Vehicle underbody structure

Abstract

To provide a lower vehicle body structure of a vehicle which can inhibit transmission of vibrational energy from a suspension to a vehicle body in addition to an impact resistance function for withstanding a collision load occurring during frontal collision and small overlap collision.SOLUTION: A vehicle body 1 includes: floor lower frames 7 each of which is fixed at a front end to a rear end of a front side frame 2 and fixed at a rear end to a lower surface of a floor panel 6 and has a fixing part 7c to which a suspension of a vehicle is fixed; first floor upper frames 8 each of which is fixed at a front end to a dash panel 3 and fixed at a rear end to an upper surface of the floor panel 6 and extends along the floor lower frame 7; second floor upper frames 9 each of which connects the dash panel 3 with a hinge pillar 5 behind the front side frame 2; and connection members 10 each of which connects the first floor upper frame 8 with a front end 4a of a side sill 4 in a vehicle width direction above the floor panel 6.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, various vehicle body structures have been proposed as structures for dispersing the collision load during a collision (hereinafter referred to as a frontal collision) between an obstacle approaching the vehicle relatively from the front of the vehicle and the vehicle. For example, in Patent Document 1, a load input from a front side frame at the front of the vehicle is dispersed to a tunnel side member on the center side in the vehicle width direction and a side sill on both sides of the vehicle via a side frame extension under the floor panel, thereby dispersing the load in the in-plane direction of the floor panel. A vehicle lower structure is disclosed.

[0003] Specifically, the vehicle lower structure described in Patent Document 1 basically includes a pair of front side frames extending in the vehicle front-rear direction on both sides in the width direction of the vehicle body front portion, a dashboard that spreads in the vehicle width direction on the rear side of the front side frame and partitions the inside and outside of the passenger compartment, and a pair of side sills located on the rear side of the dashboard and outside the vehicle width direction of each front side frame and extending in the vehicle front-rear direction. A floor panel stretched between the pair of side sills and extending rearward from the lower rear portion of the dashboard, a floor tunnel that bulges upward at the center in the width direction of the floor panel and extends in the vehicle front-rear direction, and a pair of tunnel side members extending in the vehicle front-rear direction along both side portions of the floor tunnel.

[0004] Furthermore, this vehicle understructure includes a pair of side frame extensions fixed to the rear ends of each of the pair of front side frames and extending rearward along the underside of the dashboard and the underside of the floor panel. Each side frame extension is located below the dashboard and has a side sill-side extension portion, a tunnel-side extension portion, and a branching portion that branches off from these portions. The side sill-side extension portion extends from the branching portion, sloping outward and rearward in the vehicle width direction, and is joined to the side sill. The tunnel-side extension portion extends from the branching portion, sloping inward and rearward in the vehicle width direction, and is joined to the tunnel side member.

[0005] Each branching point is equipped with a subframe mounting section for attaching the suspension subframe to the underside of the vehicle body.

[0006] Furthermore, the front end of each side sill and the branching point of the side frame extension are connected by a connecting member (a so-called torque box) that extends in the width direction of the vehicle. This connecting member allows the vehicle to withstand collision loads from the side. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2011 / 055695 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the above structure, the side sill and the side frame extension are connected by a connecting member. By having such a connecting member, when a widthwise impact load is applied to the front of the side sill during a small overlap collision (hereinafter referred to as SORB), that is, a partial frontal collision at a position biased in the width direction of the vehicle, the side sill can withstand the collision load by obtaining a widthwise reaction force to the impact load from the connecting member and the side frame extension connected to the side sill.

[0009] However, in a structure where the side sill and side frame extension are connected by a connecting member, during normal driving, the vibration energy in the width direction generated by the suspension is transmitted from the side frame extension on the underside of the floor panel to which the suspension is attached, through the connecting member to the side sill, and further transmitted to the entire vehicle body through the side sill. As a result, factors that impair the comfort of the vehicle while driving (noise, vibration, harshness, etc., so-called NVH) are exacerbated.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a vehicle lower body structure that can withstand impact loads during frontal collisions and SORBs, as well as suppress the transmission of vibration energy from the suspension to the vehicle body. [Means for solving the problem]

[0011] To solve the aforementioned problems, the lower body structure of the vehicle of the present invention comprises a pair of front side frames extending in the longitudinal direction of the vehicle on both sides in the width direction of the front of the vehicle body, a dash panel located behind the pair of front side frames and separating the interior and exterior of the passenger compartment, a pair of side sills arranged on both sides of the vehicle body behind the dash panel and extending in the longitudinal direction of the vehicle, a pair of hinge pillars extending vertically at the front ends of each of the pair of side sills, a floor panel positioned between the pair of side sills and fixed to each of the pair of side sills, a front end fixed to the rear end of each of the pair of front side frames, and extending rearward below the floor panel. The invention is characterized by comprising: an underfloor frame having a rear end fixed to the lower surface of the floor panel and a fixing portion positioned between the front end and the rear end to which the vehicle's suspension is fixed; a first upper floor frame having a front end fixed to the dash panel behind the front side frame and a rear end fixed to the upper surface of the floor panel, positioned above the floor panel and extending along the underfloor frame; a second upper floor frame connecting the dash panel and the hinge pillar behind the front side frame; and a connecting member connecting the first upper floor frame and the front end of the side sill in the vehicle width direction above the floor panel.

