Cushioning rubber sheet, method for manufacturing the same, and arrangement structure of battery cells

Abstract

This invention provides a cushioning rubber sheet designed to suppress load during compression. [Solution] The cushioning rubber sheet 1 comprises a first sheet 11 having a first flat portion 21 with a flat surface 21A and a back surface 21B, and a first hollow projection 31 having an opening 41 on the back surface 21B side of the first flat portion 21 and projecting outwards from the surface 21A side of the first flat portion 21; and a second sheet 12 having a second flat portion 22 with a flat surface 22A and a back surface 22B, and a second hollow projection 32 having an opening 42 on the back surface 22B side of the second flat portion 22 and projecting outwards from the surface 22A side of the second flat portion 22. The back surface 21B of the first flat portion 21 and the back surface 22B of the second flat portion 22 are fixed facing each other, and the sheets are arranged so that at least a portion of the opening 41 of the first projection 31 and the opening 42 of the second projection 32 overlap.

Description

Technical Field

[0001] The present invention relates to a rubber sheet that can be used as a buffer material for a battery cell, a method for manufacturing the same, and an arrangement structure of a battery cell including the rubber sheet.

Background Art

[0002] As a power source for electric vehicles (EVs), hybrid vehicles (HEVs), etc., secondary battery modules such as lithium-ion batteries are used. A secondary battery module is a package in which cells of a single secondary battery (hereinafter simply referred to as "battery cells") are densely arranged. In a secondary battery module, a rubber sheet is arranged as a buffer material between battery cells or the like. For example, Patent Document 1 describes an elastic body for a battery module formed of an elastomer material, having convex portions arranged on both surfaces of a plate-shaped base material portion and a wall thickness portion thinner than the convex portions provided on the outer periphery of the base material portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, battery cells may deteriorate in performance due to long-term use, and as a measure to delay the deterioration, the battery cells are pressurized. Therefore, it is conceivable to also utilize the reaction force of the rubber sheet used as a buffer material for pressurizing the battery cells. However, in general, for elastic bodies such as rubber, the reaction force increases as the compression amount increases. For example, when a battery cell expands, the battery cell is pressurized with a strong force (reaction force). If the pressing force is too high, it may damage the mating parts, so there has been a demand for a rubber sheet in which an increase in the reaction force is suppressed (load suppression) even when the compression amount increases.

[0005] This invention was made to solve the aforementioned problems, and aims to provide a cushioning rubber sheet that suppresses load during compression. [Means for solving the problem]

[0006] To solve these problems, the cushioning rubber sheet according to the present invention is a cushioning rubber sheet used as a cushioning material for a battery cell, comprising: a first sheet having a first flat portion having a flat surface and a flat back surface, and a first hollow projection having an opening on the back surface side of the first flat portion and arranged to protrude from the surface side of the first flat portion; and a second sheet having a second flat portion having a flat surface and a flat back surface, and a second hollow projection having an opening on the back surface side of the second flat portion and arranged to protrude from the surface side of the second flat portion, wherein the back surface of the first flat portion and the back surface of the second flat portion are fixed facing each other, and the sheets are arranged so that at least a portion of the openings of the first projection and the openings of the second projection overlap. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a cushioning rubber sheet that suppresses load during compression. [Brief explanation of the drawing]

