Vehicle lower part structure

Abstract

To prevent damage of a floor panel in the event of side collision by controlling the bending position of a floor cross member.SOLUTION: A vehicle lower part structure 10 includes a rocker 11, a floor cross member 20, a gusset 30, and a seat bracket 40. A seat bracket 40 is a longitudinal member extending in a vehicle-width direction and is provided with a low-strength portion 72 at a center in the longitudinal direction. The floor cross member 20 is provided with a strength-decreasing portion 71 at a position corresponding to the low-strength portion 72. The gusset 30 is connected to a side end 20B of the floor cross member 20 such that a pressing flange 35 on an inner side in the vehicle-width direction overlaps the strength-decreasing portion 71.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to the structure of the lower part of a vehicle.

Background Art

[0002] Structures for absorbing impact energy during a side collision of a vehicle have been proposed. For example, Patent Document 1 discloses a structure in which stepped portions with a central portion convex outward are provided on both side portions of the front and rear surfaces of a seat bracket provided on the upper portion of a floor cross member. In this structure, when the vehicle is side-collided, the stepped portions are bent and deformed to absorb impact energy.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, due to the deformation of the floor cross member during a side collision, breakage of the floor panel may occur. In particular, breakage of the floor panel may occur when the folding position of the floor cross member during a side collision cannot be controlled. On the other hand, in recent years, in order to improve safety during a side collision, it has been required to suppress damage to the floor panel during a side collision.

[0005] Therefore, an object of the present disclosure is to control the folding position of the floor cross member and suppress damage to the floor panel during a side collision.

Means for Solving the Problems

[0006] The vehicle underbody structure of the present disclosure includes a rocker disposed on a side portion of the vehicle and extending in the longitudinal direction of the vehicle, a floor cross member connected to the rocker and extending in the vehicle width direction, a gusset connected to a side end portion of the floor cross member and an inner surface of the rocker in the vehicle width direction, and a seat bracket disposed spaced apart from the rocker and attached to the floor cross member so as to straddle the side end portion of the floor cross member and a general portion adjacent to the inner side of the side end portion in the vehicle width direction. The seat bracket is a long member extending in the vehicle width direction, and a low-strength portion is provided at the center in the longitudinal direction. The floor cross member is provided with a strength reduction portion at a position corresponding to the low-strength portion. The gusset is connected to the floor cross member such that an inner end in the vehicle width direction overlaps the strength reduction portion.

[0007] Accordingly, when a side collision occurs, a force directed downward from the gusset to the strength reduction portion is transmitted. The seat bracket is bent downward starting from the low-strength portion, and the floor cross member is bent downward starting from the strength reduction portion provided at a position corresponding to the low-strength portion. Thus, the present disclosure can control the bending position of the floor cross member and reduce the amount of deformation of the floor panel during a side collision.

[0008] In the vehicle underbody structure of the present disclosure, the floor cross member may be connected to a lower portion of the rocker, the gusset may be connected to an inner surface of the rocker above the floor cross member in the vehicle width direction, and the seat bracket may be an inverted U-shaped cross-sectional member extending in the vehicle width direction and attached to the floor cross member so as to cover the gusset from above.

[0009] Accordingly, when a side collision occurs, the rocker is deformed upward, the seat bracket and the floor cross member are deformed downward, and the seat bracket in a portion outside the vehicle width direction from the low-strength portion, the floor cross member outside the vehicle width direction from the strength reduction portion, and the gusset are deformed upward and inward in the vehicle width direction so as to overlap each other, and impact energy can be absorbed.

[0010] In the vehicle underbody structure of the present disclosure, the seat bracket is an inverted U-shaped cross-sectional member including an upper plate, a front plate, and a rear plate. The low-strength portion is an inverted U-shaped notch provided in the front plate and the rear plate. The portion on the outer side in the vehicle width direction of the front plate and the rear plate with respect to the notch is connected to the side end portion on the outer side in the vehicle width direction of the strength reduction portion of the floor cross member. The portion on the inner side in the vehicle width direction of the front plate and the rear plate with respect to the notch may be connected to the general portion on the inner side in the vehicle width direction of the strength reduction portion of the floor cross member.

