Battery case

Abstract

To provide a battery case in which penetration of a sheet into resin and occurrence of underfill are restrained and the pressure resistance strength of a battery module and the battery life are improved.SOLUTION: A battery case has a side wall 13, end walls 14, and a bottom portion. In the side wall 13, a sheet S is attached on an outer wall surface 13a, and a plurality of groove portions 25 are formed on the outer wall surface 13a. The plurality of grooves 25 are formed at least partially between an edge portion S1 of the sheet S on one side in a first direction parallel to a facing direction of the end walls 14 and an outer wall surface 14a of the end wall 14 on one side in the first direction so as to be spaced apart from one another in a second direction which is parallel to the outer wall surface 13a of the side wall 13 and perpendicular to the first direction. The length direction of each groove portion 25 intersects with the second direction, and an end portion 25b on the opposite side to the bottom portion is closer to the outer wall surface 14a of the end side wall 14 on one side in the first direction than the end portion 25a on the bottom portion side in the second direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Secondary batteries used as power sources for electrically powered vehicles such as electric cars and hybrid cars are used in the form of a battery module in which a plurality of secondary batteries are electrically connected to increase charge / discharge capacity and output power. Generally, this type of secondary battery includes a battery case in which battery elements are housed. For example, Patent Document 1 discloses a battery module having single cells in which a resin battery case constitutes an integrated battery case, and the integrated battery case is divided by partitions into a plurality of battery cases in which battery elements (electrode groups, current collectors, electrolyte, etc.) are housed.

[0003] The battery module described in Patent Document 1 is a nickel-metal hydride battery, and it is necessary to prevent hydrogen generated in each cell from permeating through a resin battery case. Therefore, in this battery module, a sheet of aluminum laminate or the like is attached to the side wall of the battery case to prevent hydrogen from permeating through the battery case.

[0004] Furthermore, in the battery module described in Patent Document 1, intermediate connecting members are welded to the current collecting plates in order to shorten the current paths between the current collecting plates of the individual cells and reduce internal resistance, and an opening window is formed in the side wall of the battery case for performing the welding work for the intermediate connecting member.

[0005] Here, the battery case of the battery module as described above is formed by resin molding. During resin molding, a sheet with an opening at a portion corresponding to the portion that will become the opening window of the battery case is attached to a mold, and molten resin is injected into the cavity from the side corresponding to the bottom of the battery case. Then, the molten resin injected into the cavity flows from the portion that will become the opening window toward the opening end of the sheet, and fills the cavity. Therefore, the molten resin is likely to enter between the opening end of the sheet and the surface of the mold, and when the molten resin enters, all or part of the sheet is peeled off from the mold. As a result, there are problems in that the sheet is embedded in the side wall of the battery case after resin molding, which reduces the pressure resistance of the battery case, and when such a battery case is used in a battery module, there are problems in that the electrolyte leaks through the boundary between the sheet embedded in the side wall of the battery case and the side wall, and that electric leakage occurs through the sheet.

[0006] Therefore, the battery module described in Patent Document 1 employs a battery case having a groove portion along the edge of the opening window between the edge of the side wall close to the center of the opening window and the sheet opening edge. Fig. 9 is a schematic diagram showing the flow of molten resin in a portion of the cavity M11 of the mold M10 corresponding to the opening window of the battery case, and Fig. 10 is a cross-sectional view of the mold M10 showing the portion XX in Fig. 9. As shown in Figs. 9 and 10, this battery case is produced by forming ridges M12 in the mold M10 and molding the resin so as to transfer the shape of the ridges M12 to form the groove portion.

[0007] Therefore, in the battery module described in Patent Document 1, as shown in FIG. 10, the flow of molten resin during resin molding (the white arrows in FIG. 9 and the arrows in FIG. 10) is controlled by the protrusions M12 formed on the mold M10, making it difficult for the molten resin to penetrate between the opening end of the sheet S10 and the surface of the mold M10, thereby suppressing the sheet S10 from sinking into the molten resin. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2022-25600 Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, when the battery case is resin-molded, the location where the sheet may slip into the molten resin is not limited to the vicinity of the opening window, but may also occur at the edge of the sheet. Specifically, the molten resin injected into the cavity of the mold may hit the inner surface of the mold that forms the outer wall surface of the end side wall and bounce back toward the edge of the sheet, causing the sheet to peel off from the mold and slip into the molten resin, as in the vicinity of the opening window.

[0010] In order to prevent the edge of the sheet from slipping in, a groove extending in a direction perpendicular to the facing direction of the end side walls may be formed between the edge of the sheet and the outer wall surface of the end side wall. However, when such a mode is adopted, the following problem occurs. The above problem will be described below with reference to Figs. 11 to 14. Fig. 11 is a schematic diagram showing the flow of molten resin in a portion corresponding to the periphery of the end side wall of the battery case in the cavity M21 of the mold M20, and the white arrows in Fig. 11 indicate the flow of molten resin. Fig. 12 is a front view showing a part of a battery module 100 in which a groove 125 is formed between the edge of the sheet S11 in the battery case 110 and the outer wall surface of the end side wall 114, and the white arrows in Fig. 12 indicate the flow of cooling air. Fig. 13 is a cross-sectional view of the XIII-XIII portion of Fig. 12, and Fig. 14 is a cross-sectional view of the XIV-XIV portion of Fig. 12, and the arrows in Fig. 14 indicate the flow of cooling air.

