Battery pack

Abstract

A battery pack (10) in one embodiment of the present invention is provided with a plurality of batteries (50), and a case (60) including a case body (20) that accommodates the plurality of batteries (50) and a case lid (30) that covers an opening (22) of the case body (20). The case (60) is configured such that the case body (20) and the case lid (30) become relatively displaced in directions away from one another when the internal pressure increases due to the generation of gas, and an opening for gas exhaust is formed in a state of maintaining the coupling between the case body (20) and the case lid (30).

Description

Technical Field

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

Background Art

[0002] Non-aqueous electrolyte secondary batteries such as lithium-ion batteries may be used in the form of a battery pack in which a plurality of them are electrically connected and housed in a case. When there is an abnormality in the battery inside this battery pack, a large amount of high-temperature combustible gas may be generated from the battery. If this gas is not properly discharged outside the battery pack, there is a risk that the internal pressure of the battery pack will rise and the battery pack case will be damaged. Generally, in order to prevent water and dust from entering the battery pack, it is required that the battery pack case has a sealed structure. However, when an abnormality occurs in the battery and the internal pressure of the case rises, it is necessary to quickly discharge the gas to the outside. For example, Patent Document 1 proposes a gas discharge mechanism using a discharge duct and a cylinder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, when an abnormality occurs in the battery and the internal pressure of the battery pack rises, it is an important issue to safely and smoothly discharge the gas. The gas discharge mechanism in the battery pack of Patent Document 1 has a complicated structure and requires many dedicated parts, and there are problems particularly in terms of miniaturization and cost reduction of the battery pack.

[0005] An object of the present disclosure is to provide a battery pack including a gas discharge mechanism that can safely and smoothly discharge gas while having a simple structure.

Means for Solving the Problems

[0006] The battery pack according to the present disclosure includes a case including a plurality of batteries, a case body that houses the plurality of batteries, and a case lid that closes an opening of the case body. The case is configured such that when the internal pressure rises due to the generation of gas, the case body and the case lid are relatively displaced in a direction away from each other, and an exhaust opening for gas is formed while the connection between the case body and the case lid is maintained.

Effects of the Invention

[0007] The battery pack according to the present disclosure has a simple structure, and when an abnormality occurs in the battery and the internal pressure of the battery pack rises, gas can be discharged safely and smoothly.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, specific shapes, materials, directions, numerical values, etc. are examples for facilitating the understanding of the present disclosure and can be appropriately changed according to applications, purposes, specifications, etc. Also, selectively combining the components of the embodiments and modification examples described below is assumed from the beginning.

[0010] (First Embodiment) FIG. 1 is an external view of a battery pack 10 according to the first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. As shown in FIGS. 1 and 2, the battery pack 10 includes a plurality of batteries 50 and a case 60. The case 60 has a case body 20 that houses the plurality of batteries 50 and a case lid 30 that closes the opening 22 (see FIG. 3) of the case body 20. The case 60 has a structure in which each opening of the case body 20 formed in a rectangular tube shape is closed by the case lid 30 and the case bottom 40, respectively, and the internal space is sealed. For this reason, water and dust do not enter the inside of the case 60. Hereinafter, for convenience of explanation, the side of the case lid 30 of the case 60 is defined as the upper side, the side of the case bottom 40 is defined as the lower side, and the direction in which the case lid 30, the case body 20, and the case bottom 40 are arranged is defined as the vertical direction.

[0011] The plurality of batteries 50 are electrically connected to each other to form a battery assembly. The battery assembly has, for example, a structure in which a plurality of battery groups in which a plurality of batteries 50 are connected in parallel are connected in series, and is configured to output a voltage suitable for the device to be used. The battery 50 is, for example, a cylindrical battery. Although a cylindrical battery is illustrated as the battery 50 in FIG. 2, the battery is not limited to a cylindrical battery and may be a prismatic battery, a laminated battery, or the like. Also, the battery 50 may be an aqueous battery or a non-aqueous battery. An example of a non-aqueous battery is a lithium-ion battery.

