Rear structure of vehicle body

A rear structure of a vehicle body including: an arc-shaped frame which is fixed at a middle portion along an extending direction thereof to a rear panel, and has first reinforcing portions in which both ends along the extending direction, which extend along a longitudinal direction of the vehicle body, and which have cross sections opening toward corresponding rear frames; and a pair of rear frames fixed at a rear end thereof to the rear panel, fixed at a front end thereof to corresponding side sill, and has a second reinforcing portion which extends along the longitudinal direction and which has a cross section opening toward the corresponding first reinforcing portion, wherein the first reinforcing portions and the corresponding second reinforcing portions are fixed to each other interposing side flanges of a spare tire pan therebetween.

TECHNICAL FIELD

The present invention relates to a rear structure of a vehicle body of which the weight of the vehicle at the rear can be reduced.

Priority is claimed on Japanese Patent Application No. 2007-123385, filed on May 8, 2007, the contents of which are incorporated herein by reference.

BACKGROUND ART

A pair of rear frames which extends substantially in the longitudinal direction of a vehicle body is provided at the left and right sides of the rear portion of a vehicle. The rear frames are fixed to a rear panel which forms a rear wall of the vehicle body at the rear end thereof, and are fixed to side sills which are provided on both sides of the vehicle body at the front end thereof. The rear frames transmit the collision load to the left and right side sills and absorb the collision energy by collapsing along substantially the longitudinal direction thereof during the rear-end collision. The rear frames are fixed to each other using a cross member at the front ends and substantially the middle positions thereof. Furthermore, the rear frames are fixed to a spare tire pan where a spare tire is stored (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2004-338419).

SUMMARY OF THE INVENTION

Problems to be Solved

The left and right rear frames extend substantially linearly along the longitudinal direction of the vehicle body in the conventional rear structure of the vehicle body. Therefore, in a case of a rear-end offset collision in which an input point of load is deviated from the center area in a vehicle width direction, the ratio of the load which is born at the rear frames may be different between the collided side and the uncollided side (for example, 70% at the collided side and 30% at the uncollided side).

In the conventional rear end structure of the vehicle body, it is considered that the load is applied largely to the rear frame of the collided side during the rear-end offset collision. Therefore, it is necessary to reinforce the rear frames in order to support the large load: as a result, it is for the frame weight in the rear end of the vehicle body is increased.

Means to Solve the Problem

An object of the present invention is to provide a rear structure of a vehicle body in which the weight of a frame in the rear vehicle body can be reduced by enabling collision load during a rear-end offset collision to be supportedly dispersed at the rear end of the vehicle efficiently.

In order to solve the above problem, the present invention is a rear structure of a vehicle body including: a left-and-right pair of rear frames which extend along a longitudinal direction of a vehicle body; a spare tire pan which is supported between the rear frames; an arc-shaped frame which forms an arc-shape opening forward of the vehicle body as seen in a plan view; a rear panel which forms a rear wall of the vehicle body; and a pair of side sills which is provided on both sides of the vehicle, wherein: the arc-shaped frame is fixed at a middle portion along an extending direction thereof to the rear panel, and has first reinforcing portions in which both ends along the extending direction, which extend along the longitudinal direction, and which have cross sections opening toward the corresponding rear frames; each of the rear frames is fixed at a rear end thereof to the rear panel, is fixed at a front end thereof to the corresponding side sill, and has a second reinforcing portion which extends along the longitudinal direction and which has a cross section opening toward the corresponding first reinforcing portion; and the first reinforcing portions and the corresponding second reinforcing portions are fixed to each other interposing side flanges of the spare tire pan therebetween.

According to the present invention, when collision load is input to the rear panel via a bumper and the like during a rear-end offset collision, the collision load is input mainly to the rear end of the first frame at the collided rear frame and the top portion of the arc-shaped frame. The load input to the top portion of the arc-shaped frame is input substantially equally to the left-and-right rear frames via both ends of the arc-shaped frame. The collision load can be transmitted efficiently to the spare tire pan since the arc-shaped frame and the first frames are fixed to each other with interposing the flanges of the spare tire pan.

