JPH06127435A - Rear under body construction - Google Patents

Abstract

PURPOSE:To restrain vibration of a rear floor pan by favorably setting the fitting points of a rear subframe, in a rear under body construction in which rear floor side members on both ends in the width direction of a vehicle are combined with cross members and a rear subframe is provided in the vicinity of the combining points. CONSTITUTION:In the rear under body 10A of an automobile body, a pair of rear floor side members 12 of U-shaped section are arranged in the vicinity of both end parts in the width direction of a vehicle, and the underside 14A of a rear floor pan 14 is fitted by welding to the flanges 12B, 12D bendingly formed on the insides and outside in the vehicle width direction of them. Both end parts of a rear floor cross member 18 are combined with the middle parts of the respective side members 12 through brackets 22. A rear subframe 36 fitting lower arms 37 is fitted to the brackets 22 with bolts 38, but in this case, the fitting points S are set between a line M connecting together the axes of a pair of the side members 12 and a line N connecting together the lower end faces of the members 12, and in the territory inside the inside positions of the members 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear underbody structure of an automobile body, and more particularly to a rear underbody structure provided with a rear subframe.

[0002]

2. Description of the Related Art Generally, an input from a road surface to a tire is transmitted to a body via a suspension. In particular, when the vehicle is traveling on a rough road, the input to the tire becomes large, which increases the vibration of the body and causes road noise.

On the other hand, in order to reduce the road noise, it is sufficient to block the input from the road surface, but in this case, the steering stability deteriorates. It is also conceivable to set a sound-insulating / insulating material at the body sounding portion or to increase the rigidity of the body input portion of the suspension, and an example of increasing this rigidity is disclosed in Japanese Utility Model Laid-Open No. 3-26677.

As shown in FIG. 11, this rear underbody structure 70 has a reinforcing gasset 74 fixed to the inside of the wheel house inner 72 in the vehicle width direction.
In the structure in which the lower end of the rear floor side member 76 is embedded and fixed in the rear floor side member 76, the cross member 78 is provided between the reinforcement gusset 74 embedded portions of the rear floor side member 76.
And the rear sub-frame 80 is fixed to the lower surface portions of the left and right rear floor side members 76 where the reinforcing gusset 74 is embedded. Therefore, since the input from the rear sub-frame 80 can be transmitted to the wheel house inner 72 via the reinforcing gusset 74, the mounting rigidity of the rear sub-frame 80 can be improved and the left and right rear floor sides can be mounted. Member 76
Since the embedded fixing portions of the reinforcing gusset 74 can be connected and coupled by the cross member 78 and the rear subframe 80, the rigidity of the body input portion of the suspension can be increased.

[0005]

However, in this rear underbody structure 70, the mounting point S of the rear sub-frame 80 is on the main axis H passing through the axis P of the rear side member 76, and the mounting point S is the rear side member. The axis P of 76 is offset by Lz downward. Therefore, the influence of the moment FyLz about the axis P of the rear side member 76 by the input Fy of the input Fy acting inward in the horizontal direction and the input Fz acting in the lower side in the vertical direction which are generated at the attachment point S of the rear sub-frame 80. Becomes larger, and Fig. 1
As indicated by the imaginary line of No. 1, the cross member 78 is bent upward to vibrate the floor pan 82 and generate road noise. In order to reduce this vibration, conventionally, a dynamic damper is mounted on the rear subframe 80 to reduce the input Fy, resulting in an increase in weight.

In consideration of the above facts, an object of the present invention is to obtain a rear underbody structure capable of sufficiently suppressing the vibration of the rear floor pan without increasing the weight and sufficiently reducing the road noise.

[0007]

A rear underbody structure according to a first aspect of the present invention includes a pair of rear floor side members arranged along the vehicle front-rear direction in the vicinity of both ends in the vehicle width direction at the lower rear portion of the vehicle body, A cross member which is arranged along the vehicle width direction and whose both ends in the vehicle width direction are respectively coupled to the pair of rear floor side members, and a rear having an attachment point near a coupling portion between the pair of rear floor side members and the cross member. A rear underbody structure including a subframe, wherein a line connecting an axis of each of the pair of rear floor side members to a mounting point of the rear subframe and a line of connecting a lower end surface of the pair of rear floor side members. It is characterized in that it is provided in the region between the inner side surface positions of the pair of rear floor side members in the vehicle width direction.

