Patent Description:
A plurality of non-aqueous electrolyte secondary batteries such as lithium ion batteries may be electrically connected and housed in a case to be used in a form of a battery pack. When an abnormality occurs in a battery in the battery pack, a large amount of high-temperature combustible gas may be generated from the battery. When the gas is not appropriately exhausted to the outside of the battery pack, the internal pressure of the battery pack may increase and thus may damage the battery pack case. In general, the battery pack case is required to have a sealed structure in order to prevent water and dust from entering the inside of the battery pack, but when an abnormality occurs in the battery and the internal pressure of the case increases, it is necessary to quickly exhaust gas to the outside. For example, PTL <NUM> proposes a gas exhaust mechanism including a exhausting duct and a cylinder.

As described above, it is an important problem to exhaust gas safely and smoothly when an abnormality occurs in a battery and the internal pressure of the battery pack increases. The gas exhaust mechanism in the battery pack of PTL <NUM> has a complicated structure and requires a large number of dedicated components, and is particularly problematic in terms of downsizing, cost reduction, etc. of the battery pack.

An object of the present disclosure is to provide a battery pack including a gas exhaust mechanism capable of safely and smoothly exhausting gas while having a simple structure.

A battery pack according to the present disclosure includes: a plurality of batteries; and a case including a case body housing the plurality of batteries and a case lid covering an opening of the case body, wherein the case is configured such that when an internal pressure increases due to generation of gas, the case body and the case lid are relatively displaced in directions away from each other and a gas exhaust opening is formed in a state where a coupling between the case body and the case lid is maintained.

A battery pack according to the present disclosure can safely and smoothly exhaust gas when an abnormality occurs in a battery and the internal pressure of the battery pack increases, while having a simple structure.

An exemplary embodiment of the present disclosure is described in detail below with reference to the drawings. In the following description, specific shapes, materials, directions, numerical values, etc. are examples shown to facilitate understanding of the present disclosure and may be changed as appropriate to suit uses, purposes, specifications, or other requirements. In addition, it is initially envisaged that the configuration elements of the exemplary embodiment and the modified example thereof described hereinafter are selectively combined.

<FIG> is an external view of battery pack <NUM> according to the first exemplary embodiment of the present disclosure. <FIG> is a cross-sectional view taken along line A-A in <FIG>. As shown in <FIG> and <FIG>, battery pack <NUM> includes case <NUM> and a plurality of batteries <NUM>. Case <NUM> includes case body <NUM> that houses the plurality of batteries <NUM> and case lid <NUM> that covers opening <NUM> (see <FIG>) of case body <NUM>. Case <NUM> has a structure in which each opening of case body <NUM> formed in a rectangular tube shape is closed by case lid <NUM> and case bottom <NUM>, with the internal space sealed. Thus, water and dust are prevented from entering case <NUM>. Hereinafter, for convenience of description, case lid <NUM> side of case <NUM> is referred to as an upper side, case bottom <NUM> side is referred to as a lower side, and a direction in which case lid <NUM>, case body <NUM>, and case bottom <NUM> are arranged is referred to as a vertical direction.

The plurality of batteries <NUM> is electrically connected to each other to constitute an assembled battery. The assembled battery has, for example, a structure in which a plurality of battery groups each including a plurality of batteries <NUM> connected in parallel is connected in series, and is configured to output a voltage suitable for a device to be used. Each battery <NUM> is, for example, a cylindrical battery. Although a cylindrical battery is illustrated as battery <NUM> in <FIG>, the battery is not limited to the cylindrical battery and may be a prismatic battery, a laminate battery, etc. Further, battery <NUM> may be an aqueous battery or a non-aqueous battery. An example of the non-aqueous battery is a lithium ion battery.

Battery <NUM> is a cylindrical battery including a bottomed cylindrical outer covering can and a sealing body that covers an opening of the outer covering can. An insulating gasket is disposed between the outer covering can and the sealing body. In a cylindrical battery, generally, the sealing body serves as a positive-electrode terminal and the outer covering can serves as a negative-electrode terminal. The sealing body is provided with an exhaust valve for exhausting gas when an abnormality occurs in battery <NUM> and the internal pressure increases. The exhaust valve may be provided at the bottom of the outer covering can.

