Side structure of the vehicle body.

Abstract

A vehicle body lateral section structure 1 according to the present invention comprises: a side sill 3 formed by joining a side sill inner 3a and a side sill outer 3b; a battery pack 5 which is disposed on the interior side of the side sill 3 in the vehicle width direction; and a floor cross member 7 extending in the vehicle width direction. The floor cross member 7, which is made of a metal plate having a tensile strength on the order of 1180 MPa or more, has an end portion 7a disposed to cover an upper surface 3a2 of the side sill inner 3a without abutting on a side surface 3a1 thereof, and extends to, and abuts on, a joint surface portion 3d at an upper end portion 3c of the side sill inner 3a and the side sill outer 3b. In the event of a side collision, after the side sill outer 3b is deformed and crushed, the load input to the side sill 3 is transmitted to the floor cross member 7 so as to reduce the load transmitted to the battery pack 5.

Description

Body side structure

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

[0002] In recent years, particularly in the automotive industry, environmental concerns have led to a shift from gasoline-engine vehicles to electric vehicles. Electric vehicles and other vehicles have battery packs containing large cells (batteries) located in the floor area under the vehicle body. Because these batteries often use lithium-based materials, there is a risk of fire if the battery pack is damaged in a collision and liquid leakage occurs. Therefore, a structure to protect the battery pack is required. The battery pack is protected by a floor cross member extending in the vehicle width direction and side sills extending in the vehicle length direction on both outer sides of the vehicle width. The floor cross member is located between the two side sills, and the battery pack is located below it.

[0003] As a technology for protecting a battery pack in the event of a side impact collision of an electric vehicle or the like, for example, Patent Document 1 discloses a structure in which, in a vehicle equipped with a battery pack, side sills extending in the longitudinal direction of the vehicle body on the outer side in the vehicle width direction, and a floor cross member installed between the left and right side sills, both ends of the floor cross member are connected from the inside side portion of the side sill inner of the side sill to the joint between the side sill inner and the side sill outer.

[0004] Patent No. 6734709

[0005] In the technology disclosed in Patent Document 1, during a side collision in which a pole or other object strikes the side sill on the side of a vehicle and inputs a load, the collision load is transmitted from the side sill to the floor cross member via the connection between the floor cross member and the side sill, which extends from the vehicle-interior side of the side sill inner to the joint between the side sill outer and the side sill inner. The floor cross member amplifies the reaction force, crushing the side sill outer and the side sill inner. The side sill outer and the side sill inner are crushed and undergo compressive deformation, efficiently absorbing the crush energy. However, if the side sill collapses first, the load transmitted to the battery pack cannot be sufficiently reduced, and the battery pack cannot be adequately protected.

[0006] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a vehicle side structure that can protect a battery pack by reducing the load transmitted to the battery pack during a side collision of a vehicle body that has a side sill, a battery pack arranged on the inside of the side sill in the vehicle width direction, and a floor cross member.

[0007] The vehicle body side structure according to the present invention includes a side sill formed by joining a side sill inner and a side sill outer, the side sill inner and outer being provided on the vehicle outer side in the vehicle width direction and extending in the fore-and-aft direction of the vehicle, at their upper and lower ends in the vehicle height direction, a battery pack disposed under the vehicle body on the vehicle inner side in the vehicle width direction than the side sill, and a floor cross member disposed above the vehicle inner side in the vehicle width direction than the side sill, the floor cross member being made of a metal sheet having a tensile strength of 1180 MPa class or more, the end on the vehicle outer side in the vehicle width direction not contacting the surface of the side sill inner on the vehicle inner side in the vehicle width direction, but being disposed so as to cover the upper surface of the side sill inner in the vehicle height direction, and extending to and contacting a joining surface portion at the upper end of the side sill inner and the side sill outer, and being capable of withstanding a crushing load applied to the side sill from the vehicle outer side in the vehicle width direction. In the event of a side collision in which a load is input, after the side sill outer is deformed and crushed, the load input to the side sill is transmitted to the floor cross member, thereby reducing the load transmitted to the battery pack.

[0008] The floor cross member has a groove shape extending in the vehicle width direction, and a wall surface portion is provided at its tip that abuts the joint surface portion, and the groove shape at the end of the floor cross member is closed by the wall surface portion.