[0012] The battery 50 is a cylindrical battery having a bottomed cylindrical outer can and a sealing body that closes the opening of the outer can. Also, an insulating gasket is provided between the outer can and the sealing body. In a cylindrical battery, generally, the sealing body serves as the positive electrode terminal and the outer can serves as the negative electrode terminal. The sealing body is provided with an exhaust valve for discharging gas when an abnormality occurs in the battery 50 and the internal pressure rises. Note that the exhaust valve may be provided at the bottom of the outer can.

[0013] A plurality of batteries 50 are housed in a holder 51 within a case 60. The holder 51 fixes the arrangement of the batteries 50 and maintains the form of the assembled battery. Also, the battery pack 10 includes, for example, a terminal board that electrically connects the plurality of batteries 50. The terminal board includes a positive electrode side terminal board that is electrically connected to the sealing body, which is the positive electrode terminal of each battery 50, and a negative electrode side terminal board that is electrically connected to the outer can, which is the negative electrode terminal of each battery 50. The terminal board may be integrated with the holder 51.

[0014] The holder 51 is configured to hold the upper and lower end portions of each battery 50. For example, holes 52 are formed in the holder 51 at positions facing the sealing bodies of the respective batteries 50. The holes 52 expose the sealing bodies of the respective batteries 50 and facilitate the smooth discharge of gas from the sealing bodies (exhaust valves) when an abnormality occurs in the batteries 50. In the present embodiment, each battery 50 is arranged such that the sealing body faces the case lid 30 side, and holes 52 are formed in the holder 51 at positions overlapping the sealing bodies. For this reason, when gas is discharged from the battery 50, the case lid 30 is easily pushed upward.

[0015] The case 60 is provided with external terminals (not shown) that are electrically connected to the respective batteries 50. The external terminals are provided, for example, at the case bottom 40 and are used as terminals for supplying a DC voltage when the battery pack 10 is incorporated into a device on which it is mounted and used. Also, the external terminals are used when charging the battery pack 10 (batteries 50).

[0016] Hereinafter, with further reference to FIG. 3, the configuration of the case 60 will be described in detail. FIG. 3 is a view showing a state in which the case lid 30 is removed from the case body 20.

[0017] As shown in FIGS. 1 to 3, the case 60 constituting the battery pack 10 has a case body 20, a case lid 30, and a case bottom 40, and is formed in a rectangular parallelepiped shape that is long in the vertical direction. The case 60 may be made of resin or metal. The case body 20 is formed in a rectangular tube shape with both upper and lower ends open as described above. The case 60 has a structure in which the opening 22 on the upper end side of the case body 20 is closed by the case lid 30, and the opening on the lower end side is closed by the case bottom 40. In the internal space of the sealed case body 20, the plurality of batteries 50 are arranged with the sealing bodies facing the direction of the case lid 30, but the number, arrangement, etc. of the batteries are not limited to those illustrated in FIG. 2.

[0018] The case bottom 40 has a bottom plate 41 and side surface portions 42 erected on the peripheral edge of the bottom plate 41, and forms the bottom of the case 60. The bottom plate 41 has, for example, a quadrangular shape in a bottom view and is formed slightly larger than the opening on the lower end side of the case body 20. The side surface portions 42 have a step in the middle in the vertical direction and are formed in a rectangular tube shape in which the upper part is smaller than the lower part. The upper part of the side surface portions 42 is inserted into the case body 20 from the opening on the lower end side of the case body 20 and joined to the case body 20. In the present embodiment, the case body 20 and the case bottom 40 are separate bodies, but the case body may be a bottomed cylindrical body with one end in the axial direction closed.

[0019] The case 60 is configured such that when gas is discharged from the battery 50 and the internal pressure rises, the case body 20 and the case lid 30 are relatively displaced in a direction away from each other, and an exhaust opening for gas is formed while the connection between the case body 20 and the case lid 30 is maintained. In the present embodiment, as shown in FIG. 4 described later, when the internal pressure of the case 60 rises, the case lid 30 is pushed upward, and an exhaust opening is formed at the boundary portion between the case body 20 and the case lid 30. By forming the exhaust opening, the gas can be smoothly discharged to the outside of the case 60, and damage to the case 60 is prevented.

