Onboard battery

An onboard battery includes an accommodation case that has an upper accommodation unit and a lower accommodation unit positioned below the upper accommodation unit battery modules each having battery cells, and joints that couple the upper accommodation unit and the lower accommodation unit to each other. At least one battery module is accommodated in each of the upper accommodation unit and the lower accommodation unit. When a predetermined load or more is applied to the upper accommodation unit, a stress acts on the joints such that the upper accommodation unit and the lower accommodation unit are separated from each other, and the upper accommodation unit is moved away from the lower accommodation unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent Application No. 2014-033955 filed on Feb. 25, 2014, the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to the technical field of an onboard battery that is mounted in a vehicle such as an automobile and is provided with a battery module accommodated in an accommodation case.

2. Related Art

In various vehicles such as an automobile, an onboard battery for supplying electric power to a motor and various electrical components is mounted.

These days, vehicles such as, in particular, electric vehicle (EV), hybrid electric vehicle (HEV), and plug-in hybrid electric vehicle (PHEV) are becoming pervasive, and an onboard battery having a high power storage function is mounted on these vehicles that use electricity as power.

The onboard battery is provided with an accommodation case and a battery module accommodated in the accommodation case, and the battery module is configured by arranging a plurality of battery cells (secondary batteries) such as, e.g., nickel-metal hydride batteries and lithium ion batteries. In the onboard battery mounted in the electric vehicle or the like, in order to achieve a high capacity storage function, a plurality of the battery modules is disposed in the accommodation case, and the individual battery cells of the plurality of the battery modules are connected in series or in parallel.

The onboard battery described above includes, as a configuration in which the high power storage function is achieved, an onboard battery in which the battery modules are arranged in upper and lower tiers in the accommodation case (see, e.g., Japanese Patent No. 5206110).

The onboard battery described in Japanese Patent No. 5206110 is disposed in a trunk on the rear side, the battery module in the lower tier is inserted into a disposition depression that is formed in a floor panel so as to be opened upward, and large space is thereby secured in the trunk. The front surface on the side of the lower tier of the accommodation case that accommodates the battery module is formed as an inclined portion that is displaced forward in an upward direction. The lower tier of the onboard battery is positioned between side members (side frames) of a vehicle body.

In the onboard battery described in Japanese Patent No. 5206110, when a large load is applied to the onboard battery from the rear due to a collision of a vehicle, the inclined portion of the accommodation case is guided by a front surface forming the disposition depression, and the entire onboard battery is moved obliquely upward and forward so as to avoid a cross member positioned on the front side of the disposition depression. Consequently, the onboard battery does not collide with the cross member, and an excessive stress to the battery module accommodated in the accommodation case is suppressed.

However, in the onboard battery described in Japanese Patent No. 5206110, in the case where the large load is applied from the rear, the entire onboard battery is moved obliquely upward and forward irrespective of the position of the applied load in a vertical direction. At this point, the inclined portion is guided by the front surface forming the disposition depression. When the inclined portion is guided by the front surface, the inclined potion and the front surface forming the disposition depression come into contact with each other, and hence a reaction force (a component force in a horizontal direction) to the collision is applied to the onboard battery from the front surface.

Consequently, although the excessive stress to the battery module is suppressed by the movement of the onboard battery in the obliquely upward and forward direction, the stress may be applied to each of the battery module in the upper tier and the battery module in the lower tier that are accommodated in the accommodation case depending on the magnitude of the load (the magnitude of the reaction force).

Since the lower tier of the onboard battery is positioned between the side members, in the case where a vehicle such as a passenger car collides, the large load is less likely to be applied to the onboard battery. On the other hand, the position of the upper tier of the onboard battery corresponds to the position of a frame of a large vehicle such as a truck in the vertical direction. Thus, in the case where the large vehicle collides, the large load is applied to the onboard battery. In such case, with the large load, the stress is applied to each of the battery module in the upper tier and the battery module in the lower tier, and the possibility of occurrence of smoking or ignition resulting from damage to the battery module or the like is increased.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the above problem, and reduce the stress to the battery module at the time of the collision of the vehicle to thereby prevent the occurrence of smoking or ignition resulting from the damage to the battery module or the like.

A first aspect of the present invention provides an onboard battery including: an accommodation case that has an upper accommodation unit and a lower accommodation unit positioned below the upper accommodation unit; battery modules each having at least one battery cell, at least one of the battery modules being accommodated in each of the upper accommodation unit and the lower accommodation unit; and at least one joint that couples the upper accommodation unit and the lower accommodation unit to each other. When a predetermined load or more is applied to the upper accommodation unit, a stress acts on the at least one joint such that the upper accommodation unit and the lower accommodation unit are separated from each other, and the upper accommodation unit is moved away from the lower accommodation unit.

One of a pair of side frames of a vehicle equipped with the onboard battery may be positioned on a left and right side of the lower accommodation unit, and the other one of the pair of the side frames of the vehicle may be positioned on a right side of the lower accommodation unit.

Each of the upper accommodation unit and the lower accommodation unit may be structured to have a hollow cross section having a plurality of cavities.

