Battery pack

Abstract

To provide a battery pack capable of applying high pressure corresponding to expansion and contraction of a secondary battery to the secondary battery in which expansion and contraction due to charge and discharge are largely developed, and applicable regardless of the size of the secondary battery.SOLUTION: The battery pack includes a module M having a plurality of stacked battery cells C, a pack 2 for storing a plurality of modules M, and a slide mechanism part 3 for movably placing a part of the module M in the stacking direction of the battery cells C in accordance with expansion and contraction of the battery cells C, and the module M includes a pressurizing mechanism part 1 for pressurizing the plurality of cells C included in the module M in the stacking direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to a battery pack. [Background technology]

[0002] Patent Document 1 discloses a battery module that addresses the phenomenon of battery cell swelling caused by gas that may be generated when the battery cell is repeatedly charged and discharged. The battery module includes a constant force spring, which is said to be able to maintain a constant surface pressure on the battery cell even when swelling occurs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special table number 2022-554001 Summary of the Invention [Problem to be solved by the invention]

[0004] However, given the configuration of the battery module disclosed in Patent Document 1, pressure can only be applied in a direction perpendicular to the ground surface, and the battery module must be placed vertically. It is unclear whether such a battery module can be placed horizontally. At the same time, it is unclear whether pressure can be applied to the battery module if it is placed horizontally.

[0005] Furthermore, the swelling phenomenon described above occurs in any type of battery, for example, a lithium-ion battery, but the degree of swelling varies depending on the type of battery. For example, the amount of swelling is small in graphite-based batteries, but large in silicon-based batteries.

[0006] For example, in the case of a lithium-ion battery that uses precipitated lithium metal for the negative electrode, swelling of a single electrode is limited to a few micrometers, but when these electrodes are stacked to form a cell or module, swelling can reach extremely large values.

[0007] Furthermore, the degree of pressure required varies from battery to battery, but for example, the configuration of the battery module disclosed in the above-mentioned Patent Document 1 is not capable of applying a large pressure. As mentioned above, when applying pressure to a battery that will swell a lot, a larger pressure is required, so a structure that can apply a large pressure to stacked battery cells is required.

[0008] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a battery pack that can apply high pressure corresponding to the expansion and contraction of a secondary battery, which undergoes large expansion and contraction due to charging and discharging, and that can be applied regardless of the size of the secondary battery. [Means for solving the problem]

[0009] A battery pack in an embodiment of the present invention comprises a module having a plurality of stacked battery cells, a pack that stores a plurality of modules, and a slide mechanism that mounts a portion of the module so that it can move in the stacking direction of the battery cells in accordance with the expansion and contraction of the battery cells, and the module comprises a pressure mechanism that pressurizes the plurality of cells in the module in the stacking direction. [Effects of the Invention]

[0010] By adopting such a configuration, the present invention makes it possible to apply high pressure corresponding to the expansion and contraction of a secondary battery, which undergoes large expansion and contraction due to charging and discharging, and furthermore, can be applied regardless of the size of the secondary battery. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic perspective view showing the overall configuration of a battery pack according to an embodiment of the present invention, illustrating the state of the battery pack when the SOC is 0% and the state of the battery pack when the SOC is 100%. [Figure 2] 2A and 2B are schematic perspective views showing a pair of modules according to an embodiment of the present invention, and FIG. 2A is a schematic perspective view showing the arrangement of spirally formed leaf springs, with the pressure frame not shown. [Figure 3] FIG. 2 is a perspective view of a spiral leaf spring used in the module according to the embodiment of the present invention. [Figure 4] FIG. 2 is an exploded perspective view of the module according to the embodiment of the present invention. [Figure 5] 2(B), where (A) shows the upper part in the Z direction and (B) shows the lower part in the Z direction. [Figure 6] FIG. 2 is a schematic side view of a module according to an embodiment of the present invention, illustrating the force applied to a battery cell. [Figure 7] 1 is a schematic oblique view showing the state of the battery pack when the SOC is 0% and the state of the battery pack when the SOC is 100% in a battery pack according to an embodiment of the present invention, viewed from the bottom of the battery pack upward in the Z direction. [Figure 8] 10 is a schematic perspective view showing the overall configuration of a battery pack according to a modified example of an embodiment of the present invention, showing the state of the battery pack when the SOC is 0% and the state of the battery pack when the SOC is 100%. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings are schematic and may differ from the actual product. Furthermore, the embodiments of the present invention shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the structure, arrangement, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0013] 1 is a schematic perspective view showing the overall configuration of a battery pack P according to an embodiment of the present invention. The battery pack P according to the embodiment of the present invention includes a module M, a pack 2, and a slide mechanism 3. As will be described later, the battery pack P includes a plurality of modules M each including a battery cell C, and is used by being mounted on, for example, a vehicle.

[0014] 1 shows two such battery packs P. That is, the battery pack P on the front side is marked "SOC 0%" and the battery pack P on the back side is marked "SOC 100%." ​​Note that "SOC" here stands for "State of Charge."

[0015] That is, the battery cells C in the battery pack P indicated as "SOC 0%" are in a discharged and contracted state. On the other hand, the battery cells C in the battery pack P indicated as "SOC 100%" are in a charged and expanded state.

[0016] In other words, when the battery pack P is charged or discharged, the battery cells C arranged inside it expand or contract. The module M including the battery cells C then expands or contracts in accordance with the expansion or contraction of the battery cells C.

[0017] Therefore, the two battery packs P shown in Figure 1 are the same, and the only difference is whether they are in a charged or discharged state. The configuration of the module M and how the module M changes in response to the expansion and contraction of the battery cells C will be described in detail later.

