Battery pack

Abstract

Provided is a battery pack that can inhibit gas from entering an adjacent cell accommodation space. A battery pack according to the present disclosure comprises: a plurality of cylindrical cells arranged such that a plurality of electrode terminals face in the same direction; a resin cell holder for holding the arrangement of the plurality of cylindrical cells; a tab extending in a planar direction parallel to a direction orthogonal to the longitudinal direction of the cylindrical cells; and a case. The cell holder includes: a holder body in which a plurality of cell accommodation portions are provided in a planar direction; a bottom wall extending in a planar direction; and through holes penetrating the bottom wall. The bottom wall includes: a plurality of lid walls covering the cell accommodation portions; and a plurality of annular walls. The tab includes: a plurality of portions to be welded that are welded to the electrode terminals via the through holes; and a wiring portion that extends in a planar direction from the portions to be welded and connects the portions to be welded. At least one among the lid walls and the wiring portion is provided with a thin portion having a small thickness in the longitudinal direction. The thin portion is disposed inwards of the annular wall when viewed from the longitudinal direction.

Description

[Technical Field]

[0001] The present disclosure relates to a battery pack. [Background technology]

[0002] The battery unit installed in the battery pack has multiple cells. When the cells are cylindrical cells, the cylindrical cells are aligned in a direction perpendicular to the longitudinal direction of the cylindrical cells, and the electrode terminals are arranged on the same plane. To maintain this alignment of the multiple cylindrical cells, the battery unit has a cell holder.

[0003] The cell holder in the following patent document is provided with a plurality of cell housing sections in which cylindrical cells are housed. Each cell housing section is a cylindrical hole. The ends of the cell housing sections are open. A tab is arranged in the direction of the opening, and the tab and the electrode terminal of the cylindrical cell are welded to each other. The tab extends across adjacent cell housing sections and connects the electrode terminals of the adjacent cylindrical cells. Furthermore, a blocking wall is provided between the end of the cell holder and the tab, preventing communication between adjacent cell housing sections. Therefore, even if a cylindrical cell generates heat and high-temperature, high-pressure gas is ejected from the end of the cylindrical cell, the gas will not enter the adjacent cell housing section. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-166991 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the processing accuracy of the tab and the blocking wall is low, gaps will occur between the tab blocking wall or between the gap blocking wall and the cell accommodating section. Therefore, there is a need for the development of a battery pack that can prevent high-temperature, high-pressure gas from entering the adjacent cell accommodating section, regardless of the processing accuracy of the tab.

[0006] In view of the above-mentioned problems, an object of the present disclosure is to provide a battery pack that prevents gas from entering the housing space of an adjacent cell. [Means for solving the problem]

[0007] A battery pack according to one aspect of the present disclosure includes a plurality of cylindrical cells arranged with a plurality of electrode terminals facing the same direction, a resin cell holder that maintains the arrangement of the plurality of cylindrical cells, a metal tab extending in a planar direction parallel to a direction perpendicular to the longitudinal direction of the cylindrical cells, and a case that houses the plurality of cylindrical cells, the cell holder, and the tab. The cell holder includes a holder main body having a plurality of cell housing sections extending in the planar direction, the cell housing sections extending in the longitudinal direction, a bottom wall that extends in the planar direction and connects to an end of the holder main body, and a through hole that penetrates the bottom wall. The bottom wall includes a plurality of cover walls that cover the cell housing sections and a plurality of annular walls that extend from the cover wall toward an inner surface of the case. The tab is disposed on each of the plurality of cover walls and includes a plurality of welded portions that are welded to the electrode terminals through the through hole, and wiring that extends from the welded portions in the planar direction and connects the welded portions to each other. At least one of the cover wall and the wiring portion has a thin portion having a small thickness in the longitudinal direction, the thin portion being disposed inside the annular wall as viewed in the longitudinal direction. [Effects of the Invention]

