Patent Description:
For example, as a power source for a vehicle or the like that requires a high output voltage, there has been known a battery module formed by electrically connecting a plurality of batteries to each other. In general, each of the batteries that form the battery module is provided with a valve portion that opens in response to an increase in inner pressure. When a gas is generated in a battery due to a chemical reaction so that an inner pressure in the battery is increased, a gas having a high temperature and a high pressure is blown off from a valve portion. With respect to a battery module including such batteries, PTL <NUM> discloses a battery module which includes: a battery stack in which a plurality of batteries are stacked; and a gas discharge duct which is fixed to one surface of the battery stack in such a manner that the gas discharge duct is connected to the valve portions of the respective batteries. The document <CIT> discloses a power storage device, the document <CIT> discloses a power storage device, and the document <CIT> discloses a battery module.

In recent years, battery modules are required to further increase their capacities. In order to satisfy such requirement, the development of batteries having higher capacities has been in progress. When a capacity of a battery increases, an amount of a gas blown off from the battery increases. Accordingly, a force of an impact of the gas that the gas discharge duct receives increases. In the future, when a capacity of a battery is further increased so that an amount of gas blown off from the battery further increases, a risk that a gas discharge duct is damaged by an impact of the gas is increased so that the safety of the battery module is lowered.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a technique which can enhance safety of a battery module.

According to one aspect of the present invention, there is provided a battery module having the following configuration. The battery module includes: a battery stack including a plurality of batteries that are stacked, each of the plurality of batteries having a valve portion through which a gas is blown off; a duct plate configured to cover a surface of the battery stack on which a plurality of the valve portions are disposed, the duct plate having a gas discharge duct that extends in a stacking direction of the batteries, is connected to the valve portions of the respective batteries, and temporarily stores a blown-off gas; a cover plate placed on the duct plate; and
a flow path portion defined by the duct plate and the cover plate, the flow path portion extending from the gas discharge duct in a first direction that intersects with the stacking direction of the batteries and allowing leaking of the gas in the gas discharge duct to an outside of the battery module. The cover plate is disposed in a state where a predetermined gap is formed between the cover plate and a first wall portion of the gas discharge duct that faces the valve portion, and an opening that allows an inside of the gas discharge duct and the gap to communicate with each other is formed in the first wall portion of the gas discharge duct.

Any combinations of the above-described constituent elements, and configurations that are obtained by expressing the present invention in the form of method, apparatus, system and the like are also effective as the configuration of the present invention.

According to the present invention, the safety of a battery module can be enhanced.

Hereinafter, the present invention will be described based on a preferred exemplary embodiment with reference to the drawings. The exemplary embodiment is an exemplification and does not limit the invention. All technical features described in the exemplary embodiment and combinations of these technical features are not always essential to the invention. The same reference symbols are assigned to the identical or equivalent constituent elements, members and processes illustrated in the respective drawings. Repeated explanation of the identical or equivalent constituent elements, members, and processes is omitted when necessary. Scales or shapes of respective portions illustrated in the respective drawings are set for convenience sake to facilitate the description of the portions. The scales or shapes of the portions should not be construed as limitation unless otherwise specified. Further, in a case where terms such as "first", "second", and the like are used in the present description and claims, these terms do not mean any order or the degree of importance unless otherwise specified, and are intended to be used to distinguish one configuration and another configuration from each other. Further, in each drawing, some members that are not important for describing the exemplary embodiment are omitted.

<FIG> is a perspective view of a battery module according to an exemplary embodiment. <FIG> is an exploded perspective view of the battery module. Battery module <NUM> includes battery stack <NUM>, a pair of end plates <NUM>, cooling plate <NUM>, heat conductive layer <NUM>, side separators <NUM>, constraining members <NUM>, duct plate <NUM>, and cover plate <NUM>.

Battery stack <NUM> includes a plurality of batteries <NUM> and inter-cell separators <NUM>. Each battery <NUM> is a chargeable secondary battery such as a lithium ion battery, a nickel-hydrogen battery, or a nickel-cadmium battery, for example. Each battery <NUM> is a so-called prismatic battery, and has exterior can <NUM> having a flat rectangular parallelepiped shape. Exterior can <NUM> has a substantially rectangular opening not shown in the drawings on one surface of exterior can <NUM>. An electrode assembly, an electrolyte and the like are housed in exterior can <NUM> through the opening. Sealing plate <NUM> that closes the opening of exterior can <NUM> is disposed in the opening.

Output terminal <NUM> of a positive electrode is disposed on sealing plate <NUM> at a position close to one end of sealing plate <NUM> in a longitudinal direction, and output terminal <NUM> of a negative electrode is disposed on sealing plate <NUM> at a position close to the other end of sealing plate <NUM> in the longitudinal direction. The pair of output terminals <NUM> is respectively electrically connected to positive electrode plates and negative electrode plates that form the electrode assembly. Hereinafter, output terminal <NUM> of the positive electrode is referred to as positive electrode terminal 22a, and output terminal <NUM> of the negative electrode is referred to as negative electrode terminal 22b as appropriate. When there is no need to distinguish polarities of output terminals <NUM> from each other, positive electrode terminal 22a and negative electrode terminal 22b are collectively referred to as output terminals <NUM>.

Exterior can <NUM>, sealing plate <NUM>, and output terminals <NUM> are electric conductors and are made of metal, for example. Sealing plate <NUM> and the opening of exterior can <NUM> are joined to each other by, for example, laser welding. Respective output terminals <NUM> are inserted into through holes (not illustrated) formed in sealing plate <NUM>. A seal member (not illustrated) having insulating property is interposed between respective output terminals <NUM> and respective through holes.

In the description of the present exemplary embodiment, for convenience, sealing plate <NUM> forms an upper surface of battery <NUM>, and a bottom surface of exterior can <NUM> disposed on a side opposite to sealing plate <NUM> forms a lower surface of battery <NUM>. Battery <NUM> has two main surfaces that connect the upper surface and the lower surface of battery <NUM> to each other. The main surfaces are surfaces that have the largest area among six surfaces of battery <NUM>. The main surfaces are long side surfaces that are connected to long sides of the upper surface and long sides of the lower surface. Two remaining surfaces other than the upper surface, the lower surface, and two main surfaces form side surfaces of battery <NUM>. These side surfaces are a pair of short side surfaces that are connected to short sides of the upper surface and short sides of the lower surface.

