Cell stack restraint structure

Abstract

A pair of side walls (16) facing each other are formed in a lower case (12). An upper case (13) covers an upper part of the lower case (12). Cell stacks (14) are inserted between the side walls (16) in a state in which a plurality of cells (17) are stacked and compressed, and are constrained by frictional force against the side walls (16). Restraining plates (37) are supported by the lower case (12) or the upper case (13), face the cell stacks (14), and restrain displacement of the cell stacks (14).

Description

Cell stack restraining structure

[0001] The present invention relates to a cell stack restraining structure.

[0002] Patent Document 1 discloses that a cell stack formed by stacking a plurality of cells is inserted between side walls of a lower case in a compressed state, and the cell stack is restrained by frictional force between the cell stack and the side walls.

[0003] Japanese Unexamined Patent Publication No. 2023-55318

[0004] If an attempt is made to restrain a cell stack only by frictional force with side walls even against a large impact load such as a vehicle collision, it is necessary to increase the thickness of the cell exterior, the end holders of the cell stack, the side walls of the lower case, and the like. As a result, the volumetric energy density may decrease, or the operating temperature range may be reduced in consideration of the pressure resistance of the cells, which may lead to a decrease in battery performance. An object of the present invention is to suppress a decrease in battery performance in a cell stack restraining structure.

[0005] A cell stack restraining structure according to one aspect of the present invention includes a lower case, an upper case, a cell stack, and a stopper plate. The lower case is formed with a pair of opposing side walls. The upper case closes an upper portion of the lower case. The cell stack is inserted between the side walls in a state where a plurality of cells are stacked and compressed, and is restrained by frictional force between the cell stack and the side walls. The stopper plate is supported by the lower case or the upper case, faces the cell stack, and restrains displacement of the cell stack.

[0006] According to the present invention, since displacement of the cell stack is restrained by the stopper plate, there is no need to increase the thickness of the cell exterior, the end holders of the cell stack, the side walls of the lower case, and the like in anticipation of a large impact load. Therefore, it is possible to avoid a decrease in volumetric energy density and a reduction in the operating temperature range in consideration of the pressure resistance of the cells, thereby suppressing a decrease in battery performance.

[0007] This is a diagram showing the cell stack constraint structure. This is a diagram explaining the constraint force of the cell stack. This is a diagram showing the arrangement of the cell stack. This is a diagram showing the cell stack restraint structure. This is a diagram showing the restraint plate. This is a diagram showing the bus bar. This is a diagram showing the missing part. This is a diagram showing the lower case. This is a diagram showing the lower case.

[0008] Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings are schematic and may differ from actual examples. Furthermore, the following embodiments are illustrative examples of devices and methods for realizing the technical concept of the present invention, and do not limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0009] 《Embodiment》 《Configuration》 In the following description, the three mutually orthogonal directions will be conveniently referred to as the width direction, the front-rear direction, and the up-down direction. Figure 1 is a diagram showing the cell stack restraint structure 11. Here, the cross-sections of the cell stack restraint structure 11 along the front-rear direction and the up-down direction are shown as viewed from the width direction. The cell stack restraint structure 11 is applied to a battery device mounted on an automobile and comprises a lower case 12, an upper case 13, and a cell stack 14.

[0010] The lower case 12 is made of aluminum, for example, and is formed in a container shape with both sides in the width direction, both sides in the front-rear direction, and the bottom closed, and the top open. The lower case 12 has a pair of side walls 16 facing each other in the front-rear direction. The side walls 16 are walls that run along the width direction and the vertical direction. The upper case 13 is made of aluminum, for example, and is formed in a plate shape that runs along the width direction and the front-rear direction, and is fastened to close the upper end of the lower case 12. The cell stack 14 is made by stacking a plurality of cells 17 in the front-rear direction and sandwiching both ends with end holders 18. Therefore, the front-rear direction is the stacking direction of the cells 17. The cells 17 are secondary batteries and are formed in a flat plate shape that runs along the width direction and the vertical direction. The cell stack 14 is inserted between the side walls 16 in a compressed state in the front-rear direction and is restrained by the frictional force with the side walls 16.