[0008] In the battery pack of the present disclosure, gas ejected from the cylindrical cell ruptures the thin-walled portion and moves into the annular wall, preventing gas from moving into the adjacent cell housing. Furthermore, this effect does not depend on the processing accuracy of the tab. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view of a battery pack according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the battery unit. [Figure 3]FIG. 3 is a view showing a state in which the tab is removed from the bottom wall of the first cell holder. [Figure 4] FIG. 4 is a view showing a state in which the tab is removed from the bottom wall of the second cell holder. [Figure 5] FIG. 5 is a view of the first cell holder as seen from the first longitudinal direction. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a perspective view of the end of the cylindrical cell on the positive electrode side. [Figure 8] FIG. 8 is a cross-sectional view showing a state in which a cylindrical cell is housed in the cell housing portion. [Figure 9] FIG. 9 is a cross-sectional view showing the gas path in a cylindrical cell. [Figure 10] FIG. 10 is a cross-sectional view showing the gas path in the cell holder. [Figure 11] FIG. 11 is a diagram showing the first tab of the first modification. [Figure 12] FIG. 12 is a cross-sectional view taken along line XI-XI in FIG. [Figure 13] FIG. 13 is an enlarged view of the first cell holder of the second modification. [Figure 14] FIG. 14 is a diagram showing the second tab of the third modification. [Figure 15] FIG. 15 is an enlarged view of the first cell holder of the fourth modification. [Figure 16] FIG. 16 is a perspective view of the bottom wall side of the cell holder of the fifth modification. [Figure 17] FIG. 17 is a perspective view of the bottom wall side of the cell holder of the sixth modification. [Figure 18] FIG. 18 is an exploded perspective view of the battery pack of the seventh modification. [Figure 19] FIG. 19 is a cross-sectional view of the seventh modification. [Figure 20] FIG. 20 is a perspective view showing a second case of the eighth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the following modes for carrying out the invention (hereinafter referred to as embodiments). Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0011] (Embodiment 1) Fig. 1 is an exploded perspective view of a battery pack according to embodiment 1. As shown in Fig. 1, a battery pack 100 includes a battery unit 1 and a case 101 that houses the battery unit.

[0012] Figure 2 is an exploded perspective view of a battery unit. As shown in Figure 2, the battery unit 1 includes a plurality of cylindrical cells 2, a cell holder 10, tabs 30 (see Figures 3 and 4), and a control board 7. Hereinafter, the direction in which the cylindrical cells 2 extend will be referred to as the longitudinal direction. Electrode terminals 3 are provided at the longitudinal ends of the cylindrical cells 2. More specifically, a positive terminal 4 is provided at one longitudinal end of the cylindrical cells 2, and a negative terminal 5 is provided at the other longitudinal end.

[0013] In this embodiment, eight cylindrical cells 2 are provided. Note that the present disclosure is not particularly limited in the number of cylindrical cells 2. The eight cylindrical cells 2 are arranged so that the electrode terminals 3 face the same direction. The eight cylindrical cells 2 are arranged so that four are arranged in a direction intersecting the longitudinal direction (hereinafter referred to as the width direction) and two are arranged in a direction intersecting both the longitudinal direction and the width direction (hereinafter referred to as the stacking direction). Furthermore, the eight cylindrical cells 2 are arranged so that the electrode terminals 3 are located on the same plane. Note that the same plane is a plane extending in the width direction and the stacking direction. Hereinafter, a direction parallel to the same plane will be referred to as the planar direction. Additionally, in the battery pack of the present disclosure, the electrode terminals 3 do not have to be arranged on the same plane. In other words, the electrode terminals 3 may be arranged offset from each other in the longitudinal direction.

[0014] With respect to the orientation of the electrode terminals 3 of the cylindrical cells 2, two cylindrical cells 2 aligned in the stacking direction are arranged so that the same electrode terminal 3 faces one side of the longitudinal direction. Two cylindrical cells 2 aligned in the stacking direction are connected in parallel by tabs 30 (see FIGS. 3 and 4). Four pairs of cylindrical cells 2 aligned in the width direction (two cylindrical cells 2 aligned in the stacking direction) are arranged so that the positive electrode terminal 4 and the negative electrode terminal 5 face alternately one side of the longitudinal direction. Four pairs of cylindrical cells 2 aligned in the width direction are directly connected by tabs 30 so that a current flows as shown by arrow A in FIG. 2. As a result, the eight cylindrical cells are four pairs of cylindrical cells 2 connected in parallel and connected in series.

[0015] The cell holder 10 includes a first cell holder 11 and a second cell holder 12. The first cell holder 11 is a resin product arranged on one side in the longitudinal direction relative to the eight cylindrical cells 2. The second cell holder 12 is a resin product arranged on the other side in the longitudinal direction relative to the eight cylindrical cells 2. Hereinafter, the direction in which the first cell holder 11 is arranged as viewed from the eight cylindrical cells will be referred to as the first longitudinal direction X1, and the opposite direction will be referred to as the second longitudinal direction X2.

[0016] The first cell holder 11 and the second cell holder 12 each have a holder body 14 with eight cell receptacles 13 and a bottom wall 15 covering the ends of the cell receptacles 13. The cell receptacles 13 are holes extending in the longitudinal direction and have a circular cross-sectional shape. The ends of the cylindrical cells 2 in the first longitudinal direction X1 are inserted into the cell receptacles 13 of the first cell holder 11. The ends of the cylindrical cells 2 in the second longitudinal direction X2 are inserted into the cell receptacles 13 of the second cell holder 12. In other words, the eight cylindrical cells 2 are sandwiched between the first cell holder 11 and the second cell holder 12 in the longitudinal direction. The first cell holder 11 and the second cell holder 12 are then tightened in the longitudinal direction by screws 6. This maintains the arrangement of the eight cylindrical cells 2.