Further, the rear underbody structure of the invention described in claim 2 is, in the invention described in claim 1, from the line connecting the respective axial centers of the pair of rear floor side members to the attachment point of the rear subframe. Is set to be shorter than the length from the vertical line drawn from each axis of the pair of rear floor side members to the attachment point of the rear subframe.

[0009]

In the rear underbody structure of the invention described in claim 1, a line connecting the attachment points of the rear sub-frame to each axis of the pair of rear floor side members and a line connecting the lower end surfaces of the pair of rear floor side members. Since it is provided between the inner side positions of the pair of rear floor side members in the vehicle width direction, the input from the lower arm acts horizontally inward with respect to the mounting point of the rear subframe. The moment around the axis of the rear floor side member that occurs and the moment around the axis of the rear floor side member that occurs due to the input from the lower arm that acts vertically downward with respect to the mounting point of the rear subframe are Offset each other. For this reason,
The vertical bending of the cross member can be reduced, the vibration of the rear floor pan can be sufficiently suppressed without attaching a dynamic damper, that is, without increasing the weight, and the road noise can be sufficiently reduced.

Further, generally, the input acting from the lower arm in the horizontal direction with respect to the mounting point of the rear subframe is the lower side in the vertical direction with respect to the mounting point of the rear subframe by the input from the lower arm. Therefore, in the rear underbody structure of the invention as set forth in claim 2, the length from the line connecting the axial centers of the pair of rear floor side members to the mounting point of the rear sub-frame is set to By setting it shorter than the length from the vertical line drawn from each axis of the rear floor side member to the mounting point of the rear subframe, it is possible to make the moment around the axis of the rear floor side member after offsetting closer to zero. The road noise can be further reduced without increasing the weight.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a rear underbody structure according to the present invention will be described with reference to FIGS.

In the figure, the arrow FR indicates the front direction of the vehicle body, the arrow IN indicates the vehicle width inner direction, and the arrow UP indicates the vehicle body upward direction.

As shown in FIG. 4, a rear underbody 10A, which constitutes the lower rear part of the vehicle body 10, has a pair of rear floor side members 12 arranged in the vicinity of both ends in the vehicle width direction along the vehicle front-rear direction. . The front end portions of these rear floor side members 12 are joined to the floor side inner member 13, and the rear end portions thereof are lower back panels 1.
It is connected to 7.

As shown in FIG. 1, the cross-sectional shape of the rear floor side member 12 when viewed from the front-rear direction of the vehicle body is a U-shaped cross-section with the opening facing upward, and the upper end portion of the inner wall portion 12A in the vehicle width direction. Is a flange 12B that is bent toward the inside in the vehicle width direction, and an upper end portion of the outside wall portion 12C in the vehicle width direction is bent toward the outside in the vehicle width direction to form a flange 12D. These flanges 12B and 12D are welded to the vehicle width direction ends of the lower surface 14A of the rear floor pan 14, respectively. Therefore, the rear floor side member 12 and the rear floor pan 14 form a closed cross-section structure 16 extending in the vehicle front-rear direction.

On the other hand, the end of the rear floor pan 14 in the vehicle width direction is bent upward to form a flange 14B, which is the rear wheel house inner 1.
5 (see FIG. 4) is welded to the lower edge.

Between the pair of rear floor side members 12 which are substantially central to the rear wheel house inner,
Rear floor cross member 1 extending in a vehicle width direction on a substantially straight line
8 are arranged.

As shown in FIG. 2, the cross-sectional shape of the rear floor cross member 18 as viewed in the vehicle width direction is a U-shaped cross section with the opening facing upward, and the upper end of the front side wall portion 18A in the vehicle front-rear direction. The portion is bent toward the front side in the front-rear direction of the vehicle body to form a flange 18B.
The upper end portion of C is bent toward the rear side in the front-rear direction of the vehicle body to form a flange 18D.

As shown in FIG. 1, these flanges 1
8B and 18D are respectively the lower surface 1 of the rear floor pan 14.
It is welded to 4A. Therefore, the rear floor cross member 18 and the rear floor pan 14 form a closed cross-section structure 20 extending in the vehicle width direction.