[0011] Figure 2 illustrates the restraining force of the cell stack 14. Here, the horizontal axis represents the restraining force, and the vertical axis represents the dimension in the stacking direction. The dimension of the lower case 12 is the internal dimension along the stacking direction between the side walls 16, and the dimension of the cell stack 14 is the external dimension along the stacking direction between the end holders 18. When the cell stack 14 is inserted between the side walls 16 in a compressed state in the front-rear direction, the dimensions of the cell stack 14 are made larger than the dimensions of the lower case 12 to set the interference fit. The restraining force increases as the cell stack 14 is compressed in the stacking direction and its dimensions in the stacking direction decrease. At this time, the dimensions of the lower case 12 gradually increase due to the reaction force of the cell stack 14. The restraining force F1 is the lower limit value at which the cell stack 14 does not come off, and the restraining force F2 is the upper limit value at which compression does not cause any problems with the cell stack 14. The range from restraining force F1 to restraining force F2 is the range in which the restraining force occurs.

[0012] Figure 3 shows the arrangement of the cell stacks 14. Here, the cross-sections of the cell stack restraint structure 11 along the width and vertical directions are shown as viewed from the front and rear directions. Four cell stacks 14 are housed in the lower case 12, arranged in the width direction, and a stepped portion 21 is formed on the bottom plate of the lower case 12. The stepped portion 21 extends in the front and rear direction from the center in the width direction, and its cross-sectional shape as viewed from the front and rear directions is a hat shape that is convex upwards. The stepped portion 21 is also a saddle shape that is concave upwards when viewed from below. Two cell stacks 14 are arranged on each side in the width direction, flanking the stepped portion 21. The vertical dimension hs and the width dimension ws of the stepped portion 21 correspond to the vertical dimension hc and the width dimension hc of the cell stack 14, and are set to be approximately the same or slightly larger.

[0013] Figure 4 shows the restraint structure of the cell stack 14. Here, the cross-section along the width and vertical directions is shown from the front-rear direction in one of the width directions. The other width direction has the same configuration except that it is inverted in the width direction, so a detailed explanation is omitted. A cooling duct 31 is provided between two cell stacks 14 that are aligned in the width direction. The cooling duct 31 is a rectangular tube extending in the front-rear direction, and both sides in the width direction are sandwiched between the cell stacks 14. A bracket 36 is positioned above the cell stack 14. The bracket 36 is formed in a plate shape along the width and front-rear directions, and is integrated with the lower case 12 by fastening with electronic components such as a controller and a service disconnect switch attached. A restraint plate 37 and a restraint plate 38 are joined to the lower surface of the bracket 36. The restraint plates 37 and 38 face the cell stack 14 and restrain the displacement of the cell stack 14.

[0014] The restraining plates 37 are provided one on the outside in the width direction for each of the two cell stacks 14, and restrain the displacement of each cell stack 14 in the width direction and vertical direction. The restraining plates 37 extend along the entire length in the front-rear direction, and their upper ends are joined to the bracket 36 by welding. Here, they are joined by welding, but they may also be fastened with bolts or rivets, or integrally formed by bending. The lower end of the restraining plate 37 is formed in an L-shape when viewed from the front-rear direction by surfaces along the front-rear and width directions and surfaces along the front-rear and vertical directions, and faces the upper and side surfaces that constitute the upper corner of the cell stack 14. In the restraining plate 37, the distances in the width direction and vertical direction from the joint point with the bracket 36 to the surface facing the cell stack 14 are made as small as possible. This is to reduce the moment arm when a load is received from the displaced cell stack 14.

