Vehicular battery case and method for manufacturing vehicular battery case

A vehicular battery case includes inner and outer bottom plate portions, a lower frame, and a frame body. The outer bottom plate portion is on a lower side of the inner bottom plate portion. The lower frame is between the inner and outer bottom plate portions. The frame body stands upward from outer peripheral portions of the inner and outer bottom plate portions. The frame body includes a lower portion including a first joint surface joined to the inner bottom plate portion and a second joint surface on an outer side of the first joint surface and joined to the outer bottom plate portion. The lower frame includes an upper end portion including a first flange portion including an upper surface facing a lower surface of the inner bottom plate portion. The first flange portion is joined to the lower surface of the inner bottom plate portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2021-057834, filed on Mar. 30, 2021, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to a vehicular battery case and a method for manufacturing a vehicular battery case.

BACKGROUND DISCUSSION

JP2019-110003A (Reference1) discloses a battery case including side frames and a bottom plate member. The bottom plate member disclosed in Reference1has a sandwich structure in which a core material is sandwiched between a first plate and a second plate. The first plate includes two metal plates and elliptical-tubule-shaped pipes sandwiched between these two metal plates, and a cooling medium path for cooling a battery is formed, by the pipes, inside the first plate. The first plate and the second plate are fixed to a side cover, and thereby the bottom plate member is fixed to the side frames.

Since many steps are required in order to manufacture the battery case of Reference1, there is a problem that manufacturing cost increases. Specifically, in order to manufacture the battery case of Reference1, necessary steps include a step of manufacturing the first plate in which the cooling medium paths are formed of the two metal plates and a plurality of the elliptical pipes, a step of manufacturing the bottom plate member by superimposing the first plate, the core material, and the second plate to one another, and a step of joining the manufactured bottom plate member to the side frames. Reference1further discloses a method of joining the first plate to the side frames by rivets, and joining the second plate to the side frames by rivets or caulking. In such a method, the first plate of the bottom plate member needs to be joined to the side frames from an upper side, and the second plate of the bottom plate member needs be joined to the side frames from a lower side. For this reason, a position and an orientation of each member need to be changed in the course of the manufacturing, thus increasing the number of steps.

A need thus exists for a vehicular battery case and a method for manufacturing the same which are not susceptible to the drawback mentioned above.

SUMMARY

A vehicular battery case according to this disclosure includes a plate-shaped inner bottom plate portion, a plate-shaped outer bottom plate portion, a lower frame, and a frame body. A battery is mountable on an upper surface side of the inner bottom plate portion. The outer bottom plate portion is arranged on a lower side of the inner bottom plate portion in such a way as to be separated from the inner bottom plate portion. The lower frame is arranged between the inner bottom plate portion and the outer bottom plate portion. The frame body is provided in such a way as to stand upward from outer peripheral portions of the inner bottom plate portion and the outer bottom plate portion. The frame body includes a lower portion where first and second joint surfaces are formed. The first joint surface faces upward or downward. The second joint surface faces downward, and is on an outer side of and on a lower side of the first joint surface in the frame body. The lower frame includes an upper end portion provided with a first flange portion including an upper surface facing a lower surface of the inner bottom plate portion. The inner bottom plate portion includes the outer peripheral portion that is joined to the first joint surface in a state of overlapping the first joint surface in an up-down direction. The outer bottom plate portion includes the outer peripheral portion that is joined to the second joint surface in a state of overlapping the second joint surface in an up-down direction. The first flange portion of the lower frame is joined to the lower surface of the inner bottom plate portion.

A method for manufacturing a vehicular battery case according to this disclosure is a method for manufacturing a vehicular battery case that includes a plate-shaped inner bottom plate portion, a plate-shaped outer bottom plate portion, a lower frame, and a frame body. The inner bottom plate portion is configured in such a way that a battery is mountable on an upper surface side of the inner bottom plate portion. The outer bottom plate portion is arranged on a lower side of the inner bottom plate portion in such a way as to be separated from the inner bottom plate portion. The lower frame is arranged between the inner bottom plate portion and the outer bottom plate portion, and includes an upper end portion provided with a first flange portion including an upper surface facing a lower surface of the inner bottom plate portion. The frame body is provided in such a way as to stand upward from outer peripheral portions of the inner bottom plate portion and the outer bottom plate portion. The frame body includes a lower portion where first and second joint surfaces are formed. The first joint surface faces upward or downward. The second joint surface faces downward, and is on an outer side of and on a lower side of the first joint surface in the frame body. The method includes a step of joining the inner bottom plate portion to the frame body by applying a laser from a lower side to the outer peripheral portion of the inner bottom plate portion arranged in such a way as to overlap the first joint surface. The method further includes a step of joining the lower frame to the inner bottom plate portion by applying a laser from a lower side to the first flange portion of the lower frame arranged on a lower side of the inner bottom plate portion. The method further includes a step of joining the outer bottom plate portion to the frame body by applying a laser from a lower side to the outer peripheral portion of the outer bottom plate portion arranged in such a way as to overlap the second joint surface from a lower side.

A vehicular battery case according to this disclosure includes a plate-shaped inner bottom plate portion, a plate-shaped outer bottom plate portion, a lower frame, and a frame body. A battery is mountable on an upper surface side of the inner bottom plate portion. The outer bottom plate portion is arranged on a lower side of the inner bottom plate portion in such a way as to be separated from the inner bottom plate portion. The lower frame is arranged between the inner bottom plate portion and the outer bottom plate portion. The frame body is provided in such a way as to stand upward from outer peripheral portions of the inner bottom plate portion and the outer bottom plate portion. The frame body includes a lower portion where first and second joint surfaces are formed. The first joint surface is joined to the inner bottom plate portion. The second joint surface is on an outer side of the first joint surface in the frame body, and is joined to the outer bottom plate portion. The lower frame includes an upper end portion provided with a first flange portion including an upper surface facing a lower surface of the inner bottom plate portion. The first flange portion of the lower frame is joined by a laser to the lower surface of the inner bottom plate portion.

DETAILED DESCRIPTION

A vehicular battery case10aaccording to this embodiment is used for accommodating a battery mounted on an electric vehicle (such as an EV, a plug-in hybrid vehicle (PHV), or a hybrid vehicle (HV)). The vehicular battery case10aaccording to this embodiment is arranged at a floor portion (on a lower side of a seat) of the vehicle. The vehicular battery case10aaccording to the embodiment of this disclosure is configured in such a way as to include a path (hereinafter, referred to as “temperature control path20”) through which fluid (hereinafter, referred to as “temperature control fluid”) such as water for temperature control can flow, and to enable temperature control (cooling and heating) of the battery by making the temperature control fluid flow through the temperature control path20.

In the following description, each direction of the vehicular battery case10aaccording to this embodiment is based on a reference direction (i.e., a direction of the vehicle) in a state of being attached to the vehicle. In each of the drawings, a front side of the vehicle-mounted battery case10aaccording to the embodiment of this disclosure is indicated by the arrow Fr, a rear side of the battery case10ais indicated by the arrow Rr, an upper side of the battery case10ais indicated by the arrow Up, a lower side of the battery case10ais indicated by the arrow Dw, a right side of the battery case10ais indicated by the arrow R, and a left side of the battery case10ais indicated by the arrow L. In the following description, the vehicular battery case10aaccording to the embodiment of this disclosure is abbreviated simply as “battery case10a”.

