Vehicle battery mounting structure

A vehicle battery mounting structure includes a battery frame that is disposed at a vehicle lower side of a floor panel, and is made from resin; a ductile member that includes a main body joined to the battery frame and a flange contiguously formed at a vehicle width direction outside end of the main body, the flange having a hole, and the ductile member being fastened to a lower face of the floor panel using a fastener inserted through the hole; and a fastening portion that is formed in a region including the hole, having a substantially hat shaped cross-section profile projecting toward a vehicle upper side and having ridge lines on vehicle front-rear direction sides of the region, and the ridge lines being formed with curved or bent shape toward directions heading away from the hole on progression toward a vehicle width direction inside in plan view.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2013-267962 filed on Dec. 25, 2013, the disclosure of which is incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a vehicle battery mounting structure.

2. Related Art

A structure has been known in which battery frames for housing a drive battery that is disposed below the floor of an electric vehicle are formed from fiber reinforced plastic (FRP), and are fixed to side frames (under members) disposed on the left and right at a lower face of the floor (see, for example, Japanese Patent No. 4924684).

However, in resin battery frames, there is a concern of damage to fixing portions of the battery frame to the under members (floor side) due to collision load input when the vehicle experiences a side collision. There is accordingly a room for improvement in structures to prevent damage to fixing portions of the resin battery frame to the floor, in the event of a vehicle side collision.

SUMMARY

The present invention provides a vehicle battery mounting structure capable of preventing damage to fixing portions of a resin battery frame to a floor in the event of a vehicle side collision.

One aspect of the present invention is a vehicle battery mounting structure including: a battery frame that is disposed at a vehicle lower side of a floor panel, supports a battery, and is made from resin; a ductile member that includes a main body joined to the battery frame and a flange contiguously formed at a vehicle width direction outside end portion of the main body, the flange having a hole, and the ductile member being fastened and fixed to a lower face of the floor panel using a fastener inserted through the hole of the flange; and a fastening portion that is formed in a region including the hole of the flange, the region having a substantially hat shaped cross-section profile projecting toward a vehicle upper side and the region having ridge lines on vehicle front-rear direction sides of the region, and the ridge lines being formed with curved or bent shape toward directions heading away from the hole on progression toward a vehicle width direction inside in plan view.

According to the present aspect, the region including the hole formed at the flange of the ductile member configures the fastening portion formed with a substantially hat shaped cross-section profile projecting toward the vehicle upper side. The ridge lines at the vehicle front-rear direction sides of the region of the fastening portion are formed so as to curve or bend toward directions heading away from the hole on progression toward the vehicle width direction inside in plan view.

Accordingly, in the event of a side collision of the vehicle, collision load input to the flange of the ductile member through the fastener is distributed in directions heading away from the hole, namely in the vehicle front-rear direction, along the curving or bending ridge lines. Accordingly, in the event of a side collision of the vehicle, damage to the flange that is a location on the resin battery frame side for fixing to a floor side is suppressed or prevented.

The present aspect may be configured such that the curved or bent shape of the ridge lines of the fastening portion is formed at a position intersecting with a hypothetical tangent to a vehicle width direction inside edge of the hole in plan view.

According to the above configuration, the curved or bent shape of the ridge lines of the fastening portion is formed at a position intersecting with a hypothetical tangent at the vehicle width direction inside edge of the hole in plan view. Surface rigidity of the fastening portion is accordingly secured, and collision load input to the flange through the fastener in the event of a side collision of the vehicle is efficiently distributed in the vehicle front-rear direction along the ridge lines. Accordingly, in the event of a side collision of the vehicle, damage to the flange that is a location on the resin battery frame side for fixing to the floor side is further suppressed or prevented.

The present aspect may be configured such that a vehicle width direction outside end portion of the curved or bent shape of the ridge lines of the fastening portion is formed further inside in the vehicle width direction than a hypothetical tangent to a vehicle width direction outside edge of the hole in plan view.