[0011] First, as shown in Fig. 11, the die M20 is formed with ribs M22 for transferring the grooves of the battery case, and the ribs M22 impede the flow of the molten resin, reducing the fluidity of the molten resin toward the end walls, which makes it easy for underfill to occur in the end walls of the battery case due to an insufficient supply of molten resin.

[0012] Secondly, as shown in Fig. 12 and Fig. 13, in a battery module 100 using a battery case 110, a high stress acts on the boundary portion (part Q in Fig. 12 and Fig. 13) between the side wall 113 and the end side wall 114 due to an increase in internal pressure during use. The length direction of the groove portion 125 formed in the battery case 110 coincides with the above-mentioned boundary portion. Therefore, as shown in Fig. 13, the battery case 110 is easily damaged around the groove portion 125 when the internal pressure increases, and the battery module 100 using the battery case 110 has low pressure resistance.

[0013] 12 and 14, when cooling air for cooling the battery module 100 is caused to flow from the bottom 115 side of the battery case 110 toward the upper opening 118 side, the cooling air becomes a laminar flow, and the flow speed of the cooling air becomes extremely slow near the side wall 113 of the battery case 110. Therefore, the current collector 133 housed in the battery case 110 and the conductive plate 134 electrically connected to the current collector 133 cannot be efficiently cooled. Therefore, the battery module 100 using the battery case 110 is prone to a decrease in battery life due to an increase in temperature.

[0014] In this way, if a groove portion extending in a direction perpendicular to the opposing direction of the end side walls is formed between the edge of the sheet and the outer wall surface of the end side wall, underfill is likely to occur during resin molding, resulting in a new problem in that the pressure resistance and battery life of the battery module using the battery case are likely to decrease.

[0015] The present invention has been made in consideration of the above-mentioned situation, and has an object to provide a battery case in which the occurrence of a sheet penetrating into the resin and of underfill is suppressed, thereby improving the pressure resistance and battery life of the battery module. [Means for solving the problem]

[0016] The characteristic configuration of the battery case according to the present invention for achieving the above object is as follows: A battery case is a rectangular parallelepiped resin container having side walls, end walls, and a bottom, and constitutes a battery container in which a single battery is housed, The side wall is A sheet is attached to an outer wall surface, and a plurality of grooves are formed on the outer wall surface, The plurality of grooves include A direction parallel to the opposing direction of the end side walls is defined as a first direction, and the sheet is formed at least in a portion between an edge portion of the sheet on one side in the first direction and an outer wall surface of the end side wall on one side in the first direction, with a gap in a second direction parallel to the outer wall surface of the side wall and perpendicular to the first direction, The length direction of each groove portion intersects with the second direction, and the end portion opposite the bottom in the second direction is closer to the outer wall surface of the end side wall on one side in the first direction than the end portion on the bottom side.

[0017] In the resin molding of the battery case having the above characteristic configuration, a die is used in which a plurality of ridges are formed in at least a part between the edge of the sheet and the inner surface corresponding to the outer wall surface of the end side wall, for forming a plurality of grooves in the battery case by transfer. In this die, the cross-sectional area of ​​the cavity is reduced around the plurality of ridges compared to other parts. When the sheet is attached to this die and the molten resin is caused to flow through the cavity from the side corresponding to the bottom of the battery case to the side opposite the bottom, an increase in pressure loss occurs around the plurality of ridges. The molten resin that bounces off the inner surface of the die corresponding to the outer wall surface of the end side wall flows toward the edge of the sheet with a reduced flow rate by passing around the plurality of ridges. Therefore, in a battery case having the above characteristic configuration, when the battery case is molded from resin, the flow rate of the molten resin that bounces off the inner surface of the mold corresponding to the outer wall surface of the end side wall of the battery case and flows toward the edge of the sheet is reduced, and peeling of the sheet from the mold is suppressed. Therefore, in a battery case having the above characteristic configuration, penetration of the sheet into the resin is suppressed.