[0017] The control board 7 is mounted on a cell holder 10 and fixed to the cell holder 10 with screws 8. The control board 7 prevents over-discharge and over-charge of the cylindrical cells 2. Hereinafter, the direction in which the control board 7 is arranged as viewed from the eight cylindrical cells 2 among the stacking directions will be referred to as the first stacking direction Z1, and the opposite direction will be referred to as the second stacking direction Z2.

[0018] Fig. 3 is a diagram showing the state in which the tab has been removed from the bottom wall of the first cell holder. Fig. 4 is a diagram showing the state in which the tab has been removed from the bottom wall of the second cell holder. As shown in Figs. 3 and 4, the bottom walls 15 of the first cell holder 11 and the second cell holder 12 extend in a planar direction. Furthermore, a plurality of tabs 30 are embedded in the bottom walls 15 of the first cell holder 11 and the second cell holder 12 (see the arrows in Figs. 3 and 4).

[0019] The tabs 30 are metal plates extending in the planar direction. The multiple tabs 30 include first tabs 31 that connect the electrode terminals 3 of four cylindrical cells 2 adjacent in the stacking direction and width direction, and second tabs 40 that connect the electrodes of two cells adjacent in the stacking direction. As shown in FIG. 3, the first cell holder 11 has a first tab 31 embedded in the center and two second tabs 40 embedded on either side in the width direction. As shown in FIG. 4, two first tabs 31 are embedded in the second cell holder 12 and lined up in the width direction.

[0020] The first tab 31 has a rectangular shape when viewed in the longitudinal direction. The first tab 31 is provided with a welded portion 32 that protrudes inward in the longitudinal direction. The welded portion 32 is the portion that is welded to the electrode terminal 3 of the cylindrical cell 2. The welded portion 32 is embedded so as to overlap with the through-hole 17 in the bottom wall 15 (see the arrows in Figures 3 and 4). Two welded portions 32 are provided in each of the stacking direction and the width direction. The plate-like portion of the first tab 31 other than the welded portion 32 forms a wiring portion 33 through which current flows.

[0021] The second tab 40 is longer in the stacking direction than in the width direction. An electrode tab 41 is provided at the end of the second tab 40 in the first stacking direction Z1. This electrode tab 41 is not embedded in the bottom wall 15, but protrudes from the cell holder 10 in the stacking direction (see FIG. 2). The second tab 40 is provided with two welded portions 42 that protrude inward in the longitudinal direction and are spaced apart in the stacking direction. The welded portions 42 are embedded so as to overlap with the through holes 17 in the bottom wall 15 (see the arrows in FIGS. 3 and 4). The portion of the second tab 40 other than the welded portions 42 and the electrode tab 41 forms a wiring portion 43. The bottom wall 15 and the tab 30 will be described in detail later.

[0022] As shown in Fig. 1, the case 101 is a housing made of resin. The case 101 has a first case 102 arranged in a first loading direction Z1 and a second case 103 arranged in a second loading direction Z2. The second case 103 is a cylindrical container with a bottom that opens in the first loading direction Z1. The first case 102 is a cylindrical container with a bottom that opens in the second loading direction Z2. The first case 102 and the second case 103 are fastened together by bolts 104.

[0023] The second case 103 has a pair of opposing walls 105, 106 that face each other in the longitudinal direction. The second case 103 is longer in the stacking direction and has a larger internal capacity than the first case 102. Therefore, the pair of opposing walls 105, 106 face the bottom wall 15 of the cell holder 10.

[0024] External terminals 110 are provided on the wall of the second case 103. The external terminals 110 are connected to two electrode tabs 41 (see FIG. 2) of the battery unit. The external terminals 110 are arranged in the width direction of the cylindrical cells 2. Hereinafter, the width direction in which the external terminals 110 are arranged as viewed from the cylindrical cells 2 will be referred to as the first width direction Y, and the opposite direction will be referred to as the second width direction Y2.

[0025] Next, the bottom wall 15 and tab 30 of the cell holder 10 will be described in detail. The shape of the bottom wall 15 of the first cell holder 11 is the same as the shape of the bottom wall 15 of the second cell holder 12. Therefore, the following will describe the first cell holder 11, and the description of the second cell holder 12 will be omitted.