As shown in FIG. 2, a bracket 22 is arranged on the vehicle width direction outer side portion of the rear floor cross member 18. The cross-sectional shape of the bracket 22 as viewed in the vehicle width direction is a U-shaped cross section with the opening facing upwards.
An upper end portion of the vehicle front-rear direction front side wall portion 22A is bent toward the vehicle body front-rear direction front side to form a flange 22B, and an upper end portion of the vehicle body front-rear direction rear side wall portion 22C is bent toward the vehicle body front-rear direction rear side. It is said that.

As shown in FIG. 1, these flanges 2
2B and 22D are the lower surface 1 of the rear floor pan 14, respectively.
It is welded to 4A. Also, these flanges 22
Stepped portions 18E and 18F recessed at the vehicle width direction inner ends of the flanges 18B and 18D of the rear floor cross member 18 are welded to the lower surfaces of the B and 22D in the vehicle width direction. On the other hand, recessed step portions 22E and 22F are formed at the vehicle width direction outer end portions of these flanges 22B and 22D, and these step portions 22E and 22F are the lower surface of the flange 12B of the rear floor side member 12. Is welded to.

A projecting step portion 22H is formed at the vehicle width direction inner end portion of the base portion 22G of the bracket 22.
These step portions 22H are welded to the vehicle width direction outer end portion 18H of the base portion 18G of the rear floor cross member 18. Further, an outer side portion of the bracket 22 in the vehicle width direction is deeper than an inner side portion thereof, and an inclined portion 22J is formed in a substantially middle portion of the bracket 22 in the vehicle width direction. A flange 22J extends outwardly in the vehicle width direction at an end portion of the base portion 22G of the bracket 22 in the vehicle width direction. The flange 22J extends toward the vehicle width direction and is the base portion 12 of the rear floor side member 12.
It is welded to the lower surface of E.

An outer end portion of the front wall portion 22A in the vehicle front-rear direction of the bracket 22 is bent toward the front side in the front-rear direction of the vehicle body to form a flange 22L. The end portion is bent toward the rear side in the front-rear direction of the vehicle body to form a flange 22M.

As shown in FIG. 1, these flanges 2
2L and 22M are rear floor side members 12 respectively
Is welded to the inner side wall portion 12A of the vehicle width direction. Therefore,
The bracket 22 and the rear floor pan 14 have a closed cross-section structure 2
0 and the rear floor side member 12 are connected to each other to form a closed cross-section structure 24 extending in the vehicle width direction.

In the closed cross-section structure 24, a rectangular reinforcing plate 26 is arranged substantially horizontally.

As shown in FIG. 2, the cross-sectional shape of the reinforcing plate 26 as viewed from the vehicle width direction is a U-shaped cross section with the opening facing upward, and the front side wall portion 26A of the vehicle body front-rear direction has the bracket 22. The vehicle body front-rear direction front side wall portion 22A is welded, and the vehicle body front-rear direction rear side wall portion 26B is welded to the vehicle body front-rear direction rear side wall portion 22C. Further, at the vehicle width direction outer end portion of the base portion 26C of the reinforcing plate 26,
A side wall portion 26D is formed upward. The side wall portion 26 is welded to the vehicle width direction inner side wall portion 12A of the rear floor side member 12, and both ends thereof are connected to the vehicle body front-rear direction front side wall portion 22A and the vehicle body front-rear direction rear side wall portion 26B, respectively.

A pair of through holes 28 (see FIG. 1) are formed in the base portion 26C of the reinforcing plate 26 at a substantially central portion in the vehicle front-rear direction at a predetermined interval in the vehicle front-rear direction, and an upper surface of the base portion 26C is formed. A pair of nuts 30 are welded coaxially with the through holes 28.

A pair of elongated holes 32 are formed in a portion of the base portion 22G of the bracket 22 which faces the pair of through holes 28, and the pair of elongated holes 32 are longitudinal in the longitudinal direction of the vehicle body. ing. Base 22 of bracket 22
Between G and the base portion 26C of the reinforcing plate 26, a pair of spacers 34 is welded coaxially with the pair of through holes 28.

Therefore, as shown in FIG. 1, the rear subframe 36 to which the lower arm 37 is attached is attached to the bracket 22 by inserting the rear subframe 36 into the attaching portion 36A from below.
The leg portions 38A of the mounting bolts 38 of the book are respectively provided with the long holes 3
2, through the spacer 34 and the through hole 28, the nut 30
It is carried out by screwing into.