A positive relay and a negative relay may be provided, and at least one of the positive relay and the negative relay may be accommodated in the lower accommodation unit.

The at least joint may have at least one middle portion that is positioned between the upper accommodation unit and the lower accommodation unit, at least one upper protruded coupler that is protruded upward from the middle portion, and at least one lower protruded coupler that is protruded downward from the at least one middle portion. The at least one upper protruded coupler may be coupled to a lower end of the upper accommodation unit. The at least one lower protruded coupler may be coupled to the lower accommodation unit so as to be in contact with either one of a front surface and a rear surface of an upper end of the lower accommodation unit.

The at least one joint may have at least one middle portion that is positioned between the upper accommodation unit and the lower accommodation unit, at least one upper protruded coupler that is protruded upward from the at least one middle portion, and at least one lower protruded coupler that is protruded downward from the at least one middle portion. The at least one lower protruded coupler may be coupled to the upper end of the lower accommodation unit, and the at least one upper protruded coupler may be coupled to the upper accommodation unit so as to be in contact with either one of a front surface and a rear surface of the lower end of the upper accommodation unit.

The at least one joint may include at least one first joint and at least one second joint. The at least one first joint may have at least one middle portion that is positioned between the upper accommodation unit and the lower accommodation unit, at least one upper protruded coupler that is protruded upward from the at least one middle portion, and at least one lower protruded coupler that is protruded downward from the at least one middle portion. The at least one second joint may have at least one middle portion that is positioned between the upper accommodation unit and the lower accommodation unit, at least one upper protruded coupler that is protruded upward from the at least one middle portion, and at least one lower protruded coupler that is protruded downward from the at least one middle portion. The at least one upper protruded coupler of the at least one first joint may be coupled to the lower end of the upper accommodation unit. The at least one lower protruded coupler of the at least one second joint may be coupled to the upper end of the lower accommodation unit, and the at least one lower protruded coupler of the at least one first joint and the upper protruded coupler of the second joint may be coupled to each other in a front and rear direction.

The at least one joint may include at least one first joint and at least one second joint. The at least one first joint may have a at least one middle portion that is positioned between the upper accommodation unit and the lower accommodation unit, at least one upper protruded coupler that is protruded upward from the at least one middle portion, a at least one lower protruded coupler that is protruded downward from the at least one middle portion, and at least one middle protruded coupler that is protruded horizontally from the at least one middle portion. The at least one second joint may have at least one middle portion that is positioned between the upper accommodation unit and the lower accommodation unit, at least one upper protruded coupler that is protruded upward from the at least one middle portion, at least one lower protruded coupler that is protruded downward from the at least one middle portion, and at least one middle protruded coupler that is protruded horizontally from the at least one middle portion. The at least one upper protruded coupler of the at least one first joint may be coupled to the lower end of the upper accommodation unit. The at least one lower protruded coupler of the at least one second joint may be coupled to the upper end of the lower accommodation unit. The at least one middle protruded coupler of the at least one first joint and the at least one middle protruded coupler of the at least one second joint may be coupled to each other in a vertical direction.

An inclined surface that is inclined in the vertical direction may be formed in each of the at least one first joint and the at least one second joint. The at least one first joint and the at least one second joint may be coupled to each other in a state in which the inclined surface of the at least one first joint and the inclined surface of the at least one second joint are in contact with each other.

DETAILED DESCRIPTION

Hereinbelow, an implementation for carrying out an onboard battery of the present invention will be described with reference to the accompanying drawings.

An onboard battery1has an accommodation case2and battery modules3,3, . . . (seeFIGS. 1 and 2). The accommodation case2has an upper accommodation unit4that is opened upward, a lower accommodation unit5that is positioned below the upper accommodation unit4and is opened upward, and a flat lid6that closes the opening of the upper accommodation unit4from above. In the upper accommodation unit4, for example, four battery modules3,3, . . . are accommodated so as to be arranged in a left and right direction and, in the lower accommodation unit5, for example, two battery modules3and3are accommodated so as to be arranged in the left and right direction or in a front and rear direction.

The onboard battery1is disposed in an upper portion of a vehicle body floor300in a trunk200positioned behind a rear seat100of a vehicle (seeFIG. 1). A disposition depression301that is opened upward in the trunk200is formed in the vehicle body floor300. Under the vehicle body floor300, a fuel tank400, rear suspensions500and500, and a muffler600are positioned. The fuel tank400is positioned below the rear seat100.

The onboard battery1is disposed in the trunk200in a state in which a lower tier including the lower accommodation unit5is inserted into the disposition depression301in the vehicle body floor300. Consequently, an upper tier including the upper accommodation unit4is positioned above the upper surface of the vehicle body floor300.

Side frames700and700that serve as the framework of the vehicle body and extend in the front and rear direction are positioned immediately laterally to the lower tier of the onboard battery1, and the rear ends of the side frames700and700are positioned at the rear of the onboard battery1. A bumper beam800that extends in the left and right direction is disposed at the rear of the side frames700and700.