[0011] Accordingly, during a side impact, the portion on the outer side in the vehicle width direction and the portion on the inner side in the vehicle width direction of the front plate and the rear plate of the seat bracket with respect to the notch deform such that the lower part opens along the vehicle width direction and folds downward at the low-strength portion. Further, the floor cross member folds downward at the strength reduction portion. Thereby, the folding position of the floor cross member can be controlled, and the deformation amount of the floor panel during a side impact can be reduced.

[0012] In the vehicle underbody structure of the present disclosure, the floor cross member is a hat-shaped cross-sectional member including a web, a front flange, and a rear flange, and is arranged such that the web is on the upper side. The strength reduction portion may be a slit extending in the vehicle front-rear direction provided in the web.

[0013] Thereby, with a simple structure, the folding position of the floor cross member can be controlled, damage to the floor panel during a side impact can be suppressed, and impact energy can be absorbed.

[0014] In the vehicle underbody structure of the present disclosure, the floor cross member is a hat-shaped cross-sectional member including a web, a front flange, and a rear flange, and is arranged such that the web is on the upper side. The strength reduction portion may be a fold bead provided at the front connection ridge line between the web and the front flange and at the rear connection ridge line between the web and the rear flange.

[0015] As a result, with a simple structure, the folding position of the floor cross member can be controlled, damage to the floor panel during a side impact can be suppressed, and impact energy can be absorbed.

Advantages of the Invention

[0016] The present disclosure can control the folding position of the floor cross member and suppress damage to the floor panel during a side impact.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0018] Hereinafter, the vehicle underbody structure 10 of the embodiment will be described with reference to the drawings. First, the floor structure 61 of the vehicle 60 having the vehicle underbody structure 10 will be described with reference to FIG. 1. FIG. 1 shows the right side portion of the floor structure 61 of the vehicle 60. Since the left side portion of the floor structure 61 is symmetric with the right side portion of the floor structure 61, only the shape is shown by a two-dot chain line, and the description thereof is omitted. In addition, FR, UP, and RH shown in each figure indicate the front side, the upper side, and the right side of the vehicle 60, respectively. Also, the opposite directions of FR, UP, and RH indicate the rear side, the lower side, and the left side. Hereinafter, when simply describing using the front-rear, left-right, and up-down directions, unless otherwise specified, it shall indicate the front-rear in the front-rear direction of the vehicle 60, the left-right in the left-right direction, and the up-down in the up-down direction.

[0019] As shown in FIG. 1, the floor structure 61 of the vehicle 60 includes a rocker 11, a floor tunnel 12, a front floor cross member 15, a rear floor cross member 20, and a floor panel 13. The vehicle underbody structure 10 is the structure of the connection portion between the rear floor cross member 20 and the rocker 11. The vehicle underbody structure 10 includes a rocker 11, a floor cross member 20, a gusset 30, and a seat bracket 40.

[0020] The rocker 11 is a skeletal member disposed on the side portion of the vehicle 60 and extending in the longitudinal direction of the vehicle. The floor tunnel 12 is a corrugated plate member disposed at the center in the vehicle width direction and extending in the longitudinal direction of the vehicle. The floor tunnel 12 is a long member having a groove-shaped cross section that is convex upward and open downward. Inside the floor tunnel 12, a power transmission device, a high-voltage cable, etc. extending in the longitudinal direction of the vehicle are accommodated. The front and rear floor cross members 15 and 20 connect the rocker 11 and the floor tunnel 12 in the vehicle width direction. Bolt holes 16 and 18 for fixing a front seat (not shown) are provided near the rocker 11 and near the floor tunnel 12 of the front floor cross member 15. A gusset 30 and a seat bracket 40 are attached near the rocker 11 of the rear floor cross member 20. The seat bracket 40 is provided with a bolt hole 47 for fixing the front seat. The rear floor cross member 20 is connected to the floor tunnel 12 by a connection bracket 50. The connection bracket 50 is provided with a bolt hole 51 for fixing the front seat. The floor panel 13 is a plate member disposed between the rocker 11 and the floor tunnel 12 to form the floor of the passenger compartment.

