtained by treating flake graphite with an inorganic acid such as sulfuric acid or nitric acid, or an oxidizing agent such as concentrated nitric acid or potassium chlorate, thereby forcing the oxidizing agent into the intercalation space of the graphite carbon crystals through a chemical reaction. The expanded graphite obtained in this way has the property that when heat is applied, the intercalation material gasifies, and the resulting pressure causes it to expand several hundred times in the direction perpendicular to the graphite carbon crystal, forming a fibrous shape.

[0029] When expanded, the fibrous portions of the expanded graphite 50a become entangled with each other, forming many air layers between them. The alternating arrangement of these air layers, which have low thermal conductivity, and the expanded graphite layers results in high thermal insulation.

[0030] Expanded graphite 50a may be obtained, for example, by injecting a molten thermoplastic resin or thermosetting resin to which powdered expanded graphite has been added into a mold and then cooling it. The expanded graphite 50a obtained in this way has a thickness such as that of a plate or sheet. In this embodiment, the thermal insulation material 50 made of expanded graphite 50a is formed into a hollow rectangular prism shape that extends in the left-right direction of the vehicle along the shape of the closed cross section 30a of the cross member 30, but it is not particularly limited and may be formed into a cylindrical, elliptical, or polygonal prism shape.

[0031] The following describes in more detail four embodiments of the thermal insulation material 50 according to the present invention, which are various modifications of the form of the thermal insulation material 50 according to the present invention. Figure 4 is a schematic partial cross-sectional view along line AA in Figure 2, showing the cross member 30 and thermal insulation material 50 (expanded graphite 50a) of a battery pack according to the first embodiment of the present invention, and Figure 5 is a cross-sectional view for explaining the operation of the battery pack according to the first embodiment.

[0032] (First Embodiment) As shown in Figures 4 and 5, in the battery pack 1 of the first embodiment, the expanded graphite 50a is arranged to extend along the entire inner surface of the closed cross section 30a of the cross member 30. Since the cross member 30 is arranged in the left-right direction of the vehicle, the expanded graphite 50a is also shaped to extend in the left-right direction of the vehicle. In other words, similar to the cross member 30, the expanded graphite 50a is shaped like a hollow rectangular prism. When high-temperature gas is generated in the right-side battery cell 21 shown in Figure 5, the high-temperature gas comes into contact with the right side of the cross member 30 adjacent to the battery cell 21 (especially the right vertical wall surface of the cross member 30). At that time, heat is transferred to the expanded graphite 50a via the cross member 30, so as shown in Figure 5, the expanded graphite 50a expands in the closed cross section 30a of the cross member 30 and fills the closed cross section 30a. This insulates the heat from the high-temperature gas, thereby suppressing the transfer of heat to the left vertical wall surface of the cross member 30, and consequently suppressing the transfer of heat to the other battery modules 20 located on the left side of the cross member 30.

[0033] Since the expanded graphite 50a has rigidity before thermal expansion, it contributes to improving the rigidity of the cross member 30, and after thermal expansion, it uniformly fills the inside of the cross member 30, resulting in consistent and high thermal insulation performance in all parts.

[0034] Furthermore, the expanded graphite 50a in the first embodiment is a hollow member in the shape of a rectangular prism, and when pressed into the closed cross section 30a of the cross member 30, it can be appropriately deformed toward the center of the cross section of the cross member 30 because the inside is hollow, which reduces the press-fitting resistance with the inner circumferential surface of the cross member 30 and contributes to improved workability.

[0035] Furthermore, by placing the expanded graphite 50a in the closed cross section 30a of the cross member 30, which is a dead space, it contributes to saving space inside the battery pack 1. In addition, because the expanded graphite 50a is a conductive material, placing it in the closed cross section 30a of the cross member 30 reduces the possibility of ground faults or short circuits caused by contact with the electrical junctions of other components when it expands.

[0036] The expanded graphite 50a can also be placed on the outer surface of the cross member 30, as shown in Figure 9. In this case, the expanded graphite 50a, which expands due to heat, insulates against heat, thereby suppressing thermal damage to the cross member 30 and preventing heat transfer to other adjacent battery modules 20 through the cross member 30. In this embodiment, it is desirable to protect the electrical junctions of other components with insulating material to reduce the possibility of ground faults or short circuits during expansion.

[0037] Furthermore, the expanded graphite 50a can be placed on the outer surface, the inner surface, or both of the cross member 30. It is also not necessary to place the expanded graphite 50a across the entire surface of the cross member 30; it may be placed partially depending on the position and direction of the gas discharge section 22. By partially placing the expanded graphite 50a, the cost of the expanded graphite 50a can be reduced.

[0038] (Second Embodiment) The expanded graphite 50a may be arranged in an H-shape on the closed cross section 30a of the cross member 30, as shown in Figure 6. In this case, both ends 52a of the expanded graphite 50a are arranged along the inner surface of the vertical wall portion of the cross member 30 adjacent to the battery cell 21, and these ends 52a of the expanded graphite 50a are connected to each other by a connecting portion 51a in the central part in the vertical direction of the vehicle. In this second embodiment as well, when high-temperature gas is released from the battery cell 21 and heat is transferred to the vertical wall portion of the cross member 30 adjacent to the battery cell 21, the expanded graphite 50a that has expanded due to the heat insulates the heat, suppressing heat transfer to the other wall portion, and similarly suppressing heat transfer to other battery modules 20 adjacent across the cross member 30.

