SIDE SILL REINFORCEMENT STRUCTURE FOR ELECTRIC VEHICLE

A side sill reinforcement structure includes a battery unit for drive, a side sill extending in a vehicle front-rear direction on an outer side in a vehicle width direction of the battery unit, and a reinforcing member that connects the battery unit and the side sill. The reinforcing member includes a closed cross-sectional portion group having a first closed cross-sectional portion disposed on the innermost side in the vehicle width direction and a second closed cross-sectional portion disposed adjacent to the first closed cross-sectional portion. The first closed cross-sectional portion includes a first upper wall and a first lower wall. The second closed cross-sectional portion includes a second upper wall and a second lower wall. The thickness of the first upper wall is larger than the thickness of the second upper wall, and the thickness of the first lower wall is larger than the thickness of the second lower wall.

TECHNICAL FIELD

The present invention relates to a side sill reinforcement structure for an electric vehicle.

BACKGROUND ART

Electric vehicles are required to have higher collision safety performance than general fuel driven vehicles from the viewpoint of battery protection. In an electric vehicle, in order to secure a cruising range, a battery is widely arranged on an entire underfloor surface of a vehicle interior in many cases, and thus high collision safety performance at the time of side collision (hereinafter, also referred to as side collision) is particularly required. That is, when an object such as a pole collides with a vehicle body side portion due to spinning of the vehicle body or the like, it is necessary to protect the battery and the vehicle interior without being damaged.

For example, Patent Documents 1 and 2 disclose a vehicle body lower structure capable of suppressing deformation of a vehicle interior and improving side collision performance of a vehicle body. In the vehicle body lower structure, in order to obtain high side collision performance, a reinforcing member is disposed under a columnar member on a vehicle body lower side portion referred to as a side sill to improve the side collision performance.

PRIOR ART DOCUMENT

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The structures of Patent Documents 1 and 2 are structures in which an extruded shape material reinforcing material is disposed under a side sill, and are structures intended to absorb energy at the time of side collision by using these. In these structures, the cross-sectional wall thickness of the extruded shape material constituting the reinforcing material is set to be the same in each part. However, in order to achieve both securing battery protection performance and reducing the weight of components, it is desirable to optimize the cross-sectional wall thickness of each part by utilizing the advantage of the extruded shape material. However, such a structure that take these into account are not found.

An object of the present invention is to efficiently improve battery protection performance in a side sill reinforcement structure for an electric vehicle.

Means for Solving the Problems

The present invention provides a side sill reinforcement structure for an electric vehicle including: a battery unit for drive disposed in a vehicle interior lower portion of an electric vehicle; a side sill extending in a vehicle front-rear direction on an outer side in a vehicle width direction of the battery unit; and a reinforcing member configured to connect the battery unit and the side sill. The reinforcing member is an extruded material made of an aluminum alloy, and includes a closed cross-sectional portion group in which a plurality of closed cross-sectional portions are continuous in the vehicle width direction in a cross section perpendicular to the vehicle front-rear direction. The closed cross-sectional portion group includes a first closed cross-sectional portion disposed on an innermost side in the vehicle width direction and a second closed cross-sectional portion disposed adjacent to the first closed cross-sectional portion. The first closed cross-sectional portion includes a first upper wall and a first lower wall that extend in the vehicle width direction and are arranged to face each other while being separated from each other in a vehicle vertical direction. The second closed cross-sectional portion includes a second upper wall and a second lower wall that extend in the vehicle width direction and are arranged to face each other while being separated from each other in the vehicle vertical direction. A thickness of the first upper wall is larger than a thickness of the second upper wall, and a thickness of the first lower wall is larger than a thickness of the second lower wall.