[0015] The restraining plates 38 are provided one on the inside in the width direction for each of the two cell stacks 14, and restrain vertical displacement of each cell stack 14. The restraining plates 38 extend along the entire front-rear direction, and their upper ends are joined to the bracket 36 by welding. Here, they are joined by welding, but they may also be fastened with bolts or rivets, or integrally formed by bending. The lower end of the restraining plate 38 has a surface formed along the front-rear and width directions, and faces the upper surface that constitutes the upper corner of the cell stack 14. In the restraining plate 38, the distance in the width direction and vertical direction from the joint point with the bracket 36 to the surface facing the cell stack 14 is made as small as possible. This is to reduce the moment arm when a load is received from a displaced cell stack 14. Since one side of the cell stack 14 in the width direction is in contact with the cooling duct 31, it is not necessary to consider displacement toward the cooling duct 31.

[0016] Figure 5 shows the restraining plates 37 and 38. (a) in the figure shows the tip side of the restraining plate 37. A gap d is provided between the cell stack 14 and the restraining plate 37 in the width direction and vertical direction. (b) in the figure shows the tip side of the restraining plate 38. A gap d is provided between the cell stack 14 and the restraining plate 38 in the width direction and vertical direction. Figure 6 shows the bus bar 41. Here, one side in the width direction of the lower case 12 is shown as viewed from above. The bus bar 41 (conductor) is connected to the terminals of the cell stack 14. The aforementioned gap d is made smaller than the amount of displacement of the cell stack 14 that would cause the bus bar 41 to break, for example, about 1 to 2 mm.

[0017] Figure 7 shows the missing portions 47 and 48. Figure (a) shows the restraint plate 37 as viewed from the width direction. The restraint plate 37 has a missing portion 47 formed in the front-rear direction, which is a portion of the restraint plate 37 that is cut out to allow the harness to pass through and to avoid interference with other parts. The missing portion 47 is formed by cutting out a portion of the lower end side of the restraint plate 37 that is facing the cell stack 14. Figure (b) shows the restraint plate 38 as viewed from the width direction. The restraint plate 38 has a missing portion 47 formed in the front-rear direction, which is a portion of the restraint plate 38 that is cut out to allow the harness to pass through and to avoid interference with other parts. The missing portion 48 is formed by bending a portion of the lower end side of the restraint plate 38 that is facing the cell stack 14 to separate it from the cell stack 14. The length of the missing portions 47 and 48 in the stacking direction is smaller than the maximum number n of cells 17 that can maintain a restrained state by the frictional force between the cells 17 against a predetermined impact load G. The impact load G is the maximum possible impact load. Let m be the weight of cell 17, F be the restraining force, and μ be the coefficient of friction between cells 17. Set the maximum number n such that the following equations are satisfied: nmG < Fμ n < Fμ / mG

[0018] Figure 8 shows the lower case 12. Here, the lower case 12 is shown as viewed from above. The lower case 12 has a pair of side walls 15 that are opposite each other in the width direction. The side walls 15 are wall bodies that run along the front-rear and up-down directions. The lower case 12 has regions 51 and 52 on both sides in the width direction, separated by a stepped portion 21. One region 51 is surrounded by a pair of side walls 16, one side wall 15, and the stepped portion 21, while the other region 52 is surrounded by a pair of side walls 16, the other side wall 15, and the stepped portion 21. Regions 51 and 52 each have four bosses 56 and two bosses 57. The bosses 56 are columnar in shape, extending upward from the floor surface to the upper side of the lower case 12 at each of the four corners of regions 51 and 52 when viewed from above, and brackets 36 are fastened to the screw holes. The boss 57 is a columnar shape that extends upward from the floor surface to the upper side of the lower case 12, located in the center of the width direction along each side wall 16 of regions 51 and 52, and a cooling duct 31 is fastened to the screw hole.

[0019] The lower case 12 has mounting points 58 formed on flanges protruding from both sides in the front-rear direction to the vehicle body. The mounting points 58 are through holes that penetrate in the vertical direction, and there are two on one side in the width direction of the lower case 12, two on the other side in the width direction, and one in the center in the width direction. There is one set of these on each side in the front-rear direction, for a total of ten locations. On the stepped portion 21, bosses 59 are formed at multiple positions along the front-rear direction on both sides in the width direction of the upper surface. The bosses 59 are low-profile convex shapes, and auxiliary equipment such as junction boxes and fuses are fastened to the screw holes. There is one boss 59 at each end in the front-rear direction, and two in the center in the front-rear direction. There is one set of these on each side in the width direction, for a total of eight locations.