[0021] Next, the details of the vehicle underbody structure 10 included in the right side portion of the floor structure 61 will be described with reference to FIGS. 2 and 3. Note that the description of the vehicle underbody structure included in the left side portion of the floor structure 61 is omitted because it is symmetric to the vehicle underbody structure 10 included in the right side portion.

[0022] As shown in FIGS. 2 and 3, the vehicle underbody structure 10 includes a rocker 11, a floor panel 13, a floor cross member 20, a gusset 30, and a seat bracket 40. The rocker 11 is a skeletal member having a closed cross-section structure composed of a ceiling plate 11A, an inner plate 11B, an outer plate 11E, a bottom plate 11D, and an inclined plate 11C. The rocker 11 is disposed on the side portion of the vehicle 60 and extends in the longitudinal direction of the vehicle.

[0023] The floor panel 13 is a plate member portion that is connected to the inclined plate 11C of the rocker 11 and extends inward in the vehicle width direction from the inner plate 11B. The floor panel 13 includes a rocker connection portion 13C connected to the lower surface of the inclined plate 11C of the rocker 11, a right side portion 13B that extends obliquely downward inward in the vehicle width direction from the lower end of the inner plate 11B of the rocker 11, and a floor flat plate portion 13A that extends in the horizontal direction.

[0024] The floor cross member 20 is a hat-shaped cross-sectional member including a web 21, a front flange 22, a rear flange 23, a front arm 24, and a rear arm 25. The floor cross member 20 is disposed on the floor panel 13 such that the web 21 is on the upper side. The front flange 22 and the rear flange 23 are plate members that stand upright downward from the front end and the rear end of the web 21. The front arm 24 and the rear arm 25 are plate members that extend forward and rearward from the lower ends of the front flange 22 and the rear flange 23. The rear flange 23 includes a main body portion 23A disposed on the floor flat plate portion 13A of the floor panel 13 and a right end portion 23B disposed on the right side portion 13B of the floor panel 13. The lower end of the right end portion 23B is inclined along the right side portion 13B of the floor panel 13. Further, the rear arm 25 includes a flat plate portion 25A connected to the main body portion 23A of the rear flange 23, an inclined portion 25B connected to the right end portion 23B of the rear flange 23, and a connection flange 25C that extends upward from the right end of the inclined portion 25B. Similarly, the front flange 22 includes a main body portion 22A and a right end portion 22B, and the front arm 24 includes a flat plate portion 24A, an inclined portion 24B, and a connection flange 24C (see FIG. 3).

[0025] The flat plate portions 24A and 25A of the front arm 24 and the rear arm 25 of the floor cross member 20 are connected to the upper surface of the floor flat plate portion 13A of the floor panel 13 by spot welding 83 (indicated by an 'x' in the figure). Also, the connection flanges 24C and 25C are connected to the inner side plate 11B of the rocker 11 by spot welding 81. The web 21 is disposed at the height of the lower end of the inner side plate 11B of the rocker 11. In this way, the floor cross member 20 is connected to the lower part of the rocker 11, and the front flange 22, the rear flange 23, the front arm 24, and the rear arm 25 are disposed below the lower end of the inner side plate 11B of the rocker 11.

[0026] A slit 26 extending in the vehicle front-rear direction is provided in the web 21 of the floor cross member 20. The slit 26 constitutes a strength reduction portion 71 of the floor cross member 20. The portion of the floor cross member 20 on the right side of the slit 26 is referred to as the side end portion 20B of the floor cross member 20, and the portion at the center in the vehicle width direction of the floor cross member 20 relative to the slit 26 is referred to as the general portion 20A of the floor cross member 20.