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

[0010] In the present invention, a load transfer path for a load input to the vehicle body during a side collision is formed in the floor cross member, and the reaction force from the floor cross member toward the vehicle's outer side in the vehicle width direction is mainly applied to the joining surface where the side sill inner and side sill outer are joined. As a result, the side sill outer absorbs the collision energy by collapsing and compressing, while the side sill inner maintains its shape without collapsing. Furthermore, because the floor cross member is made of a metal plate with a tensile strength of 1180 MPa or more, the floor cross member can continue to bear the load input to the side sill without deforming, even after the side sill outer is compressed and collapsed. This makes the side sill inner less likely to deform and collapse, allowing it to maintain its impact energy absorption capacity, thereby reducing load transfer to the battery pack 5. As a result, deformation of the battery pack 5 during a side collision is suppressed, protecting the battery pack from damage and enabling the creation of a safe vehicle.

[0011] FIG. 1 is a diagram illustrating a vehicle body side structure according to an embodiment of the present invention. FIG. 2 is a diagram illustrating load transfer during a side collision in the vehicle body side structure according to an embodiment of the present invention ((a) conventional vehicle body side structure, (b) vehicle body side structure according to this embodiment, (c) load transfer path during a side collision). FIG. 3 is a diagram illustrating a specific example of a closed end shape of a floor cross member in the vehicle body side structure according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a side collision of a vehicle body analyzed in the examples. FIG. 5 is a diagram illustrating a method for evaluating the deformation of a battery pack and the input load to the battery pack in the examples ((a) evaluation position of the deformation of the battery pack, (b) input load to the battery pack). FIG. 6 is a cross-sectional view of the vehicle body side structures according to the example and comparative examples 1 and 2 in the examples at (i) a vehicle length position TL=1568 mm and (ii) a vehicle length position TL=1916 mm ((a) example, (b) comparative example 1, (c) comparative example 2). Fig. 7 is a graph showing the results of the deformation amount of the battery pack when a pole collides with the battery pack at a position TL=1916 mm in the vehicle length direction in the example. Fig. 8 is a graph showing the results of the contact reaction force calculated as the input load to the battery pack when a pole collides with the battery pack at a position TL=1916 mm in the vehicle length direction in the example.

[0012] As shown in FIG. 1 as an example, 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.

[0013] A vehicle body side structure 1 according to this embodiment will be described below with reference to Fig. 1. Fig. 1 also shows other vehicle body components such as a floor panel 9 disposed above a battery pack 5, but these other vehicle body components are not essential to the present invention and therefore will not be described below. Furthermore, in this specification and drawings, elements having the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

[0014] 1, the side sill 3 includes a side sill inner 3a and a side sill outer 3b extending in the longitudinal direction of the vehicle body on the outer side of the vehicle in the vehicle width direction. The side sill inner 3a has a groove shape that opens toward the outer side of the vehicle in the vehicle width direction, and is formed by a top plate 3a1 and a pair of vertical walls 3a2. The side sill outer 3b has a groove shape that opens toward the inner side of the vehicle in the vehicle width direction. The side sill inner 3a and the side sill outer 3b are joined at an upper end 3c and a lower end (not shown) in the vehicle height direction with their opening sides facing each other, forming a closed cross-section structure.

[0015] 1 illustrates a range of approximately one-third or more of the upper portion of the side sill 3 in the vehicle height direction in the vehicle body side structure 1. The side sill inner 3a and the side sill outer 3b each have a hat-shaped cross section, for example, including a top portion, a pair of vertical walls, and a flange portion, and the flanges at the upper and lower ends of the side sill inner 3a and the side sill outer 3b are joined together to form the side sill 3 with a closed cross-sectional structure. However, in the present invention, the side sill inner and side sill outer are not limited to those with a hat cross-section, and may be any other structure in which the upper and lower ends are joined together to form a side sill with a closed cross-sectional structure.

[0016] As shown in FIG. 1, the battery pack 5 is disposed in a lower portion of the vehicle body on the inner side of the side sill 3 in the vehicle width direction, and includes a battery cell (not shown) mounted therein.

