Vehicle body rear structure

Abstract

To suppress a repair cost arisen at a time of low-speed rear end collision.SOLUTION: A vehicle body rear structure includes a pair of right and left rear side members 2 extending in a fore-and-aft direction with a space therebetween in a vehicle width direction. Each of the rear side members 2 includes a die-cast front member 10 forming a region on a front side of the rear side member 2, and a rear member 20 that is made from a sheet metal, has a front end 20a joined to the front member 10, has a rear end 20c joined to a rear bumper part 8, and forms a region on a rear side of the rear side member 2. The rear member 20 has a deformation origin part 24, which serves as an origin when the rear member 20 is folded and deformed due to input of a load from behind a vehicle, in a middle part 20b in the fore-and-aft direction, and is folded and deformed behind a joint part 30, at which the rear member is joined to the front member 10 in case of a rear end collision.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This case relates to a rear body structure located at the rear of a vehicle. [Background technology]

[0002] Vehicles are equipped with rear body structures that are prepared for rear-end collisions (hereinafter also referred to as "rear collisions"). For example, Patent Document 1 discloses a vehicle body structural member that prevents insufficient absorption of collision energy by suppressing bending deformation in rear floor side members when a collision load is input to the vehicle during a rear collision. Also, for example, Patent Document 2 discloses a rear lower section (rear floor member) that forms a rear connecting structure for the body frame in order to absorb the impact from a rear collision and safely protect the vehicle. Note that the rear lower section in Patent Document 2 has an integrated parts structure using die casting, which reduces weight and material costs, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-117059 [Patent Document 2] Japanese Patent Publication No. 2022-151482 Summary of the Invention [Problem to be solved by the invention]

[0004] In a rear-end collision (hereinafter referred to as a "low-speed rear-end collision") where the relative speed between the vehicle and the colliding object is low (for example, about a few km / h to 30 km / h), the load input to the vehicle is relatively small, and the deformation area of ​​the vehicle body may be limited to a small area. However, with a structure such as that of Patent Document 1, even in such a low-speed rear-end collision, extensive part replacement is required, which poses a problem of high repair costs. Furthermore, in the structure of Patent Document 2, a rear side member is connected to the rear of the rear lower, but there is no focus on replacing only the rear side member in the event of a low-speed rear-end collision.

[0005] The rear vehicle body structure of this case was devised in light of the above-mentioned problems, and one of its objectives is to reduce repair costs in the event of a low-speed rear-end collision. However, in addition to this objective, another objective of this case is to achieve effects derived from the various configurations shown in the "Mode for Carrying Out the Invention" below, which are not obtainable with conventional technology. [Means for solving the problem]

[0006] The disclosed vehicle rear body structure can be realized as the following disclosed embodiments (application examples), which solve at least part of the above-mentioned problems. Each of the embodiments from embodiment 2 onwards is an embodiment that can be selected as an additional option, and each of the embodiments can be omitted. None of the embodiments from embodiment 2 onwards discloses an embodiment or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed rear vehicle body structure includes a pair of left and right rear side members extending in the front-to-rear direction and spaced apart in the vehicle width direction. Each of the rear side members includes a die-cast front member constituting a front portion of the rear side member, and a sheet metal rear member constituting a rear portion of the rear side member, the front end of which is joined to the front member and the rear end of which is joined to a rear bumper component. The rear member has a deformation origin portion in the front-to-rear middle portion, which is the origin of bending deformation of the rear member when a load is input from the rear of the vehicle, and the rear member bends and deforms rearward of the joint with the front member during a rear collision.

[0008] Aspect 2. In an aspect including the aspect 1 described above, it is preferable that the rear member includes two opposing wall portions facing each other in the vehicle width direction, and the deformation starting point portion is provided as a bent portion formed by bending at least one of the two opposing wall portions. Aspect 3. In an aspect including the aspect 1 described above, it is preferable that the rear member has a predetermined area on each of the front and rear sides of the deformation starting point, which has a cross-sectional strength higher than the cross-sectional strength of the deformation starting point. Aspect 4. In any of the aspects including the above-described aspect 3, it is preferable that the cross-sectional shape of the rear member is widened at the deformation start point in the predetermined area on the front side of the deformation start point.

[0009] Aspect 5. In an aspect including Aspect 3 above, in the specified area rearward of the deformation starting point, a support bracket included in the rear bumper part is fixed from below to the rear end of the rear member, and it is preferable that the front end of the support bracket is located near the rear of the deformation starting point. Aspect 6. In an aspect including Aspect 5 above, it is preferable that the lower surface of the support bracket, when viewed from the side of the vehicle, is an inclined surface that slopes downward as it goes rearward from the front end portion fixed to the lower surface of the rear member.

[0010] Aspect 7. In an aspect including Aspect 1 above, it is preferable that the rear member has a longitudinal cross-sectional shape along the vehicle width direction that includes a U-shaped cross-section that opens upward, and the front member has a longitudinal cross-sectional shape at its rear end that includes a U-shaped cross-section that opens upward to match the longitudinal cross-sectional shape of the rear member, and the rear end of the front member and the front end of the rear member are joined with the U-shaped cross-sections overlapping, and a reinforcing rib extending in the fore-and-aft direction is formed at the joint between the front member and the rear member.