As shown in FIG. 3A, a mounting point S of the rear subframe 36 to the bracket 22, that is, an intersection S of the lower surface of the base portion 22G of the bracket 22 and the axis 38B of the mounting bolt 38 is a pair. Between a line M connecting the axes P of the rear floor side members 12 and a line N connecting the lower end surfaces of the bases 12E of the pair of rear floor side members 12, and from the inner side surface positions L of the pair of rear floor side members 12. It is a shaded area in FIG. 3A on the inner side in the vehicle width direction.

Further, as shown in FIG. 3B, the length Lz from the line M connecting the axes P of the pair of rear floor side members to the mounting point S of the rear sub-frame is the same as that of the pair of rear floor side members. It is shorter than the length Ly from the vertical line H drawn from each axis P to the mounting point S of the rear subframe.

Next, the operation of this embodiment will be described.
The input from the tire vibrated due to traveling on a rough road is input to the rear subframe 36 via the lower arm 37, but in the rear underbody structure of this embodiment, the mounting point S of the rear subframe 36 is connected to a pair of rear floors. It is between a line M connecting each axis P of the side members 12 and a line N connecting the lower end surfaces of the pair of rear floor side members 12, and in the vehicle width direction from each inner side surface position L of the pair of rear floor side members 12. Since it is provided in the inner area (hatched area in FIG. 3 (A)), as shown in FIG. 3 (B), the input from the lower arm 37 causes it to move horizontally inward with respect to the mounting point S of the rear sub-frame 36. Around the axis P of the rear floor side member 12 generated by the acting input Fy (FIG. 3B).
In the direction opposite to the clockwise direction at) FyL
z and the input Fz acting vertically downward with respect to the mounting point S of the rear sub-frame 36 by the input from the lower arm 37, around the axis P of the rear floor side member 12 (clockwise rotation in FIG. 3B). Direction F) and the moment FzLy cancel each other out.

Therefore, the twist of the rear floor side member 12 is reduced, and the vertical deflection of the rear floor cross member 18 can be reduced. As a result, the vibration of the rear floor pan can be prevented without mounting the dynamic damper, that is, without increasing the weight. Can be sufficiently suppressed, and road noise can be sufficiently reduced.

Further, since the rear sub-frame 36 is shortened, the bending rigidity can be ensured even if the cross section of the rear sub-frame 36 is reduced, so that the weight can be further reduced.

Further, generally, the input Fy acting horizontally inward with respect to the mounting point P of the rear subframe 36 by the input from the lower arm 37 is the mounting point P of the rear subframe 36 by the input from the lower arm 37. With respect to the rear underbody structure of the present embodiment, the input Fz that acts on the lower side in the vertical direction is larger than the input Fz, and the attachment point of the rear sub-frame 36 is from the line M connecting the axes P of the pair of rear floor side members 12. By setting the length Lz to S to be shorter than the length Ly from the vertical line H drawn from each axis P of the pair of rear floor side members 12 to the mounting point S of the rear subframe 36 (Lz <Ly). , The moment around the axis P of the rear floor side member 12 after offsetting can be made closer to 0, further reducing the road noise. It can be.

Further, in this embodiment, since the reinforcing plate 26 is provided, the input from the rear sub-frame 36 can be surely transmitted to the rear floor side member 12. Further, by providing the spacer 34 and increasing the length of the mounting bolt 38, the rigidity of the rear sub-frame 36 near the mounting point S is improved.

As shown in FIG. 5, the spacer 34
Except for, the mounting position of the reinforcing plate 26 is lowered, and the base portion 22G of the bracket 22 and the base portion 26 of the reinforcing plate 26 are removed.
C may be directly welded.

Next, a second embodiment of the rear underbody structure according to the present invention will be described with reference to FIGS. 6 (A) and 6 (B).

Regarding the same members as in the first embodiment,
The same reference numerals are given and the description thereof is omitted.

As shown in FIGS. 6 (A) and 6 (B), in the bracket 22 of this embodiment, the step portion 22H is formed.
A side wall portion 22N is formed from an inner edge portion in the vehicle width direction toward the vehicle body obliquely inward, and both end portions in the vehicle body front-rear direction of the side wall portion 22N are respectively in the vehicle body front-rear direction front side wall portion 22A.
Is welded to the rear side wall portion 22C of the vehicle body front-rear direction. A flange 22P is formed at the upper end of the side wall 22N toward the inside in the vehicle width direction.
Is welded to the lower surface 14A of the rear floor pan 14.