[0020] The case lid 30 has a top plate 31 and side faces 32 erected at the peripheral edge of the top plate 31. The top plate 31 has, for example, a rectangular shape in plan view and is formed slightly larger than the opening 22 on the upper end side of the case body 20. The side faces 32 are formed in a square tube shape, and the outer surface of the side faces 32 and the outer surface of the case body 20 are flush. Further, the case lid 30 includes a slide portion 33 inserted into the case body 20. The slide portion 33 is an extension extending downward from the lower end of the side face 32 and is formed inside the case 60 rather than the side face 32.

[0021] The slide portion 33 may be formed in a part along the circumferential direction of the side face 32. For example, two plate-like slide portions 33 may be formed so as to face each other. In the present embodiment, the slide portion 33 is formed over the entire circumferential length of the side face 32 so as to surround the opening 22 of the case body 20. That is, the slide portion 33 has a square tube shape slightly smaller than the side face 32. The slide portion 33 formed in a square tube shape is formed in a size that can be inserted into the case body 20 from the opening 22.

[0022] At the lower end of the slide portion 33, a claw 34 engaging with the case body 20 is formed. In the present embodiment, a protrusion 21 is formed at the edge of the opening 22 of the case body 20, and the claw 34 engages with the protrusion 21 so that the case lid 30 is not detached from the case body 20. The claw 34 is formed at both ends of each of the two opposing side faces among the four side faces of the slide portion 33 formed in a square tube shape. Although it will be described in detail later, when the internal pressure of the case 60 rises and the case lid 30 is pushed upward, the claw 34 catches on the protrusion 21, thereby maintaining the connected state of the case body 20 and the case lid 30.

[0023] A seal member 35 that abuts against the inner surface of the case body 20 may be provided at the base of the slide portion 33. In the present embodiment, the seal member 35 is in close contact with the protrusion 21 of the case body 20, closing the gap between the case body 20 and the slide portion 33 and enhancing the sealing property inside the case 60. For the seal member 35, a rubber packing such as an O-ring is used, for example. The position of the case lid 30 may be fixed by the seal member 35 compressed between the case body 20 and the slide portion 33. Further, the case lid 30 may be biased toward the case body 20 by a biasing member (not shown).

[0024] The slide portion 33 has a plurality of exhaust holes 36 and is configured to be exposed to the outside of the case 60 when the internal pressure of the case 60 rises and the case lid 30 is pushed upward, that is, when the case body 20 and the case lid 30 are relatively displaced in a direction away from each other. In the present embodiment, the exhaust hole 36 serves as the exhaust opening, and the slide portion 33 is a main component of the gas discharge mechanism.

[0025] Although it will be described in detail later, when the internal pressure of the case 60 rises and the case lid 30 is pushed upward, a gap S (see FIG. 4) is formed between the upper end of the case body 20 and the lower end of the side surface portion 32 of the case lid 30. At this time, the slide portion 33 is exposed from this gap S. In other words, the slide portion 33 is arranged so as to close this gap S. Since a plurality of exhaust holes 36 are formed in the slide portion 33, the gas inside the case 60 is discharged to the outside through the exhaust holes 36.

[0026] The slide portion 33 is formed in a rectangular prism shape with a square cross section, and a plurality of exhaust holes 36 are formed on each of the four side surfaces of the slide portion 33. The exhaust holes 36 are formed, for example, in the same number and the same size on each side surface. In this case, the gas inside the case 60 is easily discharged evenly around the case 60. Note that the exhaust holes 36 may be formed on one side surface of the slide portion 33, or may be formed on two opposing side surfaces. Also, the number, size, etc. of the exhaust holes 36 may be different for each side surface. In this case, the gas can be preferentially discharged in a specific direction outside the case 60.

[0027] The exhaust holes 36 are formed over a wide range on each side surface of the slide portion 33. The exhaust holes 36 have, for example, a perfect circular shape and are formed in a vertical and horizontal arrangement at equal intervals. A small number of large exhaust holes 36 may be formed in the slide portion 33, but in order to discharge the gas safely and smoothly, it is preferable that a large number of small exhaust holes 36 are formed. Also, from the viewpoint of controlling gas discharge, it is preferable that the plurality of exhaust holes 36 are formed in a regular arrangement. The arrangement of the exhaust holes 36 is not limited to a vertical and horizontal arrangement as long as it is regular, and may be a staggered arrangement or the like.