[0027] The gusset 30 is a reinforcing member connected to the side end portion 20B of the floor cross member 20 and the inner side plate 11B of the rocker 11. The gusset 30 includes an upper horizontal plate 31, a front vertical plate 32, a rear vertical plate 33, an end vertical plate 34, a pressing flange 35, and a fixing flange 36. The upper horizontal plate 31, the front vertical plate 32, and the rear vertical plate 33 constitute a groove-shaped cross section with the lower side open. The upper horizontal plate 31 is disposed at the upper part of the side end portion 20B of the floor cross member 20. The front vertical plate 32 and the rear vertical plate 33 are connected to the front end and the rear end of the upper horizontal plate 31 and extend downward. The lower parts of the front vertical plate 32 and the rear vertical plate 33 extend downward along the outer surfaces of the front flange 22 and the rear flange 23 of the side end portion 20B of the floor cross member 20. The lower parts of the front vertical plate 32 and the rear vertical plate 33 are connected to the outer surfaces of the front flange 22 and the rear flange 23 of the side end portion 20B by spot welding 84. Incidentally, a hole 37 is provided in the upper horizontal plate 31 of the gusset 30.

[0028] The end vertical plate 34 is connected to the inner side in the vehicle width direction of the upper horizontal plate 31 and extends obliquely downward toward the inner side in the vehicle width direction. The front end and the rear end of the end vertical plate 34 are connected to the front vertical plate 32 and the rear vertical plate 33, respectively. The pressing flange 35 is connected to the lower end of the end vertical plate 34. The lower end of the pressing flange 35 is in contact with the upper surface of the web 21 of the floor cross member 20. A part of the lower end of the pressing flange 35 overlaps with the slit 26. Thus, the pressing flange 35 constitutes the inner end in the vehicle width direction of the gusset 30 arranged so as to overlap with the slit 26 of the floor cross member 20.

[0029] The fixing flange 36 is a plate member connected to the upper horizontal plate 31, the front vertical plate 32, and the right end of the rear vertical plate 33. The fixing flange 36 is fixed to the inner plate 11B of the rocker 11 by spot welding 82. Also, the lower part of the fixing flange 36 is fixed together with the connecting flange 24C of the floor cross member 20 by spot welding 81 to the lower part of the inner plate 11B of the rocker 11 above the floor cross member 20. Thus, the gusset 30 is connected to the inner surface in the vehicle width direction of the inner plate 11B of the rocker 11 above the floor cross member 20.

[0030] The seat bracket 40 includes an upper plate 41, a front plate 42, a rear plate 43, an end plate 44, an end flange 45, and a nut holding plate 48. The upper plate 41 is arranged above the gusset 30 so as to be separated from the rocker 11 in the vehicle width direction. The front plate 42 and the rear plate 43 are connected to the front end and the rear end of the upper plate 41 and extend downward. The upper plate 41, the front plate 42, and the rear plate 43 constitute a reverse U-shaped cross-sectional member with an open lower side. The seat bracket 40 is a long member extending in the vehicle width direction, and reverse U-shaped notches 46 are respectively provided at the longitudinal centers of the front plate 42 and the rear plate 43. The portion where the notch 46 of the seat bracket 40 is provided constitutes the low-strength portion 72 of the seat bracket 40. Therefore, the low-strength portion 72 of the seat bracket 40 is provided at the longitudinal center of the seat bracket 40.