For convenience, in battery stack <NUM>, upper surfaces of batteries <NUM> form an upper surface of battery stack <NUM>, lower surfaces of batteries <NUM> form a lower surface of battery stack <NUM>, and side surfaces of batteries <NUM> form side surfaces of battery stack <NUM>. These directions and positions are defined for convenience. Therefore, for example, the portion defined as the upper surface in the present invention does not always mean that the portion defined as the upper surface is positioned above the portion defined as the lower surface.

Valve portion <NUM> is disposed on sealing plate <NUM> between the pair of output terminals <NUM>. Valve portion <NUM> is also referred to as a safety valve. Valve portion <NUM> is a mechanism which allows each battery <NUM> to blow off a gas in battery <NUM>. Valve portion <NUM> is configured to release an internal gas by opening valve portion <NUM> when an inner pressure in exterior can <NUM> is increased to a predetermined value or more. For example, valve portion <NUM> is formed of: a thin wall portion that is formed on a portion of sealing plate <NUM> and is thinner than other portions of valve portion <NUM>; and a linear groove formed on a surface of the thin wall portion. In this configuration, when an inner pressure in exterior can <NUM> increases, the thin wall portion is torn using the groove as a tearing starting point so that valve portion <NUM> is opened by tearing. Valve portions <NUM> of respective batteries <NUM> are connected to gas discharge duct <NUM> described later, and a gas in the battery is discharged from valve portion <NUM> to gas discharge duct <NUM>.

Each battery <NUM> has insulating film <NUM>. Insulating film <NUM> is, for example, a cylindrical shrink tube, and is heated after exterior can <NUM> is made to pass through insulating film <NUM>. Accordingly, insulating film <NUM> shrinks and covers two main surfaces, two side surfaces, and bottom surface of exterior can <NUM>. Insulating film <NUM> can prevent a short circuit between batteries <NUM> disposed adjacently to each other or a short circuit between battery <NUM> and end plate <NUM> or constraining member <NUM>.

The plurality of batteries <NUM> are stacked to each other at a predetermined interval in a state where the main surfaces of batteries <NUM> disposed adjacently to each other face each other. The term "stack" means that a plurality of members are arranged in any one direction. Therefore, stacking of batteries <NUM> also includes an arrangement of the plurality of batteries <NUM> in a horizontal direction. In the present exemplary embodiment, batteries <NUM> are horizontally stacked. Accordingly, stacking direction X of batteries <NUM> is a direction extending horizontally. Hereinafter, when appropriate, a direction that is horizontal and is perpendicular to stacking direction X is referred to as horizontal direction Y, and a direction that is perpendicular to stacking direction X and horizontal direction Y is referred to as vertical direction Z.

Respective batteries <NUM> are disposed in a state where output terminals <NUM> are directed in the same direction. In the present exemplary embodiment, respective batteries <NUM> are disposed in a state where output terminals <NUM> are directed upward in the vertical direction. With respect to the respective batteries <NUM>, when batteries <NUM> disposed adjacently to each other are connected in series, batteries <NUM> are stacked in a state where positive electrode terminal 22a of one battery <NUM> and negative electrode terminal 22b of other battery <NUM> are disposed adjacently to each other. When batteries <NUM> disposed adjacently to each other are connected in parallel, batteries <NUM> are stacked to each other in a state where positive electrode terminal 22a of one battery <NUM> and positive electrode terminal 22a of other battery <NUM> are disposed adjacently to each other.

Inter-cell separator <NUM> is also referred to as an insulating spacer, and is formed of a resin sheet having an insulating property, for example. As examples of the resin that are used for forming inter-cell separator <NUM>, thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE) are named. Inter-cell separator <NUM> is disposed between two batteries <NUM> disposed adjacently to each other and electrically insulates two batteries <NUM> from each other.

Battery stack <NUM> is sandwiched between the pair of end plates <NUM>. The pair of end plates <NUM> is disposed at both ends of battery stack <NUM> in stacking direction X along which batteries <NUM> are stacked. The pair of end plates <NUM> is disposed adjacently to batteries <NUM> positioned at both ends of battery stack <NUM> in stacking direction X with external end separator <NUM> interposed between the end plate <NUM> and battery <NUM>. External end separator <NUM> can be made of the same resin material as inter-cell separator <NUM>. Each end plate <NUM> is a metal plate made of metal such as iron, stainless steel, or aluminum. By interposing external end separator <NUM> between end plate <NUM> and battery <NUM>, end plate <NUM> and battery <NUM> are electrically insulated from each other.

Each end plate <NUM> has fastening holes 4a on two surfaces that are directed in horizontal direction Y. In the present exemplary embodiment, three fastening holes 4a are disposed at a predetermined interval in vertical direction Z. The surface where fastening holes 4a are formed faces flat surface portion <NUM> of constraining member <NUM>. Flat surface portion <NUM> will be described later.

Duct plate <NUM> is placed on the upper surface of battery stack <NUM>. Duct plate <NUM> is a plate-shaped member that covers the upper surface of battery stack <NUM>, that is, duct plate <NUM> covers surfaces of respective batteries <NUM> on each of which valve portion <NUM> is disposed. Duct plate <NUM> has a plurality of openings <NUM> through which valve portions <NUM> are exposed at positions corresponding to valve portions <NUM> formed on respective batteries <NUM>. The plurality of openings <NUM> are formed in base plate <NUM> extending along the upper surface of battery stack <NUM>. Duct plate <NUM> includes gas discharge duct <NUM> that temporarily stores the gas blown off from respective batteries <NUM>. Gas discharge duct <NUM> extends in stacking direction X of batteries <NUM> and is connected to valve portions <NUM> of respective batteries <NUM>. Respective valve portions <NUM> communicate with gas discharge duct <NUM> through openings <NUM>.