According to this configuration, since the extruded material made of an aluminum alloy is adopted as the reinforcing member, the thickness can be partially changed. Accordingly, the thicknesses of the first upper wall and the first lower wall can be made larger than the thicknesses of the second upper wall and the second lower wall, respectively. In particular, since being disposed on the innermost side in the vehicle width direction in the closed cross-sectional portion group, the first closed cross-sectional portion is a closed cross-sectional portion closest to the battery unit. Furthermore, since extending in the vehicle width direction, the first upper wall and the first lower wall of the first closed cross-sectional portion are portions that receive a side collision load. Therefore, increasing the thickness of the portions efficiently can improve battery protection performance while suppressing an increase in weight and an increase in cost as compared with a case of adopting a reinforcing member having a uniform thickness. Here, the electric vehicle widely refers to a vehicle having a drive battery on the lower side of the vehicle interior. In addition, the battery unit is a unit including a battery and a battery case.

A thickness of the first upper wall may be 1.2 times or more a thickness of the second upper wall, and a thickness of the first lower wall may be 1.2 times or more a thickness of the second lower wall.

According to this configuration, it is possible to secure sufficient battery protection performance by specifically defining a necessary thickness.

The first closed cross-sectional portion may be joined to the battery unit by a bolt.

According to this configuration, since the first closed cross-sectional portion having a relatively large thickness is firmly joined to the battery unit by the bolt, high coupling rigidity can be secured.

The closed cross-sectional portion group may include a third closed cross-sectional portion disposed on an outermost side in the vehicle width direction and a fourth closed cross-sectional portion disposed on an inner side in the vehicle width direction adjacent to the third closed cross-sectional portion. The third closed cross-sectional portion may include a third upper wall and a third lower wall that extend in the vehicle width direction and are arranged to face each other while being separated from each other in the vehicle vertical direction. The fourth closed cross-sectional portion may include a fourth upper wall and a fourth lower wall that extend in the vehicle width direction and are arranged to face each other while being separated from each other in the vehicle vertical direction. A thickness of the third upper wall may be larger than a thickness of the fourth upper wall, and a thickness of the third lower wall may be larger than a thickness of the fourth lower wall.

According to this configuration, by improving the strength of the outermost portion (third closed cross-sectional portion) in the vehicle width direction first receiving deformation in the side collision, the peak value of the deformation load received at the initial stage of the side collision can be increased. When the peak value of the deformation load received at the initial stage of deformation is increased as described above, the load variation according to the progress of deformation can be suppressed, and the energy absorption efficiency can be improved.

A thickness of the first upper wall may be smaller than a thickness of the third upper wall, and a thickness of the first lower wall may be smaller than a thickness of the third lower wall.

According to this configuration, the first upper wall and the first lower wall do not become excessively thick, so that it is possible to suppress an excessive increase in weight. In addition, in the extruded material made of an aluminum alloy, when a significant difference is provided in thickness, there is a possibility that extrusion processing cannot be stably executed. Therefore, by providing the upper limit to the thickness as described above, the extrusion processing can be stably executed.

The third closed cross-sectional portion may be joined to the side sill by a bolt.

According to this configuration, since the third closed cross-sectional portion having a relatively large thickness is firmly joined to the side sill by the bolt, high coupling rigidity can be secured.

Each closed cross-sectional portion included in the closed cross-sectional portion group may include an upper wall and a lower wall that extend in the vehicle width direction and are arranged to face each other while being separated from each other in the vehicle vertical direction. Thicknesses of the upper wall and the lower wall may be sequentially decreased from an outer side to an inner side in the vehicle width direction excluding the first closed cross-sectional portion.

According to this configuration, since the deformation strength of the reinforcing member is sequentially lowered from the outer side to the inner side in the vehicle width direction in accordance with the deformation region being expanded in the vehicle width direction according to the progress of the side collision, the load according to the progress of the deformation can be further equalized. Therefore, energy absorption efficiency can be further improved. In addition, since the application is excluded with respect to the first closed cross-sectional portion, the first closed cross-sectional portion can be configured less likely to be deformed even when the region on the outer side in the vehicle width direction from the first closed cross-sectional portion is crushed. Therefore, higher battery protection performance can be secured.