The plurality of batteries <NUM> is housed by holder <NUM> inside case <NUM>. Holder <NUM> fixes the arrangement of batteries <NUM> and maintains the layout of the assembled battery. In addition, battery pack <NUM> includes, for example, a terminal plate that electrically connects the plurality of batteries <NUM>. The terminal plate includes a positive electrode side terminal plate electrically connected to the sealing body, which is the positive-electrode terminal of each battery <NUM>, and a negative electrode side terminal plate electrically connected to the outer covering can, which is the negative-electrode terminal of each battery <NUM>. The terminal plate may be integrated with holder <NUM>.

Holder <NUM> is configured to hold both upper and lower ends of each battery <NUM>. In holder <NUM>, for example, hole <NUM> is formed at a position facing the sealing body of each battery <NUM>. Hole <NUM> exposes the sealing body of each battery <NUM> and allows gas to be smoothly exhausted from the sealing body (exhaust valve) when an abnormality occurs in battery <NUM>. In the present exemplary embodiment, each battery <NUM> is arranged such that the sealing body faces case lid <NUM>, and hole <NUM> is formed in holder <NUM> at a position overlapping the sealing body. Thus, when gas is exhausted from battery <NUM>, case lid <NUM> is easily pushed upward.

Case <NUM> is provided with an external terminal (not shown) electrically connected to each battery <NUM>. The external terminal is provided on case bottom <NUM>, for example, and is used as a terminal for supplying a direct current voltage when the external terminal is installed in a device where battery pack <NUM> is mounted and used. The external terminal is also used when battery pack <NUM> (battery <NUM>) is charged.

Hereinafter, the configuration of case <NUM> is described in detail with further reference to <FIG> is a view showing a state in which case lid <NUM> is removed from case body <NUM>.

As shown in <FIG>, case <NUM> constituting battery pack <NUM> includes case body <NUM>, case lid <NUM>, and case bottom <NUM>, and is formed in a rectangular-parallelepiped shape elongated in the vertical direction. Case <NUM> may be made of resin or may be made of metal. As described above, case body <NUM> is formed in a rectangular tube shape with both upper and lower ends opened. Case <NUM> has a structure in which opening <NUM> on the upper end side of case body <NUM> is closed by case lid <NUM> and the opening on the lower end side of case body <NUM> is closed by case bottom <NUM>. In the internal space of sealed case body <NUM>, the plurality of batteries <NUM> is arranged in a state where the sealing bodies face case lid <NUM>, but the number, arrangement, etc. of the batteries are not limited to the example illustrated in <FIG>.

Case bottom <NUM> includes bottom plate <NUM> and lateral part <NUM> which is erected on a peripheral edge part of bottom plate <NUM>, and forms a bottom part of case <NUM>. Bottom plate <NUM> has, for example, a quadrangular shape in bottom view and is formed slightly larger than the opening on the lower end side of case body <NUM>. Lateral part <NUM> has a step at an intermediate part in the vertical direction, and is formed in a rectangular tube shape in which an upper part is smaller than a lower part. The upper part of lateral part <NUM> is inserted into case body <NUM> from the opening on the lower end side of case body <NUM> and is joined to case body <NUM>. In the present exemplary embodiment, case body <NUM> and case bottom <NUM> are separate bodies, but the case body may be a bottomed cylindrical part with one axial end closed.

Case <NUM> is configured such that when gas is exhausted from battery <NUM> and the internal pressure increases, case body <NUM> and case lid <NUM> are relatively displaced in directions away from each other and a gas exhaust opening is formed in a state where a coupling between case body <NUM> and case lid <NUM> is maintained. In the present exemplary embodiment, as shown in <FIG> to be described later, when the internal pressure of case <NUM> increases, case lid <NUM> is pushed upward, and an exhaust opening is formed at a boundary part between case body <NUM> and case lid <NUM>. Since the exhaust opening is formed, gas can be smoothly exhausted to the outside of case <NUM>, and damage to case <NUM> is prevented.