Gas discharge duct <NUM> is defined by: first wall portion <NUM> that covers the upper sides of the plurality of openings <NUM>; and a pair of second wall portions <NUM> which surrounds the sides of respective openings <NUM>. First wall portion <NUM> and the pair of second wall portions <NUM> respectively have an elongated shape elongated in stacking direction X. The pair of second wall portions <NUM> is arranged in horizontal direction Y with a plurality of openings <NUM> or a plurality of valve portions <NUM> interposed between the pair of second wall portions <NUM>. The respective wall surfaces are directed in the first direction (horizontal direction Y in the present exemplary embodiment) that intersects with stacking direction X of batteries <NUM>. First wall portion <NUM> has a wall surface facing the direction (vertical direction Z in the present exemplary embodiment) in which duct plate <NUM> and cover plate <NUM> are arranged, and faces each valve portion <NUM>. The pair of second wall portions <NUM> protrudes from base plate <NUM> toward cover plate <NUM>, and forms both side surfaces of gas discharge duct <NUM>. First wall portion <NUM> is fixed to upper ends of the pair of second wall portions <NUM> to form a top surface of gas discharge duct <NUM>.

Duct plate <NUM> has openings <NUM> through which output terminals <NUM> are exposed at positions corresponding to output terminals <NUM> of respective batteries <NUM>. Bus bars <NUM> are placed on respective openings <NUM>. The plurality of bus bars <NUM> are supported by duct plate <NUM>. Accordingly, duct plate <NUM> also functions as a so-called bus bar plate. Bus bar <NUM> placed in respective openings <NUM> electrically connects output terminals <NUM> of batteries <NUM> disposed adjacently to each other.

Duct plate <NUM> of the present exemplary embodiment is made of a resin such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE) except for first wall portion <NUM>. First wall portion <NUM> is made of a metal plate such as iron or aluminum. The pair of second wall portions <NUM> is integrally formed with base plate <NUM> by molding. First wall portion <NUM> is fixed to the pair of second wall portions <NUM> by fastening members (not illustrated) such as screws.

Bus bar <NUM> is a substantially strip-shaped member made of metal such as copper or aluminum. One end portion of bus bar <NUM> is connected to output terminal <NUM> of one battery <NUM>, and the other end portion of bus bar <NUM> is connected to output terminal <NUM> of another battery <NUM>. With respect to bus bars <NUM>, output terminals <NUM> having the same polarity in a plurality of batteries <NUM> disposed adjacently to each other may be connected in parallel by bus bars <NUM> to form a battery block, and these battery blocks may be connected in series by bus bars <NUM>.

Bus bars <NUM> connected to output terminals <NUM> of batteries <NUM> positioned at both ends in stacking direction X each have external connection terminal <NUM>. External connection terminal <NUM> is connected to an external load (not illustrated). Voltage detection line <NUM> is placed on duct plate <NUM>. Voltage detection line <NUM> is electrically connected to the plurality of batteries <NUM> to detect voltages of respective batteries <NUM>. Voltage detection line <NUM> includes a plurality of conductive wires (not illustrated). One end of each conductive wire is connected to each bus bar <NUM>, and the other end is connected to connector <NUM>. Connector <NUM> is connected to an external battery ECU (not illustrated) or the like. Battery ECU controls detection of a voltage or the like of each battery <NUM>, charging and discharging of each battery <NUM>, and the like.

Cooling plate <NUM> has a flat plate shape extending in stacking direction X and in horizontal direction Y, and is made of a material having high thermal conductivity such as aluminum. Cooling plate <NUM> is thermally connected to battery stack <NUM>. That is, cooling plate <NUM> is connected to battery stack <NUM> in a heat-exchangeable manner, and cools respective batteries <NUM>. In the present exemplary embodiment, battery stack <NUM> is placed on a main surface of cooling plate <NUM>. Battery stack <NUM> is placed on cooling plate <NUM> in a state where a lower surface of battery stack <NUM> faces cooling plate <NUM>. Accordingly, battery stack <NUM> and cooling plate <NUM> are arranged in vertical direction Z. Cooling plate <NUM> may be connected to an object disposed outside of battery module <NUM>, for example, a vehicle body of a vehicle on which battery module <NUM> is mounted or the like in a heat-exchangeable manner. A flow path through which a refrigerant such as water or ethylene glycol flows may be disposed in cooling plate <NUM>. With such a configuration, heat exchange efficiency between battery stack <NUM> and cooling plate <NUM> can be further enhanced and, eventually, cooling efficiency of batteries <NUM> can be further enhanced.

Heat conductive layer <NUM> is a member having an insulating property which is interposed between battery stack <NUM> and cooling plate <NUM>. That is, cooling plate <NUM> is thermally connected to battery stack <NUM> by way of heat conductive layer <NUM>. Heat conductive layer <NUM> covers the entire bottom surface of battery stack <NUM>. The thermal conductivity of heat conductive layer <NUM> is higher than the thermal conductivity of air. Heat conductive layer <NUM> can be formed of, for example, a known resin sheet having good thermal conductivity, such as an acrylic rubber sheet or a silicone rubber sheet. In addition, heat conductive layer <NUM> may be made of a known adhesive agent, grease, or the like having favorable thermal conductivity and favorable insulating property. When exterior can <NUM> is sufficiently insulated by insulating film <NUM> or the like, heat conductive layer <NUM> may not have insulating property.

By interposing heat conductive layer <NUM> between battery stack <NUM> and cooling plate <NUM>, thermal connection between respective batteries <NUM> and cooling plate <NUM> can be more reliably obtained. Therefore, the cooling efficiency of respective batteries <NUM> can be enhanced, and respective batteries <NUM> can be more uniformly cooled. In a case where heat conductive layer <NUM> has an insulating property, it is possible to prevent battery stack <NUM> and cooling plate <NUM> from being electrically connected to each other with more certainty. Heat conductive layer <NUM> can suppress displacement between battery stack <NUM> and cooling plate <NUM>.