The reinforcing member may include a lower side extending portion extending downwards the battery unit. A cross member extending in the vehicle width direction may be provided under the battery unit. The lower side extending portion may be joined to the cross member.

According to this configuration, when a side collision load is applied to the first closed cross-sectional portion, the load can be transmitted to the cross member through the lower side extending portion. Therefore, higher battery protection performance can be secured.

Effect of the Invention

According to the present invention, battery protection performance can be efficiently improved in a side sill reinforcement structure for an electric vehicle.

MODE FOR CARRYING OUT THE INVENTION

First Embodiment

Referring toFIG.1, an electric vehicle1is a vehicle that travels by driving a motor (not shown) by electric power supplied from a battery11. The electric vehicle1widely refers to a vehicle including a drive battery on the underside of the vehicle interior R, and can be, for example, an electric automobile, a plug-in hybrid vehicle, or the like. The type of the vehicle is not particularly limited, and may be a passenger car, a truck, a maintenance vehicle, other mobility, or the like. Hereinafter, as the electric vehicle1, a side sill reinforcement structure for an electric automobile of the present embodiment will be described by taking a case of a passenger car type electric vehicle as shown inFIG.1as an example.

InFIG.1, the front-rear direction of the electric vehicle1is indicated by an X direction, and the vertical direction is indicated by a Z direction. The same notation also applies to the subsequent figures, and the vehicle width direction is indicated by a Y direction inFIG.2and subsequent figures.

In the electric vehicle1, the battery unit10is mounted on the substantially entire surface under the floor of the vehicle interior R at the central portion of the vehicle body. The battery unit10includes a drive battery11and a battery case12housing the battery11.

Referring toFIG.2, the battery case12includes an upper case13and a lower case14. The upper case13includes a housing portion13ahaving an upward-recessed shape and a flange portion13bprovided around the housing portion13ain a plan view. The lower case14includes a housing portion14ahaving a downward-recessed shape and a flange portion14bprovided around the housing portion14ain a plan view. The upper case13and the lower case14are joined by bonding the flange portions13band14b. The battery11is housed in a housing space S1defined by the housing portion13aof the upper case13and the housing portion14aof the lower case14.

A hollow side sill20extending in the vehicle front-rear direction below the vehicle interior R is disposed on the outer side (left side inFIG.2) in the vehicle width direction of the battery unit10. The side sill20is a strength member constituting an outer side surface of a lower portion of the electric vehicle1.

In the side sill reinforcement structure for an electric vehicle of the present embodiment, the side sill20includes an outer member21disposed on the outer side in the vehicle width direction and an inner member22disposed on the inner side in the vehicle width direction. Both the outer member21and the inner member22are formed by bending a sheet metal into a hat shape, and are bonded so as to form an internal space S2. The outer member21and the inner member22may be made of, for example, steel. Alternatively, the outer member21and the inner member22may be made of, for example, an aluminum alloy.

A floor panel30is disposed above the battery unit10. The floor panel30is a plate material constituting a lower surface of the vehicle interior R. A cross member31extending in the vehicle width direction is disposed above the floor panel30. Although not shown in detail, a plurality of cross members31are provided at intervals in the vehicle front-rear direction. The upper portions of a pair of side sills20provided on both outer sides of the vehicle interior R in the vehicle width direction are connected to each other by the plurality of cross members31. It should be noted that inFIG.2, only one of the pair of side sills20is shown.

A reinforcing member40made of an extruded material made of an aluminum alloy is disposed below the side sill20. The reinforcing member40connects the battery unit10and the side sill20.

The reinforcing member40extends in the vehicle front-rear direction along the side sill20. The reinforcing member40has a closed cross-sectional portion group40A in which a plurality of closed cross-sectional portions are continuous in the vehicle width direction in a cross section perpendicular to the vehicle front-rear direction.