[0020] Figure 9 shows the lower case 12. Here, the lower case 12 is shown as viewed from the outside in the front-rear direction. Below the stepped portion 21 on the lower surface of the lower case 12, underfloor piping 61 of the vehicle is arranged along the front-rear direction. The underfloor piping 61 is, for example, fuel piping. Ribs 62 are formed on the outer circumferential surface of the side wall 16 of the lower case 12. The ribs 62 are provided on the side wall 16 at a position that overlaps with the cell stack 14 when viewed from the front-rear direction, and are convex outward in the front-rear direction and extend in the vertical direction. Two ribs 62 are arranged side by side in the width direction for each cell stack 14, and there is one set of these on each side in the front-rear direction, for a total of four locations.

[0021] 《Effects and Effects》 Next, the main effects and effects of the embodiment will be described. (1) The cell stack restraint structure 11 comprises a lower case 12, an upper case 13, a cell stack 14, and restraining plates 37 and 38. The lower case 12 has a pair of opposing side walls 16 formed thereon. The upper case 13 closes the top of the lower case 12. The cell stack 14 is inserted between the side walls 16 in a state where a plurality of cells 17 are stacked and compressed, and is restrained by the frictional force with the side walls 16. The restraining plates 37 and 38 are supported by the lower case 12, face the cell stack 14, and restrain the displacement of the cell stack 14. In this way, the displacement of the cell stack 14 is restrained by the restraining plates 37 and 38, so there is no need to thicken the outer casing of the cells 17, the end holders 18 of the cell stack 14, the side walls 16 of the lower case 12, etc., in anticipation of large impact loads. Therefore, it is possible to avoid a decrease in volumetric energy density or a reduction in the operating temperature range due to considerations of the pressure resistance of the cell 17, thereby suppressing a decrease in battery performance. Even when subjected to a large impact load such as a vehicle collision, the restraint plates 37 and 38 restrain the displacement of the cell stack 14, thereby suppressing rupture or short circuit of the battery circuit.

[0022] (2) The two directions perpendicular to the stacking direction of the cells 17 are the width direction and the vertical direction. The restraining plate 37 restrains the displacement of the cell stack 14 in the width direction and the vertical direction. This makes it possible to restrain the displacement of the cell stack 14 in the two directions perpendicular to the stacking direction. (3) The cell stack restraining structure 11 is equipped with a bus bar 41. The bus bar 41 is connected to the terminals of the cell stack 14. A gap d is provided between the cell stack 14 and the restraining plates 37 and 38, and the gap d is smaller than the amount of displacement of the cell stack 14 that would cause the bus bar 41 to break. This makes it possible to suppress the breakage of the bus bar 41.

[0023] (4) The cell stack restraint structure 11 includes a bracket 36. Electronic components are attached to the bracket 36. The restraining plates 37 and 38 are provided on the bracket 36. The bracket 36 is not specifically provided for attaching the restraining plates 37 and 38, but is an existing bracket to which electronic components are attached. By providing the restraining plates 37 and 38 on the existing bracket 36 in this way, the increase in the number of parts, weight, and cost can be suppressed. (5) The bracket 36 is fitted onto the cell stack 14 from above. This reduces the moment arm when the bracket 36 receives a load from the cell stack 14, and prevents the bracket 36 from falling off or deforming.

[0024] (6) The bracket 36 is integrated with the lower case 12. This allows the bracket 36 to be installed before fastening the upper case 13, improving ease of assembly. The number of parts can also be reduced by integrally molding the bracket 36 with the lower case 12 by casting. (7) The restraining plate 37 (or restraining plate 38) extends in the stacking direction of the cells 17, and a cutout portion 47 (or cutout portion 48) is formed by cutting off a part of it in the stacking direction. The length of the cutout portion 47 and the cutout portion 48 in the stacking direction is smaller than the maximum number of cells 17 that can maintain a restrained state by the frictional force between the cells 17 against a predetermined impact load. This prevents some cells 17 from coming off the cell stack 14.