Side separators <NUM> are members that have an insulating property and insulate constraining members <NUM> and battery stack <NUM> from each other. In the present exemplary embodiment, the pair of side separators <NUM> is arranged in horizontal direction Y. Each side separator <NUM> has an elongated shape elongated in stacking direction X of batteries <NUM>. Battery stack <NUM>, the pair of end plates <NUM>, cooling plate <NUM>, and heat conductive layer <NUM> are disposed between the pair of side separators <NUM>. Each side separator <NUM> is made of, for example, a resin having an insulating property. As a resin that is used for forming side separator <NUM>, in the same manner as inter-cell separator <NUM>, thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE) are named.

Side separator <NUM> of the present exemplary embodiment has first portion <NUM>, second portion <NUM>, and third portion <NUM>. First portion <NUM> has a rectangular flat plate shape, and extends in stacking direction X of batteries <NUM> along a side surface of battery stack <NUM>. Second portion <NUM> has a strip shape extending in stacking direction X, and protrudes from a lower side of first portion <NUM> toward a battery stack <NUM>. Third portion <NUM> has a strip shape extending in stacking direction X, and protrudes from an upper side of first portion <NUM> toward the battery stack <NUM>. Accordingly, second portion <NUM> and third portion <NUM> face each other in the arrangement direction of battery stack <NUM> and cooling plate <NUM>. Battery stack <NUM>, cooling plate <NUM>, and heat conductive layer <NUM> are disposed between second portion <NUM> and third portion <NUM>.

Constraining members <NUM> are also referred to as bind bars, and are long members that are elongated in stacking direction X of batteries <NUM>. In the present exemplary embodiment, the pair of constraining members <NUM> is arranged in horizontal direction Y. Each constraining member <NUM> is made of metal. As examples of metal used for forming constraining member <NUM>, iron, stainless steel, and the like are named. Battery stack <NUM>, the pair of end plates <NUM>, cooling plate <NUM>, heat conductive layer <NUM>, and the pair of side separators <NUM> are disposed between the pair of constraining members <NUM>.

In the present exemplary embodiment, constraining member <NUM> includes flat surface portion <NUM> and a pair of arm portions <NUM>. Flat surface portion <NUM> has a rectangular shape, and extends in stacking direction X along the side surface of battery stack <NUM>. The pair of arm portions <NUM> protrude toward battery stack <NUM> from end portions of flat surface portion <NUM> on both sides in vertical direction Z. That is, one arm portion <NUM> protrudes from an upper side of flat surface portion <NUM> toward the battery stack <NUM> side, and the other arm portion <NUM> protrudes from a lower side of flat surface portion <NUM> toward battery stack <NUM>. Accordingly, the pair of arm portions <NUM> faces each other in the arrangement direction that battery stack <NUM> and cooling plate <NUM> are arranged. Battery stack <NUM>, cooling plate <NUM>, heat conductive layer <NUM>, and side separators <NUM> are disposed between the pair of arm portions <NUM>.

Contact plate <NUM> is fixed to regions of flat surface portion <NUM> that face respective end plates <NUM> by welding or the like. Contact plates <NUM> are members that are elongated in vertical direction Z. Through holes <NUM> are formed in contact plate <NUM> in a penetrating manner in horizontal direction Y at positions that correspond to fastening holes 4a formed in end plate <NUM>. Through holes <NUM> are formed in flat surface portion <NUM> in horizontal direction Y in a penetrating manner at positions that correspond to through holes <NUM> formed in contact plate <NUM>.

By making the pair of end plates <NUM> engage with flat surface portions <NUM> of respective constraining members <NUM>, the plurality of batteries <NUM> are sandwiched between end plates <NUM> in stacking direction X. Specifically, battery stack <NUM> is formed by alternately arranging the plurality of batteries <NUM> and the plurality of inter-cell separators <NUM>, and such battery stack <NUM> is sandwiched between the pair of end plates <NUM> with external end separators <NUM> sandwiched between battery stack <NUM> and end plates <NUM> in stacking direction X. Heat conductive layer <NUM> is disposed below the lower surface of battery stack <NUM> and, further, cooling plate <NUM> is disposed so as to face battery stack <NUM> with heat conductive layer <NUM> interposed between cooling plate <NUM> and battery stack <NUM>. In such a state, battery stack <NUM>, the pair of end plates <NUM>, cooling plate <NUM>, and heat conductive layer <NUM> are sandwiched between the pair of side separators <NUM> in horizontal direction Y. Further, the pair of constraining members <NUM> sandwiches the whole body in horizontal direction Y from the outside of the pair of side separators <NUM>.

The pair of end plates <NUM> and the pair of constraining members <NUM> are aligned with each other such that fastening holes 4a, through holes <NUM>, and through holes <NUM> overlap with each other. Fastening members <NUM> such as screws are made to pass through through holes <NUM> and through holes <NUM> and are made to threadedly engage with fastening holes 4a. With such a configuration, the pair of end plates <NUM> and the pair of constraining members <NUM> are fixed to each other. By making the pair of end plates <NUM> and the pair of constraining members <NUM> engage with each other, the plurality of batteries <NUM> are fastened to each other and are constrained in stacking direction X. Accordingly, respective batteries <NUM> are positioned in stacking direction X.

Constraining members <NUM> sandwich the plurality of batteries <NUM> in stacking direction X. Constraining members <NUM> also sandwich battery stack <NUM>, heat conductive layer <NUM>, and cooling plate <NUM> in the arrangement direction of battery stack <NUM>, heat conductive layer <NUM>, and cooling plate <NUM>. Specifically, constraining members <NUM> sandwich the plurality of batteries <NUM> in stacking direction X in such a manner that both end portions of flat surface portions <NUM> of constraining members <NUM> in stacking direction X of batteries <NUM> engage with the pair of end plates <NUM>. Battery stack <NUM>, heat conductive layer <NUM>, and cooling plate <NUM> are sandwiched between the pair of arm portions <NUM> of constraining members <NUM> in vertical direction Z. That is, constraining members <NUM> have both a function of fastening the plurality of batteries <NUM> and a function of fastening battery stack <NUM> and cooling plate <NUM>. Therefore, unlike the conventional structure, battery stack <NUM> and cooling plate <NUM> are not fastened by screws.