Therefore, as shown in FIG. 6A, the closed cross-section structure 24 formed by the bracket 22, the rear floor side member 12, and the rear floor pan 14 has a closed cross-section structure even when viewed from the front-rear direction of the vehicle body. Become. Therefore, even if the reinforcing plate 26 described in the first embodiment is not provided, the joint rigidity of this portion can be improved.
Therefore, also in this embodiment, the same effect as that of the first embodiment can be obtained. The nut 30 is directly welded to the spacer 34.

Further, as shown in FIG. 7, the spacer 34
Except the nut 30 directly to the base 22G of the bracket 22
It may be welded to.

Next, a third embodiment of the rear underbody structure according to the present invention will be described with reference to FIG.

Regarding the same members as in the second embodiment,
The same reference numerals are given and the description thereof is omitted.

As shown in FIG. 8, in this embodiment, the portion between the pair of rear floor side members 12 of the rear floor pan 14 is curved downward in an arc shape. Also,
At the inner end in the vehicle width direction of the base portion 22G of the bracket 22,
A flange 22J is formed downward inward in the vehicle width direction. The flange 22J is an outward end 18H in the vehicle width direction of a base portion 18G of the rear floor cross member 18 curved downward in an arc shape along the rear floor pan 14. Is welded to.

Therefore, as shown in FIG. 8, when the input Fy acting inward in the horizontal direction and the input Fz acting downward in the vertical direction act on the mounting point S of the rear sub-frame 80, the rear floor side member 12 is actuated. A moment FyLz and a moment FzLy act on the axis P of. In this case, if the rear floor cross member 18 is straight,
The rear floor cross member 18 is not easily deformed by the input Fy (acting as a compressive force on the rear floor cross member 18), but in the present embodiment, the rear floor cross member 18 is curved downward in an arc shape. Therefore, the rear floor cross member 18 is bent downward by the compressive force Fy.

At this time, the displacement of the rear floor cross member 18 (arrow G (Fy) in FIG. 8) is caused by the moment FyLz about the axis P of the rear floor side member 12 generated by the input Fy, and the rear floor cross member 1 is generated.
8 is the direction opposite to the displacement of 8 (arrow G (FyLz) in FIG. 8). Therefore, the displacement G (FyLz) of the rear floor cross member 18 caused by the moment FyLz is equal to the displacement G (FzLy) of the rear floor cross member 18 caused by the moment FzLy and the displacement arrow G (Fy) of the rear floor cross member 18 caused by the compressive force Fy. And can be offset. As a result, deformation of the rear floor cross member 18 can be suppressed without significantly shifting the attachment point S inward.

In this embodiment, the rear floor pan 14 is used.
The portion between the pair of rear floor side members 12 is curved downward in an arc shape, and the base portion 18G of the rear floor cross member 18 is also curved downward along the rear floor pan 14 in an arc shape. In order to secure the rigidity of the rear floor, as shown in FIG. 9, the rear floor pan 14 may be horizontal and only the base portion 18G of the rear floor cross member 18 may be curved downward in an arc shape.

Next, a fourth embodiment of the rear underbody structure according to the present invention will be described with reference to FIG.

Regarding the same members as in the first embodiment,
The same reference numerals are given and the description thereof is omitted.

In this embodiment, as shown in FIG. 10, between the rear floor side member 12 and the bracket 22,
The rear floor side member bracket 17 is interposed. The cross-sectional shape of the rear floor side member bracket 17 when viewed from the front-rear direction of the vehicle body is a U-shaped cross-section with the opening facing upward, and the upper end of the inner wall portion 17A in the vehicle width direction is the vehicle of the rear floor side member 12. Width-direction inner wall 1
It is welded to the bottom of 2A. Further, the upper end portion of the vehicle width direction outer side wall portion 17B is welded to the lower portion of the vehicle width direction outer side wall portion 12C of the rear floor side member 12, and the rear floor side member bracket 17 forms a closed cross section with the rear floor side member 12. Below the structure 16 is a closed cross-section structure 16
A closed cross-section structure 19 is formed along the line.

Therefore, the axis P1 of the portion of the rear floor side member 12 to which the bracket 22 is attached is below the axis P of the rear floor side member 12. For this reason,
Between a line M1 connecting the respective axial centers P1 of the pair of rear floor side member brackets 17 and a line N1 connecting the lower end surfaces of the base portions 17C of the pair of rear floor side member brackets 17, and in each of the pair of rear floor side members 12. A region on the inner side in the vehicle width direction from the side surface position L (a region of a diagonal line rising to the right in FIG. 10), that is, a canceling region is a canceling region when the rear floor side member bracket 17 is not provided (FIG. 10).
The area of the mounting point S is greatly increased compared to the area of the lower right diagonal line).

