Vehicle body side structure

Abstract

A vehicle body side structure (1) according to the present invention is provided with: a side sill (3) formed by joining a side sill inner member (3a) and a side sill outer member (3b); a battery pack (5) disposed further toward the inside in the vehicle width direction than the side sill (3); and a floor cross member (7) extending in the vehicle width direction, the floor cross member (7) comprising a metal plate having a tensile strength of 1180 MPa or more, the end portion (7a) of the floor cross member (7) being disposed so as to cover the upper surface (3a2) without coming into contact with the side surface (3a1) of the side sill inner member (3a), and extending to and coming into contact with the joining surface portion (3d) of the side sill inner member (3a) and the upper end portion (3c) of the side sill outer member (3b), and the end portion (7a) of the floor cross member (7) being in contact with the joining surface portion (3d) of the side sill inner member (3a) and the upper end portion (3c) of the side sill outer member (3b) when a side collision occurs. After the lower side member outer member (3b) is deformed and crushed, the load input to the lower side member (3) is transmitted to the floor cross member (7) to reduce the load transmitted to the battery pack (5).

Description

Technical Field

[0001] The present invention relates to an automotive body side structure of an electric vehicle or the like in which a battery pack is disposed on the vehicle inner side in the vehicle width direction relative to a side sill. Background Art

[0002] In recent years, especially in the automobile industry, the replacement from gas engine cars to electric cars due to environmental issues is advancing. Electric cars and the like are equipped with a battery pack containing a large battery (storage battery) in the floor portion of the lower part of the vehicle body. Moreover, most of these storage batteries use lithium-based materials, so if the battery pack is damaged during a collision and liquid leaks from the storage battery, there is a risk of fire, so a structure to protect the battery pack is required. As components for protecting the battery pack, there are floor crossbeams extending in the vehicle width direction and lower longitudinal beams extending in the vehicle length direction on both outer sides in the vehicle width direction. The floor crossbeam is arranged between the two lower longitudinal beams to arrange the battery pack thereunder.

[0003] As a technology for protecting a battery pack during a side impact collision of an electric vehicle, for example, the following structure is disclosed in Patent Document 1, namely: a vehicle comprising a battery pack, a side sill extending along the front-rear direction of the vehicle body on the outside in the vehicle width direction, and a floor cross member spanned between the left and right side sills, wherein both ends of the floor cross member are connected from the side portions of the side sill inner of the side sill on the vehicle inner side to straddle the joint between the side sill inner and the side sill outer.

[0004] Patent Document 1: Japanese Patent No. 6734709

[0005] In the technology disclosed in Patent Document 1, when a pole or the like collides with the side beam of the vehicle side and inputs a side collision load, the collision load is transmitted from the side beam to the floor beam via the connecting portion of the floor beam and the side beam that spans the joint of the side beam outer member and the side beam inner member from the side portion of the side beam inner member on the vehicle inner side. Moreover, the reaction force is amplified by the floor beam, thereby crushing the side beam outer member and the side beam inner member, and the side beam outer member and the side beam inner member absorb the collision energy efficiently by compressive deformation caused by being crushed. However, if the side beam is crushed first, the load transmitted to the battery pack cannot be sufficiently reduced, and the battery pack cannot be fully protected. Summary of the invention

[0006] The present invention is completed to solve the above-mentioned problems, and its purpose is to provide a vehicle body side structure that can protect the battery pack by reducing the load transmitted to the battery pack during the side collision of the vehicle body, when the vehicle body is equipped with a lower longitudinal beam, a battery pack arranged on the inner side of the lower longitudinal beam in the vehicle width direction, and a floor cross beam.

