Battery pack

Abstract

The invention provides a battery pack which improves space efficiency and improves impact resistance against impact from the outside. A battery pack (10) is provided with: a plurality of stacked unit cells (40); and a case (20) that houses the plurality of unit cells (40). An opening (86a) is provided in the left wall section (86) of the case (20) in the stacking direction of the single cells (40), the periphery of the opening (86a) is closed, and a pressing plate (28) for pressing the single cells (40) toward the case (20) in the stacking direction is attached to the opening (86a).

Description

Technical Field

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

[0002] In recent years, in order to ensure that more people can obtain affordable, reliable, and sustainable modern energy, research and development related to secondary batteries that contribute to improving energy efficiency have been carried out.

[0003] For example, Patent Document 1 describes an electricity storage device including: an electricity storage unit having a plurality of electricity storage elements each having a flat shape; and an outer package body that houses the electricity storage unit. In the electricity storage device of Patent Document 1, after inserting the electricity storage unit from a second opening formed at a position facing the side wall of the outer package body and housing it inside the outer package body, a second lid portion is joined to the outer package body to close the second opening. At this time, the second lid portion presses the plurality of electricity storage elements in the arrangement direction of the plurality of electricity storage elements with a spacer interposed therebetween, thereby compressing the electricity storage unit.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2023 / 068029 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] The electricity storage device of Patent Document 1 is a Cell to Pack type in which a plurality of electricity storage elements are not unitized or modularized but are housed in an outer package body, which is advantageous in terms of space efficiency. However, since the second opening is formed by not providing the side wall on the insertion port side of the electricity storage unit in the outer package body, there is room for improvement from the viewpoint of shock resistance against external shocks.

[0009] The present invention provides a battery pack that improves space efficiency and shock resistance against external shocks. It further contributes to improving energy efficiency.

[0010] Means for Solving the Problems

[0011] The present invention relates to a battery pack including:

[0012] a plurality of stacked single cells; and

[0013] a housing that houses the plurality of single cells,

[0014] wherein an opening is provided in a side wall portion of the housing in the stacking direction of the single cells, and the periphery of the opening is closed.

[0015] A pressing plate that presses the single battery toward the housing in the stacking direction is installed at the opening portion.

[0016] Advantages of the Invention

[0017] According to the present invention, space efficiency can be improved, and impact resistance against external impacts can be enhanced. Description of the Drawings

[0018] Figure 1 It is an external perspective view of the battery pack 10.

[0019] Figure 2 It is an exploded perspective view of the battery pack 10.

[0020] Figure 3 It is an exploded perspective view of the single battery stack 30.

[0021] Figure 4 It is a cross-sectional view of the pressing plate 28 in a state where a plurality of single batteries 40 and end plates 31 are pressed.

[0022] Figure 5 It is an exploded perspective view of a modified example of the battery pack 10.

[0023] Figure 6 It is a partial perspective view of a modified example of the pressing plate 28.

[0024] Description of Reference Numerals

[0025] 10 Battery pack

[0026] 11 First seal (seal)

[0027] 13 Pressure relief valve

[0028] 16 Seal

[0029] 20 Housing

[0030] 21 Housing main body

[0031] 23 Housing cover

[0032] 28 Pressing plate

[0033] 281 Flange portion

[0034] 282 Protrusion

[0035] 31 End plate

[0036] 311 Contact surface

[0037] 312 Contact surface

[0038] 40 Single battery

[0039] 44 Safety valve

[0040] 50 Plate clamp (constraint member)

[0041] 86 Left wall portion (side wall portion)

[0042] 86a Opening

[0043] 86s Step portion. Detailed implementation manner

[0044] Hereinafter, an embodiment of the battery pack of the present invention will be described based on the drawings. In addition, in the following description, for convenience, a coordinate system composed of mutually orthogonal front-rear direction, left-right direction, and up-down direction will be used for description. In the drawings, the front is represented as Fr, the rear is represented as Rr, the left side is represented as L, the right side is represented as R, the upper side is represented as U, and the lower side is represented as D. However, these directions are independent of the direction when the battery pack is mounted on the device. For example, when the battery pack is mounted on a vehicle, the up-down direction of the battery pack can be oriented in the traveling direction of the vehicle or in the vehicle width direction when mounted on the vehicle.