[0008] [Figure 1A] This is a perspective view illustrating the general internal structure of the battery pack. [Figure 1B] This is a perspective view illustrating the general outline of a secondary battery module. [Figure 1C] This is a cross-sectional view illustrating the general arrangement structure of the battery cells according to the embodiment. [Figure 2A] This is a perspective view illustrating the general structure of the cushioning rubber sheet according to the embodiment. [Figure 2B] This is an enlarged perspective cross-sectional view illustrating the general structure of the cushioning rubber sheet according to the embodiment. [Figure 2C] This is a perspective view illustrating the general outline of the back surface of the first sheet (the back surface of the second sheet) according to the embodiment. [Figure 3A]It is a cross-sectional view schematically showing the shape of the protrusion on the first sheet before a load in the thickness direction acts thereon. [Figure 3B] It is a cross-sectional view schematically showing the deformation of the protrusion on the first sheet due to a load in the thickness direction. [Figure 4A] It is a cross-sectional view schematically showing the shape of the protrusion of the buffer rubber sheet according to the embodiment before a load in the thickness direction acts thereon. [Figure 4B] It is a cross-sectional view schematically showing the deformation of the protrusion of the buffer rubber sheet according to the embodiment due to a load in the thickness direction. [Figure 5] It is a graph exemplifying the increasing tendency of the reaction force with respect to the compression amount. [Figure 6A] It is a cross-sectional view exemplifying a modified example in which the size and interval of the protrusion are different between the first sheet and the second sheet. [Figure 6B] It is a cross-sectional view exemplifying a modified example in which the position of the protrusion is different between the first sheet and the second sheet. [Figure 7A] It is a perspective view exemplifying a spherical crown-shaped protrusion. [Figure 7B] It is a cross-sectional view exemplifying a spherical crown-shaped protrusion. [Figure 8A] It is a perspective view exemplifying a columnar protrusion. [Figure 8B] It is a cross-sectional view exemplifying a columnar protrusion. [Figure 9A] It is a perspective view exemplifying a conical protrusion. [Figure 9B] It is a cross-sectional view exemplifying a conical protrusion. [Figure 10A] It is a perspective view exemplifying a frustum of a cone-shaped protrusion. [Figure 10B] It is a cross-sectional view exemplifying a frustum of a cone-shaped protrusion. [Figure 11A] It is a perspective view exemplifying a ridge-shaped protrusion. [Figure 11B] It is a perspective view exemplifying a ridge-shaped protrusion. [Figure 11C] It is a cross-sectional view exemplifying a ridge-shaped protrusion. [Figure 12A] It is a perspective view exemplifying a modified example of a ridge-shaped protrusion. [Figure 12B] It is a perspective view illustrating a modified example of the ridge-shaped protrusion. [Figure 12C] It is a perspective view illustrating a modified example of the ridge-shaped protrusion. [Figure 13] It is a flowchart illustrating a method for manufacturing a buffer rubber sheet according to an embodiment. [Figure 14A] It is a cross-sectional view illustrating a first sheet forming step in a method for manufacturing a buffer rubber sheet according to an embodiment. [Figure 14B] It is a cross-sectional view illustrating a first sheet formed in a method for manufacturing a buffer rubber sheet according to an embodiment. [Figure 14C] It is a cross-sectional view illustrating an adhesion step in a method for manufacturing a buffer rubber sheet according to an embodiment.

Embodiments for Carrying Out the Invention

[0009] Embodiments and modified examples of the present invention will be described with reference to the drawings. Note that the present invention is not limited to these embodiments and modified examples. Also, in the drawings, some members may be omitted, and the sizes, shapes, and positional relationships of each member may be exaggerated. Further, the "surface" means the surface opposite to the "back surface".

[0010] [Buffer Rubber Sheet] The buffer rubber sheet 1 according to the embodiment will be described with reference to FIGS. 1A to 5. The buffer rubber sheet 1 is, for example, an elastic sheet disposed as a buffer material between battery cells or between a battery cell and the housing of a secondary battery module in a secondary battery module. [[ID=三十二]] As illustrated in Figure 1A, a battery pack 200 for EVs, HEVs, etc., has multiple secondary battery modules 100. As illustrated in Figure 1B, inside the secondary battery module 100, battery cells 80 of the same shape are densely arranged. Here, the battery cells 80 are roughly rectangular plates, and multiple of them are arranged side by side with their sides facing each other. A buffer rubber sheet 1 is placed between the battery cells 80. The buffer rubber sheet 1 can also be placed between the battery cells 80 and the housing of the secondary battery module 100, between the battery cells 80 and the housing of the battery pack 200, and between the secondary battery module 100 and the housing of the battery pack 200.

