JP2014008835A - Vehicle rear part structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle rear part structure which can absorb impact energy input in a rear part of a vehicle body, and can absorb the impact energy in a more stable state.SOLUTION: A vehicle body 10, to which a vehicle rear part structure is applied, includes a pair of rear side members 12, 14 which are arranged on both sides in a vehicle width direction and extend in a longitudinal direction of a vehicle. First beads 30, as starting points of bending the rear side members 12, 14 when a load is applied on the rear side members 12, 14 from behind the vehicle, are arranged on upper parts of the rear side members 12, 14. In addition, second beads 32, which are arranged on a front side of the vehicle from the first beads 30 and serve as starting points of bending the rear side members 12, 14 when the load is applied on the rear side members 12, 14 from behind the vehicle, are arranged on lower parts of the rear side members 12, 14.

Description

  The present invention relates to a vehicle rear structure.

  Patent Document 1 below discloses a vehicle rear structure that prevents a spare tire and a fuel tank from interfering with each other when a collision load is input to the rear portion of a vehicle body at the time of a rear collision.

  Briefly describing the technique described in this document, a pair of rear side members disposed on both sides in the vehicle width direction are provided at the rear of the vehicle body. Further, a low-rigidity portion serving as a deformation starting point is provided between the spare tire arrangement position and the fuel tank arrangement position in the rear side member.

  According to the above configuration, when a collision load due to a rear collision is input to the rear part of the vehicle body, the collision load is transmitted to the rear side member. When the collision load exceeds a certain value, the rear side member bends in a “<” shape starting from the low rigidity portion. This prevents the front end of the spare tire from interfering with the fuel tank.

JP 2006-205810 A

  However, in addition to increasing the absorption amount of the collision energy input to the rear part of the vehicle body, it is desirable that the collision energy absorption process be performed in a more stable state.

  In consideration of the above-mentioned facts, the present invention has an object to obtain a vehicle rear structure that can absorb the collision energy in a more stable state while increasing the absorption amount of the collision energy input to the rear part of the vehicle body. .

  A vehicle rear portion structure according to the present invention as set forth in claim 1 is provided on a rear portion of the vehicle and on both sides in the vehicle width direction, provided on a pair of rear side members extending in the front-rear direction of the vehicle, and on an upper portion of the rear side member, A first fragile portion serving as a starting point for bending the rear side member when a load from the rear of the vehicle is applied to the rear side member, and a lower portion of the rear side member, and is disposed on the vehicle front side with respect to the first fragile portion. A second fragile portion serving as a starting point for bending the rear side member when a load from the rear of the vehicle is applied to the rear side member.

  In the first aspect of the present invention, the first fragile portion and the second fragile portion are provided on the rear side member. Therefore, when the collision load due to the rear collision is input to the rear portion of the vehicle body and the collision load is transmitted to the rear side member, stress concentrates on the first fragile portion and the second fragile portion. Further, when this stress exceeds a certain value, the portion where the first fragile portion is formed on the rear side member is bent so as to project toward the vehicle lower side, and the portion where the second fragile portion is formed on the rear side member Is bent so as to project toward the upper side of the vehicle. Thus, in the present invention, the amount of collision energy absorbed is increased by bending the rear side member at two locations as described above. In the present invention, since the position and direction in which the rear side member bends are regulated by the first fragile portion and the second fragile portion, the deformation (mode) form of the rear side member is stabilized.

  According to a second aspect of the present invention, the vehicle rear structure according to the first aspect of the present invention is the vehicle rear structure according to the first aspect, wherein a section modulus of a cross section obtained by cutting a portion of the rear side member where the first weakened portion is provided in the vehicle width direction. The section of the rear side member where the second weakened portion is provided is set to be lower than the section modulus of a section cut in the vehicle width direction.