[0026] 5 is a view of the first cell holder as viewed from the first longitudinal direction. As shown in FIG. 5, the bottom wall 15 of the first cell holder 11 extends in a planar direction. A portion of the bottom wall 15 forms a circular cover wall 16 that covers the first longitudinal direction X1 of the cell storage section 13. Thus, the bottom wall 15 has eight cover walls 16. A circular through-hole 17 is provided in the center of each cover wall 16.

[0027] Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5. As shown in Figure 6, the holder body 14 has multiple partition walls 14a that separate the cell accommodating sections 13. The cover wall 16 is connected to the partition walls 14a. In other words, unless the partition walls 14a are ruptured by gas, adjacent cell accommodating sections 13 do not communicate with each other. For these reasons, regardless of the processing accuracy of the tabs 30, the cell accommodating sections 13 do not communicate with each other.

[0028] The cover wall 16 is provided with an annular wall 20 that protrudes in the first longitudinal direction X1. Hereinafter, the space inside the annular wall 20 will be referred to as an annular space 21. As shown in FIG. 5, the annular wall 20 has a cylindrical shape when viewed in the longitudinal direction. A total of eight annular walls 20 are provided on each cover wall 16. Each annular wall 20 is spaced apart from adjacent annular walls 20 in the width direction and the loading direction. Therefore, a separation space 22 that separates the annular walls 20 is provided between the adjacent annular walls 20.

[0029] The bottom wall 15 is provided with an outer peripheral wall 23 that protrudes in the first longitudinal direction X1. The outer peripheral wall 23 is an annular wall that surrounds the outer peripheral sides of the eight annular walls 20 and the separated spaces 22. The outer peripheral wall 23 is also separated from the annular walls 20. Therefore, the separated spaces 22 extend between the outer peripheral wall 23 and the annular walls 20.

[0030] 6, the annular wall 20 and the outer peripheral wall 23 have the same length in the longitudinal direction. When the battery unit 1 is housed in the case 101, the end 20a of the annular wall 20 and the end 23a of the outer peripheral wall 23 abut against the inner surface 105a of the opposing wall 105 of the case 101. Therefore, each annular space 21 and the separated space 22 are closed.

[0031] The first tab 31 and the second tab 40 are embedded in the bottom wall 15 by insert molding. The welded portion 32 of the first tab 31 and the welded portion 42 of the second tab 40 are embedded in the center of the cover wall 16 and overlap the through-hole 17. The cover wall 16 has a cell-facing surface 16a that faces the end of the cylindrical cell 2. The welded portions 32, 42 are positioned near the end of the cover wall 16 in the second longitudinal direction X2 and are flush with the cell-facing surface 16a.

[0032] The wiring portion 33 of the first tab 31 and the wiring portion 43 of the second tab (not shown in FIG. 6) are embedded in the bottom wall 15. Furthermore, the wiring portion 33 of the first tab 31 and the wiring portion 43 of the second tab are located in the longitudinal center of the bottom wall 15 (lid wall 16). Therefore, the wiring portion 33 extends inside the bottom wall 15 (lid wall 16), straddling the partition wall 14a and connecting adjacent cylindrical cells 2. The first tab 31 and the second tab 40 described above do not have a complex shape such as a U-shaped bend, which improves quality and productivity.

[0033] A recess 18 recessed in the longitudinal direction is provided on the cell-facing surface 16a of the cover wall 16. This recess 18 is annular and has a circular shape when viewed in the longitudinal direction (see FIG. 5). As a result, a thin portion 19 having a small thickness in the longitudinal direction is provided in a part of the cover wall 16. Furthermore, the recess 18 (thin portion 19) is located inside the annular wall 20 when viewed in the longitudinal direction.

[0034] FIG. 7 is a perspective view of the positive electrode end of the cylindrical cell 2. Next, the positive electrode end of the cylindrical cell 2 will be described. A top cover 200 is provided at the positive electrode end of the cylindrical cell 2. A protrusion 201 is provided in the center of the top cover 200. An opening 202 is provided on the side of this protrusion 201. This opening 202 is a hole for releasing high-temperature, high-pressure gas ejected from a safety valve (not shown) to the outside of the cylindrical cell 2. An annular cell shoulder 210 is provided on the outer periphery of the top cover 200. An annular battery annular space 215 is provided between the protrusion 201 and the cell shoulder 210. As shown in FIG. 7, when the cylindrical cell 2 is assembled to the cell holder 10, an annular seal 220 is disposed between the cell shoulder 210 and the cell-facing surface 16a of the cover wall 16 (see FIG. 6).

[0035] 8 is a cross-sectional view showing a state in which a cylindrical cell is accommodated in a cell accommodating section. Next, the assembly state of the cylindrical cell 2 to the cell holder 10 will be described. The protrusion 201 of the cylindrical cell 2 is in contact with the welded portions 32, 42 (not shown in FIG. 8) of the tab 30. Then, welding is performed from the through hole 17 side, and the welded portions 32, 42 and the protrusion 201 are joined.