Case lid <NUM> includes top plate <NUM> and lateral part <NUM> which is erected on a peripheral edge part of top plate <NUM>. Top plate <NUM> has, for example, a quadrangular shape in plan view and is formed slightly larger than opening <NUM> on the upper end side of case body <NUM>. Lateral part <NUM> is formed in a rectangular tube shape, and the outer surface of lateral part <NUM> and the outer surface of case body <NUM> are flush with each other. Case lid <NUM> includes a slide part <NUM> inserted into case body <NUM>. Slide part <NUM> is an extension part extending downward from a lower end of lateral part <NUM>, and is formed inside of case <NUM> relative to lateral part <NUM>.

Slide part <NUM> may be formed on a part of lateral part <NUM> in a circumferential direction. For example, two plate-shaped slide parts <NUM> may be formed in a manner of facing each other. In the present exemplary embodiment, slide part <NUM> is formed over the entire circumferential length of lateral part <NUM> in a manner of surrounding opening <NUM> of case body <NUM>. That is, slide part <NUM> has a rectangular tube shape that is smaller than lateral part <NUM>. Slide part <NUM> formed in the rectangular tube shape is formed to have a size that allows slide part <NUM> to be inserted into case body <NUM> from opening <NUM>.

Tab <NUM> that engages with case body <NUM> is formed at a lower end of slide part <NUM>. In the present exemplary embodiment, projection <NUM> is formed at an edge of opening <NUM> of case body <NUM>, and tab <NUM> is engaged with projection <NUM>, so that case lid <NUM> is not detached from case body <NUM>. Tabs <NUM> are formed at both ends of each of two opposing slide surfaces among four slide surfaces of slide part <NUM> formed in the rectangular tube shape. As described in detail below, when the internal pressure of case <NUM> increases and case lid <NUM> is pushed upward, tab <NUM> is caught by projection <NUM>, and thus, the coupling state between case body <NUM> and case lid <NUM> is maintained.

Sealing member <NUM> that abuts against an inner surface of case body <NUM> may be provided at a base of slide part <NUM>. In the present exemplary embodiment, sealing member <NUM> is in close contact with projection <NUM> of case body <NUM> and closes a gap between case body <NUM> and sliding part <NUM> to improve the sealing property of the inside of case <NUM>. A rubber packing such as an O-ring is used for sealing member <NUM>, for example. The position of case lid <NUM> may be fixed by sealing member <NUM> which is compressed between case body <NUM> and slide part <NUM>. Case lid <NUM> may be biased toward case body <NUM> by a biasing member, which is not shown.

Slide part <NUM> has a plurality of exhaust holes <NUM>, and is exposed to the outside of case <NUM> when the internal pressure of case <NUM> increases and case lid <NUM> is pushed upward, that is, when case body <NUM> and case lid <NUM> are relatively displaced in directions away from each other. In the present exemplary embodiment, exhaust hole <NUM> serves as the exhaust opening, and slide part <NUM> serves as a main configuration element of a gas exhaust mechanism.

As described in detail below, when the internal pressure of case <NUM> increases and case lid <NUM> is pushed upward, gap S (see <FIG>) is formed between the upper end of case body <NUM> and the lower end of lateral part <NUM> of case lid <NUM>. At this time, slide part <NUM> is exposed from gap S. In other words, slide part <NUM> is disposed so as to cover gap S. Since the plurality of exhaust holes <NUM> is formed in slide part <NUM>, gas in case <NUM> is exhausted to the outside through exhaust holes <NUM>.

Slide part <NUM> is formed in a rectangular tube shape having a quadrangular cross section, and the plurality of exhaust holes <NUM> is formed in each of the four side surfaces of slide part <NUM>. For example, exhaust holes <NUM> are formed in the same number and the same size in each side surface. In this case, gas in case <NUM> is easily exhausted evenly around case <NUM>. Note that exhaust holes <NUM> may be formed in one side surface of slide part <NUM>, or may be formed in two opposite side surfaces of slide part <NUM>. In addition, the number, size, etc. of exhaust holes <NUM> may be different for each side surface. In this case, gas can be preferentially exhausted in a specific direction outside case <NUM>.

Exhaust holes <NUM> are formed in a wide range of each side surface of slide part <NUM>. Exhaust holes <NUM> have, for example, a perfect circular shape, and are arranged in rows and columns at equal intervals. In slide part <NUM>, although a small number of large exhaust holes <NUM> may be formed, it is preferable to form a large number of small exhaust holes <NUM> in order to exhaust gas safely and smoothly. In addition, from the viewpoint of control of gas exhaust, the plurality of exhaust holes <NUM> is preferably formed to be regularly arranged. As long as the arrangement is regular, the arrangement of exhaust holes <NUM> is not limited to an arrangement in which exhaust holes <NUM> are arranged in rows and columns, and may be a staggered arrangement, etc..