[0018] 1, 12 modules M are arranged inside the battery pack P. The battery pack P is divided into three compartments, and each compartment houses multiple modules M (four in this example). In FIG. 1, the pack 2 is shown with a two-dot chain line to show the state of the modules M housed inside.

[0019] In the following description, the stacking direction of the battery cells C is referred to as the Y direction, and the direction perpendicular to the Y direction and perpendicular to the mounting surface of the module M stored in the pack 2 is referred to as the Z direction. Furthermore, the direction perpendicular to these Y direction and Z direction is referred to as the X direction.

[0020] In addition, various types of batteries are envisioned as the batteries to be stored in the battery pack P in the embodiment of the present invention, such as all-solid-state lithium ion batteries that use a solid electrolyte as the electrolyte and lithium metal or a lithium-containing alloy as the negative electrode. However, any type of battery may be stored in the battery pack P in the embodiment of the present invention as long as the battery cells undergo expansion and contraction during charging and discharging.

[0021] Each battery cell C is a laminated electrode body in which a predetermined number of flat-shaped single cells, each made by stacking a positive electrode, an electrolyte, and a negative electrode (not shown), are stacked in the thickness direction (Y direction), and the laminated electrode body is housed in an exterior material such as a laminate film.

[0022] A battery cell C has a main body that houses such a laminated electrode assembly, and electrode tabs that protrude from both sides of the main body in a direction (X direction) perpendicular to the lamination direction. The electrode tabs are joined to the current collectors of the electrodes (positive or negative electrodes) of the battery cell C. Therefore, the positive electrode tabs are connected to each positive electrode in the battery cell C, and the negative electrode tabs are connected to each negative electrode, thereby extracting current from the respective electrodes (moving electrons to the outside of the battery cell C).

[0023] In the module M according to the embodiment of the present invention, a plurality of these individual battery cells C are stacked in the Y direction. The module M also includes a pressure mechanism 1 that applies pressure to the plurality of cells C in the stacking direction.

[0024] The pressure mechanism 1 includes a pressure frame 11 arranged at one end of the stacking direction of the battery cells C, a pressure plate 12 arranged at the other end of the stacking direction in a position opposite to the pressure frame 11 and the pressure plate 12 across the battery cells C, and a spiral leaf spring 13 formed between the pressure frame 11 and the pressure plate 12 to apply pressure to the battery cells C in the stacking direction of the battery cells C.

[0025] 2A and 2B show a pair of modules M according to an embodiment of the present invention, with FIG. 2A being a schematic perspective view thereof, and FIG. 2B being a schematic perspective view showing the arrangement of spirally formed leaf springs, with the pressure frame 11 not shown.

[0026] The modules M in Fig. 2 are shown arranged such that the pressure frames 11 of the two modules M arranged in the Y direction as shown in Fig. 1 are in contact with each other. Therefore, the configuration of these two modules M is the same. Therefore, the module M shown on the right side (the far side in the Y direction) will be described as an example.

[0027] The battery cell C1 is in contact with the pressure frame 11 that constitutes the pressure mechanism 1. In the module M of FIG. 2(A), 15 battery cells C are stacked from the battery cell C1 to the right in the Y direction up to the battery cell C15.

[0028] If the position where the battery cell C1 contacts the pressure frame 11 is defined as one end in the stacking direction, the battery cell C15 is disposed at the other end in the stacking direction. The battery cell C15 contacts the pressure plate 12. That is, the stacked battery cells C contact the pressure frame 11 at one end in the stacking direction and the pressure plate 12 at the other end in the stacking direction, and are sandwiched between the pressure frame 11 and the pressure plate 12.

[0029] These stacked battery cells C are compressed by the leaf springs 13 between the pressure frame 11 and the pressure plate 12 from one end side in the stacking direction to the other end side in the stacking direction, and from the other end side in the stacking direction to one end side in the stacking direction.

[0030] The leaf springs 13 are used to apply pressure to the stacked battery cells C. The leaf springs 13 are formed in a spiral shape around a bobbin 14, and one end and the other end are disposed inside the pressure frame 11.

[0031] 3 is a perspective view of a spirally formed leaf spring 13 used in a module M according to an embodiment of the present invention. The end of the leaf spring 13 (the core of the leaf spring 13) is joined and fixed to the outer periphery of a bobbin 14. The leaf spring 13 is unwound or wound in the direction indicated by the arrow in FIG. 3 in response to the expansion and contraction of the battery cells C. A plurality of leaf springs 13 having this shape are arranged inside the pressure frame 11.

[0032] 2(B) shows the state of the leaf spring 13 arranged inside the pressure frame 11. In FIG. 2(B), the pressure frame 11 is not drawn from the module M shown in FIG. 2(A) so that the inside can be seen.

[0033] 2(B), a total of 16 leaf springs 13 are arranged inside the pressure frame 11 shown in Fig. 2, with four rows in the Z direction (vertical) and four columns in the Y direction (horizontal). The pressure applied to the battery cells C can be increased or decreased depending on the number of leaf springs 13 arranged inside the pressure frame 11. Therefore, the number of leaf springs 13 to be arranged is set so as to achieve the desired pressure.

[0034] Furthermore, Fig. 4 shows the structure of the module M according to the embodiment of the present invention, exploded into its individual components. Fig. 4 is an exploded perspective view of the module M according to the embodiment of the present invention. Fig. 4 shows the module M shown on the right side of the two modules M shown in Fig. 2 in an exploded state.

[0035] 4(A) shows the pressure frame 11. The pressure frame 11 includes a pair of side plates 111 and a pressing plate 112 connected to the pair of side plates 111. The pair of side plates 111 are arranged to face each other in the X direction. The pressing plate 112 is arranged in contact with each end of the pair of side plates 111.