  In the present invention according to claim 2, the section modulus of the cross section obtained by cutting the portion where the first fragile portion is provided in the rear side member in the vehicle width direction is cut, and the portion where the second fragile portion is provided is cut in the vehicle width direction. It is set lower than the section modulus of the section. In other words, the stress is set so that the stress is concentrated on the portion where the first fragile portion is provided rather than the portion where the second fragile portion is provided on the rear side member. Therefore, when the collision load due to the rear collision is transmitted to the rear side member, the portion where the first fragile portion is formed on the rear side member is first bent so as to project toward the vehicle lower side, and then the second fragile portion on the rear side member. The portion where the portion is formed is bent so as to protrude upwardly from the vehicle.

  According to a third aspect of the present invention, there is provided a vehicle rear portion structure according to the first or second aspect, wherein a spare tire is disposed between the pair of rear side members in a plan view of the vehicle. An intermediate portion in the vehicle front-rear direction of the spare tire is disposed between the first fragile portion and the second fragile portion in a vehicle side view.

  In the third aspect of the present invention, when the rear portion of the vehicle body is viewed from the side of the vehicle, an intermediate portion in the vehicle longitudinal direction of the spare tire is provided between the first fragile portion and the second fragile portion provided in the rear side member. Has been placed. Therefore, the portion of the rear side member where the first fragile portion is formed bends so as to protrude toward the vehicle lower side, and the portion where the second fragile portion is formed protrudes toward the vehicle upper side. Then, the spare tire is inclined (inclined so that the rear end is lower than the front end of the spare tire). That is, in the present invention, the posture of the spare tire at the time of rear collision is stabilized.

  According to a fourth aspect of the present invention, there is provided a vehicle rear portion structure according to the third aspect, wherein the rear end portions of the pair of rear side members are connected via a bumper reinforcement extending in the vehicle width direction in a vehicle plan view. And an intermediate portion of the rear side member in the vehicle front-rear direction is connected via a rear cross member extending in the vehicle width direction, and the spare tire includes the pair of rear side members, the bumper reinforcement, and the rear cross. Arranged in the area surrounded by members.

  In the present invention described in claim 4, the spare tire is disposed in a region surrounded by the pair of rear side members, the bumper reinforcement, and the rear cross member. Therefore, when a collision load due to a rear collision is applied to the rear part of the vehicle body, the rear side member is bent as described above, and a part of the collision load is transmitted from the bumper reinforcement to the spare tire, and then this load is transferred from the spare tire to the rear tire. The load transmitted to the cross member and further input to the rear cross member is transmitted from the rear cross member to the front end sides of the pair of rear side members. That is, in the present invention, a part of the collision load due to the rear collision is transmitted to the front end sides of the pair of rear side members via the bumper reinforcement, the spare tire, and the rear cross member.

  In the present invention, when the rear side member is bent as described above, the spare tire is inclined (inclined so that the rear end is lower than the front end of the spare tire). Therefore, a load in the direction of lifting the cross member upward from the vehicle is input from the front end of the spare tire to the rear cross member. As a result, the rear side member is deformed so as to be bent upward of the vehicle by the load input from the rear cross member. That is, the collision energy is absorbed by this bending deformation.

  The vehicle rear portion structure according to the present invention described in claim 5 is the vehicle rear portion structure according to any one of claims 1 to 4, wherein a rear end portion of the rear side member projects toward the vehicle lower side, In addition, a projecting portion is provided that transmits the collision load to the rear side member when a collision load is applied to the rear portion of the vehicle body.

  In the present invention described in claim 5, the rear end member is provided with the protrusion having the above-described configuration. Therefore, the collision load due to the rear collision can be received in a wide range in the vehicle vertical direction, and the collision load is reliably transmitted to the rear end portion of the rear side member.

  The vehicle rear structure according to the first aspect of the present invention has an excellent effect that the collision energy input to the rear portion of the vehicle body can be absorbed and the collision energy can be absorbed in a more stable state.