[0012] In this configuration, when a vehicle is involved in a frontal collision, the impact load received by the front side frame is divided and transmitted to the first upper floor frame and the second upper floor frame in the passenger compartment behind the dash panel and above the floor panel. Therefore, the impact load transmitted from the front side frame can be distributed and transmitted in the in-plane direction of the floor panel through two paths, the first upper floor frame and the second upper floor frame, enabling the vehicle to exhibit frontal collision performance (i.e., high impact resistance against frontal collisions).

[0013] Furthermore, inside the vehicle, the connecting member connects the first floor upper frame and the side sill in the vehicle width direction. Therefore, when an inward impact load in the vehicle width direction is applied to the front end of the side sill during a SORB collision, it generates a reaction force in the vehicle width direction, thus enabling even greater SORB collision performance (i.e., high impact resistance against SORB collisions).

[0014] Furthermore, in the above structure, the connecting member connects the first upper floor frame and the side sill at a position offset vertically (i.e., separated via the floor panel) from the fixed portion on the underfloor frame where the suspension is solidified. This makes it possible to suppress the transmission of loads in the vehicle width direction input from the suspension to the underfloor frame to other vehicle body components such as the side sill and floor panel. Therefore, it becomes possible to suppress the transmission of vibration energy from the suspension to the vehicle body.

[0015] In the lower body structure of the vehicle described above, it is preferable that the underfloor frame and the first upper floor frame each have an inclined portion that slopes toward the center in the vehicle width direction as it moves from the front end toward the rear, and a straight portion that extends rearward along the longitudinal direction of the vehicle from the rear end of the inclined portion.

[0016] With this configuration, the lower floor frame and the first upper floor frame are bent at the boundary between the inclined and straight sections, resulting in a roughly V-shape in plan view. Since the straight section is separated from the second upper floor frame, it is possible to transmit the collision load over a wide area of ​​the floor panel behind the front side frame.

[0017] In the lower body structure of the above-described vehicle, it is preferable that the floor tunnel further extends in the vehicle longitudinal direction and bulges upward at the center of the floor panel in the vehicle width direction, and that the straight sections of the lower floor frame and the first upper floor frame are composed of tunnel side members that extend to the rear of the vehicle along both ends of the floor tunnel.

[0018] With this configuration, the straight section is located furthest from the second floor upper frame in the section between the side sill of the floor panel and the floor tunnel, making it possible to transmit the collision load over the widest possible area of ​​the floor panel behind the front side frame. Moreover, since the straight section extends in the longitudinal direction of the vehicle along both ends of the floor tunnel, it is also possible to reinforce the floor tunnel.

[0019] In the lower body structure of the above-described vehicle, it is preferable that the underfloor frame and the first upper floor frame cooperate with the floor panel to form a closed cross section.

[0020] With this configuration, the underfloor frame and the first upper floor frame extending along it cooperate with the floor panel to form a closed cross-section, thereby improving the rigidity of the underfloor frame and the first upper floor frame, and improving the frontal impact performance and SORB collision performance.

[0021] In the lower body structure of the vehicle described above, the dash panel preferably has a main body portion extending in the vertical direction and a kick-up portion extending rearward and downward from the lower end of the main body portion, and the front end of the first floor frame and the front end of the second floor frame are fixed to the main body portion in an overlapping state.

[0022] With this configuration, during a frontal collision or SORB (Sudden Impact Relief), the collision load is transmitted from the main body portion of the dash panel, which extends vertically, to the first and second floor upper frames along the longitudinal direction of the vehicle, thereby improving the efficiency of load transmission to these first and second floor upper frames. Moreover, since the first and second floor upper frames are fixed to the main body portion while overlapping each other, the collision load is less likely to be transmitted to the kick-up portion, which is far from the main body portion, thus suppressing deformation of the kick-up portion.

[0023] In the lower body structure of the vehicle described above, it further includes a dash cross member extending in the vehicle width direction along the front surface of the dash panel, and it is preferable that the end portions on both sides in the vehicle width direction of the dash cross member and the front end portion fixed to the dash panel in the second floor upper frame overlap each other when viewed from the front.

[0024] According to such a configuration, since the end portions on both sides in the vehicle width direction of the dash cross member extending in the vehicle width direction and the front end portion fixed to the dash panel in the second floor upper frame overlap each other when viewed from the front, the collision load received by the dash cross member can be reliably transmitted to the hinge pillar and the side sill via the second floor upper frame, so that the vehicle body rigidity can be improved.