[0011] As illustrated in Figure 1C, the cushioning rubber sheet 1 is formed from a first sheet 11 and a second sheet 12. The first projection 31 and the second projection 32 are hollow, with openings 41 and 42 on the opposite sides of the tops 37 and 38, respectively, and the openings 41 and 42 are arranged to overlap each other. The first flat portion 21 and the second flat portion 22 are positioned between the battery cells 80, which are arranged with their sides 82 facing each other. The top 37 of the first projection 31 of the first sheet 11 and the top 38 of the second projection 32 of the second sheet 12 are in contact with the sides 82, 82 of the battery cells 80, respectively. The first flat portion 21 and the second flat portion 22 are spaced apart from the sides 82 of the battery cells 80. As a result, the cushioning rubber sheet 1 can press against the side surface 82 of the battery cell 80 while suppressing an increase in reaction force even when the amount of compression is large, and can function as a cushioning and restraining material for the battery cell 80. In other words, the cushioning rubber sheet 1 of this embodiment can suppress the load during compression. The structure and effects of the cushioning rubber sheet 1 will be described in detail below.

[0012] As illustrated in Figures 2A to 2C, the cushioning rubber sheet 1 is a cushioning rubber sheet used as a cushioning material for battery cells, and comprises a first sheet 11 and a second sheet 12. The first sheet 11 has a first flat portion 21 having a flat surface 21A and a back surface 21B, and an opening 41 on the back surface 21B side of the first flat portion 21, and a plurality of hollow first protrusions 31 that are arranged to project outwards from the surface 21A side of the first flat portion 21. The second sheet 12 has a second flat portion 22 having a flat surface 22A and a back surface 22B, and an opening 42 on the back surface 22B side of the second flat portion 22, and a plurality of hollow second protrusions 32 that are arranged to project outwards from the surface 22A side of the second flat portion 22. Furthermore, the back surface 21B of the first flat portion 21 and the back surface 22B of the second flat portion 22 are fixed facing each other, and are arranged so that at least a portion of the opening 41 of the first protrusions 31 and the opening 42 of the second protrusions 32 overlap.

[0013] (Sheet 1 and Sheet 2) The first sheet 11 is a component that forms one side of the cushioning rubber sheet 1. The second sheet 12 is positioned on the other side. The first sheet 11 and the second sheet 12 are fixed together with their back surfaces facing each other. The materials of the first sheet 11 and the second sheet 12 include, for example, thermosetting elastomers such as silicone rubber, urethane rubber, isoprene rubber, ethylene propylene rubber, natural rubber, ethylene propylene diene rubber, nitrile rubber (NBR), or styrene butadiene rubber (SBR); thermoplastic elastomers such as urethane-based, ester-based, styrene-based, olefin-based, butadiene-based, and fluorine-based elastomers, or composites thereof. The first sheet 11 and the second sheet 12 can be fixed together, for example, with an adhesive.

[0014] In this embodiment, the first sheet 11 and the second sheet 12 are identical in shape and size. Figure 2C is a perspective view showing the back surfaces of the first sheet 11 and the second sheet 12, with their respective reference numerals grouped together. The first sheet 11 has a first flat portion 21, a first projection 31, and a groove 51. Similarly, the second sheet 12 has a second flat portion 22, a second projection 32, and a groove 52. In some cases, the first flat portion 21 and the second flat portion may be described as a flat portion 20, the first projection 31 and the second projection 32 as projections 30, and the grooves 51 and 52 as grooves 50.

[0015] (flat area) The flat portion 20 is the part that forms a flat area in the cushioning rubber sheet 1. The first flat portion 21 has a flat surface 21A and a flat back surface 21B, and the second flat portion 22 has a flat surface 22A and a flat back surface 22B. The first flat portion 21 has an annular edge portion 25, which is a part with increased thickness, provided along its outer circumference. Similarly, the outer circumference of the second flat portion 22 also has an annular edge portion 26 provided. The edges 25 and 26 can suppress the occurrence of cracks and other damage due to deformation of the flat portion 20.