  The vehicle rear structure according to the second aspect of the present invention has an excellent effect that the collision energy input to the rear portion of the vehicle body can be absorbed in a more stable state.

  The vehicle rear structure according to the third aspect of the present invention has an excellent effect that it is possible to suppress the spare tire from interfering with vehicle-mounted components at the time of a rear collision.

  In the vehicle rear structure according to the present invention, a part of the collision load due to the rear collision can be distributed and received on the front end side of the pair of rear side members via a spare tire or the like, and the rear portion of the vehicle body It has an excellent effect that the collision energy input to can be further absorbed.

  The vehicle rear portion structure according to the present invention according to claim 5 has an excellent effect that the collision load due to the rear collision can be reliably transmitted to the rear end portion of the rear side member.

(A) is the top view which looked at the rear part of the vehicle body to which the vehicle rear part structure of this embodiment was applied from the vehicle upper side, (B) is the side view which looked at the rear part of the vehicle body from the vehicle side. It is the perspective view which looked at the rear part of the vehicle body to which the vehicle rear part structure of this embodiment was applied from the vehicle diagonally lower side. (A) is the top view which looked at the rear side member from the vehicle upper side, (B) is the side view which looked at the rear side member from the vehicle side. (A), (B), and (C) are enlarged views showing cross sections of the rear side member shown in FIGS. 1 and 3 cut along lines 4A-4A, 4B-4B, and 4C-4C, respectively. It is sectional drawing. FIG. 6 is a side view showing a state in which a rear side member is bent from a first bead and a second bead as a starting point when a collision load is applied to the rear portion of the vehicle body. (A) is a plan view showing a state in which the rear side member arranged on the left side in the vehicle width direction is bent starting from the first bead when a collision load is applied to the rear part of the vehicle body, and (B) is a side view thereof. is there. (A) is a top view which shows the state which the rear side member arrange | positioned at the vehicle width direction both sides bent with the 1st bead and the 2nd bead as a starting point, when a collision load is added to the rear part of a vehicle body, (B) Is a side view thereof. (A) And (B) is a side view which shows the effect | action of a gusset when a collision load is added to the rear part of a vehicle body.

  Next, the vehicle rear portion structure according to the embodiment of the present invention will be described with reference to FIGS. The vehicle longitudinal direction rear side is indicated by an arrow RR, the vehicle width direction right side and left side are indicated by arrows RH and LH, respectively, and the vehicle vertical direction upper side is indicated by arrow UP. Moreover, in the following description, when simply indicating the front-rear direction and the up-down direction, the front-rear direction of the vehicle and the up-down direction of the vehicle are indicated.

  As shown in FIG. 2, the rear portion of the vehicle body 10 to which the vehicle rear structure of the present embodiment is applied is provided on both sides in the vehicle width direction, and a pair of rear side members 12 and 14 extending in the vehicle front-rear direction, A rear floor panel 16 extending between the rear side member 12 and the rear side member 14 and a suspension member 20 for supporting the suspension arm 18 and the like are provided. 1 and 2, the rear portion of the vehicle body 10 includes a bumper reinforcement 22 that connects the rear end portions of the rear side members 12 and 14 in the vehicle width direction, and the rear side members 12 and 14 in the vehicle front-rear direction. And a rear cross member 24 that connects the intermediate portion in the vehicle width direction. Hereinafter, the rear side members 12 and 14 will be described first, then the rear floor panel 16 and the suspension member 20 will be described, and finally the bumper reinforcement 22 and the rear cross member 24 will be described.

(Rear side members 12, 14)
As shown in FIG. 4B, the rear side member 12 is configured by joining a lower panel 26 formed in a hat-shaped cross section to an upper panel 28 formed in a flat plate shape. Since the rear side member 14 is formed symmetrically with the rear side member 12 in the vehicle width direction, the rear side member 14 is denoted by the same reference numeral as the rear side member 12 and description thereof is omitted.

