Battery pack

In a battery pack (1) that accommodates a plurality of batteries (11) arranged in parallel in a case (2) that forms a cooling-air passage (3), the cooling-air passage (3) and a gas-discharge passage (4) for discharging gas leaking from the battery (11) when the battery (11) falls into abnormal state are formed and separated from each other in the case (2).

TECHNICAL FIELD

The present invention relates to a battery pack. More particularly, the present invention relates to a battery pack in which a plurality of batteries are arranged in parallel in a case and a cooling-air passage is provided in the case so as to cool the respective batteries.

BACKGROUND ART

In recent years, expectation for electric vehicles or hybrid electric vehicles has increased because of the global environmental problems. For rechargeable batteries as the power supply of those vehicles, both reduction in the size and weight and increase of the capacity and output are demanded. Thus, a battery pack in which a plurality of batteries formed by cells are connected in series is used as the power supply. Moreover, a battery pack in which, in order to cool respective batteries, the batteries are arranged in parallel in a case and a cooling air from the vehicle interior is introduced into the case is known from Japanese Patent Laid-Open Publication No. 2001-319697, for example.

Referring toFIG. 8, a plurality of batteries21are arranged in parallel in a case22with a pitch that allows an appropriate ventilation gap to be formed between the adjacent batteries21. In the case22, cooling-air passages23and24are formed on both sides of the array of the batteries21, respectively, and a cooling-air inlet25and a cooling-air outlet26are provided at one end of the cooling-air passage23and at the other end of the cooling-air passage24, respectively.

The case22mentioned above is accommodated and secured in a battery box (not shown) which has a fan provided at a position opposed to the cooling-air inlet25. Cooling air W delivered by the fan enters the cooling-air passage23of the case22from the cooling-air inlet25, flows through the ventilation gap between the batteries21and the cooling-air passage24, and is then discharged from the cooling-air outlet26. The cooling air W cools the respective batteries21while flowing in the case.

However, in a case where the aforementioned battery pack is mounted in an electric vehicle or hybrid electric vehicle, air taken from the vehicle interior is introduced into the case22as the cooling air W, and the cooling air W of which the temperature has been increased by cooling the batteries21is discharged to the outside of the vehicle. Therefore, if the battery pack falls into abnormal state and gas is discharged into the case22, the gas within the case22flows back into the vehicle interior when the fan stops.

Therefore, the present invention was made in view of the aforementioned problems of the conventional techniques, and aims to provide a battery pack that prevents gas discharged due to a trouble in a battery from flowing back through a supply passage of cooling air and prevents a trouble caused by the reverse flow of the gas.

DISCLOSURE OF THE INVENTION

A battery pack of the present invention includes a plurality of batteries arranged in parallel and accommodated in a case that forms a cooling-air passage, in which the cooling-air passage and a gas-discharge passage for discharging gas leaking from the battery when the battery falls into abnormal state are formed and separated from each other in the case. According to this structure, the gas leaking from the battery due to the battery abnormality will be discharged to the outside via the gas-discharge passage separated from the cooling-air passage. Thus, the leaking gas is prevented from flowing back through a supply passage of the cooling air and therefore a trouble caused by such reverse flow of the gas is prevented surely.

Moreover, a plurality of battery units each of which includes a plurality of batteries that are arranged coaxially and are connected in series are arranged in parallel in the case, and the gas-discharge passage is formed in regions corresponding to both sides of the case along a direction in which the batteries are arranged in parallel and a region corresponding to the connection between the batteries in the case. In this case, the use of a plurality of battery units each including a plurality of batteries that are arranged coaxially and are connected in series contributes to realization of a compact battery pack including a number of batteries, and the gas leaking from the battery when the battery falls into abnormal state will be discharged through the gas-discharge passage surely.

In addition, in a case where through holes through which the batteries are inserted are formed to extend through both sidewalls of the case and passage sidewalls for separating the gas-discharge passage from the cooling-air passage, the batteries are arranged within the case in such a manner that gas-discharge portions provided at one ends of the batteries are positioned within the gas-discharge passage, only by inserting the batteries into the corresponding through holes formed to extend through both sidewalls of the case and the passage sidewalls. Thus, it is possible to accommodate and arrange the batteries within the case with excellent productivity.

When a connection plate having connection means for sequentially connecting the batteries or battery units that are adjacent in series is provided on the outer surface of each of both sidewalls of the case, it is possible to realize series connection of the batteries accommodated and arranged in the case by using the connection plate provided on the outer surface of each sidewall of the case with excellent workability.