According to the above configuration, the vehicle width direction outside end portion of the curved or bent shape of the ridge line of the fastening portion is formed further inside in the vehicle width direction than a hypothetical tangent to the vehicle width direction outside edge of the hole in plan view. Surface rigidity of the fastening portion is accordingly secured, and collision load input to the flange through the fastener in the event of a side collision of the vehicle is efficiently distributed in the vehicle front-rear direction along the ridge lines. Accordingly, in the event of a side collision of the vehicle, damage to the flange that is a location on the resin battery frame side for fixing to the floor side is further suppressed or prevented.

The present aspect may be configured such that a vehicle width direction outside end portion of the curved or bent shape of the ridge lines of the fastening portion is formed further inside in the vehicle width direction than a hypothetical straight line running in the vehicle front-rear direction and passing through a center of the hole in plan view.

According to the above configuration, the vehicle width direction outside end portion of the curved or bent shape of the ridge line of the fastening portion is formed further to the vehicle width direction inside than a hypothetical straight line running in the vehicle front-rear direction to pass through the center of the hole in plan view. Surface rigidity of the fastening portion is accordingly increased, and collision load input to the flange through the fastener in the event of a side collision of the vehicle is even more efficiently distributed in the vehicle front-rear direction along the ridge lines. Accordingly, in the event of a side collision of the vehicle, damage to the flange that is a location on the resin battery frame side for fixing to the floor side is further suppressed or prevented.

DETAILED DESCRIPTION

Detailed explanation follows regarding an exemplary embodiment, with reference to the drawings. To aid explanation, in each of the drawings, the arrow UP indicates the vehicle upward direction, the arrow FR indicates the vehicle front direction, and the arrow IN indicates the vehicle width direction inside. Unless specifically indicated otherwise, where employed in the following explanation, the up and down, front and rear, and left and right directions indicate up and down in the vehicle up-down direction, front and rear in the vehicle front-rear direction, and left and right in the vehicle left-right direction (vehicle width direction). The left side of a vehicle body is illustrated in each of the drawings; however, since the right side of the vehicle body is configured similarly but with left-right symmetry, explanation regarding the right side of the vehicle body is omitted.

As illustrated inFIG. 1, a pair of left and right under members (side frames)14, included in a vehicle frame structure and extending in the vehicle front-rear direction, are joined to a lower face of a metal floor panel12of a vehicle floor section. The under members14are formed from metal with a substantially hat shaped cross-section profile, and flange portions15thereof projecting out in the vehicle width directions are respectively joined and fixed to the lower face of both vehicle width direction end portions of the floor panel12by welding or the like.

Plural through holes14A, through which flange bolts58, described later, are inserted, are formed at the under members14along the length direction (vehicle front-rear direction) thereof. Weld nuts52are provided coaxially to each of the through holes14A at upper faces of the under members14.

A vehicle battery mounting structure10according to the present exemplary embodiment, applied to a vehicle such as an electric car, is disposed at the vehicle lower side of the floor panel12, and includes a battery frame (stack frame)20that supports a fuel cell stack16, serving as a battery, from the vehicle lower side. The battery frame20is made from fiber reinforced plastic (FRP), for example, carbon fiber reinforced plastic (CFRP).

An outer case portion17of the fuel cell stack16is formed from metal (or resin) in a rectangular box shape, and legs18that project out toward the vehicle width direction outsides are integrally formed at plural specific positions at a lower end peripheral edge portion of the outer case portion17. Each of the legs18is formed with a through hole18A through which respective flange bolts58, described later, are inserted.

As illustrated inFIG. 1andFIG. 2, the battery frame20includes an upper frame22serving as an upper battery frame, a lower frame26serving as a lower battery frame, and a core frame30serving as an intermediate member (reinforcement member), provided between the upper frame22and the lower frame26.

The upper frame22includes: a rectangular, flat-plate shaped top plate23disposed along the horizontal direction; rectangular, flat-plate shaped inclined walls24that incline upwards toward the vehicle width direction outsides, integrally provided contiguous to both vehicle width direction end portions (outside end portions) of the top plate23so as to follow inclined walls36, described later; and rectangular, flat-plate shaped flanges25that extend substantially horizontally toward the vehicle width direction outsides, integrally provided contiguous to both vehicle width direction outside end portions of the inclined walls24so as to follow upper walls37, described later.