[0036] Therefore, the pair of side plates 111 and the pressure plate 112 are arranged in a U-shape in plan view. Since the pressure frame 11 has such a shape, the leaf spring 13 is accommodated in the space surrounded by the pair of side plates 111 and the pressure plate 112.

[0037] Note that the description here is based on the premise that the pair of side plates 111 and the pressure plate 112 are separate members, and that the two are joined together to form the pressure frame 11. However, it is also possible to form the pair of side plates 111 and the pressure plate 112 as a single unit.

[0038] 4(A), the pressure frame 11 is formed in an open state on the opposite side in the Y direction of the pressing plate 112. However, instead of this structure, for example, it is also possible to cover the open portion with, for example, a plate-like member to form a square-shaped structure.

[0039] The side plate 111 has holding portions 111a formed at 16 locations in total, four in the Y direction and four in the Z direction. The holding portions 111a hold the bobbins 14 of the leaf springs 13 to be housed. This allows the leaf springs 13 to be housed within the pressure frame 11.

[0040] In the pressure frame 11 according to the embodiment of the present invention, the holding portions 111a are formed as through holes. However, it is also possible to form the holding portions 111a as holes with bottoms. The number of holding portions 111a formed on the side plates 111 can be determined according to the number of leaf springs 13, which is set according to the pressure force applied to the battery cells C.

[0041] Furthermore, in the drawings showing the module M according to the embodiment of the present invention, a state in which leaf springs 13 are held by all of the formed holding portions 111a is shown. However, leaf springs 13 do not necessarily have to be held by all of the formed holding portions 111a, and the number of leaf springs 13 housed in the pressure frame 11 does not necessarily have to match the number of formed holding portions 111a.

[0042] The pressing plate 112 comes into contact with the battery cell C arranged in the opposing position. That is, it is arranged on one end side of the battery cell C in the stacking direction, and sandwiches the battery cell C between itself and the pressure plate 12, which will be described later.

[0043] FIG. 4(B) shows a battery cell C and a guide 15. The structure of the battery cell C is as described above. Meanwhile, the guide 15 serves to assist the movement of the leaf spring 13, which expands and contracts in response to the expansion and contraction of the battery cell C. Note that the guide 15 itself may or may not move, for example, by rotating in response to the movement of the leaf spring 13.

[0044] 4(C) shows the pressure plate 12, the leaf spring 13, and the bobbin 14 that serves as the shaft of the leaf spring 13. The pressure plate 12 comes into contact with the battery cell C that is arranged in the opposing position. In other words, the pressure plate 12 is arranged on the other end side of the battery cell C in the stacking direction, and sandwiches the battery cell C between itself and the pressing plate 112.

[0045] The surface area of ​​the pressure plate 112 of the pressure frame 11 that comes into contact with the battery cell C and the surface area of ​​the pressure plate 12 that comes into contact with the battery cell C are configured to be larger than the surface area of ​​the battery cell C that comes into contact with the pressure plate 112 or the pressure plate 12. By configuring the areas of the pressure plate 112 and the pressure plate 12 to be larger than the area of ​​the battery cell C that is to be clamped in this way, when pressure is applied to the battery cell C by the pressure plate 112 and the pressure plate 12, it is possible to apply pressure in a balanced manner to the multiple stacked battery cells C.

[0046] Furthermore, while maintaining this relationship, the size of the module M including the pressing plate 112 and the pressure plate 12 can be determined according to the size of the battery cell C to be pressed. Therefore, the pressure mechanism 1 according to the embodiment of the present invention can be configured according to the size of the battery cell C to be pressed.

[0047] The leaf spring 13 is then looped around to cover the surface of the pressure plate 12 opposite in the Y direction from the surface that contacts the battery cell C. In other words, both ends of the leaf spring 13 are housed in the pressure frame 11, and the pressure plate 12 is disposed between the ends.

[0048] A specific description will be given using Fig. 4(C). As described above, the module M shown in Fig. 4 is the module M shown on the right side of the two modules M shown in Fig. 2, and therefore leaf springs 13 are disposed in all 16 holding portions 111a provided on the pressure frame 11 shown in Fig. 4(A). Therefore, 16 bobbins 14 serving as shafts of the leaf springs 13 are also shown in Fig. 4(C).

[0049] The positions of the holders 111a that hold these bobbins 14 are formed in four columns in the Y direction and four rows in the Z direction. For the sake of explanation below, the position farthest from the pressing plate 112 will be referred to as the first column, and the positions that are gradually closer to the pressing plate 112 will be referred to as the second, third, fourth, and so on. On the other hand, in the Z direction, the highest position of the four holders 111a that are formed in rows will be referred to as the first row, and the positions that are positioned downward in the Z direction from the first row will be referred to as the second, third, and fourth rows.

[0050] For example, one end of leaf spring 13A is fixed to bobbin 14A held by holding portion 111a in the second row of the first column. The spring extends from this end, extends upward in the Z direction, changes direction along guide 15, and extends toward the back in the Y direction, i.e., toward pressure plate 12. It then extends downward in the Z direction to cover the surface of pressure plate 12 opposite in the Y direction from the surface that contacts battery cell C, then changes direction and extends toward the front in the Y direction. The spring then changes direction and extends upward in the Z direction along guide 15, and is wound onto bobbin 14B. This bobbin 14B is held by holding portion 111a in the third row of the first column. The other end of leaf spring 13A is fixed to this bobbin 14B.