[0018] Furthermore, a battery case having the above characteristic configuration has the following advantages over a battery case having a groove whose length direction is parallel to the second direction. First, a mold is used for resin molding of a battery case having the above characteristic configuration, in which the length direction of each ridge intersects with the second direction, and the end of each ridge opposite the bottom of the battery case in the second direction is closer to the inner surface corresponding to the outer wall surface of the end wall than the end of each ridge on the bottom side of the battery case. As a result, during resin molding, the molten resin flows toward the end wall while being guided by the ridge. Therefore, in resin molding of the battery case, the flowability of the molten resin toward the end wall is less likely to decrease and underfill caused by insufficient supply of molten resin is less likely to occur than in the case of resin molding in which a groove portion whose length direction is parallel to the second direction is formed. Therefore, the battery case having the above characteristic configuration is one in which underfill is suppressed. Secondly, when the battery case is used in a battery module, the length direction of each groove of the battery case does not coincide with the boundary portion between the side wall and the end side wall where high stress acts when the internal pressure increases (in other words, they intersect), so that the boundary portion of the battery case is less likely to break than when a groove portion whose length direction is parallel to the second direction is formed, and the pressure resistance strength of the battery module is increased. Thirdly, when the battery case is used in a battery module, when cooling air is caused to flow along the second direction to cool the battery module, unlike the case where a groove portion whose length direction is parallel to the second direction is formed, the cooling air flowing through the boundary portion between the side wall and the end side wall becomes turbulent and the flow speed increases near the side wall of the battery case. Therefore, the members housed in the battery case can be efficiently cooled, and a decrease in battery life due to an increase in temperature is unlikely to occur.

[0019] In this way, a battery case having the above-described characteristic configuration reduces the occurrence of the sheet penetrating into the resin and of underfill, thereby improving the pressure resistance and battery life of a battery module using the battery case.

[0020] Further characteristic configurations of the battery case according to the present invention are as follows: The end side wall is formed with a support portion protruding outward, The plurality of grooves are formed at least near the support portion between an edge of the sheet on one side in the first direction and an outer wall surface of the end side wall on one side in the first direction.

[0021] In resin molding of a battery case having outwardly protruding support parts on the end side walls, the molten resin injected into the mold flows to the parts corresponding to the support parts and hits the inner surface of the mold, and then tends to flow toward the edge of the sheet. Therefore, in such resin molding, the sheet is likely to slip under the area near the support parts. A resin molding of a battery case having the above-mentioned characteristic configuration uses a mold in which multiple ridges are formed near the location corresponding to the support between the edge of the sheet and the inner surface corresponding to the outer wall surface of the end side wall. In this mold, the cross-sectional area of ​​the cavity is reduced around the multiple ridges compared to other locations. Therefore, when molten resin is passed through the cavity, an increase in pressure loss occurs near the support where the sheet is likely to sink in. Then, the flow rate of the molten resin flowing from the location corresponding to the support toward the edge of the sheet is reduced. Therefore, in a battery case having the above characteristic configuration, peeling of the sheet from the mold near the support part is suppressed when the battery case is molded from resin. Therefore, in a battery case having the above characteristic configuration, penetration of the sheet into the resin is suppressed near the support part where penetration of the sheet is likely to occur.

[0022] Further characteristic configurations of the battery case according to the present invention are as follows: The plurality of grooves are formed over the entire area between an edge of the sheet on one side in the first direction and an outer wall surface of the end side wall on one side in the first direction.

[0023] In resin molding of a battery case having the above-mentioned characteristic configuration, a die is used in which multiple ridges are formed over the entire area between the edge of the sheet and the inner surface corresponding to the outer wall surface of the end side wall, and the cross-sectional area of ​​the cavity is reduced around the multiple ridges compared to other areas. Therefore, when molten resin is passed through the cavity, an increase in pressure loss occurs around the multiple ridges. The flow rate of the molten resin that bounces off the inner surface of the die corresponding to the outer wall surface of the end side wall and flows toward the edge of the sheet is reduced over the entire area between the edge of the sheet and the inner surface corresponding to the outer wall surface of the end side wall. Therefore, in a battery case having the above-mentioned characteristic configuration, peeling of the sheet from the mold during resin molding of the battery case is suppressed over a wider area, and therefore penetration of the sheet into the resin is suppressed over a wider area in the battery case having the above-mentioned characteristic configuration. In addition, in a battery case having the above-described characteristic configuration, the molten resin is easily guided to the entire end side wall by the ribs during resin molding, and the occurrence of underfill caused by an insufficient supply of molten resin is less likely to occur. Therefore, in a battery case having the above-described characteristic configuration, the occurrence of underfill is more suppressed. Furthermore, the battery case has a plurality of grooves whose length direction does not coincide with the boundary between the side wall and the end side wall, and the grooves are formed along the entire boundary. Therefore, the boundary is less likely to be damaged, and the pressure resistance of a battery module using the battery case is increased. In addition, the battery case has a plurality of grooves whose length direction intersects with the second direction formed over the entire area between the edge of the sheet and the outer wall surface of the end side wall. Therefore, in a battery module using the battery case, when cooling air is caused to flow along the second direction, the cooling air flowing near the boundary between the side wall and the end side wall becomes turbulent over almost the entire area from the bottom side of the battery case to the opposite side of the bottom, and the flow rate tends to be high near the side wall of the battery case. Therefore, the components inside the battery case can be cooled more efficiently, and the battery life of the battery module is less likely to decrease.