Consequently, when another vehicle having a low height such as a passenger car or the like collides with the vehicle in which the onboard battery1is mounted from the rear, the height of each of the side frames700and700and the bumper beam800of the vehicle in which the onboard battery1is mounted is substantially equal to the height of each of the side frames and the bumper beam of another vehicle such as the passenger car or the like, and hence an impact is absorbed by the side frames700and700and the bumper beam800at the rear of the onboard battery1.

Thus, when the vehicle having the low height such as the passenger car or the like collides, since the impact is absorbed by the side frames700and700and the bumper beam800, a large load is not applied to the onboard battery1, a state in which the onboard battery1is disposed in the trunk200is maintained, and it is possible to protect the onboard battery1.

As illustrated inFIGS. 2 to 4, the upper accommodation unit4has an upper front wall7that faces in the front and rear direction, an upper rear wall8that is positioned on the rear side of the upper front wall7and faces in the front and rear direction, upper side walls9and9that are positioned so as to be spaced apart from each other in the left and right direction, and an inner partition wall10that faces in the vertical direction. Each of the upper front wall7, the upper rear wall8, and the upper side walls9and9is formed by extrusion molding of, e.g., aluminum or the like, and has a hollow cross section.

Cavities7a,7a, and7athat extend in the left and right direction and are arranged in the vertical direction are formed in the upper front wall7. Duct insertion holes7b,7b, and7bare formed in the upper front wall7so as to be spaced apart from each other in the left and right direction. Cable insertion holes7cand7care formed in one end of the upper front wall7in the left and right direction.

Cavities8a,8a, and8athat extend in the left and right direction and are arranged in the vertical direction are formed in the upper rear wall8. Duct insertion holes8band8bare formed in the upper rear wall8so as to be spaced apart from each other in the left and right direction.

Cavities9a,9a, . . . that extend in the front and rear direction and are arranged in the vertical direction are formed in the upper side walls9and9.

The inner partition wall10is formed into a substantially rectangular flat shape that faces in the vertical direction. Partition protrusions10a,10a, . . . that extend in the front and rear direction are provided on the upper surface side of the inner partition wall10so as to be spaced apart from each other in the left and right direction (seeFIG. 2). The partition protrusions10a,10a, . . . are protruded upward.

As illustrated inFIGS. 2 to 4, the lower accommodation unit5has a lower front wall11that faces in the front and rear direction, a lower rear wall12that is positioned on the rear side of the lower front wall11and faces in the front and rear direction, lower side walls13and13that are positioned so as to be spaced apart from each other in the left and right direction, and a bottom wall14that faces in the vertical direction. Each of the lower front wall11, the lower rear wall12, and the lower side walls13and13is formed by extrusion molding of, e.g., aluminum or the like, and has a hollow cross section.

Cavities11a,11a, and11athat extend in the left and right direction and are arranged in the vertical direction are formed in the lower front wall11. A duct insertion hole11bis formed in the central portion of the lower front wall11in the left and right direction.

Cavities12a,12a, and12athat extend in the left and right direction and are arranged in the vertical direction are formed in the lower rear wall12. Duct insertion holes12band12bare formed in the lower rear wall12so as to be spaced apart from each other in the left and right direction.

The lower side walls13and13are inclined in a direction in which they approach each other in a downward direction. Cavities13a,13a, . . . that extend in the front and rear direction and are arranged in the vertical direction are formed in the lower side walls13and13.

The bottom wall14is formed into a substantially rectangular flat shape that faces in the vertical direction. Partition protrusions14a,14a, and14athat extend in the front and rear direction are provided on the upper surface side of the bottom wall14so as to be spaced apart from each other in the left and right direction (seeFIG. 2). The partition protrusions14a,14a, and14aare protruded upward.

The bottom wall14is coupled to the lower front wall11, the lower rear wall12, and the lower side walls13and13with lower joints15,15, . . . (seeFIGS. 2 and 4). Each of the lower joints15,15, . . . is formed by extrusion molding of, e.g., aluminum or the like, and has a hollow cross section.

Receiving protrusions15a,15a, . . . that are protruded inward are provided at the lower ends of the lower joints15,15, . . . (seeFIG. 4). The outer periphery of the bottom wall14is placed on the receiving protrusions15a,15a, . . . of the lower joints15,15, . . . , and is coupled to the lower joints15,15, . . . .

The upper ends of the lower joints15,15, . . . are coupled to the respective lower ends of the lower front wall11, the lower rear wall12, and the lower side walls13and13.

The upper accommodation unit4and the lower accommodation unit5are coupled to each other with upper joints16,16, . . . (seeFIGS. 2 to 4). Each of the upper joints16is formed by extrusion molding of, e.g., aluminum or the like and, as illustrated inFIGS. 4 and 5, the upper joint16includes a middle portion17that is positioned between the upper accommodation unit4and the lower accommodation unit5, upper protruded couplers18and18that are protruded upward from the middle portion17, and a lower protruded coupler19that is protruded downward from the middle portion17.

The thickness of the middle portion17is made larger than the thickness of each of the upper front wall7, the upper rear wall8, the upper side walls9and9, the lower front wall11, the lower rear wall12, and the lower side walls13and13. A receiving protrusion17athat is protruded inward is provided in the middle portion17.