First, an entire configuration of the battery case10ais described.FIG.1is a perspective view illustrating the configuration of the battery case10a.FIG.2is a perspective view illustrating a state where battery modules50are accommodated in the battery case10a.FIG.3is an exploded perspective view illustrating the configuration of the battery case10a, and is a view seen from a lower side.

As illustrated inFIG.1toFIG.3, the battery case10aincludes a lower panel11, a heat sink12, a front frame13, a rear frame14, left and right side frames15, a plurality of crossing members16, a plurality of crossing-member support members17, a plurality of lower frames18a, and a shared panel19. The battery case10ahas a substantially quadrilateral shape when viewed in the up-down direction, and has a bottomed box-shaped structure whose upper side is open. Specifically, the lower panel11, the heat sink12, the lower frames18a, and the shared panel19form “the bottom portion of the box”, and the front frame13, the rear frame14, and the left and right side frames15form “a side wall portion of the box”. The front frame13, the rear frame14, and the left and right side frames15further form a frame body including an opening in the up-down direction on an inner peripheral side. The battery can be accommodated in an inside (i.e., an area surrounded by the front frame13, the rear frame14, and the left and right side frames15) of this opening. On an upper side of the lower panel11, a plurality of crossing members16are arranged in such a way as to be separated from each other at predetermined intervals in the front-rear direction. However, the battery case10amay include a cover member that covers an upper side of the opening of the frame body formed by the front frame13, the rear frame14, and the left and right side frames15.

The battery case10ahas a double-bottom structure including an inner bottom plate portion and an outer bottom plate portion that are separated from each other in the up-down direction. Specifically, the lower panel11and the heat sink12are superimposed on each other in the up-down direction and joined directly to each other. The superimposed body of the lower panel11and the heat sink12forms the inner bottom plate portion of the double-bottom structure. A temperature control path20is provided between the lower panel11and the heat sink12. A configuration of the temperature control path20is described below. On a lower side of the superimposed body of the lower panel11and the heat sink12, the shared panel19is arranged. The shared panel19forms the outer bottom plate portion of the double-bottom structure. A plurality of the lower frames18aare arranged between the shared panel19(outer bottom plate portion) and the superimposed body (inner bottom plate portion) of the lower panel11and the heat sink12. Spaces are formed between the shared panel19and the superimposed body of the lower panel11and the heat sink12. In other words, the shared panel19(outer bottom plate portion) is arranged on a lower side of the superimposed body of the lower panel11and the heat sink12in such a way as to be separated from the superimposed body.

The lower panel11is configured in such a way that the battery modules50can be mounted on an upper surface side of the lower panel11. The front frame13, the rear frame14, and the left and right side frames15are arranged along outer peripheries of the lower panel11and the heat sink12when viewed in the up-down direction, and are provided in such a way as to stand up from outer peripheral portions of these. The front frame13, the rear frame14, and the left and right side frames15form a frame including an opening that is on an inner peripheral side when viewed in the up-down direction and that can accommodate the battery modules50. As illustrated inFIG.2, the battery module50is an assembly where a plurality of battery cells501are integrally coupled to each other by protective members502or the like. Each of the battery modules50is substantially rectangular in the top view. The battery case10acan accommodate a plurality of the battery modules50in such a way as to be arranged side by side in the front-rear direction at orientations of making longitudinal directions of the battery modules50parallel to the left-right direction of the battery case10a. Specifically, the battery case10ais configured in such a way as to accommodate the two battery modules50in each of areas between the crossing members16adjacent to each other, an area between the front frame13and the crossing member16located on the frontmost side, and an area between the rear frame14and the crossing member16located on the rearmost side.

Next, each member of the battery case10ais described. As illustrated inFIG.3, each of the lower panel11and the heat sink12is a plate-shaped member having a substantially quadrilateral shape when viewed in the up-down direction. The lower panel11and the heat sink12have substantially the same shapes and sizes as each other when viewed in the up-down direction. The lower panel11and the heat sink12are each formed of an aluminum plate, for example.

Extension portions111and121extending to the front side are provided at central portions in the left-right direction in front end portions (front-side edges) of the lower panel11and the heat sink12. The extension portion111of the lower panel11includes two supply-discharge portions112. These two supply-discharge portions112are holes for making an inside and an outside of the temperature control path20between the lower panel11and the heat sink12communicate with each other. Via these two supply-discharge portions112, temperature control fluid can be supplied to the temperature control path20and be discharged from the temperature control path20.

The heat sink12is provided with a path wall portion122forming the temperature control path20. The path wall portion122is a recess including an opening on an upper side, and is formed by press working. Thus, the path wall portion122bulges to a lower side.

Each of the front frame13, the rear frame14, and the left and right side frames15is a hollow and long rod-shaped member, and is formed in such a way as to have a predetermined thickness in the width direction (the front-rear direction for the front frame13and the rear frame14, and the left-right direction for the side frames15) perpendicular to a direction along the outer peripheries of the lower panel11, the heat sink12, and the shared panel19, when viewed in the up-down direction. Extruded aluminum materials for example are applied to the front frame13, the rear frame14, and the left and right side frames15.

The front frame13and the rear frame14are arranged in such a way as to be separated from each other in the front-rear direction and be in parallel to each other at orientations of making longitudinal directions of the front frame13and the rear frame14parallel to the left-right direction (vehicle width direction). First joint surfaces131and141to which the lower panel11(the superimposed body of the lower panel11and the heat sink12) is joined and second joint surfaces132and142to which the shared panel19is joined are formed at lower portions of the front frame13and the rear frame14. Each of the first joint surfaces131and141and the second joint surfaces132and142is a strip-shaped flat surface long in the left-right direction, perpendicular to the up-down direction, and facing downward.

The first joint surfaces131and141and the second joint surfaces132and142are displaced from each other in the front-rear direction and the up-down direction, and do not overlap each other when viewed in the up-down direction. The second joint surfaces132and142are located on a lower side of the first joint surfaces131and141. Specifically, at the lower portions of the front frame13and the rear frame14, protrusion portions protruding downward are provided in such a way as to extend in the left-right direction along edges that are on sides opposite to mutually facing sides, i.e., on the outer sides (outer peripheral sides). In the lower portions of the front frame13and the rear frame14, lower surfaces (on inner peripheral sides) other than the protrusion portions are the first joint surfaces131and141, and lower surfaces (on outer peripheral sides) of the protrusion portions are the second joint surfaces132and142. In the front frame13, the first joint surface131is located on a rear side of the second joint surface132, and in the rear frame14, the first joint surface141is located on a front side of the second joint surface142. In other words, the second joint surfaces132and142are on an outer side (outer peripheral side) of and on a lower side of the first joint surfaces131and141in the quadrilateral frame body formed by the front frame13, the rear frame14, and the left and right side frames15.

The lower portion of the front frame13is provided with a recess portion133for avoiding interference with the extension portions111and121of the lower panel11and the heat sink12. The recess portion133is open on the lower side in such a way that the lower panel11and the heat sink12can be attached from a lower side of the front frame13.

The left and right side frames15are arranged in such a way as to be separated from each other in the left-right direction and be in in parallel to each other, with the longitudinal directions of these being oriented in parallel to the front-rear direction. A first joint surface151to which the lower panel11(the superimposed body of the lower panel11and the heat sink12) is joined and a second joint surface152to which the shared panel19is joined are formed at lower portions of the left and right side frames15. Each of the first joint surface151and the second joint surface152is a strip-shaped flat surface long in the front-rear direction, perpendicular to the up-down direction, and facing downward.