[0017] The floor cross member 7 has a hat-shaped cross section with a bottom surface, a pair of vertical walls, and a flange. The bottom surface and the pair of vertical walls form a groove shape extending in the vehicle width direction. As shown in FIG. 1 , the floor cross member 7 extends in the vehicle width direction above the side sill 3 on the vehicle's inner side in the vehicle width direction. The cross-sectional view of the vehicle body side structure in FIG. 1 shows the cross section of the bottom surface. The floor cross member 7 is made of a metal plate with a tensile strength of 1180 MPa or higher. Its outer end 7a in the vehicle width direction does not abut the inner surface of the side sill inner 3a in the vehicle width direction, but is disposed so as to cover the upper surface of the side sill inner 3a in the vehicle height direction. It also extends to and abuts against the joint surface 3d where the side sill inner 3a and the side sill outer 3b are joined. The upper surface of the side sill inner panel 3a in the vehicle height direction refers to the vertical wall 3a2 when the side sill inner panel 3a has a hat-shaped cross section including a top plate 3a1, a vertical wall 3a2, and a flange 3a3 as shown in Figure 1. The surface of the side sill inner panel 3a on the vehicle's inner side in the vehicle width direction refers to the top plate 3a1.

[0018] In the vehicle body side structure 1, during 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 3b is compressively deformed and crushed by the collision load input to the side sill 3. After the side sill outer 3b is crushed, the floor cross member 7 continues to receive the load input to the side sill 3 without deforming, thereby reducing the load transmitted to the battery pack 5.

[0019] The effects of the vehicle body side structure 1 according to this embodiment are as follows. In a conventional vehicle body side structure 21 including a side sill 3, a battery pack 5, and a floor cross member 23, as shown in FIG. 2( a), the vehicle width direction end 23a of the floor cross member 23 extends above the side sill inner 3a, but does not abut against the joint surface 3d at the upper end 3c of the side sill 3. Therefore, when a load is applied to the side sill 3 during a side collision, the side sill outer 3b first deforms and collapses, and then the load is not sufficiently transmitted to the floor cross member 23, and the transmission of the load to the battery pack 5 cannot be sufficiently reduced.

[0020] In contrast, with the vehicle body side structure 1 according to this embodiment, as shown in FIGS. 1 and 2(b), the end 7a of the floor cross member 7 abuts against the joint surface 3d at the upper end 3c of the side sill 3. As shown in FIG. 2(c), this forms a load transfer path for the load input to the vehicle body during a side collision in the floor cross member 7. The reaction force exerted by the floor cross member 7 toward the vehicle's outboard side in the vehicle width direction is primarily applied to the joint surface 3d where the side sill inner 3a and the side sill outer 3b are joined. As a result, the side sill outer 3b absorbs the collision energy by collapsing and compressing, while the side sill inner 3a maintains its shape without collapsing. Furthermore, because the floor cross member 7 is made of a metal plate with a tensile strength of 1180 MPa or more, the floor cross member 7 can continue to bear the load input to the side sill 3 without deforming, even after the side sill outer 3b is compressed and collapsed. This makes the side sill inner less susceptible to deformation and maintains its collision energy absorption capacity, thereby reducing the load transfer to the battery pack 5. As a result, deformation of the battery pack 5 during a side collision can be suppressed, and the battery pack 5 can be protected from damage, making it possible to create a safe vehicle.

[0021] In this embodiment, the floor cross member 7 is made of a metal plate with a tensile strength of 1180 MPa or more. However, if the floor cross member is made of a metal plate with a tensile strength of less than 1180 MPa, it will easily deform when a load is transmitted to the floor cross member, and the load will not be transmitted sufficiently, making it impossible to reduce the load transmitted to the battery pack 5.

[0022] Therefore, in this embodiment, the floor cross member 7 is made of a metal plate with a tensile strength of 1180 MPa or higher, and specific examples include steel plates with tensile strengths of 1180 MPa, 1370 MPa, 1470 MPa, and 1760 MPa.

[0023] In the vehicle body side structure 1, the end 7a of the floor cross member 7 abuts against but is not connected to the joint surface 3d where the side sill inner 3a and the side sill outer 3b are joined. However, in the present invention, it is preferable that the end of the floor cross member be connected to the joint surface between the side sill inner and the side sill outer. This makes it less likely that the end of the floor cross member will shift from the joint surface between the side sill inner and the side sill outer during a side collision, maintaining the load transfer path to the floor cross member for the load input to the vehicle body (side sill). This makes it easier to transfer the load to the floor cross member, further reducing the load transferred to the battery pack.