Furthermore, in a case where the case is formed by a case body in which the cooling-air passage is formed in such a manner that one side face is opened and the other side face is closed and the gas-discharge passage is formed in such a manner that one side face is closed and the other side face is opened, and cover plates for respectively covering both side faces of the case body, the case body is manufactured with excellent productivity by using a shaping die that allows die-cutting from both sides, and the case is formed by assembling the case body and the cover plates. Therefore, it is possible to manufacture the case including the cooling-air passage and the gas-discharge passage therein at a low cost.

BEST MODE FOR CARRYING OUT THE INVENTION

A battery pack according to an embodiment of the present invention will be described hereinafter, with reference toFIGS. 1 through 7.

InFIGS. 1 through 4, a battery pack1accommodates a plurality of (ten in the shown example) battery units12in a flat and prismatic case2, that are arranged in parallel in the case2with an appropriate gap between adjacent battery units12and are connected in series. Each battery unit12includes a plurality of (two in the shown example) batteries11that are coaxially arranged and are connected in series. In the case2, a cooling-air passage3is formed to face the batteries11in each of the battery units12arranged in parallel except for portions around both ends of the batteries11, while a gas-discharge passage4is formed on regions corresponding to both sides of the case2along the direction in which the battery units12are arranged in parallel and a region corresponding to the connection between the batteries11in each battery unit12in such a manner that the gas-discharge passage4faces both ends of the respective battery11. In order to manufacture the case2with excellent productivity by using a shaping die that allows die-cutting from upper and lower sides, the case2is formed by: a case body5in which the cooling-air passage3is formed in such a manner that the upper side face is opened and the lower side face is closed and the gas-discharge passage4is formed in such a manner that the upper side face is closed and the lower side face is opened; and cover plates6aand6bfor covering both side faces of the case body5so as to close the openings of the cooling-air passage3and the gas-discharge passage4.

In sidewalls5aof the case body5that extend along the direction in which the batteries11are arranged in parallel and passage sidewalls4afor separating the gas-discharge passage4and the cooling-air passage3from each other, through holes7into which the batteries of the battery units12are inserted are provided at positions corresponding to the positions at which the battery units12are to be arranged. By inserting the battery units12into the through holes7from either sidewall5aof the case body5, the battery units12are accommodated and arranged in the case2. Moreover, sealing means, for example, a rubber gasket, a rubber ring or an appropriate sealing agent such as a pitch, may be provided at a gap between the through hole7of the passage sidewall4aand the battery unit12inserted thereinto, if necessary, thereby ensuring the sealing between the cooling-air passage3and the gas-discharge passage4.

On the outer surface of each of both sidewalls5aof the case body5, connection plates8are provided each of which includes connection means (8b) for sequentially connecting adjacent battery units12in series. Moreover, the outer surface of the connection plate8is covered with a connection cover8a. In both end walls5bof the case body5, a cooling-air inlet9aand a cooling-air outlet9bare formed in the middle portion in the vertical direction, of a region opposed to the cooling-air passage3. In addition, a gas-discharge port10is formed at an upper end portion of a region of one end wall5bof the case body5, the region facing the gas-discharge passage4.

As shown inFIGS. 2 and 5, the battery11accommodates an electrode plate assembly14together with battery electrolyte in its outer case13that is sealed with a cover15with an insulator interposed therebetween. The outer case13is formed by a deep-draw molded part that is in form of cylinder having a bottom. The molded part is made from nickel-plated steel sheet having electrolyte-resistance. The cover15is formed by a press-molded part in form of stepped bowl having a connecting cylindrical portion15ainto which the bottom of the outer case13is inserted and just fits. On the center of the cover15, a port via which the electrolyte is injected and safety mechanism (both not shown) is provided.

The electrode plate assembly14is formed by a positive electrode plate and a negative electrode plate that are wound with a separator interposed therebetween. The center core of the positive electrode plate and that of the negative electrode plate are exposed on an upper end surface and a lower end surface of the electrode plate assembly14and are connected to the cover15and the bottom of the outer case13, respectively, for example, by laser welding. The positive electrode plate is formed by applying a positive electrode material containing a positive electrode active material such as LiCoO2, LiMn2O4or LiNiO2, and a binder onto both sides of the center core made of aluminum foil. The negative electrode plate is formed by applying a negative electrode material containing a negative electrode active material such as graphite, petroleum cokes, or carbon fiber, and a binder onto both sides of the center core made of copper foil.

The battery unit12is formed by a plurality of batteries11, each having the aforementioned structure, that are connected in series. More specifically, the batteries11are connected to each other electrically and mechanically by fitting the bottom of the outer case13of one battery11into the connecting cylindrical portion15aof the cover15of the other battery11and then welding that connecting cylindrical portion15ato the outer periphery of the bottom of the outer case13. Moreover, a connection plate16having a connection terminal18projecting at the center thereof is welded to the inner periphery of the connecting cylindrical portion15aof the cover15of one battery11, while a connection member17having a connection terminal18fixed at the center thereof is welded to the outer surface of the bottom of the other battery11. The connection member17has a similar shape to that of the cover15. At the center of the connection terminal18, a screw hole18afor connection is provided.