[0007] The vehicle body side structure involved in the present invention comprises: a lower side member formed by joining an inner side member and an outer side member extending in the front-rear direction of the vehicle body on the vehicle width direction outer side of the vehicle body at an upper end and a lower end in the vehicle height direction; a battery pack arranged at the lower part of the vehicle body on the vehicle width direction inner side of the lower side member; and a floor cross member extending in the vehicle width direction above the lower side member on the vehicle width direction inner side, wherein the floor cross member is formed of a metal sheet with a tensile strength of 1180 MPa class or more, and the end portion on the vehicle width direction outer side of the vehicle is arranged to cover the upper surface of the lower side member in the vehicle height direction without contacting the surface of the lower side member in the vehicle width direction inner side of the vehicle, and extends to the joining surface (joining surface) between the upper end portion of the lower side member and the lower side member When a side collision occurs in which a collision load (crushing load) is input to the lower side beam from the outer side of the vehicle in the vehicle width direction, the lower side beam outer member is deformed and crushed, and the load input to the lower side beam is transmitted to the floor cross member to reduce the load transmitted to the battery pack.

[0008] The floor cross member may have a groove shape extending in the vehicle width direction, and a wall portion abutting against the joint portion is provided at a front end thereof, so that the groove shape at the end of the floor cross member is closed by the wall portion.

[0009] The end portion of the floor cross member may be connected to the joint surface portions of the side sill inner member and the side sill outer member.

[0010] In the present invention, a load transfer path of the load input to the vehicle body during a side collision is formed in the floor cross member, and the reaction force generated by the floor cross member toward the outside of the vehicle in the vehicle width direction is mainly applied to the joint surface where the inner part of the lower longitudinal beam is joined with the outer part of the lower longitudinal beam. As a result, the collision energy is absorbed by the outer part of the lower longitudinal beam being crushed and deformed, but the inner part of the lower longitudinal beam can maintain its shape without being crushed. In addition, the floor cross member is made of a metal plate with a tensile strength of more than 1180 MPa, so that after the outer part of the lower longitudinal beam is compressed and deformed and crushed, the floor cross member can continue to bear the load input to the lower longitudinal beam without deformation. As a result, the inner part of the lower longitudinal beam is not easily deformed and crushed, and the impact energy absorption capacity can be maintained, so the load transfer to the battery pack 5 can be reduced. As a result, the deformation of the battery pack 5 can be suppressed during a side collision, the battery pack can be protected from damage, and a safe vehicle can be manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The following are diagrams for explaining a vehicle body side structure according to an embodiment of the present invention.

[0012] Figure 2 FIG. 2 is a diagram for explaining the transmission of load during a side collision in the vehicle body side structure according to the embodiment of the present invention. Figure 2 (a) is the existing vehicle body side structure. Figure 2 (b) is a vehicle body side structure according to the present embodiment, Figure 2 (c) is the load transfer path during a side collision).

[0013] Figure 3 It is a diagram showing a specific example of the shape in which the end portion of the floor cross member is closed in the side structure of the vehicle body according to the embodiment of the present invention.

[0014] Figure 4 This is a diagram for explaining a side collision of a vehicle body that is an analysis target in the embodiment.

[0015] Figure 5 Graph showing the amount of deformation of the battery pack and the evaluation method of the input load to the battery pack in the embodiment ( Figure 5 (a) is the evaluation position of the deformation of the battery pack, Figure 5 (b) is the input load to the battery pack).

[0016] Figure 6 1 and 2 are cross-sectional views of the vehicle body side structure according to the invention example and comparative examples 1 and 2 at (i) a vehicle length direction position TL=1568 mm and (ii) a vehicle length direction position TL=1916 mm ( Figure 6 (a) is an invention example, Figure 6 (b) is Comparative Example 1, Figure 6 (c) is Comparative Example 2).

[0017] Figure 7 This is a graph showing the results of the amount of deformation of the battery pack when the rod collides at the vehicle length direction position TL=1916 mm in the embodiment.

[0018] Figure 8 The graph shows the result of the contact reaction force obtained as the input load to the battery pack when the rod collides at the vehicle length direction position TL=1916 mm in the embodiment. DETAILED DESCRIPTION

[0019] like Figure 1 As shown as an example in FIG. 2 , a vehicle body side structure 1 according to an embodiment of the present invention includes a side sill 3 , a battery pack 5 , a floor cross member 7 , and a floor panel 9 .