[0051] Similarly, consider an example of a leaf spring 13 different from leaf spring 13A. For example, leaf spring 13B has one end fixed to bobbin 14C held by holding portion 111a in the first row and fourth column. The spring extends from this end and continues to extend toward the rear in the Y direction, i.e., toward pressure plate 12. It then extends downward in the Z direction to cover the surface of pressure plate 12 opposite in the Y direction from the surface that contacts battery cell C, and then changes direction and extends toward the front in the Y direction. The spring is then wound onto bobbin 14D along guide 15. The bobbin 14D is held by holding portion 111a in the fourth row and fourth column. The other end of leaf spring 13B is fixed to bobbin 14D.

[0052] In this way, one leaf spring 13 has the pressure plate 12 wound around it, and one end is fixed to a bobbin 14 arranged in the first or second row, while the other end is fixed to a bobbin 14 arranged in the fourth or third row. In other words, one end and the other end of the leaf spring 13 are fixed to bobbins 14 arranged in the same row, midway between the first and fourth rows, i.e., at positions symmetrical with respect to the boundary between the second and third rows.

[0053] Since the leaf springs 13 are housed and arranged inside the pressure frame 11 in this way, if the battery cells C to be pressed are large in the Z direction, the leaf springs 13 are arranged in the first and fourth rows, for example, and if the battery cells C to be pressed are small in size in the Z direction, the leaf springs 13 are arranged in the second and third rows, for example. By arranging the leaf springs 13 in this way, it is possible to accommodate the size of the battery cells C.

[0054] Therefore, it is possible to increase or decrease the number of rows of leaf springs 13 depending on the size in the Z direction of the battery cells C. Because the number of rows of leaf springs 13 can be increased or decreased in this way, it is possible to flexibly change the height of module M (thickness direction of pack 2, Z direction) depending on the thickness of pack 2 (Z direction).

[0055] In this way, each of the leaf springs 13 is looped around so as to sandwich the pressure plate 12 between one end and the other end, and the leaf springs 13 are arranged so as to cover the battery cells C sandwiched between the pressure plate 12 and the pressure plate 112 of the pressure frame 11. In other words, the multiple battery cells C are in contact with the pressure plate 112 at one end in the stacking direction and with the pressure plate 12 at the other end.

[0056] As described above, the leaf spring 13 is wound between the pressing plate 112 and the pressure plate 12, so that the plurality of battery cells C are covered by the leaf spring 13 on both the upper and lower sides in the Z axis direction.

[0057] Furthermore, as explained above, in the module M according to the embodiment of the present invention, multiple leaf springs 13 are housed inside the pressure frame 11. These multiple leaf springs 13 are arranged so that they each wrap around the pressure plate 12, so that, for example, on the upper and lower sides of the Z axis covering the battery cells C, the springs extending from the multiple leaf springs 13 are stacked.

[0058] 2(B), where (A) shows the upper portion in the Z direction and (B) shows the lower portion in the Z direction. In the enlarged view, the left side of the drawing corresponds to one end of the module M, and the right side of the drawing corresponds to the other end of the module M. The portion where the two leaf springs 13 are arranged is the side plate 111, and to the right of that is visible the pressing plate 112 joined to the side plate 111.

[0059] The pressure plate 112 is in contact with the battery cells C arranged at one end in the stacking direction, and although many of them are omitted from Figure 5, multiple battery cells C are arranged toward the right (rear) side in the Y direction (stacking direction).

[0060] 5(A), the upper leaf spring 13 is the leaf spring 13B exemplified above. As described above, leaf spring 13B is arranged in the first row in the Z direction, and therefore the spring unwound from bobbin 14C extends toward the right in the Y direction along guide 15 without extending upward in the Z direction. The spring that extends toward the right in the Y direction is then finally wound onto bobbin 14D, which is arranged in the fourth row and fourth column and to which the other end of leaf spring 13B is fixed, as described above.

[0061] 5(B), the lower leaf spring 13 is leaf spring 13D, which is arranged in the fourth row in the Z direction as described above. Leaf spring 13B unwound from bobbin 14C is wound around bobbin 14D, which is arranged in the fourth row and fourth column, to which leaf spring 13D, which is the other end of leaf spring 13B, is fixed.

[0062] Meanwhile, leaf spring 13C is shown below leaf spring 13B in Figure 5(A). The arrangement position of leaf spring 13C in Figure 5 is the second row of the fourth column, in line with the previous expressions. Because leaf spring 13C is arranged in the second row, the spring unwound from one end of leaf spring 13C fixed to bobbin 14E extends upward in the Z direction. Then, guide 15 changes its direction to the right in the Y direction, and the spring continues to extend to the right in the Y direction.

[0063] The spring unwound from one end of the leaf spring 13C extends toward the rear in the Y direction, i.e., toward the pressure plate 12. It then extends downward in the Z direction to cover the surface of the pressure plate 12 opposite in the Y direction from the surface that contacts the battery cell C, and then changes direction and extends toward the front in the Y direction. The spring is then wound onto a bobbin 14F along the guide 15, as shown in FIG. 5(B). The bobbin 14F is held by a holding portion 111a in the third row and fourth column. The other end of the leaf spring 13C, the leaf spring 13F, is fixed to the bobbin 14F.

[0064] In this way, leaf spring 13C, which is disposed below leaf spring 13B in the Z direction, must first be stretched upward in the Z direction inside pressure frame 11, and then change direction and stretched to the right in the Y direction. At this time, since it is necessary to avoid contact with leaf spring 13B disposed above it in the Z direction, leaf spring 13C is held by holding portion 111a so that the central axes of bobbin 14C of leaf spring 13B and bobbin 14E of leaf spring 13C are misaligned in the Y direction.