[0028] The size of the exhaust holes 36 and the opening area of the slide portion 33 (total area of the exhaust holes 36) are determined so that the gas discharge state is appropriate. The gas discharge speed is determined by the internal pressure of the case 60, the size of each exhaust hole 36, and the opening area of the slide portion 33. Since the discharged gas contains combustible components, it is necessary to prevent ignition when the gas is discharged from the case 60. As a result of the study by the present inventors, it has been found that the gas discharge speed is an important factor in suppressing ignition, and the ignition suppression effect becomes high when it exceeds a predetermined threshold value. Therefore, it is preferable to set the size of each exhaust hole 36 and the opening area of the slide portion 33 so that the gas discharge speed exceeds this threshold value.

[0029] The slide portion 33 may have a mesh structure. The mesh structure means a lattice-like or net-like structure having periodically arranged thin linear partitions. Note that the gaps between the thin linear partitions become the exhaust holes 36. For example, the width of the partition is smaller than the width of the exhaust hole 36, and the opening ratio of the mesh structure (total area of the exhaust holes 36) is set to be larger than 50%. Also, the mesh structure is preferably made of metal.

[0030] By forming the slide portion 33 into a mesh structure, for example, it becomes easier to increase the opening area while reducing the size of each exhaust hole 36. For this reason, the discharge of gas becomes smoother, and the control of the discharge speed also becomes easier. Further, by forming the slide portion 33 into a mesh shape, it is possible to easily trap sparks while ensuring smooth gas discharge performance. When the mesh structure efficiently traps the sparks, the ignition suppression effect becomes even higher.

[0031] In the present embodiment, the opening area is configured to change according to the internal pressure of the case 60. When the internal pressure of the case 60 increases, the case lid 30 is pushed upward, but the amount of upward push of the case lid 30 depends on the internal pressure. Since the exhaust holes 36 are formed over a wide range on each side surface of the slide portion 33 that is exposed when the case lid 30 is pushed upward, the number of exhaust holes 36 exposed according to the amount of upward push of the case lid 30, that is, the internal pressure, changes, and thereby the opening area changes. The slide portion 33 may be formed long within a range where interference with the internal structure of the battery pack 10 does not pose a problem, and the longer the slide portion 33 is, the easier it is to change the opening area according to the internal pressure.

[0032] The case lid 30 may move downward by its own weight when gas is discharged from the case 60 and the internal pressure decreases, but preferably, it is biased toward the case body 20 side by a biasing member (not shown). That is, the case lid 30 is biased in a direction in which the case body 20 and the case lid 30 approach each other. In this case, the movement of the case lid 30 during normal use is more reliably suppressed. Further, since the exhaust opening closes after the gas is discharged, the inflow of air into the case 60 is suppressed, and the combustion of the battery 50 is more reliably suppressed.

[0033] The biasing member attached to the case lid 30 is, for example, a tension spring, a rubber belt, or the like. One end of the biasing member is fixed to the case body 20, and the other end is fixed to the case lid 30. The biasing member is preferably fixed inside the case 60, but may be fixed outside the case 60.

[0034] FIG. 4 is a cross-sectional view showing a state in which the gas discharge mechanism is operating, that is, a state in which the case lid 30 is pushed upward. As shown in FIG. 4, when gas is discharged from the battery 50 due to an abnormality of the battery 50 and the internal pressure of the case 60 increases, the case lid 30 is pushed upward, and a gap S is formed between the upper end of the case body 20 and the lower end of the side surface portion 32 of the case lid 30. At this time, the slide portion 33 slides along the inner surface of the case body 20 and moves upward so as to close the gap S, and is exposed to the outside of the case 60 from the gap S. Since a plurality of exhaust holes 36 are formed in the slide portion 33, the gas in the case 60 is discharged to the outside through the exhaust holes 36. That is, when the exhaust holes 36 are exposed, the exhaust holes 36 function as openings for discharging gas.