[0020] The following is based on Figure 1 A vehicle body side structure 1 according to the present embodiment will be described. Figure 1 The figure shows other body parts such as the floor panel 9 disposed above the battery pack 5, but in the following description, these other body parts are not the main parts of the present invention, and their description is omitted. In addition, in this specification and the drawings, the same reference numerals are marked on the elements having the same functional structure to omit repeated descriptions.

[0021] like Figure 1 As shown in the figure, the side sill 3 includes a side sill inner member 3a and a side sill outer member 3b which are arranged to extend in the front-rear direction of the vehicle body on the vehicle width direction outer side of the vehicle body. The side sill inner member 3a has a groove shape opening toward the vehicle width direction outer side through a top plate 3a1 and a pair of longitudinal walls 3a2, and the side sill outer member 3b has a groove shape opening toward the vehicle width direction inner side. Moreover, the side sill inner member 3a and the side sill outer member 3b are formed into a closed cross section structure by making the opening sides of each other face each other and joining the upper end 3c and the lower end (not shown) in the vehicle height direction.

[0022] exist Figure 1In the vehicle body side structure 1 shown in the figure, the range of about 1 / 3 or more of the upper part in the vehicle height direction of the side sill 3 is shown. Moreover, the side sill inner member 3a and the side sill outer member 3b are, for example, members of a hat-shaped cross section having a top portion, a pair of vertical walls, and a flange portion, and the flanges of the upper end and the lower end of the side sill inner member 3a and the side sill outer member 3b are joined to each other to form the side sill 3 of a closed cross section structure. However, in the present invention, the side sill inner member and the side sill outer member are not limited to the hat-shaped cross section shape, as long as the upper end and the lower end of each are joined to form the side sill of a closed cross section structure.

[0023] like Figure 1 As shown, the battery pack 5 is disposed at a lower portion of the vehicle body on the inner side of the side sill 3 in the vehicle width direction, and a battery cell (not shown) is mounted therein.

[0024] The floor cross member 7 has a hat-shaped cross-section having a bottom portion, a pair of vertical walls, and a flange, and has a groove shape extending in the vehicle width direction through the bottom portion and the pair of vertical walls. Figure 1 As shown in FIG. 1 , the floor cross member 7 is provided above the lower longitudinal member 3 and on the inner side of the vehicle in the vehicle width direction, extending in the vehicle width direction. Figure 1 The cross-sectional view of the vehicle body side structure shows the cross-sectional view of the bottom surface. Moreover, the floor cross member 7 is made of a metal plate with a tensile strength of 1180 MPa or above. The end portion 7a on the vehicle width direction and the vehicle outside is arranged to cover the upper surface of the lower longitudinal beam inner member 3a in the vehicle height direction, and does not abut against the surface of the lower longitudinal beam inner member 3a on the vehicle width direction and the vehicle inside. In addition, it extends to and abuts against the joint surface 3d formed by the joint of the lower longitudinal beam inner member 3a and the lower longitudinal beam outer member 3b. Figure 1 As shown, when the side sill inner member 3a has a hat-shaped cross-sectional shape including a top plate 3a1, a vertical wall 3a2 and a flange 3a3, the upper surface of the side sill inner member 3a in the vehicle height direction refers to the vertical wall 3a2. In addition, the surface of the side sill inner member 3a in the vehicle width direction on the vehicle inner side refers to the top plate 3a1.

[0025] Furthermore, in the vehicle body side structure 1, in a side collision in which a collision load is input to the side sill 3 from the vehicle outer side in the vehicle width direction, the side sill outer member 3b is compressed and deformed by the collision load input to the side sill 3. Furthermore, after the side sill outer member 3b is crushed, the floor cross member 7 continues to receive the load input to the side sill 3 without being deformed, thereby reducing the load transmitted to the battery pack 5.