[0039] Furthermore, in this embodiment, the expanded graphite 50a has a structure in which the connecting portion 51a supports a pair of opposing vertical wall surfaces of the closed cross section 30a of the cross member 30 via both ends 52a, thus contributing to improved rigidity of the cross member 30 against external forces in the longitudinal direction of the vehicle. In addition, compared to the first embodiment, the application area of ​​the expanded graphite 50a is smaller, which reduces costs.

[0040] In addition, compared to the first embodiment, when the expanded graphite 50a is pressed into the closed cross section 30a of the cross member 30, the contact area with the inner surface of the cross member 30 is reduced, which reduces the press-fitting resistance and contributes to improved workability of press-fitting the expanded graphite 50a.

[0041] (Third embodiment) As shown in Figure 7, the expanded graphite 50a may be positioned along the surface of the vertical wall portion of the closed cross section 30a of the cross member 30 adjacent to the battery cell 21. In this embodiment, the expanded graphite 50a is a plate-shaped member, and the expanded graphite 50a and the vertical wall portion of the cross member 30 are fixed using fasteners such as rivets 60. By fastening and fixing the expanded graphite 50a with rivets 60, changes in the position of the expanded graphite 50a over time can be suppressed. In this third embodiment as well, when high-temperature gas is released from the battery cell 21 and heat is transferred to the vertical wall portion of the cross member 30 adjacent to the battery cell 21, the expanded graphite 50a, which has expanded due to the heat, insulates the heat and suppresses heat transfer to the other wall portion, and similarly suppresses heat transfer to other battery modules 20 adjacent across the cross member 30.

[0042] Furthermore, in the third embodiment, the expanded graphite 50a and the cross member 30 are fastened together using rivets 60, but they may also be fixed together using fasteners such as bolts or adhesives. The number and position of fasteners, the amount and position of adhesives are not particularly limited and can be appropriately set according to the performance, shape, dimensions, etc., of the cross member 30 and the expanded graphite 50a.

[0043] Furthermore, compared to the first and second embodiments, this third embodiment reduces costs by decreasing the application area of ​​the expanded graphite 50a.

[0044] (Fourth Embodiment) The expanded graphite 50a may be arranged in an H-shape on the closed cross section 30a of the cross member 30, as shown in Figure 8. In this case, both ends 52b of the expanded graphite 50a are arranged along the inner surface of the vertical wall portion of the cross member 30 adjacent to the battery cell 21, and the central portion of both ends 52b in the vertical direction of the vehicle is convex toward the center of the cross section of the cross member 30, and the convex vertices of both ends are connected to each other by connecting portions 51b. In this fourth embodiment as well, when high-temperature gas is released from the battery cell 21 and heat is transferred to the vertical wall portion of the cross member 30 adjacent to the battery cell 21, the expanded graphite 50a that has expanded due to the heat insulates the heat, suppressing heat transfer to the other vertical wall portion, and similarly suppressing heat transfer to other battery modules 20 adjacent across the cross member 30.

[0045] Furthermore, in this embodiment, the expanded graphite 50a is structured to support a pair of opposing vertical wall surfaces of the cross member 30 via the connecting portion 51b and both ends 52b, thereby contributing to improved rigidity of the cross member 30 against external forces in the longitudinal direction of the vehicle. Also, compared to the second embodiment which is formed in the same H shape, the central portions of both ends 52b extending in the vertical direction of the vehicle are convex towards the center of the cross section of the cross member 30, so when the expanded graphite 50a is pressed into the closed cross section 30a of the cross member 30, the interference area with the internal surface of the cross member 30 is reduced. As a result, the press-fitting resistance is reduced, which also contributes to improved workability of press-fitting the expanded graphite 50a.

[0046] Furthermore, compared to the second embodiment, even if the dimensions of the connecting portion 51b and both ends 52b are manufactured with some variation, the both ends 52b will bend appropriately starting from the connection point between the connecting portion 51b and both ends 52b, thus contributing to improved press-fitting workability.

[0047] In this embodiment, one method for placing the expanded graphite 50a in the closed cross section 30a of the cross member 30 is to press-fit the expanded graphite 50a from one end of the cross member 30 towards the other end. Alternatively, the expanded graphite 50a can be placed in the closed cross section 30a of the cross member 30 by using a manufacturing method that integrally molds the expanded graphite 50a to the cross member 30. Specifically, the molded cross member 30 is placed in an injection molding die, and a molten thermoplastic resin or thermosetting resin with powdered expanded graphite added is injected into the die and cooled to place the expanded graphite 50a in the closed cross section 30a of the cross member 30. In this case, the effect of improving the adhesive strength of the resin can be obtained by making the surface roughness of the inner surface of the cross member 30 rough.

[0048] Although the above embodiment was described using an electric vehicle (EV) as an example, it can also be applied to battery packs 1 of hybrid vehicles (HVs) and fuel cell vehicles (FCVs). [Explanation of symbols]

[0049] 1 Battery pack 10 cabinets 11 Upper Case 12 lower cases 20 Battery Modules 21 battery cells 22 Gas discharge section 30 Crossmember 30a closed section 31 Outer frame members 32 Confinement Rooms 50 Insulation 50a Expanded Graphite 51a,51b connection part 52a, 52b Both ends 60 rivets

Claims

1. Multiple batteries having gas release sections, The housing has members that define a housing chamber for housing the aforementioned battery, In a battery pack in which the member has a closed cross-section and an insulating material is provided inside the closed cross-section, The thermal insulation material has an H-shaped cross-section, with both ends provided along a pair of opposing inner surfaces of the member and a connecting portion connecting the central parts of both ends. A battery pack in which the center of both ends is convex toward the center of the member.

2. The battery pack according to claim 1, wherein the insulating material is expanded graphite.

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