[0011] Aspect 8. In an aspect including aspect 1 above, it is preferable that the front member includes a suspension support portion on which rear suspension components are supported, and the rear side member is divided into the front member and the rear member behind the suspension support portion. Aspect 9. In any aspect including Aspect 1 above, the vehicle rear structure preferably includes a floor cross member extending in the vehicle width direction and connecting the rear extensions of the front members. In this case, the rear side members are preferably divided into the front member and the rear member behind the floor cross member. [Effects of the Invention]

[0012] The disclosed rear vehicle body structure can reduce repair costs in the event of a low-speed rear-end collision. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a bottom view of a vehicle rear portion to which a vehicle rear body structure according to an embodiment is applied. [Figure 2] 10A and 10B are side and bottom views of the left front member; [Figure 3] 2, (b) is a cross-sectional view taken along line BB in FIG. 2, (c) is a cross-sectional view taken along line CC in FIG. 2, and (d) is a cross-sectional view taken along line DD in FIG. [Figure 4] 10A and 10B are top, side, and rear views of the left rear member. [Figure 5] Explains the joint between the left front and rear members DETAILED DESCRIPTION OF THE INVENTION

[0014] A vehicle rear body structure according to an embodiment will be described with reference to the drawings. The following embodiment is merely an example, and is not intended to exclude various modifications or applications of techniques not explicitly described in the following embodiment. The configurations of the embodiment can be modified in various ways without departing from the spirit of the embodiment. Furthermore, they can be selected or combined as needed.

[0015] In the following description, the forward direction of the vehicle is referred to as the front of the vehicle (simply referred to as "forward", "FR" in the drawings), and the backward direction is referred to as the rear of the vehicle (simply referred to as "rear", "RR" in the drawings), with left and right defined based on the forward direction. The left and right direction can also be said to be the vehicle width direction, and the fore-aft direction of the vehicle is simply referred to as the "front-to-back direction." In the drawings, "RH" indicates the right and "LH" indicates the left. The up-down direction is defined by assuming that the direction of gravity is downward and the opposite is upward ("UP" in the drawings). The up-down direction does not have to coincide perfectly with the vertical direction and may be slightly inclined relative to the vertical direction. Similarly, the front-to-back and left-to-right directions do not have to coincide perfectly with the horizontal direction.

[0016] The structure of a vehicle (vehicle body) is often formed with near bilateral symmetry (mirror symmetry about a plane including the yaw axis and roll axis passing through the center of gravity of the vehicle), but a completely symmetrical shape is not required. Furthermore, the type of vehicle to which the vehicle body rear structure according to the embodiment is applied is not particularly limited, and the vehicle may be a gasoline-powered vehicle, an electric vehicle (EV), a hybrid vehicle (HEV, Hybrid Electric Vehicle), a plug-in hybrid vehicle (PHEV, Plug-in Hybrid Electric Vehicle), or the like. A plug-in hybrid vehicle is a hybrid vehicle capable of externally charging the battery or externally receiving power from the battery. A plug-in hybrid vehicle is provided with a charging port (inlet) for inserting a charging cable that supplies power from an external charging facility, and a power outlet (outlet) for external power supply.

[0017] [1. Configuration] [1-1. Overall structure] Fig. 1 is a bottom view of the rear of a vehicle to which a vehicle body rear structure according to this embodiment is applied. As shown in Fig. 1, the vehicle of this embodiment is provided with, as its framework members, a pair of left and right side sills 1 extending in the front-to-rear direction and spaced apart in the vehicle width direction, and a cross member 5 connecting the pair of side sills 1. The outer ends of the cross member 5 in the vehicle width direction are fixed to the left and right side sills 1, respectively. In addition, a plate-shaped floor panel 4F is deployed between the side sills 1, and the cross member 5 is also fixed to the floor panel 4F.

[0018] A wheelhouse 3 is fixed to the rear end of each side sill 1, and a plate-shaped rear floor panel 4R is disposed behind the floor panel 4F. The rear floor panel 4R is deployed between a pair of left and right rear side members 2 (described later) and has a floor cross that extends in the vehicle width direction to connect the rear side members 2. In the vehicle of this embodiment, two floor crosses 6f, 6r are disposed with a gap between them in the front-rear direction. Note that, although the rear wheels and rear suspension components located below the vehicle body are omitted in FIG. 1, the rear suspension cross members (not shown) are disposed below the floor crosses 6f, 6r.

[0019] The rear vehicle body structure includes a pair of left and right rear side members 2 that extend in the front-to-rear direction and are spaced apart in the vehicle width direction. The left rear side member 2 and the right rear side member 2 are configured symmetrically. Therefore, in the following description, unless otherwise specified, the left rear side member 2 will be described in detail. In the description of the left rear side member 2, "left side" and "inner side in the vehicle width direction ("IN" in the drawings)" are synonymous, and "right side" and "outer side in the vehicle width direction ("OUT" in the drawings)" are synonymous.

[0020] The rear side member 2 has a die-cast front member 10 and a sheet metal rear member 20. The front member 10 is a member that constitutes the front portion of the rear side member 2, and the rear member 20 is a member that constitutes the rear portion of the rear side member 2. In other words, the rear side member 2 is divided into the front member 10 and the rear member 20.

[0021] The front member 10 mainly functions to efficiently transmit the load input to the vehicle to frame members such as the side sill 1 and cross member 5 in a rear-end collision when the relative speed between the vehicle and the colliding object is not low (hereinafter referred to as a "medium- to high-speed rear-end collision"). On the other hand, the rear member 20 mainly functions to effectively absorb the load input to the vehicle and suppress deformation of the front member 10 in a rear-end collision when the relative speed between the vehicle and the colliding object is low (hereinafter referred to as a "low-speed rear-end collision"). Note that the rear member 20 may also have, together with the front member 10, the function of efficiently transmitting the load input to the vehicle to frame members in a medium- to high-speed rear-end collision.

[0022] Below, the configuration of the front member 10 will be described in detail first, then the configuration of the rear member 20 will be described in detail, and finally the configuration of the joint 30 which is the connecting portion between these will be described.