[0065] Furthermore, the presence of guide 15 makes it possible to prevent leaf spring 13 from coming into contact with battery cell C. For example, in FIG. 5(A), the position of the outer periphery of guide 15 in the Z direction is located above the upper end of battery cell C in the Z direction. Also, in FIG. 5(B), it is located below the lower end of battery cell C in the Z direction. By adjusting and arranging the center position and radius of guide 15 in this way, leaf spring 13 can be prevented from coming into contact with battery cell C.

[0066] 2(B) and 5, the leaf spring 13 is arranged so that its spiral axis, i.e., the bobbin 14, is perpendicular to the mounting surface of the module M stored in the pack 2. By storing multiple leaf springs 13 in the pressure frame 11 in this manner, it becomes possible to arrange the multiple springs that are unwound and wound from the multiple leaf springs 13 in a stacked manner.

[0067] That is, as explained above, the springs unwound from the leaf springs 13 arranged in the first and second rows are stretched to the right in the Y direction, then wrapped around the pressure plate 12, and then stretched to the left in the Y direction, and wound up in the leaf springs 13 arranged in the fourth and third rows, which are positioned symmetrically to the leaf springs 13 arranged in the first and second rows.

[0068] Therefore, the multiple springs unwound from the multiple leaf springs 13 are stacked in the Z direction between the pressing plate 112 and the pressure plate 12, which sandwich the stacked battery cells C. This state is shown in Figure 5. That is, the unwound spring arranged in the first row of the fourth column is the bottom layer, and the springs unwound from the leaf springs 13 in the second row of the fourth column, the first row of the third column, the second row of the third column, the first row of the second column, the second row of the second column, and the first row of the first column are stacked above in the Z direction. Then, the spring unwound from the leaf spring 13 arranged in the second row of the first column (the leaf spring designated by reference symbol 13A in Figure 4(C)) is the top layer in the Z direction.

[0069] By arranging the springs unwound from each leaf spring 13 so that they can be stacked to cover the stacked battery cells C in this manner, even if the pressure force that can be applied by one leaf spring 13 is small, by arranging multiple leaf springs 13, the desired large pressure force can be obtained.

[0070] The pressure applied to the battery cells C will be described with reference to the drawings. Fig. 6 is a schematic side view of the module M according to the embodiment of the present invention, and is an explanatory diagram illustrating the force applied to the battery cells C.

[0071] 2, which have been used in the explanations up to this point, the right-hand module M is used in FIG. 6 as well. Therefore, the left side in FIG. 6 is one end side of the module M, where a pressure frame 11 that houses multiple leaf springs 13 is arranged. Meanwhile, a pressure plate 12 is arranged on the right side in FIG. 6, and battery cells C are stacked between the pressure plate 12 and the pressing plate 112. Note that in FIG. 6, multiple battery cells C are collectively represented as a single battery cell C.

[0072] As described above, the springs unwound from each of the multiple leaf springs 13, one end of which is fixed to the bobbins 14 arranged in the first and second rows, are looped around the pressure plate 12 so as to cover the surface opposite in the Y direction from the surface that contacts the battery cells C, and are wound around multiple leaf springs 13, the other ends of which are fixed to the bobbins 14 arranged in the fourth and third rows. Therefore, the forces of the individual leaf springs 13 are combined via the pressure plate 112, and this combined force is applied to the stacked battery cells C. Meanwhile, because springs are looped around the pressure plate 12, force is also applied to the stacked battery cells C from the pressure plate 12.

[0073] This will be explained below using Figure 6. In Figure 6, a small arrow pointing right in the Y direction is shown for each leaf spring 13. This small arrow indicates the force applied from each of the multiple leaf springs 13 to the stacked battery cells C. Because it is the pressing plate 112 that actually contacts the battery cells C, the forces applied from these multiple leaf springs 13 combine at the pressing plate 112 and are applied to the battery cells C as a large force.

[0074] 6, a double-headed arrow is shown surrounding the battery cell C, including the pressure plate 12. This indicates the force acting on the battery cell C in the left direction (Y direction) due to the arrangement of the springs such that the spring unwound from each of the plurality of leaf springs 13 is wrapped around the pressure plate 12 and then wound around each of the plurality of leaf springs 13, as described above.

[0075] The force acting from one end of the module M to the other end (the force acting from the pressure plate 112 to the stacked battery cells C, indicated by the large right-pointing arrow in Figure 6) is balanced with the force acting from the other end to the one end (the force acting from the pressure plate 12 to the stacked battery cells C, indicated by the double-headed arrow pointing left in Figure 6).

[0076] In this way, the pressure mechanism 1 in this embodiment of the present invention employs a structure in which a spring is unwound from one end of the module M, looped around the pressure plate 12 located on the other end, and then wound up again at the other end of the module M. As a result, the forces exerted by the multiple leaf springs 13 housed inside the pressure frame 11 are combined and applied to the stacked battery cells C, enabling a large pressure force to be obtained.

[0077] The pressure frame 11 is provided with one or more rows of holding portions 111a for accommodating the leaf springs 13. For example, if only one row is provided, a greater pressure can be applied to the battery cells C when the leaf springs 13 are arranged in the first row than when the leaf springs 13 are arranged in the fourth row. In other words, the required pressure can be flexibly adjusted by changing the arrangement of the leaf springs 13 in the row direction.

[0078] Furthermore, because the stacked battery cells C are held between the pressure plate 112 on one end side and the pressure plate 12 on the other end side with a large pressure applied, it is possible to prevent downward movement in the Z direction that would occur when multiple battery cells C are stacked. In other words, in the module M according to the embodiment of the present invention, it is possible to prevent the battery cells C from coming into contact with at least the leaf springs 13 that are arranged in positions facing the mounting surface of the module M stored in the pack 2.