[0045] [Battery pack]

[0046] As Figure 1 and Figure 2 shown, in the battery pack 10, two single-cell stacks 30 are arranged and configured in the front-rear direction inside a box-shaped housing 20. As Figure 3 shown, the single-cell stack 30 has a plurality of rectangular single cells 40 stacked in the left-right direction, and an end plate 31 disposed on one side in the left-right direction (the left side in this embodiment), and they are temporarily fixed with a prescribed pressure by using a plate clamp 50. In addition, a partition (not shown) may be disposed between adjacent single cells 40. The plate clamp 50 includes a rectangular lower constraint portion 51 surrounding the bottom surface of the single-cell stack 30, a rectangular upper constraint portion 52 surrounding the upper surface of the single-cell stack 30, and a pair of side constraint portions 53 sandwiching the single-cell stack 30 in the front-rear direction, and the lower constraint portion 51 and the pair of side constraint portions 53 are integrally formed. In addition, it may be configured that another end plate, partition, etc. are disposed on the other side in the left-right direction of the single-cell stack 30 (the right side in this embodiment) so that the single cells 40 do not directly contact the housing 20 on the other side. In addition, the single-cell stack 30 may not be a structure in which a plurality of single cells 40 are constrained by the plate clamp 50, that is, it may be a structure in which a plurality of single cells 40 are directly stacked and arranged inside the housing 20.

[0047] The end plate 31 has flange portions 31f at the lower end and the upper end, and the flange portions 31f are constrained by the lower constraint portion 51 and the upper constraint portion 52, whereby the end plate 31 is fixed to the plurality of single cells 40.

[0048] The single cell 40 is a secondary battery such as a lithium ion battery. On the upper surface of the single cell 40, there are provided: a pair of terminal portions 42 which are provided at both end portions in the front-rear direction which is orthogonal to the stacking direction of the single cell 40; and a safety valve 44 which is provided at the central portion in the front-rear direction and is disposed between the pair of terminal portions 42. The pair of terminal portions 42 includes a positive terminal and a negative terminal. For example, the positive terminal is connected to the negative terminal of an adjacent single cell 40 via a bus bar (not shown), and the negative terminal is connected to the positive terminal of an adjacent single cell 40 via a bus bar (not shown), whereby a plurality of single cells 40 are electrically connected in series. For example, in order to shorten the length of the bus bar, a plurality of single cells 40 may be stacked in such a manner that the front-rear direction orientations are alternately flipped.

[0049] The safety valve 44 is a rupture type valve for preventing the outer can from rupturing when the internal pressure of the single cell 40 abnormally rises. When the internal pressure of the single cell 40 abnormally rises, the safety valve 44 ruptures, and the gas inside the single cell 40 is released to the outside. By disposing the safety valve 44 at the central portion in the front-rear direction of the single cell 40, even when a plurality of single cells 40 are stacked in such a manner that the front-rear direction orientations are alternately flipped, they can be gathered at the same position in the front-rear direction.

[0050] Return Figure 2 , an exhaust passage 46 is provided on the single cell 40, which connects the safety valves 44 of a plurality of single cells 40 and allows the gas released from the safety valves 44 to flow. For example, the exhaust passage 46 is constituted by a cover covering the safety valve 44. The exhaust passage 46 extends in the direction in which the safety valves 44 are arranged, that is, the stacking direction of the single cells 40, and guides the gas to a pressure release valve 13 described later.

[0051] The housing 20 includes a housing main body 21 having an upper opening and a housing cover 23 covering the opening portion of the housing main body 21. The housing main body 21 has: a front wall portion 82 and a rear wall portion 84 which are provided to extend in the left-right direction; a left wall portion 86 which connects the left end portions of the front wall portion 82 and the rear wall portion 84; a right wall portion 87 which connects the right end portions of the front wall portion 82 and the rear wall portion 84; and a bottom wall portion 88. The space surrounded by the front wall portion 82, the rear wall portion 84, the left wall portion 86, and the right wall portion 87 constitutes a single cell accommodation space 25 for accommodating the single cell stack 30.

[0052] In addition, the upper end portions of the front wall portion 82, the rear wall portion 84, the left wall portion 86, and the right wall portion 87 of the housing main body 21 are continuously connected along the entire circumference.