In a state where the pair of constraining members <NUM> is fixed to the pair of end plates <NUM>, first portion <NUM> of side separator <NUM> is interposed between the side surface of battery stack <NUM> and flat surface portion <NUM> of constraining member <NUM>. With such a configuration, the side surfaces of respective batteries <NUM> and flat surface portion <NUM> are electrically insulated from each other. Second portion <NUM> of side separator <NUM> is interposed between cooling plate <NUM> and arm portion <NUM> on a lower side of constraining member <NUM>. With such a configuration, cooling plate <NUM> and arm portion <NUM> of on the lower side are electrically insulated from each other. Third portion <NUM> of side separator <NUM> is interposed between the upper surface of battery stack <NUM> and arm portion <NUM> on an upper side of constraining member <NUM>. With such a configuration, the upper surfaces of respective batteries <NUM> and arm portion <NUM> on the upper side are electrically insulated from each other.

In a state where battery stack <NUM>, heat conductive layer <NUM>, and cooling plate <NUM> are sandwiched by the pair of arm portions <NUM> in vertical direction Z, heat conductive layer <NUM> is elastically deformed or plastically deformed by being pressed by battery stack <NUM> and cooling plate <NUM>. Consequently, it is possible to obtain thermal connection between battery stack <NUM> and cooling plate <NUM> with more certainty. In addition, entire battery stack <NUM> can be cooled uniformly. Further, deviation between battery stack <NUM> and cooling plate <NUM> in the XY plane direction can be further suppressed.

As an example, after assembling of these constituent elements is completed, duct plate <NUM> is placed on battery stack <NUM>. For example, duct plate <NUM> is fixed to battery stack <NUM> by making third portions <NUM> of the pair of side separators <NUM> engage with duct plate <NUM>. Then, bus bars <NUM> are mounted on output terminals <NUM> of respective batteries <NUM> so that output terminals <NUM> of the plurality of batteries <NUM> are electrically connected to each other. For example, bus bars <NUM> are fixed to output terminals <NUM> by welding.

Cover plate <NUM> is placed on an upper surface of duct plate <NUM>. Cover plate <NUM> is a plate-shaped member that covers duct plate <NUM> from above. Cover plate <NUM> according to the present exemplary embodiment is a so-called top cover that forms a portion of an outer shell of battery module <NUM>, specifically, the upper surface of battery module <NUM>. Cover plate <NUM> prevents dew condensation water, dust, or the like from being brought into contact with output terminals <NUM>, valve portions <NUM> of batteries <NUM>, bus bars <NUM> and the like. Cover plate <NUM> is made of a resin having an insulating property, for example. Cover plate <NUM> has insulating cover portions <NUM> at position overlapping with external connection terminals <NUM> in vertical direction Z.

Both end portions of cover plate <NUM> in the first direction (horizontal direction Y in the present exemplary embodiment) are fixed to duct plate <NUM>. Cover plate <NUM> of the present exemplary embodiment is fixed to duct plate <NUM> by snap-fitting. Specifically, duct plate <NUM> has a plurality of engaging claws <NUM> at both end portions of duct plate <NUM> in horizontal direction Y in a state where the plurality of engaging claws <NUM> are disposed at an interval in stacking direction X. Cover plate <NUM> has engaging holes <NUM> at positions overlapping with respective engaging claws <NUM> when viewed in vertical direction Z. Engaging claw <NUM> and engaging hole <NUM> form snap-fit portion <NUM> (see <FIG> and <FIG>). When cover plate <NUM> is placed on duct plate <NUM>, each engaging claw <NUM> is inserted into each engaging hole <NUM>. With such insertion of respective engaging claws <NUM>, engaging claws <NUM> and engaging holes <NUM> engage with each other so that both end portions of cover plate <NUM> in horizontal direction Y are fixed to duct plate <NUM>. In a state where cover plate <NUM> is placed on duct plate <NUM>, external connection terminals <NUM> are covered by insulating cover portions <NUM>.

<FIG> is a cross-sectional side view of a region in which duct plate <NUM> and cover plate <NUM> of battery module <NUM> are disposed. <FIG> is a cross-sectional perspective view of the region in which duct plate <NUM> and cover plate <NUM> of battery module <NUM> are disposed. In <FIG> and <FIG>, illustration of an internal structure of battery <NUM> is omitted.

Battery module <NUM> includes flow path portions <NUM>. Flow path portions <NUM> are flow paths that allow a gas in gas discharge duct <NUM> to leak to the outside of battery module <NUM>. Flow path portions <NUM> are defined by duct plate <NUM> and cover plate <NUM>, and extend from gas discharge duct <NUM> in the first direction (horizontal direction Y) intersecting with stacking direction X. Flow path portions <NUM> are disposed on both sides in horizontal direction Y with gas discharge duct <NUM> sandwiched between flow path portions <NUM>. Respective flow path portions <NUM> are connected to second wall portions <NUM> directed in horizontal direction Y of gas discharge duct <NUM>. More specifically, opening <NUM> is formed in each of second wall portions <NUM>, and one end portion of each of flow path portions <NUM> is connected to opening <NUM>. The other end portions of respective flow path portions <NUM> are connected to flow path outlets <NUM> disposed at the end portions of battery module <NUM> in horizontal direction Y.

The plurality of openings <NUM> are formed in second wall portion <NUM> at a predetermined interval in stacking direction X, and one end portion of flow path portion <NUM> is connected to the plurality of openings <NUM>. Flow path outlet <NUM> is an opening that is elongated in stacking direction X. Therefore, flow path portion <NUM> is a planar flow path that expands in stacking direction X and horizontal direction Y.