[0025] In the lower body structure of the vehicle described above, it is preferable that the end portions on both sides in the vehicle width direction of the dash cross member are provided so as to overlap with the rear end portion of the front side frame when viewed from the front.

[0026] According to such a configuration, the collision load can be reliably transmitted from the front side frame to both the dash cross member and the second floor upper frame, so that the vehicle body rigidity is improved.

[0027] In the lower body structure of the vehicle described above, it is preferable that the first floor upper frame, the second floor upper frame, and the connecting member are arranged in a triangular shape in plan view.

[0028] According to such a configuration, a truss structure (that is, a triangular skeletal structure) is formed in plan view by the first floor upper frame, the second floor upper frame, and the connecting member, so that the load transmission efficiency can be improved.

[0029] In the lower body structure of the above-described vehicle, the hinge pillar is preferably a hollow cylindrical member, and a segmental member is provided near the lower end of the internal space of the hinge pillar so as to divide the space vertically, and the rear end of the second floor frame is preferably fixed at the height position of the segmental member in the hinge pillar.

[0030] With this configuration, the position on the hinge pillar where the joint member is provided has the highest rigidity, and by fixing the second floor frame to that position on the hinge pillar, it is possible to achieve high frontal impact performance and SORB collision performance.

[0031] In the lower body structure of the vehicle described above, it is preferable that the front end of the first floor frame and the front end of the second floor frame fixed to the dash panel overlap in the longitudinal direction of the vehicle.

[0032] With this configuration, the collision load from the front side frame can be reliably distributed and transmitted to the first floor upper frame and the second floor upper frame, improving the load transmission efficiency to the floor panel and enabling high frontal impact performance and SORB collision performance. [Effects of the Invention]

[0033] As described above, the lower body structure of the vehicle according to the present invention not only provides impact resistance to withstand collision loads during frontal collisions and SORBs, but also achieves suppression of vibration energy transmission from the suspension to the vehicle body. [Brief explanation of the drawing]

[0034] [Figure 1] This is a plan view of the front portion of a vehicle body showing the lower body structure of a vehicle according to an embodiment of the present invention. [Figure 2] Figure 1 is a bottom view of the front portion of the vehicle body. [Figure 3] Figure 1 is a perspective view of the front portion of the vehicle body, seen from the upper left rear side of the vehicle. [Figure 4] Figure 1 is a perspective view of the front portion of the vehicle body, seen from the upper right rear side of the vehicle. [Figure 5] Figure 1 is a cross-sectional diagram illustrating the front portion of the vehicle body as seen from the rear of the vehicle. [Figure 6] This is an enlarged plan view showing the first upper frame, the second upper frame, and the connecting member that connects the first upper frame and the side sill in Figure 1. [Figure 7] Figure 1 is a perspective view of the front portion of the vehicle body, seen from the lower left front side of the vehicle. [Figure 8] This is an enlarged perspective view of the area where the rear end of the front side frame, the front end of the first lower frame, and the vehicle width-direction end of the dash cross member overlap in Figure 7. [Figure 9] This is an enlarged bottom view showing that the inclined portion of the first lower frame in Figure 7 has a part that extends rearward along the vehicle's longitudinal direction, behind the fixed portion. [Figure 10] This is a cross-sectional view along line XX in Figure 6. [Figure 11] Figure 6 shows a cross-sectional view along the line XI-XI. [Figure 12] This is a cross-sectional view taken along line XII-XII in Figure 6. [Modes for carrying out the invention]

[0035] The lower body structure of a vehicle according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0036] As shown in Figures 1 to 8, the vehicle body 1 to which the lower body structure of the vehicle according to the embodiment of the present invention is applied comprises, as an overall configuration, a pair of front side frames 2 extending in the vehicle longitudinal direction X on both sides in the vehicle width direction Y of the front part (forward X1 side) of the vehicle body 1, a dash panel 3 located rear X2 of the pair of front side frames 2, a pair of side sills 4 arranged on both sides of the vehicle body 1 on the rear X2 side of the dash panel 3 and extending in the vehicle longitudinal direction X, a pair of hinge pillars 5 extending in the vertical direction Z at the front end 4a of each of the pair of side sills 4, a floor panel 6 arranged between the pair of side sills 4 and fixed to each of the pair of side sills 4, a floor tunnel 11 bulging upward Z1 at the center of the floor panel 6 in the vehicle width direction Y and extending in the vehicle longitudinal direction X, and a dash cross member 14 extending in the vehicle width direction Y along the front surface of the dash panel 3 (specifically the main body portion 3a described later). Reference numeral 21 denotes a bumper beam that extends in the vehicle width direction Y and is connected to the front ends of a pair of front side frames 2.