The upper protruded couplers18and18are protruded upward from the outer end and the inner end of the middle portion17in the front and rear direction or in the left and right direction. Consequently, the upper joint16is formed with a fitting depression16athat is opened upward between the upper protruded couplers18and18.

The lower protruded coupler19is protruded downward from the inner end of the middle portion17in the front and rear direction or in the left and right direction. The outer surface of the lower protruded coupler19is formed as a joint surface19a.

The lower ends of the upper front wall7, the upper rear wall8, and the upper side walls9and9of the upper accommodation unit4are fit in the fitting depressions16a,16a, . . . , and the upper joints16,16, . . . are thereby coupled to the upper front wall7, the upper rear wall8, and the upper side walls9and9. In addition, the upper joints16,16, . . . are coupled to the lower front wall11, the lower rear wall12, and the lower side walls13and13with, e.g., attachment screws900,900, . . . in a state in which the joint surfaces19a,19a, . . . of the lower protruded couplers19,19, . . . are in contact with the inner surfaces of the upper ends of the lower front wall11, the lower rear wall12, and the lower side walls13and13of the lower accommodation unit5.

Note that the upper joints16,16, . . . may also be coupled to the lower front wall11, the lower rear wall12, and the lower side walls13and13by, e.g., welding or the like.

As described above, the upper joint16is coupled to each of the lower front wall11, the lower rear wall12, and the lower side walls13and13in the state in which only the joint surface19aof the lower protruded coupler19is in contact with each of the lower front wall11, the lower rear wall12, and the lower side walls13and13, and the lower protruded coupler19is protruded from one end of the middle portion17. Consequently, a boundary between the middle portion17and the lower protruded coupler19is formed as a fragile portion16bhaving low strength, and the fragile portion16bcan be ruptured when a large load is applied to the onboard battery1.

Note that the foregoing has described an example in which the joint surfaces19a,19a, . . . of the lower protruded couplers19,19, . . . are in contact with the inner surfaces of the lower front wall11, the lower rear wall12, and the lower side walls13and13of the lower accommodation unit5, but the upper joint16may also be formed into a shape in which the lower protruded coupler is protruded downward from the outer end of the middle portion17in the front and rear direction or in the left and right direction, and the joint surface is in contact with each of the outer surfaces of the lower front wall11, the lower rear wall12, and the lower side walls13and13of the lower accommodation unit5.

The inner partition wall10is coupled to the upper joints16,16, . . . with the outer periphery thereof placed on the receiving protrusions17a,17a, . . . of the upper joints16,16, . . . .

The battery modules3,3, . . . that are accommodated in the upper accommodation unit4and are positioned in the upper tier in the accommodation case2are disposed at positions defined by the partition protrusions10a,10a, . . . provided on the inner partition wall10in a state in which the battery modules are placed on the upper surface of the inner partition wall10(seeFIGS. 2 to 4). In addition, The battery modules3and3that are accommodated in the lower accommodation unit5and are positioned in the lower tier in the accommodation case2are disposed at positions defined by the partition protrusions14a,14a, and14aprovided on the bottom wall14in a state in which the battery modules are placed on the upper surface of the bottom wall14.

The battery module3has a cell cover20and a plurality of battery cells21,21, . . . that are arranged in the front and rear direction in the cell cover20(seeFIGS. 6 and 7).

The cell cover20has a front surface22that faces in the front and rear direction, a rear surface23that is positioned on the rear side of the front surface22and faces in the front and rear direction, side surfaces24and24that are positioned so as to be spaced apart from each other in the left and right direction, a top surface25that faces in the vertical direction, and chamber formation units26and26that are attached to the side surfaces24and24.

The side surfaces24and24have attachment surfaces27and27that face in the left and right direction, upper protruded surfaces28and28that are protruded from the upper edges of the attachment surfaces27and27in a direction in which they approach each other in the left and right direction, and lower protruded surfaces29and29that are protruded from the lower edges of the attachment surfaces27and27in a direction in which they approach each other in the left and right direction. An opening27athat extends through the attachment surface27in the left and right direction is formed in a portion of the attachment surface27other than its outer periphery.

The chamber formation unit26is formed into a box-like shape having openings on its side and one of the front and the rear, and an opening edge of the chamber formation unit26in the left and right direction is attached to the outer periphery of the attachment surface27. By attaching the chamber formation units26and26to the outer peripheries of the attachment surfaces27and27, spaces are formed on left and right sides in the cell cover20, and these spaces are formed as chambers30and30. The opening of one of the front and the rear of the chamber formation unit26is formed as a coupling opening26a.

In both ends of the top surface25, insertion holes25aand25athat extend through the top surface25in the vertical direction are formed.