[0052]

According to the first aspect of the present invention, the mounting point of the rear sub-frame is between the line connecting the respective axial centers of the pair of rear floor side members and the line connecting the lower end surfaces of the pair of rear floor side members, Moreover, since it is provided in the area on the inner side in the vehicle width direction of each inner side surface of the pair of rear floor side members, the vibration of the rear floor pan can be sufficiently suppressed without causing an increase in weight, and road noise can be sufficiently reduced. Have the effect.

According to the present invention, the length from the line connecting the shaft centers of the pair of rear floor side members to the mounting point of the rear subframe is lowered from the shaft centers of the pair of rear floor side members. Since it is set shorter than the length from the vertical line to the mounting point of the rear subframe, the moment around the axis of the rear floor side member after offsetting can be made closer to 0, and road noise can be further reduced. Has excellent effect.

[Brief description of drawings]

FIG. 1 is a sectional view showing a rear underbody structure of a first embodiment of the present invention as seen from the front of a vehicle body.

FIG. 2 is an exploded perspective view of a mounting portion of a rear sub-frame of the rear underbody structure of the first embodiment of the present invention, which is viewed obliquely from the front inside the vehicle body.

FIG. 3A is a cross-sectional view showing a region in which a mounting point of a rear subframe of the rear underbody structure of the first embodiment of the present invention exists, and FIG. 3B is a rear view of the first embodiment of the present invention. It is an explanatory view of an operation of an underbody structure.

FIG. 4 is a perspective view of a lower portion of the vehicle body to which the rear underbody structure of the first embodiment of the present invention is applied, as seen from diagonally front of the vehicle body.

FIG. 5 is a cross-sectional view showing a modified example of the rear underbody structure of the first embodiment of the present invention as seen from the front of the vehicle body.

FIG. 6 (A) is a sectional view of the rear underbody structure of the second embodiment of the present invention seen from the front of the vehicle body, and FIG. 6 (B) is a bracket of the rear underbody structure of the second embodiment of the present invention. FIG. 6 is a perspective view showing the inside of the vehicle as seen obliquely from the front.

FIG. 7 is a sectional view showing a modified example of the rear underbody structure of the second embodiment of the present invention as seen from the front of the vehicle body.

FIG. 8 is a sectional view showing a rear underbody structure of a third embodiment of the present invention as seen from the front of the vehicle body.

FIG. 9 is a cross-sectional view showing a modified example of the rear underbody structure of the third embodiment of the present invention as seen from the front of the vehicle body.

FIG. 10 is a sectional view showing a rear underbody structure of a fourth embodiment of the present invention as seen from the front of the vehicle body.

FIG. 11 is a sectional view showing a rear underbody structure of a conventional example as seen from the front of the vehicle body.

[Explanation of symbols]

 10 Car Body 10A Rear Underbody 12 Rear Floor Side Member 14 Rear Floor Pan 18 Rear Floor Cross Member 20 Closed Sectional Structure 22 Bracket 24 Closed Sectional Structure 26 Reinforcement Plate 30 Nut 36 Rear Subframe 37 Lower Arm

Claims (2)

[Claims] 1. A pair of rear floor side members arranged along the vehicle front-rear direction near both ends in the vehicle width direction at the rear lower part of the vehicle body, and a pair of rear floors arranged along the vehicle width direction having both ends in the vehicle width direction. A rear underbody structure including: cross members respectively coupled to side members; and a rear subframe having an attachment point near a coupling portion between the pair of rear floor side members and the cross member, the rear subbody structure comprising: The mounting point of the frame is located between the line connecting the respective axial centers of the pair of rear floor side members and the line connecting the lower end faces of the pair of rear floor side members and from the inner side surface positions of the pair of rear floor side members. Rear underbody structure characterized by being provided in the region on the inner side in the width direction. 2. A length from a line connecting the respective axial centers of the pair of rear floor side members to a mounting point of the rear sub-frame is a vertical line drawn from the respective axial centers of the pair of rear floor side members, and the rear sub The rear underbody structure according to claim 1, wherein the length is set shorter than the length up to the attachment point of the frame.