[0036] The inner peripheral surface 20b of the annular wall 20 is located outward of the inner peripheral surface 211 of the cell shoulder 210 (see auxiliary line H in FIG. 8). Therefore, when viewed in the longitudinal direction, the inner peripheral surface 211 of the cell shoulder 210 is located inward of the inner peripheral surface 20b of the annular wall 20 (see FIG. 10). The battery annular space 215 is closed by the cover wall 16. The seal 220 is located between the cell shoulder 210 and the cell-facing surface 16a, sealing the gap between the cell shoulder 210 and the cell-facing surface 16a. The recess 18 of the cover wall 16 overlaps with the battery annular space 215 when viewed in the longitudinal direction.

[0037] FIG. 9 is a cross-sectional view showing the gas path in a cylindrical cell. Next, the gas path when the cylindrical cell 2 generates heat will be described. As shown in FIG. 9, when the cylindrical cell 2 generates heat, a safety valve (not shown) opens and high-temperature, high-pressure gas is ejected from a hole 205. The hole 205 is located inside a protrusion 201 of the top cover 200. As shown by arrow B1 in FIG. 9, the gas passes through an opening 202 in the protrusion 201 and flows into the battery annular space 215. Then, the internal pressure of the battery annular space 215 increases, and high pressure acts on the cover wall 16 that closes the battery annular space 215.

[0038] The cover wall 16 has a thin portion 19. When the pressure in the battery annular space 215 reaches or exceeds a predetermined value, the thin portion 19 tears, causing a tear (not shown) in the cover wall 16. As a result, gas in the battery annular space 215 passes through the tear and moves into the annular space 21 (see arrow B2). The annular space 21 is sealed by the annular wall 20 and the inner surface 105a of the case 101 (see FIG. 6). Therefore, the gas remains in the annular space 21.

[0039] It should be noted that there is a possibility that the cover wall 16 may tear at a location other than the thin portion 19. However, the portion of the cover wall 16 on which the gas pressure acts is limited to the area inside the inner circumferential surface 210a of the cell shoulder 210. Therefore, even if the cover wall 16 tears at a location other than the thin portion 19, the tear will be inside the inner circumferential surface 20b of the annular wall 20. Therefore, the gas passing through the cover wall 16 moves reliably to the annular space 21.

[0040] FIG. 10 is a cross-sectional view showing the gas path in the cell holder. When the pressure in the annular space 21 exceeds a predetermined value, the opposing wall 105 of the case 101 or the annular wall 20 tears. As shown in FIG. 10, if the annular wall 20 tears, the gas passes through the crack in the annular wall 20 and moves to the outside of the annular wall 20, as indicated by arrow B3. The outside of the annular wall 20 is a separated space 22 surrounded by an outer peripheral wall 23. Therefore, the gas remains in the separated space 22.

[0041] As a result, the gas ejected from the cylindrical cell 2 is reliably transferred to the annular space 21. This prevents the partition wall 14a from being torn open, causing the gas to transfer to the adjacent cell housing portion 13.

[0042] Furthermore, gas may enter the cell housing portion 13, which houses the cylindrical cells 2 that are not generating heat, through the through-holes 17 in the cover wall 16. However, the outer side of the through-holes 17 in the longitudinal direction is blocked by the annular wall 20 and the inner surface 105a of the case 101. Therefore, gas is prevented from entering the cell housing portion 13 via the through-holes 17.

[0043] Furthermore, even if the annular wall 20 is torn, the gas remains in the isolated space 22. Therefore, it is possible to prevent the gas from being released into the inside of the case 101 and heating other cylindrical cells 2.

[0044] As a result, the cylindrical cells 2 that are not generating heat are prevented from being heated by the gas. Furthermore, the above-mentioned effect is exerted regardless of the processing accuracy of the tabs 30.

[0045] Although the battery pack of the first embodiment has been described above, the present disclosure is not limited to the example shown in the first embodiment. For example, in the first embodiment, the recess 18 is provided on the cell-facing surface 16a of the cover wall 16 to facilitate tearing of the cover wall. However, in the present disclosure, the recess 18 may be provided on the surface of the cover wall 16 opposite the cell-facing surface 16a. Alternatively, the recess 18 may be provided on both the cell-facing surface 16a and the opposite surface (see FIG. 13 ). Furthermore, in the present disclosure, it is sufficient that at least one of the cover wall 16 and the wiring portion 33 has a thin portion 19. Therefore, the thin portion may be provided only on the tab 30. Below, we will explain Modifications 1 to 3 in which the tab 30 has a thin portion, and Modification 4 in which the tab 30 does not have a thin portion. Furthermore, the following explanation will focus on the changes.

