Battery pack

Abstract

To provide a battery pack in which, when a battery stack is coupled to a battery pack case, the occurrence of resonance in the battery stack can be suppressed.SOLUTION: A battery pack 10 includes: a battery pack case 12 accommodating a battery stack 16 where a plurality of battery cells 18 are stacked; a plurality of fixing members 20 each including an extension part 26 extending from both end parts of the battery stack 16 in a stacking direction of the battery cells 18 to the outside in the stacking direction and coupled to a coupling part 14 formed on both wall parts of the battery pack case 12 facing the stacking direction; and a plurality of pressing members 30 extending in the stacking direction so as to press an upper surface of the battery stack 16 and having both end parts in the stacking direction coupled to the coupling parts 14 together with the extension parts 26. The pressing member 30 includes a bent convex part 34 that is convex upward on the inside in the stacking direction relative to the coupling part 14 and is configured so that a part on the inside in the stacking direction relative to the bent convex part 34 is energized downward by being coupled to the coupling part 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Battery packs that house multiple battery cells have been known for some time (see, for example, Patent Document 1). The multiple battery cells housed inside this battery pack are fixed in place by an adhesive cell retaining member that comes into contact with parts of the battery pack other than those covered with an insulating exterior body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-295381 A Summary of the Invention [Problem to be solved by the invention]

[0004] Another method for fixing a battery stack, which is made up of multiple stacked and constrained battery cells, to a battery pack case is to bolt a pressing member that presses down on the battery stack from above to the battery pack case.

[0005] However, when the pressing members are fixed by bolts, vibrations occurring when the bolts are fastened may cause resonance (transmission of vibrations) in the battery stack, which may cause the constraints on the stacked battery cells to be released. If the constraints on the stacked battery cells are released, there is a risk of short circuits occurring between the battery cells or inside the battery cells.

[0006] Therefore, an object of the present invention is to provide a battery pack that can suppress the occurrence of resonance in the battery stack when the battery stack is fastened to a battery pack case. [Means for solving the problem]

[0007] In order to achieve the above object, the battery pack described in claim 1 of the present invention comprises a battery stack formed by stacking a plurality of battery cells, a battery pack case in which the battery stack is housed, and a plurality of fixing members provided on the battery stack, the fixing members having protrusions that protrude outward from both ends in the stacking direction of the battery cells in the battery stack and are fastened to a plurality of fastening portions formed on both wall portions of the battery pack case facing the stacking direction, and a plurality of pressing members that extend in the stacking direction so as to press an upper surface of the battery stack and have both ends in the stacking direction fastened to the fastening portions together with the protrusions, the pressing members having bent convex portions that protrude upward on the inside in the stacking direction relative to the fastening portions, and are configured so that, by being fastened to the fastening portions, the inside in the stacking direction relative to the bent convex portions is urged downward.

[0008] According to the invention described in claim 1, a pressing member extending in the stacking direction of the battery cells (hereinafter simply referred to as the "stacking direction") so as to press the upper surface of the battery stack is fastened at both ends to the fastening portion of the battery pack case together with the protruding portion of the fixing member provided on the battery stack. Here, the pressing member has a bent convex portion that is convex upward on the inside of the fastening portion in the stacking direction, and therefore, when fastened to the fastening portion, a deformation load is generated downward on the inside of the bent convex portion in the stacking direction. In other words, the pressing member is biased downward on the inside of the bent convex portion in the stacking direction. Therefore, when the battery stack is fastened to the battery pack case, the battery stack is pressed from above by the pressing member, and therefore resonance in the battery stack is suppressed.

[0009] A battery pack according to a second aspect of the present invention is the battery pack according to the first aspect, wherein the bent convex portion is formed on the inside of the protruding portion in the stacking direction.

[0010] According to the invention recited in claim 2, the bent convex portion of the pressing member is formed on the inside of the protruding portion of the fixing member in the stacking direction. Therefore, compared to a case in which the bent convex portion of the pressing member is formed on the outside of the protruding portion of the fixing member in the stacking direction, there is no risk of the protruding portion inhibiting deformation of the pressing member downward on the inside of the bent convex portion in the stacking direction, and the biasing force downward on the inside of the bent convex portion in the stacking direction, i.e., the pressing force pressing the battery stack from above, is increased.