In the present embodiment, the closed cross-sectional portion group40A includes a first closed cross-sectional portion41disposed on the innermost side in the vehicle width direction (right side inFIG.2) and a second closed cross-sectional portion42disposed adjacent to the first closed cross-sectional portion41. In addition, the closed cross-sectional portion group40A includes a third closed cross-sectional portion43disposed on the outermost side in the vehicle width direction (left side inFIG.2) and a fourth closed cross-sectional portion44disposed adjacent to the third closed cross-sectional portion43. In addition, the closed cross-sectional portion group40A includes a fifth closed cross-sectional portion45disposed between the second closed cross-sectional portion42and the fourth closed cross-sectional portion44. That is, the closed cross-sectional portion group40A includes five closed cross-sectional portions41to45continuous in the vehicle width direction. The five closed cross-sectional portions41to45have rectangular shapes having substantially the same size.

Referring toFIG.3, the first closed cross-sectional portion41includes a first upper wall41aand a first lower wall41bthat extend in the vehicle width direction and are disposed to face each other while being separated from each other in the vehicle vertical direction. The first upper wall41ais disposed on a relatively upper side, and the first lower wall41bis disposed on a relatively lower side. The first upper wall41aand the first lower wall41bhave the same thickness. However, the thicknesses of the first upper wall41aand the first lower wall41bmay be different.

The second closed cross-sectional portion42includes a second upper wall42aand a second lower wall42bthat extend in the vehicle width direction and are disposed to face each other while being separated from each other in the vehicle vertical direction. The second upper wall42ais disposed on a relatively upper side, and the second lower wall42bis disposed on a relatively lower side. The second upper wall42aand the second lower wall42bhave the same thickness. However, the thicknesses of the second upper wall42aand the second lower wall42bmay be different.

The third closed cross-sectional portion43includes a third upper wall43aand a third lower wall43bthat extend in the vehicle width direction and are disposed to face each other while being separated from each other in the vehicle vertical direction. The third upper wall43ais disposed on a relatively upper side, and the third lower wall43bis disposed on a relatively lower side. The third upper wall43aand the third lower wall43bhave the same thickness. However, the thicknesses of the third upper wall43aand the third lower wall43bmay be different.

The fourth closed cross-sectional portion44includes a fourth upper wall44aand a fourth lower wall44bthat extend in the vehicle width direction and are disposed to face each other while being separated from each other in the vehicle vertical direction. The fourth upper wall44ais disposed on a relatively upper side, and the fourth lower wall44bis disposed on a relatively lower side. The fourth upper wall44aand the fourth lower wall44bhave the same thickness. However, the thicknesses of the fourth upper wall44aand the fourth lower wall44bmay be different.

The fifth closed cross-sectional portion45includes a fifth upper wall45aand a fifth lower wall45bthat extend in the vehicle width direction and are disposed to face each other while being separated from each other in the vehicle vertical direction. The fifth upper wall45ais disposed on a relatively upper side, and the fifth lower wall45bis disposed on a relatively lower side. The fifth upper wall and the fifth lower wall45bhave the same thickness. However, the thicknesses of the fifth upper wall45aand the fifth lower wall45bmay be different.

The first to fifth closed cross-sectional portions41to45are partitioned by four partition walls51to54extending in the vehicle vertical direction. Specifically, the third closed cross-sectional portion43and the fourth closed cross-sectional portion44share the partition wall51. The fourth closed cross-sectional portion44and the fifth closed cross-sectional portion45share the partition wall52. The fifth closed cross-sectional portion45and the second closed cross-sectional portion42share the partition wall53. The second closed cross-sectional portion42and the first closed cross-sectional portion41share the partition wall54. The second closed cross-sectional portion42and the first closed cross-sectional portion41share the partition wall54. The four partition walls51to54are arranged at equal intervals in the vehicle width direction.