The first joint surface151and the second joint surface152are displaced from each other in the left-right direction and the up-down direction, and do not overlap each other when viewed in the up-down direction. The second joint surface152is located on a lower side of the first joint surface151. Specifically, at the lower portions of the left and right side frames15, protrusion portions protruding downward are provided in such a way as to extend in the front-rear direction along edges that are on sides opposite to mutually facing sides, i.e., on the outer sides (outer peripheral sides). In the lower portion of the left and right side frames15, lower surfaces (on inner peripheral sides) other than the protrusion portions are the first joint surfaces151, and lower surfaces (on outer peripheral sides) of the protrusion portions are the second joint surfaces152. In the left side frame15, the first joint surface151is located on a right side of the second joint surface152, and in the right side frame15, the first joint surface151is located on a left side of the second joint surface152. In other words, the second joint surface152is on an outer side (outer peripheral side) of and on a lower side of the first joint surface151in the substantially quadrilateral frame body formed by the front frame13, the rear frame14, and the left and right side frames15.

The left and right side frames15each include an energy absorption portion153. The energy absorption portions153are portions that protrude to sides (i.e., outer sides in the vehicle width direction) opposite to mutually facing sides of the left and right side frames15, that extend in the front-rear direction, and that are integrally connected to other portions. A space is formed inside the energy absorption153. The energy absorbing portion153is configured in such a way as to alleviate impact applied to the battery modules50by being deformed when side collision or the like occurs.

A plurality of the crossing members16prevent or suppress the side frame15from being deformed and contacting with the battery module50by receiving a load in the left-right direction when side collision or the like occurs. A plurality of the crossing members16are each a long rod-shaped member, and extruded aluminum materials for example are applied to these. A plurality of the crossing members16extend in a rod shape along an upper surface of the lower panel11and are arranged side by side in the front-rear direction, with their longitudinal directions being oriented in parallel to the left-right direction.

FIG.4is a perspective view illustrating a structure of the crossing member16. As illustrated inFIG.4, the crossing member16has a substantially quadrilateral cross-sectional shape (i.e., an open cross-sectional shape) whose lower side is open. Specifically, the crossing member16includes a body portion161opening on the lower side, and a pair of opening ends162(two lower end portions separated from each other in the width direction) formed by opening of the lower side in the body portion161. The crossing member16includes flange portions163. The flange portions163extend to sides of separating, from each other, from a pair of the opening ends162(lower end portions) of the crossing member16, and extend outward in the width direction (i.e., in the front-rear direction of the battery case10a). The flange portions163of the crossing member16are provided in such a way as to extend over an entire length of the crossing member16in the longitudinal direction (i.e., the left-right direction of the battery case10a). Lower surfaces of the flange portions163are flat surfaces perpendicular to the up-down direction.

The crossing-member support members17are members for fixing both respective longitudinal-direction ends of the respective crossing members16to the respective left and right side frames15. Extruded aluminum materials for example are applied to the crossing-member support members17. However, a specific configuration of the crossing-member support member17is not particularly limited. The respective crossing-member support members17may have configurations capable of fixing both respective ends of respective crossing members16to the left and right side frames15.

The lower frame18ais a member formed in a long-rod shape. An extruded aluminum material is applied to the lower frame18a.FIG.5is a perspective view illustrating a configuration of the lower frame18a. As illustrated inFIG.5, the lower frame18aincludes a leg portion181having a standing-wall shape, a first flange portion182, and a second flange portion184. The leg portion181is formed in such a way as to extend in the standing wall shape in the up-down direction over the longitudinal direction of the lower frame18a. The first flange portion182is formed at an upper end portion of the leg portion181, and the second flange portion184is formed at a lower end portion of the leg portion181. The first flange portion182is constituted by a pair of first protrusion portions183and183extending out from an upper end of the leg portion181in directions opposite to each other, to both outer sides in the width direction of the lower frame18a(in the front-rear direction of the battery case10a). The second flange portion184is constituted by a pair of second protrusion portions185and185extending out from a lower end of the leg portion181in directions opposite to each other, to both outer sides in the width direction of the lower frame18a.

Each of an upper surface of the first flange portion182and a lower surface of the second flange portion184is a flat surface perpendicular to the up-down direction. A dimension of the first flange portion182in the width direction (the front-back direction with respect to the battery case10a) is larger than a dimension of the second flange portion184in the width direction. Specifically, a width-direction length of the second protrusion portion185constituting the second flange portion184is shorter than a width-direction length of the first protrusion portion183constituting the first flange portion182. The width-direction dimension of the first flange portion182is larger than the maximum width of the leg portion181. Thus, when the lower frame18ais viewed from a lower side, distal end portions of the first flange portion182in the width direction are seen without being hidden by the leg portion181and the second flange portion184. In addition, the lower frame18ais provided with a recess186for avoiding interference with the path wall portion122of the heat sink12.

The shared panel19is a plate-shaped member having a substantially quadrilateral shape when viewed in the up-down direction. An aluminum plate for example is applied to the shared panel19. A front-rear direction dimension and a left-right direction dimension of the shared panel19are respectively larger than front-rear direction dimensions and left-right direction dimensions of the lower panel11and the heat sink12excluding the extension portions111and121.

Here, the temperature control path20is described. The lower panel11is superimposed on an upper side of the heat sink12, and thereby, grooves formed by the path wall portion122are closed by the lower panel11(i.e., brought into a state of being covered). Thereby, the temperature control path20through which temperature control fluid can flow is formed between the lower panel11and the heat sink12(i.e., inside the inner bottom plate portion).

As illustrated inFIG.3, the temperature control path20includes two central concentration paths201, two outer peripheral concentration paths202, and branch path groups203whose number is dependent on the number of battery modules50that can be accommodated (in this embodiment, twice the number of the battery modules50that can be accommodated).

The two central concentration paths201are located substantially in the centers of the lower panel11and the heat sink12in the left-right direction, and are substantially parallel to each other and extend in the front-rear direction. Front end portions of the two central concentration paths201are located at the extension portions111and121of the lower panel11and the heat sink12. The two central concentration paths201communicate with each other at the extension portions111and121. The two central concentration paths201communicates with an outside of the superimposed body of the lower panel11and the heat sink12by one of the two supply-discharge portions112at the extension portions111and121.

The two outer peripheral concentration paths202include portions that are located near a left-right direction outer peripheries of the lower panel11and the heat sink12and that are substantially in parallel to each other and extend in the front-rear direction. The two outer peripheral concentration paths202extend, in the vicinity of these front end portions, in the left-right direction along the front ends of the lower panel11and the heat sink12. The front end portions of the two outer peripheral concentration paths202are located at the extension portions111and121of the lower panel11and the heat sink12, and communicate with each other at the extension portions111and121. The two outer peripheral concentration paths202communicate with an outside of the superimposed body of the lower panel11and the heat sink12by the other of the two supply-discharge portions112at the extension portions111and121.

Each of the branch path groups203includes a plurality of paths parallel to each other and extending in the left-right direction. The branch path groups203are provided between the central concentration path201on the right side and the outer peripheral concentration path202on the right side, and between the central concentration path201on the left side and the outer peripheral concentration path202on the left side. The branch path groups203are provided in a range where the battery modules50are mounted, when viewed in the up-down direction. Specifically, when viewed in the up-down direction, the respective branch path groups203are located between the lower frames18aadjacent to each other, between the frontmost lower frame18aand the front frame13, and between the rearmost lower frame18aand the rear frame14.