[0024] Further characteristic configurations of the battery case according to the present invention are as follows: The multiple grooves have a feature that the crossing angle between the longitudinal direction of each groove and the second direction decreases continuously or stepwise from the groove formed on the side of the bottom in the second direction to the groove formed on the opposite side of the bottom.

[0025] When molten resin is passed through the cavity from the side corresponding to the bottom of the battery case to the side opposite the bottom, the flow of the molten resin may become parallel to the second direction as it moves downstream near the portion corresponding to the end side wall. A mold is used for resin molding of a battery case having the above characteristic configuration, in which a plurality of ridges are formed such that the cross angle between the length direction and the second direction decreases continuously or stepwise from the ridges formed on the bottom side in the second direction to the ridges formed on the opposite side of the bottom. Therefore, during resin molding, the molten resin is more easily guided by the ridges toward the end side walls, and underfill is less likely to occur around the end side walls. Thus, a battery case having the above characteristic configuration has less underfill. Effect of the Invention

[0026] As described above, the battery case of the present invention suppresses the sheet from sinking into the resin and the occurrence of underfill, thereby improving the pressure resistance and battery life of a battery module using the battery case. [Brief description of the drawings]

[0027] [Figure 1] 1 is an exploded perspective view showing a battery module including a battery case according to one embodiment; [Diagram 2] FIG. 2 is a front view showing the battery module. [Diagram 3] FIG. 3 is an enlarged cross-sectional view showing part A in FIG. 2. [Figure 4] FIG. 2 is a front view showing a portion of the battery module. [Diagram 5] FIG. 3 is a cross-sectional view of a portion VV in FIG. 2. [Figure 6]FIG. 2 is a cross-sectional view of a mold showing the flow of molten resin during resin molding. [Figure 7] FIG. 7 is an enlarged view showing part C in FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] FIG. 1 is a cross-sectional view of a mold showing the flow of molten resin around a protrusion during resin molding using a conventional technique. [Figure 10] 10 is a cross-sectional view taken along the line XX in FIG. 9. [Figure 11] FIG. 4 is a cross-sectional view of a mold showing the flow of molten resin in a portion corresponding to the periphery of an end side wall of a battery case. [Figure 12] 11 is a front view showing a part of a battery module in which a groove is formed between an edge of a sheet in a battery case and an outer wall surface of an end side wall. FIG. [Figure 13] FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. [Figure 14] 14 is a cross-sectional view taken along line XIV-XIV in FIG. 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The battery case according to the present embodiment will be described below with reference to the drawings. In the following, an example will be described in which the battery case constitutes a part of a battery module including nickel-metal hydride secondary batteries as single cells. In the following, each description and each drawing will be appropriately simplified for clarity of explanation.

[0029] [Configuration of battery module 1] FIG. 1 is an exploded perspective view showing a battery module 1 including a battery case 10 according to the present embodiment as a part of its configuration. FIG. 2 is a front view showing the battery module 1. FIG. 3 is an enlarged cross-sectional view showing part A in FIG. 2. FIG. 4 is a front view showing a part of the battery module 1. FIG. 5 is a cross-sectional view showing part VV in FIG. 2. In the following description, the direction parallel to the height direction of the battery module 1 is defined as the Z-axis direction, the direction parallel to the longitudinal direction of the battery module 1 is defined as the X-axis direction, and the direction parallel to the thickness direction of the battery module 1 is defined as the Y-axis direction. The Z-axis direction is parallel to the up-down direction, and the X-axis and Y-axis directions are perpendicular to each other and parallel to the horizontal direction.

[0030] As shown in Figures 1 and 2, the battery module 1 includes a battery case 10, which is a rectangular resin container having a storage space 11 in which a battery element 31 is housed, and a single battery 30 consisting of the battery element 31 housed in the storage space 11.

[0031] [Configuration of battery case 10] 1 and 2, the battery case 10 is composed of a rectangular solid-shaped integrated battery case 12 having an opening 18 at the top formed so as to connect the storage space 11 to the outside, and a lid 2 that closes the opening 18 of the integrated battery case 12. In this embodiment, the integrated battery case 12 and the lid 2 are made of a thermoplastic resin such as polypropylene.

[0032] The integrated battery case 12 is composed of a pair of side walls 13 arranged opposite each other along the longitudinal direction (X-axis direction) and having outer wall surfaces 13a with the widest area, a pair of end walls 14 connecting the ends of the side walls 13 in the longitudinal direction (X-axis direction) and facing each other parallel to the X-axis direction, and a bottom 15 closing the bottom, which are integrally molded from resin. In this embodiment, the storage space 11 is a space formed by being surrounded by the lid 2, the side walls 13, the end walls 14 and the bottom 15, and the storage space 11 is equally separated by five partition walls 16, and six battery cases 17 are formed along the X-axis direction.

[0033] The outer wall surface 13a of each side wall 13 is provided with a plurality of position adjustment portions 19 used for aligning with adjacent battery modules 1, and passage forming protrusions 20 formed to protrude in the thickness direction (Y-axis direction) of the side wall 13 and form a cooling passage between the adjacent battery modules 1.