Each of the battery cells21,21, . . . is held by the cell cover20with the right and left ends of the battery cell21placed on the lower protruded surfaces29and29of the side surfaces24and24, and the battery cells21,21, . . . are arranged at regular intervals in a state in which each battery cell21has small gaps at the front and the rear thereof (seeFIGS. 7 and 8). A positive electrode terminal21aand a negative electrode terminal21bthat are protruded upward are provided in the battery cell21so as to be spaced apart from each other in the left and right direction. The positive electrode terminals21a,21a, . . . and the negative electrode terminals21b,21b, . . . that are positioned adjacent to each other in the front and rear direction are connected to each other with connection plates31,31, . . . each having conductivity, and the battery cells21,21, . . . are thereby connected in series to each other. The connection plate31is fixed to the battery cells21and21with fastening members such as nuts or the like (not illustrated) screwed to the positive electrode terminal21aand the negative electrode terminal21b.

A holding plate32is attached to the upper surfaces of the battery cells21,21, . . . below the top surfaces25. Disposition holes32a,32a, . . . that extend in the front and rear direction are formed in the holding plate32so as to be spaced part from each other in the front and rear direction and in the left and right direction. The positive electrode terminal21aand the negative electrode terminal21bof the battery cells21and21that are positioned adjacent to each other in the front and rear direction, and the connection plate31that connects the positive electrode terminal21aand the negative electrode terminal21bto each other are disposed in the disposition hole32a.

One battery cell21of the battery module3that is accommodated in the upper accommodation unit4and is positioned in the upper tier is connected to one battery cell21of the battery module3that is accommodated in the lower accommodation unit5and is positioned in the lower tier with a vertical bus bar33(seeFIG. 3).

A plug sensor box34and a junction box35are accommodated in left and right ends of the upper accommodation unit4of the accommodation case2(seeFIGS. 2 and 3). In addition, a battery control unit36that controls the entire onboard battery1and a charge box37in which components necessary for charging are mounted are disposed in the lower accommodation unit5of the accommodation case2.

A predetermined connection plug and a predetermined sensor are disposed in the plug sensor box34.

The junction box35has a cabinet38formed into a rectangular shape and control components39,39, . . . that are disposed in the cabinet38and control the current and the like. As the control components39,39, . . . , for example, a relay, a fuse, a connector terminal, and the like are provided. One ends of cables40and40passing through the cable insertion holes7cand7cin the upper front wall7are connected with the junction box35, and the junction box35is connected to a power supply circuit (inverter) (not illustrated) mounted below the floor of the vehicle with the cables40and40.

Note that a positive relay connected with a positive electrode power supply line and a negative relay connected with a negative electrode power supply line are provided in the junction box35, and at least one of the positive relay and the negative rely is preferably accommodated in the lower accommodation unit5.

The battery modules3,3, . . . in the upper tier are accommodated between the plug sensor box34and the junction box35in the upper accommodation unit4. In addition, the battery modules3and3in the lower tier are accommodated between the battery control unit36and the charge box37in the lower accommodation unit5.

As described above, in the state in which the battery modules3,3, . . . , the plug sensor box34, the junction box35, the battery control unit36and the charge box37are accommodated in the accommodation case2, the battery cell21of the battery module3positioned adjacent to the plug sensor box34is connected to the plug sensor box34with a first connection bus bar41, and the battery cell21of the battery module3positioned adjacent to the junction box35is connected to the junction box35with a second connection bus bar42. One end of the first connection bus bar41and one end of the second connection bus bar42are inserted into the insertion holes25aand25aformed in the top surfaces25and25of the battery modules3and3, and are connected with the positive electrode terminals21aand21aor the negative electrode terminals21band21bof the battery cells21and21.

In addition, the battery cells21,21, . . . of the adjacent battery modules3,3, . . . are connected to each other with direct current connection bus bars43,43, . . . . Both ends of the direct current connection bus bars43,43, . . . are inserted into the insertion holes25a,25a, . . . formed in the top surfaces25,25, . . . of the battery modules3,3, . . . , and are connected with the positive electrode terminals21a,21a, . . . or the negative electrode terminals21b,21b, . . . of the battery cells21,21, . . . .

Note that the plug sensor box34, the junction box35and the charge box37are connected to predetermined portions of the battery control unit36or the like with electric wires and bus bars.

Intake ducts44and44are provided on the front surface side of the battery modules3,3, . . . so as to be arranged in the left and right direction (seeFIGS. 2 and 3). The intake duct44has an intake unit45that extends in the left and right direction and a lower introduction unit46that is protruded downward from one end of the intake unit45.

Upper couplers45aand45athat are protruded rearward from one end and a middle portion of the intake unit45in the left and right direction are provided in the intake unit45. An intake opening45bis formed in the other end of the intake unit45.

A lower coupler46athat is protruded rearward from the lower end of the lower introduction unit46is provided in the lower introduction unit46.

In the intake ducts44and44, the upper couplers45a,45a, . . . are inserted into the duct insertion holes7b,7b, and7bformed in the upper front wall7, and the rear ends of the upper couplers45a,45a, . . . are coupled to the front ends of the chamber formation units26,26, . . . in the battery modules3,3, . . . in the upper tier that are arranged in the left and right direction (seeFIG. 8). In addition, in the intake ducts44and44, the lower couplers46aand46aare inserted into the duct insertion hole11bformed in the lower front wall11, and the rear ends of the lower couplers46aand46aare coupled to the front ends of the chamber formation units26and26in the battery modules3and3in the lower tier that are arranged in the left and right direction.