[0023] [1-2. Front member of rear side member] The front member 10 is made of die-cast aluminum. A front portion 10b of the front member 10 is fixed to both the side sill 1 and the cross member 5. Specifically, the outer end of the front portion 10b of the front member 10 in the vehicle width direction is fixed to the inner portion of the side sill 1 in the vehicle width direction, and the front end portion 10a of the front member 10 is fixed to the underside of the outer end of the cross member 5 in the vehicle width direction.

[0024] 2 shows a side view of the left front member 10 as seen from the left side (outside in the vehicle width direction) and a bottom view thereof. As shown in FIGS. 1 and 2, the front member 10 has an inclined portion 10c that extends rearward and diagonally upward, and a rearward extending portion 10d that extends rearward and approximately horizontally from the rear end of the inclined portion 10c. That is, in a side view of the vehicle, the front member 10 extends rearward and diagonally upward from the front portion 10b, and also extends approximately horizontally from an area above the wheels (not shown) to the rear end portion 10e.

[0025] Furthermore, in a bottom view of the vehicle, the front member 10 extends rearward and inward in the vehicle width direction from the cross member 5, and is curved so as to convexly inward in the vehicle width direction so as to bypass the wheel house 3. A rear end portion 10e of the front member 10 is disposed a predetermined distance forward of the rear bumper component. The component that connects this rear end portion 10e to the rear bumper component is the rear member 20. In this embodiment, the front portion 10b of the front member 10 is positioned further outward in the vehicle width direction than the rear end portion 10e. Therefore, the position where a load is input in the event of a rear-end collision (rear end portion 10e) and the mounting position of the front portion 10b of the front member 10 are offset in the vehicle width direction.

[0026] 3(a) to 3(d) are cross-sectional views taken along lines A to D in FIG. 2. As shown in FIGS. 3(a) to 3(d), the front member 10 has a pair of left and right vertical surface portions 11 and a horizontal surface portion 12 connecting the pair of vertical surface portions 11. Each vertical surface portion 11 is a surface portion extending along the front-rear direction and the up-down direction, and the horizontal surface portion 12 is a surface portion extending along the front-rear direction and the left-right direction. Here, the dashed line in the side view of FIG. 2 indicates the horizontal surface portion 12. As shown in the side view of FIG. 2, the horizontal surface portion 12 in this embodiment extends so as to be located at the lower end of the pair of vertical surface portions 11 in the rear extension portion 10d, and extends so as to be located midway between the pair of vertical surface portions 11 in the inclined portion 10c.

[0027] For this reason, the longitudinal cross-sectional shape of the front member 10 along the vehicle width direction and the up-down direction (hereinafter simply referred to as the "longitudinal cross-sectional shape") is not uniform in the front-to-rear direction. Specifically, the longitudinal cross-sectional shape of the front member 10 at the rear extension portion 10d is formed to include a U-shaped cross section that is open upward by the pair of vertical surface portions 11 and horizontal surface portions 12. Also, the longitudinal cross-sectional shape of the front member 10 at the inclined portion 10c is formed to include an H-shaped cross section that is open upward and downward by the pair of vertical surface portions 11 and horizontal surface portions 12.

[0028] FIG. 3(a) is a cross-sectional view of the rear end portion 10e of the front member 10 taken along line AA in FIG. 2. As shown in FIGS. 2 and 3(a), the vertical cross-sectional shape of the rear end portion 10e of the front member 10 of this embodiment includes a U-shaped cross-section that opens upward to match the vertical cross-sectional shape of the rear member 20 (described later). As described above, the "U-shaped cross-section" refers to a cross-sectional shape formed by one horizontal surface portion 12 connecting two vertical surface portions 11 being located at the lower end of the vertical surface portion 11 (a cross-sectional shape similar to the letter "U"). In the U-shaped cross-section, the two vertical surface portions 11 extend upward from both ends of the horizontal surface portion 12 in the vehicle width direction and face each other. The rear end portion 10e of this embodiment includes two flange portions 13 bent in the vehicle width direction from the upper end of each vertical surface portion 11, forming a hat-shaped cross-section. Each flange portion 13 is joined to the rear floor panel 4R (see FIG. 1).

[0029] FIG. 3(c) is a cross-sectional view of the inclined portion 10c of the front member 10 (the portion immediately behind the front portion 10b) taken along line CC in FIG. 2. As shown in FIGS. 2 and 3(c), the inclined portion 10c of the front member 10 of this embodiment has an H-shaped vertical cross-section that is open at the top and bottom. As described above, the "H-shaped cross-section" refers to a cross-sectional shape formed by one horizontal surface portion 12 connecting two vertical surface portions 11, the height position of which is located at an intermediate portion of the vertical surface portions 11, not at the lower or upper ends of the vertical surface portions 11 (a cross-sectional shape conforming to the letter "H"). In the H-shaped cross-section, the two vertical surface portions 11 forming the side surfaces are connected by the horizontal surface portion 12 at an intermediate position that is not at the lower or upper ends. In this embodiment, the inclined portion 10c has a flange portion 13 at the upper end of the vertical surface portion 11 on the inner side in the vehicle width direction, and a side-sill connecting portion 15 that connects to the side sill 1 (see FIG. 1) at the lower end of the vertical surface portion 11 on the outer side in the vehicle width direction.

[0030] As described above, the front member 10 has, in the fore-and-aft direction, a section whose longitudinal cross section has a U-shaped cross section and a section whose longitudinal cross section has an H-shaped cross section. Hereinafter, the former will be referred to as the "U-shaped cross section" and the latter will be referred to as the "H-shaped cross section." The U-shaped cross section includes at least the rear end portion 10e of the front member 10, and the H-shaped cross section is provided continuously forward of this U-shaped cross section. The boundary between the U-shaped cross section and the H-shaped cross section substantially coincides with the front end position of the rear extension portion 10d.