Each path included in each branch path group203provided between the central concentration path201on the right side and the outer peripheral concentration path202on the right side includes one end portion (the left end portion, i.e., the end portion on a central side in the left-right direction) communicating with the central concentration path201on the right side. The respective paths included in each branch path group203provided between the central concentration path201on the right side and the outer peripheral concentration path202on the right side include the opposite end portions (the right end portions, i.e., the outer end portions in the left-right direction) that communicate with each other and that each communicate with the outer peripheral concentration path202on the right side via an orifice205at one position. Similarly, each path included in each branch path group203provided between the central concentration path201on the left side and the outer peripheral concentration path202on the left side includes one end portion (right end portion) communicating with the central concentration path201on the left side. The respective paths included in each branch path group203provided between the central concentration path201on the left side and the outer peripheral concentration path202on the left side include the opposite end portions (left end portions) that communicate with each other and that each communicate with the outer peripheral concentration path202on the left side via an orifice205at one position.

According to the temperature control path20having such a configuration, temperature control fluid that has flowed from one supply-discharge portion112into the two central concentration paths201flows through the two central concentration paths201, and flows into each branch path group203. Then, the temperature control fluid that has passed through the respective paths of the respective branch path groups203flows into the respective two outer peripheral concentration paths202through the orifices205. The temperature control fluid that has flowed into the respective two outer peripheral concentration paths202is discharged to an outside of the temperature control path20through the other supply-discharge portion112. The temperature control fluid exchanges heat with the battery modules50while flowing through the temperature control path20(particularly, while flowing through each path of each branch path group203). Thereby, temperature of the battery modules50is adjusted. A flow direction of the temperature control fluid is not limited to the above-described direction, and may be the direction opposite to the above-described direction.

Next, an assembly structure of the battery case10ais described along with a manufacturing method.

End portions of the front frame13and the rear frame14in the longitudinal direction (left-right direction) are joined to end portions of the left and right side frames15in the longitudinal direction (front-rear direction). Thus, the front frame13, the rear frame14, and the left and right side frames15form a frame body that is substantially quadrilateral when viewed in the up-down direction and that includes an opening on an inner peripheral side. A plurality of the crossing members16are arranged inside an area (opening) surrounded by the front frame13, the rear frame14, and the left and right side frames15. A plurality of the crossing members16are arranged in such a way that their longitudinal directions are oriented in parallel to the left-right direction. Respective both end portions of a plurality of the crossing members16are joined to the left and right side frames15via the crossing-member support members17. Laser welding for example can be applied for joining the front frame13and the rear frame14to the left and right side frames15. Similarly, laser welding can be applied also for joining the respective crossing-member support members17to the left and right side frames15, and joining the respective crossing members16to the respective crossing-member support members17.

FIG.6is a sectional view taken by cutting, along a plane perpendicular to the left-right direction, vicinity of the front end portion of the battery case10a.FIG.7is a sectional view taken by cutting, along a plane perpendicular to the front-rear direction, vicinity of the right end portion of the battery case10a. As illustrated inFIG.6andFIG.7, the outer peripheral portion of the lower panel11overlaps, from a lower side, the front frame13, the rear frame14(not illustrated), and the left and right side frames15(the left side frame15is not illustrated), and further, the heat sink12overlap the lower panel11from a lower side. More specifically, the lower panel11and the heat sink12are arranged in such a way that the front end portions (near the front edges) and the rear end portions (near the rear edges) in the outer peripheral portions of these overlap, from a lower side, the respective first joint surfaces131and141of the front frame13and the rear frame14, respectively, and the right end portions and the left end portions (near both left and right edges) in the outer peripheral portions overlap, from a lower side, the first joint surfaces151of the left and right side frames15. In this state, the upper surface of the lower panel11contacts with the lower surfaces of the flange portions163of the respective crossing members16.

The lower panel11and the heat sink12are joined to the first joint surface131of the front frame13by laser welding, at a location overlapping the first joint surface131of the front frame13, and are joined to the first joint surface141of the rear frame14by laser welding, at a location overlapping the first joint surface141of the rear frame14. The reference sign W1inFIG.6indicates a joint location of the lower panel11and the heat sink12to the front frame13. Similarly, the lower panel11and the heat sink12are joined to the respective first joint surfaces151of the left and right side frames15by laser welding, at locations overlapping the first joint surfaces151of the left and right side frames15. The reference sign W3inFIG.7indicates a joint location of the lower panel11and the heat sink12to the right side frame15.

Specifically, the lower panel11and the heat sink12are joined to the front frame13, the rear frame14, and the left and right side frames15by applying a laser to the outer peripheral portion of the heat sink12from a lower side. At this time, the lower panel11and the heat sink12are joined to each other. The first joint surfaces131and141of the front frame13and the rear frame14and the first joint surfaces151of the left and right side frames15are surfaces provided at the lower portions of the respective frames13,14, and15and facing downward. Thus, a laser can be applied from a lower side of the lower panel11and the heat sink12to the outer peripheral portions of the lower panel11and the heat sink12in a state where these outer peripheral portions overlap, from the lower side, the first joint surfaces131,141, and151of the front frame13, the rear frame14, and the left and right side frames15, i.e., overlap the first joint surfaces131,141, and151in the up-down direction.

The flange portion163of the crossing member16and the lower panel11(the superimposed body of the lower panel11and the heat sink12) are joined to each other by laser welding.FIG.8is a sectional view taken by cutting of the battery case10aalong a plane perpendicular to the left-right direction, and is the sectional view illustrating arrangement positions of the lower frames18aand a positional relation between the crossing member16and the lower frames18a. The reference sign W5inFIG.8indicates a joint location between the flange portion163of the crossing member16and the lower panel11(the superimposed body of the lower panel11and the heat sink12). As illustrated inFIG.8, the lower panel11and the heat sink12can be joined to the flange portion163of the crossing member16by applying a laser from a lower side to a part included in the heat sink12and overlapping the flange portion163of the crossing member16when viewed in the up-down direction. At this time, the lower panel11and the heat sink12are joined to each other at the part to which the laser is applied.

The flange portions163of each crossing member16are joined (i.e., linearly welded) to the lower panel11continuously over the entire length in the longitudinal direction. According to such a configuration, it is possible to enhance an advantageous effect of protecting the battery modules50by the crossing member16, particularly an advantageous effect of preventing or suppressing deformation of the left and right side frames15at the time of a side collision. In other words, the crossing member16having an open cross-sectional shape has smaller rigidity (more easily deforms) than a crossing member having a closed cross-sectional shape (e.g., an angular-tube shape). In view of it, according to this embodiment, the flange portions163of the crossing member16are joined continuously over the entire length in the longitudinal direction. With such a configuration, the opening of the crossing member16is closed by the lower panel11(i.e., the opening ends162are connected to each other), and thus, it is possible to achieve an advantageous effect similar to that of the configuration where the crossing member16having the closed cross-sectional shape is arranged.

A plurality of the lower frames18aare arranged on a lower side of the heat sink12. Specifically, a plurality of the lower frames18aare arranged between the branch path groups203adjacent to each other, between the frontmost branch path group203and the front frame13, and between the rearmost branch path group203and the rear frame14. Thus, as illustrated inFIG.8, the three lower frames18aare arranged in a region between the crossing members16adjacent to each other. The similar matter applies to a region between the frontmost crossing member16and the front frame13, and a region between the rearmost crossing member16and the rear frame14.