Consequently, the intake ducts44and44communicate with the coupling openings26a,26a, . . . of the chamber formation units26,26, . . . , and cooling air taken in from the intake openings45band45bis sent to chambers30,30, . . . formed in the battery modules3,3, . . . in the upper and lower tiers via the intake ducts44and44. The cooling air sent to the chambers30,30, . . . is flown to the chambers30,30, . . . on the opposite side through gaps between the battery cells21,21, . . . .

On the rear surface side of the battery modules3,3, . . . , discharge ducts47and47are provided so as to be spaced apart from each other in the left and right direction (seeFIGS. 2 and 3). The discharge duct47has a fan disposition unit48having a substantially circular shape, an upper coupling protrusion49and a lower coupling protrusion50that are protruded forward from the fan disposition unit48, and a discharge unit51that is laterally protruded from the fan disposition unit48. The front end of the upper coupling protrusion49is divided into two portions.

A cooling fan52is rotatably disposed in the fan disposition unit48. The cooling fan52has the function of flowing the cooling air from the side of the upper coupling protrusion49and the lower coupling protrusions50to the side of the discharge unit51by the rotation of the cooling fan52.

A discharge opening51ais formed in the tip of the discharge unit51.

In the discharge ducts47and47, the upper coupling protrusions49and49are inserted into the duct insertion holes8band8bformed in the upper rear wall8, and the front ends of the upper coupling protrusions49and49are coupled to the rear ends of the chamber formation units26,26, . . . in the battery modules3,3, . . . in the upper tier that are arranged in the left and right direction (seeFIG. 8). In addition, in the discharge ducts47and47, the lower coupling protrusions50and50are inserted into the duct insertion holes12band12bformed in the lower rear wall12, and the front ends of the lower coupling protrusions50and50are coupled to the rear ends of the chamber formation units26and26in the battery modules3and3in the lower tier that are arranged in the left and right direction.

Consequently, the discharge ducts47and47communicate with the coupling openings26a,26a, . . . of the chamber formation units26,26, . . . , and the cooling air that has cooled the battery cells21,21, . . . is discharged from the discharge openings51aand51aof the discharge units51and51via the discharge ducts47and47through the chambers30,30, . . . .

The flow of the cooling air in the intake ducts44and44, the battery modules3,3, . . . , and the discharge ducts47and47is forcibly carried out by the cooling fans52and52, and the battery cells21,21, . . . are thereby cooled efficiently.

When another vehicle having a high height such as a truck or the like collides with the vehicle in which the onboard battery1configured as described above is mounted from the rear, the side frames and the bumper beam of another vehicle such as the truck or the like are present at positions higher than those of the side frames700and700and the bumper beam800of the vehicle in which the onboard battery1is mounted, and hence a load P resulting from an impact from another vehicle is applied to the upper tier of the onboard battery1(seeFIG. 9).

When the load P resulting from the impact from another vehicle is applied to the upper tier of the onboard battery1, the fragile portions16b,16b, . . . of the upper joints16,16, . . . are ruptured, the upper tier including the upper accommodation unit4is separated from the lower tier including the lower accommodation unit5, and the upper tier is moved forward.

Consequently, the upper tier of the onboard battery1is separated from the lower tier and is moved forward, whereby the stress resulting from the impact is reduced, and the stress resulting from the impact on the upper tier is less likely to be applied to the lower tier of the onboard battery1with the separation of the upper tier so that the stress to the battery modules3,3, . . . accommodated in the accommodation case2is reduced and it is possible to prevent the occurrence of smoking or ignition resulting from damage to the battery modules3,3, . . . .

In addition, the onboard battery1is structured such that each of the upper accommodation unit4and the lower accommodation unit5has the hollow cross section, and hence the impact at the time of the collision of another vehicle is absorbed by the structure having the hollow cross section, and it is possible to achieve an improvement in impact resistance while securing a reduction in the weight of the onboard battery1.

Further, as described above, at least one of the positive relay and the negative relay is accommodated in the lower accommodation unit5, whereby it becomes possible to perform control in which the relay accommodated in the lower accommodation unit5is turned OFF when the upper tier including the upper accommodation unit4and the lower tier including the lower accommodation unit5are separated from each other, and it is possible to prevent electric shock by interrupting a circuit at the same time as the separation of the upper tier from the lower tier.

Furthermore, the upper joint16that couples the upper accommodation unit4and the lower accommodation unit5to each other is coupled to the lower accommodation unit5in a state in which the lower protruded coupler19is in contact with one of the front surface and the rear surface of the upper end in the lower accommodation unit5, and hence the fragile portion16bas the boundary between the middle portion17and the lower protruded coupler19is easily ruptured when the load is applied to the upper tier including the upper accommodation unit4, and it is possible to easily separate the upper accommodation unit4and the lower accommodation unit5from each other when a specific load or more is applied to the upper accommodation unit4.