[0037] The dash panel 3 is a plate-shaped member that extends in the vehicle width direction Y so as to demarcate the inside and outside of the passenger compartment PR (for example, the passenger compartment PR and the engine room ER in front of it) at the rear X2 of the pair of front side frames 2. More specifically, the dash panel 3 of this embodiment has a main body portion 3a that extends straight in the vertical direction Z and a kick-up portion 3b that extends rearward X2 and downward Z2 from the lower end of the main body portion 3a (see Figures 3 and 7 in particular). The kick-up portion 3b is the part of the passenger compartment PR that is close to the occupant's feet, and it is preferable that it curves and extends rearward X2 and downward Z2 so as not to interfere with the feet. The rear end of the kick-up portion 3b and the front end of the floor panel 6 are connected by welding or the like.

[0038] The dash panel 3 further includes an upper flange portion 3c (see Figures 1 and 3) extending forward X1 from the upper end of the main body portion 3a, and a pair of side portions 3d (see Figures 3-4) that spread outward in the vehicle width direction Y and inclined rearward X2 between both widthwise ends of the main body portion 3a and the hinge pillar 5.

[0039] The hinge pillar 5 in this embodiment is a hollow cylindrical member. A nodal member 15 (see Figures 4-6) is provided near the lower end 5b of the internal space 5a of the hinge pillar 5 so as to divide the space 5a in the vertical direction Z.

[0040] As shown in Figures 7-8, the ends 14a on both sides of the dash cross member 14 in the vehicle width direction Y overlap with the rear end 2a of the front side frame 2 in a front view (i.e., viewed from the front of the vehicle X1). Specifically, the dash cross member 14 in this embodiment penetrates the rear end 2a of the front side frame 2. Of the ends 14a of the dash cross member 14 in the vehicle width direction, at least the flange portion protrudes outward in the vehicle width direction from the front side frame 2.

[0041] Furthermore, in order to enhance the frontal impact performance and SORB collision performance of the vehicle body 1, the vehicle body 1 of this embodiment is equipped with a pair of lower floor frames 7 on both sides of the floor tunnel 11 as members below the floor panel 6, and further equipped with three types of members above the floor panel 6: a pair of first upper floor frames 8, a pair of second upper floor frames 9, and a pair of connecting members 10. Each of these members will be described below.

[0042] As shown in Figures 2 to 11 (especially Figures 2 and 7), the underfloor frame 7 is a member that extends rearward X2 from the rear end 2a of the front side frame 2 in front of the main body 3a of the dash panel 3 along the underside of the kick-up portion 3b, and further extends along the underside of the floor panel 6. The underfloor frame 7 is a member with a roughly hat-shaped cross section (i.e., a cross section with a pair of flange portions 7f as shown in Figures 10 to 11) that works in cooperation with the floor panel 6 and the kick-up portion 3b of the dash panel 3 to form closed sections C1 and C2 (see Figures 10 to 11).

[0043] Specifically, as shown in Figures 1 and 3-11, the underfloor frame 7 has a front end portion 7a fixed to the rear ends of each of the pair of front side frames 2 by welding or the like, a rear end portion 7b extending rearward X2 below the floor panel 6 and fixed to the underside of the floor panel 6 by welding or the like, and a fixing portion 7c positioned between the front end portion 7a and the rear end portion 7b to which the vehicle's suspension (not shown) is fixed. The fixing portion 7c has a configuration that allows the suspension to be fixed, for example, a plane facing downward Z2 of the vehicle body, bolt holes formed in the plane, and other necessary components.

[0044] Furthermore, the underfloor frame 7, in a plan view, has an inclined portion 7d that slopes toward the center side (the side of the floor tunnel 11) in the vehicle width direction Y as it moves from the front end 7a toward the rear X2, and a straight portion 7e that extends from the rear end of the inclined portion 7d toward the rear X2 along the vehicle longitudinal direction X. In this embodiment, the rear end 7b of the underfloor frame 7 is composed of the straight portion 7e, but the shape of the rear end 7b is not an essential configuration of the present invention, so it may have a shape other than the straight portion 7e.

[0045] In this embodiment, the straight portion 7e of the underfloor frame 7 is composed of tunnel side members 12 that extend towards the rear X2 of the vehicle along both ends of the floor tunnel 11 on the underside of the floor panel 6.

[0046] As shown in Figure 9, the portion of the inclined section 7d of the underfloor frame 7 immediately behind the fixed section 7c to which the suspension is attached has a portion 7d1 that extends along the longitudinal direction X of the vehicle, making it partially wider and thus improving bending rigidity.

[0047] The first upper floor frame 8, as shown in Figures 1 and 3-6, is positioned inside the passenger compartment PR, extends along the lower floor frame 7 above it, and works in cooperation with the kick-up portion 3b of the floor panel 6 and the dash panel 3 to form closed sections C3 and C4 (see Figures 10-11). The frame has a roughly hat-shaped cross section (i.e., a cross section with a pair of flange portions 8f as shown in Figures 10-11). The first upper floor frame 8 is fixed to the kick-up portion 3b of the dash panel 3 and the upper surface of the floor panel 6 by welding or other means.

[0048] The first upper floor frame 8 is located within the passenger compartment PR and overlaps the upper side of the lower floor frame 7. It extends rearward X2 from the rear side of the main body 3a of the dash panel 3 along the upper surface of the kick-up portion 3b, and further extends along the upper surface of the floor panel 6.