[0011] A battery pack according to a third aspect of the present invention is the battery pack according to the first or second aspect, wherein a protruding portion that protrudes downward is formed in a central portion of the pressing member in the stacking direction.

[0012] According to the invention described in claim 3, a protrusion that is convex downward is formed in the center of the stacking direction of the pressing member. Here, a battery stack formed by stacking and restraining a plurality of battery cells is prone to have its center in the stacking direction lift up. Therefore, when a protrusion that is convex downward is formed in the center of the stacking direction of the pressing member, the battery stack is pressed from above more efficiently and the lift up of the battery stack to the upward direction is more effectively suppressed than when a protrusion that is convex downward is not formed in the center of the stacking direction of the pressing member.

[0013] A battery pack according to a fourth aspect of the present invention is the battery pack according to any one of the first to third aspects, in which a reinforcing rib is formed on the inside of the bent convex portion of the pressing member in the stacking direction.

[0014] According to the invention described in claim 4, a reinforcing rib is formed on the inside of the bent convex portion of the pressing member in the stacking direction. Therefore, compared to a case where a reinforcing rib is not formed on the inside of the bent convex portion of the pressing member in the stacking direction, the strength of the pressing member is improved and a deformation load directed downward toward the inside of the bent convex portion in the stacking direction is transmitted more effectively. Effect of the Invention

[0015] As described above, according to the present invention, it is possible to suppress the occurrence of resonance in the battery stack when the battery stack is fastened to a battery pack case. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is an exploded perspective view showing the battery pack according to the embodiment. [Diagram 2] FIG. 2 is a perspective view showing a pressure bracket according to the embodiment. [Diagram 3] FIG. 2 is a side view showing the pressure bracket according to the embodiment. [Figure 4] 2 is an exploded perspective view showing a state in which a battery stack is housed in a battery pack case according to the embodiment. FIG. [Diagram 5] 2 is a partially enlarged cross-sectional side view showing a battery stack housed in the battery pack case according to the embodiment; FIG. [Figure 6] 1 is a perspective view showing a battery pack according to an embodiment of the present invention; [Figure 7] 1 is a side cross-sectional view showing a battery pack according to an embodiment of the present invention. [Figure 8] 1A is a side cross-sectional view showing a state before and after the pressure bracket according to the present embodiment is fastened, and FIG. [Figure 9] 4 is a partially enlarged side cross-sectional view showing a state before fastening of the pressure bracket according to the embodiment. FIG. [Figure 10] 11 is a partially enlarged side cross-sectional view showing a state after the pressure bracket according to the embodiment is fastened. FIG. [Figure 11] 11 is a side cross-sectional view showing a modified example of the battery pack according to the embodiment. FIG. [Figure 12] 1A is a side cross-sectional view showing a state before and after fastening of a pressure bracket according to a comparative example, and FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. For ease of explanation, the arrow UP shown in each drawing indicates the upward direction of the battery pack, the arrow FR indicates the forward direction of the battery pack, and the arrow RH indicates the rightward direction of the battery pack. In the following description, unless otherwise specified, when the directions of up / down, front / rear, and left / right are described, they refer to up / down in the vertical direction of the battery pack, front / rear in the front / rear direction of the battery pack, and left / right in the left / right direction of the battery pack.

[0018] 1, a battery pack 10 according to this embodiment includes a battery pack case 12 that is open at the top and has a generally rectangular housing shape with a longitudinal direction in the front-rear direction. The battery pack case 12 is formed of a metal mainly composed of aluminum, for example, and has a rectangular flat bottom wall 12D, a front wall 12F and a rear wall 12B that are integrally erected from the front and rear ends of the bottom wall 12D, and a left side wall 12L and a right side wall 12R that are integrally erected from the left and right ends of the bottom wall 12D.

[0019] The front wall 12F and the rear wall 12B are integrally continuous with the left side wall 12L and the right side wall 12R, and the front wall 12F and the rear wall 12B and the left side wall 12L and the right side wall 12R together form the peripheral walls of the battery pack case 12. The front wall 12F and the rear wall 12B as both wall portions have a predetermined thickness, and stepped recesses 14 serving as fastening portions are integrally formed on both the left and right sides of the upper end portions of each wall.

