Battery pack

Abstract

To prevent undulation in the arrangement of a stack in a battery pack containing a stack in which a plurality of battery cells are alternately laminated in the arrangement direction while compressing the stack in the arrangement direction.SOLUTION: A battery pack includes a stack in which a plurality of battery cells and a plurality of resin frames are alternately laminated in the arrangement direction, and a lower case that accommodates the stack in a compressed state in the arrangement direction. The resin frame has a plurality of comb teeth extending in the arrangement direction on at least one of the surfaces facing the battery cells. The plurality of comb teeth include a plurality of upper comb teeth positioned above the central portion of the battery cell in the height direction, and a plurality of lower comb teeth positioned below the central portion. The plurality of upper comb teeth are configured such that the lower the upper comb teeth are positioned in the height direction, the lower the comb tooth height in the arrangement direction becomes.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a battery pack having a plurality of battery cells. [Background technology]

[0002] Patent Document 1 discloses a technology for improving the cooling performance of a battery module in which multiple storage cells are arranged. The cooling mechanism of this technology includes a heat pipe that contacts at least one of a pair of side surfaces of the battery module and a cooling flow path that contacts the heat pipe. The heat pipe has a comb-like shape, which increases the degree of freedom of deformation of the multiple branches that make up the comb. This allows each of the multiple branches to easily contact the side surface of the battery module, ensuring heat removal from the battery module. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-96479 Summary of the Invention [Problem to be solved by the invention]

[0004] Consider the manufacturing process for a battery pack in which multiple battery cells and multiple resin frames are alternately arranged and stacked. In the battery pack manufacturing process, a stack consisting of multiple battery cells and multiple resin frames arranged in one direction is compressed in the arrangement direction and housed in a stack case.

[0005] In some cases, the battery cells may bulge in a barrel shape near the center. In this case, when compressing the barrel-shaped battery cells in the arrangement direction, it is possible that the stack may swell upward, causing a convex shape. As a result, the battery cells housed in the stack case may not be able to securely contact the bottom of the case, which could result in problems such as reduced cooling performance.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a battery pack in which a stack of multiple battery cells is stacked alternately in an arrangement direction and compressed in the arrangement direction to house the stack, and which can prevent undulations from occurring in the stack arrangement. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention is applied to a battery pack. Roughly rectangular parallelepiped shape The battery pack includes a stack in which a plurality of battery cells and a plurality of resin frames are alternately stacked in an arrangement direction, and a lower case that houses the stack in a state compressed in the arrangement direction. The battery cells are stacked in an arrangement direction that intersects with the vertical direction as the height direction while standing upright, and the resin frames are stacked in the arrangement direction while being respectively disposed between adjacent battery cells so as to sandwich each of the upright battery cells on both sides in the arrangement direction. The resin frame has a plurality of comb teeth extending in the arrangement direction on at least one of its surfaces facing the battery cells. The plurality of comb teeth includes a plurality of upper comb teeth located above the center of the battery cell in the height direction and a plurality of lower comb teeth located below the center. The upper comb teeth are configured so that the comb tooth height in the arrangement direction decreases as the upper comb teeth located lower in the height direction, and the comb tooth height in the arrangement direction of the lower comb teeth is all constant and equal to or less than the comb tooth height of the upper comb teeth in the center. [Effects of the Invention]

[0008] According to the present disclosure, when a battery cell is barrel-shaped, the upper comb teeth of the resin frame are more likely to come into surface contact with the battery cell from the center upward of the battery cell. As a result, the occurrence of upwardly convex undulations in a stack using barrel-shaped battery cells can be suppressed. This can prevent a decrease in the cooling performance of the battery pack. [Brief explanation of the drawings]

[0009] [Figure 1] 1A to 1C are schematic diagrams illustrating the internal structure of a battery pack according to an embodiment of the present disclosure and a manufacturing method thereof. [Figure 2] 1A to 1C are diagrams for explaining the state of the battery pack during the manufacturing process. [Figure 3] This is an enlarged view of the periphery of a barrel-shaped bulging battery cell. [Figure 4] FIG. 10 is a diagram showing an example of a state that may occur when a stack made up of barrel-shaped expanded battery cells is compressed. [Figure 5] FIG. 10 is a diagram showing a state in which a swelled stack is housed in a lower case. [Figure 6] 1A to 1C are diagrams illustrating the structure of a resin frame employed in an embodiment of the present disclosure. [Figure 7] 10A and 10B are diagrams illustrating a state in which a stack using a resin frame according to an embodiment of the present disclosure is housed in a lower case. [Figure 8] 10A and 10B are diagrams illustrating the shape of a resin frame of a battery pack according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, when the number, quantity, amount, range, etc. of each element is mentioned in the embodiments described below, this disclosure is not limited to the mentioned numbers unless otherwise specified or clearly specified in principle. Furthermore, structures, steps, etc. described in the embodiments described below are not necessarily essential to this disclosure unless otherwise specified or clearly specified in principle.