The lower frame26includes a rectangular, flat-plate shaped bottom plate27disposed along the horizontal direction, and rectangular, flat-plate shaped side walls28projecting up substantially vertically toward the vehicle upper side, more specifically at a slight incline toward the vehicle upper outsides as viewed along the vehicle front-rear direction, and integrally provided contiguous to both vehicle width direction end portions (outside end portions) of the bottom plate27.

The height of the side walls28is set at a height almost reaching (extending to) a boundary49between a side wall47C of a lower main body47of a lower ductile member46and a lower flange48of the lower ductile member46, described later, when the lower ductile member46is joined to the lower frame26. In other words, the upper end face28A of each side wall28is positioned at substantially the same height as an upper end face73B of a block portion73of an inner member72of an energy absorption portion70, described later.

As illustrated inFIG. 2, the core frame30includes: a main body32formed with projections33, each having a substantially hat shaped cross-section profile extending along the vehicle width direction, which are arranged in plural rows (for example five rows) in the vehicle front-rear direction; and protrusions34, formed at both vehicle width direction end portions of the main body32so as to protrude toward the vehicle upper side contiguous to upper faces of the projections33.

Inclined walls36, inclining upwards toward the vehicle width direction outsides from the upper faces of the projections33, are integrally provided contiguous to vehicle width direction insides of the protrusions34. Substantially horizontal upper walls37are integrally provided extending toward the vehicle width direction outsides, contiguous to upper end portions of the inclined walls36. End faces38that make a cross-section profile substantially perpendicular to the main body32are configured at vehicle width direction outside end portions of the protrusions34. Namely, the protrusions34are formed in substantially trapezoidal shapes as viewed along the vehicle front-rear direction (as viewed from the front).

The upper faces of each of the projections33of the core frame30are joined to a lower face of the top plate23of the upper frame22using an adhesive. The lower face of the main body32of the core frame30is joined to an upper face of the bottom plate27of the lower frame26using an adhesive. The battery frame20is thus substantially configured with a rectangular closed cross-section profile.

As illustrated inFIG. 1, through holes23A,33A are respectively formed in mutual communication with each other at plural specific positions of the top plate23of the upper frame22and the projections33of the core frame30. Flange nuts54are joined to lower faces of the projections33, coaxially to each of the through holes23A,33A, using an adhesive. Metal, circular cylinder shaped collar members56are integrally and coaxially provided to upper faces of each of the flange nuts54, and the respective collar members56are inserted into the respective through holes23A,33A.

Thus, the fuel cell stack16is fastened and fixed to the battery frame20(to the upper frame22and the core frame30) by placing the fuel cell stack16on the upper face of the upper frame22(top plate23) such that the through holes18A of the legs18are in communication with through holes56A of the collar members56, inserting the flange bolts58through the through holes18A and the through holes56A from the vehicle upper side and being screwed into the flange nuts54.

As illustrated inFIG. 1andFIG. 2, upper main bodies43of a pair of left and right upper ductile members42, configuring an upper side of a ductile member40, are respectively joined to upper faces of the inclined walls24and the flanges25of the upper frame22. More specifically, the length direction of the upper ductile members42is set along the vehicle front-rear direction, and lower faces of the upper main bodies43, which are vehicle width direction inside portions thereof, are joined to the upper faces of the inclined walls24and the flanges25of the upper frame22using an adhesive.

Upper flanges44(which are vehicle width direction outside end portions of the upper ductile members42) protruding toward the vehicle width direction outside of the flanges25of the upper frame22and the end faces38of the core frame30(battery frame20) are integrally provided contiguous to vehicle width direction outside end portions of the upper main bodies43.

As illustrated inFIG. 2andFIG. 3, plural holes44B, through which the flange bolts58(seeFIG. 1) serving as fasteners are inserted, are formed through the upper flanges44at specific intervals along the vehicle front-rear direction. More specifically, respective substantially rectangular indented shapes are formed between the respective holes44B of the upper flanges44, such that plural (for example, five) regions centered on the respective holes44B form substantially rectangular, relative projection shapes (substantially hat shaped cross-section profiles projecting toward the vehicle upper side). Each of these regions (projections) respectively serves as a fastening portion44C.