[0024] In addition, in the present invention, the floor cross member 7 has a groove shape (not shown) that has a bottom surface and a pair of vertical walls and extends in the vehicle width direction, and as shown in Fig. 1, for example, it is preferable that a wall face portion 7b that is bent and continues from the bottom surface 7a1 is provided at the tip of the end 7a, and that the wall face portion 7b closes the groove shape of the end 7a of the floor cross member 7. This makes the end 7a of the floor cross member 7 less likely to be crushed, and prevents the vehicle body from being significantly deformed.

[0025] FIG. 3 shows a specific example of a closed groove shape at the end 7a of the floor cross member 7 in the vehicle width direction. The floor cross member 7 shown in FIG. 3(a) has a closed groove shape at the tip of the end 7a, where the bottom surface 7a1, a pair of vertical walls 7a2, and a wall surface portion 7b are integrally and continuously connected. The floor cross member 7 shown in FIG. 3(b) has a high vertical wall height (height in the vehicle height direction). Therefore, although the bottom surface 7a1 of the groove shape and the wall surface portion 7b at the tip are curved and continuous, the bottom surface 7a1 of the groove shape and the pair of vertical walls 7a2 are not integral and continuous. However, welding margins 7c that bend toward the vertical walls 7a2 are provided on both sides of the bottom surface 7a1 and the wall surface portion 7b, and the welding margins 7c and the vertical walls 7a2 are joined by spot welding or the like, resulting in a closed groove shape.

[0026] A specific analysis was carried out to verify the effects of the vehicle body side structure according to the present invention, and the results will be described below.

[0027] In this example, a side impact analysis was performed on a vehicle 101 equipped with a vehicle body side structure 1 (example) having the side sill 3, battery pack 5, and floor cross member 7 shown in FIG. 1 in the above-described embodiment, in which a pole 103 was collided with the vehicle from the outer side in the vehicle width direction, as shown in FIG. 4. In the vehicle body side structure 1 of this example, the battery pack 5 is supported by a battery frame assembly 11 arranged on the outer periphery in the vehicle width direction, as shown in FIG. 5(b). The battery frame assembly 11 is made up of a plurality of steel sheet parts, as shown in FIG. 5(b).

[0028] In the side collision analysis, the vehicle 101 was accelerated in the vehicle width direction to 29 km / h and collided with a rigid pole 103 against the side of the vehicle 101. The pole collision position where the pole 103 collided with the vehicle 101 was set to a position TL = 1916 mm in the vehicle length direction. When the pole 103 collided with the side sill 3 on the side of the vehicle 101, the side sill 3 (see Figure 1) was locally deformed and intruded into the vehicle interior. Therefore, in this example, the deformation amount of the battery pack 5 and the load input to the battery pack 5 during the side collision process were evaluated.

[0029] Regarding the deformation amount of the battery pack 5, the length of the battery pack 5 in the vehicle width direction was measured before and after deformation at multiple positions in the vehicle length direction (positions indicated by arrows in FIG. 5(a)), and the difference between the lengths before and after deformation was calculated, as shown in FIG. 5(a). Meanwhile, regarding the load input to the battery pack 5 side, the reaction force (contact reaction force) generated in the battery frame assembly 11 due to contact with connecting members 13 provided on the outer periphery of the battery frame assembly 11 in the vehicle width direction during the collision process was calculated, as shown in FIG.

[0030] Furthermore, in this example, for comparison, a vehicle body side structure 21 (Comparative Example 1) shown in FIG. 6(b) and a vehicle body side structure 31 (Comparative Example 2) shown in FIG. 6(c) were also subjected to a side collision analysis of the vehicle shown in FIG. 4 in the same manner as in the invention example, and the deformation amount of the battery pack 5 during the side collision process and the load input to the battery pack 5 were evaluated.

[0031] In the vehicle body side structure 21 of Comparative Example 1, the vehicle width directional end 23a of the floor cross member 23 extends so as to cover the side sill inner 3a, but does not abut the joint surface 3d between the side sill inner 3a and the side sill outer 3b.