[0049] The first floor frame 8 has a front end portion 8a fixed to the dash panel 3 by welding or the like at the rear X2 of the front side frame 2, and a rear end portion 8b fixed to the upper surface of the floor panel 6 by welding or the like.

[0050] Furthermore, the first upper floor frame 8, like the lower floor frame 7, has a portion that slopes toward the center of the vehicle body 1 in the vehicle width direction Y as it moves toward the rear X2 of the vehicle.

[0051] Specifically, the first upper floor frame 8 has an inclined portion 8d and a straight portion 8e, corresponding to the inclined portion 7d and straight portion 7e of the lower floor frame 7. That is, the first upper floor frame 8 has an inclined portion 8d that slopes toward the center of the vehicle width direction Y as it moves from the front end 8a toward the rear X2, and a straight portion 8e that extends from the rear end of the inclined portion 8d toward the rear X2 along the longitudinal direction X of the vehicle. In this embodiment, the rear end 8b of the first upper floor frame 8 is composed of a straight portion 8e, but the shape of the rear end 8b is not an essential configuration of the present invention, so it may have a shape other than the straight portion 8e.

[0052] In this embodiment, the straight section 8e of the first floor frame 8 is formed by tunnel side members 13 that extend towards the rear X2 of the vehicle along both ends of the floor tunnel 11, above the floor panel 6.

[0053] The second upper floor frame 9, like the first upper floor frame 8 described above, is a roughly hat-shaped member positioned on the inside of the passenger compartment PR, that is, behind the main body portion 3a of the dash panel 3. The second upper floor frame 9 extends along the rearward-sloping side portions 3d on both sides of the main body portion 3a of the dash panel 3, and connects the dash panel 3 and the hinge pillar 5 at the rear X2 of the front side frame 2. The second upper floor frame 9 has a front end portion 9a that is fixed to the main body portion 3a of the dash panel 3 by welding or the like, overlapping with the front end portion 8a of the first upper floor frame 8, and a rear end portion 9b that is fixed to the lower end portion 5b of the hinge pillar 5 by welding or the like.

[0054] Therefore, in this embodiment, the front end 8a of the first floor frame 8 and the front end 9a of the second floor frame 9, which is fixed to the dash panel 3, are in a positional relationship that overlaps in the vehicle longitudinal direction X. In this embodiment, the portion between the front end 9a and the rear end 9b of the second floor frame 9 is fixed to the side portion 3d of the dash panel 3 by welding or the like, but this is not an essential configuration of the present invention.

[0055] As shown in Figure 8, the ends 14a on both sides in the vehicle width direction Y of the dash cross member 14 and the front end 9a fixed to the dash panel 3 on the second floor upper frame 9 overlap when viewed from the front.

[0056] As shown in Figures 4-5, the rear end portion 9b of the second floor upper frame 9 is fixed at the height position where the joint member 15 of the hinge pillar 5 is provided.

[0057] As shown in Figures 2-6 and Figure 12, the connecting member 10 (so-called torque box) is located inside the passenger compartment PR, that is, on the rear side of the main body 3a of the dash panel 3, and is a member that extends in the vehicle width direction Y along the floor panel 6 on both sides of the floor tunnel 11. The connecting member 10 has a substantially hat-shaped cross section (i.e., a cross section with a pair of flange portions 10f as shown in Figure 12) that protrudes above Z1 above the floor panel 6. The connecting member 10 is fixed to the upper surface of the floor panel 6 by welding or the like at the flange portions 10f, and works in cooperation with the floor panel 6 to form a closed cross section.

[0058] The connecting member 10 is fixed at both ends to the first floor frame 8 and the front end 4a of the side sill 4 by welding or the like at Z1 above the floor panel 6, thereby connecting the first floor frame 8 and the front end 4a of the side sill 4 in the vehicle width direction Y.

[0059] As shown in Figure 6, the first floor frame 8, the second floor frame 9, and the connecting member 10 are arranged in a triangular shape in plan view. Specifically, the first floor frame 8, the second floor frame 9, and the connecting member 10 are arranged as follows: The front end 8a of the first floor frame 8 is positioned closer to the center in the vehicle width direction Y than the hinge pillar 5. The inclined portion 8d of the first floor frame 8 extends from the front end 8a toward the center in the vehicle width direction Y. The second floor frame 9 extends diagonally backward outward in the vehicle width direction Y as it approaches the rear X2 of the vehicle, connecting the front end 8a of the first floor frame 8 and the hinge pillar 5. The connecting member 10 extends in the vehicle width direction Y as described above, connecting the inclined portion 8d of the first floor frame 8 and the front end 4a of the side sill 4 in the vehicle width direction Y. This makes it possible to construct a truss structure (i.e., a triangular skeletal structure) in plan view using the first floor frame 8, the second floor frame 9, and the connecting member 10.