[0026] The vehicle body side structure 1 according to the present embodiment has the following effects. Figure 2In the conventional vehicle body side structure 21 including the side sill 3, the battery pack 5 and the floor cross member 23 as an example shown in (a), although the end 23a of the floor cross member 23 in the vehicle width direction extends above the side sill inner member 3a, it does not abut against the joint surface 3d of the upper end 3c of the side sill 3. Therefore, when a load is input to the side sill 3 during a side collision, first, after the side sill outer member 3b is deformed and crushed, the load is not sufficiently transmitted to the floor cross member 23, and the load transmission to the battery pack 5 cannot be sufficiently reduced.

[0027] On the other hand, according to the vehicle body side structure 1 involved in this embodiment, as shown in FIG. Figure 1 and Figure 2 As shown in (b), the end 7a of the floor cross member 7 abuts against the joint surface 3d of the upper end 3c of the lower side member 3, so that Figure 2 As shown in (c), the load transfer path of the load input to the vehicle body during a side collision is formed in the floor cross member 7. Moreover, the reaction force generated by the floor cross member 7 toward the outside of the vehicle in the vehicle width direction is mainly applied to the joint surface 3d formed by the joint of the lower longitudinal beam inner member 3a and the lower longitudinal beam outer member 3b. As a result, the collision energy is absorbed by the lower longitudinal beam outer member 3b being crushed and deformed, but the lower longitudinal beam inner member 3a can maintain its shape without being crushed. In addition, the floor cross member 7 is made of a metal plate with a tensile strength of more than 1180MPa, so that after the lower longitudinal beam outer member 3b is compressed and deformed and crushed, the floor cross member 7 can continue to bear the load input to the lower longitudinal beam 3 without deformation. As a result, the lower longitudinal beam inner member is not easily deformed and crushed, and the collision energy absorption capacity can be maintained, so the load transfer to the battery pack 5 can be reduced. As a result, the deformation of the battery pack 5 can be suppressed during a side collision, and the battery pack 5 can be protected from damage, thereby manufacturing a safe vehicle.

[0028] In the present embodiment, the floor cross member 7 is formed of a metal plate having a tensile strength of 1180 MPa or higher. However, if the floor cross member is formed of a metal plate having a tensile strength of less than 1180 MPa, the floor cross member is easily deformed when the load is transferred to the floor cross member, and the load cannot be fully transferred, thereby failing to reduce the load transferred to the battery pack 5.

[0029] Therefore, in the present embodiment, the floor cross member 7 is formed of a metal plate having a tensile strength of 1180 MPa or higher, and specifically, examples thereof include steel plates having a tensile strength of 1180 MPa, 1370 MPa, 1470 MPa, and 1760 MPa.

[0030] In the vehicle body side structure 1, the end 7a of the floor cross beam 7 abuts against the joint surface 3d formed by the joint of the lower longitudinal beam inner part 3a and the lower longitudinal beam outer part 3b, but is not connected. However, in the present invention, it is preferred that the end of the floor cross beam is connected to the joint surface of the lower longitudinal beam inner part and the lower longitudinal beam outer part. As a result, in the event of a side collision, it is not easy to cause the end of the floor cross beam to deviate from the joint surface of the lower longitudinal beam inner part and the lower longitudinal beam outer part, and the load transfer path of the load input to the vehicle body (lower longitudinal beam) to the floor cross beam can be maintained, so that it is easier to transfer the load to the floor cross beam, and the load transferred to the battery pack can be further reduced.

[0031] In the present invention, the floor cross member 7 includes a bottom surface and a pair of longitudinal walls and has a groove shape (not shown) extending in the vehicle width direction, for example, Figure 1 As shown in FIG. 1 , it is preferable to provide a wall face portion 7b that is bent and continuous from the bottom face 7a1 at the front end of the end portion 7a, and the wall face portion 7b makes the groove shape of the end portion 7a of the floor cross member 7 a closed shape. This makes it difficult for the end portion 7a of the floor cross member 7 to be crushed, and prevents the vehicle body from being greatly deformed.