An inner side wall55is disposed on the innermost side in the vehicle width direction of the reinforcing member40. The inner side wall55is included in the first closed cross-sectional portion41and extends in the vehicle vertical direction so as to connect the inner ends in the vehicle width direction of the first upper wall41aand the first lower wall41b. In addition, an outer side wall56is disposed on the outermost side in the vehicle width direction of the reinforcing member40. The outer side wall56is included in the third closed cross-sectional portion43and extends in the vehicle vertical direction so as to connect the outer ends in the vehicle width direction of the third upper wall43aand the third lower wall43b.

Referring toFIG.2, the first closed cross-sectional portion41is joined to the battery unit10by a bolt60. The bolt60extends in the vehicle vertical direction, penetrates the first upper wall41a, the first lower wall41b, the flange portion13bof the upper case13, the flange portion14bof the lower case14, and the floor panel30, and joins them. The bolt60is preferably inserted and fastened from bottom toward top from the viewpoint of efficiency of battery replacement. In addition, in order to secure high joint strength, it is preferable to suppress deformation of the fastening portion of the bolt60using the cylindrical collar61covering the periphery of the bolt60.

In addition, the third closed cross-sectional portion43is joined to the side sill20by a bolt70. The bolt70extends in the vehicle vertical direction, penetrates the third upper wall43aand the third lower wall43b, and the outer member21of the side sill20, terminates in the internal space S2, and joins them. Similarly to the above description, the bolt70is preferably inserted and fastened from bottom toward top, and it is preferable to use a cylindrical collar71covering the periphery of the bolt70.

Referring toFIG.3, the thickness tu1of the first upper wall41ais larger than the thickness tu2of the second upper wall42a(tu1>tu2). In addition, the thickness t11of the first lower wall41bis larger than the thickness t12of the second lower wall42b(t11>t12).

Preferably, the thickness tu1of the first upper wall41ais 1.2 times or more the thickness tu2of the second upper wall42a(tu11.2×tu2). Preferably, the thickness t11of the first lower wall41bis 1.2 times or more the thickness t12of the second lower wall42b(t111.2×t12). By specifically defining the required thickness in this manner, deformation of the innermost closed cross-sectional portion can be prevented even in consideration of material variations and the like, and sufficient battery protection performance can be secured.

The thickness tu3of the third upper wall43ais larger than the thickness tu4of the fourth upper wall44a(tu3>tu4). The thickness t13of the third lower wall43bis larger than the thickness t14of the fourth lower wall44b(t13>t14). Alternatively, the thickness tu3of the third upper wall43amay be the same as the thickness tu4of the fourth upper wall44a. In addition, the thickness t13of the third lower wall43bmay be the thickness t14of the fourth lower wall44b.

Preferably, the thickness tu1of the first upper wall41ais smaller than the thickness tu3of the third upper wall43a(tu1<tu3). In addition, preferably, the thickness t11of the first lower wall41bis smaller than the thickness t13of the third lower wall43b(t11<t13). By defining in this manner, the first upper wall41aand the first lower wall41bdo not become excessively thick, so that it is possible to suppress an excessive increase in weight. In addition, in the extruded material made of an aluminum alloy, when a significant difference is provided in thickness, there is a possibility that extrusion processing cannot be stably executed. Therefore, by providing the upper limit to the thickness as described above, the extrusion processing can be stably executed.

Any of the thicknesses tu2, tu4, and tu5of the second, fourth, and fifth upper walls42a,44a, and45ais the same (tu2=tu4=tu5). In addition, any of the thicknesses t12, t14, and t15of the second, fourth, and fifth lower walls42b,44b, and45bis the same (t12=t14=t15).

The thicknesses tp1to tp4of the partition walls51to54gradually increase from the outer side toward the inner side in the vehicle width direction (tp1<tp2<tp3<tp4). Accordingly, the degree of deformation can be equalized according to the progress of deformation of the reinforcing member40at the time of the side collision, and the energy absorption efficiency can be improved.