The size of exhaust hole <NUM> and the opening area of slide part <NUM> (the total area of exhaust holes <NUM>) are determined so that the gas exhaust state is appropriate. The gas exhaust speed is determined by the internal pressure of case <NUM>, the size of each exhaust hole <NUM>, and the opening area of slide part <NUM>. Since exhausted gas contains combustible components, it is necessary to prevent ignition when gas is exhausted from case <NUM>. As a result of studies by the inventor of the present disclosure, it has been found that the gas exhaust speed is an important factor for suppressing ignition and the ignition suppressing effect is enhanced when the gas exhaust speed exceeds a predetermined threshold value. Therefore, it is preferable to set the size of each exhaust hole <NUM> and the opening area of slide part <NUM> so that the gas exhaust speed exceeds the threshold value.

Sliding part <NUM> may have a mesh structure. The mesh structure means a lattice-shaped or net-shaped structure having periodically arranged fine line-shaped partitions. The gaps between the fine line-shaped partitions serve as exhaust holes <NUM>. For example, the width of the partition is set to be smaller than the width of exhaust hole <NUM>, and the opening ratio of the mesh structure (the total area of exhaust holes <NUM>) is set to be larger than <NUM>%. The mesh structure is preferably made of metal.

When slide part <NUM> has the mesh structure, for example, it is easy to increase the opening area while reducing the size of each exhaust hole <NUM>. Thus, gas is exhausted more smoothly and the exhaust speed is easily controlled. In addition, by forming slide part <NUM> in a mesh shape, it is possible to easily trap sparks while ensuring smooth gas exhaust performance. When sparks are efficiently trapped by the mesh structure, the ignition suppressing effect is further enhanced.

In the present exemplary embodiment, the opening area changes in accordance with the internal pressure of case <NUM>. When the internal pressure of case <NUM> increases, case lid <NUM> is pushed upward, and the push-up amount of case lid <NUM> depends on the internal pressure. Since exhaust holes <NUM> are formed in a wide range of each side surface of slide part <NUM> which is exposed when case lid <NUM> is pushed upward, the push-up amount of case lid <NUM> changes, that is, the number of exhaust holes <NUM> which are exposed in accordance with the internal pressure changes, and thereby the opening area changes. Slide part <NUM> may be formed to be long within a range where interference with the internal structure of battery pack <NUM> is not a problem, and as slide part <NUM> becomes longer, it is easier to change the opening area in accordance with the internal pressure.

Case lid <NUM> may move downward by its own weight when gas is exhausted from case <NUM> and the internal pressure decreases, but is preferably biased toward case body <NUM> by a biasing member (not shown). That is, case lid <NUM> is biased in a direction to make case body <NUM> and case lid <NUM> approach each other. In this case, the movement of case lid <NUM> during normal use is more reliably suppressed. In addition, since the exhaust opening is closed after gas is exhausted, inflow of air into case <NUM> is suppressed, and combustion of battery <NUM> is more reliably suppressed.

The biasing member attached to case lid <NUM> is, for example, a tension spring, a rubber belt, etc. One end of the biasing member is fixed to case body <NUM>, and the other end of the biasing member is fixed to case lid <NUM>. The biasing member is preferably fixed inside case <NUM>, but may also be fixed outside case <NUM>.

<FIG> is a cross-sectional view showing a state in which the gas exhaust mechanism is actuated, that is, a state in which case lid <NUM> is pushed upward. As shown in <FIG>, in battery pack <NUM>, when gas is exhausted from battery <NUM> due to an abnormality of battery <NUM> and the internal pressure of case <NUM> increases, case lid <NUM> is pushed upward, and gap S is formed between the upper end of case body <NUM> and the lower end of lateral part <NUM> of case lid <NUM>. At this time, slide part <NUM> slides along the inner surface of case body <NUM>, moves upward so as to close gap S, and is exposed to the outside of case <NUM> from gap S. Since the plurality of exhaust holes <NUM> is formed in slide part <NUM>, gas in case <NUM> is exhausted to the outside from exhaust holes <NUM>. That is, when exhaust holes <NUM> are exposed, exhaust holes <NUM> function as gas exhaust openings.