Cover plate <NUM> is disposed in a state where predetermined gap G is formed between cover plate <NUM> and first wall portion <NUM> that faces valve portion <NUM> of gas discharge duct <NUM>. That is, first wall portion <NUM> and cover plate <NUM> are spaced apart from each other in vertical direction Z by gap G. Openings <NUM> which allow the inside of gas discharge duct <NUM> and gap G to communicate with each other are formed in first wall portion <NUM> of gas discharge duct <NUM>. In the present exemplary embodiment, the plurality of openings <NUM> are uniformly arranged over entire first wall portion <NUM> (see <FIG>). Further, both end portions of gap G in horizontal direction Y are connected to flow path portions <NUM>. Therefore, gas discharge duct <NUM> and flow path portions <NUM> communicate with each other not only through openings <NUM> formed in second wall portions <NUM> but also through openings <NUM> formed in first wall portion <NUM> and gap G. Opening <NUM> can be formed by, for example, punching a metal plate constituting first wall portion <NUM>.

Opening <NUM> illustrated in <FIG> and <FIG> is formed by a gap formed between an upper end of second wall portion <NUM> (also referred to as a portion of the upper end of second wall portion <NUM> formed by cutting out a part of the upper end) in a region lower than other regions and first wall portion <NUM>. However, the present invention is not particularly limited to such a structure. For example, opening <NUM> may be formed of a through hole which penetrates second wall portion <NUM> in horizontal direction Y. Opening <NUM> may have a size which allows opening <NUM> to extend from the upper end to the lower end of second wall portion <NUM>. That is, the second wall portion <NUM> may be divided into a plurality of portions by opening <NUM>.

When a gas in battery <NUM> is blown off from valve portion <NUM>, the gas impinges on first wall portion <NUM> which face valve portion <NUM>. The large part of a gas that has impinged on first wall portion <NUM> flows along first wall portion <NUM> and flows into flow path portions <NUM> from openings <NUM>. The gas flowing into flow path portions <NUM> flows through flow path portions <NUM> in horizontal direction Y and in stacking direction X, and leaks from flow path outlets <NUM> to the outside of battery module <NUM>. A part of the gas that has impinged on first wall portion <NUM> flows into gap G through openings <NUM> formed in first wall portion <NUM>. The gas which has flown into gap G flows into flow path portions <NUM> from gap G and leaks out of battery module <NUM> from flow path outlets <NUM>.

At least a portion of the gas blown off from battery <NUM> is a combustible gas. The gas blown off from battery <NUM> also contains fine particles such as broken pieces of a battery structure. When a combustible gas having a high temperature and fine particles having a high temperature are discharged to the outside of battery module <NUM>, there is a possibility that a magnitude of a fire outside battery module <NUM> is increased. On the other hand, in the present exemplary embodiment, a gas blown off from valve portion <NUM> is once received by gas discharge duct <NUM>, and then is discharged to the outside of battery module <NUM> through flow path portion <NUM>. As a result, the temperature of the gas and the temperature of the fine particles can be lowered until the gas or the fine particles are released to the outside of battery module <NUM>.

In addition, by allowing a part of the gas blown off to gas discharge duct <NUM> to flow out from openings <NUM> to gap G, it is possible to suppress an excessive increase in an inner pressure in gas discharge duct <NUM>. In addition, fine particles each having a size larger than a size of each openings <NUM> are caught by openings <NUM>. As a result, some of fine particles and the gas can be separated from each other.

As viewed in vertical direction Z, gas discharge duct <NUM> is disposed at a position that overlaps with a center portion of cover plate <NUM> in the first direction (horizontal direction Y in the present exemplary embodiment). As described above, both end portions of cover plate <NUM> in the first direction are fixed to duct plate <NUM>. With such a configuration, when an amount of gas blown off from battery <NUM> increases, cover plate <NUM> is deformed in a state where the center portion of cover plate <NUM> bulges. The "center portion" is, for example, a region that includes an intermediate point at an equal distance in the first direction with respect to respective engaging holes <NUM> positioned on the outermost side on one end of cover plate <NUM> and respective engaging holes <NUM> positioned on the outermost side on the other end in the first direction.

Engaging claw <NUM> of snap-fit portion <NUM> has support strut portion 72a and protruding portion 72b. Support strut portion 72a extends in vertical direction Z along which duct plate <NUM> and cover plate <NUM> are arranged. Protruding portion 72b protrudes from support strut portion 72a toward the opposite of gas discharge duct <NUM> at a distal end of support strut portion 72a. That is, in horizontal direction Y, gas discharge duct <NUM> is disposed at a center portion of battery module <NUM>, and protruding portions 72b protrude toward the outside of battery module <NUM>. Duct plate <NUM> and cover plate <NUM> are fixed to each other in such a manner that engaging claws <NUM> are inserted into engaging holes <NUM> and protruding portions 72b are caught by peripheral edge portions of engaging holes <NUM>.

When cover plate <NUM> is deformed in a state where the center portion of cover plate <NUM> bulges, engaging holes <NUM> are displaced so as to approach the center portion of battery module <NUM>. With this displacement of engaging holes <NUM>, support strut portion 72a of engaging claw <NUM> is elastically deformed in a state where the distal end of support strut portion 72a approaches the center portion of battery module <NUM>. On the other hand, protruding portion 72b protrudes toward the outside of battery module <NUM>. Accordingly, even when support strut portion 72a is deformed so as to approach the center portion of battery module <NUM>, a state in which protruding portion 72b is caught by the peripheral edge portion of engaging hole <NUM> can be easily maintained.