According to the present invention, a load transmission path from the rear frames to the side sills and the other load transmission path from the top of the arc-shaped frame to both the rear frames and the side sills via both ends of the arc-shaped frame are provided. Therefore, without increasing the thickness of the rear frames, the collision load can be dispersed in the rear of the vehicle body. As a result, the weight of the vehicle frame can be reduced.

Further, in the present invention, flanges of the arc-shaped frame and the rear frames are fixed to each other interposing the side flanges of the spare tire pan, so that a closed cross section structure is formed. Therefore, the spare tire pan can be efficiently utilized to absorb the collision load since the collision load is transmitted to the spare tire pan. In addition, the flanges of the arc-shaped frame and the rear frames are fixed interposing the spare tire pan. Accordingly, the rigidity of the load transmission paths between the arc-shaped frame and the rear frames can be improved certainly.

In the present invention, it is preferable that each of the rear frames include: a first frame which is fixed to the rear panel; and a second frame which is fixed to the side sill and the front end of the first frame, and which has a rigidity higher than the rigidity of the first frame.

In this case, damage to a front portion of the vehicle body can be prevented since the first frame is deformed before the second frame.

In the present invention, it is preferable that the rear structure of a vehicle body further include a plurality of arc-shaped beads protruding upward and forming concentric arc shapes.

In this case, the collision load of the rear-end collision can be absorbed by deformation of the arc-shaped beads since the arc-shaped beads are easier to be deformed than the other portions in the spare tire pan.

In the present invention, it is preferable that the rear structure of a vehicle body further have linear beads extending from both ends of the arc-shaped beads and protruding upward, wherein the arc-shaped beads and the linear beads form U-shape beads opening forward of the vehicle body.

In this case, the linear beads are provided at the front of the arc-shaped beads extending in the width direction of the vehicle body. The arc-shaped beads are easier to be deformed than the linear beads having high rigidity along the longitudinal direction of the vehicle body in the rear-end collision. Accordingly, the collision load can be absorbed in the arc-shaped beads at the rear of the vehicle body, so that the deformation at the rear of the vehicle body can be prevented.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be explained below referring to drawings. Hereinafter, the words “front”, “rear”, “top”, and “bottom” in the following description denote “front”, “rear”, “top”, and “bottom” of a vehicle body if there is no explanation. An arrow F in the drawings denotes the front of the vehicle; and an arrow U denotes the top of the vehicle.

FIG. 1is a perspective view showing a vehicle1having a rear structure of a vehicle of the present invention.FIG. 2is a cross sectional view taken along the A-A line ofFIG. 1showing the vehicle1.FIG. 3is a perspective view taken along the B-B line ofFIG. 1.FIG. 4is a perspective view of the vehicle1diagonally from the bottom rear.

The vehicle1has a left-and-right pair of rear frames2which are arranged substantially along a longitudinal direction of a vehicle body on the bottom face of the rear of the vehicle body. Front ends of the rear frames2are fixed to side sills provided on left-and-right of the vehicle body and to a middle cross member4connecting rear ends of the side sills3. The rear frames2are provided with a rear cross member5at a middle portion thereof. The rear end of the rear frames2are fixed to a rear panel6forming a rear wall of the vehicle body. A bumper beam of a rear bumper (not shown) is arranged outside the rear panel6. A spare tire pan8which supports a spare tire7(refer toFIGS. 2,3) below a trunk is fixed to upper faces of the rear frames2and the rear cross member5.

The spare tire pan8includes a tire storing portion9which is depressed downward substantially in a circular shape from substantially the center of the spare tire pan8. The spare tire7is stored in the tire storing portion9(refer toFIGS. 2,3). A spare tire anchor nut10for fixing the spare tire7by a bolt is installed in a bottom wall of the tire storing portion9at the vicinity of the center portion of the bottom wall. A substantially conical portion11in which the center thereof protrudes upward so that the vicinity of the spare tire anchor nut10is at the top of the conical shape is provided on the bottom wall of the tire storing portion9.