According to the side sill reinforcement structure for an electric vehicle of the present embodiment, the following action and effect are produced.

Since an extruded material made of an aluminum alloy is used as the reinforcing member40, the thickness can be partially changed. Accordingly, the thickness tu1of the first upper wall41acan be made larger than the thickness tu2of the second upper wall42a(tu1>tu2), and the thickness t11of the first lower wall41bcan be made larger than the thickness t12of the second lower wall42b(t11>t12). In particular, since being disposed on the innermost side in the vehicle width direction in the closed cross-sectional portion group40A, the first closed cross-sectional portion41is a closed cross-sectional portion closest to the battery unit10. Furthermore, since extending in the vehicle width direction, the first upper wall41aand the first lower wall41bof the first closed cross-sectional portion41are portions that receive a side collision load. Therefore, increasing in the thickness of the portion efficiently improves battery protection performance while suppressing an increase in weight and an increase in cost as compared with a case of adopting a reinforcing member having a uniform thickness.

In addition, since the first closed cross-sectional portion41having a relatively large thickness is firmly joined to the battery unit10by the bolt60, high coupling rigidity can be secured.

In addition, the thickness tu3of the third upper wall43ais made larger than the thickness tu4of the fourth upper wall44a(tu3>tu4), and the thickness t13of the third lower wall43bis made larger than the thickness t14of the fourth lower wall44b(t13>t14). Accordingly, the strength of the outermost portion (third closed cross-sectional portion43) in the vehicle width direction first receiving deformation in the side collision is improved, and the peak value of the deformation load received at the initial stage of the side collision is increased. When the peak value of the deformation load received at the initial stage of deformation is increased as described above, the load variation according to the progress of deformation can be suppressed, and the energy absorption efficiency can be improved.

In addition, since the first closed cross-sectional portion41having a relatively large thickness is firmly joined to the battery unit10by the bolt60, high coupling rigidity can be secured.

In addition, since the third closed cross-sectional portion43having a relatively large thickness is firmly joined to the side sill20by the bolt70, high coupling rigidity can be secured.

Second Embodiment

The reinforcing member40of the side sill reinforcement structure for an electric vehicle of the second embodiment shown inFIG.4is substantially the same as that of the first embodiment except for the thicknesses tu1to tu5of the first to fifth upper walls41ato45aand the thicknesses t11to t15of the first to fifth lower walls41bto45b. Therefore, the description of portions the same as those of the first embodiment may be omitted.

The thicknesses tu1to tu5of the first to fifth upper walls41ato45aand the thicknesses t11to t15of the first to fifth lower walls41bto45bsequentially decrease from the outer side to the inner side in the vehicle width direction except for the first closed cross-sectional portion41(the first upper wall41aand the first lower wall41b). That is, the thicknesses tu2to tu5of the second to fifth upper walls42ato45asequentially decrease from the outer side to the inner side in the vehicle width direction (tu3>tu4>tu5>tu2). In addition, the thicknesses t12to t15of the second to fifth lower walls42bto45bsequentially decrease from the outer side to the inner side in the vehicle width direction (t13>t14>t15>t12).

In addition, the thickness tu1of the first upper wall41ais smaller than the thickness tu3of the third upper wall43aand larger than the thickness tu4of the fourth upper wall44a(tu4<tu1<tu3). The thickness t11of the first lower wall41bis smaller than the thickness t13of the third lower wall43band larger than the thickness t14of the fourth lower wall44b(t14<t11<t13).

According to the side sill reinforcement structure for an electric vehicle of the present embodiment, since the deformation strength of the reinforcing member40is sequentially lowered from the outer side to the inner side in the vehicle width direction in accordance with the deformation region being expanded in the vehicle front-rear direction according to the progress of the side collision, the load according to the progress of the deformation can be further equalized. Therefore, energy absorption efficiency can be further improved. In addition, since the application is excluded with respect to the first closed cross-sectional portion41, the first closed cross-sectional portion41can be configured less likely to be deformed even when the region on the outer side in the vehicle width direction from the first closed cross-sectional portion41is crushed. Therefore, higher battery protection performance can be secured.