[0011] Embodiment An embodiment will be described with reference to the drawings.

[0012] 1. Overview of the structure of the battery pack according to the embodiment The battery pack 10 of this embodiment is for storing power to be supplied to an electric motor of a vehicle, and is mounted, for example, under the floor panel of the vehicle. Figure 1 is a schematic diagram for explaining the internal structure and manufacturing method of the battery pack of this embodiment.

[0013] The battery pack 10 includes multiple battery cells 12, a resin frame 14, end plates 16, shims 18, and a lower case 20. The battery cells 12 are rechargeable batteries configured in a roughly rectangular parallelepiped shape. The multiple battery cells 12 are stacked in the arrangement direction with the cells standing upright in the height direction (vertical direction).

[0014] The resin frame 14 is a resin member arranged between adjacent battery cells 12. The resin frame 14 has multiple comb teeth formed on at least one of the surfaces facing the battery cells 12. The configuration of the comb teeth is a feature of this disclosure and will be described in detail below. The multiple resin frames 14 are arranged along the arrangement direction so as to sandwich both sides of each of the multiple battery cells 12. This forms a stack 15 in which the multiple battery cells 12 and the multiple resin frames 14 are arranged alternately. End plates 16 are arranged on both ends of the stack 15 in the arrangement direction. A shim 18 is arranged on the outer surface of one of the end plates 16. The shim 18 is a member for adjusting the dimensions of the stack relative to the lower case 20. An appropriate thickness of the shim 18 is selected according to the external dimensions of the stack 15.

[0015] The lower case 20 forms the outer shell of the battery pack 10. The lower case 20 is made of, for example, a steel plate. The lower case 20 is configured to have a substantially rectangular shape when viewed from below. The stack 15 is inserted into the lower case 20 while being compressed in the arrangement direction together with the shim 18. The stack 15 is fixed inside the lower case 20 by releasing part of the compressive force. As a result, the lower surface of each of the multiple battery cells 12 comes into contact with the inside bottom surface of the lower case 20.

[0016] A cooler 22 is arranged on the outside (lower surface) of the bottom surface of the lower case 20, sandwiching a thermally conductive material 26. The cooler 22 has a cooling water flow path 24 inside. There are no restrictions on the material of the thermally conductive material 26, as long as it is a plate material with high thermal conductivity. By circulating cooling water through the cooling water flow path 24, heat generated in the battery cells 12 of the stack 15 is absorbed via the thermally conductive material 26 and the lower case 20.

[0017] 2. Potential issues that may arise in the battery pack manufacturing process Next, we will explain the problems that may arise in the battery pack 10 shown in Figure 1. The following problems may occur in the manufacturing process of the battery pack 10. Figure 2 is a diagram for explaining the state of the battery pack during the manufacturing process. As shown in this figure, in the manufacturing process of the battery pack 10, a plurality of battery cells 12, a plurality of resin frames 14, end plates 16, and shims 18 that make up the stack 15 are arranged in an arrangement direction on a base 2. Then, the stack 15 arranged on the base 2 is compressed in the arrangement direction by the claws 4 of a compression device.

[0018] Here, the battery cells 12 may have a barrel-shaped bulge at the center in the height direction. When multiple barrel-shaped battery cells 12 are compressed in the arrangement direction, pressure is likely to concentrate at the center in the height direction of the battery cells 12. FIG. 3 is an enlarged view of the periphery of a barrel-shaped battery cell. FIG. 4 is a diagram showing an example of a state that may occur when a stack formed using barrel-shaped battery cells is compressed in the arrangement direction. As shown in FIG. 3, the resin frame 14 has multiple comb teeth 14a extending in the arrangement direction. The comb teeth 14a of the comparative example shown in FIG. 3 are configured to have a uniform height, for example. When such a resin frame 14 is used, each of the battery cells 12 arranged on the base 2 is subjected to a compressive load at the center in the height direction (the load application point indicated by the black circle in the figure). In this case, the compressed stack 15 is distorted into a shape that can withstand the load on its surface. Typically, the stack 15 placed on the base 2 cannot be deformed into a downwardly convex shape. As a result, the load is distributed to the lower surface of the stack 15 rather than the center of the height of the battery cells 12, which causes an upwardly convex, bow-shaped undulation.