[0053] An opening portion 86a for communicating the single cell accommodation space 25 with the outside is provided on the left wall portion 86. The opening portion 86a is provided at a substantially central portion of the left wall portion 86 in the up-down direction and the front-rear direction, and its periphery is closed.

[0054] As Figure 2 and Figure 4 shown, a pressure plate 28 is mounted on the opening 86a with a seal 16 (such as a rubber seal) interposed therebetween. By fixing the pressure plate 28 to the left wall portion 86, the pressure plate 28 presses the single cells 40 toward the housing 20 in the stacking direction. More specifically, by fixing the pressure plate 28 to the left wall portion 86, the pressure plate 28 contacts the end plates 31 of the two single cell stacks 30 from the opening 86a. The pressure plate 28 presses the end plates 31 in the stacking direction, whereby the plurality of single cells 40 temporarily fixed by the plate clamp 50 with a predetermined pressure are further pressed in the stacking direction and held in the housing 20. The fixing of the pressure plate 28 to the left wall portion 86 is performed by welding such as friction stir welding, for example.

[0055] Thus, in the battery pack 10, the plurality of single cells 40 can be pressed and held in the housing 20 by the pressure plate 28 without modularizing them, so that the space efficiency and energy density can be improved. In addition, since the periphery of the opening 86a is closed, compared with an opening whose periphery is not closed (for example, an opening whose upper end portion of the left wall portion has an open shape), it is possible to suppress a decrease in the rigidity of the housing 20 due to the provision of the opening 86a, and the impact resistance against external impacts can be improved.

[0056] In addition, since the pressure plate 28 faces the end plate 31 and presses the single cell 40 toward the housing 20 with the end plate 31 interposed therebetween, compared with the case where the pressure plate 28 directly presses the single cell 40 without the end plate 31 interposed therebetween, the impact on the single cell 40 can be mitigated when there is an impact from the outside.

[0057] The end plate 31 has a flange portion 31f provided on the surface that abuts against the single cell 40, and a convex portion 31p that abuts against the pressure plate 28 and protrudes toward the left wall portion 86 side. The end plate 31 is configured such that the area of the contact surface 311 (the surface on the flange portion 31f side) with the single cell 40 is larger than the area of the contact surface 312 (the surface on the convex portion 31p side) with the pressure plate 28. Thereby, local pressing of the single cell 40 can be suppressed.

[0058] In addition, the opening 86a is smaller than the contact surface 311 of the end plate 31 with the single cell 40. Specifically, the lengths of the opening 86a in the vertical direction and the front-rear direction are smaller than the length of the contact surface 311 of the end plate 31 with the single cell 40. Thus, since the opening 86a is set to be small, it is possible to further suppress a decrease in the rigidity of the housing 20 due to the provision of the opening 86a.

[0059] In addition, since the end plate 31 is integrally provided with the plurality of single cells 40 by the plate clamp 50, even when pressed by the pressure plate 28, displacement of the position relative to the single cell 40 can be prevented.

[0060] AsFigure 1 and Figure 4 As shown, two pressure release valves 13 are provided on the pressurizing plate 28, each of which is connected to the single cell storage space 25. A flow path (not shown) is formed on the pressurizing plate 28 to connect the exhaust passage 46 with the pressure release valve 13. When the internal pressure of the single cell storage space 25 rises abnormally due to the gas generated from the safety valve 44 of the single cell 40, the pressure release valve 13 opens to release the gas in the housing 20 to the outside.

[0061] Here, the pressurizing plate 28 and the opening 86a will be described in more detail.

[0062] like Figure 4 As shown, the pressure plate 28 has a flange portion 281 opposed to the peripheral portion of the opening portion 86a of the left wall portion 86, a convex portion 282 protruding from the opening portion 86a to the inside of the housing 20 and pressing the single battery 40 via the end plate 31, and two openings 283 for mounting the pressure release valve 13. The pressure plate 28 is fixed to the left wall portion 86 of the housing body 21 at the flange portion 281, and the convex portion 282 protrudes from the opening portion 86a to the inside of the housing 20 and presses the plurality of single batteries 40 via the end plate 31.