[0031] In other words, in the portion where the front member 10 extends substantially horizontally (from the rear end portion 10e to the rear extension portion 10d), the height position of the horizontal surface portion 12 is substantially constant, and the vertical cross-sectional shape is a shape that includes a U-shaped cross-section. On the other hand, in the portion where the front member 10 slopes downward toward the front (the slope portion 10c forward of the rear extension portion 10d), in the section where the height position of the horizontal surface portion 12 is substantially constant, the height position of the vertical surface portion 11 changes, and the vertical cross-sectional shape is a shape that includes an H-shaped cross-section due to the positional relationship between the vertical surface portion 11 and the horizontal surface portion 12 in the section where the height position of the horizontal surface portion 12 slopes downward.

[0032] In the front member 10 of this embodiment, a U-shaped cross-sectional section including the front end portion 10a is also provided in front of the H-shaped cross-sectional section. In other words, the front member 10 of this embodiment is configured such that an H-shaped cross-sectional section is sandwiched between two U-shaped cross-sectional sections, one in front and one in back. However, the front U-shaped cross-sectional section is not essential and can be omitted. Hereinafter, when simply referring to a "U-shaped cross-sectional section," this refers to the rear U-shaped cross-sectional section.

[0033] 3(b) is a cross-sectional view of the inclined portion 10c of the front member 10 (the portion immediately preceding the rear extension portion 10d) taken along line BB in FIG. 2. As shown in FIG. 3(b), the vertical cross section of the front member 10 at this position has a shape that includes an H-shaped cross section. At the inclined portion 10c at this cross-sectional position, a floor cross connection portion 14f is formed on the inside of the vertical surface portion 11 on the inside side in the vehicle width direction, to which a front floor cross 6f (see FIG. 1) that connects the left and right front members 10 is connected.

[0034] 1 and 2, a floor cross connection portion 14r to which a rear floor cross 6r that connects the left and right front members 10 is connected is formed in the rear extension portion 10d (U-shaped cross section) of the front member 10. In other words, the rear floor cross 6r connects the rear extension portions 10d of the front members 10. The rear side member 2 of this embodiment is divided into the front member 10 and the rear member 20 behind the rear floor cross 6r.

[0035] Figure 3(d) is a cross-sectional view of the front portion of the front part 10b of the front member 10, taken along line DD in Figure 2. As shown in Figure 3(d), the vertical cross-sectional shape of the front member 10 at this position includes a U-shaped cross-section that is open upward. Note that, at this cross-sectional position, as in Figure 3(c), a flange portion 13 is provided at the upper end of the vertical surface portion 11 on the inner side in the vehicle width direction, and a side sill connection portion 15 is provided at the lower end of the vertical surface portion 11 on the outer side in the vehicle width direction.

[0036] As shown in FIG. 2, a front mounting portion 16f (mounting portion) of the rear suspension cross member is provided at the rear of the inclined portion 10c of the front member 10. Also, a rear mounting portion 16r of the rear suspension cross member is provided immediately before the rear end portion 10e of the front member 10 (at the rearward portion of the rear extension portion 10d). In other words, the rear suspension cross member is mounted to the front member 10, not the rear member 20. Both of these mounting portions 16f, 16r are formed to be more rigid than other portions of the front member 10, ensuring the mounting rigidity of the rear suspension cross member.

[0037] In this embodiment, the height position of the lateral surface portion 12 of the front member 10 is substantially constant from the rear extension portion 10d to the position of the front mounting portion 16f of the rear suspension cross member. In other words, the lateral surface portion 12 is provided with a downward slope in the section forward of the position of the front mounting portion 16f. As shown in FIG. 5, the lateral surface portion 12 of this embodiment is provided with a plurality of ribs 17 that protrude upward and downward from the lateral surface portion 12 in order to increase the strength and rigidity of the front member 10. Furthermore, the front member 10 of this embodiment has a reinforcing rib 18 that is provided upright within the U-shaped cross section of the rear extension portion 10d.

[0038] Moreover, the front member 10 of this embodiment includes a suspension support portion 19 on which rear suspension components are supported. The suspension support portion 19 is located on the rear extension portion 10d, and extends outward in the vehicle width direction from the upper end of the vertical surface portion 11 on the outer side in the vehicle width direction. The suspension support portion 19 is provided so as to be located on the inner side of the curve of the portion of the front member 10 that is curved so as to convex inward in the vehicle width direction, when viewed from below the vehicle. As shown in FIG. 1 , the rear side member 2 of this embodiment is divided into the front member 10 and the rear member 20 behind the suspension support portion 19.

[0039] [1-3. Rear member of rear side member] Next, the configuration of the rear member 20 will be described in detail. The rear member 20 is formed by bending a plate of a metal (for example, iron) that is stronger than aluminum. As shown in FIG. 1, a front end 20a of the rear member 20 is joined to a rear end 10e of the front member 10, and a rear end 20c of the rear member 20 is joined to a support bracket 8, which is one of the rear bumper components. The rear member 20 extends rearward from the rear end 10e of the front member 10, and can also be said to be a component that connects the front member 10 and the rear bumper components.

[0040] The support bracket 8 is a component that supports the rear bumper beam 7, which is located at the rear end of the vehicle body, via a rear bumper bracket 9. The rear bumper beam 7 is a component that receives loads from behind and extends in the vehicle width direction. The left and right rear bumper brackets 9 are each connected to the support bracket 8 and are fixed to both ends of the rear bumper beam 7 in the vehicle width direction. The rear bumper beam 7 and rear bumper bracket 9 are both rear bumper components.