  The lower panel 26 includes a bottom wall 26A extending in the vehicle width direction and the vehicle front-rear direction. The lower panel 26 includes side walls 26B that bend and extend toward the vehicle upper side from left and right ends of the bottom wall 26A in the vehicle width direction. Further, the lower panel 26 includes a flange portion 26 </ b> C that is bent and extends from the upper ends of the left and right side walls 26 </ b> B to the right and left sides in the vehicle width direction and joined to the upper panel 28. A ridge line L1 and a ridge line L2 extending in the vehicle front-rear direction are formed between the bottom wall 26A and the side wall 26B and between the side wall 26B and the flange portion 26C.

  The upper panel 28 includes a top wall 28A that extends in the vehicle width direction and the vehicle front-rear direction, and forms a substantially rectangular closed cross section together with the bottom wall 26A and the side wall 26B of the lower panel 26 by joining the lower panel 26. ing. In this embodiment, the rear side member 12 is configured by joining the lower panel 26 having a cross-sectional hat shape to the upper panel 28 formed in a flat plate shape. However, the rear floor panel 16 described later has a cross-sectional hat. You may comprise a rear side member by joining the lower panel 26 formed in the type | mold.

  Further, as shown in FIGS. 3A and 3B, the rear side member 12 is attached to the rear side member 12 when a load from the rear of the vehicle (a collision load due to a rear collision) is applied to the rear side member 12. The 1st bead 30 as the 1st weak part used as the starting point to bend and the 2nd bead 32 as the 2nd weak part are formed.

  Hereinafter, the 1st bead 30 and the 2nd bead 32 which are the principal parts of the present invention are explained.

  The first bead 30 is a triangular bead that is provided at the upper part of the rear side member, and is arranged on the rear side of the intermediate portion in the vehicle front-rear direction of a spare tire 36 that will be described later in a side view of the vehicle. FIG. 4A shows an enlarged cross-sectional view of a cross section of the first bead 30 cut along the vehicle width direction at the middle portion of the first bead 30 in the vehicle front-rear direction. As shown in this figure, the first bead 30 is formed between the left and right side walls 26B and the flange portion 26C (cuts the ridge line L1 formed between the side wall 26B and the flange portion 26C). Are formed so as to protrude on the right and left sides in the vehicle width direction with respect to the side wall 26B. Further, as shown in FIG. 3B, the first bead 30 is formed so as to become smaller from the middle part in the vehicle front-rear direction to the vehicle front side and the rear side. Further, as shown in FIG. 4A, the sectional modulus of the cross section of the rear side member 12 at the portion where the first bead 30 is formed (intermediate portion of the first bead 30 in the vehicle front-rear direction) is Z1. . Further, the section modulus Z1 is set to be smaller than the section modulus Z2 (see FIG. 4C) of the cross section of the rear side member 12 at a portion where a second bead 32 described later is formed.

  As shown in FIGS. 3A and 3B, the second bead 32 is provided at the lower portion of the rear side member, and is further forward than the intermediate portion in the vehicle longitudinal direction of a spare tire 36 described later in a side view of the vehicle. Is a triangular bead. FIG. 4C shows an enlarged cross-sectional view of a cross-section of the rear side member 12 cut along the vehicle width direction at an intermediate portion of the second bead 32 in the vehicle front-rear direction. As shown in this figure, the second bead 32 is formed between the left and right side walls 26B and the bottom wall 26A (cuts the ridge line L2 formed between the side wall 26B and the bottom wall 26A). Are formed so as to be recessed toward the inside of the closed cross section of the rear side member 12. Further, as shown in FIG. 3B, the second bead 32 is formed so as to become smaller from the middle part in the vehicle front-rear direction to the vehicle front side and the rear side, similarly to the first bead 30 described above. ing. Further, as shown in FIG. 4C, the sectional modulus of the cross section of the rear side member 12 at the portion where the second bead 32 is formed (intermediate portion of the second bead 32 in the vehicle front-rear direction) is Z2. .