[0016] (protrusion) The projection 30 is a convex portion that protrudes from the flat portion 20. As illustrated in Figure 2A, the first projections 31 are all substantially the same shape and are arranged in a row, protruding from the surface side of the first flat portion 21. The second projections 32 are all substantially the same shape and are arranged in a row, protruding from the surface side of the second flat portion 22. Here, the first projections 31 and the second projections 32 are arranged in a 6x6 grid of 36 portions at equal intervals, but the number can be set as appropriate. The projections 30 are the parts whose tops come into contact with the battery cell 80 or the like. The height of the projection 30 from the surface of the flat portion 20 can be, for example, 3 mm to 30 mm. The outer diameter of the projection 30 can be, for example, 5 mm to 50 mm. The spacing between the projections 30 can be approximately the same as their outer diameter, for example, 5 mm to 50 mm. The size and spacing of the projections 30 are not particularly limited and can be adjusted to match the expected amount of compression and to generate the desired reaction force.

[0017] As illustrated in Figure 2B, the first projection 31 is hollow, and its interior is a cavity surrounded by the upper wall 31A and the side wall 31B. The first projection 31 also has an opening 41 on the back surface 21B side facing the first flat portion 21. The thickness of the upper wall 31A and the side wall 31B can be, for example, 0.5 to 10 times the thickness of the first flat portion 21. The outer shape of the first projection 31 is a frustoconical shape that tapers away from the first flat portion 21, and the internal cavity is also frustoconical. The side wall 31B is inclined to widen toward the first flat portion 21.

[0018] The second projections 32 are all substantially the same shape and are arranged in a row, protruding from the surface 22A side of the second flat portion 22. The second projections 32 are hollow, like the first projections 31, and have an upper wall portion 32A and a side wall portion 32B, and have an opening 42 on the back surface 22B side of the second flat portion 22. The outer shape of the second projections 32 is a frustoconical shape that tapers away from the second flat portion 22, and the internal cavity is also frustoconical. The side wall portion 32B is inclined to widen toward the second flat portion 22.

[0019] The opening 41 of the first projection 31 and the opening 42 of the second projection 32 are positioned so that at least a portion of them overlap. That is, the openings 41 and 42 are positioned so that they overlap in a plan view. This allows the load to be transmitted in the planar direction of the flat portion 20 and suppresses the increase in reaction force. Here, the first projection 31 and the second projection 32 have a roughly barrel shape. Planar view refers to viewing from a direction perpendicular to the flat portion 20.

[0020] Here, the second projection 32 has the same shape and size as the first projection 31, and is positioned so that its outer edge is in the same position in a plan view. That is, the cushioning rubber sheet 1 has a symmetrical shape with respect to the interface between the first sheet 11 and the second sheet 12. Also, the position where the side wall portion 31B of the first projection 31 rises from the first flat portion 21 and the position where the side wall portion 32B of the second projection 32 rises from the second flat portion 22 are the same in a plan view. Furthermore, the openings 41 and 42 have the same shape and size, and their centers are in the same position in a plan view. As a result, the cushioning rubber sheet 1 efficiently transmits the load received by the upper wall portion 30A of the projection portion 30 in the planar direction of the flat portion 20, and effectively suppresses the increase in reaction force in the direction perpendicular to the flat portion 20, i.e., in the thickness direction of the cushioning rubber sheet 1. Note that the upper wall portions 31A and 32A may be described as the upper wall portion 30A without distinction, and the side wall portions 31B and 32B may be described as the side wall portion 30B without distinction.

[0021] (Mizobe) The groove 50 is a recess provided on the back surface of the flat portion 20. The groove 50 is provided on at least one of the back surface 21B of the first flat portion 21 and the back surface 22B of the second flat portion 22, forming a communication passage 55 that connects the internal cavities of the first projection 31 and the second projection 32 to the outside. In this case, the groove 50 is provided on both the back surface 21B of the first flat portion 21 and the back surface 22B of the second flat portion 22. The grooves 50 only need to be able to connect each of the internal cavities of the projections 30 to the outside, forming a passage 55 that serves as an airway, and their shape and orientation relative to the arrangement of the projections 30 are not particularly limited. The grooves 50 allow air in the internal cavities of the projections 30 to freely enter and exit with the outside, and also allow deformation that reduces the volume of the internal cavities, thereby suppressing an increase in reaction force.