[0041] FIG. 4 shows a top view, a side view from the left side, and a rear view of the left rear member 20 with the support bracket 8 omitted. As is clear from the rear view in FIG. 4, the longitudinal cross section of the rear member 20 along the vehicle width direction includes a U-shaped cross section that opens upward. The longitudinal cross section of the rear member 20 includes a U-shaped cross section at any position in the fore-and-aft direction. In other words, the rear member 20 includes two vertical surface portions 21 (opposing wall portions) that face each other in the vehicle width direction, and a horizontal surface portion 22 that connects the two vertical surface portions 21. The vertical surface portions 21 form the side surfaces of the U-shaped cross section, and the horizontal surface portion 22 forms the bottom surface of the U-shaped cross section.

[0042] The horizontal surface portion 22 extends in the vehicle width direction and the front-rear direction, and each vertical surface portion 21 extends in the front-rear direction and the up-down direction. The two vertical surface portions 21 are erected upward from both ends of the horizontal surface portion 22 in the vehicle width direction and face each other. The rear member 20 of this embodiment includes two flange portions 23 bent in the vehicle width direction from the upper end of each vertical surface portion 21, and has a hat-shaped vertical cross section. Each flange portion 23 is joined to the rear floor panel 4R (see FIG. 1).

[0043] Each of the two vertical surface portions 21 extends forward from the rear end portion 21c, then bends toward the inside in the vehicle width direction, and extends diagonally forward. Hereinafter, this bent portion will be referred to as the "bent portion." The bent portion 21a of the vertical surface portion 21 on the inside in the vehicle width direction is located rearward of the bent portion 21b of the vertical surface portion 21 on the outside in the vehicle width direction. Hereinafter, when distinguishing between the two bent portions 21a, 21b, the former will be referred to as the "inner bent portion 21a" and the latter will be referred to as the "outer bent portion 21b." The two bent portions 21a, 21b are provided in the middle portion 20b of the rear member 20, excluding the front end portion 20a and the rear end portion 20c.

[0044] The intermediate portion 20b of the rear member 20 is provided with a deformation origin portion 24, which serves as a starting point for bending deformation of the rear member 20 when a load (rear-end collision load) is input from behind. The deformation origin portion 24 undergoes bending deformation rearward of the joint portion 30 with the front member 10 when a load is input from behind to the rear member 20 (in a rear-end collision). The deformation origin portion 24 is also the portion of the rear member 20 that is first to undergo bending deformation. Because the rear member 20 has the deformation origin portion 24, stress is concentrated at the deformation origin portion 24 in the event of a low-speed rear-end collision, causing the deformation origin portion 24 to bend, for example, upward. Therefore, in the case of a low-speed rear-end collision in which the rear-end collision load is relatively small, the rear-end collision load is absorbed by the deformation of the rear member 20, and deformation of the front member 10 is suppressed.

[0045] The deformation starting points 24 can be configured, for example, by modifying the shape of the rear member 20, adjusting the cross-sectional strength, or by both modifying the shape and adjusting the cross-sectional strength. For example, the above-mentioned bent portions 21a and 21b can serve as the deformation starting points 24. In other words, the deformation starting points 24 may be provided as the inner bent portion 21a or the outer bent portion 21b formed by bending at least one of the two vertical surface portions 21 that form the U-shaped cross section. In this embodiment, the inner bent portion 21a functions as the deformation starting point 24, and the portion indicated by the two-dot chain line in the side view of FIG. 4 serves as the deformation starting point 24.

[0046] Furthermore, when the deformation starting points 24 are configured by adjusting the sectional strength, areas having a sectional strength higher than the sectional strength of the deformation starting points 24 are set before and after the position that will be the deformation starting points 24. In other words, by setting two areas with high sectional strength apart from each other in the fore-and-aft direction in the rear member 20, an area with low sectional strength is provided as the deformation starting points 24 between these two areas.

[0047] The rear member 20 of this embodiment has predetermined areas 25, 26 on the front and rear sides of the deformation origin portion 24, each having a higher sectional strength than the sectional strength of the deformation origin portion 24. In this embodiment, in the front predetermined area 25 (hereinafter referred to as the "front area 25"), the cross-sectional shape of the rear member 20 is widened at the deformation origin portion 24. This increases the sectional strength of the front area 25 compared to the portion before the widening.

[0048] In this embodiment, a support bracket 8 is overlapped from below and fixed to the rear end portion 20c of the rear member 20 in a predetermined area 26 on the rear side (hereinafter referred to as the "rear area 26"). The front end of the support bracket 8 is located near the rear of the deformation starting point portion 24. This increases the cross-sectional strength of the rear area 26 compared to a portion without the support bracket 8. The front end of the lower surface 8d of the support bracket 8 is fixed to the lower surface 20d of the rear member 20, and forms a slope that slopes downward from the front end toward the rear in a side view of the vehicle.

[0049] Furthermore, in this embodiment, a pipe shipping 40 is arranged in the rear area 26. The pipe shipping 40 is a component that is inserted into and fixed to holes formed through the two vertical wall portions 21, and a shipping hook (not shown) is attached to the pipe shipping 40 when towing. The cross-sectional strength of the rear area 26 is also increased by the pipe shipping 40.

[0050] In this embodiment, a deformation-following portion 27 is provided immediately before the deformation origin portion 24 (at the rear of the front area 25). The deformation-following portion 27 is a portion of the rear member 20 that deforms next to the deformation origin portion 24 when a load is input from behind to the rear member 20. Because the rear member 20 has the deformation-following portion 27, in the event of a low-speed rear-end collision, stress is concentrated at the deformation origin portion 24, causing it to bend and deform, and immediately thereafter, stress is also concentrated at the deformation-following portion 27, causing the deformation-following portion 27 to undergo, for example, compressive deformation. Therefore, in the case of a low-speed rear-end collision in which the rear-end collision load is relatively small, the rear member 20 deforms sequentially from the rear side, effectively absorbing the rear-end collision load and further suppressing deformation of the front member 10. Note that the deformation-following portion 27 in this embodiment is a portion formed in a convex (or concave) shape on the vertical surface portion 21 on the outer side in the vehicle width direction.