According to battery pack <NUM>, since gap S is formed at the boundary part between case body <NUM> and case lid <NUM> and exhaust holes <NUM> of slide part <NUM> are exposed, gas is smoothly exhausted to the outside of case <NUM>, and damage to case <NUM> is prevented. At this time, since tab <NUM> of slide part <NUM> is engaged with projection <NUM> of case body <NUM>, case lid <NUM> is not detached from case body <NUM>. That is, the gas exhaust opening is formed in a state where the coupling between case body <NUM> and case lid <NUM> is maintained.

When case lid <NUM> is biased toward case body <NUM>, once the internal pressure reaches a predetermined value that overcomes a biasing force, case lid <NUM> is pushed upward against the biasing force, gap S is formed, and exhaust holes <NUM> of slide part <NUM> are exposed. Then, gas is exhausted from exhaust holes <NUM>. When gas is exhausted and the internal pressure of case <NUM> decreases, case lid <NUM> is pulled toward case body <NUM> by the biasing force, and case lid <NUM> returns to an original position with no gap S. As a result, the internal space of case <NUM> is sealed again, and inflow of air is suppressed.

The moving distance of case lid <NUM> is long when the internal pressure is high, and is short when the internal pressure is low. When the moving distance of case lid <NUM> is long, the length of slide part <NUM> exposed to the outside of case <NUM> becomes long. Then, the number of exhaust holes <NUM> exposed to the outside of case body <NUM> increases, and therefore, the total area of exposed exhaust holes <NUM> increases. That is, as the internal pressure becomes higher, the total area of exhaust holes <NUM> exposed to the outside of case body <NUM> becomes larger, and it is thus possible to quickly exhaust gas with increased pressure. Even when the internal pressure is high, if tab <NUM> is provided on slide part <NUM>, tab <NUM> is caught by projection <NUM> to restrict the movement of case lid <NUM>, and it is thus possible to prevent case lid <NUM> from being completely detached from case body <NUM>.

The opening area of the gas exhaust mechanism of battery pack <NUM> changes in accordance with the internal pressure, and the gas exhaust mechanism can exhibit exhaust capacity in accordance with the internal pressure. Battery pack <NUM> has a simple structure, in which case lid <NUM> is only provided with slide part <NUM> that engages with case body <NUM>, and thus battery pack <NUM> allows the realization of a gas exhaust mechanism which does not require a dedicated additional component and can be downsized.

Hereinafter, battery pack <NUM> according to the second exemplary embodiment of the present disclosure is described with reference to <FIG> and <FIG>. <FIG> and <FIG> are cross-sectional views of battery pack <NUM>, and <FIG> shows a state in which case lid <NUM> is pushed upward. In the description hereafter, configuration elements similar to those in the first exemplary embodiment are denoted by the same reference marks, and redundant descriptions thereof are omitted.

As shown in <FIG>, battery pack <NUM> is different from battery pack <NUM> of the first exemplary embodiment in that battery pack <NUM> includes case <NUM> in which slide part <NUM> having a plurality of exhaust holes <NUM> is formed on case body <NUM>. Similar to case <NUM> of battery pack <NUM>, case <NUM> includes case lid <NUM>, which covers the opening of case body <NUM>, and case bottom <NUM>, but on case lid <NUM>, projection <NUM> with which slide part <NUM> engages is formed, and no slide part is formed. Case lid <NUM> has top plate <NUM> and lateral part <NUM> which is erected on a peripheral edge part of top plate <NUM>, and projection <NUM> on which tab <NUM> of slide part <NUM> is caught is formed at a lower end of lateral part <NUM> formed in a rectangular tube shape.

A plurality of batteries <NUM> is housed inside case <NUM> in the same arrangement as in battery pack <NUM>. Slide part <NUM> formed on case body <NUM> is formed in a rectangular tube shape having a size that allows slide part <NUM> to be inserted into case lid <NUM>, and a plurality of exhaust holes <NUM> is regularly formed in each side surface of slide part <NUM>. At a base of sliding part <NUM>, sealing member <NUM> is provided for closing a gap between case body <NUM> and case lid <NUM> to improve the sealing property of case <NUM>. Slide part <NUM> has a structure similar to that of slide part <NUM> of battery pack <NUM>, except that slide part <NUM> extends upward from the upper end of case body <NUM>.