[0022] As illustrated in Figure 2C, the grooves 51 are formed in a grid pattern such that the openings 41 of the first projection 31 are located at the grid points. Similarly, grooves 52 are formed in the second sheet 12. In the cushioning rubber sheet 1, the grooves 51 and 52 face each other to form a single connecting passage 55.

[0023] The cushioning rubber sheet 1 having the above configuration has hollow first projections 31 and second projections 32 protruding from both sides of the cushioning rubber sheet 1, and is arranged so that at least a portion of their openings 41 and 42 overlap. This allows the load during compression to be transmitted in the planar direction of the flat portion 20 of the cushioning rubber sheet 1, thereby suppressing the load and preventing an increase in reaction force. Furthermore, the first projection 31 and the second projection 32 are hollow frustoconical shapes and have side walls 31B and 32B that slope outward toward the flat portion 20. The first projection 31 and the second projection 32 are the same shape and size, and in a plan view, the centers of the openings 41 and 42 are in the same position, and the openings 41 and 42 are arranged to overlap completely. As a result, the cushioning rubber sheet 1 can efficiently transmit the load during compression in the planar direction, thereby further suppressing the load.

[0024] Generally, elastic materials such as rubber exhibit a greater reaction force as the amount of compression increases. When the projection 30 is placed on only one side, as shown in Figure 3A, a load perpendicular to the flat section 20 causes deformation as illustrated in Figure 3B. In this deformation, the side wall 30B is predominantly compressed in a direction perpendicular to the flat section 20, generating a reaction force F1 corresponding to this compression. The same tendency is observed even when the projection 30 is solid rather than hollow. In contrast, when protrusions 30 are arranged on both sides as illustrated in Figure 4A, if a load perpendicular to the flat portion 20 is applied, the side wall portion 30B undergoes deformation that spreads in the plane direction of the flat portion 20, as illustrated in Figure 4B. This makes it possible to suppress the increase in the reaction force F1 perpendicular to the flat portion 20.

[0025] Figure 5 illustrates the trend of the reaction force in response to such compression. The compression amount is defined as the ratio (D1-D2) / D1 of the deformation amount (D1-D2) to the original thickness D1, which is obtained by subtracting the thickness D2 after deformation from the thickness D1 between the tops of the projection 30. The reaction force F1 is the force that pushes back against the deformation and is a force perpendicular to the first flat portion 21 or the second flat portion 22. Curve C1 corresponds to the case where the protrusion 30 is placed on only one side, as shown in Figures 3A and 3B, while curve C2 corresponds to the case where the protrusion 30 is placed on both sides, as shown in Figures 4A and 4B. Curve C1 has a large slope of reaction force with respect to compression, and as the compression amount increases, the slope tends to increase further, resulting in an increase in reaction force. In contrast, the slope of curve C2 is small, and as the compression amount increases, the slope tends to decrease, approaching what is known as a plateau load. A plateau load is a characteristic that produces a constant reaction force even when the compression amount is increased, and is considered an ideal characteristic for the cushioning material of a battery cell. The cushioning rubber sheet 1 has characteristics similar to those of curve C2.

[0026] When the load applied to the first flat portion 21 and the second flat portion 22 is increased, the cushioning rubber sheet 1 deforms in such a way that the inclination of the side wall portion of the first projection 31 with respect to the first flat portion 21 and the inclination of the side wall portion of the second projection 32 with respect to the second flat portion 22 decreases, thereby reducing the reaction force to the load.

[0027] Furthermore, in this embodiment, since a connecting passage 55 formed by grooves 50, 50 is provided, when compression is applied, the air inside the projection 30 can be discharged to the outside through the connecting passage 55. As a result, the projection 30 becomes more easily deformable, and the increase in reaction force can be suppressed synergistically.

[0028] Note that the first projection 31 and the second projection 32 may differ in size and spacing. As illustrated in Figure 6A, the first projection 31 is smaller than the second projection 32 and is more closely spaced. The openings 41 and 42 have overlapping regions in a plan view. Furthermore, the first projection 31 and the second projection 32 may be the same size, and the centers of the openings 41 and 42 may be at different positions. As illustrated in Figure 6B, the first projection 31 and the second projection 32 are the same size and the same distance apart. The centers of the openings 41 and 42 are offset, but they have overlapping regions in a plan view. These arrangements also transmit the load in the planar direction of the flat portion 20 of the cushioning rubber sheet 1, suppressing an increase in reaction force. Furthermore, these arrangements allow for fine adjustment of the reaction force according to the required characteristics. The grooves 51 and 52 do not necessarily have to face each other.