The front-side lower frame18aincluded in the three lower frames18aarranged in each of the regions and the rear-side lower frame18aincluded in the three lower frames18aarranged in the region adjacent from the front side to that region are arranged in such a way as to be adjacent from the rear and front sides to the crossing member16between these two regions, when viewed in the up-down direction. Specifically, when viewed in the up-down direction, the temperature control path20does not exist between the crossing member16and these two lower frames18a, and the crossing member16and these two lower frames18aare close to each other. When viewed in the up-down direction, the crossing member16and these two lower frames18aare preferably as close as possible to each other. However, when viewed in the up-down direction, the flange portions163of the crossing member16and the first flange portions182of these two lower frames18aare displaced from each other in the front-rear direction, and do not overlap each other. For example, as illustrated inFIG.8, front-rear direction positions of the front-rear direction end surfaces of the flange portions163of the crossing member16coincide with front-rear direction positions of the front-rear direction end surfaces of the first flange portions182of the two lower frames18a, or are displaced from these front-rear direction positions by an extremely small distance in the front-rear direction.

The first flange portions182of a plurality of the lower frames18aarranged on a lower side of the heat sink12extend in the front-rear direction along a lower surface of the heat sink12. Upper surfaces of the first flange portions182of a plurality of the lower frames18aface the lower surface of the heat sink12. Thus, the first flange portions182including the upper surfaces facing the lower surface of the heat sink12are provided at the upper end portions of a plurality of the lower frames18a. The first flange portion182of each lower frame18aand the heat sink12(the superimposed body of the lower panel11and the heat sink12) are joined to each other by laser welding. The reference signs W6inFIG.6andFIG.7each indicate a joint location between the first flange portion182of the lower frame18aand the heat sink12(the superimposed body of the lower panel11and the heat sink12). Specifically, the first flange portion182of each lower frame18ais joined to the heat sink12(the superimposed body of the lower panel11and the heat sink12) by applying a laser from a lower side to the first flange portion182of each lower frame18a. Since a width of the second flange portion184of the lower frame18a(a width-direction length of the second protrusion portion185) is shorter than a width of the first flange portion182(a width-direction length of the first protrusion portion183), a laser can be applied to the first flange portion182of each lower frame18afrom a lower side without being blocked by the second flange portion184.

Each crossing member16can be joined to the lower panel11and the heat sink12even after the lower frames18aare arranged on a lower side of the heat sink12(in a state where the lower frames18aare arranged on a lower side of the heat sink12). In other words, when viewed in the up-down direction, the flange portions163of each crossing member16do not overlap the first flange portion182of the lower frame18a, and thus, the first flange portion182of the lower frame18ado not overlap parts included in the lower panel11and the heat sink12and overlapping the flange portions163of each crossing member16. Further, since a width of the second flange portion184of the lower frame18a(a width-direction length of the second protrusion portion185) is shorter than a width of the first flange portion182(a width-direction length of the first protrusion portion183), the parts included in the lower panel11and the heat sink12and overlapping the flange portions163of each crossing member16do not overlap the second flange portion184of the lower frame18a, when viewed in the up-down direction. Accordingly, a laser can be applied from a lower side of the heat sink12to the parts included in the lower panel11and the heat sink12and overlapping the flange portions163of each crossing member16without being blocked by the first flange portion182and the second flange portion184of the lower frame18a.

After the respective members are joined to each other, the shared panel19is arranged on a lower side of the front frame13, the rear frame14, the left and right side frames15, the crossing members16, the lower panel11, the heat sink12, and the lower frames18a. At this time, the shared panel19is arranged in such a way that the outer peripheral portion of the shared panel19overlap, from a lower side, the second joint surfaces132and142of the front frame13and the rear frame14and the second joint surfaces152of the left and right side frames15. In this state, a lower surface of the second flange portion184of each lower frame18acontacts with an upper surface of the shared panel19.

Then, a front end portion (the portion near a front edge) of the shared panel19is joined to the second joint surface132of the front frame13, a rear end portion (the portion near a rear edge) of the shared panel19is joined to the second joint surface142of the rear frame14, and both left and right end portions (the portions near both the left and right edges) of the shared panel19are joined to the respective second joint surfaces152of the left and right side frames15. In other words, an outer peripheral portion of the shared panel19is joined to the second joint surfaces132,142, and152in a state of overlapping the second joint surfaces132,142, and152in the up-down direction. The reference sign W2inFIG.6indicates a joint location between the shared panel19and the second joint surface132of the front frame13. The reference sign W4inFIG.7indicates a joint location between the shared panel19and the second joint surface152of the side frame15. Specifically, the outer peripheral portion of the shared panel19is joined to the second joint surfaces132,142, and152of the front frame13, the rear frame14, and the left and right side frames15by applying a laser from a lower side to the outer peripheral portion of the shared panel19.

Further, the second flange portion184of each lower frame18aand the shared panel19are joined to each other. The reference signs W7inFIG.6andFIG.8each indicate a joint location between the shared panel19and the lower frame18a. As illustrated inFIG.8, the second flange portion184of the lower frame18aextends in the front-rear direction along the upper surface of the shared panel19. Thus, the lower surface of the second flange portion184of the lower frame18afaces the upper surface of the shared panel19. In other words, the second flange portion184including the lower surface facing the upper surface of the shared panel19is provided at the lower end portion of the lower frame18a. Then, the shared panel19and each lower frame18aare joined to each other by applying a laser from a lower side to the part included in the shared panel19and overlapping the second flange portion184of the lower frame18a. Thereby, each lower frame18ais arranged between the shared panel19(outer bottom plate portion) and the superimposed body (inner bottom plate portion) of the lower panel11and the heat sink12, is joined, at the first flange portion182, to the superimposed body of the lower panel11and the heat sink12, and is joined, at the second flange portion184, to the shared panel19.

According to such a configuration, the lower panel11, the heat sink12, the lower frames18a, and the shared panel19can be joined from a lower side of the front frame13, the rear frame14, and the left and right side frames15. In other words, the lower panel11, the heat sink12, the lower frames18a, and the shared panel19can be attached in one direction. Accordingly, it is not necessary to change an up-down direction orientation of each member during the manufacturing of the battery case10a, and thus, the number of manufacturing steps can be reduced. Further, a laser may be applied only from a lower side, and thus, the manufactured is enabled with equipment that can apply a laser from one direction. Accordingly, manufacturing cost can be reduced.

In fact, the battery case10acan be manufactured with each member being at an orientation of being turned upside down. In other words, the lower panel11, the heat sink12, and a plurality of the lower frames18aare placed on an upper side of (in the state of being attached to the vehicle, a lower side of) the front frame13, the rear frame14, and the left and right side frames15that have been turned upside down, and a laser is applied from an upper side of these so that these can be joined to each other. After that, the shared panel19is placed on an upper side of these, and a laser is applied from an upper side so that the shared panel19can be joined to the front frame13, the rear frame14, the left and right side frames15, and the lower frames18a.

Further, since the heat sink12and the shared panel19are separated from each other in the up-down direction, it is possible to reduce impact applied to the heat sink12when external force is applied from a lower side. In other words, in a configuration where the heat sink12and the shared panel19contact directly with each other, external force applied to the shared panel19is directly transmitted from the shared panel19to the heat sink12. Thus, in such a configuration, the external force is easily applied to the battery modules50. Further, in the configuration where the heat sink12and the shared panel19contact directly with each other, when the shared panel19is deformed, the heat sink12is also deformed. Thus, in such a configuration, when the shared panel19is deformed by external force or the like, the heat sink12is deformed accordingly, and as a result, the path wall portion122may be damaged and temperature control fluid may leak from the temperature control path20.