[0019] Figure 5 shows a state in which a wavy stack is housed in a lower case. As shown in this figure, when a wavy stack 15 is housed in a lower case 20, each battery cell 12 separates from the bottom surface of the lower case 20, creating gaps that could reduce cooling performance. In this way, a battery pack 10 configured with multiple battery cells 12 and resin frames 14 arranged alternately and compressed requires measures to deal with the upwardly convex wavy shape of the stack 15.

[0020] 3. Features of the battery pack according to this embodiment The battery pack 10 of this embodiment is characterized by the shape of the resin frame 14, which is designed to suppress undulation of the stack 15. FIG. 6 is a diagram illustrating the structure of the resin frame employed in this embodiment. As shown in this figure, the resin frame 14 of this embodiment includes multiple upper comb teeth 14b located above the center in the height direction and multiple lower comb teeth 14c located below the center. The height dimension of the resin frame 14 is approximately the same as that of the battery cells 12. The multiple upper comb teeth 14b are configured so that the height of the upper comb teeth located lower in the height direction decreases. The multiple lower comb teeth 14c all have a constant comb tooth height regardless of their position in the height direction. The comb tooth height of the lower comb teeth 14c is equal to or less than that of the upper comb teeth 14b in the center.

[0021] With this configuration of the resin frame 14, the upper comb teeth 14b are more likely to come into contact with the barrel-shaped bulging battery cells 12 from the center upward in the height direction of the bulging battery cells 12. This makes it possible to prevent the stack 15 from undulating in an upward convex direction when a compressive load is applied to the stack 15 in the arrangement direction.

[0022] 7 is a diagram illustrating a state in which a stack using a resin frame according to this embodiment is housed in lower case 20. Compressed stack 15 is housed in lower case 20. At this time, since no undulation occurs in stack 15, a gap is prevented from occurring between the bottom side of stack 15 and the bottom surface of lower case 20. This makes it possible to effectively prevent a decrease in cooling performance.

[0023] 4. Modifications of the Battery Pack of the Present Embodiment The structure of the battery pack 10 of this embodiment may be modified as follows. Several modifications will be described below, but these modifications may also be combined as appropriate to form a structure.

[0024] Figure 8 is a diagram illustrating the shape of a resin frame of a modified battery pack. The modified battery pack 10 shown in Figure 8 is configured so that the tips of the upper comb teeth 14b of the resin frame 14 are oblique along the surface of the battery cell 12. This configuration allows the tip faces of the upper comb teeth 14b to come into contact with the surface of the battery cell 12, so that the load from the battery cell 12 can be stably received. [Explanation of symbols]

[0025] 2 units 4 claws 10 Battery pack 12 battery cells 14 Resin frame 14a comb teeth 14b Upper comb teeth 14c lower comb teeth 15 stacks 16 End plate 18 Sim 20 Lower case 22 Cooler 24 Cooling water flow path 26 Thermal Conductive Materials

Claims

[Claim 1] A battery pack comprising a stack in which a plurality of battery cells of approximately rectangular parallelepiped shape and a plurality of resin frames are alternately stacked in an arrangement direction, and a lower case that houses the stack in a state compressed in the arrangement direction, wherein the plurality of battery cells are stacked in the arrangement direction that intersects with the vertical direction while standing upright with the height direction being the vertical direction, the plurality of resin frames are stacked in the arrangement direction in a state in which they are respectively disposed between adjacent ones of the plurality of upright battery cells so as to sandwich both sides of each of the plurality of upright battery cells in the arrangement direction; the resin frame has a plurality of comb teeth extending in the arrangement direction on at least one of its surfaces facing the battery cells, the plurality of comb teeth include a plurality of upper comb teeth located above a center portion of the battery cell in the height direction and a plurality of lower comb teeth located below the center portion, the plurality of upper comb teeth are configured such that the upper comb teeth located lower in the height direction have a lower comb tooth height in the arrangement direction; A battery pack characterized in that the comb tooth height of the plurality of lower comb teeth in the arrangement direction is configured to be constant and equal to or less than the comb tooth height of the upper comb teeth in the central portion.

Images