[0029] The cushioning rubber sheet 1 can be used together with the battery cells 80 to constitute the arrangement structure of the battery cells. Specifically, the cushioning rubber sheet 1 is placed between the battery cells 80 arranged with their side surfaces 82 facing each other, and the tops 37 of the first projection 31 and the tops 38 of the second projection 32 abut against the side surfaces 82 of each battery cell 80, while the first flat portion 21 and the second flat portion 22 are separated from the side surfaces 82 of each battery cell 80. This arrangement structure allows the cushioning rubber sheet 1 to press against the side surfaces 82 of the battery cells 80 while suppressing an increase in reaction force even when the amount of compression is large, and functions as a cushioning and restraining material for the battery cells 80, contributing to the delay of battery degradation.

[0030] (modified version) Next, variations in the shape of the protrusions will be explained with reference to Figures 7A to 12C. These variations allow for adjustment of the reaction force to the amount of compression and the area of ​​the top of the protrusions that contact the battery cell 80, thereby creating a cushioning rubber sheet that meets the required characteristics. Although Figures 7A to 12C show one protrusion, multiple protrusions can be arranged on the first and second sheets. As illustrated in Figure 7A, the projection 301 in the first modified example has a spherical shape, specifically a hemispherical shape. As illustrated in Figure 7B, the projection 301 is hollow, and the curved surface forming the internal cavity is also spherical. The projection 301 has an opening 40 on the flat portion 20 side and a groove 50 on the back surface of the flat portion 20. In Figures 7A to 12C, the front surface of the flat portion 20 is shown at the top of the figure, and the back surface is shown at the bottom of the figure. The presence of an opening 40 and a groove 50 on the flat portion 20 side is common to all modifications, so their explanation will be omitted in the following modifications.

[0031] As illustrated in Figure 8A, the projection 302 in the second modified example has a cylindrical outer shape. As illustrated in Figure 8B, the projection 302 is hollow, and the internal cavity is also cylindrical. The cylindrical projection has side walls that rise perpendicularly to the flat portion 20, and therefore tends to have a larger reaction force for the same amount of compression compared to the frustoconical projection. The reaction force for the same amount of compression tends to be larger in the order of cylindrical projection 302, frustoconical projection, and spherical projection. The characteristics of the cushioning rubber sheet can be adjusted by combining the shape and size of the projection, the elastic force of the material, etc., so that it generates the required reaction force and the slope of the reaction force with respect to the amount of compression is small (plateau load).

[0032] As illustrated in Figure 9A, the projection 303 according to the third modified example has a conical shape. As illustrated in Figure 9B, the projection 303 is hollow, and the internal cavity is also conical.

[0033] As illustrated in Figure 10A, the projection 304 according to the fourth modified example has an inverted frustoconical shape, tapering towards the flat portion 20. As illustrated in Figure 10B, the projection 304 is hollow, and the internal cavity is also inverted frustoconical shape.

[0034] The fifth to eighth modifications are modifications with a short, ridged outer shape. As illustrated in Figures 11A to 11C, the projection 305 in the fifth modification is ridged and comprises opposing side wall portions 305B, 305B, an inclined wall portion 305C, and a top wall portion 305A. The inclined wall portion 305C covers one end of the side wall portions 305B, 305B. As illustrated in Figure 11B, the other end of the side wall portions 305B, 305B is an opening 305D. The top wall portion 305A connects the upper parts of the side wall portions 305B, 305B in an arc shape.

[0035] As illustrated in Figure 12A, the projection 306 according to the sixth modified example is ridged and comprises opposing side wall portions 306B, 306B, inclined wall portions 306C, 306C, and a top wall portion 306A. Each side wall portion 306B and each inclined wall portion 306C is inclined to approach each other as it moves upward. The top wall portion 306A connects the upper parts of each side wall portion 306B and each inclined wall portion 306C in an arc shape.