[0025] (8) The two directions perpendicular to the stacking direction of the cells 17 are the width direction and the vertical direction. The cell stack restraint structure 11 is provided with a plurality of cell stacks 14 arranged in the width direction. On the bottom plate of the lower case 12, a hat-shaped step portion 21 is formed between the cell stacks 14 that are in the center in the width direction, extending in the stacking direction, and the cross-sectional shape viewed from the stacking direction is convex upward. This improves the rigidity of the lower case 12, suppresses variations in the amount of deformation in the side walls 16, maintains the restraining force on the cell stacks 14 within an appropriate range, and suppresses the displacement of the cell stacks 14. Furthermore, it is not necessary to thicken the outer casing of the cell 17, the end holders 18 of the cell stacks 14, the side walls 16 of the lower case 12, etc. Therefore, it is possible to avoid a decrease in volumetric energy density or a reduction in the operating temperature range and charge / discharge range of the cell 17, and suppress a decrease in battery performance. In addition, it is possible to restrain a plurality of cell stacks 14 to a common side wall 16 formed on a single lower case 12, which also provides excellent layout flexibility.

[0026] (9) The stepped portion 21 has a vertical dimension hs and a width dimension ws that correspond to the vertical dimension hc and width dimension wc of the cell stack 14. This improves the rigidity of the lower case 12, suppresses variations in the amount of deformation in the side wall 16, maintains the restraining force on the cell stack 14 within an appropriate range, and suppresses the displacement of the cell stack 14. (10) The cell stack restraining structure 11 is equipped with a bracket 36. Electronic components are fixed to the bracket 36. The lower case 12 has columnar bosses 56 that extend upward from the floor surface and to which the bracket 36 is fastened, at the four corners viewed from above in one region 51 and the other region 52 in the width direction of the stepped portion 21. This improves the rigidity of the lower case 12, suppresses variations in the amount of deformation in the side wall 16, maintains the restraining force on the cell stack 14 within an appropriate range, and suppresses the displacement of the cell stack 14.

[0027] (11) The lower case 12 has mounting points 58 for the vehicle body formed on both sides in the stacking direction at the center of the width direction of the upper end. This improves the rigidity of the lower case 12, suppresses variations in the amount of deformation in the side wall 16, maintains the restraining force on the cell stack 14 within an appropriate range, and suppresses the displacement of the cell stack 14. (12) The stepped portion 21 has bosses 59 formed at multiple positions along the stacking direction on both sides in the width direction of the upper surface, to which auxiliary equipment is fastened. This improves the rigidity of the lower case 12, suppresses variations in the amount of deformation in the side wall 16, maintains the restraining force on the cell stack 14 within an appropriate range, and suppresses the displacement of the cell stack 14. By making the bosses 59 low in height and convex, the castability of the lower case 12 is improved.

[0028] (13) Below the stepped portion 21 on the lower surface of the lower case 12, the underfloor piping 61 of the vehicle, which extends along the stacking direction, is arranged. This makes effective use of the space below the stepped portion 21. The stepped portion 21 is saddle-shaped, concave upwards when viewed from below, so arranging the underfloor piping 61 there contributes to lowering the vehicle's floor. (14) Ribs 62 extending in the vertical direction are formed on the outer circumferential surface of the side wall 16 at positions on both sides in the stacking direction. This improves the rigidity of the lower case 12, suppresses variations in the amount of deformation in the side wall 16, maintains the restraining force on the cell stack 14 within an appropriate range, and suppresses the displacement of the cell stack 14.

[0029] 《Modifications》 In the embodiment, a configuration in which the restraining plates 37 and 38 are supported by the lower case 12 via a bracket 36 has been described, but the invention is not limited thereto. That is, the restraining plates 37 and 38 may be directly or indirectly supported by the upper case 13. In the embodiment, a configuration in which the restraining plate 38 restrains only vertical displacement in the cell stack 14 has been described, but the invention is not limited thereto. That is, the restraining plate 38 may also be configured to restrain both horizontal and vertical displacement in the cell stack 14, similar to the restraining plate 37. In the embodiment, a configuration in which four cell stacks 14 are mounted on the lower case 12 has been described, but the invention is not limited thereto, and the number may be three or fewer, or five or more.