Note that the foregoing has described the upper joint16that has the joint surface19ain the lower protruded coupler19as an example, but, as illustrated inFIG. 10, the upper accommodation unit4and the lower accommodation unit5may also be coupled to each other with an upper joint16A that has a joint surface18ain the upper protruded coupler18.

The upper joint16A includes the middle portion17, the upper protruded coupler18, and the lower protruded couplers19and19, the upper protruded coupler18is protruded upward from the inner end of the middle portion17in the front and rear direction or in the left and right direction, and the lower protruded couplers19and19are protruded downward from the outer end and the inner end of the middle portion17in the front and rear direction or in the left and right direction. The outer surface of the upper protruded coupler18is formed as the joint surface18a. The fitting depression16athat is opened downward is formed between the lower protruded couplers19and19in the upper joint16. A boundary between the middle portion17and the upper protruded coupler18is formed as the fragile portion16bhaving low strength.

The upper joint16A is coupled to each of the upper front wall7, the upper rear wall8, and the upper side walls9and9with, e.g., the attachment screw900in a state in which the joint surface18aof the upper protruded coupler18is in contact with each of the inner surfaces of the lower ends of the upper front wall7, the upper rear wall8, and the upper side walls9and9of the upper accommodation unit4.

Note that the upper joint16A may also be formed into a shape in which the upper protruded coupler18is protruded upward from the outer end of the middle portion17in the front and rear direction or in the left and right direction, and the joint surface18ais in contact with each of the outer surfaces of the lower ends of the upper front wall7, the upper rear wall8, and the upper side walls9and9of the upper accommodation unit4.

Since the upper joint16A is coupled to the upper accommodation unit4in the state in which the upper protruded coupler18is in contact with one of the front surface and the rear surface of the lower end of the upper accommodation unit4, the fragile portion16bas a boundary between the middle portion17and the upper protruded coupler18is easily ruptured when the load is applied to the upper tier including the upper accommodation unit4, and it is possible to easily separate the upper accommodation unit4and the lower accommodation unit5from each other when a specific load or more is applied to the upper accommodation unit4.

Hereinbelow, individual modifications of the upper joint will be described (seeFIGS. 11 to 15).

Note that, in the following description of the individual modifications of the upper joint, only components different from those of the upper joint16described above are described in detail, the same components as those of the upper joint16are designated by the same reference numerals as those of the upper joint16, and description thereof will be omitted. Hereinbelow, the description will be given by using the upper joint that couples the upper rear wall8and the lower rear wall12to each other as an example.

As illustrated inFIG. 11, an upper joint16B according to a first modification includes a middle portion17B, the upper protruded couplers18and18, and the lower protruded coupler19, and a positioning protrusion17bthat is protruded downward is provided in the middle portion17B. In the case where the upper joint16B is used, a positioning depression12cthat is opened upward is formed in the upper end of the lower rear wall12, and the positioning protrusion17bis fit in the positioning depression12c.

Note that, similarly to the upper joint16A, the upper protruded coupler18and the lower protruded couplers19and19may be provided in the upper joint16B, and in this case, the positioning protrusion that is protruded upward is provided on the upper surface side of the middle portion17B, and the positioning depression that is opened downward is formed in the lower end of the upper rear wall8.

Since the upper joint16B has the positioning protrusion17b, it is possible to easily and reliably perform positioning relative to the lower rear wall12.

In the upper joint16B, a boundary between the middle portion17B and the lower protruded coupler19is formed as the fragile portion16b, and the fragile portion16bcan be ruptured when a large load is applied to the upper tier of the onboard battery1.

As illustrated inFIG. 12, an upper joint16C according to a second modification includes a middle portion17C, the upper protruded couplers18and18, and the lower protruded coupler19, and an inclined surface17cthat is inclined in the vertical direction is formed in the middle portion17C. In the case where the upper joint16C is used, an inclined surface12dthat is inclined in the vertical direction is formed in the upper end of the lower rear wall12, and the inclined surface17cis in contact with the inclined surface12d.

Note that, similarly to the upper joint16A, the upper protruded coupler18and the lower protruded couplers19and19may also be provided in the upper joint16C, and in this case, the inclined surface is formed on the upper surface side of the middle portion17C, and the inclined surface is formed in the lower end of the upper rear wall8.

In the upper joint16C, a boundary between the middle portion17C and the lower protruded coupler19is formed as the fragile portion16b, and the fragile portion16bcan be ruptured when a large load is applied to the upper tier of the onboard battery1. In the upper joint16C, since the inclined surface17cis in contact with the inclined surface12d, when the load is applied to the upper tier of the onboard battery1, the inclined surface17cand the inclined surface12dslide relative to each other and the separation of the upper tier of the onboard battery1from the lower tier thereof is facilitated.

Next, a third modification, a fourth modification, and a fifth modification will be described (seeFIGS. 13 to 15). Note that each of the third modification, the fourth modification, and the fifth modification is configured by coupling two upper joints.

The third modification is configured by coupling a first upper joint16D and a second upper joint16E (seeFIG. 13).