[0051] [1-4.Joint part] Finally, the configuration of the joint 30 between the front member 10 and the rear member 20 will be described. As shown in Fig. 5, the joint 30 is a region where the rear end 10e of the front member 10 and the front end 20a of the rear member 20 are joined in an overlapping state. In other words, the rear end 10e of the front member 10 and the front end 20a of the rear member 20 are joined in a state where their U-shaped cross sections are overlapped. One example of a joining method is SPR joining, where the front member 10 is overlapped on the rear member 20.

[0052] At the joint 30, the vertical cross-sectional shape of the rear end 10e of the front member 10 and the vertical cross-sectional shape of the front end 20a of the rear member 20 are shaped so that they can be joined by matching their surfaces. Specifically, at the joint 30, the vertical surface portion 11, the horizontal surface portion 12, and the flange portion 13 at the rear end 10e of the front member 10 and the vertical surface portion 21, the horizontal surface portion 22, and the flange portion 23 at the front end 20a of the rear member 20 are joined to each other in a state of surface contact.

[0053] As described above, the joint 30 is formed by overlapping the rear end 10e of the front member 10 with the front end 20a of the rear member 20. The joint 30 of this embodiment has a pair of left and right vertical surface portions 31 (vertical joint surface portions), a horizontal surface portion 32 (horizontal joint surface portion) connecting the pair of vertical surface portions 31, and a flange portion 33 (flange joint portion) bent and formed at the upper end of each vertical surface portion 31. The vertical surface portions 31, horizontal surface portions 32, and flange portions 33 of the joint 30 are respectively composed of the vertical surface portions 11 and 21, horizontal surface portions 12 and 22, and flange portions 13 and 23 of the front member 10 and the rear member 20.

[0054] The flange portion 23 of the rear member 20 is formed so that the portion that will become the flange portion 33 of the joint 30 (i.e., the portion where the flange portion 13 of the front member 10 will be overlapped) is stepped down one step from the rear portion of that portion. In other words, as shown in FIG. 4, the flange portion 23 of the rear member 20 has a stepped portion 23a formed slightly rearward of the front end portion 20a. This makes the flange portion 33 of the joint 30 and the portion of the rear member 20 excluding the portion that will become the flange portion 23 approximately flush with each other. Note that the lateral surface portion 12 of the rear end portion 10e of the front member 10 is formed thin so that its upper surface is one step lower at the joint 30. This achieves further weight reduction of the front member 10.

[0055] In the rear side member 2 of this embodiment, a portion of the reinforcing rib 18 erected on the rear extending portion 10d of the front member 10 extends to the joint 30. In other words, the reinforcing rib 18, which can be said to extend in the front-to-rear direction, is formed at the joint 30 between the front member 10 and the rear member 20, and increases the surface rigidity of the joint 30. Note that, in addition to this reinforcing rib 18, the rib 17 described above is provided on the lateral surface portion 12 of the front member 10, and therefore the reinforcing rib 18 can also be said to be a portion extended rearward from the rib 17.

[0056] [2. Actions and Effects] (1) The above-described vehicle rear body structure includes a pair of left and right rear side members 2 extending in the front-to-rear direction and spaced apart in the vehicle width direction. The rear side members 2 include a die-cast front member 10 and a sheet metal rear member 20. According to this vehicle rear body structure, weight can be reduced by using the die-cast front member 10 for the front portion of the rear side member 2. Furthermore, by connecting the rear member 20, which is a separate part, to the rear end portion 10e of the front member 10, it becomes possible to respond to a low-speed collision from behind (low-speed rear-end collision) by simply replacing the rear member 20, thereby reducing repair costs.

[0057] Specifically, the rear member 20 described above extends in the fore-and-aft direction, has a deformation origin portion 24 in its fore-and-aft intermediate portion 20b, which is the origin of bending deformation of the rear member 20 due to a load input from behind, and during a rear-end collision, the rear member 20 bends and deforms behind the joint 30. Therefore, during a low-speed rear-end collision, stress can be concentrated at the deformation origin portion 24, causing the rear member 20 to bend and deform, and deformation forward of the joint 30, i.e., of the front member 10, can be suppressed. In other words, because the load during a low-speed rear-end collision can be effectively absorbed by the deformation of the rear member 20, in the event of a low-speed rear-end collision, only the rear member 20 needs to be replaced, thereby reducing repair costs.

[0058] (2) The above-described rear member 20 includes two vertical surface portions 21 (opposing wall portions) opposing each other in the vehicle width direction, and the above-described deformation origin portion 24 is provided as a bent portion (inner bent portion 21a) formed by bending at least one (for example, the inner side in the vehicle width direction) of the two vertical surface portions 21 that form the U-shaped cross section of the rear member 20. By changing the shape of the vertical surface portion 21 in this way, the load (stress) input during a low-speed rear-end collision can be efficiently concentrated on the deformation origin portion 24, thereby achieving the desired deformation.

[0059] (3) Furthermore, the above-described rear member 20 has predetermined areas 25, 26 on the front and rear sides of the deformation origin 24, each having a higher sectional strength than the deformation origin 24. In this way, by providing predetermined areas 25, 26 on the front and rear sides of the deformation origin 24, each having a higher sectional strength than the deformation origin 24, a difference in sectional strength occurs between the deformation origin 24 and these areas 25, 26, so that the load (stress) input during a low-speed rear-end collision can be more effectively concentrated on the deformation origin 24.