Arc-shaped beads, specifically, five arc-shaped beads12ato12ewhich project upward are formed at substantially regular intervals on the substantially conical portion11of the spare tire pan8. The arc-shaped beads12ato12eare formed so as to have concentric arcs centered in the vicinity of the spare tire anchor nut10, and so that tops of the arcs face backward of the vehicle body (that is, so as to open forward of the vehicle body). Accordingly, as shown inFIG. 2, the arc-shaped beads12ato12eform a wavy pattern in a section along the longitudinal direction of the vehicle body at a rear region of the substantially conical portion11.

Linear beads13ato13eare formed in the spare tire pan along the longitudinal direction of the vehicle body so as to extend from both ends of the arc-shaped beads12ato12eto the vicinity of the rear cross member5. The linear beads13ato13eprotrude upward from the spare tire pan8as the arc-shaped beads12ato12e. The linear beads13ato13ehave cross sections continuous to cross sections of the arc-shaped beads12ato12e. The arc-shaped beads12ato12eand the linear beads13ato13eform U-shape beads opening forward of the vehicle body.

The left-and-right rear frames2which support the spare tire pan8are formed of first frames14at the rear side of the vehicle body and second frames15at the front side of the vehicle body. The first frames14are fixed to the rear panel6at rear ends thereof. The second frames15are fixed to the side sills3at front ends thereof and to the front ends of the first frame14at rear ends thereof. The first frames14and the second frames15have a hat-shaped cross section opening upward taken along a vehicle width direction; that is, in the first frames14and the second frames15, flanges are formed on both edges of a U-shape section opening upward. However, in a front portion of the first frame14, as shown inFIG. 3, a side wall facing the tire storing portion9of the spare tire pan8is gradually inclined inside of the vehicle width direction, so that substantially an L-shape second reinforcing portion is formed.

An arc-shaped frame20having substantially an arc shape as seen in the plan view connects a center portion of the rear panel6in the vehicle width direction with front regions of the first frames14. The arc-shaped frame20, as shown inFIGS. 2 and 3, has substantially an L-shape cross section orthogonal to an extending direction thereof, and is stacked and fixed to a rear flange of the spare tire pan8and the rear panel6at a top portion of the arc-shape thereof. Both ends (i.e., first reinforcing portions20a) of the arc-shaped frame20extend to the vicinity of rear ends of the left-and-right second frames15. As shown inFIG. 2, the top portion of the arc-shape of the arc-shaped frame20(that is, a middle portion in the extending direction) forms a closed boxed section together with the rear flange of the spare tire pan8.

As described above, the spare tire pan8is fixed to the upper face of the left-and-right rear frames2. Side flanges8of the first frames14at contacting portions with the second reinforcing portions16are inclined obliquely upward toward the side of the vehicle body along the upper shape of the second reinforcing portions16as shown inFIG. 3. The side flanges8aof the spare tire pan8are interposed between the first reinforcing portion20aand the second reinforcing portion16; and the arc-shaped frame20and the first frame14are fixed to each other, so that a closed box-shape section is formed. The side flanges8areinforce the arc-shaped frame20and the first frames14by connecting opposite corners of the box. Further, the spare tire pan8is firmly supported at the side flanges8aby the arc-shaped frame20and the first frame14.

FIGS. 5 to 7show successive deformations of the spare tire pan8during a rear-end collision of the vehicle1. The reference number18in the drawings denotes a fuel tank arranged below the front of the spare tire pan8between the rear cross member5and the middle cross member4.

FIG. 5shows the state before the spare tire pan8deforms. When rear-end collision load L is input to the rear panel6, the rear-end collision load L is input directly to rear ends of the left-and-right rear frames2and transmitted to the side sills3(i.e., first load transmission paths); in addition, the rear-end collision load L is transmitted to the side sills3via second load transmission paths which go to both ends from the top portion of the arc-shaped frame20. As a result, the left-and-right rear frames2begin to collapse in the longitudinal direction, and the arc-shaped beads12ato12eon the spare tire pan8are deformed with collapses at the top portions of the arc as shown inFIG. 6.