Third Embodiment

The side sill reinforcement structure for an electric vehicle of the third embodiment shown inFIG.5is substantially the same as that of the first embodiment except for the configuration related to the reinforcing member40. Therefore, the description of portions the same as those of the first embodiment may be omitted. It should be noted that inFIG.5, a portion indicated by a broken line circle is shown in an enlarged manner.

In the present embodiment, the reinforcing member40has a lower side extending portion extending downward from the battery unit10. The lower side extending portion40B extends downward from the first closed cross-sectional portion41. In a cross section perpendicular to the vehicle front-rear direction, the lower side extending portion40B includes a sixth closed cross-sectional portion46having a rectangular shape.

The lower side extending portion40B includes, so as to constitute the sixth closed cross-sectional portion46, an inner side wall57and an outer side wall58extending in the vehicle vertical direction, and a sixth upper wall46aand a sixth lower wall46bconnecting the inner side wall57and the outer side wall58and extending in the vehicle width direction. It should be noted that the sixth upper wall46aof the sixth closed cross-sectional portion46and the first lower wall41bof the first closed cross-sectional portion41are the same portion. That is, the first closed cross-sectional portion41and the sixth closed cross-sectional portion46share the first lower wall41b(that is, the sixth upper wall46a). The sixth lower wall46bincludes a flange portion46cextending inward in the vehicle width direction beyond the inner side wall57.

A plurality of cross members32extending in the vehicle width direction are provided below the battery unit10. The cross member32is disposed in the vehicle width direction of the battery unit10along the lower surface of the battery unit10.

The lower side extending portion40B is joined to the cross member32at the flange portion46c. The bolt60extends in the vehicle vertical direction, penetrates the sixth lower wall46b, the sixth upper wall46a(first lower wall41b), the first upper wall41a, the flange portion13bof the upper case13, the flange portion14bof the lower case14, and the floor panel30, and joins them.

According to the side sill reinforcement structure for an electric vehicle of the present embodiment, when a side collision load is applied to the first closed cross-sectional portion41, the load can be transmitted to the cross member32through the lower side extending portion40B. Therefore, higher battery protection performance can be secured.

A first modification of the third embodiment will be described with reference toFIG.6. It should be noted that inFIG.6, a portion indicated by a broken line circle is shown in an enlarged manner.

In a cross section perpendicular to the vehicle front-rear direction, the shape of the sixth closed cross-sectional portion46of the lower side extending portion40B is not limited to a rectangle, and may be, for example, a trapezoid. In the example ofFIG.6, the inner side wall57is disposed along the vehicle vertical direction, but the outer side wall58is disposed to be inclined from the vehicle vertical direction.

In addition, the lower side extending portion40B does not need to be joined to the cross member32(seeFIG.5). As shown in the example inFIG.6, when the battery unit10is sufficiently large in the vehicle vertical direction, the first closed cross-sectional portion41and the sixth closed cross-sectional portion46may be disposed to abut on the battery unit10. In this case, the deformation is suppressed by transmitting the side collision load to the bottom plate constituting the battery unit10rather than the cross member32.

A second modification of the third embodiment will be described with reference toFIG.7.

In the cross section perpendicular to the vehicle front-rear direction, the lower side extending portion40B (seeFIGS.5and6) does not need to be provided in order to be joined to the cross member32. For example, the first closed cross-sectional portion41may be joined to the cross member32.

In the example inFIG.7, the end portion32aon the outer side in the vehicle width direction of the cross member32is crushed. The end portion32ais joined to the first closed cross-sectional portion41by a bolt60. The bolt60extends in the vehicle vertical direction, penetrates the end portion32aof the cross member32, the first lower wall41b, the first upper wall41a, the flange portion13bof the upper case13, the flange portion14bof the lower case14, and the floor panel30, and joins them.