[0063] In the opening 86a, a step portion 86s is formed at a position outside the housing 20, and the pressure plate 28 is fixed to the left wall portion 86 in such a manner that the flange portion 281 is fitted into the step portion 86s via the seal 16. At this time, the flange portion 281 of the pressure plate 28 is provided at a position inside the outer surface of the left wall portion 86, and the pressure plate 28 does not protrude from the outside of the left wall portion 86. With such a structure, when an impact is applied from the left side of the housing 20, the left wall portion 86 receives more impact before the impact is applied to the pressure plate 28, so that the impact applied to the single cell 40 via the pressure plate 28 and the end plate 31 can be mitigated.

[0064] Furthermore, since the seal 16 is provided between the step 86s and the flange 281 of the pressure plate 28, the waterproofness of the housing 20 can be ensured. In particular, in this embodiment, since the step 86s is provided on the peripheral edge of the opening 86a, the seal 16 can be easily arranged.

[0065] Back to Figure 2, in front of and to the left of the front wall portion 82, a bulging portion 22 is formed so as to protrude further forward from the front wall portion 82. A space is formed inside the bulging portion 22, a first opening portion 91 is provided on the front surface, and a second opening portion 92 is also provided on the upper surface. A terminal block 60 for connecting and taking out the conductive member 70 is provided in the internal space of the bulging portion 22, constituting an output terminal storage space 27. On the terminal block 60, the terminal portion (output terminal) of the output conductive member 61 extending from the single battery storage space 25 to the output terminal storage space 27 is electrically connected to the terminal portion of the taking-out conductive member 70 extending into the output terminal storage space 27 from the first opening portion 91. The output conductive member 61 includes a positive-side bus bar 62 and a negative-side bus bar 63, and the positive-side bus bar 62 and the negative-side bus bar 63 extend from the positive-side output terminal and the negative-side output terminal of two single battery stacks 30 electrically connected in series, respectively. The taking-out conductive member 70 includes a positive-side bus bar 72 and a negative-side bus bar 73, and the positive-side bus bar 72 and the negative-side bus bar 73 are connected to, for example, an external positive terminal and negative terminal, respectively.

[0066] Thus, inside the housing 20, there are provided: a single battery storage space 25 that stores two single battery stacks 30; and an output terminal storage space 27 that is disposed in front of and to the left of the single battery storage space 25 and is connected to the taking-out conductive member 70. In addition, the number of the single battery stacks 30 stored in the single battery storage space 25 may be one or three or more.

[0067] The height of the region in the front wall portion 82 that separates the single battery storage space 25 and the output terminal storage space 27 (hereinafter, this part is referred to as the partition portion 85) is lower than other regions. The positive-side bus bar 62 and the negative-side bus bar 63 extend from above the partition portion 85 to the output terminal storage space 27 and are fixed to the terminal block 60 provided in the output terminal storage space 27.

[0068] In addition, as Figure 1 shown, a signal line connector 67 is provided in the output terminal storage space 27. The signal line connector 67 is connected to a signal line via a through hole that communicates the single battery storage space 25 and the output terminal storage space 27.

[0069] As Figure 2As shown, a housing cover 23 is installed at the upper ends of the front wall portion 82, left wall portion 86, right wall portion 87, and rear wall portion 84 of the housing main body 21 with a first seal 11 (e.g., a rubber seal) interposed therebetween. The housing cover 23 is fixed to the upper surface of the housing main body 21 by welding such as friction stir welding. A second seal 12 (e.g., a foam seal) is provided in the gap between the partition wall portion 85 and the housing cover 23, and the single-cell accommodation space 25 is sealed from the outside by the first seal 11 and the second seal 12. By sealing the single-cell accommodation space 25 from the outside, it is possible to prevent foreign matter from entering the single-cell accommodation space 25 and suppress deterioration of the single cells 40. In addition, it is preferable to provide a seal such as a foam seal also in the gap between the through-hole provided in the partition wall portion 85 and the signal line.

[0070] The battery pack 10 configured in this way does not include auxiliary devices such as a junction box for accommodating contactors, fuses, etc., and an ECU. Therefore, when the battery pack 10 is used alone, the junction box and / or the ECU can be connected to the battery pack 10. In addition, when multiple battery packs 10 are used, the battery packs 10 can also be electrically connected to each other through a distribution box, and the junction box and / or the ECU can be connected to the distribution box. Further, the junction box and / or the ECU can also be incorporated in the distribution box, and the multiple battery packs 10 can be connected to the junction box and / or the ECU in the distribution box.