As has been described above, battery module <NUM> according to the present exemplary embodiment includes: battery stack <NUM> having the plurality of batteries <NUM> that are stacked, duct plate <NUM> placed on battery stack <NUM>; cover plate <NUM> placed on duct plate <NUM>, and flow path portions <NUM> defined by duct plate <NUM> and cover plate <NUM>. Each of the plurality of batteries <NUM> of battery stack <NUM> has valve portion <NUM> through which a gas is blown off. Duct plate <NUM> includes gas discharge duct <NUM>, and duct plate <NUM> covers the surface of battery stack <NUM> on which the plurality of valve portions <NUM> are disposed. Gas discharge duct <NUM> extends in stacking direction X of batteries <NUM>, is connected to valve portions <NUM> of respective batteries <NUM>, and temporarily stores a blown-off gas. Flow path portions <NUM> extend from gas discharge duct <NUM> in the first direction that intersects with stacking direction X of batteries <NUM>, and makes a gas in gas discharge duct <NUM> leak to the outside of battery module <NUM>. Cover plate <NUM> is disposed in a state where predetermined gap G is formed between cover plate <NUM> and first wall portion <NUM> that faces valve portion <NUM> of gas discharge duct <NUM>. Openings <NUM> that allow the inside of gas discharge duct <NUM> and gap G to communicate with each other are formed in first wall portion <NUM> of gas discharge duct <NUM>.

By connecting respective valve portions <NUM> to gas discharge duct <NUM>, gas discharge duct <NUM> can receive an impact and a pressure of a blown-off gas. In particular, gas discharge duct <NUM> can receive a large impact or a rapidly rising pressure generated at an initial stage of blowing off of a gas. A gas blown off to gas discharge duct <NUM> gradually leaks to the outside of battery module <NUM> through flow path portions <NUM>. Accordingly, it is possible to prevent a gas from being vigorously blown off to the outside of battery module <NUM>. In addition, by allowing a gas gradually leak through flow path portions <NUM>, a temperature of the gas or fine particles can be lowered until the gas or the fine particles reach flow path outlets <NUM>. With such a configuration, it is possible to suppress the occurrence of fire outside battery module <NUM>.

By forming openings <NUM> in first wall portion <NUM> of gas discharge duct <NUM>, it is possible to suppress an excessive increase in an inner pressure of gas discharge duct <NUM>. As a result, it is possible to suppress breakage of gas discharge duct <NUM> caused by blowing off of a gas from battery <NUM>. Therefore, according to the present exemplary embodiment, safety of battery module <NUM> can be enhanced. In addition, it is possible to increase the capacity of battery module <NUM> while maintaining the safety of battery module <NUM>.

In addition, fine particles each having a size larger than a size of each openings <NUM> are caught by openings <NUM>. Therefore, it is possible to prevent the fine particles from being released to the outside of battery module <NUM>, and it is also possible to prevent the occurrence of fire outside the module. In addition, by catching fine particles by openings <NUM>, the fine particles and a gas can be separated from each other. As a result, a temperature of a gas can be lowered more quickly and hence, the occurrence of fire outside the module can be suppressed.

In the present exemplary embodiment, first wall portion <NUM> is formed of a metal plate. That is, first wall portion <NUM> has high thermal conductivity. With such a configuration, it is possible to more quickly diffuse heat of a gas blown off from battery <NUM>. As a result, a temperature of a gas leaking from battery module <NUM> can be lowered, and the occurrence of fire outside the module can be more effectively suppressed.

In addition, duct plate <NUM> includes the pair of second wall portions <NUM> that is arranged side by side with valve portions <NUM> sandwiched between the pair of second wall portions <NUM>, and defines gas discharge duct <NUM> together with first wall portion <NUM>. The pair of second wall portions <NUM> has openings <NUM> that allow gas discharge duct <NUM> and flow path portions <NUM> to communicate with each other. Accordingly, battery module <NUM> has a gas flow path that extends from gas discharge duct <NUM> to flow path portions <NUM> through openings <NUM> formed in second wall portions <NUM>, and a gas flow path that extends from gas discharge duct <NUM> to flow path portions <NUM> through openings <NUM> formed in first wall portion <NUM>. By dividing a flow path of a gas into a plurality of flow path portions in this manner, a temperature of the gas can be lowered more quickly. In addition, by allowing a gas to flow out from openings <NUM> formed in second wall portions <NUM>, the time for retaining the gas in gas discharge duct <NUM> can be prolonged compared with a case where the gas is allowed to flow out from openings <NUM> formed in first wall portion <NUM>. Therefore, the occurrence of fire outside the module can be more effectively suppressed.

In the present exemplary embodiment, both end portions of cover plate <NUM> in the first direction are fixed to duct plate <NUM>. Gas discharge duct <NUM> is disposed at a position that overlaps with the center portion of cover plate <NUM> in the first direction. With such a configuration, when an amount of gas blown off from battery <NUM> increases, cover plate <NUM> can be deformed in a state where the center portion of cover plate <NUM> bulges. Therefore, it is possible to increase a volume of a space in which gas stays in battery module <NUM> while avoiding removal of cover plate <NUM> from battery module <NUM>. Therefore, an amount of gas that can be temporarily retained in battery module <NUM> can be increased, and the retention time can be also prolonged. As a result, the occurrence of fire outside the module can be more effectively suppressed.

Battery module <NUM> according to the present exemplary embodiment includes snap-fit portions <NUM>. Each snap-fit portion <NUM> is formed of engaging claw <NUM> and engaging hole <NUM> that engage with each other to fix duct plate <NUM> and cover plate <NUM> to each other. Engaging claw <NUM> includes: support strut portion 72a extending in the direction along which duct plate <NUM> and cover plate <NUM> are arranged; and protruding portion 72b protruding from support strut portion 72a toward the opposite of gas discharge duct <NUM>. Duct plate <NUM> and cover plate <NUM> are fixed to each other in such a manner that engaging claws <NUM> are inserted into engaging holes <NUM> and protruding portions 72b are caught by peripheral edge portions of engaging holes <NUM>. By allowing protruding portion 72b to protrude to the opposite of gas discharge duct <NUM>, it is possible to prevent the engagement between engaging claw <NUM> and engaging hole <NUM> from being released when cover plate <NUM> is deformed. Therefore, cover plate <NUM> can be more stably fixed to duct plate <NUM>.