[0036] As illustrated in Figure 12B, the projection 307 according to the seventh modified example is ridged and comprises opposing side wall portions 307B, 307B, inclined wall portions 307E, 307E, and a top wall portion 307A. Each side wall portion 307B and each inclined wall portion 307E is inclined to approach each other as it moves upward. The top wall portion 307A connects the upper parts of each side wall portion 307B and each inclined wall portion 307E in an arc shape. Each inclined wall portion 307E protrudes in an arc shape in a direction that separates it from each other.

[0037] As illustrated in Figure 12C, the projection 308 according to the eighth modified example is ridged and comprises opposing side wall portions 308B, 308B and a top wall portion 308A. The top wall portion 308A connects the upper parts of the side wall portions 308B, 308B in an arc shape. One end and the other end of the side wall portions 308B, 308B are openings 308D, 308D.

[0038] The shapes of the first and second projections can be independently selected from the embodiments and modifications described above. Specifically, the shapes of the first and second projections can be selected from cylindrical, conical, frustoconical, inverted frustoconical, spherical, and ridged shapes having opposing side walls and a top wall that curves in an arc to connect the side walls. The protrusions on the first sheet may all be of the same type, or they may be a combination of different types. These modified examples may be combined, and the combination may include the protrusions 30 of the cushioning rubber sheet 1 according to the embodiment. The same applies to the second sheet. Furthermore, the first sheet and the second sheet may have the same shape, or they may be different.

[0039] [Manufacturing method for cushioning rubber sheets] Next, a method for manufacturing a cushioning rubber sheet according to the embodiment will be described with reference to Figures 13 to 14C. As illustrated in Figure 13, the method for manufacturing a cushioning rubber sheet includes a first sheet forming step S10, a second sheet forming step S20, and an adhesive bonding step S30.

[0040] (First sheet formation process) The first sheet forming step S10 is a step of forming the first sheet 11. The first sheet 11 has a first flat portion 21 having a flat surface 21A and a back surface 21B, and a hollow first projection 31 having an opening 41 on the back surface 21B side of the first flat portion 21 and protruding from the surface 21A side of the first flat portion 21. The first sheet 11 can be formed, for example, by compression molding or injection molding (transfer molding). Here, as illustrated in Figure 14A, it is formed by compression molding using a mold 90.

[0041] (Second sheet formation process) The second sheet forming step S20 is a step of forming the second sheet 12. The second sheet 12 has a second flat portion 22 having a flat surface 22A and a back surface 22B, and a hollow second projection 32 having an opening 42 on the back surface 22B side of the second flat portion 22 and protruding from the surface 22A side of the second flat portion 22. The second sheet 12 can be formed in the same manner as the first sheet 11. Here, the second sheet 12 has the same shape as the first sheet 11, and the same mold 90 as in the first sheet forming step S10 can be used.

[0042] (Adhesion process) The bonding step S30 is a step of bonding the back surface 21B of the first flat portion 21 and the back surface 22B of the second flat portion 22. In bonding step S30, the opening 41 of the first projection 31 and the opening 42 of the second projection 32 are bonded together such that at least a portion of them overlaps. The openings 41 and 42 only need to have overlapping regions in a plan view. Here, the openings 41 and 42 are bonded together such that their outer edges are in the same position in a plan view. Adhesion can be performed by applying adhesive 60 to one or both of the back surfaces 21B of the first flat portion 21 and 22B of the second flat portion 22, as illustrated in Figure 14B. Here, the adhesive is applied uniformly to the back surface of one of the first flat portion 21 and the second flat portion 22, excluding the groove 50. Then, as illustrated in Figure 14C, the back surfaces of the first sheet 11 and the second sheet 12 are bonded together.