[0071] (Modified example of battery pack)

[0072] As Figure 5 shown, the housing main body 21 may further have a central wall portion 83 extending in the left-right direction between the front wall portion 82 and the rear wall portion 84. In this case, single-cell laminates 30 are accommodated between the front wall portion 82 and the central wall portion 83, and between the central wall portion 83 and the rear wall portion 84, respectively.

[0073] In addition, in the above-described embodiment, the pressure plate 28 is installed at the opening 86a of the left wall portion 86 by welding such as friction stir welding, but it is not limited thereto. For example, as Figure 6 shown, the following structure may also be adopted: bolt through-holes 285 are provided in the pressure plate 28 and the left wall portion 86, and bolts (not shown) passing through the bolt through-holes 285 are fastened in bolt holes provided in the central wall portion 83 or the like, thereby installing the pressure plate 28 at the left wall portion 86.

[0074] The above has described one embodiment of the present invention with reference to the drawings, but the present invention is of course not limited to this embodiment. Obviously, those skilled in the art can conceive of various modification examples or correction examples within the scope described in the technical solution, and it should be understood that these modification examples and correction examples also belong to the technical scope of the present invention. In addition, within the scope not departing from the gist of the invention, the constituent elements in the above-described embodiment can be arbitrarily combined.

[0075] For example, in the above embodiment, the end plate 31 is disposed only on one side (the left side in the embodiment) of the plurality of cells 40 in the stacking direction, but may be disposed on both sides of the plurality of cells 40 in the stacking direction.

[0076] At least the following matters are described in this specification: In parentheses, corresponding components in the above-mentioned embodiment are shown as an example, but the present invention is not limited to this.

[0077] (1) A battery pack (battery pack 10) comprising:

[0078] a plurality of stacked single cells (single cells 40); and

[0079] a housing (housing 20 ) for housing the plurality of cells;

[0080] In this case, an opening (opening 86a) is provided on the side wall (left wall 86) of the housing in the stacking direction of the cells, and the periphery of the opening is closed.

[0081] A pressurizing plate (pressurizing plate 28 ) for pressing the unit cells toward the case in the stacking direction is attached to the opening.

[0082] According to (1), a plurality of cells can be pressed and held in the housing by the pressure plate without modularizing them, thereby improving the space efficiency of the battery pack. In addition, the opening of the housing provided with the pressure plate is sealed around, thereby suppressing the reduction in rigidity of the housing due to the provision of the opening, and improving the impact resistance against external impact.

[0083] (2) The battery pack according to (1), wherein:

[0084] The battery pack further includes an end plate (end plate 31 ) provided at an end of the single cells in the stacking direction and facing the pressure plate.

[0085] The pressurizing plate presses the single cell toward the case via the end plate.

[0086] According to (2), by providing the end plate between the unit cell and the pressure plate, the impact on the unit cell can be mitigated compared to the case where the unit cell is directly pressed by the pressure plate.

[0087] (3) The battery pack according to (2), wherein:

[0088] The area of ​​the contact surface (contact surface 311 ) of the end plate that contacts the battery cell is larger than the area of ​​the contact surface (contact surface 312 ) of the end plate that contacts the pressure plate.

[0089] According to (3), by increasing the contact surface between the end plate and the single cell, it is possible to suppress the local pressing of the single cell by the pressing plate.

[0090] (4) The battery pack according to (2) or (3), wherein

[0091] The opening portion is smaller than the contact surface (contact surface 311) of the end plate surface that contacts the single cell.

[0092] According to (4), by making the opening portion smaller, it is possible to suppress a decrease in the rigidity of the housing due to the provision of the opening portion.

[0093] (5) The battery pack according to any one of (2) to (4), wherein

[0094] The end plate is integrally provided with the plurality of single cells by a restraint member (plate clamp 50).

[0095] According to (5), it is possible to prevent the positional deviation of the end plate relative to the single cell.

[0096] (6) The battery pack according to any one of (1) to (5), wherein

[0097] The pressing plate has:

[0098] A flange portion (flange portion 281) that faces the peripheral portion of the opening portion; and

[0099] A convex portion (convex portion 282) that protrudes from the opening portion toward the inside of the housing and presses the single cell against the housing.