[0032] Figure 3 2 shows a specific example in which the groove shape of the end portion 7a of the floor cross member 7 in the vehicle width direction is a closed shape. Figure 3 In the floor cross member 7 shown in (a), the bottom surface 7a1, the pair of vertical walls 7a2 and the wall surface portion 7b are integrated and continuous at the front end of the end portion 7a, so that the groove shape becomes a closed shape. Figure 3 The floor cross member 7 shown in (b) has a high vertical wall height (height in the vehicle height direction), so although the bottom surface 7a1 of the groove shape is curved and continuous with the wall surface 7b at the front end, the bottom surface 7a1 of the groove shape and the pair of vertical walls 7a2 are not integrated and are discontinuous. However, welding margins 7c bent toward the vertical wall 7a2 are provided on both side edges of the bottom surface 7a1 and the wall surface 7b, and the welding margins 7c and the vertical walls 7a2 are joined by spot welding or the like, so that the groove shape becomes a closed shape.

[0033] Example

[0034] A specific analysis was performed to verify the effects of the vehicle body side structure according to the present invention, and the results will be described below.

[0035] In this embodiment, for the above-mentioned embodiment Figure 1 The vehicle 101 having the vehicle body side structure 1 (invention example) shown in FIG. Figure 4As shown in FIG. 1 , a side impact analysis was performed in which the rod 103 was collided from the outside of the vehicle in the vehicle width direction. Figure 5 As shown in (b), the battery pack 5 is supported by a battery frame assembly 11 disposed on the outer peripheral side in the vehicle width direction. Figure 5 As shown in (b), the battery frame assembly 11 is composed of a plurality of steel sheet parts.

[0036] In the side collision analysis, the vehicle 101 is accelerated to 29 km / h in the vehicle width direction, and the rod 103 as a rigid body is made to collide with the side of the vehicle 101. The rod collision position where the rod 103 collides with the vehicle 101 is set to the vehicle length direction position TL = 1916 mm. If the rod 103 collides with the side sill 3 of the side of the vehicle 101, the side sill 3 (see Figure 1 ) is locally deformed and intrudes into the vehicle interior. Therefore, in this embodiment, the deformation amount of the battery pack 5 and the load input to the battery pack 5 during the side collision are evaluated.

[0037] Regarding the deformation amount of the battery pack 5, Figure 5 As shown in (a), at multiple positions in the vehicle length direction ( Figure 5 The lengths of the battery pack 5 in the vehicle width direction before and after deformation were measured at the position indicated by the arrow in (a), and the difference between before and after deformation was obtained. On the other hand, regarding the load input to the battery pack 5 side, as shown in FIG. Figure 5 As shown in (b), the reaction force (contact reaction force) generated in the battery frame assembly 11 due to the contact of the connecting member 13 provided on the outer peripheral side of the battery frame assembly 11 in the vehicle width direction during the collision is obtained.

[0038] Furthermore, in this embodiment, as a comparison object, Figure 6 The vehicle body side structure 21 (Comparative Example 1) shown in (b) Figure 6 The vehicle body side structure 31 (comparative example 2) shown in (c) is also carried out in the same manner as in the invention example. Figure 4 The side collision analysis of the vehicle shown evaluates the deformation amount of the battery pack 5 and the load input to the battery pack 5 during the side collision.

[0039] In the vehicle body side structure 21 according to Comparative Example 1, the end portion 23a of the floor cross member 23 in the vehicle width direction extends to cover the side sill inner member 3a but does not abut against the joint surface 3d between the side sill inner member 3a and the side sill outer member 3b.

[0040] In the vehicle body side structure 31 according to Comparative Example 2, the end portion 33 a of the floor cross member 33 in the vehicle width direction does not extend above the side sill inner member 3 a .

[0041] In Comparative Examples 1 and 2, the load input to the battery pack 5 side was the same as that in the inventive example, and the contact reaction force between the connecting member 13 and the battery frame assembly 11 was obtained.