[0031] The lower parts of the front plate 42 and the rear plate 43 are divided into a lower right part 42B, 43B which is the outer part in the vehicle width direction than the notch 46, and a lower middle part 42A, 43A which is the inner part in the vehicle width direction than the notch 46. The lower right parts 42B, 43B extend downward along the outside of the front vertical plate 32 and the rear vertical plate 33 of the gusset 30. And the lower right parts 42B, 43B are connected to the outer surfaces of the front flange 22 and the rear flange 23 of the front end part 20B together with the front vertical plate 32 and the rear vertical plate 33 by spot welding 84. Also, the lower middle parts 42A, 43A are connected to the outer surfaces of the front flange 22 and the rear flange 23 of the general part 20A. Thus, the front plate 42 and the rear plate 43 are attached to the floor cross member 20 so as to straddle the side end part 20B and the general part 20A of the floor cross member 20. Also, the front plate 42 and the rear plate 43 are attached to the floor cross member 20 so that the upper plate 41 covers the gusset 30 from above. And when the front plate 42 and the rear plate 43 are attached to the floor cross member 20, the position in the vehicle width direction of the low-strength part 72 of the seat bracket 40 becomes the position corresponding to the position in the vehicle width direction of the strength reduction part 71 of the floor cross member 20.

[0032] The end plate 44 is connected to the inner side in the vehicle width direction of the upper plate 41 and extends obliquely downward toward the inner side in the vehicle width direction. The front end and the rear end of the end plate 44 are connected to the front plate 42 and the rear plate 43. The end flange 45 is connected to the lower end of the end plate 44 and extends toward the inner side in the vehicle width direction. The end flange 45 is connected to the upper surface of the web 21 of the floor cross member 20 by spot welding 85.

[0033] The nut holding plate 48 extends in the vehicle width direction along the upper plate 41 below the upper plate 41, and is fixed to the upper plate 41 and the end plate 44 by spot welding 87, 86. A nut 49 is fixed to the nut holding plate 48. A bolt (not shown) for fixing a front seat (not shown) is screwed into the nut 49.

[0034] As described above, the seat bracket 40 is disposed at a distance from the rocker 11 toward the inner side in the vehicle width direction, and is attached to the floor cross member 20 so as to straddle the side end portion 20B and the general portion 20A of the floor cross member 20, covering the gusset 30 from above. And the position in the vehicle width direction of the low-strength portion 72 of the seat bracket 40 corresponds to the position in the vehicle width direction of the strength reduction portion 71 of the floor cross member 20.

[0035] Next, with reference to FIGS. 4 and 5, the flow of the impact force during a side collision of the vehicle 60 including the vehicle lower structure 10 configured as described above and the deformation of each part of the vehicle lower structure 10 will be described. The broken line in FIG. 5 indicates the vehicle lower structure 10 after deformation.

[0036] As described above with reference to FIGS. 2 and 3, the floor cross member 20 is connected to the lower part of the rocker 11. The left end of the floor cross member 20 is connected to the floor tunnel 12. For this reason, as shown by the white arrow 91 in FIG. 4, when an impact force is input to the rocker 11 from the right side of the vehicle 60 due to a side collision, a rotational moment that rotates the rocker 11 counterclockwise is applied to the rocker 11 as shown by the arrow 94 in FIG. 4. The rotational moment applied to the rocker 11 becomes a rotational force that rotates the side end portion 20B of the floor cross member 20 counterclockwise.

[0037] Further, the impact force input to the rocker 11 is transmitted to the pressing flange 35 through the upper horizontal plate 31 and the end vertical plate 34 of the gusset 30 as shown by the white arrow 92 in FIG. 4. Then, the pressing flange 35 presses downward the strength reduction portion 71 where the slit 26 of the web 21 is disposed as shown by the white arrow 93.

[0038] As shown in FIG. 5, due to the downward pressing force from the pressing flange 35 and the rotational force transmitted from the rocker 11, the side end portion 20B of the floor cross member 20 bends and deforms counterclockwise as shown by the dashed line and the arrows 96B and 97 in FIG. 5. Further, the general portion 20A of the floor cross member 20 bends and deforms in the clockwise direction as shown by the arrow 96A and the dashed line in FIG. 5 due to the downward force from the pressing flange 35. As a result, the floor cross member 20 bends downward at the strength reduction portion 71.