[0060] (Features of this embodiment) (1) In the lower body structure of the vehicle of this embodiment, the body 1 has a configuration as described above, comprising a pair of front side frames 2, a dash panel 3, a pair of side sills 4, a pair of hinge pillars 5, and a floor panel 6, and further comprises a pair of underfloor frames 7, a pair of first upper floor frames 8, a pair of second upper floor frames 9, and a pair of connecting members 10 (torque boxes).

[0061] The underfloor frame 7 has a front end portion 7a fixed to the rear end of each of the pair of front side frames 2, a rear end portion 7b extending rearward X2 below the floor panel 6 and fixed to the underside of the floor panel 6, and a fixing portion 7c positioned between the front end portion 7a and the rear end portion 7b to which the vehicle's suspension is fixed.

[0062] The first upper floor frame 8 has a front end 8a fixed to the dash panel 3 at the rear X2 of the front side frame 2, and a rear end 8b fixed to the upper surface of the floor panel 6, and is located above the floor panel 6 Z1 and extends along the lower floor frame 7.

[0063] The second floor upper frame 9 connects the dash panel 3 and the hinge pillar 5 at the rear X2 of the front side frame 2.

[0064] The connecting member 10 connects the first floor frame 8 and the front end portion 4a of the side sill 4 in the vehicle width direction Y, above Z1 above the floor panel 6.

[0065] In this configuration, when a vehicle is involved in a frontal collision, the impact load received by the front side frame 2 is divided and transmitted to the first upper floor frame 8 and the second upper floor frame 9 within the passenger compartment PR behind the dash panel 3 X2 and above the floor panel 6. Therefore, the impact load transmitted from the front side frame 2 can be distributed and transmitted in the in-plane direction of the floor panel 6 through two paths, the first upper floor frame 8 and the second upper floor frame 9, enabling the vehicle to exhibit frontal collision performance (i.e., high impact resistance against frontal collisions).

[0066] Specifically, the first upper floor frame 8 works in cooperation with the lower floor frame 7 to transmit the load to the vicinity of the floor tunnel 11 on the widthwise center side of the floor panel 6, while the second upper floor frame 9 transmits the load to the vicinity of the side sills 4 on both widthwise ends of the floor panel 6 via the hinge pillar 5 and side sills 4. This makes it possible to distribute the load over a wide area in the in-plane direction of the floor panel 6 and transmit it to the floor panel 6.

[0067] Furthermore, within the vehicle compartment PR, the connecting member 10 connects the first floor upper frame 8 and the side sill 4 in the vehicle width direction Y. Therefore, when an inward impact load in the vehicle width direction Y is applied to the front end of the side sill 4 during a SORB collision, a reaction force in the vehicle width direction Y is generated, making it possible to further enhance SORB collision performance (i.e., high impact resistance against SORB collisions).

[0068] Furthermore, in the above structure, the connecting member 10 connects the first upper floor frame 8 and the side sill 4 at a position offset in the vertical direction Z from the fixed portion 7c to which the suspension is fixed in the lower floor frame 7. Therefore, it is possible to suppress the transmission of loads in the vehicle width direction Y from the suspension fixed to the fixed portion 7c to the lower floor frame 7 to other vehicle body components such as the side sill 4 and floor panel 6. Thus, it becomes possible to suppress the transmission of vibration energy from the suspension to the vehicle body 1.

[0069] (2) In the lower body structure of the vehicle according to this embodiment, the underfloor frame 7 and the first upper floor frame 8 each have inclined portions 7d and 8d that slope toward the center of the vehicle width direction Y as they move from their respective front ends 7a and 8a toward the rear X2, and straight portions 7e and 8e that extend toward the rear X2 along the longitudinal direction X of the vehicle from the rear ends of the inclined portions 7d and 8d.

[0070] With this configuration, the lower floor frame 7 and the first upper floor frame 8 are bent at the boundaries between the inclined sections 7d, 8d and the straight sections 7e, 8e, respectively, resulting in a roughly V-shape in plan view. As a result, the straight sections 7e, 8e are moved away from the second upper floor frame 9, making it possible to transmit the collision load over a wide area of ​​the rear X2 floor panel 6 of the front side frame 2.

[0071] (3) In the lower body structure of the vehicle of this embodiment, the vehicle body 1 further includes a floor tunnel 11 that bulges upward Z1 at the center of the vehicle width direction Y of the floor panel 6 and extends in the vehicle longitudinal direction X. The straight sections 7e and 8e of the lower floor frame 7 and the first upper floor frame 8, respectively, are composed of tunnel side members 12 and 13 that extend rearward X2 of the vehicle along both ends of the floor tunnel 11.

[0072] With this configuration, the straight sections 7e and 8e are located furthest from the second floor upper frame 9 in the section between the side sill 4 of the floor panel 6 and the floor tunnel 11, making it possible to transmit the collision load over the widest possible area of ​​the floor panel 6 in the rear X2 of the front side frame 2. Moreover, since the straight sections 7e and 8e extend along both ends of the floor tunnel 11 in the longitudinal direction X (rear X2) of the vehicle, it is also possible to reinforce the floor tunnel 11.