[0020] That is, each recess 14 is formed by cutting out a rectangle from the inner surface of the front wall 12F and the rear wall 12B to a part of the upper surface, and the depth is set to a depth such that when the protruding portion 26 of the fixed bracket 20 described later and the fastened portion 32 of the pressing bracket 30 are fastened with the bolt 40, the head 42 of the bolt 40 does not protrude upward from the upper end surface of the front wall 12F and the rear wall 12B (see Figs. 7 and 10). And, at a predetermined position on the bottom surface 14A of each recess 14, a female screw portion 14B into which the bolt 40 is screwed is formed.

[0021] The battery pack 10 also includes a battery stack 16 housed in the battery pack case 12. The battery stack 16 is an assembled battery that stores power for driving the vehicle, and is configured by stacking a number of battery cells 18 in the front-rear direction (the longitudinal direction of the battery pack case 12). That is, the battery stack 16 as a whole is formed in a roughly rectangular parallelepiped shape large enough to be placed inside the battery pack case 12 with few gaps.

[0022] The battery stack 16 is also provided with a pair of left and right metal fixing brackets 20 as fixing members. As shown in Fig. 7, the fixing bracket 20 is formed in a substantially U-shape in a side view seen from the left-right direction, and has a flat connecting portion 22 arranged in contact with the lower surface of the battery stack 16, flat standing portions 24 standing upward from both ends in the front-rear direction of the connecting portion 22 and arranged in contact with the front and rear surfaces of the battery stack 16, and flat protruding portions 26 protruding forward and rearward from upper ends of the standing portions 24, respectively.

[0023] That is, the battery stack 16, which is formed by stacking a plurality of battery cells 18, is pressed and restrained in the stacking direction by the fixing bracket 20. As shown in Fig. 5, the standing portion 24 is formed so that its height is slightly higher than the height of the battery stack 16 (battery cells 18) and higher than the position of the bottom surface 14A of the recess 14 when the battery stack 16 is housed in the battery pack case 12 (before fastening). That is, a predetermined gap S is formed in the up-down direction between the lower surface of the overhanging portion 26 and the bottom surface 14A of the recess 14.

[0024] 1 and 4, the overhanging portion 26 is formed in a substantially "Y" shape in a plan view, and is formed with a width (length along the left-right direction) that allows it to be placed in each of the recesses 14 formed in the front wall 12F and the rear wall 12B of the battery pack case 12. In other words, the width of the overhanging portion 26 is formed to be smaller than the width of the recess 14. The fixing bracket 20 is fastened to each recess 14 by inserting a shaft portion 44 of a bolt 40 (described later) between the vicinity of the bifurcated base of each overhanging portion 26 and screwing it into the female screw portion 14B.

[0025] As shown in Figures 1 and 4, the upper surface of the battery stack 16 housed in the battery pack case 12 is pressed downward (to the bottom wall 12D of the battery pack case 12) by a pair of left and right pressing members made of metal, pressing brackets 30, so that the upper surface of the battery stack 16 is pressed downward (to the bottom wall 12D of the battery pack case 12).

[0026] 1 to 4, the pressing bracket 30 extends in the front-rear direction (the stacking direction of the battery cells 18), and both ends (one end and the other end) of the pressing bracket 30, which are fastened portions 32, are fastened to the respective recesses 14 together with the protruding portions 26 of the fixing bracket 20. More specifically, the pressing bracket 30 has fastened portions 32 in the shape of a substantially rectangular plate, and each fastened portion 32 has a circular through-hole 32A (see FIG. 2) formed therein for inserting a shaft portion 44 of a bolt 40, which will be described later.

[0027] Like the protruding portion 26 of the fixing bracket 20, the fastened portion 32 is formed with a width (length along the left-right direction) that allows it to be placed in each of the recesses 14 formed in the front wall 12F and the rear wall 12B of the battery pack case 12. In other words, the width of the fastened portion 32 is formed to be smaller than the width of the recesses 14 (see FIG. 6).

[0028] 9, with the fastened portion 32 disposed on the upper surface of the protruding portion 26 of the fixing bracket 20 disposed within the recess 14, a bent convex portion 34 that protrudes upward is formed on the inner side in the longitudinal direction (extension direction, stacking direction of the battery cells 18) from the fastened portion 32 of the pressing bracket 30, and more specifically, on the inner side in the longitudinal direction from the protruding portion 26. In other words, the length L1 along the longitudinal direction from the tip of the fastened portion 32 to the bent convex portion 34 is longer than the length L2 along the longitudinal direction of the protruding portion 26.