[0032] In the vehicle body side structure 31 according to the comparative example 2, the end 33a in the vehicle width direction of the floor cross member 33 does not extend above the side sill inner 3a.

[0033] In Comparative Examples 1 and 2, the load input to the battery pack 5 side was determined as the contact reaction force between the connecting member 13 and the battery frame assembly 11, as in the invention example.

[0034] Figure 7 shows the results of the deformation amount of the battery pack 5 in the example, comparative example 1, and comparative example 2 during a side collision in which the pole collision position was at a vehicle length direction position TL = 1916 mm. As shown in Figure 7, the deformation amount of the battery pack 5 in the example and comparative example 1 was smaller than in comparative example 2 in which the end 33a of the floor cross member 33 did not extend above the side sill inner 3a. Furthermore, when comparing the example and comparative example 1, the deformation amount of the battery pack 5 was smaller in the example.

[0035] Figure 8 shows the results of the contact reaction force calculated as the load input to the battery pack 5 in the example of the invention, comparative example 1, and conventional example 2 during a side collision in which the pole collision position was at a vehicle length direction position TL = 1916 mm. As shown in Figure 8, the load input to the battery pack 5 in the example of the invention and comparative example 1 was smaller than in comparative example 2 in which the end 33a of the floor cross member 33 did not extend above the side sill inner 3a. Furthermore, when comparing the example of the invention with comparative example 1, the load input to the battery pack 5 was found to be smaller in the example of the invention.

[0036] As described above, the vehicle body side structure of the present invention has been shown to be able to sufficiently reduce the load input to the battery pack during a side collision by transmitting the load input to the vehicle to the floor cross member, thereby reducing the amount of deformation of the battery pack and protecting the battery pack.

[0037] According to the present invention, a vehicle side structure can be provided that can protect a battery pack by reducing the load transmitted to the battery pack during a side collision of a vehicle body equipped with a side sill, a battery pack arranged on the inside of the side sill in the vehicle width direction, and a floor cross member.

[0038] DESCRIPTION OF SYMBOLS 1 Vehicle body side structure 3 Side sill 3a Side sill inner 3a1 Top plate (side surface) 3a2 Vertical wall (upper surface) 3a3 Flange 3b Side sill outer 3c Upper end portion 3d Joint surface portion 5 Battery pack 7 Floor cross member 7a End portion 7a1 Bottom surface 7a2 Vertical wall 7b Wall surface portion 7c Welding allowance 9 Floor panel 11 Battery frame assembly 13 Connecting member 21 Vehicle body side structure 23 Floor cross member 23a End portion 31 Vehicle body side structure 33 Floor cross member 33a End portion

Claims

DEPCT681. The side structure of the vehicle body, comprising: the side steps extending forward-rear in the direction of the vehicle body on the outside of the vehicle body in the width direction, including the inner and outer parts of the side steps that are connected at the upper and lower ends in the height direction of the vehicle, where the inner part of the side step has a groove shape that is open towards the outside of the vehicle in the width direction, including the top part and a pair of vertical walls, and the outer part of the side step has a groove shape that is open towards the inside of the vehicle in the width direction of the vehicle; the battery pack located at the bottom of the vehicle body inside the vehicle in the width direction of the vehicle relative to the side steps; and the transverse components of the floor body extending in the width direction of the vehicle above the side steps inside the vehicle in the width direction of the vehicle, where the transverse components of the floor body are made of sheet metal with a tensile strength of 1180 megapascals or higher.and including the outer end of the vehicle in the direction along the width of the vehicle that does not come into contact with the topmost part of the inner surface of the vehicle of the inner side step in the direction along the width of the vehicle, where this end is positioned to cover the top of the inner side step in the direction along the height of the vehicle, where this end extends to and comes into contact with the connecting surface at the top end of the inner side step and the outer side step.

2. The side structure of the vehicle body under claim 1 where the transverse component of the body floor has a groove shape that extends in the direction along the width of the vehicle, the wall surface in contact with the connecting surface is provided at the distal end of the transverse component of the body floor, and the groove shape of the end of the transverse component of the body floor is covered by the wall surface.

3. The side structure of the vehicle body under claim 1 or 2 where the end of the transverse component of the body floor connects to the connecting surface between the inner side step and the outer side step;

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