[0079] That is, the battery cell C is in contact only with the pressing plate 112 and the pressure plate 12, and is not in contact with the leaf springs 13 that cover it above and below in the Z direction, and is placed in a floating state. This does not impede the movement of the leaf springs 13, which expand and contract in response to the expansion and contraction of the battery cell C, and makes it possible to apply a stable pressure force to the battery cell C at all times.

[0080] Furthermore, as explained above, the leaf springs 13 expand and contract in response to the expansion and contraction of the battery cells C, so when the module M is stored in the pack 2, the leaf springs 13 positioned opposite the bottom surface of the pack 2 do not come into contact with the bottom surface. Therefore, the leaf springs 13 positioned opposite the bottom surface of the pack 2 do not come into contact with either the stacked battery cells C positioned above them in the Z direction, or the bottom surface of the pack 2 that faces them below them in the Z direction.

[0081] The above description has been given on the assumption that the leaf spring 13 is arranged so as to be unwound from the pressure frame 11 and wound around the pressure plate 12. However, the leaf spring 13 may not be wound around the pressure plate 12, but may instead be structured so that, for example, the leaf spring 13 unwound from the pressure frame 11 is connected to the upper end of the pressure plate 12 in the Z direction, and the lower end of the pressure plate 12 is connected to the leaf spring 13 wound around the pressure frame 11.

[0082] Next, the slide mechanism 3 will be described. For example, as shown in the perspective view of the battery pack P on the left side of FIG. 1, the slide mechanism 3 is provided on the bottom surface of the pack 2. The module M is placed on the upper part of the slide mechanism 3 in the Z direction. By being placed on the slide mechanism 3 in this way, a part of the module M can move in the stacking direction of the cells C in accordance with the expansion and contraction of the cells C.

[0083] The slide mechanism 3 is formed in the shape of, for example, a flat plate. However, the slide mechanism 3 does not particularly require frictional force, and it is sufficient if it can support the pressure plate 12 so that it can move.

[0084] The slide mechanism 3 is provided on the bottom surface of the pack 2 at a position where the pressure plate 12 of the module M stored in the pack 2 is disposed. The slide mechanism 3 is provided in the Y direction across an area where the pressure plate 12 may move, so that the pressure plate 12 can move in accordance with the expansion and contraction of the battery cells C of the module M.

[0085] 1(A), the slide mechanism 3 is not provided in the region in the X direction where the leaf spring 13 is wound around the pressure plate 12, but is provided only at both ends in the X direction of the module M. Therefore, when the module M is stored in the pack 2, only the lower surface of the pressure plate 12 in the Z direction comes into contact with the slide mechanism 3.

[0086] It should be noted that it is the other end of the module M where the pressure plate 12 is located that moves in response to the expansion and contraction of the battery cells C. The pressure frame 11, which is located at one end of the module M, is fixed to the bottom surface of the pack 2 and does not move.

[0087] 1(A), in the battery pack P according to the embodiment of the present invention, the slide mechanism 3 is disposed only on the bottom surface of the pack 2 so as to be in contact with the lower side of the pressure plate 12 in the Z direction. However, the position at which the slide mechanism 3 is provided is not limited to this position.

[0088] That is, when the shape of the pack 2 storing multiple modules M therein is formed, for example, in a box shape as shown in FIG. 1, the slide mechanism part 3 may be provided not only on the bottom surface on which the modules M are placed, but also on the top surface formed at a position opposite the bottom surface.

[0089] By providing the slide mechanism part 3 at this position, the pressure plate 12 comes into contact with the slide mechanism part 3 on the upper and lower sides in the Z direction, which allows the leaf spring 13 to move more smoothly when expanding and contracting in response to the expansion and contraction of the battery cell C.

[0090] Furthermore, particularly when the battery pack P according to the embodiment of the present invention is used as an in-vehicle battery, it is conceivable that the battery pack P may move up and down in the Z direction due to vibrations of the vehicle in which it is mounted. However, if a slide mechanism 3 is provided up and down in the Z direction, the movement of the battery pack P can be restricted.

[0091] Although the description here is based on the assumption that the slide mechanism 3 is formed in a plate shape, other mechanisms such as ball bearings may also be used.

[0092] [Operation] Next, the movement of the module M when the battery cells C expand or contract due to charging and discharging will be described with reference to Fig. 7. Fig. 7 is a schematic perspective view of a battery pack according to an embodiment of the present invention, showing the state of the battery pack when the SOC is 0% and the state of the battery pack when the SOC is 100%, as viewed from below the battery pack upward in the Z direction. Fig. 7(A) shows the state of the battery pack P when the SOC is 0%, and Fig. 7(B) shows the state of the battery pack P when the SOC is 100%.

[0093] In both Figures 7(A) and 7(B), the module M depicted at the forefront will be used as an example for explanation. The module shown on the left side in Figures 7(A) and 7(B) will be referred to as module ML. On the other hand, the module shown on the right side in Figures 7(A) and 7(B) will be referred to as module MR.

[0094] First, regarding the positional relationship between the module M, pack 2, and slide mechanism 3, as is clear from Fig. 1, the two modules M stored inside the pack 2 are arranged so that their pressure frames 11 are adjacent in the Y direction. In addition, the pressure plate 12 arranged on the other end side of each module M is arranged so as to rest on the upper part of the slide mechanism 3 arranged on the bottom surface of the pack 2.

[0095] As described above, it is the pressure plates 12 that move in response to the expansion and contraction of the battery cells C. Therefore, because the modules M are arranged in this manner within the pack 2, the pressure plates 12 of the adjacent modules ML and MR can move in response to the expansion and contraction of the battery cells C without interfering with each other.