[0039] When the floor cross member 20 bends downward at the strength reduction portion 71, the lower right portions 42B and 43B of the seat bracket 40 connected to the side end portion 20B of the floor cross member 20 rotate and deform counterclockwise together with the side end portion 20B. Further, the middle lower portions 42A and 43A of the seat bracket 40 connected to the general portion 20A of the floor cross member 20 rotate and deform clockwise together with the general portion 20A. For this reason, the lower right portions 42B and 43B and the middle lower portions 42A and 43A deform so as to open in the vehicle width direction. As a result, the front plate 42, the rear plate 43, and the upper plate 41 of the seat bracket 40 bend downward at the low strength portion 72.

[0040] In this way, when the floor cross member 20 and the seat bracket 40 bend downward, the rocker 11 enters leftward while rotating counterclockwise. Since the seat bracket 40 is disposed apart from the rocker 11, before the rocker 11 contacts the seat bracket 40, the gasket 30 is rotated counterclockwise and compressed and deformed in the vehicle width direction. Then, when the gasket 30 deforms so as to collapse in the vehicle width direction, the rocker 11 rotates the seat bracket 40 counterclockwise and compresses and deforms it in the vehicle width direction. As a result, the floor cross member 20, the gasket 30, and the seat bracket 40 deform upward so as to overlap each other and deform inward in the vehicle width direction, absorbing impact energy.

[0041] As described above, in the vehicle underbody structure 10, when a force directed downward from the gusset 30 to the strength reduction portion 71 is transmitted during a side impact, the seat bracket 40 undergoes a downward folding deformation with the low-strength portion 72 as the folding starting point, and the floor cross member 20 undergoes a downward folding deformation starting from the strength reduction portion 71 provided at a position corresponding to the low-strength portion 72. Thus, in the vehicle underbody structure 10, the folding position of the floor cross member 20 can be controlled in the vicinity of the strength reduction portion 71, so that the amount of deformation of the floor panel 13 during a side impact can be reduced.

[0042] Also, in the vehicle underbody structure 10, during a side impact, the rocker 11 deforms upward, the seat bracket 40 and the floor cross member 20 deform downward, and the seat bracket 40 at a portion outside the vehicle width direction from the low-strength portion 72, the floor cross member 20 outside the vehicle width direction from the strength reduction portion 71, and the gusset 30 deform upward and inward in the vehicle width direction so as to overlap each other. Thereby, the impact energy can be absorbed.

[0043] Next, with reference to FIGS. 6 and 7, the deformation of a conventional vehicle underbody structure 100 that does not have the strength reduction portion 71 and the low-strength portion 72 and does not control the folding position of the floor cross member 20 like the vehicle underbody structure 10, and the vehicle underbody structure 100 when the vehicle 160 having the vehicle underbody structure 100 is subjected to a side impact will be described. In addition, the same parts as those of the vehicle underbody structure 10 described above with reference to FIGS. 1 to 5 are denoted by the same reference numerals and the description thereof is omitted. In addition, the broken line in FIG. 7 indicates the vehicle underbody structure 100 after deformation.

[0044] As shown in FIG. 6, the vehicle underbody structure 100 includes a rocker 11, a floor panel 13, a floor cross member 20, and a seat bracket 140. The vehicle underbody structure 100 does not include a gusset 30. The upper plate 141 of the seat bracket 140, a front plate (not shown), and a rear plate 143 are connected to the inner plate 11B of the rocker 11 via a fixed flange 146. Also, the front plate and the rear plate 143 are fixed to the front flange 22 and the rear flange 23 of the floor cross member 20 by spot welding 89. Further, an end flange 145 connected to the lower end of the end plate 144 is fixed to the upper surface of the web 21 of the floor cross member 20 by spot welding (not shown).