  Further, as shown in FIGS. 2 and 3B, a gusset 34 is provided at the rear end of the rear side member 12 so as to protrude toward the vehicle lower side. The gusset 34 has a substantially inverted triangular shape extending from the both ends in the vehicle width direction of the joint wall 34A to the bottom wall 26A (of the lower panel 26) of the rear side member 12 and extending downward from the vehicle. And a protrusion 34B. Further, the rear end of the protruding portion 34B is formed so as to incline toward the front side of the vehicle as it goes to the vehicle lower side.

  As shown in FIG. 3B, a bracket 38 that connects the top wall 28 </ b> A of the upper panel 28 and the lower back panel 50 is provided at the rear end portion of the rear side member 12. Further, the front end of the bracket 38 is disposed at a position behind the first bead 30 and close to the first bead 30.

(Rear floor panel 16)
As shown in FIGS. 1A and 2, the rear floor panel 16 extends in the vehicle front-rear direction and the vehicle width direction, and is disposed between the rear side member 12 and the rear side member 14. Further, both ends of the rear floor panel 16 in the vehicle width direction are joined to the rear side member 12 and the rear side member 14, respectively. Further, the rear floor panel 16 is formed with a recess 16A that opens to the upper side of the vehicle. The recess 16A is formed in a circular shape when viewed from above the vehicle. Further, a spare tire 36 is accommodated in the recess 16A.

(Suspension member 20)
As shown in FIGS. 1 and 2, the suspension member 20 is disposed between the left and right rear tires 52, and a suspension 54, a suspension arm 18, a stabilizer 40, and the like that suspend the rear tires 52 are attached thereto. . The suspension member 20 is fixed to the front end side of the rear side members 12 and 14 via a mount cushion and a fastener (not shown).

(Bumper reinforcement 22 and rear cross member 24)
As shown in FIGS. 1A and 1B, the bumper reinforcement 22 extends in the vehicle width direction and has a substantially rectangular cross section when viewed from the side of the vehicle. The bumper reinforcement 22 is fixed to the rear ends of the rear side members 12 and 14 via brackets 58 and 60 provided at the rear ends of the rear side members 12 and 14. Further, the bumper reinforcement 22 is disposed at a position offset to the vehicle upper side of the spare tire 36 accommodated in the recess 16A of the rear floor panel 16 in a side view of the vehicle.

  The rear cross member 24 extends in the vehicle width direction and is provided at an intermediate portion of the rear side members 12 and 14 in the vehicle front-rear direction. The rear cross member 24 is formed in a substantially rectangular cross section when viewed from the side of the vehicle, and is disposed at a position in front of the second bead 32 and close to the second bead 32. Further, both ends of the rear cross member 24 in the vehicle width direction are joined to the rear side members 12 and 14, respectively. A drive battery 42 (a battery that stores electric power for supplying power to the drive motor of the hybrid vehicle) is provided above the rear cross member 24. This drive battery 42 is fixed to the floor of the vehicle body via a bracket 44. A fuel tank 46 is provided in front of the rear cross member 24 and between the rear side member 12 and the rear side member 14. The fuel tank 46 can be supplied with fuel via an inlet pipe (not shown).

  Further, a spare tire 36 is disposed in a region surrounded by the rear side members 12, 14, the bumper reinforcement 22, and the rear cross member 24 described above.

(Operation and effect of this embodiment)
Next, the operation and effect of this embodiment will be described.