[0096] Specifically, when the SOC is 0%, the battery cells C are in a discharged state, and therefore all of the stacked battery cells C are contracted in the Y direction. Therefore, in this case, the pressure applied by the leaf springs 13 causes the pressure plates 12 to move to the right in the Y direction in the case of the module ML shown on the left side of Fig. 7(A), and to the left in the Y direction in the case of the module MR shown on the right side of Fig. 7(B). Therefore, in this case, the distance between the pressing plate 112 and the pressing plate 12 is the shortest.

[0097] When the battery cell C is charged from this state, it will eventually reach an SOC of 100%, for example. This state is shown in Figure 7(B). As shown in Figure 7(B), the stacked battery cells C expand when they are charged. The direction in which the battery cells C expand is the Y direction, which is the stacking direction.

[0098] Because the pressure plate 12 is placed on the slide mechanism 3, it moves on the slide mechanism 3 toward the left in the Y direction for module ML and toward the right in the Y direction for module MR as the battery cells C expand. In other words, if the length of module M in the Y direction is based on the length at an SOC of 0%, the length at an SOC of 100% will be more than one time.

[0099] As explained above, the pressure plate 12 moves in the Y direction to follow the expansion and contraction of the battery cells C. However, even though the pressure plate 12 moves, the battery cells C are clamped and pressed between the pressing plate 112 and the pressure plate 12 by the pressure mechanism 1, and therefore pressure continues to be applied to the stacked battery cells C.

[0100] As described above, the orientation (arrangement) of the modules M stored in the pack 2 is such that the pressure frames 11 of the two modules M are adjacent to each other in the Y direction, as shown in Fig. 1. However, the orientation (arrangement) of the modules M when stored in the pack 2 is not limited to the orientation shown in Fig. 1.

[0101] 8 is a schematic perspective view showing the overall configuration of a battery pack P1 according to a modification of the embodiment of the present invention, illustrating the state of the battery pack P1 when the SOC is 0% and the state of the battery pack P1 when the SOC is 100%. In the battery pack P1 shown in FIG. 8, the configuration of the module M is as described above.

[0102] 8, the pressure plates 12 of the two modules M are arranged to face each other. Strictly speaking, the leaf springs 13 wound around the pressure plates 12 of the two modules M are positioned to face each other, but for convenience, the pressure plates 12 will be described as members that face each other.

[0103] The pressure plate 12 moves in the Y direction, which is the stacking direction of the battery cells C, following the expansion and contraction of the battery cells C. Therefore, two adjacent modules M are arranged at a distance so that the pressure plate 12 does not come into contact with the pressure plate 12 of an adjacent module M even if it moves when a battery cell C expands.

[0104] In two adjacent modules M, the pressure plates 12 that move in response to the expansion and contraction of the battery cells C are positioned opposite each other. Therefore, the slide mechanism 3 provided between the pressure plate 12 and the bottom surface of the pack 2 is not provided for each module M, but is provided between the two modules M.

[0105] That is, the two pressure plates 12 arranged at positions opposite to each other share the slide mechanism unit 3. By sharing the slide mechanism unit 3 between a plurality of modules M in this way, the number of parts of the slide mechanism unit 3 can be reduced.

[0106] This state is shown in the battery pack P1 with an SOC of 0% shown in the foreground of Figure 8. In this case, the battery cells C are in a contracted state, so the pressure frame 11 and the pressure plate 12 are closest to each other. As a result, there is a space between the two adjacent modules M, and the pressure plates 12 are also spaced apart.

[0107] On the other hand, the state of the battery pack P1 at the back of Fig. 8 is shown when the SOC is 100%. In this case, the stacked battery cells C expand as a result of charging the charged battery pack P1. The leaf springs 13 then expand in response to the expansion of the battery cells C, and the pressure plate 12 moves in the Y direction.

[0108] 8, the pressure plates 12 of two adjacent modules M are arranged in opposing positions. Therefore, the pressure plates 12 of the two modules M move in the Y direction toward each other due to the expansion of the battery cells C.

[0109] However, as described above, when the battery cells C contract due to discharge, a space is provided between the opposing pressure plates 12. Therefore, even if the pressure plates 12 move to the maximum extent in the Y direction due to the expansion of the battery cells C, the pressure plates 12 are prevented from coming into contact with each other due to the movement.

[0110] Therefore, the distance between the opposing pressure plates 12 when the SOC for the battery cell C is 0% is set based on the maximum distance each pressure plate 12 moves when the SOC is 100%. Therefore, even if the battery cell C expands, the pressure plates 12 arranged in opposing positions do not come into contact with each other, and each can independently follow the expansion and contraction of the battery cell C.

[0111] 1 and 8 are given as examples of the arrangement direction of the module M. However, the arrangement direction of the module M is not limited to the case of FIG. 1 or 8 as long as the pressure plate 12 can be moved in accordance with the expansion and contraction of the battery cells C, rather than being limited to these arrangement directions of the module M.

[0112] [Effects of the Example] (1) A battery pack includes a module having multiple stacked battery cells, a pack that stores multiple modules, and a slide mechanism that positions a portion of the module so that it can move in the stacking direction of the battery cells in accordance with the expansion and contraction of the battery cells. The module includes a pressure mechanism that applies pressure to the multiple battery cells in the module in the stacking direction.

[0113] This battery pack structure makes it possible to apply high pressure corresponding to the expansion and contraction of secondary batteries, which undergo large expansion and contraction during charging and discharging, and can be applied regardless of the size of the secondary battery.