The first upper joint16D includes the middle portion17, the upper protruded couplers18and18, and a lower protruded coupler19D. The lower protruded coupler19D is protruded downward from the middle portion17. The second upper joint16E includes the middle portion17, an upper protruded coupler18E, and the lower protruded couplers19and19, and the receiving protrusion17ais not provided in the middle portion17. The upper protruded coupler18E is protruded upward from the middle portion17. In the first upper joint16D and the second upper joint16E, the lower protruded coupler19D and the upper protruded coupler18E are coupled to each other with, e.g., the attachment screw900.

In the first upper joint16D, a boundary between the middle portion17and the lower protruded coupler19D is formed as the fragile portion16band, in the second upper joint16E, a boundary between the middle portion17and the upper protruded coupler18E is formed as the fragile portion16b. Consequently, when a large load is applied to the upper tier of the onboard battery1, the fragile portion16bof the first upper joint16D or the fragile portion16bof the second upper joint16E can be ruptured.

Thus, in the third modification, since the lower protruded coupler19D of the first upper joint16D and the upper protruded coupler18E of the second upper joint16E are coupled to each other, when the load is applied to the upper tier including the upper accommodation unit4, the fragile portion16bas the boundary between the middle portion17and the lower protruded coupler19D or the fragile portion16bas the boundary between the middle portion17and the upper protruded coupler18E is easily ruptured, and it is possible to easily separate the upper accommodation unit4and the lower accommodation unit5from each other when a specific load or more is applied to the upper accommodation unit4.

The fourth modification is configured by coupling a first upper joint16F and a second upper joint16G to each other (seeFIG. 14).

The first upper joint16F includes the middle portion17, the upper protruded couplers18and18, and a lower protruded coupler19F. The lower protruded coupler19F is protruded from the middle portion17obliquely downward and forward, and has an inclined surface19bthat is inclined in the front and rear direction. The second upper joint16G includes the middle portion17, an upper protruded coupler18G, and the lower protruded couplers19and19, and the receiving protrusion17ais not provided in the middle portion17. The upper protruded coupler18G is protruded upward from the middle portion17, and has an inclined surface18bthat is inclined in the front and rear direction. In the first upper joint16F and the second upper joint16G, the lower protruded coupler19F and the upper protruded coupler18G are coupled to each other with, e.g., the attachment screw900in a state in which the inclined surface19band the inclined surface18bare in contact with each other.

When a large load is applied to the upper tier of the onboard battery1, the inclined surface19band the inclined surface18bslide relative to each other, and a portion900aof the attachment screw900at a boundary surface between the lower protruded coupler19F and the upper protruded coupler18G can be ruptured.

Thus, in the fourth modification, since the lower protruded coupler19F and the upper protruded coupler18G are coupled to each other in the state in which the inclined surface19bof the first upper joint16F and the inclined surface18bof the second upper joint16G are in contact with each other, the lower protruded coupler19F and the upper protruded coupler18G easily slide relative to each other at the inclined surface19band the inclined surface18b, the fragile portion900aof the attachment screw900is easily ruptured when the load is applied to the upper tier including the upper accommodation unit4, and it is possible to easily separate the upper accommodation unit4and the lower accommodation unit5from each other when a specific load or more is applied to the upper accommodation unit4.

The fifth modification is configured by coupling a first upper joint16H and a second upper joint16I to each other (seeFIG. 15).

The first upper joint16H includes the middle portion17, the upper protruded couplers18and18, a lower protruded coupler19H, and a middle protruded coupler53. The lower protruded coupler19H is protruded downward from the middle portion17, and has the inclined surface19bthat is inclined in the front and rear direction. The middle protruded coupler53is protruded horizontally from the middle portion17.

The second upper joint16I includes the middle portion17, an upper protruded coupler181, the lower protruded couplers19and19, and a middle protruded coupler54, and the receiving protrusion17ais not provided in the middle portion17. The upper protruded coupler181is protruded upward from the middle portion17, and has the inclined surface18bthat is inclined in the front and rear direction. The middle protruded coupler54is protruded horizontally from the upper protruded coupler18.

In the first upper joint16H and the second upper joint16I, the middle protruded coupler53and the middle protruded coupler54are coupled to each other with, e.g., the attachment screw900in a state in which the inclined surface19band the inclined surface18bare in contact with each other.

When a large load is applied to the upper tier of the onboard battery1, the incline surface19band the inclined surface18bslide relative to each other, and the portion900aof the attachment screw900at a boundary surface between the middle protruded coupler53and the middle protruded coupler54can be ruptured.

Thus, in the fifth modification, since the middle protruded coupler53and the middle protruded coupler54are coupled to each other in the state in which the inclined surface19bof the first upper joint16H and the inclined surface18bof the second upper joint16I are in contact with each other, the lower protruded coupler19H and the upper protruded coupler181easily slide relative to each other at the inclined surface19band the inclined surface18b, the fragile portion900aof the attachment screw900is easily ruptured when the load is applied to the upper tier including the upper accommodation unit4, and it is possible to easily separate the upper accommodation unit4and the lower accommodation unit5from each other when a specific load or more is applied to the upper accommodation unit4.