[0045] When a vehicle 160 equipped with the vehicle underbody structure 100 configured as described above is side - struck and an impact force is input to the rocker 11 as shown by the white arrow 101 in FIG. 6, a rotational moment that rotates the rocker 11 counterclockwise is applied to the rocker 11 as shown by the arrow 103 in FIG. 6. The rotational moment applied to the rocker 11 becomes a rotational force that rotates the seat bracket 140 counterclockwise. As a result, a downward force as shown by the white arrow 102 is applied to the end flange 145 of the seat bracket 140.

[0046] Then, due to this downward force, as shown by the dashed line and the arrows 106B and 107 in FIG. 7, the portion of the floor cross member 20 to the right of the end flange 145 and the seat bracket 140 are bent and deformed counterclockwise. Also, the portion of the floor cross member 20 to the left of the end flange 145 is bent and deformed clockwise as shown by the arrow 106A. As a result, the seat bracket 140 and the floor cross member 20 are bent and deformed downward at the position of the end flange 145.

[0047] In this way, when the floor cross member 20 is bent downward at the position of the end flange 145, the portion on the right side of the end flange 145 of the floor cross member 20 and the seat bracket 140 are bent and deformed counterclockwise so that the rocker 11 side moves upward. At this time, the floor panel 13 connected to the portion on the right side of the end flange 145 of the floor cross member 20 is rolled up upward, and damage to the floor panel 13 occurs.

[0048] On the other hand, in the vehicle lower structure 10 shown in FIG. 5, when a side impact occurs, the seat bracket 40 and the floor cross member 20 are bent and deformed downward at the strength reduction portion 71 and the low strength portion 72. The length of the floor cross member 20 on the right side of the strength reduction portion 71 is shorter than the portion on the right side of the end flange 145 of the vehicle lower structure 100. For this reason, in the vehicle lower structure 10, the portion of the floor panel 13 that deforms upward during a side impact is shorter than that of the vehicle lower structure 100, and damage to the floor panel 13 can be suppressed.

[0049] In this way, the vehicle lower structure 10 that can control the bending position of the floor cross member 20 has a shorter portion of the floor panel 13 that deforms upward during a side impact compared to the conventional vehicle lower structure 100 that does not control the bending position of the floor cross member 20, and damage to the floor panel 13 can be suppressed.

[0050] Next, referring to FIG. 8, the vehicle lower structure 110 of another embodiment will be described. The same parts as those of the vehicle lower structure 10 described above with reference to FIGS. 1 to 5 are denoted by the same reference numerals, and the description thereof will be omitted.

[0051] The vehicle lower structure 110 shown in FIG. 8 is provided with a fold bead 29 on the floor cross member 20 instead of the slit 26. The fold bead 29 is a recess provided at the front connection ridge line 22M between the web 21 and the front flange 22, and at the rear connection ridge line 23M between the web 21 and the rear flange 23. The fold bead 29 constitutes the strength reduction portion 73 of the floor cross member 20.

[0052] When the vehicle 65 having the vehicle underbody structure 110 shown in FIG. 8 is side - struck, the transmission and deformation of the impact force of each part are the same as those when the vehicle 60 having the vehicle underbody structure 10 described above is side - struck. The vehicle underbody structure 110 has the same functions and effects as the vehicle underbody structure 10.

[0053] In the above description, as the strength - reducing portions 71 and 73, it was described that the slit 26 or the fold bead 29 is provided in the floor cross - member 20, but it is not limited to this. For example, instead of the slit 26, a plurality of holes may be arranged side by side in the vehicle longitudinal direction. Also, instead of providing the fold bead 29 on the front connection ridge line 22M and the rear connection ridge line 23M, a V - shaped fold may be provided in the web 21 extending in the vehicle longitudinal direction. Further, although the inverted U - shaped notch 46 was described as the low - strength portion 72, it is not limited to this as long as the lower right portions 42B and 43B are connected to the side end portion 20B and the middle lower portions 42A and 43A are connected to the general portion 20A. For example, the shape of the notch 46 may be an inverted V - shape, a semi - circular shape, or a rectangular shape.