As illustrated inFIG. 4, in plan view, ridge lines44D on the vehicle front-rear direction sides of the respective fastening portions44C are formed with straight line shapes from vehicle width direction outside end portions toward the vehicle width direction inside, and are formed with curved shapes (shapes that curve around toward the vehicle front-rear direction) that curve in a circular arc shape in directions gradually turning away from the holes44B on progression toward the vehicle width direction inside.

Namely, vehicle width direction inside end portions of the curved shapes of the ridge lines44D of the respective fastening portions44C respectively extend in the vehicle front-rear direction in plan view, mutually connecting together adjacent ridge lines44D. Substantially rectangular shaped indentations44E are accordingly formed between each of the holes44B, achieving a configuration in which collision load is distributed more efficiently than with a shape in which adjacent ridge lines44D are not mutually connected together.

Moreover, in plan view, the curved shapes of the ridge lines44D of the respective fastening portions44C are formed at a position intersecting a hypothetical tangent K1 at the vehicle width direction inside edges of the holes44B. A configuration is accordingly achieved in which collision load input to the upper flanges44by the flange bolts58is efficiently distributed in the vehicle front-rear direction along the respective ridge lines44D (i.e., concentration of stress toward vehicle width direction inside edges of the holes44B is prevented).

Moreover, in plan view, vehicle width direction outside end portions (boundary portions between the curved portions and the straight line portions)44F of the curved shapes of the ridge lines44D of the fastening portions44C are formed further to the vehicle width direction inside than a hypothetical tangent K2 to the vehicle width direction outside edges of the holes44B. A configuration is accordingly achieved in which the surface rigidity (strength as a coupling seat face) of the respective fastening portions44C is secured or increased.

Note that the vehicle width direction outside end portions44F of the curved shapes of the ridge lines44D of the respective fastening portions44C are preferably formed further to the vehicle width direction inside than a hypothetical straight line K3 running in the vehicle front-rear direction to pass through the centers O of the holes44B. The surface rigidity (strength as a coupling seat face) of the respective fastening portions44C is accordingly further secured or increased.

As illustrated inFIG. 5, the ridge lines44D at the vehicle front-rear direction sides of the respective fastening portions44C may be formed with straight line shapes from the vehicle width direction outside end portions toward the vehicle width direction inside in plan view, and formed with bent shapes that change direction incrementally at angled portions44G toward directions turning away from the holes44B on progression toward the vehicle width direction inside (shapes that curve around toward the vehicle front-rear direction). Note that there is no limitation to a single angled portion44G, and plural angled portions44G may be formed gradually turning away from the holes44B.

The lower main body47of the lower ductile member46that forms the lower side of the ductile member40is joined to the upper face of the bottom plate27of the lower frame26. More specifically, the lower ductile member46includes the rectangular frame shaped lower main body47, and the lower faces of the lower main body47(including lips47B) are joined to the upper face of the bottom plate27of the lower frame26using an adhesive.

The core frame30is accordingly disposed inside the lower main body47, and in this state, the lower face of the main body32is joined to the upper face of the bottom plate27of the lower frame26using an adhesive. Both vehicle front-rear direction end portions of the lower main body47are configured with projections47A with substantially hat shaped cross-section profiles extending along the vehicle width direction. Upper faces of the projections47A are joined to the lower face of the top plate23of the upper frame22using an adhesive, together with the upper faces of the projections33of the core frame30.

Both vehicle width direction end portions of the lower main body47are integrally formed with the rectangular flat-plate shaped lips47B that jut out toward the vehicle width direction insides. Lower faces of the main body32of the core frame30at the sides of the protrusions34are joined to upper faces of the lips47B using an adhesive. Namely, the lips47B of the lower main body47are clamped and fixed between the lower frame26and the core frame30.