[0029] The inclination angle θ1 (see FIG. 9) from the tip of the fastened portion 32 to the bent convex portion 34 with respect to the horizontal direction before being fastened to the concave portion 14 by the bolt 40 is larger than the inclination angle θ2 (see FIG. 10) of the protruding portion 26 deformed when fastened to the concave portion 14 by the bolt 40 with respect to the horizontal direction. Note that the bending angle θ3 (see FIG. 9) of the bent convex portion 34 with respect to the horizontal direction before being fastened to the concave portion 14 by the bolt 40 is formed to be an obtuse angle.

[0030] According to the bent convex portion 34 formed with such length L1 and inclination angle θ1, when the fastened portion 32 is fastened to the recessed portion 14 together with the overhanging portion 26, a deforming load acts downward on the inner side in the longitudinal direction from the bent convex portion 34. In other words, this pressing bracket 30 is configured so that the inner side in the longitudinal direction from the bent convex portion 34 is biased downward.

[0031] 2 and 3, a flat portion 35 having flat upper and lower surfaces along the horizontal direction is bent and formed on the inside of the longitudinal direction of the bent convex portion 34. The height position of the flat portion 35 is approximately the same as the height position of the tip portion of the fastened portion 32 (see FIG. 3). A reinforcing rib 36 is integrally provided upright on the upper surface of the flat portion 35. That is, the rib 36 having a substantially elliptical shape in a plan view is formed at a predetermined height on the upper surface of the flat portion 35.

[0032] Further, a protruding portion 38 that is convex downward is bent on the inside in the longitudinal direction of the flat portion 35. Specifically, a bent portion 37 that is bent into a crank shape is formed on the inside in the longitudinal direction of the flat portion 35, and a protruding portion 38 that is located at the lowest height position of the pressing bracket 30 is formed on the inside in the longitudinal direction of the bent portion 37, in other words, in the center of the pressing bracket 30 in the longitudinal direction.

[0033] The protruding portion 38 has a flat lower surface that is at least along the horizontal direction, and the above-mentioned deformation load (urging force) causes the lower surface to come into contact with the upper surface of each battery cell 18 present in the longitudinal center of the battery stack 16, pressing the upper surface downward. Note that the rib 36 in this embodiment is formed to include the bent portion 37, which is the boundary between the flat portion 35 and the protruding portion 38 (see Figures 2 and 3).

[0034] Next, the operation of the battery pack 10 according to this embodiment configured as above (assembly process of the battery pack 10) will be described.

[0035] As shown in Fig. 4, first, the battery stack 16 is placed inside the battery pack case 12. That is, the battery stack 16 is housed inside the battery pack case 12. At this time, as shown in Fig. 5, the lower surface of the connecting portion 22 of the fixing bracket 20 contacts the upper surface of the bottom wall 12D of the battery pack case 12, and each of the protruding portions 26 of the fixing bracket 20 is inserted into each of the recesses 14.

[0036] At this time, since the height of the upright portion 24 of the fixed bracket 20 is higher than the position of the bottom surface 14A of the recess 14, the lower surface of the protruding portion 26 of the fixed bracket 20 is not in contact with the bottom surface 14A of the recess 14. In other words, a predetermined gap S is formed in the up-down direction between the lower surface of the protruding portion 26 and the bottom surface 14A of the recess 14.

[0037] Next, as shown in Figures 6 and 7, the battery stack 16 is pressed from above with the pressing bracket 30. That is, first, as shown in Figures 8(A) and 9, the lower surface of the fastened portion 32 of the pressing bracket 30 is placed over the upper surface of the overhanging portion 26 of the fixing bracket 20. Then, as shown in Figures 8(B) and 10, the shaft portion 44 of the bolt 40 is inserted between the through hole 32A of the fastened portion 32 and the vicinity of the bifurcated base of the overhanging portion 26, and screwed into the female thread portion 14B of the recess 14.

[0038] At this time, a bent convex portion 34 that is convex upward is formed on the inside of the fastened portion 32 of the pressing bracket 30 in the longitudinal direction. More specifically, the bent convex portion 34 is formed on the inside of the recess 14, preferably the protruding portion 26 in the longitudinal direction (in other words, length L1>length L2). The inclination angle θ1 from the fastened portion 32 to the bent convex portion 34 before fastening with respect to the horizontal direction is set to be larger than the inclination angle θ2 of the protruding portion 26 deformed by the fastening of the bolt 40 with respect to the horizontal direction.