[0034] An opening window 21 sealed by a side cover 22 is formed in each side wall 13 so as to straddle the partition wall 16. In this embodiment, three opening windows 21 are formed in one of the pair of side walls 13, and two opening windows 21 are formed in the other side wall 13. That is, in this embodiment, five opening windows 21 are formed in the battery case 10 as a whole.

[0035] The outer wall surface 13a of each side wall 13 has an opening at a location corresponding to the opening window 21, and a sheet S having an outer shape smaller than the outer wall surface 13a is attached to the outer wall surface 13a. The sheet S is attached to suppress the permeation of gases such as hydrogen generated inside each cell 30 from the resin battery case 10. Therefore, the material of the sheet S is not particularly limited as long as the sheet S has low permeability to the desired gas. In this example, a sheet S having extremely low hydrogen permeability and made of a lamination sheet in which aluminum, resin, etc. are laminated is attached to the outer wall surface 13a of the side wall 13. It is preferable that the sheet S is attached to the end side wall 14, the bottom 15, and the cover 2 in addition to the side wall 13 of the battery case 10.

[0036] In this embodiment, the sheet S is attached to the side wall 13 by a so-called two-color molding process, in which the sheet S is adsorbed and temporarily fixed in a predetermined position in the mold M during the resin molding of the integrated battery case 12 described below, and in this state, the molten resin that forms the battery case 10 is filled into the cavity M1 to form the battery case 10 with the sheet S attached to the side wall 13.

[0037] 2 and 4, a plurality of grooves 25 opening into the outer wall surface 13a of the side wall 13 are formed. Specifically, in this embodiment, fifteen grooves 25 are formed at intervals in the Z axis direction over substantially the entire area between the edge portion S1 of the sheet S in the X axis direction and the outer wall surface 14a of each end side wall 14. In this embodiment, the X axis direction corresponds to the "first direction" and the Z axis direction corresponds to the "second direction."

[0038] Each groove 25 is formed so that the length direction intersects with the Z-axis direction. Specifically, each groove 25 is formed so that the upper end (upper end) 25b is closer to the outer wall surface 14a of each end sidewall 14 than the lower end (lower end) 25a in the Z-axis direction. More specifically, each groove 25 formed on one side in the X-axis direction is formed so that the end 25b on the opening 18 side is closer to the outer wall surface 14a of the end sidewall 14 on one side in the X-axis direction than the end 25a on the bottom 15 side. On the other hand, each groove 25 formed on the other side is formed so that the end 25b on the opening 18 side is closer to the outer wall surface 14a of the end sidewall 14 on the other side than the end 25a on the bottom 15 side. In this embodiment, the lower end 25a corresponds to the "end on the bottom side" and the upper end 25b corresponds to the "end opposite to the bottom".

[0039] In this manner, in the battery module 1 of this embodiment, a plurality of grooves 25 are formed between the edge S1 of the sheet S in the X-axis direction and the outer wall surface 14a of each end side wall 14, in other words, over substantially the entire boundary B (see FIG. 4) between the side wall 13 and the end side wall 14 where high stress acts due to an increase in internal pressure during use, and the length direction of each groove 25 intersects with the length direction (Z-axis direction) of the boundary B. This improves the strength of the boundary B of the battery case 10, making it less susceptible to breakage due to an increase in internal pressure. In addition, as will be described in detail later, the sheet S is prevented from sinking into the resin and the occurrence of underfill during resin molding of the integrated battery case 12.

[0040] In addition, in the battery module 1 of the present embodiment, when cooling air for cooling the battery module 1 is flowed along the Z-axis direction during use, the cooling air becomes turbulent near the boundary B as shown in FIG. 5. The arrows in FIG. 5 indicate the flow of the cooling air. On the other hand, when no groove is formed in the boundary B or when a groove extending in the same direction as the length direction (Z-axis direction) of the boundary B is formed, the cooling air becomes laminar. Here, the flow speed of the cooling air near the side wall 13 is faster when the cooling air is turbulent than when the cooling air is laminar. Therefore, by making the cooling air turbulent near the boundary B, the current collector plate 33 and the conductive plate 34 (see FIG. 3) that are arranged near the boundary B among the members housed in the battery case 10 can be efficiently cooled.

[0041] In addition, as shown in FIG. 4, the intersection angles θ1, θ2 between the length direction of each groove 25 and the Z-axis direction of the grooves 25 in this embodiment are continuously or stepwise smaller from the grooves 25 formed on the bottom 15 side to the grooves 25 formed on the opposite side of the bottom 15 (the opening 18 side). In this application, "continuously decreasing" refers to a continuous decrease in numerical value, whether linear or nonlinear, such as "..., 30, 25, 20,..." or "..., 30, 25, 23,...". In this application, "stepwise decreasing" refers to a decrease in numerical value while at least the same numerical value appears continuously, such as "..., 30, 30, 25, 20, 20,...".