As illustrated inFIG. 1andFIG. 2, the side walls47C are formed at portions of the lower ductile member46further outside in the vehicle width direction than the lips47B of the lower main body47. The side walls47C are formed substantially vertically toward the vehicle upper side, more specifically at a slight incline toward the vehicle upper outsides as viewed along the vehicle front-rear direction (at the same angle as the side walls28), so as to follow the side walls28of the lower frame26.

The height of the side walls47C is set at substantially the same height as that of the side walls28that are vehicle width direction outside end portions of the lower frame26. Namely, the side walls28of the lower frame26extend toward the vehicle upper side as far as a height position almost reaching the boundary49between the side walls47C and the lower flange48of the lower main body47.

The lower flanges48projecting out to the vehicle width direction outsides from the upper end portions of the end faces38of the core frame30and the side walls28of the lower frame26(the battery frame20) are integrally provided contiguous to vehicle width direction outside end portions of the side walls47C. As illustrated inFIG. 2, plural holes48B, through which the flange bolts58(described later), serving as fasteners, are inserted, are formed through the lower flanges48at specific intervals along the vehicle front-rear direction.

More specifically, similarly to the upper flanges44, respective substantially rectangular shaped indented shapes are formed between the respective holes48B of the lower flanges48(configuring indentations48E), such that plural (for example five) regions centered on the respective holes48B form substantially rectangular, relative projection shapes (substantially hat shaped cross-section profiles projecting toward the vehicle upper side). Each of these regions (projections) respectively serves as a fastening portion48C.

The configuration of ridge lines48D on the vehicle front-rear direction sides of the respective fastening portions48C is similar to that of the ridge lines44D of the respective fastening portions44C of the upper flanges44. Therefore, as illustrated inFIG. 1andFIG. 6, the upper flanges44and the lower flanges48protruding out from the battery frame20toward the vehicle width direction outsides can be overlaid while being mutually positioned with respect to each other. The upper flanges44and the lower flanges48are joined together using an adhesive (or using rivets or the like).

Namely, the mutually overlaid and joined upper flanges44and lower flanges48form flanges50serving as locations on the battery frame20side for fixing to the under members14(the lower face side of the floor panel12). The holes44B and the holes48B are in communication with each other, as illustrated inFIG. 6.

The battery frame20is accordingly fastened and fixed to the under members14through the ductile member40(the flanges50) by inserting the flange bolts58through the holes48B,44B and the through holes14A from the vehicle lower side, and screwing into the weld nuts52. Note that the ductile member40(the upper ductile members42and the lower ductile member46) are made from metal, and are, for example, formed from high tensile steel plates, or extra-high tensile steel plates.

As illustrated inFIG. 1andFIG. 2, inclined portions44A are formed at the upper main body43sides of the upper flanges44, and extend from the vehicle width direction upper outside toward the vehicle width direction lower inside (toward boundaries45between the upper main bodies43and the upper flanges44) at the vehicle width direction outsides of the battery frame20. Forming the inclined portions44A achieve a configuration in which the boundaries45act as the pivot points for bending deformation of the flanges50, as described later.

Inclined portions48A are also formed on the lower main body47sides of the lower flanges48that are overlaid with and joined to the upper flanges44, at the vehicle width direction outsides of the battery frame20. The inclined portions48A extend from the vehicle width direction upper outside toward the vehicle width direction lower inside (toward boundaries49between the lower main body47and the lower flanges48), at the same angle as the inclined portions44A. A configuration is accordingly achieved in which the boundaries49, together with the boundaries45, serve as pivot points for bending deformation of the flanges50.

As illustrated inFIG. 1, vehicle width direction outside end portions of the floor panel12are formed as bent portions12A that are bent toward the vehicle upper side. Each bent portion12A is joined to an inner panel62of a metal rocker60by welding or the like. The rockers60include the inner panel62, formed into a substantially hat shaped cross-section profile, and an outer panel64, formed into a substantially hat shaped cross-section profile.

Namely, in each of the rockers60, an upper flange64A of the outer panel64is joined to an upper flange62A of the inner panel62by welding or the like, and a lower flange64B of the outer panel64is joined to a lower flange62B of the inner panel62by welding or the like, thereby forming a rectangular closed cross-section profile.