[0035] According to the battery pack 10, a gap S is formed at the boundary portion between the case body 20 and the case lid 30, and the exhaust holes 36 of the slide portion 33 are exposed, so that the gas is smoothly discharged to the outside of the case 60, and the case 60 is prevented from being damaged. At this time, since the claw 34 of the slide portion 33 engages with the protrusion 21 of the case body 20, the case lid 30 is prevented from coming off from the case body 20. That is, an opening for discharging gas is formed while the connection between the case body 20 and the case lid 30 is maintained.

[0036] When the case lid 30 is biased toward the case body 20 side, when the internal pressure reaches a predetermined value that overcomes the biasing force, the case lid 30 is pushed upward against the biasing force, a gap S is formed, and the exhaust holes 36 of the slide portion 33 are exposed. Then, the gas is discharged from the exhaust holes 36. When the gas is discharged and the internal pressure of the case 60 decreases, the case lid 30 is pulled toward the case body 20 side by the biasing force, and the case lid 30 returns to the original position without the gap S. Thereby, the internal space of the case 60 is sealed again, and the inflow of air is suppressed.

[0037] The moving distance of the case lid 30 increases when the internal pressure is high and decreases when the internal pressure is low. When the moving distance of the case lid 30 is large, the length of the slide portion 33 exposed outside the case 60 becomes long. Then, the number of exhaust holes 36 exposed outside the case body 20 increases, and thus the total area of the exposed exhaust holes 36 becomes large. That is, the higher the internal pressure, the larger the total area of the exhaust holes 36 exposed to the outside of the case body 20, and it becomes possible to quickly discharge the gas with increased pressure. In addition, even when the internal pressure is high, if the claw 34 is provided on the slide portion 33, the movement is restricted by the claw 34 being caught by the protrusion 21, and it is possible to prevent the case lid 30 from completely coming off from the case body 20.

[0038] The gas discharge mechanism of the battery pack 10 can change the opening area according to the internal pressure and can exhibit the discharge capacity according to the internal pressure. The battery pack 10 has a simple structure in which only the slide portion 33 engaged with the case body 20 is provided on the case lid 30, does not require a dedicated additional part, and can realize a gas discharge mechanism that can be miniaturized.

[0039] (Embodiment 2) Hereinafter, with reference to FIGS. 5 and 6, the battery pack 100 according to the second embodiment of the present disclosure will be described. FIGS. 5 and 6 are cross-sectional views of the battery pack 100, and FIG. 6 shows a state where the case lid 300 is pushed upward. Hereinafter, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant descriptions are omitted.

[0040] As shown in FIG. 5, the battery pack 100 is different from the battery pack 10 of the first embodiment in that it includes a case 600 in which a slide portion 203 having a plurality of exhaust holes 206 is formed in a case body 200. Similar to the case 60 of the battery pack 10, the case 600 includes a case lid 300 that closes the opening of the case body 200 and a case bottom 40. However, a protrusion 303 with which the slide portion 203 engages is formed on the case lid 300, and the slide portion is not formed. The case lid 300 has a top plate 301 and side plates 302 erected on the peripheral edge of the top plate 301. A protrusion 303 with which the claw 204 of the slide portion 203 is caught is formed at the lower end of the side plate 302 formed in a rectangular tube shape.

[0041] Inside the case 600, a plurality of batteries 50 are accommodated in the same arrangement as in the case of the battery pack 10. The slide portion 203 formed in the case body 200 is formed in a rectangular tube shape with a size that can be inserted into the case lid 300, and a plurality of exhaust holes 206 are regularly formed on each side surface of the slide portion 203. In addition, a seal member 205 for closing the gap between the case body 200 and the case lid 300 and enhancing the sealing performance of the case 600 is provided at the base of the slide portion 203. The slide portion 203 has the same structure as the slide portion 33 of the battery pack 10, except that it extends upward from the upper end of the case body 200.

[0042] Similar to the case 60, the case 600 is configured such that when the internal pressure rises due to gas generation, the case body 200 and the case lid 300 are relatively displaced in a direction away from each other, and the slide portion 203 is exposed to the outside of the case 600. Then, an exhaust opening for gas is formed while the connection between the case body 200 and the case lid 300 is maintained. Also in this case, the exhaust hole 206 serves as the exhaust opening for gas. Note that the configuration of the battery pack 10 described above can be selectively applied to the battery pack 100.