[0042] In this example, of the multiple groove portions 25, the groove portion 25 formed closest to the bottom 15 has an intersection angle θ1 between its length direction and the Z-axis direction of approximately 45°, and the groove portion 25 formed closest to the opening 18 has an intersection angle θ2 between its length direction and the Z-axis direction of approximately 15°.The other groove portions 25 between these two groove portions 25 are formed so that the intersection angles gradually decrease from the one on the bottom 15 side to the one on the opening 18 side.

[0043] A terminal mounting portion (not shown) penetrating in the thickness direction (X-axis direction) is formed on the upper end side of each end side wall 14, and a connection terminal 23 for extracting the output of the single battery 30 to the outside is attached to the terminal mounting portion.

[0044] A module support portion 28 protruding outward is formed on the lower end side of each end side wall 14. Specifically, the module support portion 28 in this embodiment has a shape in which a part of the outer wall surface 14a of each end side wall 14 protrudes in the thickness direction (X-axis direction). As shown in FIG. 3, in this embodiment, the outer wall surface 14a of each end side wall 14 is located above the module support portion 28 and is composed of a first surface F1 parallel to the XY plane, an inclined surface F2 that spreads diagonally downward from the lower end of the first surface F1, is parallel to the Y-axis direction, and intersects with the X-axis direction and the Z-axis direction, and a second surface F3 that is continuous with the lower end of the inclined surface F2 and is parallel to the XY plane. In this embodiment, the module support portion 28 corresponds to the "support portion".

[0045] The length of the lid 2 in the longitudinal direction (X-axis direction) is approximately the same as the long side of the side wall 13 of the integrated battery case 12, and the length of the lid 2 in the transverse direction (Y-axis direction) is approximately the same as the short side of the end side wall 14 of the integrated battery case 12. The lid 2 has a lower peripheral edge welded to the edge of the opening 18 of the integrated battery case 12, thereby air-tightly closing the opening 18 of the integrated battery case 12.

[0046] In addition, in this embodiment, the lid body 2 is formed as a hole penetrating in the thickness direction (Z-axis direction) and is equipped with a measurement section 6 into which a temperature sensor such as a thermocouple is inserted, and a discharge valve 7 for opening to release the internal pressure when the internal pressure of the battery case 10 reaches or exceeds a threshold value.

[0047] [Configuration of the cell 30] The cells 30 of this embodiment are nickel-metal hydride secondary batteries that are made up of battery elements 31 housed in the respective battery cases 17. As shown in FIG. 3, the battery elements 31 are made up of an electrode group 32, a current collector plate 33, a conductive plate 34, and an electrolyte (not shown). Although detailed description will be omitted, in this embodiment, the cells 30 are electrically connected via the current collector plates 33 of adjacent cells 30 and connection members 35 that connect the current collector plates 33 to each other. In addition, the electrode groups 32 arranged on both ends in the X-axis direction are electrically connected to the connection terminals 23 by the current collector plates 33 and the conductive plates 34. Thus, the battery module 1 of this embodiment has a configuration in which the cells 30 are connected in series.

[0048] [Resin molding of the integrated battery case 12] Next, an embodiment of resin molding of the integrated battery case 12 constituting the battery case 10 using a mold M will be described with reference to Figs. 6 to 8. Fig. 6 is a cross-sectional view of the mold M showing the flow of molten resin during resin molding. Fig. 7 is an enlarged view of part C in Fig. 6. Fig. 8 is a cross-sectional view of part VIII-VIII in Fig. 7. The outline arrows in Figs. 6 and 7 and the arrows in Fig. 8 show the flow of molten resin.

[0049] In this embodiment, the integrated battery case 12 is integrally molded from resin with the sheet S attached to the side wall 13 by injecting resin into the cavity M1 with the sheet S set in the mold M in advance, thereby performing so-called two-color molding.

[0050] As shown in Fig. 6, a mold M having a gate M2 provided near the center of the side corresponding to the bottom 15 of the integrated battery case 12 that constitutes the battery case 10 according to this embodiment is used for resin molding. Molten resin is injected from a nozzle through the gate M2 into a cavity M1 formed between the molds M. The injected molten resin flows along the Z-axis direction from the side corresponding to the bottom 15 toward the side corresponding to the opening 18. Therefore, in this embodiment, the resin is molded from the bottom 15 of the integrated battery case 12.

[0051] 6 to 8, in this embodiment, the shape of the cavity M1 of the mold M is such that a plurality of ridges M3 are formed to form a plurality of grooves 25 by transfer over the entire area between the edge portion S1 of the temporarily fixed sheet S and the inner surface M4 corresponding to the outer wall surface 14a of the end side wall 14 of the integrated battery case 12. The mold M has a shape in which the cross-sectional area of ​​the cavity M1 is smaller around the plurality of ridges M3 than in other portions.