In addition, although not shown in detail, when a cross member is disposed in the battery case12, the reinforcing member40may be disposed on an outer side in the vehicle width direction of the cross member so that a side collision load can be transmitted from the reinforcing member40to the cross member.

Fourth Embodiment

The side sill reinforcement structure for an electric vehicle of the fourth embodiment shown inFIGS.8and9is substantially the same as that of the first embodiment except for the configuration related to the shape and arrangement of the reinforcing member40and the shape of the side sill Therefore, the description of portions the same as those of the first embodiment may be omitted.

In the present embodiment, the reinforcing member40is disposed on an inner side in the vehicle width direction of the side sill20, and is joined to the inner member22of the side sill20by a bolt70. The inner member22includes a step portion22ahaving a shape complementary to that of the reinforcing member40, and the reinforcing member40is disposed in the step portion22a.

As described above, the arrangement of the reinforcing member40is not limited to below the side sill20as in the first to third embodiments, and may be on the inner side in the vehicle width direction of the side sill20. That is, the reinforcing member40may be disposed so as to connect the side sill20and the battery unit10in any mode.

In addition, in the present embodiment, the closed cross-sectional portion group40A of the reinforcing member40includes three rectangular closed cross-sectional portions41to43(44). As compared with the first embodiment, the fifth closed cross-sectional portion45(seeFIG.2) is omitted, and the second closed cross-sectional portion42(seeFIG.2) and the fourth closed cross-sectional portion44(seeFIG.2) are integrated. Therefore, the closed cross-sectional portion group40A of the reinforcing member40includes a first closed cross-sectional portion41disposed on the innermost side in the vehicle width direction, a third closed cross-sectional portion43disposed on the outermost side in the vehicle width direction, and a second closed cross-sectional portion42(that is, the fourth closed cross-sectional portion44) disposed between the first closed cross-sectional portion41and the third closed cross-sectional portion43.

The first to third closed cross-sectional portions41to43are partitioned by two partition walls51to52extending in the vehicle vertical direction. The third closed cross-sectional portion43and the second closed cross-sectional portion42share the partition wall51. The second closed cross-sectional portion42and the first closed cross-sectional portion41share the partition wall52.

The first closed cross-sectional portion41is joined to the battery unit10by a bolt60. The bolt60extends in the vehicle vertical direction, penetrates the first upper wall41a, the first lower wall41b, the flange portion13bof the upper case13, and the flange portion14bof the lower case14, and joins them.

As described above, the third closed cross-sectional portion43is joined to the inner member22of the side sill20by the bolt70. The bolt70extends in the vehicle vertical direction, penetrates the third upper wall43a, the third lower wall43b, and the step portion22aof the inner member22, terminates in the internal space S2, and joins them.

The relative relationship between the thicknesses of the respective walls constituting the first closed cross-sectional portion41, the second closed cross-sectional portion42(that is, the fourth closed cross-sectional portion44), and the third closed cross-sectional portion43is the same as that of the first embodiment.

As described above, the number of closed cross-sectional portions included in the reinforcing member40is not particularly limited, and may be 5 as in the first embodiment, may be 3 as in the fourth embodiment, or may be 4 or 6 or more.

As described above, although the specific embodiments and their modifications of the present invention are described, the present invention is not limited to the above-described embodiments, and can be implemented with various modifications within the scope of the present invention. For example, an appropriate combination of contents of the individual embodiments and modifications may be one embodiment of the present invention.

In addition, the shape of each closed cross-sectional portion of the reinforcing member40is not limited to a rectangle or a trapezoid as in each of the above embodiments, and may be any polygon (for example, a hexagon or the like) having an upper wall and a lower wall facing each other.

DESCRIPTION OF SYMBOLS