[0114] (2) In the battery pack described in (1) above, the pressure mechanism includes a pressure frame arranged at one end of the stacking direction of the battery cells, a pressure plate arranged at the other end of the stacking direction in a position opposite to the plurality of battery cells, and a spiral leaf spring formed between the pressure frame and the pressure plate to apply pressure to the battery cells in the stacking direction of the battery cells.

[0115] Because the battery pack is equipped with such a pressure mechanism, even if the battery cell expands or contracts, pressure can be applied to the battery cell while following the expansion or contraction. In addition, because the battery cell is sandwiched between the pressure mechanism, high pressure can be applied to the battery cell.

[0116] Furthermore, by employing such a pressure mechanism, the mechanism for applying pressure to the battery cells can be made compact, which allows for a larger battery occupancy rate, contributing to a higher capacity battery pack.

[0117] (3) In the battery pack described in (2) above, the leaf springs are arranged in a single or multiple columns and multiple rows on the pressure frame according to the pressure required to apply to the battery cells.

[0118] Therefore, the stacked battery cells are pressurized by the sum of the individual pressure forces exerted by the pressure plates of the multiple leaf springs housed in the pressure frame toward the battery cells, and the force exerted by the pressure plates toward the battery cells by the springs arranged to wrap around the pressure plates. The amount of pressure exerted is determined by the number and positions of the leaf springs arranged according to the pressure required for the battery cells.

[0119] (4) In the battery pack according to (2) or (3) above, the leaf spring is arranged so that the axis of its spiral is perpendicular to the mounting surface of the module housed in the pack.

[0120] The leaf springs are unwound from the pressure frame and then wound around the pressure frame again to wrap around the pressure plate. By arranging the bobbins that secure the ends of the leaf springs in this way, the springs unwound from each of the leaf springs can be stacked and wrapped around the pressure plate. This allows the combined pressure of the individual leaf springs to be applied to the battery cells as a large pressure force.

[0121] (5) In a battery pack according to any one of (2) to (4) above, the area of ​​the surface of the pressure frame that contacts the battery cells and the area of ​​the surface of the pressure plate that contacts the battery cells are larger than the area of ​​the surface of the battery cells that contacts the pressure frame or the pressure plate.

[0122] Because the area of ​​the pressure frame (pressure plate) and pressure plate that are in direct contact with the battery cell are larger than the area of ​​the battery cell that is in contact with the pressure plate and pressure plate, the force applied from the pressure plate to the battery cell and the force applied from the pressure plate to the battery cell are applied to the battery cell without any waste.

[0123] (6) In the battery pack according to any one of (1) to (5) above, the battery cells are not in contact with at least the leaf springs that are arranged in positions that face the mounting surface of the modules stored in the pack.

[0124] The pressure applied to the battery cells sandwiched between the pressing plate and the pressure plate is greater than the force that moves the stacked battery cells toward the mounting surface of the module in the pack. Therefore, the battery cells do not come into contact with the leaf springs, which are positioned closer to the mounting surface than the battery cells. Therefore, the pressure plate around which the leaf springs are wrapped can move in accordance with the expansion and contraction of the battery cells.

[0125] (7) In the battery pack according to any one of (1) to (6) above, the sliding mechanism is provided so that the pressure plate can move in accordance with the expansion and contraction of the battery cells. By providing such a sliding mechanism, the pressure plate, which is not fixed to the pack, can move more smoothly to follow the expansion and contraction of the battery cells.

[0126] (8) In the battery pack described in (7) above, the slide mechanism is disposed at least between the mounting surface of the module in the pack and the pressure plate. By providing the slide mechanism in this position, when the battery pack is mounted on a vehicle, the pressure plate can be moved more reliably to follow the expansion and contraction of the battery cells. [Explanation of symbols]

[0127] 1···Pressure mechanism, 11···Pressure frame, 111···Side plate, 112···Pressure plate, 12···Pressure plate, 13···Leaf spring, 14···Bobbin, 15···Guide, 2···Pack, 3···Slide mechanism, C···Battery cell, M···Module, P···Battery pack

Claims

1. a module including a plurality of stacked battery cells; a pack that stores a plurality of the modules; a slide mechanism that mounts a portion of the module so that the portion can move in the stacking direction of the battery cells in accordance with expansion and contraction of the battery cells, The battery pack is characterized in that the module includes a pressure mechanism that applies pressure to the plurality of battery cells included in the module in the stacking direction.

2. The pressure mechanism unit is a pressure frame disposed on one end side of the battery cells in the stacking direction; a pressure plate disposed on the other end side of the stacking direction and facing the plurality of battery cells; a spiral leaf spring that applies pressure to the battery cells in the stacking direction of the battery cells between the pressure frame and the pressure plate; 2. The battery pack according to claim 1, further comprising:

3. 3. The battery pack according to claim 2, wherein the leaf springs are arranged in a single or multiple columns and multiple rows in the pressure frame according to the pressure required for the battery cells.

4. 3. The battery pack according to claim 2, wherein the leaf spring is arranged so that the spiral axis of the leaf spring is perpendicular to a mounting surface of the module housed in the pack.

5. 3. The battery pack according to claim 2, wherein the area of ​​the surface of the pressure frame that contacts the battery cell and the area of ​​the surface of the pressure plate that contacts the battery cell are larger than the area of ​​the surface of the battery cell that contacts the pressure frame or the pressure plate.

6. 2. The battery pack according to claim 1, wherein the battery cells are not in contact with at least the leaf springs that are arranged in positions facing the mounting surface of the modules stored in the pack.

7. 2. The battery pack according to claim 1, wherein the slide mechanism is provided so that the pressure plate can move in accordance with the expansion and contraction of the battery cells.

8. 8. The battery pack according to claim 7, wherein the slide mechanism is disposed at least between the mounting surface of the module in the pack and the pressure plate.

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