[0043] The method for manufacturing the cushioning rubber sheet involves forming a first sheet 11 and a second sheet 12 respectively and bonding them together, thereby efficiently producing a cushioning rubber sheet having hollow protrusions 30 on both sides. [Explanation of symbols]

[0044] 1. Cushioning rubber sheet 11. Sheet 1 12. Second seat 20 Flat area 21 1st flat part 22 2nd flat part 30 Protrusion 31 1st protrusion 32 Second protrusion 40 openings 50 groove section 60 Adhesives 80 battery cells 100 secondary battery modules 200 Battery Packs

Claims

1. A cushioning rubber sheet used as a cushioning material for battery cells, A first sheet having a flat surface and a flat back surface, and a first sheet having an opening on the back surface side of the first flat surface and hollow first protrusions that protrude outwards from the surface side of the first flat surface, The invention comprises a second flat portion having a flat surface and a flat back surface, and a second sheet having an opening on the back surface side of the second flat portion and hollow second protrusions that protrude outwards from the surface side of the second flat portion, The back surface of the first flat portion and the back surface of the second flat portion are fixed facing each other. A cushioning rubber sheet is positioned such that at least a portion of the opening of the first projection and the opening of the second projection overlap.

2. The shape of the first projection and the second projection is selected from cylindrical, conical, frustoconical, inverted frustoconical, spherical, and ridged, having opposing side walls and a top wall that curves in an arc to connect the side walls, respectively, according to claim 1.

3. The cushioning rubber sheet according to claim 2, wherein the first projection and the second projection have different shapes.

4. The cushioning rubber sheet according to claim 2, wherein the first projection and the second projection have the same shape.

5. The cushioning rubber sheet according to claim 4, wherein the first projection and the second projection are of the same size and are arranged such that their outer edges are in the same position in a plan view.

6. A groove is provided on at least one of the back surfaces of the first flat portion and the back surface of the second flat portion. The cushioning rubber sheet according to any one of claims 1 to 5, wherein the groove portion forms a passage that connects the internal cavities of the first projection and the second projection to the outside.

7. A cushioning rubber sheet used as a cushioning material for battery cells, A first sheet having a flat surface and a flat back surface, and a first sheet having an opening on the back surface side of the first flat surface and hollow first protrusions that protrude outwards from the surface side of the first flat surface, The invention comprises a second flat portion having a flat surface and a flat back surface, and a second sheet having an opening on the back surface side of the second flat portion and hollow second protrusions that protrude outwards from the surface side of the second flat portion, The back surface of the first flat portion and the back surface of the second flat portion are fixed facing each other. A cushioning rubber sheet that, when a load is increased in a direction perpendicular to the first flat portion and the second flat portion, deforms such that the inclination of the side wall portion of the first projection with respect to the first flat portion and the inclination of the side wall portion of the second projection with respect to the second flat portion decrease, thereby reducing the reaction force to the load.

8. A battery cell arrangement structure comprising multiple battery cells and a cushioning rubber sheet, The aforementioned cushioning rubber sheet is A first sheet having a flat surface and a flat back surface, and a first sheet having an opening on the back surface side of the first flat surface and hollow first protrusions that protrude outwards from the surface side of the first flat surface, The invention comprises a second flat portion having a flat surface and a flat back surface, and a second sheet having an opening on the back surface side of the second flat portion and hollow second protrusions that protrude outwards from the surface side of the second flat portion, The back surface of the first flat portion and the back surface of the second flat portion are fixed facing each other. The openings of the first projection and the openings of the second projection are arranged to overlap, It is positioned between battery cells arranged with their sides facing each other. The tops of the first and second protrusions abut against the side surface of each battery cell. The first flat portion and the second flat portion are arranged in a battery cell arrangement structure that is separated from the side surface of each battery cell.

9. A first sheet forming step, which involves forming a first sheet having a first flat portion having a flat surface and a flat back surface, and a first hollow projection having an opening on the back surface side of the first flat portion and projecting outwards from the surface side of the first flat portion, A second sheet forming step, which involves forming a second sheet having a second flat portion having a flat surface and a flat back surface, and a second hollow projection having an opening on the back surface side of the second flat portion and projecting outwards from the surface side of the second flat portion, The process includes a bonding step of bonding the back surface of the first flat portion and the back surface of the second flat portion, The bonding step is a method for manufacturing a cushioning rubber sheet, in which the opening of the first projection and the opening of the second projection are bonded together such that at least a portion of them overlap.

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