  As shown in FIG. 1, when a collision load F due to a rear collision is input to the rear part of a vehicle body 10 to which the vehicle rear structure of the present embodiment is applied, the collision load F is transmitted to the rear side members 12 and 14. Then, stress concentrates on the first bead 30 and the second bead 32 formed on the rear side members 12 and 14. When this stress exceeds a certain value, as shown in FIG. 5, the portion where the first bead 30 is formed in the rear side members 12 and 14 is bent so as to protrude toward the vehicle lower side. The portions of the members 12 and 14 where the second beads 32 are formed are bent so as to protrude upward from the vehicle. As described above, in this embodiment, the collision energy is absorbed by bending the rear side members 12 and 14 as described above (bending in a substantially “Z” shape in a side view of the vehicle). In the present embodiment, since the position and direction in which the rear side members 12 and 14 are bent are regulated by the first bead 30 and the second bead 32, the deformation of the rear side members 12 and 14 is stabilized. That is, the vehicle rear portion structure of the present embodiment can absorb the collision energy input to the rear portion of the vehicle body and can absorb the collision energy in a more stable state.

  Further, in the present embodiment, as shown in FIGS. 4A and 4C, the section coefficient Z1 of a cross section obtained by cutting the portion of the rear side members 12 and 14 where the first beads 30 are provided in the vehicle width direction is as follows. The section coefficient Z2 of the cross section obtained by cutting the portion where the second bead 32 is provided in the vehicle width direction is set. In other words, the stress is set so that the stress is concentrated on the portion where the first bead 30 is provided in the rear side members 12 and 14 rather than the portion where the second bead 32 is provided. Therefore, when the collision load F due to the rear collision is transmitted to the rear side members 12, 14, first, the portion of the rear side members 12, 14 where the first bead 30 is formed is bent so as to project toward the vehicle lower side, Next, the portions of the rear side members 12 and 14 where the second beads 32 are formed are bent so as to project toward the vehicle upper side. That is, in the present embodiment, the position at which the rear side members 12 and 14 are bent and the order in which they are bent are adjusted by the first bead 30 and the second bead 32, so that the collision energy input to the rear portion of the vehicle body 10 is further increased. It can be absorbed in a stable state.

  Furthermore, in the present embodiment, when the rear portion of the vehicle body 10 is viewed from the side of the vehicle, the spare tire 36 is disposed between the first bead 30 and the second bead 32 provided on the rear side members 12 and 14 in the vehicle longitudinal direction. An intermediate part is arranged. Therefore, as shown in FIGS. 7A and 7B, the portion where the first bead 30 is formed in the rear side members 12 and 14 is bent so as to project toward the vehicle lower side, and the second bead is also formed. When the portion where 32 is formed is bent so as to protrude upward in the vehicle, the spare tire 36 is inclined (the rear end portion of the spare tire 36 is inclined so as to be lowered toward the vehicle lower side). That is, in this embodiment, the posture of the spare tire 36 at the time of rear collision is stabilized. As a result, in the present embodiment, it is possible to prevent or suppress the spare tire 36 from contacting (interfering) with the suspension member 20 or the fuel tank 46 at the time of a rear collision.

  In the present embodiment, the spare tire 36 is disposed in a region surrounded by the rear side members 12 and 14, the bumper reinforcement 22, and the rear cross member 24. Therefore, as shown in FIGS. 6 (A) and 6 (B), when a collision load F due to a rear collision is applied to a position offset to the left side in the vehicle width direction at the rear part of the vehicle body 10, it is provided on the left side in the vehicle width direction. The rear side member 12 bends with the first bead 30 as a starting point, and a part of the collision load F (load F1) is transmitted from the bumper reinforcement 22 to the spare tire. Next, the load F1 is transmitted from the spare tire 36 to the rear cross member 24, and the load F1 input to the rear cross member 24 is transmitted from the rear cross member 24 to the front end sides of the pair of rear side members 12 and 14. That is, in the present embodiment, a part of the collision load F (load F1) caused by the rear collision can be distributed and received on the front end sides of the pair of rear side members 12 and 14 via the spare tire 36 and the like.