Metal energy absorption members70are disposed between vehicle lower sides of the rockers60(including both vehicle width direction end portions of the floor panel12) and the battery frame20. Each energy absorption member70includes an inner member72disposed inside in the vehicle width direction in close proximity to the side wall28, and an outer member76disposed outside in the vehicle width direction of the inner member72across a specific gap (a sufficient gap to allow insertion of the lower flanges62B,64B).

The inner member72is formed in a shape integrally combining plural (for example, seven) blocks with closed substantially rectangular shaped cross-section profiles (tube shapes) extending along the vehicle front-rear direction. A side wall73A facing toward the vehicle width direction inside of a vehicle width direction innermost block73is disposed in close proximity to the side wall28.

More specifically, the side wall73A of the block73is formed with a slight incline toward the vehicle upper outside (at the same inclination angle as the side walls28), so as to be substantially parallel to the side wall28as viewed along the vehicle front-rear direction (as viewed from the front), and is disposed facing the side wall28across a small gap in the vehicle width direction. The upper end face73B of the side wall73A and the upper end face28A of the side wall28are positioned at substantially the same height as each other.

Note that, the block73is fastened and fixed to the under member14at a portion excluding a fastening location of the flanges50, using bolts and weld nuts, not illustrated in the drawings. At the vehicle width direction outermost side of each of the inner members72, an upper side block74is fastened and fixed to the inner panel62of the rockers60using bolts66and weld nuts68. The inner members72are thus disposed at the vehicle lower sides of both vehicle width direction end portions of the floor panel12.

The outer member76is formed in a shape integrally combining plural (for example, five) blocks with closed substantially rectangular cross-section profiles (or tube shapes) extending along the vehicle front-rear direction. At the vehicle width direction outermost side of each of the outer members76, an upper side block79is fastened and fixed to the outer panel64of the rocker60using bolts66and weld nuts68. The outer members76are thus disposed at the vehicle lower sides of the rockers60.

At the vehicle width direction outermost of the inner member72, a projection75A is formed on a lower side block75so as to protrude out toward the vehicle width direction outside. An indentation77A indented toward the vehicle width direction outside is formed at a boundary between the vehicle width direction inside lower side blocks block77and a block78of the outer member76, so as to accommodate the projection75A (without contacting the projection75A).

The indentation77A is formed so as to fit together with (contact) the projection75A when the outer member76has moved toward the inner member72side in a vehicle side collision, thereby enabling a portion of input collision load to be efficiently transmitted from the outer member76to the inner member72. Namely, the outer member76and the inner member72are capable becoming a single unit and undergoing plastic deformation (being crushed) toward the vehicle width direction inside.

Explanation follows regarding operation of the vehicle battery mounting structure10configured as described above. Namely, explanation follows regarding operation in a case in which, for example, the vehicle is involved in a side collision with a circular columnar shaped (or circular cylinder shaped) metal pole P (obstacle) extending in a vertical direction, as illustrated inFIG. 7.

As illustrated inFIG. 7, in the event that the vehicle is involved in a side collision with the pole P, excessive collision load toward the vehicle width direction inside is input to the rocker60and the energy absorption member70. When collision load is input from the vehicle width direction outside, the rocker60moves as it undergoes plastic deformation toward the vehicle width direction inside, thereby absorbing a portion of the input collision load. The remaining portion of the collision load is transmitted to the floor panel12.

When collision load is transmitted to the floor panel12, the vehicle width direction outside end portion of the floor panel12curls up, and a vehicle width direction outside end portion of the under member14fixed to the lower face of the floor panel12is moved toward the vehicle upper side. When this occurs, a bending moment M with axial direction along the vehicle front-rear direction is input to the flange50of the ductile member40fastened and fixed to the under member14.

Namely, the flange50of the ductile member40fastened and fixed to the under members14is imparted with a force to bend the flange50(upper flange44and lower flange48) upward about the boundary45between the upper main body43and the upper flange44(i.e., to move the vehicle width direction outside end portion of the flange50toward the vehicle upper side).