[0060] (4) In the front area 25 of the deformation starting point 24 described above, the cross-sectional shape of the rear member 20 is widened at the deformation starting point 24 as a boundary, so that the cross-sectional strength can be increased by the shape of the rear member 20 without increasing the number of parts. (5) Furthermore, in the rear area 26 of the above-described deformation start point 24, the support bracket 8 is fixed to the rear end portion 20c of the rear member 20, and the front end of the support bracket 8 is located near the rear of the deformation start point 24. With this configuration, the cross-sectional strength of the rear area 26 can be easily and reliably increased by the support bracket 8.

[0061] (6) The front end of the underside 8d of the support bracket 8 is fixed to the underside 20d of the rear member 20, and this underside 8d is inclined downward as it moves rearward from the front end where it is fixed to the underside 20d, as seen in a side view of the vehicle. Therefore, a moment can be generated in the rear member 20 when a load is input from the rear, which can promote bending deformation (e.g., upward bending deformation) of the rear member 20. Therefore, in the event of a low-speed rear-end collision, the rear member 20 can be deformed as intended, and repair costs can be reduced.

[0062] (7) In the above-described rear side member 2, the front member 10 and the rear member 20 are joined together in a state where their surfaces overlap at the portions including the U-shaped cross section (the rear end portion 10e and the front end portion 20a), allowing for strong fixation. In addition, the joint portion 30 is formed with the reinforcing rib 18 extending in the fore-and-aft direction, which increases the surface rigidity of the joint portion 30. This increases the joint strength between the front member 10 and the rear member 20.

[0063] (8) The above-described rear side member 2 is divided into a front member 10 and a rear member 20 behind the suspension support portion 19. In other words, the suspension support portion 19 is provided on the front member 10 of the rear side member 2. Therefore, in the event of a low-speed rear-end collision, it is not necessary to replace the suspension support portion 19 and the suspension parts supported thereby, which can effectively reduce repair costs.

[0064] (9) Furthermore, the above-mentioned rear side member 2 is divided into a front member 10 and a rear member 20 behind the rear floor cross 6r. In other words, the floor cross connection portion 14r to which the floor cross 6r is connected is provided in the front member 10 of the rear side member 2. Therefore, in the event of a low-speed rear-end collision, there is no need to replace the floor cross 6r, which contributes to reducing repair costs.

[0065] (10) In addition, in this embodiment, the front member 10 has an inclined portion 10c extending rearward and diagonally upward, and a rear extension portion 10d extending rearward substantially horizontally from the rear end of the inclined portion 10c, and the vertical cross-sectional shape of the inclined portion 10c is formed to include an H-shaped cross-section that is open at the top and bottom and is formed by a pair of vertical surface portions 11 and a horizontal surface portion 12. In other words, the vertical cross-sectional shape of the front member 10 changes from a U-shaped cross-section of the rear extension portion 10d to an H-shaped cross-section toward the front, and in the U-shaped cross-section section (the section where the horizontal surface portion 12 extends at a substantially constant height), in the event of a medium- to high-speed rear-end collision, the load received by the rear member 20 is more likely to be transmitted forward via the horizontal surface portion 12 of the front member 10, thereby improving load transmission performance. As a result, the rear-end collision load can be efficiently transmitted to the vehicle body through the front member 10 without stress concentration at the rear extension portion 10d and the inclined portion 10c of the front member 10, thereby improving load transmission performance in the event of a medium- to high-speed rear-end collision.

[0066] (11) In the front member 10 of this embodiment, the rear end 10e (rear impact load input position) to which the rear impact load is input and the mounting position of the front portion 10b of the front member 10 are offset in the vehicle width direction. Therefore, when a rear impact load is input, a load component in the vehicle width direction acts on the front member 10. However, because the rigidity in the vehicle width direction is increased in the H-shaped cross-section section, the front member 10 does not tip over sideways even when this load component acts. Therefore, also in this respect, it is possible to improve load transmission performance in a medium- to high-speed rear impact.

[0067] (12) In this embodiment, the front mounting portion 16f of the rear suspension cross member is provided on the inclined portion 10c of the front member 10, and the height position of the lateral surface portion 12 extends from the rear extension portion 10d to the position of the front mounting portion 16f at a substantially constant level. The mounting portions 16f, 16r of the rear suspension cross member are made more rigid than other portions of the front member 10. Therefore, by extending the lateral surface portion 12 at a substantially constant height from the rear extension portion 10d of the front member 10, via the rear mounting portion 16r, to the front mounting portion 16f, the front member 10 is less likely to deform along the way, and load transmission efficiency can be further improved.

[0068] (13) In this embodiment, the front portion 10b of the front member 10 is fixed to both the pair of left and right side sills 1 and the cross member 5 connecting the side sills 1. In this way, by fixing the front portion 10b of the front member 10 to both the side sills 1 and the cross member 5, which are frame members of the vehicle body, the load transmitted via the front member 10 can be reliably transmitted to the frame members.

[0069] (14) In this embodiment, the rear extension 10d of the front member 10 is formed with a floor cross connection portion 14r to which a floor cross 6r extending in the vehicle width direction and connecting the left and right front members 10 is connected. Therefore, when a rear collision load is input to the rear end portion 10e of the front member 10, even if a load component directed in the vehicle width direction acts on the front member 10, the floor cross 6r can suppress lateral tipping of the rear extension 10d. This can improve load transmission performance during a medium- to high-speed rear collision.