[0100] According to (6), it is possible to press the single cell with the convex portion of the pressing plate that protrudes from the opening portion toward the inside of the housing.

[0101] (7) The battery pack according to (6), wherein

[0102] A stepped portion (stepped portion 86s) is provided at the peripheral portion of the opening portion, and the flange portion of the pressing plate is embedded in and faces the stepped portion.

[0103] The flange portion of the pressing plate is provided at a position closer to the inside than the outer surface of the side wall portion of the housing.

[0104] According to (7), for an impact from the outside of the housing, more of the impact is received by the side wall portion of the housing, so it is possible to mitigate the impact applied to the single cell.

[0105] (8) The battery pack according to (7), wherein

[0106] A seal (seal 16) is provided between the stepped portion of the housing and the flange portion of the pressure plate.

[0107] According to (8), even in the structure where the pressure plate is provided at the opening of the side wall portion of the housing, the waterproofness of the housing can be ensured.

[0108] (9) The battery pack according to any one of (1) to (8), wherein

[0109] The housing has: a housing main body (housing main body 21) that has the side wall portion and houses the single cell; and a housing cover (housing cover 23) that covers the housing main body from above.

[0110] The upper end portions of the side wall portion of the housing main body are continuously connected along the entire circumference.

[0111] The housing cover is connected to the upper end portion of the housing main body via a seal (first seal 11).

[0112] According to (9), since the upper end portions of the side wall portion of the housing main body are continuously provided along the entire circumference, the rigidity of the housing main body can be improved. In addition, since the housing cover is connected to the upper end portion of the housing main body via a seal, the waterproofness of the housing can be ensured.

[0113] (10) The battery pack according to any one of (1) to (9), wherein

[0114] A pressure release valve (pressure release valve 13) is provided on the pressure plate, and the pressure release valve can discharge the gas released from the safety valve (safety valve 44) provided in the single cell to the outside of the housing.

[0115] According to (10), the gas released to the inside of the housing due to thermal runaway can be discharged to the outside of the housing, and the pressure inside the housing can be released. Therefore, breakage of the housing can be suppressed.

Claims

1. A battery pack comprising: A plurality of stacked single cells; and a housing for housing the plurality of cells; in, An opening is provided on the side wall of the housing in the stacking direction of the cells, and the periphery of the opening is closed. A pressure plate for pressing the unit cells toward the case in the stacking direction is attached to the opening.

2. The battery pack according to claim 1, wherein: The battery pack further includes an end plate provided at an end portion of the single cells in the stacking direction and facing the pressure plate. The pressurizing plate presses the single cell toward the case via the end plate.

3. The battery pack according to claim 2, wherein: An area of ​​a surface of the end plate that contacts the battery cell is larger than an area of ​​a surface of the end plate that contacts the pressure plate.

4. The battery pack according to claim 2, wherein: The opening is smaller than a surface of the end plate that comes into contact with the battery cell.

5. The battery pack according to claim 2, wherein: The end plate is provided integrally with the plurality of cells using a restraining member.

6. The battery pack according to any one of claims 1 to 5, wherein: The pressure plate has: a flange portion that is opposed to a peripheral edge portion of the opening portion; and The convex portion protrudes from the opening toward the inner side of the case and presses the single cell toward the case.

7. The battery pack according to claim 6, wherein: A step portion is provided at the peripheral edge of the opening, the flange portion of the pressurizing plate being embedded in the step portion and facing the flange portion of the pressurizing plate. The flange portion of the pressure plate is provided on an inner side than an outer surface of the side wall portion of the housing.

8. The battery pack according to claim 7, wherein: A seal is provided between the step portion of the housing and the flange portion of the pressure plate.

9. The battery pack according to any one of claims 1 to 5, wherein: The housing includes: a housing body having the side wall portion and accommodating the battery cell; and a housing cover covering the housing body from above. The upper end portions of the side walls of the housing body are continuously connected along the entire circumference. The housing cover is connected to the upper end portion of the housing body via a seal.

10. The battery pack according to any one of claims 1 to 5, wherein: The pressurizing plate is provided with a pressure release valve capable of discharging gas released from a safety valve provided in the single cell to the outside of the case.

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