The exemplary embodiment of the present invention has been described in detail heretofore. The above-described exemplary embodiment is merely a specific example for carrying out the present invention. The contents of the exemplary embodiment do not limit the technical scope of the present invention, and many design changes such as changes, additions, and deletions of constituent elements can be made without departing from the spirit of the invention defined in claims. Novel exemplary embodiments with a design change acquire both advantageous effects of the exemplary embodiment and the modification that are combined with each other. In the above-described exemplary embodiment, with respect to the contents where such design changes are allowable, the contents are emphasized with expressions such as "of the present exemplary embodiment" and "in the present exemplary embodiment". However, the design changes are allowable even with respect to the contents which are not emphasized with such expressions. Any arbitrary combination of constituent elements included in the exemplary embodiment is also effective as the configuration of the present invention. Hatching applied to the cross sections in the drawings does not limit materials of objects to which hatching is applied.

<FIG> is a cross-sectional side view of a region including duct plate <NUM> and cover plate <NUM> of battery module <NUM> according to a first modification. In <FIG>, the illustration of an internal structure of battery <NUM> is omitted. In battery module <NUM> of the first modification, heat transfer suppression layer <NUM> is disposed in a region where cover plate <NUM> overlaps with openings <NUM> formed in first wall portion <NUM> as viewed from a direction along which the duct plate and the cover plate are arranged (vertical direction Z in the present exemplary embodiment). Heat transfer suppression layer <NUM> suppresses the heat transfer from a gas blown off from battery <NUM> to cover plate <NUM>.

Heat transfer suppression layer <NUM> is, for example, a sheet having a heat insulating property, and is disposed on a surface of cover plate <NUM> that faces opening <NUM>. For example, heat transfer suppression layer <NUM> is laminated to the surface of cover plate <NUM> by an adhesive agent or the like. In the present exemplary embodiment, a recessed portion is formed on the surface of cover plate <NUM> that faces opening <NUM>, and heat transfer suppression layer <NUM> is fitted into the recessed portion. With such a configuration, heat transfer suppression layer <NUM> can easily be positioned.

A gas having a high temperature blown off from battery <NUM> and passing through openings <NUM> impinges on heat transfer suppression layer <NUM>. Therefore, heat of the blown-off gas can be received by heat transfer suppression layer <NUM>. Accordingly, heat transfer suppression layer <NUM> can suppress the transfer of heat of the gas to cover plate <NUM>. As a result, the heat resistance of cover plate <NUM> can be enhanced and hence, it is possible to reduce a concern that cover plate <NUM> is deformed or damaged by the heat of the gas. For example, heat transfer suppression layer <NUM> is made of a material having lower thermal conductivity than a material used for forming cover plate <NUM>. Heat transfer suppression layer <NUM> has lower thermal conductivity than air. As the material used for forming heat transfer suppression layer <NUM>, a fiber integrated body in which organic fibers, inorganic fibers and the like are integrated, a heat transfer suppression sheet formed of a heat insulating material and a laminate film can be named as examples.

Heat transfer suppression layer <NUM> may be a member having high thermal conductivity such as an aluminum tape or an iron sheet. In this case, heat of a gas can be quickly dispersed by heat transfer suppression layer <NUM> and hence, the transfer of heat to cover plate <NUM> can be suppressed.

The number of batteries <NUM> that battery module <NUM> includes is not particularly limited. The structures of respective parts of battery module <NUM> including the shape of side separator <NUM> and the fastening structure between end plates <NUM> and constraining members <NUM> are not particularly limited. Battery <NUM> may have a cylindrical shape or the like. In a case where both heat conduction and a frictional force can be sufficiently ensured between battery stack <NUM> and cooling plate <NUM>, heat conductive layer <NUM> may be omitted, and an insulating sheet made of PET or PC may be interposed between battery stack <NUM> and cooling plate <NUM>. Opening <NUM> may not be formed in second wall portions <NUM> of gas discharge duct <NUM>. In this case, all gas in gas discharge duct <NUM> flows into flow path portions <NUM> through openings <NUM> and gap G.

Claim 1:
A battery module (<NUM>) comprising:
a battery stack (<NUM>) including a plurality of batteries (<NUM>) that are stacked, the plurality of batteries (<NUM>) including the plurality of valves (<NUM>) through which a gas is blown off; the batteries being prismatic,
a duct plate (<NUM>) configured to cover a surface of the battery stack (<NUM>) on which the plurality of the valves (<NUM>) are disposed, the duct plate (<NUM>) including a gas discharge duct (<NUM>) that extends in a stacking direction (X) of the batteries (<NUM>), is connected to the valves of the batteries (<NUM>), and temporarily stores the gas blown off through the valves (<NUM>);
a cover plate (<NUM>) placed on the duct plate (<NUM>); and
a flow path portion (<NUM>) defined by the duct plate (<NUM>) and the cover plate (<NUM>), the flow path portion (<NUM>) extending from the gas discharge duct (<NUM>) in a first direction that intersects with the stacking direction (X) of the batteries (<NUM>) and allowing leaking of the gas in the gas discharge duct (<NUM>) to an outside of the battery module (<NUM>), wherein the first direction is an horizontal direction (Y),
flow path outlets (<NUM>) connected to the flow path (<NUM>) and being disposed at end portions of the battery module (<NUM>) in the horizontal direction (Y), and through which gas is discharged,
wherein the cover plate (<NUM>) is disposed in a state where a predetermined gap (G) is configured between the cover plate (<NUM>) and a first wall (<NUM>) of the gas discharge duct (<NUM>) that faces the valves (<NUM>), so that the first wall (<NUM>) and the cover plate (<NUM>) are spaced apart from each other in a vertical direction Z by the predetermined gap (G), and
an opening (<NUM>) that allows an inside of the gas discharge duct (<NUM>) and the predetermined gap (G) to communicate with each other is configured in the first wall (<NUM>) of the gas discharge duct (<NUM>),
wherein the duct plate (<NUM>) includes a pair of second walls (<NUM>) that is arranged side by side with the valve (<NUM>) sandwiched between the pair of second walls (<NUM>) and defines the gas discharge duct (<NUM>) together with the first wall (<NUM>), and
an opening (<NUM>) that allows the gas discharge duct (<NUM>) and the flow path (<NUM>) to communicate with each other is configured in the pair of second walls (<NUM>) respectively.