[0046] (Variation 1) Fig. 11 is a view showing a first tab of Modification 1. Fig. 12 is a cross-sectional view taken along line XI-XI in Fig. 11. As shown in Fig. 11, wiring portion 33A of first tab 31A of Modification 1 is provided with semicircular markings 34 extending along welded portion 32. As shown in Fig. 12, markings 34 are depressions formed by pressing the surface of wiring portion 33A. As a result, the portion of wiring portion 33A overlapping with markings 34 becomes thin portion 35A with a small longitudinal thickness.

[0047] With this thin portion 35A, the strength of the cover wall 16 including the wiring portion 33A is reduced in part, making the cover wall 16 more susceptible to cracking. Therefore, when the pressure in the battery annular space 215 exceeds a predetermined value, the portion of the cover wall 16 that overlaps with the thin portion 35A ruptures, allowing gas to reliably move into the annular space 21. This reliably prevents gas from moving to the adjacent cell housing portion 13. Note that, although the example in which the marking 34 is provided on the first tab 31A is shown in Modification 1, it may also be provided on the second tab 40.

[0048] The first tab 31A has four markings 34 corresponding to the four welded portions 32. The first tab 31A shown in FIG. 12 is disposed in the center of the first cell holder 11 in the width direction (see FIG. 3). In the first tab 31A shown in FIG. 12, the two welded portions 32 disposed closer to the second width direction Y2 are negative electrode welded portions 32b to be welded to the negative electrode terminal 5 of the cylindrical cell 2. The two welded portions 32 disposed closer to the first width direction Y1 are positive electrode welded portions 32a to be welded to the positive electrode terminal 4 of the cylindrical cell 2. Therefore, in the wiring portion 33A, a current flows from the positive electrode welded portion 32a to the negative electrode welded portion 32b (see arrow C in FIG. 11).

[0049] The marking 34b extending along the negative electrode welded portion 32b is located on the opposite side of the positive electrode welded portion 32a from the negative electrode welded portion 32b. The marking 34b extending along the positive electrode welded portion 32a is located on the opposite side of the negative electrode welded portion 32b from the positive electrode welded portion 32a. In other words, the markings 34 (34a, 34b) are not located between the negative electrode welded portion 32b and the positive electrode welded portion 32a. The resistance value increases in the area where the markings 34 are provided. Therefore, according to the first modification, it is possible to prevent the resistance value between the negative electrode welded portion 32b and the positive electrode welded portion 32a from becoming high.

[0050] (Variation 2) FIG. 13 is an enlarged view of the first cell holder of Modification 2. Modification 2 is a modification in which a thin portion 19B and a thin portion 35B are provided on the cover wall 16B and the first tab 31B, respectively. Specifically, a first recess 18a is provided on the cell-facing surface 16a of the cover wall 16B, and a second recess 18b is provided on the back surface. The first recess 18a, the second recess 18b, and the marking 34B overlap in the longitudinal direction. In other words, the thin portion 19B and the thin portion 35B overlap. This allows the thin portion 19B and the thin portion 35B to rupture under a lower pressure than in Embodiment 1. This ensures that gas in the battery annular space 215 is released into the annular space 21.

[0051] (Variation 3) Fig. 14 is a diagram showing the second tab of Modification 3. As shown in Fig. 14, the markings 34C of the first tab 31C of Modification 3 are made up of multiple linear markings 36 extending radially from the welded portion 32. The linear markings 36 are arranged at equal intervals around the welded portion 32. As such, in the present disclosure, there are no particular limitations on the shape of the markings.

[0052] (Variation 4) FIG. 15 is an enlarged view of the first cell holder of Modification 4. The first cell holder 11D of Modification 4 has a first recess 18a and a second recess 18b in the cover wall 16D. Meanwhile, the first tab 31D has no markings. The first recess 18a and the second recess 18b are located in a range that does not overlap with the first tab 31D when viewed from the longitudinal direction. As a result, the first tab 31D is not embedded in the thin portion 19D between the first recess 18a and the second recess 18b. Therefore, the thin portion 19D is made of resin only, and the metal first tab 31D does not need to be torn apart, so it can be torn apart with a lower pressure than the thin portion 19D. Next, we will explain modifications in which portions other than the thin portion are modified.

[0053] (Variation 5) 16 is a perspective view of the bottom wall side of the cell holder of Modification 5. The cell holder 10E of Modification 5 differs from Embodiment 1 in that the bottom wall 15 does not have an outer peripheral wall 23 (see FIG. 5). Even in the cell holder 10E of Modification 5, cracking occurs in the cover wall 16, and gas in the battery annular space 115 moves to the annular space 21. This prevents gas from entering the adjacent cell housing portion 13.