[0042] Figure 7 2 shows the results of the deformation amount of the battery pack 5 in the invention example, comparative example 1 and comparative example 2, when the pole collision position is set to the vehicle length direction position TL = 1916 mm. Figure 7 As shown, the deformation amount of the battery pack 5 in the invention example and comparative example 1 is smaller than that in comparative example 2 in which the end 33a of the floor cross member 33 does not extend above the lower side sill inner member 3a. In addition, when the invention example and comparative example 1 are compared, the deformation amount of the battery pack 5 in the invention example is smaller.

[0043] Figure 8 2 shows the contact reaction force obtained as the load input to the battery pack 5 in the case of a side collision in which the pole collision position is set to the vehicle length direction position TL=1916 mm in the invention example, comparative example 1, and conventional example 2. Figure 8 As shown, the load input to the battery pack 5 in the invention example and the comparative example 1 is smaller than that in the comparative example 2 in which the end 33a of the floor cross member 33 does not extend above the lower side sill inner member 3a. In addition, when the invention example and the comparative example 1 are compared, the result is that the load input to the battery pack 5 in the invention example is smaller.

[0044] As described above, according to the vehicle body side structure involved in the present invention, it is shown that by transferring the load input to the vehicle to the floor cross member during a side collision, the load input to the battery pack can be sufficiently reduced, and the deformation of the battery pack can be reduced to protect the battery pack.

[0045] Industrial Applicability

[0046] According to the present invention, a vehicle body side structure can be provided which can protect a battery pack by reducing a load transmitted to the battery pack during a side collision of a vehicle body having a side sill, a battery pack arranged on the vehicle width inner side of the side sill, and a floor cross member.

[0047] Description of Reference Numerals

[0048] 1…body side structure; 3…lower longitudinal beam; 3a…lower longitudinal beam inner part; 3a1…top plate (side); 3a2…longitudinal wall (upper surface); 3a3…flange; 3b…lower longitudinal beam outer part; 3c…upper end; 3d…joining surface; 5…battery pack; 7…floor cross beam; 7a…end; 7a1…bottom surface; 7a2…longitudinal wall; 7b…wall surface; 7c…welding allowance; 9…floor panel; 11…battery frame assembly; 13…connecting part; 21…body side structure; 23…floor cross beam; 23a…end; 31…body side structure; 33…floor cross beam; 33a…end.

Claims

1. A vehicle body side structure, comprising: a side beam formed by joining a side beam inner member and a side beam outer member extending in a vehicle body front-rear direction on an outer side of a vehicle body in a vehicle width direction to each other at an upper end and a lower end in a vehicle height direction; a battery pack disposed at a lower portion of the vehicle body on an inner side of the vehicle body in a vehicle width direction relative to the side beam; and a floor cross member extending in a vehicle width direction above the side beam on an inner side of the vehicle body in a vehicle width direction relative to the side beam, The vehicle body side structure is characterized in that: The floor cross member is formed of a metal plate having a tensile strength of 1180 MPa or higher, and the end portion on the vehicle outer side in the vehicle width direction is arranged to cover the upper surface of the lower side beam inner member in the vehicle height direction without abutting against the surface of the lower side beam inner member on the vehicle inner side in the vehicle width direction, and extends to and abuts against the joint surface portion at the upper end portion of the lower side beam inner member and the lower side beam outer member, In a side collision in which a collision load is input to the side sill from the vehicle outer side in the vehicle width direction, after the side sill outer member is deformed and crushed, the load input to the side sill is transmitted to the floor cross member to reduce the load transmitted to the battery pack.

2. The vehicle body side structure according to claim 1, characterized in that: The floor cross member has a groove shape extending in the vehicle width direction, and a wall surface portion abutting against the joint surface portion is provided at a front end thereof, so that the groove shape at the end of the floor cross member is closed by the wall surface portion.

3. The vehicle body side structure according to claim 1 or 2, characterized in that: The end portion of the floor cross member is joined to the joint surface portions of the side sill inner member and the side sill outer member.

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