Note that the flange50(ductile member40) is ductile due to being made from metal (high tensile steel plates, or extra-high tensile steel plates). Moreover, the inclined portions44A,48A, extending from the vehicle width direction upper outside toward the vehicle width direction lower inside, are formed at the upper main body43side of the upper flange44and at the lower main body47side of the lower flange48that form the flange50, and at the vehicle width direction outside than the battery frame20. Moreover, the upper flanges44and the lower flanges48are joined together using an adhesive.

Accordingly, the flange50readily undergoes bending deformation toward the vehicle upper side about the boundaries45,49. The bending moment M input to the flange50is thereby efficiently absorbed by the bending deformation of the flange50toward the vehicle upper side, suppressing or preventing transmission of the bending moment M to the battery frame20. Namely, in the event of a side collision of the vehicle, stress load imparted to the battery frame20from the under member14through the flange50can be reduced or eliminated.

Due to its ductility, the flange50merely undergoes bending deformation toward the vehicle upper side, and is not at risk of breaking (i.e., breakage of the flange50is suppressed or prevented). There is accordingly no concern of the battery frame20separating from the under member14, and no concern of the fuel cell stack16falling from the vehicle.

When collision load is input to the energy absorption member70(the outer member76and the inner member72) from the vehicle width direction outside, the energy absorption member70moves as it undergoes plastic deformation toward the vehicle width direction inside, thereby absorbing a portion of the input collision load. The remaining portion of the collision load is transmitted to the under member14and the battery frame20.

The collision load transmitted to the under member14is transmitted to the flange50(the upper flange44and the lower flange48) through the flange bolts58. Note that in plan view, the ridge lines44D at the fastening portions44C of the upper flange44are formed with straight line shapes from the vehicle width direction outside end portions toward the vehicle width direction inside, and are then formed with curved shapes curving in a circular arc shape gradually turning away from the holes44B on progression toward the vehicle width direction inside (or a bent shape changing direction incrementally at the angled portions44G).

More specifically, vehicle width direction inside end portions of the curved shapes of the ridge lines44D of the respective fastening portions44C extend in the vehicle front-rear direction in plan view, and adjacent ridge lines44D are mutually connected together. Moreover, the curved shapes of the ridge lines44D of the respective fastening portions44C are formed at a position intersecting with the hypothetical tangent K1 to the vehicle width direction inside edges of the holes44B in plan view.

Moreover, in plan view the vehicle width direction outside end portions44F of the curved shapes of the ridge lines44D of the respective fastening portions44C are formed further to the vehicle width direction inside than the hypothetical tangent K2 to the vehicle width direction outside edges of the holes44B, and more specifically, are formed further to the vehicle width direction inside than the hypothetical straight line K3 running along the vehicle front-rear direction to pass through the centers O of the holes44B. The lower flange48is likewise formed similarly to the upper flange44.

Surface rigidity of the respective fastening portions44C of the upper flange44and the respective fastening portions48C of the lower flanges48is accordingly secured or increased. A collision load Fd input from the flange bolts58to the respective fastening portions44C of the upper flange44and the respective fastening portions48C of the lower flange48is efficiently distributed in the vehicle front-rear direction, following the respective ridge lines44D and the respective ridge lines48D, as illustrated inFIG. 4andFIG. 5(i.e., localized input of collision load to the vehicle width direction inside edges of the holes44B,48B is reduced).

Accordingly damage to, or breakage of, the flange50can be suppressed or prevented even when collision load is input to the upper flange44and the lower flange48, namely to the flange50, through the flange bolts58. The flange50thus undergoes bending deformation toward the vehicle upper side about the boundaries45,49even more efficiently, and the bending moment M input to the flange50is even more efficiently absorbed by the bending deformation. Namely, transmission of the bending moment M to the battery frame20is further suppressed or prevented.

The side wall73A of the energy absorption member70is formed with a slight incline toward the vehicle upper outside, so as to be substantially parallel to the side wall28of the battery frame20as viewed from the front, and is disposed facing the side wall28across a gap. The height position of the upper end face73B of the side wall73A is substantially the same as the height position of the upper end face28A of the side wall28.