Similar to case <NUM>, case <NUM> is configured such that when the internal pressure increases due to generation of gas, case body <NUM> and case lid <NUM> are relatively displaced in directions away from each other, and slide part <NUM> is exposed to the outside of case <NUM>. Thus, in a state where a coupling between case body <NUM> and case lid <NUM> is maintained, a gas exhaust opening is formed. Also in this case, exhaust hole <NUM> serves as the gas exhaust opening. The configuration of battery pack <NUM> described above can be selectively applied to battery pack <NUM>.

As shown in <FIG>, similarly in battery pack <NUM>, when the internal pressure of case <NUM> increases, case lid <NUM> is pushed upward, and gap S is formed between the upper end of case body <NUM> and the lower end of lateral part <NUM> of case lid <NUM>. Thus, slide part <NUM> provided on case body <NUM> is exposed to the outside of case <NUM> from gap S. Since the plurality of exhaust holes <NUM> is formed in slide part <NUM>, gas in case <NUM> is exhausted to the outside from exhaust holes <NUM>.

At this time, since tab <NUM> of slide part <NUM> is engaged with projection <NUM> of case lid <NUM>, case lid <NUM> is not detached from case body <NUM>. In particular, when case lid <NUM> is biased toward case body <NUM>, it is easy to change the opening area in accordance with the internal pressure, and it is possible to control the exhaust amount of gas so that the gas exhaust speed exceeds the above-described threshold value. According to battery pack <NUM>, similar to battery pack <NUM>, it is possible to exhaust gas safely and smoothly.

Although exemplary embodiments of the present disclosure have been described above, these are merely examples, and configurations other than those described above are not excluded. For example, although the appearance of the battery pack is a rectangular parallelepiped in the above-described exemplary embodiment, the appearance is not limited thereto and may be a cylindrical shape, and other shapes are not excluded. Although each side surface of the rectangular parallelepiped has substantially the same shape, adjacent surfaces may have different sizes and shapes. The dimensional ratio between the case lid and the case body is not limited to that disclosed in the drawings. In addition, when the battery pack is actually used, the shape of the battery pack may be provided with a projection or recess, a handle, a terminal, etc. on the periphery, but those are provided in a range in which the operation of the exhaust mechanism described in the present disclosure is not affected, and do not affect the action of the exhaust mechanism of the present exemplary embodiment.

In the above-described exemplary embodiment, the engagement parts (tabs) with the case body are formed on two opposing side surfaces of the extension part constituting the gas exhaust mechanism, but the engagement parts are not limited to the two opposing side surfaces and may be formed on all the side surfaces. In addition, although the engagement parts are formed at both ends of one side of the extension part, the engagement parts may be formed only at a part of a central part of one side or may be formed over the entire length of one side.

Further, the case may be divided into left and right parts instead of being divided into upper and lower parts. By providing the exhaust mechanism as shown in the exemplary embodiment of the present disclosure as a case part, it is possible to maintain the sealed state of the battery pack and to operate the gas exhaust mechanism when gas is generated and the internal pressure increases.

Claim 1:
A battery pack (<NUM>), comprising:
a plurality of batteries (<NUM>); and
a case (<NUM>) including a case body (<NUM>) that houses the plurality of batteries (<NUM>) and a case lid (<NUM>) that closes an opening of the case body (<NUM>),
wherein the case (<NUM>) is configured to satisfy that when an internal pressure in the case (<NUM>) increases due to generation of gas, the case body (<NUM>) and the case lid (<NUM>) are relatively displaced in directions away from each other, and a gas exhaust opening is formed in a state that a coupling between the case body (<NUM>) and the case lid (<NUM>) is maintained
characterized in that
one of the case body (<NUM>) and the case lid (<NUM>) includes an extension portion (<NUM>) to be inserted into an other one of the case body (<NUM>) and the case lid (<NUM>), and
the extension part (<NUM>) includes a plurality of exhaust holes (<NUM>), and is exposed to an outside of the case (<NUM>) when the case body (<NUM>) and the case lid (<NUM>) are relatively displaced in directions away from each other.