[0070] (15) In the rear side member 2 of this embodiment, the joint 30 is formed by overlapping the rear end 10e of the front member 10 onto the front end 20a of the rear member 20. The left and right flange portions 33 of the joint 30 are formed by overlapping the flange portion 13 of the front member 10 onto the flange portion 23 of the rear member 20, but the flange portion 23 of the rear member 20 is formed in a stepped shape such that the portion that becomes the flange portion 33 of the joint 30 is one step lower than the portion rearward of that portion. In this way, by forming the stepped portion 23a in the flange portion 23 of the rear member 20, the flange portion 33 of the joint 30, formed by overlapping the front member 10 onto the rear member 20, is approximately flush with the flange portion 23 of the rear member 20 located immediately behind this flange portion 33, which makes it easier to transmit loads and improves load transmission performance.

[0071] [3. Other] The vehicle rear structure described above is an example and is not limited to the above structure. For example, the pair of left and right rear side members 2 may have a front member 10 made of aluminum die-cast and a rear member 20 made of sheet metal, and these may be joined in the front-to-rear direction, and all other configurations are examples. For example, the vertical cross-sectional shape of the front member 10 may be uniform in the front-to-rear direction, or may have only a U-shaped cross-sectional section or only an H-shaped cross-sectional section. Furthermore, for example, the front member 10 does not have to have a convex shape that bypasses the wheelhouse 3 when viewed from below the vehicle, and the front portion 10b and the rear end portion 10e do not have to be offset in the vehicle width direction.

[0072] The rear member 20 has at least its front end 20a joined to the rear end 10e of the front member 10 and its rear end 20c joined to a rear bumper component. It also has a deformation origin 24 in the longitudinal middle portion 20b, which is the origin of bending deformation of the rear member 20 when a load is input from the rear of the vehicle. All other configurations are merely examples. For example, the vertical cross-sectional shape does not have to be a U-shaped cross-section that opens upward. Furthermore, the deformation origin 24 may be provided as an outer bent portion 21b instead of an inner bent portion 21a, and the cross-sectional strength may be uniform in the longitudinal direction. Furthermore, methods other than increasing the cross-sectional area or attaching other components may be used to increase the cross-sectional strength. The support bracket 8 is an example of a rear bumper component, and other rear bumper components may be joined to the rear member 20.

[0073] The configuration and joining method of the joint 30 between the front member 10 and the rear member 20 are also examples. The rear member 20 may be joined in a state of being stacked on top of the front member 10, and the joining method is not limited to SPR joining. Furthermore, the reinforcing rib 18 is not essential. The other ribs 17 are also not essential. [Industrial Applicability]

[0074] The present invention is applicable to the manufacturing industry of vehicles to which the rear body structure is applied. [Explanation of symbols]

[0075] 1 Side sill 2 Rear side members 5 Cross members 6f, 6r Floor Cross 7 Rear bumper beam (rear bumper part) 8 Support bracket (rear bumper part) 8d Bottom 9 Bumper bracket (rear bumper part) 10 Front member 10d posterior extension 10e Rear end 14r Floor cross connection (connection) 18 Reinforcing rib 19 Suspension support 20 Rear member 20a Front end 20b middle part 20c rear end 20d bottom surface 21 Vertical surface portion (opposing wall portion) 21a Inner bend (bend) 21b Outside bending part (bending part) 22 Lateral section 23 Flange section (rear flange section) 24 Deformation origin 25 Front area (designated area at the front) 26 Rear area (specified rear area) 30 Joint

Claims

1. A pair of left and right rear side members extending in the front-rear direction at an interval in the vehicle width direction are provided, Each of the rear side members includes a die-cast front member constituting a front portion of the rear side member, and a sheet metal rear member having a front end joined to the front member and a rear end joined to a rear bumper part and constituting a rear portion of the rear side member, The rear member has a deformation origin portion in a middle portion in the front-rear direction, which is a starting point when the rear member is bent and deformed due to a load input from the rear of the vehicle, and the rear member is bent and deformed rearward of the joint with the front member during a rear collision. A vehicle rear structure characterized by:

2. the rear member includes two opposing wall portions opposing each other in the vehicle width direction, The deformation starting point portion is provided as a bent portion formed by bending at least one of the two opposing wall portions. The vehicle rear structure according to claim 1 .

3. The rear member has predetermined areas on the front and rear sides of the deformation starting point, each of which has a cross-sectional strength higher than the cross-sectional strength of the deformation starting point. The vehicle rear structure according to claim 1 or 2, characterized in that:

4. In the predetermined area on the front side of the deformation starting point, the cross-sectional shape of the rear member is widened at the deformation starting point. The vehicle rear structure according to claim 3 .

5. a support bracket included in the rear bumper component is overlapped and fixed to the rear end portion of the rear member from below in the predetermined area on the rear side of the deformation starting point portion, The front end of the support bracket is located near the rear of the deformation starting point. The vehicle rear structure according to claim 3 .

6. The lower surface of the support bracket is an inclined surface that slopes downward from the front end portion fixed to the lower surface of the rear member toward the rear in a side view of the vehicle. The vehicle rear structure according to claim 5 .

7. the rear member has a vertical cross-sectional shape along the vehicle width direction that includes a U-shaped cross-section that is open upward, the longitudinal cross-sectional shape at the rear end of the front member includes a U-shaped cross-section that opens upward to match the longitudinal cross-sectional shape of the rear member, the rear end portion of the front member and the front end portion of the rear member are joined together with the U-shaped cross sections overlapping each other, A reinforcing rib extending in the front-rear direction is formed at the joint between the front member and the rear member. The vehicle rear structure according to claim 1 .

8. the front member includes a suspension support portion on which a rear suspension component is supported; The rear side member is divided into the front member and the rear member behind the suspension support portion. The vehicle rear structure according to claim 1 .

9. a floor cross member extending in the vehicle width direction and connecting the rear extension portions of the front members; The rear side member is divided into the front member and the rear member behind the floor cross member. The vehicle rear structure according to claim 1 .

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