In contrast to this, according to this embodiment, the heat sink12and the shared panel19are separated from each other in the up-down direction, and thus, external force applied to the shared panel19is not transmitted directly to the heat sink12. Accordingly, when external force is applied from a lower side of the battery case10a, impact applied to the battery module50can be reduced. Further, since the heat sink12and the shared panel19are separated from each other, even when the shared panel19is deformed, deformation of the heat sink12can be prevented or suppressed. Thus, damage of the path wall portion122can be prevented or suppressed so that a leak of the temperature control fluid can be prevented or suppressed. In addition, external force applied to the shared panel19from a lower side is transmitted to the heat sink12via the lower frame18ajoined to the shared panel19. Here, the lower frame18ais joined to the portion that is included in the heat sink12and that is not the path wall portion122, and thus, the external force does not act directly on the path wall portion122. Such a configuration can also prevent or suppress damage of the path wall portion122.

Further, according to this embodiment, the crossing member16and the lower frame18ado not overlap each other in the up-down direction, and are adjacent to each other. According to such a configuration, when external force is applied to the shared panel19from a lower side, the external force applied to the battery module50, the lower panel11, and the heat sink12can be reduced. In addition, according to such a configuration, deformation of the shared panel19, the lower panel11, and the heat sink12can be reduced. In other words, when external force is applied to the shared panel19from a lower side, the external force is transmitted to the lower panel11and the heat sink12via the lower frame18a. Since the crossing member16and the lower frame18aare provided adjacent to each other, external force transmitted from the lower frame18ato the lower panel11and the heat sink12is transmitted to the crossing member16provided adjacent to the lower frame18a, and is received by the crossing member16. Accordingly, deformation of the shared panel19, the lower panel11, and the heat sink12can be prevented or suppressed. In other words, rigidity of the battery case10acan be enhanced by the configuration where the crossing member16and the lower frame18aare arranged adjacent to each other.

Further, in the case of the configuration where the crossing member16and the lower frame18aare adjacent to each other when viewed in the up-down direction, even in a state where the lower frame18ais arranged on a lower side of the heat sink12, the crossing member16can be joined to the lower frame18aand the heat sink12by applying a laser from a lower side.

Furthermore, the crossing member16has the open cross-sectional shape, and the crossing member16is joined linearly to the lower panel11and the heat sink12. With such a configuration, the battery case10acan be reduced in weight, and rigidity of the battery case10acan be prevented from being reduced or can be enhanced. In other words, the crossing member16has the open cross-sectional shape, and thereby, the crossing member16can be reduced in weight, compared with a configuration where the crossing member16has a closed cross-sectional shape. Thus, the battery case10acan be reduced in weight. In addition, the flange portions163of the crossing member16are joined continuously and linearly to the lower panel11and the heat sink12, and thereby, parts included in the lower panel11and the heat sink12and positioned between the flange portions163of the crossing member16function as one part of the crossing member16. In other words, it is possible to achieves an advantageous effect similar to that of the configuration where the crossing member16having the closed cross-sectional shape is arranged. Thus, rigidity of the battery case10acan be prevented or suppressed from becoming lower than that of the configuration where the crossing member having the closed cross-sectional shape (or, can be made higher than a configuration where the crossing member16is not joined linearly to the lower panel11and the heat sink12).

First Modified Example

Next, a first modified example is described.FIG.9is a sectional view illustrating a configuration of the battery case10baccording to the first modified example, and is the sectional view taken by cutting along a plane perpendicular to the left-right direction. In the above-described embodiment, one lower frame18ais arranged on each of front and rear sides of the crossing member16in the top view, whereas in the first modified example, one lower frame18boverlapping the crossing member16in the top view is arranged.

As illustrated inFIG.9, the heat sink12is provided with an opening123between the branch path groups203adjacent to each other in the front-rear direction. Although omitted inFIG.9, the central concentration paths201are provided in the central portion of the heat sink12, and the outer peripheral concentration paths202are provided at both left and right ends of the heat sink12. Accordingly, the opening123is a through hole provided in a region surrounded by the branch route groups203adjacent to each other in the front-rear direction, the central concentration path201, and the outer peripheral concentration path202.

The lower frame18bincludes two leg portions181, a pair of first flange portions182, a connection portion187, and a pair of second flange portions184. An extruded aluminum material is applied to the lower frame18b. The respective two leg portions181are parts long in the left-right direction and having standing-wall shapes, and are parallel to each other and separated from each other in the front-rear direction. A pair of the first flange portions182are parts having flat-plate shapes and extending from respective upper ends of the two leg portions181in the opposite width directions (both front and rear directions). The connection portion187is a part having a flat-plate shape and connecting a pair of the first flange portions182to each other. A pair of the first flange portions182and the connecting portion187include upper surfaces that are flat surfaces perpendicular to the up-down direction. A pair of the second flange portions184are parts having flat-plate shapes and extending from respective lower end portions of the two standing-wall portions in the opposite width directions (both front and rear directions). Lower surface of a pair of the second flange portions184are flat surfaces perpendicular to the up-down direction. A pair of the second flange portions184are not connected to each other, and are separated from each other. Thus, the lower frame18bhas a substantially “Π”-shaped cross section when viewed in the left-right direction. A distance between a pair of the second flange portions184is larger than a width-direction dimension (front-back direction dimension) of the crossing member16. Accordingly, the crossing member16do not overlap the second flange portions184in the up-down direction.

As illustrated inFIG.9, the flange portions163of the crossing member16overlap the connection portion187of the lower frame18bwhen viewed in the up-down direction, whereas the flange portions163of the crossing member16do not overlap the second flange portions184of the lower frame18b. The connection portion187and the first flange portions182of the lower frame18bare located inside the opening provided in the heat sink12, and include upper surfaces contacting with the lower surface of the lower panel11. The flange portions163of the crossing member16and the connection portion187are joined to the lower panel11. Although omitted inFIG.9, the same configuration as that of the lower frame18aof the above-described embodiment is applied to the lower frames18barranged at positions that are not adjacent to the crossing member16in the front-rear direction.

In comparison between a method for manufacturing the battery case10baccording to the first modified example and the method for manufacturing the battery case10aaccording to the above-described embodiment, in the above-described embodiment, a laser is applied from a lower side of the heat sink12, thereby joining the lower panel11to the crossing member16, whereas in the first modified example, a laser is applied from a lower side of the connection portion187of the lower frame18b, thereby joining the crossing member16to the lower panel11and joining the lower panel11to the connection portion187of the lower frame18b. In other words, the crossing member16, the lower panel11, and the lower frame18bare joined integrally to each other by the laser welding. The reference signs W8inFIG.9each indicate a location where the crossing member16, the lower panel11, and the lower frame18bare joined to each other. The flange portions163of the crossing member16are arranged at positions that do not overlap the second flange portions184of the lower frame18bwhen viewed in the up-down direction. Thus, a laser can be applied from a lower side of the lower frame18bto positions where the flange portions163of the crossing member16, the lower panel11, and the connection portion187of the lower frame18boverlap each other, without being blocked by the second flange portions184of the lower frame18b. Accordingly, one-direction attaching is enabled similarly to the above-described embodiment.

Further, according to the first modified example, the number of the lower frames18bcan be reduced, thereby enabling the number of attaching steps to be reduced. Furthermore, the lower frame18band the crossing member16can be together joined, thereby enabling the number of joining steps to be reduced. Accordingly, manufacturing cost can be reduced. In addition, according to the first modified example, the opening is provided in the heat sink12, thereby enabling the battery case10bto be reduced in weight.