[0052] The length direction of each ridge M3 of the mold M intersects with the Z-axis direction. Furthermore, each ridge M3 of the mold M has a shape such that an end M3b opposite to the bottom 15 of the integrated battery case 12 in the Z-axis direction is closer to the inner surface M4 corresponding to the outer wall surface 14a of the end wall 14 of the integrated battery case 12 than an end M3a on the side of the bottom 15 of the integrated battery case 12. In other words, each ridge M3 has a shape capable of guiding the molten resin flowing through the cavity M1 to a location corresponding to the end wall 14.

[0053] Furthermore, the crossing angle θ3 between the length direction of the multiple protrusions M3 and the Z-axis direction decreases continuously or stepwise from those formed on the bottom 15 side of the integrated battery case 12 in the Z-axis direction to those formed on the opposite side of the bottom 15. In other words, the crossing angle θ3 of the multiple protrusions M3 decreases from those formed on the upstream side to those formed on the downstream side in the flow direction of the molten resin.

[0054] One of the purposes of continuously or stepwise decreasing the crossing angle θ3 of the multiple ridges M3 is to facilitate the supply of molten resin to the portion of the mold M that corresponds to the end wall 14 of the integral battery case 12 during resin molding of the integral battery case 12. Specifically, the ridges M3 smoothly guide the molten resin injected from the gate M2 into the cavity M1 of the mold M to the portion that corresponds to the end wall 14, thereby preventing the occurrence of underfill due to an insufficient supply of molten resin.

[0055] Here, in the case of using a mold M having a single gate M2 formed at a position corresponding to the vicinity of the center of the bottom 15 of the integrated battery case 12 in the X-axis direction as in this embodiment, the flow of molten resin injected from the gate M2 into the cavity M1 tends to have a smaller intersection angle with the Z-axis direction as it moves downstream in the vicinity of the portion corresponding to the end side wall 14.

[0056] Taking this into consideration, in this example, of the multiple protrusions M3, the protrusion M3 formed closest to the bottom 15 of the integral battery case 12 has an intersection angle θ3 between its length direction and the Z-axis direction of approximately 45°, and the protrusion M3 formed closest to the opening 18 of the integral battery case 12 has an intersection angle θ3 between its length direction and the Z-axis direction of approximately 15°, and the other protrusions M3 between these two protrusions M3 have continuously smaller intersection angles from the one on the bottom 15 side to the one on the opening 18 side.

[0057] 7 and 8, in resin molding of the integrated battery case 12 using such a mold M, the molten resin injected from the gate M2 into the cavity M1 hits the inner surface M4 and bounces back toward the edge portion S1 of the sheet S. In particular, the integrated battery case 12 produced by resin molding according to this embodiment has a module support portion 28, and the molten resin injected into the cavity M1 is likely to be guided to the edge portion S1 of the sheet S along the inner surface M4a of the mold M that corresponds to the inclined surface F2 of the module support portion 28.

[0058] Here, the molten resin that has bounced off the inner surface M4 experiences increased pressure loss as it flows around the ridges M3. Therefore, as shown in Fig. 8, the molten resin flows toward the edge S1 of the sheet S at a reduced flow rate as it passes around the ridges M3. That is, in this embodiment, the flow rate of the molten resin flowing toward the edge S1 of the sheet S is reduced compared to when a die that does not have the ridges M3 is used. Therefore, in the resin molding of this example, peeling of the sheet S from the die M is unlikely to occur.

[0059] In particular, in this embodiment, the multiple protrusions M3 are formed over the entire area between the edge S1 of the sheet S and the inner surface M4 corresponding to the outer wall surface 14a of the end side wall 14 of the integrated battery case 12, and are also formed near the location corresponding to the module support portion 28. Therefore, the molten resin guided to the edge S1 of the sheet S from the location corresponding to the vicinity of the module support portion 28 where the sheet S is likely to slip under, and the molten resin that bounces off the inner surface M4, experience increased pressure loss and a reduced flow rate as they flow around the multiple protrusions M3. Therefore, during resin molding of the integrated battery case 12 in this embodiment, peeling of the sheet S from the mold M is suppressed over a wide area including the vicinity of the module support portion 28 where the sheet S is likely to slip under.

[0060] Furthermore, in the resin molding of the integral battery container 12 using the mold M, the molten resin injected into the cavity M1 of the mold M through the gate M2 is guided by the multiple ridges M3 to the portion corresponding to the end wall 14. That is, in this embodiment, compared to the case where a mold without the multiple ridges M3 is used, the flowability of the molten resin toward the portion corresponding to the end wall 14 is less likely to decrease, and underfill caused by insufficient supply of molten resin is less likely to occur around the end wall 14.