[0030] Although the above description has been made with reference to a limited number of embodiments, the scope of the rights is not limited to those embodiments, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art.

[0031] 11...Cell stack restraint structure, 12...Lower case, 13...Upper case, 14...Cell stack, 15...Side wall, 16...Side wall, 17...Cell, 18...End holder, 21...Stepped section, 31...Cooling duct, 36...Bracket, 37...Stop plate, 38...Stop plate, 41...Bus bar, 47...Missing section, 48...Missing section, 51...Area, 52...Area, 56...Boss, 57...Boss, 58...Mounting point, 59...Boss, 61...Underfloor piping, 62...Rib

Claims

1. A cell stack restraint structure characterized by comprising: a lower case having a pair of opposing side walls; an upper case closing the upper part of the lower case; a cell stack inserted between the side walls in a stacked and compressed state and restrained by frictional force with the side walls; and a restraining plate supported by the lower case or the upper case, facing the cell stack, and restraining the displacement of the cell stack.

2. The cell stack restraint structure according to claim 1, characterized in that two directions perpendicular to the stacking direction of the cells are defined as the width direction and the vertical direction, and the restraining plate restrains displacement in the width direction and the vertical direction in the cell stack.

3. The cell stack restraint structure according to claim 1, comprising a conductor connected to the terminals of the cell stack, wherein a gap is provided between the cell stack and the restraint plate, and the gap is smaller than the amount of displacement of the cell stack that would cause the conductor to break.

4. The cell stack restraint structure according to claim 1, comprising a bracket to which electronic components are attached, wherein the restraint plate is provided on the bracket.

5. The cell stack restraint structure according to claim 4, characterized in that the bracket is fitted onto the cell stack from above.

6. The cell stack restraint structure according to claim 4, characterized in that the bracket is integrated with the lower case.

7. The cell stack restraint structure according to claim 1, characterized in that the restraint plate extends in the stacking direction of the cells, a missing portion is formed by removing a part of the plate in the stacking direction, and the length of the missing portion in the stacking direction is smaller than the maximum number of cells that can maintain a restrained state by the frictional force between the cells against a predetermined impact load.

8. The cell stack restraint structure according to claim 1, wherein the two directions perpendicular to the stacking direction of the cells are the width direction and the vertical direction, and the cell stack comprises a plurality of the cell stacks arranged in the width direction, and the bottom plate of the lower case has a hat-shaped step formed thereon that extends in the stacking direction between the cell stacks that are in the center in the width direction, and whose cross-sectional shape, when viewed from the stacking direction, is convex upward.

9. The cell stack restraint structure according to claim 8, characterized in that the dimensions of the stepped portion in the vertical direction and the dimensions in the width direction correspond to the dimensions of the cell stack in the vertical direction and the width direction.

10. The cell stack restraint structure according to claim 8, comprising a bracket for which electronic components are fixed, wherein the lower case has columnar bosses formed at the four corners when viewed from above in one region and the other region in the width direction relative to the stepped portion, extending upward from the floor surface and to which the bracket is fastened.

11. The cell stack restraint structure according to claim 8, characterized in that the lower case has mounting points to the vehicle body formed on both sides in the stacking direction at the center of the width direction of the upper end.

12. The cell stack restraint structure according to claim 8, characterized in that the stepped portion has bosses formed on both sides of the upper surface in the width direction at multiple positions along the stacking direction, to which auxiliary equipment is fastened.

13. The cell stack restraint structure according to claim 8, characterized in that underfloor piping of the vehicle extending in the stacking direction is arranged below the stepped portion which is on the lower surface side of the lower case.

14. The cell stack restraint structure according to claim 8, characterized in that ribs extending in the vertical direction are formed on the outer circumferential surface of the side wall at positions on both sides in the stacking direction.

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