[0054] (Variation 6) FIG. 17 is a perspective view of the bottom wall side of the cell holder of Modification 6. The cell holder 10F of Modification 6 is similar to Modification 5 in that the bottom wall 15 does not have an outer peripheral wall 23 (see FIG. 5). However, the cell holder 10F of Modification 6 differs from Modification 5 in that the annular walls 20F are continuous with each other. In other words, the cell holder 10F of Modification 6 does not have a separation space 22. According to Modification 6, the annular wall 20F is thick. Therefore, the annular wall 20F is less likely to tear, and gas can be prevented from being released into the case 101.

[0055] (Variation 7) FIG. 18 is an exploded perspective view of a battery pack of Modification 7. FIG. 19 is a cross-sectional view of Modification 7. A case 101G of Modification 7 differs from the case 101 of Embodiment 1 in that it includes a first case 102G and a second case 103G that can be separated longitudinally. The first case 102G and the second case 103G are cylindrical containers with a bottom. The first case 102G and the second case 103G have a pair of opposing walls 105G and 106G that face each other longitudinally. Eight cylindrical fitting portions 130 are provided on the inner surfaces 105a of the pair of opposing walls 105G and 106G (the inner surfaces of the opposing walls 105G are not shown in FIG. 18). The eight fitting portions 130 are arranged four in the width direction and two in the stacking direction, corresponding to the annular wall 20.

[0056] 18, the fitting portion 130 is fitted to the outside of the annular wall 20. This ensures that the annular space 21 is sealed even if the opposing wall 105G is deformed or the length of the annular wall 20 is shortened due to a manufacturing error, and the end portion 20a of the annular wall 20 does not abut against the inner surface 105a. This prevents gas from leaking between the annular wall 20 and the opposing wall 105G.

[0057] The seventh modification has been described above. The fitting portion 130 in the seventh modification is adapted to fit onto the outside of the annular wall 20, but in the present disclosure, the fitting portion may fit onto the inside of the annular wall 20. Furthermore, when the fitting portion 130 is provided on the case 101G as shown in the seventh modification, the end 20a of the annular wall 20 in the present disclosure does not have to abut against the inner surface 105a of the opposing wall 105G. Furthermore, in the seventh modification, an example was given in which the fitting portion 130 is provided on the first case 102G and the second case 103G that are separable in the longitudinal direction, but in the present disclosure, the fitting portion 130 may be provided on the case 101 of the first embodiment that is separable in the stacking direction.

[0058] (Variation 8) FIG. 20 is a perspective view showing a second case of Modification 8. As shown in FIG. 20, second case 103H of Modification 8 differs from second case 103 of Embodiment 1 in that multiple recesses 140 are provided on inner surfaces 105a of a pair of opposing walls 105, 106 (the inner surface of opposing wall 106 is not shown). This configuration reduces the longitudinal thickness of each of the pair of opposing walls 105, 106 at the portions overlapping with the recesses 140. Hereinafter, the portions overlapping with the recesses 140 are referred to as fragile portions 141. Furthermore, when viewed from the longitudinal direction, fragile portions 141 are located inside annular wall 20. Therefore, when gas is filled in annular space 21 of annular wall 20, fragile portions 141 are easily ruptured. In other words, gas is released to the outside of case 101H, and the inside of case 101H is not filled with gas. In the eighth modification, the recesses 140 are provided on the inner surfaces 105a of the pair of opposing walls 105, 106, but in the present disclosure, they may be provided on the outer surfaces of the pair of opposing walls 105, 106. [Explanation of symbols]

[0059] 1 Battery unit 2 Cylindrical cells 3 electrode terminal 10, 10E, 10F Cell Holder 11, 11D First cell holder 12 Second cell holder 13 Cell storage section 14 Holder body 15 Bottom Wall 16, 16B, 16D Lid wall 17 Through hole 18 Recess 19, 19B Thin section 20th and 20th floor circular wall 21 Annular Space 22 Separate space 23 Outer wall 30 tabs 31, 31A, 31B 1st tab 32, 42 Welded parts 32a Positive electrode welded part 32b Negative electrode welded part 33, 33A, 43 wiring section 34, 34B, 34C stamp 35A, 35B thin section 36 Linear engraving 40 Second Tab 100 battery packs 101, 101G, 101H Case 102, 102G Case 1 103, 103G, 103H Second Case 105, 106 Opposite walls 105a Inside 130 fitting part 140 recess 141 Weak part 200 top cover 201 Convex 202 Opening 210 Cell shoulder 215 Battery annular space 220 stickers