[0039] Therefore, when the fastened portion 32 is fastened together with the overhanging portion 26 by the bolt 40 to the recess 14, a deformation load acts downward on the protruding portion 38 which is located longitudinally inward from the bent convex portion 34, i.e., the central portion in the longitudinal direction. In other words, the protruding portion 38 which is longitudinally inward from the bent convex portion 34 is biased downward. Below, a comparative example will be given to explain this.

[0040] As shown in Figure 12, in the case of a pressure bracket 130 relating to a comparative example in which a bent convex portion 34 is not formed, when an attempt is made to fasten the fastening portion 132 together with the protrusion portion 26 to the recess 14 with a bolt 40, a gap S (see Figure 5) exists between the bottom surface 14A of the recess 14 and the underside of the protrusion portion 26, so that when the bolt 40 is screwed in, the protrusion portion 26 gradually begins to tilt so that the outer side in the longitudinal direction is lower and the inner side in the longitudinal direction is higher.

[0041] Then, the fastened portion 132 overlapping the upper surface of the overhanging portion 26 also begins to incline so that the outer side in the longitudinal direction is lower and the inner side in the longitudinal direction is higher, and the pressing bracket 130 is flexed and deformed so that the protruding portion 138, which is the central portion in the longitudinal direction, protrudes upward. In other words, in the case of a pressing bracket 130 in which the bent convex portion 34 is not formed, an upward deformation load acts on the protruding portion 138, and therefore the protruding portion 138 cannot press the upper surface of the battery stack 16 downward.

[0042] In contrast, the pressing bracket 30 according to this embodiment has a bent convex portion 34. Therefore, as shown in Fig. 8(B) and Fig. 10, when the fastened portion 32 is fastened together with the overhanging portion 26 to the recessed portion 14 by the bolt 40, the fastened portion 32 overlapping the upper surface of the overhanging portion 26 also begins to tilt so that the outer side in the longitudinal direction is lower and the inner side in the longitudinal direction is higher, and accordingly, a deforming load (biasing force) toward the downward side begins to be generated in the longitudinal center portion of the pressing bracket 30, i.e., the protruding portion 38.

[0043] As a result, the upper surface of the battery stack 16 begins to be pressed downward by the protrusions 38, and when the bolts 40 are being screwed in, the battery stack 16 is effectively pressed from above by the pressing brackets 30. This makes it possible to suppress resonance in the battery stack 16 when fastening the battery stack 16 to the battery pack case 12 with the bolts 40. In other words, according to this embodiment, the risk of the restraint on the multiple battery cells 18 being released is reduced.

[0044] Furthermore, the bent convex portion 34 of the pressing bracket 30 according to this embodiment is formed on the inside in the longitudinal direction of not only the concave portion 14 but also the overhanging portion 26. Therefore, compared to a case in which the bent convex portion 34 of the pressing bracket 30 is formed on the outside in the longitudinal direction of the overhanging portion 26, there is no risk that the overhanging portion 26 will hinder the deformation of the pressing bracket 30 downward on the inside in the longitudinal direction of the bent convex portion 34, and it is possible to increase the biasing force downward on the inside in the longitudinal direction of the bent convex portion 34, i.e., the pressing force pressing the battery stack 16 from above.

[0045] Moreover, a protrusion 38 that protrudes downward is formed in the longitudinal center of the pressing bracket 30 according to this embodiment. Here, the battery stack 16 formed by stacking and restraining a plurality of battery cells 18 tends to rise up so that the center in the stacking direction as a whole protrudes upward. In other words, a gap that extends in the up-down direction is likely to be formed between the lower surface of the battery stack 16 and the upper surface of the bottom wall 12D of the battery pack case 12 with variation in the front-rear direction.

[0046] Therefore, when a protrusion 38 that convexes downward is formed in the longitudinal center of the pressing bracket 30, the top surface of the battery stack 16 (particularly the top surface of the center in the stacking direction) can be pressed from above more efficiently than when a protrusion 38 that convexes downward is not formed in the longitudinal center of the pressing bracket 30, and the battery stack 16 (each battery cell 18) can be effectively prevented from floating up upward.