The battery units12mentioned above are inserted into the corresponding through holes7from one of the sidewalls5aof the case body5in such a manner that the positive connection terminals18and the negative connection terminals18are alternately arranged. In this way, a predetermined number of battery units12are accommodated and arranged in the case2. Then, as shown inFIGS. 2 and 6, the connection plates8are placed on the outer surfaces of both sidewalls5aso as to bring the connection means8bformed by a metal plate embedded in each connection plate8into contact with the positive connection terminal18and the negative connection terminal18of the adjacent battery units12. By fastening the connection means8bby means of screw bolts19together, the battery units12are connected in series. The outer surface of this connection plate8is covered with the connection cover8a.

Each gas-discharge port10formed in one end wall5bof the case body5of the case2, shown inFIG. 6, is connected to a gas-discharge tube20, as shown inFIG. 7. Thus, gas is made to flow through the gas-discharge tube20to be discharged to the outside of the vehicle.

According to the above structure, air in the vehicle interior is sent as cooling air by means of a fan (not shown) provided in a ventilation passage (not shown) that communicates with the vehicle interior and the cooling air is introduced into the cooling-air passage3in the case2via the cooling-air inlet9aformed in the end wall5bof the case body5. Thus, the batteries11of each battery unit12are cooled by that cooling air except for portions around both ends of the batteries11and therefore the temperature increase in the respective batteries11is prevented surely, resulting in ensuring output characteristics and battery life of the respective batteries11. The cooling air after cooling the batteries11flows out of the cooling-air outlet9b, so as to be discharged to the outside of the vehicle.

On the other hand, when the battery11falls into abnormal state and gas leaked from the safety mechanism provided in the cover15of that battery11, the gas is discharged to the gas-discharge passage4that is formed in the case2to be separated from the cooling-air passage3, and is then discharged to the outside of the vehicle through the gas-discharge tube20. Therefore, it is possible to prevent the leaking gas from flowing into the vehicle interior through the passage for supplying the cooling air, thus preventing a trouble caused by such reverse gas flow.

Moreover, in the present embodiment, a plurality of battery units12each of which is formed by connecting a plurality of batteries11arranged coaxially in series are accommodated in the case2to be arranged in parallel. Therefore, the battery pack1including a number of batteries11is achieved with a compact structure. In addition, since the gas-discharge passage4is formed in regions corresponding to both sides of the case2and a region corresponding to the connection between the batteries11, the gas that leaked because of a trouble in each battery11will be discharged surely through the gas-discharge passage4.

Furthermore, the through hole7is formed to extend through both sidewalls5aof the case body5of the case2and the passage sidewalls4afor separating the gas-discharge passage4from the cooling-air passage3. Therefore, only by inserting a plurality of battery units12into the corresponding through holes7, respectively, the battery units12are accommodated and arranged in the case2so as to arrange a gas-discharge portion provided at one end of each battery11in the gas-discharge passage4. Thus, it is possible to accommodate and arrange the battery units12in the case2with excellent productivity.

In addition, since the connection plates8are placed on the outer surfaces of both sidewalls5aof the case body5so as to connect the batteries11or battery units12that are adjacent to each other in series sequentially, series connection of the battery units12accommodated and arranged in the case2is performed on the outer surfaces of both sidewalls of the case2with excellent workability.

Furthermore, the case2is formed by the case body5, that is manufactured by using a shaping die that allows die-cutting from both sides with excellent productivity, and the cover plates6aand6bfor covering both side faces of the base body5. Therefore, it is possible to manufacture the case having the cooling-air passage3and the gas-discharge passage4at a low cost.

Although only an example in which the battery11is formed by a lithium-ion battery is described in the description of the above embodiment, the present invention is also applicable to a battery having a structure other than the above, such as a nickel metal hydride battery and the same advantageous effects will be achieved.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, a cooling-air passage and a gas-discharge passage for discharging gas leaking from a battery when the battery falls into abnormal state are formed to be separated from each other. Therefore, it is possible to discharge the gas leaking from the battery when the battery falls into abnormal state, to the outside of a vehicle through the gas-discharge passage. This structure is suitable for surely preventing the gas from flowing back through a supplying passage of the cooling air.

Moreover, a plurality of battery units each of which includes a plurality of batteries that are arranged coaxially and are connected in series are accommodated in a case to be arranged in parallel, and the gas-discharge passage is formed in regions corresponding to both sides of the case along a direction in which the batteries are arranged in parallel and a region corresponding to the connection between the batteries. This structure is suitable for realizing a compact battery pack even if a number of batteries are used.