Claims

1. a plurality of cylindrical cells arranged such that a plurality of electrode terminals face the same direction; a resin cell holder that holds the arrangement of the plurality of cylindrical cells; a metal tab extending in a planar direction parallel to a direction perpendicular to the longitudinal direction of the cylindrical cell; a case that accommodates a plurality of the cylindrical cells, the cell holder, and the tab; Equipped with The cylindrical cells are arranged in the planar direction, the cell holder includes a first cell holder and a second cell holder; Each of the first cell holder and the second cell holder comprises: a holder body having a plurality of cell accommodating portions, which are holes extending in the longitudinal direction, provided in the planar direction; a bottom wall extending in the planar direction and connected to an end of the holder body in the longitudinal direction; a through hole penetrating the bottom wall; and one end of each of the cylindrical cells in the longitudinal direction is inserted into the cell receiving portion of the first cell holder; the other end portions of the cylindrical cells in the longitudinal direction are inserted into the cell accommodating portions of the second cell holder; the first cell holder and the second cell holder are fastened in the longitudinal direction by a fastener; The bottom wall is A plurality of cover walls that cover the cell housing portion; a plurality of annular walls extending from the cover wall toward the inner surface of the case; and The tab a plurality of welded portions disposed on the plurality of cover walls, respectively, and welded to the electrode terminals via the through holes; a wiring portion extending from the welded portion in the planar direction and connecting the welded portions to each other; and A top cover is provided at the end of the cylindrical cell on the positive electrode side, The top cover is the positive electrode terminal is disposed in a central portion of the top cover, the positive electrode terminal being a protrusion welded to the welded portion and having an opening formed on a side surface; an annular cell shoulder portion disposed on an outer peripheral side of the top cover; a battery annular space provided between the protrusion and the cell shoulder; and an annular seal is provided between the cell shoulder and the cover wall to seal the gap between the cell shoulder and the cover wall; an end of the annular wall abuts against an inner surface of the case, and a space inside the annular wall is closed by the inner surface of the case; At least one of the cover wall and the wiring portion is provided with a thin portion having a small thickness in the longitudinal direction, When viewed from the longitudinal direction, an inner circumferential surface of the cell shoulder portion is disposed inside an inner circumferential surface of the annular wall, The thin portion is disposed inside the inner circumferential surface of the cell shoulder portion when viewed from the longitudinal direction. Battery pack.

2. The wiring portion is embedded in the cover wall. The battery pack according to claim 1 .

3. The cover wall is provided with a recess recessed in the longitudinal direction, The thin portion is provided in the cover wall. The battery pack according to claim 1 .

4. The wiring portion is provided with a marking recessed in the longitudinal direction, The wiring portion is provided with the thin portion. The battery pack according to claim 1 .

5. The wiring portion is provided with a marking recessed in the longitudinal direction, When viewed from the longitudinal direction, the marking and the recess overlap, The thin portion is provided on each of the cover wall and the tab. The battery pack according to claim 3 .

6. The welded portion is a positive electrode welded portion to be welded to the positive electrode terminal of the electrode terminal; a negative electrode welded portion to be welded to the negative electrode terminal of the electrode terminal; and The marking is arranged on the opposite side of the positive electrode welded portion as viewed from the negative electrode welded portion, or on the opposite side of the negative electrode welded portion as viewed from the positive electrode welded portion. The battery pack according to claim 4.

7. a protrusion of a top cover to be welded to the welded portion is disposed in the center of the positive electrode side end of the cylindrical cell; A cell shoulder portion having an annular shape centered on the protrusion is provided on the edge portion of the end portion on the positive electrode side of the cylindrical cell, a battery annular space serving as a gas passage is provided between the protrusion and the cell shoulder; When viewed from the longitudinal direction, an inner circumferential surface of the cell shoulder is disposed inside an inner circumferential surface of the annular wall. The battery pack according to claim 1 .

8. Separation spaces are provided between the plurality of annular walls to separate the annular walls, The bottom wall is provided with an annular outer peripheral wall that surrounds the outer peripheral sides of the plurality of annular walls and the separation space, The outer peripheral wall has the same length in the longitudinal direction as the annular wall, The end of the outer peripheral wall abuts against the inner surface of the case. The battery pack according to claim 1 .

9. The plurality of annular walls are continuous with adjacent annular walls. The battery pack according to claim 1 .

10. The end of the annular wall abuts against the inner surface of the case. The battery pack according to claim 1 .

11. The inner surface of the case is provided with a plurality of fitting portions that fit with the annular wall. The battery pack according to claim 1 .

12. The inner surface of the case is provided with a plurality of weak portions each having a small thickness in the longitudinal direction, The weakened portion is disposed inside the annular wall when viewed in the longitudinal direction. The battery pack according to any one of claims 1 to 11.

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