[0073] (4) In the lower body structure of the vehicle of this embodiment, the underfloor frame 7 and the first upper floor frame 8 cooperate with the floor panel 6 to form closed sections C1 and C2, respectively, and in this embodiment, they further cooperate with the kick-up portion 3b of the dash panel 3 to form closed sections C3 and C4.

[0074] With this configuration, the underfloor frame 7 and the first upper floor frame 8 extending along it cooperate with the floor panel 6 and the kick-up portion 3b of the dash panel 3, respectively, to form closed sections C1 to C4. As a result, the rigidity of the underfloor frame 7 and the first upper floor frame 8 is improved, and the frontal impact performance and SORB collision performance are improved.

[0075] (5) In the lower body structure of the vehicle according to this embodiment, the dash panel 3 has a main body portion 3a that extends straight up and down in the vertical direction Z, and a kick-up portion 3b that extends rearward X2 and downward Z2 from the lower end of the main body portion 3a. The front end portion 8a of the first floor frame 8 and the front end portion 9a of the second floor frame 9 are fixed to the main body portion 3a in an overlapping state.

[0076] With this configuration, during a frontal collision or SORB, the collision load is transmitted from the main body portion 3a of the dash panel 3, which extends straight up and down in the vertical direction Z, to the first floor frame 8 and the second floor frame 9 along the vehicle's longitudinal direction X, thereby improving the efficiency of load transmission to the first floor frame 8 and the second floor frame 9. Moreover, since the first floor frame 8 and the second floor frame 9 are fixed to the main body portion 3a in an overlapping state, the collision load is less likely to be transmitted to the kick-up portion 3b, which is far from the main body portion 3a, thus suppressing deformation of the kick-up portion 3b.

[0077] (6) In the lower body structure of the vehicle of this embodiment, the vehicle body 1 further includes a dash cross member 14 that extends in the vehicle width direction Y along the front of the dash panel 3. The ends 14a on both sides in the vehicle width direction Y of the dash cross member 14 and the front end 9a fixed to the dash panel 3 on the second floor upper frame 9 overlap when viewed from the front.

[0078] With this configuration, the ends 14a on both sides in the vehicle width direction Y of the dash cross member 14, which extends in the vehicle width direction Y, and the front end 9a fixed to the dash panel 3 on the second floor frame 9 overlap in a front view. Therefore, the collision load received by the dash cross member 14 can be reliably transmitted to the hinge pillar 5 and side sill 4 via the second floor frame 9, thereby improving the rigidity of the vehicle body.

[0079] (7) In the lower body structure of the vehicle of this embodiment, the ends 14a on both sides of the dash cross member 14 in the vehicle width direction Y overlap with the rear end 2a of the front side frame 2 when viewed from the front. With this configuration, collision loads can be reliably transmitted from the front side frame 2 to both the dash cross member 14 and the second floor upper frame 9, thereby improving the rigidity of the vehicle body.

[0080] (8) In the lower body structure of the vehicle of this embodiment, the first upper floor frame 8, the second upper floor frame 9, and the connecting member 10 are arranged in a triangular shape in plan view. With this configuration, the first upper floor frame 8, the second upper floor frame 9, and the connecting member 10 form a truss structure (i.e., a triangular skeletal structure) in plan view, making it possible to improve load transmission efficiency.

[0081] (9) In the lower body structure of the vehicle according to this embodiment, the hinge pillar 5 is a hollow cylindrical member. A joint member 15 is provided near the lower end 5b of the internal space 5a of the hinge pillar 5 so as to divide the space 5a in the vertical direction Z. The rear end of the second floor upper frame 9 is fixed at the height position where the joint member 15 of the hinge pillar 5 is provided.

[0082] With this configuration, the position on the hinge pillar 5 where the joint member 15 is provided has the highest rigidity. Therefore, by fixing the second floor frame 9 to that position on the hinge pillar 5, it is possible to achieve high frontal impact performance and SORB collision performance.

[0083] (10) In the lower body structure of the vehicle according to this embodiment, the front end portion 8a of the first floor frame 8 and the front end portion 9a of the second floor frame 9, which is fixed to the dash panel 3, overlap in the longitudinal direction X of the vehicle.

[0084] With this configuration, the collision load from the front side frame can be reliably distributed and transmitted to the first floor frame 8 and the second floor frame 9, improving the load transmission efficiency to the floor panel 6 and enabling high frontal impact performance and SORB collision performance.

[0085] (modified version) (A) In the above embodiment, the front end 8a of the first floor frame 8 and the front end 9a of the second floor frame 9 overlap in the vehicle longitudinal direction X, but the present invention is not limited thereto. In the present invention, the second floor frame 9 only needs to connect the dash panel 3 and the hinge pillar 5 at the rear X2 of the front side frame 2, and the front end 9a of the second floor frame 9 may be fixed to the dash panel 3 at a position separated from the front end 8a of the first floor frame 8 in the vehicle width direction Y or the vertical direction Z.