In this state, since both ends of the arc-shaped beads12ato12eare rigidly fixed to the rear cross member5via the linear beads13ato13e, the collision load L is not scattered over the broad region on the spare tire pan8and focused on the vicinity of the top portions of the arc (i.e., the middle portion in the extending direction) of the arc-shaped beads12ato12e. Therefore, the spare tire pan8is deformed so that the vicinity of the top portions of the arc of the arc-shaped beads12ato12eare pleated, and the whole arc-shaped beads12ato12egradually collapse; accordingly, the collision energy is efficiently absorbed during the deformation.

When rear-end collision load L is further applied, finally, as shown inFIG. 7, the spare tire pan8is bent at the middle portion so that the vicinity of the top of the substantially conical portion11is further pushed upward, and efficiently absorb the collision energy. The spare tire pan8is deformed as above-described; as a result, crush dust “a” of the spare tire pan8does not accumulate in the deformable portion of the spare tire pan8. Accordingly, a large crushable margin of the spare tire pan8can be ensured. That is, as shown inFIG. 7by chain lines, if the spare tire pan8is bent downward at the middle portion thereof, the crush dust “a” gets between the deformed portions. Accordingly, further deformation of the spare tire pan8will be prevented; therefore, deformation of the vehicle body owing to the collision load L advances forward of the rear cross member5. However, in the present rear structure of the vehicle body, the spare tire pan8is securely bent upward at the middle portion thereof; therefore, the prevention of the spare tire pan8against the deformation owing to the crush dust “a” can be prevented.

In the conventional structure, in a case of a rear-end offset collision in which a collision portion is deviated to left or right of the vehicle width direction, collision load is input mainly to the rear frame2on the collision side. However, in the vehicle1having the rear structure of the vehicle body according to the present invention, the collision load is input to the rear frame2of the collided side and the top portion of the arc-shaped frame20at the middle of the vehicle width direction. The load input to the top portion of the arc-shaped frame20is transmitted through both ends of the arc to the middle portions of the left-and-right rear frames2. Therefore, even when the rear-end offset collision, the left-and-right rear frames2can support the load evenly. As a result, the load input to the spare tire pan8can be applied surely to the vicinity of the top portions of the arc-shaped beads12ato12e.

In the vehicle1having the present rear structure of a vehicle, the first reinforcing portions20ahaving substantially L-shapes in sections of the arc-shaped frame20and the second reinforcing portions16having substantially L-shapes in sections of the rear frames2are fixed to each other with interposing the side flanges8aof the tire spare pan8. Accordingly, the closed section structure is formed between the first reinforcing portions20aof the arc-shaped frame20and the second reinforcing portions16. Therefore, the collision load input to the rear frames2and the arc-shaped frame20can be transmitted to the spare tire pan8as a stress directed in a shearing direction. As a result, by the shearing stress applied to the spare tire pan, the left-and-right rear frames2can be prevented from offset collapse. Therefore, even when the rear-end offset collision, the arc-shaped beads12ato12eon the spare tire pan8can surely be collapsed mainly at the vicinity of the top portions. Therefore, the deformation of the vehicle1at the front of the rear cross member5can be efficiently prevented since the collision load can be absorbed by the deformation of the spare tire pan8.

Further, in the present rear structure of a vehicle body, since the first reinforcing portions20aof the arc-shaped frame20and the second reinforcing portions16of the rear frames2(the first frames14) are fixed to each other and forms the closed section, rigidity can surely be improved at joining portions of two load transmission paths (that is, the first load transmission path by the rear frames2and the second load transmission path by the arc-shaped frame20). Especially, the square section at the fixed portion of the arc-shaped frame20and the rear frames2is interposed the spare tire pan8connecting the opposed corners. Therefore, the collapse of the section can be efficiently prevented.

Meanwhile, the present invention is not limited to the above-mentioned embodiment, and may have various modifications without departing from the scope and spirit of the present invention.