[0047] Furthermore, a reinforcing rib 36 is formed on at least the upper surface of the flat portion 35 of the pressing bracket 30 according to this embodiment. Therefore, compared to a case where the reinforcing rib 36 is not formed on the upper surface of the flat portion 35, the strength of the inner portion in the longitudinal direction of the pressing bracket 30 from the bent convex portion 34 can be improved. Therefore, the above-mentioned downward deformation load (urging force) can be more effectively transmitted from the bent convex portion 34 via the flat portion 35 to the protruding portion 38 (to the inner side in the longitudinal direction from the bent convex portion 34).

[0048] Furthermore, since the pressing bracket 30 is shaped to have the bent convex portions 34, the ribs 36, the protruding portions 38, etc. as described above and can press and hold the battery stack 16 from above, it is possible to reduce the number of bolts 40 for fastening the battery stack 16 to the battery pack case 12. This makes it possible to reduce the size of the battery pack 10 and the manufacturing costs.

[0049] Furthermore, the rib 36 can increase the strength of at least the inner longitudinal portion of the pressure bracket 30 relative to the bent convex portion 34, so that when the bolt 40 is completely screwed in, as shown in Figures 6 and 7, the battery stack 16, particularly the central portion in the longitudinal direction, is effectively maintained in a state in which it is pressed from above by the pressure bracket 30 (protrusion 38) with a predetermined pressing force.

[0050] That is, the pressing bracket 30 maintains a state in which the battery stack 16 cannot fall off from the battery pack case 12. In order to further maintain this state, the battery stack 16 may be configured to be joined to the bottom wall 12D of the battery pack case 12 with an adhesive 28, as shown in Fig. 11.

[0051] For example, a pair of longitudinally extending recesses 13 may be formed on the upper surface of the bottom wall 12D of the battery pack case 12, one on the left and one on the right corresponding to each fixing bracket 20, and at least the lower surface of the connecting portion 22 of each fixing bracket 20 may be joined to the upper surface of the bottom wall 12D of the battery pack case 12 using adhesive 28 applied within each recess 13.

[0052] Although not shown in the drawings, the battery stack 16 may be configured to be fixed to the bottom wall 12D of the battery pack case 12 with bolts. That is, for example, flange portions may be made to protrude outwardly toward the front and rear from the connecting portion 22 of the fixing bracket 20, and the flange portions may be fixed to the upper surface of the bottom wall 12D of the battery pack case 12 with bolts.

[0053] Although the battery pack 10 according to the present embodiment has been described above with reference to the drawings, the battery pack 10 according to the present embodiment is not limited to the one shown in the drawings, and the design can be appropriately modified within the scope of the present invention. For example, the fixing brackets 20 and the pressing brackets 30 may be provided in plural numbers on the battery pack 10, and are not limited to two, a pair on the left and right. [Explanation of symbols]

[0054] 10 Battery pack 12 Battery pack case 14 Recess (fastening part) 16 Battery stack 18 Battery Cells 20 Fixing bracket (fixing member) 26 Overhang 30 Pressing bracket (holding member) 34 Bend convex part 36 Ribs 38 Protrusion

Claims

1. A battery stack formed by stacking a plurality of battery cells; a battery pack case that houses the battery stack; a plurality of fixing members provided on the battery stack, the fixing members having protruding portions that protrude outward from both ends of the battery stack in a stacking direction of the battery cells and are fastened to a plurality of fastening portions formed on both wall portions of the battery pack case facing the stacking direction; a plurality of pressing members extending in the stacking direction so as to press an upper surface of the battery stack, and both end portions in the stacking direction are fastened to the fastening portion together with the protruding portion; Equipped with The pressing member has a bent convex portion that convex upward on the inside of the fastening portion in the stacking direction, and the battery pack is configured such that, when fastened to the fastening portion, the inside of the stacking direction of the bent convex portion is biased downward.

2. The battery pack according to claim 1 , wherein the bent convex portion is formed on an inner side in the stacking direction than the protruding portion.

3. 3. The battery pack according to claim 1, wherein a protruding portion that protrudes downward is formed in a central portion of the pressing member in the stacking direction.

4. 4. The battery pack according to claim 1, wherein a reinforcing rib is formed on the pressing member on the inner side in the stacking direction from the bent convex portion.

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