Accordingly, when the energy absorption member70moves toward the vehicle width direction inside, the side wall73A makes efficient surface contact with (i.e., pressing contact with the entire face of) the side wall28, suppressing or preventing localized input of collision load to the side wall28(the battery frame20). The side wall28is accordingly suppressed or prevented from cracking or breaking, suppressing or preventing the occurrence of cross-sectional collapse of the battery frame20.

Even when the energy absorption member70moves further toward the vehicle width direction inside and the side wall73A presses the side wall28while turning due to the bending moment M, a collision load F input thereby is efficiently transmitted toward the vehicle width direction inside. Namely, a portion of the collision load heading toward the vehicle width direction inside input in a vehicle side collision is efficiently transmitted from the side wall28to the end face38of the core frame30, namely to the row of plural projections33, and is efficiently absorbed by the row of plural projections33. Input of collision load to the fuel cell stack16can accordingly be suppressed or prevented.

Note that the lips47B of the lower main body47of the lower ductile member46are clamped and fixed between the core frame30(main body32) and the lower frame26(bottom plate27). In the event of a side collision of the vehicle, the lips47B of the lower main body47are accordingly suppressed or prevented from separating from the core frame30and the lower frame26, even when the flanges50undergo bending deformation toward the vehicle upper side.

As illustrated inFIG. 7, force toward the vehicle upper side is imparted to the vehicle width direction outside end portion of the upper flange44when the flange50undergoes bending deformation toward the vehicle upper side, thereby imparting a (pressing) force to the upper main body43toward the side of the inclined wall24. Namely, in the event of a side collision of the vehicle, force in a direction to separate the upper main body43from the inclined wall24is not readily imparted to the upper main body43. Separation of the upper main body43from the inclined wall24is accordingly suppressed or prevented.

An indentation (not illustrated in the drawings) may be formed at the upper main body43side of the upper flange44at the vehicle width direction outside of the battery frame20, namely at the boundary45between the upper main body43and the upper flange44. The indentation may be a substantially U-shape (a substantially circular arc shape when viewing the boundary45in cross-section) or a substantially V-shape as viewed along the vehicle front-rear direction.

The vehicle width direction outside end portions of the flanges50thereby undergo bending deformation toward the vehicle upper side more readily about the boundaries45between the upper main bodies43and the upper flanges44, namely about the indentation. Stress load imparted to the battery frame20from the under member14through the flange50can accordingly be reduced or eliminated.

Explanation has been given above regarding the vehicle battery mounting structure10according to the present exemplary embodiment based on the drawings; however, the vehicle battery mounting structure10is not limited to the embodiment illustrated in the drawings, and the design may be modified as appropriate within a range not departing from the spirit of the present invention. For example, there is no limitation to forming the ductile member40from high tensile steel plates or extra-high tensile steel plates, and the ductile member40may, for example, be formed from an aluminum alloy or iron with a sufficient hardness.

The flanges50of the ductile member40are not limited to a configuration fastened and fixed to the under members14that are joined and fixed to the lower face of the floor panel12and, for example, may be fastened and fixed to brackets, not illustrated in the drawings, that are joined and fixed to the lower face of the floor panel12or to lower faces of the under members14.

Namely, the flanges50of the ductile member40may be indirectly joined to the floor panel12or the under members14. The “fastening” in the present exemplary embodiment is not limited to fastening using nuts and bolts, and fastening (attachment) may be performed using other fasteners (not illustrated in the drawings).

Moreover, there is no limitation to joining the upper main bodies43and the lower main body47of the ductile member40to the battery frame20with adhesive, and they may be joined using a joining means such as rivets or the like.

The battery frame20of the present exemplary embodiment is not limited to supporting the fuel cell stack16. For example, the battery frame20may also support auxiliary equipment to the fuel cell stack16(in addition to the fuel cell stack16). The fuel cell stack16of the present exemplary embodiment may be configured by a secondary battery.