[0061] Particularly in this embodiment, in consideration of the flow of molten resin in the vicinity of the portion of cavity M1 corresponding to end wall 14, the crossing angle θ3 between the length direction of each protrusion M3 and the Z-axis direction is made to continuously decrease from those formed on the bottom 15 side of integral battery case 12 in the Z-axis direction to those formed on the opposite side of bottom 15. Therefore, in this embodiment, the molten resin that flows to the vicinity of the portion corresponding to end wall 14 is efficiently guided by the multiple protrusions M3 to the portion corresponding to end wall 14. Therefore, in the resin molding of this example, the flowability of the molten resin in the portion corresponding to end wall 14 is less likely to decrease, and underfill is less likely to occur around end wall 14.

[0062] In this manner, in this embodiment, when the integrated battery container 12 is resin-molded, the sheet S is less likely to peel off from the mold M and sink into the resin, and underfill is less likely to occur around the end side walls 14.

[0063] As described above, according to the battery case 10 of this embodiment, the battery case 10 (specifically, the integrated battery case 12) is designed to prevent the sheet S from penetrating into the resin and to prevent the occurrence of underfilling, thereby improving the pressure resistance and battery life of the battery module 1 using the battery case 10.

[0064] [Another embodiment] [1] In the above embodiment, the grooves 25 are formed over the entire area between the edge S1 of the sheet S and the outer wall surface 14a of the end wall 14, but the present invention is not limited to this. The grooves 25 may be formed at least partially between the edge S1 of the sheet S and the outer wall surface 14a of the end wall 14. Even in this case, the strength of at least a part of the boundary B of the battery case 10 is improved, so that damage due to an increase in internal pressure is unlikely to occur, and the cooling air becomes turbulent near the boundary B, so that the members arranged near the boundary B can be efficiently cooled. In addition, in the resin molding, a mold M having a protrusion M3 at least partially between the edge S1 of the sheet S and the inner surface M4 corresponding to the outer wall surface 14a of the end wall 14 of the integrated battery case 12 is used. Therefore, in the same manner as above, peeling of the sheet S from the mold M is suppressed around the protrusions M3. Furthermore, the molten resin flowing in the cavity M1 is easily guided by the multiple protrusions M3 to the portion corresponding to the end wall 14, and the flowability of the molten resin in the portion corresponding to the end wall 14 is unlikely to decrease, making it difficult for underfill to occur around the end wall 14. In other words, even in the above-described embodiment, the battery case 10 is prevented from the sheet S sinking into the resin and from causing underfill. As described above, when the integrated battery case 12 (battery case 10) has a module support portion 28, when the integrated battery case 12 is resin-molded, the molten resin is likely to be guided to the edge portion S1 of the sheet S along the inner surface of the die near the module support portion 28, which makes it easy for the sheet S to peel off from the die M. For this reason, from the viewpoint of preventing the sheet S from peeling off from the die M and preventing the sheet S from sinking into the resin, it is preferable that a plurality of grooves are formed at least near the module support portion 28.

[0065] [2] In the above embodiment, the crossing angles θ1, θ2 of each groove 25 are continuously decreased from 45° to 15° from the groove 25 formed on the bottom 15 side to the groove 25 formed on the opening 18 side. However, the present invention is not limited to this. The crossing angles of each groove 25 may be decreased stepwise, or may be constant. The values ​​of the crossing angles θ1, θ2 are not particularly limited.

[0066] In addition, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0067] 1: Battery module 10: Battery case 13: Side wall 13a: Exterior wall surface 14: End wall 14a: Exterior wall surface 15: Bottom 17: Battery case 25: Groove 25a: Lower end (end on the bottom side) 25b: Upper end (end opposite the bottom) 28: Module support part (support part) 30: Single battery S: Seat S1:Edge θ1, θ2: Intersection angles

Claims

1. A battery case is a rectangular parallelepiped resin container having side walls, end walls, and a bottom, and constitutes a battery container in which a single battery is housed, The side wall is A sheet is attached to an outer wall surface, and a plurality of grooves are formed on the outer wall surface, The plurality of grooves include a first direction is a direction parallel to the opposing direction of the end side walls, and the sheet is formed at least in a portion between an edge portion of the sheet on one side in the first direction and an outer wall surface of the end side wall on one side in the first direction, the sheet being spaced apart in a second direction parallel to the outer wall surface of the side wall and perpendicular to the first direction; A battery case in which the length direction of each groove portion intersects with the second direction, and the end portion opposite the bottom in the second direction is closer to the outer wall surface of the end side wall on one side in the first direction than the end portion on the bottom side.

2. The end side wall is formed with a support portion protruding outward, The battery case according to claim 1 , wherein the plurality of grooves are formed at least near the support portion between an edge of the sheet on one side in the first direction and an outer wall surface of the end side wall on one side in the first direction.

3. The battery case according to claim 1 , wherein the plurality of grooves are formed over the entire area between an edge of the sheet on one side in the first direction and an outer wall surface of the end side wall on one side in the first direction.

4. The battery case according to any one of claims 1 to 3, wherein the crossing angle between the longitudinal direction of each of the plurality of grooves and the second direction decreases continuously or stepwise from the groove formed on the side of the bottom in the second direction to the groove formed on the opposite side of the bottom.

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