Explanation of Reference Numerals

[0054] 10, 100, 110 Vehicle underbody structure, 11 Rocker, 11A Ceiling panel, 11B Inner panel, 11C Inclined panel, 11D Floor panel, 11E Outer panel, 12 Floor tunnel, 13 Floor panel, 13A Floor flat part, 13B Right side part, 13C Rocker connection part, 15, 20 Floor cross member, 16, 18, 47, 51 Bolt hole, 20A General part, 20B Side end part, 21 Web, 22 Front flange, 22A, 23A Body part, 22B, 23B Right end part, 22M Front connection ridge line, 23 Rear flange, 23M Rear connection ridge line, 24 Front arm, 24A, 25A Flat part, 24B, 25B Inclined part, 24C, 25C Connection flange, 25 Rear arm, 26 Slit, 29 Folded bead, 30 Gusset, 31 Upper horizontal plate, 32 Front vertical plate, 33 Rear vertical plate, 34 End vertical plate, 35 Pressing flange, 36, 146 Fixed flange, 37 Hole, 40, 140 Seat bracket, 41, 141 Upper plate, 42 Front plate, 42A, 43A Middle lower part, 42B, 43B Right lower part, 43, 143 Rear plate, 44, 144 End plate, 45, 145 End flange, 46 Notch, 48 Nut retaining plate, 49 Nut, 50 Connection bracket, 60, 65, 160 Vehicle, 61 Floor structure, 71, 73 Strength reduction part, 72 Low strength part.

Claims

1. A rocker disposed on a side portion of a vehicle and extending in the longitudinal direction of the vehicle, a floor cross member connected to the rocker and extending in the vehicle width direction, a gusset connected to a side end portion of the floor cross member and an inner surface of the rocker in the vehicle width direction, a seat bracket disposed spaced apart from the rocker and attached to the floor cross member so as to straddle the side end portion of the floor cross member and a general portion adjacent to the inner side in the vehicle width direction of the side end portion, wherein the seat bracket is a longitudinal member extending in the vehicle width direction, and a low-strength portion is provided at the center in the longitudinal direction, the floor cross member is provided with a strength-reducing portion at a position corresponding to the low-strength portion, the gusset is connected to the side end portion of the floor cross member such that an inner end in the vehicle width direction overlaps the strength-reducing portion, A vehicle underbody structure characterized by the above.

2. The vehicle underbody structure according to claim 1, wherein the floor cross member is connected to a lower portion of the rocker, the gusset is connected to an inner surface of the rocker in the vehicle width direction above the floor cross member, the seat bracket is an inverted U-shaped cross-sectional member extending in the vehicle width direction and is attached to the floor cross member so as to cover the gusset from above, A vehicle underbody structure characterized by the above.

3. The vehicle underbody structure according to claim 2, wherein the seat bracket is an inverted U-shaped cross-sectional member including an upper plate, a front plate, and a rear plate, the low-strength portion is an inverted U-shaped notch provided in the front plate and the rear plate, a portion outside the vehicle width direction of the front plate and the rear plate with respect to the notch is connected to a side end portion outside the vehicle width direction of the strength-reducing portion of the floor cross member, a portion inside the vehicle width direction of the front plate and the rear plate with respect to the notch is connected to the general portion inside the vehicle width direction of the strength-reducing portion of the floor cross member, A vehicle underbody structure characterized by the above.

4. The vehicle underbody structure according to claim 3, wherein the floor cross member is a hat-shaped cross-sectional member including a web, a front flange, and a rear flange, and is arranged such that the web is on the upper side, the strength-reducing portion is a slit extending in the longitudinal direction of the vehicle provided in the web, A vehicle underbody structure characterized by the above.

5. The vehicle underbody structure according to claim 3, The floor cross member is a hat-shaped cross-sectional member including a web, a front flange, and a rear flange, and is arranged such that the web is upward. The strength reduction portion is a fold bead provided at a front connection ridge line between the web and the front flange and a rear connection ridge line between the web and the rear flange. A vehicle underbody structure characterized by the above.

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