[0086] (B) In the above embodiment, the underfloor frame 7 and the first upper floor frame 8 each have straight sections 7e and 8e extending rearward X2 along the longitudinal direction X of the vehicle from the rear ends of the inclined sections 7d and 8d. However, the straight sections 7e and 8e may be omitted (for example, a configuration having only the inclined sections 7d and 8d). In that case as well, it is possible to distribute the load in the in-plane direction of the floor panel 6. However, the configuration in which the underfloor frame 7 and the first upper floor frame 8 have both the inclined sections 7d and 8d and the straight sections 7e and 8e is preferable because it allows the collision load to be transmitted over a wide area of ​​the floor panel 6 rearward X2 of the front side frame 2. [Explanation of symbols]

[0087] 1. Vehicle body 2 Front side frame 2a Rear end 3. Dashboard 3a Main body 3b Kick-up section 4 Side sills 4a Front end 5. Hinged pillar 5a Space part 5b Bottom end 6 Floor Panels 7. Underfloor frame 7a Front end 7b Rear end 7c Fixed part 7d Slope 7e Straight section 8. Upper frame of the first floor 8a Front end 8b Rear end 8d Slope 8e Straight section 9. Upper frame of the second floor 9a Front end 9b Rear end 10 Connecting members 11 Floor Tunnel 12, 13 Tunnel side members 14 Dash Cross Member 14a End 15 section members C1~C4 Closed section PR cabin ER Engine Room

Claims

1. A pair of front side frames extending in the longitudinal direction of the vehicle on both sides in the width direction of the front of the vehicle body, A dash panel located behind the pair of front side frames, which separates the interior and exterior of the passenger compartment, A pair of side sills are positioned on both sides of the vehicle body at the rear of the aforementioned dashboard panel, extending in the longitudinal direction of the vehicle, A pair of hinge pillars extending vertically at the front end of each of the pair of side sills, A floor panel positioned between the pair of side sills and fixed to each of the pair of side sills, A floor frame having a front end fixed to the rear end of each of the pair of front side frames, a rear end extending rearward below the floor panel and fixed to the underside of the floor panel, and a fixing portion positioned between the front end and the rear end to which the vehicle's suspension is fixed, A first upper floor frame having a front end fixed to the dash panel at the rear of the front side frame and a rear end fixed to the upper surface of the floor panel, and positioned above the floor panel and extending along the lower floor frame, A second floor frame connecting the dash panel and the hinge pillar at the rear of the front side frame, A connecting member is provided above the floor panel to connect the first floor frame and the front end of the side sill in the vehicle width direction, A vehicle lower body structure characterized by having the following features.

2. The floor-under frame and the first floor-up frame each have an inclined portion that slopes toward the center in the vehicle width direction from the front end toward the rear, and a straight portion that extends rearward along the vehicle's longitudinal direction from the rear end of the inclined portion. The lower body structure of the vehicle according to feature 1.

3. The floor panel further comprises a floor tunnel that bulges upward at the center in the vehicle width direction and extends in the vehicle longitudinal direction, The straight sections of the floor lower frame and the first floor upper frame are each composed of tunnel side members that extend rearward along both ends of the floor tunnel. The lower body structure of the vehicle according to feature 2.

4. The floor-under frame and the first floor-up frame each cooperate with the floor panel to form a closed cross-section. A lower body structure for a vehicle according to any one of claims 1 to 3.

5. The aforementioned dash panel has a main body portion extending in the vertical direction and a kick-up portion extending rearward and downward from the lower end of the main body portion. The front end of the first floor frame and the front end of the second floor frame are fixed to the main body in an overlapping state. A lower body structure for a vehicle according to any one of claims 1 to 3.

6. The dash cross member further extends in the vehicle width direction along the front of the aforementioned dash panel, The ends of the dash cross member on both sides in the vehicle width direction and the front end of the second floor frame fixed to the dash panel overlap when viewed from the front. A lower body structure for a vehicle according to any one of claims 1 to 3.

7. The ends of the dash cross member on both sides in the vehicle width direction overlap with the rear end of the front side frame when viewed from the front. The lower body structure of the vehicle according to feature 6.

8. The first floor frame, the second floor frame, and the connecting member are arranged to form a triangular shape in a plan view. A lower body structure for a vehicle according to any one of claims 1 to 3.

9. The aforementioned hinge pillar is a hollow cylindrical member, A nodal member is provided near the lower end of the internal space of the hinge pillar so as to divide the space vertically. The rear end of the second upper floor frame is fixed at the height position where the joint member of the hinge pillar is provided. A lower body structure for a vehicle according to any one of claims 1 to 3.

10. The front end of the first floor frame and the front end of the second floor frame fixed to the dash panel overlap in the longitudinal direction of the vehicle. A lower body structure for a vehicle according to any one of claims 1 to 3.

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