Second Modified Example

Next, a battery case10caccording to the second modified example is described. The second modified example is an example where structures of joining the front frame13, the rear frame14, and the side frames15to the lower panel11and the heat sink12are different from that of the above-described embodiment.FIG.10is a sectional view illustrating the structure of joining the front frame13to the lower panel11in the battery case10caccording to the second modified example, and is the sectional view taken by cutting along a plane perpendicular to the left-right direction. Although omitted in the drawing, the structures of joining the rear frame14and the left and right side frames15to the lower panel11and the heat sink12are the same as that illustrated inFIG.10.

Lower portions of the front frame13and the rear frame14are provided with extension portions134extending to mutually facing sides. These extension portions134include upper surfaces as the first joint surfaces131and141. The first joint surfaces131and141(the upper surfaces of the extension portions134) are flat surfaces perpendicular to the up-down direction. The first joint surfaces131and141and the second joint surfaces132and142are displaced from each other in the front-rear direction and in the up-down direction, and do not overlap each other when viewed in the up-down direction. The first joint surfaces131and141(i.e., the upper surfaces of the extension portions134) are located on an upper side of the second joint surfaces132and142.

Similarly, lower portions of the left and right side frames15are provided with rib-shaped extension portions134extending to mutually facing sides. These extension portions include upper surfaces as the first joint surfaces151. The first joint surfaces151are flat surfaces perpendicular to the up-down direction. The first joint surface151and the second joint surface152are displaced from each other in the left-right direction and in the up-down direction, and do not overlap each other when viewed in the up-down direction. The first joint surface151is located on an upper side of the second joint surface152.

The heat sink12is arranged in such a way as to overlap the lower panel11from a lower side. However, the heat sink12is smaller than the lower panel11, and the heat sink12does not overlap the outer peripheral portion of the lower panel11. The front end portion and the rear end portion of the outer peripheral portion that is included in the lower panel11and that the heat sink12does not overlap are joined to the first joint surfaces131and141of the front frame13and the rear frame14, respectively, in a state of being arranged on an upper side of the first joint surfaces131and141(in a state of overlapping the extension portions134from upper sides). Similarly, the right end portion and the left end portion of the outer peripheral portion of the lower panel11are connected to the first joint surfaces151of the side frames15, in a state of being arranged on an upper side of the first joint surfaces151.

In the method for manufacturing the battery case10aaccording to the above-described embodiment, the lower panel11and the heat sink12are joined to the front frame13, the rear frame14, and the left and right side frames15by applying a laser from a lower side of the heat sink12. In contrast to this, in a method for manufacturing the battery case10caccording to the second modified example, the lower panel11is joined to the first joint surface that is the upper surface of each of the extension portions of the front frame13, the rear frame14, and the left and right side frames15by applying a laser from a lower side to the extension portions134of the front frame13and the rear frame14and the extension portions of the left and right side frames15. Accordingly, one-direction attaching is enabled similarly to the above-described embodiment.

Further, according to the second modified example, the outer peripheral portion of the lower panel11is located on an upper side of the extension portions134of the front frame13and the rear frame14and the extension portions of the left and right side frames15. Thus, when the battery modules50are placed on an upper side of the lower panel11, weight of the battery modules50can be received by the extension portions134of the front frame13and the rear frame14and the extension portions of the left and right side frames15. In other words, a joined location W1between the outer peripheral portion of the lower panel11and the first joint surfaces131and141of the front frame13and the rear frame14does not receive force in a mutually separating direction. Accordingly, durability of the battery case10ccan be improved.

Furthermore, in the second modified example, the lower panel11is joined to the first joint surfaces131and141of the front frame13and the rear frame14, and is joined to the first joint surfaces151of the left and right side frames15. Boundary surfaces between the lower panel11and the heat sink12are not located on an upper side of the first joint surfaces131and141of the front frame13and the rear frame14and the first joint surfaces151of the left and right side frames15. Accordingly, even when the lower panel11and the heat sink12are partially separated from each other at the boundary surfaces for example, and the temperature control fluid leaks out from the separated location, the leaking temperature control fluid flows on a lower side of the first joint surfaces131,141, and151, and does not flows into a space (the space where the battery modules50are arranged) on an upper side of the lower panel11that is on an upper side of the first joint surfaces131,141, and151. Thus, the leaking temperature control fluid is prevented from contacting with the battery modules50.

Although the embodiment of this disclosure described above, this disclosure is not limited to the above-described embodiment.

For example, although an example where laser welding is applied for joining the respective members to each other is given in the above-described embodiment, a method for joining the respective members to each other is not limited to laser welding. For example, the respective members may be configured in such a way as to be joined to each other by friction stir welding (FSW). Briefly, any joining methods that enable the members superimposed on each other to be joined to each other from one side in the superimposing direction may be used.

Dimensions and shapes of the front frame13, the rear frame14, and the side frames15are not limited to the ones in the above-described embodiment. The numbers of the accommodatable battery modules50, the crossing members16, and the lower frames18aor18bare not limited. Materials of the lower panel11, the heat sink12, the front frame13, the rear frame14, the side frames15, the crossing members16, the crossing-member support members17, the lower frames18aand18b, and the share panel19are not limited to aluminum. Various types of metal materials can be applied to each of these members.

A vehicular battery case according to this disclosure includes a plate-shaped inner bottom plate portion, a plate-shaped outer bottom plate portion, a lower frame, and a frame body. A battery is mountable on an upper surface side of the inner bottom plate portion. The outer bottom plate portion is arranged on a lower side of the inner bottom plate portion in such a way as to be separated from the inner bottom plate portion. The lower frame is arranged between the inner bottom plate portion and the outer bottom plate portion. The frame body is provided in such a way as to stand upward from outer peripheral portions of the inner bottom plate portion and the outer bottom plate portion. The frame body includes a lower portion where first and second joint surfaces are formed. The first joint surface faces upward or downward. The second joint surface faces downward, and is on an outer side of and on a lower side of the first joint surface in the frame body. The lower frame includes an upper end portion provided with a first flange portion including an upper surface facing a lower surface of the inner bottom plate portion. The inner bottom plate portion includes the outer peripheral portion that is joined to the first joint surface in a state of overlapping the first joint surface in an up-down direction. The outer bottom plate portion includes the outer peripheral portion that is joined to the second joint surface in a state of overlapping the second joint surface in an up-down direction. The first flange portion of the lower frame is joined to the lower surface of the inner bottom plate portion.

According to this disclosure, the inner bottom plate portion and the outer bottom plate portion can be joined to the frame body from a lower side, and the lower frame can be joined to the inner bottom plate portion from a lower side. In other words, these members can be attached from one direction. Thus, it is not necessary to change an orientation (particularly, an orientation with respect to an up-down direction) of each of these members during manufacturing of the battery case, and thereby the number of manufacturing steps can be reduced. Therefore, manufacturing cost can be reduced.