[0043] As shown in FIG. 6, also in the case of the battery pack 100, when the internal pressure of the case 600 rises, the case lid 300 is pushed upward, and a gap S is formed between the upper end of the case body 200 and the lower end of the side surface portion 302 of the case lid 300. Then, the slide portion 203 provided on the case body 200 is exposed to the outside of the case 60 through the gap S. Since a plurality of exhaust holes 206 are formed in the slide portion 203, the gas in the case 600 is discharged to the outside through the exhaust holes 206.

[0044] At this time, the claw 204 of the slide portion 203 engages with the protrusion 303 of the case lid 300, so that the case lid 300 is prevented from coming off the case body 200. Further, particularly when the case lid 300 is biased toward the case body 200 side, it becomes easy to change the opening area according to the internal pressure, and the discharge amount of the gas can be controlled so that the discharge speed of the gas exceeds the above-described threshold value. According to the battery pack 100, similarly to the battery pack 10, it is possible to discharge the gas safely and smoothly.

[0045] The embodiments of the present disclosure have been described above, but these are merely examples and do not exclude configurations other than the above. For example, in the above embodiment, the appearance of the battery pack is a rectangular parallelepiped, but the appearance is not limited to this, and it may be a cylindrical shape or other shapes are not excluded. Also, although the respective side surfaces of the rectangular parallelepiped are substantially the same shape, the sizes and shapes of adjacent surfaces may be different. The dimensional ratio between the case lid and the case body is not limited to that disclosed in the drawings. Further, as the shape when actually using the battery pack, there may be provided protrusions, recesses, handles, terminals, etc. around it, but this is done within a range that does not affect the operation of the discharge mechanism described in the present disclosure and does not affect the action of the discharge mechanism of the present embodiment.

[0046] In the above embodiment, engaging portions (claws) with the case body are formed on two opposing side surfaces of the extending portion that constitutes the gas discharge mechanism. However, the engaging portions may be formed not only on the two opposing side surfaces but on all side surfaces. Further, although the engaging portions are formed at both ends of one side of the extending portion, they may be formed only on a part of the central portion of one side or over the entire length of one side.

[0047] Also, instead of dividing the case vertically, it may be configured to be divided into left and right parts. By providing the discharge mechanism as shown in the embodiment of the present disclosure in the case parts, it is possible to maintain the sealed state of the battery pack and operate the gas discharge mechanism when gas is generated and the internal pressure rises.

[0048] The battery pack according to the present disclosure can be used as a power supply component for an electronic device. For example, there are battery packs for notebook computers, battery packs for cleaners, battery packs for power tools, etc. It is also applicable to the battery of an electric assist bicycle. Even if it is not listed here, it is applicable as long as it is the use purpose of the battery pack.

Explanation of Reference Numerals

[0049] 10, 100 Battery pack, 20, 200 Case body, 21, 303 Protrusion, 22 Opening, 30, 300 Case lid, 31, 301 Top plate, 32, 302 Side portion, 33, 203 Slide portion, 34, 204 Claw, 35, 205 Seal member, 36, 206 Exhaust hole, 40 Case bottom, 41 Bottom plate, 42 Side portion, 50 Battery, 51 Holder, 52 Hole, 60, 600 Case

Claims

1. A plurality of batteries, a case including a case body that houses the plurality of batteries and a case lid that closes an opening of the case body, and the case is configured such that when the internal pressure rises due to gas generation, the case body and the case lid are relatively displaced in a direction away from each other, and an exhaust opening for gas is formed while the connection between the case body and the case lid is maintained. One of the case body and the case lid is formed with an extension portion that is inserted into the other. The extension portion has a plurality of exhaust holes and is configured to be exposed to the outside of the case when the case body and the case lid are relatively displaced in a direction away from each other. A battery pack.

2. The battery pack according to claim 1, wherein the extension portion has a mesh structure.

3. The battery pack according to claim 1 or 2, wherein the case has a structure in which the case lid is biased in a direction in which the case body and the case lid approach each other.

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