  Further, in the present embodiment, a gusset 34 is provided at the rear ends of the rear side members 12 and 14. Therefore, as shown in FIG. 8A, the collision load F caused by the rear collision can be received in a wide range in the vehicle vertical direction, and the collision load F is more reliably received by the rear end portions of the rear side members 12 and 14. Can be transmitted. In particular, as shown in FIG. 8B, when the collision object 56 collides with a lower position in the rear portion of the vehicle body 10, the portion where the first beads 30 are formed on the rear side members 12 and 14 is first on the vehicle lower side. Bend so that it has a protruding shape. Then, the gusset 34 provided at the rear ends of the rear side members 12 and 14 comes into contact with the collision object 56. As a result, the portions of the rear side members 12 and 14 where the first beads 30 are formed are more difficult to bend. That is, in the present embodiment, the angle at which the portion where the first bead 30 is formed in the rear side members 12 and 14 can be stabilized, and as a result, the collision energy input to the rear portion of the vehicle body 10 can be further increased. It can be absorbed in a stable state.

  In the present embodiment, the example in which the gusset 34 is provided at the rear ends of the rear side members 12 and 14 has been described. However, the present invention is not limited to this, and the gusset 34 may be omitted. Further, for example, a hitch member for towing may be fixed to the gusset 34.

  Further, in the present embodiment, the example in which the spare tire 36 is disposed in a region surrounded by the rear side members 12 and 14, the bumper reinforcement 22, and the rear cross member 24 has been described. It is not limited. For example, even in a vehicle not equipped with the spare tire 36, the collision energy input to the rear portion of the vehicle body can be absorbed as described above.

  Furthermore, in this embodiment, although the example which provided the 1st bead 30 and the 2nd bead 32 has been demonstrated, this invention is not limited to this, For example, the 1st bead 30 in the rear side members 12 and 14 and the 2nd It is good also as a structure which provides the notch etc. as a 1st weak part and a 2nd weak part in the part in which the bead 32 was provided.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above, and various modifications other than the above can be implemented without departing from the spirit of the present invention. Of course.

12 Rear side member
14 Rear side member
22 Bumper reinforcement
24 Rear cross member
30 1st bead (1st weak part)
32 Second bead (second weak part)
34B Protrusion
36 Spare tires

Claims (5)

A pair of rear side members provided on both sides of the rear part of the vehicle and in the vehicle width direction and extending in the front-rear direction of the vehicle;
A first fragile portion provided at an upper portion of the rear side member, and serving as a starting point for bending the rear side member when a load from the rear of the vehicle is applied to the rear side member;
A second fragile portion that is provided at a lower portion of the rear side member and is disposed on the vehicle front side with respect to the first fragile portion, and serves as a starting point for bending the rear side member when a load from the rear of the vehicle is applied to the rear side member. When,
A vehicle rear structure comprising:   The section coefficient of the cross section of the rear side member where the first weakened portion is provided is cut in the vehicle width direction. The cross section modulus of the rear side member of the rear side member provided with the second weakened portion is the cross section of the rear side member. The vehicle rear structure according to claim 1, wherein the vehicle rear structure is set to be lower than a section modulus. A spare tire is disposed between the pair of rear side members in a plan view of the vehicle,
The vehicle rear structure according to claim 1 or 2, wherein an intermediate portion of the spare tire in the vehicle front-rear direction is disposed between the first fragile portion and the second fragile portion in a vehicle side view. Rear end members of the pair of rear side members are connected via a bumper reinforcement extending in the vehicle width direction in a plan view of the vehicle, and an intermediate portion of the rear side member in the vehicle front-rear direction extends in the vehicle width direction. Connected through
The vehicle rear structure according to claim 3, wherein the spare tire is arranged in a region surrounded by the pair of rear side members, the bumper reinforcement, and the rear cross member.   The rear end portion of the rear side member is provided with a protruding portion that protrudes downward from the vehicle and transmits the collision load to the rear side member when a collision load is applied to the rear portion of the vehicle. Item 5. The vehicle rear structure according to Item 4.