In this disclosure, the terms “upper” and “lower” used for each member constituting the battery case indicate upper and lower sides of the battery case in a state of accommodating a battery and attaching the battery to a vehicle. Accordingly, for example, concerning the inner bottom plate portion of the battery case before attaching to the vehicle, a surface on which a battery is to be mounted is an upper surface, and a surface opposite to the upper surface is a lower surface. Concerning other members, surfaces whose orientations are the same as that of the upper surface (lower surface) of the inner bottom plate portion are upper surfaces (lower surfaces), and the same sides as that of the upper surface (lower side) of the inner bottom plate portion are the upper sides (lower sides). In this disclosure, the frame body is formed in such a way as to have a predetermined thickness in a width direction perpendicular to outer peripheral directions of the inner bottom plate portion and the outer bottom plate portion, when viewed from the up-down direction, and “outer side” of the frame body indicates a side being farther away in the width direction of the frame body from an opening surrounded by the frame body. In the opposite manner, “inner side” of the frame body indicates a side becoming closer in the width direction of the frame body to the opening surrounded by the frame body

In the vehicular battery case according to this disclosure, a second flange portion may be provided at a lower end portion of the lower frame. The second flange portion may include a lower surface facing an upper surface of the outer bottom plate portion. The second flange portion of the lower frame may be joined to the upper surface of the outer bottom plate portion.

According to such a configuration, the upper surface of the outer bottom plate portion can be joined to the second flange portion of the lower frame from a lower side at a location where the second flange portion overlaps the outer bottom plate portion when viewed in the up-down direction. Accordingly, the battery case can be assembled from one direction, and thus, manufacturing cost can be reduced.

In the vehicular battery case according to this disclosure, the lower frame may be formed in an elongated shape, and include a leg portion formed in such a way as to extend in an up-down direction over a longitudinal direction. The first flange portion may be constituted of a pair of first protrusion portions extending from an upper end of the leg portion in mutually opposite directions toward width directions of the lower frame. The second flange portion may be constituted of a pair of second protrusion portions extending from a lower end of the leg portion in mutually opposite directions toward width directions of the lower frame. A length of the second protrusion portion may be shorter than a length of the first protrusion portion.

According to such a configuration, the first flange portion includes a part that does not overlap the second flange portion when viewed in the up-down direction, and thus, the non-overlapping part can be accessed from a lower side without being blocked by the second flange portion. For this reason, processing of joining the non-overlapping part to the inner bottom plate portion can be performed from a lower side. Accordingly, with such a configuration, the lower frame can be attached in one direction from a lower side similarly to other members. As a result, manufacturing cost of the battery case can be reduced.

In the vehicular battery case according to this disclosure, a rod-shaped crossing member may be arranged on an upper surface side of the inner bottom plate portion, the crossing member extending along the upper surface of the inner bottom plate portion. A lower end portion of the crossing member may be joined to the upper surface of the inner bottom plate portion.

According to such a configuration, rigidity of the battery case can be enhanced.

In the vehicular battery case according to this disclosure, a cross-sectional shape of the crossing member being cut by a plane perpendicular to a longitudinal direction of the crossing member may be an open cross-sectional shape including a body portion opened on a lower side and a pair of opening ends formed by opening on the lower side in the body portion. The crossing member may include flange portions that extend from the pair of opening ends in width directions in such a way as to be more separated from each other, and that extend in the longitudinal direction of the crossing member. The flange portion may be joined continuously to the upper surface of the inner bottom plate portion, along the longitudinal direction of the crossing member.

According to such a configuration, it is possible to achieve the same advantageous effect as that of a configuration in which a crossing member having a closed cross-sectional shape is arranged on an upper surface side of the inner bottom plate portion. Thus, while weight of the battery case can be reduced, rigidity of the battery case can be enhanced.

In the vehicular battery case according to this disclosure, the flange portion of the crossing member and the first flange portion of the lower frame may not overlap each other when viewed in an up-down direction.

According to such a configuration, a location where the flange portion of the crossing member overlaps the inner bottom plate portion is not covered by the lower frame. In other words, the location where the flange portion of the crossing member overlaps the inner bottom plate portion can be accessed from a lower side without being blocked by the lower frame. Thus, processing of joining can be applied from a lower side to the location where the flange portion of the crossing member overlaps the inner bottom plate portion. Accordingly, one-direction attaching can be performed, and thereby manufacturing cost of the battery case can be reduced.

In the vehicular battery case according to this disclosure, the first joint surface of the frame body may be a surface facing downward. The outer peripheral portion of the inner bottom plate portion may be joined to the first joint surface from a lower side.

According to such a configuration, the outer peripheral portion of the inner bottom plate portion can be made to overlap the first joint surface of the frame body from a lower side, and processing of joining can be applied from a lower side to the overlapping location. Thus, the inner bottom plate portion can be attached from one direction, and thereby manufacturing cost of the battery case can be reduced.

In the vehicular battery case according to this disclosure, the frame body may be provided with an extension portion extending inward. An upper surface of the extension portion may be the first joint surface. The outer peripheral portion of the inner bottom plate portion may be joined to the first joint surface from an upper side.

According to such a configuration, when a battery is mounted on an upper surface side of the inner bottom plate portion, weight of the battery can be received by the extension portion of the frame body. With such a configuration, in a state where the battery is mounted, mutually separating force is not applied between the first joint surface and the inner bottom plate portion. Thus, durability of the battery case can be enhanced.

A method for manufacturing a vehicular battery case according to this disclosure is a method for manufacturing a vehicular battery case that includes a plate-shaped inner bottom plate portion, a plate-shaped outer bottom plate portion, a lower frame, and a frame body. The inner bottom plate portion is configured in such a way that a battery is mountable on an upper surface side of the inner bottom plate portion. The outer bottom plate portion is arranged on a lower side of the inner bottom plate portion in such a way as to be separated from the inner bottom plate portion. The lower frame is arranged between the inner bottom plate portion and the outer bottom plate portion, and includes an upper end portion provided with a first flange portion including an upper surface facing a lower surface of the inner bottom plate portion. The frame body is provided in such a way as to stand upward from outer peripheral portions of the inner bottom plate portion and the outer bottom plate portion. The frame body includes a lower portion where first and second joint surfaces are formed. The first joint surface faces upward or downward. The second joint surface faces downward, and is on an outer side of and on a lower side of the first joint surface in the frame body. The method includes a step of joining the inner bottom plate portion to the frame body by applying a laser from a lower side to the outer peripheral portion of the inner bottom plate portion arranged in such a way as to overlap the first joint surface. The method further includes a step of joining the lower frame to the inner bottom plate portion by applying a laser from a lower side to the first flange portion of the lower frame arranged on a lower side of the inner bottom plate portion. The method further includes a step of joining the outer bottom plate portion to the frame body by applying a laser from a lower side to the outer peripheral portion of the outer bottom plate portion arranged in such a way as to overlap the second joint surface from a lower side.

When the battery case is configured in this manner, the inner bottom plate portion, the outer bottom plate portion, and the lower frame can be attached from a lower side. In other words, the battery case is assembled from one direction. Thus, manufacturing cost can be reduced.

A vehicular battery case according to this disclosure includes a plate-shaped inner bottom plate portion, a plate-shaped outer bottom plate portion, a lower frame, and a frame body. A battery is mountable on an upper surface side of the inner bottom plate portion. The outer bottom plate portion is arranged on a lower side of the inner bottom plate portion in such a way as to be separated from the inner bottom plate portion. The lower frame is arranged between the inner bottom plate portion and the outer bottom plate portion. The frame body is provided in such a way as to stand upward from outer peripheral portions of the inner bottom plate portion and the outer bottom plate portion. The frame body includes a lower portion where first and second joint surfaces are formed. The first joint surface is joined to the inner bottom plate portion. The second joint surface is on an outer side of the first joint surface in the frame body, and is joined to the outer bottom plate portion. The lower frame includes an upper end portion provided with a first flange portion including an upper surface facing a lower surface of the inner bottom plate portion. The first flange portion of the lower frame is joined by a laser to the lower surface of the inner bottom plate portion.